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Sample records for intermediates decomposition studies

  1. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4

    DOE PAGESBeta

    Guo, Xiaofeng; Wu, Di; Xu, Hongwu; Burns, Peter C.; Navrotsky, Alexandra

    2016-06-08

    The thermal decomposition of studtite (UO2)O2(H2O)2·2H2O results in a series of intermediate X-ray amorphous materials with general composition UO3+x (x = 0, 0.5, 1). As an extension of a structural study on U2O7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solution calorimetry. The thermodynamic data demonstrate the metastability ofmore » the amorphous UO3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO3+x materials that pose the risk of significant O2 gas. Quantitative knowledge of the energy landscape of amorphous UO3+x was provided for stability analysis and assessment of conditions for decomposition.« less

  2. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4

    NASA Astrophysics Data System (ADS)

    Guo, Xiaofeng; Wu, Di; Xu, Hongwu; Burns, Peter C.; Navrotsky, Alexandra

    2016-09-01

    The thermal decomposition of studtite (UO2)O2(H2O)2·2H2O results in a series of intermediate X-ray amorphous materials with general composition UO3+x (x = 0, 0.5, 1). As an extension of a structural study on U2O7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solution calorimetry. The thermodynamic data demonstrate the metastability of the amorphous UO3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO3+x materials that pose the risk of significant O2 gas. Quantitative knowledge of the energy landscape of amorphous UO3+x was provided for stability analysis and assessment of conditions for decomposition.

  3. Radiation induced decomposition of a refractory cefathiamidine intermediate.

    PubMed

    Bao, Qiburi; Chen, Lujun; Wang, Jianlong

    2014-12-01

    Diisopropylthiourea (DPT), an intermediate of a widely used cephalosporin, has been found to be one of the most refractory components in cephalosporin synthesis wastewater. This compound cannot be completely removed by conventional biological processes due to its antimicrobial property. Ionizing radiation has been applied in the decomposition of refractory pollutants in recent years and has proved effective. Therefore, the decomposition of DPT by γ-irradiation was studied. The compound was irradiated at the dose of 150-2000 Gy before a change of concentration and UV absorption of the solutions was detected. Furthermore, the decomposition kinetics and radiation yield (G-value) of DPT was investigated. The results of radiation experiments on DPT-containing aqueous showed that the DPT can be effectively degraded by γ-radiation. DPT concentration decreased with increasing absorbed doses. G-values of radiolytic decomposition for DPT (20 mg/L) were 1.04 and 0.47 for absorbed doses of 150 and 2000 Gy, respectively. The initial concentration and pH of the solutions affected the degradation. As the concentration of substrate increased, the decomposition was reduced. The decrease of removal rate and radiation efficacy under alkaline condition suggested that lower pH values benefit the γ-induced degradation. UV absorption from 190 to 250 nm decreased after radiation while that from 250 to 300 nm increased, indicating the formation of by-products.

  4. Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation.

    PubMed

    Pinto, R M; Dias, A A; Costa, M L; Rodrigues, P; Barros, M T; Ogden, J S; Dyke, J M

    2011-08-01

    Methyl 2-azidopropionate (N(3)CH(3)CHCOOCH(3), M2AP) has been synthesized and characterized by different spectroscopic methods, and the thermal decomposition of this molecule has been investigated by matrix isolation infrared (IR) spectroscopy and ultraviolet photoelectron spectroscopy (UVPES). Computational methods have been employed in the spectral simulation of both UVPES and matrix IR spectra and in the rationalization of the thermal decomposition results. M2AP presents a HOMO vertical ionization energy (VIE) of 9.60 ± 0.03 eV and contributions from all four lowest-energy conformations of this molecule are detected in the gas phase. Its thermal decomposition starts at ca. 400 °C and is complete at ca. 650 °C, yielding N(2), CO, CO(2), CH(3)CN, and CH(3)OH as the final decomposition products. Methyl formate (MF) and CH(4) are also found during the pyrolysis process. Analysis of the potential energy surface of the decomposition of M2AP indicates that M2AP decomposes preferentially into the corresponding imine (M2IP), through a 1,2-H shift synchronous with the N(2) elimination (Type 1 mechanism), requiring an activation energy of 160.8 kJ/mol. The imine further decomposes via two competitive routes: one accounting for CO, CH(3)OH, and CH(3)CN (ΔE(G3) = 260.2 kJ/mol) and another leading to CO(2), CH(4), and CH(3)CN (ΔE(G3) = 268.6 kJ/mol). A heterocyclic intermediate (Type 2 mechanism)-4-Me-5-oxazolidone-can also be formed from M2AP via H transfer from the remote O-CH(3) group, together with the N(2) elimination (ΔE(G3) = 260.2 kJ/mol). Finally, a third pathway which accounts for the formation of MF through an M2AP isomer is envisioned.

  5. Intermediate Mathematics Study Guide.

    ERIC Educational Resources Information Center

    Stanford Univ., CA. School Mathematics Study Group.

    This SMSG study guide is intended to provide teachers who use "Intermediate Mathematics," as a textbook with references to materials which will help them to gain a better understanding of the mathematics contained in the text. For each chapter of the text a brief resume of its content is followed by a list of annotated references which are…

  6. First-Principles Prediction of Intermediate Products in the Decomposition of Metal Amidoboranes

    SciTech Connect

    Zhang, Yongsheng; Autrey, Tom; Wolverton, C.

    2012-12-27

    The non-volatile products remaining after the thermal decomposition of metal amidoboranes ([M]n+[NH2BH3]- , M = alkali or alkaline metal atom) are amorphous and incompletely characterized increasing the complexity of devising regeneration strategies for these potential hydrogen storage materials. Utilizing the combined prototype electrostatic ground state search (PEGS) and density-functional theory (DFT) methodology (PEGS+DFT), we have searched for crystal structures of possible intermediate phases with [NHBH2]-, [NBH]-, [N3H2B3H3]-, and polymer-M[NHBH2] anion groups in the decomposition of lithium amidoborane (LiAB) and calcium amidoborane (CaAB). All these potential reaction products are calculated to be significantly endothermic, in contrast to the experimentally measured nearly thermo neutral values [3 to 5 kJ/(mol H2) in LiAB and 3.5 kJ/(mol H2) in CaAB] suggesting that there are alternative products formed. The dianion group [NHBHNHBH3]2- has recently been suggested to form in the decomposition of a calcium amidoborane complex in solution. In LiAB and CaAB, we use PEGS+DFT calculations to predict intermediate metal-dianion compounds, and the static H2 release enthalpy is 27.4 kJ/(mol H2) in LiAB and 27.3 kJ/(mol H2) in CaAB, respectively. Introducing vibrational effects by phonon calculations, the enthalpies are shifted down by a roughly constant amount, _25 kJ/(mol H2) at 0 K and _22 kJ/(mol H2) at 300 K. Thus, our theoretical H2 release enthalpies agree with the experimentally measured nearly thermo-neutral data in the decomposition of LiAB and CaAB. This agreement supports the existence of the dianion phases as products in the decomposition of metal amidoboranes. Then, using the dianion compound as an intermediate in the decomposition of MAB, we further study the stability trends of a series of MAB (M=Li, Na, K, Ca), and find that the reaction enthalpies generally obey the following trend: The

  7. Effect of intermediate soil cover on municipal solid waste decomposition.

    PubMed

    Márquez-Benavides, L; Watson-Craik, I

    2003-01-01

    A complex series of chemical and microbiological reactions is initiated with the burial of refuse in a sanitary landfill. At the end of each labour day, the municipal solid wastes (MSW) are covered with native soil (or an alternative material). To investigate interaction between the intermediate cover and the MSW, five sets of columns were set up, one packed with refuse only, and four with a soil-refuse mixture (a clay loam, an organic-rich peaty soil, a well limed sandy soil and a chalky soil). The anaerobic degradation over 6 months was followed in terms of leachate volatile fatty acids, chemical oxygen demand, pH and ammoniacal-N performance. Results suggest that the organic-rich peaty soil may accelerate the end of the acidogenic phase. Clay appeared not to have a significant effect on the anaerobic degradation process. PMID:14531450

  8. An isomer-specific study of solid nitromethane decomposition pathways - Detection of aci-nitromethane (H2CNO(OH)) and nitrosomethanol (HOCH2NO) intermediates

    NASA Astrophysics Data System (ADS)

    Maksyutenko, Pavlo; Förstel, Marko; Crandall, Parker; Sun, Bing-Jian; Wu, Mei-Hung; Chang, Agnes H. H.; Kaiser, Ralf I.

    2016-08-01

    An isomer specific study of energetic electron exposed nitromethane ices was performed via photoionization - reflectron time of flight mass spectrometry (PI-ReTOF-MS) of the subliming products employing tunable vacuum ultraviolet light for ionization. Supported by electronic structure calculations, nitromethane (CH3NO2) was found to isomerize to methyl nitrite (CH3ONO) and also via hydrogen migration to the hitherto elusive aci-nitromethane isomer (H2CNO(OH)). The latter isomerizes to nitrosomethanol (HOCH2NO) through hydroxyl group (OH) migration, and, probably, ring closure to the cyclic 2-hydroxy-oxaziridine isomer (c-H2CON(OH)) as well. The importance of hydrogen migrations was also verified via the nitrosomethane (CH3NO) - formaldehyde oxime isomer (CH2NOH) pair.

  9. Mechanistic insight into the hydrazine decomposition on Rh(111): effect of reaction intermediate on catalytic activity.

    PubMed

    Deng, Zhigang; Lu, Xiaoqing; Wen, Zengqiang; Wei, Shuxian; Liu, Yunjie; Fu, Dianling; Zhao, Lianming; Guo, Wenyue

    2013-10-14

    Periodic density functional theory (DFT) calculations have been performed to systematically investigate the effect of reaction intermediate on catalytic activity for hydrazine (N2H4) decomposition on Rh(111). Reaction mechanisms via intramolecular and NH2-assisted N2H4 decompositions are comparatively analyzed, including adsorption configuration, reaction energy and barrier of elementary step, and reaction network. Our results show that the most favorable N2H4 decomposition pathway starts with the initial N-N bond scission to the NH2 intermediate, followed by stepwise H stripping from adsorbed N2Hx (x = 1-4) species, and finally forms the N2 and NH3 products. Comparatively, the stepwise intramolecular dehydrogenation via N2H4→ N2H3→ N2H2→ N2H → N2, and N2H4→ NH2→ NH → N with or without NH2 promotion effect, are unfavorable due to higher energy barriers encountered. Energy barrier analysis, reaction rate constants, and electronic structures are used to identify the crucial competitive route. The promotion effect of the NH2 intermediate is structurally reflected in the weakening of the N-H bond and strengthening of the N-N bond in N2Hx in the coadsorption system; it results intrinsically from the less structural deformation of the adsorbate, and weakening of the interaction between dehydrogenated fragment and departing H in transition state. Our results highlight the crucial effect of reaction intermediate on catalytic activity and provide a theoretical approach to analyze the effect. PMID:23990024

  10. Mechanistic insight into the hydrazine decomposition on Rh(111): effect of reaction intermediate on catalytic activity.

    PubMed

    Deng, Zhigang; Lu, Xiaoqing; Wen, Zengqiang; Wei, Shuxian; Liu, Yunjie; Fu, Dianling; Zhao, Lianming; Guo, Wenyue

    2013-10-14

    Periodic density functional theory (DFT) calculations have been performed to systematically investigate the effect of reaction intermediate on catalytic activity for hydrazine (N2H4) decomposition on Rh(111). Reaction mechanisms via intramolecular and NH2-assisted N2H4 decompositions are comparatively analyzed, including adsorption configuration, reaction energy and barrier of elementary step, and reaction network. Our results show that the most favorable N2H4 decomposition pathway starts with the initial N-N bond scission to the NH2 intermediate, followed by stepwise H stripping from adsorbed N2Hx (x = 1-4) species, and finally forms the N2 and NH3 products. Comparatively, the stepwise intramolecular dehydrogenation via N2H4→ N2H3→ N2H2→ N2H → N2, and N2H4→ NH2→ NH → N with or without NH2 promotion effect, are unfavorable due to higher energy barriers encountered. Energy barrier analysis, reaction rate constants, and electronic structures are used to identify the crucial competitive route. The promotion effect of the NH2 intermediate is structurally reflected in the weakening of the N-H bond and strengthening of the N-N bond in N2Hx in the coadsorption system; it results intrinsically from the less structural deformation of the adsorbate, and weakening of the interaction between dehydrogenated fragment and departing H in transition state. Our results highlight the crucial effect of reaction intermediate on catalytic activity and provide a theoretical approach to analyze the effect.

  11. HCOOH decomposition on Pt(111): A DFT study

    NASA Astrophysics Data System (ADS)

    Scaranto, Jessica; Mavrikakis, Manos

    2016-06-01

    Formic acid (HCOOH) decomposition on transition metal surfaces is important for hydrogen production and for its electro-oxidation in direct HCOOH fuel cells. HCOOH can decompose through dehydrogenation leading to formation of CO2 and H2 or dehydration leading to CO and H2O; because CO can poison metal surfaces, dehydrogenation is typically the desirable decomposition path. Here we report a mechanistic analysis of HCOOH decomposition on Pt(111), obtained from a plane wave density functional theory (DFT-PW91) study. We analyzed the dehydrogenation mechanism by considering the two possible pathways involving the formate (HCOO) or the carboxyl (COOH) intermediate. We also considered several possible dehydration paths leading to CO formation. We studied HCOO and COOH decomposition both on the clean surface and in the presence of other relevant co-adsorbates. The results suggest that COOH formation is energetically more difficult than HCOO formation. In contrast, COOH dehydrogenation is easier than HCOO decomposition. We found that CO2 is the main product through both pathways and that CO is produced mainly through the dehydroxylation of the COOH intermediate.

  12. Decomposition

    USGS Publications Warehouse

    Middleton, Beth A.

    2014-01-01

    A cornerstone of ecosystem ecology, decomposition was recognized as a fundamental process driving the exchange of energy in ecosystems by early ecologists such as Lindeman 1942 and Odum 1960). In the history of ecology, studies of decomposition were incorporated into the International Biological Program in the 1960s to compare the nature of organic matter breakdown in various ecosystem types. Such studies still have an important role in ecological studies of today. More recent refinements have brought debates on the relative role microbes, invertebrates and environment in the breakdown and release of carbon into the atmosphere, as well as how nutrient cycling, production and other ecosystem processes regulated by decomposition may shift with climate change. Therefore, this bibliography examines the primary literature related to organic matter breakdown, but it also explores topics in which decomposition plays a key supporting role including vegetation composition, latitudinal gradients, altered ecosystems, anthropogenic impacts, carbon storage, and climate change models. Knowledge of these topics is relevant to both the study of ecosystem ecology as well projections of future conditions for human societies.

  13. Anaerobic decomposition of benzoic acid during methane fermentation: Specific activity of fatty acid intermediates and postion of radioactive label

    SciTech Connect

    Bridges, R.L.

    1990-01-01

    A study of the pathway of anaerobic decomposition of benzoic acid by a mixed methanogenic culture of bacteria was conducted. Specific activities of the possible fatty acid intermediates cyclohexanecarboxylic acid, propanoic acid, and acetic acid were determined. In the case of propanoic acid, the position of the radioactive label was also determined by isotropic trapping and Phares-Schmidt degradation of the intermediate. The specific activities of cyclohexanecarboxylic acid and propanoic acid are the same as the benzoate substrate fed to the mixed methanogenic cultures. These fatty acids must be direct breakdown products from the aromatic ring. When (4{minus}{sup 14}C) benzoate is the substrate, the propanoic acid produced is labeled exclusively in the carboxyl position. This supports the pathway proposed by Keith et al. (1978), but would be unlikely for the pathway proposed by Evans (1977). The specific activity of the acetic acid isolated from a culture fed (4{minus}{sup 14}C) benzoate is 42% of the specific activity of the substrate. This is possible only if the methylmalonyl-CoA pathway for the conversion of propanoate to acetate is not being utilized. The amount of various intermediates found indicates that at least three syntrophically linked organisms are present in the mixed methanogenic culture. One is responsible for the production of cyclohexanecarboxylic acid, one for the production of acetate from propanoate, and one for the production of methane.

  14. Two alternate kinetic routes for the decomposition of the phosphorylated intermediate of sarcoplasmic reticulum Ca2+-ATPase.

    PubMed

    Nakamura, Y

    1984-07-10

    The decomposition of the phosphorylated intermediate (EP) of sarcoplasmic reticulum ATPase, purified by the method of deoxycholic acid extraction, was studied by first phosphorylating with [gamma-32P]ATP, then diluting the reaction mixture with 20 volumes of medium containing nonradioactive ATP, and finally quenching serial samples with acid for determination of residual [32P]EP. The time course of [32P]EP decomposition consists of an initial fast phase followed by a slow phase. The two components of EP, EPfast (1.1 nmol/mg) and EPslow (2.8 nmol/mg), decomposed with the rate constants of 6 and 0.8 min-1, respectively, in the presence of 0.5 mM CaCl2, 5mM MgCl2, and 90 mM KCl at pH 7.0 and O degrees C. The sum of the hydrolytic activities corresponding to the two components accounts for the steady state velocity of the Pi production under the same conditions, indicating that the two components represent simultaneous pathways, rather than sequential steps of EP decomposition. As the time of phosphorylation with [gamma-32P]ATP is increased from 2 to 15 s, the fraction of EPfast decreases in favor of EPslow. This conversion decreases the rate of total Pi production by the enzyme following an initial Pi burst. Conversion of EPfast to EPslow is favored by millimolar concentrations of Ca2+. On the other hand, conversion of EPslow to EPfast is obtained by reducing Ca2+ or raising Mg2+ concentration, but is prevented by removal of ADP. The EPslow fraction decreases in favor of EPfast as the temperature is increased from 0 to 22 degrees C. PMID:6234309

  15. Unimolecular Decomposition Rate of the Criegee Intermediate (CH3)2COO Measured Directly with UV Absorption Spectroscopy.

    PubMed

    Smith, Mica C; Chao, Wen; Takahashi, Kaito; Boering, Kristie A; Lin, Jim Jr-Min

    2016-07-14

    The unimolecular decomposition of (CH3)2COO and (CD3)2COO was measured by direct detection of the Criegee intermediate at temperatures from 283 to 323 K using time-resolved UV absorption spectroscopy. The unimolecular rate coefficient kd for (CH3)2COO shows a strong temperature dependence, increasing from 269 ± 82 s(-1) at 283 K to 916 ± 56 s(-1) at 323 K with an Arrhenius activation energy of ∼6 kcal mol(-1). The bimolecular rate coefficient for the reaction of (CH3)2COO with SO2, kSO2, was also determined in the temperature range 283 to 303 K. Our temperature-dependent values for kd and kSO2 are consistent with previously reported relative rate coefficients kd/kSO2 of (CH3)2COO formed from ozonolysis of tetramethyl ethylene. Quantum chemical calculations of kd for (CH3)2COO are consistent with the experiment, and the combination of experiment and theory for (CD3)2COO indicates that tunneling plays a significant role in (CH3)2COO unimolecular decomposition. The fast rates of unimolecular decomposition for (CH3)2COO measured here, in light of the relatively slow rate for the reaction of (CH3)2COO with water previously reported, suggest that thermal decomposition may compete with the reactions with water and with SO2 for atmospheric removal of the dimethyl-substituted Criegee intermediate.

  16. Theoretical study of formamide decomposition pathways.

    PubMed

    Nguyen, Vinh Son; Abbott, Heather L; Dawley, M Michele; Orlando, Thomas M; Leszczynski, Jerzy; Nguyen, Minh Tho

    2011-02-10

    The chemical transformations of formamide (NH(2)CHO), a molecule of prebiotic interest as a precursor for biomolecules, are investigated using methods of electronic structure computations and Rice-Rampserger-Kassel-Marcus (RRKM) theory. Specifically, quantum chemical calculations applying the coupled-cluster theory CCSD(T), whose energies are extrapolated to the complete basis set limit (CBS), are carried out to construct the [CH(3)NO] potential energy surface. RRKM theory is then used to systematically examine decomposition channels leading to the formation of small molecules including CO, NH(3), H(2)O, HCN, HNC, H(2), HNCO, and HOCN. The energy barriers for the decarboxylation, dehydrogenation, and dehydration processes are found to be in the range of 73-78 kcal/mol. H(2) loss is predicted to be a one-step process although a two-step process is competitive. CO elimination is found to prefer a two-step pathway involving the carbene isomer NH(2)CHO (aminohydroxymethylene) as an intermediate. This CO-elimination channel is also favored over the one-step H(2) loss, in agreement with experiment. The H(2)O loss is a multistep process passing through a formimic acid conformer, which subsequently undergoes a rate-limiting dehydration. The dehydration appears to be particularly favored in the low-temperature regime. The new feature identifies aminohydroxymethylene as a transient but crucial intermediate in the decarboxylation of formamide. PMID:21229996

  17. [Intermediate phenotype studies in psychiatric disorder].

    PubMed

    Hashimoto, Ryota

    2016-02-01

    The concept of intermediate phenotype was proposed by Dr. Weinberger of the National Institute of Mental Health (NIMH). The risk genes for mental disorders define intermediate phenotypes, neurobiological characteristics observed in psychiatric disorders, and intermediate phenotypes increase the risk of mental disorders. The author worked at Dr. Weinberger's laboratory, and after returning home, introduced the concept to Japan, creating a term "Chukanhyogengata" to translate "intermediate phenotype". Intermediate phenotype has been proposed as a tool for the identification of risk genes for mental disorders, spreading the concept as a biomarker for the bridging between genes and behaviors. Intermediate phenotype studies later became one of the main pillars of psychiatric research. As a large number of data and samples are needed for intermediate phenotype research, we built a research resource database that combines the brain phenotype and bioresources. We performed genome-wide association analysis of cognitive decline in schizophrenia and identified the DEGS2 gene using this sample. This research resource database was developed for a multicenter study by COCORO (Cognitive Genetics Collaborative Research Organization). COCORO carried out genome-wide association analysis of the gray matter volume of the superior temporal gyrus and identified genome-wide significant loci. In this paper, we introduce the concept and history of intermediate phenotype study of mental illness and the latest trends. We hope to contribute to the future development of mental illness research through translational research. PMID:27044135

  18. [Intermediate phenotype studies in psychiatric disorder].

    PubMed

    Hashimoto, Ryota

    2016-02-01

    The concept of intermediate phenotype was proposed by Dr. Weinberger of the National Institute of Mental Health (NIMH). The risk genes for mental disorders define intermediate phenotypes, neurobiological characteristics observed in psychiatric disorders, and intermediate phenotypes increase the risk of mental disorders. The author worked at Dr. Weinberger's laboratory, and after returning home, introduced the concept to Japan, creating a term "Chukanhyogengata" to translate "intermediate phenotype". Intermediate phenotype has been proposed as a tool for the identification of risk genes for mental disorders, spreading the concept as a biomarker for the bridging between genes and behaviors. Intermediate phenotype studies later became one of the main pillars of psychiatric research. As a large number of data and samples are needed for intermediate phenotype research, we built a research resource database that combines the brain phenotype and bioresources. We performed genome-wide association analysis of cognitive decline in schizophrenia and identified the DEGS2 gene using this sample. This research resource database was developed for a multicenter study by COCORO (Cognitive Genetics Collaborative Research Organization). COCORO carried out genome-wide association analysis of the gray matter volume of the superior temporal gyrus and identified genome-wide significant loci. In this paper, we introduce the concept and history of intermediate phenotype study of mental illness and the latest trends. We hope to contribute to the future development of mental illness research through translational research.

  19. Density functional theory studies of HCOOH decomposition on Pd(111)

    NASA Astrophysics Data System (ADS)

    Scaranto, Jessica; Mavrikakis, Manos

    2016-08-01

    The investigation of formic acid (HCOOH) decomposition on transition metal surfaces is important to derive useful insights for vapor phase catalysis involving HCOOH and for the development of direct HCOOH fuel cells (DFAFC). Here we present the results obtained from periodic, self-consistent, density functional theory (DFT-GGA) calculations for the elementary steps involved in the gas-phase decomposition of HCOOH on Pd(111). Accordingly, we analyzed the minimum energy paths for HCOOH dehydrogenation to CO2 + H2 and dehydration to CO + H2O through the carboxyl (COOH) and formate (HCOO) intermediates. Our results suggest that HCOO formation is easier than COOH formation, but HCOO decomposition is more difficult than COOH decomposition, in particular in the presence of co-adsorbed O and OH species. Therefore, both paths may contribute to HCOOH decomposition. CO formation goes mainly through COOH decomposition.

  20. Spark decomposition studies of dielectric gas mixtures

    NASA Astrophysics Data System (ADS)

    Sauers, I.; Christophorou, L. G.

    The ultimate usefulness of a high voltage insulating gas depends not only on the ability of the gas to withstand high voltages, but also on the degradation of the gas resulting from spark discharges, corona or prolonged electrical stress and the effect(s) of the by-products on the equipment and, possibly, the environment. In view of these considerations, the study of long-range spark decomposition was undertaken in an effort to improve the decomposition characteristics of dielectric gases through proper tailoring of gas mixtures while maintaining high breakdown strengths. The data reported are on the analyses of gases sparked by capactive (0.1 micro F) discharge into a 0.5-mm gap, resulting in an energy input of approximately 5 J per spark. The nature of the decomposition products of SF6 formed by high voltage discharges observed is found to be critically dependent on impurities (particularly H2O), electrode material and insulating materials present in the system.

  1. Theoretical study of the decomposition pathways and products of C5- perfluorinated ketone (C5 PFK)

    NASA Astrophysics Data System (ADS)

    Fu, Yuwei; Wang, Xiaohua; Li, Xi; Yang, Aijun; Han, Guohui; Lu, Yanhui; Wu, Yi; Rong, Mingzhe

    2016-08-01

    Due to the high global warming potential (GWP) and increasing environmental concerns, efforts on searching the alternative gases to SF6, which is predominantly used as insulating and interrupting medium in high-voltage equipment, have become a hot topic in recent decades. Overcoming the drawbacks of the existing candidate gases, C5- perfluorinated ketone (C5 PFK) was reported as a promising gas with remarkable insulation capacity and the low GWP of approximately 1. Experimental measurements of the dielectric strength of this novel gas and its mixtures have been carried out, but the chemical decomposition pathways and products of C5 PFK during breakdown are still unknown, which are the essential factors in evaluating the electric strength of this gas in high-voltage equipment. Therefore, this paper is devoted to exploring all the possible decomposition pathways and species of C5 PFK by density functional theory (DFT). The structural optimizations, vibrational frequency calculations and energy calculations of the species involved in a considered pathway were carried out with DFT-(U)B3LYP/6-311G(d,p) method. Detailed potential energy surface was then investigated thoroughly by the same method. Lastly, six decomposition pathways of C5 PFK decomposition involving fission reactions and the reactions with a transition states were obtained. Important intermediate products were also determined. Among all the pathways studied, the favorable decomposition reactions of C5 PFK were found, involving C-C bond ruptures producing Ia and Ib in pathway I, followed by subsequent C-C bond ruptures and internal F atom transfers in the decomposition of Ia and Ib presented in pathways II + III and IV + V, respectively. Possible routes were pointed out in pathway III and lead to the decomposition of IIa, which is the main intermediate product found in pathway II of Ia decomposition. We also investigated the decomposition of Ib, which can undergo unimolecular reactions to give the formation

  2. Using Drosophila for Studies of Intermediate Filaments.

    PubMed

    Bohnekamp, Jens; Cryderman, Diane E; Thiemann, Dylan A; Magin, Thomas M; Wallrath, Lori L

    2016-01-01

    Drosophila melanogaster is a useful organism for determining protein function and modeling human disease. Drosophila offers a rapid generation time and an abundance of genomic resources and genetic tools. Conservation in protein structure, signaling pathways, and developmental processes make studies performed in Drosophila relevant to other species, including humans. Drosophila models have been generated for neurodegenerative diseases, muscular dystrophy, cancer, and many other disorders. Recently, intermediate filament protein diseases have been modeled in Drosophila. These models have revealed novel mechanisms of pathology, illuminated potential new routes of therapy, and make whole organism compound screens feasible. The goal of this chapter is to outline steps to study intermediate filament function and model intermediate filament-associated diseases in Drosophila. The steps are general and can be applied to study the function of almost any protein. The protocols outlined here are for both the novice and experienced Drosophila researcher, allowing the rich developmental and cell biology that Drosophila offers to be applied to studies of intermediate filaments.

  3. Singular value decomposition with self-modeling applied to determine bacteriorhodopsin intermediate spectra: analysis of simulated data.

    PubMed

    Zimányi, L; Kulcsár, A; Lanyi, J K; Sears, D F; Saltiel, J

    1999-04-13

    An a priori model-independent method for the determination of accurate spectra of photocycle intermediates is developed. The method, singular value decomposition with self-modeling (SVD-SM), is tested on simulated difference spectra designed to mimic the photocycle of the Asp-96 --> Asn mutant of bacteriorhodopsin. Stoichiometric constraints, valid until the onset of the recovery of bleached bacteriorhodopsin at the end of the photocycle, guide the self-modeling procedure. The difference spectra of the intermediates are determined in eigenvector space by confining the search for their coordinates to a stoichiometric plane. In the absence of random noise, SVD-SM recovers the intermediate spectra and their time evolution nearly exactly. The recovery of input spectra and kinetics is excellent although somewhat less exact when realistic random noise is included in the input spectra. The difference between recovered and input kinetics is now visually discernible, but the same reaction scheme with nearly identical rate constants to those assumed in the simulation fits the output kinetics well. SVD-SM relegates the selection of a photocycle model to the late stage of the analysis. It thus avoids derivation of erroneous model-specific spectra that result from global model-fitting approaches that assume a model at the outset. PMID:10200275

  4. Density-based Energy Decomposition Analysis for Intermolecular Interactions with Variationally Determined Intermediate State Energies

    SciTech Connect

    Wu, Q.; Ayers, P.W.; Zhang, Y.

    2009-10-28

    The first purely density-based energy decomposition analysis (EDA) for intermolecular binding is developed within the density functional theory. The most important feature of this scheme is to variationally determine the frozen density energy, based on a constrained search formalism and implemented with the Wu-Yang algorithm [Q. Wu and W. Yang, J. Chem. Phys. 118, 2498 (2003) ]. This variational process dispenses with the Heitler-London antisymmetrization of wave functions used in most previous methods and calculates the electrostatic and Pauli repulsion energies together without any distortion of the frozen density, an important fact that enables a clean separation of these two terms from the relaxation (i.e., polarization and charge transfer) terms. The new EDA also employs the constrained density functional theory approach [Q. Wu and T. Van Voorhis, Phys. Rev. A 72, 24502 (2005)] to separate out charge transfer effects. Because the charge transfer energy is based on the density flow in real space, it has a small basis set dependence. Applications of this decomposition to hydrogen bonding in the water dimer and the formamide dimer show that the frozen density energy dominates the binding in these systems, consistent with the noncovalent nature of the interactions. A more detailed examination reveals how the interplay of electrostatics and the Pauli repulsion determines the distance and angular dependence of these hydrogen bonds.

  5. Studying Reaction Intermediates Formed at Graphenic Surfaces

    NASA Astrophysics Data System (ADS)

    Sarkar, Depanjan; Sen Gupta, Soujit; Narayanan, Rahul; Pradeep, Thalappil

    2014-03-01

    We report in-situ production and detection of intermediates at graphenic surfaces, especially during alcohol oxidation. Alcohol oxidation to acid occurs on graphene oxide-coated paper surface, driven by an electrical potential, in a paper spray mass spectrometry experiment. As paper spray ionization is a fast process and the time scale matches with the reaction time scale, we were able to detect the intermediate, acetal. This is the first observation of acetal formed in surface oxidation. The process is not limited to alcohols and the reaction has been extended to aldehydes, amines, phosphenes, sugars, etc., where reaction products were detected instantaneously. By combining surface reactions with ambient ionization and mass spectrometry, we show that new insights into chemical reactions become feasible. We suggest that several other chemical transformations may be studied this way. This work opens up a new pathway for different industrially and energetically important reactions using different metal catalysts and modified substrate.

  6. Quenched nonisothermal decomposition studies of Department of Energy western reference oil shales: Preliminary results

    SciTech Connect

    Miknis, F.P.; Thomas, B.E.

    1989-12-01

    Quenched nonisothermal pyrolysis studies have been conducted on a Tipton Member, Green River Formation oil shale from Wyoming and a Parachute Creek Member, Green River Formation oil shale from Colorado. These shales have been designated as western reference oil shales by the US Department of Energy. The conversion of kerogen to bitumen and volatiles (oil + gas) was obtained for heating rates of 2 and 10 K/min in the temperature range of 573 to 773 K using a modified thermogravimetric analyzer. Particular attention was paid to the formation of the intermediate bitumen during decomposition of the shale. The maximum amount of extractable bitumen increases with temperature and heating rate. This observation is consistent with an oil shale decomposition model in which the activation energy for kerogen decomposition is greater than the activation energy of bitumen decomposition. This is also consistent with previous isothermal decomposition studies on the same oil shales. A nonlinear least-squares program was used to fit the quenched nonisothermal data to a simple model that incorporates bitumen formation, bitumen decomposition, and volatiles evolution. Although seemingly good fits were obtained the parameter statistics were poor and showed a high degree of linear dependency. 18 refs., 11 figs., 3 tabs.

  7. Mechanistic and kinetic studies of the thermal decomposition of TNAZ and NDNAZ

    SciTech Connect

    Anderson, K.; Homsy, J.; Behrens, R.; Bulusu, S.

    1998-12-31

    The authors have studied the mechanism and detailed reaction kinetics of the thermal decomposition of 1,3,3-trinitroazetidine (TNAZ), and separately, its key decomposition intermediate, 1-nitroso-3,3-dinitroacetidine (NDNAZ), using a simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS). These decompositions were conducted in a sealed alumina cell with a 2.5 {micro}m orifice, at varying temperatures and at a range of isothermal temperatures (at 10 C intervals from 120--160 C for NDNAZ and 160--210 C for TNAZ). The gaseous products have been identified and their rates of formation have been measured as a function of time, temperature, and pressure. This system is complex, with TNAZ decomposing by four separate routes, one of which leads to NDNAZ, which itself decomposes by at least two distinct routes.

  8. Trends in Formic Acid Decomposition on Model Transition Metal Surfaces: A Density Functional Theory Study

    SciTech Connect

    Herron, Jeffrey A.; Scaranto, Jessica; Ferrin, Peter A.; Li, Sha; Mavrikakis, Manos

    2014-12-05

    We present a first-principles, self-consistent periodic density functional theory (PW91-GGA) study of formic acid (HCOOH) decomposition on model (111) and (100) facets of eight fcc metals (Au, Ag, Cu, Pt, Pd, Ni, Ir, and Rh) and (0001) facets of four hcp (Co, Os, Ru, and Re) metals. The calculated binding energies of key formic acid decomposition intermediates including formate (HCOO), carboxyl (COOH), carbon monoxide (CO), water (H2O), carbon dioxide (CO2), hydroxyl (OH), carbon (C), oxygen (O), and hydrogen (H; H2) are presented. Using these energetics, we develop thermochemical potential energy diagrams for both the carboxyl-mediated and the formate-mediated dehydrogenation mechanisms on each surface. We evaluate the relative stability of COOH, HCOO, and other isomeric intermediates (i.e., CO + OH, CO2 + H, CO + O + H) on these surfaces. These results provide insights into formic acid decomposition selectivity (dehydrogenation versus dehydration), and in conjunction with calculated vibrational frequency modes, the results can assist with the experimental search for the elusive carboxyl (COOH) surface intermediate. Results are compared against experimental reports in the literature.

  9. Theoretical study of decomposition of methanediol in aqueous solution.

    PubMed

    Inaba, Satoshi

    2015-06-01

    Methanediol is a product of the hydration of formaldehyde and is more abundant than formaldehyde in aqueous solution. We carried out a number of quantum chemical simulations to study the decomposition of methanediol in aqueous solution. The decomposition of a methanediol proceeds by transferring a proton from a hydroxyl to an oxygen atom of the other hydroxyl in the methanediol. The decomposition of the methanediol completes after the cleavage of the bond between the formaldehyde and the water molecule. The probability of the proton transfer increases by the quantum mechanical tunneling at the low temperature because the width of the potential barrier for the decomposition becomes similar to the de Broglie wavelength of the proton. We consider the catalytic effect of water molecules in aqueous solution. The structure of the methanediol is not required to change significantly when undergoing decomposition due to the active role of water molecules to transfer a proton. We consider three types of arrangement for water molecules with respect to a methanediol: (1) a ring structure formed by a methanediol and water molecules; (2) a water cluster attracted to a methanediol by hydrogen bonds; and (3) a water cluster and additional water molecules, both of which are attracted to a methanediol by hydrogen bonds. The activation energy for the decomposition is reduced by a water cluster more efficiently than water molecules in a ring structure. However, the activation energy reduced by a water cluster is still larger than that obtained from laboratory experiments. We include water molecules that are attracted to a methanediol by hydrogen bonds during the water-cluster-catalyzed decomposition of a methanediol. The hydrogen bonds with the water molecules permit little change in the structure of the methanediol during the decomposition and play a significant role to reduce the activation energy for the decomposition. The rate constant obtained from the theoretical simulation

  10. IN SITU INFRARED STUDY OF CATALYTIC DECOMPOSITION OF NO

    SciTech Connect

    KHALID ALMUSAITEER; RAM KRISHNAMURTHY; STEVEN S.C. CHUANG

    1998-08-18

    The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiments including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterized the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.

  11. In Situ Infrared Study of Catalytic Decomposition of NO

    SciTech Connect

    Cher-Dip Tan; Steven S.C. Chuang

    1997-07-17

    The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emmissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccesful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiments including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterized the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.

  12. Comparative Density Functional Study of Methanol Decomposition on Cu4 and Co4 Clusters

    SciTech Connect

    Mehmood, Faisal; Greeley, Jeffrey P.; Zapol, Peter; Curtiss, Larry A.

    2010-11-18

    A density functional theory study of the decomposition of methanol on Cu4 and Co4 clusters is presented. The reaction intermediates and activation barriers have been determined for reaction steps to form H2 and CO. For both clusters, methanol decomposition initiated by C-H and O-H bond breaking was investigated. In the case of a Cu4 cluster, methanol dehydrogenation through hydroxymethyl (CH2OH), hydroxymethylene (CHOH), formyl (CHO), and carbon monoxide (CO) is found to be slightly more favorable. For a Co4 cluster, the dehydrogenation pathway through methoxy (CH3O) and formaldehyde (CH2O) is slightly more favorable. Each of these pathways results in formation of CO and H2. The Co cluster pathway is very favorable thermodynamically and kinetically for dehydrogenation. However, since CO binds strongly, it is likely to poison methanol decomposition to H2 and CO at low temperatures. In contrast, for the Cu cluster, CO poisoning is not likely to be a problem since it does not bind strongly, but the dehydrogenation steps are not energetically favorable. Pathways involving C-O bond cleavage are even less energetically favorable. The results are compared to our previous study of methanol decomposition on Pd4 and Pd8 clusters. Finally, all reaction energy changes and transition state energies, including those for the Pd clusters, are related in a linear, Broensted-Evans-Polanyi plot.

  13. Kinetics of stabilised Criegee intermediates derived from alkene ozonolysis: reactions with SO2, H2O and decomposition under boundary layer conditions.

    PubMed

    Newland, Mike J; Rickard, Andrew R; Alam, Mohammed S; Vereecken, Luc; Muñoz, Amalia; Ródenas, Milagros; Bloss, William J

    2015-02-14

    The removal of SO2 in the presence of alkene-ozone systems has been studied for ethene, cis-but-2-ene, trans-but-2-ene and 2,3-dimethyl-but-2-ene, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity for all four alkene-ozone systems confirming a significant reaction for stabilised Criegee intermediates (SCI) with H2O. The observed SO2 removal kinetics are consistent with relative rate constants, k(SCI + H2O)/k(SCI + SO2), of 3.3 (±1.1) × 10(-5) for CH2OO, 26 (±10) × 10(-5) for CH3CHOO derived from cis-but-2-ene, 33 (±10) × 10(-5) for CH3CHOO derived from trans-but-2-ene, and 8.7 (±2.5) × 10(-5) for (CH3)2COO derived from 2,3-dimethyl-but-2-ene. The relative rate constants for k(SCI decomposition)/k(SCI + SO2) are -2.3 (±3.5) × 10(11) cm(-3) for CH2OO, 13 (±43) × 10(11) cm(-3) for CH3CHOO derived from cis-but-2-ene, -14 (±31) × 10(11) cm(-3) for CH3CHOO derived from trans-but-2-ene and 63 (±14) × 10(11) cm(-3) for (CH3)2COO. Uncertainties are ±2σ and represent combined systematic and precision components. These values are derived following the approximation that a single SCI is present for each system; a more comprehensive interpretation, explicitly considering the differing reactivity for syn- and anti-SCI conformers, is also presented. This yields values of 3.5 (±3.1) × 10(-4) for k(SCI + H2O)/k(SCI + SO2) of anti-CH3CHOO and 1.2 (±1.1) × 10(13) for k(SCI decomposition)/k(SCI + SO2) of syn-CH3CHOO. The reaction of the water dimer with CH2OO is also considered, with a derived value for k(CH2OO + (H2O)2)/k(CH2OO + SO2) of 1.4 (±1.8) × 10(-2). The observed SO2 removal rate constants, which technically represent upper limits, are consistent with decomposition being a significant, structure dependent, sink in the atmosphere for syn-SCI.

  14. Kinetics of stabilised Criegee intermediates derived from alkene ozonolysis: reactions with SO2, H2O and decomposition under boundary layer conditions.

    PubMed

    Newland, Mike J; Rickard, Andrew R; Alam, Mohammed S; Vereecken, Luc; Muñoz, Amalia; Ródenas, Milagros; Bloss, William J

    2015-02-14

    The removal of SO2 in the presence of alkene-ozone systems has been studied for ethene, cis-but-2-ene, trans-but-2-ene and 2,3-dimethyl-but-2-ene, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity for all four alkene-ozone systems confirming a significant reaction for stabilised Criegee intermediates (SCI) with H2O. The observed SO2 removal kinetics are consistent with relative rate constants, k(SCI + H2O)/k(SCI + SO2), of 3.3 (±1.1) × 10(-5) for CH2OO, 26 (±10) × 10(-5) for CH3CHOO derived from cis-but-2-ene, 33 (±10) × 10(-5) for CH3CHOO derived from trans-but-2-ene, and 8.7 (±2.5) × 10(-5) for (CH3)2COO derived from 2,3-dimethyl-but-2-ene. The relative rate constants for k(SCI decomposition)/k(SCI + SO2) are -2.3 (±3.5) × 10(11) cm(-3) for CH2OO, 13 (±43) × 10(11) cm(-3) for CH3CHOO derived from cis-but-2-ene, -14 (±31) × 10(11) cm(-3) for CH3CHOO derived from trans-but-2-ene and 63 (±14) × 10(11) cm(-3) for (CH3)2COO. Uncertainties are ±2σ and represent combined systematic and precision components. These values are derived following the approximation that a single SCI is present for each system; a more comprehensive interpretation, explicitly considering the differing reactivity for syn- and anti-SCI conformers, is also presented. This yields values of 3.5 (±3.1) × 10(-4) for k(SCI + H2O)/k(SCI + SO2) of anti-CH3CHOO and 1.2 (±1.1) × 10(13) for k(SCI decomposition)/k(SCI + SO2) of syn-CH3CHOO. The reaction of the water dimer with CH2OO is also considered, with a derived value for k(CH2OO + (H2O)2)/k(CH2OO + SO2) of 1.4 (±1.8) × 10(-2). The observed SO2 removal rate constants, which technically represent upper limits, are consistent with decomposition being a significant, structure dependent, sink in the atmosphere for syn-SCI. PMID:25562069

  15. Electron spin resonance study of chromium(V) formation and decomposition by basalt-inhabiting bacteria.

    PubMed

    Kalabegishvili, Tamaz L; Tsibakhashvili, Nelly Y; Holman, Hoi-Ying N

    2003-10-15

    Bacterial reduction of Cr(VI) to Cr(III) compounds may produce reactive intermediates Cr(V) and Cr(IV), which can affect the mobility and toxicity of chromium in environments. To address this important subject, we conducted an electron spin resonance (ESR) study to understand the kinetics of the formation and decomposition of Cr(V) during Cr(VI) reduction by different gram-positive Cr(VI)-tolerant bacteria, which were isolated from polluted basalts from the United States of America and the Republic of Georgia. Results from our batch experiments show that during Cr(VI) reduction, the macromolecules at the cell wall of these bacteria could act as an electron donor to Cr(VI) to form a stable square-pyramidal Cr(V) complexes, which were reduced further probably via a one-electron transfer pathway to form Cr(IV) and Cr(III) compounds. The Cr(V) peak at the ESR spectrum possessed superhyperfine splitting characteristic of the Cr(V) complexes with diol-containing molecules. It appears that the kinetics of Cr(V) formation and decomposition depended on the bacterial growth phase and on the species. Both formation and decomposition of Cr(V) occurred more quickly when Cr(VI) was added at the exponential phase. In comparison with other gram-positive bacteria from the republic of Georgia, the formation and decomposition of Cr(V) in Arthrobacter species from the Unites States was significantly slower.

  16. Debugging decomposition data--comparative taphonomic studies and the influence of insects and carcass size on decomposition rate.

    PubMed

    Simmons, Tal; Adlam, Rachel E; Moffatt, Colin

    2010-01-01

    Comparison of data from a variety of environments and ambient temperatures has previously been difficult as few studies used standardized measures of time/temperature and decomposition. In this paper, data from previous studies and recent experiments are compared using simple conversions. These conversions allow comparison across multiple environments and experiments for the first time. Plotting decomposition score against logADD allows the exponential progression of decomposition to be expressed as a simple linear equation. Data comparison from many environments and temperatures shows no difference in decomposition progression when measured using Accumulated Degree Days. The major effector of change in rate was insect presence, regardless of depositional environment, species, or season. Body size is significant when carcasses are accessed by insects; when insects are excluded, while bodies are indoors, submerged, or buried, then decomposition progresses at the same rate regardless of body size.

  17. Experimental study of MgB{sub 2} decomposition

    SciTech Connect

    Fan, Z. Y.; Hinks, D. G.; Newman, N.; Rowell, J. M.

    2001-07-02

    The thermal stability of MgB{sub 2} has been studied experimentally to determine the role of thermodynamic and kinetic barriers in the decomposition process. The MgB{sub 2} decomposition rate approaches one monolayer per second at 650 C and has an activation energy of 2.0 eV. The evaporation coefficient is inferred to be {approx}10{sup -4}, indicating that this process is kinetically limited. These values were inferred from in situ measurements using a quartz crystal microbalance and a residual gas analyzer, in conjunction with ex situ measurements of redeposited material by Rutherford backscattering spectroscopy and secondary ion mass spectroscopy. The presence of a large kinetic barrier to decomposition indicates that the synthesis of MgB{sub 2} thin films conditions may be possible with vacuum processing, albeit within a narrow window in the reactive growth conditions.

  18. MHD oxidant intermediate temperature ceramic heater study

    NASA Technical Reports Server (NTRS)

    Carlson, A. W.; Chait, I. L.; Saari, D. P.; Marksberry, C. L.

    1981-01-01

    The use of three types of directly fired ceramic heaters for preheating oxygen enriched air to an intermediate temperature of 1144K was investigated. The three types of ceramic heaters are: (1) a fixed bed, periodic flow ceramic brick regenerative heater; (2) a ceramic pebble regenerative heater. The heater design, performance and operating characteristics under conditions in which the particulate matter is not solidified are evaluated. A comparison and overall evaluation of the three types of ceramic heaters and temperature range determination at which the particulate matter in the MHD exhaust gas is estimated to be a dry powder are presented.

  19. Adhesive micropatterns to study intermediate filament function in nuclear positioning.

    PubMed

    Dupin, Isabelle; Elric, Julien; Etienne-Manneville, Sandrine

    2015-01-01

    The nucleus is generally found near the cell center; however its position can vary in response to extracellular or intracellular signals, leading to a polarized intracellular organization. Nuclear movement is mediated by the cytoskeleton and its associated motors. While the role of actin and microtubule cytoskeletons in nuclear positioning has been assessed in various systems, the contribution of intermediate filaments is less established due in part to the lack of tools to study intermediate filament functions. The methods described here use micropatterned substrates to impose reproducible cell shape and nucleus position. Intermediate filament organization can be perturbed using gene downregulation or upregulation; intermediate filaments can also be visualized using fluorescent intermediate filament proteins. This protocol is valuable for characterizing the role of intermediate filaments in a variety of live or fixed adherent cells.

  20. Scoping study for the adsorption of tetraphenylborate decomposition products

    SciTech Connect

    Martin, K.B.

    2000-03-30

    This study examined the adsorption (Kd) of tetraphenylborate decomposition products - triphenylborane (3PB), diphenylborinic acid (2PB), and phenylboronic acid (1PB) from a simulated waste solution. The focus areas included three adsorbents: activated carbon, silica bonded with octyldecylsilane (C18), and silica bonded with a quaternary ammonium salt (Quat). The study examined the adsorbents at two concentrations, 100 and 200 g/L in salt simulant.

  1. Some studies on anaerobic decomposition of leucaena leucocephala leaves

    SciTech Connect

    Torane, J.V.; Lokhande, C.D.; Pawar, S.H. )

    1990-01-01

    Batch type anaerobic decomposition process in leucaena leucocephala plant material (leaves) has been carried out under mesophilic conditions (below 35{degrees}C). The results of studies involving variations in pH, conductivity, temperature, and optical density of digester slurry for four weeks are reported. The gas production rate was also studied which reveals that the use of leucaena leucocephala for biogas production will be helpful.

  2. Computational studies of polysiloxanes : oxidation potentials and decomposition reactions.

    SciTech Connect

    Assary, R. S.; Curtiss, L. A.; Redfern, P. C.; Zhang, Z.; Amine, K.

    2011-06-23

    Silicon-containing solvents have tremendous potential for application as electrolytes for electrical energy storage devices such as lithium-ion (air) batteries and supercapacitors. Quantum chemical methods were employed to investigate trends in oxidation potentials and decomposition reactions of a series of polysiloxanes. Various electron-donating and -withdrawing substituents can be used to tune the oxidation potential in shorter chain siloxanes but not in longer ones. Decomposition reactions of siloxanes in their oxidized states were investigated and compared against their carbon analogues. These studies suggest that the Si-O group provides added stability for siloxanes over their carbon analogues. Computational studies have also been performed for various disiloxanes and siloxanes with spacer groups to understand their thermochemical stability and oxidation potentials.

  3. Nuclear structure studies with intermediate energy probes

    SciTech Connect

    Lee, T.S.H.

    1993-10-01

    Nuclear structure studies with pions are reviewed. Results from a recent study of 1 p-shell nuclei using (e,e{prime}), ({pi}, {pi}{prime}), and ({gamma},{pi}) reactions are reported. Future nuclear structure studies with GeV electrons at CEBAF are also briefly discussed.

  4. Bringing Word Study to Intermediate Classrooms

    ERIC Educational Resources Information Center

    Bloodgood, Janet W.; Pacifici, Linda C.

    2004-01-01

    This article addresses word study for upper elementary and middle school classrooms. Word study is often neglected in classrooms due to misconceptions and fears of classroom teachers, especially teachers of older students. Conclusions from a research project conducted with teachers reveal both positive and negative understandings of implementing…

  5. Ferroelectric Surface Chemistry: FIrst-principle study of NOx Decomposition

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2012-02-01

    NOx molecules are critical and regulated air pollutants produced during automotive combustion. As part of a long-term effort to design viable catalysts for NOx decomposition that operate at higher temperatures and thus would allow for greater fuel efficiency, we are studying NOx chemistry on ferroelectric perovskite surfaces. Changing the direction of the ferroelectric polarization can modify surface properties and thus can lead to switchable surface chemistry. We will discuss our results for NO and NO2 on the polar (001) surfaces of PbTiO3 as function of ferroelectric polarization, surface stoichiometry, and various molecular or dissociated binding modes.

  6. Computational Kinetic Study for the Unimolecular Decomposition Pathways of Cyclohexanone.

    PubMed

    Zaras, Aristotelis M; Dagaut, Philippe; Serinyel, Zeynep

    2015-07-16

    There has been evidence lately that several endophytic fungi can convert lignocellulosic biomass into ketones among other oxygenated compounds. Such compounds could prove useful as biofuels for internal combustion engines. Therefore, their combustion properties are of high interest. Cyclohexanone was identified as an interesting second-generation biofuel ( Boot , M. ; et al. Cyclic Oxygenates: A New Class of Second-Generation Biofuels for Diesel Engines? Energy Fuels 2009 , 23 , 1808 - 1817 ; Klein-Douwel , R. J. H. ; et al. Soot and Chemiluminescence in Diesel Combustion of Bio-Derived, Oxygenated and Reference Fuels . Proc. Combust. Inst. 2009 , 32 , 2817 - 2825 ). However, until recently ( Serinyel , Z. ; et al. Kinetics of Oxidation of Cyclohexanone in a Jet- Stirred Reactor: Experimental and Modeling . Proc. Combust. Inst. 2014 ; DOI: 10.1016/j.proci.2014.06.150 ), no previous studies on the kinetics of oxidation of that fuel could be found in the literature. In this work, we present the first theoretical kinetic study of the unimolecular decomposition pathways of cyclohexanone, a cyclic ketone that could demonstrate important fuel potential. Using the quantum composite G3B3 method, we identified six different decomposition pathways for cyclohexanone and computed the corresponding rate constants. The rate constants were calculated using the G3B3 method coupled with Rice-Ramsperger-Kassel-Marcus theory in the temperature range of 800-2000 K. Our calculations show that the kinetically more favorable channel for thermal decomposition is pathway 2 that produces 1,3-butadien-2-ol, which in turn can isomerize easily to methyl vinyl ketone through a small barrier. The results presented here can be used in a future kinetic combustion mechanism.

  7. Computational Kinetic Study for the Unimolecular Decomposition Pathways of Cyclohexanone.

    PubMed

    Zaras, Aristotelis M; Dagaut, Philippe; Serinyel, Zeynep

    2015-07-16

    There has been evidence lately that several endophytic fungi can convert lignocellulosic biomass into ketones among other oxygenated compounds. Such compounds could prove useful as biofuels for internal combustion engines. Therefore, their combustion properties are of high interest. Cyclohexanone was identified as an interesting second-generation biofuel ( Boot , M. ; et al. Cyclic Oxygenates: A New Class of Second-Generation Biofuels for Diesel Engines? Energy Fuels 2009 , 23 , 1808 - 1817 ; Klein-Douwel , R. J. H. ; et al. Soot and Chemiluminescence in Diesel Combustion of Bio-Derived, Oxygenated and Reference Fuels . Proc. Combust. Inst. 2009 , 32 , 2817 - 2825 ). However, until recently ( Serinyel , Z. ; et al. Kinetics of Oxidation of Cyclohexanone in a Jet- Stirred Reactor: Experimental and Modeling . Proc. Combust. Inst. 2014 ; DOI: 10.1016/j.proci.2014.06.150 ), no previous studies on the kinetics of oxidation of that fuel could be found in the literature. In this work, we present the first theoretical kinetic study of the unimolecular decomposition pathways of cyclohexanone, a cyclic ketone that could demonstrate important fuel potential. Using the quantum composite G3B3 method, we identified six different decomposition pathways for cyclohexanone and computed the corresponding rate constants. The rate constants were calculated using the G3B3 method coupled with Rice-Ramsperger-Kassel-Marcus theory in the temperature range of 800-2000 K. Our calculations show that the kinetically more favorable channel for thermal decomposition is pathway 2 that produces 1,3-butadien-2-ol, which in turn can isomerize easily to methyl vinyl ketone through a small barrier. The results presented here can be used in a future kinetic combustion mechanism. PMID:25354027

  8. Theoretical study of the decomposition of ethyl and ethyl 3-phenyl glycidate.

    PubMed

    Josa, Daniela; Peña-Gallego, Angeles; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M

    2013-01-01

    The mechanism of the decomposition of ethyl and ethyl 3-phenyl glycidate in gas phase was studied by density functional theory (DFT) and MP2 methods. A proposed mechanism for the reaction indicates that the ethyl side of the ester is eliminated as ethylene through a concerted six-membered cyclic transition state, and the unstable intermediate glycidic acid decarboxylates rapidly to give the corresponding aldehyde. Two possible pathways for glycidic acid decarboxylation were studied: one via a five-membered cyclic transition state, and the other via a four-membered cyclic transition state. The results of the calculations indicate that the decarboxylation reaction occurs via a mechanism with five-membered cyclic transition state.

  9. Bullying during the Intermediate School Phase: A South African Study

    ERIC Educational Resources Information Center

    Greeff, P.; Grobler, A. A.

    2008-01-01

    Bullying in the intermediate school phase was studied, using the Revised Olweus Bully/Victim Questionnaire (R-OBVQ). The total sample comprised 360 grade 4 to 6 pupils from English-medium, single-sex schools in Bloemfontein, South Africa. To ensure a more homogeneous sample, the grade (grades 4 to 6) and race (black and white) of the participants…

  10. Experimental study of hydrogen production by direct decomposition of water

    NASA Astrophysics Data System (ADS)

    Bilgen, E.; Galindo, J.; Baykara, S. Z.

    The hydrogen production by direct decomposition of water in a solar furnace is studied. The set-up is a horizontal axis system consisting of two 1.0 kW parabolic concentrators, both powered by a single heliostat. A temperature of 3000 K is possible. The water is fed to the reactor installed at the focal space of the concentrator, and the steam is decomposed at about 2500 K. The reactor consisted of a cylindrical cavity type refractory receiver covered with a silica cupola. The steam was introduced at a known rate into the cavity and the product gases were quenched. After the condensation of steam, hydrogen and oxygen were collected in a reservoir. Results indicate that with an optimized system, it is possible to produce hydrogen at about 70 percent rate of the theoretical value at the temperature level studied.

  11. Batch Studies of Sodium Tetraphenylborate Decomposition on Reduced Palladium Catalyst

    SciTech Connect

    Barnes, M.J.

    2001-02-13

    In these batch experiments we obtained preliminary information on palladium based catalytic decomposition of sodium tetraphenylborate (NaTPB). These preliminary data provide necessary data to design subsequent catalytic decomposition experiments for NaTPB using a continuous stirred tank reactor (CSTR).

  12. First-principles study of high explosive decomposition energetics

    SciTech Connect

    Wu, C J

    1998-08-21

    The mechanism of the gas phase unimolecular decomposition of hexahydro-1,3,5,- trinitro- 1,3,5,-triazine (RDX) has been investigated using first principles gradient corrected density functional theory. Our results show that the dominant reaction channel is the N-NO* bond rupture, which has a barrier of 34.2 kcal/mol at the B- PW9 l/cc-pVDZ level and is 18.3 kcal/mol lower than that of the concerted ring fission to three methylenenitramine molecules. In addition, we have carried out a systematic study of homolytic bond dissociation energies of 14 other high explosives at the B-PW91/D95V level. We find that the correlation between the weakest bond strength and high explosive sensitivity is strong

  13. Novel Fragmentation Pathways of Anionic Adducts of Steroids Formed by Electrospray Anion Attachment Involving Regioselective Attachment, Regiospecific Decompositions, Charge-Induced Pathways, and Ion-Dipole Complex Intermediates

    NASA Astrophysics Data System (ADS)

    Rannulu, Nalaka S.; Cole, Richard B.

    2012-09-01

    The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion]- adducts of these steroids revealed that fluoride adduct [M + F]- precursors first lose HF to produce [M - H]- and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d4-pregnenolone, are also discussed.

  14. Fundamental mechanistic studies in formic acid decomposition on transition metal surfaces

    NASA Astrophysics Data System (ADS)

    Mavrikakis, Manos

    2014-03-01

    Formic acid (HCOOH) is a simple molecule that is an abundant product of biomass processing and can serve as an internal source of hydrogen for oxygen removal and upgrading of biomass to chemicals and fuels. In addition, HCOOH can be used as a fuel for low temperature direct fuel cells. We present a systematic study of the HCOOH decomposition reaction mechanism starting from first-principles and including reactivity experiments and microkinetic modeling. In particular, periodic self-consistent Density Functional Theory (DFT) calculations are performed to determine the stability of reactive intermediates and activation energy barriers of elementary steps. Pre-exponential factors are determined from vibrational frequency calculations. Mean-field microkinetic models are developed and calculated reaction rates and reaction orders are then compared with experimentally measured ones. These comparisons provide useful insights on the nature of the active site, most-abundant surface intermediates as a function of reaction conditions and feed composition. Trends across metals on the fundamental atomic-scale level up to selectivity trends will be discussed. Finally, we identify from first-principles alloy surfaces, which may possess better catalytic properties for selective dehydrogenation of HCOOH than monometallic surfaces, thereby guiding synthesis towards promising novel catalytic materials. Work supported as part of the Institute of Atom-efficient Chemical Transformation (IACT), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  15. Theoretical study of gas hydrate decomposition kinetics: model predictions.

    PubMed

    Windmeier, Christoph; Oellrich, Lothar R

    2013-11-27

    In order to provide an estimate of intrinsic gas hydrate dissolution and dissociation kinetics, the Consecutive Desorption and Melting Model (CDM) was developed in a previous publication (Windmeier, C.; Oellrich, L. R. J. Phys. Chem. A 2013, 117, 10151-10161). In this work, an extensive summary of required model data is given. Obtained model predictions are discussed with respect to their temperature dependence as well as their significance for technically relevant areas of gas hydrate decomposition. As a result, an expression for determination of the intrinsic gas hydrate decomposition kinetics for various hydrate formers is given together with an estimate for the maximum possible rates of gas hydrate decomposition. PMID:24199870

  16. Theoretical study of water cluster catalyzed decomposition of formic acid.

    PubMed

    Inaba, Satoshi

    2014-04-24

    We have performed a number of quantum chemical simulations to examine water cluster catalyzed decomposition of formic acid. The decomposition of formic acid consists of two competing pathways, dehydration, and decarboxylation. We use the Gaussian 4 method of the Gaussian09 software to locate and optimize a transition state of the decomposition reaction and obtain the activation energy. The decomposition starts by transferring a proton of a formic acid to a water molecule. The de Broglie wavelength of a proton is similar to the width of the potential barrier of the decomposition reaction at low temperature. The tunneling, in which a proton penetrates the potential barrier, enhances the decomposition rate. Water molecules serve as the catalyst in the decomposition and reduce the activation energy. The relay of a proton from a water molecule to a neighboring water molecule is accomplished with little change of the geometry of a molecule, resulting in the reduction of the activation energy. Two water molecules are actively involved in the decomposition reaction to reduce the activation energy. We have also examined the effect of water clusters with three, four, and five water molecules on the decomposition reaction. The noncovalent distance between a hydrogen atom of a water molecule and an oxygen atom of a neighboring water molecule decreases in a water cluster due to the cooperative many-body interactions. A water molecule in a water cluster becomes a better proton donor as well as a better proton acceptor. The activation energy of the decomposition is further decreased by the catalytic effect of a water cluster. We calculate the reaction rate using the transition state theory corrected by the tunneling effect of a proton. The calculated reaction rate of the decarboxylation is smaller than that of the dehydration when less than three water molecules are included in the simulation. However, the major product of the decomposition of a formic acid becomes carbon dioxide

  17. Inter-year repeatability study of volatile organic compounds from surface decomposition of human analogues.

    PubMed

    Stadler, Sonja; Desaulniers, Jean-Paul; Forbes, Shari L

    2015-05-01

    Decomposition odour and volatile organic compounds (VOCs) have gained considerable attention recently due to their use by insects and scent detection canines to locate remains. However, a comprehensive and accurate profile of decomposition odour is yet to be confirmed. This is, in part, due to the geographical diversity in the studies conducted and the variation in the methodology and compounds being reported. To date, no repeatability studies of decomposition odour have been conducted in the same environment. In order to address this current gap in the scientific literature, this study conducted three replicate trials in order to evaluate the inter-year repeatability of the decomposition VOC profile in a southern Canadian environment. Surface decomposition trials were conducted during the spring and summer months and the VOCs were analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). This study was able to demonstrate that decomposition VOCs are produced consistently during their characteristic stages and that this relationship is maintained under varying environmental factors which influence the rate of decomposition. This consistent production of decomposition VOCs can lead to a better understanding of the mechanisms of soft tissue decomposition and their sources of variation, and it could potentially lead to improved applications of these compounds for the detection of decomposed remains.

  18. Ozone decomposition

    PubMed Central

    Batakliev, Todor; Georgiev, Vladimir; Anachkov, Metody; Rakovsky, Slavcho

    2014-01-01

    Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers). Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates. PMID:26109880

  19. Ozone decomposition.

    PubMed

    Batakliev, Todor; Georgiev, Vladimir; Anachkov, Metody; Rakovsky, Slavcho; Zaikov, Gennadi E

    2014-06-01

    Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers). Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates. PMID:26109880

  20. Ozone decomposition.

    PubMed

    Batakliev, Todor; Georgiev, Vladimir; Anachkov, Metody; Rakovsky, Slavcho; Zaikov, Gennadi E

    2014-06-01

    Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers). Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates.

  1. Jellyfish (Cyanea nozakii) decomposition and its potential influence on marine environments studied via simulation experiments.

    PubMed

    Qu, Chang-Feng; Song, Jin-Ming; Li, Ning; Li, Xue-Gang; Yuan, Hua-Mao; Duan, Li-Qin; Ma, Qing-Xia

    2015-08-15

    A growing body of evidence suggests that the jellyfish population in Chinese seas is increasing, and decomposition of jellyfish strongly influences the marine ecosystem. This study investigated the change in water quality during Cyanea nozakii decomposition using simulation experiments. The results demonstrated that the amount of dissolved nutrients released by jellyfish was greater than the amount of particulate nutrients. NH4(+) was predominant in the dissolved matter, whereas the particulate matter was dominated by organic nitrogen and inorganic phosphorus. The high N/P ratios demonstrated that jellyfish decomposition may result in high nitrogen loads. The inorganic nutrients released by C. nozakii decomposition were important for primary production. Jellyfish decomposition caused decreases in the pH and oxygen consumption associated with acidification and hypoxia or anoxia; however, sediments partially mitigated the changes in the pH and oxygen. These results imply that jellyfish decomposition can result in potentially detrimental effects on marine environments.

  2. An electrophysiological study of the intermediate syndrome of organophosphate poisoning.

    PubMed

    Lorenzoni, Paulo José; Gasparetto, Juliano; Kay, Cláudia Suemi Kamoi; Scola, Rosana Herminia; Werneck, Lineu César

    2010-09-01

    Acute organophosphate (OP) poisoning is commonly seen in emergency medicine. Neurologists must be alert to detect neuromuscular transmission failure and other neurological complications that follow OP poisoning. We report a 37-year-old male with acute OP poisoning to emphasize the electrophysiological abnormalities during the intermediate syndrome (IMS). Motor nerve conduction studies revealed that a single nerve stimulation evoked a repetitive compound muscle action potential, whereas repetitive nerve stimulation resulted in a combination of a decrement-increment pattern and a repetitive fade response. Thus, electrophysiological studies can be used to monitor patients with IMS, and these test results correlate well with clinical findings in acute OP poisoning. PMID:20483619

  3. Studies of Corn Stover Decomposition Using the Litter Bag Technique

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Decomposition rates of residue from three genetically-modified corn hybrids expressing one or more Bt endotoxins were compared to that of residue from a near isogenic, unmodified hybrid. The corn hybrids were (i) DKC60-16 (Yieldguard Corn Borer), (ii) DKC60-12 (Yieldguard Corn Rootworm), (iii) DKC60...

  4. Study of Moroccan oil shale thermal decomposition kinetics

    SciTech Connect

    Bekri, O.; Baba-Habib, H.; Cha, C.Y.; Edelman, M.C.

    1983-04-01

    Oil shale samples from the M, X, Y, and T-Zones of the Timhadit reserves in Morocco have been tested with a Thermogravimetric Analyzer (TGA) to provide nonisothermal weight loss data. Analysis of this data has provided several of the kinetic values necessary for the understanding and modeling of the thermal decomposition mechanisms of kerogen pyrolysis and inorganic carbonate decomposition in Timahdit oil shale. Several methods of data analysis were developed which utilize both the differential and integral forms of the reaction rate equations. In addition, the relationship between the temperature at which the maximum reaction rate occurs and the heating rate was derived for the first-order reactions. This relationship can be used to determine the activation energy and frequency factor using the weight loss data obtained at constant heating rate. These methods are discussed and the analytical procedures, calculations, and results are presented for the determination of the kinetics of kerogen pyrolysis and inorganic carbonate decomposition in Moroccan oil shale from the Timahdit reserves.

  5. Adiabatic calorimetric decomposition studies of 50 wt.% hydroxylamine/water.

    PubMed

    Cisneros, L O; Rogers, W J; Mannan, M S

    2001-03-19

    Calorimetric data can provide a basis for determining potential hazards in reactions, storage, and transportation of process chemicals. This work provides calorimetric data for the thermal decomposition behavior in air of 50wt.% hydroxylamine/water (HA), both with and without added stabilizers, which was measured in closed cells with an automatic pressure tracking adiabatic calorimeter (APTAC). Among the data provided are onset temperatures, reaction order, activation energies, pressures of noncondensable products, thermal stability at 100 degrees C, and the effect of HA storage time. Discussed also are the catalytic effects of carbon steel, stainless steel, stainless steel with silica coating, inconel, titanium, and titanium with silica coating on the reaction self-heat rates and onset temperatures. In borosilicate glass cells, HA was relatively stable at temperatures up to 133 degrees C, where the HA decomposition self-heat rate reached 0.05 degrees C/min. The added stabilizers appeared to reduce HA decomposition rates in glass cells and at ambient temperatures. The tested metals and metal surfaces coated with silica acted as catalysts to lower the onset temperatures and increase the self-heat rates. PMID:11165058

  6. Thermal decomposition of NH4-analcime: a kinetic study

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, Yu. M.; Drebushchak, V. A.

    2003-04-01

    NH4-analcime was prepared by cation exchange from natural analcime (Russia, East Siberia, Nidym river). Crystals with dimensions 0.2-0.4 mm across were treated with an aqueous solution of NH4NO3 (150C, 4 days). The composition of the analcime framework was determined by X-ray fluorescence analysis, and residual sodium was determined by flame atomic absorption spectrophotometry. The chemical formula of the NH4-analcime calculated considering the charge balance is (NH4)14.4Na0.6(Al15Si33O96). In general, thermal decomposition of ammonium zeolites includes three steps: dehydration, deammoniation, and dehydroxylation. All three steps are detected by thermogravimetry. NH4-analcime contains no water molecules, so its weight loss is due only to the last two steps. The decomposition was investigated using a TG-209 (NETZSCH). The measurements were carried out by scanning heating at heating rates of 10, 5, 2, 1, 0.5, 0.2, and 0.1 K/min. The kinetic curves obtained are very similar in shape and look like single-step decomposition. Deammoniation and dehydroxylation overlap and cannot be separated at any heating rate. Financial assistance for this work was provided by the United Institute of Geology, Geophysics and Mineralogy, Novosibirsk, Russia (VMTK No1779) and a joint grant from the CRDF (USA) and the Ministry of Education (Russian Federation): REC-008.

  7. Adiabatic calorimetric decomposition studies of 50 wt.% hydroxylamine/water.

    PubMed

    Cisneros, L O; Rogers, W J; Mannan, M S

    2001-03-19

    Calorimetric data can provide a basis for determining potential hazards in reactions, storage, and transportation of process chemicals. This work provides calorimetric data for the thermal decomposition behavior in air of 50wt.% hydroxylamine/water (HA), both with and without added stabilizers, which was measured in closed cells with an automatic pressure tracking adiabatic calorimeter (APTAC). Among the data provided are onset temperatures, reaction order, activation energies, pressures of noncondensable products, thermal stability at 100 degrees C, and the effect of HA storage time. Discussed also are the catalytic effects of carbon steel, stainless steel, stainless steel with silica coating, inconel, titanium, and titanium with silica coating on the reaction self-heat rates and onset temperatures. In borosilicate glass cells, HA was relatively stable at temperatures up to 133 degrees C, where the HA decomposition self-heat rate reached 0.05 degrees C/min. The added stabilizers appeared to reduce HA decomposition rates in glass cells and at ambient temperatures. The tested metals and metal surfaces coated with silica acted as catalysts to lower the onset temperatures and increase the self-heat rates.

  8. A comparative density functional study of methanol decomposition on Cu{sub 4} and Co{sub 4} clusters.

    SciTech Connect

    Mehmood, F.; Greeley, J.; Zapol, P.; Curtiss, L. A.

    2010-08-12

    A density functional theory study of the decomposition of methanol on Cu{sub 4} and Co{sub 4} clusters is presented. The reaction intermediates and activation barriers have been determined for reaction steps to form H{sub 2} and CO. For both clusters, methanol decomposition initiated by C-H and O-H bond breaking was investigated. In the case of a Cu{sub 4} cluster, methanol dehydrogenation through hydroxymethyl (CH{sub 2}OH), hydroxymethylene (CHOH), formyl (CHO), and carbon monoxide (CO) is found to be slightly more favorable. For a Co{sub 4} cluster, the dehydrogenation pathway through methoxy (CH{sub 3}O) and formaldehyde (CH{sub 2}O) is slightly more favorable. Each of these pathways results in formation of CO and H{sub 2}. The Co cluster pathway is very favorable thermodynamically and kinetically for dehydrogenation. However, since CO binds strongly, it is likely to poison methanol decomposition to H{sub 2} and CO at low temperatures. In contrast, for the Cu cluster, CO poisoning is not likely to be a problem since it does not bind strongly, but the dehydrogenation steps are not energetically favorable. Pathways involving C-O bond cleavage are even less energetically favorable. The results are compared to our previous study of methanol decomposition on Pd{sub 4} and Pd{sub 8} clusters. Finally, all reaction energy changes and transition state energies, including those for the Pd clusters, are related in a linear, Broensted?Evans?Polanyi plot.

  9. Thermal decomposition studies of 1,3,3-trinitroazetidine (TNAZ) and 1-nitroso-3,3-dinitroazetidine (NDNAZ) by simultaneous thermogravimetric modulated beam mass spectroscopy

    SciTech Connect

    Behrens, R. Jr.; Bulusu, S.

    1995-12-01

    The initial results from a study of the thermal decomposition of TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ using the simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS) are presented. The major products formed in the decomposition of TNAZ are NO{sub 2} and NO with slightly lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}, CO{sub 2}/N{sub 2}O and NDNAZ. The major product formed in the decomposition of NDNAZ is NO with lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}O. The lower molecular weight products are similar to those observed in RSFTIR and IRMPD studies conducted previously by others. However, this study has shown that the mononitroso analogue of TNAZ, NDNAZ, is an important intermediate formed during the decomposition of TNAZ. It plays an important role in determining the identity of the products formed in the decomposition of TNAZ. The temporal behaviors Of the ion signals associated with the various thermal decomposition products from TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ are also presented. The illustrate the evolution sequence of the various products that are associated with the different reaction pathways that control the decomposition of these materials. In particular, the study of the {sup 15}N-labeled sample revealed that NO{sub 2} originates from both the likely sites in the TNAZ molecule and that the cleavage of the nitramine-NO{sub 2} group precedes that of the C-NO{sub 2} cleavage, resulting in similar sequences in the formation of NO and NDNAZ also.

  10. Decomposition and plant-available nitrogen in biosolids: laboratory studies, field studies, and computer simulation.

    PubMed

    Gilmour, John T; Cogger, Craig G; Jacobs, Lee W; Evanylo, Gregory K; Sullivan, Dan M

    2003-01-01

    This research combines laboratory and field studies with computer simulation to characterize the amount of plant-available nitrogen (PAN) released when municipal biosolids are land-applied to agronomic crops. In the laboratory studies, biosolids were incubated in or on soil from the land application sites. Mean biosolids total C, organic N, and C to N ratio were 292 g kg(-1), 41.7 g kg(-1), and 7.5, respectively. Based on CO2 evolution at 25 degrees C and optimum soil moisture, 27 of the 37 biosolids-soil combinations had two decomposition phases. The mean rapid and slow fraction rate constants were 0.021 and 0.0015 d(-1), respectively, and the rapid fraction contained 23% of the total C assuming sequential decomposition. Where only one decomposition phase existed, the mean first order rate constant was 0.0046 d(-1). The mean rate constant for biosolids stored in lagoons for an extended time was 0.00097 d(-1). The only treatment process that was related to biosolids treatment was stabilization by storage in a lagoon. Biosolids addition rates (dry basis) ranged from 1.3 to 33.8 Mg ha(-1) with a mean value of 10.6 Mg ha(-1). A relationship between fertilizer N rate and crop response was used to estimate observed PAN at each site. Mean observed PAN during the growing season was 18.9 kg N Mg(-1) or 37% of the biosolids total N. Observed PAN was linearly related to biosolids total N. Predicted PAN using the computer model Decomposition, actual growing-season weather, actual analytical data, and laboratory decomposition kinetics compared well with observed PAN. The mean computer model prediction of growing-season PAN was 19.2 kg N Mg(-1) and the slope of the regression between predicted and observed PAN was not significantly different from unity. Predicted PAN obtained using mean decomposition kinetics was related to predicted PAN using actual decomposition kinetics suggesting that mean rate constants, actual weather, and actual analytical data could be used in

  11. Study of the kinetics of catalytic decomposition of hydrazine vapors on palladium

    NASA Technical Reports Server (NTRS)

    Khomenko, A. A.; Apelbaum, L. O.

    1987-01-01

    The decomposition rates of N2H4 on a palladium surface are studied. Experiments were conducted in a circulating unit at atmosphere pressure. The experimental method is described. The laws found for the reaction kinetics are explained by equations.

  12. Soft X-ray induced decomposition of phenylalanine and tyrosine: Acomparative study

    SciTech Connect

    Zubavichus, Y.; Zharnikov, M.; Shaporenko, A.; Fuchs, O.; Weinhart, L.; Heske, C.; Umbach, E.; Denlinger, J.D.; Grunze, M.

    2003-11-19

    The pristine state and soft X-ray induced decomposition of two aromatic amino acids, viz. phenylalanine and tyrosine, have been studied by means of XPS and NEXAFS. The spectroscopic data on the radiation decomposition have been supplemented by a mass-spectral analysis of desorbed species in the residual gas. Despite very similar chemical structures, the two amino acids show a drastically different behavior towards ionizing radiation: phenylalanine degrades very quickly whereas tyrosine shows a prominent stability against radiation damage. Reasons for this difference are discussed in relation to radical-mediated reactions responsible for the decomposition.

  13. Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study

    NASA Astrophysics Data System (ADS)

    Nguyen, Thanh Lam; McCaslin, Laura; McCarthy, Michael C.; Stanton, John F.

    2016-10-01

    The thermal decomposition of syn-ethanal-oxide (syn-CH3CHOO) through vinyl hydrogen peroxide (VHP) leading to hydroxyl radical is characterized using a modification of the HEAT thermochemical protocol. The isomerization step of syn-CH3CHOO to VHP via a 1,4 H-shift, which involves a moderate barrier of 72 kJ/mol, is found to be rate determining. A two-dimensional master equation approach, in combination with semi-classical transition state theory, is employed to calculate the time evolution of various species as well as to obtain phenomenological rate coefficients. This work suggests that, under boundary layer conditions in the atmosphere, thermal unimolecular decomposition is the most important sink of syn-CH3CHOO. Thus, the title reaction should be included into atmospheric modeling. The fate of cold VHP, the intermediate stabilized by collisions with a third body, has also been investigated.

  14. Experimental studies of pion-nucleus interactions at intermediate energies

    SciTech Connect

    Not Available

    1991-12-31

    This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting {pi}{sup 0} mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized {sup 3}He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure.

  15. Chunk decomposition contributes to forming new mental representations: An ERP study.

    PubMed

    Zhang, Zhonglu; Xing, Qiang; Li, Hong; Warren, Christopher Michael; Tang, Zhiwen; Che, Jingshang

    2015-06-26

    Whereas previous studies mainly focused on the role of chunk decomposition on how to break impasse in insight occurrence, our study aimed to investigate the role of chunk decomposition in forming new mental representations. For this purpose, the Chinese riddle comprehension task was employed in which the riddle involves either tight or loose chunk decomposition. The event-related potentials (ERPs) were measured after the onset of an answer hint, with which participants were instructed to comprehend the Chinese riddles. The behavioral results showed that participants performed worse on riddle comprehension in tight chunk condition than in loose chunk condition. In addition, we found larger N100 and P300 deflections in the former condition than in the latter condition. These findings suggest that early perceptual processing is crucially required by chunk decomposition, which contributes to forming new mental representations by integrating the perceptual and semantic information.

  16. Theoretical studies on the unimolecular decomposition of ethylene glycol.

    PubMed

    Ye, Lili; Zhao, Long; Zhang, Lidong; Qi, Fei

    2012-01-12

    The unimolecular decomposition processes of ethylene glycol have been investigated with the QCISD(T) method with geometries optimized at the B3LYP/6-311++G(d,p) level. Among the decomposition channels identified, the H(2)O-elimination channels have the lowest barriers, and the C-C bond dissociation is the lowest-energy dissociation channel among the barrierless reactions (the direct bond cleavage reactions). The temperature and pressure dependent rate constant calculations show that the H(2)O-elimination reactions are predominant at low temperature, whereas at high temperature, the direct C-C bond dissociation reaction is dominant. At 1 atm, in the temperature range 500-2000 K, the calculated rate constant is expressed to be 7.63 × 10(47)T(-10.38) exp(-42262/T) for the channel CH(2)OHCH(2)OH → CH(2)CHOH + H(2)O, and 2.48 × 10(51)T(-11.58) exp(-43593/T) for the channel CH(2)OHCH(2)OH → CH(3)CHO + H(2)O, whereas for the direct bond dissociation reaction CH(2)OHCH(2)OH → CH(2)OH + CH(2)OH the rate constant expression is 1.04 × 10(71)T(-16.16) exp(-52414/T).

  17. Revisiting formic acid decomposition on metallic powder catalysts: Exploding the HCOOH decomposition volcano curve

    NASA Astrophysics Data System (ADS)

    Tang, Yadan; Roberts, Charles A.; Perkins, Ryan T.; Wachs, Israel E.

    2016-08-01

    This study revisits the classic volcano curve for HCOOH decomposition by metal catalysts by taking a modern catalysis approach. The metal catalysts (Au, Ag, Cu, Pt, Pd, Ni, Rh, Co and Fe) were prepared by H2 reduction of the corresponding metal oxides. The number of surface active sites (Ns) was determined by formic acid chemisorption. In situ IR indicated that both monodentate and bidentate/bridged surface HCOO* were present on the metals. Heats of adsorption (ΔHads) for surface HCOO* values on metals were taken from recently reported DFT calculations. Kinetics for surface HCOO* decomposition (krds) were determined with TPD spectroscopy. Steady-state specific activity (TOF = activity/Ns) for HCOOH decomposition over the metals was calculated from steady-state activity (μmol/g-s) and Ns (μmol/g). Steady-state TOFs for HCOOH decomposition weakly correlated with surface HCOO* decomposition kinetics (krds) and ΔHads of surface HCOO* intermediates. The plot of TOF vs. ΔHads for HCOOH decomposition on metal catalysts does not reproduce the classic volcano curve, but shows that TOF depends on both ΔHads and decomposition kinetics (krds) of surface HCOO* intermediates. This is the first time that the classic catalysis study of HCOOH decomposition on metallic powder catalysts has been repeated since its original publication.

  18. The Use of Withaferin A to Study Intermediate Filaments.

    PubMed

    Mohan, Royce; Bargagna-Mohan, Paola

    2016-01-01

    Withaferin A (WFA), initially identified as a compound that inhibits experimental angiogenesis, has been shown to bind to soluble vimentin (sVim) and other type III intermediate filament (IF) proteins. We review WFA's dose-related activities (Section 1), examining nanomolar concentrations effects on sVim in cell proliferation and submicromolar effects on lamellipodia and focal adhesion formation. WFA effects on polymeric IFs are especially interesting to the study of cell migration and invasion that depend on IF mechanical contractile properties. WFA interferes with NF-κB signaling, though this anti-inflammatory mechanism may occur via perturbation of sVim-protein complexes, and possibly also via targeting IκB kinase β directly. However, micromolar concentrations that induce vimentin cleavage to promote apoptosis may increasingly show off-target effects via targeting other IFs (neurofilaments and keratin) and non-IFs (tubulin, heat-shock proteins, proteasome). Thus, in Section 2, we describe our studies combining cell cultures with animal models of injury to validate relevant type III IF-targeting mechanisms of WFA. In Section 3, we illuminate from investigating myofibroblast differentiation how sVim phosphorylation may govern cell type-selective sensitivity to WFA, offering impetus for exploring vimentin phosphorylation isoforms as targets and biomarkers of fibrosis. These different WFA targets and activities are listed in a summary table.

  19. How to Study Intermediate Filaments in Atomic Detail.

    PubMed

    Chernyatina, Anastasia A; Hess, John F; Guzenko, Dmytro; Voss, John C; Strelkov, Sergei V

    2016-01-01

    Studies of the intermediate filament (IF) structure are a prerequisite of understanding their function. In addition, the structural information is indispensable if one wishes to gain a mechanistic view on the disease-related mutations in the IFs. Over the years, considerable progress has been made on the atomic structure of the elementary building block of all IFs, the coiled-coil dimer. Here, we discuss the approaches, methods and practices that have contributed to this advance. With abundant genetic information on hand, bioinformatics approaches give important insights into the dimer structure, including the head and tail regions poorly assessable experimentally. At the same time, the most important contribution has been provided by X-ray crystallography. Following the "divide-and-conquer" approach, many fragments from several IF proteins could be crystallized and resolved to atomic resolution. We will systematically cover the main procedures of these crystallographic studies, suggest ways to maximize their efficiency, and also discuss the possible pitfalls and limitations. In addition, electron paramagnetic resonance with site-directed spin labeling was another method providing a major impact toward the understanding of the IF structure. Upon placing the spin labels into specific positions within the full-length protein, one can evaluate the proximity of the labels and their mobility. This makes it possible to make conclusions about the dimer structure in the coiled-coil region and beyond, as well as to explore the dimer-dimer contacts.

  20. Study of Intermediate Age (~10-30 Myr) Open Clusters

    NASA Astrophysics Data System (ADS)

    Olguin, Lorenzo; Michel, Raul; Contreras, Maria; Hernandez, Jesus; Schuster, William; Chavarria-Kleinhenn, Carlos

    2013-07-01

    We present the study of a sample of intermediate age open clusters (age ~ 10-30 Myr) using optical (UBVRI) and infrared photometric data. Optical photometry was obtained as part of the San Pedro Martir Open Clusters Project (SPM-OCP, Schuster et al. 2007; Michel et al. 2013). Infrared photometry was retrieved from 2MASS public data archive and WISE database. Open clusters included in the SPM-OCP were selected from catalogues presented by Dias et al. (2002) and Froebrich, Scholz & Raftery (2007). One of the main goals of the SPM-OCP is to compile a self-consistent and homogeneous set of cluster fundamental parameters such as reddening, distance, age, and metallicity whenever possible. In this work, we have analyzed a set of 25 clusters from the SPM-OCP with estimated ages between 10 and 30 Myr. Derived fundamental parameters for each cluster in the sample as well as an example of typical color-color and color-magnitude diagrams are presented. Kinematic membership was established by using proper motion data taken from the literature. Based on infrared photometry, we have searched for candidate stars to posses a circumstellar disk within each clusters. For those selected candidates a follow-up spectroscpic study is being carried out. This work was partially supported by UNAM-PAPIIT grant IN-109311.

  1. Breast tissue decomposition with spectral distortion correction: A postmortem study

    SciTech Connect

    Ding, Huanjun; Zhao, Bo; Baturin, Pavlo; Behroozi, Farnaz; Molloi, Sabee

    2014-10-15

    Purpose: To investigate the feasibility of an accurate measurement of water, lipid, and protein composition of breast tissue using a photon-counting spectral computed tomography (CT) with spectral distortion corrections. Methods: Thirty-eight postmortem breasts were imaged with a cadmium-zinc-telluride-based photon-counting spectral CT system at 100 kV. The energy-resolving capability of the photon-counting detector was used to separate photons into low and high energy bins with a splitting energy of 42 keV. The estimated mean glandular dose for each breast ranged from 1.8 to 2.2 mGy. Two spectral distortion correction techniques were implemented, respectively, on the raw images to correct the nonlinear detector response due to pulse pileup and charge-sharing artifacts. Dual energy decomposition was then used to characterize each breast in terms of water, lipid, and protein content. In the meantime, the breasts were chemically decomposed into their respective water, lipid, and protein components to provide a gold standard for comparison with dual energy decomposition results. Results: The accuracy of the tissue compositional measurement with spectral CT was determined by comparing to the reference standard from chemical analysis. The averaged root-mean-square error in percentage composition was reduced from 15.5% to 2.8% after spectral distortion corrections. Conclusions: The results indicate that spectral CT can be used to quantify the water, lipid, and protein content in breast tissue. The accuracy of the compositional analysis depends on the applied spectral distortion correction technique.

  2. IN SITU INFRARED STUDY OF CATALYTIC DECOMPOSITION OF NITRIC OXIDE (NO)

    SciTech Connect

    Unknown

    1999-12-31

    The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. The authors have investigated the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. The silanation approach failed to stabilize Cu-ZSM-5 activity under hydrothermal condition. Silanation blocked the oxygen migration and inhibited oxygen desorption. Oxygen spillover was found to be an effective approach for promoting NO decomposition activity on Pt-based catalysts. Detailed mechanistic study revealed the oxygen inhibition in NO decomposition and reduction as the most critical issue in developing an effective catalytic approach for controlling NO emission.

  3. Resonance Raman spectroscopic studies of enzymesubstrate intermediates at 5 K

    NASA Astrophysics Data System (ADS)

    Kim, Munsok; Carey, Paul R.

    1991-01-01

    A simple and versatile system for resonance Raman (RR) spectroscopic analysis of enzymesubstrate complexes at liquid helium temperatures is described. The system allows us to record high-quality RR spectra for dithioacyl papain intermediates (MeO-Phe-Gly- and MeO-Gly-Gly-Phe-Gly-C (dbnd S)S-papain) in ice matrices at 5 K. Based on established structure-spectra correlations, it is concluded that the active-site conformation of the intermediates about the φ', ψ' glycinic linkages and cysteine-25 side chain is B-G+-PH both in ice matrices at 5 K and in solution at room temperature.

  4. A Study of Japan for the Intermediate Grades.

    ERIC Educational Resources Information Center

    Sauer, Susan

    Arranged in outline form, this unit on Japan contains over 40 activities for intermediate grade students. Subjects covered are human and physical geography, social history, life style, communication and travel, occupations, recreation, art, education, government, and relations with the United States. Four to 10 activities are described under each…

  5. Formaldehyde adsorption and decomposition on rutile (110): A first-principles study

    NASA Astrophysics Data System (ADS)

    Liu, Liming; Zhao, Jin

    2016-10-01

    We investigated the adsorption and decomposition of formaldehyde (HCHO) molecule on stoichiometric rutile TiO2(110) surface using first principles-calculations. By comparing the adsorption energy of one bidentate and two monodentate configurations, we found the bidentate configuration is the most stable one because of an additional C-O bond formation. The monodentate configuration can change into the bidentate configuration by overcoming a small barrier less than 0.1 eV. Then, we investigated the decomposition of HCHO which involves two deprotonation processes starting from different adsorption structures. The energy barrier of the first deprotonation is 1.3 eV and 1.1 eV for bidentate and monodentate configurations. After the first deprotonation, an adsorbed formate HCOO specie is formed. The second deprotonation needs 1.74 eV and 1.64 eV for bidentate and monodentate configurations, respectively. After that, an adsorbed CO2 is formed. It can desorb from the surface after overcoming a small barrier of 0.12 eV. In principle, it is also possible to obtain a CO molecule from the surface. Yet a large energy barrier higher than 1.74 eV needs to be overcome. By analyzing the energy level alignment of molecular orbitals with TiO2 energy band edges, we discussed the photocatalytic activity of the reactants and intermediates during the decomposition process. Our results give a clear description of the adsorption structure and thermal decomposition process of HCHO on rutile TiO2(110) surface. The discussion of photocatalytic reactivity based on energy level alignment provides valuable insights to understand the combined photocatalytic and thermally catalytic reactions.

  6. A radial velocity study of the intermediate polar EX Hydrae

    NASA Astrophysics Data System (ADS)

    Echevarría, J.; Ramírez-Torres, A.; Michel, R.; Hernández Santisteban, J. V.

    2016-09-01

    A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high-dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated with the orbital modulation. Since our eclipse timings have been obtained almost 91 000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system shows double-peaked H α, H β and He I λ5876 Å emission lines, with almost no other lines present. As H α is the only line with enough S/N ratio in our observations, we have concentrated our efforts in its study, in order to obtain a reliable radial velocity semi-amplitude. From the profile of this line, we find two important components; one with a steep rise and velocities not larger than ˜1000 km s-1 and another broader component extending up to ˜2000 km s-1, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to K1 = 58 ± 5 km s-1 from H α, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving K1. This value is compatible with the values found in high resolution both in the ultraviolet and X-ray. Using the published inclination angle of i =78° ± 1° and semi-amplitude K2 = 432 ± 5 km s-1, we find: M1 = 0.78 ± 0.03 M⊙, M2 = 0.10 ± 0.02 M⊙ and a = 0.67 ± 0.01 R⊙. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions

  7. Studies of the marine crustal magnetization at intermediate wavelengths

    NASA Technical Reports Server (NTRS)

    Labrecque, J. L.; Cande, S. C.; Raymond, C. A.

    1985-01-01

    The data can be filtered at intermediate wavelengths to provde a data set which complements the satellite fields of MAGSAT, TSS and GRM. The filtered marine data set provides a high resolution data set which is closer to the source bodies than satellite survey data. However, the GRM and TSS could provide the necessary resolution to match the filtered sea surface field. The added resolution determines the nature of crustal magnetizations which give rise to the intermediate wavelength field. It is found that remanent magnetization is an important component over the oceans. Crustal deformation and plate motions result in magnetization vectors which differ significantly from the present day field directions. Induced magnetization or GRM are important components over the oceanic plateaus and spreading centers.

  8. New simultaneous thermogravimetry and modulated molecular beam mass spectrometry apparatus for quantitative thermal decomposition studies

    SciTech Connect

    Behrens, R. Jr.

    1987-03-01

    A new type of instrument has been designed and constructed to measure quantitatively the gas phase species evolving during thermal decompositions. These measurements can be used for understanding the kinetics of thermal decomposition, determining the heats of formation and vaporization of high-temperature materials, and analyzing sample contaminants. The new design allows measurements to be made on the same time scale as the rates of the reactions being studied, provides a universal detection technique to study a wide range of compounds, gives quantitative measurements of decomposition products, and minimizes interference from the instrument on the measurements. The instrument design is based on a unique combination of thermogravimetric analysis (TGA), differential thermal analysis (DTA), and modulated beam mass spectroscopy (MBMS) which are brought together into a symbiotic relationship through the use of differentially pumped vacuum systems, modulated molecular beam techniques, and computer control and data-acquisition systems. A data analysis technique that calculates partial pressures in the reaction cell from the simultaneous microbalance force measurements and the modulated mass spectrometry measurements has been developed. This eliminates the need to know the ionization cross section, the ion dissociation channels, the quadrupole transmission, and the ion detector sensitivity for each thermal decomposition product prior to quantifying the mass spectral data. The operation of the instrument and the data analysis technique are illustrated with the thermal decomposition of contaminants from a precipitated palladium powder.

  9. Trend extraction using empirical mode decomposition and statistical empirical mode decomposition: Case study: Kuala Lumpur stock market

    NASA Astrophysics Data System (ADS)

    Jaber, Abobaker M.

    2014-12-01

    Two nonparametric methods for prediction and modeling of financial time series signals are proposed. The proposed techniques are designed to handle non-stationary and non-linearity behave and to extract meaningful signals for reliable prediction. Due to Fourier Transform (FT), the methods select significant decomposed signals that will be employed for signal prediction. The proposed techniques developed by coupling Holt-winter method with Empirical Mode Decomposition (EMD) and it is Extending the scope of empirical mode decomposition by smoothing (SEMD). To show performance of proposed techniques, we analyze daily closed price of Kuala Lumpur stock market index.

  10. Thermal decomposition pathway and desorption study of isopropanol and tert-butanol on Si(100)

    NASA Astrophysics Data System (ADS)

    Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

    2002-09-01

    Thermal decomposition pathway and desorption of isopropanol (IPA) and tert-butanol on Si(100) were studied using temperature programed desorption. Adsorbed alcohols studied were decomposed into atomic hydrogen and alkoxy on the surface. During heating the sample up to 1000 K, acetone, propylene, and hydrogen were desorbed as decomposition products of IPA on Si(100). Desorption pathways of IPA on Si(100) were largely consistent with those on metal surfaces: beta-hydride elimination reaction to acetone and C-O scission to propylene. For tert-butanol, which has no beta-hydrogen, isobutene and hydrogen were observed as main desorption products. copyright 2002 American Vacuum Society.

  11. Theoretical study of isomerization and decomposition of propenal

    SciTech Connect

    Chin, Chih-Hao; Lee, Shih-Huang

    2011-01-28

    We investigated the dynamics of isomerization and multi-channel dissociation of propenal (CH{sub 2}CHCHO), methyl ketene (CH{sub 3}CHCO), hydroxyl propadiene (CH{sub 2}CH{sub 2}CHOH), and hydroxyl cyclopropene (cyclic-C{sub 3}H{sub 3}-OH) in the ground potential-energy surface using quantum-chemical calculations. Optimized structures and vibrational frequencies of molecular species were computed with method B3LYP/6-311G(d,p). Total energies of molecules at optimized structures were computed at the CCSD(T)/6-311+G(3df,2p) level of theory. We established the potential-energy surface for decomposition to CH{sub 2}CHCO + H, CH{sub 2}CH + HCO, CH{sub 2}CH{sub 2}/CH{sub 3}CH + CO, CHCH/CH{sub 2}C + H{sub 2}CO, CHCCHO/CH{sub 2}CCO + H{sub 2}, CHCH + CO + H{sub 2}, CH{sub 3}+ HCCO, CH{sub 2}CCH + OH, and CH{sub 2}CC/cyclic-C{sub 3}H{sub 2}+ H{sub 2}O. Microcanonical rate coefficients of various reactions of trans-propenal with internal energies 148 and 182 kcal mol{sup -1} were calculated using Rice-Ramsperger-Kassel-Marcus and Variational transition state theories. Product branching ratios were derivable using numerical integration of kinetic master equations and the steady-state approximation. The concerted three-body dissociation of trans-propenal to fragments C{sub 2}H{sub 2}+ CO + H{sub 2} is the prevailing channel in present calculations. In contrast, C{sub 3}H{sub 3}O + H, C{sub 2}H{sub 3}+ HCO and C{sub 2}H{sub 4}+ CO were identified as major channels in the photolysis of trans-propenal. The discrepancy between calculations and experiments in product branching ratios indicates that the three major photodissociation channels occur mainly on an excited potential-energy surface whereas the other channels occur mainly on the ground potential-energy surface. This work provides profound insight in the mechanisms of isomerization and multichannel dissociation of the system C{sub 3}H{sub 4}O.

  12. The FB-Line and F-Canyon HAN/Nitric Acid Decomposition Study

    SciTech Connect

    Hang, T.

    1998-08-19

    Separations requested SRTC study the autocatalytic decomposition of the hydroxylamine nitrate which may occur in the presence of concentrated nitric acid with respect to making-up cold feed solutions. The data obtained from this study will provide Separations an envelope within which safe operations can be conducted.

  13. Improving interMediAte Risk management. MARK study

    PubMed Central

    2011-01-01

    Background Cardiovascular risk functions fail to identify more than 50% of patients who develop cardiovascular disease. This is especially evident in the intermediate-risk patients in which clinical management becomes difficult. Our purpose is to analyze if ankle-brachial index (ABI), measures of arterial stiffness, postprandial glucose, glycosylated hemoglobin, self-measured blood pressure and presence of comorbidity are independently associated to incidence of vascular events and whether they can improve the predictive capacity of current risk equations in the intermediate-risk population. Methods/Design This project involves 3 groups belonging to REDIAPP (RETICS RD06/0018) from 3 Spanish regions. We will recruit a multicenter cohort of 2688 patients at intermediate risk (coronary risk between 5 and 15% or vascular death risk between 3-5% over 10 years) and no history of atherosclerotic disease, selected at random. We will record socio-demographic data, information on diet, physical activity, comorbidity and intermittent claudication. We will measure ABI, pulse wave velocity and cardio ankle vascular index at rest and after a light intensity exercise. Blood pressure and anthropometric data will be also recorded. We will also quantify lipids, glucose and glycosylated hemoglobin in a fasting blood sample and postprandial capillary glucose. Eighteen months after the recruitment, patients will be followed up to determine the incidence of vascular events (later follow-ups are planned at 5 and 10 years). We will analyze whether the new proposed risk factors contribute to improve the risk functions based on classic risk factors. Discussion Primary prevention of cardiovascular diseases is a priority in public health policy of developed and developing countries. The fundamental strategy consists in identifying people in a high risk situation in which preventive measures are effective and efficient. Improvement of these predictions in our country will have an immediate

  14. Neural Correlates of Morphological Decomposition in a Morphologically Rich Language: An fMRI Study

    ERIC Educational Resources Information Center

    Lehtonen, Minna; Vorobyev, Victor A.; Hugdahl, Kenneth; Tuokkola, Terhi; Laine, Matti

    2006-01-01

    By employing visual lexical decision and functional MRI, we studied the neural correlates of morphological decomposition in a highly inflected language (Finnish) where most inflected noun forms elicit a consistent processing cost during word recognition. This behavioral effect could reflect suffix stripping at the visual word form level and/or…

  15. Gas-phase NMR technique for studying the thermolysis of materials: thermal decomposition of ammonium perfluorooctanoate.

    PubMed

    Krusic, Paul J; Roe, D Christopher

    2004-07-01

    The kinetics of the thermal decomposition of ammonium perfluorooctanoate (APFO) has been studied by high-temperature gas-phase nuclear magnetic resonance spectroscopy over the temperature range 196-234 degrees C. We find that APFO cleanly decomposes by first-order kinetics to give the hydrofluorocarbon 1-H-perfluoroheptane and is completely decomposed (>99%) in a matter of minutes at the upper limit of this temperature range. Based on the temperature dependence of the measured rate constants, we find that the enthalpy and entropy of activation are DeltaH++ = 150 +/- 11 kJ mol(-1) and DeltaS++ = 3 +/- 23 J mol(-)(1) deg(-1). These activation parameters may be used to calculate the rate of APFO decomposition at the elevated temperatures (350-400 degrees C) at which fluoropolymers are processed; for example, at 350 degrees C the half-life for APFO is estimated to be less than 0.2 s. Our studies provide the fundamental parameters involved in the decomposition of the ammonium salt of perfluorooctanoic acid and indicate the utility of gas-phase NMR for thermolysis studies of a variety of materials that release compounds that are volatile at the temperature of decomposition and that contain an NMR-active nucleus.

  16. Study of Humidity Effect on Benzene Decomposition by the Dielectric Barrier Discharge Nonthermal Plasma Reactor

    NASA Astrophysics Data System (ADS)

    Ma, Tianpeng; Zhao, Qiong; Liu, Jianqi; Zhong, Fangchuan

    2016-06-01

    The humidity effects on the benzene decomposition process were investigated by the dielectric barrier discharge (DBD) plasma reactor. The results showed that the water vapor played an important role in the benzene oxidation process. It was found that there was an optimum humidity value for the benzene removal efficiency, and at around 60% relative humidity (RH), the optimum benzene removal efficiency was achieved. At a SIE of 378 J/L, the removal efficiency was 66% at 0% RH, while the removal efficiency reached 75.3% at 60% RH and dropped to 69% at 80% RH. Furthermore, the addition of water inhibited the formation of ozone and NO2 remarkably. Both of the concentrations of ozone and NO2 decreased with increasing of the RH at the same specific input energy. At a SIE of 256 J/L, the concentrations of ozone and NO2 were 5.4 mg/L and 1791 ppm under dry conditions, whereas they were only 3.4 mg/L and 1119 ppm at 63.5% RH, respectively. Finally, the outlet gas after benzene degradation was qualitatively analyzed by FT-IR and GC-MS to determine possible intermediate byproducts. The results suggested that the byproducts in decomposition of benzene primarily consisted of phenol and substitutions of phenol. Based on these byproducts a benzene degradation mechanism was proposed. supported by National Natural Science Foundation of China (Nos. 11205007 and 11205029)

  17. Thermal decomposition of 1-pentanol and its isomers: a theoretical study.

    PubMed

    Zhao, Long; Ye, Lili; Zhang, Feng; Zhang, Lidong

    2012-09-20

    Pentanol is one of the promising "next generation" alcohol fuels with high energy density and low hygroscopicity. In the present work, dominant reaction channels of thermal decomposition of three isomers of pentanol: 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol were investigated by CBS-QB3 calculations. Subsequently, the temperature- and pressure-dependent rate constants for these channels were computed by RRKM/master equation simulations. The difference between the thermal decomposition behavior of pentanol and butanol were discussed, while butanol as another potential alternative alcohol fuel has been extensively studied both experimentally and theoretically. Rate constants of barrierless bond dissociation reactions of pentanol isomers were treated by the variational transition state theory. The comparison between various channels revealed that the entropies of variational transition states significantly impact the rate constants of pentanol decomposition reactions. This work provides sound quality kinetic data for major decomposition channels of three pentanol isomers in the temperature range of 800-2000 K with pressure varying from 7.6 to 7.6 × 10(4) Torr, which might be valuable for developing detailed kinetic models for pentanol combustion.

  18. First-principles study of the paths of the decomposition reaction of LiBH4

    NASA Astrophysics Data System (ADS)

    Caputo, Riccarda; Züttel, Andreas

    2010-05-01

    A clear description of the paths of thermal decomposition of complex borohydrides represents a crucial step forward to their utilisation as a reservoir of hydrogen and hence as materials for solid state hydrogen storage. We present in this work a theoretical study of the possible paths of decomposition of LiBH4 by means of density functional theory approach. Our first-principles calculations showed the possibility to form linear chains of tetraborate of lithium in the residue of decomposition, among other thermodynamically competitive reactions. Their analytical formula LiBH x agreed with the quantitative analysis already reported by Schlesinger and co-workers in the 1940s. The structure showed the formula unit Li4B4H10, and the analytical formula LiBH2.5, of which the Gibbs free energy of formation was -111.76 kJ mol-1. The lattice stability was confirmed by the phonon calculations, which revealed all positive normal modes. Comparatively, the formation of lithium dodecaborate(12) is presented and discussed. The calculated standard Gibbs free energy of the decomposition reactions considered in the present work were in the range (158,286) kJ mol-1 of LiBH4 decomposed.

  19. Shock Tube Studies on Thermal Decomposition of 2-Chloroethylbenzene

    NASA Astrophysics Data System (ADS)

    Kiran Singh, M.; Reddy, K. P. J.; Arunan, E.

    The pyrolysis of 2-chloroethylbenzene (2-CEB) in Argon bath has been studied by exposing the sample and Ar mixture to a single-pulse shock wave generated in the shock tube available in the laboratory. The sample has been exposed to high temperatures ranging from 985 K to 1445 K. The dwell times of the experiments ranges from 1.25 to 1.72 ms. The qualitative and the quantitative analysis of the various pyrolysis products have been done using Gas-chromatography (GC) and Gas Chromatography-mass spectrometer (GC-MS). The analysis showed the formation of styrene and benzene as the main products. The theoretical calculations have also been done for the comparative study.

  20. Accumulation of tetrahedral intermediates in cholinesterase catalysis: a secondary isotope effect study.

    PubMed

    Tormos, Jose R; Wiley, Kenneth L; Wang, Yi; Fournier, Didier; Masson, Patrick; Nachon, Florian; Quinn, Daniel M

    2010-12-22

    In a previous communication, kinetic β-deuterium secondary isotope effects were reported that support a mechanism for substrate-activated turnover of acetylthiocholine by human butyrylcholinesterase (BuChE) wherein the accumulating reactant state is a tetrahedral intermediate ( Tormos , J. R. ; et al. J. Am. Chem. Soc. 2005 , 127 , 14538 - 14539 ). In this contribution additional isotope effect experiments are described with acetyl-labeled acetylthiocholines (CL(3)COSCH(2)CH(2)N(+)Me(3); L = H or D) that also support accumulation of the tetrahedral intermediate in Drosophila melanogaster acetylcholinesterase (DmAChE) catalysis. In contrast to the aforementioned BuChE-catalyzed reaction, for this reaction the dependence of initial rates on substrate concentration is marked by pronounced substrate inhibition at high substrate concentrations. Moreover, kinetic β-deuterium secondary isotope effects for turnover of acetylthiocholine depended on substrate concentration, and gave the following: (D3)k(cat)/K(m) = 0.95 ± 0.03, (D3)k(cat) = 1.12 ± 0.02 and (D3)βk(cat) = 0.97 ± 0.04. The inverse isotope effect on k(cat)/K(m) is consistent with conversion of the sp(2)-hybridized substrate carbonyl in the E + A reactant state into a quasi-tetrahedral transition state in the acylation stage of catalysis, whereas the markedly normal isotope effect on k(cat) is consistent with hybridization change from sp(3) toward sp(2) as the reactant state for deacylation is converted into the subsequent transition state. Transition states for Drosophila melanogaster AChE-catalyzed hydrolysis of acetylthiocholine were further characterized by measuring solvent isotope effects and determining proton inventories. These experiments indicated that the transition state for rate-determining decomposition of the tetrahedral intermediate is stabilized by multiple protonic interactions. Finally, a simple model is proposed for the contribution that tetrahedral intermediate stabilization provides to

  1. Photofragment imaging study of the CH{sub 2}CCH{sub 2}OH radical intermediate of the OH+allene reaction

    SciTech Connect

    Raman, Arjun S.; Justine Bell, M.; Lau, K.-C.; Butler, Laurie J.

    2007-10-21

    These velocity map imaging experiments characterize the photolytic generation of one of the two radical intermediates formed when OH reacts via an addition mechanism with allene. The CH{sub 2}CCH{sub 2}OH radical intermediate is generated photolytically from the photodissociation of 2-chloro-2-propen-1-ol at 193 nm. Detecting the Cl atoms using [2+1] resonance-enhanced multiphoton ionization evidences an isotropic angular distribution for the Cl+CH{sub 2}CCH{sub 2}OH photofragments, a spin-orbit branching ratio for Cl({sup 2}P{sub 1/2}):Cl({sup 2}P{sub 3/2}) of 0.28, and a bimodal recoil kinetic energy distribution. Conservation of momentum and energy allows us to determine from this data the internal energy distribution of the nascent CH{sub 2}CCH{sub 2}OH radical cofragment. To assess the possible subsequent decomposition pathways of this highly vibrationally excited radical intermediate, we include electronic structure calculations at the G3//B3LYP level of theory. They predict the isomerization and dissociation transition states en route from the initial CH{sub 2}CCH{sub 2}OH radical intermediate to the three most important product channels for the OH+allene reaction expected from this radical intermediate: formaldehyde+C{sub 2}H{sub 3}, H+acrolein, and ethene+CHO. We also calculate the intermediates and transition states en route from the other radical adduct, formed by addition of the OH to the center carbon of allene, to the ketene+CH{sub 3} product channel. We compare our results to a previous theoretical study of the O+allyl reaction conducted at the CBS-QB3 level of theory, as the two reactions include several common intermediates.

  2. ELF communications system ecological monitoring program: Litter decomposition and microflora studies

    NASA Astrophysics Data System (ADS)

    Bruhn, Johann N.; Bagley, Susan T.; Pickens, James B.

    1994-10-01

    The U.S. Navy has completed a program monitoring flora, fauna, and ecological relationships for possible effects from electromagnetic fields produced by its Extremely Low Frequency (ELF) Communications System. This report documents studies of litter decomposition and soil microflora conducted near its transmitting antenna in Michigan. From 1982 through 1993 researchers from the Michigan Technological University (MTU) monitored overall litter decomposition, as well as microflora (bacteria and fungi) important both as processors of organic material and causative agents of tree disease. Studies were performed in areas near (treatment) and far (control) from the ELF antenna Study parameters included total number of streptomycete individuals and species; mass loss of maple, oak, and pine leaf litter; and frequency of red pine mortality from Armillaria root disease. The MTU research team used several statistical models; however, nested analysis of covariance was the most frequently used test. Based on the results of their study, MTU investigators conclude that the EM fields produced by the Naval Radio Transmitting Facility-Republic, Michigan did not affect soil bacteria populations or the spread of the root disease. Loss of foliar mass suggests a statistically significant, but modest, increase in the rate of litter decomposition, possibly associated with electromagnetic exposure.

  3. Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

    SciTech Connect

    Everett, Susan M; Rawn, Claudia J; Keffer, David J.; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy Joe

    2013-01-01

    Gas hydrates are known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice termed self-preservation or anomalous preservation. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Two regions of slowed decomposition for methane hydrate, 180 200 K and 230 260 K, were observed, and the kinetics were studied by in situ low temperature x-ray powder diffraction. The kinetic constants for ice formation from methane hydrate were determined by the Avrami model within each region and activation energies, Ea, were determined by the Arrhenius plot. Ea determined from the data for 180 200 K was 42 kJ/mol and for 230 260 K was 22 kJ/mol. The higher Ea in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

  4. Theoretical study of the decomposition mechanisms and kinetics of the ingredients RDX in composition B.

    PubMed

    Zhang, Jian-Guo; Wang, Kun; Niu, Xiao-Qing; Zhang, Shao-Wen; Feng, Xiao-Jun; Zhang, Tong-Lai; Zhou, Zun-Ning

    2012-08-01

    RDX as a component in composition B (TNT + RDX) was first studied by us on its mechanism and kinetics of decomposition reactions in this paper. We have pointed out three possible pathways and found a new low-energy process of its decomposition. The N-N bond cleavage in composition B has higher dissociation energies than the monomer, but it is also the initial step. The optimized structures and the frequencies of all the stationary points were calculated at the B3LYP/6-31G(d) level. The minimum-energy paths were obtained by using the intrinsic reaction coordinate (IRC) theory, and the reaction potential energy curve was corrected with zero-point energy. Finally, the rate constants were calculated in a wide temperature region from 200 to 2500 K using TST, TST/Eckart theories. The obtained results also indicate that the tunneling effects are remarkable at low temperature (200 K

  5. Raman study of the temperature-induced decomposition of the fullerene dimers C120

    NASA Astrophysics Data System (ADS)

    Meletov, K. P.; Arvanitidis, J.; Christofilos, D.; Kourouklis, G. A.; Davydov, V. A.

    2016-06-01

    Raman spectra of the C120 crystalline fullerene dimers, synthesized by high-pressure/high-temperature (HPHT) treatment of the C60 fullerite, were measured at ambient and elevated temperatures (T > 130 °C) in order to study the kinetics of their thermal decomposition. Measurements exhibit an intensity decrease of the dimer-related pentagon pinch (PP) mode and an increase of the monomer's one. The relative intensity of the dimer's PP mode decreases exponentially with the thermal treatment time and becomes faster at elevated temperatures. The activation energy EA of the dimer decomposition, obtained from the Arrhenius dependence of the exponential decay time constant on temperature, is (1.71 ± 0.06) eV.

  6. Density functional theory study of ethanol decomposition on 3Ni/α-Al₂O₃(0001) surface.

    PubMed

    Chiang, Hsin-Ni; Wang, Chia-Ching; Cheng, Ya-Chin; Jiang, Jyh-Chiang; Hsieh, Horng-Ming

    2010-10-19

    We have investigated the decomposition of ethanol (EtOH) on a 3Ni/α-Al₂O₃(0001) surface using periodic density functional theory calculations. A triangular Ni trimer doped on a 2 × 2 α-Al₂O₃(0001) surface was used to represent the 3Ni/α-Al₂O₃(0001) surface. We considered several possible pathways for EtOH decomposition over the 3Ni/α-Al₂O₃(0001) surface, including dehydrogenation and C-C bond cleavage. Our calculated results indicated that (i) the 3Ni/α-Al₂O₃(0001) surface possesses high activity to inhibit coke formation and (ii) the CH₂CH₂O((a)) → CH₂CHO((a)) + H((a)) reaction is the rate-determining step for the overall reaction [CH₃CH₂OH((a)) → CH(2(a)) + CO((a)) + 4 H((a))] with an energy barrier of 1.20 eV. One feasible channel leading to C-C bond cleavage is weakening of the C-C bond in the stable CH₂CO intermediate via transformation of the adsorbed structure to a metastable structure, thereby increasing the coordination number of the two C atoms to the Ni trimer. In addition, we also investigated the nature of the metal-ethanol bonding through scrutiny of density of states (DOS) and electron density difference contour plots. The DOS analysis allowed us to characterize the state interactions between ethanol and the surfaces; the electron density difference plots provide evidence that is consistent with the prediction from DOS analysis. PMID:20839873

  7. Macroalgal decomposition: Laboratory studies with particular regard to microorganisms and meiofauna

    NASA Astrophysics Data System (ADS)

    Rieper-Kirchner, M.

    1990-09-01

    The microbial degradation of North Sea macroalgae was studied in laboratory microcosms, containing autoclaved seawater and a mixture of equal parts of air-dried Delesseria sanguinea, Ulva lactuca, and Laminaria saccharina (red, green and brown algae, respectively). To determine the influence of different organisms on the decomposition rate (expressed in terms of algal dry weight loss relative to the material present at time zero) and their development during decomposition processes, yeast, flagellates, ciliates, nematodes and a harpacticoid copepod species were introduced to the microcosms. Results show that microbial degradation compared to the controls was enhanced in the presence of non-axenic nematodes ( Monhystera sp.) and protozoans, including bacterivorous ciliates ( Euplotes sp. and a Uronema-like sp.) and flagellates. No enhancement occurred with yeast ( Debaryomyces hansenii) or with the harpacticoid copepod Tisbe holothuriae. The most rapid algal dry weight loss (78.7% after 14 d at 18°C) occurred with the addition of raw seawater sampled near benthic algal vegetation and containing only the natural microorganisms present. These consisted mainly of bacteria with different morphological properties, whereby their numbers alone (viable counts) could not be correlated with algal dry weight loss. Although no single dominant species could be determined, lemon yellow pigmented colonies were frequently found. During decomposition in all microcosms the formation of algal particles 40 400 μm was observed, which were rapidly colonized by the other organisms present.

  8. Study on the characteristic decomposition components of air-insulated switchgear cabinet under partial discharge

    NASA Astrophysics Data System (ADS)

    Gui, Yingang; Zhang, Xiaoxing; Zhang, Ying; Qiu, Yinjun; Chen, Lincong

    2016-07-01

    Air-insulated switchgear cabinet plays a critical role in entire power transmission and distribution system. Its stability directly affects the operational reliability of the power system. And the on-line gas detection method, which evaluates the insulation status of insulation equipment by detecting the decomposition components of filled air in cabinet, becomes an innovative way to ensure the running stability of air-insulated switchgear cabinet. In order to study the characteristic gas types and production regularity of decomposition components under partial discharge, three insulation defects: needle-plate, air-gap and impurity defect are proposed to simulate the insulation defects under partial discharge in air-insulated switchgear cabinet. Firstly, the generation pathways and mechanism of composition components are discussed. Then CO and NO2 are selected as the characteristic decomposition components to characterize the partial discharge due to their high concentration and chemical stability. Based on the different change regularity of CO and NO2 concentration under different insulation defect, it provides an effective way to evaluate and predict the insulation defect type and severity in the field.

  9. Ester prodrugs of acyclic nucleoside thiophosphonates compared to phosphonates: synthesis, antiviral activity and decomposition study.

    PubMed

    Roux, Loïc; Priet, Stéphane; Payrot, Nadine; Weck, Clément; Fournier, Maëlenn; Zoulim, Fabien; Balzarini, Jan; Canard, Bruno; Alvarez, Karine

    2013-05-01

    9-[2-(Thiophosphonomethoxy)ethyl]adenine [S-PMEA, 8] and (R)-9-[2-(Thiophosphonomethoxy)propyl]adenine [S-PMPA, 9] are acyclic nucleoside thiophosphonates we described recently that display the same antiviral spectrum (DNA viruses) as approved and potent phosphonates PMEA and (R)-PMPA. Here, we describe the synthesis, antiviral activities in infected cell cultures and decomposition study of bis(pivaloyloxymethoxy)-S-PMEA [Bis-POM-S-PMEA, 13] and bis(isopropyloxymethylcarbonyl)-S-PMPA [Bis-POC-S-PMPA, 14] as orally bioavailable prodrugs of the S-PMEA 8 and S-PMPA 9, in comparison to the equivalent "non-thio" derivatives [Bis-POM-PMEA, 11] and [Bis-POC-PMPA, 12]. Compounds 11, 12, 13 and 14 were evaluated for their in vitro antiviral activity against HIV-1-, HIV-2-, HBV- and a broad panel of DNA viruses, and found to exhibit moderate to potent antiviral activity. In order to determine the decomposition pathway of the prodrugs 11, 12, 13 and 14 into parent compounds PMEA, PMPA, 8 and 9, kinetic data and decomposition pathways in several media are presented. As expected, bis-POM-S-PMEA 13 and bis-POC-S-PMPA 14 behaved as prodrugs of S-PMEA 8 and S-PMPA 9. However, thiophosphonates 8 and 9 were released very smoothly in cell extracts, in contrast to the release of PMEA and PMPA from "non-thio" prodrugs 11 and 12. PMID:23603046

  10. A Review of Study on Thermal Energy Transport System by Synthesis and Decomposition Reactions of Methanol

    NASA Astrophysics Data System (ADS)

    Liu, Qiusheng; Yabe, Akira; Kajiyama, Shiro; Fukuda, Katsuya

    The study on thermal energy transport system by synthesis and decomposition reactions of methanol was reviewed. To promote energy conservation and global environment protection, a two-step liquid-phase methanol synthesis process, which starts with carbonylation of methanol to methyl formate, then followed by the hydrogenolysis of the formate, was studied to recover wasted or unused discharged heat from industrial sources for the thermal energy demands of residential and commercial areas by chemical reactions. The research and development of the system were focused on the following three points. (1) Development of low-temperature decomposition and synthetic catalysts, (2) Development of liquid phase reactor (heat exchanger accompanying chemical reaction), (3) Simulation of the energy transport efficiency of entire system which contains heat recovery and supply sections. As the result of the development of catalyst, promising catalysts which agree with the development purposes for the methyl formate decomposition reaction and the synthetic reaction are being developed though some studies remain for the methanol decomposition and synthetic reactions. In the fundamental development of liquid phase reactor, the solubilities of CO and H2 gases in methanol and methyl formate were measured by the method of total pressure decrease due to absorption under pressures up to 1500kPa and temperatures up to 140°C. The diffusivity of CO gas in methanol was determined by measuring the diameter and solution time of single CO bubbles in methanol. The chemical reaction rate of methanol synthesis by hydrogenolysis of methyl formate was measured using a plate-type of Raney copper catalyst in a reactor with rectangular channel and in an autoclave reactor. The reaction characteristics were investigated by carrying out the experiments at various temperatures, flow rates and at various catalyst development conditions. We focused on the effect of Raney copper catalyst thickness on the liquid

  11. Fundamental studies of reactive intermediates in homogeneous catalysis

    SciTech Connect

    Not Available

    1993-10-01

    The studies involve dissociation of Fe(CO){sub n}{sup {minus}}, Ni(CO){sub n}{sub {minus}}, and other carbonyl anions; decarboxylation of (CO){sub 4}FeCOOH{sup {minus}} to form CO{sub 2} and (CO){sub 4}FeH{sup {minus}} in the water gas shift reaction; gas-phase bimolecular reactions of carbonyl anions and O{sub 2}; reaction of O{sub 2} with CpMn(CO){sub 2}{sup {minus}}; gas-phase chemistry of fullerene anions; and gas-phase thermochemistry of bicarbonate ion, bisulfite ion, and their conjugate acids (sulfonate ion was produced).

  12. An intermediate temperature modeling study of the combustion of neopentane

    SciTech Connect

    Curran, H.J.; Pitz, W.J.; Westbrook, C.K.

    1995-10-01

    Low temperature hydrocarbon fuel oxidation proceeds via straight and branched chain reactions involving alkyl and alkyl peroxy radicals. These reactions play a critical role in the chemistry leading to knock or autoignition in spark ignition engines. As part of an on-going study in the understanding of low temperature oxidation of hydrocarbon fuels, the authors have investigated neopentane oxidation. A detailed chemical kinetic reaction mechanism is used to study the oxidation of neopentane in a closed reactor at 500 Torr pressure, and at a temperature of 753 K when small amounts of neopentane are added to slowly reacting mixtures of H{sub 2} + O{sub 2} + N{sub 2}. The major primary products formed in the experiments included isobutene, 3,3-dimethyloxetan, acetone, methane and formaldehyde. The major secondary products were, 2,2-dimethyloxiran, propene, isobuteraldehyde, methacrolein, and 2-methylprop-2-en-1-ol. It was found that the current model was able to explain both primary and secondary product formation with a high degree of accuracy. Furthermore, it was found that almost all secondary product formation could be explained through the oxidation of isobutene--a major primary product.

  13. Crystallographic Study of the LUMI Intermediate of Squid Rhodopsin.

    PubMed

    Murakami, Midori; Kouyama, Tsutomu

    2015-01-01

    Upon absorption of light, the retinal chromophore in rhodopsin isomerizes from the 11-cis to the trans configuration, initiating a photoreaction cycle. The primary photoreaction state, bathorhodopsin (BATHO), relaxes thermally through lumirhodopsin (LUMI) into a photoactive state, metarhodopsin (META), which stimulates the conjugated G-protein. Previous crystallographic studies of squid and bovine rhodopsins have shown that the structural change in the primary photoreaction of squid rhodopsin is considerably different from that observed in bovine rhodopsin. It would be expected that there is a fundamental difference in the subsequent thermal relaxation process between vertebrate and invertebrate rhodopsins. In this work, we performed crystallographic analyses of the LUMI state of squid rhodopsin using the P62 crystal. When the crystal was illuminated at 100 K with blue light, a half fraction of the protein was converted into BATHO. This reaction state relaxed into LUMI when the illuminated crystal was warmed in the dark to 170 K. It was found that, whereas trans retinal is largely twisted in BATHO, it takes on a more planar configuration in LUMI. This relaxation of retinal is accompanied by reorientation of the Schiff base NH bond, the hydrogen-bonding partner of which is switched to Asn185 in LUMI. Unlike bovine rhodopsin, the BATHO-to-LUMI transition in squid rhodopsin was accompanied by no significant change in the position/orientation of the beta-ionone ring of retinal.

  14. The decomposition of methyltrichlorosilane: Studies in a high-temperature flow reactor

    SciTech Connect

    Allendorf, M.D.; Osterheld, T.H.; Melius, C.F.

    1994-01-01

    Experimental measurements of the decomposition of methyltrichlorosilane (MTS), a common silicon carbide precursor, in a high-temperature flow reactor are presented. The results indicate that methane and hydrogen chloride are major products of the decomposition. No chlorinated silane products were observed. Hydrogen carrier gas was found to increase the rate of MTS decomposition. The observations suggest a radical-chain mechanism for the decomposition. The implications for silicon carbide chemical vapor deposition are discussed.

  15. The application of the intermediate disturbance hypothesis to physical systems: a case study on floodplain soils

    NASA Astrophysics Data System (ADS)

    Rayburg, Scott; Neave, Melissa; Thompson-Laing, Justin

    2010-05-01

    Disturbances, defined as discrete events that disrupt physical and/or biological systems, are a component of every natural system. Disturbance ecology has been dominated, for the last 30 years or so, by the intermediate disturbance hypothesis that states that biological diversity will be maximised where disturbance occurs at an intermediate level. A wide range of disturbances and organisms have been examined with respect to the intermediate disturbance hypothesis and in many cases (especially with respect to sessile organisms) the theory has proven valid. In rivers, lakes, wetlands and floodplains, the predominant agent of disturbance is flooding. In flood disturbed environments, the intermediate disturbance hypothesis has been shown to apply to terrestrial and aquatic vegetation, but conflicting results have been observed when dealing with mobile organisms like macroinvertebrates, fish or amphibians. The argument for the validity of the intermediate disturbance hypothesis (irrespective of disturbance type) stems from the notion that an intermediate frequency of disturbance promotes diversity by: 1) preventing the competitive exclusion by the dominant species that can arise in infrequently disturbed sites; and 2) facilitating greater diversity than that observed in highly-disturbed sites where only species tolerant of the disturbance can thrive. A singular omission in this logic, and indeed in research into the intermediate disturbance hypothesis more generally, has been the lack of focus on its application or relation to physical systems. This study addresses this lack by investigating whether an intermediate level of flood disturbance leads to a greater diversity of soil character (assessed using a wide range of physical and geochemical soil properties). Four flood frequency (or disturbance frequency) categories are included in this study spanning the range from frequent through to infrequent flood disturbance. These are: a high-inundation-frequency flood zone

  16. Comprehensive study of the chemical reactions resulting from the decomposition of chloroform in alkaline aqueous solution

    NASA Astrophysics Data System (ADS)

    Estevez Mews, Jorge

    Chloroform (CHCl3) is a volatile liquid, which has a rather slow rate of decomposition in ground water. It is a known carcinogen and one of the most common contaminants found at toxic waste sites. The dominant degradation process for chloroform in both the atmosphere and the groundwater is the reaction with the hydroxyl radical or hydroxide ion. This process triggers a sequence of reactions which ultimately yield carbon monoxide, hydrogen chloride, and formic acid. The rate of chloroform degradation is considerably larger in solution than that in the gas phase and it increases dramatically with increasing pH. However, only one of the viable reactions had been studied previously at a high level of theory in solution. It is of great interest to gain a deeper understanding of the decomposition reaction mechanism. Quantum mechanical methods are well suited for studying the mechanism of organic reactions. However, a full quantum mechanical treatment of the entire fluid system is not computationally feasible. In this work, combined quantum mechanical and molecular mechanical (QM/MM) methods are used for studying chemical reactions in condensed phases. In these calculations, the solute molecules are treated quantum mechanically (QM), whereas the solvent molecules are approximated by empirical (MM) potential energy functions. The use of quantum mechanics and statistical sampling simulation is necessary to determine the reaction free energy profile. In the present study, the ab initio Hartree-Fock theory along with the 3-21G basis set was used in the quantum mechanical calculations to elucidate the reaction pathways of chloroform decomposition, with a focus on basic reaction conditions. Statistical mechanical Monte Carlo approach was then applied in molecular mechanical simulations, employing the empirical TIP3P model for water. We employed state-of-the-art electronic structure methods to determine the gas-phase inter-nuclear potential energy profile for all the relevant

  17. Decomposition of NO studied by infrared emission and CO laser absorption

    NASA Technical Reports Server (NTRS)

    Hanson, R. K.; Monat, J. P.; Flower, W. L.; Kruger, C. H.

    1975-01-01

    A diagnostic technique for monitoring the concentration of NO using absorption of CO laser radiation has been developed and applied in a study of the decomposition kinetics of NO. Simultaneous measurements of infrared emission by NO at 5.3 microns were also made to validate the laser absorption technique. The data were obtained behind incident shocks in NO-N2O-Ar (or Kr) mixtures, with temperatures in the range 2400-4100 K. The rate constant for the dominant reaction of O and NO to yield N and O2 was inferred from comparisons with computer simulations of the reactive flow.

  18. Decomposition of NO studied by infrared emission and CO laser absorption

    NASA Technical Reports Server (NTRS)

    Hanson, R. K.; Flower, W. L.; Monat, J. P.; Kruger, C. H.

    1974-01-01

    A diagnostic technique for monitoring the concentration of NO using absorption of CO laser radiation was developed and applied in a study of the decomposition kinetics of NO. Simultaneous measurements of infrared emission by NO at 5.3 microns were also made to validate the laser absorption technique. The data were obtained behind incident shocks in NO-N2O-Ar (or Kr) mixtures, with temperatures in the range 2400-4100 K. Rate constants for dominant reactions were inferred from comparisons with computer simulations of the reactive flow.

  19. Probing the Natural World, Level III, Teacher's Edition: Environmental Science. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the teacher's edition of one of the eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). This unit and its activities focuses on environmental pollution and hazards. Optional excursions are suggested for students who wish to study an area in greater depth. An introduction describes the problem…

  20. Factors That Influence Students' Performance in Intermediate Algebra Classes at the College: A Longitudinal Research Study

    ERIC Educational Resources Information Center

    Ramirez, Sonia; Siadat, M. Vali

    2008-01-01

    The purpose of this study is to identify factors that influence students' performance in the intermediate algebra classes at the college by analyzing parameters such as test scores, grades, attitude towards mathematics, time lapse between subsequent courses, placement, and teaching practices. This study will investigate the correlation of several…

  1. A Study of the Curricular Organization of Intermediate Sciences in a County in New York State

    ERIC Educational Resources Information Center

    Nettuno, Thomas

    2012-01-01

    This study of a County in New York State gathered information about the means for teaching the intermediate science curriculum in middle schools. The study collected 43 surveys and conducted ten follow-up interviews with administrators responsible for curriculum. Data included the division of content among grade level, starting grade level,…

  2. Probing the Natural World, Level III, Teacher's Edition: Well-Being. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the teacher's edition of one of the eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). This unit focuses on hazards to the body from drug use. Activities are given that relate to the topic. Optional excursions are suggested for students who wish to study an area in greater depth. An…

  3. A quantitative acoustic emission study on fracture processes in ceramics based on wavelet packet decomposition

    SciTech Connect

    Ning, J. G.; Chu, L.; Ren, H. L.

    2014-08-28

    We base a quantitative acoustic emission (AE) study on fracture processes in alumina ceramics on wavelet packet decomposition and AE source location. According to the frequency characteristics, as well as energy and ringdown counts of AE, the fracture process is divided into four stages: crack closure, nucleation, development, and critical failure. Each of the AE signals is decomposed by a 2-level wavelet package decomposition into four different (from-low-to-high) frequency bands (AA{sub 2}, AD{sub 2}, DA{sub 2}, and DD{sub 2}). The energy eigenvalues P{sub 0}, P{sub 1}, P{sub 2}, and P{sub 3} corresponding to these four frequency bands are calculated. By analyzing changes in P{sub 0} and P{sub 3} in the four stages, we determine the inverse relationship between AE frequency and the crack source size during ceramic fracture. AE signals with regard to crack nucleation can be expressed when P{sub 0} is less than 5 and P{sub 3} more than 60; whereas AE signals with regard to dangerous crack propagation can be expressed when more than 92% of P{sub 0} is greater than 4, and more than 95% of P{sub 3} is less than 45. Geiger location algorithm is used to locate AE sources and cracks in the sample. The results of this location algorithm are consistent with the positions of fractures in the sample when observed under a scanning electronic microscope; thus the locations of fractures located with Geiger's method can reflect the fracture process. The stage division by location results is in a good agreement with the division based on AE frequency characteristics. We find that both wavelet package decomposition and Geiger's AE source locations are suitable for the identification of the evolutionary process of cracks in alumina ceramics.

  4. Study of intermediates from transition metal excited-state electron-transfer reactions

    SciTech Connect

    Hoffman, M.Z.

    1992-07-31

    Conventional and fast-kinetics techniques of photochemistry, photophysics, radiation chemistry, and electrochemistry were used to study the intermediates involved in transition metal excited-state electron-transfer reactions. These intermediates were excited state of Ru(II) and Cr(III) photosensitizers, their reduced forms, and species formed in reactions of redox quenchers and electron-transfer agents. Of particular concern was the back electron-transfer reaction between the geminate pair formed in the redox quenching of the photosensitizers, and the dependence of its rate on solution medium and temperature in competition with transformation and cage escape processes. (DLC)

  5. Study of thermal decomposition mechanisms and low-level detection of explosives using pulsed photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Yehya, F.; Chaudhary, A. K.; Srinivas, D.; Muralidharan, K.

    2015-11-01

    We report a novel time-resolved photoacoustic-based technique for studying the thermal decomposition mechanisms of some secondary explosives such as RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), picric acid, 4,6-dinitro-5-(4-nitro-1 H-imidazol-1-yl)-1 H-benzo[ d] [1-3] triazole, and 5-chloro-1-(4-nitrophenyl)-1 H-tetrazole. A comparison of the thermal decomposition mechanisms of these secondary explosives was made by detecting NO2 molecules released under controlled pyrolysis between 25 and 350 °C. The results show excellent agreement with the thermogravimetric and differential thermal analysis (TGA-DTA) results. A specially designed PA cell made of stainless steel was filled with explosive vapor and pumped using second harmonic, i.e., λ = 532 nm, pulses of duration 7 ns at a 10 Hz repetition rate, obtained using a Q-switched Nd:YAG laser. The use of a combination of PA and TGA-DTA techniques enables the study of NO2 generation, and this method can be used to scale the performance of these explosives as rocket fuels. The minimum detection limits of the four explosives were 38 ppmv to 69 ppbv, depending on their respective vapor pressures.

  6. Decomposition mechanisms of trinitroalkyl compounds: a theoretical study from aliphatic to aromatic nitro compounds.

    PubMed

    Fayet, Guillaume; Rotureau, Patricia; Minisini, Benoit

    2014-04-14

    The chemical mechanisms involved in the decomposition of trinitroethyl compounds were studied for both aliphatic and aromatic derivatives using density functional theory calculations. At first, in the case of 1,1,1-trinitrobutane, used as a reference molecule, two primary channels were highlighted among the five investigated ones: the breaking of the C-N bond and the HONO elimination. Then, the influence of various structural parameters was studied for these two reactions by changing the length of the carbon chain, adding substituents or double bonds along the carbon chain. If some slight changes in activation energies were observed for most of these features, no modification of the competition between the two investigated reactions was highlighted and the breaking of the C-N bond remained the favoured mechanism. At last, the reactions involving the trinitroalkyl fragments were highlighted to be more competitive than reactions involving nitro groups linked to aromatic cycles in two aromatic systems (4-(1,1,1-trinitrobutyl)-nitrobenzene and 2-(1,1,1-trinitrobutyl)-nitrobenzene). This showed that aromatic nitro compounds with trinitroalkyl derivatives decompose from their alkyl part and may be considered more likely as aliphatic than as aromatic regarding the initiation of their decomposition process.

  7. Probing the Natural World, Level III, Student Guide: Winds and Weather. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the student's text of one of the units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). The chapters contain basic information about weather, its measurement and predictions, activities related to the subject, and optional excursions. A section of introductory notes to the student discusses how to use…

  8. Probing the Natural World, Level III, Student Guide: Environmental Science. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the student's edition of one of the Intermediate Science Curriculum Study (ISCS) units for level III students (grade 9). The chapters contain basic information about environmental pollution and hazards, activities related to the subject, and optional excursions. A section on introductory notes to the student discusses how to use the book…

  9. Probing the Natural World, Level III, Student Guide: In Orbit. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the student's text of one unit of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). This unit focuses on the properties of sunlight, the use of spectrums and spectroscopes, the heat and energy of the sun, the measurement of astronomical distances, and the size of the sun. Activities are student-centered and…

  10. Probing the Natural World, Level III, Teacher's Edition: In Orbit. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the teacher's edition of one of the eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). This unit focuses on the properties of sunlight, the use of spectrums and spectroscopes, the heat and energy of the sun, the measurement of astronomical distances, and the size of the sun. Optimal…

  11. An Observational Study of Intermediate Band Students' Self-Regulated Practice Behaviors

    ERIC Educational Resources Information Center

    Miksza, Peter; Prichard, Stephanie; Sorbo, Diana

    2012-01-01

    The purpose of this study was to investigate intermediate musicians' self-regulated practice behaviors. Thirty sixth- through eighth-grade students were observed practicing band repertoire individually for 20 min. Practice sessions were coded according to practice frame frequency and duration, length of musical passage selected, most prominent…

  12. Laser Spectroscopic Study on Oxygen Isotope Effects in Ozone Surface Decomposition

    NASA Astrophysics Data System (ADS)

    Minissale, Marco; Boursier, Corinne; Elandaloussi, Hadj; Te, Yao; Jeseck, Pascal; Rouille, Christian; Zanon-Willette, Thomas; Janssen, Christof

    2016-04-01

    The isotope kinetics of ozone formation in the Chapman reaction [1] O + O2 + M → O3 + M (1) provides the primary example for a chemically induced oxygen isotope anomaly and is associated with large [2] and mass independent [3] oxygen isotope enrichments in the product molecule, linked to a symmetry selection in the ozone formation kinetics [4-5]. The isotopic composition of ozone and its transfer to other molecules is a powerful tracer in the atmospheric and biogeochemical sciences [6] and serves as a primary model for a possible explanation of the oxygen isotopic heterogeneity in the Solar system [7-8]. Recently, the isotope fractionation in the photolytic decomposition process O3 + hν → O2 + O (2) using visible light has been studied in detail [9-10]. Much less is currently known about the isotope fractionation in the dry deposition or in the gas phase thermal decomposition of ozone O3 + M → O2 + O +M. (3) Here we report on first spectroscopic studies of non-photolytic ozone decomposition using a cw-quantum cascade laser at 9.5 μm. The concentration of individual ozone isotopomers (16O3,16O16O17O, and 16O17O16O) in a teflon coated reaction cell is followed in real time at temperatures between 25 and 150 °C. Observed ozone decay rates depend on homogeneous (reaction (3)) processes in the gas phase and on heterogeneous reactions on the wall. A preliminary analysis reveals agreement with currently recommended ozone decay rates in the gas phase and the absence of a large symmetry selection in the surface decomposition process, indicating the absence of a mass independent fractionation effect. This result is in agreement with previous mass spectrometer (MS) studies on heterogeneous ozone formation on pyrex [11], but contradicts an earlier MS study [12] on ozone surface decomposition on pyrex and quartz. Implications for atmospheric chemistry will be discussed. [1] Morton, J., Barnes, J., Schueler, B. and Mauersberger, K. J. Geophys. Res. 95, 901 - 907 (1990

  13. Mechanism of benzaldehyde lyase studied via thiamin diphosphate-bound intermediates and kinetic isotope effects.

    PubMed

    Chakraborty, Sumit; Nemeria, Natalia; Yep, Alejandra; McLeish, Michael J; Kenyon, George L; Jordan, Frank

    2008-03-25

    Direct spectroscopic observation of thiamin diphosphate-bound intermediates was achieved on the enzyme benzaldehyde lyase, which carries out reversible and highly enantiospecific conversion of ( R)-benzoin to benzaldehyde. The key enamine intermediate could be observed at lambda max 393 nm in the benzoin breakdown direction and in the decarboxylase reaction starting with benzoylformate. With benzaldehyde as substrate, no intermediates could be detected, only formation of benzoin at 314 nm. To probe the rate-limiting step in the direction of ( R)-benzoin synthesis, the (1)H/ (2)H kinetic isotope effect was determined for benzaldehyde labeled at the aldehyde position and found to be small (1.14 +/- 0.03), indicating that ionization of the C2alphaH from C2alpha-hydroxybenzylthiamin diphosphate is not rate limiting. Use of the alternate substrates benzoylformic and phenylpyruvic acids (motivated by the observation that while a carboligase, benzaldehyde lyase could also catalyze the slow decarboxylation of 2-oxo acids) enabled the observation of the substrate-thiamin covalent intermediate via the 1',4'-iminopyrimidine tautomer, characteristic of all intermediates with a tetrahedral C2 substituent on ThDP. The reaction of benzaldehyde lyase with the chromophoric substrate analogue ( E)-2-oxo-4(pyridin-3-yl)-3-butenoic acid and its decarboxylated product ( E)-3-(pyridine-3-yl)acrylaldehyde enabled the detection of covalent adducts with both. Neither adduct underwent further reaction. An important finding of the studies is that all thiamin-related intermediates are in a chiral environment on benzaldehyde lyase as reflected by their circular dichroism signatures.

  14. METHANE HYDRATE STUDIES: DELINEATING PROPERTIES OF HOST SEDIMENTS TO ESTABLISH REPRODUCIBLE DECOMPOSITION KINETICS.

    SciTech Connect

    Mahajan, Devinder; Jones, Keith W.; Feng, Huan; Winters, William J.

    2004-12-01

    The use of methane hydrate as an energy source requires development of a reliable method for its extraction from its highly dispersed locations in oceanic margin sediments and permafrost. The high pressure (up to 70 MPa) and low temperature (272 K to 278 K) conditions under which hydrates are stable in the marine environment can be mimicked in a laboratory setting and several kinetic studies of pure methane hydrate decomposition have been reported. However, the effect of host sediments on methane hydrate occurrence and decomposition are required to develop reliable hydrate models. In this paper, we describe methods to measure sediment properties as they relate to pore-space methane gas hydrate. Traditional geotechnical techniques are compared to the micrometer level by use of the synchrotron Computed Microtomography (CMT) technique. CMT was used to measure the porosity at the micrometer level and to show pore-space pathways through field samples. Porosities for three sediment samples: one from a site on Georges Bank and two from the known Blake Ridge methane hydrate site, from different depths below the mud line were measured by traditional drying and by the new CMT techniques and found to be in good agreement. The integration of the two analytical approaches is necessary to enable better understanding of methane hydrate interactions with the surrounding sediment particles.

  15. Density functional theory study of nitrous oxide decomposition over Fe- and Co-ZSM-5

    SciTech Connect

    Ryder, Jason A.; Chakraborty, Arup K.; Bell, Alexis T.

    2001-12-19

    Iron- and cobalt-exchanged ZSM-5 are active catalysts for the dissociation of nitrous oxide. In this study, density functional theory was used to assess a possible reaction pathway for the catalytic dissociation of N2O. The active center was taken to be mononuclear [FeO]+ or [CoO]+, and the surrounding portion of the zeolite was represented by a 24-atom cluster. The first step of N2O decomposition involves the formation of [FeO2]+ or [CoO2]+ and the release of N2. The metal-oxo species produced in this step then reacts with N2O again, to release N2 and O2. The apparent activation energies for N2O dissociation in Fe-ZSM-5 and Co-ZSM-5 are 39.4 and 34.6 kcal/mol, respectively. The preexponential factor for the apparent first-order rate coefficient is estimated to be of the order 107 s-1 Pa-1. While the calculated activation energy for Fe-ZSM-5 is in good agreement with that measured experimentally, the value of the preexponential factor is an order of magnitude smaller than that observed . The calculated activation energy for Co-ZSM-5 is higher than that reported experimentally. However, consistent with experiment, the rate of N2O decomposition on Co-ZSM-5 is predicted to be significantly higher than that on Fe-ZSM-5.

  16. Internal friction study of decomposition kinetics of SAF 2507 type duplex stainless steel

    SciTech Connect

    Smuk, O.; Smuk, S.; Hanninen, H.; Jagodzinski, Yu.; Tarasenko, O.

    1999-01-08

    During the last decade, super duplex stainless steels (DSSs) with increased nitrogen content have been an object of intensive studies. Present work is devoted to the study of the peculiarities of {delta}-ferrite decomposition in SAF 2507 type duplex steel, and redistribution of nitrogen between ferrite and austenite phases in a wide temperature range by means of internal fraction (IF). Unlike local methods of electron microscopy or engineering methods of hardness or impact toughness testing, which give basically information on the formation of brittle intermetallic phases, the internal friction technique allows to study the state of solid solution and kinetics of changes in the relative amounts of ferrite and austenite phases during thermal treatment.

  17. Influence of density and environmental factors on decomposition kinetics of amorphous polylactide - Reactive molecular dynamics studies.

    PubMed

    Mlyniec, A; Ekiert, M; Morawska-Chochol, A; Uhl, T

    2016-06-01

    In this work, we investigate the influence of the surrounding environment and the initial density on the decomposition kinetics of polylactide (PLA). The decomposition of the amorphous PLA was investigated by means of reactive molecular dynamics simulations. A computational model simulates the decomposition of PLA polymer inside the bulk, due to the assumed lack of removal of reaction products from the polymer matrix. We tracked the temperature dependency of the water and carbon monoxide production to extract the activation energy of thermal decomposition of PLA. We found that an increased density results in decreased activation energy of decomposition by about 50%. Moreover, initiation of decomposition of the amorphous PLA is followed by a rapid decline in activation energy caused by reaction products which accelerates the hydrolysis of esters. The addition of water molecules decreases initial energy of activation as well as accelerates the decomposition process. Additionally, we have investigated the dependency of density on external loading. Comparison of pressures needed to obtain assumed densities shows that this relationship is bilinear and the slope changes around a density equal to 1.3g/cm(3). The conducted analyses provide an insight into the thermal decomposition process of the amorphous phase of PLA, which is particularly susceptible to decomposition in amorphous and semi-crystalline PLA polymers.

  18. GC × GC-TOFMS and supervised multivariate approaches to study human cadaveric decomposition olfactive signatures.

    PubMed

    Stefanuto, Pierre-Hugues; Perrault, Katelynn A; Stadler, Sonja; Pesesse, Romain; LeBlanc, Helene N; Forbes, Shari L; Focant, Jean-François

    2015-06-01

    In forensic thanato-chemistry, the understanding of the process of soft tissue decomposition is still limited. A better understanding of the decomposition process and the characterization of the associated volatile organic compounds (VOC) can help to improve the training of victim recovery (VR) canines, which are used to search for trapped victims in natural disasters or to locate corpses during criminal investigations. The complexity of matrices and the dynamic nature of this process require the use of comprehensive analytical methods for investigation. Moreover, the variability of the environment and between individuals creates additional difficulties in terms of normalization. The resolution of the complex mixture of VOCs emitted by a decaying corpse can be improved using comprehensive two-dimensional gas chromatography (GC × GC), compared to classical single-dimensional gas chromatography (1DGC). This study combines the analytical advantages of GC × GC coupled to time-of-flight mass spectrometry (TOFMS) with the data handling robustness of supervised multivariate statistics to investigate the VOC profile of human remains during early stages of decomposition. Various supervised multivariate approaches are compared to interpret the large data set. Moreover, early decomposition stages of pig carcasses (typically used as human surrogates in field studies) are also monitored to obtain a direct comparison of the two VOC profiles and estimate the robustness of this human decomposition analog model. In this research, we demonstrate that pig and human decomposition processes can be described by the same trends for the major compounds produced during the early stages of soft tissue decomposition.

  19. Study of Oil spill in Norwegian area using Decomposition Techniques on RISAT-1 Hybrid Polarimetric Data.

    NASA Astrophysics Data System (ADS)

    Jayasri, P. V.; Usha Sundari, H. S. V.; Kumari, E. V. S. Sita; Prasad, A. V. V.

    2014-11-01

    Over past few years Synthetic Aperture Radar(SAR) has received a considerable attention for monitoring and detection of oil spill due to its unique capabilities to provide wide-area surveillance and day and night measurements, almost independently from atmospheric conditions. The critical part of the oil spill detection is to distinguish oil spills from other natural phenomena. Stokes vector analysis of the image data is studied to estimate the polarized circular and linear components of the backscatter signal which essentially utilize the degree of polarization(m) and relative phase (δ) of the target. In a controlled oil spill experiment conducted at Norwegian bay during 17th to 22nd June 2014, RISAT-1 hybrid polarimetry images were utilized to study the characteristics of oil spill in the sea. The preliminary results obtained by using polarimetric decomposition technique on hybrid polarimetric data to decipher the polarimetric characteristics of oil spills from natural waters are discussed in the paper.

  20. Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier

    SciTech Connect

    Wu, Y.; Xu, Z.; Li, Z. H.; Tang, C. X.

    2012-07-15

    In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.

  1. Experimental and theoretical study on the thermal decomposition of C3H6 (propene).

    PubMed

    Hung, Wei-Chung; Tsai, Chieh-Ying; Matsui, Hiroyuki; Wang, Niann-Shiah; Miyoshi, Akira

    2015-02-26

    The mechanism of the thermal unimolecular decomposition of C3H6 (propene) is studied both theoretically and experimentally. The potential energy surfaces for possible reaction pathways are investigated by CBS-QB3 level of quantum chemical calculations, and RRKM/master-equation calculation is performed for the main channels. The time evolutions of H atoms are observed experimentally by using a highly sensitive detection technique (ARAS, detection limit ≈ 10(11) atoms cm(-3)) behind reflected shock waves (0.5-1.0 ppm C3H6 diluted in Ar, 1450-1710 K at 2.0 atm). The objective of this study is to examine the main product channels by combining the experimental and theoretical investigations on the yield and the rates of H atom production. Present quantum chemical calculations identify reactions (1a-1d) as the candidates of product channels: C3H6 → aC3H5 (allyl radical) + H (1a), C3H6 → CH3 + C2H3 (vinyl radical) (1b), C3H6 → CH4 + :CCH2 (singlet vinyldene radical) (1c), and C3H6 → C3H4 (allene) + H2 (1d). The RRKM calculations reveal the branching fractions for (1a), (1b), and (1c) to be approximately 0.8, 0.2, and 0.01, respectively. Reaction (1d) and other product channels are negligible (< 0.1 %), and the pressure dependence of the branching fraction is small under the present experimental conditions. The experimental yield of H atoms (1.7-2.0) is consistent with the theoretical branching fractions considering the H-atom production from the rapid subsequent thermal decomposition of a C3H5 and C2H3. From the observed time profiles of H atoms, the rate of overall thermal decomposition of C3H6 can be evaluated as Ln(k1/s(-1)) = (38.05 ± 1.18) - (48.91 ± 1.85) × 10(3) K/T, which is in excellent agreement with the theoretical prediction.

  2. Aridity and decomposition processes in complex landscapes

    NASA Astrophysics Data System (ADS)

    Ossola, Alessandro; Nyman, Petter

    2015-04-01

    Decomposition of organic matter is a key biogeochemical process contributing to nutrient cycles, carbon fluxes and soil development. The activity of decomposers depends on microclimate, with temperature and rainfall being major drivers. In complex terrain the fine-scale variation in microclimate (and hence water availability) as a result of slope orientation is caused by differences in incoming radiation and surface temperature. Aridity, measured as the long-term balance between net radiation and rainfall, is a metric that can be used to represent variations in water availability within the landscape. Since aridity metrics can be obtained at fine spatial scales, they could theoretically be used to investigate how decomposition processes vary across complex landscapes. In this study, four research sites were selected in tall open sclerophyll forest along a aridity gradient (Budyko dryness index ranging from 1.56 -2.22) where microclimate, litter moisture and soil moisture were monitored continuously for one year. Litter bags were packed to estimate decomposition rates (k) using leaves of a tree species not present in the study area (Eucalyptus globulus) in order to avoid home-field advantage effects. Litter mass loss was measured to assess the activity of macro-decomposers (6mm litter bag mesh size), meso-decomposers (1 mm mesh), microbes above-ground (0.2 mm mesh) and microbes below-ground (2 cm depth, 0.2 mm mesh). Four replicates for each set of bags were installed at each site and bags were collected at 1, 2, 4, 7 and 12 months since installation. We first tested whether differences in microclimate due to slope orientation have significant effects on decomposition processes. Then the dryness index was related to decomposition rates to evaluate if small-scale variation in decomposition can be predicted using readily available information on rainfall and radiation. Decomposition rates (k), calculated fitting single pool negative exponential models, generally

  3. Use of Adomian decomposition method in the study of parallel plate flow of a third grade fluid

    NASA Astrophysics Data System (ADS)

    Siddiqui, A. M.; Hameed, M.; Siddiqui, B. M.; Ghori, Q. K.

    2010-09-01

    In this paper, Adomian's decomposition method is used to solve non-linear differential equations which arise in fluid dynamics. We study basic flow problems of a third grade non-Newtonian fluid between two parallel plates separated by a finite distance. The technique of Adomian decomposition is successfully applied to study the problem of a non-Newtonian plane Couette flow, fully developed plane Poiseuille flow and plane Couette-Poiseuille flow. The results obtained show the reliability and efficiency of this analytical method. Numerical solutions are also obtained by solving non-linear ordinary differential equations using Chebyshev spectral method. We present a comparative study between the analytical solutions and numerical solutions. The analytical results are found to be in good agreement with numerical solutions which reveals the effectiveness and convenience of the Adomian decomposition method.

  4. Thermogravimetric and decomposition kinetic studies of Mesua ferrea L. deoiled cake.

    PubMed

    Chutia, Rahul Singh; Kataki, Rupam; Bhaskar, Thallada

    2013-07-01

    The present study aims to explore the physico-chemical properties of Mesua ferrea L. (Iron wood tree) deoiled cake (MFDC) and decomposition parameters for thermochemical methods of conversion. The physico-chemical characteristics of MFDC were investigated by bomb calorimetry, TG/DTA (10, 20 and 40°C min(-1)), elemental analysis (CHN) and FTIR spectroscopy. The proximate composition was calculated using standard ASTM methodology. The temperature profile, activation energy (E), pre-exponential factor (A) and reaction order (n) for the active pyrolysis zone of the species under investigation have been provided for the respective heating rates using Arrhenius, Coats-Redfern, Flynn-Wall-Ozawa (FWO) and Global independent reactions model. The current investigation suggests that within the realm of existing biomass conversion technologies, MFDC can be used as a feedstock for thermochemical conversion. PMID:23644072

  5. Catalytic performance of carbon nanotubes in H2O2 decomposition: experimental and quantum chemical study.

    PubMed

    Voitko, Katerina; Tóth, Ajna; Demianenko, Evgenij; Dobos, Gábor; Berke, Barbara; Bakalinska, Olga; Grebenyuk, Anatolij; Tombácz, Etelka; Kuts, Volodymyr; Tarasenko, Yurij; Kartel, Mykola; László, Krisztina

    2015-01-01

    The catalytic performance of multi-walled carbon nanotubes (MWCNTs) with different surface chemistry was studied in the decomposition reaction of H2O2 at various values of pH and temperature. A comparative analysis of experimental and quantum chemical calculation results is given. It has been shown that both the lowest calculated activation energy (∼18.9 kJ/mol) and the highest rate constant correspond to the N-containing CNT. The calculated chemisorption energy values correlate with the operation stability of MWCNTs. Based on the proposed quantum chemical model it was found that the catalytic activity of carbon materials in electron transfer reactions is controlled by their electron donor capability.

  6. Assays to Study Consequences of Cytoplasmic Intermediate Filament Mutations: The Case of Epidermal Keratins.

    PubMed

    Tan, Tong San; Ng, Yi Zhen; Badowski, Cedric; Dang, Tram; Common, John E A; Lacina, Lukas; Szeverényi, Ildikó; Lane, E Birgitte

    2016-01-01

    The discovery of the causative link between keratin mutations and a growing number of human diseases opened the way for a better understanding of the function of the whole intermediate filament families of cytoskeleton proteins. This chapter describes analytical approaches to identification and interpretation of the consequences of keratin mutations, from the clinical and diagnostic level to cells in tissue culture. Intermediate filament pathologies can be accurately diagnosed from skin biopsies and DNA samples. The Human Intermediate Filament Database collates reported mutations in intermediate filament genes and their diseases, and can help clinicians to establish accurate diagnoses, leading to disease stratification for genetic counseling, optimal care delivery, and future mutation-aligned new therapies. Looking at the best-studied keratinopathy, epidermolysis bullosa simplex, the generation of cell lines mimicking keratinopathies is described, in which tagged mutant keratins facilitate live-cell imaging to make use of today's powerful enhanced light microscopy modalities. Cell stress assays such as cell spreading and cell migration in scratch wound assays can interrogate the consequences of the compromised cytoskeletal network. Application of extrinsic stresses, such as heat, osmotic, or mechanical stress, can enhance the differentiation of mutant keratin cells from wild-type cells. To bring the experiments to the next level, 3D organotypic human cultures can be generated, and even grafted onto the backs of immunodeficient mice for greater in vivo relevance. While development of these assays has focused on mutant K5/K14 cells, the approaches are often applicable to mutations in other intermediate filaments, reinforcing fundamental commonalities in spite of diverse clinical pathologies.

  7. Assays to Study Consequences of Cytoplasmic Intermediate Filament Mutations: The Case of Epidermal Keratins.

    PubMed

    Tan, Tong San; Ng, Yi Zhen; Badowski, Cedric; Dang, Tram; Common, John E A; Lacina, Lukas; Szeverényi, Ildikó; Lane, E Birgitte

    2016-01-01

    The discovery of the causative link between keratin mutations and a growing number of human diseases opened the way for a better understanding of the function of the whole intermediate filament families of cytoskeleton proteins. This chapter describes analytical approaches to identification and interpretation of the consequences of keratin mutations, from the clinical and diagnostic level to cells in tissue culture. Intermediate filament pathologies can be accurately diagnosed from skin biopsies and DNA samples. The Human Intermediate Filament Database collates reported mutations in intermediate filament genes and their diseases, and can help clinicians to establish accurate diagnoses, leading to disease stratification for genetic counseling, optimal care delivery, and future mutation-aligned new therapies. Looking at the best-studied keratinopathy, epidermolysis bullosa simplex, the generation of cell lines mimicking keratinopathies is described, in which tagged mutant keratins facilitate live-cell imaging to make use of today's powerful enhanced light microscopy modalities. Cell stress assays such as cell spreading and cell migration in scratch wound assays can interrogate the consequences of the compromised cytoskeletal network. Application of extrinsic stresses, such as heat, osmotic, or mechanical stress, can enhance the differentiation of mutant keratin cells from wild-type cells. To bring the experiments to the next level, 3D organotypic human cultures can be generated, and even grafted onto the backs of immunodeficient mice for greater in vivo relevance. While development of these assays has focused on mutant K5/K14 cells, the approaches are often applicable to mutations in other intermediate filaments, reinforcing fundamental commonalities in spite of diverse clinical pathologies. PMID:26795473

  8. Quantum chemistry study of the oxidation-induced stability and decomposition of propylene carbonate-containing complexes.

    PubMed

    Wang, Yating; Xing, Lidan; Borodin, Oleg; Huang, Wenna; Xu, Mengqing; Li, Xiaoping; Li, Weishan

    2014-04-14

    Oxidation-induced decomposition reactions of the representative complexes of propylene carbonate (PC)-based electrolytes were investigated using density functional theory (DFT) and a composite G4MP2 method. The cluster-continuum approach was used, where the oxidized PCn cluster was surrounded by the implicit solvent modeled via a polarized continuum model (PCM). The oxidative stability of the PCn (n = 2, 3, and 4) complexes was found to be around 5.4-5.5 V vs. Li(+)/Li, which is not only lower than the stability of an isolated PC but also lower than the stability of the PC-PF6(-), PC-BF4(-) or PC-ClO4(-) complexes surrounded by the implicit solvent. The oxidation-induced decomposition reactions were studied. The decomposition products of the oxidized PC2 contained CO2, acetone, propanal, propene, and carboxylic acid in agreement with the previous experimental studies.

  9. A comparative study of the decomposition of pig carcasses in a methyl methacrylate box and open air conditions.

    PubMed

    Li, Liangliang; Wang, Jiangfeng; Wang, Yu

    2016-08-01

    Analysis of the process of decomposition is essential in establishing the postmortem interval. However, despite the fact that insects are important players in body decomposition, their exact function within the decay process is still unclear. There is also limited knowledge as to how the decomposition process occurs in the absence of insects. In the present study, we compared the decomposition of a pig carcass in open air with that of one placed in a methyl methacrylate box to prevent insect contact. The pig carcass in the methyl methacrylate box was in the fresh stage for 1 day, the bloated stage from 2 d to 11 d, and underwent deflated decay from 12 d. In contrast, the pig carcass in open air went through the fresh, bloated, active decay and post-decay stages; and 22.3 h (0.93 d), 62.47 h (2.60 d), 123.63 h (5.15 d) and 246.5 h (10.27 d) following the start of the experiment respectively, prior to entering the skeletonization stage. A large amount of soft tissue were remained on the pig carcass in the methyl methacrylate box on 26 d, while only scattered bones remained on the pig carcass in open air. The results indicate that insects greatly accelerate the decomposition process.

  10. Cryoradiolysis and cryospectroscopy for studies of heme-oxygen intermediates in cytochromes P450

    PubMed Central

    Denisov, I.G.; Grinkova, Y.V.; Sligar, S.G.

    2014-01-01

    Cryogenic radiolytic reduction is one of the most simple and convenient methods of generation and stabilization of reactive iron-oxygen intermediates for mechanistic studies in chemistry and biochemistry. The method is based on one-electron reduction of the precursor complex in frozen solution via exposure to the ionizing radiation at cryogenic temperatures. Such approach allows for accumulation of the fleeting reactive complexes which otherwise could not be generated at sufficient amount for structural and mechanistic studies. Application of this method allowed for characterizing of peroxoferric and hydroperoxo-ferric intermediates, which are common for the oxygen activation mechanism in cytochromes P450, heme oxygenases and nitric oxide synthases, as well as for the peroxide metabolism by peroxidases and catalases. PMID:22573452

  11. [Studies in intermediate energy nuclear physics]. Technical progress report, [October 1, 1992--September 30, 1993

    SciTech Connect

    Peterson, R.J.

    1993-10-01

    This report summarizes work carried out between October 1, 1992 and September 30, 1993 at the Nuclear Physics Laboratory of the University of Colorado, Boulder. The experimental program in intermediate-energy nuclear physics is very broadly based; it includes pion-nucleon and pion-nucleus studies at LAMPF and TRIUMF, kaon-nucleus scattering at the AGS, and equipment development for experiments at the next generation of accelerator facilities.

  12. Further studies into the photodissociation pathways of 2-bromo-2-nitropropane and the dissociation channels of the 2-nitro-2-propyl radical intermediate.

    PubMed

    Booth, Ryan S; Brynteson, Matthew D; Lee, Shih-Huang; Lin, J J; Butler, Laurie J

    2014-07-01

    These experiments investigate the decomposition mechanisms of geminal dinitro energetic materials by photolytically generating two key intermediates: 2-nitropropene and 2-nitro-2-propyl radicals. To characterize the unimolecular dissociation of each intermediate, we form them under collision-free conditions using the photodissociation of 2-bromo-2-nitropropane; the intermediates are formed at high internal energies and undergo a multitude of subsequent unimolecular dissociation events investigated herein. Complementing our prior work on this system, the new data obtained with a crossed-laser molecular beam scattering apparatus with VUV photoionization detection at Taiwan's National Synchrotron Radiation Research Center (NSRRC) and new velocity map imaging data better characterize two of the four primary 193 nm photodissociation channels. The C-Br photofission channel forming the 2-nitro-2-propyl radicals has a trimodal recoil kinetic energy distribution, P(ET), suggesting that the 2-nitro-2-propyl radicals are formed both in the ground electronic state and in two low-lying excited electronic states. The new data also revise the HBr photoelimination P(ET) forming the 2-nitropropene intermediate. We then resolved the multiple competing unimolecular dissociation channels of each photoproduct, confirming many of the channels detected in the prior study, but not all. The new data detected HONO product at m/e = 47 using 11.3 eV photoionization from both intermediates; analysis of the momentum-matched products allows us to establish that both 2-nitro-2-propyl → HONO + CH3CCH2 and 2-nitropropene → HONO + C3H4 occur. Photoionization at 9.5 eV allowed us to detect the mass 71 coproduct formed in OH loss from 2-nitro-2-propyl; a channel missed in our prior study. The dynamics of the highly exothermic 2-nitro-2-propyl → NO + acetone dissociation is also better characterized; it evidences a sideways scattered angular distribution. The detection of some stable 2

  13. Kinetic and microstructural studies of thermal decomposition in uranium mononitride compacts subjected to heating in high-purity helium

    NASA Astrophysics Data System (ADS)

    Lunev, A. V.; Mikhalchik, V. V.; Tenishev, A. V.; Baranov, V. G.

    2016-07-01

    Although uranium mononitride has a high melting point (≈3100 K), it often decomposes well below this temperature. The threshold and kinetics of thermal decomposition depend on samples' chemical content and on gas environment. However, most experiments with uranium nitride samples were done so far in vacuum conditions and did not allow thorough examination of reaction kinetics at high temperatures. This research focuses on studying the different stages of thermal decomposition in uranium nitride samples subjected to heating in helium. Mass loss and thermal effects are identified with simultaneous thermal analysis (STA), while scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to register phase and compositional changes. Thermal decomposition in uranium nitride samples is found to be a multi-stage process with the final stage characterized by uranium vaporization. The results are useful for estimating the high-temperature behaviour of uranium nitride fuel during its fabrication and performance in some of Gen IV reactors.

  14. Thermal decomposition studies of chlorocarbon molecules in a shock tube using the Cl-atom ARAS method

    SciTech Connect

    Lim, K.P.; Michael, J.V.

    1994-02-01

    Because of needs for understanding the chemical kinetic mechanism in chlorocarbon molecule incineration, we have recently completed studies on the thermal decompositions of COCl{sub 2}, CH{sub 3}Cl, CH{sub 2}Cl{sub 2}, CCl{sub 4}, and CF{sub 3} Cl. The shock tube technique combined with atomic resonance absorption spectrometry (ARAS), as applied to Cl atoms, has been used to obtain absolute rate data for these reactions. In all cases, the decompositions are nearly in the second-order regime. Theoretical calculations, using the Troe formalism, have been performed. In these calculations, both the threshold energies for decomposition, E{sub o}, and the energy transferred per down collision, {Delta}E{sub down}, are varied parametrically for best fitting to the data. The latter quantity determines the collisional deactivation efficiency factor, {beta}{sub c}.

  15. Photogenerated radical intermediates of vitamin K 1: a time-resolved resonance Raman study

    NASA Astrophysics Data System (ADS)

    Balakrishnan, G.; Umapathy, S.

    1999-01-01

    Quinones play a vital role in the process of electron transfer in bacterial photosynthetic reaction centers. It is of interest to investigate the photochemical reactions involving quinones with a view to elucidating the structure-function relationships in the biological processes. Resonance Raman spectra of radical anions and the time-resolved resonance Raman spectra of vitamin K 1 (model compound for Q A in Rhodopseudomonas viridis, a bacterial photosynthetic reception center) are presented. The photochemical intermediates of vitamin K 1, viz. radical anion, ketyl radical and o-quinone methide have been identified. The vibrational assignments of all these intermediates are made on the basis of comparison with our earlier TR3 studies on radical anions of naphthoquinone and menaquinone.

  16. Retrofit photovoltaic systems for intermediate sized applications - A design and market study

    NASA Astrophysics Data System (ADS)

    Noel, G. T.; Hagely, J. R.

    An assessment of the technical and economic feasibility of retrofitting a significant portion of the existing intermediate sector building/application inventory with photovoltaic systems is presented. The assessment includes the development of detailed engineering and architectural designs as well as cost estimates for 12 representative installations. Promising applications include retail stores, warehouses, office buildings, religious buildings, shopping centers, education buildings, hospitals, and industrial sites. A market study indicates that there is a national invetory of 1.5 to 2.0 million feasible intermediate sector applications, with the majority being in the 20 to 400 kW size range. The present cost of the major systems components and the cost of necessary building modifications are the primary current barriers to the realization of a large retrofit photovoltaic system market. The development of standardized modular system designs and installation techniques are feasible ways to minimize costs.

  17. Reaction mechanism of methylamine decomposition on Ru(0001): a density functional theory study.

    PubMed

    Lv, Cun-Qin; Liu, Jian-Hong; Song, Xiao-Fei; Guo, Yong; Wang, Gui-Chang

    2014-03-01

    The reaction mechanism of methylamine decomposition on Ru(0001) has been systematically investigated by density functional theory slab calculations. The decomposition network has also been described. The adsorption energies under the most stable configuration of the possible species and the energy barriers of the possible elementary reactions involved are obtained. Desorption is preferred for adsorbing methylamine and hydrogen, whereas for the other species, decomposition is more favorable. Our calculated results show that methylamine decomposition on Ru(0001) starts with H₂CNH₂ formation from methyl dehydrogenation, followed by subsequent methylene dehydrogenation, bond breaking of N--H and C--N in HCNH₂, CH dehydrogenation and C-N bond cleavage in HCNH, and dehydrogenation of NH₂, NH, and CH.

  18. MECHANISTIC STUDIES OF SURFACE CATALYZED H2O2 DECOMPOSITION AND CONTAMINANT DEGRADATION IN THE PRESENCE OF SAND. (R823402)

    EPA Science Inventory

    This study examined the mechanism and kinetics of surface catalyzed hydrogen peroxide decomposition and degradation of contaminants in the presence of sand collected from an aquifer and a riverbed. Batch experiments were conducted using variable sand concentrations (0.2 to 1.0&nb...

  19. Kinetic Study of the Acid Degradation of Lignin Model Compound Intermediates

    SciTech Connect

    Sturgeon, M.; Kim, S.; Chmely, S. C.; Foust, T. D.; Beckham, G. T.

    2012-01-01

    Lignin is a major constituent of biomass, which remains underutilized in selective biomass conversion strategies to renewable fuels and chemicals. Here we are interested in understanding the mechanisms related to the acid deconstruction of lignin with a combined theoretical and experimental approach. Two model dimers with a b-O-4 aryl ether linkage (2-phenoxy-1-phenethanol and 2-phenoxy-1-phenyl-1,3 propanediol) were synthesized and deconstructed in H2SO4. The major products of the acidolysis of the b-O-4 compounds consisted of phenol and two aldehydes, phenylacetaldehyde and benzaldehyde. Quantum mechanical calculations were employed to elucidate possible deconstruction mechanisms with transition state theory. To confirm the proposed mechanisms a kentic study of several possible intermediates was done under similar acidolysis conditions. Epoxystyrene and 1-phenyl-1,2-ethandiol were used as intermediates. 2-phenoxyvinylbenzene was synthesized and subsequently deconstructed in H2SO4. The kinetics and product distribution of these intermediates were then used in confirming our proposed mechanisms.

  20. Electron Paramagnetic Resonance and Electron-Nuclear Double Resonance Studies of the Reactions of Cryogenerated Hydroperoxoferric–Hemoprotein Intermediates

    PubMed Central

    2015-01-01

    The fleeting ferric peroxo and hydroperoxo intermediates of dioxygen activation by hemoproteins can be readily trapped and characterized during cryoradiolytic reduction of ferrous hemoprotein–O2 complexes at 77 K. Previous cryoannealing studies suggested that the relaxation of cryogenerated hydroperoxoferric intermediates of myoglobin (Mb), hemoglobin, and horseradish peroxidase (HRP), either trapped directly at 77 K or generated by cryoannealing of a trapped peroxo-ferric state, proceeds through dissociation of bound H2O2 and formation of the ferric heme without formation of the ferryl porphyrin π-cation radical intermediate, compound I (Cpd I). Herein we have reinvestigated the mechanism of decays of the cryogenerated hydroperoxyferric intermediates of α- and β-chains of human hemoglobin, HRP, and chloroperoxidase (CPO). The latter two proteins are well-known to form spectroscopically detectable quasistable Cpds I. Peroxoferric intermediates are trapped during 77 K cryoreduction of oxy Mb, α-chains, and β-chains of human hemoglobin and CPO. They convert into hydroperoxoferric intermediates during annealing at temperatures above 160 K. The hydroperoxoferric intermediate of HRP is trapped directly at 77 K. All studied hydroperoxoferric intermediates decay with measurable rates at temperatures above 170 K with appreciable solvent kinetic isotope effects. The hydroperoxoferric intermediate of β-chains converts to the S = 3/2 Cpd I, which in turn decays to an electron paramagnetic resonance (EPR)-silent product at temperature above 220 K. For all the other hemoproteins studied, cryoannealing of the hydroperoxo intermediate directly yields an EPR-silent majority product. In each case, a second follow-up 77 K γ-irradiation of the annealed samples yields low-spin EPR signals characteristic of cryoreduced ferrylheme (compound II, Cpd II). This indicates that in general the hydroperoxoferric intermediates relax to Cpd I during cryoanealing at low temperatures, but

  1. Mechanistic studies of cyclohexanone monooxygenase: chemical properties of intermediates involved in catalysis.

    PubMed

    Sheng, D; Ballou, D P; Massey, V

    2001-09-18

    Cyclohexanone monooxygenase (CHMO), a bacterial flavoenzyme, carries out an oxygen insertion reaction on cyclohexanone to form a seven-membered cyclic product, epsilon-caprolactone. The reaction catalyzed involves the four-electron reduction of O2 at the expense of a two-electron oxidation of NADPH and a two-electron oxidation of cyclohexanone to form epsilon-caprolactone. Previous studies suggested the participation of either a flavin C4a-hydroperoxide or a flavin C4a-peroxide intermediate during the enzymatic catalysis [Ryerson, C. C., Ballou, D. P., and Walsh, C. (1982) Biochemistry 21, 2644-2655]. However, there was no kinetic or spectral evidence to distinguish between these two possibilities. In the present work we used double-mixing stopped-flow techniques to show that the C4a-flavin-oxygen adduct, which is formed rapidly from the reaction of oxygen with reduced enzyme in the presence of NADP, can exist in two states. When the reaction is carried out at pH 7.2, the first intermediate is a flavin C4a-peroxide with maximum absorbance at 366 nm; this intermediate becomes protonated at about 3 s(-1) to form what is believed to be the flavin C4a-hydroperoxide with maximum absorbance at 383 nm. These two intermediates can be interconverted by altering the pH, with a pK(a) of 8.4. Thus, at pH 9.0 the flavin C4a-peroxide persists mainly in the deprotonated form. Further kinetic studies also demonstrated that only the flavin C4a-peroxide intermediate could oxygenate the substrate, cyclohexanone. The requirement in catalysis of the deprotonated flavin C4a-peroxide, a nucleophile, is consistent with a Baeyer-Villiger rearrangement mechanism for the enzymatic oxygenation of cyclohexanone. In the course of these studies, the Kd for cyclohexanone to the C4a-peroxyflavin form of CHMO was determined to be approximately 1 microM. The rate-determining step in catalysis was shown to be the release of NADP from the oxidized enzyme.

  2. Role of Lactobacillus Species in the Intermediate Vaginal Flora in Early Pregnancy: A Retrospective Cohort Study

    PubMed Central

    Farr, Alex; Kiss, Herbert; Hagmann, Michael; Machal, Susanne; Holzer, Iris; Kueronya, Verena; Husslein, Peter Wolf; Petricevic, Ljubomir

    2015-01-01

    Background Poor obstetrical outcomes are associated with imbalances in the vaginal flora. The present study evaluated the role of vaginal Lactobacillus species in women with intermediate vaginal flora with regard to obstetrical outcomes. Methods We retrospectively analysed data from all women with singleton pregnancies who had undergone routine screening for asymptomatic vaginal infections at our tertiary referral centre between 2005 and 2014. Vaginal smears were Gram-stained and classified according to the Nugent scoring system as normal flora (score 0–3), intermediate vaginal flora (4–6), or bacterial vaginosis (7–10). Only women with intermediate vaginal flora were investigated. Women with a Nugent score of 4 were categorised into those with and without Lactobacilli. Follow-up smears were obtained 4–6 weeks after the initial smears. Descriptive data analysis, the Welch’s t-test, the Fisher’s exact test, and multiple regression analysis with adjustment for confounders were performed. Gestational age at delivery and birth weight were the outcome measures. Results At antenatal screening, 529/8421 women presented with intermediate vaginal flora. Amongst these, 349/529 (66%) had a Nugent score of 4, 94/529 (17.8%) a Nugent score of 5, and 86/529 (16.2%) a Nugent score of 6. Amongst those with a Nugent score of 4, 232/349 (66.5%) women were in the Lactobacilli group and 117/349 (33.5%) in the Non-Lactobacilli group. The preterm delivery rate was significantly lower in the Lactobacilli than in the Non-Lactobacilli group (OR 0.34, CI 0.21–0.55; p<0.001). Mean birth weight was 2979 ± 842 g and 2388 ± 1155 g in the study groups, respectively (MD 564.12, CI 346.23–781.92; p<0.001). On follow-up smears, bacterial vaginosis rates were 9% in the Lactobacilli and 7.8% in the Non-Lactobacilli group. Conclusions The absence of vaginal Lactobacillus species and any bacterial colonisation increases the risks of preterm delivery and low birth weight in women with

  3. (Studies of target fragmentation in intermediate energy, relativistic and ultra-relativistic nuclear collisions)

    SciTech Connect

    Loveland, W.D.

    1991-08-01

    The work described herein is part of a project involving the study of low energy (< 10 MeV/A), intermediate energy (10--100 MeV/A) and relativistic (> 250 MeV/A) heavy ion reactions. In the low energy regime, we published a monograph on the properties of the heaviest elements and used that publication as a basis for making a set of best'' semi-empirical predictions of heavy element decay properties. The intermediate energy research effort focussed upon the completion of studies already begun and the initiation of a number of new experiments. In our study of a interaction of 21 MeV/nucleon {sup 129}Xe with {sup 197}Au, we compared the characteristics of the observed deep inelastic phenomena with various models of dissipative reactions and found significant discrepancies between observations and predictions. These discrepancies seemed to be caused by an improper treatment of pre-equilibrium in the early stages of the collision. In our study of the relativistic interaction of 400 MeV/nucleon {sup 12}C with {sup 197}Au, we reported the first direct physical measurement of the properties of the spallation residues from a nucleus-nucleus collision. We found the residue energies to be much lower than those predicted by the intranuclear cascade model, indicating some substantial modifications of that model are needed. But, we also found, indications of significant, non-zero values of the residue transverse momentum, a finding that calls into question the interpretation of a number of radiochemical recoil studies of the kinematics of high energy reactions. A program of performing numerical simulations of intermediate and high energy nuclear collisions using the QMD model was initiated.

  4. Studies on thermal decomposition mechanism of CL-20 by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS).

    PubMed

    Naik, N H; Gore, G M; Gandhe, B R; Sikder, A K

    2008-11-30

    The thermal decomposition study of CL-20 (hexanitrohexaazaisowurtzitane) using pyrolysis GC/MS was carried out mainly by electron impact (EI) mode. Chemical ionization (CI) mode was used for further confirmation of identified species. Mass spectrum of CL-20 decomposition products predominantly revealed fragments with m/z 81 and 96 corresponding to C(4)H(5)N(2)(+) and C(4)H(4)N(2)O(+) ions, respectively. The total ion chromatogram (TIC) of CL-20 pyrolysis shows peak within first 2 min due to the presence of low molecular weight gases. Peaks corresponding to several other products were also observed including the atmospheric gases. Cyanogen formation (C(2)N(2), m/z 52) observed to be enriched at the scan number 300-500. The low molecular mass range decomposition products formed by cleavage of C-N ring structure were found in majority. Additional structural information was sought by employing chemical ionization mode. The data generated during this study was instrumented in determining decomposition pathways of CL-20.

  5. In situ infrared study of catalytic decomposition of NO. Semiannual technical progress report, February 1--August 1, 1996

    SciTech Connect

    Chuang, S.S.C.; Tan, C.D.

    1996-09-20

    During the second semi-annual period, promotion of oxygen desorption to enhance direct NO decomposition over Tb-Pt/Al{sub 2}O{sub 3} catalyst has been studied. Promotion of oxygen desorption at low temperatures holds the key to the development of an effective NO decomposition catalyst. Addition of Tb-oxide to Pt/Al{sub 2}O{sub 3} allows oxygen from dissociated NO to desorb at 593 K which is significantly lower than the reported oxygen desorption temperatures for Pt catalysts. Combined temperature-programmed desorption/reaction with in situ infrared study reveals that desorbed oxygen is produced from decomposition of chelating bidentate nitrato which may be resulted from the reaction of adsorbed oxygen on Pt and adsorbed NO on Tb-oxide. The Tb-promoted Pt/Al{sub 2}O{sub 3} catalyst which possess oxygen desorption capability at low temperatures shows the activity for decomposition of NO to N{sub 2}, N{sub 2}O, and O{sub 2} at 723 K.

  6. Studies on thermal decomposition mechanism of CL-20 by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS).

    PubMed

    Naik, N H; Gore, G M; Gandhe, B R; Sikder, A K

    2008-11-30

    The thermal decomposition study of CL-20 (hexanitrohexaazaisowurtzitane) using pyrolysis GC/MS was carried out mainly by electron impact (EI) mode. Chemical ionization (CI) mode was used for further confirmation of identified species. Mass spectrum of CL-20 decomposition products predominantly revealed fragments with m/z 81 and 96 corresponding to C(4)H(5)N(2)(+) and C(4)H(4)N(2)O(+) ions, respectively. The total ion chromatogram (TIC) of CL-20 pyrolysis shows peak within first 2 min due to the presence of low molecular weight gases. Peaks corresponding to several other products were also observed including the atmospheric gases. Cyanogen formation (C(2)N(2), m/z 52) observed to be enriched at the scan number 300-500. The low molecular mass range decomposition products formed by cleavage of C-N ring structure were found in majority. Additional structural information was sought by employing chemical ionization mode. The data generated during this study was instrumented in determining decomposition pathways of CL-20. PMID:18468788

  7. Case study for model validation : assessing a model for thermal decomposition of polyurethane foam.

    SciTech Connect

    Dowding, Kevin J.; Leslie, Ian H.; Hobbs, Michael L.; Rutherford, Brian Milne; Hills, Richard Guy; Pilch, Martin M.

    2004-10-01

    A case study is reported to document the details of a validation process to assess the accuracy of a mathematical model to represent experiments involving thermal decomposition of polyurethane foam. The focus of the report is to work through a validation process. The process addresses the following activities. The intended application of mathematical model is discussed to better understand the pertinent parameter space. The parameter space of the validation experiments is mapped to the application parameter space. The mathematical models, computer code to solve the models and its (code) verification are presented. Experimental data from two activities are used to validate mathematical models. The first experiment assesses the chemistry model alone and the second experiment assesses the model of coupled chemistry, conduction, and enclosure radiation. The model results of both experimental activities are summarized and uncertainty of the model to represent each experimental activity is estimated. The comparison between the experiment data and model results is quantified with various metrics. After addressing these activities, an assessment of the process for the case study is given. Weaknesses in the process are discussed and lessons learned are summarized.

  8. Theoretical study of formamide decomposition pathways over (6,0) silicon-carbide nanotube.

    PubMed

    Esrafili, Mehdi D; Ghanbari, Mozhgan; Nurazar, Roghaye; Nematollahi, Parisa

    2015-04-01

    In this study, we systematically identified possible reaction pathways for the catalytic decomposition of formamide (FM) on a (6,0) silicon-carbide nanotube surface by means of density functional theory. To gain insight into the catalytic activity of the surface, the interaction between the FM and SiCNT is analyzed by detailed electronic analysis such as adsorption energy, charge density difference and activation barrier. The energy barriers for the dehydrogenation, decarbonylation, and dehydration processes are found to be in the range of 0.2-49 kcal. Our results indicate that dehydrogenation and decarbonylation pathways are possible routes to get gaseous HNCO, H2, NH3, and CO molecules. In contrast, the reaction of HCONH → CONH + H presents a large activation energy (about 49 kcal mol(-1)) which makes the FM dehydration an unfavorable reaction. Moreover, the dehydrogenation appears to be particularly favorable at low temperatures. The theoretical insights gained in this study could be useful for designing and developing metal-free catalysts based on SiC nanostructures. PMID:25783993

  9. Decomposition techniques

    USGS Publications Warehouse

    Chao, T.T.; Sanzolone, R.F.

    1992-01-01

    Sample decomposition is a fundamental and integral step in the procedure of geochemical analysis. It is often the limiting factor to sample throughput, especially with the recent application of the fast and modern multi-element measurement instrumentation. The complexity of geological materials makes it necessary to choose the sample decomposition technique that is compatible with the specific objective of the analysis. When selecting a decomposition technique, consideration should be given to the chemical and mineralogical characteristics of the sample, elements to be determined, precision and accuracy requirements, sample throughput, technical capability of personnel, and time constraints. This paper addresses these concerns and discusses the attributes and limitations of many techniques of sample decomposition along with examples of their application to geochemical analysis. The chemical properties of reagents as to their function as decomposition agents are also reviewed. The section on acid dissolution techniques addresses the various inorganic acids that are used individually or in combination in both open and closed systems. Fluxes used in sample fusion are discussed. The promising microwave-oven technology and the emerging field of automation are also examined. A section on applications highlights the use of decomposition techniques for the determination of Au, platinum group elements (PGEs), Hg, U, hydride-forming elements, rare earth elements (REEs), and multi-elements in geological materials. Partial dissolution techniques used for geochemical exploration which have been treated in detail elsewhere are not discussed here; nor are fire-assaying for noble metals and decomposition techniques for X-ray fluorescence or nuclear methods be discussed. ?? 1992.

  10. HPLC and HPLC/MS/MS Studies on Stress, Accelerated and Intermediate Degradation Tests of Antivirally Active Tricyclic Analog of Acyclovir.

    PubMed

    Lesniewska, Monika A; Dereziński, Paweł; Klupczyńska, Agnieszka; Kokot, Zenon J; Ostrowski, Tomasz; Zeidler, Joanna; Muszalska, Izabela

    2015-01-01

    The degradation behavior of a tricyclic analog of acyclovir [6-(4-MeOPh)-TACV] was determined in accordance with International Conference on Harmonization guidelines for good clinical practice under different stress conditions (neutral hydrolysis, strong acid/base degradation, oxidative decomposition, photodegradation, and thermal degradation). Accelerated [40±2°C/75%±5% relative humidity (RH)] and intermediate (30±2°C/65%±5% RH) stability tests were also performed. For observation of the degradation of the tested compound the RP-HPLC was used, whereas for the analysis of its degradation products HPLC/MS/MS was used. Degradation of the tested substance allowed its classification as unstable in neutral environment, acidic/alkaline medium, and in the presence of oxidizing agent. The tested compound was also light sensitive and was classified as photolabile both in solution and in the solid phase. However, the observed photodegradation in the solid phase was at a much lower level than in the case of photodegradation in solution. The study showed that both air temperature and RH had no significant effect on the stability of the tested substance during storage for 1 month at 100°C (dry heat) as well as during accelerated and intermediate tests. Based on the HPLC/MS/MS analysis, it can be concluded that acyclovir was formed as a degradation product of 6-(4-MeOPh)-TACV.

  11. Decomposition of soil organic matter by ectomycorrhizal fungi studied by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Nicolás, César; Tunlid, Anders; Persson, Per

    2015-04-01

    Boreal forests accumulate a fifth of the global soil organic matter (SOM) pool and play an important role in the carbon cycling. Most trees in these boreal forests live in symbiosis with ectomycorrhizal fungi (EMF) that sheath the plant root tips. In the symbiotic relationship, EMF provide nutrients from the soil to plants such as nitrogen and phosphorous, and trees give carbon in return to the fungi. When foraging for these nutrients, EMF use different strategies to explore the soil matrix. Long-distance exploration types grow far into the soil surroundings of the roots, while short-medium distance exploration ones grow close to the root tips. Despite these morphological differences among EMF, there is still little evidence of their functional role in the SOM decomposition. In this study, two ectomycorrhizal fungi Paxillus involutus and Laccaria bicolor, which belong to long and medium-distance smooth exploration types respectively, were grown in axenic cultures on SOM extracted from forest litter. To trigger the fungal decomposing activity, the extracts were supplemented with glucose. Chemical analysis and infrared spectroscopy were used to analyze the organic matter and chemometric tools such as principal component analysis (PCA), two-dimensional (2D) correlation analysis and multivariate curve resolution-alternating least squares (MCR-ALS) analysis were applied to further understand the chemical changes in the SOM. The first principal component of PCA explained 77% of the total variability and separated the treatments based on two infrared spectral regions: polysaccharides (970-1,150 cm-1) and carbonyl region (1,620-1,800 cm-1). Moreover, the 2D correlation analysis showed that the polysaccharides region in both treatments was negatively correlated with the carbonyl region, suggesting the production of oxidized compounds such as ketones during the uptake of glucose. The 2D correlation analysis also revealed that the diminution of intensity in the

  12. Thermal decomposition of t-butylamine borane studied by in situ solid state NMR

    SciTech Connect

    Feigerle, J.; Smyrl, N. R.; Morrell, J. S.; Stowe, A. C.

    2010-03-18

    of the amine borane fuel more feasible [22]. In the present study, tert-butylamine borane is investigated by heteronuclear in situ solid state NMR to understand hydrogen release from a hydrocarbon containing amine borane. tbutylamine borane has similar physical properties to amine borane with a melting point of 96 C. A single proton has been replaced with a t-butylamine group resulting in a weakening of the dihydrogen bonding framework. t-butylamine borane has a theoretical gravimetric hydrogen density of 15.1%; however, isobutane can also be evolved rather than hydrogen. If decomposition yields one mole isobutane and two moles hydrogen, 4.5 wt% H2 gas will be evolved. More importantly for the present work, the resulting spent fuel should be comprised of both (BNH)n and (CBNH)n polyimidoboranes.

  13. Shock-induced decomposition of high energy materials: A ReaxFF molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tiwari, Subodh; Mishra, Ankit; Nomura, Ken-Ichi; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya

    Atomistic simulations of shock-induced detonation provide critical information about high-energy (HE) materials such as sensitivity, crystallographic anisotropy, detonation velocity, and reaction pathways. However, first principles methods are unable to handle systems large enough to describe shock appropriately. We report reactive-force-field ReaxFF simulations of shock-induced decomposition of 1, 3, 5-triamino-2, 3, 6-trinitrobenzene (TATB) and 1,1-diamino 2-2-dinitroethane (FOX-7) crystal. A flyer acts as mechanical stimuli to introduce a shock, which in turn initiated chemical reactions. Our simulation showed a shock speed of 9.8 km/s and 8.23 km/s for TATB and FOX-7, respectively. Reactivity analysis proves that FOX-7 is more reactive than TATB. Chemical reaction pathways analysis revealed similar pathways for the formation of N2 and H2O in both TATB and FOX-7. However, abundance of NH3 formation is specific to FOX-7. Large clusters formed during the reactions also shows different compositions between TATB and FOX-7. Carbon soot formation is much more pronounced in TATB. Overall, this study provides a detailed comparison between shock induced reaction pathway between FOX-7 and TATB. This work was supported by the Office of Naval Research Grant No. N000014-12-1-0555.

  14. Material decomposition and virtual non-contrast imaging in photon counting computed tomography: an animal study

    NASA Astrophysics Data System (ADS)

    Gutjahr, R.; Polster, C.; Kappler, S.; Pietsch, H.; Jost, G.; Hahn, K.; Schöck, F.; Sedlmair, M.; Allmendinger, T.; Schmidt, B.; Krauss, B.; Flohr, T. G.

    2016-03-01

    The energy resolving capabilities of Photon Counting Detectors (PCD) in Computed Tomography (CT) facilitate energy-sensitive measurements. The provided image-information can be processed with Dual Energy and Multi Energy algorithms. A research PCD-CT firstly allows acquiring images with a close to clinical configuration of both the X-ray tube and the CT-detector. In this study, two algorithms (Material Decomposition and Virtual Non-Contrast-imaging (VNC)) are applied on a data set acquired from an anesthetized rabbit scanned using the PCD-CT system. Two contrast agents (CA) are applied: A gadolinium (Gd) based CA used to enhance contrasts for vascular imaging, and xenon (Xe) and air as a CA used to evaluate local ventilation of the animal's lung. Four different images are generated: a) A VNC image, suppressing any traces of the injected Gd imitating a native scan, b) a VNC image with a Gd-image as an overlay, where contrast enhancements in the vascular system are highlighted using colored labels, c) another VNC image with a Xe-image as an overlay, and d) a 3D rendered image of the animal's lung, filled with Xe, indicating local ventilation characteristics. All images are generated from two images based on energy bin information. It is shown that a modified version of a commercially available dual energy software framework is capable of providing images with diagnostic value obtained from the research PCD-CT system.

  15. Time Domain Strain/Stress Reconstruction Based on Empirical Mode Decomposition: Numerical Study and Experimental Validation

    PubMed Central

    He, Jingjing; Zhou, Yibin; Guan, Xuefei; Zhang, Wei; Zhang, Weifang; Liu, Yongming

    2016-01-01

    Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil) are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided. PMID:27537889

  16. Mechanistic Studies on the Radiolytic Decomposition of Perchlorates on the Martian Surface

    NASA Astrophysics Data System (ADS)

    Turner, Andrew M.; Abplanalp, Matthew J.; Kaiser, Ralf I.

    2016-04-01

    Perchlorates—inorganic compounds carrying the perchlorate ion ({{ClO}}4{}-)—were discovered at the north polar landing site of the Phoenix spacecraft and at the southern equatorial landing site of the Curiosity Rover within the Martian soil at levels of 0.4-0.6 wt%. This study explores in laboratory experiments the temperature-dependent decomposition mechanisms of hydrated perchlorates—namely magnesium perchlorate hexahydrate (Mg(ClO4)2·6H2O)—and provides yields of the oxygen-bearing species formed in these processes at Mars-relevant surface temperatures from 165 to 310 K in the presence of galactic cosmic-ray particles (GCRs). Our experiments reveal that the response of the perchlorates to the energetic electrons is dictated by the destruction of the perchlorate ion ({{ClO}}4{}-) and the inherent formation of chlorates ({{ClO}}3{}-) plus atomic oxygen (O). Isotopic substitution experiments reveal that the oxygen is released solely from the perchlorate ion and not from the water of hydration (H2O). As the mass spectrometer detects only molecular oxygen (O2) and no atomic oxygen (O), atomic oxygen recombines to molecular oxygen within the perchlorates, with the overall yield of molecular oxygen increasing as the temperature drops from 260 to 160 K. Absolute destruction rates and formation yields of oxygen are provided for the planetary modeling community.

  17. Spectral decomposition aids AVO analysis in reservoir characterization: A case study of Blackfoot field, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Jung Yoon, Wang; Farfour, Mohammed

    2012-09-01

    Blackfoot field, Alberta, Canada, has produced oil and gas from a Glauconitic compound incised valley-system. In this area channels can be filled with sands and/or shales. Differentiation of prospective channel sands and non-productive shales was always problematic due to the similarity in P-wave impedance of these two lithotypes. We study the spectral decomposition response to the hydrocarbons presence in the Glauconitic channel of Early Cretaceous age. From previous AVO analysis and modeling, a strong Class III AVO anomaly has been observed at the top of the porous sandstone in the upper valley, whereas shale had a very different AVO response. Furthermore, AVO inversion revealed additional information about lithology and fluid content in the channel. Our workflow starts from selecting a continuous horizon that was close and conforms to the channel interval; we then run spectral analyses for the channel area. Short Window Fourier Transform workflow could successfully image the channel's stratigraphic features and confirm results obtained from AVO analysis and inversion run on the data before being stacked. Additionally, the producing oil wells in the sand-fill channel were found to be correlating with high spectrum amplitude; while the dry wells in the shale-plugged channel fell in low amplitude anomaly.

  18. Time Domain Strain/Stress Reconstruction Based on Empirical Mode Decomposition: Numerical Study and Experimental Validation.

    PubMed

    He, Jingjing; Zhou, Yibin; Guan, Xuefei; Zhang, Wei; Zhang, Weifang; Liu, Yongming

    2016-08-16

    Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil) are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided.

  19. Time Domain Strain/Stress Reconstruction Based on Empirical Mode Decomposition: Numerical Study and Experimental Validation.

    PubMed

    He, Jingjing; Zhou, Yibin; Guan, Xuefei; Zhang, Wei; Zhang, Weifang; Liu, Yongming

    2016-01-01

    Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil) are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided. PMID:27537889

  20. Validation of an in vitro digestive system for studying macronutrient decomposition in humans.

    PubMed

    Kopf-Bolanz, Katrin A; Schwander, Flurina; Gijs, Martin; Vergères, Guy; Portmann, Reto; Egger, Lotti

    2012-02-01

    The digestive process transforms nutrients and bioactive compounds contained in food to physiologically active compounds. In vitro digestion systems have proven to be powerful tools for understanding and monitoring the complex transformation processes that take place during digestion. Moreover, the investigation of the physiological effects of certain nutrients demands an in vitro digestive process that is close to human physiology. In this study, human digestion was simulated with a 3-step in vitro process that was validated in depth by choosing pasteurized milk as an example of a complex food matrix. The evolution and decomposition of the macronutrients was followed over the entire digestive process to the level of intestinal enterocyte action, using protein and peptide analysis by SDS-PAGE, reversed-phase HPLC, size exclusion HPLC, and liquid chromatography-MS. The mean peptide size after in vitro digestion of pasteurized milk was 5-6 amino acids (AA). Interestingly, mostly essential AA (93.6%) were released during in vitro milk digestion, a significantly different relative distribution compared to the total essential AA concentration of bovine milk (44.5%). All TG were degraded to FFA and monoacylglycerols. Herein, we present a human in vitro digestion model validated for its ability to degrade the macronutrients of dairy products comparable to physiological ranges. It is suited to be used in combination with a human intestinal cell culture system, allowing ex vivo bioavailability measurements and assessment of the bioactive properties of food components.

  1. Study of Tachyon Warm Intermediate and Logamediate Inflationary Universe from Loop Quantum Cosmological Perspective

    NASA Astrophysics Data System (ADS)

    Das Mandal, Jyotirmay; Debnath, Ujjal

    2016-08-01

    We have studied the tachyon intermediate and logamediate warm inflation in loop quantum cosmological background by taking the dissipative co-efficient Γ = Γ0 (where Γ0 is a constant) in “intermediate” inflation and Γ = V(ϕ), (where V(ϕ) is the potential of tachyonic field) in “logamediate” inflation. We have assumed slow-roll condition to construct scalar field ϕ, potential V, N-folds, etc. Various slow-roll parameters have also been obtained. We have analyzed the stability of this model through graphical representations.

  2. Inverse Kinematics Studies of Intermediate-Energy Reactions Relevant for SEE and Medical Problems

    NASA Astrophysics Data System (ADS)

    Aichelin, J.; Bargholtz, Ch.; Blomgren, J.; Budzanowski, A.; Chubarov, M.; Czech, B.; Ekström, C.; Gerén, L.; Jakobsson, B.; Kolozhvari, A.; Lozhkin, O.; Murin, Yu.; Nomokonov, P.; Olsson, N.; Persson, H.; Pljuschev, V.; Skwirczynska, I.; Tang, H. H. K.; Tegnér, P.-E.; Westerberg, L.; Zartova, I.; Zubkov, M.; Watanabe, Y.

    2005-05-01

    The lack of systematic experimental checks on the intermediate-energy nuclear model simulations of heavily ionizing recoils from nucleon-nucleus collisions — critical inputs for the Single Event Effect analysis of microelectronics and dosimetry calculations including high-LET components in the cancer tumor radiation therapy — has been a primary motivation for a new experiment planned at the CELSIUS nuclear storage ring of The Svedberg Laboratory, Uppsala, Sweden. Details of the experiment and the first results from a feasibility study are presented here.

  3. Study of phase decomposition and coarsening of γ′ precipitates in Ni-12 at.% Ti alloy

    SciTech Connect

    Garay-Reyes, C.G.; Hernández-Santiago, F.; Cayetano-Castro, N.; López-Hirata, V.M.; García-Rocha, J.; Hernández-Rivera, J.L.; Dorantes-Rosales, H.J.; Cruz-Rivera, J.J.

    2013-09-15

    The early stages of phase decomposition, morphological evolution of precipitates, coarsening kinetics of γ′ precipitates and micro-hardness in Ni-12 at.% Ti alloy are studied by transmission electron microscopy (TEM) and Vickers hardness tests (VHN). Disk-shaped specimens are solution treated at 1473 K (1200 °C) and aged at 823, 923 and 1023 K (550, 650 and 750 °C) during several periods of time. TEM results show that a conditional spinodal of order occurs at the beginning of the phase decomposition and exhibit the following decomposition sequence and morphological evolution of precipitates: α{sub sss} → γ″ irregular–cuboidal + γ{sub s} → γ′ cuboidal–parallelepiped + γ → η plates + γ. In general during the coarsening of γ′ precipitates, the experimental coarsening kinetics do not fit well to the LSW or TIDC (n = 2.281) theoretical models, however the activation energies determined using the TIDC and LSW theories (262.846 and 283.6075 kJ mol{sup −1}, respectively) are consistent with previously reported values. The highest hardness obtained at 823, 923 and 1023 K (550, 650 and 750 °C) is associated with the presence of γ′ precipitates. - Highlights: • It was studied the conditional spinodal during early stages of phase decomposition. • It was obtained decomposition sequence and morphological evolution of precipitates. • It was experimentally evaluated the coarsening kinetics of γ′ precipitates. • The maximum hardness is associated with the γ′ precipitates.

  4. Causal inference in longitudinal comparative effectiveness studies with repeated measures of a continuous intermediate variable.

    PubMed

    Wang, Chen-Pin; Jo, Booil; Brown, C Hendricks

    2014-09-10

    We propose a principal stratification approach to assess causal effects in nonrandomized longitudinal comparative effectiveness studies with a binary endpoint outcome and repeated measures of a continuous intermediate variable. Our method is an extension of the principal stratification approach originally proposed for the longitudinal randomized study "Prevention of Suicide in Primary Care Elderly: Collaborative Trial" to assess the treatment effect on the continuous Hamilton depression score adjusting for the heterogeneity of repeatedly measured binary compliance status. Our motivation for this work comes from a comparison of the effect of two glucose-lowering medications on a clinical cohort of patients with type 2 diabetes. Here, we consider a causal inference problem assessing how well the two medications work relative to one another on two binary endpoint outcomes: cardiovascular disease-related hospitalization and all-cause mortality. Clinically, these glucose-lowering medications can have differential effects on the intermediate outcome, glucose level over time. Ultimately, we want to compare medication effects on the endpoint outcomes among individuals in the same glucose trajectory stratum while accounting for the heterogeneity in baseline covariates (i.e., to obtain 'principal effects' on the endpoint outcomes). The proposed method involves a three-step model estimation procedure. Step 1 identifies principal strata associated with the intermediate variable using hybrid growth mixture modeling analyses. Step 2 obtains the stratum membership using the pseudoclass technique and derives propensity scores for treatment assignment. Step 3 obtains the stratum-specific treatment effect on the endpoint outcome weighted by inverse propensity probabilities derived from Step 2.

  5. Causal inference in longitudinal comparative effectiveness studies with repeated measures of a continuous intermediate variable.

    PubMed

    Wang, Chen-Pin; Jo, Booil; Brown, C Hendricks

    2014-09-10

    We propose a principal stratification approach to assess causal effects in nonrandomized longitudinal comparative effectiveness studies with a binary endpoint outcome and repeated measures of a continuous intermediate variable. Our method is an extension of the principal stratification approach originally proposed for the longitudinal randomized study "Prevention of Suicide in Primary Care Elderly: Collaborative Trial" to assess the treatment effect on the continuous Hamilton depression score adjusting for the heterogeneity of repeatedly measured binary compliance status. Our motivation for this work comes from a comparison of the effect of two glucose-lowering medications on a clinical cohort of patients with type 2 diabetes. Here, we consider a causal inference problem assessing how well the two medications work relative to one another on two binary endpoint outcomes: cardiovascular disease-related hospitalization and all-cause mortality. Clinically, these glucose-lowering medications can have differential effects on the intermediate outcome, glucose level over time. Ultimately, we want to compare medication effects on the endpoint outcomes among individuals in the same glucose trajectory stratum while accounting for the heterogeneity in baseline covariates (i.e., to obtain 'principal effects' on the endpoint outcomes). The proposed method involves a three-step model estimation procedure. Step 1 identifies principal strata associated with the intermediate variable using hybrid growth mixture modeling analyses. Step 2 obtains the stratum membership using the pseudoclass technique and derives propensity scores for treatment assignment. Step 3 obtains the stratum-specific treatment effect on the endpoint outcome weighted by inverse propensity probabilities derived from Step 2. PMID:24577715

  6. Study on the validity of 3 × 3 Mueller matrix decomposition.

    PubMed

    Wang, Yunfei; Guo, Yihong; Zeng, Nan; Chen, Dongsheng; He, Honghui; Ma, Hui

    2015-06-01

    Using Monte Carlo simulations based on previously developed scattering models consisting of spherical and cylindrical scatterers imbedded in birefringent interstitial medium, we compare the polarization parameters extracted from the 3×3 and 4×4 Mueller matrix decomposition methods in forward and backward scattering directions. The results show that the parameters derived from the 3×3 Mueller matrix decomposition are usually not the same as those from the 4×4 Mueller matrix decomposition but display similar qualitative relations to changes in the microstructure of the sample, such as the density, size, and orientation distributions of the scatterers, and birefringence of the interstitial medium. The simulations are backed up by experiments when suitable samples are available. PMID:26039383

  7. Fundamental study of the austenite formation and decomposition in low-silicon, aluminum added TRIP steels

    NASA Astrophysics Data System (ADS)

    Garcia-Gonzalez, Jose Enrique

    2005-11-01

    TRIP (Transformation Induced Plasticity) steels are under development for automotive applications that require high strength and excellent formability. Conventional TRIP steels consist of a multiphase microstructure comprised of a ferrite matrix with a dispersion of bainite and metastable retained austenite. The high ductility exhibited by these steels results from the transformation of the metastable retained austenite to martensite during straining. In conventional TRIP steel processing, the multiphase microstructure is obtained by controlled cooling from the alpha + gamma region to an isothermal holding temperature. During this holding, bainite forms and carbon is rejected out into the austenite, which lowers the Ms temperature and stabilizes the austenite to room temperature. In this research project, a fundamental study of a low-Si, Mo-Nb added cold rolled TRIP steel with and without Al additions was conducted. In this study, the recrystallization of cold-rolled ferrite, the formation of austenite during intercritical annealing and the characteristics of the decomposition of the intercritically annealed austenite by controlled cooling rates were systematically assessed. Of special interest were: (i) the effect of the initial hot band microstructure, (ii) the formation of epitaxial ferrite during cooling from the intercritical annealing temperature to the isothermal holding temperature, (iii) the influence of the intercritically annealed austenite on the formation of bainite during the isothermal holding temperature, and (iv) the influence of the processing variables on the type, amount, composition and stability of the retained austenite. During this research study, techniques such as OM, SEM, EBSD, TEM, XRD and Magnetometry were used to fully characterize the microstructures. Furthermore, a Gleeble 3500 unit at US Steel Laboratories was used for dilatometry studies and to simulate different CGL processing routes, from which specimens were obtained to evaluate

  8. Puget Sound Dissolved Oxygen Modeling Study: Development of an Intermediate-Scale Hydrodynamic Model

    SciTech Connect

    Yang, Zhaoqing; Khangaonkar, Tarang; Labiosa, Rochelle G.; Kim, Taeyun

    2010-11-30

    The Washington State Department of Ecology contracted with Pacific Northwest National Laboratory to develop an intermediate-scale hydrodynamic and water quality model to study dissolved oxygen and nutrient dynamics in Puget Sound and to help define potential Puget Sound-wide nutrient management strategies and decisions. Specifically, the project is expected to help determine 1) if current and potential future nitrogen loadings from point and non-point sources are significantly impairing water quality at a large scale and 2) what level of nutrient reductions are necessary to reduce or dominate human impacts to dissolved oxygen levels in the sensitive areas. In this study, an intermediate-scale hydrodynamic model of Puget Sound was developed to simulate the hydrodynamics of Puget Sound and the Northwest Straits for the year 2006. The model was constructed using the unstructured Finite Volume Coastal Ocean Model. The overall model grid resolution within Puget Sound in its present configuration is about 880 m. The model was driven by tides, river inflows, and meteorological forcing (wind and net heat flux) and simulated tidal circulations, temperature, and salinity distributions in Puget Sound. The model was validated against observed data of water surface elevation, velocity, temperature, and salinity at various stations within the study domain. Model validation indicated that the model simulates tidal elevations and currents in Puget Sound well and reproduces the general patterns of the temperature and salinity distributions.

  9. Structure based aggregation studies reveal the presence of helix-rich intermediate during α-Synuclein aggregation

    PubMed Central

    Ghosh, Dhiman; Singh, Pradeep K.; Sahay, Shruti; Jha, Narendra Nath; Jacob, Reeba S.; Sen, Shamik; Kumar, Ashutosh; Riek, Roland; Maji, Samir K.

    2015-01-01

    Mechanistic understanding of nucleation dependent polymerization by α-synuclein (α-Syn) into toxic oligomers and amyloids is important for the drug development against Parkinson's disease. However the structural and morphological characterization during nucleation and subsequent fibrillation process of α-Syn is not clearly understood. Using a variety of complementary biophysical techniques monitoring entire pathway of nine different synucleins, we found that transition of unstructured conformation into β-sheet rich fibril formation involves helix-rich intermediates. These intermediates are common for all aggregating synucleins, contain high solvent-exposed hydrophobic surfaces, are cytotoxic to SHSY-5Y cells and accelerate α-Syn aggregation efficiently. A multidimensional NMR study characterizing the intermediate accompanied with site-specific fluorescence study suggests that the N-terminal and central portions mainly participate in the helix-rich intermediate formation while the C-terminus remained in an extended conformation. However, significant conformational transitions occur at the middle and at the C-terminus during helix to β-sheet transition as evident from Trp fluorescence study. Since partial helix-rich intermediates were also observed for other amyloidogenic proteins such as Aβ and IAPP, we hypothesize that this class of intermediates may be one of the important intermediates for amyloid formation pathway by many natively unstructured protein/peptides and represent a potential target for drug development against amyloid diseases. PMID:25784353

  10. Experimental Study of Wake Instabilities of a Blunt Trailing Edge Profiled Body at Intermediate Reynolds Numbers

    NASA Astrophysics Data System (ADS)

    Naghib-Lahouti, Arash; Lavoie, Philippe; Hangan, Horia

    2011-11-01

    The periodic shedding of von Kármán vortices is the primary instability in the wake of nominally 2D bluff bodies, beyond a critical Reynolds number around 45-49. When Reynolds number passes a second threshold, which can be as high as 700 depending on profile geometry, secondary instabilities emerge and accompany the von Kármán vortices. For most bluff bodies, these instabilities appear as pairs of counter-rotating streamwise vortices, and spanwise undulations of the von Kármán vortices. The mechanism and scale of these instabilities depend on the bluff body geometry and Reynolds number. The focus of the present study is to identify and characterize the dominant secondary instability in the wake of a blunt trailing edge profiled body at intermediate Reynolds numbers between 8,000 and 20,000 based on the body thickness. The experiments, which include PIV and hot-wire measurements in the wake, complement previous studies involving the same bluff body at higher and lower Reynolds numbers, and make it possible to determine the scale and mechanism of the secondary instability at intermediate Reynolds numbers. Funded partly by the Government of Ontario, MITACS and Bombardier Aerospace.

  11. Denaturation and intermediates study of two sturgeon hemoglobins by n-dodecyl trimethylammonium bromide.

    PubMed

    Ariaeenejad, Shohreh; Habibi-Rezaei, Mehran; Kavousi, Kaveh; Jamili, Shahla; Fatemi, Mohammad Reza; Hong, Jun; Poursasan, Najmeh; Sheibani, Nader; Moosavi-Movahedi, Ali A

    2013-02-01

    Varieties of hemoglobin (Hb) forms exist in fish, which are usually well adapted to the different ecological conditions or various habitats. In the current study, Hbs from two Sturgeon species of the Southern Caspian Sea Basin were purified and studied upon interaction with n-dodecyl trimethylammonium bromide (DTAB; as a cationic surfactant) by various methods including UV-visible absorption, dynamic light scattering (DLS), and ANS fluorescence spectrophotometry. The chemometric analysis of Hbs was investigated upon interaction with DTAB under titration, using UV-visible absorption spectra. The chemometric resolution techniques were used to determine the number of the components and mole fraction of the oxidized Hbs. These results provided the evidence for the existence of three different molecular components including native (N), intermediate (I) and denatured (D) in sturgeon Hbs. According to the distribution of intermediates, which were broadened in a range of DTAB concentration, the aggregation states, DLS experiments, and thermal stability (T(m) obtained by differential scanning calorimetry (DSC)), the Acipenser stellatus Hb was more stable compared to Acipenser persicus Hb. These results demonstrate a significant relationship between the stability of fish Hbs and the habitat depth requirements.

  12. Denaturation and intermediates study of two sturgeon hemoglobins by n-dodecyl trimethylammonium bromide

    PubMed Central

    Ariaeenejad, Shohreh; Habibi-Rezaei, Mehran; Kavousi, Kaveh; Jamili, Shahla; Fatemi, Mohammad Reza; Hong, Jun; Poursasan, Najmeh; Sheibani, Nader; Moosavi-Movahedi, Ali. A.

    2013-01-01

    Varieties of hemoglobin (Hb) forms exist in fish, which are usually well adapted to the different ecological conditions or various habitats. In the current study, Hbs from two Sturgeon species of the Southern Caspian Sea Basin were purified and studied upon interaction with n-dodecyl trimethylammonium bromide (DTAB; as a cationic surfactant) by various methods including UV-visible absorption, dynamic light scattering (DLS), and ANS fluorescence spectrophotometry. The chemometric analysis of Hbs was investigated upon interaction with DTAB under titration, using UV-visible absorption spectra. The chemometric resolution techniques were used to determine the number of the components and mole fraction of the oxidized Hbs. These results provided the evidence for the existence of three different molecular components including native (N), intermediate (I) and denatured (D) in sturgeon Hbs. According to the distribution of intermediates, which were broadened in a range of DTAB concentration, the aggregation states, DLS experiments, and thermal stability (Tm obtained by differential scanning calorimetry (DSC)), the Acipenser stellatus Hb was more stable compared to Acipenser persicus Hb. These results demonstrate a significant relationship between the stability of fish Hbs and the habitat depth requirements. PMID:23142155

  13. Impact of the uncertainties of the ISM when studying the IMF at intermediate masses

    NASA Astrophysics Data System (ADS)

    Mor, R.; Robin, A. C.; Lemasle, B.; Figueras, F.

    We evaluate the impact of the uncertainties in the 3D structure of the Interstellar Medium (ISM) when studying the Initial Mass Function (IMF) at intermediate masses using classical Galactic Cepheids. For that we use the Besan\\c{c}on Galaxy Model (BGM, \\citealt{Robin2003} and \\citealt{Czekaj2014}) and assume different IMFs and different interstellar structure maps to simulate magnitude limited samples of young intermediate mass stars. As our strategy to derive the IMF is based on star counts (in proceedings \\cite{Mor2015} and Mor et al. 2016 in prep.), we quantify the differences in star counts by comparing the whole-sky simulations with Tycho-2 catalogue up to V_T=11 and using Healpix maps. Moreover we compare simulations with different extinction models up to Gaia magnitude G=20. As expected, larger discrepancies between simulations and observations are found in the Galactic Plane, showing that the interstellar extinction in the plane is one of the major source of uncertainty in our study. We show how even with the uncertainties due to the ISM we are able to distinguish between different IMFs.

  14. Comparative Study of Magnetar Intermediate Flares and Recurrent Short Bursts from SGR1900+14

    NASA Astrophysics Data System (ADS)

    Ibrahim, Alaa I.

    2015-08-01

    We present a comparative study of 48 short recurrent bursts and intermediate flares from the soft gamma repeater SGR 1900+14 during its last major activity, observed by the Burst Alert Telescope (BAT) onboard NASA’s Swift Gamma-ray mission. This activity is distinguished by the emission of 10 rare long-duration, high-fluence intermediate flares (duration up to ~ 1.5 s, fluence ~ 2.9´10-6 - 1.6´10-5 erg cm-2), the largest observed from the source during a single period of activity, among 38 other recurrent short bursts (duration ~ 0.1 s, fluence ~ 0.8´10-8 - 0.9´10-6 erg cm-2). Comparing the two classes of bursts, we find the intermediate flares (IF) to show the following behaviors compared to the recurrent short bursts (R): (a) harder spectra G IF (0.50±0.01) < G R (1.46±0.04), kTBB S IF (5.60±0.04) > kTBB S R (4.33±0.03), with lower high-energy cut-off EC IF (15.98±0.52) < EC R (34.54±4.18) and comparable hard blackbody temperatures kTBB H IF (10.74±0.16) ~ kTBB H R (11.90±0.20) (b) larger blackbody radii RBB S IF (26.37±5.56) > RBB S R (17.26±2.04) and RBB H IF (6.13±0.12) > RBB H R (1.87±0.18) (c) less steep power-law indices in the RBB 2 vs. kTBB correlation in the hard temperature region (a H IF = - 2.10 ± 0.60 vs. a H R = - 4.26 ± 0.90) with comparable indices in the soft temperature region (a S IF = - 2.04 ± 0.24 vs. a S R = - 2.00 ± 0.44); and finally (d) steeper power-law index in the blackbody hard-soft luminosity correlation (b IF = 0.85±0.20 vs. b R = 0.71±0.04). These spectral differences are further confirmed by and reflected in the joint spectra of the intermediate flares and recurrent bursts. Furthermore, we find that while intermediate flares and recurrent bursts may overlap in the duration range, they have non-overlapping fluence ranges, and their positive duration-fluence correlation is comparable. We also compare the observed intermediate flares with five others detected from the source during 1998 - 2001 as well as those

  15. Density Functional Theory Study of Selectivity Considerations for C–C Versus C–O Bond Scission in Glycerol Decomposition on Pt(111)

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey

    2012-05-01

    Glycerol decomposition via a combination of dehydrogenation, C–C bond scission, and C–O bond scission reactions is examined on Pt(111) with periodic Density Functional Theory (DFT) calculations. Building upon a previous study focused on C–C bond scission in glycerol, the current work presents a first analysis of the competition between C–O and C–C bond cleavage in this reaction network. The thermochemistry of various species produced from C–O bond breaking in glycerol dehydrogenation intermediates is estimated using an extension of a previously introduced empirical correlation scheme, with parameters fit to DFT calculations. Brønsted–Evans–Polanyi (BEP) relationships are then used to estimate the kinetics of C–O bond breaking. When combined with the previous results, the thermochemical and kinetic analyses imply that, while C–O bond scission may be competitive with C–C bond scission during the early stages of glycerol dehydrogenation, the overall rates are likely to be very low. Later in the dehydrogenation process, where rates will be much higher, transition states for C–C bond scission involving decarbonylation are much lower in energy than are the corresponding transition states for C–O bond breaking, implying that the selectivity for C–C scission will be high for glycerol decomposition on smooth platinum surfaces. Finally, it is anticipated that the correlation schemes described in this work will provide an efficient strategy for estimating thermochemical and kinetic energetics for a variety of elementary bond breaking processes on Pt(111) and may ultimately facilitate computational catalyst design for these and related catalytic processes.

  16. The Products of the Thermal Decomposition of CH3CHO

    SciTech Connect

    Vasiliou, AnGayle; Piech, Krzysztof M.; Zhang, Xu; Nimlos, Mark R.; Ahmed, Musahid; Golan, Amir; Kostko, Oleg; Osborn, David L.; Daily, John W.; Stanton, John F.; Ellison, G. Barney

    2011-04-06

    We have used a heated 2 cm x 1 mm SiC microtubular (mu tubular) reactor to decompose acetaldehyde: CH3CHO + DELTA --> products. Thermal decomposition is followed at pressures of 75 - 150 Torr and at temperatures up to 1700 K, conditions that correspond to residence times of roughly 50 - 100 mu sec in the mu tubular reactor. The acetaldehyde decomposition products are identified by two independent techniques: VUV photoionization mass spectroscopy (PIMS) and infrared (IR) absorption spectroscopy after isolation in a cryogenic matrix. Besides CH3CHO, we have studied three isotopologues, CH3CDO, CD3CHO, and CD3CDO. We have identified the thermal decomposition products CH3(PIMS), CO (IR, PIMS), H (PIMS), H2 (PIMS), CH2CO (IR, PIMS), CH2=CHOH (IR, PIMS), H2O (IR, PIMS), and HC=CH (IR, PIMS). Plausible evidence has been found to support the idea that there are at least three different thermal decomposition pathways for CH3CHO: Radical decomposition: CH3CHO + DELTA --> CH3 + [HCO] --> CH3 + H + CO Elimination: CH3CHO + DELTA --> H2 + CH2=C=O. Isomerization/elimination: CH3CHO + DELTA --> [CH2=CH-OH] --> HC=CH + H2O. Both PIMS and IR spectroscopy show compelling evidence for the participation of vinylidene, CH2=C:, as an intermediate in the decomposition of vinyl alchohol: CH2=CH-OH + DELTA --> [CH2=C:] + H2O --> HC=CH + H2O.

  17. Woodland Decomposition.

    ERIC Educational Resources Information Center

    Napier, J.

    1988-01-01

    Outlines the role of the main organisms involved in woodland decomposition and discusses some of the variables affecting the rate of nutrient cycling. Suggests practical work that may be of value to high school students either as standard practice or long-term projects. (CW)

  18. A study of the process of nonisothermal decomposition of phenolformaldehyde polymers by differential thermal analysis

    SciTech Connect

    Petrova, O.M.; Fedoseev, S.D.; Komarova, T.V.

    1984-01-01

    A calculation has been made of the activation energy of the thermal decomposition of phenol-formaldehyde polymers. It has been established that for nonisothermal conditions the rate of performance of the process does not affect the effective activation energy calculated by means of Piloyan's equation.

  19. Peat decomposition - shaping factors, significance in environmental studies and methods of determination; a literature review

    NASA Astrophysics Data System (ADS)

    Drzymulska, Danuta

    2016-03-01

    A review of literature data on the degree of peat decomposition - an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.

  20. The Feasibility of Using Hydrogen Peroxide Decomposition Studies for High School Chemistry.

    ERIC Educational Resources Information Center

    Carter, Gillian E.

    1986-01-01

    Highlights difficulties that occur when teachers attempt to devise new experiments (use of hydrogen peroxide decomposition) and how seemingly useless results can be turned into productive student projects. Considers effects of ions present in tap water, pH, dust, and nature of vessel's surface. Reaction order and safety precautions are noted. (JN)

  1. Using Xenopus Embryos to Study Transcriptional and Posttranscriptional Gene Regulatory Mechanisms of Intermediate Filaments.

    PubMed

    Wang, Chen; Szaro, Ben G

    2016-01-01

    Intermediate filament genes exhibit highly regulated, tissue-specific patterns of expression during development and in response to injury. Identifying the responsible cis-regulatory gene elements thus holds great promise for revealing insights into fundamental gene regulatory mechanisms controlling tissue differentiation and repair. Because much of this regulation occurs in response to signals from surrounding cells, characterizing them requires a model system in which their activity can be tested within the context of an intact organism conveniently. We describe methods for doing so by injecting plasmid DNAs into fertilized Xenopus embryos. A prokaryotic element for site-specific recombination and two dual HS4 insulator elements flanking the reporter gene promote penetrant, promoter-typic expression that persists through early swimming tadpole stages, permitting the observation of fluorescent reporter protein expression in live embryos. In addition to describing cloning strategies for generating these plasmids, we present methods for coinjecting test and reference plasmids to identify the best embryos for analysis, for analyzing reporter protein and RNA expression, and for characterizing the trafficking of expressed reporter RNAs from the nucleus to polysomes. Thus, this system can be used to study the activities of cis-regulatory elements of intermediate filament genes at multiple levels of transcriptional and posttranscriptional control within an intact vertebrate embryo, from early stages of embryogenesis through later stages of organogenesis and tissue differentiation.

  2. Adsorption and thermal decomposition of benzene on Ni(110) studied by chemical, spectroscopic, and computational methods

    SciTech Connect

    Huntley, D.R.; Jordan, S.L.; Grimm, F.A.

    1992-02-06

    The chemisorption and reactions of benzene on Ni(110) have been studied by temperature-programmed desorption (TPD) including isotopic labeling, X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), and low-energy electron diffraction (LEED) as a function of coverage and adsorption temperature between 100 and 300 K. At saturation, 70-80% of the benzene is irreversibly chemisorbed, and C-H bond scission commences at 320 K. For high exposures, molecular desorption competes with decomposition. A c(4x2) LEED patterns is observed at saturation coverage of chemisorbed benzene (0.2 monolayer by XPS). HREEL spectroscopy indicates that the benzene ring lies parallel to the surface. Semiempirical molecular orbital calculations have been made and predict the most likely adsorption site for benzene chemisorption to be the atop site at a height of about 1.75 {angstrom} or the short bridge site at 1.90 {angstrom}. Upon annealing above 300 K, the benzene decomposes, evolving H{sub 2} and forming a surface carbide. Additionally, a species forms which ultimately desorbs as benzene at 460 K but also undergoes H-D exchange with benzene-d{sub 6}. An unambiguous identification of this fragment has not been made, but the vibrational spectroscopy and isotopic exchange data are consistent with the assignment of a phenyl or benzyne group. The major effects of coadsorbed sulfur and oxygen are to inhibit dissociation and to weaken the interaction between the benzene and the surface. 41 refs., 12 figs., 3 tabs.

  3. Scattering studies of self-assembling processes of polymer blends in spinodal decomposition. II. Temperature dependence

    NASA Astrophysics Data System (ADS)

    Takenaka, Mikihito; Hashimoto, Takeji

    1992-04-01

    Our previous work on time evolution of the interfacial structure for a near critical mixture of polybutadiene and polyisoprene undergoing the spinodal decomposition (SD) [T. Hashimoto, M. Takenaka, and H. Jinnai, J. Appl. Crystallogr. 24, 457 (1991)] was extended to explore the behavior as a function of temperature T, again using the time-resolved light scattering method. The study involved the investigation of the time evolutions of various characteristic parameters such as the wave number qm(t;T ) of the dominant mode of the concentration fluctuations, the maximum scattered intensity Im(t;T ), the scaled structure factor F(x;T ), the interfacial area density Σ(t;T ), and the characteristic interfacial thickness tI(t;T ) from the early-to-late stage SD, where t refers to time after the onset of SD and x refers to the reduced scattering vector defined by x=q/qm(t;T ); q is the magnitude of the scattering vector. The results confirm the model previously proposed at a given T over a wider temperature range corresponding to the quench depth ΔT=T-Ts =5.5-34.5 K, or ɛT=(χ-χs)/χs =4.50×10-2 to 2.79×10-1, where Ts is the spinodal temperature, and χ and χs are the Flory interaction parameters at T and Ts, respectively. This blend is noted to have a phase diagram of the lower critical solution temperature type.

  4. Thermal decomposition of CH3CHO studied by matrix infrared spectroscopy and photoionization mass spectroscopy.

    PubMed

    Vasiliou, AnGayle K; Piech, Krzysztof M; Reed, Beth; Zhang, Xu; Nimlos, Mark R; Ahmed, Musahid; Golan, Amir; Kostko, Oleg; Osborn, David L; David, Donald E; Urness, Kimberly N; Daily, John W; Stanton, John F; Ellison, G Barney

    2012-10-28

    A heated SiC microtubular reactor has been used to decompose acetaldehyde and its isotopomers (CH(3)CDO, CD(3)CHO, and CD(3)CDO). The pyrolysis experiments are carried out by passing a dilute mixture of acetaldehyde (roughly 0.1%-1%) entrained in a stream of a buffer gas (either He or Ar) through a heated SiC reactor that is 2-3 cm long and 1 mm in diameter. Typical pressures in the reactor are 50-200 Torr with the SiC tube wall temperature in the range 1200-1900 K. Characteristic residence times in the reactor are 50-200 μs after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 μTorr. The reactor has been modified so that both pulsed and continuous modes can be studied, and results from both flow regimes are presented. Using various detection methods (Fourier transform infrared spectroscopy and both fixed wavelength and tunable synchrotron radiation photoionization mass spectrometry), a number of products formed at early pyrolysis times (roughly 100-200 μs) are identified: H, H(2), CH(3), CO, CH(2)=CHOH, HC≡CH, H(2)O, and CH(2)=C=O; trace quantities of other species are also observed in some of the experiments. Pyrolysis of rare isotopomers of acetaldehyde produces characteristic isotopic signatures in the reaction products, which offers insight into reaction mechanisms that occur in the reactor. In particular, while the principal unimolecular processes appear to be radical decomposition CH(3)CHO (+M) → CH(3) + H + CO and isomerization of acetaldehyde to vinyl alcohol, it appears that the CH(2)CO and HCCH are formed (perhaps exclusively) by bimolecular reactions, especially those involving hydrogen atom attacks. PMID:23126711

  5. Thermal Decomposition of NCN: Shock-Tube Study, Quantum Chemical Calculations, and Master-Equation Modeling.

    PubMed

    Busch, Anna; González-García, Núria; Lendvay, György; Olzmann, Matthias

    2015-07-16

    The thermal decomposition of cyanonitrene, NCN, was studied behind reflected shock waves in the temperature range 1790-2960 K at pressures near 1 and 4 bar. Highly diluted mixtures of NCN3 in argon were shock-heated to produce NCN, and concentration-time profiles of C atoms as reaction product were monitored with atomic resonance absorption spectroscopy at 156.1 nm. Calibration was performed with methane pyrolysis experiments. Rate coefficients for the reaction (3)NCN + M → (3)C + N2 + M (R1) were determined from the initial slopes of the C atom concentration-time profiles. Reaction R1 was found to be in the low-pressure regime at the conditions of the experiments. The temperature dependence of the bimolecular rate coefficient can be expressed with the following Arrhenius equation: k1(bim) = (4.2 ± 2.1) × 10(14) exp[-242.3 kJ mol(-1)/(RT)] cm(3) mol(-1) s(-1). The rate coefficients were analyzed by using a master equation with specific rate coefficients from RRKM theory. The necessary molecular data and energies were calculated with quantum chemical methods up to the CCSD(T)/CBS//CCSD/cc-pVTZ level of theory. From the topography of the potential energy surface, it follows that reaction R1 proceeds via isomerization of NCN to CNN and subsequent C-N bond fission along a collinear reaction coordinate without a tight transition state. The calculations reproduce the magnitude and temperature dependence of the rate coefficient and confirm that reaction R1 is in the low-pressure regime under our experimental conditions.

  6. Ab initio kinetics of gas phase decomposition reactions.

    PubMed

    Sharia, Onise; Kuklja, Maija M

    2010-12-01

    The thermal and kinetic aspects of gas phase decomposition reactions can be extremely complex due to a large number of parameters, a variety of possible intermediates, and an overlap in thermal decomposition traces. The experimental determination of the activation energies is particularly difficult when several possible reaction pathways coexist in the thermal decomposition. Ab initio calculations intended to provide an interpretation of the experiment are often of little help if they produce only the activation barriers and ignore the kinetics of the decomposition process. To overcome this ambiguity, a theoretical study of a complete picture of gas phase thermo-decomposition, including reaction energies, activation barriers, and reaction rates, is illustrated with the example of the β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) molecule by means of quantum-chemical calculations. We study three types of major decomposition reactions characteristic of nitramines: the HONO elimination, the NONO rearrangement, and the N-NO(2) homolysis. The reaction rates were determined using the conventional transition state theory for the HONO and NONO decompositions and the variational transition state theory for the N-NO(2) homolysis. Our calculations show that the HMX decomposition process is more complex than it was previously believed to be and is defined by a combination of reactions at any given temperature. At all temperatures, the direct N-NO(2) homolysis prevails with the activation barrier at 38.1 kcal/mol. The nitro-nitrite isomerization and the HONO elimination, with the activation barriers at 46.3 and 39.4 kcal/mol, respectively, are slow reactions at all temperatures. The obtained conclusions provide a consistent interpretation for the reported experimental data. PMID:21077597

  7. FTIR/TDS studies of reaction paths and surface intermediates following multilayer adsorption of formamide on Ni(111)

    SciTech Connect

    Gao, Quanyin; Hemminger, J.C. ); Erley, W.; Sander, D.; Ibach, H. )

    1991-01-10

    The adsorption and reaction of HCONH{sub 2} and HCOND{sub 2} molecules on Ni(111) were studied following initial multilayer exposures with thermal desorption spectroscopy (TDS) and reflection absorption infrared spectroscopy (RAIR). At 90 K, formamide molecules (HCONH{sub 2}) adsorb on Ni(111) forming multilayers. Three molecular desorption peaks were observed at 160, 170, and 190 K, respectively. Heating this system to above 220 K leads to the decomposition of formamide molecules. Two parallel decomposition paths were observed. One path leads to the production of NH{sub 3}, H{sub 2}, and CO. The other path, which is first reported here, gives HNCO and H{sub 2}. Possible surface precursors for the two decomposition paths are discussed. The temperature-dependent RAIR spectra indicated that ammonia (NH{sub 3(a)}) was formed at about 230 K, isocyanic acid (HNCO{sub (a)}) at about 285 K, and CO at about 285 K. The observed desorption temperature from TDS are 260 K for ammonia (NH{sub 3}) 325 K for isocyanic acid (HNCO), 340 K for hydrogen (H{sub 2}), and 410 K for carbon monoxide (CO). The competing route for formamide decomposition that leads to HNCO production on Ni(111) has not been reported on other transition-metal substrates.

  8. Ammonia decomposition catalysis using lithium-calcium imide.

    PubMed

    Makepeace, Joshua W; Hunter, Hazel M A; Wood, Thomas J; Smith, Ronald I; Murray, Claire A; David, William I F

    2016-07-01

    Lithium-calcium imide is explored as a catalyst for the decomposition of ammonia. It shows the highest ammonia decomposition activity yet reported for a pure light metal amide or imide, comparable to lithium imide-amide at high temperature, with superior conversion observed at lower temperatures. Importantly, the post-reaction mass recovery of lithium-calcium imide is almost complete, indicating that it may be easier to contain than the other amide-imide catalysts reported to date. The basis of this improved recovery is that the catalyst is, at least partially, solid across the temperature range studied under ammonia flow. However, lithium-calcium imide itself is only stable at low and high temperatures under ammonia, with in situ powder diffraction showing the decomposition of the catalyst to lithium amide-imide and calcium imide at intermediate temperatures of 200-460 °C. PMID:27092374

  9. A kinetic study on decomposition of proton-bound dimer using data obtained by ion mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Jazan, Elham; Ghazali Khoob, Abdolhosein S.

    2014-08-01

    In this study, an equation for measuring the rate constant of the proton-bound dimer decomposition reaction was derived using the data obtained by ion mobility spectrometry (IMS) technique. The ion mobility spectra of cyclohexanone (as the test compound) were obtained at various temperatures and different electric fields. The applied electric field for each temperature was varied between 375 and 500 V cm-1 and the rate constant values of 188.24, 180.54, 280.64, 288.34 and 379.60 s-1 were obtained at different temperatures of 463, 468, 473, 478 and 483 K, respectively. Subsequently, the activation energy and pre-exponential factor were calculated to be 69.5 kJ mol-1 and 1.2 × 1010 s-1, respectively. In addition, the standard enthalpy changes were calculated for the dimer decomposition reaction of cyclohexanone at the above-mentioned temperatures.

  10. Image processing using proper orthogonal and dynamic mode decompositions for the study of cavitation developing on a NACA0015 foil

    NASA Astrophysics Data System (ADS)

    Prothin, Sebastien; Billard, Jean-Yves; Djeridi, Henda

    2016-10-01

    The purpose of the present study is to get a better understanding of the hydrodynamic instabilities of sheet cavities which develop along solid walls. The main objective is to highlight the spatial and temporal behavior of such a cavity when it develops on a NACA0015 foil at high Reynolds number. Experimental results show a quasi-steady, periodic, bifurcation domain, with aperiodic cavity behavior corresponding to σ/2 α values of 5.75, 5, 4.3 and 3.58. Robust mathematical methods of signal postprocessing (proper orthogonal decomposition and dynamic mode decomposition) were applied in order to emphasize the spatio-temporal nature of the flow. These new techniques put in evidence the 3D effects due to the reentrant jet instabilities or due to propagating shock wave mechanism at the origin of the shedding process of the cavitation cloud.

  11. Nanostructured copper, chromium, and tin oxide multicomponent materials as catalysts for methanol decomposition: 11C-radiolabeling study.

    PubMed

    Tsoncheva, Tanya; Sarkadi-Priboczki, Eva; Dimitrov, Momtchil; Genova, Izabela

    2013-01-01

    Copper and chromium modified tin oxide nanocomposites were obtained via incipient wetness impregnation of high surface area nanosized SnO(2) with the corresponding metal acetylacetonates and their further decomposition in air. Powder X-ray diffraction (XRD), Nitrogen physisorption, UV-Vis, and Temperature-programmed reduction (TPR) with hydrogen were applied for the samples characterization. The catalytic activity of the obtained materials was tested in methanol conversion. A new approach based on the selective coverage of the surface with (11)C-methanol was used for the characterization of the catalytic sites. It was demonstrated that the products distribution could be controlled by the surface coverage with methanol and the role of different active sites was discussed. The modification of SnO(2) with copper oxide increased the activity in methanol decomposition to CO(2)via dioxymethylene intermediates, but the catalyst suffered considerable loss of activity due to the reduction transformations by the reaction medium and formation of an inactive intermetallic alloy. The modification with chromium changed the acid-basic properties of SnO(2) by the formation of Cr(2)O(3) nanoparticles as well as anchored to the support chromate species. The former particles facilitated the formation of dimethyl ether (DME), while the latter species converted methanol predominantly to hydrocarbons. The fraction of chromate species increased in Cu-Cr-Sn oxide multicomponent nanocomposites and promoted the formation of hydrocarbons over DME at low temperatures, while at higher temperatures, the activity of the copper species leading to CO(2) formation was more pronounced. PMID:23031492

  12. Comparative study of ECG signal denoising by wavelet thresholding in empirical and variational mode decomposition domains.

    PubMed

    Lahmiri, Salim

    2014-09-01

    Hybrid denoising models based on combining empirical mode decomposition (EMD) and discrete wavelet transform (DWT) were found to be effective in removing additive Gaussian noise from electrocardiogram (ECG) signals. Recently, variational mode decomposition (VMD) has been proposed as a multiresolution technique that overcomes some of the limits of the EMD. Two ECG denoising approaches are compared. The first is based on denoising in the EMD domain by DWT thresholding, whereas the second is based on noise reduction in the VMD domain by DWT thresholding. Using signal-to-noise ratio and mean of squared errors as performance measures, simulation results show that the VMD-DWT approach outperforms the conventional EMD-DWT. In addition, a non-local means approach used as a reference technique provides better results than the VMD-DWT approach. PMID:26609387

  13. Phase decomposition and ordering in Ni-11.3 at.% Ti studied with atom probe tomography.

    PubMed

    Al-Kassab, T; Kompatscher, M; Kirchheim, R; Kostorz, G; Schönfeld, B

    2014-09-01

    The decomposition behavior of Ni-rich Ni-Ti was reassessed using Tomographic Atom Probe (TAP) and Laser Assisted Wide Angle Tomographic Atom Probe. Single crystalline specimens of Ni-11.3 at.% Ti were investigated, the states selected from the decomposition path were the metastable γ″ and γ' states introduced on the basis of small-angle neutron scattering (SANS) and the two-phase model for evaluation. The composition values of the precipitates in these states could not be confirmed by APT data as the interface of the ordered precipitates may not be neglected. The present results rather suggest to apply a three-phase model for the interpretation of SANS measurements, in which the width of the interface remains nearly unchanged and the L12 structure close to 3:1 stoichiometry is maintained in the core of the precipitates from the γ″ to the γ' state.

  14. Comparative study of the dynamics of lipid membrane phase decomposition in experiment and simulation.

    PubMed

    Burger, Stefan; Fraunholz, Thomas; Leirer, Christian; Hoppe, Ronald H W; Wixforth, Achim; Peter, Malte A; Franke, Thomas

    2013-06-25

    Phase decomposition in lipid membranes has been the subject of numerous investigations by both experiment and theoretical simulation, yet quantitative comparisons of the simulated data to the experimental results are rare. In this work, we present a novel way of comparing the temporal development of liquid-ordered domains obtained from numerically solving the Cahn-Hilliard equation and by inducing a phase transition in giant unilamellar vesicles (GUVs). Quantitative comparison is done by calculating the structure factor of the domain pattern. It turns out that the decomposition takes place in three distinct regimes in both experiment and simulation. These regimes are characterized by different rates of growth of the mean domain diameter, and there is quantitative agreement between experiment and simulation as to the duration of each regime and the absolute rate of growth in each regime. PMID:23713610

  15. A domain decomposition study of massively parallel computing in compressible gas dynamics

    SciTech Connect

    Wong, C.C.; Blottner, F.G.; Payne, J.L.; Soetrisno, M.

    1995-01-01

    The appropriate utilization of massively parallel computers for solving the Navier-Stokes equations is investigated and determined from an engineering perspective. The issues investigated are: (1) Should strip or patch domain decomposition of the spatial mesh be used to reduce computer time? (2) How many computer nodes should be used for a problem with a given sized mesh to reduce computer time? (3) Is the convergence of the Navier-Stokes solution procedure (LU-SGS) adversely influenced by the domain decomposition approach? The results of the paper show that the present Navier-Stokes solution technique has good performance on a massively parallel computer for transient flow problems. For steady-state problems with a large number of mesh cells, the solution procedure will require significant computer time due to an increased number of iterations to achieve a converged solution. There is an optimum number of computer nodes to use for a problem with a given global mesh size.

  16. Theoretical Study of Decomposition Pathways for HArF and HKrF

    NASA Technical Reports Server (NTRS)

    Chaban, Galina M.; Lundell, Jan; Gerber, R. Benny; Kwak, Donchan (Technical Monitor)

    2002-01-01

    To provide theoretical insights into the stability and dynamics of the new rare gas compounds HArF and HKrF, reaction paths for decomposition processes HRgF to Rg + HF and HRgF to H + Rg + F (Rg = Ar, Kr) are calculated using ab initio electronic structure methods. The bending channels, HRgF to Rg + HF, are described by single-configurational MP2 and CCSD(T) electronic structure methods, while the linear decomposition paths, HRgF to H + Rg + F, require the use of multi-configurational wave functions that include dynamic correlation and are size extensive. HArF and HKrF molecules are found to be energetically stable with respect to atomic dissociation products (H + Rg + F) and separated by substantial energy barriers from Rg + HF products, which ensure their kinetic stability. The results are compatible with experimental data on these systems.

  17. 11C-radiolabeling study of methanol decomposition on copper oxide modified mesoporous SBA-15 silica

    NASA Astrophysics Data System (ADS)

    Tsoncheva, Tanya; Sarkadi-Priboczki, Eva

    2011-05-01

    11C-radiolabeling technique is applied to investigate methanol decomposition on copper oxide modified SBA-15. Nitrogen physisorption, XRD, FTIR, UV-vis and TPR techniques are used for catalyst characterization. Selective adsorption coverage of the catalytic active sites with 11C- and 12C-methanol molecules is carried out and the products of their conversion are followed. The mechanism of methyl formate, methylal and CO 2 formation from methanol is discussed.

  18. Thermodynamic and Kinetic Studies for Intensifying Selective Decomposition of Zinc Ferrite

    NASA Astrophysics Data System (ADS)

    Han, Junwei; Liu, Wei; Qin, Wenqing; Jiao, Fen; Wang, Dawei; Liang, Chao

    2016-01-01

    A novel method to intensify the selective decomposition of zinc ferrite by a roasting process including reduction and magnetization stages was proposed. The relevant thermodynamic analysis with HSC [enthalpy (H), entropy (S) and heat capacity (C)] Chemistry 5.0 and experimental research on a laboratory scale were investigated. The thermodynamic calculations show that increasing the temperature and the CO amount promote not only the decomposition of zinc ferrite but also the formation of wustite, which can be converted to magnetite using sufficient CO2 at 823 K. The experimental results indicate that the zinc ferrite was decomposed into zinc oxide and wustite by reduction roasting under a gas mixture of 20% CO, 20% CO2 and 60% N2 at 1023 K for 90 min, and the decomposition degree of zinc ferrite reached 94%. Then, the generated wustite was transformed into magnetite by magnetization roasting under CO2 atmosphere at 823 K for 75 min, after which the selective extraction of zinc from zinc ferrite could be well achieved by low acid leaching. Increasing temperature and time were conducive to the magnetization within low temperature range, but when the temperature was above 823 K the zinc ferrite could be regenerated.

  19. Ozonolysis of fluoroethene: theoretical study of unimolecular decomposition paths of primary and secondary fluorozonide.

    PubMed

    Ljubić, Ivan; Sabljić, Aleksandar

    2005-03-17

    A theoretical investigation into unimolecular decomposition paths of primary (POZF) and secondary (SOZF) fluorozonide was carried out by utilizing the multiconfigurational CASSCF/cc-pVTZ level in optimizations of the stationary points and calculations of the harmonic vibrational frequencies. The dynamical electron correlation was accounted for via the multireference CASPT2/cc-pVTZ treatment based on the zeroth-order CASSCF/cc-pVTZ reference. The CASPT2 was substituted with the CCSD(T)/6-311G(2d,2p) correction whenever the former resulted in negative activation barriers. The most favorable decomposition route of POZF is a concerted cleavage to carbonyl oxide (CO) and formyl fluoride (FF) with fragments in the anti conformation, with regard to the orientation of the terminal oxygen in the carbonyl oxide and the flourine atom of the carbonyl compound. The ratio of unimolecular rate constants calculated within the RRKM formalism suggests that the CO-FF channel of cleavage amounts to 98%, which agrees well with the upper bound of experimental esimates. The SOZF decomposition most readily takes place in a stepwise manner initiated by the O-O bond rupture. Two conformational minima are exhibited by SOZF, the O-O and H(2)C-O half-chairs. The calculated rotational constants and scaled frequencies for the O-O half-chair are in good agreement with the experimental values. PMID:16839009

  20. Methylamine adsorption and decomposition on B12N12 nanocage: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Nurazar, Roghaye

    2014-08-01

    Density functional theory calculations are performed to investigate the adsorption and decomposition of methylamine (CH3NH2) on the surface of a B12N12 fullerene-like nanocage. Two adsorption types and two reaction channels are identified. It is found that the electrical conductivity of the nanocage can be modified upon the adsorption of CH3NH2. The pathways of CH3NH2 decomposition via bond scission of the Csbnd N and Nsbnd H bonds are examined. The results indicate that Nsbnd H bond scission is the most favorable pathway on the B12N12 surface. The side reaction that generates CH3 and NH2 fragments is endothermic by 15.6 kcal/mol with an energy-barrier height of 81.5 kcal/mol. For the CH3NH2 decomposition on the B12N12 surface, the rate-determining step appears to be as the following reaction: CH3NH → CH3N + H.

  1. A DFT study of the unimolecular decomposition of 1,2,4-butanetriol trinitrate.

    PubMed

    Zhu, Weihua; Yan, Qingli; Pang, Aimin; Chi, Xuehui; Du, Xijuan; Xiao, Heming

    2014-02-01

    To improve understanding of the unimolecular decomposition mechanism of 1,2,4-butanetriol trinitrate (BTTN) in the gas phase, density functional theory calculations were performed to determine various decomposition pathways at the B3LYP/6-311G** level. Two main mechanisms for the unimolecular decomposition of BTTN were found. In the first, homolysis of one of the O-NO2 bonds occurs to form •NO2 and CH2ONO2CHONO2CH2CH2O•, which subsequently decomposes to form CH3CHO + •CHO + 3NO2 + HCHO. In the second, successive HONO elimination reactions yield three HONO and OHCCH2CHONO2CH2ONO2 fragments, which subsequently decompose to form CH3CHO + 2CO + 3HONO. We also found that the first pathway has a slightly lower activation energy than the second. The results show that the pathway involving O-NO2 cleavage is slightly more energetically favorable than that involving HONO elimination.

  2. Theoretical study of the decomposition of formamide in the presence of water molecules.

    PubMed

    Nguyen, Vinh Son; Orlando, Thomas M; Leszczynski, Jerzy; Nguyen, Minh Tho

    2013-03-28

    Formamide (NH2CHO, FM) has been considered an active key precursor in prebiotic chemistry on early Earth. Under certain conditions such as dry lagoons, FM can decompose to produce reactants that lead to formation of more complex biomolecules. Specifically, FM decomposition follows many reactive channels producing small molecules such as H2, CO, H2O, HCN, HNC, NH3, and HNCO with comparable energy barriers in the range of 73-82 kcal/mol. Due to the likely presence of water on prebiotic Earth and the intrinsic presence of water following FM decomposition, we explore the effects of water oligomers, (H2O)n with n = 1-3, on its dehydration, dehydrogenation, and decarbonylation reactions using quantum chemical computations. Geometries are optimized using MP2/aug-cc-pVxZ calculations (x = D,T), and relative energies are evaluated using coupled-cluster theory CCSD(T) with the aug-cc-pVxZ basis sets (x = D, T, Q). Where possible the coupled-cluster energies are extrapolated to the complete basis set limit (CBS). Water classically acts as an efficient bifunctional catalyst for decomposition. With the presence of one water molecule, the dehydration pathway leading to HCN is favored. When two and three water molecules are involved, dehydration remains energetically favored over other channels and attains an energy barrier of ~30 kcal/mol. PMID:23461351

  3. Thermodynamic and Kinetic Studies for Intensifying Selective Decomposition of Zinc Ferrite

    NASA Astrophysics Data System (ADS)

    Han, Junwei; Liu, Wei; Qin, Wenqing; Jiao, Fen; Wang, Dawei; Liang, Chao

    2016-09-01

    A novel method to intensify the selective decomposition of zinc ferrite by a roasting process including reduction and magnetization stages was proposed. The relevant thermodynamic analysis with HSC [enthalpy (H), entropy (S) and heat capacity (C)] Chemistry 5.0 and experimental research on a laboratory scale were investigated. The thermodynamic calculations show that increasing the temperature and the CO amount promote not only the decomposition of zinc ferrite but also the formation of wustite, which can be converted to magnetite using sufficient CO2 at 823 K. The experimental results indicate that the zinc ferrite was decomposed into zinc oxide and wustite by reduction roasting under a gas mixture of 20% CO, 20% CO2 and 60% N2 at 1023 K for 90 min, and the decomposition degree of zinc ferrite reached 94%. Then, the generated wustite was transformed into magnetite by magnetization roasting under CO2 atmosphere at 823 K for 75 min, after which the selective extraction of zinc from zinc ferrite could be well achieved by low acid leaching. Increasing temperature and time were conducive to the magnetization within low temperature range, but when the temperature was above 823 K the zinc ferrite could be regenerated.

  4. Shock wave and modeling study of the thermal decomposition reactions of pentafluoroethane and 2-H-heptafluoropropane.

    PubMed

    Cobos, C J; Sölter, L; Tellbach, E; Troe, J

    2014-06-01

    The thermal decomposition reactions of CF3CF2H and CF3CFHCF3 have been studied in shock waves by monitoring the appearance of CF2 radicals. Temperatures in the range 1400-2000 K and Ar bath gas concentrations in the range (2-10) × 10(-5) mol cm(-3) were employed. It is shown that the reactions are initiated by C-C bond fission and not by HF elimination. Differing conclusions in the literature about the primary decomposition products, such as deduced from experiments at very low pressures, are attributed to unimolecular falloff effects. By increasing the initial reactant concentrations in Ar from 60 to 1000 ppm, a retardation of CF2 formation was observed while the final CF2 yields remained close to two CF2 per C2F5H or three CF2 per C3F7H decomposed. This is explained by secondary bimolecular reactions which lead to comparably stable transient species like CF3H, releasing CF2 at a slower rate. Quantum-chemical calculations and kinetic modeling help to identify the reaction pathways and provide estimates of rate constants for a series of primary and secondary reactions in the decomposition mechanism.

  5. In situ ESEM study of the thermal decomposition of chrysotile asbestos in view of safe recycling of the transformation product.

    PubMed

    Gualtieri, Alessandro F; Gualtieri, Magdalena Lassinantti; Tonelli, Massimo

    2008-08-15

    The thermal transformation of asbestos into non-hazardous crystalline phases and their recycling is a promising solution for the "asbestos problem". The most common asbestos-containing industrial material produced worldwide is cement-asbestos. Knowledge of the kinetics of thermal transformation of asbestos fibers in cement-asbestos is of paramount importance for the optimization of the firing process at industrial scale. Here, environmental scanning electron microscopy (ESEM) was used for the first time to follow in situ the thermal transformation of chrysotile fibers present in cement-asbestos. It was found that the reaction kinetics of thermal transformation of chrysotile was highly slowed down in the presence of water vapor in the experimental chamber with respect to He. This was explained by chemisorbed water on the surface of the fibers which affected the dehydroxylation reaction and consequently the recrystallization into Mg-silicates. In the attempt to investigate alternative and faster firing routes for the decomposition of asbestos, a low melting glass was mixed with cement-asbestos and studied in situ to assess to which extent the decomposition of asbestos is favored. It was found that the addition of a low melting glass to cement-asbestos greatly improved the decomposition reaction and decreased the transformation temperatures. PMID:18234421

  6. In vivo, Ex Vivo, and In Vitro Approaches to Study Intermediate Filaments in the Eye Lens.

    PubMed

    Jarrin, Miguel; Young, Laura; Wu, Weiju; Girkin, John M; Quinlan, Roy A

    2016-01-01

    The role of the eye lens is to focus light into the retina. To perform this unique function, the ocular lens must be transparent. Previous studies have demonstrated the expression of vimentin, BFSP1, and BFSP2 in the eye lens. These intermediate filament (IF) proteins are essential to the optical properties of the lens. They are also important to its biomechanical properties, to the shape of the lens fiber cells, and to the organization and function of the plasma membrane. The eye lens is an iconic model in developmental studies, as a result different vertebrate models, including zebrafish, have been developed to study lens formation. In the present chapter, we have summarized the new approaches and the more breakthrough models (e.g., iPSc) that can be used to study the function of IFs in the ocular lens. We have presented three different groups of models. The first group includes in vitro models, where IFs can be studied and manipulated in lens cell cultures. The second includes ex vivo models. These replicate better the complex lens cell differentiation processes and the role(s) played by IFs. The third class is the in vivo models, and here, we have focused on Zebrafish and new imaging approaches using selective plane illumination microscopy. Finally, we present protocols on how to use these lens models to study IFs.

  7. A comparative study of the optical pulsations in the intermediate polars

    NASA Astrophysics Data System (ADS)

    Welsh, William F.; Martell, Phillip J.

    1996-10-01

    An attempt is made to assemble all known published measurements of the optical spectrum of the pulsations in the intermediate polar stars, and to convert these measurements to an absolute flux scale for the purpose of examining similarities and correlations among this class of cataclysmic variables. By using only absolute amplitudes (not relative or fractional amplitudes), we may investigate the intrinsic nature of the pulsations. For all systems studied, a power law is able to provide a good fit to the pulse spectrum. With the exception of DQ Her itself, all the pulses are intrinsically blue, generally declining monotonically with wavelength. We find no universal features common to all systems, not do we find any strong correlations. For some systems a blackbody can adequately fit the data, and from these fits we derive estimates for the temperatures and areas of the pulse-emitting region. For the two cases where data are available, the sideband pulse spectra are flatter in their energy distribution than the spin pulse spectra, lending credibility to the belief that they are the result of reprocessing. Although not a sideband pulse, the pulse in DQ Her itself does come from reprocessing, and from our blackbody fit we estimate that between 6 and 23 per cent of the disc area is involved in the reprocessing. We speculate that in many of the intermediate polars, optically thin emission should be able to provide a good fit to the pulse spectrum; indeed, for those spectra whose slope is bluer than the Rayleigh-Jeans slope, this is the only simple and plausible emission mechanism.

  8. Application of the model-free approach to the study of non-isothermal decomposition of un-irradiated and γ-irradiated hydrated gadolinium acetylacetonate

    NASA Astrophysics Data System (ADS)

    Mahfouz, R. M.; Ahmed, G. A.-W.; Alshammari, M. R.

    2014-06-01

    The non-isothermal decomposition of unirradiated and γ-irradiated hydrated gadolinium acetylacetone with 102 kGy γ-ray absorbed dose was carried out in air and in nitrogen atmospheres and in the temperature range of 25-1000°C. The results indicate that gadolinium acetylacetonate decomposes through four main decomposition steps leading to the formation of intermediate products whose chemical structure is independent of the gas atmosphere applied and on the investigated absorbed dose. The final product at 820°C was found to be Gd2O3 irrespective of the gas atmosphere and the irradiation conditions. The non-isothermal data were analyzed using linear Flynn-Wall-Ozawa and non-linear Vyazovkin (VYZ) iso-conversional methods. The results of the application of these free models on the present kinetic data showed that the activation energy, Ea is independent of α in a very wide conversion range (0.1-0.9) indicating that the decomposition process is controlled by a unique kinetic model. The results of the model-fitting analysis showed that the decomposition course of the four decomposition steps of hydrated gadolinium acetylacetone was controlled by the D3 Jander diffusion model. Pure phase of Gd2O3 nanoparticles was obtained by thermal oxidation of γ-irradiated GdAcAc.3 H2O at 800°C for 6 h. X-ray diffraction, transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques were employed for characterization of the as-synthesized nanoparticles. This is the first attempt to prepare Gd2O3 nanoparticles by solid-state thermal decomposition of γ-irradiated hydrated gadolinium acetylacetone.

  9. Observational Studies of the Clearing Phase in Proto-Planetary Disks Surrounding Intermediate Mass Stars

    NASA Technical Reports Server (NTRS)

    Grady, Carol A.

    1999-01-01

    A detailed study of circumstellar gas associated with young, intermediate-mass stars has demonstrated that, far from being unique or an infrequently occurring phenomenon, beta Pic-like infall activity is routinely observed in stars younger than 10-50 Myr when the observer's line of sight lies within 15 degrees of the disk mid-plane. Detailed studies of 2 Herbig Ae/Be stars, AB Aur and HD 163296 demonstrate that enhanced infall episodes last 20-60 hours, comparable to the duration of similar episodes in beta Pictoris. The infall activity is consistent with detection of the comae of swarms of star-grazing bodies of asteroidal to cometary composition. Episodic fluctuations in the infall activity are clearly present by approximately 6 Myr, and may indicate the presence of massive planets within the disk. This study has therefore, directly contributed to NASA's Origins of Planetary Systems theme by identifying under what conditions extra-solar planetesimals can be remotely sensed, indicating that such bodies appear to be routinely detectable among young stars in the 1-10 Myr range, and suggesting that temporal studies of spectroscopic variability may provide a means of identifying those systems harboring massive planets. This study has resulted in 2 refereed review papers, 13 other refereed papers, and 17 conference papers.

  10. Influence of Different Forest System Management Practices on Leaf Litter Decomposition Rates, Nutrient Dynamics and the Activity of Ligninolytic Enzymes: A Case Study from Central European Forests

    PubMed Central

    Schulz, Elke; Schloter, Michael; Buscot, François; Hofrichter, Martin; Krüger, Dirk

    2014-01-01

    Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling. PMID:24699676

  11. Influence of different forest system management practices on leaf litter decomposition rates, nutrient dynamics and the activity of ligninolytic enzymes: a case study from central European forests.

    PubMed

    Purahong, Witoon; Kapturska, Danuta; Pecyna, Marek J; Schulz, Elke; Schloter, Michael; Buscot, François; Hofrichter, Martin; Krüger, Dirk

    2014-01-01

    Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling.

  12. Synthesis Characterization and Decomposition Studies of tris[N-N-dibenzyidithocarbaso)Indium (III) Chemical Spray Deposition of Polycrystalline CuInS2 on Copper Films

    NASA Technical Reports Server (NTRS)

    Hehemann, David G.; Lau, J. Eva; Harris, Jerry D.; Hoops, Michael D.; Duffy, Norman V.

    2005-01-01

    This paper presents the results of the synthesis characterization and decomposition studies of tris[N-N-dibenzyidithocarbaso)Indium (III) with chemical spray deposition of polycrystalline CuInS2 on Copper Films.

  13. Experimental studies of pion-nucleus interactions at intermediate energies. Annual progress report

    SciTech Connect

    Not Available

    1991-12-31

    This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting {pi}{sup 0} mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized {sup 3}He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure.

  14. Study of SF6 gas decomposition products based on spectroscopy technology

    NASA Astrophysics Data System (ADS)

    Cai, Ji-xing; Na, Yan-xiang; Ni, Wei-yuan; Li, Guo-wei; Feng, Ke-cheng; Song, Gui-cai

    2011-08-01

    With the rapid development of power industry, the number of SF6 electrical equipment are increasing, it has gradually replaced the traditional insulating oil material as insulation and arc media in the high-voltage electrical equipment. Pure SF6 gas has excellent insulating properties and arc characteristics; however, under the effect of the strong arc, SF6 gas will decompose and generate toxic substances, then corroding electrical equipment, thereby affecting the insulation and arc ability of electrical equipment. If excessive levels of impurities in the gas that will seriously affect the mechanical properties, breaking performance and electrical performance of electrical equipment, it will cause many serious consequences, even threaten the safe operation of the grid. This paper main analyzes the basic properties of SF6 gas and the basic situation of decomposition in the discharge conditions, in order to simulate the actual high-voltage electrical equipment, designed and produced a simulation device that can simulate the decomposition of SF6 gas under a high voltage discharge, and using fourier transform infrared spectroscopy to analyze the sample that produced by the simulation device. The result show that the main discharge decomposition product is SO2F2 (sulfuryl fluoride), the substance can react with water and generate corrosive H2SO4(sulfuric acid) and HF (hydrogen fluoride), also found that the increase in the number with the discharge, SO2F2concentration levels are on the rise. Therefore, the material can be used as one of the main characteristic gases to determine the SF6 electrical equipment failure, and to monitor their concentration levels.

  15. The Csbnd O rotation in the gaseous glycine. An energy decomposition analysis study

    NASA Astrophysics Data System (ADS)

    Chang, Xin; Chen, ZuoChang; Su, Peifeng; Wu, Wei

    2015-11-01

    The physical origins of the Csbnd O rotations in glycine are explored theoretically. By the localized molecular orbital energy decomposition analysis (LMO-EDA) method, the rotation barriers are decomposed into the electrostatic, exchange-repulsion, polarization, correlation and geometrical relaxation terms. In general, the Csbnd O rotations are controlled by Pauli repulsion and polarization interactions. However, if the rotated conformer has obvious inter-group interaction between COOH and NH2, the physical origin of the Csbnd O rotation is changed, which is governed by polarization and correlation interactions.

  16. Nonadiabatic decomposition of gas-phase RDX through conical intersections: an ONIOM-CASSCF study.

    PubMed

    Bhattacharya, A; Bernstein, E R

    2011-05-01

    Topographical exploration of nonadiabatically coupled ground- and excited-electronic-state potential energy surfaces (PESs) of the isolated RDX molecule was performed using the ONIOM methodology: Computational results were compared and contrasted with the previous experimental results for the decomposition of this nitramine energetic material following electronic excitation. One of the N-NO(2) moieties of the RDX molecule was considered to be an active site. Electronic excitation of RDX was assumed to be localized in the active site, which was treated with the CASSCF algorithm. The influence of the remainder of the molecule on the chosen active site was calculated by either a UFF MM or RHF QM method. Nitro-nitrite isomerization was predicted to be a major excited-electronic-state decomposition channel for the RDX molecule. This prediction directly corroborates previous experimental results obtained through photofragmentation-fragment detection techniques. Nitro-nitrite isomerization of RDX was found to occur through a series of conical intersections (CIs) and was finally predicted to produce rotationally cold but vibrationally hot distributions of NO products, also in good agreement with the experimental observation of rovibrational distributions of the NO product. The ONIOM (CASSCF:UFF) methodology predicts that the final step in the RDX dissociation occurs on its S(0) ground-electronic-state potential energy surface (PES). Thus, the present work clearly indicates that the ONIOM method, coupled with a suitable CASSCF method for the active site of the molecule, at which electronic excitation is assumed to be localized, can predict hitherto unexplored excited-electronic-state PESs of large energetic molecules such as RDX, HMX, and CL-20. A comparison of the decomposition mechanism for excited-electronic-state dimethylnitramine (DMNA), a simple analogue molecule of nitramine energetic materials, with that for RDX, an energetic material, was also performed. CASSCF

  17. A Study on Brain Mapping Technique Based on Hierarchical Decomposition Analysis

    NASA Astrophysics Data System (ADS)

    Oura, Kunihiko

    In this paper, brain functional mapping method by hierarchical decomposition analysis (HDA) is proposed. HDA is one of the multi-dimensional AR modeling methods and well-known for its validity to detect temporal lobe seizures. The author transforms the estimated AR model in the form of transfer function from the inner blood flow signal to the cerebral cortex. The signal for HDA is oxidized hemoglobin density HbO, which is measured by near infrared spectroscopy (NIRS). Comparing the 2 tasks which use arithmetic sense, the difference of brain activity becomes clear by proposed technique.

  18. Microscale heat transfer enhancement using spinodal decomposition

    NASA Astrophysics Data System (ADS)

    Poesio, Pietro; Molin, Dafne; Hadjiconstantinou, Nicolas G.; Beretta, Gian Paolo

    2011-11-01

    In many cases, miniaturization is limited by our ability to quickly remove heat; current state-of-the-art cooling approaches have significant limitations, particularly for high heat flux applications. Recent studies have shown that phase separation of a binary liquid-liquid mixture quenched to a temperature below the spinodal curve can be used to enhance heat transfer in small-scale devices. In particular, it has been shown that the self propulsion of single droplets formed during the intermediate stage of spinodal decomposition can produce considerable agitation and, as a result, enhanced heat transport. Spinodal phase separation dynamics can be described by the coupled Cahn-Hilliard/Navier-Stokes equations; unfortunately, simulation of these equations at the device scale is computationally costly due to the mulltiscale nature of spinodal decomposition, which requires resolution of the phase interface between the two fluids which is of atomistic size. In this talk we discuss possible approaches for reducing this computational cost by calculating the resulting transport from synthetic fluctuating fields that simulate the effect of spinodal decomposition but are generated stochastically without solving the Cahn-Hilliard equation at close-to-atomistic resolution.

  19. Decomposition Pathways of Glycerol via C–H, O–H, and C–C Bond Scission on Pt(111): A Density Functional Theory Study

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey P.

    2011-10-13

    Glycerol decomposition on Pt(111) via dehydrogenation or C–C bond scission is examined with periodic density functional theory (DFT) calculations. The thermochemistry of dehydrogenation intermediates is first estimated using an empirical correlation scheme with parameters fit to selected DFT calculations; the resulting estimates for the more stable intermediates are refined with full DFT calculations. Brønsted–Evans–Polanyi (BEP) relationships for dehydrogenation and C–C bond scission reactions are developed and used to estimate the kinetics of elementary dehydrogenation and C–C bond scission steps in the reaction network. The combined thermochemical and kinetic analysis implies that glycerol dehydrogenation products at intermediate levels of dehydrogenation are the most thermochemically stable. Additionally, although C–C bond scission transition state energies are high for glycerol and for intermediates at early stages of dehydrogenation, these energies decrease as the intermediates are successively dehydrogenated, reaching a minimum after the removal of several hydrogen atoms from glycerol. At these levels of dehydrogenation, the C–C scission transition state energies become comparable to those of O–H or C–H scission. These results suggest that C–C bonds are only broken after glycerol has been significantly dehydrogenated and demonstrate that DFT-based analyses, combined with simple correlation schemes, can be effective for elucidating general features of complex biomassic reaction networks.

  20. Decomposition Pathways of Glycerol via C–H, O–H, and C–C Bond Scission on Pt(111): A Density Functional Theory Study

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey

    2011-09-01

    Glycerol decomposition on Pt(111) via dehydrogenation or C–C bond scission is examined with periodic density functional theory (DFT) calculations. The thermochemistry of dehydrogenation intermediates is first estimated using an empirical correlation scheme with parameters fit to selected DFT calculations; the resulting estimates for the more stable intermediates are refined with full DFT calculations. Brønsted–Evans–Polanyi (BEP) relationships for dehydrogenation and C–C bond scission reactions are developed and used to estimate the kinetics of elementary dehydrogenation and C–C bond scission steps in the reaction network. The combined thermochemical and kinetic analysis implies that glycerol dehydrogenation products at intermediate levels of dehydrogenation are the most thermochemically stable. Additionally, although C–C bond scission transition state energies are high for glycerol and for intermediates at early stages of dehydrogenation, these energies decrease as the intermediates are successively dehydrogenated, reaching a minimum after the removal of several hydrogen atoms from glycerol. At these levels of dehydrogenation, the C–C scission transition state energies become comparable to those of O–H or C–H scission. These results suggest that C–C bonds are only broken after glycerol has been significantly dehydrogenated and demonstrate that DFT-based analyses, combined with simple correlation schemes, can be effective for elucidating general features of complex biomassic reaction networks.

  1. Clinicopathologic study on combined hepatocellular carcinoma and cholangiocarcinoma: with emphasis on the intermediate cell morphology.

    PubMed

    Park, Ho Sung; Bae, Jun Sang; Jang, Kyu Yun; Lee, Ju Hyung; Yu, Hee Chul; Jung, Ji Hyeon; Cho, Baik Hwan; Chung, Myoung Ja; Moon, Woo Sung

    2011-08-01

    Combined hepatocellular carcinoma and cholangiocarcinoma (combined HCC-CC) is a rare subtype of primary liver cancer. We investigated the histopathologic features of transitional or intermediate areas in 21 combined HCC-CCs and immunophenotypes using different hepatic progenitor cell markers (CK7, CK19, c-kit, NCAM, and EpCAM). Major histologic findings of transitional or intermediate areas of 21 combined HCC-CCs included strands/trabeculae of small, uniform, oval-shaped cells with scant cytoplasm and hyperchromatic nuclei embedded within an abundant stroma, small cells with an antler-like anastomosing pattern, and solid nests of intermediate hepatocyte-like cells surrounded by small cells in periphery, in order of frequency. The intermediate area of one tumor was composed predominantly of spindle cells arranged in short fascicles. Immunophenotype of tumor cells with intermediate morphology suggested a progenitor cell origin for this tumor. Clinical findings of combined HCC-CC showed a closer resemblance with those of HCC than those of CC. In univariate analysis, tumor size, TNM stage, and serum alpha-fetoprotein levels showed a significant association with poor patient survival. Serum alpha-fetoprotein level was an independent prognostic indicator in multivariate analysis. In conclusion, an awareness of the clinicopathologic features, specifically the various morphologic features of intermediate areas in this tumor, is essential for prevention of potential misdiagnosis as another tumor.

  2. A Chandra Study of Temperature Substructures in Intermediate-Redshift Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Gu, Liyi; Xu, Haiguang; Gu, Junhua; Wang, Yu; Zhang, Zhongli; Wang, Jingying; Qin, Zhenzhen; Cui, Haijuan; Wu, Xiang-Ping

    2009-08-01

    By analyzing the gas temperature maps created from the Chandra archive data, we reveal the prevailing existence of temperature substructures on ~100 h -1 70 kpc scales in the central regions of nine intermediate-redshift (z ≈ 0.1) galaxy clusters, which resemble those found in the Virgo and Coma Clusters. Each substructure contains a clump of hot plasma whose temperature is about 2-3 keV higher than the environment, corresponding to an excess thermal energy of ~1058-1060 erg per clump. If there were no significant nongravitational heating sources, these substructures would have perished in 108-109 yr due to thermal conduction and turbulent flows, whose velocity is found to range from about 200 to 400 km s-1, we conclude that the substructures cannot be created and sustained by inhomogeneous radiative cooling. We also eliminate the possibilities that the temperature substructures are caused by supernova explosions, or by the nonthermal X-ray emission due to the inverse-Comptonization of the cosmic microwave background photons. By calculating the rising time of active galactic nucleus (AGN)-induced buoyant bubbles, we speculate that the intermittent AGN outbursts (>=1060 erg per burst) may have played a crucial role in the formation of the high-temperature substructures. Our results are supported by the recent study of McNamara and Nulsen, posing a tight observational constraint on future theoretical and numerical studies.

  3. Computer modeling of data from pulse radiolysis studies of aqueous solutions containing scavengers of spur intermediates

    SciTech Connect

    Trumbore, C.N.; Youngblade, W.; Short, D.R.

    1984-10-11

    With the calculations reported here, all of the data from a comprehensive study of the kinetics of hydrated-electron decay in the 14-MeV-electron pulse radiolysis of pure water and aqueous solutions have been modeled within experimental error. The overlapping-spur model utilized employs a constant-energy fraction (0.2) of high, constant spur density regions (representing blobs/short tracks) and another constant-energy fraction (0.8) of a low, variable spur density region (representing isolated spurs) whose spur density is proportional to the pulse dose. The model also contains a new hydrated-electron probability density distribution function with the maximum in the probability density displaced from the center of the spur. Adjustments made to fit experimental data from different aqueous-solution pulse radiolysis studies have been minor. Hydrated-electron decay kinetics have been modeled within experimental error for a variety of scavengers of transient reactive intermediates originating in the spur. Thus, this new spur model has been successfully tested against experimental data for 14-MeV electrons over a wide range of pulse doses (0.5-80 Gy), time regimes (10/sup -11/-10/sup -5/ s), and types of scavengers of the major spur transients (e/sub aq//sup -/, .OH, and H/sup +/).

  4. Experimental study of turbulence in isothermal jet impingement at intermediate plate spacings

    NASA Astrophysics Data System (ADS)

    Landfried, D. Tyler; Valentino, Alex; Mazumdar, Sagnik; Jana, Anirban; Kimber, Mark

    2013-11-01

    One fundamental problem in fluid dynamics is that of the axisymmetric round flow impinging on a plate placed some distance downstream of the jet. Impinging jets have a rich history of applications including small plate spacings, H/D ~ 1, such as encountered in electronics cooling, or large plate spacings, H/D ~ 102, such as vertical takeoff aircrafts and rocket engines. However, intermediate plate spacings, such as the lower plenum of the next generation nuclear reactors, are not typically studied. In this paper, an experimental study is conducted investigating the effect of the impingement plate on the flow behavior compared to the near free jet behavior when the plate is removed. Using air as the working fluid, a single jet is considered at jet Reynolds numbers of 10000, 20000, and 30000. A three-wire anemometer probe is used to quantify the mean components of velocities as well as the Reynolds stress and the third-order moments in the flow field at various distances between the jet outlet and the impingement plate. When present, the impingement plate is placed a distance of 8, 11, 14, and 17 diameters downstream of the jet. Additionally trends in the kinetic energy and dissipation are investigated for validation with numerical models.

  5. A study of domain decomposition methods applied to the discretized Helmholtz equation

    NASA Astrophysics Data System (ADS)

    Tramel, Robert Wallace

    2001-09-01

    In this work a domain decomposition based preconditioner of the additive Schwarz type is developed and tested on the linear systems which arise out of the application of the Green's Function/Wave Expansion Discretization. (GFD/WED) method to Helmholtz's equation. In order to develop the additive Schwarz preconditioner, use is made of a class of one-sided Artificial Radiation Boundary Conditions (ARBC) developed during the course of this work. These ARBCs are computationally shown to be quite accurate for use on their own. The ARBC's are used to radiatively couple the various sub-domains which are naturally part of domain decomposition based methods in such a manner as to ensure that the system matrix, when restricted to the sub-domains, is non-singular. In addition, the inter-domain ARBC is constructed such that the solution to the global linear system is unaffected by the presence of the artificial boundaries. The efficacy and efficiency of the method is demonstrated on one, two, and three-dimensional test cases.

  6. Skeletons in the Stream: A Temporal Study of In-Stream Leaf Decomposition

    NASA Astrophysics Data System (ADS)

    Delmonte, J. M.; Minshall, G. W.; Smith, R. J.

    2005-05-01

    Allochthonous leaf litter plays a pivotal role in streams. Laboratory exercises highlighting its ecological role can examine several components simultaneously. The rate of leaf decomposition is an ecosystem-level process that represents the composite effects of microbial, invertebrate, and physical activity. Leaves that fall into streams often cluster together in "packs" behind rocks and woody debris. In this exercise, students construct leaf packs by collecting leaves from surrounding vegetation or the ground. The leaves are placed into plastic mesh bags and secured in the stream. Subsets of the packs are collected at weekly intervals, colonizing invertebrates are removed and identified, and the remaining leaf material is dried and weighed. Students design and carry out their own experiments, the broad areas of which can include; (1) decomposition rates among streams or leaf type, (2) upstream-downstream effects, (3) distribution of shredding invertebrates, and (4) land-use correlations. We will present examples of results from both high school and college level experiments along with recommendations for successful implementation.

  7. Theoretical Study of the Thermal Decomposition of Carboxylic Acids at Pyrolysis Temperature

    SciTech Connect

    Clark, J. M.; Robichaud, D. J.; Nimlos, M. R.

    2013-01-01

    Carboxylic acids are important in the processing of biomass into renewable fuels and chemicals. They are formed from the pretreatment and pyrolysis of hemicellulose biopolymers and are released from the decomposition of sugars. They result from the deconstruction of polyhydroxyalkanoates (bacterial carbon storage polymers) from fatty acids derived from algae, bacteria, and oil crops. The thermal deoxygenation of carboxylic acids is an important step in the conversion of biomass into aliphatic hydrocarbons suitable for use in renewable biofuels and as petrochemical replacements. Decarboxylation, a primary decomposition pathway under pyrolysis conditions, represents an ideal conversion process, because it eliminates two atoms of oxygen for every carbon atom removed. Problematically, additional deoxygenation processes exist (e.g. dehydration) that are in direct competition with decarboxylation and result in the formation of reactive and more fragmented end products. To better understand the competition between decarboxylation and other deoxygenation processes and to gain insight into possible catalysts that would favor decarboxylation, we have investigated the mechanisms and thermochemistry of the various unimolecular and bimolecular deoxygenation pathways for a family of C1-C4 organic acids using electronic structure calculations at the M06-2X/6-311++G(2df,p) level of theory.

  8. Mueller matrix differential decomposition.

    PubMed

    Ortega-Quijano, Noé; Arce-Diego, José Luis

    2011-05-15

    We present a Mueller matrix decomposition based on the differential formulation of the Mueller calculus. The differential Mueller matrix is obtained from the macroscopic matrix through an eigenanalysis. It is subsequently resolved into the complete set of 16 differential matrices that correspond to the basic types of optical behavior for depolarizing anisotropic media. The method is successfully applied to the polarimetric analysis of several samples. The differential parameters enable one to perform an exhaustive characterization of anisotropy and depolarization. This decomposition is particularly appropriate for studying media in which several polarization effects take place simultaneously. PMID:21593943

  9. Experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies

    SciTech Connect

    Not Available

    1990-10-01

    This report summarizes the work on experimental research in intermediate energy nuclear and particle physics carried out by New Mexico State University in 1988--91. Most of these studies have involved investigations of neutron-proton and pion-nucleus interactions. The neutron-proton research is part of a program of studies of interactions between polarized nucleons that we have been involved with for more than ten years. Its purpose has been to help complete the determination of the full set of ten complex nucleon-nucleon amplitudes at energies up to 800 MeV, as well as to continue investigating the possibility of the existence of dibaryon resonances. The give complex isospin-one amplitudes have been fairly well determined, partly as a result of this work. Our work in this period has involved measurements and analysis of data on elastic scattering and total cross sections for polarized neutrons on polarized protons. The pion-nucleus research continues our studies of this interaction in regions where it has not been well explored. One set of experiments includes studies of pion elastic and double-charge-exchange scattering at energies between 300 and 550 MeV, where our data is unique. Another involves elastic and single-charge-exchange scattering of pions from polarized nuclear targets, a new field of research which will give the first extensive set of information on spin-dependent pion-nucleus amplitudes. Still another involves the first set of detailed studies of the kinematic correlations among particles emitted following pion absorption in nuclei.

  10. Study on an Efficient Dehumidifying Air-conditioning System utilizing Phase Change of Intermediate Pressure Refrigerant

    NASA Astrophysics Data System (ADS)

    Maeda, Kensaku; Inaba, Hideo

    The present study has proven a new dehumidifying system that aimed to reduce the sensible heat factor(SHF) of cooling process without using additional heat to relieve the internationally indicated conflict between energy saving and dehumidification necessary for keeping adequate indoor air quality (IAQ). In this system, we used intermediate pressure refrigerant in a vapor compression refrigerating cycle as heat transfer medium of a characteristic heat exchanger to precool the process air entering into an evaporator as well as to reheat the process air leaving from the evaporator. By this system, the present results achieved higher moisture removal and consequently higher efficiency of dehumidifying process. In addition to this fact, since this system has capability of integration into air-conditioning apparatus(HVAC system), it will be able to work for wide range of cooling load by variable SHF function. In the present paper, technical information, experimental results, and simulation results which assumed to apply this system into HVAC system are reported.

  11. Metabolic Studies on Intermediates in the myo-Inositol Oxidation Pathway in Lilium longiflorum Pollen: II. Evidence for the Participation of Uridine Diphosphoxylose and Free Xylose as Intermediates.

    PubMed

    Rosenfield, C L; Loewus, F A

    1978-01-01

    myo-Inositol-linked glucogenesis in germinated lily (Lilium longiflorum Thunb., cv. Ace) pollen was investigated by studying the effects of added l-arabinose or d-xylose on metabolism of myo-[2-(3)H]inositol and by determining the distribution of radioisotope in pentosyl and hexosyl residues of polysaccharides from pollen labeled with myo-[2-(14)C]inositol, myo-[2-(3)H]inositol, l-[5-(14)C]arabinose, and d-[5R,5S-(3)H]xylose.myo-[2-(14)C]Inositol and l-[5-(14)C]arabinose produced labeled glucose with similar patterns of distribution of (14)C, 35% in C1, and 55% in C6. Arabinosyl units were labeled exclusively in C5. Incorporation of (3)H into arabinosyl and xylosyl units in pollen labeled with myo-[2-(3)H]inositol was repressed when unlabeled l-arabinose was included in the germination medium and a related (3)H exchange with water was stimulated. Results are consistent with a process of glucogenesis in which the myo-inositol oxidation pathway furnishes UDP-d-xylose as a key intermediate for conversion to hexose via free d-xylose and the pentose phosphate pathway.Additional evidence for this process was obtained from pollen labeled with d-[5R,5S-(3)H]xylose or myo-[2-(3)H]inositol which produces d-[5R-(3)H]xylose. Glucosyl units from polysaccharides in the former had 11% of the (3)H in C1 and 78% in C6 while glucosyl units in the latter had only 4% in C1 and 78% in C6. Stereochemical considerations involving selective exchange with water of prochiral-R (3)H in C1 of fructose-6-P during conversion to glucose provide explanation for observed differences in the metabolism of these 5-labeled xyloses.Incorporation of (3)H from myo-[2-(3)H]inositol into arabinosyl and xylosyl units of pollen polysaccharides was unaffected by the presence of unlabeled d-xylose in the medium. Exchange of (3)H with water was greatly affected, decreasing from a value of 21% exchange in the absence of unlabeled d-xylose to 5% in the presence of 6.7 mmd-xylose.d-Xylose was rapidly utilized for

  12. Spectral computed tomography for quantitative decomposition of vulnerable plaques using a dual-energy technique: a Monte Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Jo, B. D.; Park, S.-J.; Kim, H. M.; Kim, D. H.; Kim, H.-J.

    2016-02-01

    A spectral computed tomography (CT) system based on an energy-resolved photon-counting Cadmium Zinc Telluride (CZT) detector with a dual energy technique can provide spectral information and can possibly distinguish between two or more materials with a single X-ray exposure using energy thresholds. This work provides the potential for three-material decomposition of vulnerable plaques using two inverse fitting functions. Additionally, there exists the possibility of using gold nanoparticles as a contrast agent for the spectral CT system in conjunction with a CZT photon-counting detector. In this simulation study, we used fan beam CT geometry that consisted of a 90 kVp X-ray spectrum and performed calculations by using the SpekCal program (REAL Software, Inc.) with Monte Carlo simulations. A basic test phantom was imaged with the spectral CT system for the calibration and decomposition process. This phantom contained three different materials, including lipid, iodine and gold nanoparticles, with six holes 3 mm in diameter. In addition to reducing pile-up and charge sharing effect, the photon counting detector was considered an ideal detector. Then, the accuracy of material decomposition techniques with two inverse fitting functions were evaluated between decomposed images and reference images in terms of root mean square error (RMSE). The results showed that decomposed images had a good volumetric fraction for each material, and the RMSE between the measured and true volumes of lipid, iodine and gold nanoparticle fractions varied from 12.51% to 1.29% for inverse fitting functions. The study indicated that spectral CT in conjunction with a CZT photon-counting detector in conjunction with a dual energy technique can be used to identifying materials and may be a promising modality for quantifying material properties of vulnerable plaques.

  13. On the nature of the reaction intermediate in the HIV-1 protease: a quantum chemical study

    NASA Astrophysics Data System (ADS)

    Carnevale, V.; Raugei, S.; Piana, S.; Carloni, P.

    2008-07-01

    Several mechanistic aspects of Aspartic Proteases' enzymatic reaction are currently highly controversial. There is general consensus that the first step of the reaction involves a nucleophilic attack of a water molecule to the substrate carbonyl carbon with subsequent formation of a metastable intermediate (INT). However, the exact nature of this intermediate is subject of debate. While ab initio and QM/MM calculations predict that INT is a neutral gem-diol specie, empirical valence bond calculations suggest that the protein frame can stabilize a charged oxyanion intermediate. Here the relative stability of the gem diol and oxyanion intermediate is calculated by performing density functional and post-Hartree-Fock calculations. The robustness of the results is assessed by increasing the size of the system and of the basis set and by performing QM/MM calculations that explicitly include protein/solvent electrostatic effects. Our results suggest that the neutral gem-diol intermediate is 20-30 kcal/mol more stable than the charged oxyanion. It is therefore concluded that only the neutral specie is populated during the enzymatic reaction.

  14. ERP and Adaptive Autoregressive identification with spectral power decomposition to study rapid auditory processing in infants.

    PubMed

    Piazza, C; Cantiani, C; Tacchino, G; Molteni, M; Reni, G; Bianchi, A M

    2014-01-01

    The ability to process rapidly-occurring auditory stimuli plays an important role in the mechanisms of language acquisition. For this reason, the research community has begun to investigate infant auditory processing, particularly using the Event Related Potentials (ERP) technique. In this paper we approach this issue by means of time domain and time-frequency domain analysis. For the latter, we propose the use of Adaptive Autoregressive (AAR) identification with spectral power decomposition. Results show EEG delta-theta oscillation enhancement related to the processing of acoustic frequency and duration changes, suggesting that, as expected, power modulation encodes rapid auditory processing (RAP) in infants and that the time-frequency analysis method proposed is able to identify this modulation.

  15. Comparison of sugar molecule decomposition through glucose and fructose: a high-level quantum chemical study.

    SciTech Connect

    Assary, R. S.; Curtiss, L. A.

    2012-02-01

    Efficient chemical conversion of biomass is essential to produce sustainable energy and industrial chemicals. Industrial level conversion of glucose to useful chemicals, such as furfural, hydroxymethylfurfural, and levulinic acid, is a major step in the biomass conversion but is difficult because of the formation of undesired products and side reactions. To understand the molecular level reaction mechanisms involved in the decomposition of glucose and fructose, we have carried out high-level quantum chemical calculations [Gaussian-4 (G4) theory]. Selective 1,2-dehydration, keto-enol tautomerization, isomerization, retro-aldol condensation, and hydride shifts of glucose and fructose molecules were investigated. Detailed kinetic and thermodynamic analyses indicate that, for acyclic glucose and fructose molecules, the dehydration and isomerization require larger activation barriers compared to the retro-aldol reaction at 298 K in neutral medium. The retro-aldol reaction results in the formation of C2 and C4 species from glucose and C3 species from fructose. The formation of the most stable C3 species, dihydroxyacetone from fructose, is thermodynamically downhill. The 1,3-hydride shift leads to the cleavage of the C-C bond in the acyclic species; however, the enthalpy of activation is significantly higher (50-55 kcal/mol) than that of the retro-aldol reaction (38 kcal/mol) mainly because of the sterically hindered distorted four-membered transition state compared to the hexa-membered transition state in the retro-aldol reaction. Both tautomerization and dehydration are catalyzed by a water molecule in aqueous medium; however, water has little effect on the retro-aldol reaction. Isomerization of glucose to fructose and glyceraldehyde to dihydroxyacetone proceeds through hydride shifts that require an activation enthalpy of about 40 kcal/mol at 298 K in water medium. This investigation maps out accurate energetics of the decomposition of glucose and fructose molecules

  16. Solid-state NMR studies of the dynamics and structure of mouse keratin intermediate filaments

    SciTech Connect

    Mack, J.W.; Torchia, D.A.; Steinert, P.M.

    1988-07-26

    The molecular dynamics and structural organization of mouse epidermal keratin intermediate filaments (IF) have been studied via solid-state nuclear magnetic resonance (NMR) experiments performed on IF labeled both in vivo and in vitro with isotopically enriched amino acids. As a probe of the organization of the peripheral glycine-rich end domains of the IF, carbon-13 NMR experiments have been performed on subfilamentous forms (prekeratin) and on IF reassembled in vitro that had been labeled with either (1-/sup 13/C)glycine or (2-/sup 13/C)glycine, as more than 90% of the glycines of the keratins are located in the end domains. Measurements of carbon relaxation times, nuclear Overhauser enhancements, and signal intensities show that the motions of the peptide backbone in the end domains are effectively isotropic. These results indicate that the end domains of IF are remarkably flexible and have little or no structural order. To probe the structural organization of the coiled-coil rod domains of the IF, separate samples of native keratin IF, raised in primary tissue culture, were labeled with L-(1-/sup 13/C)leucine, L-(/sup 2/H/sub 10/)leucine, or L-(2,3,3-/sup 2/H/sub 3/)leucine, as greater than 90% of the leucyl residues of the keratin IF types studied are located in the coiled coils which form the central core of IF. Deuterium NMR experiments performed on IF labeled with deuteriated leucines indeed reveal a marked degree of peptide backbone rigidity within the coiled coils, confirming the initial conclusions of the carbon-13 data. These data, demonstrating relative peptide backbone rigidity yet side-chain flexibility, are interpreted to mean that the coiled coils of these keratin IF are not tightly packed together but rather form a somewhat looser structure which permits a significant degree of side-chain mobility.

  17. A CHANDRA STUDY OF TEMPERATURE SUBSTRUCTURES IN INTERMEDIATE-REDSHIFT GALAXY CLUSTERS

    SciTech Connect

    Gu Liyi; Xu Haiguang; Gu Junhua; Wang Yu; Wang Jingying; Qin Zhenzhen; Cui Haijuan; Zhang Zhongli; Wu Xiangping

    2009-08-01

    By analyzing the gas temperature maps created from the Chandra archive data, we reveal the prevailing existence of temperature substructures on {approx}100 h{sup -1}{sub 70} kpc scales in the central regions of nine intermediate-redshift (z {approx} 0.1) galaxy clusters, which resemble those found in the Virgo and Coma Clusters. Each substructure contains a clump of hot plasma whose temperature is about 2-3 keV higher than the environment, corresponding to an excess thermal energy of {approx}10{sup 58}-10{sup 60} erg per clump. If there were no significant nongravitational heating sources, these substructures would have perished in 10{sup 8}-10{sup 9} yr due to thermal conduction and turbulent flows, whose velocity is found to range from about 200 to 400 km s{sup -1}, we conclude that the substructures cannot be created and sustained by inhomogeneous radiative cooling. We also eliminate the possibilities that the temperature substructures are caused by supernova explosions, or by the nonthermal X-ray emission due to the inverse-Comptonization of the cosmic microwave background photons. By calculating the rising time of active galactic nucleus (AGN)-induced buoyant bubbles, we speculate that the intermittent AGN outbursts ({>=}10{sup 60} erg per burst) may have played a crucial role in the formation of the high-temperature substructures. Our results are supported by the recent study of McNamara and Nulsen, posing a tight observational constraint on future theoretical and numerical studies.

  18. Multiple 'Stable' States of Antarctic Intermediate Water: A Study from the Subantarctic South-West Atlantic.

    NASA Astrophysics Data System (ADS)

    Roberts, J.; Hodell, D. A.; Peck, V. L.; Kender, S.

    2014-12-01

    Modelling studies suggest that density changes in Antarctic Intermediate Water (AAIW) played a significant role in the reorganisation of Atlantic Meridional Overturning Circulation over the last glacial period. From its principal site of formation in the SE Pacific, a significant proportion of AAIW is entrained in the Antarctic circumpolar current and enters the Atlantic through Drake Passage. Air-sea interaction within the subAntarctic SW Atlantic modifies this AAIW further, producing a cooler and fresher Atlantic end member of AAIW. Our core site is located where this branch of AAIW subducts and travels northwards along the western margin of the Atlantic basin. We present the first high-resolution, multi-proxy study of AAIW in the sub-Antarctic SW Atlantic over the last 140 kyrs. Here, we focus on the temperature and salinity records over the last two glacial terminations and at the onset of the last glaciation. We use a combination of benthic stable isotopes and elemental ratios (Mg/Ca) on the shallow infaunal species Uvigerina peregrina to reconstruct AAIW temperature and salinity. Our records suggest that AAIW temperature both increased and decreased in a step-wise manner over the last 120 kyrs hinting at 3 'stable' states for AAIW through the last glacial cycle (see shaded areas within figure). Another common feature is a transient interval of apparently warm, saline AAIW observed at the onset of both glacial terminations - could this be evidence of the 'deep, salty blob' or of increased outflow of Pacific surface waters? We identify some fundamental differences between termination I and termination II; AAIW appears to have been markedly warmer during MIS6 than at the LGM. Furthermore, the glacial-interglacial potential density difference is much greater over termination I than termination II.

  19. Intermediate Heat Transfer Loop Study for High Temperature Gas-Cooled Reactor

    SciTech Connect

    C. H. Oh; C. Davis; S. Sherman

    2008-08-01

    A number of possible configurations for a system that transfers heat between the nuclear reactor and the hydrogen and/or electrical generation plants were identified. These configurations included both direct and indirect cycles for the production of electricity. Both helium and liquid salts were considered as the working fluid in the intermediate heat transport loop. Methods were developed to perform thermal-hydraulic and cycleefficiency evaluations of the different configurations and coolants. The thermal-hydraulic evaluations estimated the sizes of various components in the intermediate heat transport loop for the different configurations. This paper also includes a portion of stress analyses performed on pipe configurations.

  20. Probing the Natural World, Level III, Teacher's Edition: Why You're You. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

    Bonar, John R., Ed.; Hathway, James A., Ed.

    This is the teacher's edition of one of the eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). The chapters include basic information about heredity, activities, and optional "excursions." The answers to all activities are included. An introduction describes the work of Gregor Mendel and his…

  1. Maghemite nanosorbcats for methylene blue adsorption and subsequent catalytic thermo-oxidative decomposition: Computational modeling and thermodynamics studies.

    PubMed

    El-Qanni, Amjad; Nassar, Nashaat N; Vitale, Gerardo; Hassan, Azfar

    2016-01-01

    In this study methylene blue (MB) has been investigated for its adsorption and subsequent catalytic thermo-oxidative decomposition on surface of maghemite (γ-Fe2O3) nanoparticles. The experimental adsorption isotherm fit well to the Freundlich model, indicating multi-sites adsorption. Computational modeling of the interaction between the MB molecule and γ-Fe2O3 nanoparticle surface was carried out to get more insights into its adsorption behavior. Adsorption energies of MB molecules on the surface indicated that there are different adsorption sites on the surface of γ-Fe2O3 confirming the findings regarding the adsorption isotherm. The catalytic activity of the γ-Fe2O3 nanoparticles toward MB thermo-oxidative decomposition has been confirmed by subjecting the adsorbed MB to a thermo oxidation process up to 600 °C in a thermogravimetric analyzer. The experimental results showed a catalytic activity for post adsorption oxidation. The oxidation kinetics were studied using the Ozawa-Flyn-Wall (OFW) corrected method. The most probable mechanism functions were fifth and third orders for virgin MB and MB adsorbed onto γ-Fe2O3 nanoparticles, respectively. Moreover, the results of thermodynamic transition state parameters, namely changes in Gibbs free energy of activation (ΔG(‡)), enthalpy of activation (ΔH(‡)), and entropy of activation (ΔS(‡)), emphasized the catalytic activity of γ-Fe2O3 nanoparticles toward MB oxidation.

  2. Comparative study on DBPs formation profiles of intermediate organics from hydroxyl radicals oxidation of microbial cells.

    PubMed

    Ou, Tai-You; Wang, Gen-Shuh

    2016-05-01

    This study assessed the characteristics of disinfection byproducts (DBPs) formation from intermediate organics during UV/H2O2 treatment of activated sludge and algae cells under various reaction conditions. The DBPs including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs) and haloacetonitriles (HANs) in UV/H2O2-treated and chlorinated water were measured. The results showed that both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) increased during the initial stage of UV/H2O2 treatment due to the lysis of sludge and algae cells, which enhanced the formation of both C- and N-DBPs; however, both DOC and DON decreased after longer reaction times. During the UV/H2O2 treatments, THMs formation potential (THMFP) peaked earlier than did HAAs formation potential (HAAFP). This shows that the dissolved organics released from lysis of microbial cells in the early stages of oxidation favor the production of THMs over HAAs; however, HAAs precursors increased with the oxidation time. Chlorination with bromide increased the formation of THMs and HAAs but less HKs and HANs were produced. Comparisons of normalized DBP formation potential (DBPFP) of samples collected during UV/H2O2 treatments of four different types of organic matter showed that the highest DBPFP occurred in filtered treated wastewater effluent, followed by samples of activated sludge, filtered eutrophicated pond water, and samples of algae cells. With increasing oxidation time, the dominant DBP species shifted from THMs to HAAs in the samples of activated sludge and algae cells. The DBPFP tests also showed that more HAAs were formed in biologically treated wastewater effluent, while the eutrophicated source water produced more THMs.

  3. Comparative study on DBPs formation profiles of intermediate organics from hydroxyl radicals oxidation of microbial cells.

    PubMed

    Ou, Tai-You; Wang, Gen-Shuh

    2016-05-01

    This study assessed the characteristics of disinfection byproducts (DBPs) formation from intermediate organics during UV/H2O2 treatment of activated sludge and algae cells under various reaction conditions. The DBPs including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs) and haloacetonitriles (HANs) in UV/H2O2-treated and chlorinated water were measured. The results showed that both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) increased during the initial stage of UV/H2O2 treatment due to the lysis of sludge and algae cells, which enhanced the formation of both C- and N-DBPs; however, both DOC and DON decreased after longer reaction times. During the UV/H2O2 treatments, THMs formation potential (THMFP) peaked earlier than did HAAs formation potential (HAAFP). This shows that the dissolved organics released from lysis of microbial cells in the early stages of oxidation favor the production of THMs over HAAs; however, HAAs precursors increased with the oxidation time. Chlorination with bromide increased the formation of THMs and HAAs but less HKs and HANs were produced. Comparisons of normalized DBP formation potential (DBPFP) of samples collected during UV/H2O2 treatments of four different types of organic matter showed that the highest DBPFP occurred in filtered treated wastewater effluent, followed by samples of activated sludge, filtered eutrophicated pond water, and samples of algae cells. With increasing oxidation time, the dominant DBP species shifted from THMs to HAAs in the samples of activated sludge and algae cells. The DBPFP tests also showed that more HAAs were formed in biologically treated wastewater effluent, while the eutrophicated source water produced more THMs. PMID:26894677

  4. Studies of N{sub 2}0 adsorption and decomposition on Fe-ZSM-5

    SciTech Connect

    Wood, Benjamin R.; Reimer, Jeffrey A.; Bell, Alexis T.

    2002-03-08

    The interactions of N2O with H-ZSM-5 and Fe-ZSM-5 have been investigated using infrared spectroscopy and temperature-programmed reaction. Fe-ZSM-5 samples with Fe/Al ratios of 0.17 and 0.33 were prepared by solid-state exchange. It was determined that most of the iron in the samples of Fe-ZSM-5 is in the form of isolated cations, which have exchanged with Bronsted acid H+ in H-ZSM-5. The infrared spectrum of N2O adsorbed on H-ZSM-5 at 298 K exhibits bands at 2226 and 1308 cm-1 associated with vibrations of the N-N and N-O bonds, respectively. The positions of these bands relative to those seen in the gas phase suggest that N2O adsorbs through the nitrogen end of the molecule. The heat of N2O adsorption in H-ZSM-5 is estimated to be 5 kcal/mol. In the case of Fe-ZSM-5, additional infrared bands are observed at 2282 and 1344 cm-1 due to the interactions of N2O with the iron cations. Here too, the directions of the shifts in the vibrational features relative to those for gas-phase N2O suggest that the molecule adsorbs through its nitrogen end. The heat of adsorption of N2O on the Fe sites is estimated to be 16 kcal/mol. The extent of N2O adsorption on Fe depends on the oxidation state of Fe. The degree of N2O adsorption is higher following pretreatment of the sample in He or CO at 773 K, than following pretreatment in O2 or N2O at the same temperature. Temperature-programmed decomposition of N2O was performed on the Fe-ZSM-5 samples and revealed that N2O decomposes stoichiometrically to N2 and O2. A higher activity was observed if the catalysts were pretreated in He than if they were pretreated in N2O. For the He-pretreated samples, the activation energy for N2O decomposition was estimated to be 42 kcal/mol and the preexponential factor of the rate coefficient for this process was found to increase with Fe/Al ratio. This trend was attributed to the increasing auto reducibility of Fe3+ cations to Fe2+ cations with increasing Fe/Al ratio.

  5. Study on decomposition of indoor air contaminants by pulsed atmospheric microplasma.

    PubMed

    Shimizu, Kazuo; Kuwabara, Tomoya; Blajan, Marius

    2012-01-01

    Decomposition of formaldehyde (HCHO) by a microplasma reactor in order to improve Indoor Air Quality (IAQ) was achieved. HCHO was removed from air using one pass through reactor treatment (5 L/min). From an initial concentration of HCHO of 0.7 ppm about 96% was removed in one pass treatment using a discharge power of 0.3 W provided by a high voltage amplifier and a Marx Generator with MOSFET switches as pulsed power supplies. Moreover microplasma driven by the Marx Generator did not generate NOx as detected by a chemiluminescence NOx analyzer. In the case of large volume treatment the removal ratio of HCHO (initial concentration: 0.5 ppm) after 60 minutes was 51% at 1.2 kV when using HV amplifier considering also a 41% natural decay ratio of HCHO. The removal ratio was 54% at 1.2 kV when a Marx Generator energized the electrodes with a 44% natural decay ratio after 60 minutes of treatment. PMID:23202173

  6. Study on Decomposition of Indoor Air Contaminants by Pulsed Atmospheric Microplasma

    PubMed Central

    Shimizu, Kazuo; Kuwabara, Tomoya; Blajan, Marius

    2012-01-01

    Decomposition of formaldehyde (HCHO) by a microplasma reactor in order to improve Indoor Air Quality (IAQ) was achieved. HCHO was removed from air using one pass through reactor treatment (5 L/min). From an initial concentration of HCHO of 0.7 ppm about 96% was removed in one pass treatment using a discharge power of 0.3 W provided by a high voltage amplifier and a Marx Generator with MOSFET switches as pulsed power supplies. Moreover microplasma driven by the Marx Generator did not generate NOx as detected by a chemiluminescence NOx analyzer. In the case of large volume treatment the removal ratio of HCHO (initial concentration: 0.5 ppm) after 60 minutes was 51% at 1.2 kV when using HV amplifier considering also a 41% natural decay ratio of HCHO. The removal ratio was 54% at 1.2 kV when a Marx Generator energized the electrodes with a 44% natural decay ratio after 60 minutes of treatment. PMID:23202173

  7. Thermal decomposition study of Mn doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Malek, Tasmira J.; Chaki, S. H.; Tailor, J. P.; Deshpande, M. P.

    2016-05-01

    Fe3O4 is an excellent magnetic material among iron oxides. It has a cubic inverse spinel structure exhibiting distinguished electric and magnetic properties. In this paper the authors report the synthesis of Mn doped Fe3O4 nanoparticles by wet chemical reduction technique at ambient temperature and its thermal characterization. Ferric chloride hexa-hydrate (FeCl3•6H2O), manganese chloride tetra-hydrate (MnCl2•4H2O) and sodium boro-hydrate (NaBH4) were used for synthesis of Fe3O4 nanoparticles at ambient temperature. The elemental composition of the as-synthesized Mn doped Fe3O4 nanoparticles were determined by energy dispersive analysis of X-rays (EDAX) technique. Thermogravimetric (TG) and differential thermal analysis (DTA) were carried out on the Mn doped Fe3O4 nanoparticles in the temperature range of ambient to 1124 K. The thermo-curves revealed that the particles decompose by four steps. The kinetic parameters were evaluated using non-mechanistic equations for the thermal decomposition.

  8. The petrogenetic characterization of intermediate and silicic charnockites in high-grade terrains: a case study from southern India

    NASA Astrophysics Data System (ADS)

    Rajesh, H. M.

    2007-11-01

    Large charnockite massifs occur in some of the Precambrian high-grade terrains like the southern Indian granulite terrain. The Cardamom Hill charnockite massif from the Madurai Block, southern India, consists of an intermediate type and silicic type, with the intermediate type showing similarities to high-Ba-Sr granitoids with low K2O/Na2O ratios and the silicic type showing similarities to high-Ba-Sr granitoids with high K2O/Na2O ratios. Within the constraints imposed by near basaltic composition of the most mafic samples and their relatively high concentrations of both compatible and incompatible elements, comparison with recent experimental studies on various source compositions, and trace- and rare-earth-element modeling, the distinctive features of the intermediate charnockites can be best explained in terms of assimilation-fractional crystallization (AFC) models involving interaction between a mantle-derived basaltic magma and lower crustal materials. Silicic charnockites on the other hand are high temperature melts of moderately hydrous basaltic magmas. A two-stage model which involves an initial partial melting of hydrous basaltic magma and later fractionation explains the geochemical features of the silicic charnockites, with the fractionation stage most probably an open system AFC. It is suggested that for massifs showing spatial association of intermediate and silicic charnockites, a model taking into account their compositional difference in terms of the effect of variations in the conditions (e.g., temperature, water fugacity) that prevailed, can account for plausible petrogenetic scenarios.

  9. A method for intermediate strain rate compression testing and study of compressive failure mechanism of Mg-Al-Zn alloy

    NASA Astrophysics Data System (ADS)

    Gupta, Nikhil; Luong, Dung D.; Rohatgi, Pradeep K.

    2011-05-01

    Obtaining meaningful information from the test results is a challenge in the split-Hopkinson pressure bar (SHPB) test method if the specimen does not fail during the test. Although SHPB method is now widely used for high strain rate testing, this limitation has made it difficult to use it for characterization of materials in the intermediate strain rate range (typically 10-1000 s-1). In the present work, a method is developed to characterize materials in the intermediate strain rate range using SHPB setup. In this method, the specimen is repeatedly tested under compression at a given strain rate until failure is achieved. The stress-strain graphs obtained from each test cycle are used to plot the master stress-strain graph for that strain rate. This method is used to study the strain rate dependence of compressive response of a Mg-Al-Zn alloy in the intermediate strain rate range. A remarkable difference is observed in the failure mechanism of the alloy under quasi-static and intermediate strain rate compression. Matrix cracking is the main failure mechanism under quasi-static compression, whereas shattering of intermetallic precipitates, along with plastic deformation of the matrix, is discovered to become prominent as the strain rate is increased.

  10. Study of intermediates from transition metal excited-state electron-transfer reactions

    SciTech Connect

    Hoffman, M.Z.

    1991-12-31

    During this period, conventional and fast-kinetics techniques of photochemistry, photophysics, radiation chemistry, and electrochemistry were used for the characterization of the intermediates that are involved in transition metal excited-state electron-transfer reactions. The intermediates of interest were the excited states of Ru(II) and Cr(III) photosensitizers, their reduced forms, and the species formed in the reactions of redox quenchers and electron-transfer agents. Of particular concern has been the back electron-transfer reaction between the geminate pair formed in the redox quenching of the photosensitizers, and the dependence of its rate on solution medium and temperature in competition with transformation and cage escape processes.

  11. Combined PDF and Rietveld studies of ADORable zeolites and the disordered intermediate IPC-1P.

    PubMed

    Morris, Samuel A; Wheatley, Paul S; Položij, Miroslav; Nachtigall, Petr; Eliášová, Pavla; Čejka, Jiří; Lucas, Tim C; Hriljac, Joseph A; Pinar, Ana B; Morris, Russell E

    2016-09-28

    The disordered intermediate of the ADORable zeolite UTL has been structurally confirmed using the pair distribution function (PDF) technique. The intermediate, IPC-1P, is a disordered layered compound formed by the hydrolysis of UTL in 0.1 M hydrochloric acid solution. Its structure is unsolvable by traditional X-ray diffraction techniques. The PDF technique was first benchmarked against high-quality synchrotron Rietveld refinements of IPC-2 (OKO) and IPC-4 (PCR) - two end products of IPC-1P condensation that share very similar structural features. An IPC-1P starting model derived from density functional theory was used for the PDF refinement, which yielded a final fit of Rw = 18% and a geometrically reasonable structure. This confirms the layers do stay intact throughout the ADOR process and shows PDF is a viable technique for layered zeolite structure determination. PMID:27527381

  12. Positron lifetime studies of decomposition in 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) alloys

    SciTech Connect

    Dlubek, G. |; Lademann, P.; Krause, H.; Krause, S.; Unger, R.

    1998-09-04

    In the current paper, the decomposition behavior of the engineering alloys 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) is studied using positron lifetime measurements. Positrons probe open volume defects such as vacancies and dislocations. However, they may also be used to investigate coherent zones and incoherent precipitates. In order to understand the rather complicated precipitation sequences and the response of positrons to different type of precipitates occurring in 2024 and 7010 alloys, binary and ternary laboratory alloys were also investigated under the same experimental conditions as the engineering alloys. The interpretations of the results are based on experiences of the group from extensive positron studies of laboratory alloys such as Al-Zn, Al-Zn-Mg, Al-Cu, and further Al alloys (see also the review (4)). Their collected results are shown as lifetimes and curve-shape parameters S of the electron-positron momentum distribution curves characteristic for different precipitates in Al alloys.

  13. Decomposition of polycyclic aromatic hydrocarbons in atmospheric aqueous droplets through sulfate anion radicals: an experimental and theoretical study.

    PubMed

    Wang, Degao; Li, Yifan; Yang, Meng; Han, Min

    2008-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that have received considerable attention because of their carcinogenic and mutagenic effects. PAHs can be degraded by sulfate anion radicals in atmospheric aqueous droplets. This study was to investigate the mechanism and degradation products of sulfate anion radical reaction with anthracene (ANT) by experimental and quantum chemical approaches. From these observations of the experiments, the sulfate anion radical is capable of oxidizing ANT rapidly and three intermediates anthraquinone (ATQ), 1-hydroxyanthraquinone (1-hATQ), and 1,4-dihydroxyanthraquinone (1,4-dhATQ) were detected as degradation products by GC-MS. The proposed one-electronic transfer mechanism of sulfate anion radical reaction with ANT was modeled using hybrid density function theory (BHandHLYP) methods. Geometry optimization and vibrational frequency analysis calculation were performed for reactants, transition states, intermediates, and products. The potential energy surfaces of these reactions are explored to establish structures and relative energies of reactants, intermediates, transition states, and products. Computational results suggest that initial electron transfer step is predicted to have activation energy of -3.35 kcal/mol in water, indicating that ANT can be oxidized quickly in atmospheric aqueous droplets. The reaction pathways have been proposed on the basis of these experimental and theoretical findings. The results may provide useful information for a better understanding of the sulfate anion radical-initiated reactions in atmospheric aqueous droplets such as clouds, rains or fogs.

  14. A sulfonium cation intermediate in the mechanism of methionine sulfoxide reductase B: a DFT study.

    PubMed

    Robinet, Jesse J; Dokainish, Hisham M; Paterson, David J; Gauld, James W

    2011-07-28

    The hybrid density functional theory method B3LYP in combination with three systematically larger active site models has been used to investigate the substrate binding and catalytic mechanism by which Neisseria gonorrhoeae methionine sulfoxide reductase B (MsrB) reduces methionine-R-sulfoxide (Met-R-SO) to methionine. The first step in the overall mechanism is nucleophilic attack of an active site thiolate at the sulfur of Met-R-SO to form an enzyme-substrate sulfurane. This occurs with concomitant proton transfer from an active site histidine (His480) residue to the substrates oxygen center. The barrier for this step, calculated using our largest most complete active site model, is 17.2 kJ mol(-1). A subsequent conformational rearrangement and intramolecular -OH transfer to form an enzyme-derived sulfenic acid ((Cys495)S-OH) is not enzymatically feasible. Instead, transfer of a second proton from a second histidyl active site residue (His477) to the sulfurane's oxygen center to give water and a sulfonium cation intermediate is found to be greatly preferred, occurring with a quite low barrier of just 1.2 kJ mol(-1). Formation of the final product complex in which an intraprotein disulfide bond is formed with generation of methionine preferably occurs in one step via nucleophilic attack of the sulfur of a second enzyme thiolate ((Cys440)S(-)) at the S(Cys495) center of the sulfonium intermediate with a barrier of 23.8 kJ mol(-1). An alternate pathway for formation of the products via a sulfenic acid intermediate involves enzymatically feasible, but higher energy barriers. The role and impact of hydrogen bonding and active site residues on the properties and stability of substrate and mechanism intermediates and the affects of mutating His477 are also examined and discussed. PMID:21721538

  15. Serine Protease Catalysis: A Computational Study of Tetrahedral Intermediates and Inhibitory Adducts.

    PubMed

    Ngo, Phong D; Mansoorabadi, Steven O; Frey, Perry A

    2016-08-01

    Peptide boronic acids and peptidyl trifluoromethyl ketones (TFKs) inhibit serine proteases by forming monoanionic, tetrahedral adducts to serine in the active sites. Investigators regard these adducts as analogs of monoanionic, tetrahedral intermediates. Density functional theory (DFT) calculations and fractional charge analysis show that tetrahedral adducts of model peptidyl TFKs are structurally and electrostatically very similar to corresponding tetrahedral intermediates. In contrast, the DFT calculations show the structures and electrostatic properties of analogous peptide boronate adducts to be significantly different. The peptide boronates display highly electrostatically positive boron, with correspondingly negative ligands in the tetrahedra. In addition, the computed boron-oxygen and boron-carbon bond lengths in peptide boronates (which are identical or very similar to the corresponding bonds in a peptide boronate adduct of α-lytic protease determined by X-ray crystallography at subangstrom resolution) are significantly longer than the corresponding bond lengths in model tetrahedral intermediates. Since protease-peptidyl TFKs incorporate low-barrier hydrogen bonds (LBHBs) between an active site histidine and aspartate, while the protease-peptide boronates do not, these data complement the spectroscopic and chemical evidence for the participation of LBHBs in catalysis by serine proteases. Moreover, while the potency of these classes of inhibitors can be correlated to the structures of the peptide moieties, the present results indicate that the strength of their bonds to serine contribute significantly to their inhibitory properties. PMID:27387593

  16. Introducing the Improved Heaviside Approach to Partial Fraction Decomposition to Undergraduate Students: Results and Implications from a Pilot Study

    ERIC Educational Resources Information Center

    Man, Yiu-Kwong

    2012-01-01

    Partial fraction decomposition is a useful technique often taught at senior secondary or undergraduate levels to handle integrations, inverse Laplace transforms or linear ordinary differential equations, etc. In recent years, an improved Heaviside's approach to partial fraction decomposition was introduced and developed by the author. An important…

  17. Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde.

    PubMed

    Sivaramakrishnan, Raghu; Michael, Joe V; Harding, Lawrence B; Klippenstein, Stephen J

    2015-07-16

    The mechanism for the thermal decomposition of acetaldehyde has been revisited with an analysis of literature kinetics experiments using theoretical kinetics. The present modeling study was motivated by recent observations, with very sensitive diagnostics, of some unexpected products in high temperature microtubular reactor experiments on the thermal decomposition of CH3CHO and its deuterated analogs, CH3CDO, CD3CHO, and CD3CDO. The observations of these products prompted the authors of these studies to suggest that the enol tautomer, CH2CHOH (vinyl alcohol), is a primary intermediate in the thermal decomposition of acetaldehyde. The present modeling efforts on acetaldehyde decomposition incorporate a master equation reanalysis of the CH3CHO potential energy surface (PES). The lowest-energy process on this PES is an isomerization of CH3CHO to CH2CHOH. However, the subsequent product channels for CH2CHOH are substantially higher in energy, and the only unimolecular process that can be thermally accessed is a reisomerization to CH3CHO. The incorporation of these new theoretical kinetics predictions into models for selected literature experiments on CH3CHO thermal decomposition confirms our earlier experiment and theory-based conclusions that the dominant decomposition process in CH3CHO at high temperatures is C-C bond fission with a minor contribution (∼10-20%) from the roaming mechanism to form CH4 and CO. The present modeling efforts also incorporate a master-equation analysis of the H + CH2CHOH potential energy surface. This bimolecular reaction is the primary mechanism for removal of CH2CHOH, which can accumulate to minor amounts at high temperatures, T > 1000 K, in most lab-scale experiments that use large initial concentrations of CH3CHO. Our modeling efforts indicate that the observation of ketene, water, and acetylene in the recent microtubular experiments are primarily due to bimolecular reactions of CH3CHO and CH2CHOH with H-atoms and have no bearing on

  18. Studies on CO 2 decomposition over H 2-reduced MFe 2O 4 (M = Ni, Cu, Co, Zn)

    NASA Astrophysics Data System (ADS)

    Ma, Lingjuan; Wu, Rui; Liu, Huadong; Xu, Wenju; Chen, Linshen; Chen, Songying

    2011-12-01

    Decomposition of CO 2 over reduced MFe 2O 4 (M = Ni, Co, Cu, Zn) was studied by H 2-TPR, H 2-TG, and CO 2-TG. XRD Rietveld analysis was used for determining phase composition and crystallite size of reduced and oxidized samples. The results indicate that spinel CoFe 2O 4 and CuFe 2O 4 are reduced to metals by H 2, while ZnFe 2O 4 and NiFe 2O 4 only partly reduced at 350 °C. The CoFe 2O 4 spinel ferrite shows the best activity in decomposing CO 2 and the ZnFe 2O 4 shows the best recovery ability in the process of redox.

  19. Perfluoropolyalkylether decomposition on catalytic aluminas

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1994-01-01

    The decomposition of Fomblin Z25, a commercial perfluoropolyalkylether liquid lubricant, was studied using the Penn State Micro-oxidation Test, and a thermal gravimetric/differential scanning calorimetry unit. The micro-oxidation test was conducted using 440C stainless steel and pure iron metal catalyst specimens, whereas the thermal gravimetric/differential scanning calorimetry tests were conducted using catalytic alumina pellets. Analysis of the thermal data, high pressure liquid chromatography data, and x-ray photoelectron spectroscopy data support evidence that there are two different decomposition mechanisms for Fomblin Z25, and that reductive sites on the catalytic surfaces are responsible for the decomposition of Fomblin Z25.

  20. Membrane fusion intermediates and the effect of cholesterol: An in-house X-ray scattering study

    NASA Astrophysics Data System (ADS)

    Aeffner, S.; Reusch, T.; Weinhausen, B.; Salditt, T.

    2009-10-01

    We have developed an X-ray scattering setup which allows to study membrane fusion intermediates or other nonlamellar lipid mesophases by laboratory-scale X-ray sources alone, thus taking advantage of unrestricted beamtime compared to synchrotron sources. We report results of a study of pure lipid bilayers and phospholipid/cholesterol binary mixtures. Stalks, putative intermediate structures occurring during the membrane fusion process, can clearly be identified from reconstructed electron density maps. Phase diagrams of the lyotropic phase behavior of DOPC/cholesterol and DPhPC/cholesterol samples are presented. If cholesterol is present in moderate concentrations, it can substantially promote the formation of stalks at higher degree of hydration. In addition, a possibly new phase in DOPC/cholesterol is found at high cholesterol content in the low humidity range.

  1. Study of the decomposition pathway of 12-molybdophosphoric acid in aqueous solutions by micro Raman spectroscopy.

    PubMed

    Bajuk-Bogdanović, D; Uskoković-Marković, S; Hercigonja, R; Popa, A; Holclajtner-Antunović, I

    2016-01-15

    Micro Raman spectroscopy was applied to investigate the speciation of heteropoly and isopoly molybdates in 0.05 and 0.005 M aqueous solutions of 12-molybdophosphoric acid at pH values between 1 and 6. For comparative purposes, (31)P NMR spectroscopy was applied too. It is shown that stability of Keggin anion is influenced both by pH and concentration of solution. The Keggin structure is stable in acidic solutions (pH<1.6) while defective Keggin structures are formed with further alkalization (up to pH5.6). Monolacunary anion PMo11O(39)(7-) is the main component in the pH region from 1.6 to 3.4. Further removal of molybdenyl species causes the appearance of other vacant Keggin structures such as PMo9O31(OH)(3)(6-) and PMo6O(25)(9-) at about pH4. At pH5.0, anion PMo6O(25)(9-) is the main species. In solutions with pH greater than 5.0, heteropolymolybdates disappear completely and isopolymolybdates Mo7O(24)(6-) and MoO(4)(2-) are formed in higher amounts. In more diluted solution of 0.005 M, the decomposition scheme of 12-molybdophosphoric acid solution with increasing of pH takes place without observation of significant amounts of Mo7O(24)(6-) species. If alkalinization is performed with 0.5 M instead of 5 M NaOH, there are no significant changes in the Raman spectra of solutions. It is shown that the spectra of evaporated samples may be used for the identification of molecular species in corresponding concentrated solutions. However, Raman spectra of dry residues of more diluted solutions differ from spectra of corresponding solutions due to the reactions performed during the process of drying and cannot be used for unambiguous identification of species in solution. Acidification of 0.05 M solution of Na2MoO4 shows that at pH>5.6, molybdate anion MoO(4)(2-) dominates, while in the pH range between 5.6 and 1, heptamolybdate anion Mo7O(24)(6-) is preferentially formed.

  2. Decomposition in northern Minnesota peatlands

    SciTech Connect

    Farrish, K.W.

    1985-01-01

    Decomposition in peatlands was investigated in northern Minnesota. Four sites, an ombrotrophic raised bog, an ombrotrophic perched bog and two groundwater minerotrophic fens, were studied. Decomposition rates of peat and paper were estimated using mass-loss techniques. Environmental and substrate factors that were most likely to be responsible for limiting decomposition were monitored. Laboratory incubation experiments complemented the field work. Mass-loss over one year in one of the bogs, ranged from 11 percent in the upper 10 cm of hummocks to 1 percent at 60 to 100 cm depth in hollows. Regression analysis of the data for that bog predicted no mass-loss below 87 cm. Decomposition estimates on an area basis were 2720 and 6460 km/ha yr for the two bogs; 17,000 and 5900 kg/ha yr for the two fens. Environmental factors found to limit decomposition in these peatlands were reducing/anaerobic conditions below the water table and cool peat temperatures. Substrate factors found to limit decomposition were low pH, high content of resistant organics such as lignin, and shortages of available N and K. Greater groundwater influence was found to favor decomposition through raising the pH and perhaps by introducing limited amounts of dissolved oxygen.

  3. Thermal decomposition of energetic materials by ReaxFF reactive molecular dynamics

    NASA Astrophysics Data System (ADS)

    Zhang, L.

    2005-07-01

    Understanding the complex physicochemical processes that govern the initiation and decomposition kinetics of energetic materials can pave the way for modifying the explosive or propellant formulation to improve their performance and reduce the sensitivity. In this work, we used molecular dynamics (MD) simulations with the reactive force field (ReaxFF) to study the thermal decomposition of pure crystals (RDX, HMX) as well as crystals bonded with polyurethane chains (Estane). The preliminary simulation results show that pure RDX and HMX crystals exhibit similar decomposition kinetics with main products (e.g., N2, H2O, CO2, and CO) and intermediates (NO2, NO, HONO, OH) in a good agreement with experiment. We also studied the effect of temperature on decomposition rate which increases at higher temperatures. With addition of polymer binders, we found that the reactivity of these energetic materials is reduced, and the polymer chains packing along different planes may also influence their thermal decomposition. In addition, we studied the thermal decomposition of TATP and hydrazine which are examples of ReaxFF development for non- nitramine based energetic materials.

  4. Nitrogen Amendment Stimulated Decomposition of Maize Straw-Derived Biochar in a Sandy Loam Soil: A Short-Term Study

    PubMed Central

    Lu, Weiwei; Ding, Weixin; Zhang, Junhua; Zhang, Huanjun; Luo, Jiafa; Bolan, Nanthi

    2015-01-01

    This study examined the effect of nitrogen (N) on biochar stability in relation to soil microbial community as well as biochar labile components using δ13C stable isotope technology. A sandy loam soil under a long-term rotation of C3 crops was amended with biochar produced from maize (a C4 plant) straw in absence (BC0) and presence (BCN) of N and monitored for dynamics of carbon dioxide (CO2) flux, phospholipid fatty acids (PLFAs) profile and dissolved organic carbon (DOC) content. N amendment significantly increased the decomposition of biochar during the first 5 days of incubation (P < 0.05), and the proportions of decomposed biochar carbon (C) were 2.30% and 3.28% in BC0 and BCN treatments, respectively, during 30 days of incubation. The magnitude of decomposed biochar C was significantly (P < 0.05) higher than DOC in biochar (1.75%) and part of relatively recalcitrant biochar C was mineralized in both treatments. N amendment increased soil PLFAs concentration at the beginning of incubation, indicating that microorganisms were N-limited in test soil. Furthermore, N amendment significantly (P < 0.05) increased the proportion of gram-positive (G+) bacteria and decreased that of fungi, while no noticeable changes were observed for gram-negative (G−) bacteria and actinobacteria at the early stage of incubation. Our results indicated that N amendment promoted more efficiently the proliferation of G+ bacteria and accelerated the decomposition of relatively recalcitrant biochar C, which in turn reduced the stability of maize straw-derived biochar in test soil. PMID:26192282

  5. Feasibility study of sparse-angular sampling and sinogram interpolation in material decomposition with a photon-counting detector

    NASA Astrophysics Data System (ADS)

    Kim, Dohyeon; Jo, Byungdu; Park, Su-Jin; Kim, Hyemi; Kim, Hee-Joung

    2016-03-01

    Spectral computed tomography (SCT) is a promising technique for obtaining enhanced image with contrast agent and distinguishing different materials. We focused on developing the analytic reconstruction algorithm in material decomposition technique with lower radiation exposure and shorter acquisition time. Sparse-angular sampling can reduce patient dose and scanning time for obtaining the reconstruction images. In this study, the sinogram interpolation method was used to improve the quality of material decomposed images in sparse angular sampling. A prototype of spectral CT system with 64 pixels CZT-based photon counting detector was used. The source-to-detector distance and the source-tocenter of rotation distance were 1200 and 1015 mm, respectively. The x-ray spectrum at 90 kVp with a tube current of 110 μA was used. Two energy bins (23-33 keV and 34-44 keV) were set to obtain the two images for decomposed iodine and calcification. We used PMMA phantom and its height and radius were 50 mm and 17.5 mm, respectively. The phantom contained 4 materials including iodine, gadolinium, calcification, and liquid state lipid. We evaluated the signal to noise ratio (SNR) of materials to examine the significance of sinogram interpolation method. The decomposed iodine and calcification images were obtained by projection based subtraction method using two energy bins with 36 projection data. The SNR in decomposed images were improved by using sinogram interpolation method. And these results indicated that the signal of decomposed material was increased and the noise of decomposed material was reduced. In conclusion, the sinogram interpolation method can be used in material decomposition method with sparse-angular sampling.

  6. Nitrogen Amendment Stimulated Decomposition of Maize Straw-Derived Biochar in a Sandy Loam Soil: A Short-Term Study.

    PubMed

    Lu, Weiwei; Ding, Weixin; Zhang, Junhua; Zhang, Huanjun; Luo, Jiafa; Bolan, Nanthi

    2015-01-01

    This study examined the effect of nitrogen (N) on biochar stability in relation to soil microbial community as well as biochar labile components using δ13C stable isotope technology. A sandy loam soil under a long-term rotation of C3 crops was amended with biochar produced from maize (a C4 plant) straw in absence (BC0) and presence (BCN) of N and monitored for dynamics of carbon dioxide (CO2) flux, phospholipid fatty acids (PLFAs) profile and dissolved organic carbon (DOC) content. N amendment significantly increased the decomposition of biochar during the first 5 days of incubation (P < 0.05), and the proportions of decomposed biochar carbon (C) were 2.30% and 3.28% in BC0 and BCN treatments, respectively, during 30 days of incubation. The magnitude of decomposed biochar C was significantly (P < 0.05) higher than DOC in biochar (1.75%) and part of relatively recalcitrant biochar C was mineralized in both treatments. N amendment increased soil PLFAs concentration at the beginning of incubation, indicating that microorganisms were N-limited in test soil. Furthermore, N amendment significantly (P < 0.05) increased the proportion of gram-positive (G+) bacteria and decreased that of fungi, while no noticeable changes were observed for gram-negative (G-) bacteria and actinobacteria at the early stage of incubation. Our results indicated that N amendment promoted more efficiently the proliferation of G+ bacteria and accelerated the decomposition of relatively recalcitrant biochar C, which in turn reduced the stability of maize straw-derived biochar in test soil.

  7. Studies on the decomposition of the oxime HI 6 in aqueous solution.

    PubMed

    Eyer, P; Hell, W; Kawan, A; Klehr, H

    1986-12-01

    HI 6 has been shown to be efficacious in soman intoxication of laboratory animals by reactivation of acetylcholinesterase. To assess possible risks involved in the administration of HI 6 its degradation products were analyzed at pH 2.0, 4.0, 7.4, and 9.0. At pH 2.0, where HI 6 in aqueous solution has its maximal stability, attack on the aminal-acetal bond of the "ether bridge" predominates, with formation of formaldehyde, isonicotinamide, and pyridine-2-aldoxime. Besides, HI 6 decomposes at the oxime group yielding 2-cyanopyridine. Liberation of hydrocyanic acid at pH 2.0 is below 5%. At pH 7.4, primary attack is on the oxime group, resulting in formation of the corresponding pyridone via an intermediate nitrile. The pyridone has been isolated and identified as 2-pyridinone, 1-[(4-carbamoylpyridinio)methoxy)methyl)formate. This major metabolite deaminates further to the 2-pyridinone, 1-[(4-carboxypyridinio)methoxy)methyl) derivative, which ultimately decomposes into formaldehyde, isonicotinic acid, and 2-pyridone. Hydrolysis of the acid amide group probably also occurs with HI 6 itself. Significant amounts of free hydrocyanic acid were only detected in the presence of an alkali trap; otherwise hydrocyanic acid reacts with formaldehyde to yield hydroxyacetonitrile from which hydrocyanic acid can be liberated again. Up to 0.6 equivalents of hydrocyanic acid were evolved at pH 7.4. After repetitive administration and impaired renal elimination of HI 6, e.g. during renal shock, there might be some risk of cyanide intoxication. PMID:3827594

  8. Ab initio study of protonated nitrosamide: a possible intermediate in the deNO x process

    NASA Astrophysics Data System (ADS)

    Kulkarni, Sudhir A.; Pundlik, Savita S.

    1995-10-01

    Ab initio calculations on protonated nitrosamide, a possible intermediate in the deNO x process, have been performed. A mechanism involving the formation of an intermediate NH 3NO + was proposed by Egsgaard, Carlsen and Madsen and tested by performing flame experiments with mass spectrometry. In the present work, the absence of NH 3NO + in the flame has been supported on the basis of its structure. This cation is observed to be a loosely bound adduct of NH 3 and NO + at and beyond the HF level of theory. On the other hand, NH 2NOH + is found to be a covalently bonded compound at all theoretical levels. Topographical analysis of electron density and electrostatic potential has been utilized to gain insight into bonding properties and to predict the possible sites of protonation. The vibrational spectra of both protonated nitrosamide cations are reported. The feasibility of proton transfer reactions of NH 3NO + with ammonia and water are investigated using heats of reactions. These values indicate that such a reaction is possible with NH 3 but unfavorable with H 2O.

  9. Catalytic Mechanism of Nitrile Hydratase Subsequent to Cyclic Intermediate Formation: A QM/MM Study.

    PubMed

    Kayanuma, Megumi; Shoji, Mitsuo; Yohda, Masafumi; Odaka, Masafumi; Shigeta, Yasuteru

    2016-04-01

    The catalytic mechanism of an Fe-containing nitrile hydratase (NHase) subsequent to the formation of a cyclic intermediate was investigated using a hybrid quantum mechanics/molecular mechanics (QM/MM) method. We identified the following mechanism: (i) proton transfer from βTyr72 to the substrate via αSer113, and cleavage of the S-O bond of αCys114-SO(-) and formation of a disulfide bond between αCys109 and αCys114; (ii) direct attack of a water molecule on the sulfur atom of αCys114, which resulted in the generation of both an imidic acid and a renewed sulfenic cysteine; and (iii) isomerization of the imidic acid to the amide. In addition, to clarify the role of βArg56K, which is one of the essential amino residues in the enzyme, we analyzed a βR56K mutant in which βArg56 was replaced by Lys. The results suggest that βArg56 is necessary for the formation of disulfide intermediate by stabilizing the cleavage of the S-O bond via a hydrogen bond with the oxygen atom of αCys114-SO(-). PMID:27007978

  10. Site study plan for intermediate hydrology clusters tests wells Deaf Smith County Site, Texas

    SciTech Connect

    Not Available

    1988-01-01

    To characterize the geologic, geochemical, and hydrologic characteristics of intermediate-depth formations at the proposed Deaf Smith County, Texas, repository site, wells called Intermediate Hydrology clusters will test the Dewey Lake, Alibates, Salado, Yates, Upper and Lower Seven Rivers, and Queen Grayburg Formations. Sixteen wells will be installed at six locations. One location will have four wills, two locations will have three wells, and three locations will have two wells for a total of 16 wells. Testing of the formations is to proceed from the bottom up, with 2-day pumping tests at the less permeable formations. Tracer tests and tests for verticall hydraulic properties will be designed and performed after other hydrologic tests are completed. After testing, selected wells are to be completed as single or possibly dual monitoring wells to observe water-level trends. To develop a hydrogeologic testing plan, the response of each formation to potential testing procedures was evaluated using design values and an assumend range for hydraulic parameters. These evaluations indicate that hydraulic properties of a sandy zone of the Dockum, the lower Sever Rivers, and possibly the Alibates and Queen/Grayburg can be determined by pumping tests. Standard of shut-in slug tests must be conducted in the remaining formations. Tests of very long duration would be required to determine the verticla properties of less permeable formations. Tracer tests would also require weeks or months. 61 figs., 34 refs., 4 tabs.

  11. FTIR studies of iron-carbonyl intermediates in allylic alcohol photoisomerization.

    PubMed

    Chong, Thiam Seong; Tan, Sze Tat; Fan, Wai Yip

    2006-06-23

    The 532 or 355 nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe(3)(CO)(12)] or [Fe(CO)(4)PPh(3)] in hexane was investigated. The Fourier transform infrared (FTIR) absorption spectra of iron-carbonyl intermediate species such as [Fe(CO)(5)], [Fe(CO)(4)(R-C(3)H(4)OH)], and more importantly the pi-allyl iron-carbonyl hydride species [FeH(CO)(3)(R-C(3)H(3)OH)] (R=H, Me, Ph) were recorded during the catalytic process using [Fe(3)(CO)(12)] as the catalytic precursor. When [Fe(CO)(4)PPh(3)] was photolyzed with 355 nm, [FeH(CO)(3)(R-C(3)H(3)OH)] was also generated indicating the common occurrence of the species in these two systems. The pi-allyl hydride species is long believed to be a key intermediates and its detection here lends support to the pi-allyl mechanism of the photoisomerization of allyl alcohols.

  12. Intermediates in dioxygen activation by methane monooxygenase: A QM/MM study

    PubMed Central

    Rinaldo, David; Philipp, Dean M.; Lippard, Stephen J.; Friesner, Richard A.

    2008-01-01

    Protein effects in the activation of dioxygen by methane monooxygenase (MMO) were investigated by using combined QM/MM and broken-symmetry Density Functional Theory (DFT) methods. The effects of a novel empirical scheme recently developed by our group on the relative DFT energies of the various intermediates in the catalytic cycle are investigated. Inclusion of the protein leads to much better agreement between the experimental and computed geometric structures for the reduced form (MMOHred). Analysis of the electronic structure of MMOHred reveals that the two iron atoms have distinct environments. Different coordination geometries tested for the MMOHperoxo intermediate reveal that, in the protein environment, the μ-η2,η2 structure is more stable than the others. Our analysis also shows that the protein helps to drive reactants towards products along the reaction path. Furthermore, these results demonstrate the importance of including the protein environment in our models and the usefulness of the QM/MM approach for accurate modeling of enzymatic reactions. A discrepancy remains in our calculation of the Fe-Fe distance in our model of HQ as compared to EXAFS data obtained several years ago, for which we currently do not have an explanation. PMID:17326634

  13. Key intermediates in nitrogen transformation during microwave pyrolysis of sewage sludge: a protein model compound study.

    PubMed

    Zhang, Jun; Tian, Yu; Cui, Yanni; Zuo, Wei; Tan, Tao

    2013-03-01

    The nitrogen transformations with attention to NH3 and HCN were investigated at temperatures of 300-800°C during microwave pyrolysis of a protein model compound. The evolution of nitrogenated compounds in the char, tar and gas products were conducted. The amine-N, heterocyclic-N and nitrile-N compounds were identified as three important intermediates during the pyrolysis. NH3 and HCN were formed with comparable activation energies competed to consume the same reactive substances at temperatures of 300-800°C. The deamination and dehydrogenation of amine-N compounds from protein cracking contributed to the formation of NH3 (about 8.9% of Soy-N) and HCN (6.6%) from 300 to 500°C. The cracking of nitrile-N and heterocyclic-N compounds from the dehydrogenation and polymerization of amine-N generated HCN (13.4%) and NH3 (31.3%) between 500 and 800°C. It might be able to reduce the HCN and NH3 emissions through controlling the intermediates production at temperatures of 500-800°C.

  14. Manifestation of intermediate phase in mechanical properties: Nano-indentation studies on Ge-Te-Si bulk chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Das, Chandasree; Kiran, M. S. R. N.; Ramamurty, U.; Asokan, S.

    2012-12-01

    Nano-indentation studies have been undertaken on bulk Ge15Te85-xSix glasses (0≤x≤9), to estimate hardness, H and elastic modulus, E. It is found that E and H increase initially with the increase in the atomic percent of Si. Further, a plateau is seen in the composition dependence of E and H in the composition range 2≤x≤6. It is also seen that the addition of up to 2 at% Si increases the density ρ of the glass considerably; however, further additions of Si lead to a near linear reduction in ρ, in the range 2≤x≤6. Beyond x=6, ρ increases again with Si content. The variation of molar volume Vm brings out a more fascinating picture. A plateau is seen in the intermediate phase suggesting that the molecular structure of the glasses is adapting to keep the count of constraints fixed in this particular phase. The observed variations in mechanical properties are associated with the Boolchand's intermediate phase in the present glassy system, in the composition range 2≤x≤6, suggested earlier from calorimetric and electrical switching studies. The present results reveal rather directly the existence of the intermediate phase in elastic and plastic properties of chalcogenide glasses.

  15. Combustion chemistry via metadynamics: benzyl decomposition revisited.

    PubMed

    Polino, Daniela; Parrinello, Michele

    2015-02-12

    Large polycyclic aromatic hydrocarbons (PAHs) are thought to be responsible for the formation of soot particles in combustion processes. However, there are still uncertainties on the course that leads small molecules to form PAHs. This is largely due to the high number of reactions and intermediates involved. Metadynamics combined with ab initio molecular dynamics can provide a very precious contribution because offers the possibility to explore new possible pathways and suggest new mechanisms. Here, we adopt this method to investigate the chemical evolution of the benzyl radical, whose role is very important in PAHs growth. This species has been intensely studied, and though most of its chemistry is known, there are still open questions regarding its decomposition. The simulation reproduces the most commonly accepted decomposition pathway and it suggests also a new one which can explain recent experimental data that are in contradiction with the old mechanism. In addition, quantitative free energy evaluation of some key reaction steps sheds light on the role of entropy.

  16. Capillary electrophoretic study of dibasic acids of different structures: Relation to separation of oxidative intermediates in remediation

    SciTech Connect

    Yu, Z.; Cocke, D.L.

    1998-09-01

    Dicarboxylic acids are important in environmental chemistry because they are intermediates in oxidative processes involved in natural remediation and waste management processes such as oxidative detoxification and advanced oxidation. Capillary electrophoresis (CE), a promising technique for separating and analyzing these intermediates, has been used to examine a series of dibasic acids of different structures and conformations. This series includes malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, fumaric acid, phthalic acid, and trans, trans-muconic acid. The CE parameters as well as structural variations (molecular structure and molecular isomers, buffer composition, pH, applied voltage, injection mode, current, temperature, and detection wavelength) that affect the separations and analytical results have been examined in this study. Those factors that affect the separation have been delineated. Among these parameters, the pH has been found to be the most important, which affects the double-layer of the capillary wall, the electro-osmotic flow and analyte mobility. The optimum pH for separating these dibasic acids, as well as the other parameters are discussed in detail and related to the development of methods for analyzing oxidation intermediates in oxidative waste management procedures.

  17. Pulsed magnetic field study of the spin gap in intermediate valence compound SmB 6

    NASA Astrophysics Data System (ADS)

    Flachbart, K.; Bartkowiak, M.; Demishev, S.; Gabani, S.; Glushkov, V.; Herrmannsdorfer, T.; Moshchalkov, V.; Shitsevalova, N.; Sluchanko, N.

    2009-10-01

    In this work, we report the behavior of electrical resistivity of SmB 6 at temperatures between 2.2 and 70 K in pulsed magnetic fields up to 54 T. A strong negative magnetoresistance was detected with increasing magnetic field, when lowering the temperature in the range T<30 K. We show that the amplitude of negative magnetoresistance reaches its maximum dR/R~70% at B=54 T, in the vicinity of phase transition occurring in this strongly correlated electron system at TC~5 K. The crossover from negative magnetoresistance to positive magnetoresistance found at intermediate temperatures at T>30 K is discussed within the framework of exciton-polaron model of local charge fluctuations in SmB 6 proposed by Kikoin and Mishchenko. It seems that these exciton-polaron in-gap states are influenced both by temperature and magnetic field.

  18. Flexible response and the INF (Intermediate-range Nuclear Force) Treaty: what next. Study project

    SciTech Connect

    Williams, H.A.

    1988-03-14

    The prospect of the Intermediate-range Nuclear Force (INF) Treaty led the former Supreme Allied Commander, Europe, GEN Bernard Rogers, to claim that NATO would lose weapons vital to the Alliance's defense when Pershing II (PII) and Ground-Launched Cruise Missiles (GLCM) were withdrawn from Europe. Nuclear weapons and the NATO strategy of flexible response are inseparably dependent upon each other. GEN Rogers' comments focus directly on the capability which PII and GLCM provided NATO to strike Soviet territory in event of conflict and if such an escalatory step was deemed necessary. Various sources were researched to determine if the INF Treaty will cripple the flexible response strategy; while it should not, certain changes in NATO's approach to defense are suggested. Specifically, conventional and nuclear improvements, the latter within the terms of the INF Treaty, are suggested, as are conventional force reduction negotiations and the Europeanization of NATO.

  19. Fundamental studies of reactive intermediates in homogeneous catalysis. Final technical report

    SciTech Connect

    1998-09-01

    The chief aims during the contract period were to design, construct and implement a new flowing afterglow-guided ion beam instrument for use in determining thermochemical properties of organometallic species pertinent to homogeneous catalysis, and to develop an electrospray ionization (ESI) source for the flowing afterglow-triple quadrupole apparatus for use in real-time analysis of reactive intermediates in catalytically active solutions. Both goals were achieved. In parallel with development of the guided ion beam and electrospray ionization experiments, the author used existing equipment to work on some of the problems outlined in the previous proposal, and to open up new research areas. A summary of research activities and publications acknowledging DOE support follows.

  20. UV photolysis of catalase revisited: a spectral study of photolytic intermediates.

    PubMed

    Aubailly, M; Haigle, J; Giordani, A; Morlière, P; Santus, R

    2000-06-01

    The 365-nm irradiation of 4.6 microM (approximately equal to 1.1 mg/ml) catalase solutions in pH 7.4 phosphate buffer induces spectral modifications. Difference spectra show maxima at 434, 555, 584 nm at the beginning of the irradiation, then a final spectrum with a maximum at 568 nm and a shoulder at 530 nm is observed. These results suggest the formation of compound III (oxyferrous catalase) and compound II, respectively. In deaerated 0.1 M, pH 8.7 borate buffer, the ferrous catalase is characterized by maxima at 563 and 594 nm. Hydrogen donors such as ethyl alcohol, formate and p-cresol inhibit, but citrate ions enhance the formation of these intermediates. A mechanism involving Fe(III) reduction according to an internal electron transfer is proposed. PMID:11073317

  1. Comparative electron paramagnetic resonance study of radical intermediates in turnip peroxidase isozymes.

    PubMed

    Ivancich, A; Mazza, G; Desbois, A

    2001-06-12

    The occurrence of isozymes in plant peroxidases is poorly understood. Turnip roots contain seven season-dependent isoperoxidases with distinct physicochemical properties. In the work presented here, multifrequency electron paramagnetic resonance spectroscopy has been used to characterize the Compound I intermediate obtained by the reaction of turnip isoperoxidases 1, 3, and 7 with hydrogen peroxide. The broad (2500 G) Compound I EPR spectrum of all three peroxidases was consistent with the formation of an exchange-coupled oxoferryl-porphyrinyl radical species. A dramatic pH dependence of the exchange interaction of the [Fe(IV)=O por(*+)] intermediate was observed for all three isoperoxidases and for a pH range of 4.5-7.7. This result provides substantial experimental evidence for previous proposals concerning the protein effect on the ferro- or antiferromagnetic character of the exchange coupling of Compound I based on model complexes. Turnip isoperoxidase 7 exhibited an unexpected pH effect related to the nature of the Compound I radical. At basic pH, a narrow radical species ( approximately 50 G) was formed together with the porphyrinyl radical. The g anisotropy of the narrow radical Delta(g) = 0.0046, obtained from the high-field (190 and 285 GHz) EPR spectrum, was that expected for tyrosyl radicals. The broad g(x) edge of the Tyr* spectrum centered at a low g(x) value (2.00660) strongly argues for a hydrogen-bonded tyrosyl radical in a heterogeneous microenvironment. The relationship between tyrosyl radical formation and the higher redox potential of turnip isozyme 7, as compared to that of isozyme 1, is discussed. PMID:11389600

  2. Comparative study of differential matrix and extended polar decomposition formalisms for polarimetric characterization of complex tissue-like turbid media.

    PubMed

    Kumar, Satish; Purwar, Harsh; Ossikovski, Razvigor; Vitkin, I Alex; Ghosh, Nirmalya

    2012-10-01

    Development of methodologies for quantification/unique interpretation of the intrinsic polarimetry characteristics of biological tissues are important for various applications involving tissue characterization/diagnosis. A detailed comparative evaluation of the polar decomposition and the differential matrix decomposition of Mueller matrices for extraction/quantification of the intrinsic polarimetry characteristics (with special emphasis on linear retardance δ, optical rotation Ψ and depolarization Δ parameters was performed, because these are the most prominent tissue polarimetry effects) from complex tissue-like turbid media exhibiting simultaneous scattering and polarization effects. The results suggest that for media exhibiting simultaneous linear retardance and optical rotation polarization events, the use of retarder polar decomposition with its associated analysis which assumes sequential occurrence of these effects, results in systematic underestimation of δ and overestimation of Ψ parameters. Analytical relationships between the polarization parameters (δ, Ψ) extracted from both the retarder polar decomposition and the differential matrix decomposition for either simultaneous or sequential occurrence of the linear retardance and optical rotation effects were derived. The self-consistency of both decompositions is validated on experimental Mueller matrices recorded from tissue-simulating phantoms (whose polarization properties are controlled, known a-priori, and exhibited simultaneously) of increasing biological complexity. Additional theoretical validation tests were performed on Monte Carlo-generated Mueller matrices from analogous turbid media exhibiting simultaneous depolarization (Δ), linear retardance (δ) and optical rotation (Ψ) effects. After successful evaluation, the potential advantage of the differential matrix decomposition over the polar decomposition formalism was explored for monitoring of myocardial tissue regeneration following

  3. Remarkable influence of surface composition and structure of oxidized iron layer on orange I decomposition mechanisms.

    PubMed

    Atenas, Gonzalo Montes; Mielczarski, Ela; Mielczarski, Jerzy A

    2005-09-01

    Although the decomposition of water pollutants in the presence of metallic iron is known, the reaction pathways and mechanisms of the decomposition of azo-dyes have been meagerly investigated. The interface phenomena taking place during orange I decomposition have been investigated with the use of infrared external reflection spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The studies presented in this paper establish that there are close relationships between the composition and structure of the iron surface oxidized layers and the kinetics and reaction pathway of orange decomposition. The influence of the molecular structure of azo-dye on the produced intermediates was also studied. There are remarkable differences in orange I decomposition between pH 3 and pH 5 at 30 degrees C. Decomposition at pH 3 is very fast with pseudo-first-order kinetics, whereas at pH 5 the reaction is slower with pseudo-zero-order kinetics. At pH 3, only one amine, namely 1-amino-4-naphthol, was identified as an intermediate that undergoes future decomposition. Sulfanilic acid, the second harmful reduction product, was not found in our studies. At pH 3, the iron surface is covered only by a very thin layer of polymeric Fe(OH)(2) mixed with FeO that ensures orange reduction by a combination of an electron transfer reaction and a catalytic hydrogenation reaction. At pH 5, the iron surface is covered up to a few micrometers thick, with a very spongy and porous layer of lepidocrocite enriched in Fe(2+) ions, which slows the electron transfer process. The fastest decomposition reaction was found at a potential near -300 mV (standard hydrogen electrode). An addition of Fe(2+) ions to solution, iron preoxidation in water, or an increase of temperature all result in an increasing decomposition rate. There is no single surface product that would inhibit the decomposition of orange. This information is crucial to perform efficient, clean and low cost waste water

  4. Effect of CaO on the selectivity of N2O decomposition products: A combined experimental and DFT study

    NASA Astrophysics Data System (ADS)

    Wu, Lingnan; Hu, Xiaoying; Qin, Wu; Gao, Pan; Dong, Changqing; Yang, Yongping

    2016-09-01

    The effect of CaO on N2O decomposition and the selectivity of its decomposition products (NO and N2) was investigated using a fixed-bed flow reactor with varying temperatures from 317 °C to 947 °C. The selectivity of NO from CaO-catalyzed N2O decomposition is much lower than the N2 selectivity with the N2/NO products ratio greater than 12.1. Compared to N2O homogeneous decomposition with the minimum N2/NO products ratio of 6.2 at 718 °C, CaO also decreases the NO selectivity from 718 °C to 947 °C. Density functional theory calculations provide possible N2O decomposition routes on the CaO (1 0 0) surface considering both N2 and NO as N2O decomposition products. The N2 formation route is more favorable than the NO formation route in terms of energy barrier and reaction energy, and NO formation on the CaO (1 0 0) surface is likely to proceed via N2O + Osurf2- → N2 + O2 , surf2- and N2O + O2 , surf2- → 2NO + Osurf2-.

  5. Reaction behaviors of decomposition of monocrotophos in aqueous solution by UV and UV/O processes.

    PubMed

    Ku, Y; Wang, W; Shen, Y S

    2000-02-01

    The decomposition of monocrotophos (cis-3-dimethoxyphosphinyloxy-N-methyl-crotonamide) in aqueous solution by UV and UV/O(3) processes was studied. The experiments were carried out under various solution pH values to investigate the decomposition efficiencies of the reactant and organic intermediates in order to determine the completeness of decomposition. The photolytic decomposition rate of monocrotophos was increased with increasing solution pH because the solution pH affects the distribution and light absorbance of monocrotophos species. The combination of O(3) with UV light apparently promoted the decomposition and mineralization of monocrotophos in aqueous solution. For the UV/O(3) process, the breakage of the >C=C< bond of monocrotophos by ozone molecules was found to occur first, followed by mineralization by hydroxyl radicals to generate CO(3)(2-), PO4(3-), and NO(3)(-) anions in sequence. The quasi-global kinetics based on a simplified consecutive-parallel reaction scheme was developed to describe the temporal behavior of monocrotophos decomposition in aqueous solution by the UV/O(3) process. PMID:10648946

  6. Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates

    SciTech Connect

    De Graaff, Marie-Anne; Classen, Aimee T; Castro Gonzalez, Hector F; Schadt, Christopher Warren

    2010-01-01

    Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g{sup -1} soil) to soils amended with and without {sup 13}C-labeled plant residue. We measured CO{sub 2} respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g{sup -1}) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g{sup -1}) had no impact on plant residue decomposition, while greater concentrations of C (> 7.2 mg C g{sup -1}) reduced decomposition (-50%). Concurrently, high exudate concentrations (> 3.6 mg C g{sup -1}) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (< 3.6 mg C g{sup -1}) increased metabolic activity rather than gene copy numbers. These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria.

  7. Feasibility study: Application of the geopressured-geothermal resource to pyrolytic conversion or decomposition/detoxification processes

    SciTech Connect

    Propp, W.A.; Grey, A.E.; Negus-de Wys, J.; Plum, M.M.; Haefner, D.R.

    1991-09-01

    This study presents a preliminary evaluation of the technical and economic feasibility of selected conceptual processes for pyrolytic conversion of organic feedstocks or the decomposition/detoxification of hazardous wastes by coupling the process to the geopressured-geothermal resource. The report presents a detailed discussion of the resource and of each process selected for evaluation including the technical evaluation of each. A separate section presents the economic methodology used and the evaluation of the technically viable process. A final section presents conclusions and recommendations. Three separate processes were selected for evaluation. These are pyrolytic conversion of biomass to petroleum like fluids, wet air oxidation (WAO) at subcritical conditions for destruction of hazardous waste, and supercritical water oxidation (SCWO) also for the destruction of hazardous waste. The scientific feasibility of all three processes has been previously established by various bench-scale and pilot-scale studies. For a variety of reasons detailed in the report the SCWO process is the only one deemed to be technically feasible, although the effects of the high solids content of the geothermal brine need further study. This technology shows tremendous promise for contributing to solving the nation's energy and hazardous waste problems. However, the current economic analysis suggests that it is uneconomical at this time. 50 refs., 5 figs., 7 tabs.

  8. Decomposition of Rare Earth Loaded Resin Particles

    SciTech Connect

    Voit, Stewart L; Rawn, Claudia J

    2010-09-01

    resin is made of sulfonic acid functional groups attached to a styrene divinylbenzene copolymer lattice (long chained hydrocarbon). The metal cation binds to the sulfur group, then during thermal decomposition in air the hydrocarbons will form gaseous species leaving behind a spherical metal-oxide particle. Process development for resin applications with radioactive materials is typically performed using surrogates. For americium and curium, a trivalent metal like neodymium can be used. Thermal decomposition of Nd-loaded resin in air has been studied by Hale. Process conditions were established for resin decomposition and the formation of Nd{sub 2}O{sub 3} particles. The intermediate product compounds were described using x-ray diffraction (XRD) and wet chemistry. Leskela and Niinisto studied the decomposition of rare earth (RE) elements and found results consistent with Hale. Picart et al. demonstrated the viability of using a resin loading process for the fabrication of uranium-actinide mixed oxide microspheres for transmutation of minor actinides in a fast reactor. For effective transmutation of actinides, it will be desirable to extend the in-reactor burnup and minimize the number of recycles of used actinide materials. Longer burn times increases the chance of Fuel Clad Chemical or Mechanical Interaction (FCCI, FCMI). Sulfur is suspected of contributing to Irradiation Assisted Stress Corrosion Cracking (IASCC) thus it is necessary to maximize the removal of sulfur during decomposition of the resin. The present effort extends the previous work by quantifying the removal of sulfur during the decomposition process. Neodymium was selected as a surrogate for trivalent actinide metal cations. As described above Nd was dissolved in nitric acid solution then contacted with the AG-50W resin column. After washing the column, the Nd-resin particles are removed and dried. The Nd-resin, seen in Figure 1 prior to decomposition, is ready to be converted to Nd oxide microspheres.

  9. Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

    NASA Astrophysics Data System (ADS)

    Carraher, Jack McCaslin

    Reactive species like high-valent metal-oxo complexes and carbon and oxygen centered radicals are important intermediates in enzymatic systems, atmospheric chemistry, and industrial processes. Understanding the pathways by which these intermediates form, their relative reactivity, and their fate after reactions is of the utmost importance. Herein are described the mechanistic detail for the generation of several reactive intermediates, synthesis of precursors, characterization of precursors, and methods to direct the chemistry to more desirable outcomes yielding 'greener' sources of commodity chemicals and fuels. High-valent Chromium from Hydroperoxido-Chromium(III). The decomposition of pentaaquahydroperoxido chromium(III) ion (hereafter Cr aqOOH2+) in acidic aqueous solutions is kinetically complex and generates mixtures of products (Craq3+, HCrO 4-, H2O2, and O2). The yield of high-valent chromium products (known carcinogens) increased from a few percent at pH 1 to 70 % at pH 5.5 (near biological pH). Yields of H 2O2 increased with acid concentration. The reproducibility of the kinetic data was poor, but became simplified in the presence of H2O2 or 2,2‧-azinobis(3-ethylbenzothiazoline-6-sulfonate) dianion (ABTS2-). Both are capable of scavenging strongly oxidizing intermediates). The observed rate constants (pH 1, [O2] ≤ 0.03 mM) in the presence of these scavengers are independent of [scavenger] and within the error are the same (k,ABTS2- = (4.9 +/- 0.2) x 10-4 s-1 and kH2O2 = (5.3 +/- 0.7) x 10-4 s-1); indicating involvement of the scavengers in post-rate determining steps. In the presence of either scavenger, decomposition of CrOOH2+ obeyed a two-term rate law, k obs / s-1 = (6.7 +/- 0.7) x 10-4 + (7.6 +/- 1.1) x 10-4 [H+]. Effect of [H+] on the kinetics and the product distribution, cleaner kinetics in the presence of scavengers, and independence of kobs on [scavenger] suggest a dual-pathway mechanism for the decay of Craq OOH2+. The H+-catalyzed path

  10. Study of the laser-induced decomposition of HNO3/ 2-Nitropropane mixture at static high pressures

    NASA Astrophysics Data System (ADS)

    Bouyer, Viviane; Hébert, Philippe; Doucet, Michel

    2007-06-01

    HNO3 / 2-Nitropropane is a well known energetic material on which Raman spectroscopy measurements at static high pressure in a diamond anvil cell (DAC) have already been conducted at CEA/LE RIPAULT in order to examine the evolution of the mixture as a function of composition and pressure [1]. The purpose of the work presented here was to study the laser-induced decomposition of these energetic materials at static high pressures by measuring the combustion front propagation rate in the DAC. First of all, the feasibility of the experimental device was checked with a well known homogeneous explosive, nitromethane. Our results were consistent with those of Rice and Foltz [2]. Then, we investigated the initiation of NA / 2NP mixture as a function of nitric acid proportion, for a given pressure. We chose the mixture for which both the combustion propagation rate and detonation velocity are maximum and we examined the evolution of the front propagation velocity as a function of pressure and energy deposit. [1] Hebert, P., Regache, I., and Lalanne, P., ``High-Pressure Raman Spectroscopy study of HNO3 / 2-Nitropropane Mixtures. Influence of the Composition.'' Proceedings of the 42nd European High-Pressure Research Group Meeting, Lausanne, Suisse, 2004 [2] Rice, S.F., et al., Combustion and Flame 87 (1991) 109-122.

  11. Using Data Mining and Computational Approaches to Study Intermediate Filament Structure and Function.

    PubMed

    Parry, David A D

    2016-01-01

    Experimental and theoretical research aimed at determining the structure and function of the family of intermediate filament proteins has made significant advances over the past 20 years. Much of this has either contributed to or relied on the amino acid sequence databases that are now available online, and the data mining approaches that have been developed to analyze these sequences. As the quality of sequence data is generally high, it follows that it is the design of the computational and graphical methodologies that are of especial importance to researchers who aspire to gain a greater understanding of those sequence features that specify both function and structural hierarchy. However, these techniques are necessarily subject to limitations and it is important that these be recognized. In addition, no single method is likely to be successful in solving a particular problem, and a coordinated approach using a suite of methods is generally required. A final step in the process involves the interpretation of the results obtained and the construction of a working model or hypothesis that suggests further experimentation. While such methods allow meaningful progress to be made it is still important that the data are interpreted correctly and conservatively. New data mining methods are continually being developed, and it can be expected that even greater understanding of the relationship between structure and function will be gleaned from sequence data in the coming years.

  12. In Vitro Assembly Kinetics of Cytoplasmic Intermediate Filaments: A Correlative Monte Carlo Simulation Study

    PubMed Central

    Mücke, Norbert; Winheim, Stefan; Merlitz, Holger; Buchholz, Jan; Langowski, Jörg; Herrmann, Harald

    2016-01-01

    Intermediate filament (IF) elongation proceeds via full-width “mini-filaments”, referred to as “unit-length” filaments (ULFs), which instantaneously form by lateral association of extended coiled-coil complexes after assembly is initiated. In a comparatively much slower process, ULFs longitudinally interact end-to-end with other ULFs to form short filaments, which further anneal with ULFs and with each other to increasingly longer filaments. This assembly concept was derived from time-lapse electron and atomic force microscopy data. We previously have quantitatively verified this concept through the generation of time-dependent filament length-profiles and an analytical model that describes assembly kinetics well for about the first ten minutes. In this time frame, filaments are shorter than one persistence length, i.e. ~1 μm, and thus filaments were treated as stiff rods associating via their ends. However, when filaments grow several μm in length over hours, their flexibility becomes a significant factor for the kinetics of the longitudinal annealing process. Incorporating now additional filament length distributions that we have recorded after extended assembly times by total internal reflection fluorescence microscopy (TIRFM), we developed a Monte Carlo simulation procedure that accurately describes the underlying assembly kinetics for large time scales. PMID:27304995

  13. Propene oxidation at low and intermediate temperatures: A detailed chemical kinetic study

    SciTech Connect

    Wilk, R.D.; Cernansky, N.P.; Pitz, W.J.; Westbrook, C.K.

    1987-03-24

    A detailed chemical kinetic mechanism for propene oxidation is developed and used to model reactions in a static reactor at temperatures of 575-715 K, equivalence ratios of 0.8 - 2.0, and a pressure of 600 torr. Modeling of hydrocarbon oxidation in this temperature range is important for the validation of detailed models to be used for performing calculations related to automotive engine knock. The model predicted induction periods and species concentrations for all the species and all conditions measured experimentally in the static reactor. Overall, the calculated concentrations of carbon monoxide, acetaldehyde, acrolein, and propane oxide agreed well with those measured. The calculated concentrations of ethane are low compared to the experimental measurements, and the calculated concentrations of formaldehyde are high. Agreement for concentrations of carbon dioxide, methane, and methanol is mixed. The characteristic s-shape of the fuel concentration history is well predicted. Modeling calculations identified some of the key reaction steps at the present conditions. Addition of OH to propene and H atom abstraction by OH from propene are important steps in determining the subsequent distributions of intermediate products, such as acetaldehyde, acrolein and formaldehyde. Allyl radicals are very abundant in propene oxidation, and the primary steps found to be responsible for their consumption are reaction with CH/sub 3/O/sub 2/ and HO/sub 2/. 37 refs., 5 figs., 1 tab.

  14. Propene oxidation at low and intermediate temperatures: A detailed chemical kinetic study

    SciTech Connect

    Wilk, R.D.; Gernansky, N.P.; Pitz, W.J.; Westbrook, C.K.

    1987-01-01

    A detailed chemical kinetic mechanism for propene oxidation is developed and used to model reactions in a static reactor at temperatures of 575-715 K, equivalence ratios of 0.8 - 2.0, and a pressure of 600 torr. Modeling of hydrocarbon oxidation in this temperature range is important for the validation of detailed models to be used for performing calculations related to automotive engine knock. The model predicted induction periods and species concentrations for all the species and all conditions measured experimentally in the static reactor. Overall, the calculated concentrations of carbon monoxide, acetaldehyde, acrolein, and propene oxide agreed well with those measured. The calculated concentrations of ethene are low compared to the experimental measurements, and the calculated concentrations of formaldehyde are high. Agreement for concentrations of carbon dioxide, methane, and methanol is mixed. The characteristic s-shape of the fuel concentration history is well predicted. Modeling calculations identified some of the key reaction steps at the present conditions. Addition of OH to propene and H atom abstraction by OH from propene are important steps in determining the subsequent distributions of intermediate products, such as acetaldehyde, acrolein and formaldehyde. Allyl radicals are very abundant in propene oxidation, and the primary steps found to be responsible for their consumption are reaction with CH/sub 3/O/sub 2/ and HO/sub 2/.

  15. Photocatalytic removal of pesticide dichlorvos from indoor air: a study of reaction parameters, intermediates and mineralization.

    PubMed

    Sleiman, Mohamad; Ferronato, Corinne; Chovelon, Jean-Marc

    2008-04-15

    This paper presents for the first time the investigation of TiO2 photocatalysis for the removal of pesticides in gas phase. Dichlorvos was used as a model pesticide, and experiments were carried out using both static and dynamic reaction systems to explore the different aspects of the process. Thus, adsorption, reaction kinetics, and the influence of several operational parameters such as relative humidity (RH), inlet concentration, flow rate, and association of TiO2 with activated carbon (AC) were all examined in detail. Furthermore, a special attention was devoted to the analysis of reaction products by means of various analytical techniques such as Fourier transform infrared spectroscopy, automated thermal desorption technique coupled to gas chromatography-mass spectrometry instrument, gas chromatography equipped with a pulse discharge helium photoionization detector, and ion chromatography. The results showed an immediate and total removal of dichlorvos at ppbv levels (50-350 ppbv) along with a high mineralization extent (50-85%) into harmless final products (CO2, HCl, PO43-). Moreover, RH was found to significantly affectthe mineralization extent and the formation of reaction intermediates. On the basis of identification data, direct charge transfer and chlorine radical (Cl*) attack were shown to play a key role in the reaction mechanism at low RH, whereas at high RH, HO* radicals were the predominant active species.

  16. Studies in new materials for intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Skinner, Alex W.

    Ceramic materials have historically been of interest for their thermal and mechanical properties. However, certain ceramic materials can have very interesting electrical, magnetic and optical properties, leading to a new subclass, the electroceramics. Perovskites, in particular, have become the subject of intense research in this field. Specifically, doped barium zirconates have shown high proton conductivity in the intermediate temperature range (600--800°C), making them advantageous for use in solid oxide fuel cells. Solid oxide fuel cells (SOFCs) are electrochemical devices that convert chemical energy into electricity using ion-conducting oxide ceramics as electrolytes. The anode component of the cell is also of interest. Cermets or ceramic metals can serve a dual role as substrates for thin film electrolytes and anodes in the cell. Thin films of gadolinium and ytterbium doped barium zirconate were deposited using pulsed laser deposition (KrF; 1--3 J/cm2) on several substrates, including cermets developed in our lab, in a 10--400 mTorr oxygen environment with various substrate temperatures. Crystalline structure and chemical composition was determined by X-ray diffraction (XRD) and energy dispersive x-ray analysis, respectively. Preliminary electrical measurements of the electrolyte/cermet structure were taken using electrochemical impedance spectroscopy. Keywords: solid oxide fuel cells (SOFCs), perovskites, proton conductors, electroceramics, gadolinium-doped barium zirconate (BZG).

  17. Preparation and properties of a papillomavirus infectious intermediate and its utility for neutralization studies

    PubMed Central

    Wang, Joshua W.; Jagu, Subhashini; Kwak, Kihyuck; Wang, Chenguang; Peng, Shiwen; Kirnbauer, Reinhard; Roden, Richard B.S.

    2014-01-01

    We show that minor capsid protein L2 is full length in clinical virion isolates and prepare furin-cleaved pseudovirus (fcPsV) as a model of the infectious intermediate for multiple human papillomavirus (HPV) types. These fcPsV do not require furin for in vitro infection, and are fully infectious in vivo. Both the γ-secretase inhibitor XXI and carrageenan block fcPsV infection in vitro and in vivo implying that they act after furin-cleavage of L2. Despite their enhanced exposure of L2 epitopes, vaccination with fcPsV particles fails to induce L2 antibody, although L1-specific responses are similar to PsV with intact L2. FcPsV can be applied in a simple, high-throughput neutralization assay that detects L2-specific neutralizing antibodies with >10-fold enhanced sensitivity compared with the PsV-based assay. The PsV and fcPsV-based assays exhibit similar sensitivity for type-specific antibodies elicited by L1 virus-like particles (VLP), but the latter improves detection of L1-specific cross-type neutralizing antibodies. PMID:24418565

  18. Ethanol decomposition on transition metal nanoparticles during carbon nanotube growth: ab initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Shibuta, Yasushi; Shimamura, Kohei; Oguri, Tomoya; Arifin, Rizal; Shimojo, Fuyuki; Yamaguchi, Shu

    2015-03-01

    The growth mechanism of carbon nanotubes (CNT) has been widely discussed both from experimental and computational studies. Regarding the computational studies, most of the studies focuses on the aggregation of isolate carbon atoms on the catalytic metal nanoparticle, whereas the initial dissociation of carbon source molecules should affect the yield and quality of the products. On the other hand, we have studied the dissociation process of carbon source molecules on the metal surface by the ab initio molecular dynamics simulation. In the study, we investigate the ethanol dissociation on Pt and Ni clusters by ab initio MD simulations to discuss the initial stage of CNT growth by alcohol CVD technique. Part of this research is supported by the Grant-in-Aid for Young Scientists (a) (No. 24686026) from MEXT, Japan.

  19. Ab initio molecular dynamics study on the initial chemical events in nitramines: thermal decomposition of CL-20.

    PubMed

    Isayev, Olexandr; Gorb, Leonid; Qasim, Mo; Leszczynski, Jerzy

    2008-09-01

    CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane or HNIW) is a high-energy nitramine explosive. To improve atomistic understanding of the thermal decomposition of CL-20 gas and solid phases, we performed a series of ab initio molecular dynamics simulations. We found that during unimolecular decomposition, unlike other nitramines (e.g., RDX, HMX), CL-20 has only one distinct initial reaction channelhomolysis of the N-NO2 bond. We did not observe any HONO elimination reaction during unimolecular decomposition, whereas the ring-breaking reaction was followed by NO 2 fission. Therefore, in spite of limited sampling, that provides a mostly qualitative picture, we proposed here a scheme of unimolecular decomposition of CL-20. The averaged product population over all trajectories was estimated at four HCN, two to four NO2, two to four NO, one CO, and one OH molecule per one CL-20 molecule. Our simulations provide a detailed description of the chemical processes in the initial stages of thermal decomposition of condensed CL-20, allowing elucidation of key features of such processes as composition of primary reaction products, reaction timing, and Arrhenius behavior of the system. The primary reactions leading to NO2, NO, N 2O, and N2 occur at very early stages. We also estimated potential activation barriers for the formation of NO2, which essentially determines overall decomposition kinetics and effective rate constants for NO2 and N2. The calculated solid-phase decomposition pathways correlate with available condensed-phase experimental data. PMID:18686996

  20. Mechanistic Studies of Reactions of Peroxodiiron(III) Intermediates in T201 Variants of Toluene/o-Xylene Monooxygenase Hydroxylase†

    PubMed Central

    Song, Woon Ju; Lippard, Stephen J.

    2011-01-01

    Site-directed mutagenesis studies of a strictly conserved T201 residue in the active site of toluene/o-xylene monooxygenase hydroxylase (ToMOH) revealed that a single mutation can facilitate kinetic isolation of two distinctive peroxodiiron(III) species, designated T201peroxo and ToMOHperoxo, during dioxygen activation. Previously we characterized both oxygenated intermediates by UV-vis and Mössbauer spectroscopy, proposed structures from DFT and QM/MM computational studies, and elucidated chemical steps involved in dioxygen activation through the kinetic studies of T201peroxo formation. In the current study, we investigated the kinetics of T201peroxo decay to explore the reaction mechanism of the oxygenated intermediates following O2 activation. The decay rates of T201peroxo were monitored in the absence and presence of external (phenol) or internal (tryptophan residue in an I100W variant) substrates under pre-steady-state conditions. Three possible reaction pathways were evaluated and the results demonstrate that T201peroxo is on the pathway of arene oxidation and appears to be in equilibrium with ToMOHperoxo. PMID:21595439

  1. Adaptive kinetic Monte Carlo simulation of methanol decomposition on Cu(100)

    SciTech Connect

    Xu, Lijun; Mei, Donghai; Henkelman, Graeme A.

    2009-12-31

    The adaptive kinetic Monte Carlo method was used to calculate the dynamics of methanol decomposition on Cu(100) at room temperature over a time scale of minutes. Mechanisms of reaction were found using min-mode following saddle point searches based upon forces and energies from density functional theory. Rates of reaction were calculated with harmonic transition state theory. The dynamics followed a pathway from CH3-OH, CH3-O, CH2-O, CH-O and finally C-O. Our calculations confirm that methanol decomposition starts with breaking the O-H bond followed by breaking C-H bonds in the dehydrogenated intermediates until CO is produced. The bridge site on the Cu(100) surface is the active site for scissoring chemical bonds. Reaction intermediates are mobile on the surface which allows them to find this active reaction site. This study illustrates how the adaptive kinetic Monte Carlo method can model the dynamics of surface chemistry from first principles.

  2. Chemiluminescence efficiency of catalyzed 1,2-dioxetanone decomposition determined by steric effects.

    PubMed

    Bartoloni, Fernando Heering; de Oliveira, Marcelo Almeida; Ciscato, Luiz Francisco Monteiro Leite; Augusto, Felipe Alberto; Bastos, Erick Leite; Baader, Wilhelm Josef

    2015-04-17

    The chemiluminescent decomposition of 1,2-dioxetanones (α-peroxylactones), catalyzed by an appropriate fluorescent activator, is an important simple model for efficient bioluminescent transformations. In this work, we report experimental data on the catalyzed decomposition of two spiro-substituted 1,2-dioxetanone derivatives, which support the occurrence of an intermolecular electron transfer from the activator to the peroxide. The low efficiency of the studied systems is associated with steric hindrance during the chemiexcitation sequence, rationalized using the concept of supermolecule formation between the peroxide and the catalyst. This approach explains the difference in the chemiexcitation efficiencies in the decomposition of four-membered cyclic peroxide derivatives: 1,2-dioxetanes, 1,2-dioxetanones, and 1,2-dioxetanedione (the intermediate in the peroxyoxalate reaction), which are the most important model compounds for excited-state formation in chemiluminescence and bioluminescence processes. PMID:25831218

  3. Influence of activated-carbon-supported transition metals on the decomposition of polychlorobiphenyls. Part II: Chemical and physical characterization and mechanistic study.

    PubMed

    Sun, Yifei; Liu, Lina; Oshita, Kazuyuki; Zeng, Xiaolan; Wang, Wei; Zhang, Yibo

    2016-09-01

    This paper studies the synergism between transition metals (TMs) and activated carbon (AC) as a catalyst support used in the catalytic decomposition of PCBs. A series of AC-supported TM catalysts was prepared according to two distinct methods: impregnation and ion exchange which were defined as LaTM-C and IRTM-C, respectively. The catalytic reactions between 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) and AC-supported Fe, Ni, Cu and Zn catalysts were conducted under N2 atmosphere. Changes in the nature of the catalysts as well as the decomposition mechanism of PCB-153 are discussed. Important findings include: (i) a higher metal concentration and a better metal distribution on AC is realized using ion-exchange, despite a lower AC specific surface area, (ii) IRTM-C had better effects on the decomposition of PCB-153 than LaTM-C, (iii) the role of Ni, Cu, and Fe as electron donors in PCB dechlorination was evaluated vs. the stability of Zn, and (iv) both temperature and chemical composition of TM catalysts influenced the decomposition efficiency of PCBs.

  4. Influence of activated-carbon-supported transition metals on the decomposition of polychlorobiphenyls. Part II: Chemical and physical characterization and mechanistic study.

    PubMed

    Sun, Yifei; Liu, Lina; Oshita, Kazuyuki; Zeng, Xiaolan; Wang, Wei; Zhang, Yibo

    2016-09-01

    This paper studies the synergism between transition metals (TMs) and activated carbon (AC) as a catalyst support used in the catalytic decomposition of PCBs. A series of AC-supported TM catalysts was prepared according to two distinct methods: impregnation and ion exchange which were defined as LaTM-C and IRTM-C, respectively. The catalytic reactions between 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) and AC-supported Fe, Ni, Cu and Zn catalysts were conducted under N2 atmosphere. Changes in the nature of the catalysts as well as the decomposition mechanism of PCB-153 are discussed. Important findings include: (i) a higher metal concentration and a better metal distribution on AC is realized using ion-exchange, despite a lower AC specific surface area, (ii) IRTM-C had better effects on the decomposition of PCB-153 than LaTM-C, (iii) the role of Ni, Cu, and Fe as electron donors in PCB dechlorination was evaluated vs. the stability of Zn, and (iv) both temperature and chemical composition of TM catalysts influenced the decomposition efficiency of PCBs. PMID:27320438

  5. Thermal decomposition study of monovarietal extra virgin olive oil by simultaneous thermogravimetry/differential scanning calorimetry: relation with chemical composition.

    PubMed

    Vecchio, Stefano; Cerretani, Lorenzo; Bendini, Alessandra; Chiavaro, Emma

    2009-06-10

    Thermal decomposition of 12 monovarietal extra virgin olive oils from different geographical origins (eight from Italy, two from Spain, and the others from Tunisia) was evaluated by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses. All extra virgin olive oils showed a complex multistep decomposition pattern with the first step that exhibited a quite different profile among samples. Thermal properties of the two peaks obtained by the deconvolution of the first step of decomposition by DSC were related to the chemical composition of the samples (triacylglycerols, fatty acids, total phenols and antioxidant activity). Onset temperatures of the thermal decomposition transition and T(p) values of both deconvoluted peaks as well as the sum of enthalpy were found to exhibit statistically significant correlations with chemical components of the samples, in particular palmitic and oleic acids and related triacylglycerols. Activation energy values of the second deconvoluted peak obtained by the application of kinetic procedure to the first step of decomposition were also found to be highly statistically correlated to the chemical composition, and a stability scale among samples was proposed on the basis of its values.

  6. Towards Understanding the Decomposition/Isomerism Channels of Stratospheric Bromine Species: Ab Initio and Quantum Topology Study

    PubMed Central

    Aziz, Saadullah G.; Alyoubi, Abdulrahman O.; Elroby, Shaaban A.; Osman, Osman I.; Hilal, Rifaat H.

    2015-01-01

    The present study aims at a fundamental understanding of bonding characteristics of the C–Br and O–Br bonds. The target molecular systems are the isomeric CH3OBr/BrCH2OH system and their decomposition products. Calculations of geometries and frequencies at different density functional theory (DFT) and Hartree–Fock/Møller–Plesset (HF/MP2) levels have been performed. Results have been assessed and evaluated against those obtained at the coupled cluster single-double (Triplet) (CCSD(T)) level of theory. The characteristics of the C–Br and O–Br bonds have been identified via analysis of the electrostatic potential, natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM). Analysis of the electrostatic potential (ESP) maps enabled the quantitative characterization of the Br σ-holes. Its magnitude seems very sensitive to the environment and the charge accumulated in the adjacent centers. Some quantum topological parameters, namely ∇2ρ, ellipticity at bond critical points and the Laplacian bond order, were computed and discussed. The potential energy function for internal rotation has been computed and Fourier transformed to characterize the conformational preferences and origin of the barriers. NBO energetic components for rotation about the C–Br and O–Br bonds as a function of torsion angle have been computed and displayed. PMID:25815595

  7. Towards understanding the decomposition/isomerism channels of stratospheric bromine species: ab initio and quantum topology study.

    PubMed

    Aziz, Saadullah G; Alyoubi, Abdulrahman O; Elroby, Shaaban A; Osman, Osman I; Hilal, Rifaat H

    2015-03-25

    The present study aims at a fundamental understanding of bonding characteristics of the C-Br and O-Br bonds. The target molecular systems are the isomeric CH3OBr/BrCH2OH system and their decomposition products. Calculations of geometries and frequencies at different density functional theory (DFT) and Hartree-Fock/Møller-Plesset (HF/MP2) levels have been performed. Results have been assessed and evaluated against those obtained at the coupled cluster single-double (Triplet) (CCSD(T)) level of theory. The characteristics of the C-Br and O-Br bonds have been identified via analysis of the electrostatic potential, natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM). Analysis of the electrostatic potential (ESP) maps enabled the quantitative characterization of the Br σ-holes. Its magnitude seems very sensitive to the environment and the charge accumulated in the adjacent centers. Some quantum topological parameters, namely Ñ2ρ, ellipticity at bond critical points and the Laplacian bond order, were computed and discussed. The potential energy function for internal rotation has been computed and Fourier transformed to characterize the conformational preferences and origin of the barriers. NBO energetic components for rotation about the C-Br and O-Br bonds as a function of torsion angle have been computed and displayed.

  8. Decomposition into Multiple Morphemes during Lexical Access: A Masked Priming Study of Russian Nouns

    ERIC Educational Resources Information Center

    Kazanina, Nina; Dukova-Zheleva, Galina; Geber, Dana; Kharlamov, Viktor; Tonciulescu, Keren

    2008-01-01

    The study reports the results of a masked priming experiment with morphologically complex Russian nouns. Participants performed a lexical decision task to a visual target that differed from its prime in one consonant. Three conditions were included: (1) "transparent," in which the prime was morphologically related to the target and contained the…

  9. Study of water molecule decomposition in plasma by diode laser spectroscopy and optical actinometry methods

    NASA Astrophysics Data System (ADS)

    Bernatskiy, A. V.; Lagunov, V. V.; Ochkin, V. N.; Tskhai, S. N.

    2016-07-01

    The methods of diode laser radiation absorption at vibrational–rotational molecule transitions and optical actinometry with measurements of its electron emission spectra are used independently to study water molecule dissociation in glow discharge plasma in a mixture of water vapor and inert gases at reduced pressure. The methods yield close results. The dissociation reaches 98%.

  10. Spectro-Timing Study of GX 339-4 in a Hard Intermediate State

    NASA Astrophysics Data System (ADS)

    Fürst, F.; Grinberg, V.; Tomsick, J. A.; Bachetti, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Grefenstette, B.; Hailey, C. J.; Harrison, F. A.; Madsen, K. K.; Parker, M. L.; Pottschmidt, K.; Stern, D.; Walton, D. J.; Wilms, J.; Zhang, W. W.

    2016-09-01

    We present an analysis of Nuclear Spectroscopic Telescope Array observations of a hard intermediate state of the transient black hole GX 339-4 taken in 2015 January. With the source softening significantly over the course of the 1.3 day long observation we split the data into 21 sub-sets and find that the spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from ˜1.69 to ˜1.77 over the course of the observation. The accretion disk is truncated at around nine gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which increases in frequency from ˜0.68 to ˜1.05 Hz with time. The frequency change is well correlated with the softening of the spectrum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of ˜100 {M}⊙ , which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii, as obtained from spectral fitting, is difficult to reconcile with current models.

  11. Spectro-Timing Study of GX 339-4 in a Hard Intermediate State

    NASA Astrophysics Data System (ADS)

    Fürst, F.; Grinberg, V.; Tomsick, J. A.; Bachetti, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Grefenstette, B.; Hailey, C. J.; Harrison, F. A.; Madsen, K. K.; Parker, M. L.; Pottschmidt, K.; Stern, D.; Walton, D. J.; Wilms, J.; Zhang, W. W.

    2016-09-01

    We present an analysis of Nuclear Spectroscopic Telescope Array observations of a hard intermediate state of the transient black hole GX 339‑4 taken in 2015 January. With the source softening significantly over the course of the 1.3 day long observation we split the data into 21 sub-sets and find that the spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from ˜1.69 to ˜1.77 over the course of the observation. The accretion disk is truncated at around nine gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which increases in frequency from ˜0.68 to ˜1.05 Hz with time. The frequency change is well correlated with the softening of the spectrum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of ˜100 {M}ȯ , which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii, as obtained from spectral fitting, is difficult to reconcile with current models.

  12. Sulfur species behavior in soil organic matter during decomposition

    USGS Publications Warehouse

    Schroth, A.W.; Bostick, B.C.; Graham, M.; Kaste, J.M.; Mitchell, M.J.; Friedland, A.J.

    2007-01-01

    Soil organic matter (SOM) is a primary re??servoir of terrestrial sulfur (S), but its role in the global S cycle remains poorly understood. We examine S speciation by X-ray absorption near-edge structure (XANES) spectroscopy to describe S species behavior during SOM decomposition. Sulfur species in SOM were best represented by organic sulfide, sulfoxide, sulfonate, and sulfate. The highest fraction of S in litter was organic sulfide, but as decomposition progressed, relative fractions of sulfonate and sulfate generally increased. Over 6-month laboratory incubations, organic sulfide was most reactive, suggesting that a fraction of this species was associated with a highly labile pool of SOM. During humification, relative concentrations of sulfoxide consistently decreased, demonstrating the importance of sulfoxide as a reactive S phase in soil. Sulfonate fractional abundance increased during humification irrespective of litter type, illustrating its relative stability in soils. The proportion of S species did not differ systematically by litter type, but organic sulfide became less abundant in conifer SOM during decomposition, while sulfate fractional abundance increased. Conversely, deciduous SOM exhibited lesser or nonexistent shifts in organic sulfide and sulfate fractions during decomposition, possibly suggesting that S reactivity in deciduous litter is coupled to rapid C mineralization and independent of S speciation. All trends were consistent in soils across study sites. We conclude that S reactivity is related to spqciation in SOM, particularly in conifer forests, and S species fractions in SOM change, during decomposition. Our data highlight the importance of intermediate valence species (sulfoxide and sulfonate) in the pedochemical cycling of organic bound S. Copyright 2007 by the American Geophysical Union.

  13. Reactivity of TEMPO toward 16- and 17-electron organometallic reaction intermediates: a time-resolved IR study.

    PubMed

    Lomont, Justin P; Nguyen, Son C; Harris, Charles B

    2013-07-31

    The (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO) has been employed for an extensive range of chemical applications, ranging from organometallic catalysis to serving as a structural probe in biological systems. As a ligand in an organometallic complex, TEMPO can exhibit several distinct coordination modes. Here we use ultrafast time-resolved infrared spectroscopy to study the reactivity of TEMPO toward coordinatively unsaturated 16- and 17-electron organometallic reaction intermediates. TEMPO coordinates to the metal centers of the 16-electron species CpCo(CO) and Fe(CO)4, and to the 17-electron species CpFe(CO)2 and Mn(CO)5, via an associative mechanism with concomitant oxidation of the metal center. In these adducts, TEMPO thus behaves as an anionic ligand, characterized by a pyramidal geometry about the nitrogen center. Density functional theory calculations are used to facilitate interpretation of the spectra and to further explore the structures of the TEMPO adducts. To our knowledge, this study represents the first direct characterization of the mechanism of the reaction of TEMPO with coordinatively unsaturated organometallic complexes, providing valuable insight into its reactions with commonly encountered reaction intermediates. The similar reactivity of TEMPO toward each of the species studied suggests that these results can be considered representative of TEMPO's reactivity toward all low-valent transition metal complexes.

  14. Case study of urban environmental education in the intermediate-grade curriculum: an investigation of content and process

    SciTech Connect

    Pace, R.

    1987-01-01

    This case study was an attempt to divulge the presence of environmental education (EE) in the intermediate-grade curriculum, along with the factors influencing it both positively and negatively. It was designed in response to Goal No. 7 of the New York State Regents Action Plan, which advocates EE in all subject areas and at all grade levels. The site of the study was a public school in Queens, New York, The participants included 7 teachers, the school librarian, 2 administrators, and 15 fourth, fifth, and sixth graders, as well as 3 educators from outside the school. This research was conducted between February and June, 1986. The data-collection techniques involved observations, in-depth interviews, and artifact reviews. The findings revealed that EE does exist both blatantly and subtly in the intermediate-grade curriculum; however, much more can be done. In science, exploration of plants, animals, energy, climate, air and water quality are replete with environmental ramifications. In social studies, consideration of the dependence of human cultural development on the natural environment is key. Environmental themes are employed to teach mathematical, reading, and language arts skills. Much music is developed around the imitation of the sounds of nature. Current events bring environmental issues to the foreground.

  15. Adsorption and decomposition of H2O on cobalt surfaces: A DFT study

    NASA Astrophysics Data System (ADS)

    Ma, F. F.; Ma, S. H.; Jiao, Z. Y.; Dai, X. Q.

    2016-10-01

    Water adsorption and dissociation on clean and O-covered Co(100), Co(110) and Co(111) surfaces are studied using the density functional theory calculations. The results indicate that molecular water weakly binds to the surfaces and is feasible to desorption from the clean surfaces. Moreover, the pre-adsorption of O atom increases the binding of water to the surfaces, and prominently decreases the activation barriers of water dissociation into OH, especially on Co(110) surface. In contrast, the activation barrier for OH dissociation is slightly affected in the presence of O atom. Overall, this study reveals that O-assisted H2O favorably adsorbs dissociatively, forming OH chemisorbed on the surfaces, which further hinders H2O dissociation, and also illustrates the fact that molecular water dissociation is structure-sensitive on metal surfaces.

  16. Gunshot residues on dry bone after decomposition--a pilot study.

    PubMed

    Taborelli, Anna; Gibelli, Daniele; Rizzi, Agostino; Andreola, Salvatore; Brandone, Alberto; Cattaneo, Cristina

    2012-09-01

    Very little literature exists concerning radiochemical and microscopic analyses of gunshot wounds in decomposed material, and even less concerning skeletonized samples; the most advanced technologies may provide useful indications for the diagnosis of suspect lesions, especially if gunshot wounds are no longer recognizable. However, we know very little of the survival of gunshot residues (GSR) in skeletonized samples. This study examined nine gunshot wounds produced on pig heads which then underwent skeletonization for 4 years, and four gunshot entries on human heads from judicial cases which were then macerated to the bone in water; the samples underwent scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX) analysis. Positive results for GSR were observed only in four of the nine animal samples and in all four human samples. Among the human samples, two lesions showed Pb and Sb, one lesion only Pb, and one Pb, Sb, and Ba. This pilot study showed the survival of GSR in skeletal material and therefore the crucial importance of SEM-EDX analyses on skeletonized material. Further studies are needed in order to ascertain the role of environmental modifications of GSR.

  17. Coupled thermal and electromagnetic induced decomposition in the molecular explosive αHMX; a reactive molecular dynamics study.

    PubMed

    Wood, Mitchell A; van Duin, Adri C T; Strachan, Alejandro

    2014-02-01

    We use molecular dynamics simulations with the reactive potential ReaxFF to investigate the initial reactions and subsequent decomposition in the high-energy-density material α-HMX excited thermally and via electric fields at various frequencies. We focus on the role of insult type and strength on the energy increase for initial decomposition and onset of exothermic chemistry. We find both of these energies increase with the increasing rate of energy input and plateau as the processes become athermal for high loading rates. We also find that the energy increase required for exothermic reactions and, to a lesser extent, that for initial chemical reactions depend on the insult type. Decomposition can be induced with relatively weak insults if the appropriate modes are targeted but increasing anharmonicities during heating lead to fast energy transfer and equilibration between modes that limit the effect of loading type.

  18. Adsorption and decomposition of monopropellant molecule HAN on Pd(100) and Ir(100) surfaces: A DFT study

    NASA Astrophysics Data System (ADS)

    Banerjee, Sourav; Shetty, Sharath A.; Gowrav, M. N.; Oommen, Charlie; Bhattacharya, Atanu

    2016-11-01

    We have performed density functional theory calculations with the generalized gradient approximation to investigate the catalytic decomposition reactions of one of the most promising monopropellants, hydroxylammonium nitrate (HAN), on two catalytically active single crystal Pd(100) and Ir(100) surfaces, aiming at exploring different reaction pathways and reactivities of these two surfaces towards the catalytic decomposition of HAN. We find that the HAN molecule binds both the Pd(100) and Ir(100) surfaces molecularly in different orientations with respect to the surface. The HONO elimination is found to possess the lowest activation energy on the Pd(100) surface; whereas, NO2 elimination is predicted to show the lowest activation energy on the Ir(100) surface. Exothermicities associated with different reaction steps are also discussed. This is the first theoretical report on the catalytic decomposition reactions of the HAN molecule on the single crystal Pd(100) and the Ir(100) surfaces using the periodic DFT calculations.

  19. Task decomposition: a framework for comparing diverse training models in human brain plasticity studies

    PubMed Central

    Coffey, Emily B. J.; Herholz, Sibylle C.

    2013-01-01

    Training studies, in which the structural or functional neurophysiology is compared before and after expertise is acquired, are increasingly being used as models for understanding the human brain’s potential for reorganization. It is proving difficult to use these results to answer basic and important questions like how task training leads to both specific and general changes in behavior and how these changes correspond with modifications in the brain. The main culprit is the diversity of paradigms used as complex task models. An assortment of activities ranging from juggling to deciphering Morse code has been reported. Even when working in the same general domain, few researchers use similar training models. New ways to meaningfully compare complex tasks are needed. We propose a method for characterizing and deconstructing the task requirements of complex training paradigms, which is suitable for application to both structural and functional neuroimaging studies. We believe this approach will aid brain plasticity research by making it easier to compare training paradigms, identify “missing puzzle pieces,” and encourage researchers to design training protocols to bridge these gaps. PMID:24115927

  20. Task decomposition: a framework for comparing diverse training models in human brain plasticity studies.

    PubMed

    Coffey, Emily B J; Herholz, Sibylle C

    2013-01-01

    Training studies, in which the structural or functional neurophysiology is compared before and after expertise is acquired, are increasingly being used as models for understanding the human brain's potential for reorganization. It is proving difficult to use these results to answer basic and important questions like how task training leads to both specific and general changes in behavior and how these changes correspond with modifications in the brain. The main culprit is the diversity of paradigms used as complex task models. An assortment of activities ranging from juggling to deciphering Morse code has been reported. Even when working in the same general domain, few researchers use similar training models. New ways to meaningfully compare complex tasks are needed. We propose a method for characterizing and deconstructing the task requirements of complex training paradigms, which is suitable for application to both structural and functional neuroimaging studies. We believe this approach will aid brain plasticity research by making it easier to compare training paradigms, identify "missing puzzle pieces," and encourage researchers to design training protocols to bridge these gaps. PMID:24115927

  1. A study of the thermal decomposition of adulterated cocaine samples under optimized aerobic pyrolytic conditions.

    PubMed

    Gostic, T; Klemenc, S; Stefane, B

    2009-05-30

    The pyrolysis behaviour of pure cocaine base as well as the influence of various additives was studied using conditions that are relevant to the smoking of illicit cocaine by humans. For this purpose an aerobic pyrolysis device was developed and the experimental conditions were optimized. In the first part of our study the optimization of some basic experimental parameters of the pyrolysis was performed, i.e., the furnace temperature, the sampling start time, the heating period, the sampling time, and the air-flow rate through the system. The second part of the investigation focused on the volatile products formed during the pyrolysis of a pure cocaine free base and mixtures of cocaine base and adulterants. The anaesthetics lidocaine, benzocaine, procaine, the analgesics phenacetine and paracetamol, and the stimulant caffeine were used as the adulterants. Under the applied experimental conditions complete volatilization of the samples was achieved, i.e., the residuals of the studied compounds were not detected in the pyrolysis cell. Volatilization of the pure cocaine base showed that the cocaine recovery available for inhalation (adsorbed on traps) was approximately 76%. GC-MS and NMR analyses of the smoke condensate revealed the presence of some additional cocaine pyrolytic products, such as anhydroecgonine methyl ester (AEME), benzoic acid (BA) and carbomethoxycycloheptatrienes (CMCHTs). Experiments with different cocaine-adulterant mixtures showed that the addition of the adulterants changed the thermal behaviour of the cocaine. The most significant of these was the effect of paracetamol. The total recovery of the cocaine (adsorbed on traps and in a glass tube) from the 1:1 cocaine-paracetamol mixture was found to be only 3.0+/-0.8%, versus 81.4+/-2.9% for the pure cocaine base. The other adulterants showed less-extensive effects on the recovery of cocaine, but the pyrolysis of the cocaine-procaine mixture led to the formation of some unique pyrolytic products

  2. Adsorption and decomposition of hexamethyldisiloxane on platinum: an XPS, UPS and TDS study

    NASA Astrophysics Data System (ADS)

    Colin, L.; Cassuto, A.; Ehrhardt, J. J.; Ruiz-Lopez, M. F.; Jamois, D.

    1996-07-01

    We have studied with XPS, UPS and TDS, in UHV conditions, the adsorption of HMDS on various platinum surfaces and different temperatures. At low temperature, a multilayer is formed which desorbs at 150 K, leaving on the surface an undistorted monolayer. With temperature increase, several products appear in the gas phase (methane, lighter organodisiloxanes and hydrogen) leaving on the surface methyl radicals that undergo progressive dehydrogenation leading to the formation of amorphous carbon and graphitization at above 700 K. The carbon residue is readily removed by an oxygen treatment at moderate temperatures. Almost no silicon or oxygen remain on the surface above 300 K, a result which cannot explain the poisoning effect of HMDS on platinum sensors used to detect methane in coal mines. It shows that the low pressure mechanism differs from the ambient pressure mechanism. Differences are possibly due to the presence of oxygen at ambient pressures and deserve further investigations.

  3. Time-domain Surveys and Data Shift: Case Study at the intermediate Palomar Transient Factory

    NASA Astrophysics Data System (ADS)

    Rebbapragada, Umaa; Bue, Brian; Wozniak, Przemyslaw R.

    2015-01-01

    Next generation time-domain surveys are susceptible to the problem of data shift that is caused by upgrades to data processing pipelines and instruments. Data shift degrades the performance of automated machine learning classifiers that vet detections and classify source types because fundamental assumptions are violated when classifiers are built in one data regime but are deployed on data from another. This issue is not currently discussed within the astronomical community, but will be increasingly pressing over the next decade with the advent of new time domain surveys.We look at the problem of data shift that was caused by a data pipeline upgrade when the intermediate Palomar Transient Factory (iPTF) succeeded the Palomar Transient Factory (PTF) in January 2013. iPTF relies upon machine-learned Real-Bogus classifiers to vet sources extracted from subtracted images on a scale of zero to one where zero indicates a bogus (image artifact) and one indicates a real astronomical transient, with the overwhelming majority of candidates are scored as bogus. An effective Real-Bogus system filters all but the most promising candidates, which are presented to human scanners who make decisions about triggering follow up assets.The Real-Bogus systems currently in operation at iPTF (RB4 and RB5) solve the data shift problem. The statistical models of RB4 and RB5 were built from the ground up using examples from iPTF alone, whereas an older system, RB2, was built using PTF data, but was deployed after iPTF launched. We discuss the machine learning assumptions that are violated when a system is trained on one domain (PTF) but deployed on another (iPTF) that experiences data shift. We provide illustrative examples of data parameters and statistics that experienced shift. Finally, we show results comparing the three systems in operation, demonstrating that systems that solve domain shift (RB4 and RB5) are superior to those that don't (RB2).Research described in this abstract was

  4. Is Gray Matter Volume an Intermediate Phenotype for Schizophrenia? A VBM Study of Patients with Schizophrenia and their Healthy Siblings

    PubMed Central

    Honea, Robyn A.; Meyer-Lindenberg, Andreas; Hobbs, Katherine B.; Pezawas, Lukas; Mattay, Venkata S.; Egan, Michael F.; Verchinski, Beth; Passingham, Richard E.; Weinberger, Daniel R.; Callicott, Joseph H.

    2008-01-01

    Objective: Shared neuropathological characteristics of patients with schizophrenia and their siblings may represent intermediate phenotypes that could be used to investigate genetic susceptibility to the illness. We sought to discover previously unidentified gray matter volume differences in patients with schizophrenia and their siblings using optimized Voxel-Based Morphometry (VBM). Methods: We studied 169 patients with schizophrenia, 213 of their unaffected siblings, and 212 healthy volunteers from the CBDB/NIMH Genetic Study of Schizophrenia with magnetic resonance imaging (MRI). Results: Patients with schizophrenia had significant regional gray matter decreases in the frontal, temporal, and parietal cortices compared with healthy volunteers. Their unaffected siblings tended to share gray matter decreases in the medial frontal, superior temporal and insular cortices, but these decreases were not significant after correction for multiple comparisons, even when we looked at a subgroup of siblings with a past history of mood disorder. As an exploratory analysis, we estimated heritability using regions of interest from the VBM analysis, as well as from the hippocampus. Hippocampal volume was significantly correlated within sibling-pairs. Conclusions: Our findings confirm and extend previous VBM analyses in ill subjects with schizophrenia. Furthermore, these data argue that while siblings may share some regional gray matter decreases with their affected siblings, the pattern of regional differences may be a weak intermediate phenotype for schizophrenia. PMID:17689500

  5. Computational study on the aminolysis of beta-hydroxy-alpha,beta-unsaturated ester via the favorable path including the formation of alpha-oxo ketene intermediate.

    PubMed

    Jin, Lu; Xue, Ying; Zhang, Hui; Kim, Chan Kyung; Xie, Dai Qian; Yan, Guo Sen

    2008-05-15

    The possible mechanisms of the aminolysis of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone (beta-hydroxy-alpha,beta-unsaturated ester) with dimethylamine are investigated at the hybrid density functional theory B3LYP/6-31G(d,p) level in the gas phase. Single-point computations at the B3LYP/6-311++G(d,p) and the Becke88-Becke95 1-parameter model BB1K/6-311++G(d,p) levels are performed for more precise energy predictions. Solvent effects are also assessed by single-point calculations at the integral equation formalism polarized continuum model IEFPCM-B3LYP/6-311++G(d,p) and IEFPCM-BB1K/6-311++G(d,p) levels on the gas-phase optimized geometries. Three possible pathways, the concerted pathway (path A), the stepwise pathway involving tetrahedral intermediates (path B), and the stepwise pathway via alpha-oxo ketene intermediate due to the participation of beta-hydroxy (path C), are taken into account for the title reaction. Moreover, path C includes two sequential processes. The first process is to generate alpha-oxo ketene intermediate via the decomposition of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone; the second process is the addition of dimethylamine to alpha-oxo ketene intermediate. Our results indicate that path C is more favorable than paths A and B both in the gas phase and in solvent (heptane). In path C, the first process is the rate-determining step, and the second process is revealed to be a [4+2] pseudopericyclic reaction without the energy barrier. Being independent of the concentration of amine, the first process obeys the first-order rate law. PMID:18402429

  6. High-temperature Raman study of L-alanine, L-threonine and taurine crystals related to thermal decomposition

    NASA Astrophysics Data System (ADS)

    Cavaignac, A. L. O.; Lima, R. J. C.; Façanha Filho, P. F.; Moreno, A. J. D.; Freire, P. T. C.

    2016-03-01

    In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.

  7. Experimental and theoretical study of the decomposition of [Zn(NO3)3]-

    NASA Astrophysics Data System (ADS)

    Hester, Thomas H.; Goebbert, Daniel J.

    2016-09-01

    Zinc nitrate anion complexes, [Zn(NO3)3]- and [ZnO(NO3)2]-, were generated by electrospray ionization and studied by tandem mass spectrometry. Dissociation of [Zn(NO3)3]- yields two direct fragments, [ZnO(NO3)2]- and NO3-. In contrast, the [ZnO(NO3)2]- complex produces several zinc-containing fragments. Three direct elimination products from [ZnO(NO3)2]- are identified as [Zn(NO2)(NO3)]-, [ZnO2(NO3)]-, and [ZnO(NO3)]-. The [ZnO2(NO3)]- product undergoes further elimination of O2 to yield either [ZnO(NO2)]- or [Zn(NO3)]-. Theory predicts a mixture of the product isomers, [ZnO(NO2)]- and [Zn(NO3)]-, is formed due to similar energetics. The increased reactivity of [ZnO(NO3)2]- is attributed to radical anion character on the unique oxygen atom.

  8. Preliminary study of acrylamide monomer decomposition during methane fermentation of dairy waste sludge.

    PubMed

    Mroczek, Ewelina; Konieczny, Piotr; Lewicki, Andrzej; Waśkiewicz, Agnieszka; Dach, Jacek

    2016-07-01

    Polyacrylamide (PAM) used in sludge dewatering exists widely in high-solid anaerobic digestion. Acrylamide is registered in the list of chemicals demonstrating toxic, carcinogenic and mutagenic properties. Therefore, it is reasonable to ask about the mobility of such residual substances in the environment. The study was carried out to assess the impact of the mesophilic (39±1°C) and thermophilic (54±1°C) fermentation process on the level of acrylamide monomer (AMD) content in the dairy sludge. The material was analysed using high-performance liquid chromatography (HPLC) for quantification of AMD. The results indicate that the process of methane fermentation continues regardless of the temperature effects on the degradation of AMD in dairy sludge. The degree of reduction of acrylamide monomer for thermophilic fermentation is 100%, while for mesophilic fermentation it is 91%. In practice, this means that biogas technology eliminates the risk of AMD migration to plant tissue. Moreover, it should be stressed that 90% of cumulative biogas and methane production was reached one week earlier under thermophilic conditions - the dynamics of the methanisation process were over 20% faster. PMID:27372124

  9. Study of thermal treatment combined with radiation on the decomposition of polysaccharides in sugarcane bagasse

    NASA Astrophysics Data System (ADS)

    Duarte, C. L.; Ribeiro, M. A.; Oikawa, H.; Mori, M. N.

    2013-03-01

    Sugarcane bagasse pretreatment is a physical and chemical process that reduces the crystalline structure and disrupts the hydrogen bonding of cellulose to improve the accessibility to hydrolytic depolymerization reactions. The combination of pretreatment technologies intends to decrease the severity of the processes and to avoid excessive sugar degradation and formation of toxic by-products. An effective pretreatment preserves the pentose fractions and limits the formation of degradation products that inhibits the growth of fermentative microorganisms. This study presents the evaluation of the cleavage of polysaccharides from sugarcane bagasse using ionizing radiation combined with thermal and diluted acid treatment to further enzymatic or chemical hydrolysis of cellulose. Samples of sugarcane bagasse were irradiated using a Radiation Dynamics electron beam accelerator with 1.5 MeV and 37 kW, with different absorbed doses, and then were submitted to thermal and acid (0.1% sulfuric acid, m/m) hydrolysis for 10, 20 and 40 min at 180 °C. Taking into account the sugars and by-products liberated in these treatments the conversion rates of cellulose and hemicelluloses were calculated.

  10. Decomposition of PCBs in Oils Using Gamma Radiolysis A Treatability Study - Final Report

    SciTech Connect

    B. J. Mincher; R. E. Arbon

    1996-08-01

    Several legacy hydraulic oil waste streams contaminated with Aroclor 1260 and small amounts of Cesium-137 have been in storage at the Idaho National Engineering Laboratory (INEL) due to the lack of appropriate treatment facilities. The goal of this study was to demonstrate that polychlorinated biphenyls (PCBs) could be selectively decomposed in the oils. Removal of the PCB component to less than the 2 mg/L treatment standard should result in a waste oil that is not regulated by the Toxic Substances Control Act. Irradiation of the oils with high gamma-ray doses produces free electrons in the solution that react with PCBs. The reaction results in dechlorination of the PCBs to produce biphenyl. The gamma-ray source was spent reactor fuel stored in the Advanced Test Reactor canal at the INEL. A dry tube extends into the canal which allowed for positioning of samples in the proximity of the fuel. The gamma-ray dose rates at the samples varied from 10 to 30 kGy/h. This was measured using commercially available FWT-60 dosimeters. Irradiation of samples in a series of progressively increasing absorbed doses allowed the generation of rate constants used to predict absorbed doses necessary to meet the 2 mg/kg treatment standard. Three separate irradiation experiments were performed. The first irradiation used a maximum absorbed dose of 183 kGy. This experiment demonstrated that the PCB concentration decreased and allowed calculation of preliminary rate constants. The second irradiation used a maximum absorbed dose of 760 kGy. From this experiment, accurate rate constants were calculated, and the necessary absorbed dose to achieve the treatment standard was calculated. In the third irradiation of 2,242 kGy, all three waste streams were adequately decontaminated.

  11. Monte Carlo study for physiological interference reduction in near-infrared spectroscopy based on empirical mode decomposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Sun, JinWei; Rolfe, Peter

    2010-12-01

    Near-infrared spectroscopy (NIRS) can be used as the basis of non-invasive neuroimaging that may allow the measurement of haemodynamic changes in the human brain evoked by applied stimuli. Since this technique is very sensitive, physiological interference arising from the cardiac cycle and breathing can significantly affect the signal quality. Such interference is difficult to remove by conventional techniques because it occurs not only in the extracerebral layer but also in the brain tissue itself. Previous work on this problem employing temporal filtering, spatial filtering, and adaptive filtering have exhibited good performance for recovering brain activity data in evoked response studies. However, in this study, we present a time-frequency adaptive method for physiological interference reduction based on the combination of empirical mode decomposition (EMD) and Hilbert spectral analysis (HSA). Monte Carlo simulations based on a five-layered slab model of a human adult head were implemented to evaluate our methodology. We applied an EMD algorithm to decompose the NIRS time series derived from Monte Carlo simulations into a series of intrinsic mode functions (IMFs). In order to identify the IMFs associated with symmetric interference, the extracted components were then Hilbert transformed from which the instantaneous frequencies could be acquired. By reconstructing the NIRS signal by properly selecting IMFs, we determined that the evoked brain response is effectively filtered out with even higher signal-to-noise ratio (SNR). The results obtained demonstrated that EMD, combined with HSA, can effectively separate, identify and remove the contamination from the evoked brain response obtained with NIRS using a simple single source-detector pair.

  12. Effects of internal stresses and intermediate phases on the coarsening of coherent precipitates: A phase-field study

    SciTech Connect

    M. Asle Zaeem; H. El Kadiri; M. F. Horstemeyer; M. Khafizov; Z. Utegulov

    2012-03-01

    Phase stability, topology and size evolution of precipitates are important factors in determining the mechanical properties of crystalline materials. In this article, the Cahn-Hilliard type of phase-field model was coupled to elasticity equations within a mixed-order Galerkin finite element framework to study the coarsening morphology of coherent precipitates. The effects of capillarity, particle size and fraction, compositional strain, and inhomogeneous elasticity on the kinetics and kinematics of coherent precipitates in a binary dual phase crystal admitting a third intermediate stable/meta-stable phase were investigated. The results demonstrated the ability of the model to simulate coarsening under the concomitant action of Ostwald ripening and mismatch elastic strain mechanisms. Using a phenomenological coarsening power law, coarsening rates were determined to depend on precipitate size and volume fraction, compositional strain, and strain mismatch between precipitates and the matrix. Results also showed that the necking incubation time between two neighboring precipitates depends inversely on the precipitate's initial sizes; however, under fixed volume fraction of precipitates, any increase in the initial sizes of the precipitates mitigates the coarsening. Meanwhile, the compositional strain and the growth of the intermediate stable/meta-stable phase leads to substantial enhancements of precipitate coarsening.

  13. Decomposition Rate and Pattern in Hanging Pigs.

    PubMed

    Lynch-Aird, Jeanne; Moffatt, Colin; Simmons, Tal

    2015-09-01

    Accurate prediction of the postmortem interval requires an understanding of the decomposition process and the factors acting upon it. A controlled experiment, over 60 days at an outdoor site in the northwest of England, used 20 freshly killed pigs (Sus scrofa) as human analogues to study decomposition rate and pattern. Ten pigs were hung off the ground and ten placed on the surface. Observed differences in the decomposition pattern required a new decomposition scoring scale to be produced for the hanging pigs to enable comparisons with the surface pigs. The difference in the rate of decomposition between hanging and surface pigs was statistically significant (p=0.001). Hanging pigs reached advanced decomposition stages sooner, but lagged behind during the early stages. This delay is believed to result from lower variety and quantity of insects, due to restricted beetle access to the aerial carcass, and/or writhing maggots falling from the carcass.

  14. Nanosecond Time Resolved and Steady State Infrared Studies of Photoinduced Decomposition of TATB at Ambient and Elevated Pressures

    SciTech Connect

    Glascoe, E A; Zaug, J M; Armstrong, M R; Crowhurst, J C; Grant, C D; Fried, L E

    2009-03-05

    The timescale and/or products of photo-induced decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were investigated at ambient pressure and compared with products formed at elevated pressure (i.e. 8 GPa). Ultrafast time-resolved infrared and steady state Fourier transform IR (FTIR) spectroscopies were used to probe TATB and its products after photoexcitation with a 5 ns pulse of 532 nm light. At ambient pressure, transient spectra of TATB indicate that the molecule has significantly decomposed within 60 ns; transient spectra also indicate that formation of CO{sub 2}, an observed decomposition product, is complete within 30-40 s. Proof of principle time resolved experiments at elevated pressures were performed and are discussed briefly. Comparison of steady-state FTIR spectra obtained at ambient and elevated pressure (ca. 8 GPa) indicate that the decomposition products vary with pressure. We find evidence for water as a decomposition product only at elevated pressure.

  15. Study of limestone calcination with CO{sub 2} capture: decomposition behavior in a CO{sub 2} atmosphere

    SciTech Connect

    Yin Wang; Shiying Lin; Yoshizo Suzuki

    2007-12-15

    In the present work, the effects of temperature (up to 1293 K) and residence time on the decomposition behaviors of limestone particles (0.25-0.5 mm) in a CO{sub 2} atmosphere were investigated using a continuously operating fluidized bed reactor for CO{sub 2} capture. The results show that the rate of limestone decomposition was strongly dependent upon the pressure difference between the equilibrium CO{sub 2} pressure and CO{sub 2} partial pressure in experiments (P{asterisk} - P{sub CO{sub 2}}) with temperature. Decomposition conversions (CaCO{sub 3} {yields} CaO) were 73% at 1193 K and 95% at 1293 K, with a 70 min average residence time of particles in the bed. A model was proposed to describe the distribution of limestone particles in the fluidized bed reactor with residence time. The hydration and carbonation reactivities of CaO produced by the limestone decomposition were also tested. The results show that CaO hydration (CaO to Ca(OH){sub 2}) can be completed within 11 min; however, the conversion of CaO to CaCO{sub 3} in the CaO carbonation test was below 60%. 16 refs., 10 figs., 3 tabs.

  16. Decomposition as a Complex-Skill Acquisition Strategy in Management Education: A Case Study in Business Forecasting

    ERIC Educational Resources Information Center

    Adya, Monica; Lusk, Edward J.; Balhadjali, Moncef

    2009-01-01

    Graduate business education has been criticized for utilizing simplistic teaching strategies that compromise the presentation of real-world complex skills in the classroom. In this article, we propose that complex management functions can be effectively taught using decomposition strategies. We demonstrate the usefulness of this strategy in the…

  17. Teaching a New Method of Partial Fraction Decomposition to Senior Secondary Students: Results and Analysis from a Pilot Study

    ERIC Educational Resources Information Center

    Man, Yiu-Kwong; Leung, Allen

    2012-01-01

    In this paper, we introduce a new approach to compute the partial fraction decompositions of rational functions and describe the results of its trials at three secondary schools in Hong Kong. The data were collected via quizzes, questionnaire and interviews. In general, according to the responses from the teachers and students concerned, this new…

  18. Quantitative study and modelling of the litter decomposition in a European alluvial forest. Is there an influence of overstorey tree species on the decomposition of ivy litter ( Hedera helix L.)?

    NASA Astrophysics Data System (ADS)

    Badre, Bouchra; Nobelis, Photis; Trémolières, Michèle

    1998-12-01

    The influence on the decomposition rate of ivy litter ( Hedera helix L.) of three ligneous overstorey species (oak, Quercus robur L., white poplar, Populus alba and ash, Fraxinus excelsior L.) that support ivy was studied in an alluvial hardwood forest. The ivy provides an abundant litter at the end of spring. The decomposition of ivy litter and the nutrient release rate were analyzed over four months during the growing season of the canopy trees, the hypothesis being that throughfall could slow down the mass loss rate of ivy depending on the support species. Mathematical models for mass loss and nutrient (P, N, K and Mg) release rates were developed. Mass loss rate and the release rate of magnesium, nitrogen and phosphorus show significant differences depending on species whereas no influence of species was observed on the release rate of potassium. The results illustrate the significant effect of oak compared to ash and poplar in slowing down mass loss rate and nitrogen, phosphorus and magnesium release rates. The mass loss rate over time under the three species followed the proposed exponential model, whereas the release rates of phosphorus and magnesium did not follow this model. This model is fitted to the data in two cases out of three for potassium. Magnesium and potassium are released more rapidly when nitrogen accumulates and the phosphorus content does not change significantly. No species × date interaction was observed, except in the case of magnesium. The species effect is interpreted as an effect of composition of throughfalls and presence or absence of inhibitory substances such as phenolic compounds.

  19. Study of the solid-phase thermal decomposition of NTO using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS)

    NASA Technical Reports Server (NTRS)

    Minier, L.; Behrens, R.; Burkey, T. J.

    1997-01-01

    The solid phase thermal reaction chemistry of NTO between 190 and 250 C is presently being evaluated by utilizing STMBMS, a technique that enables the authors to measure the vapor pressure of NTO and to explore the reaction mechanisms and chemical kinetics associated with the NTO thermal decomposition process. The vapor pressure of NTO is expressed as Log(sub 10) p(torr) = 12.5137 + 6,296.553(1/t(k)) and the Delta-H(sub subl) = 28.71 +/- 0.07 kcal/mol (120.01 +/- 0.29 kJ/mol). The pyrolysis of NTO results in the formation of gaseous products and a condensed-phase residue. The identity of the major gaseous products and their origin from within the NTO molecules are determined based on the results from pyrolysis of NTO, NTO-3-C-13, NTO-1,2- (15)N2 and NTO-(2)H2. Identification of the products show the major gaseous products to be N2, CO2, NO, HNCO, H2O and some N2O, CO, HCN and NH3. The N2 is mostly derived from the N-1 and N-2 positions with some being from the N-4 and N-1 or N-2 positions. The CO2 is derived from both carbons in the NTO molecule in comparable amounts. The residue has an elemental formula of C(2.1)H(.26)N(2.9)O and FTIR analysis suggests that the residue is polyurea- and polycarbamate- like in nature. The temporal behaviors of the rates of formation of the gaseous products indicate that the overall thermal decomposition of NTO in the temperature range evaluated involves four major processes: (1) NTO sublimation; (2) an apparent solid-solid phase transition between 190 and 195 C; (3) a decomposition regime induced by the presence of exogenous H2O at the onset of decomposition; and (4) a decomposition regime that occurs at the onset of decomposition and continues until the depletion of NTO. Decomposition pathways that are consistent with the data are presented.

  20. A study of the solid-phase thermal decomposition of NTO using simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS)

    SciTech Connect

    Minier, L.; Behrens, R.; Burkey, T.J.

    1997-01-01

    The solid phase thermal reaction chemistry of NTO between 190 and 250 C is presently being evaluated by utilizing STMBMS, a technique that enables the authors to measure the vapor pressure of NTO and to explore the reaction mechanisms and chemical kinetics associated with the NTO thermal decomposition process. The vapor pressure of NTO is expressed as Log{sub 10} p(torr) = 12.5137 + 6,296.553(1/t{sub k}) and the {Delta}H{sub subl} = 28.71 {+-} 0.07 kcal/mol (120.01 {+-} 0.29 kJ/mol). The pyrolysis of NTO results in the formation of gaseous products and a condensed-phase residue. The identity of the major gaseous products and their origin from within the NTO molecules are determined based on the results from pyrolysis of NTO, NTO-3-{sup 13}C, NTO-1,2-{sup 15}N{sub 2} and NTO-{sup 2}H{sub 2}. Identification of the products show the major gaseous products to be N{sub 2}, CO{sub 2}, NO, HNCO, H{sub 2}O and some N{sub 2}O, CO, HCN and NH{sub 3}. The N{sub 2} is mostly derived from the N-1 and N-2 positions with some being from the N-4 and N-1 or N-2 positions. The CO{sub 2} is derived from both carbons in the NTO molecule in comparable amounts. The residue has an elemental formula of C{sub 2.1}H{sub .26}N{sub 2.9}O and FTIR analysis suggests that the residue is polyurea- and polycarbamate-like in nature. The temporal behaviors of the rates of formation of the gaseous products indicate that the overall thermal decomposition of NTO in the temperature range evaluated involves four major processes: (1) NTO sublimation; (2) an apparent solid-solid phase transition between 190 and 195 C; (3) a decomposition regime induced by the presence of exogenous H{sub 2}O at the onset of decomposition; and (4) a decomposition regime that occurs at the onset of decomposition and continues until the depletion of NTO. Decomposition pathways that are consistent with the data are presented.

  1. Making the Grade: Increasing Intermediate Students' Spelling Test Scores through the Improvement of Study Skills.

    ERIC Educational Resources Information Center

    Weiner, Michele S.

    A study skills program was developed and implemented to improve spelling grades while incorporating new study skill techniques in a multi-ethnic and multicultural elementary school. A target group of eight fifth-grade students who lacked these skills was established. The program contained five basic strategies for increasing study skills and…

  2. No Adverse Effect of Genetically Modified Antifungal Wheat on Decomposition Dynamics and the Soil Fauna Community – A Field Study

    PubMed Central

    Duc, Caroline; Nentwig, Wolfgang; Lindfeld, Andreas

    2011-01-01

    The cultivation of genetically modified (GM) plants has raised several environmental concerns. One of these concerns regards non-target soil fauna organisms, which play an important role in the decomposition of organic matter and hence are largely exposed to GM plant residues. Soil fauna may be directly affected by transgene products or indirectly by pleiotropic effects such as a modified plant metabolism. Thus, ecosystem services and functioning might be affected negatively. In a litterbag experiment in the field we analysed the decomposition process and the soil fauna community involved. Therefore, we used four experimental GM wheat varieties, two with a race-specific antifungal resistance against powdery mildew (Pm3b) and two with an unspecific antifungal resistance based on the expression of chitinase and glucanase. We compared them with two non-GM isolines and six conventional cereal varieties. To elucidate the mechanisms that cause differences in plant decomposition, structural plant components (i.e. C∶N ratio, lignin, cellulose, hemicellulose) were examined and soil properties, temperature and precipitation were monitored. The most frequent taxa extracted from decaying plant material were mites (Cryptostigmata, Gamasina and Uropodina), springtails (Isotomidae), annelids (Enchytraeidae) and Diptera (Cecidomyiidae larvae). Despite a single significant transgenic/month interaction for Cecidomyiidae larvae, which is probably random, we detected no impact of the GM wheat on the soil fauna community. However, soil fauna differences among conventional cereal varieties were more pronounced than between GM and non-GM wheat. While leaf residue decomposition in GM and non-GM wheat was similar, differences among conventional cereals were evident. Furthermore, sampling date and location were found to greatly influence soil fauna community and decomposition processes. The results give no indication of ecologically relevant adverse effects of antifungal GM wheat on the

  3. No adverse effect of genetically modified antifungal wheat on decomposition dynamics and the soil fauna community--a field study.

    PubMed

    Duc, Caroline; Nentwig, Wolfgang; Lindfeld, Andreas

    2011-01-01

    The cultivation of genetically modified (GM) plants has raised several environmental concerns. One of these concerns regards non-target soil fauna organisms, which play an important role in the decomposition of organic matter and hence are largely exposed to GM plant residues. Soil fauna may be directly affected by transgene products or indirectly by pleiotropic effects such as a modified plant metabolism. Thus, ecosystem services and functioning might be affected negatively. In a litterbag experiment in the field we analysed the decomposition process and the soil fauna community involved. Therefore, we used four experimental GM wheat varieties, two with a race-specific antifungal resistance against powdery mildew (Pm3b) and two with an unspecific antifungal resistance based on the expression of chitinase and glucanase. We compared them with two non-GM isolines and six conventional cereal varieties. To elucidate the mechanisms that cause differences in plant decomposition, structural plant components (i.e. C∶N ratio, lignin, cellulose, hemicellulose) were examined and soil properties, temperature and precipitation were monitored. The most frequent taxa extracted from decaying plant material were mites (Cryptostigmata, Gamasina and Uropodina), springtails (Isotomidae), annelids (Enchytraeidae) and Diptera (Cecidomyiidae larvae). Despite a single significant transgenic/month interaction for Cecidomyiidae larvae, which is probably random, we detected no impact of the GM wheat on the soil fauna community. However, soil fauna differences among conventional cereal varieties were more pronounced than between GM and non-GM wheat. While leaf residue decomposition in GM and non-GM wheat was similar, differences among conventional cereals were evident. Furthermore, sampling date and location were found to greatly influence soil fauna community and decomposition processes. The results give no indication of ecologically relevant adverse effects of antifungal GM wheat on the

  4. Thermal decomposition of energetic materials by STMBMS measurements: Application of Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS) to the study of energetic materials

    SciTech Connect

    Behrens, R. Jr.

    1995-08-01

    Simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and time-of-flight velocity (TOF) spectra have been developed to study reactions that occur during the thermal decomposition of liquids and solids. The data obtained with these techniques are the identity of the reaction products and their rates of gas formation as a function of time. Over the past several years, these techniques have been applied to the study of energetic materials that are used in propellants and explosives. In this presentation, the details of the STMBMS and TOF velocity spectra techniques will be reviewed, the advantages of the techniques over more conventional thermal analysis and mass spectrometry measurements will be discussed, and the use of the techniques will be illustrated with results on the thermal decomposition of hexahydro-1,3,5-trinitro-s-triazine (RDX).

  5. [Study on mechanism of ceramic honeycomb-catalytic ozonation for the decomposition of trace nitrobenzene in aqueous solution].

    PubMed

    Zhao, Lei; Ma, Jun; Sun, Zhi-Zhong; Liu, Zheng-Qian; Yang, Yi-Xin; Lu, Wei

    2007-02-01

    The experiment investigated effects of the presence of hydroxyl radical inhibitor on degradation efficiency of trace nitrobenzene in aqueous solution in the processes of ozonation alone and ceramic honeycomb-catalyzed ozonation, including HCO3-, CO3(2-), HPO4(2-), H2PO4- and tert-butanol, and studied preliminarily on their mechanism. The results indicated that degradation rate of the two processes both increased firstly and decreased subsequently with the increase of the concentration of HCO3- (0 - 200 mg x L(-1)), and reached the climax at the concentration of bicarbonate ion 50 mg x L(-1) under the same experimental condition. The degradation rates of ozonation alone and ozonation/ ceramic honeycomb both declined by 16.57% and 27.52% with the increase of the concentration of CO3(2-) (0 - 20 mg x L(-1)), respectively, and decreased by 13.61% and 17.52% with the addition of the concentration of HPO4(2-) (0 - 12 mg x L(-1)), and reduced by 6.61% and 12.52% with the enhancement of the concentration of H2PO4- (0 - 120 mg x L(-1)), and dropped by 30.06% and 46.09% with the increasing of the concentration of tert-butanol (0 - 10 mg x L(-1)). The experimental results indicated that decomposition of nitrobenzene in both processes all followed the mechanism of oxidization by OH free radical, and tert-butanol is a more suitable indicator for the radical type reaction. The removal rate of ozonation alone rose with the increase of the concentration of pH (3.02 - 10.96), but that of ozonation/ceramic honeycomb process reached the maximum at pH = 9.23.

  6. Thermal decomposition of CH{sub 3}CHO studied by matrix infrared spectroscopy and photoionization mass spectroscopy

    SciTech Connect

    Vasiliou, AnGayle K.; Piech, Krzysztof M.; Reed, Beth; Ellison, G. Barney; Zhang Xu; Nimlos, Mark R.; Ahmed, Musahid; Golan, Amir; Kostko, Oleg; Osborn, David L.; David, Donald E.; Urness, Kimberly N.; Daily, John W.; Stanton, John F.

    2012-10-28

    A heated SiC microtubular reactor has been used to decompose acetaldehyde and its isotopomers (CH{sub 3}CDO, CD{sub 3}CHO, and CD{sub 3}CDO). The pyrolysis experiments are carried out by passing a dilute mixture of acetaldehyde (roughly 0.1%-1%) entrained in a stream of a buffer gas (either He or Ar) through a heated SiC reactor that is 2-3 cm long and 1 mm in diameter. Typical pressures in the reactor are 50-200 Torr with the SiC tube wall temperature in the range 1200-1900 K. Characteristic residence times in the reactor are 50-200 {mu}s after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 {mu}Torr. The reactor has been modified so that both pulsed and continuous modes can be studied, and results from both flow regimes are presented. Using various detection methods (Fourier transform infrared spectroscopy and both fixed wavelength and tunable synchrotron radiation photoionization mass spectrometry), a number of products formed at early pyrolysis times (roughly 100-200 {mu}s) are identified: H, H{sub 2}, CH{sub 3}, CO, CH{sub 2}=CHOH, HC{identical_to}CH, H{sub 2}O, and CH{sub 2}=C=O; trace quantities of other species are also observed in some of the experiments. Pyrolysis of rare isotopomers of acetaldehyde produces characteristic isotopic signatures in the reaction products, which offers insight into reaction mechanisms that occur in the reactor. In particular, while the principal unimolecular processes appear to be radical decomposition CH{sub 3}CHO (+M) {yields} CH{sub 3}+ H + CO and isomerization of acetaldehyde to vinyl alcohol, it appears that the CH{sub 2}CO and HCCH are formed (perhaps exclusively) by bimolecular reactions, especially those involving hydrogen atom attacks.

  7. Kinetics of the thermal decomposition and isomerization of pyrazine (1,4 diazine)

    SciTech Connect

    Doughty, A.; Mackie, J.C.; Palmer, J.M.

    1994-12-31

    The isomerization and decomposition of pyrazine have been studied over the temperature range 1,200--1,480 K. The major products of decomposition were found to be acetylene and HCN, with cyanoacetylene and acrylonitrile also being significant products, although lower yields of these products were observed. The decomposition has been successfully modeled using a free radical mechanisms, with the major chain carriers being CN radicals and H atoms. The initiation reaction was found to be C{single_bond}H bond fission, to yield H atoms and pyrazyl radicals. Kinetic modeling allowed the rate of initiation to be determined, yielding a first-order rate constant given by the expression k = 10{sup 15.7} exp({minus}96.5 kcal/mol/RT) s{sup {minus}1}. The importance of CN radicals as chain carriers appears to be a significant difference in the decomposition of the dizziness compared with pyridine or 2-picoline. Accompanying the decomposition of pyrazine was the isomerization of pyrazine to pyrimidine. By kinetic modeling, the isomerization of pyrazine to pyrimidine was found to occur via a fulvenelike intermediate. The rate and mechanism of the isomerization are analogous to the isomerization of fulvene to benzene described by Melius and Miller. The thermal reactions of these species are being studied because of their relevance to the mechanism of formation of NO{sub x} through the oxidation of fuel-bound nitrogen (FBN) in coal during the combustion of coal and heavy fuels.

  8. Effect of variable rates of daily sampling of fly larvae on decomposition and carrion insect community assembly: implications for forensic entomology field study protocols.

    PubMed

    Michaud, Jean-Philippe; Moreau, Gaétan

    2013-07-01

    Experimental protocols in forensic entomology successional field studies generally involve daily sampling of insects to document temporal changes in species composition on animal carcasses. One challenge with that method has been to adjust the sampling intensity to obtain the best representation of the community present without affecting the said community. To this date, little is known about how such investigator perturbations affect decomposition-related processes. Here, we investigated how different levels of daily sampling of fly eggs and fly larvae affected, over time, carcass decomposition rate and the carrion insect community. Results indicated that a daily sampling of <5% of the egg and larvae volumes present on a carcass, a sampling intensity believed to be consistent with current accepted practices in successional field studies, had little effect overall. Higher sampling intensities, however, slowed down carcass decomposition, affected the abundance of certain carrion insects, and caused an increase in the volume of eggs laid by dipterans. This study suggests that the carrion insect community not only has a limited resilience to recurrent perturbations but that a daily sampling intensity equal to or <5% of the egg and larvae volumes appears adequate to ensure that the system is representative of unsampled conditions. Hence we propose that this threshold be accepted as best practice in future forensic entomology successional field studies.

  9. Regular Decompositions for H(div) Spaces

    SciTech Connect

    Kolev, Tzanio; Vassilevski, Panayot

    2012-01-01

    We study regular decompositions for H(div) spaces. In particular, we show that such regular decompositions are closely related to a previously studied “inf-sup” condition for parameter-dependent Stokes problems, for which we provide an alternative, more direct, proof.

  10. Lactobacillus species isolated from vaginal secretions of healthy and bacterial vaginosis-intermediate Mexican women: a prospective study

    PubMed Central

    2013-01-01

    Background Lactobacillus jensenii, L. iners, L. crispatus and L. gasseri are the most frequently occurring lactobacilli in the vagina. However, the native species vary widely according to the studied population. The present study was performed to genetically determine the identity of Lactobacillus strains present in the vaginal discharge of healthy and bacterial vaginosis (BV) intermediate Mexican women. Methods In a prospective study, 31 strains preliminarily identified as Lactobacillus species were isolated from 21 samples collected from 105 non-pregnant Mexican women. The samples were classified into groups according to the Nugent score criteria proposed for detection of BV: normal (N), intermediate (I) and bacterial vaginosis (BV). We examined the isolates using culture-based methods as well as molecular analysis of the V1–V3 regions of the 16S rRNA gene. Enterobacterial repetitive intergenic consensus (ERIC) sequence analysis was performed to reject clones. Results Clinical isolates (25/31) were classified into four groups based on sequencing and analysis of the 16S rRNA gene: L. acidophilus (14/25), L. reuteri (6/25), L. casei (4/25) and L. buchneri (1/25). The remaining six isolates were presumptively identified as Enterococcus species. Within the L. acidophilus group, L. gasseri was the most frequently isolated species, followed by L. jensenii and L. crispatus. L. fermentum, L. rhamnosus and L. brevis were also isolated, and were placed in the L. reuteri, L. casei and L. buchneri groups, respectively. ERIC profile analysis showed intraspecific variability amongst the L. gasseri and L. fermentum species. Conclusions These findings agree with previous studies showing that L. crispatus, L. gasseri and L. jensenii are consistently present in the healthy vaginal ecosystem. Additional species or phylotypes were detected in the vaginal microbiota of the non-pregnant Mexican (Hispanic-mestizo) population, and thus, these results further our understanding of

  11. Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species

    PubMed Central

    Dossa, Gbadamassi G. O.; Paudel, Ekananda; Cao, Kunfang; Schaefer, Douglas; Harrison, Rhett D.

    2016-01-01

    Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11–1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition. PMID:27698461

  12. A Mixed Methods Explanatory Study of Intermediate School Collaboration and Inclusion

    ERIC Educational Resources Information Center

    Sanchez, Sandra J.

    2012-01-01

    This mixed methods explanatory study addressed the problem of continuing disparity in achievement between students with special needs and their peers in the educational setting, despite mandates requiring schools to educate these students in the least restrictive environment. The purpose of this study was to determine the types and extent of…

  13. Magneto-optical study of the intermediate state in type-I superconductors: Effects of sample shape and applied current

    SciTech Connect

    Hoberg, Jacob Ray

    2008-01-01

    The magnetic flux structures in the intermediate state of bulk, pinning-free Type-I superconductors are studied using a high resolution magneto-optical imaging technique. Unlike most previous studies, this work focuses on the pattern formation of the coexisting normal and superconducting phases in the intermediate state. The influence of various parameters such as sample shape, structure defects (pinning) and applied current are discussed in relation to two distinct topologies: flux tubes (closed topology) and laminar (open topology). Imaging and magnetization measurements performed on samples of different shapes (cones, hemispheres and slabs), show that contrary to previous beliefs, the tubular structure is the equilibrium topology, but it is unstable toward defects and flux motion. Moreover, the application of current into a sample with the geometric barrier can replace an established laminar structure with flux tubes. At very high currents, however, there exists a laminar 'stripe pattern.' Quantitative analysis of the mean tube diameter is shown to be in good agreement with the prediction proposed by Goren and Tinkham. This is the first time that this model has been confirmed experimentally. Further research into the flux tube phase shows a direct correlation with the current loop model proposed in the 1990's by Goldstein, Jackson and Dorsey. There also appears a range of flux tube density that results in a suprafroth structure, a well-formed polygonal mesh, which behaves according to the physics of foams, following standard statistical laws such as von Neumann and Lewis. The reaction of flux structures to a fast-ramped magnetic field was also studied. This provided an alignment of the structure not normally observed at slow ramp rates.

  14. Leukocyte Subtype Counts and Its Association with Vascular Structure and Function in Adults with Intermediate Cardiovascular Risk. MARK Study

    PubMed Central

    Gomez-Sanchez, Leticia; García-Ortiz, Luis; Recio-Rodríguez, José I.; Patino-Alonso, Maria C.; Agudo-Conde, Cristina; Rigo, Fernando; Ramos, Rafel; Martí, Ruth; Gomez-Marcos, Manuel A.

    2015-01-01

    Objectives We investigated the relationship between leukocyte subtype counts and vascular structure and function based on carotid intima-media thickness, pulse wave velocity, central augmentation index and cardio-ankle vascular index by gender in intermediate cardiovascular risk patients. Methods This study analyzed 500 subjects who were included in the MARK study, aged 35 to 74 years (mean: 60.3±8.4), 45.6% women. Measurement: Brachial ankle Pulse Wave Velocity (ba-PWV) estimate by equation, Cardio-AnkleVascular Index (CAVI) using the VaSera device and Carotid ultrasound was used to measure carotid Intima Media Thickness (IMT). The Mobil-O-Graph was used to measure the Central Augmentation Index (CAIx). Results Total leukocyte, neutrophil and monocyte counts were positively correlated with IMT (p < 0.01) in men. Monocyte count was positively correlated with CAIx in women (p < 0.01). In a multiple linear regression analysis, the IMT mean maintained a positive association with the neutrophil count (β = 1.500, p = 0.007) in men. CAIx maintained a positive association with the monocyte count (β = 2.445, p = 0.022) in women. Conclusion The results of this study suggest that the relationship between subtype circulating leukocyte counts and vascular structure and function, although small, may be different by gender. In men, the neutrophil count was positively correlated with IMT and in women, the monocyte count with CAIx, in a large sample of intermediate-risk patients. These association were maintained after adjusting for age and other confounders. Trial Registration ClinicalTrials.gov NCT01428934 PMID:25885665

  15. Studies of waveform requirements for intermediate mass-ratio coalescence searches with advanced gravitational-wave detectors

    NASA Astrophysics Data System (ADS)

    Smith, R. J. E.; Mandel, I.; Vecchio, A.

    2013-08-01

    The coalescence of a stellar-mass compact object into an intermediate-mass black hole (intermediate mass-ratio coalescence; IMRAC) is an important astrophysical source for ground-based gravitational-wave interferometers in the so-called advanced (or second-generation) configuration. However, the ability to carry out effective matched-filter-based searches for these systems is limited by the lack of reliable waveforms. Here we consider binaries in which the intermediate-mass black hole has a mass in the range 24M⊙-200M⊙ with a stellar-mass companion having masses in the range 1.4M⊙-18.5M⊙. In addition, we constrain the mass ratios, q, of the binaries to be in the range 1/140≤q≤1/10 and we restrict our study to the case of circular binaries with nonspinning components. We investigate the relative contribution to the signal-to-noise ratio (SNR) of the three different phases of the coalescence—inspiral, merger and ringdown—using waveforms computed within the effective one-body formalism matched to numerical relativity. We show that merger and ringdown contribute to a substantial fraction of the total SNR over a large portion of the mass parameter space, although in a limited portion the SNR is dominated by the inspiral phase. We further identify three regions in the IMRAC mass space in which (i) inspiral-only searches could be performed with losses in detection rates L in the range 10%≲L≲27%, (ii) searches based on inspiral-only templates lead to a loss in detection rates in the range 27%≲L≲50%, and (iii) templates that include merger and ringdown are essential to prevent losses in detection rates greater than 50%. In addition we find that using inspiral-only templates as filters can lead to large biases in the estimates of the mass parameters of IMRACs. We investigate the effectiveness with which the inspiral-only portion of the IMRAC waveform space is covered by comparing several existing waveform families in this regime. We find that

  16. Laue diffraction as a tool in dynamic studies: Hydrolysis of a transiently stable intermediate in catalysis by trypsin

    SciTech Connect

    Singer, P.T.; Berman, L.E.; Cai, Z.; Mangel, W.F.; Jones, K.W.; Sweet, R.M. ); Carty, R.P. . Dept. of Biochemistry); Schlichting, I. . Rosenstiel Basic Medical Science Center); Stock, A. (Center for Advanced Biotechnology and Medicine, Piscataway, NJ (Un

    1992-01-01

    A transiently stable intermediate in trypsin catalysis, guanidinobenzyol-Ser-195 trypsin, can be trapped and then released by control of the pH in crystals of the enzyme. This effect has been investigated by static and dynamic white-beam Laue crystallography. Comparison of structures determined before and immediately after a pH jump reveals the nature of concerted changes that accompany activation of the enzyme. Careful analysis of the results of several structure determinations gives information about the reliability of Laue results in general. A study of multiple exposures taken under differing conditions of beam intensity, crystal quality, and temperature revealed information about ways to control damage of specimens by the x-ray beam.

  17. Theoretical Studies on the Photochemistry of Pentose Aminooxazoline, a Hypothetical Intermediate Product in the Prebiotic Synthetic Scenario of RNA Nucleotides.

    PubMed

    Ai, Yuejie; Xia, Shuhua; Liao, Rong-Zhen

    2016-09-01

    2-Aminooxazole is generally considered a prebiotic precursor of ribonucleotides on the early earth. Its pentose compound, pentose aminooxazoline, has been suggested to be a key intermediate in the prebiotic synthetic scenario. In this article, detailed mechanism of the photochemistry of pentose aminooxazoline has been studied by performing density functional theory and multireference complete active space self-consistent field calculations. Parallel to the "ring-puckering" process, which leads to ultrafast nonradiative deactivation, several other photodissociation channels are explored in detail. In addition, the influences of the pentose structure and solvation effects with both implicit and explicit water models have been uncovered for both neutral and protonated forms. The current theoretical results provide very important information not only for the photostability of RNA nucleotides but also for an in-depth understanding of the synthesis of other prebiotic nucleotides. PMID:27525736

  18. Theoretical Studies on the Photochemistry of Pentose Aminooxazoline, a Hypothetical Intermediate Product in the Prebiotic Synthetic Scenario of RNA Nucleotides.

    PubMed

    Ai, Yuejie; Xia, Shuhua; Liao, Rong-Zhen

    2016-09-01

    2-Aminooxazole is generally considered a prebiotic precursor of ribonucleotides on the early earth. Its pentose compound, pentose aminooxazoline, has been suggested to be a key intermediate in the prebiotic synthetic scenario. In this article, detailed mechanism of the photochemistry of pentose aminooxazoline has been studied by performing density functional theory and multireference complete active space self-consistent field calculations. Parallel to the "ring-puckering" process, which leads to ultrafast nonradiative deactivation, several other photodissociation channels are explored in detail. In addition, the influences of the pentose structure and solvation effects with both implicit and explicit water models have been uncovered for both neutral and protonated forms. The current theoretical results provide very important information not only for the photostability of RNA nucleotides but also for an in-depth understanding of the synthesis of other prebiotic nucleotides.

  19. Laue diffraction as a tool in dynamic studies: Hydrolysis of a transiently stable intermediate in catalysis by trypsin

    SciTech Connect

    Singer, P.T.; Berman, L.E.; Cai, Z.; Mangel, W.F.; Jones, K.W.; Sweet, R.M.; Carty, R.P.; Schlichting, I.; Stock, A.; Smalas, A.

    1992-11-01

    A transiently stable intermediate in trypsin catalysis, guanidinobenzyol-Ser-195 trypsin, can be trapped and then released by control of the pH in crystals of the enzyme. This effect has been investigated by static and dynamic white-beam Laue crystallography. Comparison of structures determined before and immediately after a pH jump reveals the nature of concerted changes that accompany activation of the enzyme. Careful analysis of the results of several structure determinations gives information about the reliability of Laue results in general. A study of multiple exposures taken under differing conditions of beam intensity, crystal quality, and temperature revealed information about ways to control damage of specimens by the x-ray beam.

  20. Laser beam direct writing of fine lines of alpha-Fe2O3 from metalorganic spin-coated films and transient behavior study of laser decomposition process

    NASA Astrophysics Data System (ADS)

    Xue, Songsheng; Ousi-Benomar, Wahib; Lessard, Roger A.

    1994-07-01

    Fine lines of (alpha) -Fe2O3 have been formed on quartz substrates by laser beam direct writing on metalorganic spin-coated films. A modulated krypton ion writing laser beam and a He-Ne probing laser beam were colinearly focused onto the films with a spot size about 10 to 50 micrometers in diameter. A series of characterizations have been conducted on the written lines by employing different techniques ranging from thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron spectroscopy, and x-ray diffraction to transmission electron microscopy. In this way, a better understanding has been achieved regarding the metalorganic decomposition mechanism, structure, and morphology of the laser written lines. From the time-resolved transmittance change induced by the krypton ion laser pulse irradiation, transient behavior of laser decomposition process of metalorganic materials has also been studied.

  1. Prognostic sub-classification of intermediate-stage hepatocellular carcinoma: a multicenter cohort study with propensity score analysis.

    PubMed

    Ramaswami, Ramya; Pinato, David J; Kubota, Keiichi; Ishizuka, Mitsuru; Arizumi, Tadaaki; Kudo, Masatoshi; Jang, Jeong Won; Kim, Young Woon; Pirisi, Mario; Allara, Elias; Sharma, Rohini

    2016-10-01

    There is significant heterogeneity in the clinicopathological characteristics of intermediate hepatocellular carcinoma (IHCC). This also translates to treatment as transarterial chemoembolization (TACE) is used as first-line therapy for patients with IHCC; however, in Asia liver resection (LR) is preferred. Prognostic tools are required to help guide clinicians in deciding treatment options. This study evaluates the prognostic impact of the Intermediate Stage Score (ISS) on overall survival (OS) in a large, multicenter cohort study of patients with IHCC treated with TACE or surgery LR. Consecutive patients from centers in Japan, Korea, Italy and the United Kingdom who underwent TACE or LR between 2001 and 2015 were enrolled. Propensity score (PS) adjustment was used to remove residual confounding and applied to LR (n = 162) and TACE (n = 449) to determine the prognostic significance of ISS. Among 611 patients, 75 % were men and 25 % women, with a mean age of 70 years. ISS is a valid prognostic tool in the BCLC-B population with a median OS ISS 1-51, 2-38.3, 3-24.3, 4-15.6, 5-16 months (p < 0.0001). ISS was analyzed within each treatment modality, and this was a valid prognostic score among those treated with TACE and LR (p < 0.001 vs. p = 0.008). In the PS-adjusted model, ISS retained its prognostic utility in TACE and LR groups (p < 0.001 vs. p = 0.007). ISS optimizes prognostic prediction in IHCC, reducing clinical heterogeneity, and is a useful tool for patients treated for TACE or LR. PMID:27601241

  2. Lost Opportunities: A Study of the Education of Language Minority Students in the Intermediate Grades.

    ERIC Educational Resources Information Center

    Gersten, Russell; Woodward, John

    A study investigated how schools and teachers attempt to meet the needs of language minority students and to utilize literature as a means to teach English language reading to students while building their English language capacities. Language arts and reading instruction was observed in 12 third- through fifth-grade classrooms in three elementary…

  3. Learning Intermediate Algebra with Graphing Calculator in Community College: A Study of Graphing Calculator Implementation

    ERIC Educational Resources Information Center

    Reznichenko, Nataliya

    2012-01-01

    Since technology has taken its place in almost all classrooms in schools and colleges across the country, there is a need to know how technology influences the mathematics that is taught and how students learn. In this study, the graphing calculator (GC) (namely the Texas Instruments TI-83) was implemented as a tool to enhance learning of function…

  4. Theoretical kinetic study for methyl levulinate: oxidation by OH and CH3 radicals and further unimolecular decomposition pathways.

    PubMed

    Thion, S; Zaras, A M; Szőri, M; Dagaut, P

    2015-09-28

    Biofuels may represent a promising alternative in terms of energy sustainability and emission control. Until recently, simple compounds including only a single specific functional group was in the focus of the biofuel research while reported data on more complex structures are scarcer. Presence of multiple functional groups can make molecules more attractive for oxidative species providing attacking site for fast oxidation. Including both a carbonyl and an ester group, methyl levulinate (ML) can be such an excellent biofuel candidate due to its cellulosic origin, although its combustion kinetics is still unresolved. This work reports the first computational kinetic study on methyl levulinate oxidation relevant to combustion conditions. Absolute rate constants for H-abstraction reactions by OH and CH3 radicals were calculated using the G3//MP2/aug-cc-pVDZ level of theory coupled with Transition State Theory (TST). The fate of the forming ML radicals was also investigated by computing absolute rate constants for β-scission as well as for H-transfer reactions. The outcomes of this work show that the sites between the two functional groups are the most favorable for H-abstraction reactions, and that methyl vinyl ketone (MVK) and methyl acrylate (MAC) are expected to be the main intermediate products of methyl levulinate oxidation. The present results will be useful for further detailed kinetic modeling.

  5. Model Catalytic Studies of Liquid Organic Hydrogen Carriers: Dehydrogenation and Decomposition Mechanisms of Dodecahydro-N-ethylcarbazole on Pt(111)

    PubMed Central

    2014-01-01

    Liquid organic hydrogen carriers (LOHC) are compounds that enable chemical energy storage through reversible hydrogenation. They are considered a promising technology to decouple energy production and consumption by combining high-energy densities with easy handling. A prominent LOHC is N-ethylcarbazole (NEC), which is reversibly hydrogenated to dodecahydro-N-ethylcarbazole (H12-NEC). We studied the reaction of H12-NEC on Pt(111) under ultrahigh vacuum (UHV) conditions by applying infrared reflection–absorption spectroscopy, synchrotron radiation-based high resolution X-ray photoelectron spectroscopy, and temperature-programmed molecular beam methods. We show that molecular adsorption of H12-NEC on Pt(111) occurs at temperatures between 173 and 223 K, followed by initial C–H bond activation in direct proximity to the N atom. As the first stable dehydrogenation product, we identify octahydro-N-ethylcarbazole (H8-NEC). Dehydrogenation to H8-NEC occurs slowly between 223 and 273 K and much faster above 273 K. Stepwise dehydrogenation to NEC proceeds while heating to 380 K. An undesired side reaction, C–N bond scission, was observed above 390 K. H8-NEC and H8-carbazole are the dominant products desorbing from the surface. Desorption occurs at higher temperatures than H8-NEC formation. We show that desorption and dehydrogenation activity are directly linked to the number of adsorption sites being blocked by reaction intermediates. PMID:24527267

  6. In situ XPS and MS study of methanol decomposition and oxidation on Pd(111) under millibar pressure range

    NASA Astrophysics Data System (ADS)

    Kaichev, V. V.; Miller, A. V.; Prosvirin, I. P.; Bukhtiyarov, V. I.

    2012-02-01

    The methanol decomposition and oxidation on a Pd(111) single crystal have been investigated in situ using ambient-pressure X-ray photoelectron spectroscopy (XPS) and mass-spectrometry (MS) in the temperature range of 300-600 K. It was found that even in the oxygen presence the methanol decomposition on palladium proceeds through two competitive routes: fast dehydrogenation to CO and H2, and slow decomposition of methanol via the C-O bond scission. The rate of the second route is significant even in the millibar pressure range, which leads to a blocking of the palladium surface by carbon and to a prevention of the further methanol conversion. As a result, no gas phase products of methanol decomposition were detected by mass-spectrometry at 0.1 mbar CH3OH in the whole temperature range. The methanol C-O bond scission produces CHx species, which fast dehydrogenate to atomic carbon even at room temperature and further partially dissolve in the palladium bulk at 400 K with the formation of the PdCx phase. According to in situ XPS data, the PdCx phase forms even in the oxygen excess. The application of an in situ XPS-MS technique unambiguously shows a good correlation between a decrease in the surface concentration of all carbon-containing species and the rate of methanol conversion. Since these carbon species have a high reactivity towards oxygen, heating of Pd(111) above 450 K in a methanol-oxygen mixture yields CO, CO2, and water. The product distribution indicates that the main route of methanol conversion is the dehydrogenation of methanol to CO and hydrogen. However, under the experimental conditions used, hydrogen is completely oxidized to water, while CO is partially oxidized to CO2. No palladium oxide was detected by XPS in these conditions.

  7. Studies on comparative decomposition rate by rat liver homogenate and on micronucleus test of nitrated polycyclic aromatic hydrocarbons

    SciTech Connect

    Ohe, T.

    1985-05-01

    Nitrated polycyclic aromatic hydrocarbons (nitrated PAHs) have been detected in various environmental samples and shown to be responsible for a substantial portion of the observed direct-acting mutagenicity in the Salmonella assay by many researchers. This paper describes the results on the comparative decomposition rate of some nitrated PAHs by rat liver homogenate and the micronucleus test in mice after administering 1-nitropyrene, 2-nitrofluorene and 1-aminopyrene.

  8. Chinese Orthographic Decomposition and Logographic Structure

    ERIC Educational Resources Information Center

    Cheng, Chao-Ming; Lin, Shan-Yuan

    2013-01-01

    "Chinese orthographic decomposition" refers to a sense of uncertainty about the writing of a well-learned Chinese character following a prolonged inspection of the character. This study investigated the decomposition phenomenon in a test situation in which Chinese characters were repeatedly presented in a word context and assessed…

  9. English and Turkish Pupils' Understanding of Decomposition

    ERIC Educational Resources Information Center

    Cetin, Gulcan

    2007-01-01

    This study aimed to describe seventh grade English and Turkish students' levels of understanding of decomposition. Data were analyzed descriptively from the students' written responses to four diagnostic questions about decomposition. Results revealed that the English students had considerably higher sound understanding and lower no understanding…

  10. Using personas as an intermediate construct in the development of tailored messages: a case study.

    PubMed

    Vosbergen, Sandra; Wiggers, Anne-Marieke; Lacroix, Joyca; Jaspers, Monique; Peek, Niels

    2013-01-01

    Tailoring health education messages to patients' preferences for message style is believed to increase patients' susceptibility to the given advice. This paper presents a persona-centered approach towards creating tailored health messages for chronically ill patients. A case study of tailoring messages to the preferences of patients with coronary heart disease illustrates the approach and shows the need for patient-centered data collection so that personas reflect patients' preferences. Based on these personas, a manageable set of tailored messages can be created in a step-by-step approach.

  11. Comparative Phylogenetic Studies on Schistosoma japonicum and Its Snail Intermediate Host Oncomelania hupensis: Origins, Dispersal and Coevolution

    PubMed Central

    Attwood, Stephen W.; Ibaraki, Motomu; Saitoh, Yasuhide; Nihei, Naoko; Janies, Daniel A.

    2015-01-01

    Background Schistosoma japonicum causes major public health problems in China and the Philippines; this parasite, which is transmitted by freshwater snails of the species Oncomelania hupensis, causes the disease intestinal schistosomiasis in humans and cattle. Researchers working on Schistosoma in Africa have described the relationship between the parasites and their snail intermediate hosts as coevolved or even as an evolutionary arms race. In the present study this hypothesis of coevolution is evaluated for S. japonicum and O. hupensis. The origins and radiation of the snails and the parasite across China, and the taxonomic validity of the sub-species of O. hupensis, are also assessed. Methodology/Principal Findings The findings provide no evidence for coevolution between S. japonicum and O. hupensis, and the phylogeographical analysis suggests a heterochronous radiation of the parasites and snails in response to different palaeogeographical and climatic triggers. The results are consistent with a hypothesis of East to West colonisation of China by Oncomelania with a re-invasion of Japan by O. hupensis from China. The Taiwan population of S. japonicum appears to be recently established in comparison with mainland Chinese populations. Conclusions/Significance The snail and parasite populations of the western mountain region of China (Yunnan and Sichuan) appear to have been isolated from Southeast Asian populations since the Pleistocene; this has implications for road and rail links being constructed in the region, which will breach biogeographical barriers between China and Southeast Asia. The results also have implications for the spread of S. japonicum. In the absence of coevolution, the parasite may more readily colonise new snail populations to which it is not locally adapted, or even new intermediate host species; this can facilitate its dispersal into new areas. Additional work is required to assess further the risk of spread of S. japonicum. PMID:26230619

  12. Pursuit eye movements as an intermediate phenotype across psychotic disorders: Evidence from the B-SNIP study.

    PubMed

    Lencer, Rebekka; Sprenger, Andreas; Reilly, James L; McDowell, Jennifer E; Rubin, Leah H; Badner, Judith A; Keshavan, Matcheri S; Pearlson, Godfrey D; Tamminga, Carol A; Gershon, Elliot S; Clementz, Brett A; Sweeney, John A

    2015-12-01

    Smooth pursuit eye tracking deficits are a promising intermediate phenotype for schizophrenia and possibly for psychotic disorders more broadly. The Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) consortium investigated the severity and familiality of different pursuit parameters across psychotic disorders. Probands with schizophrenia (N=265), schizoaffective disorder (N=178), psychotic bipolar disorder (N=231), their first-degree relatives (N=306, N=217, N=273, respectively) and healthy controls (N=305) performed pursuit tracking tasks designed to evaluate sensorimotor and cognitive/predictive aspects of pursuit. Probands from all diagnostic groups were impaired on all pursuit measures of interest compared to controls (p<0.001). Schizophrenia probands were more impaired than other proband groups on both early pursuit gain and predictive gain. Relatives with and without enhanced psychosis spectrum personality traits were impaired on initial eye acceleration, the most direct sensorimotor pursuit measure, but not on pursuit gain measures. This suggests that alterations in early sensorimotor function may track susceptibility to psychosis even in the absence of psychosis related personality traits. There were no differences in pursuit measures between relatives of the three proband groups. Familiality estimates of pursuit deficits indicate that early pursuit gain was more familial than predictive gain, which has been the most widely used measure in previous family studies of psychotic disorders. Thus, while disease-related factors may induce significant impairments of pursuit gain, especially in schizophrenia, the pattern of deficits in relatives and their familiality estimates suggest that alterations in sensorimotor function at pursuit onset may indicate increased susceptibility across psychotic disorders.

  13. ESR studies on the thermal decomposition of trimethylamine oxide to formaldehyde and dimethylamine in jumbo squid (Dosidicus gigas) extract.

    PubMed

    Zhu, Junli; Jia, Jia; Li, Xuepeng; Dong, Liangliang; Li, Jianrong

    2013-12-15

    The effects of ferrous iron, heating temperature and different additives on the decomposition of trimethylamine oxide (TMAO) to formaldehyde (FA) and dimethylamine (DMA) and generation of free radicals in jumbo squid (Dosidicus gigas) extract during heating were evaluated by electron spin resonance (ESR). The thermal decomposition of TMAO to TMA, DMA and FA and free radical signals was observed in squid extract, whereas no DMA, FA and free radical signals were detected in cod extract or in aqueous TMAO solution in vitro at high temperatures. Significant increase in levels of DMA, FA and radicals intensity were observed in squid extract and TMAO solution in the presence of ferrous iron with increasing temperature. Hydrogen peroxide stimulated the production of DMA, FA and ESR signals in squid extract, while citric acid, trisodium citrate, calcium chloride, tea polyphenols and resveratrol had the opposite effect. Similar ESR spectra of six peaks regarded as amminium radical were detected in the squid extract and TMAO-iron(II) solution, suggesting that the amminium radical was involved in the decomposition of TMAO.

  14. Thermal decomposition of 1,3,3-trinitroazetidine (TNAZ): A density functional theory and ab initio study

    SciTech Connect

    Veals, Jeffrey D.; Thompson, Donald L.

    2014-04-21

    Density functional theory and ab initio methods are employed to investigate decomposition pathways of 1,3,3-trinitroazetidine initiated by unimolecular loss of NO{sub 2} or HONO. Geometry optimizations are performed using M06/cc-pVTZ and coupled-cluster (CC) theory with single, double, and perturbative triple excitations, CCSD(T), is used to calculate accurate single-point energies for those geometries. The CCSD(T)/cc-pVTZ energies for NO{sub 2} elimination by N–N and C–N bond fission are, including zero-point energy (ZPE) corrections, 43.21 kcal/mol and 50.46 kcal/mol, respectively. The decomposition initiated by trans-HONO elimination can occur by a concerted H-atom and nitramine NO{sub 2} group elimination or by a concerted H-atom and nitroalkyl NO{sub 2} group elimination via barriers (at the CCSD(T)/cc-pVTZ level with ZPE corrections) of 47.00 kcal/mol and 48.27 kcal/mol, respectively. Thus, at the CCSD(T)/cc-pVTZ level, the ordering of these four decomposition steps from energetically most favored to least favored is: NO{sub 2} elimination by N–N bond fission, HONO elimination involving the nitramine NO{sub 2} group, HONO elimination involving a nitroalkyl NO{sub 2} group, and finally NO{sub 2} elimination by C–N bond fission.

  15. Computational fluid dynamics study on the decomposition of ammonia in a selective porous membrane - article no. 42

    SciTech Connect

    Athanasios Sideridis; Dimitrios Koutsonikolas; Dimitrios Missirlis

    2008-07-01

    The development of alternative technologies for the removal of gas pollutants is an important aspect for the environmental friendliness of energy production. During coal gasification, N{sub 2} contained in coal is converted to NH{sub 3} and, as much as 50% of the ammonia in the fuel gas can be converted to nitrogen oxides (NOx). At these conditions, decomposition seems to be the only applicable solution for the removal of NH{sub 3}. The application of a high temperature catalytic membrane reactor process appears to offer an efficient and cost effective method of removing the NH{sub 3} from coal gasification gas streams. The present work examines the operation of such a selective membrane, used for the decomposition of NH{sub 3}, under a 2-D axissymetric CFD approach where the flow field, the chemical reactions and the selective porous membrane behavior are being modeled and computed. The main target of this effort was to obtain a more detailed view of the flow field and to investigate the decomposition of ammonia in comparison with a simpler 1-D modeling approach and, thus, to evaluate the advantages and disadvantages of each method.

  16. Thermal decomposition products of butyraldehyde.

    PubMed

    Hatten, Courtney D; Kaskey, Kevin R; Warner, Brian J; Wright, Emily M; McCunn, Laura R

    2013-12-01

    The thermal decomposition of gas-phase butyraldehyde, CH3CH2CH2CHO, was studied in the 1300-1600 K range with a hyperthermal nozzle. Products were identified via matrix-isolation Fourier transform infrared spectroscopy and photoionization mass spectrometry in separate experiments. There are at least six major initial reactions contributing to the decomposition of butyraldehyde: a radical decomposition channel leading to propyl radical + CO + H; molecular elimination to form H2 + ethylketene; a keto-enol tautomerism followed by elimination of H2O producing 1-butyne; an intramolecular hydrogen shift and elimination producing vinyl alcohol and ethylene, a β-C-C bond scission yielding ethyl and vinoxy radicals; and a γ-C-C bond scission yielding methyl and CH2CH2CHO radicals. The first three reactions are analogous to those observed in the thermal decomposition of acetaldehyde, but the latter three reactions are made possible by the longer alkyl chain structure of butyraldehyde. The products identified following thermal decomposition of butyraldehyde are CO, HCO, CH3CH2CH2, CH3CH2CH=C=O, H2O, CH3CH2C≡CH, CH2CH2, CH2=CHOH, CH2CHO, CH3, HC≡CH, CH2CCH, CH3C≡CH, CH3CH=CH2, H2C=C=O, CH3CH2CH3, CH2=CHCHO, C4H2, C4H4, and C4H8. The first ten products listed are direct products of the six reactions listed above. The remaining products can be attributed to further decomposition reactions or bimolecular reactions in the nozzle.

  17. Kinetics of the Thermal Decomposition of Tetramethylsilane behind the Reflected Shock Waves in a Single Pulse Shock Tube (SPST) and Modeling Study

    NASA Astrophysics Data System (ADS)

    Parandaman, A.; Sudhakar, G.; Rajakumar, B.

    Thermal reactions of Tetramethylsilane (TMS) diluted in argon were studied behind the reflected shock waves in a single-pulse shock tube (SPST) over the temperature range of 1085-1221 K and pressures varied between 10.6 and 22.8 atm. The stable products resulting from the decomposition of TMS were identified and quantified using gas chromatography and also verified with Fourier Transform Infrared (FTIR) spectrometer. The major reaction products are methane (CH4) and ethylene (C2H4). The minor reaction products are ethane (C2H6) and propylene (C3H6). The initiation of mechanism in the decomposition of TMS takes plays via the Si-C bond scission by ejecting the methyl radicals (CH3) and trimethylsilyl radicals ((CH3)3Si). The measured temperature dependent rate coefficient for the total decomposition of TMS was to be ktotal = 1.66 ×1015 exp (-64.46/RT) s-1 and for the formation of CH4 reaction channel was to be k = 2.20 × 1014 exp (-60.15/RT) s-1, where the activation energies are given in kcal mol-1. A kinetic scheme containing 17 species and 28 elementary reactions was used for the simulation using chemical kinetic simulator over the temperature range of 1085-1221 K. The agreement between the experimental and simulated results was satisfactory.

  18. Theoretical study of the neutral decomposition of SF6 in the presence of H2O and O2 in discharges in power equipment

    NASA Astrophysics Data System (ADS)

    Fu, Yuwei; Yang, Aijun; Wang, Xiaohua; Murphy, Anthony B.; Li, Xi; Liu, Dingxin; Wu, Yi; Rong, Mingzhe

    2016-09-01

    In the presence of H2O and O2, the dissociation products of SF6 will decompose to form several main stable byproducts (i.e. SOF2, SOF4 and SO2F2) in an electrical discharge. These byproducts are chemically active and have been shown experimentally to be associated with discharge faults. However, the relationships between the discharges and types of decomposition components are still not clear, mainly due to the fact that the complex chemical processes during SF6 discharges are not fully understood. In order to comprehensively investigate the decomposition of SF6, an approach combining density functional theory (DFT) and transition state theory (TST) was used to study the pathways of SF6 decomposition in mixtures with H2O and O2 that involve electrically-neutral species. The complex chemical reactions were analyzed, and the corresponding rate constants were predicted. The structural optimizations, vibrational frequency calculations and zero-point energy calculations of the species involved in each chemical reaction considered were carried out using the DFT-B3LYP method. Single-point energies were calculated using the CCSD(T) method. Based on the energy information obtained, the rate constants were predicted by TST, over a large temperature range, from 300 to 12 000 K.

  19. Experimental studies of pion-nucleus interactions at intermediate energies. Annual progress report

    SciTech Connect

    Not Available

    1992-12-31

    This report summarizes investigations of various pion-nucleus interactions and nucleon-nucleus charge-exchange reactions. The work was carried out with the LAMPF accelerator at the Los Alamos National Laboratory and the cyclotrons at the Paul Scherrer Institute (PSI) near Zurich, Switzerland, and at Indiana University (IUCF), as a collaborative effort among several laboratories and universities. The experimental activity at LAMPF involved measurements of new data on pion double-charge-exchange scattering, some initial work on a new Neutral Meson Spectrometer system, a search for deeply-bound pionic atoms, measurements of elastic scattering, and studies of the (n,p) reaction on various nuclei. At PSI measurements of pion quasielastic scattering were carried out, with detection of the recoil proton. Work on the analysis of data from a previous experiment at PSI on pion absorption in nuclei was continued. This experiment involved using a detector system that covered nearly the full solid angle.

  20. Metabolomics of Oxidative Stress in Recent Studies of Endogenous and Exogenously Administered Intermediate Metabolites

    PubMed Central

    Liu, Jia; Litt, Lawrence; Segal, Mark R.; Kelly, Mark J. S.; Pelton, Jeffrey G.; Kim, Myungwon

    2011-01-01

    Aerobic metabolism occurs in a background of oxygen radicals and reactive oxygen species (ROS) that originate from the incomplete reduction of molecular oxygen in electron transfer reactions. The essential role of aerobic metabolism, the generation and consumption of ATP and other high energy phosphates, sustains a balance of approximately 3000 essential human metabolites that serve not only as nutrients, but also as antioxidants, neurotransmitters, osmolytes, and participants in ligand-based and other cellular signaling. In hypoxia, ischemia, and oxidative stress, where pathological circumstances cause oxygen radicals to form at a rate greater than is possible for their consumption, changes in the composition of metabolite ensembles, or metabolomes, can be associated with physiological changes. Metabolomics and metabonomics are a scientific disciplines that focuse on quantifying dynamic metabolome responses, using multivariate analytical approaches derived from methods within genomics, a discipline that consolidated innovative analysis techniques for situations where the number of biomarkers (metabolites in our case) greatly exceeds the number of subjects. This review focuses on the behavior of cytosolic, mitochondrial, and redox metabolites in ameliorating or exacerbating oxidative stress. After reviewing work regarding a small number of metabolites—pyruvate, ethyl pyruvate, and fructose-1,6-bisphosphate—whose exogenous administration was found to ameliorate oxidative stress, a subsequent section reviews basic multivariate statistical methods common in metabolomics research, and their application in human and preclinical studies emphasizing oxidative stress. Particular attention is paid to new NMR spectroscopy methods in metabolomics and metabonomics. Because complex relationships connect oxidative stress to so many physiological processes, studies from different disciplines were reviewed. All, however, shared the common goal of ultimately developing

  1. Microbial interactions during carrion decomposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This addresses the microbial ecology of carrion decomposition in the age of metagenomics. It describes what is known about the microbial communities on carrion, including a brief synopsis about the communities on other organic matter sources. It provides a description of studies using state-of-the...

  2. Ecological studies of Bulinus rohlfsi, the intermediate host of Schistosoma haematobium in the Volta Lake

    PubMed Central

    Klumpp, R. K.; Chu, K. Y.

    1977-01-01

    In the present ecological study of cercarial transmission of Schistosoma haematobium in the Volta Lake, Ghana, habitat observations and sampling of Bulinus truncatus rohlfsi were conducted within a 60-km stretch of shoreline. Observations revealed that human water contact sites in each village undergo constant changes in shape and vegetation. Snail sampling surveys in water contact sites were carried out monthly (for 27 months) in 8 villages using newly designed palm-leaf traps, and in 8 additional villages (for 16 months) using a modification of Olivier & Sneidermann's man—time method. Results to date confirm the finding by Chu & Vanderburg that cercarial transmission in the lake takes place almost exclusively within water contact sites. Additional results indicate that even within individual water contact sites this transmission is focal, most infected snails being found very close to the shoreline. Transmission also varies significantly according to shape, vegetation, and geographical location of the water contact sites, and is distinctly seasonal in most villages. These findings lead us to conclude that control of cercarial transmission in the Volta Lake is both attainable and feasible with existing methods. PMID:304396

  3. Photometric and spectroscopic study of the intermediate-age open cluster NGC 2355

    NASA Astrophysics Data System (ADS)

    Donati, P.; Bragaglia, A.; Carretta, E.; D'Orazi, V.; Tosi, M.; Cusano, F.; Carini, R.

    2015-11-01

    In this paper we analyse the evolutionary status and properties of the old open cluster NGC 2355, located in the Galactic anticentre direction, as a part of the long-term programme Bologna Open Clusters Chemical Evolution. NGC 2355 was observed with the Large Binocular Camera at the Large Binocular Telescope using the Bessel B, V, and Ic filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram method, as done in other papers of this series. Additional spectroscopic observations with the Fibre-fed Echelle Spectrograph at the Nordic Optical Telescope of three giant stars were used to determine the chemical properties of the cluster. Our analysis shows that NGC 2355 has metallicity slightly less than solar, with [Fe/H]= -0.06 dex, age between 0.8 and 1 Gyr, reddening E(B - V) in the range 0.14-0.19 mag, and distance modulus (m - M)0 of about 11 mag. We also investigate the abundances of O, Na, Al, α, iron-peak, and neutron capture elements, showing that NGC 2355 falls within the abundance distribution of similar clusters (same age and metallicity). The Galactocentric distance of NGC 2355 places it at the border between two regimes of metallicity distribution; this makes it an important cluster for the study of the chemical properties and evolution of the disc.

  4. Planck intermediate results. XV. A study of anomalous microwave emission in Galactic clouds

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Arnaud, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Cardoso, J.-F.; Casassus, S.; Catalano, A.; Chamballu, A.; Chen, X.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson; , C.; Diego, J. M.; Donzelli, S.; Doré, O.; Dupac, X.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Ghosh, T.; Giard, M.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lawrence, C. R.; Leonardi, R.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Patanchon, G.; Pearson, T. J.; Peel, M.; Perdereau, O.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reich, W.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Tibbs, C. T.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Verstraete, L.; Vielva, P.; Villa, F.; Wandelt, B. D.; Watson, R.; Wilkinson, A.; Ysard, N.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-05-01

    Anomalous microwave emission (AME) is believed to be due to electric dipole radiation from small spinning dust grains. The aim of this paper is a statistical study of the basic properties of AME regions and the environment in which they emit. We used WMAP and Planck maps, combined with ancillary radio and IR data, to construct a sample of 98 candidate AME sources, assembling SEDs for each source using aperture photometry on 1°-smoothed maps from 0.408 GHz up to 3000 GHz. Each spectrum is fitted with a simple model of free-free, synchrotron (where necessary), cosmic microwave background (CMB), thermal dust, and spinning dust components. We find that 42 of the 98 sources have significant (>5σ) excess emission at frequencies between 20 and 60 GHz. An analysis of the potential contribution of optically thick free-free emission from ultra-compact H ii regions, using IR colour criteria, reduces the significant AME sample to 27 regions. The spectrum of the AME is consistent with model spectra of spinning dust. Peak frequencies are in the range 20-35 GHz except for the California nebula (NGC 1499), which appears to have a high spinning dust peak frequency of (50 ± 17) GHz. The AME regions tend to be more spatially extended than regions with little or no AME. The AME intensity is strongly correlated with the sub-millimetre/IR flux densities and comparable to previous AME detections in the literature. AME emissivity, defined as the ratio of AME to dust optical depth, varies by an order of magnitude for the AME regions. The AME regions tend to be associated with cooler dust in the range 14-20 K and an average emissivity index, βd, of +1.8, while the non-AME regions are typically warmer, at 20-27 K. In agreement with previous studies, the AME emissivity appears to decrease with increasing column density. This supports the idea of AME originating from small grains that are known to be depleted in dense regions, probably due to coagulation onto larger grains. We also find a

  5. Decomposition of Sodium Tetraphenylborate

    SciTech Connect

    Barnes, M.J.

    1998-11-20

    The chemical decomposition of aqueous alkaline solutions of sodium tetraphenylborate (NaTPB) has been investigated. The focus of the investigation is on the determination of additives and/or variables which influence NaTBP decomposition. This document describes work aimed at providing better understanding into the relationship of copper (II), solution temperature, and solution pH to NaTPB stability.

  6. Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

    SciTech Connect

    Carraher, Jack McCaslin

    2014-01-01

    Reactive species like high-valent metal-oxo complexes and carbon and oxygen centered radicals are important intermediates in enzymatic systems, atmospheric chemistry, and industrial processes. Understanding the pathways by which these intermediates form, their relative reactivity, and their fate after reactions is of the utmost importance. Herein are described the mechanistic detail for the generation of several reactive intermediates, synthesis of precursors, characterization of precursors, and methods to direct the chemistry to more desirable outcomes yielding ‘greener’ sources of commodity chemicals and fuels.

  7. Erbium hydride decomposition kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2006-11-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

  8. Study of Uranium Transport Utilizing Reactive Numerical Modeling and Experimental Data from Heterogeneous Intermediate-Scale Tanks

    NASA Astrophysics Data System (ADS)

    Rodriguez, D.; Miller, A.; Honeyman, B.

    2007-12-01

    The study of the transport of contaminants in groundwater is critical in order to mitigate risks to downstream receptors from sites where past releases of these contaminants has resulted in the degradation of the water quality of the underlying aquifer. In most cases, the fate and transport of these contaminants occurs in a chemically and physically heterogeneous environment; thereby making the prediction of the ultimate fate of these contaminants difficult. In order to better understand the fundamental processes that have the greatest effect on the transport of these contaminants, careful laboratory study must be completed in a controlled environment. Once the experimental data has been generated, the validation of numerical models may then be achieved. Questions on the management of contaminated sites may center on the long-term release (e.g., desorption, dissolution) behavior of contaminated geomedia. Data on the release of contaminants is often derived from bench-scale experiments or, in rare cases, through field-scale experiments. A central question, however, is how molecular-scale processes (e.g., bond breaking) are expressed at the macroscale. This presentation describes part of a collaborative study between the Colorado School of Mines, the USGS and Lawrence Berkeley National Lab on upscaling pore-scale processes to understanding field-scale observations. In the work described here, two experiments were conducted in two intermediate-scale tanks (2.44 m x 1.22 m x 7.6 cm and 2.44 m x 0.61 m x 7.6 cm) to generate data to quantify the processes of uranium dissolution and transport in fully saturated conditions, and to evaluate the ability of two reactive transport models to capture the relevant processes and predict U behavior at the intermediate scale. Each tank was designed so that spatial samples could be collected from the side of the tank, as well as samples from the effluent end of the tank. The larger tank was packed with a less than 2mm fraction of a

  9. Transition Metal Donor-Peptide-Acceptor Complexes: From Intramolecular Electron Transfer Reactions to the Study of Reactive Intermediates

    SciTech Connect

    Isied, Stephan S.

    2003-03-11

    The trans-polyproline (PII) oligomers (Figure 1) are unusually rigid peptide structures which have been extensively studied by our group for peptide mediated intramolecular electron transfer (ET) at long distances. We have previously studied ET across a series of metal ion donor (D) acceptor (A) oligoproline peptides with different distances, driving forces and reorganizational energies. The majority of these experiments involve generating the ET intermediate using pulse radiolysis methods, although more recently photochemical methods are also used. Results of these studies showed that ET across peptides can vary by more than twelve orders of magnitude. Using ruthenium bipyridine donors, ET reaction rate constants across several proline residues (n = 4 - 9) occurred in the millisecond (ms) to {micro}s timescale, thus limiting the proline peptide conformational motions to only minor changes (far smaller than the large changes that occur on the ms to sec timescale, such as trans to cis proline isomerization). The present report describes our large data base of experimental results for D-peptide-A complexes in terms of a model where the involvement of both superexchange and hopping (hole and electron) mechanisms account for the long range ET rate constants observed. Our data shows that the change from superexchange to hopping mechanisms occurs at different distances depending on the type of D and A and their interactions with the peptides. Our model is also consistent with generalized models for superexchange and hopping which have been put forward by a number of theoretical groups to account for long range ET phenomena.

  10. Surface chemical and photocatalytic consequences of Ca-doping of BiFeO3 as probed by XPS and H2O2 decomposition studies

    NASA Astrophysics Data System (ADS)

    Zaki, Mohamed I.; Ramadan, Wegdan; Katrib, Ali; Rabee, Abdallah I. M.

    2014-10-01

    Pure and Ca-doped Bi1-xCaxFeO3 samples were prepared with x = 0.0-0.2, adopting a sol-gel method. Previously reported studies performed on similarly composed and prepared samples revealed that Ca-doping, above solubility limit (namely at ≥10%-Ca), results in phase separation and formation of BiFeO3/α(γ)-Fe2O3 nanocomposite particles. Hetero p/n nanojunctions thus established were considered to help separating photo-generated electron-hole pairs and, therefore, explain consequent promotion of photo-Fenton catalytic activity of BiFeO3 towards methylene blue degradation in presence of H2O2 additive. However, the encompassed decomposition of H2O2 was not addressed. To bridge this gap of knowledge, the present investigation was designed to assess Ca-doping-effected surface chemical modifications and gauge its impact on the heterogeneous photo-/thermo-catalytic activity of BiFeO3 towards H2O2 decomposition, by means of X-ray photoelectron spectroscopy (XPS) and H2O2 decomposition gravimetry. XPS results revealed generation of high binding energy Bi 4f and Fe 2p states, as well as enhancement of the surface basicity, upon doping to 10%-Ca. These surface chemical consequences are rendered hardly detectable upon further increase of the dopant magnitude to 20%-Ca. In parallel, the H2O2 decomposition activity of the ferrite, under natural visible light, is enhanced to optimize upon Ca-doping at 10%, and, then, decreased on further doping to 20%. H2O2 decomposition experiments carried out in absence of light indicate that the doping promoting impact is reflected essentially in the photocatalytic activity. Accordingly, the observed surface chemical consequences of Ca-doping are considered to consolidate the p/n nanojunctions consequently established in the material bulk, by retarding recombination of visible light generated electron-hole pairs, thus enhancing the heterogeneous photocatalytic activity of BiFeO3.

  11. Thermal decomposition of magnesium and calcium sulfates

    SciTech Connect

    Roche, S L

    1982-04-01

    The effect of catalyst on the thermal decomposition of MgSO/sub 4/ and CaSO/sub 4/ in vacuum was studied as a function of time in Knudsen cells and for MgSO/sub 4/, in open crucibles in vacuum in a Thermal Gravimetric Apparatus. Platinum and Fe/sub 2/O/sub 3/ were used as catalysts. The CaSO/sub 4/ decomposition rate was approximately doubled when Fe/sub 2/O/sub 3/ was present in a Knudsen cell. Platinum did not catalyze the CaSO/sub 4/ decomposition reaction. The initial decomposition rate for MgSO/sub 4/ was approximately 5 times greater than when additives were present in Knudsen cells but only about 1.5 times greater when decomposition was done in an open crucible.

  12. M31AGES: Studying the intermediate-aged populations in the satellites, smooth halo, and substructure of Andromeda

    NASA Astrophysics Data System (ADS)

    Hamren, Katherine; Beaton, Rachael; Guhathakurta, Puragra; Majewski, Steven R.; M31AGES Survey Team

    2016-01-01

    Recent large-scale surveys of M31 have enabled the study of its satellites, smooth halo, and substructure in exquisite detail. In particular, the Spectroscopic Landscape of Andromeda's Stellar Halo (SPLASH) survey has obtained moderate resolution optical spectra with the DEIMOS spectrograph on the Keck II/10-m telescope, and optical photometry from various ground-based telescopes. These data have been used to map the kinematics and metallicity distributions in the dSphs and dEs, detect and characterize substructure, and study the large-scale radial surface brightness and metallicity profiles of the "smooth" halo. Notwithstanding this progress [or] In spite of these advances, there are a number of outstanding questions that cannot be answered with these data alone, including the fraction of the halo that was formed in situ vs by accretion, and the degeneracy between massive early accretion events and less massiverecent accretion events. The M31 Asymptotic Giant Extended Survey (M31AGES) aims to address these questions by using NIR photometry to identify intermediate-age AGB stars in the satellites, streams, and smoothhalo of M31. We present the details of the observations (now completed), the plan for public release of data products, and preliminary results.

  13. A Gemini/GMOS Study of Intermediate Luminosity Early-type Virgo Cluster Galaxies. I. Globular Cluster and Stellar Kinematics

    NASA Astrophysics Data System (ADS)

    Li, Biao; Peng, Eric W.; Zhang, Hong-xin; Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Jordán, Andrés; Liu, Chengze; Mei, Simona; Puzia, Thomas H.; Takamiya, Marianne; Trancho, Gelys; West, Michael J.

    2015-06-01

    We present a kinematic analysis of the globular cluster (GC) systems and diffuse stellar light of four intermediate luminosity (sub-L*) early-type galaxies in the Virgo cluster based on Gemini Multi-Object Spectrographs (GMOS) data. Our galaxy sample is fainter (-23.8\\lt {{M}K}\\lt -22.7) than most previous studies, nearly doubling the number of galaxies in this magnitude range that now have GC kinematics. The data for the diffuse light extends to 4Re, and the data for the GCs reaches 8-12Re. We find that the kinematics in these outer regions are all different despite the fact that these four galaxies have similar photometric properties, and are uniformly classified as “fast rotators” from their stellar kinematics within 1Re. The GC systems exhibit a wide range of kinematic morphology. The rotation axis and amplitude can change between the inner and outer regions, including a case of counter-rotation. This difference shows the importance of wide-field kinematic studies, and shows that stellar and GC kinematics can change significantly as one moves beyond the inner regions of galaxies. Moreover, the kinematics of the GC systems can differ from that of the stars, suggesting that the formation of the two populations are also distinct.

  14. Pairwise decomposition of residue interaction energies using semiempirical quantum mechanical methods in studies of protein-ligand interaction.

    PubMed

    Raha, Kaushik; van der Vaart, Arjan J; Riley, Kevin E; Peters, Martin B; Westerhoff, Lance M; Kim, Hwanho; Merz, Kenneth M

    2005-05-11

    Pairwise decomposition of the interaction energy between molecules is shown to be a powerful tool that can increase our understanding of macromolecular recognition processes. Herein we calculate the pairwise decomposition of the interaction energy between the protein human carbonic anhydrase II (HCAII) and the fluorine-substituted ligand N-(4-sulfamylbenzoyl)benzylamine (SBB) using semiempirical quantum mechanics based methods. We dissect the interaction between the ligand and the protein by dividing the ligand and the protein into subsystems to understand the structure-activity relationships as a result of fluorine substitution. In particular, the off-diagonal elements of the Fock matrix that is composed of the interaction between the ionic core and the valence electrons and the exchange energy between the subsystems or atoms of interest is examined in detail. Our analysis reveals that the fluorine-substituted benzylamine group of SBB does not directly affect the binding energy. Rather, we find that the strength of the interaction between Thr199 of HCAII and the sulfamylbenzoyl group of SBB affects the binding affinity between the protein and the ligand. These observations underline the importance of the sulfonamide group in binding affinity as shown by previous experiments (Maren, T. H.; Wiley: C. E. J. Med. Chem. 1968, 11, 228-232). Moreover, our calculations qualitatively agree with the structural aspects of these protein-ligand complexes as determined by X-ray crystallography.

  15. A Feasibility Study of the Flare-Cylinder Configuration as a Reentry Body Shape for an Intermediate Range Ballistic Missile

    NASA Technical Reports Server (NTRS)

    Garland, B. J.; Hall, J. R.

    1958-01-01

    A study has been made of a flare-cylinder configuration to investigate its feasibility as a reentry body of an intermediate range ballistic missile. Factors considered were heating, weight, stability, and impact velocity. A series of trajectories covering the possible range of weight-drag ratios were computed for simple truncated nose shapes of varying pointedness, and hence varying weight-drag ratios. Four trajectories were chosen for detailed temperature computation from among those trajectories estimated to be possible. Temperature calculations were made for both "conventional" (for example, copper, Inconel, and stainless steel) and "unconventional" (for example, beryllium and graphite) materials. Results of the computations showed that an impact Mach number of 0.5 was readily obtainable for a body constructed from conventional materials. A substantial increase in subsonic impact velocity above a Mach number of 0.5 was possible without exceeding material temperature limits. A weight saving of up to 134 pounds out of 822 was possible with unconventional materials. This saving represents 78 percent of the structural weight. Supersonic impact would require construction of the body from unconventional materials but appeared to be well within the range of attainability.

  16. Mechanistic studies of a novel C-S lyase in ergothioneine biosynthesis: the involvement of a sulfenic acid intermediate

    PubMed Central

    Song, Heng; Hu, Wen; Naowarojna, Nathchar; Her, Ampon Sae; Wang, Shu; Desai, Rushil; Qin, Li; Chen, Xiaoping; Liu, Pinghua

    2015-01-01

    Ergothioneine is a histidine thio-derivative isolated in 1909. In ergothioneine biosynthesis, the combination of a mononuclear non-heme iron enzyme catalyzed oxidative C-S bond formation reaction and a PLP-mediated C-S lyase (EgtE) reaction results in a net sulfur transfer from cysteine to histidine side-chain. This demonstrates a new sulfur transfer strategy in the biosynthesis of sulfur-containing natural products. Due to difficulties associated with the overexpression of Mycobacterium smegmatis EgtE protein, the proposed EgtE functionality remained to be verified biochemically. In this study, we have successfully overexpressed and purified M. smegmatis EgtE enzyme and evaluated its activities under different in vitro conditions: C-S lyase reaction using either thioether or sulfoxide as a substrate in the presence or absence of reductants. Results from our biochemical characterizations support the assignment of sulfoxide 4 as the native EgtE substrate and the involvement of a sulfenic acid intermediate in the ergothioneine C-S lyase reaction. PMID:26149121

  17. Structure of viroid replicative intermediates: physico-chemical studies on SP6 transcripts of cloned oligomeric potato spindle tuber viroid.

    PubMed

    Steger, G; Tabler, M; Brüggemann, W; Colpan, M; Klotz, G; Sänger, H L; Riesner, D

    1986-12-22

    The structure and structural transitions of transcripts of cloned oligomeric viroid were studied in physico-chemical experiments and stability calculations. Transcripts of (+) and (-) polarity, from unit up to sixfold length, were synthesized from DNA clones of the potato spindle tuber viroid (PSTV) with the SP6 transcription system. Their structural properties were investigated by optical denaturation curves, high performance liquid chromatography (HPLC), electron microscopy, sedimentation-diffusion equilibrium and velocity sedimentation. Secondary structures of the RNAs and theoretical denaturation curves were calculated using an energy optimization program. The secondary structure of lowest free energy for unit length and oligomeric transcripts is a rod-like structure similar to that of the mature circular viroids. When this structure is used as a model for calculations, there is a large degree of agreement between the theoretical and the experimental denaturation curves. At high temperatures, however, (+) strand transcripts exhibited a transition which was more stable than expected from the calculations or than was known from curves of mature viroids. This transition arises from a rearrangement of the central conserved region of viroids to a helical region of 28 stable base pairs either intermolecularly leading to bimolecular complexes, or intramolecularly giving rise to a branched secondary structure. The rearrangement could be detected by electron microscopy, HPLC, and analytical ultracentrifugation. The helical region serves to divide up the oligomeric (+) strand into structural units which may be recognized by cleavage and ligation enzymes which process the oligomeric intermediates to circular mature viroids.

  18. An Isoratio Method to Study Free Energy and Temperature Effects in Intermediate Mass Fragments Produced in Heavy-Ion Collisions

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Qiao, Chun-Yuan; Ding, Tian-Tian; Niu, Fei; Song, Yi-Dan; Niu, Yi-Fei

    2016-07-01

    An isoratio method, i.e., the isotopic (isotonic) ratio among three isotopes (isotones), is proposed to study the free energy and temperature effects in the intermediate mass fragments produced in heavy-ion collisions. The parameterizations for the free energy of nucleus at low temperature, which have been proposed in the framework of the density functional theory using the SKM skymre interaction, are adopted to calculate the temperature-dependent free energy of fragment. By analyzing the measured yields of fragments in the 140A MeV 58,64Ni + 9Be reactions, it is verified that the free energy in the isoratio is almost the same for different reactions. A temperature-dependent pairing-energy is introduced into the parameterizations for free energy, which reveals that the weakened pairing energy at the low temperature accounts for the weakened or disappearing odd-even staggering in isoratio. Supported by the Program for Science and Technology Innovation Talents in Universities of Henan Province under Grant No. 13HASTIT046, the Creative Experimental Project of National Undergraduate Students (CEPNU201510476017)

  19. Structure of viroid replicative intermediates: physico-chemical studies on SP6 transcripts of cloned oligomeric potato spindle tuber viroid.

    PubMed Central

    Steger, G; Tabler, M; Brüggemann, W; Colpan, M; Klotz, G; Sänger, H L; Riesner, D

    1986-01-01

    The structure and structural transitions of transcripts of cloned oligomeric viroid were studied in physico-chemical experiments and stability calculations. Transcripts of (+) and (-) polarity, from unit up to sixfold length, were synthesized from DNA clones of the potato spindle tuber viroid (PSTV) with the SP6 transcription system. Their structural properties were investigated by optical denaturation curves, high performance liquid chromatography (HPLC), electron microscopy, sedimentation-diffusion equilibrium and velocity sedimentation. Secondary structures of the RNAs and theoretical denaturation curves were calculated using an energy optimization program. The secondary structure of lowest free energy for unit length and oligomeric transcripts is a rod-like structure similar to that of the mature circular viroids. When this structure is used as a model for calculations, there is a large degree of agreement between the theoretical and the experimental denaturation curves. At high temperatures, however, (+) strand transcripts exhibited a transition which was more stable than expected from the calculations or than was known from curves of mature viroids. This transition arises from a rearrangement of the central conserved region of viroids to a helical region of 28 stable base pairs either intermolecularly leading to bimolecular complexes, or intramolecularly giving rise to a branched secondary structure. The rearrangement could be detected by electron microscopy, HPLC, and analytical ultracentrifugation. The helical region serves to divide up the oligomeric (+) strand into structural units which may be recognized by cleavage and ligation enzymes which process the oligomeric intermediates to circular mature viroids. Images PMID:3808953

  20. Mechanistic studies of a novel C-S lyase in ergothioneine biosynthesis: the involvement of a sulfenic acid intermediate.

    PubMed

    Song, Heng; Hu, Wen; Naowarojna, Nathchar; Her, Ampon Sae; Wang, Shu; Desai, Rushil; Qin, Li; Chen, Xiaoping; Liu, Pinghua

    2015-01-01

    Ergothioneine is a histidine thio-derivative isolated in 1909. In ergothioneine biosynthesis, the combination of a mononuclear non-heme iron enzyme catalyzed oxidative C-S bond formation reaction and a PLP-mediated C-S lyase (EgtE) reaction results in a net sulfur transfer from cysteine to histidine side-chain. This demonstrates a new sulfur transfer strategy in the biosynthesis of sulfur-containing natural products. Due to difficulties associated with the overexpression of Mycobacterium smegmatis EgtE protein, the proposed EgtE functionality remained to be verified biochemically. In this study, we have successfully overexpressed and purified M. smegmatis EgtE enzyme and evaluated its activities under different in vitro conditions: C-S lyase reaction using either thioether or sulfoxide as a substrate in the presence or absence of reductants. Results from our biochemical characterizations support the assignment of sulfoxide 4 as the native EgtE substrate and the involvement of a sulfenic acid intermediate in the ergothioneine C-S lyase reaction.

  1. Gas-phase chemistry during the conversion of cyclohexane to carbon: Flow reactor studies at low and intermediate pressure

    SciTech Connect

    Osterheld, T.H.; Allendorf, M.D.; Larson, R.

    1995-07-01

    The gas-phase branching during the conversion of cyclohexane to solid carbon has been measured in a high-temperature-flow reactor. The experiments show that cyclohexane decomposes into a broad distribution of hydrocarbons that further decompose into the more kinetically stable products hydrogen, methane, acetylene, ethylene, benzene, and PAH. At 1363 K, the evolution to these species occurs quickly. We also observe the buildup of significant amounts of aromatic molecules at later stages in the decomposition, with as much as 15% of the total carbon in PAH and 25% in benzene. At later stages, the gas-phase molecules react slowly, even though the system is not at equilibrium, because of their kinetic stability and the smaller radical pool. The decomposition does not appear to depend sensitively on pressure in the regime of 25 to 250 torr. Thus, to a first approximation, these results can be extrapolated to atmospheric pressure.

  2. Does P450-type catalysis proceed through a peroxo-iron intermediate? A review of studies with microperoxidase.

    PubMed

    Veeger, Cees

    2002-07-25

    Recent stopped-flow kinetics demonstrated the existence of an intermediate before the occurrence of the final product of the reaction of both iron-containing microperoxidase-8 (Fe(III)MP-8) and manganese-containing microperoxidase-8 (Mn(III)MP-8) with H(2)O(2). The intermediate was assigned to be (hydro)peroxo-iron. With both mini-catalysts the final state obtained after 30-40 ms showed a resemblance to PorM(IV)MP-8[double bond]O(R(+)*); (R(+)*) is a radical located at the peptide. Quantum mechanical calculations indicate that hydroperoxo-iron is inactive as a catalytic intermediate in cytochrome P450 (P450)-type catalysis. Instead, the calculations suggest that peroxo-iron acts as the catalytic intermediate in P450-type catalysis. In addition, the calculations demonstrate that, although less likely, the possibility that oxenoid-iron acts as a catalytic intermediate in P450 catalysis cannot be fully excluded. An interesting aspect of the reactions catalysed by MP-8 is the possibility that, in view of the reversibility of the reactions between (hydro)peroxo-iron and oxenoid-iron, H(2)O plays a decisive role, at least in some cytochromes P450, in the removal of halogens, avoiding the production of compounds hazardous to the organism. PMID:12121760

  3. Development and evaluation of intermediate frequency magnetic field exposure system for studies of in vitro biological effects.

    PubMed

    Fujita, Atsushi; Hirota, Izuo; Kawahara, Yoshinobu; Omori, Hideki

    2007-10-01

    We have developed an intermediate frequency (IF) magnetic field exposure system for in vitro studies. Since there are no previous studies on exposure to heating-frequency magnetic fields generated from an induction heating (IH) cook top, there is a strong need for such an exposure system and for biological studies of IF magnetic fields. This system mainly consists of a magnetic-field-generating coil housed inside an incubator, inside which cultured cells can be exposed to magnetic field. Two systems were prepared to allow the experiment to be conducted in a double-blind manner. The level of the generated magnetic field was set to 532 microT rms in the exposure space, 23 kHz, 80 times the value in the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines, with a spatial field uniformity better than 3.8%. The waveforms were nearly sinusoidal. It was also confirmed that the parasitic electric field was 157 V/m rms and the induced electric field was 1.9 V/m rms. The temperature was maintained at 36.5 +/- 0.5 degrees C for 2 h. Furthermore, leaked magnetic flux density was 0.7 microT rms or lower at extremely low frequency (ELF) and IF in the stopped system when the other system was being operated, and the environmental magnetic flux density was 0.1 microT rms or lower at the center of the coils. As a result, it was confirmed that this system could be successfully used to evaluate the biological effects of exposure to IF magnetic fields.

  4. Early, intermediate and late infectious complications after transcatheter or surgical aortic-valve replacement: a prospective cohort study.

    PubMed

    Falcone, M; Russo, A; Mancone, M; Carriero, G; Mazzesi, G; Miraldi, F; Pennacchi, M; Pugliese, F; Tritapepe, L; Vullo, V; Fedele, F; Sardella, G; Venditti, M

    2014-08-01

    Transcatheter aortic valve implantation (TAVI) has been proposed to treat older surgical high-risk patients with severe symptomatic aortic stenosis. There are no data regarding short-term and long-term infectious complications in these patients. The objective of this study was to define the incidence, aetiology and outcome of early and late infectious complications following TAVI compared with patients >65 years old undergoing traditional surgical aortic replacement (SAR). This was a prospective observational study evaluating all consecutive patients who underwent TAVI or SAR. Follow up was performed up to 1 year after the procedure of valve implantation. Fifty-one patients underwent TAVI and were compared with 102 patients who underwent SAR. Compared with SAR patients, those who underwent TAVI had lower incidence of early post-operative (11.7% vs 26.4%, p 0.04), intermediate (5.9% vs 17.6%, p 0.01) and late (7.8% vs 11.7%, p 0.03) infections. Among SAR patients the most common infections were bloodstream infections, pneumonias, urinary tract infections and sternal wound infections. Patients who underwent TAVI had a longer survival without infection (358 days vs 312.9, p 0.006). There were no significant differences in 12-month crude survival between the two study populations. Despite a high frequency of coexisting illnesses, patients undergoing TAVI develop few infectious complications. TAVI appears to be a reasonable and safe option in high-risk patients with severe symptomatic aortic stenosis.

  5. Using eye-tracking to study the on-line processing of case-marking information among intermediate L2 learners of German

    PubMed Central

    Jackson, Carrie N.; Dussias, Paola E.; Hristova, Adelina

    2012-01-01

    This study uses eye-tracking to examine the processing of case-marking information in ambiguous subject- and object-first wh-questions in German. The position of the lexical verb was also manipulated via verb tense to investigate whether verb location influences how intermediate L2 learners process L2 sentences. Results show that intermediate L2 German learners were sensitive to case-marking information, exhibiting longer processing times on subject-first than object-first sentences, regardless of verb location. German native speakers exhibited the opposite word order preference, with longer processing times on object-first than subject-first sentences, replicating previous findings. These results are discussed in light of current L2 processing research, highlighting how methodological constraints influence researchers’ abilities to measure the on-line processing of morphosyntactic information among intermediate L2 learners. PMID:23493761

  6. Study of intermediates from transition metal excited-state electron-transfer reactions. [Annual] progress report, August 1, 1989--July 31, 1992

    SciTech Connect

    Hoffman, M.Z.

    1992-07-31

    Conventional and fast-kinetics techniques of photochemistry, photophysics, radiation chemistry, and electrochemistry were used to study the intermediates involved in transition metal excited-state electron-transfer reactions. These intermediates were excited state of Ru(II) and Cr(III) photosensitizers, their reduced forms, and species formed in reactions of redox quenchers and electron-transfer agents. Of particular concern was the back electron-transfer reaction between the geminate pair formed in the redox quenching of the photosensitizers, and the dependence of its rate on solution medium and temperature in competition with transformation and cage escape processes. (DLC)

  7. Orthogonal tensor decompositions

    SciTech Connect

    Tamara G. Kolda

    2000-03-01

    The authors explore the orthogonal decomposition of tensors (also known as multi-dimensional arrays or n-way arrays) using two different definitions of orthogonality. They present numerous examples to illustrate the difficulties in understanding such decompositions. They conclude with a counterexample to a tensor extension of the Eckart-Young SVD approximation theorem by Leibovici and Sabatier [Linear Algebra Appl. 269(1998):307--329].

  8. Modeling DNA Replication Intermediates

    SciTech Connect

    Broyde, S.; Roy, D.; Shapiro, R.

    1997-06-01

    While there is now available a great deal of information on double stranded DNA from X-ray crystallography, high resolution NMR and computer modeling, very little is known about structures that are representative of the DNA core of replication intermediates. DNA replication occurs at a single strand/double strand junction and bulged out intermediates near the junction can lead to frameshift mutations. The single stranded domains are particularly challenging. Our interest is focused on strategies for modeling the DNA of these types of replication intermediates. Modeling such structures presents special problems in addressing the multiple minimum problem and in treating the electrostatic component of the force field. We are testing a number of search strategies for locating low energy structures of these types and we are also investigating two different distance dependent dielectric functions in the coulombic term of the force field. We are studying both unmodified DNA and DNA damaged by aromatic amines, carcinogens present in the environment in tobacco smoke, barbecued meats and automobile exhaust. The nature of the structure adopted by the carcinogen modified DNA at the replication fork plays a key role in determining whether the carcinogen will cause a mutation during replication that can initiate the carcinogenic process. In the present work results are presented for unmodified DNA.

  9. Apical Sealing Ability of Mineral Trioxide Aggregate, Intermediate Restorative Material and Calcium Enriched Mixture Cement: A Bacterial Leakage Study

    PubMed Central

    Shahriari, Shahriar; Faramarzi, Farhad; Alikhani, Mohammad-Yousef; Farhadian, Maryam; Hendi, Seyedeh Sareh

    2016-01-01

    Introduction: This in vitro study compared the apical sealing ability of three common root end filling materials namely mineral trioxide aggregate (MTA), intermediate restorative material (IRM) and calcium-enriched mixture (CEM) cement using a bacterial leakage model. Methods and Materials: The study was conducted on 83 single-rooted human teeth. Tooth crowns were cut and root canals were prepared using the step-back technique. Apical 3 mm of the roots were cut and a three-mm-deep cavity was prepared using an ultrasonic instrument. The samples were divided into three groups (n=25) according to the root-end filling material including MTA, IRM and CEM cement. The roots were inserted into cut-end microtubes. After sterilization with ethylene oxide, microtubes were placed in sterile vials containing 10 mL of Brain Heart Infusion (BHI) broth and incubated at 37°C and 0.1 mL of Enterococcus faecalis suspension compatible with 0.5 McFarland standard (1.5×108 cell/ ml), which was refreshed daily. This procedure was continued for 70 days. The data were analyzed using the chi-square, Kruskal-Wallis and log rank tests. The level of significance was set at 0.05. Results: No significant difference was found in bacterial microleakage among three groups; MTA showed slightly (but not significantly) less microleakage than IRM and CEM. However, the difference in the mean time of microleakage was significant among the groups (P<0.04) and in MTA samples leakage occurred in a longer time than CEM (P<0.012). Conclusion: The three tested root end filling materials had equal sealing efficacy for preventing bacterial leakage. PMID:27790267

  10. Gas chromatographic/matrix isolation/FTIR studies of decomposition products of Irganox 1010 in an aqueous ethanol system

    NASA Astrophysics Data System (ADS)

    Chen, Jo-Yun T.; Mossoba, Madgi M.; Varner, S. L.; Roach, J. A.; Sphon, J. A.; Page, Samuel W.

    1989-12-01

    Irganox 1010 is an antioxidant used in food packaging. The degradation products of Irganox 1010 in a 50% aqueous ethanol system at 90C were examined by GC/MS and GC/MI/FTIR. The data suggest Irganox 10101 is hydrolyzed to form (3) benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl)4-hydroxy-which reacts with solvent ethanol to form (f) its ethyl ester. The 4 other decomposition products (a) 2.5 cyclohexadiene-I,4-dione, 2,6-bis(1.1-dimethylethyl)-; (B) 3.5-bis-(1,1,-dimethylethyl)-2.5 cyclohexadiene-4-one spiro (5'-tetrahydrofuran-2'-one); (C) benzofuran, 2,3-dihydro-3.3-dimethyl-5 ethenyl-7-(1,1-dimethylethyl)-and (D) benzaldehyede, 3.5-bis-(1,1-dimethylethyl)-4-hydroxy-, can result from osidation, dehydration and decarboxylation processes of (E).

  11. α-Tocopherol impact on oxy-radical induced free radical decomposition of DMSO: Spin trapping EPR and theoretical studies

    NASA Astrophysics Data System (ADS)

    Jerzykiewicz, Maria; Ćwieląg-Piasecka, Irmina; Witwicki, Maciej; Jezierski, Adam

    2011-05-01

    EPR spin trapping and theoretical methods such as density functional theory (DFT) as well as combined DFT and quadratic configuration interaction approach (DFT/QCISD) were used to identify the radicals produced in the reaction of oxy-radicals and dimethyl sulfoxide (DMSO) in the presence and absence of α-tocopherol. Additionally, the mixtures of α-tocopherol with linolenic acid and glyceryl trilinoleate as well as bioglycerols (glycerol fractions from biodiesel production) were tested. α-Tocopherol inhibited oxidation of the main decomposition product of DMSO, •CH 3 to •OCH 3 but did not prevent the transformation process of N-t-butyl- α-phenylnitrone (PBN) into 2-methyl-2-nitrosopropane (MNP). Theoretical investigations confirmed the structures of proposed spin adducts and allowed to correlate the EPR parameters observed in the experiment with the spin adducts electronic structure.

  12. A STUDY OF THE PROPERTIES OF CP: COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS AND REACTION TO SPARK, FRICTION AND IMPACT

    SciTech Connect

    Weese, R K; Burnham, A K; Fontes, A T

    2005-03-30

    The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear heating rates, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Using differential scanning calorimetry, DSC, CP was decomposed at linear heating rates of 1, 3, and 7 C/min and the kinetic triplet calculated using the LLNL code Kinetics05. Values are also reported for spark, friction, and impact sensitivity.

  13. Study on the decomposition mechanism of alkyl carbonate on lithium metal by pyrolysis-gas chromatography-mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Mogi, Ryo; Inaba, Minoru; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi

    The surface films formed on deposited lithium in electrolyte solutions based on ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were analyzed by pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS). In 1 M LiClO 4/EC, the main component of the surface film was easily hydrolyzed to give ethylene glycol after exposure to air, and hence was considered to have a chemical structure of ROCH 2CH 2OR', of which OR and OR' are OLi or OCO 2Li. Ethylene oxide, acetaldehyde, and 1,4-dioxane were detected in decomposition products, and they were considered to have been formed by pyrolysis of ROCH 2CH 2OR' in the pyrolyzer. The presence of ethanol in decomposition products confirmed that ring cleavage at the CH 2O bonds of EC occurs by one electron reduction. In addition, the presence of methanol implied the cleavage of the CC bond of EC upon reduction. From the surface films formed in 1 M LiClO 4/DEC and /DMC, ethanol and methanol, respectively, were detected, which suggested that corresponding lithium alkoxides and/or lithium alkyl carbonates were the main components. In 1 M LiClO 4/EC+DEC (1:1), EC dominantly decomposed to form the surface film. The surface film formed in 1 M LiPF 6/EC+DEC (1:1) contained a much smaller amount of organic compounds.

  14. Will the world run out of land? A Kaya-type decomposition to study past trends of cropland expansion

    NASA Astrophysics Data System (ADS)

    Huber, Veronika; Neher, Ina; Bodirsky, Benjamin L.; Höfner, Kathrin; Schellnhuber, Hans Joachim

    2014-01-01

    Globally, the further expansion of cropland is limited by the availability of adequate land and by the necessity to spare land for nature conservation and carbon sequestration. Analyzing the causes of past land-use changes can help to better understand the potential drivers of land scarcities of the future. Using the FAOSTAT database, we quantify the contribution of four major factors, namely human population growth, rising per-capita caloric consumption (including food intake and household waste), processing losses (including conversion of vegetal into animal products and non-food use of crops), and yield gains, to cropland expansion rates of the past (1961-2007). We employ a Kaya-type decomposition method that we have adapted to be applicable to drivers of cropland expansion at global and national level. Our results indicate that, all else equal, without the yield gains observed globally since 1961, additional land of the size of Australia would have been put under the plough by 2007. Under this scenario the planetary boundary on global cropland use would have already been transgressed today. By contrast, without rising per-capita caloric consumption and population growth since 1961, an area as large as nearly half and all of Australia could have been spared, respectively. Yield gains, with strongest contributions from maize, wheat and rice, have approximately offset the increasing demand of a growing world population. Analyses at the national scale reveal different modes of land-use transitions dependent on development stage, dietary standards, and international trade intensity of the countries. Despite some well-acknowledged caveats regarding the non-independence of decomposition factors, these results contribute to the empirical ranking of different drivers needed to set research priorities and prepare well-informed projections of land-use change until 2050 and beyond.

  15. Interim report on the genetic and animal toxicity testing of SRC-I products, intermediates, and waste materials. Appendix D. Acute animal studies reports

    SciTech Connect

    Drozdowicz, B.Z.; Kelly, C.M.

    1983-09-01

    Appendix D is a collection of 25 individual reports on the toxicity of SRC-I products, intermediates and residues to rabbits, rats and guinea pigs with acute oral, dermal and inhalation exposure. It includes also eye and dermal irritation tests in rabbits and guinea pigs and dermal sensitization studies in albino guinea pigs. (LTN)

  16. The products of the thermal decomposition of CH{sub 3}CHO

    SciTech Connect

    Vasiliou, AnGayle; Piech, Krzysztof M.; Barney Ellison, G.; Zhang Xu; Nimlos, Mark R.; Ahmed, Musahid; Golan, Amir; Kostko, Oleg; Osborn, David L.; Daily, John W.; Stanton, John F.

    2011-07-07

    We have used a heated 2 cm x 1 mm SiC microtubular ({mu}tubular) reactor to decompose acetaldehyde: CH{sub 3}CHO +{Delta}{yields} products. Thermal decomposition is followed at pressures of 75-150 Torr and at temperatures up to 1675 K, conditions that correspond to residence times of roughly 50-100 {mu}s in the {mu}tubular reactor. The acetaldehyde decomposition products are identified by two independent techniques: vacuum ultraviolet photoionization mass spectroscopy (PIMS) and infrared (IR) absorption spectroscopy after isolation in a cryogenic matrix. Besides CH{sub 3}CHO, we have studied three isotopologues, CH{sub 3}CDO, CD{sub 3}CHO, and CD{sub 3}CDO. We have identified the thermal decomposition products CH{sub 3} (PIMS), CO (IR, PIMS), H (PIMS), H{sub 2} (PIMS), CH{sub 2}CO (IR, PIMS), CH{sub 2}=CHOH (IR, PIMS), H{sub 2}O (IR, PIMS), and HC{identical_to}CH (IR, PIMS). Plausible evidence has been found to support the idea that there are at least three different thermal decomposition pathways for CH{sub 3}CHO; namely, radical decomposition: CH{sub 3}CHO +{Delta}{yields} CH{sub 3}+[HCO]{yields} CH{sub 3}+ H + CO; elimination: CH{sub 3}CHO +{Delta}{yields} H{sub 2}+ CH{sub 2}=C=O; isomerization/elimination: CH{sub 3}CHO +{Delta}{yields}[CH{sub 2}=CH-OH]{yields} HC{identical_to}CH + H{sub 2}O. An interesting result is that both PIMS and IR spectroscopy show compelling evidence for the participation of vinylidene, CH{sub 2}=C:, as an intermediate in the decomposition of vinyl alcohol: CH{sub 2}=CH-OH +{Delta}{yields}[CH{sub 2}=C:]+ H{sub 2}O {yields} HC{identical_to}CH + H{sub 2}O.

  17. A quantum-chemical study of intermediates of the 1O2 photogeneration sensitized by buckminsterfullerene and accompanying photochemical reactions

    NASA Astrophysics Data System (ADS)

    Semenov, S. G.; Bedrina, M. E.

    2014-02-01

    The intermediates of hypothetical photochemical reactions that accompany the quenching of the 3C{60/*} triplet state by triplet oxygen are studied by the (U)PBE0 quantum-chemical method. The diradical C60-O-O formed from 3O2 and photoexcited buckminsterfullerene 3C{60/*} is characterized by a negative binding energy -1.11 eV (with respect to C60 and 3O2), the singlet-triplet splitting Δ E ST of 0.07 eV, and the dipole moment of 3.2 D at the equilibrium internuclear separations 1.522 Å (CO) and 1.294 Å (OO). Its decay produces 1O2. The formation of a dioxetane circle lowers the energy by 0.8 eV. The ground-state energy of diketone C58(C=O)2 is 2.0 eV lower than the energy of C60-O-O. The metastable centrosymmetric diradical C60-C60, formed upon ineffective light absorption by clusters (C60)N, has a single interpolyhedral C-C bond (1.657 Å). Its triplet state T 1 lies 0.16 eV higher than the S 1 singlet. The S 1 → S 0 relaxation leads to the formation of a stable C60-C60 dimer with a shorter (1.584 Å) bis-single exothermic (+0.24 eV) bond of polyhedra. The photoexcited C60-C60 dimer is able to form isomeric metastable diradicals C60-C60-O-O.

  18. Biodentine versus Mineral Trioxide Aggregate versus Intermediate Restorative Material for Retrograde Root End Filling: An Invitro Study

    PubMed Central

    Soundappan, Saravanapriyan; Sundaramurthy, Jothi Latha; Raghu, Sandhya; Natanasabapathy, Velmurugan

    2014-01-01

    Objective The aim of this study was to evaluate the marginal adaptation of Biodentine in comparison with Mineral Trioxide Aggregate (MTA) and Intermediate Restorative Material (IRM), as a root end filling material, using Scanning Electron Microscopy (SEM). Materials and Methods: Thirty permanent maxillary central incisors were chemo-mechanically prepared and obturated. Three millimetres of the root end were resected and 3mm retro cavity preparation was done using ultrasonic retrotips. The samples were randomly divided into three groups (n=10) and were restored with root end filling materials: Group I – MTA, Group II – Biodentine, Group III – IRM. The root ends were sectioned transversely at 1mm and 2mm levels and evaluated for marginal adaptation using SEM. The gap between dentin and retro filling material was measured at four quadrants. The mean gap at 1mm level and 2mm level from the resected root tip and combined mean were calculated. The data were statistically analyzed, using one-way ANOVA and Tukey’s HSD post hoc test for intergroup analysis and paired t-test for intragroup analysis. Results: The overall results showed no statistically significant difference between MTA and IRM but both were superior when compared to Biodentine. At 1mm level there was no statistically significant difference among any of the tested materials. At 2mm level MTA was superior to both IRM and Biodentine. Conclusion: In overall comparison, MTA and IRM were significantly superior when compared to Biodentine in terms of marginal adaptation, when used as retrograde filling material. PMID:24910689

  19. Ab initio kinetics and thermal decomposition mechanism of mononitrobiuret and 1,5-dinitrobiuret

    NASA Astrophysics Data System (ADS)

    Sun, Hongyan; Vaghjiani, Ghanshyam L.

    2015-05-01

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice-Ramsperger-Kassel-Marcus/multi-well master equation simulations, the results of which reveal the formation

  20. Ab initio kinetics and thermal decomposition mechanism of mononitrobiuret and 1,5-dinitrobiuret.

    PubMed

    Sun, Hongyan; Vaghjiani, Ghanshyam L

    2015-05-28

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice-Ramsperger-Kassel-Marcus/multi-well master equation simulations, the results of which reveal the formation

  1. Ab initio kinetics and thermal decomposition mechanism of mononitrobiuret and 1,5-dinitrobiuret.

    PubMed

    Sun, Hongyan; Vaghjiani, Ghanshyam L

    2015-05-28

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice-Ramsperger-Kassel-Marcus/multi-well master equation simulations, the results of which reveal the formation

  2. Ab Initio Kinetics and Thermal Decomposition Mechanism of Mononitrobiuret and 1,5- Dinitrobiuret

    SciTech Connect

    Sun, Hongyan; Vaghjiani, Ghanshyam G.

    2015-05-26

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice–Ramsperger–Kassel–Marcus/multi-well master equation simulations, the results of which reveal the

  3. Cobalt (II) oxide and nickel (II) oxide alloys as potential intermediate-band semiconductors: A theoretical study

    NASA Astrophysics Data System (ADS)

    Alidoust, Nima; Lessio, Martina; Carter, Emily A.

    2016-01-01

    Solar cells based on single pn junctions, employing single-gap semiconductors can ideally achieve efficiencies as high as 34%. Developing solar cells based on intermediate-band semiconductors (IBSCs), which can absorb light across multiple band gaps, is a possible way to defy this theoretical limit and achieve efficiencies as high as 60%. Here, we use first principles quantum mechanics methods and introduce CoO and Co0.25Ni0.75O as possible IBSCs. We show that the conduction band in both of these materials is divided into two distinct bands separated by a band gap. We further show that the lower conduction band (i.e., the intermediate band) is wider in Co0.25Ni0.75O compared with CoO. This should enhance light absorption from the valence band edge to the intermediate band, making Co0.25Ni0.75O more appropriate for use as an IBSC. Our findings provide the basis for future attempts to partially populate the intermediate band and to reduce the lower band gap in Co0.25Ni0.75O in order to enhance the potential of this material for use in IBSC solar cell technologies. Furthermore, with proper identification of heterojunctions and dopants, CoO and Co0.25Ni0.75O could be used in multi-color light emitting diode and laser technologies.

  4. Decomposition of peracetic acid catalyzed by vanadium complexes

    SciTech Connect

    Makarov, A.P.; Gekhman, A.E.; Moiseev, I.I.; Polotryuk, O.Y.

    1986-02-01

    This paper studies the decomposition of peracetic acid (AcOOH) in acetic acid (AcOH) catalyzed by vanadium complexes. It is shown that peractic acid in acetic acid solutions of ammonium anadate decomposes with the predominant formation of 0/sub 2/ and small amounts of CO/sub 2/, the yield of which increases with increasing temperature and peracetic acid concentration. Both reactions proceed without the formation of free radicals in amounts detectable by ESR spectroscopy. The rate of oxygen release under conditions in which the formation of CO/sub 2/ is insignificant obeys a kinetic equation indicating the intermediate formation of a complex between V/sup 5 +/ ions and peracetic acid and the slow conversion of this complex into the observed products.

  5. Decomposition of heterogeneous organic matterand its long-term stabilization in soils

    USGS Publications Warehouse

    Sierra, Carlos A.; Harmon, Mark E.; Perakis, Steven S.

    2011-01-01

    Soil organic matter is a complex mixture of material with heterogeneous biological, physical, and chemical properties. Decomposition models represent this heterogeneity either as a set of discrete pools with different residence times or as a continuum of qualities. It is unclear though, whether these two different approaches yield comparable predictions of organic matter dynamics. Here, we compare predictions from these two different approaches and propose an intermediate approach to study organic matter decomposition based on concepts from continuous models implemented numerically. We found that the disagreement between discrete and continuous approaches can be considerable depending on the degree of nonlinearity of the model and simulation time. The two approaches can diverge substantially for predicting long-term processes in soils. Based on our alternative approach, which is a modification of the continuous quality theory, we explored the temporal patterns that emerge by treating substrate heterogeneity explicitly. The analysis suggests that the pattern of carbon mineralization over time is highly dependent on the degree and form of nonlinearity in the model, mostly expressed as differences in microbial growth and efficiency for different substrates. Moreover, short-term stabilization and destabilization mechanisms operating simultaneously result in long-term accumulation of carbon characterized by low decomposition rates, independent of the characteristics of the incoming litter. We show that representation of heterogeneity in the decomposition process can lead to substantial improvements in our understanding of carbon mineralization and its long-term stability in soils.

  6. Decomposition of heterogeneous organic matter and its long-term stabilization in soils

    USGS Publications Warehouse

    Sierra, C.A.; Harmon, M.E.; Perakis, S.S.

    2011-01-01

    Soil organic matter is a complex mixture of material with heterogeneous biological, physical, and chemical properties. Decomposition models represent this heterogeneity either as a set of discrete pools with different residence times or as a continuum of qualities. It is unclear though, whether these two different approaches yield comparable predictions of organic matter dynamics. Here, we compare predictions from these two different approaches and propose an intermediate approach to study organic matter decomposition based on concepts from continuous models implemented numerically. We found that the disagreement between discrete and continuous approaches can be considerable depending on the degree of nonlinearity of the model and simulation time. The two approaches can diverge substantially for predicting long-term processes in soils. Based on our alternative approach, which is a modification of the continuous quality theory, we explored the temporal patterns that emerge by treating substrate heterogeneity explicitly. The analysis suggests that the pattern of carbon mineralization over time is highly dependent on the degree and form of nonlinearity in the model, mostly expressed as differences in microbial growth and efficiency for different substrates. Moreover, short-term stabilization and destabilization mechanisms operating simultaneously result in long-term accumulation of carbon characterized by low decomposition rates, independent of the characteristics of the incoming litter. We show that representation of heterogeneity in the decomposition process can lead to substantial improvements in our understanding of carbon mineralization and its long-term stability in soils. ?? 2011 by the Ecological Society of America.

  7. Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 1. Criteria for the development of the branching chain dark decomposition reaction of iodides

    SciTech Connect

    Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N

    2009-02-28

    The scheme of chemical processes proceeding in the active medium of a pulsed chemical oxygen-iodine laser (COIL) is analysed. Based on the analysis performed, the complete system of differential equations corresponding to this scheme is replaced by a simplified system of equations describing in dimensionless variables the chain dark decomposition of iodides - atomic iodine donors, in the COIL active medium. The procedure solving this system is described, the basic parameters determining the development of the chain reaction are found and its specific time intervals are determined. The initial stage of the reaction is analysed and criteria for the development of the branching chain decomposition reaction of iodide in the COIL active medium are determined. (active media)

  8. Understanding the thermal decomposition mechanism of a halogen-free chelated orthoborate-based ionic liquid: a combined computational and experimental study.

    PubMed

    Golets, M; Shimpi, M R; Wang, Y-L; Antzutkin, O N; Glavatskih, S; Laaksonen, A

    2016-08-10

    In the last few decades, ionic liquids (ILs) have gained significant attention as lubricants and lubricant additives due to their polar nature, low vapour pressure and tunable physicochemical properties. In this work, quantum chemistry calculations and atomistic Molecular Dynamics (MD) simulations were employed to predict thermal degradation mechanisms of a potential lubricating agent - the tributyloctylphosphonium bis(oxalato)borate ([P4,4,4,8][BOB]) IL. It was found that the onset of decomposition of the studied IL coincides with a cleavage of the B-O bonds in the [BOB](-) anion. Consequently, a series of chemical reactions of the [P4,4,4,8](+) cation with the [BOB](-) anion was triggered yielding alkylboranes, alkenes, trialkylphosphines, CO and CO2. Another ionic system, consisting of [P4,4,4,8][Cl], was also tested for a comparison. Thermogravimetric measurements have shown a higher thermal stability of [P4,4,4,8][BOB] compared to that of [P4,4,4,8][Cl] at least at the initial stage of decomposition, in accord with the presented calculations. Quantum chemical frequency calculations also agreed with the experimental Fourier Transform Infrared (FTIR) spectroscopy results.

  9. Orbital-free density functional theory study of amorphous Li-Si alloys and introduction of a simple density decomposition formalism

    NASA Astrophysics Data System (ADS)

    Xia, Junchao; Carter, Emily A.

    2016-03-01

    We propose a simple density decomposition formalism within orbital-free (OF) density functional theory (DFT) based on the Wang-Govind-Carter-decomposition (WGCD) kinetic energy density functional (KEDF). The resulting simple-WGCD (sWGCD) KEDF provides efficient density optimization, full cell relaxation, reasonable bulk properties for various materials compared to both the original OFDFT-WGCD and the Kohn-Sham (KS) DFT values, and has various numerical benefits including more stable convergence and lower computational cost (twice as fast as the WGCD KEDF). We also study amorphous (a-) Li-Si alloys with KSDFT and OFDFT using the Huang-Carter (HC), WGCD, and sWGCD KEDFs. The a-Li-Si alloy samples are prepared with the anneal-and-quench method using NVT molecular dynamics simulations. We report structural properties, equilibrium volumes, bulk moduli, and alloy formation energies for each a-alloy. The HC, WGCD, and sWGCD KEDFs within OFDFT all predict accurate equilibrium volumes compared against KSDFT benchmarks. The HC KEDF bulk moduli agree with KSDFT benchmarks whereas the WGCD/sWGCD KEDFs generally overestimate the bulk moduli, especially for alloys with low Li concentrations. All three KEDFs show limited ability to predict alloy formation energies, which indicates the lack of transferability of these KEDFs among such systems and motivates future developments in OFDFT and KEDF formalisms.

  10. Ab initio calculations of the reaction pathways for methane decomposition over the Cu (111) surface

    NASA Astrophysics Data System (ADS)

    Gajewski, Grzegorz; Pao, Chun-Wei

    2011-08-01

    Growth of large-area, few-layer graphene has been reported recently through the catalytic decomposition of methane (CH4) over a Cu surface at high temperature. In this study, we used ab initio calculations to investigate the minimum energy pathways of successive dehydrogenation reactions of CH4 over the Cu (111) surface. The geometries and energies of all the reaction intermediates and transition states were identified using the climbing image nudged elastic band method. The activation barriers for CH4 decomposition over this Cu surface are much lower than those in the gas phase; furthermore, analysis of electron density differences revealed significant degrees of charge transfer between the adsorbates and the Cu atoms along the reaction path; these features reveal the role of Cu as the catalytic material for graphene growth. All the dehydrogenation reactions are endothermic, except for carbon dimer (C2) formation, which is, therefore, the most critical step for subsequent graphene growth, in particular, on Cu (111) surface.

  11. A global HMX decomposition model

    SciTech Connect

    Hobbs, M.L.

    1996-12-01

    HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) decomposes by competing reaction pathways to form various condensed and gas-phase intermediate and final products. Gas formation is related to the development of nonuniform porosity and high specific surface areas prior to ignition in cookoff events. Such thermal damage enhances shock sensitivity and favors self-supported accelerated burning. The extent of HMX decomposition in highly confined cookoff experiments remains a major unsolved experimental and modeling problem. The present work is directed at determination of global HMX kinetics useful for predicting the elapsed time to thermal runaway (ignition) and the extent of decomposition at ignition. Kinetic rate constants for a six step engineering based global mechanism were obtained using gas formation rates measured by Behrens at Sandia National Laboratories with his Simultaneous Modulated Beam Mass Spectrometer (STMBMS) experimental apparatus. The six step global mechanism includes competition between light gas (H[sub 2]Awe, HCN, CO, H[sub 2]CO, NO, N[sub 2]Awe) and heavy gas (C[sub 2]H[sub 6]N[sub 2]Awe and C[sub 4]H[sub 10]N0[sub 2]) formation with zero order sublimation of HMX and the mononitroso analog of HMX (mn-HMX), C[sub 4]H[sub 8]N[sub 8]Awe[sub 7]. The global mechanism was applied to the highly confined, One Dimensional Time to eXplosion (ODTX) experiment and hot cell experiments by suppressing the sublimation of HMX and mn-HMX. An additional gas-phase reaction was also included to account for the gas-phase reaction of N[sub 2]Awe with H[sub 2]CO. Predictions compare adequately to the STMBMS data, ODTX data, and hot cell data. Deficiencies in the model and future directions are discussed.

  12. Microeconomic Concepts Students Should Learn before Intermediate Macroeconomics.

    ERIC Educational Resources Information Center

    Salemi, Michael K.

    1996-01-01

    Identifies four microeconomic concepts students should learn before entering the study of intermediate macroeconomics. Included are relative prices, general versus partial equilibrium, constrained optimization, and the nature of production concepts. Recommends making intermediate microeconomics a prerequisite for intermediate macroeconomics. (MJP)

  13. A review of plutonium oxalate decomposition reactions and effects of decomposition temperature on the surface area of the plutonium dioxide product

    NASA Astrophysics Data System (ADS)

    Orr, R. M.; Sims, H. E.; Taylor, R. J.

    2015-10-01

    Plutonium (IV) and (III) ions in nitric acid solution readily form insoluble precipitates with oxalic acid. The plutonium oxalates are then easily thermally decomposed to form plutonium dioxide powder. This simple process forms the basis of current industrial conversion or 'finishing' processes that are used in commercial scale reprocessing plants. It is also widely used in analytical or laboratory scale operations and for waste residues treatment. However, the mechanisms of the thermal decompositions in both air and inert atmospheres have been the subject of various studies over several decades. The nature of intermediate phases is of fundamental interest whilst understanding the evolution of gases at different temperatures is relevant to process control. The thermal decomposition is also used to control a number of powder properties of the PuO2 product that are important to either long term storage or mixed oxide fuel manufacturing. These properties are the surface area, residual carbon impurities and adsorbed volatile species whereas the morphology and particle size distribution are functions of the precipitation process. Available data and experience regarding the thermal and radiation-induced decompositions of plutonium oxalate to oxide are reviewed. The mechanisms of the thermal decompositions are considered with a particular focus on the likely redox chemistry involved. Also, whilst it is well known that the surface area is dependent on calcination temperature, there is a wide variation in the published data and so new correlations have been derived. Better understanding of plutonium (III) and (IV) oxalate decompositions will assist the development of more proliferation resistant actinide co-conversion processes that are needed for advanced reprocessing in future closed nuclear fuel cycles.

  14. Nucleon spin decomposition and orbital angular momentum in the nucleon

    NASA Astrophysics Data System (ADS)

    Wakamatsu, Masashi

    2014-09-01

    To get a complete decomposition of nucleon spin is a fundamentally important homework of QCD. In fact, if our researches end up without accomplishing this task, a tremendous efforts since the 1st discovery of the nucleon spin crisis would end in the air. We now have a general agreement that there are at least two physically inequivalent gauge-invariant decompositions of the nucleon. In these two decompositions, the intrinsic spin parts of quarks and gluons are just common. What discriminate these two decompositions are the orbital angular momentum (OAM) parts. The OAMs of quarks and gluons appearing in the first decomposition are the so-called ``mechanical'' OAMs, while those appearing in the second decomposition are the generalized (gauge-invariant) ``canonical'' ones. By this reason, these decompositions are broadly called the ``mechanical'' and ``canonical'' decompositions of the nucleon spin. Still, there remains several issues, which have not reached a complete consensus among the experts. (See the latest recent). In the present talk, I will mainly concentrate on the practically most important issue, i.e. which decomposition is more favorable from the observational viewpoint. There are two often-claimed advantages of canonical decomposition. First, each piece of this decomposition satisfies the SU(2) commutation relation or angular momentum algebra. Second, the canonical OAM rather than the mechanical OAM is compatible with free partonic picture of constituent orbital motion. In the present talk, I will show that both these claims are not necessarily true, and push forward a viewpoint that the ``mechanical'' decomposition is more physical in that it has more direct connection with observables. I also emphasize that the nucleon spin decomposition accessed by the lattice QCD analyses is the ``mechanical'' decomposition not the ``canonical'' one. The recent lattice QCD studies of the nucleon spin decomposition are also briefly overviewed.

  15. Study of recognizing human motion observed from an arbitrary viewpoint based on decomposition of a tensor containing multiple view motions

    NASA Astrophysics Data System (ADS)

    Hori, Takayuki; Ohya, Jun; Kurumisawa, Jun

    2011-03-01

    We propose a Tensor Decomposition based algorithm that recognizes the observed action performed by an unknown person and unknown viewpoint not included in the database. Our previous research aimed motion recognition from one single viewpoint. In this paper, we extend our approach for human motion recognition from an arbitrary viewpoint. To achieve this issue, we set tensor database which are multi-dimensional vectors with dimensions corresponding to human models, viewpoint angles, and action classes. The value of a tensor for a given combination of human silhouette model, viewpoint angle, and action class is the series of mesh feature vectors calculated each frame sequence. To recognize human motion, the actions of one of the persons in the tensor are replaced by the synthesized actions. Then, the core tensor for the replaced tensor is computed. This process is repeated for each combination of action, person, and viewpoint. For each iteration, the difference between the replaced and original core tensors is computed. The assumption that gives the minimal difference is the action recognition result. The recognition results show the validity of our proposed method, the method is experimentally compared with Nearest Neighbor rule. Our proposed method is very stable as each action was recognized with over 75% accuracy.

  16. Room acoustics analysis using circular arrays: an experimental study based on sound field plane-wave decomposition.

    PubMed

    Torres, Ana M; Lopez, Jose J; Pueo, Basilio; Cobos, Maximo

    2013-04-01

    Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis.

  17. Decomposition Studies in Two Central Ontario Lakes Having Surficial pHs of 4.6 and 6.6.

    PubMed

    Hoeniger, J F

    1986-09-01

    The rates of cellulose breakdown, composition of detrital microflora, and density of bacterial populations were determined in the epilimnetic sediments and water columns of two poorly buffered, oligotrophic, Canadian Shield lakes having mean surficial pHs of 4.6 (Bat Lake) and 6.6 (Harp Lake). The decomposition rate was significantly lower in oxic sediment of the acidified lake than of the circumneutral lake, but water column rates were almost identical in the two lakes. These results are explained in terms of the groups of cellulolytic microorganisms which were observed by phase-contrast microscopy as being active at the different sites: fungi in Bat Lake water and Cytophaga-like bacteria in the water and sediment of Harp Lake. Cytophaga-like bacteria were also the main decomposers in Bat Lake sediment, but their activity was restricted at porewater pHs of <5.0. Acridine orange direct counts of bacteria in the top centimeter of sediment ranged from 3.7 x 10 to 1.0 x 10 per g, and counts in planktonic water samples ranged from 4.9 x 10 to 1.2 x 10 per ml. Bacterial densities at most sites decreased significantly (P < 0.001) from August to late October, but did not show a consistent pattern of differences related to pH. PMID:16347147

  18. Decomposition Studies in Two Central Ontario Lakes Having Surficial pHs of 4.6 and 6.6

    PubMed Central

    Hoeniger, Judith F. M.

    1986-01-01

    The rates of cellulose breakdown, composition of detrital microflora, and density of bacterial populations were determined in the epilimnetic sediments and water columns of two poorly buffered, oligotrophic, Canadian Shield lakes having mean surficial pHs of 4.6 (Bat Lake) and 6.6 (Harp Lake). The decomposition rate was significantly lower in oxic sediment of the acidified lake than of the circumneutral lake, but water column rates were almost identical in the two lakes. These results are explained in terms of the groups of cellulolytic microorganisms which were observed by phase-contrast microscopy as being active at the different sites: fungi in Bat Lake water and Cytophaga-like bacteria in the water and sediment of Harp Lake. Cytophaga-like bacteria were also the main decomposers in Bat Lake sediment, but their activity was restricted at porewater pHs of <5.0. Acridine orange direct counts of bacteria in the top centimeter of sediment ranged from 3.7 × 108 to 1.0 × 109 per g, and counts in planktonic water samples ranged from 4.9 × 105 to 1.2 × 106 per ml. Bacterial densities at most sites decreased significantly (P < 0.001) from August to late October, but did not show a consistent pattern of differences related to pH. Images PMID:16347147

  19. Decomposition studies in two central Ontario lakes having surficial pHs of 4. 6 and 6. 6

    SciTech Connect

    Hoeniger, J.F.M.

    1986-09-01

    The rates of cellulose breakdown, composition of detrital microflora, and density of bacterial populations were determined in the epilimnetic sediments and water columns of two poorly buffered, oligotrophic, Canadian Shield lakes having mean surficial pHs of 4.6 (Bat Lake) and 6.6 (Harp Lake). The decomposition rate was significantly lower in oxic sediment of the acidified lake than of the circumneutral lake, but water column rates were almost identical in the two lakes. These results are explained in terms of the groups of cellulolytic microorganisms which were observed by phase-contrast microscopy as being active at the different sites: fungi in Bat Lake water and Cytophaga-like bacteria in the water and sediment of Harp Lake. Cytophaga-like bacteria were also the main decomposers in Bat Lake sediment, but their activity was restricted at porewater pHs of <5.0. Acridine orange direct counts of bacteria in the top centimeter of sediment ranged from 3.7 x 10/sup 8/ to 1.0 x 10/sup 9/ per g, and counts in planktonic water samples ranged from 4.9 to 10/sup 5/ to 1.2 x 10/sup 6/ per ml. Bacterial densities at most sites decreased significantly from August to late October, but did not show a consistent pattern of differences related to pH.

  20. Hardware Implementation of Singular Value Decomposition

    NASA Astrophysics Data System (ADS)

    Majumder, Swanirbhar; Shaw, Anil Kumar; Sarkar, Subir Kumar

    2016-06-01

    Singular value decomposition (SVD) is a useful decomposition technique which has important role in various engineering fields such as image compression, watermarking, signal processing, and numerous others. SVD does not involve convolution operation, which make it more suitable for hardware implementation, unlike the most popular transforms. This paper reviews the various methods of hardware implementation for SVD computation. This paper also studies the time complexity and hardware complexity in various methods of SVD computation.

  1. Decomposing Nekrasov decomposition

    NASA Astrophysics Data System (ADS)

    Morozov, A.; Zenkevich, Y.

    2016-02-01

    AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions — this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition — into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.

  2. Intermediate state during the crystal transition in aspartame, studied with thermal analysis, solid-state NMR, and molecular dynamics simulation.

    PubMed

    Ebisawa, K; Nagashima, N; Fukuhara, K; Kumon, S; Kishimoto, S; Suzuki, E; Yoneda, S; Umeyama, H

    2000-05-01

    Aspartame (L-alpha-aspartyl-L-phenylalanine methyl ester) is a dipeptide sweetener about 200 times as sweet as sugar. It exists in crystal forms such as IA, IB, IIA, and IIB, which differ in crystal structure and in the degree of hydration. Among these, IIA is the most stable crystal form, and its crystal structure has been well determined (Hatada et al., J. Am. Chem. Soc., 107, 4279-4282 (1985)). To elucidate the structural factors of thermal stability in the IIA form of aspartame and to examine the physical process in the crystal transformation between the IIA and IIB forms, we performed a thermal analysis and solid-state NMR measurements. We found that a quasi-stable intermediate state exists in the transformation, and it has the same crystal lattice as the usual IIA form, despite the dehydration from 1/2 mol to 1/3 mol per 1 mol of aspartame. The results of the energy component analysis and the molecular dynamics simulation suggest that the entropic effect promotes the generation of the intermediate state, which is presumably caused by the evaporation of the water of crystallization and the increase of molecular motion in aspartame. Thus, the thermal stability of the IIA form is attributable to a structural property, i.e., the crystal lattice itself is retained during the above dehydration. Moreover, the molecular dynamics simulations suggest that the aspartame molecules have two kinds of conformational flexibility in the intermediate state. PMID:10823710

  3. Structural Studies of E. coli Topoisomerase III-DNA Complexes Reveal a Novel Type IA Topoisomerase-DNA Conformational Intermediate

    SciTech Connect

    Changela, Anita; DiGate, Russell J.; Mondragon, Alfonso

    2010-03-05

    Escherichia coli DNA topoisomerase III belongs to the type IA family of DNA topoisomerases, which transiently cleave single-stranded DNA (ssDNA) via a 5{prime} phosphotyrosine intermediate. We have solved crystal structures of wild-type E. coli topoisomerase III bound to an eight-base ssDNA molecule in three different pH environments. The structures reveal the enzyme in three distinct conformational states while bound to DNA. One conformation resembles the one observed previously with a DNA-bound, catalytically inactive mutant of topoisomerase III where DNA binding realigns catalytic residues to form a functional active site. Another conformation represents a novel intermediate in which DNA is bound along the ssDNA-binding groove but does not enter the active site, which remains in a catalytically inactive, closed state. A third conformation shows an intermediate state where the enzyme is still in a closed state, but the ssDNA is starting to invade the active site. For the first time, the active site region in the presence of both the catalytic tyrosine and ssDNA substrate is revealed for a type IA DNA topoisomerase, although there is no evidence of ssDNA cleavage. Comparative analysis of the various conformational states suggests a sequence of domain movements undertaken by the enzyme upon substrate binding.

  4. Intermediate state during the crystal transition in aspartame, studied with thermal analysis, solid-state NMR, and molecular dynamics simulation.

    PubMed

    Ebisawa, K; Nagashima, N; Fukuhara, K; Kumon, S; Kishimoto, S; Suzuki, E; Yoneda, S; Umeyama, H

    2000-05-01

    Aspartame (L-alpha-aspartyl-L-phenylalanine methyl ester) is a dipeptide sweetener about 200 times as sweet as sugar. It exists in crystal forms such as IA, IB, IIA, and IIB, which differ in crystal structure and in the degree of hydration. Among these, IIA is the most stable crystal form, and its crystal structure has been well determined (Hatada et al., J. Am. Chem. Soc., 107, 4279-4282 (1985)). To elucidate the structural factors of thermal stability in the IIA form of aspartame and to examine the physical process in the crystal transformation between the IIA and IIB forms, we performed a thermal analysis and solid-state NMR measurements. We found that a quasi-stable intermediate state exists in the transformation, and it has the same crystal lattice as the usual IIA form, despite the dehydration from 1/2 mol to 1/3 mol per 1 mol of aspartame. The results of the energy component analysis and the molecular dynamics simulation suggest that the entropic effect promotes the generation of the intermediate state, which is presumably caused by the evaporation of the water of crystallization and the increase of molecular motion in aspartame. Thus, the thermal stability of the IIA form is attributable to a structural property, i.e., the crystal lattice itself is retained during the above dehydration. Moreover, the molecular dynamics simulations suggest that the aspartame molecules have two kinds of conformational flexibility in the intermediate state.

  5. Neutron diffraction and quasielastic neutron scattering studies of films of intermediate-length alkanes adsorbed on a graphite surface

    NASA Astrophysics Data System (ADS)

    Diama, Armand

    Over the past several years, we have conducted a variety of elastic neutron diffraction and quasielastic neutron scattering experiments to study the structure and the dynamics of films of two intermediate-length alkane molecules (C nH2n+2), adsorbed on a graphite basal-plane surface. The two molecules are the normal alkane n-tetracosane [n-CH 3(CH2)22CH3] and the branched alkane squalane (C30H62 or 2, 6, 10, 15, 19, 23-hexamethyltetracosane) whose carbon backbone is the same length as teteracosane. The temperature dependence of the monolayer structure of tetracosane and squalane was investigated using elastic neutron diffraction and evidence of two phase transitions was observed. Both the low-coverage tetracosane (C 24H50) and squalane (C30H62) monolayers have crystalline-to-"smectic" and "smectic"-to-isotropic fluid phase transitions upon heating. The diffusive motion in the tetracosane and squalane monolayers has been investigated by quasielastic neutron scattering. Two different quasielastic neutron scattering spectrometers at the Center for Neutron Research, National Institute of Standards and Technology (NIST) have been used. The spectrometers differ in both their dynamic range and energy resolution allowing molecular motions to be investigated on time scales in the range 10-13--10 -9 s. On these time scales, we observe evidence of translational, rotational, and intermolecular diffusive motions in the tetracosane and squalane monolayers. We conclude that the molecular diffusive motion in the two monolayers is qualitatively similar. Thus, despite the three methyl sidegroups at each end of the squalane molecule, its monolayer structure, phase transitions, and dynamics are qualitatively similar to that of a monolayer of the unbranched tetracosane molecules. With the higher resolution spectrometer at NIST, we have also investigated the molecular diffusive motion in multilayer tetracosane films. The analysis of our measurements indicates slower diffusive motion in

  6. Aflatoxin decomposition in various soils

    SciTech Connect

    Angle, J.S.

    1986-08-01

    The persistence of aflatoxin in the soil environment could potentially result in a number of adverse environmental consequences. To determine the persistence of aflatoxin in soil, /sup 14/C-labeled aflatoxin B1, was added to silt loam, sandy loam, and silty clay loam soils and the subsequent release of /sup 14/CO/sub 2/ was determined. After 120 days of incubation, 8.1% of the original aflatoxin added to the silt loam soil was released as CO/sub 2/. Aflatoxin decomposition in the sandy loam soil proceeded more quickly than the other two soils for the first 20 days of incubation. After this time, the decomposition rate declined and by the end of the study, 4.9% of the aflatoxin was released as CO/sub 2/. Aflatoxin decomposition proceeded most slowly in the silty clay loam soil. Only 1.4% of aflatoxin added to the soil was released as CO/sub 2/ after 120 days incubation. To determine whether aflatoxin was bound to the silty clay loam soil, aflatoxin B1 was added to this soil and incubated for 20 days. The soil was periodically extracted and the aflatoxin species present were determined using thin layer chromatographic (TLC) procedures. After one day of incubation, the degradation products, aflatoxins B2 and G2, were observed. It was also found that much of the aflatoxin extracted from the soil was not mobile with the TLC solvent system used. This indicated that a conjugate may have formed and thus may be responsible for the lack of aflatoxin decomposition.

  7. Will the world run out of land? A Kaya-like-decomposition to study past trends of cropland expansion

    NASA Astrophysics Data System (ADS)

    Huber, V.; Neher, I.; Bodirsky, B.

    2011-12-01

    Around 12 % of the global ice-free land cover is currently used as cropland. Further expansion is limited by the amount of adequate land and even more so by the necessity to spare land for nature conservation and carbon sequestration. Analyzing the causes of past land-use changes with an integrative global approach can help to better understand the potential land scarcities of the future. Using the FAOSTAT database, we quantify the contribution of five major factors, namely human population growth, rising caloric demands, shifting diets, waste intensity, and yield gains, to cropland expansion rates of the past (1961-2007). We employ a Kaya-like-decomposition method that we have adapted to be applicable to drivers of cropland expansion at global, regional, and national level. Our results indicate that, all else equal, without the yield gains observed since 1961 the world would have used 63% more cropland area in 2007. Under this scenario the sustainable limit of cropland area would have already been transgressed today. By contrast, without population growth and rising caloric demands since 1961 the crop demand could have been fulfilled with 33% and 79% of currently used cropland area, respectively. Yield gains, with strongest contributions from maize, wheat and rice, have roughly offset the increasing demand of a growing world population. Analyses at the regional and local scale reveal different modes of land-use transitions dependent on development stage and dietary preferences of the countries. These results contribute to the empirical basis needed to prepare well-informed projections of land-use change until 2050 and beyond.

  8. Small-angle x-ray scattering study of kinetics of spinodal decomposition in {ital N}-isopropylacrylamide gels

    SciTech Connect

    Liao, G.; Xie, Y.; Ludwig, K.F. Jr.; Bansil, R.; Gallagher, P.; Xie, Y.; Gallagher, P.

    1999-10-01

    We present synchrotron-based time-resolved small-angle x-ray scattering (SAXS) measurements of spinodal decomposition in a covalently cross-linked N-isopropylacrylamide gel. The range of wave numbers examined is well beyond the position of the maximum in the structure factor S(q,t). The equilibrium structure factor is described by the sum of a Lorentzian and a Gaussian. Following a temperature jump into the two phase region, the scattered intensity increases with time and eventually saturates. For early times the linear Cahn-Hilliard-Cook (CHC) theory can be used to describe the time evolution of the scattered intensity. From this analysis we found that the growth rate R(q) is linearly dependent on q{sup 2}, in agreement with mean-field theoretical predictions. However the Onsager transport coefficient {Lambda}(q){approximately}q{sup {minus}4}, which is stronger than the {ital q} dependence predicted by the mean-field theory. We found that the growth rate R(q){gt}0, even though the wave numbers {ital q} probed by SAXS are greater than {radical} (2) q{sub m} where q{sub m} is the position of the peak of S(q,t), also in agreement with the mean-field predictions for a deep quench. We have also examined the range of validity of the linear CHC theory, and found that its breakdown occurs earlier at higher wave numbers. At later times, a pinning of the structure was observed. The relaxation to a final, microphase-separated morphology is faster and occurs earlier at the highest wave numbers, which probe length scales comparable to the average distance between crosslinks. {copyright} {ital 1999} {ital The American Physical Society}

  9. Mechanistic insight into the chemiluminescent decomposition of firefly dioxetanone.

    PubMed

    Yue, Ling; Liu, Ya-Jun; Fang, Wei-Hai

    2012-07-18

    The peroxide decomposition that generates the excited-state carbonyl compound is the key step in most organic chemiluminescence, and chemically initiated electron exchange luminescence (CIEEL) has been widely accepted for decades as the general mechanism for this decomposition. The firefly dioxetanone, which is a peroxide, is the intermediate in firefly bioluminescence, and its decomposition is the most important step leading to the emission of visible light by a firefly. However, the firefly dioxetanone decomposition mechanism has never been explored at a reliable theoretical level, because the decomposition process includes biradical, charge-transfer (CT) and several nearly degenerate states. Herein, we have investigated the thermolysis of firefly dioxetanone in its neutral (FDOH) and anionic (FDO(-)) forms using second-order multiconfigurational perturbation theories in combination with the ground-state intrinsic reaction coordinate calculated via the combined hybrid functional with Coulomb attenuated exchange-correlation, and considered the solvent effect on the ground-state reaction path using the combined hybrid functional with Coulomb attenuated exchange-correlation. The calculated results indicate that the chemiluminescent decomposition of FDOH or FDO(-) does not take place via the CIEEL mechanism. An entropic trap was found to lead to an excited-state carbonyl compound for FDOH, and a gradually reversible CT initiated luminescence (GRCTIL) was proposed as a new mechanism for the decomposition of FDO(-).

  10. Thermal decomposition and reconstruction of CaFe-layered double hydroxide studied by X-ray diffractometry and 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bugris, Valéria; Ádok-Sipiczki, Mónika; Anitics, Tamás; Kuzmann, Ernő; Homonnay, Zoltán; Kukovecz, Ákos; Kónya, Zoltán; Sipos, Pál; Pálinkó, István

    2015-06-01

    In spite of numerous investigations on the various processes of the thermal decomposition and rehydration of layered double hydroxides (LDHs) by a variety sophisticated experimental means, many details are still unexplored and some contradictions are still unresolved. In this work, our efforts were focussed on clarifying the composition, structure and properties of thermally decomposed metaphases originating from CaFe-LDH, heat treated in the 373-973 K temperature range. The structure reconstruction ability of mixed metal oxide phases obtained after heat treatments was also investigated, mainly concentrating on the changes in the microenvironment of Fe(III), in the presence of controlled amount of water vapour (i.e., at different relative humidities). All samples were characterised by X-ray diffractometry, and the iron-containing phases were studied by 57Fe Mössbauer spectroscopy.

  11. The mechanism of methanol decomposition by CuO. A theoretical study based on the reaction force and reaction electronic flux analysis.

    PubMed

    Cerón, Maria Luisa; Herrera, Barbara; Araya, Paulo; Gracia, Francisco; Toro-Labbé, Alejandro

    2011-07-01

    A theoretical study of methanol decomposition using a model representing the initial step of the reaction CH₃OH + CuO → CH₂O + H₂O + Cu is presented. Theoretical calculations using B3LYP/6-31 G along with Lanl2DZ pseudopotentials on metallic centers were performed and the results discussed within the framework of the reaction force analysis. It has been found that the reaction takes place following a stepwise mechanism: first, copper reduction (Cu⁺² → Cu⁺) accompanies the oxygen transposition and then a second reduction takes place (Cu⁺ → Cu₀) together with a proton transfer that produce formaldehyde and release a water molecule.

  12. Excited electronic state decomposition mechanisms and dynamics of nitramine energetic materials and model systems

    NASA Astrophysics Data System (ADS)

    Greenfield, Margo

    Energetic materials play an important role in aeronautics, the weapon industry, and the propellant industry due to their broad applications as explosives and fuels. RDX (1,3,5-trinitrohexahydro-s-triazine), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), and CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) are compounds which contain high energy density. Although RDX and HMX have been studied extensively over the past several decades a complete understanding of their decomposition mechanisms and dynamics is unknown. Time of flight mass spectroscopy (TOFMS) UV photodissociation (ns) experiments of gas phase RDX, HMX, and CL-20 generate the NO molecule as the initial decomposition product. Four different vibronic transitions of the initial decomposition product, the NO molecule, are observed: A2Sigma(upsilon'=0)←X 2pi(upsilon"=0,1,2,3). Simulations of the rovibronic intensities for the A←X transitions demonstrate that NO dissociated from RDX, HMX, and CL-20 is rotationally cold (˜20 K) and vibrationally hot (˜1800 K). Conversely, experiments on the five model systems (nitromethane, dimethylnitramine (DMNA), nitropyrrolidine, nitropiperidine and dinitropiperazine) produce rotationally hot and vibrationally cold spectra. Laser induced fluorescence (LIF) experiments are performed to rule out the possible decomposition product OH, generated along with NO, perhaps from the suggested HONO elimination mechanism. The OH radical is not observed in the fluorescence experiments, indicating the HONO decomposition intermediate is not an important pathway for the excited electronic state decomposition of cyclic nitramines. The NO molecule is also employed to measure the dynamics of the excited state decomposition. A 226 nm, 180 fs light pulse is utilized to photodissociate the gas phase systems. Stable ion states of DMNA and nitropyrrolidine are observed while the energetic materials and remaining model systems present the NO molecule as the only

  13. Study of the intermediate layer at the n{sup +}-CdS/p-CdTe interface

    SciTech Connect

    Muzafarova, S. A. Aitbaev, B. U.; Mirsagatov, Sh. A.; Durshimbetov, K.; Zhanabergenov, Zh.

    2008-12-15

    The effect of production conditions and subsequent stimulation by ultrasonic irradiation on the formation of a solid solution at the n-CdS/p-CdTe interface in solar cells has been investigated. The phase composition of the solid-solution transient layer was investigated by a nondestructive photoelectric method (measurement of the spectral distribution of photosensitivity in the gate and photodiode modes). It is shown that the phase composition and thickness of the intermediate CdTe{sub 1-x}S{sub x} layer depend strongly on the heterostructure formation conditions.

  14. Study of insect succession and rate of decomposition on a partially burned pig carcass in an oil palm plantation in Malaysia.

    PubMed

    Heo, Chong Chin; Mohamad, Abdullah Marwi; Ahmad, Firdaus Mohd Salleh; Jeffery, John; Kurahashi, Hiromu; Omar, Baharudin

    2008-12-01

    Insects found associated with corpse can be used as one of the indicators in estimating postmortem interval (PMI). The objective of this study was to compare the stages of decomposition and faunal succession between a partially burnt pig (Sus scrofa Linnaeus) and natural pig (as control). The burning simulated a real crime whereby the victim was burnt by murderer. Two young pigs weighed approximately 10 kg were used in this study. Both pigs died from pneumonia and immediately placed in an oil palm plantation near a pig farm in Tanjung Sepat, Selangor, Malaysia. One pig was partially burnt by 1-liter petrol while the other served as control. Both carcasses were visited twice per day for the first week and once thereafter. Adult flies and larvae on the carcasses were collected and later processed in a forensic entomology laboratory. Results showed that there was no significant difference between the rate of decomposition and sequence of faunal succession on both pig carcasses. Both carcasses were completely decomposed to remain stage after nine days. The species of flies visiting the pig carcasses consisted of blow flies (Chrysomya megacephala, Chrysomya rufifacies, Hemipyrellia ligurriens), flesh fly (Sarcophagidae.), muscid fly (Ophyra spinigera), soldier fly (Hermetia illucens), coffin fly (Phoridae) and scavenger fly (Sepsidae). The only difference noted was in the number of adult flies, whereby more flies were seen in the control carcass. Faunal succession on both pig carcasses was in the following sequence: Calliphoridae, Sarcophagidae, Muscidae, Phoridae and lastly Stratiomyidae. However, there was overlap in the appearance of members of these families. Blowflies continued to oviposit on both carcasses. Hence postmortem interval (PMI) can still be estimated from the partially burnt pig carcass. PMID:19287358

  15. Study of insect succession and rate of decomposition on a partially burned pig carcass in an oil palm plantation in Malaysia.

    PubMed

    Heo, Chong Chin; Mohamad, Abdullah Marwi; Ahmad, Firdaus Mohd Salleh; Jeffery, John; Kurahashi, Hiromu; Omar, Baharudin

    2008-12-01

    Insects found associated with corpse can be used as one of the indicators in estimating postmortem interval (PMI). The objective of this study was to compare the stages of decomposition and faunal succession between a partially burnt pig (Sus scrofa Linnaeus) and natural pig (as control). The burning simulated a real crime whereby the victim was burnt by murderer. Two young pigs weighed approximately 10 kg were used in this study. Both pigs died from pneumonia and immediately placed in an oil palm plantation near a pig farm in Tanjung Sepat, Selangor, Malaysia. One pig was partially burnt by 1-liter petrol while the other served as control. Both carcasses were visited twice per day for the first week and once thereafter. Adult flies and larvae on the carcasses were collected and later processed in a forensic entomology laboratory. Results showed that there was no significant difference between the rate of decomposition and sequence of faunal succession on both pig carcasses. Both carcasses were completely decomposed to remain stage after nine days. The species of flies visiting the pig carcasses consisted of blow flies (Chrysomya megacephala, Chrysomya rufifacies, Hemipyrellia ligurriens), flesh fly (Sarcophagidae.), muscid fly (Ophyra spinigera), soldier fly (Hermetia illucens), coffin fly (Phoridae) and scavenger fly (Sepsidae). The only difference noted was in the number of adult flies, whereby more flies were seen in the control carcass. Faunal succession on both pig carcasses was in the following sequence: Calliphoridae, Sarcophagidae, Muscidae, Phoridae and lastly Stratiomyidae. However, there was overlap in the appearance of members of these families. Blowflies continued to oviposit on both carcasses. Hence postmortem interval (PMI) can still be estimated from the partially burnt pig carcass.

  16. Hydrazine decomposition and other reactions

    NASA Technical Reports Server (NTRS)

    Armstrong, Warren E. (Inventor); La France, Donald S. (Inventor); Voge, Hervey H. (Inventor)

    1978-01-01

    This invention relates to the catalytic decomposition of hydrazine, catalysts useful for this decomposition and other reactions, and to reactions in hydrogen atmospheres generally using carbon-containing catalysts.

  17. Intermediate ions in the atmosphere

    NASA Astrophysics Data System (ADS)

    Tammet, Hannes; Komsaare, Kaupo; Hõrrak, Urmas

    2014-01-01

    Intermediate air ions are charged nanometer-sized aerosol particles with an electric mobility of about 0.03-0.5 cm2 V- 1 s- 1 and a diameter of about 1.5-7.5 nm. Intensive studies of new particle formation provided good knowledge about intermediate ions during burst events of atmospheric aerosol nucleation. Information about intermediate ions during quiet periods between the bursts remained poor. The new mobility analyzer SIGMA can detect air ions at concentrations of mobility fractions of about 1 cm- 3 and enables studying intermediate ions during quiet periods. It became evident that intermediate ions always exist in atmospheric air and should be considered an indicator and a mediator of aerosol nucleation. The annual average concentration of intermediate ions of one polarity in Tartu, Estonia, was about 40 cm- 3 while 5% of the measurements showed a concentration of less than 10 cm- 3. The fraction concentrations in logarithmic 1/8-decade mobility bins between 0.1 and 0.4 cm2 V- 1 s- 1 often dropped below 1 cm- 3. The bursts of intermediate ions at stations separated by around 100 km appeared to be correlated. The lifespan of intermediate ions in the atmosphere is a few minutes, and they cannot be carried by wind over long distances. Thus the observed long-range correlation of intermediate ions is explained by simultaneous changes in air composition in widely spaced stations. A certain amount of intermediate ion bursts, predominantly of negative polarity, are produced by the balloelectric effect at the splashing of water drops during rain. These bursts are usually excluded when speaking about new particle formation because the balloelectric particles are assumed not to grow to the size of the Aitken mode. The mobility distribution of balloelectric ions is uniform in shape in all measurements. The maximum is located at a mobility of about 0.2 cm2 V- 1 s- 1, which corresponds to the diameter of particles of about 2.5 nm.

  18. A characterization of the two-step reaction mechanism of phenol decomposition by a Fenton reaction

    NASA Astrophysics Data System (ADS)

    Valdés, Cristian; Alzate-Morales, Jans; Osorio, Edison; Villaseñor, Jorge; Navarro-Retamal, Carlos

    2015-11-01

    Phenol is one of the worst contaminants at date, and its degradation has been a crucial task over years. Here, the decomposition process of phenol, in a Fenton reaction, is described. Using scavengers, it was observed that decomposition of phenol was mainly influenced by production of hydroxyl radicals. Experimental and theoretical activation energies (Ea) for phenol oxidation intermediates were calculated. According to these Ea, phenol decomposition is a two-step reaction mechanism mediated predominantly by hydroxyl radicals, producing a decomposition yield order given as hydroquinone > catechol > resorcinol. Furthermore, traces of reaction derived acids were detected by HPLC and GS-MS.

  19. A new complete basis set model (CBS-QB3) study on the possible intermediates in chemiluminescence

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Zeng, Xi-Rui; You, Xiao-Zeng

    2000-11-01

    The new highly accurate complete basis set model, CBS-QB3, was employed here to elucidate the long experimentally discussed problem in a general class of chemiluminescent reactions involving peroxyoxalate systems. Both the stability comparison and the vibrational spectra favor that the intermediate is better to be recognized as the cyclic singlet 1,2-dioxetanedione with the C2v symmetry, which verifies the experimental suggestion yet provides more characterization information. Another two kinds of minimum species in its potential energy surface (PES) are two kinds of product: (1) two carbon dioxide and (2) two carbon monoxide and one oxygen, where the thermodynamic parameters correctly identify their relative yield in the experiment—the former is much more abundant than the latter. In a complete search of minimum states in its PES, the triplet C2v and D2h states were found, which is energetically unfavorable compared with the singlet C2v state. Their vibrational data also support some experimental conclusions of ruling out a radical intermediate. In contrast, the singlet D2h state was found to be a transition state for the "up" and "down" singlet C2v states. The complete active space self-consistent-field calculations with the second-order Möller-Plesset correlation energy correction also support that the most stable species is the singlet C2v state and the singlet D2h state is more energetically favorable than its triplet counterpart.

  20. An extensive photometric study of the recently discovered intermediate polar V515 And (XSS J00564+4548)

    NASA Astrophysics Data System (ADS)

    Kozhevnikov, V. P.

    2012-05-01

    We report the results of photometry of the intermediate polar V515 And. Observations were obtained over 33 nights in 2008 and 2009. The total duration of the observations was 233 h. We clearly detected two oscillations with periods of 465.484 93 ± 0.000 07 and 488.618 22 ± 0.000 09 s, which may be the white dwarf spin period and the orbital sideband. The semi-amplitudes of the oscillations are accordingly 25 and 20 mmag. The oscillation with a period of 465.484 93 s has a stable smooth asymmetric pulse profile, whereas the pulse profile of the oscillation with a period of 488.618 22 s reveals significant changes from a quasi-sinusoidal shape to a shape somewhat resembling a light curve of an eclipsing binary. Two detected oscillations imply an orbital period of 2.73 h. V515 And is one of the most rapidly spinning intermediate polars with orbital periods less than 3 h and may not be in spin equilibrium. This could be proved by future observations. For this purpose, we obtained oscillation ephemerides with a formal shelf life of about 100 yr (a 1σ confidence level).

  1. X-ray, FT-IR, NMR and PM5 structural studies and antibacterial activity of unexpectedly stable salinomycin-benzotriazole intermediate ester

    NASA Astrophysics Data System (ADS)

    Huczyński, Adam; Janczak, Jan; Antoszczak, Michał; Stefańska, Joanna; Brzezinski, Bogumil

    2012-08-01

    The unexpectedly stable benzotriazole ester of salinomycin (SAL-HOBt) - an intermediate product of the amidation reaction of salinomycin has been isolated and structurally characterised (using a single crystal) by X-ray, FT-IR, NMR and semiempirical methods. The results of the X-ray and spectroscopic studies demonstrated that this intermediate ester exist in the solid state and in solution exclusively as the stable O-acyl form. The molecular structure of SAL-HOBt is stabilised by relatively weak intramolecular hydrogen bonds. The PM5 calculation of possible structures of SAL-HOBt has shown that the O-acyl form is more energetically favourable than its N-oxide-N-acyl isomers. The antimicrobial tests show that SAL-HOBt is active against Gram-positive bacteria and clinical isolates methicillin-resistant Staphylococcus aureus (MIC = 1-2 μg/ml).

  2. [Intermediate phenotype of schizophrenia].

    PubMed

    Hashimoto, Ryota

    2013-04-01

    Genes are major contributors to schizophrenia. The intermediate phenotype concept represents a strategy for identifying risk genes for schizophrenia and for characterizing the neural systems affected by risk gene variants to elucidate quantitative, mechanistic aspects of brain function implicated in schizophrenia. Intermediate phenotypes are defined by being heritable, being able to measure quantitatively; being related to the disorder and its symptoms in the general population; being stable over time; showing increased expression in unaffected relatives of probands; and cosegregation with the disorder in families. Intermediate phenotypes in schizophrenia are neurocognition, neuroimaging, neurophysiology, etc. In this review, we present concept, recent work, and future perspective of intermediate phenotype.

  3. Reduction of 2,4,6-trinitrotoluene by Clostridium acetobutylicum through hydroxylamino-nitrotoluene intermediates

    SciTech Connect

    Hughes, J.B.; Wang, C.Y.; Bhadra, R.; Richardson, A.; Bennett, G.N.; Rudolph, F.B.

    1998-03-01

    Studies were conducted to isolate and identify intermediates of 2,4,6-trinitrotoluene (TNT) transformation by Clostridium acetobutylicum and to quantify their concentrations in active whole cell cultures. Only two intermediates of TNT reduction were detected in cell cultures and were identified as 4-hydroxylamino-2,6-dinitrotoluene and 2,4-dihydroxylamino-6-nitrotoluene. Structures were confirmed with {sup 1}H-NMR, {sup 13}C-NMR, and desorption chemical ionization mass spectroscopy. When cells were suspended in a non-growth saline medium, both hydroxylamine forms accumulated. In media capable of supporting cell growth, the 2,4-dihydroxylamino-6-nitrotoluene accumulated with concentrations of 4-hydroxylamino-2,6-dinitrotoluene remaining near detection limits. Studies using purified 2,4-dihydroxylamino-6-nitrotoluene confirmed that its biotransformation rate in active cultures greatly exceeded abiotic decomposition in aqueous medium.

  4. Decomposition of forest products buried in landfills

    SciTech Connect

    Wang, Xiaoming; Padgett, Jennifer M.; Powell, John S.; Barlaz, Morton A.

    2013-11-15

    Highlights: • This study tracked chemical changes of wood and paper in landfills. • A decomposition index was developed to quantify carbohydrate biodegradation. • Newsprint biodegradation as measured here is greater than previous reports. • The field results correlate well with previous laboratory measurements. - Abstract: The objective of this study was to investigate the decomposition of selected wood and paper products in landfills. The decomposition of these products under anaerobic landfill conditions results in the generation of biogenic carbon dioxide and methane, while the un-decomposed portion represents a biogenic carbon sink. Information on the decomposition of these municipal waste components is used to estimate national methane emissions inventories, for attribution of carbon storage credits, and to assess the life-cycle greenhouse gas impacts of wood and paper products. Hardwood (HW), softwood (SW), plywood (PW), oriented strand board (OSB), particleboard (PB), medium-density fiberboard (MDF), newsprint (NP), corrugated container (CC) and copy paper (CP) were buried in landfills operated with leachate recirculation, and were excavated after approximately 1.5 and 2.5 yr. Samples were analyzed for cellulose (C), hemicellulose (H), lignin (L), volatile solids (VS), and organic carbon (OC). A holocellulose decomposition index (HOD) and carbon storage factor (CSF) were calculated to evaluate the extent of solids decomposition and carbon storage. Samples of OSB made from HW exhibited cellulose plus hemicellulose (C + H) loss of up to 38%, while loss for the other wood types was 0–10% in most samples. The C + H loss was up to 81%, 95% and 96% for NP, CP and CC, respectively. The CSFs for wood and paper samples ranged from 0.34 to 0.47 and 0.02 to 0.27 g OC g{sup −1} dry material, respectively. These results, in general, correlated well with an earlier laboratory-scale study, though NP and CC decomposition measured in this study were higher than

  5. Central role of phenanthroline mono-N-oxide in the decomposition reactions of tris(1,10-phenanthroline)iron(II) and -iron(III) complexes.

    PubMed

    Bellér, Gábor; Lente, Gábor; Fábián, István

    2010-05-01

    1,10-Phenanthroline mono-N-oxide (phenO) is a product of the decomposition of tris(1,10-phenanthroline)iron(III), Fe(phen)(3)(3+), and has a slight autocatalytic effect on the overall reaction. The mechanism is proposed to involve Fe(phen)(3)(4+) as a minor intermediate. The addition of phenO significantly influences the kinetic features of the decomposition of Fe(phen)(3)(3+) and the oxidation of Fe(phen)(3)(2+) by HSO(5)(-). The autocatalytic decomposition explains the difficulties in the preparation of Fe(phen)(3)(3+) and may contribute to exotic kinetic phenomena studied using Fe(phen)(3)(3+)/Fe(phen)(3)(3+) as a supposedly innocent indicator.

  6. Decomposition of Furan on Pd(111)

    SciTech Connect

    Xu, Ye

    2012-01-01

    Periodic density functional theory calculations (GGA-PBE) have been performed to investigate the mechanism for the decomposition of furan up to CO formation on the Pd(111) surface. At 1/9 ML coverage, furan adsorbs with its molecular plane parallel to the surface in several states with nearly identical adsorption energies of -1.0 eV. The decomposition of furan begins with the opening of the ring at the C-O position with an activation barrier of E{sub a} = 0.82 eV, which yields a C{sub 4}H{sub 4}O aldehyde species that rapidly loses the {alpha} H to form C{sub 4}H{sub 3}O (E{sub a} = 0.40 eV). C{sub 4}H{sub 3}O further dehydrogenates at the {delta} position to form C{sub 4}H{sub 2}O (E{sub a} = 0.83 eV), before the {alpha}-{beta} C-C bond dissociates (E{sub a} = 1.08 eV) to form CO. Each step is the lowest-barrier dissociation step in the respective species. A simple kinetic analysis suggests that furan decomposition begins at 240-270 K and is mostly complete by 320 K, in close agreement with previous experiments. It is suggested that the C{sub 4}H{sub 2}O intermediate delays the decarbonylation step up to 350 K.

  7. Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) at boron doped diamond (BDD) and platinum-iridium anodes.

    PubMed

    Madsen, Henrik Tækker; Søgaard, Erik Gydesen; Muff, Jens

    2014-08-01

    Electrochemical oxidation is a promising technique for degradation of otherwise recalcitrant organic micropollutants in waters. In this study, the applicability of electrochemical oxidation was investigated concerning the degradation of the groundwater pollutant 2,6-dichlorobenzamide (BAM) through the electrochemical oxygen transfer process with two anode materials: Ti/Pt90-Ir10 and boron doped diamond (Si/BDD). Besides the efficiency of the degradation of the main pollutant, it is also of outmost importance to control the formation and fate of stable degradation intermediates. These were investigated quantitatively with HPLC-MS and TOC measurements and qualitatively with a combined HPLC-UV and HPLC-MS protocol. 2,6-Dichlorobenzamide was found to be degraded most efficiently by the BDD cell, which also resulted in significantly lower amounts of intermediates formed during the process. The anodic degradation pathway was found to occur via substitution of hydroxyl groups until ring cleavage leading to carboxylic acids. For the BDD cell, there was a parallel cathodic degradation pathway that occurred via dechlorination. The combination of TOC with the combined HPLC-UV/MS was found to be a powerful method for determining the amount and nature of degradation intermediates.

  8. Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) at boron doped diamond (BDD) and platinum-iridium anodes.

    PubMed

    Madsen, Henrik Tækker; Søgaard, Erik Gydesen; Muff, Jens

    2014-08-01

    Electrochemical oxidation is a promising technique for degradation of otherwise recalcitrant organic micropollutants in waters. In this study, the applicability of electrochemical oxidation was investigated concerning the degradation of the groundwater pollutant 2,6-dichlorobenzamide (BAM) through the electrochemical oxygen transfer process with two anode materials: Ti/Pt90-Ir10 and boron doped diamond (Si/BDD). Besides the efficiency of the degradation of the main pollutant, it is also of outmost importance to control the formation and fate of stable degradation intermediates. These were investigated quantitatively with HPLC-MS and TOC measurements and qualitatively with a combined HPLC-UV and HPLC-MS protocol. 2,6-Dichlorobenzamide was found to be degraded most efficiently by the BDD cell, which also resulted in significantly lower amounts of intermediates formed during the process. The anodic degradation pathway was found to occur via substitution of hydroxyl groups until ring cleavage leading to carboxylic acids. For the BDD cell, there was a parallel cathodic degradation pathway that occurred via dechlorination. The combination of TOC with the combined HPLC-UV/MS was found to be a powerful method for determining the amount and nature of degradation intermediates. PMID:24873711

  9. A study of impurities in intermediates and 3,4-methylenedioxymethamphetamine (MDMA) samples produced via reductive amination routes.

    PubMed

    Gimeno, P; Besacier, F; Bottex, M; Dujourdy, L; Chaudron-Thozet, H

    2005-12-20

    Impurities found in various sources of precursors (sassafras oil, safrol, isosafrol, piperonal), intermediates (beta-nitroisosafrol, piperonylmethylketone (PMK)) and final product (3,4-methylenedioxymethamphetamine (MDMA)) are presented and discussed. Particular attention is paid to the chemical origin of each impurity found in the prepared samples. Impurity profiles of isosafrol, piperonal, and PMK samples obtained from industrial sources or from sassafras oil were first compared. Then PMK samples produced from isosafrol through isosafrol glycol or through beta-nitroisosafrol were compared. At last, attention was paid to the reductive amination of PMK to MDMA using different reductive agents. Possible use of this profiling method to determine the synthesis route is discussed for all products.

  10. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: Entropic sampling study

    NASA Astrophysics Data System (ADS)

    Kamala Latha, B.; Jose, Regina; Murthy, K. P. N.; Sastry, V. S. S.

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence NB-NB1-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases.

  11. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: entropic sampling study.

    PubMed

    Kamala Latha, B; Jose, Regina; Murthy, K P N; Sastry, V S S

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence N(B)-N(B1)-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases.

  12. Studies on the inhibition of sphingosine-1-phosphate lyase by stabilized reaction intermediates and stereodefined azido phosphates.

    PubMed

    Sanllehí, Pol; Abad, José-Luís; Bujons, Jordi; Casas, Josefina; Delgado, Antonio

    2016-11-10

    Two kinds of inhibitors of the PLP-dependent enzyme sphingosine-1-phosphate lyase have been designed and tested on the bacterial (StS1PL) and the human (hS1PL) enzymes. Amino phosphates 1, 12, and 32, mimicking the intermediate aldimines of the catalytic process, were weak inhibitors on both enzyme sources. On the other hand, a series of stereodefined azido phosphates, resulting from the replacement of the amino group of the natural substrates with an azido group, afforded competitive inhibitors in the low micromolar range on both enzyme sources. This similar behavior represents an experimental evidence of the reported structural similarities for both enzymes at their active site level. Interestingly, the anti-isomers of the non-natural enantiomeric series where the most potent inhibitors on hS1PL.

  13. A Comparative Study of Academic Achievement and Problem-Solving Abilities of Black Pupils at the Intermediate Level in Computer-Supported Instruction and Self-Contained Instructional Programs.

    ERIC Educational Resources Information Center

    Nabors, Donald Gene

    The purpose of this study was to make comparisons between intermediate grade black pupils in an individualized, computer-supported instructional program and intermediate grade black pupils who were in a traditional, self-contained classroom instructional program. Specifically, the basic problem was that of determining the extent to which an…

  14. Changes in myocardial cytoskeletal intermediate filaments and myocyte contractile dysfunction in dilated cardiomyopathy: an in vivo study in humans

    PubMed Central

    Di, S; Marotta, M; Salvatore, G; Cudemo, G; Cuda, G; De Vivo, F; Di, B; Ciaramella, F; Caputo, G; de Divitiis, O

    2000-01-01

    AIM—To investigate in vivo the intermediate cytoskeletal filaments desmin and vimentin in myocardial tissues from patients with dilated cardiomyopathy, and to determine whether alterations in these proteins are associated with impaired contractility.
METHODS—Endomyocardial biopsies were performed in 12 patients with dilated cardiomyopathy and in 12 controls (six women with breast cancer before anthracycline chemotherapy and six male donors for heart transplantation). Biopsy specimens were analysed by light microscopy and immunochemistry (desmin, vimentin). Myocyte contractile protein function was evaluated by the actin-myosin in vitro motility assay. Left ventricular ejection fraction was assessed by echocardiography and radionuclide ventriculography.
RESULTS—Patients with dilated cardiomyopathy had a greater cardiomyocyte diameter than controls (p < 0.01). The increase in cell size was associated with a reduction in contractile function, as assessed by actin-myosin motility (r = −0.643; p < 0.01). Quantitative immunochemistry showed increased desmin and vimentin contents (p < 0.01), and the desmin distribution was disturbed in cardiomyopathy. There was a linear relation between desmin distribution and actin-myosin sliding in vitro (r = 0.853; p < 0.01) and an inverse correlation between desmin content and ejection fraction (r = −0.773; p < 0.02). Negative correlations were also found between myocardial vimentin content and the actin-myosin sliding rate (r = −0.74; p < 0.02) and left ventricular ejection fraction (r = −0.68; p < 0.01).
CONCLUSIONS—Compared with normal individuals, the myocardial tissue of patients with dilated cardiomyopathy shows alterations of cytoskeletal intermediate filament distribution and content associated with reduced myocyte contraction.


Keywords: dilated cardiomyopathy; desmin; vimentin; cardiac biopsy; actin-myosin PMID:11083750

  15. Assessment of site conditions for disposal of low- and intermediate-level radioactive wastes: a case study in southern China.

    PubMed

    Yi, Shuping; Ma, Haiyi; Zheng, Chunmiao; Zhu, Xiaobin; Wang, Hua'an; Li, Xueshan; Hu, Xueling; Qin, Jianbo

    2012-01-01

    Near surface disposal of low- and intermediate-level radioactive wastes (LILW) requires evaluating the field conditions of the candidate site. However, assessment of the site conditions may be challenging due to the limited prior knowledge of some remote sites, and various multi-disciplinary data requirements at any given site. These situations arise in China as in the rest of the industrialized world, particularly since a regional strategy for LILW disposal has been implemented to protect humans and the environment. This paper presents a demonstration of the site assessment process through a case study focusing mainly on the geologic, hydrogeologic and geochemical characteristics of the candidate site. A joint on-site and laboratory investigation, supplemented by numerical modeling, was implemented in this assessment. Results indicate that no fault is present in the site area, although there are some minor joints and fractures, primarily showing a north-south trend. Most of the joints are filled with quartz deposits and would thus function hydraulically as impervious barriers. Investigation of local hydrologic boundaries has shown that the candidate site represents an essentially isolated hydrogeologic unit, and that little or no groundwater flow occurs across its boundaries on the north or east, or across the hilly areas to the south. Groundwater in the site area is recharged by precipitation and discharges primarily by evapo-transpiration and surface flow through a narrow outlet to the west. Groundwater flows slowly from the hilly area to the foot of the hills and discharges mainly into the inner brooks and marshes. Some groundwater circulates in deeper granite in a slower manner. The vadose zone in the site was investigated specially for their significant capability for restraining the transport of radionuclides. Results indicate that the vadose zone is up to 38m in thickness and is made up of alluvial clay soils and very highly weathered granite. The vadose

  16. Spinodal decomposition in Fe-Cr alloys: Experimental study at the atomic level and comparison with computer models. 2: Development of domain size and composition amplitude

    SciTech Connect

    Hyde, J.M.; Hetherington, M.G.; Cerezo, A.; Smith, G.D.W.; Miller, M.K.; Elliott, C.M.

    1995-09-01

    The three-dimensional interconnected microstructures resulting from spinodal decomposition in a series of thermally aged Fe-Cr alloys have been analyzed in terms of scale and composition amplitude. The development of the microstructure scale was found to fit a power law with a time exponent considerably smaller than that predicted by the LSW theory but in agreement with Monte Carlo simulations of the decomposition. Numerical solutions to the classical non-linear Cahn-Hilliard-Cook equation were found to fit the classical LSW theory. A model, based on the non-linear theory of spinodal decomposition by Langer et al. is used to quantify the composition amplitude at any stage of the phase separation. A detailed comparison between the atomic scale experimental results and computer simulations of spinodal decomposition is given.

  17. In Situ XAS of the Solvothermal Decomposition of Dithiocarbamate Complexes

    NASA Astrophysics Data System (ADS)

    Islam, Husn-Ubayda; Roffey, Anna; Hollingsworth, Nathan; Catlow, Richard; Wolthers, Mariette; De Leeuw, Nora; Bras, Wim; Sankar, Gopinathan; Hogarth, Graeme

    2013-04-01

    An in situ XAS study of the solvothermal decomposition of iron and nickel dithiocarbamate complexes was performed in order to gain understanding of the decomposition mechanisms. This work has given insight into the steps involved in the decomposition, showing variation in reaction pathways between the iron and nickel dithiocarbamates, and the non-innocent role of oleylamine as the solvent and capping agent in the reaction.

  18. Adaptive autoregressive identification with spectral power decomposition for studying movement-related activity in scalp EEG signals and basal ganglia local field potentials

    NASA Astrophysics Data System (ADS)

    Foffani, Guglielmo; Bianchi, Anna M.; Priori, Alberto; Baselli, Giuseppe

    2004-09-01

    We propose a method that combines adaptive autoregressive (AAR) identification and spectral power decomposition for the study of movement-related spectral changes in scalp EEG signals and basal ganglia local field potentials (LFPs). This approach introduces the concept of movement-related poles, allowing one to study not only the classical event-related desynchronizations (ERD) and synchronizations (ERS), which correspond to modulations of power, but also event-related modulations of frequency. We applied the method to analyze movement-related EEG signals and LFPs contemporarily recorded from the sensorimotor cortex, the globus pallidus internus (GPi) and the subthalamic nucleus (STN) in a patient with Parkinson's disease who underwent stereotactic neurosurgery for the implant of deep brain stimulation (DBS) electrodes. In the AAR identification we compared the whale and the exponential forgetting factors, showing that the whale forgetting provides a better disturbance rejection and it is therefore more suitable to investigate movement-related brain activity. Movement-related power modulations were consistent with previous studies. In addition, movement-related frequency modulations were observed from both scalp EEG signals and basal ganglia LFPs. The method therefore represents an effective approach to the study of movement-related brain activity.

  19. [Studies of target fragmentation in intermediate energy, relativistic and ultra-relativistic nuclear collisions]. Nuclear chemistry progress report, August 1, 1990--August 1, 1991

    SciTech Connect

    Loveland, W.D.

    1991-08-01

    The work described herein is part of a project involving the study of low energy (< 10 MeV/A), intermediate energy (10--100 MeV/A) and relativistic (> 250 MeV/A) heavy ion reactions. In the low energy regime, we published a monograph on the properties of the heaviest elements and used that publication as a basis for making a set of ``best`` semi-empirical predictions of heavy element decay properties. The intermediate energy research effort focussed upon the completion of studies already begun and the initiation of a number of new experiments. In our study of a interaction of 21 MeV/nucleon {sup 129}Xe with {sup 197}Au, we compared the characteristics of the observed deep inelastic phenomena with various models of dissipative reactions and found significant discrepancies between observations and predictions. These discrepancies seemed to be caused by an improper treatment of pre-equilibrium in the early stages of the collision. In our study of the relativistic interaction of 400 MeV/nucleon {sup 12}C with {sup 197}Au, we reported the first direct physical measurement of the properties of the spallation residues from a nucleus-nucleus collision. We found the residue energies to be much lower than those predicted by the intranuclear cascade model, indicating some substantial modifications of that model are needed. But, we also found, indications of significant, non-zero values of the residue transverse momentum, a finding that calls into question the interpretation of a number of radiochemical recoil studies of the kinematics of high energy reactions. A program of performing numerical simulations of intermediate and high energy nuclear collisions using the QMD model was initiated.

  20. Multicomponent kinetic analysis and theoretical studies on the phenolic intermediates in the oxidation of eugenol and isoeugenol catalyzed by laccase.

    PubMed

    Qi, Yan-Bing; Wang, Xiao-Lei; Shi, Ting; Liu, Shuchang; Xu, Zhen-Hao; Li, Xiqing; Shi, Xuling; Xu, Ping; Zhao, Yi-Lei

    2015-11-28

    Laccase catalyzes the oxidation of natural phenols and thereby is believed to initialize reactions in lignification and delignification. Numerous phenolic mediators have also been applied in laccase-mediator systems. However, reaction details after the primary O-H rupture of phenols remain obscure. In this work two types of isomeric phenols, EUG (eugenol) and ISO (trans-/cis-isoeugenol), were used as chemical probes to explore the enzymatic reaction pathways, with the combined methods of time-resolved UV-Vis absorption spectra, MCR-ALS, HPLC-MS, and quantum mechanical (QM) calculations. It has been found that the EUG-consuming rate is linear to its concentration, while the ISO not. Besides, an o-methoxy quinone methide intermediate, (E/Z)-4-allylidene-2-methoxycyclohexa-2,5-dienone, was evidenced in the case of EUG with the UV-Vis measurement, mass spectra and TD-DFT calculations; in contrast, an ISO-generating phenoxyl radical, a (E/Z)-2-methoxy-4-(prop-1-en-1-yl) phenoxyl radical, was identified in the case of ISO. Furthermore, QM calculations indicated that the EUG-generating phenoxyl radical (an O-centered radical) can easily transform into an allylic radical (a C-centered radical) by hydrogen atom transfer (HAT) with a calculated activation enthalpy of 5.3 kcal mol(-1) and then be fast oxidized to the observed eugenol quinone methide, rather than an O-radical alkene addition with barriers above 12.8 kcal mol(-1). In contrast, the ISO-generating phenoxyl radical directly undergoes a radical coupling (RC) process, with a barrier of 4.8 kcal mol(-1), while the HAT isomerization between O- and C-centered radicals has a higher reaction barrier of 8.0 kcal mol(-1). The electronic conjugation of the benzyl-type radical and the aromatic allylic radical leads to differentiation of the two pathways. These results imply that competitive reaction pathways exist for the nascent reactive intermediates generated in the laccase-catalyzed oxidation of natural phenols, which is