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1

Pincer-type di(1,2,4-triazolin-5-ylidene)Pd(II) complexes and their catalytic activities towards Cu- and amine-free Sonogashira reaction.  

PubMed

Pd(II) complexes [PdBr(A-?(3)CNC)]Br (1) and [PdBr(B-?(3)CNC)]Br (2) with new CNC pincer-type ligands derived from 1,2,4-triazolin-5-ylidenes have been synthesized and characterized by multinuclei NMR spectroscopies, ESI mass spectrometry and X-ray diffraction analysis. The more soluble complex 1 proved to be an efficient pre-catalyst in copper- and amine-free Sonogashira reaction with high turnover numbers. The potential for recycling of the catalyst was also demonstrated. PMID:23483051

Huynh, Han Vinh; Lee, Chen-Shiang

2013-05-21

2

Copper-free and amine-free Sonogashira coupling in air in a mixed aqueous medium by palladium complexes of N\\/ O-functionalized N-heterocyclic carbenes  

Microsoft Academic Search

Highly convenient copper-free and amine-free Sonogashira coupling of aryl bromides and iodides with terminal acetylenes under amenable conditions in air and in a mixed aqueous medium are reported using several new, user friendly and robust palladium precatalysts (1–5) of N\\/O-functionalized N-heterocyclic carbenes (NHCs). In particular, the precatalysts, 1 and 2, were synthesized from the imidazolium chloride salts by the treatment

Manoja K. Samantaray; Mobin M. Shaikh; Prasenjit Ghosh

2009-01-01

3

Reactions at supercritical conditions: Applications and fundamentals  

Microsoft Academic Search

Supercritical fluids possess properties that make them attractive as media for chemical reactions. Conducting chemical reactions at supercritical conditions affords opportunities to manipulate the reaction environment (Solvent properties) by manipulating pressure, to enhance the solubilities of reactants and products, to eliminate interphase transport limitations on reaction rates, and to integrate reaction and separation unit operations. Supercritical conditions may be advantageous

Phillip E. Savage; Sudhama Gopalan; Thamid I. Mizan; Christopher J. Martino; Eric E. Brock

1995-01-01

4

Application of Highly Efficient, Recyclable Organic–Inorganic Hybrid Material Immobilized Palladium Catalyst in Amine? and Phosphine?Free Suzuki–Miyaura Reaction  

Microsoft Academic Search

Palladium immobilized on organic–inorganic (silica?gel) hybrid materials behaves as a very efficient heterogeneous catalyst in the Suzuki–Miyaura coupling reaction. Aryl iodides, bromides, and activated chlorides, coupled with organoboronic acids (Suzuki–Miyaura reaction), smoothly afford the corresponding cross?coupling products in excellent yields under phosphine?free and amine?free reaction conditions in the presence of 3?aminopropyl functionalized silica?gel immobilized palladium (silica?APTS?Pd) as catalyst. Furthermore, the

Liyuan Zhang; Lei Wang; Hongji Li; Pinhua Li

2008-01-01

5

Aluminum/water reactions under extreme conditions  

NASA Astrophysics Data System (ADS)

We discuss mechanisms that may control the reaction of aluminum and water under extreme conditions. We are particularly interested in the high-temperature, high-strain regime where the native oxide layer is destroyed and fresh aluminum is initially in direct contact with liquid or supercritical water. Disparate experimental data over the years have suggested rapid oxidation of aluminum is possible in such situations, but no coherent picture has emerged as to the basic oxidation mechanism or the physical processes that govern the extent of reaction. We present theoretical and computational analysis of traditional metal/water reaction mechanisms that treat diffusion through a dynamic oxide layer or reaction limited by surface kinetics. Diffusion through a fresh solid oxide layer is shown to be far too slow to have any effect on the millisecond timescale (even at high temperatures). Quantum molecular dynamics simulations of liquid Al and water surface reactions show rapid water decomposition at the interface, catalyzed by adjacent water molecules in a Grotthus-like relay mechanism. The surface reaction barriers are far too low for this to be rate-limiting in any way. With these straightforward mechanisms ruled out, we investigate two more complex possibilities for the rate-limiting factor; first, we explore the possibility that newly formed oxide remains a metastable liquid well below its freezing point, allowing for diffusion-limited reactions through the oxide shell but on a much faster timescale. The extent of reaction would then be controlled by the solidification kinetics of alumina. Second, we discuss preliminary analysis on surface erosion and turbulent mixing, which may play a prominent role during hypervelocity penetration of solid aluminum projectiles into water.

Hooper, Joseph

2013-03-01

6

Biogeochemical Reactions Under Simulated Europa Ocean Conditions  

NASA Astrophysics Data System (ADS)

Galileo data have demonstrated the probable presence of a liquid water ocean on Europa, and existence of salts and carbon dioxide in the satellite's surface ice (e.g., Carr et al., 1998; McCord et al., 1999, Pappalardo et al., 1999; Kivelson et al., 2000). Subsequently, the discovery of chemical signatures of extinct or extant life in Europa's ocean and on its surface became a distinct possibility. Moreover, understanding of Europa's potential habitability is now one of the major goals of the Europa Orbiter Flagship mission. It is likely, that in the early stages of Europa's ocean formation, moderately alkaline oceanic sulfate-carbonate species and a magnetite-silicate mantel could have participated in low-temperature biogeochemical sulfur, iron and carbon cycles facilitated by primitive organisms (Zolotov and Shock, 2004). If periodic supplies of fresh rock and sulfate-carbonate ions are available in Europa's ocean, then an exciting prospect exists that life may be present in Europa's ocean today. In our laboratory, we began the study of the plausible biogeochemical reactions under conditions appropriate to Europa's ocean using barophilic psychrophilic organisms that thrive under anaerobic conditions. In the near absence of abiotic synthetic pathways due to low Europa's temperatures, the biotic synthesis may present a viable opportunity for the formation of the organic and inorganic compounds under these extreme conditions. This work is independent of assumptions regarding hydrothermal vents at Europa's ocean floor or surface-derived oxidant sources. For our studies, we have fabricated a high-pressure (5,000 psi) reaction vessel that simulates aqueous conditions on Europa. We were also successful at reviving barophilic psychrophilic strains of Shewanella bacterium, which serve as test organisms in this investigation. Currently, facultative barophilic psychrophilic stains of Shewanella are grown in the presence of ferric food source; the strains exhibiting iron reduction capability will be later selected and used to facilitate biogeochemical reduction of iron under simulated temperature and pressure of Europa's ocean. The results of this work will enable us to ascertain whether Europa's cold, high-pressure ocean is capable of supporting life. In addition, the data from this study will help in generating a list of organic and inorganic target molecules for future remote sensing and in situ exploration missions.

Amashukeli, X.; Connon, S. A.; Gleeson, D. F.; Kowalczyk, R. S.; Pappalardo, R. T.

2007-12-01

7

Transketolase reaction under credible prebiotic conditions.  

PubMed

A transketolase reaction was catalyzed by cyanide ion under prebiotic conditions instead of its modern catalyst, thiamine pyrophosphate (TPP). Cyanide ion converted fructose plus glyceraldehyde to erythrose plus xylulose, the same products as are formed in modern biochemistry (but without the phosphate groups on the sugars). Cyanide was actually a better catalyst than was TPP in simple solution, where there is a negligible concentration of the C-2 anion of TPP, but of course not with an enzyme in modern biology. The cyanide ion was probably not toxic on prebiotic earth, but only when the oxygen atmosphere developed and iron porphyrin species were needed, which cyanide poisons. Thus, catalyses by TPP that are so important in modern biochemistry in the Calvin cycle for photosynthesis and the gluconic acid pathway for glucose oxidation, among other processes, were probably initially performed instead by cyanide ion until its toxicity with metalloproteins became a problem and primitive enzymes were present to work with TPP, or most likely its primitive precursors. PMID:23440198

Breslow, Ronald; Appayee, Chandrakumar

2013-02-25

8

Transketolase reaction under credible prebiotic conditions  

PubMed Central

A transketolase reaction was catalyzed by cyanide ion under prebiotic conditions instead of its modern catalyst, thiamine pyrophosphate (TPP). Cyanide ion converted fructose plus glyceraldehyde to erythrose plus xylulose, the same products as are formed in modern biochemistry (but without the phosphate groups on the sugars). Cyanide was actually a better catalyst than was TPP in simple solution, where there is a negligible concentration of the C-2 anion of TPP, but of course not with an enzyme in modern biology. The cyanide ion was probably not toxic on prebiotic earth, but only when the oxygen atmosphere developed and iron porphyrin species were needed, which cyanide poisons. Thus, catalyses by TPP that are so important in modern biochemistry in the Calvin cycle for photosynthesis and the gluconic acid pathway for glucose oxidation, among other processes, were probably initially performed instead by cyanide ion until its toxicity with metalloproteins became a problem and primitive enzymes were present to work with TPP, or most likely its primitive precursors.

Breslow, Ronald; Appayee, Chandrakumar

2013-01-01

9

Action of bimetallic nanocatalysts under reaction conditions and during catalysis: evolution of chemistry from high vacuum conditions to reaction conditions.  

PubMed

Bimetallic catalysts are one of the main categories of metal catalysts due to the tunability of electronic and geometric structures through alloying a second metal. The integration of a second metal creates a vast number of possibilities for varying the surface structure and composition of metal catalysts toward designing new catalysts. It is well acknowledged that the surface composition, atomic arrangement, and electronic state of bimetallic catalysts could be different from those before a chemical reaction or catalysis based on ex situ studies. Thanks to advances in electron-based surface analytical techniques, the surface chemistry and structure of bimetallic nanoparticles can be characterized under reaction conditions and during catalysis using ambient pressure analytical techniques including ambient pressure XPS, ambient pressure STM, X-ray absorption spectroscopy and others. These ambient pressure studies revealed various restructurings in the composition and arrangement of atoms in the surface region of catalysts under reaction conditions or during catalysis compared to that before reaction. These restructurings are driven by thermodynamic and kinetic factors. The surface energy of the constituent metals and adsorption energy of reactant molecules or dissociated species on a metal component are two main factors from the point of view of thermodynamics. Correlations between the authentic surface structure and chemistry of catalysts during catalysis and simultaneous catalytic performance were built for understanding catalytic mechanisms of bimetallic catalysts toward designing new catalysts with high activity, selectivity, and durability. PMID:23023152

Tao, Franklin Feng; Zhang, Shiran; Nguyen, Luan; Zhang, Xueqiang

2012-12-21

10

An age extended progress variable for conditioning reaction rates  

Microsoft Academic Search

An aging progress variable (APV) is proposed as a convenient tool for conditioning quantities used to calculate reaction rates in premixed turbulent combustion. The APV is defined to obey an advection-diffusion-reaction equation where the source term is linearly related to the fuel consumption rate when the APV is less than a threshold representative of the trailing edge of the fuel

R. W. Grout

2007-01-01

11

GREEN CHEMICAL SYNTHESIS THROUGH CATALYSIS AND ALTERNATE REACTION CONDITIONS  

EPA Science Inventory

Green chemical synthesis through catalysis and alternate reaction conditions Encompassing green chemistry techniques and methodologies, we have initiated several projects at the National Risk Management Research laboratory that focus on the design and development of chemic...

12

Reaction conditions for laccase catalyzed polymerization of catechol  

Microsoft Academic Search

Poly(catechol) was synthesized in batch runs with laccase from Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone and sodium acetate buffer for pH control. The effects of the solvent mixture, monomer (catechol), enzyme, medium pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion

Nahit Akta?; Abdurrahman Tanyolaç

2003-01-01

13

High explosive violent reaction (HEVR) from slow heating conditions  

SciTech Connect

The high explosives (HEs) developed and used at the Los Alamos National Laboratory are designed to be insensitive to impact and thermal insults under all but the most extreme conditions. Nevertheless, violent reactions do occasionally occur when HE is involved in an accident. The HE response is closely dependent on the type of external stimulus that initiates the reaction. For example, fast heating of conventional HE will probably result in fairly benign burning, while long-term, slow heating of conventional HE is more likely to produce an HEVR that will do much more damage to the immediate surroundings. An HEVR (High Explosive Violent Reaction) can be defined as the rapid release of energy from an explosive that ranges from slightly faster than a deflagration (very rapid burning) to a reaction that approaches a detonation. A number of thermal analyses have been done to determine slow heat/cook-off conditions that produce HE self-heating that can build up to a catastrophic runaway reaction. The author specifies the conditions that control reaction violence, describes experiments that produced an HEVR, describes analyses done to determine a heating rate threshold for HEVR, and lists possible HEVR situations.

Vigil, A.S.

1999-03-01

14

Interesting reaction of the indanone oximes under Beckmann rearrangement conditions  

Microsoft Academic Search

Attempted Beckmann rearrangement of the 6-methoxyindanone oximes in conventional conditions resulted in the formation of the two kinds of unexpected products: 2-sulfonyloxyindanone and the dimeric product. Related rearrangement was also observed in the reaction with RhCl–trifluoromethansulfonic acid system.

Yasuhiro Torisawa; Takao Nishi; Jun-ichi Minamikawa

2002-01-01

15

Conditions on exchange mechanisms for polarization effects in inclusive reactions  

Microsoft Academic Search

In the framework of Mueller-Regge phenomenology we investigate under which conditions one could expect to observe polarization effects in the fragmentation region for inclusive reactions. On the basis of kinematical considerations and parity relations only, we find that this requires exchange of states with mixed naturalities.

Ph. Salin; J. Soffer

1974-01-01

16

Fulleranes by Direct Reaction with Hydrogen Gas at Elevated Conditions  

NASA Astrophysics Data System (ADS)

Reaction of solid fullerenes with hydrogen gas occurs with or without catalysts at elevated conditions. Composition of hydrofullerene mixture obtained in this reaction depends strongly on temperature (350-450°C), hydrogen pressure (typically 10-120 bar) and duration of treatment. Saturation of hydrogenation occurs after tens of hours, depending on temperature of reaction. In case of extra strong hydrogenation prolonged reaction leads to formation of fulleranes with composition C60Hx approaching number of hydrogen atoms X = 60. These fulleranes are highly unstable and decompose first with formation of fragmented hydrofullerenes with progressively smaller number of carbon atoms C59, C58, C57 etc., followed by collapse of cage structure. Since the collapse occurs at the conditions of high temperature and high hydrogen pressure, all breaking C-C bonds are saturated immediately with hydrogen and new C-H bonds are formed. Therefore, large fragments of fullerane molecules are able to survive and large polycyclic aromatic hydrocarbons (PAH's) formed as a result of cage structure collapse.

Talyzin, Alexandr V.

17

Construction of functional group reactivity database under various reaction conditions automatically extracted from reaction database in a synthesis design system.  

PubMed

To be able to estimate the reactivity of functional groups under certain reaction conditions, we have stored three types of data: (1) data of change or destruction of the functional groups by the conditions of the reaction conditions; (2) data showing no influence of the reaction conditions on the functional groups; and (3) data showing the relative reactivity of two functional groups in the presence of certain reaction conditions. These three types of data, considered together, form entities that are referenced as "interaction data". These interaction data are used in a synthesis design system called SYNSUP. A new module in our system has been constructed that automatically generates interaction data from the reaction databases. From 15 265 reactions in the database, our program selected 2763 useful reactions with yields of > or =90% and one functional group change. From these useful reactions, data regarding 465 interferences, 815 cases of inert functional groups (under the reaction conditions), and 62 relative rate data could be extracted. In addition, with the use of multiple relative rate datasets, the reactivity of more than two functional groups could be deduced. PMID:20187659

Tanaka, Akio; Okamoto, Hideho; Bersohn, Malcolm

2010-03-22

18

Heat of Reaction of the Hydrolysis-Polymerization Process of Tetraethyl Orthosilicate in Acidic Condition  

Microsoft Academic Search

Heat of reaction of the hydrolysis-polymerization process of tetraethyl orthosilicate with water in acidic condition was investigated to clarify the thermodynamic driving force of sol-gel reactions. Heat of reaction was measured using an isoperibol calorimeter by mixing a dilute tetraethyl orthosilicate (TEOS) ethanolic solution with another solution of water, ethanol, and hydrochloric acid. The temperature change of the reaction cell

Jun Matsuoka; Minoru Numaguchi; Satoshi Yoshida; Naohiro Soga

2000-01-01

19

Amine-Free Approach toward N-Toluenesulfonyl Amidine Construction: A Phosphite-Mediated Beckmann-Like Coupling of Oximes and p-Toluenesulfonyl Azide.  

PubMed

Atom hopping: A chlorophosphite-mediated Beckmann ligation of oximes and p-toluenesulfonyl azide gives access to N-sulfonyl phosphoramidines in good to excellent yields. The reaction proceeds under exceptionally mild conditions and constitutes a bioorthogonal approach toward amidines by avoiding the use of amines and transition-metal catalysts. dmp-ol=3,3-dimethylpropanediol. PMID:24038711

Fleury, Lauren M; Wilson, Erin E; Vogt, Monika; Fan, Tiffany J; Oliver, Allen G; Ashfeld, Brandon L

2013-09-05

20

Influence of reaction conditions on MS values and physical properties of waxy maize starch derivatized by reaction with propylene oxide  

Microsoft Academic Search

Waxy maize starch was hydroxypropylated under different swelling conditions (pH, temperature, salt type, salt concentration) to determine the effect of reaction conditions on the extent of modification. MS, pasting temperatures, and paste characteristics of the products were determined. pH had the greatest effect on the extent of reaction. MS values increased as the pH was raised from 10.7 to 11.7.

Jung-Ah Han; James N. BeMiller

2006-01-01

21

Efficient Biginelli Reaction Catalyzed by Sulfamic Acid or Silica Sulfuric Acid under Solvent?Free Conditions  

Microsoft Academic Search

Sulfamic acid efficiently catalyzes the three?component condensation reaction of aldehydes, 1,3?dicarbonyl compounds, and urea\\/thiourea under solvent?free conditions to afford the corresponding dihydropyrimidinones and thio?derivatives in high yields. Silica sulfuric acid is also found to be an efficient catalyst for the Biginelli reaction under solvent?free conditions. Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of

2007-01-01

22

Effects of Meteorological Conditions on Reactions to Noise Exposure.  

National Technical Information Service (NTIS)

More than 80,000 residents' responses to transportation noise at different times of year provide the best, but imprecise, statistical estimates of the effects of season and meteorological conditions on community response to noise. Annoyance with noise is ...

K. P. Shepherd J. M. Fields

2004-01-01

23

The potent vasodilator ethyl nitrite is formed upon reaction of nitrite and ethanol under gastric conditions  

Microsoft Academic Search

By acting as a bioreactor, affording chemical and mechanical conditions for the reaction between dietary components, the stomach may be a source of new bioactive molecules. Using gas chromatography-mass spectrometry we here demonstrate that, under acidic gastric conditions, ethyl nitrite is formed in µM concentrations from the reaction of red wine or distilled alcoholic drinks with physiological amounts of nitrite.

Bruno Gago; Thomas Nyström; Carlos Cavaleiro; Bárbara S. Rocha; Rui M. Barbosa; João Laranjinha; Jon O. Lundberg

2008-01-01

24

Achieving Chemical Equilibrium: The Role of Imposed Conditions in the Ammonia Formation Reaction  

ERIC Educational Resources Information Center

|Under conditions of constant temperature T and pressure P, chemical equilibrium occurs in a closed system (fixed mass) when the Gibbs free energy G of the reaction mixture is minimized. However, when chemical reactions occur under other conditions, other thermodynamic functions are minimized or maximized. For processes at constant T and volume V,…

Tellinghuisen, Joel

2006-01-01

25

Liquid fuels from biomass: catalysts and reaction conditions  

Microsoft Academic Search

The use of ..cap alpha..-phellandrene as a hydrogen transfer agent in wood liquefaction was studied at 200°C. No significant thermally promoted hydrogen transfer occurred under these conditions. Dilute sulfuric acid was added to test the possibility of hydride transfer from ..cap alpha..-phellandrene to wood. Extensive solvent alkylation of the wood occurred in the presence of up to 2 wt %

M. Seth; S. Ergun; T. Vermeulen; R. Djafar

1980-01-01

26

Regimes of chemical reaction waves initiated by nonuniform initial conditions for detailed chemical reaction models  

NASA Astrophysics Data System (ADS)

Regimes of chemical reaction wave propagation initiated by initial temperature nonuniformity in gaseous mixtures, whose chemistry is governed by chain-branching kinetics, are studied using a multispecies transport model and a detailed chemical model. Possible regimes of reaction wave propagation are identified for stoichiometric hydrogen-oxygen and hydrogen-air mixtures in a wide range of initial pressures and temperature levels, depending on the initial non-uniformity steepness. The limits of the regimes of reaction wave propagation depend upon the values of the spontaneous wave speed and the characteristic velocities of the problem. It is shown that one-step kinetics cannot reproduce either quantitative neither qualitative features of the ignition process in real gaseous mixtures because the difference between the induction time and the time when the exothermic reaction begins significantly affects the ignition, evolution, and coupling of the spontaneous reaction wave and the pressure wave, especially at lower temperatures. We show that all the regimes initiated by the temperature gradient occur for much shallower temperature gradients than predicted by a one-step model. The difference is very large for lower initial pressures and for slowly reacting mixtures. In this way the paper provides an answer to questions, important in practice, about the ignition energy, its distribution, and the scale of the initial nonuniformity required for ignition in one or another regime of combustion wave propagation.

Liberman, M. A.; Kiverin, A. D.; Ivanov, M. F.

2012-05-01

27

Conditional symmetries and exact solutions of nonlinear reaction-diffusion systems with non-constant diffusivities  

NASA Astrophysics Data System (ADS)

Q-conditional symmetries (nonclassical symmetries) for the general class of two-component reaction-diffusion systems with non-constant diffusivities are studied. Using the recently introduced notion of Q-conditional symmetries of the first type, an exhausted list of reaction-diffusion systems admitting such symmetry is derived. The results obtained for the reaction-diffusion systems are compared with those for the scalar reaction-diffusion equations. The symmetries found for reducing reaction-diffusion systems to two-dimensional dynamical systems, i.e., ODE systems, and finding exact solutions are applied. As result, multiparameter families of exact solutions in the explicit form for a nonlinear reaction-diffusion system with an arbitrary diffusivity are constructed. Finally, the application of the exact solutions for solving a biologically and physically motivated system is presented.

Cherniha, Roman; Davydovych, Vasyl'

2012-08-01

28

PEG 400 promoted nucleophilic substitution reaction of halides into organic azides under mild conditions  

Microsoft Academic Search

Polyethylene glycol 400 (PEG 400) has been demonstrated as an efficient and eco-friendly reaction medium for the preparation of organic azides from structurally diverse halides by nucleophilic substitution reaction with NaN3 under mild conditions. The advantages of this protocol are: operational simplicity, environmental safety, broad substrate scope, excellent functional group tolerance, and short reaction time. The PEG 400 can be

Hongyao Zeng; Qiang Tian; Huawu Shao

2011-01-01

29

The influence of reaction conditions on the photooxidation of diisopropyl ether  

Microsoft Academic Search

The hydroxyl radical initiated oxidation of diisopropyl ether has been studied in the large-volume outdoor European Photoreactor (EUPHORE) and in a small, laboratory-based reactor system. The product distributions determined from the experiments were found to be significantly dependent on the reaction conditions and provide strong evidence for the existence of three distinct regimes within the reaction system. In the presence

E. M. Collins; H. W. Sidebottom; J. C. Wenger; S. Le Calvé; A. Mellouki; G. LeBras; E. Villenave; K. Wirtz

2005-01-01

30

Threshold dynamics of a delayed reaction diffusion equation subject to the Dirichlet condition.  

PubMed

We establish the threshold dynamics of a delayed reaction diffusion equation subject to the homogeneous Dirichlet boundary condition when the delayed reaction term is non-monotone. We illustrate the main results by two examples, including the delayed Nicholson's blowflies diffusion equation. PMID:22880838

Yi, Taishan; Chen, Yuming; Wu, Jianhong

2009-03-01

31

Formation of phenol under conditions of the reaction of oxidative carbonylation of benzene to benzoic acid  

SciTech Connect

This paper describes conditions for the oxidation of benzene to phenol. It is shown that a reaction mixture of water, carbon monoxide, and oxygen are essential to the oxidation. The oxidation is a side reaction found to occur during the oxidative carbonylation of benzene to benzoic acid in a medium of trifluoroacetic acid.

Kalinovsky, I.O.; Leshcheva, A.N.; Pogorelov, V.V.; Gelbshtein, A.I.

1993-12-31

32

Phosphine oxide-catalysed chlorination reactions of alcohols under Appel conditions.  

PubMed

A phosphine oxide-catalysed chlorination reaction of primary and secondary alcohols has been developed. This process represents the first triphenylphosphine oxide-catalysed alcohol chlorination under Appel conditions. PMID:20386856

Denton, Ross M; An, Jie; Adeniran, Beatrice

2010-03-26

33

Lower Boundary Condition Effects on LIM (Linear Induction Motors) Reaction Rail Mechanical Behavior: Analysis and Experiments.  

National Technical Information Service (NTIS)

Comparison of analytical results with field experiments conducted at Lomita, California, has shown that the lateral behavior of the LIM reaction rail is strongly influenced by the type of boundary conditions used in the analysis along the lower rail edge....

E. C. Haight W. A. Hutchens

1972-01-01

34

Influence of Processing Conditions on the Microstructure and Mechanical Properties of Reaction Sintered Silicon Nitride.  

National Technical Information Service (NTIS)

The microstructure of reaction bonded silicon nitride (RBSN) was changed in a wide range by varying green density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of individual microstruc...

J. Heinrich

1980-01-01

35

Boundary conditions for flows with chemical reactions occurring on a surface  

Microsoft Academic Search

With the use of a solution of a model Boltzmann equation for a binary mixture in the Knudsen layer, we obtain the boundary conditions for the equations of gas dynamics when the reactionliAi?ljAj (li molecules of Ai change intolj molecules of Aj, and vice versa) is occurring on a surface. The boundary condition that we obtain differs from those that

M. N. Kogan; N. K. Makashev

1972-01-01

36

A first example of a reaction under viscous conditions: oxidation of solid benzoins with manganese dioxide  

Microsoft Academic Search

A new, general, and efficient technique for the reaction of solid substrates under viscous conditions with shaking at room\\u000a temperature is described, which can overcome some of the problems existing in common solvent-free reactions solids as the\\u000a starting materials. In this manuscript we present as a first example of this method the oxidation of solid benzoins into the\\u000a corresponding benzils

Ji-Dong Lou; Xiu L. Lu; Aizen J. Marrogi; Feng Li; Chun-Ling Gao; Xiaoping Yu

2008-01-01

37

Esterification reaction using solid heterogeneous acid catalysts under solvent-less condition  

Microsoft Academic Search

The preparation of di-2-ethylhexylphthalate (DOP) via esterification reaction of phthalic anhydride by 2-ethylhexanol in the presence of solid acidic catalysts has been investigated. The used catalysts were natural zeolite, synthetic zeolites (ZEOKAR-2, ASHNCH-3), heteropolyacid H4Si(W3O10)4 and sulfated ZrO2. The reactions were carried out under solvent-less conditions. It was observed that sulfated ZrO2 has higher reactivity and efficiency among the investigated

Firdovsi Tataroglu Sejidov; Yagoub Mansoori; Nadereh Goodarzi

2005-01-01

38

An efficient and recyclable water-soluble cyclopalladated complex for aqueous Suzuki reactions under aerial conditions  

Microsoft Academic Search

Several water-soluble cyclopalladated complexes with five- or six-membered rings have been prepared as air-stable solids from Schiff base ligands bearing an N-phenyl sulfonate groups. Cyclopalladated complexes with six-membered rings show high catalytic efficiency for the Suzuki reactions of aryl bromides with phenylboronic acid in aqueous solvents under mild conditions. Palladium complex 1 can be used for five reaction cycles in

Jin Zhou; Xiaoyan Li; Hongjian Sun

2010-01-01

39

A stronger necessary condition for the multistationarity of chemical reaction networks.  

PubMed

Biochemical reaction networks grow bigger and bigger, fed by the high-throughput data provided by biologists and bred in open repositories of models allowing merging and evolution. Nevertheless, since the available data is still very far from permitting the identification of the increasing number of kinetic parameters of such models, the necessity of structural analyses for describing the dynamics of chemical networks appears stronger every day.Using the structural information, notably from the stoichiometric matrix, of a biochemical reaction system, we state a more strict version of the famous Thomas' necessary condition for multistationarity. In particular, the obvious cases where Thomas' condition was trivially satisfied, mutual inhibition due to a multimolecular reaction and mutual activation due to a reversible reaction, can now easily be ruled out.This more strict condition shall not be seen as some version of Thomas' circuit functionality for the continuous case but rather as related and complementary to the whole domain of the structural analysis of (bio)chemical reaction systems, as pioneered by the chemical reaction network theory. PMID:24048547

Soliman, Sylvain

2013-09-19

40

Carboxymethylation of Cassava Starch in Different Solvents and Solvent-Water Mixtures: Optimization of Reaction Conditions  

NASA Astrophysics Data System (ADS)

The influence of reaction medium on carboxymethylation process was investigated by treating cassava starch with sodium monochloroacetate in different solvents and solvent-water mixtures under alkaline conditions. The amount of carboxyl groups introduced into the starch moiety was determined titrimetrically and used to calculate the Degree of Substitution (DS) and Reaction Efficiency (RE). The results showed that carboxymethylation is significantly affected by the nature of reaction medium at p<0.05. Carboxymethylation in different solvent-water mixtures showed that aqueous 80% n-propanol offered the best medium for carboxymethylation. Optimization of reaction conditions in aqueous 80% n-propanol showed that the best condition for carboxymethylation was at starch-liquor ratio of 1:3, NaOH/reagent molar ratio of 4.0 and reagent-starch molar ratio of 0.35. An increase in temperature was required to effect the reaction at shorter time. At 55°C the highest values of DS and RE achieved in 0.5 h would require three hours to achieve the same values of DS and RE at 45°C.

Nwokocha, Louis M.; Ogunmola, Gabiel B.

41

Pavlovian conditioning of drug reactions: Some implications for problems of drug addiction  

Microsoft Academic Search

This paper reviews the classical conditioning of drug reactions, with special emphasis on the relationship of this phenomenon\\u000a to drug addiction. Several aspects of drug addiction such as drug craving, high relapse tendencies, and the recurrence of\\u000a withdrawal symptoms are reviewed and interpreted in light of classical conditioning theory and data. A theory is proposed\\u000a that attempts to account for

James J. Lynch; Allen P. Fertziger; Harry A. Teitelbaum; Joseph W. Cullen; W. Horsley Gantt

1973-01-01

42

Using Group-Inquiry to Study Differing Reaction Conditions in the E2 Elimination of Cyclohexyl Halides  

ERIC Educational Resources Information Center

|In this experiment, students individually conduct one of several variations of an E2 dehydrohalogenation reaction on a cyclohexyl halide substrate for 30 min, which is sufficient only for a partial reaction to occur. The variations examine reaction conditions including different leaving groups, decreased reaction temperature, or reduced base…

Long, Robert D.

2012-01-01

43

[The effect of noradrenaline on the neuronal reactions of the motor cortex evoked by conditional stimulation].  

PubMed

In chronic experiments on cats the influence of iontophoretic application of adrenomimetic ephedrin and beta-adrenoblocker obsidan (propranolol) on motor cortex neuron reactions following conditional stimuli was investigated under instrumental placing reaction. It was shown for a majority of neurons that the background impulse activity and reactions following conditional stimulation were suppressed by the influence of ephedrin and on the contrary were increased by obsidan application. It is concluded that there exists a consistent tonic suppressing influence of the noradrenergic system on background and evoked cortical neurons impulse activity in the natural state. It is supposed that noradrenergic influence temporal increase may serve as an important link in mechanisms of external inhibition during stress situations, aversive effects, and distractive external excitations. PMID:2263296

Storozhuk, V M; Stezhka, V V; Ivanova, S F

1990-01-01

44

Conditional and opposed reaction path diagrams for the analysis of fluid-chemistry interactions  

SciTech Connect

This conference paper considers how to use reaction path diagrams to better understand the output of reacting flow simulations. Briefly, these diagrams have long been used to depict the reactants and products in networks of chemical reactions. The diagrams can be generated in several ways from computer simulations of chemically reacting fluids to depict how the fluid moderates the chemistry by determining which species are brought into contact to react in quantity. The concept of a conditional diagram is introduced which depicts the reactions occurring in only a portion of the fluid domain, thus enabling comparisons between different regions of the fluid and the overall reaction network. Several examples are provided of the paths occurring in methane diffusion flames.

Grcar, Joseph F.; Day, Marcus S.; Bell, John B.

2003-06-06

45

An evaluation of detailed reaction mechanisms for hydrogen combustion under gas turbine conditions  

Microsoft Academic Search

Chemical kinetics in hydrogen combustion for elevated pressures have recently become more relevant because of the implementation of hydrogen as a fuel in future gas turbine combustion applications, such as IGCC or IRCC systems. The aim of this study is to identify a reaction mechanism that accurately represents H2\\/O2 kinetics over a large range of conditions, particularly at elevated pressures

Jochen Ströhle; Tore Myhrvold

2007-01-01

46

Optimization of reaction conditions for enzymatic synthesis of palm fatty hydrazides using response surface methodology.  

PubMed

Optimization of the enzymatic synthesis of palm fatty hydrazide by the response surface methodology (RSM) was conducted using the Design-Expert 6 software. The palm fatty hydrazide was synthesized from refined, bleached and deodorized palm olein (RBDPOo) and neutralized hydrazine monohydrate in the presence of Rhizomucor miehei lipase, Lipozyme RMIM, an immobilized lipase in n-hexane. The reaction conditions such as the percentage of enzyme, reaction temperature, stirring speed and reaction time were selected as independent variables or studied factors, while the amount of crude palm fatty hydrazide obtained was selected as a dependent variable or response. The study was conducted using a central composite design (CCD) at five coded levels and the experimental data were analyzed using a quadratic model. The analysis of variance (ANOVA) indicates that the model was significant at 95% confidence level with Prob>F of 0.0033, where the regression coefficient value, R² was 0.8415 and lack-of-fit of 0.0984. A percentage of enzyme of 6%, a reaction temperature of 40°C, a stirring speed of 350 rpm and a reaction time of 18 h were found to be the optimum conditions for the conversion of RBDPOo into palm fatty hydrazide. PMID:22531058

Tuan Noor Maznee, T I; Hazimah, A H; Wan Zin, W Y

2012-01-01

47

Analysis of initial reactions of MALDI based on chemical properties of matrixes and excitation condition.  

PubMed

This investigation concerns the initial chemical reactions that affect the ionization of matrixes in matrix-assisted laser desorption/ionization (MALDI). The study focuses on the relaxations of photon energy that occur on a comparable time scale to that of ionization, in which the available laser energy is shared and the ionization condition is changed. The relaxations include fluorescence, fragmentation, and nonradiative relaxation from the excited state to the ground state. With high absorption cross section and long excited-state lifetime, photoionization of matrix plays an important role if sufficient laser energy is used. Under other conditions, thermal ionization of the molecule in the ground state is predicted to be one of the important reactions. Evidence of change in the branching ratio of initial reactions with the matrix and the excitation wavelength was obtained with ?-cyano-4-hydroxycinnamic acid, sinapinic acid, 2,5-dihydroxybenzoic acid, and 2,4,6-trihydroxyacetophenone. These matrixes are studied by obtaining their mixed crystal absorption spectra, fluorescence properties, laser-induced infrared emission, and product ions. The exact ionization pathway depends on the chemical properties of matrixes and the excitation conditions. This concept may explain the diversity of experimental results observed in MALDI experiments, which provides an insight into the ensemble of chemical reactions that govern the generation of ions. PMID:22799495

Lai, Yin-Hung; Wang, Chia-Chen; Chen, Chiu Wen; Liu, Bo-Hong; Lin, Sheng Hsien; Lee, Yuan Tseh; Wang, Yi-Sheng

2012-08-01

48

Reaction of dopa decarboxylase with L-aromatic amino acids under aerobic and anaerobic conditions.  

PubMed

Analysis of the reaction of dopa decarboxylase (DDC) with L-dopa reveals that loss of decarboxylase activity with time is observed at enzyme concentrations approximately equal to the binding constant, K(d), of the enzyme for pyridoxal 5'-phosphate (PLP). Instead, at enzyme concentrations higher than K(d) the course of product formation proceeds linearly until complete consumption of the substrate. Evidence is provided that under both experimental conditions no pyridoxamine 5'-phosphate (PMP) is formed during the reaction and that dissociation of coenzyme occurs at low enzyme concentration, leading to the formation of a PLP-L-dopa Pictet-Spengler cyclic adduct. Taken together, these results indicate that decarboxylation-dependent transamination does not accompany the decarboxylation of L-dopa proposed previously [O'Leary and Baughn (1977) J. Biol. Chem. 252, 7168-7173]. Nevertheless, when the reaction of DDC with L-dopa is studied under anaerobic conditions at an enzyme concentration higher than K(d), we observe that (1) the enzyme is gradually inactivated and inactivation is associated with PMP formation and (2) the initial velocity of decarboxylation is approximately half of that in the presence of O(2). Similar behaviour is observed by comparing the reaction with L-5-hydroxytryptophan occurring in aerobiosis or in anaerobiosis. Therefore the reaction of DDC with L-aromatic amino acids seems to be under O(2) control. In contrast, the reactivity of the enzyme with L-aromatic amino acids does not change in the presence or absence of O(2). These and other results, together with previous results on the effect exerted by O(2) on reaction specificity of DDC towards aromatic amines [Bertoldi, Frigeri, Paci and Borri Voltattorni (1999) J. Biol. Chem. 274, 5514-5521], suggest a productive effect of O(2) on an intermediate complex of the reaction of the enzyme with L-aromatic amino acids or aromatic amines. PMID:11085948

Bertoldi, M; Borri Voltattorni, C

2000-12-01

49

Silica gel-mediated organic reactions under organic solvent-free conditions.  

PubMed

Silica gel was found to be an excellent medium for some useful organic transformations under organic solvent-free conditions, such as (1) the Friedel-Crafts-type nitration of arenes using commercial aqueous 69% nitric acid alone at room temperature, (2) one-pot Wittig-type olefination of aldehydes with activated organic halides in the presence of tributyl- or triphenylphosphine and Hunig's base, and (3) the Morita-Baylis-Hillman reaction of aldehydes with methyl acrylate. After the reactions, the desired products were easily obtained in good to excellent yields through simple manipulation. PMID:23018922

Onitsuka, Satoaki; Jin, Yong Zhi; Shaikh, Ajam C; Furuno, Hiroshi; Inanaga, Junji

2012-09-27

50

Catalytic transamidation reactions compatible with tertiary amide metathesis under ambient conditions.  

PubMed

The carbon-nitrogen bond of carboxamides is extremely stable under most conditions. The present study reveals that simple zirconium- and hafnium-amido complexes are highly efficient catalysts for equilibrium-controlled transamidation reactions between secondary amines and tertiary amides. In a number of cases, transamidation proceeds rapidly at room temperature. We find that these new catalysts are sufficiently active to promote the metathesis of tertiary amides, which arises from successive transamidation cycles. The catalytic activities we observe are unprecedented and represent a substantial step toward a long-range goal of conducting equilibrium-controlled reactions with carboxamides. PMID:19621957

Stephenson, Nickeisha A; Zhu, Jiang; Gellman, Samuel H; Stahl, Shannon S

2009-07-29

51

Contaminant transport in soil with depth-dependent reaction coefficients and time-dependent boundary conditions.  

PubMed

Predicting the fate and movement of contaminant in soils and groundwater is essential to assess and reduce the risk of soil contamination and groundwater pollution. Reaction processes of contaminant often decreased monotonously with depth. Time-dependent input sources usually occurred at the inlet of natural or human-made system such as radioactive waste disposal site. This study presented a one-dimensional convection-dispersion equation (CDE) for contaminant transport in soils with depth-dependent reaction coefficients and time-dependent inlet boundary conditions, and derived its analytical solution. The adsorption coefficient and degradation rate were represented as sigmoidal functions of soil depth. Solute breakthrough curves (BTCs) and concentration profiles obtained from CDE with depth-dependent and constant reaction coefficients were compared, and a constant effective reaction coefficient, which was calculated by arithmetically averaging the depth-dependent reaction coefficient, was proposed to reflect the lumped depth-dependent reaction effect. With the effective adsorption coefficient and degradation rate, CDE could produce similar BTCs and concentration profiles as those from CDE with depth-dependent reactions in soils with moderate chemical heterogeneity. In contrast, the predicted concentrations of CDE with fitted reaction coefficients at a certain depth departed significantly from those of CDE with depth-dependent reactions. Parametric analysis was performed to illustrate the effects of sinusoidally and exponentially decaying input functions on solute BTCs. The BTCs and concentration profiles obtained from the solutions for finite and semi-infinite domain were compared to investigate the effects of effluent boundary condition. The finite solution produced higher concentrations at the increasing limb of the BTCs and possessed a higher peak concentration than the semi-infinite solution which had a slightly long tail. Furthermore, the finite solution gave a higher concentration in the immediate vicinity of the exit boundary than the semi-infinite solution. The applicability of the proposed model was tested with a field herbicide and tracer leaching experiment in an agricultural area of northeastern Greece. The simulation results indicated that the proposed CDE with depth-dependent reaction coefficients was able to capture the evolution of metolachlor concentration at the upper soil depths. However, the simulation results at deep depths were not satisfactory as the proposed model did not account for preferential flow observed in the field. PMID:23490106

Gao, Guangyao; Fu, Bojie; Zhan, Hongbin; Ma, Ying

2013-02-26

52

Analysis of extrathalamic synaptic influences on reactions of sensorimotor cortical neurons during conditioning.  

PubMed

The effects of iontophoretic application of acetylcholine, noradrenaline, serotonin and their blockers on neuronal activity were studied in the cat before and during fulfillment of conditioned instrumental placing reflex. It was found that acetylcholine increased the background neuronal activity through muscarinic cholinergic receptors and noradrenaline decreased it through beta-adrenoceptors in a considerable proportion of the cortical neurons. Serotonin had no reliable effect on the background activity. At the same time, it facilitated an initial component of the impulse reaction to conditioned stimulus and part of the impulse reaction preceding the start of the conditioned movement. Acetylcholine applied iontophoretically also facilitated the evoked responses in some cortical neurons via nicotinic cholinergic receptors. On the contrary, iontophoretic application of noradrenaline or ephedrine decreased the evoked activity of some neurons. Application of beta-adrenergic receptor blocker, propranolol, led to an increase of neuronal responses to conditioned stimuli. Evidently, noradrenergic projections exert a steady inhibitory influence on the cortical neurons during natural functioning of the cortex. It is concluded that cortical reactions evoked by activation of thalamic projections and intracortical connections are modulated and regulated by extrathalamic projections to the cortex. PMID:1347652

Storozhuk, V M; Ivanova SPh; Stezhka, V V

1992-01-01

53

Optimum Reaction Conditions for Human Lactate Dehydrogenase lsoenzymes as They Affect Total Lactate Dehydrogenase Activity  

Microsoft Academic Search

Optimum reaction conditions at 30#{176} ± 0.5#{176} for two continuous spectrophotometric assayprocedures,lactate to pyruvate (L- P) and pyruvate to lactate (P- L), were determined with respect to pH at 30#{176} (pH30) substrate concentration, and coenzyme concentration for the human LDH isoenxymes. For the P - L procedure, broad pH30optima were within the range of 7.20-7.40 for all the LDH isoenzymes.The

Royal J. Gay; Robert B. McComb; George N. Bowers

54

A necessary and sufficient condition for global existence for a quasilinear reaction-diffusion system  

Microsoft Academic Search

We show that the reaction-diffusion system ut = ??(u)+f (v), vt = ??(v)+g(u), with homogeneous Neumann boundary conditions, has a positive global solution on ? × (0, ? )i f and only if ? ds\\/ f(F ?1(G(s))) =? (or, equivalently, ? ds\\/g(G?1(F(s))) =? ), where F(s) = s 0 f (r)dr and G(s) = s 0 g(r)dr. The domain ?

Alan V. Lair

2005-01-01

55

Experimental study of the reaction of methane with petroleum hydrocarbons in geological conditions  

NASA Astrophysics Data System (ADS)

In order to assess the possible role of methane in petroleum formation, we studied the reaction of methane with liquid hydrocarbons representing the three main classes of compounds dominant in crude oil. The experimental reaction conditions simulated those of a geological setting for petroleum formations, at 1000 atm and 150-250°C in the presence of montmorillonite, a natural clay catalyst. Since we expected very slow reaction rates and thus low yields, we used 14C labeled methane to trace the reaction products. We report here the detection of ethylbenzene and ethyltoluene formed by the interaction of methane with benzene and toluene, respectively. Instead of methylation of benzene, predominantly C 2 addition occurred, although very small amounts of products corresponding to C 1 addition were also detected. We propose that catalytic dissociation of methane occurred, forming ethylene which participated in a Friedel-Crafts type alkylation process of the aromatic ring on the catalyst surface. In addition to ring alkylation, side reactions such as polymerization of unsaturates (ethylene, acetylene) appeared to have occurred on the catalyst surface. The nature of these polymers is yet to be determined.

Gold, Thomas; Gordon, Benjamin E.; Streett, William; Bilson, Elizabeth; Patnaik, Pradyot

1986-11-01

56

Study on the reaction kinetics in pulsed RF discharges under RIE conditions  

NASA Astrophysics Data System (ADS)

In the present-day electronics industry, reactive ion etching (RIE) is a technique widely used to etch thin films anisotropically. The subject of this thesis is the determination of (reaction) kinetics of rf discharges under RIE conditions. Special attention is given to determining quantitatively the rise and decay of densities and energy distributions of plasma particles. A production-type RIE reactor was used for all experiments. In chapter 2 the ion density is determined by LIF spectroscopy in a model (N2) discharge under RIE conditions. Chapter 3 concerns energy-flux density measurements on the various parts of the etch reactor in contact with a 30 Pa nitrogen rf discharge. Chapter 4 concerns the etch mechanism of various organic polymers in oxygen and argon of discharges under RIE conditions studied by performing energy-flux density and ion-flux density measurements on the powered electrode. The polymers of interest are a novolac-based photoresist, polyimide and polymethylmethacrylate (PMMA). The density and the reaction kinetics of ground-state methylidyne (CH radical) are determined by LIF in order to determine whether small molecules in addition to atoms are sputtered from the polymer surface. In chapter 5 a model is set up in which diffusion of CH from the substrate into the gas phase and chemical reactions in the gas phase are taken into account.

Baggerman, Jacobus Antonius Gijsbertus

1993-10-01

57

Search for reaction conditions and catalyst for selective prebiotic formation of Aldopentoses from Glycolaldehyde and Formaldehyde  

NASA Astrophysics Data System (ADS)

Formation of organic compounds from simple precursors appears to have been one of the first steps from geochemistry towards modern biochemistry. The Earth lagoons, hydrothermal springs, cosmic dust, meteorites, protoplanetary disk, etc. has been considered as the possible ``reactors'' in which the prebiotic synthesis could have taken place. The finding of reactions and reaction conditions which allow to produce the high yields of the biologically relevant substances from simple compounds could help us to verify different hypothesis of plausible prebotic conditions. In this work we have studied the formation of vitally important sugars, namely aldopentoses (ribose, xylose, lyxose and arabinose), from glycolaldehyde and formaldehyde over catalysts. Aldopentoses nowadays play the important roles as the components of polysaccharides, glycosides, nucleic acids and ATP. Glycolaldehyde is the simplest monosaccharide, which was found in the interstellar space [1], where it could be generated as a result of several processes, for instance, condensation of formaldehyde under UV-radiation [2]. In this work the peculiarities of interaction between glycolaldehyde and formaldehyde in the presence of soluble (phosphate and borate buffers) and solid (minerals apatite and montmorillonites) catalysts were studied. The dependences of composition of the reaction products on the catalyst nature, molar ratio of substrates, pH value of reaction mixture were revealed. The yields of aldopentoses amount to ca. 60-65% in the presence of borate catalyst under optimized reaction conditions. Borate acts not only as a catalyst, but also as the stabilizer of active intermediates and aldopentoses from side reactions [3]. Borates are present in some mineral and clays (serpentine, montmorillonite etc.) and in water of Cityhot springs (Geyser valley, placeKamchatka) in rather high concentrations. Therefore catalysis by borates could be considered as plausible prebotic condition. Acknowledgements. We thank Dr. S. Yashnik for providing the montmorillonite clays. The financial support of Program RAS (program ``Origin of biosphere and evolution biogeology systems'') is gratefully acknowledged. Hollis, J., Jewell, P., Lovas, F., et al., The Astrophysical Journal. 613, L45--L48, 2004 Pestunova, O., Simonov, A., Snytnikov, V., et al., Adv. Space Res. 36/2, 214-219, 2005. Ricardo, A., Carrigan, M.A., Olcott, A.N., Benner, S.A. Science. 303, 5655, 196, 2004.

Delidovich, Irina; Taran, Oxana; Parmon, Valentin; Gromov, Nikolay

2012-07-01

58

Swellings due to alkali-silica reaction and delayed ettringite formation: Characterisation of expansion isotropy and effect of moisture conditions  

Microsoft Academic Search

This paper investigates the effect of different conditions on the development of concrete expansions due to alkali-silica reaction (ASR), delayed ettringite formation (DEF) and their combination. The presence of products of the two reactions has been observed during structure diagnosis. The aim of this research is to study the two reactions in concretes with close mix designs but with various

Hassina Bouzabata; Stéphane Multon; Alain Sellier; Hacène Houari

59

Influence of reaction conditions on the location of reactions in waxy maize starch granules reacted with a propylene oxide analog at low substitution levels  

Microsoft Academic Search

A constant amount of an anionic propylene oxide analog was reacted with waxy maize starch under conditions in which temperature, pH, and swelling-inhibiting salt type and concentration were varied. Reaction sites were located utilizing a reflectance confocal laser scanning microscopy (R-CLSM) method. Results confirm that uniformity of reaction within granules and molar substitution (MS) levels are a function of reaction

Jonathan A. Gray; James N. BeMiller

2005-01-01

60

Role of five synthetic reaction conditions on the stable isotopic composition of 3,4-methylenedioxymethamphetamine.  

PubMed

The identification of links between seizures of illicit 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") has been a global target of law enforcement agencies in recent years. Previous work has shown that, when the reaction conditions are carefully repeated from batch to batch, stable isotope ratios allow the discrimination of MDMA.HCl batches according to synthetic route used for manufacture. In this study, the effects of altering five reaction conditions relating to the Pt/H(2) reductive amination synthesis were, for the first time, systematically investigated using a two level, five factor factorial design. Results indicate that the delta(2)H values of MDMA.HCl are affected by the length of imine stir time, and the delta(15)N values are affected by the degree of excess methylamine employed. Furthermore, the delta(13)C and delta(18)O values have been shown to be affected by the efficiency of the reaction, despite the similarity in carbon and oxygen composition of the starting material and product molecules. In addition to being of theoretical importance in this field of analytical science overall, this work is essential in order to more fully contextualize the interpretation of IRMS data which may be used as potential forensic evidence. PMID:20515061

Buchanan, Hilary A S; Daéid, Niamh Nic; Kerr, William J; Carter, James F; Hill, Jenny C

2010-07-01

61

Measurement of transverse dispersion and reaction in heterogeneous porous media under transient flow conditions  

NASA Astrophysics Data System (ADS)

Natural attenuation (mainly biodegradation) of organic pollutants in groundwater often depends on mixing of electron donors and acceptors in the plume fringes, the spatial distribution of these highly reactive zones, compared to the volume of the whole plume, is quite small and characterized by steep concentration gradients. Mixing in the field is the result of transverse dispersion, which is a function of groundwater flow velocity, the typical length scale in the aquifer (e.g. grain size) as well as the aquifer heterogeneities, and the dynamics of the natural flow system. The objectives of this work are to investigate dispersion-limited reactions in well-controlled bench-scale experiments i.e. to elaborate how heterogeneities and transient conditions at the field scale (in time and space) influence the overall natural attenuation rates of organic pollutants in groundwater. Experiments in which (a) the spreading of a conservative tracer cloud or (b) the reaction of two reaction partners at the plume fringe is limited by transverse dispersion are currently investigated in the lab. As the quantification of transverse dispersivities in heterogeneous media under transient flow conditions requires monitoring with high resolution in space and time new optical tools (CCD camera) are employed for the quantitative mapping of the plumes.The first experiments were conducted at bench scale using a continuous injection of a conservative colour tracers (fluorescine), which show absorption only at a specific range of wavelengths in the visible spectrum, a quantification of this tracers is thus possible by its colour depth. Quality control of the quantification obtained by the CCD set-up is done via conventional sampling and analysis at the outlet ports during steady state flow conditions. Currently, well controlled acid-base reactions, are monitored by the colour changes of pH-indicators.This efficient spatially and time-resolved monitoring of concentration gradient changes by the CCD set-up finally provides the high resolution data required for the validation of numerical modelling. Therefore the data acquisition of these experiments will consequently be followed by the comparison to modelling results obtained by the reactive transport code PHT3D (Prommer et al., 2003, http://www.pht3d.org). This code combines the transport simulator MT3DMS (Zheng and Wang, 1999) with the geochemical model PHREEQC-2 (Parkhurst and Appelo, 1999) and was proven to be suitable to resolve the steep concentration gradients which occur at the plume fringes.This work was funded by Deutsche Forschungsgemeinschaft, Research Group 525 "Analysis and modelling of diffusion/dispersion-limited reactions in porous media".

Grathwohl, P.; Piepenbrink, M.; Eberhardt, C.; Kasper, M.; Gauglitz, G.

2005-12-01

62

Reaction mechanisms in the formation of lead zirconate titanate solid solutions under hydrothermal conditions  

SciTech Connect

Reaction mechanisms in the formation of PZT solid solution were studied under hydrothermal conditions (Pb/(Zr + Ti) = 1.0 to 1.9, Zr/Ti = 0/10 to 10/0, 1M to 5M KOH, 100C to 220C, 2 h). A yellow tabular crystallite with tetragonal symmetry and Pb/Ti [approx] 2 was formed at 100 to 130C. A PZT crystallite was formed just above 150C. The crystallite was a mixture of Ti-rich PZT and Zr-rich PZT phases. When the temperature and KOH concentration were increased, the composition of the PZT product tended to be homogeneous. The PZT in the morphotropic phase boundary zone was formed at Zr/Ti = 5/5, 5M KOH, 220C, 2h. Neither PbTiO[sub 3] nor PbZrO[sub 3] was detected as a separate phase under the above hydrothermal conditions.

Humin Cheng; Jiming Ma; Bin Zhu; Yuhong Cui (Peking Univ., Beijing (China). Dept. of Chemistry)

1993-03-01

63

Thermodynamic forward modeling of progressive dehydration reactions during subduction of oceanic crust under greenschist facies conditions  

NASA Astrophysics Data System (ADS)

We developed a new approach to the study of dehydration reactions using thermodynamic forward modeling based on the differential thermodynamic approach (the Gibbs' method) and the use of mass balance equations. We applied the modeling to mafic systems under conditions of the greenschist facies in order to investigate continuous, progressive dehydration reactions during subduction of oceanic crust. By specifying the changes in P-T, the model enables us to predict changes in modal mineralogy and composition as well as the incremental amount of water produced. Calculations for rocks of MORB (mid-ocean ridge basalt) bulk composition subducting along several typical P-T paths show that dehydration proceeds rapidly near the boundary between the greenschist and (epidote-) amphibolite facies, where chlorite is reacted out. The calculated depths for peak rates of dehydration correlate well with peaks in clusters of seismic activity and the depth ranges of low-frequency tremors and high-Poisson's ratio in the subduction zones of SW Japan and Cape Mendocino. This finding indicates a strong causal linkage between seismic phenomena and dehydration reactions in subducting oceanic crust.

Kuwatani, Tatsu; Okamoto, Atsushi; Toriumi, Mitsuhiro

2011-07-01

64

Calculation of the cumulative reaction probability via a discrete variable representation with absorbing boundary conditions  

SciTech Connect

A new method is suggested for the calculation of the microcanonical cumulative reaction probability {ital via} flux autocorrelation relations. The Hamiltonian and the flux operators are computed in a discrete variable representation (DVR) and a well-behaved representation for the Green's operator, {ital G}({ital E}{sup +}), is obtained by imposing absorbing boundary conditions (ABC). Applications to a one-dimensional-model problem and to the collinear H+H{sub 2} reaction show that the DVR-ABC scheme provides a very efficient method for the {ital direct} calculation of the microcanonical probability, circumventing the need to compute the state-to-state dynamics. Our results indicate that the cumulative reaction probability can be calculated to a high accuracy using a rather small number of DVR points, confined to the vicinity of the transition state. Only limited information regarding the potential-energy surface is therefore required, suggesting that this method would be applicable also to higher dimensionality problems, for which the complete potential surface is often unknown.

Seideman, T.; Miller, W.H. (Department of Chemistry, University of California, Berkeley, California 94720 (United States))

1992-03-15

65

Metabolic properties of a mixed culture of aerobic ammonia oxidizers and its optimal reaction conditions.  

PubMed

The aerobic ammonia oxidation is an important process for nitrogen removal from wastewater with high ammonia concentration. Here, we investigated the metabolic properties of a mixed culture of aerobic ammonia oxidizers and determined its optimal reaction conditions. The maximum specific rate of NO(2)(-)-N formation of the culture was 14.9 mg N mg(protein)(-1) d(-1). The ammonia oxidation capacity was positively correlated with the microbial biomass concentration. Haldane model showed that the half-saturation constant (K(s)) for NH(4)(+)-N of the culture was 78.5 mg L(-1), and the inhibition constant (K(i)) for NH(4)(+)-N was 393.4 mg L(-1). The acetic acid and beef extract had significant inhibitory effects on ammonia oxidation, while there was little effect of methanol and glucose on ammonia oxidation. Orthogonal experiments with range analysis, variance analysis, factor contribution analysis and response surface analysis confirmed the optimal reaction conditions for ammonia oxidation to be 30-32 °C, pH 7.8-8.0, and 150-200 mg L(-1) NH(4)(+)-N concentration. PMID:22100242

Shen, Li-dong; Chen, Peng; He, Fan-zhong; Hu, An-hui; Zheng, Ping; Xu, Xiang-yang; Hu, Bao-lan

2011-10-31

66

Rapid and effective oxidative pretreatment of woody biomass at mild reaction conditions and low oxidant loadings  

PubMed Central

Background One route for producing cellulosic biofuels is by the fermentation of lignocellulose-derived sugars generated from a pretreatment that can be effectively coupled with an enzymatic hydrolysis of the plant cell wall. While woody biomass exhibits a number of positive agronomic and logistical attributes, these feedstocks are significantly more recalcitrant to chemical pretreatments than herbaceous feedstocks, requiring higher chemical and energy inputs to achieve high sugar yields from enzymatic hydrolysis. We previously discovered that alkaline hydrogen peroxide (AHP) pretreatment catalyzed by copper(II) 2,2?-bipyridine complexes significantly improves subsequent enzymatic glucose and xylose release from hybrid poplar heartwood and sapwood relative to uncatalyzed AHP pretreatment at modest reaction conditions (room temperature and atmospheric pressure). In the present work, the reaction conditions for this catalyzed AHP pretreatment were investigated in more detail with the aim of better characterizing the relationship between pretreatment conditions and subsequent enzymatic sugar release. Results We found that for a wide range of pretreatment conditions, the catalyzed pretreatment resulted in significantly higher glucose and xylose enzymatic hydrolysis yields (as high as 80% for both glucose and xylose) relative to uncatalyzed pretreatment (up to 40% for glucose and 50% for xylose). We identified that the extent of improvement in glucan and xylan yield using this catalyzed pretreatment approach was a function of pretreatment conditions that included H2O2 loading on biomass, catalyst concentration, solids concentration, and pretreatment duration. Based on these results, several important improvements in pretreatment and hydrolysis conditions were identified that may have a positive economic impact for a process employing a catalyzed oxidative pretreatment. These improvements include identifying that: (1) substantially lower H2O2 loadings can be used that may result in up to a 50-65% decrease in H2O2 application (from 100 mg H2O2/g biomass to 35–50 mg/g) with only minor losses in glucose and xylose yield, (2) a 60% decrease in the catalyst concentration from 5.0 mM to 2.0 mM (corresponding to a catalyst loading of 25 ?mol/g biomass to 10 ?mol/g biomass) can be achieved without a subsequent loss in glucose yield, (3) an order of magnitude improvement in the time required for pretreatment (minutes versus hours or days) can be realized using the catalyzed pretreatment approach, and (4) enzyme dosage can be reduced to less than 30 mg protein/g glucan and potentially further with only minor losses in glucose and xylose yields. In addition, we established that the reaction rate is improved in both catalyzed and uncatalyzed AHP pretreatment by increased solids concentrations. Conclusions This work explored the relationship between reaction conditions impacting a catalyzed oxidative pretreatment of woody biomass and identified that significant decreases in the H2O2, catalyst, and enzyme loading on the biomass as well as decreases in the pretreatment time could be realized with only minor losses in the subsequent sugar released enzymatically. Together these changes would have positive implications for the economics of a process based on this pretreatment approach.

2013-01-01

67

Iron complex with ionic tag-catalyzed olefin reduction under oxidative conditions--a different reaction for iron.  

PubMed

An iron(III) complex with ionic tags was applied to the reduction of alkenes in imidazolium-based ionic liquids (ILs) under oxidative conditions. The catalyst is very efficient to promote reactions of biomass derivatives. At least ten recycling reactions were performed without any loss of catalytic activity. Some important mechanistic insights for this new reaction are also provided based mostly on electrospray ionization quadrupole-time of flight mass spectrometry (ESI-QTOF-MS). PMID:23139173

dos Santos, Marcelo R; Gomes, Alexandre F; Gozzo, Fabio C; Suarez, Paulo A Z; Neto, Brenno A D

2012-11-08

68

Laboratory Experiments and Investigations on the Reaction Rates of Mg-sulfates Under Mars Relevant Conditions  

NASA Astrophysics Data System (ADS)

Large deposits of hydrous Mg-sulfates was identified on Mars by orbital remote sensing (OMEGA on Mars Express and CRISM on Mars Reconnaissance Orbiter). Kieserite (MgSO4.H2O) and a non-specific “polyhydrated sulfates” are among the most observed and widely distributed sulfates (Bibring et al., 2005, Murchie et al., 2007). They frequently co-exist (Gendrin et al., 2005) and sometimes occur in alternative stratigraphic layers (Roach et al., 2008). Mg-sulfates were suggested, by compositional correlations and mineral models, to exist in Meridiani outcrops (Clark et al., 2005) and in rocks and regolith at Gusev (Squyres et al., 2006, Haskin et al., 2005, Wang et al., 2006, 2008); but no information on the hydration state of these sulfates can be extracted. We have conducted 188 experiments to investigate the stability fields and phase transition pathways of hydrous Mg-sulfates (Wang et al., 2009). In addition, we can extract the information on the reaction rates of five important dehydration and rehydration processes involved in these experiments. Our experiments were done at four temperatures (50°C, 21°C, 5°C, and -10°C) and ten relative humidity levels, with five hydrous Mg-sulfate species as starting phases. The rate information was extracted from the mineral identifications of the intermediate reaction products, measured by non-invasive Raman spectroscopy at regular time intervals during the entire duration of experiments (tens’ thousands hours). The rates for five processes are all strongly controlled by temperatures. We found that the experimental results match Arrhenius equation very well, thus the rate constants for dehydration and rehydration processes of Mg-sulfates at lower temperatures (down to 180K) can be approximately estimated by using the experimentally derived pre-exponential factor(s) and activation energy(s). In this study, only the orders of magnitudes for reaction rate ratios at different temperatures were considered. The estimated reaction rate ratios at different temperatures for five important processes helped us to understand the stable, especially the metastable, Mg-sulfate species that could be seen at Mars surface in non-polar regions during a moderate obliquity period. Therefore in addition to exam the spectral similarity, we now can use the knowledge gained through the laboratory experiments on stability field, phase transition pathway, and reaction rate of Mg-sulfates to evaluate the realistic mineral candidates for “polyhydrated sulfates”, that were so widely observed on Mars by OMEGA and CRISM. Furthermore, we will be able to investigate the formation mechanism of alternative stratigraphic layers of sulfates on Mars and the paleo-climatic conditions that they may imply.

Wang, A.; Freeman, J. J.

2009-12-01

69

Design and demonstration of a dynamometric horseshoe for measuring ground reaction loads of horses during racing conditions  

Microsoft Academic Search

Because musculoskeletal injuries to racehorses are common, instrumentation for the study of factors (e.g. track surface), which affect the ground reaction loads in horses during racing conditions, would be useful. The objectives of the work reported by this paper were to (1) design and construct a novel dynamometric horseshoe that is capable of measuring the complete ground reaction loading during

Elizabeth S. Roland; Maury L. Hull; Susan M. Stover

2005-01-01

70

The Influence of Processing Conditions on the Microstructure and the Mechanical Properties of Reaction Sintered Silicon Nitride.  

National Technical Information Service (NTIS)

The microstructure of reaction sintered silicon nitride was changed by varying green density, grain size of the silicon powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical pro...

J. Heinrich

1979-01-01

71

Global Exponential Stability of Cohen-Grossberg Neural Networks with Reaction-Diffusion and Dirichlet Boundary Conditions  

NASA Astrophysics Data System (ADS)

In this paper, global exponential stability of Cohen-Grossberg neural networks with reaction-diffusion and Dirichlet boundary conditions is considered by using an approach based on the delay differential inequality and the fixed-point theorem. Some sufficient conditions are obtained to guarantee that the reaction-diffusion Cohen-Grossberg neural networks are globally exponentially stable. The results presented in this paper are the improvement and extension of the existed ones in some existing works.

Fu, Chaojin; Zhu, Chongjun

72

Conditions of polymerase chain reaction amplification by magnetic enrichment and nanoscale detection sensitivity.  

PubMed

In this research, we reported a method of polymerase chain reaction (PCR) amplification by means of magnetic enrichment. First, after denaturation, the target sequence was combined with biotin-modified specific primer through hybridization and enriched at the surface of gamma-Fe2O3 by biotin-avidin special interaction. Then single target sequence was gained through denaturation, and general PCR amplification was performed. The experiment conditions such as the hybridization temperature between target sequence and biotin-modified specific primer, and the dosage of magnetic nanoparticles gamma-Fe2O3 were optimized. Finally, the sensitivity of the method was checked. The lowest concentration of target sequence was detected as low as 5 x 10(-7) ng/mL. This simple method could provide a quick and early diagnosis of malignant infectious diseases such as SARS, avian flu and swine flu etc., that occur occasionally nowadays. PMID:22852317

He, Nongyue; Mou, Xianbo; Deng, Yan; Liu, Hongna; Li, Song; Xu, Lijian; Li, Xiaolong

2012-05-01

73

Effect of reaction conditions on the morphology of elemental metals by composite-hydroxide-mediated approach  

NASA Astrophysics Data System (ADS)

Metal micro- and nanostructures play important roles in many different areas. Micro- and nanostructures of elemental metals can be obtained by the composite-hydroxide-mediated (CHM) method. The detailed profile of results demonstrated that the morphologies of metal crystals were quite different, when we chose different materials, Zn or Fe powder and with or without adding H2O. The mechanism agrees with it that the acidity (pH2O value) of the hydroxide melts can affect the dissolution of the reactant. Our study shows that elemental metals and their morphologies can be achieved by controlling the reaction conditions. Moreover, this CHM approach provides a useful route for the synthesis of elemental metals crystals, which may be extended to synthesize other elemental micro- and nanomaterials. It is expected that the present research may offer useful guidelines to the design and application of micro- and nanostructures metal and devices.

Xi, Y.; Yang, D. Z.; Hou, Z. J.; Zhang, C. L.

2012-07-01

74

REtools: A laboratory program for restriction enzyme work: enzyme selection and reaction condition assistance  

PubMed Central

Background Restriction enzymes are one of the everyday tools used in molecular biology. The continuously expanding panel of known restriction enzymes (several thousands) renders their optimal use virtually impossible without computerized assistance. Several manufacturers propose on-line sites that assist scientists in their restriction enzyme work, however, none of these sites meet all the actual needs of laboratory workers, and they do not take into account the enzymes actually present in one's own laboratory. Results Using FileMaker Pro, we developed a stand-alone application which can run on both PCs and Macintoshes. We called it REtools, for Restriction Enzyme tools. This program, which references all currently known enzymes (>3500), permits the creation and update of a personalized list of restriction enzymes actually available in one's own laboratory. Upon opening the program, scientists will be presented with a user friendly interface that will direct them to different menus, each one corresponding to different situations that restriction enzyme users commonly encounter. We particularly emphasized the ease of use to make REtools a solution that laboratory members would actually want to use. Conclusion REtools, a user friendly and easily customized program to organize any laboratory enzyme stock, brings a software solution that will make restriction enzyme use and reaction condition determination straightforward and efficient. The usually unexplored potential of isoschizomers also becomes accessible to all, since REtools proposes all possible enzymes similar to the one(s) chosen by the user. Finally, many of the commonly overlooked subtleties of restriction enzyme work, such as methylation requirement, unusual reaction conditions, or the number of flanking bases required for cleavage, are automatically provided by REtools.

Martin, Patrick; Boulukos, Kim E; Pognonec, Philippe

2006-01-01

75

Chemical and Physical Reactions of Wellbore Cement under CO2 Storage Conditions: Effects of Cement Additives  

NASA Astrophysics Data System (ADS)

Sequestration of CO2 into geologic formations requires long-term storage and low leakage rates to be effective. Active and abandoned wells in candidate storage formations must be evaluated as potential leakage points. Wellbore integrity is an important part of an overall integrated assessment program being developed at NETL to assess potential risks at CO2 storage sites. Such a program is needed for ongoing policy and regulatory decisions for geologic carbon sequestration. The permeability and integrity of the cement in the well is a primary factor affecting its ability to prevent leakage. Cement must be able to maintain low permeability over lengthy exposure to reservoir conditions in a CO2 injection and storage scenario. Although it is known that cement may be altered by exposure to CO2, the results of ongoing research indicate that cement curing conditions, fluid properties, and cement additives play a significant role in the rate of alteration and reaction. The objective of this study is to improve understanding of the factors affecting wellbore cement integrity for large-scale geologic carbon sequestration projects. Due to the high frequency use of additives (pozzolan) in wellbore cement, it is also essential to understand the reaction of these cement-pozzolan systems upon exposure to CO2 under sequestration conditions (15.5 MPa and 50°C). Laboratory experiments were performed to determine the physical and chemical changes, as well as the rate of alteration of commonly used pozzolan-cement systems under simulated sequestration reservoir conditions, including both supercritical CO2 and CO2-saturated brine. The rate of alteration of the cement-pozzolan systems is considerably faster than with neat cement. However, the alteration of physical properties is much less significant with the pozzolanic blends. Permeability of a carbonated pozzolanic cement paste remains sufficiently small to block significant vertical migration of CO2 in a wellbore. All of the experiments run to date suggest that the cement-pozzolans used will be an effective seal for CO2, as long as the well was properly installed and is initially undamaged.

Kutchko, B. G.; Strazisar, B. R.; Huerta, N.; Lowry, G. V.; Dzombak, D. A.; Thaulow, N.

2008-12-01

76

Changes in Subsidiary Reaction Time and Heart-Rate During Car Driving, Passenger Travel and Stationary Conditions  

Microsoft Academic Search

A reaction time (RT) task was used in three conditions, each lasting 2 h, during which six female subjects: (i) drove on a 5 km closed track, (ii) were driven as passenger on the same track, and (iii) were tested in a stationary vehicle. There was an increase in RT only in the driving condition. Furthermore, there was a progressively

H. LAURELL; H.-O. LISPER

1976-01-01

77

A Knoevenagel Initiated Annulation Reaction Using Room Temperature or Microwave Conditions  

ERIC Educational Resources Information Center

|An experiment is presented that has the student execute a Knoevenagel initiated annulation reaction. The reaction can be carried out either through use of a microwave reactor or by allowing the mixture to stand at room temperature for two days. The student is then challenged to identify the reaction product through a guided prelab exercise of the…

Cook, A. Gilbert

2007-01-01

78

A Knoevenagel Initiated Annulation Reaction Using Room Temperature or Microwave Conditions  

ERIC Educational Resources Information Center

An experiment is presented that has the student execute a Knoevenagel initiated annulation reaction. The reaction can be carried out either through use of a microwave reactor or by allowing the mixture to stand at room temperature for two days. The student is then challenged to identify the reaction product through a guided prelab exercise of the…

Cook, A. Gilbert

2007-01-01

79

Runaway reactions, their courses and the methods to establish safe process conditions  

Microsoft Academic Search

Much of the literature on runaway reactions deals with the consequences such as mechanical damage toxic and flammable release. The DIERS literature provides effective methods for vent sizing where experimental information is requested. Thermal stability measurements provide information on the onset temperature and kinetic data for chemical reactions. There is less information on the way the runaway reactions occur whereas

J. L. Gustin

1991-01-01

80

Cardiac muscle ultrastructure and cyclic AMP reactions to altered gravity conditions  

SciTech Connect

Morphological and biochemical analyses of heart muscle of rats subjected to microgravity on Spacelab 3(SL-3) flight and rats born and reared under increased gravity (1.7 G) conditions were compared with 1-G controls. Electronmicroscopic studies showed an increase in the number of lipid droplets and in areas of glycogen storage. Distribution changes of microtubules and cytoskeletal elements from both SL-3 and 1.7-G groups were observed. The high K/sub m/(2,8-/sup 3/H) cyclic AMP phosphodiesterase activity was lower in SL-3 heart muscle, and low K/sub m/ activity was lower in 1.7-G males but was unaltered in females. Cyclic AMP-dependent protein kinase (cA-PK) activity was decreased in subcellular fractions of heart muscle of SL-3 animals. Recompartmentalization of cA-PK activity occurred in particulate tissue fraction of 1.7-g animals (70.3% of total for 1.7 G vs. 35.9% for controls). Phosphorylation of endogenous low-mobility proteins increased in SL-3 heart-soluble fractions. Photoaffinity labeling (18 h, 4/sup 0/C) decreased in type II cA-PK regulatory (R) subunits in both SL-3 and in 1.7-G male heart tissue particulate fractions. The 1.7-G female heart R subunit distribution did not differ from controls. These findings indicate that in heart muscle altered gravity conditions influenced physiological reactions similar to catecholamine-induced receptor-mediated hormonal responses.

Mednieks, M.I.; Fine, A.S.; Oyama, J.; Philpott, D.E.

1987-02-01

81

Chemical reactions involved in the deep fat frying of foods. I. A laboratory apparatus for frying under simulated restaurant conditions  

Microsoft Academic Search

A laboratory apparatus has been designed which can be used to quantitatively collect the volatile decomposition products produced\\u000a during deep fat frying under simulated restaurant conditions. In order to study the chemical reactions of frying fat without\\u000a any inter-reaction with the food fried, moist cotton balls were fried in corn oil.\\u000a \\u000a The oil used for frying was shown to differ

R. G. Krishnamurthy; Tsukasa Kawada; S. S. Chang

1965-01-01

82

An Efficient Protocol for Aza-Michael Addition Reactions Under Solvent-Free Condition Employing Sulfated Zirconia Catalyst  

Microsoft Academic Search

The aza-Michael addition reactions of amines with ?,?-unsaturated carbonyl compounds were efficiently carried out at room\\u000a temperature under solvent-free condition employing sulfated zirconia as a reusable heterogeneous catalyst. The desired products\\u000a were formed in short reaction times and in high yields. The bulk and surface properties of the synthesized catalyst was examined\\u000a by X-ray powder diffraction, BET surface area, temperature

Benjaram M. Reddy; Meghshyam K. Patil; Baddam T. Reddy

2008-01-01

83

Toward safer methodologies for the synthesis of polyheterocyclic systems: intramolecular arylation of arenes under Mizoroki-Heck reaction conditions.  

PubMed

[reaction: see text] A straightforward synthesis of ibudilast-related pyrazolo[1,5-f]phenanthridines is accomplished by a tandem amine-exchange/heterocyclization of arylenaminones followed by an intramolecular biaryl coupling of the so-formed diarylpyrazoles. The direct, environmentally convenient ring-closure of the latter pyrazole intermediates, which show a close resemblance to the antiinflammatory drug celecoxib, is efficiently performed under Mizoroki-Heck reaction conditions. PMID:12659582

Hernández, Susana; SanMartin, Raul; Tellitu, Imanol; Domínguez, Esther

2003-04-01

84

[Formation of a conditioned motor food-getting reaction with a two-way connection in grape snails].  

PubMed

Tactile stimulation of the snail's skin normally evokes avoidance reactions; however after 150--300 reinforcements by food placed in a definite spot, this stimulus began to elicit food-searching reactions of the animal with its turning towards usual food position. The conditioned reflex was stable and reappeared spontaneously following active extinction. It could be recorded 6 weeks after the end of the training. Presentation of food evoked avoidance reactions in 35--60% of cases, but this feedback connection appeared irregularly. PMID:484036

Maksimova, O A

85

A comparison between taste avoidance and conditioned disgust reactions induced by ethanol and lithium chloride in preweanling rats  

PubMed Central

Adult rats display taste avoidance and disgust reactions when stimulated with gustatory stimuli previously paired with aversive agents such as lithium chloride (LiCl). By the second postnatal week of life, preweanling rats also display specific behaviors in response to a tastant conditioned stimulus (CS) that predicts LiCl-induced malaise. The present study compared conditioned disgust reactions induced by LiCl or ethanol (EtOH) in preweanling rats. In Experiment 1 we determined doses of ethanol and LiCl that exert similar levels of conditioned taste avoidance. After having equated drug dosage in terms of conditioned taste avoidance, 13-Day old rats were given a single pairing of a novel taste (saccharin) and either LiCl or ethanol (2.5 g/kg; Experiment 2). Saccharin intake and emission of disgust reactions were assessed 24 and 48 hours after training. Pups given paired presentations of saccharin and the aversive agents (ethanol or LiCl) consumed less saccharin during the first testing Day than controls. These pups also showed more aversive behavioral reactions to the gustatory CS than controls. Specifically, increased amounts of grooming, general activity, head shaking and wall climbing as well as reduced mouthing were observed in response to the CS. Conditioned aversive reactions but not taste avoidance were still evident on the second testing Day. In conclusion, a taste CS paired with post-absorptive effects of EtOH and LiCl elicited a similar pattern of conditioned rejection reactions in preweanling rats. These results suggest that similar mechanisms may be underlying CTAs induced by LiCl and a relatively high EtOH dose.

Arias, Carlos; Pautassi, Ricardo Marcos; Molina, Juan Carlos; Spear, Norman E.

2011-01-01

86

Investigation of OH reaction products. Excimer laser photolysis/slab laser fluorescence under tropospheric conditions  

NASA Astrophysics Data System (ADS)

Absolute rate constants of OH reactions were measured up to total pressures of 1 bar and in the presence of strongly quenching gases. In the presence of O2, the effective disappearance rate of OH is diminished at all total pressures by a factor of 4 due to reproduction of OH by fast secondary processes. This can be described quantitatively by a reaction model, which includes a fast reaction of the OH+C2H2-adduct with O2, producing OH with a yield of 89 percent. Besides the decay of OH the formation and decay of vinoxy radicals as a minor intermediate product and the formation of glyoxal as a major product of the reaction in the presence of O2 could be followed with the LIF technique. Similar secondary reactions in the presence of O2 leading to reproduction of OH are found for the reactions of OH with propine and ethylenoxide.

Fink, E. H.; Schmidt, V.

1985-12-01

87

Catalysis of phosphorus(V)-mediated transformations: dichlorination reactions of epoxides under Appel conditions.  

PubMed

A stereospecific triphenylphosphine oxide-catalyzed 1,2-dichlorination reaction of epoxides has been developed. The reaction is effective for a range of terminal and internal epoxides. In contrast to the classical Appel-type dichlorination of epoxides, oxalyl chloride is used as a stoichiometric reagent to generate the chlorophosphonium salt responsible for dichlorination from catalytic triphenylphosphine oxide. PMID:20845932

Denton, Ross M; Tang, Xiaoping; Przeslak, Adam

2010-10-15

88

The Aldol Addition and Condensation: The Effect of Conditions on Reaction Pathway  

ERIC Educational Resources Information Center

|The reaction of a ketone and an aldehyde in aqueous Na[subscript 2]CO[subscript 2] is described. This experiment is performed in the absence of strong bases or organic solvents and offers the opportunity for students to observe the critical role that reaction temperature and base strength have in determining the product of the base-mediated…

Crouch, R. David; Richardson, Amie; Howard, Jessica L.; Harker, Rebecca L.; Barker, Kathryn H.

2007-01-01

89

Reaction-Transport Modeling of Biological Mediated Isotope Fractionation With Complete Substrate Consumption as Boundary Condition  

Microsoft Academic Search

Reaction-transport modeling of biological mediated processes is a commonly used technique to analyze the subsurface distribution of dissolved species. Coupled with isotope geochemical data, it becomes a powerful tool to investigate metabolic processes. However, numerical instabilities limits its usefulness to cases without complete substrate consumption. This is a consequence of the reaction term dependence on total substrate concentration and isotopic

B. M. Chernyavsky; U. G. Wortmann

2005-01-01

90

Viscous fingering in a horizontal flow through a porous medium induced by chemical reactions under isothermal and adiabatic conditions  

NASA Astrophysics Data System (ADS)

In this work we analyze the viscous fingering instability induced by an autocatalytic chemical reaction in a liquid flowing horizontally through a porous medium. We have analyzed the behavior of the system for isothermal as well as adiabatic conditions. The kinetics of the reaction is chosen so that the rate depends on the concentration of only a single species. Since the reaction is autocatalytic the system admits a traveling wave solution. For endothermic reactions the concentration wave and temperature wave are mirror images, whereas for an exothermic reaction they are similar or parallel. The viscosity of the fluid is assumed to depend strongly on the concentration of the product and temperature of the medium. The dependence of viscosity on concentration (decrease with concentration) can destabilize the traveling wave resulting in the formation of viscous fingers. We have performed a linear stability analysis to determine the stability of the base traveling wave solution. The stability predictions have been confirmed by nonlinear simulations of the governing equations based on a finite difference scheme. We observe that including the temperature dependency of viscosity stabilizes the flow for an endothermic reaction, i.e., regions which exhibited viscous fingering now demonstrate stable displacement. For exothermic systems, however, the system exhibits less stable behavior under adiabatic conditions, i.e., it is destabilized by both concentration and temperature dependencies of viscosity.

Swernath, Subramanian; Pushpavanam, S.

2007-11-01

91

Hydrothermal growth of well-aligned TiO 2 nanorod arrays: Dependence of morphology upon hydrothermal reaction conditions  

Microsoft Academic Search

Well-aligned TiO2 nanorod arrays (TNAs) were prepared on pretreated quartz substrates via hydrothermal method. The effect of the different\\u000a preparation conditions on the growth morphologies of TNAs was systematically investigated by X-ray diffraction (XRD) and field-emission\\u000a scanning electron microscopy (FE-SEM). The photocatalytic properties were tested by photodegradation of a methyl blue solution.\\u000a It is demonstrated that the hydrothermal reaction conditions,

Yuxiang Li; Mei Zhang; Min Guo; Xidong Wang

2010-01-01

92

State-to-state quantum dynamics of O + O2 isotope exchange reactions reveals nonstatistical behavior at atmospheric conditions  

PubMed Central

The O + O2 exchange reaction is a prerequisite for the formation of ozone in Earth’s atmosphere. We report here state-to-state differential and integral cross sections for several O + O2 isotope-exchange reactions obtained by dynamically exact quantum scattering calculations at collision energies relevant to atmospheric conditions. These reactions are shown to be highly nonstatistical, evidenced by dominant forward scattering and deviation of the integral cross section from the statistical limit. Mechanistic analyses revealed that the nonstatistical channel is facilitated by short-lived osculating resonances. The theoretical results provided an in-depth interpretation of a recent molecular beam experiment of the exchange reaction and shed light on the initial step of ozone recombination.

Sun, Zhigang; Liu, Lan; Lin, Shi Ying; Schinke, Reinhard; Guo, Hua; Zhang, Dong H.

2010-01-01

93

Relationship between the types of behavioral reaction in a conditioned shake-off reflex and neocortical lateralization.  

PubMed

The nature of the spike activity and interhemisphere interactions of neurons in the parietal cortex (somatosensory representation of the ear) during the intersignal period before active shake-off and passive (freezing) reactions to stimuli was studied in rabbits after acquisition of a conditioned defensive escape reflex. Before passive reactions, in contrast to the situation before active shake-off, there were increases in right-sided influences on cells in the left hemisphere with delays of up to 100 msec, leading to asymmetry in interhemisphere interactions with right-sided dominance. Passive reactions were preceded by increases in the extent of frequencies in the delta range in the spike activity of individual neurons and in interactions between pairs of cells. These data provide evidence that the existence and nature of interhemisphere asymmetry before stimulation is one of the factors determining the passive or active type of behavioral reaction and reflecting the level of activation of the cortex. PMID:18802771

Pavlova, I V; Vanetsian, G L

2008-09-18

94

Ethical Dilemmas in Testing for Late Onset Conditions: Reactions to Testing and Perceived Impact on Other Family Members  

Microsoft Academic Search

This paper examines some of the ethical dilemmas that arise when testing for the late onset, untreatable condition of Huntington disease (HD) specifically now that technology allows us to test younger generations of the family for the mutant gene. Drawing on interview data from families with Huntington disease, the reactions to testing and perceived impact on other family members are

Elizabeth Chapman

2002-01-01

95

Manganese Triazacyclononane Oxidation Catalysts Grafted under Reaction Conditions on Solid Co-Catalytic Supports  

SciTech Connect

Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H{sub 2}O{sub 2}. Here, carboxylic acid-functionalized SiO{sub 2} simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H{sub 2}O{sub 2} and the functionalized support are both necessary to transform the inactive [(tmtacn)Mn{sup IV}({mu}-O)3Mn{sup IV}(tmtacn)]{sup 2+} into the active, dicarboxylate-bridged [(tmtacn)Mn{sup III}({mu}-O)({mu}-RCOO){sub 2}Mn{sup III}(tmtacn)]{sup 2+}. This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H{sub 2}O{sub 2} and near zero order in all other species, including H{sub 2}O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H{sub 2}O{sub 2} activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 {+-} 6 kJ/mol are comparable to H{sub 2}O{sub 2} activation by related soluble catalysts. Undesired decomposition of H{sub 2}O{sub 2} is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 C and initial H{sub 2}O{sub 2} concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood like traditional carboxylic acids to activate non-heme oxidation catalysts while enabling higher throughput and providing the separation and handling benefits of a solid catalyst.

Schoenfeldt, Nicholas J.; Ni, Zhenjuan; Korinda, Andrew W.; Meyer, Randall J.; Notestein, Justin M. (NWU); (UIC)

2012-01-23

96

Fluoro-substituted ketones from nitriles using acidic and basic reaction conditions  

PubMed Central

Fluoro-substituted aliphatic nitriles are shown to undergo the Houben-Hoesch reactions with arenes in CF3SO3H to give fluoro-substituted ketones in good yields. The fluorine substituents appear to enhance the reactivities of the nitriles (and the nitrilium ion intermediates) compared to similar aliphatic nitriles. Fluoro-substituted ketones are also shown to be accessible through the reactions of organometallic reagents and fluoro-substituted nitriles.

Raja, Erum; Klumpp, Douglas A.

2011-01-01

97

A comparison of periodic travelling wave generation by Robin and Dirichlet boundary conditions in oscillatory reaction-diffusion equations  

NASA Astrophysics Data System (ADS)

Periodic travelling waves are an important solution form in oscillatory reaction-diffusion equations. I have shown previously that such waves arise naturally near a boundary at which a Dirichlet condition is applied. This result has applications in ecology, providing a potential explanation for the periodic waves seen in a number of natural populations. However, in ecological applications the Dirichlet boundary condition typically arises as a simple approximation to a more realistic Robin condition. In this paper, I consider the generation of periodic travelling waves by Robin boundary conditions and how the wave amplitude compares with that arising from Dirichlet conditions. I study a {lambda}-{omega}' system of equations, which is the normal form of an oscillatory reaction-diffusion system with scalar diffusion matrix close to a Hopf bifurcation. I consider a Robin boundary condition close to the Dirichlet limit, with proximity measured by a small parameter{epsilon} , and I study the equations as a perturbation problem in this small parameter. I show that the perturbation is singular and that although the solution itself changes at O({epsilon}), the amplitude of the periodic travelling wavewhich this solution approaches far from the boundary is unchanged at both O({epsilon}) and O({epsilon}2). This provides strong justification for the use of the Dirichlet approximation to the Robin condition when studying periodic travelling wave generation in equations of{lambda} -{omega} type. Finally, I discuss the ecological applications of the results.

Sherratt, Jonathan A.

2008-10-01

98

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

PubMed

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. PMID:15518968

Lever, Sarah D; Papadaki, Maria

2004-11-11

99

The influence of a weak artificial magnetic 10 Hz field on the extinction of a conditioned flight reaction in rats.  

PubMed

36 three to four months old albino rats were conditioned to flee after the onset of an acoustic stimulus (1000 Hz). During the period of extinction of the flight reaction half of the animals were exposed to an alternating magnetic field (10 Hz, 0.03 mT peak to peak) for the time of investigation. These animals showed a significantly higher number of flight reactions than the control animals investigated without magnetic field, on the 4th, 5th, and 6th day of exposure (p less than 0.05). PMID:2080906

Jentsch, A; Thoss, F

1990-01-01

100

The Rivalta's test as a diagnostic variable in feline effusions - evaluation of optimum reaction and storage conditions.  

PubMed

Objective: The Rivalta's test is used to diagnose feline infectious peritonitis (FIP) in cats with effusion. Only little information on the influence of sample storage and reaction conditions on test results is available, and diagnostic sensitivity and specificity to diagnose FIP vary considerably between few available studies. This study determined the influence of storage of effusion, modifications on reaction conditions, and inter-observer variation. Material and methods: The Rivalta's test was repeated up to 21 days after storage at room temperature, in the refrigerator, or freezer. The test was performed by two independent, blinded investigators. It was also performed using different volumes of acetic acid, different acids, and different kinds of water. Results: Even after storage for 21 days, test results were comparable. While inter-observer variation revealed substantial disagreement, different modifications in performance showed no major influence on test outcome. Conclusion: The Rivalta's test seems to be a very robust test concerning storage conditions. Modifications in reaction condition also do not substantially influence outcome. However, the test is subjective and depends on the evaluating person. PMID:24127026

Fischer, Y; Weber, K; Sauter-Louis, C; Hartmann, K

2013-10-15

101

Reaction time latencies of eye and hand movements in single- and dual-task conditions  

Microsoft Academic Search

The goal of this study was to investigate whether ocular and hand motor systems operate independently or whether they share processes. Using dualtask methodology, reaction time (RT) latencies of saccadic eye and hand motor responses were measured. In experiment 1, the hand and eye motor systems produced rapid, aimed pointing movements to a visual target, which could occur either to

Harold Bekkering; Jos J. Adam; Herman Kingma; A. Huson; H. T. A. Whiting

1994-01-01

102

Iodine-steel reactions under severe accident conditions in light-water reactors  

Microsoft Academic Search

Owing to large surface areas, the reaction of volatile molecular iodine (I2) with steel surfaces in the containment may play an important role in predicting the source term to the environment. Both wall retention of iodine and conversion of volatile into non-volatile iodine compounds at steel surfaces have to be considered. Two types of laboratory experiment were carried out at

F. Funke; G.-U. Greger; S. Hellmann; A. Bleier; W. Morell

1996-01-01

103

Reduction of a detailed reaction mechanism for hydrogen combustion under gas turbine conditions  

Microsoft Academic Search

The aim of this study is to find a reduced mechanism that accurately represents chemical kinetics for lean hydrogen combustion at elevated pressures, as present in a typical gas turbine combustor. Calculations of autoignition, extinction, and laminar premixed flames are used to identify the most relevant species and reactions and to compare the results of several reduced mechanisms with those

Jochen Stroehle; Tore Myhrvold

2006-01-01

104

Programming strategies for rapid aiming movements under simple and choice reaction time conditions  

Microsoft Academic Search

Increases in reaction time (RT) as a function of response complexity have been shown to differ between simple and choice RT tasks. Of interest in the present study was whether the influence of response complexity on RT depends on the extent to which movements are programmed in advance of movement initiation versus during execution (i.e., online). The task consisted of

Michael A. Khan; Gavin P. Lawrence; Eric Buckolz; Ian M. Franks

2006-01-01

105

Effect of varying conditions of fear on immobility reactions in domestic chickens (Gallus gallus)  

Microsoft Academic Search

3 studies were run to test the fear hypothesis of immobility reactions in Production Red chickens (N = 48, 40, and 20). Exp. I, as a replication of earlier work, found significantly enhanced immobility on the part of Ss given preinduction electric shock. Exp. II showed that duration of immobility varied reliably as a function of the amount of shock.

Gordon G. Gallup; Richard F. Nash; Randolph J. Potter; Nelson H. Donegan

1970-01-01

106

Gas–liquid reactions under supercritical conditions—phase equilibria and thermodynamic modeling  

Microsoft Academic Search

The application of supercritical fluids to catalytic hydrogenation reactions is studied, on the basis of phase equilibrium predictions by a group contribution with association equation of state (GCA–EOS). Two hydrogenation processes are analyzed: the hydrogenation of triglycerides (TAGs) and that of fatty acid methyl esters (FAME). New binary parameters are given for the interaction between H2 and the remaining functional

S. Pereda; S. B. Bottini; E. A. Brignole

2002-01-01

107

Improvement of the stoichiometric network analysis for determination of instability conditions of complex nonlinear reaction systems  

Microsoft Academic Search

Stoichiometric network analysis (SNA), a known method for analyzing complex reaction systems including biochemical ones, is improved and applied to a nonlinear process studied far from equilibrium in a continuously fed, well stirred tank reactor (CSTR). A particular attention is focused on the determination of the narrow range of the control parameter values where the main steady state is unstable

Ljiljana Kolar-Ani?; Željko ?upi?; Guy Schmitz; Slobodan Ani?

2010-01-01

108

Sexing a wider range of avian species based on two CHD1 introns with a unified reaction condition.  

PubMed

Identifying the sex of a bird is important to ensure successful breeding strategies and effective conservation programs. Sex may be identified from the intron size of the CHD1 gene located on the avian sex chromosomes Z and W. However, because of the great nucleotide diversity across different avian species, no given intron is in widespread use without ambiguous results. Complicated modifications of the reaction condition are required to suit different species. Two CHD1 introns were used with a unified reaction condition in this study to simplify the procedure. Consequently, genders of 73 avian species covering 19 families were successfully identified based on this two-intron approach. This means the ability to sex a wider range of avian species using a simplified procedure, greatly assisting in population management at zoos. Zoo Biol 26:425-431, 2007. (c) 2007 Wiley-Liss, Inc. PMID:19360591

Wang, Lih-Chiann; Chen, Chi-Tsong; Lee, Hsiao-Yuan; Li, Shou-Hsien; Lir, Jihn-Tsair; Chin, Shin-Chien; Pu, Chang-En; Wang, Ching-Ho

2007-09-01

109

A mechanism of the diffuse component of the conditioned-reflex reaction  

Microsoft Academic Search

In investigating the dynamics of electrical activity in varous zones of the cerebral cortex it was noted that during the elaboration of defense and food conditioned reflexes in dogs in response to the action of unconditioned (defense and food) stimuli or conditioned sound signal oscillations resembling by their appearance induced potentials observed during the action of rhythmic light stimulation appeared

T. S. Naumova; N. N. Lyubimov; L. G. Trofimov

1964-01-01

110

Subcortical correlates of differential classical conditioning of aversive emotional reactions in social phobia  

Microsoft Academic Search

Background: Conditioning processes have been proposed to play a role in the development of anxiety disorders. As yet, the neurobiologic correlates of emotional learning have not been fully understood in these patients. Accordingly, brain activity was studied in subcortical and cortical regions involved in the processing of negative affect during differential aversive classical conditioning.Methods: Twelve patients with social phobia and

Frank Schneider; Ute Weiss; Christoph Kessler; Hans-Wilhelm Müller-Gärtner; Stefan Posse; Jasmin B. Salloum; Wolfgang Grodd; Frank Himmelmann; Wolfgang Gaebel; Niels Birbaumer

1999-01-01

111

Modulation of Low-Frequency EEG Rhythms under Conditions of an Activation Reaction: Dependence on Psychological Characteristics of Personality  

Microsoft Academic Search

In a group of 118 adults of both sexes, we studied modulation of the low-frequency EEG components (? and ? rhythms) under\\u000a conditions of an activation reaction resulting from opening of the eyes. Typical changes of the ? rhythm (considerable depression\\u000a in a great majority of the tested subjects) was accompanied by diverse, in their direction, shifts of the spectral

I. N. Konareva

2011-01-01

112

Main mineral melting behavior and mineral reaction mechanism at molecular level of blended coal ash under gasification condition  

Microsoft Academic Search

The main mineral melting behavior and mineral reaction mechanism at molecular level of Chinese blended coal ash under gasification condition (30% H2, 66% CO, 4% CO2) from 1073K to 1573K were studied through the ASTM test, X-ray diffraction (XRD), ternary phase diagram system and quantum chemistry calculation with ab-initio calculations. The results show that with increasing blending mass fraction of

Xiaojiang Wu; Zhongxiao Zhang; Yushuang Chen; Tuo Zhou; Junjie Fan; Guilin Piao; Nobusuke Kobayashi; Shigekatsu Mori

2010-01-01

113

Impact of redox potential electrochemical modification and storage conditions on the oxidation reaction prevention in dairy emulsion  

Microsoft Academic Search

Oxidation reactions in milk conclude to negative consequences such as lipid oxidation, undesirable flavors, degradation of\\u000a vitamins, and changes in microbial flora of milk. The objective of the study was to investigate the effect of electroreduction\\u000a and storage conditions on an oil\\/water emulsion made of canola oil and reconstituted skim milk. The electroreduction treatments\\u000a were carried out at two different

Sanaz Haratifar; Laurent Bazinet; Nathalie Manoury; Michel Britten; Paul Angers

114

EFFECT OF DEGREE OF REACTION ON CRITICAL CONDITIONS AND TIMES TO IGNITION OF A GAS MIXTURE EXPLOSION  

Microsoft Academic Search

The effect of degree of reaction on critical conditions and times to ignition of a gas-mixture explosion is theoretically examined in detail. The Arrhenius form of the chemical kinetic rate and the Frank-Kamenetskii approximation for that form is considered. The study offers analytical and numerical solutions of the problem in pressure-time, temperature-time, and temperature-pressure planes. The analytical solution presented analytical

SAAD A. EL-SAYED

2006-01-01

115

Effect of calcination conditions on phase formation and particle size of zinc niobate powders synthesized by solid-state reaction  

Microsoft Academic Search

A columbite-like phase of zinc niobate, ZnNb2O6, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The formation of the ZnNb2O6 phase in the calcined powders has been investigated as a function of calcination conditions by TG–DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques.

A. Ngamjarurojana; O. Khamman; R. Yimnirun; S. Ananta

2006-01-01

116

Effect of method of heterogenization of ephedrine and reaction conditions on the enantioselectivity of Michael additions  

SciTech Connect

A series of heterogeneous catalysts for asymmetric Michael additions was synthesized based on ephedrine chemically bound to the surface of silica. The length of the hydrocarbon chain binding the active center to the support surface affects the sign of rotation of the reaction product from the asymmetric addition of thiophenol to benzylideneacetophenone. Grafting ephedrine to the silica surface via a short hydrocarbon chain results in a change in the configuration of the reaction product. Silanol groups on the silica surface are involved in the transition state, as evidenced by data obtained using silica which has been exhaustively treated with trimethylchlorosilane. The absolute specific rotation of 1,3-diphenyl-3-thiophenylpropan-1-one has been established.

Krotov, V.V.; Staroverov, S.M.; Nesterenko, P.N.; Lisichkin. G.V.

1987-11-10

117

Intrinsic reaction rate and the effects of operating conditions in dimethyl ether synthesis from methanol dehydration  

Microsoft Academic Search

The kinetic behavior of a commercial ?-Al2O3 catalyst for the methanol to dimethyl ether (DME) dehydration reaction has been investigated using a differential fixed bed\\u000a reactor at the pressure range 1–16 barg within a temperature range of 260–380 °C. The experimental runs were performed in\\u000a a wide range of feed to water ratios. The experiments were designed by general full

Gholamreza Moradi; Fereydoon Yaripour; Hossein Abbasian; Mostefa Rahmanzadeh

2010-01-01

118

The influence of reaction conditions on SO2 oxidation in a discharge plasma reactor  

Microsoft Academic Search

In this paper, experimental approaches have been carried out to investigate the removal of sulfur dioxide (SO2) using pulsed discharge nonthermal plasma in the absence of ammonia (NH3). The gas-phase reaction was found to be less attractive due to its large energy cost. The increase in temperature decreased the SO2 removal rate, resulting in large energy cost. SO2 removal was

Hyun Ha Kim; Chunxi Wu; Youhei Kinoshita; Kazunori Takashima; Shinji Katsura; Akira Mizuno

2001-01-01

119

Thermal reactions of methyl linoleate. I. Heating conditions, isolation techniques, biological studies and chemical changes  

Microsoft Academic Search

Methyl linoleate, diluted with an equal weight of methyl laurate, was heated without exclusion of air at 200C for 200 hours.\\u000a The reaction mixture was separated by means of molecular distillation, urea adduction, column chromatography, and gas chromatography.\\u000a Cyclic and aromatic materials were detected in the nonurea adductable monomer fractions. The dimer was separated into polar\\u000a and nonpolar fractions. Analytical

W. R. Michael; J. Craig Alexander; Neil R. Artman

1966-01-01

120

Solubility and Reaction Rates of Aluminum Solid Phases Under Geothermal Conditions  

SciTech Connect

Experimental studies involving equilibrium solubility and dissolution/precipitation rates were initiated on aluminum hydroxide phases prevalent under geothermal reservoir conditions. A large capacity, hydrogen-electrode concentration cell (HECC) was constructed specifically for this purpose.

Benezeth, P.; Palmer, D.A.; Wesolowski, D.J.; Anovitz, L.M.

2000-05-28

121

Continuous enzymatic transesterification of sesame oil and a fully hydrogenated fat: effects of reaction conditions on product characteristics.  

PubMed

An immobilized lipase from Thermomyces lanuginosus (TL IM) was employed to mediate the continuous transesterification of sesame oil and fully hydrogenated soybean oil (FHSBO) in a packed-bed reactor operating at 70 degrees C. Reactions between sesame oil (rich in LLL (15.97%), LOL (31.56%), and OLO (21.15%) [L = linoleic; O = oleic]) and the fully hydrogenated fat ((73.7% SSS, 26.3% SPS) [S = stearic; P = palmitic]) produced semi-solid fats. These products are complex mixtures of triacylglycerol (TAG) species whose compositions depend on reaction conditions. The dependence of the steady state product TAG profile on space time was determined for four initial weight ratios of sesame oil to hydrogenated fat (90:10, 80:20, 70:30, and 60:40). Except for the trial involving a weight ratio of sesame oil to FHSBO of 60:40, near equilibrium conditions were achieved at space times of 30 min-1 h. The chemical, physical, and functional properties of the product semi-solid fats were characterized. The predominant TAG species in the quasi-equilibrium products obtained from the mixture initially containing 90% (w/w) sesame oil and 10% FHSBO were LOL (26.22%) and OLO (21.92%). For transesterification of 80% sesame oil and 20% FHSBO, the major product species were OOP (21.27%), LOL (17.46%), and OLO (13.93%). OOP (24.38%) was the major product for reaction of 70% sesame oil with 30% FHSBO. Appropriate choices of reaction conditions and initial ratios of sesame oil to FHSBO lead to TAG with melting profiles and solid fat contents (SFC) similar to those of a variety of commercial products. PMID:16718681

Otero, Cristina; López-Hernandez, Arnoldo; García, Hugo S; Hernández-Martín, Estela; Hill, Charles G

2006-08-01

122

Kinetics of elementary steps in the reactions of atomic bromine with isoprene and 1,3-butadiene under atmospheric conditions.  

PubMed

Laser flash photolysis of CF(2)Br(2) has been coupled with time-resolved detection of atomic bromine by resonance fluorescence spectroscopy to investigate the gas-phase kinetics of early elementary steps in the Br-initiated oxidations of isoprene (2-methyl-1,3-butadiene, Iso) and 1,3-butadiene (Bu) under atmospheric conditions. At T ? 526 K, measured rate coefficients for Br + isoprene are independent of pressure, suggesting that hydrogen transfer (1a) is the dominant reaction pathway. The following Arrhenius expression adequately describes all kinetic data at 526 K ? T ? 673 K: k(1a)(T) = (1.22 ± 0.57) × 10(-11) exp[(-2100 ± 280)/T] cm(3) molecule(-1) s(-1) (uncertainties are 2? and represent precision of the Arrhenius parameters). At 271 K ? T ? 357 K, kinetic evidence for the reversible addition reactions Br + Iso ? Br-Iso (k(1b), k(-1b)) and Br + Bu ? Br-Bu (k(3b), k(-3b)) is observed. Analysis of the approach to equilibrium data allows the temperature- and pressure-dependent rate coefficients k(1b), k(-1b), k(3b), and k(-3b) to be evaluated. At atmospheric pressure, addition of Br to each conjugated diene occurs with a near-gas-kinetic rate coefficient. Equilibrium constants for the addition/dissociation reactions are obtained from k(1b)/k(-1b) and k(3b)/k(-3b), respectively. Combining the experimental equilibrium data with electronic structure calculations allows both second- and third-law analyses of thermochemistry to be carried out. The following thermochemical parameters for the addition reactions 1b and 3b at 0 and 298 K are obtained (units are kJ mol(-1) for ?(r)H and J mol(-1) K(-1) for ?(r)S; uncertainties are accuracy estimates at the 95% confidence level): ?(r)H(0)(1b) = -66.6 ± 7.1, ?(r)H(298)(1b) = -67.5 ± 6.6, and ?(r)S(298)(3b) = -93 ± 16; ?(r)H(0)(3b) = -62.4 ± 9.0, ?(r)H(298)(3b) = -64.5 ± 8.5, and ?(r)S(298)(3b) = -94 ± 20. Examination of the effect of added O(2) on Br kinetics under conditions where reversible adduct formation is observed allows the rate coefficients for the Br-Iso + O(2) (k(2)) and Br-Bu + O(2) (k(4)) reactions to be determined. At 298 K, we find that k(2) = (3.2 ± 1.0) × 10(-13) cm(3) molecule(-1) s(-1) independent of pressure (uncertainty is 2?, precision only; pressure range is 25-700 Torr) whereas k(4) increases from 3.2 to 4.7 × 10(-13) cm(3) molecule(-1) s(-1) as the pressure increases from 25 to 700 Torr. Our results suggest that under atmospheric conditions, Br-Iso and Br-Bu react with O(2) to produce peroxy radicals considerably more rapidly than they undergo unimolecular decomposition. Hence, the very fast addition reactions appear to control the rates of Br-initiated formation of Br-Iso-OO and Br-Bu-OO radicals under atmospheric conditions. The peroxy radicals are relatively weakly bound, so conjugated diene regeneration via unimolecular decomposition reactions, though unimportant on the time scale of the reported experiments (milliseconds), is likely to compete effectively with bimolecular reactions of peroxy radicals under relatively warm atmospheric conditions as well as in 298 K competitive kinetics experiments carried out in large chambers. PMID:22435953

Laine, Patrick L; Sohn, Yoon S; Nicovich, J Michael; McKee, Michael L; Wine, Paul H

2012-05-14

123

Stoichiometry and apparent dissociation constant of the calcium-arsenazo III reaction under physiological conditions.  

PubMed Central

In vitro and in situ tests have been run to characterize the reaction of the mettalochromic indicator, arsenazo III, with calcium. Job plots as well as plots of indicator absorbance vs. [Ca2+] at different indicator concentrations show a 1:1 reaction stoichiometry. Equilibrium analysis and analysis using Adair's equation are also consistent with 1:1 complexes being formed and give estimates of 34 and 45 muM for the apparent dissociation constant. In situ tests were carried out using giant neurons from Archidoris monteryensis, a marine gastropod mollusc. Dye absorbance changes were measured during voltage clamp pulses which produced a fixed calcium influx. The dependence of absorbance change on total dye concentration is consistent with the formation of a 1:1 complex of Ca with ArIII if measurements are made during the initial period of the loading pulse, less than 300 ms, although the apparent dependency changes with longer delay in measurements from the onset of the pulse.

Ahmed, Z; Kragie, L; Connor, J A

1980-01-01

124

Stereoselective synthesis of unsaturated and functionalized L-NHBoc amino acids, using Wittig reaction under mild phase-transfer conditions.  

PubMed

The stereoselective synthesis of a new amino acid phosphonium salt was described by quaternization of melting triphenylphosphine with the ?-iodo NHBoc-amino ester, derived from L-aspartic acid. The deprotection of the carboxylic acid function to afford the phosphonium salt with a free carboxylic acid group was achieved by a palladium-catalyzed desallylation reaction. This phosphonium salt was used in the Wittig reaction with aromatic or aliphatic aldehydes and trifluoroacetophenone, under solid-liquid phase-transfer conditions in chlorobenzene and in the presence of K(3)PO(4) as weak base, to afford the corresponding unsaturated amino acids without racemization. Thus, the reaction with substituted aldehydes allows to graft various functionalized groups on the lateral chain of the amino acid, such as trifluoromethyl, cyano, nitro, ferrocenyl, boronato, or azido. In addition, the reaction of the amino acid Wittig reagent with ?,?-unsaturated aldehydes leads to amino acids bearing a diene on the lateral chain. Finally, this amino acid phosphonium salt appears to be a new powerful tool for the preparation of unsaturated and non-proteinogenic ?-amino acids, directly usable for the synthesis of customized peptides. PMID:22870957

Rémond, Emmanuelle; Bayardon, Jérôme; Ondel-Eymin, Marie-Joëlle; Jugé, Sylvain

2012-08-23

125

Simultaneous Adsorption of Gases by a Methanation Catalyst under Reaction-Close Conditions.  

National Technical Information Service (NTIS)

The simultaneous adsorption of the reactants (H sub 2 , CO, CO sub 2 , CH sub 4 ) by self-made Ni-B catalyst has been investigated in connection with the technical methanation of CO and CO sub 2 . The conditions were adapted to the usual practical tempera...

W. Mundel

1980-01-01

126

Solubility and Reaction Rates of Aluminum Solid Phases Under Hydrothermal Conditions  

SciTech Connect

Experimental studies involving equilibrium solubility and dissolution/precipitation rates were initiated on boehmite (AIOOH) using a hydrogen-electrode concentration cell (HECC). This cell provides continuous, accurate in situ pH measurements of solid/solution mixtures to 295 C with provision for either removing solution samples for analysis of the metal content, or adding either of two titrants. This cell has been recently used to measure the solubility of minerals such as brucite; boehmite, zincite, arid magnetite. The ability to perturb pH, isothermally by addition of acidic or basic titrant opens the door for studies of the kinetics of dissolution/precipitation, even for relatively fast reactions. By monitoring the change in pH, with time, detailed kinetic information can be obtained without the need for sampling.

Benezeth, P.; Palmer, D.A.; Wesolowski, D.

1999-11-14

127

A new synthesis of TATB using inexpensive starting materials and mild reaction conditions  

SciTech Connect

TATB is currently manufactured in US by nitration of the expensive TCB to give 2,4,6-trichloro-1,3,5-trinitrobenzene which is then aminated to yield TATB. Elevated temperatures (150 C) are required for both reactions. There is a need for a more economical synthesis of TATB that also addresses current environmental issues. We have recently found that 1,1,1-trimethylhydrazinium iodide (TMHI) allows the amination of nitroarenes at ambient temperature via Vicarious Nucleophilic Substitution of hydrogen. TMHI reacts with picramide in presence of strong base (NaOMe or t-BuOK) to give TATB in over 95% yield. TMHI and picramide can be obtained from either inexpensive starting materials or surplus energetic materials from demilitarization activities, such as the 30,000 metric tons of UDMH (surplus rocket propellant) from the former Soviet Union.

Mitchell, A.R.; Pagoria, P.F.; Schmidt, R.D.

1996-04-01

128

Influence of process conditions on carboxylation of higher alkylphenols by Kolbe-Schmidt reaction  

SciTech Connect

The authors present experimental data on the carboxylation of higher alkylphenols prepared by alkylating phenol with a 240-320/sup 0/C alpha-olefin cut obtained by thermal cracking of the paraffins, on KU-2 catalyst. Experiments were performed to determine the influence of temperature and pressure on the conversion of sodium alkylphenolate to alkylsalicylate. The content of alkylphenols in the carboxylated products was demonstrated by solubilizing the carboxylate in water, subsequently centrifuging the water-organic mixture that was obtained. From the data presented here, it follows that in the carboxylation of sodium alkylphenolate, side reactions can be minimized if the process is performed at 130-135/sup 0/C with a CO/sub 2/ pressure no lower than 2 MPa.

Gordash, Yu.T.; Voloshin, N.L.; Prusak, A.G.; Tambiev, G.G.; Samolysov, A.S.

1987-01-01

129

Accurate Time-dependent Wave Packet Study of the H++LiH Reaction at Early Universe Conditions  

NASA Astrophysics Data System (ADS)

The dynamics and kinetics of the H+ + LiH reaction have been studied using a quantum reactive time-dependent wave packet (TDWP) coupled-channel quantum mechanical method on an ab initio potential energy surface at conditions of the early universe. The total reaction probabilities for the H+ + LiH(v = 0, j = 0) ? H+ 2 + Li process have been calculated from 5 × 10-3 eV up to 1 eV for total angular momenta J from 0 to 110. Using a Langevin model, integral cross sections have been calculated in that range of collision energies and extrapolated for energies below 5 × 10-3 eV. The calculated rate constants are found to be nearly independent of temperature in the 10-1000 K interval with a value of ?10-9 cm3 s-1, which is in good agreement with estimates used in evolutionary models of the early universe lithium chemistry.

Aslan, E.; Bulut, N.; Castillo, J. F.; Bañares, L.; Aoiz, F. J.; Roncero, O.

2012-11-01

130

Mass spectrometry studies of the retro-cycloaddition reaction of pyrrolidino and 2-pyrazolinofullerene derivatives under negative ESI conditions.  

PubMed

Substituted pyrrolidino- and 3-alkyl-2-pyrazolinofullerenes ionize under ESI and MALDI mass spectrometry conditions and negative mode of detection undergoing mass spectral fragmentations, which can be easily correlated with the reported results for the thermal and electrochemical retro-cycloaddition reactions of these compounds. 2-Pyrazolinofullerenes lead directly to a [60]fullerene product ion formed through a retro-cycloaddition process regardless of the substituents attached at the carbon and nitrogen atoms of the heterocyclic ring. These results are different from whose reported for the thermal and electrochemical processes. In contrast, pyrrolidinofullerenes undergo different fragmentative reactions depending upon the substituents (hydrogen, alkyl, or acyl) attached at the nitrogen atom of the heterocyclic ring leading eventually to the pristine C(60) in the last step of the fragmentation pathway. PMID:21472574

Delgado, Juan Luis; Filippone, Salvatore; Martín-Domenech, Angel; Altable, Margarita; Maroto, Enrique; Langa, Fernando; Martín, Nazario; Martínez-Alvarez, Roberto

2011-01-29

131

Influence of HCl on the homogeneous reactions of CO and NO in postcombustion conditions -- A kinetic modeling study  

SciTech Connect

Several fuels used in industrial furnaces contain high amounts of chlorine. These fuels include high chlorine coals and various waste products, like municipal and hazardous wastes and spent liquors from wood pulping processes. The influence of hydrogen chloride on homogeneous gas-phase reactions of carbon monoxide and nitric oxide was studied in typical postcombustion conditions of industrial furnaces using detailed kinetic modeling. A well-established reaction mechanism (203 reactions) describing the oxidation of moist CO, as well as of NH{sub 3} and HCN was extended by a recently published subset of 36 reactions for the oxidation of HCl. Validation of modeling predictions was achieved in that the effect of HCl on the CO burnout showed excellent agreement with available independent laboratory data. The modeling results led to the conclusion that the presence of HCl (100--600 ppmv) has a strong effect on the CO oxidation at low temperatures of approximately 1,023 K. The effect is dependent on the H{sub 2}O concentration and the presence of NO. Very interestingly, at high concentrations of H{sub 2}O (7 vol %) and without any NO, HCl led to a totally unexpected acceleration of the CO burnout at residence times longer than 0.5 s. Around and above 1,123 K the influence of HCl on the CO burnout was found to be very small for all conditions investigated. Furthermore, it was predicted that in the presence of ammonia, HCl extends the temperature window for NO reduction, particularly on the low temperature side.

Mueller, C. [Ruhr-Univ. Bochum (Germany). Lehrstuhl fuer Energieanlagentechnik; Kilpinen, P.; Hupa, M. [Aabo Akademi Univ., Turku (Finland). Dept. of Chemical Engineering

1998-06-01

132

Characterization and activity of ferric-sulfide-based catalyst in model reactions of direct coal liquefaction: Effect of preparation conditions  

SciTech Connect

The authors studied the activity of various ferric-sulfide-based catalysts in model hydrogenation and cracking reactions under conditions typical of direct coal liquefaction (DCL). The catalysts used were mixtures of FeS{sub 2} (pyrite, PY) and nonstoichiometric FeS{sub x} (pyrrhotite, PH) obtained by high-temperature disproportionation of ferric sulfide in a nitrogen atmosphere or a hydrogen atmosphere. The structural changes in the catalyst were also examined, both before and after the model reactions. The cracking functionality of the catalysts was studied by using cumene, and the hydrocracking functionality was studied by using diphenylmethane. Phenanthrene was used as a model compound for hydrogenation and hydrogen shuttling. Phenanthrene hydrogenation was studied in the presence of H{sub 2}(g), and hydrogen shuttling was studied when a hydrogen donor (tetralin) was present in the absence of H{sub 2}(g). All the model reactions were performed under conditions typical of DCL: 400 C and 1,000 psig for 30 min. The surface and bulk of the catalysts were characterized by Auger electron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic absorption spectroscopy. The performance of the catalysts was found to vary with the type of reaction, the initial ratio of FeS{sub x} to FeS{sub 2} (PH/PY) found in the catalyst, and the catalyst age. Catalysts freshly prepared in a nitrogen atmosphere were most active for model hydrogenation and hydrocracking runs. Catalysts freshly prepared in hydrogen were most active in shuttling. A simple model was developed to explain changes in the surface and bulk of the catalysts.

Chadha, A.; Stinespring, C.D.; Stiller, A.H.; Zondlo, J.W.; Dadyburjor, D.B. [West Virginia Univ., Morgantown, WV (United States). Dept. of Chemical Engineering

1997-02-01

133

Reaction mechanism of carbon gasification in CO 2 under non-isothermal conditions  

Microsoft Academic Search

Experiments of carbon (graphite) gasification in CO2 have been carried out by thermal analysis techniques (TG-DTG-DSC) under non-isothermal conditions. The results indicate that\\u000a the entire carbon gasification process can be divided into an exothermic slow gasification stage during the initial period\\u000a and an endothermic fast gasification later. The analyses of energy conservation and non-isothermal kinetics arrive at the\\u000a following conclusions;

Zhong-Suo Liu; Qi Wang; Zong-Shu Zou; Guang-Lei Tan

2011-01-01

134

Effects of relative humidity and temperature conditions on pollen fluorochromatic reaction of Rosmarinus officinalis L. (Lamiaceae)  

Microsoft Academic Search

Summary.  Mediterranean ecosystems are characterized by seasonal and annual fluctuations in humidity and temperature which are considered\\u000a limiting factors for plant growth and might have played a key role in the selection of species that compose the present vegetation.\\u000a After anther release, pollen is generally exposed to various changes of temperature and humidity conditions, therefore its\\u000a viability and consequently successful fruit

G. Aronne; V. De Micco; M. Scala

2006-01-01

135

Synthesis of starch acetate: Statistical designed experiments to optimize the reaction conditions  

Microsoft Academic Search

The synthesis conditions for Durabond A corn starch acetate (SA) were varied by using statistical designed experiments with the aim to optimize the yield and solubility, and to minimize the color. The thirty experiments in the design vary the: (1) Percentage water in the starch (0, 3, 6); (2) catalyst concentration (0.25, 0.60, 0.95 wt%); (3) total amount of acetic

Stefanos Lepeniotis; Bernice I. Feuer

1997-01-01

136

Pentavalent Uranium Oxide via Reduction of [UO2]2+ Under Hydrothermal Reaction Conditions  

SciTech Connect

The synthesis, crystal structure and spectroscopic characterization of [UV(H2O)2(UVIO2)2O4(OH)](H2O)4 (1), a mixed-valent UV/UVI oxide material, are reported. The hydrothermal reaction of UO22+ with Zn and hydrazine at 120 °C for three days yields 1 in the form of a dark red crystalline solid. Compound 1 has been characterized by a combination of single-crystal and powder X-ray diffraction (XRD), elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The structure consists of an extended sheet of edge and point shared UVI pentagonal bipyramids that are further connected by edge sharing to square bipyramidal UV units. The overall topology is similar to the mineral ianthinite. The uranium L|||-edge XAS revealed features consistent with those observed by single-crystal X-ray diffraction. High resolution XPS data analysis of the U4f region confirmed the oxidation states of U as originally assigned from XRD analysis and bond valence summations.

Belai, Nebebech; Frisch, Mark; Ilton, Eugene S.; Ravel, Bruce; Cahill, Christopher L.

2008-11-03

137

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions.  

PubMed

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids. PMID:10227201

McCollom, T M; Ritter, G; Simoneit, B R

1999-03-01

138

Communications : Suppression of sintering of size-selected Pd clusters under realistic reaction conditions for catalysis.  

SciTech Connect

The stability of model catalysts based on size-selected Pd clusters supported on graphite surfaces has been explored under realistic conditions for catalytic oxidation of methane at mild temperatures. The experimental results show that aggregated films of nanoparticles are highly unstable, but clusters pinned to the surface in the submonolayer coverage regime are much more stable against sintering. The degree of sintering of the pinned clusters, which does occur, proceeds by the release of clusters from their pinning sites. The suppression of sintering depends on the cluster deposition energy with respect to the pinning threshold.

Yin, F.; Lee, S.; Abdela, A.; Vajda, S.; Palmer, R. E. (Center for Nanoscale Materials); ( MSD); ( XSD); (Univ. of Birmingham); (Yale Univ.)

2011-04-08

139

Reaction Kinetics of Primary Rock-forming Minerals under Ambient Conditions  

NASA Astrophysics Data System (ADS)

Mineral dissolution kinetics influence such phenomena as development of soil fertility, amelioration of the effects of acid rain, formation of karst, acid mine drainage, transport and sequestration of contaminants, sequestration of carbon dioxide at depth in the earth, ore deposition, and metamorphism. On a global basis, mineral weathering kinetics are also involved in the long-term sink for CO2 in the atmosphere:CaSiO3+CO2=CaCO3+SiO2(1)MgSiO3+CO2=MgCO3+SiO2(2)These reactions (Urey, 1952) describe the processes that balance the volcanic and metamorphic CO2 production to maintain relatively constant levels of atmospheric CO2 over 105-106 yr timescales. In these equations, Ca- and MgSiO3 represent all calcium- and magnesium-containing silicates. Calcium- and magnesium-silicates at the Earth's surface are predominantly plagioclase feldspars, Ca-Mg-pyroxenes, amphiboles, and phyllosilicates, Ca-Mg orthosilicates. Although dissolution of the other main rock-forming mineral class, carbonate minerals, does not draw down CO2 from the atmosphere over geologic timescales, carbonate dissolution is globally important in controlling river and ground water chemistry.Despite the importance of mineral dissolution, field weathering rates are generally observed to be up to five orders of magnitude slower than laboratory dissolution rates (White, 1995), and the reason for this discrepancy remains a puzzle. For example, mean lifetimes of 1 mm spheres of rock-forming minerals calculated from measured rate data following Lasaga (1984) are much smaller than the mean half-life of sedimentary rocks (600 My, Garrels and Mackenzie, 1971). As pointed out by others ( Velbel, 1993a), the order of stability of minerals calculated from measured dissolution kinetics ( Table 1) generally follow weathering trends observed in the field (e.g., Goldich, 1938) with some exceptions. Some have suggested that quantitative prediction of field rates will be near-impossible, although such rate trends may be predictable ( Casey et al., 1993a). For studies with mineral substrates identical between laboratory and field, however, the discrepancy between field and laboratory rate estimate is generally on the order of one to two orders of magnitude (e.g., Schnoor, 1990; Swoboda-Colberg and Drever, 1993; White and Brantley, in press). Some of the discrepancy may be related to factors in the field that have not been well mimicked in laboratory systems ( White (in press) see Chapter 5.05). For example, to extrapolate mineral reaction rates from one system to another, the following variables must be understood: (i) mechanism of dissolution, (ii) reactive surface area, (iii) mineral composition, (iv) temperature of dissolution, (v) chemistry of dissolving solutions, (vi) chemical affinity of dissolving solutions, (vii) duration of dissolution, (viii) hydrologic parameters, and (ix) biological factors. In this chapter, general techniques of measurement of dissolution and precipitation rates of rock-forming silicates and carbonates are discussed, and then, seven of these nine factors are discussed sequentially. A full discussion of the biological effects (discussed by Berner et al. in Chapter 5.06) and hydrological parameters are outside the scope of this chapter.

Brantley, S. L.

2003-12-01

140

The propensity for deamidation and transamidation of peptides by transglutaminase 2 is dependent on substrate affinity and reaction conditions.  

PubMed

Transglutaminase 2 (TG2) catalyzes cross-linking or deamidation of glutamine residues in peptides and proteins. The in vivo deamidation of gliadin peptides plays an important role in the immunopathogenesis of celiac disease (CD). Although deamidation is considered to be a side-reaction occurring in the absence of suitable amines or at a low pH, a recent paper reported the selective deamidation of the small heat shock protein 20 (Hsp20), suggesting that deamidation could be a substrate dependent event. Here we have measured peptide deamidation and transamidation in the same reaction to reveal factors that affect the relative propensity for the two possible products. We report that the propensity for deamidation by TG2 is both substrate dependent and influenced by the reaction conditions. Direct deamidation is favored for poor substrates and at low concentrations of active TG2, while indirect deamidation (i.e. hydrolysis of transamidated product) can significantly contribute to the deamidation of good peptide substrates at higher enzyme concentrations. Further, we report for the first time that TG2 can hydrolyze iso-peptide bonds between two peptide substrates. This was observed also for gliadin peptides introducing a novel route for the generation of deamidated T cell epitopes in celiac disease. PMID:18793760

Stamnaes, Jorunn; Fleckenstein, Burkhard; Sollid, Ludvig M

2008-08-28

141

Synthesis of branched cores by poly-O-alkylation reaction under phase transfer conditions. A systematic study  

NASA Astrophysics Data System (ADS)

In the present paper is described a systematic study of poly-O-alkylation reactions of pentaerythritol (PE) and 1,1,1-tris(hydroxymethyl)ethane (TME) by 1,4 Michael addition, under phase transfer catalysis (PTC), considering the effect of: (1) the organophilicity of PTC (three different catalysts were tested), (2) PTC concentration (from catalytic to equimolar conditions), and (3) the regime of addition of reactants coexisting in the aqueous phase of the heterogeneous reaction system. The less organophilic transfer agent showed the best performance on these reactions. In our case, benzyltriethylammonium chloride (TEBAC) gathers the best features. The presence of NaOH as base, promotes the interfacial mechanism and not the bulk one. Out of the optimal range of concentration of NaOH (35–40%), competition between nucleophiles can occur, due to the saturation of the medium. Regarding the regime of addition of reactants, the scenario where NaOH and TEBAC are less time in contact, favors the formation of the desired products. Finally, the deprotection of tert-butyl groups of the poly-O-alkylated compounds is described, to get branched cores with terminal carboxylic acid groups in good yields (90–94%). Spectroscopic properties, such as IR, 1H and 13C NMR, of the synthesized compounds are also described.

Landeros, José M.; Silvestre, Hugo A.; Guadarrama, Patricia

2013-04-01

142

Effect of reaction conditions on size and morphology of ultrasonically prepared Ni(OH)(2) powders.  

PubMed

Modern electrochemical devices require the morphological control of the active material. In this paper the synthesis of nickel hydroxide, as common active compound of such devices, is presented. The influence of ultrasound in the synthesis of nickel hydroxide from aqueous ammonia complexes is studied showing that ultrasound allows the fabrication of flower-like particles with sizes ranging in between 0.7 and 1.0?m in contrast with the 6-8?m particles obtained in the absence of ultrasound. The influence of gas flow, temperature of the process and surfactants in the ultrasonically prepared powders is discussed in term of shape, size and agglomeration of the particles. Adjusting the experimental condition, spherical or platelet-like particles are obtained with sizes ranging from 1.3?m to 200nm. PMID:21190889

Cabanas-Polo, S; Suslick, K S; Sanchez-Herencia, A J

2010-12-04

143

Adaptive locomotor training on an end-effector gait robot: evaluation of the ground reaction forces in different training conditions.  

PubMed

The main goal of robotic gait rehabilitation is the restoration of independent gait. To achieve this goal different and specific patterns have to be practiced intensively in order to stimulate the learning process of the central nervous system. The gait robot G-EO Systems was designed to allow the repetitive practice of floor walking, stair climbing and stair descending. A novel control strategy allows training in adaptive mode. The force interactions between the foot and the ground were analyzed on 8 healthy volunteers in three different conditions: real floor walking on a treadmill, floor walking on the gait robot in passive mode, floor walking on the gait robot in adaptive mode. The ground reaction forces were measured by a Computer Dyno Graphy (CDG) analysis system. The results show different intensities of the ground reaction force across all of the three conditions. The intensities of force interactions during the adaptive training mode are comparable to the real walking on the treadmill. Slight deviations still occur in regard to the timing pattern of the forces. The adaptive control strategy comes closer to the physiological swing phase than the passive mode and seems to be a promising option for the treatment of gait disorders. Clinical trials will validate the efficacy of this new option in locomotor therapy on the patients. PMID:22275689

Tomelleri, Christopher; Waldner, Andreas; Werner, Cordula; Hesse, Stefan

2011-01-01

144

Synthesis of silica supported AuCu nanoparticle catalysts and the effects of pretreatment conditions for the CO oxidation reaction  

SciTech Connect

The reaction of CH{sub 3}CHCl{sub 2} over the nearly-stoichiometric {alpha}-Cr{sub 2}O{sub 3} (10{bar 1} > 2) surface produces an ethylidene intermediate that yields primarily gas phase CH{sub 2} {double_bond} CH{sub 2} and surface chlorine adatoms; however, trace amounts of HC {triple_bond} CH, CH{sub 3}CH{sub 3}, H{sub 2} and CH{sub 3}CH {double_bond} CHCH{sub 3} are also observed. A rate-limiting intramolecular isomerization (2,1-hydrogen shift) in the surface ethylidene species produces gas phase CH{sub 2} {double_bond} CH{sub 2}. The chlorine freed from the dissociation of CH{sub 3}CHCl{sub 2} binds at the five-coordinate surface Cr{sup 3+} sites on the stoichiometric surface, completing the octahedral coordination sphere, and inhibits the surface chemistry by simple site blocking. No surface carbon deposition is observed from the thermal reaction of 1,1-dichloroethane under the conditions of this study, demonstrating that the ethylidene intermediate is not a primary coke forming intermediate over (10{bar 1} > 2) facets of {alpha}-Cr{sub 2}O{sub 3} under the conditions of this study.

Chen, Tsung-Liang [ORNL; Mullins, David R [ORNL; Brooks, John [Virginia Polytechnic Institute and State University (Virginia Tech); Cox, David F. [Virginia Polytechnic Institute and State University (Virginia Tech)

2011-01-01

145

conditions  

Microsoft Academic Search

Real-time scheduling is both based on a broad theoretical background and available through a multitude of tools and infrastructures. The central input parameters to this discipline are the demand for execution time and the real- time conditions given as deadlines or periods. The former has attracted a lot of research efforts, mainly in the scope of worst case execution time

Dieter Z

146

Conditions  

Microsoft Academic Search

A shallow, RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine)- contaminated aquifer at Naval Submarine Base Bangor has been characterized as predominantly manganese-reducing, anoxic with local pockets of oxic conditions. The potential contribution of microbial RDX degradation to localized decreases observed in aquifer RDX concentrations was assessed in sediment microcosms amended with (U- 14 C) RDX. Greater than 85% mineralization of 14 C-RDX to 14 CO2

Paul M. Bradley; Richard S. Dinicola

147

Reactions between primary and secondary acceptors of photosystem II in Chlorella pyrenoidosa under anaerobic conditions as studied by chlorophyll fluorescence.  

PubMed

The kinetics of the fluorescence yield phi of chlorophyll a in Chlorella pyrenoidosa were studied under anaerobic conditions in the time range from 50 mus to several minutes after short (t 1/2 = 30 ns or 5 mus) saturating flashes. The fluorescence yield "in the dark" increased from phi = 1 at the beginning to phi approximately 5 in about 3 h when single flashes separated by dark intervals of about 3 min were given. After one saturating flash, phi increased to a maximum value (4-5) at 50 mus, then phi decreased to about 3 with a half time of about 10 ms and to the initial value with a half time of about 2 s. When two flashes separated by 0.2 s were given, the first phase of the decrease after the second flash occurred within 2 ms. After one flash given at high initial fluorescence yield, the 10-ms decay was followed by a 10 s increase to the initial value. After the two flashes 0.2 s apart, the rapid decay was not followed by a slow increase. These and other experiments provided additional evidence for and extend an earlier hypothesis concerning the acceptor complex of Photosystem II (Bouges-Bocquet, B. (1973) Biochim. Biophys. Acta 314, 250-256; Velthuys, B. R. and Amesz. J. (1974) Biochim. Biophys. Acta 333, 85-94): reaction center 2 contains an acceptor complex QR consisting of an electron-transferring primary acceptor molecule Q, and a secondary electron acceptor R, which can accept two electrons in succession, but transfers two electrons simultaneously to a molecule of the tertiary acceptor pool, containing plastoquinone (A). Furthermore, the kinetics indicate that 2 reactions centers of System I, excited by a short flash, cooperate directly or indirectly in oxidizing a plastohydroquinone molecule (A2-). If initially all components between photoreaction 1 and 2 are in the reduced state the following sequence of reactions occurs after a flash has oxidised A2- via System I: Q-R2- + A leads to Q-R + A2- leads to QR- + A2-. During anaerobiosis two slow reactions manifest themselves: the reduction of R (and A) within 1 s, presumably by an endogenous electron donor D1, and the reduction of Q in about 10 s when R is in the state R- and A in the state A2-. An endogenous electron donor, D2, and Q- complete in reducing the photooxidized donor complex of System II in reactions with half times of the order of 1 s. PMID:1191654

van Best, J A; Duysens, L N

1975-11-11

148

Personnel Reactions to Incentives, Naval Conditions and Experiences (PRINCE): Demographic and Background Information, Expectations, Attitudes, Values and Motivations of New Recruits.  

National Technical Information Service (NTIS)

As part of a longitudinal study of the reactions of enlisted personnel incentives, Naval conditions and experiences, information on backgrounds, expectations, attitudes, values and motivations were obtained at entry into the Navy from 6,795 recruits in Ca...

A. Katz

1971-01-01

149

Attentional focus influences postural control and reaction time performances only during challenging dual-task conditions in healthy young adults.  

PubMed

The dual-task paradigm has previously been used to investigate the attentional demands associated with postural control. Previous studies have identified both the focus of attention and the difficulty of a postural task as potential factors influencing dual-task performance. The aim of this study was to examine how the instructed focus of attention influences dual-task performance during quiet standing tasks of various levels of difficulty. Thirteen young adults participated in two testing sessions consisting of standing as still as possible on a force platform in different postural conditions, while simultaneously performing a simple reaction time (RT) task. Postural task difficulty was manipulated by various combinations of three bases of support (feet together, tandem and single leg) and two visual conditions (eyes opened and closed). Participants were instructed to focus on either their balance or their RT performance, depending on the testing session. When comparing postural control with respect to session focus, anterior-posterior sway velocity decreased with the addition of the simple RT task when the focus was on balance, but only during the more difficult dual-task conditions. In contrast, sway area and medial-lateral sway velocity did not change between the two instructed focus sessions. Participants responded faster in all dual-task conditions when focusing on RT performance than on balance. The modified attention allocation index indicated that participants' ability to modulate their allocation of attentional resources to respond positively to instruction was more pronounced in the most challenging postural condition. The present findings could have important implications for the interpretation of dual-task performance in both clinical and research settings. PMID:23995564

Remaud, Anthony; Boyas, Sébastien; Lajoie, Yves; Bilodeau, Martin

2013-08-31

150

Nitration of polynuclear aromatic hydrocarbons in coal combustors and exhaust streams. [Determination of conditions of nitration, reactions,etc  

SciTech Connect

Nitro-polynuclear aromatic hydrocarbons (nitro-PAH) are the predominant mutagens on respirable particles from coal-fired boilers. Since nitro-PAH are not primary products of coal devolatilization, their formation must involve secondary chemistry at elevated temperatures. However, it is not known where in the combustion or exhaust processes they form, which reaction species are involved, or how concentrations are influenced by operating conditions. Results from this study will help to relate the environmental impact of mutagenic emissions to boiler firing strategies. The objectives of this three-year project are to (1) identify the conditions which promote the nitration of PAH during primary combustion, reburning, hot gas cleanup, and particulate removal; and (2) investigate the potential relationship between NO{sub x} abatement and PAH nitration. A novel coal flow reactor burning actual coal products operates over the domains of heating rates, temperatures, fuel-equivalence ratios, and residence times in utility boilers. A fluidized bed will be built for studies of simulated hot gas cleanup at lower temperatures. Gas chromatography with chemiluminescence detection will measure the aggregate amount of nitro groups present, to determine when nitro-PAH first appear, and how nitration is affected by the operating conditions. Tars from primary and secondary pyrolysis and oxidative pyrolysis will be fractionated into chain hydrocarbons, polynuclear aromatics, oxygenated species, and a basic fraction, so that their ring number distribution can be monitored with high performance liquid chromatography.

Yu, Liya; Dadamio, J.; Hildemann, L.; Niksa, S.

1992-08-01

151

An investigation of the NO\\/H 2\\/O 2 reaction on noble-metal catalysts at low temperatures under lean-burn conditions  

Microsoft Academic Search

The NO\\/H2\\/O2 reaction has been studied under lean-burn conditions at low temperatures. Maxima in the NO conversions have been observed for a Pt\\/Al2O3 catalyst at 140°C (50% conversion) and for a 1% Pt\\/SiO2 catalyst at 90°C (75% conversion). The selectivity to N2O is sensitive to the reaction conditions and decreases as the temperature is raised. Addition of water has a

R Burch; M. D Coleman

1999-01-01

152

ACCURATE TIME-DEPENDENT WAVE PACKET STUDY OF THE H{sup +}+LiH REACTION AT EARLY UNIVERSE CONDITIONS  

SciTech Connect

The dynamics and kinetics of the H{sup +} + LiH reaction have been studied using a quantum reactive time-dependent wave packet (TDWP) coupled-channel quantum mechanical method on an ab initio potential energy surface at conditions of the early universe. The total reaction probabilities for the H{sup +} + LiH(v = 0, j = 0) {yields} H{sup +} {sub 2} + Li process have been calculated from 5 Multiplication-Sign 10{sup -3} eV up to 1 eV for total angular momenta J from 0 to 110. Using a Langevin model, integral cross sections have been calculated in that range of collision energies and extrapolated for energies below 5 Multiplication-Sign 10{sup -3} eV. The calculated rate constants are found to be nearly independent of temperature in the 10-1000 K interval with a value of Almost-Equal-To 10{sup -9} cm{sup 3} s{sup -1}, which is in good agreement with estimates used in evolutionary models of the early universe lithium chemistry.

Aslan, E.; Bulut, N. [Department of Physics, Firat University, 23169 Elazig (Turkey); Castillo, J. F.; Banares, L.; Aoiz, F. J. [Departamento de Quimica Fisica I, Facultad de Ciencias Quimicas (Unidad Asociada CSIC), Universidad Complutense de Madrid, 28040 Madrid (Spain); Roncero, O., E-mail: jfernand@quim.ucm.es [Instituto de Fisica Fundamental, CSIC, C/Serrano 123, E-28006 Madrid (Spain)

2012-11-01

153

[A computer analysis of EEG intersignal reactions during the the acquisition of conditioned motor-food reflexes in dogs].  

PubMed

Background electric activity was studied of different neocortex areas in interstimulus intervals at the stage of generalization during elaboration of motor alimentary conditioned reflexes in dogs. For this stage the appearance is typical of short-term (0.1-0.3 s) packs of high frequencies (above 40 osc./s) significantly exceeding the adjacent initial background by frequency and amplitude (along side with motor interstimulus reactions). The index of specific variation, elaborated by us, allowed to single out this EEG pattern in the initial realizations of the background activity during their input in the computer. With the purpose of further evaluation of the above phenomenon parameters non-standard approaches of computer analyses were used, directed to decomposition of the EEG curve into the system of oscillations and receipt of corresponding amplitudes frequencies distributions (maps). It was shown, the described high frequencies packs were localized on these maps in definite sufficiently compact places. PMID:1369561

Dumenko, V N; Kozlov, M K

154

H2S-CO2 Reaction with Hydrated Class H Well Cement under Geologic Sequestration Conditions  

NASA Astrophysics Data System (ADS)

The technology to inject CO2 into geological formations is available and practiced at several locations in the world, e.g. Sleipner, Norway and the Weyburn project in Alberta, Canada. In addition to CO2, acid gas (a mixture of CO2 and H2S) injection is also currently employed and on the rise. For example, there are currently over 40 wells used for acid gas injection in Alberta, Canada. Few studies address the physical and chemical characteristics of well cement exposed to acid gas under geologic sequestration conditions. The objective of this study is to determine how oilwell cement is affected by the addition of H2S in a CO2 injection scenario. Laboratory experiments have been performed in order to determine the physical and chemical changes in cement exposed to acid gas vs. pure CO2 under simulated sequestration reservoir conditions, including both aqueous and supercritical CO2. Obvious differences were observed between the H2S-CO2 and CO2-only exposed cement. Differences were also observed between the submerged and headspace exposed portions of the samples. The H2S-CO2 exposed cement underwent a combination of carbonation and redox reactions that ultimately affected the physical properties. The outer rim of the cylindrical cement samples were characterized by a zone of carbonation and the sulfidation of tetracalcium aluminoferrites to pyrite. Beyond the carbonation rim is evidence of significant impact from the H2S in the form of ettringite and very small grains of pyrite. Ettringite is formed due to oxidation of H2S which produces sulfides which in turn reacts with Ca-compounds. The carbonation reaction lowers the pH in the cement matrix to allow dissolution of ettringite and the tetracalcium aluminoferrite for pyrite formation. Implications regarding geologic co-sequestration and wellbore integrity are significant.

Kutchko, B. G.; Hawthorne, S.; Strazisar, B. R.; Miller, D.

2009-12-01

155

Diagnosis of foot-and mouth disease by real time reverse transcription polymerase chain reaction under field conditions in Brazil  

PubMed Central

Background Foot-and-mouth disease (FMD) is an economically important and highly contagious viral disease that affects cloven-hoofed domestic and wild animals. Virus isolation and enzyme-linked immunosorbent assay (ELISA) are the gold standard tests for diagnosis of FMD. As these methods are time consuming, assays based on viral nucleic acid amplification have been developed. Results A previously described real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay with high sensitivity and specificity under laboratorial and experimental conditions was used in the current study. To verify the applicability of this assay under field conditions in Brazil, 460 oral swabs from cattle were collected in areas free of FMD (n = 200) and from areas with outbreaks of FMD (n = 260). Three samples from areas with outbreaks of FMD were positive by real-time RT-PCR, and 2 of those samples were positive by virus isolation and ELISA. Four other samples were considered inconclusive by real-time RT-PCR (threshold cycle [Ct] > 40); whereas all 200 samples from an area free of FMD were real-time RT-PCR negative. Conclusion real-time RT-PCR is a powerful technique for reliable detection of FMDV in a fraction of the time required for virus isolation and ELISA. However, it is noteworthy that lack of infrastructure in certain areas with high risk of FMD may be a limiting factor for using real-time RT-PCR as a routine diagnostic tool.

Paixao, Tatiane A; Neta, Alcina V Carvalho; Paiva, Naimes O; Reis, Jorge R; Barbosa, Meirivan S; Serra, Claudia V; Silva, Rene R; Beckham, Tammy R; Martin, Barbara M; Clarke, Neville P; Adams, L Garry; Santos, Renato L

2008-01-01

156

Reaction of (1 S,2 S)-2-amino-1-phenyl-1,3-propanediol with thioacids under the Mitsunobu reaction condition  

Microsoft Academic Search

The Mitsunibu thioesterification was applied to the title 2-amino-1,3-propanediol (1). The regio- and stereochemistry of the reaction was investigated in correlation with the nature of substituents attached to the nitrogen.

Maria D. Rozwadowska

1997-01-01

157

Emissions of volatile organic compounds from Quercus ilex L. measured by Proton Transfer Reaction Mass Spectrometry under different environmental conditions  

NASA Astrophysics Data System (ADS)

Volatile organic compound (VOC) emissions of the Mediterranean holm oak (Quercus ilex L.) were investigated using a fast Proton Transfer Reaction Mass Spectrometry (PTR-MS) instrument for analysis. This technique is able to measure compounds with a proton affinity higher than water with a high time resolution of 1 s per compound. Hence nearly all VOCs can be detected on-line. We could clearly identify the emission of methanol, acetaldehyde, ethanol, acetone, acetic acid, isoprene, monoterpenes, toluene, and C10-benzenes. Some other species could be tentatively denominated. Among these are the masses 67 (cyclo pentadiene), mass 71 (tentatively attributed to methyl vinyl ketone (MVK) and metacrolein (MACR)), 73 (attributed to methyl ethyl ketone (MEK)), 85 (C6H12 or hexanol), and 95 (vinylfuran or phenol). The emissions of all these compounds (identified as well as nonidentified) together represent 99% of all masses detected and account for a carbon loss of 0.7-2.9% of the net photosynthesis. Of special interest was a change in the emission behavior under changing environmental conditions such as flooding or fast light/dark changes. Flooding of the root system caused an increase of several VOCs between 60 and 2000%, dominated by the emission of ethanol and acetaldehyde, which can be explained by the well described production of ethanol under anoxic conditions of the root system and the recently described subsequent transport and partial oxidation to acetaldehyde within the green leaves. However, ethanol emissions were dominant. Additionally, bursts of acetaldehyde with lower ethanol emission were also found under fast light/dark changes. These bursts are not understood.

Holzinger, R.; Sandoval-Soto, L.; Rottenberger, S.; Crutzen, P. J.; Kesselmeier, J.

2000-08-01

158

Reactions of transplanted neurocentral synchondroses to different conditions of mechanical stress. A methodological study on the rat.  

PubMed Central

In order to elucidate the reactions of neurocentral synchondroses to different forces, the first cervical vertebra of 10 or 25 days old rats was transplanted into sex-matched litter mates. Some vertebrae were transplanted as a whole, in some only the ventral part with its synchondroses was transplanted and, in others the lumen was furnished with an expanding sponge or a spring. The transplantation was done subcutaneously and, in the case of the fragments, intracerebrally as well. The synchondroses of the vertebrae transplanted at 10 days did not differ very much from those of the host 5, 10 or 15 days after the operation, whereas in the vertebrae transplanted at 25 days the synchondroses underwent synostosis earlier than in situ. The synchondroses of the transplanted fragments, and especially of those placed intracerebrally, remained open longer than those in the whole vertebral transplants; the sponge and and the spring also delayed closure. In the synchondroses transplanted at 25 days there was a strong reduction in alcian blue staining, whereas in the spring loaded synchondroses the stainability persisted longer, maybe as an adaptation to the tensile force. It seems that the inherent potential of the neurocentral synchondroses to obliterate at a certain time can be altered by changing the biomechanical conditions. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5

Ronning, O; Kylamarkula, S

1979-01-01

159

Conditional Differences in Mean Reaction Time Explain Effects of Response Congruency, but not Accuracy, on Posterior Medial Frontal Cortex Activity.  

PubMed

According to the conflict-monitoring model of cognitive control, the posterior medial frontal cortex (pMFC) plays an important role in detecting conflict between competing motor responses. Consistent with this view, pMFC activity is greater in high-conflict trials (e.g., incongruent trials and errors) than in low-conflict trials (e.g., congruent trials and correct responses) of distractor interference tasks. However, in both low- and high-conflict trials, pMFC activity increases linearly with reaction time (RT). Thus, heightened pMFC activity in high-conflict trials may simply reflect the fact that mean RT is longer in high-conflict than in low-conflict trials. To investigate this hypothesis, we reanalyzed data from a previously published fMRI study in which participants performed an event-related version of the multi-source interference task. Critically, after controlling for conditional differences in mean RT, effects of response congruency on pMFC activity were eliminated; in contrast, effects of response accuracy on pMFC activity remained robust. These findings indicate that effects of response congruency on pMFC activity may index any of several processes whose recruitment increases with time on task (e.g., sustained attention). However, effects of response accuracy reflect processes unique to error trials. We conclude that effects of response accuracy on pMFC activity provide stronger support for the conflict-monitoring model than effects of response congruency. PMID:21212836

Carp, Joshua; Kim, Kamin; Taylor, Stephan F; Fitzgerald, Kate Dimond; Weissman, Daniel H

2010-12-24

160

CO2 reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures.  

PubMed

The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO2 and CO2-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing, wells on CO2 storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan-cement blends were exposed to supercritical CO2 and CO2-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm for both the CO2-saturated brine and supercritical CO2 after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO2, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 microD. Analyses of 50: 50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO2, which are consistent with our laboratory findings. PMID:19544912

Kutchko, Barbara G; Strazisar, Brian R; Huerta, Nicolas; Lowry, Gregory V; Dzombak, David A; Thaulow, Niels

2009-05-15

161

Clean bio-oil production from fast pyrolysis of sewage sludge: effects of reaction conditions and metal oxide catalysts.  

PubMed

Fast pyrolysis of sewage sludge was carried out under different reaction conditions, and its effects on bio-oil characteristics were studied. The effect of metal oxide catalysts on the removal of chlorine in the bio-oil was also investigated for four types of catalysts. The optimal pyrolysis temperature for bio-oil production was found to be 450 degrees C, while much smaller and larger feed sizes adversely influenced production. Higher flow and feeding rates were more effective but did not greatly affect bio-oil yields. The use of the product gas as the fluidizing medium gave an increased bio-oil yield. Metal oxide catalysts (CaO and La2O3) contributed to a slight decrease in bio-oil yield and an increase in water content but were significantly effective in removal of chlorine from the bio-oil. The fixed catalyst bed system exhibited a higher removal rate than when metal oxide-supported alumina was used as the fluidized bed material. PMID:19635664

Park, Hyun Ju; Heo, Hyeon Su; Park, Young-Kwon; Yim, Jin-Heong; Jeon, Jong-Ki; Park, Junhong; Ryu, Changkook; Kim, Seung-Soo

2009-07-26

162

Isolation of lipase producing thermophilic bacteria: optimization of production and reaction conditions for lipase from Geobacillus sp.  

PubMed

Lipases catalyze the hydrolysis and the synthesis of esters formed from glycerol and long chain fatty acids. Lipases occur widely in nature, but only microbial lipases are commercially significant. In the present study, thirty-two bacterial strains, isolated from soil sample of a hot spring were screened for lipase production. The strain TS-4, which gave maximum activity, was identified as Geobacillus sp. at MTCC, IMTECH, Chandigarh. The isolated lipase producing bacteria were grown on minimal salt medium containing olive oil. Maximal quantities of lipase were produced when 30 h old inoculum was used at 10% (v/v) in production medium and incubated in shaking conditions (150 rpm) for 72 h. The optimal temperature and pH for the bacterial growth and lipase production were found to be 60°C and 9.5, respectively. Maximal enzyme production resulted when mustard oil was used as carbon source and yeast extract as sole nitrogen source at a concentration of 1% (v/v) and 0.15% (w/v), respectively. The different optimized reaction parameters were temperature 65°C, pH 8.5, incubation time 10 min and substrate p-nitrophenyl palmitate. The Km and Vmax values of enzyme were found to be 14 mM and 17.86 ?mol ml-1min-1, respectively, with p-nitrophenyl palmitate as substrate. All metal ions studied (1 mM) increased the lipase activity. PMID:23195552

Mehta, Akshita; Kumar, Rakesh; Gupta, Reena

2012-12-01

163

Synthesis of different-sized silver nanoparticles by simply varying reaction conditions with leaf extracts of Bauhinia variegata L.  

PubMed

Green synthesis of nanoparticles is one of the crucial requirements in today's climate change scenario all over the world. In view of this, leaf extract (LE) of Bauhinia variegata L. possessing strong antidiabetic and antibacterial properties has been used to synthesise silver nanoparticles (SNP) in a controlled manner. Various-sized SNP (20-120?nm) were synthesised by varying incubation temperature, silver nitrate and LE concentrations. The rate of SNP synthesis and their size increased with increase in AgNO(3) concentration up to 4?mM. With increase in LE concentration, size and aggregation of SNP was increased. The size and aggregation of SNP were also increased at temperatures above and below 40°C. This has suggested that size and dispersion of SNP can be controlled by varying reaction components and conditions. Polarity-based fractionation of B. variegata LE has suggested that only water-soluble fraction is responsible for SNP synthesis. Fourier transform infrared spectroscopy analysis revealed the attachment of polyphenolic and carbohydrate moieties to SNP. The synthesised SNPs were found stable in double distilled water, BSA and phosphate buffer (pH 7.4). On the contrary, incubation of SNP with NaCl induced aggregation. This suggests the safe use of SNP for various in vivo applications. PMID:22423864

Kumar, V; Yadav, S K

2012-03-01

164

Solvent?Free Reactions of Fullerenes with Diethyl Bromomalonate in the Presence of Inorganic Bases Under High?Speed Vibration Milling Conditions  

Microsoft Academic Search

Solvent?free reactions of C60 and C70 with diethyl bromomalonate in the presence of various inorganic bases were investigated under the high?speed vibration milling (HSVM) conditions, and are shown to give methanofullerenes 1 and 2 in good to excellent yields based on consumed fullerenes. Several weak inorganic bases were found to be quite effective in promoting the solvent?free mechanochemical Bingel reactions

Yasujiro Murata; Koichi Komatsu

2004-01-01

165

Role of precursors on the kinetics of acrylamide formation and elimination under low moisture conditions using a multiresponse approach – Part II: Competitive reactions  

Microsoft Academic Search

The effect of addition of amino acids, other than asparagine, on the kinetics of acrylamide formation and elimination reactions was investigated under low moisture conditions using equimolar asparagine-glucose-amino acid model systems, heated at temperatures between 120 and 200°C. To this end, glutamine and cysteine were selected. A mechanistic model was proposed, composed of the basic reactions occurring in an asparagine-glucose

Kristel De Vleeschouwer; Iesel Van der Plancken; Ann Van Loey; Marc E. Hendrickx

2009-01-01

166

Combined temperature-programmed reaction and in-situ x-ray scattering studies of size-selected silver clusters under realistic reaction conditions in the epoxidation of propene.  

SciTech Connect

The catalytic activity and dynamical shape changes in size-selected nanoclusters at work are studied under realistic reaction conditions by using a combination of simultaneous temperature-programmed reaction with in situ grazing-incidence small angle x-ray scattering. This approach allows drawing a direct correlation between nanocatalyst size, composition, shape, and its function under realistic reaction conditions for the first time. The approach is illustrated in a chemical industry highly relevant selective partial oxidation of propene on a monodisperse silver nanocatalyst. The shape of the catalyst undergoes rapid change already at room temperature upon the exposure to the reactants, followed by a complex evolution of shape with increasing temperature. Acrolein formation is observed around 50 C while the formation of the propylene oxide exhibits a sharp onset at 80 C and is leveling off at 150 C. At lower temperatures acrolein is produced preferentially to propylene oxide; at temperatures above 100 C propylene oxide is favored.

Vajda, S.; Lee, S.; Sell, K.; Barke, I.; Kleibert, A.; von Oeynhausen, V.; Meiwes-Broer, K. H.; Rodriguez, A. F.; Elam, J. W.; Pellin, M. M.; Lee, B.; Seifert, S.; Winans, R. W.; Yale Univ.; Univ. Rostock; Swiss Light Source

2009-09-28

167

Reactions of peroxynitrite with uric acid: formation of reactive intermediates, alkylated products and triuret, and in vivo production of triuret under conditions of oxidative stress.  

PubMed

Hyperuricemia is associated with hypertension, metabolic syndrome, preeclampsia, cardio-vascular disease and renal disease, all conditions associated with oxidative stress. We hypothesized that uric acid, a known antioxidant, might become prooxidative following its reaction with oxidants; and, thereby contribute to the pathogenesis of these diseases. Uric acid and 1,3-(15)N(2)-uric acid were reacted with peroxynitrite in different buffers and in the presence of alcohols, antioxidants and in human plasma. The reaction products were identified using liquid chromatography-mass spectrometry (LC-MS) analyses. The reactions generate reactive intermediates that yielded triuret as their final product. We also found that the antioxidant, ascorbate, could partially prevent this reaction. Whereas triuret was preferentially generated by the reactions in aqueous buffers, when uric acid or 1,3-(15)N(2)-uric acid was reacted with peroxynitrite in the presence of alcohols, it yielded alkylated alcohols as the final product. By extension, this reaction can alkylate other biomolecules containing OH groups and others containing labile hydrogens. Triuret was also found to be elevated in the urine of subjects with preeclampsia, a pregnancy-specific hypertensive syndrome that is associated with oxidative stress, whereas very little triuret is produced in normal healthy volunteers. We conclude that under conditions of oxidative stress, uric acid can form reactive intermediates, including potential alkylating species, by reacting with peroxynitrite. These reactive intermediates could possibly explain how uric acid contributes to the pathogenesis of diseases such as the metabolic syndrome and hypertension. PMID:19219741

Gersch, Christine; Palii, Sergiu P; Imaram, Witcha; Kim, Kyung Mee; Karumanchi, S Ananth; Angerhofer, Alexander; Johnson, Richard J; Henderson, George N

2009-02-01

168

REACTIONS OF PEROXYNITRITE WITH URIC ACID: FORMATION OF REACTIVE INTERMEDIATES, ALKYLATED PRODUCTS AND TRIURET, AND IN VIVO PRODUCTION OF TRIURET UNDER CONDITIONS OF OXIDATIVE STRESS  

PubMed Central

Hyperuricemia is associated with hypertension, metabolic syndrome, preeclampsia, cardiovascular disease and renal disease, all conditions associated with oxidative stress. We hypothesized that uric acid, a known antioxidant, might become prooxidative following its reaction with oxidants; and, thereby contribute to the pathogenesis of these diseases. Uric acid and 1,3-15N2-uric acid were reacted with peroxynitrite in different buffers and in the presence of alcohols, antioxidants and in human plasma. The reaction products were identified using liquid chromatography-mass spectrometry (LC-MS) analyses. The reactions generate reactive intermediates that yielded triuret as their final product. We also found that the antioxidant, ascorbate, could partially prevent this reaction. Whereas triuret was preferentially generated by the reactions in aqueous buffers, when uric acid or 1,3-15N2-uric acid was reacted with peroxynitrite in the presence of alcohols, it yielded alkylated alcohols as the final product. By extension, this reaction can alkylate other biomolecules containing OH groups and others containing labile hydrogens. Triuret was also found to be elevated in the urine of subjects with preeclampsia, a pregnancy-specific hypertensive syndrome that is associated with oxidative stress, whereas very little triuret is produced in normal healthy volunteers. We conclude that under conditions of oxidative stress, uric acid can form reactive intermediates, including potential alkylating species, by reacting with peroxynitrite. These reactive intermediates could possibly explain how uric acid contributes to the pathogenesis of diseases such as the metabolic syndrome and hypertension.

Gersch, Christine; Palii, Sergiu P.; Imaram, Witcha; Kim, Kyung Mee; Karumanchi, S. Ananth; Angerhofer, Alexander; Johnson, Richard J.; Henderson, George N.

2009-01-01

169

The effect of reaction condition on composition and properties of ultrafine amorphous powders in (Fe, Co, Ni)-b systems prepared by chemical reduction  

Microsoft Academic Search

Amorphous ultrafine powders in (Fe, Co, Ni)-B binary systems were prepared in different reduction conditions of metal ions\\u000a in an aqueous solution by use of KBH4, with the aim of clarifying the effect of reaction conditions on the composition, thermal stability, and magnetic properties\\u000a of the resultant amorphous powders. As the mol ratio of KBH4 to metal ions decreases, the

Junji Saida; Akihisa Inoue; Tsuyoshi Masumoto

1991-01-01

170

Effects of reaction conditions on RNA secondary structure and on the helicase activity of Escherichia coli transcription termination factor rho 1 1 Edited by D. Draper  

Microsoft Academic Search

The ATPase and helicase activities of the Escherichia coli transcription termination protein rho have been studied under a variety of reaction conditions that alter its transcription termination activity. These conditions include KCl, KOAc, or KGlu concentrations from 50 to 150 mM and Mg(OAc)2 concentrations from 1 to 5 mM (in the presence of 1 mM ATP). In higher KCl or

Katherine M Walstrom; Jody M Dozono; Peter H von Hippel

1998-01-01

171

Efficient batch and continuous flow Suzuki cross-coupling reactions under mild conditions, catalysed by polyurea-encapsulated palladium (II) acetate and tetra-n-butylammonium salts.  

PubMed

Suzuki cross-coupling reactions are effected in both conventional organic solvents, under continuous flow conditions at 70 degree C, and in batch mode in supercritical carbon dioxide (scCO2), at temperatures as low as 40 degrees C in the presence of palladium(II) acetate microencapsulated in polyurea [PdEnCat] and tetra-n-butylammonium salts. PMID:15846438

Lee, Connie K Y; Holmes, Andrew B; Ley, Steven V; McConvey, Ian F; Al-Duri, Bushra; Leeke, Gary A; Santos, Regina C D; Seville, Jonathan P K

2005-03-09

172

Tandem decarboxylative hydroformylation-hydrogenation reaction of ?,?-unsaturated carboxylic acids toward aliphatic alcohols under mild conditions employing a supramolecular catalyst system.  

PubMed

A new atom economic catalytic method for a highly chemoselective reduction of ?,?-unsaturated carboxylic acids to the corresponding saturated alcohols under mild reaction conditions, compatible with a wide range reactive functional groups, is reported. The new methodology consists of a novel tandem decarboxylative hydroformylation/aldehyde reduction sequence employing a unique supramolecular catalyst system. PMID:24022335

Diab, Lisa; Gellrich, Urs; Breit, Bernhard

2013-09-26

173

Enantioselective direct aldol reaction of ?-keto esters catalyzed by (S(a))-binam-D-prolinamide under quasi solvent-free conditions.  

PubMed

(S(a))-Binam-D-prolinamide (20 mol%), instead of (S(a))-binam-L-prolinamide, in combination with chloroacetic acid (100 mol%) is an efficient organocatalyst for the direct aldol reaction between ?-keto esters as electrophiles and alkyl and ?-functionalised ketones, under quasi solvent-free conditions, providing access to highly functionalised chiral quaternary ?-keto ?-hydroxyesters with up to 92% ee. PMID:22514086

Viózquez, Santiago F; Bañón-Caballero, Abraham; Guillena, Gabriela; Nájera, Carmen; Gómez-Bengoa, Enrique

2012-04-18

174

CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-CIN-1437 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Catalyst-free Reactions under Solvent-fee Conditions: Microwave-assisted Synthesis of Heterocyclic Hydrazones below the Melting Point of Neat Reactants. Published in: Chemical Communications 18:1716-1717 (200...

175

HIGHLY DIASTEREOSELECTIVE MICHAEL REACTION UNDER SOLVENT-FREE CONDITIONS USING MICROWAVES: CONJUGATE ADDITION OF FLAVANONE TO ITS CHALCONE PRECURSOR  

EPA Science Inventory

Microwave-assisted reaction of 2'-hydroxychalcones in the presence of DBU resulted in the formation of hitherto unknown dimers by conjugate addition of the intermediate cyclic ketone to the starting enone....

176

Direct ethanol fuel cell (DEFC): Electrical performances and reaction products distribution under operating conditions with different platinum-based anodes  

Microsoft Academic Search

Ethanol electro-oxidation at different Pt-based electrodes was investigated in a single direct ethanol fuel cell (DEFC) in terms of reaction product distribution depending on the anode catalyst. In DEFC experiments, only three reaction products were detected using HPLC: acetaldehyde (AAL), acetic acid (AA) and CO2. The addition of tin to platinum increases the activity of the catalyst by several order

S. Rousseau; C. Coutanceau; C. Lamy; J.-M. Léger

2006-01-01

177

The effects of reaction conditions and catalyst deactivation on the mechanism of n-butane isomerization on sulfated zirconia  

Microsoft Academic Search

The mechanism of n-butane isomerization on a widely studied unpromoted sulfated zirconia catalyst was studied at low conversions in a once-through reactor using 13C-labeled n-butane as a reactant. The comparison of results from GC\\/MS analysis of isobutane produced from 12C containing n-butane and 13C-labelled n-butane suggests that, at reaction temperatures ?250°C, the reaction proceeds mainly via the bimolecular mechanism. The

Soo Y Kim; James G Goodwin; Dan F?rca?iu

2001-01-01

178

Kinetics of sulfur isotope exchange between aqueous sulfide and thiosulfate involving intra- and intermolecular reactions at hydrothermal conditions  

Microsoft Academic Search

Sulfur isotope exchange between sulfide (H2S) and thiosulfate (HSSO3H) can be described by the general rate law for a two-compound system (X and AB) with three exchangeable atoms (X, A, and B) proposed by [X. Chu, H. Ohmoto, Kinetics of isotope exchange reactions involving intra- and intermolecular reactions: I. Rate law for a system with two chemical compounds and three

Xuelei Chu; Hiroshi Ohmoto; David R. Cole

2004-01-01

179

An LMI approach to stability analysis of reaction-diffusion Cohen-Grossberg neural networks concerning Dirichlet boundary conditions and distributed delays.  

PubMed

The global asymptotic stability problem for a class of reaction-diffusion Cohen-Grossberg neural networks with both time-varying delay and infinitely distributed delay is investigated under Dirichlet boundary conditions. Instead of using the M-matrix method and the algebraic inequality method, under some suitable assumptions and using a matrix decomposition method, we adopt the linear matrix inequality method to propose two sufficient stability conditions for the concerned neural networks with Dirichlet boundary conditions and different kinds of activation functions, respectively. The obtained results are easy to check and improve upon the existing stability results. Two examples are given to demonstrate the effectiveness of the obtained results. PMID:20371408

Wang, Zhanshan; Zhang, Huaguang; Li, Ping

2010-04-05

180

How Pragmatic Interpretations Arise from Conditionals: Profiling the Affirmation of the Consequent Argument with Reaction Time and EEG Measures  

ERIC Educational Resources Information Center

|Conditional reasoning consists in combining a conditional premise with a categorical premise and inferring a conclusion from them. Two well-known conditional arguments are Modus Ponens (MP: "If P then Q; P//"therefore Q), which is logically valid and Affirmation of the Consequent (AC: "If P then Q; Q//"therefore "P"), which is not. The latter is…

Bonnefond, Mathilde; Van der Henst, Jean-Baptiste; Gougain, Marion; Robic, Suzanne; Olsen, Matthew D.; Weiss, Oshri; Noveck, Ira

2012-01-01

181

In situ monitoring of the acetylene decomposition and gas temperature at reaction conditions for the deposition of carbon nanotubes using linear Raman scattering.  

PubMed

To understand the reaction mechanisms taking place by growing carbon nanotubes via the catalytic chemical vapor deposition process, a strategy to monitor in situ the gas phase at reaction conditions was developed applying linear Raman spectroscopy. The simultaneous determination of the gas temperature and composition was possible by a new strategy of the evaluation of the Raman spectra. In agreement to the well-known exothermic decomposition of acetylene, a gas temperature increase was quantified when acetylene was added to the incident flow. Information about exhaust gas recirculation and location of the maximal acetylene conversion was derived from the composition measurements. PMID:20721212

Reinhold-López, Karla; Braeuer, Andreas; Popovska, Nadejda; Leipertz, Alfred

2010-08-16

182

An experimental investigation of the reaction of hydrogen chloride with lead oxide under simulated hazardous waste incineration conditions  

SciTech Connect

To simulate the behavior of lead during hazardous waste incineration, pellets of sintered lead oxide were treated with hydrogen chloride at concentrations of 2000 and 4000 ppm in air in a laboratory tube furnace. The chemical reaction kinetics and mass transfer properties of the solid-gas and solid-liquid reactions were examined at temperatures between 260 and 680{degrees}C. Lead dichloride was found to form and became more volatile at elevated temperatures. At temperatures above 300{degrees}C, chemical reaction kinetic limitations were absent and mass transfer resistance in the developing liquid lead oxide, lead dichloride eutectic phases were controlling. Above 590{degrees}C, a curious anomaly occurred: The observed global reaction rate appeared to increase slightly while the volatilization of lead dichloride dropped during the initial stages of the reaction. A thick film of a lead oxychloride compound was found which displayed low lead dichloride activity. Below 590{degrees}C, a different lead oxychloride compound was identified by x-ray diffraction in which lead dichloride activity was high, and this compound was much more volatile than the oxychloride formed above 5900{degrees}C.

Shor, J.T. [Oak Ridge National Lab., TN (United States); Frazier, G.C. [Univ. of Tennessee, Knoxville, TN (United States)

1996-04-01

183

LENGTH-HETEROGENEITY POLYMERASE CHAIN REACTION (LH-PCR) AS AN INDICATOR OF STREAM SANITARY AND ECOLOGICAL CONDITION: OPTIMAL SAMPLE SIZE AND HOLDING CONDITIONS  

EPA Science Inventory

The use of coliform plate count data to assess stream sanitary and ecological condition is limited by the need to store samples at 4oC and analyze them within a 24-hour period. We are testing LH-PCR as an alternative tool to assess the bacterial load of streams, offering a cost ...

184

Bifunctional nickel precatalysts of amido-functionalized N-heterocyclic carbenes for base-free Michael reaction under ambient conditions  

Microsoft Academic Search

A series of new bifunctional nickel precatalysts, [1-(R)-3-N-(benzylacetamido)imidazol-2-ylidene]2 Ni [R = Me (1b), i-Pr (2b), and CH2Ph (3b)], containing a Lewis acidic metal site and a Lewis basic amido-N site in a pendent ligand sidearm, have been successfully designed for base-free Michael addition reaction. Specifically, the nickel (1–3)b complexes catalyzed the highly desired base-free Michael addition reactions of representative cyclic 5-membered ?-dicarbonyl

Sachin Kumar; Anantha Narayanan; Mitta Nageswar Rao; Mobin M. Shaikh; Prasenjit Ghosh

185

Effect of Particle Morphology on Critical Conditions for Shock-Initiated Reactions in Titanium-Silicon Powder Mixtures  

NASA Astrophysics Data System (ADS)

The effect of titanium particle morphology on the shock sensitivity of titanium-silicon powder mixtures has been investigated experimentally. The powder mixtures were tested in a planar recovery capsule, with the shock loading produced by a high explosive booster charge placed on top of the capsule and a PMMA attenuator. Reactions were not observed for equimolar mixtures of large (95 ?m) spherical Ti particles with fine (15 ?m) Si particles for incident peak shock pressures of up to 23 GPa, estimated with LS-DYNA. In contrast, mixtures with fine (40 ?m) spherical Ti particles or irregularly-shaped fine (31 ?m) Ti particles exhibited a threshold attenuator thickness, and hence shock pressure, for reaction initiation. Microscopy and microprobe backscatter analysis were used to identify the degree of intermixing between the particles for shock loading just below the reaction threshold. For the largest spherical Ti particles, little particle intermixing was evident. For the finer particles, penetration of Si particles into the larger, more ductile Ti particles was observed. Although large deformation of the irregular Ti particles was observed, in contrast with the spherical particles, the threshold shock pressure for reaction initiation was 7+/-2 GPa, independent of particle morphology.

Frost, David L.; Jetté, François-Xavier; Goroshin, Samuel; Higgins, Andrew J.; Lee, Julian J.

2009-12-01

186

Photocatalytic dechlorination of PCB 138 using leuco-methylene blue and visible light; reaction conditions and mechanisms.  

PubMed

A study of dechlorination of PCB 138, under visible light employing methylene blue (MB) and triethylamine (TEA) in acetonitrile/water has been conducted to investigate the details of the mechanism of dechlorination and to determine the efficiency of the process for this representative congener. Two other amines, N-methyldiethanolamine (MEDA) and (triethanolamine) TEOA also replaced TEA and two other solvents, methanol and ethanol replacing acetonitrile were examined for effects on reaction rates. The results show that PCB 138 can be dechlorinated efficiently in this photocatalytic reaction. Clarifying ambiguities in several previous reports, the reduced form of MB, leuco-methylene blue (LMB) was identified as responsible for the photoreaction with its excited state transferring an electron to PCBs; oxidized LMB (i.e. MB) is reduced back to LMB by the excess amine present. The reaction depends on a cycle driven by the amine as a sacrificial electron donor. MEDA proved to be the most efficient electron donor; apparently in consequence of the most favourable steady state concentration of LMB. Methanol and ethanol may be used to replace acetonitrile with little change in the efficiency of the reaction. PMID:20542375

Izadifard, Maryam; Langford, Cooper H; Achari, Gopal

2010-05-12

187

Optimization of conditions for the polymerase chain reaction amplification of DNA from culturable and nonculturable cells of Vibrio vulnificus  

Microsoft Academic Search

A series of 16 buffers, differing in pH and MgCl2 concentration, were used to optimize the polymerase chain reaction (PCR) amplification of a 388 bp region of the hemolysin \\/ cytolysin gene from cells of Vibrio vulnificus present in both the culturable and nonculturable states. Both the opaque and translucent morphotypes were examined. Using whole cell lysates, we were able

Shirley S. Coleman; James D. Oliver

1996-01-01

188

Estimate Calculations by PLEXUS Code to Verify the Safety Condition for the First Test of Sodium: Water Reaction Flash Programme.  

National Technical Information Service (NTIS)

This report presents a detailed analysis of the results obtained from five risk assessments of the safety of the first test of the sodium-water reaction experimental program, FLASH. This program is being carried out within the framework of the LMFBR RandD...

P. Agostini A. Daneri G. Toselli

1988-01-01

189

Prediction of reaction barriers and force-induced instabilities under mechanochemical conditions with an approximate model: A case study of the ring opening of 1,3-cyclohexadiene  

NASA Astrophysics Data System (ADS)

Mechanochemistry, the use of mechanical stresses to activate chemical reactions, has emerged as a topic of significant interest. The present study examines the use of an approximate model for the prediction of reaction barriers under mechanochemical conditions using the ring opening of 1,3-cyclohexadiene along conrotatory and disrotatory directions as a specific test case. To do this, reaction barriers are evaluated using quantum chemical methods with an external force applied between various pairs of atoms. The results show that the consequent effects on the barrier exhibit a significant dependence on the locations of the atoms used to apply the external force, and in some cases, force-induced instabilities occur that alter the fundamental nature of the reaction pathway. The ability of an approximate model based on a second-order expansion of the force-modified potential energy with respect to nuclear coordinates to reproduce this behavior is then assessed. Good agreement between the results obtained through the quantum chemical calculations and approximate model is attained when force-induced instabilities do not occur. In addition, a strategy for predicting when such instabilities occur is presented and found to yield results that are in qualitative agreement with the quantum chemical calculations. Finally, the response of the system to the external force is interpreted in terms of the parameters entering the model, which correspond to interatomic distances and stiffnesses, and possibly sheds lights on ways to design molecules that exhibit a desired chemical response to mechanochemical conditions.

Bailey, Adrian; Mosey, Nicholas J.

2012-01-01

190

Metal-doped (Ti, WC) diamond-like-carbon coatings: Reactions with extreme-pressure oil additives under tribological and static conditions  

Microsoft Academic Search

In contrast to non-doped diamond-like-carbon (DLC) coatings, reliable chemical evidence of the reactions between metal-doped DLC coatings and oil additives under tribological conditions using state-of-the-art surface-sensitive chemical analyses is still scarce. In this study we have investigated the reactivity of metal-doped (Ti, WC) DLC coatings with the extreme-pressure (EP) dialkyl dithiophosphate additive — without the presence of a steel counter

M. Kalin; E. Roman; L. Ožbolt; J. Vižintin

2010-01-01

191

Dopamine D 1 Receptors Regulate the Extracellular Citrulline Level in the Nucleus Accumbens During Performance of a Conditioned Reflex Fear Reaction  

Microsoft Academic Search

Intracerebral microdialysis studies on Sprague–Dawley rats using HPLC showed that performance of a conditioned reflex fear\\u000a reaction was accompanied by an increase in the extracellular citrulline (a co-product of nitric oxide synthesis) level in\\u000a the nucleus accumbens. Administration of the selective D1 receptor antagonist SCH-23390 (100 ?M) into the nucleus accumbens had no long-lasting effect on the extracellular citrulline\\u000a level in

N. B. Saul’skaya; N. V. Fofonova

2009-01-01

192

Encouraging conceptual change: the use of bridging analogies in the teaching of action reaction forces and the `at rest' condition in physics  

Microsoft Academic Search

The qualitative study described in this paper examined the effectiveness of bridging analogies intended to bring about conceptual change as part of a constructivist approach to teaching about action reaction forces in the `at rest' condition in physics. Twenty-one 15-year-old students were involved in the investigation with subgroups previously exposed to different information regarding forces, weight and the accepted cause

Tom Bryce; Kenneth MacMillan

2005-01-01

193

Effects of calcination conditions on phase formation and particle size of indium niobate nanopowders synthesized by the solid-state reaction  

Microsoft Academic Search

A wolframite-type phase of indium niobate, InNbO4, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The formation of the InNbO4 phase in the calcined powders has been investigated as a function of calcination conditions by TG–DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques.

S. Wongsaenmai; R. Yimnirun; S. Ananta

2007-01-01

194

Fluid flow behavior and the rate of an enzyme reaction in deep microchannel reactor under high-throughput condition  

Microsoft Academic Search

Two different types of deep microchannel reactors, T- and To-types, were fabricated using glass substrates, and the reaction interface formed in each of them was observed using a flow visualization technique. The flow maldistribution was not observed even when the flow rate was increased to 100mL\\/min in experiments using the To-type reactor. Analysis on the basis of a computational fluid

Ken-Ichiro Sotowa; Kaname Takagi; Shigeru Sugiyama

2008-01-01

195

A model of silver–iodine reactions in a light water reactor containment sump under severe accident conditions  

Microsoft Academic Search

Metallic silver and iodine form insoluble AgI in the containment sump which has a major impact on iodine volatility and hence on the source term to the environment. Resistance-in-series models are developed and validated against separate-effects tests. The reaction between I2 and Ag is limited by mass transfer in the liquid. The rate does not follow a parabolic law for

Elisabeth Krausmann; Yannis Drossinos

1999-01-01

196

The propensity for deamidation and transamidation of peptides by transglutaminase 2 is dependent on substrate affinity and reaction conditions  

Microsoft Academic Search

Transglutaminase 2 (TG2) catalyzes cross-linking or deamidation of glutamine residues in peptides and proteins. The in vivo deamidation of gliadin peptides plays an important role in the immunopathogenesis of celiac disease (CD). Although deamidation is considered to be a side-reaction occurring in the absence of suitable amines or at a low pH, a recent paper reported the selective deamidation of

Jorunn Stamnaes; Burkhard Fleckenstein; Ludvig M. Sollid

2008-01-01

197

Effect of Calcination Condition on Phase Formation of Zirconium Titanate Powders Synthesized by the Solid-State Reaction  

Microsoft Academic Search

Zirconium titanate (ZrTiO4; ZT) powders have been prepared by using a solid-state reaction combined with a vibro-milling technique. The effects of calcination temperature, dwell time and heating\\/cooling rates on phase formation and morphology of the powders were examined. The calcination temperature and dwell time have been found to show a pronounced effect on the phase formation of the calcined zirconium

Anurak Prasatkhetragarn; Rattikorn Yimnirun; Supon Ananta

2007-01-01

198

Urchinlike nanostructure of single-crystalline nanorods of Sb2S3 formed at mild reaction condition.  

PubMed

Urchinlike nanostructure of well-defined Sb(2)S(3) crystals of 3-4 ?m in length and 30-150 nm in diameter oriented along [001] direction have been produced at a mild reaction temperature of 90 °C from SbCl(3) and S-methyl 3-phenyldithiocarbazate [C(6)H(5)NHNHC(S)SMe] in ethylene glycol medium. During the reaction, the amorphous Sb(2)S(3) spheres of 1.4 ?m in diameter were formed at early reaction stage and then crystalline nanorods were continuously grown at the surface of Sb(2)S(3) spheres while transforming their morphology into urchinlike structure. The urchinlike Sb(2)S(3) was composed of single-crystalline Sb(2)S(3) nanorods, belong to the orthorhombic phase with cell parameters a = 11.307 Å, b = 11.278 Å, c = 3.847 Å and absorbed the light up to 750 nm-wavelength region. The urchinlike Sb(2)S(3) architecture was applied to the photoelectrochemical cell. PMID:22869461

Maiti, Nilkamal; Im, Sang Hyuk; Lee, Yong Hui; Seok, Sang Il

2012-08-21

199

Effects of calcination conditions on phase and morphology evolution of lead zirconate powders synthesized by solid-state reaction  

Microsoft Academic Search

Lead zirconate (PbZrO3) powder has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The effects of calcination temperature,\\u000a dwell time and heating\\/cooling rates on phase formation, morphology, particle size and chemical composition of the powders\\u000a have been investigated by TG-DTA, XRD, SEM and EDX techniques. The results indicated that at calcination temperature lower\\u000a than 800 °C minor phases

W. Chaisan; O. Khamman; R. Yimnirun; S. Ananta

2007-01-01

200

Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritial conditions  

SciTech Connect

A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

Diefenbacher, J.; McKelvy, M.; Chizemeshya, A.V.; Wolf, G.H. (ASU)

2010-07-13

201

The reduction of (ImH)[trans-RuIIICl4(dmso)(Im)] under physiological conditions: preferential reaction of the reduced complex with human serum albumin.  

PubMed

A systematic study of the reduction of (ImH)[trans-RuCl(4)(dmso)(Im)] (NAMI-A; dmso is dimethyl sulfoxide, Im is imidazole), a promising antimetastasing agent, by L-ascorbic acid under physiological conditions is reported. Under blood plasma conditions (pH 7.4, 0.1-0.15 M NaCl , 37 degrees C) the rapid reduction of trans-[Ru(III)Cl(4)(dmso)(Im)](-) results in the formation of trans-[Ru(II)Cl(4)(dmso)(Im)](2-) within seconds, and is followed by successive dissociation of the chloride ligands, whereas neither dmso nor imidazole ligands are released during the reaction. Under our experimental conditions, the formation of the ascorbate dianion is the rate-determining step, and once it has formed it reacts rapidly with NAMI-A. Moreover, the NAMI-A complex is very unstable at physiological pH (7.4); therefore, the hydrolysis of NAMI-A cannot be excluded as a competing reaction. During hydrolysis, aquated derivatives via stepwise dissociation of chloride and dmso ligands are formed, and most of these species have a higher redox potential and are expected to be even more easily reduced by ascorbic acid. Thus, it is very likely that the reduced form of NAMI-A or the reduction products of its hydrolytic derivatives react with albumin. The reaction of reduced NAMI-A with human serum albumin leads to the formation of stable adducts, with a binding efficiency very similar to that of the parent complex, viz., 3.2+/-0.3 and 4.0+/-0.4 mol of Ru(II) and Ru(III) per mole of albumin, respectively, however with a significantly higher reactivity. PMID:18438690

Brindell, Malgorzata; Stawoska, Iwona; Supel, Justyna; Skoczowski, Andrzej; Stochel, Grazyna; van Eldik, Rudi

2008-04-26

202

Modeling Enterococcus densities measured by quantitative polymerase chain reaction and membrane filtration using environmental conditions at four Great Lakes beaches.  

PubMed

Data collected by the US Environmental Protection Agency (EPA) during the summer months of 2003 and 2004 at four US Great Lakes beaches were analyzed using linear regression analysis to identify relationships between meteorological, physical water characteristics, and beach characteristics data and the fecal indicator bacteria, Enterococcus. Water samples were analyzed for Enterococcus densities by quantitative polymerase chain reaction (qPCR) and membrane filtration (MF). This paper investigates the ability of regression models to accurately predict Enterococcus densities above or below a threshold value, using environmental data on a beach-by-beach basis for both methods. The ability to create statistical models for real-time water quality analysis would allow beach managers to make more accurate decisions regarding beach safety. Results from linear regression models indicate that environmental factors explain more of the variability in Enterococcus densities measured by MF than Enterococcus densities measured by qPCR. Results also show that models for both methods did not perform well at predicting occurrences in which water quality levels exceeded a threshold. PMID:19651425

Telech, Justin W; Brenner, Kristen P; Haugland, Rich; Sams, Elizabeth; Dufour, Alfred P; Wymer, Larry; Wade, Timothy J

2009-07-08

203

Synthesis of Triazolo Isoquinolines and Isochromenes from 2-Alkynylbenzaldehyde via Domino Reactions under Transition-Metal-Free Conditions.  

PubMed

We describe two simple straightforward syntheses of triazolo isoquinolines (3) and isochromenes (7) from 2-alkynylbenzaldehydes (1) as a common synthon. The synthetic strategy for 3 involves formation of the (E)-1-(2-nitrovinyl)-2-(alkynyl)benzene species 2 via condensation of synthon 1 with nitromethane followed by a [3 + 2] cycloaddition/extrusion of the nitro group/regioselective 6-endo cyclization domino sequence. In yet another strategy, the synthon 1 was condensed with nitromethane followed by electrophilic iodo cyclization of the resulting 2-nitro-1-(2-(alkynyl)phenyl)ethanol (6) to furnish iodo isochromene derivatives. The salient feature of the above two strategies involves formation of the corresponding heterocycles under metal-free conditions in good yields. PMID:24079602

Arigela, Rajesh K; Samala, Srinivas; Mahar, Rohit; Shukla, Sanjeev K; Kundu, Bijoy

2013-10-10

204

Laboratory Studies of Heterogeneous Reactions of HO2 Radical with Inorganic Aerosol Particles under the Ambient Conditions  

NASA Astrophysics Data System (ADS)

The HO2 uptake coefficient for aerosol particles ((NH4)2SO4 and NaCl) under ambient conditions (760Torr and 296K) was measured using an aerosol flow tube(AFT) coupled with a chemical conversion/laser-induced fluorescence(CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere(~108 molecules cm-3). HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position dependent profiles of LIF intensity were measured as a function of aerosol concentration at various relative humilities(RH). The uptake coefficients of dry aerosol (NaCl and (NH4)2SO4) particles were < 0.05, while the uptake coefficients of wet particles of NaCl and (NH4)2SO4 were estimated to be 0.10 and 0.15, respectively, which suggested that heterogeneous loss was enhanced by the particle containing water. To estimate the contribution of heterogeneous loss of HO2 by aerosol, the diurnal variation of HO2 using a box-model calculation was demonstrated. As a result, the daytime maximum concentrations of HO2 were changed to 95 and 70 %, relative to an absence of heterogeneous loss for marine and urban areas, respectively.

Taketani, F.; Kanaya, Y.; Akimoto, H.

2007-12-01

205

Formation and reactions of singlet oxygen, O[sub 2]([sup 1][Delta]g), under atmospheric conditions  

SciTech Connect

Singlet molecular oxygen, O[sub 2]([sup 1][Delta][sub g]), plays a significant role in photochemical air pollution as a reactive and a deleterious oxidant. Gas phase O[sub 2]([sup 1][Delta][sub g]) formation by homogeneous photosensitization at atmospheric pressure was studied using a variety of compounds found in the atmosphere. The formation of O[sub 2]([sup 1][Delta][sub g]) was demonstrated by observing its 1.27 [mu]m emission using a liquid nitrogen-cooled germanium photodiode detector, and by performing chemical trapping studies with 2,3-dimethyl-2-butene (TME) and quenching studies with triethylamine (TEA). The factors affecting O[sub 2]([sup 1][Delta][sub g]) formation included sensitizer concentration, gas composition (%N[sub 2]/%O[sub 2]), total gas flow rate, irradiation wavelength, and light intensity. The disappearance of seven polycyclic aromatic hydrocarbons (PAHs) adsorbed on zeolite particles was studied under simulated atmospheric conditions. Benzo[ghi]perylene, chrysene, and benzo[e]pyrene were less susceptible to photooxidation than benz[a]anthracene (B[a]A), pyrene, dibenz[ah]anthracene, and benzo[a]pyrene. The disappearance of B[a]A in the presence of light and air involved a self-sensitized photooxidation with the formation of O[sub 2]([sup 1][Delta][sub g]) as a major process. These studies were directed at identifying viable processes for forming atmospheric O[sub 2]([sup 1][Delta][sub g]) and deleterious substances that might be formed when environmental pollutants react with O[sub 2]([sup 1][Delta][sub g]).

deSilva, M.S.W.

1993-01-01

206

Synthesis of Silica Supported AuCu Nanoparticle Catalysts and the Effects of Pretreatment Conditions for the CO Oxidation Reaction  

SciTech Connect

Supported gold nanoparticles have generated an immense interest in the field of catalysis due to their extremely high reactivity and selectivity. Recently, alloy nanoparticles of gold have received a lot of attention due to their enhanced catalytic properties. Here we report the synthesis of silica supported AuCu nanoparticles through the conversion of supported Au nanoparticles in a solution of Cu(C{sub 2}H{sub 3}O{sub 2}){sub 2} at 300 C. The AuCu alloy structure was confirmed through powder XRD (which indicated a weakly ordered alloy phase), XANES, and EXAFS. It was also shown that heating the AuCu/SiO{sub 2} in an O{sub 2} atmosphere segregated the catalyst into a Au-CuO{sub x} heterostructure between 150 C to 240 C. Heating the catalyst in H{sub 2} at 300 C reduced the CuO{sub x} back to Cu{sup 0} to reform the AuCu alloy phase. It was found that the AuCu/SiO{sub 2} catalysts were inactive for CO oxidation. However, various pretreatment conditions were required to form a highly active and stable Au-CuO{sub x}/SiO{sub 2} catalyst to achieve 100% CO conversion below room-temperature. This is explained by the in situ FTIR result, which shows that CO molecules can be chemisorbed and activated only on the Au-CuOx/SiO{sub 2} catalyst but not on the AuCu/SiO{sub 2} catalyst.

J Bauer; D Mullins; M Li; Z Wu; E Payzant; S Overbury; S Dai

2011-12-31

207

Synthesis of silica supported AuCu nanoparticle catalysts and the effects of pretreatment conditions for the CO oxidation reaction  

SciTech Connect

Supported gold nanoparticles have generated an immense interest in the field of catalysis due to their extremely high reactivity and selectivity. Recently, alloy nanoparticles of gold have received a lot of attention due to their enhanced catalytic properties. Here we report the synthesis of silica supported AuCu nanoparticles through the conversion of supported Au nanoparticles in a solution of Cu(C{sub 2}H{sub 3}O{sub 2}){sub 2} at 300 C. The AuCu alloy structure was confirmed through powder XRD (which indicated a weakly ordered alloy phase), XANES, and EXAFS. It was also shown that heating the AuCu/SiO{sub 2} in an O{sub 2} atmosphere segregated the catalyst into a Au-CuO{sub x} heterostructure between 150 C to 240 C. Heating the catalyst in H{sub 2} at 300 C reduced the CuO{sub x} back to Cu{sup 0} to reform the AuCu alloy phase. It was found that the AuCu/SiO{sub 2} catalysts were inactive for CO oxidation. However, various pretreatment conditions were required to form a highly active and stable Au-CuO{sub x}/SiO{sub 2} catalyst to achieve 100% CO conversion below room-temperature. This is explained by the in situ FTIR result, which shows that CO molecules can be chemisorbed and activated only on the Au-CuO{sub x}/SiO{sub 2} catalyst but not on the AuCu/SiO{sub 2} catalyst.

Dai, Sheng [ORNL; Mullins, David R [ORNL; Li, Meijun [ORNL; Payzant, E Andrew [ORNL; Overbury, Steven {Steve} H [ORNL; Wu, Zili [ORNL

2011-01-01

208

Solvent-free reactions of C60 with active methylene compounds, either with or without carbon tetrabromide, in the presence of bases under high-speed vibration milling conditions.  

PubMed

Solvent-free reactions of C(60) with active methylene compounds, either with or without carbon tetrabromide (CBr(4)), in the presence of a base under high-speed vibration milling (HSVM) conditions were investigated. The reaction of C(60) with diethyl bromomalonate was conducted under HSVM conditions in the presence of piperidine, triethylamine or Na(2)CO(3) to afford cyclopropane derivative. In the presence of CBr(4), methanofullerenes, and could be obtained by the direct reaction of C(60) with diethyl malonate, dimethyl malonate, ethyl acetoacetate and ethyl cyanoacetate, respectively, with the aid of 1,8-diazabicyclo[5,4,0]undec-7-ene, piperidine, triethylamine or Na(2)CO(3). More interestingly, 1,4-bisadducts and were produced by the reaction of C(60) with diethyl malonate and dimethyl malonate in the presence of piperidine, triethylamine or Na(2)CO(3) under HSVM conditions. On the other hand, dihydrofuran-fused C(60) derivatives, and were obtained from the reaction of C(60) with ethyl acetoacetate, 2,4-pentanedione and 5,5-dimethyl-1,3-cyclohexanedione with the aid of a base. Under the same conditions, less activated aryl methyl ketones such as 2-acetylpyridine, 2-acetylpyrazine and acetophenone provided monocarbonylated methanofullerene derivatives, and. Except for the Bingel reactions, all other reactions under the HSVM conditions are considered to proceed according to a single-electron-transfer mechanism. PMID:15188036

Zhang, Ting-Hu; Wang, Guan-Wu; Lu, Ping; Li, Yu-Jin; Peng, Ru-Fang; Liu, You-Cheng; Murata, Yasujiro; Komatsu, Koichi

2004-05-20

209

Degradation of ferroelectric SrBi2Ta2O9 materials under reducing conditions and their reaction with Pt electrodes  

NASA Astrophysics Data System (ADS)

The degradation of ferroelectric SrBi2Ta2O9 in an H2-containing reducing atmosphere and its recovery by subsequent annealing in oxygen have been reproduced experimentally by using bulk ceramic samples. SrBi2Ta2O9 decomposes into Bi metal and Sr-Ta oxide(s) in H2 above 300 °C, and the decomposition rate increases as the annealing temperature rises. The recovery of SrBi2Ta2O9 is achieved through oxidation of Bi metal into ?-Bi2O3, followed by a reaction of ?-Bi2O3 and Sr-Ta oxide(s). In the presence of Pt, which is usually used as an electrode, the decomposition of SrBi2Ta2O9 is accelerated. Bi-Pt alloy and Bi-Pt oxide are produced under the reducing and oxidizing conditions, respectively. Our findings have important implications concerning the degradation of SrBi2Ta2O9 capacitors and the reaction between SrBi2Ta2O9 materials and Pt electrodes during thin-film device fabrication.

Shimakawa, Y.; Kubo, Y.

1999-11-01

210

Reaction mechanisms, physical conditions, and mass transfer during hydrothermal alteration of mica and feldspar in granitic rocks from south-central Maine, USA  

Microsoft Academic Search

Samples of granitic rock from south-central Maine contain primary igneous minerals altered by hydrothermal fluids. The reaction mechanisms (by which the over-all mineralogical change during the alteration was accomplished) involve several different mineral-fluid reactions at different reaction sites in the rock. The reactions involve both molecular and charged species in solution. The different reaction sites correspond to alteration of different

J. M. Ferry

1979-01-01

211

Coordination Modes of Multidentate Ligands in fac-[Re(CO)3(polyaminocarboxylate)] Analogues of 99mTc Radiopharmaceuticals. Dependence on Aqueous Solution Reaction Conditions  

PubMed Central

We study Re analogues of 99mTc renal agents to interpret previous results at the 99mTc tracer level. The relative propensities of amine donors vs. carboxylate oxygen donors of four L = polyaminocarboxylate ligands to coordinate in fac-[ReI(CO)3L]n complexes were assessed by examining the reaction of fac-[ReI(CO)3(H2O)3]+ under conditions differing in acidity and temperature. All four L [N,N-bis-(2-aminoethyl)glycine (DTGH), N,N-ethylenediaminediacetic acid, diethylenetriamine-N-malonic acid, and diethylenetriamine-N-acetic acid] can coordinate as tridentate ligands while creating a dangling chain terminated in a carboxyl group. Dangling carboxyl groups facilitate renal clearance in fac-[99mTcI(CO)3L]n agents. Under neutral conditions, the four ligands each gave two fac-[ReI(CO)3L]n products with HPLC traces correlating well with known traces of the fac-[99mTcI(CO)3L]n mixtures. Such mixtures are common in renal agents because the needed dangling carboxyl group can compete for a coordination site. However, the HPLC separations needed to assess the biodistribution of a single tracer are impractical in a clinical setting. One goal in investigating this Re chemistry is to identify conditions for avoiding this problem of mixtures in preparations of fac-[99mTcI(CO)3L]n renal tracers. After separation and isolation of the fac-[ReI(CO)3L]n products, NMR analysis of all products and single crystal X-ray crystallographic analysis of both DTGH products as well as one product each from the other L allowed us to establish coordination mode unambiguously. The product favored in acidic conditions has a dangling amine chain and more bound oxygen. The product favored in basic conditions has a dangling carboxyl chain and more bound nitrogen. At the elevated temperatures used for simulating tracer preparation, equilibration was facile (ca. one hour or less), allowing selective formation of one product by utilizing acidic or basic conditions. The results of this fundamental study offer protocols and guidance useful for the design and preparation of fac-[99mTcI(CO)3L]n agents consisting of a single tracer.

Lipowska, Malgorzata; He, Haiyang; Xu, Xiaolong; Taylor, Andrew T.; Marzilli, Patricia A.; Marzilli, Luigi G.

2010-01-01

212

Effect of Reaction Conditions and 3AB on the Mutation Rate of Poliovirus RNA-Dependent RNA Polymerase in a ?-Complementation Assay  

PubMed Central

The fidelity of poliovirus RNA-dependent RNA polymerase (3Dpol) was determined using a modified ?-complementation assay. Several polymerases have been analyzed by this approach allowing comparisons to be drawn. Various conditions including high and low MgCl2, replacing MgCl2 with MnCl2, skewed nucleotide pools, and the presence of poliovirus protein 3AB were analyzed. The assay included RNA synthesis by 3Dpol on an RNA template that coded for a region of the alpha peptide of ?-galactosidase (LacZ-?). The product of this reaction was used as a template for a second round of 3Dpol synthesis and the resulting RNA was reverse transcribed to DNA by reverse transcriptase. The DNA was amplified by PCR and inserted into a vector used to transform E. coli. The bacteria were screened for ?-galactosidase activity by blue-white phenotype analysis with white or faint blue colonies scored as errors made during synthesis on lacZ-?. Although 3AB strongly stimulated 3Dpol synthesis as expected, no change in fidelity was detected. Changes in MgCl2 also showed little effect. Mutation rates of ~9 × 10?5 (~1 error per 11,000 incorporations) were estimated for these conditions. In contrast, MnCl2 or skewed nucleotide pools were highly mutagenic resulting in lowered fidelity.

DeStefano, Jeffrey J.

2009-01-01

213

Influence of deformation mechanisms and metamorphic reactions during strain localization in the continental crust under lower amphibolite facies conditions: an example from the Gotthard massif  

NASA Astrophysics Data System (ADS)

Ductile shear zones are the result of the process of strain localization in the continental crust. Depending on the metamorphic conditions during deformation, strain localization is coeval with dramatic changes in microstructures, mineralogy and mass transfers, due to the interactions with externally-derived fluid. Therefore, to accurately model the mechanisms of strain localization, it is critical to identify deformation mechanisms related to the recrystallization of the quartzo-feldspathic assemblages, and to better constrain the role of metamorphic reactions during deformation. The aim of this contribution is to characterize the mineralogical, geochemical, textural and microstructural evolution of a high strain zone from the Fibbia granite, which is located in the Gotthard Massif (External Crystalline Massif, Central Alps). This variscan massif has been affected by Alpine Tertiary metamorphism and deformation under lower amphibolite facies conditions. The strain gradient is approximately a meter width. The rock texture evolves from a weakly deformed granite, toward an orthogneiss, a mylonite and a ~10 cm-wide ultramylonite. The mineralogical assemblage changes from a metastable magmatic assemblage consisting of Qtz + Kspar + Pla + Bio ± Pheng ± Grt ± Ep to a fine banded texture consisting of a quartzo-feldspathic matrix, with metamorphic phyllosilicates (biotite and phengite) and garnet in the ultramylonite. Cathodoluminescence (CL) imaging has been used to quantify the modal proportions of phases in the quartzo-feldspathic matrix in this strain gradient. More specifically, in the orthogneiss and the mylonite, CL imaging reveals a subtle layering consisting of alternating bands of quartz-rich ribbons, K-feldspars and coupled quartz- and plagioclase-rich ribbons. The texture in the ultramylonite is more homogeneous with isolated single quartz and K-feldspar grains. CL imaging has also revealed chemical zoning, as "core and mantle" texture in plagioclases. With increasing strain, modal abundance of K-feldspars decreases from 28% to 16%, whereas both micas increase from 5% to 21%. Similarly, albite evolves from 25% to 8%, whereas oligoclase evolves from 5% to 25%. Deformation mechanisms responsible for these microstructures have been studied by combining a quantitative textural analysis (CSD, SPO, grain boundary frequency and orientation - PolyLX MatlabTM toolbox; Lexa, 2005) and a crystallographic study by EBSD. Deformation mechanisms of quartz, K-feldspar and plagioclase are a combination of SGR and GBM in the orthogneiss and in the mylonite, whereas GBS is active in the ultramylonite. CPO characteristic features are still a matter of debate. Because mass transfers occurred in this shear zone (gains of MnO, CaO, Fe2O3, P2O5 and TiO2) without volume change, thermodynamic modeling of phase relations in such open system must consider the variations of effective bulk rock composition during deformation. In this example, phase relations have been mapped using Perple_X'07 (Connolly, 2005) as a function of P, T, M(H2O) and X(bulk composition), in order to highlight the influence of subtle mass transfers on the syn-deformation stability of mineral assemblages at 500°C and 7.2 kbars. A particular attention has been paid to the role of water content on the stable assemblage and on compositions of metamorphic phyllosilicates. Water under-saturated conditions induce the stability of aluminosilicates, and should increase the Xmg in biotite and decrease the amount of tschermak substitution in phengite. P- and T-M(H20) diagram suggest that the Alpine ductile shear zones occurred under water-saturated conditions. This study reveals that strain localization is related to the metamorphic reactions (breakdowns of K-feldspars to phengites and magmatic plagioclase to albite and oligoclase), which induce a strong decrease in grain size reduction and a switch in deformation mechanism from SGR and GBM to GBS in the ultramylonite. The good agreement between phase diagram section predictions and the observations suggest that high

Oliot, E.; Goncalves, P.; Schulmann, K.; Marquer, D.

2009-04-01

214

Research on active particle distribution in the crop stalk plasma reaction under the condition of streaming and discharging micro electric current  

NASA Astrophysics Data System (ADS)

In order to further study sugar-production mechanism in the crop stalk plasma reaction under the condition of streaming and discharging micro electric current with N2 and H2O as the electro-discharging gases, the active particles distribution is researched and analyzed. Through the study of methods and theories of statistical mechanics and statistica thermodynamics, the ionization process of the mixed discharging gas and the distribution features of the active particles changing with temperature in the plasma reactor are discussed. The constant pressure form of Saha equation that applies to this experiment is deduced. And the active particles generated in the dense ionization discharging process and the crop stalk conversion processes are also analyzed. The experimental results show that N2 and H2 can ionize synchronously. And it is found that during the crop stalk conversion process, while one gas is ionised, the other gas will not take the energy away, which will not affect the conversion. Among the discharging gases consisting of water vapour and nitrogen, the main components are ions of H2O+, H+, N2+ and molecules of N2, H2O, which are all beneficial to a high sugar yield.

Song, C. L.; Pi, S. G.; Liu, X. Y.; Xu, H. B.

2013-03-01

215

Growth and transcriptional response of Salmonella Typhimurium LT2 to glucose–lysine-based Maillard reaction products generated under low water activity conditions  

Microsoft Academic Search

This study reports the growth and transcriptional responses of Salmonella Typhimurium LT2 to Maillard reaction products (MRPs) generated in a simulation of the reaction during food processing and storage. Maillard reactions between N-?-acetyl-lysine and glucose were stopped at 4, 23, or 143h to generate sub-samples with prevailing Amadori compound, advanced glycation end products (AGEs), or melanoidins, respectively. When used as

Vesela I. Chalova; Oswaldo Hernández-Hernández; Arunachalam Muthaiyan; Sujata A. Sirsat; Senthil Natesan; María Luz Sanz; F. Javier Moreno; Corliss A. O'Bryan; Philip G. Crandall; Steven C. Ricke

216

Anti-Inflammatory Drugs Block Cytokine mRNA Accumulation in the Skin and Improve the Clinical Condition of Reactional Leprosy Patients  

Microsoft Academic Search

The aim of this study was to investigate in what ways in vivo anti-inflammatory treatment affects cytokine mRNA expression in situ in both erythema nodosum leprosum and reversal reaction patients. Serial biopsies were collected from the patients undergoing leprosy reactions before and during pentoxifylline (n = 7) or thalidomide (n = 3) treatment for erythema nodosum leprosum and prednisone (n

Milton O. Moraes; Euzenir N. Sarno; Rosane M. B. Teles; Alexandre S. Almeida; Bruno C. C. Saraiva; Jose A. C. Nery; Elizabeth P. Sampaio

2000-01-01

217

Three-component green reaction of arylaldehydes, 6-amino-1,3- dimethyluracil and active methylene compounds catalyzed by Zr(HSO4)4 under solvent-free conditions.  

PubMed

A convenient one-pot, three-component reaction of aromatic aldehydes, 6-amino-1,3-dimethyluracil and active methylene compounds in the presence of Zr(HSO4)4 as a heterogeneous catalyst, under solvent-free conditions brings a very simple and highly efficient method for the preparation of pyrimido[4,5-b]quinolines, pyrimido[5',4':5,6]pyrido[2,3- d]pyrimidines, indeno[2',1':5,6]pyrido[2,3-d]pyrimidines and a new class of pyrimidinedione derivatives in excellent yields. This approach is general and provides several advantages such as simple reaction set-up, very mild reaction conditions, high yields, recyclability of the catalyst and environmentally friendly benign. PMID:23092170

Abdolmohammadi, Shahrzad; Balalaie, Saeed; Barari, Mohammad; Rominger, Frank

2013-02-01

218

Piper-betle-shaped nano-S-catalyzed synthesis of 1-amidoalkyl-2-naphthols under solvent-free reaction condition: a greener "nanoparticle-catalyzed organic synthesis enhancement" approach.  

PubMed

Nano-S prepared by an annealing process showed excellent catalytic activity for the synthesis of 1-amidoalkyl-2-naphthols under solvent-free reaction condition at 50 °C. The catalyst could be reused up to the fifth cycle without loss in its action. The green-ness of the present protocol was also measured using green metrics drawing its superiority. PMID:23472638

Das, Vijay K; Borah, Madhurjya; Thakur, Ashim J

2013-03-19

219

Production of bio-oil from rice straw and bamboo sawdust under various reaction conditions in a fast pyrolysis plant equipped with a fluidized bed and a char separation system  

Microsoft Academic Search

Rice straw and bamboo sawdust were pyrolyzed in a bubbling fluidized bed equipped with a char separation system. The effects of the reaction conditions on the production of bio-oil, and the efficiency of a char removal system, were investigated. In each experiment, the mass balance was established and the products’ chemical and physical characteristics were examined. To elucidate how the

Su-Hwa Jung; Bo-Sung Kang; Joo-Sik Kim

2008-01-01

220

Bench- and Pilot-Scale Studies of Reaction and Regeneration of Ni-Mg-K/Al2O3 for Catalytic Conditioning of Biomass-Derived Syngas  

SciTech Connect

The National Renewable Energy Laboratory (NREL) is collaborating with both industrial and academic partners to develop technologies to help enable commercialization of biofuels produced from lignocellulosic biomass feedstocks. The focus of this paper is to report how various operating processes, utilized in-house and by collaborators, influence the catalytic activity during conditioning of biomass-derived syngas. Efficient cleaning and conditioning of biomass-derived syngas for use in fuel synthesis continues to be a significant technical barrier to commercialization. Multifunctional, fluidizable catalysts are being developed to reform undesired tars and light hydrocarbons, especially methane, to additional syngas, which can improve utilization of biomass carbon. This approach also eliminates both the need for downstream methane reforming and the production of an aqueous waste stream from tar scrubbing. This work was conducted with NiMgK/Al{sub 2}O{sub 3} catalysts. These catalysts were assessed for methane reforming performance in (i) fixed-bed, bench-scale tests with model syngas simulating that produced by oak gasification, and in pilot-scale, (ii) fluidized tests with actual oak-derived syngas, and (iii) recirculating/regenerating tests using model syngas. Bench-scale tests showed that the catalyst could be completely regenerated over several reforming reaction cycles. Pilot-scale tests using raw syngas showed that the catalyst lost activity from cycle to cycle when it was regenerated, though it was shown that bench-scale regeneration by steam oxidation and H{sub 2} reduction did not cause this deactivation. Characterization by TPR indicates that the loss of a low temperature nickel oxide reduction feature is related to the catalyst deactivation, which is ascribed to nickel being incorporated into a spinel nickel aluminate that is not reduced with the given activation protocol. Results for 100 h time-on-stream using a recirculating/regenerating reactor suggest that this type of process could be employed to keep a high level of steady-state reforming activity, without permanent deactivation of the catalyst. Additionally, the differences in catalyst performance using a simulated and real, biomass-derived syngas stream indicate that there are components present in the real stream that are not adequately modeled in the syngas stream. Heavy tars and polycyclic aromatics are known to be present in real syngas, and the use of benzene and naphthalene as surrogates may be insufficient. In addition, some inorganics found in biomass, which become concentrated in the ash following biomass gasification, may be transported to the reforming reactor where they can interact with catalysts. Therefore, in order to gain more representative results for how a catalyst would perform on an industrially-relevant scale, with real contaminants, appropriate small-scale biomass solids feeders or slip-streams of real process gas should be employed.

Magrini-Bair, K. A.; Jablonski, W. S.; Parent, Y. O.; Yung, M. M.

2012-05-01

221

Design, development, and demonstration of a fully LabVIEW controlled in situ electrochemical Fourier transform infrared setup combined with a wall-jet electrode to investigate the electrochemical interface of nanoparticulate electrocatalysts under reaction conditions.  

PubMed

We present a detailed description of the construction of an in situ electrochemical ATR-FTIR setup combined with a wall-jet electrode to investigate the electrocatalytic properties of nanoparticulate catalysts in situ under controlled mass transport conditions. The presented setup allows the electrochemical interface to be probed in combination with the simultaneous determination of reaction rates. At the same time, the high level of automation allows it to be used as a standard tool in electrocatalysis research. The performance of the setup was demonstrated by probing the oxygen reduction reaction on a platinum black catalyst in sulfuric electrolyte. PMID:23902087

Nesselberger, Markus; Ashton, Sean J; Wiberg, Gustav K H; Arenz, Matthias

2013-07-01

222

Pt\\/K–?Al 2O 3 solid electrolyte cell as a “smart electrochemical catalyst” for the effective removal of NO x under wet reaction conditions  

Microsoft Academic Search

This study has shown that the phenomenon of electrochemical promotion can be used to activate a metal catalyst for the selective catalytic reduction of nitrogen oxides (NOx) in the presence of water in the feed. The application of different potentials optimized the catalytic performance of the Pt catalyst-working electrode at each reaction temperature range. In addition, the measurement of the

Antonio de Lucas-Consuegra; Ángel Caravaca; Fernando Dorado; José L. Valverde

2009-01-01

223

Simple and Efficient Method for N-Boc Protection of Amines Using PEG400 as a Reaction Medium Under Mild Conditions  

Microsoft Academic Search

Simple and efficient method for N-Boc protection of amines using PEG-400 as an eco-friendly reaction medium at room temperature is described. Various aromatic, heteroaromatic, and aliphatic amines were converted to the corresponding N-tert-butyl-carbamates in good to excellent yields in short times.

Hongyao Zeng; Yongjia Li; Huawu Shao

2011-01-01

224

Untersuchung von OH-Reaktionen Mittels Excimerlaserphotolyse/Farbstofflaserfluoreszenz Unter Troposphaerischen Bedingungen (Investigation of OH Reaction Products. Excimer Laser Photolysis/Slab Laser Fluorescence under Tropospheric Conditions).  

National Technical Information Service (NTIS)

Absolute rate constants of OH reactions were measured up to total pressures of 1 bar and in the presence of strongly quenching gases. In the presence of O2, the effective disappearance rate of OH is diminished at all total pressures by a factor of 4 due t...

E. H. Fink V. Schmidt

1985-01-01

225

Dynamics of Intracellular Dopamine Contents in the Rat Brain during the Formation of Conditioned Contextual Fear and Extinction of an Acoustic Startle Reaction  

Microsoft Academic Search

Extracellular dopamine contents in the caudate nucleus, nucleus accumbens, and prefrontal cortex of the rat brain were measured during two sessions of extinction of an acoustic startle reaction – each consisting of ten sound stimuli, the two sessions separated by 24 h – with simultaneous recording of freezing behavior. The results demonstrated a decrease in extracellular dopamine levels in the

Z. I. Storozheva; I. I. Afanas'ev; A. T. Proshin; V. S. Kudrin

2003-01-01

226

Influence of the Reaction Conditions and Catalytic Properties on the Liquid-Phase Hydrodechlorination of Chlorobenzene over Palladium-Supported Catalysts: Activity and Deactivation  

Microsoft Academic Search

The liquid-phase hydrodechlorination of chlorobenzene with molecular hydrogen was studied over palladium-supported catalysts. The reaction takes place at a gradually decreasing rate through progressive poisoning of the active phase by chloride ions. It is found that the correct choice of the metallic precursor (free of chloride ions) is crucial for the optimum performance of the final solid obtained. In addition,

M. A. Aramend??a; V. Boráu; I. M. Garc??a; C. Jiménez; F. Lafont; A. Marinas; J. M. Marinas; F. J. Urbano

1999-01-01

227

CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones with a variety of aromatic and heteroaromatic hydrazines are remarkable accelerated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent thus providing an environmentally frie...

228

Aldehyde-alcohol reactions catalyzed under mild conditions by chromium(III) terephthalate metal organic framework (MIL-101) and phosphotungstic acid composites.  

PubMed

Porous materials based on chromium(III) terephthalate metal organic frameworks (MIL-101) and their composites with phosphotungstic acid (PTA) were studied as heterogeneous acid catalysts in aldehyde-alcohol reactions exemplified by acetaldehyde-phenol (A-P) condensation and dimethylacetal formation from benzaldehyde and methanol (B-M reaction). The MIL-101 was synthesized solvothermically in water, and the MIL101/PTA composite materials were obtained by either impregnation of the already prepared MIL-101 porous matrix with phosphotungstic acid solution or by solvothermic treatment of aqueous mixtures of Cr(NO(3))(3), and terephthalic and phosphotungstic acids. The MIL101/PTA materials appeared to be effective catalysts for both A-P and B-M reactions occurring at room temperature, with half-lives ranging from 0.5 h (A-P) to 1.5-2 h (B-M) and turnover numbers over 600 for A-P and over 2900 for the B-M reaction, respectively. A synergistic effect of the strong acidic moieties (PTA) addition to mildly acidic Brønsted and Lewis acid cites of the MIL-101 was observed with the MIL101/PTA composites. The ability of the PTA and MIL101/PTA materials to strongly absorb and condense acetaldehyde vapors was discovered, with the MIL101/PTA absorbing over 10-fold its dry weight of acetaldehyde condensate at room temperature. The acetaldehyde was converted rapidly to crotonaldehyde and higher-molecular-weight compounds while in contact with MIL-101 and MIL101/PTA materials. The stability of the MIL-101 and MIL101/PTA catalysts was assessed within four cycles of the 1-day alcohol-aldehyde reactions in terms of the overall catalyst recovery, PTA or Cr content, and reaction rate constants in each cycle. The loss of the catalyst over 4 cycles was approximately 10 wt % for all tested catalysts due to the incomplete recovery and minute dissolution of the components. The reaction rates in all cycles remained unchanged and the catalyst losses stopped after the third cycle. The developed MIL101/PTA composites appear to be feasible for industrial catalytic applications. PMID:22091761

Bromberg, Lev; Hatton, T Alan

2011-12-05

229

Measurement of mutation and repair in mammalian cells/action of specific mutagens and antimutagens/genome exposure reaction in cancer and other disease conditions. Final subcontract report, April 1, 1996- March 31, 1996  

SciTech Connect

This is the final report for the project dealing with the the measurement of mutation and repair in mammalian cells, action of specific mutagens and antimutagens, and genome exposure reaction in cancer and other disease conditions. The overall objectives of this research are threefold: to develop and improve methodology for measurement of mutation and repair in mammalian cells and to apply it to measurement of the effectiveness of mutagens, antimutagens, and other molecules to as to achieve greater power in prevention of cancer and genetic disease; to analyze theoretically and experimentally the action of specific mutagens and antimutagens; and to investigate the role of genome exposure reaction in cancer and other disease conditions to secure improve preventive and treatment modalities.

Puck, T.T. [Eleanor Roosevelt Institute for Cancer Research, Inc., Denver, CO (United States)

1996-09-01

230

Studies in Reaction to Disability. XII: Structure of Attitudes toward the Physically Disabled; Disability Factor Scales--Amputation, Blindness, Cosmetic Conditions.  

ERIC Educational Resources Information Center

|To describe and to develop instruments to measure attitudes toward amputees, the blind, and those with cosmetic conditions, three groups of subjects responded to one of three large pools of items tapping attitudes toward the three disability conditions. Three new groups of about 500 subjects of diverse demographic characteristics were given one…

Siller, Jerome; And Others

231

Studies in Reaction to Disability. XII: Structure of Attitudes toward the Physically Disabled; Disability Factor Scales--Amputation, Blindness, Cosmetic Conditions.  

ERIC Educational Resources Information Center

To describe and to develop instruments to measure attitudes toward amputees, the blind, and those with cosmetic conditions, three groups of subjects responded to one of three large pools of items tapping attitudes toward the three disability conditions. Three new groups of about 500 subjects of diverse demographic characteristics were given one of…

Siller, Jerome; And Others

232

A portable multi-flash kinetic fluorimeter for measurement of donor and acceptor reactions of Photosystem 2 in leaves of intact plants under field conditions  

Microsoft Academic Search

A newly-developed field-portable multi-flash kinetic fluorimeter for measuring the kinetics of the microsecond to millisecond reactions of the oxidizing and reducing sides of photosystem 2 in leaves of intact plants is described and demonstrated. The instrumental technique is a refinement of that employed in the ‘double-flash’ kinetic fluorimeter (Joliot 1974 Biochim Biophys Acta 357: 439–448) where a low-intensity short-duration light

David M. Kramer; Howard R. Robinson; Antony R. Crofts

1990-01-01

233

Kinetics of the reactions of hydroxyl radicals with alkyl nitrates and with some oxygen-containing organic compounds studied under simulated atmospheric conditions  

Microsoft Academic Search

Rate constants have been measured for the reactions of hydroxyl radicals with alkyl nitrates and with some oxygen-containing organic compounds by a competitive technique. Mixtures of synthetic air containing a few ppm of nitrous acid, ethylene and the organic substrate were photolysed in a Teflon bag smog chamber. Based on the value kHO+C2H4}=8.1×10-12 cm3 molecule-1 s-1 the following rate constants

J. Alistair Kerr; David W. Stocker

1986-01-01

234

Influence of the reaction conditions and catalytic properties on the liquid-phase hydrodebromination of bromobenzene over palladium supported catalysts: activity and deactivation  

Microsoft Academic Search

The liquid-phase hydrodebromination of bromobenzene with molecular hydrogen over palladium supported catalysts was studied. The reaction was found to be structure-sensitive as regards both the initial activity and the final conversion (deactivation). The influence of the palladium content and the catalytic support effect on the initial activity were negligible in catalysts of similar metal dispersion. The supports tested, viz. SiO2\\/AlPO4,

M. A. Aramend??a; V. Boráu; I. M. Garc??a; C. Jiménez; J. M. Marinas; F. J. Urbano

1999-01-01

235

Effect of calcination condition on phase formation and particle size of lead titanate powders synthesized by the solid-state reaction  

Microsoft Academic Search

A perovskite-like phase of lead titanate, PbTiO3, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. Phase formation of the calcined powders has been investigated as a function of calcination temperature, soaking time and heating\\/cooling rates by DTA and X-ray diffraction (XRD) techniques. Moreover, morphology and particle size evolution have been determined via SEM technique, respectively. It

A. Udomporn; S. Ananta

2004-01-01

236

Development of a detailed high-pressure reaction model for methane\\/methanol mixtures under pyrolytic and oxidative conditions and comparison with experimental data  

Microsoft Academic Search

Experimental data of methanol in a flow reactor are obtained under pyrolysis, fuel lean condition (?=0.75), and stoichiometric condition (?=1.0), and as mixtures with methane; both temperature and pressure are varied. Methanol pyrolysis is studied at 1073 K over a pressure range of 1–10 atm. Methanol oxidation experiments are conducted over a temperature range of 873–1073 K and a pressure

Wen-Chiun Ing; Chad Y. Sheng; Joseph W. Bozzelli

2003-01-01

237

Reactions & Rates  

NSDL National Science Digital Library

Explore what makes a reaction happen by colliding atoms and molecules. Design experiments with different reactions, concentrations, and temperatures. When are reactions reversible? What affects the rate of a reaction?

Simulations, Phet I.; Koch, Linda; Lemaster, Ron; Loeblein, Trish; Perkins, Kathy; Gratny, Mindy

2006-12-01

238

Drug Reactions  

MedlinePLUS

... version Drug Reactions Drug Reactions What is an adverse drug reaction? Medicines can treat or prevent illness ... medicines can cause problems. These problems are called adverse drug reactions. You should know what to do ...

239

Optimization of Reaction Conditions towards Multiple Types of Framework Isomers and Periodic-Increased Porosity: Luminescence Properties and Selective CO2 Adsorption over N2.  

PubMed

Three new metal-organic frameworks (MOFs) were prepared by solvo(hydro)thermolysis and further characterized as framework isomers. The structural transformation from non-porous to porous MOFs and the purity of these products can be modulated by controlling the reaction temperature. The periodic-increased porosity observed was further confirmed by CO2 adsorption isotherms. Owing to the presence of acylamide groups in the pore walls and the flexible nature of the skeleton of these MOFs, highly selective CO2 adsorption over N2 was observed, as well as structure-dependent periodic varieties in luminescence properties. PMID:24038959

Wu, Xiao-Liu; Luo, Feng; Sun, Gong-Ming; Zheng, An-Min; Zhang, Jian; Luo, Ming-Biao; Xu, Wen-Yuan; Zhu, Yan; Zhang, Xiao-Min; Huang, Shu-Yun

2013-09-03

240

Development of a real-time polymerase chain reaction assay for the simultaneous detection of Mycoplasma gallisepticum and Mycoplasma synoviae under industry conditions.  

PubMed

In this research we developed a real-time SYBR green assay to detect both Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) in a single reaction. A total of 30,000 samples from broiler breeder flocks were screened using traditional serology (plate agglutination, enzyme-linked immunosorbent assay, hemagglutination inhibition) and polymerase chain reaction (PCR; traditional and real-time). It was determined that the real-time SYBR green PCR assay developed in this research was more rapid than all three methods tested and more sensitive and specific than culturing or serology. The SYBR green assay was optimized and could detect as few as 30 template copies of DNA per sample. In addition, the SYBR green assay was less expensive than traditional culturing and serology. MG and MS are infectious bacteria that can rapidly spread and infect commercial chicken flocks. These diseases can cause a significant loss to the poultry industry and especially to broiler breeders because infected flocks are destroyed under the National Poultry Improvement Plan MG and MS clean programs. The real-time SYBR green assay developed in this research has the potential to reduce the time it takes to reach a correct diagnosis and to arrest outbreaks of MG and MS. PMID:19432006

Jarquin, Robin; Schultz, Joseph; Hanning, Irene; Ricke, Steven C

2009-03-01

241

Synthesis of new pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) cyanosilylated derivatives using sulphated zirconia and hydrotalcite as catalysts in microwave-assisted reactions under solvent free conditions.  

PubMed

A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered. PMID:21818059

Guerra-Navarro, Nahí Adriana; Palacios-Grijalva, Laura Nadxieli; Angeles-Beltrán, Deyanira; Negrón-Silva, Guillermo E; Lomas-Romero, Leticia; González-Zamora, Eduardo; Gaviño-Ramírez, Rubén; Navarrete-Bolaños, Juan

2011-08-04

242

In vitro studies on the influence of precultural conditioning method on osteoblast reactions of a new type of injectable calcium cement material.  

PubMed

A new injectable dicalcium phosphate dehydrate (DCPD)-based cement material "PD" VitalOs Cement was studied to elucidate the process of equilibrium occurring in the early stage of implantation. The present study investigated the pH variations of the cement sample-immersing culture medium at determined intervals, time-dependent calcium/phosphate release, cell proliferation, and vitality in the cells-cement coculture milieu, after different preculture conditionings of the samples. Measurement of pH variation showed that without renewing the medium, pH value of sample lixiviate medium first dropped and, after 70 h, gradually balanced. When medium was renewed each day, pH value of lixiviate medium first descended and, after 24 h, gradually returned to pH 7.2. The cell viability revealed an excellent cytocompatibility of the cement. Both cell proliferation and vitality test showed that the preculture conditioning treatment is important at least for good performance of osteoblasts growing on the surface of calcium phosphate hydraulic cement (CPHC) samples in vitro. The results of calcium and phosphate assays clearly showed that this cement material can continuously dissolve to release calcium and phosphate in the liquid cell culture environment. The decrease of proliferation in some experimental groups with short conditioning is due to an excess of acid, which still can have some influence on cell growth after 24 h, since the biological milieu is not continuously renewed as in in vivo conditions. PMID:16245289

Chai, Feng; Blanchemain, Nicolas; Lefèvre, Annie; Hildebrand, Hartmut F

2006-04-01

243

Reaction of common bean cultivars to the Asian soybean rust pathogen, Phakopsora pachyrhizi, under field conditions in South Africa and Brazil.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Phakopsora pachyrhizi, the Asian soybean rust (ASR) pathogen, infects soybeans (Glycine max) and some 95 other leguminous species, including dry and snap beans (Phaseolus vulgaris). This pathogen has been reported infecting dry beans under field conditions in South Africa and the United States in 20...

244

Rhodium colloidal suspension deposition on porous silica particles by dry impregnation: Study of the influence of the reaction conditions on nanoparticles location and dispersion and catalytic reactivity  

Microsoft Academic Search

Rhodium composite nanomaterials were synthesized by an innovating process called dry impregnation in a fluidized bed. It consists in spraying an aqueous colloidal suspension of rhodium on silica porous particles. The use of this precursor solution containing preformed nanoparticles avoids calcination\\/activation step.Different composite nanomaterials were prepared displaying various metal loadings. The operating conditions were tuned to modify ?s, the solvent

L. Barthe; M. Hemati; K. Philippot; B. Chaudret; A. Denicourt-nowicki; A. Roucoux

2009-01-01

245

REACTIONS OF MONKEYS TO EXPERIMENTALLY INDUCED INFLUENZA VIRUS A INFECTION : AN ANALYSIS OF THE RELATIVE ROLES OF HUMORAL AND CELLULAR IMMUNITY UNDER CONDITIONS OF OPTIMAL OR DEFICIENT NUTRITION.  

PubMed

1. Macaca mulatta monkeys on a normal diet have proved resistant to intranasal but not to intratracheal inoculation of influenza virus. 2. Neutralizing antibodies appeared 8 to 10 days after inoculation with either living or heat-inactivated virus. The antibodies were noted to be still present as long as 9 months after infection with living virus. 3. A specific granulopenic leucopenia characteristically followed primary influenza virus inoculation, regardless of altered conditions of diet, exposure, and route of inoculation, but it was not observed in monkeys previously infected with the same virus, all of which invariably survived. 4. Nutritional deficiency and exposure to cold increased the susceptibility of monkeys on intranasal instillation of the virus; the leucopenia was profound and fatalities frequently occurred even though neutralizing humoral antibodies developed as promptly and in relatively the same titer as under optimum nutritional conditions. PMID:19871557

Saslaw, S; Wilson, H E; Doan, C A; Woolpert, O C; Schwab, J L

1946-07-31

246

Mixed sites and promoter segregation: A DFT study of the manifestation of Le Chatelier's principle for the Co(Ni)MoS active phase in reaction conditions  

Microsoft Academic Search

The phase diagrams and equilibrium 2D-morphologies of Co(Ni)MoS nano-crystallites with various promoter contents are determined by periodic DFT calculations coupled to a thermodynamic model. The edge energies of the crystallite depend on two key parameters: the chemical potential of sulfur (??S), representing the sulfo-reductive conditions of the gas phase, and the number and distribution of promoter atoms at the edges.High

E. Krebs; B. Silvi; P. Raybaud

2008-01-01

247

Simulation of blast-furnace raceway conditions in a wire-mesh reactor: interference by the reactions of molybdenum mesh and initial results  

Microsoft Academic Search

A novel trapped air injection system has been built for a wire-mesh reactor to enable tests with short exposure times to air that are intended to simulate typical residence times in blast-furnace raceways. Initial tests have shown that the molybdenum wire-mesh sample-holder reacts with Oâ under conditions intended for this work. By varying the proportions of solid MoOâ (weight gain),

Long Wu; N. Paterson; D. R. Dugwell; R. Kandiyoti

2006-01-01

248

Trajectory dynamics study of collision-induced dissociation of the Ar + CH4 reaction at hyperthermal conditions: vibrational excitation and isotope substitution.  

PubMed

We investigate the role of vibrational energy excitation of methane and two deuterated species (CD(4) and CH(2)D(2)) in the collision-induced dissociation (CID) process with argon at hyperthermal energies. The quasi-classical trajectory method has been applied, and the reactive Ar + CH(4) system has been modeled by using a modified version of the CH(4) potential energy surface of Duchovic et al. (J. Phys. Chem. 1984, 88, 1339) and the Ar-CH(4) intermolecular potential function obtained by Troya (J. Phys. Chem. A 2005, 109, 5814). This study clearly shows that CID is markedly enhanced with vibrational excitation and, to a lesser degree, with collision energy. In general, CID increases by exciting stretch vibrational modes of the reactant molecule. For the direct dissociation of CH(4), however, the CID cross sections appear to be essentially independent of which vibrational mode is initially excited. In all situations studied, the CID cross sections are always greater for the Ar + CD(4) reaction than for the Ar + CH(4) one, the Ar + CH(2)D(2) being an intermediate situation. A detailed analysis of the energy transfer processes, including their relation with CID, is also presented. PMID:16737261

Marques, J M C; Martínez-Núñez, E; Vazquez, S A

2006-06-01

249

Role of anions and reaction conditions in the preparation of uranium(VI), neptunium(VI), and plutonium(VI) borates.  

PubMed

U(VI), Np(VI), and Pu(VI) borates with the formula AnO(2)[B(8)O(11)(OH)(4)] (An = U, Np, Pu) have been prepared via the reactions of U(VI) nitrate, Np(VI) perchlorate, or Pu(IV) or Pu(VI) nitrate with molten boric acid. These compounds are all isotypic and consist of a linear actinyl(VI) cation, AnO(2)(2+), surrounded by BO(3) triangles and BO(4) tetrahedra to create an AnO(8) hexagonal bipyramidal environment. The actinyl bond lengths are consistent with actinide contraction across this series. The borate anions bridge between actinyl units to create sheets. Additional BO(3) triangles and BO(4) tetrahedra extend from the polyborate layers and connect these sheets together to form a three-dimensional chiral framework structure. UV-vis-NIR absorption and fluorescence spectroscopy confirms the hexavalent oxidation state in all three compounds. Bond-valence parameters are developed for Np(VI). PMID:21291194

Wang, Shuao; Villa, Eric M; Diwu, Juan; Alekseev, Evgeny V; Depmeier, Wulf; Albrecht-Schmitt, Thomas E

2011-02-03

250

Access to 2'-substituted binaphthyl monoalcohols via complementary nickel-catalyzed Kumada coupling reactions under mild conditions: key role of a P,O ligand.  

PubMed

Two complementary Kumada coupling methods for the conversion of monotriflated 1,1'-binaphthalene-2,2'-diol (BINOL) into 2'-substituted binaphthyl monoalcohols under mild conditions are reported. A protocol using NiCl2(dppe), in combination with an improved preparation of the monotriflate, is effective for 1,1'-binaphthalene-2-ols containing unsubstituted or electron-poor aryl or benzyl 2'-substituents. An alternative procedure, using a potentially hemilabile-bidentate phosphinan-4-ol ligand, is superior for products containing neopentyl or electron-rich aryl 2'-substituents. The obtained binaphthyl alcohols represent potentially useful synthons for chiral ligands and auxiliaries. PMID:23672533

Handa, Sachin; Mathota Arachchige, Yohan L N; Slaughter, LeGrande M

2013-05-23

251

Application of empirical design methodologies to the study of the influence of reaction conditions and N-alpha-protecting group structure on the enzymatic X-Phe-Leu-NH(2) dipeptide synthesis in buffer/dimethylformamide solvents systems.  

PubMed

The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the alpha-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH(2) was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-alpha protection choice. Boc and Z were the most reactive N-alpha groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement. PMID:18600980

Calvet, S; Clapés, P; Vigo, J P; Xaus, N; Jorba, X; Mas, R M; Torres, J L; Valencia, G; Serralheiro, M L; Cabral, J M; Empis, J M

1992-03-01

252

Measurement of electroweak effects and topological branching conditions in the reaction e(+)e(-) yields tau(+)tau(-) in the storage ring PETRA  

NASA Astrophysics Data System (ADS)

The detection of the electroweak interference in the production of tau-lepton-pairs at the highest obtainable energies in e(+)e(-) storage rings was investigated. Using the detector CELLO and Monte Carlo simulations, total cross section and charge asymmetry, for the production of tau-pairs are obtained. The measured cross sections are in agreement with theoretical expectations, from quantum electrodynamics and the Glashow-Salam-Weinberg (GSW) theory. The observed electroweak effects, leading to a charge asymmetry in the differential cross sections concord with GSW-expectations, and with the axial vector coupling constants of the tau-lepton. The tau-coupling constants agree with those of the electrons and muons, supporting the hypothesis of the universal coupling of leptons to the weak current. The measurement of the topological branching conditions of the tau-lepton is improved and previous measurements are confirmed.

Wiedenmann, Werner

1988-10-01

253

In situ infrared emission spectroscopy for quantitative gas-phase measurement under high temperature reaction conditions: an analytical method for methane by means of an innovative small-volume flowing cell.  

PubMed

We have used infrared emission spectroscopy (IRES) in order to perform in situ studies under flowing gas-phase conditions. When the small-volume cell developed herein is used, we can (1) observe emission spectra from a hot gas-phase sample having an effective volume much less than one milliliter, (2) observe spectra of typical molecular species present, and (3) observe spectra of the more important molecular species down to below 10% and in some cases even as low as 1%. In addition, an analytical method has been derived in order to conduct quantitative studies under typical reaction conditions. We show that simplifications can be made in the data acquisition and handling for a direct linear correlation between band intensity and concentration with only simple background correction. The practical lower limit for methane in the present setup is approximately 0.5-1% v/v depending on the selected temperature. Our data were collected at 500, 600, and 700 degrees C, respectively. The major features of the present cell design are fairly simple and basically formed by a quartz tube (outer diameter=6 mm, inner diameter=4 mm) inside a metal pipe and two tubular ceramic heaters. This simple setup has advantages and attractive features that have extended the application of IRES to new fields and, in particular, for in situ studies of hydrocarbon reactions at different residence times at high temperature. PMID:20149274

Usseglio, Sandro; Thorshaug, Knut; Karlsson, Arne; Dahl, Ivar M; Nielsen, Claus J; Jens, Klaus-J; Tangstad, Elisabeth

2010-02-01

254

Influence of metal ions, coligands and reaction conditions on the structural versatility and properties of 5-pyrimidyl-tetrazolate containing complexes.  

PubMed

Eight new complexes containing the versatile multidentate ligand 5-pyrimidyl-tetrazolate (pmtz), namely [Cu(mu(3)-pmtz)](n) (1), [Pd(2)(mu-pmtz)(2)Cl(2)] (2), [Ni(pmtz)(en)(2)]Cl x 2 H(2)O (3), [Cu(tren)(pmtz)(ClO(4))] (4), [Co(2)(tren)(2)(mu-pmtz)(mu-O(2))](ClO(4))(3) x 3 H(2)O (5), [Fe(2)(pmtz)(4)(H(2)O)(2)(mu-O)] x 5 H(2)O (6), [(UO(2))(4)(mu-pmtz)(2)(mu-OH)(2)(mu(3)-O)(2)(H(2)O)(4)] x 6 H(2)O (7) and [Dy(2)(pmtz)(4)(mu-pmtz)(H(2)O)(6)](pmtz) x 6 H(2)O (8), have been prepared by either conventional solution or hydrothermal techniques and characterised by single-crystal X-ray diffraction. Those compounds prepared under hydrothermal conditions ((1), (2), (7) and (8)) exhibit chelating/bridging coordination modes that connect two or three metal ions generating polynuclear species. Thus, compound is a 2D polymer where the ligand exhibits a new chelating/bridging kappa(2)N(1),N(7):kappaN(2):kappaN(3) coordination mode, whereas complexes (2) and (7) are dinuclear and tetranuclear species, respectively, in which the ligand displays a kappa(2)N(1),N(7):kappaN(2) coordination mode. The increase of the metal size favours the adoption of the kappa(2)N(1),N(7):kappa(2)N(4),N(11) bis(chelating)bridging mode. This is the case of compound (8) that contains bulky Dy(III) metal ions. Despite the large size of the UO(2+) metal ion, the pmtz ligand in (7) does not adopt the expected bis(chelating)bridging mode because the uranyl cation hydrolyzes to the highly stable bis(mu(3)-oxo) tetranuclear unit. Conventional mild solution conditions lead to complexes containing monodentate or chelating coordination modes. Thus, compounds (3) and (6) are mononuclear and mu-oxo dinuclear species, respectively, which contain kappa(2)N(1),N(7) chelating pmtz ligands. Compound (4) is mononuclear with the ligand acting in a new monodentate form through the N(1) atom of the tetrazolato ring, whereas (5) is a dinuclear complex where pmtz adopts a new exo-bidentate N(2),N(3) bridging coordination mode. Variable-temperature magnetic measurements of (6) indicate that the oxo-bridge mediates a very strong antiferromagnetic interaction between the iron(III) ions with a J = -222.7 cm(-1). Luminescence measurements show that the pmtz ligands act as "antenna" for energy absorption and transfer to the uranyl emissive state. PMID:19859613

Rodríguez-Diéguez, Antonio; Mota, Antonio J; Seco, José M; Palacios, María A; Romerosa, Antonio; Colacio, Enrique

2009-09-23

255

Retrospective Clinical and Molecular Analysis of Conditioned Laboratory Dogs (Canis familiaris) with Serologic Reactions to Ehrlichia canis, Borrelia burgdorferi, and Rickettsia rickettsii  

PubMed Central

Dogs are susceptible to different tickborne infections, including members of the Anaplasmataceae (Ehrlichia canis, E. ewingii, E. chaffeensis, Anaplasma phagocytophilum, A. platys), Borrelia burgdorferi, and Rickettsia rickettsii. These diseases can manifest with clinical signs including fever, anorexia, malaise, lameness, rash, and bleeding episodes; however, these signs are nonpathognomonic, and infections can occur in the absence of clinical signs. Hematologic abnormalities can include leukopenia, thrombocytopenia, hyperproteinemia and hypergammaglobulinemia. In biomedical research, diseases such as canine monocytic ehrlichiosis, Lyme disease, and Rocky Mountain spotted fever may cause morbidity among exposed dogs and confound research results. Random-source dogs are susceptible to these diseases because of their increased risk of arthropod exposure. Nonpurpose bred, randomly selected conditioned dogs (n = 21) were examined; blood samples were taken for hematology, biochemistry analysis, tickborne pathogen serology, and PCR. Of these, 2 dogs (10% of the population) presented with illness characterized by fever, malaise, lameness, or hemostatic abnormalities, and 15 (71%) had antibodies to one or more tickborne pathogens. No specific hematologic or biochemical differences were apparent between seronegative dogs and seropositive dogs reactive to all 3 pathogens. E. canis and B. burgdorferi PCR of tissues and blood were negative for all dogs. PCR amplification of several Ehrlichia and Anaplasma genes yielded no positive samples. From this cohort of dogs, serologic and molecular results indicate prior exposure without active infection or clinical disease. Exposure to and potential for infection with these bacteria and other pathogens may contribute to blood and tissue alterations that could confound experiments and lead to misinterpretation of data in canine models.

Scorpio, Diana G; Wachtman, Lynn M; Tunin, Richard S; Barat, Nicole C; Garyu, Justin W; Dumler, J Stephen

2008-01-01

256

An investigation of the reactivity of chars formed in fluidized bed gasifiers: the effect of reaction conditions and particle size on coal char reactivity  

SciTech Connect

Coal-derived chars formed during air-blown gasification processes may rapidly lose reactivity, and this can limit the extent of their conversion. To study this effect, a laboratory-scale fluidized bed reactor has been modified to enable char samples to be prepared under strictly controlled conditions of temperature, pressure, particle size, gaseous environment, and residence time. This has been used to gain an insight into the deactivation of the chars as they form and during their subsequent residence time in the bed of the gasifier. The work shows that the char reactivity declines rapidly during its formation as part of the pyrolysis of the coal. This is thought to result from the rapid deposition of secondary, unreactive char within the pores of the material. In this work, it has been shown to occur within the initial 10 s in the reactor, but in reality, this effect probably occurred within 1 s. Temperature, pressure, and particle size have an impact on this process. Subsequently, and over a longer time scale, structural reorganization occurs in the solid char, and this anneals the structure by graphitization. This has been indicated by the identification of graphite, by X-ray diffraction in long-residence-time chars. The presence of steam in the fluidizing gas seemed to reduce the reactivity of small char particles, which could be due to the gasification of the more reactive parts. This effect does not seem to be present in data obtained with larger particles, and this is thought to be due to the greater influence of secondary char deposition in the larger particles. The reactivities of the largest particles formed over the longest time in this work are getting close to the reactivity values seen in char particles formed in a pilot-scale gasifier. 21 refs., 15 figs., 2 tabs.

A. Cousins; N. Paterson; D.R. Dugwell; R. Kandiyoti [Imperial College London, London (United Kingdom). Department of Chemical Engineering

2006-12-15

257

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

PubMed

Building on the known photophysical properties of well-defined copper-carbazolide complexes, we have recently described photoinduced, copper-catalyzed N-arylations and N-alkylations of carbazoles. Until now, there have been no examples of the use of other families of heteroatom nucleophiles in such photoinduced processes. Herein, we report a versatile photoinduced, copper-catalyzed method for coupling aryl thiols with aryl halides, wherein a single set of reaction conditions, using inexpensive CuI as a precatalyst without the need for an added ligand, is effective for a wide range of coupling partners. As far as we are aware, copper-catalyzed C-S cross-couplings at 0 °C have not previously been achieved, which renders our observation of efficient reaction of an unactivated aryl iodide at -40 °C especially striking. Mechanistic investigations are consistent with these photoinduced C-S cross-couplings following a SET/radical pathway for C-X bond cleavage (via a Cu(I)-thiolate), which contrasts with nonphotoinduced, copper-catalyzed processes wherein a concerted mechanism is believed to occur. PMID:23697882

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

2013-06-13

258

Monotonicity in chemical reaction systems  

Microsoft Academic Search

This article discusses the question of when the dynamical systems arising from chemical reaction networks are monotone, preserving an order induced by some proper cone. The reaction systems studied are defined by the reaction network structure while the kinetics is only constrained very weakly. Necessary and sufficient conditions on cones preserved by these systems are presented. Linear coordinate changes which

Murad Banaji

2009-01-01

259

Ab Initio Chemical Kinetics for SiH2 + Si2H6 and SiH3 + Si2H5 Reactions and the Related Unimolecular Decomposition of Si3H8 under a-Si/H CVD Conditions.  

PubMed

The kinetics and mechanisms for SiH2 + Si2H6 and SiH3 + Si2H5 reactions and the related unimolecular decomposition of Si3H8 have been investigated by ab initio molecular orbital theory based on the QCISD(T)/CBS//QCISD/6-311++G(d,p) method in conjunction with quantum statistical variational Rice-Ramsperger-Kassel-Marcus (RRKM) calculations. For the barrierless radical association processes, their variational transition states have been characterized by the CASPT2//CASSCF method. The species involved in the study are known to coexist under CVD conditions. The results show that the association reaction of SiH2 and Si2H6 producing Si3H8 occurs by insertion via its lowest-energy path forming a loose hydrogen-bonding molecular complex with 8.3 kcal/mol binding energy; the reaction is exothermic by 55.0 kcal/mol. The chemically activated Si3H8 adduct can fragment by several paths, producing SiH4 + SiH3SiH (-0.7 kcal/mol), Si(SiH3)2 + H2 (-1.4 kcal/mol), and SiH3SiH2SiH + H2 (-1.4 kcal/mol). The predicted enthalpy changes as given agree well with available thermochemical data. Three other decomposition channels of Si3H8 occurring by Si-H or Si-Si breaking were found to be highly endothermic, and the reactions take place without a well-defined barrier. The heats of formation of Si3H8, SiH2SiH, Si2H4, i-Si3H7, n-Si3H7, Si(SiH3)2, and SiH3SiH2SiH have been predicted and found to be in close agreement with those available data in the literature. The product branching rate constants for SiH2 + Si2H6 and SiH3 + Si2H5 reactions and the thermal unimolecular decomposition of Si3H8 for all low-energy paths have been calculated with multichannel variational RRKM theory covering varying P,T conditions typically employed in PECVD and Cat-CVD processes for hydrogenated amorphous silicon (a-Si/H) film growth. The results were also found to be in good agreement with available kinetic data. Our kinetic results may be employed to model and control very large-area a-Si/H film growth for a new generation of solar cell applications. PMID:24059703

Raghunath, P; Lin, M C

2013-10-09

260

FACILITATED CHEMICAL SYNTHESIS UNDER ALTERNATE REACTION CONDITIONS  

EPA Science Inventory

The chemical research in the late 1990's witnessed a paradigm shift towards "environmentally-friendly chemistry" more popularly known as "green chemistry" due to the increasing environmental concerns and legislative requirements to curb the release of chemical waste into the atmo...

261

Biogeochemical Reactions Under Simulated Europa Ocean Conditions  

Microsoft Academic Search

Galileo data have demonstrated the probable presence of a liquid water ocean on Europa, and existence of salts and carbon dioxide in the satellite's surface ice (e.g., Carr et al., 1998; McCord et al., 1999, Pappalardo et al., 1999; Kivelson et al., 2000). Subsequently, the discovery of chemical signatures of extinct or extant life in Europa's ocean and on its

X. Amashukeli; S. A. Connon; D. F. Gleeson; R. S. Kowalczyk; R. T. Pappalardo

2007-01-01

262

Chemical Reactions  

NSDL National Science Digital Library

We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

National Science Teachers Association (NSTA)

2009-05-01

263

Special Reactions  

NSDL National Science Digital Library

The basics of chemical reactions were covered in the first chemistry book, including how to write and balance chemical equations that represent those reactions. There is also a quick review of chemical reactions in Chapter 1 of this book. We're going to d

Robertson, William C.

2010-03-01

264

One-pot Synthesis of Lactams Using Domino Reactions: Combination of Schmidt Reaction with Sakurai and Aldol Reactions  

PubMed Central

A series of domino reactions in which the intramolecular Schmidt reaction is combined with either a Sakurai reaction, an aldol reaction, or both is reported. The Sakurai reaction of an allylsilane with an azido-containing enone under Lewis acidic conditions followed by protonation of the resulting titanium enolate species allowed for a subsequent intramolecular Schmidt reaction. Alternatively, the intermediate titanium enolate could undergo an aldol reaction, followed by the intramolecular Schmidt reaction to form lactam products with multiple stereogenic centers. The stereochemical features of the titanium enolate aldol reaction with several 3-azidoaldehyde substrates during this domino process is discussed.

Huh, Chan Woo; Somal, Gagandeep K.; Katz, Christopher E.; Pei, Huaxing; Zeng, Yibin; Douglas, Justin T.; Aube, Jeffrey

2009-01-01

265

Modeling of a gas–liquid reactor in batch conditions. Study of the intermediate regime when part of the reaction occurs within the film and part within the bulk  

Microsoft Academic Search

A model is proposed for irreversible gas–liquid reactions, especially in the so-called ‘intermediate regime’ where the liquid phase mass transfer coefficient and the chemical reaction rate lead to a situation where part of the reaction occurs within the bulk and part occurs within the film. Firstly, the film theory is used but a new parameter, the depletion factor, is introduced

Hassen Benbelkacem; Hubert Debellefontaine

2003-01-01

266

Named Reactions  

NSDL National Science Digital Library

This Web site lists 95 of the most important named reactions in organic chemistry. Each is linked to a Web page that gives the primary reference and equations for one or more recent literature examples that illustrate the use of the reaction.

267

Oscillations in Catalytic Reactions  

Microsoft Academic Search

This paper deals with the status of knowledge concerning open catalytic reaction systems which, though exposed to constant conditions, exhibit sustained oscillatory states. Such behavior arouses interest because, aside from the practical aspects and matters of fundamental importance, it has a battling quality – it usually defles physical explantion offered in the total absence of a mathematical analysis, and hence

M. Sheintuch; H. A. Schmitz

1977-01-01

268

Reaction Time Sound Explanation  

NSDL National Science Digital Library

This experiment presents auditory stimuli and requires the participant to respond after hearing target stimuli under different conditions. This experiment gives students the opportunity to determine whether their reaction times are reliably different for tasks that require slightly different decisions. This page provides guidance for faculty who wish to incorporate this activity into their classroom.

269

Nuclear reaction rates in a plasma  

Microsoft Academic Search

The problem of determining the effects of the surrounding plasma on nuclear reaction rates in stars is formulated {ital ab initio}, using the techniques of quantum statistical mechanics. Subject to the condition that the nuclear reactions ensue only at very close approach of the fusing ions and the condition that the reaction be slow, the authors derive a result that

Lowell S. Brown; R. F. Sawyer

1997-01-01

270

Nuclear reaction rates in a plasma  

Microsoft Academic Search

The problem of determining the effects of the surrounding plasma on nuclear reaction rates in stars is formulated ab initio, using the techniques of quantum statistical mechanics. Subject to the condition that the nuclear reactions ensue only at very close approach of the fusing ions and the condition that the reaction be slow, the authors derive a result that expresses

Lowell S. Brown; R. F. Sawyer

1997-01-01

271

Novelty as a stimulus of special reactions  

Microsoft Academic Search

The stimulus which is of nutritional significance employed in the usual environment of feeding causes simultaneously a general reaction (orientation reflex) and the corresponding food reaction. A new stimulus, especially employed in unusual conditions, causes a general (orientation) reaction and the reflex of biological caution. Novelty, as a stimulus, causes special reactions reflecting congenital or acquired experience of the animals.

E. F. Polezhaev; V. V. Parin

1959-01-01

272

Drug Reactions  

MedlinePLUS

Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...

273

Enzyme Reactions  

NSDL National Science Digital Library

The enzyme reaction rate activity allows students to simulate the effects of variables such as temperature and pH on the reaction rate of the enzyme catalase. This computer simulation is best used after the students have done a wet lab experiment. The value of the simulation is that it requires the students to interpret and analyze the graphical representation of data and it enables the running of mutiple experiments in a short amount of time.

School, Maryland V.

274

[Reactions of dairy calves exposed to transport stress at 60 days of age. Effects of various rearing conditions in the developmental quality of calves on physiological variables and their changes].  

PubMed

Dairy calves reared in groups of constant (Gk, N = 16, m 8, w 8) and changing composition (Gw, N = 16, m 8, w 8) and single box reared calves (E, N = 15, m 8, w 7) were exposed to transport stress lasting around 60 minutes at 60 days of age. Long term measurements of heart rate (HF) were combined with blood sampling (V. jugularis) before and immediately after transport and at the following day as well. Mean differences of HF, Hb, Hk, lactate and blood urea between groups were found at all sampling points. After transport mean values of HF, MetHb, pO2, O2SAT and O2CONT were increased in all calves and such of HHb were decreased. Measures of acid-base balance and lactate changed differently in calves of the three rearing groups concerning direction and degree. Changing of the variables after transport comparing the starting values was different between rearing groups in 16 out of 25 possible cases. Changing of variables immediately after transport showed strong negative correlations with starting values in case of pH, HCO3, base excess, COHb, total protein, albumin, lactate, glucose and Ca in all groups, in all other cases not in all groups. Strong correlations between sampling points of Hb, Hk, MCHC, O2CONT, O2CAP, creatinine, blood urea and of the minerals indicate a high individual specificity of these measures. Results proof variation components of physiological variables in calves caused by husbandry conditions and their effects on reactions of animals in case of transport stress. PMID:10743335

Steinhardt, M; Thielscher, H H

2000-02-01

275

Fundamental reaction pathways during coprocessing  

SciTech Connect

The objective of this research was to investigate the fundamental reaction pathways in coal petroleum residuum coprocessing. Once the reaction pathways are defined, further efforts can be directed at improving those aspects of the chemistry of coprocessing that are responsible for the desired results such as high oil yields, low dihydrogen consumption, and mild reaction conditions. We decided to carry out this investigation by looking at four basic aspects of coprocessing: (1) the effect of fossil fuel materials on promoting reactions essential to coprocessing such as hydrogen atom transfer, carbon-carbon bond scission, and hydrodemethylation; (2) the effect of varied mild conditions on the coprocessing reactions; (3) determination of dihydrogen uptake and utilization under severe conditions as a function of the coal or petroleum residuum employed; and (4) the effect of varied dihydrogen pressure, temperature, and residence time on the uptake and utilization of dihydrogen and on the distribution of the coprocessed products. Accomplishments are described.

Stock, L.M.; Gatsis, J.G. (Chicago Univ., IL (United States). Dept. of Chemistry)

1992-12-01

276

Hypersensitivity Reactions to Corticosteroids.  

PubMed

Hypersensitivity reactions to corticosteroids (CS) are rare in the general population, but they are not uncommon in high-risk groups such as patients who receive repeated doses of CS. Hypersensitivity reactions to steroids are broadly divided into two categories: immediate reactions, typically occurring within 1 h of drug administration, and non-immediate reactions, which manifest more than an hour after drug administration. The latter group is more common. We reviewed the literature using the search terms "hypersensitivity to steroids, adverse effects of steroids, steroid allergy, allergic contact dermatitis, corticosteroid side effects, and type I hypersensitivity" to identify studies or clinical reports of steroid hypersensitivity. We discuss the prevalence, mechanism, presentation, evaluation, and therapeutic options in corticosteroid hypersensitivity reactions. There is a paucity of literature on corticosteroid allergy, with most reports being case reports. Most reports involve non-systemic application of corticosteroids. Steroid hypersensitivity has been associated with type I IgE-mediated allergy including anaphylaxis. The overall prevalence of type I steroid hypersensitivity is estimated to be 0.3-0.5 %. Allergic contact dermatitis (ACD) is the most commonly reported non-immediate hypersensitivity reaction and usually follows topical CS application. Atopic dermatitis and stasis dermatitis of the lower extremities are risk factors for the development of ACD from topical CS. Patients can also develop hypersensitivity reactions to nasal, inhaled, oral, and parenteral CS. A close and detailed evaluation is required for the clinician to confirm the presence of a true hypersensitivity reaction to the suspected drug and choose the safest alternative. Choosing an alternative CS is not only paramount to the patient's safety but also ameliorates the worry of developing an allergic, and potentially fatal, steroid hypersensitivity reaction. This evaluation becomes especially important in high-risk groups where steroids are a life-saving treatment. The assessment should be done when the patient's underlying condition is in a quiescent state. PMID:23567983

Vatti, Rani R; Ali, Fatima; Teuber, Suzanne; Chang, Christopher; Gershwin, M Eric

2013-04-01

277

Palladium complexes derived from N,N-bidentate NH-iminophosphorane ligands: synthesis and use as catalysts in the Sonogashira reaction.  

PubMed

The addition of primary amines to the C=C bond of diphenylalkenyl iminophosphoranes yielded a new subtype of N,N-bidentate ligands bearing N=P(V)-C-C-NH backbones. These donor ligands reacted with PdCl(2)(COD) to give the corresponding ?N,?N-palladium complexes containing secondary amino groups, bearing an intrinsically chiral nitrogen atom, and iminophosphorane units. These new complexes have been fully characterized by the use of spectroscopic techniques and X-ray crystallography. The comparison of the data extracted from their solution NMR spectra with their solid state structures demonstrated the conformational stability of their six-membered chelate ring and also the configurational stability of the chiral nitrogen atom, thus ruling out an arm-off racemization process. The addition of the chiral, racemic ?-methylbenzylamine to the prochiral P-alkenyl iminophosphoranes yielded mixtures of the two expected diasteroisomeric ligands in low diastereoisomeric ratios. One of these mixtures was resolved into their components, each one in turn giving rise to a pair of diasteromeric palladium complexes epimeric at the amino nitrogen atom. One selected example of the new complexes efficiently catalyzes the copper- and amine-free Sonogashira reaction of aryl halides with acetylenes. PMID:22930075

Alajarin, Mateo; Lopez-Leonardo, Carmen; Llamas-Lorente, Pilar; Raja, Rosalia; Bautista, Delia; Orenes, Raul-Angel

2012-10-21

278

"Greening up" the Suzuki Reaction  

ERIC Educational Resources Information Center

This article describes the rapid, green synthesis of a biaryl compound (4-phenylphenol) via a Pd(0)-catalyzed Suzuki cross-coupling reaction in water. Mild reaction conditions and operational simplicity makes this experiment especially amenable to both mid- and upper-level undergraduates. The methodology exposes students to purely aqueous…

Aktoudianakis, Evangelos; Chan, Elton; Edward, Amanda R.; Jarosz, Isabel; Lee, Vicki; Mui, Leo; Thatipamala, Sonya S.; Dicks, Andrew P.

2008-01-01

279

"Greening up" the Suzuki Reaction  

ERIC Educational Resources Information Center

|This article describes the rapid, green synthesis of a biaryl compound (4-phenylphenol) via a Pd(0)-catalyzed Suzuki cross-coupling reaction in water. Mild reaction conditions and operational simplicity makes this experiment especially amenable to both mid- and upper-level undergraduates. The methodology exposes students to purely aqueous…

Aktoudianakis, Evangelos; Chan, Elton; Edward, Amanda R.; Jarosz, Isabel; Lee, Vicki; Mui, Leo; Thatipamala, Sonya S.; Dicks, Andrew P.

2008-01-01

280

Conditioned hunger  

Microsoft Academic Search

Made a methodological analysis of the conditioned hunger problem. Independent measures were taken to determine if the necessary and sufficient conditions to establish a conditioned hunger response had been satisfied. In 2 experiments, using 20 male Long-Evans rats in each, the attempt to establish these conditions was not successful, and in neither case was conditioned hunger demonstrated. The methodological evaluations

Richard W. Cravens; K. Edward Renner

1969-01-01

281

Reaction Time  

NSDL National Science Digital Library

This lab is not an inquiry activity. There are some students whose reaction times will not allow them to catch a 12 inch ruler. They may use a dowel, stick, strip of cardboard, etc. Although the students are led to believe that the point of the lab is to

Horton, Michael

2009-05-30

282

Nanoparticle Reactions on Chip  

NASA Astrophysics Data System (ADS)

The handling of heterogenous systems in micro reactors is difficult due to their adhesion and transport behaviour. Therefore, the formation of precipitates and gas bubbles has to be avoided in micro reaction technology, in most cases. But, micro channels and other micro reactors offer interesting possibilities for the control of reaction conditions and transport by diffusion and convection due to the laminar flow caused by small Reynolds numbers. This can be used for the preparation and modification of objects, which are much smaller than the cross section of microchannels. The formation of colloidal solutions and the change of surface states of nano particles are two important tasks for the application of chip reactors in nanoparticle technology. Some concepts for the preparation and reaction of nanoparticles in modular chip reactor arrangements will be discussed.

Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.

283

SABIO Reaction Kinetics Database (Homepage)  

NSDL National Science Digital Library

The SABIO-RK (System for the Analysis of Biochemical Pathways - Reaction Kinetics) is a web-based application based on the SABIO relational database that contains information about biochemical reactions, their kinetic equations with their parameters, and the experimental conditions under which these parameters were measured. It aims to support modellers in the setting-up of models of biochemical networks, but it is also useful for experimentalists or researchers with interest in biochemical reactions and their kinetics. Information about reactions and their kinetics can be exported in SBML (Systems Biology Mark-Up Language) format.

Scientific Databases And Visualization Group At The Eml Research In Heidelberg, Germany

284

Biomass gasification reaction velocities  

SciTech Connect

The propagation of gaseous flames is determined by the flame velocity, V/sub f/ (the rate at which the flame propagates into the unburned fuel/oxidant). In the same way, gasification of solid fuels depends on the gasification reaction velocity (V/sub r), the rate at which the reaction interface can move into the unreacted solid fuel. We have developed a simple laboratory transparent downdraft gasifier for measuring this velocity for a variety of fuels and conditions. Air or oxygen is drawn down through a 5-cm-diameter quartz tube. If the reaction zone remains stationary in the tube, V/sub r/ is simply the volumetric feed rate. For some input conditions, the position of the incandescent reaction zone is quite stable in the quartz tube. This position depends on the relative rates of production of charcoal by pyrolysis of the biomass and gasification of the charcoal by the pyrolysis combustion gases and can move up or down, depending on conditions. In an uninsulated tube the zone may move down indicating that the char gasification rate exceeds the pyrolysis rate. Adding insulation to the tube increases the tendency for the zone to move up, indicating that the pyrolysis rate is faster than the gasification rate. In practical gasifiers it is necessary to stabilize the reaction front such that the propagation rate equals the feed rate. A number of methods of stabilizing this front have been found. We believe the data and observations presented here help form the basis for a model of downdraft biomass gasification which is significantly different from previous models, and we are continuing to gather data for this model.

Reed, T.B.; Markson, M.

1983-09-01

285

Investigation of the rh-catalyzed asymmetric reductive aldol reaction. Expanded scope based on reaction analysis.  

PubMed

[reaction: see text] A series of experiments are described that suggest that the Rh-catalyzed reductive aldol reaction proceeds by addition of a Rh(I) hydride, generated in situ, to the reacting acrylate followed by a stereochemistry-controlling aldol addition reaction. On the basis of this hypothesis, reaction conditions are engineered that allow for increased substrate scope. PMID:15228266

Russell, Albert E; Fuller, Nathan O; Taylor, Steven J; Aurriset, Pauline; Morken, James P

2004-07-01

286

Reactions inside nanoscale protein cages  

NASA Astrophysics Data System (ADS)

Chemical reactions are traditionally carried out in bulk solution, but in nature confined spaces, like cell organelles, are used to obtain control in time and space of conversion. One way of studying these reactions in confinement is the development and use of small reaction vessels dispersed in solution, such as vesicles and micelles. The utilization of protein cages as reaction vessels is a relatively new field and very promising as these capsules are inherently monodisperse, in that way providing uniform reaction conditions, and are readily accessible to both chemical and genetic modifications. In this review, we aim to give an overview of the different kinds of nanoscale protein cages that have been employed as confined reaction spaces.

Bode, Saskia A.; Minten, Inge J.; Nolte, Roeland J. M.; Cornelissen, Jeroen J. L. M.

2011-06-01

287

Related Conditions  

MedlinePLUS

... the above. Food Intolerances With the exception of celiac disease (see below), food intolerances do not involve the ... Large doses of dairy may cause increased symptoms. Celiac Disease An adverse reaction to gluten is known as ...

288

Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles  

NASA Astrophysics Data System (ADS)

Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

Liechty, Derek S.; Lewis, Mark J.

2011-05-01

289

Synthesis of methacrylic acid by selective oxidation of isobutane, catalysed by Keggin-type polyoxometalates: relationship between catalytic performance, reaction conditions and chemical–physical features of the catalyst  

Microsoft Academic Search

The ammonium salt of 12-molybdophosphoric acid, (NH4)3PMo12O40 (polyoxometalate, POM), having the Keggin-type structure was prepared and tested as a heterogeneous catalyst for the selective oxidation of isobutane to methacrylic acid. This reaction might represent an alternative to the current industrial process for methyl methacrylate production, the acetone–cyanohydrin process, which is characterized by a no longer acceptable environmental impact. The POM

Fabrizio Cavani; Roberto Mezzogori; Anne Pigamo; Ferruccio Trifirò

2000-01-01

290

Decomposition of Methane over Iron Catalysts at the Range of Moderate Temperatures: The Influence of Structure of the Catalytic Systems and the Reaction Conditions on the Yield of Carbon and Morphology of Carbon Filaments  

Microsoft Academic Search

Decomposition of high-purity methane in the presence of ?-Fe-based catalysts to produce filamentous carbon was investigated. The reaction was studied in the temperature range of 650 to 800°C. Filamentous carbon was demonstrated to form at temperatures not lower than 680°C in the presence of both bare ?-Fe and catalysts based thereon with admixtures of various hard-to-reduce oxides (SiO2, Al2O3, ZrO2,

Marina A Ermakova; Dmitry Yu Ermakov; Andrey L Chuvilin; Gennady G Kuvshinov

2001-01-01

291

Explosive Reactions Produced by Spark Ignition on Mixtures of Fluorine with Fluorocarbons and Chlorofluorocarbons.  

National Technical Information Service (NTIS)

Conditions exist for an explosive reaction whenever a mixture is formed from two or more gases which are thermodynamically unstable toward their gaseous reaction products. Reaction under these conditions may be triggered by a localized electric discharge ...

H. A. Bernhardt C. F. Hale E. J. Barber

1968-01-01

292

Recursive conditioning  

Microsoft Academic Search

We introduce an any-space algorithm for exact inference in Bayesian networks, called recursive conditioning. On one extreme, recursive conditioning takes O(n) space and O(n exp(w log n)) time— where n is the size of a Bayesian network and w is the width of a given elimination order—therefore, establishing a new complexity result for linear-space inference in Bayesian networks. On the

Adnan Darwiche

2001-01-01

293

Dissociable effects of AMPA-induced lesions of the vertical limb diagonal band of Broca on performance of the 5-choice serial reaction time task and on acquisition of a conditional visual discrimination  

Microsoft Academic Search

The aim of the present study was to investigate the role of the cholinergic innervation of the cingulate cortex in visual attentional function and acquisition of a visual conditional discrimination task. Following AMPA (?-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid) lesions of the vertical limb diagonal band of Broca (VDB) which provides the main cholinergic projection to cingulate cortex, animals were not significantly impaired on

Janice L. Muir; Timothy J. Bussey; Barry J. Everitt; Trevor W. Robbins

1996-01-01

294

Rotation-induced conditioned rejection in the taste reactivity test.  

PubMed

The taste reactivity test was used to evaluate the ability of motion sickness to produce conditioned rejection reactions, a putative measure of nausea in rats. Following three conditioning trials, rats displayed conditioned rejection reactions during an intraoral infusion of a rotation-paired saccharin solution. This is the first demonstration of conditioned rejection produced with a non-pharmacological emetic agent and provides support that the conditioned rejection reaction may serve as a rat model of nausea. PMID:10380980

Cordick, N; Parker, L A; Ossenkopp, K P

1999-05-14

295

Detecting strictly detailed balanced subnetworks in open chemical reaction networks  

Microsoft Academic Search

The notion “strictly detailed balanced subnetwork” is introduced, for chemical reaction networks which are open and spatially homogeneous, to refer to any set of reactions the net rates of which vanish in each asymptotically stable steady state, regardless of the kinetic parameters of any reaction in the whole network. Necessary and sufficient conditions for sets of reactions to be strictly

Stefan Schuster; Ronny Schuster

1991-01-01

296

Mechanism of the formation of carbon oxides under conditions of the oxidative chlorination of methane: IV. Kinetics of the reaction of CCl 4 with oxygen on copper-containing salt catalysts for methane oxychlorination at reduced partial pressures of Cl 2 in the reaction mixture  

Microsoft Academic Search

The kinetics of the oxidative dechlorination of CCl4 on two supported salt catalysts for methane oxychlorination (CuCl2-KCl and CuCl2-KCl-LaCl3) in the presence of methane at 350–450°C was studied using a gradientless method. It was found that, at $$\\u000aP_{Cl_2 } \\u000a$$ > 0.15 kPa, the presence of methane in the reaction mixture had no effect on the kinetics of CCl4

A. G. Aglulin

2009-01-01

297

Dopamine D1-like and D2-like receptors in the dorsal striatum control different aspects of attentional performance in the five-choice serial reaction time task under a condition of increased activity of corticostriatal inputs.  

PubMed

We investigated the interaction between the corticostriatal glutamatergic afferents and dopamine D1-like and D2-like receptors in the dorsomedial striatum (dm-STR) in attention and executive response control in the five-choice serial reaction time (5-CSRT) task. The competitive NMDA receptor antagonist 3-(R)-2-carboxypiperazin-4-propyl-1-phosphonic acid (CPP) injected in the mPFC impaired accuracy and increased premature and perseverative responding, raising GLU, DA, and GABA release in the dm-STR. The D1-like antagonist SCH23390 injected in the dm-STR reversed the CPP-induced accuracy deficit but did not affect the increase in perseverative responding. In contrast, the D2-like antagonist haloperidol injected in the dm-STR reduced the CPP-induced increase in perseverative responding but not the accuracy deficit. The different roles of dorsal striatal D1-like and D2-like receptor were further supported by the finding that activation of D1-like receptor in the dm-STR by SKF38393 impaired accuracy but not perseverative responding while the D2-like agonist quinpirole injected in the dm-STR increased perseverative responding but did not affect accuracy. These findings suggest that integration of cortical information by D1-like receptors in the dm-STR is a key mechanism of the input selection process of attention while the integration of corticostriatal signals by D2-like receptors preserves the ability to switch from one act/response to the next in a complex motor sequence, thus providing for behavioral flexibility. PMID:23232445

Agnoli, Laura; Mainolfi, Pierangela; Invernizzi, Roberto W; Carli, Mirjana

2012-11-19

298

Conditional Probability  

NSDL National Science Digital Library

This site, created by the Department of Statistics at Yale University gives an explanation, a definition and an example of conditional probability. Topics include the probabilities of intersections of events and Bayes' formula. Overall, this is a great resource for any mathematics classroom studying statistics.

Lacey, Michelle

2008-12-23

299

Syngas Conditioning  

SciTech Connect

A brief review of water gas shift (WGS) catalysis is provided. An overview of the four general classes of WGS catalysts is presented, which include: 1) high temperature shift (HTS), 2) low temperature shift (LTS), 3) sulfur-tolerant shift catalysts, and 4) precious metal-based shift catalysts. A review of WGS utilizing monoliths or other reactor technologies that pertain to fuel cell applications, an area of increasing interest over the past several years, is also presented. Ratnasamy and Wagner have recently provided an outstanding and comprehensive review of WGS catalysis. A particular emphasis of that work is “catalyst surface structures, active sites, reaction intermediates, and mechanisms”, particularly for noble metal-based catalysts1. The summary provided here is a succinct review of water gas shift catalysis and reactors, with an emphasis on fuel processing applications for fuel cells, and is not intended to provide a comprehensive review of WGS technology.

Dagle, Robert A.; Karim, Ayman M.; Li, Guosheng; Su, Yu; King, David L.

2011-04-29

300

Developmental changes in cognitive reaction time of children aged 6–12 years  

Microsoft Academic Search

Using a visual Go\\/Nogo paradigm and subtraction methods, we examined detailed developmental changes in the cognitive reaction times of 153 healthy children aged 6–12 years. Three conditions were studied: simple reaction, even rate reaction (50% Go), and high rate reaction (80% Go). The subtraction of simple reaction time from even rate reaction time was considered to reflect discrimination time, while

Yukako Iida; Makoto Miyazaki; Sunao Uchida

2010-01-01

301

Catalysis of Photochemical Reactions.  

ERIC Educational Resources Information Center

|Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)|

Albini, A.

1986-01-01

302

Catalysis of Photochemical Reactions.  

ERIC Educational Resources Information Center

Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

Albini, A.

1986-01-01

303

Liquid uranium reaction with coated graphite crucibles  

Microsoft Academic Search

Carbon contamination in uranium from yttria-coated graphite crucibles containing uncoated defects has been measured at typical foundry melting conditions as a function of defect area. The reaction of liquid uranium with graphite at crucible coating defects is proportional to the defect surface area and is approx.270 times greater than the reaction at a coated region of equivalent area. Uranium carbon

1987-01-01

304

Cutaneous reactions to transdermal therapeutic systems.  

PubMed

Transdermal therapeutic systems (TTSs) are commonly used to treat many diverse medical conditions. There are several advantages to this form of drug delivery; however, adverse cutaneous reactions are common. This review article provides an update on skin reactions due to TTSs containing medications newly available in TTS form, including buprenorphine, diclofenac, lidocaine, oxybutynin, rotigotine, methylphenidate, rivastigmine, teriparatide, and nicardipine. PMID:21781635

Bershow, Andrea; Warshaw, Erin

305

Adsorption Isotherms and Surface Reaction Kinetics  

ERIC Educational Resources Information Center

|Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)|

Lobo, L. S.; Bernardo, C. A.

1974-01-01

306

Demonstration of HF Chain Reaction Laser.  

National Technical Information Service (NTIS)

A theoretical and experimental investigation was conducted to evaluate the performance potential of the HF/DF chain reaction laser. The program consisted of: theoretical calculations to aid in the selection of design conditions and laser operating conditi...

C. E. Kepler T. J. Sadowski R. Roback R. A. Meinzer

1974-01-01

307

Liquid Uranium Reaction with Coated Graphite Crucibles.  

National Technical Information Service (NTIS)

Carbon contamination in uranium from yttria-coated graphite crucibles containing uncoated defects has been measured at typical foundry melting conditions as a function of defect area. The reaction of liquid uranium with graphite at crucible coating defect...

R. H. Reiner

1987-01-01

308

The Mechanism of the Formaldehyde Clock Reaction.  

ERIC Educational Resources Information Center

|Provides background information and problems with the formaldehyde clock reaction, including comparisons of experimental clock times reported in the literature and conditions for the reliable use of the formaldehyde clock based on a method discussed. (JN)|

Burnett, M. G.

1982-01-01

309

Quality control of Photosystem II: an FtsH protease plays an essential role in the turnover of the reaction center D1 protein in Synechocystis PCC 6803 under heat stress as well as light stress conditions.  

PubMed

The role of an AAA protease FtsH (slr0228) in the turnover of the D1 protein was studied under moderate heat stress conditions using wild-type cells of the cyanobacterium Synechocystis PCC 6803 and the mutant cells lacking a homologue of FtsH (slr0228). When the growth temperature of the wild-type was shifted from 30 degrees C to 40 degrees C, growth and oxygen-evolving activity were partially inhibited. Under the same heat stress, growth of the mutant was inhibited more significantly (63% inhibition after 5 days heat stress, compared with 26% inhibition with the wild-type cells) and the oxygen-evolving activity was also impaired in parallel. With heat stress at 42 degrees C, the level of the D1 protein of wild type cells was decreased, whereas that in mutant cells was not. The responses of cyanobacterial cells to heat stress observed here are quite similar to those to light stress that were reported previously. From these results, we suggest that the FtsH protease (slr0228) is responsible for both the heat-induced and light-induced degradation of the D1 protein. Notably, the amount of FtsH increased when the wild-type cells were exposed to heat stress or light stress, indicating that the up-regulation of the FtsH protease in the thylakoids is crucial for the cyanobacterial cells to cope with these abiotic stresses. PMID:16307111

Kamata, Takashi; Hiramoto, Hideki; Morita, Noriko; Shen, Jian-Ren; Mann, Nicholas H; Yamamoto, Yasusi

2005-09-09

310

Nuclear excitations and reaction mechanisms  

NASA Astrophysics Data System (ADS)

Research concerning nuclear excitations and reaction mechanisms is described. Among the various subjects discussed are: photon scattering, consistency condition between seagull quadrapole terms and the absorption sum rule, Raman scattering to negative-parity states, non-local terms due to exchange and retardation effects in charge-transfer equations, consistency and meaning of various approximate channel coupling array equations, derivation of equations used in empirical nuclear reaction analyses, multi-cluster n-particle scattering theory, converged molecular bound state calculations, and WKB-type approximation in angular momenta for central potentials.

Fallieros, S.; Levin, S. F.; Li, C. T.

1980-10-01

311

Assessment of reaction-rate predictions of a collision-energy approach for chemical reactions in atmospheric flows.  

SciTech Connect

A recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates is assessed for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary non-equilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological nonequilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, significant differences can be found. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert

2010-06-01

312

Dimethylzinc-initiated radical reactions.  

PubMed

Developments in modern organic synthesis owe much to the field of radical chemistry. Mild reaction conditions, high selectivity, good functional group tolerance and high product yield are features that have made reactions involving radical species indispensable tools for synthetic chemists. In part, the discovery of new radical initiators has led to the efficiency that now characterizes most radical reactions. This Account describes our investigations of radical reactions initiated by dimethylzinc. In 2001, we unexpectedly observed this reaction while investigating the amidophosphane-copper-catalyzed asymmetric addition of dimethylzinc to N-sulfonyl imines with tetrahydrofuran (THF) as reaction solvent. However, instead of adding the desired methyl group to the N-sulfonyl imine, we produced the THF adduct in excellent yield. This result laid the foundation for our discovery of novel modes of reactivity. Further investigations of the unexpected addition reaction revealed that a trace amount of air was needed for reaction progress, indicating that radical intermediates were involved. Indeed, controlled injection of air into the reaction flask by a syringe pump through a sodium hydroxide tube afforded the products in good to excellent yield. In addition, the reaction proved to be chemoselective for a C=N bond over a C=O bond, as well as for 1,4-addition over 1,2-addition. We developed asymmetric variants of the radical addition reaction of ethers to imines using chiral N-sulfinyl imines to produce the adducts in reasonably high stereoselectivity (up to 11:1). A 93:7 diastereomeric ratio of the adduct was obtained when bis(8-phenylmenthyl) benzylidenemalonate was used in the radical addition of ethers to C=C bonds. Interestingly, in the presence of dimethylzinc and air, arylamines, alkoxyamines, and dialkylhydrazines react with THF to give amino alcohols, oximes, and hydrazones, respectively, in moderate to high yields. We performed a tin-free intermolecular addition of functionalized primary alkyl groups, generated from their corresponding iodides, to N-sulfonyl imines using dimethylzinc, air, boron trifluoride diethyl etherate, and a catalytic amount of copper(II) triflate. Direct C-H bond cleavage from cycloalkanes was also feasible in the presence of dimethylzinc, air, and boron trifluoride diethyl etherate to give the corresponding cycloalkyl radicals, which were suitable nucleophiles for N-sulfonyl imines. In all of the above reactions, dimethylzinc was a superior radical initiator than other conventional initiators such as dibenzoyl peroxide, diethylzinc, and triethylborane. We hope the coming decades will witness the report of other novel radical initiators that would complement the reactivity modes of existing ones. PMID:19113862

Akindele, Tito; Yamada, Ken-ichi; Tomioka, Kiyoshi

2009-02-17

313

Reaction rates and reaction sequences in the rp-process  

NASA Astrophysics Data System (ADS)

Hot hydrogen burning has been analyzed for temperatures and densities typical for explosive burning on compact objects and in supernovae. Reaction flow impedances due to cyclic reaction sequences, the role of waiting point nuclei, and the transition from the rp-process to the alpha p-process are discussed as a function of increasing temperature and nuclear properties. The analysis gives a clear indication of which nuclei play a crucial role in the burning process. It is here where experimental verifications of the presented reaction rate estimates are highly desirable. The same nuclei can also be utilized to devise minimum-size energy generation networks to be employed in hydrodynamic explosion calculations. Examples for specific conditions during supernova explosions, nova outbursts, or the evolution of Thorne-Zytkow objects are given, with typical abundance patterns expected in such events.

van Wormer, L.; Goerres, J.; Iliadis, C.; Wiescher, M.; Thielemann, F.-K.

1994-09-01

314

Mathematical model to predict drivers' reaction speeds.  

PubMed

Mental distractions and physical impairments can increase the risk of accidents by affecting a driver's ability to control the vehicle. In this article, we developed a linear mathematical model that can be used to quantitatively predict drivers' performance over a variety of possible driving conditions. Predictions were not limited only to conditions tested, but also included linear combinations of these tests conditions. Two groups of 12 participants were evaluated using a custom drivers' reaction speed testing device to evaluate the effect of cell phone talking, texting, and a fixed knee brace on the components of drivers' reaction speed. Cognitive reaction time was found to increase by 24% for cell phone talking and 74% for texting. The fixed knee brace increased musculoskeletal reaction time by 24%. These experimental data were used to develop a mathematical model to predict reaction speed for an untested condition, talking on a cell phone with a fixed knee brace. The model was verified by comparing the predicted reaction speed to measured experimental values from an independent test. The model predicted full braking time within 3% of the measured value. Although only a few influential conditions were evaluated, we present a general approach that can be expanded to include other types of distractions, impairments, and environmental conditions. PMID:22431214

Long, Benjamin L; Gillespie, A Isabella; Tanaka, Martin L

2012-02-01

315

Biochemical Reactions as Computations  

Microsoft Academic Search

Two main mechanisms behind the functioning of biochemical reactions are facilitation and inhibition; these mechanisms are\\u000a also central for the interaction between biochemical reactions. This observation underlies the theory of reaction systems\\u000a which is a formal framework for the investigation of biochemical reactions, and especially interactions between them.

Andrzej Ehrenfeucht; Grzegorz Rozenberg

2007-01-01

316

Catalytic asymmetric Henry reaction  

Microsoft Academic Search

The classical Henry reaction, the coupling of a nitroalkane with a carbonyl compound in the presence of a base, is an important C–C bond forming reaction in organic chemistry giving ?-nitroalcohols, which are useful synthons in organic synthesis. However, an asymmetric version of the reaction, that has been developed recently, gives a new dimension to the classical Henry reaction whereby

Joshodeep Boruwa; Naminita Gogoi; Partha Pratim Saikia; Nabin C. Barua

2006-01-01

317

The Glyoxal Clock Reaction  

ERIC Educational Resources Information Center

|Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

2007-01-01

318

Operant conditioning.  

PubMed

Operant behavior is behavior "controlled" by its consequences. In practice, operant conditioning is the study of reversible behavior maintained by reinforcement schedules. We review empirical studies and theoretical approaches to two large classes of operant behavior: interval timing and choice. We discuss cognitive versus behavioral approaches to timing, the "gap" experiment and its implications, proportional timing and Weber's law, temporal dynamics and linear waiting, and the problem of simple chain-interval schedules. We review the long history of research on operant choice: the matching law, its extensions and problems, concurrent chain schedules, and self-control. We point out how linear waiting may be involved in timing, choice, and reinforcement schedules generally. There are prospects for a unified approach to all these areas. PMID:12415075

Staddon, J E R; Cerutti, D T

2002-06-10

319

Knoevenagel Reaction of Unprotected Sugars  

NASA Astrophysics Data System (ADS)

The Knoevenagel reaction of unprotected sugars was investigated in the 1950s using zinc chloride as promoter. The so-called Garcia Gonzalez reaction had been almost forgotten for 50 years, until the emergence of new water tolerant catalysts having Lewis acid behavior. The reaction was thus reinvestigated and optimal conditions have been found to prepare trihydroxylated furan derivatives from pentose or ?-tetrahydrofuranylfuran from hexoses with non-cyclic ?-keto ester or ?-diketones. Other valuable compounds such as ?-linked tetrahydrobenzofuranyl glycosides or hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione can be obtained using cyclic ?-dicarbonylic derivatives. Apart from one report in the 1950s, the Knoevenagel reaction of unprotected carbohydrate in basic condition has been studied only in the mid-1980s to prepare C-glycosyl barbiturates from barbituric acids and, later on, from non-cyclic ?-diketones, ?-C-glycosidic ketones. The efficient method exploited to prepare such compounds has found an industrial development in cosmetics.

Scherrmann, Marie-Christine

320

Thermodynamics in the limit of irreversible reactions  

NASA Astrophysics Data System (ADS)

For many complex real physicochemical systems, the detailed mechanism includes both reversible and irreversible reactions. Such systems are typical in homogeneous combustion and heterogeneous catalytic oxidation. Most complex enzyme reactions include irreversible steps. Classical thermodynamics has no limit for irreversible reactions, whereas kinetic equations may have such a limit. We represent systems with irreversible reactions as the limits of fully reversible systems when some of the equilibrium concentrations tend to zero. The structure of the limit reaction system crucially depends on the relative rates of this tendency to zero. We study the dynamics of the limit system and describe its limit behavior as t??. If the reversible systems obey the principle of detailed balance then the limit system with some irreversible reactions must satisfy the extended principle of detailed balance. It is formulated and proven in the form of two conditions: (i) the reversible part satisfies the principle of detailed balance and (ii) the convex hull of the stoichiometric vectors of the irreversible reactions does not intersect the linear span of the stoichiometric vectors of the reversible reactions. These conditions imply the existence of the global Lyapunov functionals and allow an algebraic description of the limit behavior. Thermodynamic theory of the irreversible limit of reversible reactions is illustrated by the analysis of hydrogen combustion.

Gorban, A. N.; Mirkes, E. M.; Yablonsky, G. S.

2013-03-01

321

First trial postural reactions to unexpected balance disturbances: a comparison with the acoustic startle reaction.  

PubMed

Unexpected support-surface movements delivered during stance elicit "first trial" postural reactions, which are larger and cause greater instability compared with habituated responses. The nature of this first trial reaction remains unknown. We hypothesized that first trial postural reactions consist of a generalized startle reaction, with a similar muscle synergy as the acoustic startle response, combined with an automatic postural reaction. Therefore we compared acoustic startle responses to first trial postural reactions. Eight healthy subjects stood on a support surface that unexpectedly rotated backwards 10 times, followed by 10 startling acoustic stimuli, or vice versa. Outcome measures included full body kinematics and surface EMG from muscles involved in startle reactions or postural control. Postural perturbations and startling acoustic stimuli both elicited a clear first trial reaction, as reflected by larger kinematic and EMG responses. The ensuing habituation rate to repeated identical stimuli was comparable for neck and trunk muscles in both conditions. Onset latencies in neck muscles occurred significantly later for first trial perturbations compared with startle responses, but earlier in trunk muscles. Our results show that platform tilting initially induces reactions larger than needed to maintain equilibrium. For neck and trunk muscles, these first trial postural reactions resembled acoustic startle reflexes. First trial postural reactions may be triggered by interaction of afferent volleys formed by somatosensory and vestibular inputs. Acoustic startle reactions may also be partially triggered by vestibular inputs. Similar muscle activation driven by vestibular inputs may be the common element of first trial postural responses and acoustic startle reactions. PMID:20810688

Oude Nijhuis, Lars B; Allum, John H J; Valls-Solé, Josep; Overeem, Sebastiaan; Bloem, Bastiaan R

2010-09-01

322

Quantifying mixing using equilibrium reactions  

SciTech Connect

A method of quantifying equilibrium reactions in a microchannel using a fluorometric reaction of Fluo-4 and Ca{sup 2+} ions is presented. Under the proper conditions, equilibrium reactions can be used to quantify fluid mixing without the challenges associated with constituent mixing measures such as limited imaging spatial resolution and viewing angle coupled with three-dimensional structure. Quantitative measurements of CaCl and calcium-indicating fluorescent dye Fluo-4 mixing are measured in Y-shaped microchannels. Reactant and product concentration distributions are modeled using Green's function solutions and a numerical solution to the advection-diffusion equation. Equilibrium reactions provide for an unambiguous, quantitative measure of mixing when the reactant concentrations are greater than 100 times their dissociation constant and the diffusivities are equal. At lower concentrations and for dissimilar diffusivities, the area averaged fluorescence signal reaches a maximum before the species have interdiffused, suggesting that reactant concentrations and diffusivities must be carefully selected to provide unambiguous, quantitative mixing measures. Fluorometric equilibrium reactions work over a wide range of pH and background concentrations such that they can be used for a wide variety of fluid mixing measures including industrial or microscale flows.

Wheat, Philip M. [Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287-6106 (United States); Posner, Jonathan D. [Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287-6106 (United States); Department of Chemical Engineering, Arizona State University, Tempe, Arizona 85287-6106 (United States)

2009-03-15

323

Dynamical model of surrogate reactions  

SciTech Connect

A new dynamical model is developed to describe the whole process of surrogate reactions: Transfer of several nucleons at an initial stage, thermal equilibration of residues leading to washing out of shell effects, and decay of populated compound nuclei are treated in a unified framework. Multidimensional Langevin equations are employed to describe time evolution of collective coordinates with a time-dependent potential energy surface corresponding to different stages of surrogate reactions. The new model is capable of calculating spin distributions of the compound nuclei, one of the most important quantities in the surrogate technique. Furthermore, various observables of surrogate reactions can be calculated, for example, energy and angular distribution of ejectile and mass distributions of fission fragments. These features are important to assess validity of the proposed model itself, to understand mechanisms of the surrogate reactions, and to determine unknown parameters of the model. It is found that spin distributions of compound nuclei produced in {sup 18}O+{sup 238}U{yields}{sup 16}O+{sup 240}*U and {sup 18}O+{sup 236}U{yields}{sup 16}O+{sup 238}*U reactions are equivalent and much less than 10({h_bar}/2{pi}) and therefore satisfy conditions proposed by Chiba and Iwamoto [Phys. Rev. C 81, 044604 (2010)] if they are used as a pair in the surrogate ratio method.

Aritomo, Y.; Chiba, S.; Nishio, K. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

2011-08-15

324

NTNU Java: Reaction time measurement  

NSDL National Science Digital Library

This Java applet measures braking distance and reaction time for stopping a car. Initial velocity is controlled by the user, and the coefficient of friction can be set from 0 to 1.5 to simulate varying road conditions. Once initial parameters are set, click "Start", then click "Brake" when you see the light turn yellow. Did you set a safe speed for the road conditions, or did you run the red light? Editor's Note: This simulation can be adapted for a wide range of age groups and course levels since its pre-set parameters include constant initial velocity.

Hwang, Fu-Kwun

2008-07-11

325

[Adverse reactions to insulin].  

PubMed

The prevalence of allergic reactions to insuline has decreased during the last few years. Probably this is due to the use of the newly-developed recombinant human insuline. At present, adverse reactions to insuline occur in 5-10% of patients on therapy with insuline. Adverse reactions may be local (more frequent) or systemic (rare). Insuline resistance consists in a different type of immunological reaction. Diagnosis of allergy to insuline is based on clinical history and cutaneous and serological tests. Treatment depends upon the severity of the reaction. When insuline is indispensable despite a previous allergic reaction, a desensitization protocol may be implemented. PMID:9410127

Liñana, J J; Montoro, F J; Hernández, M D; Basomba, A

1997-07-01

326

Learning to predict chemical reactions.  

PubMed

Being able to predict the course of arbitrary chemical reactions is essential to the theory and applications of organic chemistry. Approaches to the reaction prediction problems can be organized around three poles corresponding to: (1) physical laws; (2) rule-based expert systems; and (3) inductive machine learning. Previous approaches at these poles, respectively, are not high throughput, are not generalizable or scalable, and lack sufficient data and structure to be implemented. We propose a new approach to reaction prediction utilizing elements from each pole. Using a physically inspired conceptualization, we describe single mechanistic reactions as interactions between coarse approximations of molecular orbitals (MOs) and use topological and physicochemical attributes as descriptors. Using an existing rule-based system (Reaction Explorer), we derive a restricted chemistry data set consisting of 1630 full multistep reactions with 2358 distinct starting materials and intermediates, associated with 2989 productive mechanistic steps and 6.14 million unproductive mechanistic steps. And from machine learning, we pose identifying productive mechanistic steps as a statistical ranking, information retrieval problem: given a set of reactants and a description of conditions, learn a ranking model over potential filled-to-unfilled MO interactions such that the top-ranked mechanistic steps yield the major products. The machine learning implementation follows a two-stage approach, in which we first train atom level reactivity filters to prune 94.00% of nonproductive reactions with a 0.01% error rate. Then, we train an ensemble of ranking models on pairs of interacting MOs to learn a relative productivity function over mechanistic steps in a given system. Without the use of explicit transformation patterns, the ensemble perfectly ranks the productive mechanism at the top 89.05% of the time, rising to 99.86% of the time when the top four are considered. Furthermore, the system is generalizable, making reasonable predictions over reactants and conditions which the rule-based expert does not handle. A web interface to the machine learning based mechanistic reaction predictor is accessible through our chemoinformatics portal ( http://cdb.ics.uci.edu) under the Toolkits section. PMID:21819139

Kayala, Matthew A; Azencott, Chloé-Agathe; Chen, Jonathan H; Baldi, Pierre

2011-09-02

327

Reaction of plagioclase feldspars with CO 2 under hydrothermal conditions  

Microsoft Academic Search

Geological storage of CO2 in plagioclase-bearing sediments, granitic rocks and fractured basalts is expected to have a variety of geochemical and geomechanical effects, including mineral trapping and porosity-permeability changes. The amount of CO2 trapped by mineralisation and the extent of any changes in host rock transport or mechanical properties depend on rock composition. To date, studies of mineralisation have mainly

Suzanne J. T. Hangx; Christopher J. Spiers

2009-01-01

328

Coupling nuclear reaction rates with temperature in explosive conditions  

NASA Astrophysics Data System (ADS)

We present a straightforward integration method to compute the abundance and temperature evolution in explosive scenarios. In this approach the thermal equation is implicitely coupled with chemical equations in order to avoid instabilities and ensure a gentle transition from the normal combustion regime to the quasi (QSE) and complete nuclear statistical equilibrium (NSE). Two nuclear networks, with 14 nuclei (?-network) and 86 nuclei (including protons and neutrons) respectively, have been considered. The scheme is suitable to cope with a variety of explosive burning regimes.

García-Senz, Domingo; Cabezón Gómez, Rubén M.

2003-05-01

329

GREENER ORGANIC SYNTHESES USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

The diverse nature of chemical entities requires various green' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable...

330

CHEMICAL SYNTHESIS USING 'GREENER' ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

The chemical research during the last decade has witnessed a paradigm shift towards "environmentally-friendly chemistry" more popularly known as "green chemistry" due to the increasing environmental concerns and legislative requirements to curb the release of chemical waste into ...

331

ENVIRONMENTALLY FRIENDLIER SYNTHESIS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

The diverse nature of chemical universe requires various 'greener' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recycla...

332

ENVIRONMENTALLY FRIENDLIER SYNTHESES USING MICROWAVES AND ALTERNATIVE REACTION CONDITIONS  

EPA Science Inventory

A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable mineral supports such as alumina, silica, clay, or doped surfaces is presented which is applicable to a wide range of cleavage, c...

333

EFFICIENT CHEMICAL TRANSFORMATIONS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

The diverse nature of chemical entities requires various green' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable...

334

Simulation of chemical reaction equilibria by the reaction ensemble Monte Carlo method: a review†  

Microsoft Academic Search

Understanding and predicting the equilibrium behaviour of chemically reacting systems in highly non-ideal environments is critical to many fields of science and technology, including solvation, nanoporous materials, catalyst design, combustion and propulsion science, shock physics and many more. A method with recent success in predicting the equilibrium behaviour of reactions under non-ideal conditions is the reaction ensemble Monte Carlo method

C. Heath Turner; John K. Brennan; Martin Lísal; William R. Smith; J. Karl Johnson; Keith E. Gubbins

2008-01-01

335

Aromaticity and Pericyclic Reactions.  

National Technical Information Service (NTIS)

Pericyclic reactions formally resemble the conversion of one Kekule structure into another; the transition state may be 'aromatic', 'nonaromatic', or 'antiaromatic'. Thermally induced pericyclic reactions proceed preferentially via aromatic transition sta...

M. J. S. Dewar

1971-01-01

336

Pulmonary Transfusion Reactions  

PubMed Central

Summary Background In recent years, pulmonary transfusion reactions have gained increasing importance as serious adverse transfusion events. Methods Review of the literature. Results Pulmonary transfusion reactions are not extremely rare and, according to hemovigilance data, important causes of transfusion-induced major morbidity and death. They can be classified as primary with predominant pulmonary injury and secondary as part of another transfusion reaction. Primary reactions include transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO) and transfusion-associated dyspnea (TAD). Secondary pulmonary reactions are often observed in the wake of hemolytic transfusion reactions, hypotensive/anaphylactic reactions, and transfusion-transmitted bacterial infections. Conclusion Knowledge and careful management of cases of pulmonary transfusion reactions are essential for correct reporting to blood services and hemovigilance systems. Careful differentiation between TRALI and TACO is important for taking adequate preventive measures.

Bux, Jurgen; Sachs, Ulrich J. H.

2008-01-01

337

Chemical Reactions (Netorials)  

NSDL National Science Digital Library

Chemical Reactions: this is a resource in the collection "Netorials". The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

338

Microscale Thermite Reactions.  

ERIC Educational Resources Information Center

Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana

1998-01-01

339

Microfluidic chemical reaction circuits  

DOEpatents

New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

Lee, Chung-cheng (Irvine, CA); Sui, Guodong (Los Angeles, CA); Elizarov, Arkadij (Valley Village, CA); Kolb, Hartmuth C. (Playa del Rey, CA); Huang, Jiang (San Jose, CA); Heath, James R. (South Pasadena, CA); Phelps, Michael E. (Los Angeles, CA); Quake, Stephen R. (Stanford, CA); Tseng, Hsian-rong (Los Angeles, CA); Wyatt, Paul (Tipperary, IE); Daridon, Antoine (Mont-Sur-Rolle, CH)

2012-06-26

340

EXPERIMENTAL BONE MARROW REACTIONS  

PubMed Central

1. The effect produced by intravenous administration of gum shellac solution varied directly with the strength of the solution and the amount injected. (a) Strong solutions were intensely toxic and fatal to all the animals injected. Toxicity was abolished by the presence of carbon particles in the solution. (b) Medium strength solutions produced a marked normoblastosis followed by an erythroblastosis if injections were continued, accompanied either by an initial rise of red blood cells and hemoglobin followed by a decrease or an initial decline followed by an increase. The decrease of erythrocytes and hemoglobin did not amount to an actual anemia, and was usually concomitant with the greatest outpouring of nucleated red cells. (c) Small doses elicited the same kind of response except that the normoblastosis was less marked, the decrease of red cells and hemoglobin minimal or absent, the increase of red blood cells and hemoglobin marked in most instances. (d) Minimal doses elicited no appreciable reaction. 2. The bone marrow in animals killed after a course of injections showed intense erythrocytic hyperplasia. This disappeared after a variable length of time with a return of the bone marrow to apparently normal condition. 3. Toxic effects with non-fatal doses in form of hemorrhages were produced mainly in the bone marrow and occasionally in the kidney under the following conditions. (a) After one injection in an animal with hyperplastic marrow (hemorrhages ih the bone marrow only). (b) After the fourth and fifth dose when administered at long intervals (4 to 19 day intervals). (c) After one injection given 40 days after several successive injections (one animal only). 4. Small and divided doses administered at long intervals produced no apparent ill effect. 5. Subcutaneous administrations did not elicit any marked systemic reactions. Locally there was induration and edema. 6. The conclusion was drawn that gum shellac solution stimulates markedly the production of erythrocytes in the bone marrow. The mechanism of stimulation is not clear, but it seems unlikely that it is due to destruction of red blood cells in the peripheral blood stream.

Muller, Gulli Lindh

1927-01-01

341

Noneczematous Contact Reactions  

Microsoft Academic Search

\\u000a Not all skin contact reactions present as eczema or dermatitis. There are several distinct noneczematous contact reactions\\u000a which are more commonly seen. The mechanisms of these reactions are not clearly elucidated yet. It is very useful to clinicians\\u000a to be able to identify these dermatoses as contact reactions so that they may be confirmed with patch testing and other unnecessary

Anthony Goon; Chee-Leok Goh

342

Insights into the mechanisms on chemical reactions: reaction paths for chemical reactions. [Li + HF; OH + Hâ  

Microsoft Academic Search

We report reaction paths for two prototypical chemical reactions: Li + HF, an electron transfer reaction, and OH + Hâ, an abstraction reaction. In the first reaction we consider the connection between the energetic terms in the reaction path Hamiltonian and the electronic changes which occur upon reaction. In the second reaction we consider the treatment of vibrational effects in

T. H. Jr. Dunning; E. Rosen; R. A. Eades

1987-01-01

343

Current issues in sol-gel reaction kinetics.  

National Technical Information Service (NTIS)

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative f...

R. A. Assink B. D. Kay

1990-01-01

344

Droplet heat transfer and chemical reactions during direct containment heating  

SciTech Connect

A simplified model of heat transfer and chemical reaction has been adapted to evaluate the expected behavior of droplets containing unreacted Zircaloy and stainless steel moving through the containment atmosphere during postulated accidents involving direct containment heating. The model includes internal and external diffusive resistances to reaction. The results indicate that reactions will be incomplete for many conditions characteristic of direct containment heating sequences.

Baker, L. Jr.

1986-01-01

345

The effect of certain variables on visual and auditory reaction times  

Microsoft Academic Search

1. An apparatus for recording visual and auditory reaction times is described. 2. The reaction times of 178 male Ss varying in age from 17 to 53 years are recorded under different conditions. 3. The influence of certain variables on these reaction times is considered statistically. 4. Reaction times to light and sound are only partially dependent. 5. The reaction

G. Forbes

1945-01-01

346

Chemical Reactions: Investigating Exothermic and Endothermic Reactions  

NSDL National Science Digital Library

This activity is an inquiry-based investigation where students discover the indicators of chemical reactions (endothermic and exothermic) by collecting data and using that data to develop a testable question for further experimentation.

347

Reaction coordinates for electron transfer reactions  

SciTech Connect

The polarization fluctuation and energy gap formulations of the reaction coordinate for outer sphere electron transfer are linearly related to the constant energy constraint Lagrangian multiplier m in Marcus' theory of electron transfer. The quadratic dependence of the free energies of the reactant and product intermediates on m and m+1, respectively, leads to similar dependence of the free energies on the reaction coordinates and to the same dependence of the activation energy on the reorganization energy and the standard reaction free energy. Within the approximations of a continuum model of the solvent and linear response of the longitudinal polarization to the electric field in Marcus' theory, both formulations of the reaction coordinate are expected to lead to the same results.

Rasaiah, Jayendran C. [Department of Chemistry, University of Maine, Orono, Maine 04469 (United States); Zhu Jianjun [Department of Chemistry, State University of New York, Stonybrook, New York 11790 (United States) and Department of Chemistry, Henan Normal University, Xinxiang, Henan (China)

2008-12-07

348

The Dibenzalacetone Reaction Revisited  

Microsoft Academic Search

A modification of a classic experiment is described that incorporates a discovery approach to organic synthesis. Groups of students are assigned target molecules of the dibenzalketone type and are given a sample procedure for the parent dibenzalacetone reaction. They are asked to design a synthesis of their target based on the model reaction and to modify the model reaction so

Leslie A. Hull

2001-01-01

349

Current issues in sol-gel reaction kinetics  

SciTech Connect

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse are significant for TMOS sol-gels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water-and alcohol-producing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address diverse experimental findings. 9 refs., 3 figs., 1 tab.

Assink, R.A.; Kay, B.D.

1990-01-01

350

Suzuki-Miyaura coupling reaction using pentafluorophenylboronic acid.  

PubMed

[reaction: see text] We have found new conditions for the Suzuki-Miyaura coupling reaction applicable to pentafluorophenylboronic acid (C(6)F(5)B(OH)(2)) (1), which is an inactive substrate under normal conditions. The reactions of 1 with phenyl iodide or bromide under Pd(PPh(3))(4)/CsF/Ag(2)O or Pd(2)(dba)(3)/P(t-Bu)(3)/CsF/Ag(2)O catalytic system conditions gave 2,3,4,5,6-pentafluoro-1,1'-biphenyl (3a) in more than 90% yields. Combination of CsF and Ag(2)O was essential for promoting these reactions. PMID:16235921

Korenaga, Toshinobu; Kosaki, Takahiro; Fukumura, Rokki; Ema, Tadashi; Sakai, Takashi

2005-10-27

351

Reactions at Oxygen Atoms  

NASA Astrophysics Data System (ADS)

Synthetic protocols based on carbohydrates require the differentiation of their abundant hydroxyl groups, by and large, in order to expose just one single hydroxyl group to the selected reagent. This differentiation is usually carried out with the assistance of protecting groups that block the rest of the hydroxyl groups while being compatible with the given reaction conditions. By corollary, the knowledge and apt choice of the appropriate protecting groups is a key factor in successful synthetic endeavors. In this chapter, an overview of the most commonly employed protecting groups in carbohydrate chemistry is given. Alkyl ethers, being robust protecting groups, have a long history in synthetic carbohydrate chemistry and in related structural studies of polysaccharides. Acetals and ketals, which are of fundamental importance in carbohydrate chemistry, are then discussed. Acyl and silyl protecting groups, which also play an important role in modern monosaccharide transformations, are also presented. Finally, recent blocking strategies are described, including orthogonal strategies, by which the protecting groups are harmoniously combined in modern carbohydrate chemistry.

Gómez, Ana M.

352

The preparation of astatine labelled tyrosine using an electrophilic reaction  

Microsoft Academic Search

Carrier-free astatotyrosine has been synthesized using an electrophilic reaction in acidic media. Temperature of 150–160°C and reaction time of 20–30 min were chosen as optimal conditions for the synthesis of astatotyrosine. Under the selected conditions the yield was about 90%.

Yu. V. Norseyev; D. D. Nhan; V. A. Khalkin; N. Q. Huan; L. Vasaros

1985-01-01

353

Chemical dynamics of the CH(X2?) + C2H4(X1A1g), CH(X2?) + C2D4(X1A1g), and CD(X2?) + C2H4(X1A1g) reactions studied under single collision conditions.  

PubMed

The crossed beam reactions of the methylidyne radical with ethylene (CH(X(2)?) + C(2)H(4)(X(1)A(1g))), methylidyne with D4-ethylene (CH(X(2)?) + C(2)D(4)(X(1)A(1g))), and D1-methylidyne with ethylene (CD(X(2)?) + C(2)H(4)(X(1)A(1g))) were conducted at nominal collision energies of 17-18 kJ mol(-1) to untangle the chemical dynamics involved in the formation of distinct C(3)H(4) isomers methylacetylene (CH(3)CCH), allene (H(2)CCCH(2)), and cyclopropene (c-C(3)H(4)) via C(3)H(5) intermediates. By tracing the atomic hydrogen and deuterium loss pathways, our experimental data suggest indirect scattering dynamics and an initial addition of the (D1)-methylidyne radical to the carbon-carbon double bond of the (D4)-ethylene reactant forming a cyclopropyl radical intermediate (c-C(3)H(5)/c-C(3)D(4)H/c-C(3)H(4)D). The latter was found to ring-open to the allyl radical (H(2)CCHCH(2)/D(2)CCHCD(2)/H(2)CCDCH(2)). This intermediate was found to be long lived with life times of at least five times its rotational period and decomposed via atomic hydrogen/deuterium loss from the central carbon atom (C2) to form allene via a rather loose exit transition state in an overall strongly exoergic reaction. Based on the experiments with partially deuterated reactants, no compelling evidence could be provided to support the formation of the cyclopropene and methylacetylene isomers under single collision conditions. Likewise, hydrogen/deuterium shifts in the allyl radical intermediates or an initial insertion of the (D1)-methylidyne radical into the carbon-hydrogen/deuterium bond of the (D4)-ethylene reactant were found to be-if at all-of minor importance. Our experiments propose that in hydrocarbon-rich atmospheres of planets and their moons such as Saturn's satellite Titan, the reaction of methylidyne radicals should lead predominantly to the hitherto elusive allene molecule in these reducing environments. PMID:22108533

Zhang, Fangtong; Maksyutenko, Pavlo; Kaiser, Ralf I

2011-11-23

354

Dimethylcarbonate for eco-friendly methylation reactions  

Microsoft Academic Search

Dimethylcarbonate (DMC), an environmentally friendly substitute for dimethylsulfate and methyl halides in methylation reactions, is a very selective reagent. Both under gas–liquid phase transfer catalysis (GL-PTC) and under batch conditions, with potassium carbonate as the catalyst, the reactions of DMC with methylene-active compounds (arylacetonitriles and arylacetoesters, aroxyacetonitriles and methyl aroxyacetates, benzylaryl- and alkylarylsulphones) produce monomethylated derivatives, with a selectivity not

S. Memoli; M. Selva; P. Tundo

2001-01-01

355

Kinetics and mechanisms of homogeneous catalytic reactions  

Microsoft Academic Search

A kinetic study of the homogeneous hydroformylation of 1-hexene to the corresponding aldehydes (heptanal and 2-methyl-hexanal) was carried out using a rhodium catalyst formed by addition of 1equiv. of 1,2-bis(diphenylphosphino)ethane (dppe) to Rh(acac)(CO)2 under mild reaction conditions (80°C, 1–7atm H2 and 1–7atm CO) in toluene; in all cases linear to branched ratios were close to 2. The reaction rate is

Merlin Rosales; Angel González; YusbeIi Guerrero; Inés Pacheco; Roberto A. Sánchez-Delgado

2007-01-01

356

Reaction diffusion pulses: a combustion model  

Microsoft Academic Search

We focus on a reaction-diffusion approach proposed recently for experiments on combustion processes, where the heat released by combustion follows first-order reaction kinetics. This case allows us to perform an exhaustive analytical study. Specifically, we obtain the exact expressions for the speed of the thermal pulses, their maximum temperature and the condition of self-sustenance. Finally, we propose two generalizations of

Daniel Campos; Joaquim Fort

2004-01-01

357

Acetone condensation reaction on acid catalysts  

SciTech Connect

The condensation reaction of acetone on alumina and acid zeolites has been followed by FTIR. Under identical conditions, the reaction rate is faster on alumina, and the condensation goes beyond the formation of mesityl oxide. Zeolites without nonframework aluminum are poor catalysts. On HZSM-5 the reaction is about two orders of magnitude slower than on USY at 105 C. From these data, it appears that Lewis sites, even if they bound acetone less energetically than Broensted sites, are responsible for the activation of the molecule. On alumina, the reaction would take place between gas phase acetone and acetone adsorbed on Lewis sites. On zeolites with nonframework aluminum and, thus, with Lewis sites, the reaction would involve acetone molecules adsorbed on Broensted and Lewis sites, the activation occurring on the Lewis site.

Panov, A.G.; Fripiat, J.J. [Univ. of Wisconsin, Milwaukee, WI (United States)

1998-08-15

358

Microwave Irradiation and Multicomponent Reactions  

NASA Astrophysics Data System (ADS)

A common theme throughout drug discovery and process development is speed. With the emergence of combinatorial chemistry and high-speed parallel synthesis, multicomponent reactions (MCRs) have seen a resurgence of interest. MCRs are therefore becoming increasingly popular since they provide the possibility to introduce a large degree of chemical diversity in only one step! Microwave irradiation under controlled conditions has been shown to be an invaluable technology since it often allows to dramatically reduce reaction times from days or hours to minutes or even seconds. Compound libraries can be rapidly synthesized in either a parallel or sequential way using this new, enabling technology. The current chapter highlights the application of microwave irradiation for MCRs during the last 4 years. More than 110 recent literature reports have been covered.

Bariwal, Jitender B.; Trivedi, Jalpa C.; van der Eycken, Erik V.

359

Reactions of C1 Building Blocks  

NASA Astrophysics Data System (ADS)

The chapter “Reactions of C1 Building Blocks” covers the direct conversion of methane to aromatics, the methanol-to-hydrocarbons (MTHC) conversion with respect to gasoline (methanol to gasoline) and olefins (methanol to olefins, methanol-to-propene) as well as some combinations like the TIGAS and Mobil's olefin-to-gasoline and distillate processes. The main focus within this chapter will be on the industrial processes, especially concerning the MTHC reactions - including catalytic systems, reaction conditions, process - and to a minor extent related to the mechanistic aspects and kinetic considerations.

Stöcker, Michael

360

Liquid uranium reaction with coated graphite crucibles  

SciTech Connect

Carbon contamination in uranium from yttria-coated graphite crucibles containing uncoated defects has been measured at typical foundry melting conditions as a function of defect area. The reaction of liquid uranium with graphite at crucible coating defects is proportional to the defect surface area and is approx.270 times greater than the reaction at a coated region of equivalent area. Uranium carbon contamination is much more sensitive to coating defects than to furnace pressure, coating-graphite reaction, or binder outgassing. Although the typical contribution of coating defects is small, perturbations in production crucible loading or coating procedures could increase the defect area to produce uranium alloy castings with high carbon content.

Reiner, R.H.

1987-01-30

361

Beyond diusion: conditional dispersal in ecological models  

Microsoft Academic Search

Abstract Reaction-diusion,models have been widely used to describe the dynamics of dispersing populations. However, many organisms disperse in ways that depend on environmental conditions or the densities of other populations. Those can include advection along environmental gradients and nonlinear diusion, among other possibilities. In this paper I will give a survey of some models involving conditional dispersal and discuss its

Chris Cosner

362

Noncanonical Reactions of Flavoenzymes  

PubMed Central

Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates.

Sobrado, Pablo

2012-01-01

363

Ruthenium nanocatalysis on redox reactions.  

PubMed

Nanoparticles have generated intense interest over the past 20 years due to their high potential applications in different areas such as catalysis, sensors, nanoscale electronics, fuel and solar cells and optoelectronics. As the large fractions of metal atoms are exposed to the surface, the use of metal nanoparticles as nanocatalysts allows mild reaction conditions and high catalytic efficiency in a large number of chemical transformations. They have emerged as sustainable heterogeneous catalysts and catalyst supports alternative to conventional materials. This review focuses on the synthesis, characterization and catalytic role of ruthenium nanoparticles (RuNPs) on the redox reactions of heteroatom containing organic compounds with the green reagent H2O2, a field that has attracted immense interest among the chemical, materials and industrial communities. We intend to present a broad overview of Ru nanocatalysts for redox reactions with an emphasis on their performance, stability and reusability. The growth in the chemistry of organic sulfoxides and N-oxides during last decade was due to their importance as synthetic intermediates for the production of a wide range of chemically and biologically active molecules. Thus design of efficient methods for the synthesis of sulfoxides and N-oxides becomes important. This review concentrates on the catalysis of RuNPs on the H2O2 oxidation of organic sulfides to sulfoxides and amines to N-oxides. The deoxygenation reactions of sulfoxides to sulfides and reduction of nitro compounds to amines are fundamental reactions in both chemistry and biology. Here, we also highlight the catalysis of metal nanoparticles on the deoxygenation of sulfoxides and sulfones and reduction of nitro compounds with particular emphasis on the mechanistic aspects. PMID:23901501

Veerakumar, Pitchaimani; Ramdass, Arumugam; Rajagopal, Seenivasan

2013-07-01

364

The Dibenzalacetone Reaction Revisited  

NASA Astrophysics Data System (ADS)

A modification of a classic experiment is described that incorporates a discovery approach to organic synthesis. Groups of students are assigned target molecules of the dibenzalketone type and are given a sample procedure for the parent dibenzalacetone reaction. They are asked to design a synthesis of their target based on the model reaction and to modify the model reaction so it will work for their synthesis. They show they have synthesized the target with 1H NMR.

Hull, Leslie A.

2001-02-01

365

Reaction-diffusion textures  

Microsoft Academic Search

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01

366

Sleeve reaction chamber system  

DOEpatents

A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

Northrup, M. Allen (Berkeley, CA); Beeman, Barton V. (San Mateo, CA); Benett, William J. (Livermore, CA); Hadley, Dean R. (Manteca, CA); Landre, Phoebe (Livermore, CA); Lehew, Stacy L. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

2009-08-25

367

Metal-mullite reactions  

SciTech Connect

Mullite was reacted with pure Al and with Ti or Zr dissolved in Ag-Cu eutectic alloys at 1100 C in Ar. Analysis of the Ti and Zr-containing specimens showed reaction zones with compositions of Ti{sub 50}Cu{sub 3O}O{sub 20} and ZrO{sub 2}, respectively. The Al-mullite specimen showed much more extensive penetration into the ceramic and a more diffuse reaction zone than the other two systems. Al{sub 2}O{sub 3} and Si were the main reaction products for Al-mullite reaction.

Loehman, R.E. [Sandia National Labs., Albuquerque, NM (United States); Tomsia, A.P. [Pask Research and Engineering, Berkeley, CA (United States)

1993-11-01

368

Breakup Reactions of Halo Nuclei  

SciTech Connect

Different reaction mechanisms of breakup reactions are discussed and the microscopic reaction model for two-neutron halo dissociation is presented. Some examples of halo breakup in reactions with electrons, nucleons, and nuclei are given.

Ershov, S.N. [Bogolyubov Laboratory of Theoretical Physics, Joint Institute of Nuclear Research, Dubna, Moscow oblast, 141980 (Russian Federation)

2004-10-01

369

Organocatalytic asymmetric epoxidation and tandem epoxidation/Passerini reaction under eco-friendly reaction conditions.  

PubMed

An eco-friendly synthesis of highly functionalized epoxides and their incorporation into an organocatalytic multicomponent approach are reported. For this, a modified class of diarylprolinol silyl ethers was designed to enable high catalytic activity in an environmentally benign solvent system. The one-pot procedure showed great efficiency in promoting stereoselective multicomponent transformations in a tandem, 'green' fashion. Because of its non-residual, efficient and selective character, this synthetic design shows promise for large-scale applications in both diversity and target-oriented syntheses. PMID:22918441

Deobald, Anna Maria; Corrêa, Arlene G; Rivera, Daniel G; Paixão, Márcio Weber

2012-10-14

370

Temperature-compensated chemical reactions  

NASA Astrophysics Data System (ADS)

Circadian rhythms are daily oscillations in behaviors that persist in constant light/dark conditions with periods close to 24h . A striking feature of these rhythms is that their periods remain fairly constant over a wide range of physiological temperatures, a feature called temperature compensation. Although circadian rhythms have been associated with periodic oscillations in mRNA and protein levels, the question of how to construct a network of chemical reactions that is temperature compensated remains unanswered. We discuss a general framework for building such a network.

Rajan, Kanaka; Abbott, L. F.

2007-02-01

371

Fear potentiated startle at short intervals following conditioned stimulus onset during delay but not trace conditioning.  

PubMed

The latency of conditioned fear after delay and trace conditioning was investigated. Some argue that delay conditioning is not dependent on awareness. In contrast, trace conditioning, where there is a gap between the conditioned stimulus (CS) and the unconditioned stimulus (US), is assumed to be dependent on awareness. In the present study, a tone CS signaled a noise US presented 1000 ms after CS onset in the delay conditioning group. In the trace conditioning group, a 200-ms tone CS was followed by an 800-ms gap prior to US presentation. Fear-potentiated startle should be seen at shorter intervals after delay conditioning compared to trace conditioning. Analyses showed increased startle at 30, 50, 100, and 150 ms after CS onset following delay conditioning compared to trace conditioning. This implies that fear-relevant stimuli elicit physiological reactions before extended processing of the stimuli occur, following delay, but not trace conditioning. PMID:19386051

Asli, Ole; Kulvedrøsten, Silje; Solbakken, Line E; Flaten, Magne Arve

2009-04-06

372

Chemical Reaction Problem Solving.  

ERIC Educational Resources Information Center

|Discusses the role of chemical-equation problem solving in helping students predict reaction products. Methods for helping students learn this process must be taught to students and future teachers by using pedagogical skills within the content of chemistry. Emphasizes that solving chemical reactions should involve creative cognition where…

Veal, William

1999-01-01

373

Applications of Reaction Rate  

ERIC Educational Resources Information Center

|This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why…

Cunningham, Kevin

2007-01-01

374

Clock Reaction: Outreach Attraction  

ERIC Educational Resources Information Center

|Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

2010-01-01

375

Emotional reactions to infidelity  

Microsoft Academic Search

We sought to identify emotional reactions to a partner's sexual infidelity and emotional infidelity. In a preliminary study, 53 participants nominated emotional reactions to a partner's sexual and emotional infidelity. In a second study, 655 participants rated each emotion for how likely it was to occur following sexual and emotional infidelity. Principal components analysis revealed 15 emotion components, including Hostile\\/Vengeful,

Todd K. Shackelford; Gregory J. LeBlanc; Elizabeth Drass

2000-01-01

376

Applications of Reaction Rate  

ERIC Educational Resources Information Center

This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

Cunningham, Kevin

2007-01-01

377

Nonadiabatic chemical reactions  

Microsoft Academic Search

A mixed quantum-classical approach where the environment is treated classically and the reactive degrees of freedom are considered to be quantum mechanical can be used to describe many chemical reactions, such as proton and electron transfer processes. We present reactive flux correlation function expressions for the rate constants of nonadiabatic chemical reactions occurring in quantum-classical systems. By means of a

Alessandro Sergi; Raymond Kapral

2005-01-01

378

Surface catalyzed mercury transformation reactions  

NASA Astrophysics Data System (ADS)

Mercury is a known pollutant that has detrimental effect on human health and environment. The anthropogenic emissions of mercury account for 10 to 30% of worldwide mercury emissions. There is a need to control/reduce anthropogenic mercury emissions. Many mercury control technologies are available but their effectiveness is dependent on the chemical form of mercury, because different chemical forms of mercury have different physical and chemical properties. Mercury leaves the boiler in its elemental form but goes through various transformations in the post-combustion zone. There is a need to understand how fly ash and flue gas composition affect speciation, partitioning, and reactions of mercury under the full range of post-combustion zone conditions. This knowledge can then be used to predict the chemical transformation of mercury (elemental, oxidized or particulate) in the post combustion zone and thus help with the control of mercury emissions from coal-burning power plants. To accomplish this goal present study was conducted using five coal fly ashes. These ashes were characterized and their catalytic activity was compared under selected reaction conditions in a fixed bed reactor. Based on the results from these fly ash experiments, three key components (carbon, iron oxide and calcium oxide) were chosen. These three components were then used to prepare model fly ashes. Silica/alumina was used as a base for these model fly ashes. One, two or three component model fly ashes were then prepared to investigate mercury transformation reactions. The third set of experiments was performed with five different oxidation catalysts to further understand the mercury oxidation process. Based on the results of these three studies the key components were predicted for different fly ash compositions under variety of flue gas conditions. A fixed bed reactor system was used to conduct this study. In all the experiments, the inlet concentration of Hg0(g) was maintained at 35 mug/m 3 using a diffusion tube as the source of Hg0(g). All experiments were conducted using 4% O2 in nitrogen mix as a reaction gas, and other reactants (HCl, H2O and SO2, NO 2, Br2) were added as required. The fixed bed reactor was operated over a temperature range of 200 to 400°C. In each experiment, the reactor effluent was analyzed using the modified Ontario-Hydro method. After each experiment, fly ash particles were also analyzed for mercury. The results show that the ability of fly ash to adsorb and/or oxidize mercury is primarily dependent on its carbon, iron and calcium content. There can be either one or more than one key component at a particular temperature and flue gas condition. Surface area played a secondary role in effecting the mercury transformations when compared to the concentration of the key component in the fly ash. Amount carbon and surface area played a key important role in the adsorption of mercury. Increased concentration of gases in the flue gas other than oxygen and nitrogen caused decreased the amount of mercury adsorbed on carbon surface. Mercury adsorption by iron oxide primarily depended on the crystalline structure of iron oxide. alpha-iron oxide had no effect on mercury adsorption or oxidation under most of the flue gas conditions, but gamma-iron oxide adsorbed mercury under most of the flue gas conditions. Bromine is a very good oxidizing agent for mercury. But in the presence of calcium oxide containing fly ashes, all the oxidized mercury would be reduced to elemental form. Among the catalysts, it was observed that presence of free lattice chlorine in the catalyst was very important for the oxidation of mercury. But instead of using the catalyst alone, using it along with carbon may better serve the purpose by providing the adsorption surface for mercury and also some extra surface area for the reaction to occur (especially for fly ashes with low surface area).

Varanasi, Patanjali

379

Controlling diastereoselectivity in the reactions of enantiomerically pure alpha-bromoacyl-imidazolidinones with nitrogen nucleophiles: substitution reactions with retention or inversion of configuration.  

PubMed

Diastereoselective substitution reactions of [small alpha]-bromoacyl-imidazolidinones with nitrogen nucleophiles can be promoted with either retention or inversion of configuration by carrying out reactions under epimerising or non-epimerising conditions. PMID:15795770

Treweeke, N R; Hitchcock, P B; Pardoe, D A; Caddick, S

2005-02-08

380

Modeling of surface reactions  

SciTech Connect

Mathematical models are used to elucidate properties of the monomer-monomer and monomer-dimer type chemical reactions on a two-dimensional surface. The authors use mean-field and lattice gas models, detailing similarities and differences due to correlations in the lattice gas model. The monomer-monomer, or AB surface reaction model, with no diffusion, is investigated for various reaction rates k. Study of the exact rate equations reveals that poisoning always occurs if the adsorption rates of the reactants are unequal. If the adsorption rates of the reactants are equal, simulations show slow poisoning, associated with clustering of reactants. This behavior is also shown for the two-dimensional voter model. The authors analyze precisely the slow poisoning kinetics by an analytic treatment for the AB reaction with infinitesimal reaction rate, and by direct comparison with the voter model. They extend the results to incorporate the effects of place-exchange diffusion, and they compare the AB reaction with infinitesimal reaction rate and no diffusion to the voter model with diffusion at rate 1/2. They also consider the relationship of the voter model to the monomer-dimer model, and investigate the latter model for small reaction rates. The monomer-dimer, or AB[sub 2] surface reaction model is also investigated. Specifically, they consider the ZGB-model for CO-oxidation, and in generalizations of this model which include adspecies diffusion. A theory of nucleation to describe properties of non-equilibrium first-order transitions, specifically the evolution between [open quote]reactive[close quote] steady states and trivial adsorbing states, is derived. The behavior of the [open quote]epidemic[close quote] survival probability, P[sub s], for a non-poisoned patch surrounded by a poisoned background is determined below the poisoning transition.

Ray, T.R.

1993-01-01

381

Microwave assisted reactions of some azaheterocylic compounds.  

PubMed

A fast, general, environmentally friendly and facile method for preparation of five- and six-membered ring diazaheterocylic salts under microwave irradiation is presented. The N-alkylation reactions of imidazole, pyrimidine, pyridazine and phthalazine have been studied. The microwaves remarkably accelerated these N-alkylations, the reaction times decreased dramatically, the reaction conditions were milder, the consumed energy decreased considerably and the amount of solvents used was reduced substantially. Consequently, the microwave assisted alkylation of N-containing heterocycles could be considered eco-friendly. In some cases, under MW irradiation the yields are also higher. A comparative study of microwave vs. classical conditions (liquid solvents) has been done. Twelve new diazaheterocylic salts of potential practical interest were obtained. PMID:19145217

Zbancioc, Gheorghita; Bejan, Vasilichia; Risca, Marian; Moldoveanu, Costel; Mangalagiu, Ionel I

2009-01-15

382

Reaction Rate Calculations in Dense Stellar Matter  

NASA Astrophysics Data System (ADS)

Pycnonuclear fusion processes take place in the extreme density conditions anticipated to exist in the cores of white dwarfs and the crusts of neutron stars. Accurate modelling of pycnonuclear reactions is essential for understanding energy generation and transport in neutron stars. Calculation of pycnonuclear fusion rates strongly relies on knowledge of reaction cross sections. In most cases relevant cross section data is not availble and as such, cross section models must be used that are validated when ever possible by experimental measurements. Recently a formalism for calculating pycnonuclear reactions was developed for isotopes between boron and silicon. The pycnonuclear reaction rates will be presented and the results of the nucleosynthesis simulations will be discussed. This work was supported by the Joint Institute for Nuclear Astrophysics (NSF-PHY-0822648).

Beard, Mary; Brown, E.; Gasques, L.; Lau, R.; Schatz, H.; Wiescher, M.; Yakovlev, D.

2012-05-01

383

NEUTRONIC REACTION SYSTEM  

DOEpatents

A nuclear reactor system is described for breeding fissionable material, including a heat-exchange tank, a high- and a low-pressure chamber therein, heat- exchange tubes connecting these chambers, a solution of U/sup 233/ in heavy water in a reaction container within the tank, a slurry of thorium dioxide in heavy water in a second container surrounding the first container, an inlet conduit including a pump connecting the low pressure chamber to the reaction container, an outlet conduit connecting the high pressure chamber to the reaction container, and means of removing gaseous fission products released in both chambers. (AEC)

Wigner, E.P.

1963-09-01

384

[Abnormal pupils' reactions].  

PubMed

Examination of the pupils' light reaction and estimation of the pupils' diameter are the components of the routine physical examination of a patient. Disturbances in pupils' light reaction, unequal size of the pupils indicate damage of the nervous system and require careful diagnosis, both neurological and ophthalmological. Different aspects of anatomy, physiology and the most common pathological syndromes associated with disturbed pupils' light reaction and unequal diameters of the pupils were presented in the article. Early diagnosis and proper treatment can allow to improve prognosis in the analyzed patient group. PMID:20825073

Kowal, Joanna; Strza?ka, Anna; Kubicka-Trzaska, Agnieszka; Romanowska-Dixon, Bozena

2010-01-01

385

Maillard reaction products inhibit apple polyphenoloxidase  

Microsoft Academic Search

The effects of Maillard reaction products (MRP) on apple polyphenol oxidase (PPO) were evaluated spectrophotometrically at 400 nm after oxidation of 4-methylcatechol. MRP, synthesized under different conditions including heating time, type of amino acids, pH and concentration of both amino acid and glucose, showed different effects on apple PPO. The inhibitory effects of MRP. heated for 7 h at 90

B. K. Tan; N. D. Harris

1995-01-01

386

The reaction rate in nuclear fusion  

Microsoft Academic Search

Summary  A method to evaluate the reaction rate in nuclear fusion is proposed. This method is obtained in the framework of the elastic\\u000a model for subbarrier fusion. Conditions for the validity of the method are given. Some examples are discussed.

A. Scalia

1988-01-01

387

Hydrothermal reaction of fly ash. Final report  

Microsoft Academic Search

The reactions which occur when fly ash is treated under hydrothermal conditions were investigated. This was done for the following primary reasons. The first of these is to determine the nature of the phases that form to assess the stabilities of these phases in the ambient environment and, finally, to assess whether these phases are capable of sequestering hazardous species.

1994-01-01

388

Recent studies of simple reaction time  

Microsoft Academic Search

An assessment is made of the current scientific status of simple reaction time (RT), based primarily on a literature review of the last 20 years. Considered are the effects on RT of stimulus-receptor factors, of central and motor factors, and of special factors such as prolonged readiness, certain common drugs, temperature, sleep conditions, etc. While further research probing is indicated,

Warren H. Teichner

1954-01-01

389

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping  

PubMed Central

Summary A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels–Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions.

Stockinger, Skrollan

2013-01-01

390

A Comparison of Bimolecular Reaction Models for Stochastic Reaction-Diffusion Systems.  

PubMed

Stochastic reaction-diffusion models have become an important tool in studying how both noise in the chemical reaction process and the spatial movement of molecules influences the behavior of biological systems. There are two primary spatially-continuous models that have been used in recent studies: the diffusion limited reaction model of Smoluchowski, and a second approach popularized by Doi. Both models treat molecules as points undergoing Brownian motion. The former represents chemical reactions between two reactants through the use of reactive boundary conditions, with two molecules reacting instantly upon reaching a fixed separation (called the reaction-radius). The Doi model uses reaction potentials, whereby two molecules react with a fixed probability per unit time, ?, when separated by less than the reaction radius. In this work, we study the rigorous relationship between the two models. For the special case of a protein diffusing to a fixed DNA binding site, we prove that the solution to the Doi model converges to the solution of the Smoluchowski model as ???, with a rigorous [Formula: see text] error bound (for any fixed ?>0). We investigate by numerical simulation, for biologically relevant parameter values, the difference between the solutions and associated reaction time statistics of the two models. As the reaction-radius is decreased, for sufficiently large but fixed values of ?, these differences are found to increase like the inverse of the binding radius. PMID:23579988

Agbanusi, I C; Isaacson, S A

2013-04-12

391

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping.  

PubMed

A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels-Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions. PMID:24062850

Stockinger, Skrollan; Trapp, Oliver

2013-09-10

392

Explosive reactions produced by spark ignition on mixtures of fluorine with fluorocarbons and chlorofluorocarbons. [Trichloroheptafluorobutane; perfluorodimethylcyclohexane  

Microsoft Academic Search

Conditions exist for an explosive reaction whenever a mixture is formed from two or more gases which are thermodynamically unstable toward their gaseous reaction products. Reaction under these conditions may be triggered by a localized electric discharge or thermally by elevation of the gas temperature above the adiabatic combustion temperature of the gas mixture. Once initiated, the flame propagates in

H. A. Bernhardt; C. F. Hale; E. J. Barber

1968-01-01

393

Characterisation of micromixing efficiency by the iodide–iodate reaction system. Part II: kinetic study  

Microsoft Academic Search

In a previous paper (Part I), the operating conditions of the iodide–iodate reaction system used to quantify micromixing phenomena in chemical reactors and mixers has been presented. In order to determine the micromixing time through models, the complete kinetics of the reactions must be known. This paper presents the kinetics of the Dushman reaction obtained in operating conditions close to

Pierrette Guichardon; Laurent Falk; Jacques Villermaux

2000-01-01

394

Laccase-generated quinones in naphthoquinone synthesis via Diels–Alder reaction  

Microsoft Academic Search

The tandem synthesis of naphthoquinones was conducted from the reaction of laccase-generated quinones and acyclic dienes via Diels–Alder reaction. This reaction was carried out under mild condition in aqueous medium and yielded naphthoquinones up to 80%. In addition, the effect of solvent was also investigated and water was shown to be optimal for this reaction.

Suteera Witayakran; Abdullah Zettili; Arthur J. Ragauskas

2007-01-01

395

Diseases and Conditions  

MedlinePLUS

... Diseases & Conditions Health & Wellness Studies & Data Patient Treatment Employee Health About Us Site Search Diseases & Conditions Home ... Diseases & Conditions Health & Wellness Studies & Data Patient Treatment Employee Health About You are here: Home » Diseases & Conditions ...

396

Gold-based catalysts for the water–gas shift reaction: Active sites and reaction mechanism  

Microsoft Academic Search

The water–gas shift (WGS, CO+H2O?H2+CO2) reaction was studied on a series of gold\\/oxide catalysts. The results of in situ measurements with X-ray absorption spectroscopy indicate that the active phase of Au-ceria and Au-titania catalysts under the reaction conditions of the water–gas shift consists of metallic nanoparticles of gold on a partially reduced oxide support. In spite of the lack of

José A. Rodriguez

2011-01-01

397

An Illuminating Reaction.  

ERIC Educational Resources Information Center

|Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)|

Matthews, Catherine E.

1996-01-01

398

TALYS: Nuclear Reaction Simulator  

NASA Astrophysics Data System (ADS)

TALYS is a nuclear reaction code that estimates the Maxwellian-averaged reaction rates that are of astrophysical relevance. This enables reaction rates to be calculated with increased accuracy and reliability and the approximations of previous codes to be investigated. The TALYS predictions for the thermonuclear rates of relevance to astrophysics are detailed and compared with those derived by widely-used codes for the same nuclear ingredients. TALYS predictions may differ significantly from those of previous codes, in particular for nuclei for which no or little nuclear data is available. The pre-equilibrium process is shown to influence the astrophysics rates of exotic neutron-rich nuclei significantly. The TALYS code provides a tool to estimate all nuclear reaction rates of relevance to astrophysics with improved accuracy and reliability.

Koning, Arjan; Hilaire, Stephane; Duijvestijn, Marieke

2012-02-01

399

Chemical reaction on polysaccharides  

Microsoft Academic Search

The article discusses the synthesis of pullulan derivatives containing chloroalkyl groups by the reaction of crosslinked pullulan microparticles with different chloroalkyl chlorides in organic basic solvents. These new products may allow the attachment of various bioactive compounds by covalent bonding.

G Mocanu; D Vizitiu; D Mihai; A Carpov

1999-01-01

400

Response reactions: equilibrium coupling.  

PubMed

It is pointed out and illustrated in the present paper that if a homogeneous multiple equilibrium system containing k components and q species is composed of the reactants actually taken and their reactions contain only k + 1 species, then we have a unique representation with (q - k) stoichiometrically independent reactions (SIRs). We define these as coupling reactions. All the other possible combinations with k + 1 species are the coupled reactions that are in equilibrium when the (q - k) SIRs are in equilibrium. The response of the equilibrium state for perturbation is determined by the coupling and coupled equilibria. Depending on the circumstances and the actual thermodynamic data, the effect of coupled equilibria may overtake the effect of the coupling ones, leading to phenomena that are in apparent contradiction with Le Chatelier's principle. PMID:16722770

Hoffmann, Eufrozina A; Nagypal, Istvan

2006-06-01

401

Adverse reactions to sulfites  

PubMed Central

Sulfites are widely used as preservatives in the food and pharmaceutical industries. In the United States more than 250 cases of sulfite-related adverse reactions, including anaphylactic shock, asthmatic attacks, urticaria and angioedema, nausea, abdominal pain and diarrhea, seizures and death, have been reported, including 6 deaths allegedly associated with restaurant food containing sulfites. In Canada 10 sulfite-related adverse reactions have been documented, and 1 death suspected to be sulfite-related has occurred. The exact mechanism of sulfite-induced reactions is unknown. Practising physicians should be aware of the clinical manifestations of sulfite-related adverse reactions as well as which foods and pharmaceuticals contain sulfites. Cases should be reported to health officials and proper advice given to the victims to prevent further exposure to sulfites. The food industry, including beer and wine manufacturers, and the pharmaceutical industry should consider using alternative preservatives. In the interim, they should list any sulfites in their products.

Yang, William H.; Purchase, Emerson C.R.

1985-01-01

402

Common Reactions After Trauma  

MedlinePLUS

... trauma? All kinds of trauma survivors commonly experience stress reactions. This is true for veterans, children, and disaster rescue or relief workers. If you understand what is happening when ...

403

Untoward penicillin reactions  

PubMed Central

The literature on untoward reactions following the administration of penicillin is reviewed. These reactions, including a certain number of deaths which have been reported, are of particular interest to health administrations and to WHO in view of the large-scale programmes for controlling the treponematoses which are now under way—programmes affecting millions of people in many parts of the world. The most serious problems are anaphylactic sensitivity phenomena and superinfection or cross-infection with penicillin-resistant organisms, and the reactions involved range in intensity from the mildest to the fatal; the incidence of the latter is estimated at 0.1-0.3 per million injections. The authors point out that with increasing use of penicillin, more persons are likely to become sensitized and the number of reactions can therefore be expected to rise. The best prevention against such an increase is the restriction of the unnecessary use of penicillin.

Guthe, T.; Idsoe, O.; Willcox, R. R.

1958-01-01

404

Skin Reactions to Cold  

PubMed Central

Although skin reactions to cold are seen surprisingly infrequently in Canada, it is important to manage them correctly when they do occur. Frostbite, cold urticarias, Raynaud's disease and phenomenon, and several miscellaneous changes are discussed.

Talpash, Orest

1976-01-01

405

Bad Reaction to Cosmetics?  

MedlinePLUS

... Tobacco Products Vaccines, Blood & Biologics Bad Reaction to Cosmetics? Tell FDA Search the Consumer Updates Section Lash ... M.D., director of the agency’s Office of Cosmetics and Colors. “So, consumers are one of FDA’s ...

406

Reactor for exothermic reactions  

DOEpatents

A liquid phase process is described for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

Smith, L.A. Jr.; Hearn, D.; Jones, E.M. Jr.

1993-03-02

407

Reactor for exothermic reactions  

DOEpatents

A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.

Smith, Jr., Lawrence A. (Bellaire, TX); Hearn, Dennis (Houston, TX); Jones, Jr., Edward M. (Friendswood, TX)

1993-01-01

408

Polyatomic Reaction Dynamics.  

National Technical Information Service (NTIS)

It is difficult to study the reaction dynamics of polyatomic systems. One of the principal problems is the calculation of the Born-Oppenheimer potential energy surface. In this thesis several useful approximations to the full potential energy surface are ...

T. Carrington

1985-01-01

409

An Illuminating Reaction.  

ERIC Educational Resources Information Center

Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)

Matthews, Catherine E.

1996-01-01

410

Iodine Clock Reaction.  

ERIC Educational Resources Information Center

|Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)|

Mitchell, Richard S.

1996-01-01

411

Suspected adverse reactions, 2008  

Microsoft Academic Search

Reports to the UK Suspected Adverse Reaction Surveillance Scheme (SARSS) in 2008 increase by around 11 per cent compared with 2007Low incidence of suspected adverse reactions following bluetongue virus vaccinationIncrease in reports of suspected lack of efficacy to canine parvovirus vaccinationRabbit deaths reported after off-label use of dexmedetomidineThese are some of the results from the SARSS in 2008, as discussed

F. Dyer; E. Brown; S. Cooles; A. Tait

2009-01-01

412

Ligase Chain Reaction  

Microsoft Academic Search

\\u000a Nucleic acid amplification technologies have greatly facilitated medical diagnostics for genetic and infectious diseases through\\u000a the exquisite sensitivity and specificity associated with these methods. Polymerase chain reaction (PCR) (see\\u000a Chapter 6) ushered in these technologies and was soon accompanied by numerous newly developed amplification techniques, including\\u000a ligase chain reaction (LCR). These nucleic acid amplification techniques result in the exponential increase

Carla Osiowy

413

Adverse reaction to tetrazepam.  

PubMed

Adverse reactions caused by benzodiazepines rarely occur. We present a case of a 70-year-old man who developed a maculopapular exanthema after the ingestion of tetrazepam. For his diagnosis, skin tests were performed, including prick and patch tests, not only with the benzodiazepine implicated in the reaction, but also with benzodiazepines of other groups. Single-blind oral challenge tests were also performed in the patient, in order to assess his tolerance to other benzodiazepines. PMID:11642573

Palacios Benito, R; Domínguez Ortega, J; Alonso Llamazares, A; Rodríguez Morales, A; Plaza Díaz, A; Chamorro Gómez, M; Martínez-Cócera, C

2001-01-01

414

Jets in hadronic reactions  

SciTech Connect

Recent experimental data on the properties of jets in hadronic reactions are reviewed and compared with theoretical expectations. Jets are clearly established as the dominant process for high E/sub T/ events in hadronic reactions. The cross section and the other properties of these events are in qualitative and even semiquantitative agreement with expectations based on perturbative QCD. However, we can not yet make precise tests of QCD, primarily because there are substantial uncertainties in the theoretical calculations. 45 references. (WHK)

Paige, F.E.

1983-01-01

415

Reactions of cresol in hot aqueous borate solutions  

SciTech Connect

Phenol and methylphenol (cresol) are constituents of certain waste streams being considered for underground injection. We studied reactions of these compounds in solutions with other constituents of the waste streams and suspended clay at concentrations and temperatures higher than expected in natural situations, i.e. at 200{degrees}C and 250{degrees}C. Under these conditions, the predominant reaction was the demethylation of cresol to form phenol. This reaction was catalyzed strongly by clay. We were able to quantify phenol production. Other important reactions were a variety of condensation reactions in which two cresol molecules fuse. We found evidence of the intermolecular migration of methyl groups from the molecular weights of some of these condensation reactions. By digesting a sample of reacted clay with hydrofluoric acid we determined that under these conditions phenol and cresol did not bind appreciably to clay but that the condensation products did.

Tsao, L. [Lawrence Berkeley Lab., CA (United States); Weres, O. [Sonoma Research Co., Vineburg, CA (United States)

1992-04-01

416

Characterization of the Maillard reaction in bread crisps  

Microsoft Academic Search

Maillard reaction (MR) is one of the main chemical event occurring during baking. To study the reaction in bakery products,\\u000a a dry model system is more useful than an aqueous one. In this work, the effects of formulation and processing conditions\\u000a in a crisp bread system were investigated to test the effects of different additives on both the overall reaction

Edoardo Capuano; Antonella Ferrigno; Iolanda Acampa; Lamia Ait-Ameur; Vincenzo Fogliano

2008-01-01

417

Ultrasound assisted reactions of steroid analogous of anticipated biological activities.  

PubMed

A new, fast, efficient and general method for preparation of steroid analogous of anticipated biological activity under ultrasound irradiation and classical heating is reported. The reaction pathway involves two steps: quaternization of phthalazine heterocycle followed by a 3+2 dipolar cycloaddition of cycloimmonium ylides to dienophiles. Under ultrasound the reaction time decreases substantially, the yields are higher, the reaction conditions are milder. A comparative study ultrasound verses classical heating has been done. PMID:19081283

Bejan, Vasilichia; Moldoveanu, Costel; Mangalagiu, Ionel I

2008-11-05

418

New Chemical Analysis Methods Based on Redox Reactions Coupled with Chemiluminescence Measurements,  

National Technical Information Service (NTIS)

The fundamental chemistry of gold-catalyzed oxidation/reduction reactions of organic and inorganic compounds with nitrogen dioxide and nitric acid has been studied to better understand the surface chemistry, effects of reaction conditions, catalyst config...

R. S. Hutte

1985-01-01

419

Eco-friendly polyethylene glycol promoted Michael addition reactions of α,β-unsaturated carbonyl compounds  

EPA Science Inventory

Abstract- Intra- and inter-nucleophilic addition reactions of different unsaturated compounds were found to be highly effective without any additives in PEG-400 as a recyclable reaction medium under neutral conditions. ...

420

Transfer reactions with HELIOS  

NASA Astrophysics Data System (ADS)

Nucleon-transfer reactions have formed the backbone of nuclear- structure studies for several decades, providing a wealth of information about the energies, quantum numbers, and wave functions of single-particle states in nuclei throughout the nuclear chart. Current trends in nuclear-structure physics and the modern emphasis on properties of neutron-rich nuclei far from stability have renewed interest in such transfer reactions with radioactive beams. Here, the usual combination of light beam and heavy target cannot be used, and measurements must be performed in "inverse kinematics," with a heavy, unstable beam incident on a light target. This arrangement introduces several technical difficulties, including the identification of the reaction products and the resolution of the states of interest in the residual nuclei. A new device, HELIOS (the HELIcal Orbit Spectrometer) at the ATLAS facility at Argonne National Laboratory, solves many of the problems encountered with inverse kinematics including particle identification and energy resolution in the center-of-mass frame. The device utilizes the uniform magnetic field of a large, superconducting solenoid to transport light reaction products from the target to a linear array of position-sensitive silicon detectors. The properties of HELIOS will be described, and examples from the initial research program that focuses on neutron transfer with the (d,p) reaction, using both stable and unstable beams with mass A=11 to 136, will be presented.

Wuosmaa, Alan H.

2011-04-01

421

Aspects and Reaction Rates for Pycnonuclear Fusion at High Densities  

Microsoft Academic Search

Pycnonuclear reactions are of great importance in the nuclear astrophysics of high density conditions such as the centers of white dwarf starts, and the deep layers of accreting neutron stars. We present here a single phenomenological expression for the calculation of pycnonuclear reaction rates which is not only valid in mixed component plasma, but can also be extended to cover

Mary Beard; Michael Wiescher; Anatoli Afanasjev; Leandro Gasques; Dima Yakovlev

2008-01-01

422

Chemical reactions of organic compounds on clay surfaces  

SciTech Connect

Chemical reactions of organic compounds including pesticides at the interlayer and exterior surfaces of clay minerals and with soil organic matter are reviewed. Representative reactions under moderate conditions possibly occurring in natural soils are described. Attempts have been made to clarify the importance of the chemical nature of molecules, their structures and their functional groups, and the Broensted or Lewis acidity of clay minerals.

Soma, Yuko; Soma, Mitsuyuki (National Institute for Environmental Studies, Ibaraki (Japan))

1989-11-01

423

Change experience and employee reactions: developing capabilities for change  

Microsoft Academic Search

Purpose – The purpose of this paper is to explore how experience with organizational change influences employees' reactions to change. While exposure to an increasingly frequent organizational change can lead to change fatigue and cynicism, it can also generate more positive reactions to change. The authors identify experience-based change capabilities and explore conditions for developing such capabilities. Design\\/methodology\\/approach – The

Inger G. Stensaker; Christine B. Meyer

2012-01-01

424

Chemical reactions of organic compounds on clay surfaces.  

PubMed Central

Chemical reactions of organic compounds including pesticides at the interlayer and exterior surfaces of clay minerals and with soil organic matter are reviewed. Representative reactions under moderate conditions possibly occurring in natural soils are described. Attempts have been made to clarify the importance of the chemical nature of molecules, their structures and their functional groups, and the Brönsted or Lewis acidity of clay minerals.

Soma, Y; Soma, M

1989-01-01

425

Application of the Le Chatelier principle on gas reactions  

Microsoft Academic Search

Le Chatelier's principle has been the subject of much discussion and controversy because it sometimes seems to give the wrong predictions. A classic example is the ammonia gas reaction. The principle is now re-examined, starting from a strict and general derivation given recently. A chemical reaction in a gas mixture is then considered and the conditions are derived under which

Zi-Kui Liu; John Ågren; Mats Hillert

1996-01-01

426

N-acyl oxazolidin-2-selones promoted aldol reactions  

SciTech Connect

Selenocarbonyls that are housed in a chiral environment have been found to play a pivotal role aldol reactions. We have found that, in general,, the aldol reaction affords the non-Evans aldol syn products. However, the use of glycolate donors with glycoaldehydes, under proper conditions, gave rise to predominately the anti aldol.

Li, Zizhong; Wu, R. (Ruilian); Silks, L. A. (Louis A.), III; Michalczyk, R. (Ryszard)

2001-01-01

427

Adventures in Gold-Catalyzed Cascade Reactions and Rearrangements  

Microsoft Academic Search

Gold-catalyzed organic transformations have been a hot topic of research in synthetic organic community over the last few years. Amazingly, most of the reactions can be performed under mild conditions using a catalytic amount of gold complexes. One of the widely reported reactions using gold catalysts is heterocyclization that involves an activation of a pi-system followed by a nucleophilic attack

Dinesh Vinod Vidhani

2010-01-01

428

Reaction time behavior after caffeine and coffee consumption  

Microsoft Academic Search

Five female subjects possessing equal normal (established normal) reaction time, equal age, height and weight were used in this investigation. Each subject was habituated to one cup of coffee per day prior to the experimental period. By means of Metfessel's psychodometer the reaction time of each subject was studied under normal, caffeine-treated, coffee-treated, and capsulated starch control conditions. Results show

R. H. Cheney

1936-01-01

429

Coordinated Studies of Platelet and Protein Reactions on Artificial Materials.  

National Technical Information Service (NTIS)

Coordinated studies of platelet and protein reactions on artificial materials were studied with emphasis on protein adsorption and platelet adhesion under dynamic conditions generated by spinning discs of test materials in pools of protein solution or blo...

E. F. Leonard S. Kochwa R. Litwak R. Rosenfield M. Lauren

1976-01-01

430

Solid-phase tandem radical addition-cyclization reaction: triethylborane-induced reaction of oxime ethers anchored to polymer support.  

PubMed

Tandem radical addition-cyclization of oxime ethers anchored to polymer support was studied. The reaction of oxime ethers with stannyl radical proceeded effectively by the use of triethylborane as a radical initiator. The alkyl radical addition-cyclization reactions of oxime ether connected with alpha,beta-unsaturated carbonyl group proceeded under iodine atom-transfer reaction conditions to give the functionalized azacycles via two carbon-carbon bonds-forming process. PMID:15256705

Miyabe, Hideto; Tanaka, Hirotaka; Naito, Takeaki

2004-07-01

431

Effect of inclusion complex on nitrous acid reaction with flavonoids  

NASA Astrophysics Data System (ADS)

The kinetic of the nitrous acid reactions with quercetin and catechin has been studied using spectrophotometric method in aqueous solution. The results show that these antioxidants participate in oxidation reactions with nitrous acid which is derived from protonation of nitrite ion in mild acidic conditions. Corresponding o-quinones as relatively stable products were detected by spectrophotometric techniques. pH dependence of the reactions has been examined and the rate constants of reactions were obtained by non-linear fitting of kinetic profiles. The effect of ?-cyclodextrin on the oxidation pathway was another object of this study. It is shown that ?-cyclodextrin has an inhibitory effect on the oxidation reaction. The rate constants of oxidation reactions for complexed forms and their stability constants were obtained based on changes in the reaction rates as a function of ?-cyclodextrin concentration.

Khalafi, Lida; Rafiee, Mohammad; Sedaghat, Sajjad

2011-10-01

432

Reaction kinetics of hydrothermal carbonization of loblolly pine.  

PubMed

Hydrothermal carbonization (HTC) is a pretreatment process to convert diverse feedstocks to homogeneous energy-dense solid fuels. Understanding of reaction kinetics is necessary for reactor design and optimization. In this study, the reaction kinetics and effects of particle size on HTC were investigated. Experiments were conducted in a novel two-chamber reactor maintaining isothermal conditions for 15s to 30 min reaction times. Loblolly pine was treated at 200, 230, and 260°C. During the first few minutes of reaction, the solid-product mass yield decreases rapidly while the calorific value increases rapidly. A simple reaction mechanism is proposed and validated, in which both hemicellulose and cellulose degrade in parallel first-order reactions. Activation energy of hemicellulose and cellulose degradation were determined to be 30 and 73 kJ/mol, respectively. For short HTC times, both reaction and diffusion effects were observed. PMID:23651600

Reza, M Toufiq; Yan, Wei; Uddin, M Helal; Lynam, Joan G; Hoekman, S Kent; Coronella, Charles J; Vásquez, Victor R

2013-04-15

433

Conditional Deduction Under Uncertainty  

Microsoft Academic Search

Conditional deduction in binary logic basically consists of deriving new statements from an existing set of statements and conditional rules. Modus Ponens, which is the classical example of a conditional deduction rule, expresses a conditional relationship between an antecedent and a consequent. A generali- sation of Modus Ponens to probabilities in the form of probabilistic conditional inference is also well

Audun Jøsang; Simon Pope; Milan Daniel

2005-01-01

434

Turing instability in reaction-subdiffusion systems  

NASA Astrophysics Data System (ADS)

We determine the conditions for the occurrence of Turing instabilities in activator-inhibitor systems, where one component undergoes subdiffusion and the other normal diffusion. If the subdiffusing species has a nonlinear death rate, then coupling between the nonlinear kinetics and the memory effects of the non-Markovian transport process advances the Turing instability if the inhibitor subdiffuses and delays the Turing instability if the activator subdiffuses. We apply the results of our analysis to the Schnakenberg model, the Gray-Scott model, the Oregonator model of the Belousov-Zhabotinsky reaction, and the Lengyel-Epstein model of the chlorine dioxide-iodine-malonic acid reaction.

Yadav, A.; Milu, Shane M.; Horsthemke, Werner

2008-08-01

435

Positron Reaction Microscope  

NASA Astrophysics Data System (ADS)

We are developing a positron reaction microscope to measure kinematically complete ionization reactions of atoms and dissociative ionization of simple molecules by positron impact. The experiment is designed to use the slow positron beamline at the ARC Centre for Antimatter Matter Studies (CAMS) node at the Australian National University (ANU). This project is a collaboration among the University of North Texas, CAMS, and the Max Planck Insitute for Kern Phyzik in Heidelberg. Initial measurements and apparatus calibration will be performed using electrons. For positron measurements, the apparatus will be rolled into position on the slow positron beamline at the CAMS site at ANU.

Mueller, Dennis; Armitage, Simon; Vermet, Corbin; Lee, Chistopher; Dorn, Alexander; Buckman, Stephen; Sullivan, James

2012-10-01

436

Foreign Media Reaction  

NSDL National Science Digital Library

This Daily Digest of foreign media reaction, prepared Monday through Friday by the United States Information Agency, is a valuable addition to any course that discusses US foreign policy or current events. "Each Digest provides a global round-up of editorial and op-ed reaction to a major foreign policy issue or event. The reports include commentary--sorted by country and region--from major newspapers, magazines and broadcast media around the world." The searchable archive section contains all Daily Digests published since November 1994.

Agency., United S.

1994-01-01

437

Velocity pump reaction turbine  

DOEpatents

An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

House, Palmer A. (Walnut Creek, CA)

1984-01-01

438

Velocity pump reaction turbine  

DOEpatents

An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

House, Palmer A. (Walnut Creek, CA)

1982-01-01

439

Surface aligned reaction  

NASA Astrophysics Data System (ADS)

This paper reflects on three decades during which the study of surface aligned reaction (SAR) has advanced. The objective in SAR, which in considerable part still lies ahead, is the simultaneous control of atomic and molecular ``collision energies, collision angles, and impact parameter.'' Following a discussion of the benefits of such an approach we review the progress made, and, as a stimulus to experiment, present new calculations of SAR dynamics for bimolecular reaction at a metal surface. It seems reasonable to suppose that we are now entering a decade in which a combination of scanning tunneling microscopy and femtosecond laser spectroscopy will bring the full realisation of SAR.

Ning, Zhanyu; Polanyi, John C.

2012-09-01

440

Clay and acid catalysed isomerisation and cyclisation reactions of highly branched isoprenoid (HBI) alkenes: implications for sedimentary reactions and distributions  

Microsoft Academic Search

Several highly branched isoprenoid alkenes isolated from the diatom Haslea ostrearia have been subjected to laboratory simulations of early diagenetic reactions under mild acid conditions including addition of K-10 Montmorillonite clay. The products of these reactions have been found to be highly dependent on the degree of unsaturation of the alkenes. For dienes, double bond migration and geometric isomerisation are

Simon T Belt; W. Guy Allard; Janne Rintatalo; Lesley A Johns; Adri C. T van Duin; Steven J Rowland

2000-01-01

441

Absence of expected side-reactions in the dehydration reaction of fructose to HMF in water over niobic acid catalyst  

Microsoft Academic Search

The catalytic dehydration of fructose (FRU) to 5-hydroxymethylfurfural (HMF) usually runs with the formation of several side products. Among these, levulinic acid (LA) is often reported as the product of a consecutive reaction of HMF re-hydration. In this work, side reactions of the dehydration of FRU performed in very green conditions (water as solvent and niobic acid as solid catalyst)

Paolo Carniti; Antonella Gervasini; Matteo Marzo

2011-01-01

442

Positive Feedback Mechanisms Between Reaction and Deformation Processes in Plagioclase-Olivine Rocks  

NASA Astrophysics Data System (ADS)

We studied interactions between mineral reaction and deformation processes in plagioclase peridotite during the reaction Plg + Ol ? Opx + Cpx + Sp ± Gnt. Hydrostatic and direct shear deformation experiments were performed on dry anorthite-forsterite (An92-Fo93) rocks at 900°C, at confining pressures between 1000-1600 MPa and with constant shear strain rates of ~5x10^{-5}s-1 in a Griggs apparatus. The applied P,T conditions represent different amounts of pressure overstepping of the An- Fo stability field. Our results fall into two categories: Reaction-induced weakening: Syntectonic reaction between anorthite and forsterite is correlated to mechanical weakening at all studied confining pressures. The peak differential stress conditions are associated with the onset of reaction (P~1000 MPa) and the development of reaction products rims (P~1500 MPa). The reaction induces weakening by a switch from dislocation creep to grain size sensitive creep through the development of fine-grained (size<0.5?m) polyphase reaction products. These fine- grained products coalesce and accommodate most of the applied strain in interconnecting layers. In absence of reaction, samples strain-harden to the point of embrittlement. Deformation-enhanced reaction: The onset of reaction in hydrostatic samples is delayed and low reaction rates demonstrate sluggish nucleation of reaction products at dry conditions, even at 700-900 MPa pressure overstepping. The rate of reaction in deforming samples is significantly higher than in samples under hydrostatic conditions. This increase in reaction rate is attributed to high differential stress conditions and strain (dislocation microstructures) in the reactants during deformation, causing an increase in nucleation rate of reaction products. Thus, deformation and reaction processes in plagioclase-olivine rocks appear to be interdependent and positively influence each other: rheological weakening may result from reaction, and localisation of reaction progress in shear zones can be enhanced by deformation.

de Ronde, A.; Stünitz, H.; Tullis, J.; Heilbronner, R.

2006-12-01

443

Hand and Arm Conditions  

MedlinePLUS

... Public & Patients > Hand and Arm Conditions Hand and Arm Conditions Page Content If you know the name ... below. Otherwise click on an area of the arm below to learn more about common hand conditions. ...

444

Intact implicit learning in autism spectrum conditions  

Microsoft Academic Search

Individuals with autism spectrum condition (ASC) have diagnostic impairments in skills that are associated with an implicit acquisition; however, it is not clear whether ASC individuals show specific implicit learning deficits. We compared ASC and typically developing (TD) individuals matched for IQ on five learning tasks: four implicit learning tasks—contextual cueing, serial reaction time, artificial grammar learning, and probabilistic classification

Jamie Brown; Balazs Aczel; Luis Jiménez; Scott Barry Kaufman; Kate Plaisted Grant

2010-01-01

445

Three Reaction Papers.  

ERIC Educational Resources Information Center

In reaction to presentations at the Airlie House Conference on the Implications of Research on Teaching for Practice, two papers (by O. Smith and N. L. Gage, respectively) discuss how far research on teaching has come as a field, while a third (by G. D. Fenstermacher) explains how implications of research on teaching can be used. (MP)

Smith, B. Othanel; And Others

1983-01-01

446

Azoxy rearrangement reactions  

NASA Astrophysics Data System (ADS)

The mechanisms of several types of azoxy compound (XN(O)NY) rearrangement reactions have been studied using density functional theory (DFT) with the B3LYP exchange-correlation potential. The substituents X and Y are taken from the set H, CH , F, C H , Cl and CN. The 6-311 + G(d,p) basis set was used to optimize up to ten equilibrium and transition state structures for a given pair of X and Y substituents; except for azoxybenzene where a 6- 311(+)G(d) basis set was used. All geometric structures were characterized by a frequency calculation. The reaction path for converting XN (O)N Y to XN N (O)Y via a concerted intramolecular shift of the oxygen atom from N to N involves three equilibrium and two saddle-point structures. The relatively high (about 70-80 kcalmol1) calculated barrier height to reaction and its independence of the nature of the X and Y substituents is attributed to characteristic orbital, atomic charge and structural factors along the reaction path. Cis trans isomerization across N-- N in the NH(O)NH azoxy compound and across N-N in the ring XNONY oxadiaziridine intermediate is found to have a barrier height of at least - 1 about 30 kcalmol . Single-point CCSD(T)/DFT energy differences are found to be somewhat smaller than the DFT calculated values. 3 6 5

Basch, Harold; Hoz, Tova

447

Exocharmic Reactions up Close  

ERIC Educational Resources Information Center

|The exocharmic reactions that can be observed microscopically are discussed. The students can discover the optimal concentration of an acidic lead nitrate solution, so that a crystal of potassium iodide, nudged to the edge of a drop, results in glinting golden hexagons of lead iodide.|

Ramette, R. W.

2007-01-01

448

Geotropic Reaction of Plants.  

National Technical Information Service (NTIS)

Data on the physiology (auxins, amino acids, and other metabolites) of the geotropic reaction of plants is presented. Systems of perception and fixation of the geotropic stimulus are examined, as in the response phase of geotropic bending. The text is a m...

A. I. Merkis

1976-01-01

449

A Principal's Reaction  

ERIC Educational Resources Information Center

|This article presents a principal's reaction to Catherine Marshall and Michael Ward's article on research on social justice and training for leadership. The author applauds Marshall and Ward's efforts to address what is undoubtedly among the most fundamentally important issues facing principals today. Marshall and Ward illuminate the importance…

Zaretsky, Lindy

2004-01-01

450

Chain Reaction Polymerization.  

ERIC Educational Resources Information Center

The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

McGrath, James E.

1981-01-01

451

Introducing the Wittig Reaction.  

ERIC Educational Resources Information Center

An experiment is described which provides a simple example of the application of the Wittig reaction to the synthesis of unsaturated compounds. The experiment was designed with British HNC chemistry students in mind, but it is also suitable as a project-type exercise for final year GCE A-level students. (Author/BB)

Armstead, D. E. F.

1979-01-01

452

Modelling Reaction Times  

Microsoft Academic Search

We discuss the simulation of reaction times in connectionist systems. The obvious way to do this involves thinking in terms of neural activations building up towards some threshold in cascaded systems, but it has also been suggested that the output activation error scores in standard back-propagation networks should also be correlated with response times. The idea is that in the

John A. Bullinaria

453

A World of Reactions  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the first of four Science Objects in the Chemical Reactions SciPack. It explains tha

National Science Teachers Association (NSTA)

2009-07-10

454

Rates of Chemical Reactions  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Chemical Reactions SciPack. It demonstrates

National Science Teachers Association (NSTA)

1900-01-01

455

Reactions to Others' Intimacy.  

ERIC Educational Resources Information Center

Research using behavioral measures has indicated that men react less positively to the touch of a same sex individual than women, that both men and women react more positively to the touch of an opposite sex individual than to the touch of a same sex individual, and that men and women do not differ in their reactions to opposite sex touch. This…

Neufeldt, David E.; Olinger, Evanelle J.

456

Theory of resonance reactions  

Microsoft Academic Search

A general formal theory of resonance reactions and scattering is ; developed without the use of channel radii. The approach employed allows a ; simple physical interpretation of the two energies, one of which must be kept ; fixed while the other one is varied in order for a Breit-Wigner denominator to ; vanish. A new result, obtained without a

Luciano Fonda; Roger G. Newton

1960-01-01

457

Exocharmic Reactions up Close  

ERIC Educational Resources Information Center

The exocharmic reactions that can be observed microscopically are discussed. The students can discover the optimal concentration of an acidic lead nitrate solution, so that a crystal of potassium iodide, nudged to the edge of a drop, results in glinting golden hexagons of lead iodide.

Ramette, R. W.

2007-01-01

458

Gas Producing Micro-Reaction  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals and metals to examine reactions that produce gaseous substances. Learners will identify the gases produced and write a balanced equation for each reaction. Use this activity to also introduce learners to single displacement and double displacement reactions, two types of chemical reactions.

House, The S.

2013-05-15

459

Inorganic Reaction Mechanisms. Part I  

ERIC Educational Resources Information Center

|Provides a collection of data on the mechanistic aspects of inorganic chemical reactions. Wherever possible includes procedures for classroom demonstration or student project work. The material covered includes gas phase reactions, reactions in solution, mechanisms of electron transfer, the reaction between iron III and iodine, and hydrolysis.…

Cooke, D. O.

1976-01-01

460

Reaction chain modeling of denitrification reactions during a push-pull test.  

PubMed

Field quantitative estimation of reaction kinetics is required to enhance our understanding of biogeochemical reactions in aquifers. We extended the analytical solution developed by Haggerty et al. (1998) to model an entire 1st order reaction chain and estimate the kinetic parameters for each reaction step of the denitrification process. We then assessed the ability of this reaction chain to model biogeochemical reactions by comparing it with experimental results from a push-pull test in a fractured crystalline aquifer (Ploemeur, French Brittany). Nitrates were used as the reactive tracer, since denitrification involves the sequential reduction of nitrates to nitrogen gas through a chain reaction (NO3(-)?NO2(-)?NO?N2O?N2) under anaerobic conditions. The kinetics of nitrate consumption and by-product formation (NO2(-), N2O) during autotrophic denitrification were quantified by using a reactive tracer (NO3(-)) and a non-reactive tracer (Br(-)). The formation of reaction by-products (NO2(-), N2O, N2) has not been previously considered using a reaction chain approach. Comparison of Br(-) and NO3(-) breakthrough curves showed that 10% of the injected NO3(-) molar mass was transformed during the 12 h experiment (2% into NO2(-), 1% into N2O and the rest into N2 and NO). Similar results, but with slower kinetics, were obtained from laboratory experiments in reactors. The good agreement between the model and the field data shows that the complete denitrification process can be efficiently modeled as a sequence of first order reactions. The 1st order kinetics coefficients obtained through modeling were as follows: k1=0.023 h(-1), k2=0.59 h(-1), k3=16 h(-1), and k4=5.5 h(-1). A next step will be to assess the variability of field reactivity using the methodology developed for modeling push-pull tracer tests. PMID:23500936

Boisson, A; de Anna, P; Bour, O; Le Borgne, T; Labasque, T; Aquilina, L

2013-02-24

461

Inertial effects in diffusion-limited reactions  

NASA Astrophysics Data System (ADS)

Diffusion-limited reactions are commonly found in biochemical processes such as enzyme catalysis, colloid and protein aggregation and binding between different macromolecules in cells. Usually, such reactions are modeled within the Smoluchowski framework by considering purely diffusive boundary problems. However, inertial effects are not always negligible in real biological or physical media on typical observation time frames. This is all the more so for non-bulk phenomena involving physical boundaries, that introduce additional time and space constraints. In this paper, we present and test a novel numerical scheme, based on event-driven Brownian dynamics, that allows us to explore a wide range of velocity relaxation times, from the purely diffusive case to the underdamped regime. We show that our algorithm perfectly reproduces the solution of the Fokker-Planck problem with absorbing boundary conditions in all the regimes considered and is thus a good tool for studying diffusion-guided reactions in complex biological environments.

Dorsaz, N.; De Michele, C.; Piazza, F.; Foffi, G.

2010-03-01

462

Mechanism of the Pummerer reaction: a computational study.  

PubMed

DFT calculations are used to investigate the mechanism of the Pummerer reaction between a chiral sulfoxide and acetic anhydride under classical and stereoselective reaction conditions (without and with additives, respectively). The first step involving acetylation of the sulfoxide with release of acetate is found to be rate-determining in both cases. For the stereoselective Pumm