A Silica-Supported Iron Oxide Catalyst Capable of Activating Hydrogen Peroxide at Neutral pH Values

PubMed Central

Pham, Anh Le-Tuan; Lee, Changha; Doyle, Fiona M.; Sedlak, David L.

2009-01-01

Iron oxides catalyze the conversion of hydrogen peroxide (H2O2) into oxidants capable of transforming recalcitrant contaminants. Unfortunately, the process is relatively inefficient at circumneutral pH values due to competing reactions that decompose H2O2 without producing oxidants. Silica- and alumina-containing iron oxides prepared by sol-gel processing of aqueous solutions containing Fe(ClO4)3, AlCl3 and tetraethyl orthosilicate efficiently catalyzed the decomposition of H2O2 into oxidants capable of transforming phenol at circumneutral pH values. Relative to hematite, goethite and amorphous FeOOH, the silica-iron oxide catalyst exhibited a stoichiometric efficiency, defined as the number of moles of phenol transformed per mole of H2O2 consumed, that was 10 to 40 times higher than that of the iron oxides. The silica-alumina-iron oxide catalyst had a stoichiometric efficiency that was 50 to 80 times higher than that of the iron oxides. The significant enhancement in oxidant production is attributable to the interaction of Fe with Al and Si in the mixed oxides, which alters the surface redox processes, favoring the production of strong oxidants during H2O2 decomposition. PMID:19943668

Possibility of H2O2 decomposition in thin liquid films on Mars

NASA Astrophysics Data System (ADS)

Kereszturi, Akos; Gobi, Sandor

2014-11-01

In this work the pathways and possibilities of H2O2 decomposition on Mars in microscopic liquid interfacial water were analyzed by kinetic calculations. Thermal and photochemical driven decomposition, just like processes catalyzed by various metal oxides, is too slow compared to the annual duration while such microscopic liquid layers exist on Mars today, to produce substantial decomposition. The most effective analyzed process is catalyzed by Fe ions, which could decompose H2O2 under pH<4.5 with a half life of 1-2 days. This process might be important during volcanically influenced periods when sulfur release produces acidic pH, and rotational axis tilt change driven climatic changes also influence the volatile circulation and spatial occurrence just like the duration of thin liquid layer. Under current conditions, using the value of 200 K as the temperature in interfacial water (at the southern hemisphere), and applying Phoenix lander's wet chemistry laboratory results, the pH is not favorable for Fe mobility and this kind of decomposition. Despite current conditions (especially pH) being unfavorable for H2O2 decomposition, microscopic scale interfacial liquid water still might support the process. By the reaction called heterogeneous catalysis, without acidic pH and mobile Fe, but with minerals surfaces containing Fe decomposition of H2O2 with half life of 20 days can happen. This duration is still longer but not several orders than the existence of springtime interfacial liquid water on Mars today. This estimation is relevant for activation energy controlled reaction rates. The other main parameter that may influence the reaction rate is the diffusion speed. Although the available tests and theoretical calculations do not provide firm values for the diffusion speed in such a “2-dimensional” environment, using relevant estimations this parameter in the interfacial liquid layer is smaller than in bulk water. But the 20 days' duration mentioned above is still relevant, as the activation energy driven reaction rate is the main limiting factor in the decomposition and not the diffusion speed. The duration of dozen(s) days is still longer but not with orders of magnitude than the expected duration for the existence of springtime interfacial liquid water on Mars today. The results suggest such decomposition may happen today, however, because of our limited knowledge on chemical processes in thin interfacial liquid layers, this possibility waits for confirmation - and also points to the importance of conducting laboratory tests to validate the possible process. Although some tests were already realized for diffusion in an almost 2-dimensional liquid, the same is not true for activation energy, where only the value from the “normal” measurements was applied. Even if H2O2 decomposition is too slow today, the analysis of such a process is important, as under volcanic influence more effective decomposition might take place in thin interfacial liquids close to the climate of today if released sulfur produces pH<4.5. Large quantity and widespread occurrence of bulk liquid phase are not expected in the Amazonian period, but interfacial liquid water probably appeared regularly, and its locations, especially during volcanically active periods, might make certain sites than others more interesting for astrobiology with the lower concentration of oxidizing H2O2.

Solid state green synthesis and catalytic activity of CuO nanorods in thermal decomposition of potassium periodate

NASA Astrophysics Data System (ADS)

Patel, Vinay Kumar; Bhattacharya, Shantanu

2017-09-01

The present study reports a facile solid state green synthesis process using the leaf extracts of Hibiscus rosa-sinensis to synthesize CuO nanorods with average diameters of 15-20 nm and lengths up to 100 nm. The as-synthesized CuO nanorods were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and selected area electron diffraction. The formation mechanism of CuO nanorods has been explained by involving the individual role of amide I (amino groups) and carboxylate groups under excess hydroxyl ions released from NaOH. The catalytic activity of CuO nanorods in thermal decomposition of potassium periodate microparticles (µ-KIO4) microparticles was studied by thermo gravimetric analysis measurement. The original size (~100 µm) of commercially procured potassium periodate was reduced to microscale length scale to about one-tenth by PEG200 assisted emulsion process. The CuO nanorods prepared by solid state green route were found to catalyze the thermal decomposition of µ-KIO4 with a reduction of 18 °C in the final thermal decomposition temperature of potassium periodate.

Synthesis of polycrystalline Co{sub 3}O{sub 4} nanowires with excellent ammonium perchlorate catalytic decomposition property

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

Zhou, Hai; University of Chinese Academy of Sciences, Beijing 100049; Lv, Baoliang, E-mail: lbl604@sxicc.ac.cn

2014-12-15

Graphical abstract: Co{sub 3}O{sub 4} nanowires with excellent ammonium perchlorate catalytic decomposition property were synthesized via a methanamide-assisted hydrolysis and subsequent dissolution–recrystallization process in the presence of methanamide. - Abstract: Co{sub 3}O{sub 4} nanowires, with the length of tens of micrometers and the width of several hundred nanometers, were produced by a hydrothermal treatment and a post-anneal process. X-ray diffraction (XRD) result showed that the Co{sub 3}O{sub 4} nanowires belong to cubic crystal system. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analysis indicated that the Co{sub 3}O{sub 4} nanowires, composed by single crystalline nanoparticles, were of polycrystallinemore » nature. On the basis of time-dependent experiments, methanamide-assisted hydrolysis and subsequent dissolution–recrystallization process were used to explain the precursors' formation process of the polycrystalline Co{sub 3}O{sub 4} nanowires. The TGA experiments showed that the as-obtained Co{sub 3}O{sub 4} nanowires can catalyze the thermal decomposition of ammonium perchlorate (AP) effectively.« less

Demonstration of base catalyzed decomposition process, Navy Public Works Center, Guam, Mariana Islands

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

Schmidt, A.J.; Freeman, H.D.; Brown, M.D.

1996-02-01

Base Catalyzed Decomposition (BCD) is a chemical dehalogenation process designed for treating soils and other substrate contaminated with polychlorinated biphenyls (PCB), pesticides, dioxins, furans, and other hazardous organic substances. PCBs are heavy organic liquids once widely used in industry as lubricants, heat transfer oils, and transformer dielectric fluids. In 1976, production was banned when PCBs were recognized as carcinogenic substances. It was estimated that significant quantities (one billion tons) of U.S. soils, including areas on U.S. military bases outside the country, were contaminated by PCB leaks and spills, and cleanup activities began. The BCD technology was developed in response tomore » these activities. This report details the evolution of the process, from inception to deployment in Guam, and describes the process and system components provided to the Navy to meet the remediation requirements. The report is divided into several sections to cover the range of development and demonstration activities. Section 2.0 gives an overview of the project history. Section 3.0 describes the process chemistry and remediation steps involved. Section 4.0 provides a detailed description of each component and specific development activities. Section 5.0 details the testing and deployment operations and provides the results of the individual demonstration campaigns. Section 6.0 gives an economic assessment of the process. Section 7.0 presents the conclusions and recommendations form this project. The appendices contain equipment and instrument lists, equipment drawings, and detailed run and analytical data.« less

BASE-CATALYZED DESTRUCTION OF PCBS-NEW DONORS, NEW TRANSFER AGENTS/CATALYSTS

EPA Science Inventory

The use of hydrogen transfer agents and catalysts to improve the base-catalyzed decomposition of polychlorinated biphenyls (PCBs) was investigated. The reaction proceeded only in the presence of base, but the rate of PCB disappearance increased with increasing amount of hydrogen ...

Spectral studies related to dissociation of HBr, HCl and BrO

NASA Technical Reports Server (NTRS)

Ginter, M. L.

1986-01-01

Concern over halogen catalyzed decomposition of O3 in the upper atmosphere has generated need for data on the atomic and molecular species X, HX and XO (where X is Cl and Br). Of special importance are Cl produced from freon decomposition and Cl and Br produced from natural processes and from other industrial and agricultural chemicals. Basic spectral data is provided on HCl, HBr, and BrO necessary to detect specific states and energy levels, to enable detailed modeling of the processes involving molecular dissociation, ionization, etc., and to help evaluate field experiments to check the validity of model calculations for these species in the upper atmosphere. Results contained in four published papers and two major spectral compilations are summarized together with other results obtained.

Synthesis of graphene by cobalt-catalyzed decomposition of methane in plasma-enhanced CVD: Optimization of experimental parameters with Taguchi method

NASA Astrophysics Data System (ADS)

Mehedi, H.-A.; Baudrillart, B.; Alloyeau, D.; Mouhoub, O.; Ricolleau, C.; Pham, V. D.; Chacon, C.; Gicquel, A.; Lagoute, J.; Farhat, S.

2016-08-01

This article describes the significant roles of process parameters in the deposition of graphene films via cobalt-catalyzed decomposition of methane diluted in hydrogen using plasma-enhanced chemical vapor deposition (PECVD). The influence of growth temperature (700-850 °C), molar concentration of methane (2%-20%), growth time (30-90 s), and microwave power (300-400 W) on graphene thickness and defect density is investigated using Taguchi method which enables reaching the optimal parameter settings by performing reduced number of experiments. Growth temperature is found to be the most influential parameter in minimizing the number of graphene layers, whereas microwave power has the second largest effect on crystalline quality and minor role on thickness of graphene films. The structural properties of PECVD graphene obtained with optimized synthesis conditions are investigated with Raman spectroscopy and corroborated with atomic-scale characterization performed by high-resolution transmission electron microscopy and scanning tunneling microscopy, which reveals formation of continuous film consisting of 2-7 high quality graphene layers.

Synthesis of graphene by cobalt-catalyzed decomposition of methane in plasma-enhanced CVD: Optimization of experimental parameters with Taguchi method

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

Mehedi, H.-A.; Baudrillart, B.; Gicquel, A.

2016-08-14

This article describes the significant roles of process parameters in the deposition of graphene films via cobalt-catalyzed decomposition of methane diluted in hydrogen using plasma-enhanced chemical vapor deposition (PECVD). The influence of growth temperature (700–850 °C), molar concentration of methane (2%–20%), growth time (30–90 s), and microwave power (300–400 W) on graphene thickness and defect density is investigated using Taguchi method which enables reaching the optimal parameter settings by performing reduced number of experiments. Growth temperature is found to be the most influential parameter in minimizing the number of graphene layers, whereas microwave power has the second largest effect on crystalline qualitymore » and minor role on thickness of graphene films. The structural properties of PECVD graphene obtained with optimized synthesis conditions are investigated with Raman spectroscopy and corroborated with atomic-scale characterization performed by high-resolution transmission electron microscopy and scanning tunneling microscopy, which reveals formation of continuous film consisting of 2–7 high quality graphene layers.« less

Degradation of Perfluorooctanoic Acid and Perfluoroctane Sulfonate by Enzyme Catalyzed Oxidative Humification Reactions

NASA Astrophysics Data System (ADS)

Huang, Q.

2016-12-01

Poly- and perfluoroalkyl substances (PFASs) are alkyl based chemicals having multiple or all hydrogens replaced by fluorine atoms, and thus exhibit high thermal and chemical stability and other unusual characteristics. PFASs have been widely used in a wide variety of industrial and consumer products, and tend to be environmentally persistent. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are two representative PFASs that have drawn particular attention because of their ubiquitous presence in the environment, resistance to degradation and toxicity to animals. This study examined the decomposition of PFOA and PFOS in enzyme catalyzed oxidative humification reactions (ECOHR), a class of reactions that are ubiquitous in the environment involved in natural organic humification. Reaction rates and influential factors were examined, and high-resolution mass spectrometry was used to identify possible products. Fluorides and partially fluorinated compounds were identified as likely products from PFOA and PFOS degradation, which were possibly formed via a combination of free radical decomposition, rearrangements and coupling processes. The findings suggest that PFOA and PFOS may be transformed during humification, and ECOHR can potentially be used for the remediation of these chemicals.

Demonstration of the Catalytic Decomposition of Hydrogen Peroxide.

ERIC Educational Resources Information Center

Conklin, Alfred R. Jr.; Kessinger, Angela

1996-01-01

Describes a demonstration known as Elephant's Toothpaste in which the decomposition of hydrogen peroxide is catalyzed by iodide. Oxygen is released and soap bubbles are produced. The foam produced is measured, and results show a good relationship between the amount of foam and the concentration of the hydrogen peroxide. (DDR)

Nickel-catalyzed asymmetric α-arylation and heteroarylation of ketones with chloroarenes: effect of halide on selectivity, oxidation state, and room-temperature reactions.

PubMed

Ge, Shaozhong; Hartwig, John F

2011-10-19

We report the α-arylation of ketones with a range of aryl chlorides with enantioselectivities from 90 to 99% ee catalyzed by the combination of Ni(COD)(2) and (R)-BINAP and the coupling of ketones with a range of heteroaryl chlorides with enantioselectivities up to 99% ee catalyzed by Ni(COD)(2) and (R)-DIFLUORPHOS. The analogous reactions of bromoarenes occur with much lower enantioselectivities. Mechanistic studies showed that the difference in the rates of decomposition of the arylnickel(II) halide intermediates to {[(R)-BINAP]NiX}(2) likely accounts for the difference in the enantioselectivities of the reactions of bromoarenes and chloroarenes. This catalyst decomposition can be overcome by conducting the reactions with [(R)-BINAP]Ni(η(2)-NC-Ph) (4), which undergoes oxidative addition to haloarenes at room temperature.

Dinitrosyl iron complexes and S-nitrosothiols are two possible forms for stabilization and transport of nitric oxide in biological systems.

PubMed

Vanin, A F

1998-07-01

The physicochemical properties, mechanisms of synthesis and decomposition of dinitrosyl iron complexes (DNICs) with thiol-containing ligands and of S-nitrosothiols (RS-NO), and the potential role of these compounds in storage and transport of NO in biological systems are reviewed. Special attention is given to the phenomenon of mutual transformation of DNIC and RS-NO catalyzed by Fe2+. Each Fe2+ binds two neutral NO molecules in the DNICs, catalyzes their mutual oxidation--reduction with formation of nitrous oxide and nitrosonium ions appearing in the DNICs. These ions S-nitrosate thiol-compounds with RS-NO formation. Fe2+ binds two RS-NO molecules and catalyzes their mutual oxidation--reduction followed by decomposition of the resulting molecules. Mutual conversion of DNICs and RS-NO regulated by iron, thiol, and NO levels is suggested to provide NO transport in cells and tissues.

Behaviors of glucose decomposition during acid-catalyzed hydrothermal hydrolysis of pretreated Gelidium amansii.

PubMed

Jeong, Tae Su; Choi, Chang Ho; Lee, Ji Ye; Oh, Kyeong Keun

2012-07-01

Acid-catalyzed hydrothermal hydrolysis is one path to cellulosic glucose and subsequently to its dehydration end products such as hydroxymethyl furfural (HMF), formic acid and levulinic acid. The effect of sugar decomposition not only lowers the yield of fermentable sugars but also forms decomposition products that inhibit subsequent fermentation. The present experiments were conducted with four different acid catalysts (H(2)SO(4), HNO(3), HCl, and H(3)PO(4)) at various acid normalities (0.5-2.1N) in batch reactors at 180-210 °C. From the results, H(2)SO(4) was the most suitable catalyst for glucose production, but glucose decomposition occurred during the hydrolysis. The glucose production was maximized at 160.7 °C, 2.0% (w/v) H(2)SO(4), and 40 min, but resulted in a low glucan yield of 33.05% due to the decomposition reactions, which generated formic acid and levulinic acid. The highest concentration of levulinic acid, 7.82 g/L, was obtained at 181.2 °C, 2.0% (w/v) H(2)SO(4), and 40 min. Copyright © 2012 Elsevier Ltd. All rights reserved.

Microorganisms detected by enzyme-catalyzed reaction

NASA Technical Reports Server (NTRS)

Vango, S. P.; Weetall, H. H.; Weliky, N.

1966-01-01

Enzymes detect the presence of microorganisms in soils. The enzyme lysozymi is used to release the enzyme catalase from the microorganisms in a soil sample. The catalase catalyzes the decomposition of added hydrogen peroxide to produce oxygen which is detected manometrically. The partial pressure of the oxygen serves as an index of the samples bacteria content.

Occurrence and Characteristics of a Rapid Exchange of Phosphate Oxygens Catalyzed by Sarcoplasmic Reticulum Vesicles

DOE R&D Accomplishments Database

Kanazawa, T.; Boyer, P. D.

1972-01-01

Sarcoplasmic reticulum vesicles isolated from skeletal muscle actively take up Ca{sup ++} from the medium in the presence of Mg{sup ++} and ATP. This transport is coupled to ATP hydrolysis catalyzed by membrane-bound Ca{sup++}, Mg{sup ++}-ATPase which is activated by concurrent presence of Ca{sup ++} and Mg{sup ++}. Considerable informations have accumulated that give insight into the ATPase and its coupling to the calcium transport. The hydrolysis of ATP by this enzyme occurs through a phosphorylated intermediate. Formation and decomposition of the intermediate show vectorial requirements for Ca{sup ++} and Mg{sup ++}, suggesting an intimate involvement of the intermediate in the transport process. ATP synthesis from P{sub i} and ADP coupled to outflow of Ca{sup ++} from sarcoplasmic reticulum vesicles has recently been demonstrated. This indicates the reversibility of the entire process of calcium transport in sarcoplasmic reticulum vesicles.

Energy Diagram for the Catalytic Decomposition of Hydrogen Peroxide

ERIC Educational Resources Information Center

Tatsuoka, Tomoyuki; Koga, Nobuyoshi

2013-01-01

Drawing a schematic energy diagram for the decomposition of H[subscript 2]O[subscript 2] catalyzed by MnO[subscript 2] through a simple thermometric measurement outlined in this study is intended to integrate students' understanding of thermochemistry and kinetics of chemical reactions. The reaction enthalpy, delta[subscript r]H, is…

Towards a paradigm shift in the modeling of soil organic carbon decomposition for earth system models

NASA Astrophysics Data System (ADS)

He, Yujie

Soils are the largest terrestrial carbon pools and contain approximately 2200 Pg of carbon. Thus, the dynamics of soil carbon plays an important role in the global carbon cycle and climate system. Earth System Models are used to project future interactions between terrestrial ecosystem carbon dynamics and climate. However, these models often predict a wide range of soil carbon responses and their formulations have lagged behind recent soil science advances, omitting key biogeochemical mechanisms. In contrast, recent mechanistically-based biogeochemical models that explicitly account for microbial biomass pools and enzyme kinetics that catalyze soil carbon decomposition produce notably different results and provide a closer match to recent observations. However, a systematic evaluation of the advantages and disadvantages of the microbial models and how they differ from empirical, first-order formulations in soil decomposition models for soil organic carbon is still needed. This dissertation consists of a series of model sensitivity and uncertainty analyses and identifies dominant decomposition processes in determining soil organic carbon dynamics. Poorly constrained processes or parameters that require more experimental data integration are also identified. This dissertation also demonstrates the critical role of microbial life-history traits (e.g. microbial dormancy) in the modeling of microbial activity in soil organic matter decomposition models. Finally, this study surveys and synthesizes a number of recently published microbial models and provides suggestions for future microbial model developments.

A comparative evaluation of explosion hazards in chemical and mechanical pulp bleaching systems

Treesearch

P.W. Hart; Alan Rudie

2010-01-01

Three pulp mills in North America using 50% hydrogen peroxide have suffered explosions of pumps, mixers, and tanks. In two instances, alkali-catalyzed decomposition of peroxide is implicated in the explosion. Although many mechanical pulping facilities use hydrogen peroxide to bleach pulp, no &-catalyzed explosions have been reported. This research uses a kinetic...

Proceedings of International Pyrotechnics Seminar (4th), Held at Steamboat Village, Colorado, 22-26 July 1974

DTIC Science & Technology

1974-06-17

10-1 I1. Burning Rate Modifiers, D.R. Dillehay ............................. 11-1 12. Spectroscopic Analysis of Azide Decomposition Products for use...solid, and Pit that they ignite a short distance from the surface. Further- more, decomposition of sodium nitrate, which produces the gas to blow the...decreasing U the thermal conductivity of the basic binary. Class 2 compounds, con- sisting of nanganese oxides, catalyze the normal decomposition of

Highly efficient and stable catalyst for peroxynitrite decomposition

Treesearch

Yurii V. Geletii; Alan J. Bailey; Jennifer J. Cowan; Ira A. Weinstock; Craig L. Hill

2001-01-01

The new cobalt substituted-polyoxometalate K7[CoAlW11O39]•15H2O and the simple CoCl2•6H2O salt are efficient catalysts for peroxynitrite decomposition. These compounds also catalyze the oxidation of ascorbic acid and the nitration of phenol by peroxynitrite.

Toward a Better Quantitative Understanding of Polar Stratospheric Ozone Loss

NASA Technical Reports Server (NTRS)

Frieler, K.; Rex, M.; Salawitch, R. J.; Canty, T.; Streibel, M.; Stimpfle, R. M.; Pfeilsticker, K.; Dorf, M.; Weisenstein, D. K.; Godin-Beekmann, S.

2006-01-01

Previous studies have shown that observed large O3 loss rates in cold Arctic Januaries cannot be explained with current understanding of the loss processes, recommended reaction kinetics, and standard assumptions about total stratospheric chlorine and bromine. Studies based on data collected during recent field campaigns suggest faster rates of photolysis and thermal decomposition of ClOOCl and higher stratospheric bromine concentrations than previously assumed. We show that a model accounting for these kinetic changes and higher levels of BrO can largely resolve the January Arctic O3 loss problem and closely reproduces observed Arctic O3 loss while being consistent with observed levels of ClO and ClOOCl. The model also suggests that bromine catalyzed O3 loss is more important relative to chlorine catalyzed loss than previously thought.

Apparatus for hydrogen and carbon production via carbon aerosol-catalyzed dissociation of hydrocarbons

NASA Technical Reports Server (NTRS)

Tabatabaie-Raissi, Ali (Inventor); Muradov, Nazim Z. (Inventor); Smith, Franklyn (Inventor)

2012-01-01

A novel process and apparatus is disclosed for sustainable, continuous production of hydrogen and carbon by catalytic dissociation or decomposition of hydrocarbons at elevated temperatures using in-situ generated carbon particles. Carbon particles are produced by decomposition of carbonaceous materials in response to an energy input. The energy input can be provided by at least one of a non-oxidative and oxidative means. The non-oxidative means of the energy input includes a high temperature source, or different types of plasma, such as, thermal, non-thermal, microwave, corona discharge, glow discharge, dielectric barrier discharge, or radiation sources, such as, electron beam, gamma, ultraviolet (UV). The oxidative means of the energy input includes oxygen, air, ozone, nitrous oxide (NO.sub.2) and other oxidizing agents. The method, apparatus and process of the present invention is applicable to any gaseous or liquid hydrocarbon fuel and it produces no or significantly less CO.sub.2 emissions compared to conventional processes.

Rhodium enalcarbenoids: direct synthesis of indoles by rhodium(II)-catalyzed [4+2] benzannulation of pyrroles.

PubMed

Dawande, Sudam Ganpat; Kanchupalli, Vinaykumar; Kalepu, Jagadeesh; Chennamsetti, Haribabu; Lad, Bapurao Sudam; Katukojvala, Sreenivas

2014-04-14

Disclosed herein is the design of an unprecedented electrophilic rhodium enalcarbenoid which results from rhodium(II)-catalyzed decomposition of a new class of enaldiazo compounds. The synthetic utility of these enalcarbenoids has been successfully demonstrated in the first transition-metal-catalyzed [4+2] benzannulation of pyrroles, thus leading to substituted indoles. The new benzannulation has been applied to the efficient synthesis of the natural product leiocarpone as well as a potent adipocyte fatty-acid binding protein inhibitor. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pt and Pd catalyzed oxidation of Li 2O 2 and DMSO during Li–O 2 battery charging

DOE PAGES

Gittleson, Forrest S.; Ryu, Won-Hee; Schwab, Mark; ...

2016-01-01

Rechargeable Li-O 2 and Li-air batteries require electrode and electrolyte materials that synergistcally promote long-term cell operation. We investigate the role of noble metals Pt and Pd as catalysts for the Li-O 2 oxidation process and their compatibility with a dimethyl sulfoxide (DMSO) based electrolyte. Lastly, we identify a basis for low potential Li 2O 2 evolution followed by oxidative decomposition of the electrolyte to form carbonate side products.

Nitrosonium-Catalyzed Decomposition of S-Nitrosothiols in Solution

PubMed Central

Zhao, Yi-Lei; McCarren, Patrick R.; Houk, K. N.; Choi, Bo Yoon; Toone, Eric J.

2008-01-01

The decomposition of S-nitrosothiols (RSNO) in solution under oxidative conditions is significantly faster than can be accounted for by homolysis of the S-N bond. Here we propose a cationic chain mechanism in which nitrosylation of nitrosothiol produces a nitrosylated cation that, in turn, reacts with a second nitrosothiol to produce disulfide and the NO dimer. Nitrosylated dimer acts as a source of nitrosonium for nitrosothiol nitrosylation, completing the catalytic cycle. The mechanism accounts for several unexplained facets of nitrosothiol chemistry in solution, including the observation that the decomposition of an RSNO is accelerated by O2, mixtures of O2 and NO, and other oxidants, that decomposition is inhibited by thiols and other antioxidants, that decomposition is dependent on sulfur substitution, and that decomposition often shows non-integral kinetic orders. PMID:16076198

STUDIES OF HALOGENATED HYDROCARBONS. PART 1 - STABILITY OF FLUOROCARBONS IN AIR OVER HOPCALITE CATALYST OR STAINLESS STEEL

DTIC Science & Technology

A study was made of the catalytic decomposition of a number of fluorine-containing halogenated hydrocarbons in air, using Hopcalite catalyst in a... Hopcalite catalyst had no significant effect on the rate of decomposition of the chlorofluorocarbons. Sulfur hexafluoride in air was stable over Hopcalite ...as those of nuclear submarines. Where they are needed, as in refrigeration systems, it is recommended that R-114, R-14, or R-12 be used since they show the greatest resistance to Hopcalite -catalyzed decomposition.

Biochemical characterization of a novel tyrosine phenol-lyase from Fusobacterium nucleatum for highly efficient biosynthesis of l-DOPA.

PubMed

Zheng, Ren-Chao; Tang, Xiao-Ling; Suo, Hui; Feng, Li-Lin; Liu, Xiao; Yang, Jian; Zheng, Yu-Guo

2018-05-01

Tyrosine phenol-lyase (TPL) catalyzes the reversible cleavage of l-tyrosine to phenol, pyruvate and ammonia. When pyrocatechol is substituted for phenol, l-dihydroxyphenylalanine (l-DOPA) is produced. The TPL-catalyzed route was regarded as the most economic process for l-DOPA production. In this study, a novel TPL from Fusobacterium nucleatum (Fn-TPL) was successfully overexpressed in Escherichia coli and screened for l-DOPA synthesis with a specific activity of 2.69Umg -1 . Fn-TPL was found to be a tetramer, and the optimal temperature and pH for α, β-elimination of l-tyrosine was 60°C and pH 8.5, respectively. The enzyme showed broad substrate specificity toward natural and synthetic l-amino acids. Kinetic analysis suggested that the k cat /K m value for l-tyrosine decomposition was much higher than that for l-DOPA decomposition, while Fn-TPL exhibited similar catalytic efficiency for synthesis of l-tyrosine and l-DOPA. With whole cells of recombinant E. coli as biocatalyst, l-DOPA yield reached 110gL -1 with a pyrocatechol conversion of 95%, which was comparable to the reported highest level. The results demonstrated the great potential of Fn-TPL for industrial production of l-DOPA. Copyright © 2017 Elsevier Inc. All rights reserved.

Nitrosonium-catalyzed decomposition of s-nitrosothiols in solution: a theoretical and experimental study.

PubMed

Zhao, Yi-Lei; McCarren, Patrick R; Houk, K N; Choi, Bo Yoon; Toone, Eric J

2005-08-10

The decomposition of S-nitrosothiols (RSNO) in solution under oxidative conditions is significantly faster than can be accounted for by homolysis of the S-N bond. Here we propose a cationic chain mechanism in which nitrosation of nitrosothiol produces a nitrosated cation that, in turn, reacts with a second nitrosothiol to produce nitrosated disulfide and the NO dimer. The nitrosated disulfide acts as a source of nitrosonium for nitrosothiol nitrosation, completing the catalytic cycle. The mechanism accounts for several unexplained facets of nitrosothiol chemistry in solution, including the observation that the decomposition of an RSNO is accelerated by O(2), mixtures of O(2) and NO, and other oxidants, that decomposition is inhibited by thiols and other antioxidants, that decomposition is dependent on sulfur substitution, and that decomposition often shows nonintegral kinetic orders.

A Modified Demonstration of the Catalytic Decomposition of Hydrogen Peroxide

NASA Astrophysics Data System (ADS)

Trujillo, Carlos Alexander

2005-06-01

A safer and cheaper version of the popular catalyzed decomposition of hydrogen peroxide demonstration commonly called the “Elephants’ Toothpaste” is presented. Hydrogen peroxide is decomposed in the presence of a surfactant by the enzyme catalase producing foam. Catalase has a higher activity compared with the traditional iodide and permits the use of diluted hydrogen peroxide solutions. The demonstration can be made with household products with similar amazing effects.

Hydrogenation catalysts were derived from Mo(Co)/sub 6//alumina

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

Bowman, R.G.

1979-01-01

Alumina hydrogenation catalysts were derived from mo(CO)/sub 6//alumina with characteristics dependent upon the activation temperature, degree of alumina hydroxylation, and carrier gas used. Decomposition of Mo(CO)/sub 6/ at 100/sup 0/C on partially hydroxylated alumina in helium or hydrogen yielded Mo(CO)/sub 3//alumina, which catalyzed olefin metathesis in helium carrier and both metathesis and hydrogenation in hydrogen carrier. Decomposition of Mo(CO)/sub 6/ on dehydroxylated alumina at 100/sup 0/C in helium and in hydrogen resulted in complete decarbonylation and partial oxidation of molybdenum; this catalyst was 10 times as active as Mo(CO)/sub 3//alumina for hydrogenation. Decomposition of Mo(CO)/sub 6/ on dehydroxylated alumina atmore » 500/sup 0/C in helium gave essentially Mo(0)/alumina, which catalyzed hydrogenation, methanation, and hydrogenolysis in hydrogen. Catalysts activated on dehydroxylated alumina were ten times more active for methanation at 300/sup 0/C than catalyst activated on partially hydroxylated alumina and showed differences in selectivity for cyclopropane hydrogenolysis at 100/sup 0/C.« less

Biotransformation of hexahydro-1,3,5-trinitro-1,3,5-tiazine catalyzed by a NAD(P)H: nitrate oxidoreductase from Aspergillus niger.

PubMed

Bhushan, Bharat; Halasz, Annamaria; Spain, Jim; Thiboutot, Sonia; Ampleman, Guy; Hawari, Jalal

2002-07-15

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) can be efficiently mineralized with anaerobic domestic sludge, but the initial enzymatic processes involved in its transformation are unknown. To test the hypothesis that the initial reaction involves reduction of nitro group(s), we designed experiments to test the ability of a nitrate reductase (EC 1.6.6.2) to catalyze the initial reaction leading to ring cleavage and subsequent decomposition. A nitrate reductase from Aspergillus niger catalyzed the biotransformation of RDX most effectively at pH 7.0 and 30 degrees C under anaerobic conditions using NADPH as electron donor. LC/MS (ES-) chromatograms showed the formation of hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) and methylenedinitramine as key initial products of RDX, but neither the dinitroso neither (DNX) nor trinitroso (TNX) derivatives were observed. None of the above detected products persisted, and their disappearance was accompanied by the accumulation of nitrous oxide (N20), formaldehyde (HCHO), and ammonium ion (NH4+). Stoichiometric studies showed that three NADPH molecules were consumed, and one molecule of methylenedinitramine was produced per RDX molecule. The carbon and nitrogen mass balances were 96.14% and 82.10%, respectively. The stoichiometries and mass balance measurements supported a mechanism involving initial transformation of RDX to MNX via a two-electron reduction mechanism. Subsequent reduction of MNX followed by rapid ring cleavage gave methylenedinitramine which in turn decomposed in water to produce quantitatively N2O and HCHO. The results clearly indicate that an initial reduction of a nitro group by nitrate reductase is sufficient for the decomposition of RDX.

Environmental life-cycle comparisons of two polychlorinated biphenyl remediation technologies: incineration and base catalyzed decomposition.

PubMed

Hu, Xintao; Zhu, Jianxin; Ding, Qiong

2011-07-15

Remediation action is critical for the management of polychlorinated biphenyl (PCB) contaminated sites. Dozens of remediation technologies developed internationally could be divided in two general categories incineration and non-incineration. In this paper, life cycle assessment (LCA) was carried out to study the environmental impacts of these two kinds of remediation technologies in selected PCB contaminated sites, where Infrared High Temperature Incineration (IHTI) and Base Catalyzed Decomposition (BCD) were selected as representatives of incineration and non-incineration. A combined midpoint/damage approach was adopted by using SimaPro 7.2 and IMPACTA2002+ to assess the human toxicity, ecotoxicity, climate change impact, and resource consumption from the five subsystems of IHTI and BCD technologies, respectively. It was found that the major environmental impacts through the whole lifecycle arose from energy consumption in both IHTI and BCD processes. For IHTI, primary and secondary combustion subsystem contributes more than 50% of midpoint impacts concerning with carcinogens, respiratory inorganics, respiratory organics, terrestrial ecotoxity, terrestrial acidification/eutrophication and global warming. In BCD process, the rotary kiln reactor subsystem presents the highest contribution to almost all the midpoint impacts including global warming, non-renewable energy, non-carcinogens, terrestrial ecotoxity and respiratory inorganics. In the view of midpoint impacts, the characterization values for global warming from IHTI and BCD were about 432.35 and 38.5 kg CO(2)-eq per ton PCB-containing soils, respectively. LCA results showed that the single score of BCD environmental impact was 1468.97 Pt while IHTI's score is 2785.15 Pt, which indicates BCD potentially has a lower environmental impact than IHTI technology in the PCB contaminated soil remediation process. Copyright © 2011 Elsevier B.V. All rights reserved.

Gold(I)-catalyzed diazo cross-coupling: a selective and ligand-controlled denitrogenation/cyclization cascade.

PubMed

Xu, Guangyang; Zhu, Chenghao; Gu, Weijin; Li, Jian; Sun, Jiangtao

2015-01-12

An unprecedented gold-catalyzed ligand-controlled cross-coupling of diazo compounds by sequential selective denitrogenation and cyclization affords N-substituted pyrazoles in a position-switchable mode. This novel transformation features selective decomposition of one diazo moiety and simultaneous preservation of the other one from two substrates. Notably, the choice of the ancillary ligand to the gold complex plays a pivotal role on the chemo- and regioselectivity of the reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanocrystal assembly for tandem catalysis

DOEpatents

Yang, Peidong; Somorjai, Gabor; Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu

2014-10-14

The present invention provides a nanocrystal tandem catalyst comprising at least two metal-metal oxide interfaces for the catalysis of sequential reactions. One embodiment utilizes a nanocrystal bilayer structure formed by assembling sub-10 nm platinum and cerium oxide nanocube monolayers on a silica substrate. The two distinct metal-metal oxide interfaces, CeO.sub.2--Pt and Pt--SiO.sub.2, can be used to catalyze two distinct sequential reactions. The CeO.sub.2--Pt interface catalyzed methanol decomposition to produce CO and H.sub.2, which were then subsequently used for ethylene hydroformylation catalyzed by the nearby Pt--SiO.sub.2 interface. Consequently, propanal was selectively produced on this nanocrystal bilayer tandem catalyst.

Catalytic effects of inorganic acids on the decomposition of ammonium nitrate.

PubMed

Sun, Jinhua; Sun, Zhanhui; Wang, Qingsong; Ding, Hui; Wang, Tong; Jiang, Chuansheng

2005-12-09

In order to evaluate the catalytic effects of inorganic acids on the decomposition of ammonium nitrate (AN), the heat releases of decomposition or reaction of pure AN and its mixtures with inorganic acids were analyzed by a heat flux calorimeter C80. Through the experiments, the different reaction mechanisms of AN and its mixtures were analyzed. The chemical reaction kinetic parameters such as reaction order, activation energy and frequency factor were calculated with the C80 experimental results for different samples. Based on these parameters and the thermal runaway models (Semenov and Frank-Kamenestkii model), the self-accelerating decomposition temperatures (SADTs) of AN and its mixtures were calculated and compared. The results show that the mixtures of AN with acid are more unsteady than pure AN. The AN decomposition reaction is catalyzed by acid. The calculated SADTs of AN mixtures with acid are much lower than that of pure AN.

Techno-Economic Analysis of Magnesium Extraction from Seawater via a Catalyzed Organo-Metathetical Process

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

Liu, Jian; Bearden, Mark D.; Fernandez, Carlos A.

Magnesium (Mg) has many useful applications especially in various Mg alloys which can decrease weight while increasing strength. To increase the affordability and minimize environment consequence, a novel catalyzed organo-metathetical (COMET) process was proposed to extract Mg from seawater aiming to achieve significant reduction in total energy and production cost comparing with the melting salt electrolysis method currently adopted by US Mg LLC. A process flowsheet for a reference COMET process was set-up using Aspen Plus which included five key steps, anhydrous MgCl2 production, transmetallation, dibutyl Mg decomposition, n-BuLi regeneration, and LiCL electrolysis. The energy and production cost and CO2more » emission were estimated based on the Aspen modeling using Aspen economic analyzer. Our results showed that it is possible to produce Mg from seawater with a production cost of $2.0/kg-Mg while consuming about 35.3 kWh/kg-Mg and releasing 7.0 kg CO2/kg-Mg. A simplified US Mg manufacturing process was also generated using Aspen and the cost and emission results were estimated for comparison purpose. Under our simulation conditions, the reference COMET process maintain a comparable CO2 emission rate and can save about 40% in production cost and save about 15% energy compared to the simplified US Mg process.« less

Effect of Copper Oxide, Titanium Dioxide, and Lithium Fluoride on the Thermal Behavior and Decomposition Kinetics of Ammonium Nitrate

NASA Astrophysics Data System (ADS)

Vargeese, Anuj A.; Mija, S. J.; Muralidharan, Krishnamurthi

2014-07-01

Ammonium nitrate (AN) is crystallized along with copper oxide, titanium dioxide, and lithium fluoride. Thermal kinetic constants for the decomposition reaction of the samples were calculated by model-free (Friedman's differential and Vyzovkins nonlinear integral) and model-fitting (Coats-Redfern) methods. To determine the decomposition mechanisms, 12 solid-state mechanisms were tested using the Coats-Redfern method. The results of the Coats-Redfern method show that the decomposition mechanism for all samples is the contracting cylinder mechanism. The phase behavior of the obtained samples was evaluated by differential scanning calorimetry (DSC), and structural properties were determined by X-ray powder diffraction (XRPD). The results indicate that copper oxide modifies the phase transition behavior and can catalyze AN decomposition, whereas LiF inhibits AN decomposition, and TiO2 shows no influence on the rate of decomposition. Possible explanations for these results are discussed. Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Energetic Materials to view the free supplemental file.

Soil organic matter-hydrogen peroxide dynamics in the treatment of contaminated soils and groundwater using catalyzed H2O2 propagations (modified Fenton's reagent).

PubMed

Bissey, Lauren L; Smith, Jeffrey L; Watts, Richard J

2006-07-01

The interactions between catalyzed H(2)O(2) propagations (CHP-i.e. modified Fenton's reagent) and soil organic matter (SOM) during the treatment of contaminated soils and groundwater was studied in a well-characterized surface soil. The fate of two fractions of SOM, particulate organic matter (POM) and nonparticulate organic matter (NPOM), during CHP reactions was evaluated using concentrations of hydrogen peroxide from 0.5 to 3M catalyzed by soluble iron (III), an iron (III)-ethylenediamine tetraacetic acid (EDTA) chelate, or naturally-occurring soil minerals. The destruction of total SOM in CHP systems was directly proportional to the hydrogen peroxide dosage, and was significantly greater at pH 3 than at neutral pH; furthermore, SOM destruction occurred predominantly in the NPOM fraction. At pH 3, SOM did not affect hydrogen peroxide decomposition rates or hydroxyl radical activity in CHP reactions. However, at neutral pH, increasing the mass of SOM decreased the hydrogen peroxide decomposition rate and increased the rate of hydroxyl radical generation in CHP systems. These results show that, while CHP reactions destroy some of the organic carbon pools, SOM does not have a significant effect on the CHP treatment of soils and groundwater.

NDMA formation by chloramination of ranitidine: kinetics and mechanism.

PubMed

Roux, Julien Le; Gallard, Hervé; Croué, Jean-Philippe; Papot, Sébastien; Deborde, Marie

2012-10-16

The kinetics of decomposition of the pharmaceutical ranitidine (a major precursor of NDMA) during chloramination was investigated and some decomposition byproducts were identified by using high performance liquid chromatography coupled with mass spectrometry (HPLC-MS). The reaction between monochloramine and ranitidine followed second order kinetics and was acid-catalyzed. Decomposition of ranitidine formed different byproducts depending on the applied monochloramine concentration. Most identified products were chlorinated and hydroxylated analogues of ranitidine. In excess of monochloramine, nucleophilic substitution between ranitidine and monochloramine led to byproducts that are critical intermediates involved in the formation of NDMA, for example, a carbocation formed from the decomposition of the methylfuran moiety of ranitidine. A complete mechanism is proposed to explain the high formation yield of NDMA from chloramination of ranitidine. These results are of great importance to understand the formation of NDMA by chloramination of tertiary amines.

Studies on the thermal breakdown of common Li-ion battery electrolyte components

DOE PAGES

Lamb, Joshua; Orendorff, Christopher J.; Roth, Emanuel Peter; ...

2015-08-06

While much attention is paid to the impact of the active materials on the catastrophic failure of lithium ion batteries, much of the severity of a battery failure is also governed by the electrolytes used, which are typically flammable themselves and can decompose during battery failure. The use of LiPF 6 salt can be problematic as well, not only catalyzing electrolyte decomposition, but also providing a mechanism for HF production. This work evaluates the safety performance of the common components ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in the context of the gassesmore » produced during thermal decomposition, looking at both the quantity and composition of the vapor produced. EC and DEC were found to be the largest contributors to gas production, both producing upwards of 1.5 moles of gas/mole of electrolyte. DMC was found to be relatively stable, producing very little gas regardless of the presence of LiPF 6. EMC was stable on its own, but the addition of LiPF 6 catalyzed decomposition of the solvent. As a result, while gas analysis did not show evidence of significant quantities of any acutely toxic materials, the gasses themselves all contained enough flammable components to potentially ignite in air.« less

Kinetics of Platinum-Catalyzed Decomposition of Hydrogen Peroxide

NASA Astrophysics Data System (ADS)

Vetter, Tiffany A.; Colombo, D. Philip, Jr.

2003-07-01

CIBA Vision Corporation markets a contact lens cleaning system that consists of an AOSEPT disinfectant solution and an AOSEPT lens cup. The disinfectant is a buffered 3.0% m/v hydrogen peroxide solution and the cup includes a platinum-coated AOSEPT disc. The hydrogen peroxide disinfects by killing bacteria, fungi, and viruses found on the contact lenses. Because the concentration of hydrogen peroxide needed to disinfect is irritating to eyes, the hydrogen peroxide needs to be neutralized, or decomposed, before the contact lenses can be used again. A general chemistry experiment is described where the kinetics of the catalyzed decomposition of the hydrogen peroxide are studied by measuring the amount of oxygen generated as a function of time. The order of the reaction with respect to the hydrogen peroxide, the rate constant, and the energy of activation are determined. The integrated rate law is used to determine the time required to decompose the hydrogen peroxide to a concentration that is safe for eyes.

Dye-sensitized TiO2-catalyzed photodegradation of sulfamethoxazole under blue or yellow light.

PubMed

Lu, Norman; Yeh, Yun-Peng; Wang, Guan-Bo; Feng, Tsung-Yao; Shih, Yang-Hsin; Chen, Dong

2017-01-01

Visible light-induced photocatalysis is potentially advantageous and could be an efficient approach to degrade contaminants because it can be used to selectively target specific wavelength for decomposition of organic contaminants in water and wastewater. This study demonstrates the photodegradation of sulfamethoxazole (SMX) using [Pt(3,3'-dicarboxy-2,2'-bpy)(1,2-benzenedithiolate)] (Complex 1)-sensitized and [Pt(4,4'-dicarboxy-2,2'-bpy)(1,2-benzenedithiolate)] (Complex 2)-sensitized titanium dioxide (TiO 2 ) under blue or yellow light (420 or 580 nm, respectively) irradiation in water. The Complex 1-sensitized TiO 2 photocatalytic oxidation of SMX reached almost 100 % removal under 420 nm irradiation for 3 h in water. In addition, the formation of hydroxyl radicals can be facilitated by bubbling O 2 during the photodegradation in which an effective decomposition of SMX was observed. Based on HPLC and UV-Vis studies of the decomposed products, it was found that SMX underwent cleavage of aromatic rings during the photodegradation process.

Do pH and flavonoids influence hypochlorous acid-induced catalase inhibition and heme modification?

PubMed

Krych-Madej, Justyna; Gebicka, Lidia

2015-09-01

Hypochlorous acid (HOCl), highly reactive oxidizing and chlorinating species, is formed in the immune response to invading pathogens by the reaction of hydrogen peroxide with chloride catalyzed by the enzyme myeloperoxidase. Catalase, an important antioxidant enzyme, catalyzing decomposition of hydrogen peroxide to water and molecular oxygen, hampers in vitro HOCl formation, but is also one of the main targets for HOCl. In this work we have investigated HOCl-induced catalase inhibition at different pH, and the influence of flavonoids (catechin, epigallocatechin gallate and quercetin) on this process. It has been shown that HOCl-induced catalase inhibition is independent on pH in the range 6.0-7.4. Preincubation of catalase with epigallocatechin gallate and quercetin before HOCl treatment enhances the degree of catalase inhibition, whereas catechin does not affect this process. Our rapid kinetic measurements of absorption changes around the heme group have revealed that heme modification by HOCl is mainly due to secondary, intramolecular processes. The presence of flavonoids, which reduce active catalase intermediate, Compound I to inactive Compound II have not influenced the kinetics of HOCl-induced heme modification. Possible mechanisms of the reaction of hypochlorous acid with catalase are proposed and the biological consequences are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Kinetics of non-catalyzed hydrolysis of tannin in high temperature liquid water*

PubMed Central

Lu, Li-li; Lu, Xiu-yang; Ma, Nan

2008-01-01

High temperature liquid water (HTLW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions, especially acid-/base-catalyzed reactions. Non-catalyzed hydrolyses of gallotannin and tara tannin in HTLW for the simultaneous preparation of gallic acid (GA) and pyrogallol (PY) are under investigation in our laboratory. In this study, the hydrolysis kinetics of gallotannin and tara tannin were determined. The reaction is indicated to be a typical consecutive first-order one in which GA has formed as a main intermediate and PY as the final product. Selective decomposition of tannin in HTLW was proved to be possible by adjusting reaction temperature and time. The present results provide an important basic data and reference for the green preparation of GA and PY. PMID:18500780

Computational Chemistry and Lubrication

NASA Technical Reports Server (NTRS)

Zehe, Michael J.

1998-01-01

Members of NASA Lewis Research Center's Tribology and Surface Science Branch are applying high-level computational chemistry techniques to the development of new lubrication systems for space applications and for future advanced aircraft engines. The next generation of gas turbine engines will require a liquid lubricant to function at temperatures in excess of 350 C in oxidizing environments. Conventional hydrocarbon-based lubricants are incapable of operating in these extreme environments, but a class of compounds known as the perfluoropolyether (PFAE) liquids (see the preceding illustration) shows promise for such applications. These commercially available products are already being used as lubricants in conditions where low vapor pressure and chemical stability are crucial, such as in satellite bearings and composite disk platters. At higher temperatures, however, these compounds undergo a decomposition process that is assisted (catalyzed) by metal and metal oxide bearing surfaces. This decomposition process severely limits the applicability of PFAE's at higher temperatures. A great deal of laboratory experimentation has revealed that the extent of fluid degradation depends on the chemical properties of the bearing surface materials. Lubrication engineers would like to understand the chemical breakdown mechanism to design a less vulnerable PFAE or to develop a chemical additive to block this degradation.

A Twist on Measuring Catalase

ERIC Educational Resources Information Center

Bryer, Pamela

2016-01-01

"Catalase," an enzyme found in both plant and animal cells, prevents the accumulation of toxic levels of hydrogen peroxide (H[subscript 2]O[subscript 2]) by catalyzing its decomposition to water and oxygen gas. Because this enzyme is ubiquitous, it is frequently used in high school biology laboratories to explore enzyme reactions. This…

Micro Chemical Oxygen-Iodine Laser (COIL)

DTIC Science & Technology

2007-10-01

required to form a good o-ring seal. Steam generator design A pumping system based on steam ejectors was designed during the course of the previous HEL-JTO...options for the steam generator design . The first is to catalyze the decomposition of hydrogen peroxide through the use of a standard solid

Path Integral Simulation of the H/D Kinetic Isotope Effect in Monoamine Oxidase B Catalyzed Decomposition of Dopamine.

PubMed

Mavri, Janez; Matute, Ricardo A; Chu, Zhen T; Vianello, Robert

2016-04-14

Brain monoamines regulate many centrally mediated body functions, and can cause adverse symptoms when they are out of balance. A starting point to address challenges raised by the increasing burden of brain diseases is to understand, at atomistic level, the catalytic mechanism of an essential amine metabolic enzyme-monoamine oxidase B (MAO B). Recently, we demonstrated that the rate-limiting step of MAO B catalyzed conversion of amines into imines represents the hydride anion transfer from the substrate α-CH2 group to the N5 atom of the flavin cofactor moiety. In this article we simulated for MAO B catalyzed dopamine decomposition the effects of nuclear tunneling by the calculation of the H/D kinetic isotope effect. We applied path integral quantization of the nuclear motion for the methylene group and the N5 atom of the flavin moiety in conjunction with the QM/MM treatment on the empirical valence bond (EVB) level for the rest of the enzyme. The calculated H/D kinetic isotope effect of 12.8 ± 0.3 is in a reasonable agreement with the available experimental data for closely related biogenic amines, which gives strong support for the proposed hydride mechanism. The results are discussed in the context of tunneling in enzyme centers and advent of deuterated drugs into clinical practice.

MEMS-Based Satellite Micropropulsion Via Catalyzed Hydrogen Peroxide Decomposition

NASA Technical Reports Server (NTRS)

Hitt, Darren L.; Zakrzwski, Charles M.; Thomas, Michael A.; Bauer, Frank H. (Technical Monitor)

2001-01-01

Micro-electromechanical systems (MEMS) techniques offer great potential in satisfying the mission requirements for the next generation of "micro-scale" satellites being designed by NASA and Department of Defense agencies. More commonly referred to as "nanosats", these miniature satellites feature masses in the range of 10-100 kg and therefore have unique propulsion requirements. The propulsion systems must be capable of providing extremely low levels of thrust and impulse while also satisfying stringent demands on size, mass, power consumption and cost. We begin with an overview of micropropulsion requirements and some current MEMS-based strategies being developed to meet these needs. The remainder of the article focuses the progress being made at NASA Goddard Space Flight Center towards the development of a prototype monopropellant MEMS thruster which uses the catalyzed chemical decomposition of high concentration hydrogen peroxide as a propulsion mechanism. The products of decomposition are delivered to a micro-scale converging/diverging supersonic nozzle which produces the thrust vector; the targeted thrust level approximately 500 N with a specific impulse of 140-180 seconds. Macro-scale hydrogen peroxide thrusters have been used for satellite propulsion for decades; however, the implementation of traditional thruster designs on a MEMS scale has uncovered new challenges in fabrication, materials compatibility, and combustion and hydrodynamic modeling. A summary of the achievements of the project to date is given, as is a discussion of remaining challenges and future prospects.

PROCESSING ALTERNATIVES FOR DESTRUCTION OF TETRAPHENYLBORATE

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

Lambert, D; Thomas Peters, T; Samuel Fink, S

Two processes were chosen in the 1980's at the Savannah River Site (SRS) to decontaminate the soluble High Level Waste (HLW). The In Tank Precipitation (ITP) process (1,2) was developed at SRS for the removal of radioactive cesium and actinides from the soluble HLW. Sodium tetraphenylborate was added to the waste to precipitate cesium and monosodium titanate (MST) was added to adsorb actinides, primarily uranium and plutonium. Two products of this process were a low activity waste stream and a concentrated organic stream containing cesium tetraphenylborate and actinides adsorbed on monosodium titanate (MST). A copper catalyzed acid hydrolysis process wasmore » built to process (3, 4) the Tank 48H cesium tetraphenylborate waste in the SRS's Defense Waste Processing Facility (DWPF). Operation of the DWPF would have resulted in the production of benzene for incineration in SRS's Consolidated Incineration Facility. This process was abandoned together with the ITP process in 1998 due to high benzene in ITP caused by decomposition of excess sodium tetraphenylborate. Processing in ITP resulted in the production of approximately 1.0 million liters of HLW. SRS has chosen a solvent extraction process combined with adsorption of the actinides to decontaminate the soluble HLW stream (5). However, the waste in Tank 48H is incompatible with existing waste processing facilities. As a result, a processing facility is needed to disposition the HLW in Tank 48H. This paper will describe the process for searching for processing options by SRS task teams for the disposition of the waste in Tank 48H. In addition, attempts to develop a caustic hydrolysis process for in tank destruction of tetraphenylborate will be presented. Lastly, the development of both a caustic and acidic copper catalyzed peroxide oxidation process will be discussed.« less

An Experiment to Illustrate the Hazards of Exothermic Reaction Scale-Up

ERIC Educational Resources Information Center

Clark, William; Lei, Melinda; Kirichenko, Erika; Dickerson, Kellie; Prytko, Robert

2017-01-01

Exothermic reactions can present safety hazards and there is a recognized need for reaction safety education at the undergraduate level. We present an experiment that illustrates the pitfall of direct scale-up of an exothermic reaction that can lead to thermal runaway. The iodide-catalyzed hydrogen peroxide decomposition reaction yields…

Pyrolysis-crystallinity relationships in cellulose

Treesearch

M. Weinstein; A. Broido

1970-01-01

During pyrolysis of pure cellulose, the Crystallinity Index (Crl) remained fairly constant over more than 50% weight loss before dropping rapidly as the X-ray pattern deteriorated. With samples first treated with trace quantities of inorganic salts, heating first increased the Crl—the results implying a preferentially catalyzed decomposition of the amorphous regions....

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-.

Palladium-atom catalyzed formic acid decomposition and the switch of reaction mechanism with temperature.

PubMed

He, Nan; Li, Zhen Hua

2016-04-21

Formic acid decomposition (FAD) reaction has been an innovative way for hydrogen energy. Noble metal catalysts, especially palladium-containing nanoparticles, supported or unsupported, perform well in this reaction. Herein, we considered the simplest model, wherein one Pd atom is used as the FAD catalyst. With high-level theoretical calculations of CCSD(T)/CBS quality, we investigated all possible FAD pathways. The results show that FAD catalyzed by one Pd atom follows a different mechanism compared with that catalyzed by surfaces or larger clusters. At the initial stage of the reaction, FAD follows a dehydration route and is quickly poisoned by CO due to the formation of very stable PdCO. PdCO then becomes the actual catalyst for FAD at temperatures approximately below 1050 K. Beyond 1050 K, there is a switch of catalyst from PdCO to Pd atom. The results also show that dehydration is always favoured over dehydrogenation on either the Pd-atom or PdCO catalyst. On the Pd-atom catalyst, neither dehydrogenation nor dehydration follows the formate mechanism. In contrast, on the PdCO catalyst, dehydrogenation follows the formate mechanism, whereas dehydration does not. We also systematically investigated the performance of 24 density functional theory methods. We found that the performance of the double hybrid mPW2PLYP functional is the best, followed by the B3LYP, B3PW91, N12SX, M11, and B2PLYP functionals.

BASE CATALYZED DECOMPOSITION (BCD) OF PCB AND DIOXIN CONTAMINATED CONDENSATE OIL FROM THE REMEDIATION OF THE WARREN COUNTY LANDFILL, NC

EPA Science Inventory

In the late 1970s thousands of gallons of transformer fluid contaminated with PCBs were illegally sprayed along approximately 210 miles of North Carolina state roadways. Listed as a Superfund site, the contaminated roadway berms were excavated and disposed in an approved PCB land...

Assembly of catalase-based bioconjugates for enhanced anticancer efficiency of photodynamic therapy in vitro.

PubMed

Zhao, Jie; Fei, Jinbo; Du, Cuiling; Cui, Wei; Ma, Hongchao; Li, Junbai

2013-11-25

An oxygen generation core-shell structure uploading rose bengal has been fabricated by covalent assembly of catalase and alginate dialdehyde via Schiff's base. The composite can catalyze the decomposition of intracellular H2O2 to increase the concentration of O2, which effectively enhances the anticancer efficiency of photodynamic therapy in vitro.

A quantum chemical study of the decomposition of Keggin-structured heteropolyacids.

PubMed

Janik, Michael J; Bardin, Billy B; Davis, Robert J; Neurock, Matthew

2006-03-09

Heterpolyacids (HPAs) demonstrate catalytic activity for oxidative and acid-catalyzed hydrocarbon conversion processes. Deactivation and thermal instability, however, have prevented their widespread use. Herein, ab initio density functional theory is used to study the thermal decomposition of the Keggin molecular HPA structure through the desorption of constitutional water molecules. The overall reaction energy and activation barrier are computed for the overall reaction HnXM12O40-->Hn-2XM12O39+H2O. and subsequently used to predict the effect of HPA composition on thermal stability. For example, the desorption of a constitutional water molecule is found to be increasingly endothermic in the order silicomolybdic acid (H4SiMo12O40)

Combustion chemistry of solid propellants

NASA Technical Reports Server (NTRS)

Baer, A. D.; Ryan, N. W.

1974-01-01

Several studies are described of the chemistry of solid propellant combustion which employed a fast-scanning optical spectrometer. Expanded abstracts are presented for four of the studies which were previously reported. One study of the ignition of composite propellants yielded data which suggested early ammonium perchlorate decomposition and reaction. The results of a study of the spatial distribution of molecular species in flames from uncatalyzed and copper or lead catalyzed double-based propellants support previously published conclusions concerning the site of action of these metal catalysts. A study of the ammonium-perchlorate-polymeric-fuel-binder reaction in thin films, made by use of infrared absorption spectrometry, yielded a characterization of a rapid condensed-phase reaction which is likely important during the ignition transient and the burning process.

Activation of Hydrogen Peroxide by Iron-Containing Minerals and Catalysts in Circumneutral pH Solutions: Implications for ex situ and in situ Treatment of Contaminated Water and Soil

NASA Astrophysics Data System (ADS)

Pham, Anh Le Tuan

The decomposition of hydrogen peroxide (H2O2) on iron minerals can generate hydroxyl radical (•OH), a strong oxidant capable of transforming a wide range of contaminants. This reaction is critical to ex situ advanced oxidation processes employed in waste treatment systems, as well as in situ chemical oxidation processes used for soil and groundwater remediation. Unfortunately, the process in the ex situ treatment systems is relatively inefficient at circumneutral pH values. In this research, the development of iron-containing catalysts with improved efficiency was investigated. In addition, little is known about the factors that control the performance of in situ treatment systems. Another aim of this dissertation was to elucidate those factors to provide a basis for improving the efficiency of the remediation method. Two types of silica- and alumina-containing iron (hydr)oxide catalysts were synthesized by sol-gel processing techniques (Chapter 2). Relative to iron oxides, such as hematite and goethite, these catalysts were 10 to 80 times more effective in catalyzing the production of •OH from H2O2 under circumneutral conditions. The higher efficiency makes these catalysts promising candidates for ex situ advanced oxidation processes. Moreover, because alumina and silica alter the reactivity of the iron oxides with H2O2, understanding the activity of iron associated with natural aluminosilicates and silica-containing minerals in the subsurface is crucial to explaining the variability of •OH production observed in in situ treatment systems. In addition to the sol-gel technique used in Chapter 2, silica-containing iron (hydr)oxide catalysts were synthesized by immobilizing iron oxide onto mesoporous silica supports, such as SBA-15 (Chapter 5). The iron-containing SBA-15 was 10 times more effective than iron oxides in catalyzing the production of •OH from H2O2. Moreover, this catalyst could be employed for selective oxidation of small organic contaminants based on size exclusion. However, a major drawback of the mesoporous silica-based catalysts is their instability under circumneutral conditions (Chapter 6). The dissolution of mesoporous silica materials raises questions about their use for water treatment, because silica dissolution might compromise the behavior of the material. To gain insight into factors that control H2O2 persistence and •OH yield in in situ processes, the decomposition of H2O2 and transformation of contaminants were investigated in the presence of iron-containing minerals and aquifer materials (Chapter 3). Consistent with the observation described in Chapter 2, iron-containing aluminosilicates were more effective than iron oxides in converting H2O2 into •OH. In both iron-containing mineral and aquifer material systems, the yield of •OH was inversely correlated with the rate of H 2O2 decomposition. In the aquifer material systems, the yield also inversely correlated with the Mn content, consistent with the fact that the decomposition of H2O2 on manganese oxides does not produce •OH. The inverse correlation between Mn content and H2O2 loss rate and •OH yield suggests that the amount of Mn in aquifer materials could serve as a proxy for predicting H2O2 decomposition rates and contaminant oxidation efficiency. In addition to the surface and structure properties of iron solids, the presence of solutes, such as dissolved silica, also affected the decomposition of H2O2 (Chapter 4). The adsorption of dissolved silica onto mineral surfaces altered the catalytic sites, thereby decreasing the reactivity of iron- and manganese-containing minerals with H2O 2. Therefore, the presence of dissolved SiO2 could lead to greater persistence of H2O2 in groundwater, which should be considered in the design of in situ H2O 2-based treatment systems. In addition to in situ treatment, dissolved silica also can affect the reactivity of iron-containing catalysts used in ex situ processes. Therefore, its presence in contaminated industrial wastewater should be considered when ex situ treatment systems are designed.

Acid-catalyzed oxidation of 2,4-dichlorophenoxyacetic acid by ammonium nitrate in aqueous solution

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

Leavitt, D.D.; Abraham, M.A.

1990-04-01

2,4-Dichlorophenoxyacetic acid (2,4-D) was oxidized to CO{sub 2} and water by homogeneous, liquid-phase reaction with ammonium nitrate at temperatures between 250 and 450{degree}F and pressures below 100 psi. N{sub 2} and N{sub 2}O were produced from the thermal decomposition of the ammonium nitrate oxidant. An unexpected maximum in conversion was observed at an intermediate reaction temperature, which was consistent with rapid thermal decomposition of the NH{sub 4}NO{sub 3} oxidant. Postulated reaction pathways consisting of simultaneous oxidation of 2,4-D and decomposition of the oxidant allowed estimation of kinetic constants from best-fit analysis of the data. The proposed reaction model provided amore » mathematical description of 2,4-D conversion, which allowed extrapolation of the results to reaction conditions and reactor configurations that were not experimentally investigated.« less

Data-Driven Microbial Modeling for Soil Carbon Decomposition and Stabilization

NASA Astrophysics Data System (ADS)

Luo, Yiqi; Chen, Ji; Chen, Yizhao; Feng, Wenting

2017-04-01

Microorganisms have long been known to catalyze almost all the soil organic carbon (SOC) transformation processes (e.g., decomposition, stabilization, and mineralization). Representing microbial processes in Earth system models (ESMs) has the potential to improve projections of SOC dynamics. We have recently examined (1) relationships of microbial functions with environmental factors and (2) microbial regulations of decomposition and other key soil processes. According to three lines of evidence, we have developed a data-driven enzyme (DENZY) model to simulate soil microbial decomposition and stabilization. First, our meta-analysis of 64 published field studies showed that field experimental warming significantly increased soil microbial communities abundance, which is negatively correlated with the mean annual temperature. The negative correlation indicates that warming had stronger effects in colder than warmer regions. Second, we found that the SOC decomposition, especially the transfer between labile SOC and protected SOC, is nonlinearly regulated by soil texture parameters, such as sand and silt contents. Third, we conducted a global analysis of the C-degrading enzyme activities, soil respiration, and SOC content under N addition. Our results show that N addition has contrasting effects on cellulase (hydrolytic C-degrading enzymes) and ligninase (oxidative C-degrading enzymes) activities. N-enhanced cellulase activity contributes to the minor stimulation of soil respiration whereas N-induced repression on ligninase activity drives soil C sequestration. Our analysis links the microbial extracellular C-degrading enzymes to the SOC dynamics at ecosystem scales across scores of experimental sites around the world. It offers direct evidence that N-induced changes in microbial community and physiology play fundamental roles in controlling the soil C cycle. Built upon those three lines of empirical evidence, the DENZY model includes two enzyme pools and explicitly characterizes two classes of extracellular enzyme activities: one that degrades organic molecules containing both C and N (e.g., chitin or protein) and another that degrades only C (e.g., cellulose). The DENZY model assumes that the microbes allocate resources to different enzyme pools so as to exactly satisfy microbial CN ratio stoichiometry in response to changes in climate conditions and soil attributes. The DENZY model can simulate differential effects of nitrogen fertilization on the two groups of enzymes and thus soil respiration and SOC dynamics. We will select field experimental sites to test the DENZY model. With increasing amounts of available observations and data synthesis, this DENZY model will be better parameterized and have a potential to reveal how responses of microbial enzymes to environmental changes regulate soil carbon decomposition and stabilization.

A comparative evaluation of explosion hazards in chemical and mechanical pulp bleaching systems

Treesearch

Peter W. Hart; Alan W. Rudie

2010-01-01

Over the past several years, at least three pulp mills in North America have experienced catastrophic events that resulted in the explosion of pumps, mixers, and tanks. All these mills were using 50% concentration hydrogen peroxide at the site of the explosions. In at least two instances, alkali catalyzed decomposition of peroxide is implicated in the explosion....

Bromamine Decomposition Revisited: A Holistic Approach for Analyzing Acid and Base Catalysis Kinetics.

PubMed

Wahman, David G; Speitel, Gerald E; Katz, Lynn E

2017-11-21

Chloramine chemistry is complex, with a variety of reactions occurring in series and parallel and many that are acid or base catalyzed, resulting in numerous rate constants. Bromide presence increases system complexity even further with possible bromamine and bromochloramine formation. Therefore, techniques for parameter estimation must address this complexity through thoughtful experimental design and robust data analysis approaches. The current research outlines a rational basis for constrained data fitting using Brønsted theory, application of the microscopic reversibility principle to reversible acid or base catalyzed reactions, and characterization of the relative significance of parallel reactions using fictive product tracking. This holistic approach was used on a comprehensive and well-documented data set for bromamine decomposition, allowing new interpretations of existing data by revealing that a previously published reaction scheme was not robust; it was not able to describe monobromamine or dibromamine decay outside of the conditions for which it was calibrated. The current research's simplified model (3 reactions, 17 constants) represented the experimental data better than the previously published model (4 reactions, 28 constants). A final model evaluation was conducted based on representative drinking water conditions to determine a minimal model (3 reactions, 8 constants) applicable for drinking water conditions.

Hydrothermal carbonization of Opuntia ficus-indica cladodes: Role of process parameters on hydrochar properties.

PubMed

Volpe, Maurizio; Goldfarb, Jillian L; Fiori, Luca

2018-01-01

Opuntia ficus-indica cladodes are a potential source of solid biofuel from marginal, dry land. Experiments assessed the effects of temperature (180-250°C), reaction time (0.5-3h) and biomass to water ratio (B/W; 0.07-0.30) on chars produced via hydrothermal carbonization. Multivariate linear regression demonstrated that the three process parameters are critically important to hydrochar solid yield, while B/W drives energy yield. Heating value increased together with temperature and reaction time and was maximized at intermediate B/W (0.14-0.20). Microscopy shows evidence of secondary char formed at higher temperatures and B/W ratios. X-ray diffraction, thermogravimetric data, microscopy and inductively coupled plasma mass spectrometry suggest that calcium oxalate in the raw biomass remains in the hydrochar; at higher temperatures, the mineral decomposes into CO 2 and may catalyze char/tar decomposition. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Fermentation production of microbial catalase and its application in textile industry].

PubMed

Zhang, Dongxu; Du, Guocheng; Chen, Jian

2010-11-01

Microbial catalase is an important industrial enzyme that catalyzes the decomposition of hydrogen peroxide to water and oxygen. This enzyme has great potential of application in food, textile and pharmaceutical industries. The production of microbial catalase has been significantly improved thanks to advances in bioprocess engineering and genetic engineering. In this paper, we review the progresses in fermentation production of microbial catalase and its application in textile industry. Among these progresses, we will highlight strain isolation, substrate and environment optimization, enzyme induction, construction of engineering strains and application process optimization. Meanwhile, we also address future research trends for microbial catalase production and its application in textile industry. Molecular modification (site-directed mutagenesis and directed revolution) will endue catalase with high pH and temperature stabilities. Improvement of catalase production, based on the understanding of induction mechanism and the process control of recombinant stain fermentation, will further accelerate the application of catalase in textile industry.

Preparation and characterization of ligand types intermediate in the metal catalyzed conversion of coal to methane, methanol, and higher alkanes and alcohols. Second technical progress report, September 1, 1979-February 28, 1981

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

Gladysz, J. A.

1980-11-10

Mechanistic studies of anionic formyl complexes were made. The rate of decomposition of the formyl (CO)/sub 4/Mn(COC/sub 6/H/sub 5/)(CHO)/sup -/ anion as a function of counter-ion and trialkylborane present was examined. The deuterated formyl (CO)/sub 4/Mn(COC/sub 6/H/sub 5/)(CDO)/sup -/ was prepared and its decomposition was monitored by H/sup 2/ NMR. The data obtained indicate that the formyl decomposes by a disproportionative pathway not by initial CO loss, as commonly noted for formyl complexes.

Coating for components requiring hydrogen peroxide compatibility

NASA Technical Reports Server (NTRS)

Yousefiani, Ali (Inventor)

2010-01-01

The present invention provides a heretofore-unknown use for zirconium nitride as a hydrogen peroxide compatible protective coating that was discovered to be useful to protect components that catalyze the decomposition of hydrogen peroxide or corrode when exposed to hydrogen peroxide. A zirconium nitride coating of the invention may be applied to a variety of substrates (e.g., metals) using art-recognized techniques, such as plasma vapor deposition. The present invention further provides components and articles of manufacture having hydrogen peroxide compatibility, particularly components for use in aerospace and industrial manufacturing applications. The zirconium nitride barrier coating of the invention provides protection from corrosion by reaction with hydrogen peroxide, as well as prevention of hydrogen peroxide decomposition.

Remote catalyzation for direct formation of graphene layers on oxides.

PubMed

Teng, Po-Yuan; Lu, Chun-Chieh; Akiyama-Hasegawa, Kotone; Lin, Yung-Chang; Yeh, Chao-Hui; Suenaga, Kazu; Chiu, Po-Wen

2012-03-14

Direct deposition of high-quality graphene layers on insulating substrates such as SiO(2) paves the way toward the development of graphene-based high-speed electronics. Here, we describe a novel growth technique that enables the direct deposition of graphene layers on SiO(2) with crystalline quality potentially comparable to graphene grown on Cu foils using chemical vapor deposition (CVD). Rather than using Cu foils as substrates, our approach uses them to provide subliming Cu atoms in the CVD process. The prime feature of the proposed technique is remote catalyzation using floating Cu and H atoms for the decomposition of hydrocarbons. This allows for the direct graphitization of carbon radicals on oxide surfaces, forming isolated low-defect graphene layers without the need for postgrowth etching or evaporation of the metal catalyst. The defect density of the resulting graphene layers can be significantly reduced by tuning growth parameters such as the gas ratios, Cu surface areas, and substrate-to-Cu distance. Under optimized conditions, graphene layers with nondiscernible Raman D peaks can be obtained when predeposited graphite flakes are used as seeds for extended growth. © 2012 American Chemical Society

Magnetic Nanoparticle-Based Imaging of RNA Transcripts in Breast Cancer Cells

DTIC Science & Technology

2009-06-01

iron oxide NPs via thermal decomposition. - Prepared gold-coated iron oxide NPs. - Developed a click chemistry protocol (i.e. Cu-catalyzed terminal...D.L.J., Elias, D.R., Tsourkas, A. (2009) Comparative analysis of nanoparticle-antibody conjugations: carbodiimide versus click chemistry . Submitted...carbodiimide versus click chemistry . Submitted. APPENDICES: 1) Thorek, D.L.J., Tsourkas, A. (2008) Size, charge, and concentration dependent

N-Heterocycle-Fused Pentalenes by a Gold-Catalyzed Annulation of Diethynyl-Quinoxalines and -Phenazines.

PubMed

Sekine, Kohei; Stuck, Fabian; Schulmeister, Jürgen; Wurm, Thomas; Zetschok, Dominik; Rominger, Frank; Rudolph, Matthias; Hashmi, A Stephen K

2018-06-19

The gold-catalyzed annulation of diethynyl N-heterocycles for the synthesis of quinoxaline-/phenazine-based pentalenes, and the study of their optoelectronic properties is described. The inhibition of the gold catalyst by the nitrogen centers in the substrate and the product could be overcome by increasing the reaction temperature to 130 °C, which in gold catalysis usually leads to catalyst decomposition. At 130 °C 6,7-di(arylethynyl)quinoxalines in chlorobenzene at afford the corresponding pentalenes. The annulation of 2,3-di(arylethynyl)quinoxalines requires an even higher temperature under microwave irradiation. The quinoxaline-based pentalenes showed lower LUMO levels compared to the corresponding naphthalene-based pentalenes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Substrate-dependent temperature sensitivity of soil organic matter decomposition

NASA Astrophysics Data System (ADS)

Myachina, Olga; Blagodatskaya, Evgenia

2015-04-01

Activity of extracellular enzymes responsible for decomposition of organics is substrate dependent. Quantity of the substrate is the main limiting factor for enzymatic or microbial heterotrophic activity in soils. Different mechanisms of enzymes response to temperature suggested for low and high substrate availability were never proved for real soil conditions. We compared the temperature responses of enzymes-catalyzed reactions in soils. Basing on Michaelis-Menten kinetics we determined the enzymes affinity to substrate (Km) and mineralization potential of heterotrophic microorganisms (Vmax) 1) for three hydrolytic enzymes: β-1,4-glucosidase, N-acetyl- β -D-glucosaminidase and phosphatase by the application of fluorogenically labeled substrates and 2) for mineralization of 14C-labeled glucose by substrate-dependent respiratory response. Here we show that the amount of available substrate is responsible for temperature sensitivity of hydrolysis of polymers in soil, whereas monomers oxidation to CO2 does not depend on substrate amount and is mainly temperature governed. We also found that substrate affinity of enzymes (which is usually decreases with the temperature) differently responded to warming for the process of depolymerisation versus monomers oxidation. We suggest the mechanism to temperature acclimation based on different temperature sensitivity of enzymes kinetics for hydrolysis of polymers and for monomers oxidation.

Molecular mechanism of metal-independent decomposition of lipid hydroperoxide 13-HPODE by halogenated quinoid carcinogens.

PubMed

Qin, Hao; Huang, Chun-Hua; Mao, Li; Xia, Hai-Ying; Kalyanaraman, Balaraman; Shao, Jie; Shan, Guo-Qiang; Zhu, Ben-Zhan

2013-10-01

Halogenated quinones are a class of carcinogenic intermediates and newly identified chlorination disinfection by-products in drinking water. 13-Hydroperoxy-9,11-octadecadienoic acid (13-HPODE) is the most extensively studied endogenous lipid hydroperoxide. Although it is well known that the decomposition of 13-HPODE can be catalyzed by transition metal ions, it is not clear whether halogenated quinones could enhance its decomposition independent of metal ions and, if so, what the unique characteristics and similarities are. Here we show that 2,5-dichloro-1,4-benzoquinone (DCBQ) could markedly enhance the decomposition of 13-HPODE and formation of reactive lipid alkyl radicals such as pentyl and 7-carboxyheptyl radicals, and the genotoxic 4-hydroxy-2-nonenal (HNE), through the complementary application of ESR spin trapping, HPLC-MS, and GC-MS methods. Interestingly, two chloroquinone-lipid alkoxyl conjugates were also detected and identified from the reaction between DCBQ and 13-HPODE. Analogous results were observed with other halogenated quinones. This represents the first report that halogenated quinoid carcinogens can enhance the decomposition of the endogenous lipid hydroperoxide 13-HPODE and formation of reactive lipid alkyl radicals and genotoxic HNE via a novel metal-independent nucleophilic substitution coupled with homolytic decomposition mechanism, which may partly explain their potential genotoxicity and carcinogenicity. Copyright © 2013 Elsevier Inc. All rights reserved.

Solution phase and membrane immobilized iron-based free radical reactions: Fundamentals and applications for water treatment

NASA Astrophysics Data System (ADS)

Lewis, Scott Romak

Membrane-based separation processes have been used extensively for drinking water purification, wastewater treatment, and numerous other applications. Reactive membranes synthesized through functionalization of the membrane pores offer enhanced reactivity due to increased surface area at the polymer-solution interface and low diffusion limitations. Oxidative techniques utilizing free radicals have proven effective for both the destruction of toxic organics and non-environmental applications. Most previous work focuses on reactions in the homogeneous phase; however, the immobilization of reactants in membrane pores offers several advantages. The use of polyanions immobilized in a membrane or chelates in solution prevents ferric hydroxide precipitation at near-neutral pH, a common limitation of iron(Fe(II/III))-catalyzed hydrogen peroxide (H 2O2) decomposition. The objectives of this research are to develop a membrane-based platform for the generation of free radicals, degrade toxic organic compounds using this and similar solution-based reactions, degrade toxic organic compounds in droplet form, quantify hydroxyl radical production in these reactions, and develop kinetic models for both processes. In this study, a functionalized membrane containing poly(acrylic acid) (PAA) was used to immobilize iron ions and conduct free radical reactions by permeating H2O2 through the membrane. The membrane's responsive behavior to pH and divalent cations was investigated and modeled. The conversion of Fe(II) to Fe(III) in the membrane and its effect on the decomposition of hydrogen peroxide were monitored and used to develop kinetic models for predicting H2O2 decomposition in these systems. The rate of hydroxyl radical production, and hence contaminant degradation can be varied by changing the residence time, H2O2 concentration, and/or iron loading. Using these membrane-immobilized systems, successful removal of toxic organic compounds, such as pentachlorophenol (PCP), from water was demonstrated. Another toxic organic compound of interest for water treatment applications is trichloroethylene (TCE). Due to its limited solubility in water, a majority of the TCE is often present in the form of droplets. In this study, effective TCE droplet degradation using chelate-modified, iron-catalyzed free radical reactions at near-neutral pH was demonstrated. In order to predict the degradation of aqueous and non-aqueous phase TCE for these reactions, a mathematical model was constructed through the use of droplet mass transfer correlations and free radical reaction kinetics. KEYWORDS: Functionalized membrane, free radical, hydrogen peroxide, chelate-modified, membrane reactor

Decomposition mechanism of an artemisinin-type compound via hemin-electrocatalysis.

PubMed

Chen, H Y; Chen, Y; Zhu, S M; Bian, N S; Shan, F; Li, Y

1999-01-01

The interaction between a typical derivative of artemisinin and hemin was investigated by electrochemical and spectroelectrochemical methods. This derivative can be reduced via hemin-catalysis at the glassy carbon electrode, the cathodic overpotential is decreased by ca. 650 mV. A HPLC method for separating the products of the catalytic reaction was established. They were identified either in H(2)O-CH(3)CN solution or in tetrahydrofuran, respectively. The structures of these products show that the hemin-catalyzed decomposition of an artemisinin-type compound on the glassy carbon or reticulated vitreous carbon electrode can be achieved by both electrochemical reduction and rearrangement. The conclusion that the reaction of artemisinin with hemin is a critical step in the antimalarial mechanism of artemisinin can be drawn.

Modern biofuel cells for waste recycling in life support systems

NASA Technical Reports Server (NTRS)

Chen, L.; Bockris, J. OM.

1989-01-01

Innovative ways of treating urea in waste water reprocessing for long duration space exploration are being considered. Urea is very stable and therefore there are few effective ways for its decomposition. The feasibility of the use of the enzyme urease is to catalyze the hydrolysis of urea to ammonia and carbon dioxide is discussed, including a methodology, potential problems, the capabilities and advantages of such a system.

The influence of cyclomaltooligosaccharides (cyclodextrins) on the enzymatic decomposition of l-phenylalanine catalyzed by phenylalanine ammonia-lyase.

PubMed

Gubica, Tomasz; Pełka, Agnieszka; Pałka, Katarzyna; Temeriusz, Andrzej; Kańska, Marianna

2011-09-27

Cyclomaltohexaose (α-cyclodextrin) and cyclomaltoheptaose (β-cyclodextrin) as well as their four methyl ether derivatives, that is, hexakis(2,3-di-O-methyl)cyclomaltohexaose, hexakis(2,3,6-tri-O-methyl)cyclomaltohexaose, heptakis(2,3-di-O-methyl)cyclomaltoheptaose, and heptakis(2,3,6-tri-O-methyl)cyclomaltoheptaose were investigated as the additives in the course of enzymatic decomposition of l-phenylalanine catalyzed by phenylalanine ammonia-lyase. Only a few of those additives behaved like classical inhibitors of the enzymatic reaction under investigation because the values of the Michaelis constants that were obtained, as well as the maximum velocity values depended mostly atypically on the concentrations of those additives. In most cases cyclodextrins caused mixed inhibition, both competitive and noncompetitive, but they also acted as activators for selected concentrations. This atypical behaviour of cyclodextrins is caused by three different and independent effects. The inhibitory effect of cyclodextrins is connected with the decrease of substrate concentration and unfavourable influence on the flexibility of the enzyme molecules. On the other hand, the activating effect is connected with the decrease of product concentration (the product is an inhibitor of the enzymatic reaction under investigation). All these effects are caused by the ability of the cyclodextrins to form inclusion complexes. Copyright © 2011 Elsevier Ltd. All rights reserved.

Kinetic Studies on Enzyme-Catalyzed Reactions: Oxidation of Glucose, Decomposition of Hydrogen Peroxide and Their Combination

PubMed Central

Tao, Zhimin; Raffel, Ryan A.; Souid, Abdul-Kader; Goodisman, Jerry

2009-01-01

The kinetics of the glucose oxidase-catalyzed reaction of glucose with O2, which produces gluconic acid and hydrogen peroxide, and the catalase-assisted breakdown of hydrogen peroxide to generate oxygen, have been measured via the rate of O2 depletion or production. The O2 concentrations in air-saturated phosphate-buffered salt solutions were monitored by measuring the decay of phosphorescence from a Pd phosphor in solution; the decay rate was obtained by fitting the tail of the phosphorescence intensity profile to an exponential. For glucose oxidation in the presence of glucose oxidase, the rate constant determined for the rate-limiting step was k = (3.0 ± 0.7) ×104 M−1s−1 at 37°C. For catalase-catalyzed H2O2 breakdown, the reaction order in [H2O2] was somewhat greater than unity at 37°C and well above unity at 25°C, suggesting different temperature dependences of the rate constants for various steps in the reaction. The two reactions were combined in a single experiment: addition of glucose oxidase to glucose-rich cell-free media caused a rapid drop in [O2], and subsequent addition of catalase caused [O2] to rise and then decrease to zero. The best fit of [O2] to a kinetic model is obtained with the rate constants for glucose oxidation and peroxide decomposition equal to 0.116 s−1 and 0.090 s−1 respectively. Cellular respiration in the presence of glucose was found to be three times as rapid as that in glucose-deprived cells. Added NaCN inhibited O2 consumption completely, confirming that oxidation occurred in the cellular mitochondrial respiratory chain. PMID:19348778

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

Lian, Suoyuan; School of Chemical Engineering and Materials, Dalian Polytechnic University, Dalian 116034; Tsang, Chi Him A.

Graphical abstract: H-SiNWs can catalyze hydroxylation of benzene and degradation of methyl red under visible light irradiation. Highlights: Black-Right-Pointing-Pointer Hydrogen-terminated silicon nanowires were active photocatalyst in the hydroxylation of benzene under light. Black-Right-Pointing-Pointer Hydrogen-terminated silicon nanowires were also effective in the decomposition of methyl red dye. Black-Right-Pointing-Pointer The Si/SiO{sub x} core-shell structure is the main reason of the obtained high selectivity during the hydroxylation. -- Abstract: Hydrogen-terminated silicon nanowires (H-SiNWs) were used as heterogeneous photocatalysts for the hydroxylation of benzene and for the decomposition of methyl red under visible light irradiation. The above reactions were monitored by GC-MS and UV-Vismore » spectrophotometry, respectively, which shows 100% selectivity for the transformation of benzene to phenol. A complete decomposition of a 2 Multiplication-Sign 10{sup -4} M methyl red solution was achieved within 30 min. The high selectivity for the hydroxylation of benzene and the photodecomposition demonstrate the catalytic activity of ultrafine H-SiNWs during nanocatalysis.« less

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

Xiong, W; Zhou, Yunshen; Hou, Wenjia

Direct formation of graphene with controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications. Despite significant progress achieved in understanding the formation of graphene on metallic surfaces through chemical vapor deposition (CVD) of hydrocarbons, very limited research is available elucidating the graphene formation process via rapid thermal processing (RTP) of solid-state amorphous carbon, through which graphene is formed directly on dielectric surfaces accompanied by autonomous nickel evaporation. It is suggested that a metastable hexagonal nickel carbide (Ni 3C) intermediate phase plays a critical role in transforming amorphous carbon to 2D crystalline graphene and contributing tomore » the autonomous Ni evaporation. Temperature resolved carbon and nickel evolution in the RTP process is investigated using Auger electron spectroscopic (AES) depth profiling and glancing-angle X-ray diffraction (GAXRD). Formation, migration and decomposition of the hexagonal Ni 3C are confirmed to be responsible for the formation of graphene and the evaporation of Ni at 1100 °C. The Ni 3C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation, and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.« less

Carbon Isotopes of Alkanes in Hydrothermal Abiotic Organic Synthesis Processes at High Temperatures and Pressures: An Experimental Study

NASA Technical Reports Server (NTRS)

Fu, Qi; Socki, Richard A.; Niles, Paul B.

2010-01-01

Observation of methane in the Martian atmosphere has been reported by different detection techniques [1-4]. With more evidence showing extensive water-rock interaction in Martian history [5-7], abiotic formation by Fischer-Tropsch Type (FTT) synthesis during serpentization reactions may be one possible process responsible for methane generation on Mars [8, 9]. While the experimental studies performed to date leave little doubt that chemical reactions exist for the abiotic synthesis of organic compounds by mineral surface-catalyzed reactions [10-12], little is known about the reaction pathways by which CO2 and/or CO are reduced under hydrothermal conditions. Carbon and hydrogen isotope measurements of alkanes have been used as an effective tool to constrain the origin and reaction pathways of hydrocarbon formation. Alkanes generated by thermal breakdown of high molecular weight organic compounds have carbon and hydrogen isotopic signatures completely distinct from those formed abiotically [13-15]. Recent experimental studies, however, showed that different abiogenic hydrocarbon formation processes (e.g., polymerization vs. depolymerization) may have different carbon and hydrogen isotopic patterns [16]. Results from previous experiments studying decomposition of higher molecular weight organic compounds (lignite) also suggested that pressure could be a crucial factor affecting fractionation of carbon isotopes [17]. Under high pressure conditions, no experimental data are available describing fractionation of carbon isotope during mineral catalyzed FTT synthesis. Thus, hydrothermal experiments present an excellent opportunity to provide the requisite carbon isotope data. Such data can also be used to identify reaction pathways of abiotic organic synthesis under experimental conditions.

Application of biocatalysts to Space Station ECLSS and PMMS water reclamation

NASA Technical Reports Server (NTRS)

Jolly, Clifford D.; Bagdigian, Robert M.

1989-01-01

Immobilized enzyme reactors have been developed and tested for potential water reclamation applications in the Space Station Freedom Environmental Control and Life Support System (ECLSS) and Process Materials Management System (PMMS). The reactors convert low molecular weight organic contaminants found in ECLSS and PMMS wastewaters to compounds that are more efficiently removed by existing technologies. Demonstration of the technology was successfully achieved with two model reactors. A packed bed reactor containing immobilized urease was found to catalyze the complete decomposition of urea to by-products that were subsequently removed using conventional ion exchange results. A second reactor containing immobilized alcohol oxidase showed promising results relative to its ability to convert methanol and ethanol to the corresponding aldehydes for subsequent removal. Preliminary assessments of the application of biocatalysts to ECLSS and PMMS water reclamation sytems are presented.

40 CFR 268.40 - Applicability of treatment standards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... chlorinated aliphatic hydrocarbons by free radical catalyzed processes. These chlorinated aliphatic... chlorinated aliphatic hydrocarbons, by free radical catalyzed processes. These chlorinated aliphatic... production of certain chlorinated aliphatic hydrocarbons, by free radical catalyzed processes. These...

40 CFR 268.40 - Applicability of treatment standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... chlorinated aliphatic hydrocarbons by free radical catalyzed processes. These chlorinated aliphatic... chlorinated aliphatic hydrocarbons, by free radical catalyzed processes. These chlorinated aliphatic... production of certain chlorinated aliphatic hydrocarbons, by free radical catalyzed processes. These...

Mechanism of xanthine oxidase catalyzed biotransformation of HMX under anaerobic conditions.

PubMed

Bhushan, Bharat; Paquet, Louise; Halasz, Annamaria; Spain, Jim C; Hawari, Jalal

2003-06-27

Enzyme catalyzed biotransformation of the energetic chemical octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is not known. The present study describes a xanthine oxidase (XO) catalyzed biotransformation of HMX to provide insight into the biodegradation pathway of this energetic chemical. The rates of biotransformation under aerobic and anaerobic conditions were 1.6+/-0.2 and 10.5+/-0.9 nmolh(-1)mgprotein(-1), respectively, indicating that anaerobic conditions favored the reaction. The biotransformation rate was about 6-fold higher using NADH as an electron-donor compared to xanthine. During the course of reaction, the products obtained were nitrite (NO(2)(-)), methylenedinitramine (MDNA), 4-nitro-2,4-diazabutanal (NDAB), formaldehyde (HCHO), nitrous oxide (N(2)O), formic acid (HCOOH), and ammonium (NH(4)(+)). The product distribution gave carbon and nitrogen mass-balances of 91% and 88%, respectively. A comparative study with native-, deflavo-, and desulfo-XO and the site-specific inhibition studies showed that HMX biotransformation occurred at the FAD-site of XO. Nitrite stoichiometry revealed that an initial single N-denitration step was sufficient for the spontaneous decomposition of HMX.

Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

NASA Astrophysics Data System (ADS)

Kuznetsov, N. Yu; Bubnov, Yu N.

2015-07-01

The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references.

Review of iron-free Fenton-like systems for activating H2O2 in advanced oxidation processes.

PubMed

Bokare, Alok D; Choi, Wonyong

2014-06-30

Iron-catalyzed hydrogen peroxide decomposition for in situ generation of hydroxyl radicals (HO(•)) has been extensively developed as advanced oxidation processes (AOPs) for environmental applications. A variety of catalytic iron species constituting metal salts (in Fe(2+) or Fe(3+) form), metal oxides (e.g., Fe2O3, Fe3O4), and zero-valent metal (Fe(0)) have been exploited for chemical (classical Fenton), photochemical (photo-Fenton) and electrochemical (electro-Fenton) degradation pathways. However, the requirement of strict acidic conditions to prevent iron precipitation still remains the bottleneck for iron-based AOPs. In this article, we present a thorough review of alternative non-iron Fenton catalysts and their reactivity towards hydrogen peroxide activation. Elements with multiple redox states (like chromium, cerium, copper, cobalt, manganese and ruthenium) all directly decompose H2O2 into HO(•) through conventional Fenton-like pathways. The in situ formation of H2O2 and decomposition into HO(•) can be also achieved using electron transfer mechanism in zero-valent aluminum/O2 system. Although these Fenton systems (except aluminum) work efficiently even at neutral pH, the H2O2 activation mechanism is very specific to the nature of the catalyst and critically depends on its composition. This review describes in detail the complex mechanisms and emphasizes on practical limitations influencing their environmental applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Studies of a Diazo Cyclopropanation Strategy for the Total Synthesis of (-)-Lundurine A.

PubMed

Huang, Hong-Xiu; Jin, Shuai-Jiang; Gong, Jin; Zhang, Dan; Song, Hao; Qin, Yong

2015-09-14

The bioactive Kopsia alkaloids lundurines A-D are the only natural products known to contain indolylcyclopropane. Achieving their syntheses can provide important insights into their biogenesis, as well as novel synthetic routes for complex natural products. Asymmetric total synthesis of (-)-lundurine A has previously been achieved through a Simmons-Smith cyclopropanation strategy. Here, the total synthesis of (-)-lundurine A was carried out using a metal-catalyzed diazo cyclopropanation strategy. In order to avoid a carbene CH insertion side reaction during cyclopropanation of α-diazo- carboxylates or cyanides, a one-pot, copper-catalyzed Bamford-Stevens diazotization/diazo decomposition/cyclopropanation cascade was developed, involving hydrazone. This approach simultaneously generates the C/D/E ring system and the two chiral quaternary centers at C2 and C7. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-propelled micromotors based on Au-mesoporous silica nanorods

NASA Astrophysics Data System (ADS)

Wang, Ying-Shuai; Xia, Hong; Lv, Chao; Wang, Lei; Dong, Wen-Fei; Feng, Jing; Sun, Hong-Bo

2015-07-01

Here, a chemical powered micromotor from the assembly of Au-SiO2 nanorods is presented. This new micromotor can be propelled efficiently by hydrogen bubbles generated from a hydrolysis reaction of aqueous NaBH4 and KBH4 and by oxygen bubbles produced by decomposition of H2O2. The monodisperse Au nanoparticles in mesoporous silica particles could catalyze the decomposition of two different kinds of fuels and produce bubbles. High speeds of 80 μm s-1 and recycles of more than 30 times are achieved in both NaBH4 and H2O2 media. Locomotion and rolling forms of movement were found. The locomotion forms can be obtained in a larger proportion by patterning the Au-SiO2 nanorods and a PDMS membrane. These micromotors that use multiple fuel sources to power them offer a broader scope of preparation and show considerable promise for diverse applications of nanomotors in different chemical environments.Here, a chemical powered micromotor from the assembly of Au-SiO2 nanorods is presented. This new micromotor can be propelled efficiently by hydrogen bubbles generated from a hydrolysis reaction of aqueous NaBH4 and KBH4 and by oxygen bubbles produced by decomposition of H2O2. The monodisperse Au nanoparticles in mesoporous silica particles could catalyze the decomposition of two different kinds of fuels and produce bubbles. High speeds of 80 μm s-1 and recycles of more than 30 times are achieved in both NaBH4 and H2O2 media. Locomotion and rolling forms of movement were found. The locomotion forms can be obtained in a larger proportion by patterning the Au-SiO2 nanorods and a PDMS membrane. These micromotors that use multiple fuel sources to power them offer a broader scope of preparation and show considerable promise for diverse applications of nanomotors in different chemical environments. Electronic supplementary information (ESI) available: More electronic microscopy graphs, UV-Vis spectra and N2 adsorption isotherms. See DOI: 10.1039/c5nr02545a

Process for treating alkaline wastes for vitrification

DOEpatents

Hsu, Chia-lin W.

1994-01-01

According to its major aspects and broadly stated, the present invention is a process for treating alkaline waste materials, including high level radioactive wastes, for vitrification. The process involves adjusting the pH of the wastes with nitric acid, adding formic acid (or a process stream containing formic acid) to reduce mercury compounds to elemental mercury and MnO{sub 2} to the Mn(II) ion, and mixing with class formers to produce a melter feed. The process minimizes production of hydrogen due to noble metal-catalyzed formic acid decomposition during, treatment, while producing a redox-balanced feed for effective melter operation and a quality glass product. An important feature of the present invention is the use of different acidifying and reducing, agents to treat the wastes. The nitric acid acidifies the wastes to improve yield stress and supplies acid for various reactions; then the formic acid reduces mercury compounds to elemental mercury and MnO{sub 2}) to the Mn(II) ion. When the pH of the waste is lower, reduction of mercury compounds and MnO{sub 2}) is faster and less formic acid is needed, and the production of hydrogen caused by catalytically-active noble metals is decreased.

Silicon Nanowire Growth at Chosen Positions and Orientations

NASA Technical Reports Server (NTRS)

Getty, Stephanie A.

2009-01-01

It is now possible to grow silicon nanowires at chosen positions and orientations by a method that involves a combination of standard microfabrication processes. Because their positions and orientations can be chosen with unprecedented precision, the nanowires can be utilized as integral parts of individually electronically addressable devices in dense arrays. Nanowires made from silicon and perhaps other semiconductors hold substantial promise for integration into highly miniaturized sensors, field-effect transistors, optoelectronic devices, and other electronic devices. Like bulk semiconductors, inorganic semiconducting nanowires are characterized by electronic energy bandgaps that render them suitable as means of modulating or controlling electronic signals through electrostatic gating, in response to incident light, or in response to molecules of interest close to their surfaces. There is now potential for fabricating arrays of uniform, individually electronically addressable nanowires tailored to specific applications. The method involves formation of metal catalytic particles at the desired positions on a substrate, followed by heating the substrate in the presence of silane gas. The figure illustrates an example in which a substrate includes a silicon dioxide surface layer that has been etched into an array of pillars and the catalytic (in this case, gold) particles have been placed on the right-facing sides of the pillars. The catalytic thermal decomposition of the silane to silicon and hydrogen causes silicon columns (the desired nanowires) to grow outward from the originally catalyzed spots on the substrate, carrying the catalytic particles at their tips. Thus, the position and orientation of each silicon nanowire is determined by the position of its originally catalyzed spot on the substrate surface, and the orientation of the nanowire is perpendicular to the substrate surface at the originally catalyzed spot.

Alumina nanowire growth by water decomposition and the peritectic reaction of decagonal Al{sub 65}Cu{sub 15}Co{sub 20} quasicrystals

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

Téllez-Vázquez, J.O., E-mail: oswald.tellez@gmail.com; Patiño-Carachure, C., E-mail: cpatino@pampano.unacar.mx; Rosas, G., E-mail: grtrejo@yahoo07.com.mx

2016-02-15

In this paper, the results of the Al{sub 2}O{sub 3} nanowires' growth through a chemical reaction between Al and water vapor at 1050 °C are presented. Our approach is based on two primary considerations. First, at room temperature, the Al{sub 65}Cu{sub 15}Co{sub 20} alloy is affected by the following mechanism: 2Al (s) + 3H{sub 2}O (g) → Al{sub 2}O{sub 3} (s) + H{sub 2} (g). In this reaction, the released hydrogen induces cleavage fracture of the material to form small particles. Second, the Al{sub 65}Cu{sub 15}Co{sub 20} quasicrystalline phase is transformed on heating to liquid + Al (Cu, Co) cubicmore » phase through a peritectic reaction at 1050 °C. The Al-rich liquid then reacts with water vapor, forming Al{sub 2}O{sub 3} nanowires. X-ray diffraction (XRD) analysis shows that the formed nanowires have a hexagonal structure, and infrared analysis further confirms the presence of α-Al{sub 2}O{sub 3} phase in the final products. Transmission electron microscopy observations show that nanoparticles are present at the end of nanowires, suggesting the VLS growth mechanism. Elemental analysis by energy dispersive spectroscopy (EDS) indicates that the particles at the tip of the nanowires are mainly formed by Co and Cu alloying elements and small amounts of Al. Electron microscopy observations showed nanowires with diameters ranging from 20 to 70 nm; the average diameter was 37 nm and the nanowire lengths were up to several micrometers. - Highlights: • Hexagonal alumina nanowires are grown at 1050 °C through the VLS process. • Alumina nanowires are obtained by the decomposition of decagonal quasicrystalline phase. • The decagonal phase decomposition follows a peritectic reaction at 1030 °C. • Nanoparticles are obtained by hydrogen embrittlement mechanism. • The nanoparticles catalyze the water decomposition to form wires.« less

Reactions catalyzed by haloporphyrins

DOEpatents

Ellis, P.E. Jr.; Lyons, J.E.

1996-02-06

The invention provides novel methods for the oxidation of hydrocarbons with oxygen-containing gas to form hydroxy-group containing compounds and for the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts used in the methods of the invention comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The catalyst compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of alkanes is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of alkanes and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of alkanes and decomposition of alkyl hydroperoxides.

Reactions catalyzed by haloporphyrins

DOEpatents

Ellis, Jr., Paul E.; Lyons, James E.

1996-01-01

The invention provides novel methods for the oxidation of hydrocarbons with oxygen-containing gas to form hydroxy-group containing compounds and for the decomposition of hydroperoxides to form hydroxygroup containing compounds. The catalysts used in the methods of the invention comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The catalyst compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of alkanes is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of alkanes and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of alkanes and decomposition of alkyl hydroperoxides.

Ru(III) catalyzed permanganate oxidation of aniline at environmentally relevant pH.

PubMed

Zhang, Jing; Zhang, Ying; Wang, Hui; Guan, Xiaohong

2014-07-01

Ru(III) was employed as catalyst for aniline oxidation by permanganate at environmentally relevant pH for the first time. Ru(III) could significantly improve the oxidation rate of aniline by 5-24 times with its concentration increasing from 2.5 to 15 μmol/L. The reaction of Ru(III) catalyzed permanganate oxidation of aniline was first-order with respect to aniline, permanganate and Ru(III), respectively. Thus the oxidation kinetics can be described by a third-order rate law. Aniline degradation by Ru(III) catalyzed permanganate oxidation was markedly influenced by pH, and the second-order rate constant (ktapp) decreased from 643.20 to 2.67 (mol/L)⁻¹sec⁻¹ with increasing pH from 4.0 to 9.0, which was possibly due to the decrease of permanganate oxidation potential with increasing pH. In both the uncatalytic and catalytic permanganate oxidation, six byproducts of aniline were identified in UPLC-MS/MS analysis. Ru(III), as an electron shuttle, was oxidized by permanganate to Ru(VI) and Ru(VII), which acted the co-oxidants for decomposition of aniline. Although Ru(III) could catalyze permanganate oxidation of aniline effectively, dosing homogeneous Ru(III) into water would lead to a second pollution. Therefore, efforts would be made to investigate the catalytic performance of supported Ru(III) toward permanganate oxidation in our future study. Copyright © 2014. Published by Elsevier B.V.

A comparative study of ozonation, iron coated zeolite catalyzed ozonation and granular activated carbon catalyzed ozonation of humic acid.

PubMed

Gümüş, Dilek; Akbal, Feryal

2017-05-01

This study compares ozonation (O 3 ), iron coated zeolite catalyzed ozonation (ICZ-O 3 ) and granular activated carbon catalyzed ozonation (GAC-O 3 ) for removal of humic acid from an aqueous solution. The results were evaluated by the removal of DOC that specifies organic matter, UV 254 absorbance, SUVA (Specific Ultraviolet Absorbance at 254 nm) and absorbance at 436 nm. When ozonation was used alone, DOC removal was 21.4% at an ozone concentration of 10 mg/L, pH 6.50 and oxidation time of 60 min. The results showed that the use of ICZ or GAC as a catalyst increased the decomposition of humic acid compared to ozonation alone. DOC removal efficiencies were 62% and 48.1% at pH 6.5, at a catalyst loading of 0.75 g/L, and oxidation time of 60 min for ICZ and GAC, respectively. The oxidation experiments were also carried out using <100 kDa and <50 kDa molecular size fractions of humic acid in the presence of ICZ or GAC. Catalytic ozonation also yielded better DOC and UV 254 reduction in both <50 kDa and <100 kDa fractions of HA compared to ozonation. Copyright © 2017 Elsevier Ltd. All rights reserved.

An Overview of Hydrogen Generation and Storage for Low-Temperature PEM Fuel Cells

DTIC Science & Technology

1999-11-01

environment. Otherwise, the wt % of stored hydrogen is attractive; e.g., LiH is 25 percent. Thermal stability of pure alkali and alkaline earth- metal ...nanofibers can be prepared by metal -catalyzed decomposition (at 450 to 750 °C) of carbon-containing gases to possess a cross-sectional area between 30 to ...respect to the face of the metal particle. Separation distance between layers depends on the type of catalyst, gas, and reaction conditions used

Atomic and molecular adsorption on Fe(110)

DOE PAGES

Xu, Lang; Kirvassilis, Demetrios; Bai, Yunhai; ...

2017-09-12

Iron is the principal catalyst for the ammonia synthesis process and the Fischer–Tropsch process, as well as many other heterogeneously catalyzed reactions. It is thus of fundamental importance to understand the interactions between the iron surface and various reaction intermediates. Here in this paper, we present a systematic study of atomic and molecular adsorption behavior over Fe(110) using periodic, self-consistent density functional theory (DFT-GGA) calculations. The preferred binding sites, binding energies, and the corresponding surface deformation energies of five atomic species (H, C, N, O, and S), six molecular species (NH 3, CH 4, N 2, CO, HCN, and NO),more » and eleven molecular fragments (CH, CH 2, CH 3, NH, NH 2, OH, CN, COH, HCO, NOH, and HNO) were determined on the Fe(110) surface at a coverage of 0.25 monolayer. The binding strengths calculated using the PW91 functional decreased in the following order: C> CH > N > O > S > NH > COH > CN > CH2 > NOH > OH > HNO > HCO > NH2 > H > NO > HCN > CH 3 > CO > N 2 > NH 3. No stable binding structures were observed for CH 4. The estimated diffusion barriers and pathways, as well as the adsorbate-surface and intramolecular vibrational modes of all the adsorbates at their preferred binding sites, were identified. Using the calculated adsorption energetics, we constructed the potential energy surfaces for a few surface reactions including the decomposition of methane, ammonia, dinitrogen, carbon monoxide, and nitric oxide. These potential energy surfaces provide valuable insight into the ability of Fe(110) to catalyze common elementary steps.« less

Catalytic reduction of dinitrogen to ammonia at a single molybdenum center

PubMed Central

Weare, Walter W.; Dai, Xuliang; Byrnes, Matthew J.; Chin, Jia Min; Schrock, Richard R.; Müller, Peter

2006-01-01

Since our discovery of the catalytic reduction of dinitrogen to ammonia at a single molybdenum center, we have embarked on a variety of studies designed to further understand this complex reaction cycle. These include studies of both individual reaction steps and of ligand variations. An important step in the reaction sequence is exchange of ammonia for dinitrogen in neutral molybdenum(III) compounds. We have found that this exchange reaction is first order in dinitrogen and relatively fast (complete in <1 h) at 1 atm of dinitrogen. Variations of the terphenyl substituents in the triamidoamine ligand demonstrate that the original ligand is not unique in its ability to yield successful catalysts. However, complexes that contain sterically less demanding ligands fail to catalyze formation of ammonia from dinitrogen; it is proposed as a consequence of a base-catalyzed decomposition of a diazenido (MoNNH) intermediate. PMID:17085586

Naphthenic acids removal from high TDS produced water by persulfate mediated iron oxide functionalized catalytic membrane, and by nanofiltration.

PubMed

Aher, Ashish; Papp, Joseph; Colburn, Andrew; Wan, Hongyi; Hatakeyama, Evan; Prakash, Prakhar; Weaver, Ben; Bhattacharyya, Dibakar

2017-11-01

Oil industries generate large amounts of produced water containing organic contaminants, such as naphthenic acids (NA) and very high concentrations of inorganic salts. Recovery of potable water from produced water can be highly energy intensive is some cases due to its high salt concentration, and safe discharge is more suitable. Here, we explored catalytic properties of iron oxide (Fe x O y nanoparticles) functionalized membranes in oxidizing NA from water containing high concentrations of total dissolved solids (TDS) using persulfate as an oxidizing agent. Catalytic decomposition of persulfate by Fe x O y functionalized membranes followed pseudo-first order kinetics with an apparent activation energy of 18 Kcal/mol. Fe x O y functionalized membranes were capable of lowering the NA concentrations to less than discharge limits of 10 ppm at 40 °C. Oxidation state of iron during reaction was quantified. Membrane performance was investigated for extended period of time. A coupled process of advanced oxidation catalyzed by membrane and nanofiltration was also evaluated. Commercially available nanofiltration membranes were found capable of retaining NA from water containing high concentrations of dissolved salts. Commercial NF membranes, Dow NF270 (Dow), and NF8 (Nanostone) had NA rejection of 79% and 82%, respectively. Retentate for the nanofiltration was further treated with advanced oxidation catalyzed by Fe x O y functionalized membrane for removal of NA.

Catalysis and co-catalysis of bond cleavages in coal and coal analogs. Final report, August 1, 1990--January 31, 1994

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

Miller, B.

1994-05-01

In work prior to the inception of this project, the authors observed that mixtures of phenolic materials and polyalkoxyaromatic molecules were appreciably more effective in catalyzing the decompositions of di-2-naphthyl ether and of di-1-naphthyl sulfide in tetralin solutions at 450{degrees}C than were the phenols by themselves, even though the polyalkoxyaromatic molecules, in the absence of phenolic co- catalysts, show essentially no catalytic activity. This was of appreciable interest in coal research because dinapthyl ether and dinapthyl sulfide have been employed as model compounds for coals in studies aimed at cleaving ether and sulfide bonds similar to those in coals. Themore » authors proposed (R. K. Sharma, K. P. Raman, and B. Miller) that the mixed catalysts used in these studies catalyze cleavages of ether and sulfide bonds by means of a mechanism involving electron transfer from the polyalkoxyaromatics to the substrates, which are activated as electron acceptors by hydrogen bonding to phenols. Since phenols themselves are electron donors, they also proposed that the well known effects of phenols in catalyzing the conversion of coals are due to similar electron transfer mechanisms.« less

Rank-based decompositions of morphological templates.

PubMed

Sussner, P; Ritter, G X

2000-01-01

Methods for matrix decomposition have found numerous applications in image processing, in particular for the problem of template decomposition. Since existing matrix decomposition techniques are mainly concerned with the linear domain, we consider it timely to investigate matrix decomposition techniques in the nonlinear domain with applications in image processing. The mathematical basis for these investigations is the new theory of rank within minimax algebra. Thus far, only minimax decompositions of rank 1 and rank 2 matrices into outer product expansions are known to the image processing community. We derive a heuristic algorithm for the decomposition of matrices having arbitrary rank.

Bicarbonate is a recycling substrate for cyanase.

PubMed

Johnson, W V; Anderson, P M

1987-07-05

Cyanase is an inducible enzyme in Escherichia coli that catalyzes bicarbonate-dependent decomposition of cyanate to ammonia and bicarbonate. Previous studies provided evidence that carbamate is an initial product and that the kinetic mechanism is rapid equilibrium random (bicarbonate serving as substrate as opposed to activator); the following mechanism was proposed (Anderson, P. M. (1980) Biochemistry 19, 2282-2888; Anderson, P. M., and Little, R. M. (1986) Biochemistry 25, 1621-1626). (formula; see text) Direct evidence for this mechanism was obtained in this study by 1) determining whether CO2 or HCO3- serves as substrate and is formed as product, 2) identifying the products formed from [14C]HCO3- and [14C] OCN-, 3) identifying the products formed from [13C] HCO3- and [12C]OCN- in the presence of [18O]H2O, and 4) determining whether 18O from [18O]HCO3- is incorporated into CO2 derived from OCN-. Bicarbonate (not CO2) is the substrate. Carbon dioxide (not HCO3-) is produced in stoichiometric amounts from both HCO3- and OCN-. 18O from [18O]H2O is not incorporated into CO2 formed from either HCO3- or OCN-. Oxygen-18 from [18O]HCO3- is incorporated into CO2 derived from OCN-. These results support the above mechanism, indicating that decomposition of cyanate catalyzed by cyanase is not a hydrolysis reaction and that bicarbonate functions as a recycling substrate.

Self-consistent nonlocal feedback theory for electrocatalytic swimmers with heterogeneous surface chemical kinetics

NASA Astrophysics Data System (ADS)

Nourhani, Amir; Crespi, Vincent H.; Lammert, Paul E.

2015-06-01

We present a self-consistent nonlocal feedback theory for the phoretic propulsion mechanisms of electrocatalytic micromotors or nanomotors. These swimmers, such as bimetallic platinum and gold rods catalyzing decomposition of hydrogen peroxide in aqueous solution, have received considerable theoretical attention. In contrast, the heterogeneous electrochemical processes with nonlocal feedback that are the actual "engines" of such motors are relatively neglected. We present a flexible approach to these processes using bias potential as a control parameter field and a locally-open-circuit reference state, carried through in detail for a spherical motor. While the phenomenological flavor makes meaningful contact with experiment easier, required inputs can also conceivably come from, e.g., Frumkin-Butler-Volmer kinetics. Previously obtained results are recovered in the weak-heterogeneity limit and improved small-basis approximations tailored to structural heterogeneity are presented. Under the assumption of weak inhomogeneity, a scaling form is deduced for motor speed as a function of fuel concentration and swimmer size. We argue that this form should be robust and demonstrate a good fit to experimental data.

Unified mechanism of alkali and alkaline earth catalyzed gasification reactions of carbon by CO2 and H2O

USGS Publications Warehouse

Chen, S.G.; Yang, R.T.

1997-01-01

From molecular orbital calculations, a unified mechanism is proposed for the gasification reactions of graphite by CO2 and H2O, both uncatalyzed and catalyzed by alkali and alkaline earth catalysts. In this mechanism, there are two types of oxygen intermediates that are bonded to the active edge carbon atoms: an in-plane semiquinone type, Cf(O), and an off-plane oxygen bonded to two saturated carbon atoms that are adjacent to the semiquinone species, C(O)Cf(O). The rate-limiting step is the decomposition of these intermediates by breaking the C-C bonds that are connected to Cf(O). A new rate equation is derived for the uncatalyzed reactions, and that for the catalyzed reactions is readily available from the proposed mechanism. The proposed mechanism can account for several unresolved experimental observations: TPD and TK (transient kinetics) desorption results of the catalyzed systems, the similar activation energies for the uncatalyzed and catalyzed reactions, and the relative activities of the alkali and alkaline earth elements. The net charge of the edge carbon active site is substantially changed by gaining electron density from the alkali or alkaline earth element (by forming C-O-M, where M stands for metal). The relative catalytic activities of these elements can be correlated with their abilities of donating electrons and changing the net charge of the edge carbon atom. As shown previously (Chen, S. G.; Yang, R. T. J. Catal. 1993, 141, 102), only clusters of the alkali compounds are active. This derives from the ability of the clusters to dissociate CO2 and H2O to form O atoms and the mobility of the dissociated O atoms facilitated by the clusters.

Reversibility of Noble Metal-Catalyzed Aprotic Li-O₂ Batteries.

PubMed

Ma, Shunchao; Wu, Yang; Wang, Jiawei; Zhang, Yelong; Zhang, Yantao; Yan, Xinxiu; Wei, Yang; Liu, Peng; Wang, Jiaping; Jiang, Kaili; Fan, Shoushan; Xu, Ye; Peng, Zhangquan

2015-12-09

The aprotic Li-O2 battery has attracted a great deal of interest because, theoretically, it can store far more energy than today's batteries. Toward unlocking the energy capabilities of this neotype energy storage system, noble metal-catalyzed high surface area carbon materials have been widely used as the O2 cathodes, and some of them exhibit excellent electrochemical performances in terms of round-trip efficiency and cycle life. However, whether these outstanding electrochemical performances are backed by the reversible formation/decomposition of Li2O2, i.e., the desired Li-O2 electrochemistry, remains unclear due to a lack of quantitative assays for the Li-O2 cells. Here, noble metal (Ru and Pd)-catalyzed carbon nanotube (CNT) fabrics, prepared by magnetron sputtering, have been used as the O2 cathode in aprotic Li-O2 batteries. The catalyzed Li-O2 cells exhibited considerably high round-trip efficiency and prolonged cycle life, which could match or even surpass some of the best literature results. However, a combined analysis using differential electrochemical mass spectrometry and Fourier transform infrared spectroscopy, revealed that these catalyzed Li-O2 cells (particularly those based on Pd-CNT cathodes) did not work according to the desired Li-O2 electrochemistry. Instead the presence of noble metal catalysts impaired the cells' reversibility, as evidenced by the decreased O2 recovery efficiency (the ratio of the amount of O2 evolved during recharge/that consumed in the preceding discharge) coupled with increased CO2 evolution during charging. The results reported here provide new insights into the O2 electrochemistry in the aprotic Li-O2 batteries containing noble metal catalysts and exemplified the importance of the quantitative assays for the Li-O2 reactions in the course of pursuing truly rechargeable Li-O2 batteries.

Application of the base catalyzed decomposition process to treatment of PCB-contaminated insulation and other materials associated with US Navy vessels. Final report

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

Schmidt, A.J.; Zacher, A.H.; Gano, S.R.

1996-09-01

The BCD process was applied to dechlorination of two types of PCB-contaminated materials generated from Navy vessel decommissioning activities at Puget Sound Naval Shipyard: insulation of wool felt impregnated with PCB, and PCB-containing paint chips/debris from removal of paint from metal surfaces. The BCD process is a two-stage, low-temperature chemical dehalogenation process. In Stage 1, the materials are mixed with sodium bicarbonate and heated to 350 C. The volatilized halogenated contaminants (eg, PCBs, dioxins, furans), which are collected in a small volume of particulates and granular activated carbon, are decomposed by the liquid-phase reaction (Stage 2) in a stirred-tank reactor,more » using a high-boiling-point hydrocarbon oil as the reaction medium, with addition of a hydrogen donor, a base (NaOH), and a catalyst. The tests showed that treating wool felt insulation and paint chip wastes with Stage 2 on a large scale is feasible, but compared with current disposal costs for PCB-contaminated materials, using Stage 2 would not be economical at this time. For paint chips generated from shot/sand blasting, the solid-phase BCD process (Stage 1) should be considered, if paint removal activities are accelerated in the future.« less

Continuous process for singlet oxygenation of hydrophobic substrates in microemulsion using a pervaporation membrane.

PubMed

Caron, Laurent; Nardello, Véronique; Mugge, José; Hoving, Erik; Alsters, Paul L; Aubry, Jean-Marie

2005-02-15

Chemically generated singlet oxygen (1O2, 1Deltag) is able to oxidize a great deal of hydrophobic substrates from molybdate-catalyzed hydrogen peroxide decomposition, provided a suitable reaction medium such as a microemulsion system is used. However, high substrate concentrations or poorly reactive organics require large amounts of H2O2 that generate high amounts of water and thus destabilize the system. We report results obtained on combining dark singlet oxygenation of hydrophobic substrates in microemulsions with a pervaporation membrane process. To avoid composition alterations after addition of H2O2 during the peroxidation, the reaction mixture circulates through a ceramic membrane module that enables a partial and selective dewatering of the microemulsion. Optimization phase diagrams of sodium molybdate/water/alcohol/anionic surfactant/organic solvent have been elaborated to maximize the catalyst concentration and therefore the reaction rate. The membrane selectivity towards the mixture constituents has been investigated showing that a high retention is observed for the catalyst, for organic solvents and hydrophobic substrates, but not for n-propanol (cosurfactant) and water. The efficiency of such a process is illustrated with the peroxidation of a poorly reactive substrate, viz., beta-pinene.

Theoretical study on stabilization mechanisms of nitrate esters using aromatic amines as stabilizers.

PubMed

Sun, Zhi-Dan; Fu, Xiao-Long; Yu, Hong-Jian; Fan, Xue-Zhong; Ju, Xue-Hai

2017-10-05

The propellants of nitrate esters can be stabilized by some aromatic amines practically. To probe the mechanism of this phenomenon, we performed DFT calculations on: (1) The decompositions of nitrate esters (with and without the catalysis of NO 2 ) and (2) the reaction between the stabilizers and the nitro dioxide (NO 2 is released during the storage of nitrate esters). The structures on the reaction paths (reactants, intermediates and products) were optimized at the (U)B3LYP/6-31G** level. It was shown that NO 2 lowers the activation energy barrier in the decomposition of nitrate ester by 11.82-17.86kJ/mol and efficiently catalyzes the rupture of ONO 2 bond. However, the aromatic amines, typical stabilizers for nitrate esters, can easily eliminate NO 2 with activation barriers as low as 27-113kJ/mol (with one exception of 128kJ/mol). These values are, for most cases, lower or much lower than the activation energy barriers for reactions between nitrate esters and NO 2 (127-137kJ/mol). Consequently, the stabilizers can block the NO 2 catalysis for the decompositions of nitrate esters. Copyright © 2017 Elsevier B.V. All rights reserved.

The dynamics of surface-catalyzed reactions studied by infrared chemiluminescence of the CO and CO{sub 2} products

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

Watanabe, K.; Uetsuka, H.; Ohnuma, H.

The infrared chemiluminescence technique has been applied to the selective formation of syngas (CO + H{sub 2}) from the oxidation of small alkanes on Pt, the decomposition and oxidation of CH{sub 3}OH and HCOOH on Pt and Ni, and CO oxidation on Pd(111) and Pd(110). The different internal (vibrational and rotational) energy states of the CO and CO{sub 2} products have been observed, which reflect the difference in the dynamics of these reactions.

Solid-state graphene formation via a nickel carbide intermediate phase [Nickel carbide (Ni 3C) as an intermediate phase for graphene formation

DOE PAGES

Xiong, W; Zhou, Yunshen; Hou, Wenjia; ...

2015-11-10

Direct formation of graphene with controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications. Despite significant progress achieved in understanding the formation of graphene on metallic surfaces through chemical vapor deposition (CVD) of hydrocarbons, very limited research is available elucidating the graphene formation process via rapid thermal processing (RTP) of solid-state amorphous carbon, through which graphene is formed directly on dielectric surfaces accompanied by autonomous nickel evaporation. It is suggested that a metastable hexagonal nickel carbide (Ni 3C) intermediate phase plays a critical role in transforming amorphous carbon to 2D crystalline graphene and contributing tomore » the autonomous Ni evaporation. Temperature resolved carbon and nickel evolution in the RTP process is investigated using Auger electron spectroscopic (AES) depth profiling and glancing-angle X-ray diffraction (GAXRD). Formation, migration and decomposition of the hexagonal Ni 3C are confirmed to be responsible for the formation of graphene and the evaporation of Ni at 1100 °C. The Ni 3C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation, and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.« less

Total aerobic destruction of azo contaminants with nanoscale zero-valent copper at neutral pH: promotion effect of in-situ generated carbon center radicals.

PubMed

Dong, Guohui; Ai, Zhihui; Zhang, Lizhi

2014-12-01

In this study, nanoscale zero-valent copper (nZVC) was synthesized with a facile solvothermal method and used for the aerobic removal of azo contaminants at neutral pH for the first time. We found that both Cu(I) and OH generated during the nZVC induced molecular oxygen activation process accounted for the rapid total destruction of azo contaminants in the nZVC/Air system, where nZVC could activate molecular oxygen to produce H2O2, and also release Cu(I) to break the -NN- bond of azo contaminants via the sandmeyer reaction for the generation of carbon center radicals. The in-situ generated carbon center radicals would then react with OH produced by the Cu(I) catalyzed decomposition of H2O2, resulting in the generation of low molecular weight organic acids and their subsequent mineralization. The indispensible role of Cu(I) catalyzed sandmeyer reaction and the promotion effect of in-situ generated carbon center radicals on the rapid total destruction of azo contaminants in the nZVC/Air system were confirmed by gas chromatography-mass spectrometry analysis. This study can deepen our understanding on the degradation of organic pollutant with molecular oxygen activated by zero valent metal, and also provide a new method to remove azo contaminants at neutral pH. Copyright © 2014 Elsevier Ltd. All rights reserved.

Muon Catalyzed Fusion

NASA Technical Reports Server (NTRS)

Armour, Edward A.G.

2007-01-01

Muon catalyzed fusion is a process in which a negatively charged muon combines with two nuclei of isotopes of hydrogen, e.g, a proton and a deuteron or a deuteron and a triton, to form a muonic molecular ion in which the binding is so tight that nuclear fusion occurs. The muon is normally released after fusion has taken place and so can catalyze further fusions. As the muon has a mean lifetime of 2.2 microseconds, this is the maximum period over which a muon can participate in this process. This article gives an outline of the history of muon catalyzed fusion from 1947, when it was first realised that such a process might occur, to the present day. It includes a description of the contribution that Drachrnan has made to the theory of muon catalyzed fusion and the influence this has had on the author's research.

Acid-catalyzed conversion of mono- and poly-sugars into platform chemicals: effects of molecular structure of sugar substrate.

PubMed

Hu, Xun; Wu, Liping; Wang, Yi; Song, Yao; Mourant, Daniel; Gunawan, Richard; Gholizadeh, Mortaza; Li, Chun-Zhu

2013-04-01

Hydrolysis/pyrolysis of lignocellulosic biomass always produces a mixture of sugars with distinct structures as intermediates or products. This study tried to elucidate the effects of molecular structure of sugars on their acid-catalyzed conversions in ethanol/water. Location of carbonyl group in sugars (fructose versus glucose) and steric configuration of hydroxyl groups (glucose versus galactose) significantly affected yields of levulinic acid/ester (fructose>glucose>galactose). The dehydration of fructose to 5-(hydroxymethyl)furfural produces much less soluble polymer than that from glucose and galactose, which results in high yields of levulinic acid/ester from fructose. Anhydrate sugar such as levoglucosan tends to undergo the undesirable decomposition to form less levulinic acid/ester. Catalytic behaviors of the poly-sugars (sucrose, maltose, raffinose, β-cyclodextrins) were determined much by their basic units. However, their big molecular sizes create the steric hindrance that significantly affects their followed conversion over solid acid catalyst. Copyright © 2013 Elsevier Ltd. All rights reserved.

Growth and Detachment of Oxygen Bubbles Induced by Gold-Catalyzed Decomposition of Hydrogen Peroxide

PubMed Central

2017-01-01

Whereas bubble growth out of gas-oversatured solutions has been quite well understood, including the formation and stability of surface nanobubbles, this is not the case for bubbles forming on catalytic surfaces due to catalytic reactions, though it has important implications for gas evolution reactions and self-propulsion of micro/nanomotors fueled by bubble release. In this work we have filled this gap by experimentally and theoretically examining the growth and detachment dynamics of oxygen bubbles from hydrogen peroxide decomposition catalyzed by gold. We measured the bubble radius R(t) as a function of time by confocal microscopy and find R(t) ∝ t1/2. This diffusive growth behavior demonstrates that the bubbles grow from an oxygen-oversaturated environment. For several consecutive bubbles detaching from the same position in a short period of time, a well-repeated growing behavior is obtained from which we conclude the absence of noticeable depletion effect of oxygen from previous bubbles or increasing oversaturation from the gas production. In contrast, for two bubbles far apart either in space or in time, substantial discrepancies in their growth rates are observed, which we attribute to the variation in the local gas oversaturation. The current results show that the dynamical evolution of bubbles is influenced by comprehensive effects combining chemical catalysis and physical mass transfer. Finally, we find that the size of the bubbles at the moment of detachment is determined by the balance between buoyancy and surface tension and by the detailed geometry at the bubble’s contact line. PMID:28983387

Growth and Detachment of Oxygen Bubbles Induced by Gold-Catalyzed Decomposition of Hydrogen Peroxide.

PubMed

Lv, Pengyu; Le The, Hai; Eijkel, Jan; Van den Berg, Albert; Zhang, Xuehua; Lohse, Detlef

2017-09-28

Whereas bubble growth out of gas-oversatured solutions has been quite well understood, including the formation and stability of surface nanobubbles, this is not the case for bubbles forming on catalytic surfaces due to catalytic reactions , though it has important implications for gas evolution reactions and self-propulsion of micro/nanomotors fueled by bubble release. In this work we have filled this gap by experimentally and theoretically examining the growth and detachment dynamics of oxygen bubbles from hydrogen peroxide decomposition catalyzed by gold. We measured the bubble radius R ( t ) as a function of time by confocal microscopy and find R ( t ) ∝ t 1/2 . This diffusive growth behavior demonstrates that the bubbles grow from an oxygen-oversaturated environment. For several consecutive bubbles detaching from the same position in a short period of time, a well-repeated growing behavior is obtained from which we conclude the absence of noticeable depletion effect of oxygen from previous bubbles or increasing oversaturation from the gas production. In contrast, for two bubbles far apart either in space or in time, substantial discrepancies in their growth rates are observed, which we attribute to the variation in the local gas oversaturation. The current results show that the dynamical evolution of bubbles is influenced by comprehensive effects combining chemical catalysis and physical mass transfer. Finally, we find that the size of the bubbles at the moment of detachment is determined by the balance between buoyancy and surface tension and by the detailed geometry at the bubble's contact line.

Catalytic Graphitization of Coal-Based Carbon Materials with Light Rare Earth Elements.

PubMed

Wang, Rongyan; Lu, Guimin; Qiao, Wenming; Yu, Jianguo

2016-08-30

The catalytic graphitization mechanism of coal-based carbon materials with light rare earth elements was investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, selected-area electron diffraction, and high-resolution transmission electron microscopy. The interface between light rare earth elements and carbon materials was carefully observed, and two routes of rare earth elements catalyzing the carbon materials were found: dissolution-precipitation and carbide formation-decomposition. These two simultaneous processes certainly accelerate the catalytic graphitization of carbon materials, and light rare earth elements exert significant influence on the microstructure and thermal conductivity of graphite. Moreover, by virtue of praseodymium (Pr), it was found that a highly crystallographic orientation of graphite was induced and formed, which was reasonably attributed to the similar arrangements of the planes perpendicular to (001) in both graphite and Pr crystals. The interface between Pr and carbon was found to be an important factor for the orientation of graphite structure.

Detailed mechanistic investigation into the S-nitrosation of cysteamine.

PubMed

Morakinyo, Moshood K; Chipinda, Itai; Hettick, Justin; Siegel, Paul D; Abramson, Jonathan; Strongin, Robert; Martincigh, Bice S; Simoyi, Reuben H

The nitrosation of cysteamine (H 2 NCH 2 CH 2 SH) to produce cysteamine- S -nitrosothiol (CANO) was studied in slightly acidic medium by using nitrous acid prepared in situ. The stoichiometry of the reaction was H 2 NCH 2 CH 2 SH + HNO 2 → H 2 NCH 2 CH 2 SNO + H 2 O. On prolonged standing, the nitrosothiol decomposed quantitatively to yield the disulfide, cystamine: 2H 2 NCH 2 CH 2 SNO → H 2 NCH 2 CH 2 S-SCH 2 CH 2 NH 2 + 2NO. NO 2 and N 2 O 3 are not the primary nitrosating agents, since their precursor (NO) was not detected during the nitrosation process. The reaction is first order in nitrous acid, thus implicating it as the major nitrosating agent in mildly acidic pH conditions. Acid catalyzes nitrosation after nitrous acid has saturated, implicating the protonated nitrous acid species, the nitrosonium cation (NO + ) as a contributing nitrosating species in highly acidic environments. The acid catalysis at constant nitrous acid concentrations suggests that the nitrosonium cation nitrosates at a much higher rate than nitrous acid. Bimolecular rate constants for the nitrosation of cysteamine by nitrous acid and by the nitrosonium cation were deduced to be 17.9 ± 1.5 (mol/L) -1 s -1 and 6.7 × 10 4 (mol/L) -1 s -1 , respectively. Both Cu(I) and Cu(II) ions were effective catalysts for the formation and decomposition of the cysteamine nitrosothiol. Cu(II) ions could catalyze the nitrosation of cysteamine in neutral conditions, whereas Cu(I) could only catalyze in acidic conditions. Transnitrosation kinetics of CANO with glutathione showed the formation of cystamine and the mixed disulfide with no formation of oxidized glutathione (GSSG). The nitrosation reaction was satisfactorily simulated by a simple reaction scheme involving eight reactions.

Detailed mechanistic investigation into the S-nitrosation of cysteamine

PubMed Central

Morakinyo, Moshood K.; Chipinda, Itai; Hettick, Justin; Siegel, Paul D.; Abramson, Jonathan; Strongin, Robert; Martincigh, Bice S.; Simoyi, Reuben H.

2015-01-01

The nitrosation of cysteamine (H2NCH2CH2SH) to produce cysteamine-S-nitrosothiol (CANO) was studied in slightly acidic medium by using nitrous acid prepared in situ. The stoichiometry of the reaction was H2NCH2CH2SH + HNO2 → H2NCH2CH2SNO + H2O. On prolonged standing, the nitrosothiol decomposed quantitatively to yield the disulfide, cystamine: 2H2NCH2CH2SNO → H2NCH2CH2S–SCH2CH2NH2 + 2NO. NO2 and N2O3 are not the primary nitrosating agents, since their precursor (NO) was not detected during the nitrosation process. The reaction is first order in nitrous acid, thus implicating it as the major nitrosating agent in mildly acidic pH conditions. Acid catalyzes nitrosation after nitrous acid has saturated, implicating the protonated nitrous acid species, the nitrosonium cation (NO+) as a contributing nitrosating species in highly acidic environments. The acid catalysis at constant nitrous acid concentrations suggests that the nitrosonium cation nitrosates at a much higher rate than nitrous acid. Bimolecular rate constants for the nitrosation of cysteamine by nitrous acid and by the nitrosonium cation were deduced to be 17.9 ± 1.5 (mol/L)−1 s−1 and 6.7 × 104 (mol/L)−1 s−1, respectively. Both Cu(I) and Cu(II) ions were effective catalysts for the formation and decomposition of the cysteamine nitrosothiol. Cu(II) ions could catalyze the nitrosation of cysteamine in neutral conditions, whereas Cu(I) could only catalyze in acidic conditions. Transnitrosation kinetics of CANO with glutathione showed the formation of cystamine and the mixed disulfide with no formation of oxidized glutathione (GSSG). The nitrosation reaction was satisfactorily simulated by a simple reaction scheme involving eight reactions. PMID:26594054

Capturing molecular multimode relaxation processes in excitable gases based on decomposition of acoustic relaxation spectra

NASA Astrophysics Data System (ADS)

Zhu, Ming; Liu, Tingting; Wang, Shu; Zhang, Kesheng

2017-08-01

Existing two-frequency reconstructive methods can only capture primary (single) molecular relaxation processes in excitable gases. In this paper, we present a reconstructive method based on the novel decomposition of frequency-dependent acoustic relaxation spectra to capture the entire molecular multimode relaxation process. This decomposition of acoustic relaxation spectra is developed from the frequency-dependent effective specific heat, indicating that a multi-relaxation process is the sum of the interior single-relaxation processes. Based on this decomposition, we can reconstruct the entire multi-relaxation process by capturing the relaxation times and relaxation strengths of N interior single-relaxation processes, using the measurements of acoustic absorption and sound speed at 2N frequencies. Experimental data for the gas mixtures CO2-N2 and CO2-O2 validate our decomposition and reconstruction approach.

Exploring the conformational changes of the ATP binding site of gyrase B from Escherichia coli complexed with different established inhibitors by using molecular dynamics simulation: protein-ligand interactions in the light of the alanine scanning and free energy decomposition methods.

PubMed

Saíz-Urra, Liane; Cabrera, Miguel Angel; Froeyen, Matheus

2011-02-01

Currently, bacterial diseases cause a death toll around 2 million people a year encouraging the search for new antimicrobial agents. DNA gyrase is a well-established antibacterial target consisting of two subunits, GyrA and GyrB, in a heterodimer A(2)B(2). GyrA is involved in DNA breakage and reunion and GyrB catalyzes the hydrolysis of ATP. The GyrB subunit from Escherichia coli has been investigated, namely the ATP binding pocket both considering the protein without ligands and bound with the inhibitors clorobiocin, novobiocin and 5'-adenylyl-β-γ-imidodiphosphate. The stability of the systems was studied by molecular dynamics simulation with the further analysis of the time dependent root-mean-square coordinate deviation (RMSD) from the initial structure, and temperature factors. Moreover, exploration of the conformational space of the systems during the MD simulation was carried out by a clustering data mining technique using the average-linkage algorithm. Recognizing the key residues in the binding site of the enzyme that are involved in the binding mode with the aforementioned inhibitors was investigated by using two techniques: free energy decomposition and computational alanine scanning. The results from these simulations highlight the important residues in the ATP binding site and can be useful in the design process of potential new inhibitors. Copyright © 2010 Elsevier Inc. All rights reserved.

Thermal decomposition behavior of nano/micro bimodal feedstock with different solids loading

NASA Astrophysics Data System (ADS)

Oh, Joo Won; Lee, Won Sik; Park, Seong Jin

2018-01-01

Debinding is one of the most critical processes for powder injection molding. The parts in debinding process are vulnerable to defect formation, and long processing time of debinding decreases production rate of whole process. In order to determine the optimal condition for debinding process, decomposition behavior of feedstock should be understood. Since nano powder affects the decomposition behavior of feedstock, nano powder effect needs to be investigated for nano/micro bimodal feedstock. In this research, nano powder effect on decomposition behavior of nano/micro bimodal feedstock has been studied. Bimodal powders were fabricated with different ratios of nano powder, and the critical solids loading of each powder was measured by torque rheometer. Three different feedstocks were fabricated for each powder depending on solids loading condition. Thermogravimetric analysis (TGA) experiment was carried out to analyze the thermal decomposition behavior of the feedstocks, and decomposition activation energy was calculated. The result indicated nano powder showed limited effect on feedstocks in lower solids loading condition than optimal range. Whereas, it highly influenced the decomposition behavior in optimal solids loading condition by causing polymer chain scission with high viscosity.

Geometrical flexibility of platinum nanoclusters: impacts on catalytic decomposition of ethylene glycol.

PubMed

Mahmoodinia, Mehdi; Trinh, Thuat T; Åstrand, Per-Olof; Tran, Khanh-Quang

2017-11-01

Catalytic decomposition of ethylene glycol on the Pt 13 cluster was studied as a model system for hydrogen production from a lignocellulosic material. Ethylene glycol was chosen as a starting material because of two reasons, it is the smallest oxygenate with a 1 : 1 carbon to oxygen ratio and it contains the C-H, O-H, C-C, and C-O bonds also present in biomass. Density functional theory calculations were employed for predictions of reaction pathways for C-H, O-H, C-C and C-O cleavages, and Brønsted-Evans-Polanyi relationships were established between the final state and the transition state for all mechanisms. The results show that Pt 13 catalyzes the cleavage reactions of ethylene glycol more favourably than a Pt surface. The flexibility of Pt 13 clusters during the reactions is the key factor in reducing the activation barrier. Overall, the results demonstrate that ethylene glycol and thus biomass can be efficiently converted into hydrogen using platinum nanoclusters as catalysts.

Self-propelled micromotors based on Au-mesoporous silica nanorods.

PubMed

Wang, Ying-Shuai; Xia, Hong; Lv, Chao; Wang, Lei; Dong, Wen-Fei; Feng, Jing; Sun, Hong-Bo

2015-07-28

Here, a chemical powered micromotor from the assembly of Au-SiO2 nanorods is presented. This new micromotor can be propelled efficiently by hydrogen bubbles generated from a hydrolysis reaction of aqueous NaBH4 and KBH4 and by oxygen bubbles produced by decomposition of H2O2. The monodisperse Au nanoparticles in mesoporous silica particles could catalyze the decomposition of two different kinds of fuels and produce bubbles. High speeds of 80 μm s(-1) and recycles of more than 30 times are achieved in both NaBH4 and H2O2 media. Locomotion and rolling forms of movement were found. The locomotion forms can be obtained in a larger proportion by patterning the Au-SiO2 nanorods and a PDMS membrane. These micromotors that use multiple fuel sources to power them offer a broader scope of preparation and show considerable promise for diverse applications of nanomotors in different chemical environments.

Data-driven process decomposition and robust online distributed modelling for large-scale processes

NASA Astrophysics Data System (ADS)

Shu, Zhang; Lijuan, Li; Lijuan, Yao; Shipin, Yang; Tao, Zou

2018-02-01

With the increasing attention of networked control, system decomposition and distributed models show significant importance in the implementation of model-based control strategy. In this paper, a data-driven system decomposition and online distributed subsystem modelling algorithm was proposed for large-scale chemical processes. The key controlled variables are first partitioned by affinity propagation clustering algorithm into several clusters. Each cluster can be regarded as a subsystem. Then the inputs of each subsystem are selected by offline canonical correlation analysis between all process variables and its controlled variables. Process decomposition is then realised after the screening of input and output variables. When the system decomposition is finished, the online subsystem modelling can be carried out by recursively block-wise renewing the samples. The proposed algorithm was applied in the Tennessee Eastman process and the validity was verified.

Smectite clays in Mars soil: evidence for their presence and role in Viking biology experimental results.

PubMed

Banin, A; Rishpon, J

1979-12-01

Various chemical, physical and geological observations indicate that smectite clays are probably the major components of the Martian soil. Satisfactory ground-based chemical simulation of the Viking biology experimental results was obtained with the smectite clays nontronite and montmorillonite when they contained iron and hydrogen as adsorbed ions. Radioactive gas was released from the medium solution used in the Viking Labeled Release (LR) experiment when interacted with the clays, at rates and quantities similar to those measured by Viking on Mars. Heating of the active clay (mixed with soluble salts) to 160 degrees C in CO2 atmosphere reduced the decomposition activity considerably, again, as was observed on Mars. The decomposition reaction in LR experiment is postulated to be iron-catalyzed formate decomposition on the clay surface. The main features of the Viking Pyrolytic Release (PR) experiment were also simulated recently (Hubbard, 1979) which the iron clays, including a relatively low '1st peak' and significant '2nd peak'. The accumulated observations on various Martian soil properties and the results of simulation experiments, thus indicate that smectite clays are major and active components of the Martian soil. It now appears that many of the results of the Viking biology experiments can be explained on the basis of their surface activity in catalysis and adsorption.

Spontaneous Oscillations and Waves during Chemical Vapor Deposition of InN

NASA Astrophysics Data System (ADS)

Jiang, F.; Munkholm, A.; Wang, R.-V.; Streiffer, S. K.; Thompson, Carol; Fuoss, P. H.; Latifi, K.; Elder, K. R.; Stephenson, G. B.

2008-08-01

We report observations of self-sustaining spatiotemporal chemical oscillations during metal-organic chemical vapor deposition of InN onto GaN. Under constant supply of vapor precursors trimethylindium and NH3, the condensed-phase cycles between crystalline islands of InN and elemental In droplets. Propagating fronts between regions of InN and In occur with linear, circular, and spiral geometries. The results are described by a model in which the nitrogen activity produced by surface-catalyzed NH3 decomposition varies with the exposed surface areas of GaN, InN, and In.

Spontaneous oscillations and waves during chemical vapor deposition of InN.

PubMed

Jiang, F; Munkholm, A; Wang, R-V; Streiffer, S K; Thompson, Carol; Fuoss, P H; Latifi, K; Elder, K R; Stephenson, G B

2008-08-22

We report observations of self-sustaining spatiotemporal chemical oscillations during metal-organic chemical vapor deposition of InN onto GaN. Under constant supply of vapor precursors trimethylindium and NH3, the condensed-phase cycles between crystalline islands of InN and elemental In droplets. Propagating fronts between regions of InN and In occur with linear, circular, and spiral geometries. The results are described by a model in which the nitrogen activity produced by surface-catalyzed NH3 decomposition varies with the exposed surface areas of GaN, InN, and In.

Understanding How the Distal Environment Directs Reactivity in Chlorite Dismutase: Spectroscopy and Reactivity of Arg183 Mutants

PubMed Central

Blanc, Béatrice; Mayfield, Jeffery A.; McDonald, Claudia A.; Lukat-Rodgers, Gudrun S.; Rodgers, Kenton R.; DuBois, Jennifer L.

2012-01-01

The chlorite dismutase from Dechloromonas aromatica (DaCld) catalyzes the highly efficient decomposition of chlorite to O2 and chloride. Spectroscopic, equilibrium thermodynamic, and kinetic measurements have indicated that Cld has two pH sensitive moieties; one is the heme, and Arg183 in the distal heme pocket has been hypothesized to be the second. This active site residue has been examined by site-directed mutagenesis to understand the roles of positive charge and hydrogen bonding in O–O bond formation. Three Cld mutants, Arg183 to Lys (R183K), Arg183 to Gln (R183Q), and Arg183 to Ala (R183A), were investigated to determine their respective contributions to the decomposition of chlorite ion, the spin state and coordination states of their ferric and ferrous forms, their cyanide and imidazole binding affinities, and their reduction potentials. UV–visible and resonance Raman spectroscopies showed that DaCld(R183A) contains five-coordinate high-spin (5cHS) heme, the DaCld(R183Q) heme is a mixture of five-coordinate and six-coordinate high spin (5c/6cHS) heme, and DaCld(R183K) contains six-coordinate low-spin (6cLS) heme. In contrast to wild-type (WT) Cld, which exhibits pKa values of 6.5 and 8.7, all three ferric mutants exhibited pH-independent spectroscopic signatures and kinetic behaviors. Steady state kinetic parameters of the chlorite decomposition reaction catalyzed by the mutants suggest that in WT DaCld the pKa of 6.5 corresponds to a change in the availability of positive charge from the guanidinium group of Arg183 to the heme site. This could be due to either direct acid–base chemistry at the Arg183 side chain or a flexible Arg183 side chain that can access various orientations. Current evidence is most consistent with a conformational adjustment of Arg183. A properly oriented Arg183 is critical for the stabilization of anions in the distal pocket and for efficient catalysis. PMID:22313119

A statistical approach based on accumulated degree-days to predict decomposition-related processes in forensic studies.

PubMed

Michaud, Jean-Philippe; Moreau, Gaétan

2011-01-01

Using pig carcasses exposed over 3 years in rural fields during spring, summer, and fall, we studied the relationship between decomposition stages and degree-day accumulation (i) to verify the predictability of the decomposition stages used in forensic entomology to document carcass decomposition and (ii) to build a degree-day accumulation model applicable to various decomposition-related processes. Results indicate that the decomposition stages can be predicted with accuracy from temperature records and that a reliable degree-day index can be developed to study decomposition-related processes. The development of degree-day indices opens new doors for researchers and allows for the application of inferential tools unaffected by climatic variability, as well as for the inclusion of statistics in a science that is primarily descriptive and in need of validation methods in courtroom proceedings. © 2010 American Academy of Forensic Sciences.

Environmental implications and applications of engineered ...

EPA Pesticide Factsheets

This review focus on environmental implications and applications of engineered magnetite (Fe3O4) nanoparticles (MNPs) as a single phase or a component of a hybrid nanocomposite that take advantages of their superparamagnetism and high surface area. MNPs are synthesized via co-precipitation, thermal decomposition, hydrothermal process, emulsion, and microbial process. Aggregation/sedimentation and transport of MNPs depend on surface charge of MNPs and geochemical parameters such as pH, ionic strength, and organic matter. MNPs generally have low toxicity to humans and ecosystem. MNPs are used for making excellent anode electrode materials in lithium-ion battery, for constructing biosensors, and for catalyzing a variety of chemical reactions. MNPs are used for air cleanup and carbon sequestration. MNP nanocomposites are made as antimicrobial agent for water disinfection and flocculants for water treatment. Conjugated MNPs are widely used for adsorptive/separative removal of organics, dye, oil, arsenic, Cr(VI), heavy metals, radionuclides, and rare earth elements. MNPs can degrade organic/inorganic contaminants via chemical reduction or oxidation in water, sediment, and soil. Future studies should further explore mechanisms of MNP interactions with other nanomaterials and contaminants, economic and green approaches of MNP synthesis, and field scale demonstration of MNP utilization. Submit to Journal of Hazardous Materials.

Study of Silicidation Process of Tungsten Catalyzer during Silicon Film Deposition in Catalytic Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Honda, Kazuhiro; Ohdaira, Keisuke; Matsumura, Hideki

2008-05-01

In catalytic chemical vapor deposition (Cat-CVD), often called hot-wire CVD, source gases are decomposed by catalytic cracking reactions with heated catalyzing metal wires. In the case of silicon (Si) film deposition, such metal wires are often converted to silicide, which shortens the lifetime of catalyzing wires. As a catalyzer, tungsten (W) is widely used. Thus, the process of silicidation of a W catalyzer at temperatures over 1650 °C, which is the temperature used in Cat-CVD for Si film deposition, was studied extensively in various experiments. It is found that two phases of tungsten-silicide, WSi2 and W5Si3, are formed at this temperature, and that the radiation emissivity of WSi2 is 1.2 to 1.7 times higher than that of W5Si3 and pure W. The increase of surface emissivity due to the formation of WSi2 decreases the catalyzer surface temperature which induces further growth of the tungsten-silicide layer. It is also found that the suppression of WSi2 formation by elevating catalyzer temperatures over 1750 °C is a key to extending the lifetime of the W catalyzer in Cat-CVD.

Evolution of Enzymatic Activities in the Enolase Superfamily: D-Tartrate Dehydratase from Bradyrhizobium japonicum

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

Yew,W.; Fedorov, A.; Fedorov, E.

2006-01-01

We focus on the assignment of function to and elucidation of structure-function relationships for a member of the mechanistically diverse enolase superfamily encoded by the Bradyrhizobium japonicum genome (bll6730; GI:27381841). As suggested by sequence alignments, the active site contains the same functional groups found in the active site of mandelate racemase (MR) that catalyzes a 1,1-proton transfer reaction: two acid/base catalysts, Lys 184 at the end of the second {beta}-strand, and a His 322-Asp 292 dyad at the ends of the seventh and sixth -strands, respectively, as well as ligands for an essential Mg{sup 2+}, Asp 213, Glu 239, andmore » Glu 265 at the ends of the third, fourth, and fifth {beta}-strands, respectively. We screened a library of 46 acid sugars and discovered that only D-tartrate is dehydrated, yielding oxaloacetate as product. The kinetic constants (k{sub cat} = 7.3 s{sup -1}; k{sub cat}/K{sub M} = 8.5 x 10{sup 4} M{sup -1} s{sup -1}) are consistent with assignment of the D-tartrate dehydratase (TarD) function. The kinetic phenotypes of mutants as well as the structures of liganded complexes are consistent with a mechanism in which Lys 184 initiates the reaction by abstraction of the {alpha}-proton to generate a Mg{sup 2+}-stabilized enediolate intermediate, and the vinylogous -elimination of the 3-OH group is general acid-catalyzed by the His 322, accomplishing the anti-elimination of water. The replacement of the leaving group by solvent-derived hydrogen is stereorandom, suggesting that the enol tautomer of oxaloacetate is the product; this expectation was confirmed by its observation by {sup 1}H NMR spectroscopy. Thus, the TarD-catalyzed reaction is a 'simple' extension of the two-step reaction catalyzed by MR: base-catalyzed proton abstraction to generate a Mg{sup 2+}-stabilized enediolate intermediate followed by acid-catalyzed decomposition of that intermediate to yield the product.« less

Converting Chemical Energy to Electricity through a Three-Jaw Mini-Generator Driven by the Decomposition of Hydrogen Peroxide.

PubMed

Xiao, Meng; Wang, Lei; Ji, Fanqin; Shi, Feng

2016-05-11

Energy conversion from a mechanical form to electricity is one of the most important research advancements to come from the horizontal locomotion of small objects. Until now, the Marangoni effect has been the only propulsion method to produce the horizontal locomotion to induce an electromotive force, which is limited to a short duration because of the specific property of surfactants. To solve this issue, in this article we utilized the decomposition of hydrogen peroxide to provide the propulsion for a sustainable energy conversion from a mechanical form to electricity. We fabricated a mini-generator consisting of three parts: a superhydrophobic rotator with three jaws, three motors to produce a jet of oxygen bubbles to propel the rotation of the rotator, and three magnets integrated into the upper surface of the rotator to produce the magnet flux. Once the mini-generator was placed on the solution surface, the motor catalyzed the decomposition of hydrogen peroxide. This generated a large amount of oxygen bubbles that caused the generator and integrated magnets to rotate at the air/water interface. Thus, the magnets passed under the coil area and induced a change in the magnet flux, thus generating electromotive forces. We also investigated experimental factors, that is, the concentration of hydrogen peroxide and the turns of the solenoid coil, and found that the mini-generator gave the highest output in a hydrogen peroxide solution with a concentration of 10 wt % and under a coil with 9000 turns. Through combining the stable superhydrophobicity and catalyst, we realized electricity generation for a long duration, which could last for 26 000 s after adding H2O2 only once. We believe this work provides a simple process for the development of horizontal motion and provides a new path for energy reutilization.

Process for remediation of plastic waste

DOEpatents

Pol, Vilas G [Westmont, IL; Thiyagarajan, Pappannan [Germantown, MD

2012-04-10

A single step process for degrading plastic waste by converting the plastic waste into carbonaceous products via thermal decomposition of the plastic waste by placing the plastic waste into a reactor, heating the plastic waste under an inert or air atmosphere until the temperature of 700.degree. C. is achieved, allowing the reactor to cool down, and recovering the resulting decomposition products therefrom. The decomposition products that this process yields are carbonaceous materials, and more specifically egg-shaped and spherical-shaped solid carbons. Additionally, in the presence of a transition metal compound, this thermal decomposition process produces multi-walled carbon nanotubes.

Unexpected Reaction Pathway for butyrylcholinesterase-catalyzed inactivation of “hunger hormone” ghrelin

NASA Astrophysics Data System (ADS)

Yao, Jianzhuang; Yuan, Yaxia; Zheng, Fang; Zhan, Chang-Guo

2016-02-01

Extensive computational modeling and simulations have been carried out, in the present study, to uncover the fundamental reaction pathway for butyrylcholinesterase (BChE)-catalyzed hydrolysis of ghrelin, demonstrating that the acylation process of BChE-catalyzed hydrolysis of ghrelin follows an unprecedented single-step reaction pathway and the single-step acylation process is rate-determining. The free energy barrier (18.8 kcal/mol) calculated for the rate-determining step is reasonably close to the experimentally-derived free energy barrier (~19.4 kcal/mol), suggesting that the obtained mechanistic insights are reasonable. The single-step reaction pathway for the acylation is remarkably different from the well-known two-step acylation reaction pathway for numerous ester hydrolysis reactions catalyzed by a serine esterase. This is the first time demonstrating that a single-step reaction pathway is possible for an ester hydrolysis reaction catalyzed by a serine esterase and, therefore, one no longer can simply assume that the acylation process must follow the well-known two-step reaction pathway.

Decomposition Mechanism and Decomposition Promoting Factors of Waste Hard Metal for Zinc Decomposition Process (ZDP)

NASA Astrophysics Data System (ADS)

Pee, J. H.; Kim, Y. J.; Kim, J. Y.; Seong, N. E.; Cho, W. S.; Kim, K. J.

2011-10-01

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc steam pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 hrs at 650 °C, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of γ-β1 phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at 1000 °C. The small amount of zinc remaining in the tungsten carbide-cobalt powder which was completely decomposed was fully removed by using phosphate solution which had a slow cobalt dissolution speed.

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.

Hydrogen concentrations as an indicator of the predominant terminal electron-accepting reactions in aquatic sediments

USGS Publications Warehouse

Lovley, D.R.; Goodwin, S.

1988-01-01

Factors controlling the concentration of dissolved hydrogen gas in anaerobic sedimentary environments were investigated. Results, presented here or previously, demonstrated that, in sediments, only microorganisms catalyze the oxidation of H2 coupled to the reduction of nitrate, Mn(IV), Fe(III), sulfate, or carbon dioxide. Theoretical considerations suggested that, at steady-state conditions, H2 concentrations are primarily dependent upon the physiological characteristics of the microorganism(s) consuming the H2 and that organisms catalyzing H2 oxidation, with the reduction of a more electrochemically positive electron acceptor, can maintain lower H2 concentrations than organisms using electron acceptors which yield less energy from H2 oxidation. The H2 concentrations associated with the specified predominant terminal electron-accepting reactions in bottom sediments of a variety of surface water environments were: methanogenesis, 7-10 nM; sulfate reduction, 1-1.5 nM; Fe(III) reduction, 0.2 nM; Mn(IV) or nitrate reduction, less than 0.05 nM. Sediments with the same terminal electron acceptor for organic matter oxidation had comparable H2 concentrations, despite variations in the rate of organic matter decomposition, pH, and salinity. Thus, each terminal electron-accepting reaction had a unique range of steady-state H2 concentrations associated with it. Preliminary studies in a coastal plain aquifer indicated that H2 concentrations also vary in response to changes in the predominant terminal electron-accepting process in deep subsurface environments. These studies suggest that H2 measurements may aid in determining which terminal electron-accepting reactions are taking place in surface and subsurface sedimentary environments. ?? 1988.

40 CFR 261.31 - Hazardous wastes from non-specific sources.

Code of Federal Regulations, 2011 CFR

2011-07-01

... free radical catalyzed processes. These chlorinated aliphatic hydrocarbons are those having carbon... spent desiccant wastes from the production of certain chlorinated aliphatic hydrocarbons, by free radical catalyzed processes. These chlorinated aliphatic hydrocarbons are those having carbon chain...

40 CFR 261.31 - Hazardous wastes from non-specific sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... free radical catalyzed processes. These chlorinated aliphatic hydrocarbons are those having carbon... spent desiccant wastes from the production of certain chlorinated aliphatic hydrocarbons, by free radical catalyzed processes. These chlorinated aliphatic hydrocarbons are those having carbon chain...

Process for remediation of plastic waste

DOEpatents

Pol, Vilas G; Thiyagarajan, Pappannan

2013-11-12

A single step process for degrading plastic waste by converting the plastic waste into carbonaceous products via thermal decomposition of the plastic waste by placing the plastic waste into a reactor, heating the plastic waste under an inert or air atmosphere until the temperature of about 700.degree. C. is achieved, allowing the reactor to cool down, and recovering the resulting decomposition products therefrom. The decomposition products that this process yields are carbonaceous materials, and more specifically carbon nanotubes having a partially filled core (encapsulated) adjacent to one end of the nanotube. Additionally, in the presence of a transition metal compound, this thermal decomposition process produces multi-walled carbon nanotubes.

Perovskite-type La0.8Sr0.2Co0.8Fe0.2O3 with uniform dispersion on N-doped reduced graphene oxide as an efficient bi-functional Li-O2 battery cathode.

PubMed

Cheng, Junfang; Jiang, Yuexing; Zhang, Ming; Zou, Lu; Huang, Yizhen; Wang, Ziling; Chi, Bo; Pu, Jian; Li, Jian

2017-04-19

A composite cathode including N-rGO with homogeneously dispersed perovskite La 0.8 Sr 0.2 Co 0.8 Fe 0.2 O 3 on the surface is studied. Li-O 2 batteries with LSCF@N-rGO cathode show better performance than those with LSCF-SP or N-rGO cathode. EIS and morphology analysis indicate that LSCF is beneficial to remold the shape of Li 2 O 2 and catalyze the decomposition of Li 2 O 2 .

Densification of PZT Ceramics with V2O5 Additive.

DTIC Science & Technology

1979-01-01

Additions of V2O5 from 0.1 to 8.0 w/o to a coprecipitated Pb(Zr.53 Ti.47) O3 ceramic promoted rapid densification below 1025 C, eliminating the need...for PbO atmosphere control. Dielectric properties were found to be dependent on the amount of V2O5 added and on the microstructure developed, but were...comparable to reported values for this PZT composition for additions of V2O5 or = 1.5 W/O. The indicated densification mechanism is one of activated sintering catalyzed by generation of oxygen defects on decomposition of the V2O5 .

A Mild, Ferrocene-Catalyzed C–H Imidation of (Hetero)Arenes

PubMed Central

2015-01-01

A simple method for direct C–H imidation is reported using a new perester-based self-immolating reagent and a base-metal catalyst. The succinimide products obtained can be easily deprotected in situ (if desired) to reveal the corresponding anilines directly. The scope of the reaction is broad, the conditions are extremely mild, and the reaction is tolerant of oxidizable and acid-labile functionality, multiple heteroatoms, and aryl iodides. Mechanistic studies indicate that ferrocene (Cp2Fe) plays the role of an electron shuttle in the decomposition of the perester reagent, delivering a succinimidyl radical ready to add to an aromatic system. PMID:24654983

Application of decomposition techniques to the preliminary design of a transport aircraft

NASA Technical Reports Server (NTRS)

Rogan, J. E.; Mcelveen, R. P.; Kolb, M. A.

1986-01-01

A multifaceted decomposition of a nonlinear constrained optimization problem describing the preliminary design process for a transport aircraft has been made. Flight dynamics, flexible aircraft loads and deformations, and preliminary structural design subproblems appear prominently in the decomposition. The use of design process decomposition for scheduling design projects, a new system integration approach to configuration control, and the application of object-centered programming to a new generation of design tools are discussed.

Challenges of including nitrogen effects on decomposition in earth system models

NASA Astrophysics Data System (ADS)

Hobbie, S. E.

2011-12-01

Despite the importance of litter decomposition for ecosystem fertility and carbon balance, key uncertainties remain about how this fundamental process is affected by nitrogen (N) availability. Nevertheless, resolving such uncertainties is critical for mechanistic inclusion of such processes in earth system models, towards predicting the ecosystem consequences of increased anthropogenic reactive N. Towards that end, we have conducted a series of experiments examining nitrogen effects on litter decomposition. We found that both substrate N and externally supplied N (regardless of form) accelerated the initial decomposition rate. Faster initial decomposition rates were linked to the higher activity of carbohydrate-degrading enzymes associated with externally supplied N and the greater relative abundances of Gram negative and Gram positive bacteria associated with green leaves and externally supplied organic N (assessed using phospholipid fatty acid analysis, PLFA). By contrast, later in decomposition, externally supplied N slowed decomposition, increasing the fraction of slowly decomposing litter and reducing lignin-degrading enzyme activity and relative abundances of Gram negative and Gram positive bacteria. Our results suggest that elevated atmospheric N deposition may have contrasting effects on the dynamics of different soil carbon pools, decreasing mean residence times of active fractions comprising very fresh litter, while increasing those of more slowly decomposing fractions including more processed litter. Incorporating these contrasting effects of N on decomposition processes into models is complicated by lingering uncertainties about how these effects generalize across ecosystems and substrates.

Thermal Decomposition of Nd3(+), Sr2(+) and Pb2(+) Exchanged Beta’’ Aluminas,

DTIC Science & Technology

1987-07-01

reconstructive recrystallization process is responsible for the formation of the MP phase; this perhaps is a surprising result. The decomposition processes of Nd3... eutectics may be present. A general trend for all decompositions of metastable substituted " aluminas would therefore seem to be that when occurring

Tandem reactions initiated by copper-catalyzed cross-coupling: a new strategy towards heterocycle synthesis.

PubMed

Liu, Yunyun; Wan, Jie-Ping

2011-10-21

Copper-catalyzed cross-coupling reactions which lead to the formation of C-N, C-O, C-S and C-C bonds have been recognized as one of the most useful strategies in synthetic organic chemistry. During past decades, important breakthroughs in the study of Cu-catalyzed coupling processes demonstrated that Cu-catalyzed reactions are broadly applicable to a variety of research fields related to organic synthesis. Representatively, employing these coupling transformations as key steps, a large number of tandem reactions have been developed for the construction of various heterocyclic compounds. These tactics share the advantages of high atom economics of tandem reactions as well as the broad tolerance of Cu-catalyst systems. Therefore, Cu-catalyzed C-X (X = N, O, S, C) coupling transformation-initiated tandem reactions were quickly recognized as a strategy with great potential for synthesizing heterocyclic compounds and gained worldwide attention. In this review, recent research progress in heterocycle syntheses using tandem reactions initiated by copper-catalyzed coupling transformations, including C-N, C-O, C-S as well as C-C coupling processes are summarized.

QM/MM MD and Free Energy Simulation Study of Methyl Transfer Processes Catalyzed by PKMTs and PRMTs.

PubMed

Chu, Yuzhuo; Guo, Hong

2015-09-01

Methyl transfer processes catalyzed by protein lysine methyltransferases (PKMTs) and protein arginine methyltransferases (PRMTs) control important biological events including transcriptional regulation and cell signaling. One important property of these enzymes is that different PKMTs and PRMTs catalyze the formation of different methylated product (product specificity). These different methylation states lead to different biological outcomes. Here, we review the results of quantum mechanics/molecular mechanics molecular dynamics and free energy simulations that have been performed to study the reaction mechanism of PKMTs and PRMTs and the mechanism underlying the product specificity of the methyl transfer processes.

QM/MM MD and free energy simulation study of methyl transfer processes catalyzed by PKMTs and PRMTs.

PubMed

Chu, Yuzhuo; Guo, Hong

2015-01-16

Methyl transfer processes catalyzed by protein lysine methyltransferases (PKMTs) and protein arginine methyltransferases (PRMTs) control important biological events including transcriptional regulation and cell signaling. One important property of these enzymes is that different PKMTs and PRMTs catalyze the formation of different methylated product (product specificity). These different methylation states lead to different biological outcomes. Here we review the results of quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) and free energy simulations that have been performed to study the reaction mechanism of PKMTs and PRMTs and the mechanism underlying the product specificity of the methyl transfer processes.

Transition metal-catalyzed oxidation of sulfur(IV) oxides. Atmospheric-relevant processes and mechanisms

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

Brandt, C.; Eldik, R. van

1995-01-01

The transition metal-catalyzed oxidation of sulfur(IV) oxides has been known for more than 100 years. There is a significant lack of information on the actual role of the transition metal-catalyzed reactions, and much of the earlier work was performed without a detailed knowledge of the chemical system. For this reason attention is focused on the role of transition metal ions in the oxidation of sulfur(IV) oxides in terms of the coordination chemistry involved, as well as the stability and chemical behavior of the various participating species. The oxidation process of sulfur(IV) oxides plays an important role in atmospheric chemistry (e.g.more » acid rain formation) as well as industrial processes (e.g. desulfurization of plume gases and ore). The present report deals with the mechanism of the transition metal-catalyzed oxidation of sulfur(IV) oxides with the aim to discuss this in terms of atmospheric and chemical processes. In addition, the authors would like to emphasize the key role of oxygen in these processes. 1,076 refs.« less

What Role Does Photodegradation Play in Influencing Plant Litter Decomposition and Biogeochemistry in Coastal Marsh Ecosystems?

NASA Astrophysics Data System (ADS)

Tobler, M.; White, D. A.; Abbene, M. L.; Burst, S. L.; McCulley, R. L.; Barnes, P. W.

2016-02-01

Decomposition is a crucial component of global biogeochemical cycles that influences the fate and residence time of carbon and nutrients in organic matter pools, yet the processes controlling litter decomposition in coastal marshes are not fully understood. We conducted a series of field studies to examine what role photodegradation, a process driven in part by solar UV radiation (280-400 nm), plays in the decomposition of the standing dead litter of Sagittaria lancifolia and Spartina patens, two common species in marshes of intermediate salinity in southern Louisiana, USA. Results indicate that the exclusion of solar UV significantly altered litter mass loss, but the magnitude and direction of these effects varied depending on species, height of the litter above the water surface and the stage of decomposition. Over one growing season, S. lancifolia litter exposed to ambient solar UV had significantly less mass loss compared to litter exposed to attenuated UV over the initial phase of decomposition (0-5 months; ANOVA P=0.004) then treatment effects switched in the latter phase of the study (5-7 months; ANOVA P<0.001). Similar results were found in S. patens over an 11-month period. UV exposure reduced total C, N and lignin by 24-33% in remaining tissue with treatment differences most pronounced in S. patens. Phospholipid fatty-acid analysis (PFLA) indicated that UV also significantly altered microbial (bacterial) biomass and bacteria:fungi ratios of decomposing litter. These findings, and others, indicate that solar UV can have positive and negative net effects on litter decomposition in marsh plants with inhibition of biotic (microbial) processes occurring early in the decomposition process then shifting to enhancement of decomposition via abiotic (photodegradation) processes later in decomposition. Photodegradation of standing litter represents a potentially significant pathway of C and N loss from these coastal wetland ecosystems.

Residue decomposition of submodel of WEPS

USDA-ARS?s Scientific Manuscript database

The Residue Decomposition submodel of the Wind Erosion Prediction System (WEPS) simulates the decrease in crop residue biomass due to microbial activity. The decomposition process is modeled as a first-order reaction with temperature and moisture as driving variables. Decomposition is a function of ...

Preparation and characterization of mesoporous ZnO-ZrO2 doped by Cr, Nd and Dy as a catalyst for conversion of coumarin using ultrasensitive fluorometric method

NASA Astrophysics Data System (ADS)

Ibrahim, M. M.

2017-04-01

Doping of mesoporous ZnO-ZrO2 nanoparticles with transition metal and lanthanides (Cr, Nd, Dy) were used as a catalyst to develop an ultrasensitive fluorometric method for the conversion of non fluorescent coumarin to highly fluorescent 7-hydroxycoumarin using H2O2 or light. It was found that doped- ZnO-ZrO2 mixed oxide can catalyze the decomposition of H2O2 to produce •OH radicals, which in turn convert coumarin to 7-hydroxycoumarin. At contrast, the doping has deleterious effect on conversion of coumarin by light due to high band gap and high concentrations of doping increase the recombination rate of electron and holes. Doped mixed oxides prepared by impregnation method and characterized by studying their structural, surface and optical properties. Chromium doped ZnO-ZrO2 had the highest rate of formation of hydroxyl radical due to decomposition of H2O2 and therefore 7-hydroxycoumarin due to surface area, small crystal size and high redox potential.

Natural Magnetite: an efficient catalyst for the degradation of organic contaminant

NASA Astrophysics Data System (ADS)

He, Hongping; Zhong, Yuanhong; Liang, Xiaoliang; Tan, Wei; Zhu, Jianxi; Yan Wang, Christina

2015-05-01

Iron (hydr)oxides are ubiquitous earth materials that have high adsorption capacities for toxic elements and degradation ability towards organic contaminants. Many studies have investigated the reactivity of synthetic magnetite, while little is known about natural magnetite. Here, we first report the reactivity of natural magnetites with a variety of elemental impurities for catalyzing the decomposition of H2O2 to produce hydroxyl free radicals (•OH) and the consequent degradation of p-nitrophenol (p-NP). We observed that these natural magnetites show higher catalytic performance than that of the synthetic pure magnetite. The catalytic ability of natural magnetite with high phase purity depends on the surface site density while that for the magnetites with exsolutions relies on the mineralogical nature of the exsolved phases. The pleonaste exsolution can promote the generation of •OH and the consequent degradation of p-NP; the ilmenite exsolution has little effect on the decomposition of H2O2, but can increase the adsorption of p-NP on magnetite. Our results imply that natural magnetite is an efficient catalyst for the degradation of organic contaminants in nature.

Multifunctional Co₀.₈₅Se/graphene hybrid nanosheets: controlled synthesis and enhanced performances for the oxygen reduction reaction and decomposition of hydrazine hydrate.

PubMed

Zhang, Lin-fei; Zhang, Chun-yang

2014-01-01

Ultrathin nanosheets possess novel electronic structures and physical properties as compared with their corresponding bulk samples. However, the controlled synthesis of ultrathin monolayer nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of two-dimensional (2D) structures. Here we demonstrate, for the first time to our knowledge, the in situ synthesis of large-scale ultrathin single-crystalline Co₀.₈₅Se nanosheets on graphene oxide (GO) sheets, with a thickness of 3 nm. Owing to the synergetic chemical coupling effects between GO and Co₀.₈₅Se, the Co₀.₈₅Se/graphene hybrid nanosheets exhibit the highest catalytic performance among the available cobalt chalcogenide-based catalysts for the oxygen reduction reaction (ORR). Moreover, Co₀.₈₅Se/graphene hybrid nanosheets can catalyze the decomposition of hydrazine hydrate rapidly, with 97% of hydrazine hydrate being degraded in 12 min and the degradation rate remaining constant over 10 consecutive cycles, thus having great potential as long-term catalysts in wastewater treatment.

Application of decomposition techniques to the preliminary design of a transport aircraft

NASA Technical Reports Server (NTRS)

Rogan, J. E.; Kolb, M. A.

1987-01-01

A nonlinear constrained optimization problem describing the preliminary design process for a transport aircraft has been formulated. A multifaceted decomposition of the optimization problem has been made. Flight dynamics, flexible aircraft loads and deformations, and preliminary structural design subproblems appear prominently in the decomposition. The use of design process decomposition for scheduling design projects, a new system integration approach to configuration control, and the application of object-centered programming to a new generation of design tools are discussed.

Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets.

PubMed

Shi, Dashuang; Caldovic, Ljubica; Tuchman, Mendel

2018-06-12

Carbamyl phosphate (CP) is well-known as an essential intermediate of pyrimidine and arginine/urea biosynthesis. Chemically, CP can be easily synthesized from dihydrogen phosphate and cyanate. Enzymatically, CP can be synthesized using three different classes of enzymes: (1) ATP-grasp fold protein based carbamyl phosphate synthetase (CPS); (2) Amino-acid kinase fold carbamate kinase (CK)-like CPS (anabolic CK or aCK); and (3) Catabolic transcarbamylase. The first class of CPS can be further divided into three different types of CPS as CPS I, CPS II, and CPS III depending on the usage of ammonium or glutamine as its nitrogen source, and whether N -acetyl-glutamate is its essential co-factor. CP can donate its carbamyl group to the amino nitrogen of many important molecules including the most well-known ornithine and aspartate in the arginine/urea and pyrimidine biosynthetic pathways. CP can also donate its carbamyl group to the hydroxyl oxygen of a variety of molecules, particularly in many antibiotic biosynthetic pathways. Transfer of the carbamyl group to the nitrogen group is catalyzed by the anabolic transcarbamylase using a direct attack mechanism, while transfer of the carbamyl group to the oxygen group is catalyzed by a different class of enzymes, CmcH/NodU CTase, using a different mechanism involving a three-step reaction, decomposition of CP to carbamate and phosphate, transfer of the carbamyl group from carbamate to ATP to form carbamyladenylate and pyrophosphate, and transfer of the carbamyl group from carbamyladenylate to the oxygen group of the substrate. CP is also involved in transferring its phosphate group to ADP to generate ATP in the fermentation of many microorganisms. The reaction is catalyzed by carbamate kinase, which may be termed as catabolic CK (cCK) in order to distinguish it from CP generating CK. CP is a thermally labile molecule, easily decomposed into phosphate and cyanate, or phosphate and carbamate depending on the pH of the solution, or the presence of enzyme. Biological systems have developed several mechanisms including channeling between enzymes, increased affinity of CP to enzymes, and keeping CP in a specific conformation to protect CP from decomposition. CP is highly important for our health as both a lack of, or decreased, CP production and CP accumulation results in many disease conditions.

Iron catalyzed conversion of NO into nitrosonium (NO+) and nitroxyl (HNO/NO-) species.

PubMed

Stojanović, Srdjan; Stanić, Dragana; Nikolić, Milan; Spasić, Mihailo; Niketić, Vesna

2004-11-01

The conversion of NO into its congeners, nitrosonium (NO+) and nitroxyl (HNO/NO-) species, has important consequences in NO metabolism. Dinitrosyl iron complex (DNIC) combined with thiol ligands was shown to catalyze the conversion of NO into NO+, resulting in the synthesis of S-nitrosothiols (RSNO) both in vitro and in vivo. The formation mechanism of DNIC was proposed to involve the intermediate release of nitroxyl. Since the detection of hydroxylamine (as the product of a rapid reaction of HNO/NO- with thiols) is taken as the evidence for nitroxyl generation, we examined the formation of hydroxylamine, RSNO, and nitrite (the product of a rapid reaction of NO+ with water) in neutral solutions containing iron ions and thiols exposed to NO under anaerobic conditions. Hydroxylamine was detected in NO treated solutions of iron ions in the presence of cysteine, but not glutathione (GSH). The addition of urate, a major "free" iron-binding agent in humans, to solutions of GSH and iron ions, and the subsequent treatment of these solutions with NO increased the synthesis of GSNO and resulted in the formation of hydroxylamine. This caused a loss of urate and yielded a novel nitrosative/nitration product. GSH attenuated the urate decomposition to such a degree that it could be reflected as the function of GSH:urate. Results described here contribute to the understanding of the role of iron ions in catalyzing the conversion of NO into HNO/NO- and point to the role of uric acid not previously described.

Formation of polycyclic lactones through a ruthenium-catalyzed ring-closing metathesis/hetero-Pauson-Khand reaction sequence.

PubMed

Finnegan, David F; Snapper, Marc L

2011-05-20

Processes that form multiple carbon-carbon bonds in one operation can generate molecular complexity quickly and therefore be used to shorten syntheses of desirable molecules. We selected the hetero-Pauson-Khand (HPK) cycloaddition and ring-closing metathesis (RCM) as two unique carbon-carbon bond-forming reactions that could be united in a tandem ruthenium-catalyzed process. In doing so, complex polycyclic products can be obtained in one reaction vessel from acyclic precursors using a single ruthenium additive that can catalyze sequentially two mechanistically distinct transformations.

Initial Reaction(s) in Biotransformation of CL-20 Is Catalyzed by Salicylate 1-Monooxygenase from Pseudomonas sp. Strain ATCC 29352

PubMed Central

Bhushan, Bharat; Halasz, Annamaria; Spain, Jim C.; Hawari, Jalal

2004-01-01

CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) (C6H6N12O12), a future-generation high-energy explosive, is biodegradable by Pseudomonas sp. strain FA1 and Agrobacterium sp. strain JS71; however, the nature of the enzyme(s) involved in the process was not understood. In the present study, salicylate 1-monooxygenase, a flavin adenine dinucleotide (FAD)-containing purified enzyme from Pseudomonas sp. strain ATCC 29352, biotransformed CL-20 at rates of 0.256 ± 0.011 and 0.043 ± 0.003 nmol min−1 mg of protein−1 under anaerobic and aerobic conditions, respectively. The disappearance of CL-20 was accompanied by the release of nitrite ions. Using liquid chromatography/mass spectrometry in the negative electrospray ionization mode, we detected a metabolite with a deprotonated mass ion [M − H]− at 345 Da, corresponding to an empirical formula of C6H6N10O8, produced as a result of two sequential N denitration steps on the CL- 20 molecule. We also detected two isomeric metabolites with [M − H]− at 381 Da corresponding to an empirical formula of C6H10N10O10. The latter was a hydrated product of the metabolite C6H6N10O8 with addition of two H2O molecules, as confirmed by tests using 18O-labeled water. The product stoichiometry showed that each reacted CL-20 molecule produced about 1.7 nitrite ions, 3.2 molecules of nitrous oxide, 1.5 molecules of formic acid, and 0.6 ammonium ion. Diphenyliodonium-mediated inhibition of salicylate 1-monooxygenase and a comparative study between native, deflavo, and reconstituted enzyme(s) showed that FAD site of the enzyme was involved in the biotransformation of CL-20 catalyzed by salicylate 1-monooxygenase. The data suggested that salicylate 1-monooxygenase catalyzed two oxygen-sensitive single-electron transfer steps necessary to release two nitrite ions from CL-20 and that this was followed by the secondary decomposition of this energetic chemical. PMID:15240281

Initial reaction(s) in biotransformation of CL-20 is catalyzed by salicylate 1-monooxygenase from Pseudomonas sp. strain ATCC 29352.

PubMed

Bhushan, Bharat; Halasz, Annamaria; Spain, Jim C; Hawari, Jalal

2004-07-01

CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) (C(6)H(6)N(12)O(12)), a future-generation high-energy explosive, is biodegradable by Pseudomonas sp. strain FA1 and Agrobacterium sp. strain JS71; however, the nature of the enzyme(s) involved in the process was not understood. In the present study, salicylate 1-monooxygenase, a flavin adenine dinucleotide (FAD)-containing purified enzyme from Pseudomonas sp. strain ATCC 29352, biotransformed CL-20 at rates of 0.256 +/- 0.011 and 0.043 +/- 0.003 nmol min(-1) mg of protein(-1) under anaerobic and aerobic conditions, respectively. The disappearance of CL-20 was accompanied by the release of nitrite ions. Using liquid chromatography/mass spectrometry in the negative electrospray ionization mode, we detected a metabolite with a deprotonated mass ion [M - H](-) at 345 Da, corresponding to an empirical formula of C(6)H(6)N(10)O(8), produced as a result of two sequential N denitration steps on the CL- 20 molecule. We also detected two isomeric metabolites with [M - H](-) at 381 Da corresponding to an empirical formula of C(6)H(10)N(10)O(10). The latter was a hydrated product of the metabolite C(6)H(6)N(10)O(8) with addition of two H(2)O molecules, as confirmed by tests using (18)O-labeled water. The product stoichiometry showed that each reacted CL-20 molecule produced about 1.7 nitrite ions, 3.2 molecules of nitrous oxide, 1.5 molecules of formic acid, and 0.6 ammonium ion. Diphenyliodonium-mediated inhibition of salicylate 1-monooxygenase and a comparative study between native, deflavo, and reconstituted enzyme(s) showed that FAD site of the enzyme was involved in the biotransformation of CL-20 catalyzed by salicylate 1-monooxygenase. The data suggested that salicylate 1-monooxygenase catalyzed two oxygen-sensitive single-electron transfer steps necessary to release two nitrite ions from CL-20 and that this was followed by the secondary decomposition of this energetic chemical.

Controlling First-Row Catalysts: Amination of Aryl and Heteroaryl Chlorides and Bromides with Primary Aliphatic Amines Catalyzed by a BINAP-Ligated Single-Component Ni(0) Complex

PubMed Central

2015-01-01

First-row metal complexes often undergo undesirable one-electron redox processes during two-electron steps of catalytic cycles. We report the amination of aryl chlorides and bromides with primary aliphatic amines catalyzed by a well-defined, single-component nickel precursor (BINAP)Ni(η2-NC-Ph) (BINAP = 2,2′-bis(biphenylphosphino)-1,1′-binaphthalene) that minimizes the formation of Ni(I) species and (BINAP)2Ni. The scope of the reaction encompasses electronically varied aryl chlorides and nitrogen-containing heteroaryl chlorides, including pyridine, quinoline, and isoquinoline derivatives. Mechanistic studies support the catalytic cycle involving a Ni(0)/Ni(II) couple for this nickel-catalyzed amination and are inconsistent with a Ni(I) halide intermediate. Monitoring the reaction mixture by 31P NMR spectroscopy identified (BINAP)Ni(η2-NC-Ph) as the resting state of the catalyst in the amination of both aryl chlorides and bromides. Kinetic studies showed that the amination of aryl chlorides and bromides is first order in both catalyst and aryl halide and zero order in base and amine. The reaction of a representative aryl chloride is inverse first order in PhCN, but the reaction of a representative aryl bromide is zero order in PhCN. This difference in the order of the reaction in PhCN indicates that the aryl chloride reacts with (BINAP)Ni(0), formed by dissociation PhCN from (BINAP)Ni(η2-NC-Ph), but the aryl bromide directly reacts with (BINAP)Ni(η2-NC-Ph). The overall kinetic behavior is consistent with turnover-limiting oxidative addition of the aryl halide to Ni(0). Several pathways for catalyst decomposition were identified, such as the formation of the catalytically inactive bis(amine)-ligated arylnickel(II) chloride, (BINAP)2Ni(0), and the Ni(I) species [(BINAP)Ni(μ-Cl)]2. By using a well-defined nickel complex as catalyst, the formation of (BINAP)2Ni(0) is avoided and the formation of the Ni(I) species [(BINAP)Ni(μ-Cl)]2 is minimized. PMID:24397570

Catalyzed Atomic Layer Deposition of Silicon Oxide at Ultralow Temperature Using Alkylamine.

PubMed

Mayangsari, Tirta R; Park, Jae-Min; Yusup, Luchana L; Gu, Jiyeon; Yoo, Jin-Hyuk; Kim, Heon-Do; Lee, Won-Jun

2018-06-12

We report the catalyzed atomic layer deposition (ALD) of silicon oxide using Si 2 Cl 6 , H 2 O, and various alkylamines. The density functional theory (DFT) calculations using the periodic slab model of the SiO 2 surface were performed for the selection of alternative Lewis base catalysts with high catalytic activities. During the first half-reaction, the catalysts with less steric hindrance such as pyridine would be more effective than bulky alkylamines despite lower nucleophilicity. On the other hand, during the second half-reaction, the catalysts with a high nucleophilicity such as triethylamine (Et 3 N) would be more efficient because the steric hindrance is less critical. The in situ process monitoring shows that the calculated atomic charge is a good indicator for expecting the catalyst activity in the ALD reaction. The use of Et 3 N in the second half-reaction was essential to improving the growth rate as well as the step coverage of the film because the Et 3 N-catalyzed process deposited a SiO 2 film with a step coverage of 98% that is better than 93% of the pyridine-catalyzed process. The adsorption of pyridine, ammonia (NH 3 ), or trimethylamine (Me 3 N) salts was more favorable than that of Et 3 N, n-Pr 3 N, or i Pr 3 N salts. Therefore, Et 3 N was expected to incorporate less amine salts in the film as compared to pyridine, and the compositional analyses confirmed that the concentrations of Cl and N by the Et 3 N-catalyzed process were significantly lower than those by the pyridine-catalyzed process.

Gas-phase production of single-walled carbon nanotubes from carbon monoxide: a review of the hipco process

NASA Technical Reports Server (NTRS)

Nikolaev, Pavel

2004-01-01

The latest process for producing large quantities of single-walled carbon nanotubes (SWNTs) to emerge from the Rice University, dubbed HiPco, is living up to its promise. The current production rates approach 450 mg/h (or 10 g/day), and nanotubes typically have no more than 7 mol % of iron impurities. Second-generation HiPco apparatus can run continuously for 7-10 days at a time. In the HiPco process nanotubes grow in high-pressure, high-temperature flowing CO on catalytic clusters of iron. Catalyst is formed in situ by thermal decomposition of iron pentacarbonyl, which is delivered intact within a cold CO flow and then rapidly mixed with hot CO in the reaction zone. Upon heating, the Fe(CO)5 decomposes into atoms that condense into larger clusters. SWNTs nucleate and grow on these particles in the gas phase via CO disproportionation: CO + CO --> CO2 + C (SWNT), catalyzed by the Fe surface. The concentration of CO2 produced in this reaction is equal to that of carbon and can therefore serve as a useful real-time feedback parameter. It was used to study and optimize SWNT production as a function of temperature, pressure, and Fe(CO)5 concentration. The results of the parametric study are in agreement with current understanding of the nanotube formation mechanism.

Catalytic N 2O decomposition and reduction by NH 3 over Fe/Beta and Fe/SSZ-13 catalysts

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

Wang, Aiyong; Wang, Yilin; Walter, Eric D.

Fe/zeolites are important N 2O abatement catalysts, efficient in direct N 2O decomposition and (selective) catalytic N 2O reduction. In this study, Fe/Beta and Fe/SSZ-13 were synthesized via solution ion-exchange and used to catalyze these two reactions. Nature of the Fe species was probed with UV-vis, Mössbauer and EPR spectroscopies and H2-TPR. The characterizations collectively indicate that isolated and dinuclear Fe sites dominate in Fe/SSZ-13, whereas Fe/Beta contains higher concentrations of oligomeric Fe xO y species. H 2-TPR results suggest that Fe-O interactions are weaker in Fe/SSZ-13, as evidenced by the lower reduction temperatures and higher extents of autoreduction duringmore » high-temperature pretreatments in inert gas. Kinetic measurements show that Fe/SSZ-13 has higher activity in catalytic N 2O decomposition, thus demonstrating a positive correlation between activity and Fe-O binding, consistent with O 2 desorption being rate-limiting for this reaction. However, Fe/Beta was found to be more active in catalyzing N 2O reduction by NH 3. This indicates that larger active ensembles (i.e., oligomers) are more active for this reaction, consistent with the fact that both N 2O and NH 3 need to be activated in this case. The authors from PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle. Aiyong Wang gratefully acknowledges the China Scholarship Council for the Joint-Training Scholarship Program with the Pacific Northwest National Laboratory (PNNL). The authors from East China University of Science and Technology acknowledge National Basic Research Program of China (2013CB933200), National Natural Science Foundation of China (21577035, 21577034), Commission of Science and Technology of Shanghai Municipality (15DZ1205305) and 111 Project (B08021) for supports.« less

Decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H2O2 and UV/TiO2 oxidation processes.

PubMed

Yan, Yingjie; Liao, Qi-Nan; Ji, Feng; Wang, Wei; Yuan, Shoujun; Hu, Zhen-Hu

2017-02-01

3,5-Dinitrobenzamide has been widely used as a feed additive to control coccidiosis in poultry, and part of the added 3,5-dinitrobenzamide is excreted into wastewater and surface water. The removal of 3,5-dinitrobenzamide from wastewater and surface water has not been reported in previous studies. Highly reactive hydroxyl radicals from UV/hydrogen peroxide (H 2 O 2 ) and UV/titanium dioxide (TiO 2 ) advanced oxidation processes (AOPs) can decompose organic contaminants efficiently. In this study, the decomposition of 3,5-dinitrobenzamide in aqueous solution during UV/H 2 O 2 and UV/TiO 2 oxidation processes was investigated. The decomposition of 3,5-dinitrobenzamide fits well with a fluence-based pseudo-first-order kinetics model. The decomposition in both two oxidation processes was affected by solution pH, and was inhibited under alkaline conditions. Inorganic anions such as NO 3 - , Cl - , SO 4 2- , HCO 3 - , and CO 3 2- inhibited the degradation of 3,5-dinitrobenzamide during the UV/H 2 O 2 and UV/TiO 2 oxidation processes. After complete decomposition in both oxidation processes, approximately 50% of 3,5-dinitrobenzamide was decomposed into organic intermediates, and the rest was mineralized to CO 2 , H 2 O, and other inorganic anions. Ions such as NH 4 + , NO 3 - , and NO 2 - were released into aqueous solution during the degradation. The primary decomposition products of 3,5-dinitrobenzamide were identified using time-of-flight mass spectrometry (LCMS-IT-TOF). Based on these products and ions release, a possible decomposition pathway of 3,5-dinitrobenzamide in both UV/H 2 O 2 and UV/TiO 2 processes was proposed.

Kinetics of Thermal Decomposition of Ammonium Perchlorate by TG/DSC-MS-FTIR

NASA Astrophysics Data System (ADS)

Zhu, Yan-Li; Huang, Hao; Ren, Hui; Jiao, Qing-Jie

2014-01-01

The method of thermogravimetry/differential scanning calorimetry-mass spectrometry-Fourier transform infrared (TG/DSC-MS-FTIR) simultaneous analysis has been used to study thermal decomposition of ammonium perchlorate (AP). The processing of nonisothermal data at various heating rates was performed using NETZSCH Thermokinetics. The MS-FTIR spectra showed that N2O and NO2 were the main gaseous products of the thermal decomposition of AP, and there was a competition between the formation reaction of N2O and that of NO2 during the process with an iso-concentration point of N2O and NO2. The dependence of the activation energy calculated by Friedman's iso-conversional method on the degree of conversion indicated that the AP decomposition process can be divided into three stages, which are autocatalytic, low-temperature diffusion and high-temperature, stable-phase reaction. The corresponding kinetic parameters were determined by multivariate nonlinear regression and the mechanism of the AP decomposition process was proposed.

Lanthanum(III)-catalyzed disproportionation of hydrogen peroxide: a heterogeneous generator of singlet molecular oxygen-1O2 (1Deltag)-in near-neutral aqueous and organic media for peroxidation of electron-rich substrates.

PubMed

Nardello, Véronique; Barbillat, Jacques; Marko, Jean; Witte, Peter T; Alsters, Paul L; Aubry, Jean-Marie

2003-01-20

The decomposition of hydrogen peroxide into singlet molecular oxygen-(1)O(2) ((1)Delta(g))-in the presence of lanthanum(iii) salts was studied by monitoring its characteristic IR luminescence at 1270 nm. The process was found to be heterogeneously catalyzed by La(III), provided that the heterogeneous catalyst is generated in situ. The yield of (1)O(2) generation was assessed as 45+/-5 % both in water and in methanol. The pH-dependence on the rate of (1)O(2) generation corresponds to a bell-shaped curve from pH 4.5 to 13 with a maximum around pH 8. The study of the influence of H(2)O(2) showed that the formation of (1)O(2) begins as soon as one equivalent of H(2)O(2) is introduced. It then increases drastically up to two equivalents and more smoothly above. Unlike all other metal salt catalyst systems known to date for H(2)O(2) disproportionation, this chemical source of (1)O(2) is able to generate (1)O(2) not only in basic media, but also under neutral and slightly acidic conditions. In addition, this La-based catalyst system has a very low tendency to induce unwanted oxygenating side reactions, such as epoxidation of alkenes. These two characteristics of the heterogeneous lanthanum catalyst system allow non-photochemical (i.e., "dark") singlet oxygenation of substrate classes that cannot be peroxidized successfully with conventional molybdate catalysts, such as allylic alcohols and alkenyl amines.

Understanding Litter Input Controls on Soil Organic Matter Turnover and Formation are Essential for Improving Carbon-Climate Feedback Predictions for Arctic, Tundra Ecosystems

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

Wallenstein, Matthew

The Arctic region stored vast amounts of carbon (C) in soils over thousands of years because decomposition has been limited by cold, wet conditions. Arctic soils now contain roughly as much C that is contained in all other soils across the globe combined. However, climate warming could unlock this oil C as decomposition accelerates and permafrost thaws. In addition to temperature-driven acceleration of decomposition, several additional processes could either counteract or augment warming-induced SOM losses. For example, increased plant growth under a warmer climate will increase organic matter inputs to soils, which could fuel further soil decomposition by microbes, butmore » will also increase the production of new SOM. Whether Arctic ecosystems store or release carbon in the future depends in part on the balance between these two counteracting processes. By differentiating SOM decomposition and formation and understanding the drivers of these processes, we will better understand how these systems function. We did not find evidence of priming under current conditions, defined as an increase in the decomposition of native SOM stocks. This suggests that decomposition is unlikely to be further accelerated through this mechanism. We did find that decomposition of native SOM did occur when nitrogen was added to these soils, suggesting that nitrogen limits decomposition in these systems. Our results highlight the resilience and extraordinary C storage capacity of these soils, and suggest shrub expansion may partially mitigate C losses from decomposition of old SOM as Arctic soils warm.« less

Nickel-Catalyzed Coupling of Alkenes, Aldehydes, and Silyl Triflates

PubMed Central

Ng, Sze-sze; Ho, Chun-Yu; Jamison, Timothy F.

2011-01-01

A full account of two recently developed nickel-catalyzed coupling reactions of alkenes, aldehydes and silyl triflates is presented. These reactions provide either allylic alcohol or homoallylic alcohol derivatives selectively, depending on the ligand employed. These processes are believed to be mechanistically distinct from Lewis acid-catalyzed carbonyl-ene reactions, and several lines of evidence supporting this hypothesis are discussed. PMID:16939275

Decomposition of gas-phase trichloroethene by the UV/TiO2 process in the presence of ozone.

PubMed

Shen, Y S; Ku, Y

2002-01-01

The decomposition of gas-phase trichloroethene (TCE) in air streams by direct photolysis, the UV/TiO2 and UV/O3 processes was studied. The experiments were carried out under various UV light intensities and wavelengths, ozone dosages, and initial concentrations of TCE to investigate and compare the removal efficiency of the pollutant. For UV/TiO2 process, the individual contribution to the decomposition of TCE by direct photolysis and hydroxyl radicals destruction was differentiated to discuss the quantum efficiency with 254 and 365 nm UV lamps. The removal of gaseous TCE was found to reduce by UV/TiO2 process in the presence of ozone possibly because of the ozone molecules could scavenge hydroxyl radicals produced from the excitation of TiO2 by UV radiation to inhibit the decomposition of TCE. A photoreactor design equation for the decomposition of gaseous TCE by the UV/TiO2 process in air streams was developed by combining the continuity equation of the pollutant and the surface catalysis reaction rate expression. By the proposed design scheme, the temporal distribution of TCE at various operation conditions by the UV/TiO2 process can be well modeled.

Soil fauna and plant litter decomposition in tropical and subalpine forests

Treesearch

G. Gonzalez; T.R. Seastedt

2001-01-01

The decomposition of plant residues is influenced by their chemical composition, the physical-chemical environment, and the decomposer organisms. Most studies interested in latitudinal gradients of decomposition have focused on substrate quality and climate effects on decomposition, and have excluded explicit recognition of the soil organisms involved in the process....

Mechanistic Insight Facilitates Discovery of a Mild and Efficient Copper-Catalyzed Dehydration of Primary Amides to Nitriles Using Hydrosilanes.

PubMed

Liu, Richard Y; Bae, Minwoo; Buchwald, Stephen L

2018-02-07

Metal-catalyzed silylative dehydration of primary amides is an economical approach to the synthesis of nitriles. We report a copper-hydride(CuH)-catalyzed process that avoids a typically challenging 1,2-siloxane elimination step, thereby dramatically increasing the rate of the overall transformation relative to alternative metal-catalyzed systems. This new reaction proceeds at ambient temperature, tolerates a variety of metal-, acid-, or base-sensitive functional groups, and can be performed using a simple ligand, inexpensive siloxanes, and low catalyst loading.

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.

Tracking Hierarchical Processing in Morphological Decomposition with Brain Potentials

ERIC Educational Resources Information Center

Lavric, Aureliu; Elchlepp, Heike; Rastle, Kathleen

2012-01-01

One important debate in psycholinguistics concerns the nature of morphological decomposition processes in visual word recognition (e.g., darkness = {dark} + {-ness}). One theory claims that these processes arise during orthographic analysis and prior to accessing meaning (Rastle & Davis, 2008), and another argues that these processes arise through…

Enhancing Catalyzed Decomposition of Na2CO3 with Co2MnO x Nanowire-Decorated Carbon Fibers for Advanced Na-CO2 Batteries.

PubMed

Fang, Cong; Luo, Jianmin; Jin, Chengbin; Yuan, Huadong; Sheng, Ouwei; Huang, Hui; Gan, Yongping; Xia, Yang; Liang, Chu; Zhang, Jun; Zhang, Wenkui; Tao, Xinyong

2018-05-23

The metal-CO 2 batteries, especially Na-CO 2 , batteries come into sight owing to their high energy density, ability for CO 2 capture, and the abundance of sodium resource. Besides the sluggish electrochemical reactions at the gas cathodes and the instability of the electrolyte at a high voltage, the final discharge product Na 2 CO 3 is a solid and poor conductor of electricity, which may cause the high overpotential and poor cycle performance for the Na-CO 2 batteries. The promotion of decomposition of Na 2 CO 3 should be an efficient strategy to enhance the electrochemical performance. Here, we design a facile Na 2 CO 3 activation experiment to screen the efficient cathode catalyst for the Na-CO 2 batteries. It is found that the Co 2 MnO x nanowire-decorated carbon fibers (CMO@CF) can promote the Na 2 CO 3 decomposition at the lowest voltage among all these metal oxide-decorated carbon fiber structures. After assembling the Na-CO 2 batteries, the electrodes based on CMO@CF show lower overpotential and better cycling performance compared with the electrodes based on pristine carbon fibers and other metal oxide-modified carbon fibers. We believe this catalyst screening method and the freestanding structure of the CMO@CF electrode may provide an important reference for the development of advanced Na-CO 2 batteries.

Catalytic effect of different reactor materials under subcritical water conditions: decarboxylation of cysteic acid into taurine

NASA Astrophysics Data System (ADS)

Faisal, M.

2018-03-01

In order to understand the influence of reactor materials on the catalytic effect for a particular reaction, the decomposition of cysteic acid from Ni/Fe-based alloy reactors under subcritical water conditions was examined. Experiments were carried out in three batch reactors made of Inconel 625, Hastelloy C-22 and SUS 316 over temperatures of 200 to 300 °C. The highest amount of eluted metals was found for SUS 316. The results demonstrated that reactor materials contribute to the resulting product. Under the tested conditions, cysteic acid decomposes readily with SUS 316. However, the Ni-based materials (Inconel 625 and Hastelloy C-22) show better resistance to metal elution. It was found that among the materials used in this work, SUS 316 gave the highest reaction rate constant of 0.1934 s‑1. The same results were obtained at temperatures of 260 and 300 °C. Investigation of the Arrhenius activation energy revealed that the highest activation energy was for Hastelloy C-22 (109 kJ/mol), followed by Inconel 625 (90 kJ/mol) and SUS 316 (70 kJ/mol). The decomposition rate of cysteic acid was found to follow the results for the trend of the eluted metals. Therefore, it can be concluded that the decomposition of cysteic acid was catalyzed by the elution of heavy metals from the surface of the reactor. The highest amount of taurine from the decarboxylation of cysteic acid was obtained from SUS 316.

Catalyzed pyrolysis of grape and olive bagasse. Influence of catalyst type and chemical treatment

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

Encinar, J.M.; Beltran, F.J.; Ramiro, A.

1997-10-01

Catalyzed pyrolysis of grape and olive bagasse under different experimental conditions has been studied. Variables investigated were temperature and type and concentration of catalysts. Experiments were carried out in an isothermal manner. Products of pyrolysis are gases (H{sub 2}, CO, CO{sub 2}, and CH{sub 4}), liquids (methanol, acetone, furfurylic alcohol, phenol, furfural, naphthalene, and o-cresol), and solids (chars). Temperature is a significant variable, yielding increases of fixed carbon content, gases, and to a lesser extent, ash percentage. Catalyst presence also yields increases of solid phase content, but the amount of liquid components decrease. Among catalysts applied those of Fe andmore » Zn are the most advisable to obtain gases. Chemical treatment of bagasses with sulfuric or phosphoric acid washing leads to lower char yields, although fixed carbon content is higher and ash presence diminishes with respect to catalyst pyrolysis without chemical pretreatment. A pyrolysis kinetic study based on gas generation from thermal decomposition of residues has been carried out. From the model proposed, rate constants for the formation of each gas, reaction order of the catalyst, and activation energies were determined.« less

Gold-catalyzed synthesis of benzil derivatives and α-keto imides via oxidation of alkynes.

PubMed

Xu, Cheng-Fu; Xu, Mei; Jia, Yi-Xia; Li, Chuan-Ying

2011-03-18

An efficient process based on the gold-catalyzed redox reaction has been developed to oxidize 1,2-diarylacetylene or ynamide to 1,2-diaryldiketone or α-keto imide respectively. This process can tolerate a variety of functional groups and affords 1,2-dicarbonyl compounds in excellent yields under mild reaction conditions.

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

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.

A Key Enzyme of the NAD+ Salvage Pathway in Thermus thermophilus: Characterization of Nicotinamidase and the Impact of Its Gene Deletion at High Temperatures

PubMed Central

Taniguchi, Hironori; Sungwallek, Sathidaphorn; Chotchuang, Phatcharin; Okano, Kenji

2017-01-01

ABSTRACT NAD (NAD+) is a cofactor related to many cellular processes. This cofactor is known to be unstable, especially at high temperatures, where it chemically decomposes to nicotinamide and ADP-ribose. Bacteria, yeast, and higher organisms possess the salvage pathway for reconstructing NAD+ from these decomposition products; however, the importance of the salvage pathway for survival is not well elucidated, except for in pathogens lacking the NAD+ de novo synthesis pathway. Herein, we report the importance of the NAD+ salvage pathway in the thermophilic bacterium Thermus thermophilus HB8 at high temperatures. We identified the gene encoding nicotinamidase (TTHA0328), which catalyzes the first reaction of the NAD+ salvage pathway. This recombinant enzyme has a high catalytic activity against nicotinamide (Km of 17 μM, kcat of 50 s−1, kcat/Km of 3.0 × 103 s−1 · mM−1). Deletion of this gene abolished nicotinamide deamination activity in crude extracts of T. thermophilus and disrupted the NAD+ salvage pathway in T. thermophilus. Disruption of the salvage pathway led to the severe growth retardation at a higher temperature (80°C), owing to the drastic decrease in the intracellular concentrations of NAD+ and NADH. IMPORTANCE NAD+ and other nicotinamide cofactors are essential for cell metabolism. These molecules are unstable and decompose, even under the physiological conditions in most organisms. Thermophiles can survive at high temperatures where NAD+ decomposition is, in general, more rapid. This study emphasizes that NAD+ instability and its homeostasis can be one of the important factors for thermophile survival in extreme temperatures. PMID:28630126

Inactivation of the Lactobacillus leichmannii ribonucleoside triphosphate reductase by 2'-chloro-2'-deoxyuridine 5'-triphosphate: stoichiometry of inactivation, site of inactivation, and mechanism of the protein chromophore formation

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

Ashley, G.W.; Harris, G.; Stubbe, J.A.

1988-06-14

The ribonucleoside triphosphate reductase (RTPR) of Lactobacillus leichmannii is inactivated by the substrate analogue 2'-chloro-2'-deoxyuridine 5'-triphosphate (ClUTP). Inactivation is due to alkylation by 2-methylene-3(2H)-furanone, a decomposition product of the enzymic product 3'-keto-2'-deoxyuridine triphosphate. The former has been unambiguously identified as 2-((ethylthio)methyl)-3(2H)-furanone, an ethanethiol trapped adduct, which is identical by /sup 1/H NMR spectroscopy with material synthesized chemically. Subsequent to rapid inactivation, a slow process occurs that results in formation of a new protein-associated chromophore absorbing maximally near 320 nm. The terminal stages of the inactivation have now been investigated in detail. The alkylation and inactivation stoichiometries were studied as amore » function of the ratio of ClUTP to enzyme. The amount of labeling of RTPR increased with increasing ClUTP concentration up to the maximum of approximately 4 labels/RTPR, yet the degree of inactivation did not increase proportionally. This suggests that (1) RTPR may be inactivated by alkylation of a single site and (2) decomposition of 3'-keto-dUTP is not necessarily enzyme catalyzed. The formation of the new protein chromophore was also monitored during inactivation and found to reach its full extent upon the first alkylation . Thus, out of four alkylation sites, only one appears capable of undergoing the subsequent reaction to form the new chromophore. Model studies suggest that the new chromophore is due to addition of an amino group to the 5-position of enzyme-bound furanone, followed by ring opening and tautomerization to give a ..beta..-aminoenone structure.« less

A Key Enzyme of the NAD+ Salvage Pathway in Thermus thermophilus: Characterization of Nicotinamidase and the Impact of Its Gene Deletion at High Temperatures.

PubMed

Taniguchi, Hironori; Sungwallek, Sathidaphorn; Chotchuang, Phatcharin; Okano, Kenji; Honda, Kohsuke

2017-09-01

NAD (NAD + ) is a cofactor related to many cellular processes. This cofactor is known to be unstable, especially at high temperatures, where it chemically decomposes to nicotinamide and ADP-ribose. Bacteria, yeast, and higher organisms possess the salvage pathway for reconstructing NAD + from these decomposition products; however, the importance of the salvage pathway for survival is not well elucidated, except for in pathogens lacking the NAD + de novo synthesis pathway. Herein, we report the importance of the NAD + salvage pathway in the thermophilic bacterium Thermus thermophilus HB8 at high temperatures. We identified the gene encoding nicotinamidase (TTHA0328), which catalyzes the first reaction of the NAD + salvage pathway. This recombinant enzyme has a high catalytic activity against nicotinamide ( K m of 17 μM, k cat of 50 s -1 , k cat / K m of 3.0 × 10 3 s -1 · mM -1 ). Deletion of this gene abolished nicotinamide deamination activity in crude extracts of T. thermophilus and disrupted the NAD + salvage pathway in T. thermophilus Disruption of the salvage pathway led to the severe growth retardation at a higher temperature (80°C), owing to the drastic decrease in the intracellular concentrations of NAD + and NADH. IMPORTANCE NAD + and other nicotinamide cofactors are essential for cell metabolism. These molecules are unstable and decompose, even under the physiological conditions in most organisms. Thermophiles can survive at high temperatures where NAD + decomposition is, in general, more rapid. This study emphasizes that NAD + instability and its homeostasis can be one of the important factors for thermophile survival in extreme temperatures. Copyright © 2017 American Society for Microbiology.

Utilization of a balanced steady state free precession signal model for improved fat/water decomposition.

PubMed

Henze Bancroft, Leah C; Strigel, Roberta M; Hernando, Diego; Johnson, Kevin M; Kelcz, Frederick; Kijowski, Richard; Block, Walter F

2016-03-01

Chemical shift based fat/water decomposition methods such as IDEAL are frequently used in challenging imaging environments with large B0 inhomogeneity. However, they do not account for the signal modulations introduced by a balanced steady state free precession (bSSFP) acquisition. Here we demonstrate improved performance when the bSSFP frequency response is properly incorporated into the multipeak spectral fat model used in the decomposition process. Balanced SSFP allows for rapid imaging but also introduces a characteristic frequency response featuring periodic nulls and pass bands. Fat spectral components in adjacent pass bands will experience bulk phase offsets and magnitude modulations that change the expected constructive and destructive interference between the fat spectral components. A bSSFP signal model was incorporated into the fat/water decomposition process and used to generate images of a fat phantom, and bilateral breast and knee images in four normal volunteers at 1.5 Tesla. Incorporation of the bSSFP signal model into the decomposition process improved the performance of the fat/water decomposition. Incorporation of this model allows rapid bSSFP imaging sequences to use robust fat/water decomposition methods such as IDEAL. While only one set of imaging parameters were presented, the method is compatible with any field strength or repetition time. © 2015 Wiley Periodicals, Inc.

Termites promote resistance of decomposition to spatiotemporal variability in rainfall.

PubMed

Veldhuis, Michiel P; Laso, Francisco J; Olff, Han; Berg, Matty P

2017-02-01

The ecological impact of rapid environmental change will depend on the resistance of key ecosystems processes, which may be promoted by species that exert strong control over local environmental conditions. Recent theoretical work suggests that macrodetritivores increase the resistance of African savanna ecosystems to changing climatic conditions, but experimental evidence is lacking. We examined the effect of large fungus-growing termites and other non-fungus-growing macrodetritivores on decomposition rates empirically with strong spatiotemporal variability in rainfall and temperature. Non-fungus-growing larger macrodetritivores (earthworms, woodlice, millipedes) promoted decomposition rates relative to microbes and small soil fauna (+34%) but both groups reduced their activities with decreasing rainfall. However, fungus-growing termites increased decomposition rates strongest (+123%) under the most water-limited conditions, making overall decomposition rates mostly independent from rainfall. We conclude that fungus-growing termites are of special importance in decoupling decomposition rates from spatiotemporal variability in rainfall due to the buffered environment they create within their extended phenotype (mounds), that allows decomposition to continue when abiotic conditions outside are less favorable. This points at a wider class of possibly important ecological processes, where soil-plant-animal interactions decouple ecosystem processes from large-scale climatic gradients. This may strongly alter predictions from current climate change models. © 2016 by the Ecological Society of America.

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. Copyright © 2016 Elsevier Inc. All rights reserved.

A new family of nucleophiles for photoinduced, copper-catalyzed cross-couplings via single-electron transfer: reactions of thiols with aryl halides under mild conditions (O °C).

PubMed

Uyeda, Christopher; Tan, Yichen; Fu, Gregory C; Peters, Jonas C

2013-06-26

Building on the known photophysical properties of well-defined copper-carbazolide complexes, we have recently described photoinduced, copper-catalyzed N-arylations and N-alkylations of carbazoles. Until now, there have been no examples of the use of other families of heteroatom nucleophiles in such photoinduced processes. Herein, we report a versatile photoinduced, copper-catalyzed method for coupling aryl thiols with aryl halides, wherein a single set of reaction conditions, using inexpensive CuI as a precatalyst without the need for an added ligand, is effective for a wide range of coupling partners. As far as we are aware, copper-catalyzed C-S cross-couplings at 0 °C have not previously been achieved, which renders our observation of efficient reaction of an unactivated aryl iodide at -40 °C especially striking. Mechanistic investigations are consistent with these photoinduced C-S cross-couplings following a SET/radical pathway for C-X bond cleavage (via a Cu(I)-thiolate), which contrasts with nonphotoinduced, copper-catalyzed processes wherein a concerted mechanism is believed to occur.

A reductionist biomimetic model system that demonstrates highly effective Zn(II)-catalyzed cleavage of an RNA model.

PubMed

Liu, C Tony; Neverov, Alexei A; Brown, R Stan

2007-03-05

The cyclization of the RNA model 2-hydroxypropyl p-nitrophenyl phosphate (HPNPP, 1) promoted by Zn2+ alone and the 1,5,9-triazacyclododecane complex of Zn2+ (Zn2+:[12]aneN3) is studied in ethanol in the presence of 0.5 equiv of -OEt/Zn2+ to investigate the effect of a low polarity/dielectric medium on a metal-catalyzed reaction of biological relevance. Ethanol exerts a medium effect that promotes strong binding of HPNPP to Zn2+, followed by a dimerization to form a catalytically active complex (HPNPP:Zn2+)2 in which the phosphate undergoes cyclization with a rate constant of kcat = 2.9 s(-1) at s(s)pH 7.1. In the presence of the triaza ligand:Zn2+ complex, the change from water to methanol and then to ethanol brings about a mechanism where two molecules of the complex, suggested as EtOH:Zn2+:[12]aneN3 and its basic form, EtO-:Zn2+:[12]aneN3, bind to HPNPP and catalyze its decomposition with a rate constant of kcat of 0.13 s(-1) at s(s)pH 7.1. Overall, the acceleration exhibited in these two situations is 4 x 10(14)-fold and 1.7 x 10(12)-fold relative to the background ethoxide-promoted reactions at the respective s(s)pH values. The implications of these findings are discussed within the context of the idea that enzymatic catalysis is enhanced by a reduced effective dielectric constant within the active site.

Bacterial dehalogenases: biochemistry, genetics, and biotechnological applications.

PubMed Central

Fetzner, S; Lingens, F

1994-01-01

This review is a survey of bacterial dehalogenases that catalyze the cleavage of halogen substituents from haloaromatics, haloalkanes, haloalcohols, and haloalkanoic acids. Concerning the enzymatic cleavage of the carbon-halogen bond, seven mechanisms of dehalogenation are known, namely, reductive, oxygenolytic, hydrolytic, and thiolytic dehalogenation; intramolecular nucleophilic displacement; dehydrohalogenation; and hydration. Spontaneous dehalogenation reactions may occur as a result of chemical decomposition of unstable primary products of an unassociated enzyme reaction, and fortuitous dehalogenation can result from the action of broad-specificity enzymes converting halogenated analogs of their natural substrate. Reductive dehalogenation either is catalyzed by a specific dehalogenase or may be mediated by free or enzyme-bound transition metal cofactors (porphyrins, corrins). Desulfomonile tiedjei DCB-1 couples energy conservation to a reductive dechlorination reaction. The biochemistry and genetics of oxygenolytic and hydrolytic haloaromatic dehalogenases are discussed. Concerning the haloalkanes, oxygenases, glutathione S-transferases, halidohydrolases, and dehydrohalogenases are involved in the dehalogenation of different haloalkane compounds. The epoxide-forming halohydrin hydrogen halide lyases form a distinct class of dehalogenases. The dehalogenation of alpha-halosubstituted alkanoic acids is catalyzed by halidohydrolases, which, according to their substrate and inhibitor specificity and mode of product formation, are placed into distinct mechanistic groups. beta-Halosubstituted alkanoic acids are dehalogenated by halidohydrolases acting on the coenzyme A ester of the beta-haloalkanoic acid. Microbial systems offer a versatile potential for biotechnological applications. Because of their enantiomer selectivity, some dehalogenases are used as industrial biocatalysts for the synthesis of chiral compounds. The application of dehalogenases or bacterial strains in environmental protection technologies is discussed in detail. PMID:7854251

Radial Growth of Self-Catalyzed GaAs Nanowires and the Evolution of the Liquid Ga-Droplet Studied by Time-Resolved in Situ X-ray Diffraction.

PubMed

Schroth, Philipp; Jakob, Julian; Feigl, Ludwig; Mostafavi Kashani, Seyed Mohammad; Vogel, Jonas; Strempfer, Jörg; Keller, Thomas F; Pietsch, Ullrich; Baumbach, Tilo

2018-01-10

We report on a growth study of self-catalyzed GaAs nanowires based on time-resolved in situ X-ray structure characterization during molecular-beam-epitaxy in combination with ex situ scanning-electron-microscopy. We reveal the evolution of nanowire radius and polytypism and distinguish radial growth processes responsible for tapering and side-wall growth. We interpret our results using a model for diameter self-stabilization processes during growth of self-catalyzed GaAs nanowires including the shape of the liquid Ga-droplet and its evolution during growth.

Copper-catalyzed oxidative homo- and cross-coupling of Grignard reagents using diaziridinone.

PubMed

Zhu, Yingguang; Xiong, Tao; Han, Wenyong; Shi, Yian

2014-12-05

Transition-metal-catalyzed cross-coupling reactions are among the most powerful synthetic transformations. This paper describes an efficient copper-catalyzed homo- and cross-coupling of Grignard reagents with di-tert-butyldiaziridinone as oxidant under mild conditions, giving the coupling products in good to excellent yields. The reaction process has a broad substrate scope and is also effective for the C(sp)-C(sp(3)) coupling.

Zinc-catalyzed allenylations of aldehydes and ketones.

PubMed

Fandrick, Daniel R; Saha, Jaideep; Fandrick, Keith R; Sanyal, Sanjit; Ogikubo, Junichi; Lee, Heewon; Roschangar, Frank; Song, Jinhua J; Senanayake, Chris H

2011-10-21

The general zinc-catalyzed allenylation of aldehydes and ketones with an allenyl boronate is presented. Preliminary mechanistic studies support a kinetically controlled process wherein, after a site-selective B/Zn exchange to generate a propargyl zinc intermediate, the addition to the electrophile effectively competes with propargyl-allenyl zinc equilibration. The utility of the methodology was demonstrated by application to a rhodium-catalyzed [4+2] cycloaddition. © 2011 American Chemical Society

Mechanism insight of pollutant degradation and bromate inhibition by Fe-Cu-MCM-41 catalyzed ozonation.

PubMed

Chen, Weirui; Li, Xukai; Tang, Yiming; Zhou, Jialu; Wu, Dan; Wu, Yin; Li, Laisheng

2018-03-15

A flexible catalyst, Fe-Cu-MCM-41, was employed to enhance diclofenac (DCF) mineralization and inhibit bromate formation in catalytic ozonation process. Greater TOC removal was achieved in Fe-Cu-MCM-41/O 3 process (78%) than those in Fe-MCM-41/O 3 (65%), Cu-MCM-41/O 3 (73%) and sole ozonation (42%). But it was interesting that both Cu-MCM-41/O 3 and Fe-MCM-41/O 3 achieved 93% bromate inhibition efficiency, only 71% inhibition efficiency was observed in Fe-Cu-MCM-41/O 3 . Influence of pH, TBA/NaHSO 3 and detection of by-products were conducted to explore the mechanism. By Pyridine adsorption-IR and XPS, a relationship was found among activity of catalysts, Lewis acid sites and electron transfer effect between Fe (II/III) and Cu (I/II). Fe-Cu-MCM-41 promoted ozone decomposition to generate OH, which accounted for enhanced DCF mineralization. The consumption of aqueous O 3 also suppressed the oxidative of Br - and HBrO/Br - . More HBrO/BrO - accumulated in catalytic ozonation process and less bromate generated. Bromate formation in Fe-Cu-MCM-41/O 3 process was sensitive with pH value, the acidic condition was not favor for bromate formation. Both DCF mineralization and bromate inhibition were influenced by surface reaction. Moreover, Fe-Cu-MCM-41 showed excellent catalytic performance in suppressing the accumulation of carboxylic acid, especially for oxalic acid. Nearly no oxalic acid was detected during Fe-Cu-MCM-41/O 3 process. Copyright © 2017 Elsevier B.V. All rights reserved.

Formate as a CO surrogate for cascade processes: Rh-catalyzed cooperative decarbonylation and asymmetric Pauson-Khand-type cyclization reactions.

PubMed

Lee, Hang Wai; Chan, Albert S C; Kwong, Fuk Yee

2007-07-07

A rhodium-(S)-xyl-BINAP complex-catalyzed tandem formate decarbonylation and [2 + 2 + 1] carbonylative cyclization is described; this cooperative process utilizes formate as a condensed CO source, and the newly developed cascade protocol can be extended to its enantioselective version, providing up to 94% ee of the cyclopentenone adducts.

A density functional theory study of the decomposition mechanism of nitroglycerin.

PubMed

Pei, Liguan; Dong, Kehai; Tang, Yanhui; Zhang, Bo; Yu, Chang; Li, Wenzuo

2017-08-21

The detailed decomposition mechanism of nitroglycerin (NG) in the gas phase was studied by examining reaction pathways using density functional theory (DFT) and canonical variational transition state theory combined with a small-curvature tunneling correction (CVT/SCT). The mechanism of NG autocatalytic decomposition was investigated at the B3LYP/6-31G(d,p) level of theory. Five possible decomposition pathways involving NG were identified and the rate constants for the pathways at temperatures ranging from 200 to 1000 K were calculated using CVT/SCT. There was found to be a lower energy barrier to the β-H abstraction reaction than to the α-H abstraction reaction during the initial step in the autocatalytic decomposition of NG. The decomposition pathways for CHOCOCHONO 2 (a product obtained following the abstraction of three H atoms from NG by NO 2 ) include O-NO 2 cleavage or isomer production, meaning that the autocatalytic decomposition of NG has two reaction pathways, both of which are exothermic. The rate constants for these two reaction pathways are greater than the rate constants for the three pathways corresponding to unimolecular NG decomposition. The overall process of NG decomposition can be divided into two stages based on the NO 2 concentration, which affects the decomposition products and reactions. In the first stage, the reaction pathway corresponding to O-NO 2 cleavage is the main pathway, but the rates of the two autocatalytic decomposition pathways increase with increasing NO 2 concentration. However, when a threshold NO 2 concentration is reached, the NG decomposition process enters its second stage, with the two pathways for NG autocatalytic decomposition becoming the main and secondary reaction pathways.

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.

Cryptic diversity and ecosystem functioning: a complex tale of differential effects on decomposition.

PubMed

De Meester, N; Gingold, R; Rigaux, A; Derycke, S; Moens, T

2016-10-01

Marine ecosystems are experiencing accelerating population and species loss. Some ecosystem functions are decreasing and there is growing interest in the link between biodiversity and ecosystem functioning. The role of cryptic (morphologically identical but genetically distinct) species in this biodiversity-ecosystem functioning link is unclear and has not yet been formally tested. We tested if there is a differential effect of four cryptic species of the bacterivorous nematode Litoditis marina on the decomposition process of macroalgae. Bacterivorous nematodes can stimulate or slow down bacterial activity and modify the bacterial assemblage composition. Moreover, we tested if interspecific interactions among the four cryptic species influence the decomposition process. A laboratory experiment with both mono- and multispecific nematode cultures was conducted, and loss of organic matter and the activity of two key extracellular enzymes for the degradation of phytodetritus were assessed. L. marina mainly influenced qualitative aspects of the decomposition process rather than its overall rate: an effect of the nematodes on the enzymatic activities became manifest, although no clear nematode effect on bulk organic matter weight loss was found. We also demonstrated that species-specific effects on the decomposition process existed. Combining the four cryptic species resulted in high competition, with one dominant species, but without complete exclusion of other species. These interspecific interactions translated into different effects on the decomposition process. The species-specific differences indicated that each cryptic species may play an important and distinct role in ecosystem functioning. Functional differences may result in coexistence among very similar species.

Gold-nanoparticle-catalyzed synthesis of propargylamines: the traditional A3-multicomponent reaction performed as a two-step flow process.

PubMed

Abahmane, Lahbib; Köhler, J Michael; Gross, G Alexander

2011-03-01

The alkyne, aldehyde, amine A(3)-coupling reaction, a traditional multicomponent reaction (MCR), has been investigated as a two-step flow process. The implicated aminoalkylation reaction of phenylacetylene with appropriate aldimine intermediates was catalyzed by gold nanoparticles impregnated on alumina. The aldimine formation was catalyzed by Montmorillonite K10 beforehand. The performance of the process has been investigated with respect to different reaction regimes. Usually, the A(3)-multicomponent reaction is performed as a "one-pot" process. Diversity-oriented syntheses using MCRs often have the shortcoming that only low selectivity and low yields are achieved. We have used a flow-chemistry approach to perform the A(3)-MCR in a sequential manner. In this way, the reaction performance was significantly enhanced in terms of shortened reaction time, and the desired propargylamines were obtained in high yields. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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 decreased with increasing aridity with k going from 0.0025 day-1 on equatorial (dry) facing slopes to 0.0040 day-1 on polar (wet) facing slopes. However, differences in temperature as a result of morning vs afternoon sun on east and west aspects, respectively, (not captured in the aridity metric) resulted in poor prediction of decomposition for the sites located in the intermediate aridity range. Overall the results highlight that relatively small differences in microclimate due to slope orientation can have large effects on decomposition. Future research will aim to refine the aridity metric to better resolve small scale variation in surface temperature which is important when up-scaling decomposition processes to landscapes.

The processing of aluminum gasarites via thermal decomposition of interstitial hydrides

NASA Astrophysics Data System (ADS)

Licavoli, Joseph J.

Gasarite structures are a unique type of metallic foam containing tubular pores. The original methods for their production limited them to laboratory study despite appealing foam properties. Thermal decomposition processing of gasarites holds the potential to increase the application of gasarite foams in engineering design by removing several barriers to their industrial scale production. The following study characterized thermal decomposition gasarite processing both experimentally and theoretically. It was found that significant variation was inherent to this process therefore several modifications were necessary to produce gasarites using this method. Conventional means to increase porosity and enhance pore morphology were studied. Pore morphology was determined to be more easily replicated if pores were stabilized by alumina additions and powders were dispersed evenly. In order to better characterize processing, high temperature and high ramp rate thermal decomposition data were gathered. It was found that the high ramp rate thermal decomposition behavior of several hydrides was more rapid than hydride kinetics at low ramp rates. This data was then used to estimate the contribution of several pore formation mechanisms to the development of pore structure. It was found that gas-metal eutectic growth can only be a viable pore formation mode if non-equilibrium conditions persist. Bubble capture cannot be a dominant pore growth mode due to high bubble terminal velocities. Direct gas evolution appears to be the most likely pore formation mode due to high gas evolution rate from the decomposing particulate and microstructural pore growth trends. The overall process was evaluated for its economic viability. It was found that thermal decomposition has potential for industrialization, but further refinements are necessary in order for the process to be viable.

Copper-Catalyzed Oxidative Homo- and Cross-Coupling of Grignard Reagents Using Diaziridinone

PubMed Central

2015-01-01

Transition-metal-catalyzed cross-coupling reactions are among the most powerful synthetic transformations. This paper describes an efficient copper-catalyzed homo- and cross-coupling of Grignard reagents with di-tert-butyldiaziridinone as oxidant under mild conditions, giving the coupling products in good to excellent yields. The reaction process has a broad substrate scope and is also effective for the C(sp)–C(sp3) coupling. PMID:25420218

Decomposition of energetic chemicals contaminated with iron or stainless steel.

PubMed

Chervin, Sima; Bodman, Glenn T; Barnhart, Richard W

2006-03-17

Contamination of chemicals or reaction mixtures with iron or stainless steel is likely to take place during chemical processing. If energetic and thermally unstable chemicals are involved in a manufacturing process, contamination with iron or stainless steel can impact the decomposition characteristics of these chemicals and, subsequently, the safety of the processes, and should be investigated. The goal of this project was to undertake a systematic approach to study the impact of iron or stainless steel contamination on the decomposition characteristics of different chemical classes. Differential scanning calorimetry (DSC) was used to study the decomposition reaction by testing each chemical pure, and in mixtures with iron and stainless steel. The following classes of energetic chemicals were investigated: nitrobenzenes, tetrazoles, hydrazines, hydroxylamines and oximes, sulfonic acid derivatives and monomers. The following non-energetic groups were investigated for contributing effects: halogens, hydroxyls, amines, amides, nitriles, sulfonic acid esters, carbonyl halides and salts of hydrochloric acid. Based on the results obtained, conclusions were drawn regarding the sensitivity of the decomposition reaction to contamination with iron and stainless steel for the chemical classes listed above. It was demonstrated that the most sensitive classes are hydrazines and hydroxylamines/oximes. Contamination of these chemicals with iron or stainless steel not only destabilizes them, leading to decomposition at significantly lower temperatures, but also sometimes causes increased severity of the decomposition. The sensitivity of nitrobenzenes to contamination with iron or stainless steel depended upon the presence of other contributing groups: the presence of such groups as acid chlorides or chlorine/fluorine significantly increased the effect of contamination on decomposition characteristics of nitrobenzenes. The decomposition of sulfonic acid derivatives and tetrazoles was not impacted by presence of iron or stainless steel.

Long-term patterns of mass loss during the decomposition of leaf and fine root litter: an intersite comparison

Treesearch

Mark E. Harmon; Whendee L. Silver; Becky Fasth; Hua Chen; Ingrid C. Burke; William J. Parton; Stephen C. Hart; William S. Currie; Ariel E. Lugo

2009-01-01

Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter...

Aging-driven decomposition in zolpidem hemitartrate hemihydrate and the single-crystal structure of its decomposition products.

PubMed

Vega, Daniel R; Baggio, Ricardo; Roca, Mariana; Tombari, Dora

2011-04-01

The "aging-driven" decomposition of zolpidem hemitartrate hemihydrate (form A) has been followed by X-ray powder diffraction (XRPD), and the crystal and molecular structures of the decomposition products studied by single-crystal methods. The process is very similar to the "thermally driven" one, recently described in the literature for form E (Halasz and Dinnebier. 2010. J Pharm Sci 99(2): 871-874), resulting in a two-phase system: the neutral free base (common to both decomposition processes) and, in the present case, a novel zolpidem tartrate monohydrate, unique to the "aging-driven" decomposition. Our room-temperature single-crystal analysis gives for the free base comparable results as the high-temperature XRPD ones already reported by Halasz and Dinnebier: orthorhombic, Pcba, a = 9.6360(10) Å, b = 18.2690(5) Å, c = 18.4980(11) Å, and V = 3256.4(4) Å(3) . The unreported zolpidem tartrate monohydrate instead crystallizes in monoclinic P21 , which, for comparison purposes, we treated in the nonstandard setting P1121 with a = 20.7582(9) Å, b = 15.2331(5) Å, c = 7.2420(2) Å, γ = 90.826(2)°, and V = 2289.73(14) Å(3) . The structure presents two complete moieties in the asymmetric unit (z = 4, z' = 2). The different phases obtained in both decompositions are readily explained, considering the diverse genesis of both processes. Copyright © 2010 Wiley-Liss, Inc.

Multidisciplinary optimization for engineering systems - Achievements and potential

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw

1989-01-01

The currently common sequential design process for engineering systems is likely to lead to suboptimal designs. Recently developed decomposition methods offer an alternative for coming closer to optimum by breaking the large task of system optimization into smaller, concurrently executed and, yet, coupled tasks, identified with engineering disciplines or subsystems. The hierarchic and non-hierarchic decompositions are discussed and illustrated by examples. An organization of a design process centered on the non-hierarchic decomposition is proposed.

Multidisciplinary optimization for engineering systems: Achievements and potential

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw

1989-01-01

The currently common sequential design process for engineering systems is likely to lead to suboptimal designs. Recently developed decomposition methods offer an alternative for coming closer to optimum by breaking the large task of system optimization into smaller, concurrently executed and, yet, coupled tasks, identified with engineering disciplines or subsystems. The hierarchic and non-hierarchic decompositions are discussed and illustrated by examples. An organization of a design process centered on the non-hierarchic decomposition is proposed.

An iron/amine-catalyzed cascade process for the enantioselective functionalization of allylic alcohols.

PubMed

Quintard, Adrien; Constantieux, Thierry; Rodriguez, Jean

2013-12-02

Three is a lucky number: An enantioselective transformation of allylic alcohols into β-chiral saturated alcohols has been developed by combining two distinct metal- and organocatalyzed catalytic cycles. This waste-free triple cascade process merges an iron-catalyzed borrowing-hydrogen step with an aminocatalyzed nucleophilic addition reaction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Incorporating perylene moiety into poly(phenothiazine-co-bithiophene) backbone for higher charge transport.

PubMed

Tang, Weihua; Ke, Lin; Chen, Zhi-Kuan

2008-03-27

Low band gap pi-conjugated polymers composed of phenothiazine, bithiophene, and perylene moieties were prepared in high yields by using a palladium-catalyzed Suzuki coupling reaction. The polymers were characterized by NMR, gel permeation chromatography, and elemental analysis. The characterizations revealed that high-molecular weight (weight-average molecular weight up to 42,400 g/mol) polymers were thermally stable with a decomposition temperature in the region of 338-354 degrees C and their glass transition temperatures (Tg) ranging from 124 to 136 degrees C. All polymers demonstrated broad optical absorption in the region of 300-550 nm with efficient blue-green light emission. The absorption was broadened further (for ca. 50 nm) when the perylene moiety was incorporated. Cyclic voltammograms displayed that the p- and n-doping processes of all the polymers were partially reversible and that electrochemical band gaps were as low as -2.30 eV with the incorporation of a perylene moiety. The hole mobility of polymers was evaluated by using the space-charge-limited current model with a device structure of ITO/PEDOT:PSS/polymer/Ca. The results show that the incorporation of perylene is beneficial for improving the hole mobility of the conjugated polymers.

Interactions of nitrite with catalase: Enzyme activity and reaction kinetics studies.

PubMed

Krych-Madej, Justyna; Gebicka, Lidia

2017-06-01

Catalase, a heme enzyme, which catalyzes decomposition of hydrogen peroxide to water and molecular oxygen, is one of the main enzymes of the antioxidant defense system of the cell. Nitrite, used as a food preservative has long been regarded as a harmful compound due to its ability to form carcinogenic nitrosamines. Recently, much evidence has been presented that nitrite plays a protective role as a nitric oxide donor under hypoxic conditions. In this work the effect of nitrite on the catalytic reactions of catalase was studied. Catalase was inhibited by nitrite, and this process was pH-dependent. IC 50 values varied from about 1μM at pH5.0 to about 150μM of nitrite at pH7.4. The presence of chloride significantly enhanced nitrite-induced catalase inhibition, in agreement with earlier observations. The kinetics of the reactions of nitrite with ferric catalase, its redox intermediate, Compound I, and catalase inactive form, Compound II, was also studied. Possible mechanisms of nitrite-induced catalase inhibition are analyzed and the biological consequences of the reactions of catalase with nitrite are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

Vacancy-mediated dehydrogenation of sodium alanate

PubMed Central

Gunaydin, Hakan; Houk, Kendall N.; Ozoliņš, Vidvuds

2008-01-01

Clarification of the mechanisms of hydrogen release and uptake in transition-metal-doped sodium alanate, NaAlH4, a prototypical high-density complex hydride, has fundamental importance for the development of improved hydrogen-storage materials. In this and most other modern hydrogen-storage materials, H2 release and uptake are accompanied by long-range diffusion of metal species. Using first-principles density-functional theory calculations, we have determined that the activation energy for Al mass transport via AlH3 vacancies is Q = 85 kJ/mol·H2, which is in excellent agreement with experimentally measured activation energies in Ti-catalyzed NaAlH4. The activation energy for an alternate decomposition mechanism via NaH vacancies is found to be significantly higher: Q = 112 kJ/mol·H2. Our results suggest that bulk diffusion of Al species is the rate-limiting step in the dehydrogenation of Ti-doped samples of NaAlH4 and that the much higher activation energies measured for uncatalyzed samples are controlled by other processes, such as breaking up of AlH4− complexes, formation/dissociation of H2 molecules, and/or nucleation of the product phases. PMID:18299582

Development Of Polarimetric Decomposition Techniques For Indian Forest Resource Assessment Using Radar Imaging Satellite (Risat-1) Images

NASA Astrophysics Data System (ADS)

Sridhar, J.

2015-12-01

The focus of this work is to examine polarimetric decomposition techniques primarily focussed on Pauli decomposition and Sphere Di-Plane Helix (SDH) decomposition for forest resource assessment. The data processing methods adopted are Pre-processing (Geometric correction and Radiometric calibration), Speckle Reduction, Image Decomposition and Image Classification. Initially to classify forest regions, unsupervised classification was applied to determine different unknown classes. It was observed K-means clustering method gave better results in comparison with ISO Data method.Using the algorithm developed for Radar Tools, the code for decomposition and classification techniques were applied in Interactive Data Language (IDL) and was applied to RISAT-1 image of Mysore-Mandya region of Karnataka, India. This region is chosen for studying forest vegetation and consists of agricultural lands, water and hilly regions. Polarimetric SAR data possess a high potential for classification of earth surface.After applying the decomposition techniques, classification was done by selecting region of interests andpost-classification the over-all accuracy was observed to be higher in the SDH decomposed image, as it operates on individual pixels on a coherent basis and utilises the complete intrinsic coherent nature of polarimetric SAR data. Thereby, making SDH decomposition particularly suited for analysis of high-resolution SAR data. The Pauli Decomposition represents all the polarimetric information in a single SAR image however interpretation of the resulting image is difficult. The SDH decomposition technique seems to produce better results and interpretation as compared to Pauli Decomposition however more quantification and further analysis are being done in this area of research. The comparison of Polarimetric decomposition techniques and evolutionary classification techniques will be the scope of this work.

A simple method for decomposition of peracetic acid in a microalgal cultivation system.

PubMed

Sung, Min-Gyu; Lee, Hansol; Nam, Kibok; Rexroth, Sascha; Rögner, Matthias; Kwon, Jong-Hee; Yang, Ji-Won

2015-03-01

A cost-efficient process devoid of several washing steps was developed, which is related to direct cultivation following the decomposition of the sterilizer. Peracetic acid (PAA) is known to be an efficient antimicrobial agent due to its high oxidizing potential. Sterilization by 2 mM PAA demands at least 1 h incubation time for an effective disinfection. Direct degradation of PAA was demonstrated by utilizing components in conventional algal medium. Consequently, ferric ion and pH buffer (HEPES) showed a synergetic effect for the decomposition of PAA within 6 h. On the contrary, NaNO3, one of the main components in algal media, inhibits the decomposition of PAA. The improved growth of Chlorella vulgaris and Synechocystis PCC6803 was observed in the prepared BG11 by decomposition of PAA. This process involving sterilization and decomposition of PAA should help cost-efficient management of photobioreactors in a large scale for the production of value-added products and biofuels from microalgal biomass.

A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration.

PubMed

Boyero, Luz; Pearson, Richard G; Gessner, Mark O; Barmuta, Leon A; Ferreira, Verónica; Graça, Manuel A S; Dudgeon, David; Boulton, Andrew J; Callisto, Marcos; Chauvet, Eric; Helson, Julie E; Bruder, Andreas; Albariño, Ricardo J; Yule, Catherine M; Arunachalam, Muthukumarasamy; Davies, Judy N; Figueroa, Ricardo; Flecker, Alexander S; Ramírez, Alonso; Death, Russell G; Iwata, Tomoya; Mathooko, Jude M; Mathuriau, Catherine; Gonçalves, José F; Moretti, Marcelo S; Jinggut, Tajang; Lamothe, Sylvain; M'Erimba, Charles; Ratnarajah, Lavenia; Schindler, Markus H; Castela, José; Buria, Leonardo M; Cornejo, Aydeé; Villanueva, Verónica D; West, Derek C

2011-03-01

The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback. © 2011 Blackwell Publishing Ltd/CNRS.

Chemoenzymatic Synthesis of Oligo(L-cysteine) for Use as a Thermostable Bio-Based Material.

PubMed

Ma, Yinan; Sato, Ryota; Li, Zhibo; Numata, Keiji

2016-01-01

Oligomerization of thiol-unprotected L-cysteine ethyl ester (Cys-OEt) catalyzed by proteinase K in aqueous solution has been used to synthesize oligo(L-cysteine) (OligoCys) with a well-defined chemical structure and relatively large degree of polymerization (DP) up to 16-17 (average 8.8). By using a high concentration of Cys-OEt, 78.0% free thiol content was achieved. The thermal properties of OligoCys are stable, with no glass transition until 200 °C, and the decomposition temperature could be increased by oxidation. Chemoenzymatically synthesized OligoCys has great potential for use as a thermostable bio-based material with resistance to oxidation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A One-Pot Synthesis of Dibenzofurans from 6-Diazo-2-cyclohexenones.

PubMed

Zhao, Hua; Yang, Ke; Zheng, Hongyan; Ding, Ruichao; Yin, Fangjie; Wang, Ning; Li, Yun; Cheng, Bin; Wang, Huifei; Zhai, Hongbin

2015-12-04

A novel and efficient protocol for the rapid construction of dibenzofuran motifs from 6-diazo-2-cyclohexenone and ortho-haloiodobenzene has been developed. The process involves one-pot Pd-catalyzed cross-coupling/aromatization and Cu-catalyzed Ullmann coupling.

Dissolved organic matter release in overlying water and bacterial community shifts in biofilm during the decomposition of Myriophyllum verticillatum.

PubMed

Zhang, Lisha; Zhang, Songhe; Lv, Xiaoyang; Qiu, Zheng; Zhang, Ziqiu; Yan, Liying

2018-08-15

This study investigated the alterations in biomass, nutrients and dissolved organic matter concentration in overlying water and determined the bacterial 16S rRNA gene in biofilms attached to plant residual during the decomposition of Myriophyllum verticillatum. The 55-day decomposition experimental results show that plant decay process can be well described by the exponential model, with the average decomposition rate of 0.037d -1 . Total organic carbon, total nitrogen, and organic nitrogen concentrations increased significantly in overlying water during decomposition compared to control within 35d. Results from excitation emission matrix-parallel factor analysis showed humic acid-like and tyrosine acid-like substances might originate from plant degradation processes. Tyrosine acid-like substances had an obvious correlation to organic nitrogen and total nitrogen (p<0.01). Decomposition rates were positively related to pH, total organic carbon, oxidation-reduction potential and dissolved oxygen but negatively related to temperature in overlying water. Microbe densities attached to plant residues increased with decomposition process. The most dominant phylum was Bacteroidetes (>46%) at 7d, Chlorobi (20%-44%) or Proteobacteria (25%-34%) at 21d and Chlorobi (>40%) at 55d. In microbes attached to plant residues, sugar- and polysaccharides-degrading genus including Bacteroides, Blvii28, Fibrobacter, and Treponema dominated at 7d while Chlorobaculum, Rhodobacter, Methanobacterium, Thiobaca, Methanospirillum and Methanosarcina at 21d and 55d. These results gain the insight into the dissolved organic matter release and bacterial community shifts during submerged macrophytes decomposition. Copyright © 2018 Elsevier B.V. All rights reserved.

Nuclear driven water decomposition plant for hydrogen production

NASA Technical Reports Server (NTRS)

Parker, G. H.; Brecher, L. E.; Farbman, G. H.

1976-01-01

The conceptual design of a hydrogen production plant using a very-high-temperature nuclear reactor (VHTR) to energize a hybrid electrolytic-thermochemical system for water decomposition has been prepared. A graphite-moderated helium-cooled VHTR is used to produce 1850 F gas for electric power generation and 1600 F process heat for the water-decomposition process which uses sulfur compounds and promises performance superior to normal water electrolysis or other published thermochemical processes. The combined cycle operates at an overall thermal efficiency in excess of 45%, and the overall economics of hydrogen production by this plant have been evaluated predicated on a consistent set of economic ground rules. The conceptual design and evaluation efforts have indicated that development of this type of nuclear-driven water-decomposition plant will permit large-scale economic generation of hydrogen in the 1990s.

Copper-catalyzed synthesis of phenanthridine derivatives under an oxygen atmosphere starting from biaryl-2-carbonitriles and Grignard reagents.

PubMed

Zhang, Line; Ang, Gim Yean; Chiba, Shunsuke

2010-08-20

A copper-catalyzed synthesis of phenanthridine derivatives was developed starting from biaryl-2-carbonitriles and Grignard reagents. The present transformation is carried out by a sequence of nucleophilic addition of Grignard reagents to biaryl-2-carbonitriles to form N-H imines and their Cu-catalyzed C-N bond formation on the aromatic C-H bond, where molecular oxygen is a prerequisite to achieve the catalytic process.

Cosmic strings and baryon decay catalysis

NASA Technical Reports Server (NTRS)

Gregory, Ruth; Perkins, W. B.; Davis, A.-C.; Brandenberger, R. H.

1989-01-01

Cosmic strings, like monopoles, can catalyze proton decay. For integer charged fermions, the cross section for catalysis is not amplified, unlike in the case of monopoles. The catalysis processes are reviewed both in the free quark and skyrmion pictures and the implications for baryogenesis are discussed. A computation of the cross section for monopole catalyzed skyrmion decay is presented using classical physics. Also discussed are some effects which can screen catalysis processes.

Early stage litter decomposition across biomes

Treesearch

Ika Djukic; Sebastian Kepfer-Rojas; Inger Kappel Schmidt; Klaus Steenberg Larsen; Claus Beier; Björn Berg; Kris Verheyen; Adriano Caliman; Alain Paquette; Alba Gutiérrez-Girón; Alberto Humber; Alejandro Valdecantos; Alessandro Petraglia; Heather Alexander; Algirdas Augustaitis; Amélie Saillard; Ana Carolina Ruiz Fernández; Ana I. Sousa; Ana I. Lillebø; Anderson da Rocha Gripp; André-Jean Francez; Andrea Fischer; Andreas Bohner; Andrey Malyshev; Andrijana Andrić; Andy Smith; Angela Stanisci; Anikó Seres; Anja Schmidt; Anna Avila; Anne Probst; Annie Ouin; Anzar A. Khuroo; Arne Verstraeten; Arely N. Palabral-Aguilera; Artur Stefanski; Aurora Gaxiola; Bart Muys; Bernard Bosman; Bernd Ahrends; Bill Parker; Birgit Sattler; Bo Yang; Bohdan Juráni; Brigitta Erschbamer; Carmen Eugenia Rodriguez Ortiz; Casper T. Christiansen; E. Carol Adair; Céline Meredieu; Cendrine Mony; Charles A. Nock; Chi-Ling Chen; Chiao-Ping Wang; Christel Baum; Christian Rixen; Christine Delire; Christophe Piscart; Christopher Andrews; Corinna Rebmann; Cristina Branquinho; Dana Polyanskaya; David Fuentes Delgado; Dirk Wundram; Diyaa Radeideh; Eduardo Ordóñez-Regil; Edward Crawford; Elena Preda; Elena Tropina; Elli Groner; Eric Lucot; Erzsébet Hornung; Esperança Gacia; Esther Lévesque; Evanilde Benedito; Evgeny A. Davydov; Evy Ampoorter; Fabio Padilha Bolzan; Felipe Varela; Ferdinand Kristöfel; Fernando T. Maestre; Florence Maunoury-Danger; Florian Hofhansl; Florian Kitz; Flurin Sutter; Francisco Cuesta; Francisco de Almeida Lobo; Franco Leandro de Souza; Frank Berninger; Franz Zehetner; Georg Wohlfahrt; George Vourlitis; Geovana Carreño-Rocabado; Gina Arena; Gisele Daiane Pinha; Grizelle González; Guylaine Canut; Hanna Lee; Hans Verbeeck; Harald Auge; Harald Pauli; Hassan Bismarck Nacro; Héctor A. Bahamonde; Heike Feldhaar; Heinke Jäger; Helena C. Serrano; Hélène Verheyden; Helge Bruelheide; Henning Meesenburg; Hermann Jungkunst; Hervé Jactel; Hideaki Shibata; Hiroko Kurokawa; Hugo López Rosas; Hugo L. Rojas Villalobos; Ian Yesilonis; Inara Melece; Inge Van Halder; Inmaculada García Quirós; Isaac Makelele; Issaka Senou; István Fekete; Ivan Mihal; Ivika Ostonen; Jana Borovská; Javier Roales; Jawad Shoqeir; Jean-Christophe Lata; Jean-Paul Theurillat; Jean-Luc Probst; Jess Zimmerman; Jeyanny Vijayanathan; Jianwu Tang; Jill Thompson; Jiří Doležal; Joan-Albert Sanchez-Cabeza; Joël Merlet; Joh Henschel; Johan Neirynck; Johannes Knops; John Loehr; Jonathan von Oppen; Jónína Sigríður Þorláksdóttir; Jörg Löffler; José-Gilberto Cardoso-Mohedano; José-Luis Benito-Alonso; Jose Marcelo Torezan; Joseph C. Morina; Juan J. Jiménez; Juan Dario Quinde; Juha Alatalo; Julia Seeber; Jutta Stadler; Kaie Kriiska; Kalifa Coulibaly; Karibu Fukuzawa; Katalin Szlavecz; Katarína Gerhátová; Kate Lajtha; Kathrin Käppeler; Katie A. Jennings; Katja Tielbörger; Kazuhiko Hoshizaki; Ken Green; Lambiénou Yé; Laryssa Helena Ribeiro Pazianoto; Laura Dienstbach; Laura Williams; Laura Yahdjian; Laurel M. Brigham; Liesbeth van den Brink; Lindsey Rustad; al. et

2018-01-01

Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litter and methodologies...

Compositional aspects of herbaceous litter decomposition in the freshwater marshes of the Florida Everglades

USDA-ARS?s Scientific Manuscript database

Litter decomposition in wetlands is an important component of ecosystem function in these detrital systems. In oligotrophic wetlands, such as the Florida Everglades, litter decomposition processes are dependent on nutrient availability and litter quality. However, not much is known about how the che...

Modeling evolution of hydrogen bonding and stabilization of transition states in the process of cocaine hydrolysis catalyzed by human butyrylcholinesterase.

PubMed

Gao, Daquan; Zhan, Chang-Guo

2006-01-01

Molecular dynamics (MD) simulations and quantum mechanical/molecular mechanical (QM/MM) calculations were performed on the prereactive enzyme-substrate complex, transition states, intermediates, and product involved in the process of human butyrylcholinesterase (BChE)-catalyzed hydrolysis of (-)-cocaine. The computational results consistently reveal a unique role of the oxyanion hole (consisting of G116, G117, and A199) in BChE-catalyzed hydrolysis of cocaine, compared to acetylcholinesterase (AChE)-catalyzed hydrolysis of acetylcholine. During BChE-catalyzed hydrolysis of cocaine, only G117 has a hydrogen bond with the carbonyl oxygen (O31) of the cocaine benzoyl ester in the prereactive BChE-cocaine complex, and the NH groups of G117 and A199 are hydrogen-bonded with O31 of cocaine in all of the transition states and intermediates. Surprisingly, the NH hydrogen of G116 forms an unexpected hydrogen bond with the carboxyl group of E197 side chain and, therefore, is not available to form a hydrogen bond with O31 of cocaine in the acylation. The NH hydrogen of G116 is only partially available to form a weak hydrogen bond with O31 of cocaine in some structures involved in the deacylation. The change of the estimated hydrogen-bonding energy between the oxyanion hole and O31 of cocaine during the reaction process demonstrates how the protein environment can affect the energy barrier for each step of the BChE-catalyzed hydrolysis of cocaine. These insights concerning the effects of the oxyanion hole on the energy barriers provide valuable clues on how to rationally design BChE mutants with a higher catalytic activity for the hydrolysis of (-)-cocaine. 2005 Wiley-Liss, Inc.

Modeling Evolution of Hydrogen Bonding and Stabilization of Transition States in the Process of Cocaine Hydrolysis Catalyzed by Human Butyrylcholinesterase

PubMed Central

Gao, Daquan; Zhan, Chang-Guo

2010-01-01

Molecular dynamics (MD) simulations and quantum mechanical/molecular mechanical (QM/MM) calculations were performed on the prereactive enzyme-substrate complex, transition states, intermediates, and product involved in the process of human butyrylcholinesterase (BChE)-catalyzed hydrolysis of (−)-cocaine. The computational results consistently reveal a unique role of the oxyanion hole (consisting of G116, G117, and A199) in BChE-catalyzed hydrolysis of cocaine, as compared to acetylcholinesterase (AChE)-catalyzed hydrolysis of acetylcholine. During BChE-catalyzed hydrolysis of cocaine, only G117 has a hydrogen bond with the carbonyl oxygen (O31) of the cocaine benzoyl ester in the prereactive BChE-cocaine complex, and the NH groups of G117 and A199 are hydrogen-bonded with O31 of cocaine in all of the transition states and intermediates. Surprisingly, the NH hydrogen of G116 forms an unexpected hydrogen bond with the carboxyl group of E197 side chain and, therefore, is not available to form a hydrogen bond with O31 of cocaine in the acylation. The NH hydrogen of G116 is only partially available to form a weak hydrogen bond with O31 of cocaine in some structures involved in the deacylation. The change of the estimated hydrogen bonding energy between the oxyanion hole and O31 of cocaine during the reaction process demonstrates how the protein environment can affect the energy barrier for each step of the BChE-catalyzed hydrolysis of cocaine. These insights concerning the effects of the oxyanion hole on the energy barriers provide valuable clues on how to rationally design BChE mutants with a higher catalytic activity for the hydrolysis of (−)-cocaine. PMID:16288482

Nonequilibrium adiabatic molecular dynamics simulations of methane clathrate hydrate decomposition

NASA Astrophysics Data System (ADS)

Alavi, Saman; Ripmeester, J. A.

2010-04-01

Nonequilibrium, constant energy, constant volume (NVE) molecular dynamics simulations are used to study the decomposition of methane clathrate hydrate in contact with water. Under adiabatic conditions, the rate of methane clathrate decomposition is affected by heat and mass transfer arising from the breakup of the clathrate hydrate framework and release of the methane gas at the solid-liquid interface and diffusion of methane through water. We observe that temperature gradients are established between the clathrate and solution phases as a result of the endothermic clathrate decomposition process and this factor must be considered when modeling the decomposition process. Additionally we observe that clathrate decomposition does not occur gradually with breakup of individual cages, but rather in a concerted fashion with rows of structure I cages parallel to the interface decomposing simultaneously. Due to the concerted breakup of layers of the hydrate, large amounts of methane gas are released near the surface which can form bubbles that will greatly affect the rate of mass transfer near the surface of the clathrate phase. The effects of these phenomena on the rate of methane hydrate decomposition are determined and implications on hydrate dissociation in natural methane hydrate reservoirs are discussed.

Nonequilibrium adiabatic molecular dynamics simulations of methane clathrate hydrate decomposition.

PubMed

Alavi, Saman; Ripmeester, J A

2010-04-14

Nonequilibrium, constant energy, constant volume (NVE) molecular dynamics simulations are used to study the decomposition of methane clathrate hydrate in contact with water. Under adiabatic conditions, the rate of methane clathrate decomposition is affected by heat and mass transfer arising from the breakup of the clathrate hydrate framework and release of the methane gas at the solid-liquid interface and diffusion of methane through water. We observe that temperature gradients are established between the clathrate and solution phases as a result of the endothermic clathrate decomposition process and this factor must be considered when modeling the decomposition process. Additionally we observe that clathrate decomposition does not occur gradually with breakup of individual cages, but rather in a concerted fashion with rows of structure I cages parallel to the interface decomposing simultaneously. Due to the concerted breakup of layers of the hydrate, large amounts of methane gas are released near the surface which can form bubbles that will greatly affect the rate of mass transfer near the surface of the clathrate phase. The effects of these phenomena on the rate of methane hydrate decomposition are determined and implications on hydrate dissociation in natural methane hydrate reservoirs are discussed.

Efficient material decomposition method for dual-energy X-ray cargo inspection system

NASA Astrophysics Data System (ADS)

Lee, Donghyeon; Lee, Jiseoc; Min, Jonghwan; Lee, Byungcheol; Lee, Byeongno; Oh, Kyungmin; Kim, Jaehyun; Cho, Seungryong

2018-03-01

Dual-energy X-ray inspection systems are widely used today for it provides X-ray attenuation contrast of the imaged object and also its material information. Material decomposition capability allows a higher detection sensitivity of potential targets including purposely loaded impurities in agricultural product inspections and threats in security scans for example. Dual-energy X-ray transmission data can be transformed into two basis material thickness data, and its transformation accuracy heavily relies on a calibration of material decomposition process. The calibration process in general can be laborious and time consuming. Moreover, a conventional calibration method is often challenged by the nonuniform spectral characteristics of the X-ray beam in the entire field-of-view (FOV). In this work, we developed an efficient material decomposition calibration process for a linear accelerator (LINAC) based high-energy X-ray cargo inspection system. We also proposed a multi-spot calibration method to improve the decomposition performance throughout the entire FOV. Experimental validation of the proposed method has been demonstrated by use of a cargo inspection system that supports 6 MV and 9 MV dual-energy imaging.

Rise in the pH of an unfrozen solution in ice due to the presence of NaCl and promotion of decomposition of gallic acids owing to a change in the pH.

PubMed

Takenaka, Norimichi; Tanaka, Masayuki; Okitsu, Kenji; Bandow, Hiroshi

2006-09-14

Oxidative decomposition of gallic acid occurs in alkaline solutions but hardly arises in acidic solutions. We have found that the addition of sodium chloride promotes the decomposition of gallic acid caused by freezing even under neutral and acidic conditions. Even at pH 4.5, gallic acid was decomposed by freezing in the presence of NaCl; however, in the absence of NaCl, it was hardly decomposed by freezing at pH lower than 7. Chloride ions are more easily incorporated in ice than sodium ions when the NaCl solution is frozen. The unfrozen solution in ice becomes positively charged, and as a result, protons transfer from the unfrozen solution to the ice. We measured the pH in the unfrozen solution which coexists with single-crystal ice formed from a 5 mmol dm(-3) NaCl solution and determined the pH to be 8.6 at equilibrium with CO(2) of 380 ppm or 11.3 in the absence of CO(2) compared to pH 5.6 in the original solution. From the model calculation performed for gallic acid solution in the presence of 5 mmol dm(-3) NaCl, it can be estimated that the amount of OH(-) transferred from the ice to the solution corresponds to 1.26 x 10(-5) mol dm(-3). The amount of OH(-) transferred is concentrated into the unfrozen solution and affects the pH of the unfrozen solution. Therefore, the pH in an unfrozen gallic acid solution in ice becomes alkaline, and the decomposition of gallic acid proceeds. It is expected that other base-catalyzed reactions in weakly acidic solutions also proceed by freezing in the presence of NaCl without the need for any alkaline reagents.

Detecting the Extent of Cellular Decomposition after Sub-Eutectoid Annealing in Rolled UMo Foils

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

Kautz, Elizabeth J.; Jana, Saumyadeep; Devaraj, Arun

2017-07-31

This report presents an automated image processing approach to quantifying microstructure image data, specifically the extent of eutectoid (cellular) decomposition in rolled U-10Mo foils. An image processing approach is used here to be able to quantitatively describe microstructure image data in order to relate microstructure to processing parameters (time, temperature, deformation).

Changes in bacterial and eukaryotic communities during sewage decomposition in Mississippi River water

EPA Science Inventory

Microbial decay processes are one of the mechanisms whereby sewage contamination is reduced in the environment. This decomposition process involves a highly complex array of bacterial and eukaryotic communities from both sewage and ambient waters. However, relatively little is kn...

Optimal cost design of water distribution networks using a decomposition approach

NASA Astrophysics Data System (ADS)

Lee, Ho Min; Yoo, Do Guen; Sadollah, Ali; Kim, Joong Hoon

2016-12-01

Water distribution network decomposition, which is an engineering approach, is adopted to increase the efficiency of obtaining the optimal cost design of a water distribution network using an optimization algorithm. This study applied the source tracing tool in EPANET, which is a hydraulic and water quality analysis model, to the decomposition of a network to improve the efficiency of the optimal design process. The proposed approach was tested by carrying out the optimal cost design of two water distribution networks, and the results were compared with other optimal cost designs derived from previously proposed optimization algorithms. The proposed decomposition approach using the source tracing technique enables the efficient decomposition of an actual large-scale network, and the results can be combined with the optimal cost design process using an optimization algorithm. This proves that the final design in this study is better than those obtained with other previously proposed optimization algorithms.

Conception of discrete systems decomposition algorithm using p-invariants and hypergraphs

NASA Astrophysics Data System (ADS)

Stefanowicz, Ł.

2016-09-01

In the article author presents an idea of decomposition algorithm of discrete systems described by Petri Nets using pinvariants. Decomposition process is significant from the point of view of discrete systems design, because it allows separation of the smaller sequential parts. Proposed algorithm uses modified Martinez-Silva method as well as author's selection algorithm. The developed method is a good complement of classical decomposition algorithms using graphs and hypergraphs.

Kinetic analysis of overlapping multistep thermal decomposition comprising exothermic and endothermic processes: thermolysis of ammonium dinitramide.

PubMed

Muravyev, Nikita V; Koga, Nobuyoshi; Meerov, Dmitry B; Pivkina, Alla N

2017-01-25

This study focused on kinetic modeling of a specific type of multistep heterogeneous reaction comprising exothermic and endothermic reaction steps, as exemplified by the practical kinetic analysis of the experimental kinetic curves for the thermal decomposition of molten ammonium dinitramide (ADN). It is known that the thermal decomposition of ADN occurs as a consecutive two step mass-loss process comprising the decomposition of ADN and subsequent evaporation/decomposition of in situ generated ammonium nitrate. These reaction steps provide exothermic and endothermic contributions, respectively, to the overall thermal effect. The overall reaction process was deconvoluted into two reaction steps using simultaneously recorded thermogravimetry and differential scanning calorimetry (TG-DSC) curves by considering the different physical meanings of the kinetic data derived from TG and DSC by P value analysis. The kinetic data thus separated into exothermic and endothermic reaction steps were kinetically characterized using kinetic computation methods including isoconversional method, combined kinetic analysis, and master plot method. The overall kinetic behavior was reproduced as the sum of the kinetic equations for each reaction step considering the contributions to the rate data derived from TG and DSC. During reproduction of the kinetic behavior, the kinetic parameters and contributions of each reaction step were optimized using kinetic deconvolution analysis. As a result, the thermal decomposition of ADN was successfully modeled as partially overlapping exothermic and endothermic reaction steps. The logic of the kinetic modeling was critically examined, and the practical usefulness of phenomenological modeling for the thermal decomposition of ADN was illustrated to demonstrate the validity of the methodology and its applicability to similar complex reaction processes.

Porous silicon formation during Au-catalyzed etching

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

Algasinger, Michael; Bernt, Maximilian; Koynov, Svetoslav

2014-04-28

The formation of “black” nano-textured Si during the Au-catalyzed wet-chemical etch process was investigated with respect to photovoltaic applications. Cross-sectional scanning electron microscopy (SEM) images recorded at different stages of the etch process exhibit an evolution of a two-layer structure, consisting of cone-like Si hillocks covered with a nano-porous Si (np-Si) layer. Optical measurements confirm the presence of a np-Si phase which appears after the first ∼10 s of the etch process and continuously increases with the etch time. Furthermore, the etch process was investigated on Si substrates with different doping levels (∼0.01–100 Ω cm). SEM images show a transition frommore » the two-layer morphology to a structure consisting entirely of np-Si for higher doping levels (<0.1 Ω cm). The experimental results are discussed on the basis of the model of a local electrochemical etch process. A better understanding of the metal-catalyzed etch process facilitates the fabrication of “black” Si on various Si substrates, which is of significant interest for photovoltaic applications.« less

Placement-aware decomposition of a digital standard cells library for double patterning lithography

NASA Astrophysics Data System (ADS)

Wassal, Amr G.; Sharaf, Heba; Hammouda, Sherif

2012-11-01

To continue scaling the circuit features down, Double Patterning (DP) technology is needed in 22nm technologies and lower. DP requires decomposing the layout features into two masks for pitch relaxation, such that the spacing between any two features on each mask is greater than the minimum allowed mask spacing. The relaxed pitches of each mask are then processed on two separate exposure steps. In many cases, post-layout decomposition fails to decompose the layout into two masks due to the presence of conflicts. Post-layout decomposition of a standard cells block can result in native conflicts inside the cells (internal conflict), or native conflicts on the boundary between two cells (boundary conflict). Resolving native conflicts requires a redesign and/or multiple iterations for the placement and routing phases to get a clean decomposition. Therefore, DP compliance must be considered in earlier phases, before getting the final placed cell block. The main focus of this paper is generating a library of decomposed standard cells to be used in a DP-aware placer. This library should contain all possible decompositions for each standard cell, i.e., these decompositions consider all possible combinations of boundary conditions. However, the large number of combinations of boundary conditions for each standard cell will significantly increase the processing time and effort required to obtain all possible decompositions. Therefore, an efficient methodology is required to reduce this large number of combinations. In this paper, three different reduction methodologies are proposed to reduce the number of different combinations processed to get the decomposed library. Experimental results show a significant reduction in the number of combinations and decompositions needed for the library processing. To generate and verify the proposed flow and methodologies, a prototype for a placement-aware DP-ready cell-library is developed with an optimized number of cell views.

Sol-gel preparation of hydrophobic silica antireflective coatings with low refractive index by base/acid two-step catalysis.

PubMed

Cai, Shuang; Zhang, Yulu; Zhang, Hongli; Yan, Hongwei; Lv, Haibing; Jiang, Bo

2014-07-23

Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A "core-shell" particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated.

Diastereo- and enantioselective iridium-catalyzed allylation of cyclic ketone enolates: synergetic effect of ligands and barium enolates.

PubMed

Chen, Wenyong; Chen, Ming; Hartwig, John F

2014-11-12

We report asymmetric allylic alkylation of barium enolates of cyclic ketones catalyzed by a metallacyclic iridium complex containing a phosphoramidite ligand derived from (R)-1-(2-naphthyl)ethylamine. The reaction products contain adjacent quaternary and tertiary stereocenters. This process demonstrates that unstabilized cyclic ketone enolates can undergo diastereo- and enantioselective Ir-catalyzed allylic substitution reactions with the proper choice of enolate countercation. The products of these reactions can be conveniently transformed to various useful polycarbocyclic structures.

Copper-catalyzed trifluoromethylthiolation of aryl halides with diverse directing groups.

PubMed

Xu, Jiabin; Mu, Xin; Chen, Pinhong; Ye, Jinxing; Liu, Guosheng

2014-08-01

The expansion of cross-coupling components in Cu-catalyzed C-X bond forming reactions have received much attention recently. A novel Cu-catalyzed trifluoromethylthiolation of aryl bromides and iodides with the assistance of versatile directing groups such as pyridyl, methyl ester, amide, imine and oxime was reported. CuBr was used as the catalyst, and 1,10-phenanthroline as the ligand. By changing the solvent from acetonitrile to DMF, the coupling process could even take place at room temperature.

Diastereo- and enantioselective iridium-catalyzed allylation of cyclic ketone enolates: Synergetic effect of ligands and barium enolates

DOE PAGES

Chen, Wenyong; Chen, Ming; Hartwig, John F.

2014-10-22

Here, we report asymmetric allylic alkylation of barium enolates of cyclic ketones catalyzed by a metallacyclic iridium complex containing a phosphoramidite ligand derived from ( R)-1-(2-naphthyl)ethylamine. The reaction products contain adjacent quaternary and tertiary stereocenters. This process demonstrates that unstabilized cyclic ketone enolates can undergo diastereo- and enantioselective Ir-catalyzed allylic substitution reactions with the proper choice of enolate countercation. The products of these reactions can be conveniently transformed to various useful polycarbocyclic structures.

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. Copyright © 2016 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

Biomass is the main driver of changes in ecosystem process rates during tropical forest succession.

PubMed

Lohbeck, Madelon; Poorter, Lourens; Martínez-Ramos, Miguel; Bongers, Frans

2015-05-01

Over half of the world's forests are disturbed, and the rate at which ecosystem processes recover after disturbance is important for the services these forests can provide. We analyze the drivers' underlying changes in rates of key ecosystem processes (biomass productivity, litter productivity, actual litter decomposition, and potential litter decomposition) during secondary succession after shifting cultivation in wet tropical forest of Mexico. We test the importance of three alternative drivers of ecosystem processes: vegetation biomass (vegetation quantity hypothesis), community-weighted trait mean (mass ratio hypothesis), and functional diversity (niche complementarity hypothesis) using structural equation modeling. This allows us to infer the relative importance of different mechanisms underlying ecosystem process recovery. Ecosystem process rates changed during succession, and the strongest driver was aboveground biomass for each of the processes. Productivity of aboveground stem biomass and leaf litter as well as actual litter decomposition increased with initial standing vegetation biomass, whereas potential litter decomposition decreased with standing biomass. Additionally, biomass productivity was positively affected by community-weighted mean of specific leaf area, and potential decomposition was positively affected by functional divergence, and negatively by community-weighted mean of leaf dry matter content. Our empirical results show that functional diversity and community-weighted means are of secondary importance for explaining changes in ecosystem process rates during tropical forest succession. Instead, simply, the amount of vegetation in a site is the major driver of changes, perhaps because there is a steep biomass buildup during succession that overrides more subtle effects of community functional properties on ecosystem processes. We recommend future studies in the field of biodiversity and ecosystem functioning to separate the effects of vegetation quality (community-weighted mean trait values and functional diversity) from those of vegetation quantity (biomass) on ecosystem processes and services.

Kinetics of non-isothermal decomposition of cinnamic acid

NASA Astrophysics Data System (ADS)

Zhao, Ming-rui; Qi, Zhen-li; Chen, Fei-xiong; Yue, Xia-xin

2014-07-01

The thermal stability and kinetics of decomposition of cinnamic acid were investigated by thermogravimetry and differential scanning calorimetry at four heating rates. The activation energies of this process were calculated from analysis of TG curves by methods of Flynn-Wall-Ozawa, Doyle, Distributed Activation Energy Model, Šatava-Šesták and Kissinger, respectively. There are only one stage of thermal decomposition process in TG and two endothermic peaks in DSC. For this decomposition process of cinnamic acid, E and log A[s-1] were determined to be 81.74 kJ mol-1 and 8.67, respectively. The mechanism was Mampel Power law (the reaction order, n = 1), with integral form G(α) = α (α = 0.1-0.9). Moreover, thermodynamic properties of Δ H ≠, Δ S ≠, Δ G ≠ were 77.96 kJ mol-1, -90.71 J mol-1 K-1, 119.41 kJ mol-1.

Validating the performance of one-time decomposition for fMRI analysis using ICA with automatic target generation process.

PubMed

Yao, Shengnan; Zeng, Weiming; Wang, Nizhuan; Chen, Lei

2013-07-01

Independent component analysis (ICA) has been proven to be effective for functional magnetic resonance imaging (fMRI) data analysis. However, ICA decomposition requires to optimize the unmixing matrix iteratively whose initial values are generated randomly. Thus the randomness of the initialization leads to different ICA decomposition results. Therefore, just one-time decomposition for fMRI data analysis is not usually reliable. Under this circumstance, several methods about repeated decompositions with ICA (RDICA) were proposed to reveal the stability of ICA decomposition. Although utilizing RDICA has achieved satisfying results in validating the performance of ICA decomposition, RDICA cost much computing time. To mitigate the problem, in this paper, we propose a method, named ATGP-ICA, to do the fMRI data analysis. This method generates fixed initial values with automatic target generation process (ATGP) instead of being produced randomly. We performed experimental tests on both hybrid data and fMRI data to indicate the effectiveness of the new method and made a performance comparison of the traditional one-time decomposition with ICA (ODICA), RDICA and ATGP-ICA. The proposed method demonstrated that it not only could eliminate the randomness of ICA decomposition, but also could save much computing time compared to RDICA. Furthermore, the ROC (Receiver Operating Characteristic) power analysis also denoted the better signal reconstruction performance of ATGP-ICA than that of RDICA. Copyright © 2013 Elsevier Inc. All rights reserved.

Nanodiamonds as pH-switchable oxidation and reduction catalysts with enzyme-like activities for immunoassay and antioxidant applications.

PubMed

Chen, T M; Tian, X M; Huang, L; Xiao, J; Yang, G W

2017-10-19

Nanodiamonds (NDs) have recently become a focus of interest from the viewpoints of both science and technology. Their intriguing properties make them suitable as biologically active substrates, in biosensor applications as well as diagnostic and therapeutic biomedical imaging probes. Here, we demonstrate that NDs, as oxidation and reduction catalysts, possess intrinsic enzyme mimetic properties of oxidase, peroxidase and catalase, and these behaviors can be switched by modulating the pH value. NDs not only catalyze the reduction of oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ) at acidic pH, but also catalyze the dismutation decomposition of H 2 O 2 to produce O 2 at alkaline pH. It was proposed that the molecular mechanism of their peroxidase-like activity is electron-transfer acceleration, the source of which is likely derived from oxygen containing functional groups on their surface. Based on the color reaction, a nanodiamond-based enzyme linked immunosorbent assay (ELISA) was established for the detection of immunoglobulin G (IgG). Surprisingly, NDs display an excellent antioxidant activity due to the protective effect against H 2 O 2 -induced cellular oxidative damage. These findings make NDs a promising enzyme mimetic candidate and expand their applications in biocatalysis, bioassays and nano-biomedicine.

Photocatalytic degradation of 5-nitro-1,2,4-triazol-3-one NTO in aqueous suspension of TiO2. Comparison with Fenton oxidation.

PubMed

Le Campion, L; Giannotti, C; Ouazzani, J

1999-03-01

5-nitro-1,2,4-triazol-3-one (NTO) is a powerful insensitive explosive, present in industrial waste waters. A remediation method based on photochemical decomposition and Fenton oxidation of NTO has been evaluated by monitoring the mineralization of 14C-labelled NTO. The TiO2-catalyzed photodegradation (lambda > 290 nm, TiO2 0.4 g/l, NTO 150 mg/l)) leads to the complete mineralization of NTO in 3 hours. This degradation involves a simultaneous denitrification and ring scission of NTO leading to nitrites, nitrates and carbon dioxide. No significant photo-degradation of NTO was detected in the absence of the catalyst. Long term irradiation over one week, leads to a complete degradation of concentrated NTO (5 g/l), suggesting that this method could be useful to clean-up NTO wastes. Fenton oxidation offers an efficient cost-effective method for NTO remediation. This reaction is faster that the TiO2 catalyzed photolysis and find application on the mineralization of high concentrations of NTO (15 g/l). Fenton oxidation provokes ring cleavage and subsequent elimination of the two carbon atoms of NTO as CO2. During this reaction, the nitro group is completely transformed into nitrates.

Oxidation of nitroxyl anion to nitric oxide by copper ions

PubMed Central

Nelli, Silvia; Hillen, Mark; Buyukafsar, Kansu; Martin, William

2000-01-01

This study made use of a nitric oxide-sensitive electrode to examine possible means of generating nitric oxide from nitroxyl anion (NO−) released upon the decomposition of Angeli's salt. Our results show that copper ions (from CuSO4) catalyze the rapid and efficient oxidation of nitroxyl to nitric oxide. Indeed, the concentrations of copper required to do so (0.1–100 μM) are roughly 100-times lower than those required to generate equivalent amounts of nitric oxide from S-nitroso-N-acetyl-D,L-penicillamine (SNAP). Experiments with ascorbate (1 mM), which reduces Cu2+ ions to Cu+, and with the Cu2+ chelators, EDTA and cuprizone, and the Cu+ chelator, neocuproine, each at 1 mM, suggest that the oxidation is catalyzed by copper ions in both valency states. Some compounds containing other transition metals, i.e. methaemoglobin, ferricytochrome c and Mn(III)TMPyP, were much less efficient than CuSO4 in catalyzing the formation of nitric oxide from nitroxyl, while FeSO4, FeCl3, MnCl2, and ZnSO4 were inactive. Of the copper containing enzymes examined, Cu-Zn superoxide dismutase and ceruloplasmin were weak generators of nitric oxide from nitroxyl, even at concentrations (2500 and 30 u ml−1, respectively) vastly greater than are present endogenously. Two others, ascorbate oxidase (10 u ml−1) and tyrosinase (250 u ml−1) were inactive. Our findings suggest that a copper-containing enzyme may be responsible for the rapid oxidation of nitroxyl to nitric oxide by cells, but the identity of such an enzyme remains elusive. PMID:10991931

Paving the way to a full chip gate level double patterning application

NASA Astrophysics Data System (ADS)

Haffner, Henning; Meiring, Jason; Baum, Zachary; Halle, Scott

2007-10-01

Double patterning lithography processes can offer significant yield enhancement for challenging circuit designs. Many decomposition (i.e. the process of dividing the layout design into first and second exposures) techniques are possible, but the focus of this paper is on the use of a secondary "cut" mask to trim away extraneous features left from the first exposure. This approach has the advantage that each exposure only needs to support a subset of critical features (e.g. dense lines with the first exposure, isolated spaces with the second one). The extraneous features ("printing assist features" or PrAFs) are designed to support the process window of critical features much like the role of the subresolution assist features (SRAFs) in conventional processes. However, the printing nature of PrAFs leads to many more design options, and hence a greater process and decomposition parameter exploration space, than are available for SRAFs. A decomposition scheme using PRAFs was developed for a gate level process. A critical driver of the work was to deliver improved across-chip linewidth variation (ACLV) performance versus an optimized single exposure process while providing support for a larger range of critical features. A variety of PRAF techniques were investigated by simulation, with a PrAF scheme similar to standard SRAF rules being chosen as the optimal solution [1]. This paper discusses aspects of the code development for an automated PrAF generation and placement scheme and the subsequent decomposition of a layout into two mask levels. While PrAF placement and decomposition is straightforward for layouts with pitch and orientation restrictions, it becomes rather complex for unrestricted layout styles. Because this higher complexity yields more irregularly shaped PrAFs, mask making becomes another critical driver of the optimum placement and clean-up strategies. Examples are given of how those challenges are met or can be successfully circumvented. During subsequent decomposition of the PrAF-enhanced layout into two independent mask levels, various geometric decomposition parameters have to be considered. As an example, the removal of PrAFs has to be guaranteed by a minimum required overlap of the cut mask opening past any PrAF edge. It is discussed that process assumptions such as CD tolerances and overlay as well as inter-level relationship ground rules need to be considered to successfully optimize the final decomposition scheme. Furthermore, simulation and experimental results regarding not only ACLV but also across-device linewidth variation (ADLV) are analyzed.

Alkanes from Bioderived Furans by using Metal Triflates and Palladium-Catalyzed Hydrodeoxygenation of Cyclic Ethers.

PubMed

Song, Hai-Jie; Deng, Jin; Cui, Min-Shu; Li, Xing-Long; Liu, Xin-Xin; Zhu, Rui; Wu, Wei-Peng; Fu, Yao

2015-12-21

Using a metal triflate and Pd/C as catalysts, alkanes were prepared from bioderived furans in a one-pot hydrodeoxygenation (HDO) process. During the reaction, the metal triflate plays a crucial role in the ring-opening HDO of furan compounds. The entire reaction process has goes through two major phases: at low temperatures, saturation of the exocyclic double bond and furan ring are catalyzed by Pd/C; at high temperatures, the HDO of saturated furan compounds is catalyzed by the metal triflate. The reaction mechanism was verified by analyzing the changes of the intermediates during the reaction. In addition, different metal triflates, solvents, and catalyst recycling were also investigated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preliminary application of Structure from Motion and GIS to document decomposition and taphonomic processes.

PubMed

Carlton, Connor D; Mitchell, Samantha; Lewis, Patrick

2018-01-01

Over the past decade, Structure from Motion (SfM) has increasingly been used as a means of digital preservation and for documenting archaeological excavations, architecture, and cultural material. However, few studies have tapped the potential of using SfM to document and analyze taphonomic processes affecting burials for forensic sciences purposes. This project utilizes SfM models to elucidate specific post-depositional events that affected a series of three human cadavers deposited at the South East Texas Applied Forensic Science Facility (STAFS). The aim of this research was to test the ability for untrained researchers to employ spatial software and photogrammetry for data collection purposes. For a series of three months a single lens reflex (SLR) camera was used to capture a series of overlapping images at periodic stages in the decomposition process of each cadaver. These images are processed through photogrammetric software that creates a 3D model that can be measured, manipulated, and viewed. This project used photogrammetric and geospatial software to map changes in decomposition and movement of the body from original deposition points. Project results indicate SfM and GIS as a useful tool for documenting decomposition and taphonomic processes. Results indicate photogrammetry is an efficient, relatively simple, and affordable tool for the documentation of decomposition. Copyright © 2017 Elsevier B.V. All rights reserved.

Parallel processing for pitch splitting decomposition

NASA Astrophysics Data System (ADS)

Barnes, Levi; Li, Yong; Wadkins, David; Biederman, Steve; Miloslavsky, Alex; Cork, Chris

2009-10-01

Decomposition of an input pattern in preparation for a double patterning process is an inherently global problem in which the influence of a local decomposition decision can be felt across an entire pattern. In spite of this, a large portion of the work can be massively distributed. Here, we discuss the advantages of geometric distribution for polygon operations with limited range of influence. Further, we have found that even the naturally global "coloring" step can, in large part, be handled in a geometrically local manner. In some practical cases, up to 70% of the work can be distributed geometrically. We also describe the methods for partitioning the problem into local pieces and present scaling data up to 100 CPUs. These techniques reduce DPT decomposition runtime by orders of magnitude.

Catalytic asymmetric epoxidation of alpha,beta-unsaturated amides: efficient synthesis of beta-aryl alpha-hydroxy amides using a one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process.

PubMed

Nemoto, Tetsuhiro; Kakei, Hiroyuki; Gnanadesikan, Vijay; Tosaki, Shin-Ya; Ohshima, Takashi; Shibasaki, Masakatsu

2002-12-11

The catalytic asymmetric epoxidation of alpha,beta-unsaturated amides using Sm-BINOL-Ph3As=O complex was succeeded. Using 5-10 mol % of the asymmetric catalyst, a variety of amides were epoxidized efficiently, yielding the corresponding alpha,beta-epoxy amides in up to 99% yield and in more than 99% ee. Moreover, the novel one-pot tandem process, one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process, was developed. This method was successfully utilized for the efficient synthesis of beta-aryl alpha-hydroxy amides, including beta-aryllactyl-leucine methyl esters. Interestingly, it was found that beneficial modifications on the Pd catalyst were achieved by the constituents of the first epoxidation, producing a more suitable catalyst for the Pd-catalyzed epoxide opening reaction in terms of chemoselectivity.

Highly efficient chemical process to convert mucic acid into adipic acid and DFT studies of the mechanism of the rhenium-catalyzed deoxydehydration.

PubMed

Li, Xiukai; Wu, Di; Lu, Ting; Yi, Guangshun; Su, Haibin; Zhang, Yugen

2014-04-14

The production of bulk chemicals and fuels from renewable bio-based feedstocks is of significant importance for the sustainability of human society. Adipic acid, as one of the most-demanded drop-in chemicals from a bioresource, is used primarily for the large-volume production of nylon-6,6 polyamide. It is highly desirable to develop sustainable and environmentally friendly processes for the production of adipic acid from renewable feedstocks. However, currently there is no suitable bio-adipic acid synthesis process. Demonstrated herein is the highly efficient synthetic protocol for the conversion of mucic acid into adipic acid through the oxorhenium-complex-catalyzed deoxydehydration (DODH) reaction and subsequent Pt/C-catalyzed transfer hydrogenation. Quantitative yields (99 %) were achieved for the conversion of mucic acid into muconic acid and adipic acid either in separate sequences or in a one-step process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Decomposition of sulfamethoxazole and trimethoprim by continuous UVA/LED/TiO2 photocatalysis: Decomposition pathways, residual antibacterial activity and toxicity.

PubMed

Cai, Qinqing; Hu, Jiangyong

2017-02-05

In this study, continuous LED/UVA/TiO 2 photocatalytic decomposition of sulfamethoxazole (SMX) and trimethoprim (TMP) was investigated. More than 90% of SMX and TMP were removed within 20min by the continuous photoreactor (with the initial concentration of 400ppb for each). The removal rates of SMX and TMP decreased with higher initial antibiotics loadings. SMX was much easier decomposed in acidic condition, while pH affected little on TMP's decomposition. 0.003% was found to be the optimum H 2 O 2 dosage to enhance SMX photocatalytic decomposition. Decomposition pathways of SMX and TMP were proposed based on the intermediates identified by using LC-MS-MS and GC-MS. Aniline was identified as a new intermediate generated during SMX photocatalytic decomposition. Antibacterial activity study with a reference Escherichia coli strain was also conducted during the photocatalytic process. Results indicated that with every portion of TMP removed, the residual antibacterial activity decreased by one portion. However, the synergistic effect between SMX and TMP tended to slow down the antibacterial activity removal of SMX and TMP mixture. Chronic toxicity studies conducted with Vibrio fischeri exhibited 13-20% bioluminescence inhibition during the decomposition of 1ppm SMX and 1ppm TMP, no acute toxicity to V. fischeri was observed during the photocatalytic process. Copyright © 2016 Elsevier B.V. All rights reserved.

Decomposition characteristics of three different kinds of aquatic macrophytes and their potential application as carbon resource in constructed wetland.

PubMed

Wu, Suqing; He, Shengbing; Zhou, Weili; Gu, Jianya; Huang, Jungchen; Gao, Lei; Zhang, Xu

2017-12-01

Decomposition of aquatic macrophytes usually generates significant influence on aquatic environment. Study on the aquatic macrophytes decomposition may help reusing the aquatic macrophytes litters, as well as controlling the water pollution caused by the decomposition process. This study verified that the decomposition processes of three different kinds of aquatic macrophytes (water hyacinth, hydrilla and cattail) could exert significant influences on water quality of the receiving water, including the change extent of pH, dissolved oxygen (DO), the contents of carbon, nitrogen and phosphorus, etc. The influence of decomposition on water quality and the concentrations of the released chemical materials both followed the order of water hyacinth > hydrilla > cattail. Greater influence was obtained with higher dosage of plant litter addition. The influence also varied with sediment addition. Moreover, nitrogen released from the decomposition of water hyacinth and hydrilla were mainly NH 3 -N and organic nitrogen while those from cattail litter included organic nitrogen and NO 3 - -N. After the decomposition, the average carbon to nitrogen ratio (C/N) in the receiving water was about 2.6 (water hyacinth), 5.3 (hydrilla) and 20.3 (cattail). Therefore, cattail litter might be a potential plant carbon source for denitrification in ecological system of a constructed wetland. Copyright © 2017 Elsevier Ltd. All rights reserved.

Relationship between the Decomposition Process of Coarse Woody Debris and Fungal Community Structure as Detected by High-Throughput Sequencing in a Deciduous Broad-Leaved Forest in Japan

PubMed Central

Yamashita, Satoshi; Masuya, Hayato; Abe, Shin; Masaki, Takashi; Okabe, Kimiko

2015-01-01

We examined the relationship between the community structure of wood-decaying fungi, detected by high-throughput sequencing, and the decomposition rate using 13 years of data from a forest dynamics plot. For molecular analysis and wood density measurements, drill dust samples were collected from logs and stumps of Fagus and Quercus in the plot. Regression using a negative exponential model between wood density and time since death revealed that the decomposition rate of Fagus was greater than that of Quercus. The residual between the expected value obtained from the regression curve and the observed wood density was used as a decomposition rate index. Principal component analysis showed that the fungal community compositions of both Fagus and Quercus changed with time since death. Principal component analysis axis scores were used as an index of fungal community composition. A structural equation model for each wood genus was used to assess the effect of fungal community structure traits on the decomposition rate and how the fungal community structure was determined by the traits of coarse woody debris. Results of the structural equation model suggested that the decomposition rate of Fagus was affected by two fungal community composition components: one that was affected by time since death and another that was not affected by the traits of coarse woody debris. In contrast, the decomposition rate of Quercus was not affected by coarse woody debris traits or fungal community structure. These findings suggest that, in the case of Fagus coarse woody debris, the fungal community structure is related to the decomposition process of its host substrate. Because fungal community structure is affected partly by the decay stage and wood density of its substrate, these factors influence each other. Further research on interactive effects is needed to improve our understanding of the relationship between fungal community structure and the woody debris decomposition process. PMID:26110605

Catalytic processing of lactic acid over Pt/Nb(2)O(5).

PubMed

Serrano-Ruiz, Juan Carlos; Dumesic, James A

2009-01-01

Dilute aqueous solutions of lactic acid (30 %wt.) can be catalytically processed at 573 K and 57 bar over a low-metal-content Pt(0.1 %)/Nb(2)O(5) catalyst in a spontaneously separating organic phase rich in valuable products such as C(4)-C(7) ketones. An increase in the lactic acid concentration to 60 wt % allows conversion of approximately 50 % of the carbon feed in this organic layer, while maintaining good stability of the catalyst. Experiments at low conversion showed that lactic acid reacts first over Pt(0.1 %)/Nb(2)O(5) to produce acetaldehyde and propanoic acid (along with CO and CO(2) in the gas phase). These compounds (less oxygenated than lactic acid but still reactive) are the key intermediates in the overall process, and they react differently depending on the nature of the catalyst support. In particular, reaction kinetics studies with propanoic acid as feed showed that Pt(0.1 %)/Nb(2)O(5) favored the formation of pentanones by ketonization reactions, whereas a monofunctional Pt(0.1 %)/carbon catalyst produced ethane and CO(x) by decomposition reactions. In the same manner, acetaldehyde was preferentially hydrogenated to ethanol over Pt(0.1 %)/carbon, whereas the presence of niobia allowed this intermediate to react (by successive aldol condensations) to form C(4)-C(7) condensation products stored in the organic phase. Finally, reaction pathways are proposed to explain the catalytic processing of lactic acid over bifunctional Pt(0.1 %)/Nb(2)O(5). In this scheme, metal sites catalyze hydrogenation reactions and niobia promotes C--C coupling processes (ketonization and aldol condensation), in contrast to C--C cleavage reactions which take place preferentially over Pt(0.1 %)/carbon and lead to loss of carbon in the gas effluent as CO, CO(2), and methane.

Comparison of the Decomposition VOC Profile during Winter and Summer in a Moist, Mid-Latitude (Cfb) Climate

PubMed Central

Forbes, Shari L.; Perrault, Katelynn A.; Stefanuto, Pierre-Hugues; Nizio, Katie D.; Focant, Jean-François

2014-01-01

The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC×GC-TOFMS were demonstrated for detecting and identifying trace levels of VOCs, particularly ethers, which are rarely reported as decomposition VOCs. PMID:25412504

Comparison of the decomposition VOC profile during winter and summer in a moist, mid-latitude (Cfb) climate.

PubMed

Forbes, Shari L; Perrault, Katelynn A; Stefanuto, Pierre-Hugues; Nizio, Katie D; Focant, Jean-François

2014-01-01

The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography--time-of-flight mass spectrometry (GC × GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC × GC-TOFMS were demonstrated for detecting and identifying trace levels of VOCs, particularly ethers, which are rarely reported as decomposition VOCs.

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

Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species.

PubMed

Dossa, Gbadamassi G O; Paudel, Ekananda; Cao, Kunfang; Schaefer, Douglas; Harrison, Rhett D

2016-10-04

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.

Kinetic Analysis of Isothermal Decomposition Process of Sodium Bicarbonate Using the Weibull Probability Function—Estimation of Density Distribution Functions of the Apparent Activation Energies

NASA Astrophysics Data System (ADS)

Janković, Bojan

2009-10-01

The decomposition process of sodium bicarbonate (NaHCO3) has been studied by thermogravimetry in isothermal conditions at four different operating temperatures (380 K, 400 K, 420 K, and 440 K). It was found that the experimental integral and differential conversion curves at the different operating temperatures can be successfully described by the isothermal Weibull distribution function with a unique value of the shape parameter ( β = 1.07). It was also established that the Weibull distribution parameters ( β and η) show independent behavior on the operating temperature. Using the integral and differential (Friedman) isoconversional methods, in the conversion (α) range of 0.20 ≤ α ≤ 0.80, the apparent activation energy ( E a ) value was approximately constant ( E a, int = 95.2 kJmol-1 and E a, diff = 96.6 kJmol-1, respectively). The values of E a calculated by both isoconversional methods are in good agreement with the value of E a evaluated from the Arrhenius equation (94.3 kJmol-1), which was expressed through the scale distribution parameter ( η). The Málek isothermal procedure was used for estimation of the kinetic model for the investigated decomposition process. It was found that the two-parameter Šesták-Berggren (SB) autocatalytic model best describes the NaHCO3 decomposition process with the conversion function f(α) = α0.18(1-α)1.19. It was also concluded that the calculated density distribution functions of the apparent activation energies ( ddfE a ’s) are not dependent on the operating temperature, which exhibit the highly symmetrical behavior (shape factor = 1.00). The obtained isothermal decomposition results were compared with corresponding results of the nonisothermal decomposition process of NaHCO3.

Iodide-catalyzed synthesis of N-nitrosamines via C-N cleavage of nitromethane.

PubMed

Zhang, Jie; Jiang, Jiewen; Li, Yuling; Wan, Xiaobing

2013-11-15

An iodide-catalyzed process to synthesize N-nitrosamines has been developed using TBHP as the oxidant. The mild catalytic system succeeded in cleaving the carbon-nitrogen bond in nitromethane. This methodology uses commercially available, inexpensive catalysts and oxidants and has a wide substrate scope and operational simplicity.

New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

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

Huang, Qinhua

2004-12-19

The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I 2, ICl, PhSeCl, PhSCl and p-O 2NC 6H 4SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellentmore » yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that these palladium-catalyzed C-H activation reactions parallel electrophilic aromatic substitution. A relatively efficient synthesis of cyclopropanes has been developed using palladium-catalyzed C-H activation chemistry, in which two new carbon-carbon bonds are formed in a single step. This method involves the palladium-catalyzed activation of relatively unreactive C-H bonds, and provides a very efficient way to synthesize cyclopropapyrrolo[1,2-a]indoles, analogues of the mitomycin antibiotics.« less

Layout compliance for triple patterning lithography: an iterative approach

NASA Astrophysics Data System (ADS)

Yu, Bei; Garreton, Gilda; Pan, David Z.

2014-10-01

As the semiconductor process further scales down, the industry encounters many lithography-related issues. In the 14nm logic node and beyond, triple patterning lithography (TPL) is one of the most promising techniques for Metal1 layer and possibly Via0 layer. As one of the most challenging problems in TPL, recently layout decomposition efforts have received more attention from both industry and academia. Ideally the decomposer should point out locations in the layout that are not triple patterning decomposable and therefore manual intervention by designers is required. A traditional decomposition flow would be an iterative process, where each iteration consists of an automatic layout decomposition step and manual layout modification task. However, due to the NP-hardness of triple patterning layout decomposition, automatic full chip level layout decomposition requires long computational time and therefore design closure issues continue to linger around in the traditional flow. Challenged by this issue, we present a novel incremental layout decomposition framework to facilitate accelerated iterative decomposition. In the first iteration, our decomposer not only points out all conflicts, but also provides the suggestions to fix them. After the layout modification, instead of solving the full chip problem from scratch, our decomposer can provide a quick solution for a selected portion of layout. We believe this framework is efficient, in terms of performance and designer friendly.

Decoupling the direct and indirect effects of climate on plant litter decomposition: Accounting for stress-induced modifications in plant chemistry.

PubMed

Suseela, Vidya; Tharayil, Nishanth

2018-04-01

Decomposition of plant litter is a fundamental ecosystem process that can act as a feedback to climate change by simultaneously influencing both the productivity of ecosystems and the flux of carbon dioxide from the soil. The influence of climate on decomposition from a postsenescence perspective is relatively well known; in particular, climate is known to regulate the rate of litter decomposition via its direct influence on the reaction kinetics and microbial physiology on processes downstream of tissue senescence. Climate can alter plant metabolism during the formative stage of tissues and could shape the final chemical composition of plant litter that is available for decomposition, and thus indirectly influence decomposition; however, these indirect effects are relatively poorly understood. Climatic stress disrupts cellular homeostasis in plants and results in the reprogramming of primary and secondary metabolic pathways, which leads to changes in the quantity, composition, and organization of small molecules and recalcitrant heteropolymers, including lignins, tannins, suberins, and cuticle within the plant tissue matrix. Furthermore, by regulating metabolism during tissue senescence, climate influences the resorption of nutrients from senescing tissues. Thus, the final chemical composition of plant litter that forms the substrate of decomposition is a combined product of presenescence physiological processes through the production and resorption of metabolites. The changes in quantity, composition, and localization of the molecular construct of the litter could enhance or hinder tissue decomposition and soil nutrient cycling by altering the recalcitrance of the lignocellulose matrix, the composition of microbial communities, and the activity of microbial exo-enzymes via various complexation reactions. Also, the climate-induced changes in the molecular composition of litter could differentially influence litter decomposition and soil nutrient cycling. Compared with temperate ecosystems, the indirect effects of climate on litter decomposition in the tropics are not well understood, which underscores the need to conduct additional studies in tropical biomes. We also emphasize the need to focus on how climatic stress affects the root chemistry as roots contribute significantly to biogeochemical cycling, and on utilizing more robust analytical approaches to capture the molecular composition of tissue matrix that fuel microbial metabolism. © 2017 John Wiley & Sons Ltd.

Multilevel decomposition of complete vehicle configuration in a parallel computing environment

NASA Technical Reports Server (NTRS)

Bhatt, Vinay; Ragsdell, K. M.

1989-01-01

This research summarizes various approaches to multilevel decomposition to solve large structural problems. A linear decomposition scheme based on the Sobieski algorithm is selected as a vehicle for automated synthesis of a complete vehicle configuration in a parallel processing environment. The research is in a developmental state. Preliminary numerical results are presented for several example problems.

Interacting effects of insects and flooding on wood decomposition.

Treesearch

Michael Ulyshen

2014-01-01

Saproxylic arthropods are thought to play an important role in wood decomposition but very few efforts have been made to quantify their contributions to the process and the factors controlling their activities are not well understood. In the current study, mesh exclusion bags were used to quantify how arthropods affect loblolly pine (Pinus taeda L.) decomposition rates...

Lewis acid catalysis and ligand exchange in the asymmetric binaphthol-catalyzed propargylation of ketones.

PubMed

Grayson, Matthew N; Goodman, Jonathan M

2013-09-06

1,1'-Bi-2-naphthol (BINOL)-derived catalysts catalyze the asymmetric propargylation of ketones. Density functional theory (DFT) calculations show that the reaction proceeds via a closed six-membered transition structure (TS) in which the chiral catalyst undergoes an exchange process with the original cyclic boronate ligand. This leads to a Lewis acid type activation mode, not a Brønsted acid process, which accurately predicts the stereochemical outcome observed experimentally.

Effect of hexadecyltrimethylammonium bromide-based microemulsions on the rate of decomposition of the beta-lactam antibiotic cephaclor.

PubMed

De Oliveira, A G; Scarpa, M V; Chaimovich, H

1997-05-01

Microemulsions of hexadecyltrimethylammonium bromide (HTAB)/n-butanol/hexadecane/water catalyze the intramolecular degradation of cephaclor. The rate increase is a sensitive function of the microemulsion volume fraction and salt concentration. The effects of microemulsions, analyzed quantitatively using a pseudophase ion-exchange model, assumed that the extent of ion dissociation from the microemulsions varies with volume fraction. Comparison of micellar and microemulsion effects on the same reaction shows that microemulsions are less effective catalysts. Acceleration decreased significantly by increasing the relative proportion of n-butanol ratio in microemulsions and by addition of n-butanol in HTAB micelles. Comparison of the activation parameters of the reaction in aqueous solution, microemulsions, and micelles suggests that catalysis by both aggregates is driven mainly by entropic contributions.

Tea polyphenols dominate the short-term tea (Camellia sinensis) leaf litter decomposition*

PubMed Central

Fan, Dong-mei; Fan, Kai; Yu, Cui-ping; Lu, Ya-ting; Wang, Xiao-chang

2017-01-01

Polyphenols are one of the most important secondary metabolites, and affect the decomposition of litter and soil organic matter. This study aims to monitor the mass loss rate of tea leaf litter and nutrient release pattern, and investigate the role of tea polyphenols played in this process. High-performance liquid chromatography (HPLC) and classical litter bag method were used to simulate the decomposition process of tea leaf litter and track the changes occurring in major polyphenols over eight months. The release patterns of nitrogen, potassium, calcium, and magnesium were also determined. The decomposition pattern of tea leaf litter could be described by a two-phase decomposition model, and the polyphenol/N ratio effectively regulated the degradation process. Most of the catechins decreased dramatically within two months; gallic acid (GA), catechin gallate (CG), and gallocatechin (GC) were faintly detected, while others were outside the detection limits by the end of the experiment. These results demonstrated that tea polyphenols transformed quickly and catechins had an effect on the individual conversion rate. The nutrient release pattern was different from other plants which might be due to the existence of tea polyphenols. PMID:28124839

Tea polyphenols dominate the short-term tea (Camellia sinensis) leaf litter decomposition.

PubMed

Fan, Dong-Mei; Fan, Kai; Yu, Cui-Ping; Lu, Ya-Ting; Wang, Xiao-Chang

Polyphenols are one of the most important secondary metabolites, and affect the decomposition of litter and soil organic matter. This study aims to monitor the mass loss rate of tea leaf litter and nutrient release pattern, and investigate the role of tea polyphenols played in this process. High-performance liquid chromatography (HPLC) and classical litter bag method were used to simulate the decomposition process of tea leaf litter and track the changes occurring in major polyphenols over eight months. The release patterns of nitrogen, potassium, calcium, and magnesium were also determined. The decomposition pattern of tea leaf litter could be described by a two-phase decomposition model, and the polyphenol/N ratio effectively regulated the degradation process. Most of the catechins decreased dramatically within two months; gallic acid (GA), catechin gallate (CG), and gallocatechin (GC) were faintly detected, while others were outside the detection limits by the end of the experiment. These results demonstrated that tea polyphenols transformed quickly and catechins had an effect on the individual conversion rate. The nutrient release pattern was different from other plants which might be due to the existence of tea polyphenols.

Characterization of nanosized TiO2 synthesized inside a porous glass ceramic monolith by metallo-organic decomposition process

NASA Astrophysics Data System (ADS)

Mazali, Italo Odone; Alves, Oswaldo Luiz

2005-01-01

This work reports the preparation of TiO2 by decomposition of a metallo-organic precursor (MOD process) in the pores of an α-NbPO5 glass-ceramic monolith (PGC-NbP) and the study of the TiO2 anatase-rutile transition phase. The impregnation of titanium di-(propoxy)-di-(2-ethylhexanoate) in the PGC-NbP was confirmed by diffuse reflectance infrared spectroscopy. In the restrictive porous environment the decomposition of the metallo-organic compound exhibits a lower initial decomposition temperature but a higher final decomposition temperature, in comparison to the free precursor. The pure TiO2 rutile phase is formed only above 700 °C when the titanium precursor is decomposed outside the pores. The TiO2 anatase obtained inside the PGC-NbP was stabilized up to 750 °C and exhibits a smaller average crystallite size in comparison with the MOD process performed without PGC-NbP. Furthemore, the temperature of the TiO2 anatase-rutile transformation depends on crystallite size, which was provided by XRD and Raman spectroscopy. The precursor impregnation-decomposition cycle revealed a linear mass increment inside PGC-NbP. Micro-Raman spectroscopy shows the presence of a gradient concentration of the TiO2 inside the PGC-NbP. The use of the MOD process in the PGC-NbP pores has several advantages: control of the amount and the nature of the phase formed and preservation of the pore structure of PGC-NbP for subsequent treatments and reactions.

A comparison between decomposition rates of buried and surface remains in a temperate region of South Africa.

PubMed

Marais-Werner, Anátulie; Myburgh, J; Becker, P J; Steyn, M

2018-01-01

Several studies have been conducted on decomposition patterns and rates of surface remains; however, much less are known about this process for buried remains. Understanding the process of decomposition in buried remains is extremely important and aids in criminal investigations, especially when attempting to estimate the post mortem interval (PMI). The aim of this study was to compare the rates of decomposition between buried and surface remains. For this purpose, 25 pigs (Sus scrofa; 45-80 kg) were buried and excavated at different post mortem intervals (7, 14, 33, 92, and 183 days). The observed total body scores were then compared to those of surface remains decomposing at the same location. Stages of decomposition were scored according to separate categories for different anatomical regions based on standardised methods. Variation in the degree of decomposition was considerable especially with the buried 7-day interval pigs that displayed different degrees of discolouration in the lower abdomen and trunk. At 14 and 33 days, buried pigs displayed features commonly associated with the early stages of decomposition, but with less variation. A state of advanced decomposition was reached where little change was observed in the next ±90-183 days after interment. Although the patterns of decomposition for buried and surface remains were very similar, the rates differed considerably. Based on the observations made in this study, guidelines for the estimation of PMI are proposed. This pertains to buried remains found at a depth of approximately 0.75 m in the Central Highveld of South Africa.

Monitoring mass transport in heterogeneously catalyzed reactions by field-gradient NMR for assessing reaction efficiency in a single pellet

NASA Astrophysics Data System (ADS)

Buljubasich, L.; Blümich, B.; Stapf, S.

2011-09-01

An important aspect in assessing the performance of a catalytically active reactor is the accessibility of the reactive sites inside the individual pellets, and the mass transfer of reactants and products to and from these sites. Optimal design often requires a suitable combination of micro- and macropores in order to facilitate mass transport inside the pellet. In an exothermic reaction, fluid exchange between the pellet and the surrounding medium is enhanced by convection, and often by the occurrence of gas bubbles. Determining mass flow in the vicinity of a pellet thus represents a parameter for quantifying the reaction efficiency and its dependence on time or external reaction conditions. Field gradient Nuclear Magnetic Resonance (NMR) methods are suggested as a tool for providing parameters sensitive to this mass flow in a contact-free and non-invasive way. For the example of bubble-forming hydrogen peroxide decomposition in an alumina pellet, the dependence of the mean-squared displacement of fluid molecules on spatial direction, observation time and reaction time is presented, and multi-pulse techniques are employed in order to separate molecular displacements from coherent and incoherent motion on the timescale of the experiment. The reaction progress is followed until the complete decomposition of H 2O 2.

Comparative studies of the influence of cyclodextrins on the stability of the sunscreen agent, 2-ethylhexyl-p-methoxycinnamate.

PubMed

Scalia, Santo; Casolari, Alberto; Iaconinoto, Antonietta; Simeoni, Silvia

2002-11-07

The effects of beta-cyclodextrin (beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the base-catalyzed degradation and light-induced decomposition of the sunscreen agent, trans-2-ethylhexyl-p-methoxycinnamate (trans-EHMC) were investigated. Reversed-phase liquid chromatography was used to study the interaction between natural and modified cyclodextrins, added to the mobile phase, and the sunscreen. Among the available cyclodextrins (beta-CD, HP-beta-CD, hydroxypropyl-alpha-cyclodextrin and hydroxypropyl-gamma-cyclodextrin), only HP-beta-CD and beta-CD produced a significant decrease in the chromatographic retention of trans-EHMC. The complexation of the sunscreen agent with HP-beta-CD and beta-CD was confirmed by thermal analysis and nuclear magnetic resonance spectroscopy. beta-CD depressed the decomposition of trans-EHMC in alkaline solutions more effectively than HP-beta-CD. Moreover, the irradiation-induced degradation of the sunscreen agent in emulsion vehicles was reduced by complexation with beta-CD (the extent of degradation was 26.1% for the complex compared to 35.8% for free trans-EHMC) whereas HP-beta-CD had no significant effect. Therefore, the complex of beta-CD with trans-EHMC enhances the chemical- and photo-stability of the sunscreen agent. Moreover, it limits adverse interactions of the UV filter with other formulation ingredients.

Microbial community assembly and metabolic function during mammalian corpse decomposition

USGS Publications Warehouse

Metcalf, Jessica L; Xu, Zhenjiang Zech; Weiss, Sophie; Lax, Simon; Van Treuren, Will; Hyde, Embriette R.; Song, Se Jin; Amir, Amnon; Larsen, Peter; Sangwan, Naseer; Haarmann, Daniel; Humphrey, Greg C; Ackermann, Gail; Thompson, Luke R; Lauber, Christian; Bibat, Alexander; Nicholas, Catherine; Gebert, Matthew J; Petrosino, Joseph F; Reed, Sasha C.; Gilbert, Jack A; Lynne, Aaron M; Bucheli, Sibyl R; Carter, David O; Knight, Rob

2016-01-01

Vertebrate corpse decomposition provides an important stage in nutrient cycling in most terrestrial habitats, yet microbially mediated processes are poorly understood. Here we combine deep microbial community characterization, community-level metabolic reconstruction, and soil biogeochemical assessment to understand the principles governing microbial community assembly during decomposition of mouse and human corpses on different soil substrates. We find a suite of bacterial and fungal groups that contribute to nitrogen cycling and a reproducible network of decomposers that emerge on predictable time scales. Our results show that this decomposer community is derived primarily from bulk soil, but key decomposers are ubiquitous in low abundance. Soil type was not a dominant factor driving community development, and the process of decomposition is sufficiently reproducible to offer new opportunities for forensic investigations.

Microbial community assembly and metabolic function during mammalian corpse decomposition

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

Metcalf, J. L.; Xu, Z. Z.; Weiss, S.

2015-12-10

Vertebrate corpse decomposition provides an important stage in nutrient cycling in most terrestrial habitats, yet microbially mediated processes are poorly understood. Here we combine deep microbial community characterization, community-level metabolic reconstruction, and soil biogeochemical assessment to understand the principles governing microbial community assembly during decomposition of mouse and human corpses on different soil substrates. We find a suite of bacterial and fungal groups that contribute to nitrogen cycling and a reproducible network of decomposers that emerge on predictable time scales. Our results show that this decomposer community is derived primarily from bulk soil, but key decomposers are ubiquitous in lowmore » abundance. Soil type was not a dominant factor driving community development, and the process of decomposition is sufficiently reproducible to offer new opportunities for forensic investigations.« less

Recent advances in transition metal-catalyzed N -atom transfer reactions of azides

PubMed Central

Driver, Tom G.

2011-01-01

Transition metal-catalyzed N-atom transfer reactions of azides provide efficient ways to construct new carbon–nitrogen and sulfur–nitrogen bonds. These reactions are inherently green: no additive besides catalyst is needed to form the nitrenoid reactive intermediate, and the by-product of the reaction is environmentally benign N2 gas. As such, azides can be useful precursors for transition metal-catalyzed N-atom transfer to sulfides, olefins and C–H bonds. These methods offer competitive selectivities and comparable substrate scope as alternative processes to generate metal nitrenoids. PMID:20617243

Dynamic Load Balancing Based on Constrained K-D Tree Decomposition for Parallel Particle Tracing

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

Zhang, Jiang; Guo, Hanqi; Yuan, Xiaoru

Particle tracing is a fundamental technique in flow field data visualization. In this work, we present a novel dynamic load balancing method for parallel particle tracing. Specifically, we employ a constrained k-d tree decomposition approach to dynamically redistribute tasks among processes. Each process is initially assigned a regularly partitioned block along with duplicated ghost layer under the memory limit. During particle tracing, the k-d tree decomposition is dynamically performed by constraining the cutting planes in the overlap range of duplicated data. This ensures that each process is reassigned particles as even as possible, and on the other hand the newmore » assigned particles for a process always locate in its block. Result shows good load balance and high efficiency of our method.« less

PROCESS OF COATING WITH NICKEL BY THE DECOMPOSITION OF NICKEL CARBONYL

DOEpatents

Hoover, T.B.

1959-04-01

An improved process is presented for the deposition of nickel coatings by the thermal decomposition of nickel carbonyl vapor. The improvement consists in incorporating a small amount of hydrogen sulfide gas in the nickel carbonyl plating gas. It is postulated that the hydrogen sulfide functions as a catalyst. i

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.

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.

Fabricating Large-Area Sheets of Single-Layer Graphene by CVD

NASA Technical Reports Server (NTRS)

Bronikowski, Michael; Manohara, Harish

2008-01-01

This innovation consists of a set of methodologies for preparing large area (greater than 1 cm(exp 2)) domains of single-atomic-layer graphite, also called graphene, in single (two-dimensional) crystal form. To fabricate a single graphene layer using chemical vapor deposition (CVD), the process begins with an atomically flat surface of an appropriate substrate and an appropriate precursor molecule containing carbon atoms attached to substituent atoms or groups. These molecules will be brought into contact with the substrate surface by being flowed over, or sprayed onto, the substrate, under CVD conditions of low pressure and elevated temperature. Upon contact with the surface, the precursor molecules will decompose. The substituent groups detach from the carbon atoms and form gas-phase species, leaving the unfunctionalized carbon atoms attached to the substrate surface. These carbon atoms will diffuse upon this surface and encounter and bond to other carbon atoms. If conditions are chosen carefully, the surface carbon atoms will arrange to form the lowest energy single-layer structure available, which is the graphene lattice that is sought. Another method for creating the graphene lattice includes metal-catalyzed CVD, in which the decomposition of the precursor molecules is initiated by the catalytic action of a catalytic metal upon the substrate surface. Another type of metal-catalyzed CVD has the entire substrate composed of catalytic metal, or other material, either as a bulk crystal or as a think layer of catalyst deposited upon another surface. In this case, the precursor molecules decompose directly upon contact with the substrate, releasing their atoms and forming the graphene sheet. Atomic layer deposition (ALD) can also be used. In this method, a substrate surface at low temperature is covered with exactly one monolayer of precursor molecules (which may be of more than one type). This is heated up so that the precursor molecules decompose and form one monolayer of the target material.

Biogeochemistry of Decomposition and Detrital Processing

NASA Astrophysics Data System (ADS)

Sanderman, J.; Amundson, R.

2003-12-01

Decomposition is a key ecological process that roughly balances net primary production in terrestrial ecosystems and is an essential process in resupplying nutrients to the plant community. Decomposition consists of three concurrent processes: communition or fragmentation, leaching of water-soluble compounds, and microbial catabolism. Decomposition can also be viewed as a sequential process, what Eijsackers and Zehnder (1990) compare to a Russian matriochka doll. Soil macrofauna fragment and partially solubilize plant residues, facilitating establishment of a community of decomposer microorganisms. This decomposer community will gradually shift as the most easily degraded plant compounds are utilized and the more recalcitrant materials begin to accumulate. Given enough time and the proper environmental conditions, most naturally occurring compounds can completely be mineralized to inorganic forms. Simultaneously with mineralization, the process of humification acts to transform a fraction of the plant residues into stable soil organic matter (SOM) or humus. For reference, Schlesinger (1990) estimated that only ˜0.7% of detritus eventually becomes stabilized into humus.Decomposition plays a key role in the cycling of most plant macro- and micronutrients and in the formation of humus. Figure 1 places the roles of detrital processing and mineralization within the context of the biogeochemical cycling of essential plant nutrients. Chapin (1991) found that while the atmosphere supplied 4% and mineral weathering supplied no nitrogen and <1% of phosphorus, internal nutrient recycling is the source for >95% of all the nitrogen and phosphorus uptake by tundra species in Barrow, Alaska. In a cool temperate forest, nutrient recycling accounted for 93%, 89%, 88%, and 65% of total sources for nitrogen, phosphorus, potassium, and calcium, respectively ( Chapin, 1991). (13K)Figure 1. A decomposition-centric biogeochemical model of nutrient cycling. Although there is significant external input (1) and output (2) from neighboring ecosystems (such as erosion), weathering of primary minerals (3), loss of secondary minerals (4), atmospheric deposition and N-fixation (5) and volatilization (6), the majority of plant-available nutrients are supplied by internal recycling through decomposition. Nutrients that are taken up by plants (7) are either consumed by fauna (8) and returned to the soil through defecation and mortality (10) or returned to the soil through litterfall and mortality (9). Detritus and humus can be immobilized into microbial biomass (11 and 13). Humus is formed by the transformation and stabilization of detrital (12) and microbial (14) compounds. During these transformations, SOM is being continually mineralized by the microorganisms (15) replenishing the inorganic nutrient pool (after Swift et al., 1979). The second major ecosystem role of decomposition is in the formation and stabilization of humus. The cycling and stabilization of SOM in the litter-soil system is presented in a conceptual model in Figure 2. Parallel with litterfall and most root turnover, detrital processing is concentrated at or near the soil surface. As labile SOM is preferentially degraded, there is a progressive shift from labile to passive SOM with increasing depth. There are three basic mechanisms for SOM accumulation in the mineral soil: bioturbation or physical mixing of the soil by burrowing animals (e.g., earthworms, gophers, etc.), in situ decomposition of roots and root exudates, and the leaching of soluble organic compounds. In the absence of bioturbation, distinct litter layers often accumulate above the mineral soil. In grasslands where the majority of net primary productivity (NPP) is allocated belowground, root inputs will dominate. In sandy soils with ample rainfall, leaching may be the major process incorporating carbon into the soil. (11K)Figure 2. Conceptual model of carbon cycling in the litter-soil system. In each horizon or depth increment, SOM is represented by three pools: labile SOM, slow SOM, and passive SOM. Inputs include aboveground litterfall and belowground root turnover and exudates, which will be distributed among the pools based on the biochemical nature of the material. Outputs from each pool include mineralization to CO2 (dashed lines), humification (labile→slow→passive), and downward transport due to leaching and physical mixing. Communition by soil fauna will accelerate the decomposition process and reveal previously inaccessible materials. Soil mixing and other disturbances can also make physically protected passive SOM available to microbial attack (passive→slow). There exists an amazing body of literature on the subject of decomposition that draws from many disciplines - including ecology, soil science, microbiology, plant physiology, biochemistry, and zoology. In this chapter, we have attempted to draw information from all of these fields to present an integrated analysis of decomposition in a biogeochemical context. We begin by reviewing the composition of detrital resources and SOM (Section 8.07.2), the organisms responsible for decomposition ( Section 8.07.3), and some methods for quantifying decomposition rates ( Section 8.07.4). This is followed by a discussion of the mechanisms behind decomposition ( Section 8.07.5), humification ( Section 8.07.6), and the controls on these processes ( Section 8.07.7). We conclude the chapter with a brief discussion on how current biogeochemical models incorporate this information ( Section 8.07.8).

Aligning observed and modelled behaviour based on workflow decomposition

NASA Astrophysics Data System (ADS)

Wang, Lu; Du, YuYue; Liu, Wei

2017-09-01

When business processes are mostly supported by information systems, the availability of event logs generated from these systems, as well as the requirement of appropriate process models are increasing. Business processes can be discovered, monitored and enhanced by extracting process-related information. However, some events cannot be correctly identified because of the explosion of the amount of event logs. Therefore, a new process mining technique is proposed based on a workflow decomposition method in this paper. Petri nets (PNs) are used to describe business processes, and then conformance checking of event logs and process models is investigated. A decomposition approach is proposed to divide large process models and event logs into several separate parts that can be analysed independently; while an alignment approach based on a state equation method in PN theory enhances the performance of conformance checking. Both approaches are implemented in programmable read-only memory (ProM). The correctness and effectiveness of the proposed methods are illustrated through experiments.

Leaf Litter Mixtures Alter Microbial Community Development: Mechanisms for Non-Additive Effects in Litter Decomposition

PubMed Central

Chapman, Samantha K.; Newman, Gregory S.; Hart, Stephen C.; Schweitzer, Jennifer A.; Koch, George W.

2013-01-01

To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate. PMID:23658639

Characteristic of root decomposition in a tropical rainforest in Sarawak, Malaysi

NASA Astrophysics Data System (ADS)

Ohashi, Mizue; Makita, Naoki; Katayam, Ayumi; Kume, Tomonori; Matsumoto, Kazuho; Khoon Kho, L.

2016-04-01

Woody roots play a significant role in forest carbon cycling, as up to 60 percent of tree photosynthetic production can be allocated to belowground. Root decay is one of the main processes of soil C dynamics and potentially relates to soil C sequestration. However, much less attention has been paid for root litter decomposition compared to the studies of leaf litter because roots are hidden from view. Previous studies have revealed that physico-chemical quality of roots, climate, and soil organisms affect root decomposition significantly. However, patterns and mechanisms of root decomposition are still poorly understood because of the high variability of root properties, field environment and potential decomposers. For example, root size would be a factor controlling decomposition rates, but general understanding of the difference between coarse and fine root decompositions is still lacking. Also, it is known that root decomposition is performed by soil animals, fungi and bacteria, but their relative importance is poorly understood. In this study, therefore, we aimed to characterize the root decomposition in a tropical rainforest in Sarawak, Malaysia, and clarify the impact of soil living organisms and root sizes on root litter decomposition. We buried soil cores with fine and coarse root litter bags in soil in Lambir Hills National Park. Three different types of soil cores that are covered by 1.5 cm plastic mesh, root-impermeable sheet (50um) and fungi-impermeable sheet (1um) were prepared. The soil cores were buried in February 2013 and collected 4 times, 134 days, 226 days, 786 days and 1151 days after the installation. We found that nearly 80 percent of the coarse root litter was decomposed after two years, whereas only 60 percent of the fine root litter was decomposed. Our results also showed significantly different ratio of decomposition between different cores, suggesting the different contribution of soil living organisms to decomposition process.

Pd-catalyzed one-pot synthesis of polysubstituted acrylamidines from isocyanides, diazo compounds, and imines.

PubMed

Yan, Xu; Liao, Jinxi; Lu, Yongzhi; Liu, Jinsong; Zeng, Youlin; Cai, Qian

2013-05-17

A novel and efficient Pd-catalyzed one-pot reaction of ethyl diazoacetate, isocyanides, and imines for the synthesis of acrylamidines was developed. The multicomponent reaction may have occurred through an unpredicted ring-opening process of the ketenimine-imine [2 + 2] intermediate to form the acrylamidine products.

Kinetic profiling of prolinate-catalyzed α-amination of aldehydes.

PubMed

Hein, Jason E; Armstrong, Alan; Blackmond, Donna G

2011-08-19

Deconvolution of the role of off-cycle species from the desired catalytic cycle leads to an optimized protocol for the prolinate-catalyzed amination of aldehydes. The scope of complex reaction networks will be greatly broadened by understanding ancillary rate processes that influence the productive catalytic pathway. © 2011 American Chemical Society

Impacts Of Long-Term Prescribed Fire On Decomposition And Litter Quality In Uneven-Aged Loblolly Pine Stands

Treesearch

Michele L. Renschin; Hal O. Liechty; Michael G. Shelton

2002-01-01

Abstract - Although fire has long been an important forest management tool in the southern United States, little is known concerning the effects of long-term fire use on nutrient cycling and decomposition. To better understand the effects of fire on these processes, decomposition rates, and foliage litter quality were quantified in a study...

Laboratory Tests to Determine the Chemical and Physical Characteristics of Propellant-Solvent-Fuel Oil Mixtures

DTIC Science & Technology

1990-02-01

Decomposition ................ 165 Part IV. Thermal Decomposition - Analytical Methodologies .............. 167 Part V. Miscellaneous...500C ................... 45 12 Differential Scanning Calorimetry Curve for the Decomposition of a Smokeless-Grade Nitrocellulose .......... 62 13 Process...cellulose backbone with nitrating acids of high water content resulted in hydrolysis of the pentosans without the desired 3 result of nitration. Furthermore

Fungal colonization and decomposition of leaves and stems of Salix arctica on deglaciated moraines in high-Arctic Canada

NASA Astrophysics Data System (ADS)

Osono, Takashi; Matsuoka, Shunsuke; Hirose, Dai; Uchida, Masaki; Kanda, Hiroshi

2014-06-01

Fungal colonization, succession, and decomposition of leaves and stems of Salix arctica were studied to estimate the roles of fungi in the decomposition processes in the high Arctic. The samples were collected from five moraines with different periods of development since deglaciation to investigate the effects of ecosystem development on the decomposition processes during the primary succession. The total hyphal lengths and the length of darkly pigmented hyphae increased during decomposition of leaves and stems and were not varied with the moraines. Four fungal morphotaxa were frequently isolated from both leaves and stems. The frequencies of occurrence of two morphotaxa varied with the decay class of leaves and/or stems. The hyphal lengths and the frequencies of occurrence of fungal morphotaxa were positively or negatively correlated with the contents of organic chemical components and nutrients in leaves and stems, suggesting the roles of fungi in chemical changes in the field. Pure culture decomposition tests demonstrated that the fungal morphotaxa were cellulose decomposers. Our results suggest that fungi took part in the chemical changes in decomposing leaves and stems even under the harsh environment of the high Arctic.

Scoring of Decomposition: A Proposed Amendment to the Method When Using a Pig Model for Human Studies.

PubMed

Keough, Natalie; Myburgh, Jolandie; Steyn, Maryna

2017-07-01

Decomposition studies often use pigs as proxies for human cadavers. However, differences in decomposition sequences/rates relative to humans have not been scientifically examined. Descriptions of five main decomposition stages (humans) were developed and refined by Galloway and later by Megyesi. However, whether these changes/processes are alike in pigs is unclear. Any differences can have significant effects when pig models are used for human PMI estimation. This study compared human decomposition models to the changes observed in pigs. Twenty pigs (50-90 kg) were decomposed over five months and decompositional features recorded. Total body scores (TBS) were calculated. Significant differences were observed during early decomposition between pigs and humans. An amended scoring system to be used in future studies was developed. Standards for PMI estimation derived from porcine models may not directly apply to humans and may need adjustment. Porcine models, however, remain valuable to study variables influencing decomposition. © 2016 American Academy of Forensic Sciences.

Theoretical studies of the decomposition mechanisms of 1,2,4-butanetriol trinitrate.

PubMed

Pei, Liguan; Dong, Kehai; Tang, Yanhui; Zhang, Bo; Yu, Chang; Li, Wenzuo

2017-12-06

Density functional theory (DFT) and canonical variational transition-state theory combined with a small-curvature tunneling correction (CVT/SCT) were used to explore the decomposition mechanisms of 1,2,4-butanetriol trinitrate (BTTN) in detail. The results showed that the γ-H abstraction reaction is the initial pathway for autocatalytic BTTN decomposition. The three possible hydrogen atom abstraction reactions are all exothermic. The rate constants for autocatalytic BTTN decomposition are 3 to 10 40 times greater than the rate constants for the two unimolecular decomposition reactions (O-NO 2 cleavage and HONO elimination). The process of BTTN decomposition can be divided into two stages according to whether the NO 2 concentration is above a threshold value. HONO elimination is the main reaction channel during the first stage because autocatalytic decomposition requires NO 2 and the concentration of NO 2 is initially low. As the reaction proceeds, the concentration of NO 2 gradually increases; when it exceeds the threshold value, the second stage begins, with autocatalytic decomposition becoming the main reaction channel.

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. © 2015 American Academy of Forensic Sciences.

Palladium-Catalyzed Borylation of Primary Alkyl Bromides

PubMed Central

Joshi-Pangu, Amruta; Ma, Xinghua; Diane, Mohamed; Iqbal, Sidra; Kribs, Robert J.; Huang, Richard; Wang, Chao-Yuan

2012-01-01

A mild Pd-catalyzed process for the borylation of alkyl bromides has been developed using bis(pinacolato)diboron as a boron source. This process accommodates the use of a wide range of functional groups on the alkyl bromide substrate. Primary bromides react with complete selectivity in the presence of a secondary bromide. The generality of this approach is demonstrated by its extension to the use of alkyl iodides and alkyl tosylates, as well as borylation reactions employing bis(neopentyl glycolato)diboron as the boron source. PMID:22774861

Ruthenium-catalyzed insertion of adjacent diol carbon atoms into C-C bonds: Entry to type II polyketides.

PubMed

Bender, Matthias; Turnbull, Ben W H; Ambler, Brett R; Krische, Michael J

2017-08-25

Current catalytic processes involving carbon-carbon bond activation rely on π-unsaturated coupling partners. Exploiting the concept of transfer hydrogenative coupling, we report a ruthenium(0)-catalyzed cycloaddition of benzocyclobutenones that functionalizes two adjacent saturated diol carbon-hydrogen bonds. These regio- and diastereoselective processes enable convergent construction of type II polyketide substructures. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Insight into litter decomposition driven by nutrient demands of symbiosis system through the hypha bridge of arbuscular mycorrhizal fungi.

PubMed

Kong, Xiangshi; Jia, Yanyan; Song, Fuqiang; Tian, Kai; Lin, Hong; Bei, Zhanlin; Jia, Xiuqin; Yao, Bei; Guo, Peng; Tian, Xingjun

2018-02-01

Arbuscular mycorrhizal fungi (AMF) play an important role in litter decomposition. This study investigated how soil nutrient level affected the process. Results showed that AMF colonization had no significant effect on litter decomposition under normal soil nutrient conditions. However, litter decomposition was accelerated significantly under lower nutrient conditions. Soil microbial biomass in decomposition system was significantly increased. Especially, in moderate lower nutrient treatment (condition of half-normal soil nutrient), litters exhibited the highest decomposition rate, AMF hypha revealed the greatest density, and enzymes (especially nitrate reductase) showed the highest activities as well. Meanwhile, the immobilization of nitrogen (N) in the decomposing litter remarkably decreased. Our results suggested that the roles AMF played in ecosystem were largely affected by soil nutrient levels. At normal soil nutrient level, AMF exhibited limited effects in promoting decomposition. When soil nutrient level decreased, the promoting effect of AMF on litter decomposition began to appear, especially on N mobilization. However, under extremely low nutrient conditions, AMF showed less influence on decomposition and may even compete with decomposer microorganisms for nutrients.

The catalytic role of tungsten electrode material in the plasmachemical activity of a pulsed corona discharge in water

NASA Astrophysics Data System (ADS)

Lukes, Petr; Clupek, Martin; Babicky, Vaclav; Sisrova, Irena; Janda, Vaclav

2011-06-01

The effects of tungsten material used as a high-voltage needle electrode on the production of hydrogen peroxide and the degradation of dimethylsulfoxide (DMSO) caused by a pulsed corona discharge in water were investigated. A reactor of needle-plate electrode geometry was used. The erosion of the tungsten electrodes by the discharge was evaluated. The yields of H2O2 production and the decomposition of DMSO by the discharge, which were obtained using the tungsten electrodes, were compared with those determined for titanium electrodes. The electrode erosion increased significantly with an increase in the solution conductivity. A large fraction (50-70%) of the eroded tungsten electrode material was released into the solution in dissolved form as tungstate WO_4^{2-} ions. A correlation between the amount of eroded tungsten material released into the solution and the chemical effects induced by the discharge was determined. Lower yields of H2O2 and a higher degradation of DMSO by the discharge were obtained using the tungsten electrodes than were determined using titanium electrodes. Tungstate ions were shown to play a dominant role in the decomposition of H2O2, which was produced by the discharge using a tungsten electrode. The higher degradation of DMSO that was determined for tungsten was attributed to the tungstate-catalyzed oxidation of DMSO by H2O2, in addition to the oxidation of DMSO by OH radicals. Such a mechanism was supported by the detection of degradation by-products of DMSO (methanesulfonate, sulfate and dimethyl sulfone). The catalytic role of tungstate ions in the plasmachemical activity of the discharge generated using a tungsten electrode was also demonstrated on a pH-dependent decomposition of H2O2 and DMSO.

Lysosome-controlled efficient ROS overproduction against cancer cells with a high pH-responsive catalytic nanosystem

NASA Astrophysics Data System (ADS)

Fu, Jingke; Shao, Yiran; Wang, Liyao; Zhu, Yingchun

2015-04-01

Excess reactive oxygen species (ROS) have been proved to damage cancer cells efficiently. ROS overproduction is thus greatly desirable for cancer therapy. To date, ROS production is generally uncontrollable and outside cells, which always bring severe side-effects in the vasculature. Since most ROS share a very short half-life and primarily react close to their site of formation, it would be more efficient if excess ROS are controllably produced inside cancer cells. Herein, we report an efficient lysosome-controlled ROS overproduction via a pH-responsive catalytic nanosystem (FeOx-MSNs), which catalyze the decomposition of H2O2 to produce considerable ROS selectively inside the acidic lysosomes (pH 5.0) of cancer cells. After a further incorporation of ROS-sensitive TMB into the nanosystem (FeOx-MSNs-TMB), both a distinct cell labeling and an efficient death of breast carcinoma cells are obtained. This lysosome-controlled efficient ROS overproduction suggests promising applications in cancer treatments.Excess reactive oxygen species (ROS) have been proved to damage cancer cells efficiently. ROS overproduction is thus greatly desirable for cancer therapy. To date, ROS production is generally uncontrollable and outside cells, which always bring severe side-effects in the vasculature. Since most ROS share a very short half-life and primarily react close to their site of formation, it would be more efficient if excess ROS are controllably produced inside cancer cells. Herein, we report an efficient lysosome-controlled ROS overproduction via a pH-responsive catalytic nanosystem (FeOx-MSNs), which catalyze the decomposition of H2O2 to produce considerable ROS selectively inside the acidic lysosomes (pH 5.0) of cancer cells. After a further incorporation of ROS-sensitive TMB into the nanosystem (FeOx-MSNs-TMB), both a distinct cell labeling and an efficient death of breast carcinoma cells are obtained. This lysosome-controlled efficient ROS overproduction suggests promising applications in cancer treatments. Electronic supplementary information (ESI) available: Experimental section, supplementary figures and characterization of as-prepared compounds. See DOI: 10.1039/c5nr00706b

A compositional approach to building applications in a computational environment

NASA Astrophysics Data System (ADS)

Roslovtsev, V. V.; Shumsky, L. D.; Wolfengagen, V. E.

2014-04-01

The paper presents an approach to creating an applicative computational environment to feature computational processes and data decomposition, and a compositional approach to application building. The approach in question is based on the notion of combinator - both in systems with variable binding (such as λ-calculi) and those allowing programming without variables (combinatory logic style). We present a computation decomposition technique based on objects' structural decomposition, with the focus on computation decomposition. The computational environment's architecture is based on a network with nodes playing several roles simultaneously.

Thermal decomposition kinetics of hydrazinium cerium 2,3-Pyrazinedicarboxylate hydrate: a new precursor for CeO2.

PubMed

Premkumar, Thathan; Govindarajan, Subbiah; Coles, Andrew E; Wight, Charles A

2005-04-07

The thermal decomposition kinetics of N(2)H(5)[Ce(pyrazine-2,3-dicarboxylate)(2)(H(2)O)] (Ce-P) have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), for the first time; TGA analysis reveals an oxidative decomposition process yielding CeO(2) as the final product with an activation energy of approximately 160 kJ mol(-1). This complex may be used as a precursor to fine particle cerium oxides due to its low temperature of decomposition.

Pursuing reliable thermal analysis techniques for energetic materials: decomposition kinetics and thermal stability of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50).

PubMed

Muravyev, Nikita V; Monogarov, Konstantin A; Asachenko, Andrey F; Nechaev, Mikhail S; Ananyev, Ivan V; Fomenkov, Igor V; Kiselev, Vitaly G; Pivkina, Alla N

2016-12-21

Thermal decomposition of a novel promising high-performance explosive dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) was studied using a number of thermal analysis techniques (thermogravimetry, differential scanning calorimetry, and accelerating rate calorimetry, ARC). To obtain more comprehensive insight into the kinetics and mechanism of TKX-50 decomposition, a variety of complementary thermoanalytical experiments were performed under various conditions. Non-isothermal and isothermal kinetics were obtained at both atmospheric and low (up to 0.3 Torr) pressures. The gas products of thermolysis were detected in situ using IR spectroscopy, and the structure of solid-state decomposition products was determined by X-ray diffraction and scanning electron microscopy. Diammonium 5,5'-bistetrazole-1,1'-diolate (ABTOX) was directly identified to be the most important intermediate of the decomposition process. The important role of bistetrazole diol (BTO) in the mechanism of TKX-50 decomposition was also rationalized by thermolysis experiments with mixtures of TKX-50 and BTO. Several widely used thermoanalytical data processing techniques (Kissinger, isoconversional, formal kinetic approaches, etc.) were independently benchmarked against the ARC data, which are more germane to the real storage and application conditions of energetic materials. Our study revealed that none of the Arrhenius parameters reported before can properly describe the complex two-stage decomposition process of TKX-50. In contrast, we showed the superior performance of the isoconversional methods combined with isothermal measurements, which yielded the most reliable kinetic parameters of TKX-50 thermolysis. In contrast with the existing reports, the thermal stability of TKX-50 was determined in the ARC experiments to be lower than that of hexogen, but close to that of hexanitrohexaazaisowurtzitane (CL-20).

Soil respiration in the cold desert environment of the Colorado Plateau (USA): Abiotic regulators and thresholds

USGS Publications Warehouse

Fernandez, D.P.; Neff, J.C.; Belnap, J.; Reynolds, R.L.

2006-01-01

Decomposition is central to understanding ecosystem carbon exchange and nutrient-release processes. Unlike mesic ecosystems, which have been extensively studied, xeric landscapes have received little attention; as a result, abiotic soil-respiration regulatory processes are poorly understood in xeric environments. To provide a more complete and quantitative understanding about how abiotic factors influence soil respiration in xeric ecosystems, we conducted soil- respiration and decomposition-cloth measurements in the cold desert of southeast Utah. Our study evaluated when and to what extent soil texture, moisture, temperature, organic carbon, and nitrogen influence soil respiration and examined whether the inverse-texture hypothesis applies to decomposition. Within our study site, the effect of texture on moisture, as described by the inverse texture hypothesis, was evident, but its effect on decomposition was not. Our results show temperature and moisture to be the dominant abiotic controls of soil respiration. Specifically, temporal offsets in temperature and moisture conditions appear to have a strong control on soil respiration, with the highest fluxes occurring in spring when temperature and moisture were favorable. These temporal offsets resulted in decomposition rates that were controlled by soil moisture and temperature thresholds. The highest fluxes of CO2 occurred when soil temperature was between 10 and 16??C and volumetric soil moisture was greater than 10%. Decomposition-cloth results, which integrate decomposition processes across several months, support the soil-respiration results and further illustrate the seasonal patterns of high respiration rates during spring and low rates during summer and fall. Results from this study suggest that the parameters used to predict soil respiration in mesic ecosystems likely do not apply in cold-desert environments. ?? Springer 2006.

Coupling experimental data and a prototype model to probe the physical and chemical processes of 2,4-dinitroimidazole solid-phase thermal decomposition

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

Behrens, R.; Minier, L.; Bulusu, S.

1998-12-31

The time-dependent, solid-phase thermal decomposition behavior of 2,4-dinitroimidazole (2,4-DNI) has been measured utilizing simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) methods. The decomposition products consist of gaseous and non-volatile polymeric products. The temporal behavior of the gas formation rates of the identified products indicate that the overall thermal decomposition process is complex. In isothermal experiments with 2,4-DNI in the solid phase, four distinguishing features are observed: (1) elevated rates of gas formation are observed during the early stages of the decomposition, which appear to be correlated to the presence of exogenous water in the sample; (2) this is followed bymore » a period of relatively constant rates of gas formation; (3) next, the rates of gas formation accelerate, characteristic of an autocatalytic reaction; (4) finally, the 2,4-DNI is depleted and gaseous decomposition products continue to evolve at a decreasing rate. A physicochemical and mathematical model of the decomposition of 2,4-DNI has been developed and applied to the experimental results. The first generation of this model is described in this paper. Differences between the first generation of the model and the experimental data collected under different conditions suggest refinements for the next generation of the model.« less

Young Children's Thinking About Decomposition: Early Modeling Entrees to Complex Ideas in Science

NASA Astrophysics Data System (ADS)

Ero-Tolliver, Isi; Lucas, Deborah; Schauble, Leona

2013-10-01

This study was part of a multi-year project on the development of elementary students' modeling approaches to understanding the life sciences. Twenty-three first grade students conducted a series of coordinated observations and investigations on decomposition, a topic that is rarely addressed in the early grades. The instruction included in-class observations of different types of soil and soil profiling, visits to the school's compost bin, structured observations of decaying organic matter of various kinds, study of organisms that live in the soil, and models of environmental conditions that affect rates of decomposition. Both before and after instruction, students completed a written performance assessment that asked them to reason about the process of decomposition. Additional information was gathered through one-on-one interviews with six focus students who represented variability of performance across the class. During instruction, researchers collected video of classroom activity, student science journal entries, and charts and illustrations produced by the teacher. After instruction, the first-grade students showed a more nuanced understanding of the composition and variability of soils, the role of visible organisms in decomposition, and environmental factors that influence rates of decomposition. Through a variety of representational devices, including drawings, narrative records, and physical models, students came to regard decomposition as a process, rather than simply as an end state that does not require explanation.

Effect of pressure on rate of burning /decomposition with flame/ of liquid hydrazine.

NASA Technical Reports Server (NTRS)

Antoine, A. C.

1966-01-01

Liquid hydrazine decomposition process to determine what chemical or physical changes may be occurring that cause breaks in burning rate/ pressure curves, measuring flame temperature and light emission

Ab initio kinetics of gas phase decomposition reactions.

PubMed

Sharia, Onise; Kuklja, Maija M

2010-12-09

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.

Microbial community assembly and metabolic function during mammalian corpse decomposition.

PubMed

Metcalf, Jessica L; Xu, Zhenjiang Zech; Weiss, Sophie; Lax, Simon; Van Treuren, Will; Hyde, Embriette R; Song, Se Jin; Amir, Amnon; Larsen, Peter; Sangwan, Naseer; Haarmann, Daniel; Humphrey, Greg C; Ackermann, Gail; Thompson, Luke R; Lauber, Christian; Bibat, Alexander; Nicholas, Catherine; Gebert, Matthew J; Petrosino, Joseph F; Reed, Sasha C; Gilbert, Jack A; Lynne, Aaron M; Bucheli, Sibyl R; Carter, David O; Knight, Rob

2016-01-08

Vertebrate corpse decomposition provides an important stage in nutrient cycling in most terrestrial habitats, yet microbially mediated processes are poorly understood. Here we combine deep microbial community characterization, community-level metabolic reconstruction, and soil biogeochemical assessment to understand the principles governing microbial community assembly during decomposition of mouse and human corpses on different soil substrates. We find a suite of bacterial and fungal groups that contribute to nitrogen cycling and a reproducible network of decomposers that emerge on predictable time scales. Our results show that this decomposer community is derived primarily from bulk soil, but key decomposers are ubiquitous in low abundance. Soil type was not a dominant factor driving community development, and the process of decomposition is sufficiently reproducible to offer new opportunities for forensic investigations. Copyright © 2016, American Association for the Advancement of Science.

Basic dye decomposition kinetics in a photocatalytic slurry reactor.

PubMed

Wu, Chun-Hsing; Chang, Hung-Wei; Chern, Jia-Ming

2006-09-01

Wastewater effluent from textile plants using various dyes is one of the major water pollutants to the environment. Traditional chemical, physical and biological processes for treating textile dye wastewaters have disadvantages such as high cost, energy waste and generating secondary pollution during the treatment process. The photocatalytic process using TiO2 semiconductor particles under UV light illumination has been shown to be potentially advantageous and applicable in the treatment of wastewater pollutants. In this study, the dye decomposition kinetics by nano-size TiO2 suspension at natural solution pH was experimentally studied by varying the agitation speed (50-200 rpm), TiO2 suspension concentration (0.25-1.71 g/L), initial dye concentration (10-50 ppm), temperature (10-50 degrees C), and UV power intensity (0-96 W). The experimental results show the agitation speed, varying from 50 to 200 rpm, has a slight influence on the dye decomposition rate and the pH history; the dye decomposition rate increases with the TiO2 suspension concentration up to 0.98 g/L, then decrease with increasing TiO2 suspension concentration; the initial dye decomposition rate increases with the initial dye concentration up to a certain value depending upon the temperature, then decreases with increasing initial dye concentration; the dye decomposition rate increases with the UV power intensity up to 64 W to reach a plateau. Kinetic models have been developed to fit the experimental kinetic data well.

Enzyme Activities at Different Stages of Plant Biomass Decomposition in Three Species of Fungus-Growing Termites

PubMed Central

Pedersen, Kristine S. K.; Aanen, Duur K.

2017-01-01

ABSTRACT Fungus-growing termites rely on mutualistic fungi of the genus Termitomyces and gut microbes for plant biomass degradation. Due to a certain degree of symbiont complementarity, this tripartite symbiosis has evolved as a complex bioreactor, enabling decomposition of nearly any plant polymer, likely contributing to the success of the termites as one of the main plant decomposers in the Old World. In this study, we evaluated which plant polymers are decomposed and which enzymes are active during the decomposition process in two major genera of fungus-growing termites. We found a diversity of active enzymes at different stages of decomposition and a consistent decrease in plant components during the decomposition process. Furthermore, our findings are consistent with the hypothesis that termites transport enzymes from the older mature parts of the fungus comb through young worker guts to freshly inoculated plant substrate. However, preliminary fungal RNA sequencing (RNA-seq) analyses suggest that this likely transport is supplemented with enzymes produced in situ. Our findings support that the maintenance of an external fungus comb, inoculated with an optimal mixture of plant material, fungal spores, and enzymes, is likely the key to the extraordinarily efficient plant decomposition in fungus-growing termites. IMPORTANCE Fungus-growing termites have a substantial ecological footprint in the Old World (sub)tropics due to their ability to decompose dead plant material. Through the establishment of an elaborate plant biomass inoculation strategy and through fungal and bacterial enzyme contributions, this farming symbiosis has become an efficient and versatile aerobic bioreactor for plant substrate conversion. Since little is known about what enzymes are expressed and where they are active at different stages of the decomposition process, we used enzyme assays, transcriptomics, and plant content measurements to shed light on how this decomposition of plant substrate is so effectively accomplished. PMID:29269491

Enzyme Activities at Different Stages of Plant Biomass Decomposition in Three Species of Fungus-Growing Termites.

PubMed

da Costa, Rafael R; Hu, Haofu; Pilgaard, Bo; Vreeburg, Sabine M E; Schückel, Julia; Pedersen, Kristine S K; Kračun, Stjepan K; Busk, Peter K; Harholt, Jesper; Sapountzis, Panagiotis; Lange, Lene; Aanen, Duur K; Poulsen, Michael

2018-03-01

Fungus-growing termites rely on mutualistic fungi of the genus Termitomyces and gut microbes for plant biomass degradation. Due to a certain degree of symbiont complementarity, this tripartite symbiosis has evolved as a complex bioreactor, enabling decomposition of nearly any plant polymer, likely contributing to the success of the termites as one of the main plant decomposers in the Old World. In this study, we evaluated which plant polymers are decomposed and which enzymes are active during the decomposition process in two major genera of fungus-growing termites. We found a diversity of active enzymes at different stages of decomposition and a consistent decrease in plant components during the decomposition process. Furthermore, our findings are consistent with the hypothesis that termites transport enzymes from the older mature parts of the fungus comb through young worker guts to freshly inoculated plant substrate. However, preliminary fungal RNA sequencing (RNA-seq) analyses suggest that this likely transport is supplemented with enzymes produced in situ Our findings support that the maintenance of an external fungus comb, inoculated with an optimal mixture of plant material, fungal spores, and enzymes, is likely the key to the extraordinarily efficient plant decomposition in fungus-growing termites. IMPORTANCE Fungus-growing termites have a substantial ecological footprint in the Old World (sub)tropics due to their ability to decompose dead plant material. Through the establishment of an elaborate plant biomass inoculation strategy and through fungal and bacterial enzyme contributions, this farming symbiosis has become an efficient and versatile aerobic bioreactor for plant substrate conversion. Since little is known about what enzymes are expressed and where they are active at different stages of the decomposition process, we used enzyme assays, transcriptomics, and plant content measurements to shed light on how this decomposition of plant substrate is so effectively accomplished. Copyright © 2018 da Costa et al.

Detritus Quality Controls Macrophyte Decomposition under Different Nutrient Concentrations in a Eutrophic Shallow Lake, North China

PubMed Central

Li, Xia; Cui, Baoshan; Yang, Qichun; Tian, Hanqin; Lan, Yan; Wang, Tingting; Han, Zhen

2012-01-01

Macrophyte decomposition is important for carbon and nutrient cycling in lake ecosystems. Currently, little is known about how this process responds to detritus quality and water nutrient conditions in eutrophic shallow lakes in which incomplete decomposition of detritus accelerates the lake terrestrialization process. In this study, we investigated the effects of detritus quality and water nutrient concentrations on macrophyte decomposition in Lake Baiyangdian, China, by analyzing the decomposition of three major aquatic plants at three sites with different pollution intensities (low, medium, and high pollution sites). Detritus quality refers to detritus nutrient contents as well as C∶N, C∶P, and N∶P mass ratios in this study. Effects of detritus mixtures were tested by combining pairs of representative macrophytes at ratios of 75∶25, 50∶50 and 25∶75 (mass basis). The results indicate that the influence of species types on decomposition was stronger than that of site conditions. Correlation analysis showed that mass losses at the end of the experimental period were significantly controlled by initial detritus chemistry, especially by the initial phosphorus (P) content, carbon to nitrogen (C∶N), and carbon to phosphorus (C∶P) mass ratios in the detritus. The decomposition processes were also influenced by water chemistry. The NO3-N and NH4-N concentrations in the lake water retarded detritus mass loss at the low and high pollution sites, respectively. Net P mineralization in detritus was observed at all sites and detritus P release at the high pollution site was slower than at the other two sites. Nonadditive effects of mixtures tended to be species specific due to the different nutrient contents in each species. Results suggest that the nonadditive effects varied significantly among different sites, indicating that interactions between the detritus quality in species mixtures and site water chemistry may be another driver controlling decomposition in eutrophic shallow lakes. PMID:22848699

The neural basis of novelty and appropriateness in processing of creative chunk decomposition.

PubMed

Huang, Furong; Fan, Jin; Luo, Jing

2015-06-01

Novelty and appropriateness have been recognized as the fundamental features of creative thinking. However, the brain mechanisms underlying these features remain largely unknown. In this study, we used event-related functional magnetic resonance imaging (fMRI) to dissociate these mechanisms in a revised creative chunk decomposition task in which participants were required to perform different types of chunk decomposition that systematically varied in novelty and appropriateness. We found that novelty processing involved functional areas for procedural memory (caudate), mental rewarding (substantia nigra, SN), and visual-spatial processing, whereas appropriateness processing was mediated by areas for declarative memory (hippocampus), emotional arousal (amygdala), and orthography recognition. These results indicate that non-declarative and declarative memory systems may jointly contribute to the two fundamental features of creative thinking. Copyright © 2015 Elsevier Inc. All rights reserved.

Rhodium-Catalyzed Acyloxy Migration of Propargylic Esters in Cycloadditions, Inspiration from Recent “Gold Rush”

PubMed Central

Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M.

2012-01-01

Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative addition, migratory insertion, and reductive elimination may lead to ample new opportunities for the design of new reactions. This tutorial review summarizes recent developments in Rh-catalyzed 1,3- and 1,2-acyloxy migration of propargylic esters in a number of cycloaddition reactions. Related Au- and Pt-catalyzed cycloadditions involving acyloxy migration are also discussed. PMID:22895533

Transesterification of oil mixtures catalyzed by microencapsulated cutinase in reversed micelles.

PubMed

Badenes, Sara M; Lemos, Francisco; Cabral, Joaquim M S

2010-03-01

Recombinant cutinase from Fusarium solani pisi was used to catalyze the transesterification reaction between a mixture of triglycerides (oils) and methanol in reversed micelles of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in isooctane for the purposes of producing biodiesel. The use of a bi-phase lipase-catalyzed system brings advantages in terms of catalyst re-use and the control of water activity in the medium and around the enzyme micro-environment. Small-scale batch studies were performed to study the influence of the initial enzyme and alcohol concentrations, and the substrates molar ratio. Conversions in excess of 75 were obtained with reaction times under 24 h, which makes this enzymatic process highly competitive when compared to similar lipase catalyzed reactions for biodiesel production using methanol.

Biodiesel Production using Heterogeneous Catalyst in CSTR: Sensitivity Analysis and Optimization

NASA Astrophysics Data System (ADS)

Keong, L. S.; Patle, D. S.; Shukor, S. R.; Ahmad, Z.

2016-03-01

Biodiesel as a renewable fuel has emerged as a potential replacement for petroleum-based diesels. Heterogeneous catalyst has become the focus of researches in biodiesel production with the intention to overcome problems associated with homogeneous catalyzed processes. The simulation of heterogeneous catalyzed biodiesel production has not been thoroughly studied. Hence, a simulation of carbon-based solid acid catalyzed biodiesel production from waste oil with high FFA content (50 weight%) was developed in the present work to study the feasibility and potential of the simulated process. The simulated process produces biodiesel through simultaneous transesterification and esterification with the consideration of reaction kinetics. The developed simulation is feasible and capable to produce 2.81kmol/hr of FAME meeting the international standard (EN 14214). Yields of 68.61% and 97.19% are achieved for transesterification and esterification respectively. Sensitivity analyses of FFA composition in waste oil, methanol to oil ratio, reactor pressure and temperature towards FAME yield from both reactions were carried out. Optimization of reactor temperature was done to maximize FAME products.

Application of hydrometallurgy techniques in quartz processing and purification: a review

NASA Astrophysics Data System (ADS)

Lin, Min; Lei, Shaomin; Pei, Zhenyu; Liu, Yuanyuan; Xia, Zhangjie; Xie, Feixiang

2018-04-01

Although there have been numerous studies on separation and purification of metallic minerals by hydrometallurgy techniques, applications of the chemical techniques in separation and purification of non-metallic minerals are rarely reported. This paper reviews disparate areas of study into processing and purification of quartz (typical non-metallic ore) in an attempt to summarize current work, as well as to suggest potential for future consolidation in the field. The review encompasses chemical techniques of the quartz processing including situations, progresses, leaching mechanism, scopes of application, advantages and drawbacks of micro-bioleaching, high temperature leaching, high temperature pressure leaching and catalyzed high temperature pressure leaching. Traditional leaching techniques including micro-bioleaching and high temperature leaching are unequal to demand of modern glass industry for quality of quartz concentrate because the quartz products has to be further processed. High temperature pressure leaching and catalyzed high temperature pressure leaching provide new ways to produce high-grade quartz sand with only one process and lower acid consumption. Furthermore, the catalyzed high temperature pressure leaching realizes effective purification of quartz with extremely low acid consumption (no using HF or any fluoride). It is proposed that, by integrating the different chemical processes of quartz processing and expounding leaching mechanisms and scopes of application, the research field as a monopolized industry would benefit.

Selectively improving the bio-oil quality by catalytic fast pyrolysis of heavy-metal-polluted biomass: take copper (Cu) as an example.

PubMed

Liu, Wu-Jun; Tian, Ke; Jiang, Hong; Zhang, Xue-Song; Ding, Hong-Sheng; Yu, Han-Qing

2012-07-17

Heavy-metal-polluted biomass derived from phytoremediation or biosorption is widespread and difficult to be disposed of. In this work, simultaneous conversion of the waste woody biomass into bio-oil and recovery of Cu in a fast pyrolysis reactor were investigated. The results show that Cu can effectively catalyze the thermo-decomposition of biomass. Both the yield and high heating value (HHV) of the Cu-polluted fir sawdust biomass (Cu-FSD) derived bio-oil are significantly improved compared with those of the fir sawdust (FSD) derived bio-oil. The results of UV-vis and (1)H NMR spectra of bio-oil indicate pyrolytic lignin is further decomposed into small-molecular aromatic compounds by the catalysis of Cu, which is in agreement with the GC-MS results that the fractions of C7-C10 compounds in the bio-oil significantly increase. Inductively coupled plasma-atomic emission spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy analyses of the migration and transformation of Cu in the fast pyrolysis process show that more than 91% of the total Cu in the Cu-FSD is enriched in the char in the form of zerovalent Cu with a face-centered cubic crystalline phase. This study gives insight into catalytic fast pyrolysis of heavy metals, and demonstrates the technical feasibility of an eco-friendly process for disposal of heavy-metal-polluted biomass.

Wood decomposition following clearcutting at Coweeta Hydrologic Laboratory

Treesearch

Kim G. Mattson; Wayne T. Swank

2014-01-01

Most of the forest on Watershed (WS) 7 was cut and ledt on site to decompose. This Chapter describes the rate and manner of wood decomposition and also quantifies the fluxes from decaying wood to the forest floor on WS 7. In doing so, we make the case that wood and its process of decomposition contributes to ecosystem stability. We also review some of the history of...

Decomposition rate comparisons between frequently burned and unburned areas of uneven-aged loblolly pine stands in southeastern Arkansas

Treesearch

Miclele Renschin; Hal O. Leichty; Michael G. Shelton

2001-01-01

Although fire has been used extensively over long periods of time in loblolly pine (Pinis taeda L.) ecosystems, little is known concerning the effects of frequent fire use on nutrient cycling and decomposition. To better understand the long-term effects of fire on these processes, foliar litter decomposition rates were quantified in a study...

Kinetic Behavior of Exchange-Driven Growth with Catalyzed-Birth Processes

NASA Astrophysics Data System (ADS)

Wang, Hai-Feng; Lin, Zhen-Quan; Kong, Xiang-Mu

2006-12-01

Two catalyzed-birth models of n-species (n>=2) aggregates with exchange-driven growth processes are proposed and compared. In the first one, the exchange reaction occurs between any two aggregates Amk and Amj of the same species with the rate kernels Km(k,j) = Kmkj (m = 1,2,...,n, n>=2), and aggregates of An species catalyze a monomer-birth of Al species (l = 1,2,...,n-1) with the catalysis rate kernel Jl(k,j) = Jlkjυ. The kinetic behaviors are investigated by means of the mean-field theory. We find that the evolution behavior of aggregate-size distribution alk(t) of Al species depends crucially on the value of the catalysis rate parameter υ: (i) alk(t) obeys the conventional scaling law in the case of υ<=0, (ii) alk(t) satisfies a modified scaling form in the case of υ>0. In the second model, the mechanism of monomer-birth of An-species catalyzed by Al species is added on the basis of the first model, that is, the aggregates of Al and An species catalyze each other to cause monomer-birth. The kinetic behaviors of Al and An species are found to fall into two categories for the different υ: (i) growth obeying conventional scaling form with υ<=0, (ii) gelling at finite time with υ>0.

Functional Dissection of the Bipartite Active Site of the Class I Coenzyme A (CoA)-Transferase Succinyl-CoA:Acetate CoA-Transferase.

PubMed

Murphy, Jesse R; Mullins, Elwood A; Kappock, T Joseph

2016-01-01

Coenzyme A (CoA)-transferases catalyze the reversible transfer of CoA from acyl-CoA thioesters to free carboxylates. Class I CoA-transferases produce acylglutamyl anhydride intermediates that undergo attack by CoA thiolate on either the internal or external carbonyl carbon atoms, forming distinct tetrahedral intermediates <3 Å apart. In this study, crystal structures of succinyl-CoA:acetate CoA-transferase (AarC) from Acetobacter aceti are used to examine how the Asn347 carboxamide stabilizes the internal oxyanion intermediate. A structure of the active mutant AarC-N347A bound to CoA revealed both solvent replacement of the missing contact and displacement of the adjacent Glu294, indicating that Asn347 both polarizes and orients the essential glutamate. AarC was crystallized with the nonhydrolyzable acetyl-CoA (AcCoA) analog dethiaacetyl-CoA (1a) in an attempt to trap a closed enzyme complex containing a stable analog of the external oxyanion intermediate. One active site contained an acetylglutamyl anhydride adduct and truncated 1a, an unexpected result hinting at an unprecedented cleavage of the ketone moiety in 1a. Solution studies confirmed that 1a decomposition is accompanied by production of near-stoichiometric acetate, in a process that seems to depend on microbial contamination but not AarC. A crystal structure of AarC bound to the postulated 1a truncation product (2a) showed complete closure of one active site per dimer but no acetylglutamyl anhydride, even with acetate added. These findings suggest that an activated acetyl donor forms during 1a decomposition; a working hypothesis involving ketone oxidation is offered. The ability of 2a to induce full active site closure furthermore suggests that it subverts a system used to impede inappropriate active site closure on unacylated CoA.

Functional Dissection of the Bipartite Active Site of the Class I Coenzyme A (CoA)-Transferase Succinyl-CoA:Acetate CoA-Transferase

PubMed Central

Murphy, Jesse R.; Mullins, Elwood A.; Kappock, T. Joseph

2016-01-01

Coenzyme A (CoA)-transferases catalyze the reversible transfer of CoA from acyl-CoA thioesters to free carboxylates. Class I CoA-transferases produce acylglutamyl anhydride intermediates that undergo attack by CoA thiolate on either the internal or external carbonyl carbon atoms, forming distinct tetrahedral intermediates <3 Å apart. In this study, crystal structures of succinyl-CoA:acetate CoA-transferase (AarC) from Acetobacter aceti are used to examine how the Asn347 carboxamide stabilizes the internal oxyanion intermediate. A structure of the active mutant AarC-N347A bound to CoA revealed both solvent replacement of the missing contact and displacement of the adjacent Glu294, indicating that Asn347 both polarizes and orients the essential glutamate. AarC was crystallized with the nonhydrolyzable acetyl-CoA (AcCoA) analog dethiaacetyl-CoA (1a) in an attempt to trap a closed enzyme complex containing a stable analog of the external oxyanion intermediate. One active site contained an acetylglutamyl anhydride adduct and truncated 1a, an unexpected result hinting at an unprecedented cleavage of the ketone moiety in 1a. Solution studies confirmed that 1a decomposition is accompanied by production of near-stoichiometric acetate, in a process that seems to depend on microbial contamination but not AarC. A crystal structure of AarC bound to the postulated 1a truncation product (2a) showed complete closure of one active site per dimer but no acetylglutamyl anhydride, even with acetate added. These findings suggest that an activated acetyl donor forms during 1a decomposition; a working hypothesis involving ketone oxidation is offered. The ability of 2a to induce full active site closure furthermore suggests that it subverts a system used to impede inappropriate active site closure on unacylated CoA. PMID:27242998

Functional dissection of the bipartite active site of the class I coenzyme A (CoA)-transferase succinyl-CoA:acetate CoA-transferase

DOE PAGES

Murphy, Jesse R.; Mullins, Elwood A.; Kappock, T. Joseph

2016-05-23

Coenzyme A (CoA)-transferases catalyze the reversible transfer of CoA from acyl-CoA thioesters to free carboxylates. Class I CoA-transferases produce acylglutamyl anhydride intermediates that undergo attack by CoA thiolate on either the internal or external carbonyl carbon atoms, forming distinct tetrahedral intermediates <3 Å apart. Here in this study, crystal structures of succinyl-CoA:acetate CoA-transferase (AarC) from Acetobacter aceti are used to examine how the Asn347 carboxamide stabilizes the internal oxyanion intermediate. A structure of the active mutant AarC-N347A bound to CoA revealed both solvent replacement of the missing contact and displacement of the adjacent Glu294, indicating that Asn347 both polarizes andmore » orients the essential glutamate. AarC was crystallized with the nonhydrolyzable acetyl-CoA (AcCoA) analog dethiaacetyl-CoA (1a) in an attempt to trap a closed enzyme complex containing a stable analog of the external oxyanion intermediate. One active site contained an acetylglutamyl anhydride adduct and truncated 1a, an unexpected result hinting at an unprecedented cleavage of the ketone moiety in 1a. Solution studies confirmed that 1a decomposition is accompanied by production of near-stoichiometric acetate, in a process that seems to depend on microbial contamination but not AarC. A crystal structure of AarC bound to the postulated 1a truncation product (2a) showed complete closure of one active site per dimer but no acetylglutamyl anhydride, even with acetate added. These findings suggest that an activated acetyl donor forms during 1a decomposition; a working hypothesis involving ketone oxidation is offered. Finally, the ability of 2a to induce full active site closure furthermore suggests that it subverts a system used to impede inappropriate active site closure on unacylated CoA.« less

A procedure for the assessment of the toxicity of intermediates and products formed during the accidental thermal decomposition of a chemical species.

PubMed

Di Somma, Ilaria; Pollio, Antonino; Pinto, Gabriele; De Falco, Maria; Pizzo, Elio; Andreozzi, Roberto

2010-04-15

The knowledge of the substances which form when a molecule undergoes chemical reactions under unusual conditions is required by European legislation to evaluate the risks associated with an industrial chemical process. A thermal decomposition is often the result of a loss of control of the process which leads to the formation of many substances in some cases not easily predictable. The evaluation of the change of an overall toxicity passing from the parent compound to the mixture of its thermal decomposition products has been already proposed as a practical approach to this problem when preliminary indications about the temperature range in which the molecule decomposes are available. A new procedure is proposed in this work for the obtainment of the mixtures of thermal decomposition products also when there is no previous information about the thermal behaviour of investigated molecules. A scanning calorimetric run that is aimed to identify the onset temperature of the decomposition process is coupled to an isoperibolic one in order to obtain and collect the products. An algal strain is adopted for toxicological assessments of chemical compounds and mixtures. An extension of toxicological investigations to human cells is also attempted. 2009 Elsevier B.V. All rights reserved.

Fe0 catalyzed photo-Fenton process to detoxify the biodegraded products of azo dye Mordant Yellow 10.

PubMed

Brindha, R; Muthuselvam, P; Senthilkumar, S; Rajaguru, P

2018-06-01

Inspired by the efficiency of the photo-Fenton process on oxidation of organic pollutants, we herein present the feasibility of visible light driven photo-Fenton process as a post treatment of biological method for the effective degradation and detoxification of monoazo dye Mordant Yellow 10 (MY10). Anaerobic degradation of MY10 by Pseudomonas aeroginosa formed aromatic amines which were further degraded in the subsequent Fe catalyzed photo-Fenton process carried out at pH 3.0, with iron shavings and H 2 O 2 under blue LED light illumination. LC-MS and stoichiometric analysis confirmed that reductive azo bond cleavage was the major reaction in anaerobic bacterial degradation of MY10 producing 4-amino benzene sulfonic acid (4-ABS) and 5-amino salicylic acid (5-ASA) which were further degraded into hydroxyl amines, nitroso and di/tri carboxylic acids by the photo-Fenton process. Toxicity studies with human small cell lung cancer A549 cells provide evidence that incorporation of Fe 0 catalyzed photo-Fenton step after anaerobic bacterial treatment improved the mineralization and detoxification of MY10 dye. Copyright © 2018 Elsevier Ltd. All rights reserved.

Method for facilitating catalyzed oxidation reactions, device for facilitating catalyzed oxidation reactions

DOEpatents

Beuhler, Robert J [East Moriches, NY; White, Michael G [Blue Point, NY; Hrbek, Jan [Rocky Point, NY

2006-08-15

A catalytic process for the oxidation of organic. Oxygen is loaded into a metal foil by heating the foil while in contact with an oxygen-containing fluid. After cooling the oxygen-activated foil to room temperature, oxygen diffuses through the foil and oxidizes reactants exposed to the other side of the foil.

EFFECTS OF AQUATIC HUMIC SUBSTANCES ON ANALYSIS FOR HYDROGEN PEROXIDE USING PEROXIDASE-CATALYZED OXIDATIONS OF TRIARYLMETHANES OR P-HYDROXYPENYLACETIC ACID (JOURNAL VERSION)

EPA Science Inventory

A sensitive procedure is described for trace analysis of hydrogen peroxide in water. The process involves the peroxide-catalyzed oxidation of the leuco forms of two dyes, crystal violet and malachite green. The sensitivity of this procedure, as well as of another procedure based ...

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

2008-09-04

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.

Analytical separations of mammalian decomposition products for forensic science: a review.

PubMed

Swann, L M; Forbes, S L; Lewis, S W

2010-12-03

The study of mammalian soft tissue decomposition is an emerging area in forensic science, with a major focus of the research being the use of various chemical and biological methods to study the fate of human remains in the environment. Decomposition of mammalian soft tissue is a postmortem process that, depending on environmental conditions and physiological factors, will proceed until complete disintegration of the tissue. The major stages of decomposition involve complex reactions which result in the chemical breakdown of the body's main constituents; lipids, proteins, and carbohydrates. The first step to understanding this chemistry is identifying the compounds present in decomposition fluids and determining when they are produced. This paper provides an overview of decomposition chemistry and reviews recent advances in this area utilising analytical separation science. Copyright © 2010 Elsevier B.V. All rights reserved.

Biological decomposition efficiency in different woodland soils.

PubMed

Herlitzius, H

1983-03-01

The decomposition (meaning disappearance) of different leaf types and artificial leaves made from cellulose hydrate foil was studied in three forests - an alluvial forest (Ulmetum), a beech forest on limestone soil (Melico-Fagetum), and a spruce forest in soil overlying limestone bedrock.Fine, medium, and coarse mesh litter bags of special design were used to investigate the roles of abiotic factors, microorganisms, and meso- and macrofauna in effecting decomposition in the three habitats. Additionally, the experimental design was carefully arranged so as to provide information about the effects on decomposition processes of the duration of exposure and the date or moment of exposure. 1. Exposure of litter samples oor 12 months showed: a) Litter enclosed in fine mesh bags decomposed to some 40-44% of the initial amount placed in each of the three forests. Most of this decomposition can be attributed to abiotic factors and microoganisms. b) Litter placed in medium mesh litter bags reduced by ca. 60% in alluvial forest, ca. 50% in beech forest and ca. 44% in spruce forest. c) Litter enclosed in coarse mesh litter bags was reduced by 71% of the initial weights exposed in alluvial and beech forests; in the spruce forest decomposition was no greater than observed with fine and medium mesh litter bags. Clearly, in spruce forest the macrofauna has little or no part to play in effecting decomposition. 2. Sequential month by month exposure of hazel leaves and cellulose hydrate foil in coarse mesh litter bags in all three forests showed that one month of exposure led to only slight material losses, they did occur smallest between March and May, and largest between June and October/November. 3. Coarse mesh litter bags containing either hazel or artificial leaves of cellulose hydrate foil were exposed to natural decomposition processes in December 1977 and subsampled monthly over a period of one year, this series constituted the From-sequence of experiments. Each of the From-sequence samples removed was immediately replaced by a fresh litter bag which was left in place until December 1978, this series constituted the To-sequence of experiments. The results arising from the designated From- and To-sequences showed: a) During the course of one year hazel leaves decomposed completely in alluvial forest, almost completely in beech forest but to only 50% of the initial value in spruce forest. b) Duration of exposure and not the date of exposure is the major controlling influence on decomposition in alluvial forest, a characteristic reflected in the mirror-image courses of the From- and To-sequences curves with respect to the abscissa or time axis. Conversely the date of exposure and not the duration of exposure is the major controlling influence on decomposition in the spruce forest, a characteristic reflected in the mirror-image courses of the From-and To-sequences with respect to the ordinate or axis of percentage decomposition. c) Leaf powder amendment increased the decomposition rate of the hazel and cellulose hydrate leaves in the spruce forest but had no significant effect on their decomposition rate in alluvial and beech forests. It is concluded from this, and other evidence, that litter amendment by leaf fragments of phytophage frass in sites of low biological decomposition activity (eg. spruce) enhances decomposition processes. d) The time course of hazel leaf decomposition in both alluvial and beech forest is sigmoidal. Three s-phases are distinguished and correspond to the activity of microflora/microfauna, mesofauna/macrofauna, and then microflora/microfauna again. In general, the sigmoidal pattern of the curve can be considered valid for all decomposition processes occurring in terrestrial situations. It is contended that no decomposition (=disappearance) curve actually follows an e-type exponential function. A logarithmic linear regression can be constructed from the sigmoid curve data and although this facilitates inter-system comparisons it does not clearly express the dynamics of decomposition. 4. The course of the curve constructed from information about the standard deviations of means derived from the From- and To-sequence data does reflect the dynamics of litter decomposition. The three s-phases can be recognised and by comparing the actual From-sequence deviation curve with a mirror inversion representation of the To-sequence curve it is possible to determine whether decomposition is primarily controlled by the duration of exposure or the date of exposure. As is the case for hazel leaf decomposition in beech forest intermediate conditions can be readily recognised.

Reactivity continuum modeling of leaf, root, and wood decomposition across biomes

NASA Astrophysics Data System (ADS)

Koehler, Birgit; Tranvik, Lars J.

2015-07-01

Large carbon dioxide amounts are released to the atmosphere during organic matter decomposition. Yet the large-scale and long-term regulation of this critical process in global carbon cycling by litter chemistry and climate remains poorly understood. We used reactivity continuum (RC) modeling to analyze the decadal data set of the "Long-term Intersite Decomposition Experiment," in which fine litter and wood decomposition was studied in eight biome types (224 time series). In 32 and 46% of all sites the litter content of the acid-unhydrolyzable residue (AUR, formerly referred to as lignin) and the AUR/nitrogen ratio, respectively, retarded initial decomposition rates. This initial rate-retarding effect generally disappeared within the first year of decomposition, and rate-stimulating effects of nutrients and a rate-retarding effect of the carbon/nitrogen ratio became more prevalent. For needles and leaves/grasses, the influence of climate on decomposition decreased over time. For fine roots, the climatic influence was initially smaller but increased toward later-stage decomposition. The climate decomposition index was the strongest climatic predictor of decomposition. The similar variability in initial decomposition rates across litter categories as across biome types suggested that future changes in decomposition may be dominated by warming-induced changes in plant community composition. In general, the RC model parameters successfully predicted independent decomposition data for the different litter-biome combinations (196 time series). We argue that parameterization of large-scale decomposition models with RC model parameters, as opposed to the currently common discrete multiexponential models, could significantly improve their mechanistic foundation and predictive accuracy across climate zones and litter categories.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Solvable Catalyzed Birth-Death-Exchange Competition Model of Three Species

NASA Astrophysics Data System (ADS)

Wang, Hai-Feng; Lin, Zhen-Quan; Gao, Yan; Zhang, Heng

2009-10-01

A competition model of three species in exchange-driven aggregation growth is proposed. In the model, three distinct aggregates grow by exchange of monomers and in parallel, birth of species A is catalyzed by species B and death of species A is catalyzed by species C. The rates for both catalysis processes are proportional to kjν and kjω respectively, where ν(Ω) is a parameter reflecting the dependence of the catalysis reaction rate of birth (death) on the catalyst aggregate's size. The kinetic evolution behaviors of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A-species ak(t) is found to be dependent crucially on the two catalysis rate kernel parameters. The results show that (i) in case of μ <= 0, the form of ak(t) mainly depends on the competition between self-exchange of species A and species-C-catalyzed death of species A; (ii) in case of ν > 0, the form of ak(t) mainly depends on the competition between species-B-catalyzed birth of species A and species-C-catalyzed death of species A.

Aerogel composites and method of manufacture

DOEpatents

Cao, Wanqing; Hunt, Arlon Jason

1999-01-01

Disclosed herewith is a process of forming an aerogel composite which comprises introducing a gaseous material into a formed aerogel monolith or powder, and causing decomposition of said gaseous material in said aerogel in amounts sufficient to cause deposition of the decomposition products of the gas on the surfaces of the pores of the said aerogel. Also disclosed are the composites made by the process.

Two Dimensional Finite Element Based Magnetotelluric Inversion using Singular Value Decomposition Method on Transverse Electric Mode

NASA Astrophysics Data System (ADS)

Tjong, Tiffany; Yihaa’ Roodhiyah, Lisa; Nurhasan; Sutarno, Doddy

2018-04-01

In this work, an inversion scheme was performed using a vector finite element (VFE) based 2-D magnetotelluric (MT) forward modelling. We use an inversion scheme with Singular value decomposition (SVD) method toimprove the accuracy of MT inversion.The inversion scheme was applied to transverse electric (TE) mode of MT. SVD method was used in this inversion to decompose the Jacobian matrices. Singular values which obtained from the decomposition process were analyzed. This enabled us to determine the importance of data and therefore to define a threshold for truncation process. The truncation of singular value in inversion processcould improve the resulted model.

An effective hierarchical model for the biomolecular covalent bond: an approach integrating artificial chemistry and an actual terrestrial life system.

PubMed

Oohashi, Tsutomu; Ueno, Osamu; Maekawa, Tadao; Kawai, Norie; Nishina, Emi; Honda, Manabu

2009-01-01

Under the AChem paradigm and the programmed self-decomposition (PSD) model, we propose a hierarchical model for the biomolecular covalent bond (HBCB model). This model assumes that terrestrial organisms arrange their biomolecules in a hierarchical structure according to the energy strength of their covalent bonds. It also assumes that they have evolutionarily selected the PSD mechanism of turning biological polymers (BPs) into biological monomers (BMs) as an efficient biomolecular recycling strategy We have examined the validity and effectiveness of the HBCB model by coordinating two complementary approaches: biological experiments using existent terrestrial life, and simulation experiments using an AChem system. Biological experiments have shown that terrestrial life possesses a PSD mechanism as an endergonic, genetically regulated process and that hydrolysis, which decomposes a BP into BMs, is one of the main processes of such a mechanism. In simulation experiments, we compared different virtual self-decomposition processes. The virtual species in which the self-decomposition process mainly involved covalent bond cleavage from a BP to BMs showed evolutionary superiority over other species in which the self-decomposition process involved cleavage from BP to classes lower than BM. These converging findings strongly support the existence of PSD and the validity and effectiveness of the HBCB model.

Rh(V) -Nitrenoid as a Key Intermediate in Rh(III) -Catalyzed Heterocyclization by C-H Activation: A Computational Perspective on the Cycloaddition of Benzamide and Diazo Compounds.

PubMed

Zhou, Tao; Guo, Wei; Xia, Yuanzhi

2015-06-15

A mechanistic study of the substituent-dependent ring formations in Rh(III) -catalyzed C-H activation/cycloaddition of benzamide and diazo compounds was carried out by using DFT calculations. The results indicated that the decomposition of the diazo is facilitated upon the formation of the five-membered rhodacycle, in which the Rh(III) center is more electrophilic. The insertion of carbenoid into Rh-C(phenyl) bond occurs readily and forms a 6-membered rhodacycle, however, the following C-N bond formation is difficult both kinetically and thermodynamically by reductive elimination from the Rh(III) species. Instead, the Rh(V) -nitrenoid intermediate could be formed by migration of the pivalate from N to Rh, which undergoes the heterocyclization much more easily and complementary ring-formations could be modulated by the nature of the substituent at the α-carbon. When a vinyl is attached, the stepwise 1,3-allylic migration occurs prior to the pivalate migration and the 8-membered ring product will be formed. On the other hand, the pivalate migration becomes more favorable for the phenyl-contained intermediate because of the difficult 1,3-allylic migration accompanied by dearomatization, thus the 5-membered ring product was formed selectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal Decomposition Behavior of Hydroxytyrosol (HT) in Nitrogen Atmosphere Based on TG-FTIR Methods.

PubMed

Tu, Jun-Ling; Yuan, Jiao-Jiao

2018-02-13

The thermal decomposition behavior of olive hydroxytyrosol (HT) was first studied using thermogravimetry (TG). Cracked chemical bond and evolved gas analysis during the thermal decomposition process of HT were also investigated using thermogravimetry coupled with infrared spectroscopy (TG-FTIR). Thermogravimetry-Differential thermogravimetry (TG-DTG) curves revealed that the thermal decomposition of HT began at 262.8 °C and ended at 409.7 °C with a main mass loss. It was demonstrated that a high heating rate (over 20 K·min -1 ) restrained the thermal decomposition of HT, resulting in an obvious thermal hysteresis. Furthermore, a thermal decomposition kinetics investigation of HT indicated that the non-isothermal decomposition mechanism was one-dimensional diffusion (D1), integral form g ( x ) = x ², and differential form f ( x ) = 1/(2 x ). The four combined approaches were employed to calculate the activation energy ( E = 128.50 kJ·mol -1 ) and Arrhenius preexponential factor (ln A = 24.39 min -1 ). In addition, a tentative mechanism of HT thermal decomposition was further developed. The results provide a theoretical reference for the potential thermal stability of HT.

Conceptual design optimization study

NASA Technical Reports Server (NTRS)

Hollowell, S. J.; Beeman, E. R., II; Hiyama, R. M.

1990-01-01

The feasibility of applying multilevel functional decomposition and optimization techniques to conceptual design of advanced fighter aircraft was investigated. Applying the functional decomposition techniques to the conceptual design phase appears to be feasible. The initial implementation of the modified design process will optimize wing design variables. A hybrid approach, combining functional decomposition techniques for generation of aerodynamic and mass properties linear sensitivity derivatives with existing techniques for sizing mission performance and optimization, is proposed.

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines.

PubMed

Bennett, John M; Shapiro, Jonathan D; Choinski, Krystina N; Mei, Yingbin; Aulita, Sky M; Dominguez, Giovanny M; Majireck, Max M

2018-01-03

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile N-(2-alkoxyvinyl)sulfonamides, which react under a variety of conditions to afford useful N- and O-containing compounds. Acid-catalyzed addition of alcohols or thiols to N-(2-alkoxyvinyl)sulfonamide-containing phthalans provides access to ketals and thioketals, respectively. Selective reduction of the vinyl group in N-(2-alkoxyvinyl)sulfonamide-containing phthalans via hydrogenation yields the corresponding phthalan in good yield, whereas reduction with sodium bis(2-methoxyethoxy)aluminumhydride generates a ring-opened phenethylamine analogue. Because the N-(2-alkoxyvinyl)sulfonamide functional group is synthetically versatile, but often hydrolytically unstable, this protocol emphasizes key techniques in preparing, handling, and reacting these pivotal substrates in several useful transformations.

Three-Dimensional Atom-Probe Tomography: Advances and Applications

NASA Astrophysics Data System (ADS)

Seidman, David N.

2007-08-01

This review presents the historical temporal evolution of an atom-probe tomograph (APT) from its genesis (1973) from field-ion microscope images of individual tungsten atoms (1955). The capabilities of modern APTs employing either electrical or laser pulsing are discussed. The results of the application of APTs to specific materials science problems are presented for research performed at Northwestern University on the following problems: (a) the segregation of Mg at α-Al/Al3Sc heterophase interfaces, (b) phase decomposition in ternary Ni-Al-Cr and quaternary Ni-Al-Cr-Re alloys, and (c) 3-D nanoscale composition mapping of an InAs semiconductor nanowire whose growth was catalyzed by gold. These results demonstrate that it is now possible to obtain highly quantitative information from APT that can be compared with modeling, theory, simulations, and/or first-principles calculations.

Pd/C Synthesized with Citric Acid: An Efficient Catalyst for Hydrogen Generation from Formic Acid/Sodium Formate

PubMed Central

Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

2012-01-01

A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H2 mol−1 catalyst h−1, respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

Effect of decomposition and organic residues on resistivity of copper films fabricated via low-temperature sintering of complex particle mixed dispersions

NASA Astrophysics Data System (ADS)

Yong, Yingqiong; Nguyen, Mai Thanh; Tsukamoto, Hiroki; Matsubara, Masaki; Liao, Ying-Chih; Yonezawa, Tetsu

2017-03-01

Mixtures of a copper complex and copper fine particles as copper-based metal-organic decomposition (MOD) dispersions have been demonstrated to be effective for low-temperature sintering of conductive copper film. However, the copper particle size effect on decomposition process of the dispersion during heating and the effect of organic residues on the resistivity have not been studied. In this study, the decomposition process of dispersions containing mixtures of a copper complex and copper particles with various sizes was studied. The effect of organic residues on the resistivity was also studied using thermogravimetric analysis. In addition, the choice of copper salts in the copper complex was also discussed. In this work, a low-resistivity sintered copper film (7 × 10-6 Ω·m) at a temperature as low as 100 °C was achieved without using any reductive gas.

Understanding the critical challenges of self-aligned octuple patterning

NASA Astrophysics Data System (ADS)

Yu, Ji; Xiao, Wei; Kang, Weiling; Chen, Yijian

2014-03-01

In this paper, we present a thorough investigation of self-aligned octuple patterning (SAOP) process characteristics, cost structure, integration challenges, and layout decomposition. The statistical characteristics of SAOP CD variations such as multi-modality are analyzed and contributions from various features to CDU and MTT (mean-to-target) budgets are estimated. The gap space is found to have the worst CDU+MTT performance and is used to determine the required overlay accuracy to ensure a satisfactory edge-placement yield of a cut process. Moreover, we propose a 5-mask positive-tone SAOP (pSAOP) process for memory FEOL patterning and a 3-mask negative-tone SAOP (nSAOP) process for logic BEOL patterning. The potential challenges of 2-D SAOP layout decomposition for BEOL applications are identified. Possible decomposition approaches are explored and the functionality of several developed algorithm is verified using 2-D layout examples from Open Cell Library.

Bench scale demonstration and conceptual engineering for DETOX{sup SM} catalyzed wet oxidation

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

Moslander, J.; Bell, R.; Robertson, D.

1994-06-01

Laboratory and bench scale studies of the DETOX{sup SM} catalyzed wet oxidation process have been performed with the object of developing the process for treatment of hazardous and mixed wastes. Reaction orders, apparent rates, and activation energies have been determined for a range of organic waste surrogates. Reaction intermediates and products have been analyzed. Metals` fates have been determined. Bench scale units have been designed, fabricated, and tested with solid and liquid organic waste surrogates. Results from the laboratory and bench scale studies have been used to develop conceptual designs for application of the process to hazardous and mixed wastes.

A Highly Stereocontrolled, One-Pot Approach toward Pyrrolobenzoxazinones and Pyrroloquinazolinones through a Lewis Acid-Catalyzed [3 + 2]-Cycloannulation Process.

PubMed

Boomhoff, Michael; Ukis, Rostyslav; Schneider, Christoph

2015-08-21

We report herein a stereocontrolled [3 + 2]-cycloheteroannulation of bis-silyl dienediolate 1 with 2-aminobenzoic acid- and 2-aminobenzamide-derived imines to furnish highly substituted pyrrolo[1,2-a]benzoxazinones 3 and pyrrolo[1,2-a]quinazolinones 4, respectively, in good overall yields. This one-pot process rapidly generates molecular complexity and comprises a Lewis acid-catalyzed, vinylogous Mannich reaction of 1 followed by an intramolecular N,O-acetal- and N,N-aminal formation, respectively, which proceeds with good to excellent stereocontrol.

Ionization-Enhanced Decomposition of 2,4,6-Trinitrotoluene (TNT) Molecules

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

Wang, Bin; Wright, David; Cliffel, David

2011-01-01

The unimolecular decomposition reaction of TNT can in principle be used to design ways to either detect or remove TNT from the environment. Here, we report the results of a density functional theory study of possible ways to lower the reaction barrier for this decomposition process by ionization, so that decomposition and/or detection can occur at room temperature. We find that ionizing TNT lowers the reaction barrier for the initial step of this decomposition. We further show that a similar effect can occur if a positive moiety is bound to the TNT molecule. The positive charge produces a pronounced electronmore » redistribution and dipole formation in TNT with minimal charge transfer from TNT to the positive moiety.« less

Scare Tactics: Evaluating Problem Decompositions Using Failure Scenarios

NASA Technical Reports Server (NTRS)

Helm, B. Robert; Fickas, Stephen

1992-01-01

Our interest is in the design of multi-agent problem-solving systems, which we refer to as composite systems. We have proposed an approach to composite system design by decomposition of problem statements. An automated assistant called Critter provides a library of reusable design transformations which allow a human analyst to search the space of decompositions for a problem. In this paper we describe a method for evaluating and critiquing problem decompositions generated by this search process. The method uses knowledge stored in the form of failure decompositions attached to design transformations. We suggest the benefits of our critiquing method by showing how it could re-derive steps of a published development example. We then identify several open issues for the method.

Plant Diversity Impacts Decomposition and Herbivory via Changes in Aboveground Arthropods

PubMed Central

Ebeling, Anne; Meyer, Sebastian T.; Abbas, Maike; Eisenhauer, Nico; Hillebrand, Helmut; Lange, Markus; Scherber, Christoph; Vogel, Anja; Weigelt, Alexandra; Weisser, Wolfgang W.

2014-01-01

Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ecosystem processes is an important but little studied piece of information. In a grassland biodiversity experiment, we addressed this gap by assessing aboveground decomposer and herbivore communities and linking their abundance and diversity to rates of decomposition and herbivory. Path analyses showed that increasing plant diversity led to higher abundance and diversity of decomposing arthropods through higher plant biomass. Higher species richness of decomposers, in turn, enhanced decomposition. Similarly, species-rich plant communities hosted a higher abundance and diversity of herbivores through elevated plant biomass and C:N ratio, leading to higher herbivory rates. Integrating trophic interactions into the study of biodiversity effects is required to understand the multiple pathways by which biodiversity affects ecosystem functioning. PMID:25226237

Theoretical study of the reaction mechanism of CH₃NO₂ with NO₂, NO and CO: the bimolecular reactions that cannot be ignored.

PubMed

Zhang, Ji-Dong; Kang, Li-Hua; Cheng, Xin-Lu

2015-01-01

The intriguing decompositions of nitro-containing explosives have been attracting interest. While theoretical investigations have long been concentrated mainly on unimolecular decompositions, bimolecular reactions have received little theoretical attention. In this paper, we investigate theoretically the bimolecular reactions between nitromethane (CH3NO2)-the simplest nitro-containing explosive-and its decomposition products, such as NO2, NO and CO, that are abundant during the decomposition process of CH3NO2. The structures and potential energy surface (PES) were explored at B3LYP/6-31G(d), B3P86/6-31G(d) and MP2/6-311 + G(d,p) levels, and energies were refined using CCSD(T)/cc-pVTZ methods. Quantum chemistry calculations revealed that the title reactions possess small barriers that can be comparable to, or smaller than, that of the initial decomposition reactions of CH3NO2. Considering that their reactants are abundant in the decomposition process of CH3NO2, we consider bimolecular reactions also to be of great importance, and worthy of further investigation. Moreover, our calculations show that NO2 can be oxidized by CH3NO2 to NO3 radical, which confirms the conclusion reached formerly by Irikura and Johnson [(2006) J Phys Chem A 110:13974-13978] that NO3 radical can be formed during the decomposition of nitramine explosives.

Impact of litter quantity on the soil bacteria community during the decomposition of Quercus wutaishanica litter.

PubMed

Zeng, Quanchao; Liu, Yang; An, Shaoshan

2017-01-01

The forest ecosystem is the main component of terrestrial ecosystems. The global climate and the functions and processes of soil microbes in the ecosystem are all influenced by litter decomposition. The effects of litter decomposition on the abundance of soil microorganisms remain unknown. Here, we analyzed soil bacterial communities during the litter decomposition process in an incubation experiment under treatment with different litter quantities based on annual litterfall data (normal quantity, 200 g/(m 2 /yr); double quantity, 400 g/(m 2 /yr) and control, no litter). The results showed that litter quantity had significant effects on soil carbon fractions, nitrogen fractions, and bacterial community compositions, but significant differences were not found in the soil bacterial diversity. The normal litter quantity enhanced the relative abundance of Actinobacteria and Firmicutes and reduced the relative abundance of Bacteroidetes, Plantctomycets and Nitrospiare. The Beta-, Gamma-, and Deltaproteobacteria were significantly less abundant in the normal quantity litter addition treatment, and were subsequently more abundant in the double quantity litter addition treatment. The bacterial communities transitioned from Proteobacteria-dominant (Beta-, Gamma-, and Delta) to Actinobacteria-dominant during the decomposition of the normal quantity of litter. A cluster analysis showed that the double litter treatment and the control had similar bacterial community compositions. These results suggested that the double quantity litter limited the shift of the soil bacterial community. Our results indicate that litter decomposition alters bacterial dynamics under the accumulation of litter during the vegetation restoration process, which provides important significant guidelines for the management of forest ecosystems.

Designer synthetic media for studying microbial-catalyzed biofuel production

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

Tang, Xiaoyu; da Costa Sousa, Leonardo; Jin, Mingjie

Background: The fermentation inhibition of yeast or bacteria by lignocellulose-derived degradation products, during hexose/pentose co-fermentation, is a major bottleneck for cost-effective lignocellulosic biorefineries. To engineer microbial strains for improved performance, it is critical to understand the mechanisms of inhibition that affect fermentative organisms in the presence of major components of a lignocellulosic hydrolysate. The development of a synthetic lignocellulosic hydrolysate (SH) media with a composition similar to the actual biomass hydrolysate will be an important advancement to facilitate these studies. In this work, we characterized the nutrients and plant-derived decomposition products present in AFEX™ pretreated corn stover hydrolysate (ACH). Themore » SH was formulated based on the ACH composition and was further used to evaluate the inhibitory effects of various families of decomposition products during Saccharomyces cerevisiae 424A (LNH-ST) fermentation. Results: The ACH contained high levels of nitrogenous compounds, notably amides, pyrazines, and imidazoles. In contrast, a relatively low content of furans and aromatic and aliphatic acids were found in the ACH. Though most of the families of decomposition products were inhibitory to xylose fermentation, due to their abundance, the nitrogenous compounds showed the most inhibition. From these compounds, amides (products of the ammonolysis reaction) contributed the most to the reduction of the fermentation performance. However, this result is associated to a concentration effect, as the corresponding carboxylic acids (products of hydrolysis) promoted greater inhibition when present at the same molar concentration as the amides. Due to its complexity, the formulated SH did not perfectly match the fermentation profile of the actual hydrolysate, especially the growth curve. However, the SH formulation was effective for studying the inhibitory effect of various compounds on yeast fermentation. Conclusions: The formulation of SHs is an important advancement for future multi-omics studies and for better understanding the mechanisms of fermentation inhibition in lignocellulosic hydrolysates. The SH formulated in this work was instrumental for defining the most important inhibitors in the ACH. Major AFEX decomposition products are less inhibitory to yeast fermentation than the products of dilute acid or steam explosion pretreatments; thus, ACH is readily fermentable by yeast without any detoxification.« less

Designer synthetic media for studying microbial-catalyzed biofuel production

DOE PAGES

Tang, Xiaoyu; da Costa Sousa, Leonardo; Jin, Mingjie; ...

2015-01-01

Background: The fermentation inhibition of yeast or bacteria by lignocellulose-derived degradation products, during hexose/pentose co-fermentation, is a major bottleneck for cost-effective lignocellulosic biorefineries. To engineer microbial strains for improved performance, it is critical to understand the mechanisms of inhibition that affect fermentative organisms in the presence of major components of a lignocellulosic hydrolysate. The development of a synthetic lignocellulosic hydrolysate (SH) media with a composition similar to the actual biomass hydrolysate will be an important advancement to facilitate these studies. In this work, we characterized the nutrients and plant-derived decomposition products present in AFEX™ pretreated corn stover hydrolysate (ACH). Themore » SH was formulated based on the ACH composition and was further used to evaluate the inhibitory effects of various families of decomposition products during Saccharomyces cerevisiae 424A (LNH-ST) fermentation. Results: The ACH contained high levels of nitrogenous compounds, notably amides, pyrazines, and imidazoles. In contrast, a relatively low content of furans and aromatic and aliphatic acids were found in the ACH. Though most of the families of decomposition products were inhibitory to xylose fermentation, due to their abundance, the nitrogenous compounds showed the most inhibition. From these compounds, amides (products of the ammonolysis reaction) contributed the most to the reduction of the fermentation performance. However, this result is associated to a concentration effect, as the corresponding carboxylic acids (products of hydrolysis) promoted greater inhibition when present at the same molar concentration as the amides. Due to its complexity, the formulated SH did not perfectly match the fermentation profile of the actual hydrolysate, especially the growth curve. However, the SH formulation was effective for studying the inhibitory effect of various compounds on yeast fermentation. Conclusions: The formulation of SHs is an important advancement for future multi-omics studies and for better understanding the mechanisms of fermentation inhibition in lignocellulosic hydrolysates. The SH formulated in this work was instrumental for defining the most important inhibitors in the ACH. Major AFEX decomposition products are less inhibitory to yeast fermentation than the products of dilute acid or steam explosion pretreatments; thus, ACH is readily fermentable by yeast without any detoxification.« less

Cu(II)-catalyzed esterification reaction via aerobic oxidative cleavage of C(CO)-C(alkyl) bonds.

PubMed

Ma, Ran; He, Liang-Nian; Liu, An-Hua; Song, Qing-Wen

2016-02-04

A novel Cu(II)-catalyzed aerobic oxidative esterification of simple ketones for the synthesis of esters has been developed with wide functional group tolerance. This process is assumed to go through a tandem sequence consisting of α-oxygenation/esterification/nucleophilic addition/C-C bond cleavage and carbon dioxide is released as the only byproduct.

Copper-catalyzed aerobic C(sp2)-H functionalization for C-N bond formation: synthesis of pyrazoles and indazoles.

PubMed

Li, Xianwei; He, Li; Chen, Huoji; Wu, Wanqing; Jiang, Huanfeng

2013-04-19

A simple, practical, and highly efficient synthesis of pyrazoles and indazoles via copper-catalyzed direct aerobic oxidative C(sp(2))-H amination has been reported herein. This process tolerated a variety of functional groups under mild conditions. Further diversification of pyrazoles was also investigated, which provided its potential for drug discovery.

Pd-catalyzed intramolecular oxidative C-H amination: synthesis of carbazoles.

PubMed

Youn, So Won; Bihn, Joon Hyung; Kim, Byung Seok

2011-07-15

A Pd-catalyzed oxidative C-H amination of N-Ts-2-arylanilines under ambient temperature using Oxone as an inexpensive, safe, and easy-to-handle oxidant has been developed. This process represents a green and practical method for the facile construction of carbazoles with a broad substrate scope and wide functional group tolerance. © 2011 American Chemical Society

Copper-catalyzed tandem reactions of 1-(2-iodoary)-2-yn-1-ones with isocyanides for the synthesis of 4-oxo-indeno[1,2-b]pyrroles.

PubMed

Cai, Qian; Zhou, Fengtao; Xu, Tianfeng; Fu, Liangbing; Ding, Ke

2011-01-21

A novel copper-catalyzed tandem reaction of 1-(2-iodoaryl)-2-yn-1-ones with isocyanides is described. The reaction is through a formal [3 + 2] cycloaddition/coupling tandem process and leads to efficient formation of 4-oxo-indeno[1,2-b]pyrroles.

Cobalt-Catalyzed Trifluoromethylation-Peroxidation of Unactivated Alkenes with Sodium Trifluoromethanesulfinate and Hydroperoxide.

PubMed

Zhang, Hong-Yu; Ge, Chao; Zhao, Jiquan; Zhang, Yuecheng

2017-10-06

Disclosed herein is an unprecedented cobalt-catalyzed trifluoromethylation-peroxidation of unactivated alkenes. In this process the hydroperoxide acts as a radical initiator as well as a coupling partner. The cheap and readily available sodium trifluoromethanesulfinate serves as the CF 3 source in the reaction. Various alkenes are transformed into vicinal trifluoromethyl-peroxide compounds in moderate to good yields.

Catalyzed formation of α,β-unsaturated ketones or aldehydes from propargylic acetates by a recoverable and recyclable nanocluster catalyst

NASA Astrophysics Data System (ADS)

Li, Man-Bo; Tian, Shi-Kai; Wu, Zhikun

2014-05-01

An active, recoverable, and recyclable nanocluster catalyst, Au25(SR)18-, has been developed to catalyze the formation of α,β-unsaturated ketones or aldehydes from propargylic acetates. The catalytic process has been proposed to be initialized by an SN2' addition of OH-. Moreover, a dramatic solvent effect was observed, for which a rational explanation was provided.An active, recoverable, and recyclable nanocluster catalyst, Au25(SR)18-, has been developed to catalyze the formation of α,β-unsaturated ketones or aldehydes from propargylic acetates. The catalytic process has been proposed to be initialized by an SN2' addition of OH-. Moreover, a dramatic solvent effect was observed, for which a rational explanation was provided. Electronic supplementary information (ESI) available: Experimental procedures, UV-Vis spectra and fluorescence spectra of catalysts, characterization data, and copies of MS spectra. See DOI: 10.1039/c4nr00658e

Susceptibility of Goethite to Fe2+-Catalyzed Recrystallization over Time.

PubMed

Joshi, Prachi; Fantle, Matthew S; Larese-Casanova, Philip; Gorski, Christopher A

2017-10-17

Recent work has shown that iron oxides, such as goethite and hematite, may recrystallize in the presence of aqueous Fe 2+ under anoxic conditions. This process, referred to as Fe 2+ -catalyzed recrystallization, can influence water quality by causing the incorporation/release of environmental contaminants and biological nutrients. Accounting for the effects of Fe 2+ -catalyzed recrystallization on water quality requires knowing the time scale over which recrystallization occurs. Here, we tested the hypothesis that nanoparticulate goethite becomes less susceptible to Fe 2+ -catalyzed recrystallization over time. We set up two batches of reactors in which 55 Fe 2+ tracer was added at two different time points and tracked the 55 Fe partitioning in the aqueous and goethite phases over 60 days. Less 55 Fe uptake occurred between 30 and 60 days than between 0 and 30 days, suggesting goethite recrystallization slowed with time. Fitting the data with a box model indicated that 17% of the goethite recrystallized after 30 days of reaction, and an additional 2% recrystallized between 30 and 60 days. The decreasing susceptibility of goethite to recrystallize as it reacted with aqueous Fe 2+ suggested that recrystallization is likely only an important process over short time scales.

Three-Component Decomposition of Polarimetric SAR Data Integrating Eigen-Decomposition Results

NASA Astrophysics Data System (ADS)

Lu, Da; He, Zhihua; Zhang, Huan

2018-01-01

This paper presents a novel three-component scattering power decomposition of polarimetric SAR data. There are two problems in three-component decomposition method: volume scattering component overestimation in urban areas and artificially set parameter to be a fixed value. Though volume scattering component overestimation can be partly solved by deorientation process, volume scattering still dominants some oriented urban areas. The speckle-like decomposition results introduced by artificially setting value are not conducive to further image interpretation. This paper integrates the results of eigen-decomposition to solve the aforementioned problems. Two principal eigenvectors are used to substitute the surface scattering model and the double bounce scattering model. The decomposed scattering powers are obtained using a constrained linear least-squares method. The proposed method has been verified using an ESAR PolSAR image, and the results show that the proposed method has better performance in urban area.

Photogeneration of active formate decomposition catalysts to produce hydrogen from formate and water

DOEpatents

King, Jr., Allen D.; King, Robert B.; Sailers, III, Earl L.

1983-02-08

A process for producing hydrogen from formate and water by photogenerating an active formate decomposition catalyst from transition metal carbonyl precursor catalysts at relatively low temperatures and otherwise mild conditions is disclosed. Additionally, this process may be expanded to include the generation of formate from carbon monoxide and hydroxide such that the result is the water gas shift reaction.

Analysis and Prediction of Sea Ice Evolution using Koopman Mode Decomposition Techniques

DTIC Science & Technology

2018-04-30

Title: Analysis and Prediction of Sea Ice Evolution using Koopman Mode Decomposition Techniques Subject: Monthly Progress Report Period of...Resources: N/A TOTAL: $18,687 2 TECHNICAL STATUS REPORT Abstract The program goal is analysis of sea ice dynamical behavior using Koopman Mode Decompo...sition (KMD) techniques. The work in the program’s first month consisted of improvements to data processing code, inclusion of additional arctic sea ice

The rate of synthesis and decomposition of tissue proteins in hypokinesia and increased muscular activity

NASA Technical Reports Server (NTRS)

Fedorov, I. V.; Chernyy, A. V.; Fedorov, A. I.

1978-01-01

During hypokinesia and physical loading (swimming) of rats, the radioactivity of skeletal muscle, liver, kidney, heart, and blood proteins was determined after administration of radioactive amino acids. Tissue protein synthesis decreased during hypokinesia, and decomposition increased. Both synthesis and decomposition increased during physical loading, but anabolic processes predominated in the total tissue balance. The weights of the animals decreased in hypokinesia and increased during increased muscle activity.

Dynamics of Potassium Release and Adsorption on Rice Straw Residue

PubMed Central

Li, Jifu; Lu, Jianwei; Li, Xiaokun; Ren, Tao; Cong, Rihuan; Zhou, Li

2014-01-01

Straw application can not only increase crop yields, improve soil structure and enrich soil fertility, but can also enhance water and nutrient retention. The aim of this study was to ascertain the relationships between straw decomposition and the release-adsorption processes of K+. This study increases the understanding of the roles played by agricultural crop residues in the soil environment, informs more effective straw recycling and provides a method for reducing potassium loss. The influence of straw decomposition on the K+ release rate in paddy soil under flooded condition was studied using incubation experiments, which indicated the decomposition process of rice straw could be divided into two main stages: (a) a rapid decomposition stage from 0 to 60 d and (b) a slow decomposition stage from 60 to 110 d. However, the characteristics of the straw potassium release were different from those of the overall straw decomposition, as 90% of total K was released by the third day of the study. The batches of the K sorption experiments showed that crop residues could adsorb K+ from the ambient environment, which was subject to decomposition periods and extra K+ concentration. In addition, a number of materials or binding sites were observed on straw residues using IR analysis, indicating possible coupling sites for K+ ions. The aqueous solution experiments indicated that raw straw could absorb water at 3.88 g g−1, and this rate rose to its maximum 15 d after incubation. All of the experiments demonstrated that crop residues could absorb large amount of aqueous solution to preserve K+ indirectly during the initial decomposition period. These crop residues could also directly adsorb K+ via physical and chemical adsorption in the later period, allowing part of this K+ to be absorbed by plants for the next growing season. PMID:24587364

Dynamics of potassium release and adsorption on rice straw residue.

PubMed

Li, Jifu; Lu, Jianwei; Li, Xiaokun; Ren, Tao; Cong, Rihuan; Zhou, Li

2014-01-01

Straw application can not only increase crop yields, improve soil structure and enrich soil fertility, but can also enhance water and nutrient retention. The aim of this study was to ascertain the relationships between straw decomposition and the release-adsorption processes of K(+). This study increases the understanding of the roles played by agricultural crop residues in the soil environment, informs more effective straw recycling and provides a method for reducing potassium loss. The influence of straw decomposition on the K(+) release rate in paddy soil under flooded condition was studied using incubation experiments, which indicated the decomposition process of rice straw could be divided into two main stages: (a) a rapid decomposition stage from 0 to 60 d and (b) a slow decomposition stage from 60 to 110 d. However, the characteristics of the straw potassium release were different from those of the overall straw decomposition, as 90% of total K was released by the third day of the study. The batches of the K sorption experiments showed that crop residues could adsorb K(+) from the ambient environment, which was subject to decomposition periods and extra K(+) concentration. In addition, a number of materials or binding sites were observed on straw residues using IR analysis, indicating possible coupling sites for K(+) ions. The aqueous solution experiments indicated that raw straw could absorb water at 3.88 g g(-1), and this rate rose to its maximum 15 d after incubation. All of the experiments demonstrated that crop residues could absorb large amount of aqueous solution to preserve K(+) indirectly during the initial decomposition period. These crop residues could also directly adsorb K(+) via physical and chemical adsorption in the later period, allowing part of this K(+) to be absorbed by plants for the next growing season.

A General, Concise Strategy that Enables Collective Total Syntheses of over 50 Protoberberine and Five Aporhoeadane Alkaloids within Four to Eight Steps.

PubMed

Zhou, Shiqiang; Tong, Rongbiao

2016-05-17

A concise, catalytic, and general strategy that allowed efficient total syntheses of 22 natural 13-methylprotoberberines within four steps for each molecule is reported. This synthesis represents the most efficient and shortest route to date, featuring three catalytic processes: CuI-catalyzed redox-A(3) reaction, Pd-catalyzed reductive carbocyclization, and PtO2 -catalyzed hydrogenation. Importantly, this new strategy to the tetracyclic framework has also been applied to the collective concise syntheses of >30 natural protoberberines (without 13-methyl group) and five aporhoeadane alkaloids. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal explosion analysis of methyl ethyl ketone peroxide by non-isothermal and isothermal calorimetric applications.

PubMed

Chi, Jen-Hao; Wu, Sheng-Hung; Shu, Chi-Min

2009-11-15

In the past, process incidents attributed to organic peroxides (OPs) that involved near misses, over-pressures, runaway reactions, and thermal explosions occurred because of poor training, human error, incorrect kinetic assumptions, insufficient change management, and inadequate chemical knowledge in the manufacturing process. Calorimetric applications were employed broadly to test organic peroxides on a small-scale because of their thermal hazards, such as exothermic behavior and self-accelerating decomposition in the laboratory. In essence, methyl ethyl ketone peroxide (MEKPO) is highly reactive and exothermically unstable. In recent years, it has undergone many thermal explosions and runaway reaction incidents in the manufacturing process. Differential scanning calorimetry (DSC), vent sizing package 2 (VSP2), and thermal activity monitor (TAM) were employed to analyze thermokinetic parameters and safety index. The intent of the analyses was to facilitate the use of various auto-alarm equipments to detect over-pressure, over-temperature, and hazardous materials leaks for a wide spectrum of operations. Results indicated that MEKPO decomposition is detected at low temperatures (30-40 degrees C), and the rate of decomposition was shown to exponentially increase with temperature and pressure. Determining time to maximum rate (TMR), self-accelerating decomposition temperature (SADT), maximum temperature (T(max)), exothermic onset temperature (T(0)), and heat of decomposition (DeltaH(d)) was essential for identifying early-stage runaway reactions effectively for industries.

A study of photothermal laser ablation of various polymers on microsecond time scales.

PubMed

Kappes, Ralf S; Schönfeld, Friedhelm; Li, Chen; Golriz, Ali A; Nagel, Matthias; Lippert, Thomas; Butt, Hans-Jürgen; Gutmann, Jochen S

2014-01-01

To analyze the photothermal ablation of polymers, we designed a temperature measurement setup based on spectral pyrometry. The setup allows to acquire 2D temperature distributions with 1 μm size and 1 μs time resolution and therefore the determination of the center temperature of a laser heating process. Finite element simulations were used to verify and understand the heat conversion and heat flow in the process. With this setup, the photothermal ablation of polystyrene, poly(α-methylstyrene), a polyimide and a triazene polymer was investigated. The thermal stability, the glass transition temperature Tg and the viscosity above Tg were governing the ablation process. Thermal decomposition for the applied laser pulse of about 10 μs started at temperatures similar to the start of decomposition in thermogravimetry. Furthermore, for polystyrene and poly(α-methylstyrene), both with a Tg in the range between room and decomposition temperature, ablation already occurred at temperatures well below the decomposition temperature, only at 30-40 K above Tg. The mechanism was photomechanical, i.e. a stress due to the thermal expansion of the polymer was responsible for ablation. Low molecular weight polymers showed differences in photomechanical ablation, corresponding to their lower Tg and lower viscosity above the glass transition. However, the difference in ablated volume was only significant at higher temperatures in the temperature regime for thermal decomposition at quasi-equilibrium time scales.

Photodecomposition of dyes on Fe-C-TiO(2) photocatalysts under UV radiation supported by photo-Fenton process.

PubMed

Tryba, B; Piszcz, M; Grzmil, B; Pattek-Janczyk, A; Morawski, A W

2009-02-15

Fe-C-TiO(2) photocatalysts were prepared by mechanical mixing of commercial anatase TiO(2) precursor with FeC(2)O(4) and heating at 500-800 degrees C under argon flow. These photocatalysts were tested for dyes decomposition: Methylene Blue (MB), Reactive Black (RB) and Acid Red (AR). The preliminary adsorption of dyes on the photocatalysts surface was performed. Modification of anatase by FeC(2)O(4) caused reducing of zeta potential of the photocatalyst surface from +12 to -7mV and decreasing of their adsorption ability towards RB and AR, which were negatively charged, -46.8 and -39.7, respectively. Therefore, unmodified TiO(2) showed the highest degree of RB and AR decompositions in the combination of dyes adsorption and UV irradiation. Methylene Blue, which had zeta potential of +4.3 in the aqueous solution was poorly adsorbed on all the tested photocatalysts and also slowly decomposed under UV irradiation. The high rate of dyes decomposition was noted on Fe-C-TiO(2) photocatalysts under UV irradiation with addition of H(2)O(2). It was observed, that at lower temperatures of heat treatment such as 500 degrees C higher content of carbon is remained in the sample, blocking the built in of iron into the TiO(2) lattice. This iron is reactive in the photo-Fenton process resulting in high production of OH radicals and also high activity of the photocatalyst. At higher temperatures of heat treatment, less active FeTiO(3) phase is formed, therefore Fe-C-TiO(2) sample prepared at 800 degrees C showed low photocatalytic activity for dyes decomposition. Fe-C-TiO(2) photocatalysts are active under visible light irradiation, however, the efficiency of a dye decomposition is lower than under UV light. In a dark Fenton process there is observed an insignificant generation of OH radicals and very little decomposition of a dye, what suggests the powerful of photo-Fenton process in the dyes decomposition.

DETOX{sup SM} catalyzed wet oxidation as a highly suitable pretreatment for vitrification

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

Rogers, T.W.; Dhooge, P.M.; Goldblatt, S.D.

1995-11-01

A catalyzed wet oxidation process has been developed which uses ferric iron in an acidic water solution to oxidize organic compounds in the presence of platinum ion and/or ruthenium ion catalysts. The process is capable of oxidizing a wide range of organic compounds to carbon dioxide and water with great efficiency. The process has been tested in the bench-scale with many different types of organics. Conceptual engineering for application of the process to treatment of liquid and solid organic waste materials has been followed by engineering design for a demonstration unit. Fabrication of the unit and demonstration on hazardous andmore » mixed wastes at two Department of Energy sites is planned in 1995 through 1997.« less

Silver-mordenite for radiologic gas capture from complex streams. Dual catalytic CH 3I decomposition and I confinement

DOE PAGES

Nenoff, Tina M.; Rodriguez, Mark A.; Soelberg, Nick R.; ...

2014-05-09

The selective capture of radiological iodine ( 129I) is a persistent concern for safe nuclear energy. In these nuclear fuel reprocessing scenarios, the gas streams to be treated are extremely complex, containing several distinct iodine-containing molecules amongst a large variety of other species. Silver-containing mordenite (MOR) is a longstanding benchmark for radioiodine capture, reacting with molecular iodine (I 2) to form AgI. However the mechanisms for organoiodine capture is not well understood. Here we investigate the capture of methyl iodide from complex mixed gas streams by combining chemical analysis of the effluent gas stream with in depth characterization of themore » recovered sorbent. Tools applied include infrared spectroscopy, thermogravimetric analysis with mass spectrometry, micro X-ray fluorescence, powder X-ray diffraction analysis, and pair distribution function analysis. Moreover, the MOR zeolite catalyzes decomposition of the methyl iodide through formation of surface methoxy species (SMS), which subsequently reacts with water in the mixed gas stream to form methanol, and with methanol to form dimethyl ether, which are both detected downstream in the effluent. The liberated iodine reacts with Ag in the MOR pore to the form subnanometer AgI clusters, smaller than the MOR pores, suggesting that the iodine is both physically and chemically confined within the zeolite.« less

Monitoring mass transport in heterogeneously catalyzed reactions by field-gradient NMR for assessing reaction efficiency in a single pellet.

PubMed

Buljubasich, L; Blümich, B; Stapf, S

2011-09-01

An important aspect in assessing the performance of a catalytically active reactor is the accessibility of the reactive sites inside the individual pellets, and the mass transfer of reactants and products to and from these sites. Optimal design often requires a suitable combination of micro- and macropores in order to facilitate mass transport inside the pellet. In an exothermic reaction, fluid exchange between the pellet and the surrounding medium is enhanced by convection, and often by the occurrence of gas bubbles. Determining mass flow in the vicinity of a pellet thus represents a parameter for quantifying the reaction efficiency and its dependence on time or external reaction conditions. Field gradient Nuclear Magnetic Resonance (NMR) methods are suggested as a tool for providing parameters sensitive to this mass flow in a contact-free and non-invasive way. For the example of bubble-forming hydrogen peroxide decomposition in an alumina pellet, the dependence of the mean-squared displacement of fluid molecules on spatial direction, observation time and reaction time is presented, and multi-pulse techniques are employed in order to separate molecular displacements from coherent and incoherent motion on the timescale of the experiment. The reaction progress is followed until the complete decomposition of H2O2. Copyright © 2011 Elsevier Inc. All rights reserved.

Effect of aluminum on metabolism of organic acids and chemical forms of aluminum in root tips of Eucalyptus camaldulensis Dehnh.

PubMed

Ikka, Takashi; Ogawa, Tsuyoshi; Li, Donghua; Hiradate, Syuntaro; Morita, Akio

2013-10-01

Eucalyptus (Eucalyptus camaldulensis) has relatively high resistance to aluminum (Al) toxicity than the various herbaceous plants and model plant species. To investigate Al-tolerance mechanism, the metabolism of organic acids and the chemical forms of Al in the target site (root tips) in Eucalyptus was investigated. To do this, 2-year old rooted cuttings of E. camaldulensis were cultivated in half-strength Hoagland solution (pH 4.0) containing Al (0, 0.25, 0.5, 1.0, 2.5 and 5.0mM) salts for 5weeks; growth was not affected at concentrations up to 2.5mM even with Al concentration reaching 6000μgg(-1) DW. In roots, the citrate content also increased with increasing Al application. Concurrently, the activities of aconitase and NADP(+)-isocitrate dehydrogenase, which catalyze the decomposition of citrate, decreased. On the other hand, the activity of citrate synthase was not affected at concentrations up to 2.5mM Al. (27)Al-NMR spectroscopic analyses were carried out where it was found that Al-citrate complexes were a major chemical form present in cell sap of root tips. These findings suggested that E. camaldulensis detoxifies Al by forming Al-citrate complexes, and that this is achieved through Al-induced citrate accumulation in root tips via suppression of the citrate decomposition pathway. Copyright © 2013 Elsevier Ltd. All rights reserved.

Direct and Indirect Effects of UV-B Exposure on Litter Decomposition: A Meta-Analysis

PubMed Central

Song, Xinzhang; Peng, Changhui; Jiang, Hong; Zhu, Qiuan; Wang, Weifeng

2013-01-01

Ultraviolet-B (UV-B) exposure in the course of litter decomposition may have a direct effect on decomposition rates via changing states of photodegradation or decomposer constitution in litter while UV-B exposure during growth periods may alter chemical compositions and physical properties of plants. Consequently, these changes will indirectly affect subsequent litter decomposition processes in soil. Although studies are available on both the positive and negative effects (including no observable effects) of UV-B exposure on litter decomposition, a comprehensive analysis leading to an adequate understanding remains unresolved. Using data from 93 studies across six biomes, this introductory meta-analysis found that elevated UV-B directly increased litter decomposition rates by 7% and indirectly by 12% while attenuated UV-B directly decreased litter decomposition rates by 23% and indirectly increased litter decomposition rates by 7%. However, neither positive nor negative effects were statistically significant. Woody plant litter decomposition seemed more sensitive to UV-B than herbaceous plant litter except under conditions of indirect effects of elevated UV-B. Furthermore, levels of UV-B intensity significantly affected litter decomposition response to UV-B (P<0.05). UV-B effects on litter decomposition were to a large degree compounded by climatic factors (e.g., MAP and MAT) (P<0.05) and litter chemistry (e.g., lignin content) (P<0.01). Results suggest these factors likely have a bearing on masking the important role of UV-B on litter decomposition. No significant differences in UV-B effects on litter decomposition were found between study types (field experiment vs. laboratory incubation), litter forms (leaf vs. needle), and decay duration. Indirect effects of elevated UV-B on litter decomposition significantly increased with decay duration (P<0.001). Additionally, relatively small changes in UV-B exposure intensity (30%) had significant direct effects on litter decomposition (P<0.05). The intent of this meta-analysis was to improve our understanding of the overall effects of UV-B on litter decomposition. PMID:23818993

Plant Identity Influences Decomposition through More Than One Mechanism

PubMed Central

McLaren, Jennie R.; Turkington, Roy

2011-01-01

Plant litter decomposition is a critical ecosystem process representing a major pathway for carbon flux, but little is known about how it is affected by changes in plant composition and diversity. Single plant functional groups (graminoids, legumes, non-leguminous forbs) were removed from a grassland in northern Canada to examine the impacts of functional group identity on decomposition. Removals were conducted within two different environmental contexts (fertilization and fungicide application) to examine the context-dependency of these identity effects. We examined two different mechanisms by which the loss of plant functional groups may impact decomposition: effects of the living plant community on the decomposition microenvironment, and changes in the species composition of the decomposing litter, as well as the interaction between these mechanisms. We show that the identity of the plant functional group removed affects decomposition through both mechanisms. Removal of both graminoids and forbs slowed decomposition through changes in the decomposition microenvironment. We found non-additive effects of litter mixing, with both the direction and identity of the functional group responsible depending on year; in 2004 graminoids positively influenced decomposition whereas in 2006 forbs negatively influenced decomposition rate. Although these two mechanisms act independently, their effects may be additive if both mechanisms are considered simultaneously. It is essential to understand the variety of mechanisms through which even a single ecosystem property is affected if we are to predict the future consequences of biodiversity loss. PMID:21858210

Biodiesel from Citrullus colocynthis Oil: Sulfonic-Ionic Liquid-Catalyzed Esterification of a Two-Step Process

PubMed Central

Ali Elsheikh, Yasir; Hassan Akhtar, Faheem

2014-01-01

Biodiesel was prepared from Citrullus colocynthis oil (CCO) via a two-step process. The first esterification step was explored in two ionic liquids (ILs) with 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHSO4) and 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate (MSIMHSO4). Both ILs appeared to be good candidates to replace hazardous acidic catalyst due to their exceptional properties. However, the two sulfonic chains existing in DSIMHSO4 were found to increase the acidity to the IL than the single sulfonic chain in MSIMHSO4. Based on the results, 3.6 wt% of DSIMHSO4, methanol/CCO molar ratio of 12 : 1, and 150°C offered a final FFA conversion of 95.4% within 105 min. A 98.2% was produced via second KOH-catalyzed step in 1.0%, 6 : 1 molar ratio, 600 rpm, and 60°C for 50 min. This new two-step catalyzed process could solve the corrosion and environmental problems associated with the current acidic catalysts. PMID:24987736

Functional and Structural Succession of Soil Microbial Communities below Decomposing Human Cadavers

PubMed Central

Cobaugh, Kelly L.; Schaeffer, Sean M.; DeBruyn, Jennifer M.

2015-01-01

The ecological succession of microbes during cadaver decomposition has garnered interest in both basic and applied research contexts (e.g. community assembly and dynamics; forensic indicator of time since death). Yet current understanding of microbial ecology during decomposition is almost entirely based on plant litter. We know very little about microbes recycling carcass-derived organic matter despite the unique decomposition processes. Our objective was to quantify the taxonomic and functional succession of microbial populations in soils below decomposing cadavers, testing the hypotheses that a) periods of increased activity during decomposition are associated with particular taxa; and b) human-associated taxa are introduced to soils, but do not persist outside their host. We collected soils from beneath four cadavers throughout decomposition, and analyzed soil chemistry, microbial activity and bacterial community structure. As expected, decomposition resulted in pulses of soil C and nutrients (particularly ammonia) and stimulated microbial activity. There was no change in total bacterial abundances, however we observed distinct changes in both function and community composition. During active decay (7 - 12 days postmortem), respiration and biomass production rates were high: the community was dominated by Proteobacteria (increased from 15.0 to 26.1% relative abundance) and Firmicutes (increased from 1.0 to 29.0%), with reduced Acidobacteria abundances (decreased from 30.4 to 9.8%). Once decay rates slowed (10 - 23 d postmortem), respiration was elevated, but biomass production rates dropped dramatically; this community with low growth efficiency was dominated by Firmicutes (increased to 50.9%) and other anaerobic taxa. Human-associated bacteria, including the obligately anaerobic Bacteroides, were detected at high concentrations in soil throughout decomposition, up to 198 d postmortem. Our results revealed the pattern of functional and compositional succession in soil microbial communities during decomposition of human-derived organic matter, provided insight into decomposition processes, and identified putative predictor populations for time since death estimation. PMID:26067226

Decomposition patterns of buried remains at different intervals in the Central Highveld region of South Africa.

PubMed

Marais-Werner, A; Myburgh, J; Meyer, A; Nienaber, W C; Steyn, M

2017-07-01

Burial of remains is an important factor when one attempts to establish the post-mortem interval as it reduces, and in extreme cases, excludes oviposition by Diptera species. This in turn leads to modification of the decomposition process. The aim of this study was to record decomposition patterns of buried remains using a pig model. The pattern of decomposition was evaluated at different intervals and recorded according to existing guidelines. In order to contribute to our knowledge on decomposition in different settings, a quantifiable approach was followed. Results indicated that early stages of decomposition occurred rapidly for buried remains within 7-33 days. Between 14 and 33 days, buried pigs displayed common features associated with the early to middle stages of decomposition, such as discoloration and bloating. From 33 to 90 days advanced decomposition manifested on the remains, and pigs then reached a stage of advanced decomposition where little change was observed in the next ±90-183 days after interment. Throughout this study, total body scores remained higher for surface remains. Overall, buried pigs followed a similar pattern of decomposition to those of surface remains, although at a much slower rate when compared with similar post-mortem intervals in surface remains. In this study, the decomposition patterns and rates of buried remains were mostly influenced by limited insect activity and adipocere formation which reduces the rate of decay in a conducive environment (i.e. burial in soil).

More of the same? In situ leaf and root decomposition rates do not vary between 80 native and nonnative deciduous forest species.

PubMed

Jo, Insu; Fridley, Jason D; Frank, Douglas A

2016-01-01

Invaders often have greater rates of production and produce more labile litter than natives. The increased litter quantity and quality of invaders should increase nutrient cycling through faster litter decomposition. However, the limited number of invasive species that have been included in decomposition studies has hindered the ability to generalize their impacts on decomposition rates. Further, previous decomposition studies have neglected roots. We measured litter traits and decomposition rates of leaves for 42 native and 36 nonnative woody species, and those of fine roots for 23 native and 25 nonnative species that occur in temperate deciduous forests throughout the Eastern USA. Among the leaf and root traits that differed between native and invasive species, only leaf nitrogen was significantly associated with decomposition rate. However, native and nonnative species did not differ systematically in leaf and root decomposition rates. We found that among the parameters measured, litter decomposer activity was driven by litter chemical quality rather than tissue density and structure. Our results indicate that litter decomposition rate per se is not a pathway by which forest woody invasive species affect North American temperate forest soil carbon and nutrient processes. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

High temperature phase decomposition in Ti{sub x}Zr{sub y}Al{sub z}N

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

Lind, Hans; Pilemalm, Robert; Rogström, Lina

2014-12-15

Through a combination of theoretical and experimental observations we study the high temperature decomposition behavior of c-(Ti{sub x}Zr{sub y}Al{sub z}N) alloys. We show that for most concentrations the high formation energy of (ZrAl)N causes a strong tendency for spinodal decomposition between ZrN and AlN while other decompositions tendencies are suppressed. In addition we observe that entropic effects due to configurational disorder favor a formation of a stable Zr-rich (TiZr)N phase with increasing temperature. Our calculations also predict that at high temperatures a Zr rich (TiZrAl)N disordered phase should become more resistant against the spinodal decomposition despite its high and positivemore » formation energy due to the specific topology of the free energy surface at the relevant concentrations. Our experimental observations confirm this prediction by showing strong tendency towards decomposition in a Zr-poor sample while a Zr-rich alloy shows a greatly reduced decomposition rate, which is mostly attributable to binodal decomposition processes. This result highlights the importance of considering the second derivative of the free energy, in addition to its absolute value in predicting decomposition trends of thermodynamically unstable alloys.« less

Incorporating DSA in multipatterning semiconductor manufacturing technologies

NASA Astrophysics Data System (ADS)

Badr, Yasmine; Torres, J. A.; Ma, Yuansheng; Mitra, Joydeep; Gupta, Puneet

2015-03-01

Multi-patterning (MP) is the process of record for many sub-10nm process technologies. The drive to higher densities has required the use of double and triple patterning for several layers; but this increases the cost of the new processes especially for low volume products in which the mask set is a large percentage of the total cost. For that reason there has been a strong incentive to develop technologies like Directed Self Assembly (DSA), EUV or E-beam direct write to reduce the total number of masks needed in a new technology node. Because of the nature of the technology, DSA cylinder graphoepitaxy only allows single-size holes in a single patterning approach. However, by integrating DSA and MP into a hybrid DSA-MP process, it is possible to come up with decomposition approaches that increase the design flexibility, allowing different size holes or bar structures by independently changing the process for every patterning step. A simple approach to integrate multi-patterning with DSA is to perform DSA grouping and MP decomposition in sequence whether it is: grouping-then-decomposition or decomposition-then-grouping; and each of the two sequences has its pros and cons. However, this paper describes why these intuitive approaches do not produce results of acceptable quality from the point of view of design compliance and we highlight the need for custom DSA-aware MP algorithms.

Copper-catalyzed oxidative desulfurization-oxygenation of thiocarbonyl compounds using molecular oxygen: an efficient method for the preparation of oxygen isotopically labeled carbonyl compounds.

PubMed

Shibahara, Fumitoshi; Suenami, Aiko; Yoshida, Atsunori; Murai, Toshiaki

2007-06-21

A novel copper-catalyzed oxidative desulfurization reaction of thiocarbonyl compounds, using molecular oxygen as an oxidant and leading to formation of carbonyl compounds, has been developed, and the utility of the process is demonstrated by its application to the preparation of a carbonyl-18O labeled sialic acid derivative.

Indole synthesis by palladium-catalyzed tandem allylic isomerization - furan Diels-Alder reaction.

PubMed

Xu, Jie; Wipf, Peter

2017-08-30

A Pd(0)-catalyzed elimination of an allylic acetate generates a π-allyl complex that is postulated to initiate a novel intramolecular Diels-Alder cycloaddition to a tethered furan (IMDAF). Under the reaction conditions, this convergent, microwave-accelerated cascade process provides substituted indoles in moderate to good yields after Pd-hydride elimination, aromatization by dehydration, and in situ N-Boc cleavage.

Facile synthesis of unsymmetrical acridines and phenazines by a Rh(III)-catalyzed amination/cyclization/aromatization cascade.

PubMed

Lian, Yajing; Hummel, Joshua R; Bergman, Robert G; Ellman, Jonathan A

2013-08-28

We report formal [3 + 3] annulations of aromatic azides with aromatic imines and azobenzenes to give acridines and phenazines, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine.

Synthesis of a Crushed Fullerene C60H24 through Sixfold Palladium‐Catalyzed Arylation

PubMed Central

Dorel, Ruth; de Mendoza, Paula; Calleja, Pilar; Pascual, Sergio; González‐Cantalapiedra, Esther; Cabello, Noemí

2016-01-01

The synthesis of a new C 3v‐symmetric crushed fullerene C60H24 (5) has been accomplished in three steps from truxene through sixfold palladium‐catalyzed intramolecular arylation of a syn‐trialkylated truxene precursor. Laser irradiation of 5 induces cyclodehydrogenation processes that result in the formation of C60, as detected by LDI‐MS. PMID:27774038

Thiazolylidene-catalyzed cleavage of methyl oleate-derived α-hydroxy ketone to the corresponding free aldehydes.

PubMed

Deruer, Elsa; Duguet, Nicolas; Lemaire, Marc

2015-08-10

The thiazolylidene-catalyzed cleavage of the α-hydroxy ketone derived from methyl oleate gave the corresponding aldehydes under nonoxidative conditions through a retro-benzoin process. The aldehydes produced are in equilibrium with their corresponding acyloins. To illustrate the synthetic utility of this protocol, the aldehydes were recovered by distillation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous In Vitro Evolution of a Ribozyme that Catalyzes Three Successive Nucleotidyl Addition Reactions

NASA Technical Reports Server (NTRS)

McGinness, Kathleen E.; Wright, Martin C.; Joyce, Gerald F.

2002-01-01

Variants of the class I ligase ribozyme, which catalyzes joining of the 3' end of a template bound oligonucleotide to its own 5' end, have been made to evolve in a continuous manner by a simple serial transfer procedure that can be carried out indefinitely. This process was expanded to allow the evolution of ribozymes that catalyze three successive nucleotidyl addition reactions, two template-directed mononucleotide additions followed by RNA ligation. During the development of this behavior, a population of ribozymes was maintained against an overall dilution of more than 10(exp 406). The resulting ribozymes were capable of catalyzing the three-step reaction pathway, with nucleotide addition occurring in either a 5' yieldig 3' or a 3' yielding 5' direction. This purely chemical system provides a functional model of a multi-step reaction pathway that is undergoing Darwinian evolution.

Manganese-Catalyzed Aminomethylation of Aromatic Compounds with Methanol as a Sustainable C1 Building Block.

PubMed

Mastalir, Matthias; Pittenauer, Ernst; Allmaier, Günter; Kirchner, Karl

2017-07-05

This study represents the first example of a manganese-catalyzed environmentally benign, practical three-component aminomethylation of activated aromatic compounds including naphtols, phenols, pyridines, indoles, carbazoles, and thiophenes in combination with amines and MeOH as a C1 source. These reactions proceed with high atom efficiency via a sequence of dehydrogenation and condensation steps which give rise to selective C-C and C-N bond formations, thereby releasing hydrogen and water. A well-defined hydride Mn(I) PNP pincer complex, recently developed in our laboratory, catalyzes this process in a very efficient way, and a total of 28 different aminomethylated products were synthesized and isolated yields of up to 91%. In a preliminary study, a related Fe(II) PNP pincer complex was shown to catalyze the methylation of 2-naphtol rather than its aminomethylation displaying again the divergent behavior of isoelectronic Mn(I) and Fe(II) PNP pincer systems.

Nickel-catalyzed cross-coupling of photoredox-generated radicals: uncovering a general manifold for stereoconvergence in nickel-catalyzed cross-couplings.

PubMed

Gutierrez, Osvaldo; Tellis, John C; Primer, David N; Molander, Gary A; Kozlowski, Marisa C

2015-04-22

The cross-coupling of sp(3)-hybridized organoboron reagents via photoredox/nickel dual catalysis represents a new paradigm of reactivity for engaging alkylmetallic reagents in transition-metal-catalyzed processes. Reported here is an investigation into the mechanistic details of this important transformation using density functional theory. Calculations bring to light a new reaction pathway involving an alkylnickel(I) complex generated by addition of an alkyl radical to Ni(0) that is likely to operate simultaneously with the previously proposed mechanism. Analysis of the enantioselective variant of the transformation reveals an unexpected manifold for stereoinduction involving dynamic kinetic resolution (DKR) of a Ni(III) intermediate wherein the stereodetermining step is reductive elimination. Furthermore, calculations suggest that the DKR-based stereoinduction manifold may be responsible for stereoselectivity observed in numerous other stereoconvergent Ni-catalyzed cross-couplings and reductive couplings.

Regioselective, borinic acid-catalyzed monoacylation, sulfonylation and alkylation of diols and carbohydrates: expansion of substrate scope and mechanistic studies.

PubMed

Lee, Doris; Williamson, Caitlin L; Chan, Lina; Taylor, Mark S

2012-05-16

Synthetic and mechanistic aspects of the diarylborinic acid-catalyzed regioselective monofunctionalization of 1,2- and 1,3-diols are presented. Diarylborinic acid catalysis is shown to be an efficient and general method for monotosylation of pyranoside derivatives bearing three secondary hydroxyl groups (7 examples, 88% average yield). In addition, the scope of the selective acylation, sulfonylation, and alkylation is extended to 1,2- and 1,3-diols not derived from carbohydrates (28 examples); the efficiency, generality, and operational simplicity of this method are competitive with those of state-of-the-art protocols including the broadly applied organotin-catalyzed or -mediated reactions. Mechanistic details of the organoboron-catalyzed processes are explored using competition experiments, kinetics, and catalyst structure-activity relationships. These experiments are consistent with a mechanism in which a tetracoordinate borinate complex reacts with the electrophilic species in the turnover-limiting step of the catalytic cycle.

Potential role of gas hydrate decomposition in generating submarine slope failures: Chapter 12

USGS Publications Warehouse

Pauli, Charles K.; Ussler, William III; Dillon, William P.; Max, Michael D.

2003-01-01

Gas hydrate decomposition is hypothesized to be a factor in generating weakness in continental margin sediments that may help explain some of the observed patterns of continental margin sediment instability. The processes associated with formation and decomposition of gas hydrate can cause the strengthening of sediments in which gas hydrate grow and the weakening of sediments in which gas hydrate decomposes. The weakened sediments may form horizons along which the potential for sediment failure is increased. While a causal relationship between slope failures and gas hydrate decomposition has not been proven, a number of empirical observations support their potential connection.

Services Textbook of Explosives

DTIC Science & Technology

1972-03-01

described the use of wood ashes in this process, whereby, by double- decomposition of calcium nitrate present in the crude salt, a greater yield of true...the Italians had worked on the nitration of hexamine, but had not developed successful processes. In 1945 , however, it was found that the Germans had...of the propellant. It was later, and unexpectedly, found to have the valuable property of absorbing the (acidic) products of decomposition of

Unraveling the catalyzing behaviors of different iron species (Fe2+ vs. Fe0) in activating persulfate-based oxidation process with implications to waste activated sludge dewaterability.

PubMed

Zhen, Guangyin; Lu, Xueqin; Su, Lianghu; Kobayashi, Takuro; Kumar, Gopalakrishnan; Zhou, Tao; Xu, Kaiqin; Li, Yu-You; Zhu, Xuefeng; Zhao, Youcai

2018-05-01

Dewatering of waste activated sludge (WAS) is of major interest in its volume reduction, transportation and ultimate disposal. Persulfate-based oxidation process is a newly developed option for enhancing WAS dewaterability through the generation of powerful sulfate radicals (SO 4 - ·). However, the enhancement in WAS dewaterability by persulfate differs with the species of iron catalysts used. In this study, two types of iron catalysts (i.e. Fe 2+ vs. Fe 0 ) were employed to initiate the persulfate (S 2 O 8 2- ), and the catalyzing behaviors and the underlying principles in enhancing WAS dewaterability were investigated and compared. The Fe 2+ exhibited the high effectiveness in catalyzing the decomposition of persulfate to sulfate radicals (SO 4 - ·), inducing the greater improvement in WAS dewatering. The WAS dewaterability (indicated by dry solids content after filtration) increased with the added S 2 O 8 2- /Fe 2+ dosages, with the dry solids content reaching up to 5.1 ± 0.8 wt% at S 2 O 8 2- /Fe 2+ dosages of 1.2/1.5 mmol/g-VS after only 30 s' filtration, roughly 1.8-fold increase than raw WAS (1.8 ± 0.1 wt%). In contrast, the influence of the persulfate oxidation when activated with Fe 0 on WAS dewaterability was statistically insignificant. The WAS dewaterability remained nearly unchanged (i.e. dry solids content of 2.0 ± 0.0 wt%), irrespective of the employed S 2 O 8 2- /Fe 0 dosages. Further analysis demonstrated that the WAS dewaterability negatively corresponded to loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS). The abundant SO 4 - · from S 2 O 8 2- /Fe 2+ system could effectively disrupt the gel-like EPS matrix, break apart the cells and subsequently arouse the release of the water inside EPS and cells, facilitating water-solid separation. In the case of S 2 O 8 2- /Fe 0 , the dissolution of Fe 0 particles was the rate-limiting step, due to the formation of oxide iron layer near Fe 0 metallic surface, which resulted in the slow SO 4 - · production and thus hardly promoted WAS dewaterability. The pH adjustment could accelerate Fe 0 dissolution and enhance the dewatering performance of S 2 O 8 2- /Fe 0 process to a certain degree, but the effect was unsatisfactory. Additionally, the observations regarding the dissolved organic matters and ammonium collectively revealed that except for enhancing WAS dewatering, S 2 O 8 2- /Fe 2+ oxidation could concurrently degrade COD and ammonia from WAS filtrate, lighten the burden of the subsequent sewage treatment facilities and reduce operational expense. Hence, from an environmental and economic perspective, the S 2 O 8 2- /Fe 2+ system possesses much greater promise for WAS dewatering. Copyright © 2018 Elsevier Ltd. All rights reserved.

Hydrology or biology? Modeling simplistic physical constraints on lake carbon biogeochemistry to identify when and where biology is likely to matter

NASA Astrophysics Data System (ADS)

Jones, S.; Zwart, J. A.; Solomon, C.; Kelly, P. T.

2017-12-01

Current efforts to scale lake carbon biogeochemistry rely heavily on empirical observations and rarely consider physical or biological inter-lake heterogeneity that is likely to regulate terrestrial dissolved organic carbon (tDOC) decomposition in lakes. This may in part result from a traditional focus of lake ecologists on in-lake biological processes OR physical-chemical pattern across lake regions, rather than on process AND pattern across scales. To explore the relative importance of local biological processes and physical processes driven by lake hydrologic setting, we created a simple, analytical model of tDOC decomposition in lakes that focuses on the regulating roles of lake size and catchment hydrologic export. Our simplistic model can generally recreate patterns consistent with both local- and regional-scale patterns in tDOC concentration and decomposition. We also see that variation in lake hydrologic setting, including the importance of evaporation as a hydrologic export, generates significant, emergent variation in tDOC decomposition at a given hydrologic residence time, and creates patterns that have been historically attributed to variation in tDOC quality. Comparing predictions of this `biologically null model' to field observations and more biologically complex models could indicate when and where biology is likely to matter most.

Mixing effects on litter decomposition rates in a young tree diversity experiment

NASA Astrophysics Data System (ADS)

Setiawan, Nuri Nurlaila; Vanhellemont, Margot; De Schrijver, An; Schelfhout, Stephanie; Baeten, Lander; Verheyen, Kris

2016-01-01

Litter decomposition is an essential process for biogeochemical cycling and for the formation of new soil organic matter. Mixing litter from different tree species has been reported to increase litter decomposition rates through synergistic effects. We assessed the decomposition rates of leaf litter from five tree species in a recently established tree diversity experiment on a post-agriculture site in Belgium. We used 20 different leaf litter compositions with diversity levels ranging from 1 up to 4 species. Litter mass loss in litterbags was assessed 10, 20, 25, 35, and 60 weeks after installation in the field. We found that litter decomposition rates were higher for high-quality litters, i.e., with high nitrogen content and low lignin content. The decomposition rates of mixed litter were more affected by the identity of the litter species within the mixture than by the diversity of the litter per se, but the variability in litter decomposition rates decreased as the litter diversity increased. Among the 15 different mixed litter compositions in our study, only three litter combinations showed synergistic effects. Our study suggests that admixing tree species with high-quality litter in post-agricultural plantations helps in increasing the mixture's early-stage litter decomposition rate.

Integrating a Genetic Algorithm Into a Knowledge-Based System for Ordering Complex Design Processes

NASA Technical Reports Server (NTRS)

Rogers, James L.; McCulley, Collin M.; Bloebaum, Christina L.

1996-01-01

The design cycle associated with large engineering systems requires an initial decomposition of the complex system into design processes which are coupled through the transference of output data. Some of these design processes may be grouped into iterative subcycles. In analyzing or optimizing such a coupled system, it is essential to be able to determine the best ordering of the processes within these subcycles to reduce design cycle time and cost. Many decomposition approaches assume the capability is available to determine what design processes and couplings exist and what order of execution will be imposed during the design cycle. Unfortunately, this is often a complex problem and beyond the capabilities of a human design manager. A new feature, a genetic algorithm, has been added to DeMAID (Design Manager's Aid for Intelligent Decomposition) to allow the design manager to rapidly examine many different combinations of ordering processes in an iterative subcycle and to optimize the ordering based on cost, time, and iteration requirements. Two sample test cases are presented to show the effects of optimizing the ordering with a genetic algorithm.

Size-controlled magnetic nanoparticles with lecithin for biomedical applications

NASA Astrophysics Data System (ADS)

Park, S. I.; Kim, J. H.; Kim, C. G.; Kim, C. O.

2007-05-01

Lecithin-adsorbed magnetic nanoparticles were prepared by three-step process that the thermal decomposition was combined with ultrasonication. Experimental parameters were three items—molar ratio between Fe(CO) 5 and oleic acid, keeping time at decomposition temperature and lecithin concentration. As the molar ratio between Fe(CO) 5 and oleic acid, and keeping time at decomposition temperature increased, the particle size increased. However, the change of lecithin concentration did not show the remarkable particle size variation.

Verbs in the lexicon: Why is hitting easier than breaking?

PubMed

McKoon, Gail; Love, Jessica

2011-11-01

Adult speakers use verbs in syntactically appropriate ways. For example, they know implicitly that the boy hit at the fence is acceptable but the boy broke at the fence is not. We suggest that this knowledge is lexically encoded in semantic decompositions. The decomposition for break verbs (e.g. crack, smash) is hypothesized to be more complex than that for hit verbs (e.g. kick, kiss). Specifically, the decomposition of a break verb denotes that "an entity changes state as the result of some external force" whereas the decomposition for a hit verb denotes only that "an entity potentially comes in contact with another entity." In this article, verbs of the two types were compared in a lexical decision experiment - Experiment 1 - and they were compared in sentence comprehension experiments with transitive sentences (e.g. the car hit the bicycle and the car broke the bicycle) - Experiments 2 and 3. In Experiment 1, processing times were shorter for the hit than the break verbs and in Experiments 2 and 3, processing times were shorter for the hit sentences than the break sentences, results that are in accord with the complexities of the postulated semantic decompositions.

Morphological characteristics of waste polyethylene/polypropylene plastics during pyrolysis and representative morphological signal characterizing pyrolysis stages.

PubMed

Wang, H; Chen, D; Yuan, G; Ma, X; Dai, X

2013-02-01

In this work, the morphological characteristics of waste polyethylene (PE)/polypropylene (PP) plastics during their pyrolysis process were investigated, and based on their basic image changing patterns representative morphological signals describing the pyrolysis stages were obtained. PE and PP granules and films were used as typical plastics for testing, and influence of impurities was also investigated. During pyrolysis experiments, photographs of the testing samples were taken sequentially with a high-speed infrared camera, and the quantitative parameters that describe the morphological characteristics of these photographs were explored using the "Image Pro Plus (v6.3)" digital image processing software. The experimental results showed that plastics pyrolysis involved four stages: melting, two stages of decomposition which are characterized with bubble formation caused by volatile evaporating, and ash deposition; and each stage was characterized with its own phase changing behaviors and morphological features. Two stages of decomposition are the key step of pyrolysis since they took up half or more of the reaction time; melting step consumed another half of reaction time in experiments when raw materials were heated up from ambient temperatures; and coke-like deposition appeared as a result of decomposition completion. Two morphological signals defined from digital image processing, namely, pixel area of the interested reaction region and bubble ratio (BR) caused by volatile evaporating were found to change regularly with pyrolysis stages. In particular, for all experimental scenarios with plastics films and granules, the BR curves always exhibited a slowly drop as melting started and then a sharp increase followed by a deep decrease corresponding to the first stage of intense decomposition, afterwards a second increase - drop section corresponding to the second stage of decomposition appeared. As ash deposition happened, the BR dropped to zero or very low values. When impurities were involved, the shape of BR curves showed that intense decomposition started earlier but morphological characteristics remained the same. In addition, compared to parameters such as pressure, the BR reflects reaction stages better and its change with pyrolysis process of PE/PP plastics with or without impurities was more intrinsically process correlated; therefore it can be adopted as a signal for pyrolysis process characterization, as well as offering guide to process improvement and reactor design. Copyright © 2012 Elsevier Ltd. All rights reserved.

In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites

PubMed Central

2016-01-01

Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for higher temperatures (400–800 °C) Ni-catalyzed isothermal graphitization of the amorphous carbon matrix sets in, which we link to bulk-diffusion-mediated phase separation of the nanocomposite into coarser Ni and graphite grains. Upon natural cooling, only minimal precipitation of additional carbon from the Ni is observed, showing that even for highly carbon saturated systems precipitation upon cooling can be kinetically quenched. Our findings demonstrate that phase transformations of the filler and morphology modifications of the nanocomposite can be decoupled, which is advantageous from a manufacturing perspective. Our in situ study also identifies the high carbon content of the Ni filler crystallites at all stages of processing as the key hallmark feature of such metal–carbon nanocomposites that governs their entire thermal evolution. In a wider context, we also discuss our findings with regard to the much debated potential role of metastable Ni3C as a catalyst phase in graphene and carbon nanotube growth. PMID:27746852

Microbial Community Functional Change during Vertebrate Carrion Decomposition

PubMed Central

Pechal, Jennifer L.; Crippen, Tawni L.; Tarone, Aaron M.; Lewis, Andrew J.; Tomberlin, Jeffery K.; Benbow, M. Eric

2013-01-01

Microorganisms play a critical role in the decomposition of organic matter, which contributes to energy and nutrient transformation in every ecosystem. Yet, little is known about the functional activity of epinecrotic microbial communities associated with carrion. The objective of this study was to provide a description of the carrion associated microbial community functional activity using differential carbon source use throughout decomposition over seasons, between years and when microbial communities were isolated from eukaryotic colonizers (e.g., necrophagous insects). Additionally, microbial communities were identified at the phyletic level using high throughput sequencing during a single study. We hypothesized that carrion microbial community functional profiles would change over the duration of decomposition, and that this change would depend on season, year and presence of necrophagous insect colonization. Biolog EcoPlates™ were used to measure the variation in epinecrotic microbial community function by the differential use of 29 carbon sources throughout vertebrate carrion decomposition. Pyrosequencing was used to describe the bacterial community composition in one experiment to identify key phyla associated with community functional changes. Overall, microbial functional activity increased throughout decomposition in spring, summer and winter while it decreased in autumn. Additionally, microbial functional activity was higher in 2011 when necrophagous arthropod colonizer effects were tested. There were inconsistent trends in the microbial function of communities isolated from remains colonized by necrophagous insects between 2010 and 2011, suggesting a greater need for a mechanistic understanding of the process. These data indicate that functional analyses can be implemented in carrion studies and will be important in understanding the influence of microbial communities on an essential ecosystem process, carrion decomposition. PMID:24265741

Molecular C dynamics downstream: the biochemical decomposition sequence and its impact on soil organic matter structure and function.

PubMed

Grandy, A Stuart; Neff, Jason C

2008-10-15

Advances in spectroscopic and other chemical methods have greatly enhanced our ability to characterize soil organic matter chemistry. As a result, the molecular characteristics of soil C are now known for a range of ecosystems, soil types, and management intensities. Placing this knowledge into a broader ecological and management context is difficult, however, and remains one of the fundamental challenges of soil organic matter research. Here we present a conceptual model of molecular soil C dynamics to stimulate inter-disciplinary research into the ecological implications of molecular C turnover and its management- and process-level controls. Our model describes three properties of soil C dynamics: 1) soil size fractions have unique molecular patterns that reflect varying degrees of biological and physical control over decomposition; 2) there is a common decomposition sequence independent of plant inputs or other ecosystem properties; and 3) molecular decomposition sequences, although consistent, are not uniform and can be altered by processes that accelerate or slow the microbial transformation of specific molecules. The consequences of this model include several key points. First, lignin presents a constraint to decomposition of plant litter and particulate C (>53 microm) but exerts little influence on more stable mineral-associated soil fractions <53 microm. Second, carbon stabilized onto mineral fractions has a distinct composition related more to microbially processed organic matter than to plant-related compounds. Third, disturbances, such as N fertilization and tillage, which alter decomposition rates, can have "downstream effects"; that is, a disturbance that directly alters the molecular dynamics of particulate C may have a series of indirect effects on C stabilization in silt and clay fractions.

Shrub encroachment in Arctic tundra: Betula nana effects on above- and belowground litter decomposition.

PubMed

McLaren, Jennie R; Buckeridge, Kate M; van de Weg, Martine J; Shaver, Gaius R; Schimel, Joshua P; Gough, Laura

2017-05-01

Rapid arctic vegetation change as a result of global warming includes an increase in the cover and biomass of deciduous shrubs. Increases in shrub abundance will result in a proportional increase of shrub litter in the litter community, potentially affecting carbon turnover rates in arctic ecosystems. We investigated the effects of leaf and root litter of a deciduous shrub, Betula nana, on decomposition, by examining species-specific decomposition patterns, as well as effects of Betula litter on the decomposition of other species. We conducted a 2-yr decomposition experiment in moist acidic tundra in northern Alaska, where we decomposed three tundra species (Vaccinium vitis-idaea, Rhododendron palustre, and Eriophorum vaginatum) alone and in combination with Betula litter. Decomposition patterns for leaf and root litter were determined using three different measures of decomposition (mass loss, respiration, extracellular enzyme activity). We report faster decomposition of Betula leaf litter compared to other species, with support for species differences coming from all three measures of decomposition. Mixing effects were less consistent among the measures, with negative mixing effects shown only for mass loss. In contrast, there were few species differences or mixing effects for root decomposition. Overall, we attribute longer-term litter mass loss patterns to patterns created by early decomposition processes in the first winter. We note numerous differences for species patterns between leaf and root decomposition, indicating that conclusions from leaf litter experiments should not be extrapolated to below-ground decomposition. The high decomposition rates of Betula leaf litter aboveground, and relatively similar decomposition rates of multiple species below, suggest a potential for increases in turnover in the fast-decomposing carbon pool of leaves and fine roots as the dominance of deciduous shrubs in the Arctic increases, but this outcome may be tempered by negative litter mixing effects during the early stages of encroachment. © 2017 by the Ecological Society of America.

Efficient catalytic decomposition of formic acid for the selective generation of H2 and H/D exchange with a water-soluble rhodium complex in aqueous solution.

PubMed

Fukuzumi, Shunichi; Kobayashi, Takeshi; Suenobu, Tomoyoshi

2008-01-01

Formic acid (HCOOH) decomposes efficiently to afford H2 and CO2 selectively in the presence of a catalytic amount of a water-soluble rhodium aqua complex, [Rh(III)(Cp*)(bpy)(H2O)]2+ (Cp*=pentamethylcyclopentadienyl, bpy=2,2'-bipyridine) in aqueous solution at 298 K. No CO was produced in this catalytic decomposition of HCOOH. The decomposition rate reached a maximum value at pH 3.8. No deterioration of the catalyst was observed during the catalytic decomposition of HCOOH, and the catalytic activity remained the same for the repeated addition of HCOOH. The rhodium-hydride complex was detected as the catalytic active species that undergoes efficient H/D exchange with water. When the catalytic decomposition of HCOOH was performed in D2O, D2 was produced selectively. Such an efficient H/D exchange and the observation of a deuterium kinetic isotope effect in the catalytic decomposition of DCOOH in H2O provide valuable mechanistic insight into this efficient and selective decomposition process.

Ruthenium-Catalyzed Cascade Annulation of Indole with Propargyl Alcohols.

PubMed

Kaufmann, Julia; Jäckel, Elisabeth; Haak, Edgar

2018-05-14

Cascade transformations forming multiple bonds and one-pot procedures provide rapid access to natural-product-like scaffolds from simple precursors. These atom-economic processes are valuable tools in organic synthesis and drug discovery. Herein, we report on ruthenium-catalyzed cascade annulations of indole with readily available propargyl alcohols. These provide rapid access to diverse carbazoles, cyclohepta[b]indoles, and further fused polycycles with high selectivity. A bifunctional ruthenium complex featuring a redox-coupled cyclopentadienone ligand acts as a common catalyst for the different cascade processes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enzymatic synthesis of chiral amino‐alcohols by coupling transketolase and transaminase‐catalyzed reactions in a cascading continuous‐flow microreactor system

PubMed Central

Gruber, Pia; Carvalho, Filipe; Marques, Marco P. C.; O'Sullivan, Brian; Subrizi, Fabiana; Dobrijevic, Dragana; Ward, John; Hailes, Helen C.; Fernandes, Pedro; Wohlgemuth, Roland; Baganz, Frank

2017-01-01

Abstract Rapid biocatalytic process development and intensification continues to be challenging with currently available methods. Chiral amino‐alcohols are of particular interest as they represent key industrial synthons for the production of complex molecules and optically pure pharmaceuticals. (2S,3R)‐2‐amino‐1,3,4‐butanetriol (ABT), a building block for the synthesis of protease inhibitors and detoxifying agents, can be synthesized from simple, non‐chiral starting materials, by coupling a transketolase‐ and a transaminase‐catalyzed reaction. However, until today, full conversion has not been shown and, typically, long reaction times are reported, making process modifications and improvement challenging. In this contribution, we present a novel microreactor‐based approach based on free enzymes, and we report for the first time full conversion of ABT in a coupled enzyme cascade for both batch and continuous‐flow systems. Using the compartmentalization of the reactions afforded by the microreactor cascade, we overcame inhibitory effects, increased the activity per unit volume, and optimized individual reaction conditions. The transketolase‐catalyzed reaction was completed in under 10 min with a volumetric activity of 3.25 U ml−1. Following optimization of the transaminase‐catalyzed reaction, a volumetric activity of 10.8 U ml−1 was attained which led to full conversion of the coupled reaction in 2 hr. The presented approach illustrates how continuous‐flow microreactors can be applied for the design and optimization of biocatalytic processes. PMID:28986983

Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

PubMed

Joshi, Prachi; Gorski, Christopher A

2016-07-19

When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

Alkaloids May Not be Responsible for Endophyte Associated Reductions in Tall Fescue Decomposition Rates

USDA-ARS?s Scientific Manuscript database

1. Fungal endophyte - grass symbioses can have dramatic ecological effects, altering individual plant physiology, plant and animal community structure and function, and ecosystem processes such as litter decomposition and nutrient cycling. 2. Within the tall fescue (Schedonorus arundinaceus) - funga...

From the Rainbow Crow To Polar Bears: Introducing Science Concepts through Children's Literature.

ERIC Educational Resources Information Center

Burns, John Eric

1997-01-01

Describes an activity that integrates chemistry, physics, and a Native American legend to help students imitate the thought processes of scientists who have observed chemical decomposition and the refraction of light. Includes a laboratory experiment for sugar decomposition. (DKM)

Students' Understanding of Quadratic Equations

ERIC Educational Resources Information Center

López, Jonathan; Robles, Izraim; Martínez-Planell, Rafael

2016-01-01

Action-Process-Object-Schema theory (APOS) was applied to study student understanding of quadratic equations in one variable. This required proposing a detailed conjecture (called a genetic decomposition) of mental constructions students may do to understand quadratic equations. The genetic decomposition which was proposed can contribute to help…

Factors and processes causing accelerated decomposition in human cadavers - An overview.

PubMed

Zhou, Chong; Byard, Roger W

2011-01-01

Artefactually enhanced putrefactive and autolytic changes may be misinterpreted as indicating a prolonged postmortem interval and throw doubt on the veracity of witness statements. Review of files from Forensic Science SA and the literature revealed a number of external and internal factors that may be responsible for accelerating these processes. Exogenous factors included exposure to elevated environmental temperatures, both outdoors and indoors, exacerbated by increased humidity or fires. Situations indoor involved exposure to central heating, hot water, saunas and electric blankets. Deaths within motor vehicles were also characterized by enhanced decomposition. Failure to quickly or adequately refrigerate bodies may also lead to early decomposition. Endogenous factors included fever, infections, illicit and prescription drugs, obesity and insulin-dependent diabetes mellitus. When these factors or conditions are identified at autopsy less significance should, therefore, be attached to changes of decomposition as markers of time since death. Copyright © 2010 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

Reactive molecular dynamics simulation of solid nitromethane impact on (010) surfaces induced and nonimpact thermal decomposition.

PubMed

Guo, Feng; Cheng, Xin-lu; Zhang, Hong

2012-04-12

Which is the first step in the decomposition process of nitromethane is a controversial issue, proton dissociation or C-N bond scission. We applied reactive force field (ReaxFF) molecular dynamics to probe the initial decomposition mechanisms of nitromethane. By comparing the impact on (010) surfaces and without impact (only heating) for nitromethane simulations, we found that proton dissociation is the first step of the pyrolysis of nitromethane, and the C-N bond decomposes in the same time scale as in impact simulations, but in the nonimpact simulation, C-N bond dissociation takes place at a later time. At the end of these simulations, a large number of clusters are formed. By analyzing the trajectories, we discussed the role of the hydrogen bond in the initial process of nitromethane decompositions, the intermediates observed in the early time of the simulations, and the formation of clusters that consisted of C-N-C-N chain/ring structures.

Recovery and removal of nutrients from swine wastewater by using a novel integrated reactor for struvite decomposition and recycling

PubMed Central

Huang, Haiming; Xiao, Dean; Liu, Jiahui; Hou, Li; Ding, Li

2015-01-01

In the present study, struvite decomposition was performed by air stripping for ammonia release and a novel integrated reactor was designed for the simultaneous removal and recovery of total ammonia-nitrogen (TAN) and total orthophosphate (PT) from swine wastewater by internal struvite recycling. Decomposition of struvite by air stripping was found to be feasible. Without supplementation with additional magnesium and phosphate sources, the removal ratio of TAN from synthetic wastewater was maintained at >80% by recycling of the struvite decomposition product formed under optimal conditions, six times. Continuous operation of the integrated reactor indicated that approximately 91% TAN and 97% PT in the swine wastewater could be removed and recovered by the proposed recycling process with the supplementation of bittern. Economic evaluation of the proposed system showed that struvite precipitation cost can be saved by approximately 54% by adopting the proposed recycling process in comparison with no recycling method. PMID:25960246

Rotational-path decomposition based recursive planning for spacecraft attitude reorientation

NASA Astrophysics Data System (ADS)

Xu, Rui; Wang, Hui; Xu, Wenming; Cui, Pingyuan; Zhu, Shengying

2018-02-01

The spacecraft reorientation is a common task in many space missions. With multiple pointing constraints, it is greatly difficult to solve the constrained spacecraft reorientation planning problem. To deal with this problem, an efficient rotational-path decomposition based recursive planning (RDRP) method is proposed in this paper. The uniform pointing-constraint-ignored attitude rotation planning process is designed to solve all rotations without considering pointing constraints. Then the whole path is checked node by node. If any pointing constraint is violated, the nearest critical increment approach will be used to generate feasible alternative nodes in the process of rotational-path decomposition. As the planning path of each subdivision may still violate pointing constraints, multiple decomposition is needed and the reorientation planning is designed as a recursive manner. Simulation results demonstrate the effectiveness of the proposed method. The proposed method has been successfully applied in two SPARK microsatellites to solve onboard constrained attitude reorientation planning problem, which were developed by the Shanghai Engineering Center for Microsatellites and launched on 22 December 2016.

Determination of the Volume of Water for Suppressing the Thermal Decomposition of Forest Combustibles

NASA Astrophysics Data System (ADS)

Volkov, R. S.; Zhdanova, A. O.; Kuznetsov, G. V.; Strizhak, P. A.

2017-07-01

From the results of experimental studies of the processes of suppressing the thermal decomposition of the typical forest combustibles (birch leaves, fir needles, asp twigs, and a mixture of these three materials) by water aerosol, the minimum volumes of the fire-extinguishing liquid have been determined (by varying the volume of samples of the forest combustibles from 0.00002 m3 to 0.0003 m3 and the area of their open surface from 0.0001 m2 to 0.018 m2). The dependences of the minimum volume of water on the area of the open surface of the forest combustible have been established. Approximation expressions for these dependences have been obtained. Forecast has been made of the minimum volume of water for suppressing the process of thermal decomposition of forest combustibles in areas from 1 cm2 to 1 km2, as well as of the characteristic quenching times by varying the water concentration per unit time. It has been shown that the amount of water needed for effective suppression of the process of thermal decomposition of forest combustibles is several times less than is customarily assumed.

Matrix decomposition graphics processing unit solver for Poisson image editing

NASA Astrophysics Data System (ADS)

Lei, Zhao; Wei, Li

2012-10-01

In recent years, gradient-domain methods have been widely discussed in the image processing field, including seamless cloning and image stitching. These algorithms are commonly carried out by solving a large sparse linear system: the Poisson equation. However, solving the Poisson equation is a computational and memory intensive task which makes it not suitable for real-time image editing. A new matrix decomposition graphics processing unit (GPU) solver (MDGS) is proposed to settle the problem. A matrix decomposition method is used to distribute the work among GPU threads, so that MDGS will take full advantage of the computing power of current GPUs. Additionally, MDGS is a hybrid solver (combines both the direct and iterative techniques) and has two-level architecture. These enable MDGS to generate identical solutions with those of the common Poisson methods and achieve high convergence rate in most cases. This approach is advantageous in terms of parallelizability, enabling real-time image processing, low memory-taken and extensive applications.

Metal-Doped Silver Oxide Films as a Mask Layer for the Super-RENS Disk

NASA Astrophysics Data System (ADS)

Shima, Takayuki; Buechel, Dorothea; Mihalcea, Christophe; Kim, Jooho; Atoda, Nobufumi; Tominaga, Junji

Various kinds of metal (Co, Pd, Pt and Au) were doped into Ag2O and AgO sputtered films to study its effect on the thermal decomposition process. The oxygen composition ratio was evaluated by the X-ray fluorescence spectroscopy method after annealing up to 260,oC. The optical transmittance change was measured during heating of the film to 600,oC. Noble metal doping was found to modify the AgO decomposition process, and the oxygen content decreased gradually compared to the undoped case. Super-RENS disks with a metal-doped AgO mask were prepared, and the laser power necessary for super-resolutional readout was evaluated. It slightly shifted to the higher-power side when the noble metal was doped, and this agrees with the modification of the decomposition process.Japan Science and Technology Corporation, Domestic Research Fellow

Process for coating an object with silicon carbide

NASA Technical Reports Server (NTRS)

Levin, Harry (Inventor)

1989-01-01

A process for coating a carbon or graphite object with silicon carbide by contacting it with silicon liquid and vapor over various lengths of contact time. In the process, a stream of silicon-containing precursor material in gaseous phase below the decomposition temperature of said gas and a co-reactant, carrier or diluent gas such as hydrogen is passed through a hole within a high emissivity, thin, insulating septum into a reaction chamber above the melting point of silicon. The thin septum has one face below the decomposition temperature of the gas and an opposite face exposed to the reaction chamber. The precursor gas is decomposed directly to silicon in the reaction chamber. A stream of any decomposition gas and any unreacted precursor gas from said reaction chamber is removed. The object within the reaction chamber is then contacted with silicon, and recovered after it has been coated with silicon carbide.

Extraction of Curcumin Pigment from Indonesian Local Turmeric with Its Infrared Spectra and Thermal Decomposition Properties

NASA Astrophysics Data System (ADS)

Nandiyanto, A. B. D.; Wiryani, A. S.; Rusli, A.; Purnamasari, A.; Abdullah, A. G.; Ana; Widiaty, I.; Hurriyati, R.

2017-03-01

Curcumin is one of the pigments which is used as a spice in Asian cuisine, traditional cosmetic, and medicine. Therefore, process for getting curcumin has been widely studied. Here, the purpose of this study was to demonstrate the simple method for extracting curcumin from Indonesian local turmeric and investigate the infrared spectra and thermal decomposition properties. In the experimental procedure, the washed turmeric was dissolved into an ethanol solution, and then put into a rotary evaporator to enrich curcumin concentration. The result showed that the present method is effective to isolate curcumin compound from Indonesian local turmeric. Since the process is very simple, this method can be used for home industrial application. Further, understanding the thermal decomposition properties of curcumin give information, specifically relating to the selection of treatment when curcumin must face the thermal-related process.

Consecutive three-component synthesis of (hetero)arylated propargyl amides by chemoenzymatic aminolysis-Sonogashira coupling sequence.

PubMed

Hassan, Sidra; Ullrich, Anja; Müller, Thomas J J

2015-02-07

A novel chemoenzymatic three-component synthesis of (hetero)arylated propargyl amides in good yields based upon Novozyme® 435 (Candida antarctica lipase B (CAL-B)) catalyzed aminolysis of methyl carboxylates followed by Sonogashira coupling with (hetero)aryliodides in a consecutive one-pot fashion has been presented. This efficient methodology can be readily concatenated with a CuAAC (Cu catalyzed alkyne azide cycloaddition) as a third consecutive step to furnish 1,4-disubstituted 1,2,3-triazole ligated arylated propargyl amides. This one-pot process can be regarded as a transition metal catalyzed sequence that takes advantage of the copper source still present from the cross-coupling step.

Ruthenium-Catalyzed Cascade C—H Functionalization of Phenylacetophenones**

PubMed Central

Mehta, Vaibhav P; García-López, José-Antonio; Greaney, Michael F

2014-01-01

Three orthogonal cascade C—H functionalization processes are described, based on ruthenium-catalyzed C—H alkenylation. 1-Indanones, indeno indenes, and indeno furanones were accessed through cascade pathways by using arylacetophenones as substrates under conditions of catalytic [{Ru(p-cymene)Cl2}2] and stoichiometric Cu(OAc)2. Each transformation uses C—H functionalization methods to form C—C bonds sequentially, with the indeno furanone synthesis featuring a C—O bond formation as the terminating step. This work demonstrates the power of ruthenium-catalyzed alkenylation as a platform reaction to develop more complex transformations, with multiple C—H functionalization steps taking place in a single operation to access novel carbocyclic structures. PMID:24453063

Nickel-Catalyzed, Carbonyl-Ene-Type Reactions: Selective for Alpha Olefins and More Efficient with Electron-Rich Aldehydes

PubMed Central

Ho, Chun-Yu; Ng, Sze-Sze; Jamison, Timothy F.

2011-01-01

Described are several classes of unusual or unprecedented carbonyl-ene-type reactions, including those between alpha olefins and aromatic aldehydes. Catalyzed by nickel, these processes complement existing Lewis acid-catalyzed methods in several respects. Not only are monosubstituted alkenes, aromatic aldehydes, and tert-alkyl aldehydes effective substrates, but monosubstituted olefins also react faster than those that are more substituted, and large or electron-rich aldehydes are more effective than small or electron-poor ones. Conceptually, in the presence of a nickel-phosphine catalyst, the combination of off-the-shelf alkenes, silyl triflates, and triethylamine functions as a replacement for an allylmetal reagent. PMID:16620106

Aminoxyl (nitroxyl) radicals in the early decomposition of the nitramine RDX.

PubMed

Irikura, Karl K

2013-03-14

The explosive nitramine RDX (1,3,5-trinitrohexahydro-s-triazine) is thought to decompose largely by homolytic N-N bond cleavage, among other possible initiation reactions. Density-functional theory (DFT) calculations indicate that the resulting secondary aminyl (R2N·) radical can abstract an oxygen atom from NO2 or from a neighboring nitramine molecule, producing an aminoxyl (R2NO·) radical. Persistent aminoxyl radicals have been detected in electron-spin resonance (ESR) experiments and are consistent with autocatalytic "red oils" reported in the experimental literature. When the O-atom donor is a nitramine, a nitrosamine is formed along with the aminoxyl radical. Reactions of aminoxyl radicals can lead readily to the "oxy-s-triazine" product (as the s-triazine N-oxide) observed mass-spectrometrically by Behrens and co-workers. In addition to forming aminoxyl radicals, the initial aminyl radical can catalyze loss of HONO from RDX.

METABOLISM OF ω-AMINO ACIDS V.

PubMed Central

Hardman, John K.; Stadtman, Thressa C.

1963-01-01

Hardman, John K. (National Heart Institute, National Institutes of Health, Bethesda, Md.) and Thressa C. Stadtman. Metabolism of ω-amino acids. V. Energetics of the γ-aminobutyrate fermentation by Clostridium aminobutyricum. J. Bacteriol. 85:1326–1333. 1963.—Clostridium aminobutyricum utilizes γ-aminobutyrate as its sole carbon, nitrogen, and energy source, producing ammonia, acetate, and butyrate as a result of this fermentation. Coenzyme A (CoA)-transferase, phosphotransacetylase, and acetokinase activities have been demonstrated in crude extracts of the organism; the coupling of the reactions catalyzed by these enzymes to the fermentation reactions provides a mechanism whereby C. aminobutyricum can obtain energy, in the form of adenosine triphosphate, from the decomposition of γ-aminobutyrate. Indirect evidence of additional phosphorylation, at the electron-transport level, has been obtained from molar growth yield studies and from the inhibition by 2,4-dinitrophenol of butyrate synthesis from γ-aminobutyrate and from crotonyl-CoA. PMID:14047225

Simple citric acid-catalyzed surface esterification of cellulose nanocrystals.

PubMed

Ávila Ramírez, Jhon Alejandro; Fortunati, Elena; Kenny, José María; Torre, Luigi; Foresti, María Laura

2017-02-10

A simple straightforward route for the surface esterification of cellulose nanocrystals (CNC) is herein proposed. CNC obtained from microcrystalline cellulose were acetylated using as catalyst citric acid, a α-hydroxy acid present in citrus fruits and industrially produced by certain molds in sucrose or glucose-containing medium. No additional solvent was added to the system; instead, the acylant (acetic anhydride) was used in sufficient excess to allow CNC dispersion and proper suspension agitation. By tuning the catalyst load, CNC with two different degree of substitution (i.e. DS=0.18 and 0.34) were obtained. Acetylated cellulose nanocrystals were characterized in terms of chemical structure, crystallinity, morphology, thermal decomposition and dispersion in a non-polar solvent. Results illustrated for the first time the suitability of the protocol proposed for the simple surface acetylation of cellulose nanocrystals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison of inert-gas-fusion and modified Kjeldahl techniques for determination of nitrogen in niobium alloys

NASA Technical Reports Server (NTRS)

Merkle, E. J.; Graab, J. W.; Davis, W. F.

1974-01-01

This report compares results obtained for the determination of nitrogen in a selected group of niobium-base alloys by the inert-gas-fusion and the Kjeldahl procedures. In the inert-gas-fusion procedure the sample is heated to approximately 2700 C in a helium atmosphere in a single-use graphite crucible. A platinum flux is used to facilitate melting of the sample. The Kjeldahl method consisted of a rapid decomposition with a mixture of hydrofluoric acid, phosphoric acid, and potassium chromate; distillation in the presence of sodium hydroxide; and highly sensitive spectrophotometry with nitroprusside-catalyzed indophenol. In the 30- to 80-ppm range, the relative standard deviation was 5 to 7 percent for the inert-gas-fusion procedure and 2 to 8 percent for the Kjeldahl procedure. The agreement of the nitrogen results obtained by the two techniques is considered satisfactory.

Dynamic analysis of reactive oxygen nitrogen species in plasma-activated culture medium by UV absorption spectroscopy

NASA Astrophysics Data System (ADS)

Brubaker, Timothy R.; Ishikawa, Kenji; Takeda, Keigo; Oh, Jun-Seok; Kondo, Hiroki; Hashizume, Hiroshi; Tanaka, Hiromasa; Knecht, Sean D.; Bilén, Sven G.; Hori, Masaru

2017-12-01

The liquid-phase chemical kinetics of a cell culture basal medium during treatment by an argon-fed, non-equilibrium atmospheric-pressure plasma source were investigated using real-time ultraviolet absorption spectroscopy and colorimetric assays. Depth- and time-resolved NO2- and NO3- concentrations were strongly inhomogeneous and primarily driven by convection during and after plasma-liquid interactions. H2O2 concentrations determined from deconvolved optical depth spectra were found to compensate for the optical depth spectra of excluded reactive species and changes in dissolved gas content. Plasma-activated media remained weakly basic due to NaHCO3 buffering, preventing the H+-catalyzed decomposition of NO2- seen in acidic plasma-activated water. An initial increase in pH may indicate CO2 sparging. Furthermore, the pH-dependency of UV optical depth spectra illustrated the need for pH compensation in the fitting of optical depth data.

Electrochemical performance investigations on the hydrogen depolarized CO2 concentrator

NASA Technical Reports Server (NTRS)

Aylward, J. R.

1976-01-01

An extensive investigation of anode and cathode polarization in complete cells and half cells was conducted to determine the factors affecting HDC electrode polarization and the nature of this polarization. Matrix-electrolyte-electrode interactions and cell electrolyte composition were also investigated. The electrodes were found to have normal performance capabilities. The HDC anode polarization characteristics were correlated with a theoretical kinetic analysis; and, except for some quantitative details, a rather complete understanding of the causes for HDC electrode polarization was formulated. One of the important finding resulting from the kinetic analysis was that platinum appears to catalyze the decomposition of carbonic acid to carbon dioxide and water. It was concluded that the abnormal voltage performance of the One Man ARS HDC cells was caused by insufficient cell electrolyte volume under normal operating conditions due to deficiencies in the reservoir to cell interfacing.

Crystallographic Snapshots of the Complete Catalytic Cycle of the Unregulated Aspartate Transcarbamoylase from Bacillus subtilis

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

K Harris; G Cockrell; D Puleo

2011-12-31

Here, we report high-resolution X-ray structures of Bacillus subtilis aspartate transcarbamoylase (ATCase), an enzyme that catalyzes one of the first reactions in pyrimidine nucleotide biosynthesis. Structures of the enzyme have been determined in the absence of ligands, in the presence of the substrate carbamoyl phosphate, and in the presence of the bisubstrate/transition state analog N-phosphonacetyl-L-aspartate. Combining the structural data with in silico docking and electrostatic calculations, we have been able to visualize each step in the catalytic cycle of ATCase, from the ordered binding of the substrates, to the formation and decomposition of the tetrahedral intermediate, to the ordered releasemore » of the products from the active site. Analysis of the conformational changes associated with these steps provides a rationale for the lack of cooperativity in trimeric ATCases that do not possess regulatory subunits.« less

Surface Immobilization of Molecular Electrocatalysts for Energy Conversion

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

Bullock, R. Morris; Das, Atanu K.; Appel, Aaron M.

2017-03-22

Electrocatalysts are critically important for a secure energy future, as they facilitate the conversion between electrical energy and chemical energy. Molecular catalysts offer precise control of their structure, and the ability to modify the substituents to understand structure-reactivity relationships that are more difficult to achieve with heterogeneous catalysts. Molecular electrocatalysts can be immobilized on surfaces by covalent bonds or through non-covalent interactions. Advantages of surface immobilization include the need for less catalyst, avoidance of bimolecular decomposition pathways, and easier determination of catalyst lifetime. Copper-catalyzed click reactions are often used to form covalent bonds to surfaces, and pi-pi stacking of pyrenemore » substituents appended to the ligand of a molecular complex is a frequently used method to achieve non-covalent surface immobilization. This mini-review highlights surface confinement of molecular electrocatalysts for reduction of O2, oxidation of H2O, production of H2, and reduction of CO2.« less

The stability of N-[2-(4-o-fluorophenylpiperazin-1-yl)ethyl]-2,5-dimethyl-1 -phenylpyrrole-3,4-dicarboximide in aqueous-organic solutions.

PubMed

Zajac, Marianna; Sobczak, Agnieszka; Malinka, Wiesław; Redzicka, Aleksandra

2010-01-01

The first-order reaction of solvolysis of N-[2-(4-o-fluorophenylpiperazin-1-yl)ethyl]-2,5-dimethyl-1-phenylpyrrole-3,4-dicarboximide (PDI) was investigated as a function of pH at 333, 328, 323, 318 and 308 K in the pH range 1.11 - 12.78. The decomposition of PDI was followed by the HPLC method (Nucleosil 10-C8 column (250 x 4 mm I.D., dp = 10 microm), mobile phase: 0.018 mol/L ammonia acetate - acetonitrile (40: 60 v/v), UV detector: 240 nm, flow rate: 1 mL/min. Specific acid-base catalysis involves solvolysis of the undissociated molecules of PDI catalyzed by hydroxide ions and spontaneous solvolysis of the undissociated and monoprotonated forms of PDI under the influence of solvents. The thermodynamic parameters of the reactions--activation energy (E(a)), enthalpy (DH(#)), entropy (DS(#))--were calculated.

Fast heap transform-based QR-decomposition of real and complex matrices: algorithms and codes

NASA Astrophysics Data System (ADS)

Grigoryan, Artyom M.

2015-03-01

In this paper, we describe a new look on the application of Givens rotations to the QR-decomposition problem, which is similar to the method of Householder transformations. We apply the concept of the discrete heap transform, or signal-induced unitary transforms which had been introduced by Grigoryan (2006) and used in signal and image processing. Both cases of real and complex nonsingular matrices are considered and examples of performing QR-decomposition of square matrices are given. The proposed method of QR-decomposition for the complex matrix is novel and differs from the known method of complex Givens rotation and is based on analytical equations for the heap transforms. Many examples illustrated the proposed heap transform method of QR-decomposition are given, algorithms are described in detail, and MATLAB-based codes are included.

Cobalt/rhodium heterobimetallic nanoparticle-catalyzed carbonylative [2+2+1] cycloaddition of allenes and bisallenes to Pauson-Khand-type reaction products.

PubMed

Park, Ji Hoon; Kim, Eunha; Kim, Hyeong-Mook; Choi, Soo Young; Chung, Young Keun

2008-05-28

The first catalytic intra- and intermolecular [2+2+1] cocyclization reactions of allenes and carbon monoxide have been developed. In the Co(2)Rh(2) heterobimetallic nanoparticle-catalyzed carbonylative [2+2+1] cycloaddition of allenes and carbon monoxide, the allenes formally serve both as an excellent alkene- and alkyne-like moiety within a Pauson-Khand-type process.

Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation reactions.

PubMed

Hua, Yuanda; Nguyen, Hiep H; Scaggs, William R; Jeon, Junha

2013-07-05

Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation of homoallyl silyl ethers (1) exploiting either BINAP or 1,6-bis(diphenylphosphino)hexane (dpph) has been developed. This method permits selective access to either trans-oxasilacyclopentanes (trans-2) or oxasilacyclohexanes (3) at will. A substoichiometric amount of norbornene markedly increased both yield and selectivity. A norbornene-mediated hydride shuttle process is discussed.

Direct Synthesis of 5-Aryl Barbituric Acids by Rhodium(II)-Catalyzed Reactions of Arenes with Diazo Compounds**

PubMed Central

Best, Daniel; Burns, David J; Lam, Hon Wai

2015-01-01

A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N—H groups are tolerated on the barbituric acid, with no complications arising from N—H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. PMID:25959544

Palladium-Catalyzed Atom-Transfer Radical Cyclization at Remote Unactivated C(sp3 )-H Sites: Hydrogen-Atom Transfer of Hybrid Vinyl Palladium Radical Intermediates.

PubMed

Ratushnyy, Maxim; Parasram, Marvin; Wang, Yang; Gevorgyan, Vladimir

2018-03-01

A novel mild, visible-light-induced palladium-catalyzed hydrogen atom translocation/atom-transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5-HAT process of previously unknown hybrid vinyl palladium radical intermediates, thus leading to iodomethyl carbo- and heterocyclic structures. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile Synthesis of Unsymmetrical Acridines and Phenazines by a Rhodium(III)-Catalyzed Amination, Cyclization and Aromatization Cascade

PubMed Central

Lian, Yajing; Hummel, Joshua R.; Bergman, Robert G.; Ellman, Jonathan A.

2013-01-01

New formal [3 + 3] annulations have been developed to obtain acridines and phenazines from aromatic azides and aromatic imines and azobenzenes, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine. PMID:23957711

Palladium-Catalyzed Asymmetric Allylic Alkylation of 4-Substituted Isoxazolidin-5-ones: Straightforward Access to β2,2 -Amino Acids.

PubMed

Nascimento de Oliveira, Marllon; Arseniyadis, Stellios; Cossy, Janine

2018-04-03

We report here an unprecedented and highly enantioselective palladium-catalyzed allylic alkylation applied to 4-substituted isoxazolidin-5-ones. Ultimately, the process provides a straightforward access to β 2,2 -amino acids bearing an all-carbon quaternary stereogenic center in great yields and a high degree of enantioselectivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

N-heterocyclic carbene catalyzed regioselective oxo-acyloxylation of alkenes with aromatic aldehydes: a high yield synthesis of α-acyloxy ketones and esters.

PubMed

Reddi, Rambabu N; Malekar, Pushpa V; Sudalai, Arumugam

2013-10-14

An N-heterocyclic carbene (NHC)-catalyzed reaction of alkenes with aromatic aldehydes providing for a high yield synthesis of α-acyloxy ketones and esters has been described. This unprecedented regioselective oxidative process employs NBS and Et3N in stoichiometric amounts and O2 (1 atm) as an oxidant under ambient conditions in DMSO as a solvent.

An NN-Based SRD Decomposition Algorithm and Its Application in Nonlinear Compensation

PubMed Central

Yan, Honghang; Deng, Fang; Sun, Jian; Chen, Jie

2014-01-01

In this study, a neural network-based square root of descending (SRD) order decomposition algorithm for compensating for nonlinear data generated by sensors is presented. The study aims at exploring the optimized decomposition of data 1.00,0.00,0.00 and minimizing the computational complexity and memory space of the training process. A linear decomposition algorithm, which automatically finds the optimal decomposition of N subparts and reduces the training time to 1N and memory cost to 1N, has been implemented on nonlinear data obtained from an encoder. Particular focus is given to the theoretical access of estimating the numbers of hidden nodes and the precision of varying the decomposition method. Numerical experiments are designed to evaluate the effect of this algorithm. Moreover, a designed device for angular sensor calibration is presented. We conduct an experiment that samples the data of an encoder and compensates for the nonlinearity of the encoder to testify this novel algorithm. PMID:25232912

Interactions between soil and tree roots accelerate long-term soil carbon decomposition.

PubMed

Dijkstra, Feike A; Cheng, Weixin

2007-11-01

Decomposition of soil organic carbon (SOC) is the main process governing the release of CO(2) into the atmosphere from terrestrial systems. Although the importance of soil-root interactions for SOC decomposition has increasingly been recognized, their long-term effect on SOC decomposition remains poorly understood. Here we provide experimental evidence for a rhizosphere priming effect, in which interactions between soil and tree roots substantially accelerate SOC decomposition. In a 395-day greenhouse study with Ponderosa pine and Fremont cottonwood trees grown in three different soils, SOC decomposition in the planted treatments was significantly greater (up to 225%) than in soil incubations alone. This rhizosphere priming effect persisted throughout the experiment, until well after initial soil disturbance, and increased with a greater amount of root-derived SOC formed during the experiment. Loss of old SOC was greater than the formation of new C, suggesting that increased C inputs from roots could result in net soil C loss.

The development of a post-mortem interval estimation for human remains found on land in the Netherlands.

PubMed

Gelderman, H T; Boer, L; Naujocks, T; IJzermans, A C M; Duijst, W L J M

2018-05-01

The decomposition process of human remains can be used to estimate the post-mortem interval (PMI), but decomposition varies due to many factors. Temperature is believed to be the most important and can be connected to decomposition by using the accumulated degree days (ADD). The aim of this research was to develop a decomposition scoring method and to develop a formula to estimate the PMI by using the developed decomposition scoring method and ADD.A decomposition scoring method and a Book of Reference (visual resource) were made. Ninety-one cases were used to develop a method to estimate the PMI. The photographs were scored using the decomposition scoring method. The temperature data was provided by the Royal Netherlands Meteorological Institute. The PMI was estimated using the total decomposition score (TDS) and using the TDS and ADD. The latter required an additional step, namely to calculate the ADD from the finding date back until the predicted day of death.The developed decomposition scoring method had a high interrater reliability. The TDS significantly estimates the PMI (R 2  = 0.67 and 0.80 for indoor and outdoor bodies, respectively). When using the ADD, the R 2 decreased to 0.66 and 0.56.The developed decomposition scoring method is a practical method to measure decomposition for human remains found on land. The PMI can be estimated using this method, but caution is advised in cases with a long PMI. The ADD does not account for all the heat present in a decomposing remain and is therefore a possible bias.

An Efficient Local Correlation Matrix Decomposition Approach for the Localization Implementation of Ensemble-Based Assimilation Methods

NASA Astrophysics Data System (ADS)

Zhang, Hongqin; Tian, Xiangjun

2018-04-01

Ensemble-based data assimilation methods often use the so-called localization scheme to improve the representation of the ensemble background error covariance (Be). Extensive research has been undertaken to reduce the computational cost of these methods by using the localized ensemble samples to localize Be by means of a direct decomposition of the local correlation matrix C. However, the computational costs of the direct decomposition of the local correlation matrix C are still extremely high due to its high dimension. In this paper, we propose an efficient local correlation matrix decomposition approach based on the concept of alternating directions. This approach is intended to avoid direct decomposition of the correlation matrix. Instead, we first decompose the correlation matrix into 1-D correlation matrices in the three coordinate directions, then construct their empirical orthogonal function decomposition at low resolution. This procedure is followed by the 1-D spline interpolation process to transform the above decompositions to the high-resolution grid. Finally, an efficient correlation matrix decomposition is achieved by computing the very similar Kronecker product. We conducted a series of comparison experiments to illustrate the validity and accuracy of the proposed local correlation matrix decomposition approach. The effectiveness of the proposed correlation matrix decomposition approach and its efficient localization implementation of the nonlinear least-squares four-dimensional variational assimilation are further demonstrated by several groups of numerical experiments based on the Advanced Research Weather Research and Forecasting model.

Partial differential equation-based approach for empirical mode decomposition: application on image analysis.

PubMed

Niang, Oumar; Thioune, Abdoulaye; El Gueirea, Mouhamed Cheikh; Deléchelle, Eric; Lemoine, Jacques

2012-09-01

The major problem with the empirical mode decomposition (EMD) algorithm is its lack of a theoretical framework. So, it is difficult to characterize and evaluate this approach. In this paper, we propose, in the 2-D case, the use of an alternative implementation to the algorithmic definition of the so-called "sifting process" used in the original Huang's EMD method. This approach, especially based on partial differential equations (PDEs), was presented by Niang in previous works, in 2005 and 2007, and relies on a nonlinear diffusion-based filtering process to solve the mean envelope estimation problem. In the 1-D case, the efficiency of the PDE-based method, compared to the original EMD algorithmic version, was also illustrated in a recent paper. Recently, several 2-D extensions of the EMD method have been proposed. Despite some effort, 2-D versions for EMD appear poorly performing and are very time consuming. So in this paper, an extension to the 2-D space of the PDE-based approach is extensively described. This approach has been applied in cases of both signal and image decomposition. The obtained results confirm the usefulness of the new PDE-based sifting process for the decomposition of various kinds of data. Some results have been provided in the case of image decomposition. The effectiveness of the approach encourages its use in a number of signal and image applications such as denoising, detrending, or texture analysis.

Comparison of decomposition rates between autopsied and non-autopsied human remains.

PubMed

Bates, Lennon N; Wescott, Daniel J

2016-04-01

Penetrating trauma has been cited as a significant factor in the rate of decomposition. Therefore, penetrating trauma may have an effect on estimations of time-since-death in medicolegal investigations and on research examining decomposition rates and processes when autopsied human bodies are used. The goal of this study was to determine if there are differences in the rate of decomposition between autopsied and non-autopsied human remains in the same environment. The purpose is to shed light on how large incisions, such as those from a thorocoabdominal autopsy, effect time-since-death estimations and research on the rate of decomposition that use both autopsied and non-autopsied human remains. In this study, 59 non-autopsied and 24 autopsied bodies were studied. The number of accumulated degree days required to reach each decomposition stage was then compared between autopsied and non-autopsied remains. Additionally, both types of bodies were examined for seasonal differences in decomposition rates. As temperature affects the rate of decomposition, this study also compared the internal body temperatures of autopsied and non-autopsied remains to see if differences between the two may be leading to differential decomposition. For this portion of this study, eight non-autopsied and five autopsied bodies were investigated. Internal temperature was collected once a day for two weeks. The results showed that differences in the decomposition rate between autopsied and non-autopsied remains was not statistically significant, though the average ADD needed to reach each stage of decomposition was slightly lower for autopsied bodies than non-autopsied bodies. There was also no significant difference between autopsied and non-autopsied bodies in the rate of decomposition by season or in internal temperature. Therefore, this study suggests that it is unnecessary to separate autopsied and non-autopsied remains when studying gross stages of human decomposition in Central Texas and that penetrating trauma may not be a significant factor in the overall rate of decomposition. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Morphological Decomposition in Reading Hebrew Homographs

ERIC Educational Resources Information Center

Miller, Paul; Liran-Hazan, Batel; Vaknin, Vered

2016-01-01

The present work investigates whether and how morphological decomposition processes bias the reading of Hebrew heterophonic homographs, i.e., unique orthographic patterns that are associated with two separate phonological, semantic entities depicted by means of two morphological structures (linear and nonlinear). In order to reveal the nature of…

Implementing Linear Algebra Related Algorithms on the TI-92+ Calculator.

ERIC Educational Resources Information Center

Alexopoulos, John; Abraham, Paul

2001-01-01

Demonstrates a less utilized feature of the TI-92+: its natural and powerful programming language. Shows how to implement several linear algebra related algorithms including the Gram-Schmidt process, Least Squares Approximations, Wronskians, Cholesky Decompositions, and Generalized Linear Least Square Approximations with QR Decompositions.…

Chemical indicators of cryoturbation and microbial processing throughout an alaskan permafrost soil depth profile

USDA-ARS?s Scientific Manuscript database

Although permafrost soils contain vast stores of carbon, we know relatively little about the chemical composition of their constituent organic matter. Soil organic matter chemistry is an important predictor of decomposition rates, especially in the initial stages of decomposition. Permafrost, organi...

Decomposition of carbon dioxide by recombining hydrogen plasma with ultralow electron temperature

NASA Astrophysics Data System (ADS)

Yamazaki, Masahiro; Nishiyama, Shusuke; Sasaki, Koichi

2018-06-01

We examined the rate coefficient for the decomposition of CO2 in low-pressure recombining hydrogen plasmas with electron temperatures between 0.15 and 0.45 eV, where the electron-impact dissociation was negligible. By using this ultralow-temperature plasma, we clearly observed decomposition processes via vibrational excited states. The rate coefficient of the overall reaction, CO2 + e → products, was 1.5 × 10‑17 m3/s in the ultralow-temperature plasma, which was 10 times larger than the decomposition rate coefficient of 2 × 10‑18 m3/s in an ionizing plasma with an electron temperature of 4 eV.

Heterogeneous decomposition of silane in a fixed bed reactor

NASA Technical Reports Server (NTRS)

Iya, S. K.; Flagella, R. N.; Dipaolo, F. S.

1982-01-01

Heterogeneous decomposition of silane in a fluidized bed offers an attractive route for the low-cost production of silicon for photovoltaic application. To obtain design data for a fluid bed silane pyrolysis reactor, deposition experiments were conducted in a small-scale fixed bed apparatus. Data on the decomposition mode, plating rate, and deposition morphology were obtained in the temperature range 600-900 C. Conditions favorable for heterogeneous decomposition with good deposition morphology were identified. The kinetic rate data showed the reaction to be first order with an activation energy of 38.8 kcal/mol, which agrees well with work done by others. The results are promising for the development of an economically attractive fluid bed process.

Laccase-Catalyzed Surface Modification of Thermo-Mechanical Pulp (TMP) for the Production of Wood Fiber Insulation Boards Using Industrial Process Water

PubMed Central

Schubert, Mark; Ruedin, Pascal; Civardi, Chiara; Richter, Michael; Hach, André; Christen, Herbert

2015-01-01

Low-density wood fiber insulation boards are traditionally manufactured in a wet process using a closed water circuit (process water). The water of these industrial processes contains natural phenolic extractives, aside from small amounts of admixtures (e.g., binders and paraffin). The suitability of two fungal laccases and one bacterial laccase was determined by biochemical characterization considering stability and substrate spectra. In a series of laboratory scale experiments, the selected commercial laccase from Myceliophtora thermophila was used to catalyze the surface modification of thermo-mechanical pulp (TMP) using process water. The laccase catalyzed the covalent binding of the phenolic compounds of the process water onto the wood fiber surface and led to change of the surface chemistry directly via crosslinking of lignin moieties. Although a complete substitution of the binder was not accomplished by laccase, the combined use of laccase and latex significantly improved the mechanical strength properties of wood fiber boards. The enzymatically-treated TMP showed better interactions with the synthetic binder, as shown by FTIR-analysis. Moreover, the enzyme is extensively stable in the process water and the approach requires no fresh water as well as no cost-intensive mediator. By applying a second-order polynomial model in combination with the genetic algorithm (GA), the required amount of laccase and synthetic latex could be optimized enabling the reduction of the binder by 40%. PMID:26046652

Pilot-scale study on the acid-catalyzed steam explosion of rice straw using a continuous pretreatment system.

PubMed

Chen, Wen-Hua; Tsai, Chia-Chin; Lin, Chih-Feng; Tsai, Pei-Yuan; Hwang, Wen-Song

2013-01-01

A continuous acid-catalyzed steam explosion pretreatment process and system to produce cellulosic ethanol was developed at the pilot-scale. The effects of the following parameters on the pretreatment efficiency of rice straw feedstocks were investigated: the acid concentration, the reaction temperature, the residence time, the feedstock size, the explosion pressure and the screw speed. The optimal presteaming horizontal reactor conditions for the pretreatment process are as follows: 1.7 rpm and 100-110 °C with an acid concentration of 1.3% (w/w). An acid-catalyzed steam explosion is then performed in the vertical reactor at 185 °C for 2 min. Approximately 73% of the total saccharification yield was obtained after the rice straw was pretreated under optimal conditions and subsequent enzymatic hydrolysis at a combined severity factor of 0.4-0.7. Moreover, good long-term stability and durability of the pretreatment system under continuous operation was observed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Benchmarking Quantum Mechanics/Molecular Mechanics (QM/MM) Methods on the Thymidylate Synthase-Catalyzed Hydride Transfer.

PubMed

Świderek, Katarzyna; Arafet, Kemel; Kohen, Amnon; Moliner, Vicent

2017-03-14

Given the ubiquity of hydride-transfer reactions in enzyme-catalyzed processes, identifying the appropriate computational method for evaluating such biological reactions is crucial to perform theoretical studies of these processes. In this paper, the hydride-transfer step catalyzed by thymidylate synthase (TSase) is studied by examining hybrid quantum mechanics/molecular mechanics (QM/MM) potentials via multiple semiempirical methods and the M06-2X hybrid density functional. Calculations of protium and tritium transfer in these reactions across a range of temperatures allowed calculation of the temperature dependence of kinetic isotope effects (KIE). Dynamics and quantum-tunneling effects are revealed to have little effect on the reaction rate, but are significant in determining the KIEs and their temperature dependence. A good agreement with experiments is found, especially when computed for RM1/MM simulations. The small temperature dependence of quantum tunneling corrections and the quasiclassical contribution term cancel each other, while the recrossing transmission coefficient seems to be temperature-independent over the interval of 5-40 °C.

Optimization of sodium loading on zeolite support for catalyzed transesterification of triolein with methanol.

PubMed

Wang, Yu-Yuan; Chou, Hsin-Yu; Chen, Bing-Hung; Lee, Duu-Jong

2013-10-01

Optimization of sodium loading on zeolite HY for catalyzed transesterification of triolein in excess methanol to biodiesel was studied. Zeolite HY catalyst was activated by loading sodium ions to their surface via an ion-exchange method. The effects of ion-exchange process parameters, including the temperature, the process time, the pH value, as well as concentrations and sources of Na(+) cations (NaOH, NaCl and Na2SO4), on the conversion yield of triolein to biodiesel were investigated. Most of these Na(+)-activated zeolite HY catalysts could really facilitate the catalyzed transesterification reaction of triolein to biodiesel at a lower temperature near 65°C. Consequently, a high conversion yield of triglycerides to biodiesel at 97.3% was obtained at 65°C. Moreover, the durability of zeolite catalysts was examined as well. Catalytic performance tests of these zeolite catalysts in transesterification did not show a significant decrease in catalysis at least for three batch cycles. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mass-transfer limitations for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor.

PubMed

Xiu, G H; Jiang, L; Li, P

2001-07-05

A mathematical model has been developed for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor in which the enzyme-catalyzed reaction (the irreversible uni-uni competitive Michaelis-Menten kinetics is chosen as an example) was coupled with intraparticle diffusion, external mass transfer, and axial dispersion. The effects of mass-transfer limitations, competitive inhibition of substrates, deactivation on the enzyme effective enantioselectivity, and the optical purity and yield of the desired product are examined quantitatively over a wide range of parameters using the orthogonal collocation method. For a first-order reaction, an analytical solution is derived from the mathematical model for slab-, cylindrical-, and spherical-enzyme supports. Based on the analytical solution for the steady-state resolution process, a new concise formulation is presented to predict quantitatively the mass-transfer limitations on enzyme effective enantioselectivity and optical purity and yield of the desired product for a continuous steady-state kinetic resolution process in a fixed-bed reactor. Copyright 2001 John Wiley & Sons, Inc.

Pd(II) and Pt(II) complexes of α-keto stabilized sulfur ylide: Synthesis, structural, theoretical and catalytic activity studies

NASA Astrophysics Data System (ADS)

Sabounchei, Seyyed Javad; Hashemi, Ali; Sedghi, Asieh; Bayat, Mehdi; Akhlaghi Bagherjeri, Fateme; Gable, Robert W.

2017-05-01

Reaction of dimethyl sulfide with 2, 3‧-dibromoacetophenone led to formation of sulfonium salt [Me2SCH2C(O)C6H4-m-Br]Br (1). The resulted sulfonium salt was treated with NaOH and gave the α-keto stabilized sulfur ylide Me2SC(H)C(O)C6H4-m-Br (2). This ligand was reacted with [MCl2(cod)] (M = Pd, Pt; cod = 1,5-cyclooctadiene) to form the new cis- and trans-[MCl2(ylide)2] (M = Pd (cis- and trans-3), Pt (cis- and trans-4)) complexes. Characterization of the obtained compounds was performed by elemental analysis, IR, 1H and 13C NMR. Recrystallization of dichlorobis(ylide) palladium(II) and platinum(II) complexes from DMSO solution yielded the crystalline products, which X-ray diffraction data revealed that the both compounds were crystallized as cis-[MCl2(ylide)(DMSO)] (M = Pd (5), Pt (6)) complexes. Also, a theoretical study on structure and nature of the Msbnd C bonding between the Y ligand (ylide) and [MCl2·DMSO] fragments in [YMCl2·DMSO] (M = Pd, Pt) complexes has been reported via NBO and energy-decomposition analysis (EDA). Furthermore, the palladium catalyzed Suzuki-Miyaura reaction of various aryl chlorides with arylboronic acids was performed. The results showed that the Pd(II) complexes cis- and trans-3 catalyzed efficiently coupling reactions at low catalyst loading and short reaction time.

Spectroscopic investigation and direct comparison of the reactivities of iron pyridyl oxidation catalysts

NASA Astrophysics Data System (ADS)

Song, Yang; Mayes, Howard G.; Queensen, Matthew J.; Bauer, Eike B.; Dupureur, Cynthia M.

2017-03-01

The growing interest in green chemistry has fueled attention to the development and characterization of effective iron complex oxidation catalysts. A number of iron complexes are known to catalyze the oxidation of organic substrates utilizing peroxides as the oxidant. Their development is complicated by a lack of direct comparison of the reactivities of the iron complexes. To begin to correlate reactivity with structural elements, we compare the reactivities of a series of iron pyridyl complexes toward a single dye substrate, malachite green (MG), for which colorless oxidation products are established. Complexes with tetradentate, nitrogen-based ligands with cis open coordination sites were found to be the most reactive. While some complexes reflect sensitivity to different peroxides, others are similarly reactive with either H2O2 or tBuOOH, which suggests some mechanistic distinctions. [Fe(S,S-PDP)(CH3CN)2](SbF6)2 and [Fe(OTf)2(tpa)] transition under the oxidative reaction conditions to a single intermediate at a rate that exceeds dye degradation (PDP = bis(pyridin-2-ylmethyl) bipyrrolidine; tpa = tris(2-pyridylmethyl)amine). For the less reactive [Fe(OTf)2(dpa)] (dpa = dipicolylamine), this reaction occurs on a timescale similar to that of MG oxidation. Thus, the spectroscopic method presented herein provides information about the efficiency and mechanism of iron catalyzed oxidation reactions as well as about potential oxidative catalyst decomposition and chemical changes of the catalyst before or during the oxidation reaction.

Reaction mechanism of WGS and PROX reactions catalyzed by Pt/oxide catalysts revealed by an FeO(111)/Pt(111) inverse model catalyst.

PubMed

Xu, Lingshun; Wu, Zongfang; Jin, Yuekang; Ma, Yunsheng; Huang, Weixin

2013-08-07

We have employed XPS and TDS to study the adsorption and surface reactions of H2O, CO and HCOOH on an FeO(111)/Pt(111) inverse model catalyst. The FeO(111)-Pt(111) interface of the FeO(111)/Pt(111) inverse model catalyst exposes coordination-unsaturated Fe(II) cations (Fe(II)CUS) and the Fe(II)CUS cations are capable of modifying the reactivity of neighbouring Pt sites. Water facilely dissociates on the Fe(II)CUS cations at the FeO(111)-Pt(111) interface to form hydroxyls that react to form both water and H2 upon heating. Hydroxyls on the Fe(II)CUS cations can react with CO(a) on the neighbouring Pt(111) sites to produce CO2 at low temperatures. Hydroxyls act as the co-catalyst in the CO oxidation by hydroxyls to CO2 (PROX reaction), while they act as one of the reactants in the CO oxidation by hydroxyls to CO2 and H2 (WGS reaction), and the recombinative reaction of hydroxyls to produce H2 is the rate-limiting step in the WGS reaction. A comparison of reaction behaviors between the interfacial CO(a) + OH reaction and the formate decomposition reaction suggest that formate is the likely surface intermediate of the CO(a) + OH reaction. These results provide some solid experimental evidence for the associative reaction mechanism of WGS and PROX reactions catalyzed by Pt/oxide catalysts.

Kinetics of the cellular decomposition of supersaturated solid solutions

NASA Astrophysics Data System (ADS)

Ivanov, M. A.; Naumuk, A. Yu.

2014-09-01

A consistent description of the kinetics of the cellular decomposition of supersaturated solid solutions with the development of a spatially periodic structure of lamellar (platelike) type, which consists of alternating phases of precipitates on the basis of the impurity component and depleted initial solid solution, is given. One of the equations, which determines the relationship between the parameters that describe the process of decomposition, has been obtained from a comparison of two approaches in order to determine the rate of change in the free energy of the system. The other kinetic parameters can be described with the use of a variational method, namely, by the maximum velocity of motion of the decomposition boundary at a given temperature. It is shown that the mutual directions of growth of the lamellae of different phases are determined by the minimum value of the interphase surface energy. To determine the parameters of the decomposition, a simple thermodynamic model of states with a parabolic dependence of the free energy on the concentrations has been used. As a result, expressions that describe the decomposition rate, interlamellar distance, and the concentration of impurities in the phase that remain after the decomposition have been derived. This concentration proves to be equal to the half-sum of the initial concentration and the equilibrium concentration corresponding to the decomposition temperature.

Measurement of the energy dependence of X-ray-induced decomposition of potassium chlorate.

PubMed

Pravica, Michael; Bai, Ligang; Sneed, Daniel; Park, Changyong

2013-03-21

We report the first measurements of the X-ray induced decomposition of KClO3 as a function of energy in two experiments. KClO3 was pressurized to 3.5 GPa and irradiated with monochromatic synchrotron X-rays ranging in energy from 15 to 35 keV in 5 keV increments. A systematic increase in the decomposition rate as the energy was decreased was observed, which agrees with the 1/E(3) trend for the photoelectric process, except at the lowest energy studied. A second experiment was performed to access lower energies (10 and 12 keV) using a beryllium gasket; suggesting an apparent resonance near 15 keV or 0.83 Ǻ maximizing the chemical decomposition rate. A third experiment was performed using KIO3 to ascertain the anionic dependence of the decomposition rate, which was observed to be far slower than in KClO3, suggesting that the O-O distance is the critical factor in chemical reactions. These results will be important for more efficiently initiating chemical decomposition in materials using selected X-ray wavelengths that maximize decomposition to aid useful hard X-ray-induced chemistry and contribute understanding of the mechanism of X-ray-induced decomposition of the chlorates.

Epoxy resin synthesis using low molecular weight lignin separated from various lignocellulosic materials.

PubMed

Asada, Chikako; Basnet, Sunita; Otsuka, Masaya; Sasaki, Chizuru; Nakamura, Yoshitoshi

2015-03-01

A low molecular weight lignin from various lignocellulosic materials was used for the synthesis of bio-based epoxy resins. The lignin extracted with methanol from steam-exploded samples (steaming time of 5 min at steam pressure of 3.5 MPa) from different biomasses (i.e., cedar, eucalyptus, and bamboo) were functionalized by the reaction with epichlorohydrin, catalyzed by a water-soluble phase transfer catalyst tetramethylammonium chloride, which was further reacted with 30 wt% aqueous NaOH for ring closure using methyl ethyl ketone as a solvent. The glycidylated products of the lignin with good yields were cured to epoxy polymer networks with bio-based curing agents i.e., lignin itself and a commercial curing agent TD2131. Relatively good thermal properties of the bio-based epoxy network was obtained and thermal decomposition temperature at 5% weight loss (Td5) of cedar-derived epoxy resin was higher than that derived from eucalyptus and bamboo. The bio-based resin satisfies the stability requirement of epoxy resin applicable for electric circuit boards. The methanol-insoluble residues were enzymatically hydrolyzed to produce glucose. This study indicated that the biomass-derived methanol-soluble lignin may be a promising candidate to be used as a substitute for petroleum-based epoxy resin derived from bisphenol A, while insoluble residues may be processed to give a bioethanol precursor i.e., glucose. Copyright © 2015 Elsevier B.V. All rights reserved.

DFT investigations of phosphotriesters hydrolysis in aqueous solution: a model for DNA single strand scission induced by N-nitrosoureas.

PubMed

Liu, Tingting; Zhao, Lijiao; Zhong, Rugang

2013-02-01

DNA phosphotriester adducts are common alkylation products of DNA phosphodiester moiety induced by N-nitrosoureas. The 2-hydroxyethyl phosphotriester was reported to hydrolyze more rapidly than other alkyl phosphotriesters both in neutral and in alkaline conditions, which can cause DNA single strand scission. In this work, DFT calculations have been employed to map out the four lowest activation free-energy profiles for neutral and alkaline hydrolysis of triethyl phosphate (TEP) and diethyl 2-hydroxyethyl phosphate (DEHEP). All the hydrolysis pathways were illuminated to be stepwise involving an acyclic or cyclic phosphorane intermediate for TEP or DEHEP, respectively. The rate-limiting step for all the hydrolysis reactions was found to be the formation of phosphorane intermediate, with the exception of DEHEP hydrolysis in alkaline conditions that the decomposition process turned out to be the rate-limiting step, owing to the extraordinary low formation barrier of cyclic phosphorane intermediate catalyzed by hydroxide. The rate-limiting barriers obtained for the four reactions are all consistent with the available experimental information concerning the corresponding hydrolysis reactions of phosphotriesters. Our calculations performed on the phosphate triesters hydrolysis predict that the lower formation barriers of cyclic phosphorane intermediates compared to its acyclic counter-part should be the dominant factor governing the hydrolysis rate enhancement of DEHEP relative to TEP both in neutral and in alkaline conditions.

Biocatalytic Synthesis of Flavonoid Esters by Lipases and Their Biological Benefits.

PubMed

de Araújo, Maria Elisa M B; Franco, Yollanda E M; Messias, Marcia C F; Longato, Giovanna B; Pamphile, João A; Carvalho, Patricia de O

2017-01-01

Several studies have described important biological activities of flavonoids such as coronary heart disease prevention, hepatoprotective, anti-inflammatory and anticancer activities, enzyme inhibition activity, and antibacterial, antifungal, and antiviral activities. Flavonoids show promising activity as natural plant-based antioxidants due to their antioxidant and free radical scavenging properties. However, their primary applications as antioxidants in the pharmaceutical, cosmetic, and food industries are limited because of their moderately hydrophilic nature. Enzymatic acylation of natural polyphenols with fatty acids or other acyl donors has been suggested for improving the lipophilic nature of the glycosylated flavonoids. This approach increases flavonoid solubility and stability in lipophilic systems. Acylation of flavonoids with different acyl donors may also introduce beneficial properties to the molecule, such as penetration through the cell membrane and improved antioxidant, antimicrobial, anti-inflammatory, antiproliferative, cytogenetic, and enzyme inhibition activities. Chemical methods for the synthesis of flavonoid esters lead to the formation of side products and the simultaneous decomposition of the flavonoids due to harsh reaction conditions. In contrast, biocatalytic acylation of flavonoids by lipases offers advantages associated to the wide availability of these enzymes, their low cost, chemo-, regio-, and enantioselectivity, mild condition processing and non-requirement of cofactors. This article is focused on the recent development of lipase-catalyzed synthesis of flavonoid esters and the impact of the acylation reaction on their biological activities. Georg Thieme Verlag KG Stuttgart · New York.

A systems level predictive model for global gene regulation of methanogenesis in a hydrogenotrophic methanogen

PubMed Central

Yoon, Sung Ho; Turkarslan, Serdar; Reiss, David J.; Pan, Min; Burn, June A.; Costa, Kyle C.; Lie, Thomas J.; Slagel, Joseph; Moritz, Robert L.; Hackett, Murray; Leigh, John A.; Baliga, Nitin S.

2013-01-01

Methanogens catalyze the critical methane-producing step (called methanogenesis) in the anaerobic decomposition of organic matter. Here, we present the first predictive model of global gene regulation of methanogenesis in a hydrogenotrophic methanogen, Methanococcus maripaludis. We generated a comprehensive list of genes (protein-coding and noncoding) for M. maripaludis through integrated analysis of the transcriptome structure and a newly constructed Peptide Atlas. The environment and gene-regulatory influence network (EGRIN) model of the strain was constructed from a compendium of transcriptome data that was collected over 58 different steady-state and time-course experiments that were performed in chemostats or batch cultures under a spectrum of environmental perturbations that modulated methanogenesis. Analyses of the EGRIN model have revealed novel components of methanogenesis that included at least three additional protein-coding genes of previously unknown function as well as one noncoding RNA. We discovered that at least five regulatory mechanisms act in a combinatorial scheme to intercoordinate key steps of methanogenesis with different processes such as motility, ATP biosynthesis, and carbon assimilation. Through a combination of genetic and environmental perturbation experiments we have validated the EGRIN-predicted role of two novel transcription factors in the regulation of phosphate-dependent repression of formate dehydrogenase—a key enzyme in the methanogenesis pathway. The EGRIN model demonstrates regulatory affiliations within methanogenesis as well as between methanogenesis and other cellular functions. PMID:24089473

Quantum Chemical Calculations of Amine-Catalyzed Polymerization of Silanol

NASA Astrophysics Data System (ADS)

Gu, Hongyu; Xu, Wenbin; Zhang, Jinlin; Qi, Zhenyi; Zhang, Tao; Song, Lixin

2018-03-01

Because of the technical importance of organosilicon materials, insight into the related synthetic processes is significantly essential. In this paper, the amine-catalyzed polymerization of silanol has been investigated by the density functional theory (DFT) method. Our data have shown that amines can catalytically promote the hydrogen transfer process by substantially reducing the energy barrier. The activation barrier via hydrogen transfer with catalysis is 38.32 kJ/mol, much lower than that of catalysis-free process (120.88 kJ/mol). The lower energy barrier is in agreement with the much more intense polymerization of silanols with amine catalysts. Based on the above results, amines and other catalysts capable of assisting hydrogen transfer are expected to be used as catalysts for silanol polymerization.

Evaluation of Hydrogen Isotope Exchange Methodology on Adsorbents for Tritium Removal

DOE PAGES

Morgan, Gregg A.; Xiao, S. Xin

2015-03-06

The Savannah River National Laboratory has demonstrated a potential process that can be used to remove tritium from tritiated water using Pt-catalyzed molecular sieves. The process is an elemental isotope exchange process in which H 2 (when flowed through the molecular sieves) will exchange with the adsorbed water, D 2O, leaving H 2O adsorbed on the molecular sieves. Various formulations of catalyzed molecular sieve material were prepared using two different techniques, Pt-implantation and Pt-ion exchange. This technology has been demonstrated for a protium (H) and deuterium (D) system, but can also be used for the removal of tritium from contaminatedmore » water (T 2O, HTO, and DTO) using D 2 (or H 2)« less

New mechanism for autocatalytic decomposition of H2CO3 in the vapor phase.

PubMed

Ghoshal, Sourav; Hazra, Montu K

2014-04-03

In this article, we present high level ab initio calculations investigating the energetics of a new autocatalytic decomposition mechanism for carbonic acid (H2CO3) in the vapor phase. The calculation have been performed at the MP2 level of theory in conjunction with aug-cc-pVDZ, aug-cc-pVTZ, and 6-311++G(3df,3pd) basis sets as well as at the CCSD(T)/aug-cc-pVTZ level. The present study suggests that this new decomposition mechanism is effectively a near-barrierless process at room temperature and makes vapor phase of H2CO3 unstable even in the absence of water molecules. Our calculation at the MP2/aug-cc-pVTZ level predicts that the effective barrier, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state and the total energy of the isolated starting reactants in terms of bimolecular encounters, is nearly zero for the autocatalytic decomposition mechanism. The results at the CCSD(T)/aug-cc-pVTZ level of calculations suggest that the effective barrier, as defined above, is sensitive to some extent to the levels of calculations used, nevertheless, we find that the effective barrier height predicted at the CCSD(T)/aug-cc-pVTZ level is very small or in other words the autocatalytic decomposition mechanism presented in this work is a near-barrierless process as mentioned above. Thus, we suggest that this new autocatalytic decomposition mechanism has to be considered as the primary mechanism for the decomposition of carbonic acid, especially at its source, where the vapor phase concentration of H2CO3 molecules reaches its highest levels.

Surface-Mediated Solvent Decomposition in Li–Air Batteries: Impact of Peroxide and Superoxide Surface Terminations

DOE PAGES

Kumar, Nitin; Radin, Maxwell D.; Wood, Brandon C.; ...

2015-04-13

A viable Li/O 2 battery will require the development of stable electrolytes that do not continuously decompose during cell operation. In some recent experiments it is suggested that reactions occurring at the interface between the liquid electrolyte and the solid lithium peroxide (Li 2O 2) discharge phase are a major contributor to these instabilities. To clarify the mechanisms associated with these reactions, a variety of atomistic simulation techniques, classical Monte Carlo, van der Waals-augmented density functional theory, ab initio molecular dynamics, and various solvation models, are used to study the initial decomposition of the common electrolyte solvent, dimethoxyethane (DME), onmore » surfaces of Li 2O 2. Comparisons are made between the two predominant Li 2O 2 surface charge states by calculating decomposition pathways on peroxide-terminated (O 2 2–) and superoxide-terminated (O 2 1–) facets. For both terminations, DME decomposition proceeds exothermically via a two-step process comprised of hydrogen abstraction (H-abstraction) followed by nucleophilic attack. In the first step, abstracted H dissociates a surface O 2 dimer, and combines with a dissociated oxygen to form a hydroxide ion (OH –). In the remaining surface oxygen then attacks the DME, resulting in a DME fragment that is strongly bound to the Li 2O 2 surface. DME decomposition is predicted to be more exothermic on the peroxide facet; nevertheless, the rate of DME decomposition is faster on the superoxide termination. The impact of solvation (explicit vs implicit) and an applied electric field on the reaction energetics are investigated. Finally, our calculations suggest that surface-mediated electrolyte decomposition should out-pace liquid-phase processes such as solvent auto-oxidation by dissolved O 2.« less

The implications of microbial and substrate limitation for the fates of carbon in different organic soil horizon types of boreal forest ecosystems: a mechanistically based model analysis

USGS Publications Warehouse

He, Y.; Zhuang, Q.; Harden, Jennifer W.; McGuire, A. David; Fan, Z.; Liu, Y.; Wickland, Kimberly P.

2014-01-01

The large amount of soil carbon in boreal forest ecosystems has the potential to influence the climate system if released in large quantities in response to warming. Thus, there is a need to better understand and represent the environmental sensitivity of soil carbon decomposition. Most soil carbon decomposition models rely on empirical relationships omitting key biogeochemical mechanisms and their response to climate change is highly uncertain. In this study, we developed a multi-layer microbial explicit soil decomposition model framework for boreal forest ecosystems. A thorough sensitivity analysis was conducted to identify dominating biogeochemical processes and to highlight structural limitations. Our results indicate that substrate availability (limited by soil water diffusion and substrate quality) is likely to be a major constraint on soil decomposition in the fibrous horizon (40–60% of soil organic carbon (SOC) pool size variation), while energy limited microbial activity in the amorphous horizon exerts a predominant control on soil decomposition (>70% of SOC pool size variation). Elevated temperature alleviated the energy constraint of microbial activity most notably in amorphous soils, whereas moisture only exhibited a marginal effect on dissolved substrate supply and microbial activity. Our study highlights the different decomposition properties and underlying mechanisms of soil dynamics between fibrous and amorphous soil horizons. Soil decomposition models should consider explicitly representing different boreal soil horizons and soil–microbial interactions to better characterize biogeochemical processes in boreal forest ecosystems. A more comprehensive representation of critical biogeochemical mechanisms of soil moisture effects may be required to improve the performance of the soil model we analyzed in this study.

Mycorrhizal associations of trees have different indirect effects on organic matter decomposition

Treesearch

Melanie K. Taylor; Richard A. Lankau; Nina Wurzburger; Franciska de Vries

2016-01-01

1. Organic matter decomposition is the main process by which carbon (C) is lost from terrestrialecosystems, and mycorrhizal associations of plants (i.e. arbuscular mycorrhizas (AM) and ectomycorrhizas(ECM)) may have different indirect effects on this loss pathway. AM and ECM plants differin the soil...

An integrated spectroscopic and wet chemical approach to investigate grass litter decomposition chemistry

USDA-ARS?s Scientific Manuscript database

Litter decomposition is a key process for soil organic matter formation and terrestrial biogeochemistry. Yet we still lack complete understanding of the chemical transformations which occur in the litter residue as it decomposes. A number of methods such as bulk nutrient concentrations, chemical fra...

Source, habitat and nutrient enrichment effects on decomposition of detritus in Lower Mississippi River Basin bayous

USDA-ARS?s Scientific Manuscript database

Potential differences in storage and processing of detritus in agricultural landscapes may alter freshwater ecosystem function. We compared decomposition rates of maize (Zea mays) and willow oak (Quercus phellos) from three bayous located within the Lower Mississippi River Basin of NW Mississippi, ...

Purification of Hydrogen

DOEpatents

Newton, A S

1950-12-05

Disclosed is a process for purifying hydrogen containing various gaseous impurities by passing the hydrogen over a large surface of uranium metal at a temperature above the decomposition temperature of uranium hydride, and below the decomposition temperature of the compounds formed by the combination of the uranium with the impurities in the hydrogen.

[Decomposition of corpses--a microbial degradation process with special reference to mummification, formation of adipocere and incomplete putrified corpes].

PubMed

Schoenen, Dirk

2013-01-01

Decomposition of the human body is a microbial process. It is influenced by the environmental situation and it depends to a high degree on the exchange of substances between the corpse and the environment. Mummification occurs at low humidity or frost. Adipocere arises from lack of oxygen, incomplete putrified corpses develop when there is no exchange of air or water between the corpse and the environment.

Decomposition of algal lipids in clay-enriched marine sediment under oxic and anoxic conditions

NASA Astrophysics Data System (ADS)

Lü, Dongwei; Song, Qian; Wang, Xuchen

2010-01-01

A series of laboratory incubation experiments were conducted to examine the decomposition of algal organic matter in clay-enriched marine sediment under oxic and anoxic conditions. During the 245-day incubation period, changes in the concentrations of TOC, major algal fatty acid components (14:0, 16:0, 16:1, 18:1 and 20:5), and n-alkanes (C16-C23) were quantified in the samples. Our results indicate that the organic matters were degraded more rapidly in oxic than anoxic conditions. Adsorption of fatty acids onto clay minerals was a rapid and reversible process. Using a simple G model, we calculated the decomposition rate constants for TOC, n-alkanes and fatty acids which ranged from 0.017-0.024 d-1, 0.049-0.103 d-1 and 0.011 to 0.069 d-1, respectively. Algal organic matter degraded in two stages characterized by a fast and a slow degradation processes. The addition of clay minerals montmorillonite and kaolinite to the sediments showed significant influence affecting the decomposition processes of algal TOC and fatty acids by adsorption and incorporation of the compounds with clay particles. Adsorption/association of fatty acids by clay minerals was rapid but appeared to be a slow reversible process. In addition to the sediment redox and clay influence, the structure of the compounds also played important roles in affecting their degradation dynamic in sediments.

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

Niu, T; Dong, X; Petrongolo, M

Purpose: Dual energy CT (DECT) imaging plays an important role in advanced imaging applications due to its material decomposition capability. Direct decomposition via matrix inversion suffers from significant degradation of image signal-to-noise ratios, which reduces clinical value. Existing de-noising algorithms achieve suboptimal performance since they suppress image noise either before or after the decomposition and do not fully explore the noise statistical properties of the decomposition process. We propose an iterative image-domain decomposition method for noise suppression in DECT, using the full variance-covariance matrix of the decomposed images. Methods: The proposed algorithm is formulated in the form of least-square estimationmore » with smoothness regularization. It includes the inverse of the estimated variance-covariance matrix of the decomposed images as the penalty weight in the least-square term. Performance is evaluated using an evaluation phantom (Catphan 600) and an anthropomorphic head phantom. Results are compared to those generated using direct matrix inversion with no noise suppression, a de-noising method applied on the decomposed images, and an existing algorithm with similar formulation but with an edge-preserving regularization term. Results: On the Catphan phantom, our method retains the same spatial resolution as the CT images before decomposition while reducing the noise standard deviation of decomposed images by over 98%. The other methods either degrade spatial resolution or achieve less low-contrast detectability. Also, our method yields lower electron density measurement error than direct matrix inversion and reduces error variation by over 97%. On the head phantom, it reduces the noise standard deviation of decomposed images by over 97% without blurring the sinus structures. Conclusion: We propose an iterative image-domain decomposition method for DECT. The method combines noise suppression and material decomposition into an iterative process and achieves both goals simultaneously. The proposed algorithm shows superior performance on noise suppression with high image spatial resolution and low-contrast detectability. This work is supported by a Varian MRA grant.« less