Your name:
Presenter’s name(s):
Date:
TITILE:
Motivation(s)/Statement of problem(s):
Objective(s):
Approach(s):
a. Materials:
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LETTERS
nature materials | VOL 3 | APRIL 2004 | www.nature.com/naturematerials 249
T issue engineering aims to replace, repair or regeneratetissue/organ function, by delivering signalling molecules andcells on a three-dimensional (3D) biomaterials scaffold that
supports cell infiltration and tissue organization1,2. To control cell
behaviour and ultimately induce structural and functional tissue
formation on surfaces, planar substrates have been patterned with
adhesion signals that mimic the spatial cues to guide cell attachment
and function3–5. The objective of this study is to create biochemical
channels in 3D hydrogel matrices for guided axonal growth. An agarose
hydrogel modified with a cysteine compound containing a sulphydryl
protecting group provides a photolabile substrate that can be
patterned with biochemical cues. In this transparent hydrogel we
immobilized the adhesive fibronectin peptide fragment, glycine–
arginine–glycine–aspartic acid–serine (GRGDS),in selected volumes of
the matrix using a focused laser.We verified in vitro the guidance effects
of GRGDS oligopeptide-modified channels on the 3D cell migration
and neurite outgrowth. This method for immobilizing biomolecules in
3D matrices can generally be applied to any optically clear hydrogel,
offering a solution to construct scaffolds with programmed spatial
features for tissue engineering applications.
Hydrogels have been widely studied as tissue scaffolds because they
are biocompatible and non-adhesive to cells, allowing cell adhesion
to be programmed in6–8. Current microfabrication methods for
3D hydrogel matrices with controlled intrinsic structure mainly
include photolithographic patterning9–11, microfluidic patterning12,
electrochemical deposition13 and 3D printing14. Notably, although these
layering techniques can conveniently shape the hydrogel on X–Y planes,
they have limited control over both the coherence of the layers along the
z direction and the local chemistry. Combining photolabile hydrogel
matrices with focused light provides the possibility of eliminating the
layering process and directly modifying the local physical or chemical
properties in 3D. This results in a promising (and perhaps facile) way to
fabricate novel tissue constructs15,16, as is described herein to control cell
behaviour by controlling the local chemical properties of gels.
Reconstituting adhesive biomolecules into biomaterials is of great
importance to understanding cell–substrate interactions that can be
translated to tissue-regeneration designs. Using 2D lithographic
techniques, adhesive biomolecules can be localized in arbitrary shapes
and sizes17,18. For example, patterning narrow strips of the extracellular
matrix (ECM) adhesion protein, laminin, on non-cell-adhesive 2D
substrates elicited ...
Austin Biomolecules: open access is a peer reviewed, scholarly journal dedicated to publish articles covering all areas of Biomolecules.
The journal aims to promote latest information and provide a forum for doctors, researchers, physicians, and healthcare professionals to find most recent advances in the areas of Biomolecules. Austin Biomolecules: open access accepts research articles, reviews, mini reviews, case reports and rapid communications covering all aspects of Biomolecules.
Austin Biomolecules: open access strongly supports the scientific up gradation and fortification in related scientific research community by enhancing access to peer reviewed scientific literary works. Austin Publishing Group also brings universally peer reviewed journals under one roof thereby promoting knowledge sharing, mutual promotion of multidisciplinary science.
1) The document describes a small molecule crosslinker called 1,6-diazidohexane (DAZH) that can enhance the efficiency and stability of organic solar cells.
2) DAZH acts as both a crosslinker and additive by covalently bonding polymer chains to "lock" the morphology, preventing phase separation over time for increased stability, without impairing efficiency.
3) Experiments show DAZH preferentially reacts with alkyl regions of the donor polymer and fullerene acceptor rather than perturbing the conjugated backbone, maintaining optical and charge transport properties critical for performance.
This document describes the development of an in vitro model to study the foreign body response by modulating biomaterial surface properties. The model uses polymeric rods with tailored surface topography, roughness, wettability and chemistry achieved through surface modification techniques. Results showed that surface microstructuring increased cell adhesion, proliferation, and balanced cytokine secretion to optimize collagen and elastin synthesis for tissue regeneration. By linking surface parameters to cell activity, the fate of regenerated tissue could be determined to create successful soft tissue replacements.
The document discusses dye sensitized solar cells (DSSCs) and describes methods to improve their efficiency through controlling the morphology of the TiO2 electrodes. It summarizes a study that demonstrated tuning the pore size of mesoporous TiO2 thin film electrodes from 6-50 nm using chemical modification techniques. This allowed for higher dye adsorption and electron transport, improving the energy conversion efficiency of DSSCs. The document also reports methods to synthesize ordered mesoporous TiO2 thin films using templates and discusses their characterization and potential use in DSSCs.
A designed surface modification to disperse silica powder into polyurethaneTrang Le
This document describes a method for modifying silica powder nanoparticles through surface grafting of polyurethane (PU) oligomers or short chains to improve dispersion in PU matrices. Silica particles were first modified with 3-isocyanatepropyltriethoxysilane to introduce isocyanate groups on the surface. Further surface-initiated condensation reactions were carried out in steps using diols, triols and diisocyanates to graft PU oligomers of varying lengths. Characterization techniques confirmed grafting and showed the surface density of initial isocyanate groups could be controlled. Hybrid films with modified silica particles dispersed in PU matrices showed improved optical, thermal and mechanical properties compared to films with unmodified particles
This document describes research using a spectroscopic sensor and neural network model to monitor droplet size distributions (DSDs) in metal working fluid (MWF) emulsions. The sensor measured light absorption and scattering spectra of MWF samples. A neural network model was trained using spectroscopic data and reference DSD measurements. The model accurately estimated DSDs for new samples, distinguishing monomodal and bimodal distributions. This technique could monitor MWF emulsion aging and destabilization in industrial processes.
Facile synthesis of water-dispersible Cu2O nanocrystal–reduced graphene oxide...Haocheng Quan
This document summarizes the facile synthesis of a water-dispersible Cu2O nanocrystal-reduced graphene oxide (CRGO) hybrid material and its potential as a cancer therapeutic agent under both visible and near-infrared (NIR) light irradiation. The CRGO hybrid exhibits efficient photothermal killing of both normal and cancer cells under NIR light due to heat generation. In contrast, under visible light irradiation, the photocatalytic effect of the material results in the selective killing of cancer cells through reactive oxygen species production, avoiding damage to healthy cells. This dual mode of anticancer activity under different light sources could provide a safe and effective approach for cancer therapy.
Austin Biomolecules: open access is a peer reviewed, scholarly journal dedicated to publish articles covering all areas of Biomolecules.
The journal aims to promote latest information and provide a forum for doctors, researchers, physicians, and healthcare professionals to find most recent advances in the areas of Biomolecules. Austin Biomolecules: open access accepts research articles, reviews, mini reviews, case reports and rapid communications covering all aspects of Biomolecules.
Austin Biomolecules: open access strongly supports the scientific up gradation and fortification in related scientific research community by enhancing access to peer reviewed scientific literary works. Austin Publishing Group also brings universally peer reviewed journals under one roof thereby promoting knowledge sharing, mutual promotion of multidisciplinary science.
1) The document describes a small molecule crosslinker called 1,6-diazidohexane (DAZH) that can enhance the efficiency and stability of organic solar cells.
2) DAZH acts as both a crosslinker and additive by covalently bonding polymer chains to "lock" the morphology, preventing phase separation over time for increased stability, without impairing efficiency.
3) Experiments show DAZH preferentially reacts with alkyl regions of the donor polymer and fullerene acceptor rather than perturbing the conjugated backbone, maintaining optical and charge transport properties critical for performance.
This document describes the development of an in vitro model to study the foreign body response by modulating biomaterial surface properties. The model uses polymeric rods with tailored surface topography, roughness, wettability and chemistry achieved through surface modification techniques. Results showed that surface microstructuring increased cell adhesion, proliferation, and balanced cytokine secretion to optimize collagen and elastin synthesis for tissue regeneration. By linking surface parameters to cell activity, the fate of regenerated tissue could be determined to create successful soft tissue replacements.
The document discusses dye sensitized solar cells (DSSCs) and describes methods to improve their efficiency through controlling the morphology of the TiO2 electrodes. It summarizes a study that demonstrated tuning the pore size of mesoporous TiO2 thin film electrodes from 6-50 nm using chemical modification techniques. This allowed for higher dye adsorption and electron transport, improving the energy conversion efficiency of DSSCs. The document also reports methods to synthesize ordered mesoporous TiO2 thin films using templates and discusses their characterization and potential use in DSSCs.
A designed surface modification to disperse silica powder into polyurethaneTrang Le
This document describes a method for modifying silica powder nanoparticles through surface grafting of polyurethane (PU) oligomers or short chains to improve dispersion in PU matrices. Silica particles were first modified with 3-isocyanatepropyltriethoxysilane to introduce isocyanate groups on the surface. Further surface-initiated condensation reactions were carried out in steps using diols, triols and diisocyanates to graft PU oligomers of varying lengths. Characterization techniques confirmed grafting and showed the surface density of initial isocyanate groups could be controlled. Hybrid films with modified silica particles dispersed in PU matrices showed improved optical, thermal and mechanical properties compared to films with unmodified particles
This document describes research using a spectroscopic sensor and neural network model to monitor droplet size distributions (DSDs) in metal working fluid (MWF) emulsions. The sensor measured light absorption and scattering spectra of MWF samples. A neural network model was trained using spectroscopic data and reference DSD measurements. The model accurately estimated DSDs for new samples, distinguishing monomodal and bimodal distributions. This technique could monitor MWF emulsion aging and destabilization in industrial processes.
Facile synthesis of water-dispersible Cu2O nanocrystal–reduced graphene oxide...Haocheng Quan
This document summarizes the facile synthesis of a water-dispersible Cu2O nanocrystal-reduced graphene oxide (CRGO) hybrid material and its potential as a cancer therapeutic agent under both visible and near-infrared (NIR) light irradiation. The CRGO hybrid exhibits efficient photothermal killing of both normal and cancer cells under NIR light due to heat generation. In contrast, under visible light irradiation, the photocatalytic effect of the material results in the selective killing of cancer cells through reactive oxygen species production, avoiding damage to healthy cells. This dual mode of anticancer activity under different light sources could provide a safe and effective approach for cancer therapy.
Statistical analysis of electrodeposited in2 s3 films techconnect conferenceArkansas State University
In2S3 has received attention as an alternative to CdS as the buffer layer in heterojunction solar cells. Although having a bandgap of 2.0 eV relative to 2.5 eV for CdS, the lower toxicity and environmental impact of indium relative to cadmium, and significant photosensitivity, compel ongoing research [1]. Indium sulfide thin films were deposited onto molybdenum-coated glass (SiO2) substrates by electrodeposition from organic baths (ethylene glycol-based) containing indium chloride (InCl3), sodium chloride (NaCl), and sodium thiosulfate (Na2S2O3.5H2O), the latter used as an additional sulfur source along with elemental sulfur (S). The Taguchi method was used to optimize the deposition paramters so as to minimize non-uniformity, cracks, and improper stoichiometry. The measured performance characteristics (molar ratio (In:S) and crack density) for all of the In2S3 films were calculated to analyze the effect of each deposition factor (deposition voltage, deposition temperature, composition of solution, and deposition time) involved in the electrodeposition process by calculating the sensitivity (signal to noise, S/N, ratios).
This document describes a new lithographic technique called beam pen lithography (BPL) that combines scanning probe lithography with photolithography. BPL allows precise control over the position, height, and diameter of polymer features patterned on a surface. Specifically, acrylate and methacrylate monomers were deposited on a surface using BPL and photopolymerized upon exposure to UV light, resulting in brush polymer features. For the first time, these techniques were used to create glycan arrays by functionalizing methacrylate brush polymers with glucose residues. The binding of fluorescently labeled concanavalin A to these glycan arrays was then assessed, demonstrating significantly higher fluorescence compared to monolayer glycan arrays. The
Greener cum chemical synthesis and characterization of Mg doped ZnS nanoparti...IJERA Editor
In the present investigations, high-quality Mg doped ZnS nanoparticles were synthesized by Greener cum
chemical process with the assistance of polyvinyl pyrrolidone (PVP) with two different Mg concentrations.
Doping of Mg metal in nanoparticles were found to be a good technique for tuning the band gap of ZnS
nanoparticles. Simultaneously, Mg doping also inhibited the growth of particle size and it decreased from 33.2
nm to 18.3 nm with the increase in doping concentration from 0% to 5%. Band gap was found to rise from 3.12
eV to 3.38 eV and photoluminescence studies exposed that visible Photoluminescence (PL) emission was
improved with doping concentration. The nanoparticles have been characterized by Field Emission Scanning
Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy,
Ultra Violet visible (UV–vis) spectroscopy, and Energy Dispersive X-ray Analysis (EDAX).
This paper investigates the shell properties and concentration stability of a new acoustofluidic delivery agent liposome in comparison to DefinityTM microbubbles. Frequency dependent attenuation measurements were used to estimate the shell stiffness (Sp) and friction (Sf) parameters of both agents. The liposome had lower Sp and Sf values compared to DefinityTM microbubbles. Temperature increase resulted in decreased Sf for both agents but increased Sp for liposomes and decreased Sp for microbubbles. Size distribution measurements using tunable resistive pulse sensing showed the liposomes maintained >80% concentration for 24 hours at physiological temperature, while microbubbles maintained only 27% over the same period.
Performance Investigation and Enhancement of Fiber Bragg Gratingfor Efficient...IOSRJECE
In this paper, the performance of various windowfunctions for Fiber Bragg Grating Sensor (FBGS)is investigated and evaluated in order to get optimized reflection spectrum with high reflectivity and an efficient side lobe suppression for efficient sensing measurement applications.For this purpose, a wide range of design parameters which include grating length and refractive index modulation amplitudehas been chosen to evaluate the sensor design. The performances of the different windowfunctions have been then compared in terms of reflectivity, full width half maximum bandwidth (FWHM), and sidelobe level(SLL) so as to get the most suitable design parametersto be used for sensing measurement.The simulation results presented in this paper show the effectiveness of the optimizedFBG sensor, which can be further implemented for high performance sensing applications.
Passivative effect of polyethylene glycol and carboxylmethly cellulose as cap...Alexander Decker
The document summarizes a study on the effect of polyethylene glycol (PEG) and carboxylmethly cellulose (CMC) as capping agents on the particle size of ZnS nanoparticles synthesized using wet chemical co-precipitation. ZnS nanoparticles were prepared with PEG and CMC and characterized. The estimated crystal sizes from XRD were 3.92 nm for ZnS/PEG and 3.89 nm for ZnS/CMC. The band gaps were blue shifted to 3.76 eV and 3.88 eV respectively. FTIR analysis confirmed interaction of the capping agents with ZnS. CMC was found to be a better capping agent, producing nanoparticles with a larger band gap and smaller size.
The document describes a study on the facile preparation of silver sulfide (Ag2S) nanoparticles with broad photoelectric response. Ag2S nanoparticles were prepared via a simple one-step hydrothermal synthesis using thiourea and silver nitrate as precursors. Different concentrations of the surfactants glutathione and sodium dodecyl sulfate were used to obtain Ag2S nanoparticles with various particle diameters. Characterization techniques confirmed the formation of Ag2S nanoparticles. Surface photovoltage measurements showed the Ag2S nanoparticles exhibited intense photoelectric response in the near infrared and visible light regions, indicating potential application as a photoelectric detector.
Flexible all-carbon photovoltaics with improved thermal stabilityAndrew Siordia
1) Graphene nanoribbons (GNRs) are explored as a protective layer to suppress the dissociation of C60 fullerene molecules from the basal plane of single-walled carbon nanotubes (SWCNTs) under thermal stimuli.
2) Molecular dynamics simulations reveal that GNR membranes of varying sizes can significantly improve the thermal stability of C60:SWCNT binary assemblies by preventing the dissociation of C60s.
3) Flexible photovoltaic devices are fabricated using a GNR-stabilized C60:SWCNT composite as the active layer, demonstrating improved thermal stability and the ability to withstand iterative mechanical bending without degradation in performance.
The document describes a method for synthesizing and characterizing fluorescent dye-labeled smart polymers (microgels). Microgels based on N-isopropylacrylamide were synthesized and coupled with the amine-reactive fluorescent dye Nuclear Fast Red using standard coupling chemistry. Analytical techniques including DLS, FTIR, HS-DSC and fluorescence spectroscopy showed that the dye was successfully conjugated to the microgels. The dye-labeled microgels were larger in size and had a higher volume phase transition temperature compared to unlabeled microgels.
This document summarizes research on using quartz-binding peptides (QBPs) as molecular linkers to pattern multifunctional substrates. The researchers:
1) Used QBPs conjugated to fluorescent molecules or biotin to pattern fluorescein and quantum dots on quartz surfaces via microcontact printing.
2) Showed that a strongly binding QBP (QBP1) efficiently patterned molecules, while a weakly binding QBP (QBP2) did not produce patterns.
3) Demonstrated the material specificity of QBPs by showing that QBP1 did not pattern molecules on gold surfaces.
4) Were able to sequentially pattern quantum dots and fluores
Within the last few years, there has been notable progress in understanding the growth mechanisms of semiconductor thin films for photovoltaic (PV) applications. Electrodeposition continues to be a complex deposition technique that can lead to regions of low quality (for example, cracks) in films. Such cracks can form porous zones on the substrate and diminish the heterojunction interface quality of a PV cell. In this paper, electrodeposition of In2S3 films was systematically and quantitatively investigated by varying electrodeposition parameters including bath composition, current density, deposition time, and deposition temperature. Their effects upon the morphology, composition, and film growth mechanism were studied with the help of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and digital imaging analysis (using fracture and buckling analysis software). In addition, the effect of different annealing treatments (200 oC, 300 oC, and 400 oC in air) and coated glass-substrates (Mo, ITO, and FTO) upon the properties of the In2S3 films was analyzed. Furthermore, the Taguchi/Design of Experiments (DOE) Method was used to determine the optimal electrodeposition parameters in order to improve the properties.
The fabrication of nanostructured layer-by-layer (LbL) films strives for molecular control of the film properties directly connected with modifications in the film architecture. In the present report, the photoinduced birefringence and formation of the surface-relief gratings in LbL films obtained with an azopolymer (PS119) are shown to be strongly affected by the generation of the dendrimer employed in the alternating layers. Stronger adsorption of PS119 occurred when polypropylenimine tetrahexacontaamine dendrimer (DAB) of higher generations is used, due to a larger number of sites available to interact with azochromophores in PS119. In contrast, the photoinduced birefringence for LbL films
made with the generation 1 dendrimer (DABG1) was higher, which can be explained by weaker interactions between
adjacent layers. Strong interactions in LbL films consisting of PS119 and generation 3 or 5 dendrimers restrict the
chromophore mobility, leading to a smaller birefringence. The interpretation is supported by the fact that surface-relief gratings with larger amplitudes were obtained for 35-bilayer films of DABG1/PS119 (31 nm) in comparison with films from DABG5/PS119 (5 nm). These gratings were formed with mass transport arising from a light-driven mechanism, as photoinscription was successful only with p-polarized light and not with s-polarized light.
Characterisation of NanostructuredLead Selenide (PbSe) Thin Films for Solar D...IOSR Journals
The document summarizes research characterizing nanostructured lead selenide (PbSe) thin films deposited using chemical bath deposition for potential solar device applications. PbSe thin films were deposited on glass substrates at varying pH levels of the deposition bath. Characterization of the structural, optical and electrical properties of the films showed that film thickness and properties like band gap energy and conductivity could be controlled by varying the deposition parameters like pH. Higher pH levels resulted in films with lower conductivity and band gap, indicating the properties of PbSe could be tuned for different functions. The nanostructured PbSe thin films showed potential for use in solar energy devices based on their optical absorption properties.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This document summarizes research on starPEG-heparin cryogel scaffolds and microcarriers for cell culture studies. The scaffolds and microcarriers have a macroporous structure with interconnected pores ranging from 20-300 μm that allow cell infiltration and nutrient transport. The starPEG-heparin hydrogel system can be customized by varying the starPEG to heparin ratio to tune physical properties and secondary functionalization to confer biomolecular properties. Cell studies show that human endothelial and stem cells proliferate throughout the 3D scaffolds and microcarriers, demonstrating their potential as engineered vascularized tissues.
The document discusses improving the performance of photopolymer resins used in 3D printing through oxygen desensitization. It examines adding visco enhancers and antioxidants to photopolymer resins to protect the ruthenium catalyst from deactivating in the presence of oxygen. Testing found that increasing the resin viscosity by 30x improved its ambient lifespan by over 100x. Adding the antioxidant 4-methoxyphenol (MEHQ) at 0.1-0.2 wt.% also improved performance by 9x. Raman spectroscopy confirmed MEHQ was the most effective antioxidant at protecting the catalyst compared to others tested. The modifications aim to allow photopolymer resins to polymerize after longer exposures to ambient oxygen levels.
Preparation and study of optical properties of (polymer nickel nitrate) compo...Alexander Decker
This document summarizes an academic article that studied the optical properties of polymer-nickel nitrate composite materials. It discusses how composites of polyvinyl alcohol doped with different concentrations of nickel nitrate were prepared and their optical characteristics analyzed. The study found that absorption increased with higher nickel nitrate concentration, while the optical band gap decreased. The refractive index, extinction coefficient, and dielectric constants were also found to increase with greater amounts of the nickel nitrate dopant. The composites showed potential for applications in areas like integrated optics or holography due to their tunable optical properties.
Morphological and Optical Study of Sol-Gel SpinCoated Nanostructured CdSThin ...iosrjce
Nanostructured CdS thin films of different thicknesses were deposited on a cleaned glass substrate
using sol-gel spin coating technique. CdS thin films were prepared using cadmium acetate as cadmium source
and thiourea as sulfur source. The Morphological, chemical composition, and optical properties of the spin- coated
CdS thin film were studied using field emission- scanning electron microscopy (FE-SEM), Energy dispersive X –ray
(EDX) spectroscopy, and a UV-Vis-NIR spectrophotometer.The morphological results revealed that the films consist
of agglomerated spherical CdS nanoparticles with diameter < 20 nm, which distributed uniformly on the substrate
surface.The films show high transmittance > 90% and very strong absorption edge at 295 nm.The absorption edge
shifts towards longer wavelength as the film thickness increased.
Enhanced electrophoretic resolution of monosulfate GAG disacchride isomers on...Yong Zhang
This document describes research on improving the separation of monosulfate glycosaminoglycan disaccharide isomers by microchip electrophoresis. Key findings include:
1) Addition of 1,4-dioxane (DO) to the running buffer dramatically improved resolution of the isomers, likely due to solvation effects.
2) Methylcellulose was used to suppress electroosmotic flow and analyte adsorption to the poly(methyl methacrylate) microchip surface.
3) Optimization of buffer pH, addition of beta-cyclodextrin, and concentration of 1,4-dioxane enhanced resolution of the monosulfate isomers.
4) Under optimized conditions,
This document presents a novel method for quantifying surface modifications of glass fibre-reinforced polyester composites exposed to UV radiation. The method involves staining the composites with methylene blue dye after UV exposure. Colour analysis of digital images of the stained composites is then used to assess degradation, as degradation leads to increased dye adsorption and darker staining. The colour changes correlated well with FTIR spectroscopy and microscopy results. The method is presented as being easier, faster and cheaper than traditional analysis techniques for evaluating UV degradation of such composites.
Per the text, computers are playing an increasingly important role i.docxodiliagilby
Per the text, computers are playing an increasingly important role in the practice of law. Successful paralegals must be comfortable with using electronic databases and research tools.
Write a two to three (2-3) page paper in which you:
Discuss a paralegal’s ethical obligation to conduct competent electronic research. Provide two (2) examples of the potential consequences of inept electronic research practices.
Determine whether or not traditional reference materials (e.g., State and Federal Reporters, West’s Encyclopedia, etc.) can be as current as electronic resources. Provide two (2) advantages and two (2) disadvantages to using traditional resource materials.
Use at least two (2) quality references.
Note:
Wikipedia and other Websites do not qualify as academic resources.
THIS IS PART 1.
.
Pennsylvania was the leader in sentencing and correctional reform .docxodiliagilby
Pennsylvania was the leader in sentencing and correctional reform in the early history of the United States. Discuss what groups were associated with this reform.
Why did they want the reform?
Examine whether it was successful and if the reform brought forth further changes.
What influences does the system have on the correctional system today?
What influences have changed? Why?
Use the Internet, library, and any other resources available to research your answer. Submit a 4 page paper (double-spaced) to your instructor. Support your reasoning with outside sources. Be sure to reference all sources using APA style.
The following will be the grading criteria for this assignment:
20%:
Discuss what groups were associated with this reform.
10%:
Why did they want the reform?
20%:
Examine whether it was successful and if the reform brought forth further changes.
25%:
What direct influences do you see the Pennsylvania system in the correctional systems used today?
25%:
What influences have changed? Why?
4 pages. APA format. No plagerism. 5 sources referenced throughout the paper. Reference Page and Abstract.
.
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In2S3 has received attention as an alternative to CdS as the buffer layer in heterojunction solar cells. Although having a bandgap of 2.0 eV relative to 2.5 eV for CdS, the lower toxicity and environmental impact of indium relative to cadmium, and significant photosensitivity, compel ongoing research [1]. Indium sulfide thin films were deposited onto molybdenum-coated glass (SiO2) substrates by electrodeposition from organic baths (ethylene glycol-based) containing indium chloride (InCl3), sodium chloride (NaCl), and sodium thiosulfate (Na2S2O3.5H2O), the latter used as an additional sulfur source along with elemental sulfur (S). The Taguchi method was used to optimize the deposition paramters so as to minimize non-uniformity, cracks, and improper stoichiometry. The measured performance characteristics (molar ratio (In:S) and crack density) for all of the In2S3 films were calculated to analyze the effect of each deposition factor (deposition voltage, deposition temperature, composition of solution, and deposition time) involved in the electrodeposition process by calculating the sensitivity (signal to noise, S/N, ratios).
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Greener cum chemical synthesis and characterization of Mg doped ZnS nanoparti...IJERA Editor
In the present investigations, high-quality Mg doped ZnS nanoparticles were synthesized by Greener cum
chemical process with the assistance of polyvinyl pyrrolidone (PVP) with two different Mg concentrations.
Doping of Mg metal in nanoparticles were found to be a good technique for tuning the band gap of ZnS
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3) Demonstrated the material specificity of QBPs by showing that QBP1 did not pattern molecules on gold surfaces.
4) Were able to sequentially pattern quantum dots and fluores
Within the last few years, there has been notable progress in understanding the growth mechanisms of semiconductor thin films for photovoltaic (PV) applications. Electrodeposition continues to be a complex deposition technique that can lead to regions of low quality (for example, cracks) in films. Such cracks can form porous zones on the substrate and diminish the heterojunction interface quality of a PV cell. In this paper, electrodeposition of In2S3 films was systematically and quantitatively investigated by varying electrodeposition parameters including bath composition, current density, deposition time, and deposition temperature. Their effects upon the morphology, composition, and film growth mechanism were studied with the help of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and digital imaging analysis (using fracture and buckling analysis software). In addition, the effect of different annealing treatments (200 oC, 300 oC, and 400 oC in air) and coated glass-substrates (Mo, ITO, and FTO) upon the properties of the In2S3 films was analyzed. Furthermore, the Taguchi/Design of Experiments (DOE) Method was used to determine the optimal electrodeposition parameters in order to improve the properties.
The fabrication of nanostructured layer-by-layer (LbL) films strives for molecular control of the film properties directly connected with modifications in the film architecture. In the present report, the photoinduced birefringence and formation of the surface-relief gratings in LbL films obtained with an azopolymer (PS119) are shown to be strongly affected by the generation of the dendrimer employed in the alternating layers. Stronger adsorption of PS119 occurred when polypropylenimine tetrahexacontaamine dendrimer (DAB) of higher generations is used, due to a larger number of sites available to interact with azochromophores in PS119. In contrast, the photoinduced birefringence for LbL films
made with the generation 1 dendrimer (DABG1) was higher, which can be explained by weaker interactions between
adjacent layers. Strong interactions in LbL films consisting of PS119 and generation 3 or 5 dendrimers restrict the
chromophore mobility, leading to a smaller birefringence. The interpretation is supported by the fact that surface-relief gratings with larger amplitudes were obtained for 35-bilayer films of DABG1/PS119 (31 nm) in comparison with films from DABG5/PS119 (5 nm). These gratings were formed with mass transport arising from a light-driven mechanism, as photoinscription was successful only with p-polarized light and not with s-polarized light.
Characterisation of NanostructuredLead Selenide (PbSe) Thin Films for Solar D...IOSR Journals
The document summarizes research characterizing nanostructured lead selenide (PbSe) thin films deposited using chemical bath deposition for potential solar device applications. PbSe thin films were deposited on glass substrates at varying pH levels of the deposition bath. Characterization of the structural, optical and electrical properties of the films showed that film thickness and properties like band gap energy and conductivity could be controlled by varying the deposition parameters like pH. Higher pH levels resulted in films with lower conductivity and band gap, indicating the properties of PbSe could be tuned for different functions. The nanostructured PbSe thin films showed potential for use in solar energy devices based on their optical absorption properties.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
This document summarizes research on starPEG-heparin cryogel scaffolds and microcarriers for cell culture studies. The scaffolds and microcarriers have a macroporous structure with interconnected pores ranging from 20-300 μm that allow cell infiltration and nutrient transport. The starPEG-heparin hydrogel system can be customized by varying the starPEG to heparin ratio to tune physical properties and secondary functionalization to confer biomolecular properties. Cell studies show that human endothelial and stem cells proliferate throughout the 3D scaffolds and microcarriers, demonstrating their potential as engineered vascularized tissues.
The document discusses improving the performance of photopolymer resins used in 3D printing through oxygen desensitization. It examines adding visco enhancers and antioxidants to photopolymer resins to protect the ruthenium catalyst from deactivating in the presence of oxygen. Testing found that increasing the resin viscosity by 30x improved its ambient lifespan by over 100x. Adding the antioxidant 4-methoxyphenol (MEHQ) at 0.1-0.2 wt.% also improved performance by 9x. Raman spectroscopy confirmed MEHQ was the most effective antioxidant at protecting the catalyst compared to others tested. The modifications aim to allow photopolymer resins to polymerize after longer exposures to ambient oxygen levels.
Preparation and study of optical properties of (polymer nickel nitrate) compo...Alexander Decker
This document summarizes an academic article that studied the optical properties of polymer-nickel nitrate composite materials. It discusses how composites of polyvinyl alcohol doped with different concentrations of nickel nitrate were prepared and their optical characteristics analyzed. The study found that absorption increased with higher nickel nitrate concentration, while the optical band gap decreased. The refractive index, extinction coefficient, and dielectric constants were also found to increase with greater amounts of the nickel nitrate dopant. The composites showed potential for applications in areas like integrated optics or holography due to their tunable optical properties.
Morphological and Optical Study of Sol-Gel SpinCoated Nanostructured CdSThin ...iosrjce
Nanostructured CdS thin films of different thicknesses were deposited on a cleaned glass substrate
using sol-gel spin coating technique. CdS thin films were prepared using cadmium acetate as cadmium source
and thiourea as sulfur source. The Morphological, chemical composition, and optical properties of the spin- coated
CdS thin film were studied using field emission- scanning electron microscopy (FE-SEM), Energy dispersive X –ray
(EDX) spectroscopy, and a UV-Vis-NIR spectrophotometer.The morphological results revealed that the films consist
of agglomerated spherical CdS nanoparticles with diameter < 20 nm, which distributed uniformly on the substrate
surface.The films show high transmittance > 90% and very strong absorption edge at 295 nm.The absorption edge
shifts towards longer wavelength as the film thickness increased.
Enhanced electrophoretic resolution of monosulfate GAG disacchride isomers on...Yong Zhang
This document describes research on improving the separation of monosulfate glycosaminoglycan disaccharide isomers by microchip electrophoresis. Key findings include:
1) Addition of 1,4-dioxane (DO) to the running buffer dramatically improved resolution of the isomers, likely due to solvation effects.
2) Methylcellulose was used to suppress electroosmotic flow and analyte adsorption to the poly(methyl methacrylate) microchip surface.
3) Optimization of buffer pH, addition of beta-cyclodextrin, and concentration of 1,4-dioxane enhanced resolution of the monosulfate isomers.
4) Under optimized conditions,
This document presents a novel method for quantifying surface modifications of glass fibre-reinforced polyester composites exposed to UV radiation. The method involves staining the composites with methylene blue dye after UV exposure. Colour analysis of digital images of the stained composites is then used to assess degradation, as degradation leads to increased dye adsorption and darker staining. The colour changes correlated well with FTIR spectroscopy and microscopy results. The method is presented as being easier, faster and cheaper than traditional analysis techniques for evaluating UV degradation of such composites.
Similar to Your namePresenter’s name(s) DateTITILE Motivatio.docx (20)
Per the text, computers are playing an increasingly important role i.docxodiliagilby
Per the text, computers are playing an increasingly important role in the practice of law. Successful paralegals must be comfortable with using electronic databases and research tools.
Write a two to three (2-3) page paper in which you:
Discuss a paralegal’s ethical obligation to conduct competent electronic research. Provide two (2) examples of the potential consequences of inept electronic research practices.
Determine whether or not traditional reference materials (e.g., State and Federal Reporters, West’s Encyclopedia, etc.) can be as current as electronic resources. Provide two (2) advantages and two (2) disadvantages to using traditional resource materials.
Use at least two (2) quality references.
Note:
Wikipedia and other Websites do not qualify as academic resources.
THIS IS PART 1.
.
Pennsylvania was the leader in sentencing and correctional reform .docxodiliagilby
Pennsylvania was the leader in sentencing and correctional reform in the early history of the United States. Discuss what groups were associated with this reform.
Why did they want the reform?
Examine whether it was successful and if the reform brought forth further changes.
What influences does the system have on the correctional system today?
What influences have changed? Why?
Use the Internet, library, and any other resources available to research your answer. Submit a 4 page paper (double-spaced) to your instructor. Support your reasoning with outside sources. Be sure to reference all sources using APA style.
The following will be the grading criteria for this assignment:
20%:
Discuss what groups were associated with this reform.
10%:
Why did they want the reform?
20%:
Examine whether it was successful and if the reform brought forth further changes.
25%:
What direct influences do you see the Pennsylvania system in the correctional systems used today?
25%:
What influences have changed? Why?
4 pages. APA format. No plagerism. 5 sources referenced throughout the paper. Reference Page and Abstract.
.
Penetration testing is a simulated cyberattack against a computer or.docxodiliagilby
Penetration testing is a simulated cyberattack against a computer or network that checks for exploitable vulnerabilities. Pen tests can involve attempting to breach application systems, APIs, servers, inputs, and code injection attacks to reveal vulnerabilities. In a well-written, highly-detailed research paper, discuss the following:
What is penetration testing
Testing Stages
Testing Methods
Testing, web applications and firewalls
Your paper should meet the following requirements:
Be approximately four to six pages in length, not including the required cover page and reference page.
Follow APA7 guidelines. Your paper should include an introduction, a body with fully developed content, and a conclusion.
Support your answers with the readings from the course and at least two scholarly journal articles to support your positions, claims, and observations, in addition to your textbook. The UC Library is a great place to find resources.
Be clearly and well-written, concise, and logical, using excellent grammar and style techniques. You are being graded in part on the quality of your writing.
.
Perform an analysis of the social demographic, technological, econ.docxodiliagilby
Perform an analysis of the social / demographic, technological, economic, environmental / geographic, and political/legal / governmental segments to understand the general environment facing Union Pacific.
Descri
be how Union Pacific will be affected by each of these external factors.
this is a strategic mangement course business 499.
.
Perform research and discuss whether text messaging is cheaper or mo.docxodiliagilby
Perform research and discuss whether text messaging is cheaper or more expensive than voice. Explain how text messaging works.
Perform research and discuss how an audio CD and an audio DVD compare. Find out why it is said that a vinyl long play record produces sounds much better. Are we going backwards with digital technology in music recording? Explain.
.
People in developed nations are fond of warning people in developing.docxodiliagilby
Developed nations warn developing nations like Indonesia to stop destroying rainforests, but this is seen as hypocritical since developed countries became wealthy by deforesting their own lands in the past. The president of Indonesia could respond that while rainforest protection is important, developing countries aim to use their resources to improve living standards, as developed countries did previously.
Pease read and incorporate the following articles from the EBSCO h.docxodiliagilby
Pease read and incorporate the following articles from the EBSCO host database into your paper:
Deakin, A. (2004, November). Finding your organization's hidden treasure.
Behavioral Health Management
, 24(6), 27-29.
Droppa, D., & Luczak, R. (2004, January). Collaboration, technology,
and outcomes—A recipe to improve service delivery.
Behavioral Health Management
, 24(1), 41-44.
To complete the research paper, you will need to include an introduction and conclusion section as well as a title page and reference section. The title of the research paper will be the
Current Issues in the Behavioral Healthcare System
.
Your final paper is due for submission. The paper should adhere to the following guidelines:
The length of the paper should be eight to ten double-spaced pages (not including the title and reference pages).
The main sections should have a:
Title page
Introduction
Body of the paper (with subheadings)
Conclusion
Reference page(s)
The paper must use the APA format for citing sources and references.
Your final paper introduction (one page) should include the following points:
An overview of the research paper
The purpose or objective of the research paper
The body of the paper (five to six pages) should address each of the following topics using information learned in the course, in combination with outside references:
Based on your previous assignments and review of the literature, what are some of the major issues faced by today’s behavioral healthcare system? How have the current and future trends that are evolving in the industry addressed some of those issues?
Do you think there is a difference between the changing trends taking place in the private sector and that of public behavioral healthcare inpatient facilities? Based on your understanding about behavioral health services and the populations being served by them, do you agree that both private and public organizations are able to provide the necessary clinical services? Provide a rationale in support of your response.
In behavioral healthcare, outcomes are the established norm for measuring the success or lack of services. What are some of the major challenges in collecting the data needed to support and report behavioral health outcomes? Provide a rationale for your response.
Quality of care and services is an important part of an outcome-based strategy. The objective behind maintaining and improving quality is to provide competent and efficient services to consumers. In your opinion, do the current regulatory and accreditation standards for the behavioral health industry help to meet that objective? How?
Your conclusion (one to two pages) should include the following points:
What conclusions can you draw from your research that would demonstrate the role played by behavioral health in the healthcare industry?
What changes would you like to bring to today's behavioral healthcare system in order to resolve the current issues identified?
Based on your literature rev.
Peer Review Journal Paper Overview of assignment due 17 April 2014 I.docxodiliagilby
Peer Review Journal Paper Overview of assignment due 17 April 2014 I want you to find a peer review article that falls into our time frame: world history from the emergence of humanity to 1500 CE. I want you to present the thesis [argument] the author is putting forward. I want you then to find two other sources on the same subject and determine if those sources agree or disagree with your original source. The theme here is peer review and the notion of historiography; whether or not how we look at an event or theme of history changes over time? The choice of topic is up to you but please let me know what you are doing by email and let me know what your peer review source is so I can be sure it is appropriate for the course. If you want some help in finding an article; please let me or a librarian know what you might be interested in. I really need to know what your article is before you start so you have something good to start with and send me a link to your article, so that I can approve it.
1. Find a peer review article on some aspect of history associated with this course.
2. Explain the thesis that author is putting forth.
3. Find two secondary sources, they need not be peer review which relate to the main article you are presenting. Do these sources compliment or contrast the thesis being put forth by the original author?
4. Leave some time & space at the end to present your perspective and opinion on the thesis as well.
5. 5-7 pages; typed doubled spaced standard borders & fonts. Please use citation; APA, MLA, Chicago are all acceptable.
The requirement of the paper starts at the middle of the 3rd page that I attached here.
We can discuss more later.
.
Perception is all EXCEPT [removed] [removed]Structuring and orga.docxodiliagilby
Perception is all EXCEPT
[removed]
[removed]Structuring and organizing incoming impulses (information)
[removed]a prognosis (guess) about what is being received
[removed]the reconstruction of reality by our brain
[removed]the transduction of incoming stimuli
[removed]a process which takes time
.
Performance Based Factors and Measures for Quality AssessmentWri.docxodiliagilby
Performance Based Factors and Measures for Quality Assessment
Write a 700- to 1,000-word paper about the Performance Based Factors and Measures for Quality Assessment. Include the following in your paper:
For any health care activity, three performance factors can be measured: structure, process, and outcome. Identify one structure measure, one process measure, and one outcome measure that could be used to evaluate the following hospital admission process:
Upon arrival, the patient reports to the hospital registration or admitting area. The patient completes paperwork and provides an insurance identification card, if insured. Often, patients register before the date of hospital admission to facilitate the registration process. An identification bracelet including the patient’s name and doctor’s name is placed around the patient’s wrist. Before any procedure is performed or any form of medical care is provided, the patient is asked to sign a consent form. If the patient is not feeling well, a family member or caregiver can help the patient complete the admission process.
Include a minimum of three peer-reviewed references, not including the textbook.
Format your paper consistent with APA 6th guidelines.
.
People. I need some help with this assignment that needs to be done .docxodiliagilby
People. I need some help with this assignment that needs to be done in Excel
Problem 1:
Oregon Surplus Inc. qualifies to use the installment-sales method for tax purposes and sold an investment on an installment basis. The total gain of $75000 was reported for financial reporting purposes in the period of sale. The installment period is 3 years; one-third of the sale price is collected in 2014 and the rest in 2015 and 2016. The tax rate was 35% in 2014, 30% in 2015, and 30% in 2016. The enacted tax rates of 2015 and 2016 are not known until 2015.
The accounting and tax data are shown below.
Financial Accounting
Tax Return
2014 (35% tax rate)
Income before temporary difference
$
175,000
$
175,000
Temporary difference
$
75,000
$
25,000
Income
$
250,000
$
200,000
2015 (30% tax rate)
Income before temporary difference
$
200,000
$
200,000
Temporary difference
$
-
$
25,000
Income
$
200,000
$
225,000
2016 (30% tax rate)
Income before temporary difference
$
180,000
$
180,000
Temporary difference
$
-
$
25,000
Income
$
180,000
$
205,000
Required:
1)
Prepare the journal entries to record the income tax expense, deferred income taxes, and the income taxes payable for 2014, 2015, and 2016. No deferred income taxes existed at the beginning of 2012.
2)
Explain how the deferred taxes will appear on the balance sheet at the end of each year. (Assume Installment Accounts Receivable is classified as a current asset.)
3)
Show the income tax expense section of the income statement for each year, beginning with “Income before income taxes.”
Problem 2:
Philadelphia Co. incurred a net operating loss of $850,000 in 2014. Combined income of 2012 and 2013 was $650,000. The tax rate for all years is 30%. Trenton elects the carry back option.
Required:
a.
Prepare the journal entries to record the benefit of loss carry back and loss carry forward option.
b.
Assuming that it is more likely than not that the entire net operating loss carry forward will not be realized in future years, prepare all the journal entries necessary at the end of 2014.
.
Perceptions and Causes of Psychopathology PaperPrepare a 1,0.docxodiliagilby
Culture determines how psychopathology is expressed. Biopsychosocial or diathesis-stress models examine causes of psychopathology from biological, psychological, and social factors. Society's perceptions of psychopathology have changed over historical time periods.
People are attracted to occupations that complement their personalit.docxodiliagilby
This document requests a 500 word essay identifying and describing the six personality types by John Holland, providing an example vocational choice for each type. It also asks the essay to analyze how dualistic and relativistic thinking contribute to vocational choices and discuss the role of commitment within relativistic thinking.
Perception of Pleasure and Pain Presentation3 slides- An explanati.docxodiliagilby
This presentation discusses the role of the somatosensory cortex in perceiving pleasure and pain through 3 slides and how damage to the cutaneous system can impact quality of life in another 3 slides. It includes one peer-reviewed source and speaker notes in APA format, needing completion by 12pm Eastern on May 4th, 2015.
Pennsylvania v. MarkMark Davis has been charged with Driving W.docxodiliagilby
Pennsylvania v. Mark
Mark Davis has been
charged
with Driving While Intoxicated (DWI) for reckless driving, speeding, four counts of felony assault, and one count of involuntary manslaughter as the result of a crash that occurred on a night out with his friends. Mark has been out on bail and pleaded not guilty when he was arraigned. The Judge set a date for Mark's trial and his defense team has been working to collect information about the technology used by the Highway Patrol to reconstruct the crash.
District Attorney O'Malley offered Mark a plea bargain, but Mark chose to take his chances at trial. Mark's attorney, Mr. Chen Long, advised Mark that accepting the plea offer was completely up to Mark, although Mr. Long advised against accepting it because the defense planned to highlight mistakes made by law enforcement during the investigation that could create reasonable doubt in the minds of the jurors.
The trial begins and during the voir dire of potential jurors, several individuals are excused because they have previous knowledge of Mark's case from the media. Two individuals stated that they could not be impartial because they had loved ones
killed
in alcohol related crashes as well. Eventually, two men and ten women were seated in Mark's trial.
District Attorney O'Malley presented the State's case clearly and concisely depicting a night on the town full of heavy drinking, which ultimately resulted in Mark's actions causing the death of one individual and injuring four others. Highway Patrolman Green explained to the jury that he immediately suspected alcohol when he arrived on scene because Mark appeared to be intoxicated when they spoke. Following the Judge ruling that it was admissible and not prejudicial, Sergeant Rodney Monroe, from the Highway Patrol Reconstruction Team presented their reconstruction complete with a high-tech computer animated reenactment of the crash. During the cross examination, Defense Attorney Long challenged the reconstruction because the Defense Crash Reconstruction Expert had discovered errors in the mathematical calculations for vehicle speed. The jury appeared to have liked the reconstruction very much regardless of the errors highlighted by the defense.
Mark was convicted of DWI, four counts of felony assault, and one count of involuntary manslaughter; however, he was acquitted of reckless driving and speeding. The Jury said they could not convict Mark of those offenses because of the mistakes made by law enforcement officers during the investigation.
Because Mark pleads not guilty, but was convicted during trial and had two prior DWI offenses, he was sentenced to ten years in the State Prison. Defense Attorney Long immediately notified the court of an impending appeal that would be filed by the defendant. In a report, using external sources to support your claims, answer the following:
Compare and contrast the roles of the Judge, Jury, District Attorney (Prosecutor), and Defense Attorney. What ar.
PBAD201-1501A-02 Public AdministrationTask NamePhase 3 Individu.docxodiliagilby
PBAD201-1501A-02 Public Administration
Task Name:
Phase 3 Individual Project
Deliverable Length:
750–1,000 words; Tabular budget
Details:
Weekly tasks or assignments (Individual or Group Projects) will be due
by
Monday and late submissions will be assigned a late penalty in accordance with the late penalty policy found in the syllabus. NOTE: All submission posting times are based on midnight Central Time.
Concern among the public sector is the demand for public organizations to be transparent about their budgets and spending habits. You have been scheduled to conduct a presentation for the State Budgeting Committee about the type of budget that the organization operates under. Identify the type of public organization for which you work, as well as what types of services, goods, or activities the organization provides to the public. Identify the size and scope of the organization.
Construct a budget using Excel that will provide a breakdown of the various budget items. Copy and paste the Excel spreadsheet of your budget into a Word document. Finally, explain how the budget is made available to the public for review. For example, is the budget made available at public meetings, on a special request, published in a newsletter, on the organization’s premises during regular business hours, via the organization’s Web site, or by some other means? If the budget is not available for the public to review, explain why. Furthermore, are there any provisions in place regarding the budget being made available for public view? Explain in detail.
Assignment Guidelines
Address the following in 750–1,000 words:
Identify the type of public organization for which you work, as well as what types of services, goods, or activities the organization provides to the public. Identify the size and scope of the organization.
Construct a budget using Excel that will provide a breakdown of the various organizational budget items.
Copy and paste the Excel spreadsheet of your budget into a Word document.
Is the budget made available to the public for review?
If yes, explain how in detail.
If no, explain in detail why it is not.
Are there any types of provisions in place regarding the budget being made available for public view? Identify and explain.
Be sure to reference all sources using APA style.
.
Part1 Q1. Classify each of the following as- (i)qual.docxodiliagilby
Part1
Q1. Classify each of the following as:-
(i)
qualitative or quantitative
(ii)
nominal, ordinal, interval or ratio scale.
a.
Times for swimmers to complete a 50meters race.
b.
Months of the year: Meskerem, Tikimit, Hidat, ---.
c.
Region numbers of Riyadh: 1, 2, 3, 4, ---.
d.
Pollen counts provided as numbers between 1 and 10 where 1 means there is almost no pollen and 10 means that it is rampant, but for which the values do not represent an actual count of grains of pollen.
e.
Packages in the city of Cleveland telephone book.
f.
Rankings of tennis players.
g.
Weights of air conditioners.
h.
Personal ID numbers
i.
Telephone numbers
j.
Temperatures inside 10 refrigerators.
k.
Salaries of the top five CEOs in the United States.
l.
Ratings of eight local plays ( poor, fair, good, excellent)
m.
Times required for mechanics to do a tune up.
n.
Ages of students in a classroom.
o.
Marital Status of patients in a physician’s office.
p.
Horsepower of tractor engines.
q.
Colors of baseball caps in a store.
r.
Classification of kids at a day care (infant, toddler, pre-school)
Q2. The following are the grades which 40 students obtained in a certain course in 1997E.C. here in Mekelle University of the Arid Campus.
75 89 66 52 90 68 83 94 77 60 38 47 87 65 97 49 65 72 73 81 63 77 31 88 74 37 85 76 74 63 69 72 91 87 76 58 63 70 72 65
a. Construct an absolute frequency distribution.
b. Convert the distribution obtained in (a) into a Relative & Percentage distribution.
c. Convert the distribution in (a) into a “Less than” &
a “More than” cumulative distribution
d. Construct a histogram, frequency polygon and ogive curve
Q3. The following distribution shows that the result obtained by 100 accounting students in the final examination of statistics in
Saudi Electronic University.
Mark of students.
0-10
10-20
20-30
30-40
40-50
No. of students
14
f1
28
f2
15
If the median mark of students is 22.5, compute:-
i.
The missing frequencies, f1 and f2.
ii.
the mode, and
iii.
the arithmetic mean
iv.
variance
Part 2
Q1.
a. (Smoking and Coffee Drinking)
Coffee
No Coffee
Total
Smoker
60
40
100
Non-Smoker
115
85
200
Total
175
125
300
What is the probability that a randomly selected person from the sample either smokes or drinks coffee.
Q1. b. What is the probability that I flip a coin and get a Head, Roll a die and get a 4 or a 6, and then pull the king of Spades and a diamond from a deck of cards.
Q2: The random variable X has the following probability distribution:
X
0
1
2
3
Total
P(x)
0.22
0.38
0.1
0.3
1
Find the expected value (E(x)) & the Variance.
Q3: A radar unit is used to measure speeds of cars on a highway. The speeds are
normally
distributed with a mean of 90 km/hr and a standard deviation of 10 km/hr. What is the probability that a car picked at random is travelling at:
a-
More than 100 km/hr?
b-
Less than 85 Km/hr?
c-
Between them?
Part 3
Q-1..
Paul’s Letter to the EphesiansThe First Letter of PeterThe Fir.docxodiliagilby
Paul’s Letter to the Ephesians
The First Letter of Peter
The First Letter to Timothy
For each document above; Identify specific content, features, or themes which permit classifying each text early Catholic in character.
At least one credible source
one and half pages
.
Past and FuturePlease respond to the followingImagine back .docxodiliagilby
"Past and Future"
Please respond to the following:
Imagine back in time to pre-Internet days. Describe how you would have established communications for international trade in these time periods: 1935 and 1977.
Imagine it is now 2050. Predict the ease and speed of international trade communications and how it will occur.
2-
"Backtracking from Globalization"
Please respond to the following:
From the e-Activity, illustrate with two examples how the U.S. has restrained trade over the past 60 years and state why you think that happened.
Some believe these restraints have been deleterious to national economic prosperity. In your estimation, speculate as to how these restraints have affected national economic prosperity.
.
Partisan considerations have increasingly influenced the selection.docxodiliagilby
Partisan considerations have increasingly influenced the selection of federal judges. Interest groups on the right and the left have insisted on the appointment of judges who hold compatible views. Presidents and members of Congress have also increasingly sought appointees who will decide issues in ways they prefer. What is your view? Should politics play such a large role in judicial appointments? Or should merit be given greater weight?
Does a merit based system favor ONLY those with money and the connections? needs to be at least 200 words APA
.
Chapter wise All Notes of First year Basic Civil Engineering.pptxDenish Jangid
Chapter wise All Notes of First year Basic Civil Engineering
Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptxEduSkills OECD
Iván Bornacelly, Policy Analyst at the OECD Centre for Skills, OECD, presents at the webinar 'Tackling job market gaps with a skills-first approach' on 12 June 2024
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
Leveraging Generative AI to Drive Nonprofit InnovationTechSoup
In this webinar, participants learned how to utilize Generative AI to streamline operations and elevate member engagement. Amazon Web Service experts provided a customer specific use cases and dived into low/no-code tools that are quick and easy to deploy through Amazon Web Service (AWS.)
2. LETTERS
nature materials | VOL 3 | APRIL 2004 |
www.nature.com/naturematerials 249
T issue engineering aims to replace, repair or
regeneratetissue/organ function, by delivering signalling
molecules andcells on a three-dimensional (3D) biomaterials
scaffold that
supports cell infiltration and tissue organization1,2. To control
cell
behaviour and ultimately induce structural and functional tissue
formation on surfaces, planar substrates have been patterned
with
adhesion signals that mimic the spatial cues to guide cell
attachment
and function3–5. The objective of this study is to create
biochemical
channels in 3D hydrogel matrices for guided axonal growth. An
agarose
hydrogel modified with a cysteine compound containing a
sulphydryl
protecting group provides a photolabile substrate that can be
patterned with biochemical cues. In this transparent hydrogel
we
immobilized the adhesive fibronectin peptide fragment,
glycine–
arginine–glycine–aspartic acid–serine (GRGDS),in selected
volumes of
the matrix using a focused laser.We verified in vitro the
guidance effects
of GRGDS oligopeptide-modified channels on the 3D cell
3. migration
and neurite outgrowth. This method for immobilizing
biomolecules in
3D matrices can generally be applied to any optically clear
hydrogel,
offering a solution to construct scaffolds with programmed
spatial
features for tissue engineering applications.
Hydrogels have been widely studied as tissue scaffolds because
they
are biocompatible and non-adhesive to cells, allowing cell
adhesion
to be programmed in6–8. Current microfabrication methods for
3D hydrogel matrices with controlled intrinsic structure mainly
include photolithographic patterning9–11, microfluidic
patterning12,
electrochemical deposition13 and 3D printing14. Notably,
although these
layering techniques can conveniently shape the hydrogel on X–
Y planes,
they have limited control over both the coherence of the layers
along the
z direction and the local chemistry. Combining photolabile
hydrogel
matrices with focused light provides the possibility of
eliminating the
layering process and directly modifying the local physical or
chemical
properties in 3D. This results in a promising (and perhaps
facile) way to
fabricate novel tissue constructs15,16, as is described herein to
control cell
behaviour by controlling the local chemical properties of gels.
Reconstituting adhesive biomolecules into biomaterials is of
4. great
importance to understanding cell–substrate interactions that can
be
translated to tissue-regeneration designs. Using 2D lithographic
techniques, adhesive biomolecules can be localized in arbitrary
shapes
and sizes17,18. For example, patterning narrow strips of the
extracellular
matrix (ECM) adhesion protein, laminin, on non-cell-adhesive
2D
substrates elicited oriented neurite growth through integrin-
receptor
mediated processes19,20. Similar results were obtained using
oligopeptides derived from laminin–integrin active sites, such
as
YIGSR, IKVAV and RGD (the letters are the standard amino
acid
symbols), among others4,21. The fidelity of neurons to the
peptide
regions was attributed to both cell-adhesive and non-adhesive
regions
that mimic the in vivo attractive and repulsive haptotactic (that
is,
contact-mediated) cues, respectively, present during
development22.
This inspired us to investigate ways to create isolated
biomolecular
channels in cell invasive, yet non-adhesive, matrices, thereby
extending 2D to 3D patterning, and better approximating
functional
ECM analogues.
In this study, we used a soft thermosensitive agarose hydrogel
as a
model material because it is optically transparent, facilitating
5. bulk
modification using light. Dilute low-gelling-temperature
agarose
hydrogel is permissive to 3D neurite outgrowth and has been
used as
spinal cord surrogates23,24.A general scheme for producing
oligopeptide
channels in the agarose gel matrices is illustrated in Fig. 1.
We hypothesized that the spatial resolution between adhesive
and
non-adhesive volumes in the agarose matrix would promote
guidance
within the peptide-modified channels.
To prepare a photolabile matrix for 3D photo-fabrication, the
photosensitive S-2-nitrobenzyl-cysteine (S-NBC), which can be
efficiently cleaved in aqueous environments to release free
nucleophile on irradiation by ultraviolet (UV) light25,26, was
first
bound to the dissolved agarose polymer through a 1,1′-
carbonyldiimidazole (CDI) activation process. There was a
direct
correlation between the amount of S-NBC-modified agarose and
the
amount of CDI activation. Moderately modified agarose (that is,
up
to 5 wt%) remained thermally reversible, easily dissolving at
high
temperatures, and forming optically transparent hydrogels on
cooling. S-NBC-modified agarose had a UV absorption peak at
266 nm, which was attributed to the 2-nitrobenzyl groups in the
gel
(Supplementary Information, S1). Photo-irradiating S-NBC-
modified agarose hydrogel matrices (using a UV lamp) resulted
in
free sulphydryl groups, which were then available to react with
7. (4.0 mW).
A 0.3-mm-diameter laser beam, focused by a convex lens with a
focal
length of 10 cm,was used to irradiate a 1.5-mm-thick,0.5 wt%
agarose gel
sample for 1 s. Free sulphydryl functional channels were
created on
irradiation, providing the template for biomolecule
immobilization.
To demonstrate the universality of this technique, we coupled
agarose with the GRGDS sequence, an oligopeptide capable of
promoting integrin-mediated cell adhesion27,28. A maleimide-
terminated GRGDS, (N-α-(3-maleimidopropionyl)-N-ε-
fluorescein) lysine-GRGDS, was prepared by solid-state peptide
synthesis, with the fluorescein added simply to facilitate the
visualization of the oligopeptide. The distribution of the peptide
in the
gel after laser fabrication was analysed by confocal microscopy
and the
peptide channels were observed penetrating the 1.5-mm-thick
sample.
Figure 2a shows a typical XY cross-section micrograph of the
oligopeptide distribution at a given depth within the agarose
matrix:
GRGDS peptides were conjugated to the gel in isolated circular
channels defined by the shape of the laser beam. These circular
peptide
domains were observed continuously at all depths in the gel.
The diameter of the channels was between 150 and 170 µm over
a 1 mm
depth, corresponding to the focal spot size of the focused laser
beam of
160 µm. The XY cross-section micrographs at all levels were
reconstructed by confocal microscopy to provide the 3D stereo
channel
8. image (Fig. 2b).
The fluorescence intensity profile of the cross-sections of two
oligopeptide channels in the bulk hydrogel was analysed (Fig.
2c).
The intensity increased sharply at the irradiated regions,
demonstrating
that homogenous agarose hydrogels cause minimal lateral
scattering
during irradiation and such gel matrices are suitable for 3D
photo-fabrication.
The transverse diameter of the biochemical channels is
determined
by the focal spot size of the focused laser, but their longitudinal
dimensions are affected by two factors: (i) the depth of focus of
the
focused beam (usually defined as the distance over which the
focal
spot size changes ±5%)29; and (ii) the transmittance of light
through
the hydrogel material, which depends on the concentration of
2-nitrobenzyl photolabile moieties and not on agarose, which
absorbs
only 1.2% of the incident 325-nm light across a 1.5-mm gel.
The theoretical depth of focus using the convex lens with a
focal
length of 10 cm is 7 cm (ref. 29; see Supplementary
Information, S3).
Thus the longitudinal dimensions of our channels are mainly
limited by
the concentration of the photolabile moiety, S-NBC. The
variation in
longitudinal fluorescent intensity in the channel is shown in
Fig. 2d,
9. where the relative fluorescence intensity decreases with depth
of
fluorescein-labelled GRGDS as a result of the S-NBC
absorption of light
travelling through the 3D hydrogel matrix. The transmittance of
light through S-NBC-modified agarose hydrogels decreases with
gel
thickness and S-NBC concentration (Fig. 3). The light intensity
at
different depths can be calculated using the Beer–Lambert law
with the
corresponding extinction coefficient for the 2-nitrobenzyl
moiety
of 1,409 L mol–1 cm–1. Generally, the lower the concentration
of
biomolecular ligands (or photolabile moiety) required, the
thicker the
photofabricated gel.
We found that irradiating agarose hydrogel matrices with the
laser
beam for more than 1 s did not further increase the
immobilization
of peptides at the gel surface region, which received the highest
dose of
energy longitudinally30.We approximated the GRGDS
concentration at
Figure 1 The general strategy used to create adhesive
biochemical channels in agarose hydrogel matrices relies on
modifying agarose with photolabile groups, focused
laser light sources and biomolecule coupling. Specifically, a,
bulk agarose is first activated with CDI followed by reaction
with 2-nitrobenzyl-protected cysteine. On exposure to UV
light, the 2-nitrobnezyl group is cleaved leaving free sulphydryl
groups that react with maleimido-terminated biomolecules.
10. b,The strategy to create biomolecular channels in agarose
hydrogel matrices uses the chemical modification strategy in (a)
and a focused laser, resulting in alternating volumes of cell-
adhesive (peptide) channels separated by non-adhesive
(agarose) volumes.
OH
OH
OH
OH
OH
OH
OH
OH
OH
NN
N NO
O
O
O
O
13. LETTERS
nature materials | VOL 3 | APRIL 2004 |
www.nature.com/naturematerials 251
the top surface of the channel at 41.5 ± 2.2 µM (0.5 wt% gel,
0.4 mM
S-NBC) (Supplementary Information, S4). By comparing the
local
irradiation intensity on the surface to that within the channel
(Fig. 3)
and assuming a linear relationship between the irradiation
intensity and
photochemical yield31, we estimated GRGDS concentration to
vary
from 41.5 ± 2.2 µM at the gel surface to 33.0 ± 2.0 µM at 1.5
mm depth.
This chemical gradient may be useful for guided regeneration3;
alternatively, it could be minimized by irradiating samples from
both
top and bottom.
To determine how neural cells responded to the GRGDS
adhesion
domains in the hydrogel, we used agarose matrices (0.5 wt%,
0.4 mM
S-NBC), which have been shown to permit neurite growth21.
Dissociated cells from explants of E9 chick dorsal root ganglia
were
plated on top (that is, the same side that had been irradiated) of
the
hydrogel matrices containing biochemical channels.Owing to
generally
poor adhesion properties of the agarose surfaces, cells formed
clusters on top of the oligopeptide channels. Intriguingly (from
14. day
three onwards after cell plating), cell clusters that aggregated
on
oligopeptide channels were observed to extend thick processes
into the
biochemical channels; the migration of cells and elongation of
cell
processes were often found to turn at the edge of the adhesive
biochemical domain, indicating the guidance effect of the
channel
chemistry. Representative images of cell behaviour inside the
hydrogel
matrices show that the GRGDS channel promoted neurite
extension
and cell migration (Fig. 4): Fig. 4a (optical image) and 4b
(fluorescent
image of green fluorescein-tagged peptide channel and red F-
actin
rhodamine–phalloidin cytoskeletal staining) show a single
process
emerging from a cell cluster. In Fig. 4c, the blue DAPI nuclear
staining
shows that multiple cells migrated into the GRGDS channel. At
day six
of cell culture, a majority of the channels (76 ± 16%, mean ±
standard
deviation, n = 50 channels) were observed to contain neurites
and cellular assemblies, having an average migration distance of
633 ± 181 µm (mean ± standard deviation, n = 50 channels).
Cell invasion into non-degradable physically crosslinked
matrices
are probably affected by both the mechanical and biochemical
properties of the hydrogel material. (Supplementary
Information, S5).
By dynamic rheological analysis, we found that there was a
15. small
difference in the local mechanical properties of modified
(storage
modulus, G′ = 17.0 ± 0.7 Pa, n = 4) and un-modified (G′ = 14.8
± 0.6 Pa)
agarose due to laser-activated chemistry. Despite a slightly
higher G′ for
the modified agarose, this difference did not affect cell
penetration,
confirming that the chemical differences between the channels
and the
surrounding volumes are responsible for the observed cellular
response.
To understand further the interaction between the GRGDS
oligopeptide channels and cells, neural cells were cultured on
matrices
modified with scrambled oligopeptide channels containing the
inactive sequence GRDGS. Neither neurite outgrowth nor cell
migration was observed inside the scrambled oligopeptide
channels.
Therefore, the guided axonal growth and cell migration
observed in
a b
c
0 200 400 600 800 1,000
Position (µm)
R
el
at
iv
17. ns
ity
0 500 1,000 1,500
Depth ( µm)
d
0 1 2 3 4 5
90
80
70
50
40
30
20
10
60
Gel thickness (mm)
Tr
as
m
itt
18. an
ce
(%
)
= 0.4 mM
= 0.8 mM
Figure 2 Biochemical channels synthesized in agarose hydrogels
were
characterized with a fluorescein-tagged GRGDS peptide. a,A
representative XY cross-
section image of green fluorescently labelled oligopeptide
channels (scale bar: 200 µm);
b,A representative image of the green fluorescently labelled
oligopeptide channels
constructed from a series of XY cross-sectional micrographs
over a 0.5 mm depth (scale
bar: 200 µm); c,The relative fluorescence intensity profile of a
line pass through the centre
of the cross-sections of two oligopeptide channels shows
intensity contrast between the
peptide modified and non-modified regions; d,The longitudinal
fluorescence intensity
profile along the central axis of the channel shows a decrease in
fluorescent intensity with
depth, indicating a concentration gradient of oligopeptide.
Figure 3 The transmittance of laser light is affected by both the
thicknesses of the
S-NBC-modified agarose hydrogel matrices and the
concentration of S-NBC of
0.4 mM and 0.8 mM (mean ± standard deviation, n = 5). The
20. cells,with
respect to the neurite number and length, when the GRGDS
concentration was varied from 13 µM to 70 µM on agarose
surfaces30.
This suggests that the ligand concentration variation in
chemical
channels (of 41.5 µM to 33 µM) observed within the 1.5-mm-
thick
channels probably had a minimal (if any) effect on cell
behaviour.
The axonal guidance that we observed in our GRGDS channels
may
result from either direct interaction between neurons and
GRGDS, or
the integrated crosstalk of multiple cell types found in the DRG
explants. Additional experiments are necessary to identify the
cellular
components inside the GRGDS channels to reveal the
mechanisms
leading to the oriented cellular assemblies.
In summary, we demonstrate a paradigm to immobilize
biomolecules in selected volumes in a 3D hydrogel matrix using
laser
fabrication techniques and photochemistry. The cellular
guidance
observed is achieved by chemical (and not physical) channels.
Provided that the hydrogel materials are cell invasive, matrices
with
heterogeneous biochemical domains are novel platforms to
facilitate
the elucidation of fundamental cell–substrate interactions.
Adhesion channels elicited oriented axonal growth in hydrogels,
suggesting that the incorporation of the biochemical channels
into
biodegradable hydrogel matrices may find clinical applications
21. for
guided nerve regeneration or be extended to other tissues.
METHODS
All chemicals were purchased from Sigma and used as received
unless otherwise specified.
MODIFICATION OF ULTRA-LOW-GELLING-
TEMPERATURE (ULGT) AGAROSE WITH S-NBC
S-NBC was synthesized by reacting L-cysteine and 2-
nitrobenzyl bromide (1:1 molar ratio) in NaOH
solution at room temperature for 2 h. The pure product was
obtained by recrystallization in water.
To conjugate S-NBC to the agarose polymer, the ULGT agarose
polymer was first dissolved in dimethyl
sulphoxide (DMSO). Under an inert nitrogen environment, CDI
was added to partially activate the
hydroxyl groups in agarose polymer. After 1 h activation, a
solution of S-NBC in DMSO was added.
The mixture was kept at room temperature overnight before it
was extensively dialysed against water to
remove the unreacted S-NBC. The substitution level of S-NBC
in the resulting agarose was determined by
measuring the absorbance at 266 nm using an ultraviolet
spectrometer (Ultraspec 4000, Biopharmacia).
CREATING PHYSIOCHEMICAL CHANNELS IN ULGT
AGAROSE HYDROGEL MATRIX
(N-α-(3-maleimidopropionyl)-N-ε-fluorescein)-lysine-GRGDS
22. was prepared by solid-state peptide
synthesis based on Fmoc chemistry. N-ε-fluorescein-lysine-
GRGDS was first synthesised without
cleaving the side-chain protecting groups on a peptide
synthesizer (Pioneer, BioApplied Systems).
3-Maleimidopropionic acid was activated using dicyclohexyl
carbodiimide in dichloromethane and
reacted with the amine terminal of the peptide on the resin. The
maleimide-activated peptide was de-
protected and cleaved from the resin using 95% aqueous
trifluoroacetic acid and lyophilised. Scrambled
maleimide-activated oligopeptide, (N-α-(3-
maleimidopropionyl)-N-ε-fluorescein)-lysine-GRDGS, was
synthesised using the same method described to synthesize
activated GRGDS.
Irradiation of the hydrogel was performed using a 325 nm He-
Cd laser (Omnichrome 3074R-S-
A03, Melles Griot). The laser was focused by a convex fused-
silica lens. 0.5 wt% S-NBC agarose solution
prepared in phosphate buffer (pH 7.4) was refrigerated at 4 °C
for 3 h to form a hydrogel sample of
~1–5 mm thick. The gel was placed at the focal spot of the
focused laser for irradiation and moved using
an XY stage. To obtain the transmittance of light through the
hydrogel matrices, the laser-beam energy
was measured before and after it penetrated through the sample
23. volume. The irradiated sample was
immersed and shaken in phosphate buffer containing maleimide-
activated GRGDS oligopeptide for 8 h.
Unreacted GRGDS peptide was removed by washing the gel for
2 days. Peptide distribution in the
hydrogel matrix was imaged using a laser scanning confocal
microscope (FV300, Olympus).
RHEOLOGICAL CHARACTERIZATION
To investigate how the photo-modification affected the
mechanical stiffness of the hydrogel, dynamic
rheological tests were performed to measure the shear modulus
of the modified and unmodified agarose
hydrogels. S-NBC agarose solutions (0.5 wt%), irradiated (1
min, 0.4 W, X-cite, EFOS) or non-irradiated,
were mixed with maleimide-GRGDS at 1 mg per ml for 1 h at
room temperature. To measure the complex
shear moduli of the modified and un-modified agarose hydrogel,
0.5 ml of solution was loaded between
the cone and plate geometry on a dynamic rheometer (AR 2000,
TA Instruments) and cooled down at
a b c
Figure 4 Primary rat dorsal root ganglia cells were plated on 3D
patterned GRGDS oligopeptide-modified, 0.5 wt% agarose gels.
Three days after plating, DRG cells grew within
GRGDS-oligopeptide-modified agarose channels only, and not
25. plated on top of the hydrogel matrices
containing either active GRGDS or scrambled GRDGS
oligopeptide channels. After culturing the cells in
the media containing 10% horse serum and 50 ng per ml nerve
growth factor for 6 days (37 °C, 5% CO2),
the samples were imaged on their side by phase
contrast/fluorescence microscopy (Zeiss LM410) and
confocal microscopy (FV300, Olympus) so as to observe the
cell behaviour inside the hydrogel matrices.
Rhodamine–phalloidin (red) and DAPI (blue) fluorescent
markers (Molecular Probes) were used to
identify cellular skeletons and nuclei, respectively, in the gel
using standard methods.
Received 2 July 2003; accepted 3 February 2004; published 21
March 2004.
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Acknowledgements
We are grateful to the Natural Sciences and Engineering
Research Council of Canada, Ontario Graduate
Scholarship and Connaught for funding and thank Ying-Fang
Chen, Patricia Musoke-Zawedde and
David Martens for their assistance.
Correspondence and requests for materials should be addressed
to M.S.
Supplementary Information accompanies the paper on
www.nature.com/naturematerials
Competing financial interests
The authors declare that they have no competing financial
interests.
nmat1092PRINT 3/11/04 11:26 AM Page 253
32. so far
provided only limited information9–14. Here we present a new
technol-
ogy that is compatible with the demands of long-term neuronal
cell
culturing and that allows for the efficient generation of precise,
repro-
ducible and arbitrarily shaped gradients of diffusible molecules.
Using
this technology, we show that growth cones, the motile sensing
struc-
tures at the tips of developing axons, are capable of detecting a
concen-
tration difference as small as about one molecule across their
spatial
extent. Furthermore, we show that this sensitivity exists across
only a
relatively small range of ligand concentrations, indicating that
adapta-
tion in these growth cones is limited.
RESULTS
Gradient generation
We established gradients by ‘printing’ drops of solution in a a
series
of ten lines 1 mm apart with increasing amounts of chemotropic
molecules onto the surface of a thin collagen gel (Fig. 1a). After
a
relatively short time, molecules diffuse to fill in the gaps
between the
printed lines and to create a profile that is independent of the
depth.
The resulting smooth gradient can be quite stable, as in general
the
time τ required for significant diffusion over a distance L scales
33. as
the square of distance, τ ≈ L2/D, where D is the diffusion
coeffi-
cient15. For nerve growth factor (NGF), the guidance factor
used in
these experiments, we have measured D = 8 × 10–7cm2/s in
collagen
(see Methods), which gives τ ≈ 52 min for L = 0.5 mm, the
distance
over which molecules must diffuse to fill in the space in
between the
lines or to reach the midplane of the gel (where the axons are
grow-
ing), but τ ≈ 3.6 d for L = 5 mm, the horizontal distance from
the
center to the end of the printed pattern. The time-dependent
con-
centration profile can be calculated using finite element
modeling of
the diffusion equation. Figure 1b,c shows the result of a two-
dimen-
sional simulation of an exponential gradient applied to a gel,
appro-
priate to the situation depicted in Figure 1a, assuming no
significant
variation in the direction parallel to the printed lines. The
printed
molecules diffused quickly into the thin gel, and the
concentration
rapidly became independent of depth (Fig. 1b). The initial
oscilla-
tions along the length of the block quickly died away, followed
by a
long period of a relatively stable gradient, particularly at the
low-
concentration end (Fig. 1c).
34. The actual concentration gradients produced by this method can
be measured with quantitative fluorescence imaging.
Concentration
profiles of fluorescently labeled casein for exponential and
linear
patterns are shown (Fig. 2a,b; casein is of similar molecular
weight to
NGF but is relatively inexpensive and easy to label). The actual
time-
dependent concentration profiles of casein that were extracted
from
the fluorescence imaging show a good match with the results of
the
finite element modeling using an independently determined
value of
D = 6 × 10–7cm2/s (Fig. 2c). This gradient generation method
has
several important advantages over previous approaches: large
num-
bers of identical gradients can be generated quickly, the often
pre-
cious chemotropic molecules are required in only very limited
quantities, the gradients are established in a short time but can
remain stable for a day or more, nonlinear gradient shapes can
be
used and gradients of multiple factors with different shapes and
arbi-
trary spatial relationships can be generated. This technique
could
also be used to provide a source of factor while axons are
growing, as
no direct contact is made with the gel.
1Department of Neuroscience, Georgetown University Medical
Center, Washington, DC, 20007, USA. 2Department of Physics,
37. a
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Application to axon guidance
We have applied this technology to a well-characterized model
system,
the response of the rat dorsal root ganglion (DRG) to NGF9,16–
18. The
sensitivity of DRG axons was measured by culturing explants in
a
three-dimensional collagen gel in the presence of an exponential
NGF
concentration gradient. This gradient shape produced a
percentage
change in concentration across the growth cone that was
independent
of its position in the gradient. Several explants were placed in a
row
that was parallel to the printed lines, between the third and
38. fourth line
of the pattern. This region of the gradient (between 1.2 and 1.3
cm) is
expected to be the most stable (Fig. 1c). The overall NGF
concentra-
tion was adjusted to be 1 nM at the location of the explants,
independ-
ent of the steepness of the gradient (see Methods). As a simple
way of
quantifying the guidance response, we defined the guidance
ratio as
the number of bright pixels representing axons on the high side
of the
gradient minus the number on the low side, normalized by the
total
number of bright pixels representing axons (ref. 19; see
Methods). If all
neurites emerged from the explant on the high-concentration
side, the
guidance ratio would be 1.
We have measured the width of rat DRG growth cones in three-
dimensional collagen to be no larger than 10 µm including
filopodia
(data not shown; see also ref. 20). We therefore defined the
gradient
steepness s as the percentage change in concentration across 10
µm.
The value of the guidance ratio after 36–40 h in culture for s =
0, 0.1,
0.2 and 0.4% is shown (Fig. 3a). There was an increase in the
guidance
ratio as the steepness of the gradient increased, and significant
guid-
ance occurred even for s = 0.1%. This was despite the fact that
DRG
39. explants are comprised of a heterogeneous population of
neurons, not
all of which are responsive to NGF21. Representative explants
with
guidance ratios close to the mean for each steepness are shown
(Figs. 3d–f). As the gradient steepness increased, the asymmetry
increased markedly.
These explants did not show obvious turning of neurites up the
gra-
dient (Figs. 3d–f), and a statistical analysis of turning for the
data set
reported in Figure 3a found no significant neurite turning
overall. To
determine whether the asymmetry in outgrowth as measured by
the
guidance ratio was simply the result of a trophic effect, whereby
the
higher concentration of NGF on the up-gradient side of the
explant
caused more undirected outgrowth than on the down-gradient
side, we
measured total neurite outgrowth as a function of absolute
concentra-
tion of NGF (Fig. 3b). The curve is bell shaped with a peak at
about
1 nM, consistent with earlier studies22. There was little change
in out-
growth between 0.3 nM and 1 nM, but there was a significant
decrease
in outgrowth between 1 nM and 3 nM (P < 10–5). In our
gradient
experiments, the difference in concentration between the two
sides of
each explant varied between about 10% (s = 0.1%) and 50% (s =
0.4%),
40. which is small compared with that required for significant
variations in
outgrowth. In any case, the decrease in outgrowth between 1 nM
and
3 nM indicates that the trophic effect of NGF by itself would
actually
produce a negative guidance ratio for concentrations around 1
nM.
To determine the range of concentrations for which growth
cones are
sensitive to shallow gradients, we established exponential NGF
gradi-
ents of steepness s = 0.2% but with NGF concentrations at the
explants
in the range of 0.0001–100 nM (Fig. 3c). The guidance ratio
curve is
bell shaped with a peak at 1–10 nM, where the guidance is
highly signif-
icant (P < 10–7). The guidance ratio is more weakly significant
for
0.1 nM (P < 0.005) and is not significant for 100 nM and for
0.01 nM
and below. Unlike the 1 nM case described above, in the 10 nM
case we
saw clear neurite turning (turning strength = 0.023; P < 0.0001;
Fig. 3g). Weaker turning was also observed in the 100 nM
condition
(turning strength = 0.015; P < 0.02) and the 0.1 nM condition
(turning
T E C H N I C A L R E P O R T
NATURE NEUROSCIENCE VOLUME 7 | NUMBER 6 | JUNE
2004 6 7 9
41. Figure 1 Gradient generation technique. (a) Lines of
chemotropic factor
were printed onto the surface of a gel using a computer-
controlled pump.
By increasing the density of droplets from one line to the next
and allowing
the factor to diffuse into the gel, a smooth gradient was created.
(b,c) Concentration profile at various times in a block of gel 3.5
cm long by
1 mm deep generated by finite element modeling. The initial
pattern
consisted of ten equally spaced lines 1 mm apart. The quantity
of factor in
each subsequent line was increased by a constant factor of 1.22
in this
case, producing an exponential concentration gradient with a
percentage
change of 0.2% every 10 µm. (b) Profile through the vertical
thickness of
the collagen. (c) Profile along the length of the collagen (least-
concentrated
line at 1.5 cm). After the initial transients have died away, a
smooth profile
remains. Although the concentration at the high end decays, at
the low end
both the concentration and gradient steepness remain relatively
stable. The
time for stabilization and eventual decay of the gradient is
inversely
proportional to the diffusion coefficient. For gradients steeper
than 0.2%,
the concentration at the low end of the gradient increases slowly
over time
as a result of diffusion from the region of higher concentration,
and the
gradient flattens somewhat.
44. strength = 0.010; P < 0.09, not significant). No significant
turning was
seen in other conditions. We conclude that these growth cones
are
unable to adapt their sensitivity to shallow gradients over a
concentra-
tion range of more than about two to three orders of magnitude.
DISCUSSION
The minimum concentration difference across a motile cell that
is
required for directional sensing is typically quoted as 1–2%
(refs.
23,24), although statistically significant responses for values as
low as
0.5% have been found for neutrophils6,7. Our results show that
axons
can be guided by gradients that are substantially shallower than
this.
This sensitivity is particularly remarkable considering the noisy
envi-
ronment in which the growth cone must operate. Statistical
fluctua-
tions in receptor binding limit the accuracy of any instantaneous
measurement of concentration25,26. For a growth cone with a
diame-
ter of 10 µm in a 0.1% gradient at 1 nM, the number of
molecules in
the vicinity of half of the growth cone is on the order of 1,000,
so the
average difference in the number of molecules between the
high- and
low-concentration sides of the growth cone is about one
molecule.
We also found a guidance ratio significantly different from zero
45. for
s = 0.2% at 0.1 nM, an average difference of about one-fifth of
a mol-
ecule across the growth cone. By contrast, the effects of
Brownian
motion will produce instantaneous fluctuations in the number of
molecules of approximately the square root of 1,000 or about 30
at
1 nM. Overcoming this noise requires averaging over many
independ-
ent measurements. A simple calculation indicates that growth
cones
would need to average concentration measurements for at least
sev-
eral minutes to achieve the sensitivity we have measured25,26,
but spe-
cific mechanisms by which this might be accomplished are
unknown.
Turning of neurites in the gradient at a concentration of 1 nM
was
not seen. We believe that we have, however, observed a
guidance effect
in this case because the degree of asymmetry in outgrowth from
the
explants is much larger than one would expect given the small
differ-
ence in NGF concentration between the two sides of the explant.
One
possibility is that turning predominately occurs before the
neurites
leave the explant. Neurite turning outside the explant was,
however,
strongly significant at 10 nM and more weakly significant at
100 nM.
Thus, surprisingly, measureable turning and biased outgrowth
46. are not
always correlated and seem to be related in a nontrivial way.
Dissociated neurons can also be used in our assay, which will
allow
the dependence of individual axon trajectories on gradient
steepness
to be probed more directly.
A recent study examining adaptation of gradient sensitivity of
Xenopus laevis spinal axons to external ligand concentrations27
meas-
ured the response of axons growing on a two-dimensional
substrate
to very steep gradients (5–10% over 10 µm) over a relatively
short
period of time (1–2 h). Adaptation was probed by introducing
rela-
tively small step changes in ligand concentration in the fluid
above the
growth cone. In contrast, we have examined mammalian axons
guided by very shallow gradients for long periods of time in a
three-
dimensional assay, more akin to the in vivo situation, and have
varied
ligand concentration at the growth cone over seven orders of
magni-
tude. We find a similar bell-shaped dependence on
concentration to
that previously measured for leukocytes5, which can be
explained the-
oretically by the effect of stochastic concentration
fluctuations28. As
the peak is expected to be roughly centered at the dissociation
con-
stant, Kd, this provides indirect evidence that the effective Kd
47. mediat-
ing guidance responses for the binding of NGF to its receptors
trkA
and p75 is about 1 nM (refs. 29,30). The relatively narrow
window of
concentration for effective guidance of axons indicates that
there
must be tight in vivo regulation of the absolute concentration of
guid-
ance factors present. Based on the less-quantitative
experimental
measurements of gradient sensitivity and the absolute
concentration
range that was previously available, we estimated the maximum
dis-
tance an axon could be guided by a single gradient of
exponential
shape to be about 1 cm (ref. 31). Results from our more
quantitative
assay now extend this estimate to about 2 cm.
Our results show the power of the technology we have
developed to
quickly and reliably produce molecular gradients that can
robustly
guide axons. The exquisite sensitivity of axonal gradient
detection
T E C H N I C A L R E P O R T
6 8 0 VOLUME 7 | NUMBER 6 | JUNE 2004 NATURE
NEUROSCIENCE
Figure 2 Fluorescence imaging of casein concentration
gradients.
(a) Concentration profile determined from fluorescence
50. e
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demonstrates that axons have developed a perhaps uniquely
effective
mechanism for integrating guidance cues. This sensitivity, and
its
variation with absolute concentration, provide important
constraints
for the in vitro control of axonal trajectories and therapies for
axonal
regeneration after injury, and for hypotheses about how ligand
gradi-
ents are transduced into signals for directed motion in growth
cones.
METHODS
Tissue preparation. DRGs were removed from the lumbar region
of P2 rat
pups, trimmed and washed in DMEM and enzymatically
digested for 12 min
in 0.25% trypsin/10 µg/ml DNAse1/Ca2+- and Mg2+-free Hanks
Balanced
Salt
51. Solution
to loosen the capsule. The reaction was stopped by addition of
FBS, and the explants were centrifuged and resuspended in
DMEM three
times. Explants were then equilibrated in 0.2% liquid collagen
at 4 °C before
being plated.
Dry collagen gels. A 0.2% collagen gel solution was prepared
under sterile
conditions by mixing on ice type I rat tail collagen stock
(Collaborative
Biomedical Products) diluted with water to contain 0.2 mg/ml
collagen, 27 µl
of a 7.5% sodium bicarbonate solution per ml of original
collagen stock, 10×
Optimem (Invitrogen) to a final concentration of 1×, 50 U
penicillin,
50 µg/ml streptomycin. We uniformly spread 750 µl of the
solution over the
bottom of a 35-mm dish and allowed it to set, forming the
52. bottom layer of
collagen (∼ 0.5 mm thick). We added a fresh layer of 750 µl of
collagen and
then arranged six explants in a line in the dish before the
collagen set
(Fig. 3g). The final collagen culture was approximately 1 mm
thick. The
dishes were returned to the incubator for 15 min for the top
layer of collagen
to set and were then ready for molecular printing. No fluid
culture medium
was added on top of the collagen, as this would provide a short
circuit for the
gradient; we therefore refer to these as dry gels. No serum was
added to the
collagen. Dishes were returned for 36–40 h to a 37 °C incubator
with 5% CO2.
We chose this time interval because it is typical of more
standard collagen gel
coculture experiments; it is unlikely that axons are exposed to a
single gradi-
ent for this length of time in vivo.
Fixation and immunohistochemistry. Explants were fixed by
covering the
53. collagen with 1.5 ml of 10% formaldehyde and 0.1% Triton X-
100 (J.T.
Baker) in PBS for several hours. Explants were washed five
times with PBS
for 1 h each and then incubated overnight in an antibody
directed against
neuronal β-tubulin (TUJ1; Babco; 1:1,000), followed by a
further five washes
in PBS for 1 h each. The explants were then incubated overnight
in the sec-
ondary antibody Alexafluor 488–conjugated goat anti-mouse
IgG
(Molecular Probes; 1:1,000), washed five times in PBS for 1 h
each and pho-
tographed with a CCD (charge-coupled device) camera on a
Nikon TE300
inverted fluorescence microscope.
T E C H N I C A L R E P O R T
NATURE NEUROSCIENCE VOLUME 7 | NUMBER 6 | JUNE
2004 6 8 1
Figure 3 Guidance of DRG axons by NGF gradients. (a)
Guidance ratio of DRG explants as a function of gradient
54. steepness. Error bars are s.e.m. For
s = 0.1%, the guidance ratios were significantly different from
zero (P < 10–8), and 80% of explants (43 of 54) had positive
guidance ratios. Responses for
s = 0.2% and 0.4% were also significantly different (P < 0.005).
For s = 0.4%, 53 of 54 explants had positive guidance ratios (54
explants per condition
pooled over three separate experiments; similar results were
seen in each experiment). (b) Outgrowth in response to NGF
after 36–40 h in culture, as
measured by the number of bright pixels representing neurites,
divided by the area of the explant (36 explants per condition
pooled over three separate
experiments). (c) Guidance as a function of absolute NGF
concentration at the explants for s = 0.2%. The probability that
the mean guidance ratio is zero
in each case is given above each data point (54–108 explants
per condition pooled over six separate experiments). Although
the 1 nM condition represents
equivalent conditions to the 0.2% condition in a, the guidance
ratios in these two cases are not exactly the same as they are
derived from a different series
of experiments. (d–f) Typical explants from experiment in a for
s = 0.1%, 0.2% and 0.4%, respectively (guidance ratios within
0.01, that is 5–10%, of the
58. Molecular printing. For printing, we used a commercially
available pump
(Gesim) that can deliver precisely repeatable nanoliter droplets
at rates of up to
1,000 drops/s. A dish containing the gel was mounted on a
computer-con-
trolled commercially available high-precision x–y translation
stage. The spac-
ing between drops can be controlled by varying the rate of
droplet ejection and
the rate of translation of the x–y stage. Gradients were
established within the
middle 10 mm × 20 mm of a 35-mm culture dish in the manner
suggested in
Figure 1a. The gradient was positioned so that the line of
explants was between
the third and fourth line of the gradient. To produce an
exponential gradient
with steepness s per 10 µm, the number of drops in each
successive line
increased by a factor of e100s. This factor is 1, 1.11, 1.22 and
1.49 for steepnesses
s = 0, 0.1, 0.2 and 0.4%, respectively. The droplet volume was
measured to be 1.4
59. nl. For Figure 3a, the solution in the pump was 117 nM NGF
(Roche
Diagnostics) in PBS. The number of drops in the first line of the
gradient was
adjusted so that the concentration at the explant position was 1
nM after the
initial concentration variations smoothed out. The total volume
of fluid
deposited on each line for every condition was equalized by the
application of
the appropriate amount of the vehicle solution (PBS) after the
deposition of the
gradient of NGF solution. In addition, a 5-mm plateau of the
vehicle solution
was added adjacent to the low-concentration side of the
gradient. For Figure 3c,
procedures were the same, except that the concentration of NGF
in the pump
was varied to achieve the desired concentration at the explant
position.
Statistical analysis. Fluorescent images of TUJ1-stained
neurites were
processed using Scion Image (Scion Corporation) to outline the
explant. The
60. image containing neurites outside the explant was then
thresholded to give a
binary image. The total number of nonzero pixels, divided by
the number of
pixels contained in the explant, was used to calculate outgrowth
(Fig. 3b). The
guidance ratio R (Fig. 3a,c) was determined from the number of
nonzero pix-
els on the high-concentration side of the explant, H, and the
number on the
low-concentration side, L, according to R = (H – L)/(H + L).
Because this is
normalized by total neurite outgrowth, it is expected to be
relatively insensitive
to total outgrowth. We quantified turning by detecting neurite
segments in the
explant images using a ridge-tracking algorithm that is similar
to one pre-
sented previously32, although we developed ours independently.
The turning
vector associated with each neurite segment was calculated as
the difference
vector between a unit vector that is parallel to the segment and
the radial unit
vector measured from the explant center. The deflection of the
61. neurite up the
gradient was measured as the component of the turning vector
along the gra-
dient, and the average of these components across all explants
was defined as
the turning strength for that condition. Significance values
quoted for the
guidance ratio and turning strength give the probability that the
mean of the
distribution is zero, as determined by a t-test.
Measurement of diffusion coefficients. Using the micropump, a
single line of
the diffusant was delivered onto a 1-mm layer of collagen in a
35-mm petri
dish. The concentration profile along the length of the gel
perpendicular to the
line was measured by fluorescence imaging of either directly
labeled protein
(casein, Sigma; labeled with Oregon Green488 FluoReporter kit,
Molecular
Probes) or immunofluorescence labeling of fixed protein (NGF).
The narrow
line spreads out into a Gaussian concentration profile and the
width of the
62. Gaussian evolves linearly in time, with a slope determined by
D. The profile
measured at each time was fit to a Gaussian curve, and D was
determined from
a linear fit to the width versus time.
Finite element modeling. The simulations shown in Figures 1b,c
and 2c were
produced by two-dimensional finite element modeling
(PDEase2D, Macsyma
Inc.) of the diffusion equation in a domain of 3.5 cm × 0.1 cm,
with no flux
boundary conditions. The printing of the lines was modeled by a
constant flux
for a brief period (10 s) in narrow regions (0.01 cm) along one
of the long
edges of the domain.
ACKNOWLEDGMENTS
We thank J. Savich, R. Arevalo, S. Mittar, C. Fleury and J.
Torri for their
assistance with technology development. Supported by the
National Institutes
of Health, the National Science Foundation, the Department of
Defense and
63. the Whitaker Foundation.
COMPETING INTERESTS STATEMENT
The authors declare that they have no competing financial
interests.
Received 13 January; accepted 23 April 2004
Published online at http://www.nature.com/natureneuroscience/
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