Biologically controlled minerals as potential indicators of life

NASA Technical Reports Server (NTRS)

Schwartz, D. E.; Mancinelli, R. L.; Kaneshiro, E.

1991-01-01

Minerals can be produced and deposited either by abiotic or biologic means. Regardless of their origin, mineral crystals reflect the environment conditions (e.g., temperature, pressure, chemical composition, and redox potential) present during crystal formation. Biologically-produced mineral crystals are grown or reworked under the control of their host organism and reflect an environment different from the abiotic environment. In addition, minerals of either biologic or abiotic origin have great longevities. For these reasons, biologically produced minerals have been proposed as biomarkers. Biomarkers are key morphological, chemical, and isotopic signatures of living systems that can be used to determine if life processes have occurred. Studies of biologically controlled minerals produced by the protist, Paramecium tetraurelia, were initiated since techniques have already been developed to culture them and isolate their crystalline material, and methods are already in place to analyze this material. Two direct crystalline phases were identified. One phase, whose chemical composition is high in Mg, was identified as struvite. The second phase, whose chemical composition is high in Ca, has not been previously found occurring naturally and may be considered a newly discovered material. Analyses are underway to determine the characteristics of these minerals in order to compare them with characteristics of these minerals in order to compare them with characteristics of minerals formed abiotically, but with the same chemical composition.

Effect of Chemical Washing Pre-treatment of Empty Fruit Bunch (EFB) biochar on Characterization of Hydrogel Biochar composite as Bioadsorbent

NASA Astrophysics Data System (ADS)

Meri, N. H.; Alias, A. B.; Talib, N.; Rashid, Z. A.; Wan, W. A.; Ghani, Ab Karim

2018-05-01

Hydrogel biochar composite (HBC) is a recent interest among researchers because of the hydrophilic characteristic which can adsorb chemical fluid and showed a versatile potential as adsorbent in removing hazardous material in wastewater and gas stream. In this study, the effect of chemical washing pre-treatment by using two different type of chemical agent Hydrochloric Acid (HCL) and Hydrogen Peroxide (H2O2) was analysed and investigated. The raw EFB biochar was prepared using microwave assisted pyrolysis under 1000W for 30 min under N2 flow with 150 mL/min. To improve the adsoprtion ability, the EFB biochar has been chemical washed pre-treatment with Hydrochloric Acid (HCl) and Hydrogen Peroxide (H2O2) before polymerization process with acrylamide (AAm) as monomer, N,N’-methylenebisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. The characterization has studied by using Fourier transform infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). FTIR result shows that, the formation of Raw EFB to Hydrogel Biochar Composite (Raw EFB > EFB Biochar > Treated Biochars (HCl & H2O2) > Hydrogel Biochar Composite) have changed in functional group. For DSC result it shows that the thermal behaviour of all samples is endothermic process and have high thermal resistance.

Interaction of tungsten with tungsten carbide in a copper melt

NASA Astrophysics Data System (ADS)

Bodrova, L. E.; Goida, E. Yu.; Pastukhov, E. A.; Marshuk, L. A.; Popova, E. A.

2013-07-01

The chemical interaction between tungsten and tungsten carbide in a copper melt with the formation of W2C at 1300°C is studied. It is shown that the mechanical activation of a composition consisting of copper melt + W and WC powders by low-temperature vibrations initiates not only the chemical interaction of its solid components but also their refinement.

Nitrate removal by Fe0/Pd/Cu nano-composite in groundwater.

PubMed

Liu, Hongyuan; Guo, Min; Zhang, Yan

2014-01-01

Nitrate pollution in groundwater shows a great threat to the safety of drinking water. Chemical reduction by zero-valent iron is being considered as a promising technique for nitrate removal from contaminated groundwater. In this paper, Fe0/Pd/Cu nano-composites were prepared by the liquid-phase reduction method, and batch experiments of nitrate reduction by the prepared Fe0/Pd/Cu nano-composites under various operating conditions were carried out. It has been found that nano-Fe0/Pd/Cu composites processed dual functions: catalytic reduction and chemical reduction. The introduction of Pd and Cu not only improved nitrate removal rate, but also reduced the generation of ammonia. Nitrate removal rate was affected by the amount of Fe0/Pd/Cu, initial nitrate concentration, solution pH, dissolved oxygen (DO), reaction temperature, the presence of anions, and organic pollutant. Moreover, nitrate reduction by Fe0/Pd/Cu composites followed the pseudo-first-order reaction kinetics. The removal rate of nitrate and total nitrogen were about 85% and 40.8%, respectively, under the reaction condition of Fe-6.0%Pd-3.0%Cu amount of 0.25 g/L, pH value of 7.1, DO of 0.42 mg/L, and initial nitrate concentration of 100 mg/L. Compared with the previous studies with Fe0 alone or Fe-Cu, nano-Fe-6%Pd-3%Cu composites showed a better selectivity to N2.

Chemical composition, water vapor permeability, and mechanical properties of yuba film influenced by soymilk depth and concentration.

PubMed

Zhang, Siran; Lee, Jaesang; Kim, Yookyung

2018-03-01

Yuba is a soy protein-lipid film formed during heating of soymilk. This study described yuba as an edible film by analyzing its chemical composition, water vapor permeability (WVP), and mechanical properties. Three yuba films were prepared by using different concentrations and depths of soymilk: HS (86 g kg -1 and 2.3 cm), LS (70 g kg -1 and 2.3 cm), and LD (70 g kg -1 and 3.0 cm). As yuba was successively skimmed, the protein, lipid, and SH content decreased, but carbohydrate and SS content increased. Though both the initial concentration and the depth of soymilk affect the properties of the films, the depth of soymilk influences WVP and tensile strength (TS) more. The WVP of the HS and LS changed the least (13-17 g mm kPa -1 m -2 day 1 ), while that of the LD changed the most (13-35 g mm kPa -1 m -2 day -1 ). There were no differences (P > 0.05) in the TS between the HS and LS. LD had the greatest decrease of TS and the lowest TS among the groups. The earlier the yuba films were collected, the greater the elongation of the films was: 129% (HS), 113% (LS), and 155% (LD). The initial concentration and the depth of soymilk changed the chemical composition and structure of the yuba films. The LS yuba produced more uniform edible films with good mechanical properties. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Thermite Reaction to Produce Artificial Reefs

NASA Astrophysics Data System (ADS)

Trevino, Alexandro; Martirosyan, Karen; Kline, Richard

The degradation of coral reefs is an ecological issue that has prompted new collaboration by different scientific communities that would assist in the regeneration of the reefs. Unfortunately, these processes can be inefficient and extremely expensive prompting a new scientific approach by using solid-state combustion synthesis to regenerate the reefs. In this report we aimed to consolidate a multi-composite material to produce artificial reefs by initiating thermite reaction based on aluminum and polytetrafluoroethylene (PTFE) with natural reefs. By Thermodynamic analysis and experimentation it was established that a range between .03-.07 number of moles of PTFE was sufficient to reach an adiabatic temperature of over 1900 K, a sustained reaction and a physically stable product was achieved. Reefs are primarily composed of carbonates but their exact chemical composition can vary. X-ray diffraction analysis was used to determine the chemical composition of the reef and revealed presence of oxides, carbonates, silicates. The dominant chemical compounds that were identified are, SiO2 -17%, MgSiO3-14.5%, CaCO3- 11.4%, Ca(Si3O4). Using our thermite reaction we aimed to achieve optimal physical, chemical, and biological properties and maintain cost efficiency of the multi-composite material.

A New Multiphase Equation of State for Composition B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coe, Joshua Damon; Margevicius, Madeline Alma

2016-07-25

We describe the construction of a complete equation of state for the high explosive Composition B in its unreacted (inert) form, as well as chemical equilibrium calculations of its detonation products. The multiphase reactant EOS is of SESAME type, and was calibrated to ambient thermal and mechanical data, the shock initiation experiments of Dattelbaum, et al., and the melt line of trinitrotoluene (TNT).

Chemical evolution in spiral and irregular galaxies

NASA Technical Reports Server (NTRS)

Torres-Peimbert, S.

1986-01-01

A brief review of models of chemical evolution of the interstellar medium in our galaxy and other galaxies is presented. These models predict the time variation and radial dependence of chemical composition in the gas as function of the input parameters; initial mass function, stellar birth rate, chemical composition of mass lost by stars during their evolution (yields), and the existence of large scale mass flows, like infall from the halo, outflow to the intergalactic medium or radial flows within a galaxy. At present there is a considerable wealth of observational data on the composition of HII regions in spiral and irregular galaxies to constrain the models. Comparisons are made between theory and the observed physical conditions. In particular, studies of helium, carbon, nitrogen and oxygen abundances are reviewed. In many molecular clouds the information we have on the amount of H2 is derived from the observed CO column density, and a standard CO/H2 ratio derived for the solar neighborhood. Chemical evolution models and the observed variations in O/H and N/O values, point out the need to include these results in a CO/H2 relation that should be, at least, a function of the O/H ratio. This aspect is also discussed.

Experimental Study on Impact-Induced Reaction Characteristics of PTFE/Ti Composites Enhanced by W Particles.

PubMed

Li, Yan; Wang, Zaicheng; Jiang, Chunlan; Niu, Haohao

2017-02-13

Metal/fluoropolymer composites are a category of energetic structural materials that release energy through exothermic chemical reactions initiated under highly dynamic loadings. In this paper, the chemical reaction mechanism of PTFE (polytetrafluoroethylene)/Ti/W composites is investigated through thermal analysis and composition analysis. These composites undergo exothermic reactions at 510 °C to 600 °C, mainly producing TiF x . The tungsten significantly reduces the reaction heat due to its inertness. In addition, the dynamic compression properties and impact-induced reaction behaviors of PTFE/Ti/W composites with different W content prepared by pressing and sintering are studied using Split Hopkinson Pressure Bar and high speed photography. The results show that both the mechanical strength and the reaction degree are significantly improved with the increasing strain rate. Moreover, as W content increases, the mechanical strength is enhanced, but the elasticity/plasticity is decreased. The PTFE/Ti/W composites tend to become more inert with the increasing W content, which is reflected by the reduced reaction degree and the increased reaction threshold for the impact ignition.

Experimental Study on Impact-Induced Reaction Characteristics of PTFE/Ti Composites Enhanced by W Particles

PubMed Central

Li, Yan; Wang, Zaicheng; Jiang, Chunlan; Niu, Haohao

2017-01-01

Metal/fluoropolymer composites are a category of energetic structural materials that release energy through exothermic chemical reactions initiated under highly dynamic loadings. In this paper, the chemical reaction mechanism of PTFE (polytetrafluoroethylene)/Ti/W composites is investigated through thermal analysis and composition analysis. These composites undergo exothermic reactions at 510 °C to 600 °C, mainly producing TiFx. The tungsten significantly reduces the reaction heat due to its inertness. In addition, the dynamic compression properties and impact-induced reaction behaviors of PTFE/Ti/W composites with different W content prepared by pressing and sintering are studied using Split Hopkinson Pressure Bar and high speed photography. The results show that both the mechanical strength and the reaction degree are significantly improved with the increasing strain rate. Moreover, as W content increases, the mechanical strength is enhanced, but the elasticity/plasticity is decreased. The PTFE/Ti/W composites tend to become more inert with the increasing W content, which is reflected by the reduced reaction degree and the increased reaction threshold for the impact ignition. PMID:28772534

The XRD Amorphous Component in John Klein Drill Fines at Yellowknife Bay, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Morris, Richard V.; Ming,, Douglas W.; Blake, David; Vaniman, David; Bish, David L; Chipera, Steve; Downs, Robert; Morrison, Shaunna; Gellert, Ralf; Campbell, Iain;

Production of refractory chamotte particle-reinforced geopolymer composite

NASA Astrophysics Data System (ADS)

Kovářík, T.; Kullová, L.; Rieger, D.

2016-04-01

Geopolymer resins are obtained by alkaline activation of aluminosilicate sources where raw calcined clays are one of the suitable potentialities. Besides the fact that chemical composition has an essential effect on final properties of the geopolymer binder, the type of filler strongly affected resulting properties of such granular composite. However, very few comparative studies have been done on detail description of composite systems: binder - granular filler, in relation to aggregate gradation design and rheology properties of the mixture. The aim of this work is to develop and describe granular composite concerning workability of the mixture and kinetics of geopolymerization/polycondensation through flow behaviour. The rheological measurements indicated that initial viscosities of the mixtures and their evolution are different for various proportions of the filler. Moreover, it was demonstrated that increase in complex viscosity responds to the creation of chemical bonds and the formation of structural network. Finally, a correlation of the mechanism of geopolymer formation was carried out by differential scanning calorimetry (DSC).

The effect of sub-zero temperature on the formation and composition of secondary organic aerosol from ozonolysis of alpha-pinene.

PubMed

Kristensen, K; Jensen, L N; Glasius, M; Bilde, M

2017-10-18

This study presents a newly constructed temperature controlled cold-room smog chamber at Aarhus University, Denmark. The chamber is herein utilized to study the effect of sub-zero temperature on the formation and chemical composition of secondary organic aerosol (SOA) from ozone initiated oxidation of α-pinene. The chemical composition of α-pinene SOA formed from dark ozonolysis of α-pinene at 293 K and 258 K was investigated using High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS) and Ultra-High Performance Liquid Chromatography/Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry (UHPLC/ESI-qToF-MS). For comparison, an OH-initiated oxidation experiment was performed at 293 K. In ozonolysis experiments it was found that oxygen-to-carbon (O : C) ratios were higher in the particles formed at 293 K compared to 258 K. A total of 16 different organic acids and 30 dimers esters were quantified in the collected particles composing up to 34% of the total α-pinene SOA mass with increased mass fraction of carboxylic acids in particles from α-pinene ozonolysis at 258 K compared to 293 K. In contrast, dimer esters showed suppressed formation at the sub-zero reaction temperature, thus contributing 3% to SOA mass at 258 K while contributing 9% at 293 K. SOA formed in the OH-initiated oxidation of α-pinene at 293 K resulted in low concentrations of dimer esters supporting Criegee intermediates as a possible pathway to dimer ester formation. Vapour pressure estimates of the identified carboxylic acids and dimer esters are presented and show how otherwise semi-volatile carboxylic acids at sufficiently low temperatures may classify as low or even extremely low volatile organic compounds (ELVOC), thus may add to an enhanced particle formation observed at the sub-zero temperature through gas-to-particle conversion. The change in chemical composition of the SOA particles with temperature is ascribed to a combination of effects: the decreased vapour pressures and hence increased condensation of carboxylic acids from the gas phase to the particle phase along with suppressed formation of the high molecular weight dimer esters and different gas and particle phase chemistry results in particles of different chemical composition as a consequence of low reaction temperatures.

Complete and Partial Photo-oxidation of Dissolved Organic Matter Draining Permafrost Soils.

PubMed

Ward, Collin P; Cory, Rose M

2016-04-05

Photochemical degradation of dissolved organic matter (DOM) to carbon dioxide (CO2) and partially oxidized compounds is an important component of the carbon cycle in the Arctic. Thawing permafrost soils will change the chemical composition of DOM exported to arctic surface waters, but the molecular controls on DOM photodegradation remain poorly understood, making it difficult to predict how inputs of thawing permafrost DOM may alter its photodegradation. To address this knowledge gap, we quantified the susceptibility of DOM draining the shallow organic mat and the deeper permafrost layer of arctic soils to complete and partial photo-oxidation and investigated changes in the chemical composition of each DOM source following sunlight exposure. Permafrost and organic mat DOM had similar lability to photomineralization despite substantial differences in initial chemical composition. Concurrent losses of carboxyl moieties and shifts in chemical composition during photodegradation indicated that photodecarboxylation could account for 40-90% of DOM photomineralized to CO2. Permafrost DOM had a higher susceptibility to partial photo-oxidation compared to organic mat DOM, potentially due to a lower abundance of phenolic moieties with antioxidant properties. These results suggest that photodegradation will likely continue to be an important control on DOM fate in arctic freshwaters as the climate warms and permafrost soils thaw.

Influence of Mechanical and Chemical Degradation in the Surface Roughness, Gloss, and Color of Microhybrid Composites.

PubMed

Lemos, Cleidiel Aa; Mauro, Silvio J; Dos Santos, Paulo H; Briso, Andre Lf; Fagundes, Ticiane C

2017-04-01

The aim of this study was to investigate the association of different degradations on the roughness, gloss, and color changes of microhybrid composites. Ten specimens were prepared for Charisma, Amelogen Plus, Point 4, and Opallis resins. Surfaces were polished and baseline measurements of roughness, gloss, and color were recorded. Specimens were then submitted to chemical and mechanical challenges, and the specimens were reevaluated. Roughness and gloss were analyzed by Kruskal -Wallis and Dunn's test (p < 0.05). Color change (ΔE) was analyzed by one-way analysis of variance and Tukey's tests (p < 0.05). The initial and final data were compared using the Wilcoxon test (p < 0.05). Spearman test checked the correlation between the roughness and gloss (p < 0.05). Regarding surface roughness and gloss, there was no difference between composites before challenges. However, all composites showed a significant increase of roughness after challenges, with highest values for Charisma. The gloss was influenced by challenges, evidencing the best gloss for Point 4. Charisma showed the highest value of color change. There was no correlation between surface roughness and gloss for the initial analysis, and after the challenges. Composites were influenced by association of challenges, and Charisma showed the highest changes for roughness, gloss, and color. The type of composite resin influenced the properties of materials, which are surface roughness, gloss, and color change. The dentist should be aware of the performance of different brands, to choose the correct required composite resin for each type of patient or region to be restored.

Compact chemical energy system for seismic applications

DOEpatents

Engelke, Raymond P.; Hedges, Robert O.; Kammerman, Alan B.; Albright, James N.

1998-01-01

A chemical energy system is formed for producing detonations in a confined environment. An explosive mixture is formed from nitromethane (NM) and diethylenetriamine (DETA). A slapper detonator is arranged adjacent to the explosive mixture to initiate detonation of the mixture. NM and DETA are not classified as explosives when handled separately and can be safely transported and handled by workers in the field. In one aspect of the present invention, the chemicals are mixed at a location where an explosion is to occur. For application in a confined environment, the chemicals are mixed in an inflatable container to minimize storage space until it is desired to initiate an explosion. To enable an inflatable container to be used, at least 2.5 wt % DETA is used in the explosive mixture. A barrier is utilized that is formed of a carbon composite material to provide the appropriate barrel geometry and energy transmission to the explosive mixture from the slapper detonator system.

Alterations in Physical State of Silver Nanoparticles Exposed to Synthetic Human Stomach Fluid

EPA Science Inventory

The bioavailability of ingested silver nanoparticles (AgNPs) depends in large part on initial particle size, shape and surface coating, properties which will influence aggregation, solubility and chemical composition during transit of the gastrointestinal tract. Citrate-stabilize...

Terahertz NDE of Stressed Composite Overwrapped Pressure Vessels - Initial Testing

NASA Technical Reports Server (NTRS)

Madaras, Eric I.; Seebo, Jeffrey P.; Anatasi, Robert F.

2009-01-01

Terahertz radiation nondestructive evaluation was applied to a set of Kevlar composite overwrapped pressure vessel bottles that had undergone a series of thermal and pressure tests to simulate stress rupture effects. The bottles in these nondestructive evaluation tests were bottles that had not ruptured but had survived various times at the elevated load and temperature levels. Some of the bottles showed evidence of minor composite failures. The terahertz radiation did detect visible surface flaws, but did not detect any internal chemical or material degradation of the thin overwraps.

Chemical consequences of the initial diffusional growth of cloud droplets - A clean marine case

NASA Technical Reports Server (NTRS)

Twohy, C. H.; Charlson, R. J.; Austin, P. H.

1989-01-01

A simple microphysical cloud parcel model and a simple representation of the background marine aerosol are used to predict the concentrations and compositions of droplets of various sizes near cloud base. The aerosol consists of an externally-mixed ammonium bisulfate accumulation mode and a sea-salt coarse particle mode. The difference in diffusional growth rates between the small and large droplets as well as the differences in composition between the two aerosol modes result in substantial differences in solute concentration and composition with size of droplets in the parcel. The chemistry of individual droplets is not, in general, representative of the bulk (volume-weighted mean) cloud water sample. These differences, calculated to occur early in the parcel's lifetime, should have important consequences for chemical reactions such as aqueous phase sulfate production.

Explosive composition with group VIII metal nitroso halide getter

DOEpatents

Walker, Franklin E.; Wasley, Richard J.

1982-01-01

An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1,500 and 10,000 meters per second and a minor amount of a getter additive comprising a non-explosive compound or mixture of non-explosive compounds capable of chemically reacting with free radicals or ions under shock initiation conditions of 2,000 calories/cm.sup.2 or less of energy fluence.

Explosive composition with group VIII metal nitroso halide getter

DOEpatents

Walker, F.E.; Wasley, R.J.

1982-06-22

An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1,500 and 10,000 meters per second and a minor amount of a getter additive comprising a non-explosive compound or mixture of non-explosive compounds capable of chemically reacting with free radicals or ions under shock initiation conditions of 2,000 calories/cm[sup 2] or less of energy fluence.

DETERMINATION OF METALS IN COMPOSITE DIET SAMPLES BY ICP-MS

EPA Science Inventory

In order to assess an individual's toal exposure to contaminants in the environment, it is essential that the contribution of dietary exposure be quantified. As a result, USEPA's National Exposure Research Laboratory has initiated a program to develop methods to measure chemical...

Ultrathin Pt xSn 1–x Nanowires for Methanol and Ethanol Oxidation Reactions: Tuning Performance by Varying Chemical Composition

DOE PAGES

Li, Luyao; Liu, Haiqing; Qin, Chao; ...

2018-02-28

Pt-based alloys denote promising catalysts for the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR), due to their enhanced activity toward alcohol-oxidation reactions and reduced cost as compared with Pt alone. Among all of these binary systems, PtSn has been reported to exhibit superior methanol/ethanol oxidation activity. In this paper, we deliberatively tailor chemical composition, reduce size, and optimize morphology of the catalyst in an effort to understand structure–property correlations that can be used to improve upon the electrocatalytic activity of these systems. Previous work performed by our group suggested that Pt-based catalysts, possessing an ultrathin one-dimensional (1D)more » structure, dramatically promote both cathodic and anodic reactions with respect to their zero-dimensional (0D) counterparts. Herein, a novel set of ultrathin binary Pt–Sn 1D nanowire (NW) catalysts with rationally controlled chemical compositions, i.e., Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3, has been synthesized using a facile, room-temperature, wet-solution-based method. The crystallinity and chemical composition of these as-prepared samples were initially characterized using XRD, XPS, and EDX. Results revealed that this synthetic protocol could successfully generate PtSn alloys with purposely tunable chemical compositions. TEM and HRTEM verified the structural integrity of our ultrathin 1D NW morphology for our Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3 samples. The effects of varying Sn content within these alloy samples toward the electro-oxidation reaction of methanol and ethanol were probed using cyclic voltammetry (CV) in acidic media. Finally, within this series, we find that the optimized chemical composition for both the MOR and the EOR is Pt 7Sn 3.« less

Ultrathin Pt xSn 1–x Nanowires for Methanol and Ethanol Oxidation Reactions: Tuning Performance by Varying Chemical Composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Luyao; Liu, Haiqing; Qin, Chao

Pt-based alloys denote promising catalysts for the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR), due to their enhanced activity toward alcohol-oxidation reactions and reduced cost as compared with Pt alone. Among all of these binary systems, PtSn has been reported to exhibit superior methanol/ethanol oxidation activity. In this paper, we deliberatively tailor chemical composition, reduce size, and optimize morphology of the catalyst in an effort to understand structure–property correlations that can be used to improve upon the electrocatalytic activity of these systems. Previous work performed by our group suggested that Pt-based catalysts, possessing an ultrathin one-dimensional (1D)more » structure, dramatically promote both cathodic and anodic reactions with respect to their zero-dimensional (0D) counterparts. Herein, a novel set of ultrathin binary Pt–Sn 1D nanowire (NW) catalysts with rationally controlled chemical compositions, i.e., Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3, has been synthesized using a facile, room-temperature, wet-solution-based method. The crystallinity and chemical composition of these as-prepared samples were initially characterized using XRD, XPS, and EDX. Results revealed that this synthetic protocol could successfully generate PtSn alloys with purposely tunable chemical compositions. TEM and HRTEM verified the structural integrity of our ultrathin 1D NW morphology for our Pt 9Sn 1, Pt 8Sn 2, and Pt 7Sn 3 samples. The effects of varying Sn content within these alloy samples toward the electro-oxidation reaction of methanol and ethanol were probed using cyclic voltammetry (CV) in acidic media. Finally, within this series, we find that the optimized chemical composition for both the MOR and the EOR is Pt 7Sn 3.« less

In vivo ultrasound and biometric measurements predict the empty body chemical composition in Nellore cattle.

PubMed

Castilhos, A M; Francisco, C L; Branco, R H; Bonilha, S F M; Mercadante, M E Z; Meirelles, P R L; Pariz, C M; Jorge, A M

2018-05-04

Evaluation of the body chemical composition of beef cattle can only be measured postmortem and those data cannot be used in real production scenarios to adjust nutritional plans. The objective of this study was to develop multiple linear regression equations from in vivo measurements, such as ultrasound parameters [backfat thickness (uBFT, mm), rump fat thickness (uRF, mm), and ribeye area (uLMA, cm2)], shrunk body weight (SBW, kg), age (AG, d), hip height (HH, m), as well as from postmortem measurements (composition of the 9th to 11th rib section) to predict the empty body and carcass chemical composition for Nellore cattle. Thirty-three young bulls were used (339 ± 36.15 kg and 448 ± 17.78 d for initial weight and age, respectively). Empty body chemical composition (protein, fat, water, and ash in kg) was obtained by combining noncarcass and carcass components. Data were analyzed using the PROC REG procedure of SAS software. Mallows' Cp values were close to the ideal value of number of independent variables in the prediction equations plus one. Equations to predict chemical components of both empty body and carcass using in vivo measurements presented higher R2 values than those determined by postmortem measurements. Chemical composition of the empty body using in vivo measurements was predicted with R2 > 0.73. Equations to predict chemical composition of the carcass from in vivo measurements showed R2 lower (R2< 0.68) than observed for empty body, except for the water (R2 = 0.84). The independent variables SBW, uRF, and AG were sufficient to predict the fat, water, energy components of the empty body, whereas for estimation of protein content the uRF, HH, and SBW were satisfactory. For the calculation of the ash, the SBW variable in the equation was sufficient. Chemical compounds from components of the empty body of Nellore cattle can be calculated by the following equations: protein (kg) = 47.92 + 0.18 × SBW - 1.46 × uRF - 30.72 × HH (R2 = 0.94, RMSPE = 1.79); fat (kg) = 11.33 + 0.16 × SBW + 2.09 × uRF - 0.06 × AG (R2 = 0.74, RMSPE = 4.18); water (kg) = - 34.00 + 0.55 × SBW + 0.10 × AG - 2.34 × uRF (R2 = 0.96, RMSPE = 5.47). In conclusion, the coefficients of determination (for determining the chemical composition of the empty body) of the equations derived from in vivo measures were higher than those of the equations obtained from rib section measurements taken postmortem, and better than coefficients of determination of the equations to predict the chemical composition of the carcass.

HA and double-layer HA-P2O5/CaO glass coatings: influence of chemical composition on human bone marrow cells osteoblastic behavior.

PubMed

Ferraz, M P; Fernandes, M H; Santos, J D; Monteiro, F J

2001-07-01

Human osteoblastic bone marrow derived cells were cultured for 28 days onto the surface of a glass reinforced hydroxyapatite (HA) composite and a commercial type HA plasma sprayed coatings, both in the "as-received" condition and after an immersion treatment with culture medium during 21 days. Cell proliferation and differentiation were analyzed as a function of the chemical composition of the coatings and the immersion treatment. Cell attachment, growth and differentiation of osteoblastic bone marrow cells seeded onto "as-received" plasma sprayed coatings were strongly affected by the time-dependent variation of the surface structure occurring during the first hours of culture. Initial interactions leading to higher amounts of adsorbed protein and zeta potential shifts towards negative charges appeared to result in surface structures with better biological performance. Cultures grown onto the pretreated coatings showed higher rate of cell proliferation and increased functional activity, as compared to those grown onto the corresponding "as-received" materials. However, the cell behavior was similar in the glass composite and HA coatings. The results showed that the glass composites present better characteristics for bone cell growth and function than HA. In addition, this work also provide evidence that the biological performance of the glass composites can be modulated and improved by manipulations in the chemical composition, namely in the content of glass added to HA. Copyright 2001 Kluwer Academic Publishers

Meso-scale investigation of anaerobic chemical reactivity of Ti-Al-B powder mixtures under impact loading

NASA Astrophysics Data System (ADS)

Gonzales, Manny; Gurumurthy, Ashok; Gokhale, Arun; Thadhani, Naresh N.

2011-06-01

Impact-initiated anaerobic chemical reactions in Ti-Al-B reactive powder mixtures under uniaxial stress conditions are investigated using a coupled experimental/computational approach. In particular, we characterize the effects of bulk composition on the threshold impact energy to initiate reaction using rod-on-anvil type tests performed on Ti-Al-B powder compacts. Statistical volume elements (SVEs) of different bulk compositions of the powder mixtures are analyzed using the continuum hydrocode CTH to quantify the effects of strain confinement and load configuration on the overall energy of the structure. These SVEs are also validated using one-point correlation functions to characterize the volume fraction and surface area of the constituents. Based on the deformation profiles from the continuum simulations, we investigate the effect of particle size distribution and clustering of Ti and B on the threshold energy required for observed reactivity. The deformation and threshold kinetic energy of the simulated system is compared with published values of the activation energy for Ti+B reactions and Al combustion in air to assess the extent of their impact-initiated reactivity. Funded by DTRA grant No. HDTRA1-10-1-0038

A procedure for the measurement of Oxygen Consumption Rates (OCRs) in red wines and some observations about the influence of wine initial chemical composition.

PubMed

Marrufo-Curtido, Almudena; Carrascón, Vanesa; Bueno, Mónica; Ferreira, Vicente; Escudero, Ana

2018-05-15

The rates at which wine consumes oxygen are important technological parameters for whose measurement there are not accepted procedures. In this work, volumes of 8 wines are contacted with controlled volumes of air in air-tight tubes containing oxygen-sensors and are further agitated at 25 °C until O 2 consumption is complete. Three exposure levels of O 2 were used: low (10 mg/L) and medium or high (18 or 32 mg/L plus the required amount to oxidize all wine SO 2 ). In each oxygen level, 2-4 independent segments following pseudo-first order kinetics were identified, plus an initial segment at which wine consumed O 2 very fast. Overall, multivariate data techniques identify six different Oxygen-Consumption-Rates (OCRs) as required to completely define wine O 2 consumption. Except the last one, all could be modeled from the wine initial chemical composition. Total acetaldehyde, Mn, Cu/Fe, blue and red pigments and gallic acid seem to be essential to determine these OCRs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago.

PubMed

Greber, Nicolas D; Dauphas, Nicolas; Bekker, Andrey; Ptáček, Matouš P; Bindeman, Ilya N; Hofmann, Axel

2017-09-22

Earth exhibits a dichotomy in elevation and chemical composition between the continents and ocean floor. Reconstructing when this dichotomy arose is important for understanding when plate tectonics started and how the supply of nutrients to the oceans changed through time. We measured the titanium isotopic composition of shales to constrain the chemical composition of the continental crust exposed to weathering and found that shales of all ages have a uniform isotopic composition. This can only be explained if the emerged crust was predominantly felsic (silica-rich) since 3.5 billion years ago, requiring an early initiation of plate tectonics. We also observed a change in the abundance of biologically important nutrients phosphorus and nickel across the Archean-Proterozoic boundary, which might have helped trigger the rise in atmospheric oxygen. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Laboratory Studies Of Titan Haze: Simultaneous In Situ Detection Of Gas And Particle Species

NASA Astrophysics Data System (ADS)

Horst, Sarah; Li, R.; Yoon, H.; Hicks, R.; de Gouw, J.; Tolbert, M.

2012-10-01

Analyses of data obtained by multiple instruments carried by Cassini and Huygens have increased our knowledge of the composition of Titan’s atmosphere. While a wealth of new information about the aerosols in Titan’s atmosphere was obtained, their composition is still not well constrained. Laboratory experiments will therefore play a key role in furthering our understanding of the chemical processes resulting in the formation of haze in Titan’s atmosphere and its possible composition. We have obtained simultaneous in situ measurements of the gas- and particle-phase compositions produced by our Titan atmosphere simulation experiments (see e.g. [1]). The gas phase composition was measured using a Proton-Transfer Ion-Trap Mass Spectrometer (PIT-MS) and the aerosol composition was measured using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). This complementary set of measurements will allow us to address the partitioning of gas- and aerosol-phase species. Knowledge of the gas phase composition in which the particles in our experiments form allows both for better comparison to the chemistry that is occurring in Titan’s atmosphere and for enabling more accurate determination of the possible pathways involved in the transition from gas phase to aerosol. We will compare the results from experiments that used two different initial gas mixtures (98% N2/2% CH4 and 98%N2/2%CH4/50 ppm CO) and two different energy sources to initiate the chemical reactions that result in particle formation (spark discharge using a Tesla coil or FUV irradiation from a deuterium lamp (115-400 nm)). [1] Trainer, M.G., et al. (2012) Astrobiology, 12, 315-326. SMH is supported by NSF Astronomy and Astrophysics Postdoctoral Fellowship AST-1102827.

Polysaccharide-based hydrogels with tunable composition as 3D cell culture systems.

PubMed

Gentilini, Roberta; Munarin, Fabiola; Bloise, Nora; Secchi, Eleonora; Visai, Livia; Tanzi, Maria Cristina; Petrini, Paola

2018-04-01

To date, cell cultures have been created either on 2-dimensional (2D) polystyrene surfaces or in 3-dimensional (3D) systems, which do not offer a controlled chemical composition, and which lack the soft environment encountered in vivo and the chemical stimuli that promote cell proliferation and allow complex cellular behavior. In this study, pectin-based hydrogels were developed and are proposed as versatile cell culture systems. Pectin-based hydrogels were produced by internally crosslinking pectin with calcium carbonate at different initial pH, aiming to control crosslinking kinetics and degree. Additionally, glucose and glutamine were added as additives, and their effects on the viscoelastic properties of the hydrogels and on cell viability were investigated. Pectin hydrogels showed in high cell viability and shear-thinning behavior. Independently of hydrogel composition, an initial swelling was observed, followed by a low percentage of weight variation and a steady-state stage. The addition of glucose and glutamine to pectin-based hydrogels rendered higher cell viability up to 90%-98% after 1 hour of incubation, and these hydrogels were maintained for up to 7 days of culture, yet no effect on viscoelastic properties was detected. Pectin-based hydrogels that offer tunable composition were developed successfully. They are envisioned as synthetic extracellular matrix (ECM) either to study complex cellular behaviors or to be applied as tissue engineering substitutes.

Effect of Fiber Esterification on Fundamental Properties of Oil Palm Empty Fruit Bunch Fiber/Poly(butylene adipate-co-terephthalate) Biocomposites

PubMed Central

Siyamak, Samira; Ibrahim, Nor Azowa; Abdolmohammadi, Sanaz; Yunus, Wan Md Zin Wan; Rahman, Mohamad Zaki AB

2012-01-01

A new class of biocomposites based on oil palm empty fruit bunch fiber and poly(butylene adipate-co-terephthalate) (PBAT), which is a biodegradable aliphatic aromatic co-polyester, were prepared using melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 wt% and characterized. Chemical treatment of oil palm empty fruit bunch (EFB) fiber was successfully done by grafting succinic anhydride (SAH) onto the EFB fiber surface, and the modified fibers were obtained in two levels of grafting (low and high weight percentage gain, WPG) after 5 and 6 h of grafting. The FTIR characterization showed evidence of successful fiber esterification. The results showed that 40 wt% of fiber loading improved the tensile properties of the biocomposite. The effects of EFB fiber chemical treatments and various organic initiators content on mechanical and thermal properties and water absorption of PBAT/EFB 60/40 wt% biocomposites were also examined. The SAH-g-EFB fiber at low WPG in presence of 1 wt% of dicumyl peroxide (DCP) initiator was found to significantly enhance the tensile and flexural properties as well as water resistance of biocomposite (up to 24%) compared with those of untreated fiber reinforced composites. The thermal behavior of the composites was evaluated from thermogravimetric analysis (TGA)/differential thermogravimetric (DTG) thermograms. It was observed that, the chemical treatment has marginally improved the biocomposites’ thermal stability in presence of 1 wt% of dicumyl peroxide at the low WPG level of grafting. The improved fiber-matrix surface enhancement in the chemically treated biocomposite was confirmed by SEM analysis of the tensile fractured specimens. PMID:22408394

Medium resolution spectroscopy and chemical composition of Galactic globular clusters

NASA Astrophysics Data System (ADS)

Khamidullina, D. A.; Sharina, M. E.; Shimansky, V. V.; Davoust, E.

We used integrated-light medium-resolution spectra of six Galactic globular clusters and model stellar atmospheres to carry out population synthesis and to derive chemical composition and age of the clusters. We used medium-resolution spectra of globular clusters published by Schiavon et al. (2005), as well as our long-slit observations with the 1.93 m telescope of the Haute Provence Observatory. The observed spectra were fitted to the theoretical ones interactively. As an initial approach, we used masses, radii and log g of stars in the clusters corresponding to the best fitting isochrones in the observed color-magnitude diagrams. The computed synthetic blanketed spectra of stars were summed according to the Chabrier mass function. To improve the determination of age and helium content, the shape and depth of the Balmer absorption lines was analysed. The abundances of Mg, Ca, C and several other elements were derived. A reasonable agreement with the literature data both in chemical composition and in age of the clusters is found. Our method might be useful for the development of stellar population models and for a better understanding of extragalactic star clusters.

The Effect of Fuel Composition, Compression Pressure, and Fuel-Air Ratio on the Compression-Ignition Characteristics of Several Fuels

DTIC Science & Technology

1948-03-01

to this arbitrary value as ntandard. The compression time was maintained unifcum by uElng a ccnstent . driving ~ essure of 500 pounds per squ=e inch...ir ratio,0.066 (chemlo~ correct); initial~ essure , 14.7 lb/sq in. abs.; intt Ml temperature, 609° F abs~ Ignitiondelay Compres- Compres- sion...chemically correct); initial ~ essure , 14.7 lb/sq in. abso; fimal pressures 379 lb/sq in. abs.; initial temperatume~ 6090 F abs.; final temperature, 1340° F abs

Multifunctional materials and composites

DOEpatents

Seo, Dong-Kyun; Jeon, Ki-Wan

2017-08-22

Forming multifunctional materials and composites thereof includes contacting a first material having a plurality of oxygen-containing functional groups with a chalcogenide compound, and initiating a chemical reaction between the first material and the chalcogenide compound, thereby replacing oxygen in some of the oxygen-containing functional groups with chalcogen from the chalcogen-containing compound to yield a second material having chalcogen-containing functional groups and oxygen-containing functional groups. The first material is a carbonaceous material or a macromolecular material. A product including the second material is collected and may be processed further to yield a modified product or a composite.

COMPARISON OF GC-FPD AND GC/AED FOR DETERMINATION OF ORGANOPHOSPHATE PESTICIDES IN COMPOSITE DIET SAMPLES

EPA Science Inventory

In order to assess an individual's total exposure to contaminants in the environment, it is essential that the contribution of dietary exposure be quantified. As a result, USEPA's National Exposure Research Laboratory has initiated a program to develop methods to measure chemical...

Start of the Wilson cycle at 3 Ga shown by diamonds from subcontinental mantle.

PubMed

Shirey, Steven B; Richardson, Stephen H

2011-07-22

Mineral inclusions encapsulated in diamonds are the oldest, deepest, and most pristine samples of Earth's mantle. They provide age and chemical information over a period of 3.5 billion years--a span that includes continental crustal growth, atmospheric evolution, and the initiation of plate tectonics. We compiled isotopic and bulk chemical data of silicate and sulfide inclusions and found that a compositional change occurred 3.0 billion years ago (Ga). Before 3.2 Ga, only diamonds with peridotitic compositions formed, whereas after 3.0 Ga, eclogitic diamonds became prevalent. We suggest that this resulted from the capture of eclogite and diamond-forming fluids in subcontinental mantle via subduction and continental collision, marking the onset of the Wilson cycle of plate tectonics.

Research into properties of wear resistant ceramic metal plasma coatings

NASA Astrophysics Data System (ADS)

Ivancivsky, V. V.; Skeeba, V. Yu; Zverev, E. A.; Vakhrushev, N. V.; Parts, K. A.

2018-03-01

The study considers one of the promising ways to improve the quality of wear resistant plasma ceramic coatings by implementing various powder mixtures. The authors present the study results of the nickel-ceramic and cobalt-ceramic coating properties and describe the specific character of the investigated coatings composition. The paper presents the results of the coating microhardness, chemical and adhesive strength studies. The authors conducted wear resistance tests of composite coatings in comparison with the plasma coatings of initial powder components.

Shock wave induced condensation in fuel-rich gaseous and gas-particles mixtures

NASA Astrophysics Data System (ADS)

Fomin, P. A.

2018-03-01

The possibility of fuel vapor condensation in shock waves in fuel-rich (cyclohexane-oxygen) gaseous mixtures and explosion safety aspects of this effect are discussed. It is shown, that condensation process can essentially change the chemical composition of the gas. For example, the molar fraction of the oxidizer can increase in a few times. As a result, mixtures in which the initial concentration of fuel vapor exceeds the Upper Flammability Limit can, nevertheless, explode, if condensation shifts the composition of the mixture into the ignition region. The rate of the condensation process is estimated. This process can be fast enough to significantly change the chemical composition of the gas and shift it into the flammable range during the compression phase of blast waves, generated by explosions of fuel-vapor clouds or rapture of pressurized chemical reactors, with characteristic size of a few meters. It is shown that the presence of chemically inert microparticles in the gas mixtures under consideration increases the degree of supercooling and the mass of fuel vapors that have passed into the liquid and reduces the characteristic condensation time in comparison with the gas mixture without microparticles. The fuel vapor condensation should be taken into account in estimation the explosion hazard of chemical reactors, industrial and civil constructions, which may contain fuel-rich gaseous mixtures of heavy hydrocarbons with air.

Cytocompatibility and Mechanical Properties of Short Phosphate Glass Fibre Reinforced Polylactic Acid (PLA) Composites: Effect of Coupling Agent Mediated Interface

PubMed Central

Hasan, Muhammad Sami; Ahmed, Ifty; Parsons, Andrew; Walker, Gavin; Scotchford, Colin

2012-01-01

In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices. PMID:24955744

Secuencias evolutivas e isocronas para estrellas de baja masa e intermedia

NASA Astrophysics Data System (ADS)

Panei, J.; Baume, G.

2016-08-01

We present theoretical evolutionary sequences for low- and intermediate-mass stars. The masses calculated range from 1.7 to 10 M. The initial chemical composition is . In addition, we have taken into account a nuclear network with 17 isotopes and 34 nuclear reactions. With respect to the mix, we considered overshooting with a parameter . The evolutionary calculations were initialized from the region of instability of Hayashi, in order to calculate isochrones of pre-sequence, too.

Towards retrievals of aerosol chemical composition from satellite observations by POLDER/PARASOL polarimeter

NASA Astrophysics Data System (ADS)

Li, L.; Dubovik, O.; Derimian, Y.; Lapyonok, T.; Schuster, G. L.; Ducos, F.

2016-12-01

The information about composition of aerosols has a great importance for monitoring and understanding of climate and environment dynamics. Such information can be obtained using situ measurements or chemical transport models. However, in situ sampling has limited spatial and temporal coverage, while estimations have large uncertainties. The present work enables the monitoring of aerosol chemical species from space-borne observations, providing observationally-based results with spatial and temporal coverage. Following the ideas of Schuster et al.(2005, 2009, 2016), we retrieve chemical composition directly from remote sensing measurements without intermediate retrieval of the refractive index (in contrast with Schuster's approach). This approach is expected to reduce the influence of modeling uncertainties, and to provide additional constraints in situations where remote sensing observations do not have enough spectral sensitivity to refractive index. One of principal difficulties is the identification of an adequate model for linking refractive index to chemical composition. Therefore, the initial effort of this work has focused on identifying an optimal "chemical composition to refractive index" conversion model. With that purpose, we first tested the retrieval approach using a simplified volume-weighting model and updated by the Maxwell Garnett mixing model. This concept was incorporated into the GRASP algorithm designed to retrieve an extended set of atmospheric parameters from remote sensing observations. Then a series of sensitivity tests using synthetic data of POLDER/PARASOL were conducted, and followed by inversion of real PARASOL observations. The sensitivity tests showed that these two models allow the retrieval to distinguish amongst the assumed chemical species. Results obtained from real PARASOL data demonstrated good agreement with the optical characteristics provided by AERONET (e.g., r2 of AOT 0.9). The obtained patterns of chemical component distribution agreed with known physical expectations. For example, the mass concentration of black and brown carbon in the biomass burning region was found five times higher than in the region mainly affected by dust. The mass concentration of quartz in western Africa is up to seven times higher than in southern Africa.

Influence of Biodegradation on the Organic Compounds Composition of Peat.

NASA Astrophysics Data System (ADS)

Serebrennikova, Olga; Svarovskaya, Lidiya; Duchko, Maria; Strelnikova, Evgeniya; Russkikh, Irina

2016-06-01

Largest wetland systems are situated on the territory of the Tomsk region. They are characterized by the high content of organic matter (OM), which undergoes transformation as a result of physical, chemical and biological processes. The composition of peat OM is determined by the nature of initial peat-forming plants, their transformation products and bacteria. An experiment in stimulated microbial impact was carried out for estimating the influence of biodegradation on the composition of peat lipids. The composition of the functional groups in the bacterial biomass, initial peat and peat after biodegradation was determined by IR-spectroscopy using the spectrometer NICOLET 5700. The IR spectra of peat and bacteria organic matter are characterized by the presence of absorption bands in ranges: 3400-3200 cm-1, which refers to the stretching vibrations of OH-group of carboxylic acids and various types of hydrogen bonds; 1738-1671 cm-1 - characteristic stretching vibrations of the C = O group of carboxylic acids and ketones; 1262 cm-1 - stretching vibrations of C-O of carboxylic acids. Group and individual composition of organic compounds in studied samples was determined by gas chromatography-mass-spectrometry.

Engineered soy oils for new value added applications

NASA Astrophysics Data System (ADS)

Tran, Phuong T.

Soybean oil is an abundant annually renewable resource. It is composed of triglycerides with long chain saturated and unsaturated fatty acids. The presence of unsaturated fatty acids allows for chemical modification to introduce new functionalities to soybean oil. A portfolio of chemically modified soy oil with suitable functional groups has been designed and engineered to serve as the starting material in applications such as polyamides, polyesters, polyurethanes, composites, and lubricants. Anhydride, hydroxyl, and silicone functionalities were introduced to soy oil. Anhydride functionality was introduced using a single-step free radical initiated process, and the chemically modified soy oils were evaluated for potential applications as a composite and lubricant. Hydroxyl functionalities were introduced in a single-step catalytic ozonolysis process recently developed in our labs, which proceeds rapidly and efficiently at room temperature without solvent. The transformed soy oil was used to successfully prepare bio-lubricants with good thermal/oxidative stability and bio-plastics such as polyamides, polyesters, and polyurethanes. A new class of organic-inorganic hybrid materials was prepared by curing vinyltrimethoxysilane functionalized soy oil. This hybrid material could have potential as biobased sealant through a moisture initiated room temperature cure. These new classes of soy-based materials are competitive both in cost and performance to petroleum based materials, but offer the advantage of being biobased.

Ultralow percolation threshold of single walled carbon nanotube-epoxy composites synthesized via an ionic liquid dispersant/initiator

NASA Astrophysics Data System (ADS)

Watters, Arianna L.; Palmese, Giuseppe R.

2014-09-01

Uniform dispersion of single walled carbon nanotubes (SWNTs) in an epoxy was achieved by a streamlined mechano-chemical processing method. SWNT-epoxy composites were synthesized using a room temperature ionic liquid (IL) with an imidazolium cation and dicyanamide anion. The novel approach of using ionic liquid that behaves as a dispersant for SWNTs and initiator for epoxy polymerization greatly simplifies nanocomposite synthesis. The material was processed using simple and scalable three roll milling. The SWNT dispersion of the resultant composite was evaluated by electron microscopy and electrical conductivity measurements in conjunction with percolation theory. Processing conditions were optimized to achieve the lowest possible percolation threshold, 4.29 × 10-5 volume fraction SWNTs. This percolation threshold is among the best reported in literature yet it was obtained using a streamlined method that greatly simplifies processing.

Polymerization contraction stress in thin resin composite layers as a function of layer thickness.

PubMed

Alster, D; Feilzer, A J; de Gee, A J; Davidson, C L

1997-05-01

In the present study, the effect of layer thickness on the curing stress in thin resin composite layers was investigated. Since the value of the contraction stress is dependent on the compliance of the measuring equipment (especially for thin films), a method to determine the compliance of the test apparatus was tested. A chemically initiated resin composite (Clearfil F2, Kuraray) was inserted between two sandblasted and silane-coated stainless steel discs in a tensilometer. The curing contraction of the cylindrical samples was continuously counteracted by feedback displacement of the tensilometer crosshead, and the curing stress development was registered. After 20 min, the samples were loaded in tension until fracture. The curing stress was determined for layer thicknesses of 50, 100, 200, 300, 400, 500, 600, 700 microns, 1.4 mm and 2.7 mm. The compliance of the apparatus was calculated with the aid of a non-linear regression analysis, using an equation derived from Hooke's Law as the model. None of the samples fractured due to contraction stress prior to tensile loading. The contraction stress after 20 min decreased from 23.3 +/- 5.3 MPa for the 50 microns layer to 5.5 +/- 0.6 MPa for the 2.7 mm layer. The compliance on the apparatus was 0.029 mm/MPa. A measuring method was developed which was found to be suitable for the determination of axial polymerization contraction stress in this films of chemically initiated resin composites. The method makes it possible to estimate the stress levels that occur in resin composite films in the clinical situation.

Radiation-induced polymerization of glass-forming systems. V. Initial polymerization rate in binary glass-forming systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaetsu, Isao; Okubo, Hiroshi; Ito, Akihiko

1973-06-01

The radiation-induced polymerization of binary systems consisting of glass-forming monomer and glass-forming solvent in supercooled phase was studied. The initial polymerization rates were markedly affected by T/sub g/ (glass transition temperature) and T/sub v/ of the system (30-50 deg C higher than T/sub g/), which are functions of the composition. The composition and temperature dependence of initial polymerization rate in binary glass-forming systems were much affected by homogeneity of the polymerization system and the T of the glass- forming solvent. The composition and temperature dependences in the glycidyl methacrylate --triacetin system as a typical homogeneous polymerization system were studied inmore » detail, and the polymerizations of hydroxyethyl methacrylate triacetln and hydroxyethyl methacrylate --isoamyl acetate systems were studied for the heterogeneous polymerization systems; the former illustrates the combination of lower T/sub g/ monomer and higher T/sub g/ solvent and the latter typifies a system consisting of higher T/sub g/ monomer and lower T/sub g/ solvent. All experimental results for the composition and temperature dependence of initial polymerization rate in binary glass-forming systems could be explained by considering the product of the effect of the physical effect relating to T/sub v/ and T/sub g/ of the system and the effect of composition in normal solution polymerization at higher temperature, which was also the product of a dilution effect and a chemical or physical acceleration effect. (auth)« less

Chemical and physical characterization of the first stages of protoplanetary disk formation

NASA Astrophysics Data System (ADS)

Hincelin, Ugo

2012-12-01

Low mass stars, like our Sun, are born from the collapse of a molecular cloud. The matter falls in the center of the cloud, creating a protoplanetary disk surrounding a protostar. Planets and other Solar System bodies will be formed in the disk. The chemical composition of the interstellar matter and its evolution during the formation of the disk are important to better understand the formation process of these objects. I studied the chemical and physical evolution of this matter, from the cloud to the disk, using the chemical gas-grain code Nautilus. A sensitivity study to some parameters of the code (such as elemental abundances and parameters of grain surface chemistry) has been done. More particularly, the updates of rate coefficients and branching ratios of the reactions of our chemical network showed their importance, such as on the abundances of some chemical species, and on the code sensitivity to others parameters. Several physical models of collapsing dense core have also been considered. The more complex and solid approach has been to interface our chemical code with the radiation-magneto-hydrodynamic model of stellar formation RAMSES, in order to model in three dimensions the physical and chemical evolution of a young disk formation. Our study showed that the disk keeps imprints of the past history of the matter, and so its chemical composition is sensitive to the initial conditions.

Is the Reaction Equilibrium Composition in Non-ideal Mixtures Uniquely Determined by the Initial Composition?

NASA Astrophysics Data System (ADS)

Sefcik, Jan

1998-05-01

Reaction equilibrium can be mathematically described by the equilibrium equation and the reaction equilibrium composition can be calculated by solving this equation. It can be proved by non-elementary thermodynamic arguments that for a generic system with given initial composition, temperature and pressure there is a unique stable equilibrium state corresponding to the global minimum of the Gibbs free energy function. However, when the concept of equilibrium is introduced in undergraduate chemistry and chemical engineering courses, such arguments are generally not accessible. When there is a single reaction equilibrium among mixture components and the components form an ideal mixture, it has been demonstrated by a simple, elegant mathematical argument that there is a unique composition satisfying the equilibrium equation. It has been also suggested that this particular argument extends to non-ideal mixtures by simply incorporating activity coefficients. We show that the argument extension to non-ideal systems is not generally valid. Increasing non-ideality can result in non-monotonicity of the function crucial for the simple uniqueness argument, and only later it leads to non-uniqueness and hence phase separation. The main feature responsible for this is a composition dependence of activity coefficients in non-ideal mixtures.

Selective Disparity of Ordinary Chondritic Precursors in Micrometeorite Flux

NASA Astrophysics Data System (ADS)

Rudraswami, N. G.; Fernandes, D.; Naik, A. K.; Shyam Prasad, M.; Carrillo-Sánchez, J. D.; Plane, J. M. C.; Feng, W.; Taylor, S.

2018-01-01

All known extraterrestrial dust (micrometeoroids) entering the Earth’s atmosphere is anticipated to have a significant contribution from ordinary chondritic precursors, as seen in meteorites, but this is an apparent contradiction that needs to be addressed. Ordinary chondrites represent a minor contribution to the overall meteor influx compared to carbonaceous chondrites, which are largely dominated by CI and/or CM chondrites. However, the near-Earth asteroid population presents a scenario with sufficient scope for generation of dust-sized debris from ordinary chondritic sources. The bulk chemical composition of 3255 micrometeorites (MMs) collected from Antarctica and deep-sea sediments has shown Mg/Si largely dominated by carbonaceous chondrites, and less than 10% having ordinary chondritic precursors. The chemical ablation model is combined with different initial chondritic compositions (CI, CV, L, LL, H), and the results clearly indicate that high-density (≥2.8 g cm‑3) precursors, such as CV and ordinary chondrites in the size range 100–700 μm and zenith angle 0°–70°, ablate at much faster rates and lose their identity even before reaching the Earth’s surface and hence are under-represented in our collections. Moreover, their ability to survive as MMs remains grim for high-velocity micrometeoroids (>16 km s‑1). The elemental ratio for CV and ordinary chondrites are also similar to each other irrespective of the difference in the initial chemical composition. In conclusion, MMs belonging to ordinary chondritic precursors’ concentrations may not be insignificant in thermosphere, as they are found on Earth’s surface.

The state of understanding of the lithium-ion-battery graphite solid electrolyte interphase (SEI) and its relationship to formation cycling

DOE PAGES

An, Seong Jin; Li, Jianlin; Daniel, Claus; ...

2016-04-09

An in-depth review is presented on the science of lithium-ion battery (LIB) solid electrolyte interphase (SEI) formation on the graphite anode, including structure, morphology, chemical composition, electrochemistry, formation mechanism, and LIB formation cycling. During initial operation of LIBs, the SEI layer forms on the graphite surfaces, the most commonly used anode material, due to side reactions with the electrolyte solvent/salt at low electro-reduction potentials. It is accepted that the SEI layer is essential to the long-term performance of LIBs, and it also has an impact on its initial capacity loss, self-discharge characteristics, cycle life, rate capability, and safety. While themore » presence of the anode SEI layer is vital, it is difficult to control its formation and growth, as the chemical composition, morphology, and stability depend on several factors. These factors include the type of graphite, electrolyte composition, electrochemical conditions, and cell temperature. Thus, SEI layer formation and electrochemical stability over long-term operation should be a primary topic of future investigation in the development of LIB technology. We review the progression of knowledge gained about the anode SEI, from its discovery in 1979 to the current state of understanding, and covers its formation process, differences in the chemical and structural makeup when cell materials and components are varied, methods of characterization, and associated reactions with the liquid electrolyte phase. It also discusses the relationship of the SEI layer to the LIB formation step, which involves both electrolyte wetting and subsequent slow charge-discharge cycles to grow the SEI.« less

[Decomposition dynamics of leaf litter in logging residue of a secondary Castanopsis carlesii plantation and its chemical composition changes].

PubMed

Ren, Wei-ling; Guo, Jian-fen; Wu, Bo-bo; Wan, Jing-juan; Ji, Shu-rong; Liu, Xiao-fei

2015-04-01

A field experiment was conducted to understand the decomposition rates and chemical composition changes of leaf litter in logging residues of a 35-year-old secondary Castanopsis carlesii plantation over a period of one year. Mass loss rate of leaf litter showed an exponential decrease with time from May 2012 to April 2013, with a total 80% loss of initial dry mass. Net potassium (K) release was observed during this period, with only 5% of initial K remained. Nitrogen ( N) featured a pattern of accumulation at the early stage and release later, while phosphorus (P) exhibited a sequence of release, accumulation, and release. The remaining of N and P were 19% and 16% of their initial mass, respectively. The release rate was highest for K and the lowest for N. Decomposition of lignin indicated a trend of release-accumulation-release from May 2012 to October 2012, with no further significant change from November 2012 to the end of the experiment. The concentration of cellulose nearly unchanged during the experiment. The N/P rate increased with decomposition, ranging from 18.6 to 21.1. The lignin/N rate fluctuated greatly at the early stage and then almost stabilized thereafter.

VizieR Online Data Catalog: Evolution of rotating very massive LC stars (Kohler, 2015)

NASA Astrophysics Data System (ADS)

Kohler, K.; Langer, N.; de Koter, A.; de Mink, S. E.; Crowther, P. A.; Evans, C. J.; Grafener, G.; Sana, H.; Sanyal, D.; Schneider, F. R. N.; Vink, J. S.

2014-11-01

A dense model grid with chemical composition appropriate for the Large Magellanic Cloud is presented. A one-dimensional hydrodynamic stellar evolution code was used to compute our models on the main sequence, taking into account rotation, transport of angular momentum by magnetic fields and stellar wind mass loss. We present stellar evolution models with initial masses of 70-500M⊙ and with initial surface rotational velocities of 0-550km/s. (2 data files).

Carbide coated fibers in graphite-aluminum composites

NASA Technical Reports Server (NTRS)

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1975-01-01

The study of protective-coupling layers of refractory metal carbides on the graphite fibers prior to their incorporation into composites is presented. Such layers should be directly wettable by liquid aluminum and should act as diffusion barriers to prevent the formation of aluminum carbide. Chemical vapor deposition was used to uniformly deposit thin, smooth, continuous coats of ZrC on the carbon fibers of tows derived from both rayon and polyacrylonitrile. A wet chemical coating of the fibers, followed by high-temperature treatment, was used, and showed promise as an alternative coating method. Experiments were performed to demonstrate the ability of aluminum alloys to wet carbide surfaces. Titanium carbide, zirconium carbide and carbide-coated graphite surfaces were successfully wetted. Results indicate that initial attempts to wet surfaces of ZrC-coated carbon fibers appear successful.

Coupling Thermal and Chemical Signatures of Crustal Magma Bodies: Energy-Constrained Eruption, Recharge, Assimilation, and Fractional Crystallization (E'RAχFC)

NASA Astrophysics Data System (ADS)

Bohrson, W. A.; Spera, F. J.

2004-12-01

Energy-Constrained Eruption, Recharge, Assimilation and Fractional Crystallization (E'RAχFC) tracks the evolution of an open-system magmatic system by coupling conservation equations governing energy, mass and species (isotopes and trace elements). By linking the compositional characteristics of a composite magmatic system (host magma, recharge magma, wallrock, eruptive reservoir) to its mass and energy fluxes, predictions can be made about the chemical evolution of systems characterized by distinct compositional and thermal characteristics. An interesting application of E'RAχFC involves documenting the influence distinct thermal regimes have on the chemical evolution of magmatic systems. Heat transfer between a magma-country rock system at epizonal depths can be viewed as a conjugate heat transfer problem in which the average country rock-magma boundary temperature, Tb, is governed by the relative vigor of hydrothermal convection in the country rock vs. magma convection. For cases where hydrothermal circulation is vigorous and magmatic heat is efficiently transported away from the boundary, contact aureole temperatures (~Tb) are low. In cases where magmatic heat can not be efficiently transported away from the boundary and hydrothermal cells are absent or poorly developed, Tb is relatively high. Simultaneous solution of the differential equations governing momentum and energy conservation and continuity for the coupled hydrothermal-magmatic conjugate heat transfer system enables calculation of the characteristic timescale for EC-RAFC evolution and development of hydrothermal deposits as a function of material and medium properties, sizes of systems and relative efficiency of hydrothermal vs. magmatic heat transfer. Characteristic timescales lie in the range 102-106 yr depending on system size, magma properties and permeability among other parameters. In E'RAχFC, Tb is approximated by the user-defined equilibration temperature, Teq, which is the temperature at which all parts of the composite magmatic system achieve thermal equilibrium. Comparison of the results of three EC-AFC simulations at different Teq (1150° C, 1050° C, 1000° C) for a mafic magma intruding middle-upper crust of mafic-intermediate composition illustrate the distinctions that can be imparted by a range of thermal regimes. Model parameters relevant to the following results include: initial Sr concentration, isotope composition and bulk D for host magma are 700 ppm, 0.7035, and 1.5, respectively; those for wallrock are 230 ppm, 0.7100, 0.05. The 1150° C case (i.e., high Tb) yields the least crust-like Sr isotope signatures. The mass of wallrock that reaches thermal equilibrium is relatively small (0.26, normalized to the mass of initial host magma), although the degree of melting is high (97%). In contrast, the 1000° C case (i.e., low Tb) yields the most crust-like Sr isotope signatures. This case is also characterized by the largest mass of wallrock (0.98, normalized to the mass of initial host magma) that achieves thermal equilibrium, but the degree to which this wallrock melts is small (10%). A fundamental issue that derives from these results is the relationship between the chemical evolution of the hydrothermal system and the chemical evolution of associated melt and cumulates. In particular, to what extent can predictions be made from the thermal interactions between magma and wallrock on the chemical signatures of the associated magmatic rocks and hydrothermal deposits?

Research & Development of Materials/Processing Methods for Continuous Fiber Ceramic Composites (CFCC) Phase 2 Final Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szweda, A.

2001-01-01

The Department of Energy's Continuous Fiber Ceramic Composites (CFCC) Initiative that begun in 1992 has led the way for Industry, Academia, and Government to carry out a 10 year R&D plan to develop CFCCs for these industrial applications. In Phase II of this program, Dow Corning has led a team of OEM's, composite fabricators, and Government Laboratories to develop polymer derived CFCC materials and processes for selected industrial applications. During this phase, Dow Corning carried extensive process development and representative component demonstration activities on gas turbine components, chemical pump components and heat treatment furnace components.

Spatially Localized Chemical Patterns around an A + B → Oscillator Front.

PubMed

Budroni, M A; Lemaigre, L; Escala, D M; Muñuzuri, A P; De Wit, A

2016-02-18

When two gels, each loaded with a different set of reactants A and B of an oscillatory reaction, are brought into contact, reaction-diffusion patterns such as waves or Turing patterns can develop in the reactive contact zone. The initial condition which separates the reactants at the beginning leads to a localization in space of the different dynamical regimes accessible to the chemical oscillator. We study here both numerically and experimentally the composite traveling structures resulting from the interaction between chemical fronts and localized waves in the case in which the reactants of such an A + B → oscillator system are those of the canonical Belousov-Zhabotinsky (BZ) oscillating reaction. A transition between different dynamics is obtained by varying the initial concentration of the organic substrate of the BZ reactants, which is one of the parameters controlling the local excitability. We show that the dynamical regime (excitable or oscillatory) characterizing the BZ oscillator in the initial contact area is the key feature which determines the spatiotemporal evolution of the system. The experimental results are in qualitative agreement with the theoretical predictions.

Predicting properties of gas and solid streams by intrinsic kinetics of fast pyrolysis of wood

DOE PAGES

Klinger, Jordan; Bar-Ziv, Ezra; Shonnard, David; ...

2015-12-12

Pyrolysis has the potential to create a biocrude oil from biomass sources that can be used as fuel or as feedstock for subsequent upgrading to hydrocarbon fuels or other chemicals. The product distribution/composition, however, is linked to the biomass source. This work investigates the products formed from pyrolysis of woody biomass with a previously developed chemical kinetics model. Different woody feedstocks reported in prior literature are placed on a common basis (moisture, ash, fixed carbon free) and normalized by initial elemental composition through ultimate analysis. Observed product distributions over the full devolatilization range are explored, reconstructed by the model, andmore » verified with independent experimental data collected with a microwave-assisted pyrolysis system. These trends include production of permanent gas (CO, CO 2), char, and condensable (oil, water) species. Elementary compositions of these streams are also investigated. As a result, close agreement between literature data, model predictions, and independent experimental data indicate that the proposed model/method is able to predict the ideal distribution from fast pyrolysis given reaction temperature, residence time, and feedstock composition.« less

Method of forming a chemical composition

DOEpatents

Bingham, Dennis N.; Wilding, Bruce M.; Klingler, Kerry M.; Zollinger, William T.; Wendt, Kraig M.

2007-10-09

A method of forming a chemical composition such as a chemical hydride is described and which includes the steps of selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of hydrogen; and exposing the selected composition to an amount of ionizing radiation to encourage the changing of the chemical bonds of the selected composition, and chemically reacting the selected composition with the source of hydrogen to facilitate the formation of a chemical hydride.

Polydopamine and MnO2 core-shell composites for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Hou, Ding; Tao, Haisheng; Zhu, Xuezhen; Li, Maoguo

2017-10-01

Polydopamine and MnO2 core-shell composites (PDA@MnO2) for high-performance supercapacitors had been successfully synthesized by a facile and fast method. The morphology, crystalline phase and chemical composition of PDA@MnO2 composites are characterized using SEM, TEM, XRD, EDS and XPS. The performance of PDA@MnO2 composites are further investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The PDA@MnO2 core-shell nanostructure composites exhibit a high capacitance of 193 F g-1 at the current density of 1A g-1 and retained over 81.2% of its initial capacitance after 2500 cycles of charge-discharge at 2 A g-1. The results manifest that the PDA@MnO2 composites can be potentially applied in supercapacitors.

Recent progress to understand stress corrosion cracking in sodium borosilicate glasses: linking the chemical composition to structural, physical and fracture properties

NASA Astrophysics Data System (ADS)

Rountree, Cindy L.

2017-08-01

This topical review is dedicated to understanding stress corrosion cracking in oxide glasses and specifically the SiO_2{\\text-B_2O_3{\\text-}Na_2O} (SBN) ternary glass systems. Many review papers already exist on the topic of stress corrosion cracking in complex oxide glasses or overly simplified glasses (pure silica). These papers look at how systematically controlling environmental factors (pH, temperature...) alter stress corrosion cracking, while maintaining the same type of glass sample. Many questions still exist, including: What sets the environmental limit? What sets the velocity versus stress intensity factor in the slow stress corrosion regime (Region I)? Can researchers optimize these two effects to enhance a glass’ resistance to failure? To help answer these questions, this review takes a different approach. It looks at how systemically controlling the glass’ chemical composition alters the structure and physical properties. These changes are then compared and contrasted to the fracture toughness and the stress corrosion cracking properties. By taking this holistic approach, researchers can begin to understand the controlling factors in stress corrosion cracking and how to optimize glasses via the initial chemical composition.

Properties of vapor detector arrays formed through plasticization of carbon black-organic polymer composites.

PubMed

Koscho, Michael E; Grubbs, Robert H; Lewis, Nathan S

2002-03-15

Arrays of vapor detectors have been formed through addition of varying mass fractions of the plasticizer diethylene glycol dibenzoate to carbon black-polymer composites of poly(vinyl acetate) (PVAc) or of poly(N-vinylpyrrolidone). Addition of plasticizer in 5% mass fraction increments produced 20 compositionally different detectors from each polymer composite. Differences in vapor sorption and permeability that effected changes in the dc electrical resistance response of these compositionally different detectors allowed identification and classification of various test analytes using standard chemometric methods. Glass transition temperatures, Tg, were measured using differential scanning calorimetry for plasticized polymers having a mass fraction of 0, 0.10, 0.20, 0.30, 0.40, or 0.50 of plasticizer in the composite. The plasticized PVAc composites with Tg < 25 degrees C showed rapid responses at room temperature to all of the test analyte vapors studied in this work, whereas composites with Tg > 25 degrees C showed response times that were highly dependent on the polymer/analyte combination. These composites showed a discontinuity in the temperature dependence of their resistance, and this discontinuity provided a simple method for determining the Tg of the composite and for determining the temperature or plasticizer mass fraction above which rapid resistance responses could be obtained for all members of the test set of analyte vapors. The plasticization approach provides a method for achieving rapid detector response times as well as for producing a large number of chemically different vapor detectors from a limited number of initial chemical feedstocks.

Method of producing particulate-reinforced composites and composites produced thereby

DOEpatents

Han, Qingyou; Liu, Zhiwei

2013-12-24

A process for producing particle-reinforced composite materials through utilization of an in situ reaction to produce a uniform dispersion of a fine particulate reinforcement phase. The process includes forming a melt of a first material, and then introducing particles of a second material into the melt and subjecting the melt to high-intensity acoustic vibration. A chemical reaction initiates between the first and second materials to produce reaction products in the melt. The reaction products comprise a solid particulate phase, and the high-intensity acoustic vibration fragments and/or separates the reaction products into solid particles that are dispersed in the melt and are smaller than the particles of the second material. Also encompassed are particle-reinforced composite materials produced by such a process.

Method of producing particulate-reinforced composites and composites produced thereby

DOEpatents

Han, Qingyou; Liu, Zhiwei

2015-12-29

A process for producing particle-reinforced composite materials through utilization of an in situ reaction to produce a uniform dispersion of a fine particulate reinforcement phase. The process includes forming a melt of a first material, and then introducing particles of a second material into the melt and subjecting the melt to high-intensity acoustic vibration. A chemical reaction initiates between the first and second materials to produce reaction products in the melt. The reaction products comprise a solid particulate phase, and the high-intensity acoustic vibration fragments and/or separates the reaction products into solid particles that are dispersed in the melt and are smaller than the particles of the second material. Also encompassed are particle-reinforced composite materials produced by such a process.

Chemical Characterization and Reactivity of Fuel-Oxidizer Reaction Product

NASA Technical Reports Server (NTRS)

David, Dennis D.; Dee, Louis A.; Beeson, Harold D.

1997-01-01

Fuel-oxidizer reaction product (FORP), the product of incomplete reaction of monomethylhydrazine and nitrogen tetroxide propellants prepared under laboratory conditions and from firings of Shuttle Reaction Control System thrusters, has been characterized by chemical and thermal analysis. The composition of FORP is variable but falls within a limited range of compositions that depend on three factors: the fuel-oxidizer ratio at the time of formation; whether the composition of the post-formation atmosphere is reducing or oxidizing; and the reaction or post-reaction temperature. A typical composition contains methylhydrazinium nitrate, ammonium nitrate, methylammonium nitrate, and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. Thermal decomposition reactions of the FORP compositions used in this study were unremarkable. Neither the various compositions of FORP, the pure major components of FORP, nor mixtures of FORP with propellant system corrosion products showed any unusual thermal activity when decomposed under laboratory conditions. Off-limit thruster operations were simulated by rapid mixing of liquid monomethylhydrazine and liquid nitrogen tetroxide in a confined space. These tests demonstrated that monomethylhydrazine, methylhydrazinium nitrate, ammonium nitrate, or Inconel corrosion products can induce a mixture of monomethylhydrazine and nitrogen tetroxide to produce component-damaging energies. Damaging events required FORP or metal salts to be present at the initial mixing of monomethylhydrazine and nitrogen tetroxide.

Vegetation community composition in wetlands created following oil sand mining in Alberta, Canada.

PubMed

Roy, Marie-Claude; Foote, Lee; Ciborowski, Jan J H

2016-05-01

Reclaiming wetlands following open pit mining for industrial oil sand extraction is challenging due to the physical and chemical conditions of the post-mined landscape. The aim of our study was to examine and compare the influence of oil sands process water (OSPW) and material (fine fluid tails or FFT) on the plant community composition of created wetlands. Compared to created-unamended and natural wetlands, the created wetlands amended with OSPW and/or FFT (created-tailings wetlands) had significantly higher water salinity, conductivity, dissolved oxygen concentration and lower oxidative-reductive potential. Water chemistry parameters of created-unamended did not differ significantly from those of natural wetlands. The sediment of created wetlands had significantly less moisture, total nitrogen, and organic content than the natural wetlands. The application of OSPW/FFT in created wetlands will likely lead to initial vegetation composition atypical of natural regional wetlands. For the objective of reclaiming vegetation composition to the status of natural regional wetlands, unamended wetlands were the best reclamation option, based on the physical and chemical parameters measured. Despite being the favored reclamation option, created-unamended wetlands' physical and chemical characteristics remain atypical of natural wetlands. Most significantly, the basin morphometry of created wetlands was significantly different from that of naturally-formed wetlands in the region, and this appears to partly explain difference in vegetation composition. We also demonstrate that species richness alone is not a useful measure in wetland monitoring. Instead, plant community composition is a better indicator of wetland conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interfacial adhesion improvement in carbon fiber/carbon nanotube reinforced hybrid composites by the application of a reactive hybrid resin initiated by gamma irradiation

NASA Astrophysics Data System (ADS)

Szebényi, G.; Faragó, D.; Lámfalusi, Cs.; Göbl, R.

2018-04-01

Interfacial adhesion is a key factor in composite materials. The effective co-working of the reinforcing materials and matrix is essential for the proper load transfer between them, and to achieve the desired reinforcing effect. In case of nanocomposites, especially carbon nanotube (CNT) reinforced nanocomposites the adhesion between the CNTs and the polymer matrix is poor. To improve the interfacial adhesion and exploit the reinforcing effect of these nanoparticles a two step curable epoxy (EP)/vinylester (VE) hybrid resin system was developed where the EP is cured using hardener in the first step, during the composite production, and in the second step the curing of the VE is initiated by gamma irradiation, which also activates the reinforcing materials and the cured matrix component. A total of six carbon fiber reinforced composite systems were compared with neat epoxy and EP/VE hybrid matrices with and without chemical initiator and MWCNT nano-reinforcement. The effect of gamma irradiation was investigated at four absorbed dose levels. According to our three point bending and interlaminar shear test results the adhesion has improved between all constituents of the composite system. It was demonstrated that gamma irradiation has beneficial effect on the static mechanical, especially interlaminar properties of both micro- and nanocomposites in terms of modulus, strength and interlaminar shear strength.

Odor Recognition vs. Classification in Artificial Olfaction

NASA Astrophysics Data System (ADS)

Raman, Baranidharan; Hertz, Joshua; Benkstein, Kurt; Semancik, Steve

2011-09-01

Most studies in chemical sensing have focused on the problem of precise identification of chemical species that were exposed during the training phase (the recognition problem). However, generalization of training to predict the chemical composition of untrained gases based on their similarity with analytes in the training set (the classification problem) has received very limited attention. These two analytical tasks pose conflicting constraints on the system. While correct recognition requires detection of molecular features that are unique to an analyte, generalization to untrained chemicals requires detection of features that are common across a desired class of analytes. A simple solution that addresses both issues simultaneously can be obtained from biological olfaction, where the odor class and identity information are decoupled and extracted individually over time. Mimicking this approach, we proposed a hierarchical scheme that allowed initial discrimination between broad chemical classes (e.g. contains oxygen) followed by finer refinements using additional data into sub-classes (e.g. ketones vs. alcohols) and, eventually, specific compositions (e.g. ethanol vs. methanol) [1]. We validated this approach using an array of temperature-controlled chemiresistors. We demonstrated that a small set of training analytes is sufficient to allow generalization to novel chemicals and that the scheme provides robust categorization despite aging. Here, we provide further characterization of this approach.

Carbide coated fibers in graphite-aluminum composites

NASA Technical Reports Server (NTRS)

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1975-01-01

The NASA-supported program at the Los Alamos Scientific Laboratory (LASL) to develop carbon fiber-aluminum matrix composites is described. Chemical vapor deposition (CVD) was used to uniformly deposit thin, smooth, continuous coats of TiC on the fibers of graphite tows. Wet chemical coating of fibers, followed by high-temperature treatment, was also used, but showed little promise as an alternative coating method. Strength measurements on CVD coated fiber tows showed that thin carbide coats can add to fiber strength. The ability of aluminum alloys to wet TiC was successfully demonstrated using TiC-coated graphite surfaces. Pressure-infiltration of TiC- and ZrC-coated fiber tows with aluminum alloys was only partially successful. Experiments were performed to evaluate the effectiveness of carbide coats on carbon as barriers to prevent reaction between alluminum alloys and carbon. Initial results indicate that composites of aluminum and carbide-coated graphite are stable for long periods of time at temperatures near the alloy solidus.

Chemistry Simulations using the MERRA-2 Reanalysis with the GMI CTM and Replay in Support of the Atmospheric Composition Community

NASA Technical Reports Server (NTRS)

Oman, Luke D.; Strahan, Susan E.

2017-01-01

Simulations using reanalysis meteorological fields have long been used to understand the causes of atmospheric composition change in the recent past. Using the new MERRA-2 reanalysis, we are conducting chemistry simulations to create products covering 1980-2016 for the atmospheric composition community. These simulations use the Global Modeling Initiative (GMI) chemical mechanism in two different models: the GMI Chemical Transport Model (CTM) and the GEOS-5 model in Replay mode. Replay mode means an integration of the GEOS-5 general circulation model that is incrementally adjusted each time step toward the MERRA-2 reanalysis. The GMI CTM is a 1 deg x 1.25 deg simulation and the MERRA-2 GMI Replay simulation uses the native MERRA-2 grid of approximately 1/2 deg horizontal resolution on the cubed sphere. A specialized set of transport diagnostics is included in both runs to better understand trace gas transport and its variability in the recent past.

Usage of FT-ICR-MS Metabolomics for Characterizing the Chemical Signatures of Barrel-Aged Whisky

PubMed Central

Roullier-Gall, Chloé; Signoret, Julie; Hemmler, Daniel; Witting, Michael A.; Kanawati, Basem; Schäfer, Bernhard; Gougeon, Régis D.; Schmitt-Kopplin, Philippe

2018-01-01

Whisky can be described as a complex matrix integrating the chemical history from the fermented cereals, the wooden barrels, the specific distillery processes, aging, and environmental factors. In this study, using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), we analyzed 150 whisky samples from 49 different distilleries, 7 countries, and ranging from 1 day new make spirit to 43 years of maturation with different types of barrel. Chemometrics revealed the unexpected impact of the wood history on the distillate's composition during barrel aging, regardless of the whisky origin. Flavonols, oligolignols, and fatty acids are examples of important chemical signatures for Bourbon casks, whereas a high number of polyphenol glycosides, including for instance quercetin-glucuronide or myricetin-glucoside as potential candidates, and carbohydrates would discriminate Sherry casks. However, the comparison of barrel aged rums and whiskies revealed specific signatures, highlighting the importance of the initial composition of the distillate and the distillery processes. PMID:29520358

Usage of FT-ICR-MS Metabolomics for characterizing the chemical signatures of barrel-aged whisky

NASA Astrophysics Data System (ADS)

Roullier-Gall, Chloé; Signoret, Julie; Hemmler, Daniel; Witting, Michael A.; Kanawati, Basem; Schäfer, Bernhard; Gougeon, Régis D.; Schmitt-Kopplin, Philippe

2018-02-01

Whisky can be described as a complex matrix integrating the chemical history from the fermented cereals, the wooden barrels, the specific distillery processes, ageing and environmental factors. In this study, using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), we analysed 150 whisky samples from 49 different distilleries, 7 countries, and ranging from 1 day new make spirit to 43 years of maturation with different types of barrel. Chemometrics revealed the unexpected impact of the wood history on the distillatés composition during barrel ageing, regardless of the whisky origin. Flavonols, oligolignols and fatty acids are examples of important chemical signatures for Bourbon casks, whereas a high number of polyphenol glycosides, including for instance quercetin-glucuronide or myricetin-glucoside as potential candidates, and carbohydrates would discriminate Sherry casks. However, the comparison of barrel aged rums and whiskies revealed specific signatures, highlighting the importance of the initial composition of the distillate and the distillery processes.

Calibrating the ChemCam LIBS for Carbonate Minerals on Mars

DOE R&D Accomplishments Database

Wiens, Roger C.; Clegg, Samuel M.; Ollila, Ann M.; Barefield, James E.; Lanza, Nina; Newsom, Horton E.

2009-01-01

The ChemCam instrument suite on board the NASA Mars Science Laboratory (MSL) rover includes the first LIBS instrument for extraterrestrial applications. Here we examine carbonate minerals in a simulated martian environment using the LIDS technique in order to better understand the in situ signature of these materials on Mars. Both chemical composition and rock type are determined using multivariate analysis (MVA) techniques. Composition is confirmed using scanning electron microscopy (SEM) techniques. Our initial results suggest that ChemCam can recognize and differentiate between carbonate materials on Mars.

Chemical approach for controlling nadimide cure temperature and rate

NASA Technical Reports Server (NTRS)

Lauver, R. W. (Inventor)

1985-01-01

Polyimide resins suitable for use as composite matrix materials are formed by copolymerization of maleic and norbornenyl end-capped monomers and oligomers. The copolymers can be cured at temperatures under about 300 C. by controlling the available concentration of the maleic end-capped reactant. This control can be achieved by adding sufficient amounts of said maleic reactant, or by chemical modification of either copolymer, to increase Diels-Alder retrogression of the norbornenyl-capped reactant and/or holding initiation and polymerization to a rate compatible with the availability of the maleic-capped reactant.

Chemical approach for controlling nadimide cure temperature and rate

NASA Technical Reports Server (NTRS)

Lauver, R. W. (Inventor)

1984-01-01

Polyimide resins suitable for use as composite matrix materials are formed by copolymerization of maleic and norbornenyl endcapped monomers and oligomers. The copolymers can be cured at temperatures under about 300 C by controlling the available concentration of the maleic capped reactant. This control can be achieved by adding sufficient amounts of said maleic reactant, or by chemical modification of either copolymer, so as to either increase Diels-Alder retrogression of the norbornenyl capped reactant and/or holding initiation and polymerization to a rate compatible with the availability of the maleic capped reactant.

Chemical approach for controlling nadimide cure temperature and rate

NASA Technical Reports Server (NTRS)

Lauver, R. W. (Inventor)

1985-01-01

Polyimide resins suitable for use as composite matrix materials are formed by copolymerization of maleic and norbornenyl endcapped monomers and oligomers. The copolymers can be cured at temperatures under about 300 C by controlling the available concentration of the maleic endcapped reactant. This control is achieved by adding sufficient amounts of said maleic reactant or by chemical modification of either copolymer, to either increase Diels-Alder retrogression of the norbornenyl capped reactant and/or hold initiation and polymerization to a rate compatible with the availability of the maleic capped reactant.

The global stoichiometry of litter nitrogen mineralization

Treesearch

Stefano Manzoni; Robert B. Jackson; John A. Trofymow; Amilcare Porporato

2008-01-01

Plant residue decomposition and the nutrient release to the soil play a major role in global carbon and nutrient cycling. Although decomposition rates vary strongly with climate, nitrogen immobilization into litter and its release in mineral forms are mainly controlled by the initial chemical composition of the residues. We used a data set of ~2800 observations to show...

pH-adjustment strategy for volatile fatty acid production from high-strength wastewater for biological nutrient removal.

PubMed

Xie, Li; Liu, Hui; Chen, Yin-Guang; Zhou, Qi

2014-01-01

Volatile fatty acid (VFA) production from three types of high-strength organic wastewater (cassava thin stillage, starch wastewater and yellow-wine processing wastewater) were compared. The results showed that cassava thin stillage was the most suitable substrate, based on its high specific VFA production (0.68 g chemical oxygen demand (COD)/g initial soluble chemical oxygen demand (SCOD)) and yield (0.72 g COD/g SCOD) as well as low nutrient content in the substrate and fermented liquid. The acid fermented cassava thin stillage was evaluated and compared with sodium acetate in a sequencing batch reactor system. Total nitrogen removal efficiency was higher with fermented cassava thin stillage than with the sodium acetate. The effects of pH and a pH-adjustment strategy on VFA production and composition were determined using cassava thin stillage. At an initial pH range of 7-11, a relatively high VFA concentration of about 9 g COD/L was obtained. The specific VFA production (g COD/g initial SCOD) increased from 0.27 to 0.47 to 0.67 at pH 8 and from 0.26 to 0.68 to 0.81 at pH 9 (initial pH, interval pH, and constant pH adjustment, respectively). The dominant VFA species changed significantly with the increasing frequency of the pH adjustment. Further studies will examine the metabolic pathways responsible for VFA composition.

Understanding Gas-Phase Ammonia Chemistry in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Chambers, Lauren; Oberg, Karin I.; Cleeves, Lauren Ilsedore

2017-01-01

Protoplanetary disks are dynamic regions of gas and dust around young stars, the remnants of star formation, that evolve and coagulate over millions of years in order to ultimately form planets. The chemical composition of protoplanetary disks is affected by both the chemical and physical conditions in which they develop, including the initial molecular abundances in the birth cloud, the spectrum and intensity of radiation from the host star and nearby systems, and mixing and turbulence within the disk. A more complete understanding of the chemical evolution of disks enables a more complete understanding of the chemical composition of planets that may form within them, and of their capability to support life. One element known to be essential for life on Earth is nitrogen, which often is present in the form of ammonia (NH3). Recent observations by Salinas et al. (2016) reveal a theoretical discrepancy in the gas-phase and ice-phase ammonia abundances in protoplanetary disks; while observations of comets and protostars estimate the ice-phase NH3/H2O ratio in disks to be 5%, Salinas reports a gas-phase NH3/H2O ratio of ~7-84% in the disk surrounding TW Hydra, a young nearby star. Through computational chemical modeling of the TW Hydra disk using a reaction network of over 5000 chemical reactions, I am investigating the possible sources of excess gas-phase NH3 by determining the primary reaction pathways of NH3 production; the downstream chemical effects of ionization by ultraviolet photons, X-rays, and cosmic rays; and the effects of altering the initial abundances of key molecules such as N and N2. Beyond providing a theoretical explanation for the NH3 ice/gas discrepancy, this new model may lead to fuller understanding of the gas-phase formation processes of all nitrogen hydrides (NHx), and thus fuller understanding of the nitrogen-bearing molecules that are fundamental for life as we know it.

Titan's Interior Chemical Composition: A Thermochemical Assessment*

NASA Astrophysics Data System (ADS)

Howard, Michael; Zaug, J. M.; Khare, B. N.; McKay, C. P.

2007-10-01

We study the interior composition of Titan using thermal chemical equilibrium calculations that are valid to high pressures and temperatures. The equations of state are based on exponential-6 fluid theory and have been validated against experimental data up to a few Mbars in pressure and approximately 20000K in temperature. In addition to CHNO molecules, we account for multi-phases of carbon, water and a variety of metals such as Al and Fe, and their oxides. With these fluid equations of state, chemical equilibrium is calculated for a set of product species. As the temperature and pressure evolves for increasing depth in the interior, the chemical equilibrium shifts. We assume that Titan is initially composed of comet material, which we assume to be solar, except for hydrogen, which we take to be depleted by a factor 1/690. We find that a significant amount of nitrogen is in the form of n2, rather than nh3. Moreover, above 12 kbars, as is the interior pressure of Titan, a significant amount of the carbon is in the form of graphite, rather than co2 and ch4. We discuss the implications of these results for understanding the atmospheric and surface composition of Titan. • This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Titan's Interior Chemical Composition: Possible Important Phase Transitions

NASA Astrophysics Data System (ADS)

Howard, Michael; Fried, L. E.; Khare, B. N.; McKay, C. P.

2008-09-01

We study the interior composition of Titan using thermal chemical equilibrium calculations that are valid to high pressures and temperatures. The equations of state are based on exponential-6 fluid theory and have been validated against experimental data up to a few Mbars in pressure and approximately 20000K in temperature. In addition to CHNO molecules, we account for multi-phases of carbon, water and a variety of metals such as Al and Fe, and their oxides. With these fluid equations of state, chemical equilibrium is calculated for a set of product species. As the temperature and pressure evolves for increasing depth in the interior, the chemical equilibrium shifts. We assume that Titan is initially composed of comet material, which we assume to be solar, except for hydrogen, which we take to be depleted by a factor 1/1000. We find that a significant amount of nitrogen is in the form of N2, rather than NH3. Moreover, above 12 kbars pressure, as is the interior pressure of Titan, a significant amount of the carbon is in the form of graphite, rather than CO2 and CH4. We discuss the implications of these results for understanding the atmospheric and surface composition of Titan. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Gold nanoparticles mediated coloring of fabrics and leather for antibacterial activity.

PubMed

Velmurugan, Palanivel; Shim, Jaehong; Bang, Keuk-Soo; Oh, Byung-Taek

2016-07-01

Metal gold nanoparticles (AuNPs) were synthesized in situ onto leather, silk and cotton fabrics by three different modules, including green, chemical, and a composite of green and chemical synthesis. Green synthesis was employed using Ginkgo biloba Linn leaf powder extract and HAuCl4 with the fabrics, and chemical synthesis was done with KBH4 and HAuCl4. For composite synthesis, G. biloba extract and KBH4 were used to color and embed AuNPs in the fabrics. The colored fabrics were tested for color coordination and fastness properties. To validate the green synthesis of AuNPs, various instrumental techniques were used including UV-Vis spectrophotometry, HR-TEM, FTIR, and XRD. The chemical and composite methods reduce Au(+) onto leather, silk and cotton fabrics upon heating, and alkaline conditions are required for bonding to fibers; these conditions are not used in the green synthesis protocol. FE-SEM image revealed the binding nature of the AuNPs to the fabrics. The AuNPs that were synthesized in situ on the fabrics were tested against a skin pathogen, Brevibacterium linens using LIVE/DEAD BacLight Bacterial Viability testing. This study represents an initial route for coloring and bio-functionalization of various fabrics with green technologies, and, accordingly, should open new avenues for innovation in the textile and garment sectors. Copyright © 2016 Elsevier B.V. All rights reserved.

High temperature chemically resistant polymer concrete

DOEpatents

Sugama, T.; Kukacka, L.E.

High temperature chemically resistant, non-aqueous polymer concrete composites consist of about 12 to 20% by weight of a water-insoluble polymer binder. The binder is polymerized in situ from a liquid vinyl-type monomer or mixture of vinyl containing monomers such as triallylcyanurate, styrene, acrylonitrile, acrylamide, methacrylamide, methyl-methacrylate, trimethylolpropane trimethacrylate and divinyl benzene. About 5 to 40% by weight of a reactive inorganic filler selected from the group consisting of tricalcium silicate and dicalcium silicate and mixtures containing less than 2% free lime, and about 48 to 83% by weight of silica sand/ and a free radical initiator such as di-tert-butyl peroxide, azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide, other orgaic peroxides and combinations to initiate polymerization of the monomer in the presence of the inorganic filers are used.

Evaluation of Graphite Fiber/Polyimide PMCs from Hot Melt vs Solution Prepreg

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Eakin, Howard; Inghram, Linda; McCorkle, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Thesken, John; Fink, Jeffrey E.

2002-01-01

Carbon fiber reinforced high temperature polymer matrix composites (PMC) have been extensively investigated as potential weight reduction replacements of various metallic components in next generation high performance propulsion rocket engines. The initial phase involves development of comprehensive composite material-process-structure-design-property-in-service performance correlations and database, especially for a high stiffness facesheet of various sandwich structures. Overview of the program plan, technical approaches and current multi-team efforts will be presented. During composite fabrication, it was found that the two large volume commercial prepregging methods (hot-melt vs. solution) resulted in considerably different composite cure behavior. Details of the process-induced physical and chemical modifications in the prepregs, their effects on composite processing, and systematic cure cycle optimization studies will be discussed. The combined effects of prepregging method and cure cycle modification on composite properties and isothermal aging performance were also evaluated.

Evaluation of Graphite Fiber/Polyimide PMCs from Hot Melt versus Solution Prepreg

NASA Technical Reports Server (NTRS)

Shin, Eugene E.; Sutter, James K.; Eakin, Howard; Inghram, Linda; McCorkle, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Thesken, John; Fink, Jeffrey E.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Carbon fiber reinforced high temperature polymer matrix composites (PMC) have been extensively investigated as potential weight reduction replacements of various metallic components in next generation high performance propulsion rocket engines. The initial phase involves development of comprehensive composite material-process-structure-design-property in-service performance correlations and database, especially for a high stiffness facesheet of various sandwich structures. Overview of the program plan, technical approaches and current multi-team efforts will be presented. During composite fabrication, it was found that the two large volume commercial prepregging methods (hot-melt vs. solution) resulted in considerably different composite cure behavior. Details of the process-induced physical and chemical modifications in the prepregs, their effects on composite processing, and systematic cure cycle optimization studies will be discussed. The combined effects of prepregging method and cure cycle modification on composite properties and isothermal aging performance were also evaluated.

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.

2012-02-01

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heatmore » released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70°C. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 °C lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This reduction in capacity was observed to be independent of the amount of charge/discharge cycles except for the composites containing siloxane, which showed less of an impact on hydrogen storage capacity as it was cycled further. While the reason for this is not clear, it may be due to a chemically stabilizing effect of the siloxane on the metal hydride. Flow-through calorimetry was used to characterize the mitigating effectiveness of the different composites relative to the neat (no polymer) material. The composites were found to be initially effective at reducing the amount of heat released during oxidation, and the best performing material was the siloxane-containing composite which reduced the heat release to less than 50% of the value of the neat material. However, upon cycling the composites, all mitigating behavior was lost. The combined results of the flow-through calorimetry, hydrogen capacity, and thermogravimetric analysis tests lead to the proposed conclusion that while the polymer composites have mitigating potential and are physically robust under cycling, they undergo a chemical change upon cycling that makes them ineffective at mitigating heat release upon oxidation of the metal hydride.« less

Identifying new persistent and bioaccumulative organics among chemicals in commerce.

PubMed

Howard, Philip H; Muir, Derek C G

2010-04-01

The goal of this study was to identify commercial chemicals that might be persistent and bioaccumulative (P&B) and that were not being considered in current Great Lakes, North American, and Arctic contaminant measurement programs. We combined the Canadian Domestic Substance List (DSL), a list of 3059 substances of "unknown or variable composition complex reaction products and biological materials" (UVCBs), and the U.S. Environmental Protection Agency (U.S. EPA) Toxic Substances Control Act (TSCA) Inventory Update Rule (IUR) database for years 1986, 1990, 1994, 1998, 2002, and 2006 yielding a database of 22263 commercial chemicals. From that list, 610 chemicals were identified by estimates from U.S EPA EPISuite software and using expert judgment. This study has yielded some interesting and probable P&B chemicals that should be considered for further study. Recent studies, following up our initial reports and presentations on this work, have confirmed the presence of many of these chemicals in the environment.

Oxygen isotopic composition of chondritic interplanetary dust particles: A genetic link between carbonaceous chondrites and comets

NASA Astrophysics Data System (ADS)

Aléon, J.; Engrand, C.; Leshin, L. A.; McKeegan, K. D.

2009-08-01

Oxygen isotopes were measured in four chondritic hydrated interplanetary dust particles (IDPs) and five chondritic anhydrous IDPs including two GEMS-rich particles (Glass embedded with metal and sulfides) by a combination of high precision and high lateral resolution ion microprobe techniques. All IDPs have isotopic compositions tightly clustered around that of solar system planetary materials. Hydrated IDPs have mass-fractionated oxygen isotopic compositions similar to those of CI and CM carbonaceous chondrites, consistent with hydration of initially anhydrous protosolar dust. Anhydrous IDPs have small 16O excesses and depletions similar to those of carbonaceous chondrites, the largest 16O variations being hosted by the two GEMS-rich IDPs. Coarse-grained forsteritic olivine and enstatite in anhydrous IDPs are isotopically similar to their counterparts in comet Wild 2 and in chondrules suggesting a high temperature inner solar system origin. The small variations in the 16O content of GEMS-rich IDPs suggest that most GEMS either do not preserve a record of interstellar processes or the initial interstellar dust is not 16O-rich as expected by self-shielding models, although a larger dataset is required to verify these conclusions. Together with other chemical and mineralogical indicators, O isotopes show that the parent-bodies of carbonaceous chondrites, of chondritic IDPs, of most Antarctic micrometeorites, and comet Wild 2 belong to a single family of objects of carbonaceous chondrite chemical affinity as distinct from ordinary, enstatite, K- and R-chondrites. Comparison with astronomical observations thus suggests a chemical continuum of objects including main belt and outer solar system asteroids such as C-type, P-type and D-type asteroids, Trojans and Centaurs as well as short-period comets and other Kuiper Belt Objects.

Synthesis of polyaniline/cellulose composite as humidity sensor

NASA Astrophysics Data System (ADS)

Putri, N. P.; Kusumawati, D. H.; Widiyanti, N.; Munasir

2018-03-01

Water hyacinth is one weed plant that has cellulose content of 60% on the stem and is a good absorbent. in this study cellulose extraction from hyacinth has been done through several stages. Polyaniline/cellulose composite (PANi/cellulose) is prepared by an in-situ chemical method using cupric sulphate as an initiator. The representative PANi/cellulose samples are characterized by Fourier Transform Infrared (FTIR). On comparing it appears that spectra PANi/cellulose contains vibrational bands due to both PANi and cellulose. This may indicate the formation of PANi/cellulose composite. From the resistance measurement results, it can be seen that with the addition of cellulose to PANi can improve the sensitivity of the polyaniline based moisture sensor

Atmospheric-pressure electric discharge as an instrument of chemical activation of water solutions

NASA Astrophysics Data System (ADS)

Rybkin, V. V.; Shutov, D. A.

2017-11-01

Results of experimental studies and numerical simulations of physicochemical characteristics of plasmas generated in different types of atmospheric-pressure discharges (pulsed streamer corona, gliding electric arc, dielectric barrier discharge, glow-discharge electrolysis, diaphragmatic discharge, and dc glow discharge) used to initiate various chemical processes in water solutions are analyzed. Typical reactor designs are considered. Data on the power supply characteristics, plasma electron parameters, gas temperatures, and densities of active particles in different types of discharges excited in different gases and their dependences on the external parameters of discharges are presented. The chemical composition of active particles formed in water is described. Possible mechanisms of production and loss of plasma particles are discussed.

Chemical and phase evolution of amorphous molybdenum sulfide catalysts for electrochemical hydrogen production [Chemical and phase evolution of amorphous molybdenum sulfide catalysts for electrochemical hydrogen production directly observed using environmental transmission electron microscopy

DOE PAGES

Lee, Sang Chul; Benck, Jesse D.; Tsai, Charlie; ...

2015-12-01

Amorphous MoS x is a highly active, earth-abundant catalyst for the electrochemical hydrogen evolution reaction. Previous studies have revealed that this material initially has a composition of MoS 3, but after electrochemical activation, the surface is reduced to form an active phase resembling MoS 2 in composition and chemical state. However, structural changes in the Mo Sx catalyst and the mechanism of the activation process remain poorly understood. In this study, we employ transmission electron microscopy (TEM) to image amorphous MoS x catalysts activated under two hydrogen-rich conditions: ex situ in an electrochemical cell and in situ in an environmentalmore » TEM. For the first time, we directly observe the formation of crystalline domains in the MoS x catalyst after both activation procedures as well as spatially localized changes in the chemical state detected via electron energy loss spectroscopy. Using density functional theory calculations, we investigate the mechanisms for this phase transformation and find that the presence of hydrogen is critical for enabling the restructuring process. Our results suggest that the surface of the amorphous MoS x catalyst is dynamic: while the initial catalyst activation forms the primary active surface of amorphous MoS 2, continued transformation to the crystalline phase during electrochemical operation could contribute to catalyst deactivation. Finally, these results have important implications for the application of this highly active electrocatalyst for sustainable H 2 generation.« less

Examination of lignocellulosic fibers for chemical, thermal, and separations properties: Addressing thermo-chemical stability issues

NASA Astrophysics Data System (ADS)

Johnson, Carter David

Natural fiber-plastic composites incorporate thermoplastic resins with fibrous plant-based materials, sometimes referred to as biomass. Pine wood mill waste has been the traditional source of natural fibrous feedstock. In anticipation of a waste wood shortage other fibrous biomass materials are being investigated as potential supplements or replacements. Perennial grasses, agricultural wastes, and woody biomass are among the potential source materials. As these feedstocks share the basic chemical building blocks; cellulose, hemicellulose, and lignin, they are collectively called lignocellulosics. Initial investigation of a number of lignocellulosic materials, applied to fiber-plastic composite processing and material testing, resulted in varied results, particularly response to processing conditions. Less thermally stable lignocellulosic filler materials were physically changed in observable ways: darkened color and odor. The effect of biomass materials' chemical composition on thermal stability was investigated an experiment involving determination of the chemical composition of seven lignocellulosics: corn hull, corn stover, fescue, pine, soy hull, soy stover, and switchgrass. These materials were also evaluated for thermal stability by thermogravimetric analysis. The results of these determinations indicated that both chemical composition and pretreatment of lignocellulosic materials can have an effect on their thermal stability. A second study was performed to investigate what effect different pretreatment systems have on hybrid poplar, pine, and switchgrass. These materials were treated with hot water, ethanol, and a 2:1 benzene/ethanol mixture for extraction times of: 1, 3, 6, 12, and 24 hours. This factorial experiment demonstrated that both extraction time and medium have an effect on the weight percent of extractives removed from all three material types. The extracted materials generated in the above study were then subjected to an evaluation of thermal stability by thermogravimetric analysis in a subsequent experiment. Overlay plots, combining individual weight loss curves, demonstrate that the experimental factors, solvent system and extraction time, produce effects on the thermal stability of the treated biomass samples. These data also indicated that the individual lignocellulosic materials had unique responses to the type of solvent used for pretreatment. Increasing extraction time had either no correlation with or a positive effect on thermal stability of the biomass samples.

In-Situ TEM Visualization Of Vacancy Injection And Chemical Partition During Oxidation Of Ni-Cr Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chong M.; Genc, Arda; Cheng, Huikai

2014-01-14

Oxidation of alloy often involves chemical partition and injection of vacancies. Chemical partition is the consequence of selective oxidation, while injection of vacancies is associated with the differences of diffusivity of cations and anions. It is far from clear as how the injected vacancies behave during oxidation of metal. Using in-situ transmission electron microscopy, we captured unprecedented details on the collective behavior of injected vacancies during oxidation of metal, featuring an initial multi-site oxide nucleation, vacancy supersaturation, nucleation of a single cavity, sinking of vacancies into the cavity and accelerated oxidation of the particle. High sensitive energy dispersive x-ray spectroscopymore » mapping reveals that Cr is preferentially oxidized even at the initial oxidation, leading to a structure that Cr oxide is sandwiched near the inner wall of the hollow particle. The work provides a general guidance on tailoring of nanostructured materials involving multi-ion exchange such as core-shell structured composite nanoparticles.« less

In-Situ TEM visualization of vacancy injection and chemical partition during oxidation of Ni-Cr nanoparticles

PubMed Central

Wang, Chong-Min; Genc, Arda; Cheng, Huikai; Pullan, Lee; Baer, Donald R.; Bruemmer, Stephen M.

2014-01-01

Oxidation of alloy often involves chemical partition and injection of vacancies. Chemical partition is the consequence of selective oxidation, while injection of vacancies is associated with the differences of diffusivity of cations and anions. It is far from clear as how the injected vacancies behave during oxidation of metal. Using in-situ transmission electron microscopy, we captured unprecedented details on the collective behavior of injected vacancies during oxidation of metal, featuring an initial multi-site oxide nucleation, vacancy supersaturation, nucleation of a single cavity, sinking of vacancies into the cavity and accelerated oxidation of the particle. High sensitive energy dispersive x-ray spectroscopy mapping reveals that Cr is preferentially oxidized even at the initial oxidation, leading to a structure that Cr oxide is sandwiched near the inner wall of the hollow particle. The work provides a general guidance on tailoring of nanostructured materials involving multi-ion exchange such as core-shell structured composite nanoparticles. PMID:24418778

Development of naphthenic acid fractionation with supercritical fluid extraction for use in wood decay testing

Treesearch

Brett Niemi; Wayne St. John; Bessie Woodward; Rodney DeGroot; Gary McGinnis

2000-01-01

In recent years, the performance of copper naphthenate as a wood preservative has been in question. To understand the varying results of copper naphthenate in preventing wood decay, a closer look at eight naphthenic acid (NA) supplies was undertaken. Initial studies of NA samples from individual suppliers revealed large differences in chemical composition and wood...

Large-Scale Aerosol Modeling and Analysis

DTIC Science & Technology

2008-09-30

novel method of simultaneous real- time measurements of ice-nucleating particle concentrations and size- resolved chemical composition of individual...is to develop a practical predictive capability for visibility and weather effects of aerosol particles for the entire globe for timely use in...prediction follows that used in numerical weather prediction, namely real- time assessment for initialization of first-principles models. The Naval

AMDTreat 5.0+ with PHREEQC titration module to compute caustic chemical quantity, effluent quality, and sludge volume

USGS Publications Warehouse

Cravotta, Charles A.; Means, Brent P; Arthur, Willam; McKenzie, Robert M; Parkhurst, David L.

2015-01-01

Alkaline chemicals are commonly added to discharges from coal mines to increase pH and decrease concentrations of acidity and dissolved aluminum, iron, manganese, and associated metals. The annual cost of chemical treatment depends on the type and quantities of chemicals added and sludge produced. The AMDTreat computer program, initially developed in 2003, is widely used to compute such costs on the basis of the user-specified flow rate and water quality data for the untreated AMD. Although AMDTreat can use results of empirical titration of net-acidic or net-alkaline effluent with caustic chemicals to accurately estimate costs for treatment, such empirical data are rarely available. A titration simulation module using the geochemical program PHREEQC has been incorporated with AMDTreat 5.0+ to improve the capability of AMDTreat to estimate: (1) the quantity and cost of caustic chemicals to attain a target pH, (2) the chemical composition of the treated effluent, and (3) the volume of sludge produced by the treatment. The simulated titration results for selected caustic chemicals (NaOH, CaO, Ca(OH)2, Na2CO3, or NH3) without aeration or with pre-aeration can be compared with or used in place of empirical titration data to estimate chemical quantities, treated effluent composition, sludge volume (precipitated metals plus unreacted chemical), and associated treatment costs. This paper describes the development, evaluation, and potential utilization of the PHREEQC titration module with the new AMDTreat 5.0+ computer program available at http://www.amd.osmre.gov/.

Aqueous fluid composition in CI chondritic materials: Chemical equilibrium assessments in closed systems

NASA Astrophysics Data System (ADS)

Zolotov, Mikhail Yu.

2012-08-01

Solids of nearly solar composition have interacted with aqueous fluids on carbonaceous asteroids, icy moons, and trans-neptunian objects. These processes altered mineralogy of accreted materials together with compositions of aqueous and gaseous phases. We evaluated chemistry of aqueous solutions coexisted with CI-type chondritic solids through calculations of chemical equilibria in closed water-rock-gas systems at different compositions of initial fluids, water/rock mass ratios (0.1-1000), temperatures (<350 °C), and pressures (<2 kbars). The calculations show that fluid compositions are mainly affected by solubilities of solids, the speciation of chlorine in initial water-rock mixtures, and the occurrence of Na-bearing secondary minerals such as saponite. The major species in modeled alkaline solutions are Na+, Cl-, CO32-,HCO3-, K+, OH-, H2, and CO2. Aqueous species of Mg, Fe, Ca, Mn, Al, Ni, Cr, S, and P are not abundant in these fluids owing to low solubility of corresponding solids. Typical NaCl type alkaline fluids coexist with saponite-bearing mineralogy that usually present in aqueously altered chondrites. A common occurrence of these fluids is consistent with the composition of grains emitted from Enceladus. Na-rich fluids with abundant CO32-,HCO3-, and OH- anions coexist with secondary mineralogy depleted in Na. The Na2CO3 and NaHCO3 type fluids could form via accretion of cometary ices. NaOH type fluids form in reduced environments and may locally occur on parent bodies of CR carbonaceous chondrites. Supposed melting of accreted HCl-bearing ices leads to early acidic fluids enriched in Mg, Fe and other metals, consistent with signs of low-pH alteration in chondrites. Neutralization of these solutions leads to alkaline Na-rich fluids. Sulfate species have negligible concentrations in closed systems, which remain reduced, especially at elevated pressures created by forming H2 gas. Hydrogen, CO2, and H2O dominate in the gaseous phase, though the abundance of methane cannot be fairly estimated.

Kinetics of transformation of deformation processed gold-matrix composite

NASA Astrophysics Data System (ADS)

Wongpreedee, Kageeporn

Gold matrix Ḏeformation-processed M&barbelow;etal M&barbelow;etal C&barbelow;omposites (DMMC) have been developed that have better strength and conductivity than conventional gold alloys. However, DMMC possess metastable two-phase microstructures, and their strength and conductivity decrease after prolonged exposure to elevated temperatures. The kinetics of the transformation from the metastable two-phase microstructure to the equilibrium single-phase solid solution is of interest. This document describes a study of the elevated temperature stability of Au DMMC's and the relationship between microstructure and resistivity of three compositions: Au-7 vol %Ag, Au-14 vol %Ag, and Au-vol 7%Pt. DMMC samples were prepared by a powder metallurgy technique and mechanical processes. The smallest final diameter of these wires was 120 mum. Avrami and Arrhenius relations were used to evaluate the kinetic transformation. The extensive deformation used to produce these composites reshaped the initially equi-axed powder particles into a nanofilamentary composite. Electrical resistivity measurements were used to determine the degree of transformation from the initial metastable nano-filamentary composite to the equilibrium solid solution condition. These measurements indicated that this transformation in Au-14 at%Ag, Au-7 at %Ag Au and Au-7 at %Pt DMMC wires proceeded with activation energies of 141, 156, and 167 kJ/mol, respectively. It is thought that these empirically determined activation energies differ from those determined in single crystal, planar interface Au-Ag and Au-Pt diffusion couples due to chemical potential, surface curvature, and strain effects. The DMMC systems reach the equilibrium solid solution condition faster than single crystal, planar interface systems for two reasons: (1) far more defects (dislocations, grain boundaries, vacancies from non-conservative dislocation motion, etc.) are present in the Au-Ag and Au-Pt DMMC composites, and (2) the small radius of curvature of the Ag and Pt filaments increases the chemical potential for diffusion in the DMMC.

Kinetically Controlled Alteration of the Chemical Record During Diagenesis: An Experimental Study on Hydrothermal Carbonate Replacement

NASA Astrophysics Data System (ADS)

Mueller, T.; Dohmen, R.; Jonas, L.; Immenhauser, A.

2016-12-01

The geological record stored in the geochemical composition of carbonates provides a direct source of information on the Earth systems. However, the robustness and accuracy of these key records can be compromised by post-depositional alteration of sediments, such as dolomitization during diagenesis or low temperature metamorphism. Hence, knowledge on the mechanisms and rates of these processes hold the key to evaluate the robustness of proxies or to evaluate the extent of geochemical alteration. Previously, we presented experimental results of hydrothermal alteration of single calcite crystals and aragonitic coral fragments leading to replacement of the original carbonate by a Ca-Mg carbonate phase of variable composition. The experiments revealed the formation of a multiphase reaction rim with multiple replacement fronts [1]. Here, the reaction rate as well as composition of the reaction products is controlled by element transport in the pore fluid. In this study we focus on the reaction path of the replacement reaction and its effect on the recorded Mg-isotope composition. XRD diffraction patterns suggest the initial precipitation of non-ordered protodolomite that is subsequently continuously recrystallizing over the duration of the experiments to form an ordered, albeit non-stoichiometric dolomite. These observations are in agreement with Mg-isotope composition measured of the bulk reaction rim showing a systematic evolution over time that cannot be explained by simple Rayleigh or equilibrium fractionation. We interpret these findings as additional, but delayed reaction fronts affecting the microstructure and chemical composition of the newly formed carbonate rim that are essentially decoupled from the initial replacement front. Our results highlight the need to quantitatively understand alteration processes during diagenesis in order to accurately interpret the preserved geochemical record stored in element and isotope ratios of carbonates. [1] Jonas L., Mueller T., Dohmen R., Baumgartner L., and Putlitz B. (2015): Transport-controlled hydrothermal replacement of calcite by Mg-carbonates, Geology, 43, 779-782.

Sandwich-structured C/C-SiC composites fabricated by electromagnetic-coupling chemical vapor infiltration.

PubMed

Hu, Chenglong; Hong, Wenhu; Xu, Xiaojing; Tang, Sufang; Du, Shanyi; Cheng, Hui-Ming

2017-10-13

Carbon fiber (CF) reinforced carbon-silicon carbide (C/C-SiC) composites are one of the most promising lightweight materials for re-entry thermal protection, rocket nozzles and brake discs applications. In this paper, a novel sandwich-structured C/C-SiC composite, containing two exterior C/SiC layers, two gradient C/C-SiC layers and a C/C core, has been designed and fabricated by two-step electromagnetic-coupling chemical vapor infiltration (E-CVI) for a 20-hour deposition time. The cross-section morphologies, interface microstructures and SiC-matrix growth characteristics and compositions of the composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Microstructure characterization indicates that the SiC growth includes an initial amorphous SiC zone, a gradual crystallization of SiC and grow-up of nano-crystal, and a columnar grain region. The sandwich structure, rapid deposition rate and growth characteristics are attributed to the formation of thermal gradient and the establishment of electromagnetic field in the E-CVI process. The composite possesses low density of 1.84 g/cm 3 , high flexural strength of 325 MPa, and low linear ablation rate of 0.38 μm/s under exposure to 5-cycle oxyacetylene flame for 1000 s at ~1700 °C.

General classification of ``hot`` particles from the nearest Chernobyl contaminated areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shabalev, S.I.; Burakov, B.E.; Anderson, E.B.

1997-12-31

The morphology and composition both chemical and radionuclide of the main types of the solid-phase hot particles formed following the accident on the Chernobyl NPP have been studied by SEM, electron microprobe and gamma-spectrometry methods. Differences in many isotopes including: {sup 106}Ru, {sup 134}Cs, {sup 137}Cs dependent upon the hot particle matrix chemical composition was observed. The classification of hot particles based upon the chemical composition of their matrices has been done. It includes three main types: (1) fuel particles with UO{sub x} matrix; (2) fuel-constructional particles with Zr-U-O matrix, (3) hot particles with metallic inclusions of Fe-Cr-Ni. Moreover, theremore » are more rare types of hot particles with silicate or metal matrices. It was shown that only metallic inclusions of Fe-Cr-Ni are concentrators of {sup 106}Ru, which caused this nuclides assimilation in the molten stainless steel during the initial stages of the accident. Soils contamination of non-radioactive lead oxide particles in the Chernobyl NPP region were noticed. It was supposed that part of metallic lead, dropped from helicopters into burning reactor during first days of accident, was evaporated and oxidized accompanying solid oxide particles formation.« less

Evolution of Size and Chemical Composition of Copper Concentrate Particles Oxidized Under Simulated Flash Smelting Conditions

NASA Astrophysics Data System (ADS)

Pérez-Tello, Manuel; Parra-Sánchez, Víctor R.; Sánchez-Corrales, Víctor M.; Gómez-Álvarez, Agustín; Brown-Bojórquez, Francisco; Parra-Figueroa, Roberto A.; Balladares-Varela, Eduardo R.; Araneda-Hernández, Eugenia A.

2018-04-01

An experimental study was conducted to elucidate the evolution of size and chemical composition of La Caridad copper concentrate particles during oxidation under simulated flash smelting conditions. Input variables tested included particle size and oxygen concentration in the process gas. The response variables included the size distributions, chemical composition, and morphology of the reacted particles at seven locations along a laboratory reactor. Particles with initial size < 45 µm contained mostly chalcopyrite, they increased their mean size and decreased the amount of dust in the population during oxidation. This was explained by a reaction path involving rapid melting followed by collision and coalescence of reacting droplets during flight. Particles with sizes > 45 µm contained varying amounts of chalcopyrite and pyrite, and tended to either maintain or decrease their mean size upon oxidation. When size reduction was observed, dust was produced because of fragmentation, and the particles showed no evidence of collisions during flight. The main oxidation products detected in the particles consisted of matte, cuprospinel, and magnetite. A plot of the mean size divided by the mean size in the feed against the fraction of sulfur eliminated generalized the experimental data so far reported in the literature, and helped identify the reaction path followed by the particles.

Advanced functionalization of polyhydroxyalkanoate via the UV-initiated thiol-ene click reaction.

PubMed

Tajima, Kenji; Iwamoto, Kosuke; Satoh, Yasuharu; Sakai, Ryosuke; Satoh, Toshifumi; Dairi, Tohru

2016-05-01

Polyhydroxyalkanoates (PHAs) incorporating vinyl-bearing 3-hydroxyalkanoates were prepared in 8.5-12.9 g L(-1) yield. The molar ratios (0-16 mol%) of the vinyl-bearing 3-hydroxyalkanoate derivatives were controlled by the continuous feeding of undecylenate at various concentrations. Subsequently, the PHAs were functionalized by UV-initiated thiol-ene click reaction and chemical modification. (1)H NMR spectra suggested that 3-mercaptopropionic acid and 2-aminoethanethiol were successfully introduced into the vinyl-bearing PHA. Subsequently, chemical modification using fluorescein or a fibronectin active fragment (GRGDS) was attempted. The former yielded a PHA derivative capable of emitting fluorescence under UV irradiation, which was useful for determining the miscibility of PHA in a composite film comprising poly-ʟ-lactic acid (PLLA) and PHA. In the latter case, PHA bearing GRGDS peptides exhibited cell adhesiveness, suggesting that its biocompatibility was improved upon peptide introduction. Taken together, the UV-initiated thiol-ene click reaction was demonstrated to be useful in PHA modification.

Influence of Bulk Chemical Composition on Relative Sensitivity Factors for 55Mn/52Cr by SIMS: Implications for the 53Mn-53Cr Chronometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matzel, J; Jacobsen, B; Hutcheon, I D

2009-09-09

The {sup 53}Mn-{sup 53}Cr systematics of meteorite samples provide an important high resolution chronometer for early solar system events. Accurate determination of the initial abundance of {sup 53}Mn ({tau}{sub 1/2} = 3.7 Ma) by secondary ion mass spectrometry (SIMS) is dependent on properly correcting for differing ion yields between Mn and Cr by use of a relative sensitivity factor (RSF). Ideal standards for SIMS analysis should be compositionally and structurally similar to the sample of interest. However, previously published Mn-Cr studies rely on few standards (e.g., San Carlos olivine, NIST 610 glass) despite significant variations in chemical composition. We investigatemore » a potential correlation between RSF and bulk chemical composition by determining RSFs for {sup 55}Mn/{sup 52}Cr in 11 silicate glass and mineral standards (San Carlos olivine, Mainz glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, BM90/21-G, and T1-G, NIST 610 glass, and three LLNL pyroxene-composition glasses). All standards were measured on the Cameca ims-3f ion microprobe at LLNL, and a subset were also measured on the Cameca ims-1270 ion microprobe at the Geological Survey of Japan. The standards cover a range of bulk chemical compositions with SiO{sub 2} contents of 40-71 wt.%, FeO contents of 0.05-20 wt.% and Mn/Cr ratios between 0.4 and 58. We obtained RSF values ranging from 0.83 to 1.15. The data obtained on the ims-1270 ion microprobe are within {approx}10% of the RSF values obtained on the ims-3f ion microprobe, and the RSF determined for San Carlos olivine (0.86) is in good agreement with previously published data. The typical approach to calculating an RSF from multiple standard measurements involves making a linear fit to measured {sup 55}Mn/{sup 52}Cr versus true {sup 55}Mn/{sup 52}Cr. This approach may be satisfactory for materials of similar composition, but fails when compositions vary significantly. This is best illustrated by the {approx}30% change in RSF we see between glasses with similar Mn/Cr ratios but variable Fe and Na content. We are developing an approach that uses multivariate analysis to evaluate the importance of different chemical components in controlling the RSF and predict the RSF of unknowns when standards of appropriate composition are not available. Our analysis suggests that Fe, Si, and Na are key compositional factors in these silicate standards. The RSF is positively correlated with Fe and Si and negatively correlated with Na. Work is currently underway to extend this analysis to a wider range of chemical compositions and to evaluate the variability of RSF on measurements obtained by NanoSIMS.« less

Do Chemistry-Climate Models Project the Same Greenhouse Gas Chemistry if Initialized with Observations of the Trace Gases: A Pre-ATom Test

NASA Astrophysics Data System (ADS)

Flynn, C. M.; Prather, M. J.; Zhu, X.; Strode, S. A.; Steenrod, S. D.; Strahan, S. E.; Lamarque, J. F.; Fiore, A. M.; Horowitz, L. W.; Mao, J.; Murray, L. T.; Shindell, D. T.

2016-12-01

Experience with climate and chemistry model intercomparison projects (MIPs) has demonstrated a diversity in model projections for the chemical greenhouse gases CH4 and O3, even when forced by the same emissions. In general, the MIPs show that models diverge in the distribution of the many key trace species that control the reactivity of the troposphere (defined here as the loss of CH4 and the production and loss of O3). Two possible sources of model differences are the chemistry-transport coupling that creates the pattern of the essential precursor species, and the calculation of reactivity. Suppose that observations, such as those planned by NASA's Atmospheric Tomography (ATom) mission, provide us with enough of a chemical climatology to constrain the modeled distribution of the essential chemical species for the current epoch. Would the models calculate the same reactivity? ATom uses the DC-8 to make in situ measurements slicing through the middle of the Pacific and Atlantic Ocean basins each season and measuring the essential trace species. Unfortunately, ATom measurements will not be available until mid-2017. Here we take the baseline chemistry from one model version (as pseudo-observations) and use it to initialize 6 other global chemistry models. In this pre-ATom MIP, we take the full chemical composition for meridional slices centered on the Dateline (UC Irvine Chemistry-Transport Model, 0.6 deg resolution, 30 layers in the troposphere). We use grid cells between 0.5 and 12 km from 60 S to 60 N to initialize grid cells in the other six models (GEOS-Chem, GFDL-AM3, GISS ModelE2, GSFC GMI, NCAR, UCI CTM). The models are then integrated for 1 day and the key chemical rates (CH4, O3) are saved. These simulations assume that the initialized parcels remain unmixed over the 24 hours, and, hence, model-to-model variations will be due to differences in photochemistry, including clouds. In addition, we assess the relative importance of the precursor species by running sensitivity tests in which each of the major precursors (e.g., NOx, HOOH, HCHO, CO) is perturbed by 10%. Such sensitivity tests can help determine the causes of model differences. Overall, this new approach allows us to characterize each model's chemistry package for a wide range of designated chemical composition. The real test will be with ATom data next year.

Development of a numerical system to improve particulate matter forecasts in South Korea using geostationary satellite-retrieved aerosol optical data over Northeast Asia

NASA Astrophysics Data System (ADS)

Lee, Sojin; Song, Chul-han; Park, Rae Seol; Park, Mi Eun; Han, Kyung man; Kim, Jhoon; Choi, Myungje; Ghim, Young Sung; Woo, Jung-Hun

2016-04-01

To improve short-term particulate matter (PM) forecasts in South Korea, the initial distribution of PM composition, particularly over the upwind regions, is primarily important. To prepare the initial PM composition, the aerosol optical depth (AOD) data retrieved from a geostationary equatorial orbit (GEO) satellite sensor, GOCI (Geostationary Ocean Color Imager) which covers a part of Northeast Asia (113-146° E; 25-47° N), were used. Although GOCI can provide a higher number of AOD data in a semicontinuous manner than low Earth orbit (LEO) satellite sensors, it still has a serious limitation in that the AOD data are not available at cloud pixels and over high-reflectance areas, such as desert and snow-covered regions. To overcome this limitation, a spatiotemporal-kriging (STK) method was used to better prepare the initial AOD distributions that were converted into the PM composition over Northeast Asia. One of the largest advantages in using the STK method in this study is that more observed AOD data can be used to prepare the best initial AOD fields compared with other methods that use single frame of observation data around the time of initialization. It is demonstrated in this study that the short-term PM forecast system developed with the application of the STK method can greatly improve PM10 predictions in the Seoul metropolitan area (SMA) when evaluated with ground-based observations. For example, errors and biases of PM10 predictions decreased by ˜ 60 and ˜ 70{%}, respectively, during the first 6 h of short-term PM forecasting, compared with those without the initial PM composition. In addition, the influences of several factors on the performances of the short-term PM forecast were explored in this study. The influences of the choices of the control variables on the PM chemical composition were also investigated with the composition data measured via PILS-IC (particle-into-liquid sampler coupled with ion chromatography) and low air-volume sample instruments at a site near Seoul. To improve the overall performances of the short-term PM forecast system, several future research directions were also discussed and suggested.

Mass-independent sulfur isotopic compositions in stratospheric volcanic eruptions.

PubMed

Baroni, Mélanie; Thiemens, Mark H; Delmas, Robert J; Savarino, Joël

2007-01-05

The observed mass-independent sulfur isotopic composition (Delta33S) of volcanic sulfate from the Agung (March 1963) and Pinatubo (June 1991) eruptions recorded in the Antarctic snow provides a mechanism for documenting stratospheric events. The sign of Delta33S changes over time from an initial positive component to a negative value. Delta33S is created during photochemical oxidation of sulfur dioxide to sulfuric acid on a monthly time scale, which indicates a fast process. The reproducibility of the results reveals that Delta33S is a reliable tracer to chemically identify atmospheric processes involved during stratospheric volcanism.

Chemical characterization of some aerobic liquids in CELSS

NASA Technical Reports Server (NTRS)

Madsen, Brooks C.

1993-01-01

Untreated aqueous soybean and wheat leachate and aerobically treated wheat leachate prepared from crop residues that are produced as a component of the Controlled Ecological Life Support System program designed to support long duration space missions were compared, and a general chemical characterization was accomplished. Solid phase extraction and high performance liquid chromatography were used to accomplish comparisons based on chromatographic and ultraviolet absorption properties of the components that are present. Specific compounds were not identified; however, general composition related to the initial presence of phenol-like compounds and their disappearance during aerobic treatment was explored.

Chemical dealloying synthesis of porous silicon anchored by in situ generated graphene sheets as anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Feng, Jinkui; Zhang, Zhen; Ci, Lijie; Zhai, Wei; Ai, Qing; Xiong, Shenglin

2015-08-01

A novel one-pot chemical dealloying method has been developed to prepare nanocomposite of reduced graphene oxide (RGO) and silicon dendrite from cheap commercial Al-Si eutectic precursor. The RGO anchoring could act as both conductive agent and buffer layer for Si volume change in the application of lithium ion batteries (LIBs). The Si/RGO composites show an initial reversible capacity of 2280 mAh g-1, excellent capacity retention of 1942 mAh g-1 even after 100 cycles, and a high capacity of 1521 mAh g-1 even at the rate of 4000 mA g-1. Electrochemical impedance spectroscopy (EIS) measurement proved that Si/RGO composite has the lower charge transfer resistance. This work proposes an economic and facile method to prepare silicon based anode material for next generation LIBs with high energy density.

Classification and regulatory perspectives of dietary fiber.

PubMed

Dai, Fan-Jhen; Chau, Chi-Fai

2017-01-01

This review discusses the history and evolution of the state of dietary fiber (DF) with account of refinements in extraction methods and legal definitions subsequent to the launch of DF hypothesis. For a long time, defining and regulating DFs relied heavily on their chemical compositions and analytical methods. Although chemical compositions and analytical methods still play an important role in the definition of DF, physiological activity has also been taken into consideration. The precise definition of DF is still evolving, particularly whether oligosaccharides degrees of polymerization (DP) 3-9 should be considered as DF or not. Decades of scientific research have initiated the expansion of the term DF to include indigestible oligosaccharides with their DP between 3 and 9; hence responding to the positive health benefits of DF as well as fulfilling the needs in food labeling regulations. Copyright © 2016. Published by Elsevier B.V.

Strong, low-density nanocomposites by chemical vapor deposition and polymerization of cyanoacrylates on aminated silica aerogels.

PubMed

Boday, Dylan J; Stover, Robert J; Muriithi, Beatrice; Keller, Michael W; Wertz, Jason T; Defriend Obrey, Kimberly A; Loy, Douglas A

2009-07-01

Strong polymer-silica aerogel composites were prepared by chemical vapor deposition of cyanoacrylate monomers onto amine-modified aerogels. Amine-modified silica aerogels were prepared by copolymerizing small amounts of (aminopropyl)triethoxysilane with tetraethoxysilane. After silation of the aminated gels with hexamethyldisilazane, they were dried as aerogels using supercritical carbon dioxide processing. The resulting aerogels had only the amine groups as initiators for the cyanoacrylate polymerizations, resulting in cyanoacrylate macromolecules that were higher in molecular weight than those observed with unmodified silica and that were covalently attached to the silica surface. Starting with aminated silica aerogels that were 0.075 g/cm(3) density, composite aerogels were made with densities up to 0.220 g/cm(3) and up to 31 times stronger (flexural strength) than the precursor aerogel and about 2.3 times stronger than an unmodified silica aerogel of the same density.

[Chemical composition of fresh bee pollen collected in the Misintá páramo from the Venezuelan Andes].

PubMed

Vit, Patricia; Santiago, B

2008-12-01

Venezuelan bee pollen has not been characterized, and marketing is not regulated. Pollen is consumed for apitherapeutical purposes for its nutritional and medicinal properties. This product of the hive is the most popular after honey; therefore it is necessary to characterize and to value it to initiate a database to support the proposal of a norm for bee pollen quality control. Samples of bee pollen collected by bees in the Misintá páramo of Mérida state were characterized accoridng to the chemical composition (moisture, ash, fat, pH, proteins) of four color fractions (yellow, orange, ochre, green). Yellow pollen was the most frequent fraction, with 2.18 g ash/100 g, 5.37 g ether extract/100 g, 14.88 g moisture/100 g, and 37.32 g proteins/100 g.

Inorganic chemical composition and chemical reactivity of settled dust generated by the World Trade Center building collapse: Chapter 12

USGS Publications Warehouse

Plumlee, Geoffrey S.; Hageman, Philip L.; Lamothe, Paul J.; Ziegler, Thomas L.; Meeker, Gregory P.; Theodorakos, Peter M.; Brownfield, Isabelle; Adams, Monique G.; Swayze, Gregg A.; Hoefen, Todd M.; Taggart, Joseph E.; Clark, Roger N.; Wilson, S.; Sutley, Stephen J.

2009-01-01

Samples of dust deposited around lower Manhattan by the September 11, 2001, World Trade Center (WTC) collapse have inorganic chemical compositions that result in part from the variable chemical contributions of concrete, gypsum wallboard, glass fibers, window glass, and other materials contained in the buildings. The dust deposits were also modified chemically by variable interactions with rain water or water used in street washing and fire fighting. Chemical leach tests using deionized water as the extraction fluid show the dust samples can be quite alkaline, due primarily to reactions with calcium hydroxide in concrete particles. Calcium and sulfate are the most soluble components in the dust, but many other elements are also readily leached, including metals such as Al, Sb, Mo Cr, Cu, and Zn. Indoor dust samples produce leachates with higher pH, alkalinity, and dissolved solids than outdoor dust samples, suggesting most outdoor dust had reacted with water and atmospheric carbon dioxide prior to sample collection. Leach tests using simulated lung fluids as the extracting fluid suggest that the dust might also be quite reactive in fluids lining the respiratory tract, resulting in dissolution of some particles and possible precipitation of new phases such as phosphates, carbonates, and silicates. Results of these chemical characterization studies can be used by health scientists as they continue to track and interpret health effects resulting from the short-term exposure to the initial dust cloud and the longer-term exposure to dusts resuspended during cleanup.

Formation and aging of secondary organic aerosol from toluene: Changes in chemical composition, volatility, and hygroscopicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hildebrandt Ruiz, L.; Paciga, A. L.; Cerully, K. M.

Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NO x under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OS c), and mass yield. The OA oxidation state generallymore » increased during photo-oxidation, and the final OA OS c ranged from –0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. In conclusion, there was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.« less

Formation and aging of secondary organic aerosol from toluene: Changes in chemical composition, volatility, and hygroscopicity

DOE PAGES

Hildebrandt Ruiz, L.; Paciga, A. L.; Cerully, K. M.; ...

2015-07-24

Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NO x under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OS c), and mass yield. The OA oxidation state generallymore » increased during photo-oxidation, and the final OA OS c ranged from –0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. In conclusion, there was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.« less

Influence of Sn on the magnetic ordering of Ni-Sn alloy synthesized using chemical reduction method

NASA Astrophysics Data System (ADS)

Dhanapal, K.; Narayanan, V.; Stephen, A.

2016-05-01

The Ni-Sn alloy was synthesized using borohydride assisted chemical reduction method. The composition of the synthesized alloy was determined using atomic absorption spectroscopy which revealed that the observed composition of Sn is high when compared to the initial composition. The ultrafine particles are clearly observed from field emission scanning electron microscope for all the sample. The X-ray diffraction measurement confirmed that the as-synthesized samples are of amorphous like nature while the samples annealed at 773 K showed crystalline nature. The Fourier transform infrared spectroscopy confirmed metallic bond stretching in the alloy samples. The crystallization and phase transition temperature was observed from differential scanning calorimetry. The shift in the crystallization temperature of Ni with increasing percentage of Sn was observed. The vibrating sample magnetometer was employed to understand the magnetic behavior of the Ni-Sn alloy. As-synthesized alloy samples showed paramagnetic nature while the annealed ones exhibit the soft ferromagnetic, antiferromagnetic and paramagnetic nature. The saturation magnetization value and magnetic ordering in the Ni-Sn alloys depend on the percentage of Sn present in the alloy.

Method of producing particulate-reinforced composites and composties produced thereby

DOEpatents

Han, Qingyou; Liu, Zhiwei

2013-12-24

A process for producing particle-reinforced composite materials through utilization of an in situ reaction to produce a uniform dispersion of a fine particulate reinforcement phase. The process includes forming a melt of a first material, and then introducing particles of a second material into the melt and subjecting the melt to high-intenisty acoustic vibration. A chemical reaction initiates between the first and second materials to produce reaction products in the melt. The reaciton products comprise a solide particulate phase, and the high-intensity acoustic vibration fragments and/or separates the reaction products into solid particles that are dispersed in the melt and are smaller than the particles of the second material. Also encompassed are particles-reinforced composite materials produced by such a process.

Origins of water and solutes in and north of the Norris-Mammoth Corridor, Yellowstone National Park

USGS Publications Warehouse

Kharaka, Yousif; Mariner, Robert; Ambats, Gil; Evans, William; White, Lloyd; Bullen, Thomas; Kennedy, B. Mack

1990-01-01

This study was initiated to investigate the impacts of geothermal development in the Corwin Springs Known Geothermal Resources Area (KGRA) on the hydrothermal features of Yellowstone National Park. To determine possible hydrogeochemical connections, we used the diagnostic stable and radioactive isotopes of several elements, and the chemical and gas compositions of thermal and cold waters from the Norris-Mammoth Corridor and areas north of the Park. The investigations were particularly comprehensive in the Mammoth Hot Springs area, Corwin Springs KGRA, and Chico Hot Springs. The geochemical tools used are still subject to uncertainties of 1 - 5%. Preliminary interpretation of the data, especially the ??D and ??18O values of water, 87Sr/86Sr ratios, ??11B values, composition and isotopes of noble gases and several conservative chemical species would indicate that the waters from Mammoth Hot Springs and La Duke Spring area have evolved chemically and isotopically by reactions with different rock types, and are probably not directly connected. These data indicate that a component (<20%) of water in Bear Creek Springs may be derived from the Mammoth system.

Requirements for Initiation and Sustained Propagation of Fuel-Air Explosives

DTIC Science & Technology

1983-06-01

of single-head spin gives the limiting composition for stable propagation of a detonation wave. I. INTRODUCTION which the effects of blockage ratio...Ihu. Dateanle;otd) equivalent chemical times derived from it) provide a much more useful parameter as input to the required theories and empirical...dimensional steady state equilibrium theory (hence static). Experience shows that the dynamic parameters reflect more intimately the detonation properties

[Effect of NH4(+) -N/NO3(-)-N ratio in applied supplementary fertilizer on nitrogen metabolism and main chemical composition of Pinellia ternata].

PubMed

Hu, Long-Jiao; Wang, Kang-Cai; Li, Can-Wen

2013-07-01

To study the effect of nitrogen forms on nitrogen metabolism and main chemical composition of Pinellia ternate. Through the soilless cultivation experiment and based at the same nitrogen level and different NH4(+) -N/NO3(-) -N ratios, nitrate reductase (NR) activity, glutamine synthetase (GS) activity, the content of nitrate nitrogen and ammonium nitrogen in different parts of P. ternate were determined. The contents of total alkaloid, free total organic acids and guanosine in the tuber were determined. The yield of bulbil and tuber was calculated. The test results showed that, with the NH4(+) -N/NO3(-) -N ratio increasing, the activity of nitrate reductase decreased, the content of nitrate nitrogen in the leaves, petioles and tuber increasing initially, then decreased, and the content of nitrate nitrogen in the root decreased. Meanwhile, with the NH4(+) -N/NO3(-) -N ratio increasing, the activity of glutamine synthetase in the leaves, petioles and root increased, the activity of glutamine synthetase in the tuber increasing initially, then decreased. The contents of ammonium nitrogen in the leaves, tuber and root increased initially, then decreased, and the contents of ammonium nitrogen in the petioles increased with the NH4(+)(-N/NO3(-)-N ratio increasing. The yield of bulbil and tuber were the highest at the NH4(+)-N/NO3(-) -N ratio of 75: 25. The content of total alkaloid and guanosine in the tuber were the highest at the NH4(+)-N/NO3(-) -N ratio of 0: 100, and the contents were 0.245% and 0.0197% respectively. With the NH4(+)-N/NO3(-) -N ratio of 50: 50, the content of free total organic acids was the highest, it reached 0.7%, however, the content of free total organic acids was the lowest at the NH4(+) -N/NO3(-) -N ratio of 0: 100. Nitrogen fertilization significant influences the nitrogen metabolism, the yield and main chemical composition of P. ternate.

Chemical Weathering on Venus

NASA Astrophysics Data System (ADS)

Zolotov, Mikhail

2018-01-01

Chemical and phase compositions of Venus's surface could reflect history of gas- and fluid-rock interactions, recent and past climate changes, and a loss of water from the Earth's sister planet. The concept of chemical weathering on Venus through gas-solid type reactions has been established in 1960s after the discovery of hot and dense CO2-rich atmosphere inferred from Earth-based and Mariner 2 radio emission data. Initial works suggested carbonation, hydration, and oxidation of exposed igneous rocks and a control (buffering) of atmospheric gases by solid-gas type chemical equilibria in the near-surface lithosphere. Calcite, quartz, wollastonite, amphiboles, and Fe oxides were considered likely secondary minerals. Since the late 1970s, measurements of trace gases in the sub-cloud atmosphere by Pioneer Venus and Venera entry probes and Earth-based infrared spectroscopy doubted the likelihood of hydration and carbonation. The H2O gas content appeared to be low to allow a stable existence of hydrated and a majority of OH-bearing minerals. The concentration of SO2 was too high to allow the stability of calcite and Ca-rich silicates with respect to sulfatization to CaSO4. In 1980s, the supposed ongoing consumption of atmospheric SO2 to sulfates gained support by the detection of an elevated bulk S content at Venera and Vega landing sites. The induced composition of the near-surface atmosphere implied oxidation of ferrous minerals to magnetite and hematite, consistent with the infrared reflectance of surface materials. The likelihood of sulfatization and oxidation has been illustrated in modeling experiments at simulated Venus conditions. Venus's surface morphology suggests that hot surface rocks and fines of mainly mafic composition contacted atmospheric gases during several hundreds of millions years since a global volcanic resurfacing. Some exposed materials could have reacted at higher and lower temperatures in a presence of diverse gases at different altitudinal, volcanic, impact, and atmospheric settings. On highly deformed tessera terrains, more ancient rocks of unknown composition could reflect interactions with putative water-rich atmospheres and even aqueous solutions. Salt-, Fe oxide, or silica-rich formations would indicate past aqueous processes. The apparent diversity of affected solids, surface temperatures, pressures, and gas/fluid compositions throughout Venus's history implies multiple signs of chemical alteration, which remain to be investigated. The current understanding of chemical weathering is limited by the uncertain composition of the deep atmosphere, by the lack of direct data on the phase composition of surface materials, and by the uncertain data on thermodynamics of minerals and their solid solutions. In the preparation for further entry probe and lander missions, rock alteration needs to be investigated through chemical kinetic experiments and calculations of solid-gas(fluid) equilibria to constrain past and present processes.

Synthesis, Consolidation and Characterization of Sol-gel Derived Tantalum-Tungsten Oxide Thermite Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes, O

2010-06-01

Energetic composite powders consisting of sol-gel (SG) derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the SG derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The SG derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO3) energetic composite was consolidated to a density of 9.17 g·cm-3more » or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy.« less

Chemical compositions, methods of making the chemical compositions, and structures made from the chemical compositions

DOEpatents

Yang, Lei; Cheng, Zhe; Liu, Ze; Liu, Meilin

2015-01-13

Embodiments of the present disclosure include chemical compositions, structures, anodes, cathodes, electrolytes for solid oxide fuel cells, solid oxide fuel cells, fuel cells, fuel cell membranes, separation membranes, catalytic membranes, sensors, coatings for electrolytes, electrodes, membranes, and catalysts, and the like, are disclosed.

Aquatic exposures of chemical mixtures in urban environments: Approaches to impact assessment.

PubMed

de Zwart, Dick; Adams, William; Galay Burgos, Malyka; Hollender, Juliane; Junghans, Marion; Merrington, Graham; Muir, Derek; Parkerton, Thomas; De Schamphelaere, Karel A C; Whale, Graham; Williams, Richard

2018-03-01

Urban regions of the world are expanding rapidly, placing additional stress on water resources. Urban water bodies serve many purposes, from washing and sources of drinking water to transport and conduits for storm drainage and effluent discharge. These water bodies receive chemical emissions arising from either single or multiple point sources, diffuse sources which can be continuous, intermittent, or seasonal. Thus, aquatic organisms in these water bodies are exposed to temporally and compositionally variable mixtures. We have delineated source-specific signatures of these mixtures for diffuse urban runoff and urban point source exposure scenarios to support risk assessment and management of these mixtures. The first step in a tiered approach to assessing chemical exposure has been developed based on the event mean concentration concept, with chemical concentrations in runoff defined by volumes of water leaving each surface and the chemical exposure mixture profiles for different urban scenarios. Although generalizations can be made about the chemical composition of urban sources and event mean exposure predictions for initial prioritization, such modeling needs to be complemented with biological monitoring data. It is highly unlikely that the current paradigm of routine regulatory chemical monitoring alone will provide a realistic appraisal of urban aquatic chemical mixture exposures. Future consideration is also needed of the role of nonchemical stressors in such highly modified urban water bodies. Environ Toxicol Chem 2018;37:703-714. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Surface properties of the conidiospores of Phanerochaete chrysosporium and their relevance to pellet formation.

PubMed Central

Gerin, P A; Dufrene, Y; Bellon-Fontaine, M N; Asther, M; Rouxhet, P G

1993-01-01

The conidiospores of the white rot basidiomycete Phanerochaete chrysosporium tend to aggregate during swelling and germination in agitated liquid medium; as time passes, the initial aggregates tend to associate together and to capture conidiospores that remain isolated. The surface chemical compositions of the conidiospores and of developed hyphae were analyzed by X-ray photoelectron spectroscopy. The data were interpreted by modelling the surface in terms of proteins, polysaccharides and hydrocarbonlike compounds. The surface molecular composition of the dormant conidiospores was estimated to be about 45% proteins, 20% carbohydrates, and 35% hydrocarbonlike compounds. There was an increase in the polysaccharide content during germination. Later, when the hyphae were developed, the polysaccharide content became still higher, and the protein content dropped. The initial step of aggregation is attributed to polysaccharide bridging; its occurrence cannot be explained by a change of the overall hydrophobicity or electrical properties of the conidiospores. Images PMID:8349553

Materials properties and dislocation dynamics in InAsP compositionally graded buffers on InP substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jandl, Adam, E-mail: jandl@mit.edu; Bulsara, Mayank T.; Fitzgerald, Eugene A.

The properties of InAs{sub x}P{sub 1−x} compositionally graded buffers grown by metal organic chemical vapor deposition are investigated. We report the effects of strain gradient (ε/thickness), growth temperature, and strain initiation sequence (gradual or abrupt strain introduction) on threading dislocation density, surface roughness, epi-layer relaxation, and tilt. We find that gradual introduction of strain causes increased dislocation densities (>10{sup 6}/cm{sup 2}) and tilt of the epi-layer (>0.1°). A method of abrupt strain initiation is proposed which can result in dislocation densities as low as 1.01 × 10{sup 5} cm{sup −2} for films graded from the InP lattice constant to InAs{sub 0.15}P{sub 0.85}.more » A model for a two-energy level dislocation nucleation system is proposed based on our results.« less

Complete chemical transformation of a molecular film by subexcitation electrons (<3 eV).

PubMed

Balog, Richard; Illenberger, Eugen

2003-11-21

The potential of slow electrons to act as a soft tool to control a chemical reaction in the condensed phase is demonstrated. By setting the energy of a well defined electron beam to values below 3 eV, the surface of a thin film of 1,2-C(2)F(4)C(l2) molecules can completely be transformed into molecular chlorine (and by-products, possibly perfluorinated polymers). At higher energies (>6 eV) some equilibrium state between product and educt composition can be achieved, however, accompanied by a gradual overall degradation of the film. The effect of complete transformation is based on both the selectivity and particular energy dependence of the initial step of the reaction which is dissociative electron attachment to C(2)F(4)C(l2), but also the fact that the initial molecule is efficiently decomposed by subexcitation electrons while the product C(l2) is virtually unaffected.

Buckybomb: Reactive Molecular Dynamics Simulation

DOE PAGES

Chaban, Vitaly V.; Fileti, Eudes Eterno; Prezhdo, Oleg V.

2015-02-24

Energetic materials, such as explosives, propellants, and pyrotechnics, are widely used in civilian and military applications. Nanoscale explosives represent a special group because of the high density of energetic covalent bonds. The reactive molecular dynamics (ReaxFF) study of nitrofullerene decomposition reported here provides a detailed chemical mechanism of explosion of a nanoscale carbon material. Upon initial heating, C 60(NO 2) 12 disintegrates, increasing temperature and pressure by thousands of Kelvins and bars within tens of picoseconds. The explosion starts with NO 2 group isomerization into C-O-N-O, followed by emission of NO molecules and formation of CO groups on the buckyballmore » surface. NO oxidizes into NO 2, and C 60 falls apart, liberating CO 2. At the highest temperatures, CO 2 gives rise to diatomic carbon. Lastly, the study shows that the initiation temperature and released energy depend strongly on the chemical composition and density of the material.« less

Carbon-Based Ion Optics Development at NASA GRC

NASA Technical Reports Server (NTRS)

Haag, Thomas; Patterson, Michael; Rawlin, Vince; Soulas, George

2002-01-01

With recent success of the NSTAR ion thruster on Deep Space 1, there is continued interest in long term, high propellant throughput thrusters to perform energetic missions. This requires flight qualified thrusters that can operate for long periods at high beam density, without degradation in performance resulting from sputter induced grid erosion. Carbon-based materials have shown nearly an order of magnitude improvement in sputter erosion resistance over molybdenum. NASA Glenn Research Center (GRC) has been active over the past several years pursuing carbon-based grid development. In 1995, NASA GRC sponsored work performed by the Jet Propulsion Laboratory to fabricate carbon/carbon composite grids using a machined panel approach. In 1999, a contract was initiated with a commercial vendor to produce carbon/carbon composite grids using a chemical vapor infiltration process. In 2001, NASA GRC purchased pyrolytic carbon grids from a commercial vendor. More recently, a multi-year contract was initiated with North Carolina A&T to develop carbon/carbon composite grids using a resin injection process. The following paper gives a brief overview of these four programs.

Investigation of protein adsorption performance of Ni2+-attached diatomite particles embedded in composite monolithic cryogels.

PubMed

Ünlü, Nuri; Ceylan, Şeyda; Erzengin, Mahmut; Odabaşı, Mehmet

2011-08-01

As a low-cost natural adsorbent, diatomite (DA) (2 μm) has several advantages including high surface area, chemical reactivity, hydrophilicity and lack of toxicity. In this study, the protein adsorption performance of supermacroporous composite cryogels embedded with Ni(2+)-attached DA particles (Ni(2+)-ADAPs) was investigated. Supermacroporous poly(2-hydroxyethyl methacrylate) (PHEMA)-based monolithic composite cryogel column embedded with Ni(2+)-ADAPs was prepared by radical cryo-copolymerization of 2-hydroxyethyl methacrylate (HEMA) with N,N'-methylene-bis-acrylamide (MBAAm) as cross-linker directly in a plastic syringe for affinity purification of human serum albumin (HSA) both from aqueous solutions and human serum. The chemical composition and surface area of DA was determined by XRF and BET method, respectively. The characterization of composite cryogel was investigated by SEM. The effect of pH, and embedded Ni(2+)-ADAPs amount, initial HSA concentration, temperature and flow rate on adsorption were studied. The maximum amount of HSA adsorption from aqueous solution at pH 8.0 phosphate buffer was very high (485.15 mg/g DA). It was observed that HSA could be repeatedly adsorbed and desorbed to the embedded Ni(2+)-ADAPs in poly(2-hydroxyethyl methacrylate) composite cryogel without significant loss of adsorption capacity. The efficiency of albumin adsorption from human serum before and after albumin adsorption was also investigated with SDS-PAGE analyses. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Understanding the Role of Temperature and Cathode Composition on Interface and Bulk: Optimizing Aluminum Oxide Coatings for Li-Ion Cathodes.

PubMed

Han, Binghong; Paulauskas, Tadas; Key, Baris; Peebles, Cameron; Park, Joong Sun; Klie, Robert F; Vaughey, John T; Dogan, Fulya

2017-05-03

Surface coating of cathode materials with Al 2 O 3 has been shown to be a promising method for cathode stabilization and improved cycling performance at high operating voltages. However, a detailed understanding on how coating process and cathode composition change the chemical composition, morphology, and distribution of coating within the cathode interface and bulk lattice is still missing. In this study, we use a wet-chemical method to synthesize a series of Al 2 O 3 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 and LiCoO 2 cathodes treated under various annealing temperatures and a combination of structural characterization techniques to understand the composition, homogeneity, and morphology of the coating layer and the bulk cathode. Nuclear magnetic resonance and electron microscopy results reveal that the nature of the interface is highly dependent on the annealing temperature and cathode composition. For Al 2 O 3 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 , higher annealing temperature leads to more homogeneous and more closely attached coating on cathode materials, corresponding to better electrochemical performance. Lower Al 2 O 3 coating content is found to be helpful to further improve the initial capacity and cyclability, which can greatly outperform the pristine cathode material. For Al 2 O 3 -coated LiCoO 2 , the incorporation of Al into the cathode lattice is observed after annealing at high temperatures, implying the transformation from "surface coatings" to "dopants", which is not observed for LiNi 0.5 Co 0.2 Mn 0.3 O 2 . As a result, Al 2 O 3 -coated LiCoO 2 annealed at higher temperature shows similar initial capacity but lower retention compared to that annealed at a lower temperature, due to the intercalation of surface alumina into the bulk layered structure forming a solid solution.

Understanding the Role of Temperature and Cathode Composition on Interface and Bulk: Optimizing Aluminum Oxide Coatings for Li-Ion Cathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Binghong; Paulauskas, Tadas; Key, Baris

Here, surface coating of cathode materials with Al 2O 3 has been shown to be a promising method for cathode stabilization and improved cycling performance at high operating voltages. However, a detailed understanding on how coating process and cathode composition changes the chemical composition, morphology and distribution of coating within cathode interface and bulk lattice, is still missing. In this study, we use a wet-chemical method to synthesize a series of Al 2O 3-coated LiNi 0.5Co 0.2Mn 0.3O 2 and LiCoO 2 cathodes treated under various annealing temperatures and a combination of structural characterization techniques to understand the composition, homogeneitymore » and morphology of coating layer and the bulk cathode. Nuclear magnetic resonance and electron microscopy results reveal that the nature of the interface is highly depended on the annealing temperature and cathode composition. For Al 2O 3-coated LiNi 0.5Co 0.2Mn 0.3O 2, higher annealing temperature leads to more homogeneous and more closely attached coating on cathode materials, corresponding to better electrochemical performance. Lower Al 2O 3 coating content is found to be helpful to further improve the initial capacity and cyclability, which can greatly outperform the pristine cathode material. For Al 2O 3-coated LiCoO 2, the incorporation of Al into the cathode lattice is observed after annealing at high temperatures, implying the transformation from “surface coatings” to “dopants”, which is not observed for LiNi 0.5Co 0.2Mn 0.3O 2. As a result, Al 2O 3-coated LiCoO 2 annealed at higher temperature shows similar initial capacity but lower retention compared to that annealed at a lower temperature, due to the intercalation of surface alumina into the bulk layered structure forming a solid solution.« less

Understanding the Role of Temperature and Cathode Composition on Interface and Bulk: Optimizing Aluminum Oxide Coatings for Li-Ion Cathodes

DOE PAGES

Han, Binghong; Paulauskas, Tadas; Key, Baris; ...

2017-04-07

Here, surface coating of cathode materials with Al 2O 3 has been shown to be a promising method for cathode stabilization and improved cycling performance at high operating voltages. However, a detailed understanding on how coating process and cathode composition changes the chemical composition, morphology and distribution of coating within cathode interface and bulk lattice, is still missing. In this study, we use a wet-chemical method to synthesize a series of Al 2O 3-coated LiNi 0.5Co 0.2Mn 0.3O 2 and LiCoO 2 cathodes treated under various annealing temperatures and a combination of structural characterization techniques to understand the composition, homogeneitymore » and morphology of coating layer and the bulk cathode. Nuclear magnetic resonance and electron microscopy results reveal that the nature of the interface is highly depended on the annealing temperature and cathode composition. For Al 2O 3-coated LiNi 0.5Co 0.2Mn 0.3O 2, higher annealing temperature leads to more homogeneous and more closely attached coating on cathode materials, corresponding to better electrochemical performance. Lower Al 2O 3 coating content is found to be helpful to further improve the initial capacity and cyclability, which can greatly outperform the pristine cathode material. For Al 2O 3-coated LiCoO 2, the incorporation of Al into the cathode lattice is observed after annealing at high temperatures, implying the transformation from “surface coatings” to “dopants”, which is not observed for LiNi 0.5Co 0.2Mn 0.3O 2. As a result, Al 2O 3-coated LiCoO 2 annealed at higher temperature shows similar initial capacity but lower retention compared to that annealed at a lower temperature, due to the intercalation of surface alumina into the bulk layered structure forming a solid solution.« less

Method of producing hydrogen

DOEpatents

Bingham, Dennis N.; Klingler, Kerry M.; Wilding, Bruce M.; Zollinger, William T.

2006-12-26

A method of producing hydrogen is disclosed and which includes providing a first composition; providing a second composition; reacting the first and second compositions together to produce a chemical hydride; providing a liquid and reacting the chemical hydride with the liquid in a manner to produce a high pressure hydrogen gas and a byproduct which includes the first composition; and reusing the first composition formed as a byproduct in a subsequent chemical reaction to form additional chemical hydride.

Fully-automated, high-throughput micro-computed tomography analysis of body composition enables therapeutic efficacy monitoring in preclinical models.

PubMed

Wyatt, S K; Barck, K H; Kates, L; Zavala-Solorio, J; Ross, J; Kolumam, G; Sonoda, J; Carano, R A D

2015-11-01

The ability to non-invasively measure body composition in mouse models of obesity and obesity-related disorders is essential for elucidating mechanisms of metabolic regulation and monitoring the effects of novel treatments. These studies aimed to develop a fully automated, high-throughput micro-computed tomography (micro-CT)-based image analysis technique for longitudinal quantitation of adipose, non-adipose and lean tissue as well as bone and demonstrate utility for assessing the effects of two distinct treatments. An initial validation study was performed in diet-induced obesity (DIO) and control mice on a vivaCT 75 micro-CT system. Subsequently, four groups of DIO mice were imaged pre- and post-treatment with an experimental agonistic antibody specific for anti-fibroblast growth factor receptor 1 (anti-FGFR1, R1MAb1), control immunoglobulin G antibody, a known anorectic antiobesity drug (rimonabant, SR141716), or solvent control. The body composition analysis technique was then ported to a faster micro-CT system (CT120) to markedly increase throughput as well as to evaluate the use of micro-CT image intensity for hepatic lipid content in DIO and control mice. Ex vivo chemical analysis and colorimetric analysis of the liver triglycerides were performed as the standard metrics for correlation with body composition and hepatic lipid status, respectively. Micro-CT-based body composition measures correlate with ex vivo chemical analysis metrics and enable distinction between DIO and control mice. R1MAb1 and rimonabant have differing effects on body composition as assessed by micro-CT. High-throughput body composition imaging is possible using a modified CT120 system. Micro-CT also provides a non-invasive assessment of hepatic lipid content. This work describes, validates and demonstrates utility of a fully automated image analysis technique to quantify in vivo micro-CT-derived measures of adipose, non-adipose and lean tissue, as well as bone. These body composition metrics highly correlate with standard ex vivo chemical analysis and enable longitudinal evaluation of body composition and therapeutic efficacy monitoring.

Time-temperature-stress capabilities of composites for supersonic cruise aircraft applications

NASA Technical Reports Server (NTRS)

Haskins, J. F.; Kerr, J. R.; Stein, B. A.

1976-01-01

A range of baseline properties was determined for representatives of 5 composite materials systems: B/Ep, Gr/Ep, B/PI, Gr/PI, and B/Al. Long-term exposures are underway in static thermal environments and in ones which simultaneously combine programmed thermal histories and mechanical loading histories. Selected results from the environmental exposure studies with emphasis placed on the 10,000-hour thermal aging data are presented. Results of residual strength determinations and changes in physcial and chemical properties during high temperature aging are discussed and illustrated using metallographic, fractographic and thermomechanical analyses. Some initial results of the long-term flight simulation tests are also included.

Effects of fungal (Lentinussajor-caju) treated oil palm frond on performance and carcass characteristics in finishing goats

PubMed Central

Chanjula, Pin; Petcharat, Vasun; Cherdthong, Anusorn

2017-01-01

Objective This experiment was conducted to investigate the effects of fungal treated oil palm fronds (FTOPF) on performance, carcass traits, meat quality, and muscle chemical composition. Methods Eighteen growing crossbred male goats (Thai Native×Anglo Nubian) with 18.7±2.0 kg of initial body weight (BW) were stratified and blocked by BW in a randomized complete block design. Three diets containing 30% of oil palm fronds (OPF) either untreated (UOPF) or treated with Lentinussajor-caju (FTOPF) with or without urea (FTOPFU) were used as roughage sources in total mixed rations (TMRs). The diets were offered ad libitum and weight gain was determined. At the end of the experimental period, the harvest data and carcass characteristics of the goats were recorded, and muscular longissimus dorsi composition was determined. Results No significant effect of fungal treated (FT) inclusion was observed in any of the feed intake, growth performance, and carcass characteristics. Likewise, no apparent effects on carcass composition and muscle chemical composition were detected in this study, except for hind leg and chump were affected (p<0.05) by FT inclusion. Conclusion In conclusion, feeding of fungal (Lentinussajor-caju) treated oil palm frond in TMR diet did not affect performance and carcass characteristics in finishing goats. PMID:28446002

Effects of fungal (Lentinussajor-caju) treated oil palm frond on performance and carcass characteristics in finishing goats.

PubMed

Chanjula, Pin; Petcharat, Vasun; Cherdthong, Anusorn

2017-06-01

This experiment was conducted to investigate the effects of fungal treated oil palm fronds (FTOPF) on performance, carcass traits, meat quality, and muscle chemical composition. Eighteen growing crossbred male goats (Thai Native×Anglo Nubian) with 18.7±2.0 kg of initial body weight (BW) were stratified and blocked by BW in a randomized complete block design. Three diets containing 30% of oil palm fronds (OPF) either untreated (UOPF) or treated with Lentinussajor-caju (FTOPF) with or without urea (FTOPFU) were used as roughage sources in total mixed rations (TMRs). The diets were offered ad libitum and weight gain was determined. At the end of the experimental period, the harvest data and carcass characteristics of the goats were recorded, and muscular longissimus dorsi composition was determined. No significant effect of fungal treated (FT) inclusion was observed in any of the feed intake, growth performance, and carcass characteristics. Likewise, no apparent effects on carcass composition and muscle chemical composition were detected in this study, except for hind leg and chump were affected (p<0.05) by FT inclusion. In conclusion, feeding of fungal ( Lentinussajor-caju ) treated oil palm frond in TMR diet did not affect performance and carcass characteristics in finishing goats.

Comet impacts and chemical evolution on the bombarded earth

NASA Technical Reports Server (NTRS)

Oberbeck, Verne R.; Aggarwal, Hans

1992-01-01

Amino acids yields for previously published shock tube experiments are used with minimum Cretaceous-Tertiary (K/T) impactor mass and comet composition to predict AIB amino acid K/T boundary sediment column density. The inferred initial concentration of all amino acids in the K/T sea and in similar primordial seas just after 10 km comet impacts would have been at least 10 exp -7 M. However, sinks for amino acids must also be considered in calculating amino acid concentrations after comet impacts and in assessing the contribution of comets to the origin of life. The changing concentration of cometary amino acids due to ultraviolet light is compared with the equilibrium concentration of amino acids produced in the sea from corona discharge in the atmosphere, deposition in water, and degradation by ultraviolet light. Comets could have been more important than endogenous agents for initial evolution of amino acids. Sites favorable for chemical evolution of amino acids are examined, and it is concluded that chemical evolution could have occurred at or above the surface even during periods of intense bombardment of earth before 3.8 billion years ago.

A chemical model for generating the sources of mare basalts - Combined equilibrium and fractional crystallization of the lunar magmasphere

NASA Technical Reports Server (NTRS)

Snyder, Gregory A.; Taylor, Lawrence A.; Neal, Clive R.

1992-01-01

A chemical model for simulating the sources of the lunar mare basalts was developed by considering a modified mafic cumulate source formed during the combined equilibrium and fractional crystallization of a lunar magma ocean (LMO). The parameters which influence the initial LMO and its subsequent crystallization are examined, and both trace and major elements are modeled. It is shown that major elements tightly constrain the composition of mare basalt sources and the pathways to their creation. The ability of this LMO model to generate viable mare basalt source regions was tested through a case study involving the high-Ti basalts.

Triplex molecular layers with nonlinear nanomechanical response

NASA Astrophysics Data System (ADS)

Tsukruk, V. V.; Ahn, H.-S.; Kim, D.; Sidorenko, A.

2002-06-01

The molecular design of surface structures with built-in mechanisms for mechanical energy dissipation under nanomechanical deformation and compression resistance provided superior nanoscale wear stability. We designed robust, well-defined trilayer surface nanostructures chemically grafted to a silicon oxide surface with an effective composite modulus of about 1 GPa. The total thickness was within 20-30 nm and included an 8 nm rubber layer sandwiched between two hard layers. The rubber layer provides an effective mechanism for energy dissipation, facilitated by nonlinear, giant, reversible elastic deformations of the rubber matrix, restoring the initial status due to the presence of an effective nanodomain network and chemical grafting within the rubber matrix.

Microencapsulation, Chemical Characterization, and Antimicrobial Activity of Mexican (Lippia graveolens H.B.K.) and European (Origanum vulgare L.) Oregano Essential Oils

PubMed Central

Regalado-González, Carlos; Vázquez-Landaverde, Pedro; Guerrero-Legarreta, Isabel; García-Almendárez, Blanca E.

2014-01-01

The effect of solvent polarity (methanol and pentane) on the chemical composition of hydrodistilled essential oils (EO's) of Lippia graveolens H.B.K. (MXO) and Origanum vulgare L. (EUO) was studied by GC-MS. Composition of modified starch microencapsulated EO's was conducted by headspace-solid-phase microextraction (HS-SPME). The antimicrobial activity of free and microencapsulated EO's was evaluated. They were tested against Salmonella sp., Brochothrix thermosphacta, Pseudomonas fragi, Lactobacillus plantarum, and Micrococcus luteus. Thymol and carvacrol were among the main components of EO's and their free and microencapsulated inhibitory activity was tested against M. luteus, showing an additive combined effect. Chemical composition of EO's varied according to the solvent used for GC analysis and to volatile fraction as evaluated by HS-SPME. Thymol (both solvents) was the main component in essential oil of MXO, while carvacrol was the main component of the volatile fraction. EUO showed α-pinene (methanol) and γ-terpinene (pentane) as major constituents, the latter being the main component of the volatile fraction. EO's showed good stability after 3 months storage at 4°C, where antimicrobial activity of microencapsulated EO's remained the same, while free EO's decreased 41% (MXO) and 67% (EUO) from initial activity. Microencapsulation retains most antimicrobial activity and improves stability of EO's from oregano. PMID:25177730

Radical production inside an acoustically driven microbubble.

PubMed

Stricker, Laura; Lohse, Detlef

2014-01-01

The chemical production of radicals inside acoustically driven bubbles is determined by the local temperature inside the bubbles and by their composition at collapse. By means of a previously validated ordinary differential equations (ODE) model [L. Stricker, A. Prosperetti, D. Lohse, Validation of an approximate model for the thermal behavior in acoustically driven bubbles, J. Acoust. Soc. Am. 130 (5) (2011) 3243-3251], based on boundary layer assumption for mass and heat transport, we study the influence of different parameters on the radical production. We perform different simulations by changing the driving frequency and pressure, the temperature of the surrounding liquid and the composition of the gas inside the bubbles. In agreement with the experimental conditions of new generation sonochemical reactors, where the bubbles undergo transient cavitation oscillations [D. F. Rivas, L. Stricker, A. Zijlstra, H. Gardeniers, D. Lohse, A. Prosperetti, Ultrasound artificially nucleated bubbles and their sonochemical radical production, Ultrason. Sonochem. 20 (1) (2013) 510-524], we mainly concentrate on the initial chemical transient and we suggest optimal working ranges for technological applications. The importance of the chemical composition at collapse is reflected in the model, including the role of entrapped water vapor. We in particular study the exothermal reactions taking place in H2 and O2 mixtures. At the exact stoichiometric mixture 2:1 the highest internal bubble temperatures are achieved. Copyright © 2013 Elsevier B.V. All rights reserved.

Why Compositional Convection Cannot Explain Substellar Objects’ Sharp Spectral-type Transitions

NASA Astrophysics Data System (ADS)

Leconte, Jérémy

2018-02-01

As brown dwarfs and young giant planets cool down, they are known to experience various chemical transitions—for example, from {CO} rich L-dwarfs to methane rich T-dwarfs. Those chemical transitions are accompanied by spectral transitions with sharpness that cannot be explained by chemistry alone. In a series of articles, Tremblin et al. proposed that some of the yet-unexplained features associated with these transitions could be explained by a reduction of the thermal gradient near the photosphere. To explain, in turn, this more isothermal profile, they invoke the presence of an instability analogous to fingering convection—compositional convection—triggered by the change in mean molecular weight of the gas due to the chemical transitions mentioned above. In this Letter, we use existing arguments to demonstrate that any turbulent transport, if present, would in fact increase the thermal gradient. This misinterpretation comes from the fact that turbulence mixes/homogenizes entropy (potential temperature) instead of temperature. So, while increasing transport, turbulence in an initially stratified atmosphere actually carries energy downward, whether it is due to fingering or any other type of compositional convection. These processes therefore cannot explain the features observed along the aforementioned transitions by reducing the thermal gradient in the atmosphere of substellar objects. Understanding the microphysical and dynamical properties of clouds at these transitions thus probably remains our best way forward.

Microencapsulation, chemical characterization, and antimicrobial activity of Mexican (Lippia graveolens H.B.K.) and European (Origanum vulgare L.) oregano essential oils.

PubMed

Hernández-Hernández, Elvia; Regalado-González, Carlos; Vázquez-Landaverde, Pedro; Guerrero-Legarreta, Isabel; García-Almendárez, Blanca E

2014-01-01

The effect of solvent polarity (methanol and pentane) on the chemical composition of hydrodistilled essential oils (EO's) of Lippia graveolens H.B.K. (MXO) and Origanum vulgare L. (EUO) was studied by GC-MS. Composition of modified starch microencapsulated EO's was conducted by headspace-solid-phase microextraction (HS-SPME). The antimicrobial activity of free and microencapsulated EO's was evaluated. They were tested against Salmonella sp., Brochothrix thermosphacta, Pseudomonas fragi, Lactobacillus plantarum, and Micrococcus luteus. Thymol and carvacrol were among the main components of EO's and their free and microencapsulated inhibitory activity was tested against M. luteus, showing an additive combined effect. Chemical composition of EO's varied according to the solvent used for GC analysis and to volatile fraction as evaluated by HS-SPME. Thymol (both solvents) was the main component in essential oil of MXO, while carvacrol was the main component of the volatile fraction. EUO showed α-pinene (methanol) and γ-terpinene (pentane) as major constituents, the latter being the main component of the volatile fraction. EO's showed good stability after 3 months storage at 4°C, where antimicrobial activity of microencapsulated EO's remained the same, while free EO's decreased 41% (MXO) and 67% (EUO) from initial activity. Microencapsulation retains most antimicrobial activity and improves stability of EO's from oregano.

A comparison of chemical compositions of reported altered oceanic crusts and global MORB data set: implication for isotopic heterogeneity of recycled materials

NASA Astrophysics Data System (ADS)

Shimoda, G.; Kogiso, T.

2017-12-01

Chemical composition of altered oceanic crust is one of important constraints to delineate chemical heterogeneity of the mantle. Accordingly, many researchers have been studied to determine bulk chemical composition of altered oceanic crust mainly based on chemical compositions of old oceanic crusts at Site 801 and Site 417/418, and young crust at Site 504 (e.g., Staudigel et al., 1996; Bach et al. 2003; Kuo et al., 2016). Their careful estimation provided reliable bulk chemical compositions of these Sites and revealed common geochemical feature of alteration. To assess effect of recycling of altered oceanic crust on chemical evolution of the mantle, it might be meaningful to discuss whether the reported chemical compositions of altered oceanic crusts can represent chemical composition of globally subducted oceanic crusts. Reported chemical compositions of fresh glass or less altered samples from Site 801, 417/418 and 504 were highly depleted compared to that of global MORB reported by Gale et al. (2013), suggesting that there might be sampling bias. Hence, it could be important to consider chemical difference between oceanic crusts of these three Sites and global MORB to discuss effect of recycling of oceanic crust on isotopic heterogeneity of the mantle. It has been suggested that one of controlling factors of chemical variation of oceanic crust is crustal spreading rate because different degree of partial melting affects chemical composition of magmas produced at a mid-ocean ridge. Crustal spreading rate could also affect intensity of alteration. Namely, oceanic crusts produced at slow-spreading ridges may prone to be altered due to existence of larger displacement faults compared to fast spreading ridges which have relatively smooth topography. Thus, it might be significant to evaluate isotopic evolution of oceanic crusts those were produced at different spreading rates. In this presentation, we will provide a possible chemical variation of altered oceanic crusts based on reported bulk chemical compositions of altered oceanic crusts and global data sets of MORB. On the basis of the chemical variation, we will discuss isotopic evolution of altered oceanic crusts to delineate isotopic variation of recycled oceanic crusts.

Influence of BN fiber coatings on the interfacial structure of sapphire fiber reinforced NiAl composites

NASA Astrophysics Data System (ADS)

Reichert, K.; Wen, K.; Cremer, R.; Hu, W.; Neuschütz, D.; Gottstein, G.

2001-07-01

A new concept for a tailored fiber-matrix interface for sapphire fiber reinforced NiAl matrix composites is proposed, consisting of an initial hexagonal boron nitride (hBN) fiber coating. For this, single crystal Al 2O 3 fibers were coated with hBN by chemical vapor deposition (CVD). Following a comprehensive characterization of the CVD coating as to composition and structure by means of X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD), the fiber reinforced NiAl matrix composites were fabricated by diffusion bonding at 1400°C. The interfaces NiAl/BN and BN/Al 2O 3 were analyzed by scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and selected area diffraction (SAD). An interfacial reaction between NiAl and hBN to form AlN was revealed using these analytical techniques.

Tantalum-tungsten oxide thermite composites prepared by sol-gel synthesis and spark plasma sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuntz, Joshua D.; Gash, Alexander E.; Cervantes, Octavio G.

2010-08-15

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and the results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High-Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta-WO{sub 3}) energetic composite was consolidated to a density of 9.17 g cm{sup -3}more » or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy. (author)« less

Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes, O; Kuntz, J; Gash, A

2009-02-13

Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17more » g.cm{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.« less

Crosslinked Carbon Nanotubes/Polyaniline Composites as a Pseudocapacitive Material with High Cycling Stability

PubMed Central

Liu, Dong; Wang, Xue; Deng, Jinxing; Zhou, Chenglong; Guo, Jinshan; Liu, Peng

2015-01-01

The poor cycling stability of polyaniline (PANI) limits its practical application as a pseudocapacitive material due to the volume change during the charge-discharge procedure. Herein, crosslinked carbon nanotubes/polyaniline (C-CNTs/PANI) composites had been designed by the in situ chemical oxidative polymerization of aniline in the presence of crosslinked carbon nanotubes (C-CNTs), which were obtained by coupling of the functionalized carbon nanotubes with 1,4-benzoquinone. The composite showed a specific capacitance of 294 F/g at the scan rate of 10 mV/s, and could retain 95% of its initial specific capacitance after 1000 CV cycles. Such high electrochemical cycling stability resulting from the crosslinked skeleton of the C-CNTs makes them potential electrode materials for a supercapacitor. PMID:28347050

Characterizing the Response of Fluvial Systems to Extreme Global Warming During the Early Eocene Climatic Optimum: An Analysis of the Wasatch and Green River Formations, Uinta Basin, UT

NASA Astrophysics Data System (ADS)

Jones, E. R.; Plink-Bjorklund, P.

2013-12-01

The Wasatch and Green River Formations in the Uinta Basin, UT contain fluvial sandstones that record changes in terrestrial sedimentation coincident with Paleocene-Eocene Thermal Maximum (PETM) and at least six post-PETM hyperthermal climate change events. While proxies for chemical weathering rates during the PETM have been developed using the marine osmium isotope record, to date there has been little research on chemical weathering rates in proximal terrestrial depocenters. This work is one part of a multi-proxy research effort combining quantitative petrographic analysis, the stable carbon isotope record, and a high-resolution stratigraphic and sedimentologic framework across the southern margin of the Uinta Basin. Relative tectonic quiescence in the Uinta Basin during the Early Eocene suggests that climate is the forcing mechanism controlling fluvial architecture and composition, and gradual basin subsidence has preserved at least six pulses of greenhouse climate change during the Early Eocene Climatic Optimum (EECO). Terrestrial records of PETM climate do not support a humid climate with increased precipitation as previously suggested from marine proxies of climate change. Instead, terrestrial records of the PETM climate show evidence of prolonged drought punctuated by intense terrestrial flooding events in mid-latitude continental interiors. Increases in chemical weathering rates during the PETM due to increased temperature and average precipitation is cited as a key carbon sink to initiate a recovery phase where atmospheric CO2 returned to normal concentrations. If terrestrial records of chemical weathering rates differ substantially from marine proxies the carbon-cycle dynamics active during the EECO must be reconsidered. Initial results of this study show that these peak hyperthermal climate change conditions in the Uinta Basin preserve more compositionally and texturally immature sediments due to extremely high erosion and deposition rates, and subdued duration of transport. In particular the relative proportions of preserved potassium and especially plagioclase feldspar are sensitive to these pulses of greenhouse climate change. This dataset suggests that the seasonality of sediment dispersal and transport can play a more important role in the preservation potential of unstable mineral phases in the sedimentary record than just variations in global chemical weathering rates. Compositional variability in perenially wet and peaked seasonality facies in fluvial sandstones in the Wasatch Formation.

Variability of chemical analysis of reinforcing bar produced in Saudi Arabia

NASA Astrophysics Data System (ADS)

Salman, A.; Djavanroodi, F.

2018-04-01

In view of the importance and demanding roles of steel rebar’s in the reinforced concrete structures, accurate information on the properties of the steels is important at the design stage. In the steelmaking process, production variations in chemical composition are unavoidable. The aim of this work is to study the variability of the chemical composition of reinforcing steel produced throughout the Saudi Arabia and asses the quality of steel rebar’s acoording to ASTM A615. 68 samples of ASTM A615 Grade 60 from different manufacturers were collected and tested using the Spectrometer test to obtain Chemical Compositions. EasyFit (5.6) software is utilized to conducted statistical analysis. Chemical compositions distributions and, control charts are generated for the compositions. Results showed that some compositions are above the upper line of the control chart. Finally, the analyses show that less than 3% of the steel failed to meet minimum ASTM standards for chemical composition.

Low concentration graphene nanoplatelets for shape stabilization and thermal transfer reinforcement of Mannitol: a phase change material for a medium-temperature thermal energy system

NASA Astrophysics Data System (ADS)

Jing, Gu; Dehong, Xia; Li, Wang; Wenqing, Ao; Zhaodong, Qi

2018-03-01

We report herein a novel series of Mannitol/GNPs (graphene nanoplatelets) composites with incremental GNPs loadings from 1 wt% to 10 wt% for further applications in medium-temperature thermal energy system. The phase change behavior and thermal conductivity of Mannitol/GNPs composite, a nanostructured PCM, have been evaluated as a function of GNPs content. Compared to the pristine Mannitol, the resultant stabilized composite with 8 wt% of GNPs displays an extremely high 1054% enhancement in thermal conductivity, and inherits 92% of phase change enthalpy of bulk Mannitol PCM (phase change material). More importantly, 92%Mannitol/GNPs composite still preserves its initial shape without any leakage even when subjected to a 400 consecutive melting/re-solidification cycles. The resulting Mannitol composites exhibit excellent chemical compatibility, large phase change enthalpy and improved thermal reliability, as compared to base PCM, which stands distinct in its class of organic with reference to the past literatures.

Mineralogical transformations controlling acid mine drainage chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peretyazhko, Tetyana; Zachara, John M.; Boily, Jean F.

2009-05-30

The role of Fe(III) minerals in controlling acid mine drainage (AMD) chemistry was studied using samples from two AMD sites [Gum Boot (GB) and Fridays-2 (FR)] located in northern Pennsylvania. Chemical extractions, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to identify and characterize Fe(III) phases. The mineralogical analysis revealed that schwertmannite and goethite were the principal Fe(III) phases in the sediments. Schwertmannite transformation occurred at the GB site where poorly-crystallized goethite rich in surface-bound sulfate was initially formed. In contrast, no schwertmannite transformation occurred at the FR site. The goethite in GBmore » sediments had spherical morphology due to preservation of schwertmannite structure by adsorbed sulfate. Results of chemical extractions showed that poorly-crystallized goethite was subject to further crystallization accompanied by sulfate desorption. Changes in sulfate speciation preceded its desorption, with a conversion of bidentate- to monodentate-bound sulfate surface complexes. Laboratory sediment incubation experiments were conducted to evaluate the effect of mineral transformation on water chemistry. Incubation experiments were carried out with schwertmannite-containing sediments and AMD waters with different pH and chemical composition. The pH decreased to 1.9-2.2 in all suspensions and the concentrations of dissolved Fe and S increased significantly. Regardless of differences in the initial water composition, pH, Fe and S were similar in suspensions of the same sediment. XRD measurements revealed that schwertmannite transformed into goethite in GB and FR sediments during laboratory incubation. The incubation experiment demonstrated that schwertmannite transformation controlled AMD water chemistry during “closed system” laboratory contact.« less

Zn0-CNTs-Fe3O4 catalytic in situ generation of H2O2 for heterogeneous Fenton degradation of 4-chlorophenol.

PubMed

Yang, Zhao; Gong, Xiao-Bo; Peng, Lin; Yang, Dan; Liu, Yong

2018-06-04

A novel Zn 0 -CNTs-Fe 3 O 4 composite was synthesized by the chemical co-precipitation combined with high sintering process at nitrogen atmosphere. The as-prepared composite was characterized by SEM, EDS, XRD, XPS, VSM and N 2 adsorption/desorption experiments. A novel heterogeneous Fenton-like system, composed of Zn 0 -CNTs-Fe 3 O 4 composite and dissolved oxygen (O 2 ) in solution, which can in situ generate H 2 O 2 and OH, was used for the degradation of 4-chlorophenol (4-CP). The influences of various operational parameters, including the initial pH, dosage of Zn 0 -CNTs-Fe 3 O 4 and initial concentration of 4-CP on the removal of 4-CP were investigated. The removal efficiencies of 4-CP and total organic carbon (TOC) were 99% and 57%, respectively, at the initial pH of 1.5, Zn 0 -CNTs-Fe 3 O 4 dosage of 2 g/L, 4-CP initial concentration of 50 mg/L and oxygen flow rate of 400 mL/min. Based on the results of the radical scavenger effect study, the hydroxyl radical was considered as the main reactive oxidants in Zn 0 -CNTs-Fe 3 O 4 /O 2 system and a possible degradation pathway of 4-CP was proposed. Copyright © 2018. Published by Elsevier Ltd.

Synthesis and electrochemical performance of mesoporous SiO{sub 2}–carbon nanofibers composite as anode materials for lithium secondary batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyun, Yura; Choi, Jin-Yeong; Park, Heai-Ku

Highlights: • Mesoporous SiO{sub 2}–carbon nanofibers composite synthesized on Ni foam without any binder. • This composite was directly applied as anode material of Li secondary batteries. • Showed the highest initial (2420 mAh/g) and discharging (2092 mAh/g) capacity. • This material achieved a retention rate of 86.4% after 30 cycles. - Abstract: In this study, carbon nanofibers (CNFs) and mesoporous SiO{sub 2}–carbon nanofibers composite were synthesized and applied as the anode materials in lithium secondary batteries. CNFs and mesoporous SiO{sub 2}–CNFs composite were grown via chemical vapor deposition method with iron-copper catalysts. Mesoporous SiO{sub 2} materials were prepared bymore » sol–gel method using tetraethylorthosilicate as the silica source and cetyltrimethylammoniumchloride as the template. Ethylene was used as the carbon source and passes into a quartz reactor of a tube furnace heated to 600 °C, and the temperature was maintained at 600 °C for 10 min to synthesize CNFs and mesoporous SiO{sub 2}–CNFs composite. The electrochemical characteristics of the as-prepared CNFs and mesoporous SiO{sub 2}–CNFs composite as the anode of lithium secondary batteries were investigated using a three-electrode cell. In particular, the mesoporous SiO{sub 2}–CNFs composites synthesized without binder after depositing mesoporous SiO{sub 2} on Ni foam showed the highest charging and discharging capacity and retention rate. The initial capacity (2420 mAh/g) of mesoporous SiO{sub 2}–CNFs composites decreased to 2092 mAh/g after 30 cycles at a retention rate of 86.4%.« less

Growth and piezoelectric properties of Ca3Nb(Al0.5Ga0.5)3Si2O14 crystals with langasite structure

NASA Astrophysics Data System (ADS)

Xiong, Kainan; Zheng, Yanqing; Tu, Xiaoniu; Jiang, Bohan; Cao, Shuoliang; Shi, Erwei

2017-06-01

Piezoelectric crystals Ca3Nb(Al0.5Ga0.5)3Si2O14 (CNAGS) with langasite structure have been successfully grown by Czochralski method. In this work, the crystal structure, quality, chemical composition, piezoelectric properties, electric resistivity and optical properties of the as-grown crystals were characterized. The full width at half-maximum (FWHM) of the rocking curve of CNAGS was found to be 23″. The chemical compositions of CNAGS crystals are very close to that of initial compositions. At room temperature, the piezoelectric coefficients d11 and d14 of CNAGS crystals are 4.12 pC/N and -5.03 pC/N, and the electromechanical coupling coefficients k12 and k26 are also determined as 11.6% and 18.3%, respectively. The electric resistivity of as-growth crystal was found to be on the order of 2×108 Ω cm at 500 °C and 1×106 Ω cm at 800 °C. And the transmittances of CNAGS crystals were found to be over 80% in the wavelength range of 700-2700 nm.

Chemistry Simulations Using MERRA-2 Reanalysis with the GMI CTM and Replay in Support of the Atmospheric Composition Community

NASA Technical Reports Server (NTRS)

Oman, Luke D.; Strahan, Susan E.

2016-01-01

Simulations using reanalyzed meteorological conditions have been long used to understand causes of atmospheric composition change over the recent past. Using the new Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) meteorology, chemistry simulations are being conducted to create products covering 1980-2016 for the atmospheric composition community. These simulations use the Global Modeling Initiative (GMI) chemical mechanism in two different models: the GMI Chemical Transport Model (CTM) and the GEOS-5 model developed Replay mode. Replay mode means an integration of the GEOS-5 general circulation model that is incrementally adjusted each time step toward the MERRA-2 analysis. The GMI CTM is a 1 x 1.25 simulation and the MERRA-2 GMI Replay simulation uses the native MERRA-2 approximately horizontal resolution on the cubed sphere. The Replay simulations is driven by the online use of key MERRA-2 meteorological variables (i.e. U, V, T, and surface pressure) with all other variables calculated in response to those variables. A specialized set of transport diagnostics is included in both runs to better understand trace gas transport and changes over the recent past.

Evaluation of PAN-based manganese dioxide composite for the sorptive removal of cesium-137 from aqueous solutions.

PubMed

Nilchi, A; Saberi, R; Garmarodi, S Rasouli; Bagheri, A

2012-02-01

Hydrous manganese dioxide-polyacrylonitrile (MnO(2)-PAN) was chemically synthesized and evaluated, as an organic-inorganic composite material, for the removal of radio-contaminant cesium-137 from aqueous solutions. The physico-chemical characterization was carried out by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), CHN elemental analysis, scanning electron microscopy (SEM), nitrogen adsorption-desorption studies and thermogravimetry-differential scanning calorimetry (TGA-DSC). Batch experiments were carried out as a function of contact time, interference of the coexisting ions and initial pH of adsorptive solution applying a radiotracer technique. The effect of temperature on the distribution coefficient of cesium has been utilized in order to evaluate the changes in the standard thermodynamic parameters. The results indicated that Cs(+) ions could be efficiently removed using MnO(2)-PAN composite in the pH range of 4-9 from aqueous solutions and the uptake of cesium is affected to varying degrees by the presence of some diverse co-ions. The equilibrium isotherms have been determined and the sorption data were successfully modeled using Freundlich model. Copyright © 2011 Elsevier Ltd. All rights reserved.

Unconventional Constraints on Nitrogen Chemistry using DC3 Observations and Trajectory-based Chemical Modeling

NASA Astrophysics Data System (ADS)

Shu, Q.; Henderson, B. H.

2017-12-01

Chemical transport models underestimate nitrogen dioxide observations in the upper troposphere (UT). Previous research in the UT succeeded in combining model predictions with field campaign measurements to demonstrate that the nitric acid formation rate (HO + NO2 → HNO3 (R1)) is overestimated by 22% (Henderson et al., 2012). A subsequent publication (Seltzer et al., 2015) demonstrated that single chemical constraint alters ozone and aerosol formation/composition. This work attempts to replicate previous chemical constraints with newer observations and a different modeling framework. We apply the previously successful constraint framework to Deep Convection Clouds and Chemistry (DC3). DC3 is a more recent field campaign where simulated nitrogen imbalances still exist. Freshly convected air parcels, identified in the DC3 dataset, as initial coordinates to initiate Lagrangian trajectories. Along each trajectory, we simulate the air parcel chemical state. Samples along the trajectories will form ensembles that represent possible realizations of UT air parcels. We then apply Bayesian inference to constrain nitrogen chemistry and compare results to the existing literature. Our anticipated results will confirm overestimation of HNO3 formation rate in previous work and provide further constraints on other nitrogen reaction rate coefficients that affect terminal products from NOx. We will particularly focus on organic nitrate chemistry that laboratory literature has yet to fully address. The results will provide useful insights into nitrogen chemistry that affects climate and human health.

PM2.5 Technology Assessment and Characterization Study in New York - PMTACS-NY: The 2001 Summer Field Intensive in Queens, NY

NASA Astrophysics Data System (ADS)

Demerjian, K. L.

2002-12-01

In the summer of 2001, an intensive field measurement campaign was carried out in Queens, NY as part of the PM2.5 Technology Assessment and Characterization Study in New York (PMTACS-NY) to characterize the physical and chemical composition of particulate matter and related precursors utilizing conventional and advanced instrumentation technologies. The measurement program, involving a team of scientists from federal, state, university and private sector organizations, was designed to provide detailed time resolved chemical and physical characterization of the urban PM2.5/co-pollutant complex in relation to the regional environment. A summary of the chemical and meteorological data defining specific events during the field intensive is presented as are results addressing specific hypothesis designed around PMTACS-NY program objectives. These include initial findings and conclusions related to 1) performance testing and evaluation of emerging measurement technologies and comparison with EPA mandated PM federal reference methods currently operational as part of the New York State and national PM2.5 monitoring network; 2) emissions characterization of CNG, standard diesel and CRT (Continuously Regenerating Technology) diesel retrofit powered vehicles; and 3) compositional comparisons of urban and regional PM2.5.

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branson, Oscar; Bonnin, Elisa A.; Perea, Daniel E.

Biomineralizing organisms exhibit exquisite control over skeletal morphology and composition. The promise of understanding and harnessing this feat of natural engineering has motivated an intense search for the mechanisms that direct in vivo mineral self-assembly. We used atom probe tomography, a sub-nanometer 3D chemical mapping technique, to examine the chemistry of a buried organic-mineral interface in biomineral calcite from a marine foraminifer. The chemical patterns at this interface capture the processes of early biomineralization, when the shape, mineralogy, and orientation of skeletal growth are initially established. Sodium is enriched by a factor of nine on the organic side of themore » interface. Based on this pattern, we suggest that sodium plays an integral role in early biomineralization, potentially altering interfacial energy to promote crystal nucleation, and that interactions between organic surfaces and electrolytes other than calcium or carbonate could be a crucial aspect of CaCO3 biomineralization.« less

Experimental Study on Reaction Characteristics of PTFE/Ti/W Energetic Materials under Explosive Loading

PubMed Central

Li, Yan; Jiang, Chunlan; Wang, Zaicheng; Luo, Puguang

2016-01-01

Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three PTFE (polytetrafluoroethylene)/Ti/W mixtures with different W contents are processed through pressing and sintering. An inert PTFE/W mixture without reactive Ti particles is also prepared to serve as a reference. Shock-induced chemical reactions are recorded by high-speed video through a narrow observation window. Related shock parameters are calculated based on experimental data, and differences in energy release are discussed. The results show that the reaction propagation of PTFE/Ti/W energetic materials with low porosity under explosive loading is not self-sustained. As propagation distance increases, the energy release gradually decreases. In addition, reaction failure distance in PTFE/Ti/W composites is inversely proportional to the W content. Porosity increased the failure distance due to higher shock temperature. PMID:28774056

Deformation behavior of additively manufactured GP1 stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clausen, B.; Brown, D. W.; Carpenter, J. S.

In-situ neutron diffraction measurements were performed in this paper during heat-treating and uniaxial loading of additively manufactured (AM) GP1 material. Although the measured chemical composition of the GP1 powder falls within the composition specifications of 17-4 PH steel, a fully martensitic alloy in the wrought condition, the crystal structure of the as-built GP1 material is fully austenitic. Chemical analysis of the as-built material shows high oxygen and nitrogen content, which then significantly decreased after heat-treating in a vacuum furnace at 650 °C for one hour. Significant austenite-to-martensite phase transformation is observed during compressive and tensile loading of the as-built andmore » heat-treated material with accompanied strengthening as martensite volume fraction increases. During loading, the initial average phase stress state in the martensite is hydrostatic compression independent of the loading direction. Finally, preferred orientation transformation in austenite and applied load accommodation by variant selection in martensite are observed via measurements of the texture development.« less

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branson, Oscar; Bonnin, Elisa A.; Perea, Daniel E.

2016-10-28

Biomineralizing organisms exhibit exquisite control over skeletal morphology and composition. The promise of understanding and harnessing this feat of natural engineering has motivated an intense search for the mechanisms that direct in vivo mineral self-assembly. We used atom probe tomography, a sub-nanometer 3D chemical mapping technique, to examine the chemistry of a buried organic-mineral interface in biomineral calcite from a marine foraminifer. The chemical patterns at this interface capture the processes of early biomineralization, when the shape, mineralogy, and orientation of skeletal growth are initially established. Sodium is enriched by a factor of nine on the organic side of themore » interface. Based on this pattern, we suggest that sodium plays an integral role in early biomineralization, potentially altering interfacial energy to promote crystal nucleation, and that interactions between organic surfaces and electrolytes other than calcium or carbonate could be a crucial aspect of CaCO3 biomineralization.« less

Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

DOE PAGES

Branson, Oscar; Bonnin, Elisa A.; Perea, Daniel E.; ...

2016-10-28

Biomineralizing organisms exhibit exquisite control over skeletal morphology and composition. The promise of understanding and harnessing this feat of natural engineering has motivated an intense search for the mechanisms that direct in vivo mineral self-assembly. We used atom probe tomography, a sub-nanometer 3D chemical mapping technique, to examine the chemistry of a buried organic-mineral interface in biomineral calcite from a marine foraminifer. Here, the chemical patterns at this interface capture the processes of early biomineralization, when the shape, mineralogy, and orientation of skeletal growth are initially established. Sodium is enriched by a factor of nine on the organic side ofmore » the interface. Based on this pattern, we suggest that sodium plays an integral role in early biomineralization, potentially altering interfacial energy to promote crystal nucleation, and that interactions between organic surfaces and electrolytes other than calcium or carbonate could be a crucial aspect of CaCO 3 biomineralization.« less

Deformation behavior of additively manufactured GP1 stainless steel

DOE PAGES

Clausen, B.; Brown, D. W.; Carpenter, J. S.; ...

2017-04-22

In-situ neutron diffraction measurements were performed in this paper during heat-treating and uniaxial loading of additively manufactured (AM) GP1 material. Although the measured chemical composition of the GP1 powder falls within the composition specifications of 17-4 PH steel, a fully martensitic alloy in the wrought condition, the crystal structure of the as-built GP1 material is fully austenitic. Chemical analysis of the as-built material shows high oxygen and nitrogen content, which then significantly decreased after heat-treating in a vacuum furnace at 650 °C for one hour. Significant austenite-to-martensite phase transformation is observed during compressive and tensile loading of the as-built andmore » heat-treated material with accompanied strengthening as martensite volume fraction increases. During loading, the initial average phase stress state in the martensite is hydrostatic compression independent of the loading direction. Finally, preferred orientation transformation in austenite and applied load accommodation by variant selection in martensite are observed via measurements of the texture development.« less

The effect of hot isostatic pressing parameters on microstructure and mechanical properties of Eurofer powder HIPed material

NASA Astrophysics Data System (ADS)

Gentzbittel, J. M.; Chu, I.; Burlet, H.

2002-12-01

The production of reduced activation ferritic/martensitic (RAFM) steel by powder metallurgy and high isostatic pressing (HIP) offers numerous advantages for different nuclear applications. The objective of this work is to optimise the Eurofer powder HIP process in order to obtain RAFM solid HIPed steel with similar mechanical properties to those of a forged material. Starting from the forged solid Eurofer steel batch, the material is atomized and the Eurofer powder is characterized in terms of granulometry, chemical composition, surface oxides, etc. Different compaction HIP cycle parameters in the temperature range (950-1100 °C) are tested. The chemical composition of the HIPed material is comparable to the initial forged Eurofer. All the obtained materials are fully dense and the microstructure of the compacted material is well martensitic. The prior austenite grain size seems to be constant in this temperature range. The mechanical tests performed at room temperature reveal acceptable hardness, tensile and Charpy impact properties regarding the ITER specification.

Release and Formation of Oxidation-Related Aldehydes during Wine Oxidation.

PubMed

Bueno, Mónica; Carrascón, Vanesa; Ferreira, Vicente

2016-01-27

Twenty-four Spanish wines were subjected to five consecutive cycles of air saturation at 25 °C. Free and bound forms of carbonyls were measured in the initial samples and after each saturation. Nonoxidized commercial wines contain important and sensory relevant amounts of oxidation-related carbonyls under the form of odorless bound forms. Models relating the contents in total aldehydes to the wine chemical composition suggest that fermentation can be a major origin for Strecker aldehydes: methional, phenylacetaldehyde, isobutyraldehyde, 2-methylbutanal, and isovaleraldehyde. Bound forms are further cleaved, releasing free aldehydes during the first steps of wine oxidation, as a consequence of equilibrium shifts caused by the depletion of SO2. At low levels of free SO2, de novo formation and aldehyde degradation are both observed. The relative importance of these phenomena depends on both the aldehyde and the wine. Models relating aldehyde formation rates to wine chemical composition suggest that amino acids are in most cases the most important precursors for de novo formation.

Temperature dependence of the biaxial modulus, intrinsic stress and composition of plasma deposited silicon oxynitride films

NASA Technical Reports Server (NTRS)

Harding, David R.; Ogbuji, Linus U. T.; Freeman, Mathieu J.

1995-01-01

Silicon oxynitride films were deposited by plasma-enhanced chemical-vapor deposition. The elemental composition was varied between silicon nitride and silicon dioxide: SiO(0.3)N(1.0), SiO(0.7)N(1.6), SiO(0.7)N(1.1), and SiO(1.7)N(0.%). These films were annealed in air, at temperatures of 40-240 C above the deposition temperature (260 C), to determine the stability and behavior or each composition. the biaxial modulus, biaxial intrinsic stress, and elemental composition were measured at discrete intervals within the annealing cycle. Films deposited from primarily ammonia possessed considerable hydrogen (up to 38 at.%) and lost nitrogen and hydrogen at anneal temperatures (260-300 C) only marginally higher than the deposition temperature. As the initial oxygen content increased a different mechanism controlled the behavior or the film: The temperature threshold for change rose to approximately equal to 350 C and the loss of nitrogen was compensated by an equivalent rise in the oxygen content. The transformation from silicon oxynitride to silica was completed after 50 h at 400 C. The initial biaxial modulus of all compositions was 21-3- GPa and the intrinsic stress was -30 to 85 MPa. Increasing the oxygen content raised the temperature threshold where cracking first occurred; the two film compositions with the highest initial oxygen content did not crack, even at the highest temperature (450 C) investigated. At 450 C the biaxial modulus increased to approximately equal to 100 GPa and the intrinsic stress was approximately equal to 200 MPa. These increases could be correlated with the observed change in the film's composition. When nitrogen was replaced by oxygen, the induced stress remained lower than the biaxial strength of the material, but, when nitrogen and hydrogen were lost, stress-relieving microcracking occurred.

Sub 2 nm Particle Characterization in Systems with Aerosol Formation and Growth

NASA Astrophysics Data System (ADS)

Wang, Yang

Aerosol science and technology enable continual advances in material synthesis and atmospheric pollutant control. Among these advances, one important frontier is characterizing the initial stages of particle formation by real time measurement of particles below 2 nm in size. Sub 2 nm particles play important roles by acting as seeds for particle growth, ultimately determining the final properties of the generated particles. Tailoring nanoparticle properties requires a thorough understanding and precise control of the particle formation processes, which in turn requires characterizing nanoparticle formation from the initial stages. The knowledge on particle formation in early stages can also be applied in quantum dot synthesis and material doping. This dissertation pursued two approaches in investigating incipient particle characterization in systems with aerosol formation and growth: (1) using a high-resolution differential mobility analyzer (DMA) to measure the size distributions of sub 2 nm particles generated from high-temperature aerosol reactors, and (2) analyzing the physical and chemical pathways of aerosol formation during combustion. Part. 1. Particle size distributions reveal important information about particle formation dynamics. DMAs are widely utilized to measure particle size distributions. However, our knowledge of the initial stages of particle formation is incomplete, due to the Brownian broadening effects in conventional DMAs. The first part of this dissertation studied the applicability of high-resolution DMAs in characterizing sub 2 nm particles generated from high-temperature aerosol reactors, including a flame aerosol reactor (FLAR) and a furnace aerosol reactor (FUAR). Comparison against a conventional DMA (Nano DMA, Model 3085, TSI Inc.) demonstrated that the increased sheath flow rates and shortened residence time indeed greatly suppressed the diffusion broadening effect in a high-resolution DMA (half mini type). The incipient particle size distributions were discrete, suggesting the formation of stable clusters that may be intermediate phases between initial chemical reactions and downstream particle growth. The evolution of incipient cluster size distributions further provided information on the gaseous precursor reaction kinetics, which matched well with the data obtained through other techniques. Part 2. The size distributions and their evolution measured by the DMAs help explain the physical pathways of aerosol formation. The chemical analysis of the incipient particles is an important counterpart to the existing characterization method. The chemical compositions of charged species were measured online with an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF). The tandem arrangement of the high-resolution DMA and the APi-TOF realized the simultaneous measurement of the mobility and the mass of combustion-generated natively charged particles, which enabled their chemical and physical formation pathways to be derived. The results showed that the initial stages of particle formation were strongly influenced by chemically ionized species during combustion, and that incipient particles composed of pure oxides did not exist. The effective densities of the incipient particles were much lower than those of bulk materials, due to their amorphous structures and different chemical compositions. Measuring incipient particles with high-resolution DMAs is limited because a DMA classifies charged particles only, while the charging characteristics of sub 2 nm particles are not well understood. The charge fraction of combustion-generated incipient particles was measured by coupling a charged particle remover and a condensation particle counter. A high charge fraction was observed, confirming the strong interaction among chemically ionized species and formed particles. The combustion system was modeled by using a unimodal aerosol dynamics model combined with Fuchs' charging theory, and showed that the charging process indeed affected particle formation dynamics during combustion.

Calibration and standardization of microwave ovens for fixation of brain and peripheral nerve tissue.

PubMed

Login, G R; Leonard, J B; Dvorak, A M

1998-06-01

Rapid and reproducible fixation of brain and peripheral nerve tissue for light and electron microscopy studies can be done in a microwave oven. In this review we report a standardized nomenclature for diverse fixation techniques that use microwave heating: (1) microwave stabilization, (2) fast and ultrafast primary microwave-chemical fixation, (3) microwave irradiation followed by chemical fixation, (4) primary chemical fixation followed by microwave irradiation, and (5) microwave fixation used in various combinations with freeze fixation. All of these methods are well suited to fix brain tissue for light microscopy. Fast primary microwave-chemical fixation is best for immunoelectron microscopy studies. We also review how the physical characteristics of the microwave frequency and the dimensions of microwave oven cavities can compromise microwave fixation results. A microwave oven can be calibrated for fixation when the following parameters are standardized: irradiation time; water load volume, initial temperature, and placement within the oven; fixative composition, volume, and initial temperature; and specimen container shape and placement within the oven. Using two recently developed calibration tools, the neon bulb array and the agar-saline-Giemsa tissue phantom, we report a simple calibration protocol that identifies regions within a microwave oven for uniform microwave fixation. Copyright 1998 Academic Press.

Multiple plagioclase crystal populations identified by crystal size distribution and in situ chemical data: Implications for timescales of magma chamber processes associated with the 1915 eruption of Lassen Peak, CA

USGS Publications Warehouse

Salisbury, M.J.; Bohrson, W.A.; Clynne, M.A.; Ramos, F.C.; Hoskin, P.

2008-01-01

Products of the 1915 Lassen Peak eruption reveal evidence for a magma recharge-magma mixing event that may have catalyzed the eruption and from which four compositional members were identified: light dacite, black dacite, andesitic inclusion, and dark andesite. Crystal size distribution, textural, and in situ chemical (major and trace element and Sr isotope) data for plagioclase from these compositional products define three crystal populations that have distinct origins: phenocrysts (long axis > 0??5 mm) that typically have core An contents between 34 and 36 mol %, microphenocrysts (long axis between 0??1 and 0??5 mm) that have core An contents of 66-69, and microlites (long axis < 0??1 mm) with variable An core contents from 64 to 52. Phenocrysts are interpreted to form in an isolated dacitic magma chamber that experienced slow cooling. Based on textural, compositional, and isotopic data for the magma represented by the dacitic component, magma recharge was not an important process until just prior to the 1915 eruption. Average residence times for phenocrysts are in the range of centuries to millennia. Microphenocrysts formed in a hybrid layer that resulted from mixing between end-member reservoir dacite and recharge magma of basaltic andesite composition. High thermal contrast between the two end-member magmas led to relatively high degrees of undercooling, which resulted in faster crystal growth rates and acicular and swallowtail crystal habits. Some plagioclase phenocrysts from the dacitic chamber were incorporated into the hybrid layer and underwent dissolution-precipitation, seen in both crystal textures and rim compositions. Average microphenocryst residence times are of the order of months. Microlites may have formed in response to decompression and/ or syn-eruptive degassing as magma ascended from the chamber through the volcanic conduit. Chemical distinctions in plagioclase microlite An contents reveal that melt of the dark andesite was more mafic than the melt of the other three compositions. We suggest that mixing of an intruding basaltic andesite and reservoir dacite before magma began ascending in the conduit allowed formation of a compositionally distinct microlite population. Melt in the other three products was more evolved because it had undergone differentiation during the months following initial mixing; as a consequence, melt and microlites among these three products have similar compositions. The results of this study highlight the integrated use of crystal size distribution, textural, and in situ chemical data in identifying distinct crystal populations and linking these populations to the thermal and chemical characteristics of complex magma bodies. ?? The Author 2008. Published by Oxford University Press. All rights reserved.

Coupling geodynamic with thermodynamic modelling for reconstructions of magmatic systems

NASA Astrophysics Data System (ADS)

Rummel, Lisa; Kaus, Boris J. P.; White, Richard

2016-04-01

Coupling geodynamic with petrological models is fundamental for understanding magmatic systems from the melting source in the mantle to the point of magma crystallisation in the upper crust. Most geodynamic codes use very simplified petrological models consisting of a single, fixed, chemistry. Here, we develop a method to better track the petrological evolution of the source rock and corresponding volcanic and plutonic rocks by combining a geodynamic code with a thermodynamic model for magma generation and evolution. For the geodynamic modelling a finite element code (MVEP2) solves the conservation of mass, momentum and energy equations. The thermodynamic modelling of phase equilibria in magmatic systems is performed with pMELTS for mantle-like bulk compositions. The thermodynamic dependent properties calculated by pMELTS are density, melt fraction and the composition of the liquid and solid phase in the chemical system: SiO2-TiO2-Al2O3-Fe2O3-Cr2O3-FeO-MgO-CaO-Na2O-K2O-P2O5-H2O. In order to take into account the chemical depletion of the source rock with increasing melt extraction events, calculation of phase diagrams is performed in two steps: 1) With an initial rock composition density, melt fraction as well as liquid and solid composition are computed over the full upper mantle P-T range. 2) Once the residual rock composition (equivalent to the solid composition after melt extraction) is significantly different from the initial rock composition and the melt fraction is lower than a critical value, the residual composition is used for next calculations with pMELTS. The implementation of several melt extraction events take the change in chemistry into account until the solidus is shifted to such high temperatures that the rock cannot be molten anymore under upper mantle conditions. An advantage of this approach is that we can track the change of melt chemistry with time, which can be compared with natural constraints. In the thermo-mechanical code the thermodynamic dependent properties from pre-computed phase diagrams are carried by each particle using marker-in-cell method . Thus the physical and chemical properties can change locally as a function of previous melt extraction events, pressure and temperature conditions. After each melt extraction event, the residual rock composition is compared with the bulk composition of previous computed phase diagrams, so that the used phase diagram is replaced by the phase diagram with the closest bulk chemistry. In the thermo-mechanical code, the melt is extracted directly to the surface as volcanites and within the crust as plutonites. The density of the crust and new generated crust is calculated with the thermodynamic modelling tool Perple_X. We have investigated the influence of several input parameters on the magma composition to compare it with real rock samples from Eifel (West-Germany). In order to take the very inhomogeneous chemistry of European mantle into account, we include not only primitive mantle but also metasomatised mantle fragments in the melting source of a plume (Eifel plume).

Environmental and Chemical Aging of Fatty-Acid-Based Vinyl Ester Composites

DTIC Science & Technology

2011-04-01

Environmental and Chemical Aging of Fatty- Acid -Based Vinyl Ester Composites by Steven E. Boyd and John J. La Scala ARL-TR-5523 April...2011 Environmental and Chemical Aging of Fatty- Acid -Based Vinyl Ester Composites Steven E. Boyd and John J. La Scala Weapons and Materials...COVERED (From - To) October 2009–September 2010 4. TITLE AND SUBTITLE Environmental and Chemical Aging of Fatty- Acid -Based Vinyl Ester Composites

Vector diagram of the chemical compositions of tektites and earth lavas

NASA Technical Reports Server (NTRS)

Kvasha, L. G.; Gorshkov, G. S.

1978-01-01

The chemical compositions of tektites and various volcanic glasses, similar in composition to tektites are compared by a petrochemical method. The advantage of the method is that a large number of chemical analyses of igneous rocks can be graphically compared with the help of vectors, plotted in relation to six parameters. These parameters, calculated from ratios of the main oxides given by silicate analysis, reflect the chief characteristics of igneous rock. Material for the study was suppled by data from chemical analysis characterizing tektites of all known locations and data from chemical analyses of obsidians similar in chemical composition to tektites of various petrographical provinces.

Nature of catalytic activities of CoO nanocrystals in thermal decomposition of ammonium perchlorate.

PubMed

Li, Liping; Sun, Xuefei; Qiu, Xiaoqing; Xu, Jiaoxing; Li, Guangshe

2008-10-06

This work addresses the chemical nature of the catalytic activity of X-ray "pure" CoO nanocrystals. All samples were prepared by a solvothermal reaction route. X-ray diffraction indicates the formation of CoO in a cubic rock-salt structure, while infrared spectra and magnetic measurements demonstrate the coexistence of CoO and Co 3O 4. Therefore, X-ray "pure" CoO nanocrystals are a unique composite structure with a CoO core surrounded by an extremely thin Co 3O 4 surface layer, which is likely a consequence of the surface passivation of CoO nanocrystals from the air oxidation at room temperature. The CoO core shows a particle size of 22 or 280 nm, depending on the types of the precursors used. This composite nanostructure was initiated as a catalytic additive to promote the thermal decomposition of ammonium perchlorate (AP). Our preliminary investigations indicate that the maximum decomposition temperature of AP is significantly reduced in the presence of CoO/Co 3O 4 composite nanocrystals and that the maximum decomposition peak shifts toward lower temperatures as the loading amount of the composite nanocrystals increases. These findings are different from the literature reports when using many nanoscale oxide additives. Finally, the decomposition heat for the low-temperature decomposition stages of AP was calculated and correlated to the chemical nature of the CoO/Co 3O 4 composite nanostructures.

An applied investigation of corn-based distillers dried grains with solubles in the production of natural fiber-plastic composites

NASA Astrophysics Data System (ADS)

Castillo, Hugo Eudosio

The main objective of this research was to examine uses for distillers dried grains with solubles (DDGS), a coproduct of ethanol production plant, in the fiber-reinforced plastic composites industry. Initially the effort intended to take advantage of the DDGS components, using chemical reactions, to produce coupling agents to improve the physical properties of the composite. Four different chemicals plus water were used to convert proteins into soluble amino acids. The results were not as expected, and appeared to show an early pyrolysis of DDGS components. This may be due to regeneration of proteins when pH of solutions is neutralized. Procedures were then investigated to utilize DDGS for different markets. Considering that oils and proteins of DDGS can thermally decompose, it seemed important to separate the major components and work with DDGS fiber alone. A procedure to extract oil from DDGS using ethanol and then to hydrolyze proteins with ethanol diluted with water, acid and sodium sulfite, was developed. The resulting DDGS fiber or residual material, with a low content of oil and proteins, was used as filler in a propylene matrix with a lubricant and coupling agent to make natural fiber plastic composites (NFPC). Composites containing wood flour (WPC) were prepared simultaneously with those of DDGS fiber to compare tensile properties and fracture surfaces of the specimens by scanning electron microscope (SEM). This study demonstrates that DDGS fiber can replace wood fiber as a filler in NFPC.

Isotope and trace element insights into heterogeneity of subridge mantle

NASA Astrophysics Data System (ADS)

Mallick, Soumen; Dick, Henry J. B.; Sachi-Kocher, Afi; Salters, Vincent J. M.

2014-06-01

Geochemical data for abyssal peridotites are used to determine the relationship to mid-ocean ridge basalts from several locations at ridge segments on the SW Indian Ridge (SWIR), the Mid-Cayman-Rise (MCR), and the Mid-Atlantic Ridge (MAR). Based on chemical and petrological criteria peridotites are categorized as being either dominantly impregnated with melt or being residual after recent melting. Those that are considered impregnated with melt also have isotopic compositions similar to the basalts indicating impregnation by an aggregate MORB melt. A SWIR and MCR residual peridotite Nd-isotopic compositions partly overlap the Nd-isotopic compositions of the basalts but extend to more radiogenic compositions. The differences between peridotite and basalt Nd-isotopic compositions can be explained by incorporating a low-solidus component with enriched isotopic signature in the subridge mantle: a component that is preferentially sampled by the basalts. At the MAR, peridotites and associated basalts have overlapping Nd-isotopic compositions, suggesting a more homogeneous MORB mantle. The combined chemistry and petrography indicates a complex history with several depletion and enrichment events. The MCR data indicate that a low-solidus component can be a ubiquitous component of the asthenosphere. Residual abyssal peridotites from limited geographic areas also show significant chemical variations that could be associated with initial mantle heterogeneities related to events predating the ridge-melting event. Sm-Nd model ages for possible earlier depletion events suggest these could be as old as 2.4 Ga. This article was corrected on 9 JULY 2014. See the end of the full text for details.

Cyclic Fatigue Durability of Uncoated and EBC Coated 3D SiC/SiC Composites Under Thermal Gradient Conditions at 2700F in Air

NASA Technical Reports Server (NTRS)

Smith, Craig; Harder, Bryan; Zhu, Dongming; Bhatt, Ramakrishna; Kalluri, Sreeramesh

2017-01-01

Ceramic matrix composites (CMCs) such as SiC/SiC are currently being designed and implemented in high temperature sections of aerospace turbine engines. Such components will be subject to through-thickness thermal gradients, which may affect the durability. In this study, SiC/SiC CMCs with a hybrid chemical vapor infiltrated (CVI) and polymer infiltration and pyrolysis (PIP) matrix were loaded in tension while one surface was heated with a laser and the opposite surface was cooled. Issues associated with laser testing will be discussed, along with initial results for coated and uncoated samples.

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

NASA Technical Reports Server (NTRS)

Dwight, D. W.; Wightman, J. P.

1977-01-01

The ability of SEM/EDAX to determine the physical and chemical composition of very small areas was used to study several diverse types of samples representative of NASA-LaRC technology. More systematic investigation was carried out on differences in the results of grit-blasting Ti 6-4 adherends and the presence of extraneous elements, primarily silicon, in some polymer/HT-S fiber composites. Initial results were obtained from a fractured (ILS) short-beam shear specimen, and from Ti 6-4 alloy, before and after a proprietary Boeing anodizing surface preparation for adhesive bonding. Photomicrographs and EDAX spectra were also obtained from new, fractured lap shear strength specimens that employed PPQ and LARC-13 adhesives.

Effect of Ionizing Radiation on the Mechanical and Structural Properties of Graphite Fiber Reinforced Composites. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Wolf, Kay Woodroof

1982-01-01

Graphite/epoxy (T300/5208) and graphite/polyimide composites (C6000/PMR 15) were exposed to various levels of 0.5 MeV electron radiation with the maximum dose being 10,000 Mrad. A three point bending test was used to evaluate the ultimate stress and modulus of the composites. In all composites except transverse samples of C6000/PMR 15 ultimate stress values remained approximately constant or increased slightly. The modulus values remained approximately constant for all composite types regardless of the radiation level. Interfacial aspects of composites were studied. Interlaminar shear tests were performed on T300/5208 and C6000/PMR 15 composites irradiated to 10,000 Mrad. There was an initial increase in interlaminar shear strength (up to 1,000 Mrad) followed by a sharp decrease with further radiation exposure. Using scanning electron microscopy no visual differences in the mode of fracture could be detected between ruptured control samples and those exposed to various levels of radiation. Electron spectroscopy for chemical analysis (ESCA) revealed little change in the surface elements present in control and highly irradiated T300/5208 composite samples.

Surface chemical composition of human maxillary first premolar as assessed by X-ray photoelectron spectroscopy (XPS)

NASA Astrophysics Data System (ADS)

Lou, Leo; Nelson, Alan E.; Heo, Giseon; Major, Paul W.

2008-08-01

The surface chemical composition of dental enamel has been postulated as a contributing factor in the variation of bond strength of brackets bonded to teeth, and hence, the probability of bracket failure during orthodontic treatment. This study systematically investigated the chemical composition of 98 bonding surfaces of human maxillary premolars using X-ray photoelectron spectroscopy (XPS) to ascertain compositional differences between right and left first premolars. The major elements detected in all samples were calcium, phosphorus, oxygen, nitrogen and carbon. Surface compositions were highly variable between samples and several elements were found to be highly correlated. No statistical significant difference in the chemical composition of the maxillary right and left first premolars was found ( p > 0.05). Knowledge of the chemical composition of enamel surfaces will facilitate future studies that relate this information to the variations in dental enamel bond strength.

Synergistic effect of manganese dioxide and diatomite for fast decolorization and high removal capacity of methyl orange.

PubMed

Peng, Hui Hua; Chen, Jie; Jiang, De Yi; Li, Min; Feng, Li; Losic, Dusan; Dong, Fan; Zhang, Yu Xin

2016-12-15

MnO 2 nanostructures with two different morphologies (nanowires and nanosheets) were uniformly deposited on diatomite via a one-pot hydrothermal method. The fast decolorization and high removal capacity for anionic dye-MO over synthesized composites had been clarified. The results revealed that the equilibrium time was shortened to as low as 10-30min, and the maximum adsorption capacities were 325mgg -1 and 420mgg -1 for nanowires and nanosheets composites, respectively, under the condition of initial pH 3 and ambient temperature. Indeed, the proposed decolorization mechanism was considered to be simultaneous multi-processes during the dye removal, including physical, physicochemical and chemical process. In principle, well-controlled cost-effective composites have promising ability to remove anionic dye pollutants for environmental remediation. Copyright © 2016 Elsevier Inc. All rights reserved.

Laboratory investigations of Titan haze formation: In situ measurement of gas and particle composition

NASA Astrophysics Data System (ADS)

Hörst, Sarah M.; Yoon, Y. Heidi; Ugelow, Melissa S.; Parker, Alex H.; Li, Rui; de Gouw, Joost A.; Tolbert, Margaret A.

2018-02-01

Prior to the arrival of the Cassini-Huygens spacecraft, aerosol production in Titan's atmosphere was believed to begin in the stratosphere where chemical processes are predominantly initiated by far ultraviolet (FUV) radiation. However, measurements taken by the Cassini Ultraviolet Imaging Spectrograph (UVIS) and Cassini Plasma Spectrometer (CAPS) indicate that haze formation initiates in the thermosphere where there is a greater flux of extreme ultraviolet (EUV) photons and energetic particles available to initiate chemical reactions, including the destruction of N2. The discovery of previously unpredicted nitrogen species in measurements of Titan's atmosphere by the Cassini Ion and Neutral Mass Spectrometer (INMS) indicates that nitrogen participates in the chemistry to a much greater extent than was appreciated before Cassini. The degree of nitrogen incorporation in the haze particles is important for understanding the diversity of molecules that may be present in Titan's atmosphere and on its surface. We have conducted a series of Titan atmosphere simulation experiments using either spark discharge (Tesla coil) or FUV photons (deuterium lamp) to initiate chemistry in CH4/N2 gas mixtures ranging from 0.01% CH4/99.99% N2 to 10% CH4/90% N2. We obtained in situ real-time measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to measure the particle composition as a function of particle size and a proton-transfer ion-trap mass spectrometer (PIT-MS) to measure the composition of gas phase products. These two techniques allow us to investigate the effect of energy source and initial CH4 concentration on the degree of nitrogen incorporation in both the gas and solid phase products. The results presented here confirm that FUV photons produce not only solid phase nitrogen bearing products but also gas phase nitrogen species. We find that in both the gas and solid phase, nitrogen is found in nitriles rather than amines and that both the gas phase and solid phase products are composed primarily of molecules with a low degree of aromaticity. The UV experiments reproduce the absolute abundances measured in Titan's stratosphere for a number of gas phase species including C4H2, C6H6, HCN, CH3CN, HC3N, and C2H5CN.

The temporal evolution of magnesium isotope fractionation during hydromagnesite dissolution, precipitation, and at equilibrium

NASA Astrophysics Data System (ADS)

Oelkers, Eric H.; Berninger, Ulf-Niklas; Pérez-Fernàndez, Andrea; Chmeleff, Jérôme; Mavromatis, Vasileios

2018-04-01

This study provides experimental evidence of the resetting of the magnesium (Mg) isotope signatures of hydromagnesite in the presence of an aqueous fluid during its congruent dissolution, precipitation, and at equilibrium at ambient temperatures over month-long timescales. All experiments were performed in batch reactors in aqueous sodium carbonate buffer solutions having a pH from 7.8 to 9.2. The fluid phase in all experiments attained bulk chemical equilibrium within analytical uncertainty with hydromagnesite within several days, but the experiments were allowed to continue for up to 575 days. During congruent hydromagnesite dissolution, the fluid first became enriched in isotopically light Mg compared to the dissolving hydromagnesite, but this Mg isotope composition became heavier after the fluid attained chemical equilibrium with the mineral. The δ26Mg composition of the fluid was up to ∼0.35‰ heavier than the initial dissolving hydromagnesite at the end of the dissolution experiments. Hydromagnesite precipitation was provoked during one experiment by increasing the reaction temperature from 4 to 50 °C. The δ26Mg composition of the fluid increased as hydromagnesite precipitated and continued to increase after the fluid attained bulk equilibrium with this phase. These observations are consistent with the hypothesis that mineral-fluid equilibrium is dynamic (i.e. dissolution and precipitation occur at equal, non-zero rates at equilibrium). Moreover the results presented in this study confirm (1) that the transfer of material from the solid to the fluid phase may not be conservative during stoichiometric dissolution, and (2) that the isotopic compositions of carbonate minerals can evolve even when the mineral is in bulk chemical equilibrium with its coexisting fluid. This latter observation suggests that the preservation of isotopic signatures of carbonate minerals in the geological record may require a combination of the isolation of fluid-mineral system from external chemical input and/or the existence of a yet to be defined dissolution/precipitation inhibition mechanism.

Enhancement of gold recovery using bioleaching from gold concentrate

NASA Astrophysics Data System (ADS)

Choi, S. H.; Cho, K. H.; Kim, B. J.; Choi, N. C.; Park, C. Y.

2012-04-01

The gold in refractory ores is encapsulated as fine particles (sometimes at a molecular level) in the crystal structure of the sulfide (typically pyrite with or without arsenopyrite) matrix. This makes it impossible to extract a significant amount of refractory gold by cyanidation since the cyanide solution cannot penetrate the pyrite/arsenopyrite crystals and dissolve gold particles, even after fine grinding. To effectively extract gold from these ores, an oxidative pretreatment is necessary to break down the sulfide matrix. The most popular methods of pretreatment include nitric acid oxidation, roasting, pressure oxidation and biological oxidation by microorganisms. This study investigated the bioleaching efficiency of Au concentrate under batch experimental conditions (adaptation cycles and chemical composition adaptation) using the indigenous acidophilic bacteria collected from gold mine leachate in Sunsin gold mine, Korea. We conducted the batch experiments at two different chemical composition (CuSO4 and ZnSO4), two different adaptation cycles 1'st (3 weeks) and 2'nd (6 weeks). The results showed that the pH in the bacteria inoculating sample decreased than initial condition and Eh increased. In the chemical composition adaptation case, the leached accumulation content of Fe and Pb was exhibited in CuSO4 adaptation bacteria sample more than in ZnSO4 adaptation bacteria samples, possibly due to pre-adaptation effect on chalcopyrite (CuFeS2) in gold concentrate. And after 21 days on the CuSO4 adaptation cycles case, content of Fe and Pb was appeared at 1'st adaptation bacteria sample(Fe - 1.82 and Pb - 25.81 times per control sample) lower than at 2'nd adaptation bacteria sample(Fe - 2.87 and Pb - 62.05 times per control sample). This study indicates that adaptation chemical composition and adaptation cycles can play an important role in bioleaching of gold concentrate in eco-/economic metallurgy process.

Illinois basin coal fly ashes. 1. Chemical characterization and solubility

USGS Publications Warehouse

Roy, W.R.; Griffin, R.A.; Dickerson, D.R.; Schuller, R.M.; Martin, S.M.C.

1984-01-01

Twelve precipitator-collected fly ash samples (nine derived from high-sulfur Illinois Basin coals and three from Western U.S. coals) were found to contain a variety of paraffins, aryl esters, phenols, and polynuclear aromatic hydrocarbons including phenanthrene, pyrene, and chrysene but all at very low concentrations. Less than 1% of the organic carbon in the samples was extractable into benzene. Solubility studies with a short-term (24-h) extraction procedure and a long-term (20-week) procedure indicate that the inorganic chemical composition of some types of fly ash effluent is time dependent and may be most toxic to aquatic ecosystems when initially mixed with water and pumped to disposal ponds. Some acidic, high-Cd fly ashes would be classified as hazardous wastes if coal ash was included in this waste category by future RCRA revisions. ?? 1984 American Chemical Society.

Research on ultrasonic excitation for the removal of drilling fluid plug, paraffin deposition plug, polymer plug and inorganic scale plug for near-well ultrasonic processing technology.

PubMed

Wang, Zhenjun; Zeng, Jing; Song, Hao; Li, Feng

2017-05-01

Near-well ultrasonic processing technology attracts more attention due to its simple operation, high adaptability, low cost and no pollution to the formation. Although this technology has been investigated in detail through laboratory experiments and field tests, systematic and intensive researches are absent for certain major aspects, such as whether ultrasonic excitation is better than chemical agent for any plugs removal; whether ultrasound-chemical combination plug removal technology has the best plugs removal effect. In this paper, the comparison of removing drilling fluid plug, paraffin deposition plug, polymer plug and inorganic scale plug using ultrasonic excitation, chemical agent and ultrasound-chemical combination plug removal technology is investigated. Results show that the initial core permeability and ultrasonic frequency play a significant role in plug removal. Ultrasonic excitation and chemical agent have different impact on different plugs. The comparison results show that the effect of removing any plugs using ultrasound-chemicals composite plug removal technology is obviously better than that using ultrasonic excitation or chemical agent alone. Such conclusion proves that ultrasonic excitation and chemical agent can cause synergetic effects. Copyright © 2016 Elsevier B.V. All rights reserved.

Reconstructing mantle volatile contents through the veil of degassing

NASA Astrophysics Data System (ADS)

Tucker, J.; Mukhopadhyay, S.; Gonnermann, H. M.

2014-12-01

The abundance of volatile elements in the mantle reveals critical information about the Earth's origin and evolution such as the chemical constituents that built the Earth and material exchange between the mantle and exosphere. However, due to magmatic degassing, volatile element abundances measured in basalts usually do not represent those in undegassed magmas and hence in the mantle source of the basalts. While estimates of average mantle concentrations of some volatile species can be obtained, such as from the 3He flux into the oceans, volatile element variability within the mantle remains poorly constrained. Here, we use CO2-He-Ne-Ar-Xe measurements in basalts and a new degassing model to reconstruct the initial volatile contents of 8 MORBs from the Mid-Atlantic Ridge and Southwest Indian Ridge that span a wide geochemical range from depleted to enriched MORBs. We first show that equilibrium degassing (e.g. Rayleigh degassing), cannot simultaneously fit the measured CO2-He-Ne-Ar-Xe compositions in MORBs and argue that kinetic fractionation between bubbles and melt lowers the dissolved ratios of light to heavy noble gas species in the melt from that expected at equilibrium. We present a degassing model (after Gonnermann and Mukhopadhyay, 2007) that explicitly accounts for diffusive fractionation between melt and bubbles. The model computes the degassed composition based on an initial volatile composition and a diffusive timescale. To reconstruct the undegassed volatile content of a sample, we find the initial composition and degassing timescale which minimize the misfit between predicted and measured degassed compositions. Initial 3He contents calculated for the 8 MORB samples vary by a factor of ~7. We observe a correlation between initial 3He and CO2 contents, indicating relatively constant CO2/3He ratios despite the geochemical diversity and variable gas content in the basalts. Importantly, the gas-rich popping rock from the North Atlantic, as well as the average mantle ratio computed from the ridge 3He flux and independently estimated CO2 content fall along the same correlation. This observation suggests that undegassed CO2 and noble gas concentrations can be reconstructed in individual samples through measurement of noble gases and CO2 in erupted basalts.

Chemical compatibility issues associated with use of SiC/SiC in advanced reactor concepts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Dane F.

2015-09-01

Silicon carbide/silicon carbide (SiC/SiC) composites are of interest for components that will experience high radiation fields in the High Temperature Gas Cooled Reactor (HTGR), the Very High Temperature Reactor (VHTR), the Sodium Fast Reactor (SFR), or the Fluoride-cooled High-temperature Reactor (FHR). In all of the reactor systems considered, reactions of SiC/SiC composites with the constituents of the coolant determine suitability of materials of construction. The material of interest is nuclear grade SiC/SiC composites, which consist of a SiC matrix [high-purity, chemical vapor deposition (CVD) SiC or liquid phase-sintered SiC that is crystalline beta-phase SiC containing small amounts of alumina-yttria impurity],more » a pyrolytic carbon interphase, and somewhat impure yet crystalline beta-phase SiC fibers. The interphase and fiber components may or may not be exposed, at least initially, to the reactor coolant. The chemical compatibility of SiC/SiC composites in the three reactor environments is highly dependent on thermodynamic stability with the pure coolant, and on reactions with impurities present in the environment including any ingress of oxygen and moisture. In general, there is a dearth of information on the performance of SiC in these environments. While there is little to no excess Si present in the new SiC/SiC composites, the reaction of Si with O 2 cannot be ignored, especially for the FHR, in which environment the product, SiO 2, can be readily removed by the fluoride salt. In all systems, reaction of the carbon interphase layer with oxygen is possible especially under abnormal conditions such as loss of coolant (resulting in increased temperature), and air and/ or steam ingress. A global outline of an approach to resolving SiC/SiC chemical compatibility concerns with the environments of the three reactors is presented along with ideas to quickly determine the baseline compatibility performance of SiC/SiC.« less

Visible-light-enhanced interactions of hydrogen sulfide with composites of zinc (oxy)hydroxide with graphite oxide and graphene.

PubMed

Seredych, Mykola; Mabayoje, Oluwaniyi; Bandosz, Teresa J

2012-01-17

Composites of zinc(oxy)hydroxide-graphite oxide and of zinc(oxy)hydroxide-graphene were used as adsorbents of hydrogen sulfide under ambient conditions. The initial and exhausted samples were characterized by XRD, FTIR, potentiometric titration, EDX, thermal analysis, and nitrogen adsorption. An increase in the amount of H(2)S adsorbed/oxidized on their surfaces in comparison with that of pure Zn(OH)(2) is linked to the structure of the composite, the relative number of terminal hydroxyls, and the kind of graphene-based phase used. Although terminal groups are activated by a photochemical process, the graphite oxide component owing to the chemical bonds with the zinc(oxy)hydroxide phase and conductive properties helps in electron transfer, leading to more efficient oxygen activation via the formation of superoxide ions. Elemental sulfur, zinc sulfide, sulfite, and sulfate are formed on the surface. The formation of sulfur compounds on the surface of zinc(oxy)hydroxide during the course of the breakthrough experiments and thus Zn(OH)(2)-ZnS heterojunctions can also contribute to the increased surface activity of our materials. The results show the superiority of graphite oxide in the formation of composites owing to its active surface chemistry and the possibility of interface bond formation, leading to an increase in the number of electron-transfer reactions. © 2011 American Chemical Society

Magnesium-Assisted Continuous Growth of Strongly Iron-Enriched Incisors.

PubMed

Srot, Vesna; Bussmann, Birgit; Salzberger, Ute; Deuschle, Julia; Watanabe, Masashi; Pokorny, Boštjan; Jelenko Turinek, Ida; Mark, Alison F; van Aken, Peter A

2017-01-24

Teeth are an excellent example where optimally designed nanoarchitectures with precisely constructed components consist of simple compounds. Typically, these simple constituent phases with insignificant properties show mechanical property amplifications when formed into composite architectures. Material properties of functional composites are generally regulated on the nanoscale, which makes their characterization particularly demanding. Using advanced analytical and imaging transmission electron microscopy techniques, we identified innovative microstructural adjustments combined with astonishing compositional adaptations in incisors of coypu. Unique constituents, recognized as an additional amorphous Fe-rich surface layer followed by a transition zone covering pigmented enamel, provide the required structural stability to withstand repeated mechanical load. The chemically diverse Fe-rich surface layer, including ferrihydrite and iron-calcium phosphates, gives the typical orange-brown coloration to the incisors. Within the spaces between elongated hydroxyapatite crystals in the pigmented enamel, only ferrihydrite was found, implying that enamel pigmentation is a very strictly controlled process. Most significantly, an unprecedentedly high amount of Mg was measured in the amorphous flake-like material within the dentinal tubules of the incisors, suggesting the presence of a (Mg,Ca) phosphate phase. This unusually high influx of Mg into the dentin of incisors, but not molars, suggests a substantial functionality of Mg in the initial formation stages and constant growth of incisors. The present results emphasize the strong mutual correlation among the microstructure, chemical composition, and mechanical properties of mineralized dental tissues.

The Hemolymph Proteome of Fed and Starved Drosophila Larvae

PubMed Central

Goetze, Sandra; Ahrens, Christian H.; Omasits, Ulrich; Marty, Florian; Simigdala, Nikiana; Meyer, Imke; Wollscheid, Bernd; Brunner, Erich; Hafen, Ernst; Lehner, Christian F.

2013-01-01

The co-operation of specialized organ systems in complex multicellular organisms depends on effective chemical communication. Thus, body fluids (like blood, lymph or intraspinal fluid) contain myriads of signaling mediators apart from metabolites. Moreover, these fluids are also of crucial importance for immune and wound responses. Compositional analyses of human body fluids are therefore of paramount diagnostic importance. Further improving their comprehensiveness should increase our understanding of inter-organ communication. In arthropods, which have trachea for gas exchange and an open circulatory system, the single dominating interstitial fluid is the hemolymph. Accordingly, a detailed analysis of hemolymph composition should provide an especially comprehensive picture of chemical communication and defense in animals. Therefore we used an extensive protein fractionation workflow in combination with a discovery-driven proteomic approach to map out the detectable protein composition of hemolymph isolated from Drosophila larvae. Combined mass spectrometric analysis revealed more than 700 proteins extending far beyond the previously known Drosophila hemolymph proteome. Moreover, by comparing hemolymph isolated from either fed or starved larvae, we provide initial provisional insights concerning compositional changes in response to nutritional state. Storage proteins in particular were observed to be strongly reduced by starvation. Our hemolymph proteome catalog provides a rich basis for data mining, as exemplified by our identification of potential novel cytokines, as well as for future quantitative analyses by targeted proteomics. PMID:23840627

The hemolymph proteome of fed and starved Drosophila larvae.

PubMed

Handke, Björn; Poernbacher, Ingrid; Goetze, Sandra; Ahrens, Christian H; Omasits, Ulrich; Marty, Florian; Simigdala, Nikiana; Meyer, Imke; Wollscheid, Bernd; Brunner, Erich; Hafen, Ernst; Lehner, Christian F

2013-01-01

The co-operation of specialized organ systems in complex multicellular organisms depends on effective chemical communication. Thus, body fluids (like blood, lymph or intraspinal fluid) contain myriads of signaling mediators apart from metabolites. Moreover, these fluids are also of crucial importance for immune and wound responses. Compositional analyses of human body fluids are therefore of paramount diagnostic importance. Further improving their comprehensiveness should increase our understanding of inter-organ communication. In arthropods, which have trachea for gas exchange and an open circulatory system, the single dominating interstitial fluid is the hemolymph. Accordingly, a detailed analysis of hemolymph composition should provide an especially comprehensive picture of chemical communication and defense in animals. Therefore we used an extensive protein fractionation workflow in combination with a discovery-driven proteomic approach to map out the detectable protein composition of hemolymph isolated from Drosophila larvae. Combined mass spectrometric analysis revealed more than 700 proteins extending far beyond the previously known Drosophila hemolymph proteome. Moreover, by comparing hemolymph isolated from either fed or starved larvae, we provide initial provisional insights concerning compositional changes in response to nutritional state. Storage proteins in particular were observed to be strongly reduced by starvation. Our hemolymph proteome catalog provides a rich basis for data mining, as exemplified by our identification of potential novel cytokines, as well as for future quantitative analyses by targeted proteomics.

Chemical variations in Yellowknife Bay formation sedimentary rocks analyzed by ChemCam on board the Curiosity rover on Mars

USGS Publications Warehouse

Mangold, Nicolas; Forni, Olivier; Dromart, G.; Stack, K.M.; Wiens, Roger C.; Gasnault, Olivier; Sumner, Dawn Y.; Nachon, Marion; Meslin, Pierre-Yves; Anderson, Ryan B.; Barraclough, Bruce; Bell, J.F.; Berger, G.; Blaney, D.L.; Bridges, J.C.; Calef, F.; Clark, Brian R.; Clegg, Samuel M.; Cousin, Agnes; Edgar, L.; Edgett, Kenneth S.; Ehlmann, B.L.; Fabre, Cecile; Fisk, M.; Grotzinger, John P.; Gupta, S.C.; Herkenhoff, Kenneth E.; Hurowitz, J.A.; Johnson, J. R.; Kah, Linda C.; Lanza, Nina L.; Lasue, Jeremie; Le Mouélic, S.; Lewin, Eric; Malin, Michael; McLennan, Scott M.; Maurice, S.; Melikechi, Noureddine; Mezzacappa, Alissa; Milliken, Ralph E.; Newsome, H.L.; Ollila, A.; Rowland, Scott K.; Sautter, Violaine; Schmidt, M.E.; Schroder, S.; D'Uston, C.; Vaniman, Dave; Williams, R.A.

2015-01-01

The Yellowknife Bay formation represents a ~5 m thick stratigraphic section of lithified fluvial and lacustrine sediments analyzed by the Curiosity rover in Gale crater, Mars. Previous works have mainly focused on the mudstones that were drilled by the rover at two locations. The present study focuses on the sedimentary rocks stratigraphically above the mudstones by studying their chemical variations in parallel with rock textures. Results show that differences in composition correlate with textures and both manifest subtle but significant variations through the stratigraphic column. Though the chemistry of the sediments does not vary much in the lower part of the stratigraphy, the variations in alkali elements indicate variations in the source material and/or physical sorting, as shown by the identification of alkali feldspars. The sandstones contain similar relative proportions of hydrogen to the mudstones below, suggesting the presence of hydrous minerals that may have contributed to their cementation. Slight variations in magnesium correlate with changes in textures suggesting that diagenesis through cementation and dissolution modified the initial rock composition and texture simultaneously. The upper part of the stratigraphy (~1 m thick) displays rocks with different compositions suggesting a strong change in the depositional system. The presence of float rocks with similar compositions found along the rover traverse suggests that some of these outcrops extend further away in the nearby hummocky plains.

Taste receptors in the gastrointestinal tract. I. Bitter taste receptors and alpha-gustducin in the mammalian gut.

PubMed

Rozengurt, Enrique

2006-08-01

Molecular sensing by gastrointestinal (GI) cells plays a critical role in the control of multiple fundamental functions in digestion and also initiates hormonal and/or neural pathways leading to the regulation of caloric intake, pancreatic insulin secretion, and metabolism. Molecular sensing in the GI tract is also responsible for the detection of ingested harmful drugs and toxins, thereby initiating responses critical for survival. The initial recognition events and mechanism(s) involved remain incompletely understood. The notion to be discussed in this article is that there are important similarities between the chemosensory machinery elucidated in specialized neuroepithelial taste receptor cells of the lingual epithelium and the molecular transducers localized recently in enteroendocrine open GI cells that sense the chemical composition of the luminal contents of the gut.

Effects of high pressure nitrogen on the thermal stability of SiC fibers

NASA Technical Reports Server (NTRS)

Jaskowiak, Martha H.

1991-01-01

Polymer-derived SiC fibers were exposed to nitrogen gas pressures of 7 and 50 atm at temperatures up to 1800 C. The fiber weight loss, chemical composition, and tensile strength were then measured at room temperature in order to understand the effects of nitrogen exposure on fiber stability. High pressure nitrogen treatments limited weight loss to 3 percent or less for temperatures up to 1800 C. The bulk Si-C-O chemical composition of the fiber remained relatively constant up to 1800 C with only a slight increase in nitrogen content after treatment at 50 atm; however, fiber strength retention was significantly improved. To further understand the effects of the nitrogen atmosphere on the fiber stability, the results of previous high pressure argon treatments were compared to those of the high pressure nitrogen treatments. High pressure inert gas can temporarily maintain fiber strength by physically inhibiting the evolution of gaseous species which result from internal reactions. In addition to this physical effect, it would appear that high pressure nitrogen further improved fiber temperature capability by chemically reacting with the fiber surface, thereby reducing the rate of gas evolution. Subsequent low pressure argon treatments following the initial nitrogen treatments resulted in stronger fibers than after argon treatment alone, further supporting the chemical reaction mechanism and its beneficial effects on fiber strength.

Impact of the chemicals, essential for the purification process of strict Fe-hydrogenase, on the corrosion of mild steel.

PubMed

Rouvre, Ingrid; Gauquelin, Charles; Meynial-Salles, Isabelle; Basseguy, Régine

2016-06-01

The influence of additional chemical molecules, necessary for the purification process of [Fe]-hydrogenase from Clostridium acetobutylicum, was studied on the anaerobic corrosion of mild steel. At the end of the purification process, the pure [Fe-Fe]-hydrogenase was recovered in a Tris-HCl medium containing three other chemicals at low concentration: DTT, dithionite and desthiobiotin. Firstly, mild steel coupons were exposed in parallel to a 0.1 M pH7 Tris-HCl medium with or without pure hydrogenase. The results showed that hydrogenase and the additional molecules were in competition, and the electrochemical response could not be attributed solely to hydrogenase. Then, solutions with additional chemicals of different compositions were studied electrochemically. DTT polluted the electrochemical signal by increasing the Eoc by 35 mV 24 h after the injection of 300 μL of control solutions with DTT, whereas it drastically decreased the corrosion rate by increasing the charge transfer resistance (Rct 10 times the initial value). Thus, DTT was shown to have a strong antagonistic effect on corrosion and was removed from the purification process. An optimal composition of the medium was selected (0.5 mM dithionite, 7.5 mM desthiobiotin) that simultaneously allowed a high activity of hydrogenase and a lower impact on the electrochemical response for corrosion tests. Copyright © 2016 Elsevier B.V. All rights reserved.

Physico-Chemical Factors Affecting Hydrothermal Resistance and Bonding of Polymeric Composites to Steel Surfaces

DTIC Science & Technology

1985-11-01

and 1.0% PM-odified zinc phosphate hydrate crystals. -117- temperature of decomposition at -1750C, is associated with the dehydration of the...reactions between divalent Ca ions released from CaO-SIO2 grains and carboxylate anions "(COO) yielded during the hydrolysis of functional pendent carboxyl...deterioration of polymers, caused by the hydrolysis of a pendent carbcxyl group, can be restrained by ionic cross-linking initiated by the strongly

PM composition and source reconciliation in Mexico City

NASA Astrophysics Data System (ADS)

Mugica, V.; Ortiz, E.; Molina, L.; De Vizcaya-Ruiz, A.; Nebot, A.; Quintana, R.; Aguilar, J.; Alcántara, E.

PM 2.5 and PM 10 were collected during 24-h sampling intervals from March 1st to 31st, 2006 during the MILAGRO campaign carried out in Mexico City's northern region, in order to determine their chemical composition, oxidative activity and the estimation of the source contributions during the sampling period by means of the chemical mass balance (CMB) receptor model. PM 2.5 concentrations ranged from 32 to 70 μg m -3 while that of PM10 did so from 51 to 132 μg m -3. The most abundant chemical species for both PM fractions were: OC, EC, SO 42-, NO 3-, NH 4+, Si, Fe and Ca. The majority of the PM mass was comprised of carbon, up to about 52% and 30% of the PM2.5 and PM10, respectively. PM2.5 constituted more than 50% of PM10. The redox activity, assessed by the dithiothreitol (DTT) assay, was greater for PM 2.5 than for PM 10, and did not display significant differences during the sampling period. The PM 2.5 source reconciliation showed that in average, vehicle exhaust emissions were its most important source in an urban site with a 42% contribution, followed by re-suspended dust with 26%, secondary inorganic aerosols with 11%, and industrial emissions and food cooking with 10% each. These results had a good agreement with the Emission Inventory. In average, the greater mass concentration occurred during O 3S that corresponds to a wind shift initially with transport to the South but moving back to the North. Taken together these results show that PM chemical composition, oxidative potential, and source contribution is influenced by the meteorological conditions.

Studies on thermal reactions and sintering behaviour of red clays by irreversible dilatometry

NASA Astrophysics Data System (ADS)

Anil, Asha; Misra, S. N.; Misra, N. M.

2018-05-01

Thermal behavior of clays strongly influences that of ceramic bodies made thereof and hence, its study is must for assessing its utility in ceramic products as well as to set the body composition. Irreversible dilatometry is an effective thermal analysis tool for evaluating thermal reactions as well as sintering behavior of clays or clay based ceramic bodies. In this study, irreversible dilatometry of four red clay samples (S, M, R and G) of Gujarat region, which vary in their chemical and mineralogical compositions was carried out using a Dilatometer and compared. Chemical analysis and XRD of red clays were carried out. XRD showed that major clay minerals in S, M and R clays are kaolinite. However, clay marked R and G showed presence of both kaolinite and illite and /muscovite. Presence of non-clay minerals such as hematite, quartz, anatase were also observed in all clays. XRD results were in agreement with chemical analyses results. Rational analyses showed variation in amount of clay and non-clay minerals in red clay samples. Evaluation of dilatometric curves showed that clay marked as S, M and R exhibit patterns typical for kaolinitic clays. Variation in linear expansion (up to 550°C) and shrinkage (above 550°C) between these three clays was found to be related to difference in amount of quartz and kaolinite respectively. However, dilatometric curve of G exhibit a pattern similar to that for an illitic clay. This study confirmed that sintering of investigated kaolinitic and illitic and / muscovitic red clays initiates at above 1060°C and 860°C respectively and this behaviour strongly depends upon type and amount of minerals and their chemical compositions.

Heterogeneous Oxidation of Laboratory-generated Mixed Composition and Biomass Burning Particles

NASA Astrophysics Data System (ADS)

Lim, C. Y.; Sugrue, R. A.; Hagan, D. H.; Cappa, C. D.; Kroll, J. H.; Browne, E. C.

2016-12-01

Heterogeneous oxidation of organic aerosol (OA) can significantly transform the chemical and physical properties of particulate matter in the atmosphere, leading to changes to the chemical composition of OA and potential volatilization of organic compounds. It has become increasingly apparent that the heterogeneous oxidation kinetics of OA depend on the phase and morphology of the particles. However, most laboratory experiments to date have been performed on single-component, purely organic precursors, which may exhibit fundamentally different behavior than more complex particles in the atmosphere. Here we present laboratory studies of the heterogeneous oxidation of two more complex chemical systems: thin, organic coatings on inorganic seed particles and biomass burning OA. In the first system, squalane (C30H62), a model compound for reduced OA, is coated onto dry ammonium sulfate particles at various thicknesses (10-20 nm) and exposed to hydroxyl radical (OH) in a flow tube reactor. In the second, we use a semi-batch reactor to study the heterogeneous OH-initiated oxidation of biomass burning particles as a part of the 2016 FIREX campaign in Missoula, MT. The resulting changes in chemical composition are monitored with an Aerodyne High Resolution Time-of-flight Aerosol Mass Spectrometer (AMS) and a soot-particle AMS for the non-refractory and refractory systems, respectively. We show that the heterogeneous oxidation kinetics of these multicomponent particles are substantially different than that of the single-component particles. The oxidation of organic coatings is rapid, undergoing dramatic changes to carbon oxidation state and losing a significant amount of organic mass after relatively low OH exposures (equivalent to several days of atmospheric processing). In the case of biomass burning particles, the kinetics are complex, with different components (inferred by aerosol mass spectrometry) undergoing oxidation at different rates.

Tying Biological Activity to Changes in Sea Spray Aerosol Chemical Composition via Single Particle Analyses

NASA Astrophysics Data System (ADS)

Sultana, C. M.; Lee, C.; Collins, D. B.; Axson, J. L.; Laskina, O.; Grandquist, J. R.; Grassian, V. H.; Prather, K. A.

2014-12-01

In remote marine environments, sea spray aerosols (SSA) often represent the greatest aerosol burden, thus having significant impacts on direct radiative interactions and cloud processes. Previous studies have shown that SSA is a complex mixture of inorganic salts and an array of dissolved and particulate organic components. Enrichment of SSA organic content is often correlated to seawater chlorophyll concentrations, a measure of oceanic biological activity. As the physical and chemical properties of aerosols control their radiative effects, recent studies conducted by the Center for Aerosol Impacts on Climate and the Environment have endeavored to further elucidate the ties between marine biological activity and primary SSA chemical composition using highly time resolved single particle analyses. A series of experiments performed in the recently developed Marine Aerosol Reference Tank evaluated the effect of changing marine microbial populations on SSA chemical composition, which was monitored via an aerosol time-of-flight mass spectrometer and a variety of offline spectroscopic and microscopic techniques. Each experiment was initiated using unfiltered and untreated seawater, thus maintaining a high level of biogeochemical complexity. This study is the first of its kind to capture daily changes in the primary SSA mixing state over the growth and death of a natural phytoplankton bloom. Increases in organic aerosol types (0.4-3 μm), internally and externally mixed with sea salt, could not be correlated to chlorophyll concentrations. Maximum production of these populations occurred two to four days after the in vivo chlorophyll fluorescence peaked in intensity. This work is in contrast to the current paradigm of correlating SSA organic content to seawater chlorophyll concentration.

Nanoparticle-triggered in situ catalytic chemical reactions for tumour-specific therapy.

PubMed

Lin, Han; Chen, Yu; Shi, Jianlin

2018-03-21

Tumour chemotherapy employs highly cytotoxic chemodrugs, which kill both cancer and normal cells by cellular apoptosis or necrosis non-selectively. Catalysing/triggering the specific chemical reactions only inside tumour tissues can generate abundant and special chemicals and products locally to initiate a series of unique biological and pathologic effects, which may enable tumour-specific theranostic effects to combat cancer without bringing about significant side effects on normal tissues. Nevertheless, chemical reaction-initiated selective tumour therapy strongly depends on the advances in chemistry, materials science, nanotechnology and biomedicine. This emerging cross-disciplinary research area is substantially different from conventional cancer-theranostic modalities in clinics. In response to the fast developments in cancer theranostics based on intratumoural catalytic chemical reactions, this tutorial review summarizes the very-recent research progress in the design and synthesis of representative nanoplatforms with intriguing nanostructures, compositions, physiochemical properties and biological behaviours for versatile catalytic chemical reaction-enabled cancer treatments, mainly by either endogenous tumour microenvironment (TME) triggering or exogenous physical irradiation. These unique intratumoural chemical reactions can be used in tumour-starving therapy, chemodynamic therapy, gas therapy, alleviation of tumour hypoxia, TME-responsive diagnostic imaging and stimuli-responsive drug release, and even externally triggered versatile therapeutics. In particular, the challenges and future developments of such a novel type of cancer-theranostic modality are discussed in detail to understand the future developments and prospects in this research area as far as possible. It is highly expected that this kind of unique tumour-specific therapeutics by triggering specific in situ catalytic chemical reactions inside tumours would provide a novel but efficient methodology for benefiting personalized biomedicine in combating cancer.

Composition and Chemical Stability of Motor Fuels,

DTIC Science & Technology

Fuels, *Hydrocarbons, Cycloalkanes, Chemical analysis, Gasoline, Diesel fuels, Fuel additives, Chemical reactions, Stability, Jet engine fuels...Aviation gasoline, Aviation fuels, Chemical composition, Aromatic hydrocarbons, Unsaturated hydrocarbons, Storage, USSR, Translations, Fuel systems, Alkanes

Rapid, facile microwave-assisted synthesis of xanthan gum grafted polyaniline for chemical sensor.

PubMed

Pandey, Sadanand; Ramontja, James

2016-08-01

Grafting method, through microwave radiation procedure is extremely productive in terms of time consumption, cost effectiveness and environmental friendliness. In this study, conductive and thermally stable composite (mwXG-g-PANi) was synthesized by grafting of aniline (ANi) on to xanthan gum (XG) using catalytic weight of initiator, ammonium peroxydisulfate in the process of microwave irradiation in an aqueous medium. The synthesis of mwXG-g-PANi were confirm by FTIR, XRD, TGA, and SEM. The influence of altering the microwave power, exposure time of microwave, concentration of monomer and the amount of initiator of graft polymerization were studied over the grafting parameters, for example, grafting percentage (%G) and grafting efficiency (%E). The maximum %G and %E achieved was 172 and 74.13 respectively. The outcome demonstrates that the microwave irradiation strategy can increase the reaction rate by 72 times over the conventional method. Electrical conductivity of XG and mwXG-g-PANi composite film was performed. The fabricated grafted sample film were then examined for the chemical sensor. The mwXG-g-PANi, effectively integrated and handled, are NH3 sensitive and exhibit a rapid sensing in presence of NH3 vapor. Chemiresistive NH3 sensors with superior room temperature sensing performance were produced with sensor response of 905 at 1ppb and 90% recovery within few second. Copyright © 2016 Elsevier B.V. All rights reserved.

Distribution of manganese between coexisting biotite and hornblende in plutonic rocks

USGS Publications Warehouse

Greenland, L.P.; Gottfried, D.; Tilling, R.I.

1968-01-01

The distribution of manganese between coexisting biotite and hornblende for 80 mineral pairs from igneous rocks of diverse provenance (including Southern California, Sierra Nevada, Boulder, and Boulder Creek batholiths and the Jemez Mountains volcanics) has been determined by neutron activation analysis. Data on the distribution ratio (Kd = Mnhornblende Mnbiotite) indicate that an equilibrium distribution of Mn is closely approached, though not completely attained, in most samples from plutonic environments. Comparison of Kd values of mineral pairs with bulk chemical composition of host rocks reveals no correlation. Because initial crystallization temperatures vary with rock composition, the lack of correlation of composition with Kd suggests that the equilibrium distribution of Mn between biotite and hornblende reflects exchange at subsolidus temperatures rather than initial crystallization temperatures. The highest Kd values are for volcanic rocks, in which rapid quenching prevents subsolidus redistribution of Mn. For sample pairs from the Southern California and Sierra Nevada batholiths there is a positive correlation of Kd with TiO2 content of biotite. Though the evidence is not compelling, Kd may also correlate with the rate of cooling and/or the presence or absence of sphene in the rock. ?? 1968.

Oxidation behavior of multiwall carbon nanotubes with different diameters and morphology

NASA Astrophysics Data System (ADS)

Mazov, Ilya; Kuznetsov, Vladimir L.; Simonova, Irina A.; Stadnichenko, Andrey I.; Ishchenko, Arkady V.; Romanenko, Anatoly I.; Tkachev, Evgeniy N.; Anikeeva, Olga B.

2012-06-01

Multiwall carbon nanotubes (MWNT) with three medium diameters (20-22, 9-13, and 6-8 nm) and different morphology were chemically oxidized using concentrated nitric acid, mixture of nitric and sulfuric acids ("mélange" solution) and mixture of sulfuric acid and hydrogen peroxide ("piranha" solution). Influence of MWNT type and structure as well as type of oxidizer on the surface composition and structure of nanotubes after oxidation was investigated. Acid-base titration, X-ray photoelectron spectroscopy and thermal gravimetric analysis were used for quantitative and qualitative investigation of surface group composition of initial and oxidized nanotubes. Amount of oxygen-containing groups on the surface of oxidized MWNT depends on the type of initial MWNT. It was found that ratio of different oxygen containing groups is less dependent on the type of oxidizer. Electrophysical properties of initial and oxidized nanotubes were investigated in temperature range 4-293 K and main types of electrical conductivity were determined. It was shown that oxidation results in decrease in electrical conductivity of all samples with simultaneous change in the conductivity mechanism. Dispersive behavior of initial and oxidized nanotubes in different commonly used solvents was investigated. It was shown that oxidation leads to the improvement of sedimentation stability of MWNT in polar solvents.

Bioresorbable composite screws manufactured via forging process: pull-out, shear, flexural and degradation characteristics.

PubMed

Felfel, R M; Ahmed, I; Parsons, A J; Rudd, C D

2013-02-01

Bioresorbable screws have the potential to overcome some of the complications associated with metallic screws currently in use. Removal of metallic screws after bone has healed is a serious issue which can lead to refracture due to the presence of screw holes. Poly lactic acid (PLA), fully 40 mol% P(2)O(5) containing phosphate unidirectional (P40UD) and a mixture of UD and short chopped strand random fibre mats (P40 70%UD/30%RM) composite screws were prepared via forging composite bars. Water uptake and mass loss for the composite screws manufactured increased significantly to ∼1.25% (P=0.0002) and ∼1.1% (P<0.0001), respectively, after 42 days of immersion in PBS at 37 °C. The initial maximum flexural load for P40 UD/RM and P40 UD composite screws was ∼60% (P=0.0047) and ∼100% (P=0.0037) higher than for the PLA screws (∼190 N), whilst the shear load was slightly higher in comparison to PLA (∼2.2 kN). The initial pull-out strengths for the P40 UD/RM and PLA screws were similar whereas that for P40 UD screws was ∼75% higher (P=0.022). Mechanical properties for the composite screws decreased initially after 3 days of immersion and this reduction was ascribed to the degradation of the fibre/matrix interface. After 3 days interval the mechanical properties (flexural, shear and pull-out) maintained their integrity for the duration of the study (at 42 days). This property retention was attributed to the chemical durability of the fibres used and stability of the matrix properties during the degradation process. It was also deemed necessary to enhance the fibre/matrix interface via use of a coupling agent in order to maintain the initial mechanical properties acquired for the required period of time. Lastly, it is also suggested that the degrading reinforcement fibres may have the potential to buffer any acidic products released from the PLA matrix. Copyright © 2012 Elsevier Ltd. All rights reserved.

Plant Species Rather Than Climate Greatly Alters the Temporal Pattern of Litter Chemical Composition During Long-Term Decomposition

NASA Astrophysics Data System (ADS)

Li, Yongfu; Chen, Na; Harmon, Mark E.; Li, Yuan; Cao, Xiaoyan; Chappell, Mark A.; Mao, Jingdong

2015-10-01

A feedback between decomposition and litter chemical composition occurs with decomposition altering composition that in turn influences the decomposition rate. Elucidating the temporal pattern of chemical composition is vital to understand this feedback, but the effects of plant species and climate on chemical changes remain poorly understood, especially over multiple years. In a 10-year decomposition experiment with litter of four species (Acer saccharum, Drypetes glauca, Pinus resinosa, and Thuja plicata) from four sites that range from the arctic to tropics, we determined the abundance of 11 litter chemical constituents that were grouped into waxes, carbohydrates, lignin/tannins, and proteins/peptides using advanced 13C solid-state NMR techniques. Decomposition generally led to an enrichment of waxes and a depletion of carbohydrates, whereas the changes of other chemical constituents were inconsistent. Inconsistent convergence in chemical compositions during decomposition was observed among different litter species across a range of site conditions, whereas one litter species converged under different climate conditions. Our data clearly demonstrate that plant species rather than climate greatly alters the temporal pattern of litter chemical composition, suggesting the decomposition-chemistry feedback varies among different plant species.

Plant Species Rather Than Climate Greatly Alters the Temporal Pattern of Litter Chemical Composition During Long-Term Decomposition

PubMed Central

Li, Yongfu; Chen, Na; Harmon, Mark E.; Li, Yuan; Cao, Xiaoyan; Chappell, Mark A.; Mao, Jingdong

2015-01-01

A feedback between decomposition and litter chemical composition occurs with decomposition altering composition that in turn influences the decomposition rate. Elucidating the temporal pattern of chemical composition is vital to understand this feedback, but the effects of plant species and climate on chemical changes remain poorly understood, especially over multiple years. In a 10-year decomposition experiment with litter of four species (Acer saccharum, Drypetes glauca, Pinus resinosa, and Thuja plicata) from four sites that range from the arctic to tropics, we determined the abundance of 11 litter chemical constituents that were grouped into waxes, carbohydrates, lignin/tannins, and proteins/peptides using advanced 13C solid-state NMR techniques. Decomposition generally led to an enrichment of waxes and a depletion of carbohydrates, whereas the changes of other chemical constituents were inconsistent. Inconsistent convergence in chemical compositions during decomposition was observed among different litter species across a range of site conditions, whereas one litter species converged under different climate conditions. Our data clearly demonstrate that plant species rather than climate greatly alters the temporal pattern of litter chemical composition, suggesting the decomposition-chemistry feedback varies among different plant species. PMID:26515033

A chemical model for lunar non-mare rocks

NASA Technical Reports Server (NTRS)

Hubbard, N. J.; Rhodes, J. M.

1974-01-01

Nearly all rocks returned from the moon are readily divided into three broad categories on the basis of their chemical compositions: (1) mare basalts, (2) non-mare rocks of basaltic composition (KREEP, VHA), and (3) anorthositic rocks. Only mare basalts may unambiguously be considered to have original igneous textures and are widely understood to have an igneous origin. Nearly all other lunar rocks have lost their original textures during metamorphic and impact processes. It is shown that for these rocks one must work primarily with chemical data in order to recognize and define rock groups and their possible modes of origin. Non-mare rocks of basaltic composition have chemical compositions consistent with an origin by partial melting of the lunar interior. The simplest origin for rocks of anorthositic chemical composition is the crystallization and removal of ferromagnesian minerals. It is proposed that the rock groups of anorthositic and non-mare basaltic chemical composition could have been generated from a single series of original but not necessarily primitive lunar materials.

Polypyrrole-MWCNT-Ag composites for electromagnetic shielding: Comparison between chemical deposition and UV-reduction approaches

NASA Astrophysics Data System (ADS)

Ebrahimi, Izadyar; Gashti, Mazeyar Parvinzadeh

2018-07-01

In this study, we focused on the synthesis of polypyrrole-MWCNT-Ag composites and we evaluated their electrical properties to determine the electromagnetic interference shielding performance. We reduced silver nanoparticles in composites using two different in situ methods: UV-reduction and chemical deposition. Composites were characterized using spectroscopic and microscopic tools for evaluation of the chemical, morphological, electrical conductivity and electromagnetic shielding effectiveness. Results from Fourier transform infrared spectroscopy and dispersive Raman microscope showed chemical interactions between silver and the polypyrrole-MWCNT composite due to the charge-transfer within the structure. X-ray diffraction confirmed appearance of two new peaks for silver nanoparticles embedded in polypyrrole-MWCNT independent to reduction method. According to microscopy images, silver nanoparticles were homogenously distributed at the PPy-MWCNTs interfaces by UV reduction, while, chemical reduction resulted to deposition of silver within the PPy matrix. Finally, our results revealed that the polypyrrole-MWCNT-Ag composite produced via UV-reduction has higher electrical conductivity and shielding effectiveness in comparison to chemically reduced one.

A chemical model for lunar non-mare rocks

NASA Technical Reports Server (NTRS)

Hubbard, N. J.; Rhodes, J. M.

1977-01-01

Nearly all rocks returned from the moon are readily divided into three broad categories on the basis of their chemical compositions: (1) mare basalts, (2) non-mare rocks of basaltic composition (KREEP, VHA), and (3) anorthositic rocks. Only mare basalts may unambiguously be considered to have original igneous textures and are widely understood to have an igneous origin. Nearly all other lunar rocks have lost their original textures during metamorphic and impact processes. For these rocks one must work primarily with chemical data in order to recognize and define rock groups and their possible modes of origin. Non-mare rocks of basaltic composition have chemical compositions consistent with an origin by partial melting of the lunar interior. The simplest origin for rocks of anorthositic chemical composition is the crystallization and removal of ferromagnesian minerals. It is proposed that the rock groups of anorthositic and non-mare basaltic chemical composition could have been generated from a single series of original, but not necessarily primitive, lunar materials.

Hydrogen addition reactions of aliphatic hydrocarbons in comets

NASA Astrophysics Data System (ADS)

Kobayashi, Hitomi; Watanabe, N.; Watanabe, Y.; Fukushima, T.; Kawakita, H.

2013-10-01

Comets are thought as remnants of early solar nebula. Their chemical compositions are precious clue to chemical and physical evolution of the proto-planetary disk. Some hydrocarbons such as C2H6, C2H2 and CH4 in comets have been observed by using near-infrared spectroscopy. Although the compositions of C2H6 were about 1% relative to the water in normal comets, there are few reports on the detection of C2H6 in ISM. Some formation mechanisms of C2H6 in ISM have been proposed, and there are two leading hypotheses; one is the dimerizations of CH3 and another is the hydrogen addition reactions of C2H2 on cold icy grains. To evaluate these formation mechanisms for cometary C2H6 quantitatively, it is important to search the C2H4 in comets, which is the intermediate product of the hydrogen addition reactions toward C2H6. However, it is very difficult to detect the C2H4 in comets in NIR (3 microns) regions because of observing circumstances. The hydrogen addition reactions of C2H2 at low temperature conditions are not well characterized both theoretically and experimentally. For example, there are no reports on the reaction rate coefficients of those reaction system. To determine the production rates of those hydrogen addition reactions, we performed the laboratory experiments of the hydrogenation of C2H2 and C2H4. We used four types of the initial composition of the ices: pure C2H4, pure C2H2, C2H2 on amorphous solid water (ASW) and C2H4 on ASW at three different temperatures of 10, 20, and 30K. We found 1) reactions are more efficient when there are ASW in the initial compositions of the ice; 2) hydrogenation of C2H4 occur more rapid than that of C2H2.

Episodic large-scale overturn of two-layer mantles in terrestrial planets

NASA Astrophysics Data System (ADS)

Herrick, D. L.; Parmentier, E. M.

1994-01-01

It is usually assumed that the upper and lower mantles of a chemically stratified planet are arranged so that the upper mantle is chemically less dense and that these layers convect separately. Possible buoyant overturn of the two mantle layers has not previously been considered. Such overturn would initially occur when thermal expansion of a chemically denser lower mantle more than offsets the compositional density difference between the layers, reversing the relative sense of buoyancy. Once overturn has occurred, the chemically denser, but thermally less dense upper mantle cools more efficiently than the lower mantle and loses its relative thermal buoyancy. If mixing is slow, this leads to repeated overturns that result in thermal histories that differ radically from those obtained without this large-scale overturning. Thermal evolution calculations, for a two-layer mantle over a wide range of parameter space, show that large-scale overturn occurs cyclically with a well-defined period. This period depends most strongly on the viscosity of the lower mantle, to which it is approximately proportional. Geologically interesting overturn periods on the order of 107 to 109 years result for lower mantle viscosities of 1022 to 1024 Pa s for the Earth and Venus, and 1021 to 1023 Pa s for Mars. The mantles of Mercury and the Moon are too thin to permit two-layer convection, and therefore the model is not appropriate for them. Overturn cannot occur on Earth or Venus if the compositional density difference between the layers exceeds about 4%, or on Mars if it exceeds about 2%. Large-scale mantle overturn could have significant tectonic consequences such as the initiation of a new plate tectonic cycle on the Earth or a major resurfacing event on Mars or Venus. Such episodic events in the evolution of a planet are not easily explained by whole mantle thermal convection.

Episodic large-scale overturn of two-layer mantles in terrestrial planets

NASA Technical Reports Server (NTRS)

Herrick, David L.; Parmentier, E. M.

1994-01-01

It is usually assumed that the upper and lower mantles of a chemically stratified planet are arranged so that the upper mantle is chemically less dense and that these layers convect separately. Possible buoyant overturn of the two mantle layers has not previously been considered. Such overturn would initially occur when thermal expansion of a chemically denser lower mantle more than offsets the compositional density difference between the layers, reversing the relative sense of buoyancy. Once overturn has occurred, the chemically denser, but thermally less dense upper mantle cools more efficiently than the lower mantle and loses its relative thermal buoyancy. If mixing is slow, this leads to repeated overturns that result in thermal histories that differ radically from those obtained without this large-scale overturning. Thermal evolution calculations, for a two-layer mantle over a wide range of parameter space, show that large-scale overturn occurs cyclically with a well-defined period. This period depends most strongly on the viscosity of the lower mantle, to which it is approximately proportional. Geologically interesting overturn periods on the order of 10(exp 7) to 10(exp 9) years result for lower mantle viscosities of 10(exp 22) to 10(exp 24) Pa s for the Earth and Venus, and 10(exp 21) to 10(exp 23) Pa s for Mars. The mantles of Mercury and the Moon are too thin to permit two-layer convection, and therefore the model is not appropriate for them. Overturn cannot occur on Earth or Venus if the compositional density difference between the layers exceeds about 4%, or on Mars if it exceeds about 2%. Large-scale mantle overturn could have significant tectonic consequences such as the initiation of a new plate tectonic cycle on the Earth or a major resurfacing event on Mars or Venus. Such episodic events in the evolution of a planet are not easily explained by whole mantle thermal convection.

Effects of glass scraps powder and glass fiber on mechanical properties of polyester composites

NASA Astrophysics Data System (ADS)

Sonsakul, K.; Boongsood, W.

2017-11-01

One concern in bus manufacturing is the high cost of glass fiber reinforced in polyester composites parts. The composites of glass fiber and polyester are low elongation and high strength, and glass scraps powder displays high hardness and good chemical compatibility with the polymer matrix and glass fiber. This research aimed to study the effects of glass scraps powder and glass fiber on mechanical performance of polyester composites. Glass fiber was randomly oriented fiber and used as new. Glass scraps were obtained from a bus factory and crushed to powder sizes of 120 and 240 μm by a ball mill. Polyester composites were prepared using Vacuum Infusion Process (VIP).Polyester reinforced with 3 layers of glass fiber was an initial condition. Then, one layer of glass fiber was replaced with glass scraps powder. Flexural strength, tensile strength, impact strength and hardness of the polyester composites were determined. Hardness was increased with a combination of smaller size and higher volume of glass scraps powder. Pictures of specimens obtained by using scanning electron microscope (SEM) confirmed that the powder of glass scraps packed in the layers of glass fiber in polyester composites.

Chemical unfolding of chicken villin headpiece in aqueous dimethyl sulfoxide solution: cosolvent concentration dependence, pathway, and microscopic mechanism.

PubMed

Roy, Susmita; Bagchi, Biman

2013-04-25

Unfolding of a protein often proceeds through partial unfolded intermediate states (PUIS). PUIS have been detected in several experimental and simulation studies. However, complete analyses of transitions between different PUIS and the unfolding trajectory are sparse. To understand such dynamical processes, we study chemical unfolding of a small protein, chicken villin head piece (HP-36), in aqueous dimethyl sulfoxide (DMSO) solution. We carry out molecular dynamics simulations at various solution compositions under ambient conditions. In each concentration, the initial step of unfolding involves separation of two adjacent native contacts, between phenyl alanine residues (11-18 and 7-18). This first step induces, under appropriate conditions, subsequent separation among other hydrophobic contacts, signifying a high degree of cooperativity in the unfolding process. The observed sequence of structural changes in HP-36 on increasing DMSO concentration and the observed sequence of PUIS, are in approximate agreement with earlier simulation results (in pure water) and experimental observations on unfolding of HP-36. Peculiar to water-DMSO mixture, an intervening structural transformation (around 15% of DMSO) in the binary mixture solvent retards the progression of unfolding as composition is increased. This is reflected in a remarkable nonmonotonic composition dependence of RMSD, radius of gyration and the fraction of native contacts. At 30% mole fraction of DMSO, we find the extended randomly coiled structure of the unfolded protein. The molecular mechanism of DMSO induced unfolding process is attributed to the initial preferential solvation of the hydrophobic side chain atoms through the methyl groups of DMSO, followed by the hydrogen bonding of the oxygen atom of DMSO to the exposed backbone NH groups of HP-36.

Growth of multi-component alloy films with controlled graded chemical composition on sub-nanometer scale

DOEpatents

Bajt, Sasa; Vernon, Stephen P.

2005-03-15

The chemical composition of thin films is modulated during their growth. A computer code has been developed to design specific processes for producing a desired chemical composition for various deposition geometries. Good agreement between theoretical and experimental results was achieved.

Post-irradiation hardness development, chemical softening, and thermal stability of bulk-fill and conventional resin-composites.

PubMed

Alshali, Ruwaida Z; Salim, Nesreen A; Satterthwaite, Julian D; Silikas, Nick

2015-02-01

To measure bottom/top hardness ratio of bulk-fill and conventional resin-composite materials, and to assess hardness changes after dry and ethanol storage. Filler content and kinetics of thermal decomposition were also tested using thermogravimetric analysis (TGA). Six bulk-fill (SureFil SDR, Venus bulk fill, X-tra base, Filtek bulk fill flowable, Sonic fill, and Tetric EvoCeram bulk-fill) and eight conventional resin-composite materials (Grandioso flow, Venus Diamond flow, X-flow, Filtek Supreme Ultra Flowable, Grandioso, Venus Diamond, TPH Spectrum, and Filtek Z250) were tested (n=5). Initial and 24h (post-cure dry storage) top and bottom microhardness values were measured. Microhardness was re-measured after the samples were stored in 75% ethanol/water solution. Thermal decomposition and filler content were assessed by TGA. Results were analysed using one-way ANOVA and paired sample t-test (α=0.05). All materials showed significant increase of microhardness after 24h of dry storage which ranged from 100.1% to 9.1%. Bottom/top microhardness ratio >0.9 was exhibited by all materials. All materials showed significant decrease of microhardness after 24h of storage in 75% ethanol/water which ranged from 14.5% to 74.2%. The extent of post-irradiation hardness development was positively correlated to the extent of ethanol softening (R(2)=0.89, p<0.001). Initial thermal decomposition temperature assessed by TGA was variable and was correlated to ethanol softening. Bulk-fill resin-composites exhibit comparable bottom/top hardness ratio to conventional materials at recommended manufacturer thickness. Hardness was affected to a variable extent by storage with variable inorganic filler content and initial thermal decomposition shown by TGA. The manufacturer recommended depth of cure of bulk-fill resin-composites can be reached based on the microhardness method. Characterization of the primary polymer network of a resin-composite material should be considered when evaluating its stability in the aqueous oral environment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Obtaining Crack-free WC-Co Alloys by Selective Laser Melting

NASA Astrophysics Data System (ADS)

Khmyrov, R. S.; Safronov, V. A.; Gusarov, A. V.

Standard hardmetals of WC-Co system are brittle and often crack at selective laser melting (SLM). The objective of this study is to estimate the range of WC/Co ratio where cracking can be avoided. Micron-sized Co powder was mixed with WC nanopowder in a ball mill to obtain uniform distribution of WC over the surface of Co particles. Continuous layers of remelted material on the surface of a hardmetal plate were obtained from this composite powder by SLM at 1.07μm wavelength. The layers have satisfactory porosity and are well bound to the substrate. The chemical composition of the layers matches the composition of the initial powder mixtures. The powder mixture with 25wt.%WC can be used for SLM to obtain materials without cracks. The powder mixture with 50wt.%WC cracks because of formation of brittle W3Co3C phase. Cracking can considerably reduce the mechanical strength, so that the use of this composition is not advised.

Role of initial heat treatment of the ferrite component on magnetic properties in the composite of ferrimagnetic Co1.75Fe1.25O4 ferrite and non-magnetic BaTiO3 oxide

NASA Astrophysics Data System (ADS)

Bhowmik, R. N.; Kazhugasalamoorthy, S.; Sinha, A. K.

2017-12-01

We have prepared a composite of ferrimagnetic ferrite Co1.75Fe1.25O4 and non-magnetic oxide BaTiO3. The ferrite composition Co1.75Fe1.25O4 has been prepared by chemical co-precipitation and subsequently heated at different temperatures. The heat treated ferrite powder has been mixed with BaTiO3 powder with mass ratio 1:1 and the mixed powder has been finally heated at 1000 °C to form composite material. Structural phase of the composite material has been confirmed by high quality Synchrotron X-ray diffraction pattern and Micro-Raman spectra. The grain surface morphology and elemental composition have been studied by Scanning electron microscope and Energy dispersive X-ray analysis. The distribution of magnetic exchange interactions and blocking behavior of the ferrimagnetic grains in composite samples has been understood by analyzing the temperature and magnetic field dependence of dc magnetization. Finally, information on modified micro-structure and ferrimagnetic parameters in composite samples has been obtained as the variation of annealing temperature of the ferrite component before making composite.

Catalytic Conversion of Carbohydrates to Initial Platform Chemicals: Chemistry and Sustainability.

PubMed

Mika, László T; Cséfalvay, Edit; Németh, Áron

2018-01-24

The replacement of fossil resources that currently provide more than 90% of our energy needs and feedstocks of the chemical industry in combination with reduced emission of carbon dioxide is one of the most pressing challenges of mankind. Biomass as a globally available resource has been proposed as an alternative feedstock for production of basic building blocks, which could partially or even fully replace the currently utilized fossil-based ones in well-established chemical processes. The destruction of lignocellulosic feed followed by oxygen removal from its cellulose and hemicellulose content by catalytic processes results in the formation of initial platform chemicals (IPCs). However, their sustainable production strongly depends on the availability of resources, their efficient or even industrially viable conversion processes, and replenishment time of feedstocks. Herein, we overview recent advances and developments in catalytic transformations of the carbohydrate content of lignocellulosic biomass to IPCs (i.e., ethanol, 3-hydroxypropionic acid, isoprene, succinic and levulinic acids, furfural, and 5-hydroxymethylfurfural). The mechanistic aspects, development of new catalysts, different efficiency indicators (yield and selectivity), and conversion conditions of their production are presented and compared. The potential biochemical production routes utilizing recently engineered microorganisms are reviewed, as well. The sustainability metrics that could be applied to the chemical industry (individual set of sustainability indicators, composite indices methods, material and energy flow analysis-based metrics, and ethanol equivalents) are also overviewed as well as an outlook is provided to highlight challenges and opportunities associated with this huge research area.

Method of producing a chemical hydride

DOEpatents

Klingler, Kerry M.; Zollinger, William T.; Wilding, Bruce M.; Bingham, Dennis N.; Wendt, Kraig M.

2007-11-13

A method of producing a chemical hydride is described and which includes selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of a hydrocarbon; and reacting the composition with the source of the hydrocarbon to generate a chemical hydride.

Europa's Crust and Ocean: Origin, Composition, and the Prospects for Life

USGS Publications Warehouse

Kargel, J.S.; Kaye, J.Z.; Head, J. W.; Marion, G.M.; Sassen, R.; Crowley, J.K.; Ballesteros, O.P.; Grant, S.A.; Hogenboom, D.L.

2000-01-01

We have considered a wide array of scenarios for Europa's chemical evolution in an attempt to explain the presence of ice and hydrated materials on its surface and to understand the physical and chemical nature of any ocean that may lie below. We postulate that, following formation of the jovian system, the europan evolutionary sequence has as its major links: (a) initial carbonaceous chondrite rock, (b) global primordial aqueous differentiation and formation of an impure primordial hydrous crust, (c) brine evolution and intracrustal differentiation, (d) degassing of Europa's mantle and gas venting, (e) hydrothermal processes, and (f) chemical surface alteration. Our models were developed in the context of constraints provided by Galileo imaging, near infrared reflectance spectroscopy, and gravity and magnetometer data. Low-temperature aqueous differentiation from a carbonaceous CI or CM chondrite precursor, without further chemical processing, would result in a crust/ocean enriched in magnesium sulfate and sodium sulfate, consistent with Galileo spectroscopy. Within the bounds of this simple model, a wide range of possible layered structures may result; the final state depends on the details of intracrustal differentiation. Devolatilization of the rocky mantle and hydrothermal brine reactions could have produced very different ocean/crust compositions, e.g., an ocean/crust of sodium carbonate or sulfuric acid, or a crust containing abundant clathrate hydrates. Realistic chemical-physical evolution scenarios differ greatly in detailed predictions, but they generally call for a highly impure and chemically layered crust. Some of these models could lead also to lateral chemical heterogeneities by diapiric upwellings and/or cryovolcanism. We describe some plausible geological consequences of the physical-chemical structures predicted from these scenarios. These predicted consequences and observed aspects of Europa's geology may serve as a basis for further analys is and discrimination among several alternative scenarios. Most chemical pathways could support viable ecosystems based on analogy with the metabolic and physiological versatility of terrestrial microorganisms. ?? 2000 Academic Press.

An Iron-Rain Model for Core Formation on Asteroid 4 Vesta

NASA Technical Reports Server (NTRS)

Kiefer, Walter S.; Mittlefehldt, David W.

2016-01-01

Asteroid 4 Vesta is differentiated into a crust, mantle, and core, as demonstrated by studies of the eucrite and diogenite meteorites and by data from NASA's Dawn spacecraft. Most models for the differentiation and thermal evolution of Vesta assume that the metal phase completely melts within 20 degrees of the eutectic temperature, well before the onset of silicate melting. In such a model, core formation initially happens by Darcy flow, but this is an inefficient process for liquid metal and solid silicate. However, the likely chemical composition of Vesta, similar to H chondrites with perhaps some CM or CV chondrite, has 13-16 weight percent S. For such compositions, metal-sulfide melting will not be complete until a temperature of at least 1350 degrees Centigrade. The silicate solidus for Vesta's composition is between 1100 and 1150 degrees Centigrade, and thus metal and silicate melting must have substantially overlapped in time on Vesta. In this chemically and physically more likely view of Vesta's evolution, metal sulfide drops will sink by Stokes flow through the partially molten silicate magma ocean in a process that can be envisioned as "iron rain". Measurements of eucrites show that moderately siderophile elements such as Ni, Mo, and W reached chemical equilibrium between the metal and silicate phases, which is an important test for any Vesta differentiation model. The equilibration time is a function of the initial metal grain size, which we take to be 25-45 microns based on recent measurements of H6 chondrites. For these sizes and reasonable silicate magma viscosities, equilibration occurs after a fall distance of just a few meters through the magma ocean. Although metal drops may grow in size by merger with other drops, which increases their settling velocities and decreases the total core formation time, the short equilibration distance ensures that the moderately siderophile elements will reach chemical equilibrium between metal and silicate before metal drop merger becomes important. In this model, there must be at least 30 percent melting of the silicate phase when metal melting is complete, corresponding to a crust thickness of at least 30 kilometers on Vesta, consistent with Dawn gravity observations. Greater degrees of silicate melting and a correspondingly thicker crust are possible if Vesta accreted sufficiently rapidly.

ToxCast Phase I

EPA Pesticide Factsheets

Background: Chemical toxicity testing is being transformed by advances in biology and computer modeling, concerns over animal use and the thousands of environmental chemicals lacking toxicity data. EPA's ToxCast program aims to address these concerns by screening and prioritizing chemicals for potential human toxicity using in vitro assays and in silico approaches. Objectives: This project aims to evaluate the use of in vitro assays for understanding the types of molecular and pathway perturbations caused by environmental chemicals and to build initial prioritization models of in vivo toxicity. Methods: We tested 309 mostly pesticide active chemicals in 467 assays across 9 technologies, including high-throughput cell-free assays and cell-based assays in multiple human primary cells and cell lines, plus rat primary hepatocytes. Both individual and composite scores for effects on genes and pathways were analyzed. Results: Chemicals display a broad spectrum of activity at the molecular and pathway levels. Many expected interactions are seen, including endocrine and xenobiotic metabolism enzyme activity. Chemicals range in promiscuity across pathways, from no activity to affecting dozens of pathways. We find a statistically significant inverse association between the number of pathways perturbed by a chemical at low in vitro concentrations and the lowest in vivo dose at which a chemical causes toxicity. We also find associations between a small set in vitro ass

About microcracking due to leaching in cementitious composites: X-ray microtomography description and numerical approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rougelot, Thomas; Burlion, Nicolas, E-mail: nicolas.burlion@polytech-lille.f; Bernard, Dominique

2010-02-15

Chemical shock of cement based materials leads to significant degradation of their physical properties. A typical scenario is a calcium leaching due to water (water with very low pH compared with that of pore fluid). The main objective of this paper is to evaluate the evolution of microstructure induced by leaching of a cementitious composite using synchrotron X-ray micro tomography, mainly from an experimental point of view. In this particular case, it was possible to identify cracking induced by leaching. After a description of the degradation mechanism and the X-ray synchrotron microtomographic analysis, numerical simulations are performed in order tomore » show that cracking is induced by an initial pre-stressing of the composite, coupled with decalcification shrinkage and dramatic decrease in tensile strength during leaching. X-ray microtomography analysis allowed to make evidence of an induced microcracking in cementitious material submitted to leaching.« less

Compositional Evolution of Pyrochlore-Group Minerals in Carbonatites of the Belaya Zima Pluton, Eastern Sayan

NASA Astrophysics Data System (ADS)

Khromova, E. A.; Doroshkevich, A. G.; Sharygin, V. V.; Izbrodin, L. A.

2017-12-01

Pyrochlore-group minerals are the main concentrators of niobium in carbonatites of the Belaya Zima alkaline pluton. Fluorcalciopyrochlore, kenopyrochlore and hydropyrochlore were identified in chemical composition. Their main characteristics are given: compositional variation, morphology, and zoning. During evolution from early calcite to late ankerite carbonatites, the UO2, TiO2, REE, and Y contents gradually increased. All carbonatite types are suggested to contain initial fluorcalciopyrochlore. However, in calcite-dolomite and ankerite carbonatites, it is partially or completely hydrated due to hydrothermal processes at the late stage of the pluton. This hydration resulted in the appearance of kenopyrochlore and hydropyrochlore due to removal of Ca, Na and F, and input of Ba, H2O, K, Si, Fe, and probably U and REE. At the last stage of the pluton, this hydrated pyrochlore was replaced by Fe-bearing columbite.

Enhanced capacity of chemically bonded phosphorus/carbon composite as an anode material for potassium-ion batteries

NASA Astrophysics Data System (ADS)

Wu, Xuan; Zhao, Wei; Wang, Hong; Qi, Xiujun; Xing, Zheng; Zhuang, Quanchao; Ju, Zhicheng

2018-02-01

Potassium-ion batteries are attracting great attention as a promising alternative to lithium-ion batteries due to the abundance and low price of potassium. Herein, the phosphorus/carbon composite, obtained by a simple ball-milling of 20 wt% commercial red phosphorus and 80 wt% graphite, is studied as a novel anode for potassium-ion batteries. Considering the high theoretical specific capacity of phosphorus and formation of stable phosphorus-carbon bond, which can alleviate the volume expansion efficiently, the phosphorus/carbon composite exhibits a high charge capacity of 323.5 mA h g-1 after 50 cycles at a current density of 50 mA g-1 with moderate rate capability and cycling stability. By the X-ray diffraction analysis, the alloying-dealloying mechanism of phosphorus is proposed to form a KP phase. Meanwhile, prepotassiation treatment is conducted to improve the low initial coulomb efficiency.

Effect of Mechanical and Thermal Loading Histories on Residual Properties of SiCf/SiC Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Almansour, Amjad; Kiser, Doug; Smith, Craig; Bhatt, Ram; Gorican, Dan; Phillips, Ron; McCue, Terry R.

2017-01-01

Silicon Carbide based Ceramic Matrix Composites (CMCs) are attractive materials for use in high-temperature structural applications in the aerospace and nuclear industries. Under high stresses and temperatures, creep degradation is the dominant damage mechanism in CMCs. Consequently, chemical vapor infiltration (CVI) SiCf/SiC ceramic matrix composites (CMC) incorporating SylramicTM-iBN SiC fibers coated with boron nitride (BN) interphase and CVI-SiC matrix were tested to examine creep behavior in air at a range of elevated temperatures of (2200 - 2700 F). Samples that survived creep tests were evaluated via RT fast fracture tensile tests to determine residual properties, with the use of acoustic emission (AE) to assess stress dependent damage initiation and progression. Microscopy of regions within the gage section of the tested specimens was performed. Observed material degradation mechanisms are discussed.

International collaborative project to compare and monitor the nutritional composition of processed foods.

PubMed

Dunford, Elizabeth; Webster, Jacqui; Metzler, Adriana Blanco; Czernichow, Sebastien; Ni Mhurchu, Cliona; Wolmarans, Petro; Snowdon, Wendy; L'Abbe, Mary; Li, Nicole; Maulik, Pallab K; Barquera, Simon; Schoj, Verónica; Allemandi, Lorena; Samman, Norma; de Menezes, Elizabete Wenzel; Hassell, Trevor; Ortiz, Johana; Salazar de Ariza, Julieta; Rahman, A Rashid; de Núñez, Leticia; Garcia, Maria Reyes; van Rossum, Caroline; Westenbrink, Susanne; Thiam, Lim Meng; MacGregor, Graham; Neal, Bruce

2012-12-01

Chronic diseases are the leading cause of premature death and disability in the world with overnutrition a primary cause of diet-related ill health. Excess energy intake, saturated fat, sugar, and salt derived from processed foods are a major cause of disease burden. Our objective is to compare the nutritional composition of processed foods between countries, between food companies, and over time. Surveys of processed foods will be done in each participating country using a standardized methodology. Information on the nutrient composition for each product will be sought either through direct chemical analysis, from the product label, or from the manufacturer. Foods will be categorized into 14 groups and 45 categories for the primary analyses which will compare mean levels of nutrients at baseline and over time. Initial commitments to collaboration have been obtained from 21 countries. This collaborative approach to the collation and sharing of data will enable objective and transparent tracking of processed food composition around the world. The information collected will support government and food industry efforts to improve the nutrient composition of processed foods around the world.

Synthesis of HNTs@PEDOT composites via in situ chemical oxidative polymerization and their application in electrode materials

NASA Astrophysics Data System (ADS)

Wang, Fang; Zhang, Xianhong; Ma, Yuhong; Yang, Wantai

2018-01-01

The hybrid composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and halloysite nanotubes (HNTs) was synthesized by a two-step process. First, poly(sodium styrene sulfonate) (PSSNa) was grafted onto HNTs via surface initiated atom transfer radical polymerization. Then with the HNTs-g-PSS as a template and the grafted PSS chains as the counterion dopant, PEDOT was precipitated onto the template via in situ oxidization polymerization of EDOT to form HNTs@PEDOT hybrid composites. The conductivity of HNTs@PEDOT can reach up to 9.35 S/cm with the content of 40% HNTs-g-PSS, which increased almost 78 times than that of pure PEDOT (about 0.12 S/cm) prepared at the similar condition. Further treated with p-toluenesulfonic acid (TsOH) as external dopant, the conductivity of HNTs@PEDOT increased to 24.3 S/cm. The electrochemical properties of the composites were investigated with cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy with three-electrode cell configuration. The results showed that the capacitance of HNTs@PEDOT composite increased 55% than that of pure PEDOT.

Improving Thermomechanical Properties of SiC/SiC Composites

NASA Technical Reports Server (NTRS)

DiCarlo, James A.; Bhatt, Ramakrishna T.

2006-01-01

Today, a major thrust toward improving the thermomechanical properties of engine components lies in the development of fiber-reinforced silicon carbide matrix composite materials, including SiC-fiber/SiC-matrix composites. These materials are lighter in weight and capable of withstanding higher temperatures, relative to state-of-the-art metallic alloys and oxide-matrix composites for which maximum use temperatures are in the vicinity of 1,100 C. In addition, the toughness or damage tolerance of the SiC-matrix composites is significantly greater than that of unreinforced silicon-based monolithic ceramics. For successful application in advanced engine systems, the SiC-matrix composites should be able to withstand component service stresses and temperatures for the desired component lifetimes. Inasmuch as the high-temperature structural lives of ceramic materials are typically limited by creep-induced growth of flaws, a key property required of such composite materials is high resistance to creep under conditions of use. Also, the thermal conductivity of the materials should be as high as possible so as to minimize component thermal gradients and thermal stresses. A state-of-the-art SiC-matrix composite is typically fabricated in a three-step process: (1) fabrication of a component-shaped architectural preform reinforced by thermally stable high-performance fibers, (2) chemical-vapor infiltration (CVI) of a fiber-coating material such as boron nitride (BN) into the preform, and (3) infiltration of an SiC-based matrix into the remaining porosity in the preform. Generally, the matrices of the highest-performing composites are fabricated by initial use of a CVI SiC matrix component that is typically more thermally stable and denser than matrix components formed by processes other than CVI. As such, the initial SiC matrix component made by CVI provides better environmental protection to the coated fibers embedded within it. Also, the denser CVI SiC imparts to the composite better resistance to propagation of cracks, enhanced thermal conductivity, and higher creep resistance.

Density fingering in spatially modulated Hele-Shaw cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toth, Tamara; Horvath, Dezso; Toth, Agota

Density fingering of the chlorite-tetrathionate reaction has been studied experimentally in a periodically heterogeneous Hele-Shaw cell where the heterogeneity is introduced in the form of spatial modulation of gap width along the front. Depending on the spatial wavelength, gap width, and chemical composition, three types of cellular structures have been observed. The initial evolution is characterized by dispersion curves, while the long time behavior is described by the change in the autocorrelation function of the front profile and in the mixing length of the patterns.

Problem Definition Studies on Potential Environmental Pollutants. 6. Preliminary Assessment of Environmental Effects of Seven Substances Used in Pyrotechnic Compositions at Pine Bluff Arsenal

DTIC Science & Technology

1979-11-01

on reveryo if nec.,ary and identify by block number) FIELD GROUP SUB-GROUP Benzanthrone, 1-Methylaminoanthraquinone, Pyrotechnics 24 03 .uramine, 1,4...necessary and identify by block number) Procurement data for the period 1965-1975 are used to estimate soil contaminatior by pyrotechnic and smoke...Project Manager for Chemical Demilitarization and Installation Restoration, has identified an initial list of substances (Table 1) requiring assessment

Development of Novel Decontamination Techniques for Chemical Agents (GB, VX, HD) Contaminated Facilities. Phase II. Laboratory Evaluation of Novel Agent Decontamination Concepts

DTIC Science & Technology

1985-06-21

mild steel, unpainted mild steel, and porous (i.e., concrete and unglazed porcelain ) test coupons contaminated with agent to a hot-gas composition near...unpainted *’ mild steel, painted stainless steel, concrete, and unglazed porcelain * coupons contaminated with HD, GB, or VX. The detectable limit for the Sub...similar decontamination efficiency was observable in the concrete and unglazed porcelain tests for an initial dose level of 1.8 mg agent/g of material

Synthesis of Polycrystalline CdSiP2 in a Gradient Temperature Field

NASA Astrophysics Data System (ADS)

Bereznaya, S. A.; Korotchenko, Z. V.; Kurasova, A. S.; Sarkisov, S. Yu.; Sarkisov, Yu. S.; Chernyshov, A. I.; Korolkov, I. V.; Kuchumov, B. M.; Saprykin, A. I.; Atuchin, V. V.

2018-05-01

A procedure for the synthesis of a CdSiP2 compound from the initial elementary components in a gradient thermal field has been developed. The phase and chemical composition of the synthesized and recrystallized material is confirmed by the data of X-ray diffraction analysis and scanning electron microscopy with an energy-dispersive system. The polycrystalline material obtained by the developed method will be used to grow bulk nonlinear optical CdSiP2 crystals.

Review on effect of chemical, thermal, additive treatment on mechanical properties of basalt fiber and their composites

NASA Astrophysics Data System (ADS)

Jain, Naman; Singh, Vinay Kumar; Chauhan, Sakshi

2017-12-01

Basalt fiber is emerging out the new reinforcing material for composites. To overcome some of the disadvantages of fibers such as poor bonding to polymers, low thermal stability and high moisture absorption fiber characteristics are modified with chemical, thermal and additive treatments. Chemical treatment corrosive resistance to alkali and acid were investigated which were used to clean and modify the surface of fiber for higher bonding with resins. To improve the thermal stability and reduce moisture uptake thermal treatment such as plasma and non thermal plasma were used which increased the surface roughness and change the chemical composition of surface of basalt fiber. Additive treatment is used to improve the mechanical properties of fibers, in basalt fiber additive treatment was done with SiO2 additive because of its chemical composition which contains major content of SiO2. In present investigation review on the effect of different treatment such as chemical, thermal and additive were studied. Effect of these treatment on chemical composition of the surface of basalt fiber and corrosion to acidic and alkali solution were studied with their effect on mechanical properties of basalt fiber and their composite.

Experiments pertaining to the formation and equilibration of planetary cores

NASA Technical Reports Server (NTRS)

Jeanloz, Raymond; Knittle, Elise; Williams, Quentin

1987-01-01

The phase diagram of FeO was experimentally determined to pressures of 155 GPa and temperatures of 4000 K using shock wave and diamond-cell techniques. Researchers discovered a metallic phase of FeO at pressures greater than 70 GPa and temperatures exceeding 1000 K. The metallization of FeO at high pressures implies that oxygen can be present as the light alloying element of the Earth's outer core, in accord with the geochemical predictions of Ringwood. The high pressures necessry for this metallization suggest that the core has acquired its composition well after the initial stages of the Earth's accretion. The core forming alloy can react chemically with oxides such as those forming the mantle. The core and mantle may never have reached complete chemical equilibrium, however. If this is the case, the core-mantle boundary is likely to be a zone of active chemical reactions.

Chemical vapor deposition of Mo thin films from Mo(CO){sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, P.; Bond, J.; Westmore, T.

1995-12-01

Low levels of carbon and/or oxygen contamination in metallic thin films significantly alter the physical and chemical properties of these films often rendering them useless for any commercial applications. These impurities are often observed in films grown by a technique called metallorganic chemical vapor deposition (MOCVD). MOCVD films are grown by heating a substrate in the presence of a metallorganic precursor. We wish to identify the source(s) of contamination in films produced from the Group VIB metal hexacarbonyls, M(CO){sub 6}. Towards attaining this goal we have initiated studies on the elemental composition of thin films deposited by MOCVD using Mo(CO){submore » 6} as the precursor. The results obtained so far indicate that the level of contamination of the films partially depends on the deposition temperature. Our results will be compared to published work on films deposited by laser assisted CVD from Mo(CO){sub 6}.« less

Structural, chemical and electrical characterisation of conductive graphene-polymer composite films

NASA Astrophysics Data System (ADS)

Brennan, Barry; Spencer, Steve J.; Belsey, Natalie A.; Faris, Tsegie; Cronin, Harry; Silva, S. Ravi P.; Sainsbury, Toby; Gilmore, Ian S.; Stoeva, Zlatka; Pollard, Andrew J.

2017-05-01

Graphene poly-acrylic and PEDOT:PSS nanocomposite films were produced using two alternative commercial graphene powders to explore how the graphene flake dimensions and chemical composition affected the electrical performance of the film. A range of analytical techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), were employed to systematically analyse the initial graphene materials as well as the nanocomposite films. Electrical measurements indicated that the sheet resistance of the films was affected by the properties of the graphene flakes used. To further explore the composition of the films, ToF-SIMS mapping was employed and provided a direct means to elucidate the nature of the graphene dispersion in the films and to correlate this with the electrical analysis. These results reveal important implications for how the dispersion of the graphene material in films produced from printable inks can be affected by the type of graphene powder used and the corresponding effect on electrical performance of the nanocomposites. This work provides direct evidence for how accurate and comparable characterisation of the graphene material is required for real-world graphene materials to develop graphene enabled films and proposes a measurement protocol for comparing graphene materials that can be used for international standardisation.

Assessment of Component-level Emission Measurements ...

EPA Pesticide Factsheets

Oil and natural gas (ONG) production facilities have the potential to emit a substantial amount of greenhouse gasses, hydrocarbons and hazardous air pollutants into the atmosphere. These emissions come from a wide variety of sources including engine exhaust, combustor gases, atmospheric venting from uncontrolled tanks and leaks. Engine exhaust, combustor gases and atmospheric tank venting are included in the initial estimation of a production facilities cumulative emissions. However, there is a large amount of uncertainty associated with magnitude and composition of leaks at these facilities. In order to understand the environmental impacts of these emissions we must first be able characterize the emission flow rate and chemical composition of these leaks/venting. A number of recent publications regarding emission flow rate measurements of components at ONG production facilities have brought into question the validity of such measurements and the sampling methodology. An accurate methodology for quantifying hydrocarbon leaks/venting is needed to support both emission inventories and environmental compliance. This interim report will summarize recent results from a small leak survey completed at ONG production facilities in Utah to characterize their flow rate and chemical composition using a suite of instruments using a high volume sampler (Bacharach Hi Flow Sampler; Bacharach, Inc.), as well as infrared (IR) cameras, a photoionization detector (PID), a fl

The chemical composition of tertiary Indian coal ash and its combustion behaviour - a statistical approach: Part 2

NASA Astrophysics Data System (ADS)

Sharma, Arpita; Saikia, Ananya; Khare, Puja; Dutta, D. K.; Baruah, B. P.

2014-08-01

In Part 1 of the present investigation, 37 representative Eocene coal samples of Meghalaya, India were analyzed and their physico-chemical characteristics and the major oxides and minerals present in ash samples were studied for assessing the genesis of these coals. Various statistical tools were also applied to study their genesis. The datasets from Part 1 used in this investigation (Part 2) show the contribution of major oxides towards ash fusion temperatures (AFTs). The regression analysis of high temperature ash (HTA) composition and initial deformation temperature (IDT) show a definite increasing or decreasing trend, which has been used to determine the predictive indices for slagging, fouling, and abrasion propensities during combustion practices. The increase or decrease of IDT is influenced by the increase of Fe2O3, Al2O3, SiO2, and CaO, respectively. Detrital-authigenic index (DAI) calculated from the ash composition and its relation with AFT indicates Sialoferric nature of these coals. The correlation analysis, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were used to study the possible fouling, slagging, and abrasion potentials in boilers during the coal combustion processes. A positive relationship between slagging and heating values of the coal has been found in this study.

Fast classification and compositional analysis of cornstover fractions using Fourier transform near-infrared techniques.

PubMed

Philip Ye, X; Liu, Lu; Hayes, Douglas; Womac, Alvin; Hong, Kunlun; Sokhansanj, Shahab

2008-10-01

The objectives of this research were to determine the variation of chemical composition across botanical fractions of cornstover, and to probe the potential of Fourier transform near-infrared (FT-NIR) techniques in qualitatively classifying separated cornstover fractions and in quantitatively analyzing chemical compositions of cornstover by developing calibration models to predict chemical compositions of cornstover based on FT-NIR spectra. Large variations of cornstover chemical composition for wide calibration ranges, which is required by a reliable calibration model, were achieved by manually separating the cornstover samples into six botanical fractions, and their chemical compositions were determined by conventional wet chemical analyses, which proved that chemical composition varies significantly among different botanical fractions of cornstover. Different botanic fractions, having total saccharide content in descending order, are husk, sheath, pith, rind, leaf, and node. Based on FT-NIR spectra acquired on the biomass, classification by Soft Independent Modeling of Class Analogy (SIMCA) was employed to conduct qualitative classification of cornstover fractions, and partial least square (PLS) regression was used for quantitative chemical composition analysis. SIMCA was successfully demonstrated in classifying botanical fractions of cornstover. The developed PLS model yielded root mean square error of prediction (RMSEP %w/w) of 0.92, 1.03, 0.17, 0.27, 0.21, 1.12, and 0.57 for glucan, xylan, galactan, arabinan, mannan, lignin, and ash, respectively. The results showed the potential of FT-NIR techniques in combination with multivariate analysis to be utilized by biomass feedstock suppliers, bioethanol manufacturers, and bio-power producers in order to better manage bioenergy feedstocks and enhance bioconversion.

Effect of irradiation on the patulin content and chemical composition of apple juice concentrate.

PubMed

Zegota, H; Zegota, A; Bachman, S

1988-09-01

The influence of ionizing radiation on the patulin content of apple juice concentrate was investigated. The results indicated that patulin, at an initial concentration of about 2 mg/kg, disappeared after irradiation of the concentrate with doses as low as 2.5 kGy. For lower doses, the extent of patulin degradation was proportional to the absorbed dose. Irradiation of the concentrate with doses sufficient for patulin disappearance did not change the titratable acidity, the content of reducing sugars and carbonyl compounds or the amino acid composition. The content of ascorbic acid slightly decreased and the colour of the concentrate brightened. The intensity of the patulin absorption spectra after irradiation of mycotoxin in aqueous solutions decreased.

Effects of dietary hop (Humulus lupulus L.) β-acids on quality attributes, composition and oxidative stability of pork meat.

PubMed

Sbardella, Maicon; Racanicci, Aline Mc; Gois, Franz D; de Lima, Cristiane B; Migotto, Dannielle L; Costa, Leandro B; Miyada, Valdomiro S

2018-04-01

The effects of dietary levels of hop β-acids on physical attributes, lipid oxidation and chemical composition of pork meat were evaluated. Thirty-two castrated male pigs obtained from a complete block design feeding experiment (6.23 ± 0.42 kg initial body weight (BW) to 20.45 ± 0.95 kg final BW) and fed diets supplemented with 0, 120, 240 or 360 mg kg -1 hop β-acids during 35 days were slaughtered to sample longissimus dorsi muscle for meat analysis. No effects (P > 0.05) of dietary hop β-acids were observed on meat physical attributes. Quadratic effects (P < 0.05) of hop β-acids were observed on lipid and protein contents and on thiobarbituric acid-reactive substance (TBARS) values of meatballs, whose equations allowed the estimation of dietary hop β-acid levels of 176, 169 and 181 mg kg -1 to provide up to 16.20% lipid reduction, 1.95% protein accretion and 23.31% TBARS reduction respectively. Dietary hop β-acids fed to pigs might reduce lipid, increase protein and reduce lipid oxidation without affecting physical attributes of the pork meat. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Chemical and histological studies of wild and hatchery salmon in fresh water

USGS Publications Warehouse

Wood, E.M.; Yasutake, W.T.; Halver, J.E.; Woodall, A.N.

1960-01-01

In a study of coho salmon (Oncorhynchus kisutch), the gross chemical and histological changes occurring over a 14-month period spent in fresh water were determined. The determinations were made at 3-month intervals on: 1) hatchery-reared fish, 2) fish hatchery-reared for 3, 6, 9, and 12 months and then planted in a controlled stream for the remainder of the period; and 3) an indigenous group of wild fish in this stream. Wild fish showed high incidence of tissue damage from spinose hairs of the moth larva, Halisidota argentata. Hatchery fish were similarly affected with the severity and incidence of lesions varying directly with the time of exposure of the larvae in the wild environment. Both groups of fish were heavily parasitized by sporozoan organisms in the kidney and spinal cord. Kidney disease appeared in both wild and planted hatchery fish. The gross chemical composition of hatchery fish transformed rapidly after planting to that of the wild fish. Although the initial rate of fat loss is essentially constant for all hatchery groups after planting, fish that were hatchery reared for 9 to 12 months did not complete the transformation to the wild-type body composition by the time of downstream migration at 14 months.

Minimizing artifact formation in magnetorheological finishing of chemical vapor deposition ZnS flats.

PubMed

Kozhinova, Irina A; Romanofsky, Henry J; Maltsev, Alexander; Jacobs, Stephen D; Kordonski, William I; Gorodkin, Sergei R

2005-08-01

The polishing performance of magnetorheological (MR) fluids prepared with a variety of magnetic and nonmagnetic ingredients was studied on four types of initial surface for chemical vapor deposition (CVD) ZnS flats from domestic and foreign sources. The results showed that it was possible to greatly improve smoothing performance of magnetorheological finishing (MRF) by altering the fluid composition, with the best results obtained for nanoalumina abrasive used with soft carbonyl iron and altered MR fluid chemistry. Surface roughness did not exceed 20 nm peak to valley and 2 nm rms after removal of 2 microm of material. The formation of orange peel and the exposure of a pebblelike structure inherent in ZnS from the CVD process were suppressed.

Effect of postnatal low-dose exposure to environmental chemicals on the gut microbiome in a rodent model.

PubMed

Hu, Jianzhong; Raikhel, Vincent; Gopalakrishnan, Kalpana; Fernandez-Hernandez, Heriberto; Lambertini, Luca; Manservisi, Fabiana; Falcioni, Laura; Bua, Luciano; Belpoggi, Fiorella; L Teitelbaum, Susan; Chen, Jia

2016-06-14

This proof-of-principle study examines whether postnatal, low-dose exposure to environmental chemicals modifies the composition of gut microbiome. Three chemicals that are widely used in personal care products-diethyl phthalate (DEP), methylparaben (MPB), triclosan (TCS)-and their mixture (MIX) were administered at doses comparable to human exposure to Sprague-Dawley rats from birth through adulthood. Fecal samples were collected at two time points: postnatal day (PND) 62 (adolescence) and PND 181 (adulthood). The gut microbiome was profiled by 16S ribosomal RNA gene sequencing, taxonomically assigned and assessed for diversity. Metagenomic profiling revealed that the low-dose chemical exposure resulted in significant changes in the overall bacterial composition, but in adolescent rats only. Specifically, the individual taxon relative abundance for Bacteroidetes (Prevotella) was increased while the relative abundance of Firmicutes (Bacilli) was reduced in all treated rats compared to controls. Increased abundance was observed for Elusimicrobia in DEP and MPB groups, Betaproteobacteria in MPB and MIX groups, and Deltaproteobacteria in TCS group. Surprisingly, these differences diminished by adulthood (PND 181) despite continuous exposure, suggesting that exposure to the environmental chemicals produced a more profound effect on the gut microbiome in adolescents. We also observed a small but consistent reduction in the bodyweight of exposed rats in adolescence, especially with DEP and MPB treatment (p < 0.05), which is consistent with our findings of a reduced Firmicutes/Bacteroidetes ratio at PND 62 in exposed rats. This study provides initial evidence that postnatal exposure to commonly used environmental chemicals at doses comparable to human exposure is capable of modifying the gut microbiota in adolescent rats; whether these changes lead to downstream health effects requires further investigation.

Chemical composition and digestibility of Trifolium exposed to elevated ozone and carbon dioxide in a free-air (FACE) fumigation system

Treesearch

R.B. Muntifering; A.H. Chappelka; J.C. Lin; D.F. Karnosky; G.L. Somers

2006-01-01

Tropospheric ozone (O3) and carbon dioxide (CO2) are significant drivers of plant growth and chemical composition. We hypothesized that exposure to elevated concentrations of O3 and CO2, singly and in combination, would modify the chemical composition of Trifolium...

An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

PubMed Central

Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

2010-01-01

Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts. PMID:20559508

Estimation of chemical carcass composition from 8th rib characteristics with Belgian blue double-muscled bulls.

PubMed

De Campeneere, S; Fiems, L O; Van de Voorde, G; Vanacker, J M; Boucque, C V; Demeyer, D I

1999-01-01

Characteristics from the 8th rib cut: chemical composition, tissue composition after dissection, specific gravity (SG) and m. longissimus thoracis (LT) composition, collected on 17 Belgian Blue double-muscled fattening bulls were used to generate equations for predicting chemical carcass composition. Carcass composition was best predicted from chemical analysis of the 8th rib cut and the empty body weight (EBW) of the bull. Carcass chemical fat content (CCF, kg) was predicted from the 8th rib cut fat content (ether extract, 8RF, kg) by the following regression: CCF=1.94+27.37 8RF (R(2)=0.957, RSD =9.89%). A higher coefficient was found for carcass water (CCW, kg) predicted from 8RF and EBW: CCW=-2.26+0.28 EBW-34.28 8RF (R(2)=0.997, RSD=1.48%). No parameter was found to improve the prediction of CCP from EBW solely: CCP=-0.86+0.08 EBW (R(2) =0.992, RSD=2.61%). Prediction equations based solely on LT composition had low R(2) values of between 0.38 and 0.67, whereas no significant equations were found using SG. However, equations based on EBW had R(2) values between 0.78 and 0.99. Chemical components of the 8th rib cut in combination with EBW are most useful in predicting the chemical composition of the carcass of Belgian-Blue double-muscled bulls.

Study of chloride ion transport of composite by using cement and starch as a binder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armynah, Bidayatul; Halide, Halmar; Zahrawani,

This study presents the chemical bonding and the structural properties of composites from accelerator chloride test migration (ACTM). The volume fractions between binder (cement and starch) and charcoal in composites are 20:80 and 60:40. The effect of the binder to the chemical composition, chemical bonding, and structural properties before and after chloride ion passing through the composites was determined by X-ray fluorescence (XRF), by Fourier transform infra-red (FTIR), and x-ray diffraction (XRD), respectively. From the XRD data, XRF data, and the FTIR data shows the amount of chemical composition, the type of binding, and the structure of composites are dependingmore » on the type of binder. The amount of chloride migration using starch as binder is higher than that of cement as a binder due to the density effects.« less

Kenaf bast cellulosic fibers hierarchy: a comprehensive approach from micro to nano.

PubMed

Karimi, Samaneh; Tahir, Paridah Md; Karimi, Ali; Dufresne, Alain; Abdulkhani, Ali

2014-01-30

Cellulosic fibers from kenaf bast were isolated in three distinct stages. Initially raw kenaf bast fibers were subjected to an alkali pulping process. Then pulped fibers undergone a bleaching process and finally both pulped and bleached fibers were separated into their constituent nanoscale cellulosic fibers by mechanical shearing. The influence of each treatment on the chemical composition of fibers was investigated. Moreover morphology, functional groups, crystallinity, and thermal behavior of fiber hierarchy at different stages of purification were studied using scanning and transmission electron microscopies, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Microscopy studies revealed that applied procedures successfully isolated nanoscale cellulosic fibers from both unbleached and bleached pulps. Chemical composition analysis and FTIR spectroscopy showed that lignin and hemicellulose were almost entirely removed by the applied treatments. XRD and TGA analyses demonstrated progressive enhancement of properties in fibers, hierarchically, in going from micro to nano scale. Interestingly no significant evolution was observed between obtained data of characterized ubnleached and bleached nanofibers. Copyright © 2013 Elsevier Ltd. All rights reserved.

Chemical composition and biological activity of the essential oil of Origanum vulgare ssp. hirtum from different areas in the Southern Apennines (Italy).

PubMed

Mancini, Emilia; Camele, Ippolito; Elshafie, Hazem S; De Martino, Laura; Pellegrino, Carlo; Grulova, Daniela; De Feo, Vincenzo

2014-04-01

The chemical composition of the essential oils of Origanum vulgare ssp. hirtum, growing wild in three different localities in the Southern Apennines, was studied by GC-FID and GC/MS analyses. In total, 103 compounds were identified. The oils were mainly composed of phenolic compounds and all oils belonged to the chemotype carvacrol/thymol. The three essential oils were evaluated for their in vitro phytotoxic activity by determining their influence on the germination and initial radicle elongation of Sinapis arvensis L., Phalaris canariensis L., Lepidium sativum L., and Raphanus sativus L. The seed germination and radicle growth were affected in various degrees. Moreover, the antifungal activity of the three essential oils was assayed against three species causing pre- and postharvest fruit decay (Monilinia laxa, M. fructigena, and M. fructicola). At 1000 ppm, the three oils completely inhibited fungal growth. The hemolytic activity of the oils was assayed and showed no effect on the cell membranes of bovine erythrocytes. Copyright © 2014 Verlag Helvetica Chimica Acta AG, Zürich.

Predictive analysis of the influence of the chemical composition and pre-processing regimen on structural properties of steel alloys using machine learning techniques

NASA Astrophysics Data System (ADS)

Krishnamurthy, Narayanan; Maddali, Siddharth; Romanov, Vyacheslav; Hawk, Jeffrey

We present some structural properties of multi-component steel alloys as predicted by a random forest machine-learning model. These non-parametric models are trained on high-dimensional data sets defined by features such as chemical composition, pre-processing temperatures and environmental influences, the latter of which are based upon standardized testing procedures for tensile, creep and rupture properties as defined by the American Society of Testing and Materials (ASTM). We quantify the goodness of fit of these models as well as the inferred relative importance of each of these features, all with a conveniently defined metric and scale. The models are tested with synthetic data points, generated subject to the appropriate mathematical constraints for the various features. By this we highlight possible trends in the increase or degradation of the structural properties with perturbations in the features of importance. This work is presented as part of the Data Science Initiative at the National Energy Technology Laboratory, directed specifically towards the computational design of steel alloys.

Treatment of textile dyehouse effluent using ceramic membrane based process in combination with chemical pretreatment.

PubMed

Bhattacharya, Priyankari; Ghosh, Sourja; Majumdar, Swachchha; Bandyopadhyay, Sibdas

2013-10-01

Treatment of highly concentrated dyebath effluent and comparatively dilute composite effluent having mixture of various reactive dyes collected from a cotton fabric dyeing unit was undertaken in the present study. Ceramic microfiltration membrane prepared from a cost effective composition of alumina and clay was used. Prior to microfiltration, a chemical pretreatment was carried out with aluminium sulphate in combination with a polymeric retention aid. An optimum dose of 100 mg/L of aluminium sulphate and 1 ml/L of a commercial flocculant Afilan RAMF was found effective for dye removal (> 98%) from the synthetic solutions of reactive dyes with initial concentration of 150 mg/L in both the single component and two component systems. In the microfiltration study, effect of operating pressure in the permeate flux was observed for both the pretreated and untreated effluents and permeate samples were analyzed for dye concentration, COD, turbidity, TSS, etc. during constant pressure filtration. About 98-99% removal of dyes was obtained in the combined process with COD reduction of 54-64%.

Fungal degradation of fiber-reinforced composite materials

NASA Technical Reports Server (NTRS)

Gu, J. D.; Lu, C.; Mitchell, R.; Thorp, K.; Crasto, A.

1997-01-01

As described in a previous report, a fungal consortium isolated from degraded polymeric materials was capable of growth on presterilized coupons of five composites, resulting in deep penetration into the interior of all materials within five weeks. Data describing the utilization of composite constituents as nutrients for the microflora are described in this article. Increased microbial growth was observed when composite extract was incubated with the fungal inoculum at ambient temperatures. Scanning electron microscopic observation of carbon fibers incubated with a naturally developed population of microorganisms showed the formation of bacterial biofilms on the fiber surfaces, suggesting possible utilization of the fiber chemical sizing as carbon and energy sources. Electrochemical impedance spectroscopy was used to monitor the phenomena occurring at the fiber-matrix interfaces. Significant differences were observed between inoculated and sterile panels of the composite materials. A progressive decline in impedance was detected in the inoculated panels. Several reaction steps may be involved in the degradation process. Initial ingress of water into the resin matrix appeared to be followed by degradation of fiber surfaces, and separation of fibers from the resin matrix. This investigation suggested that composite materials are susceptible to microbial attack by providing nutrients for growth.

An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH, version 2.0

USGS Publications Warehouse

Plummer, Niel; Prestemon, Eric C.; Parkhurst, David L.

1994-01-01

NETPATH is an interactive Fortran 77 computer program used to interpret net geochemical mass-balance reactions between an initial and final water along a hydrologic flow path. Alternatively, NETPATH computes the mixing proportions of two to five initial waters and net geochemical reactions that can account for the observed composition of a final water. The program utilizes previously defined chemical and isotopic data for waters from a hydrochemical system. For a set of mineral and (or) gas phases hypothesized to be the reactive phases in the system, NETPATH calculates the mass transfers in every possible combination of the selected phases that accounts for the observed changes in the selected chemical and (or) isotopic compositions observed along the flow path. The calculations are of use in interpreting geochemical reactions, mixing proportions, evaporation and (or) dilution of waters, and mineral mass transfer in the chemical and isotopic evolution of natural and environmental waters. Rayleigh distillation calculations are applied to each mass-balance model that satisfies the constraints to predict carbon, sulfur, nitrogen, and strontium isotopic compositions at the end point, including radiocarbon dating. DB is an interactive Fortran 77 computer program used to enter analytical data into NETPATH, and calculate the distribution of species in aqueous solution. This report describes the types of problems that can be solved, the methods used to solve problems, and the features available in the program to facilitate these solutions. Examples are presented to demonstrate most of the applications and features of NETPATH. The codes DB and NETPATH can be executed in the UNIX or DOS1 environment. This report replaces U.S. Geological Survey Water-Resources Investigations Report 91-4078, by Plummer and others, which described the original release of NETPATH, version 1.0 (dated December, 1991), and documents revisions and enhancements that are included in version 2.0. 1 The use of trade, brand or product names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

Hera - an ESA M-class Saturn Entry Probe Mission Proposal

NASA Astrophysics Data System (ADS)

Atkinson, D. H.; Mousis, O.; Spilker, T. R.; Venkatapathy, E.; Poncy, J.; Coustenis, A.; Reh, K. R.

2015-12-01

A fundamental goal of solar system exploration is to understand the origin of the solar system, the initial stages, conditions, and processes by which the solar system formed, how the formation process was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Additionally, the atmospheres of the giant planets serve as laboratories to better understand the atmospheric chemistries, dynamics, processes, and climates on all planets in the solar system including Earth, offer a context and provide a ground truth for exoplanets and exoplanetary systems, and have long been thought to play a critical role in the development of potentially habitable planetary systems. Remote sensing observations are limited when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the value of in situ measurements is provided by measurements of Jupiter's noble gas abundances and helium mixing ratio by the Galileo probe. In situ measurements provide direct access to atmospheric regions that are beyond the reach of remote sensing, enabling the dynamical, chemical and aerosol-forming processes at work from the thermosphere to the troposphere below the cloud decks to be studied. Studies for a newly proposed Saturn atmospheric entry probe mission named Hera is being prepared for the upcoming European Space Agency Medium Class (M5) mission announcement of opportunity. A solar powered mission, Hera will take approximately 8 years to reach Saturn and will carry instruments to measure the composition, structure, and dynamics of Saturn's atmosphere. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Saturn, the Hera Saturn probe will provide critical measurements of composition, structure, and processes that are not accessible by remote sensing. The results of Hera will help test competing theories of solar system and giant planet origin, chemical, and dynamical evolution.

Experimental evaporation of hyperacid brines: Effects on chemical composition and chlorine isotope fractionation

NASA Astrophysics Data System (ADS)

Rodríguez, Alejandro; van Bergen, Manfred J.; Eggenkamp, H. G. M.

2018-02-01

Hyperacid brines from active volcanic lakes are some of the chemically most complex aqueous solutions on Earth. Their compositions provide valuable insights into processes of elemental transfer from a magma body to the surface and interactions with solid rocks and the atmosphere. This paper describes changes in chemical and δ37Cl signatures observed in a 1750 h isothermal evaporation experiment on hyperacid (pH 0.1) sulphate-chloride brine water from the active lake of Kawah Ijen volcano (Indonesia). Although gypsum was the only evaporite mineral identified in the evolving brine, decreasing Si concentrations may ultimately result in amorphous silica precipitation. Geochemical simulations predict the additional formation of elemental sulphur at lower water activities (aH2O ≤ 0.65) that were not reached in the experiment. Absence of other sulphates and halides despite the high load of dissolved elements (initial TDS ca. 100 g/kg) can be attributed to increased solubility of metals, promoted by extensive formation of complexes between the variety of cations and the major anions (HSO4-, Cl-, F-) present. Chlorine deviations from a conservative behaviour point to losses of gaseous hydrogen chloride (HCl(g)) and consequently an increase in Br/Cl ratios. Chlorine isotope fractionation that accompanied the escape of HCl(g) showed a marked change in sign and magnitude in the course of progressive evaporation of the brine. The calculated factor of fractionation between HCl(g) and dissolved Cl for the initial interval (before 500 h) is positive (1000lnαHCl(g)-Cldiss. = + 1.55 ± 0.49‰to + 3.37 ± 1.11‰), indicating that, at first, the escaping HCl(g) was isotopically heavier than the dissolved Cl remaining in the brine. Conversely, fractionation shifted to the opposite direction in the subsequent interval (1000lnαHCl(g)-Cldiss. = 5.67 ± 0.17‰to - 5.64 ± 0.08‰), in agreement with values reported in literature. It is proposed that Cl isotopic fractionation in highly acidic brines is controlled by the distribution of dissolved chlorine species, which changes from Cl- to HClo dominance with the progressive pH decline. The Kawah Ijen lake acquired its extreme composition through influx of sulphur and halogen-rich magmatic gas components and extensive rock dissolution. If hyperacid brines with comparable chemical composition existed on Mars, evaporation processes up to the extent reported here (aH2O = 0.85), were likely accompanied by losses of gaseous HCl. The resulting changes in Cl isotope compositions, Br/Cl, S/Cl and other ratios in the residual brine might be potentially recorded in assemblages of halogen-bearing secondary evaporation minerals. Also, volcanic-hydrothermal brines as these would extend the stability of liquid water on the Martian surface down to a temperature of -90 °C.

Impacts of the mixing state and chemical composition on the cloud condensation nuclei (CCN) activity in Beijing during winter, 2016

NASA Astrophysics Data System (ADS)

Ren, J.; Zhang, F.

2017-12-01

Abstract.Understanding aerosol chemical composition and mixing state on CCN activity in polluted urban area is crucial to determine NCCN accurately and thus to quantify aerosol indirect effects. Aerosol hrgroscopicity, size-resolved cloud condensation nuclei (CCN) concentration and chemical composition are measured under polluted and background conditions in Beijing based on the Air Pollution and Human Health (APHH) field campaign in winter 2016. The CCN number concentration (NCCN) is predicted by using κ-Köhler theory from the PNSD and five simplified of the mixing state and chemical composition. The assumption of EIS (sulfate, nitrate and SOA internally mixed, and POA and BC externally mixed with size-resolved chemical composition) shows the best closure to predict NCCN with the ratio of predicted to measured NCCN of 0.96-1.12 both in POL and BG conditions. Under BG conditions, IB (internal mixture with bulk chemical composition) scheme achieves the best CCN closure during any periods of a day. In polluted days, EIS and IS (internal mixture with size-resolved chemical composition) scheme may achieve better closure than IB scheme due to the heterogeneity in particles composition across different size. ES (external mixture with size-resolved chemical composition) and EB (external mixture with bulk chemical composition) scheme markedly underestimate the NCCN with the ratio of predicted to measured NCCN of 0.6-0.8. In addition, we note that assumptions of size-resolved composition (IS or ES) show very limited promotes by comparing with the assumptions of bulk composition (IB or EB), furthermore, the prediction becomes worse by using size-resolved assumption in clean days. The predicted NCCN during eve-rush periods shows the most sensitivity to the five different assumptions, with ratios of the predicted and measured NCCN ranging from 0.5 to 1.4, reflecting great impacts from evening traffic and cooking sources. The result from the sensitivity examination of predict NCCN to particles mixing state and organic volume fractions with the aging of organic particles suggests that the mixing state of particles plays a minor role when the κorg exceeds 0.1. Our study could provide new dataset to evaluate the CCN parameterization in models in those heavily polluted regions with large fraction of POA and BC.

Laboratory Inquiry for Determining the Chemical Composition of a Component in a Daily Use Detergent: Sodium Sesquicarbonate

ERIC Educational Resources Information Center

Koga, Nobuyoshi; Kimura, Tomoyasu; Shigedomi, Kana

2011-01-01

An inquiry-based laboratory activity to determine the chemical composition of a component in alkaline detergents, sodium sesquicarbonate (SSC), is proposed. On the basis of introductory demonstrations by the instructor on the chemical properties and reactions of SSC, students propose the hypothetical composition of SSC and possible quantitative…

Multifaceted toxicity assessment of catalyst composites in transgenic zebrafish embryos.

PubMed

Jang, Gun Hyuk; Lee, Keon Yong; Choi, Jaewon; Kim, Sang Hoon; Lee, Kwan Hyi

2016-09-01

Recent development in the field of nanomaterials has given rise into the inquiries regarding the toxicological characteristics of the nanomaterials. While many individual nanomaterials have been screened for their toxicological effects, composites that accompany nanomaterials are not common subjects to such screening through toxicological assessment. One of the widely used composites that accompany nanomaterials is catalyst composite used to reduce air pollution, which was selected as a target composite with nanomaterials for the multifaceted toxicological assessment. As existing studies did not possess any significant data regarding such catalyst composites, this study focuses on investigating toxicological characteristics of catalyst composites from various angles in both in-vitro and in-vivo settings. Initial toxicological assessment on catalyst composites was conducted using HUVECs for cell viability assays, and subsequent in-vivo assay regarding their direct influence on living organisms was done. The zebrafish embryo and its transgenic lines were used in the in-vivo assays to obtain multifaceted analytic results. Data obtained from the in-vivo assays include blood vessel formation, mutated heart morphology, and heart functionality change. Our multifaceted toxicological assessment pointed out that chemical composites augmented with nanomaterials can too have toxicological threat as much as individual nanomaterials do and alarms us with their danger. This manuscript provides a multifaceted assessment for composites augmented with nanomaterials, of which their toxicological threats have been overlooked. Copyright © 2016 Elsevier Ltd. All rights reserved.

In vitro drug release behavior from a novel thermosensitive composite hydrogel based on Pluronic f127 and poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) copolymer

PubMed Central

Gong, Chang Yang; Shi, Shuai; Dong, Peng Wei; Zheng, Xiu Ling; Fu, Shao Zhi; Guo, Gang; Yang, Jing Liang; Wei, Yu Quan; Qian, Zhi Yong

2009-01-01

Background Most conventional methods for delivering chemotherapeutic agents fail to achieve therapeutic concentrations of drugs, despite reaching toxic systemic levels. Novel controlled drug delivery systems are designed to deliver drugs at predetermined rates for predefined periods at the target organ and overcome the shortcomings of conventional drug formulations therefore could diminish the side effects and improve the life quality of the patients. Thus, a suitable controlled drug delivery system is extremely important for chemotherapy. Results A novel biodegradable thermosensitive composite hydrogel, based on poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) and Pluronic F127 copolymer, was successfully prepared in this work, which underwent thermosensitive sol-gel-sol transition. And it was flowing sol at ambient temperature but became non-flowing gel at body temperature. By varying the composition, sol-gel-sol transition and in vitro drug release behavior of the composite hydrogel could be adjusted. Cytotoxicity of the composite hydrogel was conducted by cell viability assay using human HEK293 cells. The 293 cell viability of composite hydrogel copolymers were yet higher than 71.4%, even when the input copolymers were 500 μg per well. Vitamin B12 (VB12), honokiol (HK), and bovine serum albumin (BSA) were used as model drugs to investigate the in vitro release behavior of hydrophilic small molecular drug, hydrophobic small molecular drug, and protein drug from the composite hydrogel respectively. All the above-mentioned drugs in this work could be released slowly from composite hydrogel in an extended period. Chemical composition of composite hydrogel, initial drug loading, and hydrogel concentration substantially affected the drug release behavior. The higher Pluronic F127 content, lower initial drug loading amount, or lower hydrogel concentration resulted in higher cumulative release rate. Conclusion The results showed that composite hydrogel prepared in this paper were biocompatible with low cell cytotoxicity, and the drugs in this work could be released slowly from composite hydrogel in an extended period, which suggested that the composite hydrogel might have great potential applications in biomedical fields. PMID:19210779

Clinical and laboratory evaluation of microstructural changes in the physical, mechanical and chemical properties of dental filling materials under the influence of an electromagnetic field.

PubMed

Moiseeva, Natalia S; Kunin, Anatoly A

2018-03-01

Restorative filling materials used for dental caries prevention and treatment consist of various components including monomers or oligomers, which play a significant role in forming the main structure of these materials, as well as in characterising their physical, mechanical and chemical properties. The necessity for the development and improvement of structural characteristics of polymeric dental filling materials intended for caries prevention and their life duration increase served as the initiating factor of our research. According to the research purpose and challenges, we studied the changes in the physical, mechanical and chemical properties of composite filling materials with and without electromagnetic field influence. The investigations in vivo include the study of microstructural features of polymeric filling materials by scanning electron microscopy (SEM) and the investigations in vitro include the study of sealed and extracted human teeth chips by using X-ray spectral analysis. We also evaluated the changes in the strength characteristics of dental filling materials with and without electromagnetic field influence. The analysis of the obtained data indicates the presence of structural changes in polymeric dental filling materials, including the material microstructure condensation confirmed by the SEM results, an increase in the strength and adhesion characteristics and certain regularities of the chemical elemental composition concentration change in the area of hard tooth tissue and dental filling material. These scientific data will provide tooth caries prevention and promote the increase of treatment quality.

Astrochemical evolution along star formation: Overview of the IRAM Large Program ASAI

NASA Astrophysics Data System (ADS)

Lefloch, Bertrand; Bachiller, R.; Ceccarelli, C.; Cernicharo, J.; Codella, C.; Fuente, A.; Kahane, C.; López-Sepulcre, A.; Tafalla, M.; Vastel, C.; Caux, E.; González-García, M.; Bianchi, E.; Gómez-Ruiz, A.; Holdship, J.; Mendoza, E.; Ospina-Zamudio, J.; Podio, L.; Quénard, D.; Roueff, E.; Sakai, N.; Viti, S.; Yamamoto, S.; Yoshida, K.; Favre, C.; Monfredini, T.; Quitián-Lara, H. M.; Marcelino, N.; Roberty, H. Boechat; Cabrit, S.

2018-04-01

Evidence is mounting that the small bodies of our Solar System, such as comets and asteroids, have at least partially inherited their chemical composition from the first phases of the Solar System formation. It then appears that the molecular complexity of these small bodies is most likely related to the earliest stages of star formation. It is therefore important to characterize and to understand how the chemical evolution changes with solar-type protostellar evolution. We present here the Large Program "Astrochemical Surveys At IRAM" (ASAI). Its goal is to carry out unbiased millimeter line surveys between 80 and 272 GHz of a sample of ten template sources, which fully cover the first stages of the formation process of solar-type stars, from prestellar cores to the late protostellar phase. In this article, we present an overview of the surveys and results obtained from the analysis of the 3 mm band observations. The number of detected main isotopic species barely varies with the evolutionary stage and is found to be very similar to that of massive star-forming regions. The molecular content in O- and C- bearing species allows us to define two chemical classes of envelopes, whose composition is dominated by either a) a rich content in O-rich complex organic molecules, associated with hot corino sources, or b) a rich content in hydrocarbons, typical of Warm Carbon Chain Chemistry sources. Overall, a high chemical richness is found to be present already in the initial phases of solar-type star formation.

A Study of Chemical Composition of δ Scuti-Type Stars Based on the Observations with the BTA and RTT-150

NASA Astrophysics Data System (ADS)

Galeev, A. I.; Berdnikova, V. M.; Ivanova, D. V.; Kudryavtsev, D. O.; Shimanskaya, N. N.; Shimansky, V. V.; Balashova, M. O.

2017-06-01

The results of a study of a sample of δ Scuti-type stars obtained from the observations with the BTA and RTT-150 are presented. Based on photometric data, we measured and analyzed the fundamental parameters of all the studied stars. For eight stars (for two of them for the first time), the fundamental parameters of the atmospheres (Teff, log g, [Fe/H]) and the chemical composition for 29 elements in the LTE-approximation are received using spectroscopic observations. The chemical composition analysis demonstrates both the solar abundances of chemical elements and the anomalies of chemical composition typical of Am stars in the studied sample of δ Scuti-type stars.

The use of computer-assisted image analysis in the evaluation of the effect of management systems on changes in the color, chemical composition and texture of m. longissimus dorsi in pigs.

PubMed

Zapotoczny, Piotr; Kozera, Wojciech; Karpiesiuk, Krzysztof; Pawłowski, Rodian

2014-08-01

The effect of management systems on selected physical properties and chemical composition of m. longissimus dorsi was studied in pigs. Muscle texture parameters were determined by computer-assisted image analysis, and the color of muscle samples was evaluated using a spectrophotometer. Highly significant correlations were observed between chemical composition and selected texture variables in the analyzed images. Chemical composition was not correlated with color or spectral distribution. Subject to the applied classification methods and groups of variables included in the classification model, the experimental groups were identified correctly in 35-95%. No significant differences in the chemical composition of m. longissimus dorsi were observed between experimental groups. Significant differences were noted in color lightness (L*) and redness (a*). Copyright © 2014 Elsevier Ltd. All rights reserved.

Thermally emissive sensing materials for chemical spectroscopy analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poole, Zsolt; Ohodnicki, Paul R.

A sensor using thermally emissive materials for chemical spectroscopy analysis includes an emissive material, wherein the emissive material includes the thermally emissive materials which emit electromagnetic radiation, wherein the electromagnetic radiation is modified due to chemical composition in an environment; and a detector adapted to detect the electromagnetic radiation, wherein the electromagnetic radiation is indicative of the chemical interaction changes and hence chemical composition and/or chemical composition changes of the environment. The emissive material can be utilized with an optical fiber sensor, with the optical fiber sensor operating without the emissive material probed with a light source external to themore » material.« less

The evolution of rotating very massive stars with LMC composition

NASA Astrophysics Data System (ADS)

Köhler, K.; Langer, N.; de Koter, A.; de Mink, S. E.; Crowther, P. A.; Evans, C. J.; Gräfener, G.; Sana, H.; Sanyal, D.; Schneider, F. R. N.; Vink, J. S.

2015-01-01

Context. With growing evidence for the existence of very massive stars at subsolar metallicity, there is an increased need for corresponding stellar evolution models. Aims: We present a dense model grid with a tailored input chemical composition appropriate for the Large Magellanic Cloud (LMC). Methods: We use a one-dimensional hydrodynamic stellar evolution code, which accounts for rotation, transport of angular momentum by magnetic fields, and stellar wind mass loss to compute our detailed models. We calculate stellar evolution models with initial masses from 70 to 500 M⊙ and with initial surface rotational velocities from 0 to 550 km s-1, covering the core-hydrogen burning phase of evolution. Results: We find our rapid rotators to be strongly influenced by rotationally induced mixing of helium, with quasi-chemically homogeneous evolution occurring for the fastest rotating models. Above 160 M⊙, homogeneous evolution is also established through mass loss, producing pure helium stars at core hydrogen exhaustion independent of the initial rotation rate. Surface nitrogen enrichment is also found for slower rotators, even for stars that lose only a small fraction of their initial mass. For models above ~150 M⊙ at zero age, and for models in the whole considered mass range later on, we find a considerable envelope inflation due to the proximity of these models to their Eddington limit. This leads to a maximum ZAMS surface temperature of ~56 000 K, at ~180 M⊙, and to an evolution of stars in the mass range 50 M⊙...100 M⊙ to the regime of luminous blue variables in the Hertzsprung-Russell diagram with high internal Eddington factors. Inflation also leads to decreasing surface temperatures during the chemically homogeneous evolution of stars above ~180 M⊙. Conclusions: The cool surface temperatures due to the envelope inflation in our models lead to an enhanced mass loss, which prevents stars at LMC metallicity from evolving into pair-instability supernovae. The corresponding spin-down will also prevent very massive LMC stars to produce long-duration gamma-ray bursts, which might, however, originate from lower masses. The dataset of the presented stellar evolution models is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/573/A71Appendices are available in electronic form at http://www.aanda.org

Investigation of the influence of the chemical composition of HSLA steel grades on the microstructure homogeneity during hot rolling in continuous rolling mills using a fast layer model

NASA Astrophysics Data System (ADS)

Schmidtchen, M.; Rimnac, A.; Warczok, P.; Kozeschnik, E.; Bernhard, C.; Bragin, S.; Kawalla, R.; Linzer, B.

2016-03-01

The newly developed LaySiMS simulation tool provides new insight for inhomogeneous material flow and microstructure evolution in an endless strip production (ESP) plant. A deepened understanding of the influence of inhomogeneities in initial material state, temperature profile and material flow and their impact on the finished product can be reached e.g. by allowing for variable layer thickness distributions in the roll gap. Coupling temperature, deformation work and work hardening/recrystallization phenomena accounts for covering important effects in the roll gap. The underlying concept of the LaySiMS approach will be outlined and new insight gained regarding microstructural evolution, shear and inhomogeneous stress and strain states in the roll gap as well as local residual stresses will be presented. For the case of thin slab casting and direct rolling (TSDR) the interrelation of inhomogeneous initial state, micro structure evolution and dissolution state of micro alloying elements within the roughing section of an ESP line will be discussed. Special emphasis is put on the influence of the local chemical composition arising from direct charging on throughthickness homogeneity of the final product. It is concluded that, due to the specific combination of large reductions in the high reduction mills (HRM) and the highly inhomogeneous inverse temperature profile, the ESP-concept provides great opportunities for homogenizing the microstructure across the strip thickness.

Comparison of Nitrogen Incorporation in Tholins Produced by FUV Irradiation and Spark Discharge

NASA Technical Reports Server (NTRS)

Horst, S. M.; DeWitt, H. L.; Trainer, M. G.; Tolbert, M. A.

2012-01-01

The discovery of very heavy ions (Coates et al., 2007) in Titan's thermosphere has dramatically altered our understanding of the processes involved in the formation of the complex organic aerosols that comprise Titan's characteristic haze. Before Cassini's arrival, it was believed that aerosol production began in the stratosphere where the chemical processes were predominantly initiated by FUV radiation. This understanding guided the design of Titan atmosphere simulation experiments. However, the energy environment of the thermosphere is significantly different than the stratosphere; in particular there is a greater flux of EUV photons and energetic particles available to initiate chemical reactions, including the destruction of N2. in the upper atmosphere. Using a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), we have obtained in situ composition measurements of aerosol particles (so'called "tholins") produced in CH4/N2 gas mixtures subjected to either FUV radiation (deuterium lamp, 115-400 nm) (Trainer et al., 2012) or a spark discharge. A comparison of the composition of tholins produced using the two different energy sources will be presented, in particular with regard to the variation in nitrogen content of the two types of tholin. Titan's aerosols are known to contain significant amounts of nitrogen (Israel et al., 2005) and therefore understanding the role of nitrogen in the aerosol chemistry is important to further our knowledge of the formation and evolution of aerosols in Titan's atmosphere.

[Bioinorganic chemical composition of the lens and methods of its investigation].

PubMed

Avetisov, S E; Novikov, I A; Pakhomova, N A; Motalov, V G

2018-01-01

Bioinorganic chemical composition of the lens of human and experimental animals (cows, dogs, rats, rabbits) have been analyzed in various studies. In most cases, the studies employed different methods to determine the gross (total) composition of chemical elements and their concentrations in the examined samples. Less frequently, they included an assessment of the distribution of chemical elements in the lens and correlation of their concentration with its morphological changes. Chemical elements from all groups (series) of the periodic classification system were discovered in the lens substance. Despite similar investigation methods, different authors obtained contradicting results on the chemical composition of the lens. This article presents data suggesting possible correlation between inorganic chemical elements in the lens substance with the development and formation of lenticular opacities. All currently employed methods are known to only analyze limited number of select chemical elements in the tissues and do not consider the whole range of elements that can be analyzed with existing technology; furthermore, the majority of studies are conducted on the animal model lens. Therefore, it is feasible to continue the development of the chemical microanalysis method by increasing the sensitivity of Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) with the purpose of assessing the gross chemical composition and distribution of the elements in the lens substance, as well as revealing possible correlation between element concentration and morphological changes in the lens.

Modeling strength loss in wood by chemical composition. Part I, An individual component model for southern pine

Treesearch

J. E. Winandy; P. K. Lebow

2001-01-01

In this study, we develop models for predicting loss in bending strength of clear, straight-grained pine from changes in chemical composition. Although significant work needs to be done before truly universal predictive models are developed, a quantitative fundamental relationship between changes in chemical composition and strength loss for pine was demonstrated. In...

Adsorption behaviour of hydrogarnet for humic acid

NASA Astrophysics Data System (ADS)

Maeda, Hirotaka; Kurosaki, Yuichi; Nakayama, Masanobu; Ishida, Emile Hideki; Kasuga, Toshihiro

2018-04-01

Discharge of humic acid (HA) in aqueous environments is a key health and aesthetic issue. The present work investigates the use of hydrogarnet as a novel adsorbent for HA. Hydrogarnet was hydrothermally synthesized with different solvents to control the chemical composition. Hydrogarnet with three types of chemical compositions had better adsorption properties for HA than hydrogarnet with a single chemical composition. Controlling the chemical composition of hydrogarnet increased the number of hydroxyl groups and the overall binding energy of the system, leading to changes in the zeta potential. The enhancement of these adsorption properties is related to the increased numbers of hydroxyl groups on the surface and their diverse binding energies.

Evaluation of Beef by Electronic Tongue System TS-5000Z: Flavor Assessment, Recognition and Chemical Compositions According to Its Correlation with Flavor.

PubMed

Zhang, Xinzhuang; Zhang, Yawei; Meng, Qingxiang; Li, Ning; Ren, Liping

2015-01-01

The aim of this study was to assess the ability of electronic tongue system TS-5000Z to evaluate meat quality based on flavor assessment, recognition and correlation with the meat chemical composition. Meat was sampled from eighteen beef cattle including 6 Wagyu breed cattle, 6 Angus breed cattle and 6 Simmental breed cattle. Chemical composition including dry matter, crude protein, fat, ash, cholesterol and taurine and flavor of the meat were measured. The results showed that different breed cattle had different chemical compositions and flavor, which contains sourness, umami, saltiness, bitterness, astringency, aftertaste from astringency, aftertaste from bitterness and aftertaste from umami, respectively. A principal component analysis (PCA) showed an easily visible separation between different breeds of cattle and indicated that TS-5000Z made a rapid identification of different breeds of cattle. In addition, TS-5000Z seemed to be used to predict the chemical composition according to its correlation with the flavor. In conclusion, TS-5000Z would be used as a rapid analytical tool to evaluate the beef quality both qualitatively and quantitatively, based on flavor assessment, recognition and chemical composition according to its correlation with flavor.

Cometary coma chemical composition (C4) mission. [Abstract only

NASA Technical Reports Server (NTRS)

Carle, G. C.; Clark, B. C.; Niemann, H. B.; Alexander, M.; Knocke, P. C.; O'Hara, B. J.

1994-01-01

Cometary missions are of enormous fundamental importance for many different space science disciplines, including exobiology. Comets are presumed relics of the earliest, most primitive material in the solar nebula and are related to the planetesimals. They undoubtedly provided a general enrichment of volatiles to the inner solar system (contributing to atmospheres and oceans) and may have been key to the origin of life. A Discovery class, comet rendezvous mission, the Cometary Coma Chemical Composition (C4) Mission, was selected for further study by NASA earlier this year. The C4 Mission is a highly focused and usefully-limited subset of the Cometary Rendezvous Asteroid Flyby (CRAF) Mission, concentrating exclusively on measurements which will lead to an understanding of the chemical composition and make-up of the cometary nucleus. The scientific goals of the Cometary Coma Chemical Composition (C4) Mission are to rendezvous with a short-period comet and (1) to determine the elemental, chemical, and isotopic composition of the nucleus and (2) to characterize the chemical and isotopic nature of its atmosphere. Further, it is a goal to obtain preliminary data on the development of the coma (dust and gas composition) as a function of time and orbital position.

Two-Dimensional Nonlinear Finite Element Analysis of CMC Microstructures

NASA Technical Reports Server (NTRS)

Mital, Subodh K.; Goldberg, Robert K.; Bonacuse, Peter J.

2012-01-01

A research program has been developed to quantify the effects of the microstructure of a woven ceramic matrix composite and its variability on the effective properties and response of the material. In order to characterize and quantify the variations in the microstructure of a five harness satin weave, chemical vapor infiltrated (CVI) SiC/SiC composite material, specimens were serially sectioned and polished to capture images that detailed the fiber tows, matrix, and porosity. Open source quantitative image analysis tools were then used to isolate the constituents, from which two dimensional finite element models were generated which approximated the actual specimen section geometry. A simplified elastic-plastic model, wherein all stress above yield is redistributed to lower stress regions, is used to approximate the progressive damage behavior for each of the composite constituents. Finite element analyses under in-plane tensile loading were performed to examine how the variability in the local microstructure affected the macroscopic stress-strain response of the material as well as the local initiation and progression of damage. The macroscopic stress-strain response appeared to be minimally affected by the variation in local microstructure, but the locations where damage initiated and propagated appeared to be linked to specific aspects of the local microstructure.

[The characteristics of chemical composition of content of unicameral bone cysts depending on their growth stage].

PubMed

Stogov, M V; Luneva, S N; Mitrofanov, A I; Tkachuk, E A

2012-11-01

The article deals with the results of study of chemical composition of solitary cysts and blood serum of 27 patients. The results demonstrated that qualitative composition of f content of unicameral bone cysts is identical to chemical composition of blood serum. The results of analysis of total proteolysis activity and acid phosphatase activity in content of cysts can be used as criteria to determine the stage of cyst growth and to evaluate the effectiveness of applied treatment.

40 CFR 79.2 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... combustion or other chemical or physical reaction. (d) Fuel manufacturer means any person who, for sale or... the chemical composition of a bulk fuel, or the mixture of chemical compounds in a bulk fuel, by... fuel. (h) Chemical composition means the name and percentage by weight of each compound in an additive...

Prediction of the true digestible amino acid contents from the chemical composition of sorghum grain for poultry.

PubMed

Ebadi, M R; Sedghi, M; Golian, A; Ahmadi, H

2011-10-01

Accurate knowledge of true digestible amino acid (TDAA) contents of feedstuffs is necessary to accurately formulate poultry diets for profitable production. Several experimental approaches that are highly expensive and time consuming have been used to determine available amino acids. Prediction of the nutritive value of a feed ingredient from its chemical composition via regression methodology has been attempted for many years. The artificial neural network (ANN) model is a powerful method that may describe the relationship between digestible amino acid contents and chemical composition. Therefore, multiple linear regressions (MLR) and ANN models were developed for predicting the TDAA contents of sorghum grain based on chemical composition. A precision-fed assay trial using cecectomized roosters was performed to determine the TDAA contents in 48 sorghum samples from 12 sorghum varieties differing in chemical composition. The input variables for both MLR and ANN models were CP, ash, crude fiber, ether extract, and total phenols whereas the output variable was each individual TDAA for every sample. The results of this study revealed that it is possible to satisfactorily estimate the TDAA of sorghum grain through its chemical composition. The chemical composition of sorghum grain seems to highly influence the TDAA contents when considering components such as CP, crude fiber, ether extract, ash and total phenols. It is also possible to estimate the TDAA contents through multiple regression equations with reasonable accuracy depending on composition. However, a more satisfactory prediction may be achieved via ANN for all amino acids. The R(2) values for the ANN model corresponding to testing and training parameters showed a higher accuracy of prediction than equations established by the MLR method. In addition, the current data confirmed that chemical composition, often considered in total amino acid prediction, could be also a useful predictor of true digestible values of selected amino acids for poultry.

Laboratory Investigations of Titan Haze Formation: Characterization of Gas Phase and Particle Phase Nitrogen

NASA Astrophysics Data System (ADS)

Horst, Sarah; Yoon, Heidi; Li, Rui; deGouw, Joost; Tolbert, Margaret

2014-11-01

Prior to the arrival of the Cassini-Huygens spacecraft, aerosol production in Titan’s atmosphere was believed to begin in the stratosphere where chemical processes are predominantly initiated by far ultraviolet (FUV) radiation. However, the discovery of very heavy ions, coupled with Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation measurements that show haze absorption up to 1000 km altitude (Liang et al., 2007), indicates that haze formation initiates in the thermosphere. The energy environment of the thermosphere is significantly different from the stratosphere; in particular there is a greater flux of extreme ultraviolet (EUV) photons and energetic particles available to initiate chemical reactions, including the destruction of N2, in the upper atmosphere. The discovery of previously unpredicted nitrogen species in measurements of Titan’s atmosphere by the Cassini Ion and Neutral Mass Spectrometer (INMS) indicates that nitrogen participates in the chemistry to a much greater extent than was appreciated before Cassini (Vuitton et al., 2007). Additionally, measurements obtained by the Aerosol Collector Pyrolyzer (ACP) carried by Huygens to Titan’s surface may indicate that Titan’s aerosols contain significant amounts of nitrogen (Israël et al., 2005, 2006). The degree of nitrogen incorporation in the haze particles is important for understanding the diversity of molecules that may be present in Titan’s atmosphere and on its surface. We have conducted a series of Titan atmosphere simulation experiments using either spark discharge (tesla coil) or FUV photons (deuterium lamp) to initiate chemistry in CH4/N2 gas mixtures ranging from 0.01% CH4/99.99% N2 to 10% CH4/90% N2. We obtained in situ measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to measure the particle composition as a function of particle size and a proton-transfer ion-trap mass spectrometer (PIT-MS) to measure the composition of gas phase products. These two techniques allow us to investigate the effect of energy source and initial CH4 concentration on the degree of nitrogen incorporation in both the gas and solid phase products.

Air Quality Modeling Using the NASA GEOS-5 Multispecies Data Assimilation System

NASA Technical Reports Server (NTRS)

Keller, Christoph A.; Pawson, Steven; Wargan, Krzysztof; Weir, Brad

2018-01-01

The NASA Goddard Earth Observing System (GEOS) data assimilation system (DAS) has been expanded to include chemically reactive tropospheric trace gases including ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). This system combines model analyses from the GEOS-5 model with detailed atmospheric chemistry and observations from MLS (O3), OMI (O3 and NO2), and MOPITT (CO). We show results from a variety of assimilation test experiments, highlighting the improvements in the representation of model species concentrations by up to 50% compared to an assimilation-free control experiment. Taking into account the rapid chemical cycling of NO2 when applying the assimilation increments greatly improves assimilation skills for NO2 and provides large benefits for model concentrations near the surface. Analysis of the geospatial distribution of the assimilation increments suggest that the free-running model overestimates biomass burning emissions but underestimates lightning NOx emissions by 5-20%. We discuss the capability of the chemical data assimilation system to improve atmospheric composition forecasts through improved initial value and boundary condition inputs, particularly during air pollution events. We find that the current assimilation system meaningfully improves short-term forecasts (1-3 day). For longer-term forecasts more emphasis on updating the emissions instead of initial concentration fields is needed.

Petrology and physical conditions of metamorphism of calcsilicate rocks from low- to high-grade transition area, Dharmapuri District, Tamil Nadu

NASA Technical Reports Server (NTRS)

Narayana, B. L.; Natarajan, R.; Govil, P. K.

1988-01-01

Calc-silicate rocks comprising quartz, plagioclase, diopside, sphene, scapolite, grossularite-andradite and wollastonite occur as lensoid enclaves within the greasy migmatitic and charnockitic gneisses of the Archaean amphibolite- to granulite-facies transition zone in Dharmapuri district, Tamil Nadu. The calc-silicate rocks are characterized by the absence of K-feldspar and primary calcite, presence of large modal quartz and plagioclase and formation of secondary garnet and zoisite rims around scapolite and wollastonite. The mineral distributions suggest compositional layering. The chemical composition and mineralogy of the calc-silicate rocks indicate that they were derived from impure silica-rich calcareous sediments whose composition is similar to that of pelite-limestone mixtures. From the mineral assemblages the temperature, pressure and fluid composition during metamorphism were estimated. The observed mineral reaction sequences require a range of X sub CO2 values demonstrating that an initially CO2-rich metamorphic fluid evolved with time towards considerably more H2O-rich compositions. These variations in fluid composition suggest that there were sources of water-rich fluids external to the calc-silicate rocks and that mixing of these fluids with those of calc-silicate rocks was important in controlling fluid composition in calc-silicate rocks and some adjacent rock types as well.

Sr isotopic tracer study of the Samail ophiolite, Oman.

USGS Publications Warehouse

Lanphere, M.A.; Coleman, R.G.; Hopson, C.A.

1981-01-01

Rb and Sr concentrations and Sr-isotopic compositions were measured in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite, diabase dykes, and gabbro and websterite dykes within the metamorphic peridotite. Ten samples of cumulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have 87Sr/86Sr ratios of 0.70314 + or - 0.00030 and 0.70306 + or - 0.00034, respectively. The dispersion in Sr- isotopic composition may reflect real heterogeneities in the magma source region. The average Sr-isotopic composition of cumulate gabbro falls in the range of isotopic compositions of modern MORB. The 87Sr/86Sr ratios of noncumulate gabbro, plagiogranite, and diabase dykes range 0.7034-0.7047, 0.7038-0.7046 and 0.7037- 0.7061, respectively. These higher 87Sr/86Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with sea-water. Mineral separates from dykes that cut harzburgite tectonite have Sr-isotopic compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dykes were derived from partial melting of source regions that had similar long-term histories and chemical compositions.-T.R.

Prediction of the effects of soil-based countermeasures on soil solution chemistry of soils contaminated with radiocesium using the hydrogeochemical code PHREEQC.

PubMed

Hormann, Volker; Kirchner, Gerald

2002-04-22

For agriculturally used areas, which are contaminated by the debris from a nuclear accident, the use of chemical amendmends (e.g. potassium chloride and lime) is among the most common soil-based countermeasures. These countermeasures are intended to reduce the plant uptake of radionuclides (mainly 137Cs and 90Sr) by competitive inhibition by chemically similar ions. So far, the impacts of countermeasures on soil solution composition - and thus, their effectiveness - have almost exclusively been established experimentally, since they depend on mineral composition and chemical characteristics of the soil affected. In this study, which focuses on caesium contamination, the well-established code PHREEQC was used as a geochemical model to calculate the changes in the ionic compositions of soil solutions, which result from the application of potassium or ammonium in batch equilibrium experiments. The simple ion exchange model used by PHREEQC was improved by taking into account selective sorption of Cs+, NH4+ and K+ by clay minerals. Calculations were performed with three different initial soil solution compositions, corresponding to particular soil types (loam, sand, peat). For loamy and sandy soils, our calculational results agree well with experimental data reported by Nisbet (Effectiveness of soil-based countermeasures six months and one year after contamination of five diverse soil types with caesium-134 and strontium-90. Contract Report NRPB-M546, National Radiation Protection Board, Chilton, 1995.). For peat, discrepancies were found indicating that for organic soils a reliable set of exchange constants of the relevant cations still has to be determined experimentally. For cesium, however, these discrepancies almost disappeared if selective sites were assumed to be inaccessible. Additionally, results of sensitivity analyses are presented by which the influence of the main soil parameters on Cs+ concentrations in solution after soil treatment has been systematically studied. It is shown that calculating the impacts of soil-based chemical countermeasures on soil solution chemistry using geochemical codes such as PHREEQC offers an attractive alternative to establishing these impacts by often time-consuming and site-specific experiments.

Temperature and pressure influence on explosion pressures of closed vessel propane-air deflagrations.

PubMed

Razus, Domnina; Brinzea, Venera; Mitu, Maria; Oancea, Dumitru

2010-02-15

An experimental study on pressure evolution during closed vessel explosions of propane-air mixtures was performed, for systems with various initial concentrations and pressures ([C(3)H(8)]=2.50-6.20 vol.%, p(0)=0.3-1.2 bar). The explosion pressures and explosion times were measured in a spherical vessel (Phi=10 cm), at various initial temperatures (T(0)=298-423 K) and in a cylindrical vessel (Phi=10 cm; h=15 cm), at ambient initial temperature. The experimental values of explosion pressures are examined against literature values and compared to adiabatic explosion pressures, computed by assuming chemical equilibrium within the flame front. The influence of initial pressure, initial temperature and fuel concentration on explosion pressures and explosion times are discussed. At constant temperature and fuel/oxygen ratio, the explosion pressures are linear functions of total initial pressure, as reported for other fuel-air mixtures. At constant initial pressure and composition, both the measured and calculated (adiabatic) explosion pressures are linear functions of reciprocal value of initial temperature. Such correlations are extremely useful for predicting the explosion pressures of flammable mixtures at elevated temperatures and/or pressures, when direct measurements are not available.

Effect of alkaline treatment on mechanical properties of kenaf fiber reinforced polyester composites

NASA Astrophysics Data System (ADS)

Reddy, Bijjam Ramgopal; Dhoria, Sneha H.

2018-04-01

This paper focuses on the study of the effect of chemical treatment on mechanical properties such as tensile, flexural and impact properties of kenaf fiber reinforced polyester composites. Adhesion between the fiber and polymer is one of factors affecting the mechanical properties of composites. In order to increase the adhesion, the fibers are chemically treated with 5% of sodium hydroxide (NaOH) solution. The composite specimens are prepared in both untreated and treated forms of kenaf fibers with five levels of fiber volume fractions. The specimens are prepared according to ASTM standards. Mechanical tests such as tensile, flexural and impact are conducted to determine ultimate tensile strength, bending strength and impact strength of composites. The effect of change in volume fraction on the mechanical properties of the composites is studied for both untreated (raw) and chemically treated kenaf fibers. It has been found that the composites made of chemically treated fibers have good mechanical properties compared to untreated fibers.

Bulk chemical compositions of Antarctic meteorites in the NIPR collection

NASA Astrophysics Data System (ADS)

Kimura, M.; Imae, N.; Yamaguchi, A.; Haramura, H.; Kojima, H.

2018-03-01

Bulk chemical compositions of meteorites were traditionally analyzed by wet chemical analysis, and NIPR has data for 1162 meteorites as of September 2017. We discuss the classification of meteorites on the basis of these data. Chondrite data are distributed in an anomalously wide range of compositions on the Urey-Craig diagram. One of the reasons for such wide distribution is terrestrial weathering producing Fe2O3-bearing phases from Fe-Ni metal and sulfides. Another important factor affecting the bulk compositional data is brecciation. Our observations indicate that many brecciated chondrites contain anomalously abundant opaque minerals, or are depleted in them, resulting in unusual compositions. In case of enstatite and some carbonaceous chondrites, the bulk compositions are distributed in wider ranges than reported before. The bulk compositions of HED meteorites are consistent with their mineralogy and classification. Our study suggests that wet chemical data are still significant for the meteorite classification. However, petrographic observation is indispensable for evaluating the bulk chemistry and classification of meteorites.

ChemCam Compositional Results from the Shaler Outcrop in Gale Crater, Mars (Invited)

NASA Astrophysics Data System (ADS)

Anderson, R. B.; Leveille, R. J.; Vaniman, D.; Williams, J.; Clegg, S. M.; Le Mouelic, S.; Wiens, R. C.; Edgar, L. A.; Newsom, H. E.; Clark, B. C.; Ollila, A.; Lewis, K. W.; Gupta, S.; Team, M.

2013-12-01

The Curiosity rover first visited the outcrop known as 'Shaler' on Sol 121 of the mission. The ~1 m thick outcrop is the 'type section' for the Shaler member, which forms the uppermost part of the Yellowknife Bay formation. The Shaler outcrop exhibits multiple well-exposed cross-bedded facies with typical grain sizes of 1-2 mm, most consistent with fluvial deposition. Initial results from the two Sol 121 observations of Shaler by the ChemCam instrument showed similar composition, with a mix of mafic silicates and feldspar grains. A strong correlation between iron and titanium indicates the possible presence of titanomagnetite or ilmenite. CaO shows an anticorrelation with the total of the measured major elements, suggesting that it may be related to a non-silicate phase such as a salt. The rover returned to the outcrop on Sols 309-324. Because of the rugged nature of the outcrop, much of the exposed rock was not reachable by the rover's robotic arm. However, the ChemCam instrument can collect elemental compositional information out to a range of ~7 m using laser-induced breakdown spectroscopy (LIBS), and can acquire high-resolution images at even greater range. ChemCam analyzed 29 locations using LIBS to determine chemical composition, and four additional locations were imaged with the Remote Micro Imager. The targets analyzed included both fine- and coarse-grained facies, as well as a distinct upper unit which appears darker and less red than other Shaler units in Mastcam images, and lacks the striking alternating resistant and recessive cross-bedding observed in lower Shaler. This upper unit occurs at an elevation similar to the rocks at 'Rocknest', and similar-looking rocks appear across the cratered surface to the south and east of Shaler. Several blocks apparently derived from this upper unit were analyzed by ChemCam to test the hypothesis that the unit is related to rocks observed at Rocknest. Work is ongoing to interpret the results of the ChemCam campaign at Shaler. This work includes localization of individual laser analysis points to relate fine-scaled texture and grain size to chemical compositions, analysis of detectable minor and trace elements, identification of compositional trends related to facies type, comparison with compositions of other stratigraphic units in Gale crater, and chemical classification based on terrestrial sedimentary geochemistry.

Chemical and physical controls on the transformation of amorphous calcium carbonate into crystalline CaCO3 polymorphs

NASA Astrophysics Data System (ADS)

Blue, C. R.; Giuffre, A.; Mergelsberg, S.; Han, N.; De Yoreo, J. J.; Dove, P. M.

2017-01-01

Calcite and other crystalline polymorphs of CaCO3 can form by pathways involving amorphous calcium carbonate (ACC). Apparent inconsistencies in the literature indicate the relationships between ACC composition, local conditions, and the subsequent crystalline polymorphs are not yet established. This experimental study quantifies the control of solution composition on the transformation of ACC into crystalline polymorphs in the presence of magnesium. Using a mixed flow reactor to control solution chemistry, ACC was synthesized with variable Mg contents by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within the output suspension under stirred or quiescent conditions while characterizing the evolving solutions and solids. As the ACC transforms into a crystalline phase, the solutions record a polymorph-specific evolution of pH and Mg/Ca. The data provide a quantitative framework for predicting the initial polymorph that forms from ACC based upon the solution aMg2+/aCa2+ and aCO32-/aCa2+ and stirring versus quiescent conditions. This model reconciles discrepancies among previous studies that report on the nature of the polymorphs produced from ACC and supports the previous claim that monohydrocalcite may be an important, but overlooked, transient phase on the way to forming some aragonite and calcite deposits. By this construct, organic additives and extreme pH are not required to tune the composition and nature of the polymorph that forms. Our measurements show that the Mg content of ACC is recorded in the resulting calcite with a ≈1:1 dependence. By correlating composition of these calcite products with the Mgtot/Catot of the initial solutions, we find a ≈3:1 dependence that is approximately linear and general to whether calcite is formed via an ACC pathway or by the classical step-propagation process. Comparisons to calcite grown in synthetic seawater show a ≈1:1 dependence. The relationships suggest that the local Mg2+/Ca2+ at the time of precipitation determines the calcite composition, independent of whether growth occurs via an amorphous intermediate or classical pathway for a range of supersaturations and pH conditions. The findings reiterate the need to revisit the traditional picture of chemical and physical controls on CaCO3 polymorph selection. Mineralization by pathways involving ACC can lead to the formation of crystalline phases whose polymorphs and compositions are out of equilibrium with local growth media. As such, classical thermodynamic equilibria may not provide a reliable predictor of observed compositions.

SHEDS-HT: An Integrated Probabilistic Exposure Model for ...

EPA Pesticide Factsheets

United States Environmental Protection Agency (USEPA) researchers are developing a strategy for highthroughput (HT) exposure-based prioritization of chemicals under the ExpoCast program. These novel modeling approaches for evaluating chemicals based on their potential for biologically relevant human exposures will inform toxicity testing and prioritization for chemical risk assessment. Based on probabilistic methods and algorithms developed for The Stochastic Human Exposure and Dose Simulation Model for Multimedia, Multipathway Chemicals (SHEDS-MM), a new mechanistic modeling approach has been developed to accommodate high-throughput (HT) assessment of exposure potential. In this SHEDS-HT model, the residential and dietary modules of SHEDS-MM have been operationally modified to reduce the user burden, input data demands, and run times of the higher-tier model, while maintaining critical features and inputs that influence exposure. The model has been implemented in R; the modeling framework links chemicals to consumer product categories or food groups (and thus exposure scenarios) to predict HT exposures and intake doses. Initially, SHEDS-HT has been applied to 2507 organic chemicals associated with consumer products and agricultural pesticides. These evaluations employ data from recent USEPA efforts to characterize usage (prevalence, frequency, and magnitude), chemical composition, and exposure scenarios for a wide range of consumer products. In modeling indirec

Chemical composition of stars in Ruprecht 106 .

NASA Astrophysics Data System (ADS)

François, P.

High resolution spectra of 9 stars belonging to the globular cluster Rup 106 have been used to determine their chemical composition. The results reveal that Ruprecht 106 exhibits abundance anomalies when compared to galactic globular cluster of similar metallicity. The chemical composition of these stars is similar to what is found in Dwarf spheroidal galaxies favoring the hypothesis that Rup 106 has not been formed in our Galaxy.

Polyaniline-grafted reduced graphene oxide for efficient electrochemical supercapacitors.

PubMed

Kumar, Nanjundan Ashok; Choi, Hyun-Jung; Shin, Yeon Ran; Chang, Dong Wook; Dai, Liming; Baek, Jong-Beom

2012-02-28

An alternative and effective route to prepare conducting polyaniline-grafted reduced graphene oxide (PANi-g-rGO) composite with highly enhanced properties is reported. In order to prepare PANi-g-rGO, amine-protected 4-aminophenol was initially grafted to graphite oxide (GO) via acyl chemistry where a concomitant partial reduction of GO occurred due to the refluxing and exposure of GO to thionyl chloride vapors and heating. Following the deprotection of amine groups, an in situ chemical oxidative grafting of aniline in the presence of an oxidizing agent was carried out to yield highly conducting PANi-g-rGO. Electron microscopic studies demonstrated that the resultant composite has fibrillar morphology with a room-temperature electrical conductivity as high as 8.66 S/cm and capacitance of 250 F/g with good cycling stability.

N-15 NMR Spectroscopy as a Method for Comparing the Rates of Imidization of Several Diamines

NASA Technical Reports Server (NTRS)

Johnson, J. Christopher; Kuczmarski, Maria A.

2006-01-01

The relative rates of the conversion of amide-acid to imide was measured for a series or aromatic diamines that have been identified as potential replacements for 4,4'-methylene dianiline (MDA) in high-temperature polyimides and polymer composites. These rates were compared with the N-15 NMR resonances of the unreacted amines. The initial rates of imidization track with the difference in chemical shift between the amine nitrogens in MDA and those in the subject diamines. This comparison demonstrated that N-15 NMR spectroscopy is appropriate for the rapid screening of candidate diamines to determine their reactivity relative to MDA, and can serve to provide guidance to the process of creating the time-temperature profiles used in processing these materials into polymer matrix composites.

Analyzing the Mechanical Behavior of Polymer and Composite Materials by Means of Unique Method of Deformation Calorimetry

NASA Astrophysics Data System (ADS)

Bessonova, N. P.; Chvalun, S. N.

2018-06-01

Results are presented from long-term investigations of a wide range of polymer systems, varying from elastomers and thermoplastic elastomers to plastics and fibers. The thermophysical properties of both initial and modifying additive-containing polysiloxanes, block copolymers, and poleolefins that differ in chemical nature, structure, and composition are analyzed. It is shown that deformation calorimetry allows the simultaneous registration of mechanical (from 5 × 10-3 kg) and thermal effects (at a sensitivity of 2 × 10‒7 J/s), and the determination of changes in enthalpy, internal energy, and intra- and intermolecular contributions to the formation of the tensile stress response. In other words, it provides a unique opportunity to analyze the deformation mechanism of investigated systems and its dependence on the changing parameters.

Electrochemistry of lunar rocks

NASA Technical Reports Server (NTRS)

Lindstrom, D. J.; Haskin, L. A.

1979-01-01

Electrolysis of silicate melts has been shown to be an effective means of producing metals from common silicate materials. No fluxing agents need be added to the melts. From solution in melts of diopside (CaMgSi2O6) composition, the elements Si, Ti, Ni, and Fe have been reduced to their metallic states. Platinum is a satisfactory anode material, but other cathode materials are needed. Electrolysis of compositional analogs of lunar rocks initially produces iron metal at the cathode and oxygen gas at the anode. Utilizing mainly heat and electricity which are readily available from sunlight, direct electrolysis is capable of producing useful metals from common feedstocks without the need for expendable chemicals. This simple process and the products obtained from it deserve further study for use in materials processing in space.

Abundance Profiles for C3 Hydrocarbons in Titan's Atmosphere

NASA Astrophysics Data System (ADS)

Lombardo, Nicholas; Nixon, Conor A.; Achterberg, Richard; Jolly, Antoine; Sung, Keeyoon; Irwin, Patrick; Flasar, F. Michael

2017-10-01

The atmosphere of Titan is of astrobiological importance. Its highly reducing composition and prebiotic chemistry make it analogous to that of the early Earth. Since the Voyager era, several complex hydrocarbons and nitriles have been detected, in some cases making Titan the only known planetary body where these gasses occur naturally. In this work, we report abundance profiles of four major C3 gasses expected to occur in Titan’s atmosphere, derived from Cassini/Composite Infrared Spectrometer (CIRS) data.Using the NEMESIS iterative radiative transfer module, we retrieved vertical abundance profiles for propane (C3H8) and propyne (CHCCH3), both initially detected by the Voyager IRIS instrument. Using newly available line data, we were also able to determine the first vertical abundance profiles for propene (C3H6), initially detected in 2013. We present profiles for several latitudes and times and compare to photochemical model predictions and previous observations. We also discuss our efforts to further the search for allene (CH2CCH2), an isomer of propyne. The abundances we retrieved will help to further our understanding of the chemical pathways that occur in Titan's atmosphere.

Evaluating the influence of chemical weathering on the composition of the continental crust using lithium and its isotopes

NASA Astrophysics Data System (ADS)

Rudnick, R. L.; Liu, X.

2011-12-01

The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" of the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems document the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 8×10^9 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

Prediction of Combustion Gas Deposit Compositions

NASA Technical Reports Server (NTRS)

Kohl, F. J.; Mcbride, B. J.; Zeleznik, F. J.; Gordon, S.

1985-01-01

Demonstrated procedure used to predict accurately chemical compositions of complicated deposit mixtures. NASA Lewis Research Center's Computer Program for Calculation of Complex Chemical Equilibrium Compositions (CEC) used in conjunction with Computer Program for Calculation of Ideal Gas Thermodynamic Data (PAC) and resulting Thermodynamic Data Base (THDATA) to predict deposit compositions from metal or mineral-seeded combustion processes.

Update on the Chemical Composition Of Crystalline, Smectite, and Amorphous Components for Rocknest Soil and John Klein and Cumberland Mudstone Drill Fines at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Morris, R. V.; Ming, D. W.; Gellert, R.; Vaniman, D. T.; Bish, D. L.; Blake, D. F.; Chipera, S. J.; Morrison, S. M.; Downs, R. T.; Rampe, E. B.;

Vesper - Venus Chemistry and Dynamics Orbiter - A NASA Discovery Mission Proposal: Submillimeter Investigation of Atmospheric Chemistry and Dynamics

NASA Technical Reports Server (NTRS)

Chin, Gordon

2011-01-01

Vesper conducts a focused investigation of the chemistry and dynamics of the middle atmosphere of our sister planet- from the base of the global cloud cover to the lower thermosphere. The middle atmosphere controls the stability of the Venus climate system. Vesper determines what processes maintain the atmospheric chemical stability, cause observed variability of chemical composition, control the escape of water, and drive the extreme super-rotation. The Vesper science investigation provides a unique perspective on the Earth environment due to the similarities in the middle atmosphere processes of both Venus and the Earth. Understanding key distinctions and similarities between Venus and Earth will increase our knowledge of how terrestrial planets evolve along different paths from nearly identical initial conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zamecnik, J. R.; Edwards, T. B.

The conversions of nitrite to nitrate, the destruction of glycolate, and the conversion of glycolate to formate and oxalate were modeled for the Nitric-Glycolic flowsheet using data from Chemical Process Cell (CPC) simulant runs conducted by SRNL from 2011 to 2015. The goal of this work was to develop empirical correlations for these variables versus measureable variables from the chemical process so that these quantities could be predicted a-priori from the sludge composition and measurable processing variables. The need for these predictions arises from the need to predict the REDuction/OXidation (REDOX) state of the glass from the Defense Waste Processingmore » Facility (DWPF) melter. This report summarizes the initial work on these correlations based on the aforementioned data. Further refinement of the models as additional data is collected is recommended.« less

Correlation of rocket propulsion fuel properties with chemical composition using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry followed by partial least squares regression analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kehimkar, Benjamin; Hoggard, Jamin C.; Marney, Luke C.

There is an increased need to more fully assess and control the composition of kerosene based rocket propulsion fuels, namely RP-1 and RP-2. In particular, it is crucial to be able to make better quantitative connections between the following three attributes: (a) fuel performance, (b) fuel properties (flash point, density, kinematic viscosity, net heat of combustion, hydrogen content, etc) and (c) the chemical composition of a given fuel (i.e., specific chemical compounds and compound classes present as a result of feedstock blending and processing). Indeed, recent efforts in predicting fuel performance through modeling put greater emphasis on detailed and accuratemore » fuel properties and fuel compositional information. In this regard, advanced distillation curve (ADC) metrology provides improved data relative to classical boiling point and volatility curve techniques. Using ADC metrology, data obtained from RP-1 and RP-2 fuels provides compositional variation information that is directly relevant to predictive modeling of fuel performance. Often, in such studies, one-dimensional gas chromatography (GC) combined with mass spectrometry (MS) is typically employed to provide chemical composition information. Building on approaches using GC-MS, but to glean substantially more chemical composition information from these complex fuels, we have recently studied the use of comprehensive two dimensional gas chromatography combined with time-of-flight mass spectrometry (GC × GC - TOFMS) to provide chemical composition data that is significantly richer than that provided by GC-MS methods. In this report, by applying multivariate data analysis techniques, referred to as chemometrics, we are able to readily model (correlate) the chemical compositional information from RP-1 and RP-2 fuels provided using GC × GC - TOFMS, to the fuel property information such as that provided by the ADC method and other specification properties. We anticipate that this new chemical analysis strategy will have broad implications for the development of high fidelity composition-property models, leading to an optimized approach to fuel formulation and specification for advanced engine cycles.« less

Self-repair of cracks in brittle material systems

NASA Astrophysics Data System (ADS)

Dry, Carolyn M.

2016-04-01

One of the most effective uses for self repair is in material systems that crack because the cracks can allow the repair chemical to flow into the crack damage sites in all three dimensions. In order for the repair chemical to stay in the damage site and flow along to all the crack and repair there must be enough chemical to fill the entire crack. The repair chemical must be designed appropriately for the particular crack size and total volume of cracks. In each of the three examples of self repair in crackable brittle systems, the viscosity and chemical makeup and volume of the repair chemicals used is different for each system. Further the chemical delivery system has to be designed for each application also. Test results from self repair of three brittle systems are discussed. In "Self Repair of Concrete Bridges and Infrastructure" two chemicals were used due to different placements in bridges to repair different types of cracks- surface shrinkage and shear cracks, In "Airplane Wings and Fuselage, in Graphite" the composite has very different properties than the concrete bridges. In the graphite for airplane components the chemical also had to survive the high processing temperatures. In this composite the cracks were so definite and deep and thin that the repair chemical could flow easily and repair in all layers of the composite. In "Ceramic/Composite Demonstrating Self Repair" the self repair system not only repaired the broken ceramic but also rebounded the composite to the ceramic layer

Synthesis and Characterization of Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO) Composites Used for Pb(II) Removal

PubMed Central

Fan, Mingyi; Li, Tongjun; Hu, Jiwei; Cao, Rensheng; Wu, Qing; Wei, Xionghui; Li, Lingyun; Shi, Xuedan; Ruan, Wenqian

2016-01-01

Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were prepared by chemical deposition method and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2-sorption and X-ray photoelectron spectroscopy (XPS). Operating parameters for the removal process of Pb(II) ions, such as temperature (20–40 °C), pH (3–5), initial concentration (400–600 mg/L) and contact time (20–60 min), were optimized using a quadratic model. The coefficient of determination (R2 > 0.99) obtained for the mathematical model indicates a high correlation between the experimental and predicted values. The optimal temperature, pH, initial concentration and contact time for Pb(II) ions removal in the present experiment were 21.30 °C, 5.00, 400.00 mg/L and 60.00 min, respectively. In addition, the Pb(II) removal by nZVI/rGO composites was quantitatively evaluated by using adsorption isotherms, such as Langmuir and Freundlich isotherm models, of which Langmuir isotherm gave a better correlation, and the calculated maximum adsorption capacity was 910 mg/g. The removal process of Pb(II) ions could be completed within 50 min, which was well described by the pseudo-second order kinetic model. Therefore, the nZVI/rGO composites are suitable as efficient materials for the advanced treatment of Pb(II)-containing wastewater. PMID:28773813

Synthesis and Characterization of Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO) Composites Used for Pb(II) Removal.

PubMed

Fan, Mingyi; Li, Tongjun; Hu, Jiwei; Cao, Rensheng; Wu, Qing; Wei, Xionghui; Li, Lingyun; Shi, Xuedan; Ruan, Wenqian

2016-08-12

Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were prepared by chemical deposition method and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N₂-sorption and X-ray photoelectron spectroscopy (XPS). Operating parameters for the removal process of Pb(II) ions, such as temperature (20-40 °C), pH (3-5), initial concentration (400-600 mg/L) and contact time (20-60 min), were optimized using a quadratic model. The coefficient of determination ( R ² > 0.99) obtained for the mathematical model indicates a high correlation between the experimental and predicted values. The optimal temperature, pH, initial concentration and contact time for Pb(II) ions removal in the present experiment were 21.30 °C, 5.00, 400.00 mg/L and 60.00 min, respectively. In addition, the Pb(II) removal by nZVI/rGO composites was quantitatively evaluated by using adsorption isotherms, such as Langmuir and Freundlich isotherm models, of which Langmuir isotherm gave a better correlation, and the calculated maximum adsorption capacity was 910 mg/g. The removal process of Pb(II) ions could be completed within 50 min, which was well described by the pseudo-second order kinetic model. Therefore, the nZVI/rGO composites are suitable as efficient materials for the advanced treatment of Pb(II)-containing wastewater.

Data on the weights, specific gravities and chemical compositions of potato (Solanum tuberosum) tubers for food processing from different areas of Hokkaido, Japan.

PubMed

Sato, Hiroaki; Koizumi, Ryosuke; Nakazawa, Yozo; Yamazaki, Masao; Itoyama, Ryuichi; Ichisawa, Megumi; Negichi, Junko; Sakuma, Rui; Furusho, Tadasu; Sagane, Yoshimasa; Takano, Katsumi

2017-04-01

This data article provides the weights, specific gravities and chemical compositions (moisture, protein, fat, ash, and carbohydrate) of potato tubers, for food processing use, from the Tokachi, Kamikawa and Abashiri areas of Hokkaido, Japan. Potato tubers of four cultivars ('Toyoshiro', 'Kitahime', 'Snowden' and 'Poroshiri') were employed in the current study. The weights and specific gravities of potato tubers from each cultivar, harvested from three areas, were measured, and those of near average weight and specific gravity from each group were analyzed for their chemical composition. In this article, weight, specific gravity, and chemical composition data are provided in tables.

Evaluation of iron aluminide weld overlays for erosion - corrosion resistant boiler tube coatings in low NO{sub x} boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

DuPont, J.N.; Banovic, S.W.; Marder, A.R.

1996-08-01

Low NOx burners are being installed in many fossil fired power plants in order to comply with new Clean Air Regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion is often enhanced and premature tube failures can occur. Failures due to oxidation and solid particle erosion are also a concern. A program was initiated in early 1996 to evaluate the use of iron aluminide weld overlays for erosion/corrosion protection of boiler tubes in Low NOx boilers. Composite iron/aluminum wires will be used with the Gas Metal Arc Welding (GMAW) process to prepare overlays on boiler tubesmore » steels with aluminum contents from 8 to 16wt%. The weldability of the composite wires will be evaluated as a function of chemical composition and welding parameters. The effect of overlay composition on corrosion (oxidation and sulfidation) and solid particle erosion will also be evaluated. The laboratory studies will be complemented by field exposures of both iron aluminide weld overlays and co-extruded tubing under actual boiler conditions.« less

Effect of stacking sequence on mechanical properties neem wood veneer plastic composites

NASA Astrophysics Data System (ADS)

Nagamadhu, M.; Kumar, G. C. Mohan; Jeyaraj, P.

2018-04-01

This study investigates the effect of wood veneer stacking sequence on mechanical properties of neem wood polymer composite (WPC) experimentally. Wood laminated samples were fabricated by conventional hand layup technique in a mold and cured under pressure at room temperature and then post cured at elevated temperature. Initially, the tensile, flexural, and impact test were conducted to understand the effect of weight fraction of fiber on mechanical properties. The mechanical properties have increased with the weight fraction of fiber. Moreover the stacking sequence of neem wood plays an important role. As it has a significant impact on the mechanical properties. The results indicated that 0°/0° WPC shows highest mechanical properties as compared to other sequences (90°/90°, 0°/90°, 45°/90°, 45°/45°). The Fourier Transform Infrared Spectroscopy (FTIR) Analysis were carried out to identify chemical compounds both in raw neem wood and neem wood epoxy composite. The microstructure raw/neat neem wood and the interfacial bonding characteristics of neem wood composite investigated using Scanning electron microscopy images.

Tunable self-organization of nanocomposite multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, C. Q.; Pei, Y. T.; Shaha, K. P.

In this letter we report the controlled growth and microstructural evolution of self-assembled nanocomposite multilayers that are induced by surface ion-impingement. The nanoscale structures together with chemical composition, especially at the growing front, have been investigated with high-resolution transmission electron microscopy. Concurrent ion impingement of growing films produces an amorphous capping layer 3 nm in thickness where spatially modulated phase separation is initiated. It is shown that the modulation of multilayers as controlled by the self-organization of nanocrystallites below the capping layer, can be tuned through the entire film.

Chemical composition, nutritional value and antioxidant properties of Mediterranean okra genotypes in relation to harvest stage.

PubMed

Petropoulos, Spyridon; Fernandes, Ângela; Barros, Lillian; Ferreira, Isabel C F R

2018-03-01

The aim of the present study was to determine the effect of fruit size on nutritional value, chemical composition and antioxidant properties of Mediterranean okra genotypes. For this purpose, pods from four okra cultivars and local landraces commonly cultivated in Greece, as well as pods from four commercial cultivars from North America were collected at two sizes (3-5 and>7cm). Significant differences were observed between the studied genotypes for both nutritional value and chemical composition parameters. Small fruit had a higher nutritional value, whereas chemical composition differed in a genotype dependent manner with most of the studied cultivars showing better results when harvested in small size. In conclusion, fruit size has a genotype dependent impact on chemical composition and nutritional value of okra pods and the common practice of harvesting okra fruit while they still have a small size helps to increase nutritional value for most of the studied genotypes. Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, E.A.; Westbury, H.M. Jr.

The F- and H-Area Seepage Basins received liquid waste from the F and H chemical separation facilities from 1955 through 1988. Tree mortality in seepline fed wetlands down-slope from the basins was observed in the late 1970`s, and investigations were conducted to determine the cause and source of the impacts. Analysis of the soil and water in the tree-kill zones demonstrated a strong chemical linkage with the F- and H-Area seepage basins. Although no single cause of the mortality was determined, it was believed to be the result of interactions of alterations in the hydrology and erosional deposition, along withmore » lowering of pH and increased conductivity, sodium, aluminum, and nitrogen compounds. A mild drought during the growing season may also have increased the concentration of the chemical contaminants in the soils matrix. In 1988, the F- and H-Area Seepage Basins were closed and covered with a clay cap to reduce the rate of dispersion of the contaminants in the soil beneath the basins. Subsequent studies of the chemical composition of the tree-kill zone groundwater and toxicological characteristics of the seepline soil have shown a reduced contaminant flux. In 1993, an initial vegetation study was undertaken to determine the level of recovery by the plant communities in the tree-kill zones. This study repeats the initial vegetation investigation in order to further analyze and characterize the recovery of plant communities in the zones after an additional year of growth.« less

Software for analysis of chemical mixtures--composition, occurrence, distribution, and possible toxicity

USGS Publications Warehouse

Scott, Jonathon C.; Skach, Kenneth A.; Toccalino, Patricia L.

2013-01-01

The composition, occurrence, distribution, and possible toxicity of chemical mixtures in the environment are research concerns of the U.S. Geological Survey and others. The presence of specific chemical mixtures may serve as indicators of natural phenomena or human-caused events. Chemical mixtures may also have ecological, industrial, geochemical, or toxicological effects. Chemical-mixture occurrences vary by analyte composition and concentration. Four related computer programs have been developed by the National Water-Quality Assessment Program of the U.S. Geological Survey for research of chemical-mixture compositions, occurrences, distributions, and possible toxicities. The compositions and occurrences are identified for the user-supplied data, and therefore the resultant counts are constrained by the user’s choices for the selection of chemicals, reporting limits for the analytical methods, spatial coverage, and time span for the data supplied. The distribution of chemical mixtures may be spatial, temporal, and (or) related to some other variable, such as chemical usage. Possible toxicities optionally are estimated from user-supplied benchmark data. The software for the analysis of chemical mixtures described in this report is designed to work with chemical-analysis data files retrieved from the U.S. Geological Survey National Water Information System but can also be used with appropriately formatted data from other sources. Installation and usage of the mixture software are documented. This mixture software was designed to function with minimal changes on a variety of computer-operating systems. To obtain the software described herein and other U.S. Geological Survey software, visit http://water.usgs.gov/software/.

Compositional changes of minerals associated with dynamic recrystallizatin

NASA Astrophysics Data System (ADS)

Yund, Richard A.; Tullis, Jan

1991-09-01

The rate of compositional and isotopic exchange between minerals may be enhanced significantly if the rock is deformed simultaneously. The enhanced exchange rate may result from a reduction in grain size (shorter distance for volume diffusion), dissolution and growth of grains by diffusion creep (pressure solution), or the movement of high-angle grain boundaries through strained grains during recrystallization in the dislocation creep regime. The migration of high-angle grain boundaries provides high diffusivity paths for the rapid exchange of components during recrystallization. The operation of the latter process has been demonstrated by deforming aggregates consisting of two plagioclases (An1 and An79) at 900°C, 1 GPa confining pressure, and a strain rate of ˜2x10-6s-1. The polygonal, recrystallized grains were analyzed using an analytical transmission electron microscope and have a variable but often intermediate composition. At the conditions of these experiments, the volume interdiffusion rate of NaSi/CaAl is too slow to produce any observable chemical change, and microstructural-chemical relations indicate that the contribution from diffusion creep was insignificant except for initially fine-grained (2 10 μm) aggregates. These results indicate that strain-induced recrystallization can be an effective mechanism for enhancing the kinetics of metamorphic reactions and for resetting the isotope systematics of minerals such as feldspars, pyroxenes, and amphiboles.

Carbon Monoxide Data Assimilation for Atmospheric Composition and Climate Science: Evaluating Performance with Current and Future Observations

NASA Astrophysics Data System (ADS)

Barre, J.; Edwards, D. P.; Gaubert, B.; Worden, H. M.; Arellano, A. F.; Anderson, J. L.

2015-12-01

Current satellite observations of tropospheric composition made from low Earth orbit provide at best one or two measurements each day at any given location. Comparisons of Terra/MOPITT carbon monoxide (CO) and IASI/Metop CO observation assimilations will be presented. We use the DART Ensemble Adjustment Kalman Filter to assimilate observations in the CAM-Chem global chemistry-climate model. Data assimilation impacts due to both different instrument capabilities (i.e. vertical sensitivity and global coverage) will be discussed. Coverage is global but sparse, often with large uncertainties in individual measurements that limit examination of local and regional atmospheric composition over short time periods. This has hindered the operational uptake of these data for monitoring air quality and population exposure, and for initializing and evaluating chemical weather forecasts. By the end of the current decade there are planned geostationary Earth orbit (GEO) satellite missions for atmospheric composition over North America, East Asia and Europe with additional missions proposed. Together, these present the possibility of a constellation of geostationary platforms to achieve continuous time-resolved high-density observations of continental domains for mapping pollutant sources and variability on diurnal and local scales. We describe Observing System Simulation Experiments (OSSEs) to evaluate the contributions of these GEO missions to improve knowledge of near-surface air pollution due to intercontinental long-range transport and quantify chemical precursor emissions. Our approach uses an efficient computational method to sample a high-resolution global GEOS-5 chemistry Nature Run over each geographical region of the GEO constellation. The demonstration carbon monoxide (CO) observation simulator, which will be expanded to other chemical pollutants, currently produces multispectral retrievals (MOPITT-like) and captures realistic scene-dependent variation in measurement vertical sensitivity and cloud cover. The impact of observing over each region is evaluated independently. Winter and summer cases studies are investigated i.e. where emissions, cloud cover and CO lifetime significantly change.

Study of the structure and chemical composition of the protective coating of a fist stage gas turbine blade after regenerative heat treatment

NASA Astrophysics Data System (ADS)

Davidov, D. I.; Kazantseva, N. V.; Vinogradova, N. I.; Ezhov, I. V.

2017-12-01

Investigation of the structure and chemical composition of the protective coating of the first stage IN738 gas turbine blade after standard regenerative heat treatment was done. It was found the degradation of microstructure and chemical composition of both the blade feather and its protective coating. Redistribution of the chemical elements decreasing the corrosion resistance was observed inside the protective coating. Cracks on the boundary between the blade feather and the protective coating were found by scanning electron microscopy. The carbide transformation and sigma phase were found in the structure of the blade feather. Based upon the structural and chemical composition studies, it is concluded that the standard regenerative heat treatment of the IN738 operative gas turbine blade does not provide full structure regeneration.

Polymerization and Structure of Bio-Based Plastics: A Computer Simulation

NASA Astrophysics Data System (ADS)

Khot, Shrikant N.; Wool, Richard P.

2001-03-01

We recently examined several hundred chemical pathways to convert chemically functionalized plant oil triglycerides, monoglycerides and reactive diluents into high performance plastics with a broad range of properties (US Patent No. 6,121,398). The resulting polymers had linear, branched, light- and highly-crosslinked chain architectures and could be used as pressure sensitive adhesives, elastomers and high performance rigid thermoset composite resins. To optimize the molecular design and minimize the number of chemical trials in this system with excess degrees of freedom, we developed a computer simulation of the free radical polymerization process. The triglyceride structure, degree of chemical substitution, mole fractions, fatty acid distribution function, and reaction kinetic parameters were used as initial inputs on a 3d lattice simulation. The evolution of the network fractal structure was computed and used to measure crosslink density, dangling ends, degree of reaction and defects in the lattice. The molecular connectivity was used to determine strength via a vector percolation model of fracture. The simulation permitted the optimal design of new bio-based materials with respect to monomer selection, cure reaction conditions and desired properties. Supported by the National Science Foundation

Chemical and Physical Characteristics of Soy Proteins for New Industrial Applications

NASA Astrophysics Data System (ADS)

Arboleda Fernandez, Julio Cesar

Despite of being environmentally friendly, biocompatible, rich in chemical functionality and abundant as residual materials, soy proteins (SPs) are used for low added value applications. In this work, SPs were studied and used as potentially useful biomacromolecules for different industrial applications with high added value. Initially the effect of acid hydrolysis of soy proteins as a potential route for subsequent surface modification was studied, finding that SP hydrolysates tend to form less aggregates and to adsorb at faster rates compared with unmodified SP; nevertheless, it was also found that the amount of protein adsorbed and water contact angle of the treated surface does not change significantly. Secondly, the gel forming properties of SPs were used to produce aerogels with densities in the order of 0.1 g/cm3. To improve their mechanical properties, the reinforcement of these materials with cellulose nanofibers was studied, obtaining composite aerogels with SP loadings as high as ca. 70% that display a compression modulus of 4.4 MPa, very close to the value obtained from the pure nanofibers aerogels. The composite materials gain moisture (up to 5%) in equilibrium with 50% RH air. Futhermore, their physical integrity is unchanged upon immersion in polar and non-polar solvents, exhibiting sorption rates dependent on the aerogel composition, morphology and swelling abilities. Finally, different soy protein based products and derivatives were used to enhance the dry strength properties of wood fibers in paper production. Experiments using soy flour, soy protein isolate, soy protein isolate hydrolysates, cationized soy flour, and soy flour combined with cationic starch and chitosan were done, obtaining satisfactory results when soy protein flour was utilized in combination with conventional treatments involving cationic polymers. The current results confirm the opportunity to valorize residual soy products that are underutilized today as alternatives to oil derived chemicals used in chemical processes.

Model of Mixing Layer With Multicomponent Evaporating Drops

NASA Technical Reports Server (NTRS)

Bellan, Josette; Le Clercq, Patrick

2004-01-01

A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The study is motivated by the fact that typical real petroleum fuels contain hundreds of chemical species. Previously, for the sake of computational efficiency, spray studies were performed using either models based on a single representative species or models based on surrogate fuels of at most 15 species. The present multicomponent model makes it possible to perform more realistic simulations by accounting for hundreds of chemical species in a computationally efficient manner. The model is used to perform Direct Numerical Simulations in continuing studies directed toward understanding the behavior of liquid petroleum fuel sprays. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and the drops, respectively. This representation is consistent with the expected volumetrically small loading of the drops in gas (of the order of 10 3), although the mass loading can be substantial because of the high ratio (of the order of 103) between the densities of liquid and gas. The drops are treated as point sources of mass, momentum, and energy; this representation is consistent with the drop size being smaller than the Kolmogorov scale. Unsteady drag, added-mass effects, Basset history forces, and collisions between the drops are neglected, and the gas is assumed calorically perfect. The model incorporates the concept of continuous thermodynamics, according to which the chemical composition of a fuel is described probabilistically, by use of a distribution function. Distribution functions generally depend on many parameters. However, for mixtures of homologous species, the distribution can be approximated with acceptable accuracy as a sole function of the molecular weight. The mixing layer is initially laden with drops in its lower stream, and the drops are colder than the gas. Drop evaporation leads to a change in the gas-phase composition, which, like the composition of the drops, is described in a probabilistic manner

Starting a European Space Agency Sample Analogue Collection for Robotic Exploration Missions

NASA Astrophysics Data System (ADS)

Smith, C. L.; Mavris, C.; Michalski, J. R.; Rumsey, M. S.; Russell, S. S.; Jones, C.; Schroeven-Deceuninck, H.

2015-12-01

The Natural History Museum is working closely with the European Space Agency (ESA) and the UK Space Agency to develop a European collection of analogue materials with appropriate physical/mechanical and chemical (mineralogical) properties which can support the development and verification of both spacecraft and scientific systems for potential science and exploration missions to Phobos/Deimos, Mars, C-type asteroids and the Moon. As an ESA Collection it will be housed at the ESA Centre based at Harwell, UK. The "ESA Sample Analogues Collection" will be composed of both natural and artificial materials chosen to (as closely as possible) replicate the surfaces and near-surfaces of different Solar System target bodies of exploration interest. The analogue samples will be fully characterised in terms of both their physical/mechanical properties (compressive strength, bulk density, grain shape, grain size, cohesion and angle of internal friction) and their chemical/mineralogical properties (texture, modal mineralogy, bulk chemical composition - major, minor and trace elements and individual mineralogical compositions). The Collection will be fully curated to international standards including implementation of a user-friendly database and will be available for use by engineers and scientists across the UK and Europe. Enhancement of the initial Collection will be possible through collaborations with other ESA and UK Space Agency supported activities, such as the acquisition of new samples during field trials.

Evolution of clog formation with time in columns permeated with synthetic landfill leachate

NASA Astrophysics Data System (ADS)

VanGulck, Jamie F.; Rowe, R. Kerry

2004-11-01

Laboratory column tests conducted to gain insight regarding the biological and chemical clogging mechanisms in a porous medium are presented. To seed the porous medium with landfill bacteria, a mixture of Keele Valley Landfill and synthetic leachate permeated through the column under anaerobic conditions for the first 9 days of operation. After this, 100% synthetic leachate was used. The synthetic leachate approximated Keele Valley Landfill leachate in chemical composition but contained negligible suspended solids and bacteria compared with real leachate. The removal of volatile fatty acids (VFAs), primarily acetate, in leachate as it passed through the medium was highly correlated with the precipitation of calcium carbonate (CaCO 3(s)) from solution. The columns experienced a decrease in drainable porosity from an initial value of about 0.38 to less than 0.1 after steady state chemical oxygen demand (COD) removal, resulting in a five-order magnitude decrease in hydraulic conductivity. The decrease in drainable porosity prior to steady state COD removal was primarily due to the growth of a biofilm on the medium surface. After steady state COD removal, calcium precipitation was at least equally responsible for the decrease in drainable porosity as biofilm growth. Clog composition analyses showed that CaCO 3(s) was the dominant clog constituent and that 99% of the carbonate in the clog material was bound to calcium.

Chemical composition, antioxidant and antibacterial activities of essential oils from leaves and flowers of Eugenia klotzschiana Berg (Myrtaceae).

PubMed

Carneiro, Nárgella S; Alves, Cassia C F; Alves, José M; Egea, Mariana B; Martins, Carlos H G; Silva, Thayná S; Bretanha, Lizandra C; Balleste, Maira P; Micke, Gustavo A; Silveira, Eduardo V; Miranda, Mayker L D

2017-01-01

Many essential oils (EOs) of different plant species possess interesting antimicrobial effects on buccal bacteria and antioxidant properties. Eugenia klotzschiana Berg (pêra-do-cerrado, in Portuguese) is a species of Myrtaceae with restricted distribution in the Cerrado. The essential oils were extracted through the hydrodistillation technique using a modified Clevenger apparatus (2 hours) and chemically characterized by GC-MS. The major compounds were α-copaene (10.6 %) found in oil from leaves in natura, β-bisabolene (17.4 %) in the essential oil from dry leaves and α-(E)-bergamotene (29.9 %) in oil from flowers. The antioxidant activity of essential oils showed similarities in both methods under analysis (DPPH and ABTS˙+) and the results suggested moderate to high antioxidant activity. The antibacterial activity was evaluated by determining minimum inhibitory concentrations (MICs), using the microdilution method. MIC values below 400 µg/mL were obtained against Streptococcus salivarius (200 µg/mL), S. mutans (50 µg/mL), S. mitis (200 µg/mL) and Prevotella nigrescens (50 µg/mL). This is the first report of the chemical composition and antibacterial and antioxidant activities of the essential oils of E. klotzschiana. These results suggest that E. klotzschiana, a Brazilian plant, provide initial evidence of a new and alternative source of substances with medicinal interest.

Surface reactions of ethanol over UO 2(100) thin film

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. D. Senanayake; Mudiyanselage, K.; Burrell, A. K.

2015-10-08

The study of the reactions of oxygenates on well-defined oxide surfaces is important for the fundamental understanding of heterogeneous chemical pathways that are influenced by atomic geometry, electronic structure, and chemical composition. In this work, an ordered uranium oxide thin film surface terminated in the (100) orientation is prepared on a LaAlO 3 substrate and studied for its reactivity with a C-2 oxygenate, ethanol (CH 3CH 2OH). With the use of synchrotron X-ray photoelectron spectroscopy (XPS), we have probed the adsorption and desorption processes observed in the valence band, C 1s, O 1s, and U 4f to investigate the bondingmore » mode, surface composition, electronic structure, and probable chemical changes to the stoichiometric-UO 2(100) [smooth-UO 2(100)] and Ar +-sputtered UO 2(100) [rough-UO 2(100)] surfaces. Unlike UO 2(111) single crystal and UO 2 thin film, Ar-ion-sputtering of this UO 2(100) did not result in noticeable reduction of U cations. Upon ethanol adsorption (saturation occurred at 0.5 ML), only the ethoxy (CH 3CH 2O –) species is formed on smooth-UO 2(100) whereas initially formed ethoxy species are partially oxidized to surface acetate (CH3COO–) on the Ar +-sputtered UO 2(100) surface. Furthermore, all ethoxy and acetate species are removed from the surface between 600 and 700 K.« less

MOFwich: Sandwiched Metal-Organic Framework-Containing Mixed Matrix Composites for Chemical Warfare Agent Removal.

PubMed

Peterson, Gregory W; Lu, Annie X; Hall, Morgan G; Browe, Matthew A; Tovar, Trenton; Epps, Thomas H

2018-02-28

This work describes a new strategy for fabricating mixed matrix composites containing layered metal-organic framework (MOF)/polymer films as functional barriers for chemical warfare agent protection. Through the use of mechanically robust polymers as the top and bottom encasing layers, a high-MOF-loading, high-performance-core layer can be sandwiched within. We term this multifunctional composite "MOFwich". We found that the use of elastomeric encasing layers enabled core layer reformation after breakage, an important feature for composites and membranes alike. The incorporation of MOFs into the core layer led to enhanced removal of chemical warfare agents while simultaneously promoting moisture vapor transport through the composite, showcasing the promise of these composites for protection applications.

The Gaia-ESO Survey: evidence of atomic diffusion in M67?

NASA Astrophysics Data System (ADS)

Bertelli Motta, C.; Pasquali, A.; Richer, J.; Michaud, G.; Salaris, M.; Bragaglia, A.; Magrini, L.; Randich, S.; Grebel, E. K.; Adibekyan, V.; Blanco-Cuaresma, S.; Drazdauskas, A.; Fu, X.; Martell, S.; Tautvaišienė, G.; Gilmore, G.; Alfaro, E. J.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Heiter, U.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-07-01

Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in subgiant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

The Gaia-ESO Survey: Evidence of atomic diffusion in M67?

NASA Astrophysics Data System (ADS)

Motta, C. Bertelli; Pasquali, A.; Richer, J.; Michaud, G.; Salaris, M.; Bragaglia, A.; Magrini, L.; Randich, S.; Grebel, E. K.; Adibekyan, V.; Blanco-Cuaresma, S.; Drazdauskas, A.; Fu, X.; Martell, S.; TautvaišienÄ--, G.; Gilmore, G.; Alfaro, E. J.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Heiter, U.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-04-01

Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in sub-giant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

Composites Based on Polytetrafluoroethylene and Detonation Nanodiamonds: Filler-Matrix Chemical Interaction and Its Effect on a Composite's Properties

NASA Astrophysics Data System (ADS)

Koshcheev, A. P.; Perov, A. A.; Gorokhov, P. V.; Zaripov, N. V.; Tereshenkov, A. V.; Khatipov, S. A.

2018-06-01

Specific properties of PTFE composites filled with ultradisperse detonation diamonds (UDDs) with different surface chemistries are studied. It is found for the first time that filler in the form of UDDs affects not only the rate of PTFE thermal decomposition in vacuum pyrolysis, but also the chemical composition of the products of degradation. The wear resistance of UDD/PTFE composites is shown to depend strongly on the UDD surface chemistry. The presence of UDDs in a PTFE composite is found to result in perfluorocarbon telomeres, released as a readily condensable fraction upon composite pyrolysis. The chemical interaction between PTFE and UDDs, characterized by an increase in the rate of gas evolution and a change in the desorbed gas's composition, is found to occur at temperature as low as 380°C. It is shown that the intensity of this interaction depends on the concentration of oxygen-containing surface groups, the efficiency of UDDs in terms of the composite's wear resistance being reduced due to the presence of these groups. Based on the experimental data, a conclusion is reached about the chemical interaction between UDDs and a PTFE matrix, its dependence on the nanodiamond surface chemistry, and its effect on a composite's tribology.

Electrochemically Active Polyaniline (PANi) Coated Carbon Nanopipes and PANi Nanofibers Containing Composite.

PubMed

Ramana, G Venkata; Kumar, P Sampath; Srikanth, Vadali V S S; Padya, Balaji; Jain, P K

2015-02-01

A composite constituted by carbon nanopipes (CNPs) and polyaniline nanofibers (PANi NFs) is synthesized using in-situ chemical oxidative polymerization. Owing to its electrochemical activity the composite is found to be suitable as a working electrode material in hybrid type supercapacitors. Microstructural and phase analyses of the composite showed that (i) CNP surfaces are coated with PANi and (ii) PANi coated CNPs are distributed among PANi NFs. The composite shows an excellent electrochemical activity and a high specific capacitance of ~224.39 F/g. The electro-chemical activity of the composite is explicated in correlation with crystallinity, intrinsic oxidation state, and doping degree of PANi in the composite. The electro-chemical activity of the composite is also explicated in correlation with BET surface area and ordered meso-porosity pertaining to the composite. Charge/discharge curves indicate that the specific capacitance of the composite is a result of electric double-layer capacitance offered by CNPs and Faradaic pseudo capacitance offered by PANi NFs.

Computing Equilibrium Chemical Compositions

NASA Technical Reports Server (NTRS)

Mcbride, Bonnie J.; Gordon, Sanford

1995-01-01

Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations.

PubMed

Yu, W H; Kang, E T; Neoh, K G

2005-01-04

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.

Using different assumptions of aerosol mixing state and chemical composition to predict CCN concentrations based on field measurements in urban Beijing

NASA Astrophysics Data System (ADS)

Ren, Jingye; Zhang, Fang; Wang, Yuying; Collins, Don; Fan, Xinxin; Jin, Xiaoai; Xu, Weiqi; Sun, Yele; Cribb, Maureen; Li, Zhanqing

2018-05-01

Understanding the impacts of aerosol chemical composition and mixing state on cloud condensation nuclei (CCN) activity in polluted areas is crucial for accurately predicting CCN number concentrations (NCCN). In this study, we predict NCCN under five assumed schemes of aerosol chemical composition and mixing state based on field measurements in Beijing during the winter of 2016. Our results show that the best closure is achieved with the assumption of size dependent chemical composition for which sulfate, nitrate, secondary organic aerosols, and aged black carbon are internally mixed with each other but externally mixed with primary organic aerosol and fresh black carbon (external-internal size-resolved, abbreviated as EI-SR scheme). The resulting ratios of predicted-to-measured NCCN (RCCN_p/m) were 0.90 - 0.98 under both clean and polluted conditions. Assumption of an internal mixture and bulk chemical composition (INT-BK scheme) shows good closure with RCCN_p/m of 1.0 -1.16 under clean conditions, implying that it is adequate for CCN prediction in continental clean regions. On polluted days, assuming the aerosol is internally mixed and has a chemical composition that is size dependent (INT-SR scheme) achieves better closure than the INT-BK scheme due to the heterogeneity and variation in particle composition at different sizes. The improved closure achieved using the EI-SR and INT-SR assumptions highlight the importance of measuring size-resolved chemical composition for CCN predictions in polluted regions. NCCN is significantly underestimated (with RCCN_p/m of 0.66 - 0.75) when using the schemes of external mixtures with bulk (EXT-BK scheme) or size-resolved composition (EXT-SR scheme), implying that primary particles experience rapid aging and physical mixing processes in urban Beijing. However, our results show that the aerosol mixing state plays a minor role in CCN prediction when the κorg exceeds 0.1.

Differential effects of conifer and broadleaf litter inputs on soil organic carbon chemical composition through altered soil microbial community composition

PubMed Central

Wang, Hui; Liu, Shi-Rong; Wang, Jing-Xin; Shi, Zuo-Min; Xu, Jia; Hong, Pi-Zheng; Ming, An-Gang; Yu, Hao-Long; Chen, Lin; Lu, Li-Hua; Cai, Dao-Xiong

2016-01-01

A strategic selection of tree species will shift the type and quality of litter input, and subsequently magnitude and composition of the soil organic carbon (SOC) through soil microbial community. We conducted a manipulative experiment in randomized block design with leaf litter inputs of four native subtropical tree species in a Pinus massoniana plantation in southern China and found that the chemical composition of SOC did not differ significantly among treatments until after 28 months of the experiment. Contrasting leaf litter inputs had significant impacts on the amounts of total microbial, Gram-positive bacterial, and actinomycic PLFAs, but not on the amounts of total bacterial, Gram-negative bacterial, and fungal PLFAs. There were significant differences in alkyl/O-alkyl C in soils among the leaf litter input treatments, but no apparent differences in the proportions of chemical compositions (alkyl, O-alkyl, aromatic, and carbonyl C) in SOC. Soil alkyl/O-alkyl C was significantly related to the amounts of total microbial, and Gram-positive bacterial PLFAs, but not to the chemical compositions of leaf litter. Our findings suggest that changes in forest leaf litter inputs could result in changes in chemical stability of SOC through the altered microbial community composition. PMID:27256545

Differential effects of conifer and broadleaf litter inputs on soil organic carbon chemical composition through altered soil microbial community composition.

PubMed

Wang, Hui; Liu, Shi-Rong; Wang, Jing-Xin; Shi, Zuo-Min; Xu, Jia; Hong, Pi-Zheng; Ming, An-Gang; Yu, Hao-Long; Chen, Lin; Lu, Li-Hua; Cai, Dao-Xiong

2016-06-03

A strategic selection of tree species will shift the type and quality of litter input, and subsequently magnitude and composition of the soil organic carbon (SOC) through soil microbial community. We conducted a manipulative experiment in randomized block design with leaf litter inputs of four native subtropical tree species in a Pinus massoniana plantation in southern China and found that the chemical composition of SOC did not differ significantly among treatments until after 28 months of the experiment. Contrasting leaf litter inputs had significant impacts on the amounts of total microbial, Gram-positive bacterial, and actinomycic PLFAs, but not on the amounts of total bacterial, Gram-negative bacterial, and fungal PLFAs. There were significant differences in alkyl/O-alkyl C in soils among the leaf litter input treatments, but no apparent differences in the proportions of chemical compositions (alkyl, O-alkyl, aromatic, and carbonyl C) in SOC. Soil alkyl/O-alkyl C was significantly related to the amounts of total microbial, and Gram-positive bacterial PLFAs, but not to the chemical compositions of leaf litter. Our findings suggest that changes in forest leaf litter inputs could result in changes in chemical stability of SOC through the altered microbial community composition.

Differential effects of conifer and broadleaf litter inputs on soil organic carbon chemical composition through altered soil microbial community composition

NASA Astrophysics Data System (ADS)

Wang, Hui; Liu, Shi-Rong; Wang, Jing-Xin; Shi, Zuo-Min; Xu, Jia; Hong, Pi-Zheng; Ming, An-Gang; Yu, Hao-Long; Chen, Lin; Lu, Li-Hua; Cai, Dao-Xiong

2016-06-01

A strategic selection of tree species will shift the type and quality of litter input, and subsequently magnitude and composition of the soil organic carbon (SOC) through soil microbial community. We conducted a manipulative experiment in randomized block design with leaf litter inputs of four native subtropical tree species in a Pinus massoniana plantation in southern China and found that the chemical composition of SOC did not differ significantly among treatments until after 28 months of the experiment. Contrasting leaf litter inputs had significant impacts on the amounts of total microbial, Gram-positive bacterial, and actinomycic PLFAs, but not on the amounts of total bacterial, Gram-negative bacterial, and fungal PLFAs. There were significant differences in alkyl/O-alkyl C in soils among the leaf litter input treatments, but no apparent differences in the proportions of chemical compositions (alkyl, O-alkyl, aromatic, and carbonyl C) in SOC. Soil alkyl/O-alkyl C was significantly related to the amounts of total microbial, and Gram-positive bacterial PLFAs, but not to the chemical compositions of leaf litter. Our findings suggest that changes in forest leaf litter inputs could result in changes in chemical stability of SOC through the altered microbial community composition.

Improving short-term air quality predictions over the U.S. using chemical data assimilation

NASA Astrophysics Data System (ADS)

Kumar, R.; Delle Monache, L.; Alessandrini, S.; Saide, P.; Lin, H. C.; Liu, Z.; Pfister, G.; Edwards, D. P.; Baker, B.; Tang, Y.; Lee, P.; Djalalova, I.; Wilczak, J. M.

2017-12-01

State and local air quality forecasters across the United States use air quality forecasts from the National Air Quality Forecasting Capability (NAQFC) at the National Oceanic and Atmospheric Administration (NOAA) as one of the key tools to protect the public from adverse air pollution related health effects by dispensing timely information about air pollution episodes. This project funded by the National Aeronautics and Space Administration (NASA) aims to enhance the decision-making process by improving the accuracy of NAQFC short-term predictions of ground-level particulate matter of less than 2.5 µm in diameter (PM2.5) by exploiting NASA Earth Science Data with chemical data assimilation. The NAQFC is based on the Community Multiscale Air Quality (CMAQ) model. To improve the initialization of PM2.5 in CMAQ, we developed a new capability in the community Gridpoint Statistical Interpolation (GSI) system to assimilate Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) retrievals in CMAQ. Specifically, we developed new capabilities within GSI to read/write CMAQ data, a forward operator that calculates AOD at 550 nm from CMAQ aerosol chemical composition and an adjoint of the forward operator that translates the changes in AOD to aerosol chemical composition. A generalized background error covariance program called "GEN_BE" has been extended to calculate background error covariance using CMAQ output. The background error variances are generated using a combination of both emissions and meteorological perturbations to better capture sources of uncertainties in PM2.5 simulations. The newly developed CMAQ-GSI system is used to perform daily 24-h PM2.5 forecasts with and without data assimilation from 15 July to 14 August 2014, and the resulting forecasts are compared against AirNOW PM2.5 measurements at 550 stations across the U. S. We find that the assimilation of MODIS AOD retrievals improves initialization of the CMAQ model in terms of improved correlation coefficient and reduced bias. However, we notice a large bias in nighttime PM2.5 simulations which is primarily associated with very shallow boundary layer in the model. The developments and results will be discussed in detail during the presentation.

Chemical performance of multi-environment trials in lens (Lens culinaris M.).

PubMed

Karadavut, Ufuk; Palta, Cetin

2010-01-15

Genotype-environment (GE) interaction has been a major effect to determine stable lens (Lens culinaris (Medik.) Merr.) cultivars for chemical composition in Turkey. Utilization of the lines depends on their agronomic traits and stability of the chemical composition in diverse environments. The objectives of this study were: (i) to evaluate the influence of year and location on the chemical composition of lens genotypes; and (ii) to determine which cultivar is the most stable. Genotypes were evaluated over 3 years (2005, 2006 and 2007) at four locations in Turkey. Effects of year had the largest impact on all protein contents. GE interaction was analyzed by using linear regression techniques. Stability was estimated using the Eberhart and Russell method. 'Kişlik Kirmizi51' was the most stable cultivar for grain yield. The highest protein was obtained from 'Kişlik Kirmizi51' (4.6%) across environments. According to stability analysis, 'Firat 87' had the most stable chemical composition. This genotype had a regression coefficient (b(i) = 1) around unity, and deviations from regression values (delta(ij) = 0) around zero. Chemical composition was affected by year in this study. Temperature might have an effect on protein, oil, carbohydrate, fibre and ash. Firat 87 could be recommended for favourable environments. Copyright (c) 2009 Society of Chemical Industry.

Magma oceanography. II - Chemical evolution and crustal formation. [lunar crustal rock fractional crystallization model

NASA Technical Reports Server (NTRS)

Longhi, J.

1977-01-01

A description is presented of an empirical model of fractional crystallization which predicts that slightly modified versions of certain of the proposed whole moon compositions can reproduce the major-element chemistry and mineralogy of most of the primitive highland rocks through equilibrium and fractional crystallization processes combined with accumulation of crystals and trapping of residual liquids. These compositions contain sufficient Al to form a plagioclase-rich crust 60 km thick on top of a magma ocean that was initially no deeper than about 300 km. Implicit in the model are the assumptions that all cooling and crystallization take place at low pressure and that there are no compositional or thermal gradients in the liquid. Discussions of the cooling and crystallization of the proposed magma ocean show these assumptions to be disturbingly naive when applied to the ocean as a whole. However, the model need not be applied to the whole ocean, but only to layers of cooling liquid near the surface.

Trilateral Design and Test Code for Military Bridging and Gap-Crossing Equipment

DTIC Science & Technology

2005-05-01

Property data should be provided for individual lamina and for the ( laminat - ed) composite . The required lamina properties are identified in...Resistance Welding ....... a Brazing ......................... X Machining ..................... a Chemical Composition : Element... Machining .................. b Chemical Composition : Element % Si .................................. 0.2 max Fe

The Bulk Elemental Composition of any Terrestrial Planets in the Alpha Centauri System

NASA Astrophysics Data System (ADS)

Lineweaver, C. H.; Schonberger, B. F. G.; Robles, J. A.

2010-04-01

Based on the devolatilization patterns in the solar system, and on the differences in the chemical compositions of the Sun and Alpha Centauri, we make estimates of the chemical composition of any Earth-like planets in the Alpha Centauri system.

Application of Rhizon Porewater Samplers to Shipboard Operations, IODP Expedition 308, Northeast Gulf of Mexico

NASA Astrophysics Data System (ADS)

Gilhooly, W. P.; Macko, S. A.; Flemings, P. B.

2005-12-01

Pleistocene and Recent sediments within the Brazos-Trinity and Ursa Basins (northwestern Gulf of Mexico) were largely deposited by turbidity currents and have been deformed by a number of mass transport events. The geochemical composition of interstitial waters was determined in order to assess fluid flow within these sediments. Typical porewater sampling resolution, using advanced piston coring and the traditional Manheim squeezer technique, is approximately one sample every other core (20m) with the highest working resolution at one sample every 1.5m. In this study, Rhizon soil moisture samplers were used to attain high-resolution porewater profiles within sea floor surface sediments and for permeable sediments at depth. The small dimensions (2mm x 30mm) and pore-size (1μm) of the devices enable high-frequency placement within a core, specific targeting of the sequence of interest, and do not require sediment removal from the core, or filtering of extracted porewaters. Initial shipboard analyses derived from sediments at the Ursa Basin (Site 1322) indicate a linear decrease in salinity with depth at U1322 where the overpressure gradient is thought to be greatest. The less saline waters with depth lends evidence for potential mixing between deep-seated fluids and low salinity ones derived from the Blue Unit and seawater. Isotopic composition and concentrations of sulfur species (SO4 and H2S) dissolved in porewaters, as well as, ionic compositions (Cl, Na, K, Ca, Mg) and chemical composition of associated sediments (%C, %N, 13C, and 15N) are compared with chemical results obtained with squeezers.

Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

PubMed

Luo, Nan; Xu, Rongle; Yang, Min; Yuan, Xing; Zhong, Hui; Fan, Yaobo

2015-12-01

A novel inorganic-organic composite membrane, namely poly(vinylidene fluoride) PVDF-glass fiber (PGF) composite membrane, was prepared and reinforced by interfacial ultraviolet (UV)-grafting copolymerization to improve the interfacial bonding strength between the membrane layer and the glass fiber. The interfacial polymerization between inorganic-organic interfaces is a chemical cross-linking reaction that depends on the functionalized glass fiber with silane coupling (KH570) as the initiator and the polymer solution with acrylamide monomer (AM) as the grafting block. The Fourier transform infrared spectrometer-attenuated total reflectance (FTIR-ATR) spectra and the energy dispersive X-ray (EDX) pictures of the interface between the glass fiber and polymer matrix confirmed that the AM was grafted to the surface of the glass fiber fabric and that the grafting polymer was successfully embedded in the membrane matrix. The formation mechanisms, permeation, and anti-fouling performance of the PGF composite membrane were measured with different amounts of AM in the doping solutions. The results showed that the grafting composite membrane improved the interfacial bonding strength and permeability, and the peeling strength was improved by 32.6% for PGF composite membranes with an AM concentration at 2wt.%. Copyright © 2015. Published by Elsevier B.V.

Effect of degree of deacetylation of chitosan on adsorption capacity and reusability of chitosan/polyvinyl alcohol/TiO2 nano composite.

PubMed

Habiba, Umma; Joo, Tan Chin; Siddique, Tawsif A; Salleh, Areisman; Ang, Bee Chin; Afifi, Amalina M

2017-11-01

The chitosan/polyvinyl alcohol/TiO 2 composite was synthesized. Two different degrees of deacetylation of chitosan were prepared by hydrolysis to compare the effectiveness of them. The composite was analyzed via field emission scanning electron microscopy, Fourier transform infrared, X-ray diffraction, thermal gravimetric analysis, weight loss test and adsorption study. The FTIR and XRD results proved the interaction among chitosan, PVA and TiO 2 without any chemical reaction. It was found that, chitosan with higher degree of deacetylation has better stability. Furthermore, it also showed that higher DD of chitosan required less time to reach equilibrium for methyl orange. The adsorption followed the pseudo-second-order kinetic model. The Langmuir and Freundlich isotherm models were fitted well for isotherm study. Adsorption capacity was higher for the composite containing chitosan with higher DD. The dye removal rate was independent of the dye's initial concentration. The adsorption capacity was increased with temperature and it was found from reusability test that the composite containing chitosan with higher DD is more reusable. It was notable that adsorption capacity was even after 15 runs. Therefore, chitosan/PVA/TiO 2 composite can be a very useful material for dye removal. Copyright © 2017 Elsevier B.V. All rights reserved.

Oxidation of Boron Nitride in Composites

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.

1998-01-01

Boron nitride (BN) is a prime candidate for fiber coatings in silicon carbide (SiC) fiber-reinforced SiC matrix composites. The properties of BN allow the fiber to impart beneficial composite properties to the matrix, even at elevated temperatures. The problem with BN is that it is readily attacked by oxygen. Although BN is an internal component of the composite, a matrix crack or pore can create a path for hot oxygen to attack the BN. This type of attack is not well understood. A variety of phenomena have been observed. These include borosilicate glass formation, volatilization of the BN, and under some conditions, preservation of the BN. In this study at the NASA Lewis Research Center, a series of BN materials and BN-containing model composites were methodically examined to understand the various issues dealing with the oxidation of BN in composites. Initial studies were done with a series of monolithic BN materials prepared by hot pressing and chemical vapor deposition (CVD). From these studies, we found that BN showed a strong orientation effect in oxidation and was extremely sensitive to the presence of water vapor in the environment. In addition, CVD material deposited at a high temperature showed much better oxidation behavior than CVD material deposited at a lower temperature.

Effects of oxygen plasma treatment power on Aramid fiber III/BMI composite humidity resistance properties

NASA Astrophysics Data System (ADS)

Wang, Jing; Shi, Chen; Feng, Jiayue; Long, Xi; Meng, Lingzhi; Ren, Hang

2018-01-01

The effects of oxygen plasma treatment power on Aramid Fiber III chemical structure and its reinforced bismaleimides (BMI) composite humidity resistance properties were investigated in this work. The aramid fiber III chemical structure under different plasma treatment power were measured by FTIR. The composite bending strength and interlinear shear strength with different plasma treatment power before and after absorption water were tested respectively. The composite rupture morphology was observed by SEM. The FTIR results showed that oxygen plasma treatment do not change the fiber bulk chemical structure. The composite humidity resistance of bending strength and interlinear shear strength are similar for untreated and plasma treated samples. The retention rate of composite bending strength and interlinear shear strength are about 75% and 94%, respectively. The composite rupture mode turns to be the fiber failure after water absorption.

Astrochemical evolution along star formation: overview of the IRAM Large Program ASAI

NASA Astrophysics Data System (ADS)

Lefloch, Bertrand; Bachiller, R.; Ceccarelli, C.; Cernicharo, J.; Codella, C.; Fuente, A.; Kahane, C.; López-Sepulcre, A.; Tafalla, M.; Vastel, C.; Caux, E.; González-García, M.; Bianchi, E.; Gómez-Ruiz, A.; Holdship, J.; Mendoza, E.; Ospina-Zamudio, J.; Podio, L.; Quénard, D.; Roueff, E.; Sakai, N.; Viti, S.; Yamamoto, S.; Yoshida, K.; Favre, C.; Monfredini, T.; Quitián-Lara, H. M.; Marcelino, N.; Boechat-Roberty, H. M.; Cabrit, S.

2018-07-01

Evidence is mounting that the small bodies of our Solar system, such as comets and asteroids, have at least partially inherited their chemical composition from the first phases of the Solar system formation. It then appears that the molecular complexity of these small bodies is most likely related to the earliest stages of star formation. It is therefore important to characterize and to understand how the chemical evolution changes with solar-type protostellar evolution. We present here the Large Program `Astrochemical Surveys At IRAM' (ASAI). Its goal is to carry out unbiased millimetre line surveys between 80 and 272 GHz of a sample of 10 template sources, which fully cover the first stages of the formation process of solar-type stars, from pre-stellar cores to the late protostellar phase. In this paper, we present an overview of the surveys and results obtained from the analysis of the 3 mm band observations. The number of detected main isotopic species barely varies with the evolutionary stage and is found to be very similar to that of massive star-forming regions. The molecular content in O- and C-bearing species allows us to define two chemical classes of envelopes, whose composition is dominated by either (a) a rich content in O-rich complex organic molecules, associated with hot corino sources, or (b) a rich content in hydrocarbons, typical of warm carbon-chain chemistry sources. Overall, a high chemical richness is found to be present already in the initial phases of solar-type star formation.

Comparison of the chemical alteration trajectory of Liriodendron tulipifera L. leaf litter among forests with different earthworm abundance

NASA Astrophysics Data System (ADS)

Filley, Timothy R.; McCormick, Melissa K.; Crow, Susan E.; Szlavecz, Katalin; Whigham, Dennis F.; Johnston, Cliff T.; van den Heuvel, Ronald N.

2008-03-01

To investigate the control of earthworm populations on leaf litter biopolymer decay dynamics, we analyzed the residues of Liriodendron tulipifera L. (tulip poplar) leaves after six months of decay, comparing open surface litter and litter bag experiments among forests with different native and invasive earthworm abundances. Six plots were established in successional tulip poplar forests where sites varied in earthworm density and biomass, roughly 4-10 fold, of nonnative lumbricid species. Analysis of residues by diffuse reflectance Fourier transform infrared spectroscopy and alkaline CuO extraction indicated that open decay in sites with abundant earthworms resulted in residues depleted in cuticular aliphatic and polysaccharide components and enriched in ether-linked lignin relative to open decay in low earthworm abundance plots. Decay within earthworm-excluding litter bags resulted in an increase in aliphatic components relative to initial amendment and similar chemical trajectory to low earthworm open decay experiments. All litter exhibited a decline in cinnamyl-based lignin and an increase in nitrogen content. The influence of earthworm density on the chemical trajectory of litter decay was primarily a manifestation of the physical separation and concentration of lignin-rich and cutin-poor petioles with additional changes promoted by either microorganisms and/or mesofauna resulting in nitrogen addition and polysaccharide loss. These results illustrate how projected increases in invasive earthworm activity in northern North American forests could alter the chemical composition of organic matter in litter residues and potentially organic matter reaching the soil which may result in shifts in the aromatic and aliphatic composition of soils in different systems.

Use of valence band Auger electron spectroscopy to study thin film growth: oxide and diamond-like carbon films

NASA Astrophysics Data System (ADS)

Steffen, H. J.

1994-12-01

It is demonstrated how Auger line shape analysis with factor analysis (FA), least-squares fitting and even simple peak height measurements may provide detailed information about the composition, different chemical states and also defect concentration or crystal order. Advantage is taken of the capability of Auger electron spectroscopy to give valence band structure information with high surface sensitivity and the special aspect of FA to identify and discriminate quantitatively unknown chemical species. Valence band spectra obtained from Ni, Fe, Cr and NiFe40Cr20 during oxygen exposure at room temperature reveal the oxidation process in the initial stage of the thin layer formation. Furthermore, the carbon chemical states that were formed during low energy C(+) and Ne(+) ion irradiation of graphite are delineated and the evolution of an amorphous network with sp3 bonds is disclosed. The analysis represents a unique method to quantify the fraction of sp3-hybridized carbon in diamond-like materials.

High-pressure metallization of FeO and implications for the earth's core

NASA Technical Reports Server (NTRS)

Knittle, Elise; Jeanloz, Raymond

1986-01-01

The phase diagram of FeO has been experimentally determined to pressures of 155 GPa and temperatures of 4000 K using shock-wave and diamond-cell techniques. A metallic phase of FeO is observed at pressures greater than 70 GPa and temperatures exceeding 1000 K. The metallization of FeO at high pressures implies that oxygen can be present as the light alloying element of the earth's outer core, in accord with the geochemical predictions of Ringwood (1977 and 1979). The high pressures necessary for this metallization suggest that the core has acquired its composition well after the initial stages of the earth's accretion. Direct experimental observations at elevated pressures and temperatures indicate that core-forming alloy can react chemically with oxides such as those forming the mantle. The core and mantle may never have reached complete chemical equilibrium, however. If this is the case, the core-mantle boundary is likely to be a zone of active chemical reactions.

Palæo- and Neoproterozoic granitoids and rhyolites from the West Congolian Belt (Gabon, Congo, Cabinda, north Angola): chemical composition and geotectonic implications

NASA Astrophysics Data System (ADS)

Vicat, J.-P.; Pouclet, A.

2000-11-01

Various Palæo- and Neoproterozoic granitoid bodies and related rhyolites are located in the West Congolian Belt. The Palæoproterozoic granitoids, dated around 2 Ga, exhibit an Archæan-type tonalite-trondhjemite-granodiorite suite chemical signature and are related to the Eburnean tectnno-magmatic event. In contrast, Neoproterozoic granitoids and rhyolites, dated around 1 Ga, have chemical geotectonic signatures that range from orogenic to intraplate (Nb-negative anomaly, large ion lithophile element enrichment and high field strength element depletion). However, a late Kibaran orogenic event (1.35-1.00 Ga) is unknown in this area. The Neoproterozoic magmatism is interpreted as a consequence of the initiation of pre-Pan-African rifting, which implies the formation or the reactivation of major crustal strike-slip faults with asthenospheric upwelling and the generation of a thermal anomaly. This thermal anomaly could have been responsible for magmatic processes involving the lower crust, as encountered in post-orogenic environments.

Magnetic BiMn-α phase synthesis prediction: First-principles calculation, thermodynamic modeling and nonequilibrium chemical partitioning

DOE PAGES

Zhou, S. H.; Liu, C.; Yao, Y. X.; ...

2016-04-29

BiMn-α is promising permanent magnet. Due to its peritectic formation feature, there is a synthetic challenge to produce single BiMn-α phase. The objective of this study is to assess driving force for crystalline phase pathways under far-from-equilibrium conditions. First-principles calculations with Hubbard U correction are performed to provide a robust description of the thermodynamic behavior. The energetics associated with various degrees of the chemical partitioning are quantified to predict temperature, magnetic field, and time dependence of the phase selection. By assessing the phase transformation under the influence of the chemical partitioning, temperatures, and cooling rate from our calculations, we suggestmore » that it is possible to synthesize the magnetic BiMn-α compound in a congruent manner by rapid solidification. The external magnetic field enhances the stability of the BiMn-α phase. In conclusion, the compositions of the initial compounds from these highly driven liquids can be far from equilibrium.« less

Evaluating the effect of some mechanical properties for chemically treated various natural fibers reinforced polyester composite

NASA Astrophysics Data System (ADS)

Salih, Wafaa Mahdi; Abdulkader, Niveen Jamal; Salih, Sana Mahdi

2018-05-01

This research were studied the effect of some mechanical properties for composite materials reinforced fiber and prepared from material (polyester with various natural fibers) then studied the effect of chemical treatment on the same fiber immerse in 10% NaOH solution for half an hour and then compared, the results of the same test of composite materials without and with chemical treatment and the results proved that there is a clear effect when treat the fiber compared to non-chemical treatment of the fibers also noted that hemp fibers loaded the stress higher than other fibers for both cases to distinguish them that the hemp fiber has continuous fibers either the other fibers are characterized by the type of cross linking or chopped types in tensile test, and the results of the same test of composite materials without and with chemical treatment and the results proved that the hardness of the fiber composite while the treated fiber composite samples better than the untreated fiber, and from the figures the palm leaf has the highest value than lufa fiber, hemp fiber and the smallest value is in sisal fiber because of the nature of formation fibers materials.

Computing Properties Of Chemical Mixtures At Equilibrium

NASA Technical Reports Server (NTRS)

Mcbride, B. J.; Gordon, S.

1995-01-01

Scientists and engineers need data on chemical equilibrium compositions to calculate theoretical thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93 is general program that calculates chemical equilibrium compositions and properties of mixtures for any chemical system for which thermodynamic data are available. Includes thermodynamic data for more than 1,300 gaseous and condensed species and thermal-transport data for 151 gases. Written in FORTRAN 77.

Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1991-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

DOEpatents

Tiegs, T.N.; Lindemer, T.B.

1991-02-19

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Ceramic composites reinforced with modified silicon carbide whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1990-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Global two dimensional chemistry model and simulation of atmospheric chemical composition

NASA Astrophysics Data System (ADS)

Zhang, Renjian; Wang, Mingxing; Zeng, Qingcun

2000-03-01

A global two-dimensional zonally averaged chemistry model is developed to study the chemi-cal composition of atmosphere. The region of the model is from 90°S to 90°N and from the ground to the altitude of 20 km with a resolution of 5° x 1 km. The wind field is residual circulation calcu-lated from diabatic rate. 34 species and 104 chemical and photochemical reactions are considered in the model. The sources of CH4, CO and NOx, which are divided into seasonal sources and non-seasonal sources, are parameterized as a function of latitude and time. The chemical composi-tion of atmosphere was simulated with emission level of CH4, CO and NOx in 1990. The results are compared with observations and other model results, showing that the model is successful to simu-late the atmospheric chemical composition and distribution of CH4.

A Statistical Approach for Judging Stability of Whole Mixture Chemical Composition over Time for Highly Complex Disinfection By-Product Mixtures from EPA's Four Lab Study

EPA Science Inventory

Chemical characterization of complex mixtures and assessment of stability over time of the characterized chemicals is crucial both to characterize exposure and to use data from one mixture as a surrogate for other similar mixtures. The chemical composition of test mixtures can va...

Cactus stem (Opuntia ficus-indica Mill): anatomy, physiology and chemical composition with emphasis on its biofunctional properties.

PubMed

Ventura-Aguilar, Rosa Isela; Bosquez-Molina, Elsa; Bautista-Baños, Silvia; Rivera-Cabrera, Fernando

2017-12-01

Cactus stem (Opuntia ficus-indica Mill) is native to Mesoamerica and marketed in different forms such as fresh, frozen or pre-cooked. Worldwide, this vegetable is recognized for its pharmaceutical actions, including its antioxidant, diuretic, anticarcinogenic, anti-inflammatory, anti-diabetic, and anti-hypercholesterolemic properties, as well as their antiviral and antispermatogenic effects. However, not all of these properties have been associated with its chemical composition; therefore, this review aims to present and integrate information available on the physiology and anatomy of cactus stem and its chemical composition, focusing on some of the many factors that determine its biofunctionality. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Diffusion of multi-isotopic chemical species in molten silicates

NASA Astrophysics Data System (ADS)

Watkins, James M.; Liang, Yan; Richter, Frank; Ryerson, Frederick J.; DePaolo, Donald J.

2014-08-01

Diffusion experiments in a simplified Na2O-CaO-SiO2 liquid system are used to develop a general formulation for the fractionation of Ca isotopes during liquid-phase diffusion. Although chemical diffusion is a well-studied process, the mathematical description of the effects of diffusion on the separate isotopes of a chemical element is surprisingly underdeveloped and uncertain. Kinetic theory predicts a mass dependence on isotopic mobility, but it is unknown how this translates into a mass dependence on effective binary diffusion coefficients, or more generally, the chemical diffusion coefficients that are housed in a multicomponent diffusion matrix. Our experiments are designed to measure Ca mobility, effective binary diffusion coefficients, the multicomponent diffusion matrix, and the effects of chemical diffusion on Ca isotopes in a liquid of single composition. We carried out two chemical diffusion experiments and one self-diffusion experiment, all at 1250 °C and 0.7 GPa and using a bulk composition for which other information is available from the literature. The self-diffusion experiment is used to determine the mobility of Ca in the absence of diffusive fluxes of other liquid components. The chemical diffusion experiments are designed to determine the effect on Ca isotope fractionation of changing the counter-diffusing component from fast-diffusing Na2O to slow-diffusing SiO2. When Na2O is the main counter-diffusing species, CaO diffusion is fast and larger Ca isotopic effects are generated. When SiO2 is the main counter-diffusing species, CaO diffusion is slow and smaller Ca isotopic effects are observed. In both experiments, the liquid is initially isotopically homogeneous, and during the experiment Ca isotopes become fractionated by diffusion. The results are used as a test of a new general expression for the diffusion of isotopes in a multicomponent liquid system that accounts for both self diffusion and the effects of counter-diffusing species. Our results show that (1) diffusive isotopic fractionations depend on the direction of diffusion in composition space, (2) diffusive isotopic fractionations scale with effective binary diffusion coefficient, as previously noted by Watkins et al. (2011), (3) self-diffusion is not decoupled from chemical diffusion, (4) self diffusion can be faster than or slower than chemical diffusion and (5) off-diagonal terms in the chemical diffusion matrix have isotopic mass-dependence. The results imply that relatively large isotopic fractionations can be generated by multicomponent diffusion even in the absence of large concentration gradients of the diffusing element. The new formulations for isotope diffusion can be tested with further experimentation and provide an improved framework for interpreting mass-dependent isotopic variations in natural liquids.

Chemically Tunable, All-Inorganic-Based White-Light Emitting 0D-1D Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Shiyu; Zhou, Yuchen; Zou, Shihui

In this study, we initially created one-dimensional (1D) Mn2+-doped ZnS (ZnS: Mn) nanowires (NWs) with a unique optical signature. Specifically, these nanostructures coupled (i) ZnS defect-related self-activated emission spanning from wavelengths of 400 nm to 500 nm with (ii) Mn2+ dopant-induced emission centered at ~580 nm. These doped ZnS nanostructures were initially fabricated for the first time via a template-based co-precipitation approach followed by a post-synthesis annealing process. We subsequently formed novel 1D - zero-dimensional (0D) heterostructures incorporating ZnS: Mn NWs and AET (2-amino-ethanethiol) - CdSe quantum dots (QDs) by assembling annealed ZnS: Mn NWs with AET- capped CdSe QDsmore » as building blocks via a simple technique, involving physical sonication and stirring. Optical analyses of our heterostructures were consistent with charge (hole) and energy transfer-induced quenching of ZnS self-activated emission coupled with hole transfer-related quenching of Mn2+ emission by the QDs. The CdSe QD emission itself was impacted by competing charge (electron) and energy transfer processes occurring between the underlying ZnS host and the immobilized CdSe QDs. Chromaticity analysis revealed the significance of controlling both QD coverage density and Mn2+ dopant ratios in predictably influencing the observed color of our all-inorganic heterostructures. For example, white-light emitting behavior was especially prominent in composites, simultaneously characterized by (i) a 2.22% Mn2+ doping level and (ii) a molar compositional ratio of [ZnS: Mn2+]: [AET-capped CdSe QDs]) of 1: 1.5. Moreover, using these independent chemical ‘knobs’, we have been able to reliably tune for a significant shift within our composites from ‘cold-white’ (9604 K) to ‘warm-white’ (4383 K) light emission.« less

Chemically Tunable, All-Inorganic-Based White-Light Emitting 0D-1D Heterostructures

DOE PAGES

Yue, Shiyu; Zhou, Yuchen; Zou, Shihui; ...

2017-08-21

In this study, we initially created one-dimensional (1D) Mn2+-doped ZnS (ZnS: Mn) nanowires (NWs) with a unique optical signature. Specifically, these nanostructures coupled (i) ZnS defect-related self-activated emission spanning from wavelengths of 400 nm to 500 nm with (ii) Mn2+ dopant-induced emission centered at ~580 nm. These doped ZnS nanostructures were initially fabricated for the first time via a template-based co-precipitation approach followed by a post-synthesis annealing process. We subsequently formed novel 1D - zero-dimensional (0D) heterostructures incorporating ZnS: Mn NWs and AET (2-amino-ethanethiol) - CdSe quantum dots (QDs) by assembling annealed ZnS: Mn NWs with AET- capped CdSe QDsmore » as building blocks via a simple technique, involving physical sonication and stirring. Optical analyses of our heterostructures were consistent with charge (hole) and energy transfer-induced quenching of ZnS self-activated emission coupled with hole transfer-related quenching of Mn2+ emission by the QDs. The CdSe QD emission itself was impacted by competing charge (electron) and energy transfer processes occurring between the underlying ZnS host and the immobilized CdSe QDs. Chromaticity analysis revealed the significance of controlling both QD coverage density and Mn2+ dopant ratios in predictably influencing the observed color of our all-inorganic heterostructures. For example, white-light emitting behavior was especially prominent in composites, simultaneously characterized by (i) a 2.22% Mn2+ doping level and (ii) a molar compositional ratio of [ZnS: Mn2+]: [AET-capped CdSe QDs]) of 1: 1.5. Moreover, using these independent chemical ‘knobs’, we have been able to reliably tune for a significant shift within our composites from ‘cold-white’ (9604 K) to ‘warm-white’ (4383 K) light emission.« less

Effect of neutron irradiation at low temperature on the embrittlement of the reduced-activation ferritic steels

NASA Astrophysics Data System (ADS)

Rybin, V. V.; Kursevich, I. P.; Lapin, A. N.

1998-10-01

Effects of neutron irradiation to fluence of 2.0 × 10 24 n/m 2 ( E > 0.5 MeV) in temperature range 70-300°C on mechanical properties and structure of the experimental reduced-activation ferritic 0.1%C-(2.5-12)%Cr-(1-2)%W-(0.2-0.7)%V alloys were investigated. The steels were studied in different initial structural conditions obtained by changing the modes of heat treatments. Effect of neutron irradiation estimated by a shift in ductile-brittle transition temperature (ΔDBTT) and reduction of upper shelf energy (ΔUSE) highly depends on both irradiation condition and steel chemical composition and structure. For the steel with optimum chemical composition (9Cr-1.5WV) after irradiation to 2 × 10 24 n/m 2 ( E ⩾ 0.5 MeV) at 280°C the ΔDBTT does not exceed 25°C. The shift in DBTT increased from 35°C to 110°C for the 8Cr-1.5WV steel at a decrease in irradiation temperature from 300°C to 70°C. The CCT diagrams are presented for several reduced-activated steels.

Calcite precipitates in Slovenian bottled waters.

PubMed

Stanič, Tamara Ferjan; Miler, Miloš; Brenčič, Mihael; Gosar, Mateja

2017-06-01

Storage of bottled waters in varying ambient conditions affects its characteristics. Different storage conditions cause changes in the initial chemical composition of bottled water which lead to the occurrence of precipitates with various morphologies. In order to assess the relationship between water composition, storage conditions and precipitate morphology, a study of four brands of Slovenian bottled water stored in PET bottles was carried out. Chemical analyses of the main ions and measurements of the physical properties of water samples were performed before and after storage of water samples at different ambient conditions. SEM/EDS analysis of precipitates was performed after elapsed storage time. The results show that the presence of Mg 2+ , SO 4 2- , SiO 2 , Al, Mn and other impurities such as K + , Na + , Ba and Sr in the water controlled precipitate morphology by inhibiting crystal growth and leading to elongated rhombohedral calcite crystal forms which exhibit furrowed surfaces and calcite rosettes. Different storage conditions, however, affected the number of crystallization nuclei and size of calcite crystals. Hollow calcite spheres composed of cleavage rhombohedrons formed in the water with variable storage conditions by a combination of evaporation and precipitation of water droplets during high temperatures or by the bubble templating method.

Antifouling Thin-Film Composite Membranes by Controlled Architecture of Zwitterionic Polymer Brush Layer.

PubMed

Liu, Caihong; Lee, Jongho; Ma, Jun; Elimelech, Menachem

2017-02-21

In this study, we demonstrate a highly antifouling thin-film composite (TFC) membrane by grafting a zwitterionic polymer brush via atom-transfer radical-polymerization (ATRP), a controlled, environmentally benign chemical process. Initiator molecules for polymerization were immobilized on the membrane surface by bioinspired catechol chemistry, leading to the grafting of a dense zwitterionic polymer brush layer. Surface characterization revealed that the modified membrane exhibits reduced surface roughness, enhanced hydrophilicity, and lower surface charge. Chemical force microscopy demonstrated that the modified membrane displayed foulant-membrane interaction forces that were 1 order of magnitude smaller than those of the pristine TFC membrane. The excellent fouling resistance imparted by the zwitterionic brush layer was further demonstrated by significantly reduced adsorption of proteins and bacteria. In addition, forward osmosis fouling experiments with a feed solution containing a mixture of organic foulants (bovine-serum albumin, alginate, and natural organic matter) indicated that the modified membrane exhibited significantly lower water flux decline compared to the pristine TFC membrane. The controlled architecture of the zwitterionic polymer brush via ATRP has the potential for a facile antifouling modification of a wide range of water treatment membranes without compromising intrinsic transport properties.

Understanding Chemistry-Specific Fuel Differences at a Constant RON in a Boosted SI Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szybist, James P.; Splitter, Derek A.

The goal of the US Department of Energy Co-Optimization of Fuels and Engines (Co-Optima) initiative is to accelerate the development of advanced fuels and engines for higher efficiency and lower emissions. A guiding principle of this initiative is the central fuel properties hypothesis (CFPH), which states that fuel properties provide an indication of a fuel’s performance, regardless of its chemical composition. This is an important consideration for Co-Optima because many of the fuels under consideration are from bio-derived sources with chemical compositions that are unconventional relative to petroleum-derived gasoline or ethanol. In this study, we investigated a total of sevenmore » fuels in a spark ignition engine under boosted operating conditions to determine whether knock propensity is predicted by fuel antiknock metrics: antiknock index (AKI), research octane number (RON), and octane index (OI). Six of these fuels have a constant RON value but otherwise represent a wide range of fuel properties and chemistry. Consistent with previous studies, we found that OI was a much better predictor of knock propensity that either AKI or RON. However, we also found that there were significant fuel-specific deviations from the OI predictions. Combustion analysis provided insight that fuel kinetic complexities, including the presence of pre-spark heat release, likely limits the ability of standardized tests and metrics to accurately predict knocking tendency at all operating conditions. While limitations of OI were revealed in this study, we found that fuels with unconventional chemistry, in particular esters and ethers, behaved in accordance with CFPH as well as petroleum-derived fuels.« less

Understanding Chemistry-Specific Fuel Differences at a Constant RON in a Boosted SI Engine

DOE PAGES

Szybist, James P.; Splitter, Derek A.

2018-01-02

The goal of the US Department of Energy Co-Optimization of Fuels and Engines (Co-Optima) initiative is to accelerate the development of advanced fuels and engines for higher efficiency and lower emissions. A guiding principle of this initiative is the central fuel properties hypothesis (CFPH), which states that fuel properties provide an indication of a fuel’s performance, regardless of its chemical composition. This is an important consideration for Co-Optima because many of the fuels under consideration are from bio-derived sources with chemical compositions that are unconventional relative to petroleum-derived gasoline or ethanol. In this study, we investigated a total of sevenmore » fuels in a spark ignition engine under boosted operating conditions to determine whether knock propensity is predicted by fuel antiknock metrics: antiknock index (AKI), research octane number (RON), and octane index (OI). Six of these fuels have a constant RON value but otherwise represent a wide range of fuel properties and chemistry. Consistent with previous studies, we found that OI was a much better predictor of knock propensity that either AKI or RON. However, we also found that there were significant fuel-specific deviations from the OI predictions. Combustion analysis provided insight that fuel kinetic complexities, including the presence of pre-spark heat release, likely limits the ability of standardized tests and metrics to accurately predict knocking tendency at all operating conditions. While limitations of OI were revealed in this study, we found that fuels with unconventional chemistry, in particular esters and ethers, behaved in accordance with CFPH as well as petroleum-derived fuels.« less

Unravelling the mechanisms for plant survival on gypsum soils: an analysis of the chemical composition of gypsum plants from Turkey.

PubMed

Bolukbasi, A; Kurt, L; Palacio, S

2016-03-01

Depending on their specificity to gypsum, plants can be classified as gypsophiles (gypsum exclusive) and gypsovags (non-exclusive). The former may further be segregated into wide and narrow gypsophiles, depending on the breadth of their distribution area. Narrow gypsum endemics have a putative similar chemical composition to plants non-exclusive to gypsum (i.e. gypsovags), which may indicate their similar ecological strategy as stress-tolerant plant refugees on gypsum. However, this hypothesis awaits testing in different regions of the world. We compared the chemical composition of four narrow gypsum endemics, one widely distributed gypsophile and six gypsovags from Turkey. Further, we explored the plasticity in chemical composition of Turkish gypsovags growing on high- and low-gypsum content soils. Differences were explored with multivariate analyses (RDA) and mixed models (REML). Narrow gypsum endemics segregated from gypsovags in their chemical composition according to RDAs (mainly due to higher K and ash content in the former). Nevertheless, differences were small and disappeared when different nutrients were analysed individually. All the gypsovags studied accumulated more S and ash when growing on high-gypsum than on low-gypsum soils. Similar to narrow gypsum endemics from other regions of the world, most local gypsum endemics from Turkey show a similar chemical composition to gypsovags. This may indicate a shared ecological strategy as stress-tolerant plants not specifically adapted to gypsum. Nevertheless, the narrow gypsum endemic Gypsophila parva showed a chemical composition typical of gypsum specialists, indicating that various strategies are feasible within narrowly distributed gypsophiles. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

Method for the elucidation of the elemental composition of low molecular mass chemicals using exact masses of product ions and neutral losses: application to environmental chemicals measured by liquid chromatography with hybrid quadrupole/time-of-flight mass spectrometry.

PubMed

Suzuki, Shigeru; Ishii, Tetsuko; Yasuhara, Akio; Sakai, Shinichi

2005-01-01

A method for elucidating the elemental compositions of low molecular weight chemicals, based primarily on mass measurements made using liquid chromatography (LC) with time-of-flight mass spectrometry (TOFMS) and quadrupole/time-of-flight mass spectrometry (LC/QTOFMS), was developed and tested for 113 chemicals of environmental interest with molecular masses up to approximately 400 Da. As the algorithm incorporating the method is not affected by differences in the instrument used, or by the ionization method and other ionization conditions, the method is useful not only for LC/TOFMS, but also for all kinds of mass spectra measured with higher accuracy and precision (uncertainties of a few mDa) employing all ionization methods and on-line separation techniques. The method involves calculating candidate compositions for intact ionized molecules (ionized forms of the sample molecule that have lost or gained no more than a proton, i.e., [M+H](+) or [M-H](-)) as well as for fragment ions and corresponding neutral losses, and eliminating those atomic compositions for the molecules that are inconsistent with the corresponding candidate compositions of fragment ions and neutral losses. Candidate compositions were calculated for the measured masses of the intact ionized molecules and of the fragment ions and corresponding neutral losses, using mass uncertainties of 2 and 5 mDa, respectively. Compositions proposed for the ionized molecule that did not correspond to the sum of the compositions of a candidate fragment ion and its corresponding neutral loss were discarded. One, 2-5, 6-10, 11-20, and >20 candidate compositions were found for 65%, 39%, 1%, 1%, and 0%, respectively, for the 124 ionized molecules formed from the 113 chemicals tested (both positive and negative ions were obtained from 11 of the chemicals). However, no candidate composition was found for 2% of the test cases (i.e., 3 chemicals), for each of which the measured mass of one of the product ions was in error by 5-6.7 mDa.

Absolute parameters and chemical composition of the binary star OU Gem

NASA Astrophysics Data System (ADS)

Glazunova, L. V.; Mishenina, T. V.; Soubiran, C.; Kovtyukh, V. V.

2014-10-01

The absolute parameters and chemical composition of the BY Dra-type spectroscopic binary OU Gem (HD 45088) were determined on the basis of 10 high-resolution spectra. A new orbital solution of the binary system was determined, the binary ephemerides were specified, and the main physical and atmospheric parameters of the binary components were obtained. The chemical composition of both components was estimated for the first time for the stars of such type.

Pulsed plasma chemical synthesis of carbon-containing titanium and silicon oxide based nanocomposite

NASA Astrophysics Data System (ADS)

Kholodnaya, Galina; Sazonov, Roman; Ponomarev, Denis; Zhirkov, Igor

2018-03-01

The paper presents the results of the experimental investigation of the physical and chemical properties of the TixSiyCzOw composite nanopowders, which were first obtained using a pulsed plasma chemical method. The pulsed plasma chemical synthesis was achieved using a technological electron accelerator (TEA-500). The parameters of the electron beam are as follows: 400-450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. The main physical and chemical properties of the obtained composites were studied (morphology, chemical, elemental and phase composition). The morphology of the TixSiyCzOw composites is multiform. There are large round particles, with an average size of above 150 nm. Besides, there are small particles (an average size is in the range of 15-40 nm). The morphology of small particles is in the form of crystallites. In the TixSiyCzOw synthesised composite, the peak with a maximum of 946 cm-1 was registered. The presence of IR radiation in this region of the spectrum is typical for the deformation of atomic oscillations in the Si‒О‒Ti bond, which indicates the formation of the solid solution. The composites consist of two crystal phases - anatase and rutile. The prevailing phase of the crystal structure is rutile.

The simulation method of chemical composition of vermicular graphite iron on the basis of genetic algorithm

NASA Astrophysics Data System (ADS)

Yusupov, L. R.; Klochkova, K. V.; Simonova, L. A.

2017-09-01

The paper presents a methodology of modeling the chemical composition of the composite material via genetic algorithm for optimization of the manufacturing process of products. The paper presents algorithms of methods based on intelligent system of vermicular graphite iron design

Chemical composition of fat and oil products

USDA-ARS?s Scientific Manuscript database

Fats and oils are an important dietary component, and contribute to the nutritional and sensory quality of foods. This chapter focuses on the chemical composition of fats and oils, and how these compositions affect the functional properties of fats and oils in foods. The focus will remain on the mos...

Dynamics of shearing force and its correlations with chemical compositions and in vitro dry matter digestibility of stylo (Stylosanthes guianensis) stem.

PubMed

Zi, Xuejuan; Li, Mao; Zhou, Hanlin; Tang, Jun; Cai, Yimin

2017-12-01

The study explored the dynamics of shearing force and its correlation with chemical compositions and in vitro dry matter digestibility (IVDMD) of stylo. The shearing force, diameter, linear density, chemical composition, and IVDMD of different height stylo stem were investigated. Linear regression analysis was done to determine the relationships between the shearing force and cut height, diameter, chemical composition, or IVDMD. The results showed that shearing force of stylo stem increased with plant height increasing and the crude protein (CP) content and IVDMD decreased but fiber content increased over time, resulting in decreased forage value. In addition, tall stem had greater shearing force than short stem. Moreover, shearing force is positively correlated with stem diameter, linear density and fiber fraction, but negatively correlated with CP content and IVDMD. Overall, shearing force is an indicator more direct, easier and faster to measure than chemical composition and digestibility for evaluation of forage nutritive value related to animal performance. Therefore, it can be used to evaluate the nutritive value of stylo.

Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

NASA Astrophysics Data System (ADS)

Rudnick, R. L.; Liu, X. M.

2012-04-01

The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" that is the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems point to the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 1×10^10 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

Degradation of 2,4,6-Trichlorophenol and hydrogen production simultaneously by TiO2 nanotubes/graphene composite

NASA Astrophysics Data System (ADS)

Slamet, Raudina

2017-11-01

Industrial waters in coal pyrolysis process, synthetic chemicals and oil and gas process contain phenol derivatives that are dangerous to the environment and needs to be removed, one of them is 2,4,6-Trichlorophenol. Degradation of 2,4,6-Trichlorophenol and hydrogen production simultaneously have been investigated using TiNT/Graphene composite at various graphene loading and initial concentration of 2,4,6-Trichlorophenol. Optimal graphene loading of 0.6 wt% was obtained in the simultaneous system with 89% elimination of 2,4,6-Trichlorophenol and 986 µmol of hydrogen production. Test results showed that addition of 2,4,6-Trichlorophenol would subsequently increased 2,4,6-Trichlorophenol conversion and enhanced hydrogen production linearly. 2.7 times greater hydrogen production was found in addition of 50 ppm 2,4,6-Trichlorophenol.

Nature and composition of fat bloom from palm kernel stearin and hydrogenated palm kernel stearin compound chocolates.

PubMed

Smith, Kevin W; Cain, Fred W; Talbot, Geoff

2004-08-25

Palm kernel stearin and hydrogenated palm kernel stearin can be used to prepare compound chocolate bars or coatings. The objective of this study was to characterize the chemical composition, polymorphism, and melting behavior of the bloom that develops on bars of compound chocolate prepared using these fats. Bars were stored for 1 year at 15, 20, or 25 degrees C. At 15 and 20 degrees C the bloom was enriched in cocoa butter triacylglycerols, with respect to the main fat phase, whereas at 25 degrees C the enrichment was with palm kernel triacylglycerols. The bloom consisted principally of solid fat and was sharper melting than was the fat in the chocolate. Polymorphic transitions from the initial beta' phase to the beta phase accompanied the formation of bloom at all temperatures.

Adsorption of hexavalent chromium onto sisal pulp/polypyrrole composites

NASA Astrophysics Data System (ADS)

Tan, Y. Y.; Wei, C.; Gong, Y. Y.; Du, L. L.

2017-02-01

Sisal pulp/polypyrrole composites(SP/PPy) utilized for the removal of hexavalent chromium [Cr(VI)] from wastewater, were prepared via in-situ chemical oxidation polymerization approach. The structure and morphology of the SP/PPy were analyzed by polarizing optical microscopy (POM), field-emission scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the results indicated SP could be efficient dispersion of PPy. The hexavalent chromium adsorption results indicate adsorption capacity of the SP/PPy were dependent on the initial pH, with an optimum pH of 2.0. The sorption kinetic data fitted well to the pseudo-second order model and isotherm data fitted well to the Langmuir isotherm model. The maximum adsorption capacity determined from the Langmuir isotherm is 336.70 mg/g at 25° C.

Self-assembly and graft polymerization route to Monodispersed Fe3O4@SiO2--polyaniline core-shell composite nanoparticles: physical properties.

PubMed

Reddy, Kakarla Raghava; Lee, Kwang-Pill; Kim, Ju Young; Lee, Youngil

2008-11-01

This study describes the synthesis of monodispersed core-shell composites of silica-modified magnetic nanoparticles and conducting polyaniline by self-assembly and graft polymerization. Magnetic ferrite nanoparticles (Fe3O4) were prepared by coprecipitation of Fe+2 and Fe+3 ions in alkaline solution, and then silananized. The silanation of magnetic particles (Fe3O4@SiO2) was carried out using 3-bromopropyltrichlorosilane (BPTS) as the coupling agent. FT-IR spectra indicated the presence of Fe--O--Si chemical bonds in Fe3O4@SiO2. Core-shell type nanocomposites (Fe3O4@SiO2/PANI) were prepared by grafting polyaniline (PANI) on the surface of silanized magnetic particles through surface initiated in-situ chemical oxidative graft polymerization. The nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared (FTIR) spectra, UV-visible spectroscopy, photoluminescence (PL) spectra, electrical conductivity and magnetic characteristics. HRTEM images of the nanocomposites revealed that the silica-modified magnetic particles made up the core while PANI made up the shell. The XPS spectrum revealed the presence of silica in the composites, and the XRD results showed that the composites were more crystalline than pure PANI. PL spectra show that composites exhibit photoluminescent property. Conductivity of the composites (6.2 to 9.4 x 10(-2) S/cm) was higher than that of pristine PANI (3.7 x 10(-3) S/cm). The nanocomposites exhibited superparamagnetism. Formation mechanism of the core-shell structured nanocomposites and the effect of modified magnetic nanoparticles on the electro-magnetic properties of the Fe3O4@SiO2/PANI nanocomposites are also investigated. This method provides a new strategy for the generation of multi-functional nanocomposites that composed of other conducting polymers and metal nanoparticles.

Gas-Grain Chemical Models: Inclusion of a Grain Size Distribution and a Study Of Young Stellar Objects in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Pauly, Tyler Andrew

2017-06-01

Computational models of interstellar gas-grain chemistry have aided in our understanding of star-forming regions. Chemical kinetics models rely on a network of chemical reactions and a set of physical conditions in which atomic and molecular species are allowed to form and react. We replace the canonical single grain-size in our chemical model MAGICKAL with a grain size distribution and analyze the effects on the chemical composition of the gas and grain surface in quiescent and collapsing dark cloud models. We find that a grain size distribution coupled with a temperature distribution across grain sizes can significantly affect the bulk ice composition when dust temperatures fall near critical values related to the surface binding energies of common interstellar chemical species. We then apply the updated model to a study of ice formation in the cold envelopes surrounding massive young stellar objects in the Magellanic Clouds. The Magellanic Clouds are local satellite galaxies of the Milky Way, and they provide nearby environments to study star formation at low metallicity. We expand the model calculation of dust temperature to include a treatment for increased interstellar radiation field intensity; we vary the radiation field to model the elevated dust temperatures observed in the Magellanic Clouds. We also adjust the initial elemental abundances used in the model, guided by observations of Magellanic Cloud HII regions. We are able to reproduce the relative ice fractions observed, indicating that metal depletion and elevated grain temperature are important drivers of the envelope ice composition. The observed shortfall in CO in Small Magellanic Cloud sources can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH 3OH abundance is found to be enhanced (relative to total carbon abundance) in low-metallicity models, providing seed material for complex organic molecule formation. We conclude with a preliminary study of the recently discovered hot core in the Large Magellanic Cloud; we create a grid of models to simulate hot core formation in Magellanic Cloud environments, comparing them to models and observations of well-characterized galactic counterparts.

Hydrothermal replacement of biogenic and abiogenic aragonite by Mg-carbonates - Relation between textural control on effective element fluxes and resulting carbonate phase

NASA Astrophysics Data System (ADS)

Jonas, Laura; Müller, Thomas; Dohmen, Ralf; Immenhauser, Adrian; Putlitz, Benita

2017-01-01

Dolomitization, i.e., the secondary replacement of calcite or aragonite (CaCO3) by dolomite (CaMg[CO3]2), is one of the most volumetrically important carbonate diagenetic processes. It occurs under near surface and shallow burial conditions and can significantly modify rock properties through changes in porosity and permeability. Dolomitization fronts are directly coupled to fluid pathways, which may be related to the initial porosity/permeability of the precursor limestone, an existing fault network or secondary porosity/permeability created through the replacement reaction. In this study, the textural control on the replacement of biogenic and abiogenic aragonite by Mg-carbonates, that are typical precursor phases in the dolomitization process, was experimentally studied under hydrothermal conditions. Aragonite samples with different textural and microstructural properties exhibiting a compact (inorganic aragonite single crystal), an intermediate (bivalve shell of Arctica islandica) and open porous structure (skeleton of coral Porites sp.) were reacted with a solution of 0.9 M MgCl2 and 0.015 M SrCl2 at 200 °C. The replacement of aragonite by a Ca-bearing magnesite and a Mg-Ca carbonate of non-stoichiometric dolomitic composition takes place via a dissolution-precipitation process and leads to the formation of a porous reaction front that progressively replaces the aragonite precursor. The reaction leads to the development of porosity within the reaction front and distinctive microstructures such as gaps and cavities at the reaction interface. The newly formed reaction rim consists of chemically distinct phases separated by sharp boundaries. It was found that the number of phases and their chemical variation decreases with increasing initial porosity and reactive surface area. This observation is explained by variations in effective element fluxes that result in differential chemical gradients in the fluid within the pore space of the reaction rim. Observed reaction rates are highest for the replacement of the initially highly porous coral and lowest for the compact structure of a single aragonite crystal. Therefore, the reaction progress equally depends on effective element fluxes between the fluid at the reaction interface and the bulk solution surrounding the test material as well as the reactive surface area. This study demonstrates that the textural and microstructural properties of the parent material have a significant influence on the chemical composition of the product phase. Moreover, our data highlight the importance of effective fluid-mediated element exchange between the fluid at the reaction interface and the bulk solution controlled by the local microstructure.

A combined electrocoagulation-sorption process applied to mixed industrial wastewater.

PubMed

Linares-Hernández, Ivonne; Barrera-Díaz, Carlos; Roa-Morales, Gabriela; Bilyeu, Bryan; Ureña-Núñez, Fernando

2007-06-01

The removal of organic pollutants from a highly complex industrial wastewater by a aluminium electrocoagulation process coupled with biosorption was evaluated. Under optimal conditions of pH 8 and 45.45 Am(-2) current density, the electrochemical method yields a very effective reduction of all organic pollutants, this reduction was enhanced when the biosorption treatment was applied as a polishing step. Treatment reduced chemical oxygen demand (COD) by 84%, biochemical oxygen demand (BOD(5)) by 78%, color by 97%, turbidity by 98% and fecal coliforms by 99%. The chemical species formed in aqueous solution were determined. The initial and final pollutant levels in the wastewater were monitored using UV-vis spectrometry and cyclic voltammetry. Finally, the morphology and elemental composition of the biosorbent was characterized with scanning electron microscopy (SEM) and energy dispersion spectra (EDS).

The submarine volcano eruption at the island of El Hierro: physical-chemical perturbation and biological response

PubMed Central

Fraile-Nuez, E.; González-Dávila, M.; Santana-Casiano, J. M.; Arístegui, J.; Alonso-González, I. J.; Hernández-León, S.; Blanco, M. J.; Rodríguez-Santana, A.; Hernández-Guerra, A.; Gelado-Caballero, M. D.; Eugenio, F.; Marcello, J.; de Armas, D.; Domínguez-Yanes, J. F.; Montero, M. F.; Laetsch, D. R.; Vélez-Belchí, P.; Ramos, A.; Ariza, A. V.; Comas-Rodríguez, I.; Benítez-Barrios, V. M.

2012-01-01

On October 10 2011 an underwater eruption gave rise to a novel shallow submarine volcano south of the island of El Hierro, Canary Islands, Spain. During the eruption large quantities of mantle-derived gases, solutes and heat were released into the surrounding waters. In order to monitor the impact of the eruption on the marine ecosystem, periodic multidisciplinary cruises were carried out. Here, we present an initial report of the extreme physical-chemical perturbations caused by this event, comprising thermal changes, water acidification, deoxygenation and metal-enrichment, which resulted in significant alterations to the activity and composition of local plankton communities. Our findings highlight the potential role of this eruptive process as a natural ecosystem-scale experiment for the study of extreme effects of global change stressors on marine environments. PMID:22768379

Chemical Vapor Deposition at High Pressure in a Microgravity Environment

NASA Technical Reports Server (NTRS)

McCall, Sonya; Bachmann, Klaus; LeSure, Stacie; Sukidi, Nkadi; Wang, Fuchao

1999-01-01

In this paper we present an evaluation of critical requirements of organometallic chemical vapor deposition (OMCVD) at elevated pressure for a channel flow reactor in a microgravity environment. The objective of using high pressure is to maintain single-phase surface composition for materials that have high thermal decomposition pressure at their optimum growth temperature. Access to microgravity is needed to maintain conditions of laminar flow, which is essential for process analysis. Based on ground based observations we present an optimized reactor design for OMCVD at high pressure and reduced gravity. Also, we discuss non-intrusive real-time optical monitoring of flow dynamics coupled to homogeneous gas phase reactions, transport and surface processes. While suborbital flights may suffice for studies of initial stages of heteroepitaxy experiments in space are essential for a complete evaluation of steady-state growth.

Chemical similarity and local community assembly in the species rich tropical genus Piper.

PubMed

Salazar, Diego; Jaramillo, M Alejandra; Marquis, Robert J

2016-11-01

Community ecologists have strived to find mechanisms that mediate the assembly of natural communities. Recent evidence suggests that natural enemies could play an important role in the assembly of hyper-diverse tropical plant systems. Classic ecological theory predicts that in order for coexistence to occur, species differences must be maximized across biologically important niche dimensions. For plant-herbivore interactions, it has been recently suggested that, within a particular community, plant species that maximize the difference in chemical defense profiles compared to neighboring taxa will have a relative competitive advantage. Here we tested the hypothesis that plant chemical diversity can affect local community composition in the hyper-diverse genus Piper at a lowland wet forest location in Costa Rica. We first characterized the chemical composition of 27 of the most locally abundant species of Piper. We then tested whether species with different chemical compositions were more likely to coexist. Finally, we assessed the degree to which Piper phylogenetic relationships are related to differences in secondary chemical composition and community assembly. We found that, on average, co-occurring species were more likely to differ in chemical composition than expected by chance. Contrary to expectations, there was no phylogenetic signal for overall secondary chemical composition. In addition we found that species in local communities were, on average, more phylogenetically closely related than expected by chance, suggesting that functional traits other than those measured here also influence local assembly. We propose that selection by herbivores for divergent chemistries between closely related species facilitates the coexistence of a high diversity of congeneric taxa via apparent competition. © 2016 by the Ecological Society of America.

About the possibility of obtaining cementitious soil composites of high strength on the basis of belozems of carbonate composition

NASA Astrophysics Data System (ADS)

Karapetyan, K. A.; Hayroyan, S. G.; Manukyan, E. S.

2018-04-01

The problem of manufacturing high strength cementitious soils based on belozems of carbonate composition, which experience compression (no less than 10 MPa), without application of surface active substances is considered. The portland cement of type 400 was used as a binding agent to develop compositions of cementitious soil composites, and the ordinary pipe water was used to obtain solutions of cementitious soils. The chemical and mineralogical composition of the initial ingredients and the granulometric composition of belozems were determined. The measurements showed that the upper and lower plasticity limits, the optimum moisture content, and the maximal density of the skeleton of belozems, as well as the considered compositions of cementitious soils, are insignificant, while the plasticity index of cementitious soils is less than one for belozems. It is experimentally proved that an increase in the portland cement amount lead to an increase in the compressive strength of cementitious soils with a decreasing speed. But for the same amount of portland cement used in the cementitious soil compositions, the values of the strength ratio of the pieces tested at the age of 60 and 28 days remain the same and are approximately equal to 1.2. A comparison of experimental data showed that it seems to be real to manufacture a cementitious soil on the basis of belozems of carbonate composition, which contain 10% of cement of the weight of dry mixture and have strength more than 10 MPa, without adding any surfactants to the material composition.

The Effect of Chemical Functionalization on Mechanical Properties of Nanotube/Polymer Composites

NASA Technical Reports Server (NTRS)

Odegard, G. M.; Frankland, S. J. V.; Gates, T. S.

2003-01-01

The effects of the chemical functionalization of a carbon nanotube embedded in a nanotube/polyethylene composite on the bulk elastic properties are presented. Constitutive equations are established for both functionalized and non-functionalized nanotube composites systems by using an equivalent-continuum modeling technique. The elastic properties of both composites systems are predicted for various nanotube lengths, volume fractions, and orientations. The results indicate that for the specific composite material considered in this study, most of the elastic stiffness constants of the functionalized composite are either less than or equal to those of the non-functionalized composite.

Correlations between the in vitro and in vivo bioactivity of the Ti/HA composites fabricated by a powder metallurgy method.

PubMed

Ning, Congqin; Zhou, Yu

2008-11-01

Ti/HA composites were successfully prepared by a powder metallurgy method and the effect of phase composition on the in vitro and in vivo bioactivity of the Ti/HA composites was investigated in the present study. The correlations between the in vitro and in vivo biological behaviors were highlighted. The results showed that the in vitro and in vivo bioactivity of the Ti/HA composites was dependent on their phase composition. The in vitro bioactivity of the Ti/HA composites was evaluated in simulated body fluid with ion concentrations similar to those of human plasma. After immersion in the simulated body fluid for a certain time, apatite precipitations formed on the surface of the composites with an initial titanium content of 50 and 70 wt.%, and no apatite was found on the surface of the composite with 30% titanium. Ti(2)O was responsible for the apatite formation on the surfaces of the composites. For in vivo analysis, Ti/HA cylinders were implanted in the metaphases of the rabbit femur. At the early stage of implantation, the new bone formed on the surface of the composite with 30% titanium was much less than that on the surfaces of the composites with 50% and 70% titanium. All the Ti/HA composites formed a chemical bone-bonding interface with the host bone by 6 months after implantation. The Ti/HA composites formed the bone-bonding interface with the surrounding bone through an apatite layer. The results in the present study suggested that the in vivo results agreed well with the in vitro results.

Damage Accumulation in SiC/SiC Composites with 3D Architectures

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Yun, Hee-Mann; DiCarlo, James A.

2003-01-01

The formation and propagation of multiple matrix cracks in relatively dense ceramic matrix composites when subjected to increasing tensile stress is necessary for high strength and tough composites. However, the occurrence of matrix cracks at low stresses may limit the usefulness of some non-oxide composite systems when subjected to oxidizing environments for long times at stresses sufficient to cause matrix cracking. For SiC fiber-reinforced composites with two-dimensional woven architectures and chemically vapor infiltrated (CVI) SiC matrix and melt-infiltrated (MI) Si/SiC matrix composites, the matrix cracking behavior has been fairly well characterized for different fiber-types and woven architectures. It was found that the occurrence, degree, and growth of matrix cracks depends on the material properties of the composite constituents as well as other physical properties of the composite or architecture, e.g., matrix porosity and size of the fiber bundle. In this study, matrix cracking in SiC fiber reinforced, melt-infiltrated SiC composites with a 3D orthogonal architecture was determined for specimens tested in tension at room temperature. Acoustic emission (AE) was used to monitor the matrix cracking activity, which was later confirmed by microscopic examination of specimens that had failed. The determination of the exact location of AE demonstrated that initial cracking occurred in the matrix rich regions when a large z-direction fiber bundle was used. For specimens with large z-direction fiber tows, the earliest matrix cracking could occur at half the stress for standard 2D woven composites with similar constituents. Damage accumulation in 3D architecture composites will be compared to damage accumulation in 2D architecture composites and discussed with respect to modeling composite stress-strain behavior and use of these composites at elevated temperatures.

Rapid, Contactless and Non-Destructive Testing of Chemical Composition of Samples

NASA Astrophysics Data System (ADS)

Ivanov, O.; Vaseashta, A.; Stoychev, L.

Our results demonstrate that a new effect can be induced in each solid in a wide spectral range of electromagnetic irradiation. In the present manuscript we prove experimentally that one of the possible applications of this effect is for an express contactless control of the chemical composition of a series of samples, in this case, coins. The method has wide applicability ranging from defense and homeland security to several applications requiring rapid and nondestructive identification of chemical composition.

Chemical aspects of the formation of the solar system

NASA Technical Reports Server (NTRS)

Arrhenius, G.

1978-01-01

Application of Alfven's theory for the formation of the solar system and the constraints imposed by the chemical composition of space materials are discussed with reference to chemical processes involved in the formation of the solar system. Evidence for the chemical properties of the space medium and the chemical consequences of the postulated physical differentiation processes are outlined, and interpretations based on structure and composition of meteorite material are indicated. A large range of topics, including processes involving chemical differentiation, temperature effects, and isotope fractionation, are examined.

The Acid-Base Properties and Chemical Composition of the Surface of the InSb-ZnTe System

NASA Astrophysics Data System (ADS)

Kirovskaya, I. A.; Shubenkova, E. G.; Timoshenko, O. T.; Filatova, T. N.

2008-04-01

The acid-base properties and chemical composition of the surface of solid solutions and binary components of the InSb-ZnTe system were studied by the hydrolytic adsorption, nonaqueous conductometric titration, mechanochemistry, IR spectroscopy, and mass spectrometry methods. The strength, nature, and concentration of acid centers were determined. Changes in the concentration of acid centers caused by surface exposure to CO and changes in the composition of the system were also studied. The mechanism of acid-base interactions was established. The chemical composition of the surface of system components exposed to air included adsorbed H2O molecules, OH- groups, hydrocarbon and oxocarbon compounds, and the products of surface atom oxidation. After thermal treatment in a vacuum, the composition of the surface approached the stoichiometric composition.

Studies on thermo-mechanical properties of chemically treated jute-polyester composite

NASA Astrophysics Data System (ADS)

Chaudhari, Vikas; Chandekar, Harichandra; Saboo, Jayesh; Mascarenhas, Adlete

2018-03-01

The effect of chemical treatments on jute-polyester composites is studied in this paper. The jute fabrics are chemically treated with NaOH and benzoyl chloride and its tensile and visco-elastic properties are compared with untreated jute composite. The NaOH treated jute-polyester composite show superior tensile strength and modulus compared to other jute-polyester composites. The glass transition temperature obtained from DMA shift to higher temperature for composites in comparison to polyester resin, this is due to restriction of mobility in chains due to introduction of jute reinforcement. The DMA results also show favourable results towards NaOH treatment i.e. higher storage modulus and lower tan δ values relative to untreated jute-polyester composite. The benzoyl treated jute-polyester composite however do not show promising results which may be attributed to the fact that the adhesion properties associated with similar ester functional groups in the benzoyl treated jute fabric and polyester resin were not obtained.

Comparative Study on Synergetic Degradation of a Reactive Dye Using Different Types of Fly Ash in Combined Adsorption and Photocatalysis

NASA Astrophysics Data System (ADS)

Giri Babu, P. V. S.; Swaminathan, G.

2016-09-01

A comprehensive study was carried out on four different fly ashes used as a catalyst for the degradation of Acid Red 1 using ultraviolet rays. These fly ashes are collected from different thermal power stations located at various places in India and having different chemical compositions. Three fly ashes are from lignite-based thermal power plants, and one is from the coal-based power plant. One fly ash is classified as Class F, two fly ashes are classified as Class C and remaining one is not conforming to ASTM C618 classification. X-Ray Fluorescence analysis was used to identify the chemical composition of fly ashes and SiO2, Al2O3, CaO, Fe2O3 and TiO2 were found to be the major elements present in different proportions. Various analysis were carried out on all the fly ashes like Scanning Electron Microscopy to identify the microphysical properties, Energy Dispersive X-Ray spectroscopy to quantify the elements present in the catalyst and X-Ray Diffraction to identify the catalyst phase analysis. The radical generated during the reaction was identified by Electron paramagnetic resonance spectroscopy. The parameters such as initial pH of the dye solution, catalyst dosage and initial dye concentration which influence the dye degradation efficiency were studied and optimised. In 60 min duration, the dye degradation efficiency at optimum parametric values of pH 2.5, initial dye concentration of 10 mg/L and catalyst dosage of 1.0 g/L using various fly ashes, i.e., Salam Power Plant, Barmer Lignite Power Plant, Kutch Lignite Power Plant and Neyveli Lignite Thermal Power plant (NLTP) were found to be 40, 60, 67 and 95 % respectively. The contribution of adsorption alone was 18 % at the above mentioned optimum parametric values. Among the above four fly ash NLTP fly ashes proved to be most efficient.

In vitro screening of environmental chemicals for targeted testing prioritization: the ToxCast project.

PubMed

Judson, Richard S; Houck, Keith A; Kavlock, Robert J; Knudsen, Thomas B; Martin, Matthew T; Mortensen, Holly M; Reif, David M; Rotroff, Daniel M; Shah, Imran; Richard, Ann M; Dix, David J

2010-04-01

Chemical toxicity testing is being transformed by advances in biology and computer modeling, concerns over animal use, and the thousands of environmental chemicals lacking toxicity data. The U.S. Environmental Protection Agency's ToxCast program aims to address these concerns by screening and prioritizing chemicals for potential human toxicity using in vitro assays and in silico approaches. This project aims to evaluate the use of in vitro assays for understanding the types of molecular and pathway perturbations caused by environmental chemicals and to build initial prioritization models of in vivo toxicity. We tested 309 mostly pesticide active chemicals in 467 assays across nine technologies, including high-throughput cell-free assays and cell-based assays, in multiple human primary cells and cell lines plus rat primary hepatocytes. Both individual and composite scores for effects on genes and pathways were analyzed. Chemicals displayed a broad spectrum of activity at the molecular and pathway levels. We saw many expected interactions, including endocrine and xenobiotic metabolism enzyme activity. Chemicals ranged in promiscuity across pathways, from no activity to affecting dozens of pathways. We found a statistically significant inverse association between the number of pathways perturbed by a chemical at low in vitro concentrations and the lowest in vivo dose at which a chemical causes toxicity. We also found associations between a small set of in vitro assays and rodent liver lesion formation. This approach promises to provide meaningful data on the thousands of untested environmental chemicals and to guide targeted testing of environmental contaminants.

Modified silicon carbide whiskers

DOEpatents

Tiegs, Terry N.; Lindemer, Terrence B.

1991-01-01

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Modified silicon carbide whiskers

DOEpatents

Tiegs, T.N.; Lindemer, T.B.

1991-05-21

Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

Preparation and Characterization of Biomimetic Hydroxyapatite-Resorbable Polymer Composites for Hard Tissue Repair

NASA Astrophysics Data System (ADS)

Hiebner, Kristopher Robert

Autografts are the orthopedic "gold standard" for repairing bone voids. Autografts are osteoconductive and do not elicit an immune response, but they are in short supply and require a second surgery to harvest the bone graft. Allografts are currently the most common materials used for the repair of segmental defects in hard tissue. Unlike autografts, allografts can cause an undesirable immune response and the possibility of disease transmission is a major concern. As an alternative to the above approaches, recent research efforts have focused on the use of composite materials made from hydroxyapatite (HA) and bioresorbable polymers, such as poly-L-lactide (PLLA). Recent results have shown that the surface hydroxides on HA can initiate the ring opening polymerization (ROP) of L-lactide and other lactones creating a composite with superior interfacial strength. This thesis demonstrates that the surface of porous biologically derived HA substrates, such as coralline HA and trabecular bone, can be used to initiate the ROP of L-lactide and other lactones from the vapor phase. This process increases the strength of the porous scaffold through the deposition of a thin, uniform polymer coating, while maintaining the porous structure. The kinetics of the chemical vapor deposition polymerization (CVDP) are described using a quartz crystal microbalance (QCM). The reaction temperature and monomer vapor pressure are found to affect the rate of the polymerization. Also described in this thesis is the preparation of a porous polymer scaffold that mimics the structure of demineralized bone matrix (DBM). This demineralized bone matrix simulant (DBMS) is created using anorganic bovine bone as a template to initiate the polymerization of various lactones, followed by the removal of the HA scaffold. This material retained its shape and exhibits mechanical properties superior to DBM. Finally it is shown that HA can be used to initiate the ROP of a-caprolactam and the biocompatibility of various HA/bioresorbable polymer composites are described through the use of cell cultures run in collaboration with a research group specializing in immunology.

Composite Materials

NASA Technical Reports Server (NTRS)

1988-01-01

Langley Research Center researchers invented an advanced polymer, a chemical compound formed by uniting many small molecules to create a complex molecule with different chemical properties. The material is a thermoplastic polyimide that resists solvents. Other polymers of this generic type are soluble in solvents, thus cannot be used where solvents are present. High Technology Services (HTS), Inc. licensed technology and is engaged in development and manufacture of high performance plastics, resins and composite materials. Techimer Materials Division is using technology for composite matrix resins that offer heat resistance and protection from radiation, electrical and chemical degradation. Applications of new polymer include molding resins, adhesives and matrix resins for fiber reinforced composites.

Elemental Compositions of Comet 81P/Wild 2 Samples Collected by Stardust

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Bleuet, P.; Borg, J.; Bradley, J.; Brenker, F.; Brennan, S.; Bridges, J.; Brownlee, D. E.; Bullock, E.; Clark, B. C.;

Porous multi-component material for the capture and separation of species of interest

DOEpatents

Addleman, Raymond S.; Chouyyok, Wilaiwan; Li, Xiaohong S.; Cinson, Anthony D.; Gerasimenko, Aleksandr A

2016-06-21

A method and porous multi-component material for the capture, separation or chemical reaction of a species of interest is disclosed. The porous multi-component material includes a substrate and a composite thin film. The composite thin film is formed by combining a porous polymer with a nanostructured material. The nanostructured material may include a surface chemistry for the capture of chemicals or particles. The composite thin film is coupled to the support or device surface. The method and material provides a simple, fast, and chemically and physically benign way to integrate nanostructured materials into devices while preserving their chemical activity.

Composite electronic materials based on poly(3,4-propylenedioxythiophene) and highly charged poly(aryleneethynylene)-wrapped carbon nanotubes for supercapacitors.

PubMed

Rosario-Canales, Mariem R; Deria, Pravas; Therien, Michael J; Santiago-Avilés, Jorge J

2012-01-01

Supercapacitor charge storage media were fabricated using the semiconducting polymer poly(3,4-propylenedioxythiophene) (PProDOT) and single-walled carbon nanotubes (SWNTs) that were helically wrapped with ionic, conjugated poly[2,6-{1,5-bis(3-propoxysulfonicacidsodiumsalt)}naphthylene]ethynylene (PNES). These PNES-wrapped SWNTs (PNES-SWNTs) enable efficient dispersion of individualized nanotubes in a wide range of organic solvents. PNES-SWNT film-modified Pt electrodes were prepared by drop casting PNES-SWNT suspensions in MeOH; high stability, first-generation PProDOT/PNES/SWNT composites were realized via electropolymerization of the ProDOT parent monomer (3,4-propylenedioxythiophene) in a 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/propylene carbonate solution at the PNES-SWNT-modified electrode. The electrochemical properties of PProDOT and PProDOT/PNES/SWNT single electrodes and devices were examined using cyclic voltammetric methods. The hybrid composites were found to enhance key supercapacitor figures of merit (charge capacity and capacitance) by approximately a factor of 2 relative to those determined for benchmark Type I devices that exploited a classic PProDOT-based electrode material. The charge/discharge stability of the supercapacitors was probed by repeated rounds of cyclic voltammetric evaluation at a minimum depth of discharge of 73%; these experiments demonstrated that the hybrid PProDOT/PNES/SWNT composites retained ~90% of their initial charge capacity after 21,000 charge/discharge cycles, contrasting analogous data obtained for PProDOT-based devices, which showed only 84% retention of their initial charge capacity. © 2011 American Chemical Society

A facile FeBr3 based photoATRP for surface modification of mesoporous silica nanoparticles for controlled delivery cisplatin

NASA Astrophysics Data System (ADS)

Huang, Long; Liu, Meiying; Mao, Liucheng; Huang, Qiang; Huang, Hongye; Zeng, Guangjian; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

2018-03-01

Mesoporous silica nanoparticles (MSNs) should be one of the most important materials for biomedical application owing to their high specific surface area, regular porous structure, adjustable pore size and chemical inert. However, the biomedical applications of unmodified MSNs are largely impeded for their poor hydrophilicity and lack of functional groups. In this work, a novel photo-initiated atom transfer radical polymerization (ATRP) strategy has been reported for modified mesoporous silica nanoparticles (MSNs) with hydrophilicility copolymers using FeBr3 as the novel photocatalyst and itaconic acid (IA) and 2-methacryloyloxyethyl phosphorylcholine (MPC) as monomers. Because of the hydrophilicity and anticancer agent cis-dichlorodiamineplatinum(II) (CDDP) loading capacity of poly(MPC-co-IA), the controlled drug delivery applications MSNs-NH2-poly(MPC-co-IA) composites toward CDDP were further investigated. A series of characterization results demonstrated that MSNs-NH2-poly(MPC-co-IA) composites can be successfully fabricated through the novel photo-initiated ATRP. MSNs-NH2-poly(MPC-co-IA) composites showed obvious enhancement of water dispersibility, desirable biocompatibility, high drug loading capability, making them great potential for controlled drug delivery of CDDP. Moreover, as compared with the traditional ATRP, that using the transition metal ions and organic ligands as the catalysis systems in elevated temperature, our method provides a more facile, benign and cost-effective route for fabrication of multifunctional MSNs with great potential for biomedical applications. Finally, this FeBr3 based photoATRP strategy should be further extended for the fabrication of many other polymeric composites owing to its good monomer adoptability.

OH-initiated Aging of Biomass Burning Aerosol during FIREX

NASA Astrophysics Data System (ADS)

Lim, C. Y.; Hagan, D. H.; Cappa, C. D.; Kroll, J. H.; Coggon, M.; Koss, A.; Sekimoto, K.; De Gouw, J. A.; Warneke, C.

2017-12-01

Biomass burning emissions represent a major source of fine particulate matter to the atmosphere, and this source will likely become increasingly important in the future due to changes in the Earth's climate. Understanding the effects that increased fire emissions have on both air quality and climate requires understanding the composition of the particles emitted, since chemical and physical composition directly impact important particle properties such as absorptivity, toxicity, and cloud condensation nuclei activity. However, the composition of biomass burning particles in the atmosphere is dynamic, as the particles are subject to the condensation of low-volatility vapors and reaction with oxidants such as the hydroxyl radical (OH) during transport. Here we present a series of laboratory chamber experiments on the OH-initiated aging of biomass burning aerosol performed at the Fire Sciences Laboratory in Missoula, MT as part of the Fire Influences on Regional and Global Environments Experiment (FIREX) campaign. We describe the evolution of biomass burning aerosol produced from a variety of fuels operating the chamber in both particle-only and gas + particle mode, focusing on changes to the organic composition. In particle-only mode, gas-phase biomass burning emissions are removed before oxidation to focus on heterogeneous oxidation, while gas + particle mode includes both heterogeneous oxidation and condensation of oxidized volatile organic compounds onto the particles (secondary organic aerosol formation). Variability in fuels and burning conditions lead to differences in aerosol loading and secondary aerosol production, but in all cases aging results in a significant and rapid increases in the carbon oxidation state of the particles.

Experimental Constraints on the Chemical Differentiation of Mercurys Mantle

NASA Technical Reports Server (NTRS)

Boujibar, A.; Righter, K.; Pando, K.; Danielson, L.

2015-01-01

Mercury is known as being the most reduced terrestrial planet with the highest core/mantle ratio. Results from MESSENGER spacecraft have shown that its surface is FeO-poor (2-4 wt%) and S-rich (up to 6-7 wt%), which confirms the reducing nature of its silicate mantle. In addition several features suggest important melting stages of the Mercurian mantle: widespread volcanic deposits on its surface, a high crustal thickness (approximately 10% of the planet's volume) and chemical compositions of its surface suggesting several stages of differentiation and remelting processes. Therefore it is likely that igneous processes like magma ocean crystallization and continuous melting have induced chemical and mineralogical heterogeneities in the Mercurian mantle. The extent and nature of compositional variations produced by partial melting remains poorly constrained for the particular compositions of Mercury (very reducing conditions, low FeO-contents and high sulfur-contents). Melting experiments with bulk Mercury-analogue compositions are scarce and with poorly con-trolled starting compositions. Therefore additional experimental data are needed to better understand the differentiation processes that lead to the observed chemical compositions of Mercury's surface.

Chemical analysis of the moon at the surveyor v landing site.

PubMed

Turkevich, A L; Franzgrote, E J; Patterson, J H

1967-11-03

The chemical composition of the lunar surface material at a maria landing site has been determined by the alpha-scattering technique. Oxygen, silicon, and aluminum have been identified in the preliminary evaluation of the data. The general chemical composition is similar to that of a silicate of a basaltic type.

Chemical structure of wood charcoal by infrared spectroscopy and multivariate analysis

Treesearch

Nicole Labbe; David Harper; Timothy Rials; Thomas Elder

2006-01-01

In this work, the effect of temperature on charcoal structure and chemical composition is investigated for four tree species. Wood charcoal carbonized at various temperatures is analyzed by mid infrared spectroscopy coupled with multivariate analysis and by thermogravimetric analysis to characterize the chemical composition during the carbonization process. The...

Chemical Fingerprinting of Materials Developed Due to Environmental Issues

NASA Technical Reports Server (NTRS)

Smith, Doris A.; McCool, A. (Technical Monitor)

2000-01-01

Instrumental chemical analysis methods are developed and used to chemically fingerprint new and modified External Tank materials made necessary by changing environmental requirements. Chemical fingerprinting can detect and diagnose variations in material composition. To chemically characterize each material, fingerprint methods are selected from an extensive toolbox based on the material's chemistry and the ability of the specific methods to detect the material's critical ingredients. Fingerprint methods have been developed for a variety of materials including Thermal Protection System foams, adhesives, primers, and composites.

Sr-Nd-Pb Isotope Geochemistry of Melange Formation: Implications for Identification of Fluid Sources in the Mantle Wedge and the Arc

NASA Astrophysics Data System (ADS)

Bebout, G. E.; King, R. L.; Moriguti, T.; Nakamura, E.

2004-12-01

Paramount to our ability to decipher the behavior of fluids and melts within the mantle wedge and the overall subduction system are the chemical compositions of rocks adjacent to the slab-mantle interface. Profound metamorphic and metasomatic alteration of pre-subduction lithologies to form melange along the slab-mantle interface may yield rock types inheriting mixed chemical compositions of diverse pre-subduction lithologies. Early work on melange geochemistry indicates competitive effects between mechanical mixing, metasomatism by fluids or melts, and mineral stabilities imposed by the resulting bulk composition. We have explored the Sr-Nd-Pb isotope geochemistry of low- to high-grade melange zones in the Catalina Schist, CA, to address this crucial missing component in studies of subduction-zone mass flux. The Catalina Schist contains lawsonite-albite (LA), lawsonite-blueschist (LB), and amphibolite (AM) facies melange zones, all with mineralogy dominated by talc, chlorite, and Na-Ca amphiboles, with additional minerals such as micas, rutile, zircon, and apatite stabilized based on bulk sample chemistry. Major element compositions vary, from strongly ultramafic in the AM melange, to more crustal-like compositions (i.e., more reminiscent of basaltic to sedimentary protoliths) for LA and LB melange. However, initial Sr and Nd isotope ratios for all grades of melange are essentially indistinguishable, displaying a wide variation from 87Sr/86Sr=0.703-0.709 and ɛ Nd= +15 to -15. Covariations are generally negative, similar to that of the mantle array, but with some samples extending to higher Sr ratios at constant ɛ Nd that probably reflect inheritance of seawater Sr. No clear mixing relationships between 87Sr/86Sr and 1/Sr exist, suggesting either localized buffering of Sr isotope ratios or that mixing relations are obscured by secondary devolatilization. However, a clear mixing trend for Nd indicates two end-members, one a high-concentration, positive ɛ Nd source (AOC?), the other with low-concentration and negative ɛ Nd (devolatilized sediments?). Likewise, initial Pb isotope ratios for all grades of melange form a single array independent of rock type or inferred protolith. Melange matrix of the Catalina Schist preserves initial 206Pb/204Pb of 18.95-19.59, 207Pb/204Pb of 15.61-15.68, and 208Pb/204Pb of 37.85-39.05. Such elevated Pb ratios are typical of subducting oceanic sediments, but not of MORB-like oceanic crust or peridotites of the depleted mantle. The similarity of these initial ratios suggests pervasive alteration of Pb isotope signatures within diverse rock types by fluids during subduction. As Pb concentrations decline from LA/LB to AM melange, this suggests devolatilization of Pb from the ultramafic AM melange will transfer crustal-like Pb isotope ratios. Sr-Nd-Pb isotope systematics for arc volcanic rocks are commonly used as indicators of fluid sources from the subducting slab to the arc magma source region. Our results suggest such an assumption is extremely dangerous, as hybridization processes common to melange zones are more likely to occur along the slab-mantle interface than is preservation of a pre-subduction section. Such metamorphic mediation and buffering of "slab" compositions is essentially unknown, yet our data support an interpretation where these processes impart a fundamental control on the chemistry of fluids passed to the mantle wedge.

An isotopic study of mafic microgranular enclaves in the Katsuragi adakitic tonalite, southwestern Japan.

NASA Astrophysics Data System (ADS)

Tezuka, N.; Tsuboi, M.; Asahara, Y.

2017-12-01

The Cretaceous Katsuragi tonalite in southwestern Japan has been regarded as adakite formed by the partial melting of lower crust a) b). The tonalite is 10 x 15 km in areal extent, is composed of hornblende-biotite tonalite with a mineral assemblage of plagioclase, biotite, quartz and hornblende, and contains mafic microgranular enclaves (MME). The MME has dioritic composition with a mineral assemblage of plagioclase, biotite, hornblende and quartz. The boundary between the tonalite and the MME is sharp. To reveal the relationship between the MME and adakitic feature of the host tonalite, we have focused on the chemical and Sr-Nd isotopic compositions of the MME in the Katsuragi tonalite. Three models have been proposed for the origin of MME: restite, magma-mixing, and cumulate c). In the restite model, MME is regarded as a residual material of partial melting, and therefore chemical compositions of MME and host should show a linear trend on the Harker's diagram. However, the Katsuragi tonalite and its MME do not show one linear trend. Based on mixing of two magmas, initial 87Sr/86Sr (SrI) value of MME is basically different from that of its host. However, the SrI value of the MME is 0.70725-0.70749 and is identical to the value of 0.70728 in the Katsuragi tonalite d), indicating one magma source for the MME and its host. According to the cumulate model, MME forms from cumulate piles by subsequent feeding of congenetic magma immediately after the early crystallized minerals are solidified. The concordance of the age and SrI between the Katsuragi tonalite and its MME strongly indicate the cumulate origin c). Furthermore, the mineral assemblage of the MME resembles with the common mineral assemblage of andesitic cumulate such as plagioclase, hornblende and quartz c), and this is consistent with the cumulate model. Based on the cumulate origin of the MME, the adakitic feature of chemical composition in the host rock is potentially formed by the separation of cumulate. In the presentation, we evaluate the adakitic, chemical composition of the Katsuragi tonalite by calculation of MME separation from parental magma. a) K. Takemura, M. Tsuboi, 2014, MAGMA, 96, 31, 44. b) Y. Nishioka, 2008, 115th Ann. Meet. Geol. Soc. Japan, Abstr., 131.c) S. Chen et al., 2016, Lithos, 248, 251, 455, 468. d) K. Morioka et al., 2000, Island Arc, 9, 46, 54.

Thermal and chemical evolution in the early Solar System as recorded by FUN CAIs: Part II - Laboratory evaporation of potential CMS-1 precursor material

NASA Astrophysics Data System (ADS)

Mendybaev, Ruslan A.; Williams, Curtis D.; Spicuzza, Michael J.; Richter, Frank M.; Valley, John W.; Fedkin, Alexei V.; Wadhwa, Meenakshi

2017-03-01

We present the results of laboratory experiments in which a forsterite-rich melt estimated to be a potential precursor of Allende CMS-1 FUN CAI was evaporated into vacuum for different lengths of time at 1900 °C. The evaporation of this melt resulted in residues that define trajectories in chemical as well as magnesium, silicon and oxygen isotopic composition space and come very close to the measured properties of CMS-1. The isotopic composition of the evaporation residues was also used to determine the kinetic isotopic fractionation factors [α2,1 (vapor-melt) defined as the ratio of isotopes 2 and 1 of a given element in the evaporating gas divided by their ratio in the evaporating source] for evaporation of magnesium (α25,24 for 25Mg/24Mg), silicon (α29,28 for 29Si/28Si) and oxygen (α18,16 for 18O/16O) from the forsterite-rich melt at 1900 °C. The values of α25,24 = 0.98383 ± 0.00033 and α29,28 = 0.99010 ± 0.00038 are essentially independent of change in the melt composition as evaporation proceeds. In contrast, α18,16 changes from 0.9815 ± 0.0016 to ∼0.9911 when the residual melt composition changes from forsteritic to melilitic. Using the determined values of α25,24 and α29,28 and present-day bulk chemical composition of the CMS-1, the composition of the precursor of the inclusion was estimated to be close to the clinopyroxene + spinel + forsterite assemblage condensed from a solar composition gas. The correspondence between the chemical composition and isotopic fractionation of experimental evaporation residues and the present-day bulk chemical and isotopic compositions of CMS-1 is evidence that evaporation played a major role in the chemical evolution of CMS-1.

Characterization and prediction of chemical functions and weight fractions in consumer products.

PubMed

Isaacs, Kristin K; Goldsmith, Michael-Rock; Egeghy, Peter; Phillips, Katherine; Brooks, Raina; Hong, Tao; Wambaugh, John F

2016-01-01

Assessing exposures from the thousands of chemicals in commerce requires quantitative information on the chemical constituents of consumer products. Unfortunately, gaps in available composition data prevent assessment of exposure to chemicals in many products. Here we propose filling these gaps via consideration of chemical functional role. We obtained function information for thousands of chemicals from public sources and used a clustering algorithm to assign chemicals into 35 harmonized function categories (e.g., plasticizers, antimicrobials, solvents). We combined these functions with weight fraction data for 4115 personal care products (PCPs) to characterize the composition of 66 different product categories (e.g., shampoos). We analyzed the combined weight fraction/function dataset using machine learning techniques to develop quantitative structure property relationship (QSPR) classifier models for 22 functions and for weight fraction, based on chemical-specific descriptors (including chemical properties). We applied these classifier models to a library of 10196 data-poor chemicals. Our predictions of chemical function and composition will inform exposure-based screening of chemicals in PCPs for combination with hazard data in risk-based evaluation frameworks. As new information becomes available, this approach can be applied to other classes of products and the chemicals they contain in order to provide essential consumer product data for use in exposure-based chemical prioritization.

Separation, Characterization and Initial Reaction Studies of Magnetite Particles from Hanford Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, Donald R.; Grosz, Andrew E.; Ilton, Eugene S.

2010-04-24

Magnetic and density separation methods have been applied to composite sediment sample from the Hanford formation from sediment recovered during drilling of an uncontaminated borehole located near the 200 West Area of the Hanford Site in southeastern Washington State. This paper describes the results of using those separation methods and from the characterization and initial reactivity measurements on a highly magnetic fraction isolated from that sediment. X-ray diffraction (XRD) analysis of the highly magnetic sediment fraction indicates that this material contains predominantly magnetite (Fe3O4). Particle morphology observed by scanning electron microscopy (SEM) and compositions determined energy dispersive spectroscopy (EDS) aremore » consistent with this identification. Analyses by X-ray photoelectron spectroscopy (XPS) indicates that there is a thin coating on the particles that are likely a type of aluminosilicate. This highly magnetic fraction of material is not reactive with indigo carmine, an organic redox probe molecule that was shown to readily react with synthetic magnetite. Because of the limited amounts of material readily available, initial tests have been conducted that demonstrate the ability to complete U(VI) sorption on individual particles (nominally ~100 µm in size) of the isolated sediment and to remove and mount these individual particles for analysis of the concentration and chemical state of the sorbed U species using small area XPS.« less

Separation, Characterization and Initial Reaction Studies of Magnetite Particles from Hanford Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baer, Donald R.; Grosz, Andrew E.; Ilton, Eugene S.

2010-08-01

Magnetic and density separation methods have been applied to composite sediment sample from the Hanford formation from sediment recovered during drilling of an uncontaminated borehole located near the 200 West Area of the Hanford Site in southeastern Washington State. This paper describes the results of using those separation methods and from the characterization and initial reactivity measurements on a highly magnetic fraction isolated from that sediment. X-ray diffraction (XRD) analysis of the highly magnetic sediment fraction indicates that this material contains predominantly magnetite (Fe3O4). Particle morphology observed by scanning electron microscopy (SEM) and compositions determined energy dispersive spectroscopy (EDS) aremore » consistent with this identification. Analyses by X-ray photoelectron spectroscopy (XPS) indicates that there is a thin coating on the particles that are likely a type of aluminosilicate. This highly magnetic fraction of material is not reactive with indigo carmine, an organic redox probe molecule that was shown to readily react with synthetic magnetite. Because of the limited amounts of material readily available, initial tests have been conducted that demonstrate the ability to complete U(VI) sorption on individual particles (nominally ~100 µm in size) of the isolated sediment and to remove and mount these individual particles for analysis of the concentration and chemical state of the sorbed U species using small area XPS.« less

Relation of asphalt chemistry to physical properties and specifications.

DOT National Transportation Integrated Search

1984-01-01

This report constitutes a synthesis of published information concerning the chemical composition and characteristics of asphalt cements used in highway construction. The general relations between chemical composition and physical properties and speci...

Impact of annealing on features of BCP coating on NiTi shape memory alloy: Preparation and physicochemical characterization

NASA Astrophysics Data System (ADS)

Dulski, Mateusz; Dudek, Karolina; Grelowski, Michał; Kubacki, Jerzy; Hertlein, Justyna; Wojtyniak, Marcin; Goryczka, Tomasz

2018-04-01

A multifunctional composite structure consisting of resorbable tricalcium phosphate with non-resorbable hydroxyapatite and NiTi shape memory alloy (SMA) has been manufactured to develop a biocompatible system for long-term implant applications. The hybrid system has been vacuum sintered to consolidate and form chemical binding between phosphate biomaterials and NiTi SMA. In this context, the impact of sintering on biomaterial's features in relation to initial material has been analyzed using a combination of structural and surface sensitive approaches. Moreover, a partial decomposition of the NiTi parent phase to the equilibrium Ti2Ni with cubic structure, and non-equilibrium Ti3Ni4 with hexagonal structure has been detected. Moreover, a sintering has provided a reconstruction of the orthophosphate surface through the disintegration of calcium phosphate material and increase of hydroxyapatite with smaller particles in volume. The biomaterial surface has become more enriched in calcium in relation to the initial composition, with a simultaneous decline of the roughness parameters due to the gradual consolidation of orthophosphates. Finally, surface modification accompanied with heat treatment has led to an increase of surface Young's modulus as an effect of partial recrystallization of calcium phosphates.

Surface functionalized composite nanofibers for efficient removal of arsenic from aqueous solutions.

PubMed

Mohamed, Alaa; Osman, T A; Toprak, M S; Muhammed, M; Uheida, A

2017-08-01

A novel composites nanofiber was synthesized based on PAN-CNT/TiO 2 -NH 2 nanofibers using electrospinning technique followed by chemical modification of TiO 2 NPs. PAN-CNT/TiO 2 -NH 2 nanofiber were characterized by XRD, FTIR, SEM, and TEM. The effects of various experimental parameters such as initial concentration, contact time, and solution pH on As removal were investigated. The maximum adsorption capacity at pH 2 for As(III) and As(V) is 251 mg/g and 249 mg/g, respectively, which is much higher than most of the reported adsorbents. The adsorption equilibrium reached within 20 and 60 min as the initial solution concentration increased from 10 to 100 mg/L, and the data fitted well using the linear and nonlinear pseudo first and second order model. Isotherm data fitted well to the linear and nonlinear Langmuir, Freundlich, and Redlich-Peterson isotherm adsorption model. Desorption results showed that the adsorption capacity can remain up to 70% after 5 times usage. This work provides a simple and an efficient method for removing arsenic from aqueous solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Benzene degradation in a denitrifying biofilm reactor: activity and microbial community composition.

PubMed

van der Waals, Marcelle J; Atashgahi, Siavash; da Rocha, Ulisses Nunes; van der Zaan, Bas M; Smidt, Hauke; Gerritse, Jan

2017-06-01

Benzene is an aromatic compound and harmful for the environment. Biodegradation of benzene can reduce the toxicological risk after accidental or controlled release of this chemical in the environment. In this study, we further characterized an anaerobic continuous biofilm culture grown for more than 14 years on benzene with nitrate as electron acceptor. We determined steady state degradation rates, microbial community composition dynamics in the biofilm, and the initial anaerobic benzene degradation reactions. Benzene was degraded at a rate of 0.15 μmol/mg protein/day and a first-order rate constant of 3.04/day which was fourfold higher than rates reported previously. Bacteria belonging to the Peptococcaceae were found to play an important role in this anaerobic benzene-degrading biofilm culture, but also members of the Anaerolineaceae were predicted to be involved in benzene degradation or benzene metabolite degradation based on Illumina MiSeq analysis of 16S ribosomal RNA genes. Biomass retention in the reactor using a filtration finger resulted in reduction of benzene degradation capacity. Detection of the benzene carboxylase encoding gene, abcA, and benzoic acid in the culture vessel indicated that benzene degradation proceeds through an initial carboxylation step.

Low-melting elemental metal or fusible alloy encapsulated polymerization initiator for delayed initiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hermes, Robert E.

2017-08-15

An encapsulated composition for polymerization includes an initiator composition for initiating a polymerization reaction, and a capsule prepared from an elemental metal or fusible alloy having a melting temperature from about 20.degree. C. to about 200.degree. C. A fluid for polymerization includes the encapsulated composition and a monomer. When the capsule melts or breaks open, the initiator is released.

Changes in composition and content of food-derived peptide in human blood after daily ingestion of collagen hydrolysate for 4 weeks.

PubMed

Shigemura, Yasutaka; Suzuki, Asahi; Kurokawa, Mihoko; Sato, Yoshio; Sato, Kenji

2018-03-01

Daily ingestion of collagen hydrolysate for a long period improves skin and joint conditions. It has been speculated that the beneficial effects are exerted by food-derived hydroxyproline (Hyp) peptides, which are detected in human blood after single ingestions. In the present study, to investigate the effect of long-term ingestion of collagen hydrolysate on Hyp peptides profile in blood, the concentrations of Hyp-peptides in human blood before and after daily ingestion for a long period were examined. Hyp-peptides increased to a maximum level at 1 h after ingestion and reverted to their initial levels within 24 h during experimental period. Pro-Gly and Hyp-peptides such as Pro-Hyp-Gly, Pro-Hyp, Ile-Hyp, Leu-Hyp, Hyp-Gly, Glu-Hyp and Ala-Hyp were identified in the blood after ingestion of collagen hydrolysate at 4.5 g day -1 for 4 weeks. For the whole period, Pro-Hyp was the leading compound. The compositional rate of Hyp-Gly showed a tendency to increase, while that of Pro-Hyp tended to decrease after daily ingestion. The present results indicate that daily ingestion of collagen hydrolysate for a long period can change compositional rate of Hyp peptides in human blood. This fact suggests that long-term ingestion of collagen hydrolysate might change exo- or endo-type protease activity in the digestive tract, which may consequently promote beneficial effects. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

A Novel Strategy for Preparation of Si-HA Coatings on C/C Composites by Chemical Liquid Vaporization Deposition/Hydrothermal Treatments.

PubMed

Xin-Bo, Xiong; Xin-Ye, Ni; Ya-Yun, Li; Cen-Cen, Chu; Ji-Zhao, Zou; Xie-Rong, Zeng

2016-08-05

A novel strategy for the preparation of Si-doped hydroxyapatite (Si-HA) coatings on H2O2-treated carbon/carbon composites (C/C) was developed. HA coating was prepared on C/C through chemical liquid vaporization deposition (CLVD)/hydrothermal treatment. HA coating was immersed in an H2SiO3 solution at an autoclave at 413 K for transformation into Si-HA coating. The effects of H2SiO3 mass contents on the phase, morphology, and composition of the Si-HA coatings were studied through SEM, EDS,XRD, and FTIR. Their bonding performance to C/C was measured through a scratch test. Under the optimal content condition, the in vitro skull osteoblast response behaviors of the Si-HA coating were evaluated. Results showed that SiO3(2-) could enter into the HA lattice and occupy the PO4(3-) sites. Doped SiO3(2-) significantly improved the bonding performance of the HA coating to C/C in comparison with the untreated HA. The adhesive strength of the coatings initially increased and then decreased with increasing H2SiO3 content. Meanwhile, the cohesive strength of the Si-HA coatings was almost nearly identical. The Si-HA coating achieved at a content of 90% H2SiO3 exhibited the best bonding performance, and its osteoblast compatibility in vitro was superior to that of the untreated HA coating on C/C through CLVD/hydrothermal treatment.

Decomposition Dynamics and Changes in Chemical Composition of Wheat Straw Residue under Anaerobic and Aerobic Conditions

PubMed Central

Gao, Hongjian; Chen, Xi; Wei, Junling; Zhang, Yajie; Zhang, Ligan; Chang, Jiang; Thompson, Michael L.

2016-01-01

Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C and aromatic C in decomposing wheat straw residues under anaerobic condition were higher than those under aerobic conditions. The higher mass percentages of lignin and the higher signals of aromatic C and alkyl C functional groups in decomposing wheat residues under anaerobic conditions than under aerobic conditions were due to the slower decomposition rates of aryl C and alkyl C in wheat straw residues under anaerobic conditions. PMID:27380023

Effect of compositional heterogeneity on dissolution of non-ideal LNAPL mixtures

NASA Astrophysics Data System (ADS)

Vasudevan, M.; Johnston, C. D.; Bastow, T. P.; Lekmine, G.; Rayner, J. L.; Nambi, I. M.; Suresh Kumar, G.; Ravi Krishna, R.; Davis, G. B.

2016-11-01

The extent of dissolution of petroleum hydrocarbon fuels into groundwater depends greatly on fuel composition. Petroleum fuels can consist of thousands of compounds creating different interactions within the non-aqueous phase liquid (NAPL), thereby affecting the relative dissolution of the components and hence a groundwater plume's composition over long periods. Laboratory experiments were conducted to study the variability in the effective solubilities and activity coefficients for common constituents of gasoline fuels (benzene, toluene, p-xylene and 1,2,4-trimethylbenzene) (BTX) in matrices with an extreme range of molar volumes and chemical affinities. Four synthetic mixtures were investigated comprising BTX with the bulk of the NAPL mixtures made up of either, ethylbenzene (an aromatic like BTX with similar molar volume); 1,3,5-trimethylbenzene (an aromatic with a greater molar volume); n-hexane (an aliphatic with a low molar volume); and n-decane (an aliphatic with a high molar volume). Equilibrium solubility values for the constituents were under-predicted by Raoult's law by up to 30% (higher experimental concentrations) for the mixture with n-hexane as a filler and over-predicted by up to 12% (lower experimental concentrations) for the aromatic mixtures with ethylbenzene and 1,3,5-trimethylbenzene as fillers. Application of PP-LFER (poly-parameter linear free energy relationship) model for non-ideal mixtures also resulted in poor correlation between experimentally measured and predicted concentrations, indicating that differences in chemical affinities can be the major cause of deviation from ideal behavior. Synthetic mixtures were compared with the dissolution behavior of fresh and naturally weathered unleaded gasoline. The presence of lighter aliphatic components in the gasoline had a profound effect on estimating effective solubility due to chemical affinity differences (estimated at 0.0055 per percentage increase in the molar proportion of aliphatic) as well as reduced molar volumes (estimated at - 0.0091 in the activity coefficient per unit increase in molar volume, mL/mol). Previously measured changes in activity coefficients due to natural weathering of 0.25 compares well to 0.27 calculated here based on changes in the chemical affinity and molar volumes. The study suggests that the initial estimation of the composition of a fuel is crucial in evaluating dissolution processes due to ideal and non-ideal dissolution, and in predicting long term dissolution trends and the longevity of NAPL petroleum plume risks.

Impact of grain size and rock composition on simulated rock weathering

NASA Astrophysics Data System (ADS)

Israeli, Yoni; Emmanuel, Simon

2018-05-01

Both chemical and mechanical processes act together to control the weathering rate of rocks. In rocks with micrometer size grains, enhanced dissolution at grain boundaries has been observed to cause the mechanical detachment of particles. However, it remains unclear how important this effect is in rocks with larger grains, and how the overall weathering rate is influenced by the proportion of high- and low-reactivity mineral phases. Here, we use a numerical model to assess the effect of grain size on chemical weathering and chemo-mechanical grain detachment. Our model shows that as grain size increases, the weathering rate initially decreases; however, beyond a critical size no significant decrease in the rate is observed. This transition occurs when the density of reactive boundaries is less than ˜ 20 % of the entire domain. In addition, we examined the weathering rates of rocks containing different proportions of high- and low-reactivity minerals. We found that as the proportion of low-reactivity minerals increases, the weathering rate decreases nonlinearly. These simulations indicate that for all compositions, grain detachment contributes more than 36 % to the overall weathering rate, with a maximum of ˜ 50 % when high- and low-reactivity minerals are equally abundant in the rock. This occurs because selective dissolution of the high-reactivity minerals creates large clusters of low-reactivity minerals, which then become detached. Our results demonstrate that the balance between chemical and mechanical processes can create complex and nonlinear relationships between the weathering rate and lithology.

Pre-cometary ice composition from hot core chemistry.

PubMed

Tornow, Carmen; Kührt, Ekkehard; Motschmann, Uwe

2005-10-01

Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same prebiotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere.

Metallurgically lithiated SiOx anode with high capacity and ambient air compatibility

PubMed Central

Zhao, Jie; Lee, Hyun-Wook; Sun, Jie; Yan, Kai; Liu, Yayuan; Liu, Wei; Lu, Zhenda; Lin, Dingchang; Zhou, Guangmin; Cui, Yi

2016-01-01

A common issue plaguing battery anodes is the large consumption of lithium in the initial cycle as a result of the formation of a solid electrolyte interphase followed by gradual loss in subsequent cycles. It presents a need for prelithiation to compensate for the loss. However, anode prelithiation faces the challenge of high chemical reactivity because of the low anode potential. Previous efforts have produced prelithiated Si nanoparticles with dry air stability, which cannot be stabilized under ambient air. Here, we developed a one-pot metallurgical process to synthesize LixSi/Li2O composites by using low-cost SiO or SiO2 as the starting material. The resulting composites consist of homogeneously dispersed LixSi nanodomains embedded in a highly crystalline Li2O matrix, providing the composite excellent stability even in ambient air with 40% relative humidity. The composites are readily mixed with various anode materials to achieve high first cycle Coulombic efficiency (CE) of >100% or serve as an excellent anode material by itself with stable cyclability and consistently high CEs (99.81% at the seventh cycle and ∼99.87% for subsequent cycles). Therefore, LixSi/Li2O composites achieved balanced reactivity and stability, promising a significant boost to lithium ion batteries. PMID:27313206

Composite Materials for Thermal Energy Storage: Enhancing Performance through Microstructures

PubMed Central

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-01-01

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

30 CFR 47.2 - Operators and chemicals covered; initial miner training.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Operators and chemicals covered; initial miner... Training § 47.2 Operators and chemicals covered; initial miner training. (a) This part applies to any operator producing or using a hazardous chemical to which a miner can be exposed under normal conditions of...

30 CFR 47.2 - Operators and chemicals covered; initial miner training.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Operators and chemicals covered; initial miner... Training § 47.2 Operators and chemicals covered; initial miner training. (a) This part applies to any operator producing or using a hazardous chemical to which a miner can be exposed under normal conditions of...

30 CFR 47.2 - Operators and chemicals covered; initial miner training.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Operators and chemicals covered; initial miner... Training § 47.2 Operators and chemicals covered; initial miner training. (a) This part applies to any operator producing or using a hazardous chemical to which a miner can be exposed under normal conditions of...

30 CFR 47.2 - Operators and chemicals covered; initial miner training.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Operators and chemicals covered; initial miner... Training § 47.2 Operators and chemicals covered; initial miner training. (a) This part applies to any operator producing or using a hazardous chemical to which a miner can be exposed under normal conditions of...

30 CFR 47.2 - Operators and chemicals covered; initial miner training.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Operators and chemicals covered; initial miner... Training § 47.2 Operators and chemicals covered; initial miner training. (a) This part applies to any operator producing or using a hazardous chemical to which a miner can be exposed under normal conditions of...

Chemical composition and strength of dolomite geopolymer composites

NASA Astrophysics Data System (ADS)

Aizat, E. A.; Al Bakri, A. M. M.; Liew, Y. M.; Heah, C. Y.

2017-09-01

The chemical composition of dolomite and the compressive strength of dolomite geopolymer composites were studied. The both composites prepared with mechanical mixer manufactured by with rotor speed of 350 rpm and curing in the oven for 24 hours at 80˚C. XRF analysis showThe dolomite raw materials contain fewer amounts of Si and Al but high Ca in its composition. Dolomite geopolymer composites with 20M of NaOH shows greater and optimum compressive strength compared to dolomite geopolymer with other NaOH molarity. This indicated better interaction of dolomite raw material and alkaline activator need high molarity of NaOH in order to increase the reactivity of dolomite.

Oxygen Consumption by Red Wines. Part I: Consumption Rates, Relationship with Chemical Composition, and Role of SO₂.

PubMed

Ferreira, Vicente; Carrascon, Vanesa; Bueno, Mónica; Ugliano, Maurizio; Fernandez-Zurbano, Purificación

2015-12-30

Fifteen Spanish red wines extensively characterized in terms of SO2, color, antioxidant indexes, metals, and polyphenols were subjected to five consecutive sensor-controlled cycles of air saturation at 25 °C. Within each cycle, O2 consumption rates cannot be interpreted by simple kinetic models. Plots of cumulated consumed O2 made it possible to define a fast and highly wine-dependent initial O2 consumption rate and a second and less variable average O2 consumption rate which remains constant in saturations 2 to 5. Both rates have been satisfactorily modeled, and in both cases they were independent of Fe and SO2 and highly dependent on Cu levels. Average rates were also related to Mn, pH, Folin, protein precipitable proanthocyanidins (PPAs), and polyphenolic profile. Initial rates were strong and negatively correlated to SO2 consumption, indicating that such an initial rate is either controlled by an unknown antioxidant present in some wines or affected by a poor real availability of SO2. Remaining unreacted SO2 is proportional to initial combined SO2 and to final free acetaldehyde.

Application of three tailing-based composites in treating comprehensive electroplating wastewater.

PubMed

Liu, Hongbo; Zhu, Mengling; Gao, Saisai

2014-01-01

Heavy metals and chemical oxygen demand (COD) are major challenging pollutants for most electroplating wastewater treatment plants. A novel composite material, prepared with a mixture of calcium and sodium compounds and tailings, was simply mixed by ratios and used to treat a comprehensive electroplating wastewater with influent COD, total copper (T-Cu), and total nickel (T-Ni) respectively as 690, 4.01, and 20.60 mg/L on average. Operational parameters, i.e. the contact time, pH, mass ratio of calcium and sodium compounds and tailings, were optimized as 30 min, 10.0, and 4:2:1. Removal rates for COD, T-Cu, and T-Ni could reach 71.8, 90.5, and 98.1%, respectively. No significant effect of initial concentrations on removal of T-Cu and T-Ni was observed for the composite material. The adsorption of Cu(II) and Ni(II) on the material fitted Langmuir and Freundlich isotherms respectively. Weight of waste sludge from the calcium/sodium-tailing system after reaction was 10% less than that from the calcium-tailing system. The tailing-based composite is cost-effective in combating comprehensive electroplating pollution, which shows a possibility of applying the tailings in treating electroplating wastewater.

Laboratory synthesis of silicate glass spherules: Application to impact ejecta

NASA Astrophysics Data System (ADS)

Stoddard, P. S.; Pahlevan, K.; Tumber, S.; Weber, R.; Lee, K. K.

2012-12-01

To investigate the process by which molten droplets of impact ejecta solidify into glassy spherule tektites, we employed laser levitation experiments to recreate the hot temperatures of falling molten rock. Following models for Earth composition based on enstatite chondrites, we levitated mixtures of oxide powders in a stream of gas and melted them with a laser, producing silicate glass beads. After quenching, we polished the ~1 mm diameter samples in cross-section and analyzed with electron probe microanalysis (EPMA). Fine and coarsely-spaced EPMA transects across each bead displayed diffusion profiles at their edges, particularly in their SiO2 and MgO content. Heating altered the beads' bulk composition as well; all of the glassy spherules were compositionally different from the initial combination of powders. By comparing these changes to the environmental factors acting on the bead (e.g., temperature, type of levitation gas, duration of heating and amount of rotation), we produced a model for how molten ejecta change chemically and physically as they solidify into a glass. We find that high temperatures likely generated on impact have a strong effect on the composition of tektites; therefore, attempts to correlate tektites to their parent rocks should correct for this effect.

Enhanced electrochemical performance from 3DG/LiFePO4/G sandwich cathode material

NASA Astrophysics Data System (ADS)

Du, Yahui; Tang, Yufeng; Chang, Chengkang

2017-08-01

In this paper, we have successfully synthesized a three dimensional graphene/LiFePO4/graphene (3DG/LFP/G) sandwich composite by an in-situ hydrothermal method, in which chemical vapor deposited 3D graphene acts as the high conductivity supporting framework, while the LiFePO4 nanoparticles are anchored onto the 3D graphene framework covered by graphene sheets. XRD and SEM results confirmed the formation of the 3DG/LFP/G sandwich composite. Cyclic Voltammetry curve of the sandwich composite shows sharper redox peaks and reduced voltage separation when compared to the reference electrodes, suggesting high specific capacity and good rate performance. Further charge/discharge measurements presented high capacity of 164 mAh g-1 at 0.2 C and 124 mAh g-1 at 10 C (75.7% of its initial capacity) for the sandwich composite, with capacity retention of 95.7% after 100 cycles, implying potential application in lithium ion battery at high rates. The EIS investigation suggests that both the electronic conductivity and the Li ion diffusion are promoted by the underlined 3D graphene framework, which is regarded as the reason for the enhanced electrochemical performance.

Preparation of ZnO/SnO2 Composite Nanometer Photocatalyst and Photocatalytic Treatment of Marine Diesel Pollution

NASA Astrophysics Data System (ADS)

Zhang, J.; Yu, X. C.; Nie, Z. W.; Guo, M. C.; Liu, J. H.; Wang, L. P.

2017-12-01

The ZnO/SnO2 composite nanophotocatalyst studied in this paper was prepared by a chemical precipitation method, which were characterized by XRD and SEM. The results show that the prepared samples were rutile SnO2 particles and the average grain size is 8.41 nm. In this paper, the factors for the degradation efficiency of marine diesel oil degraded by ZnO/SnO2 composite nanophotocatalyst are the catalysts’ doping ratio, the initial concentration of oil, the pH value of seawater, the dosage of catalyst and the dosage of hydrogen peroxide. The results show that the ZnO/SnO2 composite nanophotocatalyst can effectively degrade seawater diesel oil under UV light. When the doping ratio of ZnO and SnO2 is 0.35, the reaction time is 2.5 hours, the pH value of seawater with oil is 7, The concentration of diesel oil is 0.1g/L, the dosage of catalyst is 0.3g/L and the dosage of hydrogen peroxide is 0.1 g/L, the highest degradation rate is 91.54%.

Measurements of Positive Ambient Ions in Lamont OK as Part of the Holistic Interaction of Shallow Clouds Aerosols and Land Ecosystems (HISCALE II) Field Campaign

NASA Astrophysics Data System (ADS)

Abdelhamid, A.; Stark, H.; Worsnop, D. R.; Nowak, J. B.; Kuang, C.; Bullard, R.; Browne, E. C.

2017-12-01

Atmospheric ions control the electrical properties of the atmosphere, influence chemical composition via ion-molecule and/or ion-catalyzed reactions, and affect new particle formation. Understanding the role of ions in these processes requires knowledge of ionic chemical composition. Due to the low concentration of ions, chemical composition measurements have historically been challenging. Recent advances in mass spectrometry, such as the atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF), are now making these measurements more feasible. Here, we present measurements of ambient cations during the HISCALE II field campaign (August- September 2016) in Lamont, OK. We discuss how the chemical composition of cations varies over the course of the campaign including before, during, and after new particle formation events. We specifically focus on the composition of organic nitrogen ions due to the potential importance of these compounds in atmospheric nucleation. We compare our results to measurements of neutral organic nitrogen compounds in order to gain insight into how organic nitrogen is chemically transformed in the atmosphere and how this influences new particle formation.

Characterization and Prediction of Chemical Functions and ...

EPA Pesticide Factsheets

Assessing exposures from the thousands of chemicals in commerce requires quantitative information on the chemical constituents of consumer products. Unfortunately, gaps in available composition data prevent assessment of exposure to chemicals in many products. Here we propose filling these gaps via consideration of chemical functional role. We obtained function information for thousands of chemicals from public sources and used a clustering algorithm to assign chemicals into 35 harmonized function categories (e.g., plasticizers, antimicrobials, solvents). We combined these functions with weight fraction data for 4115 personal care products (PCPs) to characterize the composition of 66 different product categories (e.g., shampoos). We analyzed the combined weight fraction/function dataset using machine learning techniques to develop quantitative structure property relationship (QSPR) classifier models for 22 functions and for weight fraction, based on chemical-specific descriptors (including chemical properties). We applied these classifier models to a library of 10196 data-poor chemicals. Our predictions of chemical function and composition will inform exposure-based screening of chemicals in PCPs for combination with hazard data in risk-based evaluation frameworks. As new information becomes available, this approach can be applied to other classes of products and the chemicals they contain in order to provide essential consumer product data for use in exposure-b

Process for derivatizing carbon nanotubes with diazonium species and compositions thereof

NASA Technical Reports Server (NTRS)

Bahr, Jeffrey L. (Inventor); Tour, James M. (Inventor); Yang, Jiping (Inventor)

2011-01-01

Methods for the chemical modification of carbon nanotubes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications, and sensor devices. The methods of derivatization include electrochemical induced reactions, thermally induced reactions, and photochemically induced reactions. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

EAST VERSUS WEST IN THE US: CHEMICAL CHARACTERISTICS OF PM 2.5 DURING THE WINTER OF 1999

EPA Science Inventory

The chemical composition of PM2.5 was investigated at four sites (Rubidoux, CA, Phoenix, AZ, Philadelphia, PA, and RTP, NC) in January and February of 1999. Three samplers were used to determine both the overall mass and the chemical composition of the aerosol. Teflon filters wer...

Tunable Fabry-Perot etalon-based long-wavelength infrared imaging spectroradiometer.

PubMed

Marinelli, W J; Gittins, C M; Gelb, A H; Green, B D

1999-04-20

Imaging spectrometry enables passive, stand-off detection and analysis of the chemical composition of gas plumes and surfaces over wide geographic areas. We describe the use of a long-wavelength infrared imaging spectroradiometer, comprised of a low-order tunable Fabry-Perot etalon coupled to a HgCdTe detector array, to perform multispectral detection of chemical vapor plumes. The tunable Fabry-Perot etalon used in this research provides coverage of the 9.5-14-microm spectral region with a resolution of 7-9 cm(-1). The etalon-based imaging system provides the opportunity to image a scene at only those wavelengths needed for chemical species identification and quantification and thereby minimize the data volume necessary for selective species detection. We present initial results using a brassboard imaging system for stand-off detection and quantification of chemical vapor plumes against near-ambient-temperature backgrounds. These data show detection limits of 22 parts per million by volume times meter (ppmv x m) and 0.6 ppmv x m for dimethyl methyphosphonate and SF6, respectively, for a gas/background DeltaT of 6 K. The system noise-equivalent spectral radiance is approximately 2 microW cm(-2) sr(-1) microm(-1). Model calculations are presented comparing the measured sensitivity of the sensor to the anticipated signal levels for two chemical release scenarios.

Frequent Prescribed Burning as a Long-term Practice in Longleaf Pine Forests Does Not Affect Detrital Chemical Composition.

PubMed

Coates, T Adam; Chow, Alex T; Hagan, Donald L; Wang, G Geoff; Bridges, William C; Dozier, James H

2017-09-01

The O horizon, or detrital layer, of forest soils is linked to long-term forest productivity and health. Fuel reduction techniques, such as prescribed fire, can alter the thickness and composition of this essential ecosystem component. Developing an understanding of the changes in the chemical composition of forest detritus due to prescribed fire is essential for forest managers and stakeholders seeking sustainable, resilient, and productive ecosystems. In this study, we evaluated fuel quantity, fuel structure, and detrital chemical composition in longleaf pine ( Miller) forests that have been frequently burned for the last 40 yr at the Tom Yawkey Wildlife Center in Georgetown, SC. Our results suggest that frequent prescribed fire reduces forest fuel quantity ( < 0.01) and vertical structure ( = 0.01). Using pyrolysis-gas chromatography/mass spectrometry as a molecular technique to analyze detrital chemical composition, including aromatic compounds and polycyclic aromatic hydrocarbons, we found that the chemical composition of forest detritus was nearly uniform for both unburned and burned detritus. Our burning activities varied in the short term, consisting of annual dormant, annual growing, and biennial dormant season burns. Seasonal distinctions were present for fuel quantity and vertical fuel structure, but these differences were not noted for the benzene/phenol ratio. These results are significant as more managers consider burning existing longleaf stands while determining effective management practices for longleaf stands yet to be established. Managers of such stands can be confident that frequent, low-intensity, low-severity prescribed burns in longleaf pine forests do little to affect the long-term chemical composition of forest detritus. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Quantitative measurement of the chemical composition of geological standards with a miniature laser ablation/ionization mass spectrometer designed for in situ application in space research

NASA Astrophysics Data System (ADS)

Neuland, M. B.; Grimaudo, V.; Mezger, K.; Moreno-García, P.; Riedo, A.; Tulej, M.; Wurz, P.

2016-03-01

A key interest of planetary space missions is the quantitative determination of the chemical composition of the planetary surface material. The chemical composition of surface material (minerals, rocks, soils) yields fundamental information that can be used to answer key scientific questions about the formation and evolution of the planetary body in particular and the Solar System in general. We present a miniature time-of-flight type laser ablation/ionization mass spectrometer (LMS) and demonstrate its capability in measuring the elemental and mineralogical composition of planetary surface samples quantitatively by using a femtosecond laser for ablation/ionization. The small size and weight of the LMS make it a remarkable tool for in situ chemical composition measurements in space research, convenient for operation on a lander or rover exploring a planetary surface. In the laboratory, we measured the chemical composition of four geological standard reference samples USGS AGV-2 Andesite, USGS SCo-l Cody Shale, NIST 97b Flint Clay and USGS QLO-1 Quartz Latite with LMS. These standard samples are used to determine the sensitivity factors of the instrument. One important result is that all sensitivity factors are close to 1. Additionally, it is observed that the sensitivity factor of an element depends on its electron configuration, hence on the electron work function and the elemental group in agreement with existing theory. Furthermore, the conformity of the sensitivity factors is supported by mineralogical analyses of the USGS SCo-l and the NIST 97b samples. With the four different reference samples, the consistency of the calibration factors can be demonstrated, which constitutes the fundamental basis for a standard-less measurement-technique for in situ quantitative chemical composition measurements on planetary surface.

Temperature response of litter and soil organic matter decomposition is determined by chemical composition of organic material.

PubMed

Erhagen, Björn; Öquist, Mats; Sparrman, Tobias; Haei, Mahsa; Ilstedt, Ulrik; Hedenström, Mattias; Schleucher, Jürgen; Nilsson, Mats B

2013-12-01

The global soil carbon pool is approximately three times larger than the contemporary atmospheric pool, therefore even minor changes to its integrity may have major implications for atmospheric CO2 concentrations. While theory predicts that the chemical composition of organic matter should constitute a master control on the temperature response of its decomposition, this relationship has not yet been fully demonstrated. We used laboratory incubations of forest soil organic matter (SOM) and fresh litter material together with NMR spectroscopy to make this connection between organic chemical composition and temperature sensitivity of decomposition. Temperature response of decomposition in both fresh litter and SOM was directly related to the chemical composition of the constituent organic matter, explaining 90% and 70% of the variance in Q10 in litter and SOM, respectively. The Q10 of litter decreased with increasing proportions of aromatic and O-aromatic compounds, and increased with increased contents of alkyl- and O-alkyl carbons. In contrast, in SOM, decomposition was affected only by carbonyl compounds. To reveal why a certain group of organic chemical compounds affected the temperature sensitivity of organic matter decomposition in litter and SOM, a more detailed characterization of the (13) C aromatic region using Heteronuclear Single Quantum Coherence (HSQC) was conducted. The results revealed considerable differences in the aromatic region between litter and SOM. This suggests that the correlation between chemical composition of organic matter and the temperature response of decomposition differed between litter and SOM. The temperature response of soil decomposition processes can thus be described by the chemical composition of its constituent organic matter, this paves the way for improved ecosystem modeling of biosphere feedbacks under a changing climate. © 2013 John Wiley & Sons Ltd.

Untangling the Chemical Evolution of Titan's Atmosphere and Surface -- From Homogeneous to Heterogeneous Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaiser, Ralf I.; Maksyutenko, Pavlo; Ennis, Courtney

The arrival of the Cassini-Huygens probe at Saturn's moon Titan - the only Solar System body besides Earth and Venus with a solid surface and a thick atmosphere with a pressure of 1.4 atm at surface level - in 2004 opened up a new chapter in the history of Solar System exploration. The mission revealed Titan as a world with striking Earth-like landscapes involving hydrocarbon lakes and seas as well as sand dunes and lava-like features interspersed with craters and icy mountains of hitherto unknown chemical composition. The discovery of a dynamic atmosphere and active weather system illustrates further themore » similarities between Titan and Earth. The aerosol-based haze layers, which give Titan its orange-brownish color, are not only Titan's most prominent optically visible features, but also play a crucial role in determining Titan's thermal structure and chemistry. These smog-like haze layers are thought to be very similar to those that were present in Earth's atmosphere before life developed more than 3.8 billion years ago, absorbing the destructive ultraviolet radiation from the Sun, thus acting as 'prebiotic ozone' to preserve astrobiologically important molecules on Titan. Compared to Earth, Titan's low surface temperature of 94 K and the absence of liquid water preclude the evolution of biological chemistry as we know it. Exactly because of these low temperatures, Titan provides us with a unique prebiotic 'atmospheric laboratory' yielding vital clues - at the frozen stage - on the likely chemical composition of the atmosphere of the primitive Earth. However, the underlying chemical processes, which initiate the haze formation from simple molecules, have been not understood well to date.« less

Real-Time Optical Monitoring and Simulations of Gas Phase Kinetics in InN Vapor Phase Epitaxy at High Pressure

NASA Technical Reports Server (NTRS)

Dietz, Nikolaus; Woods, Vincent; McCall, Sonya D.; Bachmann, Klaus J.

2003-01-01

Understanding the kinetics of nucleation and coalescence of heteroepitaxial thin films is a crucial step in controlling a chemical vapor deposition process, since it defines the perfection of the heteroepitaxial film both in terms of extended defect formation and chemical integrity of the interface. The initial nucleation process also defines the film quality during the later stages of film growth. The growth of emerging new materials heterostructures such as InN or In-rich Ga(x)In(1-x)N require deposition methods operating at higher vapor densities due to the high thermal decomposition pressure in these materials. High nitrogen pressure has been demonstrated to suppress thermal decomposition of InN, but has not been applied yet in chemical vapor deposition or etching experiments. Because of the difficulty with maintaining stochiometry at elevated temperature, current knowledge regarding thermodynamic data for InN, e.g., its melting point, temperature-dependent heat capacity, heat and entropy of formation are known with far less accuracy than for InP, InAs and InSb. Also, no information exists regarding the partial pressures of nitrogen and phosphorus along the liquidus surfaces of mixed-anion alloys of InN, of which the InN(x)P(1-x) system is the most interesting option. A miscibility gap is expected for InN(x)P(1-x) pseudobinary solidus compositions, but its extent is not established at this point by experimental studies under near equilibrium conditions. The extension of chemical vapor deposition to elevated pressure is also necessary for retaining stoichiometric single phase surface composition for materials that are characterized by large thermal decomposition pressures at optimum processing temperatures.

Enviro-HIRLAM online integrated meteorology-chemistry modelling system: strategy, methodology, developments and applications (v7.2)

NASA Astrophysics Data System (ADS)

Baklanov, Alexander; Smith Korsholm, Ulrik; Nuterman, Roman; Mahura, Alexander; Pagh Nielsen, Kristian; Hansen Sass, Bent; Rasmussen, Alix; Zakey, Ashraf; Kaas, Eigil; Kurganskiy, Alexander; Sørensen, Brian; González-Aparicio, Iratxe

2017-08-01

The Environment - High Resolution Limited Area Model (Enviro-HIRLAM) is developed as a fully online integrated numerical weather prediction (NWP) and atmospheric chemical transport (ACT) model for research and forecasting of joint meteorological, chemical and biological weather. The integrated modelling system is developed by the Danish Meteorological Institute (DMI) in collaboration with several European universities. It is the baseline system in the HIRLAM Chemical Branch and used in several countries and different applications. The development was initiated at DMI more than 15 years ago. The model is based on the HIRLAM NWP model with online integrated pollutant transport and dispersion, chemistry, aerosol dynamics, deposition and atmospheric composition feedbacks. To make the model suitable for chemical weather forecasting in urban areas, the meteorological part was improved by implementation of urban parameterisations. The dynamical core was improved by implementing a locally mass-conserving semi-Lagrangian numerical advection scheme, which improves forecast accuracy and model performance. The current version (7.2), in comparison with previous versions, has a more advanced and cost-efficient chemistry, aerosol multi-compound approach, aerosol feedbacks (direct and semi-direct) on radiation and (first and second indirect effects) on cloud microphysics. Since 2004, the Enviro-HIRLAM has been used for different studies, including operational pollen forecasting for Denmark since 2009 and operational forecasting atmospheric composition with downscaling for China since 2017. Following the main research and development strategy, further model developments will be extended towards the new NWP platform - HARMONIE. Different aspects of online coupling methodology, research strategy and possible applications of the modelling system, and fit-for-purpose model configurations for the meteorological and air quality communities are discussed.

Scaling and efficiency of PRISM in adaptive simulations of turbulent premixed flames

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tonse, Shaheen R.; Bell, J.B.; Brown, N.J.

1999-12-01

The dominant computational cost in modeling turbulent combustion phenomena numerically with high fidelity chemical mechanisms is the time required to solve the ordinary differential equations associated with chemical kinetics. One approach to reducing that computational cost is to develop an inexpensive surrogate model that accurately represents evolution of chemical kinetics. One such approach, PRISM, develops a polynomial representation of the chemistry evolution in a local region of chemical composition space. This representation is then stored for later use. As the computation proceeds, the chemistry evolution for other points within the same region are computed by evaluating these polynomials instead ofmore » calling an ordinary differential equation solver. If initial data for advancing the chemistry is encountered that is not in any region for which a polynomial is defined, the methodology dynamically samples that region and constructs a new representation for that region. The utility of this approach is determined by the size of the regions over which the representation provides a good approximation to the kinetics and the number of these regions that are necessary to model the subset of composition space that is active during a simulation. In this paper, we assess the PRISM methodology in the context of a turbulent premixed flame in two dimensions. We consider a range of turbulent intensities ranging from weak turbulence that has little effect on the flame to strong turbulence that tears pockets of burning fluid from the main flame. For each case, we explore a range of sizes for the local regions and determine the scaling behavior as a function of region size and turbulent intensity.« less

The effect of carbon surface chemical composition on the adsorption of acetanilide.

PubMed

Terzyk, Artur P

2004-04-01

The study of acetanilide adsorption-desorption performed at three temperatures (300, 310, and 320 K) and at two pH levels (7.0 and 1.5) on the series of D43/1 carbons (initial and modified with HNO3, fuming H2SO4, and gaseous NH3) is reported. Sorption data are additionally supplemented with the results of thermal analysis and calorimetric and kinetic measurements. It is shown that, generally, acetanilide adsorption at the neutral pH level is reversible (only on the more acidic carbons and at the lowest temperature does hysteresis occur due to the formation of hydrogen bonds with surface OH groups), and it decreases for the chemically modified carbons. In contrast, at the acidic pH level acetanilide adsorption is irreversible. A mechanism of irreversibility is proposed and it is shown that hysteresis is caused by the chemical reaction between the nucleophile (carbon) and the protonized acetanilide molecules. For all studied carbons, at the acidic pH level, adsorption increases and this is caused by the weakly basic character of acetanilide molecule. Adsorption results are described applying adsorbability and Dubinin-Astakhov, quasi-Freundlich and solution analogue of the Toth adsorption isotherm equations. Using the kinetic data, the effective diffusion coefficients and the energy of diffusion are calculated. It is shown that the diffusion is mainly a surface process, and the contribution of the pore diffusion increases with the rise in temperature. By applying different correlations between the parameters obtained from the theoretical description of experimental data and those characterizing the chemical composition of the studied carbons, the role of the latter in the adsorption and kinetics of acetanilide adsorption is determined.

Chemical characterization of fingerprints from adults and children

NASA Astrophysics Data System (ADS)

Buchanan, Michelle V.; Asano, Keiji; Bohanon, Arthur

1997-02-01

The observation that the fingerprints of children disappear from surfaces more quickly than those of adults initiated a study to characterize the chemical components in fingerprints. Samples were obtained from about 50 individuals ranging in age from three to 64 by extracting chemicals from the fintertips using rubbing alcohol. Using combined gas chromatography/mass spectrometry, a wide range of compounds were identified. It was found that the chemical compositions of fingerprints were quite different in children and adults. In general, the samples obtained from children contained higher levels of relatively volatile free fatty acids. Samples from adults were found to have higher concentrations of less volatile long chain esters of fatty acids. These esters are thought to originate from sebaceous glands located on the face and the levels of these compounds increase substantially after puberty. In addition to these compounds, a variety of other compounds were observed that could be used to develop improved methods for fingerprint detection at a crime scene. Further, the observation of specific compounds raises the possibility of being able to identify personal traits (gender, habits, diseases, etc.) via the analysis of components in fingerprints and/or skin.

Degradation of experimental composite materials and in vitro wear simulation

NASA Astrophysics Data System (ADS)

Givan, Daniel Allen

2001-12-01

The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects of the debris aggregate predominated the wear process. The non-linear rate of wear loss was accelerated as the facet deepened. Physical effects, such as thermal fatigue, and chemical effects were less important but contributed to the degradation process. This study provides new insight into the role(s) of high modulus third body debris in the wear of dental composites.

Chemical and Biological Sensing Using Hybridization Chain Reaction.

PubMed

Augspurger, Erik E; Rana, Muhit; Yigit, Mehmet V

2018-05-25

Since the advent of its theoretical discovery more than 30 years ago, DNA nanotechnology has been used in a plethora of diverse applications in both the fundamental and applied sciences. The recent prominence of DNA-based technologies in the scientific community is largely due to the programmable features stored in its nucleobase composition and sequence, which allow it to assemble into highly advanced structures. DNA nanoassemblies are also highly controllable due to the precision of natural and artificial base-pairing, which can be manipulated by pH, temperature, metal ions, and solvent types. This programmability and molecular-level control have allowed scientists to create and utilize DNA nanostructures in one, two, and three dimensions (1D, 2D, and 3D). Initially, these 2D and 3D DNA lattices and shapes attracted a broad scientific audience because they are fundamentally captivating and structurally elegant; however, transforming these conceptual architectural blueprints into functional materials is essential for further advancements in the DNA nanotechnology field. Herein, the chemical and biological sensing applications of a 1D DNA self-assembly process known as hybridization chain reaction (HCR) are reviewed. HCR is a one-dimensional (1D) double stranded (ds) DNA assembly process initiated only in the presence of a specific short ssDNA (initiator) and two kinetically trapped DNA hairpin structures. HCR is considered an enzyme-free isothermal amplification process, which shows substantial promise and offers a wide range of applications for in situ chemical and biological sensing. Due to its modular nature, HCR can be programmed to activate only in the presence of highly specific biological and/or chemical stimuli. HCR can also be combined with different types of molecular reporters and detection approaches for various analytical readouts. While the long dsDNA HCR product may not be as structurally attractive as the 2D and 3D DNA networks, HCR is highly instrumental for applied biological, chemical, and environmental sciences, and has therefore been studied to foster a variety of objectives. In this review, we have focused on nucleic acid, protein, metabolite, and heavy metal ion detection using this 1D DNA nanotechnology via fluorescence, electrochemical, and nanoparticle-based methodologies.

Sulfur nanocrystals anchored graphene composite with highly improved electrochemical performance for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Zhang, Jun; Dong, Zimin; Wang, Xiuli; Zhao, Xuyang; Tu, Jiangping; Su, Qingmei; Du, Gaohui

2014-12-01

Two kinds of graphene-sulfur composites with 50 wt% of sulfur are prepared using hydrothermal method and thermal mixing, respectively. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectra mapping show that sulfur nanocrystals with size of ∼5 nm dispersed on graphene sheets homogeneously for the sample prepared by hydrothermal method (NanoS@G). While for the thermal mixed graphene-sulfur composite (S-G mixture), sulfur shows larger and uneven size (50-200 nm). X-ray Photoelectron Spectra (XPS) reveals the strong chemical bonding between the sulfur nanocrystals and graphene. Comparing with the S-G mixture, the NanoS@G composite shows highly improved electrochemical performance as cathode for lithium-sulfur (Li-S) battery. The NanoS@G composite delivers an initial capacity of 1400 mAh g-1 with the sulfur utilization of 83.7% at a current density of 335 mA g-1. The capacity keeps above 720 mAh g-1 over 100 cycles. The strong adherence of the sulfur nanocrystals on graphene immobilizes sulfur and polysulfides species and suppressed the "shuttle effect", resulting higher coulombic efficiency and better capacity retention. Electrochemical impedance also suggests that the strong bonding enabled rapid electronic/ionic transport and improved electrochemical kinetics, therefore good rate capability is obtained. These results demonstrate that the NanoS@G composite is a very promising candidate for high-performance Li-S batteries.

A rapid method for the computation of equilibrium chemical composition of air to 15000 K

NASA Technical Reports Server (NTRS)

Prabhu, Ramadas K.; Erickson, Wayne D.

1988-01-01

A rapid computational method has been developed to determine the chemical composition of equilibrium air to 15000 K. Eleven chemically reacting species, i.e., O2, N2, O, NO, N, NO+, e-, N+, O+, Ar, and Ar+ are included. The method involves combining algebraically seven nonlinear equilibrium equations and four linear elemental mass balance and charge neutrality equations. Computational speeds for determining the equilibrium chemical composition are significantly faster than the often used free energy minimization procedure. Data are also included from which the thermodynamic properties of air can be computed. A listing of the computer program together with a set of sample results are included.

Chemical composition and antifungal activity of the essential oils of Schinus weinmannifolius collected in the spring and winter.

PubMed

Hernandes, Camila; Taleb-Contini, Silvia H; Bartolomeu, Ana Carolina D; Bertoni, Bianca W; França, Suzelei C; Pereira, Ana Maria S

2014-09-01

Reports on the chemical and pharmacological profile of the essential oil of Schinus weinmannifolius do not exist, although other Schinus species have been widely investigated for their biological activities. This work aimed to evaluate the chemical composition and antimicrobial activity of the essential oil of S. weinmannifolius collected in the spring and winter. The essential oils were extracted by hydrodistillation, analyzed by GC/MS and submitted to microdilution tests, to determine the minimum inhibitory concentration. The oils displayed different chemical composition and antimicrobial action. Bicyclogermacrene and limonene predominated in the oils extracted in the winter and spring, respectively, whereas only the latter oil exhibited antifungal activity.

Sensory receptors of the larynx.

PubMed

Bradley, R M

2000-03-06

The larynx is a highly reflexogenic area, and stimulation with mechanical and chemical stimuli results in a number of protective reflexes. Investigators have used anatomical, behavioral, and neurophysiological techniques to examine the receptors responsible for initiating these reflex responses. Histologic examination has revealed the presence of free nerve endings, Merkel cells, Meissner corpuscles, and taste buds. Mechanoreceptors have been classified in several different ways and are located either in the superficial mucosa or in muscles and laryngeal joints. Recordings from afferent fibers innervating laryngeal mechanoreceptors have revealed that some of them are spontaneously active whereas others are silent until stimulated. Laryngeal mechanoreceptors respond to stimulation with either a rapidly adapting or a slowly adapting response pattern. Often the mechanoreceptors respond to respiratory movement of the larynx, giving bursts of action potentials during inspiration. A large number of taste buds that are anatomically similar to lingual taste buds populates the laryngeal surface of the epiglottis. Taste buds of the larynx respond to a number of chemical stimuli and to water. They do not respond to NaCl solutions close to physiological concentrations (0.154 M) but do respond at both a lower and higher concentration. When water is the solvent for the chemical stimuli, most chemicals initiate a response in laryngeal taste buds. However, when 0.154 M saline is used as a solvent, chemicals that taste bitter or sweet when applied to the tongue are ineffective stimuli. Taste buds of the larynx tend to be stimulated by the pH and tonicity of the stimulating solution and not by the gustatory properties. These results reveal a fundamental difference between the chemoreceptors of the oral cavity and larynx and result in the conclusion that chemoreceptors of the larynx do not play a role in gustation but are adapted to detect chemicals that are not saline-like in composition.

Developing an in vitro technology to study the inflammation potential of ambient particle types

NASA Astrophysics Data System (ADS)

Haddrell, Allen E.

Elevated levels of suspended particles in the troposphere, termed particulate matter, elicit a myriad of adverse health effects in humans, ranging from shortness of breath and wheezing to myocardial infarction and death. It is currently believed that the adverse health effects associated with particulate matter are mediated by the inflammatory response initiated by the lung following particulate matter inhalation. What remains an area of much interest is elucidating the specific properties of particulate matter, physical or chemical, that cause the upregulation of proinflammatory mediators. The basic premise of this thesis was to identify the specific chemical components of particulate matter responsible for its adverse health effects. To address this issue, instrumentation and methodology were developed wherein one could design, create, levitate and deposit particles of both known chemical composition and size onto lung cells, in vitro, followed by the monitoring of the downstream biological response. An initial study focused on the role of the endotoxin component in particulate matter toxicity. Through a series of blocking studies we found that endotoxin acted synergistically with the particle core to elicit upregulation of proinflammatory mediators, including IL-1beta, TNF-alpha and ICAM-1; all of which are associated with the NF-kappaB pathway. Through characterizing this relatively simple system, one observation became apparent: the presence of the insoluble particle core had a profound effect on the cellular response; that is to say, the particle core was not simply a delivery vector, but a determinant factor in the final intracellular location of the toxic chemical. The latter observation held true as other particle types were studied and in addition, it was found that the nature of the actual chemical species itself plays a dual role in particle toxicity; first by retaining its toxic properties and second by altering the physical properties of the particle. It stems from these findings that the toxicity of the chemical components must be studied in concert and not as individual entities.

ADHESIVES WITH DIFFERENT PHS: EFFECT ON THE MTBS OF CHEMICALLY ACTIVATED AND LIGHT-ACTIVATED COMPOSITES TO HUMAN DENTIN

PubMed Central

Mallmann, André; de Melo, Renata Marques; Estrela, Verbênia; Pelogia, Fernanda; Campos, Laura; Bottino, Marco Antonio; Valandro, Luiz Felipe

2007-01-01

Purpose: To evaluate the bond strength between human dentin and composites, using two light-activated single-bottle total-etch adhesive systems with different pHs combined with chemically activated and light-activated-composites. The tested hypothesis was that the dentin bond strength is not influenced by an adhesive system of low pH, combined with chemically activated or light-activated composites. Material and Method: Flat dentin surfaces of twenty-eight human third molars were allocated in 4 groups (n=7), depending on the adhesive system: (One Step Plus-OS and Prime & Bond NT-PB) and composite (light-activated Filtek Z-100 [Z100] and chemically activated Bisfil 2B [B2B]). Each adhesive system was applied on acid-etched dentin and then one of the composites was added to form a 5 mm-high resin block. The specimens were stored in tap water (37°C/24 h) and sectioned into two axes, x and y. This was done with a diamond disk under coolant irrigation to obtain beams with a cross-section area of approximately 0.8 mm2. Each specimen was then attached to a custom-made device and submitted to the microtensile test (1 mm.min−1). Data were analyzed using two-way ANOVA and Tukey’s tests (p<0.05). Results: The anticipated hypothesis was not confirmed (p<0.0001). The bond strengths (MPa) were not statistically different between the two adhesive systems when light-activated composite was used (OS+Z100 = 24.7±7.1ª; PB+Z100 = 23.8±5.7ª). However, with use of the chemically activated composite (B2B), PB (7.8±3.6b MPa) showed significantly lower dentin bond strengths than OS (32.2±7.6ª). Conclusion: The low pH of the adhesive system can affect the bond of chemically activated composite to dentin. On the other hand, under the present conditions, the low pH did not seem to affect the bond of light-activated composites to dentin significantly. PMID:19089142

Adhesives with different pHs: effect on the MTBS of chemically activated and light-activated composites to human dentin.

PubMed

Mallmann, André; de Melo, Renata Marques; Estrela, Verbênia; Pelogia, Fernanda; Campos, Laura; Bottino, Marco Antonio; Valandro, Luiz Felipe

2007-08-01

To evaluate the bond strength between human dentin and composites, using two light-activated single-bottle total-etch adhesive systems with different pHs combined with chemically activated and light-activated-composites. The tested hypothesis was that the dentin bond strength is not influenced by an adhesive system of low pH, combined with chemically activated or light-activated composites. Flat dentin surfaces of twenty-eight human third molars were allocated in 4 groups (n=7), depending on the adhesive system: (One Step Plus-OS and Prime & Bond NT-PB) and composite (light-activated Filtek Z-100 [Z100] and chemically activated Bisfil 2B [B2B]). Each adhesive system was applied on acid-etched dentin and then one of the composites was added to form a 5 mm-high resin block. The specimens were stored in tap water (37 degrees C/24 h) and sectioned into two axes, x and y. This was done with a diamond disk under coolant irrigation to obtain beams with a cross-section area of approximately 0.8 mm(2). Each specimen was then attached to a custom-made device and submitted to the microtensile test (1 mm*min-1). Data were analyzed using two-way ANOVA and Tukey's tests (p<0.05). The anticipated hypothesis was not confirmed (p<0.0001). The bond strengths (MPa) were not statistically different between the two adhesive systems when light-activated composite was used (OS+Z100 = 24.7+/-7.1 feminine; PB+Z100 = 23.8+/-5.7 feminine). However, with use of the chemically activated composite (B2B), PB (7.8+/-3.6b MPa) showed significantly lower dentin bond strengths than OS (32.2+/-7.6 feminine). The low pH of the adhesive system can affect the bond of chemically activated composite to dentin. On the other hand, under the present conditions, the low pH did not seem to affect the bond of light-activated composites to dentin significantly.

Detailed chemical composition of classical Cepheids in the LMC cluster NGC 1866 and in the field of the SMC

NASA Astrophysics Data System (ADS)

Lemasle, B.; Groenewegen, M. A. T.; Grebel, E. K.; Bono, G.; Fiorentino, G.; François, P.; Inno, L.; Kovtyukh, V. V.; Matsunaga, N.; Pedicelli, S.; Primas, F.; Pritchard, J.; Romaniello, M.; da Silva, R.

2017-12-01

Context. Cepheids are excellent tracers of young stellar populations. They play a crucial role in astrophysics as standard candles. The chemistry of classical Cepheids in the Milky Way is now quite well-known, however despite a much larger sample, the chemical composition of Magellanic Cepheids has been only scarcely investigated. Aims: For the first time, we study the chemical composition of several Cepheids located in the same populous cluster: NGC 1866, in the Large Magellanic Cloud (LMC). To also investigate the chemical composition of Cepheids at lower metallicity, we look at four targets located in the Small Magellanic Cloud (SMC). Our sample allows us to increase the number of Cepheids with known metallicities in the LMC/SMC by 20%/25% and the number of Cepheids with detailed chemical composition in the LMC/SMC by 46%/50%. Methods: We use canonical spectroscopic analysis to determine the chemical composition of Cepheids and provide abundances for a good number of α, iron-peak, and neutron-capture elements. Results: We find that six Cepheids in the LMC cluster NGC 1866 have a very homogeneous chemical composition, also consistent with red giant branch (RGB) stars in the cluster. Period-age relations that include no or average rotation indicate that all the Cepheids in NGC 1866 have a similar age and therefore belong to the same stellar population. Our results are in good agreement with theoretical models accounting for luminosity and radial velocity variations. Using distances based on period-luminosity relations in the near- or mid-infrared, we investigate for the first time the metallicity distribution of the young population in the SMC in the depth direction. Preliminary results show no metallicity gradient along the SMC main body, but our sample is small and does not contain Cepheids in the inner few degrees of the SMC. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 082.D-0792(B).

Detonation failure characterization of non-ideal explosives

NASA Astrophysics Data System (ADS)

Janesheski, Robert S.; Groven, Lori J.; Son, Steven

2012-03-01

Non-ideal explosives are currently poorly characterized, hence limiting the modeling of them. Current characterization requires large-scale testing to obtain steady detonation wave characterization for analysis due to the relatively thick reaction zones. Use of a microwave interferometer applied to small-scale confined transient experiments is being implemented to allow for time resolved characterization of a failing detonation. The microwave interferometer measures the position of a failing detonation wave in a tube that is initiated with a booster charge. Experiments have been performed with ammonium nitrate and various fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics are influenced by factors such as chemical composition and confiner thickness. Future work is planned to calibrate models to these small-scale experiments and eventually validate the models with available large scale experiments. This experiment is shown to be repeatable, shows dependence on reactive properties, and can be performed with little required material.

Application of carbon nanotube hold-off voltage for determining gas composition

NASA Technical Reports Server (NTRS)

Schipper, John F. (Inventor); Li, Jing (Inventor)

2009-01-01

Method and system for determining chemical composition of a single-component or multiple-component gas, using a discharge holdoff mechanism. A voltage difference V between two spaced apart electrodes is brought to a selected value and held, the holdoff time interval .DELTA.t(V;ho) required before gas discharge occurs is measured, and the associated electrical current or cumulative electrical charge is measured. As the voltage difference V increases, the time interval length .DELTA.t(V;ho) decreases monotonically. Particular voltage values, V.sub..infin. and V.sub.0, correspond to initial appearance of discharge (.DELTA.t.apprxeq..infin.) and prompt discharge (.DELTA.t.apprxeq.0). The values V.sub..infin. and V.sub.0 and the rate of decrease of .DELTA.t(V;ho) and/or the rate of increase of current or cumulative charge with increasing V are characteristic of one or more gas components present.

PRE-ORE POTASSIUM METASOMATISM, CREEDE MINING DISTRICT, COLORADO.

USGS Publications Warehouse

Bethke, P.M.; Rye, R.O.; Barton, P.B.

1985-01-01

Rhyolitic welded-tuff wallrocks of the epithermal base and precious metal veins of the Creede district were pervasively altered by the addition of more than two billion metric tons of potassium some 1. 5-2 million years before mineralization. Sodium, calcium and magnesium were strongly depleted, yielding a nearly binary quartz plus potassium feldspar assemblage containing as much as 13 weight percent K//2O. This large-scale metasomatism, originally noted by Steven and Rattle (1965), took place progressively by initial alteration of plagioclase phenocrysts to orthoclase or microcline followed by alteration of the groundmass feldspar to orthoclase and gradual change of the sanidine phenocrysts to more Or-rich compositions. Oxygen isotope and chemical studies show that the metasomatism resulted from the interaction of the tuffs with deeply circulating heated ground water and suggest that the potassium metasomatism of rhyolitic rocks is the facies equivalent of propylitization of volcanic rocks of more basic composition.

The structural and electronic properties of amorphous HgCdTe from first-principles calculations

NASA Astrophysics Data System (ADS)

Zhao, Huxian; Chen, Xiaoshuang; Lu, Jianping; Shu, Haibo; Lu, Wei

2014-01-01

Amorphous mercury cadmium telluride (a-MCT) model structures, with x being 0.125 and 0.25, are obtained from first-principles calculations. We generate initial structures by computation alchemy method. It is found that most atoms in the network of amorphous structures tend to be fourfold and form tetrahedral structures, implying that the chemical ordered continuous random network with some coordination defects is the ideal structure for a-MCT. The electronic structure is also concerned. The gap is found to be 0.30 and 0.26 eV for a-Hg0.875Cd0.125Te and a-Hg0.75Cd0.25Te model structures, independent of the composition. By comparing with the properties of crystalline MCT with the same composition, we observe a blue-shift of energy band gap. The localization of tail states and its atomic origin are also discussed.

Some issues associated with the formation of the Saturnian system

NASA Technical Reports Server (NTRS)

Lunine, Jonathan I.

1992-01-01

Three of the current issues associated with the formation of the Saturn system which involve significant controversy and uncertainty and which bear on the formation of Titan itself are outlined: the notion that the formation of Jupiter and Saturn are well constrained is challenged by recent internal models, which suggest possible significant differences in the composition of planetesimals which formed the two bodies; the composition of volatile ices which was the source of the Saturnian satellites was likely a complex mix of relatively pristine solids from the collapsing interstellar cloud, gas and solid material processed in the solar nebula and material chemically processed in a nebula around Saturn or in the primitive Saturn atmosphere itself; the deuterium enhancement in Titan's atmosphere, which initially appeared to be sufficiently large that it must be a signature of pristine interstellar material, could in fact be largely due to photochemical evolution of Titan's atmosphere.

Mineralogy of the Martian Surface: Crustal Composition to Surface Processes

NASA Technical Reports Server (NTRS)

Mustard, John F.

1999-01-01

Over the course of this award we have: 1) Completed and published the results of a study of the effects of hyperfine particles on reflectance spectra of olivine and quartz, which included the development of scattering codes. Research has also progressed in the analysis of the effects of fine particle sizes on clay spectra. 2) Completed the analysis of the mineralogy of dark regions, showed the insitu compositions are highly correlated to the SNC meteorites, and determined that the martian mantle was depleted in aluminum prior to 2-3 GA ago; Studies of the mineralogic heterogeneity of surficial materials on Mars have also been conducted. and 3) Performed initial work on the study of the physical and chemical processes likely to form and modify duricrust. This includes assessments of erosion rates, solubility and transport of iron in soil environments, and models of pedogenic crust formation.

Plasma Spraying of Ceramics with Particular Difficulties in Processing

NASA Astrophysics Data System (ADS)

Mauer, G.; Schlegel, N.; Guignard, A.; Jarligo, M. O.; Rezanka, S.; Hospach, A.; Vaßen, R.

2015-01-01

Emerging new applications and growing demands of plasma-sprayed coatings initiate the development of new materials. Regarding ceramics, often complex compositions are employed to achieve advanced material properties, e.g., high thermal stability, low thermal conductivity, high electronic and ionic conductivity as well as specific thermo-mechanical properties and microstructures. Such materials however, often involve particular difficulties in processing by plasma spraying. The inhomogeneous dissociation and evaporation behavior of individual constituents can lead to changes of the chemical composition and the formation of secondary phases in the deposited coatings. Hence, undesired effects on the coating characteristics are encountered. In this work, examples of such challenging materials are investigated, namely pyrochlores applied for thermal barrier coatings as well as perovskites for gas separation membranes. In particular, new plasma spray processes like suspension plasma spraying and plasma spray-physical vapor deposition are considered. In some cases, plasma diagnostics are applied to analyze the processing conditions.

Consumer product chemical weight fractions from ingredient lists

EPA Science Inventory

Assessing human exposures to chemicals in consumer products requires composition information. However, comprehensive composition data for products in commerce are not generally available. Many consumer products have reported ingredient lists that are constructed using specific gu...

The Chemical Composition of Maple Syrup

ERIC Educational Resources Information Center

Ball, David W.

2007-01-01

Maple syrup is one of several high-sugar liquids that humans consume. However, maple syrup is more than just a concentrated sugar solution. Here, we review the chemical composition of maple syrup. (Contains 4 tables and 1 figure.)

Chemical investigations of male and female leaf extracts from Schinus molle L.

PubMed

Garzoli, Stefania; Laghezza Masci, Valentina; Turchetti, Giovanni; Pesci, Lorenzo; Tiezzi, Antonio; Ovidi, Elisa

2018-05-29

The pepper-tree Schinus molle is an evergreen ornamental plant with various and diversified list of medical uses. In this article we analysed the chemical composition of male and female leaves of this plant during the off-flowering and flowering seasons. The leaf extracts were obtained by using a sequential extraction with solvents of different polarities and the chemical composition was investigated by GC-MS. The results showed a total of twenty-three components, in which elemol is the most abundant constituent followed by bicyclogermacrene, γ-eudesmol, α-eudesmol, β-eudesmol and isocalamendiol. The petroleum ether and diethyl ether extracts from male and female flowering and off-flowering leaves consisted of sesquiterpene hydrocarbons as a major constituent followed by monoterpene hydrocarbons, while the acetone extracts showed a different composition. The obtained results show differences in the chemical composition between male and female and flowering and not flowering.

Essential Oil Composition of Phagnalon sordidum (L.) from Corsica, Chemical Variability and Antimicrobial Activity.

PubMed

Brunel, Marion; Vitrac, Caroline; Costa, Jean; Mzali, Fatima; Vitrac, Xavier; Muselli, Alain

2016-03-01

The chemical composition of Phagnalon sordidum (L.) essential oil was investigated for the first time using gas chromatography and chromatography/mass spectrometry. Seventy-six compounds, which accounted for 87.9% of the total amount, were identified in a collective essential oil of P. sordidum from Corsica. The main essential oil components were (E)-β-caryophyllene (14.4%), β-pinene (11.0%), thymol (9.0%), and hexadecanoic acid (5.3%). The chemical compositions of essential oils from 19 Corsican locations were investigated. The study of the chemical variability using statistical analysis allowed identifying direct correlation between the three populations of P. sordidum widespread in Corsica and the essential oil compositions they produce. The in vitro antimicrobial activity of P. sordidum essential oil was evaluated and it exhibited a notable activity on a large panel of clinically significant microorganisms. © 2016 Verlag Helvetica Chimica Acta AG, Zürich.

A Study of Interactions between Mixing and Chemical Reaction Using the Rate-Controlled Constrained-Equilibrium Method

NASA Astrophysics Data System (ADS)

Hadi, Fatemeh; Janbozorgi, Mohammad; Sheikhi, M. Reza H.; Metghalchi, Hameed

2016-10-01

The rate-controlled constrained-equilibrium (RCCE) method is employed to study the interactions between mixing and chemical reaction. Considering that mixing can influence the RCCE state, the key objective is to assess the accuracy and numerical performance of the method in simulations involving both reaction and mixing. The RCCE formulation includes rate equations for constraint potentials, density and temperature, which allows taking account of mixing alongside chemical reaction without splitting. The RCCE is a dimension reduction method for chemical kinetics based on thermodynamics laws. It describes the time evolution of reacting systems using a series of constrained-equilibrium states determined by RCCE constraints. The full chemical composition at each state is obtained by maximizing the entropy subject to the instantaneous values of the constraints. The RCCE is applied to a spatially homogeneous constant pressure partially stirred reactor (PaSR) involving methane combustion in oxygen. Simulations are carried out over a wide range of initial temperatures and equivalence ratios. The chemical kinetics, comprised of 29 species and 133 reaction steps, is represented by 12 RCCE constraints. The RCCE predictions are compared with those obtained by direct integration of the same kinetics, termed detailed kinetics model (DKM). The RCCE shows accurate prediction of combustion in PaSR with different mixing intensities. The method also demonstrates reduced numerical stiffness and overall computational cost compared to DKM.

Metal organic chemical vapor deposition of 111-v compounds on silicon

DOEpatents

Vernon, Stanley M.

1986-01-01

Expitaxial composite comprising thin films of a Group III-V compound semiconductor such as gallium arsenide (GaAs) or gallium aluminum arsenide (GaAlAs) on single crystal silicon substrates are disclosed. Also disclosed is a process for manufacturing, by chemical deposition from the vapor phase, epitaxial composites as above described, and to semiconductor devices based on such epitaxial composites. The composites have particular utility for use in making light sensitive solid state solar cells.