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Sample records for intermediates decomposition studies

  1. Excess Sodium Tetraphenylborate and Intermediates Decomposition Studies

    SciTech Connect

    Barnes, M.J.

    1998-12-07

    The stability of excess amounts of sodium tetraphenylborate (NaTPB) in the In-Tank Precipitation (ITP) facility depends on a number of variables. Concentration of palladium, initial benzene, and sodium ion as well as temperature provide the best opportunities for controlling the decomposition rate. This study examined the influence of these four variable on the reactivity of palladium-catalyzed sodium tetraphenylborate decomposition. Also, single effects tests investigated the reactivity of simulants with continuous stirring and nitrogen ventilation, with very high benzene concentrations, under washed sodium concentrations, with very high palladium concentrations, and with minimal quantities of excess NaTPB.

  2. Excess Sodium Tetraphenylborate and Intermediates Decomposition Studies

    SciTech Connect

    Barnes, M.J.; Peterson , R.A.

    1998-04-01

    The stability of excess amounts of sodium tetraphenylborate (NaTPB) in the In-Tank Precipitation (ITP) facility depends on a number of variables. Concentration of palladium, initial benzene, and sodium ion as well as temperature provide the best opportunities for controlling the decomposition rate. This study examined the influence of these four variables on the reactivity of palladium-catalyzed sodium tetraphenylborate decomposition. Also, single effects tests investigated the reactivity of simulants with continuous stirring and nitrogen ventilation, with very high benzene concentrations, under washed sodium concentrations, with very high palladium concentrations, and with minimal quantities of excess NaTPB. These tests showed the following.The testing demonstrates that current facility configuration does not provide assured safety of operations relative to the hazards of benzene (in particular to maintain the tank headspace below 60 percent of the lower flammability limit (lfl) for benzene generation rates of greater than 7 mg/(L.h)) from possible accelerated reaction of excess NaTPB. Current maximal operating temperatures of 40 degrees C and the lack of protection against palladium entering Tank 48H provide insufficient protection against the onset of the reaction. Similarly, control of the amount of excess NaTPB, purification of the organic, or limiting the benzene content of the slurry (via stirring) and ionic strength of the waste mixture prove inadequate to assure safe operation.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    DOE PAGES

    Guo, Xiaofeng; Wu, Di; Xu, Hongwu; ...

    2016-09-01

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

  5. Acyloxyl radical pair intermediate for the initial stage of the thermal decomposition of diacyl peroxide: a density functional study

    NASA Astrophysics Data System (ADS)

    Uchimaru, Tadafumi; Hara, Ryoma; Tanabe, Kazutoshi; Fujimori, Ken

    1997-03-01

    To examine the reaction mechanism for the thermal reorganization, or more specifically the oxygen scrambling, in diacyl peroxide, we have carried out a hybrid density functional study using formyl peroxide as a model compound. The B3LYP calculations suggest that the oxygen scrambling in diacyl peroxide is most likely to occur via a σ-acyloxyl radical pair species: the competitive pathways of the [3,3]- and [1,3]-sigmatropic shifts are highly improbable. Thus, the mechanism for the thermal oxygen scrambling in diacyl peroxide should be completely different from those for the carbon counterparts of diacyl peroxide (the Cope and Claisen rearrangement).

  6. Guiding quantum histories with intermediate decomposition of the identity

    NASA Astrophysics Data System (ADS)

    Nelson-Isaacs, Sky

    2017-05-01

    The effect of a carefully chosen measurement action is proposed to be able to influence the probability distribution of future outcomes. Using the consistent histories formalism, we may calculate the overlap between a current measurement action and an array of possible future states. We propose an interpretation of the mathematics in which a current measurement action reaches recursively into future states and returns a probability. Using intermediate decomposition of a quantum history, we decompose a state at intermediate times into a complete set of states, using a grouping which distinguishes particular outcomes. The "meaning" of the grouping is defined rigorously, and it is shown that under certain minimal assumptions a `meaningful grouping' will always increase the likelihood of a particular outcome. This is labeled "meaningful history selection." Grouping histories is not a physical process, but rather an information theoretic one that occurs during the measurement process. The model is consistent with the standard Von Neumann measurement process under normal conditions, but leads to a proposed small deviation in the presence of a conscious observer that naturally accommodates the experimental evidence of certain psi phenomena. It is proposed that the effect of a conscious observer acting on a system is to group the histories in a distinguishable way, thereby minimizing the entropy increase of the system upon measurement. Compatibility with various models of quantum theory are discussed.

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

    SciTech Connect

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

    2016-09-01

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

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

    SciTech Connect

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

    2016-09-01

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

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

    SciTech Connect

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

    2012-12-27

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

  10. Photo-Fenton decomposition of β-blockers atenolol and metoprolol; study and optimization of system parameters and identification of intermediates.

    PubMed

    Veloutsou, S; Bizani, E; Fytianos, K

    2014-07-01

    Active pharmaceutical compounds reach the wastewater treatment plants mainly through excretion and improper disposal, and, because of insufficient treating methods, they end up to surface water or even potable water in some cases. Atenolol and metoprolol are β-blockers, members of cardiovascular pharmaceuticals group. They are generally used in the treatment of disorders such as hypertension, angina and arrhythmias. They have been in long-term use in Europe and North America, and they have also been detected in the aquatic environment. In this study the degradation of atenolol and metoprolol in aqueous solutions by means of the photo-Fenton reaction was investigated. The purpose of this study was: (i) to investigate the influence of the concentrations of iron and hydrogen peroxide, by means of central composite design, (ii) to study the degradation kinetics in aqueous solutions, (iii) to evaluate the mineralization and the toxicity evolution of the target compounds and (iv) to identify the degradation products. It has been found that increase of iron and hydrogen peroxide concentration accelerate the degradation of atenolol and metoprolol, while the kinetics of the process can be characterized as pseudo-first order. In general the photo-Fenton method has proved to be effective in decomposing and mineralizing the target compounds. The determination of the by-products formed during the degradation using LC-MS/MS equipment and the evaluation of the toxicity of the treated solution in different stages of the process would offer significant, innovative information regarding the treatment of water and wastewater containing active pharmaceutical compounds, especially of the β-blocker group.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    PubMed

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

    2013-10-14

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

  13. Isomerization and decomposition of a Criegee intermediate in the ozonolysis of alkenes: dynamics using a multireference potential.

    PubMed

    Kalinowski, Jaroslaw; Räsänen, Markku; Heinonen, Petri; Kilpeläinen, Ilkka; Gerber, R Benny

    2014-01-03

    The isomerization and decomposition dynamics of the simplest Criegee intermediate CH2 OO have been studied by classical trajectory simulations using the multireference ab initio MR-PT2 potential on the fly. A new, accelerated algorithm for dynamics with MR-PT2 was used. For an initial temperature of 300 K, starting from the transition state from CH2 OO→CH2 O2  , the system reaches the dioxirane structure in around 50 fs, then isomerizes to formic acid (in ca. 2800 fs), and decomposes into CO+H2 O at around 2900 fs. The contributions of different configurations to the multiconfigurational total electronic wave function vary dramatically along the trajectory, with diradical contributions being important for transition states corresponding to H-atom transfers, while being only moderately significant for CH2 OO. The implications for reactions of Criegee intermediates are discussed.

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

    NASA Astrophysics Data System (ADS)

    Scaranto, Jessica; Mavrikakis, Manos

    2016-06-01

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

  15. 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.

  16. Electron ionization of different large perfluoroethers embedded in ultracold helium droplets: effective freezing of short-lived decomposition intermediates.

    PubMed

    Bartl, P; Tanzer, K; Mitterdorfer, C; Karolczak, S; Illenberger, E; Denifl, S; Scheier, P

    2013-01-30

    Electron ionization of three perfluoroethers (PFEs), C(6)F(14)O(3), C(8)F(18)O(4), and C(10)F(20)O(5), is studied in the gas phase and when the molecules are embedded in ultracold helium (He) droplets. The molecules investigated are model compounds for perfluoropolyethers used as lubricants in technical applications. The present study gives insight into possible radiolysis pathways upon radiation exposure. The experiments utilized a crossed electron/droplet beam apparatus consisting of a He droplet source and pick-up chamber combined with a commercial time-of-flight mass spectrometer. The doped droplets were ionized by electron ionization at 70 eV. The He environment strongly affects the ionization patterns in the way that both the molecular ion M(+) and high-mass fragment ions formed by the loss of light neutral species such as F([M-F](+)), or CF(3)OCF(2) ([M-CF(3)OCF(2)](+)), etc., became strong signals in the mass spectrum. These signals were not or only barely visible in the gas-phase experiment and were identified as short lived (< µs) dissociation intermediates which in the gas phase immediately decomposed into lower-mass fragment ions. Ionic fragmentation intermediates are frozen and subsequently stabilized in the He environment. Helium droplets can hence be viewed as a cryogenic laboratory transforming short-lived decomposition intermediates into stable fragment ions appearing as strong signals in the mass spectrum. Copyright © 2012 John Wiley & Sons, Ltd.

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

    PubMed

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

    2016-07-14

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

  18. [Intermediate phenotype studies in psychiatric disorder].

    PubMed

    Hashimoto, Ryota

    2016-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Scaranto, Jessica; Mavrikakis, Manos

    2016-08-01

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

  20. A study of two domain decomposition preconditioners.

    SciTech Connect

    Dohrmann, Clark R.

    2003-12-01

    Large-scale finite element analysis often requires the iterative solution of equations with many unknowns. Preconditioners based on domain decomposition concepts have proven effective at accelerating the convergence of iterative methods like conjugate gradients for such problems. A study of two new domain decomposition preconditioners is presented here. The first is based on a substructuring approach and can viewed as a primal counterpart of the dual-primal variant of the finite element tearing and interconnecting method called FETI-DP. The second uses an algebraic approach to construct a coarse problem for a classic overlapping Schwarz method. The numerical properties of both preconditioners are shown to scale well with problem size. Although developed primarily for structural mechanics applications, the preconditioners are also useful for other problems types. Detailed descriptions of the two preconditioners along with numerical results are included.

  1. Optimized color decomposition of localized whole slide images and convolutional neural network for intermediate prostate cancer classification

    NASA Astrophysics Data System (ADS)

    Zhou, Naiyun; Gao, Yi

    2017-03-01

    This paper presents a fully automatic approach to grade intermediate prostate malignancy with hematoxylin and eosin-stained whole slide images. Deep learning architectures such as convolutional neural networks have been utilized in the domain of histopathology for automated carcinoma detection and classification. However, few work show its power in discriminating intermediate Gleason patterns, due to sporadic distribution of prostate glands on stained surgical section samples. We propose optimized hematoxylin decomposition on localized images, followed by convolutional neural network to classify Gleason patterns 3+4 and 4+3 without handcrafted features or gland segmentation. Crucial glands morphology and structural relationship of nuclei are extracted twice in different color space by the multi-scale strategy to mimic pathologists' visual examination. Our novel classification scheme evaluated on 169 whole slide images yielded a 70.41% accuracy and corresponding area under the receiver operating characteristic curve of 0.7247.

  2. In situ spectroscopic studies on vapor phase catalytic decomposition of dimethyl oxalate.

    PubMed

    Hegde, Shweta; Tharpa, Kalsang; Akuri, Satyanarayana Reddy; K, Rakesh; Kumar, Ajay; Deshpande, Raj; Nair, Sreejit A

    2017-03-15

    Dimethyl Oxalate (DMO) has recently gained prominence as a valuable intermediate for the production of compounds of commercial importance. The stability of DMO is poor and hence this can result in the decomposition of DMO under reaction conditions. The mechanism of DMO decomposition is however not reported and more so on catalytic surfaces. Insights into the mechanism of decomposition would help in designing catalysts for its effective molecular transformation. It is well known that DMO is sensitive to moisture, which can also be a factor contributing to its decomposition. The present work reports the results of decomposition of DMO on various catalytic materials. The materials studied consist of acidic (γ-Al2O3), basic (MgO), weakly acidic (ZnAl2O4) and neutral surfaces such as α-Al2O3 and mesoporous precipitated SiO2. Infrared spectroscopy is used to identify the nature of adsorption of the molecule on the various surfaces. The spectroscopy study is done at a temperature of 200 °C, which is the onset of gas phase decomposition of DMO. The results indicate that the stability of DMO is lower than the corresponding acid, i.e. oxalic acid. It is also one of the products of decomposition. Spectroscopic data suggest that DMO decomposition is related to surface acidity and the extent of decomposition depends on the number of surface hydroxyl groups. Decomposition was also observed on α-Al2O3, which was attributed to the residual surface hydroxyl groups. DMO decomposition to oxalic acid was not observed on the basic surface (MgO).

  3. Computational study on the vinyl azide decomposition.

    PubMed

    Duarte, Darío J R; Miranda, Margarida S; Esteves da Silva, Joaquim C G

    2014-07-10

    The decomposition mechanism of vinyl azide (CH2CHN3) has been studied by calculations of the electronic structure. In addition, a study based on the topology of the electron charge density distribution and its Laplacian function, within the Quantum Theory of Atoms in Molecules (QTAIM), has been carried out with the aim of comprehending the electron redistribution mechanisms that take place in the formation of vinyl nitrenes. The electronic structure calculations reveal that the decomposition of the s-cis conformer of vinyl azide leads to the formation of ketenimine through a single-step conversion, s-cis-CH2CHN3 → CH2CNH + N2, while the conversion of the s-trans conformer to acetonitrile occurs in two steps, s-trans-CH2CHN3 → cyc-CH2NCH + N2 → CH3CN + N2. The topological analysis of the L(r) function reveals that triplet vinyl nitrene has one lone pair on the valence shell charge concentration (VSCC) of nitrogen and thus could act as a monodentate Lewis base, while singlet vinyl nitrene has two lone pairs on the VSCC of nitrogen and thus could act as a bidentate Lewis base.

  4. Using Drosophila for Studies of Intermediate Filaments.

    PubMed

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

    2016-01-01

    Drosophila melanogaster is a useful organism for determining protein function and modeling human disease. Drosophila offers a rapid generation time and an abundance of genomic resources and genetic tools. Conservation in protein structure, signaling pathways, and developmental processes make studies performed in Drosophila relevant to other species, including humans. Drosophila models have been generated for neurodegenerative diseases, muscular dystrophy, cancer, and many other disorders. Recently, intermediate filament protein diseases have been modeled in Drosophila. These models have revealed novel mechanisms of pathology, illuminated potential new routes of therapy, and make whole organism compound screens feasible. The goal of this chapter is to outline steps to study intermediate filament function and model intermediate filament-associated diseases in Drosophila. The steps are general and can be applied to study the function of almost any protein. The protocols outlined here are for both the novice and experienced Drosophila researcher, allowing the rich developmental and cell biology that Drosophila offers to be applied to studies of intermediate filaments. Copyright © 2016 Elsevier Inc. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  6. Experimental study of trimethyl aluminum decomposition

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Pan, Yang; Yang, Jiuzhong; Jiang, Zhiming; Fang, Haisheng

    2017-09-01

    Trimethyl aluminum (TMA) is an important precursor used for metal-organic chemical vapor deposition (MOCVD) of most Al-containing structures, in particular of nitride structures. The reaction mechanism of TMA with ammonia is neither clear nor certain due to its complexity. Pyrolysis of trimethyl metal is the start of series of reactions, thus significantly affecting the growth. Experimental study of TMA pyrolysis, however, has not yet been conducted in detail. In this paper, a reflectron time-of-flight mass spectrometer is adopted to measure the TMA decomposition from room temperature to 800 °C in a special pyrolysis furnace, activated by soft X-ray from the synchrotron radiation. The results show that generation of methyl, ethane and monomethyl aluminum (MMA) indicates the start of the pyrolysis process. In the low temperature range from 25 °C to 700 °C, the main product is dimethyl aluminum (DMA) from decomposition of TMA. For temperatures larger than 700 °C, the main products are MMA, DMA, methyl and ethane.

  7. Study of condition-dependent decomposition reactions; Part I. The thermal behaviour and decomposition of 2-nitrobenzoyl chloride.

    PubMed

    Lever, Sarah D; Papadaki, Maria

    2004-11-11

    The risks associated with batch processing in the manufacture of chemicals and pharmaceuticals via highly exothermic reactions are of special interest due to the possibility of runaway reactions. o-Nitrated benzoyl chlorides are intermediates in the production of agrochemicals and are produced via the reaction of o-nitrated carboxylic acids with thionyl chloride in a solvent mixture. ortho-Nitrated acyl chlorides have exploded violently on attempted distillation on numerous occasions. An inadequate investigation of the process prior to large-scale operation is the most likely cause. Here we present preliminary results of studies on the decomposition of 2-nitrobenzoyl chloride. This study has revealed that the decomposition reaction is strongly condition dependent. The heating rate of the sample plays a preponderant role in the course of the decomposition reaction. That renders the interpretation of differential scanning calorimetry (DSC) or adiabatic calorimetry measurements, which are routinely used to assess the thermochemistry and safety of the large-scale reactions, problematic. Following this on-going study, we report here key features of the system that have been identified.

  8. A study of the human decomposition sequence in central Texas.

    PubMed

    Parks, Connie L

    2011-01-01

    Decomposition studies utilizing nonhuman subjects as human analogues are well established, but fewer studies utilizing intact human remains exist. This study provides data from a controlled decomposition study involving human remains in Central Texas. A 63.5-kg unmodified cadaver was placed in an open-air site and observed over a 10-week period from April 11 through June 19, 2008. A wire enclosure restricted scavenger access. State of decomposition and environmental conditions were recorded daily for the first 36 days and then every 2 weeks thereafter. Results indicated a high degree of correlation with other decomposition studies originating in the southwestern United States, although slight deviations for the average duration of early events were noted. The data were also utilized to test a quantitative method for estimating the postmortem interval. Results indicated preliminary support for a quantitative approach. Additional research is encouraged to further establish the human decomposition data set for Central Texas.

  9. Experimental study of decomposition of aqueous nitrosyl thiocyanate.

    PubMed

    Rayson, Mark S; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

    2011-08-15

    This study has examined the kinetics of the decomposition of nitrosyl thiocyanate (ONSCN) by stopped flow UV-vis spectrophotometry, with the reaction products identified and quantified by infrared spectroscopy, membrane inlet mass spectrometry, ion chromatography, and CN(-) ion selective electrode. The reaction results in the formation of nitric oxide and thiocyanogen, the latter decomposing to sulfate and hydrogen cyanide in aqueous solution. The rate of consumption of ONSCN depends strongly on the concentration of SCN(-) ions and is inhibited by nitric oxide. We have developed a reaction mechanism that comprises three parallel pathways for the decomposition of ONSCN. At high thiocyanate concentrations, two reaction pathways operate including a second order reaction to generate NO and (SCN)(2) and a reversible reaction between ONSCN and SCN(-) producing NO and (SCN)(2)(-), with the rate limiting step corresponding to the consumption of (SCN)(2)(-) by reaction with ONSCN. The third reaction pathway, which becomes significant at low thiocyanate concentrations, involves formation of a previously unreported species, ONOSCN, via a reaction between ONSCN and HOSCN, the latter constituting an intermediate in the hydrolysis of (SCN)(2). ONOSCN contributes to the formation of NO via homolysis of the O-NO bond and subsequent dimerization and hydrolysis of OSCN. Fitting the chemical reactions of the model to the experimental measurements, which covered a wide range of reactant concentrations, afforded estimation of all relevant kinetic parameters and provided an excellent match. The reaction mechanism developed in this contribution may be applied to predict the rates of NO formation from ONSCN during the synthesis of azo dyes, the gassing of explosive emulsions, or nitrosation reactions occurring in the human body.

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

    SciTech Connect

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

    1998-12-31

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

  11. Noncovalent and covalent immobilization of oxygenase on single-walled carbon nanotube for enzymatic decomposition of aromatic hydrocarbon intermediates.

    PubMed

    Suma, Yanasinee; Kang, Christina S; Kim, Han S

    2016-01-01

    The decomposition of various aromatic hydrocarbon intermediates was examined using a recombinant oxidative enzyme immobilized on single-walled carbon nanotubes (SWCNTs). Hydroxyquinol 1,2-dioxygenase (CphA-I), which catalyzes ring cleavage of catechol and its analogues, was obtained from Arthrobacter chlorophenolicus A6 via cloning, overexpression, and subsequent purification. This recombinant enzyme was immobilized on SWCNTs by physical adsorption and covalent coupling in the absence and presence of N-hydroxysuccinimide. The immobilization yield was as high as 52.1%, and a high level of enzyme activity of up to 64.7% was preserved after immobilization. Kinetic analysis showed that the substrate utilization rates (vmax) and catalytic efficiencies (kcat/KM) of the immobilized enzyme for all substrates evaluated were similar to those of the free enzyme, indicating minimal loss of enzyme activity during immobilization. The immobilized enzyme was more stable toward extreme pH, temperature, and ionic strength conditions than the free enzyme. Thus, the oxidative enzyme immobilized on SWCNTs can be used as an effective and stable biocatalyst for the biochemical remediation process if further investigations would be carried out under field conditions.

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

    SciTech Connect

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

    2014-12-05

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

  13. Decomposition studies of filtered slurries using the enhanced comprehensive catalyst

    SciTech Connect

    Wilmarth, W.R.; Crawford, C.L.; Peterson, R.A.

    1997-11-13

    This study examined decomposition of the soluble phenylborates at elevated temperatures (45 degrees Celsius) to determine the effects of filtering the solid tetraphenylborate, solid sludge and monosodium titanate and spiking additional levels of transition metal catalyst.

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

    PubMed

    Inaba, Satoshi

    2015-06-04

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

  15. Thermal decomposition studies of explosives for component applications. [hns

    SciTech Connect

    Jungst, R.G.

    1988-01-01

    The explosives PETN and HNS are currently found in a variety of Sandia devices. We have carried out a number of special studies to measure decomposition rates of these materials in hardware at moderate temperatures. The goal of this work was to generate information to enable predictions of component lifetimes to be made. This presentation will discuss sampling and measurement techniques for decomposition products and show results of their application to components containing PETN and HNS.

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

    SciTech Connect

    Fu, Yuwei; Wang, Xiaohua E-mail: mzrong@mail.xjtu.edu.cn; Li, Xi; Yang, Aijun; Wu, Yi; Rong, Mingzhe E-mail: mzrong@mail.xjtu.edu.cn; Han, Guohui; Lu, Yanhui

    2016-08-15

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

  17. A study of SiC decomposition under laser irradiation

    NASA Astrophysics Data System (ADS)

    Adelmann, B.; Hellmann, R.

    2017-06-01

    In this experimental study we investigate the laser induced thermal decomposition of 4H-Sic under ambient conditions using fiber laser. Using a unique two-color pyrometer setup, we measure the temporal evolution of the temperature in the irradiated zone and determine the decomposition rate for various laser power levels. We find that the temporal evolution of the temperature in the irradiated area exhibits an initial heating phase up to about 1300 K, being characterized by an unaffected SiC surface. Upon an expeditious temperature increase, a decomposition phase follows with temperatures above 1700 K, being accompanied by carbonization of the SiC surface. The decomposed volume depends linearly on the duration of the decomposition phase and increases linearly with laser power. The temperature evaluation of the decomposition speed reveals an Arrhenius-type behavior allowing the calculation of the activation energy for the decomposition under ambient conditions to 613 kJ/mol in the temperature range between 2140 and 2420 K.

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

    PubMed

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

    2015-02-14

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

  19. IN SITU INFRARED STUDY OF CATALYTIC DECOMPOSITION OF NO

    SciTech Connect

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

    1998-08-18

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

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

    SciTech Connect

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

    2010-11-18

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

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

    PubMed

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

    2003-10-15

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

  2. MHD oxidant intermediate temperature ceramic heater study

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  3. Decomposition mechanism of formic acid on Cu (111) surface: A theoretical study

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Qin, Pei; Fang, Tao

    2017-02-01

    The study of formic acid decomposition on transition metal surfaces is important to obtain useful information for vapor phase catalysis involving HCOOH and for the development of direct formic acid fuel cells. In this study, periodic density functional theory calculations have been employed to investigate the dissociation pathways of HCOOH on Cu (111) surface. About adsorption, it is found that the adsorption of HCOO, COOH, HCO, CO, OH and H on Cu (111) are considered chemisorption, whereas HCOOH, CO2, H2O and H2 have the weak interaction with Cu (111) surface. Furthermore, the minimum energy pathways are analyzed for the decomposition of HCOOH to CO2 and CO through the scission of Hsbnd O, Csbnd H and Csbnd O bonds. It is found that HCOOH, HCOO and COOH prefer to dissociate in the related reactions rather than desorb. For the decomposition, it is indicated that HCO and COOH are the main dissociated intermediates of trans-HCOOH, CO2 is the main dissociated intermediates of bidentate-HCOO, and CO is the main dissociated product of cis-COOH. The co-adsorbed H atom is beneficial for the formation of CO2 from cis-COOH. Besides, it is found that the most favorable path for HCOOH decomposition on Cu (111) surface is HCOOH-HCO-CO (Path 5), where the step of CO formation from HCO dehydrogenation is considered to be the rate-determining step. The results also show that CO is preferentially formed as the dominant product of HCOOH on Cu (111) surface.

  4. A high temperature kinetic study for the thermal unimolecular decomposition of diethyl carbonate

    NASA Astrophysics Data System (ADS)

    AlAbbad, Mohammed; Giri, Binod Raj; Szőri, Milan; Viskolcz, Béla; Farooq, Aamir

    2017-09-01

    Thermal unimolecular decomposition of diethyl carbonate (DEC) was investigated in a shock tube by measuring ethylene concentration with a CO2 gas laser over 900-1200 K and 1.2-2.8 bar. Rate coefficients were extracted using a simple kinetic scheme comprising of thermal decomposition of DEC as initial step followed by rapid thermal decomposition of the intermediate ethyl hydrogen carbonate. Our results were further analysed using ab initio and master equation calculations to obtain pressure- and temperature-dependence of rate coefficients. Similar to alkyl esters, unimolecular decomposition of DEC is found to undergo six-center retro-ene elimination of ethylene in a concerted manner.

  5. Theoretical study of the thermal decomposition of dimethyl disulfide.

    PubMed

    Vandeputte, Aäron G; Reyniers, Marie-Françoise; Marin, Guy B

    2010-10-07

    Despite its use in a wide variety of industrially important thermochemical processes, little is known about the thermal decomposition mechanism of dimethyl disulfide (DMDS). To obtain more insight, the radical decomposition mechanism of DMDS is studied theoretically and a kinetic model is developed accounting for the formation of all the decomposition products observed in the experimental studies available in literature. Thermochemical data and rate coefficients are obtained using the high-level CBS-QB3 composite method. Among five methods tested (BMK/6-311G(2d,d,p), MPW1PW91/6-311G(2d,d,p), G3, G3B3, and CBS-QB3), the CBS-QB3 method was found to reproduce most accurately the experimental standard enthalpies of formation for a set of 17 small organosulfur compounds and the bond dissociation energies for a set of 10 sulfur bonds. Enthalpies of formation were predicted within 4 kJ mol(-1) while the mean absolute deviation on the bond dissociation enthalpies amounts to 7 kJ mol(-1). From the theoretical study, a new reaction path is identified for the formation of carbon disulfide via dithiirane (CH(2)S(2)). A reaction mechanism was constructed containing 36 reactions among 25 species accounting for the formation of all the decomposition products reported in literature. High-pressure limit rate coefficients for the 36 reactions in the reaction mechanism are presented. The kinetic model is able to grasp the experimental observations. With the recombination of thiyl radicals treated as being in the low-pressure limit, the experimentally reported first-order rate coefficients for the decomposition of DMDS are reproduced within 1 order of magnitude, while the observed product selectivities of most compounds are reproduced satisfactory. Simulations indicate that at high conversions most of the carbon disulfide forms according to the newly identified reaction path involving the formation of dithiirane.

  6. The effect of repeated physical disturbance on soft tissue decomposition--are taphonomic studies an accurate reflection of decomposition?

    PubMed

    Adlam, Rachel E; Simmons, Tal

    2007-09-01

    Although the relationship between decomposition and postmortem interval has been well studied, almost no studies examined the potential effects of physical disturbance occurring as a result of data collection procedures. This study compares physically disturbed rabbit carcasses with a series of undisturbed carcasses to assess the presence and magnitude of any effects resulting from repetitive disturbance. Decomposition was scored using visual assessment of soft tissue changes, and numerical data such as weight loss and carcass temperature were recorded. The effects of disturbance over time on weight loss, carcass temperature, soil pH and decomposition were studied. In addition, this study aimed to validate some of the anecdotal evidence regarding decomposition. Results indicate disturbance significantly inversely affects both weight loss and carcass temperature. No differences were apparent between groups for soil pH change or overall decomposition stage. An insect-mediated mechanism for the disturbance effect is suggested, along with indications as to why this effect may be cancelled when scoring overall decomposition.

  7. Some studies on anaerobic decomposition of leucaena leucocephala leaves

    SciTech Connect

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

    1990-01-01

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

  8. Broadband Microwave Study of Reaction Intermediates and Products Through the Pyrolysis of Oxygenated Biofuels

    NASA Astrophysics Data System (ADS)

    Abeysekera, Chamara; Hernandez-Castillo, Alicia O.; Fritz, Sean; Zwier, Timothy S.

    2017-06-01

    The rapidly growing list of potential plant-derived biofuels creates a challenge for the scientific community to provide a molecular-scale understanding of their combustion. Development of accurate combustion models rests on a foundation of experimental data on the kinetics and product branching ratios of their individual reaction steps. Therefore, new spectroscopic tools are necessary to selectively detect and characterize fuel components and reactive intermediates generated by pyrolysis and combustion. Substituted furans, including furanic ethers, are considered second-generation biofuel candidates. Following the work of the Ellison group, an 8-18 GHz microwave study was carried out on the unimolecular and bimolecular decomposition of the smallest furanic ether, 2-methoxy furan, and it`s pyrolysis intermediate, the 2-furanyloxy radical, formed in a high-temperature pyrolysis source coupled to a supersonic expansion. Details of the experimental setup and analysis of the spectrum of the radical will be discussed.

  9. The decomposition of benzenesulfonyl azide: a matrix isolation and computational study.

    PubMed

    Deng, Guohai; Dong, Xuelin; Liu, Qifan; Li, Dingqing; Li, Hongmin; Sun, Qiao; Zeng, Xiaoqing

    2017-02-01

    The thermal-decomposition and photo-decomposition of benzenesulfonyl azide, PhS(O)2N3, have been studied by combining matrix-isolation IR spectroscopy and quantum chemical calculations. Upon flash vacuum pyrolysis at 800 K, the azide splits off molecular nitrogen and exclusively furnishes phenylnitrene (PhN) and SO2 in the gas phase. In contrast, the azide favors stepwise photodecomposition in solid Ar and Ne matrices at 2.8 K. Specifically, the UV laser photolysis (193 and 266 nm) of PhS(O)2N3 results in the formation of the key nitrene intermediate PhS(O)2N in the triplet ground state, which undergoes pseudo-Curtius rearrangement into N-sulfonyl imine PhNSO2 under subsequent visible light irradiation (380-450 nm). Further fragmentation of PhNSO2 into SO2 and PhN followed by ring-expansion to didehydroazepine also occurs upon visible light irradiation. The preference of the stepwise mechanism for the decomposition of PhS(O)2N3 is supported by quantum chemical calculations using DFT B3LYP/6-311++G(3df,3pd) and CBS-QB3 methods.

  10. Thermodynamics and Mechanism of Protonated Cysteine Decomposition: A Guided Ion Beam and Computational Study

    NASA Astrophysics Data System (ADS)

    Armentrout, P. B.; Stennett, Elana M. S.

    2014-04-01

    A quantitative molecular description of the decomposition of protonated cysteine, H+Cys, is provided by studying the kinetic energy dependence of threshold collision-induced dissociation (CID) with Xe using a guided ion beam tandem mass spectrometer (GIBMS). Primary dissociation channels are deamidation (yielding both NH3 loss and NH4 + formation) and (H2O + CO) loss reactions, followed by an additional six subsequent decompositions. Analysis of the kinetic energy-dependent CID cross sections provides the 0 K barriers for six different reactions after accounting for unimolecular decay rates, internal energy of reactant ions, multiple ion-molecule collisions, and competition among the decay channels. To identify the mechanisms associated with these reactions, quantum chemical calculations performed at the B3LYP/6-311 + G(d,p) level were used to locate the transition states (TSs) and intermediates for these processes. Single point energies of the reactants, products, and key optimized TSs and intermediates are calculated at B3LYP, B3P86, and MP2(full) levels using a 6-311 + G(2d,2p) basis set. The computational characterization of the elementary steps of these reactions, including the structures of the final products, is validated by quantitative agreement with the experimental energetics. In agreement with previous work, deamidation is facilitated by anchimeric assistance of the thio group, which also leads to an interesting rearrangement of the intact amino acid identified computationally.

  11. Density Functional Studies of Decomposition Processes of Energetic Molecules

    DTIC Science & Technology

    1994-11-03

    34-- I of Energetic Molecules Dr. Richard S. Miller 6. AUTHOR(S) Peter Politzer, Jorge M. Seminario and M. Edward Grice R&T Code 4131DO2 7. PERFORMING...49) ,’i. " o MW U of. tongi.ig2 Density Functional Studies of Decomposition Processes of Energetic Molecules Peter Politzer, Jorge M. Seminario and...Initio Molecular Orbital Theory, (Wiley-Interscience, New York, 1986). 9. J. M. Seminario , M. Grodzicki and P. Politzer, in Density Functional Methods

  12. Nuclear structure studies with intermediate energy probes

    SciTech Connect

    Lee, T.S.H.

    1993-10-01

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

  13. Decomposition Studies of Isopropanol in a Variable Pressure Flow Reactor

    SciTech Connect

    Heyne, Joshua S.; Dooley, Stephen; Serinyel, Zeynep; Dryer, Frederick L.; Curran, Henry

    2015-01-28

    Abstract

    Alternatives to traditional petroleum derived transportation fuels, particularly alcohols, have been investigated increasingly over the last 5 years. Isopropanol has received little attention despite bridging the gap between smaller alcohols (methanol and ethanol) and the next generation alcohols (butyl alcohols) to be used in transportation fuels. Previous studies have shown that decomposition reactions that dehydrate are important in the high-temperature oxidation of alcohols. Here we report new data on the dehydration reaction for isopropanol (

    The C–C bond fission reaction is also investigated, but the insensitivity of the decomposition data to this reaction results in an uncertainty in the determined rate constants to approximately 2 orders of magnitude. Theoretical estimates lie within these experimental uncertainties.

  14. Isotopic ((13)C) fractionation during plant residue decomposition and its implications for soil organic matter studies.

    PubMed

    Schweizer; Fear; Cadisch

    1999-07-01

    Carbon isotopic fractionations in plant materials and those occurring during decomposition have direct implications in studies of short-and longer-term soil organic matter dynamics. Thus the products of decomposition, the evolved CO(2) and the newly formed soil organic matter, may vary in their (13)C signature from that of the original plant material. To evaluate the importance of such fractionation processes, the variations in (13)C signatures between and within plant parts of a tropical grass (Brachiaria humidicola) and tropical legume (Desmodium ovalifolium) were measured and the changes in (13)C content (signatures) during decomposition were monitored over a period of four months. As expected the grass materials were less depleted in (13)C (-11.4 to -11.9 per thousand) than those of the legume (-27.3 to -25.8 per thousand). Root materials of the legume were less (1.5 per thousand) depleted in (13)C compared with the leaves. Plant lignin-C was strongly depleted in (13)C compared with the bulk material by up to 2.5 per thousand in the legume and up to 4.7 per thousand in the grass. Plant materials were subsequently incubated in a sand/nutrient-solution/microbial inoculum mixture. The respiration product CO(2) was trapped in NaOH and precipitated as CaCO(3), suitable for analysis using an automated C/N analyser coupled to an isotope ratio mass spectrometer. Significant depletion in (13)C of the evolved CO(2) was observed during the initial stages of decomposition probably as a result of microbial fractionation as it was not associated with the (13)C signatures of the measured more decomposable fractions (non-acid detergent fibre and cellulose). While the cumulative CO(2)-(13)C signatures of legume materials became slightly enriched with ongoing decomposition, the CO(2)-C of the grass materials remained depleted in (13)C. Associated isotopic fractionation correction factors for source identification of CO(2-)C varied with time and suggested errors of 2-19% in the

  15. Degradation and intermediates of diclofenac as instructive example for decomposition of recalcitrant pharmaceuticals by hydroxyl radicals generated with pulsed corona plasma in water.

    PubMed

    Banaschik, Robert; Jablonowski, Helena; Bednarski, Patrick J; Kolb, Juergen F

    2017-08-25

    Seven recalcitrant pharmaceutical residues (diclofenac, 17α-ethinylestradiol, carbamazepine, ibuprofen, trimethoprim, diazepam, diatrizoate) were decomposed by pulsed corona plasma generated directly in water. The detailed degradation pathway was investigated for diclofenac and 21 intermediates could be identified in the degradation cascade. Hydroxyl radicals have been found primarily responsible for decomposition steps. By spin trap enhanced electron paramagnetic resonance spectroscopy (EPR), OH-adducts and superoxide anion radical adducts were detected and could be distinguished applying BMPO as a spin trap. The increase of concentrations of adducts follows qualitatively the increase of hydrogen peroxide concentrations. Hydrogen peroxide is eventually consumed in Fenton-like processes but the concentration is continuously increasing to about 2mM for a plasma treatment of 70min. Degradation of diclofenac is inversely following hydrogen peroxide concentrations. No qualitative differences between byproducts formed during plasma treatment or due to degradation via Fenton-induced processes were observed. Findings on degradation kinetics of diclofenac provide an instructive understanding of decomposition rates for recalcitrant pharmaceuticals with respect to their chemical structure. Accordingly, conclusions can be drawn for further development and a first risk assessment of the method which can also be applied towards other AOPs that rely on the generation of hydroxyl radicals. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Decomposition and Stability Studies of TAGN (Triaminoguanidium Nitrate)

    DTIC Science & Technology

    1988-12-01

    and atomic absorption spectroscopy . TAGN (Triaminoquanidinium Nitrate), DAGN (Diaminoquanidinium Nitrate), Thermal analysis, Mass Spectroscopy, RDX (Trinitrotriazacyclohexane), Decomposition chemistry.

  17. Photocatalytic decomposition of crotamiton over aqueous TiO(2) suspensions: determination of intermediates and the reaction pathway.

    PubMed

    Fukahori, Shuji; Fujiwara, Taku; Ito, Ryusei; Funamizu, Naoyuki

    2012-09-01

    The photocatalytic degradation of crotamiton in aqueous solution using TiO(2) was investigated. To investigate the effect of initial pH, the photodegradation behaviors of three types of pharmaceuticals were compared (crotamiton, clofibric acid, sulfamethoxazole). The degradation rates of crotamiton in the pH range 3-9 were nearly equal, but those of clofibric acid and sulfamethoxazole were affected by pH. At pH>6.5, TiO(2) particles, clofibric acid and sulfamethoxazole had negative charge, therefore, the repulsive force between TiO(2) particles and anionic pharmaceuticals occurred and a low reaction rate at high pH was observed. The effect of UV intensity and TiO(2) concentration on photodegradation efficiency was also investigated. Linear and logarithmical relationships between UV intensity, TiO(2) concentration and the reaction rate constant were confirmed. Furthermore, the structures of photodegradation intermediates formed concomitantly with the disappearance of crotamiton were estimated. Seven intermediates were characterized by LC/MS/MS analyses, and it was assumed that the photocatalytic degradation of crotamiton was initiated by the attack of electrophilic hydroxyl radicals on aromatic rings and alkyl chains.

  18. Shock tube study on the thermal decomposition of ethanol.

    PubMed

    Wu, Chih-Wei; Matsui, Hiroyuki; Wang, Niann-Shiah; Lin, M C

    2011-07-21

    The thermal decomposition of C(2)H(5)OH highly diluted in Ar (1 and 3 ppm) has been studied by monitoring H atoms using the atomic resonance absorption spectrometry (ARAS) technique behind reflected shock waves over the temperature range 1450-1760 K at fixed pressure: 1, 1.45, and 2 atm. The rate constant and the product branching fractions have been determined by analyzing temporal profiles of H atoms; the effect of the secondary reactions on the results has been examined by using a detailed reaction mechanism composed of 103 elementary reactions. The apparent rate constant of ethanol decomposition can be expressed as k(1)/s(-1) = (5.28 ± 0.14) × 10(10) exp[-(23,530 ± 980)/T] (T = 1450-1670 K, P = 1-2 atm) without a detectable pressure dependence within the tested pressure range of this study. Branching fractions for producing CH(3) + CH(2)OH (1a) and H(2)O + C(2)H(4) (1b) have been examined by a quantitative measurement of H atoms produced in the successive decompositions of the products CH(2)OH (1a): the pressure dependence of the branching fraction for channel 1a is obtained by a linear least-squares analysis of the experimental data and can be expressed as φ(1a) = (0.71 ± 0.07) - (826 ± 116)/T, (0.92 ± 0.04) - (1108 ± 70)/T, and (1.02 ± 0.10) - (1229 ± 168)/T for T = 1450-1760 K, at P = 0.99, 1.45, and 2.0 atm, respectively. The rate constant obtained in this study is found to be consistent with previous theoretical and experimental results; however, the pressure dependence of the branching fraction obtained in this study is smaller than those of previous theoretical works. Modification of the parameters for the decomposition rate in the falloff region is suggested to be important to improve the practical modeling of the pyrolysis and combustion of ethanol. © 2011 American Chemical Society

  19. Fundamental Studies of Beta Phase Decomposition Modes in Titanium Alloys.

    DTIC Science & Technology

    1986-01-24

    bainite , proeutectokd alpha, massive t ansformation 19. ABSTRACT (COntinue on evuerse if neeeaary and identify by block numb@-*A , TEM study" ’pf...a in Ti-C ys. A’ compar_ ve theoretical analysis has been made of the ledgewise growth of both pear and bainite , a modified version of Hillert’s...Hackney and Shiflet in an Fe-C-Mn alloy. When this condition is not fulfilled, the mode of eutectoid decomposition becomes bainitic , with one product phase

  20. Social Studies for the Intermediate Grades: An Annotated Bibliography.

    ERIC Educational Resources Information Center

    Aquino, John

    This bibliography is introduced by a short essay on social studies, concentrating on reforms since 1960 and speculating about future trends. The bibliography itself deals with current topics in social studies for intermediate grades and is divided into the following three sections: curriculum, teaching methods, and global/interpersonal learning.…

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

    PubMed

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

    2015-07-16

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

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

    PubMed

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

    2013-01-01

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

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

    ERIC Educational Resources Information Center

    Greeff, P.; Grobler, A. A.

    2008-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Rannulu, Nalaka S.; Cole, Richard B.

    2012-09-01

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

  5. Novel fragmentation pathways of anionic adducts of steroids formed by electrospray anion attachment involving regioselective attachment, regiospecific decompositions, charge-induced pathways, and ion-dipole complex intermediates.

    PubMed

    Rannulu, Nalaka S; Cole, Richard B

    2012-09-01

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

  6. Size-dependent decomposition temperature of nanoparticles: A theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Wang, Shanshan; Cui, Zixiang; Xia, Xiaoyan; Xue, Yongqiang

    2014-12-01

    Thermal decomposition of nanomaterials is often involved in the preparation and applications of nanomaterials, of which decomposition temperature can be surprisingly different from corresponding bulk materials. However, there is a lack of theoretical and experimental investigation on the relationship between the decomposition temperature and nanoparticle size. In present study, the relation between the decomposition temperature and the size of nanoparticles was derived theoretically, which indicates that the decomposition temperature decreases with the size of the nanoparticles decreasing, and there is a linear relationship between the decomposition temperature and the reciprocal of the particle size when the radius is bigger than 10 nm. Thermal decomposition experiments of nano-calcium carbonate with different sizes were carried out by thermo-gravimetric (TG), the onset decomposition temperatures (Tonset) and the temperature of the DTG peaks (Tmax) were measured and both of them present well liner relationship with the reciprocal of the particle size. The depress regularity of the onset decomposition temperature of nano-calcium carbonate agrees with the derived thermodynamic relationship. This thermodynamic theory provides a quantitative description for the decomposition temperature of nanoparticles, also it can be used to predict and explain the thermal decomposition behavior of nanomaterials.

  7. Molecular dynamics study of the M412 intermediate of bacteriorhodopsin.

    PubMed Central

    Xu, D; Sheves, M; Schulten, K

    1995-01-01

    Molecular dynamics simulations have been carried out to study the M412 intermediate of bacteriorhodopsin's (bR) photocycle. The simulations start from two simulated structures for the L550 intermediate of the photocycle, one involving a 13-cis retinal with strong torsions, the other a 13,14-dicis retinal, from which the M412 intermediate is initiated through proton transfer to Asp-85. The simulations are based on a refined structure of bR568 obtained through all-atom molecular dynamics simulations and placement of 16 waters inside the protein. The structures of the L550 intermediates were obtained through simulated photoisomerization and subsequent molecular dynamics, and simulated annealing. Our simulations reveal that the M412 intermediate actually comprises a series of conformations involving 1) a motion of retinal; 2) protein conformational changes; and 3) diffusion and reconfiguration of water in the space between the retinal Schiff base nitrogen and the Asp-96 side group. (1) turns the retinal Schiff base nitrogen from an early orientation toward Asp-85 to a late orientation toward Asp-96; (2) disconnects the hydrogen bond network between retinal and Asp-85 and tilts the helix F of bR, enlarging bR's cytoplasmic channel; (3) adds two water molecules to the three water molecules existing in the cytoplasmic channel at the bR568 stage and forms a proton conduction pathway. The conformational change (2) of the protein involves a 60 degrees bent of the cytoplasmic side of helix F and is induced through a break of a hydrogen bond between Tyr-185 and a water-side group complex in the counterion region. Images FIGURE 3 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 14 FIGURE 15 FIGURE 16 PMID:8599681

  8. First-principles study of high explosive decomposition energetics

    SciTech Connect

    Wu, C J

    1998-08-21

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

  9. Ozone decomposition

    PubMed Central

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

    2014-01-01

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

  10. Ozone decomposition.

    PubMed

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

    2014-06-01

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

  11. N-nitrosotolazoline: decomposition studies of a typical N-nitrosoimidazoline.

    PubMed

    Loeppky, Richard N; Shi, Jianzheng

    2008-02-01

    N-nitrosotolazoline ( N-nitroso-2-benzylimidazoline), a N-nitrosated drug typical of N-nitrosoimidazolines, reacts readily with aqueous acid, nitrous acid, or N-acetylcysteine to produce highly electrophilic diazonium ions capable of alkylating cellular nucleophiles. The kinetics and mechanism of the acidic hydrolytic decomposition of N-nitrosotolazoline have been determined in mineral acids and buffers. The mechanism of decomposition in acidic buffer is proposed to involve the rapid reversible protonation of the imino nitrogen atom followed by slow general base-catalyzed addition of H2O to the 2-carbon of the imidazoline ring to give a tetrahedral intermediate, which is also a alpha-hydroxynitrosamine. Rapid decomposition of this species gives rise to the diazonium from which the products are derived by nucleophilic attack, elimination, and rearrangement. The proposed mechanism is supported by the observations of general acid catalysis, a negligible deuterium solvent kinetic isotope effect ( kH/kD = 1.15) and delta S = -34 eu. In phosphate buffer at 30 degrees C, the half-lives of N-nitrosotolazoline range from 5 min at pH 3.5 to 4 h at pH 6. The main reaction product of the hydrolytic decomposition is N-(2-hydroxyethyl)phenylacetamide. This and other products are consistent with the formation of a reactive diazonium ion intermediate. N-nitrosotolazoline nitrosates 50 times more rapidly than tolazoline and results in a set of products derived from reactive diazonium ions but different from those produced from the hydrolytic decomposition of the substrate. N-acetylcysteine increases the decomposition rate of N-nitrosotolazoline by 25 times at pH 7 and results in both N-denitrosation and induced decomposition to produce electrophiles. These data suggest that N-nitrosotolazoline shares the chemical properties of many known direct-acting mutagens and carcinogens.

  12. A computational study on the kinetics and mechanism for the unimolecular decomposition of o-nitrotoluene.

    PubMed

    Chen, S C; Xu, S C; Diau, E; Lin, M C

    2006-08-24

    The kinetics and mechanism for the unimolecular decomposition of o-nitrotoluene (o-CH(3)C(6)H(4)NO(2)) have been studied computationally at the G2M(RCC, MP2)//B3LYP/6-311G(d, p) level of theory in conjunction with rate constant predictions with RRKM and TST calculations. The results of the calculations reveal 10 decomposition channels for o-nitrotoluene and its six isomeric intermediates, among them four channels give major products: CH(3)C(6)H(4) + NO(2), C(6)H(4)C(H)ON (anthranil) + H(2)O, CH(3)C(6)H(4)O (o-methyl phenoxy) + NO, and C(6)H(4)C(H(2))NO + OH. The predicted rate constants in the 500-2000 K temperature range indicate that anthranil production, taking place initially by intramolecular H-abstraction from the CH(3) group by NO(2) followed by five-membered ring formation and dehydration, dominates at temperatures below 1000 K, whereas NO(2) elimination becomes predominant above 1100 K and CH(3)C(6)H(4)O formation by the nitro-nitrite isomerization/decomposition process accounts for only 5-11% of the total product yield in the middle temperature range 800-1300 K. The branching ratio for CH(2)C(6)H(4)NO formation by the decomposition process of CH(2)C(6)H(4)N(O)OH is negligible. The predicted high-pressure-limit rate constants with the rate expression of 4.10 x 10(17) exp[-37000/T] s(-1) for the NO(2) elimination channel and 9.09 x 10(12) exp[-25800/T] s(-1) for the H(2)O elimination channel generally agree reasonably with available experimental data. The predicted high-pressure-limit rate constants for the NO and OH elimination channels are represented as 1.49 x 10(14) exp[-30000/T] and 1.31 x 10(15) exp[-38000/T] s(-1), respectively.

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

    PubMed

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

    2015-05-01

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

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

    PubMed

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

    2015-08-15

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

  15. A thermal desorption study of the kinetics of uranium hydride decomposition

    NASA Astrophysics Data System (ADS)

    Lillard, R. S.; Taylor, C. D.; Wermer, J. R.; Mara, N. A.; Cooley, J. C.

    2014-01-01

    The decomposition of uranium hydride powder was studied using thermal desorption spectroscopy (TDS). In the TDS spectra, three distinct decomposition peaks were observed. However, only the high temperature peak was associated with an activation energy, calculated to be 43 kJ/mol H. This activation energy was used to construct outgassing diagrams that can be used to estimate the temperature and time dependence of UH3 decomposition. Potential models for explaining the three decomposition peaks and, thus, the decomposition mechanism are also presented and compared with H desorption energies calculated from first principles. Additional experiments on α-U coupons containing UH3 corrosion pits were also performed. In those samples in excess of 6 peaks are observed. It is shown that the first three hydrogen peaks are related to the decomposition of UH3.

  16. Shock tube studies on the decomposition of 2-butanol.

    PubMed

    Rosado-Reyes, Claudette M; Tsang, Wing

    2012-10-04

    The thermal decomposition of 2-butanol have been studied at temperatures of 1045-1221 K and pressures of 1.5-6 bar using the single pulse shock tube technique. Dilute concentrations of 2-butanol have been decomposed in the presence of large quantities of a radical inhibitor. The mechanism for decomposition involves direct elimination of water producing cis- and trans-2-butene, and 1-butene, and C-C bond fission producing ethylene. Acetaldehyde, propionaldehyde, and propene were also observed in much smaller yields from C-C bond fission. The respective unimolecular rate expressions are as follows: k(C(3)H(6)(OH)CH(3) → cis-CH(3)CH═CHCH(3) + H(2)O) = 10(13.1 ± 0.3) exp(-33414 ± 755 K/T) s(-1); k(C(3)H(6)(OH)CH(3) → trans-CH(3)CH═CHCH(3) + H(2)O) = 10(13.5 ± 0.3) exp(-33820 ± 755 K/T) s(-1); k(C(3)H(6)(OH)CH(3) → CH(3)CH(2)CH═CH(2) + H(2)O) = 10(13.6 ± 0.3) exp(-33002 ± 755 K/T) s(-1); k(C(3)H(6)(OH)CH(3) → C(2)H(5)(•) + (•)CH(OH)CH(3)) = 10(15.9 ± 0.3) exp(-39252 ± 755 K/T) s(-1). These rate expressions are compared with analogous reactions for primary and tertiary butanols. They form a basis for the prediction of those for related systems. Comparison with estimated values used in the simulation of butanol combustion is indicative of the uncertainties in the rate constants that are used in such models. The activation energy of 326 kJ/mol leads to a bond dissociation energy of the CH(OH)CH(3) radical (H-CH(OH)CH(3)) of 400 kJ/mol, in excellent agreement with earlier calculated results from theory and disagreement with the experimental results from iodination studies in the expected range.

  17. 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 CHOCOCHONO2 (a product obtained following the abstraction of three H atoms from NG by NO2) include O-NO2 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 NO2 concentration, which affects the decomposition products and reactions. In the first stage, the reaction pathway corresponding to O-NO2 cleavage is the main pathway, but the rates of the two autocatalytic decomposition pathways increase with increasing NO2 concentration. However, when a threshold NO2 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.

  18. Thermal Decomposition of Almandine Garnet: Mössbauer Study

    NASA Astrophysics Data System (ADS)

    Barcova, K.; Mashlan, M.; Zboril, R.; Martinec, P.; Kula, P.

    2001-07-01

    The thermal decomposition of almandine garnet from Zoltye Vody, Ukraine, has been studied using57Fe Mössbauer spectroscopy. Room temperature Mössbauer spectrum of the initial powdered sample is characterised by one doublet corresponding to Fe2+ in dodecahedral position 24c. In the room temperature spectra of all heated almandine samples, a doublet corresponding to γ-Fe2O3 nanoparticles appeared. Depending on experimental conditions (heating temperature and time), the additional spectral lines of α-Fe2O3 and ɛ-Fe2O3 were observed in Mössbauer spectra. It is obvious that the thermal transformation of almandine garnet in air is related to the primary formation of γ-Fe2O3 superparamagnetic nanoparticles. γ-Fe2O3 nanoparticles are transformed into ɛ-Fe2O3 and consequently into α-Fe2O3 at higher temperatures. The mechanism and kinetics of the individual structural transformations depend on experimental conditions — mainly on the heating temperature and size of the particles.

  19. Mössbauer study of the thermal decomposition of lepidocrocite and characterization of the decomposition products

    NASA Astrophysics Data System (ADS)

    de Bakker, P. M. A.; de Grave, E.; Vandenberghe, R. E.; Bowen, L. H.; Pollard, R. J.; Persoons, R. M.

    1991-08-01

    The lepidocrocite (γ-FeOOH) to maghemite (γ-Fe2O3), and the maghemite to hematite (α-Fe2O3) transition temperatures have been monitored by TGA and DSC measurements for four initial γ-FeOOH samples with different particle sizes. The transition temperature of γ-FeOOH to γ-Fe2O3 and the size of the resulting particles were not affected by the particle size of the parent lepidocrocite. In contrast, the γ-Fe2O3 to γ-Fe2O3 transition temperature seems to depend on the amount of excess water molecules present in the parent lepidocrocite. Thirteen products obtained by heating for one hour at selected temperatures, were considered. Powder X-ray diffraction was used to qualify their composition and to determine their mean crystallite diameters. Transmission electron micrographs revealed the particle morphology. The Mössbauer spectra at 80 K and room temperature of the mixed and pure decomposition products generally had to be analyzed with a distribution of hyperfine fields and, where appropriate, with an additional quadrupole-splitting distribution. The Mössbauer spectra at variable temperature between 4.2 and 400 K of two single-phase γ-Fe2O3 samples with extremely small particles show the effect of superparamagnetism over a very broad temperature range. Only at the lowest temperatures (T⩽55 K), two distributed components were resolved from the magnetically split spectra. In the external-field spectra the ΔmI=0 transitions have not vanished. This effect is an intrinsic property of the maghemite particles, indicating a strong spin canting with respect to the applied-field direction. The spectra are successfully reproduced using a bidimensional-distribution approach in which both the canting angle and the magnetic hyperfine field vary within certain intervals. The observed distributions are ascribed to the defect structure of the maghemites (unordered vacancy distribution on B-sites, large surface-to-bulk ratio, presence of OH- groups). An important new finding

  20. Thermal decomposition of 2-phenylethanol: A computational study on mechanism

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuyuki; Ando, Hiromitsu; Oguchi, Tatsuo; Murakami, Yoshinori

    2013-01-01

    Quantum mechanical calculations for the thermal decomposition of 2-phenylethanol have been performed using the CBS-QB3 method. Based on the potential energy surfaces at the CBS-QB3 level of theory, the preferred reaction channel for the thermal decomposition of 2-phenylethanol was the six-membered cyclic rearrangement reaction and the dehydration reaction to form styrene and H2O. Further quantum chemical calculations of the subsequent reactions followed by the six-membered cyclic rearrange reaction of 2-phenylethanol were carried out and it was revealed that the barrier height for the ring opening reaction was the lowest among all of the other subsequent reactions.

  1. Photofragment imaging study of the CH2CCH2OH radical intermediate of the OH +allene reaction

    NASA Astrophysics Data System (ADS)

    Raman, Arjun S.; Justine Bell, M.; Lau, Kai-Chung; Butler, Laurie J.

    2007-10-01

    These velocity map imaging experiments characterize the photolytic generation of one of the two radical intermediates formed when OH reacts via an addition mechanism with allene. The CH2CCH2OH radical intermediate is generated photolytically from the photodissociation of 2-chloro-2-propen-1-ol at 193nm. Detecting the Cl atoms using [2+1] resonance-enhanced multiphoton ionization evidences an isotropic angular distribution for the Cl +CH2CCH2OH photofragments, a spin-orbit branching ratio for Cl(P1/22):Cl(P3/22) of 0.28, and a bimodal recoil kinetic energy distribution. Conservation of momentum and energy allows us to determine from this data the internal energy distribution of the nascent CH2CCH2OH radical cofragment. To assess the possible subsequent decomposition pathways of this highly vibrationally excited radical intermediate, we include electronic structure calculations at the G3//B3LYP level of theory. They predict the isomerization and dissociation transition states en route from the initial CH2CCH2OH radical intermediate to the three most important product channels for the OH +allene reaction expected from this radical intermediate: formaldehyde+C2H3, H +acrolein, and ethene+CHO. We also calculate the intermediates and transition states en route from the other radical adduct, formed by addition of the OH to the center carbon of allene, to the ketene+CH3 product channel. We compare our results to a previous theoretical study of the O +allyl reaction conducted at the CBS-QB3 level of theory, as the two reactions include several common intermediates.

  2. Experimental and modeling study of the thermal decomposition of methyl decanoate

    PubMed Central

    Herbinet, Olivier; Glaude, Pierre-Alexandre; Warth, Valérie; Battin-Leclerc, Frédérique

    2013-01-01

    The experimental study of the thermal decomposition of methyl decanoate was performed in a jet-stirred reactor at temperatures ranging from 773 to 1123 K, at residence times between 1 and 4 s, at a pressure of 800 Torr (106.6 kPa) and at high dilution in helium (fuel inlet mole fraction of 0.0218). Species leaving the reactor were analyzed by gas chromatography. Main reaction products were hydrogen, carbon oxides, small hydrocarbons from C1 to C3, large 1-olefins from 1-butene to 1-nonene, and unsaturated esters with one double bond at the end of the alkyl chain from methyl-2-propenoate to methyl-8-nonenoate. At the highest temperatures, the formation of polyunsaturated species was observed: 1,3-butadiene, 1,3-cyclopentadiene, benzene, toluene, indene, and naphthalene. These results were compared with previous ones about the pyrolysis of n-dodecane, an n-alkane of similar size. The reactivity of both molecules was found to be very close. The alkane produces more olefins while the ester yields unsaturated oxygenated compounds. A detailed kinetic model for the thermal decomposition of methyl decanoate has been generated using the version of software EXGAS which was updated to take into account the specific chemistry involved in the oxidation of methyl esters. This model contains 324 species and 3231 reactions. It provided a very good prediction of the experimental data obtained in jet-stirred reactor. The formation of the major products was analyzed. The kinetic analysis showed that the retro-ene reactions of intermediate unsaturated methyl esters are of importance in low reactivity systems. PMID:23710078

  3. Mechanism of ammonia decomposition on clean and oxygen-covered Cu (1 1 1) surface: A DFT study

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Qin, Pei; Fang, Tao

    2014-12-01

    Employing density functional theory (DFT), the adsorption and dehydrogenation mechanism of ammonia on clean and O-covered Cu (1 1 1) surfaces have been studied systematically. Different adsorption geometries were investigated for NH3 and related intermediates. In addition, the stable co-adsorption configurations for the relevant co-adsorption groups were identified. The projected density of states (DOS) were calculated to understand the interaction between NHx (x = 1, 3) species and Cu (1 1 1) surface and investigate the effect of oxygen atom on adsorption. Finally, transition states, energy barriers and reaction energies were determined to confirm the mechanism of dehydrogenation of NH3 on clean and oxygen-covered Cu (1 1 1) surfaces. It was shown that NH is the most abundant intermediate on clean and O-covered Cu (1 1 1) surface due to the highest energy barrier, suggesting the dehydrogenation of NH group is the rate-determining step in the overall reaction. Furthermore, the existence of oxygen atom can reduce the energy barriers drastically and promote the decomposition of NHx (x = 1-3), indicating that ammonia decomposition is more favorable on oxygen-covered Cu (1 1 1) surface.

  4. Theoretical studies on Santilli's intermediate nuclear fusions without radiations

    NASA Astrophysics Data System (ADS)

    Cai, Wei

    2012-09-01

    Experiments of intermediate controlled nuclear fusion are strongly supported by theoretical study. First, current investigation based on quantum mechanics has proved that under super-strong magnetic field, which can be produced by a sudden large current of arc, the wave function of electron cloud changes from a spherical shape to a toroidal shape, which explores nuclear of atom. Second, hadronic mechanics shows that when a trigger, for example, a sudden change of arc, pushes two explored nucleus into a distance of 10-13 cm, a non-unitary, non-linear and nonpotential interaction, introduced by Santilli, leads two nucleus strongly attract each other, while the effective mass of nucleus being renormalized and becomes larger, which leads to a new view of structure of nucleus and results to new types of nuclear fusion.

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

    SciTech Connect

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

    2010-08-12

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

  6. A Longitudinal Study on Human Outdoor Decomposition in Central Texas.

    PubMed

    Suckling, Joanna K; Spradley, M Katherine; Godde, Kanya

    2016-01-01

    The development of a methodology that estimates the postmortem interval (PMI) from stages of decomposition is a goal for which forensic practitioners strive. A proposed equation (Megyesi et al. 2005) that utilizes total body score (TBS) and accumulated degree days (ADD) was tested using longitudinal data collected from human remains donated to the Forensic Anthropology Research Facility (FARF) at Texas State University-San Marcos. Exact binomial tests examined the rate of the equation to successfully predict ADD. Statistically significant differences were found between ADD estimated by the equation and the observed value for decomposition stage. Differences remained significant after carnivore scavenged donations were removed from analysis. Low success rates for the equation to predict ADD from TBS and the wide standard errors demonstrate the need to re-evaluate the use of this equation and methodology for PMI estimation in different environments; rather, multivariate methods and equations should be derived that are environmentally specific.

  7. Mass spectral studies of thermal decomposition of metal nitrates

    NASA Astrophysics Data System (ADS)

    Jackson, Jason G.; Fonseca, Rodney W.; Holcombe, James A.

    1995-10-01

    Residual gas analysis and static secondary ion mass spectrometry are used in an attempt to elucidate the process responsible for the appearance of metal oxides in the gas phase during low temperature nitrate decomposition of Pb, Cu, Cd and Ag nitrates in vacuo. Observed signals for MO, MNO 3+ together with M 2+ species in the gas phase during the decomposition of some of the metal nitrates indicate that a physical expulsion mechanism is probably responsible for the low temperature production of these metal-containing species. The "gasification mechanism" provided by L'vov states that metal nitrates decompose in a single mechanistic step to product MO(g), O 2 and NO 2 and that the temperature of the decomposition is predictable from thermodynamics. The observation of unexplained gas phase species, the absence of O 2 during CuO + production, and the lack of agreement between activation energies and appearance temperatures fail to support the gasification model. Instead, it is suggested that during the decomposition, which is governed by the kinetics of the process, the evolution of the gaseous products, such as O 2 and NO 2, carry the observed metal-containing species into the vapor phase when the liquid state is present on the surface (e.g. AgNO 3, Cu(NO 3) 2 or Cd(NO 3) 2). The crystal rearrangement of the solid (e.g. conversion of Pb(NO 3) 2 to PbO) and subsequent loss of integrity of the crystal lattice results in the dislocation of the metal-containing species, which are swept from the surface during the O 2 and NO 2 evolution.

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

    PubMed

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

    2001-03-19

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

  9. Density functional theory study on direct catalytic decomposition of ammonia on Pd (1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Pan, Qi; Li, Mengmeng; Yan, Ting; Fang, Tao

    2014-02-01

    The adsorption and step dehydrogenation mechanism of NH3 on Pd (1 1 1) have been studied using density functional theory (DFT) together with periodic slab models. According to the optimized structural and energetic properties, it was found that NH3 and N2 prefer to adsorb on the top site, whereas NH, N, H prefer to adsorb on the fcc site and NH2 prefers on the bri site. In addition, this work identified the optimum configurations for the stable co-adsorption configurations of NHx + H, and N + N. Finally, three transition states were found for analyzing the mechanism of dehydrogenation of NH3, and the N recombination reaction was also considered. The results show that NH is the most abundant intermediate on Pd (1 1 1) surface and the dehydrogenation of NH3 is the rate-determining step in the overall reaction. The distinct differences over Pd (1 1 1) and Pd (1 0 0) surface imply that ammonia decomposition over Pd-based catalyst is a structure-sensitive reaction.

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

    SciTech Connect

    Behrens, R. Jr.; Bulusu, S.

    1995-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

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

    SciTech Connect

    Not Available

    1991-12-31

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

  13. Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Falenty, Andrzej; Chaouachi, Marwen; Haberthür, David; Kuhs, Werner F.

    2016-09-01

    In-situ synchrotron X-ray computed microtomography with sub-micrometer voxel size was used to study the decomposition of gas hydrates in a sedimentary matrix. Xenon-hydrate was used instead of methane hydrate to enhance the absorption contrast. The microstructural features of the decomposition process were elucidated indicating that the decomposition starts at the hydrate-gas interface; it does not proceed at the contacts with quartz grains. Melt water accumulates at retreating hydrate surface. The decomposition is not homogeneous and the decomposition rates depend on the distance of the hydrate surface to the gas phase indicating a diffusion-limitation of the gas transport through the water phase. Gas is found to be metastably enriched in the water phase with a concentration decreasing away from the hydrate-water interface. The initial decomposition process facilitates redistribution of fluid phases in the pore space and local reformation of gas hydrates. The observations allow also rationalizing earlier conjectures from experiments with low spatial resolutions and suggest that the hydrate-sediment assemblies remain intact until the hydrate spacers between sediment grains finally collapse; possible effects on mechanical stability and permeability are discussed. The resulting time resolved characteristics of gas hydrate decomposition and the influence of melt water on the reaction rate are of importance for a suggested gas recovery from marine sediments by depressurization.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    PubMed

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

    2016-10-07

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  18. Effects of different types of soil on decomposition: an experimental study.

    PubMed

    Tumer, Ali Riza; Karacaoglu, Emre; Namli, Ayten; Keten, Alper; Farasat, Shima; Akcan, Ramazan; Sert, Osman; Odabaşi, Aysun Balseven

    2013-05-01

    Decomposition, a postmortem process including autolysis and putrefaction, is affected by many factors (e.g., humidity, microbial activity, soil properties). The purpose of this study was to determine the importance of soil type in decomposition process. Changes occurred in two intervals (3 and 6 months) were evaluated using a total of 32 Sus scrofa limbs by burying in four different types of soil (loamy, clayey, sandy and organic). The extremities in all soils had lost weight over time; however, mass loss was greater in loamy and organic soils in both intervals. Entomological findings were also assessed. Obtained findings of soil analysis and evaluation of decomposition were compatible. In conclusion, the present study revealed that soil properties and textures should be taken into account in evaluation of decomposition and estimating postmortem interval in crime scene investigation.

  19. Synthetic, characterization and decomposition studies of indium sulfide precursors

    SciTech Connect

    Schluter, R.D.; Luten, H.A.; Rees, W.S. Jr.

    1996-12-31

    The synthesis, characterization and decomposition of several indium thiolates containing the bulky substituted aryl ligand 2,4,6-i-Pr{sub 3}C{sub 6}H{sub 2} (Ar{prime}) or the internally chelating ligands 2-CH{sub 3}O, 5-CH{sub 3}C{sub 6}H{sub 3} (Ar{double_prime}) and o-C{sub 6}H{sub 4}CH{sub 2}N(CH{sub 3}){sub 2} (Ar{prime}{double_prime}) are described. Two synthetic methods have been utilized: metathesis reactions between lithium thiolates and the appropriate metal halides and the addition of elemental metal to diaryl disulfides. The thermal decomposition of each indium precursor results in the formation of In{sub 2}S{sub 3}, based on thermogravimetric data. The homoleptic compound In(SAr{prime}){sub 3} can be isolated as a yellow oil. This liquid precursor has been derivatized by the reversible formation of acetonitrile and tetrahydroduran adducts. Although, the molecule exists as a monomer in both adducts, the coordination number of the metal and the orientation of the ligands are markedly different. The internally chelating In(SAr{double_prime}){sub 3} and In(SAr{prime}{double_prime}){sub 3} adopt contrasting dimeric and monomeric structures respectively.

  20. IRAS 21391 + 5802 - A study in intermediate mass star formation

    NASA Technical Reports Server (NTRS)

    Wilking, Bruce; Mundy, Lee; Mcmullin, Joseph; Hezel, Thomas; Keene, Jocelyn

    1993-01-01

    We present infrared and millimeter wavelength observations of the cold IRAS source 21391 + 5802 and its associated molecular core. Infrared observations at lambda = 3.5 microns reveal a heavily obscured, central point source which is coincident with a compact lambda = 2.7 mm continuum and C18O emission region. The source radiates about 310 solar luminosities, primarily at FIR wavelengths, suggesting that it is a young stellar object of intermediate mass. The steeply rising spectral energy distribution and the large fraction of the system mass residing in circumstellar material imply that IRAS 21391 + 5802 is in an early stage of evolution. The inferred dust temperature indicates a temperature gradient in the core. A comprehensive model for the surrounding core of dust and gas is devised to match the observed dust continuum emission and multitransition CS emission from this and previous studies. We find a r exp -1.5 +/- 0.2 density gradient consistent with that of a gravitationally evolved core and a total core mass of 380 solar masses. The observed dust emission is most consistent with a lambda exp -1.5 - lambda exp -2 dust emissivity law; for a lambda exp -2 law, the data are best fit by a mass opacity coefficient of 3.6 x 10 exp -3 sq cm/g at lambda = 1.25 mm.

  1. Analytical and toxicological studies of decomposition of insecticide parathion after gamma-irradiation and ozonation.

    PubMed

    Bojanowska-Czajka, Anna; Torun, Murat; Kciuk, Gabriel; Wachowicz, Mariusz; Ozbay, Dilek Solpan; Guven, Olgun; Bobrowski, Krzysztof; Trojanowicz, Marek

    2012-01-01

    The decomposition of the widely used organophosphorus pesticide parathion was carried out in aqueous solutions by the use of gamma-irradiation from a 60Co source or ozonation by means of an ozone generator, and by combined processes of ozonation and radiolysis. Factors affecting the parathion decomposition as well formation and decomposition of the main by-products, including irradiation dose, length of ozonation time, and presence of common scavengers, were investigated. The most efficient was found to be the gamma-irradiation process combined with a short ozonation period; about 1 kGy irradiation dose was sufficient to decompose the pesticide in 15 mg/L solutions. Chemical studies of the decomposition of parathion were accompanied by monitoring of toxicity changes of irradiated solutions with the Microtox test.

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

    PubMed

    Keough, Natalie; Myburgh, Jolandie; Steyn, Maryna

    2016-12-29

    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.

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

    PubMed Central

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

    2014-01-01

    Purpose: To investigate the feasibility of an accurate measurement of water, lipid, and protein composition of breast tissue using a photon-counting spectral computed tomography (CT) with spectral distortion corrections. Methods: Thirty-eight postmortem breasts were imaged with a cadmium-zinc-telluride-based photon-counting spectral CT system at 100 kV. The energy-resolving capability of the photon-counting detector was used to separate photons into low and high energy bins with a splitting energy of 42 keV. The estimated mean glandular dose for each breast ranged from 1.8 to 2.2 mGy. Two spectral distortion correction techniques were implemented, respectively, on the raw images to correct the nonlinear detector response due to pulse pileup and charge-sharing artifacts. Dual energy decomposition was then used to characterize each breast in terms of water, lipid, and protein content. In the meantime, the breasts were chemically decomposed into their respective water, lipid, and protein components to provide a gold standard for comparison with dual energy decomposition results. Results: The accuracy of the tissue compositional measurement with spectral CT was determined by comparing to the reference standard from chemical analysis. The averaged root-mean-square error in percentage composition was reduced from 15.5% to 2.8% after spectral distortion corrections. Conclusions: The results indicate that spectral CT can be used to quantify the water, lipid, and protein content in breast tissue. The accuracy of the compositional analysis depends on the applied spectral distortion correction technique. PMID:25281953

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

    SciTech Connect

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

    2014-10-15

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

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

    SciTech Connect

    Unknown

    1999-12-31

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

  6. A Study of Japan for the Intermediate Grades.

    ERIC Educational Resources Information Center

    Sauer, Susan

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

  7. Cyberbullying in a Rural Intermediate School: An Exploratory Study

    ERIC Educational Resources Information Center

    Bauman, Sheri

    2010-01-01

    Students (N = 221) in an intermediate school (grades 5-8) in a rural area of the Southwestern United States completed a survey regarding their familiarity with technology and their experiences with cyberbullying during the school year. Initial evidence of survey reliability is presented. In the sample, 1.5% of participants were classified as…

  8. Intermediate Lexicon for Information Science. A Feasibility Study. Final Report.

    ERIC Educational Resources Information Center

    Horsnell, Verina

    An intermediate lexicon is described that employs a technique which allows, for a given subject area, the automatic translation of subject indexing from one indexing scheme into another. The lexicon was structured according to the principles of faceted classification and contained approximately 1,000 entries covering the field of library and…

  9. A Study of Japan for the Intermediate Grades.

    ERIC Educational Resources Information Center

    Sauer, Susan

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

  10. 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.

  11. Clinicopathologic study of pineal parenchymal tumors of intermediate differentiation.

    PubMed

    Ito, Tamio; Kanno, Hiromi; Sato, Ken-ichi; Oikawa, Mitsuteru; Ozaki, Yoshimaru; Nakamura, Hirohiko; Terasaka, Shunsuke; Kobayashi, Hiroyuki; Houkin, Kiyohiro; Hatanaka, Kanako; Murata, Jyun-ichi; Tanaka, Shinya

    2014-01-01

    Pineal parenchymal tumors of intermediate differentiation (PPTID) are extremely rare tumor entities, and only limited data are available regarding their pathologic features and biologic behaviors. Because grading criteria of pineal parenchymal tumors (PPTs) have yet to be established, the treatment strategy and prognosis of PPTIDs remain controversial. We describe the clinicopathologic study of six patients with PPTID and compare responses for the treatment and prognosis with cases of pineocytoma (PC) and pineoblastoma (PB). From this analysis, we attempt to clarify the treatment strategy for PPTIDs. This study included 15 patients with PPTs, consisting of 6 PCs, 6 PPTIDs, and 3 PBs. We focused on the 6 patients with PPTIDs. All PPTID cases were treated surgically, and radiotherapy and chemotherapy were administered as adjuvant therapies in some cases. We have earlier reported the histopathologic study (Neuropathology 32:647-653, 2012). Briefly, we examined mitotic figures and necrosis by hematoxylin-eosin staining and immunohistochemical markers such as neuronal markers (synaptophysin, neurofilament (NF), and neuronal nuclear antigen), and an MIB-1 labeling index was determined. In the PPTID cases, the extent of resection was variable and the recurrence rates among patients varied according to stage and treatment. All PC patients underwent total resection with no recurrence. All PB patients underwent resection and adjuvant therapy with radiotherapy and chemotherapy. There were no recurrences in patients with PC or PB. The results of histopathologic findings have been already reported as mentioned above. Briefly, the results indicated no mitotic figure or necrosis in any of the six cases of PPTID, but those features were observed in PB cases. All cases even including PC and PB were immunopositive for neuronal markers. The MIB-1 labeling index of PPTID was 3.5%, whereas it was 0% in PC and 10.5% in PB. Good radiosensitivity of PPTIDs was observed in our series

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  13. Computational studies of the early intermediates of the bacteriorhodopsin photocycle.

    PubMed

    Engels, M; Gerwert, K; Bashford, D

    1995-01-01

    Starting from a refined model of bacteriorhodopsin's ground state, alternative models of the K and L intermediates with retinal in either 13-cis or 13-14-dicis configuration have been generated by molecular dynamics simulations. All models have been submitted to electrostatic calculations in order to determine the pK1/2 values of particular residues of interest in the active site. Our pK1/2 calculations for the refined ground state can reestablish our former results, this time without adjusting the intrinsic pK of the Schiff base. For the K intermediate the electrostatic calculations show no significant change in the pK1/2 values compared to the ground state for most of the titrating groups in the active site. For the L intermediate where retinal possesses a 13-cis configuration, we found that electrostatic factors decrease the pK1/2 value of the Schiff base by 4-5 pK-units compared to the ground state. The calculations suggest that changes of the electrostatic environment via a pure 13-cis model are sufficient to produce a pK reduction of the Schiff base that will promote subsequent proton transfer steps.

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

    NASA Astrophysics Data System (ADS)

    Liu, Liming; Zhao, Jin

    2016-10-01

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

  15. Pyrogenic carbon decomposition mixed to different litters : a controlled conditions study

    NASA Astrophysics Data System (ADS)

    Andreoli, R.; Abiven, S.

    2009-04-01

    In a recent study, Wardle et al. (2008) showed that the presence of pyrogenic carbon modified litter decomposition dynamics in soil, for boreal conditions. Pyrogenic carbon corresponds to the organic residues left after the incomplete combustion of vegetal biomass. It presents specific properties in term of biological, physical and chemical stability and might play a major role in biogeochemical cycles of soils. The decomposition of a mixture of different organic substrates could be very different from the mathematical average of the same substrates decaying alone. Positive interactions (for example mineral N released from one substrate available for the other one) or negative interactions (for example release of molecules with a biocide effect like polyphenols) have been observed. In an incubation study, we followed decomposition of pyrogenic carbon and of the corresponding original wood (Picea abies) mixed (1:1) to different organic substrates (leaves) with different content of nitrogen and polyphenols. We observed a positive effect of substrates rich in nitrogen on the mixture decomposition and no significant effect with the other substrates. The specific contribution of the char and the wood to the mixture decomposition will be also shown. If confirmed, this mixture interaction would have to be considered in C ecosystem mass balance.

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

    NASA Astrophysics Data System (ADS)

    Jaber, Abobaker M.

    2014-12-01

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

  17. Matrix isolation study of the early intermediates in the ozonolysis of cyclopentene and cyclopentadiene: observation of two Criegee intermediates.

    PubMed

    Hoops, Michael D; Ault, Bruce S

    2009-03-04

    Matrix isolation studies, combined with infrared spectroscopy, of the twin jet codeposition of ozone into matrices containing either cyclopentadiene or cyclopentene have led to the first observation of several early intermediates in these ozonolysis reactions. Specifically, evidence is presented for the formation, identification, and characterization of the long sought-after Criegee intermediate for each system, as well as the primary and secondary ozonides. These were observed after initial twin jet deposition and grew approximately 300% upon annealing to 35 K. Extensive isotopic labeling ((2)H, (18)O and mixtures) experiments provided important supporting data. Detailed theoretical calculations at the B3LYP/6-311++G(d,2p) and B3LYP/6-311++G(3df, 3pd) levels were carried out as well to augment the experimental work. Merged jet (flow reactor) experiments followed by cryogenic trapping in solid argon led to the formation of "late" stable oxidation products of cyclopentadiene and cyclopentene. In contrast, no thermal reaction between ozone and cyclopentane was observed. Photochemical reactions of ozone with all three organic substrates were studied as well.

  18. Improving interMediAte Risk management. MARK study

    PubMed Central

    2011-01-01

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

  19. The impact of shallow burial on differential decomposition to the body: a temperate case study.

    PubMed

    Schotsmans, Eline M J; Van de Voorde, Wim; De Winne, Joan; Wilson, Andrew S

    2011-03-20

    Extant literature contains a number of specific case studies on differential decomposition involving adipocere formation or desiccation, but few describe the co-occurrence of these features within a temperate climate. The case of a 65-year-old male, partially buried in a shallow grave for 7 months, is presented in which the soft tissues of the body were outwardly well preserved. The right leg was desiccated, some parts of the body were covered with adipocere (head, neck, right shoulder, upper torso and left leg) and other parts could be classified as in the early stages of decomposition. In this study the taphonomic variables resulting in differential decomposition with desiccation and adipocere formation are discussed.

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

    NASA Astrophysics Data System (ADS)

    Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

    2002-09-01

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

  1. Oxidative decomposition of propylene carbonate in lithium ion batteries: a DFT study.

    PubMed

    Leggesse, Ermias Girma; Lin, Rao Tung; Teng, Tsung-Fan; Chen, Chi-Liang; Jiang, Jyh-Chiang

    2013-08-22

    This paper reports an in-depth mechanistic study on the oxidative decomposition of propylene carbonate in the presence of lithium salts (LiClO4, LiBF4, LiPF6, and LiAsF6) with the aid of density functional theory calculations at the B3LYP/6-311++G(d,p) level of theory. The solvent effect is accounted for by using the implicit solvation model with density method. Moreover, the rate constants for the decompositions of propylene carbonate have been investigated by using transition-state theory. The shortening of the original carbonyl C-O bond and a lengthening of the adjacent ethereal C-O bonds of propylene carbonate, which occurs as a result of oxidation, leads to the formation of acetone radical and CO2 as a primary oxidative decomposition product. The termination of the primary radical generates polycarbonate, acetone, diketone, 2-(ethan-1-ylium-1-yl)-4-methyl-1,3-dioxolan-4-ylium, and CO2. The thermodynamic and kinetic data show that the major oxidative decomposition products of propylene carbonate are independent of the type of lithium salt. However, the decomposition rate constants of propylene carbonate are highly affected by the lithium salt type. On the basis of the rate constant calculations using transition-state theory, the order of gas volume generation is: [PC-ClO4](-) > [PC-BF4](-) > [PC-AsF6](-) > [PC-PF6](-).

  2. Acid and alkali effects on the decomposition of HMX molecule: a computational study.

    PubMed

    Zhang, Chaoyang; Li, Yuzhen; Xiong, Ying; Wang, Xiaolin; Zhou, Mingfei

    2011-11-03

    The stored and wasted explosives are usually in an acid or alkali environment, leading to the importance of exploring the acid and alkali effects on the decomposition mechanism of explosives. The acid and alkali effects on the decomposition of HMX molecule in gaseous state and in aqueous solution at 298 K are studied using quantum chemistry and molecular force field calculations. The results show that both H(+) and OH(-) make the decomposition in gaseous state energetically favorable. However, the effect of H(+) is much different from that of OH(-) in aqueous solution: OH(-) can accelerate the decomposition but H(+) cannot. The difference is mainly caused by the large aqueous solvation energy difference between H(+) and OH(-). The results confirm that the dissociation of HMX is energetically favored only in the base solutions, in good agreement with previous HMX base hydrolysis experimental observations. The different acid and alkali effects on the HMX decomposition are dominated by the large aqueous solvation energy difference between H(+) and OH(-).

  3. Synchrotron photoionization mass spectrometry study of intermediates in fuel-rich 1,2-dimethoxyethane flame

    SciTech Connect

    Lin, Z. K.; Han, D. L.; Li, S. F.; Li, Y. Y.; Yuan, T.

    2009-04-21

    Intermediates in a fuel-rich premixed laminar 1,2-dimethoxyethane (DME) flame are studied by molecular beam mass spectrometry combined with tunable synchrotron vacuum ultraviolet photoionization. About 30 intermediate species are identified in the present work, and their mole fraction profiles are evaluated. The experimental results show that the formations of intermediates, both hydrocarbons and oxygenated hydrocarbons, are closely linked to the structure of fuel, which is consistent with the previous reports. Species produced from H atom abstraction and beta scission of DME usually have much higher concentrations than others. The oxygen atoms in DME are considered to act as partitions of the primary intermediates; therefore farther reactions among these primary intermediates are difficult to occur, resulting in absence of most large intermediate species.

  4. Synchrotron photoionization mass spectrometry study of intermediates in fuel-rich 1,2-dimethoxyethane flame

    NASA Astrophysics Data System (ADS)

    Lin, Z. K.; Han, D. L.; Li, S. F.; Li, Y. Y.; Yuan, T.

    2009-04-01

    Intermediates in a fuel-rich premixed laminar 1,2-dimethoxyethane (DME) flame are studied by molecular beam mass spectrometry combined with tunable synchrotron vacuum ultraviolet photoionization. About 30 intermediate species are identified in the present work, and their mole fraction profiles are evaluated. The experimental results show that the formations of intermediates, both hydrocarbons and oxygenated hydrocarbons, are closely linked to the structure of fuel, which is consistent with the previous reports. Species produced from H atom abstraction and beta scission of DME usually have much higher concentrations than others. The oxygen atoms in DME are considered to act as partitions of the primary intermediates; therefore farther reactions among these primary intermediates are difficult to occur, resulting in absence of most large intermediate species.

  5. In situ experimental decomposition studies in estuaries: A comparison of Phragmites australis and Fucus vesiculosus

    NASA Astrophysics Data System (ADS)

    Lopes, Marta Lobão; Martins, Patrícia; Ricardo, Fernando; Rodrigues, Ana Maria; Quintino, Victor

    2011-05-01

    The decomposition rates of Phragmites australis and Fucus vesiculosus were experimentally determined in an estuarine system using the leaf-bag technique. The study was conducted in fifteen sites arranged in five areas, extending from freshwater, outside the tidal range, to the marine environment, near the mouth of the estuary. The leaf-bags (5 mm mesh), were set up with 3.0 g of dried substrate, submerged in the experimental sites at day 0 and collected at days 3, 7, 15, 30 and 60, to follow biomass loss. The biomass loss through the leaching phase (day 3) was about 16% for Phragmites australis and 33% for Fucus vesiculosus and was independent of salinity for both substrates. The difference in the remaining biomass between the two species increased with time and the decomposition rates differed along the salinity gradient. For F. vesiculosus, the decomposition rate was highest near the mouth of the estuary, corresponding to the preferential distribution area of the algae, and decreased towards freshwater. For Phragmites australis, the fastest decay was observed in the mid estuary, where Phragmites australis occurs naturally, confirming previous studies. The decomposition rates measured at different time intervals (0-15, 0-30 and 0-60 days) were always higher for the algae and decreased with time for both species. These results indicate that the use of decomposition rates as a measure of ecosystem integrity or quality status in transitional waters will not be straightforward and must take into account, among others, the test species, the study area positioning along the estuarine gradient, and the time interval for the calculation of the decomposition rate.

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

    SciTech Connect

    Hang, T.

    1998-08-19

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

  7. The decomposition of methanol on Ru(001) studied using laser induced thermal desorption

    NASA Astrophysics Data System (ADS)

    Deckert, A. A.; Brand, J. L.; Mak, C. H.; Koehler, B. G.; George, S. M.

    1987-08-01

    The decomposition reaction of methanol on Ru(001) was studied using laser induced thermal desorption (LITD). The LITD studies, combined with temperature programmed desorption and Auger electron spectroscopy measurements, allowed absolute product yields for the three competing surface pathways to be determined over the entire range of chemisorbed methanol coverages at a heating rate of β=2.6 K/s. At the lowest methanol coverages of θ≤0.07θs, where θs is the surface coverage of a saturated chemisorbed layer, all the methanol reacted between 220-280 K. This methanol decomposition reaction yielded desorption-limited H2 and CO as reaction products. At higher coverages, molecular desorption and the second methanol decomposition reaction involving C-O bond breakage became increasingly important. At θ=θs, 50% of the initial methanol coverage desorbed, 24% produced H2 and CO and 26% left C on the surface. Isothermal LITD kinetic measurements were carried out at low methanol coverages of θ≤0.07θs at various temperatures from 180 to 220 K. The initial decomposition rates obtained from the isothermal LITD studies displayed first order kinetics. The decomposition kinetics at later times could not be fit by first order kinetics and suggested a self-poisoned reaction. Subsequent LITD studies revealed that CO inhibited the decomposition reaction. The product CO inhibition was modeled by first order kinetics with a CO-coverage dependent activation barrier. The observed first order reaction kinetics at low methanol coverage could be expressed by the pre-exponential ν=106 s-1 and the coverage-dependent activation barrier E=7 kcal/mol+αθCO/θCO,s, where α=20 kcal/mol and θCO/θCO,s is the dimensionless CO coverage normalized to the CO saturation coverage θCO,s. Isotopic LITD studies revealed that the decomposition kinetics of CH3OH, CD3OH, and CH3OD were identical. This equivalence suggested that the hindered rotation of the surface methoxy species is the reaction

  8. Kinetic study of non-isothermal decomposition of a composite diasporic-boehmitic bauxite

    NASA Astrophysics Data System (ADS)

    Samouhos, M.; Angelopoulos, P.; Pilatos, G.; Taxiarchou, M.; Papageorgiou, S.

    2016-04-01

    In the current study, the kinetic of the thermal decomposition of a composite diasporic-boehmitic bauxite is investigated under non-isothermal heating conditions by means of thermogravimetric analysis. The calculation of activation energy (Ea) has been performed by various methods and the attained values range from 185000 to 190000 J.mol-1 for conversion rate of 0.5. The first-order kinetic model can adequately be used to describe thermal decomposition of bauxite composite, while the pre-exponential factor value was found to be 2.088*1011 min-1. The calculated activation energy value together with pre-exponential factor and the solid state kinetic model factors enable the simulation of the thermal decomposition under various heating conditions by the implementation of an ordinary differential equation. The calculated values are in satisfactory agreement with the experimental ones.

  9. Raman spectroelectrochemical study of electrochemical decomposition of poly(neutral red) at a gold electrode.

    PubMed

    Mazeikiene, R; Niaura, G; Malinauskas, A

    2009-08-01

    A gold electrode, modified with poly(neutral red), has been studied with surface-enhanced resonance Raman spectroscopy at 676.4 nm excitation. It has been shown that both qualitative and quantitative changes in Raman spectra occur during prolonged holding of the modified electrode in pH 7.0 solution at a controlled electrode potential ranging from -0.6 to -0.2V vs. Ag/AgCl, indicating that a decomposition of the poly(neutral red) layer proceeds. The decomposition proceeds slower at a more negative electrode potential. From kinetic data obtained, first-order decomposition rate constants have been calculated, ranging from 9.17x10(-4) to 1.09x10(-2) min(-1) for electrode potential ranging from -0.6 to -0.2 V.

  10. A study on SMO-type decomposition methods for support vector machines.

    PubMed

    Chen, Pai-Hsuen; Fan, Rong-En; Lin, Chih-Jen

    2006-07-01

    Decomposition methods are currently one of the major methods for training support vector machines. They vary mainly according to different working set selections. Existing implementations and analysis usually consider some specific selection rules. This paper studies sequential minimal optimization type decomposition methods under a general and flexible way of choosing the two-element working set. The main results include: 1) a simple asymptotic convergence proof, 2) a general explanation of the shrinking and caching techniques, and 3) the linear convergence of the methods. Extensions to some support vector machine variants are also discussed.

  11. 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.

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

    ERIC Educational Resources Information Center

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

    2006-01-01

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

  13. Soil Microarthropod Community Structure and Litter Decomposition Dynamics: A Study of Tropical and Temperate Sites

    Treesearch

    L. Heneghan; D.C. Coleman; X. Zou; D.A. Crossley; B.L. Hines

    1998-01-01

    The influence of climate, substrate quality and microarthropods on decomposition was studied by comparing the mass loss of litter at three forested sites: two tropical and one temperate. At each site,litter bags containing a dominant local litter were placed in the field in replicated plots. Half the bags were treated with naphthalene to reduce microarthropod...

  14. Combined Ab Initio, Kinetic Modeling, and Shock Tube Study of the Thermal Decomposition of Ethyl Formate.

    PubMed

    Ning, Hongbo; Wu, Junjun; Ma, Liuhao; Ren, Wei; Davidson, David F; Hanson, Ronald K

    2017-09-07

    The potential energy surfaces (PESs) and reaction rate constants of the unimolecular decomposition of ethyl formate (EF) were investigated using high-precision theoretical methods at the CCSD(T)/CBS(T-Q)//M06-2X/6-311++G(d,p) level of theory. The calculated PESs of EF dissociation and molecular decomposition reactions indicate that the intramolecular H-shift to produce formic acid and ethylene is the dominant decomposition pathway. A detailed chemical kinetic mechanism for EF pyrolysis was constructed by incorporating the important reactions of EF and its radicals into an existing mechanism previously developed for small methyl esters. The updated mechanism was first used to reproduce CO, CO2, and H2O concentration time histories during EF pyrolysis in the shock tube reported by Ren et al. [ Ren , W. , Mitchell Spearrin , R. , Davidson , D. F. , and Hanson , R. K. J. Phys. Chem. A 2014 , 118 , 1785 - 1798 ]. The rate of production and sensitivity analyses show that the competing dehydration and decarboxylation channels of the intermediate formic acid control the final product yields of EF pyrolysis. The EF mechanism was further validated against the shock tube data of OH, CO, CO2, and H2O time histories measured during EF oxidation (equivalence ratio Φ = 1.0) at 1331-1615 K and 1.52-1.74 atm. This revised EF mechanism captured all of the species' time histories over the entire temperature range. Such modeling capability was due to the more accurate rate constants of EF reactions determined by high-precision theoretical calculations and a high-fidelity C0-C2 basis mechanism.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  16. GCM studies of intermediate and deep waters in the Mediterranean

    NASA Astrophysics Data System (ADS)

    Haines, Keith; Wu, Peili

    1998-12-01

    Results from GCM simulations of the Mediterranean thermohaline circulation are presented under repeating year wind and surface buoyancy forcings and the reproduction of important physical processes is discussed. It is shown that baroclinic eddies are critical to the effective dispersal of Levantine intermediate water (LIW) throughout the eastern Mediterranean basin. These develop rapidly even in a 1/4 degree model which does not resolve the deformation radius, provided horizontal friction is small enough. It is shown that LIW enters the Adriatic basin and pre-conditions deep water formation which would not otherwise occur due to low surface salinity in winter. The dispersal of Adriatic deep waters is modelled, and it is shown that the introduction of the Gent and McWilliams advective scheme greatly improves the distribution of deep waters in the eastern basin by permitting the formation of dense overflow waters from the Otranto straits. This is achieved with very small parametrised advection that still permits the formation of baroclinic eddies unlike most applications which use the scheme to replace eddies. Results from a 100-year climate simulation are then presented in which the thermohaline circulation has reached equilibrium conditions. Dense water formation in both eastern and western basin still occur after 100 years. While the eastern basin water masses are reasonably realistic, the western basin is a little too cold and fresh, suggesting that insufficient LIW is reaching the deep water formation site in the northwest basin. Further work is needed in this area.

  17. Thermal Decomposition of 2-Pentanol: A Shock Tube Study and RRKM Calculations.

    PubMed

    Parandaman, A; Rajakumar, B

    2016-10-07

    A single pulse shock tube was used to study the thermal decomposition of 2-pentanol in the temperatures between 1110 and 1325 K. Three major decomposition products are methane, ethylene, and propylene. The minor products detected in lower concentration are ethane, acetylene, acetaldehyde, 1-pentene, and 2-pentene. The rate coefficient for the overall decomposition of 2-pentanol was found to be ktotal(exp)(1110-1325 K) = (4.01 ± 0.51) × 10(9) exp(-(36.2 ± 4.7)/RT) s(-1), where the activation energies are given in kcal mol(-1). To simulate reactant and product distribution over the experimentally studied temperatures between 1110 and 1325 K, a reaction scheme was constructed with 34 species and 39 reactions. In addition to this, the temperature and pressure dependent rate coefficients were computed for various unimolecular dissociation pathways using RRKM theory. The high pressure limit rate coefficient for overall decomposition of 2-pentanol was obtained to be ktotal(theory)(500-2500 K) = (9.67 ± 1.11) × 10(14) exp(-(67.7 ± 2.9)/RT) s(-1). The calculated high pressure rate coefficients and experimentally measured rate constants are in good agreement with each other. The reaction is primarily governed by the unimolecular elimination of water.

  18. Modeling study of carbonate decomposition in LLNL`s 4TU pilot oil shale retort

    SciTech Connect

    Thorsness, C.B.

    1994-10-14

    Lawrence Livermore National Laboratory`s (LLNL) 4 tonne-per-day oil shale Pilot Retort (4TU-Pilot) has been modeled to study the degree of carbonate decomposition occurring in the process. The modeling uses a simplified version of the processes occurring in the retort to allow parametric studies to be performed. The primary focus of the work is on the sensitivity of computed carbonate decomposition to the assumed manner in which solid material leaves the retort. It was found that for a variety of assumptions about solid passage and evolution within the process the computed carbonate decomposition varied by only a few percent. It was also determined that using available kinetic expressions based on literature data led to a consistent underestimate of the carbonate decomposition, from 12--17% low on an absolute basis and on a relative basis as much as a factor of seven times too low. A simplified kinetic expression based on limited data from laboratory experiments on the same shale as used in the 4TU-Pilot run was also employed and found to match the pilot results fairly well.

  19. Theoretical study of β-HMX decomposition mechanism of the solid phase under shock loadings

    NASA Astrophysics Data System (ADS)

    Ji, Guangfu; Ge, Nina; Chen, Xiangrong

    2015-06-01

    Study material properties under extreme conditions is a fundamental problem in the field of condensed matter physics. The decomposition mechanisms of energetic materials under the shock wave become a hot topic in recent years. In this paper, molecular dynamics simulations combined with multi-scale shock technology (MSST) are used to study the decomposition mechanism, shock sensitivity and electronic structure of β-HMX. First, the decomposition mechanism of β-HMX perfect crystal were studied at different shock speeds. We found that when the shock wave at a speed 8 km / s is loaded, the decomposition reaction start at N-NO2 bond breakage; when the shock wave at a speed of 10 km / s and 11 km / s is loaded, the the first decomposition reaction is CH bond breaking, and accompanied by the formation of five-membered ring and transfer of hydrogen ions. The simulation results also show that when the shock wave velocity is increased, the higher the pressure generated in the high-pressure N-NO2 bond cleavage was inhibited significantly. Secondly, the impact of its initial chemical reaction process along different crystal axis directions were studied, the results showed that along the a-axis and c-axis shock sensitivity is higher, and along the b-axis sensitivity is lower. We believe that the system of all sensitivity of direction is due to the rotation of the friction between the slip plane of crystals and molecules. Finally, we discussed the solid phase β-HMX electronic properties change under the shock wave loadings. We found that in the 11 km/s under the impact load, when the pressure reaches 130 GPa, zero bandgap is reached.

  20. Delineating gas bearing reservoir by using spectral decomposition attribute: Case study of Steenkool formation, Bintuni Basin

    NASA Astrophysics Data System (ADS)

    Haris, A.; Pradana, G. S.; Riyanto, A.

    2017-07-01

    Tectonic setting of the Bird Head Papua Island becomes an important model for petroleum system in Eastern part of Indonesia. The current exploration has been started since the oil seepage finding in Bintuni and Salawati Basin. The biogenic gas in shallow layer turns out to become an interesting issue in the hydrocarbon exploration. The hydrocarbon accumulation appearance in a shallow layer with dry gas type, appeal biogenic gas for further research. This paper aims at delineating the sweet spot hydrocarbon potential in shallow layer by applying the spectral decomposition technique. The spectral decomposition is decomposing the seismic signal into an individual frequency, which has significant geological meaning. One of spectral decomposition methods is Continuous Wavelet Transform (CWT), which transforms the seismic signal into individual time and frequency simultaneously. This method is able to make easier time-frequency map analysis. When time resolution increases, the frequency resolution will be decreased, and vice versa. In this study, we perform low-frequency shadow zone analysis in which the amplitude anomaly at a low frequency of 15 Hz was observed and we then compare it to the amplitude at the mid (20 Hz) and the high-frequency (30 Hz). The appearance of the amplitude anomaly at a low frequency was disappeared at high frequency, this anomaly disappears. The spectral decomposition by using CWT algorithm has been successfully applied to delineate the sweet spot zone.

  1. Initial Decomposition Mechanism study for the Energy Release from Electronical Excited Energetic Material

    NASA Astrophysics Data System (ADS)

    Yuan, Bing

    2014-03-01

    Decomposition of energetic materials FOX-7 and 3,4-dinitropyrazole (DNP) are investigated both theoretically and experimentally. The two energetic model systems 1-nitropyrazole and 4-nitropyrazole are also studied as a comparison for DNP. The NO molecule is observed as an initial decomposition product from all four materials subsequent to UV excitation and the observed NO products are rotationally cold (< 50 K). The vibrational temperature of the NO product from DNP is 3300 K, 1400 K hotter than that of its model species. The vibrational temperature of the NO product from FOX-7 is 1900 K. The initial decomposition mechanisms of these materials are explored at the complete active space self-consistent field (CASSCF) level. Potential energy surface (PES) calculations at the CASSCF(12,8)/6-31+G(d) level illustrate that conical intersections play an essential role in the decomposition mechanism. Electronically excited S2 molecules can nonradiatively relax to lower electronic states through (S2/S1)CI and (S1/S0)CI conical intersections and undergo a nitro-nitrite isomerization to generate an NO product either on the S1 state or S0 state PES. For model systems, NO is generated on the S1 state PES, while for the energetic materials FOX-7 and DNP, NO is produced on the ground state PES,

  2. Thermal decomposition of propargyl alcohol: single pulse shock tube experimental and ab initio theoretical study.

    PubMed

    Sharath, N; Reddy, K P J; Arunan, E

    2014-08-07

    Thermal decomposition of propargyl alcohol (C3H3OH), a molecule of interest in interstellar chemistry and combustion, was investigated using a single pulse shock tube in the temperature ranging from 953 to 1262 K. The products identified include acetylene, propyne, vinylacetylene, propynal, propenal, and benzene. The experimentally observed overall rate constant for thermal decomposition of propargyl alcohol was found to be k = 10((10.17 ± 0.36)) exp(-(39.70 ± 1.83)/RT) s(-1). Ab initio theoretical calculations were carried out to understand the potential energy surfaces involved in the primary and secondary steps of propargyl alcohol thermal decomposition. Transition state theory was used to predict the rate constants, which were then used and refined in a kinetic simulation of the product profile. The first step in the decomposition is C-O bond dissociation, leading to the formation of two important radicals in combustion, OH and propargyl. This has been used to study the reverse OH + propargyl radical reaction, about which there appears to be no prior work. Depending on the site of attack, this reaction leads to propargyl alcohol or propenal, one of the major products at temperatures below 1200 K. A detailed mechanism has been derived to explain all the observed products.

  3. In Situ Studies of the Decomposition of Simulated Chemical Warfare Agents on Nanoparticle Catalysts

    DTIC Science & Technology

    2009-10-04

    formed via a methoxy intermediate.98 In these studies, it was established that most of the observed activity is from reaction on ceria rather than...Interestingly, no dimethyl ether was formed in the reaction of methanol itself, which also decomposes on ceria via a methoxy intermediate. Diffuse...problems with transition metal catalysts is that phosphorus is difficult to remove from the surface and poisons that catalyst for further reaction . Thus

  4. Accumulation of Tetrahedral Intermediates in Cholinesterase Catalysis: A Secondary Isotope Effect Study

    PubMed Central

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

    2010-01-01

    In a previous communication, kinetic β-deuterium secondary isotope effects were reported that support a mechanism for substrate-activated turnover of acetylthiocholine by human butyrylcholinesterase (BuChE) wherein the accumulating reactant state is a tetrahedral intermediate (Tormos, J. R., et al. (2005) JACS 127, 14538–14539). In this paper additional isotope effect experiments are described with acetyl-labeled acetylthiocholines (CL3COSCH2CH2N+Me3; L = H or D) that also support accumulation of the tetrahedral intermediate in Drosophila melanogaster acetylcholinesterase (DmAChE) catalysis. In contrast to the aforementioned BuChE-catalyzed reaction, for this reaction the dependence of initial rates on substrate concentration is marked by pronounced substrate inhibition at high substrate concentrations. Moreover, kinetic β -deuterium secondary isotope effects for turnover of acetylthiocholine depended on substrate concentration, and gave the following: D3kcat/Km = 0.95 ± 0.03, D3kcat = 1.12 ± 0.02 and D3 β kcat = 0.97 ± 0.04. The inverse isotope effect on kcat/Km is consistent with conversion of the sp2 hybridized substrate carbonyl in the E + A reactant state into a quasi-tetrahedral transition state in the acylation stage of catalysis, whereas the markedly normal isotope effect on kcat is consistent with hybridization change from sp3 toward sp2 as the reactant state for deacylation is converted into the subsequent transition state. Transition states for Drosophila melanogaster AChE-catalyzed hydrolysis of acetylthiocholine were further characterized by measuring solvent isotope effects and determining proton inventories. These experiments indicated that the transition state for rate-determining decomposition of the tetrahedral intermediate is stabilized by multiple protonic interactions. Finally, a simple model is proposed for the contribution that tetrahedral intermediate stabilization provides to the catalytic power of acetylcholinesterase. PMID

  5. Experimental study of two material decomposition methods using multi-bin photon counting detectors

    NASA Astrophysics Data System (ADS)

    Zimmerman, Kevin C.; Sidky, Emil Y.; Gilat Schmidt, Taly

    2014-03-01

    Photon-counting detectors with multi-bin pulse height analysis (PHA) are capable of extracting energy dependent information which can be exploited for material decomposition. Iterative decomposition algorithms have been previously implemented which require prior knowledge of the source spectrum, detector spectral response, and energy threshold settings. We experimentally investigated two material decomposition methods that do not require explicit knowledge of the source spectrum and spectral response. In the first method, the effective spectrum for each energy bin is estimated from calibration transmission measurements, followed by an iterative maximum likelihood decomposition algorithm. The second investigated method, first proposed and tested through simulations by Alvarez, uses a linearized maximum likelihood estimator which requires calibration transmission measurements. The Alvarez method has the advantage of being non-iterative. This study experimentally quantified and compared the material decomposition bias, as a percentage of material thickness, and standard deviation resulting from these two material decomposition estimators. Multi-energy x-ray transmission measurements were acquired through varying thicknesses of Teon, Delrin, and neoprene at two different flux settings and decomposed into PMMA and aluminum thicknesses using the investigated methods. In addition, a series of 200 equally spaced projections of a rod phantom were acquired over 360°. The multi-energy sinograms were decomposed using both empirical methods and then reconstructed using filtered backprojection producing two images representing each basis material. The Alvarez method decomposed Delrin into PMMA with a bias of 0.5-19% and decomposed neoprene into aluminum with a bias of less than 3%. The spectral estimation method decomposed Delrin into PMMA with a bias of 0.6-16% and decomposed neoprene into aluminum with a bias of 0.1-58%. In general, the spectral estimation method resulted in

  6. Fundamental Studies of Beta Phase Decomposition Modes in Titanium Alloys.

    DTIC Science & Technology

    1988-01-31

    kinetics of the proeutectoid alpha, the massive alpha and the bainite reactions in Ti-X alloys. Because that portion of the beta matrix which is not...allotriomorphs will be completed at the same time. During the latter portion of Mr. Furuhara’s research, this program will re-enter bainite studies as he...to support the P.l.’s accelerating paperwriting activities on the bainite reaction in steel. This ,# ferrous-oriented effort is being actively aided by

  7. Fundamental Studies of Beta Phase Decomposition Modes in Titanium Alloys.

    DTIC Science & Technology

    1985-01-24

    with well-formed 𔄀’black plates’a + lower reaction temperatures. Bainite nodules in hypereutectoid Ti-Cr and in hypoeutectoid Ti-Co and Ti-Fe were...much lower density of growth ledges. A detailed study of bainite nodule formation in a hyper- , eutectoid Ti-25% Cr alloy showed extensive evidence...orientation relationship. The growth kinetics d -. " l At, ?Y4c M TT7TC Z~TjC (AYSC)Iis Thi -2- Dist " Chi f, 70hniefa l u’~ n L DivisiOD of bainite

  8. Study of Fundamental Chemical Processes in Explosive Decomposition by Laser-Powered Homogeneous Pyrolysis.

    DTIC Science & Technology

    1981-11-12

    nitrotoluenes actually represent surface- catalyzed reactions . Preliminary qualitative results for pyrolysis of ortho-nitrotoluene in the absence of hot...quantitative validity. LPHP studies of azoisopropane decomposition chosen as a radical-forming test reaction , show the accepted literature parameters to...systematic errors or by rate control exerted by secondary reactions . (2) Support from these VLPP studies for the conclusion that some previous kinetic

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

    NASA Astrophysics Data System (ADS)

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

    1994-10-01

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

  10. Confounding, causality, and confusion: the role of intermediate variables in interpreting observational studies in obstetrics.

    PubMed

    Ananth, Cande V; Schisterman, Enrique F

    2017-08-01

    Prospective and retrospective cohorts and case-control studies are some of the most important study designs in epidemiology because, under certain assumptions, they can mimic a randomized trial when done well. These assumptions include, but are not limited to, properly accounting for 2 important sources of bias: confounding and selection bias. While not adjusting the causal association for an intermediate variable will yield an unbiased estimate of the exposure-outcome's total causal effect, it is often that obstetricians will want to adjust for an intermediate variable to assess if the intermediate is the underlying driver of the association. Such a practice must be weighed in light of the underlying research question and whether such an adjustment is necessary should be carefully considered. Gestational age is, by far, the most commonly encountered variable in obstetrics that is often mislabeled as a confounder when, in fact, it may be an intermediate. If, indeed, gestational age is an intermediate but if mistakenly labeled as a confounding variable and consequently adjusted in an analysis, the conclusions can be unexpected. The implications of this overadjustment of an intermediate as though it were a confounder can render an otherwise persuasive study downright meaningless. This commentary provides an exposition of confounding bias, collider stratification, and selection biases, with applications in obstetrics and perinatal epidemiology. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    PubMed

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

    2010-10-19

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

  12. Thermal decomposition pathways for 1,1-diamino-2,2-dinitroethene (FOX-7).

    PubMed

    Booth, Ryan S; Butler, Laurie J

    2014-10-07

    In this study, we computationally investigate the initial and subsequent steps in the chemical mechanism for the gas-phase thermal decomposition of 1,1-diamino-2,2-dinitroethene (FOX-7). We determine the key exothermic step in the gas-phase thermal decomposition of FOX-7 and explore the similarities and differences between FOX-7 and other geminal dinitro energetic materials. The calculations reveal a mechanism for NO loss involving a 3-member cyclic intermediate, rather than a nitro-nitrite isomerization, that occurs in the radical intermediates formed throughout the decomposition mechanism.

  13. Thermal decomposition pathways for 1,1-diamino-2,2-dinitroethene (FOX-7)

    NASA Astrophysics Data System (ADS)

    Booth, Ryan S.; Butler, Laurie J.

    2014-10-01

    In this study, we computationally investigate the initial and subsequent steps in the chemical mechanism for the gas-phase thermal decomposition of 1,1-diamino-2,2-dinitroethene (FOX-7). We determine the key exothermic step in the gas-phase thermal decomposition of FOX-7 and explore the similarities and differences between FOX-7 and other geminal dinitro energetic materials. The calculations reveal a mechanism for NO loss involving a 3-member cyclic intermediate, rather than a nitro-nitrite isomerization, that occurs in the radical intermediates formed throughout the decomposition mechanism.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    SciTech Connect

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

    2013-01-01

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

  16. Fundamental studies of reactive intermediates in homogeneous catalysis

    SciTech Connect

    Not Available

    1993-10-01

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

  17. Study on the thermal decomposition kinetics of nano-sized calcium carbonate.

    PubMed

    Li, Dai-Xi; Shi, Hong-Yun; Jie, Deng; Xu, Yuan-Zhi

    2003-01-01

    This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA ( thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energy (a); and that the top-temperature of decomposition T(p) decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both E(a) and T(p) to decline sharply with the decrease of the average diameter of nano-particles.

  18. Kinetics of methane hydrate decomposition studied via in situ low temperature X-ray powder diffraction.

    PubMed

    Everett, S Michelle; Rawn, Claudia J; Keffer, David J; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy J

    2013-05-02

    Gas hydrate is known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Based on results from the decomposition of three nominally similar methane hydrate samples, the kinetics of two regions, 180-200 and 230-260 K, within the overall decomposition range 140-260 K, were studied by in situ low temperature X-ray powder diffraction. The kinetic rate constants, k(a), and the reaction mechanisms, n, for ice formation from methane hydrate were determined by the Avrami model within each region, and activation energies, E(a), were determined by the Arrhenius plot. E(a) determined from the data for 180-200 K was 42 kJ/mol and for 230-260 K was 22 kJ/mol. The higher E(a) in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

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

    NASA Astrophysics Data System (ADS)

    Rieper-Kirchner, M.

    1990-09-01

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

  20. Single-pool exponential decomposition models: potential pitfalls in their use in ecological studies.

    PubMed

    Adair, E Carol; Hobbie, Sarah E; Hobbie, Russell K

    2010-04-01

    The importance of litter decomposition to carbon and nutrient cycling has motivated substantial research. Commonly, researchers fit a single-pool negative exponential model to data to estimate a decomposition rate (k). We review recent decomposition research, use data simulations, and analyze real data to show that this practice has several potential pitfalls. Specifically, two common decisions regarding model form (how to model initial mass) and data transformation (log-transformed vs. untransformed data) can lead to erroneous estimates of k. Allowing initial mass to differ from its true, measured value resulted in substantial over- or underestimation of k. Log-transforming data to estimate k using linear regression led to inaccurate estimates unless errors were lognormally distributed, while nonlinear regression of untransformed data accurately estimated k regardless of error structure. Therefore, we recommend fixing initial mass at the measured value and estimating k with nonlinear regression (untransformed data) unless errors are demonstrably lognormal. If data are log-transformed for linear regression, zero values should be treated as missing data; replacing zero values with an arbitrarily small value yielded poor k estimates. These recommendations will lead to more accurate k estimates and allow cross-study comparison of k values, increasing understanding of this important ecosystem process.

  1. Experimental and numerical studies on carbon dioxide decomposition in atmospheric electrodeless microwave plasmas

    NASA Astrophysics Data System (ADS)

    Sun, Hojoong; Lee, Jungwun; Do, Hyungrok; Im, Seong-kyun; Soo Bak, Moon

    2017-07-01

    Electrodeless microwave plasmas in carbon dioxide at atmospheric pressure have been studied for carbon dioxide decomposition. Plasma optical emission spectroscopy has been conducted to measure ro-vibrational temperatures of the plasma. It is found that the temperature reaches 6200 K at the plasma center and there is little difference between the trans-rotational and vibrational temperatures. Kinetic simulations considering the trans-rotational, vibrational, and electron temperatures separately are also conducted to investigate the details of the plasma decomposition of carbon dioxide. As observed in the measurements, the kinetic simulation demonstrated that the difference between the trans-rotational and vibrational temperatures is negligible, and all the carbon dioxide within the plasma is found to be decomposed into carbon monoxide and atomic oxygen, as a result of the extremely high temperatures of the plasma. The carbon monoxide and oxygen then recombine as the temperature decreases, forming mostly carbon dioxide at the reactor exit. From the results, although the electrons in the microwave plasma selectively populate the molecules' vibrational states, the fast relaxation of these excited vibrational states raises the gas temperature instead of resulting in accumulative vibrational excitation for the efficient decomposition of carbon dioxide.

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

    PubMed

    Murakami, Midori; Kouyama, Tsutomu

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  5. A spectroscopic study of dyes decomposition by irradiated nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Rosu, M. C.; Suciu, R. C.; Kasco, I.; Dreve, S. V.; Indrea, E.; Silipas, T. D.

    2009-08-01

    The photocatalytic activity of the TiO2 films prepared by wet-chemical techniques and deposited on the ITO glass was tested by examining the decomposition of violet gentian (VG), methylen blue (MB) and methyl green (MG) aqueous solutions under UV light illumination. The photodegradation processes of dyes have been studied using UV-VIS spectrophotometry and spectrofluorimetry. The comparative results of the present study demonstrate the capability of UV irradiation of the TiO2/ITO photocatalytic system to degrade studied organic dyes from aqueous solutions.

  6. Safety and bioactivity studies of Jasad Bhasma and its in-process intermediate in Swiss mice.

    PubMed

    Chavare, Aparna; Chowdari, Praneeth; Ghosh, Sandipto; Pawar, Priyanka; Patkar, Meena; Dakave, Suresh; Gota, Vikram; Chaudhari, Pradip; Chiplunkar, S V; Kane, Shantaram; Suresh, A K; Bellare, Jayesh

    2017-02-02

    Bhasma, Ayurvedic medicinal preparations, are prepared using herbs and minerals on following long iterative procedures. However, industrially mercury and sulphur are more commonly used to prepare bhasma from its raw material. The end point of this iterative procedure is mainly judged by the traditional tests specifying physical appearance of the powders. They fail to give better idea about chemical nature of the material. Moreover, the differences in biological activity of final product verses intermediate are not addressed. To compare the physicochemical as well as biological properties of the Jasad bhasma and its in-process intermediate using modern science methods. The Jasad bhasma and its in-process intermediate are characterized for their physicochemical properties using electron microscopy, x-ray diffraction and CHNS(O) analysis. The biological effects of both the preparations are then studied. The bioaccumulation of zinc, effect on liver antioxidant status, liver and kidney function (by conventional tests as well as SPECT: Single Photon Emission Computed Tomography), effect on blood cells and effect on immune system are studied in mice model, Swiss albino. Since bhasma is given with an accompaniment (anupan), all the bioactivity studies were carried out by administering the preparation with and without Amala powder (Phyllanthus emblica L., fruit, dry powder) as anupan. The XRD results accompanied with Rietveld analysis indicate that the final bhasma is mainly oxide of zinc, whereas the intermediate is mainly sulphide of zinc. The animal studies show that the bhasma as well as its intermediate do not lead to any bioaccumulation of zinc in major organs, when administered with and without anupan. Both, bhasma and intermediate do not cause any deleterious effects on kidney and liver as indicated by blood biochemistry and SPECT studies. However, the intermediate perturbs antioxidant status more and affects the platelet turnover, in comparison with bhasma. On 28

  7. Hydrogen peroxide decomposition by a non-heme iron(III) catalase mimic: a DFT study.

    PubMed

    Sicking, Willi; Korth, Hans-Gert; Jansen, Georg; de Groot, Herbert; Sustmann, Reiner

    2007-01-01

    Non-heme iron(III) complexes of 14-membered tetraaza macrocycles have previously been found to catalytically decompose hydrogen peroxide to water and molecular oxygen, like the native enzyme catalase. Here the mechanism of this reaction is theoretically investigated by DFT calculations at the (U)B3LYP/6-31G* level, with focus on the reactivity of the possible spin states of the FeIII complexes. The computations suggest that H2O2 decomposition follows a homolytic route with intermediate formation of an iron(IV) oxo radical cation species (L.+FeIV==O) that resembles Compound I of natural iron porphyrin systems. Along the whole catalytic cycle, no significant energetic differences were found for the reaction proceeding on the doublet (S=1/2) or on the quartet (S=3/2) hypersurface, with the single exception of the rate-determining O--O bond cleavage of the first associated hydrogen peroxide molecule, for which reaction via the doublet state is preferred. The sextet (S=5/2) state of the FeIII complexes appears to be unreactive in catalase-like reactions.

  8. Laboratory study of nitrogen and phosphorus remineralization during the decomposition of coastal plankton and seston

    NASA Astrophysics Data System (ADS)

    Garber, Jonathan H.

    1984-06-01

    The decomposition of cultured marine phytoplankton ( Skeletonema costatum) and natural estuarine seston from Narragansett Bay, RI, was studied at two temperatures (8°C and 18°C) in bottles containing sterile bay-water (30‰) and in bay-water with micro-organisms small enough to pass through a glass fibre filter (nominally < 1μ). About 50% of the particulate organic nitrogen (PON) and particulate phosphorus (PP) was immediately released to the water in dissolved organic forms from both types of organic matter. Comparison of changes in the dissolved organic nitrogen (DON) fraction in the sterile and non-sterile systems indicated that nearly all of the DON initially released was subsequently remineralized. Ammonification proceeded only in non-sterile bay-water. 20-25% of the PP was converted to dissolved inorganic-P (DIP) fraction after only 7 h in both sterile and non-sterile bay-water. Following autolytic releases of DON, DOP and DIP the initial rates of N and P remineralization were temperature dependent: Q 10 values for PON and PP decay during first phase of microbially mediated decomposition ranged from 1·3 to 6·4. Rates of remineralization then slowed so that about equal amounts of nutrients were remineralized (45-50% of the N and 57-60% of the P in the phytoplankton and 60-63% of the N and 36-60% of the P in the natural seston) after 30 days storage at either temperature. During 30 days of decomposition in non-sterile seawater the N/P ratios in the dissolved inorganic fractions converged on the ratios of total-N/total-P initially present in the bottles. Kinetic analysis of the decay of total organic-N (TON) and total organic-P (TOP) in the non-sterile systems and analysis of similar sets found in the literature showed that the initial stages of the decomposition of N and P from planktonic POM in vitro could be modelled as the sequential decay, at first-order rates, of two particulate fractions. The first, more labile, fraction comprised about 60% of the

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

    SciTech Connect

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

    1994-01-01

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

  10. Numerical study of variational data assimilation algorithms based on decomposition methods in atmospheric chemistry models

    NASA Astrophysics Data System (ADS)

    Penenko, Alexey; Antokhin, Pavel

    2016-11-01

    The performance of a variational data assimilation algorithm for a transport and transformation model of atmospheric chemical composition is studied numerically in the case where the emission inventories are missing while there are additional in situ indirect concentration measurements. The algorithm is based on decomposition and splitting methods with a direct solution of the data assimilation problems at the splitting stages. This design allows avoiding iterative processes and working in real-time. In numerical experiments we study the sensitivity of data assimilation to measurement data quantity and quality.

  11. Probing the Natural World, Level III, Teacher's Edition: Winds and Weather. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

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

    This is the teacher's edition of one of eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). This unit focuses on weather, its measurement and prediction. Optional excursions are given for students who wish to study a topic in greater depth on an individualized basis. An introduction describes the…

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

    ERIC Educational Resources Information Center

    Ramirez, Sonia; Siadat, M. Vali

    2008-01-01

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

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

    ERIC Educational Resources Information Center

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

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

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

    ERIC Educational Resources Information Center

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

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

  15. Probing the Natural World, Level III, Teacher's Edition: Crusty Problems. Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

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

    This is the teacher's edition of one of the eight units of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). This unit focuses on processes that shape the earth. Optional excursions, in addition to the activities, are suggested for students who wish to study an area in greater depth on an individualized basis. An…

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

    NASA Astrophysics Data System (ADS)

    Estevez Mews, Jorge

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

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  18. The Outer Loop bioreactor: a case study of settlement monitoring and solids decomposition.

    PubMed

    Abichou, Tarek; Barlaz, Morton A; Green, Roger; Hater, Gary

    2013-10-01

    The Outer Loop landfill bioreactor (OLLB) located in Louisville, KY, USA has been in operation since 2000 and represents an opportunity to evaluate long-term bioreactor monitoring data at a full-scale operational landfill. Three types of landfill units were studied including a Control cell, a new landfill area that had a piping network installed as waste was being placed to support leachate recirculation (As-Built cell), and a conventional landfill that was modified to allow for liquid recirculation (Retrofit cell). The objective of this study is to summarize the results of settlement data and assess how these data relate to solids decomposition monitoring at the OLLB. The Retrofit cells started to settle as soon as liquids were introduced. The cumulative settlement during the 8years of monitoring varied from 60 to 100cm. These results suggest that liquid recirculation in the Retrofit cells caused a 5-8% reduction in the thickness of the waste column. The average long-term settlement in the As-Built and Control Cells was about 37% and 19%, respectively. The modified compression index (Cα(')) was 0.17 for the Control cells and 0.2-0.48 for the As-Built cells. While the As-Built cells exhibited greater settlement than the Control cells, the data do not support biodegradation as the only explanation. The increased settlement in the As-Built bioreactor cell appeared to be associated with liquid movement and not with biodegradation because both chemical (biochemical methane potential) and physical (moisture content) indicators of decomposition were similar in the Control and As-Built cells. The solids data are consistent with the concept that bioreactor operations accelerate the rate of decomposition, but not necessarily the cumulative loss of anaerobically degradable solids.

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

    SciTech Connect

    Hoffman, M.Z.

    1992-07-31

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

  20. A new tool for spatiotemporal pattern decomposition based on empirical mode decomposition: A case study of monthly mean precipitation in Taihu Lake Basin, China

    NASA Astrophysics Data System (ADS)

    Chenhua, Shen; Yani, Yan

    2017-02-01

    We present a new tool for spatiotemporal pattern decomposition and utilize this new tool to decompose spatiotemporal patterns of monthly mean precipitation from January 1957 to May 2015 in Taihu Lake Basin, China. Our goal is to show that this new tool can mine more hidden information than empirical orthogonal function (EOF). First, based on EOF and empirical mode decomposition (EMD), the time series which is an average over the study region is decomposed into a variety of intrinsic mode functions (IMFs) and a residue by means of EMD. Then, these IMFs are supposed to be explanatory variables and a time series of precipitation in every station is considered as a dependent variable. Next, a linear multivariate regression equation is derived and corresponding coefficients are estimated. These estimated coefficients are physically interpreted as spatial coefficients and their physical meaning is an orthogonal projection between IMF and a precipitation time series in every station. Spatial patterns are presented depending on spatial coefficients. The spatiotemporal patterns include temporal patterns and spatial patterns at various timescales. Temporal pattern is obtained by means of EMD. Based on this temporal pattern, spatial patterns at various timescales will be gotten. The proposed tool has been applied in decomposition of spatiotemporal pattern of monthly mean precipitation in Taihu Lake Basin, China. Since spatial patterns are associated with intrinsic frequency, the new and individual spatial patterns are detected and explained physically. Our analysis shows that this new tool is reliable and applicable for geophysical data in the presence of nonstationarity and long-range correlation and can handle nonstationary spatiotemporal series and has the capacity to extract more hidden time-frequency information on spatiotemporal patterns.

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

    SciTech Connect

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

    2014-08-28

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

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

    PubMed

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

    2013-05-01

    9-[2-(Thiophosphonomethoxy)ethyl]adenine [S-PMEA, 8] and (R)-9-[2-(Thiophosphonomethoxy)propyl]adenine [S-PMPA, 9] are acyclic nucleoside thiophosphonates we described recently that display the same antiviral spectrum (DNA viruses) as approved and potent phosphonates PMEA and (R)-PMPA. Here, we describe the synthesis, antiviral activities in infected cell cultures and decomposition study of bis(pivaloyloxymethoxy)-S-PMEA [Bis-POM-S-PMEA, 13] and bis(isopropyloxymethylcarbonyl)-S-PMPA [Bis-POC-S-PMPA, 14] as orally bioavailable prodrugs of the S-PMEA 8 and S-PMPA 9, in comparison to the equivalent "non-thio" derivatives [Bis-POM-PMEA, 11] and [Bis-POC-PMPA, 12]. Compounds 11, 12, 13 and 14 were evaluated for their in vitro antiviral activity against HIV-1-, HIV-2-, HBV- and a broad panel of DNA viruses, and found to exhibit moderate to potent antiviral activity. In order to determine the decomposition pathway of the prodrugs 11, 12, 13 and 14 into parent compounds PMEA, PMPA, 8 and 9, kinetic data and decomposition pathways in several media are presented. As expected, bis-POM-S-PMEA 13 and bis-POC-S-PMPA 14 behaved as prodrugs of S-PMEA 8 and S-PMPA 9. However, thiophosphonates 8 and 9 were released very smoothly in cell extracts, in contrast to the release of PMEA and PMPA from "non-thio" prodrugs 11 and 12. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

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

    ERIC Educational Resources Information Center

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

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

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

    ERIC Educational Resources Information Center

    Miksza, Peter; Prichard, Stephanie; Sorbo, Diana

    2012-01-01

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

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

    ERIC Educational Resources Information Center

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

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

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

    ERIC Educational Resources Information Center

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

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

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

    ERIC Educational Resources Information Center

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

    This is the teacher's edition of the Record Book for the unit "In Orbit" of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). The correct answers to the questions from the text are recorded. An introductory note to the student explains how to use the book and is followed by the notes to the teacher.…

  8. An Interdisciplinary Program Incorporating Population Studies for Intermediate Grades. Sedro-Woolley Project Report No. 13.

    ERIC Educational Resources Information Center

    Jungblom, Edwin N.

    The publication contains exercises on population education which can be used in social studies and science classes in grades 4-7. Although the language of the material is geared to the intermediate grades, the exercises can easily be adapted for primary, high school, and adult education. The publication's major objective is to change the lifestyle…

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

    ERIC Educational Resources Information Center

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

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

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

    ERIC Educational Resources Information Center

    Miksza, Peter; Prichard, Stephanie; Sorbo, Diana

    2012-01-01

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

  11. Probing the Natural World, Level III, Student Guide: What's Up? Intermediate Science Curriculum Study.

    ERIC Educational Resources Information Center

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

    This is the student's text of one unit of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). The chapters contain basic information about rockets, space, and principles of physics, as well as activities related to the subject and optional excursions. A section of introductory notes to the student discusses how the…

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

    ERIC Educational Resources Information Center

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

    This is the student's edition of the Record Book which accompanies the unit "In Orbit" of the Intermediate Science Curriculum Study (ISCS) for level III students (grade 9). Space is provided for answers to the questions from the student text as well as for the optional excursions and the self evaluation. An introductory note to the…

  13. The Special Education Core Curriculum Manual: Intermediate Level. Reading, Mathematics, Written Language, Study Skills.

    ERIC Educational Resources Information Center

    Margolis, Leonard; And Others

    The curriculum manual provides objectives and suggested activities for intermediate grade handicapped children in the areas of reading, mathematics, written language, and study skills. Within each area objectives are correlated with one or more instructional activities. Objectives are provided for such skills as the following: vocabulary, context…

  14. Pilot-scale UV/H2O2 study for emerging organic contaminants decomposition.

    PubMed

    Chu, Xiaona; Xiao, Yan; Hu, Jiangyong; Quek, Elaine; Xie, Rongjin; Pang, Thomas; Xing, Yongjie

    2016-03-01

    Human behaviors including consumption of drugs and use of personal care products, climate change, increased international travel, and the advent of water reclamation for direct potable use have led to the introduction of significant amounts of emerging organic contaminants into the aqueous environment. In addition, the lower detection limits associated with improved scientific methods of chemical analysis have resulted in a recent increase in documented incidences of these contaminants which previously were not routinely monitored in water. Such contaminants may cause known or suspected adverse ecological and/or human health effects at very low concentrations. Conventional drinking water treatment processes may not effectively remove these organic contaminants. Advanced oxidation process (AOP) is a promising treatment process for the removal of most of these emerging organic contaminants, and has been accepted worldwide as a suitable treatment process. In this study, different groups of emerging contaminants were studied for decomposition efficiency using pilot-scale UV/H2O2 oxidation setup, including EDCs, PPCPs, taste and odor (T&O), and perfluorinated compounds. Results found that MP UV/H2O2 AOP was efficient in removing all the selected contaminants except perfluorinated compounds. Study of the kinetics of the process showed that both light absorption and quantum yield of each compound affected the decomposition performance. Analysis of water quality parameters of the treated water indicated that the outcome of both UV photolysis and UV/H2O2 processes can be affected by changes in the feed water quality.

  15. Canonical Decomposition of Ictal Scalp EEG and Accurate Source Localisation: Principles and Simulation Study

    PubMed Central

    De Vos, Maarten; De Lathauwer, Lieven; Vanrumste, Bart; Van Huffel, Sabine; Van Paesschen, W.

    2007-01-01

    Long-term electroencephalographic (EEG) recordings are important in the presurgical evaluation of refractory partial epilepsy for the delineation of the ictal onset zones. In this paper, we introduce a new concept for an automatic, fast, and objective localisation of the ictal onset zone in ictal EEG recordings. Canonical decomposition of ictal EEG decomposes the EEG in atoms. One or more atoms are related to the seizure activity. A single dipole was then fitted to model the potential distribution of each epileptic atom. In this study, we performed a simulation study in order to estimate the dipole localisation error. Ictal dipole localisation was very accurate, even at low signal-to-noise ratios, was not affected by seizure activity frequency or frequency changes, and was minimally affected by the waveform and depth of the ictal onset zone location. Ictal dipole localisation error using 21 electrodes was around 10.0 mm and improved more than tenfold in the range of 0.5–1.0 mm using 148 channels. In conclusion, our simulation study of canonical decomposition of ictal scalp EEG allowed a robust and accurate localisation of the ictal onset zone. PMID:18301715

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

    PubMed

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

    2008-03-25

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

  17. Theoretical and experimental study: the size dependence of decomposition thermodynamics of nanomaterials

    NASA Astrophysics Data System (ADS)

    Cui, Zixiang; Duan, Huijuan; Li, Wenjiao; Xue, Yongqiang

    2015-07-01

    In the processes of preparation and application of nanomaterials, the decomposition reactions of nanomaterials are often involved. However, there is a dramatic difference in decomposition thermodynamics between nanomaterials and the bulk counterparts, and the difference depends on the size of the particles that compose the nanomaterials. In this paper, the decomposition model of a nanoparticle was built, the theory of decomposition thermodynamics of nanomaterials was proposed, and the relations of the size dependence of thermodynamic quantities for the decomposition reactions were deduced. In experiment, taking the thermal decomposition of nano-Cu2(OH)2CO3 with different particle sizes (the range of radius is at 8.95-27.4 nm) as a system, the reaction thermodynamic quantities were determined, and the regularities of size dependence of the quantities were summarized. These experimental regularities consist with the above thermodynamic relations. The results show that there is a significant effect of the size of particles composing a nanomaterial on the decomposition thermodynamics. When all the decomposition products are gases, the differences in thermodynamic quantities of reaction between the nanomaterials and the bulk counterparts depend on the particle size; while when one of the decomposition products is a solid, the differences depend on both the initial particle size of the nanoparticle and the decomposition ratio. When the decomposition ratio is very small, these differences are only related to the initial particle size; and when the radius of the nanoparticles approaches or exceeds 10 nm, the reaction thermodynamic functions and the logarithm of the equilibrium constant are linearly associated with the reciprocal of radius, respectively. The thermodynamic theory can quantificationally describe the regularities of the size dependence of thermodynamic quantities for decomposition reactions of nanomaterials, and contribute to the researches and the

  18. Thermal stability and decomposition kinetic studies of acyclovir and zidovudine drug compounds.

    PubMed

    Shamsipur, Mojtaba; Pourmortazavi, Seied Mahdi; Beigi, Ali Akbar Miran; Heydari, Rouhollah; Khatibi, Mina

    2013-03-01

    Investigations on thermal behavior of drug samples such as acyclovir and zidovudine are interesting not only for obtaining stability information for their processing in pharmaceutical industry but also for predicting their shelf lives and suitable storage conditions. The present work describes thermal behaviors and decomposition kinetics of acyclovir and zidovudine in solid state, studied by some thermal analysis techniques including differential scanning calorimetry (DSC) and simultaneous thermogravimetry-differential thermal analysis (TG/DTA). TG analysis revealed that thermal degradation of the acyclovir and zidovudine is started at the temperatures of 400°C and 190°C, respectively. Meanwhile, TG-DTA analysis of acyclovir indicated that this drug melts at about 256°C. However, melting of zidovudine occurred at 142°C, which is 100°C before starting its decomposition (242°C). Different heating rates were applied to study the DSC behavior of drug samples in order to compute their thermokinetic and thermodynamic parameters by non-isothermal kinetic methods. Thermokinetic data showed that both drugs at the room temperature have slow degradation reaction rates and long shelf lives. However, acyclovir is considerably more thermally stable than zidovudine.

  19. Thermal decomposition studies of energetic materials using confined rapid thermolysis/FTIR spectroscopy

    SciTech Connect

    Kim, E.S.; Lee, H.S.; Mallery, C.F.; Thynell, S.T.

    1997-07-01

    An experimental setup for performing rapid thermolysis studies of small samples of energetic materials is described. In this setup, about 8 {micro}L of a liquid sample or about 2 mg of a solid sample is heated at rates exceeding 1,500 K/s to a set temperature where decomposition occurs. The rapid heating is achieved as a result of confining the sample between two closely spaced isothermal surfaces. The gaseous decomposition products depart from the confined space through a rectangular slit into the region of detection. The evolved gases are quantified using FTIR absorption spectroscopy by accounting for the instrument line shape. To illustrate the use of this setup, the thermolysis behaviors of three different energetic materials are examined. These materials include HMX, RDX, and HAN, all of which are considered as highly energetic propellant ingredients. The results obtained in this study of the temporal evolution of species concentrations from these ingredients are in reasonably close agreement with results available in the literature.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  1. Scanning electrochemical microscopy #54. Application to the study of heterogeneous catalytic reactions-hydrogen peroxide decomposition.

    PubMed

    Fernández, José L; Hurth, Cedric; Bard, Allen J

    2005-05-19

    A scanning electrochemical microscopy (SECM) approach for the analysis of heterogeneous catalytic reactions at solid-liquid interfaces is described and applied. In this scheme, reactant, generated at a tip, undergoes a reaction (e.g., disproportionation) at the substrate. The theoretical background for this study, performed by digital simulations using a finite difference method, considers a chemical reaction at the substrate with general stoichiometry. In this case, the fraction of regenerated mediator (nu(S)) may differ with respect to a substrate reaction that is the reverse of the tip reaction, resulting in an asymmetric mediator loop. Simulated tip current transients and approach curves at different values of the kinetic rate constant for reactions where nu(S) < 1 were used to analyze this new SECM situation. This approach was used to study the catalytic decomposition of hydrogen peroxide (HO2- --> 1/2O2 + OH-), where nu(S) = 0.5, on supported catalysts. A gold-mercury amalgam tip was used to quantitatively reduce dissolved O2 (mediator) to HO2-, which was decomposed back to oxygen at the catalyst substrate. Rate constants for the decomposition reaction on immobilized catalase and Pt particles were measured at different pH values by the correlation of experimental approach curves with the theoretical dependencies.

  2. An experimental and theoretical study of the thermal decomposition of C4H6 isomers

    DOE PAGES

    Lockhart, James P. A.; Goldsmith, C. Franklin; Randazzo, John B.; ...

    2017-04-25

    The chemistry of small unsaturated hydrocarbons, such as 1,3–butadiene (1,3–C4H6), 1,2–butadiene (1,2–C4H6), 2–butyne (2–C4H6) and 1–butyne (1–C4H6), is of central importance to the modeling of combustion systems. These species are important intermediates in combustion processes, and yet their high-temperature chemistry remains poorly understood, with various dissociation and isomerization pathways proposed in the literature. Here we investigate the thermal decompositions of 1,3–C4H6, 1,2–C4H6, 2–C4H6 and 1–C4H6 inside a diaphragmless shock tube, at post shock total pressures of 26–261 Torr and temperatures ranging from 1428–2354 K, using laser schlieren densitometry. The experimental work has been complemented by high-level ab initio calculations, whichmore » collectively provide strong evidence that formally direct dissociation is the major channel for pyrolysis of 1,3–C4H6 and 2–C4H6; these paths have not been previously reported but are critical to reconciling the current work and disparate literature reports. The reaction mechanism presented here simulates the current experiments and experimental data from the literature very well. As a result, pressure and temperature dependent rate coefficients are given for the isomerization, formally direct and direct dissociation paths.« less

  3. Low and intermediate temperature oxidation of ethanol and ethanol-PRF blends: An experimental and modeling study

    SciTech Connect

    Haas, Francis M.; Chaos, Marcos; Dryer, Frederick L.

    2009-12-15

    In this brief communication, we present new experimental species profile measurements for the low and intermediate temperature oxidation of ethanol under knock-prone conditions. These experiments show that ethanol exhibits no global low temperature reactivity at these conditions, although we note the heterogeneous decomposition of ethanol to ethylene and water. Similar behavior is reported for an E85 blend in n-heptane. Kinetic modeling results are presented to complement these experiments and elucidate the interaction of ethanol and primary reference fuels undergoing cooxidation. (author)

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  5. Adsorption and decomposition of NH3 on Ir(111): A density functional theory study

    NASA Astrophysics Data System (ADS)

    Huang, Wuying; Cheng, Chun; Feng, Eryin

    2013-10-01

    The adsorption and decomposition of NH3 on Ir(111) have been studied using the density functional theory calculations. The recombinative nitrogen desorption has also been investigated. The configurations and stability of NHx(x = 0-3) species have been performed using frequency analysis. The corresponding reaction energies, the activation energies and the structure of the transition states have been determined and analyzed in detail. Including the zero point energy correction, the calculated activation barrier energy for NHx(x = 1-3) dehydrogenation is between 0.94 eV and 1.05 eV, and that for the recombination desorption of N2 is 1.55 eV, which indicates that the N2 recombinative desorption is the rate-limiting step for the NH3 decomposition on Ir(111). The NH3 desorption energy (0.82 eV) is lower than the NH3 dehydrogenation barrier, which indicates that the ammonia rather desorbs than dissociates from a thermodynamic point of view, consistent with the experimental results. But the competition between desorption and dissociation can be controlled in practice via the applied pressure and temperature.

  6. Photocatalytic ozonation of terephthalic acid: a by-product-oriented decomposition study.

    PubMed

    Fuentes, Iliana; Rodríguez, Julia L; Poznyak, Tatyana; Chairez, Isaac

    2014-11-01

    Terephthalic acid (TA) is considered as a refractory model compound. For this reason, the TA degradation usually requires a prolonged reaction time to achieve mineralization. In this study, vanadium oxide (VxOy) supported on titanium oxide (TiO2) served as a photocatalyst in the ozonation of the TA with light-emitting diodes (LEDs), having a bandwidth centered at 452 nm. The modified catalyst (VxOy/TiO2) in combination with ozone and LEDs improved the TA degradation and its by-products. The results obtained by this system were compared with photolysis, single ozonation, catalytic ozonation, and photocatalytic ozonation of VxOy/TiO2 with UV lamp. The LED-based photocatalytic ozonation showed almost the same decomposition efficiency of the TA, but it was better in comparison with the use of UV lamp. The oxalic acid accumulation, as the final product of the TA decomposition, was directly influenced by either the presence of VxOy or/and the LED irradiation. Several by-products formed during the TA degradation, such as muconic, fumaric, and oxalic acids, were identified. Besides, two unidentified by-products were completely removed during the observed time (60 min). It was proposed that the TA elimination in the presence of VxOy/TiO2 as catalyst was carried out by the combination of different mechanisms: molecular ozone reaction, indirect mechanism conducted by ·OH, and the surface complex formation.

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

    SciTech Connect

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

    2004-12-01

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

  8. 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.

  9. 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

  10. Intermediate and stable redox states of cytochrome c studied by low temperature resonance Raman spectroscopy.

    PubMed Central

    Cartling, B

    1983-01-01

    Stabilized intermediate redox states of cytochrome c are generated by radiolytic reduction of initially oxidized enzyme in glass matrices at liquid nitrogen temperature. In the intermediate states the heme group is reduced by hydrated electrons, whereas the protein conformation is restrained close to its oxidized form by the low-temperature glass matrix. The intermediate and stable redox states of cytochrome c at neutral and alkaline pH are studied by low-temperature resonance Raman spectroscopy using excitations in resonance with the B (Soret) and Q1 (beta) optical transitions. The assignments of the cytochrome c resonance Raman bands are discussed. The observed spectral characteristics of the intermediate states as well as of the alkaline transition in the oxidized state are interpreted in terms of oxidation-state marker modes, spin-state marker modes, heme iron--axial ligand stretching modes, totally symmetric in-plane porphyrin modes, nontotally symmetric in-plane modes, and out-of-plane modes. PMID:6311300

  11. 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.

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

    PubMed

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

    2016-01-01

    The discovery of the causative link between keratin mutations and a growing number of human diseases opened the way for a better understanding of the function of the whole intermediate filament families of cytoskeleton proteins. This chapter describes analytical approaches to identification and interpretation of the consequences of keratin mutations, from the clinical and diagnostic level to cells in tissue culture. Intermediate filament pathologies can be accurately diagnosed from skin biopsies and DNA samples. The Human Intermediate Filament Database collates reported mutations in intermediate filament genes and their diseases, and can help clinicians to establish accurate diagnoses, leading to disease stratification for genetic counseling, optimal care delivery, and future mutation-aligned new therapies. Looking at the best-studied keratinopathy, epidermolysis bullosa simplex, the generation of cell lines mimicking keratinopathies is described, in which tagged mutant keratins facilitate live-cell imaging to make use of today's powerful enhanced light microscopy modalities. Cell stress assays such as cell spreading and cell migration in scratch wound assays can interrogate the consequences of the compromised cytoskeletal network. Application of extrinsic stresses, such as heat, osmotic, or mechanical stress, can enhance the differentiation of mutant keratin cells from wild-type cells. To bring the experiments to the next level, 3D organotypic human cultures can be generated, and even grafted onto the backs of immunodeficient mice for greater in vivo relevance. While development of these assays has focused on mutant K5/K14 cells, the approaches are often applicable to mutations in other intermediate filaments, reinforcing fundamental commonalities in spite of diverse clinical pathologies. Copyright © 2016 Tong San Tan, Yi Zhen Ng, Cedric Badowski, Tram Dang, John E.A. Common, Lukas Lacina, Ildikó Szeverényi, and E. Birgitte Lane. Published by Elsevier Inc. All

  13. Candidate Gene Studies of a Promising Intermediate Phenotype: Failure to Replicate

    PubMed Central

    Hart, Amy B; de Wit, Harriet; Palmer, Abraham A

    2013-01-01

    Many candidate gene studies use ‘intermediate phenotypes' instead of disease diagnoses. It has been proposed that intermediate phenotypes have simpler genetic architectures such that individual alleles account for a larger percentage of trait variance. This implies that smaller samples can be used to identify genetic associations. Pharmacogenomic drug challenge studies may be an especially promising class of intermediate phenotype. We previously conducted a series of 12 candidate gene analyses of acute subjective and physiological responses to amphetamine in 99–162 healthy human volunteers (ADORA2A, SLC6A3, BDNF, SLC6A4, CSNK1E, SLC6A2, DRD2, FAAH, COMT, OPRM1). Here, we report our attempt to replicate these findings in over 200 additional participants ascertained using identical methodology. We were unable to replicate any of our previous findings. These results raise critical issues related to non-replication of candidate gene studies, such as power, sample size, multiple testing within and between studies, publication bias and the expectation that true allelic effect sizes are similar to those reported in genome-wide association studies. Many of these factors may have contributed to our failure to replicate our previous findings. Our results should instill caution in those considering similarly designed studies. PMID:23303064

  14. Shock tube study on the thermal decomposition of n-butanol.

    PubMed

    Rosado-Reyes, Claudette M; Tsang, Wing

    2012-10-11

    Dilute concentrations of normal-butanol has been decomposed in single pulse shock tube studies in the presence of large quantities of a chemical inhibitor that suppresses contributions from chain decomposition. Reaction temperatures and pressures are in the range of [1126-1231] K and [1.3-6.5] bar. Ethylene and 1-butene are the only products. The mechanism of the initial decomposition steps involves direct elimination of water and C-C bond cleavage. The fundamental high pressure unimolecular decomposition rate expressions are k(C(4)H(9)OH → CH(3) + CH(2)CH(2)CH(2)OH) = 10(16.4±0.4) exp(42410 ± 800 [K]/T) s(-1); k(C(4)H(9)OH → CH(3)CH(2) + CH(2)CH(2)OH) = 10(16.4±0.4) exp(-41150 ± 800 [K]/T) s(-1); k(C(4)H(9)OH → CH(3)CH(2)CH(2) + CH(2)OH) = 10(16.4±0.4) exp(-41150 ± 800 [K]/T) s(-1); and k(C(4)H(9)OH → CH(3)CH(2)CH═CH(2) + H(2)O) = 10(14.0±0.4) exp(-35089 ± 800 [K]/T) s(-1), where the rate expressions for C-C bond cleavage are based on assumptions regarding the relative rates of the three processes derived from earlier studies on the effect of an OH group on rate expressions. All reactions are in the high pressure limit and suggest that the step size down in the presence of argon is at least 1300 cm(-1). These rate expressions are consistent with the following H-C bond dissociation energies: BDE(H-CH(2)CH(2)CH(2)OH) = 417.2 ± 7 kJ/mol, BDE(H-CH(2)CH(2)OH) = 419.2 ± 7 kJ/mol, and BDE(H-CH(2)OH) = 401.7 ± 9 kJ/mol, with an estimated uncertainty of 6 kJ/mol. The kinetics and thermodynamic results are compared with estimates used in the building of combustion kinetics databases.

  15. Thermal decomposition studies of cotton radiolytically grafted with phosphours- and bormine-containing flame retardants

    SciTech Connect

    Mey-Marom, A.; Behar, D.

    1980-04-01

    Thermal analysis of cotton samples grafted with traillylphosphate (TAP) and 2,2,2-tribromoethyl acrylate (TBEA) was carried out. Grafting of poly-TAP causes a significant decrease in the decomposition temperature of cotton. The cotton decomposition is acid catalyzed by H/sub 3/PO/sub 4/ formed during the decomposition of the grafted poly-TAP. The HBr evolved during decomposition was monitored conitnuously during thermal analysis of cotton grafted with ploly-TBEA. No significant flame-retarding effect by HBr was found. Since grafred poly-TBEA causes a decrease in the decomposition temperature of cotton, it is suggested that the flame retardant mechanism for poly-TBEA in cotton occurs mainly in the solid phasse before most of te HBr is released.

  16. Surface studies of the thermal decomposition of triethylgallium on GaAs (100)

    NASA Astrophysics Data System (ADS)

    Murrell, A. J.; Wee, A. T. S.; Fairbrother, D. H.; Singh, N. K.; Foord, J. S.; Davies, G. J.; Andrews, D. A.

    1990-10-01

    The adsorption and surface decomposition of triethylgallium (TEG) on GaAs (100) has been studied using XPS and thermal desorption techniques. TEG is found to adsorb in a molecular form on the Ga rich (4×1) surface below 150 K. As the surface temperature is raised, this molecular state dissociates to form Ga and adsorbed ethyl species. The overall cracking reaction occurs in competition with the desorption of TEG and diethylgallium (DEG). Under the conditions of our experiments the adsorbed ethyl species formed above are found to dissociate above 600 K to form mainly gas phase ethene and hydrogen with traces of ethane, resulting in the formation of a pure Ga layer within the sensitivity limits imposed by XPS.

  17. Studies of Hydrogen Getter Material Self-decomposition and Reaction Capacity

    SciTech Connect

    Saab, A P; Dinh, L N

    2007-03-19

    Diacetylene based hydrogen getters are examined in order to gauge their self decomposition products, as well as to determine possible origins for observed losses in origins getter capacity. Simple long term (several months) thermal aging tests were conducted, with periodic solid solid-phase micro micro-extraction (SPME) sampling followed by GC/MS analysis. The results suggest that bis(diphenylethynyl) benzene tends to decompose to give phenyl contaminants more readily than diphenylbutadiyne. Transmission electron microscopy (TEM) and electron diffraction studies of the palladium catalyst following varying extents of reaction with hydrogen show that there is no change to the catalyst particles, indicating that any change in capacity originates from other causes. These causes are suggested by Sievert's-type experiments on the reaction of the getter with a low pressure (about 10 Torr) hydrogen atmosphere. The reaction data indicate that the getter capacity depends on the pressure of hydrogen to which the material is exposed, and also its thermal history.

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

    PubMed

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

    2015-01-01

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

  19. High pressure Raman and x-ray diffraction studies on the decomposition of tungsten carbonyl

    NASA Astrophysics Data System (ADS)

    Garimella, Subrahmanyam; Drozd, Vadym; Durygin, Andriy; Chen, Jiuhua

    2012-06-01

    Polycrystalline tungsten hexacarbonyl, W(CO)6, was studied using in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD) at high pressures up to 60 GPa in a diamond anvil cell. High pressure causes collapse of the Oh molecular symmetry in W(CO)6 leading to decomposition of the carbonyl compound. The decomposed material has characteristic of δ(OCO), v(C=C), v(C=O), and adsorbed CO Raman features. High pressure XRD results showed the irreversible amorphization of tungsten hexacarbonyl. A solid state vibrational coupling mechanism is proposed to explain the formation of δ(OCO) units. Further, the high pressure Raman results of W, Mo, and Cr hexacarbonyls are compared and the breakdown of the Dewar-Chatt-Duncanson model in this family is qualitatively discussed.

  20. Small-Scale Kinetic Study of the Catalyzed Decomposition of Hydrogen Peroxide

    NASA Astrophysics Data System (ADS)

    Ragsdale, Ronald O.; Vanderhooft, Jan C.; Zipp, Arden P.

    1998-02-01

    The rate of decomposition of hydrogen peroxide with pyrolusite as a catalyst was studied directly by following the formation of oxygen bubbles. The apparatus consisted of a barrel from a 2-ml Beral pipet inserted over a micropipet tip which was fitted into a one-hole stopper. The stopper assembly was placed in a 20-mL glass bottle reaction vessel. The hydrogen peroxide can be obtained from the super market and the catalyst, a piece of pyrolusite, can be recycled. The reaction order was found to be 1.1 + 0.2 by 240 pairs of students. The activation energy was 35 + 14 kJ. Reproducible data have also been obtained with the minerals, psilomelane, maganite, and groutite as catalysts.

  1. Decomposition of adsorbed VX on activated carbons studied by {sup 31}P MAS NMR

    SciTech Connect

    Ishay Columbus; Daniel Waysbort; Liora Shmueli; Ido Nir; Doron Kaplan

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. Four types of activated carbon were used, including coal-based BPL. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) ((DES){sub 2}). Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. 17 refs., 6 figs., 3 tabs.

  2. A modeling study of methane hydrate decomposition in contact with the external surface of zeolites.

    PubMed

    Smirnov, Konstantin S

    2017-08-30

    The behavior of methane hydrate (MH) enclosed between the (010) surfaces of the silicalite-1 zeolite was studied by means of molecular dynamics simulations at temperatures of 150 and 250 K. Calculations reveal that the interaction with the hydrophilic surface OH groups destabilizes the clathrate structure of hydrate. While MH mostly conserves the structure in the simulation at the low temperature, thermal motion at the high temperature breaks the fragilized cages of H-bonded water molecules, thus leading to the release of methane. The dissociation proceeds in a layer-by-layer manner starting from the outer parts of the MH slab until complete hydrate decomposition. The released CH4 molecules are absorbed by the microporous solid, whereas water is retained at the surfaces of hydrophobic silicalite and forms a meniscus in the interlayer space. Methane uptake reaches 70% of the silicalite sorption capacity. The energy necessary for the endothermic MH dissociation is supplied by the exothermic methane absorption by the zeolite.

  3. Decomposition of adsorbed VX on activated carbons studied by 31P MAS NMR.

    PubMed

    Columbus, Ishay; Waysbort, Daniel; Shmueli, Liora; Nir, Ido; Kaplan, Doron

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) {(DES)2}. Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed.

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

    SciTech Connect

    Peterson, R.J.

    1993-10-01

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

  5. Reaction mechanism of ethylene glycol decomposition on Pt model catalysts: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Lv, Cun-Qin; Yang, Bo; Pang, Xian-Yong; Wang, Gui-Chang

    2016-12-01

    Understanding and controlling bond beak sequence is important in catalytic processes. The DFT-GGA method combined with slab model was performed to study the ethylene glycol decomposition on various Pt model catalysts such as close-packed Pt(111), stepped Pt(211) and a more open one, Pt(100). Calculation results show that the adsorption energies of ethylene glycol and other decomposition species depend on the coordination number of surface atom, that is, low coordination number correspond to high adsorption energy. Moreover, it was found that final products of ethylene glycol decomposition are CO and H2 on all model catalysts, but the reaction mechanism varies: On Pt(111), the first step is Osbnd H bond scission, followed by Csbnd H bond cleavage, namely C2H6O2 → HOCH2CH2O + H → HOCH2CHO + 2H→ HOCH2CO +3H → OCH2CO + 4H → OCHCO + 5H → CO + HCO + 5H → 2CO + 6H→ 2CO + 3H2; On Pt(211) and Pt(100), however, it is a second Osbnd H bond cleavage that follows the initial Osbnd H bond scission, that is, C2H6O2 → HOCH2CH2O + H → OCH2CH2O + 2H → OCHCH2O + 3H → OCHCHO + 4H → 2HCO + 4H → 2CO + 6H → 2CO + 3H2 on Pt(211), and C2H6O2 →HOCH2CH2O+ H → OCH2CH2O + 2H→OCHCH2O+3H→OCCH2O+4H→CO+H2CO+4H→CO+HCO+5H→2CO+6H→2CO+3H2 on Pt(100) For the catalytic order of ethylene glycol to form H2, it may be determined based on the rate-controlling step, and it is Pt(111) > Pt(211) > Pt(100).

  6. 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.

  7. Size dependence of the thermal decomposition kinetics of nano- CaC2O4: A theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Fu, Qingshan; Cui, Zixiang; Xue, Yongqiang

    2015-10-01

    In the processes of preparation and application of nanomaterials, the thermal decomposition of nanoparticles is often involved. An improved general theory of thermal decomposition kinetics of nanoparticles, developed over the past 10 years, was presented in this paper where the relations between reaction kinetic parameters and particle size were derived. Experimentally, the thermal decomposition kinetics of nano-sized calcium oxalate (nano- CaC2O4 with different sizes was studied by means of Thermogravimetry Analysis (TGA) at different heating rates. The values of the apparent activation energy and the logarithm of pre-exponential factor were calculated using the equation of Iterative Kissinger-Akahira-Sunose (IKAS) and its deformations. The influence regularities of particle size on the apparent activation energy and the pre-exponential factor were summarized, which are consistent with the thermal decomposition kinetics theory of nanoparticles. Based on the theory, the method of obtaining the surface thermodynamic properties by the determination of kinetic parameters was presented. Theoretical and experimental results show that the particle size, through the effect on the surface thermodynamic properties, has notable effect on the thermal decomposition kinetics. With the particle size decreasing, the partial molar surface enthalpy and the partial molar surface entropy increases, leading to the decrease of the apparent activation energy and the pre-exponential factor, respectively. Furthermore, the apparent activation energy, the pre-exponential factor, the partial molar surface enthalpy and the partial molar surface entropy are linearly related to the reciprocal of particle diameter, respectively.

  8. Linguistic Focus of Language Related Episodes in Intermediate and Advanced EFL Learners' Group-Based Interactions: A Case Study

    ERIC Educational Resources Information Center

    Mohammadnia, Zhila; Khalili, Abdolreza

    2014-01-01

    The present study investigated linguistic focus of language related episodes (LREs),in Iranian EFL classrooms. Eighteen male participants in the advanced and intermediate levels from Urmia branch of Academic Centre of Education, Culture and Research (ACECR) participated in the study. They were assigned to intermediate and advanced levels with one…

  9. Thermal and X-ray diffraction analysis studies during the decomposition of ammonium uranyl nitrate.

    PubMed

    Kim, B H; Lee, Y B; Prelas, M A; Ghosh, T K

    Two types of ammonium uranyl nitrate (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3, were thermally decomposed and reduced in a TG-DTA unit in nitrogen, air, and hydrogen atmospheres. Various intermediate phases produced by the thermal decomposition and reduction process were investigated by an X-ray diffraction analysis and a TG/DTA analysis. Both (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3 decomposed to amorphous UO3 regardless of the atmosphere used. The amorphous UO3 from (NH4)2UO2(NO3)4·2H2O was crystallized to γ-UO3 regardless of the atmosphere used without a change in weight. The amorphous UO3 obtained from decomposition of NH4UO2(NO3)3 was crystallized to α-UO3 under a nitrogen and air atmosphere, and to β-UO3 under a hydrogen atmosphere without a change in weight. Under each atmosphere, the reaction paths of (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3 were as follows: under a nitrogen atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → U3O8, NH4UO2(NO3)3 → A-UO3 → α-UO3 → U3O8; under an air atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → U3O8, NH4UO2(NO3)3 → A-UO3 → α-UO3 → U3O8; and under a hydrogen atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → α-U3O8 → UO2, NH4 UO2(NO3)3 → A-UO3 → β-UO3 → α-U3O8 → UO2.

  10. Studies on the Interaction of the Histone Demethylase KDM5B with Tricarboxylic Acid Cycle Intermediates.

    PubMed

    Tarhonskaya, Hanna; Nowak, Radosław P; Johansson, Catrine; Szykowska, Aleksandra; Tumber, Anthony; Hancock, Rebecca L; Lang, Pauline; Flashman, Emily; Oppermann, Udo; Schofield, Christopher J; Kawamura, Akane

    2017-09-15

    Methylation of lysine-4 of histone H3 (H3K4men) is an important regulatory factor in eukaryotic transcription. Removal of the transcriptionally activating H3K4 methylation is catalyzed by histone demethylases, including the Jumonji C (JmjC) KDM5 subfamily. The JmjC KDMs are Fe(II) and 2-oxoglutarate (2OG)-dependent oxygenases, some of which are associated with cancer. Altered levels of tricarboxylic acid (TCA) cycle intermediates and the associated metabolites D- and L-2-hydroxyglutarate (2HG) can cause changes in chromatin methylation status. We report comprehensive biochemical, structural and cellular studies on the interaction of TCA cycle intermediates with KDM5B, which is a current medicinal chemistry target for cancer. The tested TCA intermediates were poor or moderate KDM5B inhibitors, except for oxaloacetate and succinate, which were shown to compete for binding with 2OG. D- and L-2HG were moderate inhibitors at levels that might be relevant in cancer cells bearing isocitrate dehydrogenase mutations. Crystallographic analyses with succinate, fumarate, L-malate, oxaloacetate, pyruvate and D- and L-2HG support the kinetic studies showing competition with 2OG. An unexpected binding mode for oxaloacetate was observed in which it coordinates the active site metal via its C-4 carboxylate rather than the C-1 carboxylate/C-2 keto groups. Studies employing immunofluorescence antibody-based assays reveal no changes in H3K4me3 levels in cells ectopically overexpressing KDM5B in response to dosing with TCA cycle metabolite pro-drug esters, suggesting that the high levels of cellular 2OG may preclude inhibition. The combined results reveal the potential for KDM5B inhibition by TCA cycle intermediates, but suggest that in cells, such inhibition will normally be effectively competed by 2OG. Copyright © 2017. Published by Elsevier Ltd.

  11. Protonation states and catalysis: Molecular dynamics studies of intermediates in tryptophan synthase.

    PubMed

    Huang, Yu-Ming M; You, Wanli; Caulkins, Bethany G; Dunn, Michael F; Mueller, Leonard J; Chang, Chia-En A

    2016-01-01

    The importance of protonation states and proton transfer in pyridoxal 5'-phosphate (PLP)-chemistry can hardly be overstated. Although experimental approaches to investigate pKa values can provide general guidance for assigning proton locations, only static pictures of the chemical species are available. To obtain the overall protein dynamics for the interpretation of detailed enzyme catalysis in this study, guided by information from solid-state NMR, we performed molecular dynamics (MD) simulations for the PLP-dependent enzyme tryptophan synthase (TRPS), whose catalytic mechanism features multiple quasi-stable intermediates. The primary objective of this work is to elucidate how the position of a single proton on the reacting substrate affects local and global protein dynamics during the catalytic cycle. In general, proteins create a chemical environment and an ensemble of conformational motions to recognize different substrates with different protonations. The study of these interactions in TRPS shows that functional groups on the reacting substrate, such as the phosphoryl group, pyridine nitrogen, phenolic oxygen and carboxyl group, of each PLP-bound intermediate play a crucial role in constructing an appropriate molecular interface with TRPS. In particular, the protonation states of the ionizable groups on the PLP cofactor may enhance or weaken the attractions between the enzyme and substrate. In addition, remodulation of the charge distribution for the intermediates may help generate a suitable environment for chemical reactions. The results of our study enhance knowledge of protonation states for several PLP intermediates and help to elucidate their effects on protein dynamics in the function of TRPS and other PLP-dependent enzymes. © 2015 The Protein Society.

  12. Molecular Modeling Studies on Aromatic Sulfonation. 1. Intermediates Formed in the Sulfonation of Toluene.

    PubMed

    Morley, John O.; Roberts, D. W.

    1997-10-17

    Molecular modeling studies suggest that the mechanism of the sulfonation of toluene with sulfur trioxide proceeds via the formation of a pi-complex (4b) which rearranges to form a Wheland intermediate (5). This structure is unable to form toluenesulfonic acid (8) directly and prefers to react with a further molecule of sulfur trioxide to form a pyrosulfonate intermediate (6a) which undergoes a facile prototropic rearrangement involving the transfer of the ring hydrogen at the sp(3) carbon of 6a to the sulfonate oxygen atom to form the corresponding acid (7). The formation of toluenesulfonic acid (8) appears to arise from an exothermic reaction of between the pyrosulfonic acid (7) and toluene. The overall calculated thermodynamic change in moving from the reaction of one molecule of sulfur trioxide with toluene to the sulfonic acid (8b) is fully consistent with an estimated experimental value of -33.5 kcal mol(-1) for the same reaction using simple alkylbenzenes.

  13. a Time-Resolved X-Ray Study of Spinodal Decomposition in Aluminium-Zinc

    NASA Astrophysics Data System (ADS)

    Mainville, Jacques

    Time resolved small angle x-ray scattering (SAXS) using synchrotron radiation was applied to the study of the kinetics of spinodal decomposition (SD) in an AlZn binary alloy at critical composition quenched into the immiscible region. These millisecond time scale measurements, performed at the National Synchrotron Light Source (Brookhaven National Labs., N.Y.), constitute the first direct experimental verification in a binary alloy of the theory proposed by Langer, Bar-on and Miller in 1975 for SD. A scheme based on the composition distribution functional is proposed to account for the decomposition taking place during the quench. The interatomic mobility, a free energy gradient coefficient and two coefficients that suffice to determine a coarse-grained (intensive) free energy have been obtained in the framework of this theory. The mobilities obtained compare well with tracer diffusion measurements reported in literature. A dependence of the coarse-grained free energy coefficients on the coarse-graining length is found and a procedure is proposed to uniquely choose the values of these coefficients based on the predicted integrated intensity from the equilibrium concentrations and on the measured integrated intensities. Late-stage coarsening regimes were also investigated. In these regimes, growth exponents higher than the value 1/3 predicted by the Lifshitz-Slyozov-Wagner theory are obtained. These higher values, comprised between 0.40 and 0.45 are consistent with predictions that alloys in which elastic effects are important can present a transition regime from a t ^{1/3} growth law to a t ^{1/2} law. The structure factors do not quite scale. They also present a shoulder at high wavevectors, a feature not reported before in metallic alloys.

  14. Causal Inference in Longitudinal Comparative Effectiveness Studies With Repeated Measures of A Continuous Intermediate Variable

    PubMed Central

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

    2014-01-01

    We propose a principal stratification approach to assess causal effects in non-randomized longitudinal comparative effectiveness studies with a binary endpoint outcome and repeated measures of a continuous intermediate variable. Our method is an extension of the principal stratification approach by Lin et al. [10,11], originally proposed for a longitudinal randomized study to assess the treatment effect of a continuous outcome adjusting for the heterogeneity of a repeatedly measured binary intermediate variable. Our motivation for this work comes from a comparison of the effect of two glucose-lowering medications on a clinical cohort of patients with type 2 diabetes. Here we consider a causal inference problem assessing how well the two medications work relative to one another on two binary endpoint outcomes: cardiovascular disease related hospitalization and all-cause mortality. Clinically, these glucose-lowering medications can have differential effects on the intermediate outcome, glucose level over time. Ultimately we want to compare medication effects on the endpoint outcomes among individuals in the same glucose trajectory stratum while accounting for the heterogeneity in baseline covariates (i.e., to obtain “principal effects” on the endpoint outcomes). The proposed method involves a 3-step model estimation procedure. Step 1 identifies principal strata associated with the intermediate variable using hybrid growth mixture modeling analyses [13]. Step 2 obtains the stratum membership using the pseudoclass technique [17,18], and derives propensity scores for treatment assignment. Step 3 obtains the stratum-specific treatment effect on the endpoint outcome weighted by inverse propensity probabilities derived from Step 2. PMID:24577715

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  16. Infrared spectroscopic study on the thermal decomposition of external and internal gelation products of simulated mixed oxide nuclear fuel.

    PubMed

    Kumar, K Suresh; Bhat, N P

    2004-02-01

    The thermal decomposition of urania-ceria gel corresponding to the composition U(0.7)Ce(0.3)O(2+x) obtained through external and internal gelation routes were studied using infrared spectroscopy (IR). In the case of externally gelated compound, the gel decomposes with the release of H2O and NH3 below 500 degrees C. A part of the NH3 released is entrapped in the solid and above 500 degrees C self reduction occurs in which U(VI) in the gel is reduced to U3O8. The decomposition products were identified to be U3O8 and CeO2. In the case of internally gelated compound, decomposition similar to the one for externally gelated compound occurred below 500 degrees C. Above 500 degrees C the carbon present in the gel reduced U(VI) to UO2 which formed solid solution with CeO2 around 650 degrees C.

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

    SciTech Connect

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

    1994-02-01

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

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

    SciTech Connect

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

    2012-01-01

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

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

    PubMed Central

    2015-01-01

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

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

    PubMed

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

    2001-09-18

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

  1. Differential scanning calorimetry study of glycerinated rabbit psoas muscle fibres in intermediate state of ATP hydrolysis

    PubMed Central

    Dergez, Timea; Lőrinczy, Dénes; Könczöl, Franciska; Farkas, Nelli; Belagyi, Joseph

    2007-01-01

    Background Thermal denaturation experiments were extended to study the thermal behaviour of the main motor proteins (actin and myosin) in their native environment in striated muscle fibres. The interaction of actin with myosin in the highly organized muscle structure is affected by internal forces; therefore their altered conformation and interaction may differ from those obtained in solution. The energetics of long functioning intermediate states of ATP hydrolysis cycle was studied in muscle fibres by differential scanning calorimetry (DSC). Results SETARAM Micro DSC-II was used to monitor the thermal denaturation of the fibre system in rigor and in the presence of nucleotide and nucleotide analogues. The AM.ADP.Pi state of the ATP hydrolysis cycle has a very short lifetime therefore, we mimicked the different intermediate states with AMP.PNP and/or inorganic phosphate analogues Vi and AlF4 or BeFx. Studying glycerol-extracted muscle fibres from the rabbit psoas muscle by DSC, three characteristic thermal transitions were detected in rigor. The thermal transitions can be assigned to myosin heads, myosin rods and actin with transition temperatures (Tm) of 52.9 ± 0.7°C, 57.9 ± 0.7°C, 63.7 ± 1.0°C. In different intermediate states of the ATP hydrolysis mimicked by nucleotide analogues a fourth thermal transition was also detected which is very likely connected with nucleotide binding domain of myosin and/or actin filaments. This transition temperature Tm4 depended on the mimicked intermediate states, and varied in the range of 66°C – 77°C. Conclusion According to DSC measurements, strongly and weakly binding states of myosin to actin were significantly different. In the presence of ADP only a moderate change of the DSC pattern was detected in comparison with rigor, whereas in ADP.Pi state trapped by Vi, AlF4 or BeFx a remarkable stabilization was detected on the myosin head and actin filament which is reflected in a 3.0 – 10.0°C shift in Tm to higher

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  4. Freeze-Quench Magnetic Circular Dichroism Spectroscopic Study of the "Very Rapid" Intermediate in Xanthine Oxidase.

    PubMed

    Jones, Robert M.; Inscore, Frank E.; Hille, Russ; Kirk, Martin L.

    1999-11-01

    Freeze-quench magnetic circular dichroism spectroscopy (MCD) has been used to trap and study the excited-state electronic structure of the Mo(V) active site in a xanthine oxidase intermediate generated with substoichiometric concentrations of the slow substrate 2-hydroxy-6-methylpurine. EPR spectroscopy has shown that the intermediate observed in the MCD experiment is the "very rapid" intermediate, which lies on the main catalytic pathway. The low-energy (< approximately 30 000 cm(-1)) C-term MCD of this intermediate is remarkably similar to that of the model compound LMoO(bdt) (L = hydrotris(3,5-dimethyl-1-pyrazolyl)borate; bdt = 1,2-benzenedithiolate), and the MCD bands have been assigned as dithiolate S(ip) --> Mo d(xy) and S(op) --> Mo d(xz,yz) LMCT transitions. These transitions result from a coordination geometry of the intermediate where the Mo=O bond is oriented cis to the ene-1,2-dithiolate of the pyranopterin. Since X-ray crystallography has indicated that a terminal sulfido ligand is oriented cis to the ene-1,2-dithiolate in oxidized xanthine oxidase related Desulfovibrio gigas aldehyde oxidoreductase, we have suggested that a conformational change occurs upon substrate binding. The substrate-mediated conformational change is extremely significant with respect to electron-transfer regeneration of the active site, as covalent interactions between the redox-active Mo d(xy) orbital and the S(ip) orbitals of the ene-1,2-dithiolate are maximized when the oxo ligand is oriented cis to the dithiolate plane. This underlies the importance of the ene-1,2-dithiolate portion of the pyranopterin in providing an efficient superexchange pathway for electron transfer. The results of this study indicate that electron-transfer regeneration of the active site may be gated by the orientation of the Mo=O bond relative to the ene-1,2-dithiolate chelate. Poor overlap between the Mo d(xy) orbital and the S(ip) orbitals of the dithiolate in the oxidized enzyme geometry may

  5. Intermediate treatments

    Treesearch

    John R. Jones; Wayne D. Shepperd

    1985-01-01

    Intermediate treatments are those applied after a new stand is successfully established and before the final harvest. These include not only intermediate cuttings - primarily thinning - but also fertilization, irrigation, and protection of the stand from damaging agents.

  6. Let's Break it Down: A Study of Organic Decomposition Rates in Clay Soil

    NASA Astrophysics Data System (ADS)

    Weiss, E.

    2016-12-01

    In this experiment I will be testing if temperature affects the organic decomposition rates in clay soil. I will need to be able to clean and weigh each filter paper without disrupting my data damaging or brushing off additional paper material. From there I need to be able to analyze and interpret my data to factor anything else that may affect the decomposition rates in the soil. Soil decomposers include bacteria and fungi. They obtain energy from plant and animal detritus through aerobic decomposition, which is similar to how humans break down sugar. The formula is: C6H12O6 + O2 → CO2 + H2O + energy. Besides oxygen and sugar the organisms need nutrients such as water and sustainable temperatures. Decomposition is important to us because it helps regulate soil structure, moisture, temperature, and provides nutrients to soil organisms. This matters on a global scale since decomposers release a large amount of carbon when breaking down matter, which contributes to greenhouse gasses such as carbon dioxide and methane. These greenhouse gasses affect the earth's climate. People who care about decomposition are farmers and those in agriculture, as well as environmental scientists. Even national parks might care because decomposition may affect park safety, how the park looks, and the amount of plants and wildlife. Things that can affect decomposition are the decomposers in the soil, temperature, and water or moisture. My secondary research also showed that PH and chemical composition of the soil affect the rate of decomposition.Cold or freezing temperatures can help preserve organic material in soil because it freezes the soil and moisture, making it too dense for the organic decomposers to break down the organic matter. Soil also can be preserved by drying out and being stored at 4º Celsius (or 39º Fahrenheit) for 28 days. However, soil can degrade slowly in these conditions because it is not frozen and can be oxidized.

  7. Transect studies on pine litter organic matter: decomposition and chemical properties of upper soil layers in Polish forests

    Treesearch

    Alicja Breymeyer; Marek Degorski; David Reed

    1998-01-01

    The relationship between litter decomposition rate, some chemical properties of upper soil layers (iron, manganese, zinc, copper, lead, mercury, nickel, chrome in humus-mineral horizon-A), and litter (the same eight elements in needle litter fraction) in pine forests of Poland was studied. Heavy metal content in organic-mineral horizon of soils was highly correlated...

  8. Wood Decomposition of Cyrilla racemiflora (Cyrillaceae) in Puerto Rican Dry and Wet Forests: A 13-year Case Study.

    Treesearch

    Juan A. Torres; Grizelle Gonzalez

    2005-01-01

    We studied the decomposition of Cyrilla racemiflora logs over a 13-yr period in tropical dry and wet forests in Puerto Rico. The mean mass loss, ratio of soft to hard wood, nutrient concentrations, and the diversity of wood-inhabiting organisms were greater in logs decomposing in the dry forest than in the wet forest. Termites were also more abundant in the logs...

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

    EPA Science Inventory

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

  10. [Tobacco withdrawal. Comparison of the efficacy of various methods. Intermediate results of a comparative study].

    PubMed

    Clavel, F; Benhamou, S

    1984-04-14

    A comparative study aimed at evaluating the effectiveness of different methods of detoxication for dependent smokers is currently in progress. In this study, the percentage of subjects who gave up smoking after 1 month and changes in this percentage over a 12-month period are determined in 3 groups of subjects: one group treated with acupuncture, one group treated with a chewing-gum containing nicotine, and a control group. The intermediate analysis results include 45% of the total number of subjects required. They show no statistically significant difference between the control group and the two treated groups. Volunteers are still being recruited.

  11. Decomposition techniques

    USGS Publications Warehouse

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

    1992-01-01

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

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

    PubMed

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

    2015-01-01

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

  13. Adsorption and decomposition mechanism of formic acid on the Ga2O3 surface by first principle studies

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Li, Zhen Hua

    2017-02-01

    The adsorption and decomposition of formic acid (FA) on the Ga2O3(100) surface was studied with density functional theory. On the perfect Ga2O3(100) surface, the preferred adsorption state of FA is a monodentate configuration while the most stable adsorption state is a bridging configuration. Heating the surface would convert FA from monodentate to bridging configuration and further heating would decompose FA into CO2 and two surface hydroxyl groups. On the other hand, on the O(2)-defect Ga2O3(100) surface the preferred adsorption state of FA is a bridging formate with one O atom of formate filling the O(2) vacancy. Heating the surface would generate CO and two surface hydroxyl groups. If the Ga2O3(100) surface is used as decomposition catalyst, then at low temperature the formation of a small amount of CO2 can be observed. On the other hand, at high temperature continuous formation of CO and H2O can be observed. The active sites for FA decomposition are the O(2) defects on the surface formed in situ from the removal of water from surface hydroxyl groups. The strong dependence of mechanism on experimental conditions explains why no consensus has been reached in the previous experimental studies regarding the adsorption and decomposition mechanism of FA.

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

    SciTech Connect

    Aichelin, J.; Bargholtz, Ch.; Geren, L.; Tegner, P.-E.; Zartova, I.; Blomgren, J.; Olsson, N.; Budzanowski, A.; Czech, B.; Skwirczynska, I.; Chubarov, M.; Lozhkin, O.; Murin, Yu.; Pljuschev, V.; Zubkov, M.; Ekstroem, C.; Kolozhvari, A.; Persson, H.; Westerberg, L.; Jakobsson, B.

    2005-05-24

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

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

    NASA Astrophysics Data System (ADS)

    Das Mandal, Jyotirmay; Debnath, Ujjal

    2016-08-01

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

  16. Study on the decomposition of trace benzene over V2O5-WO3 ...

    EPA Pesticide Factsheets

    Commercial and laboratory-prepared V2O5–WO3/TiO2-based catalysts with different compositions were tested for catalytic decomposition of chlorobenzene (ClBz) in simulated flue gas. Resonance enhanced multiphoton ionization-time of flight mass spectrometry (REMPI-TOFMS) was employed to measure real-time, trace concentrations of ClBz contained in the flue gas before and after the catalyst. The effects of various parameters, including vanadium content of the catalyst, the catalyst support, as well as the reaction temperature on decomposition of ClBz were investigated. The results showed that the ClBz decomposition efficiency was significantly enhanced when nano-TiO2 instead of conventional TiO2 was used as the catalyst support. No promotion effects were found in the ClBz decomposition process when the catalysts were wet-impregnated with CuO and CeO2. Tests with different concentrations (1,000, 500, and 100 ppb) of ClBz showed that ClBz-decomposition efficiency decreased with increasing concentration, unless active sites were plentiful. A comparison between ClBz and benzene decomposition on the V2O5–WO3/TiO2-based catalyst and the relative kinetics analysis showed that two different active sites were likely involved in the decomposition mechanism and the V=O and V-O-Ti groups may only work for the degradation of the phenyl group and the benzene ring rather than the C-Cl bond. V2O5-WO3/TiO2 based catalysts, that have been used for destruction of a wide variet

  17. The Study of Spectrum Reconstruction Based on Fuzzy Set Full Constraint and Multiendmember Decomposition

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Lin, Y.; Hu, X.; Zhao, S.; Liu, S.; Tong, Q.; Helder, D.; Yan, L.

    2017-09-01

    Hyperspectral imaging system can obtain spectral and spatial information simultaneously with bandwidth to the level of 10 nm or even less. Therefore, hyperspectral remote sensing has the ability to detect some kinds of objects which can not be detected in wide-band remote sensing, making it becoming one of the hottest spots in remote sensing. In this study, under conditions with a fuzzy set of full constraints, Normalized Multi-Endmember Decomposition Method (NMEDM) for vegetation, water, and soil was proposed to reconstruct hyperspectral data using a large number of high-quality multispectral data and auxiliary spectral library data. This study considered spatial and temporal variation and decreased the calculation time required to reconstruct the hyper-spectral data. The results of spectral reconstruction based on NMEDM showed that the reconstructed data has good qualities and certain applications, which makes it possible to carry out spectral features identification. This method also extends the application of depth and breadth of remote sensing data, helping to explore the law between multispectral and hyperspectral data.

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

    PubMed

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

    2015-04-01

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

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

    SciTech Connect

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

    2004-10-01

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

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

    PubMed

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

    2014-09-10

    We propose a principal stratification approach to assess causal effects in nonrandomized longitudinal comparative effectiveness studies with a binary endpoint outcome and repeated measures of a continuous intermediate variable. Our method is an extension of the principal stratification approach originally proposed for the longitudinal randomized study "Prevention of Suicide in Primary Care Elderly: Collaborative Trial" to assess the treatment effect on the continuous Hamilton depression score adjusting for the heterogeneity of repeatedly measured binary compliance status. Our motivation for this work comes from a comparison of the effect of two glucose-lowering medications on a clinical cohort of patients with type 2 diabetes. Here, we consider a causal inference problem assessing how well the two medications work relative to one another on two binary endpoint outcomes: cardiovascular disease-related hospitalization and all-cause mortality. Clinically, these glucose-lowering medications can have differential effects on the intermediate outcome, glucose level over time. Ultimately, we want to compare medication effects on the endpoint outcomes among individuals in the same glucose trajectory stratum while accounting for the heterogeneity in baseline covariates (i.e., to obtain 'principal effects' on the endpoint outcomes). The proposed method involves a three-step model estimation procedure. Step 1 identifies principal strata associated with the intermediate variable using hybrid growth mixture modeling analyses. Step 2 obtains the stratum membership using the pseudoclass technique and derives propensity scores for treatment assignment. Step 3 obtains the stratum-specific treatment effect on the endpoint outcome weighted by inverse propensity probabilities derived from Step 2. Copyright © 2014 John Wiley & Sons, Ltd.

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

    NASA Astrophysics Data System (ADS)

    Nicolás, César; Tunlid, Anders; Persson, Per

    2015-04-01

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

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

    SciTech Connect

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

    2010-03-18

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

  3. In depth study of acrylamide formation in coffee during roasting: role of sucrose decomposition and lipid oxidation.

    PubMed

    Kocadağlı, Tolgahan; Göncüoğlu, Neslihan; Hamzalıoğlu, Aytül; Gökmen, Vural

    2012-09-01

    Coffee, as a source of acrylamide, needs to be investigated in depth to understand the contribution of different precursors. This study aimed to investigate the contributions of sucrose decomposition and lipid oxidation on acrylamide formation in coffee during roasting. Coffee beans and model systems were used to monitor the accumulation of neo-formed carbonyls during heating through sucrose decomposition and lipid oxidation. High resolution mass spectrometry analyses confirmed the formation of 5-hydroxymethylfurfural (HMF) and 3,4-dideoxyosone, which were identified as the major sugar decomposition products in both roasted coffee and model systems. Among others, 2-octenal, 2,4-decadienal, 2,4-heptadienal, 4-hydroxynonenal, and 4,5-epoxy-2-decenal were identified in relatively high quantities in roasted coffee. Formation and elimination of HMF in coffee during roasting had a kinetic pattern similar to those of acrylamide. Its concentration rapidly increased within 10 min followed by an exponential decrease afterward. The amount of lipid oxidation products tended to increase linearly during roasting. It was concluded from the results that roasting formed a pool of neo-formed carbonyls from sucrose decomposition and lipid oxidation, and they play certain role on acrylamide formation in coffee.

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

    SciTech Connect

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

    2010-11-30

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

  5. Dominant modal decomposition method

    NASA Astrophysics Data System (ADS)

    Dombovari, Zoltan

    2017-03-01

    The paper deals with the automatic decomposition of experimental frequency response functions (FRF's) of mechanical structures. The decomposition of FRF's is based on the Green function representation of free vibratory systems. After the determination of the impulse dynamic subspace, the system matrix is formulated and the poles are calculated directly. By means of the corresponding eigenvectors, the contribution of each element of the impulse dynamic subspace is determined and the sufficient decomposition of the corresponding FRF is carried out. With the presented dominant modal decomposition (DMD) method, the mode shapes, the modal participation vectors and the modal scaling factors are identified using the decomposed FRF's. Analytical example is presented along with experimental case studies taken from machine tool industry.

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

    SciTech Connect

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

    2013-09-15

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

  7. Reaction of stabilized Criegee intermediates from ozonolysis of limonene with sulfur dioxide: ab initio and DFT study.

    PubMed

    Jiang, Lei; Xu, Yi-sheng; Ding, Ai-zhong

    2010-12-02

    The mechanism of the reaction of the sulfur dioxide (SO(2)) with four stabilized Criegee intermediates (stabCI-CH(3)-OO, stabCI-OO, stabCIx-OO, and stabCH(2)OO) produced via the ozonolysis of limonene have been investigated using ab initio and DFT (density functional theory) methods. It has been shown that the intermediate adduct formed by the initiation of these reactions may be followed by two different reaction pathways such as H migration reaction to form carboxylic acids and rearrangement of oxygen to produce the sulfur trioxide (SO(3)) from the terminal oxygen of the COO group and SO(2). We found that the reaction of stabCI-OO and stabCH(2)OO with SO(2) can occur via both the aforementioned scenarios, whereas that of stabCI-CH(3)-OO and stabCIx-OO with SO(2) is limited to the second pathway only due to the absence of migrating H atoms. It has been shown that at the CCSD(T)/6-31G(d) + CF level of theory the activation energies of six reaction pathways are in the range of 14.18-22.59 kcal mol(-1), with the reaction between stabCIx-OO and SO(2) as the most favorable pathway of 14.18 kcal mol(-1) activation energy and that the reaction of stabCI-OO and stabCH(2)OO with SO(2) occurs mainly via the second reaction path. The thermochemical analysis of the reaction between SO(2) and stabilized Criegee intermediates indicates that the reaction of SO(2) and stabilized Criegee intermediates formed from the exocyclic primary ozonide decomposition is the main pathway of the SO(3) formation. This is likely to explain the large (~100%) difference in the production rate in the favor of the exocyclic compounds observed in recent experiments on the formation of H(2)SO(4) from exocyclic and endocyclic compounds.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2012-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  13. Numerical study of hydrogen peroxide thermal decomposition in a shock tube

    NASA Astrophysics Data System (ADS)

    Bhatti, Muhammad Rizwan; Sheikh, Nadeem Ahmed; Manzoor, Shehryar; Khan, Muhammad Mahabat; Ali, Muzaffar

    2017-06-01

    Hydrogen peroxide (H2O2) has its significance during the combustion of heavy hydrocarbons in the internal combustion (IC) engines. Owing to its importance the measurements of H2O2 dissociation rate have been reported mostly using the shock tube apparatus. These types of experimental measurements are although quite reliable but require high cost. On the other hand, numerical simulations provide low cost and reliable solutions especially using computation fluid dynamics (CFD) software. In the current study an experimental shock tube flow is modeled using open access platform OpenFOAM to investigate the thermal decomposition of H2O2. Using two different convective schemes, limitedLinear and upwind, the propagation of shock wave and resultant dissociation reaction are simulated. The results of the simulations are compared with the experimental data. It is observed that the rate constant measured using the simulation data deviates from the experimental results in the low temperature range and approaches the experimental values as the temperature is raised.

  14. Molecular Dynamics Study of Cubic Boron Nitride Nanoparticles: Decomposition with Phase Segregation during Melting.

    PubMed

    Lee, Hsiao-Fang; Esfarjani, Keivan; Dong, Zhizhong; Xiong, Gang; Pelegri, Assimina A; Tse, Stephen D

    2016-11-22

    The relative stability and melting of cubic boron nitride (c-BN) nanoparticles of varying shapes and sizes are studied using classical molecular dynamics (MD) simulation. Focusing on the melting of octahedral c-BN nanoparticles, which consist solely of the most stable {111} facets, decomposition is observed to occur during melting, along with the formation of phase segregated boron clusters inside the c-BN nanoparticles, concurrent with vaporization of surface nitrogen atoms. To assess this MD prediction, a laser-heating experiment of c-BN powders is conducted, manifesting boron clusters for the post-treated powders. A general analysis of the geometrical and surface dependence of the nanoparticle ground-state energy using a Stillinger-Weber potential determines the relative stability of cube-shaped, octahedral, cuboctahedral, and truncated-octahedral c-BN nanoparticles. This stability is further examined using transient MD simulations of the melting behavior of the differently shaped nanoparticles, providing insights and revealing the key roles played by corner and edge initiated disorder as well as surface reconstruction from {100} to the more stable {111} facets in the melting process. Finally, the size dependence of the melting point of octahedral c-BN nanoparticles is investigated, showing the well-known qualitative trend of depression of melting temperature with decreasing size, albeit with different quantitative behavior from that predicted by existing analytical models.

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

    PubMed

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

    2016-08-16

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

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

    PubMed Central

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

    2015-01-01

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

  17. The Products of the Thermal Decomposition of CH3CHO

    SciTech Connect

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

    2011-04-06

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

  18. 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/TiO2 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 H2O2 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.

  19. Theoretical study of neutrino scattering off the stable even Mo isotopes at low and intermediate energies

    NASA Astrophysics Data System (ADS)

    Balasi, K. G.; Ydrefors, E.; Kosmas, T. S.

    2011-10-01

    A systematic study of the cross sections of neutral-current neutrino scattering off the stable even Mo isotopes (mass number A=92,94,96,98,100), at low and intermediate neutrino energies ( E⩽130 MeV), is presented and discussed. The required wave functions for the initial (ground state) and all accessible final nuclear states are constructed in the context of the quasi-particle random-phase approximation (QRPA) and tested against data on the low-lying energy spectra of the isotopes in question. The individual contributions coming from the polar-vector and axial-vector components of the hadronic current for the coherent and incoherent channels of each isotope are investigated. The studied Mo isotopes are contents of the detector of the MOON experiment operating at Japan with a hybrid aim to search for neutrinoless double beta decay events and to detect low- and intermediate-energy astrophysical neutrinos (solar, supernova, geo-neutrinos), and also of the NEMO neutrinoless double beta decay detector in Modane at France. For such purposes our cross section calculations are of significant importance.

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

    PubMed Central

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

    2013-01-01

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

  1. A study on intermediate buffer layer of coated Fiber Bragg Grating cryogenic temperature sensors

    NASA Astrophysics Data System (ADS)

    Freitas, R.; Araujo, F.; Araujo, J.; Neumann, H.; Ramalingam, R.

    2015-12-01

    The sensor characteristics of a coated Fiber Bragg grating (FBG) thermal sensor for cryogenic temperatures depends mainly on the coating materials. The sensitivity of the coated FBG can be improved by enhancing the effective thermal strain transfer between the different layers and the bare FBG. The dual coated FBG's has a primary layer and the secondary layer. The primary coating acts as an intermediate buffer between the secondary coating and the bare FBG. The outer secondary coating is normally made of metals with high thermal expansion coefficient. In this work, a detailed study is carried out on chromium and titanium intermediate buffer layers with various coating thicknesses and combinations. To improve the sensitivity, the secondary coating layer was tested with Indium, Lead and Tin. The sensors were then calibrated in a cryogenic temperature calibration facility at Institute of Technical Physics (ITEP), Karlsruhe Institute of Technology. The sensors were subjected to several thermal cycles between 4.2 and 80 K to study the sensor performance and its thermal characteristics. The sensor exhibits a Bragg wavelength shift of 13pm at 20K. The commercially available detection equipment with a resolution of 1pm can result in a temperature resolution of 0.076 K at 20K.

  2. Spectral Decomposition Using the CEEMD Method: A Case Study from the Carpathian Foredeep

    NASA Astrophysics Data System (ADS)

    Kwietniak, Anna; Cichostępski, Kamil; Kasperska, Monika

    2016-10-01

    The purpose of this work is to select the optimal spectral decomposition (SD) method for channel detection in the Miocene strata of the Carpathian Fordeep, SE Poland. For analysis, two spectral decomposition algorithms were tested on 3D seismic data: the first, based on Fast Fourier Transform (FFT), and second, on Complete Ensemble Empirical Mode Decomposition (CEEMD). Additionally the results of instantaneous frequency (IF) were compared with the results of peak frequency (PF) computed after the CEEMD. Both algorithms of SD enabled us to interpret channels, but the results are marginally different, i.e. the FFT shows more coarse, linear structures, that are desirable for channel interpretation, whereas the CEEMD does not highlight these structures as clearly and shows more, what the authors believe to be, noise.

  3. First-principles studies on the thermal decomposition behavior of FOX-7

    NASA Astrophysics Data System (ADS)

    Zheng, Zhaoyang; Xu, Jingcheng; Zhao, Jijun

    2010-06-01

    The thermal decomposition behavior for the molecular crystal of 1,1-diamino-2,2-dinitroethylene (FOX-7) at high temperature has been simulated using constant-temperature molecular dynamics and density functional theory up to 50 ps. We found that most of the energy is released within the first 15 ps of the reaction. The main products are N2 and H2O molecules, and their populations generally increase with time. Some charged groups (like NO2 + and OH-) observed in the initial stage of decomposition may promote further reaction. High-pressure effect on the thermal decomposition behavior has also been examined by simulating FOX-7 crystals of different densities.

  4. Molecular beam mass spectrometry studies of the thermal decomposition of tetraethoxysilane (TEOS)

    SciTech Connect

    Wierda, C.A.; Zachariah, M.R.; Burgess, D.R.F. Jr.

    1995-03-01

    Molecular beam mass spectrometry and time-of-flight techniques have been used to reveal the gas phase chemistry that occurs during the thermal decomposition of TEOS. Evidence in the authors` laboratory was consistent with the presence of the following species during decomposition at 600{degrees}C: ethylene, ethanol, acetaldehyde, possibly diethoxysilanone, triethoxysilanol, hexaethoxysiloxane. A grayish white powder, which presumably consists of silicon oxides containing residual carbon and hydrogen, was also produced. Under the following reaction conditions: reactor pressure=266 Pa (2 torr), residence time=6 ms, and TEOS partial pressure=26 Pa (0.2 torr), the onset of decomposition occurs at 400{degrees}C. The amount of TEOS decreases at residence times greater than 6 ms with concurrent increase in ethanol and ethylene. Hexaethoxysiloxane also increases at residence times between 6 and 20 ms, but then decreases at longer times probably because it reacts to form larger siloxanes and silicon oxides.

  5. Kinetic Studies of the Thermal Decomposition of Methylperoxynitrate and of Ozone-Olefin Reactions.

    NASA Astrophysics Data System (ADS)

    Bahta, Abraha

    This research concerns the thermal decomposition kinetics of CH(,3)O(,2)NO(,2) and laboratory kinetic measurements of ozone-olefin reactions. In the first system, the thermal decomposition rate of CH(,3)O(,2)NO(,2) was studied in the temperature range of 256-268 K at (TURN)350 torr total pressure and in the pressure range of 50-720 torr at 263 K by the perturbation of the equilibrium: (UNFORMATTED TABLE FOLLOWS). CH(,3)O(,2) + NO(,2) (+M) (DBLARR) CH(,3)O(,2)NO(,2) (+M) (3,-3). with NO. CH(,3)O(,2) + NO (--->) CH(,3)O + NO(,2) (4). (TABLE ENDS). The CH(,3)O(,2)NO(,2) was generated in situ by the photolysis of Cl(,2) in the presence of O(,2), CH(,4) and NO(,2). The decomposition kinetics were monitored in the presence of NO by the change in ultraviolet absorption at 250 nm. The Arrhenius expression obtained for the thermal decomposition is k(,-3) = 6 x 10('15) exp{-(21,000 (+OR-) 1500)/RT} sec('-1) at (TURNEQ)350 torr total pressure (mostly CH(,4)) where R = 1.987 cal/mole('-) K. The uncertainty in the Arrhenius parameters can be greatly reduced by combining this expression with data for k(,3) and thermodynamics data to give k(,-3) = (6 (+OR-) 3) x 10('15) exp{-(21,300 (+OR-) 300)/RT} sec('-1) at (TURNEQ)350 torr total pressure. Computations based on the pressure dependence of the forward reaction give k(,-3)('(INFIN)) = 2.1 x 10('16) exp{-(21,700 (+OR -) 300)/RT} sec('-1) k(,-3)('(DEGREES)) = 3.3 x 10(' -4) exp{-(20,150 x 300)/RT} cm('3) sec('-1). At 263 K the equilibrium constant K(,3,-3){263 K} is determined to be (2.68 (+OR-) 0.26) x 10('-10) cm('3). In the stratosphere the CH(,3)O(,2)NO(,2) lifetime will be controlled by play a role in the NO(,x) budget of the lower stratosphere. In the second part, the kinetics of the reactions of O(,3) with C(,2)H(,4), C(,3)H(,4), 1,3-C(,4)H(,6), and trans-1,3-C(,5)H(,8) were studied with initial olefin-to -ozone ratios (GREATERTHEQ) 4.9, in the presence of excess O(,2), and over the temperature range 232 to 300 K. The

  6. Structure-dependent reactivity of Criegee intermediates studied with spectroscopic methods.

    PubMed

    Jr-Min Lin, Jim; Chao, Wen

    2017-08-25

    Criegee intermediates are very reactive carbonyl oxides that are formed in reactions of unsaturated hydrocarbons with ozone (ozonolysis). Recently, Criegee intermediates have gained significant attention since a new preparation method has been reported in 2012, which employs the reaction of iodoalkyl radical with molecular oxygen: for instance, CH2I + O2 → CH2OO + I. This new synthesis route can produce Criegee intermediates with a high number density, which allows direct detection of the Criegee intermediate via various spectroscopic tools, including vacuum UV photoionization mass spectrometry, absorption and action spectroscopy in the UV and IR regions, and microwave spectroscopy. Criegee intermediates have been thought to play important roles in atmospheric chemistry, such as in OH radical formation as well as oxidation of atmospheric gases such as SO2, NO2, volatile organic compounds, organic and inorganic acids, and even water. These reactions are relevant to acid rain and aerosol formation. Kinetics data including rate coefficients, product yields and their temperature and pressure dependences are important for understanding and modeling relevant atmospheric chemistry. In fundamental physical chemistry, Criegee intermediates have unique and interesting features, which have been partially revealed through spectroscopic, kinetic, and dynamic investigations. Although previous review articles have discussed Criegee intermediates, new data and knowledge on Criegee intermediates are still being accumulated. In this tutorial review, we have focused on structure-dependent reactivity of Criegee intermediates and various spectroscopic tools that have been utilized to probe the kinetics of Criegee intermediates.

  7. Woodland Decomposition.

    ERIC Educational Resources Information Center

    Napier, J.

    1988-01-01

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

  8. Woodland Decomposition.

    ERIC Educational Resources Information Center

    Napier, J.

    1988-01-01

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

  9. Theoretical kinetic study of thermal unimolecular decomposition of cyclic alkyl radicals.

    PubMed

    Sirjean, B; Glaude, P A; Ruiz-Lopèz, M F; Fournet, R

    2008-11-20

    Whereas many studies have been reported on the reactions of aliphatic hydrocarbons, the chemistry of cyclic hydrocarbons has not been explored extensively. In the present work, a theoretical study of the gas-phase unimolecular decomposition of cyclic alkyl radicals was performed by means of quantum chemical calculations at the CBS-QB3 level of theory. Energy barriers and high-pressure-limit rate constants were calculated systematically. Thermochemical data were obtained from isodesmic reactions, and the contribution of hindered rotors was taken into account. Classical transition state theory was used to calculate rate constants. The effect of tunneling was taken into account in the case of CH bond breaking. Three-parameter Arrhenius expressions were derived in the temperature range of 500-2000 K at atmospheric pressure, and the CC and CH bond breaking reactions were studied for cyclic alkyl radicals with a ring size ranging from three to seven carbon atoms, with and without a lateral alkyl chain. For the ring-opening reactions, the results clearly show an increase of the activation energy as the pi bond is being formed in the ring (endo ring opening) in contrast to the cases in which the pi bond is formed on the side chain (exo ring opening). These results are supported by analyses of the electronic charge density that were performed with Atoms in Molecules (AIM) theory. For all cycloalkyl radicals considered, CH bond breaking exhibits larger activation energies than CC bond breaking, except for cyclopentyl for which the ring-opening and H-loss reactions are competitive over the range of temperatures studied. The theoretical results compare rather well with the experimental data available in the literature. Evans-Polanyi correlations for CC and CH beta-scissions in alkyl and cycloalkyl free radicals were derived. The results highlight two different types of behavior depending on the strain energy in the reactant.

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

    NASA Astrophysics Data System (ADS)

    Garcia-Gonzalez, Jose Enrique

    2005-11-01

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

  11. Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

    PubMed Central

    Devi, Runjun

    2017-01-01

    While the exploitation of the Sharpless asymmetric dihydroxylation as the source of chirality in the synthesis of acyclic molecules and saturated heterocycles has been tremendous, its synthetic utility toward chiral benzo-annulated heterocycles is relatively limited. Thus, in the search for wider applications of Sharpless asymmetric dihydroxylation-derived diols for the synthesis of benzo-annulated heterocycles, we report herein our studies in the asymmetric synthesis of (R)-1-((R)-6-fluorochroman-2-yl)ethane-1,2-diol, (R)-1-((S)-6-fluorochroman-2-yl)ethane-1,2-diol and (S)-6-fluoro-2-((R)-oxiran-2-yl)chroman, which have been used as late-stage intermediates for the asymmetric synthesis of the antihypertensive drug (S,R,R,R)-nebivolol. Noteworthy is that a large number of racemic and asymmetric syntheses of nebivolol and their intermediates have been described in the literature, however, the Sharpless asymmetric dihydroxylation has never been employed as the sole source of chirality for this purpose. PMID:28405237

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

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey

    2012-05-01

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

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

    ERIC Educational Resources Information Center

    Carter, Gillian E.

    1986-01-01

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

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

    ERIC Educational Resources Information Center

    Carter, Gillian E.

    1986-01-01

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

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

    SciTech Connect

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

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Drzymulska, Danuta

    2016-03-01

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

  17. Thermodynamics and Mechanisms of Protonated Diglycine Decomposition: A Guided Ion Beam Study

    NASA Astrophysics Data System (ADS)

    Armentrout, P. B.; Heaton, Amy L.

    2012-04-01

    We present a full molecular description of fragmentation reactions of protonated diglycine (H+GG) by studying their collision-induced dissociation (CID) with Xe using a guided ion beam tandem mass spectrometer (GIBMS). Analysis of the kinetic energy-dependent CID cross sections provides the 0 K barriers for the sequential H2O+CO and CO+NH3 losses from H+GG as well as for the reactions involved in y1 and a1 ion formation, after accounting for unimolecular decay rates, internal energy of reactant ions, and multiple ion-molecule collisions. Here, seven energetic barriers are measured for the fragmentation processes of H+GG, including the loss of H2O and of CO at ~140 and ~156 kJ/mol, the combined loss of (H2O+CO) and of (CO+NH3) at ~233 and ~185 kJ/mol, and formation of y1 and a1 ions at ~191 and ~212 kJ/mol, respectively, with a second channel for a1 formation opening at ~326 kJ/mol. Theoretical energies from the preceding paper are compared with our experimental energies and found to be in good agreement. This validates the mechanisms explored computationally, including unambiguous identification of the b2 ion as protonated 2-aminomethyl-5-oxazolone, thereby allowing a complete characterization of the elementary steps of H+GG decomposition. These results also demonstrate that all reactive species are available from the ground state conformation, as opposed to involving an initial broad distribution of protonated conformers. This result verifies the utility of the "mobile proton" model for understanding the fragmentation of protonated proteins.

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

    PubMed

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

    2015-07-16

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

  19. An ecological study of Bithynia snails, the first intermediate host of Opisthorchis viverrini in northeast Thailand.

    PubMed

    Wang, Yi-Chen; Ho, Richard Cheng Yong; Feng, Chen-Chieh; Namsanor, Jutamas; Sithithaworn, Paiboon

    2015-01-01

    Infection with the food-borne trematodiasis, liver fluke Opisthorchis viverrini, is a major public health concern in Southeast Asia. While epidemiology and parasitic incidence in humans are well studied, ecological information on the O. viverrini intermediate hosts remains limited. This study aimed to investigate the factors affecting the distribution and abundance of the first intermediate host, Bithynia siamensis goniomphalos snails. Water quality and snails were sampled in 31 sites in Muang District, Khon Kaen Province, Thailand from June 2012 to January 2013 to characterize the B.s. goniomphalos snail habitats. Species relative abundance and Shannon's diversity and evenness indices were employed to describe snail compositions and diversities across different habitat types. Statistical analyses were conducted to examine the extent to which the water quality variables and species interactions account for the relative abundance of B.s. goniomphalos snails. The results showed that the freshwater habitats of ponds, streams and rice paddies possessed significantly different abiotic water qualities, with water temperature and pH showing distinct statistical differences (P<0.05). Different habitats had different snail diversity and species evenness, with high B.s. goniomphalos snail abundance at rice paddy habitats. The differences in snail abundance might be due to the distinct sets of abiotic water qualities associated with each habitat types. The relative abundance of B.s. goniomphalos snails was found to be negatively correlated with that of Filopaludina martensi martensi snails (r=-0.46, P<0.05), underscoring the possible influence of species interaction on B.s. goniomphalos snail population. Field work observations revealed that rice planting seasons and irrigation could regulate snail population dynamics at rice paddy habitats. This study provides new ecological insights into the factors affecting Bithynia snail distribution and abundance. It bridges the

  20. Optimal Hydration Status for Cryopreservation of Intermediate Oily Seeds: Citrus as a Case Study

    PubMed Central

    HOR, Y. L.; KIM, Y. J.; UGAP, A.; CHABRILLANGE, N.; SINNIAH, U. R.; ENGELMANN, F.; DUSSERT, S.

    2005-01-01

    • Background and Aims The purpose of this study was to investigate the basis of the optimal hydration status for cryopreservation of intermediate oily seeds using Citrus as a model. • Methods The relationships between equilibrium relative humidity (RH), seed water content, presence of freezable water as determined by DSC analysis, and germination percentage after immersion in liquid nitrogen (LN) were investigated in Citrus aurantifolia, C. grandis, C. madurensis and C. reticulata. The relationship between the lipid content of seeds and their unfrozen water content was also investigated. • Key Results Independent of their level of seed desiccation tolerance, the optimal desiccation RH for seed tolerance to LN exposure was 75–80 % in the four species studied. This optimal hydration status always coincided with that at which presence of frozen water could not be detected in seed tissues during the cooling/thawing process. The unfrozen water content of seeds was variable between species and negatively correlated to seed lipid content. Using the present data, those obtained previously in seven coffee species and those reported by other authors for five other species, a significant linear relationship was found between the lipid content and the unfrozen water content of seeds. • Conclusions This study provides additional evidence that intermediate oily seeds do not withstand the presence of freezable water in their tissues during the cooling/warming process. Moreover, it offers two important applied perspectives: (1) independent of their level of desiccation tolerance, testing germination of seeds of a given oily seed species after equilibration in 75–80 % RH at 25 °C and LN exposure, gives a rapid and reliable evaluation of the possibility of cryopreserving whole seeds of this given species; (2) it is now possible to calculate the interval of water contents in which non-orthodox oily seeds of a given species are likely to withstand LN exposure as a

  1. Optimal hydration status for cryopreservation of intermediate oily seeds: Citrus as a case study.

    PubMed

    Hor, Y L; Kim, Y J; Ugap, A; Chabrillange, N; Sinniah, U R; Engelmann, F; Dussert, S

    2005-06-01

    The purpose of this study was to investigate the basis of the optimal hydration status for cryopreservation of intermediate oily seeds using Citrus as a model. The relationships between equilibrium relative humidity (RH), seed water content, presence of freezable water as determined by DSC analysis, and germination percentage after immersion in liquid nitrogen (LN) were investigated in Citrus aurantifolia, C. grandis, C. madurensis and C. reticulata. The relationship between the lipid content of seeds and their unfrozen water content was also investigated. Independent of their level of seed desiccation tolerance, the optimal desiccation RH for seed tolerance to LN exposure was 75-80 % in the four species studied. This optimal hydration status always coincided with that at which presence of frozen water could not be detected in seed tissues during the cooling/thawing process. The unfrozen water content of seeds was variable between species and negatively correlated to seed lipid content. Using the present data, those obtained previously in seven coffee species and those reported by other authors for five other species, a significant linear relationship was found between the lipid content and the unfrozen water content of seeds. This study provides additional evidence that intermediate oily seeds do not withstand the presence of freezable water in their tissues during the cooling/warming process. Moreover, it offers two important applied perspectives: (1) independent of their level of desiccation tolerance, testing germination of seeds of a given oily seed species after equilibration in 75-80 % RH at 25 degrees C and LN exposure, gives a rapid and reliable evaluation of the possibility of cryopreserving whole seeds of this given species; (2) it is now possible to calculate the interval of water contents in which non-orthodox oily seeds of a given species are likely to withstand LN exposure as a function of their lipid content.

  2. Studies of the intermediate and deep circulation in the western equatorial Atlantic

    NASA Technical Reports Server (NTRS)

    Desaubies, Yves; Frankignoul, C.; Merle, Jacques

    1991-01-01

    This proposal concerns the preparation and design of an experiment, the objective of which is to improve our knowledge of the intermediate and deep circulation in the western equatorial Atlantic Ocean. We shall focus on the description of the western boundary currents, of their crossing with the equator, on the estimation of their mass and heat fluxes, and their seasonal and interannual variations. We will use satellite altimetric data, tomographic measurements, and in situ observations (current measurements, hydrology, and floaters). We propose a feasibility study and the definition of a strategy based on a high-resolution Geophysical Fluid Dynamics Laboratory (GFDL) numerical model to define which in situ measurements are necessary to optimally complete the altimetric observations.

  3. Boron Nitride-supported Sub-nanometer Pd 6 Clusters for Formic Acid Decomposition: A DFT Study

    DOE PAGES

    Schimmenti, Roberto; Cortese, Remedios; Duca, Dario; ...

    2017-04-25

    A periodic, self-consistent planewave DFT study was carried out to explore the potential use of Pd6 clusters supported on a boron nitride sheet as a catalyst for the selective decomposition of formic acid (HCOOH) to CO2 and H2. The competition between formate (HCOO) and carboxyl (COOH) paths on catalytic sites, with different proximities to the support, was studied. Based on energetics alone, the reaction may mainly follow the HCOO route. Slightly lower activation energies were found at the lateral sites of the cluster as compared to top face sites. This is particularly true for the bidentate to monodentate HCOO conversion.more » Through comparison of results with similar studies on HCOOH decomposition on extended Pd surfaces, it was demonstrated that the existence of undercoordinated sites in the sub-nanometer cluster could play a key role in preferentially stabilizing HCOO over COOH, which is a common CO precursor in this reaction. A hydrogen spillover mechanism was also investigated; migration toward the boron nitride support is not favorable, at least in the early stages of the reaction. However, hydrogen diffusion on the cluster has low barriers compared to those involved in formic acid decomposition.« less

  4. Formulation development of intermediate release Nimesulide tablets by CCRD for IVIVC studies.

    PubMed

    Hanif, Muhammad; Shoaib, Muhammad Harris; Yousuf, Rabia Ismail; Sattar, Shahnila; Nadeem, Muhammad; Hussain, Liaqat; MZia, Muhammad Usman; Muhammad, Iyad Naeem; Uzair, Muhammad; Qadir, Imran

    2014-07-01

    Simple and cost effective study consisting of three steps, comparison of micromeritic properties of different blends i.e. placebo without API and Nimesulide containing, Use of central composite design (CCRD) for intermediate release Nimesulide tablets and stability results of three selected Nimesulide tablet formulations which were calculated by using R Gui. Different concentrations of Avicel, hydroxypropyl methyl cellulose (HPMC) and magnesium stearate were used as variables in central composite design and two types blend i.e., with or without Nimesulide were selected for bulk density, tap density, percentage compressibility; angle of repose and Hausner's ratio. Blending rate constant was performed after applying the different mixing times like 3, 6, 9 and 12 minutes. Twenty intermediate release formulations were designed and three formulations were chosen for compression by direct compression method on the basis of compressibility index. Physicochemical properties and best release pattern in four hours in different dissolution medium were successfully measured. Relative densities, porosity of tablets were compared with tensile strength of tablet and weight variation, hardness, friability and dissolution was performed by simple experiments. Presence of Nimesulide in the bulk increased all micromeratic tests while 9 minutes was best mixing time. The hardness of NM containing tablets increased with the increase of relative density. The release pattern was further analyzed by model dependent i.e. zero order, first order and Higuchi, Korse-meyer and Pappas, Hixson Crowell and model independent kinetic model i.e., f2 value respectively. R Gui explained the F16 formulation shows the best result in stability studies with shelf life 72 months.

  5. High altitude syndromes at intermediate altitudes: a pilot study in the Australian Alps.

    PubMed

    Slaney, Graham; Cook, Angus; Weinstein, Philip

    2013-10-01

    Our hypothesis is that symptoms of high altitude syndromes are detectable even at intermediate altitudes, as commonly encountered under Australian conditions (<2500 m above sea level). High altitude medicine has long recognised several syndromes associated with rapid ascent to altitudes above 2500 m, including high altitude pulmonary oedema (HAPE), high altitude cerebral oedema (HACE) and high altitude flatus expulsion (HAFE). Symptoms of high altitude syndromes are of growing concern because of the global trend toward increasing numbers of tourists and workers exposed to both rapid ascent and sustained physical activity at high altitude. However, in Australia, high altitude medicine has almost no profile because of our relatively low altitudes by international standards. Three factors lead us to believe that altitude sickness in Australia deserves more serious consideration: Australia is subject to rapid growth in alpine recreational industries; altitude sickness is highly variable between individuals, and some people do experience symptoms already at 1500 m; and there is potential for an occupational health and safety issue amongst workers. To test this hypothesis we examined the relationship between any high altitude symptoms and a rapid ascent to an intermediate altitude (1800 m) by undertaking an intervention study in a cohort of eight medical clinic staff, conducted during July of the 2012 (Southern Hemisphere) ski season, using self-reporting questionnaires, at Mansfield (316 m above sea level) and at the Ski Resort of Mt Buller (1800 m), Victoria, Australia. The intervention consisted of ascent by car from Mansfield to Mt Buller (approx. 40 min drive). Participants completed a self-reporting questionnaire including demographic data and information on frequency of normal homeostatic processes (fluid intake and output, food intake and output, symptoms including thirst and headaches, and frequency of passing wind or urine). Data were recorded in hourly periods

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

    PubMed

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

    2013-01-01

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

  7. Shock tube study on the thermal decomposition of fluoroethane using infrared laser absorption detection of hydrogen fluoride.

    PubMed

    Matsugi, Akira; Shiina, Hiroumi

    2014-08-28

    Motivated by recent shock tube studies on the thermal unimolecular decomposition of fluoroethanes, in which unusual trends have been reported for collisional energy-transfer parameters, the rate constants for the thermal decomposition of fluoroethane were investigated using a shock tube/laser absorption spectroscopy technique. The rate constants were measured behind reflected shock waves by monitoring the formation of HF by IR absorption at the R(1) transition in the fundamental vibrational band near 2476 nm using a distributed-feedback diode laser. The peak absorption cross sections of this absorption line have also been determined and parametrized using the Rautian-Sobel'man line shape function. The rate constant measurements covered a wide temperature range of 1018-1710 K at pressures from 100 to 290 kPa, and the derived rate constants were successfully reproduced by the master equation calculation with an average downward energy transfer, ⟨ΔEdown⟩, of 400 cm(-1).

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

    NASA Astrophysics Data System (ADS)

    Jazan, Elham; Ghazali Khoob, Abdolhosein S.

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  10. The ammonium nitrate and its mechanism of decomposition in the gas phase: a theoretical study and a DFT benchmark.

    PubMed

    Cagnina, Stefania; Rotureau, Patricia; Fayet, Guillaume; Adamo, Carlo

    2013-07-14

    The decomposition mechanism of ammonium nitrate in the gas phase was investigated and fully characterized by means of CBS-QB3 calculations. Five reaction channels were identified, leading to the formation of products (N2, H2O, O2, OH, HNO, NO3) found in the experimental works. The identified mechanism well underlines the origin of the chemical hazard of ammonium nitrate which is related to the exothermicity of the lowest decomposition channels. Furthermore, the high barrier to overcome in the rate determining step well explained the fact that the reaction is not usually spontaneous and requires a significant external stimulus for its onset. An accurate DFT benchmark study was then conducted to determine the most suitable exchange-correlation functional to accurately describe the reaction profile both in terms of structures and thermochemistry. This evaluation supports the use of the M06-2X functional as the best option for the study of ammonium nitrate decomposition and related reactions. Indeed, this level of theory provided the lowest deviations with respect to CBS-QB3 reference values, outperforming functionals especially developed for reaction kinetics.

  11. Restricted infectivity of ecotropic type C retroviruses in mouse teratocarcinoma cells: studies on viral DNA intermediates

    SciTech Connect

    Yang, W.K.; d'Auriol, L.; Yang, D.M.; Kiggans, J.O. Jr.; Ou, C.Y.; Peries, J.; Emanoil-Ravicovitch, R.

    1980-01-01

    Infectivity of retroviruses in cultured murine teratocarcinoma cells was found to be affected by the state of cellular differentiation. Present studies utilize two kinds of cell cultures from teratocarcinomas of mouse strain 129, an undifferentiated pluriopotential cell line (PCC/sub 4/) and a myoblast-derived cell line (PCD/sub 1/) which are respectively resistant and susceptible to the infection of Gross strain N-tropic type C retrovirus. Analyses of the appearance of free viral DNA intermediates in these cells from 4 to 78 h after virus inoculation were made. In both PCD/sub 1/ and PCC/sub 4/ cells, virus inoculation induced the formation of one linear form (III) and two covalently-closed supercoiled circular forms (I) of viral DNA duplexes; the linear form showing its appearance, increase, and decline in the 4 to 18 h period, and the circular forms in the 8 to 24 h period. In the period of 56 to 78 h after virus inoculation, a secondary burst of viral DNA synthesis occurred in PCD/sub 1/ cells, whereas both linear and supercoiled viral DNA duplexes became undetectable in PCC/sub 4/ cells. Free and unintegrated viral DNA preparations from PCD/sub 1/ and PCC/sub 4/ cells 10 h after virus inoculation were both infectious for N3T3 cells in a DNA transfection assay. Both PCD/sub 1/ and PCC/sub 4/ cells were very poor recipients for DNA transfection. These results indicate that restriction of retrovirus in undifferentiated teratocarcinoma cells occurs at a step beyond formation and maturation of viral DNA intermediates. (ERB)

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

    NASA Astrophysics Data System (ADS)

    Welsh, William F.; Martell, Phillip J.

    1996-10-01

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

  13. Clinical, neurophysiological and morphological study of dominant intermediate Charcot-Marie-Tooth type C neuropathy.

    PubMed

    Thomas, Florian P; Guergueltcheva, Velina; Gondim, Francisco A A; Tournev, Ivailo; Rao, Chitharanjan V; Ishpekova, Boryana; Kinsella, Laurence J; Pan, Yi; Geller, Thomas J; Litvinenko, Ivan; De Jonghe, Peter; Scherer, Steven S; Jordanova, Albena

    2016-03-01

    Dominant intermediate Charcot-Marie-Tooth neuropathy subtype C (DI-CMTC) was associated with mutations in the YARS gene, encoding tyrosyl-tRNA synthetase, in two large unrelated Bulgarian and US pedigrees and one sporadic case. Here for the first time we describe the clinical, neurophysiological and histopathological features, and phenotypic differences between these two DI-CMTC families. Twenty-one affected individuals from the US family and 27 from the Bulgarian family were evaluated. The mean age of onset in US subjects was 10.7 years in men and 7.3 years in women, while in the Bulgarian participants it was 18.2 years in men and 33.7 years in women. The course was slowly progressive. Extensor digitorum brevis atrophy was uniform. Atrophy and/or weakness of upper and lower limb muscles were found in over 50 % of the subjects. Nerve conduction studies (NCS) were abnormal in all US adults and five of six children and all Bulgarian patients except one asymptomatic 25-year-old man. Median motor NCS were in the range of 29.5-45.6 m/s in the US family and 24.7-57.8 m/s in the Bulgarian family. Sural sensory nerve action potentials were absent in 14/21 and 4/12 NCS from adult US and Bulgarian participants, respectively. Analysis of sural nerve biopsies from US patients revealed age-dependent morphological changes of axonal degeneration, absence of onion bulbs, and <10 % fibers with segmental remyelination. Our findings provide further insights into the diagnosis and pathology of intermediate CMT. They also extend the phenotypic spectrum of peripheral neuropathies associated with aminoacyl-tRNA synthetase mutations.

  14. Theoretical Study of Decomposition Pathways for HArF and HKrF

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

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

    PubMed

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

    2014-09-01

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

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

    PubMed

    Lahmiri, Salim

    2014-09-01

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

  17. A study of the Invariant Subspace Decomposition Algorithm for banded symmetric matrices

    SciTech Connect

    Bischof, C.; Sun, X.; Tsao, A.; Turnbull, T.

    1994-06-01

    In this paper, we give an overview of the Invariant Subspace Decomposition Algorithm for banded symmetric matrices and describe a sequential implementation of this algorithm. Our implementation uses a specialized routine for performing banded matrix multiplication together with successive band reduction, yielding a sequential algorithm that is competitive for large problems with the LAPACK QR code in computing all of the eigenvalues and eigenvectors of a dense symmetric matrix. Performance results are given on a variety of machines.

  18. Theoretical study of the decomposition mechanism of environmentally friendly insulating medium C3F7CN in the presence of H2O in a discharge

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxing; Li, Yi; Xiao, Song; Tian, Shuangshuang; Deng, Zaitao; Tang, Ju

    2017-08-01

    C3F7CN has been the focus of the alternative gas research field over the past two years because of its excellent insulation properties and environmental characteristics. Experimental studies on its insulation performance have made many achievements. However, few studies on the formation mechanism of the decomposition components exist. A discussion of the decomposition characteristics of insulating media will provide guidance for scientific experimental research and the work that must be completed before further engineering application. In this study, the decomposition mechanism of C3F7CN in the presence of trace H2O under discharge was calculated based on the density functional theory and transition state theory. The reaction heat, Gibbs free energy, and activation energy of different decomposition pathways were investigated. The ionization parameters and toxicity of C3F7CN and various decomposition products were analyzed from the molecular structure perspective. The formation mechanism of the C3F7CN discharge decomposition components and the influence of trace water were evaluated. This paper confirms that C3F7CN has excellent decomposition characteristics, which provide theoretical support for later experiments and related engineering applications. However, the existence of trace water has a negative impact on C3F7CN’s insulation performance. Thus, strict trace water content standards should be developed to ensure dielectric insulation and the safety of maintenance personnel.

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

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Nurazar, Roghaye

    2014-08-01

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

  20. Feasibility Study on Hydrazine Decomposition by Discharge Plasma for Spacecraft Propulsion System

    NASA Astrophysics Data System (ADS)

    Aoyagi, Junichiro; Kakami, Akira; Takegahara, Haruki; Tachibana, Takeshi; Mishima, Hiroyuki; Saitoh, Noriyoshi; Nagashima, Ryuichi; Kuriki, Kyoichi

    Conventional monopropellant thrusters for spacecraft utilize the pelletized catalyst bed to decompose the propellant, typically Hydrazine. The catalyst bed consists of Iridium catalyst supported by porous Alumina ceramics pellets. During the long-term operation of the thruster, however, the catalyst is occasionally damaged, which causes several critical problems like a deterioration of the decomposition performance or choke of the capillary tube. In order to solve or mitigate these problems, a new decomposition device was designed and its preliminary model was fabricated and evaluated in our research group. Preliminary tests were conducted to examine the new reaction mechanism using pulsed or stationary AC discharge plasma instead of pelletized catalysts in a bucket type reaction chamber. In the reaction chamber filled with Hydrazine, sudden increase of the temperature and the pressure was observed immediately after the production of plasma discharge. These results show that the plasma is capable of the decomposition of Hydrazine, and acts as catalysts, and that it is worthwhile developing a new monopropellant thruster system using plasma assisted reaction in order to eliminate the disadvantages associated with the pelletized catalyst bed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Grady, Carol A.

    1999-01-01

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

  3. Computational Study of Main Mechanisms for Gas-Phase Decomposition of 1,1- and 1,2-Dinitroethane

    NASA Astrophysics Data System (ADS)

    Tsyshevsky, Roman V.; Aristov, Ilia V.; Chachkov, Denis V.; Shamov, Alexander G.; Khrapkovskii, Grigorii M.

    2010-10-01

    The gas-phase enthalpies of formation of 1,1- and 1,2-dinitroethane and corresponding radical products were calculated using G3B3, CBS-QB3 composite methods and DFT B3LYP level of theory with various basis sets. The enthalpies of the C-N, C-C bonds dissociation and activation enthalpies for HONO elimination were also calculated and compared with available experimental data. It was found that G3B3 calculations do provide a reasonable way to tackle the problem of the decomposition channels of 1,1- and 1,2-dinitroethane. Four main mechanisms for gas-phase decomposition of 1,1- and 1,2-dinitroethane were studied using G3B3 model chemistry. HONO elimination seems to be the most favorable mechanism for the decomposition of 1,2-dinitroethane. However, the difference in energies of the HONO elimination and C-N homolytic bond cleavage in 1,1-dinitroethane does not allow to favor any of these channels, especially at the working temperature. Gauche conformation of 1,2-dinitroethane is calculated to be the lowest-energy minimum.

  4. Probing the Cognitive Mechanism of Mental Representational Change During Chunk Decomposition: A Parametric fMRI Study.

    PubMed

    Tang, Xiaochen; Pang, Jiaoyan; Nie, Qi-Yang; Conci, Markus; Luo, Junlong; Luo, Jing

    2016-07-01

    Chunk decomposition plays an important role in cognitive flexibility in particular with regards to representational change, which is critical for insight problem solving and creative thinking. In this study, we investigated the cognitive mechanism of decomposing Chinese character chunks through a parametric fMRI design. Our results from this parametric manipulation revealed widely distributed activations in frontal, parietal, and occipital cortex and negative activations in parietal and visual areas in response to chunk tightness during decomposition. To mentally manipulate the element of a given old chunk, superior parietal lobe appears to support element restructuring in a goal-directed way, whereas the negatively activated inferior parietal lobe may support preventing irrelevant objects from being attended. Moreover, determining alternative ways of restructuring requires a constellation of frontal areas in the cognitive control network, such as the right lateral prefrontal cortex in inhibiting the predominant chunk representations, the presupplementary motor area in initiating a transition of mental task set, and the inferior frontal junction in establishing task sets. In conclusion, this suggests that chunk decomposition reflects mental transformation of problem representation from an inappropriate state to a new one alongside with an evaluation of novel and insightful solutions by the caudate in the dorsal striatum. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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

    PubMed

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

    2008-08-15

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

  6. Quantification of ranitidine hydrochloride in the presence of its decomposition product by spectrophotometric methods. Application for kinetic study.

    PubMed

    Sokół, Aneta; Karpińska, Joanna; Talecka, Renata; Starczewska, Barbara

    2011-01-01

    Three spectrophotometric methods, based on a spectral analysis, are proposed for quantification of ranitidine hydrochloride (RHCl) in the presence of its decomposition product (R-ox) without isolation from the matrix. One of them is a zero-crossing derivative-spectrophotometry. A value of the first derivative at 332 nm generated by the Savitzky-Golay algorithm (delta lambda = 22 nm and the first polynomial degree) allows for quantification of RHCI in the concentration range 0.5-35.1 microg/mL. The second proposed spectrophotometric procedure, called Vierordt method, utilizes an additivity of the absorbance. The assay of studied compound was realized by the direct reading of absorbance at 312 nm and 202 nm for ranitidine hydrochloride and its decomposition product, respectively. The quantitative results were obtained by resolving of an appropriate system of equations. The third method is based on the bivariate calibration algorithm. The absorbance values were measured at optimum wavelengths found by Kaiser method at 228 nm and 202 nm and used for the quantification of RHCI in the presence of its decomposition product. The Beer's law was obeyed in the concentration range 0.5-35.1 microg/mL for RHCl. The discussion of applicability of all elaborated methods is presented. The proposed methods were applied for assay of ranitidine hydrochloride contents in its preparation Ranigast and for investigation of kinetics of its reaction with hydrogen peroxide.

  7. Initial study of arthropods succession and pig carrion decomposition in two freshwater ecosystems in the Colombian Andes.

    PubMed

    Barrios, Maria; Wolff, Marta

    2011-10-10

    Entomological succession and trophic roles of arthropods associated with different stages of carcass decomposition were studied to estimate the post-mortem submersion interval in two freshwater ecosystems in the Colombian Andes, at an altitude of 2614 m. Pig carcasses were employed as models placed 68 m apart, one in a stream (lotic) and another in an artificial lake (lentic). Decomposition time to skeletal remains was 74 days in the lake and 80 days in the stream. Six phases of decomposition were established: submerged fresh, early floating, floating decay, bloated deterioration, floating remains and sunken remains. A total of 18,832 organisms associated with the carcasses were collected: 11,487 in the lake (four orders, 19 families and 33 species) and 7345 in the stream (eight orders, 15 families and 25 species). Organisms were classified in the following ecological categories: shredders, collectors, predators, necrophagous, sarcosaprophagous and opportunists. Physical and chemical properties of the habitats, such as water temperature, CO(2) and conductivity, varied according to rainfall. In the lake, shredders (Coleoptera: Tropisternus sp. and Berosus sp.) and collectors (Diptera: Chironomus sp.) were found to be associated with submerged phases. Predators (Odonata) were only present during the first phases. Coleoptera (Dytiscidae) were found during floating decay and bloated deterioration stages. In the stream, shredders (Hyalella sp.) and collectors (Simulium sp.) were found during all stages, whereas the predator Oxelytrum discicolle was found exclusively during the floating stages, during which body temperature increased in a fashion similar to active decay in terrestrial environments.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  9. A Study of the Proper Amount of Work-in-Process Inventory for Multipurpose Intermediate Products

    NASA Astrophysics Data System (ADS)

    Izutsu, Rihito; Imoto, Takaaki; Umeda, Toyohiro

    It is difficult to calculate the amount of inventory of intermediate products in a material processing factory which has complex multiple processes. If the amount is too great, inventory assets accumulate. On the other hand, if it is too small, tardiness in due-date is caused and the lead time from accepting order to shipping is extended because demand variation and equipment failure cannot be absorbed. In this report we explain a simulation model is explained and results are shown for comparing complementary amount of intermediate products by computing the flow from allocat-ing intermediate products to orders to shipping.

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

    SciTech Connect

    Not Available

    1991-12-31

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

  11. Optimal domain decomposition strategies

    NASA Technical Reports Server (NTRS)

    Yoon, Yonghyun; Soni, Bharat K.

    1995-01-01

    The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.

  12. 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

  13. 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.

  14. The bacteriorhodopsin photocycle: direct structural study of two substrates of the M-intermediate.

    PubMed Central

    Han, B G; Vonck, J; Glaeser, R M

    1994-01-01

    Changes in protein structure that occur during the formation of the M photointermediate of bacteriorhodopsin can be directly visualized by electron diffraction techniques. A modified preparation technique for glucose-embedded crystals was employed to ensure sufficient hydration of the crystals, which was needed for the formation of the M intermediate at low temperature. Samples containing a high percentage of the M intermediate were trapped by rapidly cooling the crystals with liquid nitrogen after illumination with filtered green light at 240 and 260 K, respectively. Difference Fourier projection maps are presented for the M intermediates formed at these two temperatures. The diffraction data clearly show that statistically significant structural changes occur upon formation of the M intermediate at 240 K and then further upon formation of the second specimen that is produced at 260 K. PMID:7811931

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  17. Fuel reforming and electrical performance studies in intermediate temperature ceria-gadolinia-based SOFCs

    NASA Astrophysics Data System (ADS)

    Livermore, Stephanie J. A.; Cotton, John W.; Ormerod, R. Mark

    The methane reforming and carbon deposition characteristics of two nickel/ceria-gadolinia cermet anodes have been studied over the temperature range 550-700°C, for use in intermediate temperature ceria-gadolinia (CGO)-based solid oxide fuel cells (SOFCs), using conventional catalytic methods and temperature-programmed spectroscopy. The electrical performance and durability of planar CGO-based SOFCs with a 280-μm-thick CGO electrolyte, screen printed cathode and different screen printed nickel/CGO cermet anodes have been studied over the temperature range 500-650°C. Temperature-programmed reduction has been used to study the reduction characteristics of the anodes, and indicates the presence of "bulk" NiO particles and smaller NiO particles in intimate contact with the ceria. Both anodes show good activity towards methane steam reforming with methane activation occurring at temperatures as low as 210°C; steady-state steam reforming of methane was observed using a methane-rich mixture at 650°C, with 20% methane conversion. Post-reaction temperature-programmed oxidation has been used to determine the amount of carbon deposited during reforming and the strength of its interaction with the anode.

  18. STUDIES ON THE CHANGE OF THE CONCENTRATIONS OF INTERMEDIATES DURING PHOTOSYNTHESIS OF CHLORELLA AND ISOLATED CHLOROPLASTS.

    DTIC Science & Technology

    The chages in the concentrations of intermediates and the distribution of C(14) after photosynthesis in C(14)02 by Chlorella and isolated...changes in the concentrations of intermediates in Chlorella during the transition from light to dark and vice versa are independent of CO2, but...dependent on anaerobiosis. (2) In Chlorella photosynthesis is inhibited even by a concentration of monoiodoacetic acid which is 100 times lower than that

  19. Photocatalytic decomposition of cortisone acetate in aqueous solution.

    PubMed

    Romão, Joana Sobral; Hamdy, Mohamed S; Mul, Guido; Baltrusaitis, Jonas

    2015-01-23

    The photocatalytic decomposition of cortisone 21-acetate (CA), a model compound for the commonly used steroid, cortisone, was studied. CA was photocatalytically decomposed in a slurry reactor with the initial rates between 0.11 and 0.46 mg L(-1)min(-1) at 10 mg L(-1) concentration, using the following heterogeneous photocatalysts in decreasing order of their catalytic activity: ZnO>Evonik TiO2 P25>Hombikat TiO2>WO3. Due to the lack of ZnO stability in aqueous solutions, TiO2 P25 was chosen for further experiments. The decomposition reaction was found to be pseudo-first order and the rate constant decreased as a function of increasing initial CA concentration. Changing the initial pH of the CA solution did not affect the reaction rate significantly. The decomposition reaction in the presence of the oxidizing sacrificial agent sodium persulfate showed an observed decomposition rate constant of 0.004 min(-1), lower than that obtained for TiO2 P25 (0.040 min(-1)). The highest photocatalytic degradation rate constant was obtained combining both TiO2 P25 and S2O8(2-) (0.071 min(-1)) showing a synergistic effect. No reactive intermediates were detected using LC-MS showing fast photocatalytic decomposition kinetics of CA.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  1. Avian cestodes affect the behaviour of their intermediate host Artemia parthenogenetica: an experimental study.

    PubMed

    Sánchez, M I; Georgiev, B B; Green, A J

    2007-03-01

    The brine shrimp Artemia parthenogenetica (Crustacea, Branchiopoda) is intermediate host for several cestode species whose final hosts are waterbirds. Previous field studies have shown that brine shrimps infected with cestodes have a bright red colour and are spatially segregated in the water column. However, the ethological mechanisms explaining such field observations are unknown. Changes in appearance and behaviour induced by trophically transmitted parasites have been shown to increase the risk of predation by the final host. In this experimental study, we compared the behaviour of uninfected Artemia and those infected by avian cestodes. We found that parasitised individuals behave differently from unparasitised ones in several ways. In contrast to uninfected individuals, infected brine shrimps were photophilous and showed increased surface-swimming behaviour. These observations suggest that the modified behaviour (in addition to the bright red colour of the majority of the infected individuals) results in infected brine shrimps becoming more vulnerable to avian final hosts, which facilitates parasite transmission. We discuss our results in terms of the adaptive nature of behavioural changes and their potential implications for the hypersaline ecosystem.

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

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

  3. Solvent decompositions and physical properties of decomposition compounds in Li-ion battery electrolytes studied by DFT calculations and molecular dynamics simulations.

    PubMed

    Tasaki, Ken

    2005-02-24

    The density functional theory (DFT) calculations have been performed for the reduction decompositions of solvents widely used in Li-ion secondary battery electrolytes, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonates (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), including a typical electrolyte additive, vinylene carbonate (VC), at the level of B3LYP/6-311+G(2d,p), both in the gas phase and solution using the polarizable conductor calculation model. In the gas phase, the first electron reduction for the cyclic carbonates and for the linear carbonates is found to be exothermic and endothermic, respectively, while the second electron reduction is endothermic for all the compounds examined. On the contrary, in solution both first and second electron reductions are exothermic for all the compounds. Among the solvents and the additive examined, the likelihood of undergoing the first electron reduction in solution was found in the order of EC > PC > VC > DMC > EMC > DEC with EC being the most likely reduced. VC, on the other hand, is most likely to undergo the second electron reduction among the compounds, in the order of VC > EC > PC. Based on the results, the experimentally demonstrated effectiveness of VC as an excellent electrolyte additive was discussed. The bulk thermodynamic properties of two dilithium alkylene glycol dicarbonates, dilithium ethylene glycol dicarbonate (Li-EDC) and dilithium 1,2-propylene glycol dicarbonate (Li-PDC), as the major component of solid-electrolyte interface (SEI) films were also examined through molecular dynamics (MD) simulations in order to understand the stability of the SEI film. It was found that film produced from a decomposition of EC, modeled by Li-EDC, has a higher density, more cohesive energy, and less solubility to the solvent than the film produced from decomposition of PC, Li-PDC. Further, MD simulations of the interface between the decomposition compound and graphite suggested

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

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey P.

    2011-10-13

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

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

    SciTech Connect

    Liu, Bin; Greeley, Jeffrey

    2011-09-01

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

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

    PubMed

    Bhattacharya, A; Bernstein, E R

    2011-05-05

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  8. Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies.

    PubMed

    Khaliullin, Rustam Z; Kühne, Thomas D

    2013-10-14

    The application of newly developed first-principle modeling techniques to liquid water deepens our understanding of the microscopic origins of its unusual macroscopic properties and behaviour. Here, we review two novel ab initio computational methods: second-generation Car-Parrinello molecular dynamics and decomposition analysis based on absolutely localized molecular orbitals. We show that these two methods in combination not only enable ab initio molecular dynamics simulations on previously inaccessible time and length scales, but also provide unprecedented insights into the nature of hydrogen bonding between water molecules. We discuss recent applications of these methods to water clusters and bulk water.

  9. Time since death and decomposition of the human body: variables and observations in case and experimental field studies.

    PubMed

    Mann, R W; Bass, W M; Meadows, L

    1990-01-01

    Much of the difficulty in determining the time since death stems from the lack of systematic observation and research on the decomposition rate of the human body. Continuing studies conducted at the University of Tennessee, Knoxville, provide useful information on the impact of carrion insect activity, ambient temperature, rainfall, clothing, burial and depth, carnivores, bodily trauma, body weight, and the surface with which the body is in contact. This paper reports findings and observations accumulated during eight years of research and case studies that may clarify some of the questions concerning bodily decay.

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

    PubMed

    Rosenfield, C L; Loewus, F A

    1978-01-01

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

  11. Reactivation of model cholinesterases by oximes and intermediate phosphyloximes: a computational study.

    PubMed

    Vyas, Shubham; Hadad, Christopher M

    2008-09-25

    Phosphyloximes (POX) are generated upon the reactivation of organophosphorus (OP)-inhibited cholinesterases (ChEs) by pyridinium oximes. These POXs are known to be potent inhibitors of the ChEs following reactivation. However, they can also decompose to give an OP derivative and a cyano derivative of the oxime when a base abstracts the benzylic proton. Using density functional theory, thermodynamic properties were calculated for the reactivation and decomposition pathways of three different oximes (2-PAM, 3-PAM and 4-PAM) with six different OPs (cyclosarin, paraoxon, sarin, tabun, VR and VX). For reactivation purposes, 2-PAM is predicted to be more efficient than 3- and 4-PAM. Based on atomic charges and relative energies, 2-POXs were found to be more inclined towards the decomposition process.

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

    SciTech Connect

    Not Available

    1990-10-01

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

  13. Seasonal necrophagous insect community assembly during vertebrate carrion decomposition.

    PubMed

    Benbow, M E; Lewis, A J; Tomberlin, J K; Pechal, J L

    2013-03-01

    Necrophagous invertebrates have been documented to be a predominant driver of vertebrate carrion decomposition; however, very little is understood about the assembly of these communities both within and among seasons. The objective of this study was to evaluate the seasonal differences in insect taxa composition, richness, and diversity on carrion over decomposition with the intention that such data will be useful for refining error estimates in forensic entomology. Sus scrofa (L.) carcasses (n = 3-6, depending on season) were placed in a forested habitat near Xenia, OH, during spring, summer, autumn, and winter. Taxon richness varied substantially among seasons but was generally lower (1-2 taxa) during early decomposition and increased (3-8 taxa) through intermediate stages of decomposition. Autumn and winter showed the highest richness during late decomposition. Overall, taxon richness was higher during active decay for all seasons. While invertebrate community composition was generally consistent among seasons, the relative abundance of five taxa significantly differed across seasons, demonstrating different source communities for colonization depending on the time of year. There were significantly distinct necrophagous insect communities for each stage of decomposition, and between summer and autumn and summer and winter, but the communities were similar between autumn and winter. Calliphoridae represented significant indicator taxa for summer and autumn but replaced by Coleoptera during winter. Here we demonstrated substantial variability in necrophagous communities and assembly on carrion over decomposition and among seasons. Recognizing this variation has important consequences for forensic entomology and future efforts to provide error rates for estimates of the postmortem interval using arthropod succession data as evidence during criminal investigations.

  14. Introducing an integrated intermediate care unit improves ICU utilization: a prospective intervention study

    PubMed Central

    2014-01-01

    Background Improvement of appropriate bed use and access to intensive care (ICU) beds is essential in optimizing utilization of ICU capacity. The introduction of an intermediate care unit (IMC) integrated in the ICU care may improve this utilization. Method In a before-after prospective intervention study in a university hospital mixed ICU, the impact of introducing a six-bed mixed IMC unit supervised and staffed by ICU physicians was investigated. Changes in ICU utilization (length of stay, frequency of mechanical ventilation use), nursing workload assessed byTISS-28 score, as well as inappropriate bed use, accessibility of the ICU (number of referrals), and clinical outcome indicators (readmission and mortality rates) were measured. Results During 17 months, data of 1027 ICU patients were collected. ICU utilization improved significantly with an increased appropriate use of ICU beds. However, the number of referrals, readmissions to the ICU and mortality rates did not decrease after the IMC was opened. Conclusion The IMC contributed to a more appropriate use of ICU facilities and did result in a significant increase in mean nursing workload at the ICU. PMID:25276092

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

    NASA Astrophysics Data System (ADS)

    Maeda, Kensaku; Inaba, Hideo

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

  16. Long-lived Intermediates in Phytochrome Transformation I: In Vitro Studies.

    PubMed

    Briggs, W R

    1969-08-01

    Irradiation of phytochrome solutions with a high-intensity mixed red and far red light source causes measurable absorbancy increases at 543 nm. Evidence is presented that these absorbancy increases are caused by accumulation of intermediates on the P(R) to P(FR) pathway with relatively slow thermal decay constants. Kinetic analysis of the decay signals is consistent with the interpretation that the signals represent simultaneous independent and parallel decay of 2 species by first order kinetics to P(FR). If actinic light intensity is kept constant and exposure time changed, the relative amounts of the 2 components change, with proportionately more of the rapidly decaying species present following short exposure times. If the amount of the intermediates is decreased by decreasing actinic light intensity at constant exposure time, however, the relative amounts of the 2 remain constant. The Q(10) for intermediate decay following illumination is approximately 2.0, while that for complete phototransformation of the pigment in either direction is very close to 1.0. Incomplete transformation of P(R) to P(FR), caused by overlapping absorption of the 2 forms, is shown by the presence of intermediates (indicating cycling of the pigment) in continuous red light. Such intermediates do not appear in continuous far red, indicating a rate of pigment cycling below detection by the available instrumentation.

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

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

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

    SciTech Connect

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

    2013-01-01

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

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

    SciTech Connect

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

    2008-08-01

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

  1. Study of photovoltaic cost elements. Volume 5: Installation cost model for intermediate PV systems: Users manual

    NASA Astrophysics Data System (ADS)

    Ayers, J. B.

    1981-07-01

    A cost modeling methodology is presented for estimating installation costs associated with intermediate photovoltaic (PV) systems. With only a parametric description of an intermediate power system, the model can be used to develop an installation cost estimate for that system. The model is based on conventional cost-estimating procedures widely used by the construction industry and was validated by comparing estimates for the same 10 systems made independently by a cost engineering firm. A description of the model is included as well as an example of its use with a 200 KW solar breeder plant design to be located in Rockville, Maryland.

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

    SciTech Connect

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

    1988-07-26

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

  3. Changes in hospital costs after introducing an intermediate care unit: a comparative observational study

    PubMed Central

    Solberg, Barbara CJ; Dirksen, Carmen D; Nieman, Fred HM; van Merode, Godefridus; Poeze, Martijn; Ramsay, Graham

    2008-01-01

    Introduction The high cost of critical care resources has resulted in strategies to reduce the costs of ruling out low-risk patients by developing intermediate care units (IMCs). The aim of this study was to compare changes in total hospital costs for intensive care patients before and after the introduction of an IMC at the University Hospital Maastricht. Methods The design was a comparative longitudinal study. The setting was a university hospital with a mixed intensive care unit (ICU), an IMC, and general wards. Changes in total hospital costs were measured for patients who were admitted to the ICU before and after the introduction of the IMC. The comparison of interest was the opening of a six-bed mixed IMC. Results The mean total hospital cost per patient increased significantly. Before the introduction of the IMC, the total hospital cost per patient was €12,961 (± €14,530) and afterwards it rose to €16,513 (± €17,718). Multiple regression analysis was used to determine to what extent patient characteristics explained these higher hospital costs using mortality, type of stay, diagnostic categories, length of ICU and ward stay, and the Therapeutic Intervention Scoring System (TISS) as predictors. More surgical patients, greater requirements of therapeutic interventions on the ICU admission day, and longer ICU stay in patients did explain the increase in hospital costs, rather than the introduction of the IMC. Conclusion After the introduction of the IMC, the higher mean total hospital costs for patients with a high TISS score and longer ICU stay explained the cost increase. PMID:18482443

  4. The hagfish slime gland thread cell. I. A unique cellular system for the study of intermediate filaments and intermediate filament- microtubule interactions

    PubMed Central

    1984-01-01

    Thread cell differentiation in the slime gland of the Pacific hagfish Eptatretus stouti has been studied using light microscopy and scanning and transmission electron microscopy. Thread cell differentiation is remarkable in that the life history of the cell is largely dedicated to the production of a single, tapered, cylindrical, highly coiled, and precisely packaged cytoplasmic thread that may attain lengths of 60 cm and diameters approaching 1.5 micron. Each tapered thread, in turn, is comprised almost entirely of large numbers of intermediate filaments (IFs) bundled in parallel. During differentiation of the thread, the IFs become progressively more tightly packed. Various numbers of microtubules (MTs) are found among the bundled IFs during differentiation of the thread but disappear during the latter stages of thread differentiation. Observations of regularly spaced dots in longitudinal bisections of developing threads, diagonal striations in tangential sections of developing threads, and circumferentially oriented, filament-like structures observed at the periphery of developing threads cut in cross section have led us to postulate a helically oriented component(s) wrapped around the periphery of the developing thread. The enormous size of the fully differentiated thread cell, its apparent singular dedication to the production of IFs, the ease of isolating and purifying the threads and IF subunits (see accompanying paper), and the unique position of the hagfish in the phylogenetic scheme of vertebrate evolution all contribute to the attractiveness of the hagfish slime gland thread cell as a potential model system for studying IF subunit synthesis, IF formation from IF subunits, aggregation of IFs into IF bundles and the interaction(s) of IFs and MTs. PMID:6537952

  5. Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu(2+)metal ions within polytopic receptors.

    PubMed

    Castillo, Carmen Ester; González-García, Jorge; Llinares, José M; Máñez, M Angeles; Jimenez, Hermas R; García-España, Enrique; Basallote, Manuel G

    2013-05-07

    Potentiometric studies carried out on the interaction of two tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties are linked with 2,9-dimethylphenanthroline (L1) and 2,6-dimethylpyridine (L2) establish the formation of mono-, bi- and trinuclear Cu(2+) complexes. The values of the stability constants and paramagnetic (1)H NMR studies permit one to infer the most likely coordination modes of the various complexes formed. Kinetic studies on complex formation and decomposition have also been carried out. Complex formation occurs with polyphasic kinetics for both receptors, although a significant difference is found between both ligands with respect to the relative values of the rate constants for the metal coordination steps and the structural reorganizations following them. Complex decomposition occurs with two separate kinetic steps, the first one being so fast that it occurs within the stopped-flow mixing time, whereas the second one is slow enough to allow kinetic studies using a conventional spectrophotometer. As a whole, the kinetic experiments also provide information about the movement of the metal ion within the receptors. The differences observed between the different receptors can be interpreted in terms of changes in the network of hydrogen bonds formed in the different species.

  6. Photoinduced decomposition of trichloroethylene in soil components

    SciTech Connect

    Tao, T.; Yang, J.J.; Maciel, G.E.

    1999-01-01

    The photoinduced decomposition of trichloroethylene adsorbed on Ca-montmorillonite by long-wavelength UV irradiation has been studied in a quartz tube open to air or through which air or oxygen is passed. Solid-sample and liquid-solution NMR techniques were used to identify apparent products or intermediates of the photodecomposition. Dichloroacetic acid was identified as a major organic product/intermediate; substantial amounts of pentachloroethane and trichloroacetic acid were also identified. The formation of CO{sub 2} was characterized quantitatively by wet chemical analysis. About 40% and 57%, respectively, of the total carbon of trichloroethylene was converted to carbon dioxide in air and O{sub 2} environments over a period of 16 days. Phosgene and HCl were also detected. The photodecomposition of trichloroethylene adsorbed on whole soil, on Zn{sup 2+}-exchanged and Cu{sup 2+}-exchanged montmorillonites, on kaolinite, and on silica gel was also examined in less detail; qualitatively, the conversion of trichloroethylene to dichloroacetic acid in a 48-h period occurred with the following order of decreasing efficiencies: Zn{sup 2+}-montmorillonite > silica gel > kaolinite > Ca{sup 2+}-montmorillonite > whole soil > Cu{sup 2+}-montmorillonite. These results show that the photoinduced decomposition of adsorbed trichloroethylene occurs on a variety of adsorbents, generating products and intermediates that are similar to what have been reported previously for TiO{sub 2}-based photodecomposition but with much longer time scales. These conversions can, therefore, be expected to occur in sunlight at the air-soil interface.

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

    ERIC Educational Resources Information Center

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

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

  8. A Comparative Study of EFL Teachers' and Intermediate High School Students' Perceptions of Written Corrective Feedback on Grammatical Errors

    ERIC Educational Resources Information Center

    Jodaie, Mina; Farrokhi, Farahman; Zoghi, Masoud

    2011-01-01

    This study was an attempt to compare EFL teachers' and intermediate high school students' perceptions of written corrective feedback on grammatical errors and also to specify their reasons for choosing comprehensive or selective feedback and some feedback strategies over some others. To collect the required data, the student version of…

  9. A Study of the Measured Readability Level of Selected Intermediate Grade Social Studies Textbooks.

    ERIC Educational Resources Information Center

    DuVall, Charles R.

    It was the purpose of this study to determine the readability level of all social studies textbooks authorized for purchase in the adoption made by the Textbook Commission of the Indiana State Board of Education on December 12, 1968 for five years beginning July 1, 1969. A thorough search of the literature and research did not reveal that their…

  10. A study on forward scattering Mueller matrix decomposition in anisotropic medium.

    PubMed

    Guo, Yihong; Zeng, Nan; He, Honghui; Yun, Tianliang; Du, E; Liao, Ran; He, Yonghong; Ma, Hui

    2013-07-29

    In this work, we apply Mueller matrix polar decomposition (MMPD) method in a forward scattering configuration on anisotropic scattering samples and look for the physics origin of depolarization and retardance. Using Monte Carlo simulations on the sphere-cylinder birefringence model (SCBM), and forward scattering experiments on samples containing polystyrene microspheres, well-aligned glass fibers and polyacrylamide, we examine in detail the relationship between the MMPD parameters and the microscopic structure of the samples. The results show that the spherical scatterers and birefringent medium contribute to depolarization and retardance respectively, but the cylindrical scatterers contribute to both. Retardance due to the cylindrical scatterers changes with their density, size and order of alignment. Total retardance is a simple sum of both contributions when cylinders are in parallel to the extraordinary axis of birefringence.

  11. Study of the continuous internal bremsstrahlung spectrum from (204)Tl by using singular value decomposition.

    PubMed

    Almaz, Ekrem

    2015-05-01

    Internal bremsstrahlung (IB) accompanying the β(-) decay of (204)Tl was measured using a 5.08×5.08cm(2) NaI(Tl) detector employing a magnetic deflection method in the range of 10-760keV. A novel approach, the Singular Value Decomposition (SVD), is applied to unfold the raw detector spectrum of (204)Tl. Unfolded IB spectrum is compared with the KUB theory. The measured spectrum is found to show fairly good agreement with the KUB theory in the energy range of 100-600keV. The distribution beyond the 600keV takes a positive deviation from the theory. Copyright © 2015. Published by Elsevier Ltd.

  12. Planning-Programming-Budgeting System. Intermediate Unit Planning Study. Final Report.

    ERIC Educational Resources Information Center

    Montgomery County School Board, Norristown, PA.

    In 1965-66 most local school districts in Pennsylvania completed reorganization by consolidating 67 county school offices into 25 or 30 intermediate administrative units. This document presents the results of various task group activities and projected activities to develop a "generalized" educational planning, programing, budgeting…

  13. Statistical evaluation of test accuracy studies for Toxoplasma gondii in food animal intermediate hosts

    USDA-ARS?s Scientific Manuscript database

    The availability of accurate diagnostic tests is essential for the detection and control of Toxoplasma gondii infections in both definitive and intermediate hosts. Sensitivity, specificity and the area under the receiver-operating characteristic (ROC) curve are commonly-used measures of test accura...

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

    PubMed

    Ou, Tai-You; Wang, Gen-Shuh

    2016-05-01

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

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

    SciTech Connect

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

    2012-02-01

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

  16. A comparative study between Empirical Wavelet Transforms and Empirical Mode Decomposition Methods: Application to bearing defect diagnosis

    NASA Astrophysics Data System (ADS)

    Kedadouche, M.; Thomas, M.; Tahan, A.

    2016-12-01

    The Ensemble Empirical Mode Decomposition (EEMD) is a noise assisted method that may sometimes provide a significant improvement on Empirical Mode Decomposition (EMD). However, the amplitude and number of added noise need to be selected when applying the EEMD method. Furthermore, the computation time which depends on the number of ensemble trails is very high compared to the EMD. In this paper, a new way for choosing the appropriate added noise is presented. Conversely, a recently-developed method called the Empirical Wavelet Transform (EWT) is investigated. A comparative study between the EMD and EWT methods is conducted. The results show that the EWT is better than the EEMD and EMD on mode estimates and computation time is significantly reduced. An experimental study on bearing diagnosis is conducted. The EWT is applied to experimental data coming from damaged bearings. In the paper, an index selection is introduced that allows for the automatic selection of the Intrinsic Mode Functions (IMF) that should be used to perform the envelope spectrum. It is shown that choosing all the IMF selected by the index is more efficient than only choosing the best one. The envelope of the sum of the selected IMF clearly reveals the bearing frequencies and its harmonics which are excited by the defect. This approach seems to be an effective and efficient method for processing bearing fault signals.

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

    PubMed

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

    2016-01-01

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

  18. The use of the magnetic field effect for studying a chemiluminescent chemical reaction in aqueous solution. Reaction rate constants and lifetimes of intermediate molecules

    NASA Astrophysics Data System (ADS)

    Triebel, Michael M.; Totrov, Maxim M.; Zorinyants, George E.; Frankevich, Eugene L.

    1993-11-01

    The phase shift magnetic field effect technique is applied for investigation of the chemiluminescent (ChL) reaction of luminol oxidation by potassium ferricyanide in aqueous alkali solution. The external modulated magnetic field changed the rate constant of recombination of luminol radicals. Rate constants of intermediate stages of the reaction are obtained: 10 8 M -1 s -1 for diazaquinone reaction with hydrogen peroxide, 2 X 10 6 M -1 s -1 for diazaquinone hydrolysis and 2 X 10 5 s -1 for the decomposition of hydroperoxide, which is a precursor of the light emitter.

  19. Decomposition of methanol on oxygen-modified Fe(100) surfaces. II. Preadsorbed oxygen as poison, selectivity modifier and promoter

    NASA Astrophysics Data System (ADS)

    Lu, Jiong-Ping; Albert, Mark; Bernasek, Steven L.; Dwyer, Daniel J.

    1990-12-01

    Decomposition of methanol (CH 3OH) on the Fe(100) surface modified by low temperature adsorption of oxygen has been studied, using high resolution electron energy loss spectroscopy (HREELS) and temperature programmed reaction spectroscopy (TPRS). Fe(100) surfaces studied were modified by adsorption of O 2 at 113 K, and methanol decomposition as a function of oxygen coverage was monitored. The effect of pre-heating the oxygen overlayers on the methanol decomposition was also examined. Decomposition of methanol on these O-modified surfaces passes through a methoxy (-OCH 3) intermediate. The thermal stability of methoxy increases in the presence of pre-adsorbed oxygen. At low coverage, atomic oxygen occupies four-fold hollow sites. In this case, the effect of oxygen on the methanol decomposition is similar to that observed previously on the annealed O-modified surfaces. At higher oxygen coverage, a more weakly bound non-hollow site oxygen also exists on the surface, which reacts with hydroxyl (-OH) hydrogen of the CH 3OH, promoting the formation of methoxy. At high oxygen coverage (close to saturation coverage at 113 K), decomposition of methanol results in the formation of formaldehyde (H 2CO), without production of carbon monoxide (CO). This is very different from the decomposition of methanol on the clean Fe(100) surface, where decomposition leads to the formation of CO without H 2CO. The effect of oxygen modification is discussed in terms of changing relative probabilities of competing reaction pathways.

  20. First-principles study of electric field effects on the structure, decomposition mechanism, and stability of crystalline lead styphnate.

    PubMed

    Li, Zhimin; Huang, Huisheng; Zhang, Tonglai; Zhang, Shengtao; Zhang, Jianguo; Yang, Li

    2014-01-01

    The electric field effects on the structure, decomposition mechanism, and stability of crystalline lead styphnate have been studied using density functional theory. The results indicate that the influence of external electric field on the crystal structure is anisotropic. The electric field effects on the distance of the Pb-O ionic interactions are stronger than those on the covalent interactions. However, the changes of most structural parameters are not monotonically dependent on the increased electric field. This reveals that lead styphnate can undergo a phase transition upon the external electric field. When the applied field is increased to 0.003 a.u., the effective band gap and total density of states vary evidently. And the Franz-Keldysh effect yields larger influence on the band gap than the structural change induced by external electric field. Furthermore, lead styphnate has different initial decomposition reactions in the presence and absence of the electric field. Finally, we find that its sensitivity becomes more and more sensitive with the increasing electric field.

  1. Adsorption and decomposition of dimethyl methylphosphonate on pristine and mono-vacancy defected graphene: A first principles study

    NASA Astrophysics Data System (ADS)

    Majumder, Chiranjib

    2017-10-01

    Here we report the adsorption and decomposition behavior of dimethyl methyl-phosphonate (DMMP) on pristine and defected graphene using the first principles theory. The primary objective of this study is to highlight the importance of a vacancy defect on the adsorption mechanism of a molecule. In order to account for the weak forces involved between the molecule and graphene, we have used dispersion corrected total energy calculations along with generalized gradient approximation scheme for the exchange correlation energy. Among various possible configurations, the most stable geometry shows oxygen atom of the DMMP molecule favors to be close to the surface plane and bind with one of the unsaturated carbon atoms at the defect site. The molecule-substrate interaction energy is stronger for defected graphene than pristine graphene. The decomposition of the DMMP molecule at the vacancy site of the defected graphene has been investigated. For the dissociative adsorption, it is seen that the Csbnd H bond of the DMMP breaks and H atom is transferred to one of the low-coordinated C-atoms at the vicinity of the defect, forming new Csbnd H bond. In addition, the Csbnd C bond formation between graphene and DMMP occurs. Finally, the nature of bonding and electronic structure at the interface was interpreted through site projected electronic density of states analysis.

  2. Topological study of the late steps of the artemisinin decomposition process: modeling the outcome of the experimentally obtained products.

    PubMed

    Moles, Pamela; Oliva, Mónica; Safont, Vicent S

    2011-01-20

    By using 6,7,8-trioxabicyclo[3.2.2]nonane as the artemisinin model and dihydrated Fe(OH)(2) as the heme model, we report a theoretical study of the late steps of the artemisinin decomposition process. The study offers two viewpoints: first, the energetic and geometric parameters are obtained and analyzed, and hence, different reaction paths have been studied. The second point of view uses the electron localization function (ELF) and the atoms in molecules (AIM) methodology, to conduct a complete topological study of such steps. The MO analysis together with the spin density description has also been used. The obtained results agree nicely with the experimental data, and a new mechanistic proposal that explains the experimentally determined outcome of deoxiartemisinin has been postulated.

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Rajesh, H. M.

    2007-11-01

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

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

    SciTech Connect

    Hoffman, M.Z.

    1991-12-31

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

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

    PubMed

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

    2016-09-28

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

  7. Job Knowledge Testing as an Intermediate Criterion of Performance. A Study of US Navy Cooks

    DTIC Science & Technology

    1976-06-01

    Brooks Air Force Base, Texas, Feb. 1972. Tiffin, J. -Industrial psychology . New York: Prentice-Hall, 1952. Thorndike , R.L. Personnel selection...Payg.rade and JKT Performance D. Watch Captains vs. Subordinates . E. Education . . . F. Formal Training G. Formal vs. Correspondence Training...intermediate, and ultimate. ( Thorndike , 1949; Foley, 1974). Immediate measures are generally those which Siegel, A.I., Bergman, B.A., Federman, P

  8. Results of the general toxicity and genetic studies of an insecticide intermediate.

    PubMed

    Béres, E; Pasics, I; Pap, L; Hirka, G; Sebestyén, I; Oláh, B; Stáhl, J

    2000-07-01

    Methyl-chrysanthemate is one of the intermediates of pyrethroid type insecticides. The acute toxicity of the test item was investigated in rats after single oral, dermal and inhalation applications. The irritation effect was determined by Draize method. Buehler method was applied to evaluate the sensitization potential of the test item. The mutagenic effect was assessed on Salmonella typhimurium strains. Furthermore metaphase chromosome aberration assay was performed on CHO cell line to check the structural chromosome aberrations.

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

    PubMed

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

    2016-08-04

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

  10. [New integrated care model for older people admitted to Intermediate Care Units in Catalonia: A quasi-experimental study protocol].

    PubMed

    Santaeugènia, Sebastià J; García-Lázaro, Manuela; Alventosa, Ana María; Gutiérrez-Benito, Alícia; Monterde, Albert; Cunill, Joan

    To evaluate the clinical effectiveness of an intermediate care model based on a system of care focused on integrated care pathways compared to the traditional model of geriatric care (usual care) in Catalonia. The design is a quasi-experimental pre-post non-randomised study with non-synchronous control group. The intervention consists of the development and implementation of integrated care pathways and the creation of specialised interdisciplinary teams in each of the processes. The two groups will be compared for demographic, clinical variables on admission and discharge, geriatric syndromes, and use of resources. This quasi-experimental study, aims to assess the clinical impact of the transformation of a traditional model of geriatric care to an intermediate care model in an integrated healthcare organisation. It is believed that the results of this study may be useful for future randomised controlled studies. Copyright © 2016 SEGG. Publicado por Elsevier España, S.L.U. All rights reserved.

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

    PubMed

    Shimizu, Kazuo; Kuwabara, Tomoya; Blajan, Marius

    2012-10-29

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

  12. Thermal decomposition study of Mn doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  13. Ethylene decomposition over Pt(100): A mechanism study from first principle calculation

    NASA Astrophysics Data System (ADS)

    Wang, Yuchun; Dong, Xiuqin; Yu, Yingzhe; Zhang, Minhua

    2016-12-01

    First principle based density functional theory was used to calculate the complete step-by-step decomposition network of ethylene (C2H4) over Pt(100) as a model for understanding the carbon deposition of olefin hydrocarbon over transition metal surface. We discussed the structural and energetic properties of all the Csbnd H and Csbnd C bond cleavage reactions in order to fully understand the formation pathway of carbon monomer. It is easier for Csbnd H bond cleavage reactions to take place, as the activation barrier of these reactions is relatively lower than that of Csbnd C bond cleavage as a whole. However, vinyl (CH2CH) is likely to be the precursor of Csbnd C bond scission, as the activation barrier of Csbnd C bond cleavage reaction of CH2CH is much lower than that of CH2CH dehydrogenation and the reaction is exothermic by 0.15 eV. CC was another form of depositional carbon on Pt(100), as it is easy to form but difficult to decompose. Finally we proposed six possible routes of carbon monomer formation.

  14. An ab initio study of the photochemical decomposition of 3, 3-dimethyldiazirine

    PubMed

    Bernardi; Olivucci; Robb; Vreven; Soto

    2000-11-17

    Photochemical decomposition of 3,3-dimethyldiazirine (DMD) has been computationally investigated by using high-level ab initio calculations in conjunction with the 6-31G and cc-pvdz basis sets. The geometries of minima and transition states, as well as conical intersection points in the seam of crossing of two surfaces, have been optimized with the complete active space self-consistent field (CAS-SCF) method, and their energies, recalculated with second-order multireference perturbation (CAS/MP2) theory. The reaction path starting at the excited n-pi state of DMD is predicted to occur via a nonadiabatic mechanism, giving carbene and molecular dinitrogen (both in their singlet ground states) as the main products; the computed barrier height (1.0 kcal mol(-)(1)) agrees well with the experimental estimate of the activation energy in the singlet excited state (0.0-1.5 kcal mol(-)(1)). Ground state of dimethylcarbene is the only species where a 1,2-hydrogen shift takes place, being the only source of propene. The calculated potential energy barrier height for dimethylcarbene to propene isomerization (2.6 kcal mol(-)(1)) agrees well with the observed activation energy (2.56 kcal mol(-)(1)). No evidence for rearrangement in the first singlet excited state of DMD has been found; such a process would lead to a higher activation energy than the observed one. Consequently, 1,2-hydrogen migration concurrent with N(2) extrusion in the excited state has been ruled out.

  15. Imaging, chemical and spectroscopic studies of the methylation-induced decomposition of melanosomes.

    PubMed

    Kempf, Valerie R; Wakamatsu, Kazumasa; Ito, Shosuke; Simon, John D

    2010-01-01

    The morphological and chemical changes associated with the exposure of melanosomes to methyl iodide are assessed by a variety of analytical, imaging and spectroscopic methods. Scanning electron microscopy, light scattering and N(2) adsorption measurements all indicate significant changes in the morphology of the pigment following methylation. Solid-state nuclear magnetic resonance (SS-NMR) spectroscopy and chemical degradation analysis reveals the methylation results in the introduction of ester groups into the pigment structures. Amino acid analysis further reveals that Arg, Cys, His, Ser and Tyr undergo methylation; the SS-NMR data provide additional evidence for the methylation of the sulfur of Cys. Methylation results in increased solubility of the melanosome; the absorption properties of the dissolved material are characterized by an absorption maximum at 225 nm, with a long tail throughout the UV-A and UV-B, indicating that the solubilized material is a combination of protein and pigment. The methylation-induced decomposition of the melanosomes provides new insights into both the observed increase in O-methyl derivatives of the indolic precursor to eumelanin in the urine of melanoma patients and how increased levels of biologic methylating agents in the brain induce symptoms that resemble Parkinson's disease.

  16. Water/cortical bone decomposition: A new approach in dual energy CT imaging for bone marrow oedema detection. A feasibility study.

    PubMed

    Biondi, M; Vanzi, E; De Otto, G; Banci Buonamici, F; Belmonte, G M; Mazzoni, L N; Guasti, A; Carbone, S F; Mazzei, M A; La Penna, A; Foderà, E; Guerreri, D; Maiolino, A; Volterrani, L

    2016-12-01

    Many studies aimed at validating the application of Dual Energy Computed Tomography (DECT) in clinical practice where conventional CT is not exhaustive. An example is given by bone marrow oedema detection, in which DECT based on water/calcium (W/Ca) decomposition was applied. In this paper a new DECT approach, based on water/cortical bone (W/CB) decomposition, was investigated. Eight patients suffering from marrow oedema were scanned with MRI and DECT. Two-materials density decomposition was performed in ROIs corresponding to normal bone marrow and oedema. These regions were drawn on DECT images using MRI informations. Both W/Ca and W/CB were considered as material basis. Scatter plots of W/Ca and W/CB concentrations were made for each ROI in order to evaluate if oedema could be distinguished from normal bone marrow. Thresholds were defined on the scatter plots in order to produce DECT images where oedema regions were highlighted through color maps. The agreement between these images and MR was scored by two expert radiologists. For all the patients, the best scores were obtained using W/CB density decomposition. In all cases, DECT color map images based on W/CB decomposition showed better agreement with MR in bone marrow oedema identification with respect to W/Ca decomposition. This result encourages further studies in order to evaluate if DECT based on W/CB decomposition could be an alternative technique to MR, which would be important when short scanning duration is relevant, as in the case of aged or traumatic patients. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  17. Shock tube and theoretical studies on the thermal decomposition of propane: evidence for a roaming radical channel.

    PubMed

    Sivaramakrishnan, R; Su, M-C; Michael, J V; Klippenstein, S J; Harding, L B; Ruscic, B

    2011-04-21

    The thermal decomposition of propane has been studied using both shock tube experiments and ab initio transition state theory-based master equation calculations. Dissociation rate constants for propane have been measured at high temperatures behind reflected shock waves using high-sensitivity H-ARAS detection and CH(3) optical absorption. The two major dissociation channels at high temperature are C(3)H(8) → CH(3) + C(2)H(5) (eq 1a) and C(3)H(8) → CH(4) + C(2)H(4) (eq 1b). Ultra high-sensitivity ARAS detection of H-atoms produced from the decomposition of the product, C(2)H(5), in (1a), allowed measurements of both the total decomposition rate constants, k(total), and the branching to radical products, k(1a)/k(total). Theoretical analyses indicate that the molecular products are formed exclusively through the roaming radical mechanism and that radical products are formed exclusively through channel 1a. The experiments were performed over the temperature range 1417-1819 K and gave a minor contribution of (10 ± 8%) due to roaming. A multipass CH(3) absorption diagnostic using a Zn resonance lamp was also developed and characterized in this work using the thermal decomposition of CH(3)I as a reference reaction. The measured rate constants for CH(3)I decomposition agreed with earlier determinations from this laboratory that were based on I-atom ARAS measurements. This CH(3) diagnostic was then used to detect radicals from channel 1a allowing lower temperature (1202-1543 K) measurements of k(1a) to be determined. Variable reaction coordinate-transition state theory was used to predict the high pressure limits for channel (1a) and other bond fission reactions in C(3)H(8). Conventional transition state theory calculations were also used to estimate rate constants for other tight transition state processes. These calculations predict a negligible contribution (<1%) from all other bond fission and tight transition state processes, indicating that the bond fission

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

    PubMed

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

    2015-07-16

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

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

    SciTech Connect

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

    2015-01-01

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

  20. Calorimetric study on the decomposition of hydroxylamine in the presence of transition metals.

    PubMed

    Kumasaki, Mieko

    2004-11-11

    Hydroxylamine (HA), hydroxylamine chloride (HAC1), and hydroxylamine nitrate (HAN) were each mixed with aqueous solutions of Cr3+, Cr6+, Mn7+, Co2+, Co3+, and Cu2+, and their heat flow profiles were monitored by a small-scaled reaction calorimeter, SuperCRC. These mixing tests demonstrated that HA was less reactive than HACl and HAN with Mn7+ and Cr6+. Their UV-vis spectra confirmed that the substrates reacted when Mn7+ and Cr6+ were reduced. HA was more reactive with Cu2+ than HAC1 and HAN and exhibited the highest reactivity among the three substrates with regard to metals in the intermediate oxidation states: Cr3+, Co3+, and Co2+. During the reaction of HA and Co3+, an induction period was observed. All exothermic reactions were accompanied by precipitation or a change in the UV-vis spectra.

  1. 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.

  2. Perfluoropolyalkylether decomposition on catalytic aluminas

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1994-01-01

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

  3. Decomposition in northern Minnesota peatlands

    SciTech Connect

    Farrish, K.W.

    1985-01-01

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

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

    ERIC Educational Resources Information Center

    Man, Yiu-Kwong

    2012-01-01

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

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

    ERIC Educational Resources Information Center

    Man, Yiu-Kwong

    2012-01-01

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

  6. Studies towards simalikalactone D and quassimarin: construction of an advanced pentacyclic intermediate.

    PubMed

    Shing, Tony K M; Zhu, Xue Y; Yeung, Yeung Y

    2003-11-21

    An advanced pentacyclic intermediate, amenable to further elaboration into the target molecules simalikalactone D and quassimarin, has been synthesized from (S)-(+)-carvone in 21 steps and with an overall yield of 12 %. The synthesis is efficient, stereocontrolled, enantiospecific, and chirality productive, creating eight new chiral centres in pentacycle, and should provide opportunities for rapid access to simalikalactone D analogues and other bioactive quassinoids. The reaction sequence involves a regioselective bishydroxylmethylation, a stereocontrolled epoxidation, an epoxymethano-bridge formation, a 1,3-sigmatropic rearrangement and an intramolecular Diels-Alder reaction as the key steps.

  7. Modeling the decomposition mechanism of artemisinin.

    PubMed

    Moles, Pamela; Oliva, Mónica; Safont, Vicent S

    2006-06-08

    A theoretical study on artemisinin decomposition mechanisms is reported. The calculations have been done at the HF/3-21G and B3LYP/6-31G(d,p) theoretical levels, by using 6,7,8-trioxybicyclo[3.2.2]nonane as the molecular model for artemisinin, and a hydrogen atom, modeling the single electron transfer from heme or Fe(II) in the highly acidic parasite's food vacuole, as inductor of the initial peroxide bond cleavage. All relevant stationary points have been characterized, and the appearance of the final products can be explained in a satisfactory way. Several intermediates and radicals have been found as relatively stable species, thus giving support to the current hypothesis that some of these species can be responsible for the antimalarial action of artemisinin and its derivatives.

  8. Reef Reservoir Identification by Wavelet Decomposition and Reconstruction: A Case Study from Yuanba Gas Field in China

    NASA Astrophysics Data System (ADS)

    Cheng, Bingjie; Xu, Tianji; Robbins, Benedict; Shen, ZhongMing

    2015-08-01

    The organic reef is a special type of carbonate reservoir which always dominates the spatial distribution, reserves and accumulations of natural gas. However, it is difficult to determine the organic reef's internal structure and gas reservoirs due to numerous adverse factors such as the low resolution of seismic data, depth of burial, strong anisotropy, irregular spatial distribution and complex internal structure. A case study of wavelet decomposition and reconstruction technology applied to elucidate the features of organic reef reservoirs in the Changxing formation from Yuanba gas field shows that the seismic record reconstructed by high frequency signal can adequately describe the internal properties of organic reef reservoirs. Furthermore, the root mean square amplitude ratio of both low and high frequency data obtained from the reconstructed seismic data clearly show spatial distribution of gas and water in reef reservoirs.

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

    PubMed

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Kulkarni, Sudhir A.; Pundlik, Savita S.

    1995-10-01

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

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

    SciTech Connect

    Not Available

    1988-01-01

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

  12. A study of intermediate lobe differentiation in the human pituitary gland.

    PubMed

    McNicol, A M

    1986-11-01

    The immunohistochemical demonstration of neurofilament (NF) polypeptide was used to identify nerves in a series of 17 pituitary adenomas. NF-positive fibres were present in two out of five corticotroph adenomas sited deep in the anterior lobe, in one out of five sited in the intermediate zone and in two out of seven non-corticotroph adenomas. Such nerve fibres were often seen in relation to blood vessels. The distribution of alpha-MSH immunoreactive cells was examined in 25 normal pituitaries and in 23 cases of Cushing's disease. Such cells were scattered throughout the normal gland and there was no increase in numbers in pregnancy. alpha-MSH was demonstrated in 18 corticotroph adenomas in Cushing's disease. There was no correlation with the site of the tumour or the presence of nerve fibres. alpha-MSH cells were distributed normally in the para-adenomatous gland. Crooke's hyaline change and alpha-MSH coexisted in some corticotrophs. These findings support the concept that 'intermediate lobe' function, as found in animals, has no discrete anatomical location in man.

  13. Simulation study of InGaN intermediate-band solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Kuo-Feng; Hung, Chien-Lun; Tsai, Yao-Lung

    2016-12-01

    The performances of single-junction InGaN solar cells with various intermediate bands (IBs) have been simulated using the lifetime model of a 1D simulation program called Analysis of Microelectronic and Photonic Structures (AMPS-1D). It has been observed that the maximum efficiencies of the InGaN solar cells with one, two and three intermediate bands are 47.72%, 55.10% and 58.20%, respectively, which outperform the 25.96% efficiency of the conventional single-junction structure by far. This is primarily attributed to the outstanding capability of the light harvesting from the sub-bandgap absorption. At the optimized bandgap of 2.41 eV, two-IB InGaN solar cells with the IB positions located at 0.95-1.1 eV and 0.3-0.75 eV, respectively, may have an opportunity to realize over 50% efficiency.

  14. Genetic and intermediate phenotypic susceptibility markers of gastric cancer in Hispanic Americans: a case-control study.

    PubMed

    Sun, Yuhui; Gu, Jian; Ajani, Jaffer A; Chang, David W; Wu, Xifeng; Stroehlein, John R

    2014-10-01

    Hispanics are the largest nonwhite ethnic group in the US population, and they have higher incidence and mortality rates for gastric cancer (GC) than whites and Asians. Studies have identified several genetic susceptibility loci and intermediate phenotypic biomarkers for GC in whites and Asians. No studies have evaluated genetic susceptibility and intermediate phenotypic biomarkers in Hispanics. In a case-control study of 132 Hispanic patients with GC (cases) and a control group of 125 Hispanics (controls), the authors evaluated the association of 5 single nucleotide polymorphisms (SNPs) that predispose whites and/or Asians to GC and of 2 intermediate phenotypic markers in peripheral blood leukocytes, ie, telomere length and mitochondrial DNA (mtDNA) copy number, with the GC risk. The variant C allele of the reference SNP rs2294008 in the PSCA gene was associated with a significantly reduced risk of GC (per allele-adjusted odds ratio [aOR], 0.51; 95% confidence interval [CI], 0.33-0.77; P = .002). Leukocyte mtDNA copy numbers were significantly lower in GC cases (mean ± standard deviation, 0.91 ± 0.28) than in controls (1.29 ± 0.42; P < .001). When individuals were dichotomized into high and low mtDNA copy number groups based on the median mtDNA copy number value in the controls, those who had a low mtDNA copy number had a significantly increased risk of GC (aOR, 11.00; 95% CI, 4.79-25.23; P < .001) compared with those who had a high mtDNA copy number. Telomere length was not associated significantly with the risk of GC (aOR, 1.21; 95% CI, 0.65-2.27; P = .551). Hispanics share certain genetic susceptibility loci and intermediate phenotypic GC biomarkers with whites and Asians and may also have distinct genetic susceptibility factors. © 2014 American Cancer Society.

  15. Microstructure evolution during the isostructural decomposition of TiAlN—A combined in-situ small angle x-ray scattering and phase field study

    NASA Astrophysics Data System (ADS)

    Knutsson, A.; Ullbrand, J.; Rogström, L.; Norrby, N.; Johnson, L. J. S.; Hultman, L.; Almer, J.; Johansson Jöesaar, M. P.; Jansson, B.; Odén, M.

    2013-06-01

    This paper describes details of the spinodal decomposition and coarsening in metastable cubic Ti0.33Al0.67N and Ti0.50Al0.50N coatings during isothermal annealing, studied by in-situ small angle x-ray scattering, in combination with phase field simulations. We show that the isostructural decomposition occurs in two stages. During the initial stage, spinodal decomposition, of the Ti0.50Al0.50N alloy, the phase separation proceeds with a constant compositional wavelength of ˜2.8 nm of the AlN- and TiN-rich domains. The time for spinodal decomposition depends on annealing temperature as well as alloy composition. After the spinodal decomposition, the coherent cubic AlN- and TiN-rich domains coarsen. The coarsening rate is kinetically limited by diffusion, which allowed us to estimate the diffusivity and activation energy of the metals to 1.4 × 10-6 m2 s-1 and 3.14 eV at-1, respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Micro Raman spectroscopy was applied to investigate the speciation of heteropoly and isopoly molybdates in 0.05 and 0.005 M aqueous solutions of 12-molybdophosphoric acid at pH values between 1 and 6. For comparative purposes, 31P NMR spectroscopy was applied too. It is shown that stability of Keggin anion is influenced both by pH and concentration of solution. The Keggin structure is stable in acidic solutions (pH < 1.6) while defective Keggin structures are formed with further alkalization (up to pH 5.6). Monolacunary anion PMo11O397 - is the main component in the pH region from 1.6 to 3.4. Further removal of molybdenyl species causes the appearance of other vacant Keggin structures such as PMo9O31(OH)36 - and PMo6O259 - at about pH 4. At pH 5.0, anion PMo6O259 - is the main species. In solutions with pH greater than 5.0, heteropolymolybdates disappear completely and isopolymolybdates Mo7O246 - and MoO42 - are formed in higher amounts. In more diluted solution of 0.005 M, the decomposition scheme of 12-molybdophosphoric acid solution with increasing of pH takes place without observation of significant amounts of Mo7O246 - species. If alkalinization is performed with 0.5 M instead of 5 M NaOH, there are no significant changes in the Raman spectra of solutions. It is shown that the spectra of evaporated samples may be used for the identification of molecular species in corresponding concentrated solutions. However, Raman spectra of dry residues of more diluted solutions differ from spectra of corresponding solutions due to the reactions performed during the process of drying and cannot be used for unambiguous identification of species in solution. Acidification of 0.05 M solution of Na2MoO4 shows that at pH > 5.6, molybdate anion MoO42 - dominates, while in the pH range between 5.6 and 1, heptamolybdate anion Mo7O246 - is preferentially formed.

  17. Schumann Resonance spectra decomposition method and studies of the locations of the African thunderstorm centres

    NASA Astrophysics Data System (ADS)

    Dyrda, Michal; Kulak, Andrzej; Mlynarczyk, Janusz; Ostrowski, Michal; Kubisz, Jerzy; Michalec, Adam; Nieckarz, Zenon

    2014-05-01

    The idea, that the global atmospheric electric circuit is driven by global lightning activity was introduced at the beginning of the last century. Today, the different observational methods are used from satellites to the radio observations performed in the extremely low frequency (ELF) range to evaluate local as well as global lightning activity, its spatial and temporal variability and influence on our planet and Earth's climate. The ground-based thunderstorms observations, particularly ELF, also allow the measurements of the dipole moment of discharges. Global lightning activity excites the Earth-ionosphere cavity and the produced electromagnetic radiation is responsible for generating the Schumann resonance (SR). The interaction of the standing and travelling waves leads to asymmetric shape of the observational SR power spectra picks, which was noticed by Kułak et al. (2006). They proposed a spectral decomposition method, what allows to separate the resonant field from the travelling wave contribution, which can be dominant at small distances from the sources. In such approach, one can apply the inverse problem solution for determining a distance of the dominant signal source. The distances to the thunderstorm centres are calculated using the numerical as well as the analytical models for the electromagnetic waves propagation in the Earth-ionosphere cavity. The ELF electromagnetic waves, recorded by Hylaty ELF station, located in South-East of Poland are used to derive the distances to the most powerful thunderstorm centres located in Africa and hence to obtain 1-D thunderstorm lightning activity maps. The observational data taken in January and August 2011 were binned in 10 minute intervals and SR power spectra were derived. Then a curve describing seven asymmetric SR maxima was fitted to the spectrum for each time interval. We use chi-squared test to compare the resulted decomposed power spectra with curves obtained within the considered numerical and

  18. Kinetic Intermediates of Holo- and Apo-Myoglobin Studied Using HDX-TIMS-MS and Molecular Dynamic Simulations

    NASA Astrophysics Data System (ADS)

    Schenk, Emily R.; Almeida, Raybel; Miksovska, Jaroslava; Ridgeway, Mark E.; Park, Melvin A.; Fernandez-Lima, Francisco

    2015-04-01

    In the present work, the kinetic intermediates of holo- and apo-myoglobin were studied by correlating the ion-neutral collision cross section and time resolved H/D back exchange rate simultaneously in a trapped ion mobility spectrometer coupled to a mass spectrometer (HDX-TIMS-MS). The high mobility resolution of the TIMS cell permitted the observation of multiple IMS bands and complementary molecular dynamics simulations resulted in the assignment of candidate structures for each experimental condition studied (e.g., holo [M + 8H]+8-[M + 9H]+9 and apo [M + 9H]+9-[M + 19H]+19). Inspection of the kinetic intermediates suggests that the tertiary structure of apomyoglobin unfolds quickly upon the loss of the Fe protoporphyrin IX that stabilizes the interactions between the A, G, and H helices. In the absence of the porphyrin heme, the apomyoglobin unfolds to Xn kinetic intermediates that vary in the extent of unfolding as a result of the observed charge state.

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    PubMed Central

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

    2015-01-01

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

  2. Study of fundamental chemical processes in explosive decomposition by laser-powered homogeneous pyrolysis. Final report 1 jul 78-31 aug 81

    SciTech Connect

    McMillen, D.F.; Golden, D.M.

    1981-11-12

    Very Low-Pressure Pyrolysis studies of 2,4-dinitrotoluene decomposition resulted in decomposition rates consistent with log (ks) = 12.1 - 43.9/2.3 RT. These results support the conclusion that previously reported 'anomalously' low Arrhenius parameters for the homogeneous gas-phase decomposition of ortho-nitrotoluene actually represent surface-catalyzed reactions. Preliminary qualitative results for pyrolysis of ortho-nitrotouene in the absence of hot reactor walls, using the Laser-Powered Homogeneous Pyrolysis technique (LPHP), provide further support for this conclusion: only products resulting from Ph-NO2 bond scission were observed; no products indicating complex intramolecular oxidation-reduction or elimination processes could be detected. The LPHP technique was successfully modified to use a pulsed laser and a heated flow system, so that the technique becomes suitable for study of surface-sensitive, low vapor pressure substrates such as TNT. The validity and accuracy of the technique was demonstrated by applying it to the decomposition of substances whose Arrhenius parameters for decomposition were already well known. IR-fluorescence measurements show that the temperature-space-time behavior under the present LPHP conditions is in agreement with expectations and with requirements which must be met if the method is to have quantitative validity. LPHP studies of azoisopropane decomposition, chosen as a radical-forming test reaction, show the accepted literature parameters to be substantially in error and indicate that the correct values are in all probability much closer to those measured in this work: log (k/s) = 13.9 - 41.2/2.3 RT.

  3. Reaction of a copper(II)-nitrosyl complex with hydrogen peroxide: putative formation of a copper(I)-peroxynitrite intermediate.

    PubMed

    Kalita, Apurba; Kumar, Pankaj; Mondal, Biplab

    2012-05-14

    The reaction of a Cu(II)-nitrosyl complex (1) with hydrogen peroxide at -20 °C in acetonitrile results in the formation of the corresponding Cu(I)-peroxynitrite intermediate. The reduction of the Cu(II) center was monitored by UV-visible spectroscopic studies. Formation of the peroxynitrite intermediate has been confirmed by its characteristic phenol ring nitration reaction as well as isolation of corresponding Cu(I)-nitrate (2). On air oxidation, 2 resulted in the corresponding Cu(II)-nitrate (3). Thus, these results demonstrate a possible decomposition pathway for H(2)O(2) and NO through the formation of a peroxynitrite intermediate in biological systems.

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

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

    SciTech Connect

    1998-09-01

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

  6. Restricted infectivity of ecotropic type C retroviruses in mouse teratocarcinoma cells: studies on viral DNA intermediates

    SciTech Connect

    Yang, W.K.; d'Auriol, L.; Yang, D.M.; Kiggans, J.O. Jr.; Ou, C.; Peries, J.; Emanoil-Ravicovitch, R.

    1980-01-01

    Replication of Gross strain N-tropic type C retrovirus was markedly restricted in a pluripotential undifferentiated embryonal cell line (PCC/sub 4/) of murine teratocarcinoma, whereas the same virus could cause productive infection in a myoblast-derived differentiated line (PCD/sub 1/) of the same tumor origin. To investigate the restriction mechanism, we compared the initial viral DNA formation in these two cell lines. Analyses by means of a modified Hirt extraction procedure and a modified Southern gel transfer method indicated that PCC/sub 4/ and PCD/sub 1/ cells supported the synthesis of viral DNA intermediates after inoculation of the Gross virus. In both cells a linear DNA duplex (form III viral DNA) appeared at 4 h, reached a maximal level at 8 to 9 h, and declined rapidly thereafter, while two closed-circular supercoiled DNA duplexes (form I viral DNA) showed their appearance, increase and decline in the 8 to 24 h period. During the period from 34 to 78 h after virus inoculation, another burst of viral DNA synthesis occurred in PCD/sub 1/ cells, presumably due to secondary virus infection, while at this period both form III and form I viral DNAs became undetectable in PCC/sub 4/ cells. The Hirt supernatant DNAs prepared from PCD/sub 1/ and PCC/sub 4/ cells 10 h after virus inoculation were equally infectious for NIH3T3 cells in a DNA transfection assay. Both PCD/sub 1/ and PCC/sub 4/ cells were very poor recipients for DNA transfection, although one positive result with PCD/sub 1/ cells might suggest a difference between the two cell types in this aspect. These results indicate that restriction of type C retrovirus in undifferentiated embryonal carcinoma cells occurs at a step subsequent to formation and maturation of viral DNA intermediates.

  7. Intermediate acting non-depolarizing neuromuscular blocking agents and risk of postoperative respiratory complications: prospective propensity score matched cohort study

    PubMed Central

    Grosse-Sundrup, Martina; Henneman, Justin P; Sandberg, Warren S; Bateman, Brian T; Uribe, Jose Villa; Nguyen, Nicole Thuy; Ehrenfeld, Jesse M; Martinez, Elizabeth A; Kurth, Tobias

    2012-01-01

    Objective To determine whether use of intermediate acting neuromuscular blocking agents during general anesthesia increases the incidence of postoperative respiratory complications. Design Prospective, propensity score matched cohort study. Setting General teaching hospital in Boston, Massachusetts, United States, 2006-10. Participants 18 579 surgical patients who received intermediate acting neuromuscular blocking agents during surgery were matched by propensity score to 18 579 reference patients who did not receive such agents. Main outcome measures The main outcome measures were oxygen desaturation after extubation (hemoglobin oxygen saturation <90% with a decrease in oxygen saturation after extubation of >3%) and reintubations requiring unplanned admission to an intensive care unit within seven days of surgery. We also evaluated effects on these outcome variables of qualitative monitoring of neuromuscular transmission (train-of-four ratio) and reversal of neuromuscular blockade with neostigmine to prevent residual postoperative neuromuscular blockade. Results The use of intermediate acting neuromuscular blocking agents was associated with an increased risk of postoperative desaturation less than 90% after extubation (odds ratio 1.36, 95% confidence interval 1.23 to 1.51) and reintubation requiring unplanned admission to an intensive care unit (1.40, 1.09 to 1.80). Qualitative monitoring of neuromuscular transmission did not decrease this risk and neostigmine reversal increased the risk of postoperative desaturation to values less than 90% (1.32, 1.20 to 1.46) and reintubation (1.76, 1.38 to 2.26). Conclusion The use of intermediate acting neuromuscular blocking agents during anesthesia was associated with an increased risk of clinically meaningful respiratory complications. Our data suggest that the strategies used in our trial to prevent residual postoperative neuromuscular blockade should be revisited. PMID:23077290

  8. Effect of lavender aromatherapy on vital signs and perceived quality of sleep in the intermediate care unit: a pilot study.

    PubMed

    Lytle, Jamie; Mwatha, Catherine; Davis, Karen K

    2014-01-01

    Sleep deprivation in hospitalized patients is common and can have serious detrimental effects on recovery from illness. Lavender aromatherapy has improved sleep in a variety of clinical settings, but the effect has not been tested in the intermediate care unit. To determine the effect of inhalation of 100% lavender oil on patients' vital signs and perceived quality of sleep in an intermediate care unit. A randomized controlled pilot study was conducted in 50 patients. Control patients received usual care. The treatment group had 3 mL of 100% pure lavender oil in a glass jar in place at the bedside from 10 pm until 6 am. Vital signs were recorded at intervals throughout the night. At 6 am all patients completed the Richard Campbell Sleep Questionnaire to assess quality of sleep. Blood pressure was significantly lower between midnight and 4 am in the treatment group than in the control group (P = .03) According to the overall mean change score in blood pressure between the baseline and 6 am measurements, the treatment group had a decrease in blood pressure and the control group had an increase; however, the difference between the 2 groups was not significant (P = .12). Mean overall sleep score was higher in the intervention group (48.25) than in the control group (40.10), but the difference was not significant. Lavender aromatherapy may be an effective way to improve sleep in an intermediate care unit.

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

    SciTech Connect

    Yu, Z.; Cocke, D.L.

    1998-09-01

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

  10. Multicriteria approximation through decomposition

    SciTech Connect

    Burch, C.; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E.

    1998-06-01

    The authors propose a general technique called solution decomposition to devise approximation algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of their technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic approximation algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. Their method yields as corollaries unified solutions to a number of well studied problems and it provides the first approximation algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) the authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing; (2) they also show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria approximation algorithms for problems including the k-Hurdle and the Network Inhibition problems.

  11. Multicriteria approximation through decomposition

    SciTech Connect

    Burch, C. |; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E. |

    1997-12-01

    The authors propose a general technique called solution decomposition to devise approximation algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of the technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic approximation algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. The method yields as corollaries unified solutions to a number of well studied problems and it provides the first approximation algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) The authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing. (2) They show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria approximation algorithms for problems including the k-Hurdle and the Network Inhibition problems.

  12. Using Eye-Tracking to Study the On-Line Processing of Case-Marking Information among Intermediate L2 Learners of German

    ERIC Educational Resources Information Center

    Jackson, Carrie N.; Dussias, Paola E.; Hristova, Adelina

    2012-01-01

    This study uses eye-tracking to examine the processing of case-marking information in ambiguous subject- and object-first wh-questions in German. The position of the lexical verb was also manipulated via verb tense to investigate whether verb location influences how intermediate L2 learners process L2 sentences. Results show that intermediate L2…

  13. Adsorption and photocatalytic decomposition of roxarsone by TiO₂ and its mechanism.

    PubMed

    Lu, Donglei; Ji, Feng; Wang, Feng; Yuan, Shoujun; Hu, Zhen-Hu; Chen, Tianhu

    2014-01-01

    Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) has been widely used as organic arsenic additive in animal industry. In this study, the adsorption of roxarsone on TiO₂ under dark conditions, the photocatalytic decomposition of roxarsone under UV/TiO₂, and the possible photocatalytic pathway were investigated. At the initial concentration of 5-35 mg/L, the adsorption of roxarsone fitted well with the pseudo-second-order kinetics. The isotherms analysis showed that the Langmuir model was better than the Freundlich and Dubinin–Radushkevich models for describing the adsorption process. After 7 h of photocatalytic decomposition, a complete disappearance of roxarsone was achieved. The pH value has a significant effect on both adsorption and photocatalytic decomposition of roxarsone. The results of high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) and gas chromatography-mass spectrometry (GC/MS) analyses proved the cleavage of the As-C bond during the photocatalytic decomposition process by TiO2 and the intermediates of the decomposition. Based on the results, a possible photocatalytic decomposition pathway was proposed.

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

    SciTech Connect

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

    2010-01-01

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

  15. The Decomposition of Carbonates and Organics on Mars

    NASA Technical Reports Server (NTRS)

    Quinn, Richard C.; Zent, Aaron; McKay, Chris; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The return and analysis of pristine material that is relict of a putative period of chemical evolution is a fumdamental goal of the exobiological exploration of Mars. In order to accomplish this objective, it is desirable to find oxidant-free regions where pristine material can be accessed at the shallowest possible depth (ideally directly from the surface). The objective of our ongoing research is to understand the spatial and temporal distribution of oxidants in the martian regolith and the redox chemistry of the soil; in effect to understand the chemical mechanisms and kinetics relating to the in-situ destruction of organics and the formation of the reactive species responsible for the Viking biology results. In this work, we report on experimental studies of oxidizing processes that may contribute to carbonate and organic degradation on Mars. Organic molecules directly exposed to solar UV may decomposed either directly into CO2, or into more volatile organic fragments. Organic macromolecules not directly exposed to high UV flux are most likely to be affected by atmospheric oxidants which can diffuse to their surfaces. The oxidizing processes examined include: gas-phase oxidants, UV photolysis, and UV-assisted heterogeneous catalysis. For example, assuming a meteroritic infall rate of 4 x 10(exp -4) g/m^2yr (Flynn and McKay 1990) and a flux of organic carbon of 2 x 10(exp -5) g/m^2yr, laboratory measurements of the UV-assisted decomposition of benzenehexacarboxylic acid (mellitic acid, a likely intermediate of kerogen oxidation), indicate its decomposition rate on Mars would exceed the total flux of organic carbon to the planet by over four orders of magnitude. Our measurements indicate that although the decomposition temperature of kerogens in some cases exceeds the temperature limit of the Viking GCMS, it is unlikely kerogens or their decomposition intermediates were present at the Viking landings sites at levels above the GCMS detection limits.

  16. Survival of Danish patients with endometrial cancer in the intermediate-risk group not given postoperative radiotherapy: the Danish Endometrial Cancer Study (DEMCA).

    PubMed

    Bertelsen, Kamma; Ortoft, Gitte; Hansen, Estrid Stæhr

    2011-10-01

    In a prospective study during the years 1986 to 1988, the Danish Endometrial Cancer Group (DEMCA) demonstrated that postoperative radiotherapy was unnecessary for low-risk patients with stage I disease. In the present study, we evaluated in a population-based study if radiotherapy could also be omitted for intermediate-risk patients with stage I disease without loss of survival. From 1998 to 1999, 1166 patients newly diagnosed with carcinoma of the uterus were included in this prospective nationwide study. Of these, 232 were intermediate-risk patients with stage I disease. All intermediate-risk patients received standard primary surgery (hysterectomy, bilateral salpingo-oophorectomy, and peritoneal washings), and no postoperative radiotherapy was given. Survival analyses were performed using Kaplan-Meier survival estimates. The results were compared to the 1986-1988 DEMCA data. The 5-year overall survival (OS) rate for the entire population was 77% (stages I-IV). The patients with stage I disease were divided into low-, intermediate-, and high-risk; the OS rates were 91%, 78%, and 62%, and the endometrial cancer-specific survival rates were 97%, 87%, and 72%, respectively. Using patients' age, tumor grade, myometrial invasion, we divided the intermediate-risk group into "high risk" intermediate and "low-risk" intermediate with OS rates of 70% and 90% and cancer-specific survival of 81% and 96%, respectively. The OS rate (78%) of the intermediate-risk group after radiation had been omitted was comparable to the OS rate (79%) of the intermediate-risk group in the earlier DEMCA (1986-1988) study where postoperative radiation was still the standard of care. We conclude that in a population-based study, radiotherapy can be omitted for intermediate-risk patients with stage I endometrial cancer without loss of survival.

  17. Decomposition of Rare Earth Loaded Resin Particles

    SciTech Connect

    Voit, Stewart L; Rawn, Claudia J

    2010-09-01

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

  18. Nanosecond time-resolved and steady-state infrared studies of photoinduced decomposition of TATB at ambient and elevated pressure.

    PubMed

    Glascoe, Elizabeth A; Zaug, Joseph M; Armstrong, Michael R; Crowhurst, Jonathan C; Grant, Christian D; Fried, Laurence E

    2009-05-21

    The time scale and/or products of photoinduced decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were investigated at ambient pressure and compared with products formed at 8 GPa. Ultrafast time-resolved infrared and steady-state Fourier transform IR (FTIR) spectroscopies were used to probe TATB and its products after photoexcitation with a 5 ns pulse of 532 nm light. At ambient pressure, transient spectra of TATB indicate that the molecule has significantly decomposed within 60 ns; transient spectra also indicate that formation of CO(2), an observed decomposition product, is complete within 30-40 mus. Proof of principle time-resolved experiments at elevated pressures were performed and are discussed briefly. Comparison of steady-state FTIR spectra obtained at ambient and elevated pressure (ca. 8 GPa) indicate that the decomposition products vary with pressure. We find evidence for water as a decomposition product only at elevated pressure.

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

    NASA Astrophysics Data System (ADS)

    Carraher, Jack McCaslin

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

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

    PubMed

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

    2012-10-01

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

  1. 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-.

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

    PubMed

    Parry, David A D

    2016-01-01

    Experimental and theoretical research aimed at determining the structure and function of the family of intermediate filament proteins has made significant advances over the past 20 years. Much of this has either contributed to or relied on the amino acid sequence databases that are now available online, and the data mining approaches that have been developed to analyze these sequences. As the quality of sequence data is generally high, it follows that it is the design of the computational and graphical methodologies that are of especial importance to researchers who aspire to gain a greater understanding of those sequence features that specify both function and structural hierarchy. However, these techniques are necessarily subject to limitations and it is important that these be recognized. In addition, no single method is likely to be successful in solving a particular problem, and a coordinated approach using a suite of methods is generally required. A final step in the process involves the interpretation of the results obtained and the construction of a working model or hypothesis that suggests further experimentation. While such methods allow meaningful progress to be made it is still important that the data are interpreted correctly and conservatively. New data mining methods are continually being developed, and it can be expected that even greater understanding of the relationship between structure and function will be gleaned from sequence data in the coming years. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Field study - Steinle Ranch, an intermediate depth oil field, shows significant benefit from bauxite proppants

    SciTech Connect

    Kohlhaas, C.A.

    1982-01-01

    The Steinle Ranch field initially was developed in the mid-1970s. Wells were drilled, cased, perforated, and treated by chemical injection with lease-crude or condensate carriers to restore oil saturation to the formation, which is suspected to be hydrophobic. Stimulation by hydraulic fracturing of 4 wells was attempted from 1975 through 1977 with mixed results and no particular success. These treatments used sand and glass beads for proppant. A fifth hydraulic fracture treatment, in which sintered bauxite was used as the proppant was very successful. As a result, all wells in the field have been fractured. This program, in a mature field in late stages of depletion, at intermediate depth (10,600 ft), has been very successful; ca 940,000 bbl of additional reserves have resulted for a total cost of ca $2,000,000, a return on investment of 9.4:1. Comparing these reserves to estimated reserves if the wells had been propped with sand shows a 23:1 return by the incremental reserves on the incremental cost of the bauxite.

  4. Reaction of Stabilized Criegee Intermediates from Ozonolysis of Limonene with Water: Ab Initio and DFT Study

    PubMed Central

    Jiang, Lei; Lan, Ru; Xu, Yi-Sheng; Zhang, Wen-Jie; Yang, Wen

    2013-01-01

    The mechanism of the chemical reaction of H2O with three stabilized Criegee intermediates (stabCI-OO, stabCI-CH3-OO and stabCIx-OO) produced via the limonene ozonolysis reaction has been investigated using ab initio and DFT (Density Functional Theory) methods. It has been shown that the formation of the hydrogen-bonded complexes is followed by two different reaction pathways, leading to the formation of either OH radicals via water-catalyzed H migration or of α-hydroxy hydroperoxide. Both pathways were found to be essential sources of atmospheric OH radical and H2O2 making a significant contribution to the formation of secondary aerosols in the Earth’s atmosphere. The activation energies at the CCSD(T)/6-31G(d) + CF level of theory were found to be in the range of 14.70–21.98 kcal mol−1. The formation of α-hydroxy hydroperoxide for the reaction of stabCIx-OO and H2O with the activation energy of 14.70 kcal mol−1 is identified as the most favorable pathway. PMID:23481640

  5. Structural studies of intermediates along the cyclization pathway of Aplysia ADP-ribosyl cyclase.

    PubMed

    Kotaka, Masayo; Graeff, Richard; Chen, Zhe; Zhang, Li He; Lee, Hon Cheung; Hao, Quan

    2012-01-20

    Cyclic ADP-ribose (cADPR) is a calcium messenger that can mobilize intracellular Ca²⁺ stores and activate Ca²⁺ influx to regulate a wide range of physiological processes. Aplysia cyclase is the first member of the ADP-ribosyl cyclases identified to catalyze the cyclization of NAD⁺ into cADPR. The catalysis involves a two-step reaction, the elimination of the nicotinamide ring and the cyclization of the intermediate resulting in the covalent attachment of the purine ring to the terminal ribose. Aplysia cyclase exhibits a high degree of leniency towards the purine base of its substrate, and the cyclization reaction takes place at either the N1- or the N7-position of the purine ring. To decipher the mechanism of cyclization in Aplysia cyclase, we used a crystallization setup with multiple Aplysia cyclase molecules present in the asymmetric unit. With the use of natural substrates and analogs, not only were we able to capture multiple snapshots during enzyme catalysis resulting in either N1 or N7 linkage of the purine ring to the terminal ribose, we were also able to observe, for the first time, the cyclized products of both N1 and N7 cyclization bound in the active site of Aplysia cyclase.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Skinner, Alex W.

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

  8. Training Needs for the Professional Development of Social-Studies Teachers at the Intermediate Stage in Al-Jouf in Light of Modern Teaching Trends: A Field Study

    ERIC Educational Resources Information Center

    Almarshad, Yousef

    2017-01-01

    This study is an attempt to identify the training needs of social-studies teachers at the intermediate stage in Al-Jouf in light of modern teaching trends. It focuses on the six axes of systemic planning, varied teaching strategies, information and communication technology, innovative enrichment activities in teaching, classroom-management skills,…

  9. Thermochemical decomposition and isomerization of polysilacyclodialkynes and thermochemical and photochemical decomposition of cyclopolysilylketenes

    SciTech Connect

    Altman, Leon Berthold

    1994-05-10

    Kinetic data for elimination of silylene supports formation of a ``tighter`` transition state, indicating a silacyclopropene intermediate. This extends the silacyclopropene mechanism to the cyclicdialkyne system and validates the consistency of the mechanism for silylakynes, in general. Investigation into the other possible silacyclopropene product established the instability of the product. The work with silylketenes proved that an inherent difference exists between reactivity of monosilyl-substituted ketenes and polysilyl-substituted ketenes. Although the mechanism for thermal decomposition of bis(silyl)ketenes can be modified to account for the unexpected silylene elimination products, reasons for the difference are limited to speculation. The photochemistry of silylketenes has not been previously studied, so a model system does not exist for comparison with our polysilylketene work. The photochemical experimentation suggests that the photochemistry and thermochemistry of polysilylketenes is not the same. A more extensive study of the mechanism of the systems covered in this research as well as with monosilyl-substituted systems is needed.

  10. Mechanistic studies of the photocatalytic degradation of methyl green: an investigation of products of the decomposition processes.

    PubMed

    Chen, Chiing-Chang; Lu, Chung-Shin

    2007-06-15

    The methyl green (MG) dye dissolves into an alkaline solution when the pH value is too high (pH 9). The cationic MG dye molecules are converted into the colorless carbinol base (CB) and produce crystal violet (CV) dye and ethanol by hydroxide anion. Thirty-three intermediates of the process were separated, identified, and characterized by HPLC-ESI-MS technique in this study and their evolution during the photocatalytic reaction is presented. Moreover, the other intermediates formed in the photocatalytic degradation MG processes were separated and identified by HPLC-PDA technique. The results indicated that the N-de-methylated degradation of CV dye took place in a stepwise manner to yield N-de-methylated CV species, and the N-de-alkylated degradation of CB also took place in a stepwise manner to yield N-de-alkylated CB species generated during the processes. Moreover, the oxidative degradation of the CV dye (or CB) occurs to yield 4-(N,N-dimethylamino)phenol (DAP), 4-(N,N-dimethylamino)-4'-(N',N'-dimethylamino)benzophenone (DDBP) and their N-de-methylated products [or to yield 4-(N-ethyl-N,N-dimethyl)aminophenol (EDAP), DDBP, 4-(N-ethyl-N,N-dimethylamino)-4'-(N',N'-dimethylamino)benzophenone (EDDBP), DAP, and their N-de-alkylated products], which were found for the first time. A proposed degradation pathway of CV and CB is presented, involving mainly the N-de-alkylation and oxidation reaction.

  11. Adaptive kinetic Monte Carlo simulation of methanol decomposition on Cu(100)

    SciTech Connect

    Xu, Lijun; Mei, Donghai; Henkelman, Graeme A.

    2009-12-31

    The adaptive kinetic Monte Carlo method was used to calculate the dynamics of methanol decomposition on Cu(100) at room temperature over a time scale of minutes. Mechanisms of reaction were found using min-mode following saddle point searches based upon forces and energies from density functional theory. Rates of reaction were calculated with harmonic transition state theory. The dynamics followed a pathway from CH3-OH, CH3-O, CH2-O, CH-O and finally C-O. Our calculations confirm that methanol decomposition starts with breaking the O-H bond followed by breaking C-H bonds in the dehydrogenated intermediates until CO is produced. The bridge site on the Cu(100) surface is the active site for scissoring chemical bonds. Reaction intermediates are mobile on the surface which allows them to find this active reaction site. This study illustrates how the adaptive kinetic Monte Carlo method can model the dynamics of surface chemistry from first principles.

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

    SciTech Connect

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

    1991-09-01

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

  13. Studies on the effect of the temperature of intermediate fluid on the effectiveness of three fluid heat exchangers

    NASA Astrophysics Data System (ADS)

    Vasudevan, T.; Rakesh, S. G.

    2017-07-01

    Three fluid heat exchangers involving twothermal communications as well as three thermal communications have been investigated for the effect of change in the intermediate fluid temperature on the effectiveness of the heat exchangers, using both theoretical and simulation studies. The objective of these heat exchangers is identified as cooling of hot fluid. The simulations are repeated for hot fluids with different specific heats. The effect of change in the conducting material on the effectiveness in a three thermal communications heat exchanger has been investigated. The pressure drop calculations are also done for the heat exchangers.

  14. Pion shadowing as a tool to study the topology of heavy-ion collisions at intermediate energies

    SciTech Connect

    Badala, A.; Barbera, R.; Palmeri, A.; Pappalardo, G.S.; Riggi, F.; Russo, A.C.; Turrisi, R.; Barbera, R.; Riggi, F.; Russo, G.; Turrisi, R.; Russo, G.

    1997-05-01

    The pion reabsorption effect has been exploited, through a new analysis technique, to study the topological distribution of nuclear matter in the course of a heavy-ion collision at intermediate energies. The azimuthal angular distribution of pions with respect to the reaction plane and the angular correlations between pions and projectilelike fragments have been investigated. Quantitative estimations of the pion production time scale and of the impact parameter range involved are provided. The experimental results are successfully compared with the predictions of a microscopic theoretical model based on the solution of the Boltzmann-Nordheim-Vlasov transport equation. {copyright} {ital 1997} {ital The American Physical Society}

  15. Sulfur species behavior in soil organic matter during decomposition

    USGS Publications Warehouse

    Schroth, A.W.; Bostick, B.C.; Graham, M.; Kaste, J.M.; Mitchell, M.J.; Friedland, A.J.

    2007-01-01

    Soil organic matter (SOM) is a primary re??servoir of terrestrial sulfur (S), but its role in the global S cycle remains poorly understood. We examine S speciation by X-ray absorption near-edge structure (XANES) spectroscopy to describe S species behavior during SOM decomposition. Sulfur species in SOM were best represented by organic sulfide, sulfoxide, sulfonate, and sulfate. The highest fraction of S in litter was organic sulfide, but as decomposition progressed, relative fractions of sulfonate and sulfate generally increased. Over 6-month laboratory incubations, organic sulfide was most reactive, suggesting that a fraction of this species was associated with a highly labile pool of SOM. During humification, relative concentrations of sulfoxide consistently decreased, demonstrating the importance of sulfoxide as a reactive S phase in soil. Sulfonate fractional abundance increased during humification irrespective of litter type, illustrating its relative stability in soils. The proportion of S species did not differ systematically by litter type, but organic sulfide became less abundant in conifer SOM during decomposition, while sulfate fractional abundance increased. Conversely, deciduous SOM exhibited lesser or nonexistent shifts in organic sulfide and sulfate fractions during decomposition, possibly suggesting that S reactivity in deciduous litter is coupled to rapid C mineralization and independent of S speciation. All trends were consistent in soils across study sites. We conclude that S reactivity is related to spqciation in SOM, particularly in conifer forests, and S species fractions in SOM change, during decomposition. Our data highlight the importance of intermediate valence species (sulfoxide and sulfonate) in the pedochemical cycling of organic bound S. Copyright 2007 by the American Geophysical Union.

  16. On Soil Moisture Retrieval and Target Decomposition

    NASA Technical Reports Server (NTRS)

    Dubois, Pascale C.; vanZyl, Jakob

    1996-01-01

    In an earlier study, an empirical model was developed to infer soil moisture and surface roughness from radar data. The inversion technique was extensively tested over bare surfaces by comparing the estimated soil moisture to in situ measurements. The overall RMS error in the soil moisture estimate was found to be 3.5% and the RMS error in the RMS height estimate was less than 0.35 cm absolute for bare or slightly vegetated surfaces. However, inversion results indicate that significant amounts of vegetation cause the algorithm to underestimate soil moisture and overestimate RMS height. Among the areas over which the inversion cannot be applied, the areas with intermediate vegetation cover are of particular interest as both the vegetation and the underlying bare surface affect the backscatter. This paper concentrates mostly on these areas. Using the full polarimetric information and the Cloude target decomposition approach. Three different components of the target backscattering can be isolated. One of these three components can be identified as the surface component in the case of intermediate vegetation cover. Once the surface component of the scattering is isolated, the bare surface inversion can then be applied.

  17. On Soil Moisture Retrieval and Target Decomposition

    NASA Technical Reports Server (NTRS)

    Dubois, Pascale C.; vanZyl, Jakob

    1996-01-01

    In an earlier study, an empirical model was developed to infer soil moisture and surface roughness from radar data. The inversion technique was extensively tested over bare surfaces by comparing the estimated soil moisture to in situ measurements. The overall root mean square (RMS) error in the soil moisture estimate was found to be about 3.5% and the RMS error in the RMS height estimate was less than 0.35 cm absolute for bare or slightly vegetated surfaces. However, inversion results indicate that significant amounts of vegetation cause the algorithm to underestimate soil moisture and overestimate RMS height. Among the areas over which the inversion cannot be applied, the areas with intermediate vegetation cover are of particular interest as both the vegetation and the underlying bare surface affect the backscatter. This paper concentrates mostly on these areas. Using the full polarimetric information and the Cloude target decomposition approach, three different components of the target backscattering can be isolated. One of these three components can be identified as the surface component in the case of intermediate vegetation cover. Once the surface component of the scattering is isolated, the bare surface inversion can then be applied.

  18. Spectro-Timing Study of GX 339-4 in a Hard Intermediate State

    NASA Astrophysics Data System (ADS)

    Fürst, F.; Grinberg, V.; Tomsick, J. A.; Bachetti, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Grefenstette, B.; Hailey, C. J.; Harrison, F. A.; Madsen, K. K.; Parker, M. L.; Pottschmidt, K.; Stern, D.; Walton, D. J.; Wilms, J.; Zhang, W. W.

    2016-09-01

    We present an analysis of Nuclear Spectroscopic Telescope Array observations of a hard intermediate state of the transient black hole GX 339-4 taken in 2015 January. With the source softening significantly over the course of the 1.3 day long observation we split the data into 21 sub-sets and find that the spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from ˜1.69 to ˜1.77 over the course of the observation. The accretion disk is truncated at around nine gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which increases in frequency from ˜0.68 to ˜1.05 Hz with time. The frequency change is well correlated with the softening of the spectrum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of ˜100 {M}⊙ , which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii, as obtained from spectral fitting, is difficult to reconcile with current models.

  19. Spectro-Timing Study of GX 339-4 in a Hard Intermediate State

    NASA Technical Reports Server (NTRS)

    Furst, F.; Grinberg, V.; Tomsick, J. A.; Bachetti, M.; Boggs, S. E.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Ghandi, P.; Zhang, William W.

    2016-01-01

    We present an analysis of Nuclear Spectroscopic Telescope Array observations of a hard intermediate state of the transient black hole GX 339-4 taken in 2015 January. With the source softening significantly over the course of the 1.3 day long observation we split the data into 21 sub-sets and find that the spectrum of all of them can be well described by a power-law continuum with an additional relativistically blurred reflection component. The photon index increases from approx. 1.69 to approx. 1.77 over the course of the observation. The accretion disk is truncated at around nine gravitational radii in all spectra. We also perform timing analysis on the same 21 individual data sets, and find a strong type-C quasi-periodic oscillation (QPO), which increases in frequency from approx. 0.68 to approx. 1.05 Hz with time. The frequency change is well correlated with the softening of the spectrum. We discuss possible scenarios for the production of the QPO and calculate predicted inner radii in the relativistic precession model as well as the global disk mode oscillations model. We find discrepancies with respect to the observed values in both models unless we allow for a black hole mass of approx. 100 Mass compared to the Sun, which is highly unlikely. We discuss possible systematic uncertainties, in particular with the measurement of the inner accretion disk radius in the relativistic reflection model. We conclude that the combination of observed QPO frequencies and inner accretion disk radii, as obtained from spectral fitting, is difficult to reconcile with current models.

  20. Results of a retrospective observational study of intermediate care staffed by hospitalists: impact on mortality, co-management, and teaching.

    PubMed

    Lucena, Juan Felipe; Alegre, Félix; Rodil, Raquel; Landecho, Manuel Fortún; García-Mouriz, Alberto; Marqués, Margarita; Aquerreta, Irene; García, Nicolás; Quiroga, Jorge

    2012-01-01

    Hospitalized patients are complex and institutions have to face the high cost of critical care and the limited resources of the ward. Intermediate care appears as an attractive strategy to provide rational care according to patient needs. It is an interesting scenario to expand co-management and teaching. Retrospective observational study. Intermediate care unit (ImCU) of a single academic hospital. 456 patients admitted from April 2006 to April 2010 were included in the study. Demographics, admission physiologic parameters and in-hospital mortality were recorded. We used the Simplified Acute Physiology Score II (SAPS II) as prognostic score system. Co-management with medical and surgical teams, and the number of training residents were evaluated. In-hospital mortality was 20.6%, whereas the expected mortality was 23.2% based on SAPS II score. The correlation between SAPS II predicted and observed death rates was accurate and statistically significant (Rho = 1.0, p < 0.001). Co-management was performed with several medical and surgical teams, with an increase in perioperative comanagement of 22.7% (p = 0.014). The number of training residents in ImCU increased from 4.3% to 30.4% (p = 0.002) An ImCU led by hospitalists showed encouraging results regarding patient survival and SAPS II is an useful tool for prognostic evaluation in this population. Intermediate care serves as an expansion of role for hospitalists; and clinicians, trainees and patients may benefit from co-management and teaching opportunities at this unique level of care. Copyright © 2012 Society of Hospital Medicine.

  1. [Intermediate endpoints in clinical research].

    PubMed

    Peters, Sanne A E; Groenwold, Rolf H H; Bots, Michiel L

    2013-01-01

    An intermediate variable such as blood pressure is part of the causal pathway of mechanisms to a clinical outcome, e.g. myocardial infarction. An intervention affects a clinical outcome through its effect on that intermediate variable. In studies designed to assess the effects of interventions an intermediate variable may be used as surrogate for clinical outcomes. Such an endpoint is also known as an intermediate endpoint. Intervention studies with intermediate endpoints are commonly performed in medical research to evaluate the effects of an intervention on clinical outcomes. Intervention studies with an intermediate endpoint are conducted in a smaller study population and with a shorter duration of follow-up than studies using clinical outcomes. An intermediate variable is not eligible as an intermediate endpoint when the intervention also affects other biological mechanisms that subsequently affect the clinical endpoint. Due to a smaller sample size and shorter study duration, side effects of intervention are more difficult to evaluate in studies with an intermediate endpoint than in studies with clinical endpoints.

  2. Case study of urban environmental education in the intermediate-grade curriculum: an investigation of content and process

    SciTech Connect

    Pace, R.

    1987-01-01

    This case study was an attempt to divulge the presence of environmental education (EE) in the intermediate-grade curriculum, along with the factors influencing it both positively and negatively. It was designed in response to Goal No. 7 of the New York State Regents Action Plan, which advocates EE in all subject areas and at all grade levels. The site of the study was a public school in Queens, New York, The participants included 7 teachers, the school librarian, 2 administrators, and 15 fourth, fifth, and sixth graders, as well as 3 educators from outside the school. This research was conducted between February and June, 1986. The data-collection techniques involved observations, in-depth interviews, and artifact reviews. The findings revealed that EE does exist both blatantly and subtly in the intermediate-grade curriculum; however, much more can be done. In science, exploration of plants, animals, energy, climate, air and water quality are replete with environmental ramifications. In social studies, consideration of the dependence of human cultural development on the natural environment is key. Environmental themes are employed to teach mathematical, reading, and language arts skills. Much music is developed around the imitation of the sounds of nature. Current events bring environmental issues to the foreground.

  3. Reactivity of TEMPO toward 16- and 17-electron organometallic reaction intermediates: a time-resolved IR study.

    PubMed

    Lomont, Justin P; Nguyen, Son C; Harris, Charles B

    2013-07-31

    The (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO) has been employed for an extensive range of chemical applications, ranging from organometallic catalysis to serving as a structural probe in biological systems. As a ligand in an organometallic complex, TEMPO can exhibit several distinct coordination modes. Here we use ultrafast time-resolved infrared spectroscopy to study the reactivity of TEMPO toward coordinatively unsaturated 16- and 17-electron organometallic reaction intermediates. TEMPO coordinates to the metal centers of the 16-electron species CpCo(CO) and Fe(CO)4, and to the 17-electron species CpFe(CO)2 and Mn(CO)5, via an associative mechanism with concomitant oxidation of the metal center. In these adducts, TEMPO thus behaves as an anionic ligand, characterized by a pyramidal geometry about the nitrogen center. Density functional theory calculations are used to facilitate interpretation of the spectra and to further explore the structures of the TEMPO adducts. To our knowledge, this study represents the first direct characterization of the mechanism of the reaction of TEMPO with coordinatively unsaturated organometallic complexes, providing valuable insight into its reactions with commonly encountered reaction intermediates. The similar reactivity of TEMPO toward each of the species studied suggests that these results can be considered representative of TEMPO's reactivity toward all low-valent transition metal complexes.

  4. Vacancy-induced initial decomposition of condensed phase NTO via bimolecular hydrogen transfer mechanisms at high pressure: a DFT-D study.

    PubMed

    Liu, Zhichao; Wu, Qiong; Zhu, Weihua; Xiao, Heming

    2015-04-28

    Density functional theory with dispersion-correction (DFT-D) was employed to study the effects of vacancy and pressure on the structure and initial decomposition of crystalline 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (β-NTO), a high-energy insensitive explosive. A comparative analysis of the chemical behaviors of NTO in the ideal bulk crystal and vacancy-containing crystals under applied hydrostatic compression was considered. Our calculated formation energy, vacancy interaction energy, electron density difference, and frontier orbitals reveal that the stability of NTO can be effectively manipulated by changing the molecular environment. Bimolecular hydrogen transfer is suggested to be a potential initial chemical reaction in the vacancy-containing NTO solid at 50 GPa, which is prior to the C-NO2 bond dissociation as its initiation decomposition in the gas phase. The vacancy defects introduced into the ideal bulk NTO crystal can produce a localized site, where the initiation decomposition is preferentially accelerated and then promotes further decompositions. Our results may shed some light on the influence of the molecular environments on the initial pathways in molecular explosives.

  5. Ethanol decomposition on transition metal nanoparticles during carbon nanotube growth: ab initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Shibuta, Yasushi; Shimamura, Kohei; Oguri, Tomoya; Arifin, Rizal; Shimojo, Fuyuki; Yamaguchi, Shu

    2015-03-01

    The growth mechanism of carbon nanotubes (CNT) has been widely discussed both from experimental and computational studies. Regarding the computational studies, most of the studies focuses on the aggregation of isolate carbon atoms on the catalytic metal nanoparticle, whereas the initial dissociation of carbon source molecules should affect the yield and quality of the products. On the other hand, we have studied the dissociation process of carbon source molecules on the metal surface by the ab initio molecular dynamics simulation. In the study, we investigate the ethanol dissociation on Pt and Ni clusters by ab initio MD simulations to discuss the initial stage of CNT growth by alcohol CVD technique. Part of this research is supported by the Grant-in-Aid for Young Scientists (a) (No. 24686026) from MEXT, Japan.

  6. Time-domain Surveys and Data Shift: Case Study at the intermediate Palomar Transient Factory

    NASA Astrophysics Data System (ADS)

    Rebbapragada, Umaa; Bue, Brian; Wozniak, Przemyslaw R.

    2015-01-01

    Next generation time-domain surveys are susceptible to the problem of data shift that is caused by upgrades to data processing pipelines and instruments. Data shift degrades the performance of automated machine learning classifiers that vet detections and classify source types because fundamental assumptions are violated when classifiers are built in one data regime but are deployed on data from another. This issue is not currently discussed within the astronomical community, but will be increasingly pressing over the next decade with the advent of new time domain surveys.We look at the problem of data shift that was caused by a data pipeline upgrade when the intermediate Palomar Transient Factory (iPTF) succeeded the Palomar Transient Factory (PTF) in January 2013. iPTF relies upon machine-learned Real-Bogus classifiers to vet sources extracted from subtracted images on a scale of zero to one where zero indicates a bogus (image artifact) and one indicates a real astronomical transient, with the overwhelming majority of candidates are scored as bogus. An effective Real-Bogus system filters all but the most promising candidates, which are presented to human scanners who make decisions about triggering follow up assets.The Real-Bogus systems currently in operation at iPTF (RB4 and RB5) solve the data shift problem. The statistical models of RB4 and RB5 were built from the ground up using examples from iPTF alone, whereas an older system, RB2, was built using PTF data, but was deployed after iPTF launched. We discuss the machine learning assumptions that are violated when a system is trained on one domain (PTF) but deployed on another (iPTF) that experiences data shift. We provide illustrative examples of data parameters and statistics that experienced shift. Finally, we show results comparing the three systems in operation, demonstrating that systems that solve domain shift (RB4 and RB5) are superior to those that don't (RB2).Research described in this abstract was

  7. Low-Temperature FTIR Study of Multiple K Intermediates in the Photocycles of Bacteriorhodopsin and Xanthorhodopsin

    PubMed Central

    Dioumaev, Andrei K.; Wang, Jennifer M.; Lanyi, Janos K.

    2013-01-01

    Low-temperature FTIR spectroscopy of bacteriorhodopsin and xanthorhodopsin was used to elucidate the number of K-like bathochromic states, their sequence, and their contributions to the photo-equilibrium mixtures created by illumination at 80-180K. We conclude that in bacteriorhodopsin the photocycle includes three distinct K-like states in the sequence: bR→hvI∗→J→K0→KE→KL→L→…, and similarly in xanthorhodopsin. K0 is the main fraction in the mixture at 77K that is formed from J. K0 becomes thermally unstable above ~50K in both proteins. At 77K both J-to-K0 and K0-to-KE transitions occur and, contrarily to long-standing belief, cryogenic trapping at 77K does not produce a pure K state but a mixture of the two states, K0 and KE, with contributions from KE of ~15% and ~10% in the two retinal-proteins, respectively. Raising the temperature leads to increasing conversion of K0 to KE, and the two states coexist (without contamination from non K-like states) in the 80-140K range in bacteriorhodopsin, and in the 80-190K range in xanthorhodopsin. Temperature perturbation experiments in these regions of coexistence revealed that in spite of the observation of apparently stable mixtures of K0 and KE, the two states are not in thermally-controlled equilibrium. The K0-to-KE transition is unidirectional, and the partial transformation to KE is due to distributed kinetics, which governs the photocycle dynamics at temperatures below ~245K. From spectral deconvolution we conclude that the KE state, which is increasingly present at higher temperatures, is the same intermediate that is detected by time-resolved FTIR prior to its decay, on a time-scale of hundreds nanoseconds at ambient temperature, into the KL state. We were unable to trap the latter separately from KE at low temperature, due to the slow distributed kinetics and the increasingly faster overlapping formation of L state. Formation of the two consecutive K-like states in both proteins is accompanied by

  8. Biogeochemistry of Sulfur Intermediates in Marine Sediments - Insights from Laboratory and Field Studies

    NASA Astrophysics Data System (ADS)

    Ferdelman, T. G.; Milucka, J.; Kuypers, M. M. M.; Berg, J.; Buckner, C.; Graf, J.; Holmkvist, L.; Jørgensen, B. B.; Kamyshny, A.; Piepgras, L.

    2014-12-01

    The sulfur cycle in marine sediments exerts a major control on the redox state of the ocean and atmosphere. The overall driver in the sulfur cycle is the microbial mediated sulfate reduction to sulfide (SR), In near-surface sediments, only a small fraction of the sulfide produced becomes permanently buried in the reduced form as pyrite (FeS2) Paradoxically, the deep, reduced, sulfidic zone of marine sediments is often characterized by the presence of zero-valent sulfur compounds, e.g. elemental sulfur and polysulfides [1,2,3]. The presence of oxidized iron and manganese has been suggested as the source of oxidizing power for the formation of elemental S and polysulfides in these deep, anoxic and sulfidic sediment environments, which often lie at or below the sulfate-methane transition [1,3]. The findings of Milucka et al. [4] suggest that anaerobic oxidation of methane coupled to sulfate reduction (AOM) may provide another source of zerovalent sulfur to such environments. AOM is thought to be mediated by a consortium of methanotrophic archaea (ANME) and sulfate-reducing Deltaproteobacteria. Milucka et al. [4] show that zero-valent sulfur compounds (S0) are formed during AOM-coupled SR and conclude that the S0 is a product of a novel pathway for sulfate reduction performed by the ANME. Thus, AOM may not be an obligately syntrophic process. Furthermore, the produced S0, in the form of hydrodisulfide, can serve as a substrate for disproportionation by the Deltaproteobacteria associated with the ANME, and that this disproptionation proceeds under sulfidic conditions. These observations may have significant implications for role of sulfur intermediates in our understanding of the biogeochemical carbon and sulfur cycle in modern and past environments. [1] Holmkvist et al. (2011) Geochim. Cosmochim. Acta 75, 3581-3599. [2] Lichtschlag et al. (2013) Geochim. Cosmochim. Acta 105, 130-145. [3] Holmkvist et al. (2014) Geochim. Cosmochim. Acta, accepted. [4] Milucka et al

  9. Thermal decomposition study of monovarietal extra virgin olive oil by simultaneous thermogravimetry/differential scanning calorimetry: relation with chemical composition.

    PubMed

    Vecchio, Stefano; Cerretani, Lorenzo; Bendini, Alessandra; Chiavaro, Emma

    2009-06-10

    Thermal decomposition of 12 monovarietal extra virgin olive oils from different geographical origins (eight from Italy, two from Spain, and the others from Tunisia) was evaluated by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses. All extra virgin olive oils showed a complex multistep decomposition pattern with the first step that exhibited a quite different profile among samples. Thermal properties of the two peaks obtained by the deconvolution of the first step of decomposition by DSC were related to the chemical composition of the samples (triacylglycerols, fatty acids, total phenols and antioxidant activity). Onset temperatures of the thermal decomposition transition and T(p) values of both deconvoluted peaks as well as the sum of enthalpy were found to exhibit statistically significant correlations with chemical components of the samples, in particular palmitic and oleic acids and related triacylglycerols. Activation energy values of the second deconvoluted peak obtained by the application of kinetic procedure to the first step of decomposition were also found to be highly statistically correlated to the chemical composition, and a stability scale among samples was proposed on the basis of its values.

  10. Study of the relationship between decomposition energies of various heterocycles derived by using the PM3 method

    NASA Astrophysics Data System (ADS)

    Zubkov, V. A.; Bogdanova, S. E.; Yakimansky, A. V.

    1996-01-01

    Experimental and circumstantial data were employed to assess the reliability of PM3-calculated energies of heterocycle decompositions which result in a biradical and a molecule with a closed shell. Calculated decomposition energies ( ED) reproduced the relationship between experimental ED for oxazole, imidazole and thiazole although the calculated ED values were lower than the experimental ones. In the case of the heterocycles (HCs) containing carbonyl groups (malemide, oxazinone, etc.) the variations in ED values calculated for distinct HCs and different decomposition pathways of the same HC correlated in many cases with variations in the stabilities of the biradicals formed during the HC decompositions. The differences in relative stabilities of the resulting molecules with a closed shell, the variations in the capacity for decomposition between five- and six-membered HCs, and the differences in the heats of formation for isomeric HCs were also found to affect the ED values for HCs containing carbonyl groups. ED values for six-membered HCs containing only nitrogen atoms as heteroatoms were higher than those for other HCs considered but lower than that for benzene. A decrease in ED with an increase in the number of nitrogen atoms in such HCs seemed to be caused by the known capacity of nitrogen atoms to draw the electron density off an aromatic ring thereby weakening the bond strengths of the ring.

  11. Shock Tube/Laser Absorption Studies of the Decomposition of Fuel Surrogates

    DTIC Science & Technology

    2010-04-21

    cyclohexane, and methyl - ethyl -, n-propyl and n-butyl-cyclohexane oxidation at high temperatures. http://melchior.usc.edu/JetSurF/JetSurF1.1. 26 J. P. Orme... kerosene ) surrogate components, ndodecane and methylcyclohexane (MCH), have been studied using laser absorption in both high- and low-pressure shock tubes...two rocket fuel ( kerosene ) surrogate components, n- dodecane and methylcyclohexane (MCH), have been studied using laser absorption in both high- and

  12. Infrared matrix isolation and theoretical study of the initial intermediates in the reaction of ozone with cis-2-butene.

    PubMed

    Clay, Mary; Ault, Bruce S

    2010-03-04

    Matrix isolation studies combined with infrared spectroscopy of the twin jet codeposition of ozone and cis-2-butene into argon matrices have led to the first observation of several early intermediates in this ozonolysis reaction. Specifically, evidence is presented for the formation and identification of the long sought-after Criegee intermediate, as well as confirming evidence for earlier reports of the primary and secondary ozonides. These species were observed after initial twin jet deposition, and grew upon annealing to 35 K. Extensive isotopic labeling ((18)O and (16,18)O mixtures) experiments provided important supporting data. Detailed theoretical calculations at the B3LYP/6-311++G(d,2p) level were carried out as well to augment the experimental work. Merged jet (flow reactor) experiments followed by cryogenic trapping in solid argon led to the formation of "late", stable oxidation products. Photochemical reactions of ozone with cis-2-butene was studied as well, as was the photochemical behavior of the primary and secondary ozonides.

  13. A phase I study of intermediate dose cytarabine in combination with lenalidomide in relapsed/refractory acute myeloid leukemia.

    PubMed

    Griffiths, Elizabeth A; Brady, William E; Tan, Wei; Vigil, Carlos E; Thompson, James E; Ford, Laurie A; Dickey, Noelle M; L Bashaw, Heather; Sperrazza, Jill; Wetzler, Meir; Wang, Eunice S

    2016-04-01

    Relapsed/refractory (r/r) Acute Myeloid Leukemia (AML) remains a therapeutic challenge. Cytarabine arabinoside (AraC) forms the backbone of most regimens, with complete responses (CR) ranging from 17 to 20%. Lenalidomide (Len) is approved by the FDA for multiple myeloma and myelodysplasia and has demonstrated activity in AML. We developed a phase I study to evaluate the safety and tolerability of Len in combination with intermediate dose AraC (1.5 g/m(2)/day given on days 1-5) in adults with r/r AML. The maximally tolerated dose for this combination was 10mg daily on days 6-26 of a 28 day cycle. Dose de-escalation from 25mg was required due to rash, liver function abnormalities, and hypokalemia. Of 32 evaluable patients, five achieved CR (16%), 5CRi (16%) and 3 had hematological improvements for an overall response rate of 41% (13/32). Median overall survival (95% confidence interval) for patients treated on study was 5.8 (2.5-10.6) months and disease free survival was 3.4 (2.3-6.2) months. This single institute phase I trial of Len and intermediate dose AraC was associated with marked skin and other toxicities. At the dose and schedule tested, this combination did not appear to result in improved CR over single agent AraC for r/r AML.

  14. Thermal decomposition of tetramethyl orthosilicate in the gas phase: An experimental and theoretical study of the initiation process

    SciTech Connect

    Chu, J.C.S.; Soller, R.; Lin, M.C. ); Melius, C.F. )

    1995-01-12

    The thermal decomposition of Si(OCH[sub 3])[sub 4] (TMOS) has been studied by FTIR at temperatures between 858 and 968 K. The experiment was carried out in a static cell at a constant pressure of 700 Torr under highly diluted conditions. Additional experiments were performed by using toluene as a radical scavenger. The species monitored included TMOS, CH[sub 2]O, CH[sub 4], and CO. According to these measurements, the first-order global rate constants for the disappearance of TMOS without and with toluene can be given by k[sub g] = 1.4 x 10[sup 16] exp(-81 200/RT) s[sup [minus]1] and k[sub g] = 2.0 x 10[sup 14] exp(-74 500/RT) s[sup [minus]1], respectively. The noticeable difference between the two sets of Arrhenius parameters suggests that, in the absence of the inhibitor, the reactant was consumed to a significant extent by radical attacks at higher temperatures. The experimental data were kinetically modeled with the aid of a quantum-chemical calculation using the BAC-MP4 method. The results of the kinetic modeling, using the mechanism constructed on the basis of the quantum-chemical data and the known C/H/O chemistry, identified two rate-controlling reactions whose first-order rate constants are given here. 22 refs., 15 figs., 3 tabs.

  15. Towards understanding the decomposition/isomerism channels of stratospheric bromine species: ab initio and quantum topology study.

    PubMed

    Aziz, Saadullah G; Alyoubi, Abdulrahman O; Elroby, Shaaban A; Osman, Osman I; Hilal, Rifaat H

    2015-03-25

    The present study aims at a fundamental understanding of bonding characteristics of the C-Br and O-Br bonds. The target molecular systems are the isomeric CH3OBr/BrCH2OH system and their decomposition products. Calculations of geometries and frequencies at different density functional theory (DFT) and Hartree-Fock/Møller-Plesset (HF/MP2) levels have been performed. Results have been assessed and evaluated against those obtained at the coupled cluster single-double (Triplet) (CCSD(T)) level of theory. The characteristics of the C-Br and O-Br bonds have been identified via analysis of the electrostatic potential, natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM). Analysis of the electrostatic potential (ESP) maps enabled the quantitative characterization of the Br σ-holes. Its magnitude seems very sensitive to the environment and the charge accumulated in the adjacent centers. Some quantum topological parameters, namely Ñ2ρ, ellipticity at bond critical points and the Laplacian bond order, were computed and discussed. The potential energy function for internal rotation has been computed and Fourier transformed to characterize the conformational preferences and origin of the barriers. NBO energetic components for rotation about the C-Br and O-Br bonds as a function of torsion angle have been computed and displayed.

  16. A study of the Alboran sea mesoscale system by means of empirical orthogonal function decomposition of satellite data

    NASA Astrophysics Data System (ADS)

    Baldacci, A.; Corsini, G.; Grasso, R.; Manzella, G.; Allen, J. T.; Cipollini, P.; Guymer, T. H.; Snaith, H. M.

    2001-05-01

    This paper presents the results of a combined empirical orthogonal function (EOF) analysis of Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST) data and sea-viewing wide field-of-view sensor (SeaWiFS) chlorophyll concentration data over the Alboran Sea (Western Mediterranean), covering a period of 1 year (November 1997-October 1998). The aim of this study is to go beyond the limited temporal extent of available in situ measurements by inferring the temporal and spatial variability of the Alboran Gyre system from long temporal series of satellite observations, in order to gain insight on the interactions between the circulation and the biological activity in the system. In this context, EOF decomposition permits concise and synoptic representation of the effects of physical and biological phenomena traced by SST and chlorophyll concentration. Thus, it is possible to focus the analysis on the most significant phenomena and to understand better the complex interactions between physics and biology at the mesoscale. The results of the EOF analysis of AVHRR-SST and SeaWiFS-chlorophyll concentration data are presented and discussed in detail. These improve and complement the knowledge acquired during the in situ observational campaigns of the MAST-III Observations and Modelling of Eddy scale Geostrophic and Ageostrophic motion (OMEGA) Project.

  17. Towards Understanding the Decomposition/Isomerism Channels of Stratospheric Bromine Species: Ab Initio and Quantum Topology Study

    PubMed Central

    Aziz, Saadullah G.; Alyoubi, Abdulrahman O.; Elroby, Shaaban A.; Osman, Osman I.; Hilal, Rifaat H.

    2015-01-01

    The present study aims at a fundamental understanding of bonding characteristics of the C–Br and O–Br bonds. The target molecular systems are the isomeric CH3OBr/BrCH2OH system and their decomposition products. Calculations of geometries and frequencies at different density functional theory (DFT) and Hartree–Fock/Møller–Plesset (HF/MP2) levels have been performed. Results have been assessed and evaluated against those obtained at the coupled cluster single-double (Triplet) (CCSD(T)) level of theory. The characteristics of the C–Br and O–Br bonds have been identified via analysis of the electrostatic potential, natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM). Analysis of the electrostatic potential (ESP) maps enabled the quantitative characterization of the Br σ-holes. Its magnitude seems very sensitive to the environment and the charge accumulated in the adjacent centers. Some quantum topological parameters, namely ∇2ρ, ellipticity at bond critical points and the Laplacian bond order, were computed and discussed. The potential energy function for internal rotation has been computed and Fourier transformed to characterize the conformational preferences and origin of the barriers. NBO energetic components for rotation about the C–Br and O–Br bonds as a function of torsion angle have been computed and displayed. PMID:25815595

  18. Studies of magnetite nanoparticles synthesized by thermal decomposition of iron (III) acetylacetonate in tri(ethylene glycol)

    NASA Astrophysics Data System (ADS)

    Maity, Dipak; Kale, S. N.; Kaul-Ghanekar, Ruchika; Xue, Jun-Min; Ding, Jun

    2009-10-01

    In this paper, water-soluble magnetite nanoparticles have been directly synthesized by thermal decomposition of iron (III) acetylacetonate, Fe(acac) 3 in tri(ethyleneglycol). Size and morphology of the nanoparticles are determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements while the crystal structure is identified using X-ray diffraction (XRD). Surface charge and surface coating of the nanoparticles are recognized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectra (XPS) and zeta potential measurements. Magnetic properties are determined using vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The results show that as-prepared magnetite nanoparticles are relatively monodisperse, single crystalline and superparamagnetic in nature with the blocking temperature at around 100 K. The magnetite nanoparticles are found to be highly soluble in water due to steric and electrostatic interactions between the particles arising by the surface adsorbed tri(ethyleneglycol) molecules and associated positive charges, respectively. Cytotoxicity studies on human cervical (SiHa), mouse melanoma (B16F10) and mouse primary fibroblast cells demonstrate that up to a dose of 80 μg/ml, the magnetic nanoparticles are nontoxic to the cells. Specific absorption rate (SAR) value has been calculated to be 885 and 539 W/gm for samples with the iron concentration of 1 and 0.5 mg/ml, respectively. The high SAR value upon exposure to 20 MHz radiofrequency signifies the applicability of as-prepared magnetite nanoparticles for a feasible magnetic hyperthermia treatment.

  19. Nested Taylor decomposition in multivariate function decomposition

    NASA Astrophysics Data System (ADS)

    Baykara, N. A.; Gürvit, Ercan

    2014-12-01

    Fluctuationlessness approximation applied to the remainder term of a Taylor decomposition expressed in integral form is already used in many articles. Some forms of multi-point Taylor expansion also are considered in some articles. This work is somehow a combination these where the Taylor decomposition of a function is taken where the remainder is expressed in integral form. Then the integrand is decomposed to Taylor again, not necessarily around the same point as the first decomposition and a second remainder is obtained. After taking into consideration the necessary change of variables and converting the integration limits to the universal [0;1] interval a multiple integration system formed by a multivariate function is formed. Then it is intended to apply the Fluctuationlessness approximation to each of these integrals one by one and get better results as compared with the single node Taylor decomposition on which the Fluctuationlessness is applied.

  20. Decomposition approach of the nitrogen generation process: empirical study on the Shimabara Peninsula in Japan.

    PubMed

    Fujii, Hidemichi; Nakagawa, Kei; Kagabu, Makoto

    2016-11-01

    Groundwater nitrate pollution is one of the most prevalent water-related environmental problems worldwide. The objective of this study is to identify the determinants of nitrogen pollutant changes with a focus on the nitrogen generation process. The novelty of our research framework is to cost-effectively identify the factors involved in nitrogen pollutant generation using public data. This study focuses on three determinant factors: (1) nitrogen intensity changes, (2) structural changes, and (3) scale changes. This study empirically analyses three sectors, including crop production, farm animals, and the household, on the Shimabara Peninsula in Japan. Our results show that the nitrogen supply from crop production sectors has decreased because the production has been scaled down and shifted towards lower nitrogen intensive crops. In the farm animal sector, the nitrogen supply has also been successfully reduced due to scaling-down efforts. Households have decreased the nitrogen supply by diffusion of integrated septic tank and sewerage systems.

  1. Investigation of the decomposition mechanism of hexachlorobenzene on gamma-Al2O3.

    PubMed

    Zhanga, Lifei; Zhenga, Minghui; Zhang, Bing; Su, Guijin

    2012-09-01

    Decomposition of hexachlorobenzene (HCB) on high surface area y-alumina was comprehensively studied using in situ Fourier transform infrared spectroscopy, gas chromatography/mass spectrometry (GC-MS) and ion chromatography. Monitoring of the temperature-dependent decomposition by Fourier transform infrared spectroscopy showed that HCB decomposed as the temperature increased and phenolate species and other decomposition products formed. Pentachlorophenol (PeCP) and pentachlorobenzene were identified as the main decomposition products by GC-MS, and the time dependence of the formation of PeCP and pentachlorobenzene suggested that PeCP was the main intermediate. A trace analytical method based on derivatization and GC-MS revealed the presence of 3,4,5,6-tetrachloro-1,2-benzenediol and tetrachloro-hydroquinone. A small amount of inorganic chlorine ions produced by dechlorination of HCB was detected by ion chromatography. PeCP was the main intermediate and was transformed to 3,4,5,6-tetrachloro-1,2-benzenediol and tetrachloro-hydroquinone on the alumina surface. These compounds then decomposed to small molecules via cracking of their aromatic rings.

  2. Decomposition into Multiple Morphemes during Lexical Access: A Masked Priming Study of Russian Nouns

    ERIC Educational Resources Information Center

    Kazanina, Nina; Dukova-Zheleva, Galina; Geber, Dana; Kharlamov, Viktor; Tonciulescu, Keren

    2008-01-01

    The study reports the results of a masked priming experiment with morphologically complex Russian nouns. Participants performed a lexical decision task to a visual target that differed from its prime in one consonant. Three conditions were included: (1) "transparent," in which the prime was morphologically related to the target and contained the…

  3. Decomposition into Multiple Morphemes during Lexical Access: A Masked Priming Study of Russian Nouns

    ERIC Educational Resources Information Center

    Kazanina, Nina; Dukova-Zheleva, Galina; Geber, Dana; Kharlamov, Viktor; Tonciulescu, Keren

    2008-01-01

    The study reports the results of a masked priming experiment with morphologically complex Russian nouns. Participants performed a lexical decision task to a visual target that differed from its prime in one consonant. Three conditions were included: (1) "transparent," in which the prime was morphologically related to the target and contained the…

  4. Adsorption and decomposition of monopropellant molecule HAN on Pd(100) and Ir(100) surfaces: A DFT study

    NASA Astrophysics Data System (ADS)

    Banerjee, Sourav; Shetty, Sharath A.; Gowrav, M. N.; Oommen, Charlie; Bhattacharya, Atanu

    2016-11-01

    We have performed density functional theory calculations with the generalized gradient approximation to investigate the catalytic decomposition reactions of one of the most promising monopropellants, hydroxylammonium nitrate (HAN), on two catalytically active single crystal Pd(100) and Ir(100) surfaces, aiming at exploring different reaction pathways and reactivities of these two surfaces towards the catalytic decomposition of HAN. We find that the HAN molecule binds both the Pd(100) and Ir(100) surfaces molecularly in different orientations with respect to the surface. The HONO elimination is found to possess the lowest activation energy on the Pd(100) surface; whereas, NO2 elimination is predicted to show the lowest activation energy on the Ir(100) surface. Exothermicities associated with different reaction steps are also discussed. This is the first theoretical report on the catalytic decomposition reactions of the HAN molecule on the single crystal Pd(100) and the Ir(100) surfaces using the periodic DFT calculations.

  5. 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.

  6. An Evaluation of Two Forms of Oral Reading as a Means of Intermediate Social Studies Instruction.

    ERIC Educational Resources Information Center

    Hill, Charles H.

    A study examined the effects of "round robin reading" (RRR) as an instructional procedure in social studies. Specifically, the study asked whether an oral textbook presentation had a significant effect on learning social studies material and if grade level, reading level, social studies knowledge, and gender significantly affected the…

  7. Low-temperature FTIR study of multiple K intermediates in the photocycles of bacteriorhodopsin and xanthorhodopsin.

    PubMed

    Dioumaev, Andrei K; Wang, Jennifer M; Lanyi, Janos K

    2010-03-04

    Low-temperature FTIR spectroscopy of bacteriorhodopsin and xanthorhodopsin was used to elucidate the number of K-like bathochromic states, their sequence, and their contributions to the photoequilibrium mixtures created by illumination at 80-180 K. We conclude that in bacteriorhodopsin the photocycle includes three distinct K-like states in the sequence bR (hv)--> I* --> J --> K(0) --> K(E) --> L --> ..., and similarly in xanthorhodopsin. K(0) is the main fraction in the mixture at 77 K that is formed from J. K(0) becomes thermally unstable above approximately 50 K in both proteins. At 77 K, both J-to-K(0) and K(0)-to-K(E) transitions occur and, contrarily to long-standing belief, cryogenic trapping at 77 K does not produce a pure K state but a mixture of the two states, K(0) and K(E), with contributions from K(E) of approximately 15 and approximately 10% in the two retinal proteins, respectively. Raising the temperature leads to increasing conversion of K(0) to K(E), and the two states coexist (without contamination from non-K-like states) in the 80-140 K range in bacteriorhodopsin, and in the 80-190 K range in xanthorhodopsin. Temperature perturbation experiments in these regions of coexistence revealed that, in spite of the observation of apparently stable mixtures of K(0) and K(E), the two states are not in thermally controlled equilibrium. The K(0)-to-K(E) transition is unidirectional, and the partial transformation to K(E) is due to distributed kinetics, which governs the photocycle dynamics at temperatures below approximately 245 K (Dioumaev and Lanyi, Biochemistry 2008, 47, 11125-11133). From spectral deconvolution, we conclude that the K(E) state, which is increasingly present at higher temperatures, is the same intermediate that is detected by time-resolved FTIR prior to its decay, on a time scale of hundreds of nanoseconds at ambient temperature (Dioumaev and Braiman, J. Phys. Chem. B 1997, 101, 1655-1662), into the K(L) state. We were unable to trap the

  8. Decomposition of PCBs in oils using gamma radiolysis: A treatability study. Final report

    SciTech Connect

    Mincher, B.J.; Arbon, R.E.

    1996-04-01

    This report presents the results of a treatability study of radiologically and PCB contaminated waste hydraulic oils at the Idaho National Engineering Laboratory (INEL). The goal of the study was to demonstrate that PCBs could be selectively removed from the contaminated oils. The PCBs were selectively decomposed in an in-situ fashion via gamma-ray radiolysis. The gamma-ray source was spent nuclear fuel at the Advanced Test Reactor (ATR) canal at the Test Reactor Area (TRA), of the INEL. Exposure to gamma-rays does not induce radioactivity in the exposed solutions. The treatability study was the culmination of five years of research concerning PCB radiolysis conducted at INEL which investigated the mechanism and kinetics of the reaction in several solvents. The major findings of this research are summarized here. Based upon these findings three INEL waste streams were selected for testing of the process. The Environmental Protection Agency (EPA) treatment standard of 2 mg/kg was successfully achieved in all waste streams. The interference of contaminants other than PCBs is discussed.

  9. Computational study of the combustion and atmospheric decomposition of 2-methylfuran.

    PubMed

    Davis, Alexander C; Sarathy, S Mani

    2013-08-22

    There is a growing interest in alkylfurans as potential biofuels. Recent work has highlighted the need for further study of the atmospheric oxidation mechanism of 2-methylfuran (2MF). This study utilizes the high level composite computational methods, G4 and CBS-QB3, to determine the bond dissociation energies for the C-H bond in 2MF and the reaction enthalpies and barrier heights of several of the known possible initiation reaction pathways. This study also investigates the possible subsequent low temperature reaction pathways following the addition of OH and then O2 onto the 2MF ring. The placement of the OH and O2 on the ring, either cis or trans to each other, dictates the viability of subsequent reactions. Of particular interest is the observation that 1,4 H-migrations that abstract the hydrogen bound to the same carbon as the OH have abnormally low barrier height. This dramatic decrease puts the reaction barrier lower than concerted eliminations and 6-membered ring Waddington-type reactions. In addition, a novel reaction type, described as a Waddington concerted elimination, is reported herein. This reaction, when viable, is generally more favorable than other reactions. The results presented here are of interest to combustion modelers and atmospheric chemists, particularly those working on aromatic hydrocarbons and systems with conjugated double bonds.

  10. Gunshot residues on dry bone after decomposition--a pilot study.

    PubMed

    Taborelli, Anna; Gibelli, Daniele; Rizzi, Agostino; Andreola, Salvatore; Brandone, Alberto; Cattaneo, Cristina

    2012-09-01

    Very little literature exists concerning radiochemical and microscopic analyses of gunshot wounds in decomposed material, and even less concerning skeletonized samples; the most advanced technologies may provide useful indications for the diagnosis of suspect lesions, especially if gunshot wounds are no longer recognizable. However, we know very little of the survival of gunshot residues (GSR) in skeletonized samples. This study examined nine gunshot wounds produced on pig heads which then underwent skeletonization for 4 years, and four gunshot entries on human heads from judicial cases which were then macerated to the bone in water; the samples underwent scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX) analysis. Positive results for GSR were observed only in four of the nine animal samples and in all four human samples. Among the human samples, two lesions showed Pb and Sb, one lesion only Pb, and one Pb, Sb, and Ba. This pilot study showed the survival of GSR in skeletal material and therefore the crucial importance of SEM-EDX analyses on skeletonized material. Further studies are needed in order to ascertain the role of environmental modifications of GSR.

  11. Experimental and theoretical study of the decomposition of copper nitrate cluster anions.

    PubMed

    Pruitt, Carrie Jo M; Goebbert, Daniel J

    2015-05-21

    Copper nitrate anion clusters Cu(NO3)3(-) and Cu(NO3)2(-) were generated by electrospray ionization and studied with collision-induced dissociation and energy-resolved mass spectrometry. Collision-induced dissociation resulted in three different fragmentation reactions-loss of NO3(-), NO3(•), and NO2(•). The type of fragmentation reaction depends on the oxidation state of the metal. The Cu(NO3)3(-) cluster showed loss of NO3(•) but no loss of NO2(•), whereas the Cu(NO3)2(-) cluster showed loss of NO2(•) but no loss of NO3(•). The fragmentation reactions were studied by theoretical methods. These studies show loss of NO3(•) corresponds to reduction of the metal charge by electron transfer, whereas loss of NO2(•) and metal-oxide bond formation by O(-) abstraction in Cu(NO3)2(-) does not necessarily result in the expected oxidation of the metal.

  12. Effects of internal stresses and intermediate phases on the coarsening of coherent precipitates: A phase-field study

    SciTech Connect

    M. Asle Zaeem; H. El Kadiri; M. F. Horstemeyer; M. Khafizov; Z. Utegulov

    2012-03-01

    Phase stability, topology and size evolution of precipitates are important factors in determining the mechanical properties of crystalline materials. In this article, the Cahn-Hilliard type of phase-field model was coupled to elasticity equations within a mixed-order Galerkin finite element framework to study the coarsening morphology of coherent precipitates. The effects of capillarity, particle size and fraction, compositional strain, and inhomogeneous elasticity on the kinetics and kinematics of coherent precipitates in a binary dual phase crystal admitting a third intermediate stable/meta-stable phase were investigated. The results demonstrated the ability of the model to simulate coarsening under the concomitant action of Ostwald ripening and mismatch elastic strain mechanisms. Using a phenomenological coarsening power law, coarsening rates were determined to depend on precipitate size and volume fraction, compositional strain, and strain mismatch between precipitates and the matrix. Results also showed that the necking incubation time between two neighboring precipitates depends inversely on the precipitate's initial sizes; however, under fixed volume fraction of precipitates, any increase in the initial sizes of the precipitates mitigates the coarsening. Meanwhile, the compositional strain and the growth of the intermediate stable/meta-stable phase leads to substantial enhancements of precipitate coarsening.

  13. Molecular orbital studies of enzyme activity: I: Charge relay system and tetrahedral intermediate in acylation of serine proteinases.

    PubMed Central

    Scheiner, S; Kleier, D A; Lipscomb, W N

    1975-01-01

    The charge relay ststem and its role in the acylation of serine proteinases is studied using the partial retention of diatomic differential overlap (PRDDO) technique to perform approximate ab initio molecular orbital calculations on a model of the enzyme-substrate complex. The aspartate in the charge relay system is seen to act as the ultimate proton acceptor during the charging of the serine nucleophile. A projection of the potential energy surface is obtained in a subspace corresponding to this charge transfer and to the coupled motions of active site residues and the substrate. These results together with extended basis set results for cruder models suggest that a concerted transfer of protons from Ser-195 to His-57 and from His-57 to Asp-102 occurs with an energy barrier of 20-25 kcal/mole (84-105 kJ/mole). The subsequent nucleophilic attack on the scissile peptide linkage by the charged serine is then seen to proceed energetically downhill to the tetrahedral intermediate. The formation of the tetrahedral intermediate from the Michaelis complex is calculated to be nearly thermoneutral. PMID:1058476

  14. High-temperature Raman study of L-alanine, L-threonine and taurine crystals related to thermal decomposition

    NASA Astrophysics Data System (ADS)

    Cavaignac, A. L. O.; Lima, R. J. C.; Façanha Filho, P. F.; Moreno, A. J. D.; Freire, P. T. C.

    2016-03-01

    In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.

  15. Decomposition of N-chloroglycine in alkaline aqueous solution: kinetics and mechanism.

    PubMed

    Szabó, Mária; Baranyai, Zsolt; Somsák, László; Fábián, István

    2015-06-15

    The decomposition kinetics and mechanism of N-chloroglycine (MCG) was studied under very alkaline conditions ([OH(-)] = 0.01-0.10 M). The absorbance change is consistent with two consecutive first-order processes in the 220-350 nm wavelength range. The first reaction is linearly dependent on [OH(-)] and interpreted by the formation of a carbanion from MCG in an equilibrium step (KOH) and a subsequent loss of chloride ion from this intermediate: kobs1 = KOH k1 = (6.4 ± 0.1) × 10(-2) M(-1) s(-1), I = 1.0 M (NaClO4), and T = 25.0 °C. The second process is assigned to the first-order decomposition of N-oxalylglycine, which is also formed as an intermediate in this system: kobs2 = (1.2 ± 0.1) × 10(-3) s(-1). Systematic (1)H and (13)C NMR measurements were performed in order to identify and follow the concentration changes of the reactant, intermediate, and product. It is confirmed that the decomposition proceeds via the formation of glyoxylate ion and produces N-formylglycine as a final product. This compound is stable for an extended period of time but eventually hydrolyses into formate and glycinate ions. A detailed mechanism is postulated which resolves the controversies found in earlier literature results.

  16. Task decomposition: a framework for comparing diverse training models in human brain plasticity studies

    PubMed Central

    Coffey, Emily B. J.; Herholz, Sibylle C.

    2013-01-01

    Training studies, in which the structural or functional neurophysiology is compared before and after expertise is acquired, are increasingly being used as models for understanding the human brain’s potential for reorganization. It is proving difficult to use these results to answer basic and important questions like how task training leads to both specific and general changes in behavior and how these changes correspond with modifications in the brain. The main culprit is the diversity of paradigms used as complex task models. An assortment of activities ranging from juggling to deciphering Morse code has been reported. Even when working in the same general domain, few researchers use similar training models. New ways to meaningfully compare complex tasks are needed. We propose a method for characterizing and deconstructing the task requirements of complex training paradigms, which is suitable for application to both structural and functional neuroimaging studies. We believe this approach will aid brain plasticity research by making it easier to compare training paradigms, identify “missing puzzle pieces,” and encourage researchers to design training protocols to bridge these gaps. PMID:24115927

  17. A study of the thermal decomposition of adulterated cocaine samples under optimized aerobic pyrolytic conditions.

    PubMed

    Gostic, T; Klemenc, S; Stefane, B

    2009-05-30

    The pyrolysis behaviour of pure cocaine base as well as the influence of various additives was studied using conditions that are relevant to the smoking of illicit cocaine by humans. For this purpose an aerobic pyrolysis device was developed and the experimental conditions were optimized. In the first part of our study the optimization of some basic experim