This document summarizes an experimental study that investigated oxygen isotopic partitioning during gas-phase silicon dioxide (SiO2) formation. The experiments involved laser ablation of silicon monoxide (SiO) in the presence of oxygen (O2) with and without hydrogen (H2). SiO2 formed in experiments without H2 showed normal mass-dependent isotopic fractionation, whereas those with H2 exhibited anomalous mass-independent fractionation. The extent of mass-independent fractionation in SiO2 increased with higher H2/O2 ratios. This provides the first experimental evidence that gas-to-particle conversion reactions can produce solids like SiO2 with oxygen isotopic compositions similar to early solar system materials like calcium-
High Entropy Alloys are a new class of alloys discovered to perform at potentially useful applications. Eg : CoCrFeMnNi is useful for Cryogenic applications and MoNbTaWV is useful for Refractory applications.
This document describes a study where researchers prepared an organic-inorganic hybrid crystal through a biomimetic mineralization process. The hybrid crystal was composed of uniform, alternating organic and inorganic layers just 1-2 nm thick. The inorganic phase was calcium phosphate nanocrystals, while the organic phases consisted of bovine serum albumin protein and sodium bis(2-ethylhexyl) sulfosuccinate surfactant. Transmission electron microscopy and X-ray diffraction showed the hybrid crystal had a highly ordered lamellar structure with the organic and inorganic components intimately integrated at the nanoscale. This biomimetic material was found to be considerably flexible and elastic.
Doped strontium vanadate: Computational design of a stable, low work function...Ryan Jacobs
Presentation at the IEEE-IVEC conference in 2016 on computational modeling of perovskite work function physics and discovery of low work function materials
The OPAL reactor and neutron instruments at the Bragg Institute operated reliably in the first quarter of 2013. Thermal neutron instruments were returned to service on schedule in March and April. The installation of a new cold neutron guide and replacement of 72m of existing guides was completed ahead of schedule during the 5-month shutdown. Two cold neutron instruments (QUOKKA and PELICAN) have been running with thermal neutrons in the interim. A new backscattering spectrometer (EMU) had its vacuum vessel installed. The National Deuteration Facility continues to provide custom deuterated materials to support research. Studies were undertaken of granular materials using the strain scanner KOWARI and a time-of-flight spectrum was
High entropy alloys (HEAs) can be produced through various methods depending on their initial state - liquid, solid, or gas. They have superior mechanical and thermal properties and potential applications in industries like transportation, energy, aerospace, and food preservation due to properties like high strength, corrosion and wear resistance. While HEAs are still an emerging field being explored, continued research on new compositions and manufacturing methods may further improve our understanding and utilization of these materials.
The document discusses nanostructured ferritic alloys which are steels strengthened with nanoscale oxide precipitates. Density functional theory calculations were performed to determine the stable structures of Ti-O, Y-O, and Ti-Y-O clusters within the ferritic matrix. The calculations found that clusters resembling the structures of bulk metal oxides like TiO2 and Y2O3 were the most stable, with mixed termination and hyperstoichiometric compositions. The interfaces between oxide precipitates and the ferritic matrix were also examined using density functional theory, finding reconstructions occurred to accommodate lattice mismatches.
Comparative Study on Strength Enhancement of Concrete using Magnetic and Norm...ijtsrd
Water performs an essential function in concrete preparation and additionally in workability and power of the concrete. The big quantity of salt and mineral content is existing in regular water. It leads to affect the sturdiness of concrete shape and also life spans of shape are reduced. One of the recent technologies used to enhance the compressive strength and workability of concrete is using magnetized water as a substitute of ordinary water in concrete mixes. This new technological know how has increased the compressive strength. Using magnetized water in concrete is fantastic in terms of decrease porosity and higher. In this technology, by using passing water through a magnetic field, the range of molecules in the water cluster is breakdown into small from 13 to 5 or 6, which reasons a decrease in the surface tension of water and also expand the pH and reduces the hardness in the water with an improvement in the workability and power of concrete. Due to the smaller measurement of molecules, the water layer surrounding the cement is thinner than normal water molecules. These initiatives are examined to compare the power of normal water and magnetized water in concrete. The discount of the quantity of salt and mineral content in water will improve resistance to corrosion excessively. In this study, the effect of magnetic water and regular water on workability and power of M30 grade concrete was studied and comparative observation for NWC and MWC by means of compression strength and spit tensile strength. K. Swathi | T. Sathieshkumar "Comparative Study on Strength Enhancement of Concrete using Magnetic and Normal Water" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-3 , April 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30638.pdf Paper Url :https://www.ijtsrd.com/engineering/civil-engineering/30638/comparative-study-on-strength-enhancement-of-concrete-using-magnetic-and-normal-water/k-swathi
High Entropy Alloys are a new class of alloys discovered to perform at potentially useful applications. Eg : CoCrFeMnNi is useful for Cryogenic applications and MoNbTaWV is useful for Refractory applications.
This document describes a study where researchers prepared an organic-inorganic hybrid crystal through a biomimetic mineralization process. The hybrid crystal was composed of uniform, alternating organic and inorganic layers just 1-2 nm thick. The inorganic phase was calcium phosphate nanocrystals, while the organic phases consisted of bovine serum albumin protein and sodium bis(2-ethylhexyl) sulfosuccinate surfactant. Transmission electron microscopy and X-ray diffraction showed the hybrid crystal had a highly ordered lamellar structure with the organic and inorganic components intimately integrated at the nanoscale. This biomimetic material was found to be considerably flexible and elastic.
Doped strontium vanadate: Computational design of a stable, low work function...Ryan Jacobs
Presentation at the IEEE-IVEC conference in 2016 on computational modeling of perovskite work function physics and discovery of low work function materials
The OPAL reactor and neutron instruments at the Bragg Institute operated reliably in the first quarter of 2013. Thermal neutron instruments were returned to service on schedule in March and April. The installation of a new cold neutron guide and replacement of 72m of existing guides was completed ahead of schedule during the 5-month shutdown. Two cold neutron instruments (QUOKKA and PELICAN) have been running with thermal neutrons in the interim. A new backscattering spectrometer (EMU) had its vacuum vessel installed. The National Deuteration Facility continues to provide custom deuterated materials to support research. Studies were undertaken of granular materials using the strain scanner KOWARI and a time-of-flight spectrum was
High entropy alloys (HEAs) can be produced through various methods depending on their initial state - liquid, solid, or gas. They have superior mechanical and thermal properties and potential applications in industries like transportation, energy, aerospace, and food preservation due to properties like high strength, corrosion and wear resistance. While HEAs are still an emerging field being explored, continued research on new compositions and manufacturing methods may further improve our understanding and utilization of these materials.
The document discusses nanostructured ferritic alloys which are steels strengthened with nanoscale oxide precipitates. Density functional theory calculations were performed to determine the stable structures of Ti-O, Y-O, and Ti-Y-O clusters within the ferritic matrix. The calculations found that clusters resembling the structures of bulk metal oxides like TiO2 and Y2O3 were the most stable, with mixed termination and hyperstoichiometric compositions. The interfaces between oxide precipitates and the ferritic matrix were also examined using density functional theory, finding reconstructions occurred to accommodate lattice mismatches.
Comparative Study on Strength Enhancement of Concrete using Magnetic and Norm...ijtsrd
Water performs an essential function in concrete preparation and additionally in workability and power of the concrete. The big quantity of salt and mineral content is existing in regular water. It leads to affect the sturdiness of concrete shape and also life spans of shape are reduced. One of the recent technologies used to enhance the compressive strength and workability of concrete is using magnetized water as a substitute of ordinary water in concrete mixes. This new technological know how has increased the compressive strength. Using magnetized water in concrete is fantastic in terms of decrease porosity and higher. In this technology, by using passing water through a magnetic field, the range of molecules in the water cluster is breakdown into small from 13 to 5 or 6, which reasons a decrease in the surface tension of water and also expand the pH and reduces the hardness in the water with an improvement in the workability and power of concrete. Due to the smaller measurement of molecules, the water layer surrounding the cement is thinner than normal water molecules. These initiatives are examined to compare the power of normal water and magnetized water in concrete. The discount of the quantity of salt and mineral content in water will improve resistance to corrosion excessively. In this study, the effect of magnetic water and regular water on workability and power of M30 grade concrete was studied and comparative observation for NWC and MWC by means of compression strength and spit tensile strength. K. Swathi | T. Sathieshkumar "Comparative Study on Strength Enhancement of Concrete using Magnetic and Normal Water" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-3 , April 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30638.pdf Paper Url :https://www.ijtsrd.com/engineering/civil-engineering/30638/comparative-study-on-strength-enhancement-of-concrete-using-magnetic-and-normal-water/k-swathi
Graphene oxide is synthesized by treating graphite with strong oxidizing agents like potassium chlorate, potassium permanganate, and acids. It has a layered structure with oxygen-containing functional groups such as hydroxyl and epoxy groups bonded to the basal graphene planes. These functional groups make graphene oxide hydrophilic and soluble in water. Graphene oxide can be chemically reduced by removing oxygen groups or chemically functionalized by reacting functional groups on the basal planes with other molecules through covalent bonding.
IA Literature Review on Synthesis and Characterization of enamelled copper wi...Editor IJCATR
This paper discusses about the survey on the various magazines, conference papers and journals for understanding the
properties of enamelled copper wires mixed with nano fillers, fundamental methods for synthesis and characterization of carbon
nanotubes. From all these papers, it was noted that the research work carried out in an enamelled copper wires filled with nano fillers
has shown better results. It was also recorded that the research work was carried mostly with single metal catalysts and very little
amount of research work has been carried out on the synthesis of carbon nanotubes using bimetallic catalysts.
High-entropy alloys (HEAs) are metallic alloys composed of at least five principal elements in near-equal concentrations. While traditionally alloys were based on a single principal element, research in the late 20th century explored multi-principal-element alloys. In 1981, Brian Cantor discovered an alloy with five equal-parts elements that formed a single FCC phase. Independent work by Jien-Wei Yeh in the 1990s developed the concept of HEAs, where high entropy of mixing favors formation of solid solution phases. Yeh's 2004 paper was the first to elucidate the HEA concept and provide experimental evidence. Research in HEAs has grown rapidly since, with its unique microstructures and properties offering
IRJET- A Review on Sputtered Zirconium based Thin FilmsIRJET Journal
The document summarizes research on sputtered zirconium-based thin films. It reviews 5 studies that deposited zirconium oxynitride films using various sputtering techniques like RF magnetron sputtering and analyzed the films' properties. The studies found that deposition parameters like temperature, gas flow rates, and power affected the films' crystal structure, morphology, hardness, and optical properties. Substrate materials included stainless steel, silicon, and glass. Properties analyzed included crystal structure, grain size, roughness, thickness, band gap, and corrosion resistance. Together the studies demonstrated how sputtering can be used to deposit zirconium oxynitride thin films and influence their resulting characteristics.
This document describes an interlaboratory comparison of magnesium isotopic compositions in 12 geological standards with compositions ranging from felsic to ultramafic. The standards were analyzed in five laboratories using multicollector inductively coupled plasma mass spectrometry. The key findings were:
- Magnesium isotopic compositions agreed within uncertainties for most standards between laboratories, but some mafic samples differed by up to 0.3‰.
- The interlaboratory differences did not correlate with matrix element concentrations and likely arose from variations in column chemistry procedures between labs.
- The study highlights the need for well-calibrated standards with matrices matching samples to reduce interlaboratory biases in magnesium isotope analysis.
COMPARATIVE STUDY ON HEAVY METAL CHARACTERISTICS OF LEACHATE FROM MUNICIPAL ...IJSIT Editor
Rapid urbanization and population growth are largely responsible for very high increasing rate of
solid waste in the urban areas, its proper management and recycling is major problems of Municipal
Corporation. The analytical analysis revealed that the leachate show high concentration of heavy metals viz.,
Pb, Zn, Fe, Mn and Cu. However, their high concentration in municipal solid waste leachate may cause
contaminants for environmental pollution. Therefore, present investigation deals with analyze the heavy
metals concentration in municipal solid waste leachate.
The document discusses carbon nanotube synthesis via chemical vapor deposition (CVD) methods. It describes the CVD process which involves preparing a substrate with a metal catalyst and heating it while flowing carbon-containing and process gases to decompose at the metal sites and form nanotubes. Common catalysts used are nickel, cobalt and iron. The diameters of the nanotubes depend on catalyst particle size which can be controlled. CVD is a common industrial production method and issues involve catalyst support removal and achieving vertically aligned nanotube growth orientation.
This document provides an overview of high entropy alloys (HEAs). It discusses how HEAs were discovered in 1996 and research interest increased after 2004 papers by Yeh and Cantor. Key points include: HEAs have 5+ principal elements each between 5-35% concentration; entropy effect stabilizes solid solution phase; criteria for HEAs include parameters like entropy of mixing and valence electron concentration; four core effects are lattice distortion, sluggish diffusion, cocktail effect, and formation of solid solution phase. Examples of HEA applications discussed are coatings, bulk metallic glass, and refractory and carbide/cermet materials. The conclusion emphasizes that computational modeling of HEA properties could help address misconceptions about these materials.
Perovskite solar cells are a promising photovoltaic technology that has seen rapid increases in efficiency from 3.8% in 2009 to 19.3% in 2014. Perovskites have a unique crystal structure and can be prepared through various methods like spin coating and inkjet printing. They offer benefits such as high absorption, tunable bandgaps, and flexibility. However, challenges remain around stability issues from oxygen, moisture, UV light and heat that can be addressed through material engineering and encapsulation. With further research into replacing lead and improving stability, perovskite solar cells have the potential to become a leading solar technology of the future.
The document analyzes the microstructural evolution of two austenitic stainless steels (BS1648 and BSEN10222-5) used in nuclear reactors. Thermodynamic predictions of phase fractions were compared to experimental results. For BS1648 samples, predictions varied by up to 20% ferrite, while BSEN10222-5 was predicted to be fully austenitic. Experimental XRD and EBSD analysis found deviations from predictions, with one BS1648 sample having 30% ferrite instead of the predicted 0%. Aged BS1648 sample 5 contained 60-67% ferrite and sigma phase, lower austenite than predicted. While predictions of relative fractions were unreliable, they correctly predicted
Strain effect in the crystal structure causes enhanced catalytic effect which is very beneficial for different process. In this Presentation it is discussed how the strain is generated and what is its effect.
This document lists seven publications by Lin Gao between 2003 and 2009. It includes three journal articles, one book, and three conference presentations or posters on topics related to the structural investigation and characterization of cluster-assembled materials using techniques like mass spectrometry and transmission electron microscopy. The publications examine materials ranging from gas phase to condensed phase clusters containing elements like gold, zirconium, and transition metals.
This document proposes the synthesis of a fluorescent derivative of cholesterol for visualization of apoptosis. It involves modifying cholesterol through attachment of a BODIPY (fluorescent) moiety and trilobolid (SERCA inhibitor) to produce a "chimeric" compound. The synthesis plan involves preparation of intermediates, attachment through stable ether bonds, and characterization of the final product. The goal is to create a compound that can be used to image apoptosis in live cancer cells through its fluorescence properties and targeting of biological membranes and SERCA inhibition.
(1) The authors investigated plasmonic coupling between gold (Au) and indium tin oxide (ITO) nanocrystals by measuring their optical properties as a function of composition and interparticle spacing.
(2) They found that as more Au or ITO nanocrystals were added to films of varying composition, the plasmon peaks of both materials blueshifted and narrowed, suggesting plasmonic coupling.
(3) Decreasing the spacing between nanocrystals via ligand exchange also led to greater peak shift and broadening, further indicating coupling between Au and ITO plasmons similar to metallic nanocrystals.
The palaeomagnetism of glauconitic sedimentsJohn Smith
The palaeoenvironmental significance of glaucony has long been appreciated, but accurate palaeomagnetic dating of events recorded by glauconitic horizons requires an understanding of how glauconitic sediments acquire a remanent magnetization. Pure glauconitic minerals are paramagnetic, but glauconite grains are large and slow-forming (over periods that can exceed 100 kyr), with complex and variable morphologies. It is, thus, possible that small magnetic grains within glaucony particles may carry a significant fraction of the remanence in weakly magnetized sediments. Any remanence carried by glauconitic grains may therefore represent the geomagnetic field at a time significantly later than the time of deposition, or a time-averaged signal over some or all of the formation period. We investigated this problem using weakly magnetic Palaeocene glauconitic siltstones from southern New Zealand. We disaggregated the rock and separated it magnetically into glauconitic and non-glauconitic fractions. Results from stepwise isothermal remanent magnetization (IRM) acquisition, alternating-field demagnetization, temperature dependence of magnetic susceptibility, and stepwise thermal demagnetization of a triaxial IRM were used to demonstrate that the remanent magnetization is carried by single-domain or pseudo-single-domain magnetite in the non-glauconitic sediment fraction, and that the glauconite grains themselves make no contribution to the remanent magnetization. However, accurate measurement of the primary remanence is complicated by a strong viscous overprint and mineral alteration during thermal demagnetization studies. Identification of magnetite as the remanence carrier in sediments within a reducing diagenetic environment gives confidence that the remanence has a depositional origin. Glauconite does not carry a remanence; therefore, its effect is to dilute and weaken the overall magnetization. Furthermore, the use of rock magnetic parameters may be problematic when glauconite concentrations are (as in the studied sediments) orders of magnitude greater than remanence carrier concentrations, because in such cases the glauconite susceptibility can dominate that of the remanence carriers.
This document summarizes a study investigating the longevity of fixed partial dentures (FPDs) in relation to the alloy used. 81 clinical cases using 3 different alloy types for FPD frameworks (palladium, cobalt, and nickel) were observed over 10 years. Palladium alloys showed the highest average longevity at 11.1 years. Cobalt alloys averaged 8.2 years while nickel alloys were 9.5 years. The alloys provided stability in FPDs for an average of 9.7 years. The study concluded palladium is the most suitable alloy due to its longevity and that FPDs can have good longevity thanks to alloy properties that bond metal to ceramics.
This document discusses the use of colloidal nanostructures for environmental contaminant capture. It provides two case studies: (1) Zr-based metal organic frameworks (MOFs) that have high surface areas and pore sizes allowing them to effectively adsorb various organic and inorganic contaminants; and (2) CuZr bimetallic nanoparticles that show favorable binding of carbon dioxide through computational modeling and experiments. The document also briefly mentions other applications of multifunctional nanoparticles for water treatment and challenges in scaling up these colloidal structures.
The document provides an overview of geopolymers, including:
1) Geopolymers are inorganic materials that form long-range, covalently bonded networks, and were coined in 1978.
2) They have various uses such as fire-resistant coatings and encapsulating toxic waste.
3) Their microstructure is amorphous at room temperature but crystalline at over 500 degrees Celsius.
Vastned is a specialized high street property fund focused on premium retail locations in popular European cities. In 2013, the company further improved its property portfolio to be more focused on high-quality high street assets. The organization also placed more emphasis on hands-on management. Country teams now work more closely together and some personnel changes were made. Financing was also diversified through additional capital sources. The CEO believes choosing high street shops provides quality, stability and predictability through strong retailers that attract loyal customers and generate consistent cash flows.
Graphene oxide is synthesized by treating graphite with strong oxidizing agents like potassium chlorate, potassium permanganate, and acids. It has a layered structure with oxygen-containing functional groups such as hydroxyl and epoxy groups bonded to the basal graphene planes. These functional groups make graphene oxide hydrophilic and soluble in water. Graphene oxide can be chemically reduced by removing oxygen groups or chemically functionalized by reacting functional groups on the basal planes with other molecules through covalent bonding.
IA Literature Review on Synthesis and Characterization of enamelled copper wi...Editor IJCATR
This paper discusses about the survey on the various magazines, conference papers and journals for understanding the
properties of enamelled copper wires mixed with nano fillers, fundamental methods for synthesis and characterization of carbon
nanotubes. From all these papers, it was noted that the research work carried out in an enamelled copper wires filled with nano fillers
has shown better results. It was also recorded that the research work was carried mostly with single metal catalysts and very little
amount of research work has been carried out on the synthesis of carbon nanotubes using bimetallic catalysts.
High-entropy alloys (HEAs) are metallic alloys composed of at least five principal elements in near-equal concentrations. While traditionally alloys were based on a single principal element, research in the late 20th century explored multi-principal-element alloys. In 1981, Brian Cantor discovered an alloy with five equal-parts elements that formed a single FCC phase. Independent work by Jien-Wei Yeh in the 1990s developed the concept of HEAs, where high entropy of mixing favors formation of solid solution phases. Yeh's 2004 paper was the first to elucidate the HEA concept and provide experimental evidence. Research in HEAs has grown rapidly since, with its unique microstructures and properties offering
IRJET- A Review on Sputtered Zirconium based Thin FilmsIRJET Journal
The document summarizes research on sputtered zirconium-based thin films. It reviews 5 studies that deposited zirconium oxynitride films using various sputtering techniques like RF magnetron sputtering and analyzed the films' properties. The studies found that deposition parameters like temperature, gas flow rates, and power affected the films' crystal structure, morphology, hardness, and optical properties. Substrate materials included stainless steel, silicon, and glass. Properties analyzed included crystal structure, grain size, roughness, thickness, band gap, and corrosion resistance. Together the studies demonstrated how sputtering can be used to deposit zirconium oxynitride thin films and influence their resulting characteristics.
This document describes an interlaboratory comparison of magnesium isotopic compositions in 12 geological standards with compositions ranging from felsic to ultramafic. The standards were analyzed in five laboratories using multicollector inductively coupled plasma mass spectrometry. The key findings were:
- Magnesium isotopic compositions agreed within uncertainties for most standards between laboratories, but some mafic samples differed by up to 0.3‰.
- The interlaboratory differences did not correlate with matrix element concentrations and likely arose from variations in column chemistry procedures between labs.
- The study highlights the need for well-calibrated standards with matrices matching samples to reduce interlaboratory biases in magnesium isotope analysis.
COMPARATIVE STUDY ON HEAVY METAL CHARACTERISTICS OF LEACHATE FROM MUNICIPAL ...IJSIT Editor
Rapid urbanization and population growth are largely responsible for very high increasing rate of
solid waste in the urban areas, its proper management and recycling is major problems of Municipal
Corporation. The analytical analysis revealed that the leachate show high concentration of heavy metals viz.,
Pb, Zn, Fe, Mn and Cu. However, their high concentration in municipal solid waste leachate may cause
contaminants for environmental pollution. Therefore, present investigation deals with analyze the heavy
metals concentration in municipal solid waste leachate.
The document discusses carbon nanotube synthesis via chemical vapor deposition (CVD) methods. It describes the CVD process which involves preparing a substrate with a metal catalyst and heating it while flowing carbon-containing and process gases to decompose at the metal sites and form nanotubes. Common catalysts used are nickel, cobalt and iron. The diameters of the nanotubes depend on catalyst particle size which can be controlled. CVD is a common industrial production method and issues involve catalyst support removal and achieving vertically aligned nanotube growth orientation.
This document provides an overview of high entropy alloys (HEAs). It discusses how HEAs were discovered in 1996 and research interest increased after 2004 papers by Yeh and Cantor. Key points include: HEAs have 5+ principal elements each between 5-35% concentration; entropy effect stabilizes solid solution phase; criteria for HEAs include parameters like entropy of mixing and valence electron concentration; four core effects are lattice distortion, sluggish diffusion, cocktail effect, and formation of solid solution phase. Examples of HEA applications discussed are coatings, bulk metallic glass, and refractory and carbide/cermet materials. The conclusion emphasizes that computational modeling of HEA properties could help address misconceptions about these materials.
Perovskite solar cells are a promising photovoltaic technology that has seen rapid increases in efficiency from 3.8% in 2009 to 19.3% in 2014. Perovskites have a unique crystal structure and can be prepared through various methods like spin coating and inkjet printing. They offer benefits such as high absorption, tunable bandgaps, and flexibility. However, challenges remain around stability issues from oxygen, moisture, UV light and heat that can be addressed through material engineering and encapsulation. With further research into replacing lead and improving stability, perovskite solar cells have the potential to become a leading solar technology of the future.
The document analyzes the microstructural evolution of two austenitic stainless steels (BS1648 and BSEN10222-5) used in nuclear reactors. Thermodynamic predictions of phase fractions were compared to experimental results. For BS1648 samples, predictions varied by up to 20% ferrite, while BSEN10222-5 was predicted to be fully austenitic. Experimental XRD and EBSD analysis found deviations from predictions, with one BS1648 sample having 30% ferrite instead of the predicted 0%. Aged BS1648 sample 5 contained 60-67% ferrite and sigma phase, lower austenite than predicted. While predictions of relative fractions were unreliable, they correctly predicted
Strain effect in the crystal structure causes enhanced catalytic effect which is very beneficial for different process. In this Presentation it is discussed how the strain is generated and what is its effect.
This document lists seven publications by Lin Gao between 2003 and 2009. It includes three journal articles, one book, and three conference presentations or posters on topics related to the structural investigation and characterization of cluster-assembled materials using techniques like mass spectrometry and transmission electron microscopy. The publications examine materials ranging from gas phase to condensed phase clusters containing elements like gold, zirconium, and transition metals.
This document proposes the synthesis of a fluorescent derivative of cholesterol for visualization of apoptosis. It involves modifying cholesterol through attachment of a BODIPY (fluorescent) moiety and trilobolid (SERCA inhibitor) to produce a "chimeric" compound. The synthesis plan involves preparation of intermediates, attachment through stable ether bonds, and characterization of the final product. The goal is to create a compound that can be used to image apoptosis in live cancer cells through its fluorescence properties and targeting of biological membranes and SERCA inhibition.
(1) The authors investigated plasmonic coupling between gold (Au) and indium tin oxide (ITO) nanocrystals by measuring their optical properties as a function of composition and interparticle spacing.
(2) They found that as more Au or ITO nanocrystals were added to films of varying composition, the plasmon peaks of both materials blueshifted and narrowed, suggesting plasmonic coupling.
(3) Decreasing the spacing between nanocrystals via ligand exchange also led to greater peak shift and broadening, further indicating coupling between Au and ITO plasmons similar to metallic nanocrystals.
The palaeomagnetism of glauconitic sedimentsJohn Smith
The palaeoenvironmental significance of glaucony has long been appreciated, but accurate palaeomagnetic dating of events recorded by glauconitic horizons requires an understanding of how glauconitic sediments acquire a remanent magnetization. Pure glauconitic minerals are paramagnetic, but glauconite grains are large and slow-forming (over periods that can exceed 100 kyr), with complex and variable morphologies. It is, thus, possible that small magnetic grains within glaucony particles may carry a significant fraction of the remanence in weakly magnetized sediments. Any remanence carried by glauconitic grains may therefore represent the geomagnetic field at a time significantly later than the time of deposition, or a time-averaged signal over some or all of the formation period. We investigated this problem using weakly magnetic Palaeocene glauconitic siltstones from southern New Zealand. We disaggregated the rock and separated it magnetically into glauconitic and non-glauconitic fractions. Results from stepwise isothermal remanent magnetization (IRM) acquisition, alternating-field demagnetization, temperature dependence of magnetic susceptibility, and stepwise thermal demagnetization of a triaxial IRM were used to demonstrate that the remanent magnetization is carried by single-domain or pseudo-single-domain magnetite in the non-glauconitic sediment fraction, and that the glauconite grains themselves make no contribution to the remanent magnetization. However, accurate measurement of the primary remanence is complicated by a strong viscous overprint and mineral alteration during thermal demagnetization studies. Identification of magnetite as the remanence carrier in sediments within a reducing diagenetic environment gives confidence that the remanence has a depositional origin. Glauconite does not carry a remanence; therefore, its effect is to dilute and weaken the overall magnetization. Furthermore, the use of rock magnetic parameters may be problematic when glauconite concentrations are (as in the studied sediments) orders of magnitude greater than remanence carrier concentrations, because in such cases the glauconite susceptibility can dominate that of the remanence carriers.
This document summarizes a study investigating the longevity of fixed partial dentures (FPDs) in relation to the alloy used. 81 clinical cases using 3 different alloy types for FPD frameworks (palladium, cobalt, and nickel) were observed over 10 years. Palladium alloys showed the highest average longevity at 11.1 years. Cobalt alloys averaged 8.2 years while nickel alloys were 9.5 years. The alloys provided stability in FPDs for an average of 9.7 years. The study concluded palladium is the most suitable alloy due to its longevity and that FPDs can have good longevity thanks to alloy properties that bond metal to ceramics.
This document discusses the use of colloidal nanostructures for environmental contaminant capture. It provides two case studies: (1) Zr-based metal organic frameworks (MOFs) that have high surface areas and pore sizes allowing them to effectively adsorb various organic and inorganic contaminants; and (2) CuZr bimetallic nanoparticles that show favorable binding of carbon dioxide through computational modeling and experiments. The document also briefly mentions other applications of multifunctional nanoparticles for water treatment and challenges in scaling up these colloidal structures.
The document provides an overview of geopolymers, including:
1) Geopolymers are inorganic materials that form long-range, covalently bonded networks, and were coined in 1978.
2) They have various uses such as fire-resistant coatings and encapsulating toxic waste.
3) Their microstructure is amorphous at room temperature but crystalline at over 500 degrees Celsius.
Vastned is a specialized high street property fund focused on premium retail locations in popular European cities. In 2013, the company further improved its property portfolio to be more focused on high-quality high street assets. The organization also placed more emphasis on hands-on management. Country teams now work more closely together and some personnel changes were made. Financing was also diversified through additional capital sources. The CEO believes choosing high street shops provides quality, stability and predictability through strong retailers that attract loyal customers and generate consistent cash flows.
El plan de negocio propone crear una empresa llamada Secucrypt para desarrollar productos y servicios relacionados con la seguridad de la información utilizando números primos. Los productos serán números primos generados mediante un procedimiento exclusivo para encriptar información, y los servicios incluirán generar números primos en línea, verificar su primalidad, y encriptar/desencriptar información. La empresa obtendrá ingresos por generar números primos individualmente o en masa, y vendiéndolos a terceros.
Sabuj Chakraborty is seeking a challenging position in a large organization where he can utilize his skills. He has over 10 years of experience in accounting, auditing, taxation and financial reporting. Currently, he is a Senior Officer at Alltex Group where he prepares financial statements and reports for management. Previously, he worked as a Senior Auditor at Huda Hussain & Co. and as an Accounts Officer at Faiz Traders. He holds a Masters in Business Studies from Dhaka College and a Bachelor's in Business Studies from Mohammadpur Central University. He is proficient in Microsoft Office applications and accounting software.
This document provides an agenda and information for the 6th Annual eyeforpharma Sydney Summit taking place on October 11-12, 2016 in Sydney, Australia. The summit will focus on collaboration, access and regulation, and focusing beyond pills to patients. It will include sessions on commercial strategy, sales and marketing excellence, increasing salesforce effectiveness, employing strategic marketing tactics, embracing disruption and innovation, and boosting customer interactions. The speaker faculty will include executives from pharmaceutical companies, government agencies, and other organizations. Attendees will learn tangible solutions to issues facing the pharmaceutical industry from collaborative discussions and presentations.
Tawheed Kader or better known as TK, is the Founder and CEO of Toutapp. Toutapp allows salesmen visibility so they can track and optimize emails. TK has vast amounts of data that can be used to decipher exactly when and how to engage with your prospect.
What you will learn:
-What sales messaging is proven to work best.
-How to optimize your messaging to establish the perfect sales campaigns.
-How and when to reach out.
-How to make your company look more established when dealing with larger entities.
Visit SalesHacker.com for more sales hacks, tips, and tactics.
Este documento presenta los resultados de una encuesta de satisfacción realizada a usuarios adultos de un centro de salud en 2011 y 2014. Los resultados muestran que aunque el tiempo de espera para obtener cita ha aumentado, los usuarios están muy satisfechos con la atención recibida por el personal médico y de enfermería, así como con la limpieza de las instalaciones. La valoración global del centro de salud ha mejorado significativamente en los últimos dos años.
The future of banking - NextBank Sydney 2013Jenny Williams
The future of finance is digital. If you are a financial services company. The problem isn’t predicting whats going to happen or what you NEED to do .... its figuring out what you CAN do and HOW you are going to achieve it.
Manchester Metropolitan University lights up campus with Gewiss Street [o3]Natalie Keuroghlian
Manchester Metropolitan University installed 49 LED streetlights from Gewiss to improve safety and energy efficiency on their Crewe campus. As the leading green university, MMU is committed to using energy efficient equipment to reduce their environmental impact. The new LED streetlights will help lower MMU's energy consumption and carbon footprint. Dr. John Hindley, Head of Environmental Strategy at MMU, praised the streetlights for their high quality, energy efficiency, and stylish design.
Este documento describe los conceptos básicos de los árboles binarios, incluyendo nodos, raíces, padres, hijos, hermanos, hojas, nodos terminales, caminos, descendientes, ancestros, niveles, grados de nodos, alturas, árboles binarios completos, igualdad y semejanza de árboles binarios, pesos, y formas de recorrer árboles binarios en preorden, inorden y posorden. También describe cómo ordenar un árbol binario y cómo representar expresiones matemáticas mediante
Presentación sobre una "Introducción a la propiedad industrial: patentes y modelos de utilidad" hecha en el marco del curso de posgrado de Experto en gestión de proyectos internacionales de I+D+i de la Universidad Internacional de Andalucia, organizado por CITAndalucia el 9 de marzo de 2010
Este documento proporciona una guía detallada sobre cómo usar LinkedIn de manera efectiva para construir una marca personal. Explica qué es LinkedIn y por qué es importante estar presente, luego proporciona instrucciones paso a paso sobre cómo configurar un perfil completo, agregar experiencia y educación, y usar funciones como grupos y páginas de empresa. El objetivo general es mostrar a los lectores cómo LinkedIn puede usarse como una plataforma poderosa para establecer redes profesionales, encontrar nuevas oportunidades de empleo y proyectar una imagen
En esta sesión, los estudiantes aprenderán a expresar el diseño de partes asignadas a cultivos en un biohuerto escolar usando la multiplicación de fracciones. Trabajarán en grupos para crear un croquis de un biohuerto indicando con fracciones las parcelas destinadas a diferentes cultivos. Aprenderán a usar gráficos y procedimientos para multiplicar fracciones al resolver un problema sobre las porciones de un biohuerto asignadas a lechugas y lechugas nacionales.
Consistencia y diversidad: buscando un denominador común en la arquitectura d...Brainventures
El documento habla sobre la arquitectura de comunicación y la diferencia entre elementos explícitos e implícitos. Los explícitos son rasgos tangibles como un jingle o frase, mientras que los implícitos son intenciones, estructuras e inspiraciones sugeridas. Recomienda comenzar definiendo los implícitos como la intención, ubicación, sujetos y contexto para luego construir elementos explícitos que los expresen.
El documento describe las características de los CD-ROM y HTML. Los CD-ROM utilizan láseres para almacenar grandes cantidades de datos digitales. Pueden almacenar hasta 900 MB de información, lo suficiente como para 1000 novelas. HTML es el lenguaje estándar para crear páginas web y ha evolucionado para adaptarse a diferentes dispositivos. Utiliza etiquetas para definir el contenido y estructura de una página web.
- The presentation discusses virtual donor walls and interactive donor recognition experiences that are not tied to traditional, facility-based displays. It emphasizes maximizing the virtual and interactive aspects.
- Various experts and their views are presented, such as how social media allows for two-way communication rather than just information sharing, and how gaming can motivate people and build community.
- Effective donor recognition requires considering the donor experience and customizing approaches based on factors like donor interests, habits, and return on investment through horizontal segmentation. Testing approaches is also recommended.
El documento resume conceptos clave de la óptica como la luz, sus propiedades y características. Explica que la luz se propaga a velocidades extremadamente altas a través de ondas electromagnéticas, y describe experimentos históricos clave de Galileo, Romer y Fizeau para medir la velocidad de la luz.
This study examines lunar basalt sample 10020, which is approximately 3.7 billion years old. Paleomagnetic measurements and petrologic analysis reveal the sample contains a stable natural remanent magnetization acquired in a magnetic field of at least 12 microteslas. This provides evidence the lunar dynamo, which was likely present 4.2 billion years ago, persisted for at least another 500 million years. A long-lived lunar dynamo would have required an energy source beyond secular cooling of the lunar interior. The findings extend knowledge of the lunar dynamo and present a challenge to current dynamo theory.
This document describes research on depositing semiconductors and metals within the pores of microstructured optical fibers using high-pressure microfluidic chemical vapor deposition. Specifically, it demonstrates the fabrication of germanium nanotubes, coaxial heterojunction structures, and longitudinally patterned structures within fiber pores. This integration of functional materials into optical fibers could enable new fiber-integrated optoelectronic devices and materials.
This document presents the results of a neutron reflectometry study investigating the hydration of ultrathin antifouling organosilane adlayers on oxidized silicon wafers. The study finds that for a monoethylene glycol silane adlayer, there exists a relatively thick, continuous transition zone of water stemming from within the adlayer. In contrast, for a less effective adlayer lacking internal ether oxygen atoms, this physically distinct interfacial water phase is much thinner and confined to the adlayer-bulk water interface. These results provide further insight into the link between surface hydration and antifouling properties of organosilane adlayers.
The gravity field_and_interior_structure_of_enceladusSérgio Sacani
The gravity field and interior structure of Enceladus were determined using Doppler data from three Cassini flybys. There is a negative mass anomaly in the south polar region, largely compensated by a positive subsurface anomaly consistent with a regional subsurface sea at depths of 30-40 km extending to 50° south latitude. Enceladus deviates mildly from hydrostatic equilibrium, with estimated quadrupole coefficients indicating a differentiated body with a low-density core.
The gravity fieldandinteriorstructureofenceladusGOASA
The Cassini spacecraft measured Enceladus' gravity field during three flybys. The results indicate a negative mass anomaly over the south pole, likely compensated by a subsurface sea of water 30-40 km deep extending to 50° south latitude. Analysis of the gravity data suggests Enceladus has differentiated into a low-density core with a moment of inertia around 0.335 times its mass times the square of its radius, consistent with the presence of liquid water beneath the surface. The endogenic heat output and gravity data are best explained by models involving tidal heating of Enceladus' interior through past or current orbital resonances.
Reduction of cu o and cu2o with h2 h embedding and kinetics effects in the ...Luciana Pirone
This document summarizes a study that used time-resolved X-ray diffraction, X-ray absorption fine structure spectroscopy, and density functional theory calculations to investigate the reduction of CuO and Cu2O with hydrogen gas. The main findings were:
1) CuO reduces directly to metallic copper without forming intermediate copper suboxides like Cu4O3 or Cu2O under normal hydrogen flow rates.
2) The reduction of CuO is easier than the reduction of Cu2O, with apparent activation energies of 14.5 kcal/mol and 27.4 kcal/mol, respectively.
3) During CuO reduction, the system can reach metastable states and react with hydrogen instead of
Sodium and Strontium -Structure and solubilityyiming li
This document summarizes a study investigating the influence of sodium (Na+) and strontium (Sr2+) on the structure and solubility of bioactive glass. Three glass compositions were synthesized containing either Na+, Sr2+, or equal amounts of both. Characterization techniques found the glasses had similar structures but Sr2+ glasses had higher transition temperatures and hardness. Sr2+ glasses also showed much lower ion release rates than Na+ glasses. Cell studies found the glasses were not cytotoxic and cells adhered to all glass surfaces.
Edri And Regev 2009 “Shaken, Not Stable”: Dispersion Mechanism and Dynami...edrier
This study examines the dispersion dynamics of single-walled carbon nanotubes (SWNTs) stabilized by bovine serum albumin (BSA) protein. The researchers investigated how BSA properties like charge and conformation affect SWNT exfoliation during sonication and subsequent recovery after centrifugation. They found that bulkier BSA conformations led to faster exfoliation and higher SWNT recovery, while higher BSA-to-SWNT ratios resulted in slower exfoliation dynamics and lower recoveries. The study links the unstable state during sonication to the stable state achieved after centrifugation removal of bundles and impurities.
The document reports on a study that developed a solution processing strategy to fabricate high-quality thin films of the vacancy-ordered double perovskite Cs2SnI6. The researchers found that incorporating a slight excess of tin iodide (SnI4) in the precursor solution improved the crystallinity, uniformity, and electron mobility of the resulting Cs2SnI6 films. They further modulated the electronic properties of the films by doping with manganese and demonstrated high-performance n-channel thin film transistors and complementary inverters made from the Cs2SnI6 perovskite, showing its potential for electronic applications.
Optical properties of (polystyrene wood buckthorn peel) compositesAlexander Decker
This document summarizes research on the optical properties of polystyrene composites doped with wood buckthorn peel at different concentrations. Samples of pure polystyrene and polystyrene with 2%, 4%, and 6% wood buckthorn peel were created using casting. Absorption coefficient, energy gap, refractive index, and extinction coefficient were determined for the samples using spectroscopy. The results showed the optical constants changed with increased wood buckthorn peel concentration. Absorption decreased with increasing wavelength. Energy gap and optical constants generally depended on crystal structure and atom arrangement. Refractive index increased with photon energy while extinction coefficient varied more at high energies.
The document reports on the discovery of a β-form crystal structure in electrospun poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHx) nanofibers. Using two different collection methods - an aluminum foil with an air gap and a high-speed rotary disk - the researchers were able to induce and observe the metastable β-form crystal structure in the macroscopically aligned PHBHx nanofibers. Characterization techniques including WAXD, FTIR, SAED and AFM-IR confirmed the presence of the β-form crystals and provided insights into the structural details and orientation at both the fiber mat and
This document summarizes research on synthesizing and characterizing coated and uncoated ferrite magnetic nanoparticles. Key points include:
- Ferrite nanoparticles were synthesized using sol-gel and microwave plasma methods and coated with SiO2, ZrO2, and Co3O4.
- XRD and TEM analysis showed the nanoparticles were on the order of 10-30 nm in size and crystalline. Coating reduced agglomeration.
- AC susceptibility measurements revealed superparamagnetic and spin glass behavior in the nanoparticles. Coating reduced surface spin disorder.
- M-H loops and field dependent AC susceptibility provided information about coercivity and interactions between particles.
So in summary, the
Photo-assisted oxidation of thiols to disulfides using cobalt ‘‘Nanorust’’ un...Pawan Kumar
Heterogeneous ‘‘Nanorust’’ containing cobalt oxide has been developed for the visible light assisted
oxidation of thiols to disulfides using molecular oxygen as an oxidant under alkaline free conditions and
therefore more environmentally friendly. Pyrolysis of heterogenized tetrasulfonated cobalt(II) phthalocyanine
(CoPcS) supported on mesoporous ceria (CeO2) transforms it into a novel heterogeneous ‘‘Nanorust’’
containing CoOx-C,N@CeO2 which exhibited higher catalytic activity than the homogeneous CoPcS as well
as the ceria immobilized CoPcS catalyst. Importantly, these catalysts could easily be recovered and recycled
for several runs, which makes the process greener and cost-effective
Cyclic conformation and nucleic acid sugar puckeringDaniel Morton
Cyclic systems are ubiquitous, in nature and synthetic chemistry. Establishing an understanding of the shape preferences (e.g., strain and energetics) regarding representative cyclic models is a powerful tool in conformational analysis. The expanded review of fundamental cycloalkanes can further assist in preferential conformational analysis of associated derivatives.
Contributed by: Roland Jones, Dane Brankle, and Peter Stevenson, University of Utah, 2015
The document describes a new flexible synthesis of pyrazoles that allows for varying substituents at the C3 and C5 positions of the pyrazole ring. The synthesis involves coupling protected alkynols with acid chlorides to form alkynyl ketones, which are reacted with hydrazine to install the pyrazole nucleus. Alcohol deprotection and conversion to chlorides provides access to 5-substituted 3-(chloromethyl)- or 3-(2-chloroethyl)pyrazoles. These chlorides can then undergo nucleophilic substitution to generate other polyfunctional pyrazoles. The significance is that substituents at C5 control the steric environment around the pyrazole N-H
Nanophotonic enhancement and improved electron extraction in perovskite solar...Pawan Kumar
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the perovskite and TiO2, coupled with strong Mie scattering in the nanorod geometry results in broadband near-zero backscattering and high forward scattering, upon coating of HATNRs with perovskite. The maximum suppression of backscattering is found at ∼600 nm. The HATNRs ETL also improves the extraction of electrons from the perovskite layer and results in superior blocking of carrier recombination at the perovskite layer/FTO interface.
Nanophotonic enhancement and improved electron extraction in perovskite solar...Pawan Kumar
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the …
This document summarizes the fabrication of surface-confined heterometallic molecular triads (SURHMTs) on solid substrates. SURHMTs were fabricated using terpyridyl complexes of Fe, Os, and Ru as metalloligands and Cu2+ ions as linkers. Optical and electrochemical studies showed efficient electronic communication within the triads. The triads exhibited a combination of optical bands from the individual complexes and multiple redox peaks. One triad was investigated for use in molecular logic gates based on its interaction with a redox-active molecule.
Investigation of interfacial properties at quartz alkane interfaces using mol...IAEME Publication
The document discusses a molecular dynamics simulation investigating the interfacial properties of α-quartz/alkane interfaces. Specifically, it examines the density and orientation order parameter of decane and tetracosane molecules near hydroxyl-terminated and hydrogen-terminated α-quartz (100) surfaces at various temperatures. The simulation models the α-quartz using the Lopes force field and models the alkanes using the NERD united atom force field. Results show that adsorption of alkane molecules is more pronounced at lower temperatures. Orientation of molecules near the hydrophilic surface is more parallel to the interface than those near the hydrophobic surface. Density profiles reveal oscillating densities near the interface with higher peaks indicating more ordering.
Similar to Formation SiO2 Mass-Independent Oxygen Isotopic Partitioning During Gas-Phase (20)
Offshore fresh groundwater reserves as a global phenomenonCarlos Bella
There is mounting evidence that vast reserves of fresh and brackish groundwater exist below continental shelves around the world. These offshore fresh groundwater reserves (OFGRs) were formed when sea levels were lower during glacial periods, exposing continental shelf areas that became recharged with precipitation and glacial meltwater. While some OFGRs may still be connected to modern coastal groundwater systems, many appear to be relics of past hydrological conditions and are termed "palaeo-groundwater". The largest documented OFGR is below the New Jersey shelf, where freshwater has been found over 100km offshore. Global occurrences of OFGRs have also been identified through borehole and geophysical data in locations such as the North
Revealing letters in rolled Herculaneum papyri by X-ray phase-contrast imagingCarlos Bella
X-ray phase-contrast tomography was used to read letters hidden inside two unopened Herculaneum papyri without damaging them. In a fragment of one papyrus, two Greek words were identified on a hidden layer. In an intact rolled papyrus, several letter sequences were revealed, including "APN", "HEY", and "KI". This non-destructive technique opens opportunities to read many rolled Herculaneum papyri and enhance knowledge of ancient Greek literature.
Animal behaviour: Incipient tradition in wild chimpanzeesCarlos Bella
This study observed the adoption of a new tool use behavior, moss sponging, by chimpanzees at the Sonso community in Uganda's Budongo Forest. The dominant male was first observed using a moss sponge to drink from a small flooded waterhole. Over the next six days, six other chimpanzees began displaying this behavior after observing the dominant male and female. The researchers used a statistical technique called network-based diffusion analysis to show the spread of this innovation was consistent with social learning along social network pathways, providing the first direct evidence of cultural diffusion in wild chimpanzees.
Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075...Carlos Bella
1) The asteroid (29075) 1950 DA is rotating faster than would be allowed without cohesive forces, with a rotation period of just over 2 hours.
2) Thermal infrared observations and measurements of its orbital drift were used to determine it has a low bulk density of 1.7 g/cm3, indicating it is a rubble pile asteroid made of smaller pieces held together weakly.
3) For it to retain its fine-grained surface and resist breaking up from centrifugal forces at its rate of rotation, cohesive van der Waals forces between the grains comparable to lunar regolith are required, with a minimum cohesive strength of 64 Pa.
Detection of Radio Emission from FireballsCarlos Bella
This document summarizes the detection of radio emissions from fireballs (very bright meteors) using the Long Wavelength Array radio telescope. A search of over 11,000 hours of all-sky radio images found 49 long-duration radio transients. Ten of these transients correlated spatially and temporally with fireballs detected by an optical meteor monitoring network. This provides evidence that fireballs emit previously undiscovered low frequency radio pulses. Further analysis found characteristics inconsistent with expected radio reflections from meteor trails, suggesting a non-thermal radio emission mechanism from the fireballs. This identifies a new class of natural radio transients and provides a new probe to study meteor physics.
This document is the introduction to The Skeptic Encyclopedia of Pseudoscience. It provides an overview of the encyclopedia, which aims to objectively analyze prominent scientific and pseudoscientific claims. The introduction discusses the relationship between facts and theories in science. It notes that observations must be viewed through theoretical lenses, and references Darwin's view that observations are only useful if they are for or against some view. The introduction also discusses how views of science have changed over time between seeing it as progressively approaching truth, and as a relativistic social construct. It argues the field has moved to a more balanced middle view. The goal of the encyclopedia is to explore the borderlands where theory and data intersect, with the aim of achieving a
Preserved flora and organics in impact melt brecciasCarlos Bella
This document discusses the preservation of organic matter and plant remains in impact melt breccias found in Argentina. Analyses found centimeter-scale leaf fragments encapsulated in the impact glass that exhibited remarkable cellular-level preservation. Organic matter was also detected, including polycyclic aromatic hydrocarbons, alkanes, and pigment-like structures similar to chlorophyll. Heating experiments showed temperatures above 1500°C were required to preserve morphology, suggesting the impact process rapidly quenched and encapsulated the organic material. These findings demonstrate the potential for impact events to preserve biomarkers of early life on Mars.
A Sedna-like body with a perihelion of 80 astronomical unitsCarlos Bella
1) The document reports the discovery of 2012 VP113, the second known object after Sedna with an extremely distant perihelion of 80 AU, confirming that Sedna is not isolated.
2) Simulation results suggest there may be few inner Oort cloud objects with perihelia between 50-75 AU, and the population increases with perihelion distances greater than 75 AU.
3) Both Sedna and 2012 VP113 have similar arguments of perihelion, as do all other objects beyond 150 AU, suggesting they were perturbed by a possible unseen super-Earth mass perturber in the outer solar system that could restrict their arguments of perihelion.
Fuel gain exceeding unity in an inertially confined fusion implosionCarlos Bella
The document summarizes key results from experiments achieving fusion fuel gains exceeding unity using a "high-foot" laser pulse shape on the National Ignition Facility. Specifically:
1) Experiments achieved fusion fuel gains over unity for the first time, representing a 10x improvement over past experiments, and showed significant alpha heating and evidence of ignition requirements being met.
2) The "high-foot" pulse shape reduces instability during implosions by increasing ablation velocity and density scale length, improving stability compared to past "low-foot" experiments.
3) Improved performance is attributed to reduced mix from the ablator, with experiments pushing higher velocities through laser power and pattern optimization while maintaining hotspot shape control.
This document summarizes meteor phenomena and bodies. It discusses the different types of interactions that can occur when meteoroids collide with Earth's atmosphere, including meteors, fireballs, bolides, explosive impacts, and meteoric dust particles. It also describes the various stages of a meteoroid's trajectory through the atmosphere, including orbital motion, preheating, ablation, dark flight, and impact. Finally, it provides an overview of the size ranges and velocities associated with different meteor phenomena.
The Origin Of The 1998 June BoöTid Meteor ShowerCarlos Bella
The document analyzes the origin of the 1998 June Boötid meteor shower through comparing orbital elements and simulating particle release from the potential parent comet 7P/Pons–Winnecke. It finds that:
1) 7P/Pons–Winnecke best matches the shower orbit based on the Tisserand invariant and D-discriminant.
2) Simulations show particles released from 7P/Pons–Winnecke in 1819 and 1869 were Earth-crossing in 1998 after Jovian perturbations altered their orbits starting in the 1940s.
3) This identifies 7P/Pons–Winnecke as the parent comet and 1819 and 1869 as the active returns
Physics first spectrum of ball lightningCarlos Bella
Researchers in China measured the first spectrum of ball lightning. They observed ball lightning form after a cloud-to-ground lightning strike about 900 meters away. The spectrum contained emission lines from silicon, iron, and calcium, elements common in soil. This supports the theory that ball lightning is formed when lightning vaporizes soil, producing glowing nanoparticles. It was about 2 meters wide and drifted horizontally for 30 meters before rising a few meters. This is the first direct observation of ball lightning forming from a lightning strike and the first measurement of its emission spectrum.
1) PSR J033711715 is a millisecond pulsar discovered to be in a hierarchical triple system with two white dwarf companions, making it the first known millisecond pulsar triple system.
2) Precise timing observations using multiple radio telescopes determined the masses of the pulsar (1.4378 solar masses), inner white dwarf companion (0.19751 solar masses), and outer white dwarf companion (0.4101 solar masses) to high precision.
3) The unexpectedly coplanar and nearly circular orbits of the system indicate an exotic evolutionary history and provide an opportunity to test theories of general relativity by studying the interactions between the bodies.
Transient Water Vapor at Europa’s South PoleCarlos Bella
1) Hubble Space Telescope images from November and December 2012 of Europa's atmosphere detected statistically significant surpluses of hydrogen Lyman-α and oxygen OI130.4 nm emissions above Europa's southern hemisphere in December 2012.
2) These emissions were observed in the same region over a period of ~7 hours, suggesting an inhomogeneous atmosphere, consistent with two 200-km-high plumes of water vapor with column densities of about 1020 m−2.
3) No plumes were detected in November 2012 images or previous 1999 images, indicating variable plume activity possibly related to Europa's changing orbital phases and surface stresses. The December 2012 plume was seen when Europa was near apocenter.
Solid-state plastic deformation in the dynamic interior of a differentiated a...Carlos Bella
This document summarizes a study that analyzed the microstructural properties of olivine grains in the diogenite meteorite Northwest Africa 5480 using electron backscatter diffraction techniques. The study found evidence of solid-state plastic deformation in the olivine-dominated zones, represented by a well-defined lattice-preferred orientation that is best explained by high-temperature deformation via the pencil-glide slip system, typically seen on Earth in dry ultramafic rocks deformed in the mantle. Numerical modeling indicates this observation in the meteorite can be explained by large-scale downwelling in the asteroid's mantle within the first 50 million years after formation, providing evidence of dynamic planet-like processes occurring in the interior of
Broadband high photoresponse from pure monolayer graphene photodetectorCarlos Bella
This document summarizes a research article that reports on the development of a high-performance photodetector using pure monolayer graphene. The researchers introduced electron trapping centers and created a bandgap in graphene through band structure engineering. This allowed them to achieve a high photoresponsivity of 8.61 A/W, about three orders of magnitude higher than previous graphene photodetectors. Additionally, they demonstrated broadband photoresponse from visible to mid-infrared wavelengths, the broadest reported for a pure graphene photodetector. By introducing defects and quantum confinement effects, they were able to greatly increase the lifetime of photo-generated carriers and achieve carrier multiplication, resulting in high photoresponsivity across a wide spectrum
A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early...Carlos Bella
The article describes a newly discovered complete skull (D4500) from the site of Dmanisi, Georgia dating to 1.8 million years ago. It represents the earliest known completely preserved adult hominin skull. The skull possesses a small braincase of 546 cubic centimeters but also exhibits a large, prognathic face. This combination of features had not been seen before in the human fossil record. Analysis of this new skull and comparison to other remains from Dmanisi provides direct evidence of wide morphological variation within early members of the genus Homo, implying a single evolving lineage across continents.
Minor Planet Evidence for Water in the Rocky Debris of a Disrupted Extrasolar...Carlos Bella
Evidence has been found for water in the debris of a disrupted extrasolar minor planet orbiting a white dwarf star. Spectroscopic analysis of the white dwarf's atmosphere revealed an excess of oxygen that cannot be explained by oxide minerals alone, indicating the parent body was originally composed of about 26% water by mass. This demonstrates that water-bearing planetesimals can form around higher mass stars that eventually become white dwarfs. The disrupted planetesimal is the source of a circumstellar debris disk closely orbiting the white dwarf remnant.
Unique chemistry of a diamond-bearing pebble from the Libyan Desert Glass str...Carlos Bella
This document summarizes research on a unique black, shiny, and intensely fractured stone named "Hypatia" found in the Libyan Desert Glass strewnfield in southwest Egypt. Analysis showed the stone is composed primarily of amorphous carbonaceous matter containing nanodiamonds. Isotopic signatures of carbon and noble gases rule out a terrestrial origin and match cometary materials. The researchers propose Hypatia is a remnant of a comet nucleus fragment that was incorporated into the bolide that created the Libyan Desert Glass in an atmospheric airburst event 28.5 million years ago. Its shock transformation produced a weathering-resistant material that has been exceptionally preserved.
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdfMalak Abu Hammad
Discover how MongoDB Atlas and vector search technology can revolutionize your application's search capabilities. This comprehensive presentation covers:
* What is Vector Search?
* Importance and benefits of vector search
* Practical use cases across various industries
* Step-by-step implementation guide
* Live demos with code snippets
* Enhancing LLM capabilities with vector search
* Best practices and optimization strategies
Perfect for developers, AI enthusiasts, and tech leaders. Learn how to leverage MongoDB Atlas to deliver highly relevant, context-aware search results, transforming your data retrieval process. Stay ahead in tech innovation and maximize the potential of your applications.
#MongoDB #VectorSearch #AI #SemanticSearch #TechInnovation #DataScience #LLM #MachineLearning #SearchTechnology
Have you ever been confused by the myriad of choices offered by AWS for hosting a website or an API?
Lambda, Elastic Beanstalk, Lightsail, Amplify, S3 (and more!) can each host websites + APIs. But which one should we choose?
Which one is cheapest? Which one is fastest? Which one will scale to meet our needs?
Join me in this session as we dive into each AWS hosting service to determine which one is best for your scenario and explain why!
Nunit vs XUnit vs MSTest Differences Between These Unit Testing Frameworks.pdfflufftailshop
When it comes to unit testing in the .NET ecosystem, developers have a wide range of options available. Among the most popular choices are NUnit, XUnit, and MSTest. These unit testing frameworks provide essential tools and features to help ensure the quality and reliability of code. However, understanding the differences between these frameworks is crucial for selecting the most suitable one for your projects.
This presentation provides valuable insights into effective cost-saving techniques on AWS. Learn how to optimize your AWS resources by rightsizing, increasing elasticity, picking the right storage class, and choosing the best pricing model. Additionally, discover essential governance mechanisms to ensure continuous cost efficiency. Whether you are new to AWS or an experienced user, this presentation provides clear and practical tips to help you reduce your cloud costs and get the most out of your budget.
GraphRAG for Life Science to increase LLM accuracyTomaz Bratanic
GraphRAG for life science domain, where you retriever information from biomedical knowledge graphs using LLMs to increase the accuracy and performance of generated answers
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-und-domino-lizenzkostenreduzierung-in-der-welt-von-dlau/
DLAU und die Lizenzen nach dem CCB- und CCX-Modell sind für viele in der HCL-Community seit letztem Jahr ein heißes Thema. Als Notes- oder Domino-Kunde haben Sie vielleicht mit unerwartet hohen Benutzerzahlen und Lizenzgebühren zu kämpfen. Sie fragen sich vielleicht, wie diese neue Art der Lizenzierung funktioniert und welchen Nutzen sie Ihnen bringt. Vor allem wollen Sie sicherlich Ihr Budget einhalten und Kosten sparen, wo immer möglich. Das verstehen wir und wir möchten Ihnen dabei helfen!
Wir erklären Ihnen, wie Sie häufige Konfigurationsprobleme lösen können, die dazu führen können, dass mehr Benutzer gezählt werden als nötig, und wie Sie überflüssige oder ungenutzte Konten identifizieren und entfernen können, um Geld zu sparen. Es gibt auch einige Ansätze, die zu unnötigen Ausgaben führen können, z. B. wenn ein Personendokument anstelle eines Mail-Ins für geteilte Mailboxen verwendet wird. Wir zeigen Ihnen solche Fälle und deren Lösungen. Und natürlich erklären wir Ihnen das neue Lizenzmodell.
Nehmen Sie an diesem Webinar teil, bei dem HCL-Ambassador Marc Thomas und Gastredner Franz Walder Ihnen diese neue Welt näherbringen. Es vermittelt Ihnen die Tools und das Know-how, um den Überblick zu bewahren. Sie werden in der Lage sein, Ihre Kosten durch eine optimierte Domino-Konfiguration zu reduzieren und auch in Zukunft gering zu halten.
Diese Themen werden behandelt
- Reduzierung der Lizenzkosten durch Auffinden und Beheben von Fehlkonfigurationen und überflüssigen Konten
- Wie funktionieren CCB- und CCX-Lizenzen wirklich?
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5th LF Energy Power Grid Model Meet-up SlidesDanBrown980551
5th Power Grid Model Meet-up
It is with great pleasure that we extend to you an invitation to the 5th Power Grid Model Meet-up, scheduled for 6th June 2024. This event will adopt a hybrid format, allowing participants to join us either through an online Mircosoft Teams session or in person at TU/e located at Den Dolech 2, Eindhoven, Netherlands. The meet-up will be hosted by Eindhoven University of Technology (TU/e), a research university specializing in engineering science & technology.
Power Grid Model
The global energy transition is placing new and unprecedented demands on Distribution System Operators (DSOs). Alongside upgrades to grid capacity, processes such as digitization, capacity optimization, and congestion management are becoming vital for delivering reliable services.
Power Grid Model is an open source project from Linux Foundation Energy and provides a calculation engine that is increasingly essential for DSOs. It offers a standards-based foundation enabling real-time power systems analysis, simulations of electrical power grids, and sophisticated what-if analysis. In addition, it enables in-depth studies and analysis of the electrical power grid’s behavior and performance. This comprehensive model incorporates essential factors such as power generation capacity, electrical losses, voltage levels, power flows, and system stability.
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Formation SiO2 Mass-Independent Oxygen Isotopic Partitioning During Gas-Phase
1. Mass-Independent Oxygen Isotopic Partitioning During Gas-Phase
SiO 2 Formation
Subrata Chakraborty et al.
Science 342, 463 (2013);
DOI: 10.1126/science.1242237
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2. REPORTS
aqueous tubes cladded with the nanoparticle surfactants were smaller in diameter and exceptionally long, reminiscent of glass wool (Fig. 3G)
except that the structures are fully liquid. The 3D
nature of the morphology, the continuity of the
tubular structures, and the cladding of the interfaces by the nanoparticle surfactant are evident.
Thus, simply by stirring, a bicontinuous jammed
system—a “bijel” type of morphology—is achieved
without the need to modify and tune the surface
chemistry of the nanoparticle to achieve neutral
wetting, which is necessary to confine the nanoparticles to the liquid/liquid interface and impart
long-term stability to the morphology (13, 14).
The carboxylate-amine interactions between the
nanoparticles and functionalized silicone oil are
self-regulating, maximizing the reduction in the
interfacial energy, overcoming thermal energies
and stabilizing the nanoparticle surfactants at the
interface.
When the monofunctional end-capped silicone
oil was replaced with a difunctional PDMS, capped
on both ends with primary amines, the nanoparticle surfactant assemblies were stabilized even
further, as the PDMS chains bridge adjacent nanoparticles, effectively cross-linking the jammed
nanoparticle assembly (Fig. 4A). Shown in Fig.
4, B to E, are two drops of water with polystyrene
nanoparticles that were suspended in silicone oil
containing the difunctional PDMS. The length of
time that the drop at the bottom was in contact
with the silicone oil is 2 min, whereas the contact time of the upper drop is 30 s. A 4.6-kV/cm
electric field is applied, and the drop at the bottom does not deform, whereas the drop at the top
deforms. Even though the interfacial energy of
the drop at the bottom is lower, due to the increase in the number of nanoparticle surfactants
formed at the interface, the cross-linking of the
nanoparticle surfactants is greater, preventing
the deformation of the drop (movies S6 and S7).
The very strong resistance of the drop to deformation demonstrates an alternate route by which
drops of different shapes can be stabilized.
We have demonstrated a simple route to produce
and stabilize fluid drops having shapes far removed from their equilibrium spherical shape,
using the in situ formation of nanoparticle surfactants. The increased interfacial activity of the
nanoparticle surfactants stabilized the assemblies
against desorption, allowing them to jam at the
interface, arresting change in the drop shape, and
imparting long-term stability to drops with unusual shapes. The sequential application of external fields in different directions leads to local
unjamming and jamming of the assemblies, enabling the shape of the drop to be tailored into a
wide range of unusual shapes. We are currently
investigating the possibility of stabilizing asymmetric shapes to determine the importance on the
jamming process. Both electric and shear fields
were used to deform the drops, although other
fields, like magnetic and ultrasonic fields, are also
being investigated. Cross-linking the nanoparticle surfactant assemblies at the interface is shown
to increase the stability of the drop shape. These
stabilized assemblies provide easy routes for encapsulation, bicontinuous flow (microfluidic devices) or separations media, delivery vehicles, and
reaction platforms.
References and Notes
1. R. Hong et al., J. Am. Chem. Soc. 128, 1078–1079 (2006).
2. Y. Q. Shi, F. Li, Y. W. Chen, New J. Chem. 37, 236–244
(2013).
3. K. Bramhaiah, N. S. John, RSC Adv. 3, 7765 (2013).
4. D. Lee, D. A. Weitz, Adv. Mater. 20, 3498–3503 (2008).
5. C. N. R. Rao, K. P. Kalyanikutty, Acc. Chem. Res. 41,
489–499 (2008).
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7. Y. Lin, H. Skaff, T. Emrick, A. D. Dinsmore, T. P. Russell,
Science 299, 226–229 (2003).
8. A. B. Subramaniam, M. Abkarian, L. Mahadevan,
H. A. Stone, Nature 438, 930 (2005).
Mass-Independent Oxygen Isotopic
Partitioning During Gas-Phase
SiO2 Formation
Subrata Chakraborty,* Petia Yanchulova, Mark H. Thiemens
Meteorites contain a wide range of oxygen isotopic compositions that are interpreted as heterogeneity
in solar nebula. The anomalous oxygen isotopic compositions of refractory mineral phases may reflect
a chemical fractionation process in the nebula, but there are no experiments to demonstrate this
isotope effect during particle formation through gas-phase reactions. We report experimental results of
gas-to-particle conversion during oxidation of silicon monoxide that define a mass-independent line
(slope one) in oxygen three-isotope space of 18O/16O versus 17O/16O. This mass-independent chemical
reaction is a potentially initiating step in nebular meteorite formation, which would be capable of
producing silicate reservoirs with anomalous oxygen isotopic compositions.
T
he oxygen isotopic composition of hightemperature mineral phases in the first
condensates in the protoplanetary disk,
calcium-aluminum-rich inclusions (CAIs), are distributed along a slope one line in an oxygen threeisotope plot (18O/16O versus 17O/16O) with a large
www.sciencemag.org
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VOL 342
9. M. Abkarian et al., Phys. Rev. Lett. 99, 188301
(2007).
10. A. B. Pawar, M. Caggioni, R. Ergun, R. W. Hartel,
P. T. Spicer, Soft Matter 7, 7710 (2011).
11. K. Stratford, R. Adhikari, I. Pagonabarraga, J. C. Desplat,
M. E. Cates, Science 309, 2198–2201 (2005).
12. E. M. Herzig, K. A. White, A. B. Schofield, W. C. K. Poon,
P. S. Clegg, Nat. Mater. 6, 966–971 (2007).
13. B. P. Binks, S. O. Lumsdon, Langmuir 16, 8622–8631
(2000).
14. B. P. Binks, T. S. Horozov, Colloidal Particles at Liquid
Interfaces (Cambridge Univ. Press, Cambridge, 2006).
15. L. Li et al., Nano Lett. 11, 1997–2003 (2011).
16. C. Zeng, F. Brau, B. Davidovitch, A. D. Dinsmore,
Soft Matter 8, 8582 (2012).
17. P. S. Clegg et al., J. Phys. Condens. Matter 17, S3433
(2005).
18. P. S. Clegg et al., Langmuir 23, 5984–5994 (2007).
19. H. L. Cheng, S. S. Velankar, Langmuir 25, 4412–4420
(2009).
20. J. W. Tavacoli, J. H. J. Thijssen, A. B. Schofield,
P. S. Clegg, Adv. Funct. Mater. 21, 2020–2027 (2011).
21. S. A. F. Bon, S. D. Mookhoek, P. J. Colver, H. R. Fischer,
S. van der Zwaag, Eur. Polym. J. 43, 4839–4842 (2007).
22. D. Orsi, L. Cristofolini, G. Baldi, A. Madsen, Phys. Rev. Lett.
108, 105701 (2012).
23. Y. Lin et al., Langmuir 21, 191–194 (2005).
24. A. J. Liu, S. R. Nagel, Nature 396, 21–22 (1998).
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383–397 (1964).
26. O. Vizika, D. A. Saville, J. Fluid Mech. 239, 1 (1992).
27. D. A. Saville, Annu. Rev. Fluid Mech. 29, 27–64 (1997).
28. H. A. Stone, J. R. Lister, M. P. Brenner, Proc. R. Soc. London A
455, 329–347 (1999).
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Acknowledgments: This work was supported by the U.S.
Department of Energy Office of Basic Energy Science through
contract DE-FG02-04ER46126. There are no conflicts of
interest.
Supplementary Materials
www.sciencemag.org/content/342/6157/460/suppl/DC1
Materials and Methods
Figs. S1 to S4
Movies S1 to S7
8 July 2013; accepted 25 September 2013
10.1126/science.1242852
and equal depletion in 17O and 18O [~50 per mil (‰)
with respect to the terrestrial composition] (1).
Most chondrules (glassy globular condensates)
formed shortly (<1 million years) after CAIs (2)
display an oxygen isotopic distribution along an
approximate slope 1 line, with about equal 17O
and 18O enrichments over CAIs (3, 4). The oxygen isotopic distributions are notable because of
their departure from the normal terrestrial massdependent (MD) fractionation line observed for
equilibrium and kinetic fractionation processes
of slope one-half (5, 6). Defining the source of
the anomalous isotopic distribution of oxygen
is critical in the elucidation of the overall formation and evolutionary events in the early solar
system.
After the failure to find meteoritic supernova
debris signatures, the initially proposed nuclear
Department of Chemistry and Biochemistry, University of
California, San Diego, La Jolla, CA 92093–0356, USA.
*Corresponding author. E-mail: subrata@ucsd.edu
25 OCTOBER 2013
463
3. REPORTS
theory (1) was largely abandoned, and chemical, particularly photochemical, theories took
precedence as the favored explanation for the
observed oxygen isotopic distribution. Photochemical isotopic self-shielding of CO (7) has
been proposed on the basis of the predissociative
nature (isotopologue-specific absorption lines)
in the vacuum ultraviolet spectral region of CO, a
common phenomenon in molecular clouds (8).
Ozone formation was the first demonstration of
a mass-independent (MI) fractionation process
in a chemical reaction (9). Since this discovery,
the potential for producing a CAI-like isotopic
compositional trend in a gas-phase symmetrydriven recombination reaction has been suggested
(9–11). Marcus (12) introduced a symmetry-based
grain-surface assisted theoretical treatment of recombination of adsorbed species, e.g., O and SiO,
to explain the compositions of CAIs. At present,
there are no experiments that determine the isotopic
fractionation induced by the conversion of gasphase nebular oxygen species to solid species,
which is a key step in the early evolutionary stage
of the solar system.
Here, we present results of the measurement of oxygen isotopic compositions of SiO2
solids generated via gas-phase reactions under
controlled experimental conditions. In these experiments, ultrahigh purity (UHP) SiO nuggets
were lased with an excimer laser [Lambda Physik
Compex 110 (Coherent Incorporated, Santa Clara,
California), KrF, 248 nm] inside a vacuum chamber at two different initial conditions: set I, in the
presence of UHP O2, and set II, in mixtures of
UHP O2 and H2 of differing proportions. Lasing
of SiO generates a plume of neutral SiO gas
(see supplementary materials), which reacts with
the gases inside the chamber to form silicon
dioxide particles throughout the chamber. In set
III experiments, the product SiO2 is formed via
both mechanisms of set I and set II (as subsets)
experiments, and the products were collected
for analysis. Scanning electron microscopic
analysis provided the stoichiometry of SiO2 for
the product solids for all cases (fig. S2).
The measured oxygen isotopic compositions of SiO2 formed in set I–type experiments
(without H2) show MD fractionation, whereas
those produced in set II–type experiments (with
H2) reflect MI fractionation (Fig. 1 and table S1).
The corresponding isotopic compositions of the
residual oxygen reservoirs are fractionated in
MD and MI fashion, respectively, for set I and set
II experiments (fig. S3 and tables S2 and S3). The
extent of the MI component in SiO2, measured
by D17O (=d17O – 0.516 × d18O), increases with
increasing initial H2/O2 ratio, and the maximum
D17O value was ~1.7‰, measured at an H2/O2
ratio of 25.6. The higher ambient gas pressure suppresses the expansion of the laser plume and also
rapidly cools the plume by collisional deactivation
limiting the extent of oxidation in the higher ratio and
pressure experiments (see supplementary text).
Comparing the expected oxidation reactions
1 to 4 and 1 to 10 for set I and set II experiments
464
(Table 1), respectively, and their corresponding
experimental results (Fig. 1, fig. S3, and tables
S1 to S3), we suggest that the observed MI composition in the residual oxygen and product SiO2
may not be due to ozone formation [known to
generate a MI composition (9)]. Set I–type ex-
periments are the most oxidative and kinetically favor ozone formation compared with set II
types. The results from set I experiments are strictly MD (Fig. 1 and fig. S3) and cannot involve
ozone formation. Analyzing the entire data set,
we observed a MI composition only when H2 is
Fig. 1. Measured oxygen isotopic compositions in threeisotope plot. The compositions of
product SiO2 from set I– and set II–
types experiments in set III are shown
in blue squares and circles, respectively, with respect to the initial SiO
composition. Compositions of the starting SiO and oxygen and product SiO2
from set I–type experiments all lie
on a line with a MD slope of 0.516.
The SiO2 formed in set II–type experiments show MI compositions with
a slope value of 0.6. The calculated
isotopic compositions of SiO2 formed
by group 2 reactions (OH dominated,
see supplementary text) lie on a
regression line with a slope value of
1.09 T 0.1. The standard deviation
of data presented here are T 0.2‰ (much smaller than the size of the symbols).
Table 1. List of relevant reactions. Relevant reactions for set I and set II experiments.
Set I–type experiments
Set II–type experiments
Group 1
SiO + O2 → SiO2 + O
SiO + O → SiO2
O2 + hn → O + O
O + O2 + M → O3 + M
Group 2
O + H2 + M → OH + H + M
OH + H2 → H2O + H
SiO + OH → SiO2 + H
SiO + H2O → SiO2 + OH
H + O2 + M → HO2 + M
SiO + HO2 → SiO2 + OH
SiO + O2 → SiO2 + O
SiO + O → SiO2
O2 + hn → O + O
O + O2 + M → O3 + M
Reaction number
1
2
3
4
5
6
7
8
9
10
Fig. 2. Results of kinetic
model simulation. Timedependent change in concentrations of SiO2 formed
via group 1 and group 2 reactions and the concentration of O2 for the simulation
run with H2/O2 ratio of 30 is
shown for three different temperatures. The SiO2 amount
measured in the experiments
best matched the simulation
run of effective chamber temperature of 50°C. Although
the temperature of the laser
plume is high (>1000°C), the
estimated volume of the laser
plume is only ~1/100 of the chamber volume, and, therefore, the match at lower temperature (50°C) with the
experiment is reasonable. The result shows that, in set II–type experiments, group 1 reactions are the dominant
source of SiO2 formation, whereas group 2 reactions contribute only 11 to 18% of the total SiO2.
25 OCTOBER 2013
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4. REPORTS
present, requiring reactions 7, 8, and 10 to be the
source of the MI composition.
Because reaction 9 is a MI process (13), there
is a possibility that the isotopic composition measured in these experiments was acquired during
oxidation by HO2, a product of reaction 9, which
possesses a MI composition. To test HO2 reaction
channels, we performed photolysis of a mixture
of O2 and H2 in a glass chamber (without SiO)
with ultraviolet photons from the same laser as a
control. The residual oxygen was collected (after
separating it from H2 and water), and the oxygen
isotopic composition was determined to be MD
(fig. S3), indicating that the MI character measured in the set II experiments does not originate
from HO2 species via reaction channel 9.
The oxidation of CO by OH produces CO2 of
MI composition (14, 15); thus reaction 7 (SiO +
OH = SiO2 + H) may be the source of the measured MI effect because both CO and SiO possess
a homologous valence electron configuration in
their ground states (16). On the basis of symmetry
considerations, it has been proposed that a gasphase MI effect may arise from the reaction O +
SiO → SiO2 (17). An analogous reaction, O +
CO → CO2, has experimentally demonstrated notable mass-independently fractionated products
(18, 19). However, the results from set I experiments do not reflect the fractionation effects of this
process. In set I experiments, SiO2 formed through
reactions 1 and 2 may have a potential for isotope
exchange between O2 and O, and the original
isotopic signature (MI) from reaction 2 (e.g., O +
SiO → SiO2) may be removed by exchange, as
well as by the MD SiO2 produced by reaction
1 (e.g., O2 + SiO → SiO2 + O).
Avibrationally excited transition state (COOH*)
has been predicted for the CO + OH → CO2 + H
reaction (20–22), and the existence of a vibrationally excited intermediate was demonstrated
(23). A similar intermediate state (SiOOH)* for
the OH + SiO → SiO2 + H reaction is feasible,
and it is via this excited state that the observed MI
effect would be generated. The relevant source
would be the deactivation of intermediate states
leading to isotope selectivity in the product phase,
as is the case for ozone. There is no overall agreement on the mechanism for ozone formation, although symmetry is generally considered to be
the ultimate source (24).
Fig. 3. Similarity of oxygen isotopic distribution in atmosphere and meteorites. Left and
right panels represent Earth’s atmosphere and meteorites, respectively. (A) The existence of positive and negative D17O reservoirs in the atmosphere. (B) The presence of positive and negative D17O
reservoirs in the solar nebula (over a slope of ~1 line). (C) The composition of product ozone and
residual oxygen for the ozone formation experiment in the laboratory. (D) The compositions of SiO2
formed in the present experiments. The d values are normalized with starting oxygen and SiO compositions, respectively, for (C) and (D). See supplementary materials for a full list of references used
for this compilation.
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VOL 342
SiO2 samples collected in set II–type experiments are formed via multiple reaction channels
(Table 1). We developed a chemical kinetic network model including 17 different species and 30
different reactions relevant to the experiments.
Time-dependent concentration variations of different species were recorded in this model by
setting up appropriate differential equations (see
supplementary text). The simulation solutions
depict that a significant proportion of SiO2 (82 to
89%) is produced via oxidation in group 1 reactions (by O2 and O; MD in nature) with the remaining channel produced by group 2 oxidation
reactions (Fig. 2 and table S4). The model production of SiO2 via H2O2 oxidation is negligible
and consequently not specifically listed in Table 1.
Because the contributions from group 2 reactions
in the total production of SiO2 are much smaller
(<18%), the measured MI composition in set
II–type experiments are diluted by MD contributions from group 1 reactions (Fig. 1).
By considering the fractionations for the group
1 reactions to be those measured in set I reactions
and the above-mentioned fractions (of product
from groups 1 and 2), we performed an isotopic
mass-balance calculation to determine the compositions of SiO2 formed via group 2 reactions (see
supplementary text), which define a line of slope =
1.09 T 0.1 (1-s SD) passing through the calculated
SiO2 composition (d18O = –18.4‰, d17O = –9.5‰)
formed by the measured SiO + O2 reaction (Fig.
1 and supplementary text). The scatter in the calculated data set may be due to the use of a simplified treatment by grouping the reactions in two,
where there are six different reactions in group 2,
and, based on kinetics, they have different yields
at different subsets of experiments because of variation in pressures (table S3). The kinetic simulation shows that among all group 2 reactions
(which contribute <18% of total SiO2 production)
more than 90% of SiO2 forms via OH oxidation. It may be surmised from the observations
that the SiO + OH reaction follows a slope close
to unity.
SiO is a relevant solar nebular species detected in young protoplanetary nebulae and other
astronomical objects (25, 26) and is oxidized by
OH in the early nebula (27–29). It is plausible
that, in the hot (>1000 K) inner solar nebula, SiO
oxidation through OH is an initiating reaction in
solid silicate formation. Our results demonstrate
that the MI composition of meteoritic silicates
could be initially generated via OH oxidation of
the more reduced SiO, which proceeds along a
slope one line. However, transiting through an
intermediate excited state is not equilibrium in
nature, and the traditional isotopic fractionation
calculated on the basis of reduced partition functions (5) diminishes at high temperature limits
and is not applicable.
Earth’s atmosphere may be isotopically relevant in comparison to the solar nebula because
both systems have oxygen reservoirs consisting
of relative positive and negative MI anomalies
(Fig. 3, A and B). The oxygen-bearing species
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465
5. REPORTS
acquire MI signatures from the ozone formation
reaction (9) (Fig. 3C) via atomic oxygen interaction, creating small reservoirs with large positive D17O and vice versa (e.g., atmospheric O2 with
negative D17O). Similarly, in meteorites, a large
negative MI effect in minor phases (CAIs, chondrules and matrices in carbonaceous chondrites,
and Ureilites) and a smaller positive MI effect in
the more abundant classes (by mass, for example, ordinary chondrites and Rumaruti classes)
are observed. Meteoritic negative and positive
D17O reservoirs could have been originated during
the actual gas-to-particle formation process as
experimentally demonstrated here (Fig. 3D). Solar
system oxygen is more complicated, and the initial solar nebular bulk composition is inadequately defined. The measured oxygen composition of
solar wind from Genesis concentrator is enriched
in 16O compared with CAIs (30), but the oxygen
isotopic fractionation between the solar photosphere and the solar wind is not well established
and presently an open question.
The final step in the formation of solid silicate
from the gas-dominated nebula is a chemical reaction, and the fractionation occurring in this
process should be considered regardless of which
model is invoked. This reaction, if it occurs in a
solar nebula at high temperature, the effect may
be larger than observed in the present experiments given the inverse temperature dependency
as observed for ozone (31). Last, the observed
MI effect is unique to oxygen. The terminal atom
regulates the formation and stabilization of vibrationally excited symmetrically structured molecules (31, 32), and oxygen plays this critical role
in SiO2. This accounts for why other isotope
systems (e.g., Si) do not correlate with oxygen
and produce an observable symmetry-dependent
fractionation. Carbon and hydrogen are candidates but only possess two stable isotopes and
cannot prove the effect, and sulfur, with multiple
valence states and exchangeability, is not ideal
for preserving the effect.
References and Notes
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Strong Premelting Effect in the
Elastic Properties of hcp-Fe Under
Inner-Core Conditions
Benjamí Martorell,* Lidunka Vocadlo, John Brodholt, Ian G. Wood
ˇ
The observed shear-wave velocity VS in Earth’s core is much lower than expected from mineralogical
models derived from both calculations and experiments. A number of explanations have been
proposed, but none sufficiently explain the seismological observations. Using ab initio molecular
dynamics simulations, we obtained the elastic properties of hexagonal close-packed iron (hcp-Fe)
at 360 gigapascals up to its melting temperature Tm. We found that Fe shows a strong nonlinear
shear weakening just before melting (when T/Tm > 0.96), with a corresponding reduction in VS.
Because temperatures range from T/Tm = 1 at the inner-outer core boundary to T/Tm ≈ 0.99 at the
center, this strong nonlinear effect on VS should occur in the inner core, providing a compelling
explanation for the low VS observed.
arth’s inner core is predominantly made
of iron (Fe), but it is commonly assumed
to contain 5 to 10% Ni (1) and also light
elements such as Si, C, and S, ~2 to 3 weight per-
E
Department of Earth Sciences, University College London,
London WC1E 6BT, UK.
*Corresponding author. E-mail: b.massip@ucl.ac.uk
466
cent in total (1, 2). Seismic wave velocities through
the inner core are known, but at present, seismological and mineralogical models for the inner
core do not agree (3–9). A major discrepancy between the observed seismic data and current
mineralogical models derived from ab initio calculations is that these mineralogical models predict a shear-wave velocity VS that is up to 30%
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SCIENCE
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Acknowledgments: The authors thank the three anonymous
reviewers for their helpful critical comments, which helped
improve the manuscript. S.C. and M.H.T. acknowledge funding
support from NASA Cosmochemistry (NNX09AG93G) and
Origins in Solar System (NNX11AB39G) programs. We
acknowledge G. Dominguez for helping to develop the kinetic
model and helpful discussion with members of the Thiemens
research group. Data described in this paper are presented in
supplementary materials.
Supplementary Materials
www.sciencemag.org/content/342/6157/463/suppl/DC1
Materials and Methods
Supplementary Text
Figs. S1 to S4
Tables S1 to S5
References (33–70)
21 June 2013; accepted 11 September 2013
10.1126/science.1242237
greater than the seismically observed values
(4, 9, 10). The addition of small quantities of Ni
under these conditions does not reduce VS by a
sufficient amount to explain this (9), and although
the effect of light elements on the velocities of
Fe is not totally clear at inner-core conditions
(11, 12), all studies show that light-element effects
are too small [<5% in VS for 7% molar fraction in
Si at 5000 K and 13,000 kg m−3 (11)] to solve the
discrepancy.
Another possible cause of the discrepancy
between mineralogical models and seismic data
is that the elastic constants of Fe may soften drastically and nonlinearly very near to its melting
point Tm, as has been observed in other metals.
For instance, the shear modulus of Sn has been
experimentally and theoretically shown to decrease by more than 50% at temperatures within
~1% of its melting point (13, 14). According to
ab initio simulations, the melting point of pure
Fe at the conditions of the inner core is in the
range 6200 to 6900 K (15–17) according to phase
coexistence calculations (solid and liquid), with
upper limit estimates up to 7500 K (18) when
only the solid phase is heated until melting. The
highest temperature for which the elastic properties of hcp-Fe have been obtained computationally
is 6000 K (5); however, relative to the melting
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