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1

Facile synthesis of palladium nanoclusters and their catalytic activity in Sonogashira coupling reactions  

Microsoft Academic Search

This work reports a facile synthesis of palladium nanoclusters (PdNCs) in MeCN\\/MeOH mixture without any stabilizer. The PdNCs were found to be effective catalysts for copper-free, amine-free and ligand-free Songashira coupling reactions under ambient conditions.

J. Athilakshmi; S. Ramanathan; Dillip Kumar Chand

2008-01-01

2

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

3

Reactions at supercritical conditions: Applications and fundamentals  

SciTech Connect

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 for reactions involved in fuels processing, biomass conversion, biocatalysis, homogeneous and heterogeneous catalysis, environmental control, polymerization, materials synthesis, and chemical synthesis. Moreover, supercritical fluids can be used profitably in fundamental chemical investigations of intermolecular interactions and their influence on chemical processes. Work on chemical reactions in and with supercritical fluids is reviewed. The authors discuss both fundamental studies and applications of reactions at supercritical conditions, with focus on work published after 1985. 425 refs.

Savage, P.E.; Gopalan, S.; Mizan, T.I.; Martino, C.J.; Brock, E.E. [Univ. of Michigan, Ann Arbor, MI (United States). Chemical Engineering Dept.] [Univ. of Michigan, Ann Arbor, MI (United States). Chemical Engineering Dept.

1995-07-01

4

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

5

Palladium complexes of abnormal N-heterocyclic carbenes as precatalysts for the much preferred Cu-free and amine-free Sonogashira coupling in air in a mixed-aqueous medium.  

PubMed

A series of new PEPPSI (Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) themed precatalysts of abnormal N-heterocyclic carbenes for the highly desirable Cu-free and amine-free Sonogashira coupling in air in a mixed-aqueous medium is reported. Specifically, the PEPPSI themed (NHC)PdI2(pyridine) type precatalysts, 1b-4b, efficiently carried out the highly convenient Cu-free and amine-free Sonogashira coupling of aryl bromides and iodides with terminal acetylenes in air in a mixed aqueous medium. Complexes, 1b-4b, were synthesized by the direct reaction of the corresponding imidazo[1,2-a]pyridinium iodide salts, 1a-4a, with PdCl2 in pyridine in the presence of K2CO3 as a base while the imidazo[1,2-a]pyridinium iodide salts, 1a-4a, were in turn synthesized by the alkylation reactions of the respective imidazo[1,2-a]pyridine derivatives with alkyl iodides. The density functional theory (DFT) studies revealed that these imidazol-3-ylidene[1,2-a]pyridine derived abnormal carbenes are strongly sigma-donating and consequently significantly weaken the catalytically important labile trans pyridine ligand in 1b-4b. PMID:20023883

John, Alex; Shaikh, Mobin M; Ghosh, Prasenjit

2009-12-21

6

Fractionating Recalcitrant Lignocellulose at Modest Reaction Conditions  

SciTech Connect

Effectively releasing the locked polysaccharides from recalcitrant lignocellulose to fermentable sugars is among the greatest technical and economic barriers to the realization of lignocellulose biorefineries because leading lignocellulose pre-treatment technologies suffer from low sugar yields, and/or severe reaction conditions, and/or high cellulase use, narrow substrate applicability, and high capital investment, etc. A new lignocellulose pre-treatment featuring modest reaction conditions (50 C and atmospheric pressure) was demonstrated to fractionate lignocellulose to amorphous cellulose, hemicellulose, lignin, and acetic acid by using a non-volatile cellulose solvent (concentrated phosphoric acid), a highly volatile organic solvent (acetone), and water. The highest sugar yields after enzymatic hydrolysis were attributed to no sugar degradation during the fractionation and the highest enzymatic cellulose digestibility ({approx}97% in 24 h) during the hydrolysis step at the enzyme loading of 15 filter paper units of cellulase and 60 IU of beta-glucosidase per gram of glucan. Isolation of high-value lignocellulose components (lignin, acetic acid, and hemicellulose) would greatly increase potential revenues of a lignocellulose biorefinery.

Zhang, Y.-H. Percival [Virginia Polytechnic Institute and State University (Virginia Tech); Ding, Shi-You [National Energy Renewable Laboratory; Mielenz, Jonathan R [ORNL; Cui, Jing-Biao [Dartmouth College; Elander, Richard T. [Dartmouth College; Laser, Mark [Dartmouth College; Himmel, Michael [ORNL; McMillan, James R. [National Energy Renewable Laboratory; Lynd, L. [Dartmouth College

2007-01-01

7

The Eschenmoser coupling reaction under continuous-flow conditions  

PubMed Central

Summary The Eschenmoser coupling is a useful carbon–carbon bond forming reaction which has been used in various different synthesis strategies. The reaction proceeds smoothly if S-alkylated ternary thioamides or thiolactames are used. In the case of S-alkylated secondary thioamides or thiolactames, the Eschenmoser coupling needs prolonged reaction times and elevated temperatures to deliver valuable yields. We have used a flow chemistry system to promote the Eschenmoser coupling under enhanced reaction conditions in order to convert the demanding precursors such as S-alkylated secondary thioamides and thiolactames in an efficient way. Under pressurized reaction conditions at about 220 °C, the desired Eschenmoser coupling products were obtained within 70 s residence time. The reaction kinetics was investigated and 15 examples of different building block combinations are given. PMID:21915222

Singh, Sukhdeep; Köhler, J Michael; Schober, Andreas

2011-01-01

8

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...

9

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

10

Reactions of animals and people under conditions of brief weightlessness  

NASA Technical Reports Server (NTRS)

It has been shown that under brief weightlessness sensory reactions arise in a number of people, mainly those under these conditions for the first time, in the form of spatial and visual illusions, motor excitation, in which tonic and motor components can be distinguished, and vestibular-vegetative disturbances (nausea, vomiting, etc.). In repeated flights with creation of weightlessness, a decrease in the extent of expression and, then, disappearance of these reactions occurred in a significant majority of those studied. Experiments in weightlessness with the vision cut off and with the absence of vestibular functions in the subjects confirm the hypothesis that spatial conceptions of people in weightlessness depend on predominance of gravireceptor or visual afferent signals under these conditions.

Kitayev-Smik, L. A.

1975-01-01

11

The reaction conditions influence on hydrothermal synthesis of boehmite nanorods  

Microsoft Academic Search

Synthesis of boehmite (?-AlOOH) nanorods were performed by using aluminum nitrate and sodium hydroxide as starting materials\\u000a in conditions of controlled pH value of reaction mixture, temperature and holding time. X-ray diffraction, transmission electron\\u000a microscope, high resolution transmission electron microscope, selected area electron diffraction and N2 adsorption-desorption analysis were used to characterize morphology and structure feathers of the obtained products.

Qi Yang

2010-01-01

12

Homogeneous-heterogeneous reactions in peristaltic flow with convective conditions.  

PubMed

This article addresses the effects of homogeneous-heterogeneous reactions in peristaltic transport of Carreau fluid in a channel with wall properties. Mathematical modelling and analysis have been carried out in the presence of Hall current. The channel walls satisfy the more realistic convective conditions. The governing partial differential equations along with long wavelength and low Reynolds number considerations are solved. The results of temperature and heat transfer coefficient are analyzed for various parameters of interest. PMID:25460608

Hayat, Tasawar; Tanveer, Anum; Yasmin, Humaira; Alsaedi, Ahmed

2014-01-01

13

Structure-inheriting solid-state reactions under hydrothermal conditions  

SciTech Connect

We have explored several structure-inheriting solid-state reactions (SISSRs) under hydrothermal conditions for syntheses in the Co-Mo-O system. And we found an interesting hydrothermal SISSR from CoMoO{sub 4}.3/4H{sub 2}O to high-pressure (hp-) phase of CoMoO{sub 4}, which enabled us to considerably reduce the severe conditions for the synthesis of hp-CoMoO{sub 4}. As similar hydrothermal SISSRs are expected to be useful tools for material syntheses, we also briefly discuss them as a means of developing novel material syntheses and designs.

Eda, Kazuo [Faculty of Science, Department of Chemistry, Kobe University, Nada-ku, Kobe 657-8501 (Japan)]. E-mail: eda@kobe-u.ac.jp; Uno, Yuichi [Faculty of Science, Department of Chemistry, Kobe University, Nada-ku, Kobe 657-8501 (Japan); Nagai, Noriko [Faculty of Science, Department of Chemistry, Kobe University, Nada-ku, Kobe 657-8501 (Japan); Sotani, Noriyuki [Faculty of Science, Department of Chemistry, Kobe University, Nada-ku, Kobe 657-8501 (Japan); Chen Chen [Institute for Materials Research, State University of New York at Binghamton, Binghamton, NY 13902-6000 (United States); Stanley Whittingham, M. [Institute for Materials Research, State University of New York at Binghamton, Binghamton, NY 13902-6000 (United States)

2006-05-15

14

Effects of Meteorological Conditions on Reactions to Noise Exposure  

NASA Technical Reports Server (NTRS)

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 found to be slightly statistically significantly higher in the summer than in the winter in a seven-year study in the Netherlands. Analyses of 41 other surveys drawn from diverse countries, climates, and times of year find noise annoyance is increased by temperature, and may be increased by more sunshine, less precipitation, and reduced wind speeds. Meteorological conditions on the day of the interview or the immediately preceding days do not appear to have any more effect on reactions than do the conditions over the immediately preceding weeks or months.

Shepherd, Kevin P. (Technical Monitor); Fields, James M.

2004-01-01

15

Reactions of aminomalononitrile with electrophiles. [simulating prebiotic conditions  

NASA Technical Reports Server (NTRS)

Aminomalononitrile (HCN trimer) reacts with electrophiles such as aldehydes and acrylonitrile under very mild conditions of temperature and pH to produce intermediates which, after acid hydrolysis, yield amino acids. The following amino acids have been identified and quantitated: glycine, D,L-erythro- and D,L-threo-beta-hydroxyaspartic acids, D,L glutamic acid, and D,L-threonine and allo-threonine. The mechanism of their formation and the possible significance of these reactions in prebiotic syntheses are discussed.

Thanassi, J. W.

1975-01-01

16

MICROWAVE-ACCELERATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS  

EPA Science Inventory

The application of microwave-accelerated solventless synthetic protocols in multicomponent (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of valuable heterocyclic compounds from in situ generated intermed...

17

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

18

MICROWAVE-FACILITATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS  

EPA Science Inventory

The application of microwave-expedited solvent-free synthetic protocols in multi-component (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of heterocyclic compounds from in situ generated intermediates. R...

19

A quadrature closure for the reaction-source term in conditional-moment closure  

E-print Network

A quadrature closure for the reaction-source term in conditional-moment closure S.T. Smith a,*, R-0235, USA Abstract A Gaussian-quadrature closure is introduced for the conditional reaction-source term in conditional- moment closure, motivated by the desire to accurately model the dynamics of homogeneous

Raman, Venkat

20

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

21

Physiological reactions of a passenger to transportation conditions  

NASA Technical Reports Server (NTRS)

The effect of transportation conditions on the performance capacity of a passenger were studied, in order to establish the time for his most rapid inclusion in production activity after the trip. It was concluded that the transportation conditions impair the functional condition of the passenger's organism. The restoration of the functional state to the initial level occurs mainly in the space of one day. It is shown that it is necessary to take into consideration the adaptation of the organism during transfer to another climate zone.

Lakshin, A. M.; Novoselov, V. P.

1980-01-01

22

Intermolecular cyclocondensation reaction of 3,4-dihydropyrimidine-2-thione under the Mitsunobu reaction conditions  

Microsoft Academic Search

A self-intermolecular cyclocondensation reaction of 3,4-dihydropyrimidine-2-thione (DHPM) to give a novel tricyclic structure containing DHPM core in the presence of diethyl azodicarboxylate (DEAD) and triphenylphosphine (TPP) at room temperature is reported.

Yu Xia Da; Zhang Zhang; Zheng Jun Quan

2011-01-01

23

Uranium plasma emission at gas-core reaction conditions  

NASA Technical Reports Server (NTRS)

The results of uranium plasma emission produced by two methods are reported. For the first method a ruby laser was focused on the surface of a pure U-238 sample to create a plasma plume with a peak plasma density of about 10 to the 20th power/cu cm and a temperature of about 38,600 K. The absolute intensity of the emitted radiation, covering the range from 300 to 7000 A was measured. For the second method, the uranium plasma was produced in a 20 kilovolt, 25 kilojoule plasma-focus device. The 2.5 MeV neutrons from the D-D reaction in the plasma focus are moderated by polyethylene and induce fissions in the U-235. Spectra of both uranium plasmas were obtained over the range from 30 to 9000 A. Because of the low fission yield the energy input due to fissions is very small compared to the total energy in the plasma.

Williams, M. D.; Jalufka, N. W.; Hohl, F.; Lee, J. H.

1976-01-01

24

Speed-accuracy tradeoff in choice reaction time: Within conditions, between conditions, and between subjects  

Microsoft Academic Search

A quantitative theory of choice reaction time (CRT), developed in the context of accurate performance was successfully applied\\u000a to a speeded experiment. With estimation of a single parameter, mean criterion level, the theory described the reaction time\\u000a (RT) distributions for correct responses and errors and the details of the speed-accuracy tradeoff. The form of the tradeoff\\u000a within experiments is not

G. Robert Grice; V. Alan Spiker

1979-01-01

25

Impact of reaction conditions on architecture and rheological properties of starch graft polyacrylamide polymers  

Technology Transfer Automated Retrieval System (TEKTRAN)

We carried out experiments examining the impact that solvent selection and reaction conditions have on the radical initiated graft polymerization reaction of acrylamide onto starch. We have also evaluated the rheological properties the starch graftpolyacrylamide product when a gel is formed in water...

26

Characteristics of uranium carbonitride microparticles synthesized using different reaction conditions  

NASA Astrophysics Data System (ADS)

Three sets of experimental conditions were tested to synthesize uranium carbonitride (UC1-xNx) kernels from gel-derived urania-carbon microspheres. Primarily, three sequences of gases were used, N2 to N2-4%H2 to Ar, Ar to N2 to Ar, and Ar-4%H2 to N2-4%H2 to Ar-4%H2. Physical and chemical characteristics such as geometrical density, phase purity, and chemical compositions of the synthesized UC1-xNx were measured. Single-phase kernels were commonly obtained with densities generally ranging from 85% to 93% TD and values of x as high as 0.99. In-depth analysis of the microstrutures of UC1-xNx has been carried out and is discussed with the objective of large batch fabrication of high density UC1-xNx kernels.

Silva, Chinthaka M.; Lindemer, Terrence B.; Voit, Stewart R.; Hunt, Rodney D.; Besmann, Theodore M.; Terrani, Kurt A.; Snead, Lance L.

2014-11-01

27

An investigation of a Friedel-Crafts alkylation reaction in homogeneous supercritical CO 2 and under subcritical and splitphase reaction conditions  

Microsoft Academic Search

This study investigates the Friedel-Crafts alkylation reaction of triphenylmethanol with methoxybenzene (anisole) in supercritical and subcritical carbon dioxide, and under two-phase (gas\\/liquid) reaction conditions at moderate pressures and temperatures. The reaction was initiated using trifluoroacetic acid to produce triphenylmethlycarbocation as the reaction intermediate. Isolated product yields of the Friedel-Crafts product, p-methoxytetraphenylmethane, are reported.

John E. Chateauneuf; Kan Nie

2000-01-01

28

Macromolecular crowding conditions enhance glycation and oxidation of whey proteins in ultrasound-induced Maillard reaction.  

PubMed

High intensity ultrasound (HIUS) can promote Maillard reaction (MR). Macromolecular crowding conditions accelerate reactions and stabilise protein structure. The aim of this study was to investigate if combined application of ultrasound and macromolecular crowding can improve efficiency of MR. The presence of crowding agent (polyethylene glycol) significantly increased ultrasound-induced whey protein (WP) glycation by arabinose. An increase in glycation efficiency results only in slight change of WP structure. Macromolecular crowding intensifies oxidative modifications of WP, as well as formation of amyloid-like structures by enhancement of MR. Solubility at different pH, thermal stability and antioxidative capacity of glycated WP were increased, especially in the presence of crowding agent, compared to sonicated nonglycated proteins. The application of HIUS under crowding conditions can be a new approach for enhancement of reactions in general, enabling short processing time and mild conditions, while preserving protein structure and minimising protein aggregation. PMID:25660883

Perusko, Marija; Al-Hanish, Ayah; Cirkovic Velickovic, Tanja; Stanic-Vucinic, Dragana

2015-06-15

29

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

30

Reaction progress pathways for glass and spent fuel under unsaturated conditions  

SciTech Connect

The source term for the release of radionuclides from a nuclear waste repository is the waste form. In order to assess the performance of the repository and the engineered barrier system (EBS) compared to regulations established by the Nuclear Regulatory Commission and the Environmental Protection Agency it is necessary (1) to use available data to place bounding limits on release rates from the EBS, and (2) to develop a mechanistic predictive model of the radionuclide release and validate the model against tests done under a variety of different potential reaction conditions. The problem with (1) is that there is little experience to use when evaluating waste form reaction under unsaturated conditions such that errors in applying expert judgment to the problem may be significant. The second approach, to test and model the waste form reaction, is a more defensible means of providing input to the prediction of radionuclide release. In this approach, information related to the source term has a technical basis and provides a starting point to make reasonable assumptions for long-term behavior. Key aspects of this approach are an understanding of the reaction progress mechanism and the ability to model the tests using a geochemical code such as EQ3/6. Current knowledge of glass, UO{sub 2}, and spent fuel reactions under different conditions are described below.

Bates, J.; Finn, P.; Bourcier, W.; Stout, R.

1994-10-01

31

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.

32

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

33

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

34

Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions  

E-print Network

Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction: Understanding Ostwald ripening and disintegra- tion of supported metal particles under operating conditions has temperature and pressure. The thermodynamic criteria for the reactant assisted Ostwald ripening and induced

Li, Weixue

35

A CHANGE OF UNCONDITIONED AND CONDITIONED-REFLEX LIUKOCYTIC REACTIONS FOLLOWING X-RAY IRRADIATION  

Microsoft Academic Search

Experiments were staged on 6 dogs. A study was made of the ; unconditioned and conditioned-reflex leukocytic reactions, as well as of the ; background variations of the leukocyte count, prior to and after a single total x-; ray irradiation of the animals with the doses of 600, 50, and 3 r. During the ; first day after the irradiation,

Ulyanov

1962-01-01

36

Changes in the unconditioned and conditioned reflex leukocytic reactions following roentgen irradiation  

Microsoft Academic Search

Experiments were staged on 6 dogs. A study was made of the unconditioned and conditioned-reflex leukocytic reactions (with electrocutaneous reinforcement), as well as of the background variations of the leukocyte count prior to and after a single total x-ray irradiation of the animals with the doses of 600, 50 and 3 r. During the first day (hours) after the irradiation,

M. I. Ul'yanov; N. M. Zharikov

1963-01-01

37

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

38

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

PubMed Central

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

2000-01-01

39

Method and apparatus for measuring coupled flow, transport, and reaction processes under liquid unsaturated flow conditions  

DOEpatents

The present invention is a method and apparatus for measuring coupled flow, transport and reaction processes under liquid unsaturated flow conditions. The method and apparatus of the present invention permit distinguishing individual precipitation events and their effect on dissolution behavior isolated to the specific event. The present invention is especially useful for dynamically measuring hydraulic parameters when a chemical reaction occurs between a particulate material and either liquid or gas (e.g. air) or both, causing precipitation that changes the pore structure of the test material.

McGrail, Bernard P. (Pasco, WA); Martin, Paul F. (Richland, WA); Lindenmeier, Clark W. (Richland, WA)

1999-01-01

40

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

2013-05-01

41

A proposed abiotic reaction scheme for hydroxylamine and monochloramine under chloramination relevant drinking water conditions.  

PubMed

Drinking water monochloramine (NH2Cl) use may promote ammonia-oxidizing bacteria (AOB). AOB use (i) ammonia monooxygenase for biological ammonia (NH3) oxidation to hydroxylamine (NH2OH) and (ii) hydroxylamine oxidoreductase for NH2OH oxidation to nitrite. NH2Cl and NH2OH may react, providing AOB potential benefits and detriments. The NH2Cl/NH2OH reaction would benefit AOB by removing the disinfectant (NH2Cl) and releasing their growth substrate (NH3), but the NH2Cl/NH2OH reaction would also provide a possible additional inactivation mechanism besides direct NH2Cl reaction with cells. Because biological NH2OH oxidation supplies the electrons required for biological NH3 oxidation, the NH2Cl/NH2OH reaction provides a direct mechanism for NH2Cl to inhibit NH3 oxidation, starving the cell of reductant by preventing biological NH2OH oxidation. To investigate possible NH2Cl/NH2OH reaction implications on AOB, an understanding of the underlying abiotic reaction is first required. The present study conducted a detailed literature review and proposed an abiotic NH2Cl/NH2OH reaction scheme (RS) for chloramination relevant drinking water conditions (?M concentrations, air saturation, and pH 7-9). Next, RS literature based kinetics and end-products were evaluated experimentally between pHs 7.7 and 8.3, representing (i) the pH range for future experiments with AOB and (ii) mid-range pHs typically found in chloraminated drinking water. In addition, a (15)N stable isotope experiment was conducted to verify nitrous oxide and nitrogen gas production and their nitrogen source. Finally, the RS was slightly refined using the experimental data and an AQUASIM implemented kinetic model. A chloraminated drinking water relevant RS is proposed and provides the abiotic reaction foundation for future AOB biotic experiments. PMID:24862953

Wahman, David G; Speitel, Gerald E; Machavaram, Madhav V

2014-09-01

42

Correlation changes in EEG, conditioned and behavioral reactions with various degrees of oxygen insufficiency  

NASA Technical Reports Server (NTRS)

The dynamics of change in bioelectric activity of the brain during acute hypoxia are studied for the time that working capacity and active consciousness are preserved, and to establish the correlation between EEG changes and behavioral reactions under oxygen starvation. Changes in body functions and behavioral disturbances are related to the degree of oxygen saturation in the blood, to bioelectric activity of the brain, and to an increase in conditioned reflexes. The capacity for adequate reaction to external signals and for coordinated psychomotor activity after loss of consciousness returns to man after 30 seconds. Repeated effects of hypoxia produce changes in the physiological reactions of the body directed toward better adaptation to changing gaseous environments.

Agadzhanyan, N. A.; Zakharova, I. N.; Kalyuzhnyy, L. V.; Dvorzhak, I. I.; Moravek, M.; Tsmiral, Y. I.

1974-01-01

43

Effect of oxidation conditions on chlorination reaction of Zircaloy-4 hulls  

NASA Astrophysics Data System (ADS)

The effect of oxidation conditions on the chlorination reaction behavior was investigated by using Zircaloy-4 (Zry-4) hulls oxidized at various conditions. When the hulls were oxidized at 500, 600, and 700 °C for 5 h, decrease of reactant mass after the chlorination reaction at 380 °C for 3 h was 41.6, 26.0, and 0.0 wt.%, respectively, while that of fresh Zry-4 hulls was 54.1 wt.%. Surface analysis results revealed that the oxidation state of Zr is significantly dependent on the oxidation temperature. The effect of oxidation time was also investigated for the Zry-4 hulls oxidized at 500 and 700 °C up to 24 h. Based on the experimental results, it was concluded that the chlorination method is applicable to the Zry-4 hulls oxidized at 500 °C without removal of the surface oxide layers, while a pretreatment is required to recover Zr from the hulls oxidized at 700 °C.

Jeon, Min Ku; Kang, Kweon Ho; Heo, Chul Min; Yang, Jae Hwan; Lee, Chang Hwa; Park, Geun Il

2012-05-01

44

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

SciTech Connect

In order to assess the possible role of methane in petroleum formation, they 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/sup 0/C in the presence of montmorillonite, a natural clay catalyst. Since they expected very slow reaction rates and thus low yields, we used /sup 14/C labeled methane to trace the reaction products. They 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/sub 2/ addition occurred, although very small amounts of products corresponding to C/sub 1/ addition were also detected. They 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, T.; Gordon, B.E.; Streett, W.; Bilson, E.; Patnaik, P.

1986-11-01

45

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

46

Effects of Maillard reaction conditions on the functional properties of WPI chitosan oligosaccharide conjugates.  

PubMed

Whey proteins are widely used as food material, but their functional properties are affected by processing conditions, in which Maillard reaction commonly occurs. The objective of this study was to investigate the effects of reaction conditions (saccharide rate (SR), setting time and setting temperature) on the functional properties of conjugates of whey protein isolates (WPI) - chitosan oligosaccharide (COS), which were produced by Maillard reaction. Response surface methodology (RSM) was used in this study, models for solubility, heat stability (HS), emulsifying activity (EA) and emulsifying stability (ES) of WPI-COS were established. Results indicated that the solubility of WPI-COS was 98.8 % at 29.8 % SR, 17.4 h, 46.7 °C; the heat stability of WPI-COS was 92.95 % at 27.2 % SR, 18.1 h, 48.7 °C; the EA of WPI-COS was 1.87 at 25.3 % SR, 20.0 h, 46.1 °C; the ES of WPI-COS was 13.28 min at 32.5 % SR, 12.0 h, 35.0 °C and setting temperature was the major factor affecting EA and ES while SR was the major factor affecting solubility and heat stability. Conditions were optimized for the preparation of WPI-COS to obtain improved functional properties. PMID:25477646

Zheng, Zhe; Luo, Yongkang; Yao, Lei; Lu, Jing; Bu, Guanhao

2014-12-01

47

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

48

Test plan for reactions between spent fuel and J-13 well water under unsaturated conditions  

SciTech Connect

The Yucca Mountain Site Characterization Project is evaluating the long-term performance of a high-level nuclear waste form, spent fuel from commercial reactors. Permanent disposal of the spent fuel is possible in a potential repository to be located in the volcanic tuff beds near Yucca Mountain, Nevada. During the post-containment period the spent fuel could be exposed to water condensation since of the cladding is assumed to fail during this time. Spent fuel leach (SFL) tests are designed to simulate and monitor the release of radionuclides from the spent fuel under this condition. This Test Plan addresses the anticipated conditions whereby spent fuel is contacted by small amounts of water that trickle through the spent fuel container. Two complentary test plans are presented, one to examine the reaction of spent fuel and J-13 well water under unsaturated conditions and the second to examine the reaction of unirradiated UO{sub 2} pellets and J-13 well water under unsaturated conditions. The former test plan examines the importance of the water content, the oxygen content as affected by radiolysis, the fuel burnup, fuel surface area, and temperature. The latter test plant examines the effect of the non-presence of Teflon in the test vessel.

Finn, P.A.; Wronkiewicz, D.J.; Hoh, J.C.; Emery, J.W.; Hafenrichter, L.D.; Bates, J.K.

1993-01-01

49

Formation of flavor components by the reaction of amino acid and carbonyl compounds in mild conditions.  

PubMed

This work describe products of reactions between four alpha-dicarbonyl compounds (diacetyl, pentan-2,3-dione, glyoxal, and methylglyoxal) or two alpha-hydroxy ketones, (acetoine and acetol) and amino acids present in wines. The results shows the formation of odorous products or strong-smelling additives resulting from the Maillard and Strecker reaction in a primarily aqueous medium, at low temperature and low pH ( approximately pH 3.5) of the wine. GC/FID, GC/FPD, GC/NPD and GC/MS techniques were used. The olfactive characteristics of the products are described. In the presence of sulfur amino acids and in particular cysteine, many products were formed with a heterocycle production such as pyrazines and methylpyrazines, methylthiazoles, acetylthiazoles, acetylthiazolines, acetylthiazolidines, trimethyloxazole, and dimethylethyloxazoles. These various compounds present odors of sulfur, cornlike, pungent, nut, popcorn, roasted hazelnut, toasted, roasted, and ripe fruits. The chemical conditions of the model reactions are specified. The influence of temperature and pH on the reactions in the presence of cysteine were also studied. PMID:10995267

Pripis-Nicolau, L; de Revel, G; Bertrand, A; Maujean, A

2000-09-01

50

Organocatalytic acetylation of starch: effect of reaction conditions on DS and characterisation of esterified granules.  

PubMed

Starch acetates with varying degree of substitution (DS) were prepared by a novel solvent-free organocatalytic methodology. The acetylation protocol involved a non-toxic biobased ?-hydroxycarboxylic acid as catalyst, and proceeded with high efficiency in absence of solvents. The effect of reaction conditions including reaction temperature (90-140 °C), catalyst load (0-2.3 g/g starch), acetic anhydride/starch weight ratio (6.5-13.5 g/g), and starch moisture content (0.6-14.8%) on the DS of the esters was evaluated. The analysis performed showed that the increase of temperature and catalyst concentration resulted in higher DS values, and evidenced a beneficial contribution of native starch moisture content on the substitution level achieved. Variation of reaction conditions allowed starch esters to be obtained with DS in the 0.03-2.93 range. Starch esters were characterised in terms of morphology, chemical structure, thermal properties, and distribution in polar/non polar liquid systems. PMID:25306348

Tupa, Maribel Victoria; Ávila Ramírez, Jhon Alejandro; Vázquez, Analía; Foresti, María Laura

2015-03-01

51

Efficient and robust reforming catalyst in severe reaction conditions by nanoprecursor reduction in confined space.  

PubMed

The in situ autocombustion synthesis route is shown to be an easy and efficient way to produce nanoscaled nickel oxide containing lanthanum-doped mesoporous silica composite. Through this approach, ~3 nm NiO particles homogeneously dispersed in the pores of silica are obtained, while lanthanum is observed to cover the surface of the silica pore wall. Subsequent reduction of such composite precursors under hydrogen generates Ni(0) nanoparticles of a comparable size. Control over the size and size distribution of metallic nanoparticles clearly improved catalytic activity in the methane dry reforming reaction. In addition, these composite materials exhibit excellent stability under severe reaction conditions. This was achieved through the presence of LaOx species, which reduced active-site carbon poisoning, and the confinement effect of the mesoporous support, which reduced metallic particle sintering. PMID:24323543

Dacquin, Jean-Philippe; Sellam, Djamila; Batiot-Dupeyrat, Catherine; Tougerti, Asma; Duprez, Daniel; Royer, Sébastien

2014-02-01

52

Specificity of psychomotor reactions in the conditions of support deprivation including effects of countermeasures  

NASA Astrophysics Data System (ADS)

Activity of the cosmonaut demands high level of psychomotor reactions (PMR) which can vary during space flight under the influences of psychophysiological state’s variability and unusual inhabitancy that causes the necessity of PMR estimation’s inclusion into quality monitoring of capacity for work (CW). A main objective of research was a study of features of visual-motor reactions (VMR) and elements of CW of the person within simulation of microgravity effects via 7-day dry immersion (DI) in healthy male-volunteers 20-35 years old. The experimental data were received which testified to peculiarities of VMR and recognition of simple figures of main colors of a visible spectrum (red, green, blue, the RGB-standard) in the conditions of the DI characterized by support deprivation and decreased proprioceptive afferentation - in a control series and in a series with use of mioelectrostimulation as a countermeasure.

Nichiporuk, Igor; Ivanov, Oleg

53

Effect of moisture conditions and transfers on alkali silica reaction damaged structures  

SciTech Connect

The aim of this paper is to point out the water driving effect on the alkali silica reaction (ASR) expansion and particularly when modifications of moisture conditions occur. After being submitted to a unidirectional moisture gradient during 14 months, the upper faces of ASR reactive beams were covered by water for 9 months. This late water supply on the upper face rapidly produced large expansions, which mainly occurred along the transverse and the vertical directions resulting in large longitudinal cracks. Companion nonreactive specimens were kept in the same environmental conditions in order to quantify the basic characteristics of moisture-dependent expansive behaviour of the material. The paper focuses on the effects of late water supply or late drying on already ASR-damaged concrete, which is a significant concern for real-life structures. Both structural effects of late water supply on ASR progress in already damaged structures and interpretation of such phenomena are described.

Multon, Stephane, E-mail: multon@insa-toulouse.f [Universite de Toulouse, UPS, INSA, LMDC - Laboratoire Materiaux et Durabilite des Constructions, 135, avenue de Rangueil, F-31 077 Toulouse Cedex 04 (France); Toutlemonde, Francois [Universite Paris-Est, Laboratoire Central des Ponts et Chaussees (LCPC), 58, bd Lefebvre, 75 732 Paris Cedex 15 (France)

2010-06-15

54

Overcoming order reduction in diffusion-reaction splitting. Part 1: Dirichlet boundary conditions  

E-print Network

For diffusion-reaction equations employing a splitting procedure is attractive as it reduces the computational demand and facilitates a parallel implementation. Moreover, it opens up the possibility to construct second-order integrators that preserve positivity. However, for boundary conditions that are neither periodic nor of homogeneous Dirichlet type order reduction limits its usefulness. In the situation described the Strang splitting procedure is not more accurate than Lie splitting. In this paper, we propose a splitting procedure that, while retaining all the favorable properties of the original method, does not suffer from order reduction. We demonstrate our results by conducting numerical simulations in one and two space dimensions with inhomogeneous and time dependent Dirichlet boundary conditions. In addition, a mathematical rigorous convergence analysis is conducted that confirms the results observed in the numerical simulations.

Einkemmer, Lukas

2014-01-01

55

Growth and characterizations of magnetic nanoparticles under hydrothermal conditions: Reaction time and temperature  

NASA Astrophysics Data System (ADS)

Magnetic iron oxide nanoparticles with various sizes and magnetic properties were synthesized by using a hydrothermal method. The initial nanoparticles were obtained by co-precipitation of ferric and ferrous salts and then treated under a hydrothermal condition for 1-120 h at 160 °C. At reaction time of 12 h, further treatment on the particles was performed at 200 °C. The resultant nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD) and vibrating sample magnetometer. The images obtained by TEM showed that the particles are around spherical in shape. The mean size of particles increased from 14±4 nm to 74±9 nm as the reaction time was increased from 1 h to 120 h. From the XRD patterns, high crystalline iron oxide nanoparticles were obtained with increasing reaction time and temperature. The saturation magnetizations obtained from magnetization curves were found to be rising from 74.9 to 93.5 emu/g that is consistent with the bulk value of the magnetite.

Ozel, Fatmahan; Kockar, Hakan

2015-01-01

56

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

57

Reaction of perfluoroalkylpolyethers (PFPE) with 440C steel in vacuum under sliding conditions at room temperature  

NASA Technical Reports Server (NTRS)

Reactions of perfluoroalkylpolyethers (PFPE: Fomblin, Demnum and Krytox) were studied during the sliding contact of stainless steel specimens under ultrahigh vacuum conditions. All three fluids reacted with the steel specimens during sliding. Fomblin, which has acetal linkages, decomposed under the sliding conditions generating gaseous products, (COF2 and fluorinated carbons) which were detected by a quadrupole mass spectrometer. Gaseous products were not detected for the Demnum and Krytox fluids. The amount of gaseous products from Fomblin increased with increasing sliding speed. At the end of the sliding experiments, the wear scar and deposits on the specimens were examined by small spot size XPS. The oxide layer on the specimen surface was removed during sliding, and metal fluorides were formed on the worn surface. The surface of the wear scar and deposits were covered with adsorbed PFPE. Based on these results, it was concluded that the decomposition reaction on Fomblin was initiated by contacting the fluid with a fresh metal surface which was formed during sliding.

Mori, Shigeyuki; Morales, Wilfredo

1989-01-01

58

Electron transfer reaction dynamics of p-nitroaniline in water from liquid to supercritical conditions.  

PubMed

Photoexcitation dynamics of p-nitroaniline (pNA) have been investigated by femto-second transient absorption spectroscopy in water from liquid to supercritical conditions; along the isochoric line from the ambient condition to 664 K at 40.1 MPa and along the isothermal line from 40.1 to 36.1 MPa at 664 K. The rates of the back electron transfer reaction from the photoexcited charge transfer state to the electronic ground state was determined by the bleach recovery of the ground state absorption, and the successive vibrational relaxation in the electronic ground state was determined by the hot-band decay which was apparent at the red edge of the absorption. The variation of the back electron transfer rate was compared with the prediction based on the electron transfer theory including the Franck-Condon active vibrational modes. The results indicated that both the free energy change of the reaction and the change of the intramolecular vibrational reorganization energy cause the characteristic density (or temperature) dependence of the back electron transfer rate. The density dependence of the vibrational relaxation rate was compared with the collision frequency and the coordination number of the solvent molecule around the solute estimated by the molecular dynamics simulations. The density dependence of the coordination of a water oxygen atom to an amino hydrogen atom of pNA was found to be correlated with the density dependence of vibrational relaxation rate. PMID:22909090

Osawa, Koji; Terazima, Masahide; Kimura, Yoshifumi

2012-09-20

59

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. PMID:23971902

2013-01-01

60

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions  

PubMed Central

Summary A straightforward, efficient, and reliable redox catalyst system for the Au(I)/Au(III)-catalyzed Sonogashira cross-coupling reaction of functionalized terminal alkynes with arylboronic acids under mild conditions has been developed. PMID:21804876

Qian, Deyun

2011-01-01

61

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

62

Effect of reaction conditions on the catalytic performance of Fe-Mn catalyst for Fischer-Tropsch synthesis  

Microsoft Academic Search

The effects of reaction conditions on the performance of an Fe-Mn catalyst for Fischer-Tropsch synthesis (FTS) have been investigated in a continuous spinning basket reactor. Experiments were carried out under a wide range of industrially relevant reaction conditions including reaction temperature of 533–573K, pressure of 0.93–2.96MPa, inlet H2\\/CO molar ratio of 0.80–2.50 and space velocity of (0.46–1.85)×10?3Nm3kgcat?1s?1. The selectivities to

Ying Liu; Bo-Tao Teng; Xiao-Hui Guo; Ying Li; Jie Chang; Lei Tian; Xu Hao; Yu Wang; Hong-Wei Xiang; Yuan-Yuan Xu; Yong-Wang Li

2007-01-01

63

Firing condition for entire reactions of fluorides with water vapor in metalorganic deposition method using trifluoroacetate  

NASA Astrophysics Data System (ADS)

To obtain the YBa 2Cu 3O 7- x (YBCO) film on buffered metal tapes, we have to fire films below 800°C and avoid formation of BaF 2 in the films which leads to low Jc by metalorganic deposition using trifluoroacetate method. By estimating each process condition to reaction rate of fluorides with water vapor in precursor, we can established firing profile for YBCO film on buffered metal substrate at 725°C. With the profile, we can successfully obtained YBCO film on CeO 2/YSZ/hastelloy, which has critical current density ( Jc) of 1.72 MA/cm 2 (77 K, 0 T) and thickness of 1860 Å.

Araki, T.; Takahashi, Y.; Yamagiwa, K.; Iijima, Y.; Takeda, K.; Yamada, Y.; Shibata, J.; Hirayama, T.; Hirabayashi, I.

2001-08-01

64

Controlled release of volatiles under mild reaction conditions: from nature to everyday products.  

PubMed

Volatile organic compounds serve in nature as semiochemicals for communication between species, and are often used as flavors and fragrances in our everyday life. The quite limited longevity of olfactive perception has led to the development of pro-perfumes or pro-fragrances--ideally nonvolatile and odorless fragrance precursors which release the active volatiles by bond cleavage. Only a limited amount of reaction conditions, such as hydrolysis, temperature changes, as well as the action of light, oxygen, enzymes, or microorganisms, can be used to liberate the many different chemical functionalities. This Review describes the controlled chemical release of fragrances and discusses additional challenges such as precursor stability during product storage as well as some aspects concerning toxicity and biodegradability. As the same systems can be applied in different areas of research, the scope of this Review covers fragrance delivery as well as the controlled release of volatiles in general. PMID:17605134

Herrmann, Andreas

2007-01-01

65

The influence of reaction conditions on the Diels-Alder cycloadditions of 2-thio-3-chloroacrylamides; investigation of thermal, catalytic and microwave conditions.  

PubMed

The Diels-Alder cycloadditions of cyclopentadiene and 2,3-dimethyl-1,3-butadiene to a range of 2-thio-3-chloroacrylamides under thermal, catalytic and microwave conditions is described. The influence of reaction conditions on the outcome of the cycloadditions, in particular the stereoselectivity and reaction efficiency, is discussed. While the cycloadditions have been attempted at the sulfide, sulfoxide and sulfone levels of oxidation, use of the sulfoxide derivatives is clearly beneficial for stereoselective construction of Diels-Alder cycloadducts. PMID:20927479

Kissane, Marie; Lynch, Denis; Chopra, Jay; Lawrence, Simon E; Maguire, Anita R

2010-12-21

66

Hyporheic transport and biogeochemical reactions in pool-riffle systems under varying ambient groundwater flow conditions  

NASA Astrophysics Data System (ADS)

the interface between stream water, groundwater, and the hyporheic zone (HZ), important biogeochemical processes that play a crucial role in fluvial ecology occur. Solutes that infiltrate into the HZ can react with each other and possibly also with upwelling solutes from the groundwater. In this study, we systematically evaluate how variations of gaining and losing conditions, stream discharge, and pool-riffle morphology affect aerobic respiration (AR) and denitrification (DN) in the HZ. For this purpose, a computational fluid dynamics model of stream water flow is coupled to a reactive transport model. Scenarios of variations of the solute concentration in the upwelling groundwater were conducted. Our results show that solute influx, residence time, and the size of reactive zones strongly depend on presence, magnitude, and direction of ambient groundwater flow. High magnitudes of ambient groundwater flow lower AR efficiency by up to 4 times and DN by up to 3 orders of magnitude, compared to neutral conditions. The influence of stream discharge and morphology on the efficiency of AR and DN are minor, in comparison to that of ambient groundwater flow. Different scenarios of O2 and NO3 concentrations in the upwelling groundwater reveal that DN efficiency of the HZ is highest under low upwelling magnitudes accompanied with low concentrations of O2 and NO3. Our results demonstrate how ambient groundwater flow influences solute transport, AR, and DN in the HZ. Neglecting groundwater flow in stream-groundwater interactions would lead to a significant overestimation of the efficiency of biogeochemical reactions in fluvial systems.

Trauth, Nico; Schmidt, Christian; Vieweg, Michael; Maier, Uli; Fleckenstein, Jan H.

2014-05-01

67

Influence of reaction conditions on the properties of solution-processed Cu2ZnSnS4 nanocrystals  

NASA Astrophysics Data System (ADS)

Cu2ZnSnS4 nanocrystals were fabricated by hot injection of sulphur into a solution of metallic precursors. By careful control of the reaction conditions it was possible to control the elemental composition of the nanocrystals such that they are suitable for earth abundant photovoltaic absorbers. When the reaction temperature increased from 195 °C to 240 °C the energy band gap of the nanocrystals decreased from 1.65 eV to 1.39 eV. This variation is explained by the identification of a mixed wurtzite–kesterite phase at lower reaction temperatures and secondary phase Cu2SnS3 at higher temperatures. Moreover, the existence of wurtzite structure depends critically on the reaction cooling rate. The reaction time was also found to have a strong effect on the nanocrystals which became increasingly copper poor and zinc rich as the reaction evolved. As the reaction time increase from 15 min to 60 min, the energy band gap increased from 1.42 eV to 1.84 eV. This variation is discussed in terms of the sample doping. The results demonstrate the importance of optimizing the reaction conditions to produce high quality Cu2ZnSnS4 nanocrystals.

Qu, Yongtao; Zoppi, Guillaume; Miles, Robert W.; Beattie, Neil S.

2014-12-01

68

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

69

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

E-print Network

Calculation of the cumulative reaction probability via a discrete variable representation is suggested for the calculation of the microcanonical cumulative reaction probability uia flux autocorrelation, reaction show that the DVR-ABC scheme provides a very efficient method for the direct calculation

Miller, William H.

70

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. PMID:20806327

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

2011-01-01

71

Optimization of reaction conditions by RSM and structure characterization of sulfated locust bean gum.  

PubMed

Sulfated derivatives of galactomannan from locust bean gum (LBG) with the degree of substitution (DS) of 0.34-1.07 were synthesized using chlorosulfonic acid/pyridine (CSA/Py) method. Box-Behnken design (BBD) of response surface methodology (RSM) was employed to optimize the reaction conditions. Results of FT-IR and X-ray photoelectron spectroscopy (XPS) indicated that SO3H groups were widely present in sulfated LBG (SLBG). (13)C NMR result revealed that sulfation had occurred and C-6 substitution was predominant in SLBG. All sulfated samples showed a decrease in Mw and more broad molar mass distribution in size exclusion chromatography combined with laser light scattering (SEC-LLS) analysis. Results of MW - [Formula: see text] showed a decrease in fractal dimension (df) value. Laser light scattering results also showed a conformation transition from a compact chain conformation of branched clusters to a random coil conformation of SLBG. Compared to LBG and SLBG with low DS and molecular weight, SLBG2 exhibited an internal structure of random coil with a DS of 1.07. DS and molecular weight had great influence on its conformation in aqueous solution. Our results confirmed that the degradation of polysaccharide and SO3H groups improved significantly the stiffness of the chains due to the electrostatic effect. PMID:25263904

Wang, Junlong; Yang, Ting; Tian, Jia; Liu, Wenxi; Jing, Fan; Yao, Jian; Zhang, Ji; Lei, Ziqiang

2014-12-19

72

Subduction-related rodingites from East Othris, Greece: Mineral reactions and physicochemical conditions of formation  

NASA Astrophysics Data System (ADS)

The partly to pervasively metasomatized doleritic and gabbroic dykes or small to medium sized bodies found in East Othris, within Mid to Late Jurassic serpentinized peridotites of ophiolitic units and ophiolitic mélange formations are classified as rodingites and can be divided into two types. Type 1 rodingites are mainly characterized by the frequent occurrence of prehnite, while Type 2 rodingites include mostly garnets and vesuvianite. Isocon analysis showed that rodingitization essentially occurred with mass and volume preservation. Desilification, depletion of alkalies, as well as Ca enrichment was more intense for the Type 2 rodingites. Al, Fe and Mg remained rather immobile, while Ti, Y, Zr and REE were variably depleted. Rodingitization took place in an intraoceanic subduction system. It occurred in three successive stages during the exhumation of the mafic-ultramafic mantle wedge rocks in a fore-arc setting within a serpentinitic subduction channel, which developed close to the slab. The incorporation of the mafic rocks to the subduction channel probably resulted after entraining a directed mantle flow towards the slab. The first stage of rodingitization formed mainly grossular, hydrogrossular, Ti- and Cr-bearing hydrogarnets and calcite under relatively acidic and mildly oxidizing physicochemical conditions, with increased CO2/H2O ratio. During the second and more extensive rodingitization stage, alkaline and reducing conditions prevailed and CO2/H2O ratio was decreased. The modeling of the mineral reactions of this stage, using the software winTWQ v. 2.34 in the CFMASH system, reveals that in Type 1 rocks prehnite replaced most of the initial garnet, while Type 2 rocks continued to be rodingitized, mostly forming grossular and/or hydrogrossular and chlorite. Hydrogrossular, instead of grossular, was crystallized from hydrous fluids under high silica activity. Type 2 rodingites underwent further rodingitization during the third stage, due to infiltration of Ca-rich hydrothermal fluids of oceanic and/or subducted slab origin, at lower temperatures and depths. This stage is characterized by the appearance of hydroandradite and vesuvianite, under alkaline and oxidizing conditions, due to very low CO2/H2O ratio and relatively high fO2. All three rodingitization stages are estimated to have occurred under relatively moderate temperature and pressure (~ 300 to 400 °C; ~ 3-6 kbar respectively). Locally, Type 2 rodingites show derodingitization of variable extent, forming high-variance assemblages mostly consisting of chlorite ± pumpellyite. Some chlorite marginal zones in rodingite dykes may also have been developed by Mg-rich diffusional fluid flow, during this derodingitization process.

Koutsovitis, Petros; Magganas, Andreas; Pomonis, Panagiotis; Ntaflos, Theodoros

2013-07-01

73

Formation of ammonia in the reactions of a tungsten dinitrogen with ruthenium dihydrogen complexes under mild reaction conditions.  

PubMed

Treatment of cis-[W(N2)2(PMe2Ph)4] (5) with an equilibrium mixture of trans-[RuCl(eta 2-H2)(dppp)2]X (3) with pKa = 4.4 and [RuCl(dppp)2]X (4) [X = PF6, BF4, or OTf; dppp = 1,3-bis(diphenylphosphino)propane] containing 10 equiv of the Ru atom based on tungsten in benzene-dichloroethane at 55 degrees C for 24 h under 1 atm of H2 gave NH3 in 45-55% total yields based on tungsten, together with the formation of trans-[RuHCl(dppp)2] (6). Free NH3 in 9-16% yields was observed in the reaction mixture, and further NH3 in 36-45% yields was released after base distillation. Detailed studies on the reaction of 5 with numerous Ru(eta 2-H2) complexes showed that the yield of NH3 produced critically depended upon the pKa value of the employed Ru(eta 2-H2) complexes. When 5 was treated with 10 equiv of trans-[RuCl(eta 2-H2)(dppe)2]X (8) with pKa = 6.0 [X = PF6, BF4, or OTf; dppe = 1,2-bis(diphenylphosphino)ethane] under 1 atm of H2, NH3 was formed in higher yields (up to 79% total yield) compared with the reaction with an equilibrium mixture of 3 and 4. If the pKa value of a Ru(eta 2-H2) complex was increased up to about 10, the yield of NH3 was remarkably decreased. In these reactions, heterolytic cleavage of H2 seems to occur at the Ru center via nucleophilic attack of the coordinated N2 on the coordinated H2 where a proton (H+) is used for the protonation of the coordinated N2 and a hydride (H-) remains at the Ru atom. Treatment of 5, trans-[W(N2)2(PMePh2)4] (14), or trans-[M(N2)2(dppe)2] [M = Mo (1), W (2)] with Ru(eta 2-H2) complexes at room temperature led to isolation of intermediate hydrazido(2-) complexes such as trans-[W(OTf)(NNH2)(PMe2Ph)4]OTf (19), trans-[W(OTf)(NNH2)(PMePh2)4]OTf (20), and trans-[WX(NNH2)(dppe)2]+ [X = OTf (15), F (16)]. The molecular structure of 19 was determined by X-ray analysis. Further ruthenium-assisted protonation of hydrazido(2-) intermediates such as 19 with H2 at 55 degrees C was considered to result in the formation of NH3, concurrent with the generation of W(VI) species. All of the electrons required for the reduction of N2 are provided by the zerovalent tungsten. PMID:11151496

Nishibayashi, Y; Takemoto, S; Iwai, S; Hidai, M

2000-12-25

74

Conditions for diffusion-limited and reaction-limited recombination in nanostructured solar cells  

SciTech Connect

The performance of Dye-sensitized solar cells (DSC) and related devices made of nanostructured semiconductors relies on a good charge separation, which in turn is achieved by favoring charge transport against recombination. Although both processes occur at very different time scales, hence ensuring good charge separation, in certain cases the kinetics of transport and recombination can be connected, either in a direct or an indirect way. In this work, the connection between electron transport and recombination in nanostructured solar cells is studied both theoretically and by Monte Carlo simulation. Calculations using the Multiple-Trapping model and a realistic trap distribution for nanostructured TiO{sub 2} show that for attempt-to-jump frequencies higher than 10{sup 11}–10{sup 13} Hz, the system adopts a reaction limited (RL) regime, with a lifetime which is effectively independent from the speed of the electrons in the transport level. For frequencies lower than those, and depending on the concentration of recombination centers in the material, the system enters a diffusion-limited regime (DL), where the lifetime increases if the speed of free electrons decreases. In general, the conditions for RL or DL recombination depend critically on the time scale difference between recombination kinetics and free-electron transport. Hence, if the former is too rapid with respect to the latter, the system is in the DL regime and total thermalization of carriers is not possible. In the opposite situation, a RL regime arises. Numerical data available in the literature, and the behavior of the lifetime with respect to (1) density of recombination centers and (2) probability of recombination at a given center, suggest that a typical DSC in operation stays in the RL regime with complete thermalization, although a transition to the DL regime may occur for electrolytes or hole conductors where recombination is especially rapid or where there is a larger dispersion of energies of electron acceptors.

Ansari-Rad, Mehdi, E-mail: ansari.rad@ut.ac.ir [Department of Physics, University of Tehran, 1439955961 Tehran (Iran, Islamic Republic of) [Department of Physics, University of Tehran, 1439955961 Tehran (Iran, Islamic Republic of); Department of Physics, University of Shahrood, Shahrood (Iran, Islamic Republic of); Anta, Juan A., E-mail: anta@upo.es [Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, 41013 Sevilla (Spain); Arzi, Ezatollah [Department of Physics, University of Tehran, 1439955961 Tehran (Iran, Islamic Republic of)] [Department of Physics, University of Tehran, 1439955961 Tehran (Iran, Islamic Republic of)

2014-04-07

75

Conditions for diffusion-limited and reaction-limited recombination in nanostructured solar cells  

NASA Astrophysics Data System (ADS)

The performance of Dye-sensitized solar cells (DSC) and related devices made of nanostructured semiconductors relies on a good charge separation, which in turn is achieved by favoring charge transport against recombination. Although both processes occur at very different time scales, hence ensuring good charge separation, in certain cases the kinetics of transport and recombination can be connected, either in a direct or an indirect way. In this work, the connection between electron transport and recombination in nanostructured solar cells is studied both theoretically and by Monte Carlo simulation. Calculations using the Multiple-Trapping model and a realistic trap distribution for nanostructured TiO2 show that for attempt-to-jump frequencies higher than 1011-1013 Hz, the system adopts a reaction limited (RL) regime, with a lifetime which is effectively independent from the speed of the electrons in the transport level. For frequencies lower than those, and depending on the concentration of recombination centers in the material, the system enters a diffusion-limited regime (DL), where the lifetime increases if the speed of free electrons decreases. In general, the conditions for RL or DL recombination depend critically on the time scale difference between recombination kinetics and free-electron transport. Hence, if the former is too rapid with respect to the latter, the system is in the DL regime and total thermalization of carriers is not possible. In the opposite situation, a RL regime arises. Numerical data available in the literature, and the behavior of the lifetime with respect to (1) density of recombination centers and (2) probability of recombination at a given center, suggest that a typical DSC in operation stays in the RL regime with complete thermalization, although a transition to the DL regime may occur for electrolytes or hole conductors where recombination is especially rapid or where there is a larger dispersion of energies of electron acceptors.

Ansari-Rad, Mehdi; Anta, Juan A.; Arzi, Ezatollah

2014-04-01

76

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

77

Methanol conversion on SAPO-34: reaction condition for fixed-bed reactor  

Microsoft Academic Search

Reaction temperature and space velocity for methanol conversion to light olefins over SAPO-34 catalyst were experimentally studied in a bench-scale fixed-bed reactor. Temperature was found to be the strongest factor that affects product C2?:C3? ratio. Different C2?:C3? ratios can be obtained by adjusting reaction temperature or controlling the deactivation state of the catalyst. Higher temperature or partially deactivated catalyst produced

Xianchun Wu; Michael G. Abraha; Rayford G. Anthony

2004-01-01

78

Optimizing Reaction Conditions for the Isomerization of Fatty Acids and Fatty Acid Methyl Esters to Their Branch Chain Products  

Microsoft Academic Search

In order to improve the oxidative stability and cold flow properties of oleic acid or methyl oleate, branch chain isomerization\\u000a was conducted using a beta zeolite catalyst. Reaction conditions of temperature (200–300 °C), pressure (0.1–3.0 MPa), and\\u000a co-catalyst (0–2 wt%) were optimized based on branch chain conversion and the cloud point of the ester following the isomerization\\u000a reaction of oleic acid or

Stephen J. Reaume; Naoko Ellis

2011-01-01

79

Multivariate examination of response surfaces around the reaction conditions for the Scandinavian Society's recommended method for creatine kinase determinations.  

PubMed

We examined the reaction surfaces around five variables (imidazole, ADP, creatine phosphate, magnesium, and pH) in the Scandinavian method for determining creatine kinase, using factorial experimentation (five level, five factor) at reaction temperatures of 30 and 37 degrees C. Theoretical response surfaces were computed by fitting a quadratic polynomial equation to the experimental data by least-squares regression. Essentially no differences were apparent in the theoretical curves among the five specimens we analyzed, or between reaction temperatures. Our response-surface data showed the following: for pH and imidazole, activity optima in the region of the Scandinavian conditions; for creatine phosphate, a broad plateau over the concentration range investigated (10 to 50 mmol/L); and for magnesium and ADP, gently increasing contours with maximal creatine kinase activity at concentrations greater than those investigated in our study (magnesium 15 mmol/L, ADP 3.5 mmol/L). PMID:6744579

Sampson, E J; Whitner, V S; Ali, M; Fast, D M

1984-08-01

80

Effect of reaction conditions on size and morphology of SiO 2 powder in a sol-gel process  

Microsoft Academic Search

We have investigated effects of the reaction conditions such as mixing of solution, reactant concentration, feeding time and\\u000a molecular weight of alcohol solvents on the size and morphology of silicon oxide in a sol-gel process in Rushton type reactor.\\u000a To describe the intensity of mixing of solution the power input, which means the energy dissipated in the solution, was used.

Yeon-Woo Chang; Woon-Soo Kim; Woo-Sik Kim

1996-01-01

81

Reactions of CF 3O radicals with selected alkenes and aromatics under atmospheric conditions  

NASA Astrophysics Data System (ADS)

Rate data for the reactions of CF 3O radicals with alkenes and aromatic compounds have been determined at 298 K using a relative rate method. The data are analyzed in terms of structure-reactivity relationships, and their importance to the atmospheric chemistry of CF 3O discussed.

Kelly, Christina; Sidebottom, Howard W.; Treacy, Jack; Nielsen, Ole John

1994-02-01

82

Textured catalysts, methods of making textured catalysts, and methods of catalyzing reactions conducted in hydrothermal conditions  

DOEpatents

A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

Werpy, Todd [West Richland, WA; Wang, Yong [Richland, WA

2003-12-30

83

Reaction time performance in ADHD: improvement under fast-incentive condition and familial effects  

Microsoft Academic Search

Background. Reaction time (RT) variability is one of the strongest findings to emerge in cognitive- experimental research of attention deficit hyperactivity disorder (ADHD). We set out to confirm the association between ADHD and slow and variable RTs and investigate the degree to which RT performance improves under fast event rate and incentives. Using a group familial correlation approach, we tested

PENNY ANDREOU; BEN M. NEALE; WAI CHEN; HANNA CHRISTIANSEN; ISABEL GABRIELS; ALEXANDER HEISE; SHEERA MEIDAD; UELI C. MULLER; HENRIK UEBEL; TOBIAS BANASCHEWSKI; IRIS MANOR; ROBERT OADES; HERBERT ROEYERS; ARIBERT ROTHENBERGER; PAK SHAM; HANS-CHRISTOPH STEINHAUSEN; PHILIP ASHERSON; JONNA KUNTSI

2007-01-01

84

Light-Element Reaction Flow and the Conditions for r-Process Nucleosynthesis  

E-print Network

We deduce new constraints on the entropy per baryon ($s/k$), dynamical timescale ($\\tau_{dyn}$), and electron fraction ($Y_{e}$) consistent with heavy element nucleosynthesis in the r-process. We show that the previously neglected reaction flow throu gh the reaction sequence \\atg (n,$\\gamma$)\\Li~ significantly enhances the production of seed nuclei. We analyze the r-process nucleosynthesis in the context of a schematic exponential wi nd model. We show that fewer neutrons per seed nucleus implies that the entropy per baryon required for successful r-process nucleosynthesis must be more than a factor of two higher than previous estimates. This places new constraints on dynamical mo dels for the r-process.

T. Sasaqui; K. Otsuki; T. Kajino; G. J. Mathews

2005-07-17

85

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

86

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

87

Reaction norms in natural conditions: how does metabolic performance respond to weather variations in a small endotherm facing cold environments?  

PubMed

Reaction norms reflect an organisms' capacity to adjust its phenotype to the environment and allows for identifying trait values associated with physiological limits. However, reaction norms of physiological parameters are mostly unknown for endotherms living in natural conditions. Black-capped chickadees (Poecile atricapillus) increase their metabolic performance during winter acclimatization and are thus good model to measure reaction norms in the wild. We repeatedly measured basal (BMR) and summit (Msum) metabolism in chickadees to characterize, for the first time in a free-living endotherm, reaction norms of these parameters across the natural range of weather variation. BMR varied between individuals and was weakly and negatively related to minimal temperature. Msum varied with minimal temperature following a Z-shape curve, increasing linearly between 24°C and -10°C, and changed with absolute humidity following a U-shape relationship. These results suggest that thermal exchanges with the environment have minimal effects on maintenance costs, which may be individual-dependent, while thermogenic capacity is responding to body heat loss. Our results suggest also that BMR and Msum respond to different and likely independent constraints. PMID:25426860

Petit, Magali; Vézina, François

2014-01-01

88

Reaction Norms in Natural Conditions: How Does Metabolic Performance Respond to Weather Variations in a Small Endotherm Facing Cold Environments?  

PubMed Central

Reaction norms reflect an organisms' capacity to adjust its phenotype to the environment and allows for identifying trait values associated with physiological limits. However, reaction norms of physiological parameters are mostly unknown for endotherms living in natural conditions. Black-capped chickadees (Poecile atricapillus) increase their metabolic performance during winter acclimatization and are thus good model to measure reaction norms in the wild. We repeatedly measured basal (BMR) and summit (Msum) metabolism in chickadees to characterize, for the first time in a free-living endotherm, reaction norms of these parameters across the natural range of weather variation. BMR varied between individuals and was weakly and negatively related to minimal temperature. Msum varied with minimal temperature following a Z-shape curve, increasing linearly between 24°C and ?10°C, and changed with absolute humidity following a U-shape relationship. These results suggest that thermal exchanges with the environment have minimal effects on maintenance costs, which may be individual-dependent, while thermogenic capacity is responding to body heat loss. Our results suggest also that BMR and Msum respond to different and likely independent constraints. PMID:25426860

Petit, Magali; Vézina, François

2014-01-01

89

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

1998-06-01

90

The necessary and sufficient conditions of therapeutic personality change: Reactions to Rogers' 1957 article.  

PubMed

Carl Rogers' article (see record 2007-14639-002) on the necessary and sufficient conditions for personality change has had a significant impact on the field of psychotherapy and psychotherapy research. He emphasized the client as arbiter of his or her own subjective experience and tested his hypothesized therapist-offered conditions of change using recorded sessions. This aided in demystifying the therapeutic process and led to a radical shift in the listening stance of the therapist. I briefly outline my views regarding the influence of the ideas presented in this work, describe the intellectual and cultural context of the times, and discuss a number of ways in which the therapist-offered conditions for psychological transformation are neither necessary nor sufficient. (PsycINFO Database Record (c) 2010 APA, all rights reserved). PMID:22122256

Samstag, Lisa Wallner

2007-09-01

91

Optimisation of the reaction conditions for the production of cross-linked starch with high resistant starch content.  

PubMed

The optimum reaction conditions (temperature and pH) for the preparation of cross-linked (CL) corn and wheat starches with maximum resistant starch (RS) content were investigated by using response surface methodology (RSM). According to the preliminary results, five levels were selected for reaction temperature (38-70 °C) and pH (10-12) in the main study. RS contents of the CL corn and wheat starch samples increased with increasing temperature and pH, and pH had a greater influence on RS content than had temperature. The maximum RS content (with a maximum p value of 0.4%) was obtained in wheat starch cross-linked at 38 °C and pH 12. In the case of CL corn starch, the optimum condition was 70 °C and pH 12. CL corn and wheat starch samples were also produced separately under the optimum conditions and their RS contents were 80.4% and 83.9%, respectively. These results were also in agreement with the values predicted by RSM. PMID:25529667

Kahraman, Kevser; Koksel, Hamit; Ng, Perry K W

2015-05-01

92

Physical property changes of sandstones in Korea by supercritical CO2-sandstone-groundwater reaction at CO2 sequestration condition  

NASA Astrophysics Data System (ADS)

Lab scale experiments were performed to investigate physical property changes of sandstones by the dissolution reaction among supercritical CO2-sandstone-groundwater at sub-surface CO2 storage condition. High pressurized tank system was designed to create supercritical CO2 in the tank, simulating the sub-surface CO2 storage site. Three kinds of sandstones at Gyeongsang basin in Korea were sampled and they were cut into cylindrical cores (4.3 cm in diameter; 12 cm in height). A large stainless steel tank (2 liter of capacity) was used to create temperature and pressure conditions (50 oC and 100 bar) for CO2 sequestration, which was filled in with 1500 ml of groundwater and sandstone cores. For 60 days of reaction, physical properties of sandstones such as porosity, dry density, seismic velocity, and 1-D compression strength were measured to investigate the effect of supercritical CO2 on the sandstone at sequestration sites. The first-order dissolution coefficient (kd) of CO2-sandstone-groundwater reaction was calculated by measuring the change of the concentration of ions dissolved in groundwater and the weight of each sandstone core at the reaction time intervals. From the dissolution coefficient (kd), the dissolution time of 1 g per unit area (1 cm2) of each sandstone by CO2 injection was quantitatively predicted. The average porosity for sandstones was 8.183 % and it increased to 8.906 % after 60 days of the reaction. The average dry density, seismic velocity, and 1-D compression strength of sandstones decreased and these results were dependent on the porosity increase by the dissolution during the reaction. The average time to dissolve 1 g of B and C sandstones per unit area (1 cm2) was calculated as 1,525 years and 631 years, respectively, by using the first-order dissolution coefficient. From results, it was investigated that the physical property changes of sandstones at Gyeongsang basin in Korea rapidly occur when the supercritical CO2 is injected into CO2 sequestration sites.

Lee, M.; Kim, S.; Kim, J.; Wang, S.

2012-12-01

93

A transferable predator avoidance reaction may account for the conditioned and naive coho salmon  

E-print Network

acting as a homogeneous group in the present study. Conditioned coho salmon had learned to avoid torrent this predator predation. The maximum size of coho salmon that a torrent sculpin can catch and eat in laboratory growth is effective in limiting torrent sculpin predation on coho salmon, other factors are equally

94

Liquid Phase Hydrogenation of Benzalacetophenone: Effect of Solvent, Catalyst Support, Catalytic Metal and Reaction Conditions  

Microsoft Academic Search

Innovative catalysts based on a “porous glass” support material were developed and investigated for the reduction of benzalacetophenone. The easy preparation conditions and possibility to use different metals (e.g. Pd, Pt, Rh) for impregnation gave a broad variety of these catalysts. Hydrogenation experiments with these supported catalysts were carried out under different hydrogen pressures and temperatures. Porous glass catalysts with

Achim STOLLE; Christine SCHMÖGER; Bernd ONDRUSCHKA; Werner BONRATH; Thomas F. KELLER; Klaus D. JANDT

2011-01-01

95

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

96

The effect of preparation conditions on the structure and mechanical properties of reaction-sintered silicon nitride  

NASA Technical Reports Server (NTRS)

The microstructure of reaction sintered silicon nitride (RSSN) was changed over a wide range by varying the grain density, grain size of the silicon starting powder, nitriding conditions, and by introducing artificial pores. The influence of single microstructural parameters on mechanical properties like room temperature strength, creep behavior, and resistance to thermal shock was investigated. The essential factors influencing these properties were found to be total porosity, pore size distribution, and the fractions of alpha and beta Si3N4. In view of high temperature engineering applications of RSSN, potentials for optimizing the material's properties by controlled processing are discussed.

Heinrich, J.

1980-01-01

97

QuadraPure-Supported Palladium Nanocatalysts for Microwave-Promoted Suzuki Cross-Coupling Reaction under Aerobic Condition  

PubMed Central

Cross-linked resin-captured palladium (XL-QPPd) was readily prepared by simple physical adsorption onto the high loading QuadraPure macroporous resin and a subsequent reduction process. To enhance the mechanical stability, entrapped palladium nanocatalysts were cross-linked with succinyl chloride. Both transmission electron microscopy images and X-ray diffraction analysis revealed that the palladium nanoparticles were well dispersed with diameters ranging in 4–10?nm. The catalyst performed good catalytic activity in microwave-promoted Suzuki cross-coupling reactions in water under aerobic condition with mild condition by using various aryl halides and phenylboronic acid. In addition, the catalyst showed an excellent recyclability without significant loss of catalytic activity. PMID:25054185

Loh, Poh Lee; Juan, Joon Ching; Yarmo, Mohd Ambar; Yusop, Rahimi M.

2014-01-01

98

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

99

Adsorption and reaction of methanol on supported palladium catalysts: microscopic-level studies from ultrahigh vacuum to ambient pressure conditions.  

PubMed

We investigated the decomposition and (partial) oxidation of methanol on Pd based catalysts in an integrated attempt, simultaneously bridging both the pressure and the materials gap. Combined studies were performed on well-defined Pd model catalysts based on ordered Al(2)O(3) and Fe(3)O(4) thin films, on well-defined particles supported on powders and on Pd single crystals. The interaction of Pd nanoparticles and Pd(111) with CH(3)OH and CH(3)OH/O(2) mixtures was examined from ultrahigh vacuum conditions up to ambient pressures, utilizing a broad range of surface specific vibrational spectroscopies which included IRAS, TR-IRAS, PM-IRAS, SFG, and DRIFTS. Detailed kinetic studies in the low pressure region were performed by molecular beam methods, providing comprehensive insights into the microkinetics of the reaction system. The underlying microscopic processes were studied theoretically on the basis of specially designed 3-D nanocluster models containing approximately 10(2) metal atoms. The efficiency of this novel modelling approach was demonstrated by rationalizing and complementing pertinent experimental results. In order to connect these results to the behavior under ambient conditions, kinetic and spectroscopic investigations were performed in reaction cells and lab reactors. Specifically, we focused on (1) particle size and structure dependent effects in methanol oxidation and decomposition, (2) support effects and their relation to activity and selectivity, (3) the influence of poisons such as carbon, and (4) the role of oxide and surface oxide formation on Pd nanoparticles. PMID:17612720

Bäumer, Marcus; Libuda, Jörg; Neyman, Konstantin M; Rösch, Notker; Rupprechter, Günther; Freund, Hans-Joachim

2007-07-21

100

CO2 Hydrogenation to Methanol on Supported Au Catalysts under Moderate Reaction Conditions: Support and Particle Size Effects.  

PubMed

The potential of metal oxide supported Au catalysts for the formation of methanol from CO2 and H2 under conditions favorable for decentralized and local conversion, which could be concepts for chemical energy storage, was investigated. Significant differences in the catalytic activity and selectivity of Au/Al2 O3 , Au/TiO2 , AuZnO, and Au/ZrO2 catalysts for methanol formation under moderate reaction conditions at a pressure of 5?bar and temperatures between 220 and 240?°C demonstrate pronounced support effects. A high selectivity (>50?%) for methanol formation was obtained only for Au/ZnO. Furthermore, measurements on Au/ZnO samples with different Au particle sizes reveal distinct Au particle size effects: although the activity increases strongly with the decreasing particle size, the selectivity decreases. The consequences of these findings for the reaction mechanism and for the potential of Au/ZnO catalysts for chemical energy storage and a "green" methanol technology are discussed. PMID:25339625

Hartadi, Yeusy; Widmann, Daniel; Behm, R Jürgen

2015-02-01

101

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

102

Calcium phosphate scaffold from biogenic calcium carbonate by fast ambient condition reactions  

NASA Astrophysics Data System (ADS)

Calcium phosphate biogenic materials are biocompatible and promote bioactivity and osteoconductivity, which implies their natural affinity and tendency to bond directly to bones subsequently replacing the host bone after implantation owing to its biodegradability. Calcium hydrogen phosphate dihydrate, CaHPO 4·2H 2O, is known to be a nucleation precursor, in aqueous solutions, for apatitic calcium phosphates and, hence, a potential starting material for bone substitutes. Numerous approaches, via hydrothermal and ambient synthetic routes, have been used to produce calcium phosphate from biogenic calcium carbonate, taking advantage of the peculiar architecture and composition of the latter. In this article, the lamellar region of the cuttlefish bone ( Sepia officinalis) was used as a framework for the organized deposition of calcium phosphate crystals, at ambient conditions via a fast procedure involving an amorphous calcium carbonate intermediate, and ending with a conversion to calcium phosphate and a fixation procedure, thereby resulting in direct conversion of biogenic calcium carbonate into calcium phosphates at ambient conditions from the scale of months to hours.

Dutta, Abhishek; Fermani, Simona; Arjun Tekalur, Srinivasan; Vanderberg, Abigail; Falini, Giuseppe

2011-12-01

103

Investigation of influence of hypomagnetic conditions closely similar to interplanetary magnetic filed on behavioral and vegetative reactions of higher mammals  

NASA Astrophysics Data System (ADS)

To study the influence of long being under reduced magnetic field on behavioral and vegetative reactions of higher mammals the white rat males were put into the 700-1000 times reduced geomagnetic field (50-70 nT) for 25 days. Such field was obtained by using automatic compensation of the horizontal and vertical components of the GMF at a frequencies up to 10 Hz by means of solenoids of the experimental magnetic system. Control animals were located in the same room under usual laboratory GMF conditions (52 uT). Two days before the experiment the behavioral reactions were studied in the "open field" by means of a set of tests, characterizing the level of emotionality, moving and orientational-investigative activities of the animals under conditions of unimpeded behavior. 60 white underbred rat males with the initial body mass of 200 g were divided into three clusters. Animals with average indices were selected for the experiment. We have judged behavioral reaction disturbances of the rats under hypomagnetic conditions using videotape recordings carried out in the entire course of the chronic experiment. According to the obtained results during the period of maximum activity (from 230 to 330 a.m.) the number of interrelations between the individuals increased appreciably for experimental rats including interrelations with aggressive character. This was real during all 25 days of observation. We observed a certain dynamics of this index differed from that of the control group. We have also analyzed the final period of observation from the 21th to the 25th days. In this period we studied the 24 hours' dynamics of interrelations which were noted during 5 minutes in every hour around the clock. In the control group the number of interrelation was at a constantly low level. For experimental animals the number of interrelations was higher in the night hours than in the day ones. Moreover it exceeded the similar indexes observed from the 1st to the 20th day. For example from 300 to 305 a.m. on the 23th day we recorded 27 contacts of aggressive character between the individuals. So, in hypomagnetic field conditions the irritability of the animals' central nervous system grows, that expresses itself in the increase of contacts of aggressive and non-aggressive character between the individuals. Also we have carried out the Spirman correlation analysis between studied indices of moving activity and chemiluminescence of blood plasma and urine, electrolytic composition of urine and muscles. For control animals the quantity of correlation connections between electrolyte concentrations in studied substrata was higher than for experimental animals. The physiological sense of these correlation connections is discussed.

Krivova, Natalie; Trukhanov, Kiril; Zamotshina, Tatyana; Zaeva, Olga; Khodanovich, Marina; Misina, Tatyana; Tukhvatulin, Ravil; Suhko, Valery

104

The preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions.  

PubMed

In this comprehensive review, we report on the preparation of graft-copolymers of cellulose and cellulose derivatives using atom transfer radical polymerization (ATRP) under homogeneous conditions. The review is divided into four sections according to the cellulosic material that is graft-copolymerised; (i) cellulose, (ii) ethyl cellulose, (iii) hydroxypropyl cellulose and (iv) other cellulose derivatives. In each section, the grafted synthetic polymers are described as well as the methods used for ATRP macro-initiator formation and graft-copolymerisation. The physical properties of the graft-copolymers including their self-assembly in solution into nanostructures and their stimuli responsive behaviour are described. Potential applications of the self-assembled graft copolymers in areas such as nanocontainers for drug delivery are outlined. PMID:25016958

Joubert, Fanny; Musa, Osama M; Hodgson, David R W; Cameron, Neil R

2014-10-21

105

One-pot synthesis of dihydropyrimidones using silica-supported heteropoly acid as an efficient and reusable catalyst: Improved protocol conditions for the Biginelli reaction  

Microsoft Academic Search

An efficient synthesis of 3,4-dihydropyrimidinones or thiones (DHPMs) is described, using silica-supported heteropoly acid H3PW12O40\\/SiO2 (PW\\/SiO2) for the first time as the catalyst from an aldehyde, ?-keto ester and urea or thiourea in acetonitrile. Compared to the classical Biginelli reaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional

Ezzat Rafiee; Fomaida Shahbazi

2006-01-01

106

Experimental determination of the yield of pyrolysis products of polyethene and polypropene. Influence of reaction conditions  

SciTech Connect

The influence of temperature, residence time, concentration level of reactants and products, polymer type, and composition of the polymer mixture on the product spectra obtained from pyrolysis of polyethene (PE) and polypropene (PP) was determined. In the study the temperature was varied between 650 and 850 C, whereas residence times between 0.1 and 1 s were used. Thermodynamic calculations revealed that aromatics and methane are formed as the main products under conditions pertaining to chemical equilibrium. The ratio between these compounds is governed by the C/H ratio in the original polymer. Experiments were performed using a tubular reactor. The main products of the pyrolysis of PE and PP at 750 C and a residence time of 1 s are ethene (respectively 45 and 19 wt%), propene (24 and 45 wt%), and butene (23 and 27 wt%). At higher reactor temperatures the yields of ethane and methane increase, while the yields of both propene and butene decrease. The influences of the residence time, product concentration, polymer type, and composition of the polymer mixture on the product distribution are negligible compared to the influence of temperature.

Westerhout, R.W.J.; Kuipers, J.A.M.; Swaaij, W.P.M. van [Univ. of Twente, Enschede (Netherlands). Faculty of Chemical Engineering] [Univ. of Twente, Enschede (Netherlands). Faculty of Chemical Engineering

1998-03-01

107

Size reproducibility of gadolinium oxide based nanomagnetic particles for cellular magnetic resonance imaging: effects of functionalization, chemisorption and reaction conditions.  

PubMed

We developed biofunctionalized nanoparticles with magnetic properties by immobilizing diethyleneglycol (DEG) on Gd2O3, and PEGilation of small particulate gadolinium oxide (SPGO) with two methoxy-polyethyleneglycol-silane (mPEG-Silane 550 and 2000 Da) using a new supervised polyol route, described recently. In conjunction to the previous study to achieve a high quality synthesis and increase in the product yield of nanoparticles; assessment of the effects of functionalization, chemisorption and altered reaction conditions, such as NaOH concentration, temperature, reaction time and their solubility, on size reproducibility were determined as the goals of this study. Moreover, the effects of centrifugation, filtration and dialysis of the solution on the nono magnetic particle size values and their stability against aggregation have been evaluated. Optimization of reaction parameters led to strong coating of magnetic nanoparticles with the ligands which increases the reproducibility of particle size measurements. Furthermore, the ligand-coated nanoparticles showed enhanced colloidal stability as a result of the steric stabilization function of the ligands grafted on the surface of particles. The experiments showed that DEG and mPEG-silane (550 and 2000 Dalton) are chemisorbed on the particle surfaces of Gd2O3 and SPGO which led to particle sizes of 5.9 ± 0.13 nm, 51.3 ± 1.46 nm and 194.2 ± 22.1 nm, respectively. The small size of DEG-Gd2O3 is acceptably below the cutoff of 6nm, enabling easy diffusion through lymphatics and filtration from kidney, and thus provides a great deal of potential for further in-vivo and in-vitro application. PMID:25561907

Riyahi-Alam, Sadjad; Haghgoo, Soheila; Gorji, Ensieh; Riyahi-Alam, Nader

2015-01-01

108

Size Reproducibility of Gadolinium Oxide Based Nanomagnetic Particles for Cellular Magnetic Resonance Imaging: Effects of Functionalization, Chemisorption and Reaction Conditions  

PubMed Central

We developed biofunctionalized nanoparticles with magnetic properties by immobilizing diethyleneglycol (DEG) on Gd2O3, and PEGilation of small particulate gadolinium oxide (SPGO) with two methoxy-polyethyleneglycol-silane (mPEG-Silane 550 and 2000 Da) using a new supervised polyol route, described recently. In conjunction to the previous study to achieve a high quality synthesis and increase in the product yield of nanoparticles; assessment of the effects of functionalization, chemisorption and altered reaction conditions, such as NaOH concentration, temperature, reaction time and their solubility, on size reproducibility were determined as the goals of this study. Moreover, the effects of centrifugation, filtration and dialysis of the solution on the nono magnetic particle size values and their stability against aggregation have been evaluated. Optimization of reaction parameters led to strong coating of magnetic nanoparticles with the ligands which increases the reproducibility of particle size measurements. Furthermore, the ligand-coated nanoparticles showed enhanced colloidal stability as a result of the steric stabilization function of the ligands grafted on the surface of particles. The experiments showed that DEG and mPEG-silane (550 and 2000 Dalton) are chemisorbed on the particle surfaces of Gd2O3 and SPGO which led to particle sizes of 5.9 ± 0.13 nm, 51.3 ± 1.46 nm and 194.2 ± 22.1 nm, respectively. The small size of DEG-Gd2O3 is acceptably below the cutoff of 6nm, enabling easy diffusion through lymphatics and filtration from kidney, and thus provides a great deal of potential for further in-vivo and in-vitro application PMID:25561907

Riyahi-Alam, Sadjad; Haghgoo, Soheila; Gorji, Ensieh; Riyahi-Alam, Nader

2015-01-01

109

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

110

Ethanol Conversion to Hydrocarbons on HZSM-5: Effect of Reaction Conditions and Si/Al Ratio on the Product Distributions  

SciTech Connect

The Conversion of ethanol to hydrocarbon over HZSM-5 zeolite with different Si/Al ratios was investigated under various reaction conditions. The catalyst with a higher Si/Al ratio (low acid density) deactivated faster and generated more unsaturated compounds at a similar time-on-stream. Temperature affects the catalytic activity with respect to liquid hydrocarbon generation and the hydrocarbon product composition. At lower temperatures (~300°C), the catalyst deactivated faster with respect to the liquid hydrocarbon formation. Higher temperatures (~400°C) reduced the formation of liquid range hydrocarbons and formed more gaseous fractions. Weight hourly space velocity was also found to affect product selectivity with higher weight hourly space velocity leading to a higher extent of ethylene formation. The experimental results were analyzed in terms of the product composition and the coke content with respect to catalyst time-on-stream and compared with the catalyst lifetime with respect to the variables tested on the conversion of ethanol to hydrocarbon.

Ramasamy, Karthikeyan K.; Wang, Yong

2014-11-17

111

TaBr 5-catalyzed Biginelli reaction: one-pot synthesis of 3,4-dihydropyrimidin-2-(1 H)-ones\\/thiones under solvent-free conditions  

Microsoft Academic Search

An efficient TaBr5 (5–10mol%)-catalyzed Biginelli reaction under solvent-free conditions for one-pot syntheses of 3,4-dihydropyrimidin-2-(1H)-ones (DHPMs) and their thione analogs is reported. The catalyst is stable at room temperature and employed under mild and environmentally friendly conditions.

Naseem Ahmed; Johan E. van Lier

2007-01-01

112

Charge distribution analysis of catalysts under simulated reaction conditions. Final report, October 1, 1993--June 30, 1995  

SciTech Connect

A new technique has been developed to measure mobile charge carriers in dielectric materials, insulators and catalysts. The technique, Charge Distribution Analysis, is based on the measurement of the dielectric polarization in an electric field gradient, contact-free, at 0 Hertz under minimum perturbation conditions. The measured parameter is the force F{sup +-} experienced by the sample in a gradient of reversible polarity. CDA allows to determine the sign of the majority charge carriers and the density of surface charges which may be correlated to the chemical or catalytic activity. Throughout this work a microbalance has been used as a force-sensing device. CDA can be applied to any dielectric material, compact or porous, in inert or reactive and corrosive gas environments. To conduct CDA experiments under simulated reaction conditions that are relevant to coal liquefaction research, e.g. in reactive and in part chemically corrosive atmospheres, several modifications were introduced to the current design. In particular, the stainless steel sample chamber and furnace/electrode assembly were built, and the gas flow system was redesigned. The CDA instrument was equipped with new data acquisition capabilities. Tests were performed in inert gases and in reactive and corrosive atmosphere between ambient temperature and 500{degrees}C on iron oxide and partially sulfidized iron oxide catalysts as well as on pyrite (FeS{sub 2}) single crystals.

Freund, F.

1996-02-01

113

Conditions?  

Microsoft Academic Search

Research interests in feral hogs typically involve their negative impacts on ecosystems or their potential as a disease reservoir, especially with disease transmission to domestic swine. Authors within scientific literature state that feral hogs were captured as part of their research, but usually fail to mention specific conditions in which hogs were captured. Novice researchers of feral hogs must rely

A. Christy Wyckoff; Scott E. Henke; Kurt C. VerCauteren

114

The Combination of Salt Induced Peptide Formation Reaction and Clay Catalysis: A Way to Higher Peptides under Primitive Earth Conditions  

NASA Astrophysics Data System (ADS)

Two reactions with suggested prebiotic relevance for peptide evolution, the saltinduced peptide formation reaction and the peptide chain elongation/stabilization on clay minerals have been combined in experimental series starting from dipeptides and dipeptide/amino acid mixtures. The results show that both reactions can take place simultaneously in the same reaction environment and that the presence of mineral catalysts favours the formation of higher oligopeptides. These findings lend further support to the relevance of these reactions for peptide evolution on the primitive earth. The detailed effects of the specific clay mineral depend both on the nature of the mineral and the reactants in solution.

Rode, Bernd M.; Son, Hoang L.; Suwannachot, Yuttana; Bujdak, Juraj

1999-05-01

115

Selection of reference genes for quantitative reverse-transcription polymerase chain reaction normalization in Brassica napus under various stress conditions.  

PubMed

Data normalization is essential for reliable output of quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) assays, as the unsuitable choice of reference gene(s), whose expression might be influenced by exogenous treatments in plant tissues, could cause misinterpretation of results. To date, no systematic studies on reference genes have been performed in stressed Brassica napus. In this study, we investigated the expression variations of nine candidate reference genes in 40 samples of B. napus leaves subjected to various exogenous treatments. Parallel analyses by geNorm and NormFinder revealed that optimal reference genes differed across the different sets of samples. The best-ranked reference genes were PP2A and TIP41 for salt stress, TIP41 and ACT7 for heavy metal (Cr(6+)) stress, PP2A and UBC21 for drought stress, F-box and SAND for cold stress, F-box and ZNF for salicylic acid stress, TIP41, ACT7, and PP2A for methyl jasmonate stress, TIP41 and ACT7 for abscisic acid stress, and TIP41, UBC21, and PP2A for Sclerotinia sclerotiorum stress. Two newly employed reference genes, TIP41 and PP2A, showed better performances, suggesting their suitability in multiple conditions. To further validate the suitability of the reference genes, the expression patterns of BnWRKY40 and BnMKS1 were studied in parallel. This study is the first systematic analysis of reference gene selection for qRT-PCR normalization in B. napus, an agriculturally important crop, under different stress conditions. The results will contribute toward more accurate and widespread use of qRT-PCR in gene analysis of the genus Brassica. PMID:24770781

Wang, Zheng; Chen, Yu; Fang, Hedi; Shi, Haifeng; Chen, Keping; Zhang, Zhiyan; Tan, Xiaoli

2014-10-01

116

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

2010-01-01

117

CO{sub 2} reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures  

SciTech Connect

The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO{sub 2} and CO{sub 2}-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing wells on CO{sub 2} storage integrity. The pozzolan additive chosen, Type F flyash, a by-product of coal combustion, 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 CO{sub 2} and CO{sub 2}-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 CO{sub 2}-saturated brine and supercritical CO{sub 2} 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 CO{sub 2}, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 {mu}D. 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 CO{sub 2}, which are consistent with our laboratory findings. 16 refs., 4 figs., 1 tab.

Barbara G. Kutchko; Brian R. Strazisar; Nicolas Huerta; Gregory V. Lowry; David A. Dzombak; Niels Thaulow [United States Department of Energy, Pittsburgh, PA (United States). National Energy Technology Laboratory

2009-05-15

118

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

119

In-Cylinder Reaction Chemistry and Kinetics During Negative Valve Overlap Fuel Injection Under Low-Oxygen Conditions  

SciTech Connect

Fuel injection into the negative valve overlap (NVO) period is a common method for controlling combustion phasing in homogeneous charge compression ignition (HCCI) as well as other forms of advanced combustion. During this event, at least a portion of the fuel hydrocarbons can be converted to products containing significant levels of H2 and CO, as well as other short chain hydrocarbons by means of thermal cracking, water-gas shift, and partial oxidation reactions, depending on the availability of oxygen and the time-temperature-pressure history. The resulting products alter the autoignition properties of the combined fuel mixture for HCCI. Fuel-rich chemistry in a partial oxidation environment is also relevant to other high efficiency engine concepts (e.g., the dedicated EGR (D-EGR) concept from SWRI). In this study, we used a unique 6-stroke engine cycle to experimentally investigate the chemistry of a range of fuels injected during NVO under low oxygen conditions. Fuels investigated included iso-octane, iso-butanol, ethanol, and methanol. Products from NVO chemistry were highly dependent on fuel type and injection timing, with iso-octane producing less than 1.5% hydrogen and methanol producing more than 8%. We compare the experimental trends with CHEMKIN (single zone, 0-D model) predictions using multiple kinetic mechanisms available in the current literature. Our primary conclusion is that the kinetic mechanisms investigated are unable to accurately predict the magnitude and trends of major species we observed.

Kalaskar, Vickey B [ORNL] [ORNL; Szybist, James P [ORNL] [ORNL; Splitter, Derek A [ORNL] [ORNL; Pihl, Josh A [ORNL] [ORNL; Gao, Zhiming [ORNL] [ORNL; Daw, C Stuart [ORNL] [ORNL

2013-01-01

120

Optimization of reaction conditions to fabricate nano-silver using Couroupita guianensis Aubl. (leaf & fruit) and its enhanced larvicidal effect  

NASA Astrophysics Data System (ADS)

Currently bioactive principles of plants and their nanoproducts have been extensively studied in agriculture and medicine. In this study Couroupita guianensis Aubl. leaf and fruit extracts were selected for rapid and cost-effective synthesis of silver nanoparticles (leaf-LAgNPs and fruit-FAgNPs). Various physiological conditions such as temperature, pH, concentration of metal ions, stoichiometric proportion of reaction mixture and reaction time showed influence on the size, dispersity and synthesis rate of AgNPs. Generation of AgNPs was initially confirmed with the surface plasmon vibrations at 420 nm in UV-visible spectrophotometer. The results recorded from X-ray diffractometer (XRD) and Transmission electron microscope (TEM) supports the biosynthesis of cubic crystalline LAgNPs & FAgNPs with the size ranges between 10-45 nm and 5-15 nm respectively. Surface chemistry of synthesized AgNPs was studied with Fourier transform infrared spectroscopy (FTIR), it reveals that water soluble phenolic compounds present in the extracts act as reducing and stabilizing agent. Leaf, fruit extracts and synthesized AgNPs were evaluated against IV instar larvae of Aedes aegypti (Diptera; Culicidae). Furthermore, different extracts and synthesized AgNPs showed dose dependent larvicidal effect against A. aegypti after 24 h of treatment. Compare to all extracts such as ethyl acetate (leaf; LC50 - 44.55 ppm and LC90 - 318.39 ppm & fruit; LC50 - 49.96 ppm and LC90 - 568.84 ppm respectively) and Methanol (leaf; LC50 - 85.75 ppm and LC90 - 598.63 ppm & fruit; LC50 - 67.78 ppm and LC90 - 714.45 ppm respectively) synthesized AgNPs showed extensive mortality rate (LAgNPs; LC50 - 2.1 ppm and LC90 - 5.59 ppm & FAgNPs; LC50 - 2.09 ppm and LC90 - 5.7 ppm). Hence, this study proves that C. guianensis is a potential bioresource for stable, reproducible nanoparticle synthesis (AgNPs) and also can be used as an efficient mosquito control agent.

Vimala, R. T. V.; Sathishkumar, Gnanasekar; Sivaramakrishnan, Sivaperumal

2015-01-01

121

Molecular studies of model surfaces of metals from single crystals to nanoparticles under catalytic reaction conditions. Evolution from prenatal and postmortem studies of catalysts.  

PubMed

Molecular level studies of metal crystal and nanoparticle surfaces under catalytic reaction conditions at ambient pressures during turnover were made possible by the use of instruments developed at the University of California at Berkeley. Sum frequency generation vibrational spectroscopy (SFGVS), owing to its surface specificity and sensitivity, is able to identify the vibrational features of adsorbed monolayers of molecules. We identified reaction intermediates, different from reactants and products, under reaction conditions and for multipath reactions on metal single crystals and nanoparticles of varying size and shape. The high-pressure scanning tunneling microscope (HP-STM) revealed the dynamics of a catalytically active metallic surface by detecting the mobility of the adsorbed species during catalytic turnover. It also demonstrated the reversible and adsorbate-driven surface restructuring of platinum when exposed to molecules such as CO and ethylene. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) detected the reversible changes of surface composition in rhodium-palladium, platinum-palladium, and other bimetallic nanoparticles as the reactant atmosphere changed from oxidizing to reducing. It was found that metal nanoparticles of less than 2 nm in size are present in higher oxidation states, which alters and enhances their catalytic activity. The catalytic nanodiode (CND) confirmed that a catalytic reaction-induced current flow exists at oxide-metal interfaces, which correlates well with the reaction turnover. PMID:20860409

Somorjai, Gabor A; Aliaga, Cesar

2010-11-01

122

Basic studies on the kinetics and mechanism of the rapid dissolution reaction of plutonium dioxide under reducing conditions in acidic media  

NASA Astrophysics Data System (ADS)

Dissolution of PuO2 in aqueous solutions is a notoriously difficult task. Until the 1980s few dissolution processes existed except those based on the use of highly corrosive solutions consisting of nitric and hydrofluoric acids at boiling temperature. Thermodynamics calculations suggest that PuO2 dissolution can be achieved under strong oxidizing or reducing conditions, however. Basic results dealing with the reductive dissolution reaction of PuO2 with CrII in sulfuric acid media are presented herein. Simple heterogeneous kinetics modelling is proposed and satisfactorily accounts for the reaction rates observed under various physicochemical conditions. The electron transfer mechanism was investigated by applying O-18 -labeling techniques, which provided striking evidence of the pure heterogeneous nature of the electron transfer reaction.

Machuron-Mandard, Xavier; Madic, Charles

1994-10-01

123

Effect of reaction conditions on methyl red degradation mediated by boron and nitrogen doped TiO2  

NASA Astrophysics Data System (ADS)

Nowadays the employment of renewable and sustainable energy sources, and solar light as main option, becomes an urgent need. Photocatalytic processes received great attention in wastewater treatment due to their cheapness, environmental compatibility and optimal performances. Despite the general low selectivity of the photocatalysts, an accurate optimisation of the operational parameters needs to be carried out in order to maximise the process yield. Because of this reason, the present contribution aims to deepen either the knowledge in boron and/or nitrogen doped TiO2-based systems and their employment in methyl red removal from aqueous solutions. The samples were obtained by coprecipitation and characterised by XRD, SEM, BET specific surface area, UV-vis and XPS techniques. The catalytic activity was for the first time carefully evaluated with respect to methyl red photodegradation in different conditions as a function of working pH, counter-ions and pre-adsorption time. An ad-hoc study was performed on the importance of the pre-adsorption of the dye, suggesting that an extended adsorption is useless for the catalyst photoactivity, while a partial coverage is preferable. The photocatalytic tests demonstrate the positive influence of boron doping in photo-activated reactions and the great importance of the operational parameters with respect to the simple methyl red bleaching rather than the overall pollutant mineralisation. It is proved, indeed, that different working pH, acidifying means and substrate pre-adsorption time can enhance or limit the catalyst performances with respect to the complete pollutant degradation rather than its partial breakage.

Galenda, A.; Crociani, L.; Habra, N. El; Favaro, M.; Natile, M. M.; Rossetto, G.

2014-09-01

124

Acetamide hydrolyzing activity of Bacillus megaterium F-8 with bioremediation potential: optimization of production and reaction conditions.  

PubMed

Bacillus megaterium F-8 exhibited an intracellular acetamide hydrolyzing activity (AHA) when cultivated in modified nutrient broth with 3% tryptone, 1.5% yeast extract, and 0.5% sodium chloride, at pH 7.2, 45 °C for 24 h. Maximum AHA was recorded in the culture containing 0.1 M of sodium phosphate buffer, (pH 7.5) at 45 °C for 20 min with 0.2 % of acetonitrile and resting cells of B. megaterium F-8 equivalent to 0.2 ml culture broth. This activity was stable up to 55 °C and was completely inactivated at or above 60 °C. Maximum acyl transferase activity (ATA) was recorded in the reaction medium containing 0.1 M of potassium phosphate buffer, (pH 8.0) at 55 °C for 5 min with 0.85 mM of acetamide as acyl donor and hydroxylamine hydrochloride as acyl acceptor and resting cells of B. megaterium F-8 equivalent to 0.94 mg cells (dry weight basis). This activity was stable up to 60 °C and a rapid decline in enzyme activity was recorded above it. Under the optimized conditions, this organism hydrolyzed various nitriles and amides such as propionitrile, propionamide, caprolactam, acetamide, and acrylamide to corresponding acids. Acyl group transfer capability of this organism was used for the production of acetohydroxamic acid. ATA of B. megaterium F-8 showed broad substrate specificity such as for acetamide followed by propionamide, acrylamide, and lactamide. This amide hydrolyzing and amidotransferase activity of B. megaterium F-8 has potential applications in enzymatic synthesis of hydroxamic acids and bioremediation of nitriles and amides contaminated soil and water system. PMID:24723348

Sogani, Monika; Bakre, Prakash P; Mathur, Nupur; Sharma, Pratibha; Bhatnagar, Pradeep

2014-07-01

125

Molecular Studies of Surfaces under Reaction Conditions; Sum Frequency Generation Vibrational Spectroscopy, Scanning Tunneling Microscopy and Ambient Pressure X-Ray Photoelectron Spectroscopy  

SciTech Connect

Instruments developed in our laboratory permit the atomic and molecular level study of NPs under reaction conditions (SFG, ambient pressure XPS and high pressure STM). These studies indicate continuous restructuring of the metal substrate and the adsorbate molecules, changes of oxidation states with NP size and surface composition variations of bimetallic NPs with changes of reactant molecules.

Somorjai, G.A.

2009-11-11

126

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...

127

DATA COLLECTION CONSTRAINTS FOR THE USE OF LENGTH HETEROGENEITY POLYMERASE CHAIN REACTION (LH-PCR) AS AN INDICATOR OF STREAM SANITARY AND ECOLOGICAL CONDITION  

EPA Science Inventory

This study is part of a larger project for the development of bacterial indicators of stream sanitary and ecological condition. Here we report preliminary research on the use of Length Heterogeneity Polymerase Chain Reaction (LH-PCR), which discriminates among 16S rRNA genes bas...

128

Microgram-Scale Testing of Reaction Conditions in Solution Using Nanoliter Plugs in Microfluidics with Detection by MALDI-MS  

E-print Network

high efficiency and selectivity in organic reactions. Combinatorial methods1 and high- throughput with organic reagents and reasonably low viscosity (Supporting Information). To perform the reactions, the flow experiments were performed to characterize merging. Relative volumetric flow rates of substrate and reagent

Ismagilov, Rustem F.

129

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

2010-12-01

130

Non-precious metals catalyze formal [4 + 2] cycloaddition reactions of 1,2-diazines and siloxyalkynes under ambient conditions.  

PubMed

Copper(I) and nickel(0) complexes catalyze the formal [4 + 2] cycloaddition reactions of 1,2-diazines and siloxyalkynes, a reaction hitherto best catalyzed by silver salts. These catalysts based on earth abundant metals are not only competent, but the copper catalyst, in particular, promotes cycloadditions of pyrido[2,3-d]pyridazine and pyrido[3,4-d]pyridazine, enabling a new synthesis of quinoline and isoquinoline derivatives, as well as the formal [2 + 2] cycloaddition reaction of cyclohexenone with a siloxyalkyne. PMID:24911346

Sumaria, Chintan S; Türkmen, Yunus E; Rawal, Viresh H

2014-06-20

131

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....

132

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

Microsoft Academic Search

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°C. Lead dichloride was found

J. T. Shor; G. C. Frazier

1996-01-01

133

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

134

Type 1 reaction in leprosy: a model for a better understanding of tissue immunity under an immunopathological condition.  

PubMed

Type 1 reaction (T1R) or reversal reaction is the leading cause of physical disabilities and deformities in leprosy. Leprosy patients, even after being considered cured and released from treatment, may suffer from reactional episodes for long periods of time. Early diagnosis is a great challenge for effectively treating and managing T1R. There is an urgent need to identify the most significant biomarkers to prevent recurrent T1R and to differentiate late T1R from relapse. T1R continues to be treated with corticosteroids and complications due to iatrogenic treatment remain frequent. This review aims to provide a framework from which to approach the great challenges that still persist in T1R management and debate key issues in order to reduce the distance between basic research and the clinic. PMID:25666357

Andrade, Priscila Ribeiro; Pinheiro, Roberta Olmo; Sales, Anna Maria; Illarramendi, Ximena; de Mattos Barbosa, Mayara Garcia; Moraes, Milton Ozório; Jardim, Marcia Rodrigues; da Costa Nery, Jose Augusto; Sampaio, Elizabeth Pereira; Sarno, Euzenir Nunes

2015-03-01

135

Emissions of volatile organic compounds from Quercus ilex L. measured by proton transfer reaction mass spectrometry under different environmental conditions  

Microsoft Academic Search

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

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

2000-01-01

136

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 ...

137

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

138

Remarkable Features of the McMurry Reaction Conditions in Dimerization of Formyl- and 2-Formylvinylpurpurinimides. Electrochemistry of Monomeric Ni(II) Purpurinimide and the Corresponding Dyads  

PubMed Central

To investigate the electrochemical properties of purpurinimide dyads and electron transfer sites for their reduction and oxidation, a series of dimers with variable C-C linkages were synthesized. For the preparation of these novel structures, the formyl and 2-formylvinyl substituents were regioselectively introduced at positions-3 and 20 of Ni(II) purpurinimides by the Vilsmeier reaction. The Ni(II) complexes were then subjected to the McMurry reaction under two different conditions with unexpected results being obtained. For example, the reaction of formyl purpurinimides with TiCl3(DME)1.5 failed to produce the desired C-C dimers and the starting compounds were recovered almost quantitatively. Under similar reaction conditions, the 20-(2-formylvinyl)purpurinimide also did not dimerize but gave instead unexpected benzoisobacteriochlorins via an intramolecular cyclization. However, treatment of the 3-formyl- and 20-formyl-purpurinimides with TiCl4/Zn gave the corresponding dimers linked with one double bond (trans-) in modest yields. Under similar conditions, Ni(II) purpurinimides containing a 2-formylvinyl substituent either at position-3 or position-20 afforded the respective C-C dimers, where the purpurinimide moieties were joined with a trans-trans-trans- hexatriene linker. Molecular modeling data suggest that the nature of the conformational energy difference found in all trans- vs. trans-cis-trans- conformers of the dimers connected by a hexatriene linker at the meso- or ?-position of the macrocycle is not due to the intrinsic conformational energy difference of the linker region, which is identical for both dimers. PMID:19072690

Goswami, Lalit N.; Ethirajan, Manivannan; Dobhal, Mahabeer P.; Zhang, Min; Missert, Joseph R.; Shibata, Masayuki; Kadish, Karl M.; Pandey, Ravindra K.

2009-01-01

139

On the density dependence of single-proton and two-proton knockout reactions under quasifree conditions  

E-print Network

We consider high-energy quasifree single- and two-proton knockout reactions induced by electrons and protons and address the question what target-nucleus densities can be effectively probed after correcting for nuclear attenuation (initial- and final-state interactions). Our calculations refer to ejected proton kinetic energies of 1.5 GeV, the reactions (e,e'p), (\\gamma,pp) and (p,2p) and a carbon target. It is shown that each of the three reactions is characterized by a distinctive sensitivity to the density of the target nucleus. The bulk of the (\\gamma,pp) strength stems from the high-density regions in the deep nuclear interior. Despite the strong attenuation, sizable densities can be probed by (p,2p) provided that the energy resolution allows one to pick nucleons from s orbits. The effective mean densities that can be probed in high-energy (e,e'p) are of the order of 30-50% of the nuclear saturation density.

Wim Cosyn; Jan Ryckebusch

2009-04-06

140

Photochemical sources of organic acids. 1. Reaction of ozone with isoprene, propene, and 2-butenes under dry and humid conditions using SPME.  

PubMed

Formation of C4 and smaller carboxylic acids from gas-phase ozonolysis of several alkenes under dry (relative humidity (RH) < 1%) and humid (RH = 65%) conditions have been investigated. We have developed a technique based on solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to quantify the acids, as well as other products, and applied it to the reactions of ozone with propene, trans-2-butene, 2,3-dimethyl-2-butene, and isoprene. Acetic acid yields from propene and trans-2-butene ozonolysis in the presence of an OH scavenger were 2.7 +/- 0.6 and 2.9 +/- 0.6%, respectively, under dry conditions and 1.8 +/- 0.4 and 2.3 +/- 0.5% at 65% RH. Isoprene ozonolysis produced methacrylic and propenoic acids with yields of 5.5 +/- 1 and 3.0 +/- 1%, under dry conditions and 4.1 +/- 1 and 1.5 +/- 0.3% under wet conditions, respectively. That water inhibits acid formation indicates that the water reaction with stabilized Criegee intermediates is at most a minor source of acids. Acids that may form as coproducts of the OH radical elimination pathway, acetic acid from 2,3-dimethylbutene and isoprene, and propenoic acid from isoprene were also observed with significant yields (up to 10%), although the production of acetic acid was not a linear function of the alkene reacted. Carbonyl products are also reported. PMID:16839060

Orzechowska, Grazyna E; Paulson, Suzanne E

2005-06-23

141

Scaling Hyporheic Flow and Biogeochemical Reactions across a Wide Range of Flow and Sediment Conditions in Aquatic Systems  

NASA Astrophysics Data System (ADS)

Aquatic ecosystems are strongly influenced by advective transport from surface water into shallow sediments of the hyporheic zone. The delivery of energy and nutrient-rich materials to microbially and geochemically reactive sediment stimulates high rates of biogeochemical reactions that influence the overall metabolism of the ecosystem as well as influencing the chemistry of downstream receiving waters. Predicting hyporheic flow is difficult because of the potential involvement of many physical processes, including diffusion, shear, bedform-scale advective pumping, bed mobility and bioturbation, turbulence penetration, and head potential- driven groundwater exchange. We used published data from carefully controlled laboratory flume experiments to develop a scaling relationship that predicts hyporheic exchange based on physical descriptors (e.g. shear stress velocity, roughness height, and sediment permeability) that summarize fluid- flow and sediment characteristics. We tested the scaling relationship's predictions by comparing them with more time and labor intensive measurements of solute and reactive tracer transport made in situ in hyporheic zones. In situ measurements were acquired using the USGS MINIPOINT sampler, which allows detailed subsurface measurements without significant disturbance of sediment or the ambient surface or subsurface water fluxes. Fieldwork was undertaken in several streams that varied widely in surface water flow velocities, grain type, median grain size, sediment porosity, sediment organic content, sediment hydraulic conductivity, and groundwater specific discharge. The comparison generally supported the predictive capability of the scaling relationship in complex field settings. The value of the scaling relationship is also indicated for improving rate measurements of biogeochemical reactions in hyporheic zones (e.g. oxygen uptake, denitrification, and manganese oxidation), as well as for estimating the cumulative influence of hyporheic reactions on chemistry and water quality of downstream receiving waters.

Harvey, J. W.; O'Connor, B. L.

2008-12-01

142

Rapid and Efficient Copper-Catalyzed Finkelstein Reaction of (Hetero)Aromatics under Continuous-Flow Conditions.  

PubMed

A general, rapid, and efficient method for the copper-catalyzed Finkelstein reaction of (hetero)aromatics has been developed using continuous flow to generate a variety of aryl iodides. The described method can tolerate a broad spectrum of functional groups, including N-H and O-H groups. Additionally, in lieu of isolation, the aryl iodide solutions were used in two distinct multistep continuous-flow processes (amidation and Mg-I exchange/nucleophilic addition) to demonstrate the flexibility of this method. PMID:25378244

Chen, Mao; Ichikawa, Saki; Buchwald, Stephen L

2015-01-01

143

Cockpit thermal conditions and physiological reactions in flight: effects of mental workload on thermal regulation of aircrew while flying tasks  

Microsoft Academic Search

Thermal conditions in aircraft cockpits may affect aircrew performance, yet few in-flight measurements are available for the Japan Air Self-Defense Force (JASDF). This survey investigated the thermal environment in both the front and rear seats of the cockpit, as well as thermal strain on each of the pilots during flight, with the focus on the differences between the front and

Hirokazu Ozaki; Wataru Ogawa; Shintaro Yokoyama

2005-01-01

144

Protease-catalyzed peptide synthesis using inverse substrates: the influence of reaction conditions on the trypsin acyl transfer efficiency.  

PubMed

Benzyloxycarbonyl-L-alanine p-guanidinophenyl ester behaves as a trypsin "inverse substrate," i.e., a cationic center is included in the leaving group instead of being in the acyl moiety. Using this substrate as an acyl donor, trypsin catalyzes the synthesis of peptide bonds that cannot be split by this enzyme. An optimal acyl transfer efficiency was achieved between pH 8 and 9 at 30 degrees C.The addition of as much as 50% cosolvent was shown to be of minor influence on the acyl transfer efficiency, whereas the reaction velocity decreases by more than one order of magnitude. The efficiency of H-Leu-NH(2) and H-Val-NH(2) in deacylation is almost the same for "inverse" and normal type substrates. PMID:18600704

Schellenberger, V; Jakubke, H D; Zapevalova, N P; Mitin, Y V

1991-06-01

145

Influence of varying hydraulic conditions on hyporheic exchange and reactions in an in-stream gravel bar  

NASA Astrophysics Data System (ADS)

In the hyporheic zone (HZ) important biogeochemical transformations occur with crucial impact on nutrient cycling in fluvial systems. Here we investigate the interplay between stream flow and HZ exchange of a natural in-stream gravel bar (ISGB), by using three-dimensional steady state simulations of a coupled surface and subsurface numerical model. Stream flow is simulated by the open source computational fluid dynamics (CFD) software OpenFOAM. It is sequentially coupled by the hydraulic head distribution to the top boundary of the groundwater model code MIN3P, simulating flow, solute transport, aerobic respiration (AR) and denitrification (DN) in the HZ. The modelling approach is validated to the stream rating curve and the subsurface travel times in the ISGB based on field measurements. Hydraulic conditions are varied by stream discharge, ranging from low discharge, sufficient to allow stream water flow through both stream channels surrounding the ISGB (0.1 m³/s), to conditions where the ISGB is completely submerged (5.0 m³/s). Ambient groundwater flow is assigned by constant head boundaries upstream and downstream of the ISGB. By varying stream discharge or ambient groundwater heads the general flow field of the ISGB can be adjusted from losing via neutral to gaining conditions. Reactive transport scenarios consider stream water as the primary source of dissolved oxygen and dissolved organic carbon. Furthermore, two nitrate sources originated from the stream water and ambient groundwater are included in the model. Results show that highest hyporheic exchange and longest residence times occur under neutral conditions, where the extent of the hyporheic flow cell is at a maximum. Hence, the stronger the system is gaining and losing, the smaller is the hyporheic exchange flux and the shorter are the residence times in the HZ of the ISGB. AR and DN efficiencies of the ISGB are lowest under gaining conditions because infiltrating solutes are restriced to the hyporheic flow cells and hence to small reactive areas. In contrast, under losing conditions stream solutes infiltrate deep into the HZ and overreach the extent of the hyporheic flow cells, resulting in large reactive areas with highest AR and DN efficiencies.

Trauth, Nico; Schmidt, Christian; Maier, Uli; Fleckenstein, Jan H.

2014-05-01

146

Reaction and transport in debonded wellbore casing-cement interfaces under CO2 storage conditions: From batch reaction tests to flow-through experiments on the 2m length scale  

NASA Astrophysics Data System (ADS)

Debonding at interfaces between wellbore casing and cement is widely recognized as providing potential pathways for leakage from CO2 storage systems. This study addresses how the transport properties of such debonding-defects are affected by chemical reaction between cement, steel and CO2-bearing fluids. Our first set of experiments investigates near-static conditions, representative for stages prior to the formation of a fully connected defect network. Debonded cement-steel interfaces were simulated by constructing composite samples containing a spacer-imposed gap. Each sample was reacted with CO2 and an aqueous fluid, at 80°C and 14 MPa applied CO2 pressure, in seven sequential batch reaction runs (cumulative duration: 72 days). Permeability was measured after each run and microstructural analyses were performed after completion of the experiment. Reaction-induced permeability changes were limited, being less than one order of magnitude for all samples. Corrosion scale (Fe-carbonate, minor Fe-hydroxide) formed within the gap, on the surfaces of both the steel and cement. Here, the observed lack of Ca-carbonates suggests this corrosion scale produced a significant reduction in cement carbonation, similar to the decrease in corrosion rate observed when corrosion scale forms a protective film on steel. In contrast, Ca-carbonate did precipitate on the cement at locations beneath the spacers used to create the gap between the cement and steel plates, where corrosion scale did not form. Overall, the thin corrosion scale films on the cement surfaces seem to inhibit release of Ca from the cement into the gap and impede the precipitation of Ca- carbonates, which in other studies was found to promote sealing in fractured cement. Our batch reaction results imply that in local debonding-defects where corrosion scale development is insufficient to produce sealing, the scale's retarding effect on further reaction has the potential to maintain an open interfacial pathway. Ongoing changes in the temperature and stress state could lead these defects to propagate and connect, possibly resulting in a long-range pathway. Our second set of experiments is currently ongoing and addresses how such interconnected debonding-defects are affected by long-range chemical reaction and transport under flow-through conditions. Cement slurry was poured into a coil made of steel tube and was subsequently cured at 80°C. After curing, debonding was promoted by causing the steel tube to lift off the cement, providing us with a sample that contains a 2 m long section of (partially) debonded cement-steel interface. A flow-through permeameter, maintained at 80°C, will be used to one-sidedly flood the coil with CO2-bearing fluid, while continuously measuring sample permeability and pump/fluid volume (indicative for extent of reaction). Post-experiment microstructural analysis will be performed on the coil. To our knowledge, this will be the first experimental investigation of the cement-steel interface that includes reactive transport phenomena that occur on the metre length scale.

Wolterbeek, Tim; Peach, Colin; Spiers, Chris

2014-05-01

147

A Laboratory Test Setup for in Situ Measurements of the Dielectric Properties of Catalyst Powder Samples under Reaction Conditions by Microwave Cavity Perturbation: Set up and Initial Tests  

PubMed Central

The catalytic behavior of zeolite catalysts for the ammonia-based selective catalytic reduction (SCR) of nitrogen oxides (NOX) depends strongly on the type of zeolite material. An essential precondition for SCR is a previous ammonia gas adsorption that occurs on acidic sites of the zeolite. In order to understand and develop SCR active materials, it is crucial to know the amount of sorbed ammonia under reaction conditions. To support classical temperature-programmed desorption (TPD) experiments, a correlation of the dielectric properties with the catalytic properties and the ammonia sorption under reaction conditions appears promising. In this work, a laboratory test setup, which enables direct measurements of the dielectric properties of catalytic powder samples under a defined gas atmosphere and temperature by microwave cavity perturbation, has been developed. Based on previous investigations and computational simulations, a resonator cavity and a heating system were designed, installed and characterized. The resonator cavity is designed to operate in its TM010 mode at 1.2 GHz. The first measurement of the ammonia loading of an H-ZSM-5 zeolite confirmed the operating performance of the test setup at constant temperatures of up to 300 °C. It showed how both real and imaginary parts of the relative complex permittivity are strongly correlated with the mass of stored ammonia. PMID:25211199

Dietrich, Markus; Rauch, Dieter; Porch, Adrian; Moos, Ralf

2014-01-01

148

Determination of labile Fe(II) species complexed with seawater extractable organic matter under seawater conditions based on the kinetics of ligand-exchange reactions with ferrozine.  

PubMed

A fertilizer, comprised of a mixture of steel slag and compost, was used to restore seaweed beds in barren coastal areas. Complex Fe(II) species, supplied by steel slag, play a significant role in supplying Fe(II) to coastal areas and stimulating seaweed growth. Seawater extractable organic matter (SWEOM) from compost is generally assumed to serve as a chelator of Fe(II) in the fertilizer. It is considered that the bioavailability of Fe(II)-SWEOM complexes is higher in the dissociable (labile) species. In the present study, a method for determining labile species of Fe(II)-SWEOM complexes in seawater (pH 8.0, I = 0.7) was developed. The method is based on a ligand-exchange reaction between SWEOM and ferrozine (FZ). Because Fe(II) is readily oxidized to Fe(III) under normal seawater conditions, ascorbic acid was added as an antioxidant. The coloring for the Fe-FZ complex in the presence of SWEOM was retarded. This retarding can be attributed to a ligand-exchange reaction between FZ and labile Fe(II)-SWEOM complexes. Conditional binding constants for the labile Fe(II)-SWEOM complexes and binding capacities of labile sites in SWEOM to Fe(II) were evaluated for a variety of total Fe(II) concentrations. PMID:23842415

Iwai, Hisanori; Fukushima, Masami; Yamamoto, Mitsuo

2013-01-01

149

The ReactorSTM: atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions.  

PubMed

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions. PMID:25173272

Herbschleb, C T; van der Tuijn, P C; Roobol, S B; Navarro, V; Bakker, J W; Liu, Q; Stoltz, D; Cañas-Ventura, M E; Verdoes, G; van Spronsen, M A; Bergman, M; Crama, L; Taminiau, I; Ofitserov, A; van Baarle, G J C; Frenken, J W M

2014-08-01

150

The secondary formation of inorganic aerosols in the droplet mode through heterogeneous aqueous reactions under haze conditions  

NASA Astrophysics Data System (ADS)

Secondary inorganic aerosols play important roles in visibility reduction and in regional haze pollution. To investigate the characteristics of size distributions of secondary sulfates and nitrates as well as their formation mechanisms under hazes, size-resolved aerosols were collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) at an urban site in Jinan, China, in all four seasons (December 2007-October 2008). In haze episodes, the secondary sulfates and nitrates primarily formed in fine particles, with elevated concentration peaks in the droplet mode (0.56-1.8 ?m). The fine sulfates and nitrates were completely neutralized by ammonia and existed in the forms of (NH4)2SO4 and NH4NO3, respectively. The secondary formation of sulfates, nitrates and ammonium (SNA) was found to be related to heterogeneous aqueous reactions and was largely dependent on the ambient humidity. With rising relative humidity, the droplet-mode SNA concentration, the ratio of droplet-mode SNA to the total SNA, the fraction of SNA in droplet-mode particles and the mass median aerodynamic diameter of SNA presented an exponential, logarithmic or linear increase. Two heavily polluted multi-day haze episodes in winter and summer were analyzed in detail. The secondary sulfates were linked to heterogeneous uptake of SO2 followed by the subsequent catalytic oxidation by oxygen together with iron and manganese in winter. The fine nitrate formation was strongly associated with the thermodynamic equilibrium among NH4NO3, gaseous HNO3 and NH3, and showed different temperature-dependences in winter and summer.

Wang, Xinfeng; Wang, Wenxing; Yang, Lingxiao; Gao, Xiaomei; Nie, Wei; Yu, Yangchun; Xu, Pengju; Zhou, Yang; Wang, Zhe

2012-12-01

151

Evaluation of a Polymerase Chain Reaction Assay for Pathogen Detection in Septic Patients under Routine Condition: An Observational Study  

PubMed Central

Background Treatment of septic shock relies on appropriate antimicrobial therapy. Current culture based methods deliver final results after days, which may delay potentially lifesaving adjustments in antimicrobial therapy. This study was undertaken to compare PCR with blood culture results under routine conditions regarding 1. impact on antimicrobial therapy, and 2. time to result, in patients with presumed sepsis. Methodology/Principal Findings This was an observational study in a 50 beds ICU of a university hospital. In 245 patients with suspected sepsis, 311 concomitant blood cultures and blood for multiplex PCR (VYOO®) were obtained. 45 of 311 blood cultures (14.5%) and 94 of 311 PCRs (30.1%) were positive. However, blood culture or microbiological sampling from the presumed site of infection rarely confirmed PCR results and vice versa. Median time to positivity and interquartile range were 24.2 (18.0, 27.5) hours for the PCR and 68 (52.2, 88.5) hours for BC (p<0.01). PCR median time to result was dependent on technician availability (53.5 hours on Saturdays, 7.2 hours under optimal logistic conditions). PCR results showed good correlation with procalcitonin (p<0.001). In 34% of patients with positive PCRs antimicrobial therapy was considered inadequate according to assessment of clinical arbitrators including 5 patients with vancomycin-resistant enterococci (VRE), 3 cases with multiresistant staphylococci, and 4 patients with fungi. Conclusions The results of this observational study support the hypothesis that PCR results are available faster, are more frequently positive, and may result in earlier adjustment of antimicrobial therapy. However, shorter time to result can only be fully exploited when the laboratory is adequately staffed for a 24 hour/7 day service, or when point of care/automated assay systems become available. PMID:23029360

Bloos, Frank; Sachse, Svea; Kortgen, Andreas; Pletz, Mathias W.; Lehmann, Marc; Straube, Eberhard; Riedemann, Niels C.; Reinhart, Konrad; Bauer, Michael

2012-01-01

152

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

153

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

154

Catalytic reduction of NO by CO over rhodium catalysts. 2. Effect of oxygen on the nature, population, and reactivity of surface species formed under reaction conditions  

SciTech Connect

The effect of oxygen on the nature, population, and reactivity of surface species formed during reduction of NO by CO over Rh/TiO{sub 2} catalysts has been examined employing FTIR and transient MS techniques. It has been found that the activity of Rh is hindered by accumulation of surface oxygen originating from NO decomposition and gas-phase oxygen in the feed. Adsorbed CO and reduced TiO{sub 2{minus}x} species in the vicinity of Rh particles act as oxygen atom scavengers and, under fuel-rich conditions, remove atomic oxygen from the surface and restore the catalytic properties. Results of the present study provide additional evidence that production of N{sub 2} is related to dissociation of adsorbed Rh-NO{sup {minus}} while production of N{sub 2}O is related to the presence of Rh(NO){sub 2}. The presence of reduced RH{sup 0} sites is necessary for the formation of both reduction products. In the absence of oxygen in the feed, surface isocyanate species are also observed under reaction conditions. Their formation requires the presence of adjacent Rh{sup 0}-CO and reduced Rh{sup 0} sites. Although these species are favored under conditions in which NO conversion to reduction products is observed, there is no evidence that they are catalytically active species.

Kondarides, D.I.; Chafik, T.; Verykios, X.E.

2000-04-01

155

PAH formation under single collision conditions: reaction of phenyl radical and 1,3-butadiene to form 1,4-dihydronaphthalene.  

PubMed

The crossed beam reactions of the phenyl radical (C(6)H(5), X(2)A(1)) with 1,3-butadiene (C(4)H(6), X(1)A(g)) and D6-1,3-butadiene (C(4)D(6), X(1)A(g)) as well as of the D5-phenyl radical (C(6)D(5), X(2)A(1)) with 2,3-D2-1,3-butadiene and 1,1,4,4-D4-1,3-butadiene were carried out under single collision conditions at collision energies of about 55 kJ mol(-1). Experimentally, the bicyclic 1,4-dihydronaphthalene molecule was identified as a major product of this reaction (58 ± 15%) with the 1-phenyl-1,3-butadiene contributing 34 ± 10%. The reaction is initiated by a barrierless addition of the phenyl radical to the terminal carbon atom of the 1,3-butadiene (C1/C4) to form a bound intermediate; the latter underwent hydrogen elimination from the terminal CH(2) group of the 1,3-butadiene molecule leading to 1-phenyl-trans-1,3-butadiene through a submerged barrier. The dominant product, 1,4-dihydronaphthalene, is formed via an isomerization of the adduct by ring closure and emission of the hydrogen atom from the phenyl moiety at the bridging carbon atom through a tight exit transition state located about 31 kJ mol(-1) above the separated products. The hydrogen atom was found to leave the decomposing complex almost parallel to the total angular momentum vector and perpendicularly to the rotation plane of the decomposing intermediate. The defacto barrierless formation of the 1,4-dihydronaphthalene molecule involving a single collision between a phenyl radical and 1,3-butadiene represents an important step in the formation of polycyclic aromatic hydrocarbons (PAHs) and their partially hydrogenated counterparts in combustion and interstellar chemistry. PMID:22497458

Kaiser, R I; Parker, D S N; Zhang, F; Landera, A; Kislov, V V; Mebel, A M

2012-05-01

156

Si-rich layer formation on olivine surfaces during reaction with water and supercritical carbon dioxide under conditions relevant for geologic carbon storage  

NASA Astrophysics Data System (ADS)

The reaction of Mg-silicate minerals (i.e. olivine) with carbon dioxide (CO2) is a promising method for secure, long-term, geologic carbon storage. Several technical challenges must be overcome before implementing mineral carbonation technology on a large scale, one of which is slow reaction kinetics. This study probes surface reaction limitations of olivine carbonation, specifically the formation of a passivating, Si-rich layer on olivine surfaces upon exposure to water and CO2 under sequestration conditions (elevated temperature and pressure). A series of batch reactions were performed at 60°C and 100 bar CO2 pressure in Dickson-style rocker bombs, varying the length of reaction and the amount of mixing (rocking). The initial aqueous phase was spiked with 29Si. Fluid samples were taken periodically and analyzed for cation content, alkalinity, and dissolved inorganic carbon. At the end of each experiment, the solid products were analyzed with a Sensitive High Resolution Ion Microprobe Reverse Geometry (SHRIMP-RG) in order to measure the amount of 29Si incorporated into the Si-rich layer on reacted olivine grains. We also cut cross sections of reacted grains from each experiment using a Focused Ion Beam (FIB) which were thinned to <100nm and imaged using Transmission Electron Microscopy (TEM). SHRIMP-RG results show incorporation of 29Si on olivine grain surfaces reacted for 19 days with no mixing, and TEM images of olivine grains from the same experiment show an amorphous, Si-rich layer that is 30nm thick. Similarly, SHRIMP-RG results for olivine grains reacted for 19 days with mixing indicate 29SiO2 precipitation and TEM images reveal a Si-rich layer 60nm thick. In both experiments, EDS (energy dispersive spectroscopy) data show a step change in composition from the bulk rock to the surface layer in addition to the sharp crystalline/amorphous interface visible in the TEM images. Olivine from the unmixed experiment also has a slow decrease in Mg relative to Si before the step change, suggesting that, at least in this experiment, a Si-rich layer precipitated on top of a Mg-depleted layer that formed via a leaching process. SHRIMP-RG data also imply the presence of a precipitated Si-rich layer on top of a leached Si-rich layer, as the 29Si penetration depth is only 25-65% of the total Si-rich layer thickness. The combination of SHRIMP-RG and FIB/TEM analysis leads us to hypothesize that a Si-rich layer forms quickly on olivine surfaces due to preferential Mg removal from the surface (the traditional 'leached' layer), and as the reaction proceeds, amorphous silica reaches saturation in the fluid and precipitates on surfaces inside the reactor (including olivine grains).

Johnson, N. C.; Jackson, A.; Maher, K.; Bird, D. K.; Brown, G. E.

2013-12-01

157

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. PMID:20201565

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

2010-01-01

158

Effect of reaction conditions and 3AB on the mutation rate of poliovirus RNA-dependent RNA polymerase in a alpha-complementation assay.  

PubMed

The fidelity of poliovirus RNA-dependent RNA polymerase (3Dpol) was determined using a modified alpha-complementation assay. Several polymerases have been analyzed by this approach allowing comparisons to be drawn. Various conditions including high and low MgCl(2), replacing MgCl(2) with MnCl(2), 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 beta-galactosidase (lacZ-alpha). 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 Escherichia coli. The bacteria were screened for beta-galactosidase activity by blue-white phenotype analysis with white or faint blue colonies scored as errors made during synthesis on lacZ-alpha. Although 3AB strongly stimulated 3Dpol synthesis as expected, no change in fidelity was detected. Changes in MgCl(2) also showed little effect. Mutation rates of approximately 9 x 10(-5) (approximately 1 error per 11,000 incorporations) were estimated for these conditions. In contrast, MnCl(2) or skewed nucleotide pools were highly mutagenic resulting in lowered fidelity. PMID:19850090

DeStefano, Jeffrey J

2010-01-01

159

Combination of heterogeneous Fenton-like reaction and photocatalysis using Co-TiO2 nanocatalyst for activation of KHSO5 with visible light irradiation at ambient conditions.  

PubMed

A novel coupled system using Co-TiO2 was successfully designed which combined two different heterogeneous advanced oxidation processes, sulfate radical based Fenton-like reaction (SR-Fenton) and visible light photocatalysis (Vis-Photo), for degradation of organic contaminants. The synergistic effect of SR-Fenton and Vis-Photo was observed through comparative tests of 50mg/L Rhodamine B (RhB) degradation and TOC removal. The Rhodamine B degradation rate and TOC removal were 100% and 68.1% using the SR-Fenton/Vis-Photo combined process under ambient conditions, respectively. Moreover, based on XRD, XPS and UV-DRS characterization, it can be deduced that tricobalt tetroxide located on the surface of the catalyst is the SR-Fenton active site, and cobalt ion implanted in the TiO2 lattice is the reason for the visible light photocatalytic activity of Co-TiO2. Finally, the effects of the calcination temperature and cobalt concentration on the synergistic performance were also investigated and a possible mechanism for the synergistic system was proposed. This coupled system exhibited excellent catalytic stability and reusability, and almost no dissolution of Co(2+) was found. PMID:25499492

Chen, Qingkong; Ji, Fangying; Guo, Qian; Fan, Jianping; Xu, Xuan

2014-12-01

160

Effects of heat-moisture treatment reaction conditions on the physicochemical and structural properties of maize starch: Moisture and length of heating.  

PubMed

Changes in the properties of normal maize starch (NMS) and waxy maize starch (WMS) after heat-moisture treatment (HMT) under various reaction conditions were investigated. NMS and WMS were adjusted to moisture levels of 20%, 25% and 30% and heated at 100°C for 2, 4, 8 and 16h. The results showed that moisture content was the most important factor in determining pasting properties for NMS, whereas the heating length was more important for WMS. Swelling power decreased in NMS but increased in WMS, and while the solubility index decreased for both samples, the changes were largely determined by moisture content. The gelatinisation temperatures of both samples increased with increasing moisture content but remained unchanged with increasing heating length. The Fourier transform infrared (FT-IR) absorbance ratio was affected to different extents by the moisture levels but remained constant with increasing the heating length. The X-ray intensities increased but relative crystallinity decreased to a greater extent with increasing moisture content. This study showed that the levels of moisture content and length of heating had significant impacts on the structural and physicochemical properties of normal and waxy maize starches but to different extents. PMID:25466134

Sui, Zhongquan; Yao, Tianming; Zhao, Yue; Ye, Xiaoting; Kong, Xiangli; Ai, Lianzhong

2015-04-15

161

Amino acid/KI as multi-functional synergistic catalysts for cyclic carbonate synthesis from CO2 under mild reaction conditions: a DFT corroborated study.  

PubMed

Naturally occurring amino acids were identified as efficient co-catalysts for the alkali metal halide-mediated synthesis of cyclic carbonates from carbon dioxide and epoxides under mild, solvent free reaction conditions. The binary system of histidine/potassium iodide gave an appreciable turnover number of 535 for propylene oxide in 3 h. Detailed studies evaluating a variety of amino acids revealed that the basic amino acids afforded better conversion rates. The formation of a seven membered ring involving the zwitterionic ends of the amino acid, the metal halide, and the epoxide was considered to accelerate the catalysis rate. Density functional theory calculations were performed for the first time on amino acid co-catalyzed cycloaddition to provide further evidence for this hypothesis. The iodide ions of the alkali metal halide displayed excellent synergism with the hydrogen bonding groups of the amino acids in the production of cyclic carbonates, whereas bromide and chloride anions functioned less efficiently. The utilization of amino acids to enhance the catalytic activity of the cheap and eco-friendly alkali metal halides for cyclic carbonate synthesis represents a cost-effective, greener route towards the chemical fixation of carbon dioxide. PMID:24270098

Roshan, Kuruppathparambil Roshith; Kathalikkattil, Amal Cherian; Tharun, Jose; Kim, Dong Woo; Won, Yong Sun; Park, Dae Won

2014-02-01

162

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

PubMed

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

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

2015-01-28

163

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

164

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

165

Formation of HNCO from carbon monoxide and atomic nitrogen in their fundamental states. Investigation of the reaction pathway in conditions relevant to the interstellar medium.  

PubMed

As a simple molecule containing the four main atoms essential for life as we know it, isocyanic acid can be considered as a prebiotic molecule. As such, the understanding of reaction mechanisms leading to its formation is fundamental. Isocyanic acid is present in different physical environments in the medium. Previous studies have suggested that, in water-containing ices, on the surface of dust grains, HNCO may be formed from N and CO in their fundamental states. To further investigate the reaction process, herein we investigate this reaction by means of the matrix-isolation technique. PMID:25501292

Nourry, Sendres; Zins, Emilie-Laure; Krim, Lahouari

2015-01-28

166

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

167

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  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

168

Relative rate coefficient measurements of OH radical reactions with (Z)-2-hexen-1-ol and (E)-3-hexen-1-ol under simulated atmospheric conditions  

NASA Astrophysics Data System (ADS)

The relative rate technique was used to determine the rate coefficients of the reactions of OH radicals with (Z)-2-hexen-1-ol (k1), and (E)-3-hexen-1-ol (k2), at (296 ± 2) K and (750 ± 10) Torr of N2 or pure air. The reactions were investigated using a 200 L Teflon reaction chamber and a gas chromatograph coupled with flame-ionization detection. The following rate coefficients were derived, in units of cm3 mol-1 s-1: k1 = (1.1 ± 0.4) × 10-10 and k2 = (0.8 ± 0.1) × 10-10. This is the first experimental determination of k1 and k2. A comparison between the experimental rate coefficients (kexp) and the calculated rate coefficients using the structure-activity relationship (SAR) method (kSAR), for the reaction of different unsaturated alcohols with OH radicals is presented. The atmospheric lifetimes of the studied alcohols were estimated considering the rate coefficients of their reactions with OH and NO3 radicals. The radiative efficiencies (REs) were obtained from the infrared spectra of the two hexenols and the global warming potentials (GWPs) were then estimated. Atmospheric implications of the alcohols emission are briefly discussed.

Peirone, Silvina A.; Barrera, Javier A.; Taccone, Raúl A.; Cometto, Pablo M.; Lane, Silvia I.

2014-03-01

169

Influence of the reaction conditions and catalytic properties on the liquid-phase hydrodechlorination of chlorobenzene over palladium-supported catalysts: Activity and deactivation  

SciTech Connect

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, a better resistance to chlorine is observed when the size of the metallic particle increases. The supports tested, viz. SiO{sub 2}/AlPO{sub 4}, ZrO{sub 2}, and MgO, significantly affected catalyst deactivation. Thus, supports that can capture chloride species (e.g., ZrO{sub 2}) allow the reaction to finalize within relatively short times. The reaction appeared to be structure-sensitive in regard to the initial activity. Changing dispersion from 54 to 7% was accompanied by an increase in catalytic activity by a factor of 20.

Aramendia, M.A.; Borau, V.; Garcia, I.M.; Jimenez, C.; Lafont, F.; Marinas, A.; Marinas, J.M.; Urbano, F.J.

1999-10-25

170

Direct capture in the 130Sn(n,?)131Sn and 132Sn(n,?)133Sn reactions under r-process conditions  

NASA Astrophysics Data System (ADS)

The cross sections of the 130Sn(n,?)131Sn and 132Sn(n,?)133Sn reactions are calculated in the direct capture model at low energies below 1.5 MeV. Using recent data from (d,p) transfer experiments on 130Sn and 132Sn, it is possible to avoid global input parameters with their inherent uncertainties and to determine all inputs to the direct capture model by local adjustments. The calculated direct capture cross sections of 130Sn and 132Sn are almost identical and have uncertainties of less than a factor of 2. The stellar reaction rates NA?v show a slight increase with temperature. Finally, an estimate for the influence of low-lying resonances to the stellar reaction rates is given.

Mohr, Peter

2012-12-01

171

Drug Reactions  

MedlinePLUS

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

172

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

173

New three-component cyclocondensation reaction: microwave-assisted one-pot synthesis of 5-unsubstituted-3,4-dihydropyrimidin-2(1 H)-ones under solvent-free conditions  

Microsoft Academic Search

Sixteen 5-unsubstituted-3,4-dihydropyrimidin-2(1H)-ones have been synthesized by microwave-assisted Biginelli reactions in a short and concise manner employing ZnI2 as a catalyst under solvent-free conditions. All products were identified by IR, NMR, elemental analysis and HRMS. The advantages of this novel protocol include the excellent yield, operational simplicity, short time and the avoidance of the use of organic solvents and expensive catalysts.

Bing Liang; Xitian Wang; Jin-Xian Wang; Zhengyin Du

2007-01-01

174

ATP-synthase of Rhodobacter capsulatus: coupling of proton ow through FH to reactions in FI under the ATP synthesis and slip conditions  

E-print Network

ATP-synthase of Rhodobacter capsulatus: coupling of proton £ow through FH to reactions in FI under. Proton transfer through ATP-synthase (measured by electrochromic carotenoid bandshift and by p the amount of protons translocated by FHFI and the ATP yield decreased with the flash number from an apparent

Steinhoff, Heinz-Jürgen

175

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...

176

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

177

Miscellaneous conditions of the peritoneal cavity--peritoneal tumors, pseudomyxoma, mesothelioma, fibroblastic reaction, cocoon, cystic lymphatic malformations, blue-bleb, and chylous ascites.  

PubMed

The peritoneum is subject to both primary neoplasia and secondary malignancy from direct, trans-coelomic, or hematogenous spread from any cancer. The knowledge base in the pediatric age group is very limited due to the rarity of peritoneal conditions in children, and much of the information is extrapolated from adult literature. There have been few reports in the pediatric population on the diagnosis and management of peritoneal conditions including peritoneal malignancy. In this article, we aim to highlight some of these conditions and the treatments available with a special emphasis on the evolving role of cytoreduction surgery and hyperthermic intraperitoneal chemotherapy in the treatment of certain peritoneal malignancies in children. PMID:25459443

Dayal, Sanjeev; Ghosh, Dhruv; Moran, Brendan

2014-12-01

178

Types of Allergic Reactions  

MedlinePLUS

... allergies. Substances that don't bother some people (including certain medications) can trigger allergic reactions in others. ... | Terms and Conditions © 1996-2015 Academy of General Dentistry. All Rights Reserved.

179

Anchoring of palladium onto surface of porous metal-organic framework through post-synthesis modification and studies on Suzuki and Stille coupling reactions under heterogeneous condition.  

PubMed

An ecofriendly solid catalyst has been synthesized by anchoring palladium(II) into post synthetically modified metal organic framework IRMOF-3. The pore of IRMOF-3 was first modified with pyridine-2-aldehyde. The amine group of IRMOF-3 upon condensation with pyridine-2-aldehyde afforded a bidentate Schiff base moiety in the porous matrix. The Schiff base moieties were used to anchor palladium(II) ions. The prepared catalyst has been characterized by UV-vis, IR spectroscopy, X-ray powder diffraction, and nitrogen sorption measurements. Framework structure of the catalyst is not being destroyed in the multistep synthesis procedure as evidenced in X-ray powder diffraction studies. The catalyst has shown high activity toward the Suzuki and Stille cross-coupling reaction in 20% H2O/EtOH and EtOH medium, respectively, at 80 °C. The immobilized complex did not leach or decompose during the catalytic reactions, showing practical advantages over the homogeneous catalysis. PMID:23373729

Saha, Debraj; Sen, Rupam; Maity, Tanmoy; Koner, Subratanath

2013-03-01

180

An easy access to 2Amino5,6-dihydro-3 H -pyrimidin-4-one building blocks: The reaction under conventional and microwave conditions  

Microsoft Academic Search

Summary  A new one-stage fast multicomponent synthesis of title compounds leads to products in 21–55% isolated yields under both conventional and microwave conditions. The primary amino group in the building blocks can be easily acylated by various usual electophilic agents that can be utilized in the synthesis of diverse heterocylic compounds libraries.

Konstantin S. Ostras; Nikolay Yu. Gorobets; Sergey M. Desenko; Vladimir I. Musatov

2006-01-01

181

Reaction times  

Microsoft Academic Search

Reviews 11 studies dealing with reaction times (1910-1911). Reaction time has been utilized to study a variety of problems. The studies indicate that accurate results can not be obtained without careful attention to the technique of the method of reaction time. The topics covered include effect of intensity of stimulus on reaction time, rapidity of perception of sound and light

Herbert Woodrow

1911-01-01

182

A new cascade-less engine operated from subsonic to hypersonic conditions: designed by computational fluid dynamics of compressible turbulence with chemical reactions  

NASA Astrophysics Data System (ADS)

By using our computational fluid dynamic models, a new type of single engine capable of operating over a wide range of Mach numbers from subsonic to hypersonic regimes is proposed for airplanes, whereas traditional piston engines, turbojet engines, and scram engines work only under a narrower range of operating conditions. The new engine has no compressors or turbines such as those used in conventional turbojet engines. An important point is its system of super multijets that collide to compress gas for the transonic regime. Computational fluid dynamics is applied to clarify the potential of this engine. The peak pressure at the combustion center is over 2.5 MPa, while that just before ignition is over 1.0 MPa. The maximum power of this engine will be sufficient for actual use. Under the conditions of higher Mach numbers, the main intake passage located in front of the super multijet nozzles, takes in air more. That results in a ram or scramjet engine for supersonic and hypersonic conditions.

Naitoh, Ken; Nakamura, Kazushi; Emoto, Takehiro

2010-12-01

183

Environmental Conditions Environmental Conditions  

E-print Network

Environmental Conditions Environmental Conditions Appendix II The unique geology, hydrology and instream habitat. This chapter examines how environmental conditions in the Deschutes watershed affect, the discussion characterizes the environmental conditions within three watershed areas: the Lower Deschutes

184

Studying Biological Rhythms of Person's Skin-galvanic Reaction and Dynamics of Light Transmission by Isomeric Substance in Space Flight Conditions  

NASA Technical Reports Server (NTRS)

Intensity and amplitude of human functional systems and human most important organs are wavelike, rhythmic by nature. These waves have constant periodicity, phase and amplitude. The mentioned characteristics can vary, however their variations have a pronounced reiteration in the course of time. This indicates a hashing of several wave processes and their interference. Stochastic changes in wave processes characteristics of a human organism are explained either by 'pulsations' associated with hashing (superposition) of several wave processes and their interference, or by single influence of environmental physical factors on a human organism. Human beings have respectively periods of higher and lower efficiency, state of health and so on, depending not only of environmental factors, but also of 'internal' rhythmic factor. Sometimes peaks and falls periodicity of some or other characteristics is broken. Disturbance of steady-state biological rhythms is usually accompanied by reduction of activity steadiness of the most important systems of a human organism. In its turn this has an effect on organism's adaptation to changing living conditions as well as on general condition and efficiency of a human being. The latter factor is very important for space medicine. Biological rhythmology is a special branch of biology and medicine, it studies rhythmic activity mechanisms of organs, their systems, individuals and species. Appropriate researches were also carried out in space medicine.

Glushko, Vladimir

2004-01-01

185

Ab initio thermodynamics examination of sulfur species present on Rh, Ni, and binary Rh-Ni surfaces under steam reforming reaction conditions.  

PubMed

The stable form of adsorbed sulfur species and their coverage were investigated on Rh, Ni, and Rh-Ni binary metal surfaces using density functional theory calculations and the ab initio thermodynamics framework. S adsorption, SO(x) (x = 1-4) adsorption, and metal sulfide formation were examined on Rh(111) and Ni(111) pure metals. Both Rh and Ni metals showed a preference for S surface adsorption rather than SO(x) adsorption under steam reforming conditions. The transition temperature from a clean surface (<(1)/(9) ML) to S adsorption was identified on Rh(111), Ni(111), Rh(1)Ni(2)(111), and Rh(2)Ni(1)(111) metals at various P(H(2))/P(H(2)S) ratios. Bimetallic Rh-Ni metals transition to a clean surface at lower temperatures than does the pure Rh metal. Whereas Rh is covered with (1)/(3) ML of sulfur under the reforming conditions of 4-100 ppm S and 800 °C, Rh(1)Ni(2) is covered with (1)/(9) ML of sulfur at the lower end of this range (4-33 ppm S). The possibility of sulfate formation on Rh catalysts was examined by considering higher oxygen pressures, a Rh(221) stepped surface, and the interface between a Rh(4) cluster and CeO(2)(111) surface. SO(x) surface species are stable only at high oxygen pressure or low temperatures outside those relevant to the steam reforming of hydrocarbons. PMID:22385258

Lee, Kyungtae; Song, Chunshan; Janik, Michael J

2012-04-01

186

Kinetic Evidence for Near Irreversible Nonionic Micellar Entrapment of N-(2?-Methoxyphenyl)phthalimide (1) under the Typical Alkaline Reaction Conditions  

PubMed Central

The values of pseudo-first-order rate constants (kobs) for alkaline hydrolysis of 1, obtained at 1.0?mM NaOH and within [ CmEnT] (total concentration of CmEn) range of 3.0–5.0?mM for C12E23 and 10–20?mM for C18E20, fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversible CmEn micellar trapped 1 molecules (FIT1) vary in the range ~0–0.75 for C12E23 and ~0–0.83 for C18E20 under such conditions. The values of FIT1 become 1.0 at ?10?mM C12E23 and 50?mM C18E20. Kinetic analysis of the observed data at ?10?mM C12E23 shows near irreversible micellar entrapment of 1 molecules under such conditions. PMID:24574900

Khan, M. Niyaz; Sim, Yoke-Leng; Ariffin, Azhar

2014-01-01

187

Copper-assisted click reactions for activity-based proteomics: fine-tuned ligands and refined conditions extend the scope of application.  

PubMed

Copper-catalysed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) is the predominantly used bioconjugation method in the field of activity-based protein profiling (ABPP). Several limitations, however, including conversion efficiency, protein denaturation and buffer compatibility, restrict the scope of established procedures. We introduce an ABPP customised click methodology based on refined CuAAC conditions together with new accelerating copper ligands. A screen of several triazole compounds revealed the cationic quaternary {3-[4-({bis[(1-tert-butyl-1H-1,2,3-triazol-4-yl)methyl]amino}methyl)-1H-1,2,3-triazol-1-yl]propyl}trimethylammonium trifluoroacetate (TABTA) to be a superior ligand. TABTA exhibited excellent in vitro conjugation kinetics and optimal ABPP labelling activity while almost exclusively preserving the native protein fold. The application of this CuAAC-promoting system is amenable to existing protocols with minimal perturbations and is even compatible with previously unusable buffer systems such as Tris?HCl. PMID:24166841

Rudolf, Georg C; Sieber, Stephan A

2013-12-16

188

Reversible Reactions  

NSDL National Science Digital Library

Watch a reaction proceed over time. How does total energy affect a reaction rate? Vary temperature, barrier height, and potential energies. Record concentrations and time in order to extract rate coefficients. Do temperature dependent studies to extract Arrhenius parameters. This simulation is best used with teacher guidance because it presents an analogy of chemical reactions.

Simulations, Phet I.; Barbera, Jack; Koch, Linda; Lemaster, Ron; Adams, Wendy

2005-09-01

189

Enzyme Reactions  

NSDL National Science Digital Library

This video shows an enzyme reaction lab. The teacher demonstrates how the enzyme, catalase, reacts with hydrogen peroxide (a substrate found in cells). The teacher first demonstrates a normal enzyme reaction. He or she then goes on to show how manipulating temperature and pH will affect the reaction of an enzyme.

School, Minerva D.

2011-10-03

190

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

191

Oxidative dimerization of (E)- and (Z)-2-propenylsesamol with O2 in the presence and absence of laccases and other catalysts: selective formation of carpanones and benzopyrans under different reaction conditions.  

PubMed

The oxidative dimerization of 2-propenylsesamol to carpanone with O(2) as the oxidant, which probably proceeds as a domino phenol oxidation/anti-?,?-radical coupling/intramolecular hetero Diels-Alder reaction, can be efficiently catalyzed by laccases. Experiments with laccases and other catalysts like a Co(salen) type catalyst and PdCl(2) clearly demonstrate that the diastereoselectivity of the carpanone formation does not depend on the catalyst but on the double-bond geometry of the substrate. With (E)-2-propenylsesamol as the substrate, carpanone and a so far unknown carpanone diastereoisomer are formed in a 9:1 ratio. When (Z)-2-propenylsesamol is used as starting material, carpanone is accompanied by two carpanone diastereoisomers unknown so far in a 5:1:4 ratio. All three carpanone diastereoisomers have been separated by HPLC, and their structures have been elucidated unambiguously by NMR spectroscopy, DFT calculations, and spin work analysis. When the oxidation of 2-propenylsesamol with O(2) is performed in the absence of any catalyst two diastereoisomeric benzopyrans are formed, probably as the result of a domino oxidation/intermolecular hetero Diels-Alder reaction. Under these conditions, carpanone is formed in trace amounts only. PMID:22458664

Constantin, Mihaela-Anca; Conrad, Jürgen; Meri?or, Elena; Koschorreck, Katja; Urlacher, Vlada B; Beifuss, Uwe

2012-05-18

192

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

2013-10-24

193

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...

194

Laboratory study on new particle formation from the reaction OH + SO2: influence of experimental conditions, H2O vapour, NH3 and the amine tert-butylamine on the overall process  

NASA Astrophysics Data System (ADS)

Nucleation experiments starting from the reaction of OH radicals with SO2 have been performed in the IfT-LFT flow tube under atmospheric conditions at 293±0.5 K for a relative humidity of 13-61%. The presence of different additives (H2, CO, 1,3,5-trimethylbenzene) for adjusting the OH radical concentration and resulting OH levels in the range (4-300)·105 molecule cm-3 did not influence the nucleation process itself. The number of detected particles as well as the threshold H2SO4 concentration needed for nucleation was found to be strongly dependent on the counting efficiency of the used counting devices. High-sensitivity particle counters allowed the measurement of freshly nucleated particles with diameters down to about 1.5 nm. A parameterization of the experimental data was developed using power law equations for H2SO4 and H2O vapour. The exponent for H2SO4 from different measurement series was in the range of 1.7-2.1 being in good agreement with those arising from analysis of nucleation events in the atmosphere. For increasing relative humidity, an increase of the particle number was observed. The exponent for H2O vapour was found to be 3.1 representing a first estimate. Addition of 1.2·1011 molecule cm-3 or 1.2·1012 molecule cm-3 of NH3 (range of atmospheric NH3 peak concentrations) revealed that NH3 has a measureable, promoting effect on the nucleation rate under these conditions. The promoting effect was found to be more pronounced for relatively dry conditions. NH3 showed a contribution to particle growth. Adding the amine tert-butylamine instead of NH3, the enhancing impact for nucleation and particle growth appears to be stronger.

Berndt, T.; Stratmann, F.; Sipilä, M.; Vanhanen, J.; Petäjä, T.; Mikkilä, J.; Grüner, A.; Spindler, G.; Mauldin, R. Lee, III; Curtius, J.; Kulmala, M.; Heintzenberg, J.

2010-03-01

195

Reaction Time  

NSDL National Science Digital Library

In this activity, learners explore reaction time and challenge themselves to improve their coordination. Do you want to move faster? Catch that ball that you never seem to see in time? Use a simple test to help you improve your reaction (or response) time.

Science, New Y.

1999-01-01

196

Title: Elucidation of Environmental Fate of Artificial Sweeteners (Aspartame, Acesulfame K and Saccharin) by Determining Bimolecular Rate Constants with Hydroxyl Radical at Various pH and Temperature Conditions and Possible Reaction By-Products  

NASA Astrophysics Data System (ADS)

Use of artificial sweeteners in beverages and food has been rapidly increasing because of their non-calorie nature. In Japan, aspartame, acesulfame K and sucralose are among the most widely used artificial sweeteners. Because the artificial sweeteners are not metabolized in human bodies, they are directly excreted into the environment without chemical transformations. We initiated a study to better understand the fate of artificial sweeteners in the marine environment. The hydroxyl radical (OH), the most potent reactive oxygen species, reacts with various compounds and determines the environmental oxidation capacity and the life-time of many compounds. The steady-state OH concentration and the reaction rate constants between the compound and OH are used to estimate the life-time of the compound. In this study, we determine the bimolecular rate constants between aspartame, acefulfame K and saccharin and OH at various pH and temperature conditions using a competition kinetics technique. We use hydrogen peroxide as a photochemical source of OH. Bimolecular rate constant we obtained so far for aspartame was (2.6±1.2)×109 M-1 s-1 at pH = 3.0 and (4.9±2.3)×109 M-1 s-1 at pH = 5.5. Little effect was seen by changing the temperatures between 15 and 40 oC. Activation energy (Ea) was calculated to be -1.0 kJ mol-1 at pH = 3.0, +8.5 kJ mol-1 at pH = 5.5, which could be regarded as zero. We will report bimolecular rate constants at different pHs and temperatures for acesulfame K and saccharin, as well. Possible reaction by-products for aspartame will be also reported. We will further discuss the fate of aspartame in the coastal environment.

Teraji, T.; Arakaki, T.; Suzuka, T.

2012-12-01

197

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.

198

Facile electrochemical co-deposition of a graphene-cobalt nanocomposite for highly efficient water oxidation in alkaline media: direct detection of underlying electron transfer reactions under catalytic turnover conditions.  

PubMed

A facile electrochemical co-deposition method has been developed for the fabrication of graphene-cobalt nanocomposite modified electrodes that achieve exceptionally efficient water oxidation in highly alkaline media. In the method reported, a graphene-cobalt nanocomposite film was deposited electrochemically from a medium containing 1 mg ml(-1) graphene oxide, 0.8 mM cobalt nitrate and 0.05 M phytic acid (pH 7). The formation of the nanocomposite film was confirmed using electrochemical, Raman spectroscopic and scanning electron microscopic techniques. The nanocomposite film exhibits excellent activity and stability towards water oxidation to generate oxygen in 1 M NaOH aqueous electrolyte media. A turn over frequency of 34 s(-1) at an overpotential of 0.59 V and a faradaic efficiency of 97.7% were deduced from analysis of data obtained by rotating ring disk electrode voltammetry. Controlled potential electrolysis data suggests that the graphene supported catalyst exhibits excellent stability under these harsh conditions. Phytate anion acts as stabilizer for the electrochemical formation of cobalt nanoparticles. Fourier transformed ac voltammetry allowed the redox chemistry associated with catalysis to be detected directly under catalytic turnover conditions. Estimates of formal reversible potentials obtained from this method and derived from the overall reactions 3Co(OH)2 + 2OH(-) ? Co3O4 + 4H2O + 2e(-), Co3O4 + OH(-) ? 3CoOOH + e(-) and CoOOH + OH(-) ? CoO2 + H2O + e(-) are 0.10, 0.44 and 0.59 V vs. Ag/AgCl, respectively. PMID:25093585

Guo, Si-Xuan; Liu, Yuping; Bond, Alan M; Zhang, Jie; Esakki Karthik, P; Maheshwaran, I; Senthil Kumar, S; Phani, K L N

2014-09-21

199

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 ...

200

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.

Maryland Virtual High School

201

Oxide formation: reaction details studied,  

E-print Network

-nitrosohydroxylamines undergo an alternative decomposition under very similar reaction conditions to liberate nitrous oxide, N2O to human health. Investigation of the molecular basis of these alternative reactions of N recent work at Newcastle on the mechanisms of decomposition of N-nitrosohydroxylamines in which we

Johnson, Edward A.

202

Laboratory study on new particle formation from the reaction OH + SO2: influence of experimental conditions, H2O vapour, NH3 and the amine tert-butylamine on the overall process  

NASA Astrophysics Data System (ADS)

Nucleation experiments starting from the reaction of OH radicals with SO2 have been performed in the IfT-LFT flow tube under atmospheric conditions at 293±0.5 K for a relative humidity of 13-61%. The presence of different additives (H2, CO, 1,3,5-trimethylbenzene) for adjusting the OH radical concentration and resulting OH levels in the range (4-300) ×105 molecule cm-3 did not influence the nucleation process itself. The number of detected particles as well as the threshold H2SO4 concentration needed for nucleation was found to be strongly dependent on the counting efficiency of the used counting devices. High-sensitivity particle counters allowed the measurement of freshly nucleated particles with diameters down to about 1.5 nm. A parameterization of the experimental data was developed using power law equations for H2SO4 and H2O vapour. The exponent for H2SO4 from different measurement series was in the range of 1.7-2.1 being in good agreement with those arising from analysis of nucleation events in the atmosphere. For increasing relative humidity, an increase of the particle number was observed. The exponent for H2O vapour was found to be 3.1 representing an upper limit. Addition of 1.2×1011 molecule cm-3 or 1.2×1012 molecule cm-3 of NH3 (range of atmospheric NH3 peak concentrations) revealed that NH3 has a measureable, promoting effect on the nucleation rate under these conditions. The promoting effect was found to be more pronounced for relatively dry conditions, i.e. a rise of the particle number by 1-2 orders of magnitude at RH = 13% and only by a factor of 2-5 at RH = 47% (NH3 addition: 1.2×1012 molecule cm-3). Using the amine tert-butylamine instead of NH3, the enhancing impact of the base for nucleation and particle growth appears to be stronger. Tert-butylamine addition of about 1010 molecule cm-3 at RH = 13% enhances particle formation by about two orders of magnitude, while for NH3 only a small or negligible effect on nucleation in this range of concentration appeared. This suggests that amines can strongly influence atmospheric H2SO4-H2O nucleation and are probably promising candidates for explaining existing discrepancies between theory and observations.

Berndt, T.; Stratmann, F.; Sipilä, M.; Vanhanen, J.; Petäjä, T.; Mikkilä, J.; Grüner, A.; Spindler, G.; Mauldin, R. Lee, III; Curtius, J.; Kulmala, M.; Heintzenberg, J.

2010-08-01

203

Taxol reactions.  

PubMed

Paclitaxel (Taxol) a taxane antineoplastic agent causing irreversible microtubule aggregation with activity against breast, ovarian, lung, head and neck, bladder, testicular, esophageal, endometrial and other less common tumors was derived from the bark of the Pacific yew (Taxus brevifolia). Phase I trials conducted in the late 1980s were almost halted because of the high frequency of hypersensitivity-like reactions. Respiratory distress (dyspnea and/or bronchospasm), hypotension, and angioedema were the major manifestations, but flushing, urticaria, chest, abdomen, and extremity pains were described also. Reactions occurred on first exposure in the majority of cases raising etiologic questions. The vehicle for paclitaxel Cremophor EL (polyoxyethylated castor oil in 50% ethanol) was strongly suspect as a direct (non-immunoglobulin E dependent) histamine releaser. Premedication regimens and longer infusion times lowered the incidence of reactivity allowing phase II and III trials to progress through the early 1990s. The mechanism(s) underlying paclitaxel hypersensitivity-like reactions is still unknown, and clinical data on probable complement and mast cell activation are lacking. The original clinical trial protocols for paclitaxel required discontinuation of therapy for patients who experienced hypersensitivity-like reactions. Here, we review the current etiologic knowledge of these reactions and describe our clinical approach to allow completion of chemotherapy with this powerful plant-derived agent. PMID:12125509

Price, Kursteen S; Castells, Mariana C

2002-01-01

204

Proton Transfer Reaction Time-of-Flight Mass Spectrometric (PTR-TOF-MS) determination of volatile organic compounds (VOCs) emitted from a biomass fire developed under stable nocturnal conditions  

NASA Astrophysics Data System (ADS)

Combustion of solid and liquid fuels is the largest source of potentially toxic volatile organic compounds (VOCs), which can strongly affect health and the physical and chemical properties of the atmosphere. Among combustion processes, biomass burning is one of the largest at global scale. We used a Proton Transfer Reaction “Time-of-Flight” Mass Spectrometer (PTR-TOF-MS), which couples high sensitivity with high mass resolution, for real-time detection of multiple VOCs emitted by burned hay and straw in a barn located near our measuring station. We detected 132 different organic ions directly attributable to VOCs emitted from the fire. Methanol, acetaldehyde, acetone, methyl vinyl ether (MVE), acetic acid and glycolaldehyde dominated the VOC mixture composition. The time-course of the 25 most abundant VOCs, representing ?85% of the whole mixture of VOCs, was associated with that of carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4) emissions. The strong linear relationship between the concentrations of pyrogenic VOC and of a reference species (i.e. CO) allowed us to compile a list of emission ratios (ERs) and emission factors (EFs), but values of ER (and EF) were overestimated due to the limited mixing of the gases under the stable (non-turbulent) nocturnal conditions. In addition to the 25 most abundant VOCs, chemical formula and concentrations of the residual, less abundant VOCs in the emitted mixture were also estimated by PTR-TOF-MS. Furthermore, the evolution of the complex combustion process was described on the basis of the diverse types of pyrogenic gases recorded.

Brilli, Federico; Gioli, Beniamino; Ciccioli, Paolo; Zona, Donatella; Loreto, Francesco; Janssens, Ivan A.; Ceulemans, Reinhart

2014-11-01

205

A 3D-RISM-SCF method with dual solvent boxes for a highly polarized system: application to 1,6-anhydrosugar formation reaction of phenyl ?- and ?-D-glucosides under basic conditions.  

PubMed

One of the difficulties in application of the usual reference interaction site model self-consistent field (RISM-SCF) method to a highly polarized and bulky system arises from the approximate evaluation of electrostatic potential (ESP) with pure point charges. To improve this ESP evaluation, the ESP near a solute is directly calculated with a solute electronic wavefunction, that distant from a solute is approximately calculated with solute point charges, and they are connected with a switching function. To evaluate the fine solvation structure near the solute by incorporating the long-range solute-solvent Coulombic interaction with low computational cost, we introduced the dual solvent box protocol; one small box with the fine spacing is employed for the first and the second solvation shells and the other large box with the normal spacing is employed for long-range solute-solvent interaction. The levoglucosan formation from phenyl ?- and ?-d-glucosides under basic conditions is successfully inspected by this 3D-RISM-SCF method at the MP2 and SCS-MP2 levels, though the 1D-RISM-SCF could not be applied to this reaction due to the presence of highly polarized and bulky species. This 3D-RISM-SCF calculation reproduces the experimentally reported higher reactivity of the ?-anomer. The 3D-RISM-SCF-calculated activation free energy for the ?-anomer is closer to the experimental value than the PCM-calculated one. Interestingly, the solvation effect increases the difference in reactivity between these two anomers. The reason is successfully elucidated with 3D-RISM-SCF-calculated microscopic solvation structure and decomposition analysis of solute-solvent interaction. PMID:23525092

Aono, Shinji; Hosoya, Takashi; Sakaki, Shigeyoshi

2013-05-01

206

Reaction Time  

NSDL National Science Digital Library

In this activity, learners conduct an experiment to test how fast they can react. Learners try to catch a piece of paper with a ruler printed on it (or a ruler) as quickly as they can. Learners collect data and compare the reaction times of friends and family.

Boston, Wgbh

2003-01-01

207

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

208

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

209

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

NASA Technical Reports Server (NTRS)

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.

2010-01-01

210

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

211

Classical Conditioning  

NSDL National Science Digital Library

!!Classical Conditioning!! Classical conditioning is the use of Pavlovian conditioning procedures where a neutral stimulus becomes capable of evoking a response through pairing with an unconditioned stimulus. Click the link below to get an introduction into classical conditioning. Introduction to Classical Conditioning Now that you\\'ve been introduced to classical conditioning, view the clip at the link below, ...

Mrs. Palacios, Miss Miller, Mr. Rowser

2008-04-01

212

Metal Reactions  

NSDL National Science Digital Library

This is written as a static display, but can easily be adapted to a hands-on experiment for learners to conduct. Sodium phosphate, a clear colorless solution, is combined with six different metal ion solutions. Each metal (copper, nickel, iron, silver, cobalt, and barium) forms a different color and texture precipitate. Learners discover that a chemical reaction can be identified by a color change, and formation of a precipitate. They also learn that metals can be identified by their precipitates. For safety reasons, this activity should be conducted as a demonstration for younger audiences.

2011-11-01

213

Hot-spot reaction in unsustained shocks  

SciTech Connect

Shock waves in reactive media create hot spots which undergo further temperature change (following creation) by means of (1) chemical reaction, (2) thermal conduction, and (3) adiabatic effects resulting from pressure variation. A thermodynamic description of exothermic reaction under conditions of variable pressure is presented here. The reaction rate is assumed to be a function of temperature only, and of the Arrhenius form: the effect of variable pressure enters through its influence on temperature. Decreasing pressure significantly alters adiabatic thermal explosion times, and can, under nominal conditions, completely inhibit hot-spot reaction. This effect is discussed in terms of explosive initiation by unsustained shock waves. 7 refs., 2 figs.

Johnson, J.N.

1987-01-01

214

An Analysis of the Algebraic Method for Balancing Chemical Reactions.  

ERIC Educational Resources Information Center

Analyzes the algebraic method for balancing chemical reactions. Introduces a third general condition that involves a balance between the total amount of oxidation and reduction. Requires the specification of oxidation states for all elements throughout the reaction. Describes the general conditions, the mathematical treatment, redox reactions, and…

Olson, John A.

1997-01-01

215

Factors augmenting allergic reactions.  

PubMed

Elicitors of anaphylactic reactions are any sources of protein with allergenic capacity. However, not all allergic reactions end up in the most severe form of anaphylaxis. Augmenting factors may explain why certain conditions lead to anaphylaxis. Augmenting factors may exhibit three effects: lowering the threshold, increasing the severity, and reversing acquired clinical tolerance. Common augmenting factors are physical exercise, menstruation, NSAIDs, alcohol, body temperature, acute infections, and antacids. Therapeutic options may address causative, preventive, pragmatic, or symptomatic considerations: avoid the eliciting food, take an antihistamine before any situation with a possible risk of augmentation, separate food and sport (at least for 2 h), and carry an adrenaline autoinjector at all times. Individual patterns include summation effects and specific patterns. In conclusion, in the case of a suggestive history but a negative oral challenge, one should consider the possible involvement of augmenting factors; after anaphylactic reactions, always ask for possible augmentation and other risk factors during the recent past; if augmentation is suspected, oral food challenges should be performed in combination with augmenting factors; and in the future, standardized challenge protocols including augmenting factors should be established. PMID:25306896

Niggemann, B; Beyer, K

2014-12-01

216

Intramolecular anodic olefin coupling reactions: using competition studies to probe the mechanism of oxidative cyclization reactions.  

PubMed

A competition experiment was designed so that the relative rates of anodic cyclization reactions under various electrolysis conditions can be determined. Reactions with ketene dithioacetal and enol ether-based substrates that use lithium methoxide as a base were shown to proceed through radical cation intermediates that were trapped by a sulfonamide anion. Results for the oxidative coupling of a vinyl sulfide with a sulfonamide anion using the same conditions were consistent with the reaction proceeding through a nitrogen-radical. PMID:20302359

Xu, Hai-Chao; Moeller, Kevin D

2010-04-16

217

Intramolecular Anodic Olefin Coupling Reactions: Using Competition Studies to Probe the Mechanism of Oxidative Cyclization Reactions  

PubMed Central

A competition experiment was designed so that the relative rates of anodic cyclization reactions under various electrolysis conditions can be determined. Reactions with ketene dithioacetal and enol ether-based substrates that use lithium methoxide as a base were shown to proceed through radical cation intermediates that were trapped by a sulfonamide anion. Results for the oxidative coupling of a vinyl sulfide with a sulfonamide anion using the same conditions were consistent with the reaction proceeding through a nitrogen-radical. PMID:20302359

Xu, Hai-Chao; Moeller, Kevin D.

2014-01-01

218

Experimental Study of Serpentinization Reactions  

NASA Technical Reports Server (NTRS)

Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.

Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.

2004-01-01

219

3-haloquinolines by Friedländer reaction of ?-haloketones.  

PubMed

A general approach to 3-fluoro-, 3-chloro-, and 3-bromoquinolines which relies on organosilane-promoted Friedla?nder reaction of ?-haloketones is described. The scope of the methylene component as well as influence of the organosilane component on the outcome of the reaction is studied. The method can be used under parallel synthesis conditions. PMID:21627119

Ryabukhin, Sergey V; Naumchik, Vasiliy S; Plaskon, Andrey S; Grygorenko, Oleksandr O; Tolmachev, Andrey A

2011-07-15

220

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

221

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

222

From stereodynamics to high-throughput screening of catalysed reactions.  

PubMed

Characterising chemical reactions by kinetic analysis is of fundamental importance to experimentally obtain insights into reaction mechanisms. Based on such investigations reactions can be optimised and improved catalysts designed. Enhanced reaction conditions may drastically increase the performance of the reaction in terms of yield and (enantio-) selectivity. Understanding reaction kinetics in more complex systems involving adaptive chemical and dynamic systems on a molecular level as shown here is even more challenging. Here we review recent developments in monitoring reactions including the dynamic interconversion of stereoisomers by integrating (catalysed) reactions and chemical analysis in on-column reaction chromatographic devices. These recent developments allow rapid screening of reactions in great detail and are a central tool in determining reaction pathways and to understand how to control the stereodynamics of chiral molecules. PMID:25102302

Stockinger, Skrollan; Gmeiner, Julia; Zawatzky, Kerstin; Troendlin, Johannes; Trapp, Oliver

2014-11-28

223

A Lewis acid-promoted Pinner reaction  

PubMed Central

Summary Carbonitriles and alcohols react in a Lewis acid-promoted Pinner reaction to carboxylic esters. Best results are obtained with two equivalents of trimethylsilyl triflate as Lewis acid. Good yields are achieved with primary alcohols and aliphatic or benzylic carbonitriles, but the straightforward synthesis of acrylates and benzoates starting with acrylonitrile and benzonitrile, respectively, is similarly possible. Phenols are not acylated under these reaction conditions. The method has been used for the first total synthesis of the natural product monaspilosin. In the reaction of benzyl alcohols variable amounts of amides are formed in a Ritter-type side reaction. PMID:23946857

Pfaff, Dominik; Nemecek, Gregor

2013-01-01

224

Sequential Injection Analysis for Optimization of Molecular Biology Reactions  

PubMed Central

In order to automate the optimization of complex biochemical and molecular biology reactions, we developed a Sequential Injection Analysis (SIA) device and combined this with a Design of Experiment (DOE) algorithm. This combination of hardware and software automatically explores the parameter space of the reaction and provides continuous feedback for optimizing reaction conditions. As an example, we optimized the endonuclease digest of a fluorogenic substrate, and showed that the optimized reaction conditions also applied to the digest of the substrate outside of the device, and to the digest of a plasmid. The sequential technique quickly arrived at optimized reaction conditions with less reagent use than a batch process (such as a fluid handling robot exploring multiple reaction conditions in parallel) would have. The device and method should now be amenable to much more complex molecular biology reactions whose variable spaces are correspondingly larger. PMID:21338059

Allen, Peter B.; Ellington, Andrew D.

2011-01-01

225

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

226

Chromosomal Conditions  

MedlinePLUS

... condition. Diagnostic tests include amniocentesis or chorionic villus sampling . Your provider also can check your baby’s blood ... pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider ...

227

Visual conversion reaction in children.  

PubMed

Visual conversion reaction (VCR) is a psychosomatic illness that will occasionally be seen by optometrists and ophthalmologists. This paper discusses some of the possible aetiologies and manifestations of the condition. Investigation and management of children with suspected VCR is discussed. Four case histories are presented in which signs of VCR included amblyopia, reduced accommodation and a deterioration in handwriting. The visual field defects presented include a static quantitative anomaly. Such a defect has not previously been reported. PMID:2698460

Barnard, N A

1989-10-01

228

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

229

Removal of phenolic endocrine disrupting compounds from waste activated sludge using UV, H2O2, and UV/H2O2 oxidation processes: effects of reaction conditions and sludge matrix.  

PubMed

Removal of six phenolic endocrine disrupting compounds (EDCs) (estrone, 17?-estradiol, 17?-ethinylestradiol, estriol, bisphenol A, and 4-nonylphenols) from waste activated sludge (WAS) was investigated using ultraviolet light (UV), hydrogen peroxide (H2O2), and the combined UV/H2O2 processes. Effects of initial EDC concentration, H2O2 dosage, and pH value were investigated. Particularly, the effects of 11 metal ions and humic acid (HA) contained in a sludge matrix on EDC degradation were evaluated. A pseudo-first-order kinetic model was used to describe the EDC degradation during UV, H2O2, and UV/H2O2 treatments of WAS. The results showed that the degradation of the 6 EDCs during all the three oxidation processes fitted well with pseudo-first-order kinetics. Compared with the sole UV irradiation or H2O2 oxidation process, UV/H2O2 treatment was much more effective for both EDC degradation and WAS solubilization. Under their optimal conditions, the EDC degradation rate constants during UV/H2O2 oxidation were 45-197 times greater than those during UV irradiation and 11-53 times greater than those during H2O2 oxidation. High dosage of H2O2 and low pH were favorable for the degradation of EDCs. Under the conditions of pH = 3, UV wavelength = 253.7 nm, UV fluence rate = 0.069 mW cm(-2), and H2O2 dosage = 0.5 mol L(-1), the removal efficiencies of E1, E2, EE2, E3, BPA, and NP in 2 min were 97%, 92%, 95%, 94%, 89%, and 67%, respectively. The hydroxyl radical (OH) was proved to take the most important role for the removal of EDCs. Metal ions in sludge could facilitate the removal of EDCs during UV/H2O2 oxidation. Fe, Ag, and Cu ions had more obvious effects compared with other metal ions. The overall role of HA was dependent on the balance between its competition as organics and its catalysis/photosensitization effects. These indicate that the sludge matrix plays an important role in the degradation of EDCs. PMID:24951888

Zhang, Ai; Li, Yongmei

2014-09-15

230

Reaction mechanism of combustion synthesis of NiAl  

Microsoft Academic Search

Based on precise temperature measurements during combustion and microstructural analysis of quenched samples, the evolution of reaction of the NiAl combustion synthesis has been studied. The combustion reaction of a multilayer Ni\\/Al system takes place in a thermal explosion mode under near adiabatic conditions. The experimental results clearly show that the combustion reaction starts right after the melting of Al.

Ping Zhu; J. C. M Li; C. T Liu

2002-01-01

231

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

232

Conditional moment closure for turbulent combustion  

Microsoft Academic Search

This paper reviews the fundamentals of conditional moment closure (CMC) methods for the prediction of turbulent reacting flows, with particular emphasis on combustion. It also surveys several of the applications that have been made. CMC methods predict the conditional averages and higher moments of quantities such as species mass fractions and enthalpy, conditional on the mixture fraction or reaction progress

A. Y. Klimenko; R. W. Bilger

1999-01-01

233

Enhanced sludge dewatering by dual polyelectrolytes conditioning  

Microsoft Academic Search

Sludge dewatering by dual polyelectrolytes conditioning was investigated in this study. Single polyelectrolyte is utilized in sludge conditioning conventionally, in which charge neutralization and bridging are involved in the reactions. In the current study, both cationic and non-ionic polyelectrolytes were utilized simultaneously in the conditioning. Waste activated sludge was sampled from a synthetic fiber plant, and used in the experiment.

C. H Lee; J. C Liu

2000-01-01

234

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

235

Classification of clock reactions.  

PubMed

Autocatalytic systems are sometimes designated as clock reactions or reactions that exhibit clock behavior. To resolve the recent dispute over the term clock reaction, we describe a new approach to classify systems featuring clock behavior into three distinct groups: substrate-depletive clock reactions, autocatalysis-driven clock reactions, and systems that have pseudo clock behavior. Many of the well-known classical and recently discovered reactions can conveniently be put into these categories. We also provide a convincing argument for classifying some autocatalytic processes as clock reactions, but it does not necessarily mean that all autocatalytic processes should be classified as autocatalysis-driven clock reactions. This classification can be conveniently performed if the kinetic nature of the given system has been completely elucidated and understood. PMID:25425415

Horváth, Attila K; Nagypál, István

2015-02-23

236

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.

237

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

238

Development of Three Reaction Methodologies En Route to Nitrogen Containing Heterocycles: a Diels-Alder/Schmidt, a DIels-Alder/Acylation and a Catalytic Intramolecular Schmidt  

E-print Network

. Building on an initial positive result employing 50 mol% Sc(OTf)3 in water, conditions were explored for promoting this reaction sequence. Reaction surveys exploring solvents, Lewis and protic acids, and reaction conditions were completed. These studies led...

Hirt, Erin Elaine

2009-09-29

239

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

240

Effects of ambient odors on reaction time in humans  

Microsoft Academic Search

The perception of odors is well identified as having strong emotional correlates. The effects of ambient odors on arousal level and task performance have also been suspected but remain poorly assessed in the literature. The present study compared the reaction times of subjects between ambient odor conditions (pleasant and unpleasant) and a no-odor condition. The results showed that the reaction

Jean-Louis Millot; Gérard Brand; Nadège Morand

2002-01-01

241

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

242

Chemical Reactions and Stoichiometry  

NSDL National Science Digital Library

In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

The Concord Consortium

2011-12-11

243

Copper-Catalyzed Oxidative Heck Reactions between Alkyltrifluoroborates and Vinylarenes  

PubMed Central

We report herein that potassium alkyltrifluoroborates can be utilized in oxidative Heck-type reactions with vinyl arenes. The reaction is catalyzed by a Cu(OTf)2/1,10-phenanthroline with MnO2 as the stoichiometric oxidant. In addition to the alkyl Heck, amination, esterification and dimerization reactions of alkyltrifluoroborates are demonstrated under analogous reaction conditions. Evidence for an alkyl radical intermediate is presented. PMID:23734764

Liwosz, Timothy W.; Chemler, Sherry R.

2013-01-01

244

Characteristics of vestibulosensory reactions studied by experimental caloric test  

NASA Technical Reports Server (NTRS)

Vestibulo-sensory reactions were studied in 135 workers who were in contact with nitroethers, by the method of an experimental caloric test. The response vestibulo-sensory reactions were recorded by means of an electroencephalograph. The changes in the sensory reaction depended on the duration of the workers' contact with toxic agents. A study of illusion reactions by the labyrinth calorization widens diagnostic possibilities in the examination of functional condition of the vestibular analyser considerably.

Kapranov, V. Z.

1980-01-01

245

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

246

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.

247

Multifractality in intracellular enzymatic reactions.  

PubMed

Enzymatic kinetics adjust well to the Michaelis-Menten paradigm in homogeneous media with dilute, perfectly mixed reactants. These conditions are quite different from the highly structured cell plasm, so applications of the classic kinetics theory to this environment are rather limited. Cytoplasmic structure produces molecular crowding and anomalous diffusion of substances, modifying the mass action kinetic laws. The reaction coefficients are no longer constant but time-variant, as stated in the fractal kinetics theory. Fractal kinetics assumes that enzymatic reactions on such heterogeneous media occur within a non-Euclidian space characterized by a certain fractal dimension, this fractal dimension gives the dependence on time of the kinetic coefficients. In this work, stochastic simulations of enzymatic reactions under molecular crowding have been completed, and kinetic coefficients for the reactions, including the Michaelis-Menten parameter KM, were calculated. The simulations results led us to confirm the time dependence of michaelian kinetic parameter for the enzymatic catalysis. Besides, other chaos related phenomena were pointed out from the obtained KM time series, such as the emergence of strange attractors and multifractality. PMID:16256143

Aranda, Juan S; Salgado, Edgar; Muñoz-Diosdado, Alejandro

2006-05-21

248

Prebiotic condensation reactions using cyanamide  

NASA Technical Reports Server (NTRS)

Condensation reactions in cyanamide, 4-amino-5-imidazole-carboxamide and cyanamide, imidazole systems under dehydrating conditions at moderate temperatures (60 to 100 deg C) were investigated. The cyanamide, imidazole system was used for synthesis of palmitoylglycerols from ammonium palmitate and glycerol. With the addition of deoxythymidine to the former system, P1, P2-dideoxythymidine 5 prime-phosphate was obtained; the same cyanamide, 4-amino-5-imidazole-carboxamide system was used to synthesize deoxythymidine oligonucleotides using deoxythymidine 5 prime-phosphate and deoxythymidine 5 prime-triphosphate, and peptides using glycine, phenylalanine or isoleucine with adenosine 5 prime-triphosphate. The pH requirements for these reactions make their prebiotic significance questionable; however, it is conceivable that they could occur in stable pockets of low interlayer acidity in a clay such as montmorillonite.

Sherwood, E.; Nooner, D. W.; Eichberg, J.; Epps, D. E.; Oro, J.

1978-01-01

249

Mechanisms in Knockout Reactions  

NASA Astrophysics Data System (ADS)

We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions Be9(C9,B8+X)Y and Be9(B8,Be7+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.

2009-06-01

250

Weathering Reactions and Soil-Groundwater Reactions  

NSDL National Science Digital Library

This 11-page PDF document is part of an environmental geochemistry course taught by Dr. David Sherman at the University of Bristol. The lecture explores the weathering reactions that convert primary minerals into quartz or phyllosilicate clays and iron oxide hydroxides, and the mineral-water reactions that buffer pH and the dissolved ion concentration of groundwater. Also discussed is the manner in which phyllosilicate clays, iron oxides and hydroxides sorb pollutants via ion exchange and adsorption. Helpful diagrams and illustrations accompany the text.

Sherman, David M.; Bristol, University O.

251

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 ...

252

Mineral-alkali reactions under dynamic conditions: Topical report  

SciTech Connect

Three alkaline agents---sodium orthosilicate, sodium carbonate, and sodium bicarbonate---were injected into slim tubes packed with Wilmington (CA) sand containing synthetic Wilmington brine and Wilmington crude oil at waterflood residual saturation, and reservoir temperature, 52/degree/C. The effluent solutions during 3 pore volumes of chemical injection and 1 pore volume of water drive were analyzed for calcium, magnesium, sulfate, total alkalinity, and pH. The transmission of all components was delayed, but to different degrees. Some of the results were interpreted in terms of solubilities of calcium and magnesium silicates and carbonates, and calcium sulfate. Known ionic equilibria were used to interpret the pH history for bicarbonate injection, and indicated a loss of carbon dioxide from the samples before analysis. The orthosilicate gave the best tertiary oil recovery, but bicarbonate was transmitted with much less loss, and showed promise of being a cost-effective agent when enhanced with dilute surfactant. 17 refs., 11 figs., 5 tabs.

Thornton, S.D.; Lorenz, P.B.

1988-11-01

253

Mineral-alkali reactions under dynamic conditions: Topical report  

Microsoft Academic Search

Three alkaline agents---sodium orthosilicate, sodium carbonate, and sodium bicarbonate---were injected into slim tubes packed with Wilmington (CA) sand containing synthetic Wilmington brine and Wilmington crude oil at waterflood residual saturation, and reservoir temperature, 52\\/degree\\/C. The effluent solutions during 3 pore volumes of chemical injection and 1 pore volume of water drive were analyzed for calcium, magnesium, sulfate, total alkalinity, and

S. D. Thornton; P. B. Lorenz

1988-01-01

254

REACTIONS OF FUEL NITROGEN COMPOUNDS UNDER CONDITIONS OF INERT PYROLYSIS  

EPA Science Inventory

The paper describes the pyrolysis of fossil fuels and model nitrogen compounds in helium in a small quartz plow reactor, as part of a study of the chemical mechanisms involved in the conversion of fuel-nitrogen compounds to nitric oxide (NO) during combustion. Hydrogen cyanide (H...

255

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

256

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...

257

GREENER CHEMICAL SYNTHESES USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

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

258

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

259

Radical reactions of borohydrides.  

PubMed

Borohydrides are an important class of reagents in both organic and inorganic chemistry. Though popular as hydride-transfer reagents for reduction, since earlier work from the 1970s, borohydride reagents have also been known to serve as hydrogen-transfer reagents. In pursuit of greener tin hydride substitutes, recent progress has been made to mediate radical C-C bond forming reactions, including Giese reactions, radical carbonylation and addition to HCHO reactions, with borohydride reagents. This review article focuses on state-of-the-art borohydride based radical reactions, also covering earlier work, kinetics and some DFT calculations with respect to the hydrogen transfer mechanism. PMID:25349957

Kawamoto, Takuji; Ryu, Ilhyong

2014-12-28

260

Role of Microbes in the Smectite-to-Illite Reaction  

USGS Publications Warehouse

Temperature, pressure, and time have been thought to control the smectiteto-illite (S-I) reaction, an important diagenetic process used for petroleum exploration. We demonstrated that microorganisms can promote the S-I reaction by dissolving smectite through reduction of structural FE(III) at room temperature and 1 atmosphere within 14 days. This reaction typically requires conditions of 300?? to 350??C, 100 megapascals, and 4 to 5 months in the absence of microbial activity. These results challenge the conventional concept of the S-I reaction and of reaction kinetic models.

Kim, J.; Dong, H.; Seabaugh, J.; Newell, S.W.; Eberl, D.D.

2004-01-01

261

Capture reactions on C-14 in nonstandard big bang nucleosynthesis  

NASA Technical Reports Server (NTRS)

Nonstandard big bang nucleosynthesis leads to the production of C-14. The further reaction path depends on the depletion of C-14 by either photon, alpha, or neutron capture reactions. The nucleus C-14 is of particular importance in these scenarios because it forms a bottleneck for the production of heavier nuclei A greater than 14. The reaction rates of all three capture reactions at big bang conditions are discussed, and it is shown that the resulting reaction path, leading to the production of heavier elements, is dominated by the (p, gamma) and (n, gamma) rates, contrary to earlier suggestions.

Wiescher, Michael; Gorres, Joachim; Thielemann, Friedrich-Karl

1990-01-01

262

Getting under the skin of adverse drug reactions.  

PubMed

Cutaneous drug reactions are among the most commonly reported adverse drug reactions. Drugs prescribed by orthopedic surgeons, such as antibiotics, opiates, and nonsteroidal anti-inflammatory drugs, are common offenders. Cutaneous drug reactions can range from those that are common, mild nuisances to those that are rare, severe, and life-threatening. Medications should be considered part of a differential diagnosis for any dermatologic condition. It is important to recognize the different clinical features and common drugs that are related to each type of reaction. This review characterizes the different forms of cutaneous drug reactions and the clinical features, proposed mechanisms, and drugs frequently associated with each. PMID:23027476

Hempel, Carolyn; Martin, Craig

2012-10-01

263

Capture reactions on C-14 in nonstandard big bang nucleosynthesis  

NASA Astrophysics Data System (ADS)

Nonstandard big bang nucleosynthesis leads to the production of C-14. The further reaction path depends on the depletion of C-14 by either photon, alpha, or neutron capture reactions. The nucleus C-14 is of particular importance in these scenarios because it forms a bottleneck for the production of heavier nuclei A greater than 14. The reaction rates of all three capture reactions at big bang conditions are discussed, and it is shown that the resulting reaction path, leading to the production of heavier elements, is dominated by the (p, gamma) and (n, gamma) rates, contrary to earlier suggestions.

Wiescher, Michael; Gorres, Joachim; Thielemann, Friedrich-Karl

1990-11-01

264

Electrode kinetics: reactions  

Microsoft Academic Search

This is Volume 27 in the Comprehensive Chemical Kinetics series. The contributors are Calvo (Argentina), Hamnett (England), O'Sullivan (United States), and Weaver (United States). The book's chapters cover Redox Reactions at Metal-Solution Interfaces, Semiconductor Electrochemistry, and Reactions at Metal Oxide Electrodes. The references date from the 1960s to the mid-1980s. An index is included.

1987-01-01

265

Reactions to Attitudinal Deviancy.  

ERIC Educational Resources Information Center

This paper presents a critical review of empirical and theoretical treatments of group reaction to attitudinal deviancy. Inspired by Festinger's (1950) ideas on resolution of attitudinal discrepancies in groups, Schachter (1951) conducted an experiment that has greatly influenced subsequent research and theory concerning reaction to attitudinal…

Levine, John M.; Allen, Vernon L.

266

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

267

Smell the Maillard Reaction  

NSDL National Science Digital Library

In this activity, learners cook amino acids and sugar to explore the range of aromas released. When amino acids and sugars are heated, learners will observe a phenomenon known as the Maillard reaction, also known as the browning reaction. Caution!: Kids, please don't try this at home without the help of an adult. The corn syrup can get very hot, very quickly.

Exploratorium

2012-10-03

268

Oscillating Chemical Reactions  

ERIC Educational Resources Information Center

Describes several oscillating chemical reactions which can be used in undergraduate chemistry laboratories. In one such reaction, ferroin oscillates from red (reducing solution) to blue (oxidizing solution) for about an hour at a frequency which can readily be shown to depend on such factors as the temperature, type of solvent, and concentration…

Hawkins, M. D.; And Others

1975-01-01

269

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

270

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

2013-01-01

271

TRIMOLECULAR REACTIONS OF URANIUM HEXAFLUORIDE WITH WATER  

SciTech Connect

The hydrolysis reaction of uranium hexafluoride (UF{sub 6}) is a key step in the synthesis of uranium dioxide (UO{sub 2}) powder for nuclear fuels. Mechanisms for the hydrolysis reactions are studied here with density functional theory and the Stuttgart small-core scalar relativistic pseudopotential and associated basis set for uranium. The reaction of a single UF{sub 6} molecule with a water molecule in the gas phase has been previously predicted to proceed over a relatively sizeable barrier of 78.2 kJ {center_dot} mol{sup -1}, indicating this reaction is only feasible at elevated temperatures. Given the observed formation of a second morphology for the UO{sub 2} product coupled with the observations of rapid, spontaneous hydrolysis at ambient conditions, an alternate reaction pathway must exist. In the present work, two trimolecular hydrolysis mechanisms are studied with density functional theory: (1) the reaction between two UF{sub 6} molecules and one water molecule, and (2) the reaction of two water molecules with a single UF{sub 6} molecule. The predicted reaction of two UF{sub 6} molecules with one water molecule displays an interesting 'fluorine-shuttle' mechanism, a significant energy barrier of 69.0 kJ {center_dot} mol{sup -1} to the formation of UF{sub 5}OH, and an enthalpy of reaction ({Delta}H{sub 298}) of +17.9 kJ {center_dot} mol{sup -1}. The reaction of a single UF{sub 6} molecule with two water molecules displays a 'proton-shuttle' mechanism, and is more favorable, having a slightly lower computed energy barrier of 58.9 kJ {center_dot} mol{sup -1} and an exothermic enthalpy of reaction ({Delta}H{sub 298}) of -13.9 kJ {center_dot} mol{sup -1}. The exothermic nature of the overall UF{sub 6} + 2 {center_dot} H{sub 2}O trimolecular reaction and the lowering of the barrier height with respect to the bimolecular reaction are encouraging; however, the sizable energy barrier indicates further study of the UF{sub 6} hydrolysis reaction mechanism is warranted to resolve the remaining discrepancies between the predicted mechanisms and experimental observations.

Westbrook, M.; Becnel, J.; Garrison, S.

2010-02-25

272

The hydroarylation reaction--scope and limitations.  

PubMed

The synthetic potential of stereoselective, palladium-catalyzed hydro(het)arylation reactions of bi-, tri- and tetracyclic (hetero)alkenes in the presence of phospines and arsines as highly efficient ligands was studied. The mechanism of this reductive Heck reaction becomes more complex in the case of benzonorbornenes. Hydroarylation of diazabicyclo-[2.2.1]heptenes provides a stereoselective access to aryldiaminocyclopentanes. Electron-deficient arylpalladium complexes shift the reaction towards the product of a formal 1,2-hydrazidoarylation reaction of 1,3-cyclopentadiene by a stereoselective C-N cleavage. Due to steric reasons, rigid bicyclo[2.2.2]octenes react slower in hydroarylation reactions than the corresponding bicyclo[2.2.1]heptenes. The more flexible bicyclo[4.2.2]decene system already tends to undergo domino-Heck reactions, even under reductive conditions. When a tetracyclic cis-allylcyclopropane is carbopalladated in the presence of formates, the neighboring cyclopropane ring is attacked in the first reported example of a pi,sigma domino-Heck reaction. PMID:20657489

Namyslo, Jan C; Storsberg, Jörg; Klinge, Jens; Gärtner, Christian; Yao, Min-Liang; Ocal, Nuket; Kaufmann, Dieter Eckhard

2010-05-01

273

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

274

Effective Analysis of Reaction Time Data  

ERIC Educational Resources Information Center

Most analyses of reaction time (RT) data are conducted by using the statistical techniques with which psychologists are most familiar, such as analysis of variance on the sample mean. Unfortunately, these methods are usually inappropriate for RT data, because they have little power to detect genuine differences in RT between conditions. In…

Whelan, Robert

2008-01-01

275

Acylation of Fish Protein: Effect of Reaction  

E-print Network

that is the basis of mayonnaise. It has been shown that the functional properties of fish muscle proteins can be imAcylation of Fish Protein: Effect of Reaction Conditions on Products KANG-HO LEE, HERMAN S- proved by chemically modifying these proteins (Groninger and Miller, 1975; Miller and Groninger, 1976

276

Mechanisms in knockout reactions  

NASA Astrophysics Data System (ADS)

We report on the first detailed study of the mechanisms involved in knockout reactions, via a coincidence measurement of the residue and fast proton in one-proton knockout reactions, using the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results on the reactions ^9Be(^9C,^8B+X)Y and ^9Be(^8B,^7Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction (elastic breakup) and stripping (inelastic breakup) reaction mechanisms, as calculated in the eikonal model. The data shows a clear distinction between the two reaction mechanisms, and the observed respective proportions are very well reproduced by the reaction theory. This agreement supports the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes. In particular, this add considerable support to the use of the eikonal model as a quantitative tool, able, for example, to determine single-particle spectroscopic strengths in rare isotopes.

Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.

2009-10-01

277

Elucidation of the Chemical Structure and Determination of the Production Conditions for a Bioactive Maillard Reaction Product, [5-(5,6-Dihydro-4H-pyridin-3-ylidenemethyl)furan-2-yl]methanol, Isolated from a Glucose-Lysine Heated Mixture.  

PubMed

We previously isolated a bioactive molecule, named F3-A, from an aqueous glucose (Glc) and lysine (Lys) Maillard reaction (MR) model system. Herein, F3-A was verified as [5-(5,6-dihydro-4H-pyridin-3-ylidenemethyl)furan-2-yl]methanol (5) and was subsequently synthesized for confirmation of bioactivity. Using Taguchi and factorial designs, we determined that the conditions which best increased the yield of F3-A were at pH 6 with a sugar:amino acid ratio of 2:1 and heating time of 12 h at 100 °C. The MR mixtures containing glucose produced highest yield, compared to fructose, lactose, and sucrose. Both the F3-A recovered from Glc-Lys MR mixture and the synthesized product exhibited significant (P < 0.05), dose dependent, nitric oxide (NO) inhibitory activity in Caco-2 cells that was comparable to aminoguanidine (AG) and pyrrolidine dithiocarbamate (PDTC), respectively. Finally, an additional inhibitory effect of F3-A was determined when coincubated with AG in cytokine-induced Caco-2 cells. This bioactivity points to a potential role in preventing intestinal inflammation. PMID:25608183

Chen, Xiu-Min; Chen, Gang; Chen, Hongwen; Zhang, Yilin; Kitts, David D

2015-02-18

278

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

279

Theory of reversible associative-dissociative diffusion-influenced chemical reaction. I. Geminate reaction  

NASA Astrophysics Data System (ADS)

A many-particle, in the general case, inhomogeneous reacting system of independent pairs of reactants, where geminate reversible reaction A+Brightleftarrows C takes place, is considered in the framework of the kinetic theory approach. The kinetic equations in the thermodynamic limit are obtained, and important relations between kinetic coefficients characterizing the reaction course are established, as well as the relations between the kinetic dependencies under different initial conditions including the relations that extend the familiar literature results to the case of rather realistic model of the reacting system. Universal long-term kinetic laws of the reaction course are determined.

Doktorov, Alexander B.; Kipriyanov, Alexey A.

2011-09-01

280

Stereochemical Lability of Azatitanacyclopropanes: Dynamic Kinetic Resolution in Reductive Cross-Coupling Reactions with Allylic Alcohols‡  

PubMed Central

Azatitanacyclopropanes (titanaziridines) are shown to be stereochemically labile under reaction conditions for reductive cross-coupling. This fundamental property has been employed to realize highly selective asymmetric coupling reactions with allylic alcohols that proceed by dynamic kinetic resolution. PMID:23963189

Yang, Dexi

2014-01-01

281

Automated microreactor system for reaction development and online optimization of chemical processes  

E-print Network

Developing the optimal conditions for chemical reactions that are common in fine chemical and pharmaceutics is a difficult and expensive task. Because syntheses in these fields have multiple reaction pathways, a significant ...

McMullen, Jonathan Patrick

2010-01-01

282

Characteristics of anisometropic suppression: Simple reaction time measurements  

Microsoft Academic Search

The characteristics of artificially induced anisometropic suppression were investigated in observers with normal and abnormal\\u000a binocular vision (anisometropic amblyopia) by using a simple reaction time paradigm. Reaction time was measured as a function\\u000a of stimulus intensity for various stimulus durations. For all conditions, the reaction time increased as stimulus intensity\\u000a decreased toward threshold. We found that traditional techniques for modeling

Michael J. Planta; Michael Kalloniatis

1998-01-01

283

Reaction thrust of water jet for conical nozzles  

Microsoft Academic Search

Clear knowledge on the reaction thrust of water jet is valuable for better design of water jet propulsion system. In this\\u000a paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry\\u000a as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has\\u000a a

Guo-qin Huang; You-sheng Yang; Xiao-hui Li; Yu-quan Zhu

2009-01-01

284

Oral Hypersensitivity Reactions  

MedlinePLUS

... Million NIDCR/NIH Grant 2015 AAOM Call for Abstract Submissions Upcoming Events 2015 Annual Conference Registration is Now Open 2016 Annual Meeting in Atlanta - Save the Date! Oral Hypersensitivity Reactions ...

285

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

286

Chemisorption And Precipitation Reactions  

EPA Science Inventory

The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

287

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. PMID:13596877

Guthe, T.; Idsöe, O.; Willcox, R. R.

1958-01-01

288

Polymerase Chain Reaction  

NSDL National Science Digital Library

This interactive activity adapted from the University of Nebraska's Library of Crop Technologies depicts steps in the polymerase chain reaction (PCR) technique and explains how it is used to efficiently copy sections of DNA for analysis.

WGBH Educational Foundation

2009-12-07

289

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

290

Nitropyridines: Synthesis and reactions  

Microsoft Academic Search

Reaction of pyridine and substituted pyridines with N2O5 in an organic solvent gives the N-nitropyridinium ion. When this is reacted with SO2\\/HSO3 - in water, 3-nitropyri- dine is obtained (77 % yield). With substituted pyridines, the method gives good yields for 4-substituted and moderate yields for 3-substituted pyridines. The reaction mechanism is not an electrophilic aromatic substitution, but one in

Jan M. Bakke

2003-01-01

291

Safety of chlorination reactions  

Microsoft Academic Search

Chlorination reactions are part of various processes in the chemical industry, to manufacture heavy chemicals, specialty chemicals, pesticides and pharmaceuticals, in inorganic and organic chemistry. They are a valuable tool in organic synthesis.The hazard of processing chlorine involves:u- Gas phase explosion;- Runaway reaction or thermal explosion in the condensed phase.Gas phase explosion hazard with chlorine as an oxidizer is present

Jean-Louis Gustin; Alexandre Fines

1996-01-01

292

Polymerase Chain Reaction  

NSDL National Science Digital Library

Polymerase chain reaction (PCR) enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA. This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents Polymerase Chain Reaction through a series of illustrations of the processes involved. Users may view the animation online (Flash is required) or download it for PC or Mac.

293

Reaction Time as an Index of Traffic Sign Perception  

Microsoft Academic Search

Verbal reaction times to identify and to classify 20 traffic sign messages were measured under three conditions-sign alone, sign plus visual loading task, and sign plus visual loading task plus visual distraction. Similar trends were found in the three experiments: reaction times were smaller for the classification task than for the identification task, smaller for warning than for regulatory signs,

Robert E. Dewar; Jerry G. Ells; Glen Mundy

1976-01-01

294

Preparation and reactions of new zincated nitrogen-containing heterocycles  

Microsoft Academic Search

A range of nitrogen-containing iodinated or in some cases brominated heterocycles were converted to the corresponding zincated heterocyclic derivatives by the direct insertion of zinc dust under mild conditions (25 °C to 70 °C, 1–3 h) in a solvent like THF or DMAC. This reaction was extended to the preparation of zincated nucleic acid bases and nucleosides. The reaction of

A. S Bhanu Prasad; Thomas M Stevenson; Janakiram Rao Citineni; Valérie Nyzam; Paul Knochel

1997-01-01

295

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides  

PubMed Central

Summary A series of 4,4'-dimethoxybenzophenone mediated intra- and intermolecular photodecarboxylation reactions involving phthalimides have been examined under microflow conditions. Conversion rates, isolated yields and chemoselectivities were compared to analogous reactions in a batch photoreactor. In all cases investigated, the microreactions gave superior results thus proving the superiority of microphotochemistry over conventional technologies. PMID:21915208

Shvydkiv, Oksana; Nolan, Kieran

2011-01-01

296

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

297

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

298

Elementary reaction modeling of solid oxide electrolysis cells: Main zones for heterogeneous chemical/electrochemical reactions  

NASA Astrophysics Data System (ADS)

A theoretical model of solid oxide electrolysis cells considering the heterogeneous elementary reactions, electrochemical reactions and the transport process of mass and charge is applied to study the relative performance of H2O electrolysis, CO2 electrolysis and CO2/H2O co-electrolysis and the competitive behavior of heterogeneous chemical and electrochemical reactions. In cathode, heterogeneous chemical reactions exist near the outside surface and the electrochemical reactions occur near the electrolyte. According to the mathematical analysis, the mass transfer flux D ?c determines the main zone size of heterogeneous chemical reactions, while the charge transfer flux ? ?V determines the other one. When the zone size of heterogeneous chemistry is enlarged, more CO2 could react through heterogeneous chemical pathway, and polarization curves of CO2/H2O co-electrolysis could be prone to H2O electrolysis. Meanwhile, when the zone size of electrochemistry is enlarged, more CO2 could react through electrochemical pathway, and polarization curves of CO2/H2O co-electrolysis could be prone to CO2 electrolysis. The relative polarization curves, the ratio of CO2 participating in electrolysis and heterogeneous chemical reactions, the mass and charge transfer flux and heterogeneous chemical/electrochemical reaction main zones are simulated to study the effects of cathode material characteristics (porosity, particle diameter and ionic conductivity) and operating conditions (gas composition and temperature).

Li, Wenying; Shi, Yixiang; Luo, Yu; Cai, Ningsheng

2015-01-01

299

Merging asymmetric Henry reaction with organocatalytic cascade reaction for the construction of a chiral indolizidine alkaloid skeleton.  

PubMed

A sequential reaction combining the copper-catalyzed asymmetric Henry reaction with the organocatalytic Michael addition-hemiacetalization cascade reaction was developed. The C1-symmetric chiral diamine L1-copper complex was responsible for the first highly enantioselective Henry reaction, while diphenylprolinol silyl ether A acted as effective organocatalyst for the second cascade reaction between chiral ?-nitro alcohol and ?,?-unsaturated aldehydes. Via rational design and combination of the two independent catalytic systems, good yields and excellent enantioselectivities and diastereoselectivities were achieved for a broad substrate scope under mild reaction conditions. The synthetic utility of this sequential catalytic asymmetric cascade reaction was demonstrated as an alternative and straightforward stereoselective synthesis strategy for chiral indolizidine alkaloid and its analogues. PMID:25562620

Zhou, Yirong; Yang, Qin; Shen, Jian; Chen, Xin; Peng, Yiyuan; Gong, Yuefa

2015-02-01

300

Stellar evolution and the triple-? reactions  

SciTech Connect

Nuclear reaction rates play a crucial role in the evolution of stars. For low-mass stars, the triple-? reaction controls the helium burning stars in the red giant and asymptotic giant branch (AGB) phase. More importantly, the cross section of the triple-? reaction has a great impact on the helium ignition at the center of the electron degenerate helium core of red giants and on the helium shell flashes of AGB stars. It is to be noted that stellar evolution models are influenced not only by the value of the cross section, but also by the temperature dependence of the reaction rate. In this paper, I present the impact of the triple-? reaction rates on the evolution of low-mass metal-free stars and intermediate-mass AGB stars. According to the previous study, the constraint on the triple-? reaction rate is derived based on stellar evolution theory. It is found that the recent revisions of the rate proposed by nuclear physics calculations satisfy the condition for the ignition of the helium core flash in low-mass stars.

Suda, Takuma [Osawa 2-21-1, Mitaka, Tokyo, 181-8588 (Japan)

2014-05-02

301

[Cutaneous adverse drug reactions.  

PubMed

Cutaneous adverse drug reactions (CADR) represent a heterogeneous field including various clinical patterns without specific features suggesting drug causality. Exanthematous eruptions, urticaria and vasculitis are the most common forms of CADR. Fixed eruption is uncommon in western countries. Serious reactions (fatal outcome, sequelae) represent 2% of CADR: bullous reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), DRESS (drug reaction with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome) and acute generalized exanthematous pustulosis (AGEP). These forms must be quickly diagnosed to guide their management. The main risk factors are immunosuppression, autoimmunity and some HLA alleles in bullous reactions and DRESS. Most systemic drugs may induce cutaneous adverse reactions, especially antibiotics, anticonvulsivants, antineoplastic drugs, non-steroidal anti-inflammatory drugs, allopurinol and contrast media. Pathogenesis includes immediate or delayed immunologic mechanism, usually not related to dose, and pharmacologic/toxic mechanism, commonly dose-dependent or time-dependent. In case of immunologic mechanism, allergologic exploration is possible to clarify drug causality, with a variable sensitivity according to the drug and to the CADR type. It includes epicutaneous patch testing, prick test and intradermal test. However, no in vivo or in vitro test can confirm the drug causality. To determine the cause of the eruption, a logical approach based on clinical characteristics, chronologic factors and elimination of differential diagnosis is required, completed with a literature search. A reporting to pharmacovigilance network is essential in case of a serious CADR whatever the suspected drug and in any case if the involved drug is a newly marketed one or unusually related to cutaneous reactions. PMID:25458866

Lebrun-Vignes, B; Valeyrie-Allanore, L

2014-11-01

302

Reactions of butadiyne. 1: The reaction with hydrogen atoms  

NASA Technical Reports Server (NTRS)

The reaction of hydrogen (H) atoms with butadiene (C4H2) was studied at room temperature in a pressure range between w mbar and 10 mbar. The primary step was an addition of H to C4H2 which is in its high pressure range at p 1 mbar. Under these conditions the following addition of a second H atom lies in the transition region between low and high pressure range. Vibrationally excited C4H4 can be deactivated to form buten-(1)-yne-(3)(C4H4) or decomposes into two C2H2 molecules. The rate constant at room temperature for primary step is given. The second order rate constant for the consumption of buten-(1)-yne-(3) is an H atom excess at room temperature is given.

Schwanebeck, W.; Warnatz, J.

1984-01-01

303

Palladium-catalyzed cross-coupling reactions of 2-iodo-4-(phenylchalcogenyl)-1-butenes.  

PubMed

[reaction: see text] 2-Iodo-4-(phenylchalcogenyl)-1-butenes 2 or 3, which are derived from the ring-opening reaction of methylenecyclopropanes (MCPs) 1 by iodine, can be applied to some palladium-catalyzed cross-coupling reactions such as the Sonogashira, Heck, Kumada, Suzuki, and Negishi reactions under mild conditions to give the corresponding coupling products in good yields. These reactions proceeded smoothly at room temperature (20 degrees C) in most cases without any phosphine ligand and additive. The phenylchalcogenyl group plays an important role in the reactions and a plausible reaction mechanism has been proposed. PMID:16323852

Shi, Min; Liu, Le-Ping; Tang, Jie

2005-12-01

304

Phase and chemical equilibria in the transesterification reaction of vegetable oils with supercritical lower alcohols  

NASA Astrophysics Data System (ADS)

Calculations of thermodynamic data are performed for fatty acid triglycerides, free fatty acids, and fatty acid methyl esters, participants of the transesterification reaction of vegetable oils that occurs in methanol. Using the obtained thermodynamic parameters, the phase diagrams for the reaction mixture are constructed, and the chemical equilibria of the esterification reaction of free fatty acids and the transesterification reaction of fatty acid triglycerides attained upon treatment with supercritical methanol are determined. Relying on our analysis of the obtained equilibria for the esterification reaction of fatty acids and the transesterification reaction of triglycerides attained upon treatment with lower alcohols, we select the optimum conditions for performing the reaction in practice.

Anikeev, V. I.; Stepanov, D. A.; Ermakova, A.

2011-08-01

305

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

2013-05-01

306

Moist air reaction with excess UF{sub 6}  

SciTech Connect

The moist air reaction with uranium hexafluoride (UF{sub 6}) has been studied at conditions simulating UF{sub 6} hydrolysis during air inleakage in the cascade. In excess UF{sub 6}, the reaction mechanism is more complicated than predicted by the simple gas-phase reaction of one UF{sub 6} molecule with two water molecules to form uranyl fluoride and hydrogen fluoride. The initial UF{sub 6} consumption is significantly greater than predicted, suggesting that a metastable uranium compound is formed during the hydrolysis reaction. This intermediate uranium compound may facilitate uranyl fluoride transport in the cascade.

Reiner, R.H.

1989-08-01

307

Neurohumoral reactions to long-term vestibular stimulation in man.  

PubMed

The main purposes of present work were: 1) to examine neurohumoral reactions to long-term vestibular stimulation provocative for MS symptoms in man; 2) to compare the peculiarities of neuroendocrine reactions to short-term and to long-term vestibular stimulation; 3) to analyze the received results from the position of neuroendocrine adaptive reactions biological conformity to natural laws, and its physiological importance for human organisms; 4) to make some prognostic points of neurohumoral reaction changes on health and capacity for work in subjects influenced by professional conditions, provocative for MS manifestation development. PMID:11538529

Nichiporuk, I A; Rapotkov, A N; Orlov, O I; Grigoriev, A I

1993-02-01

308

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.

2014-01-28

309

Proton-transfer reaction dynamics  

Microsoft Academic Search

In this article we discuss the progress made in understanding intermolecular and intermolecular reactions of proton (or hydrogen-atom) transfer. Femtosecond real-time probing, together with spectroscopic studies, in molecular beams are presented with selected examples of reactions. Reaction rates, tunneling dynamics and the nature of the reaction coordinate are examined and related to two-state multidimensional potential energy surfaces.

Abderrazzak Douhal; Françoise Lahmani; Ahmed H. Zewail

1996-01-01

310

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. (GS)

Cooke, D. O.

1976-01-01

311

A taxonomy of integral reaction path analysis  

SciTech Connect

W. C. Gardiner observed that achieving understanding through combustion modeling is limited by the ability to recognize the implications of what has been computed and to draw conclusions about the elementary steps underlying the reaction mechanism. This difficulty can be overcome in part by making better use of reaction path analysis in the context of multidimensional flame simulations. Following a survey of current practice, an integral reaction flux is formulated in terms of conserved scalars that can be calculated in a fully automated way. Conditional analyses are then introduced, and a taxonomy for bidirectional path analysis is explored. Many examples illustrate the resulting path analysis and uncover some new results about nonpremixed methane-air laminar jets.

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

2004-12-23

312

Different reaction mechanisms for cis- and trans-prenyltransferases  

SciTech Connect

Octaprenyl diphosphate synthase (OPPs) and undecaprenyl diphosphate synthases (UPPs) catalyze consecutive condensation reactions of farnesyl diphosphate (FPP) with 5 and 8 isopentenyl diphosphate (IPP) to generate C{sub 40} and C{sub 55} products with trans- and cis-double bonds, respectively. In this study, we used IPP analogue, 3-bromo-3-butenyl diphosphate (Br-IPP), in conjunction with radiolabeled FPP, to probe the reaction mechanisms of the two prenyltransferases. Using this alternative substrate with electron-withdrawing bromo group at the C3 position to slow down the condensation step, trapping of farnesol in the OPPs reaction from radiolabeled FPP under basic condition was observed, consistent with a sequential mechanism. In contrast, UPPs reaction yielded no farnesyl carbocation intermediate under the same condition with radiolabeled FPP and Br-IPP, indicating a concerted mechanism. Our data demonstrate the different reaction mechanisms for cis- and tran-prenyltransferases although they share the same substrates.

Lu Yenpin [Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan (China); Liu Hunge [Institute of Biological Chemistry, 128 Academia Rd. sec. 2, Academia Sinica, Taipei 115, Taiwan (China); Liang, P-H. [Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan (China); Institute of Biological Chemistry, 128 Academia Rd. sec. 2, Academia Sinica, Taipei 115, Taiwan (China)], E-mail: phliang@gate.sinica.edu.tw

2009-02-06

313

Dynamic flexibility in the light reactions of photosynthesis governed by both electron and proton transfer reactions  

Microsoft Academic Search

Plant photosynthesis performs the remarkable feat of converting light energy into usable chemical forms, which involves taming highly reactive intermediates without harming plant cells. This requires an apparatus that is not only efficient and robust but also flexible in its responses to changing environmental conditions. It also requires that the output of the energy-storing reactions be matched with the demands

David M. Kramer; Thomas J. Avenson; Gerald E. Edwards

2004-01-01

314

Polarization in inclusive reactions  

Microsoft Academic Search

A formalism for discussing the spin dependence of inclusive reactions is presented. The role of various constraints following from conservation of parity and angular momentum conservation is discussed. Expressions for specific single and double polarization observables are presented. Predictions of the triple-Regge model for these observables are given.

Gary R. Goldstein; Joseph F. Owens

1976-01-01

315

The aromatic ene reaction  

PubMed Central

The ene reaction is a pericyclic process in which an alkene having an allylic hydrogen atom (the ene donor) reacts with a second unsaturated species (the enophile) to form a new product with a transposed ?-bond. The aromatic ene reaction, in which the alkene component is embedded in an aromatic ring, has only been reported in a few (four) instances and has proceeded in low yield (?6%). Here we show efficient aromatic ene reactions in which a thermally generated aryne engages a pendant m-alkylarene substituent to produce a dearomatized isotoluene, itself another versatile but rare reactive intermediate. Our experiments were guided by computational studies that revealed structural features conducive to the aromatic ene process. We proceeded to identify a cascade comprising three reactions: (i) hexadehydro-Diels-Alder (for aryne generation), (ii) intramolecular aromatic ene, and (iii) bimolecular Alder ene. The power of this cascade is evident from the structural complexity of the final products, the considerable scope, and the overall efficiency of these multi-stage, reagent- and byproduct-free, single-pot transformations. PMID:24345944

Niu, Dawen; Hoye, Thomas R.

2014-01-01

316

Parallelization for reaction  

E-print Network

Parallelization for reaction waves with complex chemistry Context Application Background Numerical with complex chemistry S. Descombes 2 M. Duarte 3 T. Dumont 1 V. Louvet 1 M. Massot 3 1Camille Jordan Institute - France 3EM2C Laboratory - Ecole Centrale Paris - France Workshop on Computational and Applied Mathematics

Louvet, Violaine

317

Chemical Reactions at Surfaces  

SciTech Connect

Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.

Michael Henderson and Nancy Ryan Gray

2010-04-14

318

Reaction Formulation: A Bibliography.  

ERIC Educational Resources Information Center

Reaction formation was studied by Sigmund Freud. This defense mechanism may be related to repression, substitution, reversal, and compensation (or over-compensation). Alfred Adler considered compensation a basic process in his individual psychology. Anna Freud discussed some defense mechanisms, and Bibring, Dwyer, Huntington, and Valenstein…

Pedrini, D. T.; Pedrini, Bonnie C.

319

Organic Reactions and Biofuels  

NSDL National Science Digital Library

The Advanced Technology Environmental and Energy Center (ATEEC) provides this classroom activity on organic reactions and biofuels. The goal of the lesson is to react methanol with waste oil to synthesize biodiesel. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

320

The aromatic ene reaction  

NASA Astrophysics Data System (ADS)

The ene reaction is a pericyclic process in which an alkene with an allylic hydrogen atom (the ene donor) reacts with a second unsaturated species (the enophile) to form a new product with a transposed ?-bond. The aromatic ene reaction, in which the alkene component is embedded in an aromatic ring, has only been reported in a few (four) instances and has proceeded in low yield (?6%). Here, we show efficient aromatic ene reactions in which a thermally generated aryne intermediate engages a pendant m-alkylarene substituent to produce a dearomatized isotoluene, itself another versatile but rare reactive intermediate. Our experiments were guided by computational studies that revealed structural features conducive to the aromatic ene process. We proceeded to identify a cascade comprising three reactions: (1) hexadehydro-Diels-Alder (for aryne generation), (2) intramolecular aromatic ene and (3) bimolecular Alder ene. The power of this cascade is evident from the structural complexity of the final products, the considerable scope, and the overall efficiency of these multistage, reagent- and by-product-free, single-pot transformations.

Niu, Dawen; Hoye, Thomas R.

2014-01-01

321

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 of…

Zaretsky, Lindy

2004-01-01

322

Reaction product imaging  

SciTech Connect

Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

323

The Condition of Education  

NSDL National Science Digital Library

The very title of this website would perhaps draw only hushed whispers from those commentators in the world of education policy, and thatâÂÂs probably not a bad reaction. The site makes good on the promise of its title, as it offers the casual and seasoned visitor a wide variety of indicators in the forms of tables and charts, including total enrollments in grades K-12, trends in half-day kindergarten, and past and projected undergraduate enrollment figures. Culled from annual reports created by the National Center for Education Statistics, these helpful pieces of information and data are complemented nicely by a series of special analyses, including âÂÂMobility in the Teacher Workforceâ and âÂÂPrivate Schools: A Brief PortraitâÂÂ. If visitors encounter any problems finding the information they desire, they should consult the âÂÂUserâÂÂs GuideâÂÂ, which contains directions on how to best navigate the site. Finally, the site is rounded out by a brief summary that highlights some of the findings of the 2005 Condition of Education report.

Statistics, National C.

324

Photoneutron reactions in astrophysics  

NASA Astrophysics Data System (ADS)

Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing ? --decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between 74Se and 196Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in ( ?, n), ( ?, p), or ( ?, ?) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.

Varlamov, V. V.; Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A.

2014-12-01

325

Plasmon-driven sequential chemical reactions in an aqueous environment  

PubMed Central

Plasmon-driven sequential chemical reactions were successfully realized in an aqueous environment. In an electrochemical environment, sequential chemical reactions were driven by an applied potential and laser irradiation. Furthermore, the rate of the chemical reaction was controlled via pH, which provides indirect evidence that the hot electrons generated from plasmon decay play an important role in plasmon-driven chemical reactions. In acidic conditions, the hot electrons were captured by the abundant H+ in the aqueous environment, which prevented the chemical reaction. The developed plasmon-driven chemical reactions in an aqueous environment will significantly expand the applications of plasmon chemistry and may provide a promising avenue for green chemistry using plasmon catalysis in aqueous environments under irradiation by sunlight. PMID:24958029

Zhang, Xin; Wang, Peijie; Zhang, Zhenglong; Fang, Yurui; Sun, Mengtao

2014-01-01

326

Diagnosing ignition with DT reaction history  

SciTech Connect

A full range DT reaction history of an ignition capsule, from 10{sup 9} to 10{sup 20} neutrons/ns, offers the opportunity to diagnose fuel conditions hundreds of picoseconds before and during burn. The burn history begins with a sharp rise when the first shock reaches the center of the capsule. The level of this jump reflects the combined shock strength and the adiabat of DT fuel. Changes to the four laser pulses driving the capsule implosion which are large enough to degrade the yield make measurable changes to the reaction history. Low mode asymmetries grow during convergence but change the reaction history during the final {approx}100 ps. High mode asymmetry or turbulence mixing affects only the reaction history within {approx}50 ps of peak burn rate. A capsule with a tritium fuel layer containing a small amount of deuterium ({approx}1%) creates a reaction history similar to the ignition capsule, but without the final ignition burn. A combination of gas Cerenkov detectors and the neutron temporal diagnostic could be capable of diagnosing the full history of ignition and tritium rich capsules.

Wilson, D. C.; Bradley, P. A.; Herrmann, H. W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Cerjan, C. J.; Salmonson, J. D.; Spears, B. K.; Hatchet, S. P. II [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Glebov, V. Yu. [L.L.E., University of Rochester, Rochester, New York 14623 (United States)

2008-10-15

327

Citrus Peel Additives for One-Pot Triazole Formation by Decarboxylation, Nucleophilic Substitution, and Azide-Alkyne Cycloaddition Reactions  

ERIC Educational Resources Information Center

This undergraduate organic laboratory experiment consists of three different reactions occurring in the same flask: a cycloaddition reaction, preceded by decarboxylation and nucleophilic substitution reactions. The decarboxylation and cycloaddition reactions occur using identical Cu(I) catalyst and conditions. Orange, lemon, and other citrus fruit…

Mendes, Desiree E.; Schoffstall, Allen M.

2011-01-01

328

Toward perylene dyes by the Hundsdiecker reaction.  

PubMed

An efficient method to synthesize 3,4,9,10-tetrabromoperylenes is reported under optimized Hunsdiecker conditions. Various octasubstituted perylenes were obtained by reaction of 1,6,7,12-tetrachloro-3,4,9,10-tetrabromoperylene with phenol, trimethylsilyl chloride, cooper cyanide, or sulfur via metal-catalyzed couplings or nucleophilic substitutions. These new perylenes show completely different optical and redox properties, thus opening a facile way to develop new chromophophore structures. PMID:24835560

Zagranyarski, Yulian; Chen, Long; Jänsch, Daniel; Gessner, Thomas; Li, Chen; Müllen, Klaus

2014-06-01

329

Reactions of inorganic nitrogen species in supercritical water  

SciTech Connect

Redox reactions of nitrate salts with NH3 and methanol were studied in near-critical and supercritical water at 350 to 530 C and constant pressure of 302 bar. Sodium nitrate decomposition reactions were investigated at similar conditions. Reactions were conducted in isothermal tubular reactor under plug flow. For kinetic modeling, nitrate and nitrite reactants were lumped into an NO{sub x}{sup -} reactant; kinetic expressions were developed for MNO{sub 3}/NH{sub 4}X and sodium nitrate decomposition reactions. The proposed elementary reaction mechanism for MNO{sub 3}/NH{sub 4}X reaction indicated that NO{sub 2} was the primary oxidizing species and that N{sub 2}/N{sub 2}O selectivities could be determined by the form of MNO{sub 3} used. This suggest a nitrogen control strategy for use in SCWO (supercritical water oxidation) processes; nitrate or NH3 could be used to remove the other, at reaction conditions far less severe than required by other methods. Reactions of nitrate with methanol indicated that nitrate was a better oxidant than oxygen in supercritical water. Nitrogen reaction products included NH3 and nitrite, while inorganic carbon was the major carbon reaction product. Analysis of excess experiments indicated that the reaction at 475 C was first order in methanol concentration and second order in NO{sub x}{sup -} concentration. In order to determine phase regimes for these reactions, solubility of sodium nitrate was determined for some 1:1 nitrate electrolytes. Solubilities were measured at 450 to 525 C, from 248 to 302 bar. A semi-empirical solvation model was shown to adequately describe the experimental sodium nitrate solubilities. Solubilities of Li, Na, and K nitrates revealed with cations with smaller ionic radii had greater solubilities with nitrate.

Dell`Orco, P.C. [Texas Univ., Austin, TX (United States)] [Texas Univ., Austin, TX (United States)

1994-12-31

330

The effects of reward and punishment on reaction times and autonomic activity in hyperactive and normal children  

Microsoft Academic Search

The performance of hyperactive and control children was compared on a delayed reaction time task under three reinforcement conditions: reward, punishment, and reward plus punishment. Hyperactives had slower and more variable reaction times, suggesting an attentional deficit. Although each of the three reinforcement conditions was successful in improving reaction times for both subject groups, reward led to a significant increase

Philip Firestone; Virginia Douglas

1975-01-01

331

Reaction time as a function of foreperiod duration and variability  

Microsoft Academic Search

Studied RT under 2 conditions of foreperiod variability; minimal objective variability and 20% objective variability. Found no evidence that prematurely originated reactions had an appreciable influence on either condition. Woodrow's finding of a 2-sec. optimum was not confirmed. The steady increase of RT as a function of foreperiod contradicts a previous conclusion. RT following a given foreperiod was influenced by

Lawrence Karlin

1959-01-01

332

Reaction synthesis of intermetallics  

SciTech Connect

Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, reduction ratios, and hot-pressing conditions of the intermetallics and their composites are discussed.

Deevi, S.C.; Sikka, V.K.

1994-12-31

333

The Reaction between Iron(II) Iodide and Potassium Dichromate(VI) in Acidified Aqueous Solution  

ERIC Educational Resources Information Center

This "Science note" teaching lesson explores the possible reaction between the ions in a reaction mixture consisting of iron(II) iodide and potassium dichromate(VI) in acidified aqueous solution. The electrode potentials will be used to deduce any spontaneous reactions under standard thermodynamic conditions (298 K, 1 bar (approximately…

Talbot, Christopher

2013-01-01

334

MODEL OF CHEMICAL REACTION EQUILIBRIUM OF SULFURIC ACID SALTS OF TRIOCTYLAMINE  

Microsoft Academic Search

The chemical reaction of trioctylamine (TOA) and sulfuric acid in organic solvent\\/aqueous solution was carried out. TOA salt products of various kinds were obtained based on different conditions of operation and organic solvents. An equilibrium model, based on the chemical reaction of sulfuric acid and trioctylamine, is proposed. The equilibrium constants of various reactions of trioctylamine and sulfuric acid were

MAW-LING WANG; KWAN-HUA HU

1993-01-01

335

Microwave-Assisted Organic Synthesis in the Organic Teaching Lab: A Simple, Greener Wittig Reaction  

ERIC Educational Resources Information Center

A greener, microwave-assisted Wittig reaction has been developed for the second-semester organic teaching laboratory. Utilizing this microwave technique, a variety of styrene derivatives have been successfully synthesized from aromatic aldehydes in good yields (41-68%). The reaction not only occurs under neat reaction conditions, but also employs…

Martin, Eric; Kellen-Yuen, Cynthia

2007-01-01

336

Reaction of lithium enediolates with perfluoroketene dithioacetals. Synthesis of ?-trifluoromethyl ?-dicarboxylic acid derivatives  

Microsoft Academic Search

The reaction of perfluoroketene dithioacetals with dianions of carboxylic acids proceeds through the substitution of the vinylic fluoride. The preparative value of this reaction depends strongly on the reaction and work-up conditions, the optimisation of which led to use LDA as a base and multiple extraction techniques. The overall process may be considered as a formal synthesis of ?-trifluoromethyl ?-dicarboxylic

Enrique Sotoca; Jean-Philippe Bouillon; Salvador Gil; Margarita Parra; Charles Portella

2004-01-01

337

One-pot synthesis of dihydropyrimidinones using facile and reusable polyoxometalate catalysts for the Biginelli reaction  

Microsoft Academic Search

The efficiency of various heteropoly compounds as well-known solid acids is investigated for the three-component condensation reaction of an aldehyde with ?-ketoester and urea in acetonitrile to afford the dihydropyrimidinones (DHPM). Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of excellent yields and short reaction times. Furthermore, the catalyst could be easily recovered after

Razieh Fazaeli; Shahram Tangestaninejad; Hamid Aliyan; Majid Moghadam

2006-01-01

338

Gold(III)-catalyzed three-component coupling reaction (TCC) selective toward furans.  

PubMed

An efficient three-component coupling reaction toward a variety of furan derivatives has been developed. This cascade transformation proceeds via the gold-catalyzed coupling reaction of phenylglyoxal derivatives, secondary amines, and terminal alkynes, under the reaction conditions, that undergoes cyclization into the furan core. PMID:23687935

Li, Jian; Liu, Li; Ding, Dong; Sun, Jiangtao; Ji, Yangxuan; Dong, Jialing

2013-06-01

339

General Banking Conditions 2009 General Banking Conditions  

E-print Network

General Banking Conditions 2009 r #12;#12;1 General Banking Conditions (Version 2009. 1 Scope The provisions of these General Banking Conditions shall apply to all existing and future legal relationships between the Bank and the Customer to the extent that it is not otherwise provided

Franssen, Michael

340

Heat Speeds Up Reactions  

NSDL National Science Digital Library

In this activity, learners investigate the effect of heat on a reaction. Learners first model molecular motion by moving their bodies (running, moving slowly) and pretending to be molecules at different temperatures, then by using groups of cut-out shapes (not provided) which get rearranged when they collide. After this introduction, three glow sticks are activated—one is put in ice water, one in warm water, and one left at room temperature for 15 minutes. A comparison of which glow stick gives off the most light gives an indication of the speed of the molecules and the number of reactions occurring. (The activity was originally written as part of a kit to be checked out of the library, but the kit is not required.)

Maisie Shaw

2009-01-01

341

Postmarketing adverse drug reactions  

PubMed Central

Summary Physicians play an important role in recognizing and reporting suspected adverse drug reactions (ADRs) to the Food and Drug Administration (FDA). Physicians can report suspected ADRs directly to the FDA via its MedWatch program, by contacting the manufacturer of the drug, and by publishing case reports. While this takes time, physicians have an ethical obligation to participate in recognizing and reporting ADR. PMID:24195018

Bourdette, Dennis

2013-01-01

342

Reaction Time 2: Zap!  

NSDL National Science Digital Library

This Science NetLinks lesson is the second of a two-part series that encourages students to think about their own learning and the strategies that best help them learn new skills and ideas. In this lesson, students build upon what they have already learned by participating in another online reaction-time activity--this one testing their visual and auditory abilities, both separately and together.

Science Netlinks;

2003-06-19

343

Polymerase Chain Reaction  

NSDL National Science Digital Library

Teachers' Domain presents this interactive, adapted from the University of Nebraska's Library of Crop Technologies, with reading material and animations to help students learn the basic steps of polymerase chain reaction. Following the introduction, the lesson is divided four parts: Finding and Isolating DNA, Creating the DNA Solution, Begin Thermal Cycling, and Replication. Animations help students visualize each step of the processes described. On the site, visitors will also find a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

344

Photochemical reaction dynamics  

SciTech Connect

The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

1993-12-01

345

CHEMICAL TRANSFORMATIONS USING NON-TRADITIONAL APPROACHES: MICROWAVE-ASSISTED GREENER SYNTHESES IN AQUEOUS MEDIA OR UNDER SOLVENT-FREE CONDITIONS  

EPA Science Inventory

Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a 'greener' chemical approach for expeditious N -alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N...

346

Optimum conditions for microbial carbonate precipitation  

Microsoft Academic Search

The type of bacteria, bacterial cell concentration, initial urea concentration, reaction temperature, the initial Ca2+ concentration, ionic strength, and the pH of the media are some factors that control the activity of the urease enzyme, and may have a significant impact on microbial carbonate precipitation (MCP). Factorial experiments were designed based on these factors to determine the optimum conditions that

George D. O. Okwadha; Jin Li

2010-01-01

347

Chemical Reactions in DSMC  

SciTech Connect

DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

Bird, G. A. [GAB Consulting Pty Ltd, 144/110 Sussex Street, Sydney NSW 2000 (Australia)

2011-05-20

348

Shock-induced chemical reactions in organic materials and explosives  

NASA Astrophysics Data System (ADS)

Interrogating chemical reactions behind a shock front is immensely difficult and, as a result, the details of shock-induced chemistry remain poorly understood. Previous research has shown that dimerizations, polymerizations, ring-opening and decomposition reactions can occur under shock compression, depending on molecular structure. Questions regarding the thresholds for incipient reaction, the nature of first and subsequent reaction steps, and the influence of shock input conditions on reaction kinetics remain to be answered. Here, we have applied in-situ electromagnetic gauging at multiple Lagrangian positions to elucidate the evolution of multiple-wave structures associated with shock-induced reactions of several simple functional groups: carbon-carbon double (-C=C-) and triple bonds, and nitriles. The relative order of group reactivity under single shock conditions for these simple molecules is discussed. From measurements of the reactive flow, we have obtained detailed information about the temporal evolution of the waves, and global kinetic rates associated with transformation(s) between partially- and fully-reacted states. Near the reactive thresholds, evolution in particle velocities point to reaction timescales on the order of tens-to-hundreds of nanoseconds. We further compare evidence of reaction from gas gun-driven experiments to recent results using laser-driven shocks. Spectroscopic details will be presented from both types of experiments.

Dattelbaum, Dana; Sheffield, Stephen; McGrane, Shawn; Goodwin, Peter

2012-02-01

349

Procedures for Decomposing a Redox Reaction into Half-Reaction  

ERIC Educational Resources Information Center

A simple algorithm for a complete enumeration of the possible ways a redox reaction (RR) might be uniquely decomposed into half-reactions (HRs) using the response reactions (RERs) formalism is presented. A complete enumeration of the possible ways a RR may be decomposed into HRs is equivalent to a complete enumeration of stoichiometrically…

Fishtik, Ilie; Berka, Ladislav H.

2005-01-01

350

Reaction Extrema: Extent of Reaction in General Chemistry  

ERIC Educational Resources Information Center

Nearly 100 years ago de Donder introduced the term "extent of reaction", ?. We build on that work by defining the concept of reagent extrema for an arbitrary chemical reaction, aA + bB [reversible reaction] yY + zZ. The central equation is ?^[subscript i] = -n[subscript i,0]/?[subscript i]. The symbol ?^[subscript i] represents the…

Vandezande, Jonathon E.; Vander Griend, Douglas A.; DeKock, Roger L.

2013-01-01

351

Classes of Chemical Reactions Reactions in aqueous media  

E-print Network

acid, HBr Phosphoric acid, H3PO4 Hydroiodic acid, HI Acetic acid, CH3CO2H Nitric acid, HNO3 CarbonicClasses of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid + electrolytes: a substance that conducts an electric current when dissolved in water Acids are donors of H

Zakarian, Armen

352

Black Hole Boundary Conditions and Coordinate Conditions  

E-print Network

This paper treats boundary conditions on black hole horizons for the full 3+1D Einstein equations. Following a number of authors, the apparent horizon is employed as the inner boundary on a space slice. It is emphasized that a further condition is necessary for the system to be well posed; the ``prescribed curvature conditions" are therefore proposed to complete the coordinate conditions at the black hole. These conditions lead to a system of two 2D elliptic differential equations on the inner boundary surface, which coexist nicely to the 3D equation for maximal slicing (or related slicing conditions). The overall 2D/3D system is argued to be well posed and globally well behaved. The importance of ``boundary conditions without boundary values" is emphasized. This paper is the first of a series. This revised version makes minor additions and corrections to the previous version.

Douglas M. Eardley

1997-03-11

353

Chemical memory reactions induced bursting dynamics in gene expression.  

PubMed

Memory is a ubiquitous phenomenon in biological systems in which the present system state is not entirely determined by the current conditions but also depends on the time evolutionary path of the system. Specifically, many memorial phenomena are characterized by chemical memory reactions that may fire under particular system conditions. These conditional chemical reactions contradict to the extant stochastic approaches for modeling chemical kinetics and have increasingly posed significant challenges to mathematical modeling and computer simulation. To tackle the challenge, I proposed a novel theory consisting of the memory chemical master equations and memory stochastic simulation algorithm. A stochastic model for single-gene expression was proposed to illustrate the key function of memory reactions in inducing bursting dynamics of gene expression that has been observed in experiments recently. The importance of memory reactions has been further validated by the stochastic model of the p53-MDM2 core module. Simulations showed that memory reactions is a major mechanism for realizing both sustained oscillations of p53 protein numbers in single cells and damped oscillations over a population of cells. These successful applications of the memory modeling framework suggested that this innovative theory is an effective and powerful tool to study memory process and conditional chemical reactions in a wide range of complex biological systems. PMID:23349679

Tian, Tianhai

2013-01-01

354

14 CFR 25.493 - Braked roll conditions.  

Code of Federal Regulations, 2012 CFR

...reaction multiplied by a coefficient of friction of 0.8, must be combined with the...reaction, multiplied by a coefficient of friction of 0.8, must be combined with the...static condition. ?=Coefficient of friction of 0.80. f=Dynamic response...

2012-01-01

355

14 CFR 25.493 - Braked roll conditions.  

Code of Federal Regulations, 2013 CFR

...reaction multiplied by a coefficient of friction of 0.8, must be combined with the...reaction, multiplied by a coefficient of friction of 0.8, must be combined with the...static condition. ?=Coefficient of friction of 0.80. f=Dynamic response...

2013-01-01

356

14 CFR 25.493 - Braked roll conditions.  

...reaction multiplied by a coefficient of friction of 0.8, must be combined with the...reaction, multiplied by a coefficient of friction of 0.8, must be combined with the...static condition. ?=Coefficient of friction of 0.80. f=Dynamic response...

2014-01-01

357

Single Replacement Micro-Reactions  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals and metals to explore single replacement reactions. Learners will record any color changes or gas production for each reaction as well as write a balanced equation for each.

The Science House

2014-01-28

358

ChemTeacher: Combination Reactions  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Combination Reactions page includes resources for teaching students about identifying and predicting combination reactions.

2011-01-01

359

ChemTeacher: Decomposition Reactions  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Decomposition Reactions page includes resources for teaching students about identifying and predicting decomposition reactions.

2011-01-01

360

Zip-lock Bag Reactions  

NSDL National Science Digital Library

Students conduct and observe a chemical reaction in a sealable plastic bag. Students then devise and conduct their own experiments to determine the identity of two unknown substances used in the reaction.

David A. Katz

2009-07-09

361

Hydrazine decomposition and other reactions  

NASA Technical Reports Server (NTRS)

This invention relates to the catalytic decomposition of hydrazine, catalysts useful for this decomposition and other reactions, and to reactions in hydrogen atmospheres generally using carbon-containing catalysts.

Armstrong, Warren E. (Inventor); La France, Donald S. (Inventor); Voge, Hervey H. (Inventor)

1978-01-01

362

42 CFR 494.40 - Condition: Water and dialysate quality.  

Code of Federal Regulations, 2010 CFR

...END-STAGE RENAL DISEASE FACILITIES Patient Safety § 494.40 Condition: Water...corrective action plan that ensures patient safety. (d) Standard: Adverse events...maintain active surveillance of patient reactions during and...

2010-10-01

363

ENVIRONMENTALLY FRIENDLIER ORGANIC TRANSFORMATIONS ON MINERAL SUPPORTS UNDER NONTRADITIONAL CONDITIONS  

EPA Science Inventory

Synthetic organic reactions performed under non-traditional conditions are gaining popularity primarily to circumvent the growing environmental concerns. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) either in presence of a catalyst o...

364

Synthesis, hydrothermal stability and thermal reaction behavior of nepheline hydrate i (NH I)  

Microsoft Academic Search

Summary The field of formation of nepheline hydrate I (NH I) was investigated under mild hydrothermal conditions (473 K for 5 d) using low temperature reaction of kaolinite. Therefore alkaline transformation in 2-, 4-, and 6 molar NaOH solutions was performed to investigate the influence of sodium hydroxide on the phase formation process controlled by kinetics under mild reaction conditions.

Josef-Christian Buhl

2005-01-01

365

Solid-state synthesis reaction between Al and Cu powders during ball milling  

Microsoft Academic Search

The solid-state synthesis reaction between Al and Cu during high energy ball milling has been studied. The most important effect of ball milling is that the grain size of the constituents decreased to the nanometer range and the constituents dissolved at the nanograin boundaries. This provides feasible conditions for the solid state synthesis reactions. The milling conditions have a sensitive

Shengqi Xi; Jingen Zhou; Dongwen Zhang; Xiaotian Wang

1996-01-01

366

The Vitamin C Clock Reaction.  

ERIC Educational Resources Information Center

Describes an iodine clock reaction that produces an effect similar to the Landolt clock reaction. This reaction uses supermarket chemicals and avoids iodate, bisulfite, and mercury compounds. Ascorbic acid and tincture of iodine are the main reactants with alternate procedures provided for vitamin C tablets and orange juice. (DDR)

Wright, Stephen W.

2002-01-01

367

More on Chemical Reaction Balancing.  

ERIC Educational Resources Information Center

A previous article stated that only the matrix method was powerful enough to balance a particular chemical equation. Shows how this equation can be balanced without using the matrix method. The approach taken involves writing partial mathematical reactions and redox half-reactions, and combining them to yield the final balanced reaction. (JN)

Swinehart, D. F.

1985-01-01

368

Double Replacement Micro-Reactions  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals to examine reactions that occur between two aqueous solutions. Learners will record any color changes or precipitate formation for each reaction as well as write a balanced equation for each. Learners will discover that the driving force for the reaction is the formation of an insoluble product.

2014-01-28

369

Polymerase Chain Reaction Assay and  

E-print Network

Polymerase Chain Reaction Assay and Bacterial Meningitis Surveillance in Remote Areas, Niger Fati reference laboratory for meningitis in Niger used polymerase chain reaction (PCR) to enhance) and the national reference center for menin- gitis in Niger. The polymerase chain reaction (PCR) method

Paris-Sud XI, Université de

370

Friedel–Crafts alkylation reactions in pyridinium-based ionic liquids  

Microsoft Academic Search

The Friedel–Crafts alkylations of benzene in pyridinium-based ionic liquids (ILs) were investigated. The effects of catalyst–IL composition, reactant composition, quantity of catalyst and reaction temperature on this reaction were studied. The reactions were found to proceed under mild conditions with conversion; a simple product isolation procedure was achieved. The ILs rendered this reaction green characteristics. The ILs could also be

Ying Xiao; Sanjay V. Malhotra

2005-01-01

371

Hydrothermal Synthesis of Metal Oxide Nanoparticles at Supercritical Conditions  

Microsoft Academic Search

Hydrothermal synthesis of CeO2 and AlO(OH) were conducted using a flow type apparatus over the range of temperature from 523 to 673 K at 30 MPa. Nanosize crystals were formed at supercritical conditions. The mechanism of nanoparticle formation at supercritical conditions was discussed based on the metal oxide solubility and kinetics of the hydrothermal synthesis reaction. The reaction rate of

Tadafumi Adschiri; Yukiya Hakuta; Kiwamu Sue; Kunio Arai

2001-01-01

372

Atherton–Todd reaction: mechanism, scope and applications  

PubMed Central

Summary Initially, the Atherton–Todd (AT) reaction was applied for the synthesis of phosphoramidates by reacting dialkyl phosphite with a primary amine in the presence of carbon tetrachloride. These reaction conditions were subsequently modified with the aim to optimize them and the reaction was extended to different nucleophiles. The mechanism of this reaction led to controversial reports over the past years and is adequately discussed. We also present the scope of the AT reaction. Finally, we investigate the AT reaction by means of exemplary applications, which mainly concern three topics. First, we discuss the activation of a phenol group as a phosphate which allows for subsequent transformations such as cross coupling and reduction. Next, we examine the AT reaction applied to produce fire retardant compounds. In the last section, we investigate the use of the AT reaction for the production of compounds employed for biological applications. The selected examples to illustrate the applications of the Atherton–Todd reaction mainly cover the past 15 years. PMID:24991268

Le Corre, Stéphanie S; Berchel, Mathieu; Couthon-Gourvès, Hélène; Haelters, Jean-Pierre

2014-01-01

373

Effect of polymerization conditions on the size change of poly(ethylene glycol) hydrogel nanoparticles  

NASA Astrophysics Data System (ADS)

Suspension polymerization was used to prepare PEG homopolymer particles with nanometer size. In order to achieve the optimized reaction conditions for producing the smallest nanosized particles, the effects of various reaction conditions such as sonication, monomer concentration, molecular weight of monomer, and stabilizer concentration on the size of PEG hydrogel nanoparticles were investigated. Among these reaction conditions, sonication and the molecular weight of the monomer affected significantly the size reduction of PEG hydrogel nanoparticles, that is, the particle size decreased as sonication was conducted and the molecular weight of the monomer decreased. PEG homopolymer hydrogel nanoparticles having an average size of 182.1 nm were finally obtained with optimized reaction conditions.

Kim, Youn-Hee; Chung, Minsub; Kim, Bumsang

2014-11-01

374

A new way of probing reaction networks: analyzing multidimensional parameter space.  

PubMed

Technically relevant partial oxidation reactions represent complex reaction networks. Establishing a kinetic model for a system of multiple consecutive and parallel reaction steps is a challenging goal. The synthesis of acrylic acid by oxidation of propane using MoVTeNb mixed oxide as catalyst is such a reaction network. In an on-going study, a 10- fold parallel reactor set-up is used to vary systematically reaction conditions in a broad range over a single, well-defined MoVTeNb oxide. Selectivity and product yield in a multidimensional parameter space can give insight into the reaction network. Apparent activation energies and reaction orders of propane are derived for several conditions. Optimum reaction conditions within the investigated parameter space are specified. The results presented within this contribution contain about 200 data points measured in steady states each corresponding to reaction conditions that differ in temperature, contact time, and propane feed concentration. The fact that this data was collected in less than two months shows clearly the advantage of parallel screening of reaction conditions for mechanistic studies. PMID:22023149

d'Alnoncourt, Raoul Naumann; Kolen'ko, Yury V; Schlogl, Robert; Trunschke, Annette

2012-02-01

375

Adverse drug reactions in the elderly.  

PubMed

Medications probably are the single most important health care technology in preventing illness, disability, and death in the geriatric population. Age-related changes in drug disposition and pharmacodynamic responses have significant clinical implications; increased use of a number of medications raises the risk that medicine-related problems may occur. The relationship between increased use of drugs including the prescription medication and elderly is well established. Majority of ADRs (80%) causing admission or occurring in hospital are type A reactions. Although less common occurring in elderly, type B ADRs may sometimes cause serious toxicity. Studies have correlated the integral association between old age and increased rate of adverse drug reactions arising out of confounding association between age and polypharmacy contributed by age-related changes in pharmacodynamics and pharmacokinetics at least for some medical conditions. A drug combination may sometimes cause synergistic toxicity which is greater than the sum of the risks of toxicity of either agent used alone. But, strategies to increase opportunities for identifying ADRs and related problems have not been emphasised in current international policy responses especially in India to the increase in elderly population and chronic conditions. Careful epidemiological studies that encompass large numbers of elderly drug users are required to obtain this information as increased knowledge of the frequency and cost of adverse drug reactions is important in enabling both more rational therapeutic decisions by individual clinicians and more optimal social policy. PMID:23761706

Brahma, Dhriti K; Wahlang, Julie B; Marak, Maxilline D; Ch Sangma, Marlina

2013-04-01

376

The reaction path intrinsic reaction coordinate method and the Hamilton-Jacobi theory.  

PubMed

The definition and location of an intrinsic reaction coordinate path is of crucial importance in many areas of theoretical chemistry. Differential equations used to define the path hitherto are complemented in this study with a variational principle of Fermat type, as Fukui [Int. J. Quantum Chem., Quantum Chem. Symp. 15, 633 (1981)] reported in a more general form some time ago. This definition is more suitable for problems where initial and final points are given. The variational definition can naturally be recast into a Hamilton-Jacobi equation. The character of the variational solution is studied via the Weierstrass necessary and sufficient conditions. The characterization of the local minima character of the intrinsic reaction coordinate is proved. Such result leads to a numerical algorithm to find intrinsic reaction coordinate paths based on the successive minimizations of the Weierstrass E-function evaluated on a guess curve connecting the initial and final points of the desired path. PMID:16008428

Crehuet, Ramon; Bofill, Josep Maria

2005-06-15

377

Chain-reaction crash in traffic flow controlled by taillights  

NASA Astrophysics Data System (ADS)

We study the chain-reaction crash (multiple-vehicle collision) in low-visibility condition on a road. In the traffic situation, drivers brake according to taillights of the forward vehicle. The first crash may induce more collisions. We investigate whether or not the first collision induces the chain-reaction crash, numerically and analytically. The dynamic transitions occur from no collisions through a single collision, double collisions and triple collisions, to multiple collisions with decreasing the headway. Also, we find that the dynamic transition occurs from the finite chain reaction to the infinite chain reaction when the headway is less than the critical value. We derive, analytically, the transition points and the region maps for the chain-reaction crash in traffic flow controlled by taillights.

Nagatani, Takashi

2015-02-01

378

Scaling properties of diffusion-limited reactions: Fractals  

NASA Astrophysics Data System (ADS)

We have generalized our previous scaling arguments [Sheu, Lindenberg, and Kopelman, Phys. Rev. A 42, 2279 (1990)] for diffusion-limited A+B-->0 reactions to encompass various possible connectivity properties and reaction conditions on fractal structures. The theory now allows for a more complete range of possible reaction surface configurations. While our original result (which is a special case) places a bound that is consistent with very recent simulations on critical percolation clusters, the generalization is needed to account for the behavior on finitely ramified structures such as Sierpinski gaskets and Peano curve fractal constructions. Our results yield upper and lower bounds for the oscillations of the reactant decay exponent which are typical for hierarchical structures. Our approach unites under a single framework situations such as the A+B-->0 reaction and the A+A-->0 reaction that were previously treated separately.

Lindenberg, Katja; Sheu, Wen-Shyan; Kopelman, Raoul

1991-06-01

379

Method and apparatus for controlling gas evolution from chemical reactions  

DOEpatents

The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846.

Skorpik, James R. (Kennewick, WA); Dodson, Michael G. (Richland, WA)

1999-01-01

380

Method and apparatus for controlling gas evolution from chemical reactions  

DOEpatents

The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846. 8 figs.

Skorpik, J.R.; Dodson, M.G.

1999-05-25

381

Protease-catalysed Direct Asymmetric Mannich Reaction in Organic Solvent  

PubMed Central

We reported the first enzyme-catalysed, direct, three-component asymmetric Mannich reaction using protease type XIV from Streptomyces griseus (SGP) in acetonitrile. Yields of up to 92% with enantioselectivities of up to 88% e.e. and diastereoselectivities of up to 92:8 (syn:anti) were achieved under the optimised conditions. This enzyme's catalytic promiscuity expands the application of this biocatalyst and provides a potential alternative method for asymmetric Mannich reactions. PMID:23094136

Xue, Yang; Li, Ling-Po; He, Yan-Hong; Guan, Zhi

2012-01-01

382

General chemical kinetics computer program for static and flow reactions, with application to combustion and shock-tube kinetics  

NASA Technical Reports Server (NTRS)

A general chemical kinetics program is described for complex, homogeneous ideal-gas reactions in any chemical system. Its main features are flexibility and convenience in treating many different reaction conditions. The program solves numerically the differential equations describing complex reaction in either a static system or one-dimensional inviscid flow. Applications include ignition and combustion, shock wave reactions, and general reactions in a flowing or static system. An implicit numerical solution method is used which works efficiently for the extreme conditions of a very slow or a very fast reaction. The theory is described, and the computer program and users' manual are included.

Bittker, D. A.; Scullin, V. J.

1972-01-01

383

Bray-Liebhafsky oscillatory reaction in the radiofrequency electromagnetic field  

NASA Astrophysics Data System (ADS)

Oscillatory Bray-Liebhafsky (BL) reaction is capacitively coupled with the electromagnetic radiation in the frequency range 60-110 MHz. Because of the specific reaction dynamics characterized by several characteristic parameters (induction period, period between chemical oscillations and their amplitude) it served as a good model system for the investigation of the effects of radiofrequent (RF) radiation. RF power of up to 0.2 W did not produce observable changes of the BL reaction parameters in the limit of the experiment reproductivity. Results indicate that, under the given experimental conditions, both dissipative and reactive properties of the solution are not considerably coupled with the RF electrical field.

Stanisavljev, Dragomir R.; Veliki?, Zoran; Veselinovi?, Dragan S.; Jaci?, Nevena V.; Milenkovi?, Maja C.

2014-09-01

384

Shock-induced chemical reactions in simple organic molecules  

NASA Astrophysics Data System (ADS)

Interrogating chemical reactions behind a shock front is immensely difficult and, as a result, the details of shock-induced chemistry remain poorly understood. Previous research has shown that dimerizations, polymerizations, ring-opening and decomposition reactions can occur under shock compression, depending on molecular structure. Questions regarding the thresholds for incipient reaction, the nature of first and subsequent reaction steps, and the influence of shock input conditions on reaction kinetics remain to be answered. Here, we have applied in-situ electromagnetic gauging at multiple Lagrangian positions to elucidate the evolution of multiple-wave structures associated with shock-induced reactions of several simple functional groups: carbon-carbon double (-C=C-) and triple bonds, and nitriles. The relative order of group reactivity under single shock conditions for these simple molecules is discussed. From measurements of the reactive flow, we have obtained detailed information about the temporal evolution of the waves, and global kinetic rates associated with transformation(s) between partially- and fully-reacted states. Near the reactive thresholds, evolution in particle velocities point to reaction timescales on the order of tens-to-hundreds of nanoseconds.

Dattelbaum, Dana M.; Sheffield, S. A.

2012-03-01

385

Clay and acid catalysed isomerisation and cyclisation reactions of highly branched isoprenoid (HBI) alkenes: implications for sedimentary reactions and distributions  

NASA Astrophysics Data System (ADS)

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 observed as the only reactions. In contrast, trienes undergo both isomerisation and rapid cyclisation reactions to yield substituted cyclohexenes. Molecular mechanics calculations have been performed to complement the laboratory experiments and to assist in proposing reaction mechanisms. The significance of these findings for the interpretation of the numerous reports of highly branched isoprenoids in Recent and ancient sediments is discussed.

Belt, Simon T.; Allard, W. Guy; Rintatalo, Janne; Johns, Lesley A.; van Duin, Adri C. T.; Rowland, Steven J.

2000-10-01

386

Acceleration of chemical reaction by chaotic mixing  

E-print Network

Theory of fast binary chemical reaction, ${\\cal A}+{\\cal B}\\to{\\cal C}$, in a statistically stationary chaotic flow at large Schmidt number ${Sc}$ and large Damk\\"ohler number ${Da}$ is developed. For stoichiometric condition we identify subsequent stages of the chemical reaction. The first stage corresponds to the exponential decay, $\\propto\\exp(-\\lambda t)$ (where $\\lambda$ is the Lyapunov exponent of the flow), of the chemicals in the bulk part of the flow. The second and the third stages are related to the chemicals remaining in the boundary region. During the second stage the amounts of ${\\cal A}$ and ${\\cal B}$ decay $\\propto 1/\\sqrt{t}$, whereas the decay law during the third stage is exponential, $\\propto\\exp(-\\gamma t)$, where $\\gamma\\sim\\lambda/\\sqrt{Sc}$.

M. Chertkov; V. Lebedev

2003-01-27

387

Biosensor as a Reaction-Diffusion System  

E-print Network

We model a biosensor as a reaction-diffusion process in a confined geometry. When a solution containing unknown concentration of antigens are injected into the closed chamber of the sensor, the antigens diffuse and react with a functionalised surface. These surface reactions are then converted to an optical signal, the intensity of which indicates the level of antigen content in the solution. We probe the spatio-temporal behavior of the system by studying the governing equations, using mean field approximation and numerical integration. Mean field analysis gives important insights about the dynamics, but in order to compare with real experiments and extract the values of the relevant kinetic parameters, numerical integration was necessary. We track down the operating conditions for quick and efficient response of the sensor.

Ghosh, Surya K; Sain, Anirban

2012-01-01

388

Direct Measurement of ^21Na+? Stellar Reaction  

NASA Astrophysics Data System (ADS)

Nucleosynthesis of ^22Na is an interesting subject because of possible ?-ray observation and isotopic anomalies in presolar grain. ^22Na would have been mainly produced in the NeNa cycle. At high temperature conditions, ^21Na(?,p)^24Mg reaction could play a significant role to make flow from the NeNa cycle to the next MgAl cycle and beyond. Clearly, the ^21Na(?,p)^24Mg stellar reaction would bypass ^22Na, resulting in reduction of ^22Na production, therefore, it is strongly coupled to the Ne-E problem. It could be also important to understand the early stage of the rp-process. Experiment was performed using a 39 MeV ^21Na radioactive beam obtained by the CNS Radio Isotope Beam separator CRIB of the University of Tokyo. Both protons and alphas were measured from ?+^21Na scattering with a thick ^4He gas target.

Binh Dam, Nguyen; Yamaguchi, H.; Wakabayashi, Y.; Hayakawa, S.; Hashimoto, T.; Kahl, D.; Kubono, S.; Le, H. K.; Nguyen, T. T.; Iwasa, N.; Kume, N.; Kato, S.; Teranishi, T.

2009-10-01

389

Dearomative indole (3 + 2) cycloaddition reactions.  

PubMed

A diastereoselective (3 + 2) dearomative annulation of 3-substituted indoles with ?-haloketones has been developed. Significant regiochemical control was observed. This methodology provides easy access to highly functionalized cyclopenta- or cyclohexa-fused indoline compounds, which are common structures of many natural products. The synthetic potential of this reaction was demonstrated in the concise syntheses of the core structures of vincorine, isocorymine, and aspidophylline A. DFT studies (B3LYP-D3/6-311++G**/MeOH) on cyclization mechanisms involving the 2-hydroxyallyl cation and its deprotonated oxyallyl cation have been performed. Under the reaction conditions, with a sparingly soluble Na2CO3 base, both species may be present and both pathways are viable. Both pathways support the formation of the experimentally observed O-bound intermediate, its transformation to the final product, the regiochemical and eventual stereochemical outcome of the kinetic cyclization product, and the thermodynamic preference for formation of the final stereoisomer. PMID:24739089

Li, Hui; Hughes, Russell P; Wu, Jimmy

2014-04-30

390

GENERALIZED AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY  

Microsoft Academic Search

A natural generalization of the ARCH (Autoregressive Conditional Heteroskedastic) process introduced in Engle (1982) to allow for past conditional variances in the current conditional variance equation is proposed. Stationarity conditions and autocorrelation structure for this new class of parametric models are derived. Maximum likelihood estimation and testing are also considered. Finally an empirical example relating to the uncertainty of the

Tim Bollerslev

1986-01-01

391

REACH. Air Conditioning Units.  

ERIC Educational Resources Information Center

As a part of the REACH (Refrigeration, Electro-Mechanical, Air-Conditioning, Heating) electromechanical cluster, this student manual contains individualized instructional units in the area of air conditioning. The instructional units focus on air conditioning fundamentals, window air conditioning, system and installation, troubleshooting and…

Garrison, Joe; And Others

392

ISMP Adverse Drug Reactions  

PubMed Central

The purpose of this feature is to heighten awareness of specific adverse drug reactions (ADRs), discuss methods of prevention, and promote reporting of ADRs to the US Food and Drug Administration’s (FDA’s) MedWatch program (800-FDA-1088). If you have reported an interesting, preventable ADR to MedWatch, please consider sharing the account with our readers. Write to Dr. Mancano at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-707-4936; e-mail: mmancano@temple.edu). Your report will be published anonymously unless otherwise requested. This feature is provided by the Institute for Safe Medication Practices (ISMP) in cooperation with the FDA’s MedWatch program and Temple University School of Pharmacy. ISMP is an FDA MedWatch partner. PMID:24421518

2013-01-01

393

ISMP Adverse Drug Reactions  

PubMed Central

The purpose of this feature is to heighten awareness of specific adverse drug reactions (ADRs), discuss methods of prevention, and promote reporting of ADRs to the US Food and Drug Administration’s (FDA’s) MedWatch program (800-FDA-1088). If you have reported an interesting, preventable ADR to MedWatch, please consider sharing the account with our readers. Write to Dr. Mancano at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-707-4936; e-mail: mmancano@temple.edu). Your report will be published anonymously unless otherwise requested. This feature is provided by the Institute for Safe Medication Practices (ISMP) in cooperation with the FDA’s MedWatch program and Temple University School of Pharmacy. ISMP is an FDA MedWatch partner. PMID:24421544

2013-01-01

394

ISMP Adverse Drug Reactions  

PubMed Central

The purpose of this feature is to heighten awareness of specific adverse drug reactions (ADRs), discuss methods of prevention, and promote reporting of ADRs to the US Food and Drug Administration’s (FDA’s) MedWatch program (800-FDA-1088). If you have reported an interesting, preventable ADR to MedWatch, please consider sharing the account with our readers. Write to Dr. Mancano at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-707-4936; e-mail: mmancano@temple.edu). Your report will be published anonymously unless otherwise requested. This feature is provided by the Institute for Safe Medication Practices (ISMP) in cooperation with the FDA’s MedWatch program and Temple University School of Pharmacy. ISMP is an FDA MedWatch partner. PMID:24474829

2013-01-01

395

Chemistry Under Extreme Conditions  

NASA Astrophysics Data System (ADS)

It has long been recognized that shock compression of condensed matter can generate chemical reactions. The best-known examples of this are the reactions that release energy during the detonation of a high explosive. Despite this, very little is known about molecular processes occurring behind the shock front in a condensed phase. I will describe a domain of ``extreme chemistry'' that is of particular interest and relevance. Extreme chemistry occurs when temperatures are comparable to molecular bond energies, and when molecular bond energies are strongly modified by pressure. In this region the notions of conventional chemistry must be completely rethought. I will review extreme chemistry in several contexts: the reactions of shocked liquids and plastics, reactions of detonating high explosives, and reactions under static compression. In the area of shocked liquids and plastics, I will ask whether traditional shock Hugoniot measurements can provide any information on underlying chemistry. For high explosives, I will discuss the nature of reactions at the Chapman-Jouget state. Finally, I will discuss the discovery of a novel superionic phase of water and a symmetric hydrogen bonded phase of formic acid under static compression. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Fried, Laurence

2005-07-01

396

A kinetic study of the CH2OO Criegee intermediate self-reaction, reaction with SO2 and unimolecular reaction using cavity ring-down spectroscopy.  

PubMed

Criegee intermediates are important species formed during the ozonolysis of alkenes. Reaction of stabilized Criegee intermediates with various species like SO2 and NO2 may contribute significantly to tropospheric chemistry. In the laboratory, self-reaction can be an important loss pathway for Criegee intermediates and thus needs to be characterized to obtain accurate bimolecular reaction rate coefficients. Cavity ring-down spectroscopy was used to perform kinetic measurements for various reactions of CH2OO at 293 K and under low pressure (7 to 30 Torr) conditions. For the reaction CH2OO + CH2OO (8), a rate coefficient k8 = (7.35 ± 0.63) × 10(-11) cm(3) molecule(-1) s(-1) was derived from the measured CH2OO decay rates, using an absorption cross section value reported previously. A rate coefficient of k4 = (3.80 ± 0.04) × 10(-11) cm(3) molecule(-1) s(-1) was obtained for the CH2OO + SO2 (4) reaction. An upper limit for the unimolecular CH2OO loss rate coefficient of 11.6 ± 8.0 s(-1) was deduced from studies of reaction (4). SO2 catalysed CH2OO isomerization or intersystem crossing is proposed to occur with a rate coefficient of (3.53 ± 0.32) × 10(-11) cm(3) molecule(-1) s(-1). PMID:25553776

Chhantyal-Pun, Rabi; Davey, Anthony; Shallcross, Dudley E; Percival, Carl J; Orr-Ewing, Andrew J

2015-02-01

397

A Topological Characterization of Medium-Dependent Essential Metabolic Reactions  

PubMed Central

Metabolism has frequently been analyzed from a network perspective. A major question is how network properties correlate with biological features like growth rates, flux patterns and enzyme essentiality. Using methods from graph theory as well as established topological categories of metabolic systems, we analyze the essentiality of metabolic reactions depending on the growth medium and identify the topological footprint of these reactions. We find that the typical topological context of a medium-dependent essential reaction is systematically different from that of a globally essential reaction. In particular, we observe systematic differences in the distribution of medium-dependent essential reactions across three-node subgraphs (the network motif signature of medium-dependent essential reactions) compared to globally essential or globally redundant reactions. In this way, we provide evidence that the analysis of metabolic systems on the few-node subgraph scale is meaningful for explaining dynamic patterns. This topological characterization of medium-dependent essentiality provides a better understanding of the interplay between reaction deletions and environmental conditions. PMID:24957651

Sonnenschein, Nikolaus; Marr, Carsten; Hütt, Marc-Thorsten

2012-01-01

398

ChemTeacher Resource: Oxidation Reduction Reactions  

NSDL National Science Digital Library

This computer resource goes over oxidation reduction reactions and how they are broken down into half reactions. It explains which half reaction is the oxidation reaction and which one is the reduction, then has some summary questions at the end.

2012-08-02

399

14 CFR 23.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 23.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2011-01-01

400

14 CFR 25.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 25.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2010-01-01

401

14 CFR 25.529 - Hull and main float landing conditions.  

...2014-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 25.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2014-01-01

402

14 CFR 23.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 23.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2010-01-01

403

14 CFR 25.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 25.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2013-01-01

404

14 CFR 25.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 25.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2012-01-01

405

14 CFR 23.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 23.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2012-01-01

406

14 CFR 23.529 - Hull and main float landing conditions.  

...2014-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 23.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2014-01-01

407

14 CFR 23.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 23.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2013-01-01

408

14 CFR 25.529 - Hull and main float landing conditions.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Hull and main float landing conditions. ...CATEGORY AIRPLANES Structure Water Loads § 25.529 Hull and main float landing conditions. ...and stern landings, the limit water reaction load factors are...

2011-01-01

409

Formaldehyde reactions in dark clouds  

NASA Technical Reports Server (NTRS)

The low-pressure reactions of formaldehyde (H2CO) with D(+), D2(+), D3(+), and He(+) are studied by the ion-cyclotron resonance technique. These reactions are potential loss processes for formaldehyde in cores of dark interstellar clouds. The deuterated reactants represent direct analogs for protons. Rate coefficients and branching ratios of product channels have been measured. Charge transfer is observed to be the dominant reaction of H2CO with D(+), D2(+), and He(+) ions. Only the D3(+) reaction exhibits a proton-transfer channel. All reactions proceed at rate coefficients near the collision limit. Proton-deuteron exchange reactions are found to be inefficient processes in the formaldehyde system.

Sen, A. D.; Anicich, V. G.; Federman, S. R.

1992-01-01

410

Radiation reaction in various dimensions  

Microsoft Academic Search

We discuss the radiation reaction problem for an electric charge moving in flat space-time of arbitrary dimensions. It is shown that four is the unique dimension where a local differential equation exists accounting for the radiation reaction and admitting a consistent mass-renormalization (the Dirac-Lorentz equation). In odd dimensions the Huygens principle does not hold; as a result, the radiation reaction

D. V. Gal

411

Radiation reaction in various dimensions  

Microsoft Academic Search

We discuss the radiation reaction problem for an electric charge moving in\\u000aflat space-time of arbitrary dimensions. It is shown that four is the unique\\u000adimension where a local differential equation exists accounting for the\\u000aradiation reaction and admitting a consistent mass-renormalization (the\\u000aDirac-Lorentz equation). In odd dimensions the Huygens principle does not hold;\\u000aas a result, the radiation reaction

Dmitri Gal’tsov

2002-01-01

412

Drug Hypersensitivity Reactions Involving Skin  

Microsoft Academic Search

Immune reactions to drugs can cause a variety of diseases involving the skin, liver, kidney, lungs, and other organs. Beside\\u000a immediate, IgE-mediated reactions of varying degrees (urticaria to anaphylactic shock), many drug hypersensitivity reactions\\u000a appear delayed, namely hours to days after starting drug treatment, showing a variety of clinical manifestations from solely\\u000a skin involvement to fulminant systemic diseases which may

Oliver Hausmann; Benno Schnyder; Werner J. Pichler

413

Nuclear astrophysics from direct reactions  

E-print Network

Accurate nuclear reaction rates are needed for primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are extremely difficult to measure directly in the laboratory at the small astrophysical energies. In recent years direct reactions have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this presentation.

C. A. Bertulani

2009-01-22

414

Change in Temperature: Exothermic Reaction  

NSDL National Science Digital Library

Learners add calcium chloride to a baking soda solution and observe an increase in temperature along with the production of a gas and a white precipitate. These are all signs of a chemical reaction. Learners can quantify the results of the reaction by using a thermometer to measure the temperature change. Learners also design their own experiment to alter the reaction and measure how it affects the change in temperature.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

415

Cues of maternal condition influence offspring selfishness.  

PubMed

The evolution of parent-offspring communication was mostly studied from the perspective of parents responding to begging signals conveying information about offspring condition. Parents should respond to begging because of the differential fitness returns obtained from their investment in offspring that differ in condition. For analogous reasons, offspring should adjust their behavior to cues/signals of parental condition: parents that differ in condition pay differential costs of care and, hence, should provide different amounts of food. In this study, we experimentally tested in the European earwig (Forficula auricularia) if cues of maternal condition affect offspring behavior in terms of sibling cannibalism. We experimentally manipulated female condition by providing them with different amounts of food, kept nymph condition constant, allowed for nymph exposure to chemical maternal cues over extended time, quantified nymph survival (deaths being due to cannibalism) and extracted and analyzed the females' cuticular hydrocarbons (CHC). Nymph survival was significantly affected by chemical cues of maternal condition, and this effect depended on the timing of breeding. Cues of poor maternal condition enhanced nymph survival in early broods, but reduced nymph survival in late broods, and vice versa for cues of good condition. Furthermore, female condition affected the quantitative composition of their CHC profile which in turn predicted nymph survival patterns. Thus, earwig offspring are sensitive to chemical cues of maternal condition and nymphs from early and late broods show opposite reactions to the same chemical cues. Together with former evidence on maternal sensitivities to condition-dependent nymph chemical cues, our study shows context-dependent reciprocal information exchange about condition between earwig mothers and their offspring, potentially mediated by cuticular hydrocarbons. PMID:24498046

Wong, Janine W Y; Lucas, Christophe; Kölliker, Mathias

2014-01-01

416

Nuclear Reactions & Scaling Arguments 11 October 2011  

E-print Network

Nuclear Reactions & Scaling Arguments 11 October 2011 Goals · Review nuclear reaction rates · Practice using scaling arguments Nuclear Reactions 1. Consider the simple reaction A k1 ---- B k2 ---- C = 3. #12;nuclear reactions & scaling arguments 2 3. Frequently, we approximate nuclear reaction rates

Militzer, Burkhard

417

From nuclear multifragmentation reactions to supernova explosions  

E-print Network

In this talk I discuss properties of hot stellar matter at sub-nuclear densities which is formed in supernova explosions. I emphasize that thermodynamic conditions there are rather similar to those created in the laboratory by intermediate-energy heavy-ion collisions. Theoretical methods developed for the description of multi-fragment final states in such reactions can be used also for description of the stellar matter. I present main steps of the statistical approach to the equation of state and nuclear composition, dealing with an ensemble of nuclear species instead of one "average" nucleus.

Igor N. Mishustin

2008-03-10

418

Carbon tetrachloride under extreme conditions  

NASA Astrophysics Data System (ADS)

We report on three experiments on carbon tetrachloride subjected to extreme conditions. In the first experiment, Raman spectra of CCl4 were acquired up to 28 GPa. Evidence was observed for at least two new phases of CCl4 above 14 GPa (phase VI) and above 22 GPa (phase VII). Decompression of the sample showed no evidence of pressure-induced decomposition. In the second experiment, a synchrotron x-ray diffraction study was performed up to 30 GPa verifying phase V and potential phases above 14 (VI) and 22 GPa (VII), respectively. In the third study, we examined irradiated CCl4 using synchrotron infrared spectroscopy to reduce fluorescent contamination. Some sort of carbon allotrope appears as a byproduct suggesting the following reaction with hard x-rays: CCl4+ h? ? C + 2Cl2.

Pravica, Michael; Sneed, Daniel; Wang, Yonggang; Smith, Quinlan; Subrahmanyam, Garimella

2014-05-01

419

Carbon tetrachloride under extreme conditions  

SciTech Connect

We report on three experiments on carbon tetrachloride subjected to extreme conditions. In the first experiment, Raman spectra of CCl{sub 4} were acquired up to 28 GPa. Evidence was observed for at least two new phases of CCl{sub 4} above 14 GPa (phase VI) and above 22 GPa (phase VII). Decompression of the sample showed no evidence of pressure-induced decomposition. In the second experiment, a synchrotron x-ray diffraction study was performed up to 30 GPa verifying phase V and potential phases above 14 (VI) and 22 GPa (VII), respectively. In the third study, we examined irradiated CCl{sub 4} using synchrotron infrared spectroscopy to reduce fluorescent contamination. Some sort of carbon allotrope appears as a byproduct suggesting the following reaction with hard x-rays: CCl{sub 4}+ h? ? C + 2Cl{sub 2}.

Pravica, Michael, E-mail: pravica@physics.unlv.edu; Sneed, Daniel; Wang, Yonggang; Smith, Quinlan [High Pressure Science and Engineering Center (HiPSEC) and Department of Physics, University of Nevada Las Vegas (UNLV), Las Vegas, Nevada 89154-4002 (United States)] [High Pressure Science and Engineering Center (HiPSEC) and Department of Physics, University of Nevada Las Vegas (UNLV), Las Vegas, Nevada 89154-4002 (United States); Subrahmanyam, Garimella [Canadian Light Source, Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 2V3 (Canada)] [Canadian Light Source, Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 2V3 (Canada)

2014-05-21

420

Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions  

ERIC Educational Resources Information Center

A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…

Schultz, Emeric

2008-01-01

421

ANALYSIS OF THERMAL DECOMPOSITION PRODUCTS OF FLUE GAS CONDITIONING AGENTS  

EPA Science Inventory

The report gives results of a study of reactions of several flue gas conditioning agents in a laboratory-scale facility simulating conditions in the flue gas train of a coal-burning power plant. Primary purposes of the study were to characterize the chemical species resulting fro...

422

14 CFR 29.485 - Lateral drift landing conditions.  

Code of Federal Regulations, 2010 CFR

... § 29.485 Lateral drift landing conditions. (a) The rotorcraft...is assumed to be in the level landing attitude, with— (1...reactions obtained in the level landing conditions of § 29.479...ii) For full-swiveling gear, at the center of the...

2010-01-01

423

14 CFR 23.483 - One-wheel landing conditions.  

Code of Federal Regulations, 2011 CFR

... Ground Loads § 23.483 One-wheel landing conditions. For the one-wheel landing condition, the airplane is assumed to be...contact the ground on one side of the main landing gear. In this attitude, the ground reactions...

2011-01-01

424

14 CFR 27.485 - Lateral drift landing conditions.  

Code of Federal Regulations, 2010 CFR

... § 27.485 Lateral drift landing conditions. (a) The rotorcraft...is assumed to be in the level landing attitude, with— (1...reactions obtained in the level landing conditions of § 27.479...ii) For full-swiveling gear, at the center of the...

2010-01-01

425

14 CFR 23.483 - One-wheel landing conditions.  

Code of Federal Regulations, 2010 CFR

... Ground Loads § 23.483 One-wheel landing conditions. For the one-wheel landing condition, the airplane is assumed to be...contact the ground on one side of the main landing gear. In this attitude, the ground reactions...

2010-01-01

426

14 CFR 29.485 - Lateral drift landing conditions.  

Code of Federal Regulations, 2011 CFR

... § 29.485 Lateral drift landing conditions. (a) The rotorcraft...is assumed to be in the level landing attitude, with— (1...reactions obtained in the level landing conditions of § 29.479...ii) For full-swiveling gear, at the center of the...

2011-01-01

427

14 CFR 27.485 - Lateral drift landing conditions.  

Code of Federal Regulations, 2011 CFR

... § 27.485 Lateral drift landing conditions. (a) The rotorcraft...is assumed to be in the level landing attitude, with— (1...reactions obtained in the level landing conditions of § 27.479...ii) For full-swiveling gear, at the center of the...

2011-01-01

428

Counterbalancing for Serial Order Carryover Effects in Experimental Condition Orders  

ERIC Educational Resources Information Center

Reactions of neural, psychological, and social systems are rarely, if ever, independent of previous inputs and states. The potential for serial order carryover effects from one condition to the next in a sequence of experimental trials makes counterbalancing of condition order an essential part of experimental design. Here, a method is proposed…

Brooks, Joseph L.

2012-01-01

429

Activity : Fusion Reactions  

NSDL National Science Digital Library

This activity gives students an opportunity to learn about the elements created in the cores of high-mass stars by fusion reactions. They will discover that all stars start by burning hydrogen and end up creating many heavier elements inside their cores, elements that will be released into space when it dies in a supernova explosion. Students associate a layer with an element that is being produced by the high-mass star. This will illustrate that as the temperature of the star increases with depth, the ash of each burning stage becomes the fuel for the next stage. Surrounding the core of iron nuclei is a layer of silicon fusion, then magnesium, then neon, then oxygen, then carbon, then helium, and lastly, in the relatively cool periphery of the core, hydrogen fuses into helium. Students will draw their own version of the onion-like nature of the core of a star based on the model and explain the process that occurs at each layer.

2007-12-12

430

Two chamber reaction furnace  

DOEpatents

A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

Blaugher, R.D.

1998-05-05

431

Depolymerization of sulfated polysaccharides under hydrothermal conditions.  

PubMed

Fucoidan and chondroitin sulfate, which are well known sulfated polysaccharides, were depolymerized under hydrothermal conditions (120-180°C, 5-60min) as a method for the preparation of sulfated polysaccharides with controlled molecular weights. Fucoidan was easily depolymerized, and the change of the molecular weight values depended on the reaction temperature and time. The degree of sulfation and IR spectra of the depolymerized fucoidan did not change compared with those of untreated fucoidan at reaction temperatures below 140°C. However, fucoidan was partially degraded during depolymerization above 160°C. Nearly the same depolymerization was observed for chondroitin sulfate. These results indicate that hydrothermal treatment is applicable for the depolymerization of sulfated polysaccharides, and that low molecular weight products without desulfation and deformation of the initial glycan structures can be obtained under mild hydrothermal conditions. PMID:24361592

Morimoto, Minoru; Takatori, Masaki; Hayashi, Tetsuya; Mori, Daiki; Takashima, Osamu; Yoshida, Shinichi; Sato, Kimihiko; Kawamoto, Hitoshi; Tamura, Jun-ichi; Izawa, Hironori; Ifuku, Shinsuke; Saimoto, Hiroyuki

2014-01-30

432

Heterogeneous reactions of volatile organic compounds in the atmosphere  

NASA Astrophysics Data System (ADS)

Volatile organic compounds (VOCs) are of central importance in the atmosphere because of their close relation to air quality and climate change. As a significant sink for VOCs, the fate of VOCs via heterogeneous reactions may explain the big gap between field and model studies. These reactions play as yet unclear but potentially crucial role in atmospheric processes. In order to better evaluate this reaction pathway, we present the first specific review for the progress of heterogeneous reaction studies on VOCs, including carbonyl compounds, organic acids, alcohols, and so on. Our review focuses on the processes for heterogeneous reactions of VOCs under varying experimental conditions, as well as their implications for trace gas and HOx budget, secondary organic aerosol (SOA) formation, physicochemical properties of aerosols, and human health. Finally, we propose the future direction for laboratory studies of heterogeneous chemistry of VOCs that should be carried out under more atmospherically relevant conditions, with a special emphasis on the effects of relative humidity and illumination, the multicomponent reaction systems, and reactivity of aged and authentic particles. In particular, more reliable uptake coefficients, based on the abundant elaborate laboratory studies, appropriate calibration, and logical choice criterion, are urgently required in atmospheric models.

Shen, Xiaoli; Zhao, Yue; Chen, Zhongming; Huang, Dao

2013-04-01

433

Chemical Characterization and Reactivity of Fuel-Oxidizer Reaction Product  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

434

Transition metal catalyzed carbon-silicon bond forming reactions using chlorosilanes promoted by Grignard reagents.  

PubMed

New catalytic C--Si bond-forming reactions using chlorosilanes are described. These reactions proceed efficiently under mild conditions by the combined use of Grignard reagents and transition metal catalysts, such as Ti, Zr, Ni, and Pd. It is proposed that ate complex intermediates formed by the reaction of transition metals with Grignard reagents play important roles as the active catalytic species. The present study demonstrates the practical use of chlorosilanes in transition metal catalyzed silylation reactions providing convenient methods for allyl- or vinylsilane synthesis. The reaction pathways of these transformations as well as the scope and limitations are discussed. PMID:17318829

Terao, Jun; Kambe, Nobuaki

2007-01-01

435

Inflation of Conditional Predictions  

ERIC Educational Resources Information Center

The authors report 7 experiments indicating that conditional predictions--the assessed probability that a certain outcome will occur given a certain condition--tend to be markedly inflated. The results suggest that this inflation derives in part from backward activation in which the target outcome highlights aspects of the condition that are…

Koriat, Asher; Fiedler, Klaus; Bjork, Robert A.

2006-01-01

436

Radiation reaction in various dimensions  

Microsoft Academic Search

We discuss the radiation reaction problem for an electric charge moving in flat space-time of arbitrary dimensions. It is shown that four is the unique dimension where a local differential equation exists accounting for the radiation reaction and admitting a consistent mass renormalization (the Lorentz-Dirac equation). In odd dimensions Huygens's principle does not hold, and, as a result, the radiation

Dmitri V. Gal'Tsov

2002-01-01

437

Participants' Reactions to Assessment Centers.  

ERIC Educational Resources Information Center

A study of 37 people who have gone through a one-day assessment center measures the reactions of participants (equally divided into high and low scorers) to their experiences, and compares the reactions of high scorers with those of low scorers. Recommendations are made for the use of assessment centers. (MLF)

Teel, Kenneth S.; DuBois, Henry

1983-01-01

438

Reaction/Aggregation Clment Sire  

E-print Network

and chemistry Atoms diffusing on a surface and Diffusion Limited Aggregation Atomic clusters Chemical or even d· 4 for diffusion processes) Out of equilibrium reaction/aggregation processes can leadReaction/Aggregation Processes Clément Sire Laboratoire de Physique Théorique CNRS & Université

Giraud, Olivier

439

Pharmacogenomics of adverse drug reactions  

PubMed Central

Considerable progress has been made in identifying genetic risk factors for idiosyncratic adverse drug reactions in the past 30 years. These reactions can affect various tissues and organs, including liver, skin, muscle and heart, in a drug-dependent manner. Using both candidate gene and genome-wide association studies, various genes that make contributions of varying extents to each of these forms of reactions have been identified. Many of the associations identified for reactions affecting the liver and skin involve human leukocyte antigen (HLA) genes and for reactions relating to the drugs abacavir and carbamazepine, HLA genotyping is now in routine use prior to drug prescription. Other HLA associations are not sufficiently specific for translation but are still of interest in relation to underlying mechanisms for the reactions. Progress on non-HLA genes affecting adverse drug reactions has been less, but some important associations, such as those of SLCO1B1 and statin myopathy, KCNE1 and drug-induced QT prolongation and NAT2 and isoniazid-induced liver injury, are considered. Future prospects for identification of additional genetic risk factors for the various adverse drug reactions are discussed. PMID:23360680

2013-01-01

440

Cutaneous Manifestation Of Drug Reactions  

PubMed Central

Every drug is capable of inducing an adverse reaction in susceptible individuals, and physicians should always be on the alert for this when they prescribe a drug, or when they see unusual skin rashes. This article lists some of the more commonly seen reactions, together with the drugs which induce them. ImagesFig. 1Fig. 2Fig. 3Fig. 4 PMID:20468978

Schachter, R. K.

1973-01-01

441

Foreperiod and simple reaction time  

Microsoft Academic Search

Reviews studies of simple visual and auditory reaction processes published since W. H. Teicher (1954), with emphasis on the preparatory phase of these processes, particularly the foreperiod (FP). The 1st section consists of the analysis of actual FP variables; duration, regularity, range, distribution, and preceding FPs. The 2nd section deals with factors affecting the relation between FP and reaction time

Pekka Niemi; Risto Näätänen

1981-01-01

442

Foreign body reaction to biomaterials  

Microsoft Academic Search

The foreign body reaction composed of macrophages and foreign body giant cells is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device, prosthesis, or biomaterial. A brief, focused overview of events leading to the foreign body reaction is presented. The major focus of this review is on factors that modulate the interaction of

James M. Anderson; Analiz Rodriguez; David T. Chang

2008-01-01

443

Free Radical Reactions in Food.  

ERIC Educational Resources Information Center

Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

Taub, Irwin A.

1984-01-01

444

Acute dystonic reaction with rivastigmine.  

PubMed

Dystonic reactions are adverse extrapyramidal side effects and are common to antipsychotics, antiemetics, and a variety of other drugs. Rivastigmine, an anticholinesterase of carbamate variety, is well tolerated. A case of acute dystonic reaction with rivastigmine patch is being reported. PMID:23561545

Dhikav, Vikas; Anand, Kuljeet Singh

2013-08-01

445

Chemistry of heavy ion reactions  

SciTech Connect

The use of heavy ions to induce nuclear reactions was reported as early as 1950. Since that time it has been one of the most active areas of nuclear research. Intense beams of ions as heavy as uranium with energies high enough to overcome the Coulomb barriers of even the heaviest elements are available. The wide variety of possible reactions gives rise to a multitude of products which have been studied by many ingenious chemical and physical techniques. Chemical techniques have been of special value for the separation and unequivocal identification of low yield species from the plethora of other nuclides present. Heavy ion reactions have been essential for the production of the trans-Md elements and a host of new isotopes. The systematics of compound nucleus reactions, transfer reactions, and deeply inelastic reactions have been elucidated using chemical techniques. A review of the variety of chemical procedures and techniques which have been developed for the study of heavy ion reactions and their products is given. Determination of the chemical properties of the trans-Md elements, which are very short-lived and can only be produced an ''atom-at-a-time'' via heavy ion reactions, is discussed. 53 refs., 19 figs.

Hoffman, D.C.

1988-10-01

446

Adverse Reactions to Hallucinogenic Drugs.  

ERIC Educational Resources Information Center

This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…

Meyer, Roger E. , Ed.

447

Intercalation-induced reactions of iron oxychloride  

SciTech Connect

The preparation and structure of the layered complex formed by the intercalation reaction of FeOCl with propargylamine are reported. The solid isolated from this reaction is a crystalline material with a magnetic susceptibility at room temperature of 0.9 x 10{sup {minus}2} emu g{sup {minus}1} and {mu}{sub eff} 18 BM. Reaction of this complex by heating under argon by exposure to moist air, or by washing with water results in new materials with larger susceptibilities, 1.8 x 10{sup {minus}2} emu g{sup {minus}1}, and {mu}{sub eff} 72 BM, but with a more disordered structure as determined by X-ray powder diffraction and scanning electron microscopy. The preparation of the butylamine intercalate of FeOCl under identical conditions gave only the literature-reported product. The formation of a fine-particle green rust (I) and not the hydrolysis product {gamma}-FeOOH from the propargylamine complex of FeOCl is suggested based upon magnetic susceptibility. Moessbauer spectroscopy. FTIR, and X-ray powder diffraction evidence. A model to account for the difference in the reactivity and properties of the butylamine and propargylamine complexes of FeOCl is proposed.

Pillion, J.E. [Princeton Univ., NJ (United States)] [Princeton Univ., NJ (United States); Gafney, H.D.; Rafailovich, M.H. [Univ. of New York, Flushing, NY (United States)] [and others] [Univ. of New York, Flushing, NY (United States); and others

1994-12-01

448

Heterogeneous photocatalytic reactions of sulfur aromatic compounds.  

PubMed

Sulfur aromatic compounds, such as mono-, di-, tri-, and tetraalkyl-substituted thiophene, benzothiophenes, dibenzothiophenes, are the molecular components of many fossils (petroleum, oil shale, tar sands, bitumen). Structural units of natural, cross-linked heteroaromatic polymers present in brown coals, turf, and soil are similar to those of sulfur aromatic compounds. Many sulfur aromatic compounds are found in the streams of petroleum refining and upgrading (naphthas, gas oils) and in the consumer products (gasoline, diesel, jet fuels, heating fuels). Besides fossils, the structural fragments of sulfur aromatic compounds are present in molecules of certain organic semiconductors, pesticides, small molecule drugs, and in certain biomolecules present in human body (pheomelanin pigments). Photocatalysis is the frontier area of physical chemistry that studies chemical reactions initiated by absorption of photons by photocatalysts, that is, upon electronic rather than thermal activation, under "green" ambient conditions. This review provides systematization and critical review of the fundamental chemical and physicochemical information on heterogeneous photocatalysis of sulfur aromatic compounds accumulated in the last 20-30 years. Specifically, the following topics are covered: physicochemical properties of sulfur aromatic compounds, major classes of heterogeneous photocatalysts, mechanisms and reactive intermediates of photocatalytic reactions of sulfur aromatic compounds, and the selectivity of these reactions. Quantum chemical calculations of properties and structures of sulfur aromatic compounds, their reactive intermediates, and the structure of adsorption complexes formed on the surface of the photocatalysts are also discussed. PMID:21809426

Samokhvalov, Alexander

2011-11-18

449

Sodium concrete reaction: structural considerations  

SciTech Connect

An overview of the sodium concrete reaction phenomenon, with emphasis on structural considerations, is presented. Available test results for limestone, basalt, and magnetite concrete with various test article configurations are reviewed. Generally, tests indicate reaction is self limiting before all sodium is used. Uncertainties, however, concerning the mechanism for penetration of sodium into concrete have resulted in different theories about a reaction model. Structural behavior may be significant in the progression of the reaction due to thermal-structural-chemical interactions involving tensile cracking, compressive crushing, or general deterioration of concrete and the exposure of fresh concrete surfaces to react with sodium. Structural behavior of test articles and potential factors that could enhance the progression of the reaction are discussed.

Freskakis, G.N.

1984-09-01

450

Endothermic photo-catalytic reactions  

SciTech Connect

The overall objective of this report is to present the results of an investigation to provide guidelines for future experimental work, on solar energy driven endothermic photo-catalytic reactions, and primarily to select candidate synthesis reactions which lead to high $-value products. An intensive literature search was conducted to find properties, market demand, and prices of pertinent chemicals; meeting four criteria: (1) the reaction must be endothermic and favorable; (2) the reaction must be catalytic; (3) the product must be produced from low cost feedstocks; and (4) the product must have a sales price >$1.00/lb. Initial examination of low cost feedstocks to high value products lead to consideration of n-paraffins to aromatics and substituted aromatics. Fifteen candidate endothermic synthesis reactions, meeting the above criteria, are suggested. The ratio of product price by reactant cost indicates {approximately}5--8 for the best possibilities; all can be visualized as starting with low cost paraffin and methanol feedstocks.

Prengle, H.W. Jr.; Wentworth, W.E.; Polonczyk, K.C.; Saghafi, M.; Wilking, J.A.; Kramer, K.S. (Houston Univ., TX (United States))

1992-04-01

451

[Skin reactions to tattoo ink].  

PubMed

Ritual and artistic tattoos rely on the use of numerous pigments which are not all entirely inert once placed in the dermis. The compositions of some tattoo inks are identified. However, new but less well identified compounds appear on the market. Allergic reactions can be present under different aspects. They may correspond to allergic contact dermatitis or to photodermatitis. Other reactions include allergic hypersensitivity reactions as well as lichenoid, granulomatous or pseudolymphoma reactions. Pulsed light and laser are typically used for regular tattoo removal. These procedures are not indicated in inflamed tattoos. Indeed, the pigment dispersed during photolysis may perpetuate the reaction. Pseudotattoos due to the stratum corneum staining are frequently responsible for photoeczema. PMID:21942077

Piérard-Franchimont, C; Hermanns, J-F; Piérard, G E

2011-01-01

452

Macroscopic description of a subdiffusion-controlled bimolecular reaction  

SciTech Connect

The random trap model is used to derive equations describing reaction-subdiffusion systems with diffusion-controlled (infinitely fast) bimolecular reaction. A hierarchy of equations in terms of distribution functions is closed by using a quasi-equilibrium condition in the equation for the two-particle distribution function. The reaction terms in the resulting equations contain products between concentrations and diffusion jump rates, rather than products of concentrations as dictated by the law of mass action. The same equations are also derived in the framework of a nonlinear continuous-time random walk model. The equations are used to show that inhomogeneity of the medium may manifest itself by fractional-order reaction terms.

Shkilev, V. P., E-mail: shkilevv@ukr.ne [National Academy of Sciences, Institute of Surface Chemistry (Ukraine)

2009-11-15

453

Reaction of silver nanoparticles in the disinfection process.  

PubMed

This study investigated the dissolution, aggregation, and reaction kinetics of silver nanoparticles (AgNPs) with the three types of water disinfectants (ultraviolet, sodium hypochlorite, and ozone) under the different conditions of pH, ionic strength, or humic acid (HA). The physicochemical changes of AgNPs were measured by using UV-Vis spectroscopy, transmission electron microscopy, and inductively coupled plasma optical emission spectrometer. The results showed that when AgNPs contacted the disinfectants, oxidative dissolution was the primary reaction. In addition, the reaction kinetics studies revealed that the reaction rate of AgNPs with disinfectants was significantly influenced by different disinfectants along with different pH and the presence of sodium nitrate and HA. Our research demonstrated the potential effect of disinfectants on AgNPs, which will improve our understanding of the fate of AgNPs in the disinfection processes in the water and wastewater treatment plant. PMID:23830116

Yuan, Zhihua; Chen, Yunbin; Li, Tingting; Yu, Chang-Ping

2013-10-01

454

REACTIONS OF RABBITS TO NON-HEMOLYTIC STREPTOCOCCI  

PubMed Central

1. Accompanying and following the evolution of a secondary reaction in the skin of rabbits after inoculation with suitable doses of certain non-hemolytic streptococci there quickly develops a general state of hypersensitiveness or allergy towards these streptococci. 2. This state is made evident by ophthalmic reactions following corneal inoculations, by much increased reactivity of the skin following intracutaneous reinoculations, and by lethal reactions, resembling tuberculin shock, following intravenous inoculations. 3. In a given hypersensitive rabbit there is a rough parallelism in the intensities of these different kinds of reactions. 4. This type of hypersensitiveness or bacterial allergy does not follow primary intravenous inoculation of rabbits with comparable doses of the streptococci employed. 5. As the development of this type of hypersensitiveness or bacterial allergy seems to accompany the production of focal lesions of a certain intensity, it is probable that in these foci are produced the substances or conditions which lead to this type of bacterial allergy. PMID:19869568

Derick, C. L.; Swift, Homer F.

1929-01-01

455

Investigating Ionic Effects Applied to Water Based Organocatalysed Aldol Reactions  

PubMed Central

Saturated aqueous solutions of various common salts were examined for their effect on aqueous aldol reactions catalysted by a highly active C2-symmetric diprolinamide organocatalyst developed in our laboratory. With respect to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, deionised water was always a superior medium to salt solutions though some correlation to increasing anion size and depression in enantiomeric excess could be observed. Additionally, the complete inhibition of catalyst activity observed when employing tap water could be alleviated by the inclusion of ethylenediaminetetraacetate (EDTA) into the aqueous media prior to reaction initiation. Extension of these reaction conditions demonstrated that these ionic effects vary on a case-to-case basis depending on the ketone/aldehyde combination. PMID:22272120

Delaney, Joshua P.; Henderson, Luke C.

2011-01-01

456

Investigating ionic effects applied to water based organocatalysed aldol reactions.  

PubMed

Saturated aqueous solutions of various common salts were examined for their effect on aqueous aldol reactions catalysted by a highly active C(2)-symmetric diprolinamide organocatalyst developed in our laboratory. With respect to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, deionised water was always a superior medium to salt solutions though some correlation to increasing anion size and depression in enantiomeric excess could be observed. Additionally, the complete inhibition of catalyst activity observed when employing tap water could be alleviated by the inclusion of ethylenediaminetetraacetate (EDTA) into the aqueous media prior to reaction initiation. Extension of these reaction conditions demonstrated that these ionic effects vary on a case-to-case basis depending on the ketone/aldehyde combination. PMID:22272120

Delaney, Joshua P; Henderson, Luke C

2011-01-01

457

Stereochemical study of a transannular Michael reaction cascade.  

PubMed

We systematically explored a transannular Michael reaction cascade for stereoselective synthesis of polycyclic systems. Both E,Z- and E,E-1,7-bis-enones in the form of 14-membered macrocyclic lactones underwent transannular cyclization to give polycyclic products with high efficiency and excellent diastereoselectivity. In contrast, Z,E- and Z,Z-macrocyclic lactones did not cyclize under similar reaction conditions. Our study revealed similarities and subtle stereochemical differences between this transannular cyclization process and transannular Diels-Alder reactions. An acyl ketene approach was developed for efficient synthesis of macrocyclic lactones. This investigation also illuminated the scope and limitation of macrocyclization by intramolecular Reformatsky reaction to prepare macrocyclic lactones. PMID:22984784

Xue, Haoran; Gopal, Peddabuddi; Yang, Jiong

2012-10-19

458

Eikonal reaction theory for two-neutron removal reactions  

NASA Astrophysics Data System (ADS)

The eikonal reaction theory (ERT) proposed lately is a method of calculating one-neutron removal reactions at intermediate incident energies in which Coulomb breakup is treated accurately with the continuum discretized coupled-channels method. ERT is extended to two-neutron removal reactions. ERT reproduces measured one- and two-neutron removal cross sections for He6 scattering on C12 and Pb208 targets at 240 MeV/nucleon and also on a Si28 target at 52 MeV/nucleon. For the heavier target in which Coulomb breakup is important, ERT yields much better agreement with the measured cross sections than the Glauber model.

Minomo, K.; Matsumoto, T.; Egashira, K.; Ogata, K.; Yahiro, M.

2014-08-01

459

A general synthesis of fluoroalkylated alkenes by palladium-catalyzed heck-type reaction of fluoroalkyl bromides.  

PubMed

An efficient palladium-catalyzed Heck-type reaction of fluoroalkyl halides, including perfluoroalkyl bromides, trifluoromethyl iodides, and difluoroalkyl bromides, has been developed. The reaction proceeds under mild reaction conditions with high efficiency and broad substrate scope, and provides a general and straightforward access to fluoroalkylated alkenes which are of interest in life and material sciences. PMID:25469665

Feng, Zhang; Min, Qiao-Qiao; Zhao, Hai-Yang; Gu, Ji-Wei; Zhang, Xingang

2015-01-19

460

Shock-induced reaction synthesis (SRS) of nickel aluminides  

SciTech Connect

Shock-induced chemical reactions between nickel and aluminum powders (mixed in Ni{sub 3}Al stoichiometry) are used for the synthesis of nickel aluminides. It is shown that the extent of shock-induced chemical reactions and the nature of the shock-synthesized products are influenced by the morphology of the starting powders. Irregular (flaky type) and fine morphologies of the powders undergo complete reactions in contrast to partial reactions occurring in coarse and uniform morphology powders under identical shock loading conditions. Furthermore, irregular morphology powders result in the formation of the equiatomic (B2 phase) NiAl compound while the Ni{sub 3}Al (L1{sub 2} phase) compound is the reaction product with coarse and regular morphology powders. Shock-induced reaction synthesis can be characterized as a bulk reaction process involving an intense mechanochemical'' mechanism. It is a process in which shock compression induces fluid-like plastic flow and mixing, and enhances the reactivity due to the introduction of defects and cleansing of particle surfaces, which strongly influence the synthesis process.

Thadhani, N.N.; Work, S. (Center for Explosives Technology Research (CETR), New Mexico Tech, Socorro, New Mexico 87801 (United States)); Graham, R.A.; Hammetter, W.F. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1992-05-01

461

Mechanism of cis-prenyltransferase reaction probed by substrate analogues  

SciTech Connect

Research highlights: {yields} The extremely slow trans-OPPS reaction using 2-Fluoro-FPP supports the sequential mechanism with the carbocation intermediate. {yields} The similar UPPS reaction rate under single turnover supports the concerted mechanism, without the carbocation intermediate. {yields} The secondary kinetic isotope effect also supports associate transition state for UPPS reaction, without the carbocation intermediate. -- Abstract: Undecaprenyl pyrophosphate synthase (UPPS) is a cis-type prenyltransferases which catalyzes condensation reactions of farnesyl diphosphate (FPP) with eight isopentenyl pyrophosphate (IPP) units to generate C{sub 55} product. In this study, we used two analogues of FPP, 2-fluoro-FPP and [1,1-{sup 2}H{sub 2}]FPP, to probe the reaction mechanism of Escherichia coli UPPS. The reaction rate of 2-fluoro-FPP with IPP under single-turnover condition is similar to that of FPP, consistent with the mechanism without forming a farnesyl carbocation intermediate. Moreover, the deuterium secondary KIE of 0.985 {+-} 0.022 measured for UPPS reaction using [1,1-{sup 2}H{sub 2}]FPP supports the associative transition state. Unlike the sequential mechanism used by trans-prenyltransferases, our data demonstrate E. coli UPPS utilizes the concerted mechanism.

Lu, Yen-Pin; Liu, Hon-Ge [Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, ROC (China)] [Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, ROC (China); Teng, Kuo-Hsun [Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, ROC (China)] [Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, ROC (China); Liang, Po-Huang, E-mail: phliang@gate.sinica.edu.tw [Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, ROC (China) [Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, ROC (China); Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, ROC (China)

2010-10-01

462

Photo-induced chemical reaction of trans-resveratrol.  

PubMed

Photo-induced chemical reaction of trans-resveratrol has been studied. UV B, liquid state and sufficient exposure time are essential conditions to the photochemical change of trans-resveratrol. Three principal compounds, cis-resveratrol, 2,4,6-phenanthrenetriol and 2-(4-hydroxyphenyl)-5,6-benzofurandione, were successively generated in the reaction solution of trans-resveratrol (0.25 mM, 100% ethanol) under 100 ?W cm(-2) UV B radiation for 4h. cis-Resveratrol, originated from isomerization of trans-resveratrol, resulted in 2,4,6-phenanthrenetriol through photocyclisation reaction meanwhile loss of 2 H. 2,4,6-Phenanthrenetriol played a role of photosensitizer producing singlet oxygen in the reaction pathway. The singlet oxygen triggered [4+2] cycloaddition reaction of trans-resveratrol, and then resulted in the generation of 2-(4-hydroxyphenyl)-5,6-benzofurandione through photorearrangement and oxidation reaction. The singlet oxygen reaction was closely related to the substrate concentration of trans-resveratrol in solution. PMID:25308653

Zhao, Yue; Shi, Meng; Ye, Jian-Hui; Zheng, Xin-Qiang; Lu, Jian-Liang; Liang, Yue-Rong

2015-03-15

463

Hydrocarbon reactions over transition metals: observation of surface hydrogen  

SciTech Connect

One of the difficulties in establishing the mechanism and kinetic behavior of heterogeneous catalytic reactions has been that, typically, the experimental observables are the concentrations of reactants and products in the gas phase rather than those on the surface where the reaction actually occurs. A new technique is described which permits measurement of the thermodynamic activity of chemisorbed hydrogen under reaction conditions. The method utilizes a solid state electrochemical device to measure the thermodynamic activity of hydrogen at a gas-solid interface. The device is applied to study the sorption kinetics of pure hydrogen including hydrogen spillover and other nonidealities. The kinetics of the platinum catalyzed hydrogenations of ethylene, propylene, and acetylene were investigated over a wide range of temperatures (278-700/sup 0/K) at one atmosphere total pressure. The electrode measurements indicate that during reaction gaseous hydrogen is not in equilibrium with surface hydrogen. Multiple steady states are observed for the ethylene hydrogenation reaction over platinum. Unlike the platinum catalyzed reaction, ethylene hydrogenation over nickel exhibits gas-surface hydrogen equilibrium. The adsorption and dehydrogenation of propane, butane, and cyclohexane were also investigated. At temperatures where no reaction was observed in the gas phase, paraffins adsorb dissociatively. The energetics of the observed processes are discussed in terms of a surface intermediate stabilized by hyperconjugation of the adsorbed molecule.

Mullins, M.E.

1983-01-01

464

Low Temperature Trapping: from Reactions to Spectroscopy  

NASA Astrophysics Data System (ADS)

The kinetics of ion - molecule reactions are investigated in higher-order multipole traps by observation of the temporal evolution of mass selected parent ions in the presence of a neutral reaction partner. Rate coeffients for fast reactions (proceeding at collision rate) and very slow reactions (taking millions of collisions) are determined over a wide range of temperatures. Endothermic or hindered reactions can be promoted by excitation of the ion via absorption of a photon. Scanning the photon energy while detecting the number of product ions establishes an action spectroscopy method which we developed over the last 10-15 years and termed LIR: laser or light induced reactions. The main advantages of LIR are mass selection of the parent ion and low temperature conditions in the trap. Long storage times in combination with a near unity detection efficiency make LIR one of the most sensitive spectroscopy methods. The status quo of LIR will be discussed on selected examples. Recent measurements are concerned with ro-vibrational spectra of CH_2D^+ and CH_5^+ at highest resolution using cw OPO radiation. In the particular case of CH_5^+, the lines in the mid IR have been measured at a nominal temperature of 10 K and a frequency comb has been used for absolute calibration. Line positions can be determined to an accuracy which shall enable us in the future to obtain rotational spectra in a THz-IR double resonance approach. We tested the feasibility of this two photon method recently on H_2D^+. S. Schlemmer, T. Kuhn, E. Lescop, and D. Gerlich, Laser excited N_2^+ in a 22-Pole Trap: Experimental Studies of Rotational Relaxation Processes, Int. J. Mass Spectrometry and Ion Processes, 185-187, 589-602, (1999), S.D. Ivanov, O. Asvany, A. Witt, E. Hugo, G. Mathias, B. Redlich, D. Marx and S. Schlemmer, Quantum-induced symmetry breaking explains infrared spectra of CH_5^+ isotopologues, Nature Chemistry, 2, 298-302 (2010) S. Gaertner, J. Krieg, A. Klemann, O. Asvany and S. Schlemmer, Rotational transitions of CH_2D^+ determined by high-resolution IR spectroscopy, Astron. Astrophys., 516 (2010) L3. O. Asvany, J. Krieg, and S. Schlemmer, Frequency comb assisted mid-infrared spectroscopy of cold molecular ions, Rev.Sci.Instr., 83 (2012), 076102.

Schlemmer, S.; Asvany, O.; Brunken, S.

2013-06-01

465

Photochemical reactions of various model protocell systems  

NASA Technical Reports Server (NTRS)

Models for the emergence of cellular life on the primitive Earth, and for physical environments of that era have been studied that embody these assumptions: (1) pregenetic cellular forms were phase-bounded systems primarily photosynthetic in nature, and (2) the early Earth environment was anoxic (lacking appreciable amounts of free hydrogen). It was found that organic structures can also be formed under anoxic conditions (N2, CO3=, H2O) by protracted longwavelength UV radiation. Apparently these structures form initially as organic layers upon CaCO3 crystalloids. The question remains as to whether the UV photosynthetic ability of such phase bounded structures is a curiosity, or a general property of phase bounded systems which is of direct interest to the emergence of cellular life. The question of the requirement and sailient features of a phase boundary for UV photosynthetic abilities was addressed by searching for similar general physical properties which might be manifest in a variety of other simple protocell-like structures. Since it has been shown that laboratory protocell models can effect the UV photosynthesis of low molecular weight compounds, this reaction is being used as an assay to survey other types of structures for similar UV photosynthetic reactions. Various kinds of structures surveyed are: (1) proteinoids; (2) liposomes; (3) reconstituted cell membrane spheroids; (4) coacervates; and (5) model protocells formed under anoxic conditions.

Folsome, C. E.

1986-01-01

466

REACTION KINETICS OF CA-BASED SORBENTS WITH HC1  

EPA Science Inventory

The kinetics of the reaction between CaO and HCl were investigated under conditions that minimize bulk mass transfer and pore diffusion limitations. Reactivity data from 0.2- to 1-s exposure to 5000 ppm HCl in a fixed bed reactor were analyzed by a shrinking core model of diffusi...

467

REACTION KINETICS OF CA-BASED SORBENTS WITH HC1  

EPA Science Inventory

The paper gives results of an investigation of the kinetics of the reaction between CaO and HC1 under conditions that minimize bulk mass transfer and pore diffusion limitations. eactivity data from 0.2 to 1 s exposure to 5000 ppm HC1 in a fixed-bed reactor were analyzed by a shri...

468

Prediction outcome, SR compatibility, and choice reaction time  

Microsoft Academic Search

Describes an experiment with 40 undergraduates in which intrasequential effects of prediction outcome (po) on choice rt were studied in a 2-alternative reaction task under 2 levels of stimulus-response compatibility. Given a correctly predicted event, choice rt was significantly shorter when the preceding po was correct than when it was incorrect. For incorrectly predicted events in a compatible condition, preceding

Charles P. Whitman; E. Scott Geller

1971-01-01

469

Energy Diagrams for Enzyme-Catalyzed Reactions: Concepts and Misconcepts  

ERIC Educational Resources Information Center

Despite the utility that energy diagrams have as a teaching and learning tool, a survey of their use, in seven popular Biochemistry textbooks, reveals that there is certain confusion around this topic. In our opinion, this confusion arises from the reluctance of authors to consider and indicate the conditions under which the reaction being…

Aledo, J. Carlos; Lobo, Carolina; del Valle, Alicia Esteban

2003-01-01

470

Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics  

E-print Network

Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics Giovanni force in terms of a conditional expectation which can be computed by Blue Moon sampling Introduction Fifteen years ago the Blue Moon ensemble method was introduced to sample rare events that occur

Van Den Eijnden, Eric

471

PROCESS INTENSIFICATION: MICROWAVE INITIATED REACTIONS USING A CONTINUOUS FLOW REACTOR  

EPA Science Inventory

The concept of process intensification has been used to develop a continuous narrow channel reactor at Clarkson capable of carrying out reactions under isothermal conditions whilst being exposed to microwave (MW) irradiation thereby providing information on the true effect of mi...

472

New methods for quantum mechanical reaction dynamics  

SciTech Connect

Quantum mechanical methods are developed to describe the dynamics of bimolecular chemical reactions. We focus on developing approaches for directly calculating the desired quantity of interest. Methods for the calculation of single matrix elements of the scattering matrix (S-matrix) and initial state-selected reaction probabilities are presented. This is accomplished by the use of absorbing boundary conditions (ABC) to obtain a localized (L{sup 2}) representation of the outgoing wave scattering Green`s function. This approach enables the efficient calculation of only a single column of the S-matrix with a proportionate savings in effort over the calculation of the entire S-matrix. Applying this method to the calculation of the initial (or final) state-selected reaction probability, a more averaged quantity, requires even less effort than the state-to-state S-matrix elements. It is shown how the same representation of the Green`s function can be effectively applied to the calculation of negative ion photodetachment intensities. Photodetachment spectroscopy of the anion ABC{sup -} can be a very useful method for obtaining detailed information about the neutral ABC potential energy surface, particularly if the ABC{sup -} geometry is similar to the transition state of the neutral ABC. Total and arrangement-selected photodetachment spectra are calculated for the H{sub 3}O{sup -} system, providing information about the potential energy surface for the OH + H{sub 2} reaction when compared with experimental results. Finally, we present methods for the direct calculation of the thermal rate constant from the flux-position and flux-flux correlation functions. The spirit of transition state theory is invoked by concentrating on the short time dynamics in the area around the transition state that determine reactivity. These methods are made efficient by evaluating the required quantum mechanical trace in the basis of eigenstates of the Boltzmannized flux operator.

Thompson, W.H. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; [Lawrence Berkeley Lab., CA (United States)

1996-12-01

473

Spatial Distributions and Interstellar Reaction Processes  

NASA Astrophysics Data System (ADS)

Methyl formate presents a challenge for the conventional chemical mechanisms assumed to guide interstellar organic chemistry. Previous studies of potential formation pathways for methyl formate in interstellar clouds ruled out gas-phase chemistry as a major production route, and more recent chemical kinetics models indicate that it may form efficiently from radical-radical chemistry on ice surfaces. Yet, recent chemical imaging studies of methyl formate and molecules potentially related to its formation suggest that it may form through previously unexplored gas-phase chemistry. Motivated by these findings, two new gas-phase ion-molecule formation routes are proposed and characterized using electronic structure theory with conformational specificity. The proposed reactions, acid-catalyzed Fisher esterification and methyl cation transfer, both produce the less stable trans-conformational isomer of protonated methyl formate in relatively high abundance under the kinetically controlled conditions relevant to interstellar chemistry. Gas-phase neutral methyl formate can be produced from its protonated counterpart through either a dissociative electron recombination reaction or a proton transfer reaction to a molecule with larger proton affinity. Retention (or partial retention) of the conformation in these neutralization reactions would yield trans-methyl formate in an abundance that exceeds predictions under thermodynamic equilibrium at typical interstellar temperatures of

Neill, Justin L.; Steber, Amanda L.; Muckle, Matt T.; Zaleski, Daniel P.; Lattanzi, Valerio; Spezzano, Silvia; McCarthy, Michael C.; Remijan, Anthony J.; Friedel, Douglas N.; Widicus Weaver, Susanna L.; Pate, Brooks H.

2011-05-01

474