Computer-Assisted Design and Synthetic Applications of Chiral Enol Borinates: Novel, Highly Enantioselective Aldol Reagents

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Gennari Cesare

1998-01-01

Full Text Available We have recently described the development of a quantitative transition state model for the prediction of stereoselectivity in the boron-mediated aldol reaction. This model provides qualitative insights into the factors contributing to the stereochemical outcome of a variety of reactions of synthetic importance. The force field model was used to assist the design and preparation of new chiral boron ligands derived from menthone. The chiral boron enolates were employed in various stereoselective processes, including the addition to chiral aldehydes and the reagent-controlled total synthesis of (3S,4S-statine. The chiral enolates derived from alpha-halo and alpha-oxysubstituted thioacetates were added to aldehydes and imines. Addition to imines leads to the enantioselective synthesis of chiral aziridines, a formal total synthesis of (+-thiamphenicol, and a new highly efficient synthesis of the paclitaxel (taxol® C-13 side-chain and taxol semisynthesis from baccatin III. The stereochemical outcome of the addition to imines was rationalised with the aid of computational studies. Enantioselective addition reactions of the chiral boron enolate derived from thioacetate have successfully been applied to solid phase bound aldehydes to give aldol products in comparable yields and enantioselectivities to the usual solution conditions.

Ketone deprotonation mediated by mono- and heterobimetallic alkali and alkaline earth metal amide bases: structural characterization of potassium, calcium, and mixed potassium-calcium enolates.

Science.gov (United States)

He, Xuyang; Noll, Bruce C; Beatty, Alicia; Mulvey, Robert E; Henderson, Kenneth W

2004-06-23

Potassium, calcium, and mixed potassium-calcium amide combinations have been shown to be efficient reagents in enolization reactions, and a set of representative intermediate mono- and heterobimetallic enolates have been successfully isolated and crystallographically characterized.

Bicyclic enol cyclocarbamates inhibit penicillin-binding proteins

NARCIS (Netherlands)

Dockerty, Paul; Edens, Jerre G; Tol, Menno B; Morales Angeles, Danae; Domenech Pena, Arnau; Liu, Yun; Hirsch, Anna K H; Veening, Jan-Willem; Scheffers, Dirk-Jan; Witte, Martin D

2017-01-01

Natural products form attractive leads for the development of chemical probes and drugs. The antibacterial lipopeptide Brabantamide A contains an unusual enol cyclocarbamate and we used this scaffold as inspiration for the synthesis of a panel of enol cyclocarbamate containing compounds. By

Lithium Enolates in the Enantioselective Construction of Tetrasubstituted Carbon Centers with Chiral Lithium Amides as Noncovalent Stereodirecting Auxiliaries.

Science.gov (United States)

Yu, Kai; Lu, Ping; Jackson, Jeffrey J; Nguyen, Thuy-Ai D; Alvarado, Joseph; Stivala, Craig E; Ma, Yun; Mack, Kyle A; Hayton, Trevor W; Collum, David B; Zakarian, Armen

2017-01-11

Lithium enolates derived from carboxylic acids are ubiquitous intermediates in organic synthesis. Asymmetric transformations with these intermediates, a central goal of organic synthesis, are typically carried out with covalently attached chiral auxiliaries. An alternative approach is to utilize chiral reagents that form discrete, well-defined aggregates with lithium enolates, providing a chiral environment conducive of asymmetric bond formation. These reagents effectively act as noncovalent, or traceless, chiral auxiliaries. Lithium amides are an obvious choice for such reagents as they are known to form mixed aggregates with lithium enolates. We demonstrate here that mixed aggregates can effect highly enantioselective transformations of lithium enolates in several classes of reactions, most notably in transformations forming tetrasubstituted and quaternary carbon centers. Easy recovery of the chiral reagent by aqueous extraction is another practical advantage of this one-step protocol. Crystallographic, spectroscopic, and computational studies of the central reactive aggregate, which provide insight into the origins of selectivity, are also reported.

Total Synthesis of Marine Cyclic Enol-Phosphotriester Salinipostin Compounds

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Zhao, Mingliang; Wei, Xianfeng; Liu, Xuemeng; Dong, Xueyang; Yu, Rilei; Wan, Shengbiao; Jiang, Tao

2018-06-01

Due to their structural diversity and variety of biological activities, marine natural products have been the subject of extensive study. These compounds, especially phospholipid polycyclic aromatic hydrocarbons, have a wide range of pharmacological applications, including embedded DNA and central nervous system, anti-tumor, anti-virus, anti-parasite, anti-bacterial, and antithrombotic effects. Unfortunately, the insufficient drug sources have limited the development of these compounds. In this study, we isolated salinpostin compounds from a fermentation solution of marine-derived Salinospora sp., which has a common bicyclic enol-phosphotriester core framework, as well as potent and selective antimalarial activities against P. falciparum with EC50 = 50 nmol L-1. The chemical synthesis of these compounds in greater quantities is necessary for their use in bioactivity studies. Thus we explored a short route with high yields and mild reaction conditions, which can generate combinatorial libraries for drug discovery and lead optimization. We developed a new total synthesis method for six cyclic enol-phosphotriester salinipotin compounds and their diastereomers. For the total synthesis of cyclipostin P, we prepared cyclic enol-phosphotriester salinipostin compounds in 10 steps from a readily accessible starting material, 1,3-dihydroxyacetone, and obtained an overall yield of 1.29%. We fully characterized these compounds by proton nuclear magnetic resonance (1H-NMR), carbon-13 NMR (13C-NMR), and high-resolution mass spectrometry (HRMS) analyses, and found they coincide absolutely with the same compounds reported previously.

Total syntheses of naturally occurring diacetylenic spiroacetal enol ethers.

Science.gov (United States)

Miyakoshi, Naoki; Aburano, Daisuke; Mukai, Chisato

2005-07-22

A highly stereoselective method for constructing a (2E)-methoxymethylidene-1,6-dioxaspiro[4.5]decane skeleton has been developed on the basis of the palladium(II)-catalyzed ring-closing reaction of the 3,4-dioxygenated-9-hydroxy-1-nonyn-5-one derivatives as a crucial step. The newly developed procedures could be successfully applied to the first total synthesis of five diacetylenic spiroacetal enol ether natural products starting from commercially available (R,R)- or (S,S)-diethyl tartrate.

Theoretical study on keto-enol tautomerisation of glutarimide for exploration of the isomerisation reaction pathway of glutamic acid in proteins using density functional theory

Science.gov (United States)

Fukuyoshi, Shuichi; Nakayoshi, Tomoki; Takahashi, Ohgi; Oda, Akifumi

2017-03-01

In order to elucidate the reason why glutamic acid residues have lesser racemisation reactivity than asparaginic acid, we investigated the racemisation energy barrier of piperidinedione, which is the presumed intermediate of the isomerisation reaction of L-Glu to D-Glu, by density functional theory calculations. In two-water-molecule-assisted racemisation, the activation barrier for keto-enol isomerisation was 28.1 kcal/mol. The result showed that the activation barrier for the racemisation of glutamic acid residues was not different from that for the racemisation of aspartic acid residues. Thus, glutamic acid residues can possibly cause the racemisation reaction if the cyclic intermediate stably exists.

Enantioselective Decarboxylative Alkylation Reactions: Catalyst Development, Substrate Scope, and Mechanistic Studies

Science.gov (United States)

Behenna, Douglas C.; Mohr, Justin T.; Sherden, Nathaniel H.; Marinescu, Smaranda C.; Harned, Andrew M.; Tani, Kousuke; Seto, Masaki; Ma, Sandy; Novák, Zoltán; Krout, Michael R.; McFadden, Ryan M.; Roizen, Jennifer L.; Enquist, John A.; White, David E.; Levine, Samantha R.; Petrova, Krastina V.; Iwashita, Akihiko; Virgil, Scott C.; Stoltz, Brian M.

2012-01-01

α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursors: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center. PMID:22083969

Enantioselective Decarboxylative Alkylation Reactions: Catalyst Development, Substrate Scope, and Mechanistic Studies

KAUST Repository

Behenna, Douglas C.; Mohr, Justin T.; Sherden, Nathaniel H.; Marinescu, Smaranda C.; Harned, Andrew M.; Tani, Kousuke; Seto, Masaki; Ma, Sandy; Nová k, Zoltá n; Krout, Michael R.; McFadden, Ryan M.; Roizen, Jennifer L.; Enquist, John A.; White, David E.; Levine, Samantha R.; Petrova, Krastina V.; Iwashita, Akihiko; Virgil, Scott C.; Stoltz, Brian M.

2011-01-01

α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center.

Enantioselective Decarboxylative Alkylation Reactions: Catalyst Development, Substrate Scope, and Mechanistic Studies

KAUST Repository

Behenna, Douglas C.

2011-11-14

α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center.

Surprisingly Mild Enolate-Counterion-Free Pd(0)-Catalyzed Intramolecular Allylic Alkylations

DEFF Research Database (Denmark)

Madec, David; Prestat, Guillaume; Martini, Elisabetta

2005-01-01

Palladium-catalyzed intramolecular allylic alkylations of unsaturated EWG-activated amides can take place under phase-transfer conditions or in the presence of a crown ether. These new reaction conditions are milder and higher yielding than those previously reported. A rationalization for such an...... for such an unexpected result is put forth and validated by DFT-B3LYP calculations. The results suggest cyclization via a counterion-free (E)-enolate TS....

Zinc Enolate/Sulfinate Prepared from a Single-Run Reaction Using Zinc Dust with O-Tosylated 4-Hydroxy Coumarin and Pyrone

Energy Technology Data Exchange (ETDEWEB)

Shin, Ueon Sang; Joo, Seong-Ryu; Kim, Seung-Hoi [Dankook University, Cheonan (Korea, Republic of)

2016-07-15

We demonstrated the preparation of new zinc complexes, 2-oxo-2H-chromen-4-yloxy tosylzinc (I), and 6-methyl-2-oxo-2H-pyran-4-yloxy tosylzinc (II), by the oxidative addition of readily available zinc dust into the corresponding 4-tosylated coumarin (A) and pyrone (B), respectively. Of special interest, the thus-obtained zinc complexes showed an electrophile-dependent reactivity. The subsequent coupling reactions of I and II with a variety of acid chlorides provided the O-acylation product in moderate yields. More interestingly, it should be emphasized that the thus-prepared zinc complexes (I and II) functioned both as zinc enolate and zinc sulfinate, providing C(3)-disubstituted product (b) and sulfone (c), respectively, from a single-run reaction when I or II was treated with benzyl halides. Even though somewhat low yields were achieved under the nonoptimized conditions, the novel zinc complexes present another potential application for zinc reagents. Versatile applications of this discovery are currently underway.

Zinc Enolate/Sulfinate Prepared from a Single-Run Reaction Using Zinc Dust with O-Tosylated 4-Hydroxy Coumarin and Pyrone

International Nuclear Information System (INIS)

Shin, Ueon Sang; Joo, Seong-Ryu; Kim, Seung-Hoi

2016-01-01

We demonstrated the preparation of new zinc complexes, 2-oxo-2H-chromen-4-yloxy tosylzinc (I), and 6-methyl-2-oxo-2H-pyran-4-yloxy tosylzinc (II), by the oxidative addition of readily available zinc dust into the corresponding 4-tosylated coumarin (A) and pyrone (B), respectively. Of special interest, the thus-obtained zinc complexes showed an electrophile-dependent reactivity. The subsequent coupling reactions of I and II with a variety of acid chlorides provided the O-acylation product in moderate yields. More interestingly, it should be emphasized that the thus-prepared zinc complexes (I and II) functioned both as zinc enolate and zinc sulfinate, providing C(3)-disubstituted product (b) and sulfone (c), respectively, from a single-run reaction when I or II was treated with benzyl halides. Even though somewhat low yields were achieved under the nonoptimized conditions, the novel zinc complexes present another potential application for zinc reagents. Versatile applications of this discovery are currently underway

RhII -Catalyzed β-C(sp2 )-H Alkylation of Enol Ethers, Enamides and Enecarbamates with α-Diazo Dicarbonyl Compounds.

Science.gov (United States)

McLarney, Brett D; Cavitt, Marchello A; Donnell, Theodore M; Musaev, Djamaladdin G; France, Stefan

2017-01-23

A Rh II -catalyzed method for intermolecular alkylation of the β-C(sp 2 )-H bond of enol ethers, enamides, and enecarbamates with α-diazo-1,3-dicarbonyl compounds is reported. The products are formed in up to 99 % yield and can be readily derivatized under a variety of conditions. By utilizing a combination of experimental and computational studies, the presumptive addition-elimination reaction mechanism was investigated and found to proceed under thermodynamic control at higher temperature. The acquired fundamental knowledge was translated into a strategic reaction design and yielded the first example of the β-C-H functionalizations of acyclic enol ethers using α-diazo-1,3-dicarbonyl compounds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Predicting Keto-Enol Equilibrium from Combining UV/Visible Absorption Spectroscopy with Quantum Chemical Calculations of Vibronic Structures for Many Excited States. A Case Study on Salicylideneanilines.

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Zutterman, Freddy; Louant, Orian; Mercier, Gabriel; Leyssens, Tom; Champagne, Benoît

2018-06-21

Salicylideneanilines are characterized by a tautomer equilibrium, between an enol and a keto form of different colors, at the origin of their remarkable thermochromic, solvatochromic, and photochromic properties. The enol form is usually the most stable but appropriate choice of substituents and conditions (solvent, crystal, host compound) can displace the equilibrium toward the keto form so that there is a need for fast prediction of the keto:enol abundance ratio. Here we demonstrate the reliability of a combined theoretical-experimental method, based on comparing simulated and measured UV/visible absorption spectra, to determine this keto/enol ratio. The calculations of the excitation energies, oscillator strengths, and vibronic structures of both enol and keto forms are performed for all excited states absorbing in the relevant (visible and near-UV) wavelength range at the time-dependent density functional theory level by accounting for solvent effects using the polarizable continuum model. This approach is illustrated for two salicylideneaniline derivatives, which are present, in solution, under the form of keto-enol mixtures. The results are compared to those of chemometric analysis as well as ab initio predictions of the reaction free enthalpies.

Highly Stereoselective Gold-Catalyzed Coupling of Diazo Reagents and Fluorinated Enol Silyl Ethers to Tetrasubstituted Alkenes.

Science.gov (United States)

Liao, Fu-Min; Cao, Zhong-Yan; Yu, Jin-Sheng; Zhou, Jian

2017-02-20

We report a highly stereoselective synthesis of all-carbon or fluorinated tetrasubstituted alkenes from diazo reagents and fluorinated enol silyl ethers, using C-F bond as a synthetic handle. Cationic Au I catalysis plays a key role in this reaction. Remarkable fluorine effects on the reactivity and selectivity was also observed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intramolecular Hydrogen Bonding in (2-Hydroxybenzoyl)benzoylmethane Enol

DEFF Research Database (Denmark)

Hansen, Bjarke Knud Vilster; Winther, Morten; Spanget-Larsen, Jens

2014-01-01

, and the dienol form of 1,3-dibenzoylacetone. But in these examples the two H-bonds are equivalent, while in the case of OHDBM they are chemically different, involving one enolic and one phenolic hydroxy group. OHDBM is thus an interesting model compound with two competing H-bonds to the same carbonyl group......In the stable enol tautomer of the title compound (OHDBM), one carbonyl group is flanked by two β-hydroxy groups, giving rise to bifold intramolecular H-bonding. A similar situation is found in other β,β'-dihydroxy carbonyl compounds like chrysazin, anthralin, 2,2'-dihydroxybenzophenone...

Preparation of Substituted Enol Derivatives From Terminal Alkynes and Their Synthetic Utility

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DeBergh, John R.; Spivey, Kathleen M.; Ready, Joseph M.

2009-01-01

Stereodefined enol derivatives of aldehydes are prepared from terminal alkynes. Specifically, terminal alkynes are known to undergo Cp2ZrCl2-catalyzed methylalumination. Here, we show that the resultant vinylalanes can be oxygenated with peroxyzinc species to generate trisubstituted enolates. Electrophilic trapping with carboxylic anydrides or silyl triflates yields trisubstituted enol esters or silanes, respectively. The tandem carbometalation/oxygenation tolerates free and protected alcohols, heterocycles, olefins and nitriles. Likewise, amination can be accomplished using azodicarboxylates. Stereodefined enol esters can undergo asymmetric dihydroxylation to yield optically-active α-hydroxy aldehydes. Reduction with NaBH4 provides the diols of 1,1-disubstituted olefins in excellent ee. An application of this methodology to the enantioselective synthesis of the insect pheromone frontalin is presented. Finally, α-hydroxy aldehydes are shown to undergo homologation to a terminal alkyne, reductive amination, oxidation and olefination. Preliminary results indicate that tandem carbometalation/amination can be accomplished with azodicarboxylates. In this way, ene-hydrazines are formed in excellent yield. PMID:18517202

Benchmarking Continuum Solvent Models for Keto-Enol Tautomerizations.

Science.gov (United States)

McCann, Billy W; McFarland, Stuart; Acevedo, Orlando

2015-08-13

Experimental free energies of tautomerization, ΔGT, were used to benchmark the gas-phase predictions of 17 different quantum mechanical methods and eight basis sets for seven keto-enol tautomer pairs dominated by their enolic form. The G4 method and M06/6-31+G(d,p) yielded the most accurate results, with mean absolute errors (MAE's) of 0.95 and 0.71 kcal/mol, respectively. Using these two theory levels, the solution-phase ΔGT values for 23 unique tautomer pairs composed of aliphatic ketones, β-dicarbonyls, and heterocycles were computed in multiple protic and aprotic solvents. The continuum solvation models, namely, polarizable continuum model (PCM), polarizable conductor calculation model (CPCM), and universal solvation model (SMD), gave relatively similar MAE's of ∼1.6-1.7 kcal/mol for G4 and ∼1.9-2.0 kcal/mol with M06/6-31+G(d,p). Partitioning the tautomer pairs into their respective molecular types, that is, aliphatic ketones, β-dicarbonyls, and heterocycles, and separating out the aqueous versus nonaqueous results finds G4/PCM utilizing the UA0 cavity to be the overall most accurate combination. Free energies of activation, ΔG(‡), for the base-catalyzed keto-enol interconversion of 2-nitrocyclohexanone were also computed using six bases and five solvents. The M06/6-31+G(d,p) reproduced the ΔG(‡) with MAE's of 1.5 and 1.8 kcal/mol using CPCM and SMD, respectively, for all combinations of base and solvent. That specific enolization was previously proposed to proceed via a concerted mechanism in less polar solvents but shift to a stepwise mechanism in more polar solvents. However, the current calculations suggest that the stepwise mechanism operates in all solvents.

Polyfunctional beta-Dicarbonyl Compounds by Michael Addition Reactions of Ester Enolates to alpha-Benzylidene and alpha-Alkylidene-beta-dicarbonyl Compounds

Czech Academy of Sciences Publication Activity Database

Holan, Martin; Pohl, Radek; Císařová, I.; Jahn, Ullrich

-, č. 18 (2012), s. 3459-3475 ISSN 1434-193X R&D Projects: GA ČR GA203/09/1936 Institutional research plan: CEZ:AV0Z40550506 Keywords : Michael addition * diastereoselectivity * regioselectivity * enols * dicarbonyl compounds Subject RIV: CC - Organic Chemistry Impact factor: 3.344, year: 2012

A stable enol from a 6-substituted benzanthrone and its unexpected behaviour under acidic conditions

Directory of Open Access Journals (Sweden)

Marc Debeaux

2009-06-01

Full Text Available Treatment of benzanthrone (1 with biphenyl-2-yl lithium leads to the surprisingly stable enol 4, which is converted by dehydrogenation into the benzanthrone derivative 7. Under acidic conditions 4 isomerises to the spiro compound 11 and the bicyclo[4.3.1]decane derivative 12. Furthermore, the formation of 7 and the hydrogenated compound 13 is observed. A mechanism for the formation of the reaction products is proposed and supported by DFT calculations.

The reaction of organocerium reagents with easily enolizable ketones

International Nuclear Information System (INIS)

Imamoto, Tsuneo; Kusumoto, Tetsuo; Sugiura, Yasushi; Suzuki, Nobuyo; Takiyama, Nobuyuki

1985-01-01

Organocerium (III) reagents were conveniently generated by the reaction of organolithium compounds with anhydrous cerium (III) chloride. The reagents are less basic than organolithiums and Grignard reagents, and they react readily at -78 deg C with easily enolizable ketones such as 2-tetralone to afford addition products in high yields. Cerium (III) enolates were also generated from lithium enolates and cerium (III) chloride. The cerium (III) enolates undergo aldol addition with ketones or sterically crowded aldehyde to give the corresponding β-hydroxy ketones in good to high yields. (author)

Lactone Enol Cation-Radicals. Gas-Phase Generation, Structure, Energetics, and Reactivity of the Ionized Enol of Butane-4-Lactone

Czech Academy of Sciences Publication Activity Database

Tureček, F.; Vivekananda, S.; Sadílek, M.; Polášek, Miroslav

2002-01-01

Roč. 37, - (2002), s. 829-839 ISSN 1076-5174 R&D Projects: GA ČR GA203/00/0632 Institutional research plan: CEZ:AV0Z4040901 Keywords : lactone enol ions * dissociation mechanisms * isotope effects Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.781, year: 2002

Aldol Reactions of Axially Chiral 5-Methyl-2-(o-arylimino-3-(o-aryl-thiazolidine-4-ones

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Sule Erol Gunal

2016-06-01

Full Text Available Axially chiral 5-methyl-2-(o-arylimino-3-(o-aryl-thiazolidine-4-ones have been subjected to aldol reactions with benzaldehyde to produce secondary carbinols which have been found to be separable by HPLC on a chiral stationary phase. Based on the reaction done on a single enantiomer resolved via a chromatographic separation from a racemic mixture of 5-methyl-2-(α-naphthylimino-3-(α-naphthyl-thiazolidine-4-one by HPLC on a chiral stationary phase, the aldol reaction was shown to proceed via an enolate intermediate. The axially chiral enolate of the thiazolidine-4-one was found to shield one face of the heterocyclic ring rendering face selectivity with respect to the enolate. The selectivities observed at C-5 of the ring varied from none to 11.5:1 depending on the size of the ortho substituent. Although the aldol reaction proceeded with a lack of face selectivity with respect to benzaldehyde, recrystallization returned highly diastereomerically enriched products.

Taxonomía de levaduras de origen enológico por espectrometría de masas

OpenAIRE

Gutiérrez López, Cristina

2016-01-01

Esencialmente, la tesis presentada bajo el título “Taxonomía de levaduras de origen enológico por espectrometría de masas” trata sobre la implementación del proceso de identificación y clasificación taxonómica de levaduras de interés enológico mediante el empleo de la técnica MALDI-TOF MS, como alternativa a la utilización de técnicas clásicas y moleculares. Se ha creado una librería de espectros de masas mediante MALDI-TOF MS con una extensa colección de levaduras aisladas del entorno enológ...

Enolate Stabilization by Anion-π Interactions: Deuterium Exchange in Malonate Dilactones on π-Acidic Surfaces.

Science.gov (United States)

Miros, François N; Zhao, Yingjie; Sargsyan, Gevorg; Pupier, Marion; Besnard, Céline; Beuchat, César; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

2016-02-18

Of central importance in chemistry and biology, enolate chemistry is an attractive topic to elaborate on possible contributions of anion-π interactions to catalysis. To demonstrate the existence of such contributions, experimental evidence for the stabilization of not only anions but also anionic intermediates and transition states on π-acidic aromatic surfaces is decisive. To tackle this challenge for enolate chemistry with maximal precision and minimal uncertainty, malonate dilactones are covalently positioned on the π-acidic surface of naphthalenediimides (NDIs). Their presence is directly visible in the upfield shifts of the α-protons in the (1) H NMR spectra. The reactivity of these protons on π-acidic surfaces is measured by hydrogen-deuterium (H-D) exchange for 11 different examples, excluding controls. The velocity of H-D exchange increases with π acidity (NDI core substituents: SO2 R>SOR>H>OR>OR/NR2 >SR>NR2 ). The H-D exchange kinetics vary with the structure of the enolate (malonates>methylmalonates, dilactones>dithiolactones). Moreover, they depend on the distance to the π surface (bridge length: 11-13 atoms). Most importantly, H-D exchange depends strongly on the chirality of the π surface (chiral sulfoxides as core substituents; the crystal structure of the enantiopure (R,R,P)-macrocycle is reported). For maximal π acidity, transition-state stabilizations up to -18.8 kJ mol(-1) are obtained for H-D exchange. The Brønsted acidity of the enols increases strongly with π acidity of the aromatic surface, the lowest measured pKa =10.9 calculates to a ΔpKa =-5.5. Corresponding to the deprotonation of arginine residues in neutral water, considered as "impossible" in biology, the found enolate-π interactions are very important. The strong dependence of enolate stabilization on the unprecedented seven-component π-acidity gradient over almost 1 eV demonstrates quantitatively that such important anion-π activities can be expected only from

Synthesis of 3-alkyl enol mimics inhibitors of type II dehydroquinase: factors influencing their inhibition potency.

Science.gov (United States)

Blanco, Beatriz; Sedes, Antía; Peón, Antonio; Lamb, Heather; Hawkins, Alastair R; Castedo, Luis; González-Bello, Concepción

2012-05-14

Several 3-alkylaryl mimics of the enol intermediate in the reaction catalyzed by type II dehydroquinase were synthesized to investigate the effect on the inhibition potency of replacing the oxygen atom in the side chain by a carbon atom. The length and the rigidity of the spacer was also studied. The inhibitory properties of the reported compounds against type II dehydroquinase from Mycobacterium tuberculosis and Helicobacter pylori are also reported. The binding modes of these analogs in the active site of both enzymes were studied by molecular docking using GOLD 5.0 and dynamic simulations studies.

Formation of Supported Graphene Oxide: Evidence for Enolate Species.

Science.gov (United States)

Novotny, Zbynek; Nguyen, Manh-Thuong; Netzer, Falko P; Glezakou, Vassiliki-Alexandra; Rousseau, Roger; Dohnálek, Zdenek

2018-04-18

Graphene oxides are promising materials for novel electronic devices or anchoring of the active sites for catalytic applications. Here we focus on understanding the atomic oxygen (AO) binding and mobility on different regions of graphene (Gr) on Ru(0001). Differences in the Gr/Ru lattices result in the superstructure, which offers an array of distinct adsorption sites. We employ scanning tunneling microscopy and density functional theory to map out the chemical identity and stability of prepared AO functionalities in different Gr regions. The AO diffusion is utilized to establish that in the regions that are close to the metal substrate the terminally bonded enolate groups are strongly preferred over bridge-bonded epoxy groups. No oxygen species are observed on the graphene regions that are far from the underlying Ru, indicating their low relative stability. This study provides a clear fundamental basis for understanding the local structural, electronic factors and C-Ru bond strengthening/weakening processes that affect the stability of enolate and epoxy species.

Supramolecular Influence on Keto-Enol Tautomerism and Thermochromic Properties of o-Hydroxy Schiff Bases

Directory of Open Access Journals (Sweden)

Marija Zbačnik

2016-06-01

Full Text Available This work presents a study on thermo-optical properties of three Schiff bases (imines in the solid state. The Schiff bases were obtained by means of mechanochemical synthesis using monosubstituted o-hydroxy aromatic aldehydes and monosubstituted aromatic amines. The keto-enol tautomerism and proton transfer via intramolecular O∙∙∙N hydrogen bond of the reported compounds was found to be influenced more by supramolecular interactions than by a temperature change. All products were characterised by powder X-ray diffraction (PXRD, FT-IR spectroscopy, thermogravimetric (TG analysis and differential scanning calorimetry (DSC. Molecular and crystal structures of compounds 1, 2 and 3 were determined by single crystal X-ray diffraction (SCXRD. The molecules of 1 appear to be present as the enol-imine, the molecules of 2 as the keto-amine tautomer and the molecules of 3 exhibit keto-enol tautomeric equilibrium in the solid state. An analysis of Cambridge structural database (CSD data on similar imines has been used for structural comparison. This work is licensed under a Creative Commons Attribution 4.0 International License.

Synthesis of 4-substituted tetrahydropyridines by cross-coupling of enol phosphates

DEFF Research Database (Denmark)

Larsen, U.S.; Martiny, L.; Begtrup, M.

2005-01-01

Enol phosphates, synthesized from 4-piperidone, react by palladium catalyzed cross-coupling with arylboronic acids and by iron and palladium catalyzed cross-coupling with Grignard reagents to give 4-substituted tetrahydropyridines. (c) 2005 Elsevier Ltd. All rights reserved....

Nickel-Catalyzed Alkoxy-Alkyl Interconversion with Alkylborane Reagents through C−O Bond Activation of Aryl and Enol Ethers

KAUST Repository

Guo, Lin

2016-11-07

A nickel-catalyzed alkylation of polycyclic aromatic methyl ethers as well as methyl enol ethers with B-alkyl 9-BBN and trialkylborane reagents that involves the cleavage of stable C(sp2)−OMe bonds is described. The transformation has a wide substrate scope and good chemoselectivity profile while proceeding under mild reaction conditions; it provides a versatile way to form C(sp2)−C(sp3) bonds that does not suffer from β-hydride elimination. Furthermore, a selective and sequential alkylation process by cleavage of inert C−O bonds is presented to demonstrate the advantage of this method.

Theoretical and vibrational spectroscopic approach to keto-enol tautomerism in methyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate

Science.gov (United States)

Arı, Hatice; Özpozan, Talat; Büyükmumcu, Zeki; Kabacalı, Yiğit; Saçmaci, Mustafa

2016-10-01

A carbamate compound having tricarbonyl groups, methyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate (BPOC) was investigated from theoretical and vibrational spectroscopic point of view employing quantum chemical methods. Hybrid Density Functionals (B3LYP, X3LYP and B3PW91) with 6-311 G(d,p) basis set were used for the calculations. Rotational barrier and conformational analyses were performed to find the most stable conformers of keto and enol forms of the molecule. Three transition states for keto-enol tautomerism in gas phase were determined. The results of the calculations show that enol-1 form of BPOC is more stable than keto and enol-2 forms. Hydrogen bonding investigation including Natural bond orbital analysis (NBO) for all the tautomeric structures was employed to compare intra-molecular interactions. The energies of HOMO and LUMO molecular orbitals for all tautomeric forms of BPOC were predicted. Normal Coordinate Analysis (NCA) was carried out for the enol-1 to assign vibrational bands of IR and Raman spectra. The scaling factors were calculated as 0.9721, 0.9697 and 0.9685 for B3LYP, X3LYP and B3PW91 methods, respectively. The correlation graphs of experimental versus calculated vibrational wavenumbers were plotted and X3LYP method gave better frequency agreement than the others.

Enol tautomers of Watson-Crick base pair models are metastable because of nuclear quantum effects.

Science.gov (United States)

Pérez, Alejandro; Tuckerman, Mark E; Hjalmarson, Harold P; von Lilienfeld, O Anatole

2010-08-25

Intermolecular enol tautomers of Watson-Crick base pairs could emerge spontaneously via interbase double proton transfer. It has been hypothesized that their formation could be facilitated by thermal fluctuations and proton tunneling, and possibly be relevant to DNA damage. Theoretical and computational studies, assuming classical nuclei, have confirmed the dynamic stability of these rare tautomers. However, by accounting for nuclear quantum effects explicitly through Car-Parrinello path integral molecular dynamics calculations, we find the tautomeric enol form to be dynamically metastable, with lifetimes too insignificant to be implicated in DNA damage.

1,5-Asymmetric induction in the boron-mediated aldol reaction of β-oxygenated methyl ketones

International Nuclear Information System (INIS)

Dias, Luiz C.

2007-01-01

High levels of substrate-based 1,5-stereo induction are obtained in the boron-mediated aldol reactions of β-oxygenated methyl ketones with achiral and chiral aldehydes. Remote induction from the boron enolates gives the 1,5-anti adducts, with the enolate pi-facial selectivity critically dependent upon the nature of the beta-alkoxy protecting group. This 1,5-anti aldol methodology has been strategically employed in the total synthesis of several natural products. At present, the origin of the high level of 1,5-anti induction obtained with the boron enolates is unclear, although a model based on a hydrogen bonding between the alkoxy oxygen and the formyl hydrogen has been recently proposed. (author)

Derivatization of enolic OH of piroxicam: a comparative study on esters and sulfonates

Energy Technology Data Exchange (ETDEWEB)

Jayaselli, J.; Cheemala, J. Manila Sagar; Geetha Rani, D.P.; Pal, Sarbani [MNR Post Graduate College, Kukatpally, Hyderabad (India). Dept. of Chemistry]. E-mail: sarbani277@yahoo.com

2008-07-01

A number of ester and sulfonate derivatives of piroxicam were prepared via acylation/sulfonation of the enolic OH of piroxicam. All the compounds were evaluated for their chemical stability and cyclooxygenase inhibiting properties. Data suggested that esters could be useful for the development of potential prodrugs. The sulfonate derivatives prepared for the first time were found to be stable. One of them showed a moderately selective COX-2 inhibition over COX-1 and would have lower gastrointestinal side effects than piroxicam due to the masked enolic OH group. A plausible mechanism for the acylation/sulfonation process has been proposed that involves participation of the pyridine moiety of piroxicam. Molecular structure of one of the ester was established for the first time by the crystal structure analysis from X-ray powder data. (author)

Derivatization of enolic OH of piroxicam: a comparative study on esters and sulfonates

International Nuclear Information System (INIS)

Jayaselli, J.; Cheemala, J. Manila Sagar; Geetha Rani, D.P.; Pal, Sarbani

2008-01-01

A number of ester and sulfonate derivatives of piroxicam were prepared via acylation/sulfonation of the enolic OH of piroxicam. All the compounds were evaluated for their chemical stability and cyclooxygenase inhibiting properties. Data suggested that esters could be useful for the development of potential prodrugs. The sulfonate derivatives prepared for the first time were found to be stable. One of them showed a moderately selective COX-2 inhibition over COX-1 and would have lower gastrointestinal side effects than piroxicam due to the masked enolic OH group. A plausible mechanism for the acylation/sulfonation process has been proposed that involves participation of the pyridine moiety of piroxicam. Molecular structure of one of the ester was established for the first time by the crystal structure analysis from X-ray powder data. (author)

Partial equilibrium in induced redox reactions of plutonium

Energy Technology Data Exchange (ETDEWEB)

Nikol' skii, B P; Posvol' skii, M V; Krylov, L I; Morozova, Z P

1975-01-01

A study was made of oxidation-reduction reactions of Pu in buffer solutions containing bichromate and a reducing agent which reacted with hexavalent chromium at pH=3.5. In most cases sodium nitrite was used. A rather slow reduction of Pu (6) with NaNO/sub 2/ in the course of which tetravalent plutonium was formed via disproportionation reaction of plutonium (5), became very rapid upon the addition of bichromate to the solution. The yield of tetravalent plutonium increased with an increase in the concentration of NaNO/sub 2/ and the bichromate but never reached 100%. This was due to a simultaneous occurrenc of the induced oxidation reaction of Pu(4), leading to a partial equilibrium between the valence forms of plutonium in the nitrite-bichromate system which on the whole was in a nonequilibrium state. It was shown that in the series of reactions leading to the reduction of plutonium the presence of bivalent chromium was a necessary link.

Oxidation of D-glucose and D-fructose with oxygen in aqueous, alkaline solutions. Part I. An integral reaction scheme

NARCIS (Netherlands)

de Wilt, H.G.J.; Kuster, B.F.M.

1971-01-01

The homogeneous oxidn. of D-glucose and D-fructose with O in aq., alk. solns. is studied, and a reaction scheme proposed to account for the obsd. reaction products. Formation of enolate anions is followed by non-oxidative reactions (involving double-bond migration and cleavage) and by oxidative

Synthesis of [11C]-labelled methyl esters: transesterification of enol esters versus BF3 etherate catalysed esterification - a comparative study

International Nuclear Information System (INIS)

Ackermann, U.; Falzon, C.; Issa, W.; Tochon-Danguy, H.J.; Sachinidis, J.I.; Blanc, P.; White, J.; Scott, A.M.

2005-01-01

An important issue in Positron Emission Tomography (PET) is the development of labelling techniques to incorporate positron emitting radionuclides into biologically active compounds. When labelling with 11C, the short 20 minutes half-life of the radionuclide significantly limits the number of synthetic protocols available to the radiochemist. C-l synthons such as [HCJ-methyl iodide (1) or methyl triflate (2) are readily available and are frequently used as alkylating agents for the preparation of radiopharmaceuticals. However, the use of these alkylating agents often makes it necessary to introduce protecting groups in order to prevent labelling at unwanted sites on the molecule. Since the removal of protecting groups is a time-consuming process, a more direct synthesis strategy is desirable. This has prompted us to investigate the esterification of carboxylic acids using [1 lC]-mcthanol and BF3 etherate as Lewis acid catalyst. Our results have demonstrated that the reaction conditions necessary to promote the esterification can cleave functional groups such as ethers. We have therefore shifted our attention towards the irreversible transesterification of enol esters using [HCl-methanol and a tin catalyst as an alternative strategy to [HC]-methyl ester formation. We have prepared a series of 5 aromatic ethoxy vinyl esters bearing various functional groups. The transesterification (radiolabelling) was carried out in DMSO at 150 Degrees C for 7 minutes in the presence of [HQMeOH and 1.3-dichlo-rotetrabutyldistannoxane as catalyst. We have found that the transesterification of enol esters is a mild and efficient labelling method for the formation of [HCl-methyl esters. The reaction proceeds smoothly and leaves functional groups intact. It requires only one synthesis step compared to two steps for the conventional method, and gives a radiochemical yields of 25%

Biosynthetic conversion of thebaine to codeinone. Mechanism of ketone formation from enol ether in vivo

International Nuclear Information System (INIS)

Horn, J.S.; Paul, A.G.; Rapoport, H.

1978-01-01

Biosynthesis of the morphinan alkaloids proceeds by conversion of the enol ether or thebaine to the keto group of neopinone and thence to codeinone. To determine the mechanism of this transformation, [G- 14 C,6- 18 O]thebaine was fed to Papaver somniferum and the codeine and morphine were isolated. Comparison of the 18 O/ 14 C ratios in the codeine and morphine isolated with that of the thebaine fed showed that approximately 34% of the 18 O had been retained. Parallel feedings with [G- 14 C,6- 18 O]-codeinone demonstrated that the loss was due to nonenzymic exchange. Thus, the mechanism of enol ether cleavage in thebaine is established as cleavage of the 6-O-methyl group with retention of the 6-oxygen in the codeinone

Mechanism of degradation and discoloration reaction of L-ascorbic acid

International Nuclear Information System (INIS)

Kurata, Tadao

1976-01-01

The mechanisms of decomposition and coloration reaction of L-ascorbic acid are reviewed. At the initial stage of the decomposition, it can be classified roughly into oxidative and non-oxidative processes of decomposition. ASA forms furfural by being heated and decomposed in strong acid. The mechanism of the production of furfural at varying pH in acidic region was discussed. Furfural was produced through the enol form of 3-deoxy-L-pentosulose(3DP). 3DP seemed to be produced by two different routes: the one route consists of successive reactions from ASA through lactone ring-opening, dehydration, decarboxylation, to 3DP, and the other consists of reactions from the 3-keto form of ASA, through lactone ring-opening, decarboxylation, and dehydration, to the enol form of 3DP. ASA is easily reduced and decomposed through dehydro-ASA(DHA) by the presence of an oxidizing agent. The decomposition of DHA is discussed in cases of the systems of DHA alone, DHA and α-aminoacid, and DHA and amine. DHA was decomposed by the same reaction scheme as the decomposition of ASA and yielded 2-furoic acid. In the presence of an amino acid, DHA was decomposed by the Strecker decomposition, and yielded a red compound and a radical. In the presence of an amine, the discoloration reaction seemed to take place through radical reaction mechanism. The coloration reaction of ASA occurs in an acidic medium, and is accelerated by the oxidative process of decomposition. (Nishino, S.)

The stereochemistry of the addition of chlorotitanium enolates of N-acyl oxazolidin-2-ones to 5- and 6- membered N-acyliminium ions

Directory of Open Access Journals (Sweden)

Pilli Ronaldo A.

2001-01-01

Full Text Available The stereoselective addition of chiral and achiral titanium enolates derived from the corresponding N-acyl oxazolidin-2-ones to 5- and 6- membered N-acyliminium ions afforded 2-substituted pyrrolidines in moderate to good diastereoisomeric ratio (5:1 to 14:1 while lower diastereoselection was generally observed in the formation of the corresponding 2-substituted piperidines. The stereochemical outcome was found to be modulated by the nature of the cyclic N-acyliminium ion (5- or 6-membered and of its carbamate and by the N-acyl group in the enolate precursor. The preferential lk approach seems to be dictated mainly by the minimization of non-bonding interactions between the N-acyl group in the chlorotitanium (IV enolate and the carbamate and methylene groups in the cyclic N-acyliminium ion.

The origin of enantioselectivity in the l-threonine-derived phosphine-sulfonamide catalyzed aza-Morita-Baylis-Hillman reaction: Effects of the intramolecular hydrogen bonding

KAUST Repository

Lee, Richmond

2013-01-01

l-Threonine-derived phosphine-sulfonamide 4 was identified as the most efficient catalyst to promote enantioselective aza-Morita-Baylis-Hillman (MBH) reactions, affording the desired aza-MBH adducts with excellent enantioselectivities. Density functional theory (DFT) studies were carried out to elucidate the origin of the observed enantioselectivity. The importance of the intramolecular N-H⋯O hydrogen-bonding interaction between the sulfonamide and enolate groups was identified to be crucial in inducing a high degree of stereochemical control in both the enolate addition to imine and the subsequent proton transfer step, affording aza-MBH reactions with excellent enantioselectivity. © 2013 The Royal Society of Chemistry.

La creación de productos turísticos utilizando rutas enológicas

Directory of Open Access Journals (Sweden)

Tomás J. López Guzmán

2008-01-01

Full Text Available Los cambios que se están produciendo en la actividad turística en los últimos años están llevando a la creación de nuevos productos turísticos, destacando los relacionados con las raíces locales y regionales. En este trabajo presentamos un análisis sobre la creación y desarrollo de rutas enológicas como producto turístico en determinadas áreas rurales. Y este análisis lo planteamos desde una triple perspectiva: primera, un estudio en profundidad acerca de qué son las rutas turísticas enológicas y su creación y desarrollo en otros países; segundo, un análisis de cómo se certifican en España las rutas del vino; y tercera, una referencia a una ruta del vino certificada en España, la de Montilla-Moriles en la provincia de Córdoba.

Statistical distribution of partial widths in the microscopic theory of nuclear reactions

International Nuclear Information System (INIS)

Bunakov, V.E.; Ogloblin, S.G.

1978-01-01

Using the microscopic theory of nuclear reaction the distribution function of neutron reduced partial widths is obtained. It is shown that the distribution of reduced partial widths of a radiative transition is of the same form. The distribution obtained differs from the Porter-Thomas law for neutron widths only in the presence of intermediate structures. It is noteworthy that the presence of an intermediate structure leads to a greater dispersion

N,2,3,4-Tetrasubstituted Pyrrolidines through Tandem Lithium Amide Conjugate Addition/Radical Cyclization/Oxygenation Reactions

Czech Academy of Sciences Publication Activity Database

Kafka, František; Pohl, Radek; Císařová, I.; Mackman, R.; Bahador, G.; Jahn, Ullrich

2016-01-01

Roč. 2016, č. 22 (2016), s. 3862-3871 ISSN 1434-193X R&D Projects: GA ČR GA13-40188S Grant - others:COST(XE) CM1201 Institutional support: RVO:61388963 Keywords : tandem reactions * nitrogen heterocycles * Michael addition * radical reactions * cyclization * enolates Subject RIV: CC - Organic Chemistry Impact factor: 2.834, year: 2016

Subtle trade-off existing between (anti)aromaticity, push-pull interaction, keto-enol tautomerism, and steric hindrance when defining the electronic properties of conjugated structures.

Science.gov (United States)

Kleinpeter, Erich; Bölke, Ute; Koch, Andreas

2010-07-22

The spatial magnetic properties (through space NMR shieldings, TSNMRS) of conjugated structures (benzenoid/quinonoid keto/enol tautomers, 1,3-dihydroxyaryl-2-aldehydes, Don-pi-Acc chromophores with trade-off existing push-pull vs aromatic behavior) have been calculated by the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept, and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values, thus obtained, can be successfully employed to quantify and visualize (anti)aromaticity and to identify readily hereby zwitterionic structures due to push-pull behavior of the compounds studied. In addition, the push-pull behavior was quantified by the quotient (pi*/pi) approach of the central partial C=C double bond.

Organolanthanide reagents and the Mukaiyama reaction

International Nuclear Information System (INIS)

Gong, L.

1989-01-01

The bis(pentamethylcyclopentadienyl) lutetium halide complex [(C 5 Me 5 ) 2 LuCl/center dot/THF] was synthesized and characterized. The crystal structure of this complex shows that the Lu is at the center of a distorted tetrahedron consisting of the centroids of two cyclopentadienyl rings, the oxygen atom of a tetrahydrofuran molecule and a chlorine atom. 1 H NMR studies of toluene-d 8 solutions of (C 5 Me 5 LuCl(THF) + THF, (TMS 2 CP) 2 LuCl(THF) + THF, and (MeCp) 2 LuCl(THF) + THF at various temperatures showed exchange processes between co- ordinated THF and free THF with average values of ΔG/sup ne/ of 13.0 /+-/ 0.3 kcal/mol, 11.1 /+-/ 0.1 kcal/mol and 2 Cp) 2 YbCl dimer, silyl enol ethers (R 1 R 2 C = C(OR 3 )OSiMe 3 )) react with benzaldehyde smoothly in dichloromethane at room temperature, giving >99% of the aldol silyl ether (isolated yield: 90%) within 3 h. At /minus/78/degrees/C, the reaction gives kinetically controlled diastereoselectivity, which was not observed in the TiCl 4 -mediated aldol reaction. The use of organoytterbium enolates shows promise result with respect to increased stereoselectivity, and indicates the importance of the bulky ligands on the metal center. In addition, Yb(III) species can retard retroaldol reaction owing to its mild Lewis acidity. 118 refs., 14 figs., 30 tabs

A straightforward approach towards combined α-amino and α-hydroxy acids based on Passerini reactions

Directory of Open Access Journals (Sweden)

Ameer F. Zahoor

2011-09-01

Full Text Available Complex amino acids with an α-acyloxycarbonyl functionality in the side chain are easily available through epoxide opening by chelated enolates and subsequent oxidation/Passerini reaction. This protocol works with both, aldehyde and ketone intermediates, as long as the ketones are activated by electron-withdrawing groups. In principle Ugi reactions are also possible, allowing the generation of diamino acid derivatives.

Modeling Chemical Reactions by QM/MM Calculations: The Case of the Tautomerization in Fireflies Bioluminescent Systems.

Science.gov (United States)

Berraud-Pache, Romain; Garcia-Iriepa, Cristina; Navizet, Isabelle

2018-01-01

In less than half a century, the hybrid QM/MM method has become one of the most used technique to model molecules embedded in a complex environment. A well-known application of the QM/MM method is for biological systems. Nowadays, one can understand how enzymatic reactions work or compute spectroscopic properties, like the wavelength of emission. Here, we have tackled the issue of modeling chemical reactions inside proteins. We have studied a bioluminescent system, fireflies, and deciphered if a keto-enol tautomerization is possible inside the protein. The two tautomers are candidates to be the emissive molecule of the bioluminescence but no outcome has been reached. One hypothesis is to consider a possible keto-enol tautomerization to treat this issue, as it has been already observed in water. A joint approach combining extensive MD simulations as well as computation of key intermediates like TS using QM/MM calculations is presented in this publication. We also emphasize the procedure and difficulties met during this approach in order to give a guide for this kind of chemical reactions using QM/MM methods.

Modelling chemical reactions by QM/MM calculations: the case of the tautomerization in fireflies bioluminescent systems

Science.gov (United States)

Berraud-Pache, Romain; Garcia-Iriepa, Cristina; Navizet, Isabelle

2018-04-01

In less than half a century, the hybrid QM/MM method has become one of the most used technique to model molecules embedded in a complex environment. A well-known application of the QM/MM method is for biological systems. Nowadays, one can understand how enzymatic reactions work or compute spectroscopic properties, like the wavelength of emission. Here, we have tackled the issue of modelling chemical reactions inside proteins. We have studied a bioluminescent system, fireflies, and deciphered if a keto-enol tautomerization is possible inside the protein. The two tautomers are candidates to be the emissive molecule of the bioluminescence but no outcome has been reached. One hypothesis is to consider a possible keto-enol tautomerization to treat this issue, as it has been already observed in water. A joint approach combining extensive MD simulations as well as computation of key intermediates like TS using QM/MM calculations is presented in this publication. We also emphasize the procedure and difficulties met during this approach in order to give a guide for this kind of chemical reactions using QM/MM methods.

Condensed tannins. Base-catalysed reactions of polymeric procyanidins with phloroglucinol: Intramolecular rearrangements

Science.gov (United States)

Peter E. Laks; Richard W. Hemingway; Anthony H. Conner

1987-01-01

Reactions of polymeric procyanidins with phloroglucinol at pH 12.0 and temperatures of 23 or 50°C gave epicatechin-(4β)-phloroglucinol (7), by cleavage of the interflavanoid bond between procyanidin units with subsequent addition of phloroglucinol, and (+)-catechin from the terminal unit. The phloroglucinol adduct (7) rearranged to an enolic form of 8-(3,4-...

On Hydrogen Bonding in the Intramolecularly Chelated Taitomers of Enolic Malondialdehyde and its Mono- and Dithio-Analogues

DEFF Research Database (Denmark)

Carlsen, Lars; Duus, Fritz

1980-01-01

The intramolecular hydrogen bondings in enolic malondialdehyde and it mono- and dithio-analogues have been evaluated by a semiempricial SCF–MO–CNDO method. The calculations predict that the hydrogen bonds play an important part in the stabilities of malondialdehyde and monothiomalondialdehyde...

Fundamental studies on the reaction process of partial hydropyrolysis of coal

Energy Technology Data Exchange (ETDEWEB)

O. Yamada; H. Yasuda; M. Kaiho [National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan). Energy Technology Research Institute

2005-07-01

In order to make up a simulator to support the development of coal partial hydropyrolysis process, material balance of the reaction was investigated precisely. Amount of H{sub 2} evolved by pyrolysis under inert gas atmosphere was found almost equal to that of (CO+2CO{sub 2}), therefore, most of H{sub 2} seemed to be generated through water gas reaction and shift reaction. CH{sub 4} seemed to be stable even at 1073K and 7.1MPa of H{sub 2}, its generation was simply accelerated in proportion to H{sub 2} pressure. Hydrocarbons, other than CH{sub 4}, were fundamentally unstable at 1073K and 0.93 -7.1MPa of H{sub 2}, however the rate of decomposition of them were so slow that amounts of them evolved were apparently proportion to reaction time and H{sub 2} pressure. BTX and naphthalene were increased apparently with H{sub 2} pressure when the reaction time was less than 5s. 4 refs., 20 figs.

L-Selectride-Mediated Highly Diastereoselective Asymmetric Reductive Aldol Reaction: Access to an Important Subunit for Bioactive Molecules

OpenAIRE

Ghosh, Arun K.; Kass, Jorden; Anderson, David D.; Xu, Xiaoming; Marian, Christine

2008-01-01

L-Selectride reduction of a chiral or achiral enone followed by reaction of the resulting enolate with optically active α-alkoxy aldehydes proceeded with excellent diastereoselectivity. The resulting α,α-dimethyl-β-hydroxy ketones are inherent to a variety of biologically active natural products.

L-selectride-mediated highly diastereoselective asymmetric reductive aldol reaction: access to an important subunit for bioactive molecules.

Science.gov (United States)

Ghosh, Arun K; Kass, Jorden; Anderson, David D; Xu, Xiaoming; Marian, Christine

2008-11-06

L-selectride reduction of a chiral or achiral enone followed by reaction of the resulting enolate with optically active alpha-alkoxy aldehydes proceeded with excellent diastereoselectivity. The resulting alpha,alpha-dimethyl-beta-hydroxy ketones are inherent to a variety of biologically active natural products.

Reaction of uridine diphosphate galactose 4-epimerase with a suicide inactivator

International Nuclear Information System (INIS)

Flentke, G.R.; Frey, P.A.

1990-01-01

UDPgalactose 4-epimerase from Escherichia coli is rapidly inactivated by the compounds uridine 5'-diphosphate chloroacetol (UDC) and uridine 5'-diphosphate bromoacetol (UCB). Both UDC and UDB inactivate the enzyme in neutral solution concomitant with the appearance of chromophores absorbing maximally at 325 and 328 nm, respectively. The reaction of UDC with the enzyme follows saturation kinetics characterized by a K D of 0.110 mM and k inact of 0.84 min -1 at pH 8.5 and ionic strength 0.2 M. The inactivation by UDC is competitively inhibited by competitive inhibitors of UDPgalactose 4-epimerase, and it is accompanied by the tight but noncovalent binding of UDC to the enzyme in a stoichiometry of 1 mol of UDC/mol of enzyme dimer, corresponding to 1 mol of UDC/mol of enzyme-bound NAD + . The inactivation of epimerase by uridine 5'-diphosphate [ 2 H 2 ]chloroacetol proceeds with a primary kinetic isotope effect (k H /k D ) of 1.4. The inactivation mechanism is proposed to involve a minimum of three steps: (a) reversible binding of UDC to the active site of UDPgalactose 4-epimerase; (b) enolization of the chloroacetol moiety of enzyme-bound UDC, catalyzed by an enzymic general base at the active site; (c) alkylation of the nicotinamide ring of NAD + at the active site by the chloroacetol enolate. The resulting adduct between UDC and NAD + is proposed to be the chromophore with λ max at 325 nm. The enzymic general base required to facilitate proton transfer in redox catalysis by this enzyme may be the general base that facilitates enolization of the chloroacetol moiety of UDC in the inactivation reaction

Cobalt-catalyzed hydrogenation of esters to alcohols: unexpected reactivity trend indicates ester enolate intermediacy.

Science.gov (United States)

Srimani, Dipankar; Mukherjee, Arup; Goldberg, Alexander F G; Leitus, Gregory; Diskin-Posner, Yael; Shimon, Linda J W; Ben David, Yehoshoa; Milstein, David

2015-10-12

The atom-efficient and environmentally benign catalytic hydrogenation of carboxylic acid esters to alcohols has been accomplished in recent years mainly with precious-metal-based catalysts, with few exceptions. Presented here is the first cobalt-catalyzed hydrogenation of esters to the corresponding alcohols. Unexpectedly, the evidence indicates the unprecedented involvement of ester enolate intermediates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

General and Efficient a-Oxygenation of Carbonyl Compounds by TEMPO Induced by Single-Electron-Transfer Oxidation of Their Enolates

Czech Academy of Sciences Publication Activity Database

Dinca, E.; Hartmann, P.; Smrček, Jakub; Dix, I.; Jones, P. G.; Jahn, Ullrich

-, č. 24 (2012), s. 4461-4482 ISSN 1434-193X Institutional support: RVO:61388963 Keywords : carbonyl compounds * oxidation * radicals * electron transfer * enolates Subject RIV: CC - Organic Chemistry Impact factor: 3.344, year: 2012

The origin of enantioselectivity in the l-threonine-derived phosphine-sulfonamide catalyzed aza-Morita-Baylis-Hillman reaction: Effects of the intramolecular hydrogen bonding

KAUST Repository

Lee, Richmond; Zhong, Fangrui; Zheng, Bin; Meng, Yuezhong; Lu, Yixin; Huang, Kuo-Wei

2013-01-01

in inducing a high degree of stereochemical control in both the enolate addition to imine and the subsequent proton transfer step, affording aza-MBH reactions with excellent enantioselectivity. © 2013 The Royal Society of Chemistry.

Enhanced degradation of spiro-insecticides and their leacher enol derivatives in soil by solarization and biosolarization techniques.

Science.gov (United States)

Fenoll, José; Garrido, Isabel; Vela, Nuria; Ros, Caridad; Navarro, Simón

2017-04-01

The leaching potential of three insecticides (spirodiclofen, spiromesifen, and spirotetramat) was assessed using disturbed soil columns. Small quantities of spirodiclofen and spiromesifen were detected in leachate fraction, while spirotetramat residues were not found in the leachates. In addition, the transformation products (enol derivatives) are relatively more mobile than the parent compounds and may leach into groundwater. Moreover, the use of disinfection soil techniques (solarization and biosolarization) to enhance their degradation rates in soil was investigated. The results show that both practices achieved a reduction in the number of juvenile nematodes, enhancing in a parallel way degradation rates of the insecticides and their enol derivatives as compared with the non-disinfected soil. This behavior can be mainly attributed to the increase in soil temperature and changes in microbial activity. All insecticides showed similar behavior under solarization and biosolarization conditions. As a consequence, both agronomic techniques could be considered as suitable strategies for detoxification of soils polluted with the studied pesticides.

Residue evaluation of imidacloprid, spirotetramat, and spirotetramat-enol in/on grapes (Vitis vinifera L.) and soil.

Science.gov (United States)

Mohapatra, Soudamini; Kumar, Sampath; Prakash, G S

2015-10-01

A combination of imidacloprid and spirotetramat effectively controls sucking pests on grapevines. Residues of these insecticides on grapes were evaluated after treatment with spirotetramat 12% + imidacloprid 12% (240 SC) three times at 90 and 180 g a.i. ha(-1). The samples were extracted and purified by QuEChERS method and analyzed by high-performance liquid chromatography with a photodiode array detector (imidacloprid) and gas chromatography mass spectrometry (spirotetramat and its metabolite spirotetramat-enol). Satisfactory results were obtained with ranges of 80.6-98.6% for the recovery, 3.1-10% for the relative standard deviation range, and 9.8-15.6% for the uncertainty. The limits of detection and quantification were 0.015 μg mL(-1) and 0.05 mg kg(-1), respectively. Initial residue concentrations of imidacloprid after the 90 and 180 g a.i. ha(-1) treatments were 0.912 (half-life 11 days) and 1.681 mg kg(-1) (half-life 12.4 days), respectively. For spirotetramat + spirotetramat-enol, the residue concentrations were 1.337 (half-life 5.6 days) and 2.0 mg kg(-1) (half-life 7.6 days) for the 90 and 180 g a.i. ha(-1) treatments, respectively. Spirotetramat degraded faster than spirotetramat-enol. After treatment at 90 g a.i. ha(-1), the initial residues of both insecticides were within European Union maximum residue limits and a 1-day pre-harvest interval (PHI) was adequate for safe consumption of grapes. After treatment at 180 g a.i. ha(-1), the required PHI was 7 day. Therefore, a PHI of 7 day should be used after treatment with imidacloprid and spirotetramat.

Chemical potential and reaction electronic flux in symmetry controlled reactions.

Science.gov (United States)

Vogt-Geisse, Stefan; Toro-Labbé, Alejandro

2016-07-15

In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins' Bicyclic Sugar Moiety.

Science.gov (United States)

Cachatra, Vasco; Almeida, Andreia; Sardinha, João; Lucas, Susana D; Gomes, Ana; Vaz, Pedro D; Florêncio, M Helena; Nunes, Rafael; Vila-Viçosa, Diogo; Calhorda, Maria José; Rauter, Amélia P

2015-11-20

2-O-Acyl protected-d-ribo-3-uloses reacted with [(ethoxycarbonyl)methylene]triphenylphosphorane in acetonitrile to afford regio- and stereoselectively 2-(Z)-alkenes in 10-60 min under microwave irradiation. This domino reaction is proposed to proceed via tautomerization of 3-ulose to enol, acyl migration, tautomerization to the 3-O-acyl-2-ulose, and Wittig reaction. Alternatively, in chloroform, regioselective 3-olefination of 2-O-pivaloyl-3-uloses gave (E)-alkenes, key precursors for the miharamycins' bicyclic sugar moiety.

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

Directory of Open Access Journals (Sweden)

Carmen Moreno-Marrodan

2017-04-01

Full Text Available The catalytic partial hydrogenation of substituted alkynes to alkenes is a process of high importance in the manufacture of several market chemicals. The present paper shortly reviews the heterogeneous catalytic systems engineered for this reaction under continuous flow and in the liquid phase. The main contributions appeared in the literature from 1997 up to August 2016 are discussed in terms of reactor design. A comparison with batch and industrial processes is provided whenever possible.

Ethylene Glycol Adsorption and Reaction over CeOX(111) Thin Films

Energy Technology Data Exchange (ETDEWEB)

T Chen; D Mullins

2011-12-31

This study reports the interaction of ethylene glycol with well-ordered CeO{sub x}(111) thin film surfaces. Ethylene glycol initially adsorbs on fully oxidized CeO{sub 2}(111) and reduced CeO{sub 2-x}(111) through the formation of one C-O-Ce bond and then forms a second alkoxy bond after annealing. On fully oxidized CeO{sub 2}(111) both recombination of ethylene glycol and water desorption occur at low temperature leaving stable -OCH{sub 2}CH{sub 2}O- (ethylenedioxy) intermediates and oxygen vacancies on the surface. This ethylenedioxy intermediate goes through C-C bond scission to produce formate species which then react to produce CO and CO{sub 2}. The formation of water results in the reduction of the ceria. On a reduced CeO{sub 2-x}(111) surface the reaction selectivity shifts toward a dehydration process. The ethylenedioxy intermediate decomposes by breaking a C-O bond and converts into an enolate species. Similar to the reaction of acetaldehyde on reduced CeO{sub 2-x}(111), the enolate reacts to produce acetaldehyde, acetylene, and ethylene. The loss of O from ethylene glycol leads to a small amount of oxidation of the reduced ceria.

Theoretical investigation on hydrogen bond interaction of diketo/keto-enol form uracil and thymine tautomers with intercalators.

Science.gov (United States)

Anithaa, V S; Vijayakumar, S; Sudha, M; Shankar, R

2017-11-06

The interaction of diketo and keto-enol form of thymine and uracil tautomers with acridine (Acr), phenazine (Phen), benzo[c]cinnoline (Ben), 1,10-phenanthroline (1,10-Phe), and 4,7-phenenthroline (4,7-Phe) intercalating drug molecules was studied using density functional theory at B3LYP/6-311++G** and M05-2×/6-311++G** levels of theory. From the interaction energy, it is found that keto-enol form tautomers have stronger interaction with intercalators than diketone form tautomers. On complex formation of thymine and uracil tautomers with benzo[c]cinnoline the drug molecules have high interaction energy values of -20.14 (BenT3) and -20.55 (BenU3) kcal mol -1 , while phenazine has the least interaction energy values of -6.52 (PhenT2) and -6.67 (PhenU2) kcal mol -1 . The closed shell intermolecular type interaction between the molecules with minimum elliptical value of 0.018 and 0.019 a.u at both levels of theory has been found from topological analysis. The benzo[c]cinnoline drug molecule with thymine and uracil tautomers has short range intermolecular N-H…N, C-H…O, and O-H...N hydrogen bonds (H-bonds) resulting in higher stability than other drug molecules. The proper hydrogen bonds N-H..N and O-H..N have the frequency shifted toward the lower side (red shifted) with the elongation in their bond length while the improper hydrogen bond C-H...O has the frequency shifted toward the higher side (blue shifted) of the spectral region with the contraction in their bond length. Further, the charge transfer between proton acceptor and donor along with stability of the bond is studied using natural bond orbital (NBO) analysis. Graphical abstract Hydrogen bond interaction of diketo/keto-enol form uracil and thymine tautomers with intercalators.

Statistical analysis of fragmentation patterns of electron ionization mass spectra of enolized-trimethylsilylated anabolic androgenic steroids

Science.gov (United States)

Fragkaki, A. G.; Angelis, Y. S.; Tsantili-Kakoulidou, A.; Koupparis, M.; Georgakopoulos, C.

2009-08-01

Anabolic androgenic steroids (AAS) are included in the List of prohibited substances of the World Anti-Doping Agency (WADA) as substances abused to enhance athletic performance. Gas chromatography coupled to mass spectrometry (GC-MS) plays an important role in doping control analyses identifying AAS as their enolized-trimethylsilyl (TMS)-derivatives using the electron ionization (EI) mode. This paper explores the suitability of complementary GC-MS mass spectra and statistical analysis (principal component analysis, PCA and partial least squares-discriminant analysis, PLS-DA) to differentiate AAS as a function of their structural and conformational features expressed by their fragment ions. The results obtained showed that the application of PCA yielded a classification among the AAS molecules which became more apparent after applying PLS-DA to the dataset. The application of PLS-DA yielded a clear separation among the AAS molecules which were, thus, classified as: 1-ene-3-keto, 3-hydroxyl with saturated A-ring, 1-ene-3-hydroxyl, 4-ene-3-keto, 1,4-diene-3-keto and 3-keto with saturated A-ring anabolic steroids. The study of this paper also presents structurally diagnostic fragment ions and dissociation routes providing evidence for the presence of unknown AAS or chemically modified molecules known as designer steroids.

Effect of sulfur dioxide partial pressure on the reaction of iodine, sulfur dioxide and water

International Nuclear Information System (INIS)

Nakajima, Hayato; Imai, Yoshiyuki; Kasahara, Seiji; Kubo, Shinji; Onuki, Kaoru

2007-01-01

Effect of sulfur dioxide partial pressure on the reaction of iodine, sulfur dioxide and water, which is a unit reaction in the IS process for thermochemical hydrogen production, was studied experimentally at 323 K under iodine saturation. Quasi-equilibrium state was observed in the presence of sulfur dioxide gas at constant pressure. The composition of the poly-hydriodic acid solution formed was discussed assuming an ideal desulfurization by the reverse reaction of the Bunsen reaction. The value of HI/(HI+H 2 O) of the desulfurized solution was large at high sulfur dioxide pressure and reached the maximum of 15.7 ± 0.3 mol%. (author)

Partial wave analysis of the 18O(p,α0)15N reaction

International Nuclear Information System (INIS)

Wild, L.W.J.; Spicer, B.M.

1979-01-01

A partial wave analysis of the differential cross sections for the 18 O(p,α 0 ) 15 N reaction has been carried out applying the formalism of Blatt and Biedenharn (1952), made specific for this reaction. The differential cross sections, measured at 200 keV intervals from 6.6 to 10.4 MeV bombarding energy, were subjected to least-squares fitting to this specific analytic expression. Two resonances were given by the analysis, the 19 F states being at 14.71+-0.07 MeV (1/2 - ) and 14.80 + 0.07 MeV (1/2) +

Reactions of enolisable ketones with dichloroisocyanuric acid in absence and presence of added chloride ions – a kinetic study

Directory of Open Access Journals (Sweden)

Y. L. Kumar

2015-01-01

Full Text Available Kinetics of reactions of enolisable ketones (S = acetone/2-butanone with dichloroisocyanuric acid (DCICA were studied in aqueous acetic acid and perchloric acid media in absence and presence of added chloride ions. The reactions were found to be pseudo zero order and pseudo first order on [DCICA] in absence and presence of chloride ions respectively. Both in presence and absence of chloride ions, first order and fractional order in substrate and perchloric acid were observed respectively. An increase in the rate of reaction was observed with an increase in chloride ion concentration as well as acetic acid composition. The results were interpreted in terms of probable mechanisms involving (i rate-determining enol formation from the conjugate acid of the ketone (SH+ in the absence of added chloride ions and (ii rate-determining interaction of SH+ with the most effective molecular chlorine species produced by the hydrolysis of DCICA (rather than a rate-determining interaction of enol with chlorine in the presence of added chloride ions, prior to the rapid steps of product formation. DOI: http://dx.doi.org/10.4314/bcse.v29i1.12

Interaction between the thyroid hormone receptor and co-factors on the promoter of the gene encoding phospho enol pyruvate carboxykinase

NARCIS (Netherlands)

Schmidt, E. D.; van Beeren, M.; Glass, C. K.; Wiersinga, W. M.; Lamers, W. H.

1993-01-01

Using transient transfection studies we localized a thyroid hormone-responsive element on the promoter of the rat phospho-enol pyruvate carboxykinase gene between 355 and 174 bp upstream of the transcription start site. DNAse 1 footprinting analysis within this region showed that a 28 bp fragment at

The introduction of a double bond on the steroid skeleton - the preparation of enol silyl ether derivatives from vicinal diols

Czech Academy of Sciences Publication Activity Database

Marek, Aleš; Klepetářová, Blanka; Elbert, Tomáš

2011-01-01

Roč. 76, č. 5 (2011), s. 443-456 ISSN 0010-0765 R&D Projects: GA AV ČR IAA400550801 Institutional research plan: CEZ:AV0Z40550506 Keywords : enol silyl ether * vicinal diol * steroids Subject RIV: CC - Organic Chemistry Impact factor: 1.283, year: 2011

Influence of collective nonideal shielding on fusion reaction in partially ionized classical nonideal plasmas

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-04-01

The collective nonideal effects on the nuclear fusion reaction process are investigated in partially ionized classical nonideal hydrogen plasmas. The effective pseudopotential model taking into account the collective and plasma shielding effects is applied to describe the interaction potential in nonideal plasmas. The analytic expressions of the Sommerfeld parameter, the fusion penetration factor, and the cross section for the nuclear fusion reaction in nonideal plasmas are obtained as functions of the nonideality parameter, Debye length, and relative kinetic energy. It is found that the Sommerfeld parameter is suppressed due to the influence of collective nonideal shielding. However, the collective nonideal shielding is found to enhance the fusion penetration factor in partially ionized classical nonideal plasmas. It is also found that the fusion penetration factors in nonideal plasmas represented by the pseudopotential model are always greater than those in ideal plasmas represented by the Debye-Hückel model. In addition, it is shown that the collective nonideal shielding effect on the fusion penetration factor decreases with an increase of the kinetic energy.

Cascade olefin isomerization/intramolecular Diels-Alder reaction catalyzed by N-heterocyclic carbenes.

Science.gov (United States)

Kowalczyk, Marcin; Lupton, David W

2014-05-19

The addition of an N-heterocyclic carbene to the carbonyl group of an α,β,γ,δ-unsaturated enol ester affords a hemiacetal azolium intermediate that enables a cascade olefin isomerization/Diels-Alder reaction, for which mechanistic studies implicate Lewis base catalysis. Preliminary studies into the utility of the products have been undertaken with reductive and oxidative cleavage, giving materials for potential use in complex-target synthesis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Novel β-Keto-Enol Derivatives Tethered Pyrazole, Pyridine and Furan as New Potential Antifungal and Anti-Breast Cancer Agents

Directory of Open Access Journals (Sweden)

Smaail Radi

2015-11-01

Full Text Available Recently, a new generation of highly promising inhibitors bearing β-keto-enol functionality has emerged. Reported herein is the first synthesis and use of novel designed drugs based on the β-keto-enol group embedded with heterocyclic moieties such as pyrazole, pyridine, and furan, prepared in a one-step procedure by mixed Claisen condensation. All the newly synthesized compounds were characterized by FT-IR, 1H-NMR, 13C-NMR, ESI/LC-MS, elemental analysis, and evaluated for their in vitro antiproliferative activity against breast cancer (MDA-MB241 human cell lines and fungal strains (Fusarium oxysporum f.sp albedinis FAO. Three of the synthesized compounds showed potent activity against fungal strains with IC50 values in the range of 0.055–0.092 µM. The results revealed that these compounds showed better IC50 values while compared with positive controls.

BIOACTIVITIES AND MECHANISM OF SPIRO ENOL ETHER ANALOGUES AGAINST PIERIS RAPAE

Institute of Scientific and Technical Information of China (English)

Zhi-xiangZhang; Dong-meiCheng; Han-hongXu; Yu-linWu; andJun-faFan

2004-01-01

Nineteen kinds of spiro enol ether analogues were screened with larvae of Pieris rapae for antifeedant activity. The results showed that the antifeedant activity of compounds No.20 and No.12 was higher than others. In non-choice test, AFC50 values within 24 h of compounds No.20 and No.12 against 3rd instar larvae of P. rapae were 226.93ug/mL and 370.00ug/mL, and that in choice test against 4th larvae were 280.54 ug/mL and 398.88 ug/mL, respectively. Compd. No.20 could prolong the eggs hatch time and reduce the haemolymph content and the protein content in haemolymph of 4th instar larvae obviously. Compd. No.20 could protect tested leaves and control larvae of P. rapae effectively.

From stochastic processes to numerical methods: A new scheme for solving reaction subdiffusion fractional partial differential equations

Energy Technology Data Exchange (ETDEWEB)

Angstmann, C.N.; Donnelly, I.C. [School of Mathematics and Statistics, UNSW Australia, Sydney NSW 2052 (Australia); Henry, B.I., E-mail: B.Henry@unsw.edu.au [School of Mathematics and Statistics, UNSW Australia, Sydney NSW 2052 (Australia); Jacobs, B.A. [School of Computer Science and Applied Mathematics, University of the Witwatersrand, Johannesburg, Private Bag 3, Wits 2050 (South Africa); DST–NRF Centre of Excellence in Mathematical and Statistical Sciences (CoE-MaSS) (South Africa); Langlands, T.A.M. [Department of Mathematics and Computing, University of Southern Queensland, Toowoomba QLD 4350 (Australia); Nichols, J.A. [School of Mathematics and Statistics, UNSW Australia, Sydney NSW 2052 (Australia)

2016-02-15

We have introduced a new explicit numerical method, based on a discrete stochastic process, for solving a class of fractional partial differential equations that model reaction subdiffusion. The scheme is derived from the master equations for the evolution of the probability density of a sum of discrete time random walks. We show that the diffusion limit of the master equations recovers the fractional partial differential equation of interest. This limiting procedure guarantees the consistency of the numerical scheme. The positivity of the solution and stability results are simply obtained, provided that the underlying process is well posed. We also show that the method can be applied to standard reaction–diffusion equations. This work highlights the broader applicability of using discrete stochastic processes to provide numerical schemes for partial differential equations, including fractional partial differential equations.

Partial gamma-ray cross section measurements in 109Ag(n, x n y p gamma) reactions

Energy Technology Data Exchange (ETDEWEB)

Fotiadis, Nikolaos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Devlin, Matthew James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nelson, Ronald Owen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carroll, James [US Army Research Laboratory, Adelphi, MD (United States)

2015-06-02

We report on absolute partial cross sections for production of discrete γ-rays using ¹⁰⁹Ag(n, xnypγ) reactions with x ≤ 7 and y ≤ 1 in a total of 12 reaction channels. The data were taken using the GEANIE spectrometer comprised of 20 high-purity Ge detectors with 20 BGO escape-suppression shields. The broad-spectrum pulsed neutron beam of the Los Alamos Neutron Science Center’s (LANSCE) WNR facility provided neutrons in the energy range from 0.2 to 300 MeV. The time-of- flight technique was used to determine the incident neutron energies. Partial γ-ray cross sections have been measured for a total of 109 transitions and for neutron energies 0.8 MeV< E_n<300 MeV. An estimate of the population of isomers in the (n, n'), (n, 2n) and (n, 3n) channels was made.

The Brønsted Acid-Catalyzed, Enantioselective Aza-Diels-Alder Reaction for the Direct Synthesis of Chiral Piperidones.

Science.gov (United States)

Weilbeer, Claudia; Sickert, Marcel; Naumov, Sergei; Schneider, Christoph

2017-01-12

We disclose herein the first enantioselective aza-Diels-Alder reaction of β-alkyl-substituted vinylketene silyl-O,O-acetals and imines furnishing a broad range of optically highly enriched 4-alkyl-substituted 2-piperidones. As a catalyst for this one-pot reaction we employed a chiral phosphoric acid which effects a vinylogous Mannich reaction directly followed by ring-closure to the lactam. Subsequent fully diastereoselective transformations including hydrogenation, enolate alkylation, and lactam alkylation/reduction processes converted the cycloadducts into various highly substituted piperidines of great utility for the synthesis of natural products and medicinally active compounds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

New approach to analyzing and evaluating cross sections for partial photoneutron reactions

International Nuclear Information System (INIS)

Varlamov, V. V.; Ishkhanov, B. S.; Orlin, V. N.

2012-01-01

The presence of substantial systematic discrepancies between the results of different experiments devoted to determining cross sections for partial photoneutron reactions—first of all, (γ, n), (γ, 2n), and (γ, 3n) reactions—is a strong motivation for studying the reliability and authenticity of these data and for developing methods for taking into account and removing the discrepancies in question. In order to solve the first problem, we introduce objective absolute criteria involving transitional photoneutron-multiplicity functions F 1 , F 2 , F 3 , …; by definition, their values cannot exceed 1.0, 0.5, 0.33, …, respectively. With the aim of solving the second problem, we propose a new experimental-theoretical approach. In this approach, reaction cross sections are evaluated by simultaneously employing experimental data on the cross section for the total photoneutron yield, σ expt (γ, xn) = σ expt (γ, n) + 2σ expt (γ, 2n) + 3σ expt (γ, 3n) + …, which are free from drawbacks plaguing experimental methods for sorting neutrons in multiplicity, and the results obtained by calculating the functions F theor 1 , F theor 2 , F theor 3 , … on the basis of the modern model of photonuclear reactions. The reliability and authenticity of data on the cross sections for (γ, n), (γ, 2n), and (γ, 3n) partial reactions—σ eval (γ, in) = F i theor σ expt (γ, xn)—were evaluated for the 90 Zr, 115 In, 112,114,116,117,118,119,120,122,124 Sn, 159 Tb, and 197 Au nuclei.

Synthesis of 11C labelled methyl esters: transesterification of enol esters versus BF3 catalysed esterification-a comparative study

International Nuclear Information System (INIS)

Ackermann, Uwe; Blanc, Paul; Falzon, Cheryl L.; Issa, William; White, Jonathan; Tochon-Danguy, Henri J.; Sachinidis, John I.; Scott, Andrew M.

2006-01-01

C-11 labelled methyl esters have been synthesized via the transesterification of enol esters in the presence of C-11 methanol and 1,3 dichlorodibutylstannoxane as catalyst. This method leaves functional groups intact and allows access to a wider variety of C-11 labelled methyl esters compared to the BF 3 catalysed ester formation, which uses carboxylic acids and C-11 methanol as starting materials

Explicit integration of extremely stiff reaction networks: partial equilibrium methods

International Nuclear Information System (INIS)

Guidry, M W; Hix, W R; Billings, J J

2013-01-01

In two preceding papers (Guidry et al 2013 Comput. Sci. Disc. 6 015001 and Guidry and Harris 2013 Comput. Sci. Disc. 6 015002), we have shown that when reaction networks are well removed from equilibrium, explicit asymptotic and quasi-steady-state approximations can give algebraically stabilized integration schemes that rival standard implicit methods in accuracy and speed for extremely stiff systems. However, we also showed that these explicit methods remain accurate but are no longer competitive in speed as the network approaches equilibrium. In this paper, we analyze this failure and show that it is associated with the presence of fast equilibration timescales that neither asymptotic nor quasi-steady-state approximations are able to remove efficiently from the numerical integration. Based on this understanding, we develop a partial equilibrium method to deal effectively with the approach to equilibrium and show that explicit asymptotic methods, combined with the new partial equilibrium methods, give an integration scheme that can plausibly deal with the stiffest networks, even in the approach to equilibrium, with accuracy and speed competitive with that of implicit methods. Thus we demonstrate that such explicit methods may offer alternatives to implicit integration of even extremely stiff systems and that these methods may permit integration of much larger networks than have been possible before in a number of fields. (paper)

Reaction of dimethyl hydrogen phosphite with acecyclone

International Nuclear Information System (INIS)

Arbuzov, B.A.; Fuzhenkova, A.V.; Tyryshkin, N.I.

1987-01-01

In the presence of bases acecyclone reacts with dimethyl hydrogen phosphite with the formation of gamma-keto phosphonates with conjugated and unconjugated structures, and also an enol phosphate, a product containing a bond between oxygen of the cyclone and phosphorus. In the absence of bases, as well as the beta-keto phosphonate, gamma-keto phosphonates of cis and trans structure are formed; they are products of the 1,4 addition of dimethyl hydrogen phosphite to the conjugated fragment C=C-C=O of the cyclone. The compositions of the reaction mixture were determined by IR and NMR spectroscopy and TLC. Full-scale analysis of chemical shifts and spin-spin coupling constants was performed

Arylation of beta, gamma-unsaturated lactones by a Heck-Matsuda reaction: an unexpected route to aryldiazene butenolides and pyridazinones

Energy Technology Data Exchange (ETDEWEB)

Taylor, Jason G.; Correia, Carlos Roque D., E-mail: roque@iqm.unicamp.b [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica

2010-07-01

The palladium catalysed coupling of aryldiazonium salts with {beta}-{gamma}-unsaturated lactones under basic conditions has been investigated. Both (3H)-furanone and {alpha}-angelicalactone were evaluated as substrates in the Heck Matsuda reaction but both failed to afford the desired arylated butenolides. Under basic conditions, {beta}-{gamma}-unsaturated lactones generate highly nucleophilic enolates that preferentially undergo azo coupling reactions with arenediazonium salts to afford aryldiazene butenolides. The electronic and steric effect of the substituents on the aryldiazonium salt in the azo coupling reaction is described. Aryldiazene-lactone derivatives were obtained in good yields from a highly facile and straightforward procedure. An aminoisomaleimide was formed from (3H)-furanone and cyclized to the corresponding pyridazinones in modest yield. (author)

Modified Julia Olefination on Anhydrides: Extension and Limitations. Application to the Synthesis of Maculalactone B.

Science.gov (United States)

Dussart, Nicolas; Trinh, Huu Vinh; Gueyrard, David

2016-10-07

The preparation of exo-enol esters from cyclic anhydrides is reported using a modified Julia olefination. The reaction is highly stereoselective. The Smiles rearrangement can be performed in a one-pot process, giving a straightforward access to exo-enol lactones. Furthermore, the reaction was extended to semistabilized sulfones, and this methodology was applied to the synthesis of maculalactone B.

Theoretical Kinetic Study of the Unimolecular Keto–Enol Tautomerism Propen-2-ol ↔ Acetone. Pressure Effects and Implications in the Pyrolysis of tert- and 2-Butanol

KAUST Repository

Grajales Gonzalez, Edwing

2018-03-21

The need for renewable and cleaner sources of energy has made biofuels an interesting alternative to fossil fuels, especially in the case of butanol isomers, with its favorable blend properties and low hygroscopicity. Although C4 alcohols are prospective fuels, some key reactions governing their pyrolysis and combustion have not been adequately studied, leading to incomplete kinetic models. Enols are important intermediates in the combustion of C4 alcohols, as well as in atmospheric processes. Butanol reactions kinetics is poorly understood. Specifically, the unimolecular tautomerism of propen-2-ol ↔ acetone, which is included in butanol combustion kinetic models, is assigned rate parameters based on the tautomerism vinyl alcohol ↔ acetaldehyde as an analogy. In an attempt to update current kinetic models for tert- and 2-butanol, a theoretical kinetic study of the titled reaction was carried out by means of CCSD(T,FULL)/aug-cc-pVTZ//CCSD(T)/6-31+G(d,p) ab initio calculations, with multistructural torsional anharmonicity and variational transition state theory considerations in a wide temperature and pressure range (200-3000 K; 0.1-108 kPa). Results differ from vinyl alcohol ↔ acetaldehyde analogue reaction, which shows lower rate constant values. It was observed that decreasing pressure leads to a decrease in rate constants, describing the expected falloff behavior. Tunneling turned out to be important, especially at low temperatures. Accordingly, pyrolysis simulations in a batch reactor for tert- and 2-butanol with computed rate constants showed important differences in comparison with previous results, such as larger acetone yield and quicker propen-2-ol consumption.

Theoretical Kinetic Study of the Unimolecular Keto–Enol Tautomerism Propen-2-ol ↔ Acetone. Pressure Effects and Implications in the Pyrolysis of tert- and 2-Butanol

KAUST Repository

Grajales Gonzalez, Edwing Javier; Monge Palacios, Manuel; Sarathy, Mani

2018-01-01

The need for renewable and cleaner sources of energy has made biofuels an interesting alternative to fossil fuels, especially in the case of butanol isomers, with its favorable blend properties and low hygroscopicity. Although C4 alcohols are prospective fuels, some key reactions governing their pyrolysis and combustion have not been adequately studied, leading to incomplete kinetic models. Enols are important intermediates in the combustion of C4 alcohols, as well as in atmospheric processes. Butanol reactions kinetics is poorly understood. Specifically, the unimolecular tautomerism of propen-2-ol ↔ acetone, which is included in butanol combustion kinetic models, is assigned rate parameters based on the tautomerism vinyl alcohol ↔ acetaldehyde as an analogy. In an attempt to update current kinetic models for tert- and 2-butanol, a theoretical kinetic study of the titled reaction was carried out by means of CCSD(T,FULL)/aug-cc-pVTZ//CCSD(T)/6-31+G(d,p) ab initio calculations, with multistructural torsional anharmonicity and variational transition state theory considerations in a wide temperature and pressure range (200-3000 K; 0.1-108 kPa). Results differ from vinyl alcohol ↔ acetaldehyde analogue reaction, which shows lower rate constant values. It was observed that decreasing pressure leads to a decrease in rate constants, describing the expected falloff behavior. Tunneling turned out to be important, especially at low temperatures. Accordingly, pyrolysis simulations in a batch reactor for tert- and 2-butanol with computed rate constants showed important differences in comparison with previous results, such as larger acetone yield and quicker propen-2-ol consumption.

Modeling the mechanism of glycosylation reactions between ethanol, 1,2-ethanediol and methoxymethanol.

Science.gov (United States)

Azofra, Luis Miguel; Alkorta, Ibon; Toro-Labbé, Alejandro; Elguero, José

2013-09-07

The mechanism of the S(N)2 model glycosylation reaction between ethanol, 1,2-ethanediol and methoxymethanol has been studied theoretically at the B3LYP/6-311+G(d,p) computational level. Three different types of reactions have been explored: (i) the exchange of hydroxyl groups between these model systems; (ii) the basic catalysis reactions by combination of the substrates as glycosyl donors (neutral species) and acceptors (enolate species); and (iii) the effect on the reaction profile of an explicit H2O molecule in the reactions considered in (ii). The reaction force, the electronic chemical potential and the reaction electronic flux have been characterized for the reaction path in each case. Energy calculations show that methoxymethanol is the worst glycosyl donor model among the ones studied here, while 1,2-ethanediol is the best, having the lowest activation barrier of 74.7 kJ mol(-1) for the reaction between this one and the ethanolate as the glycosyl acceptor model. In general, the presence of direct interactions between the atoms involved in the penta-coordinated TS increases the activation energies of the processes.

A dynamical theory of incomplete fusion reactions: The breakup-fusion reaction approach

International Nuclear Information System (INIS)

Udagawa, T.

1984-01-01

A dynamical theory of partial fusion reactions is presented, which may fill the gap between direct and compound nuclear reaction theories. With the new theory one can calculate partial fusion taking place in three-body (and many more) channels reached via direct reactions, e.g., breakup and knockout reactions. The authors present first the results for the cross section for such reactions, taking as an example breakup followed by fusion. They then discuss a physical picture which emerges from their theory, namely that the partial fusion reactions, particularly of the massive-transfer type, take place in a so-called deep peripheral region. It is also shown that the deep peripheral character of such processes diminishes as the mass of the fused system decreases, so that the reactions essentially evolve to the usual peripheral character. Finally, comparisons are made of results of numerical calculations with experimental data, taking as an example the /sup 159/Tb(/sup 14/N,α) reaction with E/sub lab/ = 95 MeV

First results of total and partial cross-section measurements of the 107Ag(p,γ)108Cd reaction

Science.gov (United States)

Heim, Felix; Mayer, Jan; Scholz, Philipp; Spieker, Mark; Zilges, Andreas

2018-01-01

The γ process is assumed to play an important role in the nucleosynthesis of the majority of the p nuclei. Since the network of the γ process includes so many different reactions and - mainly unstable - nuclei, cross-section values are predominantly calculated in the scope of the Hauser-Feshbach statistical model. The values heavily depend on the nuclear-physics input parameters. The results of total and partial cross-section measurements are used to improve the accuracy of the theoretical calculations. In order to extend the experimental database, the 107Ag(p,γ)108Cd reaction was studied via the in-beam method at the high-efficiency HPGe γ-ray spectrometer HORUS at the University of Cologne. Proton beams with energies between 3.5 MeV and 5.0 MeV were provided by the 10 MV FN-Tandem accelerator leading to the determination of four new total cross-section values. After slight adjustments of the nuclear level density and γ-ray strength function an excellent agreement between theoretical calculations and experimentally deduced values for both total and partial cross sections has been obtained.

Theoretical insights into the sites and mechanisms for base catalyzed esterification and aldol condensation reactions over Cu.

Science.gov (United States)

Neurock, Matthew; Tao, Zhiyuan; Chemburkar, Ashwin; Hibbitts, David D; Iglesia, Enrique

2017-04-28

Condensation and esterification are important catalytic routes in the conversion of polyols and oxygenates derived from biomass to fuels and chemical intermediates. Previous experimental studies show that alkanal, alkanol and hydrogen mixtures equilibrate over Cu/SiO 2 and form surface alkoxides and alkanals that subsequently promote condensation and esterification reactions. First-principle density functional theory (DFT) calculations were carried out herein to elucidate the elementary paths and the corresponding energetics for the interconversion of propanal + H 2 to propanol and the subsequent C-C and C-O bond formation paths involved in aldol condensation and esterification of these mixtures over model Cu surfaces. Propanal and hydrogen readily equilibrate with propanol via C-H and O-H addition steps to form surface propoxide intermediates and equilibrated propanal/propanol mixtures. Surface propoxides readily form via low energy paths involving a hydrogen addition to the electrophilic carbon center of the carbonyl of propanal or via a proton transfer from an adsorbed propanol to a vicinal propanal. The resulting propoxide withdraws electron density from the surface and behaves as a base catalyzing the activation of propanal and subsequent esterification and condensation reactions. These basic propoxides can readily abstract the acidic C α -H of propanal to produce the CH 3 CH (-) CH 2 O* enolate, thus initiating aldol condensation. The enolate can subsequently react with a second adsorbed propanal to form a C-C bond and a β-alkoxide alkanal intermediate. The β-alkoxide alkanal can subsequently undergo facile hydride transfer to form the 2-formyl-3-pentanone intermediate that decarbonylates to give the 3-pentanone product. Cu is unique in that it rapidly catalyzes the decarbonylation of the C 2n intermediates to form C 2n-1 3-pentanone as the major product with very small yields of C 2n products. This is likely due to the absence of Brønsted acid sites

Partial oxidation of jet fuels over Rh/Al_2O_3. Design and reaction kinetics of sulfur-containing surrogates

International Nuclear Information System (INIS)

Baer, Julian Nicolaas

2016-01-01

The conversion of logistic fuels via catalytic partial oxidation (CPOX) on Rh/Al_2O_3 at short contact times is an efficient method for generating hydrogen-rich synthesis gas. Depending on the inlet conditions, fuel, and catalyst, high syngas yields, low by-product formation, and rates of high fuel conversion can be achieved. CPOX is relevant for mobile hydrogen generation, e.g., on board of airplanes in order to increase the fuel efficiency via fuel cell-based auxiliary power units. Jet fuels contain hundreds of different hydrocarbons and a significant amount of sulfur. The hydrocarbon composition and sulfur content of a jet fuel vary depending on distributor, origin, and refinement of the crude oil. Little is known about the influence of the various compounds on the synthesis-gas yield and the impact of sulfur on the product yield. In this work, the influence of three main chemical compounds of a jet fuel (aromatics, alkanes, and sulfur compounds) on syngas selectivity, the catalyst deactivation process, and reaction sequence is unraveled. As representative components of alkanes and aromatics, n-dodecane and 1,2,4-trimethylbenzene were chosen for ex-situ and in-situ investigations on the CPOX over Rh/Al_2O_3, respectively. Additionally, for a fixed paraffin-to-aromatics ratio, benzothiophene or dibenzothiophene were added as a sulfur component in three different concentrations. The knowledge gained about the catalytic partial oxidation of jet fuels and their surrogates is used to identify requirements for jet fuels in mobile applications based on CPOX and to optimize the overall system efficiency. The results show an influence of the surrogate composition on syngas selectivity. The tendency for syngas formation increases with higher paraffin contents. A growing tendency for by-product formation can be observed with increasing aromatics contents in the fuel. The impact of sulfur on the reaction system shows an immediate change in the product distribution. An

Charge separation in photoinitiated electron transfer reactions induced by a polyelectrolyte

International Nuclear Information System (INIS)

Meyerstein, D.; Rabani, J.; Matheson, M.S.; Meisel, D.

1978-01-01

When uncharged molecules quench the luminescence of Ru(bpy) 3 /sup 2+*/ by electron transfer to the quencher, the addition of poly(vinyl sulfate) (PVS) may, through its potential field, affect the rate of quenching, enhance the net separated charge yield, and slow the back reaction of the separated photoredox products. In all such cases that we have studied the quenching rate in the presence of PVS was reduced to about 60% of the rate measured in the absence of PVS. For two neutral species, iron(III) nitrilotriacetate (FeNTA) and cobalt(III) acetylacetonate (Co(acac) 3 ), photoreduction of the quencher was observed, and the redox yield escaping geminate recombination was substantially increased by added PVS. In the case of FeNTA the rate of the bulk back reaction was not changed appreciably by the presence of PVS owing to the rapid neutralization of Fe(NTA) - by protonation. For Co(acac) 3 the rate of the bulk back reaction was decreased by several orders of magnitude and the back reaction was shown to occur via the enolate form of the ligand which is released to the bulk solution. 4 figures, 4 tables

Gold-Catalyzed Formal C-C Bond Insertion Reaction of 2-Aryl-2-diazoesters with 1,3-Diketones.

Science.gov (United States)

Ren, Yuan-Yuan; Chen, Mo; Li, Ke; Zhu, Shou-Fei

2018-06-29

The transition-metal-catalyzed formal C-C bond insertion reaction of diazo compounds with monocarbonyl compounds is well established, but the related reaction of 1,3-diketones instead gives C-H bond insertion products. Herein, we report a protocol for a gold-catalyzed formal C-C bond insertion reaction of 2-aryl-2-diazoesters with 1,3-diketones, which provides efficient access to polycarbonyl compounds with an all-carbon quaternary center. The aryl ester moiety plays a crucial role in the unusual chemoselectivity, and the addition of a Brønsted acid to the reaction mixture improves the yield of the C-C bond insertion product. A reaction mechanism involving cyclopropanation of a gold carbenoid with an enolate and ring-opening of the resulting donor-acceptor-type cyclopropane intermediate is proposed. This mechanism differs from that of the traditional Lewis-acid-catalyzed C-C bond insertion reaction of diazo compounds with monocarbonyl compounds, which involves a rearrangement of a zwitterion intermediate as a key step. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lecithin-cholesterol acyltransferase (LCAT) catalyzes transacylation of intact cholesteryl esters. Evidence for the partial reversal of the forward LCAT reaction

International Nuclear Information System (INIS)

Sorci-Thomas, M.; Babiak, J.; Rudel, L.L.

1990-01-01

Lecithin-cholesterol acyltransferase (LCAT) catalyzes the intravascular synthesis of lipoprotein cholesteryl esters by converting cholesterol and lecithin to cholesteryl ester and lysolecithin. LCAT is unique in that it catalyzes sequential reactions within a single polypeptide sequence. In this report we find that LCAT mediates a partial reverse reaction, the transacylation of lipoprotein cholesteryl oleate, in whole plasma and in a purified, reconstituted system. As a result of the reverse transacylation reaction, a linear accumulation of [3H]cholesterol occurred during incubations of plasma containing high density lipoprotein labeled with [3H]cholesteryl oleate. When high density lipoprotein labeled with cholesteryl [14C]oleate was also included in the incubation the labeled fatty acyl moiety remained in the cholesteryl [14C]oleate pool showing that the formation of labeled cholesterol did not result from hydrolysis of the doubly labeled cholesteryl esters. The rate of release of [3H]cholesterol was only about 10% of the forward rate of esterification of cholesterol using partially purified human LCAT and was approximately 7% in whole monkey plasma. Therefore, net production of cholesterol via the reverse LCAT reaction would not occur. [3H]Cholesterol production from [3H]cholesteryl oleate was almost completely inhibited by a final concentration of 1.4 mM 5,5'-dithiobis(nitrobenzoic acid) during incubation with either purified LCAT or whole plasma. Addition of excess lysolecithin to the incubation system did not result in the formation of [14C]oleate-labeled lecithin, showing that the reverse reaction found here for LCAT was limited to the last step of the reaction. To explain these results we hypothesize that LCAT forms a [14C]oleate enzyme thioester intermediate after its attack on the cholesteryl oleate molecule

Extent of reaction in open systems with multiple heterogeneous reactions

Science.gov (United States)

Friedly, John C.

1991-01-01

The familiar batch concept of extent of reaction is reexamined for systems of reactions occurring in open systems. Because species concentrations change as a result of transport processes as well as reactions in open systems, the extent of reaction has been less useful in practice in these applications. It is shown that by defining the extent of the equivalent batch reaction and a second contribution to the extent of reaction due to the transport processes, it is possible to treat the description of the dynamics of flow through porous media accompanied by many chemical reactions in a uniform, concise manner. This approach tends to isolate the reaction terms among themselves and away from the model partial differential equations, thereby enabling treatment of large problems involving both equilibrium and kinetically controlled reactions. Implications on the number of coupled partial differential equations necessary to be solved and on numerical algorithms for solving such problems are discussed. Examples provided illustrate the theory applied to solute transport in groundwater flow.

Stereoselective syntheses of (+- isoretronecanol and (+-5-epi-tashiromine via addition of chiral titanium (iv enolates to cyclic n-acyliminium ions

Directory of Open Access Journals (Sweden)

Elaine Pereira

2008-01-01

Full Text Available The stereoselective addition of the titanium (IV enolates derived from (S-4-isopropyl-N-4-chlorobutyryl-1,3-thiazolidine-2-thione (8 and from (S-4-isopropyl-N-4-chloropentanoyl-1,3-thiazolidine-2-thione (9 to N-Boc-2-methoxypyrrolidine (5b afforded the addition products (+-10 and (+-11 in 84% yield in both cases, as 8.6:1 and 10:1 diastereoisomeric mixtures, respectively. A three-step sequence allowed to convert these adducts to (+-isoretronecanol (1 and (+-5-epi-tashiromine (2 in 43% and 49% overall yield, respectively.

Stereoselective syntheses of (+)- isoretronecanol and (+)-5-epi-tashiromine via addition of chiral titanium (IV) enolates to cyclic n-acyliminium ions

Energy Technology Data Exchange (ETDEWEB)

Pereira, Elaine; Alves, Conceicao de Fatima; Boeckelmann, Maria Alice; Pilli, Ronaldo A [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Inst. de Quimica

2008-07-01

The stereoselective addition of the titanium (IV) enolates derived from (S)-4-isopropyl-N-4-chlorobutyryl-1,3-thiazolidine-2-thione (8) and from (S)-4-isopropyl-N-4-chloropentanoyl-1,3-thiazolidine-2-thione (9) to N-Boc-2-methoxypyrrolidine (5b) afforded the addition products (+)-10 and (+)-11 in 84% yield in both cases, as 8.6:1 and 10:1 diastereoisomeric mixtures, respectively. A three-step sequence allowed to convert these adducts to (+)-isoretronecanol (1) and (+)-5-epi-tashiromine (2) in 43% and 49% overall yield, respectively. (author)

Tandem Carbocupration/Oxygenation of Terminal Alkynes

Science.gov (United States)

Zhang, Donghui; Ready, Joseph M.

2008-01-01

A direct and general synthesis of α-branched aldehydes and their enol derivatives is described. Carbocupration of terminal alkynes and subsequent oxygenation with lithium tert-butyl peroxide generates a metallo-enolate. Trapping with various electrophiles provides α-branched aldehydes or stereo-defined trisubstituted enol esters or silyl ethers. The tandem carbocupration/oxygenation tolerates alkyl and silyl ethers, esters and tertiary amines. The reaction is effective with organocopper complexes derived from primary, secondary and tertiary Grignard reagents and from n-butyllithium. PMID:16321021

On the Green's function of the partially diffusion-controlled reversible ABCD reaction for radiation chemistry codes

Energy Technology Data Exchange (ETDEWEB)

Plante, Ianik, E-mail: ianik.plante-1@nasa.gov [Wyle Science, Technology & Engineering, 1290 Hercules, Houston, TX 77058 (United States); Devroye, Luc, E-mail: lucdevroye@gmail.com [School of Computer Science, McGill University, 3480 University Street, Montreal H3A 0E9 (Canada)

2015-09-15

Several computer codes simulating chemical reactions in particles systems are based on the Green's functions of the diffusion equation (GFDE). Indeed, many types of chemical systems have been simulated using the exact GFDE, which has also become the gold standard for validating other theoretical models. In this work, a simulation algorithm is presented to sample the interparticle distance for partially diffusion-controlled reversible ABCD reaction. This algorithm is considered exact for 2-particles systems, is faster than conventional look-up tables and uses only a few kilobytes of memory. The simulation results obtained with this method are compared with those obtained with the independent reaction times (IRT) method. This work is part of our effort in developing models to understand the role of chemical reactions in the radiation effects on cells and tissues and may eventually be included in event-based models of space radiation risks. However, as many reactions are of this type in biological systems, this algorithm might play a pivotal role in future simulation programs not only in radiation chemistry, but also in the simulation of biochemical networks in time and space as well.

On the Green's function of the partially diffusion-controlled reversible ABCD reaction for radiation chemistry codes

International Nuclear Information System (INIS)

Plante, Ianik; Devroye, Luc

2015-01-01

Several computer codes simulating chemical reactions in particles systems are based on the Green's functions of the diffusion equation (GFDE). Indeed, many types of chemical systems have been simulated using the exact GFDE, which has also become the gold standard for validating other theoretical models. In this work, a simulation algorithm is presented to sample the interparticle distance for partially diffusion-controlled reversible ABCD reaction. This algorithm is considered exact for 2-particles systems, is faster than conventional look-up tables and uses only a few kilobytes of memory. The simulation results obtained with this method are compared with those obtained with the independent reaction times (IRT) method. This work is part of our effort in developing models to understand the role of chemical reactions in the radiation effects on cells and tissues and may eventually be included in event-based models of space radiation risks. However, as many reactions are of this type in biological systems, this algorithm might play a pivotal role in future simulation programs not only in radiation chemistry, but also in the simulation of biochemical networks in time and space as well

Inicios de la microbiología enológica gallega

Directory of Open Access Journals (Sweden)

Carrascosa, Alfonso V.

2010-12-01

parte de este esfuerzo fue finalmente aplicado a la enología, cristalizando en la Teoría Ecológica del Vino. Los primeros estudios científicos de microbiología enológica gallega fueron realizados en el Departamento de Microbiología del Instituto de Fermentaciones Industriales del CSIC (IFI-CSIC en la década de los 70, y formaron parte de las evidencias que sirvieron para establecer dicha teoría. Instalaciones inadecuadas, unidas al empleo masivo de fungicidas y sulfuroso como antisépticos, fueron identificados como posibles causas de los problemas detectados durante el estudio de la vinificación. Finalmente se recomendaría como idóneo para salvaguardar el tipismo de los vinos gallegos, y reducir al mínimo el empleo de dióxido de azufre, la inoculación secuencial de los mostos con las levaduras que fueron aisladas en el estudio y que todavía se conservan en el IFI-CSIC. En este artículo se presentan los resultados de esos estudios, sus consecuencias, y la situación en la que se encontraba la microbiología enológica española en esos momentos.

Turismo enológico en Uruguay: ¿qué quiere el visitante local?

Directory of Open Access Journals (Sweden)

Gianfranca María Camussi Calvi

2016-01-01

Full Text Available El turismo enológico en Uruguay comienza a desarrollarse, con una demanda compuesta mayoritariamente por turistas extranjeros y visitantes locales en segundo plano. Con el objetivo de aportar conocimiento sobre el visitante doméstico y sus expectativas y aspiraciones, para el logro de un plan de marketing ajustado, se realizó una encuesta, a residentes de Montevideo de alto nivel socioeconómico. El 86% desea realizar enoturismo; los intereses específicos permiten separar grupos por afinidad. Respecto a las actividades propias del enoturismo, se diferencia un grupo que desea focalizarse en degustar y comprar vino, y otro que prefiere conocer el proceso productivo completo. Todos desean actividades complementarias, y se dicotomizan en - un grupo que prefiere gastronomía, cultura y arte, - mientras el otro, deportes o actividades al aire libre. Se ha identificado la amplitud de servicios para un turismo del vino exitoso que busque la satisfacción del cliente y la fidelización de los visitantes locales.

Cathodic over-potential and hydrogen partial pressure coupling in hydrogen evolution reaction of marine steel under hydrostatic pressure

International Nuclear Information System (INIS)

Xiong, X.L.; Zhou, Q.J.; Li, J.X.; Volinsky, Alex A.; Su, Y.J.

2017-01-01

Highlights: •Hydrostatic pressure increases the Volmer and the Heyrovsky reactions rates. •Hydrostatic pressure decreases the Tafel reaction rate. •Hydrogen adsorption conditions change with pressure under −1.2 and −1.3 V SSE . •Under −1.2 and −1.3 V SSE , the Heyrovsky reaction dominates the hydrogen recombination. •Under −1.0 and −1.1 V SSE , the Tafel reaction dominates the hydrogen recombination. -- Abstract: A new electrochemical impedance spectroscopy (EIS) model, which considers both the Tafel recombination and the Heyrovsky reaction under permeable boundary conditions, was developed to characterize the kinetic parameters of the hydrogen evolution reaction (HER) under hydrostatic pressure. The effect of the hydrostatic pressure on the kinetic parameters of the HER and the permeation of A514 steel in alkaline solution were measured using potentiodynamic polarization, the Devanathan cell hydrogen permeation, and EIS. The hydrostatic pressure accelerates the Volmer reaction and inhibits the Tafel recombination, which increases the number of adsorbed hydrogen atoms. On the other hand, the pressure accelerates the Heyrovsky reaction, which decreases the amount of adsorbed hydrogen atoms. At 10 to 40 MPa hydrostatic pressure within the −1.0 to −1.1 V SSE cathodic potential region, the HER is controlled by hydrogen partial pressure, and hydrogen adsorption is the Langmuir type. Within the −1.2 to −1.3 V SSE cathodic potential region, the HER is controlled by the potential, and hydrogen adsorption gradually transfers from the Langmuir type to the Temkin type with increasing hydrostatic pressure.

Enantioselective N-Heterocyclic Carbene Catalysis via the Dienyl Acyl Azolium.

Science.gov (United States)

Gillard, Rachel M; Fernando, Jared E M; Lupton, David W

2018-04-16

Herein we report the enantioselective N-heterocyclic carbene catalyzed (4+2) annulation of the dienyl acyl azolium with enolates. The reaction exploits readily accessible acyl fluorides and TMS enol ethers to give a range of highly enantio- and diastereo-enriched cyclohexenes (most >97:3 er and >20:1 dr). The reaction was found to require high nucleophilicity NHC catalysts with mechanistic studies supporting a stepwise 1,6-addition/β-lactonization. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Partial oxidation of jet fuels over Rh/Al{sub 2}O{sub 3}. Design and reaction kinetics of sulfur-containing surrogates

Energy Technology Data Exchange (ETDEWEB)

Baer, Julian Nicolaas

2016-07-01

The conversion of logistic fuels via catalytic partial oxidation (CPOX) on Rh/Al{sub 2}O{sub 3} at short contact times is an efficient method for generating hydrogen-rich synthesis gas. Depending on the inlet conditions, fuel, and catalyst, high syngas yields, low by-product formation, and rates of high fuel conversion can be achieved. CPOX is relevant for mobile hydrogen generation, e.g., on board of airplanes in order to increase the fuel efficiency via fuel cell-based auxiliary power units. Jet fuels contain hundreds of different hydrocarbons and a significant amount of sulfur. The hydrocarbon composition and sulfur content of a jet fuel vary depending on distributor, origin, and refinement of the crude oil. Little is known about the influence of the various compounds on the synthesis-gas yield and the impact of sulfur on the product yield. In this work, the influence of three main chemical compounds of a jet fuel (aromatics, alkanes, and sulfur compounds) on syngas selectivity, the catalyst deactivation process, and reaction sequence is unraveled. As representative components of alkanes and aromatics, n-dodecane and 1,2,4-trimethylbenzene were chosen for ex-situ and in-situ investigations on the CPOX over Rh/Al{sub 2}O{sub 3}, respectively. Additionally, for a fixed paraffin-to-aromatics ratio, benzothiophene or dibenzothiophene were added as a sulfur component in three different concentrations. The knowledge gained about the catalytic partial oxidation of jet fuels and their surrogates is used to identify requirements for jet fuels in mobile applications based on CPOX and to optimize the overall system efficiency. The results show an influence of the surrogate composition on syngas selectivity. The tendency for syngas formation increases with higher paraffin contents. A growing tendency for by-product formation can be observed with increasing aromatics contents in the fuel. The impact of sulfur on the reaction system shows an immediate change in the product

Palladium-Catalyzed Reductive Insertion of Alcohols into Aryl Ether Bonds

Energy Technology Data Exchange (ETDEWEB)

Wang, Meng [Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Gutiérrez, Oliver Y. [Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Camaioni, Donald M. [Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Lercher, Johannes A. [Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99352 USA; Department of Chemistry and Catalysis Research Institute, TU München, Lichtenbergstrasse 4 85748 Garching Germany

2018-03-06

Pd/C catalyzes C-O bond cleavage of aryl ethers (diphenyl ether and cyclohexyl phenyl ether) by methanol in H2. The aromatic C-O bond is cleaved by reductive methanolysis, which is initiated by Pd-catalyzed partial hydrogenation of one phenyl ring to form an enol ether. The enol ether reacts rapidly with methanol to form a ketal, which generates methoxycyclohexene by eliminating phenol or an alkanol. Subsequent hydrogenation leads to methoxycyclohexane.

Partial-wave analysis of the reaction K−p → $\\lambda$ (1520) $\\pi$ in the energy region 1915 – 2170 MeV

CERN Document Server

Litchfield, P J; Baillon, Paul; Putzer, A; Schleich, H

1974-01-01

A partial-wave analysis has been carried out on the reaction K/sup -/p to Lambda (1520) pi to K/sup -/p pi /sup 0/. The Sigma (2030) is observed with an amplitude at resonance of 0.14+or-0.03. Evidence is also presented for the formation of the /sup 3///sub 2//sup -/ Sigma (1940). (14 refs).

Study of the dynamics of the MoO2-Mo2C system for catalytic partial oxidation reactions

Science.gov (United States)

Cuba Torres, Christian Martin

On a global scale, the energy demand is largely supplied by the combustion of non-renewable fossil fuels. However, their rapid depletion coupled with environmental and sustainability concerns are the main drivers to seek for alternative energetic strategies. To this end, the sustainable generation of hydrogen from renewable resources such as biodiesel would represent an attractive alternative solution to fossil fuels. Furthermore, hydrogen's lower environmental impact and greater independence from foreign control make it a strong contender for solving this global problem. Among a wide variety of methods for hydrogen production, the catalytic partial oxidation offers numerous advantages for compact and mobile fuel processing systems. For this reaction, the present work explores the versatility of the Mo--O--C catalytic system under different synthesis methods and reforming conditions using methyl oleate as a surrogate biodiesel. MoO2 exhibits good catalytic activity and exhibits high coke-resistance even under reforming conditions where long-chain oxygenated compounds are prone to form coke. Moreover, the lattice oxygen present in MoO2 promotes the Mars-Van Krevelen mechanism. Also, it is introduced a novel beta-Mo2C synthesis by the in-situ formation method that does not utilize external H2 inputs. Herein, the MoO 2/Mo2C system maintains high catalytic activity for partial oxidation while the lattice oxygen serves as a carbon buffer for preventing coke formation. This unique feature allows for longer operation reforming times despite slightly lower catalytic activity compared to the catalysts prepared by the traditional temperature-programmed reaction method. Moreover, it is demonstrated by a pulse reaction technique that during the phase transformation of MoO2 to beta-Mo2C, the formation of Mo metal as an intermediate is not responsible for the sintering of the material wrongly assumed by the temperature-programmed method.

Reaction phenomena of catalytic partial oxidation of methane under the impact of carbon dioxide addition and heat recirculation

International Nuclear Information System (INIS)

Chen, Wei-Hsin; Lin, Shih-Cheng

2015-01-01

The reaction phenomena of CPOM (catalytic partial oxidation of methane) in a Swiss-roll reactor are studied numerically where a rhodium-based catalyst bed is embedded at the center of the reactor. CO 2 is added into the feed gas and excess enthalpy recovery is performed to evaluate their influences on CPOM performance. In the study, the mole ratio of O 2 to CH 4 (O 2 /CH 4 ratio) is fixed at 0.5 and the mole ratio of CO 2 to O 2 (CO 2 /O 2 ratio) is in the range of 0–2. The results reveal that CO 2 addition into the influent has a slight effect on methane combustion, but significantly enhances dry reforming and suppresses steam reforming. The reaction extents of steam reforming and dry reforming in CPOM without heat recovery and CO 2 addition are in a comparable state. Once CO 2 is added into the feed gas, the dry reforming is enhanced, thereby dominating CH 4 consumption. Compared to the reactor without excess enthalpy recovery, heat recirculation drastically increases the maximum reaction temperature and CH 4 conversion in the catalyst bed; it also intensifies the H 2 selectivity, H 2 yield, CO 2 conversion, and syngas production rate. The predictions indicate that the heat recirculation is able to improve the syngas formation up to 45%. - Highlights: • Catalytic partial oxidation of methane with CO 2 addition and heat recovery is studied. • CO 2 addition has a slight effect on methane combustion. • CO 2 addition significantly enhances dry reforming and suppresses steam reforming. • Dry reforming dominates CH 4 consumption when CO 2 addition is large. • Heat recirculation can improve the syngas formation up to 45%

Partial wave analysis of the Q region in the reactions K-p→K-π+π-p and K-p→antikaon neutral π-π0p at 14.3GeV/c

International Nuclear Information System (INIS)

Tovey, S.N.; Hansen, J.D.; Paler, K.; Shah, T.P.; Borg, A.; Denegri, D.; Pons, Y.; Spiro, M.

1975-01-01

The reactions K - p→K - π + π - and K - p→ antikaon-neutral π - π 0 p at 14.3GeV/c has been studied using respectively 15992 and 3723 events. Partial wave analysis of the region 1.0 + but that the partial wave substrates have very different branching ratios into (rho) and K*π, the K*π component of the 1 + state being similar to the 1 + state of the 3π system produced in the reaction πp→(3π)p [fr

Quantum Chemical Investigation on Photochemical Reactions of Nonanoic Acids at Air-Water Interface.

Science.gov (United States)

Xiao, Pin; Wang, Qian; Fang, Wei-Hai; Cui, Ganglong

2017-06-08

Photoinduced chemical reactions of organic compounds at the marine boundary layer have recently attracted significant experimental attention because this kind of photoreactions has been proposed to have substantial impact on local new particle formation and their photoproducts could be a source of secondary organic aerosols. In this work, we have employed first-principles density functional theory method combined with cluster models to systematically explore photochemical reaction pathways of nonanoic acids (NAs) to form volatile saturated and unsaturated C 9 and C 8 aldehydes at air-water interfaces. On the basis of the results, we have found that the formation of C 9 aldehydes is not initiated by intermolecular Norrish type II reaction between two NAs but by intramolecular T 1 C-O bond fission of NA generating acyl and hydroxyl radicals. Subsequently, saturated C 9 aldehydes are formed through hydrogenation reaction of acyl radical by another intact NA. Following two dehydrogenation reactions, unsaturated C 9 aldehydes are generated. In parallel, the pathway to C 8 aldehydes is initiated by T 1 C-C bond fission of NA, which generates octyl and carboxyl radicals; then, an octanol is formed through recombination reaction of octyl with hydroxyl radical. In the following, two dehydrogenation reactions result into an enol intermediate from which saturated C 8 aldehydes are produced via NA-assisted intermolecular hydrogen transfer. Finally, two dehydrogenation reactions generate unsaturated C 8 aldehydes. In these reactions, water and NA molecules are found to play important roles. They significantly reduce relevant reaction barriers. Our work has also explored oxygenation reactions of NA with molecular oxygen and radical-radical dimerization reactions.

{sup 1} H and {sup 13} C NMR studies on the enoling of 5-benzyl barbituric acids; Estudos por H-1 e C-13 RMN da enolizacao de acidos 5-benzil barbituricos

Energy Technology Data Exchange (ETDEWEB)

Villar, Jose Daniel Figueroa; Santos, Nedina Lucia dos; Cruz, Elizabete Rangel [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Quimica

1992-12-31

This work shows that the derivatives of the 5-benzyl barbituric acids hydroxylated at the ortho position of the aromatic ring only exist in the enol form. and that the alkylation of this hydroxyl gives products which exist mainly in the ketone form of the DMSO 5 refs., 2 figs., 2 tabs.

Finding of 13(2) , 17(3) -cyclopheophorbide a enol as a degradation product of chlorophyll in shrunk zooxanthellae of the coral Montipora digitata.

Science.gov (United States)

Suzuki, Toshiyuki; Casareto, Beatriz Estela; Shioi, Yuzo; Ishikawa, Yoshio; Suzuki, Yoshimi

2015-02-01

We examined the morphology and pigment composition of zooxanthellae in corals subjected to normal temperature (27°C) and thermal stress (32°C). We observed several normal and abnormal morphological types of zooxanthellar cells. Normal cells were intact and their chloroplasts were unbroken (healthy); abnormal cells were shrunken and had partially degraded or broken chloroplasts, or they were bleached and without chloroplasts. At 27°C, most healthy zooxanthellar cells were retained in the coral tissue, whereas shrunken zooxanthellae were expelled. Under thermal stress, the abundance of healthy zooxanthellae declined and the proportion of shrunken/abnormal cells increased in coral tissues. The rate of algal cell expulsion was reduced under thermal stress. Within the shrunken cells, we detected the presence of a chl-like pigment that is not ordinarily found in healthy zooxanthellae. Analysis of the absorption spectrum, absorption maxima, and retention time (by HPLC) indicated that this pigment was 13(2) , 17(3) -cyclopheophorbide a enol (cPPB-aE), which is frequently found in marine and lacustrine sediments, and in protozoans that graze on phytoplankton. The production of cPPB-aE in shrunken zooxanthellae suggests that the chls have been degraded to cPPB-aE, a compound that is not fluorescent. The lack of a fluorescence function precludes the formation of reactive oxygen species. We therefore consider the formation of cPPB-aE in shrunken zooxanthellae to be a mechanism for avoiding oxidative stress. © 2014 The Authors. Journal of Phycology published by Wiley Periodicals, Inc. on behalf of Phycological Society of America.

Partial-wave analysis of the reaction $K^{-}$ p -> $\\overline{K} \\delta$ (1230) in the energy region 1915–2170 MeV

CERN Document Server

Litchfield, P J; Baillon, Paul; Albrecht, A; Putzer, A

1974-01-01

A partial-wave analysis has been carried out on the reaction K/sup -/p to K/sup -/ Delta /sup +/(1230) to K/sup -/p pi /sup 0/ in the centre of mass energy region 1915-2170 MeV. The Sigma (2030) is observed with an amplitude at resonance of 0.16+or-0.03. Strong formation of the /sup 3///sub 2//sup -/ Sigma (1940) is also indicated. (9 refs).

Redox and Lewis acid relay catalysis: a titanocene/zinc catalytic platform in the development of multicomponent coupling reactions.

Science.gov (United States)

Gianino, Joseph B; Campos, Catherine A; Lepore, Antonio J; Pinkerton, David M; Ashfeld, Brandon L

2014-12-19

A titanocene-catalyzed multicomponent coupling is described herein. Using catalytic titanocene, phosphine, and zinc dust, zinc acetylides can be generated from the corresponding iodoalkynes to affect sequential nucleophilic additions to aromatic aldehydes. The intermediate propargylic alkoxides are trapped in situ with acetic anhydride, which are susceptible to a second nucleophilic displacement upon treatment with a variety of electron-rich species, including acetylides, allyl silanes, electron-rich aromatics, silyl enol ethers, and silyl ketene acetals. Additionally, employing cyclopropane carboxaldehydes led to ring-opened products resulting from iodine incorporation. Taken together, these results form the basis for a new mode of three-component coupling reactions, which allows for rapid access to value added products in a single synthetic operation.

Promotion effect of H2 on ethanol oxidation and NOx reduction with ethanol over Ag/Al2O3 catalyst.

Science.gov (United States)

Yu, Yunbo; Li, Yi; Zhang, Xiuli; Deng, Hua; He, Hong; Li, Yuyang

2015-01-06

The catalytic partial oxidation of ethanol and selective catalytic reduction of NOx with ethanol (ethanol-SCR) over Ag/Al2O3 were studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). The intermediates were identified by PIMS and their photoionization efficiency (PIE) spectra. The results indicate that H2 promotes the partial oxidation of ethanol to acetaldehyde over Ag/Al2O3, while the simultaneously occurring processes of dehydration and dehydrogenation were inhibited. H2 addition favors the formation of ammonia during ethanol-SCR over Ag/Al2O3, the occurrence of which creates an effective pathway for NOx reduction by direct reaction with NH3. Simultaneously, the enhancement of the formation of ammonia benefits its reaction with surface enolic species, resulting in producing -NCO species again, leading to enhancement of ethanol-SCR over Ag/Al2O3 by H2. Using VUV-PIMS, the reactive vinyloxy radical was observed in the gas phase during the NOx reduction by ethanol for the first time, particularly in the presence of H2. Identification of such a reaction occurring in the gas phase may be crucial for understanding the reaction pathway of HC-SCR over Ag/Al2O3.

An ab initio/Rice-Ramsperger-Kassel-Marcus prediction of rate constant and product branching ratios for unimolecular decomposition of propen-2-ol and related H+CH2COHCH2 reaction

Science.gov (United States)

Zhou, Chong-Wen; Li, Ze-Rong; Liu, Cun-Xi; Li, Xiang-Yuan

2008-12-01

Enols have been found to be important intermediates in the combustion flames of hydrocarbon [C. A. Taatjes et al., Science 308, 1887 (2005)]. The removal mechanism of enols in combustion flame has not been established yet. In this work, the potential energy surface for the unimolecular decomposition of syn-propen-2-ol and H+CH2COHCH2 recombination reactions have been first investigated by CCSD(T) method. The barrier heights, reaction energies, and geometrical parameters of the reactants, products, intermediates, and transition states have been investigated theoretically. The results show that the formation of CH3CO+CH3 via the CH3COCH3 intermediate is dominant for the unimolecular decomposition of syn-propen-2-ol and its branching ratio is over 99% in the whole temperature range from 700 to 3000 K, and its rate constant can be expressed as an analytical form in the range of T =700-3000 K at atmospheric pressure. This can be attributed to the lower energy barrier of this channel compared to the other channels. The association reaction of H with CH2COHCH2 is shown to be a little more complicated than the unimolecular decomposition of syn-propen-2-ol. The channel leading to CH3CO+CH3 takes a key role in the whole temperature range at atmospheric pressure. However at the higher pressure of 100 atm, the recombination by direct formation of syn-propen-2-ol through H addition is important at T 1400 K, the recombination channel leading to CH3CO+CH3 turns out to be significant.

ANÁLISIS COMPARATIVO DE LA SITUACIÓN LABORAL DE LAS MUJERES RURALES: Vitivinicultura, Industria Vitivinícola y Turismo Enológico. El Caso del Valle de Colchagua, Chile

Directory of Open Access Journals (Sweden)

Ana María Dávila

2011-11-01

Full Text Available Resumen: La inserción de la mujer rural en espacios laborales fuera de su hogar, forma parte de un escenario de cambios, que se conoce como “nueva ruralidad”. Asimismo la llegada del turismo rural a diferentes zonas y la inclusión de las mujeres rurales en esta nueva actividad productiva, son aspectos que se hacen relevantes en zonas vitivinícolas como el valle de Colchagua, Chile. Esta investigación tiene como objetivo determinar los cambios socioeconómicos en la situación de las mujeres rurales producto de su participación en empresas y actividades de turismo enológico y establecer si estos cambios observados modifican la situación de las mujeres que trabajan en la agricultura y en la agroindustria.  A través de entrevistas realizadas a tres grupos de mujeres, pertenecientes al ámbito de la agricultura, la agroindustria y el turismo de las viñas, se realiza un análisis comparativo de los cambios generados, tanto en el contexto familiar, como en las condiciones de trabajo y en aspectos de formación y capacitación de la mujer rural. Palabras claves: Turismo Enológico. Mujeres Rurales. Empleo Rural. Vale Colchagua. Chile

Knock-out reactions

International Nuclear Information System (INIS)

de Forest, T. Jr.

1977-01-01

It is pointed out that the primary motivation for performing high energy single nucleon knock-out reactions is based on the concept of quasi-elastic scattering. The validity of and corrections to the partial wave impulse approximation and kinematical invariance of knock-out reactions and tests of the reaction mechanism are treated. The effect of distortions on the momentum distribution in the effective momentum approximation for given parameters are plotted. 12 references

Reaction of phosphoenolpyruvate carboxylase with (Z)-3-bromophosphoenolpyruvate and (Z)-3-fluorophosphoenolpyruvate

International Nuclear Information System (INIS)

Diaz, E.; O'Laughlin, J.T.; O'Leary, M.H.

1988-01-01

(Z)-3-Bromophosphoenolpyruvate inactivates phosphoenolpyruvate carboxylase from maize in the presence of HCO 3 - and either Mg 2+ or Mn 2+ . The inactivation rate follows saturation kinetics. Inactivation is slower in the presence of phospholactate or epoxymaleate, both of which are inhibitors of the enzyme, or dithiothreitol. Inactivation is completely prevented by the presence of lactate dehydrogenase and NADH, and 3-bromolactate is formed during this treatment. If the reaction is conducted by using HC 18 O 3 - , the inorganic phosphate produced contains 18 O. This and other evidence indicate that phosphoenolpyruvate carboxylase catalyzes conversion of bromophosphoenolpyruvate into bromopyruvate by way of the usual carboxyphosphate-enolate intermediate, and bromopyruvate is the species responsible for enzyme inactivation. (Z)-3-fluorophosphoenolpyruvate is transformed by the enzyme into a 6:1 mixture of 3-fluoropyruvate and 3-fluorooxalacetate, presumably by the same mechanism. The enzyme is not inactivated during this treatment

Effect of Bronsted Acids and Bases, and Lewis Acid (Sn(2+)) on the Regiochemistry of the Reaction of Amines with Trifluoromethyl-β-diketones: Reaction of 3-Aminopyrrole to Selectively Produce Regioisomeric 1H-Pyrrolo[3,2-b]pyridines.

Science.gov (United States)

De Rosa, Michael; Arnold, David; Hartline, Douglas; Truong, Linda; Verner, Roman; Wang, Tianwei; Westin, Christian

2015-12-18

Reaction of 3-aminopyrrole (as its salt) with trifluoromethyl-β-diketones gave γ-1H-pyrrolo[3,2-b]pyridines via reaction at the less reactive carbonyl group. The trifluoromethyl group increased the electrophilicity of the adjacent carbonyl group and decreased the basicity of the hydroxyl group of the CF3 amino alcohol formed. This amino alcohol was formed faster, but its subsequent dehydration to the β-enaminone was slow resulting in the preferential formation of the γ-regioisomer. Reaction of 4,4,4-trifluoro-1-phenyl-1,3-butadione with 3-aminopyrrole was carried out using a series of 6 amine buffers. Yields of the α-1H-pyrrolo[3,2-b]pyridine increased as the pKa of the amine buffer decreased. Surprisingly the yield went down at higher pKas. There was a change in mechanism as the reaction mixture became more basic. With strong amines trifluoromethyl-β-diketones were present mainly or completely as the enolate. Under reductive conditions (3-nitropyrrole/Sn/AcOH/trifluoromethyl-β-diketone) the α-1H-pyrrolo[3,2-b]pyridine was the major product as a result of Lewis acid catalysis by Sn(2+). Similar α-regiochemistry was observed when the reaction of the 3-aminopyrrole salt with trifluoromethyl-β-diketones was carried out in the presence of base and tin(II) acetate.

Stereochemistry of 1,2-elimination and proton-transfer reactions: toward a unified understanding.

Science.gov (United States)

Mohrig, Jerry R

2013-07-16

Many mechanistic and stereochemical studies have focused on the breaking of the C-H bond through base-catalyzed elimination reactions. When we began our research, however, chemists knew almost nothing about the stereospecificity of addition-elimination reactions involving conjugated acyclic carbonyl compounds, even though the carbonyl group is a pivotal functional group in organic chemistry. Over the last 25 years, we have studied the addition-elimination reactions of β-substituted acyclic esters, thioesters, and ketones in order to reach a comprehensive understanding of how electronic effects influence their stereochemistry. This Account brings together our understanding of the stereochemistry of 1,2-elimination and proton-transfer reactions, describing how each study has built upon previous work and contributed to our understanding of this field. When we began, chemists thought that anti stereospecificity in base-catalyzed 1,2-elimination reactions occurred via concerted E2 mechanisms, which provide a smooth path for anti elimination. Unexpectedly, we discovered that some E1cBirrev reactions produce the same anti stereospecificity as E2 reactions even though they proceed through diffusionally equilibrated, "free" enolate-anion intermediates. This result calls into question the conventional wisdom that anti stereochemistry must result from a concerted mechanism. While carrying out our research, we developed insights ranging from the role of historical contingency in the evolution of hydratase-dehydratase enzymes to the influence of buffers on the stereochemistry of H/D exchange in D2O. Negative hyperconjugation is the most important concept for understanding our results. This idea provides a unifying view for the largely anti stereochemistry in E1cBirrev elimination reactions and a basis for understanding the stereoelectronic influence of electron-withdrawing β-substituents on proton-transfer reactions.

Inhibition of E. coli P-enolpyruvate carboxylase by P-enol-3-bromopyruvate

International Nuclear Information System (INIS)

Asem, K.; Smith, T.E.

1986-01-01

The generality of the mechanism based inhibition of P-enolpyruvate carboxylases (PEPCase) by P-enol-3-bromopyruvate (BrPEP) was tested by measuring its effects on the allosterically regulated enzyme from E. coli. In the presence of 1mM Mn 2+ , BrPEP appears to be a competitive inhibitor (K/sub i/ = 0.0087mM) of PEPCase. Incubation of 0.005mM PEPCase with 0.5mM (or 1.0mM)BrPEP along with H 14 CO 3 - and Mn 2+ , yielded, upon reduction with NaBH 4 , a protein containing radioactivity in an amount approximately proportional to that expected from the loss of catalytic activity. At both a 25- and a 50-fold excess (0.5mM and 1.0mM, respectively) of BrPEP to PEPCase subunits, first order loss of activity occurred with k values of 5.24 x 10 -3 min -1 and 1.03 x 10 -2 min -1 , respectively. At the lower concentration of BrPEP the inactivation process appeared to be reversible after 40 min with no further inhibition occurring even up to two hours of incubation. At the higher concentration of BrPEP, the rate of inhibition slowed dramatically after 50 min and appeared insignificant over the next hour. These data suggest that BrPEP irreversibly inactivates the E. coli PEP carboxylase, but that there may be considerable dissociation of the product, Br-oxaloacetate, before irreversible binding occurs, and that the reduced rate of inactivation may be due to depletion of BrPEP

Oxidative Umpolung α‐Alkylation of Ketones

DEFF Research Database (Denmark)

Shneider, O. Svetlana; Pisarevsky, Evgeni; Fristrup, Peter

2015-01-01

We disclose a hypervalent iodine mediated α-alkylative umpolung reaction of carbonyl compounds with dialkylzinc as the alkyl source. The reaction is applicable to all common classes of ketones including 1,3-dicarbonyl compounds and regular ketones via their lithium enolates. The α...

Reactions of laser ablated uranium with nitrogen studied using matrix isolation spectroscopy

International Nuclear Information System (INIS)

Sankaran, K.; Sundararajan, K.; Viswanathan, K.S.

1999-01-01

Unusual reactions were found to occur when uranium was laser ablated in the presence of nitrogen. The reaction products were trapped in a rigid inert gas matrix and studied using infrared spectroscopy. The species formed were strongly dependent on the partial pressure of nitrogen in the matrix gas used during the ablation process; at low nitrogen partial pressures uranium dinitride (NUN) was the major reaction product, while at high partial pressures of nitrogen the mononitride, UN, was the predominant product. (author)

Partial oxidation process

International Nuclear Information System (INIS)

Najjar, M.S.

1987-01-01

A process is described for the production of gaseous mixtures comprising H/sub 2/+CO by the partial oxidation of a fuel feedstock comprising a heavy liquid hydrocarbonaceous fuel having a nickel, iron, and vanadium-containing ash or petroleum coke having a nickel, iron, and vanadium-containing ash, or mixtures thereof. The feedstock includes a minimum of 0.5 wt. % of sulfur and the ash includes a minimum of 5.0 wt. % vanadium, a minimum of 0.5 ppm nickel, and a minimum of 0.5 ppm iron. The process comprises: (1) mixing together a copper-containing additive with the fuel feedstock; wherein the weight ratio of copper-containing additive to ash in the fuel feedstock is in the range of about 1.0-10.0, and there is at least 10 parts by weight of copper for each part by weight of vanadium; (2) reacting the mixture from (1) at a temperature in the range of 2200 0 F to 2900 0 F and a pressure in the range of about 5 to 250 atmospheres in a free-flow refactory lined partial oxidation reaction zone with a free-oxygen containing gas in the presence of a temperature moderator and in a reducing atmosphere to produce a hot raw effluent gas stream comprising H/sub 2/+CO and entrained molten slag; and where in the reaction zone and the copper-containing additive combines with at least a portion of the nickel and iron constituents and sulfur found in the feedstock to produce a liquid phase washing agent that collects and transports at least a portion of the vanadium-containing oxide laths and spinels and other ash components and refractory out of the reaction zone; and (3) separating nongaseous materials from the hot raw effluent gas stream

Determination of thermodynamic parameters of tautomerization in gas phase by mass spectrometry and DFT calculations: Keto-enol versus nitrile-ketenimine equilibria.

Science.gov (United States)

Giussi, Juan M; Gastaca, Belen; Albesa, Alberto; Cortizo, M Susana; Allegretti, Patricia E

2011-02-01

The study of tautomerics equilibria is really important because the reactivity of each compound with tautomeric capacity can be determined from the proportion of each tautomer. In the present work the tautomeric equilibria in some γ,δ-unsaturated β-hydroxynitriles and γ,δ-unsaturated β-ketonitriles were studied. The first family of compounds presents two possible theoretical tautomers, nitrile and ketenimine, while the second one presents four possible theoretical tautomers, keto-nitrile, enol (E and Z)-nitrile and keto-ketenimine. The equilibrium in gas phase was studied by gas chromatography-mass spectrometry (GC-MS). Tautomerization enthalpies were calculated by this methodology, and results were compared with those obtained by density functional theory (DFT) calculations, observing a good agreement between them. Nitrile tautomers were favored within the first family of compounds, while keto-nitrile tautomers were favored in the second family. Copyright © 2010 Elsevier B.V. All rights reserved.

Calculation of the energy of explosives with a partial reaction model. Comparison with cylinder test data

Energy Technology Data Exchange (ETDEWEB)

Sanchidrian, Jose A.; Lopez, Lina M. [Universidad Politecnica de Madrid - E.T.S.I. Minas, Rios Rosas 21, E-28003 Madrid (Spain)

2006-02-15

The energy delivered by explosives is described by means of the useful expansion work along the isentrope of the detonation products. A thermodynamic code (W-DETCOM) is used, in which a partial reaction model has been implemented. In this model, the reacted fraction of the explosive in the detonation state is used as a fitting factor so that the calculated detonation velocity meets the experimental value. Calculations based on such a model have been carried out for a number of commercial explosives of ANFO and emulsion types. The BKW (Becker-Kistiakowsky-Wilson) equation of state is used for the detonation gases with the Sandia parameter set (BKWS). The energy delivered in the expansion (useful work) is calculated, and the values obtained are compared with the Gurney energies from cylinder test data at various expansion ratios. The expansion work values obtained are much more realistic than those from an ideal detonation calculation and, in most cases, the values predicted by the calculation are in good agreement with the experimental ones. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

A partial wave analysis of world data for the reaction π-p → K0Λ from threshold to 2350 MeV/c

International Nuclear Information System (INIS)

Baker, R.D.; Blissett, J.A.; Bloodworth, I.J.

1977-06-01

All available world data for the reaction π - p → K 0 Λ up to 2350 MeV/c incident momentum have been analysed using both the Barrelet (Nuovo Cimento; 8A:331 (1972)) zero technique and a conventional energy-dependent fit. The results of the two methods are in good agreement. Resonances are required in the S 11 , P 11 , P 13 and D 13 partial waves. There is also an enhancement in the D 15 wave around 1900 MeV. No other resonances are required. (author)

Effects of oxygen partial pressure on Li-air battery performance

Science.gov (United States)

Kwon, Hyuk Jae; Lee, Heung Chan; Ko, Jeongsik; Jung, In Sun; Lee, Hyun Chul; Lee, Hyunpyo; Kim, Mokwon; Lee, Dong Joon; Kim, Hyunjin; Kim, Tae Young; Im, Dongmin

2017-10-01

For application in electric vehicles (EVs), the Li-air battery system needs an air intake system to supply dry oxygen at controlled concentration and feeding rate as the cathode active material. To facilitate the design of such air intake systems, we have investigated the effects of oxygen partial pressure (≤1 atm) on the performance of the Li-air cell, which has not been systematically examined. The amounts of consumed O2 and evolved CO2 from the Li-air cell are measured with a custom in situ differential electrochemical gas chromatography-mass spectrometry (DEGC-MS). The amounts of consumed O2 suggest that the oxygen partial pressure does not affect the reaction mechanism during discharge, and the two-electron reaction occurs under all test conditions. On the other hand, the charging behavior varies by the oxygen partial pressure. The highest O2 evolution ratio is attained under 70% O2, along with the lowest CO2 evolution. The cell cycle life also peaks at 70% O2 condition. Overall, an oxygen partial pressure of about 0.5-0.7 atm maximizes the Li-air cell capacity and stability at 1 atm condition. The findings here indicate that the appropriate oxygen partial pressure can be a key factor when developing practical Li-air battery systems.

Experimental and simulation analysis of hydrogen production by partial oxidation of methanol

Energy Technology Data Exchange (ETDEWEB)

Sikander, U. [National Univ. of Science and Technology, Islamabad (Pakistan)

2014-10-15

Partial oxidation of methanol is the only self-sustaining process for onboard production of hydrogen. For this a fixed bed catalytic reactor is designed, based on heterogeneous catalytic reaction. To develop an optimized process, simulation is carried out using ASPEN HYSYS v 7.1. Reaction kinetics is developed on the basis of Langmuir Hinshel wood model. 45:55:5 of CuO: ZnO: Al/sub 2/O/sub 3/ is used as a catalyst. Simulation results are studied in detail to understand the phenomenon of partial oxidation of methanol inside the reactor. An experimental rig is developed for hydrogen production through partial oxidation of methanol. Results obtained from process simulation and experimental work; are compared with each other. (author)

Partial gravity - Human impacts on facility design

Science.gov (United States)

Capps, Stephen; Moore, Nathan

1990-01-01

Partial gravity affects the body differently than earth gravity and microgravity environments. The main difference from earth gravity is human locomotion; while the main dfference from microgravity is the specific updown orientation and reach envelopes which increase volume requirements. Much data are available on earth gravity and microgravity design; however, very little information is available on human reactions to reduced gravity levels in IVA situations (without pressure suits). Therefore, if humans commit to permanent lunar habitation, much research should be conducted in the area of partial gravity effects on habitat design.

Partial oxidation of 2-propanol on perovskites

Energy Technology Data Exchange (ETDEWEB)

Sumathi, R.; Viswanathan, B.; Varadarajan, T.K. [Indian Inst. of Tech., Madras (India). Dept. of Chemistry

1998-12-31

Partial oxidation of 2-propanol was carried out on AB{sub 1-x}B`{sub x}O{sub 3} (A=Ba, B=Pb, Ce, Ti; B`=Bi, Sb and Cu) type perovskite oxides. Acetone was the major product observed on all the catalysts. All the catalysts underwent partial reduction during the reaction depending on the composition of the reactant, nature of the B site cation and the extent of substitution at B site. The catalytic activity has been correlated with the reducibility of the perovskite oxides determined from Temperature Programmed Reduction (TPR) studies. (orig.)

Development of a simultaneous partial nitrification and anaerobic ammonia oxidation process in a single reactor.

Science.gov (United States)

Cho, Sunja; Fujii, Naoki; Lee, Taeho; Okabe, Satoshi

2011-01-01

Up-flow oxygen-controlled biofilm reactors equipped with a non-woven fabric support were used as a single reactor system for autotrophic nitrogen removal based on a combined partial nitrification and anaerobic ammonium oxidation (anammox) reaction. The up-flow biofilm reactors were initiated as either a partial nitrifying reactor or an anammox reactor, respectively, and simultaneous partial nitrification and anammox was established by careful control of the aeration rate. The combined partial nitrification and anammox reaction was successfully developed in both biofilm reactors without additional biomass inoculation. The reactor initiated as the anammox reactor gave a slightly higher and more stable mean nitrogen removal rate of 0.35 (±0.19) kg-N m(-3) d(-1) than the reactor initiated as the partial nitrifying reactor (0.23 (±0.16) kg-N m(-3) d(-1)). FISH analysis revealed that the biofilm in the reactor started as the anammox reactor were composed of anammox bacteria located in inner anoxic layers that were surrounded by surface aerobic AOB layers, whereas AOB and anammox bacteria were mixed without a distinguishable niche in the biofilm in the reactor started as the partial nitrifying reactor. However, it was difficult to efficiently maintain the stable partial nitrification owing to inefficient aeration in the reactor, which is a key to development of the combined partial nitrification and anammox reaction in a single biofilm reactor. Copyright © 2010 Elsevier Ltd. All rights reserved.

Synthesis of acetylenic derivatives of hydroxynaphthoquinone

International Nuclear Information System (INIS)

Sanchez Kopper, Andres

2010-01-01

The acetylene derivatives synthesis 2-hydroxy-1 ,4-naphthoquinones was studied using different reaction conditions: coupling with copper and silver acetylides, Sonogashira reaction with and without CU (I) as cocatalyst. The reaction conditions are optimized for coupling of iodine lawson and ylide phenyl lawsone of iodine with various terminal acetylenes: phenyl acetylene, propargyl alcohol, 1-heptin and 2-methyl-3-butyne-2-ol. Also, reactants such as bromides of hidroxinaphthoquinones were used with protecting groups such as acetate, methoxy, phenyloxy, benzyloxy and tricloroetoxy. The synthesis of 2-hydroxy-3-(3-hydroxy-3-ynyl-1-methylbutane)-1,4-naphthoquinone, 2-methoxy-3-(2-phenylethynyl) -1,4-naphthoquinone and 2-(2-phenylethynyl)-3-(2,2,2-tricloroetoxy)-1,4-naphthoquinone was performed with rates of return of 22%, 57% and 67% respectively. The reaction of the yodolawsona was obtained with 3-chloro-3-methyl-1-butyne in the presence of CuI, CsI and Cs 2 Co 3 obtaining the enol ether: 3,3-dimethyl-2-methyl-2 ,3-dihydronaphto [2 ,3-b]furan-4,9-dione (dehydro-α-dunion), with a rate of return of 58%. This enol ether was used as a reactant for the formation, through a regioselective hydrogenation with PtO 2 /t-butanol of α-dunion with a yield of 50%. Furthermore, by acid hydrolysis with H 2 SO 4 has been possible to obtain a percentage yield of 75% streptocarpone. Both, α-dunion and streptocarpone, natural products extracted from Streptocarpus dunni shrub, with antiparasitic activity, and which so far had not presented an efficient synthesis. A mechanism is proposed for the reaction of formation of the enol ether where it is presumed the presence of a zwitterion-vinyl carbene as key intermediate of the reaction. All products were characterized by spectroscopy 1 H and 13 C-NMR, UV-Vis and IR. (author) [es

Design and control of the oxygen partial pressure of UO2 in TGA using the humidification system

International Nuclear Information System (INIS)

Lee, S.; Knight, T.W.; Roberts, E.

2015-01-01

Highlights: • We focus on measurement of oxygen partial pressure and change of O/M ratio under specific conditions produced by the humidification system. • This shows that the humidification system is stable, accurate, and reliable enough to be used for experiments of the oxygen partial pressure measurement for the oxide fuels. • The humidification system has benefits of easy control and flexibility for producing various oxygen partial pressures with fixed hydrogen gas flow rate. - Abstract: The oxygen to uranium (O/U) ratio of UO 2±x is determined by the oxygen content of the sample and is affected by oxygen partial pressure (pO 2 ) of the surrounding gas. Oxygen partial pressure is controllable by several methods. A common method to produce different oxygen partial pressures is the use of equilibria of different reaction gases. There are two common methods: H 2 O/H 2 reaction and CO 2 /CO reaction. In this work, H 2 O/H 2 reaction using a humidifier was employed and investigated to ensure that this humidification system for oxygen partial pressure is stable and accurate for use in Thermogravimetric Analyzer (TGA) experiments with UO 2 . This approach has the further advantage of flexibility to make a wide range of oxygen partial pressure with fixed hydrogen gas flow rate only by varying temperature of water in the humidifier. The whole system for experiments was constructed and includes the humidification system, TGA, oxygen analyzer, and gas flow controller. Uranium dioxide (UO 2 ) samples were used for experiments and oxygen partial pressure was measured at the equilibrium state of stoichiometric UO 2.0 . Oxygen partial pressures produced by humidification (wet gas) system were compared to the approach using mixed dry gases (without humidification system) to demonstrate that the humidification system provides for more stable and accurate oxygen partial pressure control. This work provides the design, method, and analysis of a humidification system for

Synthesis of N,N-Bis(nonaflyl) Squaric Acid Diamide and its Application to Organic Reactions

International Nuclear Information System (INIS)

Cheon, Cheol Hong; Yamamoto, Hisashi

2010-01-01

We have developed a new strong Brφnsted acid bearing two nonaflyl groups based on the squaric acid scaffold. The Brφnsted acid 2 showed the almost same reactivity as bistriflyl squaramide 1 in Mukaiyama aldol and Michael reactions of benzaldehyde with silyl enol ether. Moreover, the utility of Brφnsted acid 2 could be expanded to carbonyl ene reaction of rac-citronellal. Further application of this new Brφnsted acid to organic reactions and to flow system reactors is currently underway in our laboratory. Brφnsted acid catalysis is one of the growing fields in modern organic synthesis.1 Although several Brφnsted acids, such as urea/thiourea, TADDOL, and phosphoric acid, have been applied to a variety of organic reactions, other Brφnsted acid scaffolds have been much less explored. Recently, Rawal et al have developed a Brφnsted acid catalyst based on squaric acid moiety and successfully applied it as a catalyst for conjugate addition of 1,3-dicarbonyl compounds to nitroolefins. More recently, we have developed a strong Brφnsted acid derived from squaric acid by introducing a strong electron withdrawing trifluoromethanesulfonyl (Tf) group and applied it to Mukaiyama aldol and Michael reaction of a variety of aldehydes, ketones, and α,β-unsaturated ketones. As a continuing effort to develop strong Brφnsted acids based on the squaric acid scaffold, it was expected that replacement of Tf group with a longer perfluoro-alkanesulfonyl group would be able to tune the physical properties, such as solubilities in organic solvents and fluoro-philicity, without loss of reactivity. Herein, we report the development of a new Brφnsted acid based on the squaric acid scaffold carrying two nonafluorobutanesulfonyl (Nf) groups and the preliminary results of its reactivity to various organic reactions

Analysis of partial and total inelasticities obtained from inclusive reactions

International Nuclear Information System (INIS)

Bellandi, J.; Covolan, R.; Costa, C.G.; Montanha, J.; Mundim, L.M.

1994-01-01

An independent analysis of model for energetic dependence on inelasticity is presented, from experimental data of pp → c X (c = π +- , Κ +- , p +- ) type inclusive reactions. 6 refs., 2 figs., 1 tab

The Catalytic Enantioselective Total Synthesis of (+)‐Liphagal

DEFF Research Database (Denmark)

Day, Joshua J.; McFadden, Ryan M.; Virgil, Scott C.

2011-01-01

Ring a ding: The first catalytic enantioselective total synthesis of the meroterpenoid natural product (+)-liphagal is disclosed. The approach showcases a variety of technology including enantioselective enolate alkylation, a photochemical alkyne-alkene [2+2] reaction, microwaveassisted metal...

Structural characterization of tartrate dehydrogenase: a versatile enzyme catalyzing multiple reactions

International Nuclear Information System (INIS)

Malik, Radhika; Viola, Ronald E.

2010-01-01

The first structure of an NAD-dependent tartrate dehydrogenase (TDH) has been solved to 2 (angstrom) resolution by single anomalous diffraction (SAD) phasing as a complex with the intermediate analog oxalate, Mg 2+ and NADH. This TDH structure from Pseudomonas putida has a similar overall fold and domain organization to other structurally characterized members of the hydroxy-acid dehydrogenase family. However, there are considerable differences between TDH and these functionally related enzymes in the regions connecting the core secondary structure and in the relative positioning of important loops and helices. The active site in these complexes is highly ordered, allowing the identification of the substrate-binding and cofactor-binding groups and the ligands to the metal ions. Residues from the adjacent subunit are involved in both the substrate and divalent metal ion binding sites, establishing a dimer as the functional unit and providing structural support for an alternating-site reaction mechanism. The divalent metal ion plays a prominent role in substrate binding and orientation, together with several active-site arginines. Functional groups from both subunits form the cofactor-binding site and the ammonium ion aids in the orientation of the nicotinamide ring of the cofactor. A lysyl amino group (Lys192) is the base responsible for the water-mediated proton abstraction from the C2 hydroxyl group of the substrate that begins the catalytic reaction, followed by hydride transfer to NAD. A tyrosyl hydroxyl group (Tyr141) functions as a general acid to protonate the enolate intermediate. Each substrate undergoes the initial hydride transfer, but differences in substrate orientation are proposed to account for the different reactions catalyzed by TDH.

Oxygen binding to partially nitrosylated hemoglobin.

Science.gov (United States)

Fago, Angela; Crumbliss, Alvin L; Hendrich, Michael P; Pearce, Linda L; Peterson, Jim; Henkens, Robert; Bonaventura, Celia

2013-09-01

Reactions of nitric oxide (NO) with hemoglobin (Hb) are important elements in protection against nitrosative damage. NO in the vasculature is depleted by the oxidative reaction with oxy Hb or by binding to deoxy Hb to generate partially nitrosylated Hb (Hb-NO). Many aspects of the formation and persistence of Hb-NO are yet to be clarified. In this study, we used a combination of EPR and visible absorption spectroscopy to investigate the interactions of partially nitrosylated Hb with O2. Partially nitrosylated Hb samples had predominantly hexacoordinate NO-heme geometry and resisted oxidation when exposed to O2 in the absence of anionic allosteric effectors. Faster oxidation occurred in the presence of 2,3-diphosphoglycerate (DPG) or inositol hexaphosphate (IHP), where the NO-heme derivatives had higher levels of pentacoordinate heme geometry. The anion-dependence of the NO-heme geometry also affected O2 binding equilibria. O2-binding curves of partially nitrosylated Hb in the absence of anions were left-shifted at low saturations, indicating destabilization of the low O2 affinity T-state of the Hb by increasing percentages of NO-heme, much as occurs with increasing levels of CO-heme. Samples containing IHP showed small decreases in O2 affinity, indicating shifts toward the low-affinity T-state and formation of inert α-NO/β-met tetramers. Most remarkably, O2-equilibria in the presence of the physiological effector DPG were essentially unchanged by up to 30% NO-heme in the samples. As will be discussed, under physiological conditions the interactions of Hb with NO provide protection against nitrosative damage without impairing O2 transport by Hb's unoccupied heme sites. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis of 2,6-trans- and 3,3,6-trisubstituted tetrahydropyran-4-ones from Maitland-Japp derived 2H-dihydropyran-4-ones: a total synthesis of diospongin B.

Science.gov (United States)

Clarke, Paul A; Nasir, Nadiah Mad; Sellars, Philip B; Peter, Alejandra M; Lawson, Connor A; Burroughs, James L

2016-07-12

6-Substituted-2H-dihydropyran-4-one products of the Maitland-Japp reaction have been converted into tetrahydropyrans containing uncommon substitution patterns. Treatment of 6-substituted-2H-dihydropyran-4-ones with carbon nucleophiles led to the formation of tetrahydropyran rings with the 2,6-trans-stereochemical arrangement. Reaction of the same 6-substituted-2H-dihydropyran-4-ones with l-Selectride led to the formation of 3,6-disubstituted tetrahydropyran rings, while trapping of the intermediate enolate with carbon electrophiles in turn led to the formation 3,3,6-trisubstituted tetrahydropyran rings. The relative stereochemical configuration of the new substituents was controlled by the stereoelectronic preference for pseudo-axial addition of the nucleophile and trapping of the enolate from the opposite face. Application of these methods led to a synthesis of the potent anti-osteoporotic diarylheptanoid natural product diospongin B.

Reaction rate of 24Mg(p,γ)25Al

International Nuclear Information System (INIS)

Powell, D.C.; Iliadis, C.; Champagne, A.E.; Grossmann, C.A.; Hale, S.E.; Hansper, V.Y.; McLean, L.K.

1999-01-01

The proton-capture reaction on 24 Mg has been investigated in the bombarding energy range of E p =0.2-1.7 MeV. Resonance properties (strengths, branching ratios and lifetimes) of low-energy resonances have been measured. From the experimental results, accurate proton partial widths, γ-ray partial widths and total widths (Γ p , Γ γ , and Γ) have been deduced. The present experimental information establishes the 24 Mg+p reaction rates over the temperature range T=0.02-2.0 GK with statistical uncertainties of 5% to 21%. Our recommended reaction rates deviate from previous estimates by 18% to 45%. Based on our results, we can rule out the recent suggestion that the total width of the E R =223 keV resonance has a significant influence on the reaction rates. We also discuss several effects that might give rise to systematic uncertainties in the reaction rates. The astrophysical implications for hydrogen burning of 24 Mg at low stellar temperatures are presented

Transformation-Dissolution Reactions Partially Explain Adverse Effects of Metallic Silver Nanoparticles to Soil Nitrification in Different Soils.

Science.gov (United States)

Bollyn, Jessica; Willaert, Bernd; Kerré, Bart; Moens, Claudia; Arijs, Katrien; Mertens, Jelle; Leverett, Dean; Oorts, Koen; Smolders, Erik

2018-04-25

Risk assessment of metallic nanoparticles (NP) is critically affected by the concern that toxicity goes beyond that of the metallic ion. This study addressed this concern for soils with silver (Ag)-NP using the Ag-sensitive nitrification assay. Three agricultural soils (A,B,C) were spiked with equivalent Ag doses of either Ag-NP (d = 13 nm) or AgNO 3 . Soil solution was isolated and monitored over 97 days with due attention to accurate Ag fractionation at low (∼10 µg L -1 ) Ag concentrations. Truly dissolved (soils decreased with reaction half-lives of 4 to 22 days depending on the soil, denoting important Ag-ageing reactions. In contrast, truly dissolved Ag in Ag-NP-amended soils first increased by dissolution and subsequently decreased by ageing; the concentration never exceeding that in the AgNO 3 -amended soils. The half-lives of Ag-NP transformation-dissolution were about 4 days (soils A&B) and 36 days (soil C). The Ag toxic thresholds (EC10, mg Ag kg -1 soil) of nitrification, either evaluated at 21 or 35 days after spiking, were similar between the two Ag forms (soils A&B) but were factors 3 to 8 lower for AgNO 3 than for Ag-NP (soil C), largely corroborating with dissolution differences. This fate and bio-assay showed that Ag-NPs are not more toxic than AgNO 3 at equivalent total soil Ag concentrations and that differences in Ag-dissolution at least partially explain toxicity differences between the forms and among soils. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Enhanced performance of solid oxide electrolysis cells by integration with a partial oxidation reactor: Energy and exergy analyses

International Nuclear Information System (INIS)

Visitdumrongkul, Nuttawut; Tippawan, Phanicha; Authayanun, Suthida; Assabumrungrat, Suttichai; Arpornwichanop, Amornchai

2016-01-01

Highlights: • Process design of solid oxide electrolyzer integrated with a partial oxidation reactor is studied. • Effect of key operating parameters of partial oxidation reactor on the electrolyzer performance is presented. • Exergy analysis of the electrolyzer process is performed. • Partial oxidation reactor can enhance the solid oxide electrolyzer performance. • Partial oxidation reactor in the process is the highest exergy destruction unit. - Abstract: Hydrogen production without carbon dioxide emission has received a large amount of attention recently. A solid oxide electrolysis cell (SOEC) can produce pure hydrogen and oxygen via a steam electrolysis reaction that does not emit greenhouse gases. Due to the high operating temperature of SOEC, an external heat source is required for operation, which also helps to improve SOEC performance and reduce operating electricity. The non-catalytic partial oxidation reaction (POX), which is a highly exothermic reaction, can be used as an external heat source and can be integrated with SOEC. Therefore, the aim of this work is to study the effect of operating parameters of non-catalytic POX (i.e., the oxygen to carbon ratio, operating temperature and pressure) on SOEC performance, including exergy analysis of the process. The study indicates that non-catalytic partial oxidation can enhance the hydrogen production rate and efficiency of the system. In terms of exergy analysis, the non-catalytic partial oxidation reactor is demonstrated to be the highest exergy destruction unit due to irreversible chemical reactions taking place, whereas SOEC is a low exergy destruction unit. This result indicates that the partial oxidation reactor should be improved and optimally designed to obtain a high energy and exergy system efficiency.

Scientific development and modern wine industry: the origins and consolidation of Enology Station of Mendoza (Argentina, 1904-1920 Desarrollo científico e industria vitivinícola moderna: orígenes y consolidación de la Estación Enológica de Mendoza (Argentina, 1904- 1920

Directory of Open Access Journals (Sweden)

Florencia Rodríguez Vázquez

2009-01-01

Full Text Available In this article we propose to undertake a reconstruction of the development of the 'Estación Enológica', next to 'Escuela Nacional de Vitivinicultura', between 1904 to 1920 in Mendoza province. This study is of vital importance as we consider this place was a pioneer center in the achievement of scientific and technical studies. These were the basis for the consolidation of quality wine industry , which had many shortcomings by then, and they triggered changes in Mendoza's agroindustry. Besides, Estación Enológica became a meeting place for people who graduated from that school to share experiences and concerns. Apart from carrying out the reconstruction of the development, we will also investigate possibilities of applying these studies to vineyardsEn el presente artículo nos proponemos realizar una reconstrucción de la trayectoria de la Estación Enológica de Mendoza, anexa a la Escuela Nacional de Vitivinicultura, desde 1904 a 1920. El mismo cobra vital importancia en tanto la consideramos un centro pionero en la realización de estudios científicos y técnicos que sirvieron de base a la consolidación de una vitivinicultura de calidad -y que por entonces contaba con múltiples deficiencias- y un impulsor de cambios técnicos en la agroindustria local. A su vez, su importancia radicaría en que fue un espacio aglutinador de las experiencias e inquietudes de los enólogos graduados de la mencionada Escuela. Por último, nos referiremos a las posibilidades de recepción y divulgación de los estudios entre los vitivinicultores

[Partial response of solar urticaria to omalizumab therapy].

Science.gov (United States)

Kowalzick, L; Thiel, W; C Bielfeld; Ziegler, H; Eickenscheidt, L

2017-06-01

The treatment of solar urticaria is regarded as difficult. In some cases good responses to the anti-IgE antibody omalizumab (Xolair®), approved for treatment of chronic spontaneous urticaria, have been reported. We report on a 50-year-old Caucasian woman who for the last 5 years has developed localized itching and stinging erythemas following exposure to sunlight accompanied sometimes by anaphylactic reactions. Oral antihistamines in three- to four-fold doses and a topical sun screen had been only partially effective in long-term use. Positive immediate-type reactions with whealing appeared in phototesting with low doses of UVB and UVA. Three weeks after s. c. injection of 300 mg omalizumab, the minimal urticarial dose (MUD) for UVB was increased at least 20-fold (from omalizumab administration to 14 points in weeks two and three. Overall, a partial response of solar urticaria to omalizumab therapy could be observed in the present case.

DEVICE FOR CONTROL OF OXYGEN PARTIAL PRESSURE

Science.gov (United States)

Bradner, H.; Gordon, H.S.

1957-12-24

A device is described that can sense changes in oxygen partial pressure and cause a corresponding mechanical displacement sufficient to actuate meters, valves and similar devices. A piston and cylinder arrangement contains a charge of crystalline metal chelate pellets which have the peculiar property of responding to variations in the oxygen content of the ambient atmosphere by undergoing a change in dimension. A lever system amplifies the relative displacement of the piston in the cylinder, and actuates the controlled valving device. This partial pressure oxygen sensing device is useful in controlled chemical reactions or in respiratory devices such as the oxygen demand meters for high altitude aircraft.

Glucose and Fructose to Platform Chemicals: Understanding the Thermodynamic Landscapes of Acid-Catalysed Reactions Using High-Level ab Initio Methods

Energy Technology Data Exchange (ETDEWEB)

Assary, Rajeev S.; Kim, Taijin; Low, John; Greeley, Jeffrey P.; Curtiss, Larry A.

2012-12-28

Molecular level understanding of acid-catalysed conversion of sugar molecules to platform chemicals such as hydroxy-methyl furfural (HMF), furfuryl alcohol (FAL), and levulinic acid (LA) is essential for efficient biomass conversion. In this paper, the high-level G4MP2 method along with the SMD solvation model is employed to understand detailed reaction energetics of the acid-catalysed decomposition of glucose and fructose to HMF. Based on protonation free energies of various hydroxyl groups of the sugar molecule, the relative reactivity of gluco-pyranose, fructo-pyranose and fructo-furanose are predicted. Calculations suggest that, in addition to the protonated intermediates, a solvent assisted dehydration of one of the fructo-furanosyl intermediates is a competing mechanism, indicating the possibility of multiple reaction pathways for fructose to HMF conversion in aqueous acidic medium. Two reaction pathways were explored to understand the thermodynamics of glucose to HMF; the first one is initiated by the protonation of a C2–OH group and the second one through an enolate intermediate involving acyclic intermediates. Additionally, a pathway is proposed for the formation of furfuryl alcohol from glucose initiated by the protonation of a C2–OH position, which includes a C–C bond cleavage, and the formation of formic acid. The detailed free energy landscapes predicted in this study can be used as benchmarks for further exploring the sugar decomposition reactions, prediction of possible intermediates, and finally designing improved catalysts for biomass conversion chemistry in the future.

Lewis acid-promoted hydrofluorination of alkynyl sulfides to generate α-fluorovinyl thioethers

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Davide Bello

2015-10-01

Full Text Available A new method for the preparation of α-fluorovinyl thioethers is reported which involves the hydrofluorination of alkynyl sulfides with 3HF·Et3N, a process that requires Lewis acid activation using BF3·Et2O and TiF4. The method gives access to a range of α-fluorovinyl thioethers, some in high stereoselectivity with the Z-isomer predominating over the E-isomer. The α-fluorovinyl thioether motif has prospects as a steric and electronic mimetic of thioester enols and enolates, important intermediates in enzymatic C–C bond forming reactions. The method opens access to appropriate analogues for investigations in this direction.

Reaction diffusion equations with boundary degeneracy

Directory of Open Access Journals (Sweden)

Huashui Zhan

2016-03-01

Full Text Available In this article, we consider the reaction diffusion equation $$ \\frac{\\partial u}{\\partial t} = \\Delta A(u,\\quad (x,t\\in \\Omega \\times (0,T, $$ with the homogeneous boundary condition. Inspired by the Fichera-Oleinik theory, if the equation is not only strongly degenerate in the interior of $\\Omega$, but also degenerate on the boundary, we show that the solution of the equation is free from any limitation of the boundary condition.

Partial Cross Sections of Neutron-Induced Reactions on nCu at En = 6, 8, 10, 12, 14, and 16 MeV for 0νββ Background Studies

Science.gov (United States)

Gooden, M. E.; Fallin, B. A.; Finch, S. W.; Kelley, J. H.; Howell, C. R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Stanislav, V.

2014-05-01

Partial cross-section measurements of (n,n'γ) reactions on natCu were carried out at TUNL using monoenergetic neutrons at six energies of En = 6, 8, 10, 12, 14, 16 MeV. These studies were performed to provide accurate cross-section data on materials abundant in experimental setups involving HPGe detectors used to search for rare events, like the neutrino-less double-beta decay of 76Ge. Spallation and (α,n) neutrons are expected to cause the largest source of external background in the energy region of interest. At TUNL pulsed neutron beams were produced via the 2H(d,n)3He reaction and the deexcitation γ rays from the reaction natCu(n,xγ) were detected with clover HPGe detectors. Cross-section results for the strongest transtions in 63Cu and 65Cu will be reported, and will compared to model calculations and to data recently obtained at LANL with a white neutron beam.

Analyzing the dependence of oxygen incorporation current density on overpotential and oxygen partial pressure in mixed conducting oxide electrodes.

Science.gov (United States)

Guan, Zixuan; Chen, Di; Chueh, William C

2017-08-30

The oxygen incorporation reaction, which involves the transformation of an oxygen gas molecule to two lattice oxygen ions in a mixed ionic and electronic conducting solid, is a ubiquitous and fundamental reaction in solid-state electrochemistry. To understand the reaction pathway and to identify the rate-determining step, near-equilibrium measurements have been employed to quantify the exchange coefficients as a function of oxygen partial pressure and temperature. However, because the exchange coefficient contains contributions from both forward and reverse reaction rate constants and depends on both oxygen partial pressure and oxygen fugacity in the solid, unique and definitive mechanistic assessment has been challenging. In this work, we derive a current density equation as a function of both oxygen partial pressure and overpotential, and consider both near and far from equilibrium limits. Rather than considering specific reaction pathways, we generalize the multi-step oxygen incorporation reaction into the rate-determining step, preceding and following quasi-equilibrium steps, and consider the number of oxygen ions and electrons involved in each. By evaluating the dependence of current density on oxygen partial pressure and overpotential separately, one obtains the reaction orders for oxygen gas molecules and for solid-state species in the electrode. We simulated the oxygen incorporation current density-overpotential curves for praseodymium-doped ceria for various candidate rate-determining steps. This work highlights a promising method for studying the exchange kinetics far away from equilibrium.

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

Directory of Open Access Journals (Sweden)

Nina Gonsior

2012-03-01

Full Text Available The synthesis of a heterocyclic mesomeric betaine by quaternization reaction of 1-butylimidazole and tetrabromo-1,4-benzoquinone is presented. The structure was verified by means of X-ray single-crystal analysis, NMR and IR spectroscopy. Inclusion complexes of the heterocyclic mesomeric betaine with randomly methylated (1.8 β-cyclodextrin were investigated by UV–vis spectroscopy. Furthermore, the reaction conditions were applied to poly(vinylimidazole and 1,4-bis(1H-imidazol-1-ylbutane to obtain functionalized polymer networks and condensate polymers, respectively.

Characterising Complex Enzyme Reaction Data.

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Handan Melike Dönertaş

Full Text Available The relationship between enzyme-catalysed reactions and the Enzyme Commission (EC number, the widely accepted classification scheme used to characterise enzyme activity, is complex and with the rapid increase in our knowledge of the reactions catalysed by enzymes needs revisiting. We present a manual and computational analysis to investigate this complexity and found that almost one-third of all known EC numbers are linked to more than one reaction in the secondary reaction databases (e.g., KEGG. Although this complexity is often resolved by defining generic, alternative and partial reactions, we have also found individual EC numbers with more than one reaction catalysing different types of bond changes. This analysis adds a new dimension to our understanding of enzyme function and might be useful for the accurate annotation of the function of enzymes and to study the changes in enzyme function during evolution.

Partial Reduction of Esters to Aldehydes Using a Novel Modified Red-Al Reducing Agent

Energy Technology Data Exchange (ETDEWEB)

Shin, Won Kyu; Kang, Daehoon; An, Duk Keun [Kangwon National Univ., Chunchon (Korea, Republic of)

2014-07-15

We have developed a convenient alternative method for the synthesis of aldehydes from both aromatic and aliphatic esters in very good to excellent yields in the absence of any additives using a modified Red-Al that was easily prepared by reacting commercially available Red-Al with cis-2,6-dimethyl morpholine. The advantages of the present methodology are as follows: simple preparation procedure of the reducing agent, improved product yields, convenient reaction temperature, and short reaction times. Therefore, the new reagent has great potential to be a useful alternative partial reducing agent for the synthesis of aldehydes from esters in organic synthesis. Aldehydes are valuable building blocks and reactive intermediates in organic synthesis. The general and classical syntheses of aldehydes from esters involve reduction-oxidation and partial reduction using efficient partial reducing agents. Obviously, one-step partial reduction methods are more useful than two-step reduction-oxidation methods owing to their simplicity, and generality in organic synthesis.

Tantrums, Emotion Reactions and Their EEG Correlates in Childhood Benign Rolandic Epilepsy vs. Complex Partial Seizures: Exploratory Observations.

Science.gov (United States)

Potegal, Michael; Drewel, Elena H; MacDonald, John T

2018-01-01

We explored associations between EEG pathophysiology and emotional/behavioral (E/B) problems of children with two types of epilepsy using standard parent questionnaires and two new indicators: tantrums recorded by parents at home and brief, emotion-eliciting situations in the laboratory. Children with Benign Rolandic epilepsy (BRE, N = 6) reportedly had shorter, more angry tantrums from which they recovered quickly. Children with Complex Partial Seizures (CPS, N = 13) had longer, sadder tantrums often followed by bad moods. More generally, BRE correlated with anger and aggression; CPS with sadness and withdrawal. Scores of a composite group of siblings ( N = 11) were generally intermediate between the BRE and CPS groups. Across all children, high voltage theta and/or interictal epileptiform discharges (IEDs) correlated with negative emotional reactions. Such EEG abnormalities in left hemisphere correlated with greater social fear, right hemisphere EEG abnormalities with greater anger. Right hemisphere localization in CPS was also associated with parent-reported problems at home. If epilepsy alters neural circuitry thereby increasing negative emotions, additional assessment of anti-epileptic drug treatment of epilepsy-related E/B problems would be warranted.

Physiological reactions in goat breeds maintained under shade, sun and partially shaded areas

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Luís Fernando Dias Medeiros

2015-12-01

Full Text Available ABSTRACT. Medeiros L.F.D., Rodrigues V.C., Vieira D.H., Souza S.L.G. de, Neto O.C., Figueiredo N. de, Pinto C.F.D., Miranda A.L. & Violento C.B. [Physiological reactions in goat breeds maintained under shade, sun and partially shaded areas.] Reações fisiológicas de cabras em diferentes ambientes e coeficiente de tolerância ao calor em cabritos. Revista Brasileira de Medicina Veterinária, 37(4:286-296, 2015. Departamento de Reprodução e Avaliação Animal, Instituto de Zootecnia, Universidade Federal Rural do Rio de Janeiro, BR 465 Km 7, Seropédica, RJ 23851-970, Brasil. E-mail: diasmedeiros@yahoo.com.br The experiment was carried out to measure the effects of thermal stress on the rectal temperature (RT and respiratory frequency (RF, in animals of Boer and Saanen breeds, under the conditions of hot and humid climate of city of Rio de Janeiro, Baixada Fluminense, South East Region of Brazil; also the heat tolerance coefficient (HTC of Amakiri e Funcho was applied on pure and crossbreeds kids. The goats were divided into three groups, each group consisting of four females from each breed group. Each group was subjected to different surroundings, constituted by three experimental treatment: treatment A, with a sun protected enclosed area; treatment B, a sun exposed area without covering; and treatment C, area with a 50% covered section and a 50% sun exposed area, which permitted free circulation of the goats. A Balanced Latin Square was used. The RT and RF of the goats, in the afternoon periods (l5h00, were higher, than in the morning periods (09h00. The animals kept in the sun presented much higher results, especially in the afternoon periods, than the animals in the other two confinement areas. There were no differences in the RT and RF of the groups maintained in the shade or in partially covered area. There were differences in the RT and RF measurements between the two breeds, in the morning periods and in the afternoon periods

Correlation of psychomotor findings and the ability to partially weight bear

Science.gov (United States)

2012-01-01

Background Partial weight bearing is thought to avoid excessive loading that may interfere with the healing process after surgery of the pelvis or the lower extremity. The object of this study was to investigate the relationship between the ability to partially weight bear and the patient's psychomotor skills and an additional evaluation of the possibility to predict this ability with a standardized psychomotor test. Methods 50 patients with a prescribed partial weight bearing at a target load of 15 kg following surgery were verbally instructed by a physical therapist. After the instruction and sufficient training with the physical therapist vertical ground reaction forces using matrix insoles were measured while walking with forearm crutches. Additionally, psychomotor skills were tested with the Motorische Leistungsserie (MLS). To test for correlations Spearman's Rank correlation was used. For further comparison of the two groups a Mann-Withney test was performed using Bonferroni correction. Results The patient's age and body weight significantly correlated with the ability to partially weight bear at a 15 kg target load. There were significant correlations between several subtests of the MLS and ground reaction forces measured while walking with crutches. Patients that were able to correctly perform partial weight bearing showed significant better psychomotor skills especially for those subtests where both hands had to be coordinated simultaneously. Conclusions The ability to partially weight bear is associated with psychomotor skills. The MLS seems to be a tool that helps predicting the ability to keep within the prescribed load limits. PMID:22330655

Correlation of psychomotor findings and the ability to partially weight bear

Directory of Open Access Journals (Sweden)

Ruckstuhl Thomas

2012-02-01

Full Text Available Abstract Background Partial weight bearing is thought to avoid excessive loading that may interfere with the healing process after surgery of the pelvis or the lower extremity. The object of this study was to investigate the relationship between the ability to partially weight bear and the patient's psychomotor skills and an additional evaluation of the possibility to predict this ability with a standardized psychomotor test. Methods 50 patients with a prescribed partial weight bearing at a target load of 15 kg following surgery were verbally instructed by a physical therapist. After the instruction and sufficient training with the physical therapist vertical ground reaction forces using matrix insoles were measured while walking with forearm crutches. Additionally, psychomotor skills were tested with the Motorische Leistungsserie (MLS. To test for correlations Spearman's Rank correlation was used. For further comparison of the two groups a Mann-Withney test was performed using Bonferroni correction. Results The patient's age and body weight significantly correlated with the ability to partially weight bear at a 15 kg target load. There were significant correlations between several subtests of the MLS and ground reaction forces measured while walking with crutches. Patients that were able to correctly perform partial weight bearing showed significant better psychomotor skills especially for those subtests where both hands had to be coordinated simultaneously. Conclusions The ability to partially weight bear is associated with psychomotor skills. The MLS seems to be a tool that helps predicting the ability to keep within the prescribed load limits.

An abnormally slow proton transfer reaction in a simple HBO derivative due to ultrafast intramolecular-charge transfer events.

Science.gov (United States)

Alarcos, Noemí; Gutierrez, Mario; Liras, Marta; Sánchez, Félix; Douhal, Abderrazzak

2015-07-07

We report on the steady-state, picosecond and femtosecond time-resolved studies of a charge and proton transfer dye 6-amino-2-(2'-hydroxyphenyl)benzoxazole (6A-HBO) and its methylated derivative 6-amino-2-(2'-methoxyphenyl)benzoxazole (6A-MBO), in different solvents. With femtosecond resolution and comparison with the photobehaviour of 6A-MBO, we demonstrate for 6A-HBO in solution, the photoproduction of an intramolecular charge-transfer (ICT) process at S1 taking place in ∼140 fs or shorter, followed by solvent relaxation in the charge transferred species. The generated structure (syn-enol charge transfer conformer) experiences an excited-state intramolecular proton-transfer (ESIPT) reaction to produce a keto-type tautomer. This subsequent proton motion occurs in 1.2 ps (n-heptane), 14 ps (DCM) and 35 ps (MeOH). In MeOH, it is assisted by the solvent molecules and occurs through tunneling for which we got a large kinetic isotope effect (KIE) of about 13. For the 6A-DBO (deuterated sample in CD3OD) the global proton-transfer reaction takes place in 200 ps, showing a remarkable slow KIE regime. The slow ESIPT reaction in DCM (14 ps), not through tunnelling as it is not sensitive to OH/OD exchange, has however to overcome an energy barrier using intramolecular as well as solvent coordinates. The rich ESIPT dynamics of 6A-HBO in the used solutions is governed by an ICT reaction, triggered by the amino group, and it is solvent dependent. Thus, the charge injection to a 6A-HBO molecular frame makes the ICT species more stable, and the phenol group less acidic, slowing down the subsequent ESIPT reaction. Our findings bring new insights into the coupling between ICT and ESIPT reactions on the potential-energy surfaces of several barriers.

Kinetic studies of isooctane partial oxidation over a nickel-based catalyst

International Nuclear Information System (INIS)

Ibrahim, Hussameldin; Idem, Raphael; Aboudheir, Ahmed

2006-01-01

The production of hydrogen (H 2 ) for fuel cell applications in mobile vehicles by reforming technologies such as partial oxidation of various fossil fuels has gained much attention recently. In this study, the production of H 2 by the catalytic partial oxidation of isooctane ((C 8 H 18 ) used here as a surrogate for gasoline) was investigated over alumina (AI 2 O 3 )supported nickel (Ni) catalyst. The work investigated the kinetics of the partial oxidation of isooctane over a stable Ni/□-AI 2 O 3 catalyst in the range of 863 to 913 K, at atmospheric pressure, W/F i c8 in the range of 1.97 to 8.58 g h mol - 1, and molar feed ratio in the range of 2.0 to 8.0 experiments to obtain kinetic data were performed in a 12.7 mm diameter Inconel micro-reactor housed in an electrically controlled furnace. The chemical reaction was then modeled using rate models developed from the Langmuir-Hinshelwood-hougen-Watson (LHHW) and Eley-Rideal (ER) formulations. The model parameters were estimated using an adaptive Gauss-Newton and Marquardi-Levenberg minimization algorithm. Rival models were screened for their thermodynamic consistency and physicochemical significance of estimated parameters. Langmuir-Hinshelwood-hougen-Watson mechanism requiring the dissociative adsorption of isooctane and oxygen on two different sites appeared to be the most likely pathway for the partial oxidation reaction of isooctane. Reaction order with respect to isooctane indicates the strong coverage of nickel by isooctane. The activation energy of 73±3.1 kJ mol - 1 estimated from the LHHW model is consistent with the trend observed with lower hydrocarbons.(Author)

Energy independent partial wave analysis of the reactions π+-p→Nππ between 1.36 and 1.76GeV c.m.s. energy

International Nuclear Information System (INIS)

Dolbeau, J.; Triantis, F.A.; Neveu, M.; Cadiet, F.

1975-01-01

A new partial wave analysis of the three reactions π - p→pπ - π 0 , π - p→nπ + π - , and π + p→pπ + π 0 is presented at nine c.m. energies between 1.36 and 1.76GeV, using about 91300 Nππ events. Within the framework of the generalized isobar model it is possible to describe the data with Δ, rho and sigma(ππ, i=0) production, as well as to reproduce the π - p→nπ 0 π 0 and π + p→nπ + π + cross sections. New prescriptions for the description of sigma and for the centrifugal barrier term are obtained. Furthermore, at the highest energy, there is evidence for N* production and for the presence of a ππ interaction, contributing about 5% to the cross sections of the reaction π - p→pπ - π 0 and π + p→pπ + π 0 . Finally, Argand plots are presented, showing the main inelastic couplings for ten resonances in this energy range [fr

Highly Active, Carbon-supported, PdSn Nano-core, Partially ...

African Journals Online (AJOL)

Carbon-supported, Pt partially covered, PdSn alloy nanoparticles (Pt-PdSn/C) were synthesized via a metathetical reaction of PdSn alloy nanoparticles, and a platinum precursor. The electrochemical activity was evaluated by methanol oxidation. The Pt-PdSn/C catalysts were characterized by transmission electron ...

Synthesis and reactivity of compounds containing ruthenium-carbon, -nitrogen, and -oxygen bonds

International Nuclear Information System (INIS)

Hartwig, J.F.

1990-12-01

The products and mechanisms of the thermal reactions of several complexes of the general structure (PMe 3 ) 4 Ru(X)(Y) and (DMPM) 2 Ru(X)(Y) where X and Y are hydride, aryl, and benzyl groups, have been investigated. The mechanism of decomposition depends critically on the structure of the complex and the medium in which the thermolysis is carried out. The alkyl hydride complexes are do not react with alkane solvent, but undergo C-H activation processes with aromatic solvents by several different mechanisms. Thermolysis of (PMe 3 ) 4 Ru(Ph)(Me) or (PMe 3 ) 4 Ru(Ph) 2 leads to the ruthenium benzyne complex (PMe 3 ) 4 Ru(η 2 -C 6 H 4 ) (1) by a mechanism which involves reversible dissociation of phosphine. In many ways its chemistry is analogous to that of early rather than late organo transition metal complexes. The synthesis, structure, variable temperature NMR spectroscopy and reactivity of ruthenium complexes containing aryloxide or arylamide ligands are reported. These complexes undergo cleavage of a P-C bond in coordinated trimethylphosphine, insertion of CO and CO 2 and hydrogenolysis. Mechanistic studies on these reactions are described. The generation of a series of reactive ruthenium complexes of the general formula (PMe 3 ) 4 Ru(R)(enolate) is reported. Most of these enolates have been shown to bind to the ruthenium center through the oxygen atom. Two of the enolate complexes 8 and 9 exist in equilibrium between the O- and C-bound forms. The reactions of these compounds are reported, including reactions to form oxygen-containing metallacycles. The structure and reactivity of these ruthenium metallacycles is reported, including their thermal chemistry and reactivity toward protic acids, electrophiles, carbon monoxide, hydrogen and trimethylsilane. 243 refs., 10 tabs

Synthesis and reactivity of compounds containing ruthenium-carbon, -nitrogen, and -oxygen bonds

Energy Technology Data Exchange (ETDEWEB)

Hartwig, J.F.

1990-12-01

The products and mechanisms of the thermal reactions of several complexes of the general structure (PMe{sub 3}){sub 4}Ru(X)(Y) and (DMPM){sub 2}Ru(X)(Y) where X and Y are hydride, aryl, and benzyl groups, have been investigated. The mechanism of decomposition depends critically on the structure of the complex and the medium in which the thermolysis is carried out. The alkyl hydride complexes are do not react with alkane solvent, but undergo C-H activation processes with aromatic solvents by several different mechanisms. Thermolysis of (PMe{sub 3}){sub 4}Ru(Ph)(Me) or (PMe{sub 3}){sub 4}Ru(Ph){sub 2} leads to the ruthenium benzyne complex (PMe{sub 3}){sub 4}Ru({eta}{sup 2}-C{sub 6}H{sub 4}) (1) by a mechanism which involves reversible dissociation of phosphine. In many ways its chemistry is analogous to that of early rather than late organo transition metal complexes. The synthesis, structure, variable temperature NMR spectroscopy and reactivity of ruthenium complexes containing aryloxide or arylamide ligands are reported. These complexes undergo cleavage of a P-C bond in coordinated trimethylphosphine, insertion of CO and CO{sub 2} and hydrogenolysis. Mechanistic studies on these reactions are described. The generation of a series of reactive ruthenium complexes of the general formula (PMe{sub 3}){sub 4}Ru(R)(enolate) is reported. Most of these enolates have been shown to bind to the ruthenium center through the oxygen atom. Two of the enolate complexes 8 and 9 exist in equilibrium between the O- and C-bound forms. The reactions of these compounds are reported, including reactions to form oxygen-containing metallacycles. The structure and reactivity of these ruthenium metallacycles is reported, including their thermal chemistry and reactivity toward protic acids, electrophiles, carbon monoxide, hydrogen and trimethylsilane. 243 refs., 10 tabs.

Laser-induced partial oxidation of cyclohexane in liquid phase

International Nuclear Information System (INIS)

Oshima, Y.; Wu, X.W.; Koda, S.

1995-01-01

A laser-induced partial oxidation of cyclohexane was studied in the liquid phase. With KrF excimer laser (248 nm) irradiation to neat liquid cyclohexane in which O 2 was dissolved, cyclohexanol and cyclohexanone were obtained with very high selectivities, together with cyclohexane as a minor product. Radical recombination reactions to produce dicyclohexyl ether and bicyclohexyl also took place, while these products were not observed in the gas phase reaction. These experimental results were considered to be due not only to higher concentration of cyclohexane but to the cage effect in the liquid phase oxidation. To clarify the reaction progress including the photoabsorption process, the effects of laser intensity and O 2 pressure on product distribution were studied. (author)

Models for cytochrome P450 prosthetic heme alkylation. Reaction of diazoacetophenone with (tetraphenylporphyrinato)iron(II) chloride

International Nuclear Information System (INIS)

Komives, E.A.; Tew, D.; Olmstead, M.M.; Ortiz de Montellano, P.R.

1988-01-01

The reaction of diazoacetophenone with (tetraphenylporphyrinato)iron(II) yields [N-(2-phenyl-2-oxoethyl)tetraphenylporphyrinato]iron(II) chloride. The structure of this product has been established by spectroscopic methods and by x-ray crystallography. The crystal structure shows that the first carbon of the N-alkyl group is 2.94 angstrom from the iron atom and that the oxygen of the N-alkyl group points away from the iron. No evidence is seen for the Fe-C-N product expected from insertion of the diazo carbon into the metalloporphyrin iron-nitrogen bond or for intermediates in which the oxygen of the N-(2-phenyl-2-oxoethyl) group is coordinated to the iron. These results suggest it is unlikely that carbene-insertion or oxygen-coordinated intermediates will be detected during the N-alkylation of cytochrome P450 by diazo ketones. The results also rationalize the failure to detect iron-chelated enol species during N-alkylation of the prosthetic group of cytochrome P450 by catalytically activated phenylacetylene. 43 references, 5 figures, 4 tables

A partial wave analysis of the (3π)0 system from the charge exchange reaction π+n→π+π-π0p at 4 GeV/c

International Nuclear Information System (INIS)

Emms, M.J.; Jones, G.T.; Kinson, J.B.; Stacey, B.J.; Votruba, M.F.; Woodworth, P.L.; Bell, I.G.; Dale, M.; Major, J.V.; Charlesworth, J.A.; Crennell, D.J.; Sekulin, R.L.

1975-10-01

From a partial wave analysis of the (3π) 0 state in the charge exchange reaction π + n→π + π - π 0 p, strong unnatural parity is observed as well as natural parity production. The observed natural parity states are identified with well-established resonances. The unnatural parity production is consistent with Reggeized Deck model predictions, with the exception of the I = 1 Jsup(p) = 1 + state. Here there is no evidence for A 1 production at approximately 1.1 GeV, but the data could support resonance production at higher masses. (author)

Buoyancy Effect of Ionic Vacancy on the Change of the Partial Molar Volume in Ferricyanide-Ferrocyanide Redox Reaction under a Vertical Gravity Field

Directory of Open Access Journals (Sweden)

Yoshinobu Oshikiri

2013-01-01

Full Text Available With a gravity electrode (GE in a vertical gravity field, the buoyancy effect of ionic vacancy on the change of the partial molar volume in the redox reaction between ferricyanide (FERRI and ferrocyanide (FERRO ions was examined. The buoyancy force of ionic vacancy takes a positive or negative value, depending on whether the rate-determining step is the production or extinction of the vacancy. Though the upward convection over an upward electrode in the FERRO ion oxidation suggests the contribution of the positive buoyancy force arising from the vacancy production, the partial molar volume of the vacancy was not measured. On the other hand, for the downward convection under a downward electrode in the FERRI ion reduction, it was not completely but partly measured by the contribution of the negative buoyancy force from the vacancy extinction. Since the lifetime of the vacancy is decreased by the collision between ionic vacancies during the convection, the former result was ascribed to the shortened lifetime due to the increasing collision efficiency in the enhanced upward convection over an upward electrode, whereas the latter was thought to arise from the elongated lifetime due to the decreasing collision efficiency by the stagnation under the downward electrode.

Tantrums, Emotion Reactions and Their EEG Correlates in Childhood Benign Rolandic Epilepsy vs. Complex Partial Seizures: Exploratory Observations

Directory of Open Access Journals (Sweden)

Michael Potegal

2018-03-01

Full Text Available We explored associations between EEG pathophysiology and emotional/behavioral (E/B problems of children with two types of epilepsy using standard parent questionnaires and two new indicators: tantrums recorded by parents at home and brief, emotion-eliciting situations in the laboratory. Children with Benign Rolandic epilepsy (BRE, N = 6 reportedly had shorter, more angry tantrums from which they recovered quickly. Children with Complex Partial Seizures (CPS, N = 13 had longer, sadder tantrums often followed by bad moods. More generally, BRE correlated with anger and aggression; CPS with sadness and withdrawal. Scores of a composite group of siblings (N = 11 were generally intermediate between the BRE and CPS groups. Across all children, high voltage theta and/or interictal epileptiform discharges (IEDs correlated with negative emotional reactions. Such EEG abnormalities in left hemisphere correlated with greater social fear, right hemisphere EEG abnormalities with greater anger. Right hemisphere localization in CPS was also associated with parent-reported problems at home. If epilepsy alters neural circuitry thereby increasing negative emotions, additional assessment of anti-epileptic drug treatment of epilepsy-related E/B problems would be warranted.

Double-Mutated 5-Enol Pyruvylshikimate-3-phosphate Synthase Protein Expressed in MZHG0JG Corn (Zea mays L.) Has No Impact on Toxicological Safety and Nutritional Composition.

Science.gov (United States)

Matthews, Bethany A; Launis, Karen L; Bauman, Patricia A; Juba, Nicole C

2017-09-27

MZHG0JG corn will offer growers the flexibility to alternate between herbicides with two different modes of action in their weed-management programs, helping to mitigate and manage the evolution of herbicide resistance in weed populations. The proteins conferring herbicide tolerence in MZHG0JG corn, double-mutated 5-enol pyruvylshikimate-3-phosphate synthase protein (mEPSPS) and phosphinothricin acetyltransferase (PAT), as well as the MZHG0JG corn event, have been assessed by regulatory authorities globally and have been determined to be safe for humans, animals, and the environment. In addition to the safety data available for these proteins, further studies were conducted on MZHG0JG corn to assess levels of mEPSPS as compared to previously registered genetically modified (GM) corn. The results support the conclusion of no impact on toxicological safety or nutritional composition.

Photophysical properties of 1-acetoxy-8-hydroxy-1,4,4a,9a-tetrahydroanthraquinone: Evidence for excited state proton transfer reaction

International Nuclear Information System (INIS)

Singh, Rupashree Balia; Mahanta, Subrata; Guchhait, Nikhil

2007-01-01

The photophysical properties of 1-acetoxy-8-hydroxy-1,4,4a,9a-tetrahydroanthraquinone (HTHQ) have been investigated by steady state and time resolved spectroscopy in combination with quantum chemical calculations. The effects of various parameters such as the nature of solvent and pH of the medium on the spectral properties confirm the existence of different neutral and ionic species in the ground and excited states. In the ground state, HTHQ exists as intramolecularly hydrogen bonded closed conformer in non-polar and polar aprotic solvents. Apart from the closed conformer, the intermolecular hydrogen bonded solvated species and the anion of HTHQ are present in hydroxylic solvents. The closed conformer shows excited state intramolecular proton transfer in all solvents and the solvent polarity independent red shifted emission indicates only keto-enol tautomerism. Evaluation of the potential energy surfaces by quantum chemical calculation using density functional theory point towards the possibility of proton transfer reaction in the first excited state but not in the ground state

Study of consistency between (γ,xn), [(γ,n) (γ,np)] and (γ2n) reaction cross sections using data systematics

International Nuclear Information System (INIS)

Varlamov, V.V.; Ishkhanov, B.S.

2002-08-01

The majority of published data for photoneutron reaction both total and partial cross section data obtained using both bremsstrahlung and quasimonoenergetic photon beams has been analyzed systematically. The last kind data were treated separately for results obtained at USA National Lawrence Livermore Laboratory and at Centre d.Etudes Nucleaires de Saclay (France). It was found out that as a rule total photoneutron reaction cross sections obtained at Livermore differ (being smaller in amplitude) from that of other laboratories. The Saclay-Livermore data discrepancies were analyzed in details. Combined the result of this analysis with that of analysis of partial photoneutron reactions [(γ,n) + (γ,np)] and (γ,2n) cross sections balance between Livermore and Saclay data published before the following recommendation was formulated: for reliable balance of total photoneutron (γ,xn) and partial [(γ,n) + [(γ,np)] and (γ,2n) reactions cross section absolute values the Livermore (not Saclay) data must be used but multiplied to the parameter 1.122. Saclay total reaction data could be used directly but partial reaction data must be recalculated via complex procedure. (author)

Partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor

KAUST Repository

Zhang, Xuming; Cha, Min

2015-01-01

We studied the relative importance of the reduced field intensity and the background reaction temperature in the partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor. We obtained important mechanistic insight

Reaction of O+, CO+, and CH+ ions with atomic hydrogen

International Nuclear Information System (INIS)

Federer, W.; Villinger, H.; Howorka, F.; Lindinger, W.; Tosis, P.; Bassi, D.; Ferguson, E.

1984-01-01

Rate coefficients for reactions of the ions O + , CO + , and CH + with atomic hydrogen have been measured for the first time at 300 K. This provides basic data for the ion chemistry of planetary atmospheres, cometary atmospheres, and interstellar molecular clouds. The O + +H measurement supports quantal calculations of this reaction. The CO + +H reaction provides an example of partial spin nonconservation in a charge-transfer reaction occurring in a deep potential well. Reactions of the same ions with H 2 that have been measured elsewhere are also reported

Roy-Steiner equations for {pi}N scattering - The Muskhelishvili-Omnes problem for the t-channel partial waves

Energy Technology Data Exchange (ETDEWEB)

Ditsche, Christoph; Hoferichter, Martin; Kubis, Bastian [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn (Germany); Bethe Center for Theoretical Physics, Bonn (Germany); Meissner, Ulf G. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn (Germany); Institut fuer Kernphysik (Theorie), Institute for Advanced Simulations, and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Bethe Center for Theoretical Physics, Bonn (Germany)

2011-07-01

Starting from (subtracted) hyperbolic dispersion relations for {pi}N scattering, which are based on the general principles of Lorentz invariance, unitarity, crossing and analyticity as well as isospin symmetry, we propose a closed system of (subtracted) hyperbolic partial wave dispersion relations for the partial waves f{sup I}{sub l{+-}}({radical}(s)) of the s-channel reaction {pi}N{yields}{pi}N and the partial waves f{sup J}{sub {+-}}(t) of the t-channel reaction {pi}{pi}{yields} anti NN in the spirit of Roy and Steiner. A key step to the ultimate goal of solving this Roy-Steiner system is to first solve the corresponding (subtracted) Muskhelishvili-Omnes problem with inelasticities and a finite matching point for the lowest t-channel partial waves f{sup 0}{sub +}(t), f{sup 1}{sub {+-}}(t). The recent status of this ongoing effort is presented.

Partially-Functionalized Isotactic Polystyrene with Blocky Comonomer Segments

Science.gov (United States)

Siegel, Ariel; Powers, Wayne; Ryu, Chang Y.

2012-02-01

Isotactic polystyrenes (iPSs) have been functionalized in solution, while the accessibility of functionalizing agent is limited by the formation of crystalline domains at various temperatures. The chemical system used is the borylated isotactic polystyrene system, and we investigated the temperature effects on reaction kinetics to ultimately control the blockiness of borylated segments in the resulting copolymer. The chemical composition of partially borylated iPS reaches a steady state that is dependent on temperature. This synthesis has been performed at many different temperatures, with different steady states being reached at different temperatures. Further analysis by differential scanning calorimetry (DSC) has shown that the higher temperature reactions have greater effect on breaking down the crystal lattice structure of the isotactic polystyrene. As a result, the lower temperature reactions affect the crystalline structure less, and the resulting copolymer has more blockiness.

OXIDATIVE-REFORMING OF METHANE AND PARTIAL OXIDATION OF METHANE REACTIONS OVER NiO/PrO2/ZrO2 CATALYSTS: EFFECT OF NICKEL CONTENT

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Y. J. O. Asencios

Full Text Available Abstract In this work the behavior of NiO-PrO2-ZrO2 catalysts containing various nickel loadings was evaluated in the partial oxidation of methane and oxidative-reforming reactions of methane. The catalysts were characterized by X-Ray Diffraction Analysis (in situ-XRD, Temperature Programmed Reduction (H2-TPR, Scanning Electron Microscopy (SEM/EDX and Adsorption-Desorption of nitrogen (BET area. The reactions were carried out at 750 °C and 1 atm for 5 hours. The catalysts were studied with different nickel content: 0, 5, 10 and 15% (related to total weight of catalyst, wt%. In both reactions, the catalyst containing the mixture of the three oxides (NiO/PrO2/ZrO2 with 15% nickel (15NiPrZr catalyst showed the best activity for the conversion of the reactants into Syngas and showed high selectivity for H2 and CO. The results suggest that the promoter PrO2 and the Niº centers are in a good proportion in the catalyst with 15% Ni. Our results showed that low nickel concentrations in the catalyst led to high metallic dispersion; however, very low nickel concentrations did not favor the methane transformation into Syngas. The catalyst containing only NiO/ZrO2 in the mixture was not sufficient for the catalysis. The presence of the promoter PrO2 was very important for the catalysis of the POM.

Design improvement for partial penetration welds of Pressurizer heater sleeves to head junctures

International Nuclear Information System (INIS)

Kim, Jin-Seon; Lee, Kyoung-Jin; Park, Tae-Jung; Kim, Moo-Yong

2007-01-01

ASME Code, Section III allows partial penetration welds for openings for instrumentation on which there are substantially no piping reactions and requires to have interference fit or limited diametral clearance between nozzles and vessel penetrations for the partial penetration welds. Pressurizer heater sleeves are nonaxisymmetrically attached on the hill-side of bottom head by partial penetration welds. The excessive stresses in the partial penetration weld regions of the heater sleeves are induced by pressure and thermal transient loads and also by the deformation due to manual welding process. The purpose of this study is 1) to improve design for the partial penetration welds between heater sleeves to head junctures, 2) to demonstrate the structural integrity according to the requirements of ASME Code, Section III and 3) to improve welding procedure considering the proposed design

Catalyst-Directed Diastereoselective Isomerization of Allylic Alcohols for the Stereoselective Construction of C(20) in Steroid Side Chains: Scope and Topological Diversification.

Science.gov (United States)

Li, Houhua; Mazet, Clément

2015-08-26

The stereoselective construction of C20 in steroidal derivatives by a highly diastereoselective Ir-catalyzed isomerization of primary allylic alcohols is reported. A key aspect of this strategy is a straightforward access to geometrically pure steroidal enol tosylate and enol triflate intermediates for subsequent high yielding stereoretentive Negishi cross-coupling reactions to allow structural diversity to be introduced. A range of allylic alcohols participates in the diastereoselective isomerization under the optimized reaction conditions. Electron-rich and electron-poor aryl or heteroaryl substituents are particularly well-tolerated, and the stereospecific nature of the reaction provides indifferently access to the natural C20-(R) and unnatural C20-(S) configurations. Alkyl containing substrates are more challenging as they affect regioselectivity of iridium-hydride insertion. A rationale for the high diastereoselectivities observed is proposed for aryl containing precursors. The scope of our method is further highlighted through topological diversification in the side chain and within the polycyclic domain of advanced and complex steroidal architectures. These findings have the potential to greatly simplify access to epimeric structural analogues of important steroid scaffolds for applications in biological, pharmaceutical, and medical sciences.

A thermodynamic and kinetic study of the de- and rehydration of Ca(OH){sub 2} at high H{sub 2}O partial pressures for thermo-chemical heat storage

Energy Technology Data Exchange (ETDEWEB)

Schaube, F.; Koch, L. [German Aerospace Center, Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart (Germany); Woerner, A., E-mail: antje.woerner@dlr.de [German Aerospace Center, Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart (Germany); Mueller-Steinhagen, H. [German Aerospace Center, Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart (Germany)

2012-06-20

Highlights: Black-Right-Pointing-Pointer Investigation of the thermodynamic equilibrium and reaction enthalpy of 'Ca(OH){sub 2} {r_reversible} CaO + H{sub 2}O'. Black-Right-Pointing-Pointer Investigation of the reaction kinetics of the dehydration of Ca(OH){sub 2} at partial pressures up to 956 mbar. Black-Right-Pointing-Pointer Investigation of the reaction kinetics of the rehydration of Ca(OH){sub 2} at partial pressures up to 956 mbar. - Abstract: Heat storage technologies are used to improve energy efficiency of power plants and recovery of process heat. Storing thermal energy by reversible thermo-chemical reactions offers a promising option for high storage capacities especially at high temperatures. Due to its low material cost, the use of the reversible reaction Ca(OH){sub 2} Rightwards-Harpoon-Over-Leftwards-Harpoon CaO + H{sub 2}O has been proposed. This paper reports on the physical properties such as heat capacity, thermodynamic equilibrium, reaction enthalpy and kinetics. To achieve high reaction temperatures, high H{sub 2}O partial pressures are required. Therefore the cycling stability is confirmed for H{sub 2}O partial pressures up to 95.6 kPa and the dehydration and hydration kinetics are studied. Quantitative data are collected and expressions are derived which are in good agreement with the presented measurements. At 1 bar H{sub 2}O partial pressure the expected equilibrium temperature is 505 Degree-Sign C and the reaction enthalpy is 104.4 kJ/mol.

Selenium and tellurium reagents in organic synthesis

International Nuclear Information System (INIS)

Comasseto, J.V.

1984-01-01

A review of the contribution of the University of Sao Paulo (SP, Brazil) to the organic synthesis of selenium and tellurium reagents is made. Major reactions amoung selenium compounds and insaturated substrates, phosphorus, ester enolates as well as the use of phase transference catalysed reactions to produce arylselenolate are described. For tellurium, interactions of its compounds with organic substrates and reactive intermediates (e.g. benzino diazomethane) are reported. (C.L.B.) [pt

Partial oxidation of municipal sludge with activited carbon catalyst in supercritical water

International Nuclear Information System (INIS)

Guo Yang; Wang Shuzhong; Gong Yanmeng; Xu Donghai; Tang Xingying; Ma Honghe

2010-01-01

The partial oxidation (POX) characteristics of municipal sludge in supercritical water (SCW) were investigated by using batch reactor. Effects of reaction parameters such as oxidant equivalent ratio (OER), reaction time and temperature were investigated. Activated carbon (AC) could effectively improve the mole fraction of H 2 in gas product at low OER. However, high OER (greater than 0.3) not only led to the combustion reaction of CO and H 2 , but also caused corrosion of reactor inner wall. Hydrogenation and polymerization of the intermediate products are possible reasons for the relative low COD removal rate in our tests. Metal oxide leached from the reactor inner wall and the main components of the granular sludge were deposited in the AC catalyst. Reaction time had more significant effect on BET surface area of AC than OER had. Long reaction time led to the methanation reaction following hydrolysis and oxidation reaction of AC in SCW in the presence of oxygen. Correspondingly, the possible reaction mechanisms were proposed.

27Al MAS NMR spectroscopic identification of reaction intermediates in the carbothermal reduction and nitridation of alumina

International Nuclear Information System (INIS)

Jung, Woo-Sik; Chae, Seen-Ae

2010-01-01

The reaction intermediates in the carbothermal reduction and nitridation (CRN) reaction of γ-Al 2 O 3 were identified by 27 Al magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. This identification ruled out the possibility of a reaction mechanism involving the gaseous reaction intermediates. In the CRN reaction of γ-Al 2 O 3 , AlO 4 units were converted to AlN stepwise via AlN x O 4-x (x = 1, 2, 3) intermediates, while AlO 6 units were more slowly converted to AlN than AlO 4 units and the NMR peaks of partially nitridated AlO 6 units were not detected. The NMR peak intensities of partially nitridated AlO 4 units became weaker with increasing reaction temperature.

Mechanisms of the Knoevenagel hetero Diels-Alder sequence in multicomponent reactions to dihydropyrans: experimental and theoretical investigations into the role of water.

Science.gov (United States)

Frapper, Gilles; Bachmann, Christian; Gu, Yanlong; Coval De Sousa, Rodolphe; Jérôme, François

2011-01-14

The role of water in a multicomponent domino reaction (MCR) involving styrene, 2,4-pentanedione, and formaldehyde was studied. Whereas anhydrous conditions produced no reaction, the MCR successfully proceeded in the presence of water, affording the targeted dihydropyran derivatives with good yield. The mechanism of this MCR (Knoevenagel hetero Diels-Alder sequence) was studied with and without explicit water molecules using the SMD continuum solvation model in combination with the B3LYP density functional and the 6-311++G** basis set to compute the water and acetone (aprotic organic solvent) solution Gibbs free energies. In the Knoevenagel step, we found that water acted as a proton relay to favor the formation of more flexible six-membered ring transition state structures both in concerted (direct H(2)O elimination) and stepwise (keto-enol tautomerization and dehydration) pathways. The inclusion of a water molecule in our model resulted in a significant decrease (-8.5 kcal mol(-1)ΔG(water)(‡)) of the direct water elimination activation barrier. Owing to the presence of water, all chemical steps involved in the MCR mechanism had activation free energies barriers lower than 39 kcal mol(-1) at 25 °C in aqueous solvent (ZPE corrected electronic energies barriers). Consequently, the MCR proceeded without the assistance of any catalyst.

Detecting and correcting partial errors: Evidence for efficient control without conscious access.

Science.gov (United States)

Rochet, N; Spieser, L; Casini, L; Hasbroucq, T; Burle, B

2014-09-01

Appropriate reactions to erroneous actions are essential to keeping behavior adaptive. Erring, however, is not an all-or-none process: electromyographic (EMG) recordings of the responding muscles have revealed that covert incorrect response activations (termed "partial errors") occur on a proportion of overtly correct trials. The occurrence of such "partial errors" shows that incorrect response activations could be corrected online, before turning into overt errors. In the present study, we showed that, unlike overt errors, such "partial errors" are poorly consciously detected by participants, who could report only one third of their partial errors. Two parameters of the partial errors were found to predict detection: the surface of the incorrect EMG burst (larger for detected) and the correction time (between the incorrect and correct EMG onsets; longer for detected). These two parameters provided independent information. The correct(ive) responses associated with detected partial errors were larger than the "pure-correct" ones, and this increase was likely a consequence, rather than a cause, of the detection. The respective impacts of the two parameters predicting detection (incorrect surface and correction time), along with the underlying physiological processes subtending partial-error detection, are discussed.

Distinct Roles of the C-terminal 11th Transmembrane Helix and Luminal Extension in the Partial Reactions Determining the High Ca2+ Affinity of Sarco(endo)plasmic Reticulum Ca2+-ATPase Isoform 2b (SERCA2b)

DEFF Research Database (Denmark)

Clausen, Johannes D; Vandecaetsbeek, Ilse; Wuytack, Frank

2012-01-01

of each of these parts and their interactions with the SERCA environment were examined by transient kinetic analysis of the partial reaction steps in the Ca2+ transport cycle in mutant and chimeric Ca2+-ATPase constructs. Manipulations to the LE of SERCA2b markedly increased the rate of Ca2+ dissociation...

Multidimensional flamelet-generated manifolds for partially premixed combustion

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Phuc-Danh; Vervisch, Luc; Subramanian, Vallinayagam; Domingo, Pascale [CORIA - CNRS and INSA de Rouen, Technopole du Madrillet, BP 8, 76801 Saint-Etienne-du-Rouvray (France)

2010-01-15

Flamelet-generated manifolds have been restricted so far to premixed or diffusion flame archetypes, even though the resulting tables have been applied to nonpremixed and partially premixed flame simulations. By using a projection of the full set of mass conservation species balance equations into a restricted subset of the composition space, unsteady multidimensional flamelet governing equations are derived from first principles, under given hypotheses. During the projection, as in usual one-dimensional flamelets, the tangential strain rate of scalar isosurfaces is expressed in the form of the scalar dissipation rates of the control parameters of the multidimensional flamelet-generated manifold (MFM), which is tested in its five-dimensional form for partially premixed combustion, with two composition space directions and three scalar dissipation rates. It is shown that strain-rate-induced effects can hardly be fully neglected in chemistry tabulation of partially premixed combustion, because of fluxes across iso-equivalence-ratio and iso-progress-of-reaction surfaces. This is illustrated by comparing the 5D flamelet-generated manifold with one-dimensional premixed flame and unsteady strained diffusion flame composition space trajectories. The formal links between the asymptotic behavior of MFM and stratified flame, weakly varying partially premixed front, triple-flame, premixed and nonpremixed edge flames are also evidenced. (author)

Ruthenium(II) bipyridine complexes bearing new keto-enol azoimine ligands: synthesis, structure, electrochemistry and DFT calculations.

Science.gov (United States)

Al-Noaimi, Mousa; Awwadi, Firas F; Mansi, Ahmad; Abdel-Rahman, Obadah S; Hammoudeh, Ayman; Warad, Ismail

2015-01-25

The novel azoimine ligand, Ph-NH-N=C(COCH3)-NHPh(C≡CH) (H2L), was synthesized and its molecular structure was determined by X-ray crystallography. Catalytic hydration of the terminal acetylene of H2L in the presence of RuCl3·3H2O in ethanol at reflux temperature yielded a ketone (L1=Ph-N=N-C(COCH3)=N-Ph(COCH3) and an enol (L2=Ph-N=N-C(COCH3)=N-PhC(OH)=CH2) by Markovnikov addition of water. Two mixed-ligand ruthenium complexes having general formula, trans-[Ru(bpy)(Y)Cl2] (1-2) (where Y=L1 (1) and Y=L2 (2), bpy is 2.2'-bipyrdine) were achieved by the stepwise addition of equimolar amounts of (H2L) and bpy ligands to RuCl3·3H2O in absolute ethanol. Theses complexes were characterized by elemental analyses and spectroscopic (IR, UV-Vis, and NMR (1D (1)H NMR, (13)C NMR, (DEPT-135), (DEPT-90), 2D (1)H-(1)H and (13)C-(1)H correlation (HMQC) spectroscopy)). The two complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 604 mV vs. ferrocene/ferrocenium (Cp2Fe(0/+)) couple along with one electron ligand reduction at -1010 mV. The crystal structure of complex 1 showed that the bidentate ligand L1 coordinates to Ru(II) by the azo- and imine-nitrogen donor atoms. The complex adopts a distorted trans octahedral coordination geometry of chloride ligands. The electronic spectra of 1 and 1+ in dichloromethane have been modeled by time-dependent density functional theory (TD-DFT). Copyright © 2014 Elsevier B.V. All rights reserved.

Biocatalytic synthesis of the Green Note trans-2-hexenal in a continuous-flow microreactor.

Science.gov (United States)

van Schie, Morten M C H; Pedroso de Almeida, Tiago; Laudadio, Gabriele; Tieves, Florian; Fernández-Fueyo, Elena; Noël, Timothy; Arends, Isabel W C E; Hollmann, Frank

2018-01-01

The biocatalytic preparation of trans -hex-2-enal from trans -hex-2-enol using a novel aryl alcohol oxidase from Pleurotus eryngii ( Pe AAOx) is reported. As O 2 -dependent enzyme Pe AAOx-dependent reactions are generally plagued by the poor solubility of O 2 in aqueous media and mass transfer limitations resulting in poor reaction rates. These limitations were efficiently overcome by conducting the reaction in a flow-reactor setup reaching unpreceded catalytic activities for the enzyme in terms of turnover frequency (up to 38 s -1 ) and turnover numbers (more than 300000) pointing towards preparative usefulness of the proposed reaction scheme.

Effect of mass-transport limitations on the performance of a packed bed membrane reactor for partial oxidations. Intraparticle mass transport

NARCIS (Netherlands)

Sint Annaland, van M.; Kurten, U.; Kuipers, J.A.M.

2007-01-01

For partial oxidation systems, where the reaction order in oxygen of the formation rate of the target product is smaller than the reaction order in oxygen of the consecutive reaction rate toward the waste product, a packed bed membrane reactor can be applied to distributively dose oxygen along the

Effect of Mass-Transport Limitations on the Performance of a Packed Bed Membrane Reactor for Partial Oxidations. Intraparticle Mass Transport

NARCIS (Netherlands)

van Sint Annaland, M.; Kurten, U.; Kuipers, J.A.M.

2007-01-01

For partial oxidation systems, where the reaction order in oxygen of the formation rate of the target product is smaller than the reaction order in oxygen of the consecutive reaction rate toward the waste product, a packed bed membrane reactor can be applied to distributively dose oxygen along the

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

International Nuclear Information System (INIS)

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C.; Brooks, Scott C; Pace, Molly; Kim, Young Jin; Jardine, Philip M.; Watson, David B.

2007-01-01

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M. partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M. species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions.

Science.gov (United States)

Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C; Brooks, Scott C; Pace, Molly N; Kim, Young-Jin; Jardine, Philip M; Watson, David B

2007-06-16

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing N(E) equilibrium reactions and a set of reactive transport equations of M-N(E) kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

The synthesis of thebaine-1-3H

International Nuclear Information System (INIS)

Choudhry, S.C.; Serico, L.; Cupano, J.; Malarek, D.H.; Liebman, A.A.

1989-01-01

A synthesis of thebaine is described where the C-1 position is labelled with tritium to specific activity of 16 Ci/mmole. From codeine, 1-iodocodeine was prepared and converted to 1-iodothebaine in 3 steps. The subsequent key reaction was the selective hydrogenolysis of the carbon-iodine bond in 1-iodothebaine in the presence of the dienic-enol ether system. Using 10% Pd/C as catalyst, the desired reaction occurs in about 80% yield. (author)

The synthesis of thebaine-1- sup 3 H

Energy Technology Data Exchange (ETDEWEB)

Choudhry, S.C.; Serico, L.; Cupano, J.; Malarek, D.H.; Liebman, A.A. (Hoffmann-La Roche, Inc., Nutley, NJ (USA). Chemical Research Dept.)

1989-12-01

A synthesis of thebaine is described where the C-1 position is labelled with tritium to specific activity of 16 Ci/mmole. From codeine, 1-iodocodeine was prepared and converted to 1-iodothebaine in 3 steps. The subsequent key reaction was the selective hydrogenolysis of the carbon-iodine bond in 1-iodothebaine in the presence of the dienic-enol ether system. Using 10% Pd/C as catalyst, the desired reaction occurs in about 80% yield. (author).

Reactive transport in a partially molten system with binary solid solution

Science.gov (United States)

Jordan, J.; Hesse, M. A.

2017-12-01

Melt extraction from the Earth's mantle through high-porosity channels is required to explain the composition of the oceanic crust. Feedbacks from reactive melt transport are thought to localize melt into a network of high-porosity channels. Recent studies invoke lithological heterogeneities in the Earth's mantle to seed the localization of partial melts. Therefore, it is necessary to understand the reaction fronts that form as melt flows across the lithological interface of a heterogeneity and the background mantle. Simplified melting models of such systems aide in the interpretation and formulation of larger scale mantle models. Motivated by the aforementioned facts, we present a chromatographic analysis of reactive melt transport across lithological boundaries, using theory for hyperbolic conservation laws. This is an extension of well-known linear trace element chromatography to the coupling of major elements and energy transport. Our analysis allows the prediction of the feedbacks that arise in reactive melt transport due to melting, freezing, dissolution and precipitation for frontal reactions. This study considers the simplified case of a rigid, partially molten porous medium with binary solid solution. As melt traverses a lithological contact-modeled as a Riemann problem-a rich set of features arise, including a reacted zone between an advancing reaction front and partial chemical preservation of the initial contact. Reactive instabilities observed in this study originate at the lithological interface rather than along a chemical gradient as in most studies of mantle dynamics. We present a regime diagram that predicts where reaction fronts become unstable, thereby allowing melt localization into high-porosity channels through reactive instabilities. After constructing the regime diagram, we test the one-dimensional hyperbolic theory against two-dimensional numerical experiments. The one-dimensional hyperbolic theory is sufficient for predicting the

Partial strands synthesizing leads to inevitable aborting and complicated products in consecutive polymerase chain reactions (PCRs)

Institute of Scientific and Technical Information of China (English)

LUO Rui; ZHANG DaMing

2007-01-01

Various abnormal phenomena have been observed during PCR so far. The present study performed a series of consecutive PCRs (including many rounds of re-amplification continuously) and found that the abortion of re-amplification was inevitable as long as a variety of complicated product appeared.The aborting stages varied, according to the lengths of targets. Longer targets reached the abortion earlier than the shorter ones, marked by appearance of the complex that was immobile in electrophoresis. Denatured gel-electrophoresis revealed that the complex was mainly made up of shorter or partially synthesized strands, together with small amounts of full-length ones. Able to be digested by S1 nuclease but unable by restriction endonucleases (REs), the complex was proved to consist of both single regions and double-helix regions that kept the complex stable thermodynamically. Simulations gave evidence that partial strands, even at lower concentration, could disturb re-amplification effectively and lead to the abortion of re-amplifications finally. It was pointed out that the partial strands formed chiefly via polymerase's infidelity, and hence the solution to lighten the abnormality was also proposed.

Spontaneous Hedonic Reactions to Social Media Cues.

Science.gov (United States)

van Koningsbruggen, Guido M; Hartmann, Tilo; Eden, Allison; Veling, Harm

2017-05-01

Why is it so difficult to resist the desire to use social media? One possibility is that frequent social media users possess strong and spontaneous hedonic reactions to social media cues, which, in turn, makes it difficult to resist social media temptations. In two studies (total N = 200), we investigated less-frequent and frequent social media users' spontaneous hedonic reactions to social media cues using the Affect Misattribution Procedure-an implicit measure of affective reactions. Results demonstrated that frequent social media users showed more favorable affective reactions in response to social media (vs. control) cues, whereas less-frequent social media users' affective reactions did not differ between social media and control cues (Studies 1 and 2). Moreover, the spontaneous hedonic reactions to social media (vs. control) cues were related to self-reported cravings to use social media and partially accounted for the link between social media use and social media cravings (Study 2). These findings suggest that frequent social media users' spontaneous hedonic reactions in response to social media cues might contribute to their difficulties in resisting desires to use social media.

Correlation functions for fully or partially state-resolved reactive scattering calculations

International Nuclear Information System (INIS)

Manthe, Uwe; Welsch, Ralph

2014-01-01

Flux correlation functions and the quantum transition state concept are important tools for the accurate description of polyatomic reaction processes. Combined with the multi-configurational time-dependent Hartree approach, they facilitate rigorous full-dimensional calculations of cumulative and initial-state selected reaction probabilities for six atom reactions. In recent work [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)], an approach which allows one to calculate also state-to-state reaction probabilities within the quantum transition state concept has been introduced. This article presents further developments. Alternative generalized flux correlation functions are introduced and discussed. Equations for the calculation of fully state-resolved differential cross section using arbitrary definitions of the body fixed frame are derived. An approach for the efficient calculation of partially state-resolved observables as a function of the collision energy is introduced. Finally, numerical test studying the D + H 2 reaction illustrate important aspects of the formalism

Examination and experimental constraints of the stellar reaction rate factor N-A of the Ne-18(alpha, p)Na-21 reaction at temperatures of x-ray bursts

NARCIS (Netherlands)

Matic, A.; Mohr, P.

2013-01-01

The Ne-18(alpha, p)Na-21 reaction is one key for the breakout from the hot CNO cycles to the rp-process. Recent papers have provided reaction rate factors N-A which are discrepant by at least one order of magnitude. The compatibility of the latest experimental results is tested, and a partial

SXPS investigation of the Cd partial electrolyte treatment of CuInSe2 absorbers

International Nuclear Information System (INIS)

Hunger, R.; Schulmeyer, T.; Klein, A.; Jaegermann, W.; Lebedev, M.V.; Sakurai, K.; Niki, S.

2005-01-01

The chemical modification of polycrystalline CuInSe 2 absorber surfaces by the so-called Cd partial electrolyte (PE) treatment was studied by synchrotron X-ray photoelectron spectroscopy (SXPS). The Cd PE treatment was found to remove surface indium oxides and hydroxides and segregated sodium compounds. A hydroxide-terminated CdSe surface layer of one monolayer thickness is formed by the partial electrolyte treatment. The reaction mechanism is discussed as substrate site-controlled exchange reaction, where surface indium is removed and replaced by cadmium. Electronically, the Cd PE treated surface is inverted and exhibits a surface barrier which is by 0.2 eV higher than a comparable structure that was prepared by the vacuum deposition of one monolayer of CdS onto clean CuInSe 2

How does the long G·G* Watson-Crick DNA base mispair comprising keto and enol tautomers of the guanine tautomerise? The results of a QM/QTAIM investigation.

Science.gov (United States)

Brovarets', Ol'ha O; Hovorun, Dmytro M

2014-08-14

The double proton transfer (DPT) in the long G·G* Watson-Crick base mispair (|C6N1(G*)N1C6(G)| = 36.4°; C1 symmetry), involving keto and enol tautomers of the guanine (G) nucleobase, along two intermolecular neighboring O6H···O6 (8.39) and N1···HN1 (6.14 kcal mol(-1)) H-bonds that were established to be slightly anti-cooperative, leads to its transformation into the G*·G base mispair through a single transition state (|C6N1N1C6| = 37.1°; C1), namely to the interconversion into itself. It was shown that the G·G* ↔ G*·G tautomerisation via the DPT is assisted by the third specific contact, that sequentially switches along the intrinsic reaction coordinate (IRC) in an original way: (G)N2H···N2(G*) H-bond (-25.13 to -10.37) → N2···N2 van der Waals contact (-10.37 to -9.23) → (G)N2···HN2(G*) H-bond (-9.23 to 0.79) → (G*)N2···HN2(G) H-bond (0.79 to 7.35 Bohr). The DPT tautomerisation was found to proceed through the asynchronous concerted mechanism by employing the QM/QTAIM approach and the methodology of the scans of the geometric, electron-topological, energetic, polar and NBO properties along the IRC. Nine key points, that can be considered as part of the tautomerisation repertoire, have been established and analyzed in detail. Furthermore, it was shown that the G·G* or G*·G base mispair is a thermodynamically and dynamically stable structure with a lifetime of 8.22 × 10(-10) s and all 6 low-frequency intermolecular vibrations are able to develop during this time span. Lastly, our results highlight the importance of the G·G* ↔ G*·G DPT tautomerisation, which can have implications for biological and chemical sensing applications.

Reaction scheme of partial oxidation of methane to synthesis gas over yttrium-stabilized zirconia

NARCIS (Netherlands)

Zhu, J.J.; van Ommen, J.G.; Lefferts, Leonardus

2004-01-01

The partial oxidation of methane to synthesis gas over yttrium-stabilized zirconia (YSZ) was studied with in situ FTIR and both steady-state and transient experiments. The four major products, CO, H2, CO2, and H2O, are primary products of CPOM over YSZ. Besides these major products and traces of

Effect of imaginary part of an optical potential on reaction total cross sections

International Nuclear Information System (INIS)

Afanas'ev, G.N.; Dobromyslov, M.B.; Kim Yng Pkhung; Shilov, V.M.

1977-01-01

The effect of the imaginary part of optical potential on the total cross sections of reactions is explained. The complex rectangular well model is used, i.e. the real rectangular well at r 16 O + 27 Al reactions and the partial permeabilities are presented. It is demonstrated that the S-matrix has proved to be unitary. Oscillations of the partial permeabilities and cross-sections are observed for small potential values in the Wsub(o) imaginary part, which no longer occur at larger Wsub(o). This corresponds to the overlapping and nonoverlapping quasistationary levels in complex rectangular well

Modeling the reactions catalyzed by coenzyme B12-dependent enzymes.

Science.gov (United States)

Sandala, Gregory M; Smith, David M; Radom, Leo

2010-05-18

Enzymes accelerate chemical reactions with an exceptional selectivity that makes life itself possible. Understanding the factors responsible for this efficient catalysis is of utmost importance in our quest to harness the tremendous power of enzymes. Computational chemistry has emerged as an important adjunct to experimental chemistry and biochemistry in this regard, because it provides detailed insights into the relationship between structure and function in a systematic and straightforward manner. In this Account, we highlight our recent high-level theoretical investigations toward this end in studying the radical-based reactions catalyzed by enzymes dependent on coenzyme B(12) (or adenosylcobalamin, AdoCbl). In addition to their fundamental position in biology, the AdoCbl-dependent enzymes represent a valuable framework within which to understand Nature's method of efficiently handling high-energy species to execute very specific reactions. The AdoCbl-mediated reactions are characterized by the interchange of a hydrogen atom and a functional group on adjacent carbon atoms. Our calculations are consistent with the conclusion that the main role of AdoCbl is to provide a source of radicals, thus moving the 1,2-rearrangements onto the radical potential energy surface. Our studies also show that the radical rearrangement step is facilitated by partial proton transfer involving the substrate. Specifically, we observe that the energy requirements for radical rearrangement are reduced dramatically with appropriate partial protonation or partial deprotonation or sometimes (synergistically) both. Such interactions are particularly relevant to enzyme catalysis, because it is likely that the local amino acid environment in the active site of an enzyme can function in this capacity through hydrogen bonding. Finally, our calculations indicate that the intervention of a very stable radical along the reaction pathway may inactivate the enzyme, demonstrating that sustained

Partial strands synthesizing leads to inevitable aborting and complicated products in consecutive polymerase chain reactions (PCRs)

Institute of Scientific and Technical Information of China (English)

2007-01-01

Various abnormal phenomena have been observed during PCR so far. The present study performed a series of consecutive PCRs (including many rounds of re-amplification continuously) and found that the abortion of re-amplification was inevitable as long as a variety of complicated product appeared. The aborting stages varied, according to the lengths of targets. Longer targets reached the abortion earlier than the shorter ones, marked by appearance of the complex that was immobile in electropho-resis. Denatured gel-electrophoresis revealed that the complex was mainly made up of shorter or partially synthesized strands, together with small amounts of full-length ones. Able to be digested by S1 nuclease but unable by restriction endonucleases (REs), the complex was proved to consist of both single regions and double-helix regions that kept the complex stable thermodynamically. Simulations gave evidence that partial strands, even at lower concentration, could disturb re-amplification effec- tively and lead to the abortion of re-amplifications finally. It was pointed out that the partial strands formed chiefly via polymerase’s infidelity, and hence the solution to lighten the abnormality was also proposed.

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based on the mean gas temperature and the concentration of CO, O 2, NO, and HC at the flame early region of reaction. The investigation covered the influence of the nozzle cone angle, the jet exit velocity and the jet equivalence ratio. The stability results show that the flames with cone are more stable than those without cone. For conical stabilized flames, the stability results exhibit three different sensitivity regions between the jet velocity and equivalence ratio. The inflame measurements prove that the flame stability could be attributed to the triple flame structure at the flame leading edge. The data show that the triple flame structure is influenced by cone angle, the jet velocity and the equivalence ratio. The flame is believed to be controlled by the recirculation flow inside the cone. Increasing the cone angle induced higher air entrainment to the reaction zone as depicted by a higher O 2 concentration within the flame leading edge. Increasing the jet velocity to a certain limit enhances the intensity of combustion at the flame leading edge, while excessive increase in jet velocity reduces this intensity. At a fixed jet velocity the higher the equivalence ratio, the higher the amount of fuel diffused and engulfed to the reaction zone, the more delay of the combustion completion and the higher the emission concentrations of the flame. © 2012 Elsevier Inc.

Electrochemical promotion of catalytic reactions with Pt/C (or Pt/Ru/C)//PBI catalysts

DEFF Research Database (Denmark)

Petrushina, Irina; Bjerrum, Niels; Bandur, Viktor

2007-01-01

The paper is an overview of the results of the investigation on electrochemical promotion of three catalytic reactions: methane oxidation with oxygen, NO reduction with hydrogen at 135 degrees C and Fischer-Tropsch synthesis (FTS) at 170 degrees C in the [CH4/O-2(or NO/H-2 or CO/H-2)/Ar//Pt(or Pt....../Ru)//PBI(H3PO4)/H-2, Ar] fuel cell. It has been shown that the partial methane oxidation to C2H2 and the C-2 selectivity were electrochemically promoted by the negative catalyst polarization. This was also the case in NO reduction with hydrogen for low NO and H-2 partial pressures. In both cases the catalytic...... reactions have been promoted by the electrochemically produced hydrogen. It has been found that the NO reduction with hydrogen on the Pt/PBI strongly depends on NO and hydrogen partial pressures in the working gas mixture. At higher NO and H-2 partial pressures the catalysis is promoted...

Fuel processor integrated H{sub 2}S catalytic partial oxidation technology for sulfur removal in fuel cell power plants

Energy Technology Data Exchange (ETDEWEB)

Gardner, T.H.; Berry, D.A.; Lyons, K.D.; Beer, S.K.; Freed, A.D. [U.S. Department of Energy, Morgantown, WV (USA). National Energy Technology Laboratory

2002-12-01

H{sub 2}S catalytic partial oxidation technology with an activated carbon catalyst was found to be a promising method for the removal of hydrogen sulfide from fuel cell hydrocarbon feedstocks. Three different fuel cell feedstocks were considered for analysis: sour natural gas, sour effluent from a liquid middle distillate fuel processor and a Texaco O{sub 2}-blown coal-derived synthesis gas. The H{sub 2}S catalytic partial oxidation reaction, its integratability into fuel cell power plants with different hydrocarbon feedstocks and its salient features are discussed. Experimental results indicate that H{sub 2}S concentration can be removed down to the part-per-million level in these plants. Additionally, a power law rate expression was developed and reaction kinetics compared to prior literature. The activation energy for this reaction was determined to be 34.4 kJ/g mol with the reaction being first order in H{sub 2}S and 0.3 order in O{sub 2}. 18 refs., 14 figs., 3 tabs.

Carbon-coated magnetic palladium: applications in partial oxidation of alcohols and coupling reactions.

Science.gov (United States)

Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; catalyst can be used for oxidation of alcohols, amination reaction and arylation of aryl halides (cross coupli...

Cast Partial Denture versus Acrylic Partial Denture for Replacement of Missing Teeth in Partially Edentulous Patients

Directory of Open Access Journals (Sweden)

Pramita Suwal

2017-03-01

Full Text Available Aim: To compare the effects of cast partial denture with conventional all acrylic denture in respect to retention, stability, masticatory efficiency, comfort and periodontal health of abutments. Methods: 50 adult partially edentulous patient seeking for replacement of missing teeth having Kennedy class I and II arches with or without modification areas were selected for the study. Group-A was treated with cast partial denture and Group-B with acrylic partial denture. Data collected during follow-up visit of 3 months, 6 months, and 1 year by evaluating retention, stability, masticatory efficiency, comfort, periodontal health of abutment. Results: Chi-square test was applied to find out differences between the groups at 95% confidence interval where p = 0.05. One year comparison shows that cast partial denture maintained retention and stability better than acrylic partial denture (p< 0.05. The masticatory efficiency was significantly compromising from 3rd month to 1 year in all acrylic partial denture groups (p< 0.05. The comfort of patient with cast partial denture was maintained better during the observation period (p< 0.05. Periodontal health of abutment was gradually deteriorated in all acrylic denture group (p

New results on the Roper resonance and the P-11 partial wave

NARCIS (Netherlands)

Sarantsev, A. V.; Fuchs, M.; Kotulla, M.; Thoma, U.; Ahrens, J.; Annand, J. R. M.; Anisovich, A. V.; Anton, G.; Bantes, R.; Bartholomy, O.; Beck, R.; Beloglazov, Yu.; Castelijns, R.; Crede, V.; Ehmanns, A.; Ernst, J.; Fabry, I.; Flemming, H.; Foesel, A.; Funke, Chr.; Gothe, R.; Gridnev, A.; Gutz, E.; Hoeffgen, St.; Horn, I.; Hoessl, J.; Hornidge, D.; Janssen, S.; Junkersfeld, J.; Kalinowsky, H.; Klein, F.; Klempt, E.; Koch, H.; Konrad, M.; Kopf, B.; Krusche, B.; Langheinrich, J.; Loehner, H.; Lopatin, I.; Lotz, J.; McGeorge, J. C.; MacGregor, I. J. D.; Matthaey, H.; Menze, D.; Messchendorp, J. G.; Metag, V.; Nikonov, V. A.; Novinski, D.; Novotny, R.; Ostrick, M.; van Pee, H.; Pfeiffer, M.; Radkov, A.; Rosner, G.; Rost, M.; Schmidt, C.; Schoch, B.; Suft, G.; Sumachev, V.; Szczepanek, T.; Walther, D.; Watts, D. P.; Weinheimer, Chr.

2008-01-01

Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the P-11 partial wave are studied in a combined analysis of pion- and photo-induced reactions. We find the Roper pole at {(1371 +/- 7) - i(92 +/- 10)} MeV and an elasticity

Conservation-dissipation structure of chemical reaction systems.

Science.gov (United States)

Yong, Wen-An

2012-12-01

In this Brief Report, we show that balanced chemical reaction systems governed by the law of mass action have an elegant conservation-dissipation structure. From this structure a number of important conclusions can be easily deduced. In particular, with the help of this structure we can rigorously justify the classical partial equilibrium approximation in chemical kinetics.

PIERO ontology for analysis of biochemical transformations: effective implementation of reaction information in the IUBMB enzyme list.

Science.gov (United States)

Kotera, Masaaki; Nishimura, Yosuke; Nakagawa, Zen-ichi; Muto, Ai; Moriya, Yuki; Okamoto, Shinobu; Kawashima, Shuichi; Katayama, Toshiaki; Tokimatsu, Toshiaki; Kanehisa, Minoru; Goto, Susumu

2014-12-01

Genomics is faced with the issue of many partially annotated putative enzyme-encoding genes for which activities have not yet been verified, while metabolomics is faced with the issue of many putative enzyme reactions for which full equations have not been verified. Knowledge of enzymes has been collected by IUBMB, and has been made public as the Enzyme List. To date, however, the terminology of the Enzyme List has not been assessed comprehensively by bioinformatics studies. Instead, most of the bioinformatics studies simply use the identifiers of the enzymes, i.e. the Enzyme Commission (EC) numbers. We investigated the actual usage of terminology throughout the Enzyme List, and demonstrated that the partial characteristics of reactions cannot be retrieved by simply using EC numbers. Thus, we developed a novel ontology, named PIERO, for annotating biochemical transformations as follows. First, the terminology describing enzymatic reactions was retrieved from the Enzyme List, and was grouped into those related to overall reactions and biochemical transformations. Consequently, these terms were mapped onto the actual transformations taken from enzymatic reaction equations. This ontology was linked to Gene Ontology (GO) and EC numbers, allowing the extraction of common partial reaction characteristics from given sets of orthologous genes and the elucidation of possible enzymes from the given transformations. Further future development of the PIERO ontology should enhance the Enzyme List to promote the integration of genomics and metabolomics.

Reaction between CO2 and phosphate to form carboxyphosphate?

International Nuclear Information System (INIS)

Knight, W.B.; Attwood, P.V.; Cleland, W.W.

1986-01-01

Carboxyphosphate (I) is thought to be an intermediate in the enzymic carboxylation of biotin by bicarbonate and MgATP, and a plausible mechanism of carboxyl transfer to the enolate of biotin involves decarboxylation to CO 2 and phosphate. Such a process would have to be reversible, however, as carboxylase reactions are reversible. To test this possibility, the authors undertook the synthesis of I under anhydrous conditions with a high mole fraction of CO 2 present. CO 2 was distilled into capillary tubes under vacuum containing dry tris-(tetrabutyl-ammonium)-phosphate in dimethylformamide. The tubes were sealed and warmed to -10 or 20 0 C and examined by 31 P NMR. Two resonances (1.7 ppm and -5.0 ppm) in addition to phosphate (3.3 ppm) were observed. The relative ratio of each peak to the phosphate one was dependent on the temperature and the concentrations of PO 4 3- and CO 2 . Upon freezing the tubes, cracking them, and release of the CO 2 , the two additional species decomposed slowly to PO 4 3- , and more rapidly to HPO 4 3- upon the addition of H 2 O. Under some conditions they observed an additional resonance (-7.0 ppm) which is most likely pyrophosphate (PP/sub i/). At high concentrations of PO 4 3- and CO 2 , PP/sub i/ was produced and precipitated from solution. The production of PP/sub i/ is most easily explained by attack of PO 4 3- on I. They are currently trying to identify the unknown species observed in the 31 P NMR spectra

Extinction of laminar partially premixed flames

Energy Technology Data Exchange (ETDEWEB)

Aggarwal, Suresh K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 W. Taylor Street, Room 2039, MC-251, Chicago, IL 60607-7022 (United States)

2009-12-15

Flame extinction represents one of the classical phenomena in combustion science. It is important to a variety of combustion systems in transportation and power generation applications. Flame extinguishment studies are also motivated from the consideration of fire safety and suppression. Such studies have generally considered non-premixed and premixed flames, although fires can often originate in a partially premixed mode, i.e., fuel and oxidizer are partially premixed as they are transported to the reaction zone. Several recent investigations have considered this scenario and focused on the extinction of partially premixed flames (PPFs). Such flames have been described as hybrid flames possessing characteristics of both premixed and non-premixed flames. This paper provides a review of studies dealing with the extinction of PPFs, which represent a broad family of flames, including double, triple (tribrachial), and edge flames. Theoretical, numerical and experimental studies dealing with the extinction of such flames in coflow and counterflow configurations are discussed. Since these flames contain both premixed and non-premixed burning zones, a brief review of the dilution-induced extinction of premixed and non-premixed flames is also provided. For the coflow configuration, processes associated with flame liftoff and blowout are described. Since lifted non-premixed jet flames often contain a partially premixed or an edge-flame structure prior to blowout, the review also considers such flames. While the perspective of this review is broad focusing on the fundamental aspects of flame extinction and blowout, results mostly consider flame extinction caused by the addition of a flame suppressant, with relevance to fire suppression on earth and in space environment. With respect to the latter, the effect of gravity on the extinction of PPFs is discussed. Future research needs are identified. (author)

Exact solutions of some coupled nonlinear diffusion-reaction ...

Indian Academy of Sciences (India)

certain coupled diffusion-reaction (D-R) equations of very general nature. In recent years, various direct methods have been proposed to find the exact solu- tions not only of nonlinear partial differential equations but also of their coupled versions. These methods include unified ansatz approach [3], extended hyperbolic func ...

Dynamics of excited-state intramolecular proton transfer reactions in piroxicam. Role of triplet states

Science.gov (United States)

Cho, Dae Won; Kim, Yong Hee; Yoon, Minjoong; Jeoung, Sae Chae; Kim, Dongho

1994-08-01

The picosecond time-resolved fluorescence and transient absorption behavior of piroxicam at room temperature are reported. The keto tautomer in the excited singlet state ( 1K*) formed via the fast intramolecular proton transfer (≈ 20 ps) is observed. The short-lived (7.5 ns) triplet state of keto tauomer ( 3K*) is generated from 1K * in toluene whereas it is hardly observed in ethanol. Consequently, rapid reverse proton transfer takes place from 3K * to the enol triplet state ( 3E *.

FeCl3-catalysed Zn-mediated allylation of cyclic enol ethers in water

Indian Academy of Sciences (India)

Organic reactions in aqueous medium has attracted global attention from the chemists due to its safe environmentally benign character. Surprisingly, nature also permits aqueous medium for all the enzymatic processes. Since Breslow1 introduced the Diels–Alder reaction in aqueous medium, there has been an increas-.

Partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor

KAUST Repository

Zhang, Xuming

2015-01-01

We studied the relative importance of the reduced field intensity and the background reaction temperature in the partial oxidation of methane in a temperature-controlled dielectric barrier discharge reactor. We obtained important mechanistic insight from studying high-temperature and low-pressure conditions with similar reduced field intensities. In the tested range of background temperatures (297 < T < 773 K), we found that the conversion of methane and oxygen depended on both the electron-induced chemistry and the thermo-chemistry, whereas the chemical pathways to the products were overall controlled by the thermo-chemistry at a given temperature. We also found that the thermo-chemistry enhanced the plasma-assisted partial oxidation process. Our findings expand our understanding of the plasma-assisted partial oxidation process and may be helpful in the design of cost-effective plasma reformers. © 2014 The Combustion Institute.

South-Tibetan partially molten batholiths: geophysical characterization and petrological assessment of their origin

Science.gov (United States)

Hetényi, G.; Pistone, M.; Nabelek, P. I.; Baumgartner, L. P.

2017-12-01

Zones of partial melt in the middle crust of Lhasa Block, Southern Tibet, have been geophysically observed as seismically reflective "bright spots" in the past 20 years. These batholiths bear important relevance for geodynamics as they serve as the principal observation at depth supporting channel-flow models in the Himalaya-Tibet orogen. Here we assess the spatial abundance of and partial melt volume fraction within these crustal batholiths, and establish lower and upper estimate bounds using a joint geophysical-petrological approach.Geophysical imaging constrains the abundance of partial melt zones to 5.6 km3 per surface-km2 on average (minimum: 3.1 km3/km2, maximum: 7.6 km3/km2 over the mapped area). Physical properties detected by field geophysics and interpreted by laboratory measurements constrain the amount of partial melt to be between 5 and 26 percent.We evaluate the compatibility of these estimates with petrological modeling based on geotherms, crustal bulk rock compositions and water contents consistent with the Lhasa Block. These simulations determine: (a) the physico-chemical conditions of melt generation at the base of the Tibetan crust and its transport and emplacement in the middle crust; (b) the melt percentage produced at the source, transported and emplaced to form the observed "bright spots". Two main mechanisms are considered: (1) melting induced by fluids produced during mineral dehydration reactions in the underthrusting Indian lower crust; (2) dehydration-melting reactions caused by heating within the Tibetan crust. We find that both mechanisms demonstrate first-order match in explaining the formation of the partially molten "bright spots". Thermal modelling shows that the Lhasa Block batholiths have only small amounts of melt and only for geologically short times (features of the geodynamic evolution. Their transience excludes both long-distance and long-lasting channel flow transport in Tibet.

Reactions of guanine with methyl chloride and methyl bromide: O6-methylation versus charge transfer complex formation

Science.gov (United States)

Shukla, P. K.; Mishra, P. C.; Suhai, S.

Density functional theory (DFT) at the B3LYP/6-31+G* and B3LYP/AUG-cc-pVDZ levels was employed to study O6-methylation of guanine due to its reactions with methyl chloride and methyl bromide and to obtain explanation as to why the methyl halides cause genotoxicity and possess mutagenic and carcinogenic properties. Geometries of the various isolated species involved in the reactions, reactant complexes (RCs), and product complexes (PCs) were optimized in gas phase. Transition states connecting the reactant complexes with the product complexes were also optimized in gas phase at the same levels of theory. The reactant complexes, product complexes, and transition states were solvated in aqueous media using the polarizable continuum model (PCM) of the self-consistent reaction field theory. Zero-point energy (ZPE) correction to total energy and the corresponding thermal energy correction to enthalpy were made in each case. The reactant complexes of the keto form of guanine with methyl chloride and methyl bromide in water are appreciably more stable than the corresponding complexes involving the enol form of guanine. The nature of binding in the product complexes was found to be of the charge transfer type (O6mG+ · X-, X dbond Cl, Br). Binding of HCl, HBr, and H2O molecules to the PCs obtained with the keto form of guanine did not alter the positions of the halide anions in the PCs, and the charge transfer character of the PCs was also not modified due to this binding. Further, the complexes obtained due to the binding of HCl, HBr, and H2O molecules to the PCs had greater stability than the isolated PCs. The reaction barriers involved in the formation of PCs were found to be quite high (?50 kcal/mol). Mechanisms of genotoxicity, mutagenesis and carcinogenesis caused by the methyl halides appear to involve charge transfer-type complex formation. Thus the mechanisms of these processes involving the methyl halides appear to be quite different from those that involve the

Iteration scheme for implicit calculations of kinetic and equilibrium chemical reactions in fluid dynamics

International Nuclear Information System (INIS)

Ramshaw, J.D.; Chang, C.H.

1995-01-01

An iteration scheme for the implicit treatment of equilibrium chemical reactions in partial equilibrium flow has previously been described. Here we generalize this scheme to kinetic reactions as well as equilibrium reactions. This extends the applicability of the scheme to problems with kinetic reactions that are fast in regions of the flow field but slow in others. The resulting scheme thereby provides a single unified framework for the implicit treatment of an arbitrary number of coupled equilibrium and kinetic reactions in chemically reacting fluid flow. 10 refs., 2 figs

ERC Workshop on Geometric Partial Differential Equations

CERN Document Server

Novaga, Matteo; Valdinoci, Enrico

2013-01-01

This book is the outcome of a conference held at the Centro De Giorgi of the Scuola Normale of Pisa in September 2012. The aim of the conference was to discuss recent results on nonlinear partial differential equations, and more specifically geometric evolutions and reaction-diffusion equations. Particular attention was paid to self-similar solutions, such as solitons and travelling waves, asymptotic behaviour, formation of singularities and qualitative properties of solutions. These problems arise in many models from Physics, Biology, Image Processing and Applied Mathematics in general, and have attracted a lot of attention in recent years.

Increased hydrazine during partial nitritation process in upflow air-lift reactor fed with supernatant of anaerobic digester effluent

Energy Technology Data Exchange (ETDEWEB)

Choi, Jeongdong [University of Alberta, Alberta (Canada); Jung, Sokhee [Samsung SDS, Seoul (Korea, Republic of); Ahn, Young-Ho [Yeungnam University, Gyungsan (Korea, Republic of)

2013-06-15

The optimal balance of ammonium and nitrite is essential for successful operation of the subsequent anammox process. We conducted a partial nitritation experiment using an upflow air-lift reactor to provide operational parameters for achieving the optimal ratio of ammonium to nitrite, by feeding supernatant of anaerobic digester effluent, high-nitrogen containing rejection water. Semi-continuous operation results show that HRT should be set between 15 and 17 hours to achieve the optimum ration of 1.3 of NO{sub 2}-N/NH{sub 4}-N. In the UAR, nitritation was the dominant reaction due to high concentration of ammonia and low biodegradable organics. The influent contained low concentrations of hydroxylamine and hydrazine. However, hydrazine increased during partial nitritation by ⁓60-130% although there was no potential anammox activity in the reactor. The partial nitritation process successfully provided the ratio of nitrogen species for the anammox reaction, and relived the nitrite restraint on the anammox activity by increasing hydrazine concentration.

Spin distribution in preequilibrium reactions for ⁴⁸Ti + n.

Energy Technology Data Exchange (ETDEWEB)

Dashdorj, Dugersuren [North Carolina State Univ., Raleigh, NC (United States)

2005-04-12

Cross section measurements were made of prompt γ-ray production as a function of incident neutron energy on a ⁴⁸Ti sample. Partial γ-ray cross sections for transitions in ^45-48Ti, ^44-48Sc, and ^42-45Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction γ rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The γ-ray excitation functions were converted to partial γ-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). The data are presented for neutron energies E_n between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for E_n up to 20 MeV and the GNASH reaction code for E_n up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). The multistep direct (MSD) part of the FKK theory was calculated for a one-step process. The contribution from higher steps is estimated to be small. The spin distribution of the multistep compound (MSC) part of FKK theory is assumed to be the same as in the compound nucleus. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the γ-ray production cross sections were calculated and compared with experimental data. The difference in the partial γ-ray cross sections using spin distributions with and without

A simple one-step chemistry model for partially premixed hydrocarbon combustion

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Tarrazo, Eduardo [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Sanchez, Antonio L. [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, Leganes 28911 (Spain); Linan, Amable [ETSI Aeronauticos, Pl. Cardenal Cisneros 3, Madrid 28040 (Spain); Williams, Forman A. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093-0411 (United States)

2006-10-15

This work explores the applicability of one-step irreversible Arrhenius kinetics with unity reaction order to the numerical description of partially premixed hydrocarbon combustion. Computations of planar premixed flames are used in the selection of the three model parameters: the heat of reaction q, the activation temperature T{sub a}, and the preexponential factor B. It is seen that changes in q with equivalence ratio f need to be introduced in fuel-rich combustion to describe the effect of partial fuel oxidation on the amount of heat released, leading to a universal linear variation q(f) for f>1 for all hydrocarbons. The model also employs a variable activation temperature T{sub a}(f) to mimic changes in the underlying chemistry in rich and very lean flames. The resulting chemistry description is able to reproduce propagation velocities of diluted and undiluted flames accurately over the whole flammability limit. Furthermore, computations of methane-air counterflow diffusion flames are used to test the proposed chemistry under nonpremixed conditions. The model not only predicts the critical strain rate at extinction accurately but also gives near-extinction flames with oxygen leakage, thereby overcoming known predictive limitations of one-step Arrhenius kinetics. (author)

Circumvention of orbital symmetry restraints by 1,3-H-shifts of enolic radical cations.

Science.gov (United States)

Hudson, Charles E; McAdoo, David J

2004-07-01

The reaction coordinates of 1,3-H-shifts across double bonds are traced by theory for three reactions, CH(3)C(OH)CH(2)(+*) (1) --> CH(3)C(O(+*))CH(3) (2), CH(2)C(OH)(2)(+*) (3) --> CH(3)CO(2)H(+*) (4) and CH(3)C(OH)CH(2)(+*) (1) --> CH(2)C(OH)CH(3)(+*) (1'), to explore how the need to conserve orbital symmetry influences the pathways for these reactions. In the first and second reactions, prior to the start of the H-transfer the methylene rotates from being in the skeletal plane to being bisected by it. Thus these reactions are neither antarafacial nor suprafacial, but precisely between those possibilities. This stems from a counterbalancing between the need to conserve orbital symmetry and the large distorting forces required to attain an allowed antarafacial transition state. In contrast to the first two reactions, 1 --> 1' follows a suprafacial pathway. However, this pathway does not violate conservation of orbital symmetry, as it utilizes lower lying orbitals of appropriate symmetry rather than the antisymmetric uppermost occupied allyl-type orbital. Changes in geometry which presumably produce asymmetric vibrational excitation and the unequal losses of methyl that follow 1 --> 2, i.e., nonergodic behavior, are also characterized.

Development of a novel reactor concept for the partial oxidation of methane to syngas

NARCIS (Netherlands)

Smit, J.; van Sint Annaland, M.; Kuipers, J.A.M.

2004-01-01

The gas-to-liquid process, consisting of the partial oxidation of methane (POM) followed by the Fischer-Tropsch reaction, is a promising alternative to conventional oil processing for the production of liquid fuels. The cost of a conventional POM process is mainly determined by cryogenic air

Modelling of a reverse flow catalytic membrane reactor for the partial oxidation of methane

NARCIS (Netherlands)

Smit, J.; van Sint Annaland, M.; Kuipers, J.A.M.

2003-01-01

Gas-To-Liquid (GTL) processes have great potential as alternative to conventional oil and coal processing for the production of liquid fuels. In GTL-processes the partial oxidation of methane (POM) is combined with the Fischer-Tropsch reaction. An important part of the investment costs of a

A partial-wave analysis of the 3 pi system in the reaction K/sup -/p to pi /sup +/ pi /sup -/ pi /sup 0/ Lambda at 42 GeV/c

CERN Document Server

Cerrada, M; Chaloupka, V; Foster, B; Heinen, P M; Hemingway, R J; Holmgren, S O; Kittel, E W; Losty, Michael J; Massaro, G G G; Metzger, W J; Vergeest, J S M; Wagner, F; Wells, J; Wolters, G F

1977-01-01

A partial-wave analysis of the (3 pi )/sup 0/ system produced peripherally in the reaction K/sup -/p to pi /sup +/ pi /sup -/ pi /sup 0/ Lambda at 4.2 GeV/c is presented. The observation of the weak Lambda decay allows a determination of all the transverse production amplitudes except for two phases. The production of known resonances having decay modes other than 3 pi is used to test the isobar model ansatz. Significant omega (783), phi (1020) and A/sub 2/(1310) production is observed. The spin parity of the omega *(1675) is established as 3/sup -/. No evidence for production of other resonances, such as axial vector-mesons, is found. (23 refs).

Effect of Mass Transport in the Synthesis of Partially Acetylated Dendrimer: Implications for Functional Ligand–Nanoparticle Distributions

OpenAIRE

Mullen, Douglas G.; Borgmeier, Emilee L.; Fang, Ming; McNerny, Daniel Q.; Desai, Ankur; Baker, James R.; Orr, Bradford G.; Holl, Mark M. Banaszak

2010-01-01

Partial acetylation of the amine-terminated poly(amidoamine) dendrimer has been used in the preparation of dendrimer particles conjugated with a wide variety of functional ligands including targeting moieties, therapeutic agents, and dye molecules. The effectiveness of mass transport during the partial acetylation reaction was found to have a major effect on subsequent distributions of dendrimer–ligand components and to be a major source of inconsistency between batches. This study has broad ...

Kinetic modelling of hydro-treatment reactions by study of different chemical groups; Modelisation cinetique des reactions d`hydrotraitement par regroupement en familles chimiques

Energy Technology Data Exchange (ETDEWEB)

Bonnardot, J

1998-11-19

Hydro-treatment of petroleum shortcuts permits elimination of unwanted components in order to increase combustion in engine and to decrease atmospheric pollution. Hydro-desulfurization (HDS), Hydro-denitrogenation (HDN) and Hydrogenation of aromatics (HDA) of a LCO (Light Cycle Oil)-Type gas oil have been studied using a new pilot at a fixed temperature with a NiMo/Al{sub 2}O{sub 3} catalyst. A hydrodynamic study showed that reactions occurring in the up-flow fixed bed reactor that has been used during the experiments, were governed exclusively by chemical reaction rates and not by diffusion. Through detailed chemical analysis, height chemical groups have been considered: three aromatics groups, one sulfided group, one nitrogenized and NH{sub 3}, H{sub 2}S, H{sub 2}. Two Langmuir-Hinshelwood-type kinetic models with either one or two types of sites have been established. The model with two types of site - one site of hydrogenation and one site of hydrogenolysis - showed a better fit in the modeling of the experimental results. This model enables to forecast the influence of partial pressure of H{sub 2}S and partial pressure of H{sub 2} on hydro-treatment reactions of a LCO-type gas oil. (author) 119 refs.

Direct Synthesis of Methanol by Partial Oxidation of Methane with Oxygen over Cobalt Modified Mesoporous H-ZSM-5 Catalyst

Directory of Open Access Journals (Sweden)

Yuni Krisyuningsih Krisnandi

2015-11-01

Full Text Available Partial oxidation of methane over mesoporous catalyst cobalt modified H-ZSM-5 has been carried out. Mesoporous Na-ZSM-5 (Si/Al = 35.4 was successfully synthesized using double template method which has high surface area (450 m2/g and average pore diameter distribution of 1.9 nm. The as-synthesized Na-ZSM-5 was converted to H-ZSM-5 through multi-exchange treatment with ammonium ion solution, causing decreased crystallinity and surface area, but increased porous diameter, due to dealumination during treatment process. Moreover, H-ZSM-5 was loaded with cobalt (Co = 2.5% w by the incipient impregnation method and calcined at 550 °C. Partial oxidation of methane was performed in the batch reactor with 0.75 bar methane and 2 bar of nitrogen (with impurities of 0.5% oxygen as the input at various reaction time (30, 60 and 120 min. The reaction results show that cobalt species in catalyst has an important role, because H-ZSM-5 cannot produce methanol in partial oxidation of methane. The presence of molecular oxygen increased the percentage of methanol yield. The reaction is time-dependent with the highest methanol yield (79% was acquired using Co/H-ZSM-5 catalyst for 60 min.

Recurrent Partial Words

Directory of Open Access Journals (Sweden)

Francine Blanchet-Sadri

2011-08-01

Full Text Available Partial words are sequences over a finite alphabet that may contain wildcard symbols, called holes, which match or are compatible with all letters; partial words without holes are said to be full words (or simply words. Given an infinite partial word w, the number of distinct full words over the alphabet that are compatible with factors of w of length n, called subwords of w, refers to a measure of complexity of infinite partial words so-called subword complexity. This measure is of particular interest because we can construct partial words with subword complexities not achievable by full words. In this paper, we consider the notion of recurrence over infinite partial words, that is, we study whether all of the finite subwords of a given infinite partial word appear infinitely often, and we establish connections between subword complexity and recurrence in this more general framework.

Migratory and resident blue tits Cyanistes caeruleus differ in their reaction to a novel object

Science.gov (United States)

Nilsson, Anna L. K.; Nilsson, Jan-Åke; Alerstam, Thomas; Bäckman, Johan

2010-11-01

Individuals differ consistently in their behavioural reactions towards novel objects and new situations. Reaction to novelty is one part of a suit of individually consistent behaviours called coping strategies or personalities and is often summarised as bold or shy behaviour. Coping strategies could be particularly important for migrating birds exposed to novel environments on their journeys. We compared the average approach latencies to a novel object among migrants and residents in partially migratory blue tits Cyanistes caeruleus. In this test, we found migrating blue tits to have shorter approach latencies than had resident ones. Behavioural reactions to novelty can affect the readiness to migrate and short approach latency may have an adaptive value during migration. Individual behaviour towards novelty might be incorporated among the factors associated with migratory or resident behaviour in a partially migratory population.

Method for sensing and measuring a concentration or partial pressure of a reactant used in a redox reaction

Science.gov (United States)

Findl, E.

1984-12-21

A method for sensing or measuring the partial pressure or concentration of an electroactive species used in conjunction with an electrolyte, the method being characterized by providing a constant current between an anode and a cathode of an electrolyte-containing cell, while measuring changes in voltage that occur between either the anode and cathode or between a reference electrode and one of the main electrodes of the cell, thereby to determine the concentration or partial pressure of the electro-active species as a function of said measured voltage changes. The method of the invention can be practiced using either a cell having only an anode and a cathode, or using a cell having an anode and a cathode in combination with a reference electrode. Accurate measurements of small concentrations or partial pressures of electro-active species are obtainable with the method of the invention, by using constant currents of only a few microamperes between the anode and cathode of the cell, while the concentration-determining voltage is measured.

The alkali-aggregate reaction - concrete microstructure evolution

International Nuclear Information System (INIS)

Regourd, M.; Hornain, H.; Poitevin, P.

1981-01-01

The alkali-aggregate reaction has been studied by scanning electron microscopy and energy dispersive X-ray analysis, electron probe microanalysis, and X-ray diffraction in concretes containing glass aggregates or hornfels and greywacke aggregates. The surface reaction of the natural aggregates in alkaline solutions has been analysed by X-ray photo-electron spectrometry. The study of concretes with glass aggregates stored at 20 degrees Celcius and 100 percent relative humidity has revealed, irrespective of alkali content and type of cement, the formation of a gel containing SiO 2 , Na 2 O, CaO, MgO and Al 2 O 3 . Under heat and pressure (210 degrees Celcius at MPa for 48 hours), the gel crystallizes and yields silicates not very different from tobermorite found in autoclaved normal concretes but cotaining Na and K in solid solutions. The alkali reaction in two natural aggregate concretes, is also shown by the formation of gels and silicate crystals. The progressive structuring of the gels in silicate crystals is promoted by an increase in temperature. Ettringite and Ca(OH) 2 reinforce the alkali-aggregate reaction which may be looked upon as a hydration reaction, partially of the pozzolanic type

New biphasic monocomponent composite material obtained by the partial oxypropylation of bacterial cellulose

International Nuclear Information System (INIS)

Rosa, Joyce Rover; Silva, Ingrid S.V. da; Pasquini, Daniel; Santos, Daniele B. dos; Barud, Hernane S.; Ribeiro, Sidney J.L.

2011-01-01

This study aimed to partial oxypropylation of bacterial cellulose (CB), as well as the characterization of pure CB, oxypropylated CB (CBO) and oxypropylated CB after Soxhlet extraction with hexane (CBOE). The oxypropylation reaction was carried out by propylene oxide polymerization, catalyzed by KOH, in the presence of CB The CB samples, before and after modification, were subjected to analysis of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was possible verify that the partial transformation of bacterial cellulose by inserting a layer of thermoplastic polymer on its surface occurred efficiently, obtaining a biphasic monocomponent composite material. (author)

Estudos sobre o uso do NbCl5 como ácido de Lewis em reações de Povarov

Directory of Open Access Journals (Sweden)

Luiz Carlos Silva-Filho

2011-08-01

Full Text Available RESUMO: O objetivo deste trabalho foi investigar o uso de NbCl5 como ácido de Lewis em reações de cicloadição (Reação Aza-Diels-Alder (Povarov entre bases de Schiff e éteres enólicos. A comparação dos rendimentos, dos produtos formados e do tempo de reação com NbCl5 foi um ponto fundamental da pesquisa. Nas reações de aza-Diels-Alder entre bases de Schiff e éteres enólicos (di-hidropirano ou di-hidrofurano, o NbCl5 se mostrou um ótimo catalisador para a síntese de derivados de pirano- e furanoquinolinas. Estes derivados formam uma importante classe de produtos naturais que apresentam ampla atividade biológica. As reações foram conduzidas com baixa concentração de nióbio e em tempos relativamente curtos, obtendo-se rendimentos variando de 78 a 95%. Studies on the use of NbCl5 as Lewis acid in Povarov reactionsABSTRACT: The aim of this work was to investigate the use of NbCl5 as Lewis acid in cycloadittion reactions [Reaction Aza-Diels-Alder (Povarov] between Schiff bases and enol ethers. Comparison of reaction yields, obtained products as well as reaction time with NbCl5 were also a key point on this work. In the aza-Diels-Alder reactions between Schiff bases and enol ethers (dihydropyran or dihydrofuran, the NbCl5 was an excellent catalyst for the synthesis of pyrano- and furanoquinoline derivatives. These derivatives are an important class of natural products that exhibit wide range of biological activity. The reactions were carried out at low concentration of niobium and in relatively short times, resulting in yields varying from 78 to 95%.

A fast exact sequential algorithm for the partial digest problem.

Science.gov (United States)

Abbas, Mostafa M; Bahig, Hazem M

2016-12-22

Restriction site analysis involves determining the locations of restriction sites after the process of digestion by reconstructing their positions based on the lengths of the cut DNA. Using different reaction times with a single enzyme to cut DNA is a technique known as a partial digestion. Determining the exact locations of restriction sites following a partial digestion is challenging due to the computational time required even with the best known practical algorithm. In this paper, we introduce an efficient algorithm to find the exact solution for the partial digest problem. The algorithm is able to find all possible solutions for the input and works by traversing the solution tree with a breadth-first search in two stages and deleting all repeated subproblems. Two types of simulated data, random and Zhang, are used to measure the efficiency of the algorithm. We also apply the algorithm to real data for the Luciferase gene and the E. coli K12 genome. Our algorithm is a fast tool to find the exact solution for the partial digest problem. The percentage of improvement is more than 75% over the best known practical algorithm for the worst case. For large numbers of inputs, our algorithm is able to solve the problem in a suitable time, while the best known practical algorithm is unable.

Intermediate energy charge-exchange reactions induced by polarized 3He

International Nuclear Information System (INIS)

Kim, B.T.

1998-01-01

Spin polarization transfer is proven to be very useful in obtaining detailed information of the continuum nuclear responses. The data, taken for the (vector p,vector n) reactions, have enabled us to separate the response into the spin longitudinal and transverse components. These partial nuclear responses have been successfully used to make critical tests of nuclear structure models. In the present paper, we first summarize the results of the data and the theoretical analyses made so far. We then discuss information obtainable from the ( 3 vector He,vector t) reaction, emphasizing on the differences and similarities in comparison with the (vector p,vector n) reaction. The results of numerical calculations made for ( 3 vector He,vector t) reactions based on the microscopic distorted wave impulse approximation will also be reported. (orig.)

Possibility of increasing the average rate of heterogeneous catalytic reactions by operating in the self-oscillating regime

Energy Technology Data Exchange (ETDEWEB)

Chumakov, G A; Slinko, M G

1979-05-01

The possibility of increasing the average rate of heterogeneous catalytic reactions by operating in the self-oscillating regime was demonstrated by analyzing a kinetic model of hydrogen interaction with oxygen over a metallic catalyst. Within a certain interval of partial pressures of oxygen, the average reaction rate over a period of oscillation may be over five times that of the steady-state reaction.

Mechanistic insights into the dehalogenation reaction of fluoroacetate/fluoroacetic acid

Science.gov (United States)

Miranda-Rojas, Sebastián; Toro-Labbé, Alejandro

2015-05-01

Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an SN2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the SN2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the SN2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction.

Partial wave analysis of the reaction πN→Nππ and coupled channel analyses of the reactions πN in the CM energy range 1.38-1.74GeV

International Nuclear Information System (INIS)

Dolbeau, Jean.

1976-01-01

The partial wave analysis of 91314 π + -p→Nππ events at nine CM energies between 1.38 and 1.74GeV was performed using the generalized isobar model and assuming the coherent production of Δ, rho and sigma in the final state. A coupled channel analysis (K-matrix formalism) led to the determination of the arbitrary phase at each energy and to smooth the partial wave amplitudes. The paramaters (mass, total and partial widths, signs of coupling constants) of sixteen resonances, among which two new ones, are determined by two different methods. Those results help in classifying the lower-mass excited states of the nucleon in the frame of unitary symmetries, as SU6 [fr

The reaction kinetics of lithium salt with water vapor

International Nuclear Information System (INIS)

Balooch, M.; Dinh, L.N.; Calef, D.F.

2002-01-01

The interaction of lithium salt (LiH and/or LiD) with water vapor in the partial pressure range of 10 -5 -2657 Pa has been investigated. The reaction probability of water with LiH cleaved in an ultra high vacuum environment was obtained using the modulated molecular beam technique. This probability was 0.11 and independent of LiH surface temperature, suggesting a negligible activation energy for the reaction in agreement with quantum chemical calculations. The value gradually reduced, however, to 0.007 as the surface concentration of oxygen containing product approached full coverage. As the film grew beyond a monolayer, the phase lag of hydrogen product increased from 0 deg. C to 20 deg. C and the reaction probability reduced further until it approached our detection limit (∼10 -4 ). This phase lag was attributed to a diffusion-limited process in this regime. For micrometer thick hydroxide films grown in high moisture concentration environment on LiD and LiH, the reaction probability reduced to ∼4x10 -7 and was independent of exposure time. In this regime of thick hydroxide films (LiOH and/or LiOD), microcracks generated in the films to release stress provided easier pathways for moisture to reach the interface. A modified microscope, capable of both atomic force microscopy and nanoindentation, was also employed to investigate the surface morphology of hydroxide monohydrate (LiOH · H 2 O and/or LiOD · H 2 O) grown on hydroxide at high water vapor partial pressures and the kinetics of this growth

Mechanochemical Association Reaction of Interfacial Molecules Driven by Shear.

Science.gov (United States)

Khajeh, Arash; He, Xin; Yeon, Jejoon; Kim, Seong H; Martini, Ashlie

2018-05-29

Shear-driven chemical reaction mechanisms are poorly understood because the relevant reactions are often hidden between two solid surfaces moving in relative motion. Here, this phenomenon is explored by characterizing shear-induced polymerization reactions that occur during vapor phase lubrication of α-pinene between sliding hydroxylated and dehydroxylated silica surfaces, complemented by reactive molecular dynamics simulations. The results suggest that oxidative chemisorption of the α-pinene molecules at reactive surface sites, which transfers oxygen atoms from the surface to the adsorbate molecule, is the critical activation step. Such activation takes place more readily on the dehydroxylated surface. During this activation, the most strained part of the α-pinene molecules undergoes a partial distortion from its equilibrium geometry, which appears to be related to the critical activation volume for mechanical activation. Once α-pinene molecules are activated, association reactions occur between the newly attached oxygen and one of the carbon atoms in another molecule, forming ether bonds. These findings have general implications for mechanochemistry because they reveal that shear-driven reactions may occur through reaction pathways very different from their thermally induced counterparts and specifically the critical role of molecular distortion in such reactions.

Partial oxidation of n-hexadecane through decomposition of hydrogen peroxide in supercritical water

KAUST Repository

Alshammari, Y.M.

2015-01-01

© 2014 The Institution of Chemical Engineers. This work reports the experimental analysis of partial oxidation of n-hexadecane under supercritical water conditions. A novel reactor flow system was developed which allows for total decomposition of hydrogen peroxide in a separate reactor followed partial oxidation of n-hexadecane in a gasification reactor instead of having both reactions in one reactor. The kinetics of hydrothermal decomposition of hydrogen peroxide was studied in order to confirm its full conversion into water and oxygen under the desired partial oxidation conditions, and the kinetic data were found in a good agreement with previously reported literature. The gas yield and gasification efficiency were investigated under different operating parameters. Furthermore, the profile of C-C/C=C ratio was studied which showed the favourable conditions for maximising yields of n-alkanes via hydrogenation of their corresponding 1-alkenes. Enhanced hydrogenation of 1-alkenes was observed at higher O/C ratios and higher residence times, shown by the increase in the C-C/C=C ratio to more than unity, while increasing the temperature has shown much less effect on the C-C/C=C ratio at the current experimental conditions. In addition, GC-MS analysis of liquid samples revealed the formation of heavy oxygenated compounds which may suggest a new addition reaction to account for their formation under the current experimental conditions. Results show new promising routes for hydrogen production with in situ hydrogenation of heavy hydrocarbons in a supercritical water reactor.

Synthesis and Properties of Some polyurethane/ Partially Aromatic Polyester Casting Samples

International Nuclear Information System (INIS)

Sadek, E.M.; Mazroua, A.M.; Emam, A.S.; Motawie, A.M.

2005-01-01

A series of partially aromatic terephthalate polyesters were synthesized by melt transesterification of dimethyl terephthalate with various types of aliphatic diol compounds in 1:1.1 molar ratio. Ethylene-, di-, tri-, tetra ethylene glycol and polyethylene glycol with different molecular weights 1000, 4000, 6000 as well as the prepared dihydroxy natural rubber were used. Another series of partially aromatic adipate and sebacate polyesters based on the prepared bisphenol A and its tetrabromo derivative were also synthesized by direct polycondensation esterification with adipic and sebacic acid. Polyurethane with NCO/OH ratio equal 4 was prepared from the reaction of 2,4 toluene diisocyanate with polyethylene glycol 1000. The prepared polyurethane was mixed with different weight percentages (2, 4, 6, 8, 10 or 12 % w/w) of the prepared partially aromatic polyesters to give polyurethane/polyester compositions. Mechanical and electrical properties as well as water and chemical resistance of the prepared film samples with thickness 3-4 mm were determined and compared with those of polyurethane film sample without polyester. The data indicate that 10 % w/w of the added partially aromatic polyester increases polyurethane tensile strength, improves its insulation properties and hydrolytic stability as well as its chemical resistance. Film samples based on bisphenol A impart excellent properties as compared with those based on aliphatic glycol species and dihydroxy natural rubber. Keywords: Partially aromatic polyesters, Dimethyl terephthalate, Glycols, Bisphenol A, Tetrabromo bisphenol A, Natural rubber, Adipic acid, Sebacic acid, Polyurethane, Casting

Highly efficient and generalized asymmetric synthesis of quaternary stereogenic carbon-containing β-amino indanones/indanoles via Mannich-type additions between 1-indanones and N-tert-butanesulfinylketimines.

Science.gov (United States)

Wu, Lingmin; Xie, Chen; Mei, Haibo; Soloshonok, Vadim A; Han, Jianlin; Pan, Yi

2014-07-14

Here we report that, unlike other ketones, 1-indanone and acetophenone derived enolates undergo Mannich-type addition reactions with N-tert-butanesulfinyl ketimines with excellent yields (up to 98%) and diastereoselectivity (>99/1). The resulting compounds represent a new type of biologically relevant β-aminoketone derivative bearing quaternary stereogenic carbon, which could be further converted into the corresponding β-amino ketones and β-amino alcohols, possessing three consecutive stereogenic centres.

Nucleophilic Substitution Reactions of N-Methyl α-Bromoacetanilides with Benzylamines in Dimethyl Sulfoxide

International Nuclear Information System (INIS)

Adhikary, Keshab Kumar; Lee, Hai Whang

2011-01-01

Kinetic studies of the reactions of N-methyl-Y-α-bromoacetanilides with substituted X-benzylamines have been carried out in dimethyl sulfoxide at 25.0 .deg. C. The Hammett plots for substituent X variations in the nucleophiles (log k N vs σ X ) are slightly biphasic concave upwards/downwards, while the Bronsted plots (log k N vs pK a ) are biphasic concave downwards with breakpoints at X = H. The Hammett plots for substituent Y variations in the substrates (log k N vs σ Y ) are biphasic concave upwards/downwards with breakpoints at Y = H. The cross-interaction constant ρ XY values are all negative: ρ XY = -0.32 for X = Y = electron-donating: -0.22 for X = electron-withdrawing and Y = electron-donating: -1.80 for X = electron-donating and Y = electronwithdrawing: -1.43 for X = Y = electron-withdrawing substituents. Deuterated kinetic isotope effects are primary normal (k H /k D > 1) for Y = electron-donating, while secondary inverse (k H /k D < 1) for Y = electronwithdrawing substituent. The proposed mechanisms of the benzylaminolyses of N-methyl-Y-α-bromoacetanilides are a concerted mechanism with a five membered ring TS involving hydrogen bonding between hydrogen (deuterium) atom in N-H(D) and oxygen atom in C = O for Y = electron-donating, while a concerted mechanism with an enolate-like TS in which the nucleophile attacks the α-carbon for Y = electronwithdrawing substituents

Forward pion-nucleon charge exchange reaction and Regge constraints

International Nuclear Information System (INIS)

Huang Fei; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meibner, U.-G.

2009-01-01

We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude. (authors)

Response of partially premixed flames to acoustic velocity and equivalence ratio perturbations

Energy Technology Data Exchange (ETDEWEB)

Kim, K.T.; Lee, J.G.; Quay, B.D.; Santavicca, D.A. [Center for Advanced Power Generation, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA (United States)

2010-09-15

This article describes an experimental investigation of the forced response of a swirl-stabilized partially premixed flame when it is subjected to acoustic velocity and equivalence ratio fluctuations. The flame's response is analyzed using phase-resolved CH{sup *} chemiluminescence images and flame transfer function (FTF) measurements, and compared with the response of a perfectly premixed flame under acoustic perturbations. The nonlinear response of the partially premixed flame is manifested by a partial extinction of the reaction zone, leading to rapid reduction of flame surface area. This nonlinearity, however, is observed only when the phase difference between the acoustic velocity and the equivalence ratio at the combustor inlet is close to zero. The condition, {delta}{phi}{sub {phi}}'-V'{approx}0 , indicates that reactant mixtures with high equivalence ratio impinge on the flame front with high velocity, inducing large fluctuations of the rate of heat release. It is found that the phase difference between the acoustic velocity and equivalence ratio nonuniformities is a key parameter governing the linear/nonlinear response of a partially premixed flame, and it is a function of modulation frequency, inlet velocity, fuel injection location, and fuel injector impedance. The results presented in this article will provide insight into the response of a partially premixed flame, which has not been well explored to date. (author)

Adverse reaction after hyaluronan injection for minimally invasive papilla volume augmentation

DEFF Research Database (Denmark)

Bertl, Kristina; Gotfredsen, Klaus; Jensen, Simon S

2017-01-01

or mucosal necrosis or any permanent damage. CONCLUSION: Most likely, water attraction over time by the highly hygroscopic HY, exerted progressively an external vascular compression and at least partial occlusion of neighbouring blood vessels. An infection or an allergic reaction seems unlikely, since all...

Partial wave analysis of KKPI system in D and E/IOTA region

International Nuclear Information System (INIS)

Chung, S.U.; Fernow, R.; Kirk, H.

1985-01-01

A partial wave analysis and a Dalitz plot analysis of high-statistics data from reaction π - p → K + K/sub S/π - n at 8.0 GeV/c show that the D(1285) is a J/sup PG/ = 1 ++ state and the E(1420) a J/sup PG/ = 0 -+ state both with a substantial deltaπ decay mode. The 1 ++ K*anti K wave exhibits a rapid rise near threshold but no evidence of a resonance in the E region. The assignment of J/sup PG/ = O -+ to the E is confirmed from a Dalitz-plot analysis of the reaction pp → K + K/sub S/π - X 0 . 11 refs., 5 figs

On the time behaviour of the concentration of pyrazinium radical cations in the early stage of the Maillard reaction

Science.gov (United States)

Stoesser, Reinhard; Klein, Jeannette; Peschke, Simone; Zehl, Andrea; Cämmerer, Bettina; Kroh, Lothar W.

2007-08-01

During the early stage of the Maillard reaction pyrazinium radical cations were detected by ESR within the reaction system D-glucose/glycine. The spectra were characterized by completely resolved hyperfine structure. The partial pressure of oxygen and the radical concentrations were measured directly in the reaction mixture by ESR using solutions of the spin probe TEMPOL and of DPPH, respectively. There are quantitative and qualitative relations of the actual concentration of the radical ions to the partial pressure of oxygen, the temperature-time regime and the mechanical mixing of the reaction system. These macroscopic parameters significantly affect both the induction period and the velocity of the time-dependent formation of free radicals. From in situ variations of p(O 2) and p(Ar) including the connected mixing effects caused by the passing the gases through the reaction mixture, steric and chemical effects of the stabilization of the radical ions were established. The determination of suitable and relevant conditions for stabilization and subsequent radical reactions contributes to the elucidation of the macroscopically known antioxidant activity of Maillard products.

Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

Energy Technology Data Exchange (ETDEWEB)

Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J; Tsujimura, T; Osswald, P; Kohse-Hoinghaus, K

2010-12-12

Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temperature and low temperature reaction pathways. In this study, the primary experimental validation target for the model is premixed flat low-pressure flame species profiles obtained using molecular beam mass spectrometry (MBMS). The model is also validated against previously published data for premixed flame velocity and n-butanol rapid compression machine and shock tube ignition delay. The agreement with these data sets is reasonably good. The dominant reaction pathways at the various pressures and temperatures studied are elucidated. At low temperature conditions, we found that the reaction of alphahydroxybutyl with O{sub 2} was important in controlling the reactivity of the system, and for correctly predicting C{sub 4} aldehyde profiles in low pressure premixed flames. Enol-keto isomerization reactions assisted by HO{sub 2} were also found to be important in converting enols to aldehydes and ketones in the low pressure premixed flames. In the paper, we describe how the structural features of the four different butanol isomers lead to differences in the combustion properties of each isomer.

Partial tooth gear bearings

Science.gov (United States)

Vranish, John M. (Inventor)

2010-01-01

A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.

Selection of anthracnose resistant common beans using detached leaves in partially controlled environment

Directory of Open Access Journals (Sweden)

Alisson Campos Pereira

2014-08-01

Full Text Available The objectives of this study were to evaluate the possibility of selecting anthracnose resistant common bean plants using detached primary leaves in partially controlled environment of a greenhouse and identify differences in the reaction of genotypes to anthracnose. The common bean cultivars Ouro Negro, OuroVermelho, ManteigãoFosco 11, Rudá, Rudá-R, VP8, BRSMG Madrepérola, Pérola, MeiaNoite and BRSMG Talismãwere characterizedfor resistance to the races 65, 81 and 453 of Colletotrichum lindemuthianum and the method of detached primary leaves was compared to the method with the traditional inoculation of plants at the phenological stage V2. The lines Rudá, Rudá-R and Pérola were inoculated with the races 65 and 453 of C. lindemuthianum, aiming to assess the rate of coincidence of anthracnose severity by both inoculation methods. In general, the two methods presented similar results for the reaction of the cultivars. The use of detached primary leaves of common bean plants in the partially controlled environment was feasible for selection of plants resistant to anthracnose and has the advantages of low-needed infrastructure and reduction of resources, space and time.

New results on the Roper resonance and the P{sub 11} partial wave

Energy Technology Data Exchange (ETDEWEB)

Sarantsev, A.V. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Fuchs, M. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Kotulla, M. [Physikalisches Institut, Universitaet Basel (Switzerland); II. Physikalisches Institut, Universitaet Giessen (Germany); Thoma, U. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); II. Physikalisches Institut, Universitaet Giessen (Germany); Ahrens, J. [Institut fuer Kernphysik, Universitaet Mainz (Germany); Annand, J.R.M. [Department of Physics and Astronomy, University of Glasgow (United Kingdom); Anisovich, A.V. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Anton, G. [Physikalisches Institut, Universitaet Erlangen (Germany); Bantes, R. [Physikalisches Institut, Universitaet Bonn (Germany); Bartholomy, O. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Beck, R. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Institut fuer Kernphysik, Universitaet Mainz (Germany); Beloglazov, Yu. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Castelijns, R. [KVI, Groningen (Netherlands); Crede, V. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Department of Physics, Florida State University (United States); Ehmanns, A.; Ernst, J.; Fabry, I. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany); Flemming, H. [Physikalisches Institut, Universitaet Bochum (Germany); Foesel, A. [Physikalisches Institut, Universitaet Erlangen (Germany); Funke, Chr. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn (Germany)] (and others)

2008-01-17

Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined. Pole positions and residues of the P{sub 11} partial wave are studied in a combined analysis of pion- and photo-induced reactions. We find the Roper pole at {l_brace}(1371{+-}7)-i(92{+-}10){r_brace} MeV and an elasticity of 0.61{+-}0.03. The largest decay coupling is found for the N{sigma} ({sigma}=({pi}{pi})-S-wave). The analysis is based on new data on {gamma}p{yields}p{pi}{sup 0}{pi}{sup 0} for photons in the energy range from the two-pion threshold to 820 MeV from TAPS at Mainz and from 0.4 to 1.3 GeV from Crystal Barrel at Bonn and includes further data from other experiments. The partial wave analysis excludes the possibility that the Roper resonance is split into two states with different partial decay widths.

Biomass hydrolysis inhibition at high hydrogen partial pressure in solid-state anaerobic digestion.

Science.gov (United States)

Cazier, E A; Trably, E; Steyer, J P; Escudie, R

2015-08-01

In solid-state anaerobic digestion, so-called ss-AD, biogas production is inhibited at high total solids contents. Such inhibition is likely caused by a slow diffusion of dissolved reaction intermediates that locally accumulate. In this study, we investigated the effect of H2 and CO2 partial pressure on ss-AD. Partial pressure of H2 and/or CO2 was artificially fixed, from 0 to 1 557mbars for H2 and from 0 to 427mbars for CO2. High partial pressure of H2 showed a significant effect on methanogenesis, while CO2 had no impact. At high [Formula: see text] , the overall substrate degradation decreased with no accumulation of metabolites from acidogenic bacteria, indicating that the hydrolytic activity was specifically impacted. Interestingly, such inhibition did not occur when CO2 was added with H2. This result suggests that CO2 gas transfer is probably a key factor in ss-AD from biomass. Copyright © 2015 Elsevier Ltd. All rights reserved.

Reaction of ketene ions with ammonia

International Nuclear Information System (INIS)

Iraqi, M.; Lifshitz, C.; Reuben, B.G.

1991-01-01

Reactions of ketene ions with NH 3 , ND 3 , H 2 O, and CH 4 were investigated in a selected ion flow tube (SIFT). There were no observable products for H 2 O and CH 4 and no ion/neutral complex stabilization in any of the systems investigated. The ammonia system demonstrated two reaction channels, in agreement with previous FTICR data (1) distonic ion CH 2 NH 3 sm-bullet + formation, with a branching ratio of 0.2 and (2) proton transfer, with a branching ratio of 0.8. The overall second-order rate constant for NH 3 is (2.2 ± 0.15) x 10 -9 cm 3 molecule -1 s -1 , in agreement with the gas kinetic ion-dipole collision rate. Isotope scrambling was studied for primary (CH 2 CO + ) and for secondary (CH 2 NX 3 sm-bullet + and NX 4 + , X = H or D) proton-transfer reactions with ND 3 ; CH 2 NH 3 sm-bullet + appears to transfer an X + ion to ND 3 without any scrambling. CH 2 CO sm-bullet + undergoes reactions with partial scrambling and NX 4 + seems to react with almost complete scrambling. The results are compared with these of Adams, Smith, and Henchman on the NH 4 + /ND 3 system

A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions.

Science.gov (United States)

Zhou, Jicheng; Xu, Wentao; You, Zhimin; Wang, Zhe; Luo, Yushang; Gao, Lingfei; Yin, Cheng; Peng, Renjie; Lan, Lixin

2016-04-27

The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea') decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea' under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea' was determined. MW irradiation energy was partially transformed to reduce the Ea', and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology.

Mechanistic insights into the dehalogenation reaction of fluoroacetate/fluoroacetic acid

International Nuclear Information System (INIS)

Miranda-Rojas, Sebastián; Toro-Labbé, Alejandro

2015-01-01

Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an S N 2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the S N 2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the S N 2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction

Mechanistic insights into the dehalogenation reaction of fluoroacetate/fluoroacetic acid

Energy Technology Data Exchange (ETDEWEB)

Miranda-Rojas, Sebastián, E-mail: sebastian.miranda@unab.cl [Chemical Processes and Catalysis (CPC), Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Avenida República 275, Santiago (Chile); Toro-Labbé, Alejandro [Laboratorio de Química Teórica Computacional (QTC), Facultad de Química, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago (Chile)

2015-05-21

Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an S{sub N}2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the S{sub N}2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the S{sub N}2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction.

Structural changes of noble metal catalysts during ignition and extinction of the partial oxidation of methane studied by advanced QEXAFS techniques

DEFF Research Database (Denmark)

Grunwaldt, Jan-Dierk; Beier, M.; Kimmerle, B.

2009-01-01

The dynamics of the ignition and extinction of the catalytic partial oxidation (CPO) of methane to hydrogen and carbon monoxide over Pt-Rh/Al2O3 and Pt/Al2O3 were studied in the subsecond timescale using quick-EXAFS with a novel cam-driven X-ray monochromator employing Si(111) and Si(311) crystals...... to discuss the potential and limitation of this technique in catalysis and related areas. With respect to the noble metal catalysed partial oxidation of methane, several interesting observations were made: structural changes during ignition were-independent of the chosen reaction conditions......-significantly faster than during the extinction of the reaction. The dynamic behavior of the catalysts was dependent on the flow conditions and the respective noble metal component(s). Higher reaction gas flow led to a faster ignition process. While the ignition over Pt-Rh/Al2O3 occurred at lower temperature than over...

Studies toward the synthesis of palhinine lycopodium alkaloids: a Morita-Baylis-Hillman/intramolecular Diels-Alder approach.

Science.gov (United States)

Sizemore, Nicholas; Rychnovsky, Scott D

2014-02-07

A synthetic route to the isotwistane core of palhinine lycopodium alkaloids is described. A Morita-Baylis-Hillman/intramolecular Diels-Alder (IMDA) strategy sets the vicinal all-carbon quaternary centers present in this family of natural products. The regioselectivity of the IMDA reaction is dictated by the conditions employed for silyl enol ether formation, with one set of conditions providing the core of cardionine and alternate conditions generating the desired isotwistane core of isopalhinine.

Implant-tooth-supported fixed partial prostheses: correlations between in vivo occlusal bite forces and marginal bone reactions.

Science.gov (United States)

Akça, Kivanç; Uysal, Serdar; Cehreli, Murat Cavit

2006-06-01

To evaluate maximal occlusal bite forces (MOF) and marginal bone level (MBL) changes in patients with implant-tooth-supported fixed partial prostheses (FPP). Twenty nine partially edentulous patients consecutively who received 34 three-occlusal unit FPP with terminal implant and tooth support were subjected to quantification of MOFs using a sub-miniature load cell connected to a data acquisition system and measurement of the MBL changes around implants in digitalized periapical radiographs obtained at prostheses delivery and 24-month follow-up. MOFs for implant support (mean: 353.61 N) significantly differed from tooth support (mean: 275.48 N) (P 0.05). MBL changes at mesial and distal sites of the implants at 24 months of functional loading were 0.28 and 0.097 mm respectively. Although MOFs under functional loading might indicate an increase in load participation for supporting implant, the rigid connection between implant and natural tooth via three-occlusal unit FPP does not jeopardize the time-dependent MBL stability of the implant under functional loads.

Giant partially thrombosed 4 th ventricular posterior inferior cerebellar artery aneurysm; microsurgical management

Directory of Open Access Journals (Sweden)

Forhad Hossain Chowdhury

2014-01-01

Full Text Available A 42-year-old woman presented with a 3-month history of progressive occipital headache, vomiting, walking difficulty, and repeated fall. She had no history of sudden and severe headache. She had positive cerebellar signs, predominantly on the right side. Computerized tomography (CT scan, CT angiogram, and magnetic resonance image (MRI of the brain showed suspected partially thrombosed giant 4 th ventricular posterior inferior cerebellar artery aneurysm. Patient developed severe hypersensitivity reaction during both CT scan and MRI after contrast injection. Though needed, digital subtraction angiogram (DSA of cerebral vessels was not done. The aneurysm was managed by microsurgical clipping of the aneurysm neck and partial excision of thrombosed aneurysm. Here, we report the details of management of these difficult giant aneurysm without DSA.

Effect of Mass-Transport Limitations on the Performance of a Packed Bed Membrane Reactor for Partial Oxidations. Transport from the Membrane to the Packed Bed

NARCIS (Netherlands)

van Sint Annaland, M.; Kurten, U.; Kuipers, J.A.M.

2007-01-01

With a packed bed membrane reactor, the product yield can be significantly enhanced for partial oxidation systems, via distributive addition of oxygen to the reaction mixture along the axial coordinate of the reactor, provided that the reaction order in oxygen of the formation rate of the target

Effect of mass-transport limitations on the performance of a packed bed membrane reactor for partial oxidations. Transport from the membrane to the packed bed

NARCIS (Netherlands)

Sint Annaland, van M.; Kurten, U.; Kuipers, J.A.M.

2007-01-01

With a packed bed membrane reactor, the product yield can be significantly enhanced for partial oxidation systems, via distributive addition of oxygen to the reaction mixture along the axial coordinate of the reactor, provided that the reaction order in oxygen of the formation rate of the target

Experts' understanding of partial derivatives using the Partial Derivative Machine

OpenAIRE

Roundy, David; Dorko, Allison; Dray, Tevian; Manogue, Corinne A.; Weber, Eric

2014-01-01

Partial derivatives are used in a variety of different ways within physics. Most notably, thermodynamics uses partial derivatives in ways that students often find confusing. As part of a collaboration with mathematics faculty, we are at the beginning of a study of the teaching of partial derivatives, a goal of better aligning the teaching of multivariable calculus with the needs of students in STEM disciplines. As a part of this project, we have performed a pilot study of expert understanding...

Finite-rate chemistry modelling of non-conventional combustion regimes using a Partially-Stirred Reactor closure: combustion model formulation and implementation details

OpenAIRE

Li, Zhiyi; Ferrarotti, Marco; Cuoci, Alberto; Parente, Alessandro

2018-01-01

The present work focuses on the numerical simulation ofModerate or Intense Low oxygen Dilution combustion condition, using thePartially-Stirred Reactor model for turbulence-chemistry interactions.The Partially-Stirred Reactor model assumes that reactions are confinedin a specific region of the computational cell, whose mass fractiondepends both on the mixing and the chemical time scales. Therefore, theappropriate choice of mixing and chemical time scales becomes crucial toensure the accuracy ...

Partial resistance to stripe rust and its effect on sustainability of wheat yield

International Nuclear Information System (INIS)

Qamar, M.; Din, R.U.; Gardazi, D.A.

2014-01-01

Stripe rust (Puccinia striiformis Westend. f. sp. tritici) poses a serious threat to wheat production in cooler areas of Pakistan. The 70% area of wheat in Pakistan is prone to stripe rust disease. It can cause 10-17% yield losses if susceptible cultivars are planted under favorable conditions. Level of partial plant resistance in bread wheat and its impact on sustainable wheat production was studied at the National Agricultural Research Centre, Islamabad under natural conditions in the field. Eleven Pakistani commercial wheat cultivars/advance lines including check (Inqalab 91) were assessed for the level of partial resistance against stripe rust using Area Under the Disease Progress Curve (AUDPC), disease severity (DS) and epidemic growth rate in comparison with wheat cultivar, Inqalab 91. During 2007 cropping season, natural epidemic was developed and relative AUDPC was recorded from 0 to 100% whereas the 2008 cropping season was dry and no stripe rust appeared. Two advanced lines (NR 268 and NR 285) showed the infection type (IT) less than 7 (incompatible reaction) to the mixture of prevailing stripe rust inoculums. Very low level of DS and AUDPC were recorded in the remaining cultivars/lines indicating a high level of partial resistance to stripe rust compared to the susceptible check cultivar, Inqalab 91. Among eight cultivars/lines that showed compatible type of reaction (IT greater then equal to 7), one was resistant (relative AUDPC = 20% of Inqalab 91) and six showed very high resistance levels (relative AUDPC greater then equal to 5%). Maximum level of resistance (relative AUDPC = 0.1%) was observed in advanced line, NR 271. The wheat cultivars/lines that showed a slow disease development (low DS and AUDPC), could be considered as -1 partially resistant for stripe rust infection. The yield (2178 kg ha) of susceptible check cultivar Inqalab-91 during 2007 was reduced to 45% as -1 compared to its yield (3945 kg ha) in epidemic free year (2008). Thus the use

GC of catalytic reactions products involved in the promising fuel synthesis

Energy Technology Data Exchange (ETDEWEB)

Zheivot, V.; Sazonova, N. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Boreskov Inst. of Catalysis

2012-09-15

Catalytic reactions involved in the synthesis of the promising kinds of novel fuel and products formed in these reactions were systematized according to the resulting fuel type. Generalization of the retention of the substances comprising these products is presented. Chromatograms exhibiting their separation on chromatographic materials with the surface of different chemical properties are summarized. We propose procedures for gas-chromatographic analysis of the catalytic reactions products formed in the synthesis of hydrogen, methanol, dimethyl ether and hydrocarbons as a new generation of fuel alternative to petroleum and coal. For partial oxidation of methane into synthesis gas, on-line determination of the components obtained in the reaction was carried out by gas chromatography and gas analyzer based on different physicochemical methods (IR spectroscopy and electrochemical methods). Similarity of the results obtained using these methods is demonstrated. (orig.)

Gravity Effects Observed In Partially Premixed Flames

Science.gov (United States)

Puri, Ishwar K.; Aggarwal, Suresh K.; Lock, Andrew J.; Gauguly, Ranjan; Hegde, Uday

2003-01-01

Partially premixed flames (PPFs) contain a rich premixed fuel air mixture in a pocket or stream, and, for complete combustion to occur, they require the transport of oxidizer from an appropriately oxidizer-rich (or fuel-lean) mixture that is present in another pocket or stream. Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions. Partial premixing, therefore, represents that condition when the equivalence ratio (phi) in one portion of the flowfield is greater than unity, and in another section its value is less than unity. In general, for combustion to occur efficiently, the global equivalence ratio is in the range fuel-lean to stoichiometric. These flames can be established by design by placing a fuel-rich mixture in contact with a fuel-lean mixture, but they also occur otherwise in many practical systems, which include nonpremixed lifted flames, turbulent nonpremixed combustion, spray flames, and unwanted fires. Other practical applications of PPFs are reported elsewhere. Although extensive experimental studies have been conducted on premixed and nonpremixed flames under microgravity, there is a absence of previous experimental work on burner stabilized PPFs in this regard. Previous numerical studies by our group employing a detailed numerical model showed gravity effects to be significant on the PPF structure. We report on the results of microgravity experiments conducted on two-dimensional (established on a Wolfhard-Parker slot burner) and axisymmetric flames (on a coannular burner) that were investigated in a self-contained multipurpose rig. Thermocouple and radiometer data were also used to characterize the thermal transport in the flame.

Palm H-FAME Production through Partially Hydrogenation using Nickel/Carbon Catalyst to Increase Oxidation Stability

Directory of Open Access Journals (Sweden)

Ramayeni Elsa

2018-01-01

Full Text Available One of the methods to improve the oxidation stability of palm biodiesel is through partially hydrogenation. The production using Nickel/Carbon catalyst to speed up the reaction rate. Product is called Palm H-FAME (Hydrogenated FAME. Partial hydrogenation breaks the unsaturated bond on FAME (Fatty Acid Methyl Ester, which is a key component of the determination of oxidative properties. Changes in FAME composition by partial hydrogenation are predicted to change the oxidation stability so it does not cause deposits that can damage the injection system of diesel engine, pump system, and storage tank. Partial hydrogenation is carried out under operating conditions of 120 °C and 6 bar with 100:1, 100:3, 100:5, 100:10 % wt catalyst in the stirred batch autoclave reactor. H-FAME synthesis with 100:5 % wt Ni/C catalyst can decrease the iodine number which is the empirical measure of the number of unsaturated bonds from 91.78 to 82.38 (g-I2/100 g with an increase of oxidation stability from 585 to 602 minutes.

Measurement of the γγ partial width of the χ2 charmonium resonance

International Nuclear Information System (INIS)

Armstrong, T.A.; Bettoni, D.; Bharadwaj, V.; Biino, C.; Borreani, G.; Broemmelsiek, D.; Buzzo, A.; Calabrese, R.; Ceccucci, A.; Cester, R.; Church, M.; Dalpiaz, P.; Dalpiaz, P.F.; Dibenedetto, R.; Dimitroyannis, D.; Fabbri, M.; Fast, J.; Gianoli, A.; Ginsburg, C.M.; Gollwitzer, K.; Hahn, A.; Hasan, M.A.; Hsueh, S.; Lewis, R.; Luppi, E.; Macri, M.; Majewska, A.M.; Mandelkern, M.; Marchetto, F.; Marinelli, M.; Marques, J.; Marsh, W.; Martini, M.; Masuzawa, M.; Menichetti, E.; Migliori, A.; Mussa, R.; Palestini, S.; Pallavicini, M.; Pastrone, N.; Patrignani, C.; Peoples, J. Jr.; Pesando, L.; Petrucci, F.; Pia, M.G.; Rapidis, P.A.; Ray, R.; Reid, J.; Rinaudo, G.; Roccuzzo, B.; Rosen, J.; Santroni, A.; Sarmiento, M.; Savrie, M.; Scalisi, A.; Schultz, J.; Seth, K.K.; Smith, A.; Smith, G.A.; Sozzi, M.; Trokenheim, S.; Weber, M.F.; Werkema, S.; Zhang, Y.; Zhao, J.; Zioulas, G.

1993-01-01

The E760 Collaboration has studied the reaction bar pp→χ 2 →γγ using a hydrogen gas jet target in the Fermilab antiproton acumulator ring. The following values are obtained for the branching ratio and partial width to two photons; B(χ 2 →γγ)=(1.60±0.45)x10 -4 and Γ(χ 2 →γγ)=321±95 eV

Kinetic Modeling of the Reaction Rate for Quartz and Carbon Black Pellet

Science.gov (United States)

Li, Fei; Tangstad, Merete

2018-06-01

The kinetic modeling for the carbothermal reduction reaction rate in quartz and carbon black pellets is studied at different temperatures, under varying CO partial pressures in ambient atmosphere, varying carbon contents, different quartz particle sizes, and different crucible opening areas. Carbon black is produced by the cracking of natural gas. The activation energy of the SiC-producing step was determined to be 594 kJ/mol. The averaged pre-exponential factor A obtained from 1898 K, 1923 K, and 1948 K (1625 °C, 1650 °C, and 1675 °C) is 2.62E+16 min-1. The reaction rate of the gas-solid interface factor, fix-C content ( X fix-C), temperature ( T), and CO partial pressure ( X CO) can be expressed as follows: {{d/pct}}{{{d}t}} = (1 - 0.40 × X_{{{fix} - C}}^{ - 0.86} × {pct}) × 2.62 × 10^{16} × \\exp ( { - 594000/RT} ) × (2.6 - 0.015 × X_{co} ).

Heterogeneous Partial (ammOxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

Directory of Open Access Journals (Sweden)

Jacques C. Védrine

2016-01-01

Full Text Available This paper presents an overview of heterogeneous partial (ammoxidation and oxidative dehydrogenation (ODH of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the “seven pillars”, and playing a determining role in catalytic properties, are considered to be, namely: isolation of active sites (known to be composed of ensembles of atoms, Me–O bond strength, crystalline structure, redox features, phase cooperation, multi-functionality and the nature of the surface oxygen species. Other important features and physical and chemical properties of solid catalysts, more or less related to the seven pillars, are also emphasized, including reaction sensitivity to metal oxide structure, epitaxial contact between an active phase and a second phase or its support, synergy effect between several phases, acid-base aspects, electron transfer ability, catalyst preparation and activation and reaction atmospheres, etc. Some examples are presented to illustrate the importance of these key factors. They include light alkanes (C1–C4 oxidation, ethane oxidation to ethylene and acetic acid on MoVTe(SbNb-O and Nb doped NiO, propene oxidation to acrolein on BiMoCoFe-O systems, propane (ammoxidation to (acrylonitrile acrylic acid on MoVTe(SbNb-O mixed oxides, butane oxidation to maleic anhydride on VPO: (VO2P2O7-based catalyst, and isobutyric acid ODH to methacrylic acid on Fe hydroxyl phosphates. It is shown that active sites are composed of ensembles of atoms whose size and chemical composition depend on the reactants to be transformed (their chemical and size features and the reaction mechanism, often of Mars and van Krevelen type. An important aspect is the fact that surface composition and surface crystalline structure vary with reaction on stream until

Bayesian inversion analysis of nonlinear dynamics in surface heterogeneous reactions.

Science.gov (United States)

Omori, Toshiaki; Kuwatani, Tatsu; Okamoto, Atsushi; Hukushima, Koji

2016-09-01

It is essential to extract nonlinear dynamics from time-series data as an inverse problem in natural sciences. We propose a Bayesian statistical framework for extracting nonlinear dynamics of surface heterogeneous reactions from sparse and noisy observable data. Surface heterogeneous reactions are chemical reactions with conjugation of multiple phases, and they have the intrinsic nonlinearity of their dynamics caused by the effect of surface-area between different phases. We adapt a belief propagation method and an expectation-maximization (EM) algorithm to partial observation problem, in order to simultaneously estimate the time course of hidden variables and the kinetic parameters underlying dynamics. The proposed belief propagation method is performed by using sequential Monte Carlo algorithm in order to estimate nonlinear dynamical system. Using our proposed method, we show that the rate constants of dissolution and precipitation reactions, which are typical examples of surface heterogeneous reactions, as well as the temporal changes of solid reactants and products, were successfully estimated only from the observable temporal changes in the concentration of the dissolved intermediate product.

Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations

International Nuclear Information System (INIS)

Gomez, Javier A.G.; Lage, Mateus R.; Carneiro, Jose Walkimar de M.; Resende, Jackson A.L.C.; Vargas, Maria D.

2013-01-01

The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF 3 COOH/CH 2 Cl 2 yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH 3 groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter. (author)

Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations

Energy Technology Data Exchange (ETDEWEB)

Gomez, Javier A.G.; Lage, Mateus R.; Carneiro, Jose Walkimar de M.; Resende, Jackson A.L.C.; Vargas, Maria D., E-mail: mdvargas@vm.uff.br, E-mail: walk@vm.uff.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Quimica

2013-02-15

The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF{sub 3}COOH/CH{sub 2}Cl{sub 2} yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH{sub 3} groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter. (author)

Enantioselective rhodium enolate protonations. A new methodology for the synthesis of beta2-amino acids.

Science.gov (United States)

Sibi, Mukund P; Tatamidani, Hiroto; Patil, Kalyani

2005-06-23

[reaction: see text] Rhodium-catalyzed conjugate addition of an aryl boronic acid to alpha-methylamino acrylates followed by enantioselective protonation of the oxa-pi-allylrhodium intermediate provides access to aryl-substituted beta(2)-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed.

Mechanism to preserve phrenic nerve function during photosensitization reaction: drug uptake and photosensitization reaction effect on electric propagation

Science.gov (United States)

Takahashi, Haruka; Hamada, Risa; Ogawa, Emiyu; Arai, Tsunenori

2018-02-01

To study a mechanism of phrenic nerve preservation phenomena during a photosensitization reaction, we investigated an uptake of talaporfin sodium and photosensitization reaction effect on an electric propagation. Right phrenic nerve was completely preserved after superior vena cava isolations using the photosensitization reaction in canine animal experiments, in spite of adjacent myocardium was electrically blocked. We predicted that low drug uptake and/or low photosensitization reaction effect on the nerve might be a mechanism of that phenomena. To investigate uptake to various nerve tissue, a healthy extracted crayfish ventral nerve cord and an extracted porcine phrenic nerve were immersed in 20 μg/ml talaporfin sodium solution for 0-240 min. The mean talaporfin sodium fluorescence brightness increased depending on the immersion time. This brightness saturated around the immersion time of 120 min. We found that talaporfin sodium uptake inside the perineurium which directly related to the electric propagation function was lower than that of outside in the porcine phrenic nerve. To investigate photosensitization reaction effect on electric propagation, the crayfish nerve was immersed into the same solution for 15 min and irradiated by a 663 nm laser light with 120 mW/cm2. Since we found the action potential disappeared when the irradiation time was 25-65 s, we consider that the crayfish nerve does not tolerant to the photosensitization reaction on electric propagation function at atmospheric pressure. From these results, we think that the low uptake of talaporfin sodium inside the perineurium and low oxygen partial pressure of nerve might be the possible mechanism to preserve phrenic nerve in vivo.

A system for incubations at high gas partial pressure

Directory of Open Access Journals (Sweden)

Patrick eSauer

2012-02-01

Full Text Available High-pressure is a key feature of deep subsurface environments. High partial pressure of dissolved gasses plays an important role in microbial metabolism, because thermodynamic feasibility of many reactions depends on the concentration of reactants. For gases, this is controlled by their partial pressure, which can exceed one MPa at in-situ conditions. Therefore, high hydrostatic pressure alone is not sufficient to recreate true deep subsurface in-situ conditions, but the partial pressure of dissolved gasses has to be controlled as well.We developed an incubation system that allows for incubations at hydrostatic pressure up to 60 MPa, temperatures up to 120° C and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. The system is mainly made from off-the-shelf components with only very few custom-made parts. A flexible and inert PVDF incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g. fluid-gas-rock-interactions in relation to carbon dioxide sequestration.As an application of the system we extracted organic acids from sub-bituminous coal using H2O as well as a H2O-CO2 mixture at elevated temperature (90°C and pressure (5 MPa. Subsamples were taken during the incubation and analysed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulphate reduction rate upon the addition of

Chemical polishing of partially oxidized T-111 alloy

International Nuclear Information System (INIS)

Teaney, P.E.

1974-01-01

The specimens were pressure-mounted in Bakelite and ground through 600 grit on silicon carbide papers. The specimens were rough-polished on a vibratory polisher for 4 to 6 h, using a water slurry of one micron alumina on Texmet, followed by 0.3-μ alumina on Texmet overnight. Final polishing was accomplished by continuous swabbing with a chemical polish. A chemical polish consisting of ten parts lactic acid, four parts nitric acid, and four parts hydrofluoric acid worked well for the T-111 parent material specimens; however, in the partially oxidized specimens, considerable pitting and staining occurred in the oxygen-affected zone and in the transition zone between the oxygen-affected zone and the parent material. A chemical polish was developed for the partially oxidized specimens by adjusting the ratio of the acids to ten parts lactic acid, two parts nitric acid, and two parts hydrofluoric acid. This slowed the chemical attack on the oxygen-affected zone considerably and, with continuous swabbing, the pitting and stain could be avoided. The specimens were rinsed and checked occasionally on the metallograph to determine when the proper polish had been obtained. Some specimens required intermittent polishing times up to 1 / 2 hour. No relationship could be established between the oxygen content of the specimen and the time required for chemical polishing in the partially oxidized specimens. However, the microstructure of the transition zone was the most difficult to obtain, and specimens with uniform reaction zones across the width of the specimen polished quicker than those with the transition zone

Type-Directed Partial Evaluation

DEFF Research Database (Denmark)

Danvy, Olivier

1998-01-01

Type-directed partial evaluation uses a normalization function to achieve partial evaluation. These lecture notes review its background, foundations, practice, and applications. Of specific interest is the modular technique of offline and online type-directed partial evaluation in Standard ML...

Type-Directed Partial Evaluation

DEFF Research Database (Denmark)

Danvy, Olivier

1998-01-01

Type-directed partial evaluation uses a normalization function to achieve partial evaluation. These lecture notes review its background, foundations, practice, and applications. Of specific interest is the modular technique of offline and online type-directed partial evaluation in Standard ML of ...

Rigid Dipeptide Mimics: Synthesis of Enantiopure 5- and 7-Benzyl and 5,7-Dibenzyl Indolizidinone Amino Acids via Enolization and Alkylation of delta-Oxo alpha,omega-Di-[N-(9-(9-phenylfluorenyl))amino]azelate Esters.

Science.gov (United States)

Polyak, Felix; Lubell, William D.

1998-08-21

Azabicyclo[X.Y.0]alkane amino acids are tools for constructing mimics of peptide structure and templates for generating combinatorial libraries for drug discovery. Our methodology for synthesizing these conformationally rigid dipeptides has been elaborated such that alkyl groups can be appended onto the heterocycle to generate mimics of peptide backbone and side-chain structure. Inexpensive glutamic acid was employed as chiral educt in a Claisen condensation/ketone alkylation/reductive amination/lactam cyclization sequence that furnished alkyl-branched azabicyclo[4.3.0]alkane amino acid. Enantiopure 5-benzyl-, 7-benzyl-, and 5,7-dibenzylindolizidinone amino acids 2-4 were stereoselectively synthesized via efficient reaction sequences featuring the alkylation of di-tert-butyl alpha,omega-di-[N-(PhF)amino]azelate delta-ketone 5. A variety of alkyl halides were readily added to the enolate of ketone 5 to provide mono- and dialkylated ketones 6 and 7. Hydride additions to 6 and 7, methanesulfonations, and intramolecular S(N)2 displacements by the PhF amine gave 5-alkylprolines that were converted by lactam cyclizations into 7- and 5-benzyl-, as well as 5,7-dibenzyl-2-oxo-3-N-(BOC)amino-1-azabicyclo[4.3.0]nonane-9-carboxylate methyl esters 10, 11, and 14. Epimerization of the alkyl-branched stereocenter via an iminium-enaminium equilibrium proved effective for controlling diastereoselectivity in reductive aminations with 6 and 7 in order to furnish 5-alkylprolines that were similarly converted to 7- benzyl- and 5,7-dibenzylindolizidinone N-(BOC)amino esters 10 and 14. Ester hydrolysis with hydroxide ion and potassium trimethylsilanolate then gave enantiopure indolizidinone amino acids 2-4. Epimerization at C-9 of benzylindolizidinone amino esters was also used to provide alternative diastereomers of 10, 11, and 14. This practical methodology for introducing side-chain groups onto the heterocycle with regioselective and diastereoselective control is designed to enhance

Strategies for catalyst development: possibilities of the ``rational approach`` illustrated with partial oxidation reactions

Energy Technology Data Exchange (ETDEWEB)

Weiss, W.; Schedel-Niedrig, T.; Schloegl, R. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany). Abt. Oberflaechenphysik

1998-12-31

The paper discusses two petrochemical selective oxidation reactions namely the practised formation of styrene (STY) and the desired oxidative functionalisation of propane. The present knowledge about the mode of operation of oxide catalysts is critically considered. The dehydrogenation of ethylbenzene (EB) should be described by an oxidehydration with water acting as oxidant. The potential role of the coke formed during catalytic reaction as co-catalyst will be discussed. Selective oxidation is connected with the participation of lattice oxygen mechanism which transforms unselective gas phase oxygen into selective oxygen. The atomistic description of this process is still quite unclear as well as the electron structural properties of the activated oxygen atom. The Role of solid state acidity as compared to the role of lattice oxygen is much less well investigated modern multiphase-multielement oxide (MMO) catalysts. The rationale is that the significant efforts made to improve current MMO systems by chemical modifications can be very much more fruitful when in a first step the mode of action of a catalyst is clarified on the basis of suitable experiments. Such time-consuming experiments at the beginning of a campaign for catalyst improvement pay back their investment in later stages of the project when strategies of chemical development can be derived on grounds of understanding. (orig.)

C- versus O-Arylation of an Enol-Lactone Using Potassium tert-butoxide

Directory of Open Access Journals (Sweden)

El Moktar Essassi

2003-05-01

Full Text Available Abstract: The use of potassium tert-butoxide as the base in arylation reactions of an enollactone with a series of benzyl halides was explored. Our work demonstrates that the ratio of C-arylation to O-arylation varies with the substitution pattern of the aryl halide.

Off-line real-time FTIR analysis of a process step in imipenem production

Science.gov (United States)

Boaz, Jhansi R.; Thomas, Scott M.; Meyerhoffer, Steven M.; Staskiewicz, Steven J.; Lynch, Joseph E.; Egan, Richard S.; Ellison, Dean K.

1992-08-01

We have developed an FT-IR method, using a Spectra-Tech Monit-IR 400 systems, to monitor off-line the completion of a reaction in real-time. The reaction is moisture-sensitive and analysis by more conventional methods (normal-phase HPLC) is difficult to reproduce. The FT-IR method is based on the shift of a diazo band when a conjugated beta-diketone is transformed into a silyl enol ether during the reaction. The reaction mixture is examined directly by IR and does not require sample workup. Data acquisition time is less than one minute. The method has been validated for specificity, precision and accuracy. The results obtained by the FT-IR method for known mixtures and in-process samples compare favorably with those from a normal-phase HPLC method.

Synchronization of Reaction-Diffusion Neural Networks With Dirichlet Boundary Conditions and Infinite Delays.

Science.gov (United States)

Sheng, Yin; Zhang, Hao; Zeng, Zhigang

2017-10-01

This paper is concerned with synchronization for a class of reaction-diffusion neural networks with Dirichlet boundary conditions and infinite discrete time-varying delays. By utilizing theories of partial differential equations, Green's formula, inequality techniques, and the concept of comparison, algebraic criteria are presented to guarantee master-slave synchronization of the underlying reaction-diffusion neural networks via a designed controller. Additionally, sufficient conditions on exponential synchronization of reaction-diffusion neural networks with finite time-varying delays are established. The proposed criteria herein enhance and generalize some published ones. Three numerical examples are presented to substantiate the validity and merits of the obtained theoretical results.

Systematic of the slope-mass-correlations in diffractive dissociation reactions

International Nuclear Information System (INIS)

Antunes, A.C.B.; Santoro, A.F.S.; Souza, M.H.G.

1984-01-01

A set of several results of the Three Components Deck Model for Diffractive Dissociation Reactions is presented. News and recently published results are summarized to obtain a general overview of the model, its predictions and comparison with experimental results. Two kinds of correlations and amplitudes are given: The slope-mass cos theta sup(GJ) correlation and slope-mass partial wave. (Author) [pt

Polarization Observables T and F in the yp -> pi p Reaction

Energy Technology Data Exchange (ETDEWEB)

Jiang, Hao [Univ. of South Carolina, Columbia, SC (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2017-08-31

The theory that describes the interaction of quarks is Quantum Chromodynamics (QCD), but how quarks are bound inside a nucleon is not yet well understood. Pion photoproduction experiments reveal important information about the nucleon excited states and the dynamics of the quarks within it and thus provide a useful tool to study QCD. Detailed information about this reaction can be obtained in experiments that utilize polarized photon beams and polarized targets. Pion photoproduction in the γρ -> π0ρ reaction has been measured in the FROST experiment at the Thomas Jefferson National Accelerator Facility. In this experiment circularly polarized photons with electron-beam energies up to 3.082 GeV impinged on a transversely polarized frozen-spin target. Final-state protons were detected in the CEBAF Large Acceptance Spectrometer. Results of the polarization observables T and F have been extracted. The data generally agree with predictions of present partial wave analyses, but also show marked differences. The data will constrain further partial wave analyses and improve the extraction of proton resonance properties.

Construction and accuracy of partial differential equation approximations to the chemical master equation.

Science.gov (United States)

Grima, Ramon

2011-11-01

The mesoscopic description of chemical kinetics, the chemical master equation, can be exactly solved in only a few simple cases. The analytical intractability stems from the discrete character of the equation, and hence considerable effort has been invested in the development of Fokker-Planck equations, second-order partial differential equation approximations to the master equation. We here consider two different types of higher-order partial differential approximations, one derived from the system-size expansion and the other from the Kramers-Moyal expansion, and derive the accuracy of their predictions for chemical reactive networks composed of arbitrary numbers of unimolecular and bimolecular reactions. In particular, we show that the partial differential equation approximation of order Q from the Kramers-Moyal expansion leads to estimates of the mean number of molecules accurate to order Ω(-(2Q-3)/2), of the variance of the fluctuations in the number of molecules accurate to order Ω(-(2Q-5)/2), and of skewness accurate to order Ω(-(Q-2)). We also show that for large Q, the accuracy in the estimates can be matched only by a partial differential equation approximation from the system-size expansion of approximate order 2Q. Hence, we conclude that partial differential approximations based on the Kramers-Moyal expansion generally lead to considerably more accurate estimates in the mean, variance, and skewness than approximations of the same order derived from the system-size expansion.

Compatriot partiality and cosmopolitan justice: Can we justify compatriot partiality within the cosmopolitan framework?

Directory of Open Access Journals (Sweden)

Rachelle Bascara

2016-10-01

Full Text Available This paper shows an alternative way in which compatriot partiality could be justified within the framework of global distributive justice. Philosophers who argue that compatriot partiality is similar to racial partiality capture something correct about compatriot partiality. However, the analogy should not lead us to comprehensively reject compatriot partiality. We can justify compatriot partiality on the same grounds that liberation movements and affirmative action have been justified. Hence, given cosmopolitan demands of justice, special consideration for the economic well-being of your nation as a whole is justified if and only if the country it identifies is an oppressed developing nation in an unjust global order.This justification is incomplete. We also need to say why Person A, qua national of Country A, is justified in helping her compatriots in Country A over similarly or slightly more oppressed non-compatriots in Country B. I argue that Person A’s partiality towards her compatriots admits further vindication because it is part of an oppressed group’s project of self-emancipation, which is preferable to paternalistic emancipation.Finally, I identify three benefits in my justification for compatriot partiality. First, I do not offer a blanket justification for all forms of compatriot partiality. Partiality between members of oppressed groups is only a temporary effective measure designed to level an unlevel playing field. Second, because history attests that sovereign republics could arise as a collective response to colonial oppression, justifying compatriot partiality on the grounds that I have identified is conducive to the development of sovereignty and even democracy in poor countries, thereby avoiding problems of infringement that many humanitarian poverty alleviation efforts encounter. Finally, my justification for compatriot partiality complies with the implicit cosmopolitan commitment to the realizability of global justice

The Relationship Between Structural and Catalytic Activity of α and γ-Bismuth-Molybdate Catalysts for Partial Oxidation of Propylene to Acrolein

Science.gov (United States)

Fansuri, H.; Pham, G. H.; Wibawanta, S.; Zhang, D. K.; French, David

Bismuth-molybdate catalysts are known to be effective for catalytic partial oxidation of propylene to acrolein. Their properties and the kinetics and reaction mechanisms for acrolein production have been extensively studied, especially in their basic forms, such as α, β, and γ-bismuth-molybdate. Although the reaction mechanisms have been reported widely in the literature, a general agreement has not been reached, especially from a catalyst-structure point of view. The present contribution reports an effort to understand the structural changes of α and γ-bismuth-molybdate catalysts at varying temperatures as examined using high temperature XRD and to relate the catalyst performance (activity and selectivity) for propylene partial oxidation to acrolein. The XRD analysis was performed at temperature between 250 and 450°C in ambient atmosphere and the Rietveld refinement method was used to extract unit cell parameters. The results showed a distinct similarity between the shapes of the thermal expansion of the catalysts and their activity and selectivity curves, indicating a significant role that the catalyst interatomic structure plays in the overall reaction mechanism.

Extended Catalyst Longevity Via Supercritical Isobutane Regeneration of a Partially Deactivated USY Alkylation Catalyst

Energy Technology Data Exchange (ETDEWEB)

Daniel M. Ginosar; David N. Thompson; Kyle C. Burch; David J. Zalewski

2005-05-01

Off-line, in situ activity recovery of a partially deactivated USY zeolite catalyst used for isobutane/butene alkylation was examined in a continuous-flow reaction system employing supercritical isobutane. Catalyst samples were deactivated in a controlled manner by running them to either to a fixed butene conversion level of 95% or a fixed time on stream of three hours, and then exposing the catalyst to supercritical isobutane to restore activity. Activity recovery was determined by comparing alkylation activity before and after the regeneration step. Both single and multiple regenerations were performed. Use of a 95% butene conversion level criterion to terminate the reaction step afforded 86% activity recovery for a single regeneration and provided nine sequential reaction steps for the multiple regeneration studies. Employing a fixed 3 h time on stream criterion resulted in nearly complete activity recovery for a single regeneration, and 24 reaction steps were demonstrated in sequence for the multiple regeneration process, producing only minor product yield declines per step. This resulted in a 12-fold increase in catalyst longevity versus unregenerated catalyst.

Essays on partial retirement

NARCIS (Netherlands)

Kantarci, T.

2012-01-01

The five essays in this dissertation address a range of topics in the micro-economic literature on partial retirement. The focus is on the labor market behavior of older age groups. The essays examine the economic and non-economic determinants of partial retirement behavior, the effect of partial

Niobium Pentachloride Activation of Enone Derivatives: Diels-Alder and Conjugate Addition Products

Directory of Open Access Journals (Sweden)

Gil Valdo José da Silva

2002-05-01

Full Text Available Niobium pentachloride has proven to be a powerful activating agent for Diels-Alder or conjugate addition reactions of cycloenones. The Diels-Alder product was obtained only with an unsubstituted enone (cyclohexenone and the highly reactive diene cyclopentadiene; substituents in the b-position of enones seem to prevent Diels-Alder reaction: oxygenated substituents favor the formation of vinyl chlorides (ethyl ether or dichloromethane as solvents or enol ethers (ethyl acetate as solvent, while a methyl substituent prevents any kind of transformation with NbCl5. Less reactive dienes, furan and 2-methylfuran gave the conjugate addition products of the furan ring to the enone system.

Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C3-building block

Directory of Open Access Journals (Sweden)

Volker M. Schmiedel

2013-11-01

Full Text Available Herein we present the synthesis of the anhydrophytosphingosine jaspine B and three of its stereoisomers using a carbohydrate-derived alkoxyallene in order to obtain the products in enantiopure form. Key step of the reaction sequence is the addition of the lithiated alkoxyallene to pentadecanal, setting the configuration at the later C-2 of the ring system. This reaction step proceeds with moderate selectivity and therefore leads to a stereodivergent approach to the natural product and its enantiomer. The gold-catalyzed 5-endo-cyclization affords the corresponding dihydrofurans, which after separation, azidation of the enol ether moiety and two subsequent reduction steps give the natural product and its stereoisomers.

The study of the (n,α) and (n,γα) reactions on 143Nd

International Nuclear Information System (INIS)

Aldea, L.; Kardon, B.; Schult, O.W.B.; Seyfarth, H.; Wuest, N.

1977-01-01

Partial cross sections have been measured for the 143 Nd(nsub(th),α) 140 Ce reaction and also for the two-step process 143 Nd(nsub(th),γα) 140 Ce. The results of the present work confirm previous data, but due to lower background, better statistics and resolution improved precision has been obtained. The double-humped structure in the observed (n,γα) spectrum can still be explained through the Porter-Thomas fluctuations of the reduced partial γ and α widths. (orig.) [de

Determination of the partial pressure of thallium in high-pressure lamp arcs: A comparative study

International Nuclear Information System (INIS)

Karabourniotis, D.; Couris, S.; Damelincourt, J.J.; Aubes, M.

1986-01-01

The partial pressure of thallium in high-pressure Hg-TlI discharges with different mercury, thallium, and electron pressures has been measured by using the optically thin line Tl 655 nm and the self-reversed line Tl 535 nm. The partial pressure of the arc axis has been measured from the line Tl 655nm. The effective partial pressure has been measured from the self-reversed line Tl 535 nm on the basis of the multiparameter method, and it has been calculated from the known axis pressure of thallium and the calculation of its radial variation by taking into account the chemical reactions. The experimental results confirm the dispersion character of the blue wing of the line Tl 535 nm. The systematic difference obtained between the measured and calculated effective pressure, particularly at the moment of minimum electron density, may be interpreted by deviations from the local thermodynamic equilibrium (LTE) caused by overpopulation of the upper level of the line Tl 535 nm

Evaluation of partially premixed turbulent flame stability from mixture fraction statistics in a slot burner

KAUST Repository

Kruse, Stephan

2018-04-11

Partially premixed combustion is characterized by mixture fraction inhomogeneity upstream of the reaction zone and occurs in many applied combustion systems. The temporal and spatial fluctuations of the mixture fraction have tremendous impact on the combustion characteristics, emission formation, and flame stability. In this study, turbulent partially premixed flames are experimentally studied in a slot burner configuration. The local temperature and gas composition is determined by means of one-dimensional, simultaneous detection of Rayleigh and Raman scattering. The statistics of the mixture fraction are utilized to characterize the impact of the Reynolds number, the global equivalence ratio, the progress of mixing within the flame, as well as the mixing length on the mixing field. Furthermore, these effects are evaluated by means of a regime diagram for partially premixed flames. In this study, it is shown that the increase of the mixing length results in a significantly more stable flame. The impact of the Reynolds number on flame stability is found to be minor.

Evaluation of partially premixed turbulent flame stability from mixture fraction statistics in a slot burner

KAUST Repository

Kruse, Stephan; Mansour, Mohy S.; Elbaz, Ayman M.; Varea, Emilien; Grü nefeld, Gerd; Beeckmann, Joachim; Pitsch, Heinz

2018-01-01

Partially premixed combustion is characterized by mixture fraction inhomogeneity upstream of the reaction zone and occurs in many applied combustion systems. The temporal and spatial fluctuations of the mixture fraction have tremendous impact on the combustion characteristics, emission formation, and flame stability. In this study, turbulent partially premixed flames are experimentally studied in a slot burner configuration. The local temperature and gas composition is determined by means of one-dimensional, simultaneous detection of Rayleigh and Raman scattering. The statistics of the mixture fraction are utilized to characterize the impact of the Reynolds number, the global equivalence ratio, the progress of mixing within the flame, as well as the mixing length on the mixing field. Furthermore, these effects are evaluated by means of a regime diagram for partially premixed flames. In this study, it is shown that the increase of the mixing length results in a significantly more stable flame. The impact of the Reynolds number on flame stability is found to be minor.

Phase behavior and reactive transport of partial melt in heterogeneous mantle model

Science.gov (United States)

Jordan, J.; Hesse, M. A.

2013-12-01

The reactive transport of partial melt is the key process that leads to the chemical and physical differentiation of terrestrial planets and smaller celestial bodies. The essential role of the lithological heterogeneities during partial melting of the mantle is increasingly recognized. How far can enriched melts propagate while interacting with the ambient mantle? Can the melt flow emanating from a fertile heterogeneity be localized through a reactive infiltration feedback in a model without exogenous factors or contrived initial conditions? A full understanding of the role of heterogeneities requires reactive melt transport models that account for the phase behavior of major elements. Previous work on reactive transport in the mantle focuses on trace element partitioning; we present the first nonlinear chromatographic analysis of reactive melt transport in systems with binary solid solution. Our analysis shows that reactive melt transport in systems with binary solid solution leads to the formation of two separate reaction fronts: a slow melting/freezing front along which enthalpy change is dominant and a fast dissolution/precipitation front along which compositional changes are dominated by an ion-exchange process over enthalpy change. An intermediate state forms between these two fronts with a bulk-rock composition and enthalpy that are not necessarily bounded by the bulk-rock composition and enthalpy of either the enriched heterogeneity or the depleted ambient mantle. The formation of this intermediate state makes it difficult to anticipate the porosity changes and hence the stability of reaction fronts. Therefore, we develop a graphical representation for the solution that allows identification of the intermediate state by inspection, for all possible bulk-rock compositions and enthalpies of the heterogeneity and the ambient mantle. We apply the analysis to the partial melting of an enriched heterogeneity. This leads to the formation of moving precipitation

Hydrogen isotope exchange reaction rates in tritium, hydrogen and deuterium mixed gases

International Nuclear Information System (INIS)

Uda, Tatsuhiko

1992-01-01

Hydrogen isotope exchange reaction rates in H 2 +T 2 , D 2 +T 2 and H 2 +D 2 +T 2 mixed gases, as induced by tritium decay and beta radiation, were experimentally measured by laser Raman spectrometry. Initially a glass cell was filled with T 2 gas to a pressure of 30-40 kPa, and an equivalent partial pressure of H 2 and/or D 2 was added. The first-order hydrogen isotope exchange reaction rates were 5.54x10 -2 h -1 for H 2 +T 2 mixed gas and 4.76x10 -2 h -1 for D 2 +T 2 . The actual HT producing rate was nearly equivalent to the rate of DT, but the reverse reaction rate of HT was faster than that of DT. The exchange reaction rates between H, D and T showed the isotope effect, HD>HT>DT. The hydrogen isotope exchange reaction rates observed were about twenty times larger than ion formation rates by beta radiation. This result suggests that a free radical chain reaction in hydrogen isotopes is occurring. (orig.)

Nucleon charge exchange reaction and antiproton elastic scattering at intermediate energies

International Nuclear Information System (INIS)

Kronenfeld, J.

1985-02-01

This work treats the medium energy nuclear (p,n) charge exchange reaction to analog states and the low energy elastic scattering of antiprotons and investigates the central aspects of a microscopic theory based on multiple-scattering series which are pertinent to these reactions. A two-step term of the Distorted Wave Impulse Approximation (DWIA) in treating the (p,n) reaction, was included. For the very absorptive p-bar interaction with nuclei we conjecture that a partial infinite summation, constituing a renormalization of the single scattering term of the optical potential series provides the dominant feature of this interaction. In this work the excitation of analog states is calculated and it was found that the (p,n) reaction is described fairly well by the DWIA. In the first part of the work the (p,n) reaction in the energy range 100-200 MeV was treated. The DWIA calculations were based on eikonalization. In the second part of the work the p-barA interaction with the selfconsistent scheme mentioned above, for scattering energies 30-120 MeV, was examined. (author)

Study of the reaction {gamma}p {yields} p{pi}{sup 0}{eta}

Energy Technology Data Exchange (ETDEWEB)

Horn, I.; Bartholomy, O.; Beck, R.; Ehmanns, A.; Ernst, J.; Fabry, I.; Fuchs, M.; Funke, C.; Gutz, E.; Junkersfeld, J.; Kalinowsky, H.; Klempt, E.; Lotz, J.; Pee, H. van; Schmidt, C.; Szczepanek, T.; Thoma, U.; Walther, D.; Weinheimer, C. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Anisovich, A.V.; Nikonov, V.A.; Sarantsev, A.V. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Anton, G.; Bogendoerfer, R.; Foesel, A.; Hoessl, J.; Suft, G. [Universitaet Erlangen, Physikalisches Institut, Erlangen (Germany); Bantes, R.; Gothe, R.; Hoeffgen, S.; Klein, F.; Konrad, M.; Langheinrich, J.; Menze, D.; Ostrick, M.; Schmieden, H.; Schoch, B. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Beloglazov, Y.; Gridnev, A.; Lopatin, I.; Novinski, D.; Sumachev, V. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Castelijns, R.; Loehner, H. [Kernfysisch Versneller Instituut, Groningen (Netherlands); Crede, V. [Florida State University, Department of Physics, Tallahassee, FL (United States); Flemming, H.; Koch, H.; Kopf, B.; Matthaey, H. [Universitaet Bochum, Institut fuer Experimentalphysik I, Bochum (Germany); Krusche, B. [Universitaet Basel, Institut fuer Physik, Basel (Switzerland); Messchendorp, J.; Metag, V. [Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany)

2008-11-15

The reaction {gamma}p {yields} p{pi}{sup 0}{eta} has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction shows contributions from {delta}{sup +}(1232){eta}, N(1535){sup +}{pi}{sup 0} and pa{sub 0}(980) as intermediate states. A partial-wave analysis suggests that the reaction proceeds via formation of six {delta} -resonances, {delta}(1600)P{sub 33}, {delta}(1920)P{sub 33}, {delta}(1700)D{sub 33}, {delta}(1940)D{sub 33}, {delta}(1905)F{sub 35}, {delta}(2360)D{sub 33}, and two nucleon resonances N(1880)P{sub 11} and N(2200)P{sub 13}, for which pole positions and decay branching ratios are given. (orig.)

Partial-wave analysis of π-π0π0 events at 18 GeV/c

International Nuclear Information System (INIS)

Brown, D.S.

1998-01-01

A partial-wave analysis has been performed on 170 K π - π 0 π 0 events produced in the reaction π - p→pπ - π 0 π 0 , and the results of the mass-independent fits are presented. The objective was to confirm the existence of the π(1800) and the exotic J PC =1 -+ object, reported by VES. copyright 1998 American Institute of Physics

Decarboxylation of Δ 9-tetrahydrocannabinol: Kinetics and molecular modeling

Science.gov (United States)

Perrotin-Brunel, Helene; Buijs, Wim; van Spronsen, Jaap; van Roosmalen, Maaike J. E.; Peters, Cor J.; Verpoorte, Rob; Witkamp, Geert-Jan

2011-02-01

Efficient tetrahydrocannabinol (Δ 9-THC) production from cannabis is important for its medical application and as basis for the development of production routes of other drugs from plants. This work presents one of the steps of Δ 9-THC production from cannabis plant material, the decarboxylation reaction, transforming the Δ 9-THC-acid naturally present in the plant into the psychoactive Δ 9-THC. Results of experiments showed pseudo-first order reaction kinetics, with an activation barrier of 85 kJ mol -1 and a pre-exponential factor of 3.7 × 10 8 s -1. Using molecular modeling, two options were identified for an acid catalyzed β-keto acid type mechanism for the decarboxylation of Δ 9-THC-acid. Each of these mechanisms might play a role, depending on the actual process conditions. Formic acid proved to be a good model for a catalyst of such a reaction. Also, the computational idea of catalysis by water to catalysis by an acid, put forward by Li and Brill, and Churchev and Belbruno was extended, and a new direct keto-enol route was found. A direct keto-enol mechanism catalyzed by formic acid seems to be the best explanation for the observed activation barrier and the pre-exponential factor of the decarboxylation of Δ 9-THC-acid. Evidence for this was found by performing an extraction experiment with Cannabis Flos. It revealed the presence of short chain carboxylic acids supporting this hypothesis. The presented approach is important for the development of a sustainable production of Δ 9-THC from the plant.

Quantitative in situ monitoring of an elevated temperature reaction using a water-cooled mid-infrared fiber-optic probe.

Science.gov (United States)

Maclaurin, P; Crabb, N C; Wells, I; Worsfold, P J; Coombs, D

1996-04-01

A novel water-cooled mid-infrared fiber-optic probe is described which is heatable to 230 °C. The probe has chalcogenide fibers and a ZnSe internal reflection element and is compact and fully flexible, allowing access to a wide range of standard laboratory reaction vessels and fume cupboard arrangements. Performance is demonstrated via the in situ analysis of an acid-catalyzed esterification reaction in toluene at 110 °C, and the results are compared with those from a conventional extractive sampling loop flow cell arrangement. Particular emphasis is given to the quantitative interpretation of the spectroscopic data, using gas chromatographic reference data. Calibration data are presented for univariate and partial least squares models, with an emphasis on procedures for improving the quality of interpreparation calibration and prediction through the use of focused reference analysis regimes. Subset univariate procedures are presented that yield relative errors of spectroscopy combined with bias correction partial least squares procedures for the efficient in situ quantitative analysis of laboratory scale reactions.

CFD modeling of combustion processes using KIVA3V Code with partially stirred reactor model for turbulence-combustion interactions

International Nuclear Information System (INIS)

Jarnicki, R.; Sobiesiak, A.

2002-01-01

In order to solve the averaged conservation equations for turbulent reacting flow one is faced with a task of specifying the averaged chemical reaction rate. This is due to turbulence influence on the mean reaction rates that appear in the species concentration Reynolds-averaged equation. In order to investigate the Partially Stirred Reactor (PaSR) combustion model capabilities, a CFD modeling using KIVA3V Code with the PaSR model of two very different combustion processes, was performed. Experimental results were compared with modeling

Synthesis and spectroscopic characterization of some lanthanide(III nitrate complexes of ethyl 2-[2-(1-acetyl-2-oxopropylazo]-4,5-dimethyl-3-thiophenecarboxyate

Directory of Open Access Journals (Sweden)

CHEMPAKAM JANARDHANAN ATHIRA

2011-02-01

Full Text Available Ethyl 2-[2-(1-acetyl-2-oxopropylazo]-4,5-dimethyl-3-thiophenecarboxyate was synthesized by coupling diazotized ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate with acetylacetone. Based on various spectral studies and elemental analysis, an intramolecularly hydrogen-bonded azo-enol structural form was assigned for the ligand. This ligand is versatile in forming a series of lanthanide(III complexes, viz., lanthanum(III, cerium(III, praseodymium(III, neodymium(III, samarium(III and gadolinium(III, which were characterized through various spectral studies, elemental analysis, magnetic susceptibility measurements, molar conductance and thermal analysis. The spectral data revealed that the ligand acted as a neutral tridentate, coordinating to the metal ion through one of the azo nitrogen atoms, the ester carbonyl and the enolic oxygen of the acetylacetone moiety, without deprotonation. Molar conductance values adequately supported their non-electrolytic nature. The ligand and lanthanum(III complex were subjected to X-ray diffraction studies. In addition, the lanthanum(III complex underwent a facile transesterification reaction on refluxing with methanol for a long period. The thermal behaviour of the lanthanum(III complex was also examined

Synthesis of dexamethasone-4-14C

International Nuclear Information System (INIS)

Rao, P.N.; Cessac, J.W.; Hill, K.A.

1982-01-01

The bismethylenedioxy (BMD) derivative of dexamethasone 2 was silylated with trimethylchlorosilane and imidazole in dimethylformamide to give the 11β-trimethylsilyloxy BMD derivative 3. The Δ 1 -double bond in 3 was hydrogenated over 5% palladium on carbon to give the Δ 4 -3-oxo steroid 4. Oxidation of 4 with potassium permanganate-sodium metaperiodate gave the seco-acid 5 which on subsequent treatment with acetic anhydride; sodium acetate and triethylamine gave the enol-lactone 6. The enol-lactone 6 was reacted with 14 C-methylmagnesium iodide to give an adduct 7a which on heating at reflux with lithium 2,6-di-t-butylphenoxide in dioxane gave the Δ 4 -3-oxo derivative 8. Compound 8 was heated at reflux with m-iodylbenzoic acid and diphenyl diselenide in toluene to give the Δsup(1,4)-3-oxo steroid 9. The protecting BMD and silyl groups were removed in a single step by reaction with aqueous trifluoroacetic acid containing 2N hydrochloric acid at room temperature to give dexamethasone-4- 14 C 10. (author)

Modeling and optimization aspects of radiation induced grafting of 4-vinylpyridene onto partially fluorinated films

International Nuclear Information System (INIS)

Nasef, Mohamed Mahmoud; Ahmad Ali, Amgad; Saidi, Hamdani; Ahmad, Arshad

2014-01-01

Modeling and optimization aspects of radiation induced grafting (RIG) of 4-vinylpyridine (4-VP) onto partially fluorinated polymers such as poly(ethylene-co-tetrafluoroethene) (ETFE) and poly(vinylidene fluoride) (PVDF) films were comparatively investigated using response surface method (RSM). The effects of independent parameters: absorbed dose, monomer concentration, grafting time and reaction temperature on the response, grafting yield (GY) were correlated through two quadratic models. The results of this work confirm that RSM is a reliable tool not only for optimization of the reaction parameters and prediction of GY in RIG processes, but also for the reduction of the number of the experiments, monomer consumption and absorbed dose leading to an improvement of the overall reaction cost. - Highlights: • Comparative study of radiation induced grafting of 4-VP onto PVDF and ETFE films. • Optimization of reaction parameters for both grafting systems was made using RSM. • Single factor design for both grafting systems was used as a reference. • Two quadratic regression models were developed for prediction of grafting yield. • RSM is an effective tool for handling grafting reactions under different conditions

Gas phase reactions of nitrogen oxides with olefins

Energy Technology Data Exchange (ETDEWEB)

Altshuller, A P; Cohen, I

1961-01-01

The nature of the condensation products formed in the gas phase reactions of nitrogen dioxide and nitric oxide with pentene-1, 2-methylbutene-2, and 2-methylbutadiene-1,3 was investigated. The reactants were combined at partial pressures in the range of 0.1 to 2.5 mm with the total pressure at one atmosphere. The products were determined by infrared and ultraviolet spectroscopy and colorimetry. The condensates included primary and secondary nitro compounds and alkyl nitrates. Strong hydroxyl and single bond carbon to oxygen stretching vibrations indicate the presence of either nitroalcohols or simple aliphatic alcohols formed through oxidation reactions. Carbonyl stretching frequencies observable in some of the reactions support the conclusion that a portion of the reactants disappear by oxidation rather than by nitration processes. The available results do not indicate the presence of appreciable amounts of tert.-nitro compounds, conjugated nitro-olefins, or gem-dinitro-alkanes. The reactivities of the olefins with the nitrogen oxides are in the decreasing order: 2-methyl-butadiene-1,3, 2-methylbutene-2, pentene-1. 20 references.

Radiation recall secondary to adjuvant docetaxel after balloon-catheter based accelerated partial breast irradiation

International Nuclear Information System (INIS)

Wong, Nathan W.; Wong, William W.; Karlin, Nina J.; Gray, Richard J.

2010-01-01

For early stage breast cancer, wide local excision and post-operative whole breast irradiation is a standard treatment. If adjuvant chemotherapy is recommended, radiation is usually given after completion of chemotherapy. In recent years, accelerated partial breast irradiation (APBI) with balloon-cathetered based brachytherapy has become an option for selected patients. For these patients, adjuvant chemotherapy would have to be administered after radiation. The sequence of treatment with radiation followed by chemotherapy results in increased risk of radiation recall reaction (RRD) in these patients. Docetaxel is becoming a more commonly used drug as adjuvant treatment for breast cancer. Here we report a case of docetaxel induced RRD after APBI with balloon-cathetered based brachytherapy. Such reaction would have an adverse impact on the cosmetic outcome and quality of life of the patient. For patients who develop an intense skin reaction after the administration of docetaxel following APBI, RRD should be considered in the differential diagnosis.

Aplicação de taninos enológicos na elaboração de vinho Cabernet Sauvignon e seus efeitos sobre a qualidade sensorial Application of enological tannins in the development of Cabert Sauvignon and their effects on the sensory quality

Directory of Open Access Journals (Sweden)

Vitor Manfroi

2010-02-01

Full Text Available Objetivou-se estudar o efeito do uso de taninos enológicos na composição sensorial do vinho Cabernet Sauvignon. O trabalho foi conduzido em Bento Gonçalves, Rio Grande do Sul (RS, com uvas Cabernet Sauvignon, safra 2004. Trata-se de uma cultivar que se destaca no Brasil pela importância na produção de vinhos tintos de guarda. Porém, em algumas safras, possui dificuldades para uma adequada maturação, o que dificulta a elaboração de vinhos com o perfil sensorial desejado pelos consumidores. Dentre as estratégias para minimizar esse problema, está o manejo do vinhedo, aliado a ajustes tecnológicos nas etapas de elaboração do vinho. Para tal, foram usados taninos de quebracho e castanheira, aplicados em três dosagens (5,0g hl-1, 10,0g hl-1, 20,0g hl-1 e em três momentos de aplicação (maceração, descuba, e após a fermentação malolática. Nos vinhos estabilizados, realizaram-se análises sensoriais, em relação aos atributos ligados aos perfis olfativos e gustativos, com análise de oito descritores olfativos e nove descritores gustativos, além de um conceito geral. Assim, verificou-se que os taninos enológicos imprimiram algumas diferenças, principalmente no perfil aromático dos vinhos, que apresentaram acréscimo de qualidade quando tratados com os taninos enológicos. Da mesma maneira, houve superioridade olfativa e gustativa nos vinhos que receberam tratamentos com taninos na etapa de maceração.The objective of this research was to study the effect of enological tannins in the sensory composition of the Cabernet Sauvignon wine. The study was conducted in Bento Gonçalves, RS, with Cabernet Sauvignon grapes, harvest 2004. This is a cultivar that stands out in importance in Brazil for the production of red wines. However, in some crops there are difficulties for a proper maturation, which hampers the development of wines with the sensory profile desired by consumers. Among the strategies to minimize this problem

Non-invasive estimation of dissipation from non-equilibrium fluctuations in chemical reactions.

Science.gov (United States)

Muy, S; Kundu, A; Lacoste, D

2013-09-28

We show how to extract an estimate of the entropy production from a sufficiently long time series of stationary fluctuations of chemical reactions. This method, which is based on recent work on fluctuation theorems, is direct, non-invasive, does not require any knowledge about the underlying dynamics and is applicable even when only partial information is available. We apply it to simple stochastic models of chemical reactions involving a finite number of states, and for this case, we study how the estimate of dissipation is affected by the degree of coarse-graining present in the input data.

Partial Portal Vein Arterialization Attenuates Acute Bile Duct Injury Induced by Hepatic Dearterialization in a Rat Model.

Science.gov (United States)

Jiang, Jun; Wei, Jishu; Wu, Junli; Gao, Wentao; Li, Qiang; Jiang, Kuirong; Miao, Yi

2016-01-01

Hepatic infarcts or abscesses occur after hepatic artery interruption. We explored the mechanisms of hepatic deprivation-induced acute liver injury and determine whether partial portal vein arterialization attenuated this injury in rats. Male Sprague-Dawley rats underwent either complete hepatic arterial deprivation or partial portal vein arterialization, or both. Hepatic ischemia was evaluated using biochemical analysis, light microscopy, and transmission electron microscopy. Hepatic ATP levels, the expression of hypoxia- and inflammation-associated genes and proteins, and the expression of bile transporter genes were assessed. Complete dearterialization of the liver induced acute liver injury, as evidenced by the histological changes, significantly increased serum biochemical markers, decreased ATP content, increased expression of hypoxia- and inflammation-associated genes and proteins, and decreased expression of bile transporter genes. These detrimental changes were extenuated but not fully reversed by partial portal vein arterialization, which also attenuated ductular reaction and fibrosis in completely dearterialized rat livers. Collectively, complete hepatic deprivation causes severe liver injury, including bile infarcts and biloma formation. Partial portal vein arterialization seems to protect against acute ischemia-hypoxia-induced liver injury.

Partial Portal Vein Arterialization Attenuates Acute Bile Duct Injury Induced by Hepatic Dearterialization in a Rat Model

Directory of Open Access Journals (Sweden)

Jun Jiang

2016-01-01

Full Text Available Hepatic infarcts or abscesses occur after hepatic artery interruption. We explored the mechanisms of hepatic deprivation-induced acute liver injury and determine whether partial portal vein arterialization attenuated this injury in rats. Male Sprague-Dawley rats underwent either complete hepatic arterial deprivation or partial portal vein arterialization, or both. Hepatic ischemia was evaluated using biochemical analysis, light microscopy, and transmission electron microscopy. Hepatic ATP levels, the expression of hypoxia- and inflammation-associated genes and proteins, and the expression of bile transporter genes were assessed. Complete dearterialization of the liver induced acute liver injury, as evidenced by the histological changes, significantly increased serum biochemical markers, decreased ATP content, increased expression of hypoxia- and inflammation-associated genes and proteins, and decreased expression of bile transporter genes. These detrimental changes were extenuated but not fully reversed by partial portal vein arterialization, which also attenuated ductular reaction and fibrosis in completely dearterialized rat livers. Collectively, complete hepatic deprivation causes severe liver injury, including bile infarcts and biloma formation. Partial portal vein arterialization seems to protect against acute ischemia-hypoxia-induced liver injury.

First total synthesis of (-)-AL-2.

Science.gov (United States)

Miyakoshi, Naoki; Mukai, Chisato

2003-06-26

Treatment of the 3,4-dioxygenated-9-hydroxy-1-nonyn-5-one derivative, derived from diethyl l-tartrate, with a palladium catalyst in methanol under a CO atmosphere effected an intramolecular acetalization and a stereoselective construction of the (E)-methoxycarbonylmethylidene functionality resulting in formation of the core framework of the diacetylenic spiroacetal enol ether natural products. Chemical transformations of the 1,6-dioxaspiro[4.5]decane derivative thus formed led to the first total synthesis of (-)-AL-2. [reaction: see text

Structure of Unsteady Partially Premixed Flames and the Existence of State Relationships

Directory of Open Access Journals (Sweden)

Suresh K. Aggarwal

2009-09-01

Full Text Available In this study, we examine the structure and existence of state relationships in unsteady partially premixed flames (PPFs subjected to buoyancy-induced and external perturbations. A detailed numerical model is employed to simulate the steady and unsteady two-dimensional PPFs established using a slot burner under normal and zero-gravity conditions. The coflow velocity is parametrically varied. The methane-air chemistry is modeled using a fairly detailed mechanism that contains 81 elementary reactions and 24 species. Validation of the computational model is provided through comparisons of predictions with nonintrusive measurements. The combustion proceeds in two reaction zones, one a rich premixed zone and the other a nonpremixed zone. These reaction zones are spatially separated, but involve strong interactions between them due to thermochemistry and scalar transport. The fuel is mostly consumed in the premixed zone to produce CO and H2, which are transported to and consumed in the nonpremixed zone. The nonpremixed zone in turn provides heat and H-atoms to the premixed zone. For the range of conditions investigated, the zero-g partially premixed flames exhibit a stable behavior and a remarkably strong resistance to perturbations. In contrast, the corresponding normal-gravity flames exhibit oscillatory behavior at low coflow velocities but a stable behavior at high coflow velocities, and the behavior can be explained in terms of a global and convective instabilities. The effects of coflow and gravity on the flames are characterized through a parameter VR, defined as the ratio of coflow velocity to jet velocity. For VR ≤ 1 (low coflow velocity regime, the structures of both 0- and 1-g flames are strongly sensitive to changes in VR, while they are only mildly affected by coflow in the high coflow velocity regime (VR > 1. In addition, the spatio-temporal characteristics of the 0- and 1-g flames are markedly different in the first regime, but are

Anatomic partial nephrectomy: technique evolution.

Science.gov (United States)

Azhar, Raed A; Metcalfe, Charles; Gill, Inderbir S

2015-03-01

Partial nephrectomy provides equivalent long-term oncologic and superior functional outcomes as radical nephrectomy for T1a renal masses. Herein, we review the various vascular clamping techniques employed during minimally invasive partial nephrectomy, describe the evolution of our partial nephrectomy technique and provide an update on contemporary thinking about the impact of ischemia on renal function. Recently, partial nephrectomy surgical technique has shifted away from main artery clamping and towards minimizing/eliminating global renal ischemia during partial nephrectomy. Supported by high-fidelity three-dimensional imaging, novel anatomic-based partial nephrectomy techniques have recently been developed, wherein partial nephrectomy can now be performed with segmental, minimal or zero global ischemia to the renal remnant. Sequential innovations have included early unclamping, segmental clamping, super-selective clamping and now culminating in anatomic zero-ischemia surgery. By eliminating 'under-the-gun' time pressure of ischemia for the surgeon, these techniques allow an unhurried, tightly contoured tumour excision with point-specific sutured haemostasis. Recent data indicate that zero-ischemia partial nephrectomy may provide better functional outcomes by minimizing/eliminating global ischemia and preserving greater vascularized kidney volume. Contemporary partial nephrectomy includes a spectrum of surgical techniques ranging from conventional-clamped to novel zero-ischemia approaches. Technique selection should be tailored to each individual case on the basis of tumour characteristics, surgical feasibility, surgeon experience, patient demographics and baseline renal function.

Liver investigation with respect to possible reactions to radiotherapy

International Nuclear Information System (INIS)

Wolzenburg, G.

1980-01-01

A partial liver irradiation was performed in 98 patients within the framework of an Y-field- or kidney-bed-after-irradiation. The liver reaction was tested by means of scintigraphy. In 73 patients, i.e. 74.5 percent of all cases, no increase in the storage capacity of the Kupffer-cells could be found as a consequence of the radiotherapy. In 16 of the patients (16.3 percent) a focused limited band-like necess could be found that corresponded to the irradiation field. The rest of the activity distribution was standard. In 9 of the patients pathological liver processes were independent of the therapy. The values of the lencocytes and thrombocytes were examined during and after the radiation therapy for similarities in 16 patients with liver reactions against irradiation. The values were compared with the course in patients without irradiation reaction. A correlation between blood-level processes and irradiation reactions of the Kupffer star-cells could not be determined. The liver function of RES appeared limited already by 3000 rads within 3 weeks after the end of the treatment. A complete restitution appeared within 18 months - even without the attempt of a treatment. (orig.) [de

Exploring the Reaction Pathways of Bioglycerol Hydrodeoxygenation to Propene over Molybdena-Based Catalysts.

Science.gov (United States)

Zacharopoulou, Vasiliki; Vasiliadou, Efterpi S; Lemonidou, Angeliki A

2018-01-10

The one-step reaction of glycerol with hydrogen to form propene selectively is a particularly challenging catalytic pathway that has not yet been explored thoroughly. Molybdena-based catalysts are active and selective to C-O bond scission; propene is the only product in the gas phase under the standard reaction conditions, and further hydrogenation to propane is impeded. Within this context, this work focuses on the exploration of the reaction pathways and the investigation of various parameters that affect the catalytic performance, such as the role of hydrogen on the product distribution and the effect of the catalyst pretreatment step. Under a hydrogen atmosphere, propene is produced primarily via 2-propenol, whereas under an inert atmosphere propanal and glycerol dissociation products are formed mainly. The reaction most likely proceeds through a reverse Mars-van Krevelen mechanism as partially reduced Mo species drive the reaction to the formation of the desired product. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tutorial on Online Partial Evaluation

Directory of Open Access Journals (Sweden)

William R. Cook

2011-09-01

Full Text Available This paper is a short tutorial introduction to online partial evaluation. We show how to write a simple online partial evaluator for a simple, pure, first-order, functional programming language. In particular, we show that the partial evaluator can be derived as a variation on a compositionally defined interpreter. We demonstrate the use of the resulting partial evaluator for program optimization in the context of model-driven development.

Isotopic and velocity distributions of {sub 83}Bi produced in charge-pickup reactions of {sup 208}{sub 82}PB at 1 A GeV

Energy Technology Data Exchange (ETDEWEB)

Kelic, A.; Schmidt, K.H.; Enqvist, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (DE)] [and others

2004-07-01

Isotopically resolved cross sections and velocity distributions have been measured in charge-pickup reactions of 1 A GeV {sup 208}Pb with proton, deuterium and titanium target. The total and partial charge-pickup cross sections in the reactions {sup 208}Pb + {sup 1}H and {sup 208}Pb + {sup 2}H are measured to be the same in the limits of the error bars. A weak increase in the total charge-pickup cross section is seen in the reaction of {sup 208}Pb with the titanium target. The measured velocity distributions show different contributions - quasi-elastic scattering and {delta}-resonance excitation - to the charge-pickup production. Data on total and partial charge-pickup cross sections from these three reactions are compared with other existing data and also with model calculations based on the coupling of different intra-nuclear cascade codes and an evaporation code. (orig.)

MODESTY, Statistical Reaction Cross-Sections and Particle Spectra in Decay Chain

International Nuclear Information System (INIS)

Mattes, W.

1977-01-01

1 - Nature of the physical problem solved: Code MODESTY calculates all energetically possible reaction cross sections and particle spectra within a nuclear decay chain. 2 - Method of solution: It is based on the statistical nuclear model following the method of Uhl (reference 1) where the optical model is used in the calculation of partial widths and the Blatt-Weisskopf single particle model for gamma rays

Structural basis for the enzymatic formation of the key strawberry flavor compound 4-hydroxy-2,5-dimethyl-3(2H)-furanone.

Science.gov (United States)

Schiefner, André; Sinz, Quirin; Neumaier, Irmgard; Schwab, Wilfried; Skerra, Arne

2013-06-07

The last step in the biosynthetic route to the key strawberry flavor compound 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) is catalyzed by Fragaria x ananassa enone oxidoreductase (FaEO), earlier putatively assigned as quinone oxidoreductase (FaQR). The ripening-induced enzyme catalyzes the reduction of the exocyclic double bond of the highly reactive precursor 4-hydroxy-5-methyl-2-methylene-3(2H)-furanone (HMMF) in a NAD(P)H-dependent manner. To elucidate the molecular mechanism of this peculiar reaction, we determined the crystal structure of FaEO in six different states or complexes at resolutions of ≤1.6 Å, including those with HDMF as well as three distinct substrate analogs. Our crystallographic analysis revealed a monomeric enzyme whose active site is largely determined by the bound NAD(P)H cofactor, which is embedded in a Rossmann-fold. Considering that the quasi-symmetric enolic reaction product HDMF is prone to extensive tautomerization, whereas its precursor HMMF is chemically labile in aqueous solution, we used the asymmetric and more stable surrogate product 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone (EHMF) and the corresponding substrate (2E)-ethylidene-4-hydroxy-5-methyl-3(2H)-furanone (EDHMF) to study their enzyme complexes as well. Together with deuterium-labeling experiments of EDHMF reduction by [4R-(2)H]NADH and chiral-phase analysis of the reaction product EHMF, our data show that the 4R-hydride of NAD(P)H is transferred to the unsaturated exocyclic C6 carbon of HMMF, resulting in a cyclic achiral enolate intermediate that subsequently becomes protonated, eventually leading to HDMF. Apart from elucidating this important reaction of the plant secondary metabolism our study provides a foundation for protein engineering of enone oxidoreductases and their application in biocatalytic processes.

The change of steel surface chemistry regarding oxygen partial pressure and dew point

Science.gov (United States)

Norden, Martin; Blumenau, Marc; Wuttke, Thiemo; Peters, Klaus-Josef

2013-04-01

By investigating the surface state of a Ti-IF, TiNb-IF and a MnCr-DP after several series of intercritical annealing, the impact of the annealing gas composition on the selective oxidation process is discussed. On behalf of the presented results, it can be concluded that not the general oxygen partial pressure in the annealing furnace, which is a result of the equilibrium reaction of water and hydrogen, is the main driving force for the selective oxidation process. It is shown that the amounts of adsorbed gases at the strip surface and the effective oxygen partial pressure resulting from the adsorbed gases, which is mainly dependent on the water content of the annealing furnace, is driving the selective oxidation processes occurring during intercritical annealing. Thus it is concluded, that for industrial applications the dew point must be the key parameter value for process control.

Partially Observed Mixtures of IRT Models: An Extension of the Generalized Partial-Credit Model

Science.gov (United States)

Von Davier, Matthias; Yamamoto, Kentaro

2004-01-01

The generalized partial-credit model (GPCM) is used frequently in educational testing and in large-scale assessments for analyzing polytomous data. Special cases of the generalized partial-credit model are the partial-credit model--or Rasch model for ordinal data--and the two parameter logistic (2PL) model. This article extends the GPCM to the…

Partial lesions of the intratemporal segment of the facial nerve: graft versus partial reconstruction.

Science.gov (United States)

Bento, Ricardo F; Salomone, Raquel; Brito, Rubens; Tsuji, Robinson K; Hausen, Mariana

2008-09-01

In cases of partial lesions of the intratemporal segment of the facial nerve, should the surgeon perform an intraoperative partial reconstruction, or partially remove the injured segment and place a graft? We present results from partial lesion reconstruction on the intratemporal segment of the facial nerve. A retrospective study on 42 patients who presented partial lesions on the intratemporal segment of the facial nerve was performed between 1988 and 2005. The patients were divided into 3 groups based on the procedure used: interposition of the partial graft on the injured area of the nerve (group 1; 12 patients); keeping the preserved part and performing tubulization (group 2; 8 patients); and dividing the parts of the injured nerve (proximal and distal) and placing a total graft of the sural nerve (group 3; 22 patients). Fracture of the temporal bone was the most frequent cause of the lesion in all groups, followed by iatrogenic causes (p lesion of the facial nerve is still questionable. Among these 42 patients, the best results were those from the total graft of the facial nerve.

Palladium-catalyzed regio- and stereoselective cross-addition of terminal alkynes to ynol ethers and synthesis of 1,4-enyn-3-ones.

Science.gov (United States)

Babu, Madala Hari; Dwivedi, Vikas; Kant, Ruchir; Reddy, Maddi Sridhar

2015-03-16

Conjugated enynes, enol ethers, and enynones are versatile building blocks that can be elaborated by a wide variety of synthetic transformations. The selective synthesis of such units is a prerequisite for their effective utilization. The synthesis of conjugated 2-phenoxyenynes through a palladium-catalyzed cross-addition of terminal alkynes to phenylethynyl ethers (hydroalkynylation) is now presented. The reaction is highly regio-, stereo-, and chemoselective, and shows excellent tolerance toward functional groups. The addition further features very mild reaction conditions (room temperature) and an inexpensive catalytic system (without a ligand and with a cheaply available Pd catalyst). The thus synthesized enynyl ethers with allylic hydroxy tethers, which survived the reaction, were shown to be ready precursors for valuable 1-en-4-yn-3-ones. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

p-process nucleosynthesis via proton-capture reactions in thermonuclear supernovae explosions

Directory of Open Access Journals (Sweden)

Endres Anne

2015-01-01

Full Text Available Model calculations within the framework of the so-called γ process show an underproduction of the p nucleus with the highest isotopic abundace 92Mo. This discrepancy can be narrowed by taking into account the alternative production site of a type Ia supernova explosion. Here, the nucleus 92Mo can be produced by a sequence of proton-capture reactions. The amount of 92Mo nuclei produced via this reaction chain is most sensitive to the reactions 90Zr(p,γ and 91Nb(p,γ. Both rates have to be investigated experimentally to study the impact of this nucleosynthesis aspect on the long-standing 92Mo-problem. We have already measured the proton-capture reaction on 90Zr using high-resolution in-beam γ-ray spectroscopy. In this contribution, we will present our preliminary results of the total cross sections as well as the partial cross sections. Furthermore, we plan to measure the 91Nb(p,γ reaction soon. Due to the radioactive target material, the 91Nb nuclei have to be produced prior to the experiment. The current status of this production will be presented in this contribution.

Partial twisting for scalar mesons

International Nuclear Information System (INIS)

Agadjanov, Dimitri; Meißner, Ulf-G.; Rusetsky, Akaki

2014-01-01

The possibility of imposing partially twisted boundary conditions is investigated for the scalar sector of lattice QCD. According to the commonly shared belief, the presence of quark-antiquark annihilation diagrams in the intermediate state generally hinders the use of the partial twisting. Using effective field theory techniques in a finite volume, and studying the scalar sector of QCD with total isospin I=1, we however demonstrate that partial twisting can still be performed, despite the fact that annihilation diagrams are present. The reason for this are delicate cancellations, which emerge due to the graded symmetry in partially quenched QCD with valence, sea and ghost quarks. The modified Lüscher equation in case of partial twisting is given

Precise tests for the unitarized pion photoproduction impulse amplitude in exclusive nuclear reactions

International Nuclear Information System (INIS)

Wittman, R.

1986-07-01

An impulse amplitude for pion photoproduction, suitable for the nuclear problem, is constructed with improved background dynamics and unitarity. The superior features of the amplitude are demonstrated at energies between threshold (E/sub γ/ = 150 MeV) and the Δ(1232) resonance energy (E/sub γ/ = 320 MeV) by discussing their effects on partial cross sections relevant to exclusive transitions in the 1p-shell. The specific reactions of 13 C(γ,π - ) 13 N/sub g.s./ and 14 N(γ,π + ) 14 C/sub g.s./ are discussed in light of these more general partial cross sections. The nuclear structure of the A = 14 system helps to enhance the effects considered. At or near resonance, very sizable (20 to 30%) effects arise both from the unitarity and from the refined treatment of the pionic final state interaction generated in the Δ-hole approach. Other examples of charged pion photoproduction reactions for 1p-shell nuclei are discussed briefly. Future theoretical improvements and experimental possibilities are suggested. 61 refs., 58 figs

A partial-wave analysis of the neutral 3 pi system produced in the reaction pi /sup -/p to ( pi /sup +/ pi /sup -/ pi /sup 0/)n at 12 and 15 GeV/c

CERN Document Server

Corden, M J; Bellamy, E H; Corbett, I F; Dagan, S; Dowell, John D; Esterling, R J; Garvey, J; Gnat, Y; Green, M G; Harnew, N; Jobes, M; Kenyon, I R; Lipman, Norman H; Lister, J B; Lister, J R; Litchfield, P J; Mawson, J; McMahon, T; Robertson, A W; Stacey, B J; Strong, J A; Sumorok, K; Thomas, D H

1978-01-01

Data on the charge-exchange reaction pi /sup -/p to ( pi /sup +/ pi /sup -/ pi /sup 0/)n have been taken at beam momenta of 12 and 15 GeV /c, using the CERN Omega Multiparticle Spectrometer. A partial-wave analysis has been made of the (3 pi )/sup 0/ system. Both natural and unnatural spin-parity production was observed. The natural parity states can be identified with established resonances. In addition a natural spin-parity enhancement is observed at a mass of about 2 GeV/c /sup 2/ with J/sup P/=4/sup +/ preferred. This effect is called the A /sub 2/*(2030). The unnatural spin-parity production found is consistent with reggeized Deck model predictions. No unambiguous A/sub 1/ or A/sub 3/ production is observed. (15 refs).

Advancing the Theory of Nuclear Reactions with Rare Isotopes: From the Laboratory to the Cosmos

Energy Technology Data Exchange (ETDEWEB)

Elster, Charlotte [Ohio Univ., Athens, OH (United States)

2015-06-01

The mission of the TORUS Topical Collaboration is to develop new methods that will advance nuclear reaction theory for unstable isotopes by using three-body techniques to improve direct-reaction calculations, and, by using a new partial-fusion theory, to integrate descriptions of direct and compound-nucleus reactions. Ohio University concentrates its efforts on the first part of the mission. Since direct measurements are often not feasible, indirect methods, e.g. (d,p) reactions, should be used. Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. While there exist several separable representations for the nucleon-nucleon interaction, the optical potential between a neutron (proton) and a nucleus is not readily available in separable form. For this reason we first embarked in introducing a separable representation for complex phenomenological optical potentials of Woods-Saxon type.

Ontology aided modeling of organic reaction mechanisms with flexible and fragment based XML markup procedures.

Science.gov (United States)

Sankar, Punnaivanam; Aghila, Gnanasekaran

2007-01-01

The mechanism models for primary organic reactions encoding the structural fragments undergoing substitution, addition, elimination, and rearrangements are developed. In the proposed models, each and every structural component of mechanistic pathways is represented with flexible and fragment based markup technique in XML syntax. A significant feature of the system is the encoding of the electron movements along with the other components like charges, partial charges, half bonded species, lone pair electrons, free radicals, reaction arrows, etc. needed for a complete representation of reaction mechanism. The rendering of reaction schemes described with the proposed methodology is achieved with a concise XML extension language interoperating with the structure markup. The reaction scheme is visualized as 2D graphics in a browser by converting them into SVG documents enabling the desired layouts normally perceived by the chemists conventionally. An automatic representation of the complex patterns of the reaction mechanism is achieved by reusing the knowledge in chemical ontologies and developing artificial intelligence components in terms of axioms.

Turbulent piloted partially-premixed flames with varying levels of O2/N2: stability limits and PDF calculations

Science.gov (United States)

Juddoo, Mrinal; Masri, Assaad R.; Pope, Stephen B.

2011-12-01

This paper reports measured stability limits and PDF calculations of piloted, turbulent flames of compressed natural gas (CNG) partially-premixed with either pure oxygen, or with varying levels of O2/N2. Stability limits are presented for flames of CNG fuel premixed with up to 20% oxygen as well as CNG-O2-N2 fuel where the O2 content is varied from 8 to 22% by volume. Calculations are presented for (i) Sydney flame B [Masri et al. 1988] which uses pure CNG as well as flames B15 to B25 where the CNG is partially-premixed with 15-25% oxygen by volume, respectively and (ii) Sandia methane-air (1:3 by volume) flame E [Barlow et al. 2005] as well as new flames E15 and E25 that are partially-premixed with 'reconstituted air' where the O2 content in nitrogen is 15 and 25% by volume, respectively. The calculations solve a transported PDF of composition using a particle-based Monte Carlo method and employ the EMST mixing model as well as detailed chemical kinetics. The addition of oxygen to the fuel increases stability, shortens the flames, broadens the reaction zone, and shifts the stoichiometric mixture fraction towards the inner side of the jet. It is found that for pure CNG flames where the reaction zone is narrow (∼0.1 in mixture fraction space), the PDF calculations fail to reproduce the correct level of local extinction on approach to blow-off. A broadening in the reaction zone up to about 0.25 in mixture fraction space is needed for the PDF/EMST approach to be able to capture these finite-rate chemistry effects. It is also found that for the same level of partial premixing, increasing the O2/N2 ratio increases the maximum levels of CO and NO but shifts the peak to richer mixture fractions. Over the range of oxygenation investigated here, stability limits have shown to improve almost linearly with increasing oxygen levels in the fuel and with increasing the contribution of release rate from the pilot.

Partial diel migration: A facultative migration underpinned by long-term inter-individual variation.

Science.gov (United States)

Harrison, Philip M; Gutowsky, Lee F G; Martins, Eduardo G; Patterson, David A; Cooke, Steven J; Power, Michael

2017-09-01

The variations in migration that comprise partial diel migrations, putatively occur entirely as a consequence of behavioural flexibility. However, seasonal partial migrations are increasingly recognised to be mediated by a combination of reversible plasticity in response to environmental variation and individual variation due to genetic and environmental effects. Here, we test the hypothesis that while partial diel migration heterogeneity occurs primarily due to short-term within-individual flexibility in behaviour, long-term individual differences in migratory behaviour also underpin this migration variation. Specifically, we use a hierarchical behavioural reaction norm approach to partition within- and among-individual variation in depth use and diel plasticity in depth use, across short- and long-term time-scales, in a group of 47 burbot (Lota lota) tagged with depth-sensing acoustic telemetry transmitters. We found that within-individual variation at the among-dates-within-seasons and among-seasons scale, explained the dominant proportion of phenotypic variation. However, individuals also repeatedly differed in their expression of migration behaviour over the 2 year study duration. These results reveal that diel migration variation occurs primarily due to short-term within-individual flexibility in depth use and diel migration behaviour. However, repeatable individual differences also played a key role in mediating partial diel migration. These findings represent a significant advancement of our understanding of the mechanisms generating the important, yet poorly understood phenomena of partial diel migration. Moreover, given the pervasive occurrence of diel migrations across aquatic taxa, these findings indicate that individual differences have an important, yet previously unacknowledged role in structuring the temporal and vertical dynamics of aquatic ecosystems. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

Partial order infinitary term rewriting

DEFF Research Database (Denmark)

Bahr, Patrick

2014-01-01

We study an alternative model of infinitary term rewriting. Instead of a metric on terms, a partial order on partial terms is employed to formalise convergence of reductions. We consider both a weak and a strong notion of convergence and show that the metric model of convergence coincides with th...... to the metric setting -- orthogonal systems are both infinitarily confluent and infinitarily normalising in the partial order setting. The unique infinitary normal forms that the partial order model admits are Böhm trees....

Beginning partial differential equations

CERN Document Server

O'Neil, Peter V

2011-01-01

A rigorous, yet accessible, introduction to partial differential equations-updated in a valuable new edition Beginning Partial Differential Equations, Second Edition provides a comprehensive introduction to partial differential equations (PDEs) with a special focus on the significance of characteristics, solutions by Fourier series, integrals and transforms, properties and physical interpretations of solutions, and a transition to the modern function space approach to PDEs. With its breadth of coverage, this new edition continues to present a broad introduction to the field, while also addres

The chemical energy unit partial oxidation reactor operation simulation modeling

Science.gov (United States)

Mrakin, A. N.; Selivanov, A. A.; Batrakov, P. A.; Sotnikov, D. G.

2018-01-01

The chemical energy unit scheme for synthesis gas, electric and heat energy production which is possible to be used both for the chemical industry on-site facilities and under field conditions is represented in the paper. The partial oxidation reactor gasification process mathematical model is described and reaction products composition and temperature determining algorithm flow diagram is shown. The developed software product verification showed good convergence of the experimental values and calculations according to the other programmes: the temperature determining relative discrepancy amounted from 4 to 5 %, while the absolute composition discrepancy ranged from 1 to 3%. The synthesis gas composition was found out practically not to depend on the supplied into the partial oxidation reactor (POR) water vapour enthalpy and compressor air pressure increase ratio. Moreover, air consumption coefficient α increase from 0.7 to 0.9 was found out to decrease synthesis gas target components (carbon and hydrogen oxides) specific yield by nearly 2 times and synthesis gas target components required ratio was revealed to be seen in the water vapour specific consumption area (from 5 to 6 kg/kg of fuel).

Insights into the mechanisms on chemical reactions: reaction paths for chemical reactions

International Nuclear Information System (INIS)

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

1987-01-01

We report reaction paths for two prototypical chemical reactions: Li + HF, an electron transfer reaction, and OH + H 2 , an abstraction reaction. In the first reaction we consider the connection between the energetic terms in the reaction path Hamiltonian and the electronic changes which occur upon reaction. In the second reaction we consider the treatment of vibrational effects in chemical reactions in the reaction path formalism. 30 refs., 9 figs

Perceived Insider Status and Feedback Reactions: A Dual Path of Feedback Motivation Attribution

Directory of Open Access Journals (Sweden)

Weijiong Wu

2017-05-01

Full Text Available Many studies have evaluated how the characteristics of feedback receiver, feedback deliverer and feedback information influence psychological feedback reactions of the feedback receiver while largely neglecting that feedback intervention is a kind of social interaction process. To address this issue, this study proposes that employees’ perceived insider status (PIS, as a kind of employee-organization relationship, could also influence employees’ reactions to supervisory feedback. In particular, this study investigates the influence of PIS focusing on affective and cognitive feedback reactions, namely feedback satisfaction and feedback utility. Surveys were conducted in a machinery manufacturing company in the Guangdong province of China. Samples were collected from 192 employees. Data analysis demonstrated that PIS and feedback utility possessed a U-shaped relationship, whereas PIS and feedback satisfaction exhibited positively linear relationships. The analysis identified two kinds of mediating mechanisms related to feedback satisfaction and feedback utility. Internal feedback motivation attribution partially mediated the relationship between PIS and feedback satisfaction but failed to do the same with respect to the relationship between PIS and feedback utility. In contrast, external feedback motivation attribution partially mediated the relationship between PIS and feedback utility while failing to mediate the relationship between PIS and feedback satisfaction. Theoretical contributions and practical implications of the findings are discussed at the end of the paper.

The effect of catalyst support on the RWGS reaction

International Nuclear Information System (INIS)

Laosiripojana, N.; Sutthisripok, W.

2004-01-01

'Full text:' Methane steam reforming is generally applied in order to produce synthesis gas mainly consist of hydrogen and carbon monoxide for later utilization in SOFC. This reaction is always carried out with the water gas shift reaction over a catalyst at elevated temperatures resulting in some carbon dioxide production. The CO/CO2 production selectivity strongly depends on the influence of water gas shift reaction. It was observed that the reactivity of this reaction depended on the type of support material. Stabilities, activities, and kinetics of the reverse water gas shift reaction (RWGS) for commercial nickel on CeO2, ZrO2, CeO2-ZrO2, TiO2, MgO, and Al2O3 supports were studied in order to observe the influence of the support on this reaction. According to the experiment, the activities of Ni/CeO2 toward the reverse water gas shift reaction (RWGS) were very high, and reached equilibrium level at approximately 600 o C (where the conversion of CO2 was closed to 1). Other oxide supports provided lower activities toward this reaction. It was observed that the activity of Ni/Al2O3 toward this reaction was the lowest. The kinetics of this reaction was also studied. Carbon dioxide presented positive effect on the reverse water gas shift reaction. The reaction orders in carbon dioxide were observed to be positive partial value between 0-1. It slightly decreased with increasing temperature for Ni/ CeO2 and Ni/CeO2-ZrO2, whereas it seemed to be independent of the operating temperature for other materials in the range of conditions studied. Hydrogen also showed positive effect on the reverse water gas shift reaction for all materials. The reaction order in hydrogen for all materials was observed to be the positive value and less than one for the range of conditions studied. The approximate values for all catalysts were between 0.45-0.65, and seemed to be independent of the operating temperature. The estimated values of the apparent activation energy for RWGS reaction

Constraining statistical-model parameters using fusion and spallation reactions

Directory of Open Access Journals (Sweden)

Charity Robert J.

2011-10-01

Full Text Available The de-excitation of compound nuclei has been successfully described for several decades by means of statistical models. However, such models involve a large number of free parameters and ingredients that are often underconstrained by experimental data. We show how the degeneracy of the model ingredients can be partially lifted by studying different entrance channels for de-excitation, which populate different regions of the parameter space of the compound nucleus. Fusion reactions, in particular, play an important role in this strategy because they fix three out of four of the compound-nucleus parameters (mass, charge and total excitation energy. The present work focuses on fission and intermediate-mass-fragment emission cross sections. We prove how equivalent parameter sets for fusion-fission reactions can be resolved using another entrance channel, namely spallation reactions. Intermediate-mass-fragment emission can be constrained in a similar way. An interpretation of the best-fit IMF barriers in terms of the Wigner energies of the nascent fragments is discussed.

Mechanisms of LiCoO2 Cathode Degradation by Reaction with HF and Protection by Thin Oxide Coatings.

Science.gov (United States)

Tebbe, Jonathon L; Holder, Aaron M; Musgrave, Charles B

2015-11-04

Reactions of HF with uncoated and Al and Zn oxide-coated surfaces of LiCoO2 cathodes were studied using density functional theory. Cathode degradation caused by reaction of HF with the hydroxylated (101̅4) LiCoO2 surface is dominated by formation of H2O and a LiF precipitate via a barrierless reaction that is exothermic by 1.53 eV. We present a detailed mechanism where HF reacts at the alumina coating to create a partially fluorinated alumina surface rather than forming AlF3 and H2O and thus alumina films reduce cathode degradation by scavenging HF and avoiding H2O formation. In contrast, we find that HF etches monolayer zinc oxide coatings, which thus fail to prevent capacity fading. However, thicker zinc oxide films mitigate capacity loss by reacting with HF to form a partially fluorinated zinc oxide surface. Metal oxide coatings that react with HF to form hydroxyl groups over H2O, like the alumina monolayer, will significantly reduce cathode degradation.

Hyperbolic partial differential equations

CERN Document Server

Witten, Matthew

1986-01-01

Hyperbolic Partial Differential Equations III is a refereed journal issue that explores the applications, theory, and/or applied methods related to hyperbolic partial differential equations, or problems arising out of hyperbolic partial differential equations, in any area of research. This journal issue is interested in all types of articles in terms of review, mini-monograph, standard study, or short communication. Some studies presented in this journal include discretization of ideal fluid dynamics in the Eulerian representation; a Riemann problem in gas dynamics with bifurcation; periodic M

Partial differential equations

CERN Document Server

Evans, Lawrence C

2010-01-01

This text gives a comprehensive survey of modern techniques in the theoretical study of partial differential equations (PDEs) with particular emphasis on nonlinear equations. The exposition is divided into three parts: representation formulas for solutions; theory for linear partial differential equations; and theory for nonlinear partial differential equations. Included are complete treatments of the method of characteristics; energy methods within Sobolev spaces; regularity for second-order elliptic, parabolic, and hyperbolic equations; maximum principles; the multidimensional calculus of variations; viscosity solutions of Hamilton-Jacobi equations; shock waves and entropy criteria for conservation laws; and, much more.The author summarizes the relevant mathematics required to understand current research in PDEs, especially nonlinear PDEs. While he has reworked and simplified much of the classical theory (particularly the method of characteristics), he primarily emphasizes the modern interplay between funct...

Partial Cooperative Equilibria: Existence and Characterization

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Amandine Ghintran

2010-09-01

Full Text Available We study the solution concepts of partial cooperative Cournot-Nash equilibria and partial cooperative Stackelberg equilibria. The partial cooperative Cournot-Nash equilibrium is axiomatically characterized by using notions of rationality, consistency and converse consistency with regard to reduced games. We also establish sufficient conditions for which partial cooperative Cournot-Nash equilibria and partial cooperative Stackelberg equilibria exist in supermodular games. Finally, we provide an application to strategic network formation where such solution concepts may be useful.

Enhanced antiproton production in Pb(160 A GeV)+Pb reactions evidence for quark gluon matter?

CERN Document Server

Bleicher, M; Bass, S A; Soff, S; Stöcker, H

2000-01-01

The centrality dependence of the antiproton per participant ratio is studied in Pb(160 AGeV)+Pb reactions. Antiproton production in collisions of heavy nuclei at the CERN/SPS seems considerably enhanced as compared to conventional hadronic physics, given by the antiproton production rates in $pp$ and antiproton annihilation in $\\bar{p}p$ reactions. This enhancement is consistent with the observation of strong in-medium effects in other hadronic observables and may be an indication of partial restoration of chiral symmetry.

Improved stochastic approximation methods for discretized parabolic partial differential equations

Science.gov (United States)

Guiaş, Flavius

2016-12-01

We present improvements of the stochastic direct simulation method, a known numerical scheme based on Markov jump processes which is used for approximating solutions of ordinary differential equations. This scheme is suited especially for spatial discretizations of evolution partial differential equations (PDEs). By exploiting the full path simulation of the stochastic method, we use this first approximation as a predictor and construct improved approximations by Picard iterations, Runge-Kutta steps, or a combination. This has as consequence an increased order of convergence. We illustrate the features of the improved method at a standard benchmark problem, a reaction-diffusion equation modeling a combustion process in one space dimension (1D) and two space dimensions (2D).

Successful removable partial dentures.

Science.gov (United States)

Lynch, Christopher D

2012-03-01

Removable partial dentures (RPDs) remain a mainstay of prosthodontic care for partially dentate patients. Appropriately designed, they can restore masticatory efficiency, improve aesthetics and speech, and help secure overall oral health. However, challenges remain in providing such treatments, including maintaining adequate plaque control, achieving adequate retention, and facilitating patient tolerance. The aim of this paper is to review the successful provision of RPDs. Removable partial dentures are a successful form of treatment for replacing missing teeth, and can be successfully provided with appropriate design and fabrication concepts in mind.

Reaction products of densified silica fume agglomerates in concrete

International Nuclear Information System (INIS)

Diamond, Sidney; Sahu, Sadananda; Thaulow, Niels

2004-01-01

Most silica fume currently used in concrete is in the dry densified form and consists of agglomerates of sizes between 10 μm and several millimeters. Many of these agglomerates may break down only partially in normal concrete mixing. Examination of various mature silica-fume-bearing concretes using backscatter mode scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis shows that such agglomerates have reacted in situ and given rise to recognizable types of reaction products filling the space within the original outline of the agglomerate. One type is 'quiescent', and usually shows no evidence of volume instability. EDX spectra indicate that the product formed within such grains is C-S-H of very low Ca/Si ratio, with modest alkali contents. Other silica fume agglomerates may undergo a distinct alkali-silica-type reaction (ASR), with the reaction product found within the original outline of the agglomerate having significantly less calcium and usually much higher alkali contents than the quiescent type. Such reacted agglomerates show evidence of local expansion, shrinkage cracking (on drying), and other features common to ASR. Both types may be found within the same concrete, sometimes in close proximity. It further appears that exposure to seawater may convert previously formed reaction products of silica fume agglomerates to magnesium silicate hydrates

32 CFR 751.13 - Partial payments.

Science.gov (United States)

2010-07-01

... voucher and all other information related to the partial payment shall be placed in the claim file. Action... 32 National Defense 5 2010-07-01 2010-07-01 false Partial payments. 751.13 Section 751.13 National... Claims Against the United States § 751.13 Partial payments. (a) Partial payments when hardship exists...

[Acrylic resin removable partial dentures].

Science.gov (United States)

de Baat, C; Witter, D J; Creugers, N H J

2011-01-01

An acrylic resin removable partial denture is distinguished from other types of removable partial dentures by an all-acrylic resin base which is, in principle, solely supported by the edentulous regions of the tooth arch and in the maxilla also by the hard palate. When compared to the other types of removable partial dentures, the acrylic resin removable partial denture has 3 favourable aspects: the economic aspect, its aesthetic quality and the ease with which it can be extended and adjusted. Disadvantages are an increased risk of caries developing, gingivitis, periodontal disease, denture stomatitis, alveolar bone reduction, tooth migration, triggering of the gag reflex and damage to the acrylic resin base. Present-day indications are ofa temporary or palliative nature or are motivated by economic factors. Special varieties of the acrylic resin removable partial denture are the spoon denture, the flexible denture fabricated of non-rigid acrylic resin, and the two-piece sectional denture. Furthermore, acrylic resin removable partial dentures can be supplied with clasps or reinforced by fibers or metal wires.

Partial characterization of new adenoviruses found in lizards.

Science.gov (United States)

Ball, Inna; Behncke, Helge; Schmidt, Volker; Geflügel, F T A; Papp, Tibor; Stöhr, Anke C; Marschang, Rachel E

2014-06-01

In the years 2011-2012, a consensus nested polymerase chain reaction was used for the detection of adenovirus (AdV) infection in reptiles. During this screening, three new AdVs were detected. One of these viruses was detected in three lizards from a group of green striped tree dragons (Japalura splendida). Another was detected in a green anole (Anolis carolinensis). A third virus was detected in a Jackson's chameleon (Chamaeleo jacksonii). Analysis of a portion of the DNA-dependent DNA polymerase genes of each of these viruses revealed that they all were different from one another and from all previously described reptilian AdVs. Phylogenetic analysis of the partial DNA polymerase gene sequence showed that all newly detected viruses clustered within the genus Atadenovirus. This is the first description of AdVs in these lizard species.

Study of K. pi. scattering using the reactions K/sup + -/p. -->. K/sup + -/. pi. /sup +/n and K/sup + -/p. -->. K/sup + -/. pi. /sup -/. delta. /sup + +/ at 13 GeV/c

Energy Technology Data Exchange (ETDEWEB)

Estabrooks, P [McGill Univ., Montreal, Quebec (Canada); Carnegie, R K [Carleton Univ., Ottawa, Ontario (Canada); Martin, A D [Durham Univ. (UK); Dunwoodie, W M; Lasinski, T A; Leith, D W.G.S. [Stanford Linear Accelerator Center, Calif. (USA)

1978-02-27

An elastic K..pi.. partial-wave analysis is presented. It is based on high-statistics data for the reactions K/sup + -/p ..-->.. K/sup + -/..pi../sup +/n and K/sup + -/p ..-->.. K/sup + -/..pi../sup -/..delta../sup + +/ at 13 GeV obtained in a spectrometer experiment performed at SLAC. For each reaction, a t-dependent parametrization of the production amplitudes provides information on both the K..pi.. mass dependence of the production mechanisms and on K..pi.. scattering. Knowledge of the t-dependence then allows a calculation of the K..pi.. partial-wave amplitudes for K..pi.. masses from 0.7 to 1.9 GeV. The results of such analyses using data for (i) the neutral recoil reactions, (ii) the ..delta../sup + +/ recoil reactions, and (iii) both neutron and ..delta../sup + +/ recoil reactions simultaneously are presented.

IWTS metal-water reaction rate evaluation (Fauske and Associates report 99-26)

Energy Technology Data Exchange (ETDEWEB)

DUNCAN, D.R.

1999-07-29

The report presents a thermal stability analysis of partially metallic particulate in two IWTS components, the knock out pot and settlers. Particulate in the knock out pot is thermally stable for combinations of average particle size and metal mass fraction which appear realistic. Particulate in the settlers is thermally stable when a realistic account of particle reactions over time, metal fraction, and size distribution is considered.

Association between NLPR1, NLPR3, and P2X7R Gene Polymorphisms with Partial Seizures

Directory of Open Access Journals (Sweden)

Haidong Wang

2017-01-01

Full Text Available Objectives. Clinical and experimental evidence has clarified that the inflammatory processes within the brain play a pivotal role in the pathophysiology of seizures and epilepsy. Inflammasomes and P2X7 purinergic receptor (P2X7R are important mediators during the inflammatory process. Therefore, we investigated the possible association between partial seizures and inflammasomes NLPR1, NLRP3, and P2X7R gene polymorphisms in the present study. Method. A total of 163 patients and 201 health controls were enrolled in this study and polymorphisms of NLPR1, NLRP3, and P2X7R genes were detected using polymerase chain reaction- (PCR- ligase detection reaction method. Result. The frequency of rs878329 (G>C genotype with C (CG + CC was significantly lower among patients with partial seizures relative to controls (OR = 2.033, 95% CI = 1.290–3.204, p=0.002 for GC + CC versus GG. Intriguingly, we found that the significant difference of rs878329 (G>C genotype and allele frequency only existed among males (OR = 2.542, 95% CI = 1.344–4.810, p=0.004 for GC + CC versus GG, while there was no statistically significant difference among females. However, no significant results were presented for the genotype distributions of rs8079034, rs4612666, rs10754558, rs2027432, rs3751143, and rs208294 polymorphisms between patients and controls. Conclusion. Our study demonstrated the potentially significant role of NLRP1 rs878329 (G>C in developing susceptibility to the partial seizures in a Chinese Han population.

Visualizing a Catalyst at Work during the Ignition of the Catalytic Partial Oxidation of Methane

DEFF Research Database (Denmark)

Kimmerle, Bertram; Grunwaldt, Jan-Dierk; Baiker, Alfons

2009-01-01

We present a spatiotemporal operando X-ray absorption study of a highly dynamic process, the ignition of the noble metal catalyzed partial oxidation of methane. Evolvement and propagation of the platinum component's structural changes are investigated with a high-speed X-ray camera, which...... in combination with temperature profiling by IR-thermography and catalytic activity measurements by online mass spectrometry gives insight into the first stages of the ignition of the reaction toward hydrogen and carbon monoxide....

Taguchi method for partial differential equations with application in tumor growth.

Science.gov (United States)

Ilea, M; Turnea, M; Rotariu, M; Arotăriţei, D; Popescu, Marilena

2014-01-01

The growth of tumors is a highly complex process. To describe this process, mathematical models are needed. A variety of partial differential mathematical models for tumor growth have been developed and studied. Most of those models are based on the reaction-diffusion equations and mass conservation law. A variety of modeling strategies have been developed, each focusing on tumor growth. Systems of time-dependent partial differential equations occur in many branches of applied mathematics. The vast majority of mathematical models in tumor growth are formulated in terms of partial differential equations. We propose a mathematical model for the interactions between these three cancer cell populations. The Taguchi methods are widely used by quality engineering scientists to compare the effects of multiple variables, together with their interactions, with a simple and manageable experimental design. In Taguchi's design of experiments, variation is more interesting to study than the average. First, Taguchi methods are utilized to search for the significant factors and the optimal level combination of parameters. Except the three parameters levels, other factors levels other factors levels would not be considered. Second, cutting parameters namely, cutting speed, depth of cut, and feed rate are designed using the Taguchi method. Finally, the adequacy of the developed mathematical model is proved by ANOVA. According to the results of ANOVA, since the percentage contribution of the combined error is as small. Many mathematical models can be quantitatively characterized by partial differential equations. The use of MATLAB and Taguchi method in this article illustrates the important role of informatics in research in mathematical modeling. The study of tumor growth cells is an exciting and important topic in cancer research and will profit considerably from theoretical input. Interpret these results to be a permanent collaboration between math's and medical oncologists.

Two-component multistep direct reactions: A microscopic approach

International Nuclear Information System (INIS)

Koning, A.J.; Chadwick, M.B.

1998-03-01

The authors present two principal advances in multistep direct theory: (1) A two-component formulation of multistep direct reactions, where neutron and proton excitations are explicitly accounted for in the evolution of the reaction, for all orders of scattering. While this may at first seem to be a formidable task, especially for multistep processes where the many possible reaction pathways becomes large in a two-component formalism, the authors show that this is not so -- a rather simple generalization of the FKK convolution expression 1 automatically generates these pathways. Such considerations are particularly relevant when simultaneously analyzing both neutron and proton emission spectra, which is always important since these processes represent competing decay channels. (2) A new, and fully microscopic, method for calculating MSD cross sections which does not make use of particle-hole state densities but instead directly calculates cross sections for all possible particle-hole excitations (again including an exact book-keeping of the neutron/proton type of the particle and hole at all stages of the reaction) determined from a simple non-interacting shell model. This is in contrast to all previous numerical approaches which sample only a small number of such states to estimate the DWBA strength, and utilize simple analytical formulae for the partial state density, based on the equidistant spacing model. The new approach has been applied, along with theories for multistep compound, compound, and collective reactions, to analyze experimental emission spectra for a range of targets and energies. The authors show that the theory correctly accounts for double-differential nucleon spectra

Partial Actions and Power Sets

Directory of Open Access Journals (Sweden)

Jesús Ávila

2013-01-01

Full Text Available We consider a partial action (X,α with enveloping action (T,β. In this work we extend α to a partial action on the ring (P(X,Δ,∩ and find its enveloping action (E,β. Finally, we introduce the concept of partial action of finite type to investigate the relationship between (E,β and (P(T,β.

Modeling of termokinetic oscillations at partial oxidation of methane

Science.gov (United States)

Arutyunov, A. V.; Belyaev, A. A.; Inovenkov, I. N.; Nefedov, V. V.

2017-12-01

Partial oxidation of natural gas at moderate temperatures below 1500 K has significant interest for a number of industrial applications. But such processes can proceed at different unstable regimes including oscillating modes. Nonlinear phenomena at partial oxidation of methane were observed at different conditions. The investigation of the complex nonlinear system of equations that describes this process is a real method to insure its stability at industrial conditions and, at the same time, is an effective tool for its further enhancement. Numerical analysis of methane oxidation kinetics in the continuous stirred-tank reactor, with the use of detailed kinetic model has shown the possibility of the appearance of oscillating modes in the appropriate range of reaction parameters that characterize the composition, pressure, reagents flow, thermophysical features of the system, and geometry of the reactor. The appearance of oscillating modes is connected both with the reaction kinetics, heat release and sink and reagents introduction and removing. At that, oscillations appear only at a limited range of parameters, but can be accompanied by significant change in the yield of products. We have determined the range of initial temperature and pressure at which oscillations can be observed, if all other parameters remained fixed. The boundaries of existence of oscillations on the phase plane were calculated. It was shown that depending on the position inside the oscillation region the oscillations have different frequency and amplitude. It was reviled the role of heat exchange with the environment: at the absence of heat exchange the oscillating modes are impossible. In the vicinity of the boundary of phase range, where oscillations exist, significant change of concentration of some products were observed, for example, that of CO2, which in this case one of the principal products is. At that, insignificant increase in pressure not only change the character of CO2 behaving

Study of the obtainment of Mo_2C by gas-solid reaction in a fixed and rotary bed reactor

International Nuclear Information System (INIS)

Araujo, C.P.B. de; Souza, C.P. de; Souto, M.V.M.; Barbosa, C.M.; Frota, A.V.V.M.

2016-01-01

Carbides' synthesis via gas-solid reaction overcomes many of the difficulties found in other processes, requiring lower temperatures and reaction times than traditional metallurgic routes, for example. In carbides' synthesis in fixed bed reactors (FB) the solid precursor is permeated by the reducing/carburizing gas stream forming a packed bed without mobility. The use of a rotary kiln reactor (RK) adds a mixing character to this process, changing its fluid-particle dynamics. In this work ammonium molybdate was subjected to carbo-reduction reaction (CH4 / H2) in both reactors under the same gas flow (15L / h) and temperature (660 ° C) for 180 minutes. Complete conversion was observed Mo2C (dp = 18.9nm modal particles sizes' distribution) in the fixed bed reactor. In the RK reactor this conversion was only partial (∼ 40%) and Mo2C and MoO3 (34nm dp = bimodal) could be observed on the produced XRD pattern. Partial conversion was attributed to the need to use higher solids loading in the reactor CR (50% higher) to avoid solids to centrifuge. (author)

The effect of loading and particle size on the oxygen reaction in CGO impregnated Pt electrodes

DEFF Research Database (Denmark)

Lund, Anders; Hansen, Karin Vels; Jacobsen, Torben

2012-01-01

Porous platinum electrodes impregnated with Gd x Ce1−x O2−δ (CGO) are investigated to characterise how nano-sized CGO grains affect the oxygen reaction. Impedance measurements were performed at temperatures between 450 and 750 °C and at oxygen partial pressures of 0.2 and 5 × 10−5 bar for electro......Porous platinum electrodes impregnated with Gd x Ce1−x O2−δ (CGO) are investigated to characterise how nano-sized CGO grains affect the oxygen reaction. Impedance measurements were performed at temperatures between 450 and 750 °C and at oxygen partial pressures of 0.2 and 5 × 10−5 bar...... for electrodes with various CGO loadings and electrodes annealed at various temperatures. The morphology was characterised by scanning electron microscopy and the CGO grain size was determined from X-ray diffraction peak broadening. The results showed that the polarisation resistance decreased with increasing...

Nonelastic nuclear reactions induced by light ions with the BRIEFF code

CERN Document Server

Duarte, H

2010-01-01

The intranuclear cascade (INC) code BRIC has been extended to compute nonelastic reactions induced by light ions on target nuclei. In our approach the nucleons of the incident light ion move freely inside the mean potential of the ion in its center-of-mass frame while the center-of-mass of the ion obeys to equations of motion dependant on the mean nuclear+Coulomb potential of the target nucleus. After transformation of the positions and momenta of the nucleons of the ion into the target nucleus frame, the collision term between the nucleons of the target and of the ion is computed taking into account the partial or total breakup of the ion. For reactions induced by low binding energy systems like deuteron, the Coulomb breakup of the ion at the surface of the target nucleus is an important feature. Preliminary results of nucleon production in light ion induced reactions are presented and discussed.

Partial splenic artery embolization with gelatin sponge or with lipiodol for hypersplenism: a comparative study

International Nuclear Information System (INIS)

Liu Yamin; Sun Gangqing; Qin Hao; Wang Chongbao

2010-01-01

Objective: To discuss the effects and the complications of partial splenic artery embolization with gelatin sponge or with lipiodol for hypersplenism, to provide scientific information helpful for the selection of embolization materials in clinical practice. Methods: Partial splenic artery embolization with gelatin sponge was performed in forty patients with hypersplenism due to cirrhosis (gelatin sponge group) and partial splenic artery embolization with lipiodol was carried out in another thirty-nine patients (lipiodol group). The clinical data were retrospectively analyzed. The laboratory studies, complications and recurrence were observed and compared between two groups. Results: No significant difference in the reduction of splenic size, in the hemoglobin levels and in the thrombocyte and leucocyte counts existed between two groups (P > 0.05). However, the platelet count in lipiodol group was obviously decreased three months after the treatment. The occurrence of complications in gelatin sponge group was much higher than that in lipiodol group (P < 0.05). The toxic reaction of the liver and gastrointestinal tract in lipiodol group was significantly slighter than that in gelatin sponge group. Conclusion: Partial splenic artery embolization with lipiodol should be employed for the treatment of hypersplenism when the patient is elder and the disease is accompanied by poor liver function, massive ascites, severe dysfunction of blood coagulation and serious portal hypertension. (authors)

Tuning the two-dimensional electron liquid at oxide interfaces by buffer-layer-engineered redox reactions

DEFF Research Database (Denmark)

Chen, Yunzhong; Green, Robert J.; Sutarto, Ronny

2017-01-01

Polar discontinuities and redox reactions provide alternative paths to create two-dimensional electron liquids (2DELs) at oxide interfaces. Herein, we report high mobility 2DELs at interfaces involving SrTiO3 (STO) achieved using polar La7/8Sr1/8MnO3 (LSMO) buffer layers to manipulate both...... polarities and redox reactions from disordered overlayers grown at room temperature. Using resonant x-ray reflectometry experiments, we quantify redox reactions from oxide overlayers on STO as well as polarity induced electronic reconstruction at epitaxial LSMO/STO interfaces. The analysis reveals how...... these effects can be combined in a STO/LSMO/disordered film trilayer system to yield high mobility modulation doped 2DELs, where the buffer layer undergoes a partial transformation from perovskite to brownmillerite structure. This uncovered interplay between polar discontinuities and redox reactions via buffer...

The reaction np→ pp π- from threshold up to 570 MeV

International Nuclear Information System (INIS)

Daum, M.; Finger, M.; Slunecka, M.; Finger, M. Jr.; Janata, A.; Franz, J.; Heinsius, F.H.; Koenigsmann, K.; Lacker, H.; Schmitt, H.; Schweiger, W.; Sereni, P.

2002-01-01

The reaction np→ppπ - has been studied in a kinematically complete measurement with a large acceptance time-of-flight spectrometer for incident neutron energies between threshold and 570 MeV. The proton-proton invariant mass distributions show a strong enhancement due to the pp( 1 S 0 ) final state interaction. A large anisotropy was found in the pion angular distributions in contrast to the reaction pp→ppπ 0 . At small energies, a large forward/backward asymmetry has been observed. From the measured integrated cross section σ(np→ppπ - ), the isoscalar cross section σ 01 has been extracted. Its energy dependence indicates that mainly partial waves with Sp final states contribute. (orig.)

Unsaturated b-ketoesters and their Ni(II, Cu(II and Zn(II complexes

Directory of Open Access Journals (Sweden)

MUHAMMED BASHEER UMMATHUR

2009-03-01

Full Text Available A new series of b-ketoesters in which the keto group is attached to the olefinic linkage were synthesized by the reaction of methyl acetoacetate and aromatic aldehydes under specified conditions. The existence of these compounds predominantly in the intramolecularly hydrogen bonded enol form was well demonstrated from their IR, 1H-NMR and mass spectral data. Details on the formation of their [ML2] complexes with Ni(II, Cu(II and Zn(II and the nature of the bonding are discussed on the basis of analytical and spectral data.

Influence of phase transition on pattern formation during catalytic reactions

OpenAIRE

Andrade, Roberto Fernandes Silva; Lima, D.; Cunha, F. B.

2000-01-01

p.434–445 We investigate the influence of the order of surface phase transitions on pattern formation during chemical reaction on mono-crystal catalysts. We use a model consisting of two partial differential equations, one of which describes the dynamics of the surface state with the help of a Ginzburg–Landau potential. Second- or first-order transitions are described by decreasing or increasing the relative value of the third-order coefficient of the potential. We concentrate on the stabi...

Biological degradation of partially oxidated constituents of stabilized sapropel; Biologischer Abbau teiloxidierter Inhaltsstoffe stabilisierter Faulschlaemme

Energy Technology Data Exchange (ETDEWEB)

Scheminski, A.; Krull, R.; Hempel, D.C. [Technische Univ. Braunschweig (Germany). Inst. fuer Bioverfahrenstechnik

1999-07-01

Partial oxidation of sapropel with ozone destroys the cell walls of microorganisms in sludge and releases the cell constituents. Substances that are not biologically degraded because of the size or structure of their molecules are transformed into smaller, water-soluble and biologically degradable fractions by the reaction with ozone. The experiments aim to render the partially oxidated sewage sludge constituents highly biologically degradable using a minimum of oxidation agents. For the experiments described, stabilized sapropels with low biological activity are used. Hence the ozone is mainly used for the partial oxidation of recalcitrant constituents. (orig.) [German] Durch partielle Oxidation von Faulschlaemmen mit Ozon werden die Zellwaende der Mikroorganismen im Schlamm zerstoert und die Zellinhaltsstoffe freigesetzt. Dabei werden Substanzen, die aufgrund ihrer Molekuelgroesse oder -struktur biologisch nicht abgebaut werden, durch die Reaktion mit Ozon in kleinere, wasserloesliche und biologisch abbaubare Bruchstuecke ueberfuehrt. Ziel der Versuche ist es, durch den Einsatz moeglichst geringer Mengen an Oxidationsmitteln eine hohe biologische Abbaubarkeit der teiloxidierten Klaerschlamminhaltsstoffe zu erreichen. Fuer die hier vorgestellten Experimente wurden stabilisierte Faulschlaemme mit geringer biologischer Aktivitaet eingesetzt. Dadurch wird das Ozon vorwiegend zur Teiloxidation recalcitranter Inhaltsstoffe genutzt. (orig.)

Forced thermal cycling of catalytic reactions: experiments and modelling

DEFF Research Database (Denmark)

Jensen, Søren; Olsen, Jakob Lind; Thorsteinsson, Sune

2007-01-01

Recent studies of catalytic reactions subjected to fast forced temperature oscillations have revealed a rate enhancement increasing with temperature oscillation frequency. We present detailed studies of the rate enhancement up to frequencies of 2.5 Hz. A maximum in the rate enhancement is observed...... at about 1 Hz. A model for the rate enhancement that includes the surface kinetics and the dynamic partial pressure variations in the reactor is introduced. The model predicts a levelling off of the rate enhancement with frequency at about 1 Hz. The experimentally observed decrease above 1 Hz is explained...

A SIFT study of the reactions of H2ONO+ ions with several types of organic molecules

Science.gov (United States)

Smith, David; Wang, Tianshu; Spanel, Patrik

2003-11-01

A selected ion flow tube (SIFT) study has been carried out of the reactions of hydrated nitrosonium ions, NO+H2O, which theory has equated to protonated nitrous acid ions, H2ONO+. One objective of this study was to investigate if this ion exhibits the properties of both a cluster ion and a protonated acid in their reactions with a variety of organic molecules. The chosen reactant molecules comprise two each of the following types--amines, terpenes, aromatic hydrocarbons, esters, carboxylic acids, ketones, aldehydes and alcohols. The reactant H2ONO+ (NO+H2O) ions are formed in a discharge ion source and injected into helium carrier gas where they are partially vibrationally excited and partially dissociated to NO+ ions. Hence, the reactions of the H2ONO+ ions had to be studies simultaneously with NO+ ions, the reactions of the latter ions readily being studied by selectively injecting NO+ ions into the carrier gas. The results of this study indicate that the H2ONO+ ions undergo a wide variety of reaction processes that depend on the properties of the reactant molecules such as their ionisation energies and proton affinities. These processes include charge transfer with compounds, M, that have low ionisation energies (producing M+), proton transfer with compounds possessing large proton affinities (MH+), hydride ion transfer (M---H+), alkyl radical (M---R+), alkoxide radical transfer (M---OR+), ion-molecule association (NO+H2OM) and ligand switching (NO+M), producing the ions given in parentheses.

Analysis of the width correlation in 54Fe(nγ)55Fe reaction

International Nuclear Information System (INIS)

Knat'ko, V.A.; Shimanovich, E.A.

1982-01-01

To find out structural effects manifesting themselves in the form of correlation between widths of different channels of γ decay of levels and violation of Porter-Thomas distribution, calculated are partial widths of levels for 20 high-energy γ transitions in the 54 Fe(nγ) 55 Fe reaction. Calculations are carried out for widths in relation to γ transitions on 8 low p levels of 55 Fe, for 100 sets of partial γ widths (20 widths in a set). Results of analysis of theoretical values of partial γ widths of s resonances are presented in the form of the table. Results, obtained, show that consideration of contributions into γ decay of one-particle-vibrational configurations improve the accordance with experimental data, in comparison with calculations according to the model of valent capture. It is concluded that properties of γ widths of 55 Fe resonances, calculated in studied model, agree satisfactorily with properties of experimental γ widths [ru

Production and decay of baryonic resonances in pion induced reactions

Directory of Open Access Journals (Sweden)

Przygoda Witold

2016-01-01

Full Text Available Pion induced reactions give unique opportunities for an unambiguous description of baryonic resonances and their coupling channels. A systematic energy scan and high precision data, in conjunction with a partial wave analysis, allow for the study of the excitation function of the various contributions. A review of available world data unravels strong need for modern facilities delivering measurements with a pion beam. Recently, HADES collaboration collected data in pion-induced reactions on light (12C and heavy (74W nuclei at a beam momentum of 1.7 GeV/c dedicated to strangeness production. It was followed by a systematic scan at four different pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c in π− − p reaction in order to tackle the role of N(1520 resonance in conjunction with the intermediate ρ production. First results on exclusive channels with one pion (π− p and two pions (nπ+π−, pπ−π0 in the final state are discussed.

High-resolution measurement of the 16O(γ,pn) reaction

International Nuclear Information System (INIS)

Isaksson, L.

1996-10-01

The 16 O(γ,pn) reaction has been measured with a resolution high enough to resolve individual low-lying states in the residual 14 N nucleus. Partial cross-sections, available to the acceptance of the detector system, have been extracted for the individual states, and compared to a recent calculation based on absorption on one-pion exchange currents and the Δ resonance current. The experiment was performed at the Maxlab accelerator laboratory in Lund, Sweden, using tagged photons at an energy of 67 - 76 MeV. The proton detector angular range was 60 - 100 deg and the corresponding for the neutron detector 81 - 103 deg. A missing energy resolution of 1.5 MeV was obtained. The relative population of the states in the residual 14 N nucleus indicates that the reaction takes place predominantly on proton-neutron pairs coupled to (J π ,T) = (1 + ,0). The cross-section for absorption on (0 + ,1) pairs is strongly suppressed. Furthermore, the relative population of the states indicates that both L=0 and L=2 pairs participate in the reaction. 45 refs

Vitamin E-deficiency did not exacerbate partial skin reactions in mice locally irradiated with X-rays

International Nuclear Information System (INIS)

Chi, C.; Hayashi, Daisuke; Nemoto, Masato; Nyui, Minako; Anzai, Kazunori; Urano, Shiro

2011-01-01

We previously showed that free radicals and oxidative stress are involved in radiation-induced skin reactions. Since vitamin E (VE) is a particularly important lipophilic antioxidant, VE-deficient mice were used to examine its effects on radiation-induced skin damage. The VE content of the skin was reduced to one fourth of levels of normal mice. Neither the time of onset nor the extent of the reactions quantified with a scoring system differed between normal and VE-deficient mice after local X-irradiation (50 Gy). Similarly, there was no difference in the levels of the ascorbyl radical between the groups, although they were higher in irradiated skin than non-irradiated skin. X-irradiation increased the amount of Bax protein in the skin of normal mice both in the latent and acute inflammatory stages, time- and dose-dependently. The increase was associated with an increase in cytochrome c in the cytosolic fraction, indicating that apoptosis was also promoted by the irradiation. The increase in Bax protein correlated well with the thickness of the skin. Although a deficiency in VE should lower resistance to free radicals in the mitochondrial membrane and thus enhance radiation-induced Bax expression and apoptosis, it actually attenuated the increase in Bax protein caused by irradiation. (author)

Human Biomechanical and Cardiopulmonary Responses to Partial Gravity – A Systematic Review

Directory of Open Access Journals (Sweden)

Charlotte Richter

2017-08-01

Full Text Available The European Space Agency has recently announced to progress from low Earth orbit missions on the International Space Station to other mission scenarios such as exploration of the Moon or Mars. Therefore, the Moon is considered to be the next likely target for European human space explorations. Compared to microgravity (μg, only very little is known about the physiological effects of exposure to partial gravity (μg < partial gravity <1 g. However, previous research studies and experiences made during the Apollo missions comprise a valuable source of information that should be taken into account when planning human space explorations to reduced gravity environments. This systematic review summarizes the different effects of partial gravity (0.1–0.4 g on the human musculoskeletal, cardiovascular and respiratory systems using data collected during the Apollo missions as well as outcomes from terrestrial models of reduced gravity with either 1 g or microgravity as a control. The evidence-based findings seek to facilitate decision making concerning the best medical and exercise support to maintain astronauts' health during future missions in partial gravity. The initial search generated 1,323 publication hits. Out of these 1,323 publications, 43 studies were included into the present analysis and relevant data were extracted. None of the 43 included studies investigated long-term effects. Studies investigating the immediate effects of partial gravity exposure reveal that cardiopulmonary parameters such as heart rate, oxygen consumption, metabolic rate, and cost of transport are reduced compared to 1 g, whereas stroke volume seems to increase with decreasing gravity levels. Biomechanical studies reveal that ground reaction forces, mechanical work, stance phase duration, stride frequency, duty factor and preferred walk-to-run transition speed are reduced compared to 1 g. Partial gravity exposure below 0.4 g seems to be insufficient to maintain

Anion-π Catalysts with Axial Chirality.

Science.gov (United States)

Wang, Chao; Matile, Stefan

2017-09-04

The idea of anion-π catalysis is to stabilize anionic transition states by anion-π interactions on aromatic surfaces. For asymmetric anion-π catalysis, π-acidic surfaces have been surrounded with stereogenic centers. This manuscript introduces the first anion-π catalysts that operate with axial chirality. Bifunctional catalysts with tertiary amine bases next to π-acidic naphthalenediimide planes are equipped with a bulky aromatic substituent in the imide position to produce separable atropisomers. The addition of malonic acid half thioesters to enolate acceptors is used for evaluation. In the presence of a chiral axis, the selective acceleration of the disfavored but relevant enolate addition was much better than with point chirality, and enantioselectivity could be observed for the first time for this reaction with small-molecule anion-π catalysts. Enantioselectivity increased with the π acidity of the π surface, whereas the addition of stereogenic centers around the aromatic plane did not cause further improvements. These results identify axial chirality of the active aromatic plane generated by atropisomerism as an attractive strategy for asymmetric anion-π catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

KINETICS OF THE REACTION OF ELEMENTAL FLUORINE WITH ZIRCONIUM CARBIDE AND ZIRCONIUM DIBORIDE AT HIGH TEMPERATURES

Energy Technology Data Exchange (ETDEWEB)

Kuriakose, A. K.; Margrave, J. L.

1963-09-15

The reaction between ZrC and F/sub 2/ was investigated at 278 to 410 deg C, using 31 mm HgF/syb 2/. The reaction was found to be linear with time, and linear rate constants were computed. The activation energy was determined to be 22.1 plus or minus 1.6 kcal/mole. ZrB/sub 2/ is not attacked by 31 mm HgF/sub 2/ below 500 deg C. The weight losses from reaction of ZrB/sub 2/ with F/sub 2/ at 600 to 900 deg C and of ZrC with F/sub 2/ at 700 to 950 deg C, were rneasured for a F/sub 2/ pressure of 2.7 mm Hg. Zero-time linear rate constants were calculated and found not to be strongly temperature-dependent above 600 deg C, and the activation energies are essentially zero for both ZrB/sub 2/ and ZrC. For ZrC at 350 deg C and for ZrB/sub 2/ at 700 deg C, the rate is approximately proportional to the square root of F/sub 2/ partial pressure, while for ZrC at 700 deg C, it is proportional to the 1.5 power of F/sub 2/ partial pressure. (D.L.C.)

Gynecological manifestations, histopathological findings, and schistosoma-specific polymerase chain reaction results among women with Schistosoma haematobium infection

DEFF Research Database (Denmark)

Randrianasolo, Bodo Sahondra; Jourdan, Peter Mark; Ravoniarimbinina, Pascaline

2015-01-01

BACKGROUND: The pathophysiology of female genital schistosomiasis (FGS) is only partially understood. This study aims to describe the histopathological findings, polymerase chain reaction (PCR) results, and gynecological manifestations of FGS in women with different intensities of Schistosoma hae...

Liftoff characteristics of partially premixed flames under normal and microgravity conditions

Energy Technology Data Exchange (ETDEWEB)

Lock, Andrew J.; Briones, Alejandro M.; Aggarwal, Suresh K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607 (United States); Qin, Xiao [Department of Mechanical & amp; Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Puri, Ishwar K. [Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Hegde, Uday [National Center for Microgravity Research, Cleveland, OH 44135 (United States)

2005-11-01

An experimental and computational investigation on the liftoff characteristics of laminar partially premixed flames (PPFs) under normal (1-g) and microgravity ({mu}-g) conditions is presented. Lifted methane-air PPFs were established in axisymmetric coflowing jets using nitrogen dilution and various levels of partial premixing. The {mu}-g experiments were conducted in the 2.2-s drop tower at the NASA Glenn Research Center. A time-accurate, implicit algorithm that uses a detailed description of the chemistry and includes radiation effects is used for the simulations. The predictions are validated through a comparison of the flame reaction zone topologies, liftoff heights, lengths, and oscillation frequencies. The effects of equivalence ratio, gravity, jet velocity, and radiation on flame topology, liftoff height, flame length, base structure, and oscillation frequency are characterized. Both the simulations and measurements indicate that under identical conditions, a lifted {mu}-g PPF is stabilized closer to the burner compared with the 1-g flame, and that the liftoff heights of both 1-g and {mu}-g flames decrease with increasing equivalence ratio and approach their respective nonpremixed flame limits. The liftoff height also increases as the jet velocity is increased. In addition, the flame base structure transitions from a triple- to a double-flame structure as the flame liftoff height decreases. A modified flame index is developed to distinguish between the rich premixed, lean premixed, and nonpremixed reaction zones near the flame base. The 1-g lifted flames exhibit well-organized oscillations due to buoyancy-induced instability, while the corresponding {mu}-g flames exhibit steady-state behavior. The effect of thermal radiation is to slightly decrease the liftoff heights of both 1-g and {mu}-g flames under coflow conditions.

Z-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid, an α-hydroxy acid from rooibos (Aspalathus linearis) with hypoglycemic activity

DEFF Research Database (Denmark)

Muller, C.J.F.; Joubert, Elizabeth; Pheiffer, Carmen

2013-01-01

Scope: The rare enolic phenylpyruvic acid glucoside, Z-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid (PPAG) is one of the major constituents of fermented rooibos infusions. 3-Phenylpyruvic acid (2-oxo-3-phenylpropanoic acid) (PPA), without the sugar moiety and with a keto instead of enolic arr...

Algorithms over partially ordered sets

DEFF Research Database (Denmark)

Baer, Robert M.; Østerby, Ole

1969-01-01

in partially ordered sets, answer the combinatorial question of how many maximal chains might exist in a partially ordered set withn elements, and we give an algorithm for enumerating all maximal chains. We give (in § 3) algorithms which decide whether a partially ordered set is a (lower or upper) semi......-lattice, and whether a lattice has distributive, modular, and Boolean properties. Finally (in § 4) we give Algol realizations of the various algorithms....

Partial Deconvolution with Inaccurate Blur Kernel.

Science.gov (United States)

Ren, Dongwei; Zuo, Wangmeng; Zhang, David; Xu, Jun; Zhang, Lei

2017-10-17

Most non-blind deconvolution methods are developed under the error-free kernel assumption, and are not robust to inaccurate blur kernel. Unfortunately, despite the great progress in blind deconvolution, estimation error remains inevitable during blur kernel estimation. Consequently, severe artifacts such as ringing effects and distortions are likely to be introduced in the non-blind deconvolution stage. In this paper, we tackle this issue by suggesting: (i) a partial map in the Fourier domain for modeling kernel estimation error, and (ii) a partial deconvolution model for robust deblurring with inaccurate blur kernel. The partial map is constructed by detecting the reliable Fourier entries of estimated blur kernel. And partial deconvolution is applied to wavelet-based and learning-based models to suppress the adverse effect of kernel estimation error. Furthermore, an E-M algorithm is developed for estimating the partial map and recovering the latent sharp image alternatively. Experimental results show that our partial deconvolution model is effective in relieving artifacts caused by inaccurate blur kernel, and can achieve favorable deblurring quality on synthetic and real blurry images.Most non-blind deconvolution methods are developed under the error-free kernel assumption, and are not robust to inaccurate blur kernel. Unfortunately, despite the great progress in blind deconvolution, estimation error remains inevitable during blur kernel estimation. Consequently, severe artifacts such as ringing effects and distortions are likely to be introduced in the non-blind deconvolution stage. In this paper, we tackle this issue by suggesting: (i) a partial map in the Fourier domain for modeling kernel estimation error, and (ii) a partial deconvolution model for robust deblurring with inaccurate blur kernel. The partial map is constructed by detecting the reliable Fourier entries of estimated blur kernel. And partial deconvolution is applied to wavelet-based and learning

Identification and Partial Characterization of an L-Tyrosine Aminotransferase (TAT from Arabidopsis thaliana

Directory of Open Access Journals (Sweden)

Pranav R. Prabhu

2010-01-01

Full Text Available The aminotransferase gene family in the model plant Arabidopsis thaliana consists of 44 genes. Twenty six of these enzymes are classified as characterized meaning that the reaction(s that the enzyme catalyzes are documented using experimental means. The remaining 18 enzymes are uncharacterized and are therefore deemed putative. Our laboratory is interested in elucidating the function(s of the remaining putative aminotransferase enzymes. To this end, we have identified and partially characterized an aminotransferase (TAT enzyme from Arabidopsis annotated by the locus tag At5g36160. The full-length cDNA was cloned and the purified recombinant enzyme was characterized using in vitro and in vivo experiments. In vitro analysis showed that the enzyme is capable of interconverting L-Tyrosine and 4-hydroxyphenylpyruvate, and L-Phenylalanine and phenylpyruvate. In vivo analysis by functional complementation showed that the gene was able to complement an E. coli with a background of aminotransferase mutations that confers auxotrophy for L-Tyrosine and L-Phenylalanine.

Redox reaction and foaming in nuclear waste glass melting

Energy Technology Data Exchange (ETDEWEB)

Ryan, J.L.

1995-08-01

This document was prepared by Pacific Northwest Laboratory (PNL) and is an attempt to analyze and estimate the effects of feed composition variables and reducing agent variables on the expected chemistry of reactions occurring in the cold cap and in the glass melt in the nuclear waste glass Slurry-fed, joule-heated melters as they might affect foaming during the glass-making process. Numerous redox reactions of waste glass components and potential feed additives, and the effects of other feed variables on these reactions are reviewed with regard to their potential effect on glass foaming. A major emphasis of this report is to examine the potential positive or negative aspects of adjusting feed with formic acid as opposed to other feed modification techniques including but not limited to use of other reducing agents. Feed modification techniques other than the use of reductants that should influence foaming behavior include control of glass melter feed pH through use of nitric acid. They also include partial replacement of sodium salts by lithium salts. This latter action (b) apparently lowers glass viscosity and raises surface tension. This replacement should decrease foaming by decreasing foam stability.

A study of paint sludge deactivation by pyrolysis reactions

Directory of Open Access Journals (Sweden)

Muniz L.A.R.

2003-01-01

Full Text Available The production of large quantities of paint sludge is a serious environmental problem. This work evaluates the use of pyrolysis reaction as a process for deactivating paint sludge that generates a combustible gas phase, a solvent liquid phase and an inert solid phase. These wastes were classified into three types: water-based solvent (latex resin and solvents based on their resins (alkyd and polyurethane. An electrically heated stainless steel batch reactor with a capacity of 579 mL and a maximum pressure of 30 atm was used. Following the reactor, a flash separator, which was operated at atmospheric pressure, partially condensed and separated liquid and gas products. Pressure and temperature were monitored on-line by a control and data acquisition system, which adjusted the heating power supplied to the pyrolysis reactor. Reactions followed an experimental design with two factors (reaction time and temperature and three levels (10, 50 and 90 minutes; 450, 550 and 650degreesC. The response variables were liquid and solid masses and net heat of combustion. The optimal operational range for the pyrolysis process was obtained for each response variable. A significant reduction in total mass of solid waste was obtained.

Flexible single molecule simulation of reaction-diffusion processes

International Nuclear Information System (INIS)

Hellander, Stefan; Loetstedt, Per

2011-01-01

An algorithm is developed for simulation of the motion and reactions of single molecules at a microscopic level. The molecules diffuse in a solvent and react with each other or a polymer and molecules can dissociate. Such simulations are of interest e.g. in molecular biology. The algorithm is similar to the Green's function reaction dynamics (GFRD) algorithm by van Zon and ten Wolde where longer time steps can be taken by computing the probability density functions (PDFs) and then sample from the distribution functions. Our computation of the PDFs is much less complicated than GFRD and more flexible. The solution of the partial differential equation for the PDF is split into two steps to simplify the calculations. The sampling is without splitting error in two of the coordinate directions for a pair of molecules and a molecule-polymer interaction and is approximate in the third direction. The PDF is obtained either from an analytical solution or a numerical discretization. The errors due to the operator splitting, the partitioning of the system, and the numerical approximations are analyzed. The method is applied to three different systems involving up to four reactions. Comparisons with other mesoscopic and macroscopic models show excellent agreement.

Partial-Wave Analysis of Centrally Produced Two-Pseudoscalar Final States in pp Reactions at COMPASS

CERN Document Server

Austregesilo, Alexander

2014-01-01

COMPASS is a fixed-target experiment at the CERN SPS which focused on light-quark hadron spectroscopy during the data taking periods in 2008 and 2009. A world-leading data set was collected with a 190GeV/c hadron beam impinging on a liquid hydrogen target in order to study, inter alia, the central exclusive production of glueball candidates in the light-meson sector. Especially the double-Pomeron exchange mechanism is well suited for the production of mesons without valence quark content. We select centrally produced systems with two pseudo-scalar mesons in the final state from the COMPASS data set recorded with an incoming proton. The decay of this system is decomposed in terms of partial waves, where particular attention is paid to the inherent mathematical ambiguities of the amplitude analysis. Furthermore, we show that simple parametrisations are able to describe the mass dependence of the fit results with sensible Breit-Wigner parameters.

Pressure effects on electron reactions and mobility in nonpolar liquids

International Nuclear Information System (INIS)

Holroyd, R.A.; Nishikawa, Masaru

2002-01-01

High pressure studies have elucidated the mechanisms of both electron reactions and electron transport in nonpolar liquids and provided information about the partial molar volumes of ions and electrons. The very large volume changes associated with electron attachment reactions have been explained as due to electrostriction by the ions, calculated with a continuum model, but modified to include the formation of a glassy shell of solvent molecules around the ion. The mobilities of electrons in cases where the electron is trapped can now be understood by comparing the trap cavity volume with the volume of electrostriction of the solvent around the cavity. In cases where the electron is quasi-free the compressibility dependent potential fluctuations are shown to be important. The isothermal compressibility is concluded to be the single most important parameter determining the behavior of excess electrons in liquids

EFFECT OF FLUORINE AND CHLORINE IONS ON THE REACTION SINTERING OF MECHANICALLY ACTIVATED ZIRCON-ALUMINA MIXTURE

Directory of Open Access Journals (Sweden)

R. Zamani Foroshani

2015-09-01

Full Text Available The aim of this work was to study the effect of fluorine and chlorine ions on the formation of mullite during the reaction sintering of mechanically activated zircon-alumina powder mixture. The results showed that mechanical activation of zirconalumina powder mixture for 20 h led to grain refinement and partial amorphization. In the presence of fluorine and chlorine ions, complete formation of mullite in the mechanically activated sample occurred after 2 h of reaction sintering at 1300oC and 1400oC, respectively. In the sample lacking fluorine and chlorine ions, mullitization was not completed even after 2 h of reaction sintering at 1400oC. It was concluded that presence of fluorine and chlorine ions enhance the dissociation of zircon and formation of mullite during the reaction sintering of mechanically activated zircon-alumina mixture.

Buffering dissociation/formation reaction of biogenic calcium carbonate.

Science.gov (United States)

Ichikawa, Kazuhiko

2007-01-01

The oscillating stability of coral reef seawater pH has been maintained at around physiological pH values over the past 300 years (Pelejero et al., 2005). The stability mechanism of its pH has been interpreted in terms of the buffering dissolution/formation reaction of CaCO(3) as well as the proton consumption/generation reaction in CaCO(3)-saturated water. Here the pH-dependent solubility product [HCO(3)(-)][Ca(2+)] has been derived on the basis of the actual pH-dependent reactions for the atmospheric CO(2)/CO(2 (aq.))/HCO(3)(-)/CO(3)(2-)/Ca(2+)/CaCO(3) system. Overbasic pH peaks appeared between pH approximately 8 and approximately 9.5 during sodium hydroxide titration, as a result of simultaneous CaCO(3) formation and proton generation. The spontaneous and prompt water pH recovery from the acidic to the physiological range has been confirmed by the observation of acid/base time evolution, because of simultaneous CaCO(3) dissolution and proton consumption. The dissolution/formation of CaCO(3) in water at pH 7.5-9 does not take place without a proton consumption/generation reaction, or a buffering chemical reaction of HCO(3)(-)+Ca(2+)right arrow over left arrowCaCO(3)+H(+). SEM images of the CaCO(3) fragments showed that the acid water ate away at the CaCO(3) formed at physiological pH values. Natural coral reefs can thus recover the physiological pH levels of seawater from the acidic range through partial dissolution of their own skeletons.

Algebraic partial Boolean algebras

International Nuclear Information System (INIS)

Smith, Derek

2003-01-01

Partial Boolean algebras, first studied by Kochen and Specker in the 1960s, provide the structure for Bell-Kochen-Specker theorems which deny the existence of non-contextual hidden variable theories. In this paper, we study partial Boolean algebras which are 'algebraic' in the sense that their elements have coordinates in an algebraic number field. Several of these algebras have been discussed recently in a debate on the validity of Bell-Kochen-Specker theorems in the context of finite precision measurements. The main result of this paper is that every algebraic finitely-generated partial Boolean algebra B(T) is finite when the underlying space H is three-dimensional, answering a question of Kochen and showing that Conway and Kochen's infinite algebraic partial Boolean algebra has minimum dimension. This result contrasts the existence of an infinite (non-algebraic) B(T) generated by eight elements in an abstract orthomodular lattice of height 3. We then initiate a study of higher-dimensional algebraic partial Boolean algebras. First, we describe a restriction on the determinants of the elements of B(T) that are generated by a given set T. We then show that when the generating set T consists of the rays spanning the minimal vectors in a real irreducible root lattice, B(T) is infinite just if that root lattice has an A 5 sublattice. Finally, we characterize the rays of B(T) when T consists of the rays spanning the minimal vectors of the root lattice E 8

[Removable partial dentures. Oral functions and types].

Science.gov (United States)

Creugers, N H J; de Baat, C

2009-11-01

A removable partial denture enables the restoration or improvement of 4 oral functions: aesthetics, mandibular stability, mastication, and speech. However, wearing a removable partial denture should not cause oral comfort to deteriorate. There are 3 types of removable partial dentures: acrylic tissue-supported dentures, dentures with cast metal frameworks en dentures with cast metal frameworks and (semi)precision attachments. Interrupted tooth arches,free-ending tooth arches, and a combination of interrupted as well as free-ending tooth arches can be restored using these dentures. Well-known disadvantages of removable partial dentures are problematic oral hygiene, negative influence on the remaining dentition and limited oral comfort. Due to the advanced possibilities of fixed tooth- or implant-supported partial dentures, whether or not free-ending, or tooth- as well as implant-supported partial dentures, the indication of removable partial dentures is restricted. Nevertheless, for the time being the demand for removable partial dentures is expected to continue.

Modelling of the partial oxidation of {alpha}, {beta}-unsaturated aldehydes on Mo-V-oxides based catalysts

Energy Technology Data Exchange (ETDEWEB)

Boehnke, H.; Petzoldt, J.C.; Stein, B.; Weimer, C.; Gaube, J.W. [Technische Univ. Darmstadt (Germany). Inst. fuer Chemische Technologie

1998-12-31

A kinetic model based on the Mars-van Krevelen mechanism that allows to describe the microkinetics of the heterogeneously catalysed partial oxidation of {alpha}, {beta}-unsaturated aldehydes is presented. This conversion is represented by a network, composed of the oxidation of the {alpha}, {beta}-unsaturated aldehyde towards the {alpha}, {beta}-unsaturated carboxylic acid and the consecutive oxidation of the acid as well as the parallel reaction of the aldehyde to products of deeper oxidation. The reaction steps of aldehyde respectively acid oxidation and catalyst reoxidation have been investigated separately in transient experiments. The combination of steady state and transient experiments has led to an improved understanding of the interaction of the catalyst with the aldehyde and the carboxylic acids as well as to a support of the kinetic model assumptions. (orig.)

[Conventional retaining of removable partial dentures

NARCIS (Netherlands)

Keltjens, H.M.A.M.; Witter, D.J.; Creugers, N.H.J.

2009-01-01

Mechanical and biological criteria have to be met in retaining the metal frame of a removable partial denture. Additionally, a removable partial denture is part of the occlusal interface by the clasps and the denture teeth. With respect to mechanical aspects, all rigid parts of the removable partial

Nonlinear reaction-diffusion equations with delay: some theorems, test problems, exact and numerical solutions

Science.gov (United States)

Polyanin, A. D.; Sorokin, V. G.

2017-12-01

The paper deals with nonlinear reaction-diffusion equations with one or several delays. We formulate theorems that allow constructing exact solutions for some classes of these equations, which depend on several arbitrary functions. Examples of application of these theorems for obtaining new exact solutions in elementary functions are provided. We state basic principles of construction, selection, and use of test problems for nonlinear partial differential equations with delay. Some test problems which can be suitable for estimating accuracy of approximate analytical and numerical methods of solving reaction-diffusion equations with delay are presented. Some examples of numerical solutions of nonlinear test problems with delay are considered.

Invariant boxes and stability of some systems from biomathematics and chemical reactions

International Nuclear Information System (INIS)

Pavel, N.H.

1984-08-01

A general theorem on the flow-invariance of a time-dependent rectangular box with respect to a differential system is first recalled [''Analysis of some non-linear problems'' in Banach Spaces and Applications, Univ. of Iasi (Romania) (1982)]. Then a theorem applicable to the study of some differential systems from biomathematics and chemical reactions is given and proved. The theorem can be applied to enzymatic reactions, the chemical mechanism in the Belousov reaction, and the kinetic system for the chemical scheme of Hanusse of two processes with three intermediate species [in Pavel, N.H., Differential Equations, Flow-invariance and Applications, Pitman Publishing, Ltd., London (to appear)]. Next, the matrices A for which the corresponding linear system x'=Ax is component-wise positive asymptotically stable are characterized. In the Appendix a partial answer to an open problem regarding the preservation of both continuity and dissipativity in the extension of functions to a Banach space is given

Traveling wave solutions of a biological reaction-convection-diffusion equation model by using $(G'/G$ expansion method

Directory of Open Access Journals (Sweden)

Shahnam Javadi

2013-07-01

Full Text Available In this paper, the $(G'/G$-expansion method is applied to solve a biological reaction-convection-diffusion model arising in mathematical biology. Exact traveling wave solutions are obtained by this method. This scheme can be applied to a wide class of nonlinear partial differential equations.

NMR and IR investigations of strong intramolecular hydrogen bonds

DEFF Research Database (Denmark)

Hansen, Poul Erik; Spanget-Larsen, Jens

2017-01-01

been used as a parameter for hydrogen bond strength in O–H···O systems. On a broad scale, a correlation between OH stretching wavenumbers and O···O distances is observed, as demonstrated experimentally as well as theoretically, but for substituted beta-diketone enols this correlation is relatively weak.......–1, and 19 >  dOH > 15 ppm. Recent results as well as an account of theoretical advances are presented for a series of important classes of compounds such as beta-diketone enols, beta-thioxoketone enols, Mannich bases, proton sponges, quinoline N-oxides and diacid anions. The O···O distance has long...

New fundamental equations of thermodynamics for systems in chemical equilibrium at a specified partial pressure of a reactant and the standard transformed formation properties of reactants

International Nuclear Information System (INIS)

Alberty, R.A.; Oppenheim, I.

1993-01-01

When temperature, pressure, and the partial pressure of a reactant are fixed, the criterion of chemical equilibrium can be expressed in terms of the transformed Gibbs energy G' that is obtained by using a Legendre transform involving the chemical potential of the reactant that is fixed. For reactions of ideal gases, the most natural variables to use in the fundamental equation are T, P', and P B , where P' is the partial pressure of the reactants other than the one that is fixed and P B is the partial pressure of the reactant that is fixed. The fundamental equation for G' yields the expression for the transformed entropy S', and a transformed enthalpy can be defined by the additional Legendre transform H'=G'+TS'. This leads to an additional form of the fundamental equation. The calculation of transformed thermodynamic properties and equilibrium compositions is discussed for a simple system and for a general multireaction system. The change, in a reaction, of the binding of the reactant that is at a specified pressure can be calculated using one of the six Maxwell equations of the fundamental equation in G'

Partial Gene Cloning and Enzyme Structure Modeling of Exolevanase Fragment from Bacillus subtilis

Science.gov (United States)

Azhar, M.; Natalia, D.; Syukur, S.; Andriani, N.; Jamsari, J.

2018-04-01

Inulin hydrolysis thermophilic and thermotolerant bacteria are potential sources of inulin hydrolysis enzymes. Partial gene that encodes inulin hydrolysis enzymes had been isolated from Bacillus subtilis using polymerase chain reaction (PCR) method with the DPE.slFandDPE.eR degenerative primers. The partial gene was cloned into pGEM-T Easy vector with E. coli as host cells and analyzed using BLASTx, CrustalW2, and Phyre2 programs. Size of thepartial gene had been found539 bp that encoded 179aminoacid residues of protein fragment. The sequences of protein fragment was more similar to exolevanase than exoinulinase. The protein fragment had conserved motif FSGS, and specific hits GH32 β-fructosidase. It had three residues of active site and five residues of substrate binding. The active site on the protein fragment were D (1-WLNDP-5), D (125-FRDPK-129) and E (177-WEC-179). Substrate binding on the protein fragment were ND (1-WLNDP-5), Q (18-FYQY-21), FS (60-FSGS-63) RD (125-FRDPK-129) and E (177-WEC-179).

Solvent control of intramolecular proton transfer

DEFF Research Database (Denmark)

Manolova, Y.; Marciniak, Heinz; Tschierlei, S.

2017-01-01

of molecules in the enol and zwitterionic proton transfer (PT) form exists in the ground state. However, the zwitterion is the energetically favored one in the electronically excited state. Optical excitation of the enol form results in intramolecular proton transfer and formation of the PT form within 1.4 ps...

The reactions of p-nitroacetophenone with H and OH radicals

International Nuclear Information System (INIS)

Whillans, D.W.

1977-01-01

Reactions of the radiation sensitizer p-nitroacetophenone (PNAP) with H and OH radicals have been studied in detail. PNAP reacts with OH (k = (3.3 + 0.3) X 10 9 dm 3 mol -1 s -1 ), presumably in the main by ring addition, to produce a relatively weak absorption with a minor peak at 410 nm (epsilon approximately 2,000 dm 3 mol -1 cm -1 ). In contrast the electron adduct has a very strong absorption with peaks at 350 nm (epsilon approximately 18,200 dm 3 mol -1 cm -1 ) and 550 nm (epsilon approximately 2650 dm 3 mol -1 cm -1 ), in good agreement with literature values. At pH 1 the protonated adduct shows a single peak at 330 nm (epsilon approximately 20,500 dm 3 mol -1 cm -1 ). The spectra produced by reaction of PNAP with H atoms (k = (6 + - 0. 5) x 10 8 dm 3 mol -1 s -1 ) is intermediate between those with OH and with e - sub(aq), with peaks at 350 (epsilon approximately 7100 dm 3 mol -1 cm -1 ) and 550 nm (750 dm 3 mol -1 cm -1 ) at neutral pH and near 325 nm (epsilon approximately 7100 dm 3 mol -1 cm -1 ) at pH 1, but with significant shoulders near 410 nm. These data are consistent with a mechanism whereby H atoms react partially by addition to the nitro group (approximately 30%) and partially by ring addition (approximately 70%). (author)

Controlling Chemical Reactions in Confined Environments: Water Dissociation in MOF-74

Directory of Open Access Journals (Sweden)

Erika M. A. Fuentes-Fernandez

2018-02-01

Full Text Available The confined porous environment of metal organic frameworks (MOFs is an attractive system for studying reaction mechanisms. Compared to flat oxide surfaces, MOFs have the key advantage that they exhibit a well-defined structure and present significantly fewer challenges in experimental characterization. As an example of an important reaction, we study here the dissociation of water—which plays a critical role in biology, chemistry, and materials science—in MOFs and show how the knowledge of the structure in this confined environment allows for an unprecedented level of understanding and control. In particular, combining in-situ infrared spectroscopy and first-principles calculations, we show that the water dissociation reaction can be selectively controlled inside Zn-MOF-74 by alcohol, through both chemical and physical interactions. Methanol is observed to speed up water dissociation by 25% to 100%, depending on the alcohol partial pressure. On the other hand, co-adsorption of isopropanol reduces the speed of the water reaction, due mostly to steric interactions. In addition, we also investigate the stability of the product state after the water dissociation has occurred and find that the presence of additional water significantly stabilizes the dissociated state. Our results show that precise control of reactions within nano-porous materials is possible, opening the way for advances in fields ranging from catalysis to electrochemistry and sensors.

Photogenic partial seizures.

Science.gov (United States)

Hennessy, M J; Binnie, C D

2000-01-01

To establish the incidence and symptoms of partial seizures in a cohort of patients investigated on account of known sensitivity to intermittent photic stimulation and/or precipitation of seizures by environmental visual stimuli such as television (TV) screens or computer monitors. We report 43 consecutive patients with epilepsy, who had exhibited a significant EEG photoparoxysmal response or who had seizures precipitated by environmental visual stimuli and underwent detailed assessment of their photosensitivity in the EEG laboratory, during which all were questioned concerning their ictal symptoms. All patients were considered on clinical grounds to have an idiopathic epilepsy syndrome. Twenty-eight (65%) patients reported visually precipitated attacks occurring initially with maintained consciousness, in some instances evolving to a period of confusion or to a secondarily generalized seizure. Visual symptoms were most commonly reported and included positive symptoms such as coloured circles or spots, but also blindness and subjective symptoms such as "eyes going funny." Other symptoms described included nonspecific cephalic sensations, deja-vu, auditory hallucinations, nausea, and vomiting. No patient reported any clear spontaneous partial seizures, and there were no grounds for supposing that any had partial epilepsy excepting the ictal phenomenology of some or all of the visually induced attacks. These findings provide clinical support for the physiological studies that indicate that the trigger mechanism for human photosensitivity involves binocularly innervated cells located in the visual cortex. Thus the visual cortex is the seat of the primary epileptogenic process, and the photically triggered discharges and seizures may be regarded as partial with secondary generalization.

A theoretical and spectroscopic study of conformational structures of piroxicam

Science.gov (United States)

Souza, Kely Ferreira de; Martins, José A.; Pessine, Francisco B. T.; Custodio, Rogério

2010-02-01

Piroxicam (PRX) has been widely studied in an attempt to elucidate the causes and mechanisms of its side effects, mainly the photo-toxicity. In this paper fluorescence spectra in non-protic solvents and different polarities were carried out along with theoretical calculations. Preliminary potential surfaces of the keto and enol forms were obtained at AM1 level of theory providing the most stable conformers, which had their structure re-optimized through the B3LYP/CEP-31G(d,p) method. From the optimized structures, the electronic spectra were calculated using the TD-DFT method in vacuum and including the solvent effect through the PCM method and a single water molecule near PRX. A new potential surface was constructed to the enol tautomer at DFT level and the most stable conformers were submitted to the QST2 calculations. The experimental data showed that in apolar media, the solution fluorescence is raised. Based on conformational analysis for the two tautomers, keto and enol, the results indicated that the PRX-enol is the main tautomer related to the drug fluorescence, which is reinforced by the spectra results, as well as the interconvertion barrier obtained from the QST2 calculations. The results suggest that the PRX one of the enol conformers presents great possibility of involvement in the photo-toxicity mechanisms.

The partial-birth stratagem.

Science.gov (United States)

1998-06-01

In Wisconsin, physicians stopped performing abortions when a Federal District Court Judge refused to issue a temporary restraining order against the state's newly enacted "partial birth" abortion ban that was couched in such vague language it actually covered all abortions. While ostensibly attempting to ban late-term "intact dilation and extraction," the language of the law did not refer to that procedure or to late terms. Instead, it prohibited all abortions in which a physician "partially vaginally delivers a living child, causes the death of the partially delivered child with the intent to kill the child and then completes the delivery of the child." The law also defined "child" as "a human being from the time of fertilization" until birth. It is clear that this abortion ban is unconstitutional under Row v. Wade, and this unconstitutionality is compounded by the fact that the law allowed no exception to protect a woman's health, which is required by Roe for abortion bans after fetal viability. Wisconsin is only one of about 28 states that have enacted similar laws, and only two have restricted the ban to postviability abortions. Many of these laws have been struck down in court, and President Clinton has continued to veto the Federal partial-birth bill. The Wisconsin Judge acknowledged that opponents of the ban will likely prevail when the case is heard, but his action in denying the temporary injunction means that many women in Wisconsin will not receive timely medical care. The partial birth strategy is really only another anti-abortion strategy.

Method for reactivating solid catalysts used in alkylation reactions

Science.gov (United States)

Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

2003-06-17

A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

[Castleman's disease: Rapid desensitization for hypersensitivity reaction to rituximab].

Science.gov (United States)

Boin, C; Lambert, S; Thomann, P; Aujoulat, O; Kieffer, P

2016-06-01

Rapid desensitization allows secure administration of a drug and is indicated when there is no therapeutic alternative. We report a 49-year-old patient who presented with a hypersensitivity reaction following an infusion of rituximab (375mg/m(2)) in the context of a Castleman's syndrome. After a clinical flare (splenomegaly, adenopathies) despite treatment with tocilizumab, anakinra and valganciclovir, the reintroduction of rituximab was decided, according to the rapid desensitization protocol. Four full dose desensitizations were successfully performed allowing immediate clinical improvement (apyrexia, loss of sweating and lymphadenopathy, splenomegaly partial regression) and biological (negativation of HHV8 viral load, and disappearance of neutropenia, anemia and thrombocytopenia). Rapid desensitization is a promising method for the pursuit of rituximab therapy after a hypersensitivity reaction and should be considered in patients with no acceptable therapeutic alternative. Copyright © 2015 Société Nationale Française de Médecine Interne (SNFMI). Published by Elsevier SAS. All rights reserved.

Partially massless fields during inflation

Science.gov (United States)

Baumann, Daniel; Goon, Garrett; Lee, Hayden; Pimentel, Guilherme L.

2018-04-01

The representation theory of de Sitter space allows for a category of partially massless particles which have no flat space analog, but could have existed during inflation. We study the couplings of these exotic particles to inflationary perturbations and determine the resulting signatures in cosmological correlators. When inflationary perturbations interact through the exchange of these fields, their correlation functions inherit scalings that cannot be mimicked by extra massive fields. We discuss in detail the squeezed limit of the tensor-scalar-scalar bispectrum, and show that certain partially massless fields can violate the tensor consistency relation of single-field inflation. We also consider the collapsed limit of the scalar trispectrum, and find that the exchange of partially massless fields enhances its magnitude, while giving no contribution to the scalar bispectrum. These characteristic signatures provide clean detection channels for partially massless fields during inflation.

Isostable reduction with applications to time-dependent partial differential equations.

Science.gov (United States)

Wilson, Dan; Moehlis, Jeff

2016-07-01

Isostables and isostable reduction, analogous to isochrons and phase reduction for oscillatory systems, are useful in the study of nonlinear equations which asymptotically approach a stationary solution. In this work, we present a general method for isostable reduction of partial differential equations, with the potential power to reduce the dimensionality of a nonlinear system from infinity to 1. We illustrate the utility of this reduction by applying it to two different models with biological relevance. In the first example, isostable reduction of the Fokker-Planck equation provides the necessary framework to design a simple control strategy to desynchronize a population of pathologically synchronized oscillatory neurons, as might be relevant to Parkinson's disease. Another example analyzes a nonlinear reaction-diffusion equation with relevance to action potential propagation in a cardiac system.

The role of Ce(III) in BZ oscillating reactions

Science.gov (United States)

Nogueira, Paulo A.; Varela, Hamilton; Faria, Roberto B.

2012-03-01

Herein we present results on the oscillatory dynamics in the bromate-oxalic acid-acetone-Ce(III)/Ce(IV) system in batch and also in a CSTR. We show that Ce(III) is the necessary reactant to allow the emergence of oscillations. In batch, oscillations occur with Ce(III) and also with Ce(IV), but no induction period is observed with Ce(III). In a CSTR, no oscillations were found using a freshly prepared Ce(IV), but only when the cerium-containing solution was aged, allowing partial conversion of Ce(IV) to Ce(III) by reaction with acetone.

Calculation of partial molar volume of components in supercritical ammonia synthesis system

Institute of Scientific and Technical Information of China (English)

Cunwen WANG; Chuanbo YU; Wen CHEN; Weiguo WANG; Yuanxin WU; Junfeng ZHANG

2008-01-01

The partial molar volumes of components in supercritical ammonia synthesis system are calculated in detail by the calculation formula of partial molar volume derived from the R-K equation of state under different conditions. The objectives are to comprehend phase beha-vior of components and to provide the theoretic explana-tion and guidance for probing novel processes of ammonia synthesis under supercritical conditions. The conditions of calculation are H2/N2= 3, at a concentra-tion of NH3 in synthesis gas ranging from 2% to 15%, Concentration of medium in supercritical ammonia syn-thesis system ranging from 20% to 50%, temperature ran-ging from 243 K to 699 K and pressure ranging from 0.1 MPa to 187 MPa. The results show that the ammonia synthesis system can reach supercritical state by adding a suitable supercritical medium and then controlling the reaction conditions. It is helpful for the supercritical ammonia synthesis that medium reaches supercritical state under the conditions of the corresponding total pres-sure and components near the normal temperature or near the critical temperature of medium or in the range of tem-perature of industrialized ammonia synthesis.

Partial-wave analysis of the reaction K−p → $\\lambda$ (1815) $\\pi$ between threshold and 2170 MeV

CERN Document Server

Litchfield, P J; Baillon, Paul; Albrecht, H; Burkhardt, E E; Hemingway, Richard J

1974-01-01

The reaction K/sup -/p to Lambda (1815) pi /sup 0/ to K/sup -/p pi /sup 0/ is found to be dominated by the formation of the 7/2/sup +/ Sigma (2030) with an amplitude at resonance of 0.18+or-0.04. (5 refs).

A fast-fission component with small mass drift in the reaction 84Kr + 27Al at ELab = 5.9 MeV/u

International Nuclear Information System (INIS)

Heusch, B.; Freiesleben, H.; Schneider, W.F.W.; Kohlmeyer, B.; Stege, H.; Puehlhofer, F.

1985-01-01

All reaction products in the range from target- and projectile-like to fission-like fragments were measured for the system 84 Kr + 27 Al at 5.9 MeV/u beam energy. They are assigned to the various reaction mechanisms on the basis of experimental signatures (energy dissipation, mass and angular distribution). The sum of the measured partial cross sections, including the evaporation residue yield obtained previously, agrees with the total reaction cross section derived from elastic scattering. A small fast-fission component was found, discernible from deep-inelastic reactions by its 1/sinθ angular distribution, and distinguished from compound-nucleus fission by an incomplete mass asymmetry relaxation

The strategic value of partial vertical integration

OpenAIRE

Fiocco, Raffaele

2014-01-01

We investigate the strategic incentives for partial vertical integration, namely, partial ownership agreements between manufacturers and retailers, when retailers privately know their costs and engage in differentiated good price competition. The partial misalignment between the profit objectives within a partially integrated manufacturer-retailer hierarchy entails a higher retail price than under full integration. This `information vertical effect' translates into an opposite ...

Partial dynamical systems, fell bundles and applications

CERN Document Server

Exel, Ruy

2017-01-01

Partial dynamical systems, originally developed as a tool to study algebras of operators in Hilbert spaces, has recently become an important branch of algebra. Its most powerful results allow for understanding structural properties of algebras, both in the purely algebraic and in the C*-contexts, in terms of the dynamical properties of certain systems which are often hiding behind algebraic structures. The first indication that the study of an algebra using partial dynamical systems may be helpful is the presence of a grading. While the usual theory of graded algebras often requires gradings to be saturated, the theory of partial dynamical systems is especially well suited to treat nonsaturated graded algebras which are in fact the source of the notion of "partiality". One of the main results of the book states that every graded algebra satisfying suitable conditions may be reconstructed from a partial dynamical system via a process called the partial crossed product. Running in parallel with partial dynamica...

Physics of partially ionized plasmas

CERN Document Server

Krishan, Vinod

2016-01-01

Plasma is one of the four fundamental states of matter; the other three being solid, liquid and gas. Several components, such as molecular clouds, diffuse interstellar gas, the solar atmosphere, the Earth's ionosphere and laboratory plasmas, including fusion plasmas, constitute the partially ionized plasmas. This book discusses different aspects of partially ionized plasmas including multi-fluid description, equilibrium and types of waves. The discussion goes on to cover the reionization phase of the universe, along with a brief description of high discharge plasmas, tokomak plasmas and laser plasmas. Various elastic and inelastic collisions amongst the three particle species are also presented. In addition, the author demonstrates the novelty of partially ionized plasmas using many examples; for instance, in partially ionized plasma the magnetic induction is subjected to the ambipolar diffusion and the Hall effect, as well as the usual resistive dissipation. Also included is an observation of kinematic dynam...

Study of NΣ cusp in p+p → p+K{sup +}+Λ with partial wave analysis

Energy Technology Data Exchange (ETDEWEB)

Lu, S.; Muenzer, R.; Epple, E.; Fabbietti, L. [Excellenz Cluster Universe, Technische Universitaet Muenchen (Germany); Ritman, J.; Roderburg, E.; Hauenstein, F. [FZ Juelich (Germany); Collaboration: Hades and FOPI Collaboration

2016-07-01

In the last years, an analysis of exclusive reaction of p+p → p+K{sup +}+Λ has been carried out using Bonn-Gatchina Partial Wave Analysis. In a combined analysis of data from Hades, Fopi, Disto and Cosy-TOF, an energy dependent production process is determined. This analysis has shown that a sufficient description of the p+p → p+K{sup +}+Λ is quite challenging due to the presence of resonances N* and interference, which requires Partial Wave Analysis. A pronounced narrow structure is observed in its projection on the pΛ-invariant mass. This peak structure, which appears around the NΣ threshold, has a strongly asymmetric structure and is interpreted a NΣ cusp effect. In this talk, the results from a combined analysis will be shown, with a special focus on the NΣ cusp structure and a description using Flatte parametrization.

Thermal capture cross section for 58Ni (n,γ)59 Ni reaction

International Nuclear Information System (INIS)

Carbonari, A.W.; Pecequilo, B.R.S.

1989-01-01

The 58 Ni total thermal capture cross section was determined by suming the partial cross sections calculated for the primary transitions of the reaction 58 Ni (n,γ) 59 Ni. The primary transitions energies and intensities were determined from the 58 Ni thermal neutrons prompt gamma capture gamma rays spectrum in the 3.7 to 9.3 MeV region. The obtained value for the total cross section was 4.52 + 0.10b. (author) [pt

The entropy dissipation method for spatially inhomogeneous reaction-diffusion-type systems

KAUST Repository

Di Francesco, M.

2008-12-08

We study the long-time asymptotics of reaction-diffusion-type systems that feature a monotone decaying entropy (Lyapunov, free energy) functional. We consider both bounded domains and confining potentials on the whole space for arbitrary space dimensions. Our aim is to derive quantitative expressions for (or estimates of) the rates of convergence towards an (entropy minimizing) equilibrium state in terms of the constants of diffusion and reaction and with respect to conserved quantities. Our method, the so-called entropy approach, seeks to quantify convergence to equilibrium by using functional inequalities, which relate quantitatively the entropy and its dissipation in time. The entropy approach is well suited to nonlinear problems and known to be quite robust with respect to model variations. It has already been widely applied to scalar diffusion-convection equations, and the main goal of this paper is to study its generalization to systems of partial differential equations that contain diffusion and reaction terms and admit fewer conservation laws than the size of the system. In particular, we successfully apply the entropy approach to general linear systems and to a nonlinear example of a reaction-diffusion-convection system arising in solid-state physics as a paradigm for general nonlinear systems. © 2008 The Royal Society.

TORUS: Theory of Reactions for Unstable iSotopes - Year 1 Continuation and Progress Report

Energy Technology Data Exchange (ETDEWEB)

Arbanas, G; Elster, C; Escher, J; Mukhamedzhanov, A; Nunes, F; Thompson, I J

2011-02-24

The TORUS collaboration derives its name from the research it focuses on, namely the Theory of Reactions for Unstable iSotopes. It is a Topical Collaboration in Nuclear Theory, and funded by the Nuclear Theory Division of the Office of Nuclear Physics in the Office of Science of the Department of Energy. The funding started on June 1, 2010, it will have been running for nine months by the date of submission of this Annual Continuation and Progress Report on March 1, 2011. The extent of funding was reduced from the original application, and now supports one postdoctoral researcher for the years 1 through 3. The collaboration brings together as Principal Investigators a large fraction of the nuclear reaction theorists currently active within the USA. The mission of the TORUS Topical Collaboration is to develop new methods that will advance nuclear reaction theory for unstable isotopes by using three-body techniques to improve direct-reaction calculations, and, by using a new partial-fusion theory, to integrate descriptions of direct and compound-nucleus reactions. This multi-institution collaborative effort is directly relevant to three areas of interest: the properties of nuclei far from stability; microscopic studies of nuclear input parameters for astrophysics, and microscopic nuclear reaction theory.

The Porphobilinogen Conundrum in Prebiotic Routes to Tetrapyrrole Macrocycles

Science.gov (United States)

Taniguchi, Masahiko; Ptaszek, Marcin; Chandrashaker, Vanampally; Lindsey, Jonathan S.

2017-03-01

Attempts to develop a credible prebiotic route to tetrapyrroles have relied on enzyme-free recapitulation of the extant biosynthesis, but this process has foundered from the inability to form the pyrrole porphobilinogen ( PBG) in good yield by self-condensation of the precursor δ-aminolevulinic acid ( ALA). PBG undergoes robust oligomerization in aqueous solution to give uroporphyrinogen (4 isomers) in good yield. ALA, PBG, and uroporphyrinogen III are universal precursors to all known tetrapyrrole macrocycles. The enzymic formation of PBG entails carbon-carbon bond formation between the less stable enolate/enamine of one ALA molecule (3-position) and the carbonyl/imine (4-position) of the second ALA molecule; without enzymes, the first ALA reacts at the more stable enolate/enamine (5-position) and gives the pyrrole pseudo-PBG. pseudo-PBG cannot self-condense, yet has one open α-pyrrole position and is proposed to be a terminator of oligopyrromethane chain-growth from PBG. Here, 23 analogues of ALA have been subjected to density functional theoretical (DFT) calculations, but no motif has been identified that directs reaction at the 3-position. Deuteriation experiments suggested 5-(phosphonooxy)levulinic acid would react preferentially at the 3- versus 5-position, but a hybrid condensation with ALA gave no observable uroporphyrin. The results suggest efforts toward a biomimetic, enzyme-free route to tetrapyrroles from ALA should turn away from structure-directed reactions and focus on catalysts that orient the two aminoketones to form PBG in a kinetically controlled process, thereby avoiding formation of pseudo-PBG.

Synergetic mechanism of methanol–steam reforming reaction in a catalytic reactor with electric discharges

International Nuclear Information System (INIS)

Kim, Taegyu; Jo, Sungkwon; Song, Young-Hoon; Lee, Dae Hoon

2014-01-01

Highlights: • Methanol–steam reforming was performed on Cu catalysts under an electric discharge. • Discharge had a synergetic effect on the catalytic reaction for methanol conversion. • Discharge lowered the temperature for catalyst activation or light off. • Discharge controlled the yield and selectivity of species in a reforming process. • Adsorption triggered by a discharge was a possible mechanism for a synergetic effect. - Abstract: Methanol–steam reforming was performed on Cu/ZnO/Al 2 O 3 catalysts under an electric discharge. The discharge occurred between the electrodes where the catalysts were packed. The electric discharge was characterized by the discharge voltage and electric power to generate the discharge. The existence of a discharge had a synergetic effect on the catalytic reaction for methanol conversion. The electric discharge provided modified reaction paths resulting in a lower temperature for catalyst activation or light off. The discharge partially controlled the yield and selectivity of species in a reforming process. The aspect of control was examined in view of the reaction kinetics. The possible mechanisms for the synergetic effect between the catalytic reaction and electric discharge on methanol–steam reforming were addressed. A discrete reaction path, particularly adsorption triggered by an electric discharge, was suggested to be the most likely mechanism for the synergetic effect. These results are expected to provide a guide for understanding the plasma–catalyst hybrid reaction

Partial Epilepsy with Auditory Features

Directory of Open Access Journals (Sweden)

J Gordon Millichap

2004-07-01

Full Text Available The clinical characteristics of 53 sporadic (S cases of idiopathic partial epilepsy with auditory features (IPEAF were analyzed and compared to previously reported familial (F cases of autosomal dominant partial epilepsy with auditory features (ADPEAF in a study at the University of Bologna, Italy.

Insight into the mechanism of methanol assistance with syngas conversion over partially hydroxylated γ-Al2O3(110D) surface in slurry bed.

Science.gov (United States)

Bai, Bing; Bai, Hui; Cao, Hao-Jie; Gao, Zhi-Hua; Zuo, Zhi-Jun; Huang, Wei

2018-04-27

Despite numerous studies devoted to the various properties of γ-Al2O3, the explorations of its catalytic activity remain scarce. In this study, density functional theory calculations are performed to study the elementary adsorption and reaction mechanisms for syngas conversion on partially hydroxylated γ-Al2O3(110D) surface in liquid paraffin. It is found that the partially hydroxylated γ-Al2O3(110D) surface with the hydroxyl coverage of 8.9 OH nm-2 is formed by two dissociative adsorptions of H2O on the dry γ-Al2O3(110D) surface. The hydroxyl coverage conditions play a key role in determining the dominant reaction mechanism on account of the existence of strong hydrogen bonds. The preferential pathway for syngas conversion with assistance of methanol over the partially hydroxylated γ-Al2O3(110D) surface in liquid paraffin has been proven to be CH3OH → CH3O + H → CH3 + OH, CH3 + CO → CH3CO. C2H5OH is then formed by successive hydrogenation via the pathway CH3CO + 3H → CH3CHO + 2H → CH3CH2O + H → C2H5OH. Here, CH3CHO formation by CH3CO hydrogenation is not inhibited. Actually, with the assistance of partially hydroxylated γ-Al2O3, CH3CHO has been synthesized with high selectivity in our previous experiment by the reaction of methanol and syngas, which provides favorable evidence for our results. The rate-limiting step is the formation of CH3O from CH3OH dehydrogenation with an activation barrier of 122.2 kJ mol-1. Moreover, the reaction barrier of CO insertion into the adsorbed CH3 group is at least 89.4 kJ mol-1, lower than those of CH4, C2H6, and CH3OCH3 formations. ADCH charge and ESP analyses indicate that the typical (Al, O) Lewis acid-base pair may have a significant effect upon the initial C-C chain formation. Thus, the present study provides a new approach for the rational tailoring and designing of new catalysts with superior reactivity involved in syngas conversion.

New data on $K^{-}p \\rightarrow K^{-}p $and $\\overline{K}^{0}n$ and a partial wave analysis between 1840 and 2234 MeV center of mass energy

CERN Document Server

Hemingway, Richard J; Harmsen D M; Kiesling, C; Petersen, J O; Plane, D E; Putzer, A; Wittex, W; Eades, J no 1; Harmsen D M no 1; Hemingway, R J no 1; Kiesling, C no 3; Petersen, J O no 1; Plane, D E no 3; Putzer, A no 2; Wittex, W no 3

1975-01-01

The angular distributions of the reactions K/sup -/p to K/sup -/p and K/sup -/p to K/sup 0/n have been measured at 23 incident K/sup -/ momenta between 1.136 and 1.798 GeV/c using the bubble chamber technique. These data, together with other published data on the same reactions, including K/sup -/p polarisations, KN total cross sections and measurements of Re f(0)/Im f(0), have been analysed in terms of partial-wave amplitudes. Resonance behaviour is confirmed for the P /sub 03/ partial wave at 1890 MeV. The resonance parameters of the F /sub 15/(1915), F/sub 17/(2030) and G/sub 07/(2100) have been redetermined. No evidence has been found for new resonances coupling significantly to KN in the energy region explored. (24 refs).

Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy

Directory of Open Access Journals (Sweden)

Pramod Kumar Verma

2016-03-01

Full Text Available We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps followed by decay (≈390 ps to the corresponding ground state.

Role of sugar in controlling reaction pathways: A study with thymine and thymidine

Energy Technology Data Exchange (ETDEWEB)

Bose, Adity [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Sarkar, Achintya K. [Department of Chemistry, Presidency College, 86/1 College street, Kolkata 700 073 (India); Basu, Samita, E-mail: samita.basu@saha.ac.i [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

2009-10-15

Magnetic field effect in conjunction with laser flash photolysis have been used for studying interactions of 9,10-anthraquinone and 2-methyl 1,4-naphthoquinone (menadione) with a DNA base, thymine (Thy) and its nucleoside, thymidine (dThd). Irrespective of medium Thy has been found to support both electron transfer (ET) and hydrogen abstraction with the quinones while dThd has exhibited a complete reluctance towards ET. This unique behavior of dThd has been attributed to a failure in attaining aromaticity by virtue of keto-enol tautomerism upon addition of a sugar moiety. Electron withdrawing effect of sugar unit is also considered responsible for reduction of ET from dThd. Again both Thy and dThd have exhibited hydrogen abstraction in homogeneous medium, which is normally unexpected. The above behaviors of the bases have been explained on the basis of their chemical structures.

Role of sugar in controlling reaction pathways: A study with thymine and thymidine

International Nuclear Information System (INIS)

Bose, Adity; Sarkar, Achintya K.; Basu, Samita

2009-01-01

Magnetic field effect in conjunction with laser flash photolysis have been used for studying interactions of 9,10-anthraquinone and 2-methyl 1,4-naphthoquinone (menadione) with a DNA base, thymine (Thy) and its nucleoside, thymidine (dThd). Irrespective of medium Thy has been found to support both electron transfer (ET) and hydrogen abstraction with the quinones while dThd has exhibited a complete reluctance towards ET. This unique behavior of dThd has been attributed to a failure in attaining aromaticity by virtue of keto-enol tautomerism upon addition of a sugar moiety. Electron withdrawing effect of sugar unit is also considered responsible for reduction of ET from dThd. Again both Thy and dThd have exhibited hydrogen abstraction in homogeneous medium, which is normally unexpected. The above behaviors of the bases have been explained on the basis of their chemical structures.

[Removable partial dentures. Oral functions and types

NARCIS (Netherlands)

Creugers, N.H.J.; Baat, C. de

2009-01-01

A removable partial denture enables the restoration or improvement of 4 oral functions: aesthetics, mandibular stability, mastication, and speech. However, wearing a removable partial denture should not cause oral comfort to deteriorate. There are 3 types of removable partial dentures: acrylic

Exact solutions of linear reaction-diffusion processes on a uniformly growing domain: criteria for successful colonization.

Science.gov (United States)

Simpson, Matthew J

2015-01-01

Many processes during embryonic development involve transport and reaction of molecules, or transport and proliferation of cells, within growing tissues. Mathematical models of such processes usually take the form of a reaction-diffusion partial differential equation (PDE) on a growing domain. Previous analyses of such models have mainly involved solving the PDEs numerically. Here, we present a framework for calculating the exact solution of a linear reaction-diffusion PDE on a growing domain. We derive an exact solution for a general class of one-dimensional linear reaction-diffusion process on 0exact solutions with numerical approximations confirms the veracity of the method. Furthermore, our examples illustrate a delicate interplay between: (i) the rate at which the domain elongates, (ii) the diffusivity associated with the spreading density profile, (iii) the reaction rate, and (iv) the initial condition. Altering the balance between these four features leads to different outcomes in terms of whether an initial profile, located near x = 0, eventually overcomes the domain growth and colonizes the entire length of the domain by reaching the boundary where x = L(t).

Beginning partial differential equations

CERN Document Server

O'Neil, Peter V

2014-01-01

A broad introduction to PDEs with an emphasis on specialized topics and applications occurring in a variety of fields Featuring a thoroughly revised presentation of topics, Beginning Partial Differential Equations, Third Edition provides a challenging, yet accessible,combination of techniques, applications, and introductory theory on the subjectof partial differential equations. The new edition offers nonstandard coverageon material including Burger's equation, the telegraph equation, damped wavemotion, and the use of characteristics to solve nonhomogeneous problems. The Third Edition is or

Experimental and numerical investigation of the catalytic partial oxidation of methane to synthesis gas for power generation applications[Dissertation 17183

Energy Technology Data Exchange (ETDEWEB)

Schneider, A.

2007-07-01

The present work addresses the catalytic partial oxidation (CPO) of methane to synthesis gas, with particular emphasis on power generation applications. A combined experimental and numerical investigation of methane partial oxidation to synthesis gas (H{sub 2}, CO) over rhodium-based catalysts has been carried out at pressures of up to 10 bar. The reactivity of the produced hydrogen and the suitably-low light-off temperatures of the CPO reactor, greatly facilitate operation of power generation gas turbines with reduced NO{sub x} emissions, stable operation with low calorific value fuels, and new combustion strategies for efficient CO{sub 2} capture. Those strategies utilize CPO of methane with oxygen (separated from air) and large exhaust gas recycle (H{sub 2}O and CO{sub 2}). An optically accessible catalytic channel-flow reactor was used to carry out Raman spectroscopy of major gas-phase species and laser induced fluorescence (LIF) of formaldehyde, in order to gain fundamental information on the catalytic and gas-phase chemical pathways. Transverse concentration profiles measured by the spontaneous Raman scattering technique determined the catalytic reactivity, while the LIF provided flame shapes and anchoring positions that, in turn, characterized the gaseous reactivity. Comparison between measurements and 2-D CFD computations, led to the validation of detailed catalytic and gas-phase reaction mechanisms. Experiments in a subscale gas-turbine honeycomb catalytic reactor have shown that the foregoing reaction mechanisms were also appropriate under gas-turbine relevant conditions with short reactant residence times. The light-off behavior of the subscale honeycomb reactor was reproduced by transient 2-D CFD computations. Ignition and extinction in CPO was studied. It was shown that, despite the chemical impact of the H{sub 2}O diluent during the transient catalytic ignition event, the light-off times themselves were largely unaffected by the exhaust gas dilution

Numerical simulation of combustion and soot under partially premixed combustion of low-octane gasoline

KAUST Repository

An, Yanzhao

2017-09-23

In-cylinder combustion visualization and engine-out soot particle emissions were investigated in an optical diesel engine fueled with low octane gasoline. Single injection strategy with an early injection timing (−30 CAD aTDC) was employed to achieve partially premixed combustion (PPC) condition. A high-speed color camera was used to record the combustion images for 150 cycles. The regulated emission of carbon dioxide, carbon monoxide, nitrogen oxides and soot mass concentration were measured experimentally. Full cycle engine simulations were performed using CONVERGE™ and the simulation results matched with the experimental results. The in-cylinder soot particle evolution was performed by coupling a reduced toluene reference fuel mechanism including the PAHs formation/oxidation reactions with particulate size mimic model. The results showed that PPC presents typical stratified combustion characteristics, which is significantly different from the conventional diesel spray-driven combustion. The in-cylinder temperature and equivalence ratio overlaid with soot-NO formation regime revealed that PPC operating condition under study mostly avoided the main sooting conditions throughout the entire combustion. The evaluation of temperature distribution showed formaldehyde could be regarded as an indicator for low temperature reactions, while hydroxyl group represents the high temperature reactions. Soot evolution happened during the combustion process, hydroxyl radicals promoted the soot oxidation.

Numerical simulation of combustion and soot under partially premixed combustion of low-octane gasoline

KAUST Repository

An, Yanzhao; Jaasim, Mohammed; Vallinayagam, R.; Vedharaj, S.; Im, Hong G.; Johansson, Bengt.

2017-01-01

In-cylinder combustion visualization and engine-out soot particle emissions were investigated in an optical diesel engine fueled with low octane gasoline. Single injection strategy with an early injection timing (−30 CAD aTDC) was employed to achieve partially premixed combustion (PPC) condition. A high-speed color camera was used to record the combustion images for 150 cycles. The regulated emission of carbon dioxide, carbon monoxide, nitrogen oxides and soot mass concentration were measured experimentally. Full cycle engine simulations were performed using CONVERGE™ and the simulation results matched with the experimental results. The in-cylinder soot particle evolution was performed by coupling a reduced toluene reference fuel mechanism including the PAHs formation/oxidation reactions with particulate size mimic model. The results showed that PPC presents typical stratified combustion characteristics, which is significantly different from the conventional diesel spray-driven combustion. The in-cylinder temperature and equivalence ratio overlaid with soot-NO formation regime revealed that PPC operating condition under study mostly avoided the main sooting conditions throughout the entire combustion. The evaluation of temperature distribution showed formaldehyde could be regarded as an indicator for low temperature reactions, while hydroxyl group represents the high temperature reactions. Soot evolution happened during the combustion process, hydroxyl radicals promoted the soot oxidation.

[Acrylic resin removable partial dentures

NARCIS (Netherlands)

Baat, C. de; Witter, D.J.; Creugers, N.H.J.

2011-01-01

An acrylic resin removable partial denture is distinguished from other types of removable partial dentures by an all-acrylic resin base which is, in principle, solely supported by the edentulous regions of the tooth arch and in the maxilla also by the hard palate. When compared to the other types of

Discriminating the reaction types of plant type III polyketide synthases.

Science.gov (United States)

Shimizu, Yugo; Ogata, Hiroyuki; Goto, Susumu

2017-07-01

Functional prediction of paralogs is challenging in bioinformatics because of rapid functional diversification after gene duplication events combined with parallel acquisitions of similar functions by different paralogs. Plant type III polyketide synthases (PKSs), producing various secondary metabolites, represent a paralogous family that has undergone gene duplication and functional alteration. Currently, there is no computational method available for the functional prediction of type III PKSs. We developed a plant type III PKS reaction predictor, pPAP, based on the recently proposed classification of type III PKSs. pPAP combines two kinds of similarity measures: one calculated by profile hidden Markov models (pHMMs) built from functionally and structurally important partial sequence regions, and the other based on mutual information between residue positions. pPAP targets PKSs acting on ring-type starter substrates, and classifies their functions into four reaction types. The pHMM approach discriminated two reaction types with high accuracy (97.5%, 39/40), but its accuracy decreased when discriminating three reaction types (87.8%, 43/49). When combined with a correlation-based approach, all 49 PKSs were correctly discriminated, and pPAP was still highly accurate (91.4%, 64/70) even after adding other reaction types. These results suggest pPAP, which is based on linear discriminant analyses of similarity measures, is effective for plant type III PKS function prediction. pPAP is freely available at ftp://ftp.genome.jp/pub/tools/ppap/. goto@kuicr.kyoto-u.ac.jp. Supplementary data are available at Bioinformatics online. © The Author(s) 2017. Published by Oxford University Press.

PARALLEL SOLUTION METHODS OF PARTIAL DIFFERENTIAL EQUATIONS

Directory of Open Access Journals (Sweden)

Korhan KARABULUT

1998-03-01

Full Text Available Partial differential equations arise in almost all fields of science and engineering. Computer time spent in solving partial differential equations is much more than that of in any other problem class. For this reason, partial differential equations are suitable to be solved on parallel computers that offer great computation power. In this study, parallel solution to partial differential equations with Jacobi, Gauss-Siedel, SOR (Succesive OverRelaxation and SSOR (Symmetric SOR algorithms is studied.

Electrochemical and partial oxidation of methane

Science.gov (United States)

Singh, Rahul

2008-10-01

negligible coke formation on the novel fabricated anode by electroless plating process. Hydrogen is an environmentally cleaner source of energy. The recent increase in the demand of hydrogen as fuel for all types of fuel cells and petroleum refining process has boosted the need of production of hydrogen. Methane, a major component of natural gas is the major feedstock for production of hydrogen. The route of partial oxidation of methane to produce syngas (CO + H2) offers significant advantages over commercialized steam reforming process for higher efficiency and lower energy requirements. Partial oxidation of methane was studied by pulsing O2 into a CH4 flow over Rh/Al2O3 in a sequence of in situ infrared (IR) cell and fixed bed reactor at 773 K. The results obtained from the sequence of an IR cell followed by a fixed bed reactor show that (i) adsorbed CO produced possesses a long residence time, indicating that adsorbed oxygen leading to the formation of CO is significantly different from those leading to CO2 and (ii) CO2 is not an intermediate species for the formation of CO. In situ IR of pulse reaction coupled with alternating reactor sequence is an effective approach to study the primary and secondary reactions as well as the nature of their adsorbed species. As reported earlier, hydrogen remains to be the most effective fuel for fuel cells, the production of high purity hydrogen from naturally available resources such as coal, petroleum, and natural gas requires a number of energy-intensive steps, making fuel cell processes for stationary electric power generation prohibitively uneconomic. Direct use of coal or coal gas as the feed is a promising approach for low cost electricity generation. Coal gas solid oxide fuel cell was studied by pyrolyzing Ohio #5 coal to coal gas and transporting to a Cu anode solid oxide fuel cell to generate power. The study of coal-gas solid oxide fuel cell is divided into two sections, i.e., (i) understanding the composition of coal gas by

MEMS Lubrication by In-Situ Tribochemical Reactions From the Vapor Phase.

Energy Technology Data Exchange (ETDEWEB)

Dugger, Michael Thomas; Asay, David B.; Kim, Seong H.

2008-01-01

Vapor Phase Lubrication (VPL) of silicon surfaces with pentanol has been demonstrated. Two potential show stoppers with respect to application of this approach to real MEMS devices have been investigated. Water vapor was found to reduce the effectiveness of VPL with alcohol for a given alcohol concentration, but the basic reaction mechanism observed in water-free environments is still active, and devices operated much longer in mixed alcohol and water vapor environments than with chemisorbed monolayer lubricants alone. Complex MEMS gear trains were successfully lubricated with alcohol vapors, resulting in a factor of 104 improvement in operating life without failure. Complex devices could be made to fail if operated at much higher frequencies than previously used, and there is some evidence that the observed failure is due to accumulation of reaction products at deeply buried interfaces. However, if hypothetical reaction mechanisms involving heated surfaces are valid, then the failures observed at high frequency may not be relevant to operation at normal frequencies. Therefore, this work demonstrates that VPL is a viable approach for complex MEMS devices in conventional packages. Further study of the VPL reaction mechanisms are recommended so that the vapor composition may be optimized for low friction and for different substrate materials with potential application to conventionally fabricated, metal alloy parts in weapons systems. Reaction kinetics should be studied to define effective lubrication regimes as a function of the partial pressure of the vapor phase constituent, interfacial shear rate, substrate composition, and temperature.

Partial processing

International Nuclear Information System (INIS)

1978-11-01

This discussion paper considers the possibility of applying to the recycle of plutonium in thermal reactors a particular method of partial processing based on the PUREX process but named CIVEX to emphasise the differences. The CIVEX process is based primarily on the retention of short-lived fission products. The paper suggests: (1) the recycle of fission products with uranium and plutonium in thermal reactor fuel would be technically feasible; (2) it would, however, take ten years or more to develop the CIVEX process to the point where it could be launched on a commercial scale; (3) since the majority of spent fuel to be reprocessed this century will have been in storage for ten years or more, the recycling of short-lived fission products with the U-Pu would not provide an effective means of making refabrication fuel ''inaccessible'' because the radioactivity associated with the fission products would have decayed. There would therefore be no advantage in partial processing

Enantioselective Rhodium Enolate Protonations. A New Methodology for the Synthesis of β2-Amino Acids

Science.gov (United States)

Sibi, Mukund P.; Tatamidani, Hiroto; Patil, Kalyani

2008-01-01

Rhodium catalyzed conjugate addition of an aryl boronic acid to α-methylamino acrylates followed by enantioselective protonation of the oxa-π-allylrhodium intermediate provides access to aryl substituted β2-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed. PMID:15957893

Development of Partial Discharging Simulation Test Equipment

Science.gov (United States)

Kai, Xue; Genghua, Liu; Yan, Jia; Ziqi, Chai; Jian, Lu

2017-12-01

In the case of partial discharge training for recruits who lack of on-site work experience, the risk of physical shock and damage of the test equipment may be due to the limited skill level and improper operation by new recruits. Partial discharge simulation tester is the use of simulation technology to achieve partial discharge test process simulation, relatively true reproduction of the local discharge process and results, so that the operator in the classroom will be able to get familiar with and understand the use of the test process and equipment.The teacher sets up the instrument to display different partial discharge waveforms so that the trainees can analyze the test results of different partial discharge types.

Fitted Fourier-pseudospectral methods for solving a delayed reaction-diffusion partial differential equation in biology

Science.gov (United States)

Adam, A. M. A.; Bashier, E. B. M.; Hashim, M. H. A.; Patidar, K. C.

2017-07-01

In this work, we design and analyze a fitted numerical method to solve a reaction-diffusion model with time delay, namely, a delayed version of a population model which is an extension of the logistic growth (LG) equation for a food-limited population proposed by Smith [F.E. Smith, Population dynamics in Daphnia magna and a new model for population growth, Ecology 44 (1963) 651-663]. Seeing that the analytical solution (in closed form) is hard to obtain, we seek for a robust numerical method. The method consists of a Fourier-pseudospectral semi-discretization in space and a fitted operator implicit-explicit scheme in temporal direction. The proposed method is analyzed for convergence and we found that it is unconditionally stable. Illustrative numerical results will be presented at the conference.

PARTIAL TRISOMY 4p AND PARTIAL MONOSOMY 13q: CASE REPORT AND A LITERATURE REVIEW.

Science.gov (United States)

Puvabanditsin, S; Herrera-Garcia, G; Gengel, N; Hussein, K; February, M; Mayne, J; Mehta, R

2016-01-01

We report on a term first born dichorionic-diamniotic twin with deletion of the distal long arm of chromosome 13, partial trisomy of the short arm of chromosome 4, intrauterine growth retardation, and multiple anomalies including microcephaly, colpocephaly, absent corpus callosum, bulbous tip of the nose, large and low set ears, macroglossia, thin upper lip, double outlet right ventricle, atria/ventricular septal defect, cleft mitral valve, pulmonary stenosis, single umbilical artery, multicystic dysplastic left kidney, sacral dimple, anterior displacement of anus, simian creases, abnormal thumb (congenital clasped thumb), overlapping toes, and congenital hypothyroidism. This is the first report of a patient with partial trisomy 4p and partial monosomy 13q.

Partial Cancellation

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Partial Cancellation. Full Cancellation is desirable. But complexity requirements are enormous. 4000 tones, 100 Users billions of flops !!! Main Idea: Challenge: To determine which cross-talker to cancel on what “tone” for a given victim. Constraint: Total complexity is ...

Determination of transport and reaction swarm coefficients from the analysis of complex transient pulses from the pulsed Townsend experiment

International Nuclear Information System (INIS)

Bekstein, A; De Urquijo, J; Rodríguez-Luna, J C; Juárez, A M; Ducasse, O

2012-01-01

We present in this paper the interpretation and analysis of transient pulses from a pulsed Townsend experiment by solving the continuity equations of the charged carriers (electrons and ions) involved in the avalanche. The set of second order partial differential equations is solved by SIMAV, a simulator designed specifically for the pulsed Townsend avalanche. Complex situations involving processes such as electron detachment, ion-molecule reactions, Penning ionization and secondary electron emission from ion impact at the cathode, virtually impossible to solve analytically, are discussed here to illustrate the capability of the simulator to help explain the various reaction processes involved in the avalanche, and also to derive some of the transport and reaction coefficients.

Neutrino-induced charged-current reaction rates for r-process nuclei

CERN Document Server

Langanke, K

2001-01-01

Neutrino-induced reactions play an important role during and after the r-process if it occurs in an environment with extreme neutrino fluxes, as in the neutrino-driven wind model or neutron star mergers. The neutrino reactions can excite the daughter nucleus above the neutron threshold, which is quite low for r-process nuclei. Thus the daughter nucleus will decay by emission of one or several neutrons. We have calculated the relevant total (nu sub e , e sup -) cross sections as well as the partial neutron spallation cross sections for r-process nuclei with neutron numbers N=41-135 and proton numbers Z=21-82. The supernova neutrino spectrum is described by a Fermi-Dirac distribution with various temperature parameters between T=2.8 MeV and T=10 MeV and with the degeneracy parameters alpha=0 and alpha=3. Our calculations of the nuclear response are based on the random phase approximation and consider allowed as well as forbidden transitions.

Plasma-assisted partial oxidation of methane at low temperatures: numerical analysis of gas-phase chemical mechanism

Energy Technology Data Exchange (ETDEWEB)

Goujard, Valentin; Nozaki, Tomohiro; Yuzawa, Shuhei; Okazaki, Ken [Department of Mechanical and Control Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, 1528552, Tokyo (Japan); Agiral, Anil, E-mail: tnozaki@mech.titech.ac.jp [Mesoscale Chemical Systems, MESA Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, PO Box 217, 7500 AE, Enschede (Netherlands)

2011-07-13

Methane partial oxidation was investigated using a plasma microreactor. The experiments were performed at 5 and 300 deg. C. Microreactor configuration allows an efficient evacuation of the heat generated by methane partial oxidation and dielectric barrier discharges, allowing at the same time a better temperature control. At 5 deg. C, liquid condensation of low vapour pressure compounds, such as formaldehyde and methanol, occurs. {sup 1}H-NMR analysis allowed us to demonstrate significant CH{sub 3}OOH formation during plasma-assisted partial oxidation of methane. Conversion and product selectivity were discussed for both temperatures. In the second part of this work, a numerical simulation was performed and a gas-phase chemical mechanism was proposed and discussed. From the comparison between the experimental results and the simulation it was found that CH{sub 3}OO{center_dot} formation has a determinant role in oxygenated compound production, since its fast formation disfavoured radical recombination. At 5 deg. C the oxidation leads mainly towards oxygenated compound formation, and plasma dissociation was the major phenomenon responsible for CH{sub 4} conversion. At 300 deg. C, higher CH{sub 4} conversion resulted from oxidative reactions induced by {center_dot}OH radicals with a chemistry predominantly oxidative, producing CO, H{sub 2}, CO{sub 2} and H{sub 2}O.

Robot-assisted partial nephrectomy in contemporary practice

Directory of Open Access Journals (Sweden)

Youssef S. Tanagho

2013-01-01

Full Text Available Laparoscopic renal surgery is associated with reduced blood loss, shorter hospital stay, enhanced cosmesis, and more rapid convalescence relative to open renal surgery. Laparoscopic partial nephrectomy is a minimally invasive, nephron-sparing alternative to laparoscopic radical nephrectomy for the management of small renal masses. While offering similar oncological outcomes to laparoscopic radical nephrectomy, the technical challenges and prolonged learning curve associated with laparoscopic partial nephrectomy limit its wider dissemination. Robot-assisted partial nephrectomy, although still an evolving procedure with no long-term data, has emerged as a viable alternative to laparoscopic partial nephrectomy, with favorable preliminary outcomes. This article provides an overview of the role of robot-assisted partial nephrectomy in the management of renal cell carcinoma. The clinical indications and principles of surgical technique for this procedure are discussed. The oncological, renal functional, and perioperative outcomes of robot-assisted partial nephrectomy are also evaluated, as are complication rates.

Partial molar volumes and partial molar adiabatic compressibilities of a short chain perfluorosurfactant: Sodium heptafluorobutyrate in aqueous solutions at different temperatures

Energy Technology Data Exchange (ETDEWEB)

Blanco, Elena [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Ruso, Juan M. [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain)]. E-mail: faruso@usc.es; Prieto, Gerardo [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Sarmiento, Felix [Group of Biophysics and Interfaces, Department of Applied Physics, Faculty of Physics, University of Santiago de Compostela, E-15782 Santiago de Compostela (Spain)

2005-12-15

Density and ultrasound measurements of sodium heptafluorobutyrate in aqueous solutions at T = (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15) K have been obtained. From these results partial molar volumes and isentropic partial molar adiabatic compressibilities were calculated. Deviations from the Debye-Hueckel limiting law provide evidence for limited association at lower concentrations. The change of the partial molar volume and isentropic partial molar adiabatic compressibility upon aggregation was calculated. Variations of the change of partial molar volumes and isentropic partial molar adiabatic compressibility upon aggregation are discussed in terms of temperature.

Partial molar volumes and partial molar adiabatic compressibilities of a short chain perfluorosurfactant: Sodium heptafluorobutyrate in aqueous solutions at different temperatures

International Nuclear Information System (INIS)

Blanco, Elena; Ruso, Juan M.; Prieto, Gerardo; Sarmiento, Felix

2005-01-01

Density and ultrasound measurements of sodium heptafluorobutyrate in aqueous solutions at T = (283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15) K have been obtained. From these results partial molar volumes and isentropic partial molar adiabatic compressibilities were calculated. Deviations from the Debye-Hueckel limiting law provide evidence for limited association at lower concentrations. The change of the partial molar volume and isentropic partial molar adiabatic compressibility upon aggregation was calculated. Variations of the change of partial molar volumes and isentropic partial molar adiabatic compressibility upon aggregation are discussed in terms of temperature