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1

A novel amine-free dianchoring organic dye for efficient dye-sensitized solar cells.  

PubMed

An amine-free oligothiophene-based dye (BTB) featuring a tailor-made dianchoring function, a spiro-configured central unit, and bulky end-capping TIPS groups to diminish intermolecular interactions and to suppress aggregation-induced self-quenching was synthesized to achieve efficient dye-sensitized solar cells with a high power conversion efficiency of 6.52%. PMID:23215150

Ting, Hao-Chun; Tsai, Chih-Hung; Chen, Jia-Hong; Lin, Li-Yen; Chou, Shu-Hua; Wong, Ken-Tsung; Huang, Tsung-Wei; Wu, Chung-Chih

2012-12-21

2

'GREENER' CHEMICAL SYNTHESES USING ALTERNATE REACTION 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-alkylation t...

3

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

4

Latent inhibition of conditioned disgust reactions in rats.  

PubMed

The present experiments, using the latent inhibition (LI) paradigm, evaluated the effect of nonreinforced exposure to saccharin on the acquisition of an LiCl-induced saccharin aversion as measured by conditioned disgust reactions in the taste reactivity test and conditioned taste avoidance in a consumption test. When rats were preexposed to saccharin by bottle exposure (Experiments 1 and 3), LI was evidenced only by conditioned taste avoidance (bottle testing), but not by conditioned disgust reactions (intraoral [IO] testing). On the other hand, when rats were preexposed to saccharin by IO infusion (Experiments 2 and 3), LI was evidenced only by conditioned disgust reactions, but not by conditioned taste avoidance. Experiment 4 showed that LI of conditioned disgust reactions does not appear to be affected by a context shift from preexposure to testing phases. These results show that the expression of LI of both conditioned taste avoidance and conditioned disgust reactions depends critically on a common method of flavor exposure during preexposure and testing. PMID:20400737

López, Matías; Gasalla, Patricia; Vega, Mercedes; Limebeer, Cheryl L; Rock, Erin M; Tuerke, Katharine J; Bedard, Holly; Parker, Linda A

2010-05-01

5

NO/CHAR REACTIONS AT PULVERIZED COAL FLAME CONDITIONS  

EPA Science Inventory

The paper discusses nitrogen oxide (NO)/char reactions at pulverized-coal flame conditions. he effective rate of the NO/char reaction, measured over the temperature range 1250 to 1750 K, was found to be retarded by water vapor and enhanced by carbon monoxide (CO) by amounts that ...

6

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

7

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

8

Reactive boundary conditions for stochastic simulations of reaction diffusion processes  

NASA Astrophysics Data System (ADS)

Many cellular and subcellular biological processes can be described in terms of diffusing and chemically reacting species (e.g. enzymes). Such reaction-diffusion processes can be mathematically modelled using either deterministic partial-differential equations or stochastic simulation algorithms. The latter provide a more detailed and precise picture, and several stochastic simulation algorithms have been proposed in recent years. Such models typically give the same description of the reaction-diffusion processes far from the boundary of the simulated domain, but the behaviour close to a reactive boundary (e.g. a membrane with receptors) is unfortunately model-dependent. In this paper, we study four different approaches to stochastic modelling of reaction-diffusion problems and show the correct choice of the boundary condition for each model. The reactive boundary is treated as partially reflective, which means that some molecules hitting the boundary are adsorbed (e.g. bound to the receptor) and some molecules are reflected. The probability that the molecule is adsorbed rather than reflected depends on the reactivity of the boundary (e.g. on the rate constant of the adsorbing chemical reaction and on the number of available receptors), and on the stochastic model used. This dependence is derived for each model.

Erban, Radek; Chapman, S. Jonathan

2007-03-01

9

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

10

Amine-free approach toward N-toluenesulfonyl amidine construction: a phosphite-mediated Beckmann-like coupling of oximes and p-toluenesulfonyl azide.  

PubMed

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

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

2013-10-25

11

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...

12

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

Microsoft Academic Search

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

2007-01-01

13

Lawrence Berkeley National Laboratory report LBNL-52164 Conditional and Opposed Reaction Path Diagrams  

E-print Network

Lawrence Berkeley National Laboratory report LBNL-52164 Conditional and Opposed Reaction Path address: jfgrcar@lbl.gov keywords: Burke-Schumann flames, fluid-chemistry interactions, reaction path has been computed and to draw conclusions about the underlying reaction mechanisms." This paper

14

Cycloaddition reactions of hydrofullerenes with cyano-substituted alkenes under basic conditions  

E-print Network

Cycloaddition reactions of hydrofullerenes with cyano-substituted alkenes under basic conditions Yu in these reactions. It is proposed that the reactions take place via the Michael addition of C60HĂ? , generated bond of substrate 2, followed by intramolecular proton transfer and nucleophilic addition

Wang, Guan-Wu

15

Reactions of calves to handling depend on housing condition and previous experience with humans  

Microsoft Academic Search

This study investigated the influence of stockperson’s behaviour and housing conditions on calves’ behavioural reactions to people, and behavioural and physiological reactions to handling and short transport. Sixty-four Finnish Ayrshire male calves were used; half of them were housed in individual pens, the other half were housed in group pens of two calves. In both housing conditions half of the

B. J Lensink; S Raussi; X Boivin; M Pyykkönen; I Veissier

2001-01-01

16

Mild conditions for the synthesis of functionalized pyrrolidines via Pd-catalyzed carboamination reactions.  

PubMed

[reaction: see text] The palladium-catalyzed carboamination of N-protected gamma-aminoalkenes with aryl bromides and triflates has been achieved under new, mild reaction conditions using the weak base Cs(2)CO(3) in dioxane solvent. These reactions tolerate a wide variety of functional groups, including enolizable ketones, nitro groups, methyl esters, and acetates, which are not compatible with previously described conditions. PMID:17249786

Bertrand, Myra Beaudoin; Leathen, Matthew L; Wolfe, John P

2007-02-01

17

The Reaction of Ninhydrin with Trimethylbenzenes under Friedel-Crafts Reaction Conditions  

Microsoft Academic Search

The reaction of ninhydrin with 1,2,3- and 1,2,4-trimethylbenzene in the presence of H2SO4 or AlCl3 afforded 2-monoaryl and 2,2-diaryl-1,3-indanedione derivatives as the major products. With 1,3,5-trimethylbenzene as the arene nucleophile, either a reduction product or an indenoindanone derivative was obtained depending upon the catalyst employed in the reaction.

Hyun Nam Song; Hong Jung Lee; Mi Ra Seong; Keum Shin Jung; Jae Nyoung Kim

2000-01-01

18

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

19

Ionic liquids catalyzed Biginelli reaction under solvent-free conditions  

Microsoft Academic Search

3,4-Dihydropyrimidin-2(1H)-ones were synthesised in high yields by one-pot three-component Biginelli condensation in the presence of room temperature ionic liquids such as 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) or hexafluorophosphorate (BMImPF6) as catalysts under solvent-free and neutral conditions.

Jiajian Peng; Youquan Deng

2001-01-01

20

Reactions to Ostracism in Adolescents with Autism Spectrum Conditions  

ERIC Educational Resources Information Center

Little is known about how adolescents with autism spectrum conditions (ASC) experience the initial impact of ostracism. This study investigated whether a mild, short-term episode of experimentally induced ostracism (Cyberball) would affect self-reported anxiety, mood, and the extent to which four social needs (self-esteem, belonging, control and…

Sebastian, Catherine; Blakemore, Sarah-Jayne; Charman, Tony

2009-01-01

21

Reactions to Ostracism in Adolescents with Autism Spectrum Conditions  

Microsoft Academic Search

Little is known about how adolescents with autism spectrum conditions (ASC) experience the initial impact of ostracism. This\\u000a study investigated whether a mild, short-term episode of experimentally induced ostracism (Cyberball) would affect self-reported\\u000a anxiety, mood, and the extent to which four social needs (self-esteem, belonging, control and meaningful existence) were threatened\\u000a in adolescents with ASC and matched controls. Anxiety and

Catherine Sebastian; Sarah-Jayne Blakemore; Tony Charman

2009-01-01

22

Characteristics of uranium carbonitride microparticles synthesized using different reaction conditions  

SciTech Connect

Three sets of different experimental conditions by changing the cover gases during the sample preparation were tested to synthesize uranium carbonitride (UC1-xNx) microparticles. In the first two sets of experiments using (N2 to N2-4%H2 to Ar) and (Ar to N2 to Ar) environments, single phase UC1-xNx was synthesized. When reducing environments (Ar-4%H2 to N2-4%H2 to Ar-4%H2) were utilized, theoretical densities up to 97% of single phase UC1-xNx kernels were obtained. Physical and chemical characteristics such as density, phase purity, and chemical compositions of the synthesized UC1-xNx materials for the diferent experimental conditions used are provided. 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 [ORNL; Lindemer, Terrence [Harbach Engineering and Solutions; Voit, Stewart L [ORNL; Hunt, Rodney Dale [ORNL; Besmann, Theodore M [ORNL; Terrani, Kurt A [ORNL; Snead, Lance Lewis [ORNL

2014-01-01

23

Kinetics of OH + CO reaction under atmospheric conditions  

NASA Technical Reports Server (NTRS)

A pulsed laser photolysis-pulsed laser-induced fluorescence technique is used to directly measure the temperature, pressure, and H2O concentration dependence on k1 in air. K1 is found to increase linearly with increasing pressure at pressures of not greater than 1 atm, and the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. The rate constant in the low-pressure limit and the slope of the k1 versus pressure dependence are shown to be the same at 262 K as at 299 K. The present results significantly reduce the current atmospheric model uncertainties in the temperature dependence under atmospheric conditions, in the third body efficiency of O2, and in the effect of water vapor on k1.

Hynes, A. J.; Wine, P. H.; Ravishankara, A. R.

1986-01-01

24

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

25

Reactions to ostracism in adolescents with autism spectrum conditions.  

PubMed

Little is known about how adolescents with autism spectrum conditions (ASC) experience the initial impact of ostracism. This study investigated whether a mild, short-term episode of experimentally induced ostracism (Cyberball) would affect self-reported anxiety, mood, and the extent to which four social needs (self-esteem, belonging, control and meaningful existence) were threatened in adolescents with ASC and matched controls. Anxiety and the four needs were negatively affected by ostracism in both groups. However, ostracism did not modulate mood in the ASC group, and a number of possible interpretations of this group difference are discussed. In general, the results of this study suggest that normative models of ostracism are applicable to ASC. PMID:19330434

Sebastian, Catherine; Blakemore, Sarah-Jayne; Charman, Tony

2009-08-01

26

Reaction of germanium tetrachloride with oxygen under MCVD fiber preform fabrication conditions  

Microsoft Academic Search

The GeO2 yield in the reaction between GeCl4 and oxygen has been determined as a function of the reaction time under typical MCVD fiber preform fabrication conditions.\\u000a It is shown that the yield increases steadily over time and may attain 100%. In the case of the cooxidation of germanium and\\u000a silicon tetrachlorides under the same conditions, there is an optimal

M. M. Bubnov; A. N. Gur’yanov; M. Yu. Salganskii; V. F. Khopin

2007-01-01

27

Automatic Detection Of Vaccine Adverse Reactions By Incorporating Historical Medical Conditions  

E-print Network

Automatic Detection Of Vaccine Adverse Reactions By Incorporating Historical Medical Conditions This paper extends the state of art by bringing the historical medical conditions into the vaccine adverse with certain vaccines. We propose a novel measure called dual-lift for this task. It is shown that the dual

Karypis, George

28

Effect of thymoptin on passive avoidance reaction conditioning in 18-month-old and castrated rats  

Microsoft Academic Search

The effect of the immunomodulator thymoptin containing thymic peptide hormones on the conditioned passive avoidance reaction\\u000a is studied in aging and postcastration. The preparation, which inhibits atrophy of the thymus, is found to improve conditioning\\u000a in aging rats and has no effect on learning or memory in castrated rats.

Yu. V. Burov; L. E. Davydova; T. N. Robakidze

1995-01-01

29

Tribological reactions of perfluoroalkyl polyether oils with stainless steel under ultrahigh vacuum conditions at room temperature  

NASA Technical Reports Server (NTRS)

The reaction between three types of commercial perfluoroalkyl polyether (PFPE) oils and stainless steel 440C was investigated experimentally during sliding under ultrahigh vacuum conditions at room temperature. It is found that the tribological reaction of PFPE is mainly affected by the activity of the mechanically formed fresh surfaces of metals rather than the heat generated at the sliding contacts. The fluorides formed on the wear track act as a boundary layer, reducing the friction coefficient.

Mori, Shigeyuki; Morales, Wilfredo

1989-01-01

30

Experimental Studies of Hydrogenation and Other Reactions on Surfaces Under Astrophysically Relevant Conditions  

NASA Technical Reports Server (NTRS)

The goal of our project is to study hydrogen recombination reactions on solid surfaces under conditions that are relevant in astrophysics. Laboratory experiments were conducted using low-flux, cold atomic H and D beams impinging on a sample kept under ultra high vacuum conditions. Realistic analogues of interstellar dust grains were used. Our results show that current models for hydrogen recombination reactions have to be modified to take into account the role of activated diffusion of H on surfaces even at low temperature.

Vidali, Gianfranco

1998-01-01

31

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

32

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.

33

Facilitative and suppressive effects of punishment on the reaction time in humans under various conditions  

Microsoft Academic Search

The effects of brief shock as the punishing stimulus during a simple or choice reaction time task (SRT or CRT) and the change in skin resistance during a key-pressing response were investigated under various conditions. A slowing of the SRT and CRT occurred similarly during the shock phase under both the response-contingent and response-independent shock conditions. After the elimination of

Mitsuro Kida

1983-01-01

34

Review and analysis of high temperature chemical reactions and the effect of non-equilibrium conditions  

NASA Technical Reports Server (NTRS)

Chemical reactions at high temperatures have been considered extensively because of their importance to the heating effects on re-entry of space vehicles. Data on these reactions however, are not abundant and even when found there are discrepancies in data collected by various investigators. In particular, data for recombination reactions are calculated from the dissociation reactions or vice versa through the equilibrium constant. This involves the use of the principle of detailed balancing. This principle is discussed in reference to conditions where it is valid as well as to those where it is not valid. Related topics that merit further study or for which applicable information was available are briefly mentioned in an appendix to this report.

Johnson, R. E.

1986-01-01

35

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

36

Aza-Michael reaction of 12-N-carboxamide of (-)-cytisine under high pressure conditions.  

PubMed

The first example of aza-Michael reaction of 12-N-carboxamide of quinolizidine alkaloid (-)-cytisine with ?,?-unsaturated ketones, dimethyl acetylenedicarboxylate and ?-nitrostyrene under high pressure condition has been described. It has been shown that the [4+2]-cycloaddition takes place in the case with N-phenylmaleimide. PMID:25330752

Tsypysheva, Inna P; Lobov, Alexander N; Kovalskaya, Alena V; Petrova, Polina R; Ivanov, Sergey P; Rameev, Shamil A; Borisevich, Sophia S; Safiullin, Rustam L; Yunusov, Marat S

2015-01-01

37

Highly enantioselective Mukaiyama aldol reaction in aqueous conditions using a chiral iron(II) bipyridine catalyst.  

PubMed

A highly enantioselective method for the catalytic Mukaiyama aldol reaction of silyl enol ethers with aldehydes in aqueous conditions was developed. The desired aldol products were obtained in excellent yields, diastereo- and enantioselectivities. Structural evidence of the pre-catalyst revealed an unprecedented heptadentate Fe(II) complex with the chiral bipyridine ligand. PMID:22080154

Ollevier, Thierry; Plancq, Baptiste

2012-02-25

38

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, R˛ 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

39

Enzymatic enantioselective aldol reactions of isatin derivatives with cyclic ketones under solvent-free conditions.  

PubMed

Nuclease p1 from Penicillium citrinum was observed to directly catalyze the asymmetric aldol reactions between isatin derivatives and cyclic ketones with high isolated yields (up to 95%) and moderate to good stereoselectivity (dr up to >99/1, ee up to 82%). A series of reaction conditions were investigated in detail, and the addition of deionized water had a big influence upon the enzyme activity. This case of biocatalytic promiscuity not only widens the applicability of nuclease p1 to new chemical transformation in organic synthesis, but also provides a potentially valuable method to construct pharmaceutically active compounds in medicinal chemistry. PMID:24440638

Liu, Zhi-Qiang; Xiang, Zi-Wei; Shen, Zhou; Wu, Qi; Lin, Xian-Fu

2014-06-01

40

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

41

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

42

Nucleophilic reactions of phorate and terbufos with reduced sulfur species under anoxic conditions.  

PubMed

The reactions of phorate and terbufos with bisulfide (HS-), polysulfide (Sn2-), thiosulfate (S2O32-), and thiophenolate (PhS-) were examined in well-defined aqueous solution under anoxic conditions to investigate their role in the degradations of phorate and terbufos. Reactions were monitored at various concentrations of reduced sulfur species to obtain the second-order rate constants. The reactivity of the reduced sulfur species decreased in the order Sn2- > PhS- > HS- > S2O32-. Hydrolysis products, formaldehyde and diethyl disulfide/di-tert-butyl disulfide, indicated that OH-/H2O attacked the carbon atom between the two sulfur atoms, the so-called thioacetal carbon, which is very reactive due to the presence of the two neighboring sulfur atoms. The reaction of phorate and terbufos with PhS- was investigated to study the transformation products in the reactions with reduced sulfur species. The transformation products demonstrated that the observed increase in rate constants in the reaction with reduced sulfur species compared to hydrolysis could result from the nucleophilic attack of reduced sulfur species at the alpha-carbon of the ethoxy group and at the thioacetal carbon atom. The temperature dependence of measured second-order rate constants of the reaction of phorate and terbufos with HS- over 25-50 degrees C was investigated to explore activation parameters, which are not significantly different for phorate and terbufos. All of the observations may imply similar pathways in the degradation of phorate and terbufos in the presence of reduced sulfur species. Slightly higher hydrolysis rates of terbufos and second-order reaction rate constants for the reactions with sulfur species of terbufos compared with those for phorate are observed, which could be attributed to the slightly different substituents. PMID:17417867

Gan, Qiu; Jans, Urs

2007-05-01

43

Glucuronidation of bile acids under flow conditions: design of experiments and Koenigs-Knorr reaction optimization.  

PubMed

An efficient method for the C3-glucuronidation of bile acids is developed under flow conditions. A modular mesoreactor assisted flow set-up was combined with statistical design of experiments to speed up the optimization of the Koenigs-Knorr reaction in terms of yield, regioselectivity, costs, as well as technical and practical standpoints. Using the optimal conditions, selective glucuronidation of naturally occurring bile acids was successfully achieved offering a new, valuable route to C3-glucuronidated bile acids useful for biological, diagnostic and PK/ADMET investigations. PMID:25338931

Mostarda, Serena; Filipponi, Paolo; Sardella, Roccaldo; Venturoni, Francesco; Natalini, Benedetto; Pellicciari, Roberto; Gioiello, Antimo

2014-12-21

44

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

NASA Astrophysics Data System (ADS)

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

Baggerman, Jacobus Antonius Gijsbertus

1993-10-01

45

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

46

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

47

Reactive boundary conditions for stochastic simulations of reaction-diffusion processes.  

PubMed

Many cellular and subcellular biological processes can be described in terms of diffusing and chemically reacting species (e.g. enzymes). Such reaction-diffusion processes can be mathematically modelled using either deterministic partial-differential equations or stochastic simulation algorithms. The latter provide a more detailed and precise picture, and several stochastic simulation algorithms have been proposed in recent years. Such models typically give the same description of the reaction-diffusion processes far from the boundary of the simulated domain, but the behaviour close to a reactive boundary (e.g. a membrane with receptors) is unfortunately model-dependent. In this paper, we study four different approaches to stochastic modelling of reaction-diffusion problems and show the correct choice of the boundary condition for each model. The reactive boundary is treated as partially reflective, which means that some molecules hitting the boundary are adsorbed (e.g. bound to the receptor) and some molecules are reflected. The probability that the molecule is adsorbed rather than reflected depends on the reactivity of the boundary (e.g. on the rate constant of the adsorbing chemical reaction and on the number of available receptors), and on the stochastic model used. This dependence is derived for each model. PMID:17406082

Erban, Radek; Chapman, S Jonathan

2007-03-01

48

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 (0-2.3g/g starch), acetic anhydride/starch weight ratio (6.5-13.5g/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; Avila Ramírez, Jhon Alejandro; Vázquez, Analía; Foresti, María Laura

2015-03-01

49

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

50

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

51

Reactions of trimethyl (pentafluorophenyl) silane with ketones under nucleophilic-catalysis conditions  

SciTech Connect

The reactions of Me/sub 3/SiC/sub 6/F/sub 5/ with ArCOCH/sub 3/ under nucleophilic-catalysis conditions lead to the corresponding trimethylsilyl derivatives of the enols ArC)OSiMe/sub 3/)=CH/sub 2/. The rate of the reaction is determined by the character of the substituent in the aromatic fragment. The presence of bulky substituents (fluorine atoms) in the 2',6' positions makes the nucleophilic addition of Me/sub 3/SiC/sub 6/F/sub 5/ at the C=O group difficult, and the presence of alkyl substituents in the 2 position of acetophenone makes the nucleophilic replacement of the 2 proton also difficult.

Gostevskii, B.A.; Vyazankin, N.S.; Vyazankina, O.A.

1985-05-01

52

Reaction time in the agility test under simulated competitive and noncompetitive conditions.  

PubMed

The study evaluates a reaction time in the Agility Test under simulated competitive and noncompetitive conditions. A group of 16 fit men performed, in random order, 2 versions of the Agility Test: non-competitive Agility Single and Agility Dual in form of simulated competition. In both cases, subjects had to touch, as fast as possible, with either the left or the right foot 1 of 4 mats located in 4 corners outside of an 80 cm square. Mats had to be touched in accordance with the location of the stimulus in one of the corners of the screen. The test consisted of 20 visual stimuli with random generation of their location on the screen and time generation from 500 to 2,500 milliseconds. The result was total reaction time (RT) for all 20 reactions measured by a PC-based system FiTRO Agility Check. Results showed significantly (p < 0.01) better RT in the Agility Dual than in the Agility Single Test (690.6 ± 83.8 milliseconds and 805.8 ± 101.1 milliseconds, respectively). Further comparisons of RT under noncompetitive and simulated competitive conditions for the best 8 subjects proceeded in the second match showed a decrease from 781.3 ± 111.2 milliseconds to 693.6 ± 97.8 milliseconds in the first match and to 637.0 ± 53.0 milliseconds in the second match. It may be concluded that RT is better when the Agility Test is performed in simulated competitive than noncompetitive conditions. The Agility Test in form of competition may be used for children and young athletes to enhance their attention level and motivation. PMID:23524364

Zemková, Erika; Vilman, Tomáš; Ková?iková, Zuzana; Hamar, Dušan

2013-12-01

53

A Molecular Dynamics Study of Chemical Reactions of Solid Pentaerythritol Tetranitrate at Extreme Conditions  

SciTech Connect

We have carried out density functional based tight binding (DFTB) molecular dynamics (MD) simulation to study energetic reactions of solid Pentaerythritol Tetranitrate (PETN) at conditions approximating the Chapman-Jouguet (CJ) detonation state. We found that the initial decomposition of PETN molecular solid is characterized by uni-molecular dissociation of the NO{sub 2}groups. Interestingly, energy release from this powerful high explosive was found to proceed in several stages. The large portion of early stage energy release was found to be associated with the formation of H{sub 2}O molecules within a few picoseconds of reaction. It took nearly four times as long for majority of CO{sub 2} products to form, accompanied by a slow oscillatory conversion between CO and CO{sub 2}. The production of N{sub 2} starts after NO{sub 2} loses its oxygen atoms to hydrogen or carbon atoms to form H{sub 2}O or CO. We identified many intermediate species that emerge and contribute to reaction kinetics, and compared our simulation with a thermo-chemical equilibrium calculation. In addition, a detailed chemical kinetics of formation of H{sub 2}O, CO, and CO{sub 2} were developed. Rate constants of formations of H{sub 2}O, CO{sub 2} and N{sub 2} were reported.

Wu, C J; Manaa, M R; Fried, L E

2006-05-30

54

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

55

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

56

Reaction Condition Effects on Nickel Sorption Mechanisms in IlliteWater Suspensions E. J. Elzinga* and D. L. Sparks  

E-print Network

Reaction Condition Effects on Nickel Sorption Mechanisms in Illite­Water Suspensions E. J. Elzinga areas. Sorption reactions at 1995; Scheidegger et al., 1998; Scheinost et al., 1999). solid­water by ions other than K, presumably leadingNickel sorption in illite suspensions was studied as a function

Sparks, Donald L.

57

Experimental condition and the acute reaction of mouse skin to ionizing radiation  

SciTech Connect

The acute reactions of skin of the thigh-leg of normal young adult C3Hf/Sed mice following five equal radiation doses (/sup 60/Co) were studied in mice irradiated at various leg skin temperatures and while respiring various gas mixtures in control or anesthetized condition (sodium pentobarbital, 0.05 mg/g-1 body wt.) At 25 and 35 degrees C, anesthesia reduced the RD50 (2.5+ reaction) by 4-5%. An increase of temperature from 25 to 35 degrees C resulted in a decrease in RD50 by 10-12% for subjects respiring air or 5% for subjects respiring O/sub 2/ at 1 or at 3 ATA. The major modifier of radiation response was to change from respiration of air to O/sub 2/ at 1 or 3 ATA. Enhancement ratios for RD50 Air/O/sub 2/ 1 ATA were 1.4-1.5 for 25 and 35 degrees C. The ratios O/sub 2/ 1 ATA/3 ATA were 1-1.05.

Suit, H.D.; Silver, G.; Sedlacek, R.S.; Walker, A.

1983-08-01

58

Experimental condition and the acute reaction of mouse skin to ionizing radiation  

SciTech Connect

The acute reactions of skin of the thigh-leg of normal young adult C3Hf/Sed mice following five equal radiation doses (/sup 60/Co) were studied in mice irradiated at various leg skin temperatures and while respiring various gas mixtures in control or anesthetized condition (sodium pentobarbital, 0.05 mg/g/sup -1/ body wt.) At 25 and 35/sup 0/C, anesthesia reduced the RD/sub 50/ (2.5 + reaction) by 4 to 5%. An increase of temperature from 25 to 35/sup 0/C resulted in a decrease in RD/sub 50/ by 10 to 12% for subjects respiring air or 5% for subjects respiring O/sub 2/ at 1 or at 3 ATA. The major modifier of radiation response was to change from respiration of air to O/sub 2/ at 1 or 3 ATA. Enhancement ratios for RD/sub 50/ Air/O/sub 2/ 1 ATA were 1.4 to 1.5 for 25 and 35/sup 0/C. The ratios O/sub 2/ 1 ATA/3 ATA were 1 to 1.05.

Suit, H.D. (Harvard Medical School, Boston, MA); Silver, G.; Sedlacek, R.S.; Walker, A.

1983-08-01

59

Iodine-catalyzed disproportionation of aryl-substituted ethers under solvent-free reaction conditions.  

PubMed

Iodine was demonstrated to be an efficient catalyst for disproportionation of aryl-substituted ethers under solvent-free reaction conditions. Variously substituted 1,1,1',1'-tetraaryldimethyl ethers were transformed into the corresponding diarylketone and diarylmethane derivatives. I2-catalyzed transformation of 4-methoxyphenyl substituted ethers yielded mono- and dialkylated Friedel-Crafts products as well. Treatment of trityl alkyl and trityl benzyl ethers with a catalytic amount of iodine produced triphenylmethane and the corresponding aldehydes and ketones. The electron-donating substituents facilitated the reaction, while the electron-withdrawing groups retarded it; the difference in reactivity is not very high. Such an observation may be in favour of hydride transfer, predominantly from the less electron rich side of the ether with more stable carbocation formation. With the isotopic studies it was established that a substantial portion of the C-H bond scission took place in the rate-determining step, while the carbonyl oxygen atom originated from the starting ether, and not from the air. The transformation took place under air and under argon, and HI was not a functioning catalyst. PMID:23389585

Jereb, Marjan; Vraži?, Dejan

2013-03-28

60

Total synthesis of Elisabethin A: intramolecular Diels-Alder reaction under biomimetic conditions.  

PubMed

We describe the first total synthesis of the marine diterpenoid elisabethin A. The synthesis uses (S)-hydroxy-2-methyl-propionate as the chiral starting material, which is elaborated into a dienyl-iodide and added to an aryl acetic acid ester via enolate alkylation. The hydroquinoid system is oxidized to the quinone which serves as the dienophile in a highly stereocontrolled intramolecular Diels-Alder addition. This IMDA reaction, which to our knowledge is the first one to employ a terminal (Z)-diene, proceeds under biomimetic conditions (water, ferrichloride as the oxidant, room temperature) with high yield and stereoselectivity. The Diels-Alder adduct is transformed into the natural product via a three-step sequence including selective hydrogenation, base-catalyzed epimerization of the cis- into the trans-decalin system and O-demethylation. PMID:12696865

Heckrodt, Thilo J; Mulzer, Johann

2003-04-23

61

The nature of lithium battery materials under oxygen evolution reaction conditions.  

PubMed

Transition-metal oxide and phosphate materials, commonly used for lithium battery devices, are active as oxygen evolution reaction (OER) catalysts under alkaline and neutral solution conditions. Electrodes composed of LiCoO(2) and LiCoPO(4) exhibit progressive deactivation and activation for OER catalysis, respectively, upon potential cycling at neutral pH. The deactivation of LiCoO(2) and activation of LiCoPO(4) are coincident with changes in surface morphology and composition giving rise to spinel-like and amorphous surface structures, respectively. The amorphous surface structure of the activated LiCoPO(4) is compositionally similar to that obtained from the electrodeposition of cobalt oxide materials from phosphate-buffered electrolyte solutions. These results highlight the importance of a combined structural and electrochemical analysis of the materials surface when assessing the true nature of the OER catalyst. PMID:23033962

Lee, Seung Woo; Carlton, Christopher; Risch, Marcel; Surendranath, Yogesh; Chen, Shuo; Furutsuki, Sho; Yamada, Atsuo; Nocera, Daniel G; Shao-Horn, Yang

2012-10-17

62

Highly diastereoselective and regioselective copper-catalyzed nitrosoformate dearomatization reaction under aerobic-oxidation conditions.  

PubMed

An unprecedented copper-catalyzed acylnitroso dearomatization reaction, which expands the traditional acylnitroso ene reaction and acylnitroso Diels-Alder reaction to a new type of transformation, has been developed under aerobic oxidation. Intermolecular and intra-/intermolecular reaction modes demonstrate an entirely different N- or O-acylnitroso selectivity. Hence, we can utilize this reaction as a highly diastereoselective access to a series of new pyrroloindoline derivatives, which are important structural motifs for natural-product synthesis. PMID:24590772

Yang, Weibo; Huang, Long; Yu, Yang; Pflästerer, Daniel; Rominger, Frank; Hashmi, A Stephen K

2014-04-01

63

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

NASA Astrophysics Data System (ADS)

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

Vajda, Stefan; Lee, Sungsik; Sell, Kristian; Barke, Ingo; Kleibert, Armin; von Oeynhausen, Viola; Meiwes-Broer, Karl-Heinz; Rodríguez, Arantxa Fraile; Elam, Jeffrey W.; Pellin, Michael M.; Lee, Byeongdu; Seifert, Sönke; Winans, Randall E.

2009-09-01

64

Quantum mechanical reaction probabilities via a discrete variable representation-absorbing boundary condition Green's function  

E-print Network

Quantum mechanical reaction probabilities via a discrete variable representation-absorbing boundary subsequent use to determine the cumulative reaction probability for a chemical reaction, has been extended probabilities, derives a DVR for the ex- act, multidimensional Watson Hamiltonian (referenced to a transition

Miller, William H.

65

Influence of reaction conditions on sol-precipitation process producing silicon oxide particles  

Microsoft Academic Search

The influence of TEOS, water, and ammonia concentrations on the sol-precipitation process for producing silicon oxide particles was investigated. When the hydrolysis and condensation were assumed as simple first-order reactions, the hydrolysis and condensation reaction coefficients were enhanced with an increase in the ammonia concentration due to its catalytic role in the reactions. Likewise, the increased hydrolysis coefficient with increased

Kyung-Soo Kim; Jun-Kyung Kim; Woo-Sik Kim

2002-01-01

66

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

67

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

68

Reaction of carboxylic acids with vinyl ethers under solvent-free conditions using molecular iodine as a catalyst.  

PubMed

The reaction of vinyl ethers with carboxylic acids using iodine as a catalyst under solvent-free conditions was investigated. The reaction of saturated carboxylic acids with vinyl ethers gave the corresponding esters. Mechanistic studies revealed the production of the adduct of the vinyl ether with the carboxylic acid, which then rearranged to form the ester. At low temperatures, the reaction of 2-(1-hydroxycyclohexyl)acetic acid (1) and butyl vinyl ether yielded a butyl ester. However, at a reaction temperature of 80°C, both the esterification and the elimination of a water molecule occurred, yielding the unsaturated butyl ester butyl 2-cyclohexenylacetate. The reaction of 2-((1S,2S,4R)-2-hydroxy-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl)acetic acid (12) with butyl vinyl ether at low temperatures resulted in a mixture of four compounds. However, similar to the high-temperature (>60°C) reaction of 1, the esterification was accompanied by the elimination of a water molecule to give the unsaturated butyl ester (E)-butyl 2-((1S,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)acetate. While a ?-hydrogen was abstracted to form the endo-type double bond in the reaction of 1, an ?-hydrogen was abstracted to form the exo-type double bond in the reaction of 12. PMID:23357815

Hanzawa, Yohko; Kasashima, Yoshio; Hashimoto, Kahoko; Sasaki, Tatsuhiro; Tomisaki, Keita; Mino, Takashi; Sakamoto, Masami; Fujita, Tsutomu

2013-01-01

69

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

Microsoft Academic Search

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

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

2003-01-01

70

DOI: 10.1002/asia.201100535 Indene Formation under Single-Collision Conditions from the Reaction of  

E-print Network

DOI: 10.1002/asia.201100535 Indene Formation under Single-Collision Conditions from the Reaction. Mebel*[b] Introduction Soot from fossil fuel combustion is widely accepted as caus- ing detrimental),[5] to aromatic mol- ecules, such as benzene (C6H6) and the phenyl radical (C6H5), followed by the formation

Kaiser, Ralf I.

71

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

Microsoft Academic Search

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

Elizabeth Chapman

2002-01-01

72

Single step sol–gel made gold on alumina catalyst for selective reduction of NO x under oxidizing conditions: effect of gold precursor and reaction conditions  

Microsoft Academic Search

We report the effect of gold precursor and reaction conditions on the catalytic activity of gold-alumina catalysts prepared by the sol–gel process. Gold catalysts prepared by the sol–gel method were found to be the most active catalysts ever reported in the literature. We found out that the final activity of Au on alumina was a strong function of the gold

Erol Seker; Erdogan Gulari

2002-01-01

73

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

E-print Network

of ultrasound. The influence of gas flow, temperature of the process and surfactants in the ultrasonically] and Liang et al. studied the influence of pH and reaction time during hydrothermal synthesis on those parame

Suslick, Kenneth S.

74

Optimization of crucial reaction conditions for the production of nicotinamide by nitrile hydratase using response surface methodology.  

PubMed

The reaction conditions for the nicotinamide production by Rhodococcus erythropolis MTCC 1526 have been optimized by statistical experimental design. Application of this approach in the bioprocess can result in rallied product yield, reduced development time, and process variability. In this investigation, response surface methodology and central composite design were employed to predict the levels of variables such as reaction pH (6.5, 7, and 7.5), temperature (15, 20, and 25 degrees C), cell concentration (190, 200, and 210 mg/ml), and substrate concentration (18, 20, and 22 mM) on the production of nicotinamide. A total of 22 experiments were carried out in shake flasks, and a three-dimensional response surface was generated to determine the effect of crucial reaction parameters for the maximum conversion of 3-cynopyridine to nicotinamide. Using this methodology, the optimal values for the reaction conditions were reaction pH 6.85, temperature of 24.8 degrees C, cell concentration of 190.98 mg/ml, and substrate concentration of 21.98 mM. This statistical approach led to the increase of conversion of 3-cynopyridine (93%) as compared to the conversion obtained by one-factor-at-a-time approach (84%). PMID:18975144

Kamble, Ashwini; Banerjee, U C

2008-12-01

75

In situ generation of palladium nanoparticles: ligand-free palladium catalyzed pivalic acid assisted carbonylative Suzuki reactions at ambient conditions.  

PubMed

Highly selective carbonylative Suzuki reactions of aryl iodides with arylboronic acids using an in situ generated nanopalladium system furnished products in high yields. The reactions were performed under ambient conditions and in the absence of an added ligand. The key to success is the addition of pivalic acid, which can effectively suppress undesired Suzuki coupling. The synthesis can be easily scaled up, and the catalytic system can be reused up to nine times. The nature of the active catalytic species are discussed. PMID:24397578

Zhou, Qing; Wei, Shaohua; Han, Wei

2014-02-01

76

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

77

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

78

Silica-promoted Diels-Alder reactions in carbon dioxide from gaseous to supercritical conditions  

SciTech Connect

Amorphous fumed silica (SiO{sub 2}) was shown to increase yields and selectivities of several Diels-Alder reactions in gaseous and supercritical CO{sub 2}. Pressure effects on the Diels-Alder reaction were explored using methyl vinyl ketone and penta-1,3-diene at 80 C. The selectivity of the reaction was not affected by pressure/density. As pressure was increased, the yield decreased. At the reaction temperature, adsorption isotherms at various pressures were obtained for the reactants and the Diels-Alder adduct. As expected when pressure is increased, the ratio of the amount of reactants adsorbed to the amount of reactants in the fluid phase decreases, thus causing the yield to decrease. The Langmuir adsorption model fit the adsorption data. The Langmuir equilibrium partitioning constants all decreased with increasing pressure. The effect of temperature on adsorption was experimentally determined and traditional heats of adsorption were calculated. However, since supercritical CO{sub 2} is a highly compressible fluid, it is logical to examine the effect of temperature at constant density. In this case, entropies of adsorption were obtained. The thermodynamic properties that influence the real enthalpy and entropy of adsorption were derived. Methods of doping the silica and improving yields and selectivities were also explored.

Weinstein, R.D.; Renslo, A.R.; Danheiser, R.L.; Tester, J.W. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1999-04-15

79

Kinetics and Mechanism of the Reaction of Hydoxyl Radicals with Acetonitrile under Atmospheric Conditions  

NASA Technical Reports Server (NTRS)

The pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to determine absolute rate coefficients for the reaction OH + CH3CN (1) and its isotopic variants, OH + CD3CN (2), OD + CH3CN (3), and OD + CD3CN (4). Reactions 1 and 2 were studied as a function of pressure and temperature in N2, N2/O2, and He buffer gases. In the absence of O2 all four reactions displayed well-behaved kinetics with exponential OH decays and pseudo-first rate constants which were proportional to substrate concentration. Data obtained in N2 over the range 50-700 Torr at 298 K are consistent with k(sub 1), showing a small pressure dependence. The Arrhenius expression obtained by averaging data at all pressures in k(sub 1)(T) = (1.1(sup +0.5)/(sub -0.3)) x 10(exp -12) exp[(-1130 +/- 90)/T] cu cm /(molecule s). The kinetics of reaction 2 are found to be pressure dependent with k(sub 2) (298 K) increasing from (1.21 +/- 0.12) x 10(exp -14) to (2.16 +/- 0.11) x 10(exp -14) cm(exp 3)/ (molecule s) over the pressure range 50-700 Torr of N2 at 298 K. Data at pressures greater than 600 Torr give k(sub 2)(T) = (9.4((sup +13.4)(sub -5.0))) x 10(exp -13) exp[(-1180 +/- 250)/T] cu cm/(molecule s). The rates of reactions 3 and 4 are found to be independent of pressure over the range 50-700 Torr of N2 with 298 K rate coefficient given by k(sub 3) =(3.18 +/- 0.40) x 10(exp -14) cu cm/(molecule s) and k(sub 4) = (2.25 +/-0.28) x 10(exp -14) cu cm/(molecule s). In the presence of O2 each reaction shows complex (non-pseudo-first-order) kinetic behavior and/or an apparent decrease in the observed rate constant with increasing [O2], indicating the presence of significant OH or OD regeneration. Observation of regeneration of OH in (2) and OD in (3) is indicative of a reaction channel which proceeds via addition followed by reaction of the adduct, or one of its decomposition products, with O2. The observed OH and OD decay profiles have been modeled by using a simple mechanistic scheme to extract kinetic information about the adduct reations with O2 and branching ratios for OH regeneration. A plausible mechanism for OH regeneration in (2) involves OH addition to the nitrogen atom followed by O2 addition to the cyano carbon atom, isomeriazation and decomposition to D2CO + DOCN + OH. Our results suggest that the OH + CH3CN reaction occurs via a complex mechanism involving both bimolecular and termolecular pathways, analogous to the mechanisms for the the important atmospheric reactions of OH with CO and HNO3.

Hynes, A. J.; Wine, P. H.

1997-01-01

80

Sensory characteristics and consumer acceptability of beef stock containing glutathione Maillard reaction products prepared at various conditions.  

PubMed

The sensory characteristics and consumer acceptability of beef soup samples containing 9 types of glutathione Maillard reaction products (GMRPs) were investigated to examine the effects of the GMRPs produced under different reaction conditions on the flavor of the beef soup. The sensory characteristics of the beef stocks were examined using descriptive analysis. In consumer testing, 50 consumers evaluated the overall acceptability and flavor intensities of beef odor, salty taste, beef flavor, and seasoning flavor in the beef soup samples. It was found that the reaction conditions, including sugar type and pH, affected the sensory characteristics of the beef stock containing the GMRPs. The samples containing the GMRPs reacted at pH 7 were characterized with strong beef flavor, chestnut flavor, and cooked rice flavor. However, the GMRP reacted with xylose at pH 7 (XM7) was significantly stronger in beef-related sensory characteristics than the GMRPs reacted with glucose or fructose at pH 7 (GM7 and FM7). The samples containing the GMRPs reacted at pH 3 had strong acid-related attributes whereas the GMRPs reacted at pH 11 exhibited strong sulfur-related attributes and a bitter taste. Overall, the beef soup containing XM7, which was perceived as having a strong beef odor and flavor, was rated the highest consumer acceptability score. This suggests that XM7 has feasibility as a flavor enhancer. To elucidate its effectiveness further, it is required to apply XM7 in various food systems at varying levels and to compare its flavor enhancing effects with other flavor enhancers such as monosodium L-glutamate in future studies. Practical Application: This study characterized sensory attributes of glutathione Maillard reaction products (GMRPs) reacted under various conditions and evaluated their potential as a flavor enhancer by examining consumer acceptability of beef stock containing the GMRPs. This study showed that the GMRP reacted with xylose at pH 7 had strong 71 beef flavor and the highest consumer acceptability score. The results of this study will provide valuable information for understanding sensory aspect of flavors generated by Maillard reaction of GSH and sugars, since most studies on Maillard reaction focused on chemical reactions. Also, the outcome of this study will help flavor and food industries' efforts to develop a new flavor enhancer for use in a variety of processed food products. PMID:21535706

Kwon, G Y; Hong, J H; Kim, Y S; Lee, S M; Kim, K O

2011-01-01

81

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

82

Organometallic derivatives of furan. LX. Reactions of di-2-furyldimethylgermane under catalytic-hydrogenation conditions  

SciTech Connect

In the reaction of di-2-furyldimethylgermane with hydrogen in the presence of the homogeneous metal-complex catalyst RhH(CO)(PPh/sub 3/)/sub 3/ the selective hydrogenation of one of the furan rings occurs, but over heterogeneous catalysts (Raney Ni, Rh black, Pd/C) hydrogenation and hydrogenolysis reactions occur. Di-2-furyldimethylgermane is converted into (2-furyl)dimethyl(tetrahydro-2-furyl)-germane by the catalytic transfer of hydrogen from 2-propanol and cyclohexene. On the basis of the kinetic relations and quantum-chemical calculations of the electron structures of the original and partially hydrogenated furylgermanes a stagewise scheme is proposed of the hydrogenation of the furan ring and the further hydrogenolysis of the semihydrogenated germane molecule.

Lukevits, E.; Ignatovich, L.M.; Yuskovets, Zh.G.; Golender, L.O.; Shimanskaya, M.V.

1987-11-20

83

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

84

Ignition and transition conditions for inflammation and extinction for a first-order heterogeneous reaction  

Microsoft Academic Search

The problem of determining the thermal states of reacting solid surfaces or gas at a surface and the critical conditions for their inflammation and extinction is of importance both in the combustion of carbon (coal) and for some highly exothermic heterogeneous catalytic processes. This paper examines the effect of ambient temperature on the critical conditions for inflammation and extinction when

Saad A. El-Sayed

1995-01-01

85

Stochastic Bifurcations in a Bistable Reaction-Diffusion System with Neumann Boundary Conditions  

Microsoft Academic Search

It is shown for a special bistable reaction-diffusion model that an external noise shifts deterministic bifurcation maps or generates new bifurcations. Numerical results and an analytical approximation for the bifurcation map of the stationary probability density distribution of the mean concentration in a discrete model are given. The functional Fokker-Planck equation is solved approximately.Translated AbstractStochastische Bifurkationen in einem bistabilen Reaktions-Diffusionssystem

H. Malchow; W. Ebeling; R. Feistel; L. Schimansky-Geier

1983-01-01

86

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

Microsoft Academic Search

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

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

1966-01-01

87

Reaction of olefins with nitriles under solvent-free conditions using molecular iodine as a catalyst in the presence of water.  

PubMed

The reaction of olefins with nitriles using iodine as a catalyst under solvent-free conditions was investigated. The reaction of cycloolefins, such as cyclopentene and cyclohexene, with benzonitrile using iodine as a catalyst produced both amide and heterocyclic compounds. The reaction of chiral (+)-camphene with benzonitrile produced racemic (±)-N-isobornylbenzamide (N-((1S,2S,4S)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl)benzamide). This indicated that skeletal rearrangement of camphene as well as amidation occurred. The optimized conditions were determined to be as follows: temperature, 90°C; molar ratio of nitrile:alcohol:iodine:water, 1:5:0.2:1.0; and reaction time, 18 h. The yield was 87% under these conditions. The reaction of (+)-camphene also proceeded with the other aromatic and aliphatic nitriles to produce racemic isobornylamides. However, except for styrene, complex reactions occurred in the reactions of benzonitrile with other terpenic olefins. PMID:23196872

Hanzawa, Yohko; Kasashima, Yoshio; Tomono, Kazuki; Mino, Takashi; Sakamoto, Masami; Fujita, Tsutomu

2012-01-01

88

An effective rate equation approach to reaction kinetics in small volumes: theory and application to biochemical reactions in nonequilibrium steady-state conditions.  

PubMed

Chemical master equations provide a mathematical description of stochastic reaction kinetics in well-mixed conditions. They are a valid description over length scales that are larger than the reactive mean free path and thus describe kinetics in compartments of mesoscopic and macroscopic dimensions. The trajectories of the stochastic chemical processes described by the master equation can be ensemble-averaged to obtain the average number density of chemical species, i.e., the true concentration, at any spatial scale of interest. For macroscopic volumes, the true concentration is very well approximated by the solution of the corresponding deterministic and macroscopic rate equations, i.e., the macroscopic concentration. However, this equivalence breaks down for mesoscopic volumes. These deviations are particularly significant for open systems and cannot be calculated via the Fokker-Planck or linear-noise approximations of the master equation. We utilize the system-size expansion including terms of the order of Omega(-1/2) to derive a set of differential equations whose solution approximates the true concentration as given by the master equation. These equations are valid in any open or closed chemical reaction network and at both the mesoscopic and macroscopic scales. In the limit of large volumes, the effective mesoscopic rate equations become precisely equal to the conventional macroscopic rate equations. We compare the three formalisms of effective mesoscopic rate equations, conventional rate equations, and chemical master equations by applying them to several biochemical reaction systems (homodimeric and heterodimeric protein-protein interactions, series of sequential enzyme reactions, and positive feedback loops) in nonequilibrium steady-state conditions. In all cases, we find that the effective mesoscopic rate equations can predict very well the true concentration of a chemical species. This provides a useful method by which one can quickly determine the regions of parameter space in which there are maximum differences between the solutions of the master equation and the corresponding rate equations. We show that these differences depend sensitively on the Fano factors and on the inherent structure and topology of the chemical network. The theory of effective mesoscopic rate equations generalizes the conventional rate equations of physical chemistry to describe kinetics in systems of mesoscopic size such as biological cells. PMID:20649359

Grima, R

2010-07-21

89

N-Methylation of amine and nitro compounds with CO2/H2 catalyzed by Pd/CuZrO(x) under mild reaction conditions.  

PubMed

An active Pd/ZrCuOx catalyst was prepared for the reductive amination of CO2. The N-methylation of amines and nitro compounds with CO2/H2 can be realized with up to 97% yield under relatively mild reaction conditions. N-Formylation becomes the main reaction if the reaction was performed under milder conditions or using Pd/ZnZrOx as the catalyst. PMID:25238630

Cui, Xinjiang; Zhang, Yan; Deng, Youquan; Shi, Feng

2014-11-14

90

Hot-Fire Testing of 100 LB(sub F) LOX/LCH4 Reaction Control Engine at Altitude Conditions  

NASA Technical Reports Server (NTRS)

Liquid oxygen/liquid methane (LO2/LCH4 ) has recently been viewed as a potential green propulsion system for both the Altair ascent main engine (AME) and reaction control system (RCS). The Propulsion and Cryogenic Advanced Development Project (PCAD) has been tasked by NASA to develop these green propellant systems to enable safe and cost effective exploration missions. However, experience with LO2/LCH4 as a propellant combination is limited, so testing of these systems is critical to demonstrating reliable ignition and performance. A test program of a 100 lb f reaction control engine (RCE) is underway at the Altitude Combustion Stand (ACS) of the NASA Glenn Research Center, with a focus on conducting tests at altitude conditions. These tests include a unique propellant conditioning feed system (PCFS) which allows for the inlet conditions of the propellant to be varied to test warm to subcooled liquid propellant temperatures. Engine performance, including thrust, c* and vacuum specific impulse (I(sub sp,vac)) will be presented as a function of propellant temperature conditions. In general, the engine performed as expected, with higher performance at warmer propellant temperatures but better efficiency at lower propellant temperatures. Mixture ratio effects were inconclusive within the uncertainty bands of data, but qualitatively showed higher performance at lower ratios.

Marshall, William M.; Kleinhenz, Julie E.

2010-01-01

91

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

PubMed

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

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

2012-06-21

92

Palladium-Catalyzed ?-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope  

PubMed Central

The intermolecular ?-arylation of esters by palladium-catalyzed coupling of aryl bromides with zinc enolates of esters is reported. Reactions of three different types of zinc enolates have been developed. ?-Arylation of esters occurs in high yields with isolated Reformatsky reagents, with Reformatsky reagents generated from ?-bromo esters and activated zinc, and with zinc enolates generated by quenching lithium enolates of esters with zinc chloride. The use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of the arylation of esters. The reactions occur at room temperature or at 70 °C with bromoarenes containing cyano, nitro, ester, keto, fluoro, enolizable hydrogen, hydroxyl or amino functionality and with bromopyridines. The scope of esters encompasses acyclic acetates, propionates, and isobutyrates, ?-alkoxyesters, and lactones. The arylation of zinc enolates of esters was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2. PMID:23931445

Hama, Takuo; Ge, Shaozhong; Hartwig, John F.

2013-01-01

93

Palladium-catalyzed ?-arylation of zinc enolates of esters: reaction conditions and substrate scope.  

PubMed

The intermolecular ?-arylation of esters by palladium-catalyzed coupling of aryl bromides with zinc enolates of esters is reported. Reactions of three different types of zinc enolates have been developed. ?-Arylation of esters occurs in high yields with isolated Reformatsky reagents, with Reformatsky reagents generated from ?-bromo esters and activated zinc, and with zinc enolates generated by quenching alkali metal enolates of esters with zinc chloride. The use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of the arylation of esters. The reactions occur at room temperature or at 70 °C with bromoarenes containing cyano, nitro, ester, keto, fluoro, enolizable hydrogen, hydroxyl, or amino functionality and with bromopyridines. The scope of esters encompasses acyclic acetates, propionates, and isobutyrates, ?-alkoxyesters, and lactones. The arylation of zinc enolates of esters was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2. PMID:23931445

Hama, Takuo; Ge, Shaozhong; Hartwig, John F

2013-09-01

94

Spectroscopy of unbound states under quasifree scattering conditions: One-neutron knockout reaction of {sup 14}Be  

SciTech Connect

Full Faddeev-type calculations are performed for one-neutron knockout reaction of {sup 14}Be on proton target at 69 MeV/nucleon incident energy. Inclusive transverse momentum distributions for the outgoing ({sup 12}Be+n) system and semi-inclusive cross sections are presented. A significant proton-core single scattering contribution emerges where the valence neutron has nonzero angular momentum relative to the core. This indicates that distorted-wave impulse approximation is inadequate and the complete multiple scattering series must be taken into account for the considered reaction. The magnitude of the semi-inclusive cross section at quasifree scattering conditions is a clear signature of the angular momentum of the valence nucleon.

Crespo, R. [Centro de Fisica Nuclear, Universidade de Lisboa, Av. Prof. Gama Pinto 2, P-1649-003 Lisboa (Portugal); Departamento de Fisica, Instituto Superior Tecnico, Taguspark, Av. Prof. Cavaco Silva, Taguspark P-2780-990 Porto Salvo, Oeiras (Portugal); Deltuva, A.; Rodriguez-Gallardo, M.; Cravo, E.; Fonseca, A. C. [Centro de Fisica Nuclear, Universidade de Lisboa, Av. Prof. Gama Pinto 2, P-1649-003 Lisboa (Portugal)

2009-01-15

95

Hydrodechlorination of 1,2-dichloroethane by rhodium catalysts under water gas shift reaction conditions  

Microsoft Academic Search

Homogeneous catalysts prepared from rhodium trichloride in aqueous aromatic amines have been shown to reduce C–Cl bonds under mild water gas shift conditions (T=100°C, PCO=1.0 atm). In a 4-picoline\\/water solvent mixture, 1,2-dichloroethane is reduced to ethylene and ethane in yields compatible with the consumption of the reducing agent CO and with the formation of CO2. Variation of the catalyst solutions

Elizeu Trabuco; Peter C. Ford

1999-01-01

96

Silicon-based Lewis acid assisted cinchona alkaloid catalysis: highly enantioselective aza-Michael reaction under solvent-free conditions.  

PubMed

The study showed that a combination of an achiral silicon-based Lewis acid and chiral Lewis base, such as iodotrimethylsilane (TMSI) and cinchonine, generated a highly enantioselective catalyst system under solvent-free conditions which gave aromatic ?-amino ketones with up to >99% ee. Mechanistic studies demonstrate the enhanced asymmetric induction may be due to the combined and competitive activation of a carbonyl moiety of chalcone with cinchonine and the silicon-based Lewis acid in the aza-Michael reaction. PMID:22087568

Yang, Hua-Meng; Li, Li; Li, Fei; Jiang, Ke-Zhi; Shang, Jun-Yan; Lai, Guo-Qiao; Xu, Li-Wen

2011-12-16

97

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

SciTech Connect

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

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

2008-11-03

98

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

SciTech Connect

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

Balai, N.; Frisch, M; Ilton, E; Ravel, B; Cahill, C

2008-01-01

99

Biodiesel production from various oils under supercritical fluid conditions by Candida antartica lipase B using a stepwise reaction method.  

PubMed

In this study, we evaluate the effects of various reaction factors, including pressure, temperature, agitation speed, enzyme concentration, and water content to increase biodiesel production. In addition, biodiesel was produced from various oils to establish the optimal enzymatic process of biodiesel production. Optimal conditions were determined to be as follows: pressure 130 bar, temperature 45 degrees C, agitation speed 200 rpm, enzyme concentration 20%, and water contents 10%. Among the various oils used for production, olive oil showed the highest yield (65.18%) upon transesterification. However, when biodiesel was produced using a batch system, biodiesel conversion yield was not increased over 65%; therefore, a stepwise reaction was conducted to increase biodiesel production. When a reaction medium with an initial concentration of methanol of 60 mmol was used and adjusted to maintain this concentration of methanol every 1.5 h during biodiesel production, the conversion yield of biodiesel was 98.92% at 6 h. Finally, reusability was evaluated using immobilized lipase to determine if this method was applicable for industrial biodiesel production. When biodiesel was produced repeatedly, the conversion rate was maintained at over 85% after eight reuses. PMID:19132555

Lee, Jong Ho; Kwon, Cheong Hoon; Kang, Jeong Won; Park, Chulhwan; Tae, Bumseok; Kim, Seung Wook

2009-05-01

100

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

101

Role of choline and glycine betaine in the formation of N,N-dimethylpiperidinium (mepiquat) under Maillard reaction conditions.  

PubMed

This study is the first to examine the role of choline and glycine betaine, naturally present in some foods, in particular in cereal grains, to generate N,N-dimethylpiperidinium (mepiquat) under Maillard conditions via transmethylation reactions involving the nucleophile piperidine. The formation of mepiquat and its intermediates piperidine - formed by cyclisation of free lysine in the presence of reducing sugars - and N-methylpiperidine were monitored over time (240°C, up to 180 min) using high-resolution mass spectrometry in a model system comprised of a ternary mixture of lysine/fructose/alkylating agent (choline or betaine). The reaction yield was compared with data recently determined for trigonelline, a known methylation agent present naturally in coffee beans. The role of choline and glycine betaine in nucleophilic displacement reactions was further supported by experiments carried out with stable isotope-labelled precursors ((13)C- and deuterium-labelled). The results unequivocally demonstrated that the piperidine ring of mepiquat originates from the carbon chain of lysine, and that either choline or glycine betaine furnishes the N-methyl groups. The kinetics of formation of the corresponding demethylated products of both choline and glycine betaine, N,N-demethyl-2-aminoethanol and N,N-dimethylglycine, respectively, were also determined using high-resolution mass spectrometry. PMID:25333319

Bessaire, Thomas; Tarres, Adrienne; Stadler, Richard H; Delatour, Thierry

2014-12-01

102

Reaction Kinetics of Primary Rock-forming Minerals under Ambient Conditions  

NASA Astrophysics Data System (ADS)

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

Brantley, S. L.

2003-12-01

103

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

2014-09-22

104

Human leukocyte acid hydrolases: characterization of eleven lysosomal enzymes and study of reaction conditions for their automated analysis.  

PubMed

The optimal reaction conditions and kinetic properties of eleven leukocyte acid hydrolases determined with the use of fluorigenic derivatives of 4-methyl-umbelliferone are described. The enzymes studied were acid phosphatase, aryl sulfatase, alpha- and beta-glucosidase, alpha- and beta-galactosidase, alpha-mannosidase, N-acetyl-beta-glucosaminidase, N-acetyl-beta-galactosaminidase, beta-glucuronidase and alpha-fucosidase. More than 90% of the activity of each enzyme was released into a 27,000 X g supernatant by a double sonication procedure employing 0.9% sodium chloride and 0.1% Triton X-100. The Km values obtained were similar to those previously reported for chromogenic subtrates. A single Km value could not be derived for beta-galactosidase because its double reciprocal plot was not linear. All enzymes could be measured with less than 10 mug of protein within 15 min. Activators and inhibitors studied included the chloride salts of Na+, K+, Zn2+, Ca2+, Mg2+, Hg2+, and Fe2+ as well as p-chloromercuriphenysulfonate, glutathione, BAL, EDTA, EGTA, Triton X-100 and sodium taurocholate. The reaction conditions described in this report can be used for the diagnosis of various lysosomal storage diseases and should facilitate the development of automated procedures for the analysis of these eleven enzyme activities with small quantities of blood. PMID:8226

Kolodny, E H; Mumford, R A

1976-07-15

105

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

106

Hydrothermal processing of duckweed: effect of reaction conditions on product distribution and composition.  

PubMed

Influences of operating conditions such as temperature (270-380 °C), time (10-120 min), reactor loading (0.5-5.5 g), and K2CO3 loading (0-50 wt.%) on the product (e.g. crude bio-oil, water soluble, gas and solid residue) distribution from the hydrothermal processing of duckweed were determined. Of the four variables, temperature and K2CO3 loading were always the most influential factors to the relative amount of each component. The presence of K2CO3 is unfavorable for the production of bio-oil and gas. Hydrothermal processing duckweed produces a bio-oil that is enriched in carbon and hydrogen and has reduced levels of O compared with the original duckweed feedstock. The higher heating values of the bio-oil were estimated within the range of 32-36 MJ/kg. Major bio-oil constituents include ketones and their alkylated derivatives, alcohols, heterocyclic nitrogen-containing compounds, saturated fatty acids and hydrocarbons. The gaseous products were mainly CO2 and H2, with lesser amounts of CH4 and CO. PMID:23021946

Duan, Peigao; Chang, Zhoufan; Xu, Yuping; Bai, Xiujun; Wang, Feng; Zhang, Lei

2013-05-01

107

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

108

Trapping reactions of reactive carbonyl species with tea polyphenols in simulated physiological conditions.  

PubMed

The carbonyl stress that leads to the formation of advanced glycation end products (AGEs) in diabetes mellitus has drawn much attention recently. Reactive alpha-dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), have been shown to be a high potential glycation agent in vitro and in vivo. In this study, epicatechins in green tea and theaflavins in black tea were found to be able to reduce the concentration of MGO in physiological phosphate buffer conditions. Modified MGO derivatization for GC/flame ionization detector (FID) method in quantification was systematically conducted. In molar ratio of 3 (MGO/polyphenol), theaflavin-3,3'-digallate (TF3) in theaflavins and (-)-epigallocatechin (EGC) in epicatechins showed the highest MGO reduction at 66.65 and 45.74%, respectively, after 1 h of incubation. In kinetic study (molar ratio of MGO/polyphenol = 1:1), rapid MGO reduction occurred within 10 min. Identities of primary adducts between (-)-epigallocatechin gallate (EGCG) and MGO were determined. Newly generated stereoisomers at the C8 position of EGCG A-ring were isolated with a chiral column, and structurally confirmed by 2-D NMR analyses. PMID:17103374

Lo, Chih-Yu; Li, Shiming; Tan, Di; Pan, Min-Hsiung; Sang, Shengmin; Ho, Chi-Tang

2006-12-01

109

Green chemistry: a facile synthesis of polyfunctionally substituted thieno[3,4-c]pyridinones and thieno[3,4-d]pyridazinones under neat reaction conditions.  

PubMed

A facile, solvent free, ecofriendly approach for the synthesis of pyridine-2,6-diones 4a-d, pyridazinone derivatives 8a-c and thienoazines 6 and 9 is herein described employing neat reaction conditions under both microwave and ultrasound irradiations. This solventless methodology is environmentally benign as it completely eliminates the use of solvent from the reaction procedure. PMID:20064736

Al-Zaydi, Khadijah M; Borik, Rita M; Mekheimer, Ramadan A; Elnagdi, Mohamed H

2010-06-01

110

The direct catalytic asymmetric aldol reaction of ?-substituted nitroacetates with aqueous formaldehyde under base-free neutral phase-transfer conditions.  

PubMed

Enantioselective direct aldol reaction of ?-substituted nitroacetates with aqueous formaldehyde for the synthesis of ?-alkyl serines has been achieved under base-free neutral phase-transfer conditions with a bifunctional chiral phase-transfer catalyst. PMID:22349720

Shirakawa, Seiji; Ota, Kensuke; Terao, Shogo J; Maruoka, Keiji

2012-08-14

111

Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions  

NASA Technical Reports Server (NTRS)

This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

Dietz, N.; McCall, S.; Bachmann, K. J.

2001-01-01

112

Stress response in Pectobacterium atrosepticum SCRI1043 under starvation conditions: adaptive reactions at a low population density.  

PubMed

The adaptive reactions of plant pathogenic bacterium Pectobacterium atrosepticum SCRI1043 under starvation conditions were studied. The main emphasis was given to the peculiarities of stress responses depending on the bacterial population densities. When bacteria were subjected to starvation at high population densities (10(7)-10(9) CFU ml(-1)), their adaptive reactions conformed to the conventional conception of bacterial adaptation related to autolysis of part of the population, specific modification of cell ultrastructure, activation of expression of stress responsive genes and acquiring cross protection against other stress factors. In contrast, at low initial population densities (10(3)-10(5) CFU ml(-1)), as described in our recent work, the cell density increased due to multiple cell division despite the absence of exogenous growth substrate. Here we present data that demonstrate that such unconventional behavior is part of a stress response, which provides increased stress tolerance while retaining virulence. Cell morphology and gene expression in high- and low-cell-density starving Pba cultures were compared. Our investigation demonstrates the existence of alternative adaptive strategies enabling pathogenic bacteria to cope with a variety of stress factors, including starvation, especially necessary when residing outside of their host. PMID:24300393

Petrova, Olga; Gorshkov, Vladimir; Daminova, Amina; Ageeva, Marina; Moleleki, Lucy N; Gogolev, Yuri

2014-01-01

113

Dextran-based self-healing hydrogels formed by reversible diels-alder reaction under physiological conditions.  

PubMed

A dextran-based self-healing hydrogel is prepared by reversible Diels-Alder reaction under physiological conditions. Cytocompatible fulvene-modified dextran as main polymer chains and dichloromaleic-acid-modified poly(ethylene glycol) as cross-linkers are used. Both macro- and microscopic observation as well as the rheological recovery test confirm the self-healing property of the dextran-l-poly(ethylene glycol) hydrogels ("l" means "linked-by"). In addition, scanning electrochemical microscopy is used to qualitatively and quantitatively in situ track the self-healing process of the hydrogel for the first time. It is found that the longitudinal depth of scratch on hydrogel surface almost completely healed at 37 °C after 7 h. This work represents a facile approach for fabrication of polysaccharide self-healing hydrogel, which can be potentially used in several biomedical fields. PMID:23929621

Wei, Zhao; Yang, Jian Hai; Du, Xiao Jing; Xu, Feng; Zrinyi, Miklos; Osada, Yoshihito; Li, Fei; Chen, Yong Mei

2013-09-01

114

Reaction and transport in wellbore interfaces under CO2 storage conditions: Experiments simulating debonded cement-casing interfaces  

NASA Astrophysics Data System (ADS)

Debonding-defects at the interfaces between wellbore casing and cement are widely recognized as providing potential pathways for CO2 escape from geological storage systems. This study addresses how chemical reaction between CO2, cement and steel may affect the transport properties of such defects under near-static conditions, representative for early stages in leakage pathway development, 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. These were reacted with CO2 and water, brine or a solution pre-saturated with cement. Each sample was subjected to 7 sequential batch reaction runs, namely 6 runs of 5 days duration, followed by a single extended run, of 42 days, to study long-term effects. The reaction runs were conducted at 80°C and 14 MPa applied CO2-pressure. Permeability was measured after each run and microstructural analyses were performed after completion of the experiment. We investigated two ranges in gap-width, namely 50-120 ?m (denoted SA samples) and 270-350 ?m (LA samples). Reaction-induced permeability changes were limited and less than 1 order in all samples, and occurred in the early stage of testing. Corrosion product or scale (mainly Fe-carbonates, with minor Fe-hydroxides) formed extensively within the open gap, on the surfaces of both the casing steel and cement. Lack of calcium carbonates in these areas suggests the corrosion scale which formed on the cement surface produced a significant reduction in cement carbonation rate, similar to the decrease in corrosion rate observed when these precipitates create a protective film on steel surfaces only. CaCO3 precipitation occurred extensively on the cement side at locations beneath the spacers used to create the gap between the cement and steel plates, where corrosion scale did not form. Our results imply that healing of debonding defects at casing-cement interfaces in wellbores will be slower and less effective than healing of fractures in cement under comparable, near-static conditions, due to the formation of thin corrosion scale films on the cement surfaces. These films inhibit release of calcium from the cement into the aperture and impede the precipitation of calcium carbonates that was previously found to promote sealing in fractured cement when only local transport is possible. If thin corrosion scale films of the type observed in our experiments form in real wellbore systems, local small debonding defects (gaps less than a few tens of micrometres) can be expected to heal due to clogging by corrosion scale film. In larger debonding defects, where scale film development is insufficient to produce sealing, their retarding effect on further reaction has the potential to maintain an open interfacial pathway, should long-range connectivity and transport ensue. It is, therefore, important to incorporate the effects of early corrosion scale film development in future analyses of long-range leakage pathways along cement-casing interfaces.

Wolterbeek, T. K.; Peach, C. J.; Spiers, C. J.

2013-12-01

115

N8 (-) polynitrogen stabilized on multi-wall carbon nanotubes for oxygen-reduction reactions at ambient conditions.  

PubMed

Polynitrogen (PN) species (Nn , n from 3 to 8) as highly energetic materials have attracted many theoretical calculations and predictions. N3 , N4 , N5 or their ions were experimentally detected under high-pressure and high-temperature conditions. Herein, a N8 (-) PN stabilized on the positively charged sidewalls of multi-walled carbon nanotubes (MWNTs) has been synthesized using cyclic voltammetry (CV) under ambient conditions. ATR-FTIR and Raman spectroscopic data assigned on the basis of density functional theory (DFT) calculations support the successful synthesis of a C2h symmetry chain structure of the N8 anion stabilized as MWNT(+) N8 (-) . Temperature programmed desorption (TPD) data show that MWNT(+) N8 (-) is thermally stable up to 400?°C. Oxygen-reduction reaction (ORR) experiments carried out using MWNT(+) N8 (-) as the cathodic catalyst shows that it is very active for ORR with an even higher current density than that of a commercial Pt/carbon catalyst. PMID:25123821

Wu, Zhiyi; Benchafia, El Mostafa; Iqbal, Zafar; Wang, Xianqin

2014-11-10

116

Solid-state reaction synthesis of NiFe2O4 nanoparticles by optimizing the synthetic conditions  

NASA Astrophysics Data System (ADS)

Nickel ferrite (NiFe2O4) nanoparticles were synthesized via solid-state reaction. The precursors obtained by grinding the mixture of FeSO4·7H2O, NiSO4·6H2O, NaOH and dispersant (NaCl) sufficiently at room temperature were calcined under various synthetic conditions in order to get NiFe2O4 spinel nanoparticles. The effects of the synthetic parameters, namely preparation technique, dispersant content, calcination temperature and heat preservation time, on particle size and morphology have been investigated in detail to find the optimized parameters. X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) were employed to characterize the precursors and as-synthesized particles. The results indicate that structural morphology varies between needle and sphere with changing preparation technique. Proper content of NaCl as a dispersant is beneficial to obtain uniform particles with a narrow size distribution. The particle morphology changes gradually from sphere to polygon with the increase in calcination temperature. Grain growth is enhanced by prolonging heat preservation time. Room temperature magnetization results reveal a ferromagnetic behavior of the as-synthesized NiFe2O4 nanoparticles. The saturation magnetization is enhanced with the increase in grain size for less surface effect. The coercivity is decreased for larger grain size because of magnetization reversal. The solid-state reaction technique is considered to be a convenient, inexpensive and effective preparation method of NiFe2O4 in high yield.

Zhang, Zhigang; Liu, Yihan; Yao, Guangchun; Zu, Guoyin; Zhang, Xiao; Ma, Junfei

2012-08-01

117

Fe3O4 Nanoparticles as an Efficient and Magnetically Recoverable Catalyst for Friedel-Crafts Acylation Reaction in Solvent-Free Condition  

Microsoft Academic Search

Application of Fe3O4 nanoparticles (NPs) as a robust, very efficient and magnetically recoverable catalyst was investigated in Friedel-Crafts acylation (FCA) of ferrocene and aromatic compounds. This reaction was performed with acid chlorides in solvent-free conditions at room temperature. The catalyst was easily separated by an external magnetic field from the reaction mixture. The separated catalyst recycled for several consecutive runs

S. Jafar Hoseini; Hasan Nasrabadi; Mahboobeh Azizi; Alireza Salimi Beni; Reza Khalifeh

2012-01-01

118

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

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.  

PubMed

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 24h 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. PMID:25062056

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

2015-01-25

121

Experimental study on side-reaction occurrence condition in the iodine–sulfur thermochemical hydrogen production process  

Microsoft Academic Search

In iodine–sulfur thermochemical hydrogen production process (IS process), side-reactions from HI, H2SO4 and I2 mixture solution were investigated experimentally in operating temperature ranges, from 295 to 368 K. The effects of the reaction temperature, acid concentration, iodine concentration and the ratio of the amount of H2SO4 to that of HI on the sulfur formation are discussed. The quantitative reaction analysis was

Makoto Sakurai; Hayato Nakajima; Rusli Amir; Kaoru Onuki; Saburo Shimizu

2000-01-01

122

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

SciTech Connect

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

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

2009-09-28

123

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

PubMed Central

Hyperuricemia is associated with hypertension, metabolic syndrome, preeclampsia, cardiovascular disease and renal disease, all conditions associated with oxidative stress. We hypothesized that uric acid, a known antioxidant, might become prooxidative following its reaction with oxidants; and, thereby contribute to the pathogenesis of these diseases. Uric acid and 1,3-15N2-uric acid were reacted with peroxynitrite in different buffers and in the presence of alcohols, antioxidants and in human plasma. The reaction products were identified using liquid chromatography-mass spectrometry (LC-MS) analyses. The reactions generate reactive intermediates that yielded triuret as their final product. We also found that the antioxidant, ascorbate, could partially prevent this reaction. Whereas triuret was preferentially generated by the reactions in aqueous buffers, when uric acid or 1,3-15N2-uric acid was reacted with peroxynitrite in the presence of alcohols, it yielded alkylated alcohols as the final product. By extension, this reaction can alkylate other biomolecules containing OH groups and others containing labile hydrogens. Triuret was also found to be elevated in the urine of subjects with preeclampsia, a pregnancy-specific hypertensive syndrome that is associated with oxidative stress, whereas very little triuret is produced in normal healthy volunteers. We conclude that under conditions of oxidative stress, uric acid can form reactive intermediates, including potential alkylating species, by reacting with peroxynitrite. These reactive intermediates could possibly explain how uric acid contributes to the pathogenesis of diseases such as the metabolic syndrome and hypertension. PMID:19219741

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

2009-01-01

124

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

125

Impact of age and obstacles on navigation precision and reaction time during blind navigation in dual-task conditions.  

PubMed

Navigation without vision is a skill that is often employed in our daily lives, such as walking in the dark at night. Navigating without vision to a remembered target has previously been studied. However, little is known about the impact of age or obstacles on the attentional demands of a blind navigation task. This study examined the impacts of age and obstacles on reaction time (RT) and navigation precision during blind navigation in dual-task conditions. The aims were to determine the effects of age, obstacles, and auditory stimulus location on RT and navigation precision in a blind navigation task. Ten healthy young adults (24.5±2.5 years) and ten healthy older adults (69.5±2.9 years) participated in the study. Participants were asked to walk to a target located 8m ahead. In half the trials, the path was obstructed with hanging obstacles. Participants performed this task in the absence of vision, while executing a discrete RT task. Results demonstrated that older adults presented increased RT, linear distance travelled (LDT), and obstacle contact; that obstacle presence significantly increased RT compared to trials with no obstacles; and that an auditory stimulus emitted early versus late in the path increased LDT. Results suggest that the attentional demands of blind navigation are higher in older than young adults, as well as when obstacles are present. Furthermore, navigation precision is affected by age and when participants are distracted by the secondary task early in navigation, presumably because the secondary task interferes with path estimation. PMID:24238471

Richer, Natalie; Paquet, Nicole; Lajoie, Yves

2014-03-01

126

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

127

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

128

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

PubMed

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

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

2005-04-28

129

Direct one-pot conversion of acylated carbohydrates into their alkylated derivatives under heterogeneous reaction conditions using solid NaOH and a phase transfer catalyst  

Microsoft Academic Search

A convenient one-pot protocol for the direct conversion of acyl-protected carbohydrates into their alkylated counterparts has been developed by using alkyl halides in the presence of solid sodium hydroxide and a phase transfer catalyst. These economically convenient, mild, two-phase reaction conditions allow the preparation of a variety of monosaccharide intermediates for use in the synthesis of complex oligosaccharides.

Soni Kamlesh Madhusudan; Geetanjali Agnihotri; Devendra S. Negi; Anup Kumar Misra

2005-01-01

130

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

PubMed

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

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

2012-05-28

131

An efficient green protocol for the synthesis of chalcones by a Claisen–Schmidt reaction using bismuth(III)chloride as a catalyst under solvent-free condition  

Microsoft Academic Search

An environmentally benign protocol for the synthesis of chalcones by the Claisen–Schmidt condensation of aldehydes with ketones using eco-friendly non-toxic bismuth(III)chloride catalyst under solvent-free condition is reported. In this protocol, the reaction time is very short, yields are high, and there are no other pollutants formed.

Dhruva Kumar; Jagir S. Sandhu

2010-01-01

132

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...

133

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...

134

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

135

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....

136

Highly diastereoselective Michael reaction under solvent-free conditions using microwaves: conjugate addition of flavanone to its chalcone precursor  

Microsoft Academic Search

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.

Tamás Patonay; Rajender S Varma; András Vass; Albert Lévai; József Dudás

2001-01-01

137

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

Microsoft Academic Search

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

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

2006-01-01

138

Universal reaction mechanism of boronic acids with diols in aqueous solution: kinetics and the basic concept of a conditional formation constant.  

PubMed

To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (Ka(BL)) of boronic acid diol esters (HBLs) were determined based on the well-established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4-difluorophenylboronic acid and chromotropic acid, 3-nitrophenylboronic acid and alizarin red?S, and phenylboronic acid and alizarin red?S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a)?the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b)?the determined pKa values of HBLs. The use of the conditional formation constant, K', based on the main reaction: RB(OH)2 + H2L (K1)? RB(L)(OH)(-) + H3O(+) instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B') with uncomplexed diol species (L') to form boronic acid diol complex species (esters, BL') in aqueous solution at pH?5-11: B' + L' (K')? BL'. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution. PMID:25169423

Furikado, Yuki; Nagahata, Tomomi; Okamoto, Takuya; Sugaya, Tomoaki; Iwatsuki, Satoshi; Inamo, Masahiko; Takagi, Hideo D; Odani, Akira; Ishihara, Koji

2014-10-01

139

Direct boronation of allyl alcohols with diboronic acid using palladium pincer-complex catalysis. A remarkably facile allylic displacement of the hydroxy group under mild reaction conditions.  

PubMed

Allyl alcohols were converted to allyl boronic acids and subsequently to trifluoro(allyl)borates with tetrahydroxy diboron using palladium pincer-complex catalysis. These reactions are regio- and stereoselective proceeding with high isolated yields. Competitive boronation experiments indicate that under the applied reaction conditions the allylic displacement of a hydroxy group is faster than the displacement of an acetate leaving group. It is assumed that the hydroxy group of the allyl alcohol is converted to a diboronic acid ester functionality, which can easily be substituted. PMID:16594692

Olsson, Vilhelm J; Sebelius, Sara; Selander, Nicklas; Szabó, Kalman J

2006-04-12

140

Iron-promoted C-C bond cleavage of 1,3-diketones: a route to 1,2-diketones under mild reaction conditions.  

PubMed

A conceptual method for the preparation of 1,2-diketones is reported. The selective C-C bond cleavage of 1,3-diketones affords the 1,2-diketones in high yields under mild reaction conditions in air by the use of FeCl(3) as the catalyst and tert-butyl nitrite (TBN) as the oxidant without the use of solvent. The possible reaction mechanism is discussed. This protocol provides an expeditious route to the useful 1,2-diketones. PMID:21627329

Huang, Lehao; Cheng, Kai; Yao, Bangben; Xie, Yongju; Zhang, Yuhong

2011-07-15

141

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

SciTech Connect

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

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

1996-04-01

142

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

143

Heat and mass exchange in films of a reacting mixture and a cooling liquid under exothermic-reaction conditions  

Microsoft Academic Search

Conjugate turbulent heat and mass exchange in fast exothermic reactions in thin films has been investigated with allowance for the change in the pressure. A modification of the equal-flow-rate method, the most natural for problems of such a kind, has been constructed. Its distinctive feature is that it is constructed on formal passage to a rectangular domain of variation in

L. P. Kholpanov; S. E. Zakiev

2008-01-01

144

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 ...

145

Reaction of rosmarinic acid with nitrite ions in acidic conditions: discovery of nitro- and dinitrorosmarinic acids as new anti-HIV-1 agents.  

PubMed

Rosmarinic acid was reacted with nitrite ions under acidic conditions to give 6'-nitro- and 6',6''-dinitrorosmarinic acids according to the reaction time. Both compounds were active as HIV-1 integrase inhibitors at the submicromolar level. They also inhibited the viral replication in MT-4 cells with modest and similar selectivity indexes. The nitration of rosmarinic acid strongly improves the anti-integrase inhibition and the antiviral activity without increasing the cellular toxicity. PMID:18351727

Dubois, Mélanie; Bailly, Fabrice; Mbemba, Gladys; Mouscadet, Jean-François; Debyser, Zeger; Witvrouw, Myriam; Cotelle, Philippe

2008-04-24

146

Investigation of gas-phase reactions and ignition delay occurring at conditions typical for partial oxidation of methane to synthesis gas  

Microsoft Academic Search

Continuous-flow experiments in an empty aluminum oxide tube for the investigation of the homogeneous gas-phase reactions occurring at conditions typical for the partial oxidation of methane to synthesis gas were carried out at pressures from 300 to 800 kPa, temperatures from 1,030 to 1,300 K, inlet molar ratios of CHâOâ from 2.1 to 3.1, and residence times from 0.09 to

R. J. Berger; G. B. Marin

1999-01-01

147

Heat and mass exchange in films of a reacting mixture and a cooling liquid under exothermic-reaction conditions  

Microsoft Academic Search

Conjugate turbulent heat and mass exchange in fast exothermic reactions in thin films has been investigated with allowance\\u000a for the change in the pressure. A modification of the equal-flow-rate method, the most natural for problems of such a kind,\\u000a has been constructed. Its distinctive feature is that it is constructed on formal passage to a rectangular domain of variation\\u000a in

L. P. Kholpanov; S. E. Zakiev

2008-01-01

148

Reaction to the perturbation of the vertical posture under different conditions of standing and in the case of additional support  

Microsoft Academic Search

The reaction of equilibrium restoration in response to the perturbation of the vertical posture of a subject standing on a\\u000a stable or unstable support was studied. Perturbation was induced by a sudden forward or backward shift of the support surface.\\u000a In some of the experiments, the subject was holding onto a handrail suspended on a long soft belt with a

O. V. Kazennikov; V. Yu. Shlykov; Yu. S. Levik

2009-01-01

149

Reaction of the ethynyl radical, C2H, with methylacetylene, CH3CCH, under single collision conditions: Implications for astrochemistry  

Microsoft Academic Search

The reaction between the ethynyl radical, C2H (X 2?+), and methylacetylene (X 1A1?), which yields ethynylallene, pentadiyne, and butadiyne, has been studied at the density functional (B3LYP\\/6-311+G**) and coupled cluster (coupled-cluster single double perturbative triple\\/cc-pVTZ) levels of theory. These results agree with data from crossed molecular beam experiments where ethynylallene (10) and pentadiyne (13) have been observed. The C2H(1) radical

Frank Stahl; Paul von Rague´ Schleyer; H. F. Bettinger; R. I. Kaiser; Y. T. Lee; H. F. Schaefer

2001-01-01

150

Reaction of the ethynyl radical, C2H, with methylacetylene, CH3CCH, under single collision conditions: Implications for astrochemistry  

Microsoft Academic Search

The reaction between the ethynyl radical, C2H (X 2Sigma+), and methylacetylene (X 1A1'), which yields ethynylallene, pentadiyne, and butadiyne, has been studied at the density functional (B3LYP\\/6-311+G**) and coupled cluster (coupled-cluster single double perturbative triple\\/cc-pVTZ) levels of theory. These results agree with data from crossed molecular beam experiments where ethynylallene (10) and pentadiyne (13) have been observed. The C2H(1) radical

Frank Stahl; Paul von Ragué Schleyer; H. F. Bettinger; R. I. Kaiser; Y. T. Lee; H. F. Schaefer

2001-01-01

151

Formation of molecular chlorine in dark condition: Heterogeneous reaction of ozone with sea salt in the presence of ferric ion  

Microsoft Academic Search

Uptake coefficients of O3 on NaCl and synthetic sea salt (SSS) were found to be enhanced from <10-5 to ~3.5×10-2 in the presence of water-soluble Fe3+ in the Fe\\/Na weight ratio larger than 0.1 %. Cl2 release was observed without radiation in the reaction of O3 and a FeCl3\\/NaCl mixture with surface adsorbed water at the yields of 0.48 and

Yasuhiro Sadanaga; Jun Hirokawa; Hajime Akimoto

2001-01-01

152

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

153

Nature of Ptn/TiO2(110) Interface under Water-Gas Shift Reaction Conditions: A Constrained ab Initio Thermodynamics Study  

SciTech Connect

The electronic structure of small Ptn (n = 1-8) clusters supported on the stoichiometric and partially reduced rutile TiO2(110) surface have been investigated using density functional theory. Pt atoms prefer to form a close-packed structure with (111) facet near an oxygen vacancy of the TiO2 support and a less dense structure with (100) facet away from oxygen vacant sites. Themain focus of this study is on identifying a realistic catalyst model for the Pt/TiO2 interface under watergas shift (WGS) reaction conditions. Constrained ab initio thermodynamic simulations on the stability of oxygen vacancies and formation of adsorbed gas phase molecules such as oxygen, CO, and hydrogen at the metal/oxide interface reveal that under WGS reaction conditions the formation of surface oxygen vacancies are thermodynamically favorable, platinum oxide species (PtOx) can easily be reduced and should not be present, CO adsorbs only weakly on interfacial Pt atoms, and CO poisoning of these sites should be less important. While hydrogen generally interacts weakly with interfacial Pt atoms, it forms very stable hydride species on Pt atoms neighboring an oxygen vacancy of the TiO2(110) support, possibly negatively affecting the WGS reaction rate.

Ammal, Salai Cheettu; Heyden, Andreas

2011-10-06

154

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

NASA Astrophysics Data System (ADS)

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.

Herbschleb, C. T.; van der Tuijn, P. C.; Roobol, S. B.; Navarro, V.; Bakker, J. W.; Liu, Q.; Stoltz, D.; Cańas-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

155

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

156

High-temperature, high-pressure in situ reaction monitoring of heterogeneous catalytic processes under supercritical conditions by CIR-FTIR  

SciTech Connect

An in situ cylindrical internal reflection infrared technique (CIR-FTIR) was developed, which permits the real time analysis of supercritical fluids and heterogeneous catalytic processes at temperatures up to 500{degrees}C and 1000 psi pressure (1 psi = 6850 Pa). High-quality spectra were obtained at both high temperatures and high pressures under in situ reaction conditions. The molecular thermal transitions that a hydrocarbon undergoes in the supercritical regime, the properties of a hydrocarbon within the pores of a zeolite, and the interactions of a hydrocarbon with the active acid sites of the zeolite during catalytic cracking were studied by this technique. The results showed that the stretching frequency of the C-H bonds was altered in supercritical heptane, probably due to intermolecular hydrogen bonding. IR data also demonstrated an increased heptane concentration within the micropores of a commercial catalytic cracking, Y-type zeolite (promoted Octacat) during catalytic cracking at supercritical conditions. This method also enabled a determination of the types of hydroxyl groups contained within the zeolite (i.e., Bronsted acid sites in the supercages and sodalite cages, terminal silanols, and superacid sites) and their relative concentration changes with increasing temperature. Finally, the alteration of the concentrations of the various catalytic active sites together with the appearance of new bands was also monitored in situ during catalytic cracking of heptane at 475{degrees}C under subcritical and supercritical conditions. 38 refs., 11 figs.

Dardas, Z.; Suer, M.G.; Ma, Yi.H.; Moser, W.R. [Worcester Polytechnic Institute, Worcester, MA (United States)] [Worcester Polytechnic Institute, Worcester, MA (United States)

1996-03-01

157

Dissolution of weak acids under laminar flow and rotating disk hydrodynamic conditions: application of a comprehensive convection-diffusion-migration-reaction transport model.  

PubMed

A steady-state mass transfer model that incorporates convection, diffusion, ionic migration, and ionization reaction processes was extended to describe the dissolution of weak acids under laminar flow and a rotating disk hydrodynamics. The model accurately predicted the experimental dissolution rates of benzoic acid, 2-naphthoic acid, and naproxen in unbuffered and monoprotic buffers within the physiological pH range for both hydrodynamic systems. Simulations at various flow rates indicated a cube root dependency of dissolution rate on the flow rate for a given bulk pH value for the laminar hydrodynamic system, as proposed earlier by Shah and Nelson (1975. J Pharm Sci 64(9):1518-1520) for neutral compounds. The model has limitations in its ability to accurately predict the dissolution of weak acids under certain conditions that imposed steep concentration gradients, such as high pH values, and for polyprotic buffer systems that caused the numerical solution to be unstable, suggesting that alternative numerical techniques may be required to obtain a stable numerical solution at all conditions. The model presents many advantages, most notably the ability to successfully predict the complex process under physiological conditions without simplifying assumptions, and therefore accurately representing the system in a comprehensive manner. PMID:22623113

Neervannan, Seshadri; Southard, Marylee Z; Stella, Valentino J

2012-09-01

158

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

SciTech Connect

A novel trapped air injection system has been built for a wire-mesh reactor to enable tests with short exposure times to air that are intended to simulate typical residence times in blast-furnace raceways. Initial tests have shown that the molybdenum wire-mesh sample-holder reacts with O{sub 2} under conditions intended for this work. By varying the proportions of solid MoO{sub 2} (weight gain), vapor phase oxides (weight loss) may form, depending on reaction conditions. Oxide formation pathways thus become relevant to coal weight loss determinations during experiments. If, in addition to solid MoO{sub 2} formation, significant formation of vapor phase oxides occurs, then the weight change is more complicated to understand and the impact on the O{sub 2} concentration cannot be unravelled. Furthermore, it turns out that O{sub 2}-scavenging by the mesh affects the amount of O{sub 2} that is available to react with the coal sample. It was concluded that it is only possible to conduct reliable tests under conditions which the favor the formation of solid MoO{sub 2} only, as this leads to a quantifiable weight gain. Its impact can then be accounted for in the evaluation of the experimental weight change. In the case of MoO{sub 2} formation, the impact of the mesh oxidation on the amount of O{sub 2} available to react with the sample can also be estimated. It has been found that the wire-mesh reactor, equipped with the trapped air injection system, can be used to obtain valid data at up to 1600{sup o} C and 0.5 MPa. This pressure is similar to that of the blast-furnace raceway, but the temperature is several hundred degrees lower. However, preliminary tests have shown that useful kinetic data on the extents of reaction can be obtained with the equipment, provided it is operated under conditions that minimize the formation of vapor phase Mo oxides. 18 refs., 13 figs., 3 tabs.

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

2006-12-15

159

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

160

Involvement of different types of dopamine receptors in the formation of latent inhibition of a conditioned passive avoidance reaction in rats.  

PubMed

The effects of systemic injections of dopaminergic agents on normal and weak latent inhibition of a conditioned passive avoidance reaction were studied in rats. Formation of normal latent inhibition was induced using 20 pre-exposures to a contextual conditioned stimulus prior to training. Weak latent inhibition was modeled using 10 pre-exposures. The effects of the D(2)/D(3) receptor agonist quinpirole (1 mg/kg) and the D(1) receptor agonist SKF 38393 (1 mg/kg) separately and in combination with haloperidol (0.5 mg/kg) were tested. Quinpirole induced the expression of normal latent inhibition but had no effect on weak latent inhibition. Activation of D(1) receptors with SKF 38393 had no effect on the formation of latent inhibition regardless of the number of pre-exposures. Haloperidol significantly strengthened weak latent inhibition but impaired normal latent inhibition. Administration of haloperidol in combination with SKF 38393 prevented this impairment. These results suggest that while D(1) receptors have no influence as an independent substrate on the formation of latent inhibition, activation of these receptors is required for the complete manifestation of D(2)-mediated modulation of this process. PMID:20490693

Loskutova, L V; Kostyunina, N V; Dubrovina, N I

2010-06-01

161

Reaction mechanism for the aqueous-phase mineral carbonation of heat-activated serpentine at low temperatures and pressures in flue gas conditions.  

PubMed

Mineral carbonation is known as one of the safest ways to sequester CO2. Nevertheless, the slow kinetics and low carbonation rates constitute a major barrier for any possible industrial application. To date, no studies have focused on reacting serpentinite with a relatively low partial pressure of CO2 (pCO2) close to flue gas conditions. In this work, finely ground and heat-treated serpentinite [Mg3Si2O5(OH)4] extracted from mining residues was reacted with a 18.2 vol % CO2 gas stream at moderate global pressures to investigate the effect on CO2 solubility and Mg leaching. Serpentinite dissolution rates were also measured to define the rate-limiting step. Successive batches of gas were contacted with the same serpentinite to identify surface-limiting factors using scanning electron microscopy (SEM) analysis. Investigation of the serpentinite carbonation reaction mechanisms under conditions close to a direct flue gas treatment showed that increased dissolution rates could be achieved relative to prior work, with an average Mg dissolution rate of 3.55 × 10(-11) mol cm(-2) s(-1). This study provides another perspective of the feasibility of applying a mineral carbonation process to reduce industrial greenhouse gas (GHG) emissions from large emission sources. PMID:24669999

Pasquier, Louis-César; Mercier, Guy; Blais, Jean-François; Cecchi, Emmanuelle; Kentish, Sandra

2014-05-01

162

Influence of experimental conditions on the formation of PCDD/Fs during the thermal reactions of 2,4,6-trichlorophenol.  

PubMed

In order to obtain information on thermochemical reactions of chlorophenols, which are well known as dioxin precursors, occurring during the combustion of municipal solid wastes, the combustion of 2,4,6-trichlorophenol (2,4,6-T(3)CP) in an air stream was investigated over a temperature range of 500-800 degrees C for a residence time of 1-20s using a quartz flow reactor. Gas chromatographic/mass spectrometric (GC/MS) analysis of the gaseous products and residues showed that 2,4,6-T(3)CP began to decompose at 500 degrees C and produced several compounds, with 1,3,6,8- and 1,3,7,9-tetrachlorodibenzo-p-dioxins (T(4)CDD) as the major products. In addition, more than fifty organic products were observed in our experimental conditions. The yields of polychlorinated benzenes, phenols, dibenzofurans, and dibenzo-p-dioxins formed during the combustion of 2,4,6-T(3)CP were plotted as a function of temperature and residence time. Furthermore, it was found that the yields and the compositions of these gaseous products were strongly dependent on the residence time in the flow reactor. PMID:19398119

Kishi, Tomohiro; Suzuki, Shota; Takagi, Mai; Kawakami, Tsuyoshi; Onodera, Sukeo

2009-06-01

163

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

164

Silver Crystals Through Tollen's Reaction.  

National Technical Information Service (NTIS)

A method for the formation of regular-shaped silver crystals through a wet chemical reaction (Tollen's reaction) is presented. The growth of the Ag crystals (size, morphology and aggregation) can be controlled via adjusting reaction conditions such as tem...

D. Fries, X. Ding

2005-01-01

165

Comparison of human serum and bovine serum albumins on oxidation dynamics induced by talaporfin sodium photosensitization reaction with albumin rich conditions: solution experiments  

NASA Astrophysics Data System (ADS)

In order to understand extracellular-photosensitization reaction (PR) using talaporfin sodium, we studied comparison of oxidation dynamics of albumin and talaporfin sodium in solution system by visible and ultraviolet absorption spectrum measurements. Almost all talaporfin sodium particles may be bound to albumin in interstitial fluid, and this binding would affect the oxidation dynamics during this PR. Bovine serum albumin (BSA) is commonly used in vitro study but its binding characteristics with talaporfin sodium are different from human serum albumin (HSA). PR was operated in a solution composed of 20 ?g/ml talaporfin sodium and 1.3 mg/ml HSA or BSA to simulate myocardial extracellular PR condition. Laser radiation of 662 nm was irradiated to this solution with irradiance of 0.29 W/cm2. Absorption spectra of these solutions were measured during the PR. We estimated oxidized ratio by absorption difference around 240 nm before and after the PR. Talaporfin sodium was oxidized 100% with HSA and BSA by the PR of 100 J/cm2 in radiant exposure. On the other hand, HSA and BSA were oxidized 60% and 94%, respectively in this radiant exposure. Q-band absorption peak of talaporfin sodium with HSA was shifted to 1 nm longer wavelength increasing radiant exposure up to 100 J/cm2. This longer wavelength shift would mean binding ratio of non-oxidized talaporfin sodium to non-oxidized HSA was increased with increasing radiant exposure. Therefore it would be possible that PR with talaporfin sodium bound to HSA might present efficient PDT than PR bound to BSA.

Kurotsu, Mariko; Nakamura, Tetsuya; Takahashi, Mei; Ogawa, Emiyu; Arai, Tsunenori

2014-02-01

166

Effect of continuous irradiation with terahertz electromagnetic waves of the NO frequency range on behavioral reactions of male albino rats under stress conditions.  

PubMed

We studied the effect of terahertz waves (NO frequency range, 150.176-150.664 GHz) on stress-induced variations in behavioral reactions of male albino rats during hypokinetic stress. THz irradiation was followed by partial or complete normalization of behavioral reactions of male albino rats after hypokinetic stress. The most significant effect was observed after continuous irradiation for 30 min. PMID:24952484

Kirichuk, V F; Antipova, O N; Krylova, Ya A

2014-06-01

167

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

SciTech Connect

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

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

2012-05-01

168

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

169

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

170

Reactions & Rates  

NSDL National Science Digital Library

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

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

2006-12-01

171

Measurement of the rotational distribution for the OD product from the reaction ND3 D2O~ND4 OD under translationally thermal conditions  

E-print Network

that are present. LIF detec- tion offers two advantages: LIF can be used to detect the products with rotationalMeasurement of the rotational distribution for the OD product from the reaction ND3 D2O~ND4 OD product buildup, the rotational distribution of the OD(v 0) product is measured by recording the OD A2 X2

Zare, Richard N.

172

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...

173

Optimization of reaction conditions in selective oxidation of styrene over fine crystallite spinel-type CaFe{sub 2}O{sub 4} complex oxide catalyst  

SciTech Connect

The CaFe{sub 2}O{sub 4} spinel-type catalyst was synthesized by citrate gel method and well characterized by thermogravimetric analysis, atomic absorption spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The crystallization temperature of the spinel particle prepared by citrate gel method was 600 {sup o}C which was lower than that of ferrite prepared by other methods. CaFe{sub 2}O{sub 4} catalysts prepared by citrate gel method show better activity for styrene oxidation in the presence of dilute H{sub 2}O{sub 2} (30%) as an oxidizing agent. In this reaction the oxidative cleavage of carbon-carbon double bond of styrene takes place selectively with 38 {+-} 2 mol% conversion. The major product of the reaction is benzaldehyde up to 91 {+-} 2 mol% and minor product phenyl acetaldehyde up to 9 {+-} 2 mol%, respectively. The products obtained in the styrene oxidation reaction were analyzed by gas chromatography and mass spectroscopy. The influence of the catalyst, reaction time, temperature, amount of catalyst, styrene/H{sub 2}O{sub 2} molar ratio and solvents on the conversion and product distribution were studied.

Pardeshi, Satish K., E-mail: skpar@chem.unipune.ernet.in [Department of Chemistry, University of Pune, Ganeshkhind, Pune 411007 (India); Pawar, Ravindra Y. [Department of Chemistry, University of Pune, Ganeshkhind, Pune 411007 (India)] [Department of Chemistry, University of Pune, Ganeshkhind, Pune 411007 (India)

2010-05-15

174

Connecting the dots: Semi-analytical and random walk numerical solutions of the diffusion-reaction equation with stochastic initial conditions  

NASA Astrophysics Data System (ADS)

We study a system with bimolecular irreversible kinetic reaction A+B?? where the underlying transport of reactants is governed by diffusion, and the local reaction term is given by the law of mass action. We consider the case where the initial concentrations are given in terms of an average and a white noise perturbation. Our goal is to solve the diffusion-reaction equation which governs the system, and we tackle it with both analytical and numerical approaches. To obtain an analytical solution, we develop the equations of moments and solve them approximately. To obtain a numerical solution, we develop a grid-less Monte Carlo particle tracking approach, where diffusion is modeled by a random walk of the particles, and reaction is modeled by annihilation of particles. The probability of annihilation is derived analytically from the particles' co-location probability. We rigorously derive the relationship between the initial number of particles in the system and the amplitude of white noise represented by that number. This enables us to compare the particle simulations and the approximate analytical solution and offer an explanation of the late time discrepancies.

Paster, Amir; Bolster, Diogo; Benson, David A.

2014-04-01

175

The 5HT 1A agonist 8-OH-DPAT dose-dependently interferes with the establishment and the expression of lithium-induced conditioned rejection reactions in rats  

Microsoft Academic Search

  Abstract\\u000a \\u000a \\u000a Rationale. The present experiments evaluated the potential of the 5-HT1A agonist, 8-OH-DPAT (DPAT), which reduces serotonin availability, to interfere with both the establishment and with the expression\\u000a of lithium-induced conditioned rejection reactions (experiment 1) and lithium-induced taste avoidance (experiment 2).\\u000a \\u000a \\u000a \\u000a \\u000a Objectives. To determine the effect of reduced serotonin availability on conditioned rejection reactions, a rat model of nausea.\\u000a \\u000a \\u000a \\u000a \\u000a Methods.

Cheryl L. Limebeer; Linda A. Parker

2003-01-01

176

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

177

Aluminium(III) fluoride originating from decomposition of hydrazinium fluoroaluminate(III) under oxidative conditions: Syntheses, X-ray photoelectron spectroscopy and some catalytic reactions  

Microsoft Academic Search

Decomposition of hydrazinium pentafluoroaluminate under oxidative (F2) conditions leads to aluminium(III) fluoride whose properties are highly dependent on the conditions used for synthesis. In the presence of anhydrous HF, which probably acts as a heat exchange agent, samples have high BET areas, whereas BET areas of samples prepared under gas–solid conditions are small. XPS data are consistent with the presence

Tomaž Skapin; Zoran Mazej; Anna Makarowicz; Adolf Jesih; Mahmood Nickkho-Amiry; Sven L. M. Schroeder; Norbert Weiher; Boris Žemva; John M. Winfield

2011-01-01

178

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

179

Asymmetric Epoxidation of Allylic Alcohols Catalyzed by (?SiO) x Ta(OEt) 3- x (Dialkyl Tartrate Diolate): Influence of the Reaction Conditions  

Microsoft Academic Search

Silica-supported chiral tantalum alkoxides are active catalysts for the asymmetric epoxidation of propenol and trans hex-2-en-1ol. The influence of different parameters on their catalytic performance was followed: the impregnation duration by a tartrate (step in their preparation); the nature of the solvent (CH2Cl2, pentane, toluene) and of the oxidant (TBHP, CHP, H2O2); poisoning effects by water or t-butanol; the reaction

Damien Meunier; Aimery de Mallmann; Jean-Marie Basset

2003-01-01

180

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

181

Hydride as a leaving group in the reaction of pinacolborane with halides under ambient Grignard and Barbier conditions. One-pot synthesis of alkyl, aryl, heteroaryl, vinyl, and allyl pinacolboronic esters.  

PubMed

Grignard reagents (aliphatic, aromatic, heteroaromatic, vinyl, or allylic) react with 1 equiv of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (pinacolborane, PinBH) at ambient temperature in tetrahydrofuran (THF) to afford the corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride intermediate quickly eliminates hydridomagnesium bromide (HMgBr) and affords the product boronic ester in very good yield. Hydridomagnesium bromide (HMgBr) in turn disproportionates to a 1:1 mixture of magnesium hydride (MgH(2)) and magnesium bromide (MgBr(2)) on addition of pentane to the reaction mixture. DFT calculations (Gaussian09) at the B3LYP/6-31G(d) level of theory show that disproportionation of HMgBr to MgH(2) and MgBr(2) is viable in the coordinating ethereal solvents. This reaction also can be carried out under Barbier conditions, where the neat PinBH is added to the flask prior to the in situ formation of Grignard reagent from the corresponding organic halide and magnesium metal. Pinacolboronic ester synthesis under Barbier conditions does not give Wurtz coupling side products from reactive halides, such as benzylic and allylic halides. The reaction between PinBH and various Grignard reagents is an efficient, mild, and general method for the synthesis of pinacolboronates. PMID:22040316

Clary, Jacob W; Rettenmaier, Terry J; Snelling, Rachel; Bryks, Whitney; Banwell, Jesse; Wipke, W Todd; Singaram, Bakthan

2011-12-01

182

Stochastic stability criteria with LMI conditions for Markovian jumping impulsive BAM neural networks with mode-dependent time-varying delays and nonlinear reaction-diffusion  

NASA Astrophysics Data System (ADS)

In this paper, the problem of stochastic stability for Markovian jumping impulsive BAM neural networks with mode-dependent time-varying delays and nonlinear diffusion has been investigated. The non-linear p-Laplace diffusion gives a great difficulty in playing its role about judging the stability of stochastic system. By employing the Lyapunov technique, the linear matrix inequality (LMI) approach and variational methods in Sobolev space W(?), a series of new criteria are obtained. The new criteria have advantages over some previous ones due to less conservatism and higher computational efficiency. Besides, since linear Laplace reaction-diffusion is only the special example of p-Laplacian (in the case of p=2), the new criteria and the numerical example's methods are more general than some existing results. A numerical example is given to illustrate the effectiveness of the proposed methods.

Rao, Ruofeng; Zhong, Shouming; Wang, Xiongrui

2014-01-01

183

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

Microsoft Academic Search

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

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

2009-01-01

184

The role of Fe and redox conditions in olivine carbonation rates: An experimental study of the rate limiting reactions at 90 and 150 °C in open and closed systems  

NASA Astrophysics Data System (ADS)

The mechanisms and rates of olivine carbonation reactions have been the object of a number of studies, but the thermodynamic limitations and the kinetics of the elementary processes that control the overall reaction are still poorly understood and characterized. The main objective of this study is to probe the effect of Fe on the measured rates of olivine carbonation and its role in the formation of Si-rich surface layers, which can significantly inhibit olivine dissolution and limit the extent of the carbonation reaction. A series of batch and flow-through reactor experiments was conducted in pure water at 90 and 150 °C and under a CO2 partial pressure of 100 and 200 bar, using both a natural sample of Fe-bearing olivine (Fo88) and a synthetic sample of pure forsterite (Fo100). Experimental results show that Fe plays an ambivalent role in the carbonation rates of olivine. On one hand, the presence of Fe favors the formation of Fe-Si-rich protective layers at the interface between olivine and aqueous solution, slowing down the dissolution reaction and limiting the extent of carbonation, whereas pure silica coatings have little to no inhibiting effect on measured carbonation rates. On the other hand, Fe enhances olivine to carbonate conversion rates at low degrees of supersaturation, by promoting the formation of fast precipitating Mg-Fe carbonate solid solutions. The passivating properties of Fe-Si-rich layers originate from the strong Fe(III)-Si interaction and are linked to the permanence of oxidizing conditions in the aqueous fluid. As a consequence, under reducing conditions, olivine carbonation rates can be significantly increased by higher extents of dissolution and by the formation of ferroan magnesites (Mg,Fe)CO3, which nucleate faster than the pure Mg end-member. Forsterite and olivine carbonation reactions can be hindered by the formation of secondary Mg sheet-silicates but, at the conditions studied, the formation of such silicate phases was observed to be transitional and not affecting significantly the rates of carbonation at the end of one-month long experimental runs. This work presents new measurements of olivine carbonation rates and delivers relevant information that suggest new reference criteria for the assessment of the sequestration potential of CO2 repositories and the optimization of the mineral carbonation process in mafic and ultramafic rocks.

Saldi, Giuseppe D.; Daval, Damien; Morvan, Gilles; Knauss, Kevin G.

2013-10-01

185

Role of Anions and Reaction Conditions in the Preparation of Uranium(VI), Neptunium(VI), and Plutonium(VI) Borates  

SciTech Connect

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

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

2011-01-01

186

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

PubMed

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

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

2006-06-01

187

CO2 Reaction Induced Wettability Alteration and its Impacts on CO2 Storage: Pore to Core Scale Reservoir Condition Experimental Studies  

NASA Astrophysics Data System (ADS)

Wettability of the mineral surfaces plays an important role in subsurface multiphase flow and transport. Wettability affects the capillary pressure-saturation (Pc- S) relations, relative permeability (kr) of each fluid phase, and relative phase occupancy in reservoir pores. Although wettability issues have been studied extensively in other fields, significant knowledge gaps remain when applying the existing understanding to geological carbon sequestration; due largely to the unique physical-chemical properties of supercritical (sc) CO2 relative to other common non-wetting fluids such as air and oil. Here, we report our recent progress on wettability alteration upon reaction with CO2 and the resulting differences in capillary trapping of CO2 versus air. (1) Pore Scale Studies. There are conflict predictions in the literature concerning the effect of wettability on capillary trapping; some find that larger contact angles lead to lower capillary trapping while others have found opposite behavior. We hypothesized that spontaneous imbibition becomes energetically unfavorable with decreased wettability, so that increased residual trapping of scCO2 should occur during the post-injection inbibition stage. We developed a laboratory high-pressure and elevated temperature microscopic-micromodel system that is capable of controlling fine scale capillary pressure of scCO2-brine, and enabled us to conduct imbibition under controlled capillary pressures at the pore scale. We found that the de-wetting enhanced scCO2 capillary trapping is significant. These results suggest that scCO2 reaction induced dewetting can result in higher degrees of CO2 residual trapping in the post-injection stage than previously predicted. (2) Core Scale Studies. Capillary scaling is used routinely to predict Pc(S) relations for scCO2-brine systems at field scale, based on relations measured with air-water or mercury porosimetry. However, scaling-based predictions for CO2-brine systems have not been fully tested. Current limitations include the fact that imbibition curves are seldom measured due to experimental difficulties in controlling capillary pressure, and wettability (contact angles) is usually unknown and applied as adjustable parameters. Applying a new laboratory system to accurately control Pc at high total P, and we measured Pc(S) of a homogeneous quartz sand (selected because its 'normal' hydraulic properties are very well constrained). Drainage and imbibition experiments were conducted to directly measure Pc(S) with air-brine, then with scCO2-brine. With scCO2, intermediate levels of S shifted to Pc values 30% to 90% lower than predicted based on scaling with interfacial tension. Capillary trapping of CO2 were measured at Pc = 0 during brine imbibition, with trapped volumes for scCO2 significantly greater than for trapped air. We conclude that the observed deviations from scaling predictions make predicting the hydraulic behavior of scCO2 in reservoirs more challenging, and that an understanding of scCO2-induced wettability change is needed.

Wan, J.; Tokunaga, T. K.; Kim, Y.; Jung, J.; Kim, T.; Dong, W.

2013-12-01

188

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

189

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

190

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

191

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

192

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

193

Nuclear Reactions  

Microsoft Academic Search

Nuclear reactions generate energy in nuclear reactors, in stars, and are responsible for the existence of all elements heavier than hydrogen in the universe. Nuclear reactions denote reactions between nuclei, and between nuclei and other fundamental particles, such as electrons and photons. A short description of the conservation laws and the definition of basic physical quantities is presented, followed by

C. A. Bertulani

2009-01-01

194

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

195

Special Reactions  

NSDL National Science Digital Library

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

Robertson, William C.

2010-03-01

196

Heterogeneous reactions of particulate matter-bound PAHs and NPAHs with NO3/N2O5, OH radicals, and O3 under simulated long-range atmospheric transport conditions: reactivity and mutagenicity.  

PubMed

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO3/N2O5, OH radicals, and O3 were studied in a laboratory photochemical chamber. Ambient PM2.5 and PM10 samples were collected from Beijing, China, and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O3 and OH and NO3 radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO3/N2O5, OH radicals, and O3. In general, O3 exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O3 and NO3/N2O5). However, NPAHs were most effectively formed during the Beijing PM exposure to NO3/N2O5. In ambient air, 2-nitrofluoranthene (2-NF) is formed from the gas-phase NO3 radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from the gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO3/N2O5 resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas-phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction. PMID:25119270

Jariyasopit, Narumol; Zimmermann, Kathryn; Schrlau, Jill; Arey, Janet; Atkinson, Roger; Yu, Tian-Wei; Dashwood, Roderick H; Tao, Shu; Simonich, Staci L Massey

2014-09-01

197

Green chemistry approaches to the synthesis of 5-alkoxycarbonyl-4-aryl-3,4- dihydropyrimidin-2(1H)-ones by a three-component coupling of one-pot condensation reaction: comparison of ethanol, water, and solvent-free conditions.  

PubMed

A general and practical green chemistry route to the Biginelli cyclocondensation reaction using cerium(III) chloride as the catalyst (25% mol) is described under three different sets of reaction conditions. This method provides an efficient and much improved modification of original Biginelli reaction reported in 1893, in terms of high yields, short reaction times, and simple work-up procedure, and it has the ability to tolerate a wide variety of substitutions in all three components, which is lacking in existing procedures. PMID:12530887

Bose, D Subhas; Fatima, Liyakat; Mereyala, Hari Babu

2003-01-24

198

Nuclear Reactions  

Microsoft Academic Search

Nuclear reactions generate energy in nuclear reactors, in stars, and are\\u000aresponsible for the existence of all elements heavier than hydrogen in the\\u000auniverse. Nuclear reactions denote reactions between nuclei, and between nuclei\\u000aand other fundamental particles, such as electrons and photons. A short\\u000adescription of the conservation laws and the definition of basic physical\\u000aquantities is presented, followed by

C. A. Bertulani; B. Kinematics

2009-01-01

199

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...

200

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

201

Environmental Conditions Environmental Conditions  

E-print Network

, developed complex life histories through time that responded to the subbasin's considerable variation in this habitat. Loss of grassland habitat greatly reduced such populations. Today subbasin habitat conditions/optimal) conditions in the year 2050, and examines what future conditions might be expected if no additional future

202

Chemical Reactions  

NSDL National Science Digital Library

We are going go over a general view of reactions to prepare us for our unit on Chemical Reactions! Have fun learning! WARNING: If you are caught looking at ANY other site, without permission, you will be sent to the ALC, and you will not participate in any other computer activities for the rest of the year. Get your worksheet and begin! Overview Take this quiz and have me come over and sign off on your worksheet when you have completed the quiz! Overview Quiz Next let's take a look at what effect the rate of a chemical reaction. Rates of Reactions Another quiz, another check off by me! Rates of Reactions Quiz Now how do we measure how fast a ...

Hicken, Mrs.

2009-05-04

203

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

204

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

205

QD-antibody conjugates via carbodiimide-mediated coupling: a detailed study of the variables involved and a possible new mechanism for the coupling reaction under basic aqueous conditions.  

PubMed

A detailed study into the optimization of carbodiimide-mediated coupling of antibodies (Ab) and quantum dots (QD) for use in cellular imaging has been undertaken. This involved the grafting of commercially available carboxyl-modified QDs (Evident Technologies "Lake Placid Blue" Evitag and eBioscience's eflour nanocrystals) with anti-Cdc8 Abs to produce conjugates with specific affinity for fission yeast tropomyosin Cdc8 protein. The water-soluble carbodiimide 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was used to activate the QDs prior to their incubation with antibody, and a range of QD-carboxyl/EDC/Ab mole ratios were used in the experiments in attempts to optimize fluorescence and bioaffinity of the conjugate products (EDC to QD-carboxyl-600 nmol/15 pmol to 0.12 nmol/15 pmol and QD to Ab 120 pmol/24 pmol to 120 pmol/1.2 pmol). It was observed that a specific "optimum" ratio of the three reactants was required to produce the most fluorescent and biologically active product and that it was generated at alkaline pH 10.8. Increasing the ratio of Ab to QD produced conjugate which was less fluorescent while reducing the ratio of EDC to QD in the activation step led to increased fluorescence of product. Conjugates were tested for their possession of antibody by measurement of their absorption at OD(280 nm) and for their fluorescence by assay ?(max(em)) at 495 nm. A quantitative assay of the bioactivity of the conjugates was developed whereby a standardized amount of Cdc8 antigen was spotted onto nylon membranes and reacted with products from conjugation reactions in a sandwich-type colormetric assay The "best" conjugate was used in intracellular imaging of yeast Cdc8 protein and produced brighter, higher definition images of fixed yeast cell actin structure than a fluorescein-Ab conjugate routinely produced in our laboratory. The QD-Ab conjugate was also significantly more resistant to photobleaching than the fluorescein-Ab conjugate. Results from other experiments involving EDC, the water-soluble carbodiimide 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulphonate (CMC), and EDC.HCl have suggested a new reaction mechanism for EDC coupling under basic aqueous conditions. In summary, a robust understanding of commercial QD-COOH surface chemistry and the variables involved in the materials' efficient conjugation with a bioligand using carbidiimide has been obtained along with an optimized approach for Ab-QD conjugate production. A novel assay has been developed for bioassay of QD-Ab conjugates and a new mechanism for EDC coupling under basic aqueous conditions is proposed. PMID:21970592

East, Daniel A; Mulvihill, Daniel P; Todd, Michael; Bruce, Ian J

2011-11-15

206

Laser-initiated chemical chain reactions  

Microsoft Academic Search

A detailed kinetic and experimental analysis is presented for chemical chain reaction processes initiated by well-controlled, low power laser pulses. Realtime evolution of the chain reaction is followed by direct detection of infrared chemiluminescence from vibrationally excited HCl product molecules produced by one of the propagation reactions in the chain. By appropriate choice of conditions, the chain reactions may be

David J. Nesbitt; Stephen R. Leone

1980-01-01

207

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 ...

208

Allergic Reactions  

MedlinePLUS

... For instance, if you have an allergy to pollen, your immune system identifies pollen as an invader or allergen . Your immune system ... it can affect a child's speech and language development. Diagnosing and Treating Allergic Reactions An allergist / immunologist, ...

209

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.

210

Enzyme Reactions  

NSDL National Science Digital Library

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

School, Maryland V.

211

Fundamental reaction pathways during coprocessing  

SciTech Connect

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

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

1992-12-01

212

Wittig Reaction 33 Reaction: Synthesis of Alkenes  

E-print Network

elimination reactions (E1 or E2 reactions from alcohols or alkyl halides, for example), in eliminationWittig Reaction 33 The Wittig Reaction: Synthesis of Alkenes Intro The "Wittig Reaction" is one reactions the carbon skeleton is already pre-assembled. In the Wittig reaction, however, two smaller carbon

Jasperse, Craig P.

213

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

214

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

215

Granulomatous Reaction to Descemet'S Membrane.  

National Technical Information Service (NTIS)

A granulomatous reaction to Descemet's membrane was found in 28 of 298 consecutive eyes with corneal ulcer or keratitis. The reaction was seen in a variety of corneal conditions but most frequently in eyes with a disciform keratitis, either with or withou...

W. R. Green, L. E. Zimmerman

1967-01-01

216

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

217

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

218

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

219

Recent advances in Sonogashira reactions.  

PubMed

The coupling of aryl or vinyl halides with terminal acetylenes catalysed by palladium and other transition metals, commonly termed as Sonogashira cross-coupling reaction, is one of the most important and widely used sp(2)-sp carbon-carbon bond formation reactions in organic synthesis, frequently employed in the synthesis of natural products, biologically active molecules, heterocycles, molecular electronics, dendrimers and conjugated polymers or nanostructures. This critical review focuses on developments in the Sonogashira reaction achieved in recent years concerning catalysts, reaction conditions and substrates (352 references). PMID:21655588

Chinchilla, Rafael; Nájera, Carmen

2011-10-01

220

Formation of three N-acetyl-L-cysteine monoadducts and one diadduct by the reaction of S-(1,2-dichlorovinyl)-L-cysteine sulfoxide with N-acetyl-L-cysteine at physiological conditions: chemical mechanisms and toxicological implications.  

PubMed

Previously, our laboratory has shown that S-(1,2-dichlorovinyl)-L-cysteine sulfoxide (DCVCS), a Michael acceptor produced by a flavin-containing monooxygenase 3 (FMO3)-mediated oxidation of S-(1,2-dichlorovinyl)-L-cysteine (DCVC), is a more potent nephrotoxicant than DCVC. In the present study, we characterized reactions of DCVCS with nucleophilic amino acids. DCVCS incubations with N-acetyl-L-cysteine (NAC) at pH 7.4 and 37 degrees C for 1 h resulted in the formation of three monoadducts and one diadduct characterized by LC/MS, 1H NMR, and 1H-detected heteronuclear single quantum correlation. The formation of all adducts (with relative ratios of 29, 31, 24, and 12%, respectively) was rapid and time-dependent; the half-lives of the two DCVCS diastereomers in the presence of NAC were 13.8 (diastereomer I) and 9.4 min (diastereomer II). Adducts 1 and 2 were determined to be diastereomers of S-[1-chloro-2-(N-acetyl-L-cystein- S-yl)vinyl]-L-cysteine sulfoxide formed by Michael addition of NAC to the terminal vinylic carbon of DCVCS followed by loss of HCl. Adduct 4 was determined to be S-[2-chloro-2-(N-acetyl-L-cystein- S-yl)vinyl]-L-cysteine sulfoxide formed from the initial Michael addition product followed by a less favorable loss of HCl and/or by a rearrangement of adduct 2 through the formation of a cyclic chloronium ion. The addition of another molecule of NAC to monoadducts 1, 2, or 4 resulted in the formation of the novel diadduct, S-[2,2-( N-acetyl-L-cystein-S-yl)vinyl]-L-cysteine sulfoxide (adduct 3), whose detection in relatively large amount suggests that DCVCS could act as a cross-linking agent. DCVCS was not reactive with N-acetyl-L-lysine or L-valinamide at similar incubation conditions. Collectively, the results suggest selective reactivity of DCVCS toward protein sulfhydryl groups. Furthermore, the cross-linking properties of DCVCS may in part explain its high nephrotoxic potency. PMID:17892265

Barshteyn, Nella; Elfarra, Adnan A

2007-10-01

221

Formamidine Reactions  

E-print Network

.36$, 8.44$ Calculated for C ^ O ^ B r , nitrogen = 3.16$. METHYL IS0XAZ0L0N DERIVATIVES. The amido methylene derivatives of methyl lsoxazolon should be obtainable by the same methods as those of phenyl lsoxazolon. There are however, two practical... hydrochloid is neutralized. If it is neutralized with pyirldene the following reaction takes place. CH3 0 -==-C 'COHHR H«C - 0 * COINHR ' 1 II /I 0 CH v " " 1 - = N-O-O-OH, + H,0 f-R UH- H * flTO 3 HO- JT/Ha I t This gives the aMde of 5-methyl...

Griffin, E. L.

1913-05-15

222

Subdiffusion-reaction processes with A ?B reactions versus subdiffusion-reaction processes with A +B?B reactions  

NASA Astrophysics Data System (ADS)

We consider the subdiffusion-reaction process with reactions of a type A +B?B (in which particles A are assumed to be mobile, whereas B are assumed to be static) in comparison to the subdiffusion-reaction process with A ?B reactions which was studied by Sokolov, Schmidt, and Sagués [Phys. Rev. E 73, 031102 (2006), 10.1103/PhysRevE.73.031102]. In both processes a rule that reactions can only occur between particles which continue to exist is taken into account. Although in both processes a probability of the vanishing of particle A due to a reaction is independent of both time and space variables (assuming that in the system with the A +B?B reactions, particles B are distributed homogeneously), we show that subdiffusion-reaction equations describing these processes as well as their Green's functions are qualitatively different. The reason for this difference is as follows. In the case of the former reaction, particles A and B have to meet with some probability before the reaction occurs in contradiction with the case of the latter reaction. For the subdiffusion process with the A +B?B reactions we consider three models which differ in some details concerning a description of the reactions. We base the method considered in this paper on a random walk model in a system with both discrete time and discrete space variables. Then the system with discrete variables is transformed into a system with both continuous time and continuous space variables. Such a method seems to be convenient in analyzing subdiffusion-reaction processes with partially absorbing or partially reflecting walls. The reason is that within this method we can determine Green's functions without a necessity of solving a fractional differential subdiffusion-reaction equation with boundary conditions at the walls. As an example, we use the model to find the Green's functions for a subdiffusive reaction system (with the reactions mentioned above), which is bounded by a partially absorbing wall. This example shows how the model can be used to analyze the subdiffusion-reaction process in a system with partially absorbing or reflecting thin membranes. Employing a simple phenomenological model, we also derive equations related to the reaction parameters used in the considered models.

Koszto?owicz, Tadeusz; Lewandowska, Katarzyna D.

2014-09-01

223

Radicals and Hydroxy Radical Reactions in Troposphere  

E-print Network

with same molecule? { Which dominates? Depends on reaction rates-details of conditions and molecule. The art that OH can abstract in an exothermic reaction, this generally occurs #15; Bond strengths important: O HRadicals and Hydroxy Radical Reactions in Troposphere Examples of ground state radicals: 1. H atom

Schofield, Jeremy

224

Incidents of chemical reactions in cell equipment  

SciTech Connect

Strongly exothermic reactions can occur between equipment structural components and process gases under certain accident conditions in the diffusion enrichment cascades. This paper describes the conditions required for initiation of these reactions, and describes the range of such reactions experienced over nearly 50 years of equipment operation in the US uranium enrichment program. Factors are cited which can promote or limit the destructive extent of these reactions, and process operations are described which are designed to control the reactions to minimize equipment damage, downtime, and the possibility of material releases.

Baldwin, N.M.; Barlow, C.R. [Uranium Enrichment Organization, Oak Ridge, TN (United States)

1991-12-31

225

Thermal explosion of autocatalytic reaction  

Microsoft Academic Search

Analytical and numerical solutions are used to determine the critical conditions for thermal explosion of autocatalytic reaction. The solutions covers both the reaction governed by the Arrhenius kinetics equation and the Frank-Kamenetskii approximation for that equation. The definition of criticality as the point at which d2?\\/d?2=0, d3?\\/d?3=0 and d?\\/d??0 is used here. The study is dealt with low and high

Saad A. El-Sayed

2003-01-01

226

Chromosomal Conditions  

MedlinePLUS

... 150 babies is born with a chromosomal condition. Down syndrome is an example of a chromosomal condition. Because ... all pregnant women be offered prenatal tests for Down syndrome and other chromosomal conditions. A screening test is ...

227

Low Energy Nuclear Reactions?  

E-print Network

After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

CERN. Geneva; Faccini, R.

2014-01-01

228

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

229

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

230

Nanoplasmonic probes of catalytic reactions.  

PubMed

Optical probes of heterogeneous catalytic reactions can be valuable tools for optimization and process control because they can operate under realistic conditions, but often probes lack sensitivity. We have developed a plasmonic sensing method for such reactions based on arrays of nanofabricated gold disks, covered by a thin (approximately 10 nanometer) coating (catalyst support) on which the catalyst nanoparticles are deposited. The sensing particles monitor changes in surface coverage of reactants during catalytic reaction through peak shifts in the optical extinction spectrum. Sensitivities to below 10(-3) monolayers are estimated. The capacity of the method is demonstrated for three catalytic reactions, CO and H2 oxidation on Pt, and NO(x) conversion to N2 on Pt/BaO. PMID:19933104

Larsson, Elin M; Langhammer, Christoph; Zori?, Igor; Kasemo, Bengt

2009-11-20

231

Adalimumab induced pulmonary sarcoid reaction  

PubMed Central

Sarcoidosis is a multisystem granulomatous inflammatory disease of unknown etiology. There is evidence that Tumor Necrosis Factor alpha (TNF-?) antagonists are useful in the treatment of advanced or refractory disease. However, sarcoidosis-like reaction has been reported with TNF-? blockade in other inflammatory conditions. Here we report a case of sarcoid-like reaction in a patient with psoriatic arthritis shortly after initiation of adalimumab therapy. Stopping adalimumab and systemic anti-inflammatory therapy with corticosteroids resulted in resolution of pulmonary symptoms and chest radiographic findings. Though TNF-? plays a critical role in pathogenesis of sarcoidosis, the development of sarcoid reaction with TNF-? blockade is paradoxical and the mechanism of this response remains unknown. TNF-? induced sarcoid-reaction could involve multiple organs. Its development with one agent does not preclude therapy with other TNF-? blockers.

Bhargava, S.; Perlman, D.M.; Allen, T.L.; Ritter, J.H.; Bhargava, M.

2013-01-01

232

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

233

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

234

Continuity and change?: Exploring reactions to a guided self-management intervention in a randomised controlled trial for IBS with reference to prior experience of managing a long term condition  

Microsoft Academic Search

Self-care interventions are promoted as effective strategies for improving the quality of life and health outcomes for individuals with long-term health conditions. Outcome measures used in evaluations using Randomised Controlled Trials (RCTs) are not designed to consider patients' prior management strategies and experience of illness. Yet the experience of illness literature suggests that adjusting to living with chronic illness, together

Anne Rogers; Victoria Lee; Anne Kennedy

2007-01-01

235

The isothermal sulphation reactions of natural sorbents  

Microsoft Academic Search

The chemical reaction between sulphur dioxide and calcined limestone and dolomite particles was investigated using a thermogravimetric analyser. The samples used in this study originated from different parts of Turkey. Sulphation reactions were conducted under isothermal conditions in a gaseous mixture consisting of 15 vol% CO2, 0.35 vol% SO2 and a balance of dry air by volume. Before sulphation all

Ay?egül Er?oy-Meriçboyu; Sadriye Küçükbayrak

1995-01-01

236

Cutaneous reactions to transdermal therapeutic systems.  

PubMed

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

Bershow, Andrea; Warshaw, Erin

2011-01-01

237

Alder-ene reactions of arynes.  

PubMed

Efficient Alder-ene reactions of various arynes generated directly from bis-1,3-diynes are described. The reactivity of ene donors with different tethers was examined under thermal and metal-catalyzed conditions, which indicates that both the formation of aryne intermediates and their ene reactions are less sensitive to the catalyst than to the structural features of the substrates. PMID:23540274

Karmakar, Rajdip; Mamidipalli, Phani; Yun, Sang Young; Lee, Daesung

2013-04-19

238

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

239

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

SciTech Connect

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

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

2010-06-01

240

Investigation of reaction products of sulphuric acid with ilmenite  

Microsoft Academic Search

The reaction of sulphuric acid with titanium raw materials runs violently with simultaneous emission of gases. Such run of\\u000a reaction creates danger of explosion. This process is very complicated from the reason of complexity of reactions and variety\\u000a of compounds in reaction mixture. To determine safe conditions of reaction with high efficiency, it is necessary to investigate\\u000a phase composition products

M. Jab?o?ski

2008-01-01

241

IC ................................... ... Reaction Product Imaging  

E-print Network

offers two modes of operation. One mode involves imaging of the atomic fragment or reaction productIC ................................... ... Reaction Product Imaging: The H + D2 Reaction Theofanis reaction product imaging. In this experiment, a photolytically produced beam of hydrogen (H) atoms crossed

Zare, Richard N.

242

Iodine Clock Reaction  

NSDL National Science Digital Library

This site allows the user to vary initial solution concentration and temperature for the iodine clock reaction. A simulation of the reaction lets reaction times be measured. The data can then be used to determine the order of reaction for the various components.

243

Mathematical model to predict drivers' reaction speeds.  

PubMed

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

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

2012-02-01

244

Epidemiology of cutaneous drug-induced reactions.  

PubMed

Cutaneous reactions represent in many surveillance systems, the most frequent adverse events attributable to drugs. The spectrum of clinical manifestations is wide and virtually encompasses any known dermatological disease. The introduction of biological agents and so-called targeted therapies has further enlarged the number of reaction patterns especially linked with cytokine release or in balance. The frequency and clinical patterns of cutaneous reactions are influenced by drug use, prevalence of specific conditions (e.g., HIV infection) and pharmacogenetic traits of a population, and they may vary greatly among the different populations around the world. Studies of reaction rates in cohorts of hospitalized patients revealed incidence rates ranging from, 1 out 1000 to 2 out 100 of all hospitalized patients. For drugs such as aminopenicillines and sulfamides the incidence of skin reactions is in the order of 3-5 cases out of 100 exposed people. Although the majority of cutaneous reactions are mild and self-limiting, there are reactions such as Stevens Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS) which are associated with significant morbidity and mortality. Surveillance systems routed on sound epidemiologic methodology, are needed to raise signals and to assess risks associated with specific reactions and drug exposures. Identification of risk factors for adverse reactions and appropriate genetic screening of groups at higher risk may improve the outcomes of skin reactions. PMID:24819642

Naldi, L; Crotti, S

2014-04-01

245

Skin Conditions  

MedlinePLUS

... certain diseases and immune system problems can cause rashes, hives, and other skin conditions. Many skin problems, such as acne, also affect your appearance. NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases

246

Conditional Immunomodulation  

Microsoft Academic Search

Interest in central nervous-immune system interactions was inspired largely by the work on conditional immunomodulation (Ader and Cohen, 1975, 1985). Ader and Cohen (1975) reported that rats trained such that a taste cue (saccharine, SAC) predicted an injection of an immunosuppressant (cyclophosphamide, CY) subsequently exhibited a conditional immunosuppression in response to SAC alone.\\u000aExperiments 1-3 were designed to evaluate reports

Glenda Marlene MacQueen

1989-01-01

247

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

248

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

249

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

250

Treatment and Managing Reactions  

MedlinePLUS

Treatment & Managing Reactions Currently, the only way to prevent a food-allergic reaction is to avoid the problem food. ... treatment plan includes all of the following: Strict avoidance of problem foods Working with your doctor to ...

251

Passivation of Anodic Reactions.  

National Technical Information Service (NTIS)

Extending the Wagner definition of passivity to anodic reactions of chemical species on inert electrodes, passivation of a Pt electrode for the hydrogen oxidation reaction can be explained as being caused by small amounts (fraction of a monolayer) of adso...

S. Schuldiner

1968-01-01

252

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

253

Syngas Conditioning  

SciTech Connect

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

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

2011-04-29

254

Microscale Thermite Reactions  

NASA Astrophysics Data System (ADS)

The reaction of aluminum with the oxides of a variety of elements (aluminothermy, or the Goldschmidt process) illustrates exothermic reactions that require a high activation energy. It is also an appropriate experiment with regard to the discussion of Ellingham diagrams. Because it is spectacular, this reaction is a favorite for demonstrations. When drama is not the main objective, conducting these reactions at microscale level offers numerous advantages over the usual scale.

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

1998-12-01

255

Nuclear Reactions Some Basics  

E-print Network

Q in a reaction ­ Definition: Q = masses BEFORE the reaction ­ masses AFTER the reaction ­ Example: e + 3He e + p + d: Q = (Me + M3He) - (Me + Mp + Md) ­ Q may be >0 (exothermic) or ?) measurements made in a nuclear physics lab experiment. #12;Formal Definition of Cross Section · Consider a beam

Gilfoyle, Jerry

256

Chemical Reactions at Surfaces  

Microsoft Academic Search

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

Nancy Ryan Gray Michael Henderson

2010-01-01

257

Calculation of interchange reaction rates by a `nearest resonance' method  

Microsoft Academic Search

Thermal and suprathermal energy gas reaction rates for exothermic processes involving molecules or molecular ions are treated generally in terms of the adiabatic criterion. An absolute cross section function is derived in terms of a near-resonance energy defect which allows the determination of the dependence of reaction rate on temperature under conditions of complete or partial thermodynamic equilibrium. The reaction

D K Bohme; J B Hasted; P P Ong

1968-01-01

258

Distribution function, reaction rates and spectral line profile  

Microsoft Academic Search

Quantum mechanics predicts the existence of power law “tails” in the distribution function over momentum in dense media even at the condition of thermodynamics equilibrium. Generalized expressions for the threshold process reaction rates show that reaction rates with released energy (e.g. vibrational-translational relaxation, chemical reaction, fusion rates) may be substantially increased due to quantum corrections. Spectral line profile also may

A. N Starostin; A. G Leonov; Yu. V Petrushevich; Vl. K Roerich

2004-01-01

259

Distribution function, reaction rates and spectral line profile  

Microsoft Academic Search

Quantum mechanics predicts the existence of power law ``tails'' in the distribution function over momentum in dense media even at the condition of thermodynamics equilibrium. Generalized expressions for the threshold process reaction rates show that reaction rates with released energy (e.g. vibrational-translational relaxation, chemical reaction, fusion rates) may be substantially increased due to quantum corrections. Spectral line profile also may

A. N. Starostin; A. G. Leonov; Yu. V. Petrushevich; Vl. K. Roerich

2004-01-01

260

EXPERIMENTAL BONE MARROW REACTIONS  

PubMed Central

1. The effect produced by intravenous administration of gum shellac solution varied directly with the strength of the solution and the amount injected. (a) Strong solutions were intensely toxic and fatal to all the animals injected. Toxicity was abolished by the presence of carbon particles in the solution. (b) Medium strength solutions produced a marked normoblastosis followed by an erythroblastosis if injections were continued, accompanied either by an initial rise of red blood cells and hemoglobin followed by a decrease or an initial decline followed by an increase. The decrease of erythrocytes and hemoglobin did not amount to an actual anemia, and was usually concomitant with the greatest outpouring of nucleated red cells. (c) Small doses elicited the same kind of response except that the normoblastosis was less marked, the decrease of red cells and hemoglobin minimal or absent, the increase of red blood cells and hemoglobin marked in most instances. (d) Minimal doses elicited no appreciable reaction. 2. The bone marrow in animals killed after a course of injections showed intense erythrocytic hyperplasia. This disappeared after a variable length of time with a return of the bone marrow to apparently normal condition. 3. Toxic effects with non-fatal doses in form of hemorrhages were produced mainly in the bone marrow and occasionally in the kidney under the following conditions. (a) After one injection in an animal with hyperplastic marrow (hemorrhages ih the bone marrow only). (b) After the fourth and fifth dose when administered at long intervals (4 to 19 day intervals). (c) After one injection given 40 days after several successive injections (one animal only). 4. Small and divided doses administered at long intervals produced no apparent ill effect. 5. Subcutaneous administrations did not elicit any marked systemic reactions. Locally there was induration and edema. 6. The conclusion was drawn that gum shellac solution stimulates markedly the production of erythrocytes in the bone marrow. The mechanism of stimulation is not clear, but it seems unlikely that it is due to destruction of red blood cells in the peripheral blood stream. PMID:19869286

Muller, Gulli Lindh

1927-01-01

261

Unraveling reaction pathways and specifying reaction kinetics for complex systems.  

PubMed

Many natural and industrial processes involve a complex set of competing reactions that include several different species. Detailed kinetic modeling of such systems can shed light on the important pathways involved in various transformations and therefore can be used to optimize the process conditions for the desired product composition and properties. This review focuses on elucidating the various components involved in modeling the kinetics of pyrolysis and oxidation of polymers. The elementary free radical steps that constitute the chain reaction mechanism of gas-phase/nonpolar liquid-phase processes are outlined. Specification of the rate coefficients of the various reaction families, which is central to the theme of kinetics, is described. Construction of the reaction network on the basis of the types of end groups and reactive moieties in a polymer chain is discussed. Modeling frameworks based on the method of moments and kinetic Monte Carlo are evaluated using illustrations. Finally, the prospects and challenges in modeling biomass conversion are addressed. PMID:22468596

Vinu, R; Broadbelt, Linda J

2012-01-01

262

Diels-Alder reaction of maldoxin with an isopropenylallene.  

PubMed

The Diels-Alder reaction of maldoxin with an isopropenylallene at 60-75 °C afforded an adduct closely related to chloropestolide A (24%) and a second adduct (0-11%) that underwent an ene reaction to generate the chloropupukeanolide D (11-22%) skeleton. The Diels-Alder reaction occurred with good selectively (>5:1) from a single face of maldoxin under much milder conditions than previously reported for the analogous dimethoxycyclohexadienone. Furthermore, the ene reaction took place under mild conditions whereas the analogous Diels-Alder adduct from the dimethoxycyclohexadienone did not undergo an ene reaction. PMID:22518065

Yu, Min; Snider, Barry B

2011-12-01

263

Mechanisms in knockout reactions  

E-print Network

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 $^9$Be($^9$C,$^8$B+X)Y and $^9$Be($^8$B,$^7$Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction and stripping 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.

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

2009-02-16

264

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

265

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

266

Terminal functionalization of polypropylene via the Alder Ene reaction  

Microsoft Academic Search

A terminally anhydride functionalized polypropylene was synthesized via the Alder Ene reaction from a low molecular weight amorphous polypropylene. A Lewis acid, SnCl2·2H2O, was found to catalyse the reaction, thereby improving anhydride content in the polymer for reaction conditions comparable to those in an extrusion environment, i.e. elevated temperature and short residence time. The reaction was carried out at 230°C

M. R Thompson; C Tzoganakis; G. L Rempel

1998-01-01

267

Mukaiyama Aldol Reactions in Aqueous Media  

PubMed Central

Mukaiyama aldol reactions in aqueous media have been surveyed. While the original Mukaiyama aldol reactions entailed stoichiometric use of Lewis acids in organic solvents under strictly anhydrous conditions, Mukaiyama aldol reactions in aqueous media are not only suitable for green sustainable chemistry but are found to produce singular phenomena. These findings led to the discovery of a series of water-compatible Lewis acids such as lanthanide triflates in 1991. Our understanding on these beneficial effects in the presence of water will be deepened through the brilliant examples collected in this review. 1 Introduction 2 Rate Enhancement by Water in the Mukaiyama Aldol Reaction 3 Lewis Acid Catalysis in Aqueous or Organic Solvents 3.1 Water-Compatible Lewis Acids 4 Lewis-Base Catalysis in Aqueous or Organic Solvents 5 The Mukaiyama Aldol Reactions in 100% Water 6 Asymmetric Catalysts in Aqueous Media and Water 7 Conclusions and Perspective PMID:24971045

Kitanosono, Taku; Kobayashi, Shu

2013-01-01

268

The trapping of phenyldiazenes in cycloaddition reactions.  

PubMed

The reactivity of phenyldiazenes was studied intensively in the late 1960s, but not much is known about their behavior under acidic conditions. Based on the formation of phenyldiazenes from phenylazocarboxylates, we herein describe how reactions of phenyldiazenes can be directed into ionic or radical pathways. Cycloaddition reactions with furans leading to pyridazinium salts represent the first examples for the direct trapping of phenyldiazenes with conservation of the N?N moiety. PMID:25154799

Fehler, Stefanie K; Pratsch, Gerald; Heinrich, Markus R

2014-10-13

269

Dimethylcarbonate for eco-friendly methylation reactions  

Microsoft Academic Search

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

S. Memoli; M. Selva; P. Tundo

2001-01-01

270

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...

271

EFFICIENT CHEMICAL TRANSFORMATIONS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

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

272

GREENER ORGANIC SYNTHESES USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

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

273

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 ...

274

ENVIRONMENTALLY FRIENDLIER SYNTHESIS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

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

275

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...

276

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...

277

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.

278

Noncanonical Reactions of Flavoenzymes  

PubMed Central

Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates. PMID:23203060

Sobrado, Pablo

2012-01-01

279

Reaction-diffusion textures  

Microsoft Academic Search

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01

280

Classic Organic Reactions  

NSDL National Science Digital Library

Despite the fact that the Classic Organic Reactions Page was designed for commercial purposes, to demonstrate the capabilities of ChemPen chemical structure drawing software for Windows, the page offers a useful resource for chemistry students and professionals. The creator of this page, and author and proprietor of ChemPen, Dr. Hilton Evans, has cited the literature for each reaction. The site contains drawings for over 300 alphabetically listed classic organic reactions. The list begins with the Acetoacetic Ester Condensation and ends with the Zinke-Suhl Reaction.

2007-05-12

281

Nuclear Reaction Data Centers  

SciTech Connect

The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab.

McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.

1988-01-01

282

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

283

Reactions of alkyl radicals  

Microsoft Academic Search

Recent investigations into the reactions of alkyl radicals are reviewed. Reactions discussed are: heats of formation, association, addition, dissociation, hydrogen atom transfer and oxidation. A trend towards the greater use of direct time-resolved methods for measuring rate coefficients is noted and future developments, based on the availability of high-quality ab initio potential energy surfaces, are anticipated.

Michael J. Pilling; V. Kay Proudler

1990-01-01

284

Fractal reaction kinetics.  

PubMed

Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal "memories." The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of "fractal-like kinetics" are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. PMID:17820893

Kopelman, R

1988-09-23

285

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

286

Computational analysis of the mechanism of chemical reactions in terms of reaction phases: hidden intermediates and hidden transition States.  

PubMed

Computational approaches to understanding chemical reaction mechanisms generally begin by establishing the relative energies of the starting materials, transition state, and products, that is, the stationary points on the potential energy surface of the reaction complex. Examining the intervening species via the intrinsic reaction coordinate (IRC) offers further insight into the fate of the reactants by delineating, step-by-step, the energetics involved along the reaction path between the stationary states. For a detailed analysis of the mechanism and dynamics of a chemical reaction, the reaction path Hamiltonian (RPH) and the united reaction valley approach (URVA) are an efficient combination. The chemical conversion of the reaction complex is reflected by the changes in the reaction path direction t(s) and reaction path curvature k(s), both expressed as a function of the path length s. This information can be used to partition the reaction path, and by this the reaction mechanism, of a chemical reaction into reaction phases describing chemically relevant changes of the reaction complex: (i) a contact phase characterized by van der Waals interactions, (ii) a preparation phase, in which the reactants prepare for the chemical processes, (iii) one or more transition state phases, in which the chemical processes of bond cleavage and bond formation take place, (iv) a product adjustment phase, and (v) a separation phase. In this Account, we examine mechanistic analysis with URVA in detail, focusing on recent theoretical insights (with a variety of reaction types) from our laboratories. Through the utilization of the concept of localized adiabatic vibrational modes that are associated with the internal coordinates, q(n)(s), of the reaction complex, the chemical character of each reaction phase can be identified via the adiabatic curvature coupling coefficients, A(n,s)(s). These quantities reveal whether a local adiabatic vibrational mode supports (A(n,s) > 0) or resists (A(n,s) < 0) the curving of the path, and thus the structural changes of the reaction complex. URVA can show the mechanism of a reaction expressed in terms of reaction phases, revealing the sequence of chemical processes in the reaction complex and making it possible to determine those electronic factors that control the mechanism and energetics of the reaction. The magnitude of adiabatic curvature coupling coefficients is related to strength and polarizability of the bonds being broken. Transient points along the reaction path are associated with hidden intermediates and hidden transition states, which can be converted into real intermediates and transition states when the reaction conditions or the substitution pattern of the reaction complex are appropriately changed. Accordingly, URVA represents a theoretical tool with tremendous experimental potential, offering the chemist the ability to assert greater control over reactions. PMID:20232791

Kraka, Elfi; Cremer, Dieter

2010-05-18

287

Cycloaddition reactions of ICNO  

NASA Astrophysics Data System (ADS)

The mechanism and selectivity of cycloaddition reactions of iodonitrile oxide, ICNO, have been studied with theoretical methods for the first time using MR-AQCC coupled-cluster and B3LYP DFT methods. Calculations have predicted that the favoured ICNO dimerisation process is a multi-step reaction to diiodofuroxan involving dinitrosoethylene-like intermediates. The ICNO cycloaddition with nitriles and ethynyl derivatives is a synchronous process favouring the formation of 1,2,4-oxadiazole and 1,2-oxazole derivatives, respectively. The cycloaddition reactions of ICNO have been studied experimentally by generating ICNO from AgCNO and iodine. Diiodofuroxan is obtained, however, even at the presence of nitriles.

Pasinszki, Tibor; Krebsz, Melinda; Hajgató, Balázs

2009-05-01

288

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

289

Role of microbes in the smectite-to-illite reaction  

NASA Technical Reports Server (NTRS)

Temperature, pressure, and time have been thought to control the smectite-to-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 degrees to 350 degrees 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, Jinwook; Dong, Hailiang; Seabaugh, Jennifer; Newell, Steven W.; Eberl, Dennis D.

2004-01-01

290

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping  

PubMed Central

Summary A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels–Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions. PMID:24062850

Stockinger, Skrollan

2013-01-01

291

Organocatalytic aza-Michael/retro-aza-Michael reaction: pronounced chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction.  

PubMed

A detailed experimental investigation of an aza-Michael reaction of aniline and chalcone is presented. A series of Cinchona alkaloid-derived organocatalysts with different functional groups were prepared and used in the aza-Michael and retro-aza-Michael reaction. There was an interesting finding that a complete reversal of stereoselectivity when a benzoyl group was introduced to the cinchonine and cinchonidine. The chirality amplification vs. time proceeds in the quinine-derived organocatalyst containing silicon-based bulky group, QN-TBS, -catalyzed aza-Michael reaction under solvent-free conditions. In addition, we have demonstrated for the first time that racemization was occurred in suitable solvents under mild conditions due to retro-aza-Michael reaction of the Michael adduct of aniline with chalcone. These indicate the equilibrium of retro-aza-Michael reaction and aza-Michael reaction produce the happening of chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction under different conditions, which would be beneficial to the development of novel chiral catalysts for the aza-Michael reactions. PMID:21465570

Cai, Yong-Feng; Li, Li; Luo, Meng-Xian; Yang, Ke-Fang; Lai, Guo-Qiao; Jiang, Jian-Xiong; Xu, Li-Wen

2011-05-01

292

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...

293

Autocatalysis in reaction networks.  

PubMed

The persistence conjecture is a long-standing open problem in chemical reaction network theory. It concerns the behavior of solutions to coupled ODE systems that arise from applying mass-action kinetics to a network of chemical reactions. The idea is that if all reactions are reversible in a weak sense, then no species can go extinct. A notion that has been found useful in thinking about persistence is that of "critical siphon." We explore the combinatorics of critical siphons, with a view toward the persistence conjecture. We introduce the notions of "drainable" and "self-replicable" (or autocatalytic) siphons. We show that: Every minimal critical siphon is either drainable or self-replicable; reaction networks without drainable siphons are persistent; and nonautocatalytic weakly reversible networks are persistent. Our results clarify that the difficulties in proving the persistence conjecture are essentially due to competition between drainable and self-replicable siphons. PMID:25245394

Deshpande, Abhishek; Gopalkrishnan, Manoj

2014-10-01

294

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

295

Bad Reaction to Cosmetics?  

MedlinePLUS

... for the person who had the reaction; the age, gender, and ethnicity of the product’s user; the name ... was purchased. And be sure to give the age, gender, and ethnicity of the person who had the ...

296

Oral Hypersensitivity Reactions  

MedlinePLUS

... a hypersensitivity reaction in the mouth? A: A large number of substances. The most common causes are food, ... What is the “Latex-Fruit Syndrome”? A: A large number of individuals who are allergic to latex products ...

297

Iodine Clock Reaction.  

ERIC Educational Resources Information Center

Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

Mitchell, Richard S.

1996-01-01

298

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.; Idsoe, O.; Willcox, R. R.

1958-01-01

299

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

300

The reaction rate in nuclear fusion  

Microsoft Academic Search

Summary  A method to evaluate the reaction rate in nuclear fusion is proposed. This method is obtained in the framework of the elastic\\u000a model for subbarrier fusion. Conditions for the validity of the method are given. Some examples are discussed.

A. Scalia

1988-01-01

301

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

302

THE CLASSICAL THEORIES OF RADIATION REACTION  

Microsoft Academic Search

Classical theories of radiation reaction are critically reviewed. The ; renormalized Dirac theory is discussed in particular detail. it is shown that all ; regularization prescriptions for this theory may be derived from a general ; dynamical correspondence principle. It is also shown that the physical content ; of the theory is severely limited by a general radiation condition. Various

Thomas Erber

1961-01-01

303

Solvent-free Reactions  

Microsoft Academic Search

For reasons of economy and pollution, solvent-free methods are of great interest in order to modernize classical procedures\\u000a making them more clean, safe and easy to perform. Reactions on solid mineral supports, reactions without any solvent\\/support\\u000a or catalyst, and solid-liquid phase transfer catalysis can be thus employed with noticeable increases in reactivity and selectivity.\\u000a A comprehensive review of these techniques

André Loupy

304

Phototoxic and Photoallergic Reactions  

Microsoft Academic Search

\\u000a Phototoxic and photoallergic reactions represent skin reactions to the sun, in the presence of photoactive chemicals applied\\u000a on the skin or taken systemically. They have a highly polymorphic clinical presentation – photocontact urticaria, eczema on\\u000a sun-exposed areas sometimes with erythema multiforme, exaggerated sunburn, linear phytophotodermatitis, pseudoporphyria, photoonycholysis,\\u000a dyschromia, and lupus erythematosus. Also, skin cancers are increasingly associated with exposure to

Margarida Gonçalo

305

Reaction imaging with interferometry.  

PubMed

We analyze scattering into a double-slit interferometer with target-fragment recoil detection as a monitor of quantum correlation and entanglement in few-body reaction amplitudes. We thus investigate two-slit interference with which-way information as an enhancement to modern reaction-fragment detection. We briefly consider charged-particle scattering with recoil-ion detection from the point of view of quantum information. PMID:11384415

Feagin, J M; Han, S

2001-05-28

306

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.

2013-07-09

307

Pot-in-pot reactions: Heterogenization of homogeneous reaction processes for otherwise impossible cascades  

NASA Astrophysics Data System (ADS)

Many excellent examples of homogeneous catalysts have been developed that elegantly and efficiently catalyze one reaction. Although the use of catalysts is ubiquitous in chemical synthesis, reactions must be carried out sequentially; else the catalysts/reagents may poison one another or require incompatible reaction conditions. These limitations make synthesis of vital molecules a tedious, expensive, and wasteful process. The process of multi-step synthesis is also not environmentally benign based on the sheer volume of waste generated per step. To overcome some of these limitations, catalysts have been site-isolated from each other therefore facilitating several steps in one reaction pot. However, available site-isolation methods have major shortcomings. Therefore, a general approach that works with already known chemistry and catalysts---without the need for further modification, is desired. This thesis reports a new approach to catalyst site-isolation. We exploited the advantages of both heterogeneous and homogeneous processes to develop new cascade reaction sequences by employing polydimethylsiloxane thimbles as selective semi-permeable walls. These thimbles allow small organic molecules to diffuse through while retaining polar reagents and/or organometallic catalysts. A felicitous choice of reaction conditions led to the development of pot-in-pot reactions, a new concept in organic catalysis. To demonstrate how dynamic this new techniques is, we performed 2- and 3-step cascade reactions. This new approach circumvents the need to isolate intermediates, therefore enabling synthesis of otherwise challenging molecules. The genesis of our work was the occlusion of an organometallic catalyst in polydimethylsiloxane to perform catalysis in water. Also, by simply occluding the catalyst in a polymer matrix, it was possible to dictate whether the catalyst gave a metathesis or an isomerization product. Since the work summarized herein demonstrates site-isolation of a whole reaction process there was a need to redefine the term catalysis to accommodate the heterogenization of homogeneous reaction processes.

Thuo, Martin

308

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

309

Bereavement: Reactions, Consequences, and Care.  

National Technical Information Service (NTIS)

Contents: PART I. BEREAVEMENT: REACTIONS AND CONSEQUENCES--Epidemiologic Perspectives on the Health Consequences of Bereavement; Adults' Reactions to Bereavement; Reactions to Particular Types of Bereavement; Bereavement During Childhood and Adolescence; ...

M. Osterweis, M. Green

1984-01-01

310

Chemical reactions at aqueous interfaces  

NASA Astrophysics Data System (ADS)

Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1) Adsorption of dilute PFOS(aq) and PFOA(aq) to acoustically cavitating bubble interfaces was greater than equilibrium expectations due to high-velocity bubble radial oscillations; 2) Relative ozone oxidation kinetics of aqueous iodide, sulfite, and thiosulfate were at variance with previously reported bulk aqueous kinetics; 3) Organics that directly chelated with the anode surface were oxidized by direct electron transfer, resulting in immediate carbon dioxide production but slower overall oxidation kinetics. Chemical reactions at aqueous interfaces can be the rate-limiting step of a reaction network and often display novel mechanisms and kinetics as compared to homogeneous chemistry.

Vecitis, Chad David

311

Ignition, extinction, and thermal hysteresis of a heterogeneous exothermic reaction  

Microsoft Academic Search

Critical conditions of ignition and extinction are studied theoretically for the case of a heterogeneous exothermic reaction\\u000a proceeding on the uniformly accessible surface of a channel or a pore. Particular emphasis is placed on the thermal-hysteresis\\u000a effect of the reaction (an ignition temperature in excess of the extinction temperature), which ensures stability of the reaction\\u000a against changes in the external

I. G. Assovskii

1998-01-01

312

Self-organization effects in reactions of macromolecules  

NASA Astrophysics Data System (ADS)

The ability of biomacromolecules to coordinate fast reaction events in their active centers with slow rearrangements of their structure is focused upon. Under real conditions of many sequential reaction turnovers of the macromolecule, the structural shifts caused by single turnovers can be of cumulative character. This, in turn, leads to drastic threshold-like changes of the reaction cycle. In this way, the creative role of dynamical substrate-conformation interactions in the formation of functional regimes of the macromolecule is consistently uncovered.

Christophorov, L. N.

313

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

314

Eco-friendly polyethylene glycol promoted Michael addition reactions of a,ß-unsaturated carbonyl compounds  

EPA Science Inventory

Abstract- Intra- and inter-nucleophilic addition reactions of different unsaturated compounds were found to be highly effective without any additives in PEG-400 as a recyclable reaction medium under neutral conditions. ...

315

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

316

Eco-friendly polyethylene glycol promoted Michael addition reactions of ?,?-unsaturated carbonyl compounds  

Microsoft Academic Search

Intra- and inter-nucleophilic addition reactions of different ?,?-unsaturated carbonyl compounds were found to be highly effective without any additives in PEG-400 as a recyclable reaction medium under neutral conditions.

Dalip Kumar; Gautam Patel; Braja G. Mishra; Rajender S. Varma

2008-01-01

317

Iodine Oxide Thermite Reactions: Physical and Biological Effects  

NASA Astrophysics Data System (ADS)

We investigated the potential for some thermite-like material reactions to kill bacteria spores. Iodine oxides and silver oxides react vigorously with metals like aluminum, tantalum, and neodymium. These reactions theoretically produce temperatures as high as 8000K, leading to vaporization of the reactants, producing very hot iodine and/or silver gases. We performed a series of computations and experiments to characterize these reactions under both quasi-static and ballistic impact conditions. Criteria for impact reaction were established. Measurements of temperature and pressure changes and chemical evolution will be reported. Basic combustion characterizations of these reactions, such as thermal equilibrium analysis and reaction propagation rates as well as ignition sensitivity, will be discussed. Additionally, testing protocols were developed to characterize the biocidal effects of these reactive materials on B. subtilis spores. The evidence from these tests indicates that these reactions produce heat, pressure, and highly biocidal gases.

Russell, Rod; Pantoya, Michelle; Bless, Stephan; Clark, William

2009-06-01

318

NO sub x char reactions: Kinetics and transport aspects  

Microsoft Academic Search

The principal goal of this project is to develop a mechanistic understanding of the processes by which carbons reduce NO to Nâ. The reaction of interest may be represented by the non-stoichiometric equation: C + NO â CO, COâ, Nâ. The relative yields of CO and COâ depend upon the reaction conditions, as will be described below. The carbon selected

J. M. Calo; E. M. Suuberg; H. Teng; I. D. Milosavljevic

1990-01-01

319

Friedel-Crafts acylation reactions in pyridinium based ionic liquids  

Microsoft Academic Search

The Friedel-Crafts acylations of representative aromatic compounds with acetic anhydride in pyridinium based ionic liquids (ILs) were investigated. The effect of factors such as reactant composition, catalyst-IL composition, catalyst dosage and reaction temperature were studied. The reactions were found to proceed under relatively mild conditions with excellent conversions; and a simple product isolation procedure was achieved. ILs could also be

Ying Xiao; Sanjay V. Malhotra

2005-01-01

320

Computational studies on glyceraldehyde and glycine Maillard reaction-II  

Microsoft Academic Search

Density functional theory calculations have been performed on the proposed mechanism for the intermediate stage of glyceraldehyde and glycine Maillard reaction under different pH conditions at the standard state. By following the total mass balance, possibility of the formation of different compounds in the proposed mechanism has been tested by estimating the Gibb's free energy changes of the reaction. Electronic

2004-01-01

321

Kinetics of a Substitution Reaction of Sulfitopentaaminecobalt(III).  

ERIC Educational Resources Information Center

Describes a laboratory experiment to determine the rate law for a substitution reaction of a transition metal. Derives the corresponding rate law from the accepted mechanism for the reaction using the steady state approximation and determines the conditions under which the two agree. (CW)

Richards, Lynne

1988-01-01

322

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

323

Suicide substrate reaction-diffusion equations: Varying the source  

Microsoft Academic Search

The suicide substrate reaction is a model for certain enzyme-inhibiting drugs. This reaction system is examined assuming that the substrate diffuses freely while the enzyme remains fixed. Two sets of initial and boundary conditions are examined: one modelling an instantaneous point source, akin to an injection of substrate, the other, a continuous point source, akin to a continuing influx, or

MEGHAN A. BURKE; P. K. MAINI; J. D. MURRAY

1993-01-01

324

Adventures in Gold-Catalyzed Cascade Reactions and Rearrangements  

Microsoft Academic Search

Gold-catalyzed organic transformations have been a hot topic of research in synthetic organic community over the last few years. Amazingly, most of the reactions can be performed under mild conditions using a catalytic amount of gold complexes. One of the widely reported reactions using gold catalysts is heterocyclization that involves an activation of a pi-system followed by a nucleophilic attack

Dinesh Vinod Vidhani

2010-01-01

325

Diels-Alder Reaction 91 Diels-Alder Reaction  

E-print Network

Diels-Alder Reaction 91 Diels-Alder Reaction General Diels-Alder Reaction: A conjugated "diene as a student-friendly low-smell Diels- Alder diene, with the labeled carbons functioning as the reactive diene/reactivity principle). The "cyclohexene" ring produced in every Diels-Alder reaction is hard to visualize, but consists

Jasperse, Craig P.

326

Studies on the thermal reactions of aluminium oxides and hydroxides  

Microsoft Academic Search

The gibbsite ??-alumina decomposition (in air) and the?-alumina ? boehmite transformation (under hydrothermal conditions) were investigated isothermally. Reaction products were characterized by TG and X-ray diffraction.

C. Novák; G. Pokol; K. Tomor; J. K?míves; S. Gál

1988-01-01

327

Velocity pump reaction turbine  

DOEpatents

An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

House, Palmer A. (Walnut Creek, CA)

1984-01-01

328

Dissipation of oxytetracycline in soils under different redox conditions  

Microsoft Academic Search

This study investigated the dissipation kinetics of oxytetracycline in soils under aerobic and anoxic conditions. Laboratory experiments showed that the dissipation of oxytetracycline in soil followed first-order reaction kinetics and its dissipation rates decreased with increasing concentration. Oxytetracycline dissipated faster in soil under aerobic conditions than under anoxic conditions. The half-lives for oxytetracycline in soil under aerobic conditions ranged between

Ji-Feng Yang; Guang-Guo Ying; Li-Jun Zhou; Shan Liu; Jian-Liang Zhao

2009-01-01

329

Gas Producing Micro-Reaction  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals and metals to examine reactions that produce gaseous substances. Learners will identify the gases produced and write a balanced equation for each reaction. Use this activity to also introduce learners to single displacement and double displacement reactions, two types of chemical reactions.

House, The S.

2014-01-28

330

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.

331

Azoxy rearrangement reactions  

NASA Astrophysics Data System (ADS)

The mechanisms of several types of azoxy compound (XN(O)NY) rearrangement reactions have been studied using density functional theory (DFT) with the B3LYP exchange-correlation potential. The substituents X and Y are taken from the set H, CH , F, C H , Cl and CN. The 6-311 + G(d,p) basis set was used to optimize up to ten equilibrium and transition state structures for a given pair of X and Y substituents; except for azoxybenzene where a 6- 311(+)G(d) basis set was used. All geometric structures were characterized by a frequency calculation. The reaction path for converting XN (O)N Y to XN N (O)Y via a concerted intramolecular shift of the oxygen atom from N to N involves three equilibrium and two saddle-point structures. The relatively high (about 70-80 kcalmol1) calculated barrier height to reaction and its independence of the nature of the X and Y substituents is attributed to characteristic orbital, atomic charge and structural factors along the reaction path. Cis trans isomerization across N-- N in the NH(O)NH azoxy compound and across N-N in the ring XNONY oxadiaziridine intermediate is found to have a barrier height of at least - 1 about 30 kcalmol . Single-point CCSD(T)/DFT energy differences are found to be somewhat smaller than the DFT calculated values. 3 6 5

Basch, Harold; Hoz, Tova

332

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

333

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

334

Radical-Radical Reactions  

Microsoft Academic Search

Radical-radical reactions generally proceed on potential energy surfaces that have no maximum. Collisional deactivation leads to a stable molecular product; alternatively, radical or molecular products can be formed via dissociation channels additional to those regenerating the reactants. Models of the transition states must take into account the loose internal motion of the fragments, and a variational approach is necessary. The

M. J. Pilling

1996-01-01

335

Asymmetric reactions in sonochemistry  

Microsoft Academic Search

Sonochemical processes involved in asymmetric synthesis are reviewed. The goal of this overview is to provide a comprehensive picture about the fields of both enantioselective and diastereoselective reactions accelerated or initiated by ultrasounds. Since the most, in many cases comparative, data are available in heterogeneous metal catalysis, the emphasis will be placed on these enantioselective hydrogenations, however, other applications such

Béla Török; Katalin Balázsik; Károly Felföldi; Mihály Bartók

2001-01-01

336

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.

2011-02-16

337

Exocharmic Reactions up Close  

ERIC Educational Resources Information Center

The exocharmic reactions that can be observed microscopically are discussed. The students can discover the optimal concentration of an acidic lead nitrate solution, so that a crystal of potassium iodide, nudged to the edge of a drop, results in glinting golden hexagons of lead iodide.

Ramette, R. W.

2007-01-01

338

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

339

A World of Reactions  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the first of four Science Objects in the Chemical Reactions SciPack. It explains tha

National Science Teachers Association (NSTA)

2009-07-10

340

Categorizing Chemical Reactions  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the second of four Science Objects in the Chemical Reactions SciPack. It provides an

National Science Teachers Association (NSTA)

2009-07-10

341

Rates of Chemical Reactions  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Chemical Reactions SciPack. It demonstrates

National Science Teachers Association (NSTA)

1900-01-01

342

The aromatic ene reaction.  

PubMed

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. PMID:24345944

Niu, Dawen; Hoye, Thomas R

2014-01-01

343

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

344

Aqueous oxidative Heck reaction as a protein-labeling strategy.  

PubMed

An increasing number of chemical reactions are being employed for bio-orthogonal ligation of detection labels to protein-bound functional groups. Several of these strategies, however, are limited in their application to pure proteins and are ineffective in complex biological samples such as cell lysates. Here we present the palladium-catalyzed oxidative Heck reaction as a new and robust bio-orthogonal strategy for linking functionalized arylboronic acids to protein-bound alkenes in high yields and with excellent chemoselectivity even in the presence of complex protein mixtures from living cells. Advantageously, this reaction proceeds under aerobic conditions, whereas most other metal-catalyzed reactions require inert atmosphere. PMID:24376051

Ourailidou, Maria Eleni; van der Meer, Jan-Ytzen; Baas, Bert-Jan; Jeronimus-Stratingh, Margot; Gottumukkala, Aditya L; Poelarends, Gerrit J; Minnaard, Adriaan J; Dekker, Frank J

2014-01-24

345

Common Conditions in Newborns  

MedlinePLUS

... Baby > Common Conditions in Newborns Ages & Stages Listen Common Conditions in Newborns Article Body Some physical conditions are especially common during the first couple of weeks after birth. ...

346

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

347

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

348

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

349

Laser Induced Nuclear Reactions  

NASA Astrophysics Data System (ADS)

In the last decade the intensities of light fields which can be produced in a laser focus increased by four orders of magnitude from 1016 to 1020 W/cm2. Intensities exceeding 1018 W/cm2 allow for the production of relativistic laser plasmas, that is the quiver energy of plasma electrons reaches the electron rest mass. These plasmas are sources of a whole spectrum of energetic particles, such as highly relativistic electrons, hard bremsstrahlung [13], protons with energies up to a few hundred MeV [7,14], neutrons [4,11,13] and deuterons [4, 17]. These particles can be used to induce nuclear reactions like photo-fission (?,f) [3,6,8,12], neutron generation by (?,n)- (p,n)- or (d,n)-reactions, neutron capture or fusion [4, 17].

Ewald, Friederike; Schwoerer, Heinrich; Magill, Joseph; Galy, Jean; Schenkel, Roland; Sauerbrey, Roland

350

Magnetically suspended reaction wheels  

NASA Technical Reports Server (NTRS)

Magnetic suspensions offer several advantages over conventional bearings, arising because of the contactless nature of the load support. In application to spacecraft reaction wheels, the advantages are low drag torque, wearfree, unlubricated, vacuum-compatible operation, and unlimited life. By the provision of redundancy in the control electronics, single-point failures are eliminated. The rational for selection of a passive radial, active axial, dc magnetic suspension is presented, and the relative merits of 3-loop and single-loop magnetic suspensions are discussed. The design of a .678 N-m-sec (.5 ft-lb-sec) reaction wheel using the single loop magnetic suspension was developed; the design compares favorably with current ball bearing wheels in terms of weight and power.

Sabnis, A. V.; Stocking, G. L.; Dendy, J. B.

1975-01-01

351

Reaction chemistry of cerium  

SciTech Connect

It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

NONE

1997-01-01

352

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 activatedâone 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.)

Shaw, Maisie; Gomez, Maria

2009-01-01

353

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

354

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.

2010-10-05

355

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

356

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

357

Resilience in reaction-diffusion systems  

NASA Astrophysics Data System (ADS)

Reaction-diffusion systems with zero-flux Neumann boundaries are widely used to model various kinds of interaction in, for example, the scientific fields of ecology, biology, chemistry, medicine and industry. The physical systems within these fields are often known to be (conditionally or unconditionally) resilient with respect to shocks, disturbances or catastrophies in the immediate environment. In order to be good mathematical models of such situations the reaction-diffusion systems must have the same resilient or asymptotic behaviour as that of the physical situation. Three fundamentally different kinds of reaction terms are usually distinguished according to the entry signs of the reaction Jacobian: mutualism, mixed (predator-prey) interaction and competition. The asymptotic stability (in the Poincare sense) of mutualistic systems has already been studied extensively, but the results cannot be generalized (globally) to the other two fundamental types, which are not order-preserving. A partial (local) generalization is, however given here for these two types, involving simple Jacobian inequalities and knowledge (often prompted by the underlying physical situation) of invariant sets in solution space. The return time of resilient systems and the approach rate of asymptotically stable solutions are also estimated. Key words: reaction-diffusion system; competition; resilience; asymptotic stability.

van Vuuren, J. H.

1999-10-01

358

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

359

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

360

Quasiglobal reaction model for ethylene combustion  

NASA Technical Reports Server (NTRS)

The objective of this study is to develop a reduced mechanism for ethylene oxidation. The authors are interested in a model with a minimum number of species and reactions that still models the chemistry with reasonable accuracy for the expected combustor conditions. The model will be validated by comparing the results to those calculated with a detailed kinetic model that has been validated against the experimental data.

Singh, D. J.; Jachimowski, Casimir J.

1994-01-01

361

Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction  

Microsoft Academic Search

Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. The authors have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization.

A. K. Chaudhary; E. J. Beckman; A. J. Russell

1998-01-01

362

Urea hydrolysis and calcium carbonate reaction fronts  

NASA Astrophysics Data System (ADS)

The mobility of toxic or radioactive metal contaminants in subsurface environments can be reduced by the formation of mineral precipitates that form co-precipitates with the contaminants or that isolate them from the mobile fluid phase. An engineering challenge is to control the spatial distribution of precipitation reactions with respect to: 1) the location of a contaminant, and 2) where reactants are introduced into the subsurface. One strategy being explored for immobilizing contaminants, such as Sr-90, involves stimulating mineral precipitation by forming carbonate ions and hydroxide via the in situ, microbially mediated hydrolysis of urea. A series of column experiments have been conducted to explore how the construction or design of such an in situ reactant production strategy can affect the temporal and spatial distribution of calcium carbonate precipitation, and how the distribution is coupled to changes in permeability. The columns were constructed with silica gel as the porous media. An interval midway through the column contained an adsorbed urease enzyme in order to simulate a biologically active zone. A series of influent solutions were injected to characterize hydraulic properties of the column (e.g., bromide tracer), profiles of chemical conditions and reaction products as the enzyme catalyzes urea hydrolysis (e.g., pH, ammonia, urea), and changes that occur due to CaCO3 precipitation with the introduction of a calcium+urea solutions. In one experiment, hydraulic conductivity was reduced as precipitate accumulated in a layer within the column that had a higher fraction of fine grained silica gel. Subsequent reduction of permeability and flow (for a constant head condition) resulted in displacement of the hydrolysis and precipitation reaction profiles upstream. In another experiment, which lacked the physical heterogeneity (fine grained layer), the precipitation reaction did not result in loss of permeability or flow velocity and the reaction profile, characterized by the pH profile and hydrolysis reaction species, was extended downstream of the enzyme zone. Downstream extension of the reaction profile was due partially to the partial mobility of the enzyme in the column. The experiments are helping to illustrate the complexity of transient reaction fronts as well as the needs and challenges for advanced modeling approaches. A modeling platform developed at the Idaho National Laboratory, which is capable of simulating tightly coupled physical-chemical processes (the Reactive Transport simulator), is being applied to pre-experimental simulations and post-experimental interpretation of results.

Fox, D. T.; Redden, G. D.; Henriksen, J.; Fujita, Y.; Guo, L.; Huang, H.

2010-12-01

363

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.

Katz, David A.

2009-07-09

364

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

365

Coping with Traumatic Stress Reactions  

MedlinePLUS

... Guidelines Hospital Quality Data Medical Inspector Patient Safety Organizations Administrative Clinical Quick Links Enter ZIP code here Enter ZIP code here Coping with Traumatic Stress Reactions Coping with Traumatic Stress Reactions Available in ...

366

Laser induced nuclear reactions  

NASA Astrophysics Data System (ADS)

Dramatic improvements in laser technology since 1984 have revolutionised high power laser technology. Application of chirped-pulse amplification techniques has resulted in laser intensities in excess of 1019W/cm2. In the mid to late eighties, C. K. Rhodes and K. Boyer discussed the possibility of shining laser light of this intensity onto solid surfaces and to cause nuclear transitions. In particular, irradiation of a uranium target could induce electro- and photofission in the focal region of the laser. In this paper it is shown that ?Ci of 62Cu can be generated via the (?,n) reaction by a laser with an intensity of about 1019Wcm-2.

Ledingham, Ken; McCanny, Tom; Graham, Paul; Fang, Xiao; Singhal, Ravi; Magill, Joe; Creswell, Alan; Sanderson, David; Allott, Ric; Neely, David; Norreys, Peter; Santala, Marko; Zepf, Matthew; Watts, Ian; Clark, Eugene; Krushelnick, Karl; Tatarakis, Michael; Dangor, Bucker; Machecek, Antonin; Wark, Justin

1998-12-01

367

Reactions of the Formamidines  

E-print Network

correct is furnished by the fact that a secondary product, methyl-bis- methylphenylpyrazolone, according to this reaction. N = C - CH3 I / CH c+ RII: CHNHR Mt==== Ph N - CO Me N = C I Q . JJ I 0 - CH( ' + 2RNH Ph B - GOH CO — NPh This is the first... FOR THE DEGREE OF MASTER OF SCIENCE BY TENNYSON MYERS JUNE 1 1912 Page 1. Pormainidines are substituted formic acids * Thus aim- pie formamidine HC is formic acid with the hydroxyl nNH 0 group replaced by an &mido and the oxygen replaced by an imido group...

Myers, Tennyson

1912-06-01

368

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

369

The classification of chemical reactions  

Microsoft Academic Search

The classification and shorthand designation of chemical reactions are considered. It is concluded that single-step reactions can be divided into a finite number of types, each of which could be represented by an unambiguous symbol. The various types are listed and illustrated. Multi-step reactions, however, cannot be classified (in any detail) in a limited number of ways and for such

D. P. N. Satchell

1977-01-01

370

Mass Transfer with Chemical Reaction.  

ERIC Educational Resources Information Center

Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

DeCoursey, W. J.

1987-01-01

371

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

372

Intact implicit learning in autism spectrum conditions  

Microsoft Academic Search

Individuals with autism spectrum condition (ASC) have diagnostic impairments in skills that are associated with an implicit acquisition; however, it is not clear whether ASC individuals show specific implicit learning deficits. We compared ASC and typically developing (TD) individuals matched for IQ on five learning tasks: four implicit learning tasks—contextual cueing, serial reaction time, artificial grammar learning, and probabilistic classification

Jamie Brown; Balazs Aczel; Luis Jiménez; Scott Barry Kaufman; Kate Plaisted Grant

2010-01-01

373

New advances in agitation technology for exothermic reactions in very large reactors  

Microsoft Academic Search

Organic reactions, such as polymerisations, often require precisely controlled homogeneous reaction conditions in order to achieve high product quality, minimise waste or rework, and therefore reduce environmental impact. Many such processes were originally manufactured in moderately sized reactors with a height–diameter ratio of around 1. Operators have subsequently driven up their production rates by intensifying the reaction and by increasing

W. Himmelsbach; D. Houlton; D. Ortlieb; M. Lovallo

2006-01-01

374

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

375

Effect of segmented fluid flow, sonication and phase transfer catalysis on biphasic reactions in capillary microreactors  

Microsoft Academic Search

The contact between immiscible liquids in a microfluidic system creating segmented flow offers great potential in the study of biphasic reactions in organic chemistry with significant advantages with respect to conventional flask techniques.For a simple biphasic hydrolysis, we show that the application of various reaction conditions in microreactors using segmented flow can dramatically increase the reaction rate, especially when sonication

Batoul Ahmed-Omer; David Barrow; Thomas Wirth

2008-01-01

376

Investigations of the nature and occurrence of starch granule channels and their influence on granular reactions  

Microsoft Academic Search

The purpose of these experiments was twofold: (1) to determine if the location of chemical reactions within starch granules can be controlled by altering reaction conditions; and (2) to investigate channels in starch granules and determine the implication of their presence. To address the first objective, a rapid, valid method was needed to locate granular reaction sites. A reflection confocal

Jonathan Arthur Gray

2003-01-01

377

Plasmonic smart dust for probing local chemical reactions.  

PubMed

Locally probing chemical reactions or catalytic processes on surfaces under realistic reaction conditions has remained one of the main challenges in materials science and heterogeneous catalysis. Where conventional surface interrogation techniques usually require high-vacuum conditions or ensemble average measurements, plasmonic nanoparticles excel in extreme light focusing and can produce highly confined electromagnetic fields in subwavelength volumes without the need for complex near-field microscopes. Here, we demonstrate an all-optical probing technique based on plasmonic smart dust for monitoring local chemical reactions in real time. The silica shell-isolated gold nanoparticles that form the smart dust can work as strong light concentrators and optically report subtle environmental changes at their pinning sites on the probed surface during reaction processes. As a model system, we investigate the hydrogen dissociation and subsequent uptake trajectory in palladium with both "dust-on-film" and "film-on-dust" platforms. Using time-resolved single particle measurements, we demonstrate that our technique can in situ encode chemical reaction information as optical signals for a variety of surface morphologies. The presented technique offers a unique scheme for real-time, label-free, and high-resolution probing of local reaction kinetics in a plethora of important chemical reactions on surfaces, paving the way toward the development of inexpensive and high-output reaction sensors for real-world applications. PMID:23458121

Tittl, Andreas; Yin, Xinghui; Giessen, Harald; Tian, Xiang-Dong; Tian, Zhong-Qun; Kremers, Christian; Chigrin, Dmitry N; Liu, Na

2013-04-10

378

Unimolecular Reaction Dynamics of Large Polyatomic Molecules.  

NASA Astrophysics Data System (ADS)

Scope and method of study. Classical and semiclassical dynamics were used in an attempt to at least partially answer the following questions: (i) Can we predict the presence or absence of statistical behavior in polyatomic molecules and, in either case, explain why? (ii) To what degree can we model the detailed, full-dimensional unimolecular reaction dynamics of large molecules? (iii) Are the vibrational dynamics of highly excited polyatomic molecules chaotic? (iv) Can the "zero-point energy problem" in classical trajectory calculations be "corrected"? (v) Can we induce mode specificity in symmetric, double-well tunneling splittings?. Findings and conclusions. (i) Classical trajectory calculations performed on 2-chloroethyl radical indicate that the system is not mode specific. Moreover, comparison of the trajectory results to those obtained using Monte Carlo transition-state theory reveals that 2-chloroethyl behaves statistically. We suggest that three conditions likely to favor nonstatistical behavior are (a) low levels of excitation (relative to the reaction threshold); (b) a reaction coordinate that does not lead to large changes in the chemical bonding; (c) the existence of an activation coordinate that is strongly coupled to the reaction coordinate but only weakly coupled to the "bath". (ii) The unimolecular reaction dynamics of the RDX molecule were studied. First -order rate coefficients, branching ratios, and product -state distributions were computed from microcanonical ensembles of trajectories. The results are in qualitative accord with experimental data. We conclude that classical trajectories can be used to treat the reaction dynamics in large systems. (iii) Power spectra were used to study the vibrational dynamics of vibrationally excited SiF_4, C_2H_4, CH _3ONO, 2-chloroethyl radical, and RDX. The results indicate that the intramolecular dynamics of large, highly excited polyatomic molecules are largely nonchaotic, leaving open the possibility of mode-specific effects in large-molecule reaction dynamics. (iv) Two methods for constraining zero-point energies in classical trajectories were examined. Neither of the constraints is suitable for use in realistic systems. We are led to question whether it is possible to actively treat the zero -point energy problem without introducing problems of a far more serious nature than those we are trying to remedy. (v) A simple semiclassical method was used to compute the tunneling splitting in a prototypical malonaldehyde molecule as a function of various excitation schemes. The results indicate a sensitive dependence of the splitting on the kind of initial conditions used.

Sewell, Thomas Dan

379

Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions.  

PubMed

Radical reactions are a powerful class of chemical transformations. However, the formation of radical species to initiate these reactions has often required the use of stoichiometric amounts of toxic reagents, such as tributyltin hydride. Recently, the use of visible-light-mediated photoredox catalysis to generate radical species has become popular, but the scope of these radical precursors has been limited. Here, we describe the identification of reaction conditions under which photocatalysts such as fac-Ir(ppy)3 can be utilized to form radicals from unactivated alkyl, alkenyl and aryl iodides. The generated radicals undergo reduction via hydrogen atom abstraction or reductive cyclization. The reaction protocol utilizes only inexpensive reagents, occurs under mild reaction conditions, and shows exceptional functional group tolerance. Reaction efficiency is maintained upon scale-up and decreased catalyst loading, and the reaction time can be significantly shortened when the reaction is performed in a flow reactor. PMID:23001000

Nguyen, John D; D'Amato, Erica M; Narayanam, Jagan M R; Stephenson, Corey R J

2012-10-01

380

Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions  

NASA Astrophysics Data System (ADS)

Radical reactions are a powerful class of chemical transformations. However, the formation of radical species to initiate these reactions has often required the use of stoichiometric amounts of toxic reagents, such as tributyltin hydride. Recently, the use of visible-light-mediated photoredox catalysis to generate radical species has become popular, but the scope of these radical precursors has been limited. Here, we describe the identification of reaction conditions under which photocatalysts such as fac-Ir(ppy)3 can be utilized to form radicals from unactivated alkyl, alkenyl and aryl iodides. The generated radicals undergo reduction via hydrogen atom abstraction or reductive cyclization. The reaction protocol utilizes only inexpensive reagents, occurs under mild reaction conditions, and shows exceptional functional group tolerance. Reaction efficiency is maintained upon scale-up and decreased catalyst loading, and the reaction time can be significantly shortened when the reaction is performed in a flow reactor.

Nguyen, John D.; D'Amato, Erica M.; Narayanam, Jagan M. R.; Stephenson, Corey R. J.

2012-10-01

381

Efficient Synthesis of Ferrocenylcyclohexenone Under Solvent-Free Conditions  

Microsoft Academic Search

An efficient method for the synthesis of a series of ferrocenylcyclohexenones via tandem Michael–aldol reaction of ferrocenyl-substituted chalcones with dibenzyl ketone under solvent-free conditions is described. It was found that the factors including the electronic nature of chalcone, basicity of the base, reaction time, and temperature have effects on the formation of the ferrocenylcyclohexenones.

Zhi-Liang Shen; Wei-Juan Zhou; Jin-Ming Yang; Shun-Jun Ji

2009-01-01

382

Synthesis Under 'Greener' Conditions: Role of Sustainable Nano-Catalysts  

EPA Science Inventory

The presentation summarizes our recent activity in chemical synthesis involving benign alternatives, such as the use of supported reagents, and greener reaction medium in aqueous or solvent-free conditions.1 The synthesis of heterocyclic compounds, coupling reactions, and a varie...

383

Diseases and Conditions  

MedlinePLUS

... Conditions Public Health Public Health Public Health Home Military Exposures Military Exposures Home 4 Ways to Find Exposures Related ... Studies Publications & Reports Diseases & Conditions Diseases & Conditions Index Military Exposure Related Health Concerns Gulf War Veterans' Illnesses ...

384

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...

385

Atherton-Todd reaction: mechanism, scope and applications.  

PubMed

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-Gourvčs, Hélčne; Haelters, Jean-Pierre; Jaffrčs, Paul-Alain

2014-01-01

386

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, Stephanie S; Berchel, Mathieu; Couthon-Gourves, Helene; Haelters, Jean-Pierre

2014-01-01

387

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...

388

The hexadehydro-Diels-Alder reaction  

PubMed Central

Summary o-Benzynes (arynes) are among the most versatile of all reactive (short-lived) intermediates in organic chemistry. These species can be trapped to give products that are valuable from the perspective of both fine (pharmaceuticals) and commodity (agrochemicals, dyes, polymers, etc.) chemicals. Here we show a fundamentally new strategy that unites a de novo generation of benzynes, through the title hexadehydro-Diels–Alder (HDDA) reaction, with their in situ elaboration into structurally complex benzenoid products. In the HDDA reaction a 1,3-diyne is engaged in a [4+2] cycloisomerization with a third (pendant) alkyne–the diynophile–to produce the highly reactive benzyne intermediate. The metal- and reagent-free reaction conditions for this simple, thermal transformation are notable. The subsequent and highly efficient trapping reactions increase the power of the overall process. Finally, we provide examples of how this de novo benzyne generation approach allows new modes of intrinsic reactivity to be revealed. PMID:23060191

Hoye, Thomas R.; Baire, Beeraiah; Niu, Dawen; Willoughby, Patrick H.; Woods, Brian P.

2012-01-01

389

General Banking Conditions 2009 General Banking Conditions  

E-print Network

or to the integrity of the financial system. 3 Activities and objectives The Customer provides information to the Bank activities. The Bank may give goods, docu- ments of title, securities or financial instruments that belongGeneral Banking Conditions 2009 r #12;#12;1 General Banking Conditions (Version 2009

Franssen, Michael

390

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. Shuster at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-947-7797; fax: 215-914-1492; e-mail: joel.shuster@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:24421415

2013-01-01

391

Fission in Spallation Reactions  

NASA Astrophysics Data System (ADS)

Some properties of fission in spallation reactions in the GeV range are examined. It is shown on theoretical grounds that the charge, mass and excitation energy are strongly fluctuating. The range of accessible excitation energies is determined. The ability of a particular intranuclear plus evaporation model, namely the INCL4+ABLA model to describe the existing data is demonstrated. In view of the numerous parameters used in the fission model, the sensitivity of the results to these parameters is investigated. It is shown that, due to the complexity of the fission modeling, it is hard to get reliable information on the level density parameters at high excitation energy. Finally the influence of the nature of the incident projectile is shortly discussed.

Cugnon, J.; Aoust, Th.; Boudard, A.

2008-04-01

392

Polymerase chain reaction  

SciTech Connect

This paper discusses the polymerase chain reaction (PCR) an in-vitro method of amplifying DNA sequences. Beginning with DNA of any origin- bacterial, viral, plant, or animal- PCR can increase the amount of a DNA sequence hundreds of millions to billions of times. The procedure can amplify a targeted sequence even when it makes up less than one part in a million of the total initial sample. PCR is an enzymatic process that is carried out in discrete cycles of amplification, each of which can double the amount of target DNA in the sample. Thus, n cycles can produce 2{sup n} times as much target as was present to begin with. This paper discusses how PCR has had an impact on molecular biology, human genetics, infectious and genetic disease diagnosis, forensic science, and evolutionary biology.

Arnhelm, N. (Univ. of Southern California, CA (US)); Levenson, C.H. (Cetus Corp. (US))

1990-10-01

393

FERMENTATION REACTIONS OF ERYSIPELOTHRIX RHUSIOPATHIAE  

PubMed Central

White, Thomas G. (U. S. Department of Agriculture, Ames, Iowa), and Richard D. Shuman. Fermentation reactions of Erysipelothrix rhusiopathiae. J. Bacteriol. 82:595–599. 1961.—A study was made to determine the effect of four different basal media, to which fermentable carbon compounds had been added, upon 22 selected strains of Erysipelothrix rhusiopathiae (insidiosa). Acid production was measured by (i) chemical indicator, (ii) change in pH, and (iii) production of titrable acidity. At least two determinations, usually four, were made for each test on each strain. The fermentation pattern varied according to the medium, the indicator, and the method of measuring acid production. Andrade's base plus serum was the most dependable medium because it permitted the least variation in the total number of different patterns. Of the three methods used to measure acid production, the chemical indicator gave the most valid and reproducible results. The within-strain variation was not extreme and most strains persisted in a given fermentation pattern under like conditions of growth and acid production. Results of the study indicated that, regardless of the medium and indicator routinely used, one should be familiar with the fermentation pattern of known strains of the erysipelas organism. PMID:14006576

White, Thomas G.; Shuman, Richard D.

1961-01-01

394

High temperature chemical kinetic study of the H2-CO-CO2-NO reaction system  

NASA Technical Reports Server (NTRS)

An experimental study of the kinetics of the H2-CO-CO2-NO reaction system was made behind incident shock waves at temperatures of 2460 and 2950 K. The overall rate of the reaction was measured by monitoring radiation from the CO + O yields CO2 + h upoilon reaction. Correlation of these data with a detailed reaction mechanism showed that the high-temperature rate of the reaction N + OH yields NO + H can be described by the low-temperature (320 K) rate coefficient. Catalytic dissociation of molecular hydrogen was an important reaction under the tests conditions.

Jachimowski, C. J.

1975-01-01

395

Children's reactions to apologies  

Microsoft Academic Search

In 2 experiments, 221 kindergartners and 1st, 4th, and 7th graders judged actors who committed a transgression under conditions of low or high responsibility and low or high consequences. The actor's motives were good or bad and the act was intended or accidental. The actor then either did nothing or employed 1 of 3 increasingly elaborate apologies. As hypothesized, the

Bruce W. Darby; Barry R. Schlenker

1982-01-01

396

Study of chemical reactions under the influence of ultrasound  

SciTech Connect

At Los Alamos the author is interested in sonochemistry because there is potential for accelerating reactions involving the synthesis of certain nitro compounds and for reducing the possibility of decomposition under milder reaction conditions. The author has initiated the study of the nitration of 2,4-dihydro-3H-1,2,4-triazol-3-one with concentrated nitric acid under sonication. The preparation of 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2-dihydro-1,2,4,5-tetrazine, and oxidation of 3,6-diamino-1,2,4,5-tetrazine were also studied. Sonication reaction conditions and results of these reactions under ultrasound are discussed in detail.

Lee, Kien-Yin

1993-07-01

397

Study of chemical reactions under the influence of ultrasound  

SciTech Connect

At Los Alamos the author is interested in sonochemistry because there is potential for accelerating reactions involving the synthesis of certain nitro compounds and for reducing the possibility of decomposition under milder reaction conditions. The author has initiated the study of the nitration of 2,4-dihydro-3H-1,2,4-triazol-3-one with concentrated nitric acid under sonication. The preparation of 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2-dihydro-1,2,4,5-tetrazine, and oxidation of 3,6-diamino-1,2,4,5-tetrazine were also studied. Sonication reaction conditions and results of these reactions under ultrasound are discussed in detail.

Lee, Kien-Yin.

1993-01-01

398

THE HYDROVINYLATION AND RELATED REACTIONS: NEW PROTOCOLS AND CONTROL ELEMENTS IN SEARCH OF GREATER SYNTHETIC EFFICIENCY AND SELECTIVITY. (R826120)  

EPA Science Inventory

New reaction conditions and stereochemical control elements for heterodimerization between ethylene (or propylene) and functionalized vinyl arenes are highlighted (see equation). For example, an enantioselective version of the hydrovinylation reaction uses [{(allyl)NiBr}...

399

Production of unknown transactinides in asymmetry-exit-channel quasifission reactions  

SciTech Connect

Possibilities of production of new isotopes of superheavy nuclei with charge numbers 104-108 in asymmetry-exit-channel quasifission reactions are studied for the first time. The optimal conditions for the synthesis are suggested in this type of reaction. The products of suggested reactions can fill a gap of unknown isotopes between the isotopes of heaviest nuclei obtained in cold and hot complete fusion reactions.

Adamian, G.G. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Institute of Nuclear Physics, 702132 Tashkent (Uzbekistan); Antonenko, N. V.; Zubov, A. S. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)

2005-03-01

400

Synthesis of Pyridazinones through the Copper(I)-Catalyzed Multicomponent Reaction of Aldehydes, Hydrazines, and Alkynylesters.  

PubMed

The copper-catalyzed multicomponent cyclization reaction, which combined aldehydes, hydrazines, and alkynylesters, was applied in the synthesis of pyridazinones. The reaction was regioselective and gave only six-membered pyridazinones in the complete absence of five-membered pyrazoles or a regioisomeric mixture. During this investigation, the use of 2-halobenzaldehyde as the starting material, under identical reaction conditions, gave 6-(2-ethoxyphenyl)pyridazinones after sequential Michael addition/1,2-addition/Ullmann cross-coupling reactions. PMID:25124722

Mantovani, Anderson C; Goulart, Tales A C; Back, Davi F; Zeni, Gilson

2014-09-22

401

Fundamental studies of retrograde reactions in direct liquefaction  

SciTech Connect

The overall objective of the program was to improve the understanding of retrograde reactions and their dependencies on coal rank and structure, and/or coal modifications and reaction conditions. Because retrograde reactions are competitive with bond breaking reactions, an understanding of both is required to shift the competition in favor of the latter. Related objectives were to clarify the conflicting observations reported in literature on such major topics as the role of oxygen groups in retrograde reactions and to provide a bridge from very fundamental studies on pure compounds to phenomenological studies on actual coal. This information was integrated into the FG-DVC model, which was improved and extended to the liquefaction context.

Serio, M.A.; Solomon, P.R.; Kroo, E.; Charpenay, S.; Bassilakis, R.

1991-12-17

402

Upscaling geochemical reaction rates using pore-scale network modeling  

NASA Astrophysics Data System (ADS)

Geochemical reaction rate laws are often measured using crushed minerals in well-mixed laboratory systems that are designed to eliminate mass transport limitations. Such rate laws are often used directly in reactive transport models to predict the reaction and transport of chemical species in consolidated porous media found in subsurface environments. Due to the inherent heterogeneities of porous media, such use of lab-measured rate laws may introduce errors, leading to a need to develop methods for upscaling reaction rates. In this work, we present a methodology for using pore-scale network modeling to investigate scaling effects in geochemical reaction rates. The reactive transport processes are simulated at the pore scale, accounting for heterogeneities of both physical and mineral properties. Mass balance principles are then used to calculate reaction rates at the continuum scale. To examine the scaling behavior of reaction kinetics, these continuum-scale rates from the network model are compared to the rates calculated by directly using laboratory-measured reaction rate laws and ignoring pore-scale heterogeneities. In this work, this methodology is demonstrated by upscaling anorthite and kaolinite reaction rates under simulation conditions relevant to geological CO 2 sequestration. Simulation results show that under conditions with CO 2 present at high concentrations, pore-scale concentrations of reactive species and reaction rates vary spatially by orders of magnitude, and the scaling effect is significant. With a much smaller CO 2 concentration, the scaling effect is relatively small. These results indicate that the increased acidity associated with geological sequestration can generate conditions for which proper scaling tools are yet to be developed. This work demonstrates the use of pore-scale network modeling as a valuable research tool for examining upscaling of geochemical kinetics. The pore-scale model allows the effects of pore-scale heterogeneities to be integrated into system behavior at multiple scales, thereby identifying important factors that contribute to the scaling effect.

Li, Li; Peters, Catherine A.; Celia, Michael A.

2006-09-01

403

Exploring Transition Metal Catalyzed Reactions via AB Initio Reaction Pathways  

NASA Astrophysics Data System (ADS)

The study and prediction of chemical reactivity is one of the most influential contributions of quantum chemistry. A central concept in the theoretical treatment of chemical reactions is the reaction pathway, which can be quite difficult to integrate accurately and efficiently. This talk will outline our developments in the integration of these pathways on ab initio potential energy surfaces. We will also describe results from recent studies on the kinetics of transition metal catalyzed reactions, including the importance of vibrational coupling to the reaction coordinate and the role of this coupling in catalytic rate enhancement.

Hratchian, Hrant P.

2011-06-01

404

Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction  

SciTech Connect

Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. The authors have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation ({approximately} 15.1 Kcal/mol).

Chaudhary, A.K.; Beckman, E.J.; Russell, A.J. [Univ. of Pittsburgh, PA (United States)] [Univ. of Pittsburgh, PA (United States)

1998-08-20

405

Modeling of the isothermal sulphation reactions of natural sorbents  

Microsoft Academic Search

The sulphation reaction of the calcines produced from four limestone and one dolomite samples were investigated and modeled. The experiments were conducted in a thermogravimetric analyzer under isothermal conditions and in a gaseous atmosphere consisting of 15vol% CO2, 0.35vol% SO2 and balance of dry air by volume. The variation of reaction rate with temperature was determined by sulphating of calcines

Ay?egül Ersoy-Meriçboyu; Sadriye Küçükbayrak

1998-01-01

406

Chemical reactions of organic compounds on clay surfaces.  

PubMed Central

Chemical reactions of organic compounds including pesticides at the interlayer and exterior surfaces of clay minerals and with soil organic matter are reviewed. Representative reactions under moderate conditions possibly occurring in natural soils are described. Attempts have been made to clarify the importance of the chemical nature of molecules, their structures and their functional groups, and the Brönsted or Lewis acidity of clay minerals. PMID:2533556

Soma, Y; Soma, M

1989-01-01

407

A Review on Chemical Reactions of Solid Lubricants During Friction  

Microsoft Academic Search

A historical background on chemical reactions between solids, in which the chemical activation energy is generated by mechanical forces, is presented and a literature review on “mechano-chemical” or “tribo-chemical” reactions occurring between solid lubricants such as MoS2 and Zn2P2O7 and metal surfaces is given. According to the work reviewed, MoS2 reacts with steel surfaces under boundary friction conditions forming FeS

J. Gansheimer

1972-01-01

408

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

409

Reaction kinetics of Ca-based sorbents with HC1  

Microsoft Academic Search

The paper gives results of an investigation of the kinetics of the reaction between CaO and HCl 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 diffusion and chemical reaction control, either singly or

B. K. Gulett; W. Jozewicz; L. A. Stefanski

1992-01-01

410

Molecule-based approach for computing chemical-reaction rates in upper atmosphere hypersonic flows.  

SciTech Connect

This report summarizes the work completed during FY2009 for the LDRD project 09-1332 'Molecule-Based Approach for Computing Chemical-Reaction Rates in Upper-Atmosphere Hypersonic Flows'. The goal of this project was to apply a recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary nonequilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological non-equilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, the difference between the two models can exceed 10 orders of magnitude. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates. Extensions of the model to reactions typically found in combustion flows and ionizing reactions are also found to be in very good agreement with available measurements, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

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

2009-08-01

411

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

412

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

413

On the possibility of negative activation energies in bimolecular reactions  

NASA Technical Reports Server (NTRS)

The temperature dependence of the rate constants for model reacting systems was studied to understand some recent experimental measurements which imply the existence of negative activation energies. A collision theory model and classical trajectory calculations are used to demonstrate that the reaction probability can vary inversely with collision energy for bimolecular reactions occurring on attractive potential energy surfaces. However, this is not a sufficient condition to ensure that the rate constant has a negative temperature dependence. On the basis of these calculations, it seems unlikely that a true bimolecular reaction between neutral molecules will have a negative activation energy.

Jaffe, R. L.

1978-01-01

414

Modeling Second-Order Chemical Reactions using Cellular Automata  

NASA Astrophysics Data System (ADS)

Cellular automata (CA) are discrete, agent-based, dynamic, iterated, mathematical computational models used to describe complex physical, biological, and chemical systems. Unlike the more computationally demanding molecular dynamics and Monte Carlo approaches, which use "force fields" to model molecular interactions, CA models employ a set of local rules. The traditional approach for modeling chemical reactions is to solve a set of simultaneous differential rate equations to give deterministic outcomes. CA models yield statistical outcomes for a finite number of ingredients. The deterministic solutions appear as limiting cases for conditions such as a large number of ingredients or a finite number of ingredients and many trials. Here we present a 2-dimensional, probabilistic CA model of a second-order gas phase reaction A + B ? C, using a MATLAB basis. Beginning with a random distribution of ingredients A and B, formation of C emerges as the system evolves. The reaction rate can be varied based on the probability of favorable collisions of the reagents A and B. The model permits visualization of the conversion of reagents to products, and allows one to plot concentration vs. time for A, B and C. We test hypothetical reaction conditions such as: limiting reagents, the effects of reaction probabilities, and reagent concentrations on the reaction kinetics. The deterministic solutions of the reactions emerge as statistical averages in the limit of the large number of cells in the array. Modeling results for dynamic processes in the atmosphere will be presented.

Hunter, N. E.; Barton, C. C.; Seybold, P. G.; Rizki, M. M.

2012-12-01

415

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

416

Resonances in the cumulative reaction probability for a model electronically nonadiabatic reaction  

SciTech Connect

The cumulative reaction probability, flux{endash}flux correlation function, and rate constant are calculated for a model, two-state, electronically nonadiabatic reaction, given by Shin and Light [S. Shin and J. C. Light, J. Chem. Phys. {bold 101}, 2836 (1994)]. We apply straightforward generalizations of the flux matrix/absorbing boundary condition approach of Miller and co-workers to obtain these quantities. The upper adiabatic electronic potential supports bound states, and these manifest themselves as {open_quote}{open_quote}recrossing{close_quote}{close_quote} resonances in the cumulative reaction probability, at total energies above the barrier to reaction on the lower adiabatic potential. At energies below the barrier, the cumulative reaction probability for the coupled system is shifted to higher energies relative to the one obtained for the ground state potential. This is due to the effect of an additional effective barrier caused by the nuclear kinetic operator acting on the ground state, adiabatic electronic wave function, as discussed earlier by Shin and Light. Calculations are reported for five sets of electronically nonadiabatic coupling parameters. {copyright} {ital 1996 American Institute of Physics.}

Qi, J.; Bowman, J.M. [Department of Chemistry and Cherry L. Emerson Center for Science Computation, Emory University, Atlanta, Georgia 30322 (United States)] [Department of Chemistry and Cherry L. Emerson Center for Science Computation, Emory University, Atlanta, Georgia 30322 (United States)

1996-05-01

417

Enzymatic reactions on immobilised substrates.  

PubMed

This review gives an overview of enzymatic reactions that have been conducted on substrates attached to solid surfaces. Such biochemical reactions have become more important with the drive to miniaturisation and automation in chemistry, biology and medicine. Technical aspects such as choice of solid surface and analytical methods are discussed and examples of enzyme reactions that have been successful on these surfaces are provided. PMID:23579870

Gray, Christopher J; Weissenborn, Martin J; Eyers, Claire E; Flitsch, Sabine L

2013-08-01

418

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

419

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

2008-02-23

420

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

421

A biomolecule-compatible visible-light-induced azide reduction from a DNA-encoded reaction-discovery system  

Microsoft Academic Search

Using a system that accelerates the serendipitous discovery of new reactions by evaluating hundreds of DNA-encoded substrate combinations in a single experiment, we explored a broad range of reaction conditions for new bond-forming reactions. We discovered reactivity that led to a biomolecule-compatible, Ru(II)-catalysed azide-reduction reaction induced by visible light. In contrast to current azide-reduction methods, this reaction is highly chemoselective

Yiyun Chen; Adam S. Kamlet; Jonathan B. Steinman; David R. Liu

2011-01-01

422

Conditions affecting the formation of chlorinated carbon compounds during carbochlorination  

NASA Astrophysics Data System (ADS)

The Bureau of Mines, United States Department of the Interior, has conducted an extensive study of the relationship between various metal oxide carbochlorination reactions and carbon compound byproducts. Experiments in which oxides of titanium, zirconium, and aluminum with graphite, charcoal, metallurgical coke, and pctroleum coke were chlorinated at 600° to 1000 °C produced 136 identified and quantified carbon byproduct compounds. The 20 most abundant of these compounds were correlated with reactants and reaction conditions. Experimental results support a proposed carbochlorination reaction with an initial chlorine-carbon step followed by a reaction between the resulting chlorine-carbon products and the metal oxide.

Landsberg, A.; Wilson, R. D.; Burns, W.

1988-06-01

423

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.

Dr. Martin McClinton, Debbie McClinton, Dr. Miriam Douglass

2011-01-01

424

Catalytic enantioselective decarboxylative reactions using organocatalysts.  

PubMed

Catalytic decarboxylative reactions are attractive as biomimetic reactions and environmentally friendly reaction processes. In this review, the origin and recent development of organocatalytic enantioselective decarboxylative reactions of malonic acid half oxy- or thioesters, or ?-ketoacids are summarized. PMID:24270735

Nakamura, Shuichi

2014-01-21

425

Radiation reaction in fusion plasmas.  

PubMed

The effects of a radiation reaction on thermal electrons in a magnetically confined plasma, with parameters typical of planned burning plasma experiments, are studied. A fully relativistic kinetic equation that includes the radiation reaction is derived. The associated rate of phase-space contraction is computed and the relative importance of the radiation reaction in phase space is estimated. A consideration of the moments of the radiation reaction force show that its effects are typically small in reactor-grade confined plasmas, but not necessarily insignificant. PMID:15600530

Hazeltine, R D; Mahajan, S M

2004-10-01

426

Kinematically complete chemical reaction dynamics  

NASA Astrophysics Data System (ADS)

Kinematically complete studies of molecular reactions offer an unprecedented level of insight into the dynamics and the different mechanisms by which chemical reactions occur. We have developed a scheme to study ion-molecule reactions by velocity map imaging at very low collision energies. Results for the elementary nucleophilic substitution (SN2) reaction Cl- + CH3I ? ClCH3 + I- are presented and compared to high-level direct dynamics trajectory calculations. Furthermore, an improved design of the crossed-beam imaging spectrometer with full three-dimensional measurement capabilities is discussed and characterization measurements using photoionization of NH3 and photodissociation of CH3I are presented.

Trippel, S.; Stei, M.; Otto, R.; Hlavenka, P.; Mikosch, J.; Eichhorn, C.; Lourderaj, U.; Zhang, J. X.; Hase, W. L.; Weidemüller, M.; Wester, R.

2009-11-01

427

Charge Transfer Reactions  

NASA Astrophysics Data System (ADS)

Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

Dennerl, Konrad

2010-12-01

428

[Electroencephalographic analysis of a conditioned reflex to time].  

PubMed

EEG parameters in different cortical territories of free moving dogs were analyzed during formation of conditioned reflex to time, in situation of instrumental alimentary conditioning. It was shown that in organization of a reflex to time as a complex reaction(present, trace and rhythmic processes), different brain systems play different roles in the formation of its stages. Sensory systems provide for the complex of trace processes underlying reaction to time. Associative structures are involved in the afferent synthesis necessary for the present moment. Integrative-triggering formations attach formed reaction to a strictly fixed time. PMID:7386013

Mukhin, E I

1980-01-01

429

Effective reaction parameters for mixing controlled reactions in heterogeneous media  

Microsoft Academic Search

Sound understanding of mixing-controlled reactions in heterogeneous media is needed for the realistic modeling of contaminant transport in aquifers and is a precondition for the evaluation of natural attenuation processes, the design of nuclear waste disposal, and the engineered remediation of contaminated sites. In this work, we study the bimolecular dissolution-precipitation equilibrium reaction, adapted after De Simoni et al. (2005).

Jian Luo; Marco Dentz; Jesus Carrera; Peter Kitanidis

2008-01-01

430

Critical conditions for phytoplankton blooms.  

PubMed

We motivate and analyse a reaction-advection-diffusion model for the dynamics of a phytoplankton species. The reproductive rate of the phytoplankton is determined by the local light intensity. The light intensity decreases with depth due to absorption by water and phytoplankton. Phytoplankton is transported by turbulent diffusion in a water column of given depth. Furthermore, it might be sinking or buoyant depending on its specific density. Dimensional analysis allows the reduction of the full problem to a problem with four dimensionless parameters that is fully explored. We prove that the critical parameter regime for which a stationary phytoplankton bloom ceases to exist, can be analysed by a reduced linearized equation with particular boundary conditions. This problem is mapped exactly to a Bessel function problem, which is evaluated both numerically and by asymptotic expansions. A final transformation from dimensionless parameters back to laboratory parameters results in a complete set of predictions for the conditions that allow phytoplankton bloom development. Our results show that the conditions for phytoplankton bloom development can be captured by a critical depth, a compensation depth, and zero, one or two critical values of the vertical turbulent diffusion coefficient. These experimentally testable predictions take the form of similarity laws: every plankton-water-light-system characterized by the same dimensionless parameters will show the same dynamics. PMID:11732178

Ebert, U; Arrayás, M; Temme, N; Sommeijer, B; Huisman, J

2001-11-01

431

Highly restrictive diffusion under hydrotreating reactions of heavy residue oils  

SciTech Connect

The effect of the ratio ({lambda}) of reactant molecular diameter to catalyst pore diameter on the restrictive diffusion under a highly restrictive regime of hydrotreating reactions of heavy residue oils over CoMo/alumina-alumina phosphate catalysts was investigated. Hydrotreating reactions of residual oils were carried out in a trickle bed reactor at 663 K and 7.6 MPa over a series of CoMo/alumina-aluminum phosphate catalysts. The values of the effective diffusivities and the relevant effectiveness factors for HDS and HDM reactions were determined by applying the Thiele relation to catalytic reactions. The effective diffusivities for the HDM reaction are always smaller than those for the HDS reaction. In addition, the effective diffusivity values decreased with increasing ratios of reactant molecular diameters to catalyst pore diameters for both HDS and HDM reactions, indicating a large restrictive diffusion effect. Two different regimes for restrictive diffusion were observed. The restrictive effect under reaction conditions is still severe for low values of {lambda}. However, this effect does not seem prominent for high values of {lambda}

Li, C. [Chinese Petroleum Corp., Chia-Yi (Taiwan, Province of China). Refining and Manufacturing Research Center; Chen, Y.W.; Tsai, M.C. [National Central Univ., Chung-Li (Taiwan, Province of China). Dept. of Chemical Engineering

1995-03-01

432

Laboratory Kinetics of Chemical Reactions occurring in Astrophysical Environments  

NASA Astrophysics Data System (ADS)

To model the dynamics and molecular evolution of interstellar clouds, a great deal of information on chemical kinetics is required, preferably under the appropriate conditions of kinetic temperature and internal excitation. This kinetics includes (i) gas phase ionic (ion-molecule and electron-ion) and (ii) neutral-neutral reactions and (iii) heterogeneous surface catalysis, all from simple species to those as complex as polyaromatic hydrocarbons and pre-life molecules. The current situation in these three areas will be briefly reviewed with more emphasis on ionic reactions for which the most data are available. The classes of reactions will include charge and proton transfer, atom insertion and abstraction, radiative association, electron-ion and ion-ion recombination, reactions with atoms, reactions involving isotopes, reaction and production of structural isomers, ring formation and destruction, and condensation. Information on rates of reaction, product identity and state of excitation will be presented wherever possible. Some mention will also be made of the reactions of negative ions. Most recent data will be presented, specifically involving the understudied process of electron-ion recombination. Some possible future directions will also be suggested. Funding of my research program by ACF-PRF, NASA and NSF is gratefully acknowledged.

Adams, N. G.; Babcock, L. M.

2005-05-01

433

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

434

Implications of dehydration reactions on the earthquake mechanics and faulting  

NASA Astrophysics Data System (ADS)

Dehydration reactions are inferred to occur along subduction zones where rocks from the oceanic crust undergo a series of metamorphic reactions during their burial. Metamorphic dehydration reactions of hydrous minerals such as clays and serpentines have been suggested as a possible origin for intermediate depth earthquakes in subducting slabs. Indeed, fluid releasing and mechanical compaction of pores during dehydration reactions may induce fault instabilities. However, our understanding of the feedbacks between dehydration reaction, fluid flow properties and mechanical behavior is not yet integrated into a single unified model. In this study, we try to unravel the behavior of dehydration reactions from laboratory experiments conducted on gypsum with a triaxial deformation rigs under controlled temperature (30-140°C) and confining pressure (0-300 MPa). The aim of our set of experiments is to understand the coupling and feedbacks between the state of stress, the mechanical and hydraulic properties of gypsum and the metamorphic reactions. We monitor fluid expulsion, fluid pressure and strain evolution for a given confining pressure, differential stress and temperature during all experiments. In parallel, SEM observations and EBSD analyses are used to constrain reaction and deformation mechanisms occurring at grain scale during each experiment. These analyses conducted at grain scale allow us to discriminate the mechanism of deformation occurring in parallel of dehydration reaction and give information about the rheological laws and behavior of the material for the tested conditions. Llana Funez et al. (2012) focused on the link between fluid pressure and reaction rate. The samples, being porous, compacted, and in new work we examine that process in more detail. The results of laboratory experiments and microstructural analyses are then used to estimate the implications of dehydration reaction on earthquake mechanics and faulting in seismogenic geological contexts such as subduction zones or crustal fault zones composed of hydrous minerals.

Wheeler, J.; LECLČRE, H.; Faulkner, D. R.; Mariani, E.

2013-12-01

435

Native transfer RNA catalyzes Diels-Alder reaction.  

PubMed

In this paper we show that transfer ribonucleic acids (tRNAs) catalyze the Diels-Alder cycloaddition reaction. A new DNA oxidative damage product, 6-furfuryladenine (kinetin) or its riboside (diene), was transformed with dimethyl acetylenedicarboxylate or maleic anhydride (dienophile). The reaction proceeds in the presence of tRNA at high pressure but not at ambient condition. If so tRNA in prebiotic conditions (RNA world) had at least two functions: catalytic and a carrier of genetic information. It means that tRNA at high pressure shows catalytic properties and is a true Diels-Alderase. PMID:12054754

Mielcarek, Michal; Barciszewska, Miroslawa Z; Sa?anski, Piotr; Stobiecki, Maciej; Jurczak, Janusz; Barciszewski, Jan

2002-05-31

436

What's conditioned in conditioned place preference?  

PubMed

Conditioned place preference (CPP) is a learned behavior shown in many vertebrates, including humans. CPP occurs when a subject comes to prefer one place more than others because the preferred location has been paired previously with rewarding events. The CPP paradigm is widely used to explore the reinforcing effects of natural and pharmacological stimuli, including drugs of addiction. There is a general assumption that an acquired place preference is based on classical conditioning derived 'incentive motivation'. However, this may be an oversimplification of the multiple learning processes involved. We argue that although CPP may appear as an incentive-driven behavior related to secondary reinforcers, it may also be a result of operant conditioning of behavior prevailing at the conditioning site, as well as a result of conditioned treatment effects. Here, we outline alternative explanations for an observed CPP, which may fundamentally affect the interpretation of results with this paradigm in its use as a screening tool for rewarding properties of treatments. PMID:23384389

Huston, Joseph P; Silva, Maria A de Souza; Topic, Bianca; Müller, Christian P

2013-03-01

437

Homogeneous and heterogeneous asymmetric reactions: Part 11  

Microsoft Academic Search

Enantioselective sonochemical hydrogenation of ?,?,?-trifluoromethyl ketones, namely 1,1,1-trifluoroacetophenone and 1,1,1-trifluoro-phenylacetone was carried out over various platinum catalysts modified by cinchonidine in different solvents. Both compounds yielded the (R)-alcohol as major product. The reaction rates and the enantiomeric excesses were determined over Pt\\/C, Pt\\/SiO2, Pt\\/K-10 and Pt\\/Al2O3 catalysts under conventional conditions. Since Pt\\/Al2O3 exhibited the best catalytic performance the effect of

Katalin Balázsik; Béla Török; Károly Felföldi; Mihály Bartók

1999-01-01

438

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

439

Nucleation and reaction rates controlled by local reaction volume and reaction-induced stress - spinel layer growth as an example  

NASA Astrophysics Data System (ADS)

We observed the growth of spinel sensu stricto (MgAl2O4) between periclase (MgO) and corundum (Al2O3) in thin films deposited by the pulsed laser deposition method on crystallographically oriented single crystal substrates. The starting samples consisted of cut and ultra polished single crystals of either corundum (parallel (0001)) or periclase (parallel (111)) and an amorphous source layer of the respective reactant that in the very first stages of the experiments became polycrystalline. The cutting direction in the substrate minerals ensures that the substrate phases start to react along their close-packed hexagonal oxygen layers which allows topotactical growth of the newly formed spinel. The entire layer setup on the substrate crystals was only a few 100 nm thick. The growth of these spinel product layers was monitored in-situ using a heating attachment and synchrotron X-ray diffraction. From the reacted samples we took electron transparent foils by the focused ion beam method and analysed them ex-situ by TEM. At 1000°C we found a difference in spinel growth rate between one and two orders of magnitude between the two substrates, all other parameters held constant. At 900 and 1000 °C spinel had formed after one hour by 0.004 nm/s (900°C) and 0.034 nm/s (1000°C) on corundum substrate, while on periclase substrate the reaction had gone completely through the Al2O3 source layer transforming it to spinel by at least 15-30 times higher reaction rates (boundary values) and probably even faster. At 800°C no reaction occurred between periclase layers and corundum single crystals, whereas spinel crystallized at a (linearized) rate of 46 nm/h on periclase single crystals. We explain our findings by the local reaction volume at the periclase-corundum interface. Many studies (including this one) have established that spinel grows by cation exchange in a rather immobile oxygen sublattice. This mechanism implies a negative volume change at the Sp-Per interface (by -13 %) and a positive volume change at the Sp-Cor interface (by +17 %). We observed in TEM images formation of porosity at the Sp-Per substrate interface and lattice strain in the polycrystalline corundum substrate at the Sp-Cor substrate interface, both observations being fully in line with the respective local volume changes. We infer that the local stress field between the growing reaction layer and the rigid single crystal substrate is responsible for the dramatic effect on both the nucleation and reaction rates. With respect to minerals growing at dry conditions in the Earth's crust (granulite facies) we infer that rates of reactions might strongly depend on local volume changes at interfaces, that reactions are impeded by compressive reaction-induced stress applied to rigid neighboring grains, and that nucleation of thermodynamically stable phases on grain boundaries might be suppressed by a positive reaction volume.

Götze, Lutz C.; Milke, Ralf; Dohmen, Ralf; Wirth, Richard

2014-05-01

440

Methionine peptide formation under primordial earth conditions.  

PubMed

According to recent research on the origin of life it seems more and more likely that amino acids and peptides were among the first biomolecules formed on earth and that a peptide/protein world was thus a key starting point in evolution towards life. Salt-induced Peptide Formation (SIPF) has repeatedly been shown to be the most universal and plausible peptide-forming reaction currently known under prebiotic conditions and forms peptides from amino acids with the help of copper ions and sodium chloride. In this paper we present experimental results for salt-induced peptide formation from methionine. This is the first time that a sulphur-containing amino acid was investigated in this reaction. The possible catalytic effects of glycine and L-histidine in this reaction were also investigated and a possible distinction between the L- and D-forms of methionine was studied as well. PMID:18262274

Li, Feng; Fitz, Daniel; Fraser, Donald G; Rode, Bernd M

2008-01-01

441

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

442

Understanding the novolak synthesis reaction  

Microsoft Academic Search

We describe new tools for the characterization of novolac resins, for the understanding of the novolac synthesis reaction, and for the prediction of resin structures. These tools have been used to optimize the performance of photoresists for microlithography. The current state-of- the-art describes novolac copolymer compositions as the ratio of monomers charged in the reaction, even though it is well

Leonard E. Bogan

1993-01-01

443

Theory of hybrid nuclear reactions  

SciTech Connect

A theory of hybrid nuclear reactions, which are partially direct and partially compound, is presented. We review first the formulation of the theory, based on the optical theorem, and then its applications to a few example reactions. Discussions will be given on the physical picture (deep peripheral nature) of such hybrid processes emerging from the numerical studies. 25 references, 10 figures.

Udagawa, T.

1983-01-01

444

Semiclassical aspects of transfer reactions  

SciTech Connect

Semiclassical analysis of heavy ion induced transfer reactions are discussed for the quasielastic region. Some unique aspects of these reactions are shown, the variety of features which can be understood semiclassically is demonstrated, and some open problems are indicated. 28 refs., 16 figs. (LEW)

Bond, P.D.

1985-01-01

445

Reciprocity theory of homogeneous reactions  

Microsoft Academic Search

The reciprocity formalism is applied to the homogeneous gaseous reactions in which the structure of the participating molecules changes upon collision with one another, resulting in a change in the composition of the gas. The approach is applied to various classes of dissociation, recombination, rearrangement, ionizing, and photochemical reactions. It is shown that for the principle of reciprocity to be

Adolf A. Agbormbai

1990-01-01

446

PHENOTHIAZINE ATARAXICS--Extrapyramidal Reactions  

PubMed Central

Thirty-nine cases of extrapyramidal reactions caused by seven chemically different phenothiazine medications are presented. Historical, pharmacological, diagnostic, and therapeutic factors are considered. It is important that the physician prescribing phenothiazines be well aware of the reactions which may occur so that therapy may be discontinued at the first untoward signs. PMID:13806816

Cain, Harvey D.; Malcolm, Mary

1960-01-01

447

Allergic reactions to insect secretions.  

PubMed

Some products derived from insects can induce allergic reactions. The main characteristics of some products from honeybees, cochineal and silkworms are summarised here. We review allergic reactions from honey-derived products (propolis, wax, royal jelly), from cochineal products (shellac and carmine) and from silk : clinical features, allergological investigations and allergens if they are known. PMID:24449611

Pecquet, Catherine

2013-01-01

448

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

449

The Variance Reaction Time Model  

ERIC Educational Resources Information Center

The variance reaction time model (VRTM) is proposed to account for various recognition data on reaction time, the mirror effect, receiver-operating-characteristic (ROC) curves, etc. The model is based on simple and plausible assumptions within a neural network: VRTM is a two layer neural network where one layer represents items and one layer…

Sikstrom, Sverker

2004-01-01

450

REACTION OF URANIUM WITH NITROGEN  

Microsoft Academic Search

Studies of U reactions with nitrogen at 400 to 920 deg C and 200 mm Hg ; nitrogen pressure indicated no nitriding below 400 deg . The reaction rate at ; 590 and 710 deg C and 20 to 600 mm Hg pressure is directly proportional to the ; square root of the pressure and is not influenced by nitrogen

A. F. Bessonov; V. G. Vlasov

1962-01-01

451

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

452

Modality, rationalism, and conditionals  

E-print Network

This thesis consists of three interconnected papers on apriority, modality, and conditionals. In "Playground Conditionals," I look at three philosophical debates, each of which turns on the epistemic status of a certain ...

Decker, Jason (Jason Andrew)

2007-01-01

453

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

454

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

455

Cues of Maternal Condition Influence Offspring Selfishness  

PubMed Central

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; Kolliker, Mathias

2014-01-01

456

Noncomputable Conditional Distributions  

Microsoft Academic Search

We study the computability of conditional proba- bility, a fundamental notion in probability theory and Bayesian statistics. In the elementary discrete setting, a ratio of proba- bilities defines conditional probability. In more general settings, conditional probability is defined axiomatically, and the search for more constructive definitions is the subject of a rich literature in probability theory and statistics. However, we

Nathanael L. Ackerman; Cameron E. Freer; Daniel M. Roy

2011-01-01

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Boundary Conditions Copenhagen University  

E-print Network

Boundary Conditions Gerd Grubb Copenhagen University Lecture in memory of Lars H¨ormander 26th Nordic and 1st Nordic-European Congress of Mathematicians June 2013 Gerd Grubb Copenhagen University, and the people involved. Gerd Grubb Copenhagen University Boundary Conditions #12;On boundary conditions

Grubb, Gerd