This document summarizes a research paper that proposes using dielectrophoresis in a microfluidic device to separate live and dead biological cells. It describes how an applied non-uniform electric field can induce dipole moments in cells, causing them to be attracted to either high or low field regions depending on their dielectric properties. The document outlines the design of a microfluidic device with a 3D electrode structure intended to exploit these differences and separate live and dead mammalian cells based on their dielectric behavior over 50-70 kHz frequencies.
This document summarizes a study on the photoelectrochemical properties of nanocrystalline indium selenide (In2Se3) thin films deposited via a chemical bath deposition method. The In2Se3 films exhibited n-type conductivity. Current-voltage measurements in the dark showed non-symmetrical rectifying behavior with a junction ideality factor of 3.85, suggesting the influence of series resistance and structural imperfections. Capacitance-voltage measurements determined a flat band potential of -0.530V versus saturated calomel electrode. Barrier height measurements from reverse saturation current at different temperatures yielded a barrier height. Under 30 mW/cm2 illumination, the cell demonstrated an open circuit voltage of 153mV
International Journal of Engineering Research and Development (IJERD)IJERD Editor
This summary provides the key details about the document in 3 sentences:
The document analyzes the surface tension of osteoblast cells in a microchip. It studies how electrical pulses, electrode configuration, microchannel dimensions, and suspension media properties affect the surface tension of the inner and outer layers of osteoblast cell membranes. The document develops a 3D microfluidic model and electrical circuit model to investigate the membrane surface tension and how it is impacted by various parameters like pulse characteristics, electrodes, microchannel, and suspension media.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
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
Performance comparison of selection nanoparticles for insulation of three cor...IJECEIAES
This paper presents an investigation on the enhancement of electrical insulations of power cables materials using a new multi-nanoparticles technique. It has been studied the effect of adding specified types and concentrations of nanoparticles to polymeric materials such as PVC for controlling on electric and dielectric performance. Prediction of effective dielectric constant has been done for the new nanocomposites based on Interphase Power Law (IPL) model. The multi-nanoparticles technique has been succeeded for enhancing electric and dielectric performance of power cables insulation compared with adding individual nanoparticles. Finally, it has been investigated on electric field distribution in the new proposed modern insulations for three-phase core belted power cables. This research has focused on studying development of PVC nanocomposite materials performance with electric field distribution superior to the unfilled matrix, and has stressed particularly the effect of filler volume fraction on the electric field distribution.
This document discusses improving the performance of a microstrip antenna using a fractal electronic band gap (EBG) structure and vias. A fractal EBG unit cell design is presented using a square shape with nested smaller squares. Microstrip antennas were designed with and without this EBG structure, and with and without vias connecting the EBG patches to the ground plane. Measurements showed the bandwidth and S11 were improved, back radiation was reduced, and directivity was increased for the antenna with both the EBG structure and vias compared to designs without them. Specifically, bandwidth increased by 1.125% and S11 decreased by 4.188dB with the EBG structure and vias.
This document presents a novel 7.5 GHz wideband electromagnetic band gap (EBG) structure for antenna applications. The EBG structure is a mushroom-like cell with a rectangular spiral shape etched into the top metal layer. Simulation results show a 7.5 GHz band gap is created between 7.49-14.94 GHz where surface waves are prohibited. The band gap properties are analyzed using dispersion diagrams and by simulating a microstrip line above an array of the EBG cells, showing high attenuation within the band gap frequencies. This wideband EBG structure has potential applications in suppressing surface waves in antenna design.
11.property analysis of quantum dot cuboid nanocrystals with different nanost...Alexander Decker
This document discusses simulation results of the properties of quantum dot cuboid nanocrystals with different nanostructures. It first describes how quantum dots offer advantages over traditional fluorophores such as long-term photostability. It then details simulations conducted on a 3D cuboid structure with specific dimensions and material properties. The results show light and dark transitions, energy states, and absorption properties for different polarizations. Similar simulations of pyramid structures were also conducted. Finally, it concludes that the characteristics are equivalent for different nanostructures under the same boundary conditions.
This document summarizes a study on the photoelectrochemical properties of nanocrystalline indium selenide (In2Se3) thin films deposited via a chemical bath deposition method. The In2Se3 films exhibited n-type conductivity. Current-voltage measurements in the dark showed non-symmetrical rectifying behavior with a junction ideality factor of 3.85, suggesting the influence of series resistance and structural imperfections. Capacitance-voltage measurements determined a flat band potential of -0.530V versus saturated calomel electrode. Barrier height measurements from reverse saturation current at different temperatures yielded a barrier height. Under 30 mW/cm2 illumination, the cell demonstrated an open circuit voltage of 153mV
International Journal of Engineering Research and Development (IJERD)IJERD Editor
This summary provides the key details about the document in 3 sentences:
The document analyzes the surface tension of osteoblast cells in a microchip. It studies how electrical pulses, electrode configuration, microchannel dimensions, and suspension media properties affect the surface tension of the inner and outer layers of osteoblast cell membranes. The document develops a 3D microfluidic model and electrical circuit model to investigate the membrane surface tension and how it is impacted by various parameters like pulse characteristics, electrodes, microchannel, and suspension media.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
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
Performance comparison of selection nanoparticles for insulation of three cor...IJECEIAES
This paper presents an investigation on the enhancement of electrical insulations of power cables materials using a new multi-nanoparticles technique. It has been studied the effect of adding specified types and concentrations of nanoparticles to polymeric materials such as PVC for controlling on electric and dielectric performance. Prediction of effective dielectric constant has been done for the new nanocomposites based on Interphase Power Law (IPL) model. The multi-nanoparticles technique has been succeeded for enhancing electric and dielectric performance of power cables insulation compared with adding individual nanoparticles. Finally, it has been investigated on electric field distribution in the new proposed modern insulations for three-phase core belted power cables. This research has focused on studying development of PVC nanocomposite materials performance with electric field distribution superior to the unfilled matrix, and has stressed particularly the effect of filler volume fraction on the electric field distribution.
This document discusses improving the performance of a microstrip antenna using a fractal electronic band gap (EBG) structure and vias. A fractal EBG unit cell design is presented using a square shape with nested smaller squares. Microstrip antennas were designed with and without this EBG structure, and with and without vias connecting the EBG patches to the ground plane. Measurements showed the bandwidth and S11 were improved, back radiation was reduced, and directivity was increased for the antenna with both the EBG structure and vias compared to designs without them. Specifically, bandwidth increased by 1.125% and S11 decreased by 4.188dB with the EBG structure and vias.
This document presents a novel 7.5 GHz wideband electromagnetic band gap (EBG) structure for antenna applications. The EBG structure is a mushroom-like cell with a rectangular spiral shape etched into the top metal layer. Simulation results show a 7.5 GHz band gap is created between 7.49-14.94 GHz where surface waves are prohibited. The band gap properties are analyzed using dispersion diagrams and by simulating a microstrip line above an array of the EBG cells, showing high attenuation within the band gap frequencies. This wideband EBG structure has potential applications in suppressing surface waves in antenna design.
11.property analysis of quantum dot cuboid nanocrystals with different nanost...Alexander Decker
This document discusses simulation results of the properties of quantum dot cuboid nanocrystals with different nanostructures. It first describes how quantum dots offer advantages over traditional fluorophores such as long-term photostability. It then details simulations conducted on a 3D cuboid structure with specific dimensions and material properties. The results show light and dark transitions, energy states, and absorption properties for different polarizations. Similar simulations of pyramid structures were also conducted. Finally, it concludes that the characteristics are equivalent for different nanostructures under the same boundary conditions.
Property analysis of quantum dot cuboid nanocrystals with different nanostruc...Alexander Decker
The document summarizes simulation results of quantum dot cuboid nanocrystals with different nanostructures. It first describes taking a 3D cuboid structure and simulating its 3D wavefunction, energy states, and light/dark transitions under different polarizations. It finds the characteristics are equivalent for different structures given the same boundary conditions. It then simulates a pyramid structure and finds its absorption peaks differ in number but are otherwise equivalent to the cuboid. The conclusion states that for different nanostructures, the characteristics are almost equivalent under the same boundary conditions.
10.1016-j.mssp.2015.01.037-Electrochemical investigation of graphene_nanoporo...Mahdi Robat Sarpoushi
This study investigated the effect of mixing graphene nanosheets and nanoporous carbon black on the surface morphology and electrochemical performance of electrodes prepared for supercapacitors. Electrodes containing 80% nanoporous carbon black, 10% graphene nanosheets, and 10% PTFE binder showed the highest specific capacitance of 10.22 F/g. The addition of nanoporous carbon black increased the proportion of outer charge stored on the electrode relative to the total charge stored, indicating higher current response and voltage reversal at the end potentials. Scanning electron microscopy images showed that adding nanoporous carbon black particles arranged the graphene nanosheets in different directions, increasing the specific surface area and changing diffusion characteristics to improve capacitance and reversibility
2 d electrical resistivity tomography (ert) survey using the multi electrode ...Alexander Decker
1) 2D electrical resistivity tomography (ERT) surveys were conducted along six radial profiles at the Bosumtwi impact crater in Ghana using a modified multi-electrode gradient array.
2) The cable take-outs of the resistivity imaging system were modified from 2m to 5m spacing, allowing investigation of the subsurface to depths of around 75m.
3) The ERT models identified three subsurface formations - low resistivity lake sediments, moderately resistive impact breccias, and highly resistive basement metamorphic rocks.
Theoretical Study of Density of States of Magnesium diboride Superconductor b...ijsrd.com
Magnesium diboride with Tc = 39K is a record breaking compound among s-p metals & alloys. Many experiments performed on Magnesium diboride suggest that there are two superconducting gaps. Considering a multiband model Hamiltonian with intra- & inter band pair transfer interactions we have derived the normal and anomalous one-particle Green's function & self-consistent equations for superconducting order parameter(ÃŽâ€) using Green's function technique & equation of motion method, we have studied the density of states. The results are quite encouraging.
The Effect of Plasma-Treated Boron Nitride on Partial Discharge Characteristi...IJECEIAES
Power supply reliability is a key factor in a country economic stability. It is contributed by the reliable power distributor via transmission lines, overhead or underground cables. However, the power cables and accessories are always exposed to pre-breakdown phenomena known as partial discharges (PD) which commonly occur in microvoids, defects or protrusions inside the insulation.To improve the performance of the cable insulation against PD, nanofillers are added into the insulating materials. However, to achieve superior performance of PD resistance, the nanofillers must be homogeneously dispersed into the polymer matrices withtightly bonded interfacial zones. Therefore, this could be achieved by employing method of surface functionalization by using cold atmospheric plasma to strengthen the filler/polymer interfaces. In view of foregoing, this study investigated the effects of surface treated boron nitride (BN) nanoparticles in Low Density Polyethylene (LDPE) on the PD characteristics by following CIGRE Method II at 7 kVrmsapplied voltage. The phase resolved PD characteristics were performed. The results revealed that by treating the nanofillers with cold plasma, the PD resistance of LDPE were highly achieved compared with the untreated BN nanofillers.
Numerical simulation model of multijunction solar cellAlexander Decker
This document presents a simulation model of multi-junction solar cells. The model simulates the performance characteristics of dual-junction solar cells with InGaP/GaAs and triple-junction solar cells with InGaP/GaAs/Ge. The model accounts for the solar cells and tunnel junctions that connect the cells. Simulation results show the multi-junction cells have higher open-circuit voltages than individual cells due to current matching, though overall current is reduced. The model agrees with experimental data and can be used to analyze effects of material properties on cell performance.
The document describes an experiment where quantum state transfer was realized between atomic and photonic qubits. Efficiencies of 0.04 and 0.03 were measured for the read and write processes respectively. It is estimated that implementing a second node and joint detection of signal photons could realize quantum repeater protocols and distant teleportation of atomic qubits at a rate of around 3 x 10-7 s-1. Improvements to efficiency through increasing optical thickness or eliminating transmission losses could increase the rate by several orders of magnitude. The results also demonstrate the possibility of multiple atomic qubits in a quantum node using multiple light beams.
E = g lk+ 2
+ − − +
r m 0 m 0 4 ε 0 h ( ε 0 2 e 0 m 0
8 em hm πεr 2 2ε ) m m hm
Brus, L. E. J. Phys. Chem. 1986, 90, 2555
Semiconductor quantum dots are nanocrystals made of semiconductor materials such as CdSe, ZnSe, ZnS, and ZnO. They exhibit size-dependent optical and electronic properties due to
This document provides an introduction to dielectric materials and their importance in modern technology. It discusses the early history and development of the field, including Faraday's discovery of dielectric polarization and Debye's theory relating molecular dipole moments to macroscopic dielectric properties. Modern applications demand materials with specific dielectric properties tailored for uses like integrated circuits, wireless communication technologies, and microwave devices. The document outlines the classical theory of dielectrics, including the different polarization mechanisms (electronic, atomic/ionic, dipolar/orientational, space charge) that contribute to a material's overall dielectric constant and frequency-dependent behavior.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
1) Vertical electrical sounding using Schlumberger array was conducted at 40 stations to determine subsurface layers and depth to bedrock at the Centre for Energy Research and Training in Zaria, Nigeria.
2) Resistivity values and thickness were derived for three predominant layers - topsoil (2-738 ohm-m thickening 1-3.9m), weathered basement (32-1735 ohm-m thickening 0.52-23m), and fresh basement bedrock (100-6036 ohm-m).
3) Results identified areas suitable for structures and boreholes, and recommended depth of sewage systems to avoid groundwater contamination based on the subsurface resistivity and thickness parameters.
Optimization of electric energy density in epoxy aluminiumiaemedu
This document discusses optimizing the electric energy density of epoxy-aluminum nanocomposites for use as dielectric materials. It presents a three-phase model to characterize the nanocomposite's dielectric properties as a function of aluminum particle size and volume fraction. Numerical results show that permittivity increases drastically near the percolation threshold. While breakdown strength decreases with higher volume fractions, the overall energy density is significantly higher than pure epoxy. Maximum energy density occurs at an optimal particle size and concentration balancing high permittivity and maintaining breakdown strength. Careful control of microstructure is important to avoid defects and achieve expected energy density gains.
Optimization of electric energy density in epoxy aluminium nanocompositeiaemedu
This document summarizes research on optimizing the electric energy density of epoxy-aluminum nanocomposites. It models the nanocomposite as a three-phase material and evaluates how aluminum particle size and filler loading affect permittivity, breakdown strength, and energy density. Numerical results show permittivity increases drastically near the percolation threshold. As filler volume increases, breakdown strength decreases but energy density notably increases. The optimal filler size and concentration for maximum energy density are evaluated, with inter-particle distance controlling breakdown strength significantly impacting energy storage capacity.
Flexible dual band dipole antenna incorporates with Electromagnetic Band Gap (EBG) to improve the well-known low profile characteristics of dipole antenna. The antenna operates at 2.45 GHz and 5.8 GHz which is printed on Fast film with 0.13 mm thickness. While the EBG is designed at 5.8 GHz by using Arlon AD350 with 1.016 mm thickness. EBG works as a ground plane for the antenna and helps by improving the realized gainandradiation pattern. Besides, EBG also act as a filter as the resonant frequency of the antenna is close to the EBG band gap. The 2.45 GHz of is eliminated while the performances of antenna at 5.8 GHz is improved. Thus the realized gain is increased up to 6.86 dB and the back lobes are clearly reduced. The designs of dipole antenna with EBG application such as Wifi and others on-body communication devices.
This document summarizes a study on the electrical properties of electrodeposited zinc-copper-telluride (ZnCuTe) ternary nanowires embedded in polycarbonate membranes. Scanning electron microscopy confirmed the formation of uniform diameter nanowires equal to the pore diameters of 200nm, 100nm, and 50nm templates used. Electrical measurements found the nanowires exhibited linear and ohmic characteristics. Larger diameter nanowires showed higher electron transport than smaller ones. Temperature-dependent measurements from 308K-423K revealed electrical conductivity increased with temperature and decreased with smaller nanowire size, with ZnCuTe nanowires exhibiting negative temperature coefficients of resistance.
SIMULATION OF THE SOLAR CELLS WITH PC1D, APPLICATION TO CELLS BASED ON SILICONAEIJjournal2
A way of exploiting the solar energy is to use cells photovoltaic which convert the energy conveyed by the incidental radiation in a continuous electric current. This conversation is based on the photovoltaic effect engendered by the absorption of photons. A part of the absorbed photons generates pairs electron-hole in which an electric field created in the zone of load of space of a junction p–n. Thus, the junction p-n, its characteristics, its components and its dimensions are the parameters responsible of the efficiency and the performances of a solar cell. To study this, we are going to use a very known software in the mode of the simulation of solar cells, the PC1D, and we are going, at the end, to draw a conclusion around the ideal parameters that a good solar cell has to have.
Design optimization of bifacial solar cell by pc1 d simulationAlexander Decker
The document summarizes a study that used PC1D software to optimize the design of a bifacial solar cell through simulation. Key parameters such as emitter doping, bulk doping, minority carrier lifetime, wafer thickness, and front/rear surface properties were varied in the simulations. The highest efficiencies obtained were 16.42% for illumination from the front surface and 14.18% for the rear surface. The results provide insights into potential fabrication parameters for bifacial solar cells and show that minority carrier lifetime and wafer thickness are particularly important for performance.
This document discusses unsupervised techniques for deciphering encrypted documents. It presents an approach using noisy-channel modeling and expectation-maximization (EM) to find the most likely plaintext given a ciphertext. As an example, it applies this method to deciphering a basic English letter substitution cipher. The algorithm initializes substitution probabilities uniformly, then iterates to adjust the probabilities based on plaintext and ciphertext letter co-occurrence counts to converge on the most probable plaintext.
Mobile application development involves creating apps for smartphones and tablets. Key points about mobile app development include:
1. The mobile app market is large and growing, with over 1.5 billion mobile devices sold in 2011 and the app market reaching $15 billion by 2013.
2. Smartphones have become "smarter" with powerful processors and operating systems like Android that allow developers to create powerful apps. Over 600,000 apps are available across platforms.
3. Mobile apps have different requirements than desktop apps due to limitations of mobile devices like smaller screens, memory constraints, and intermittent network connectivity.
4. The Android platform provides tools and APIs for developers to create apps that will run on Android devices. It
Learning phoneme mappings for transliteration without parallel dataAttaporn Ninsuwan
The document presents a method for learning cross-language phoneme mappings without parallel data by framing transliteration as a decipherment problem and using monolingual resources to learn mappings between English and Japanese phonemes. It compares this unsupervised approach to a supervised approach using parallel data and finds the unsupervised method achieves 40% accuracy on a name transliteration task, similar to the supervised approach. The goal is to develop transliteration systems that do not require parallel resources for any language pair.
The document discusses Microsoft's Live@edu services which provide single sign-on access for students and faculty to Outlook, Office Web Apps, and SkyDrive storage. It highlights features like customization, built-in collaboration tools, and the ability to create and manage Office documents from any device. The presentation concludes with a demo of a school portal showing how single sign-on allows access to digital campus resources from anywhere with one identity.
Property analysis of quantum dot cuboid nanocrystals with different nanostruc...Alexander Decker
The document summarizes simulation results of quantum dot cuboid nanocrystals with different nanostructures. It first describes taking a 3D cuboid structure and simulating its 3D wavefunction, energy states, and light/dark transitions under different polarizations. It finds the characteristics are equivalent for different structures given the same boundary conditions. It then simulates a pyramid structure and finds its absorption peaks differ in number but are otherwise equivalent to the cuboid. The conclusion states that for different nanostructures, the characteristics are almost equivalent under the same boundary conditions.
10.1016-j.mssp.2015.01.037-Electrochemical investigation of graphene_nanoporo...Mahdi Robat Sarpoushi
This study investigated the effect of mixing graphene nanosheets and nanoporous carbon black on the surface morphology and electrochemical performance of electrodes prepared for supercapacitors. Electrodes containing 80% nanoporous carbon black, 10% graphene nanosheets, and 10% PTFE binder showed the highest specific capacitance of 10.22 F/g. The addition of nanoporous carbon black increased the proportion of outer charge stored on the electrode relative to the total charge stored, indicating higher current response and voltage reversal at the end potentials. Scanning electron microscopy images showed that adding nanoporous carbon black particles arranged the graphene nanosheets in different directions, increasing the specific surface area and changing diffusion characteristics to improve capacitance and reversibility
2 d electrical resistivity tomography (ert) survey using the multi electrode ...Alexander Decker
1) 2D electrical resistivity tomography (ERT) surveys were conducted along six radial profiles at the Bosumtwi impact crater in Ghana using a modified multi-electrode gradient array.
2) The cable take-outs of the resistivity imaging system were modified from 2m to 5m spacing, allowing investigation of the subsurface to depths of around 75m.
3) The ERT models identified three subsurface formations - low resistivity lake sediments, moderately resistive impact breccias, and highly resistive basement metamorphic rocks.
Theoretical Study of Density of States of Magnesium diboride Superconductor b...ijsrd.com
Magnesium diboride with Tc = 39K is a record breaking compound among s-p metals & alloys. Many experiments performed on Magnesium diboride suggest that there are two superconducting gaps. Considering a multiband model Hamiltonian with intra- & inter band pair transfer interactions we have derived the normal and anomalous one-particle Green's function & self-consistent equations for superconducting order parameter(ÃŽâ€) using Green's function technique & equation of motion method, we have studied the density of states. The results are quite encouraging.
The Effect of Plasma-Treated Boron Nitride on Partial Discharge Characteristi...IJECEIAES
Power supply reliability is a key factor in a country economic stability. It is contributed by the reliable power distributor via transmission lines, overhead or underground cables. However, the power cables and accessories are always exposed to pre-breakdown phenomena known as partial discharges (PD) which commonly occur in microvoids, defects or protrusions inside the insulation.To improve the performance of the cable insulation against PD, nanofillers are added into the insulating materials. However, to achieve superior performance of PD resistance, the nanofillers must be homogeneously dispersed into the polymer matrices withtightly bonded interfacial zones. Therefore, this could be achieved by employing method of surface functionalization by using cold atmospheric plasma to strengthen the filler/polymer interfaces. In view of foregoing, this study investigated the effects of surface treated boron nitride (BN) nanoparticles in Low Density Polyethylene (LDPE) on the PD characteristics by following CIGRE Method II at 7 kVrmsapplied voltage. The phase resolved PD characteristics were performed. The results revealed that by treating the nanofillers with cold plasma, the PD resistance of LDPE were highly achieved compared with the untreated BN nanofillers.
Numerical simulation model of multijunction solar cellAlexander Decker
This document presents a simulation model of multi-junction solar cells. The model simulates the performance characteristics of dual-junction solar cells with InGaP/GaAs and triple-junction solar cells with InGaP/GaAs/Ge. The model accounts for the solar cells and tunnel junctions that connect the cells. Simulation results show the multi-junction cells have higher open-circuit voltages than individual cells due to current matching, though overall current is reduced. The model agrees with experimental data and can be used to analyze effects of material properties on cell performance.
The document describes an experiment where quantum state transfer was realized between atomic and photonic qubits. Efficiencies of 0.04 and 0.03 were measured for the read and write processes respectively. It is estimated that implementing a second node and joint detection of signal photons could realize quantum repeater protocols and distant teleportation of atomic qubits at a rate of around 3 x 10-7 s-1. Improvements to efficiency through increasing optical thickness or eliminating transmission losses could increase the rate by several orders of magnitude. The results also demonstrate the possibility of multiple atomic qubits in a quantum node using multiple light beams.
E = g lk+ 2
+ − − +
r m 0 m 0 4 ε 0 h ( ε 0 2 e 0 m 0
8 em hm πεr 2 2ε ) m m hm
Brus, L. E. J. Phys. Chem. 1986, 90, 2555
Semiconductor quantum dots are nanocrystals made of semiconductor materials such as CdSe, ZnSe, ZnS, and ZnO. They exhibit size-dependent optical and electronic properties due to
This document provides an introduction to dielectric materials and their importance in modern technology. It discusses the early history and development of the field, including Faraday's discovery of dielectric polarization and Debye's theory relating molecular dipole moments to macroscopic dielectric properties. Modern applications demand materials with specific dielectric properties tailored for uses like integrated circuits, wireless communication technologies, and microwave devices. The document outlines the classical theory of dielectrics, including the different polarization mechanisms (electronic, atomic/ionic, dipolar/orientational, space charge) that contribute to a material's overall dielectric constant and frequency-dependent behavior.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
1) Vertical electrical sounding using Schlumberger array was conducted at 40 stations to determine subsurface layers and depth to bedrock at the Centre for Energy Research and Training in Zaria, Nigeria.
2) Resistivity values and thickness were derived for three predominant layers - topsoil (2-738 ohm-m thickening 1-3.9m), weathered basement (32-1735 ohm-m thickening 0.52-23m), and fresh basement bedrock (100-6036 ohm-m).
3) Results identified areas suitable for structures and boreholes, and recommended depth of sewage systems to avoid groundwater contamination based on the subsurface resistivity and thickness parameters.
Optimization of electric energy density in epoxy aluminiumiaemedu
This document discusses optimizing the electric energy density of epoxy-aluminum nanocomposites for use as dielectric materials. It presents a three-phase model to characterize the nanocomposite's dielectric properties as a function of aluminum particle size and volume fraction. Numerical results show that permittivity increases drastically near the percolation threshold. While breakdown strength decreases with higher volume fractions, the overall energy density is significantly higher than pure epoxy. Maximum energy density occurs at an optimal particle size and concentration balancing high permittivity and maintaining breakdown strength. Careful control of microstructure is important to avoid defects and achieve expected energy density gains.
Optimization of electric energy density in epoxy aluminium nanocompositeiaemedu
This document summarizes research on optimizing the electric energy density of epoxy-aluminum nanocomposites. It models the nanocomposite as a three-phase material and evaluates how aluminum particle size and filler loading affect permittivity, breakdown strength, and energy density. Numerical results show permittivity increases drastically near the percolation threshold. As filler volume increases, breakdown strength decreases but energy density notably increases. The optimal filler size and concentration for maximum energy density are evaluated, with inter-particle distance controlling breakdown strength significantly impacting energy storage capacity.
Flexible dual band dipole antenna incorporates with Electromagnetic Band Gap (EBG) to improve the well-known low profile characteristics of dipole antenna. The antenna operates at 2.45 GHz and 5.8 GHz which is printed on Fast film with 0.13 mm thickness. While the EBG is designed at 5.8 GHz by using Arlon AD350 with 1.016 mm thickness. EBG works as a ground plane for the antenna and helps by improving the realized gainandradiation pattern. Besides, EBG also act as a filter as the resonant frequency of the antenna is close to the EBG band gap. The 2.45 GHz of is eliminated while the performances of antenna at 5.8 GHz is improved. Thus the realized gain is increased up to 6.86 dB and the back lobes are clearly reduced. The designs of dipole antenna with EBG application such as Wifi and others on-body communication devices.
This document summarizes a study on the electrical properties of electrodeposited zinc-copper-telluride (ZnCuTe) ternary nanowires embedded in polycarbonate membranes. Scanning electron microscopy confirmed the formation of uniform diameter nanowires equal to the pore diameters of 200nm, 100nm, and 50nm templates used. Electrical measurements found the nanowires exhibited linear and ohmic characteristics. Larger diameter nanowires showed higher electron transport than smaller ones. Temperature-dependent measurements from 308K-423K revealed electrical conductivity increased with temperature and decreased with smaller nanowire size, with ZnCuTe nanowires exhibiting negative temperature coefficients of resistance.
SIMULATION OF THE SOLAR CELLS WITH PC1D, APPLICATION TO CELLS BASED ON SILICONAEIJjournal2
A way of exploiting the solar energy is to use cells photovoltaic which convert the energy conveyed by the incidental radiation in a continuous electric current. This conversation is based on the photovoltaic effect engendered by the absorption of photons. A part of the absorbed photons generates pairs electron-hole in which an electric field created in the zone of load of space of a junction p–n. Thus, the junction p-n, its characteristics, its components and its dimensions are the parameters responsible of the efficiency and the performances of a solar cell. To study this, we are going to use a very known software in the mode of the simulation of solar cells, the PC1D, and we are going, at the end, to draw a conclusion around the ideal parameters that a good solar cell has to have.
Design optimization of bifacial solar cell by pc1 d simulationAlexander Decker
The document summarizes a study that used PC1D software to optimize the design of a bifacial solar cell through simulation. Key parameters such as emitter doping, bulk doping, minority carrier lifetime, wafer thickness, and front/rear surface properties were varied in the simulations. The highest efficiencies obtained were 16.42% for illumination from the front surface and 14.18% for the rear surface. The results provide insights into potential fabrication parameters for bifacial solar cells and show that minority carrier lifetime and wafer thickness are particularly important for performance.
This document discusses unsupervised techniques for deciphering encrypted documents. It presents an approach using noisy-channel modeling and expectation-maximization (EM) to find the most likely plaintext given a ciphertext. As an example, it applies this method to deciphering a basic English letter substitution cipher. The algorithm initializes substitution probabilities uniformly, then iterates to adjust the probabilities based on plaintext and ciphertext letter co-occurrence counts to converge on the most probable plaintext.
Mobile application development involves creating apps for smartphones and tablets. Key points about mobile app development include:
1. The mobile app market is large and growing, with over 1.5 billion mobile devices sold in 2011 and the app market reaching $15 billion by 2013.
2. Smartphones have become "smarter" with powerful processors and operating systems like Android that allow developers to create powerful apps. Over 600,000 apps are available across platforms.
3. Mobile apps have different requirements than desktop apps due to limitations of mobile devices like smaller screens, memory constraints, and intermittent network connectivity.
4. The Android platform provides tools and APIs for developers to create apps that will run on Android devices. It
Learning phoneme mappings for transliteration without parallel dataAttaporn Ninsuwan
The document presents a method for learning cross-language phoneme mappings without parallel data by framing transliteration as a decipherment problem and using monolingual resources to learn mappings between English and Japanese phonemes. It compares this unsupervised approach to a supervised approach using parallel data and finds the unsupervised method achieves 40% accuracy on a name transliteration task, similar to the supervised approach. The goal is to develop transliteration systems that do not require parallel resources for any language pair.
The document discusses Microsoft's Live@edu services which provide single sign-on access for students and faculty to Outlook, Office Web Apps, and SkyDrive storage. It highlights features like customization, built-in collaboration tools, and the ability to create and manage Office documents from any device. The presentation concludes with a demo of a school portal showing how single sign-on allows access to digital campus resources from anywhere with one identity.
The document discusses the rule of thirds in visual composition. It states that the rule of thirds involves imagining an image divided into nine equal parts by two horizontal and two vertical lines, and placing key elements of the composition along these lines or their intersections. Proponents claim this creates more tension and interest than centering the subject. The rule is a compositional guideline used in photography, painting, and design.
The document discusses opportunities for Indo-US cooperation in human resource development and higher education to support the growing knowledge economy. It outlines challenges facing India's higher education system including faculty shortages and inadequate research infrastructure. It proposes ambitious programs for nurturing faculty and Indian participation in large-scale US science projects to better link India's education system to skill demands. Strengthening Indo-US collaboration holds potential benefits for both countries in developing the skilled workforce needed for the future.
This document describes an experiment to study how yeast cells move when subjected to non-uniform electric fields (dielectrophoresis). Yeast cells were placed in a suspension between two pointed platinum electrode tips and exposed to alternating electric fields of varying frequency. The motion and clustering of cells at the electrode tips, where the electric field was strongest, was observed under a microscope over time. The clustering behavior depended on factors like field strength, frequency, suspension conductivity, and biological characteristics of the yeast cells.
This document summarizes the design, fabrication, and testing of a microfluidic chip prototype for manipulating particles using dielectrophoresis (DEP). Finite element modeling was used to simulate the electric field distributions around quadrupole and comb electrode geometries. A prototype was fabricated containing these electrode designs in two separate microchannels. Silica microspheres were successfully manipulated within the chip using positive and negative DEP sequences, concentrating particles in the electrode areas. Testing demonstrated the potential of this technique for manipulating and separating microparticles in integrated microfluidic devices.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
This document summarizes a study on the photoelectrochemical properties of nanocrystalline indium selenide (In2Se3) thin films deposited via a chemical bath deposition method. The In2Se3 films exhibited n-type conductivity based on photoelectrochemical characterization including I-V and C-V measurements in dark conditions. These measurements were used to determine properties like the ideality factor, flat band potential, and barrier height. Under illumination, the In2Se3 films showed a maximum power output of 3.1 μW/cm2 with an open circuit voltage of 153 mV and short circuit current of 20 μA.
Pandey S, White M. "Detection of dielectrophoretic driven passage of single cells through micro-apertures in a silicon nitride membrane".
Conf Proc IEEE Eng Med Biol Soc. 2004;2004:1956-9.
doi: 10.1109/IEMBS.2004.1403578. PMID: 17272098.
https://ieeexplore.ieee.org/document/1403578
Partially filled electrode for DMF devicesWaleed Salman
This document describes research into partially filled electrodes for digital microfluidic devices. The researchers conducted simulations and experiments to evaluate how reducing the filled area of electrodes affects actuation forces on droplets. The simulations showed that actuation force decreases linearly as electrode fill percentage decreases. However, forces were independent of the vertical location of removed electrode areas. Experiments confirmed that partially filled electrodes can still achieve droplet actuation speeds sufficient for many applications, with frequencies over 10 electrodes per second achieved at 40% fill area. Partially filled electrodes also allow integration of additional on-chip elements and transmission microscopy imaging of droplets.
Electrophoresis is a scientific laboratory technique that is used to separate DNA, RNA, or protein molecules based on their size and electrical charge. An electric current is passed through the molecules to move them so that they can be separated via a gel. The pores present in the gel work like a sieve, allowing smaller molecules to pass through more quickly and easily than the larger molecules. According to the way conditions are adjusted during electrophoresis, the molecules can be separated in the desired size range.
What is electrophoresis and what are its uses?
Electrophoresis is a very broadly used technique that, fundamentally, applies electric current to biological molecules – they’re usually DNA, but they can be protein or RNA, too – and separates these fragments into pieces that are larger or smaller in size.
The phenomenon of electrophoresis was first observed by Russian professors Peter Ivanovich Strakhov and Ferdinand Frederic Reuss in 1807 at Moscow University. A constant application of electric field caused the particles of clay dispersed in water to migrate, showing an electrokinetic phenomenon.
Electrophoresis can be defined as an electrokinetic process that separates charged particles in a fluid using an electrical field of charge. Electrophoresis of cations or positively charged ions is sometimes referred to as cataphoresis (or cataphoretic electrophoresis). In contrast, sometimes, the electrophoresis of anions or negatively charged ions is referred to as anaphoresis (or anaphoric electrophoresis).
It’s used in a variety of applications. Though it is most often used in life sciences to separate protein molecules or DNA, it can be achieved through several different techniques and methods depending upon the type and size of the molecules.
The methods differ in some ways, but all we need is a source for the electrical charge, a support medium and a buffer solution. Electrophoresis is also used in laboratories for the separation of molecules based on their size, density and purity.
The method used to separate macromolecules such as DNA, RNA, or protein molecules is known as gel electrophoresis.
It is used in forensics for –
Nucleic acid molecule sizing
DNA fragmentation for southern blotting
RNA fragmentation for northern blotting
Protein fragmentation for western blotting
Separation of PCR products analysis
Detection and analysis of variations or mutations in the sequence
Its clinical applications involve –
Serum protein electrophoresis
Lipoprotein analysis
Diagnosis of haemoglobinopathies and hemoglobin A1c.
The fundamental principle of electrophoresis is the existence of charge separation between the surface of a particle and the fluid immediately surrounding it. An applied electric field acts on the resulting charge density, causing the particle to migrate and the fluid around the particle to flow.
It is the process of separation or purification of protein molecules, DNA, or RNA that differ in charge, size.
This study examined the surface area that contributes to current density in microbial electrochemical systems. Experiments used a graphite plate working electrode and Geobacter subterraneus to form biofilms on both sides. Chronoamperometry showed biofilms formed on both sides. Cyclic voltammetry identified a direct electron transfer mechanism with a defined potential. Confocal laser scanning microscopy and modeling found the biofilms were uniformly thick at ~75 μm and contributed equally to the current density of ~2.5 A/m2, demonstrating both sides of a planar electrode can transfer electrons regardless of orientation.
Electron Beam Lithography review paper - EE541 Dublin City UniversityRay Tyndall
Electron beam lithography (EBL) uses a focused beam of electrons to pattern nanostructures onto a resist. EBL can produce features smaller than 10nm. High energy electrons (10-100keV) are focused into a narrow beam and used to expose regions on an electron-sensitive resist. The resolution is limited by electron scattering within the resist and substrate, which causes the exposed area to be larger than the beam size. EBL is widely used in semiconductor manufacturing for patterning at the nanoscale but proximity effects from electron scattering make it challenging to produce small, dense features. Techniques such as higher beam voltages, dose modulation, and multiple resist layers help overcome these limitations.
The document reports on a study of the AC and DC conductivity of three glycine family nonlinear optical (NLO) single crystals: Trisglycine Zinc Chloride (TGZC), Triglycine Acetate (TGAc), and Glycine Lithium Sulphate (GLS). The AC conductivity was measured from 50 Hz to 5 MHz and increased with temperature for all crystals. The activation energies calculated from the AC conductivity were 0.035 eV for TGZC, 0.075 eV for TGAc, and 0.10 eV for GLS. The DC conductivity also increased with temperature from 313 K to 423 K, and the activation energies calculated were 0.050 eV for TGZC, 0.060 eV
DIELECTROPHORETIC DEFORMATION OF ERYTHROCYTES ON TRANSPARENT INDIUM TIN OXIDE...Larry O'Connell
1. The document presents a protocol for patterning transparent indium tin oxide (ITO) electrodes and investigates their efficacy for dielectrophoretically deforming erythrocytes compared to existing gold electrodes.
2. ITO electrodes were fabricated through a multi-step reactive ion etching process involving photoresist patterning and chromium/nickel masking layers. The transparent ITO electrodes allow full visualization of adhered cells, unlike opaque gold electrodes.
3. Erythrocytes suspended in a glucose solution were dielectrophoretically deformed at increasing electric field strengths on the ITO electrodes. Images were captured at each voltage step to measure cell deformation without occlusion from the electrodes.
This document summarizes research investigating graphene/cerium oxide nanoparticles as an electrode material for supercapacitors. Scanning electron microscopy images showed the layered structure of graphene with cerium oxide nanoparticles dispersed across the surface. Electrochemical testing found the electrode achieved a maximum specific capacitance of 11.09 F g−1 in 3 M NaCl electrolyte. Charge/discharge cycling showed good reversibility and 37% increase in capacitance after 500 cycles. The graphene/cerium oxide composite performed better than cerium oxide alone due to graphene's conductivity and the formation of an electrical double layer at the electrode interface.
1) The study investigated the effect of adding zirconium oxide nanoparticles to carbon black electrode materials on surface morphology and electrochemical performance.
2) Scanning electron microscopy showed that adding nanoparticles partially filled gaps between carbon black particles, increasing the specific surface area available for charge storage.
3) Electrochemical analysis found that increasing nanoparticle content initially increased total charge storage due to higher surface area and pseudocapacitive charge storage, but further increases reduced performance due to higher electrode resistance.
This document discusses experiments to control charging during critical dimension measurements of photomasks using a scanning electron microscope. Introducing a low-pressure gas environment around the mask eliminates charging issues seen at high vacuum. With gas present, the mask's surface potential is stabilized, improving metrology accuracy and precision. Backscattered electron imaging provides benefits over secondary electron imaging in some cases. Faster environmental scattered electron detectors are needed to fully utilize secondary electron signals in a gas environment.
This document summarizes research on designing annular ring frequency selective surfaces (FSS) using different dielectric substrate materials. The research aims to achieve dual-band frequency response with controllable shift in resonance frequencies. FSS designs with annular ring elements are simulated using substrates like Teflon, Mica and FR4. Simulation results show dual transmission bands in C-band and X-band, with the frequencies shifting based on the dielectric constant of the material. Teflon provides the highest resonance frequencies while Mica and FR4 shift the frequencies down as their dielectric constants increase. The study demonstrates annular ring FSS can produce dual-band response with substrate material choice enabling predictable frequency shifts.
the effect of nickel incorporation on some physical properties of epoxy resinINFOGAIN PUBLICATION
The J-E characteristics of samples of epoxy resins mixed with nickel powder in different concentrations have been tested and a log-log straight line behaviour in both the low- and high field regions is observed. Ni-concentration has significant influence on the calculated constants of the J-E relationship. The d.c. electrical resistivity (ρ) of the samples are measured from the room temperature up to about 400 K. The variation of ρ with T obeys the exponential relation of ordinary dielectrics in three temperature regions. The parameters characterizing the ρ -T dependence change considerably with Ni-concentration. Due to the existence of nickel in different concentration a "true" compensation effect is observed with three characteristic compensation temperatures. The mechanical hardness of the samples was investigated as a function of Ni-concentration.
Dielectric Spectroscopy in Time and Frequency DomainGirish Gupta
This presentation describes the basics and technicalities of Dielectric Spectroscopy in both time and frequency domain. IT also includes the procedure and results involved in Dielectric Spectroscopy on different dielectrics.
This document describes a discontinuous design for a negative index metamaterial based on hybridization of modes in paired electric inductor-capacitor (ELC) resonators. The design achieves a negative index by overlapping the spectral region of negative permeability from the second magnetic resonance mode with the region of negative permittivity from the first electric resonance mode. Simulations and experiments on a prototype structure show a narrow band of negative refractive index around 15.5 GHz, with simultaneously negative permeability and permittivity, demonstrating the proposed discontinuous design approach.
Zno and znopbs heterojunction photo electrochemical cellseSAT Journals
Abstract Photo Electrochemical Cell (PEC) can also be used for splitting of water into hydrogen and Oxygen. Here, ZnO nanorod PEC has been prepared in hydrothermal method and ZnO/PbS quantum dot PEC has been prepared by hydrothermal method and chemical bath deposition method. UV-Visible spectroscopy has been observed. Flat band voltage, bandwidth and majority charge carriers have been calculated from Mott-Schottky. Impedance variation at semiconductor and electrolyte junction has been observed with Electrochemical Impedance Spectroscopy (EIS). Keywords: Hydrothermal, Chemical bath, ZnO/PbS, UV-Vis, Mott-Schottky, EIS.
The document studies the capacitance-voltage (C-V) characteristics of thin n+-p-p+ silicon solar cells and induced junction n-p-p+ cell structures of different thicknesses. C-V measurements were carried out on the cells in both reverse and forward bias conditions under dark at room temperature. It was found that the capacitance can be divided into two regions - one representing the junction properties (transition capacitance) and the other representing the effectiveness of the back surface field (diffusion capacitance). The induced junction structures were found to have a shallower junction and better back surface field than the conventional solar cells.
This document is a table of contents and introduction for a book titled "jQuery Fundamentals" by Rebecca Murphey. The book covers jQuery basics, core concepts, events, effects, Ajax, plugins, and advanced topics. It includes over 50 code examples to demonstrate jQuery syntax and techniques. The book is available under a Creative Commons license and the source code is hosted on GitHub.
This document provides a preface and table of contents for a book on jQuery concepts. The preface explains that the book is intended to teach intermediate and advanced jQuery concepts through code examples. It highlights some stylistic approaches used in the book, such as emphasizing code over text explanations and using color coding. It also defines some key terms that will be used, and recommends reviewing the jQuery documentation and understanding how the text() method works before reading the book. The table of contents then outlines the book's 12 chapters and their respective sections, which cover topics like selecting, traversing, manipulating, events, plugins and more.
This document proposes techniques for embedding unique codewords in electronic documents to discourage illicit copying and distribution. It describes three coding methods - line-shift coding, word-shift coding, and feature coding - that alter document formatting or text elements in subtle, hard-to-detect ways. Experimental results show the line-shift coding method can reliably decode documents even after photocopying, enabling identification of the intended recipient. The techniques aim to make unauthorized distribution at least as difficult as obtaining documents legitimately from the publisher.
This document discusses the field of computer forensics. It defines computer forensics as the collection, preservation, and analysis of computer-related evidence. The goal is to provide solid legal evidence that can be admitted in court and understood by laypeople. Computer forensics is used to investigate various incidents including human behavior like fraud, physical events like hardware failures, and organizational issues like staff changes. It aims to determine the root cause of system disruptions and failures.
This document discusses techniques for data hiding, which involves embedding additional data into digital media files like images, audio, or text. It describes several constraints on data hiding, such as the amount of data to hide, ensuring the data remains intact if the file is modified, and preventing unauthorized access to the hidden data. The document outlines traditional and novel data hiding techniques and evaluates them for applications like copyright protection, tamper-proofing, and adding supplemental data to files. It also discusses tradeoffs between hiding more data versus making the data more robust against modifications to the file.
This document summarizes an analysis of over 200,000 websites engaged in badware behavior according to Google's Safe Browsing initiative. The analysis found that over half of infected sites were located in China, with the top three Chinese network blocks accounting for 68% of infections in that country. In contrast, infected sites in the US were more distributed. Compared to the previous year, the total number of infected sites increased, likely due to expanded scanning and increased malware distribution through websites.
Steganography has been used for over 2500 years to hide secret messages. The paper explores steganography's history from ancient times through modern digital applications. It discusses early examples like Johannes Trithemius' steganographic treatise in the 15th century. Modern uses include microdots, digital images, audio, and digital watermarks for copyright protection. Terrorist groups may use steganography but there is no public evidence yet. Steganography continues to evolve with technology while attackers work to defeat new techniques.
The document discusses various cryptographic techniques including symmetric and asymmetric encryption. Symmetric encryption uses the same key for encryption and decryption, while asymmetric encryption uses two different keys. The document then describes the Data Encryption Standard (DES) algorithm and its variants, including Triple DES. It also covers the Advanced Encryption Standard (AES) algorithm, its design principles, and modes of operation for block ciphers like ECB, CBC, CFB and OFB.
This document discusses the topic of steganography, which is hiding secret messages within other harmless messages. It outlines different techniques for hiding messages in text, images, and audio files. For text, it describes line shift coding, word shift coding, and feature coding methods. For images, it explains least significant bit insertion and exploiting the limitations of the human visual system. For audio, it mentions low-bit encoding and other techniques like phase coding and spread spectrum. It also discusses steganalysis, which aims to detect and destroy hidden messages within files.
This document discusses the need for computer security and provides an introduction to key concepts. It explains that security is necessary to protect vital information, provide authentication and access control, and ensure availability of resources. The document then outlines common security threats like firewall exploits, software bugs, and denial of service attacks. It also discusses basic security components of confidentiality, integrity, and availability as well as goals of preventing attacks, detecting violations, and enabling recovery.
The document discusses various types of malicious programs including buffer overflows, viruses, worms, Trojan horses, backdoors, and logic bombs. It describes how buffer overflows can corrupt the program stack and be exploited by attackers. It explains that viruses attach themselves to other programs and replicate, worms replicate across networks, and Trojan horses masquerade as legitimate programs. It also outlines different approaches for antivirus software including signature-based, heuristic, activity monitoring, and full-featured protection.
This document discusses various topics relating to web security, including:
1) Different types of web pages like static, dynamic, and active pages and the technologies used to create them like JavaScript, Java, and CGI.
2) Security issues associated with technologies like ActiveX, Java applets, JavaScript, and cookies.
3) Protocols for secure communication like HTTPS, digital certificates, and single sign-on systems.
4) Methods for secure electronic commerce including SET and digital cash technologies.
This document provides an overview of network security topics including attacks like diffing, sniffing, session hijacking and spoofing. It discusses protocols for secure communication including SSL, TLS and IPSec. SSL and TLS provide security at the transport layer by encrypting data between a client and server. IPSec provides security at the network layer for both transport and tunnel modes. Authentication Header and Encapsulating Security Payload are the two security protocols used in IPSec.
This document provides an overview of network security topics including diffing, sniffing, session hijacking, spoofing, SSL, TLS, IPSec, and VPNs. It discusses how these attacks work and methods to protect against them, such as encryption. Network layer security protocols like IPSec are described, which uses authentication headers or encapsulating security payloads to provide security services to packets. Transport layer security protocols SSL and TLS are also summarized, including how they establish encrypted sessions between clients and servers.
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This document discusses the continuous-time Fourier transform. It begins by developing the Fourier transform representation of aperiodic signals as the limit of Fourier series coefficients as the period increases. It then defines the Fourier transform pairs and discusses properties like convergence. Several examples of calculating the Fourier transform of common signals like exponentials, pulses and periodic signals are provided. Key concepts like the sinc function are also introduced.
Chapter3 - Fourier Series Representation of Periodic SignalsAttaporn Ninsuwan
This document discusses Fourier series representation of periodic signals. It introduces continuous-time periodic signals and their representation as a linear combination of harmonically related complex exponentials. The coefficients in the Fourier series representation can be determined by multiplying both sides of the representation by complex exponentials and integrating over one period. The key steps are: 1) multiplying both sides by e-jω0t, 2) integrating both sides from 0 to T=2π/ω0, and 3) using the fact that the integral equals T when k=n and 0 otherwise to obtain an expression for the coefficients an. Examples are provided to illustrate these concepts.
Chapter3 - Fourier Series Representation of Periodic Signals
Diaz payen
1. Biological cell separation using dielectrophoresis in a
microfluidic device
R. Díaz, S. Payen
University of California, Berkeley
Bio and Thermal Engineering Laboratory
EECS 245
Abstract
Basic IC fabrication techniques are employed in this paper with the purpose of designing a micro-
fluidic device with a 3D electrode arrangement to separate live and dead biological cells. This is done us-
ing the concept of dielectrophoresis, which describes the transnational motion of particles due to the appli-
cation of a non-uniform electrical field. The simulations where carried out using the protoplast model for
mammalian spherical cells [4] in a wide range of electric field frequencies. Analytically, we have found
that the Clausius-Mossoti Factor is negligible for live mammalian cells over a frequency range of 50 – 70
KHz whereas is maximum for the dead cells. Since the Clausius-Mossoti factor is the important term in the
dielectrophoretic force formulae, we can envision our microfluidic design as a feasible tool to separate live
and dead mammalian cells.
1. Introduction desired to separate the cells to selectively apply medicine or
for gene therapy using electroporation techniques [1,2].
In the past few years, there has been an extensive re-
search in the manipulation and analysis of biological cells 2. Theory of Dielectrophoresis
at the micro scale. There is an increase interest in applying
microelectromechanical systems (MEMS) for selective Electrophoresis and dielectrophoresis describe the
trapping, manipulation and separation of bioparticles. Al- movement of particles under the influence of applied elec-
though there is a huge demand of automated single-cell tric fields. Whereas electrophoresis is the movement of
manipulation and analysis in immunology, developmental charged particles in direct current (DC) or low-frequency
biology and tumor biology calling for the development of alternating current fields, dielectrophoresis is the movement
suitable microsystems, the approaches currently available to of particles in non-uniform electric fields. The dipole mo-
meet those needs are limited [7]. ment m induced in the particle can be represented by the
The term dielectrophoresis (DEP) was first introduced generation of equal and opposite charges (+q and –q) at the
by Pohl [9] to describe the transnational motion of particles particle boundary. The magnitude of the induced charge q is
due to the application of non-uniform electrical fields. The small, equivalent to around 0.1 % of the net surface charge
dielectrophoretic motion is determined by the magnitude normally carried by cells and microorganisms, and can be
and polarity of the charges induced in a particle by the ap- generated within about a microsecond. The important fact is
plied field [8]. Usually, dielectrophoresis is performed un- that this induced charge is not uniformly distributed over
der an alternating current (AC) field over a wide range of the bioparticle surface, but creates a macroscopic dipole.
frequencies. If the applied field is non-uniform, the local electric field E
The DEP force is dependent on several parameters: the and resulting force (E.δq) on each side of the particle will
dielectric properties and size of the particle, the frequency be different. Thus, depending on the relative polarizability
of the applied field and the electrical properties (conductiv- of the particle with respect to the surrounding medium, it
ity and permittivity) of the medium. Therefore, if is desired will be induced to move either towards the inner electrode
to achieve a good particle manipulation say cell separation, and the high-electric-field region (positive DEP) or towards
detailed analysis and careful selection need to be done in the outer electrode, where the field is weaker (negative
order to obtain the desired results. DEP).
In this paper, we are going to propose and analyze a micro- Following established theory, the DEP force FDEP acting on
electrode system incorporated in a microfluidic device, de- a spherical particle of radius r suspended in a fluid of abso-
signed for the separation of live and dead biological cells lute dielectric permittivity εm is given by:
using the dielectrophoretic force. As an application, it is
FDEP = 2π R 3ε 1{Re[ K ( w)]}∇E 2 , (*)
2. where Re[K(w)] is the Clausius-Mossoti function and de- The bottom layer fabrication process consists on the deposi-
termines the effective polarizability of the particle and the tion and patterning of a 4 µm layer of silicon nitride (Si3N4)
factor ∇E2 is proportional to the gradient and the strength of on the silicon wafer. The pattern on the Si3N4 is going to be
the applied electric field. The polarizability parameter 2 µm deep and it will be used to deposit the 3 µm wide
Re[K(w)] varies as a function of the frequency of the ap- platinum (Pt) electrodes by employing the liftoff technique
plied field and, depending on the dielectric properties of the (see Fig. 1a). The arrangement of the electrodes is going to
particle and the surrounding medium, can theoretically have be identical on both layers to achieve the desired electric
a value between +1.0 and –0.5. The value for Re[K(w)] at field around the cells.
frequencies below 1kHz is determined largely by polariza-
tions associated with particle surface charge. While in-
creasing frequency, first the effective conductivity and sec-
ond the effective permeability are the dominant contribut-
ing factors. A positive value for Re[K(w)] leads to an in-
duced dipole moment aligned with the applied field and to a
positive DEP force. A negative value for Re[K(w)] results
in an induced dipole moment aligned against the field and
produces a negative DEP. The fact that the field appears as
∇E2 in the equation of the DEP force indicates that revers-
ing the polarity of the applied voltage does not reverse the
DEP force. AC voltages can therefore be employed and, for
a wide range of applied frequencies (typically 500Hz to
50MHz), the dielectric properties of the particle, as embod-
ied in the parameter Re[K(w)], can be fully exploited.
The advantages of using microelectrodes
The advantages to be gained by reducing the scale of the
electrode design can be illustrated using the example of the
spherical electrodes for the case of a particle located one-
tenth of the distance from the inner to the outer electrode
[12]. For a 100-fold reduction of electrode size, a 1000-fold
reduction of operating voltage will therefore produce the
same DEP force on a particle in the same relative location.
In addition to the practical advantage of being able to use
lower operating voltages for a given desired DEP force, Figure 1: Micro fabrication cross-sections.
there is also a significant reduction in electrical heating and
electrochemical effects. The energy deposition form the Subsequently, a 25 µm layer of negative photoresist (SU-8)
field is proportional to σE2, where σ is the conductivity of is going to be deposited and patterned to form the walls of
the suspending fluid. In the example just given, for a 100- the microchannel, which are going to be 200 µm apart (see
fold reduction of electrode scale, because there is a ten-fold fig, 1b). SU-8 was chosen because of the ease to deal with
reduction in the applied electric field strength, the electrical and because of the good isolation properties. The top layer
heating is reduced 100-fold. In addition, as the surface area is going to undergo the same process as the bottom layer
of the electrodes in contact with the fluid is decreased, sur- but with a glass wafer and without the SU-8 walls. The two
face electrochemical processes are reduced. layers are going to be bonded together carefully to achieve
symmetry using NEA 121, Norland Products (see fig. 1c).
3. Test Structure Wells will be strategically etched on the SU-8 to simplify
the gluing process (not shown above).
The test structure will be composed of two layers (bottom The operation of the microfluidic device is simple. We are
layer and top layer) that are going to be bonded together to going to employ figure 2 to explain the details of the test
form a microfluidic channel with a 3D electrode structure. structure. The cells will be injected from a syringe pump
The fabrication cross sections are depicted on figure 1. gauge 18 using a 1.5 mm diameter plastic tube that is going
Both layers are going to undergo almost the same fabrica- to be glued to the wafer in section 1. The cells are going to
tion process with one difference, for the bottom layer we flow through section A until they arrive at section B where
are going to use a single crystal silicon wafer (SCS) and for the electrodes are going to centralize the cells to the middle
the top layer we are going to use a glass wafer. The glass of the microchannel [7]. The dielectrophoretic forces
wafer for the top layer was chosen to gain visual contact caused by the gradient of the electric field in the out of
while the micro device is in operation. plane direction are canceled because of the electrode sym-
metry arrangement. The actual cell separation is occurring
3. at section C. A non-uniform electric field is chosen such From [4], we found that the formula for the Clausius-
that the dead cells are affected by a high positive dielectro- Mossotti function is the following:
phoretic force while the live cells are not affected or par- w 2 (τ 1τ m − τ cτ m ) + jw(τ m − τ 1 − τ m ) − 1
* *
tially affected by a weak negative dielectrophoretic force. K ( w) = −
The differences in dielectric properties of the cells allow us w 2 (2τ 1τ m + τ cτ m ) − jw(τ m + 2τ 1 + τ m ) − 2
* *
to perform this. The live cells are going to continue an un- The quantities cm and R are the effective capacitance of the
affected straight path through section D and the dead cells membrane and the radius of the cell respectively, while
are going to be forced to take the path towards section E τm=cmR/σc and τc=εc/σc are the time constants where σc is
where they are being collected. the electrical conductivity and εc is the electrical permitivity
of the cytoplasm. We suppose that the conductance gm is
negligible (loss-less membrane). Finally the other constants
are τ1=ε1/σ1 and τm*=cmR/σ1.
To model a dead cell, we supposed that its membrane be-
came irreversibly permeable. For this case the Clausius-
Mossotti function is as follows:
ε c − ε 1 − j (σ 2 − σ 1 ) / w
K ( w) =
ε c + 2ε 1 − j (σ 2 + 2σ 1 ) / w
We choose DI water as very resistive suspension medium.
Its parameters are ε1=78*ε0, σ1=10-3 S/m.
The other model parameters are:
- Cytoplasm: εc=60*ε0, σc=0.5 S/m, R=2.0 µm.
- Loss-less membrane: cm=1.0 µF/cm2, gm=0.
Figure 4 is the result of the numerical simulation for the
Clausius-Mossotti function.
1.2
1.0
Figure 2: Top view of the test structure. 0.8
0.6 Alive cell
Re[K(w)]
0.4 Dead cell
4. Numerical calculations and results 0.2
0.0
In order for the system to work adequately, some numerical -0.2 0 2 4 6 8 10
calculations are needed to find the corresponding frequency -0.4
that is going to influence the cells in a desirable way. -0.6
The mammalian cell model, which is going to be used, is Electric field frequency (Log)
the protoplast model [4]. The protoplasts are spherical par-
ticles where it is possible to identify a cytoplasm and a loss- Figure 4: The Clausius-Mossotti function for
less membrane (see figure 3). dead and alive mammalian cells
It is important to notice that the dielectrophoretic force is
directly proportional to the Clausius-Mossoti function. This
membrane : cm, gm relation is given by equation (*).
R Alignment:
Cytoplasm: Sections B, D and E, from figure 3, allow us to align the
εc , σc cells and prevent contact between the cells and the walls of
External medium: the microfluidic channels. In these sections, we can work
ε1 , σ1 with frequencies around 10 MHz where the Clausius-
Mossoti factor is the same for dead and alive cells, there-
Figure 3: Protoplast model parameters fore having similar dielectrophoretic forces.
Separation:
In section C, where the separation is occurring, we want to
work in the region where Re[K(w)] is zero for live cells and
4. around one for dead cells. In this case, we know that the 6. References
dead cells will experience a positive DEP toward the bot-
tom channel (section E), whereas the live cells will not ex- 1. Dev, S.B., et al., Medical applications of electropora-
perience any force. We calculated that the desired fre- tion. ARTICLE Practical, 2000. 28(1): p. 206-23.
quency is around 70 kHz. 2. Huang, Y. and B. Rubinsky, Microfabricated electropo-
Finally, we will work with voltage around 10 volts and ration chip for single cell membrane permeabilization. ARTICLE
Practical, 2001. A89(3): p. 242-9.
flows around 3500 µm/s, according to reference [7]. How-
3. Hughes, M.P., R. Pethig, and W. Xiao-Bo, Dielectro-
ever it is important to know that we will need to adjust this phoretic forces on particles in travelling electric fields. ARTICLE
numbers, in order to separate effectively the dead and live Theoretical or Mathematical, 1996. 29(2): p. 474-82.
particles. 4. Jones, T.B., Book, 1995.
6. Masuda, S., M. Washizu, and I. Kawabata, Movement of
5. Review blood cells in liquid by nonuniform traveling field. ARTICLE
Theoretical or Mathematical, 1988. 24(2): p. 217-22.
7. Muller, T., et al., A 3-D microelectrode system for han-
The goal of this paper was to use the technique of dielec-
dling and caging single cells and particles. ARTICLE
trophoresis to separate dead and live mammalian cells. The Experimental, 1999. 14(3): p. ARTICLE-Experimental.
theory of DEP is well known but it is not obvious to predict 8. Pethig, R. and G.H. Markx, Applications of dielectro-
how DEP will act on mammalian cells because these cells phoresis in biotechnology. Trends in Biotechnology, 1997. 15(10):
are complex: they are not simple sphere. A cell is a mem- p. 426-432.
brane and a cytoplasm. These two parts play a very impor- 9. Pohl, H.A., Book, 1978.
tant role in the calculation of the Clausius-Mossotti func- 10. Talary, M.S., et al., Electromanipulation and separation
tion. To simplify the problem, we used the model of proto- of cells using travelling electric fields. ARTICLE Experimental,
plasts for live cells and simple sphere for dead cells. These 1996. 29(8): p. ARTICLE-Experimental.
11. Washizu, M., T. Nanba, and S. Masuda. Handling of
assumptions allowed us to graphically represent Re[K(w)]
biological cells using fluid integrated circuit. in No.88CH2565-0).
and then find frequencies where we can expect to separate 1988. Pittsburgh, PA, USA: IEEE.
alive and dead cells. However, there is always the uncer- 12. Markx, G.H. and R. Pethig, Dielectrophoretic Separa-
tainty of the theoretical analysis versus the real world. That tion of Cells - Continuous Separation. Biotechnology and Bioen-
is why we need the experimentation of the test structure, to gineering, 1995. 45(4): p. 337-343.
make sure that our assumptions and simplifications are
valid. If they are not valid, a reevaluation of the theory and
the system is required.
If it works, what can we expect from this device?
If the test structure experimentally works, is evident that
optimization is the next step. There are certain variables
that must be clarified, like how fast can we deliver the sepa-
ration of cells. Moreover, with what kind of cells this proc-
ess can be performed. The separation speed is directly pro-
portional to the size of the microfluidic device as well as
the electrodes dimensions and dielectrophoretic force. The
variety of cells in which this process can be performed de-
pends on the dielectric properties of the particles as well as
its size and shape. It is safe to say that a more thorough
analysis should be carried out from a biological and fluid
mechanics point of view.
However, it is possible to foresee a possible application for
this system when coupled with electroporation. Electropo-
ration employs electrical pulses applied across a cell for cell
membrane permeabilization [2]. This technique is com-
monly used in biotechnology for genetic engineering or
medicine application for cells in a batch. Our system will
be of use for this particular application when the electropo-
ration is performed only on the viable cells and not the dead
cells. This will save a big amount of time when this process
is performed in a continuous basis. In addition, the latest
electroporation techniques are being carried out in chips
fully compatible with the IC fabrication process, making it
favorable for adaptation with our microfluidic system.