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Sample records for sequential cross-aldol reactions

  1. Metal-catalyzed asymmetric aldol reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Luiz C.; Lucca Junior, Emilio C. de; Ferreira, Marco A. B.; Polo, Ellen C., E-mail: ldias@iqm.unicamp.br [Universidade de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica

    2012-12-15

    The aldol reaction is one of the most powerful and versatile methods for the construction of C-C bonds. Traditionally, this reaction was developed in a stoichiometric version; however, great efforts in the development of chiral catalysts for aldol reactions were performed in recent years. Thus, in this review article, the development of metal-mediated chiral catalysts in Mukaiyama-type aldol reaction, reductive aldol reaction and direct aldol reaction are discussed. Moreover, the application of these catalysts in the total synthesis of complex molecules is discussed. (author)

  2. Direct catalytic asymmetric aldol-Tishchenko reaction.

    Science.gov (United States)

    Gnanadesikan, Vijay; Horiuchi, Yoshihiro; Ohshima, Takashi; Shibasaki, Masakatsu

    2004-06-30

    A direct catalytic asymmetric aldol reaction of propionate equivalent was achieved via the aldol-Tishchenko reaction. Coupling an irreversible Tishchenko reaction to a reversible aldol reaction overcame the retro-aldol reaction problem and thereby afforded the products in high enantio and diastereoselectivity using 10 mol % of the asymmetric catalyst. A variety of ketones and aldehydes, including propyl and butyl ketones, were coupled efficiently, yielding the corresponding aldol-Tishchenko products in up to 96% yield and 95% ee. Diastereoselectivity was generally below the detection limit of 1H NMR (>98:2). Preliminary studies performed to clarify the mechanism revealed that the aldol products were racemic with no diastereoselectivity. On the other hand, the Tishchenko products were obtained in a highly enantiocontrolled manner.

  3. Cross-Aldol Reaction of Activated Carbonyls with Nitrosocarbonyl Intermediates: Stereoselective Synthesis toward α-Hydroxy-β-amino Esters and Amides.

    Science.gov (United States)

    Mallik, Sumitava; Bhajammanavar, Vinod; Ramakrishna, Isai; Baidya, Mahiuddin

    2017-07-21

    A practical and flexible strategy toward α-hydroxy-β-amino esters and amides, which are important biological motifs, based on an organocatalytic cross-aldol reaction of in situ-generated nitrosocarbonyl intermediates followed by hydrogenation is presented. The protocol features operational simplicity, high yields, a wide substrate scope, and high regio- and diastereoselectivity profiles. The utility of this method was showcased through the synthesis of bestatin analogues and indole formation.

  4. alpha-Methoxymethyl ketones via aldol reaction

    Czech Academy of Sciences Publication Activity Database

    Kasal, Alexander; Buděšínský, Miloš

    2013-01-01

    Roč. 69, č. 46 (2013), s. 9663-9674 ISSN 0040-4020 R&D Projects: GA TA ČR(CZ) TE01020028 Institutional support: RVO:61388963 Keywords : NMR * steroids * synthesis * aldol reaction Subject RIV: CC - Organic Chemistry Impact factor: 2.817, year: 2013

  5. ALDOL- AND MANNICH-TYPE REACTIONS VIA IN SITU OLEFIN MIGRATION IN IONIC LIQUID

    Science.gov (United States)

    An aldol-type and a Mannich-type reaction via the cross-coupling of aldehydes and imines with allylic alcohols catalyzed by RuCl2(PPh3)3 was developed with ionic liquid as the solvent. The solvent/catalyst system could be reused for at least five times with no loss of reactiv...

  6. RUTHENIUM-CATALYZED TANDEM OLEFIN MIGRATION-ALDOL AND MANNICH-TYPE REACTIONS IN IONIC LIQUID.

    Science.gov (United States)

    In the presence of a catalytic amount of RuCl2(PPh3)3, a cross-coupling of 3-buten-2-ol with aldehydes and imines was developed via a tandem olefin migration--aldol--Mannich reaction in bmim[PF6]. With In(OAc)3 as a co-catalyst, a-vinylbenzyl alcohol and aldehydes underwent sim...

  7. Investigating Ionic Effects Applied to Water Based Organocatalysed Aldol Reactions

    Directory of Open Access Journals (Sweden)

    Joshua P. Delaney

    2011-12-01

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

  8. Sequential charged particle reaction

    International Nuclear Information System (INIS)

    Hori, Jun-ichi; Ochiai, Kentaro; Sato, Satoshi; Yamauchi, Michinori; Nishitani, Takeo

    2004-01-01

    The effective cross sections for producing the sequential reaction products in F82H, pure vanadium and LiF with respect to the 14.9-MeV neutron were obtained and compared with the estimation ones. Since the sequential reactions depend on the secondary charged particles behavior, the effective cross sections are corresponding to the target nuclei and the material composition. The effective cross sections were also estimated by using the EAF-libraries and compared with the experimental ones. There were large discrepancies between estimated and experimental values. Additionally, we showed the contribution of the sequential reaction on the induced activity and dose rate in the boundary region with water. From the present study, it has been clarified that the sequential reactions are of great importance to evaluate the dose rates around the surface of cooling pipe and the activated corrosion products. (author)

  9. Engineering the donor selectivity of D-fructose-6-phosphate aldolase for biocatalytic asymmetric cross-aldol additions of glycolaldehyde.

    Science.gov (United States)

    Szekrenyi, Anna; Soler, Anna; Garrabou, Xavier; Guérard-Hélaine, Christine; Parella, Teodor; Joglar, Jesús; Lemaire, Marielle; Bujons, Jordi; Clapés, Pere

    2014-09-22

    D-Fructose-6-phosphate aldolase (FSA) is a unique catalyst for asymmetric cross-aldol additions of glycolaldehyde. A combination of a structure-guided approach of saturation mutagenesis, site-directed mutagenesis, and computational modeling was applied to construct a set of FSA variants that improved the catalytic efficiency towards glycolaldehyde dimerization up to 1800-fold. A combination of mutations in positions L107, A129, and A165 provided a toolbox of FSA variants that expand the synthetic possibilities towards the preparation of aldose-like carbohydrate compounds. The new FSA variants were applied as highly efficient catalysts for cross-aldol additions of glycolaldehyde to N-carbobenzyloxyaminoaldehydes to furnish between 80-98 % aldol adduct under optimized reaction conditions. Donor competition experiments showed high selectivity for glycolaldehyde relative to dihydroxyacetone or hydroxyacetone. These results demonstrate the exceptional malleability of the active site in FSA, which can be remodeled to accept a wide spectrum of donor and acceptor substrates with high efficiency and selectivity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Catalyst-free aldol reaction of N-substituted rhodanines on aqueous ...

    Indian Academy of Sciences (India)

    N S DEVI

    2018-02-07

    Feb 7, 2018 ... catalytic aldol reaction is very common in organic sol- vents and ... −1. ). 1H NMR and 13C NMR spectra were recorded at 400 and 100 MHz in CDCl3. Chemical shifts ... 2.2 General procedure for the synthesis of rhodanine.

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

    Directory of Open Access Journals (Sweden)

    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.

  12. Asymmetric Alkylation and Aldol Reactions of D-Mannitol-Derived Chiral Oxazolidin-2-one Derivatives

    International Nuclear Information System (INIS)

    Maeng, Yun Hee; Jun, Jong Gab

    2004-01-01

    In the preceding article, we have introduced a new chiral oxazolidin-2-one auxiliary (1) derived from a cheap Dmannitol, and demonstrated the chiral selectivity in alkylation, aldol reaction and β-lactam synthesis.1 The present work began with a search for useful chiral directing groups with which to control the chiral selectivity. Because the rigidity of cyclic structures contributes significantly to control of chirality,2 the 1,2:5,6-di-O-cyclohexylidene-Dmannitol (2) was used for the synthesis of oxazolidin-2-one chiral auxiliary (3) comparing the selectivity with the auxiliary (1) in alkylation and aldol reactions.

  13. Aggregation and Cooperative Effects in the Aldol Reactions of Lithium Enolates

    NARCIS (Netherlands)

    Larrañaga, O.; de Cózar, A.; Bickelhaupt, F.M.; Zangi, R.; Cossío, F.P.

    2013-01-01

    Density functional theory and Car-Parrinello molecular dynamics simulations have been carried out for model aldol reactions involving aggregates of lithium enolates derived from acetaldehyde and acetone. Formaldehyde and acetone have been used as electrophiles. It is found that the geometries of the

  14. Synthesis of D-manno-heptulose via a cascade aldol/hemiketalization reaction

    Directory of Open Access Journals (Sweden)

    Yan Chen

    2017-04-01

    Full Text Available A [4 + 3] synthesis of D-manno-heptulose is described. The cascade aldol/hemiketalization reaction of a C4 aldehyde with a C3 ketone provides the differentially protected ketoheptose building block, which can be further reacted to furnish target D-manno-heptulose.

  15. Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

    DEFF Research Database (Denmark)

    Musko, Nikolai; Grunwaldt, Jan-Dierk

    2011-01-01

    Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100 °C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO2 and MCM-41) and basic (hydrotalcite) materials showed interesting performance in this pre...

  16. An Investigation of the Enolization and Isomeric Products Distribution in the Water Promoted Aldol Reaction of Tropinone and Granatanone

    Directory of Open Access Journals (Sweden)

    Ryszard Lazny

    2016-01-01

    Full Text Available The exo,anti/exo,syn-diastereoselectivity of water promoted direct aldol reactions of tropinone and granatanone (pseudopelletierine is strongly dependent on the amount of water added and aromatic aldehyde used. DFT methods were applied to calculate the free energies of tropinone and granatanone enols, transition states, and isomeric aldol products. A theoretical model was verified by comparison of results from several DFT methods and functionals with experiments. The 6-31g(d/CPCM method proved most suited to the problem, although all methods tested predicted similar trends. Explicit inclusion of a water molecule bonded to the amino ketones resulted in increased stability of the enol forms. The dependence of the anti/syn-diastereoselectivity on the amount of water used may be rationalized on the basis of change in the polarity of the reaction medium. The predicted stabilities of competing products agreed with experimental results supporting the notion of thermodynamic control. The isomeric products distributions for the aldol reaction of several aromatic aldehydes in solventless (neat conditions were accurately calculated from free energies of the aldol addition step in the gas phase using B3LYP/6-31g(d method and in aqueous conditions using the CPCM-B3LYP/6-31g(d model. Our methodology can be useful for predicting the outcome of this type of aldol reactions.

  17. Enantioselective H-atom transfer reaction: a strategy to synthesize formaldehyde aldol products.

    Science.gov (United States)

    Sibi, Mukund P; Patil, Kalyani

    2005-04-14

    [reaction: see text] Enantioselective radical alkylation of Baylis-Hillman adducts furnished aldol products in good yield and selectivity. The results illustrate that the selectivity in the hydrogen atom transfer is dependent on the size of the ester substituent, with smaller substituents providing better enantioselectivity.

  18. Expedient synthesis of C-aryl carbohydrates by consecutive biocatalytic benzoin and aldol reactions.

    Science.gov (United States)

    Hernández, Karel; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Pohl, Martina; Clapés, Pere

    2015-02-16

    The introduction of aromatic residues connected by a C-C bond into the non-reducing end of carbohydrates is highly significant for the development of innovative structures with improved binding affinity and selectivity (e.g., C-aril-sLex). In this work, an expedient asymmetric "de novo" synthetic route to new aryl carbohydrate derivatives based on two sequential stereoselectively biocatalytic carboligation reactions is presented. First, the benzoin reaction of aromatic aldehydes to dimethoxyacetaldehyde is conducted, catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I. Then, the α-hydroxyketones formed are reduced by using NaBH4 yielding the anti diol. After acetal hydrolysis, the aldol addition of dihydroxyacetone, hydroxyacetone, or glycolaldehyde catalyzed by the stereocomplementary D-fructose-6-phosphate aldolase and L-rhamnulose-1-phosphate aldolase is performed. Both aldolases accept unphosphorylated donor substrates, avoiding the need of handling the phosphate group that the dihydroxyacetone phosphate-dependent aldolases require. In this way, 6-C-aryl-L-sorbose, 6-C-aryl-L-fructose, 6-C-aryl-L-tagatose, and 5-C-aryl-L-xylose derivatives are prepared by using this methodology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. An overview of dehydration, aldol-condensation and hydrogenation processes for production of liquid alkanes from biomass-derived carbohydrates

    Energy Technology Data Exchange (ETDEWEB)

    Chheda, Juben N.; Dumesic, James A. [University of Wisconsin-Madison, Department of Chemical and Biological Engineering, Madison, WI 53706 (United States)

    2007-05-30

    We present results for the conversion of carbohydrate feedstocks to liquid alkanes by the combination of dehydration, aldol-condensation/hydrogenation, and dehydration/hydrogenation processing. With respect to the first dehydration step, we demonstrate that HMF can be produced in good selectivity from abundantly available polysaccharides (such as inulin, sucrose) containing fructose monomer units using a biphasic batch reactor system. The reaction system can be optimized to achieve good yields to 5-hydroxymethylfurfural (HMF) from fructose by varying the contents of aqueous-phase modifiers such as dimethylsulfoxide (DMSO) and 1-methyl-2-pyrrolidinone (NMP). Regarding the aldol-condensation/hydrogenation step, we present the development of stable, solid base catalysts in aqueous environments. We address the effects of various reaction parameters such as the molar ratio of reactants and temperature on overall product yield for sequential aldol-condensation and hydrogenation steps. Overall, our results show that it is technically possible to convert carbohydrate feedstocks to produce liquid alkanes by the combination of dehydration, aldol-condensation/hydrogenation, and dehydration/hydrogenation processing; however, further optimization of these processes is required to decrease the overall number of separate steps (and reactors) required in this conversion. (author)

  20. A green route to methyl acrylate and acrylic acid by an aldol condensation reaction over H-ZSM-35 zeolite catalysts.

    Science.gov (United States)

    Ma, Zhanling; Ma, Xiangang; Liu, Hongchao; He, Yanli; Zhu, Wenliang; Guo, Xinwen; Liu, Zhongmin

    2017-08-10

    A one-step aldol condensation reaction to produce MA and AA is a green and promising strategy. Here, the aldol condensation reaction was first conducted with DMM and MAc over different types of zeolite catalysts. The H-ZSM-35 zeolite demonstrates excellent catalytic performance with a DMM conversion of 100% and a MA + AA selectivity of up to 86.2% and superior regeneration ability, with great potential for industrial operation.

  1. Cooperative Effects Between Arginine and Glutamic Acid in the Amino Acid-Catalyzed Aldol Reaction.

    Science.gov (United States)

    Valero, Guillem; Moyano, Albert

    2016-08-01

    Catalysis of the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde by mixtures of L-Arg and of L-Glu in wet dimethyl sulfoxide (DMSO) takes place with higher enantioselectivity (up to a 7-fold enhancement in the anti-aldol for the 1:1 mixture) than that observed when either L-Glu or L-Arg alone are used as the catalysts. These results can be explained by the formation of a catalytically active hydrogen-bonded complex between both amino acids, and demonstrate the possibility of positive cooperative effects in catalysis by two different α-amino acids. Chirality 28:599-605, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  2. Halogeno Aldol Reaction of Ethyl Vinyl Ketone and Aldehydes Mediated by Titanium Tetrachloride

    Directory of Open Access Journals (Sweden)

    Guigen Li

    2000-12-01

    Full Text Available A three-component halogeno aldol reaction has been developed by using titanium tetrachloride as the halogen source as well as the Lewis acid mediator. The dehydration and elimination of hydrogen chloride were inhibited by conducting the reaction at 0 °C in dichloromethane or at room temperature with a shortened reaction time. Seven examples were examined, giving good to high yields (61 - 92% and modest stereoselectivity (syn/anti: 2.2/1.0 - 8.4/1.0.

  3. Dynamic structural change of the self-assembled lanthanum complex induced by lithium triflate for direct catalytic asymmetric aldol-Tishchenko reaction.

    Science.gov (United States)

    Horiuchi, Yoshihiro; Gnanadesikan, Vijay; Ohshima, Takashi; Masu, Hyuma; Katagiri, Kosuke; Sei, Yoshihisa; Yamaguchi, Kentaro; Shibasaki, Masakatsu

    2005-09-05

    The development of a direct catalytic asymmetric aldol-Tishchenko reaction and the nature of its catalyst are described. An aldol-Tishchenko reaction of various propiophenone derivatives with aromatic aldehydes was promoted by [LaLi3(binol)3] (LLB), and reactivity and enantioselectivity were dramatically enhanced by the addition of lithium trifluoromethanesulfonate (LiOTf). First, we observed a dynamic structural change of LLB by the addition of LiOTf using 13C NMR spectroscopy, electronspray ionization mass spectrometry (ESI-MS), and cold-spray ionization mass spectrometry (CSI-MS). X-ray crystallography revealed that the structure of the newly generated self-assembled complex was a binuclear [La2Li4(binaphthoxide)5] complex 6. A reverse structural change of complex 6 to LLB by the addition of one equivalent of Li2(binol) was also confirmed by ESI-MS and experimental results. The drastic concentration effects on the direct catalytic asymmetric aldol-Tishchenko reaction suggested that the addition of LiOTf to LLB generated an active oligomeric catalyst species.

  4. Cooperative organocatalysis of Mukaiyama-type aldol reactions by thioureas and nitro compounds

    KAUST Repository

    Bukhriakov, Konstantin; Desyatkin, Victor G.; Rodionov, Valentin

    2016-01-01

    A unique organocatalytic system for Mukaiyama-type aldol reactions based on the cooperative action of nitro compounds and thioureas has been identified. This system is compatible with a wide range of substrates and does not require low temperatures, inert atmospheres, or an aqueous workup. A catalytic mechanism based on nitro group-mediated silyl cation transfer has been proposed. © The Royal Society of Chemistry 2016.

  5. Cooperative organocatalysis of Mukaiyama-type aldol reactions by thioureas and nitro compounds

    KAUST Repository

    Bukhriakov, Konstantin

    2016-05-16

    A unique organocatalytic system for Mukaiyama-type aldol reactions based on the cooperative action of nitro compounds and thioureas has been identified. This system is compatible with a wide range of substrates and does not require low temperatures, inert atmospheres, or an aqueous workup. A catalytic mechanism based on nitro group-mediated silyl cation transfer has been proposed. © The Royal Society of Chemistry 2016.

  6. Cross-Aldol condensation of isobutyraldehyde and formaldehyde using phase transfer catalyst

    Directory of Open Access Journals (Sweden)

    Azhar Hashmi

    2016-09-01

    Full Text Available The hydroxypivaldehyde (HPA precursor intermediate for the synthesis of neopentyl glycol (NPG is prepared by novel cross Aldol condensation of isobutyraldehyde and formaldehyde at 20 °C using benzyltrimethylammonium hydroxide, a basic phase transfer catalyst. A feed mole ratio of 1.1:1.0:0.04 (isobutyraldehyde:formaldehyde:benzyltrimethylammonium hydroxide afforded hydroxypivaldehyde as white solid in almost quantitative yield with ∼100% selectivity.

  7. Cross-Aldol condensation of isobutyraldehyde and formaldehyde using phase transfer catalyst

    OpenAIRE

    Azhar Hashmi

    2016-01-01

    The hydroxypivaldehyde (HPA) precursor intermediate for the synthesis of neopentyl glycol (NPG) is prepared by novel cross Aldol condensation of isobutyraldehyde and formaldehyde at 20 °C using benzyltrimethylammonium hydroxide, a basic phase transfer catalyst. A feed mole ratio of 1.1:1.0:0.04 (isobutyraldehyde:formaldehyde:benzyltrimethylammonium hydroxide) afforded hydroxypivaldehyde as white solid in almost quantitative yield with ∼100% selectivity.

  8. 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)

  9. Enantioselective organocatalyzed Oxa-Michael-Aldol cascade reactions: Construction of chiral 4H-chromenes with a trifluoromethylated tetrasubstituted carbon stereocenter

    KAUST Repository

    Zhang, Jing; Ajitha, Manjaly John; He, Lin; Liu, Kai; Dai, Bin; Huang, Kuo-Wei

    2015-01-01

    The first organocatalytic asymmetric synthesis of 4H-chromenes bearing a trifluoromethylated tetrasubstituted carbon center is presented. Chiral secondary amines promote the oxa-Michael-aldol cascade reaction between alkynals and 2

  10. Direct asymmetric vinylogous aldol reaction of allyl ketones with isatins: Divergent synthesis of 3-hydroxy-2-oxindole derivatives

    KAUST Repository

    Zhu, Bo; Zhang, Wen; Lee, Richmond; Han, Zhiqiang; Yang, Wenguo; Tan, Davin; Huang, Kuo-Wei; Jiang, Zhiyong

    2013-01-01

    6 in 1: The highly enantioselective title reaction is mediated by a bifunctional catalyst and leads to E-configured vinylogous aldol products (see scheme). These products are used as common intermediates in the synthesis of six biologically active 3

  11. Tandem Aldol-Michael Reactions in Aqueous Diethylamine Medium: A Greener and Efficient Approach to Bis-Pyrimidine Derivatives

    Directory of Open Access Journals (Sweden)

    Abdullah M. Al-Majid

    2013-12-01

    Full Text Available A simple protocol, involving the green synthesis for the construction of novel bis-pyrimidine derivatives, 3a–i and 4a–e are accomplished by the aqueous diethylamine media promoted tandem Aldol-Michael reaction between two molecules of barbituric acid derivatives 1a,b with various aldehydes. This efficient synthetic protocol using an economic and environmentally friendly reaction media with versatility and shorter reaction time provides bis-pyrimidine derivatives with high yields (88%–99%.

  12. N-Heterocyclic Carbene-Catalyzed Vinylogous Mukaiyama Aldol Reaction of α-Keto Esters and α-Trifluoromethyl Ketones

    KAUST Repository

    Du, Guang-Fen; Wang, Ying; Xing, Fen; Xue, Mei; Guo, Xu-Hong; Huang, Kuo-Wei; Dai, Bin

    2015-01-01

    © Georg Thieme Verlag Stuttgart · New York · Synthesis 2016. N-Heterocyclic carbene (NHC)-catalyzed vinylogous Mukaiyama aldol reaction of ketones was developed. Under the catalysis of 5 mol% NHC, α-keto esters and α-trifluoromethyl ketones reacted with 2-(trimethysilyloxy)furan efficiently to produce γ-substituted butenolides containing adjacent quaternary and tertiary carbon centers in high yields with good diastereoselectivities.

  13. Boehmite-An Efficient and Recyclable Acid-Base Bifunctional Catalyst for Aldol Condensation Reaction.

    Science.gov (United States)

    Reshma, P C Rajan; Vikneshvaran, Sekar; Velmathi, Sivan

    2018-06-01

    In this work boehmite was used as an acid-base bifunctional catalyst for aldol condensation reactions of aromatic aldehydes and ketones. The catalyst was prepared by simple sol-gel method using Al(NO3)3·9H2O and NH4OH as precursors. The catalyst has been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (DRS), BET surface area analyses. Boehmite is successfully applied as catalyst for the condensation reaction between 4-nitrobenzaldehyde and acetone as a model substrate giving α, β-unsaturated ketones without any side product. The scope of the reaction is extended for various substituted aldehydes. A probable mechanism has been suggested to explain the cooperative behavior of the acidic and basic sites. The catalyst is environmentally friendly and easily recovered from the reaction mixture. Also the catalyst is reusable up to 3 catalytic cycles.

  14. Study of Liquid Alkanes Production from Biomass-Derived Carbohydrates by Aldol-Condensation and Hydrogenation Processes

    Directory of Open Access Journals (Sweden)

    Navadol Laosiripojana

    2010-10-01

    Full Text Available This research aims to synthesis liquid alkanes from biomass-derived hydroxyl methyl furfural (HMF and furfural by aldol-condensation and hydrogenation processes over several catalysts i.e. TiO2, TiO2-ZrO2, Pd/Al2O3 and Pd/CeO2. It was found that the catalysts make significant impact on the selectivity and yield of alkanes product. It is noted that Pd/Al2O3 provided the highest alkane yield and selectivity. The aldol-condensation and hydrogenation of HMF over Pd/Al2O3 provide high C12 selectivity whereas the aldol-condensation and hydrogenation of furfural over Pd/Al2O3 provide high C8 selectivity. The effects of reaction temperature, reaction pressure and reaction time were then studied. The effect of inlet furfural to acetone molar ratio was also determined. It was also found that the optimized conditions to maximize the yield of alkane production from the aldol-condensation/hydrogenation of HMF and furfural are (i at 53oC and 24 hr for aldol-condenstation of HMF, (ii 80oC and 24 hr for aldol-condenstation of furfural, and (iii 120oC for 6 hr with HMF to acetone molar ratio of 3:1 and furfural to acetone molar ratio of 4:1 in the presence of Pd/Al2O3 (calcined at 500oC for hydrogenation reaction.

  15. Enantioselective organocatalyzed Oxa-Michael-Aldol cascade reactions: Construction of chiral 4H-chromenes with a trifluoromethylated tetrasubstituted carbon stereocenter

    KAUST Repository

    Zhang, Jing

    2015-03-13

    The first organocatalytic asymmetric synthesis of 4H-chromenes bearing a trifluoromethylated tetrasubstituted carbon center is presented. Chiral secondary amines promote the oxa-Michael-aldol cascade reaction between alkynals and 2-trifluoroacetylphenols via iminium-allenamine activation to produce pharmaceutically important heterocycles with excellent enantioselectivities. The proposed reaction can be scaled-up easily with maintenance of the excellent enantioselectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Direct asymmetric vinylogous aldol reaction of allyl ketones with isatins: Divergent synthesis of 3-hydroxy-2-oxindole derivatives

    KAUST Repository

    Zhu, Bo

    2013-05-03

    6 in 1: The highly enantioselective title reaction is mediated by a bifunctional catalyst and leads to E-configured vinylogous aldol products (see scheme). These products are used as common intermediates in the synthesis of six biologically active 3-hydroxy-2-oxindole derivatives (e.g., CPC-1). Computational studies indicated that the observed stereoselectivity is a result of favorable secondary π-π* and H-bonding interactions in the transition state. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. 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

  18. Application of a new tandem isomerization-aldolization reaction of allylic alcohols to the synthesis of three diastereoisomers of (2R)-1,2-O-isopropylidene-4-methylpentane-1,2,3,5-tetraol.

    Science.gov (United States)

    Cuperly, David; Crévisy, Christophe; Grée, René

    2003-08-08

    The tandem isomerization-aldolization reaction of (2R)-1,2-O-isopropylidene-4-penten-1,2,3-triol 3 and formaldehyde gives a mixture of two aldol products 2a and 2b. The stereoselective reduction of each compound by l-Selectride affords two diastereoisomers of (2R)-1,2-O-Isopropylidene-4-methylpentane-1,2,3,5-tetraol while a third diastereoisomer is obtained by stereoselective reduction with Me(4)NHB(OAc)(3).

  19. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

    Science.gov (United States)

    Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

    2013-11-01

    This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

  20. Sequential series for nuclear reactions

    International Nuclear Information System (INIS)

    Izumo, Ko

    1975-01-01

    A new time-dependent treatment of nuclear reactions is given, in which the wave function of compound nucleus is expanded by a sequential series of the reaction processes. The wave functions of the sequential series form another complete set of compound nucleus at the limit Δt→0. It is pointed out that the wave function is characterized by the quantities: the number of degrees of freedom of motion n, the period of the motion (Poincare cycle) tsub(n), the delay time t sub(nμ) and the relaxation time tausub(n) to the equilibrium of compound nucleus, instead of the usual quantum number lambda, the energy eigenvalue Esub(lambda) and the total width GAMMAsub(lambda) of resonance levels, respectively. The transition matrix elements and the yields of nuclear reactions also become the functions of time given by the Fourier transform of the usual ones. The Poincare cycles of compound nuclei are compared with the observed correlations among resonance levels, which are about 10 -17 --10 -16 sec for medium and heavy nuclei and about 10 -20 sec for the intermediate resonances. (auth.)

  1. Plasmon-driven sequential chemical reactions in an aqueous environment.

    Science.gov (United States)

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

    2014-06-24

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

  2. Enantioselective radical addition/trapping reactions with alpha,beta-disubstituted unsaturated imides. Synthesis of anti-propionate aldols.

    Science.gov (United States)

    Sibi, Mukund P; Petrovic, Goran; Zimmerman, Jake

    2005-03-02

    This manuscript describes a highly diastereo- and enantioselective intermolecular radical addition/hydrogen atom transfer to alpha,beta-disubstituted enoates. Additionally, we show that anti-propionate aldol-like products can be easily prepared from alpha-methyl-beta-acyloxyenoates in good yields and high diastereo- and enantioselectivities.

  3. ACT-XN: Revised version of an activation calculation code for fusion reactor analysis. Supplement of the function for the sequential reaction activation by charged particles

    International Nuclear Information System (INIS)

    Yamauchi, Michinori; Sato, Satoshi; Nishitani, Takeo; Konno, Chikara; Hori, Jun-ichi; Kawasaki, Hiromitsu

    2007-09-01

    The ACT-XN is a revised version of the ACT4 code, which was developed in the Japan Atomic Energy Research Institute (JAERI) to calculate the transmutation, induced activity, decay heat, delayed gamma-ray source etc. for fusion devices. The ACT4 code cannot deal with the sequential reactions of charged particles generated by primary neutron reactions. In the design of present experimental reactors, the activation due to sequential reactions may not be of great concern as it is usually buried under the activity by primary neutron reactions. However, low activation material is one of the important factors for constructing high power fusion reactors in future, and unexpected activation may be produced through sequential reactions. Therefore, in the present work, the ACT4 code was newly supplemented with the calculation functions for the sequential reactions and renamed the ACT-XN. The ACT-XN code is equipped with functions to calculate effective cross sections for sequential reactions and input them in transmutation matrix. The FISPACT data were adopted for (x,n) reaction cross sections, charged particles emission spectra and stopping powers. The nuclear reaction chain data library were revised to cope with the (x,n) reactions. The charged particles are specified as p, d, t, 3 He(h) and α. The code was applied to the analysis of FNS experiment for LiF and Demo-reactor design with FLiBe, and confirmed that it reproduce the experimental values within 15-30% discrepancies. In addition, a notice was presented that the dose rate due to sequential reaction cannot always be neglected after a certain period cooling for some of the low activation material. (author)

  4. Improvement of the stability of basic mixed oxides used as catalysts for aldol condensation of bio-derived compounds by palladium addition

    International Nuclear Information System (INIS)

    Faba, Laura; Díaz, Eva; Ordóñez, Salvador

    2013-01-01

    Aqueous-phase aldol condensation of biomass-derived ketones and aldehydes is a key step in the preparation of fuels and chemicals from renewable resources. Furfural–acetone aldol condensation yielding C 8 and C 13 adducts was studied at 323 K and 1 MPa in a stirred batch reactor. We propose a new strategy for minimizing catalytic deactivation, consisting of modifying catalysts (MgO–ZrO 2 and MgO–Al 2 O 3 ) by Pd addition (2%). This modification slightly changes the morphology and surface chemistry of the supports, leading to changes on the catalysts performance but not reaction mechanism modifications. If condensation is performed in hydrogen atmosphere, the partial hydrogenation of the condensation adducts increases its water solubility, minimizing catalyst deactivation. In that way, the selectivity for C13 adduct decreases only 25% between two successive reaction cycles using Pd/MgO–ZrO 2 catalyst, whereas this decrease is of 90% for the un-doped mixed oxides. These effects are less marked for the MgO–Al 2 O 3 catalyst. Highlights: •Furfural and acetone aldolization on Pd/MgO–ZrO 2 and Pd/MgO–Al 2 O 3 . •Conversion and selectivity towards C8 and C13 low and unstable catalysts. •Aldolization in H 2 decreases coke formation: higher reusability of the catalysts

  5. Aldol Condensation of Citral with Acetone on Basic Solid Catalysts

    Directory of Open Access Journals (Sweden)

    NODA C.

    1998-01-01

    Full Text Available The catalytic performance of solids with basic properties, such as CaO, MgO and hydrotalcites, was evaluated in the aldol condensation of citral and acetone, the first step in the synthesis of ionones from citral. The best results were obtained with CaO and hydrotalcite with high conversions (98% and selectivities (close to 70% for the main product observed for both of the catalyst. Such pseudoionone yields were greater than those reported in the literature for the homogeneous reaction.

  6. Forging Fluorine‐Containing Quaternary Stereocenters by a Light‐Driven Organocatalytic Aldol Desymmetrization Process

    Science.gov (United States)

    Cuadros, Sara; Dell'Amico, Luca

    2017-01-01

    Abstract Reported herein is a light‐triggered organocatalytic strategy for the desymmetrization of achiral 2‐fluoro‐substituted cyclopentane‐1,3‐diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy‐o‐quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon–fluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2‐fluoro‐3‐hydroxycyclopentanones. PMID:28746742

  7. Natural Occurrence of Aldol Condensation Products in Valencia Orange Oil.

    Science.gov (United States)

    Abreu, Ingo; Da Costa, Neil C; van Es, Alfred; Kim, Jung-A; Parasar, Uma; Poulsen, Mauricio L

    2017-12-01

    Cold pressed orange oils contain predominantly d-limonene (approximately 95%) and various other lower concentration monoterpenes, sesquiterpenes, sinensals plus 3 key aliphatic aldehydes: hexanal, octanal. and decanal. The aldol self-condensation products or "dimers" for each aldehyde have been postulated as being present at low concentrations in the oil. However, to date only the hexanal dimer has been previously reported. In this paper, cold pressed Valencia orange oil was fractionally distilled/folded and analyzed by GC and high resolution GC-MS to detect these compounds on 2 different capillary column phases. Subsequently the hexanal, octanal, and decanal self-aldol condensation products, 2-butyl-2-octenal, 2-hexyl-2-decenal, and 2-octyl-2-dodecenal, respectively, were detected in the folded oil. These predominantly trans configuration isomeric compounds were synthesized, to confirm them as being present in nature and evaluated organoleptically by a panel of evaluators. To further confirm the mechanism of their formation, the enriched oil was made into a simple beverage to show the effect on the formation of these aldol compounds under acidic conditions. Finally aliphatic aldehydes from hexanal to undecanal were reacted together in various combinatorial pairs to give an additional 33 self and mixed aldol condensation products, some of which were also detected in the folded oil. This paper discloses the structural elucidation and synthesis of 8 novel aldol condensation products found at trace concentrations in citrus and leading to a further 31 mass spectrally determined aldol products. Sensory evaluations and application of some of these components were demonstrated in a model citrus beverage. © 2017 Institute of Food Technologists®.

  8. Modified calcium oxide as stable solid base catalyst for Aldol

    Indian Academy of Sciences (India)

    A highly efficient and stable solid-base catalyst for Aldol condensation was prepared by modifying commercial CaO with benzyl bromide in a simple way. It was found that modified CaO can effectively catalyse the Aldol condensation of cyclohexanone and benzaldehyde, as well as various benzaldehydes, to produce ...

  9. Forging Fluorine-Containing Quaternary Stereocenters by a Light-Driven Organocatalytic Aldol Desymmetrization Process.

    Science.gov (United States)

    Cuadros, Sara; Dell'Amico, Luca; Melchiorre, Paolo

    2017-09-18

    Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro-substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon-fluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2-fluoro-3-hydroxycyclopentanones. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

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

    Directory of Open Access Journals (Sweden)

    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.

  11. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities.

    Science.gov (United States)

    Van Wyngarden, A L; Pérez-Montaño, S; Bui, J V H; Li, E S W; Nelson, T E; Ha, K T; Leong, L; Iraci, L T

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H 2 SO 4 ) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and 1 H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal

  12. Convergent fabrication of a nanoporous two-dimensional carbon network from an aldol condensation on metal surfaces

    International Nuclear Information System (INIS)

    Landers, John; De Santis, Maurizio; Bendiab, Nedjma; Magaud, Laurence; Coraux, Johann; Chérioux, Frédéric; Lamare, Simon

    2014-01-01

    We report a convergent surface polymerization reaction scheme on Au(111), based on a triple aldol condensation, yielding a carbon-rich, covalent nanoporous two-dimensional network. The reaction is not self-poisoning and proceeds up to a full surface coverage. The deposited precursor molecules 1, 3, 5-tri(4’-acetylphenyl) first form supramolecular assemblies that are converted to the porous covalent network upon heating. The formation and structure of the network and of the intermediate steps are studied with scanning tunneling microscopy, Raman spectroscopy and density functional theory. (paper)

  13. Cross-Domain Statistical-Sequential Dependencies Are Difficult To Learn

    Directory of Open Access Journals (Sweden)

    Anne McClure Walk

    2016-02-01

    Full Text Available Recent studies have demonstrated participants’ ability to learn cross-modal associations during statistical learning tasks. However, these studies are all similar in that the cross-modal associations to be learned occur simultaneously, rather than sequentially. In addition, the majority of these studies focused on learning across sensory modalities but not across perceptual categories. To test both cross-modal and cross-categorical learning of sequential dependencies, we used an artificial grammar learning task consisting of a serial stream of auditory and/or visual stimuli containing both within- and cross-domain dependencies. Experiment 1 examined within-modal and cross-modal learning across two sensory modalities (audition and vision. Experiment 2 investigated within-categorical and cross-categorical learning across two perceptual categories within the same sensory modality (e.g. shape and color; tones and non-words. Our results indicated that individuals demonstrated learning of the within-modal and within-categorical but not the cross-modal or cross-categorical dependencies. These results stand in contrast to the previous demonstrations of cross-modal statistical learning, and highlight the presence of modality constraints that limit the effectiveness of learning in a multimodal environment.

  14. One-pot aldol condensation and hydrodeoxygenation of biomass-derived carbonyl compounds for biodiesel synthesis.

    Science.gov (United States)

    Faba, Laura; Díaz, Eva; Ordóñez, Salvador

    2014-10-01

    Integrating reaction steps is of key interest in the development of processes for transforming lignocellulosic materials into drop-in fuels. We propose a procedure for performing the aldol condensation (reaction between furfural and acetone is taken as model reaction) and the total hydrodeoxygenation of the resulting condensation adducts in one step, yielding n-alkanes. Different combinations of catalysts (bifunctional catalysts or mechanical mixtures), reaction conditions, and solvents (aqueous and organic) have been tested for performing these reactions in an isothermal batch reactor. The results suggest that the use of bifunctional catalysts and aqueous phase lead to an effective integration of both reactions. Therefore, selectivities to n-alkanes higher than 50% were obtained using this catalyst at typical hydrogenation conditions (T=493 K, P=4.5 MPa, 24 h reaction time). The use of organic solvent, carbonaceous supports, or mechanical mixtures of monofunctional catalysts leads to poorer results owing to side effects; mainly, hydrogenation of reactants and adsorption processes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Aldol condensation of furfural and acetone on zeolites

    Czech Academy of Sciences Publication Activity Database

    Kikhtyanin, O.; Kelbichová, V.; Vitvarová, Dana; Kubů, Martin; Kubička, D.

    2014-01-01

    Roč. 227, MAY 2014 (2014), s. 154-162 ISSN 0920-5861 R&D Projects: GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : aldol condensation * oligomerization * zeolites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.893, year: 2014

  16. Activated hydrotalcites as solid base catalysts in aldol condensations

    NARCIS (Netherlands)

    Roelofs, J.C.A.A.

    2001-01-01

    The development of new catalytic materials and routes to replace environmentally unacceptable processes in the fine chemical industry is emerging due to stringent legislation. Replacement of currently applied alkali bases in liquid-phase aldol condensations can result in diminishing of waste water

  17. Nuclear structure effects in multi-nucleon transfer and sequential fission reactions

    International Nuclear Information System (INIS)

    Biswas, D.C.

    2001-01-01

    The role of the nuclear structure in multi-nucleon transfer and sequential fission reactions has been discussed. The recent results on multi-nucleon transfer and transfer induced fission reaction, have brought out many interesting features in understanding the reaction mechanism and collective dynamics of heavy ion reactions. The structure of the projectile nucleus has strong influence on the transfer of multi-nucleons and/or clusters from the projectile to the target. The mechanism of multi-nucleon transfer between two heavy nuclei is a complex process which has a strong dependence on the ground state Q-value of the reaction as well as on the number of transferred nucleons

  18. Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

    Directory of Open Access Journals (Sweden)

    Henning Hopf

    2014-08-01

    Full Text Available Under basic conditions 4,5,12,13-tetraacetyl[2.2]paracyclophane (9 cyclizes by a double aldol condensation to provide the two aldols 12 and 15 in a 3:7 ratio. The structures of these compounds were obtained from X-ray structural analysis, spectroscopic data, and mechanistic considerations. On acid treatment 12 is dehydrated to a mixture of the condensed five-membered [2.2]paracyclophane derivatives 18–20, whereas 15 yields a mixture of the isomeric cyclopentadienones 21–23. The structures of these elimination products are also deduced from X-ray and spectroscopic data. The sequence presented here constitutes the simplest route so far to cyclophanes carrying an annelated five-membered ring.

  19. Modified calcium oxide as stable solid base catalyst for Aldol ...

    Indian Academy of Sciences (India)

    A highly efficient and stable solid-base catalyst for Aldol condensation was ... was bonded on surface of CaO chemically and almost no Ca(OH)2 formed during the modification process. ... cation, corrosion and waste generation attract great.

  20. DESAIN DAN SINTESIS SENYAWA ACES (ANALOG CURCUMIN SERIES DENGAN METODE SOLID PHASE REACTION SEBAGAI SENYAWA ANTIKANKER POTEN DENGAN MEKANISME MENGHAMBAT PROTEIN NF-kB

    Directory of Open Access Journals (Sweden)

    Monica Sabrina Widiapranolo

    2016-04-01

    Full Text Available Abstract: Analog of curcumin in forms of enone and dienone aromatic is known for their activity as an NF-κB inhibitor. In this study, will be synthesize 2-(4'-N, N-dimethylamino benzilidine cyclohexane-1,3-dione as an analog that predicted has an activity as an NF-κB inhibitor. This research was conducted based on the crossed aldol condensation reaction by reacting 3 mmole pN,N-dimethylamino benzaldehide and 6 mmole cyclohexane-1,3-dione with hydrochloric acid as the catalyst using solid phase reaction method. Based on computational analysis, 2-(4'-N,Ndimethylamino benzilidine cyclohexane-1,3-dione showed a better interaction with NF-κB protein with PLANTSPLP score was -69,7895. The outcome of the reaction was yellow colored powder, no odor and soluble in hydrochloric acid 3N. The yield value was 78.8%. Liquid chromatography showed 100% purity. The melting point range was 237.5-240.3°C. The results of structure elucidation by 1H-NMR, infrared and mass spectroscopy tests indicated the compound was 2-(4-(dimetilaminobenzilidena-4-(3-oksosiklohex-1-enil sikloheksana-1,3-dion. Key words: 2-(4'-N, N-dimethylamino benzilidine cyclohexane-1,3-dione, crossed aldol condensation, solid phase reaction.

  1. EncM, a versatile enterocin biosynthetic enzyme involved in Favorskii oxidative rearrangement, aldol condensation, and heterocycle-forming reactions

    Science.gov (United States)

    Xiang, Longkuan; Kalaitzis, John A.; Moore, Bradley S.

    2004-01-01

    The bacteriostatic natural product enterocin from the marine microbe “Streptomyces maritimus” has an unprecedented carbon skeleton that is derived from an aromatic polyketide biosynthetic pathway. Its caged tricyclic, nonaromatic core is derived from a linear poly-β-ketide precursor that formally undergoes a Favorskii-like oxidative rearrangement. In vivo characterization of the gene encM through mutagenesis and heterologous biosynthesis demonstrated that its protein product not only is solely responsible for the oxidative C—C rearrangement, but also facilitates two aldol condensations plus two heterocycle forming reactions. In total, at least five chiral centers and four rings are generated by this multifaceted flavoprotein. Heterologous expression of the enterocin biosynthesis genes encABCDLMN in Streptomyces lividans resulted in the formation of the rearranged metabolite desmethyl-5-deoxyenterocin and the shunt products wailupemycins D-G. Addition of the methyltransferase gene encK, which was previously proposed through mutagenesis to additionally assist EncM in the Favorskii rearrangement, shifted the production to the O-methyl derivative 5-deoxyenterocin. The O-methyltransferase EncK seems to be specific for the pyrone ring of enterocin, because bicyclic polyketides bearing pyrone rings are not methylated in vivo. Expression of encM with different combinations of homologous actinorhodin biosynthesis genes did not result in the production of oxidatively rearranged enterocin-actinorhodin hybrid compounds as anticipated, suggesting that wild-type EncM may be specific for its endogenous type II polyketide synthase or for benzoyl-primed polyketide precursors. PMID:15505225

  2. Asymmetric Aldol Additions: A Guided-Inquiry Laboratory Activity on Catalysis

    Science.gov (United States)

    King, Jorge H. Torres; Wang, Hong; Yezierski, Ellen J.

    2018-01-01

    Despite the importance of asymmetric catalysis in both the pharmaceutical and commodity chemicals industries, asymmetric catalysis is under-represented in undergraduate chemistry laboratory curricula. A novel guided-inquiry experiment based on the asymmetric aldol addition was developed. Students conduct lab work to compare the effectiveness of…

  3. [Development of boomerang-type intramolecular cascade reactions and application to natural product synthesis].

    Science.gov (United States)

    Takasu, K

    2001-12-01

    Intramolecular cascade reaction has received much attention as a powerful methodology to construct a polycyclic framework in organic synthesis. We have been developing "boomerang-type cascade reaction" to construct a variety of polycyclic skeletons efficiently. In the above reactions, a nucleophilic function of substrates changes the character into an electrophile after the initial reaction, and the electrophilic group acts as a nucleophile in the second reaction. That is, the reaction center stepwise moves from one functional group back to the same one via other functional groups. The stream of the electron concerning the cascade reaction is like a locus of boomerang. We show here three different boomerang-type reactions via ionic species or free radicals. 1) Diastereoselective Michael-aldol reaction based on the chiral auxiliary method and enantioselective Michael-aldol reaction by the use of external chiral sources. 2) Short and efficient total syntheses of longifolane sesquiterpenes utilizing intramolecular double Michael addition as a key step. 3) Development of boomerang-type radical cascade reaction of halopolyenes to construct terpenoid skeletons and its regioselectivity.

  4. Synthesis of novel chromeno-annulated cis-fused pyrano[3,4-c]benzopyran and naphtho pyran derivatives via domino aldol-type/hetero Diels-Alder reaction and their cytotoxicity evaluation.

    Science.gov (United States)

    Madda, Jyothi; Venkatesham, Akkaladevi; Naveen Kumar, Bejjanki; Nagaiah, Kommu; Sujitha, Pombala; Ganesh Kumar, C; Rao, Tadikamalla Prabhakar; Jagadeesh Babu, Nanubolu

    2014-09-15

    New chromeno-annulated cis-fused pyrano[3,4-c]benzopyran and naphtho pyran derivatives have been synthesized by domino aldol-type reaction/hetero Diels-Alder reaction generated from o-quinone methide in situ from 7-O-prenyl derivatives of 8-formyl-2,3-disubstituted chromenones with resorcinols/naphthols in the presence of 20 mol% ethylenediamine diacetate (EDDA), triethylamine (2 mL) as co-catalyst in CH3CN under reflux conditions in good yields. The structures were established based on spectroscopic data, and further confirmed by X-ray diffraction analysis. The results showed that compounds 4h and 4j exhibited very potent cytotoxicity against human cervical cancer cell line (HeLa). Compound 4h displayed good inhibitory activity against both breast cancer cell lines, MDA-MB-231 and MCF-7. Further, the compound 4i exhibited good cytotoxicity against only MDA-MB-231, and compound 4j showed promising activity against human lung cancer cell line, A549 with IC50 value of 2.53±0.07 μM, which was comparable to the standard doxorubicin (IC50=1.21±0.1 μM). Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Reduction methodology for reaction cross sections induced by weakly bound nuclei

    International Nuclear Information System (INIS)

    Deshmukh, N.N.; Mukherjee, S.; Appannababu, S.; Guimaraees, V.; Lubian, J.; Gomes, P.R.S.

    2009-01-01

    The interest in nuclear reactions with weakly bound nuclei has increased considerably along the last decade. Several experiments with stable and unstable projectiles have been performed and a variety of theoretical approaches have been developed. In particular, fusion and breakup reactions induced by such projectiles have been the object of several studies. Owing to the weak binding of the projectile, the breakup cross section may be quite large and coupling with the breakup channel can strongly affect the fusion cross section at near barrier energies. This influence stems from two effects, one of a static and the other of a dynamic nature, which are, however, not easy to be disentangled. The static effect results from the more diffuse density of the weakly bound nuclei, as compared with a strongly bound one. The contribution from weakly bound nucleons to the nuclear density extends further out and this gives rise to a lower and thicker potential barrier. There is general understanding that this static effect enhances the fusion cross section at near barrier energies. On the other hand, there is the dynamic effect corresponding to the coupling with the breakup channel. It is well known that the coupling with a finite number of bound channels enhances the sub-barrier fusion cross section. However, the effect of coupling to channels in the continuum (breakup) is controversial. In first place, one should have in mind that there are different fusion processes in collisions of weakly bound projectiles. One of such processes is the complete fusion, which takes place when the whole mass of the projectile fuses with the target. There may be fusion following breakup. In this case, the compound nucleus may contain the whole mass of the projectile (through sequential fusion of the fragments), or some fragment can escape the interaction region. The former corresponds also to complete fusion (sequential complete fusion) while the latter is known as incomplete fusion. So far

  6. Single-meson inclusive cross sections and sequential decay of Reggeons, 2

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Toshihiro

    1984-09-01

    The single-particle inclusive cross sections of pions and kaons produced from the incident particles in pp and anti pp scattering is investigated under the assumption of the sequential decay mechanism of Reggeons. The many-particle production effect and the initial-decay effect are estimated from experimental data on pion production cross section with small momentum transfer at 100 and 175 GeV/c. Their Feynman-x dependence is in good agreement with the power-law behaviours C(1-X sub(F))/sup 5/ and C(1-X sub(F))/sup 3/. Predictions are given on kaon production cross section.

  7. Peculiar behavior of MWW materials in aldol condensation of furfural and acetone.

    Science.gov (United States)

    Kikhtyanin, Oleg; Chlubná, Pavla; Jindrová, Tereza; Kubička, David

    2014-07-21

    MWW family of different structural types (MCM-22, MCM-49, MCM-56 and MCM-36) was used as catalysts for aldol condensation of furfural and acetone studied in a batch reactor at 100 °C, autogenous pressure and a reaction time of 0-4 h. To establish a relation between physico-chemical and catalytic properties of microporous materials, the samples were characterized by XRD, SEM, N2 adsorption, FTIR and TGA. It was found that the acidic solids possessed appreciable activity in the reaction and resulted in the formation of products of aldehyde-ketone interaction. Surprisingly, MCM-22 and MCM-49, i.e. three-dimensional materials containing internal supercages, exhibited higher activity than two MCM-36 catalysts with two-dimensional character having larger accessible external surface area due to expansion of the interlayer space by swelling and pillaring treatments. Moreover, all MWW family catalysts gave higher conversion than the large-pore zeolite BEA. Nevertheless, furfural conversion decreased rapidly for all the studied materials due to coke formation. Unexpectedly, the deactivation was found to be more severe for MCM-36 catalysts than for MCM-22 and MCM-49, which was attributed to the reaction taking place also in supercages that are protected by 10-ring channels from severe coking. In contrast the cups located on the external surface were coked rapidly.

  8. Green chemistry: solvent- and metal-free Prins cyclization. Application to sequential reactions.

    Science.gov (United States)

    Clarisse, Damien; Pelotier, Béatrice; Piva, Olivier; Fache, Fabienne

    2012-01-04

    Prins cyclization between a homoallylic alcohol and an aldehyde, promoted by trimethylsilyl halide, afforded 4-halo-tetrahydropyrans with good to excellent yields. Thanks to the absence of the solvent and metal, the THP thus obtained have been implicated without purification in several other reactions, in a sequential way, affording in particular new indole derivatives. This journal is © The Royal Society of Chemistry 2012

  9. Regio- and Stereoselective Cascades via Aldol Condensation and 1,3-Dipolar Cycloaddition for Construction of Functional Pyrrolizidine Derivatives.

    Science.gov (United States)

    Mao, Zhuo-Ya; Liu, Yi-Wen; Han, Pan; Dong, Han-Qing; Si, Chang-Mei; Wei, Bang-Guo; Lin, Guo-Qiang

    2018-02-16

    An efficient and step-economical approach to access functionalized pyrrolizidine derivatives by a one-pot tandem sequence, including an aldol condensation and subsequent 1,3-dipolar cycloaddition process, has been developed, starting from acetone, aldehyde, and proline. A number of substituted aromatic aldehydes were amenable to this transformation, and the desired products, racemic 7a-7w and chiral 9a-9m, were obtained with excellent regioselectivities and outstanding diastereoselectivities. Moreover, in situ NMR studies revealed MgSO 4 could effectively promote the aldol condensation pathway in this tandem process.

  10. Tandem ring-closing metathesis/isomerization reactions for the total synthesis of violacein

    DEFF Research Database (Denmark)

    Petersen, Mette Terp; Nielsen, Thomas Eiland

    2013-01-01

    A series of 5-substituted 2-pyrrolidinones was synthesized through a one-pot ruthenium alkylidene-catalyzed tandem RCM/isomerization/nucleophilic addition sequence. The intermediates resulting from RCM/isomerization showed reactivity toward electrophiles in aldol condensation reactions which...

  11. Molecular shape selectivity of hydrotalcite in mixed aldol condensations of aldehydes and ketones

    Czech Academy of Sciences Publication Activity Database

    Červený, J.; Šplíchalová, J.; Kačer, P.; Kovanda, F.; Kuzma, Marek; Červený, L.

    2008-01-01

    Roč. 285, 1-2 (2008), s. 150-154 ISSN 1381-1169 R&D Projects: GA ČR GA104/07/1239 Institutional research plan: CEZ:AV0Z50200510 Keywords : hydrocalcite * aldol condensation * molecular modeling Subject RIV: EE - Microbiology, Virology Impact factor: 2.814, year: 2008

  12. Cyclopalladated complexes in enantioselective catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Dunina, Valeria V; Gorunova, Olga N; Zykov, P A; Kochetkov, Konstantin A

    2011-01-31

    The results of the use of optically active palladacycles in enantioselective catalysis of [3,3]-sigmatropic rearrangements, aldol condensation, the Michael reaction and cross-coupling are analyzed. Reactions with allylic substrates or reagents and some other transformations are considered.

  13. Cross-sectional versus sequential quality indicators of risk factor management in patients with type 2 diabetes

    NARCIS (Netherlands)

    Voorham, Jaco; Denig, Petra; Wolffenbuttel, Bruce H. R.; Haaijer-Ruskamp, Flora M.

    Background: The fairness of quality assessment methods is under debate. Quality indicators incorporating the longitudinal nature of care have been advocated but their usefulness in comparison to more commonly used cross-sectional measures is not clear. Aims: To compare cross-sectional and sequential

  14. Effects of neostriatal 6-OHDA lesion on performance in a rat sequential reaction time task.

    Science.gov (United States)

    Domenger, D; Schwarting, R K W

    2008-10-31

    Work in humans and monkeys has provided evidence that the basal ganglia, and the neurotransmitter dopamine therein, play an important role for sequential learning and performance. Compared to primates, experimental work in rodents is rather sparse, largely due to the fact that tasks comparable to the human ones, especially serial reaction time tasks (SRTT), had been lacking until recently. We have developed a rat model of the SRTT, which allows to study neural correlates of sequential performance and motor sequence execution. Here, we report the effects of dopaminergic neostriatal lesions, performed using bilateral 6-hydroxydopamine injections, on performance of well-trained rats tested in our SRTT. Sequential behavior was measured in two ways: for one, the effects of small violations of otherwise well trained sequences were examined as a measure of attention and automation. Secondly, sequential versus random performance was compared as a measure of sequential learning. Neurochemically, the lesions led to sub-total dopamine depletions in the neostriatum, which ranged around 60% in the lateral, and around 40% in the medial neostriatum. These lesions led to a general instrumental impairment in terms of reduced speed (response latencies) and response rate, and these deficits were correlated with the degree of striatal dopamine loss. Furthermore, the violation test indicated that the lesion group conducted less automated responses. The comparison of random versus sequential responding showed that the lesion group did not retain its superior sequential performance in terms of speed, whereas they did in terms of accuracy. Also, rats with lesions did not improve further in overall performance as compared to pre-lesion values, whereas controls did. These results support previous results that neostriatal dopamine is involved in instrumental behaviour in general. Also, these lesions are not sufficient to completely abolish sequential performance, at least when acquired

  15. Operando Spectroscopy of the Gas-Phase Aldol Condensation of Propanal over Solid Base Catalysts

    NARCIS (Netherlands)

    Hernández-giménez, Ana M.; Ruiz-martínez, Javier; Puértolas, Begoña; Pérez-ramírez, Javier; Bruijnincx, Pieter C. A.; Weckhuysen, Bert M.

    2017-01-01

    The gas-phase aldol condensation of propanal, taken as model for the aldehyde components in bio-oils, has been studied with a combined operando set-up allowing to perform FT-IR & UV–Vis diffuse reflectance spectroscopy (DRS) with on-line mass spectrometry (MS). The selected solid base catalysts, a

  16. Development of a novel algorithm and production of new nuclear data libraries for the treatment of sequential (x,n) reactions in fusion material activation calculations

    International Nuclear Information System (INIS)

    Cierjacks, S.W.; Oblozinsky, P.; Kelzenberg, S.; Rzehorz, B.

    1993-01-01

    A new algorithm and three major nuclear data libraries were developed for the kinematically complete treatment of sequential (x,n) reactions in fusion material activation calculations. The new libraries include data for virtually all isotopes with Z ≤ 84 (A ≤ 210) and half-lives exceeding 1 day; primary neutron energies E n 3 He, and α with energies E x < 24 MeV. While production cross sections of charged particles for primary (n,x) reactions can be deduced from the European activation file, the KFKSPEC data file was created for the corresponding normalized charged-particle spectra. The second data file, KFKXN, contains cross sections for secondary (x,n) reactions. The third data file, KFKSTOP, has a complete set of differential ranges for all five aforementioned light charged particles and all elements from hydrogen to uranium. The KFKSPEC and KFKXN libraries are based essentially on nuclear model calculations using the statistical evaporation model superimposed with the pre-equilibrium contribution as implemented in the Lawrence Livermore National Laboratory ALICE code. The KFKSPEC library includes 633 isotopes, of which 55 are in their isomeric states, and contains 63,300 spectra of the (n,x) type with almost 1.5 million data points. The KFKXN library also includes 633 isotopes and contains all (x,n) and partly (x,2n) cross sections for 4431 reactions with ∼ 106,000 data points. The KFKSTOP library is considered complete and has 11,040 data points. 42 refs., 2 figs., 4 tabs

  17. Divalent metal ion differentially regulates the sequential nicking reactions of the GIY-YIG homing endonuclease I-BmoI.

    Directory of Open Access Journals (Sweden)

    Benjamin P Kleinstiver

    Full Text Available Homing endonucleases are site-specific DNA endonucleases that function as mobile genetic elements by introducing double-strand breaks or nicks at defined locations. Of the major families of homing endonucleases, the modular GIY-YIG endonucleases are least understood in terms of mechanism. The GIY-YIG homing endonuclease I-BmoI generates a double-strand break by sequential nicking reactions during which the single active site of the GIY-YIG nuclease domain must undergo a substantial reorganization. Here, we show that divalent metal ion plays a significant role in regulating the two independent nicking reactions by I-BmoI. Rate constant determination for each nicking reaction revealed that limiting divalent metal ion has a greater impact on the second strand than the first strand nicking reaction. We also show that substrate mutations within the I-BmoI cleavage site can modulate the first strand nicking reaction over a 314-fold range. Additionally, in-gel DNA footprinting with mutant substrates and modeling of an I-BmoI-substrate complex suggest that amino acid contacts to a critical GC-2 base pair are required to induce a bottom-strand distortion that likely directs conformational changes for reaction progress. Collectively, our data implies mechanistic roles for divalent metal ion and substrate bases, suggesting that divalent metal ion facilitates the re-positioning of the GIY-YIG nuclease domain between sequential nicking reactions.

  18. A tandem cross-metathesis/semipinacol rearrangement reaction.

    Science.gov (United States)

    Plummer, Christopher W; Soheili, Arash; Leighton, James L

    2012-05-18

    An efficient and (E)-selective synthesis of a 6-alkylidenebicyclo[3.2.1]octan-8-one has been developed. The key step is a tandem cross-metathesis/semipinacol rearrangement reaction, wherein the Hoveyda-Grubbs II catalyst, or more likely a derivative thereof, serves as the Lewis acid for the rearrangement. Despite the fact that both the starting alkene and the cross-metathesis product are viable rearrangement substrates, only the latter rearranges, suggesting that the Lewis acidic species is generated only after the cross-metathesis reaction is complete.

  19. Reaction cross section calculation of some alkaline earth elements

    Science.gov (United States)

    Tel, Eyyup; Kavun, Yusuf; Sarpün, Ismail Hakki

    2017-09-01

    Reaction cross section knowledge is crucial to application nuclear physics such as medical imaging, radiation shielding and material evaluations. Nuclear reaction codes can be used if the experimental data are unavailable or are improbably to be produced because of the experimental trouble. In this study, there action cross sections of some target alkaline earth elements have been calculated by using pre-equilibrium and equilibrium nuclear reaction models for nucleon induced reactions. While these calculations, the Hybrid Model, the Geometry Dependent Hybrid Model, the Full Exciton Model, the Cascade Exciton Model for pre-equilibrium reactions and the Weisskopf-Ewing Model for equilibrium reactions have been used. The calculated cross sections have been discussed and compared with the experimental data taken from Experimental Nuclear Reaction Data library.

  20. On the adsorption/reaction of acetone on pure and sulfate-modified zirconias.

    Science.gov (United States)

    Crocellà, Valentina; Cerrato, Giuseppina; Morterra, Claudio

    2013-08-28

    In situ FTIR spectroscopy was employed to investigate some aspects of the ambient temperature (actually, IR-beam temperature) adsorption of acetone on various pure and sulfate-doped zirconia specimens. Acetone uptake yields, on all examined systems and to a variable extent, different types of specific molecular adsorption, depending on the kind/population of available surface sites: relatively weak H-bonding interaction(s) with surface hydroxyls, medium-strong coordinative interaction with Lewis acidic sites, and strong H-bonding interaction with Brønsted acidic centres. Moreover acetone, readily and abundantly adsorbed in molecular form, is able to undergo the aldol condensation reaction (yielding, as the main reaction product, adsorbed mesityl oxide) only if the adsorbing material possesses some specific surface features. The occurrence/non-occurrence of the acetone self-condensation reaction is discussed, and leads to conclusions concerning the sites that catalyze the condensation reaction that do not agree with either of two conflicting interpretations present in the literature of acetone uptake/reaction on, mainly, zeolitic systems. In particular, what turns out to be actually necessary for the acetone aldol condensation reaction to occur on the examined zirconia systems is the presence of coordinatively unsaturated O(2-) surface sites of basicity sufficient to lead to the extraction of a proton from one of the CH3 groups of adsorbed acetone.

  1. Reference Cross Sections for Charged-particle Monitor Reactions

    Science.gov (United States)

    Hermanne, A.; Ignatyuk, A. V.; Capote, R.; Carlson, B. V.; Engle, J. W.; Kellett, M. A.; Kibédi, T.; Kim, G.; Kondev, F. G.; Hussain, M.; Lebeda, O.; Luca, A.; Nagai, Y.; Naik, H.; Nichols, A. L.; Nortier, F. M.; Suryanarayana, S. V.; Takács, S.; Tárkányi, F. T.; Verpelli, M.

    2018-02-01

    Evaluated cross sections of beam-monitor reactions are expected to become the de-facto standard for cross-section measurements that are performed over a very broad energy range in accelerators in order to produce particular radionuclides for industrial and medical applications. The requirements for such data need to be addressed in a timely manner, and therefore an IAEA coordinated research project was launched in December 2012 to establish or improve the nuclear data required to characterise charged-particle monitor reactions. An international team was assembled to recommend more accurate cross-section data over a wide range of targets and projectiles, undertaken in conjunction with a limited number of measurements and more extensive evaluations of the decay data of specific radionuclides. Least-square evaluations of monitor-reaction cross sections including uncertainty quantification have been undertaken for charged-particle beams of protons, deuterons, 3He- and 4He-particles. Recommended beam monitor reaction data with their uncertainties are available at the IAEA-NDS medical portal http://www-nds.iaea.org/medical/monitor_reactions.html.

  2. 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

  3. Reaction cross section calculation of some alkaline earth elements

    Directory of Open Access Journals (Sweden)

    Tel Eyyup

    2017-01-01

    Full Text Available Reaction cross section knowledge is crucial to application nuclear physics such as medical imaging, radiation shielding and material evaluations. Nuclear reaction codes can be used if the experimental data are unavailable or are improbably to be produced because of the experimental trouble. In this study, there action cross sections of some target alkaline earth elements have been calculated by using pre-equilibrium and equilibrium nuclear reaction models for nucleon induced reactions. While these calculations, the Hybrid Model, the Geometry Dependent Hybrid Model, the Full Exciton Model, the Cascade Exciton Model for pre-equilibrium reactions and the Weisskopf-Ewing Model for equilibrium reactions have been used. The calculated cross sections have been discussed and compared with the experimental data taken from Experimental Nuclear Reaction Data library.

  4. Cross-section and reaction rates for some reactions involved in explosive nucleosynthesis

    International Nuclear Information System (INIS)

    Cheng, C.W.

    1979-03-01

    Total proton-induced and alpha-induced reaction cross sections have been determined for the 24 Mg(α,n), 25 Mg(p,n), 26 Mg(p,n), 27 Al(p,n), 28 Si(α,n), 42 Ca(p,γ), 42 Ca(α,n) and 44 Ca(p,n) reactions from energies near threshold (except the exothermic (p,γ) reaction) to about 3 to 4 MeV above threshold. The product nuclei are all positron emitters with half-lives ranging from about 3 sec to about 4 hours. From the measured cross sections reaction rates have been calculated in the temperature range 1 9 9 =1, at which the discrepancy is large. Included also are analytic forms for (p,n), (α,n), and (p,γ) reactions which can be used to describe the reaction rate within the temperature range 1 9 <=6 and which agree with the experimental rates at the discrete temperatures where the reaction rates have been calculated

  5. A method for measuring light ion reaction cross-sections

    International Nuclear Information System (INIS)

    Carlson, R.F.; Ingemarsson, A.; Lantz, M.; Arendse, G.J.; Auce, A.; Cox, A.J.; Foertsch, S.V.; Jacobs, N.M.; Johansson, R.; Nyberg, J.; Peavy, J.; Renberg, P.-U.; Sundberg, O.; Stander, J.A.; Steyn, G.F.; Tibell, G.; Zorro, R.

    2005-01-01

    An experimental procedure for measuring reaction cross-sections of light ions in the energy range 20-50 MeV/nucleon, using a modified attenuation technique, is described. The detection method incorporates a forward detector that simultaneously measures the reaction cross-sections for five different sizes of the solid angle in steps from 99.1% to 99.8% of the total solid angle. The final reaction cross-section values are obtained by extrapolation to the full solid angle

  6. A method for measuring light ion reaction cross sections

    International Nuclear Information System (INIS)

    Carlson, R.F.; Ingemarsson, A.; Lantz, M.

    2005-03-01

    An experimental procedure for measuring reaction cross sections of light ions in the energy range 20-50 MeV/nucleon, using a modified attenuation technique, is described. The detection method incorporates a forward detector that simultaneously measures the reaction cross sections for five different sizes of the solid angles in steps from 99.1 to 99.8% of the total solid angle. The final reaction cross section values are obtained by extrapolation to the full solid angle

  7. Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

    Directory of Open Access Journals (Sweden)

    Masato Ohashi

    2014-09-01

    Full Text Available In this review, we summarize our recent development of palladium(0-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE to palladium(0 was promoted by the addition of lithium iodide, affording a trifluorovinyl palladium(II iodide. Based on this finding, the first palladium-catalyzed cross-coupling reaction of TFE with diarylzinc was developed in the presence of lithium iodide, affording α,β,β-trifluorostyrene derivatives in excellent yield. This coupling reaction was expanded to the novel Pd(0/PR3-catalyzed cross-coupling reaction of TFE with arylboronates. In this reaction, the trifluorovinyl palladium(II fluoride was a key reaction intermediate that required neither an extraneous base to enhance the reactivity of organoboronates nor a Lewis acid additive to promote the oxidative addition of a C–F bond. In addition, our strategy utilizing the synergetic effect of Pd(0 and lithium iodide could be applied to the C–F bond cleavage of unreactive hexafluorobenzene (C6F6, leading to the first Pd(0-catalyzed cross-coupling reaction of C6F6 with diarylzinc compounds.

  8. Nanocatalysts for Suzuki cross-coupling reactions

    KAUST Repository

    Fihri, Aziz

    2011-01-01

    This critical review deals with the applications of nanocatalysts in Suzuki coupling reactions, a field that has attracted immense interest in the chemical, materials and industrial communities. We intend to present a broad overview of nanocatalysts for Suzuki coupling reactions with an emphasis on their performance, stability and reusability. We begin the review with a discussion on the importance of Suzuki cross-coupling reactions, and we then discuss fundamental aspects of nanocatalysis, such as the effects of catalyst size and shape. Next, we turn to the core focus of this review: the synthesis, advantages and disadvantages of nanocatalysts for Suzuki coupling reactions. We begin with various nanocatalysts that are based on conventional supports, such as high surface silica, carbon nanotubes, polymers, metal oxides and double hydroxides. Thereafter, we reviewed nanocatalysts based on non-conventional supports, such as dendrimers, cyclodextrin and magnetic nanomaterials. Finally, we discuss nanocatalyst systems that are based on non-conventional media, i.e., fluorous media and ionic liquids, for use in Suzuki reactions. At the end of this review, we summarise the significance of nanocatalysts, their impacts on conventional catalysis and perspectives for further developments of Suzuki cross-coupling reactions (131 references). © 2011 The Royal Society of Chemistry.

  9. One-pot sequential 1,2-addition, Pd-catalysed cross-coupling of organolithium reagents with Weinreb amides

    NARCIS (Netherlands)

    Giannerini, M.; Vila, C.; Hornillos, V.; Feringa, B. L.

    2016-01-01

    An efficient sequential 1,2-addition/cross-coupling of Weinreb amides with two organolithium reagents is reported. This synthetic approach allows access to a wide variety of functionalized ketones in a modular way. The one-pot procedure presented here takes advantage of a kinetically stable

  10. The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

    Science.gov (United States)

    Yu, Xiaofang; Yu, Xiaobo; Wu, Shujie; Liu, Bo; Liu, Heng; Guan, Jingqi; Kan, Qiubin

    2011-02-01

    Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N 2 adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization.

  11. Tin-Containing Silicates: Identification of a Glycolytic Pathway via 3-Deoxyglucosone

    DEFF Research Database (Denmark)

    Tolborg, Søren; Meier, Sebastian; Sádaba, I.

    2016-01-01

    a cascade of four to five sequential steps. Currently, there is a limited understanding of the competing glycolytic pathways within these systems. Here we identify dehydration of glucose to 3-deoxyglucosone as an important pathway that occurs in addition to retro-aldol reaction of hexoses when using tin......-containing silicates. It is possible to influence the relative carbon flux through these pathways by controlling the amount of alkali metal salts present in the reaction mixture. In the absence of added potassium carbonate, at least 15–30% carbon flux via 3-deoxyglucosone is observed. Addition of just a few ppm...

  12. Tuning Catalytic Performance through a Single or Sequential Post-Synthesis Reaction(s) in a Gas Phase

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Junjun [Department; Department; Zhang, Shiran [Department; Department; Choksi, Tej [Department; Nguyen, Luan [Department; Department; Bonifacio, Cecile S. [Department; Li, Yuanyuan [Department; Zhu, Wei [Department; Department; College; Tang, Yu [Department; Department; Zhang, Yawen [College; Yang, Judith C. [Department; Greeley, Jeffrey [Department; Frenkel, Anatoly I. [Department; Tao, Franklin [Department; Department

    2016-12-05

    Catalytic performance of a bimetallic catalyst is determined by geometric structure and electronic state of the surface or even the near-surface region of the catalyst. Here we report that single and sequential postsynthesis reactions of an as-synthesized bimetallic nanoparticle catalyst in one or more gas phases can tailor surface chemistry and structure of the catalyst in a gas phase, by which catalytic performance of this bimetallic catalyst can be tuned. Pt–Cu regular nanocube (Pt–Cu RNC) and concave nanocube (Pt–Cu CNC) are chosen as models of bimetallic catalysts. Surface chemistry and catalyst structure under different reaction conditions and during catalysis were explored in gas phase of one or two reactants with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The newly formed surface structures of Pt–Cu RNC and Pt–Cu CNC catalysts strongly depend on the reactive gas(es) used in the postsynthesis reaction(s). A reaction of Pt–Cu RNC-as synthesized with H2 at 200 °C generates a near-surface alloy consisting of a Pt skin layer, a Cu-rich subsurface, and a Pt-rich deep layer. This near-surface alloy of Pt–Cu RNC-as synthesized-H2 exhibits a much higher catalytic activity in CO oxidation in terms of a low activation barrier of 39 ± 4 kJ/mol in contrast to 128 ± 7 kJ/mol of Pt–Cu RNC-as synthesized. Here the significant decrease of activation barrier demonstrates a method to tune catalytic performances of as-synthesized bimetallic catalysts. A further reaction of Pt–Cu RNC-as synthesized-H2 with CO forms a Pt–Cu alloy surface, which exhibits quite different catalytic performance in CO oxidation. It suggests the capability of generating a different surface by using another gas. The capability of tuning surface chemistry and structure of bimetallic catalysts was also demonstrated in restructuring of Pt–Cu CNC-as synthesized.

  13. Mechanochemically synthesized LiAlOx catalyst for aqueous aldol condensation of furfural with acetone

    Directory of Open Access Journals (Sweden)

    Stepanova L. N.

    2017-10-01

    Full Text Available In the present study, the mechanochemical method is proposed for synthesis of LiAl-layered double hydroxides (LDHs. This method is eco-friendly and allows obtaining LiAl-LDH under relatively mild conditions (centripetal acceleration of milling bodies 300 m s-2 and in a short period of time (15 minutes. The structures of as-prepared LiAl-LDH, LiAl-mixed oxide (calcined LDH and “activated” LiAl-LDH obtained after rehydration of the corresponding mixed oxide were confirmed by X-ray diffraction. The basicity of LiAlOx was measured by temperature-programmed desorption of CO2 and double isotherm technique. According to data obtained, LiAl-mixed oxide has a significant higher carbon dioxide adsorption capacity compared to MgAlmixed oxides prepared by conventional co-precipitation method. This indicates a large amount of basic surface sites with different strength (strong, medium and weak for Li-containing systems. The formation of “activated” LiAl-LDH having Bronsted basic sites (OH groups in the interlayer space provides an increased catalytic activity of LiAlOx in the reaction of aqueous-phase aldol condensation between furfural and acetone.

  14. Neutron-induced capture cross sections via the surrogate reaction method

    International Nuclear Information System (INIS)

    Boutoux, G.; Jurado, B.; Aiche, M.; Barreau, G.; Capellan, N.; Companis, I.; Czajkowski, S.; Dassie, D.; Haas, B.; Mathieu, L.; Meot, V.; Bail, A.; Bauge, E.; Daugas, J. M.; Faul, T.; Gaudefroy, L.; Morel, P.; Pillet, N.; Roig, O.; Romain, P.; Taieb, J.; Theroine, C.; Burke, J.T.; Companis, I.; Derkx, X.; Gunsing, F.; Matea, I.; Tassan-Got, L.; Porquet, M.G.; Serot, O.

    2011-01-01

    The surrogate reaction method is an indirect way of determining cross sections for nuclear reactions that proceed through a compound nucleus. This technique enables neutron-induced cross sections to be extracted for nuclear reactions on short-lived unstable nuclei that otherwise can not be measured. This technique has been successfully applied to determine the neutron-induced fission cross sections of several short-lived nuclei. In this work, we investigate whether this powerful technique can also be used to determine of neutron-induced capture cross sections. For this purpose we use the surrogate reaction 174 Yb( 3 He, pγ) 176 Lu to infer the well known 175 Lu(n, γ) cross section and compare the results with the directly measured neutron-induced data. This surrogate experiment has been performed in March 2010. The experimental technique used and the first preliminary results will be presented. (authors)

  15. Nuclear-reaction studies via the observation of unbound outgoing systems

    International Nuclear Information System (INIS)

    Bice, A.N.

    1982-01-01

    The mechanisms involved in the production of fast α-particles in 12 C induced reactions have been investigated for the 12 C + 208 Pb system at bombarding energies of E( 12 C) = 132, 187 and 230 MeV. Absolute cross sections have been determined for the reactions 208 Pb ( 12 C, 8 Be (g.s.)), 208 Pb( 12 C, 8 Be (2.94 MeV)) and 208 Pb ( 12 C, 12 C* → α + 8 Be) by double and triple coincidence measurements of the sequential decay α-particles. Inclusive α-particle production cross sections were also measured at E ( 12 C) = 187 MeV for comparison. It is found that the simple inelastic scattering process ( 12 C, 12 C* → α + 8 Be) does not contribute significantly to the production of fast α-particles but that the production of 8 Be nuclei by projectile fragmentation is an important source of α-particles. At the highest bombarding energy investigated (19 MeV/A) it appears that the 12 C → 3α fragmentation reaction becomes more prominent at the expense of the 12 C → α + 8 Be fragmentation channel. It is concluded that projectile spectroscopic properties and/or final state interactions are important in fragmentation reactions for these bombarding energies. In a kinematically complete experiment the direct and the sequential breakup channels of 10 MeV/A 7 Li projectiles have been investigated with 12 C and 208 Pb targets. By appropriate arrangement of detector telescopes it was possible to define a kinematical window which allowed for the unambigious observation of both the direct (to the α-t continuum) and the sequential components of a heavy-ion projectile breakup reaction. A semiclassical Monte Carlo type projectile breakup calculation was constructed which qualitatively reproduced the measured α-t coincidence cross section as a function of the laboratory angle

  16. Cross sections for multistep direct reactions

    International Nuclear Information System (INIS)

    Demetriou, Paraskevi; Marcinkowski, Andrzej; Marianski, Bohdan

    2002-01-01

    Inelastic scattering and charge-exchange reactions have been analysed at energies ranging from 14 to 27 MeV using the modified multistep direct reaction theory (MSD) of Feshbach, Kerman and Koonin. The modified theory considers the non-DWBA matrix elements in the MSD cross section formulae and includes both incoherent particle-hole excitations and coherent collective excitations in the continuum, according to the prescriptions. The results show important contributions from multistep processes at all energies considered. (author)

  17. Reference Cross Sections for Charged-particle Monitor Reactions

    Czech Academy of Sciences Publication Activity Database

    Hermanne, A.; Ignatyuk, A. V.; Capote, R.; Carlson, B. V.; Engle, J. W.; Kellett, M. A.; Kibédi, T.; Kim, G.; Kondev, F. G.; Hussain, M.; Lebeda, Ondřej; Luca, A.; Nagai, Y.; Naik, H.; Nichols, A. L.; Nortier, F. M.; Suryanarayana, S. V.; Takacs, S.; Tarkanyi, F. T.; Verpelli, M.

    2018-01-01

    Roč. 148, SI (2018), s. 338-382 ISSN 0090-3752 Institutional support: RVO:61389005 Keywords : deuteron induced reactions * proton induced reactions * cross sections Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Nuclear physics Impact factor: 1.146, year: 2016

  18. Mechanistic Implications for the Ni(I-Catalyzed Kumada Cross-Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Linda Iffland

    2017-11-01

    Full Text Available Herein we report on the cross-coupling reaction of phenylmagnesium bromide with aryl halides using the well-defined tetrahedral Ni(I complex, [(TriphosNiICl] (Triphos = 1,1,1-tris(diphenylphosphinomethylethane. In the presence of 0.5 mol % [(TriphosNiICl], good to excellent yields (75–97% of the respective coupling products within a reaction time of only 2.5 h at room temperature were achieved. Likewise, the tripodal Ni(IIcomplexes [(κ2-TriphosNiIICl2] and [(κ3-TriphosNiIICl](X (X = ClO4, BF4 were tested as potential pre-catalysts for the Kumada cross-coupling reaction. While the Ni(II complexes also afford the coupling products in comparable yields, mechanistic investigations by UV/Vis and electron paramagnetic resonance (EPR spectroscopy indicate a Ni(I intermediate as the catalytically active species in the Kumada cross-coupling reaction. Based on experimental findings and density functional theory (DFT calculations, a plausible Ni(I-catalyzed reaction mechanism for the Kumada cross-coupling reaction is presented.

  19. Single step sequential polydimethylsiloxane wet etching to fabricate a microfluidic channel with various cross-sectional geometries

    Science.gov (United States)

    Wang, C.-K.; Liao, W.-H.; Wu, H.-M.; Lo, Y.-H.; Lin, T.-R.; Tung, Y.-C.

    2017-11-01

    Polydimethylsiloxane (PDMS) has become a widely used material to construct microfluidic devices for various biomedical and chemical applications due to its desirable material properties and manufacturability. PDMS microfluidic devices are usually fabricated using soft lithography replica molding methods with master molds made of photolithogrpahy patterned photoresist layers on silicon wafers. The fabricated microfluidic channels often have rectangular cross-sectional geometries with single or multiple heights. In this paper, we develop a single step sequential PDMS wet etching process that can be used to fabricate microfluidic channels with various cross-sectional geometries from single-layer PDMS microfluidic channels. The cross-sections of the fabricated channel can be non-rectangular, and varied along the flow direction. Furthermore, the fabricated cross-sectional geometries can be numerically simulated beforehand. In the experiments, we fabricate microfluidic channels with various cross-sectional geometries using the developed technique. In addition, we fabricate a microfluidic mixer with alternative mirrored cross-sectional geometries along the flow direction to demonstrate the practical usage of the developed technique.

  20. The Maximum Cross-Correlation approach to detecting translational motions from sequential remote-sensing images

    Science.gov (United States)

    Gao, J.; Lythe, M. B.

    1996-06-01

    This paper presents the principle of the Maximum Cross-Correlation (MCC) approach in detecting translational motions within dynamic fields from time-sequential remotely sensed images. A C program implementing the approach is presented and illustrated in a flowchart. The program is tested with a pair of sea-surface temperature images derived from Advanced Very High Resolution Radiometer (AVHRR) images near East Cape, New Zealand. Results show that the mean currents in the region have been detected satisfactorily with the approach.

  1. Theoretical calculations of the reaction cross-sections for proton-induced reactions on natural copper using ALICE-IPPE code

    International Nuclear Information System (INIS)

    Alharbi, A.A.; Azzam, A.

    2012-01-01

    A theoretical study of the nuclear-reaction cross sections for proton-induced reactions on 63 Cu and 65 Cu was performed in the proton energy range from threshold values up to 50 MeV. The produced nuclei were different isotopes of Zn, Cu, Ni, Co and Mn, some of which have important applications. The reaction cross-section calculations were performed using the ALICE-IPPE code, which depends on the pre-equilibrium compound nucleus model. This code is suitable for the studied energy and isotopic mass ranges. Approximately 14 excitation functions for the different reactions have been constructed from the calculated cross-section values. The excitation function curves for the proton reactions with natural copper targets have been constructed from those for enriched targets using the natural abundance of the copper isotopes. Comparisons between the calculated excitation functions with those previously experimentally measured are given whenever the experimental values were available. Some statistical parameters were introduced to control the quality of the fitting between both the experimental and the theoretical calculated cross-section values. - Highlights: ► We performed reaction cross section calculations using ALICE-IPPE code. ► We constructed 14 excitation functions for nat Cu(p,xn)Zn,Cu,Ni,Co,Mn reactions. ► The available experimental data were fitted to the performed ALICE-IPPE calculations. ► Statistical parameters were introduced to control the quality of the fitting. ► The code failed to fit the experimental data for reactions with large nucleon emissions.

  2. (n,α reactions cross section research at IPPE

    Directory of Open Access Journals (Sweden)

    Giorginis G.

    2012-02-01

    Full Text Available An experimental set-up based on an ionization chamber with a Frisch grid and wave form digitizer was used for (n,α cross section measurements. Use of digital signal processing allowed us to select a gaseous cell inside the sensitive area of the ionization chamber and determine the target atoms in it with high accuracy. This kind of approach provided us with a powerful method to suppress background arising from the detector structure and parasitic reactions on the working gas components. This method is especially interesting to study neutron reactions with elements for which solid target preparation is difficult (noble gases for example. In the present experiments we used a set of working gases which contained admixtures of nitrogen, oxygen, neon, argon and boron. Fission of 238U was used as neutron flux monitor. The cross section of the (n,α reaction for 16O, 14N, 20Ne, 36Ar, 40Ar and the yield ratio α0/α1 of 10B(n,α0 to 10B(n,α1 reactions was measured for neutron energies between 1.5 and 7 MeV. Additionally a measurement of the 50Cr(n,α cross section using a solid chromium target is also reported.

  3. The Symmetry of Adverse Local Tissue Reactions in Patients with Bilateral Simultaneous and Sequential ASR Hip Replacement.

    Science.gov (United States)

    Madanat, Rami; Hussey, Daniel K; Donahue, Gabrielle S; Potter, Hollis G; Wallace, Robert; Bragdon, Charles R; Muratoglu, Orhun K; Malchau, Henrik

    2015-10-01

    The purpose of this study was to evaluate whether patients with bilateral metal-on-metal (MoM) hip replacements have symmetric adverse local tissue reactions (ALTRs) at follow-up. An MRI of both hips was performed at a mean time of six years after surgery in 43 patients. The prevalence and severity of ALTRs were found to be similar in simultaneous hips but differences were observed in sequential hips. The order and timing of sequential hip arthroplasties did not affect the severity of ALTRs. Thus, in addition to metal ion exposure from an earlier MoM implant other factors may also play a role in the progression of ALTRs. Bilateral implants should be given special consideration in risk stratification algorithms for management of patients with MoM hip arthroplasty. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. A Generalizable Top-Down Nanostructuring Method of Bulk Oxides: Sequential Oxygen-Nitrogen Exchange Reaction.

    Science.gov (United States)

    Lee, Lanlee; Kang, Byungwuk; Han, Suyoung; Kim, Hee-Eun; Lee, Moo Dong; Bang, Jin Ho

    2018-05-27

    A thermal reaction route that induces grain fracture instead of grain growth is devised and developed as a top-down approach to prepare nanostructured oxides from bulk solids. This novel synthesis approach, referred to as the sequential oxygen-nitrogen exchange (SONE) reaction, exploits the reversible anion exchange between oxygen and nitrogen in oxides that is driven by a simple two-step thermal treatment in ammonia and air. Internal stress developed by significant structural rearrangement via the formation of (oxy)nitride and the creation of oxygen vacancies and their subsequent combination into nanopores transforms bulk solid oxides into nanostructured oxides. The SONE reaction can be applicable to most transition metal oxides, and when utilized in a lithium-ion battery, the produced nanostructured materials are superior to their bulk counterparts and even comparable to those produced by conventional bottom-up approaches. Given its simplicity and scalability, this synthesis method could open a new avenue to the development of high-performance nanostructured electrode materials that can meet the industrial demand of cost-effectiveness for mass production. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Application of Carbohydrate-Templated Asymmetric Diels-Alder Reaction to the Syntheses of ent-Penicillones A and B.

    Science.gov (United States)

    Weng, Chia-Hao; Hsu, Day-Shin; Liao, Chun-Chen

    2016-11-18

    Total syntheses of ent-penicillones A (ent-1) and B (ent-2) from 3,5-dimethylcatechol (3) were accomplished in 10 and 9 synthetic steps, respectively. A carbohydrate-templated asymmetric intramolecular Diels-Alder reaction of a masked o-benzoquinone (MOB) 9 and an aqueous acid-catalyzed intramolecular aldol reaction are the key synthetic steps. In addition, the absolute configurations of the bicyclo[2.2.2]oct-5-en-2-one core obtained from the per-O-benzylated α-d-glucopyranosyl as a carbohydrate template in the intramolecular Diels-Alder reaction of MOBs were revised.

  6. Activation cross section and isomeric cross section ratios for the (n ,2 n ) reaction on 153Eu

    Science.gov (United States)

    Luo, Junhua; Jiang, Li; Li, Suyuan

    2017-10-01

    The 153Eu(n ,2 n ) m1,m2,g152Eu cross section was measured by means of the activation technique at three neutron energies in the range 13-15 MeV. The quasimonoenergetic neutron beam was formed via the 3H(d ,n ) 4He reaction, in the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The activities induced in the reaction products were measured using high-resolution γ-ray spectroscopy. The cross section of the population of the second high-spin (8-) isomeric state was measured along with the reaction cross section populating both the ground (3-) and the first isomeric state (0-). Cross sections were also evaluated theoretically using the numerical code TALYS-1.8, with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

  7. Nuclear-reaction studies via the observation of unbound outgoing systems

    Energy Technology Data Exchange (ETDEWEB)

    Bice, A.N.

    1982-01-01

    The mechanisms involved in the production of fast ..cap alpha..-particles in /sup 12/C induced reactions have been investigated for the /sup 12/C + /sup 208/Pb system at bombarding energies of E(/sup 12/C) = 132, 187 and 230 MeV. Absolute cross sections have been determined for the reactions /sup 208/Pb (/sup 12/C, /sup 8/Be (g.s.)), /sup 208/Pb(/sup 12/C, /sup 8/Be (2.94 MeV)) and /sup 208/Pb (/sup 12/C, /sup 12/C* ..-->.. ..cap alpha.. + /sup 8/Be) by double and triple coincidence measurements of the sequential decay ..cap alpha..-particles. Inclusive ..cap alpha..-particle production cross sections were also measured at E (/sup 12/C) = 187 MeV for comparison. It is found that the simple inelastic scattering process (/sup 12/C, /sup 12/C* ..-->.. ..cap alpha.. + /sup 8/Be) does not contribute significantly to the production of fast ..cap alpha..-particles but that the production of /sup 8/Be nuclei by projectile fragmentation is an important source of ..cap alpha..-particles. At the highest bombarding energy investigated (19 MeV/A) it appears that the /sup 12/C ..-->.. 3..cap alpha.. fragmentation reaction becomes more prominent at the expense of the /sup 12/C ..-->.. ..cap alpha.. + /sup 8/Be fragmentation channel. It is concluded that projectile spectroscopic properties and/or final state interactions are important in fragmentation reactions for these bombarding energies. In a kinematically complete experiment the direct and the sequential breakup channels of 10 MeV/A /sup 7/Li projectiles have been investigated with /sup 12/C and /sup 208/Pb targets. By appropriate arrangement of detector telescopes it was possible to define a kinematical window which allowed for the unambigious observation of both the direct (to the ..cap alpha..-t continuum) and the sequential components of a heavy-ion projectile breakup reaction. A semiclassical Monte Carlo type projectile breakup calculation was constructed which qualitatively reproduced the measured ..cap alpha

  8. Toward understanding of the role of Lewis acidity in aldol condensation of acetone and furfural using MOF and zeolite catalysts

    Czech Academy of Sciences Publication Activity Database

    Kikhtyanin, O.; Kubička, D.; Čejka, Jiří

    2015-01-01

    Roč. 243, APR 2015 (2015), s. 158-162 ISSN 0920-5861 R&D Projects: GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : metal organic framework * aldol condensation * acidic catalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.312, year: 2015

  9. Cross sections and reaction rates of d+{sup 8}Li reactions involved in Big Bang nucleosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Balbes, M.J. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Farrell, M.M. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Boyd, R.N. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics]|[Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States); Gu, X. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Hencheck, M. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Kalen, J.D. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Mitchell, C.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Kolata, J.J. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Lamkin, K. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Smith, R. [Division of Nuclear Medicine, Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104 (United States); Tighe, R. [Lawrence Berkeley Laboratory, Berkeley, CA 94720 (United States); Ashktorab, K. [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Becchetti, F.D. [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Brown, J. [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Roberts, D. [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Wang, T.F. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Humphrey, D. [Department of Physics, University of Western Kentucky, Bowling Green, KY 42101 (United States); Vourvopoulos, G. [Department of Physics, University of Western Kentucky, Bowling Green, KY 42101 (United States); Islam, M.S. [Department of Physics, Ball State University, Muncie, IN 47306 (United States)

    1995-02-20

    We have measured angular distributions of the {sup 2}H({sup 8}Li, {sup 7}Li){sup 3}H and {sup 2}H({sup 8}Li, {sup 9}Be)n reactions at E{sub c.m.}=1.5 to 2.8 MeV using an {sup 8}Li-radioactive-beam technique. Astrophysical S-factors and reaction rates were calculated from the measured cross sections. Although the {sup 2}H({sup 8}Li, {sup 9}Be)n cross section is small, it can contribute to {sup 9}Be synthesis. The {sup 2}H({sup 8}Li, {sup 7}Li){sup 3}H reaction has a sufficiently large cross section to destroy {sup 8}Li, which may decrease the synthesis of heavier elements. No products from the {sup 2}H({sup 8}Li, {sup 9}Li)p reaction were detected. We also present the results of calculations using the inhomogeneous model of primordial nucleosynthesis in several regions of parameter space. ((orig.))

  10. Total cross-sections for reactions of high energy particles (including elastic, topological, inclusive and exclusive reactions). Subvol. b

    International Nuclear Information System (INIS)

    Schopper, H.; Moorhead, W.G.; Morrison, D.R.O.

    1988-01-01

    The aim of this report is to present a compilation of cross-sections (i.e. reaction rates) of elementary particles at high energy. The data are presented in the form of tables, plots and some fits, which should be easy for the reader to use and may enable him to estimate cross-sections for presently unmeasured energies. We have analyzed all the data published in the major Journals and Reviews for momenta of the incoming particles larger than ≅ 50 MeV/c, since the early days of elementary particle physics and, for each reaction, we have selected the best cross-section data available. We have restricted our attention to integrated cross-sections, such as total cross-sections, exclusive and inclusive cross-sections etc., at various incident beam energies. We have disregarded data affected by geometrical and/or kinematical cuts which would make them not directly comparable to other data at different energies. Also, in the case of exclusive reactions, we have left out data where not all of the particles in the final state were unambiguously identified. This work contains reactions induced by neutrinos, gammas, charged pions, kaons, nucleons, antinucleons and hyperons. (orig./HSI)

  11. Physico-Chemical Properties of MgGa Mixed Oxides and Reconstructed Layered Double Hydroxides and Their Performance in Aldol Condensation of Furfural and Acetone

    Directory of Open Access Journals (Sweden)

    Oleg Kikhtyanin

    2018-05-01

    Full Text Available MgGa layered double hydroxides (Mg/Ga = 2–4 were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH3-TPD, CO2-TPD, SEM, and DRIFT and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO2-TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T = 450°C on CO2-TPD curve was attributed to the decomposition of carbonates newly formed by CO2 interaction with interlayer carbonates rather than to CO2 desorption from basic sites. Accordingly, CO2-TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had

  12. Physico-Chemical Properties of MgGa Mixed Oxides and Reconstructed Layered Double Hydroxides and Their Performance in Aldol Condensation of Furfural and Acetone.

    Science.gov (United States)

    Kikhtyanin, Oleg; Čapek, Libor; Tišler, Zdeněk; Velvarská, Romana; Panasewicz, Adriana; Diblíková, Petra; Kubička, David

    2018-01-01

    MgGa layered double hydroxides (Mg/Ga = 2-4) were synthesized and used for the preparation of MgGa mixed oxides and reconstructed hydrotalcites. The properties of the prepared materials were examined by physico-chemical methods (XRD, TGA, NH 3 -TPD, CO 2 -TPD, SEM, and DRIFT) and tested in aldol condensation of furfural and acetone. The as-prepared phase-pure MgGa samples possessed hydrotalcite structure, and their calcination resulted in mixed oxides with MgO structure with a small admixture phase characterized by a reflection at 2θ ≈ 36.0°. The interaction of MgGa mixed oxides with pure water resulted in reconstruction of the HTC structure already after 15 s of the rehydration with maximum crystallinity achieved after 60 s. TGA-MS experiments proved a substantial decrease in carbonates in all rehydrated samples compared with their as-prepared counterparts. This allowed suggesting presence of interlayer hydroxyls in the samples. Acido-basic properties of MgGa mixed oxides determined by TPD technique did not correlate with Mg/Ga ratio which was explained by the specific distribution of Ga atoms on the external surface of the samples. CO 2 -TPD method was also used to evaluate the basic properties of the reconstructed MgGa samples. In these experiments, an intensive peak at T = 450°C on CO 2 -TPD curve was attributed to the decomposition of carbonates newly formed by CO 2 interaction with interlayer carbonates rather than to CO 2 desorption from basic sites. Accordingly, CO 2 -TPD method quantitatively characterized the interlayer hydroxyls only indirectly. Furfural conversion on reconstructed MgGa materials was much larger compared with MgGa mixed oxides confirming that Brønsted basic sites in MgGa catalysts, like MgAl catalysts, were active in the reaction. Mg/Ga ratio in mixed oxides influenced product selectivity which was explained by the difference in textural properties of the samples. In contrast, Mg/Ga ratio in reconstructed catalysts had practically

  13. Neutron-induced cross sections of actinides via the surrogate-reaction method

    Directory of Open Access Journals (Sweden)

    Tveten G. M.

    2013-03-01

    Full Text Available The surrogate-reaction method is an indirect way of determining cross sections for reactions that proceed through a compound nucleus. This technique may enable neutron-induced cross sections to be extracted for short-lived nuclei that otherwise cannot be measured. However, the validity of the surrogate method for extracting capture cross sections has to be investigated. In this work we study the reactions 238U(d,p239U, 238U(3He,t238Np, 238U(3He,4He237U as surrogates for neutroninduced reactions on 238U, 237Np and 236U, respectively, for which good quality data exist. The experimental set-up enabled the measurement of fission and gamma-decay probabilities. First results are presented and discussed.

  14. Complex fragment emission in the reaction 197Au → 197Au at an incident energy of 15 MeV/u

    International Nuclear Information System (INIS)

    Schmoll, R.

    1988-07-01

    For the study of the dominant decay processes in the reaction 15 MeV/u 197 Au → 197 Au in one-particle inclusive experiments the emission characteristics of all ejectiles in the mass range 24 ≤ A ≤ 197 were studied. The deflection function of the projectile-like fragments is for all energy losses at the grazing angle Θ cm gr =27.5 degrees peaked and in fact even for scattering events in which the whole available kinetic energy was dissipated in the collisions. The systematic analysis of the velocity spectra shows that the lightest fragments are formed in double-sequential fission of the highly excited gold-like fragments from the first deep inelastic reaction stage before reaching of a global equilibrium. On the other side symmetrical fission products, which are part of the narrow branch of the mass distribution, are emitted in simple-sequential non-equilibrium fission. This simple-sequential breakup is very closely limited to excitation energies of 75 ≤ E * ≤ 275 MeV of the primary, gold-like fragments, while the probability for double-sequential fission above E * ≅ 200 MeV increases very strongly. Contrarily to equilibrated compound-nucleus fission these processes are characterized by a in the source system strongly anisotropic angular distribution with distinct foreward/backward asymmetry and by an extremely asymmetric mass split. The study of the mass distribution shows that non-equilibrium fission at 15 MeV/u is both in view of the reaction cross section and regarding the creation of the complex fragments is the dominant decay process. The integral cross section of the broad four-body distribution corresponds to 60% of the total reaction cross section; the integral cross section of the narrow three-body distribution corresponds to 10%. (orig./HSI) [de

  15. Applications of Palladium-Catalyzed C-N Cross-Coupling Reactions.

    Science.gov (United States)

    Ruiz-Castillo, Paula; Buchwald, Stephen L

    2016-10-12

    Pd-catalyzed cross-coupling reactions that form C-N bonds have become useful methods to synthesize anilines and aniline derivatives, an important class of compounds throughout chemical research. A key factor in the widespread adoption of these methods has been the continued development of reliable and versatile catalysts that function under operationally simple, user-friendly conditions. This review provides an overview of Pd-catalyzed N-arylation reactions found in both basic and applied chemical research from 2008 to the present. Selected examples of C-N cross-coupling reactions between nine classes of nitrogen-based coupling partners and (pseudo)aryl halides are described for the synthesis of heterocycles, medicinally relevant compounds, natural products, organic materials, and catalysts.

  16. Cross-section calculations for neutron-induced reactions up to 50 MeV

    International Nuclear Information System (INIS)

    Yamamuro, Nobuhiro.

    1996-01-01

    In the field of accelerator development, medium-energy reaction cross-section data for structural materials of accelerator and shielding components are required, especially for radiation protection purposes. For a d + Li stripping reaction neutron source used in materials research, neutron reaction cross sections up to 50 MeV are necessary for the design study of neutron irradiation facilities. The current version of SINCROS-II is able to calculate neutron and proton-induced reaction cross sections up to ∼ 50 MeV with some modifications and extensions of the cross-section calculation code. The production of isotopes when structural materials and other materials are bombarded with neutrons or protons is calculated using a revised code in the SINCROS-II system. The parameters used in the cross-section calculations are mainly examined with proton-induced reactions because the experimental data for neutrons above 20 MeV are rare. The status of medium mass nuclide evaluations for aluminum, silicon, chromium, manganese, and copper is presented. These data are useful to estimate the radiation and transmutation of nuclei in the materials

  17. Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on {sup 132,134}Ba

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Junhua [Hexi Univ., Zhangye (China). School of Physics and Electromechanical Engineering; Hexi Univ., Zhangye (China). Inst. of New Energy; Wu, Chunlei; Jiang, Li [Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Nuclear Physics and Chemistry; Li, Suyuan [Hexi Univ., Zhangye (China). Inst. of New Energy

    2017-07-01

    Cross sections of the {sup 132}Ba(n,2n){sup 131m,g}Ba and {sup 134}Ba(n,2n){sup 133m,g}Ba reactions and their isomeric cross section ratios σ{sub m}/σ{sub g} have been measured by means of the activation technique at three neutron energies in the range 13-15 MeV. BaCO{sub 3} samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The quasimonoenergetic neutrons beam were produced via the {sup 3}H(d,n){sup 4}He reaction at the Pd-300 Neutron Generator of the Chinese Academy of Engineering Physics (CAEP). The activities induced in the reaction products were measured using high-resolution γ ray spectroscopy. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. Cross sections were also evaluated theoretically using the numerical nuclear model code, TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

  18. Properties of simultaneous and sequential two-nucleon transfer

    International Nuclear Information System (INIS)

    Pinkston, W.T.; Satchler, G.R.

    1982-01-01

    Approximate forms of the first- and second-order distorted-wave Born amplitudes are used to study the overall structure, particularly the selection rules, of the amplitudes for simultaneous and sequential transfer of two nucleons. The role of the spin-state assumed for the intermediate deuterons in sequential (t, p) reactions is stressed. The similarity of one-step and two-step amplitudes for (α, d) reactions is exhibited, and the consequent absence of any obvious J-dependence in their interference is noted. (orig.)

  19. Biomimicry Promotes the Efficiency of a 10-Step Sequential Enzymatic Reaction on Nanoparticles, Converting Glucose to Lactate.

    Science.gov (United States)

    Mukai, Chinatsu; Gao, Lizeng; Nelson, Jacquelyn L; Lata, James P; Cohen, Roy; Wu, Lauren; Hinchman, Meleana M; Bergkvist, Magnus; Sherwood, Robert W; Zhang, Sheng; Travis, Alexander J

    2017-01-02

    For nanobiotechnology to achieve its potential, complex organic-inorganic systems must grow to utilize the sequential functions of multiple biological components. Critical challenges exist: immobilizing enzymes can block substrate-binding sites or prohibit conformational changes, substrate composition can interfere with activity, and multistep reactions risk diffusion of intermediates. As a result, the most complex tethered reaction reported involves only 3 enzymes. Inspired by the oriented immobilization of glycolytic enzymes on the fibrous sheath of mammalian sperm, here we show a complex reaction of 10 enzymes tethered to nanoparticles. Although individual enzyme efficiency was higher in solution, the efficacy of the 10-step pathway measured by conversion of glucose to lactate was significantly higher when tethered. To our knowledge, this is the most complex organic-inorganic system described, and it shows that tethered, multi-step biological pathways can be reconstituted in hybrid systems to carry out functions such as energy production or delivery of molecular cargo. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Measurement of reaction cross sections of {sup 129}I induced by DT neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Daisuke; Murata, Isao; Takahashi, Akito [Osaka Univ., Suita (Japan). Faculty of Engineering

    1997-03-01

    The cross sections were measured for the {sup 129}I(n,2n){sup 128}I and {sup 129}I(n,{gamma}){sup 130}I reactions by DT neutrons, at OKTAVIAN facility of Osaka University, Japan. The foil activation method was used in the measurement. The sample was a sealed source of {sup 129}I, which was covered with a Cd foil. The irradiations were performed for 75 minutes to obtain the cross section of reaction producing {sup 128}I (T{sub 1/2}=24.99m) and 22 hours for the {sup 130}I (T{sub 1/2}=12.36h), respectively. The gamma-rays emitted from the irradiated sample were measured with a high purity Ge detector. The measured cross sections of {sup 129}I(n,2n){sup 128}I and {sup 129}I(n,{gamma}){sup 130}I reactions were 0.92{+-}0.11 barn and 0.013{+-}0.002 barn, respectively. For the {sup 129}I(n,2n){sup 128}I reaction, the evaluation of JENDL-3.2 overestimates cross section about 60% to the experimental result. However, especially for the {sup 129}I(n,{gamma}) reaction, the measured cross section may include the contribution from the neutrons in MeV region as well as epithermal ones. Also, the obtained cross section of the {sup 129}I(n,{gamma}){sup 130}I reaction was evaluated as an effective production cross section of {sup 130}I including {sup 129}I(n,{gamma}){sup 130m}I reaction. In order to remove the contribution from the epithermal and MeV region neutrons. A new method was proposed for the measurement of (n,{gamma}) reaction cross section. (author)

  1. Sequential fission process observed in the reaction (16.7 MeV/u) 238U + nat.Au using mica as dielectric track detector

    International Nuclear Information System (INIS)

    Shahzad, Muhammad Ikram; Qureshi, Imtinan Elahi; Manzoor, Shahid; Khan, Hameed Ahmed

    1999-01-01

    The evidence of sequential fission has been found in the heavy-ion reaction (16.7 MeV/u) 238 U + nat. Au, using muscovite mica as Dielectric Track Detector (DTD) placed in a 2π-geometry configuration. The reaction products originating from the interactions of 238 U ions with the atoms of gold were registered in the detector in the form of tracks and identified for performing a detailed kinematical analysis. For this purpose the spherical polar coordinates of the correlated tracks of the multipronged events have been analyzed on an event-by-event basis. Automatic, semi-automatic and manual measuring methods have been employed to collect and manipulate the track data. The known characteristics of binary and ternary events observed in the reaction have been used for the calibration of the detectors. The computed masses, Q-values and relative velocities of the reaction products determined in this analysis are compared with theoretical predictions based on sequential fission process. Agreement within one standard deviation with respect to the experimental values has been found for the majority of analyzed events. Therefore, it is concluded that three particles in the exit channel of the reaction are produced in two successive steps. In the first step of the reaction, two intermediate nuclei are formed as a result of an inelastic collision between projectile and target atoms while in the second step the fission of one of the intermediate nuclei of the previous step takes place. Furthermore no proximity effects have been observed

  2. Benford's law and cross-sections of A(n,α)B reactions

    International Nuclear Information System (INIS)

    Liu, X.J.; Ni, D.D.; Zhang, X.P.; Ren, Z.Z.

    2011-01-01

    Benford's law, also called the first-digit law, states that in lists of numbers from many quite disparate databases, the leading digit is distributed in a non-uniform but actually logarithmic way. We have investigated the first-digit distribution of experimental cross-sections of A(n, α)B reactions. In the case of below-barrier α -particle emission from compound nucleus, it is found that the (n, α) reaction cross-sections approximately follow the first-digit distribution indicated by Benford's law. The origin of this first-digit distribution is discussed within the framework of the statistical model. In addition, Benford's law is used to test the evaluated cross-sections of A(n, α)B reactions. (orig.)

  3. 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)

  4. Investigation of Thermochemistry Associated with the Carbon–Carbon Coupling Reactions of Furan and Furfural Using ab Initio Methods

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Cong; Assary, Rajeev S.; Curtiss, Larry A.

    2014-06-26

    Upgrading of furan and small oxygenates obtained from the decomposition of cellulosic materials via formation of carbon-carbon bonds is critical to effective conversion of biomass to liquid transportation fuels. Simulation-driven molecular level understanding of carbon-carbon bond formation is required to design efficient catalysts and processes. Accurate quantum chemical methods are utilized here to predict the reaction energetics for conversion of furan (C4H4O) to C5-C8 ethers and the transformation of furfural (C5H6O2) to C13-C26 alkanes. Furan, can be coupled with various C1 to C4 lower molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase to produce C5-C8 cyclic ethers. The computed reaction barriers for these reactions (~25 kcal/mol) are lower than the cellulose activation or decomposition reactions (~50 kcal/mol). Cycloaddition of C5-C8 cyclo-ethers with furans can also occur in the gas phase, and the computed activation energy is similar to that of the first Diels-Alder reaction. Furfural, obtained from biomass, can be coupled with aldehydes or ketones with α-hydrogen atoms to form longer chain aldol products and these aldol products can undergo vapor phase hydrocycloaddition (activation barrier of ~20 kcal/mol) to form the precursors of C26 cyclic hydrocarbons. These thermochemical studies provide the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to longer chain hydrocarbons.

  5. Study of the p+{sup 12}C reaction at energies up to 30 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Masahide; Yamamoto, A.; Yoshioka, S. [Kyushu Univ., Fukuoka (Japan)] [and others

    1998-03-01

    Double differential cross sections of charged-particles emitted in the p+{sup 12}C reaction were measured in the energy region from 14 to 26 MeV. The observed continuous components of emitted protons and {alpha}-particles were analyzed by assuming sequential decay of intermediate reaction products and/or simultaneous breakup process. It was found that the three body simultaneous decay, p+{alpha}+{sup 8}Be, and the sequential decay via p+{sup 12}C{sup *}{sub 3-} and {alpha}+{sup 9}B{sub g.s.} are most important in the proton-induced breakup of {sup 12}C for energies up to 30 MeV. (author)

  6. New spiro (thio barbiturates based on cyclohexanone and bicyclo [3.1.1]heptan-6-one by nonconcerted [1+5] cycloaddition reaction and their conformational structures

    Directory of Open Access Journals (Sweden)

    N. N. Pesyan

    2014-09-01

    Full Text Available Crossed-aldol condensation reaction of aromatic aldehydes with ketones such as; acetone and cyclohexanone leads to the efficient formation of cross conjugated α,β-unsaturated ketones in excellent yield. The intermolecular and then intramolecular Michael addition reaction of α,β-unsaturated ketones derived from acetone and cyclohexanone with (thiobarbituric acids lead to synthesis new type of 7,11-diaryl-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraone and 2,4-diaryl-1'H-spiro[bicyclo[3.3.1]nonane-3,5'-pyrimidine]-2',4',6',9(3'H-tetraone, respectively in good yield. Structure elucidation is carried out by 1H NMR, 13C NMR, FT-IR, UV-Visible, mass spectroscopy and X-ray crystallography techniques. A possible mechanism of the formation is discussed. The structural conformation also demonstrated by coupling constants derived from dihedral angles between vicinal and geminal protons. The 1H NMR spectra of NH protons of spiro compounds derived from barbituric acid show a broad singlet peak instead, these protons in the spiro compounds derived from thiobarbituric acid show two distinct peaks. DOI: http://dx.doi.org/10.4314/bcse.v28i3.12

  7. Sequential rhodium/palladium catalysis: enantioselective formation of dihydroquinolinones in the presence of achiral and chiral ligands.

    Science.gov (United States)

    Zhang, Lei; Qureshi, Zafar; Sonaglia, Lorenzo; Lautens, Mark

    2014-12-08

    Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Crossed molecular beam studies of unimolecular reaction dynamics

    International Nuclear Information System (INIS)

    Buss, R.J.

    1979-04-01

    The study of seven radical-molecule reactions using the crossed molecular beam technique with supersonic nozzle beams is reported. Product angular and velocity distributions were obtained and compared with statistical calculations in order to identify dynamical features of the reactions. In the reaction of chlorine and fluorine atoms with vinyl bromide, the product energy distributions are found to deviate from predictions of the statistical model. A similar effect is observed in the reaction of chlorine atoms with 1, 2 and 3-bromopropene. The reaction of oxygen atoms with ICl and CF 3 I has been used to obtain an improved value of the IO bond energy, 55.0 +- 2.0 kcal mol -1 . In all reactions studied, the product energy and angular distributions are found to be coupled, and this is attributed to a kinematic effect of the conservation of angular momentum

  9. Measurement of (n,Xn) reaction cross sections at 96 MeV

    International Nuclear Information System (INIS)

    Sagrado Garcia, Melle Inmaculada C.

    2006-10-01

    Nucleon induced reactions in the 20-200 MeV energy range are intensively studied since a long time. The evaporation and the pre-equilibrium processes correspond to an important contribution of the production cross section in these reactions. Several theoretical approaches have been proposed and their predictions must be tested. The experimental results shown in this work are the only complete set of data for the (n,Xn) reactions in this energy range. Neutron double differential cross section measurements using lead and iron targets for an incident neutron beam at 96 MeV were carried out at TSL Laboratory in Uppsala, Sweden. The measurements have been performed for the first time with an energy threshold of 2 MeV and for a wide angular range (15 angle - 98 angle). Neutrons have been detected using two independent setups, DECOI and DEMON and CLODIA and SCANDAL, in order to cover the whole energy range (2-100) MeV. The angular distributions, the differential cross sections and the total inelastic production cross sections have been calculated using the double differential cross sections. The comparison between the experimental data and the predictions given by two of the most popular simulation codes, GEANT3 and MCNPX, have been performed, as well as the comparison with the predictions of the microscopic simulation model DYWAN, selected for its treatment of nucleon-nucleon reactions. (author)

  10. Diazo compounds and N-tosylhydrazones: novel cross-coupling partners in transition-metal-catalyzed reactions.

    Science.gov (United States)

    Xiao, Qing; Zhang, Yan; Wang, Jianbo

    2013-02-19

    Transition-metal-catalyzed carbene transformations and cross-couplings represent two major reaction types in organometallic chemistry and organic synthesis. However, for a long period of time, these two important areas have evolved separately, with essentially no overlap or integration. Thus, an intriguing question has emerged: can cross-coupling and metal carbene transformations be merged into a single reaction cycle? Such a combination could facilitate the development of novel carbon-carbon bond-forming methodologies. Although this concept was first explored about 10 years ago, rapid developments inthis area have been achieved recently. Palladium catalysts can be used to couple diazo compounds with a wide variety of organic halides. Under oxidative coupling conditions, diazo compounds can also react with arylboronic acids and terminal alkynes. Both of these coupling reactions form carbon-carbon double bonds. As the key step in these catalytic processes, Pd carbene migratory insertion plays a vital role in merging the elementary steps of Pd intermediates, leading to novel carbon-carbon bond formations. Because the diazo substrates can be generated in situ from N-tosylhydrazones in the presence of base, the N-tosylhydrazones can be used as reaction partners, making this type of cross-coupling reaction practical in organic synthesis. N-Tosylhydrazones are easily derived from the corresponding aldehydes or ketones. The Pd-catalyzed cross-coupling of N-tosylhydrazones is considered a complementary reaction to the classic Shapiro reaction for converting carbonyl functionalities into carbon-carbon double bonds. It can also serve as an alternative approach for the Pd-catalyzed cross-coupling of carbonyl compounds, which is usually achieved via triflates. The combination of carbene formation and cross-coupling in a single catalytic cycle is not limited to Pd-catalyzed reactions. Recent studies of Cu-, Rh-, Ni-, and Co-catalyzed cross-coupling reactions with diazo

  11. Fission neutron spectrum averaged cross sections for threshold reactions on arsenic

    International Nuclear Information System (INIS)

    Dorval, E.L.; Arribere, M.A.; Kestelman, A.J.; Comision Nacional de Energia Atomica, Cuyo Nacional Univ., Bariloche; Ribeiro Guevara, S.; Cohen, I.M.; Ohaco, R.A.; Segovia, M.S.; Yunes, A.N.; Arrondo, M.; Comision Nacional de Energia Atomica, Buenos Aires

    2006-01-01

    We have measured the cross sections, averaged over a 235 U fission neutron spectrum, for the two high threshold reactions: 75 As(n,p) 75 mGe and 75 As(n,2n) 74 As. The measured averaged cross sections are 0.292±0.022 mb, referred to the 3.95±0.20 mb standard for the 27 Al(n,p) 27 Mg averaged cross section, and 0.371±0.032 mb referred to the 111±3 mb standard for the 58 Ni(n,p) 58m+g Co averaged cross section, respectively. The measured averaged cross sections were also evaluated semi-empirically by numerically integrating experimental differential cross section data extracted for both reactions from the current literature. The calculations were performed for four different representations of the thermal-neutron-induced 235 U fission neutron spectrum. The calculated cross sections, though depending on analytical representation of the flux, agree with the measured values within the estimated uncertainties. (author)

  12. anti p-3He reaction cross section at 200 MeV/c

    International Nuclear Information System (INIS)

    Balestra, F.; Bossolasco, S.; Bussa, M.P.; Busso, L.; Ferrero, L.; Grasso, A.; Panzieri, D.; Piragino, G.; Tosello, F.; Barbieri, R.; Bendiscioli, G.; Rotondi, A.; Salvini, P.; Venaglioni, A.; Zenoni, A.; Batusov, Yu.A.; Falomkin, I.V.; Pontecorvo, G.B.; Sapozhnikov, M.G.; Tretyak, V.I.; Breivik, F.O.; Jacobsen, T.; Soerensen, S.O.

    1988-01-01

    Inelastic anti p- 3 He events at 192.8 MeV/c are detected with a self-shunted streamer chamber. The measured reaction cross section is 392±23.8 mb. This result is briefly discussed and compared with other reaction cross sections for low-energy anti p with light nuclei. (orig.)

  13. Cross-flow electrochemical reactor cells, cross-flow reactors, and use of cross-flow reactors for oxidation reactions

    Science.gov (United States)

    Balachandran, Uthamalingam; Poeppel, Roger B.; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Udovich, Carl A.

    1994-01-01

    This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors comprise a hollow ceramic blade positioned across a gas stream flow or a stack of crossed hollow ceramic blades containing a channel or channels for flow of gas streams. Each channel has at least one channel wall disposed between a channel and a portion of an outer surface of the ceramic blade, or a common wall with adjacent blades in a stack comprising a gas-impervious mixed metal oxide material of a perovskite structure having electron conductivity and oxygen ion conductivity. The invention includes reactors comprising first and second zones seprated by gas-impervious mixed metal oxide material material having electron conductivity and oxygen ion conductivity. Prefered gas-impervious materials comprise at least one mixed metal oxide having a perovskite structure or perovskite-like structure. The invention includes, also, oxidation processes controlled by using these electrochemical reactors, and these reactions do not require an external source of electrical potential or any external electric circuit for oxidation to proceed.

  14. 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

  15. Studies towards the synthesis of radiolabeled R106-1(LY295337)

    International Nuclear Information System (INIS)

    Rodriguez, M.J.; Zweifel, M.J.

    1996-01-01

    A unique semisynthetic pathway has been used as a route to acquire radiolabeled material of a complex natural product, R106. The retro-aldol reaction of R106-1 gave a key intermediate R106-sarcosine that was used in a subsequent aldol reaction to incorporate acetone--[2- 14 C]. (author)

  16. Synthesis of Arylthiopyrimidines by Copper-catalyzed Aerobic Oxidative C-S Cross-coupling

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ok Suk; Kim, Hyeji; Sohn, Jeong-Hun [Chungnam National University, Daejeon (Korea, Republic of); Lee, Hee-Seung [KAIST, Daejeon (Korea, Republic of); Shin, Hyunik [Yonsung Fine Chemicals R and D Center, Suwon (Korea, Republic of)

    2016-02-15

    Copper-catalyzed C–S cross-coupling reactions have been considered as powerful tools in synthetic chemistry and utilized for diverse heterocycle syntheses. In the reactions, the aspects of no need of ligands has been particular advantage over other metal catalysis. We have developed a Cu-catalyzed cascade reaction for the synthesis of fully substituted 2-arylthiopyrimidines from 3,4-dihydropyrimidine-2(1H)-thiones (DHPMs) under aerobic conditions. This cascade reaction of DHPM with aryl iodide proceeds presumably via sequential tautomerization, C–S cross-coupling, and oxidative dehydrogenation (oxidation followed by elimination). Considering that DHPM substrates were easily synthesized by Biginelli three component coupling reaction of aryl aldehyde, β-ketoester, and thiourea, the present method provides a direct access toward diverse 2-arylthiopyrimidines which have been used as a prominent substructure of drug molecules.

  17. Cross section of the 197Au(n,2n196Au reaction

    Directory of Open Access Journals (Sweden)

    Kalamara A.

    2017-01-01

    Full Text Available The 197Au(n,2n196Au reaction cross section has been measured at two energies, namely at 17.1 MeV and 20.9 MeV, by means of the activation technique, relative to the 27Al(n,α24Na reference reaction cross section. Quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR “Demokritos”, by means of the 3H(d,n4He reaction, implementing a new Ti-tritiated target of ∼ 400 GBq activity. The induced γ-ray activity at the targets and reference foils has been measured with HPGe detectors. The cross section for the population of the second isomeric (12− state m2 of 196Au was independently determined. Auxiliary Monte Carlo simulations were performed using the MCNP code. The present results are in agreement with previous experimental data and with theoretical calculations of the measured reaction cross sections, which were carried out with the use of the EMPIRE code.

  18. Splitting Schemes & Segregation In Reaction-(Cross-)Diffusion Systems

    OpenAIRE

    Carrillo, José A.; Fagioli, Simone; Santambrogio, Filippo; Schmidtchen, Markus

    2017-01-01

    One of the most fascinating phenomena observed in reaction-diffusion systems is the emergence of segregated solutions, i.e. population densities with disjoint supports. We analyse such a reaction cross-diffusion system. In order to prove existence of weak solutions for a wide class of initial data without restriction about their supports or their positivity, we propose a variational splitting scheme combining ODEs with methods from optimal transport. In addition, this approach allows us to pr...

  19. Sequential capillary electrophoresis analysis using optically gated sample injection and UV/vis detection.

    Science.gov (United States)

    Liu, Xiaoxia; Tian, Miaomiao; Camara, Mohamed Amara; Guo, Liping; Yang, Li

    2015-10-01

    We present sequential CE analysis of amino acids and L-asparaginase-catalyzed enzyme reaction, by combing the on-line derivatization, optically gated (OG) injection and commercial-available UV-Vis detection. Various experimental conditions for sequential OG-UV/vis CE analysis were investigated and optimized by analyzing a standard mixture of amino acids. High reproducibility of the sequential CE analysis was demonstrated with RSD values (n = 20) of 2.23, 2.57, and 0.70% for peak heights, peak areas, and migration times, respectively, and the LOD of 5.0 μM (for asparagine) and 2.0 μM (for aspartic acid) were obtained. With the application of the OG-UV/vis CE analysis, sequential online CE enzyme assay of L-asparaginase-catalyzed enzyme reaction was carried out by automatically and continuously monitoring the substrate consumption and the product formation every 12 s from the beginning to the end of the reaction. The Michaelis constants for the reaction were obtained and were found to be in good agreement with the results of traditional off-line enzyme assays. The study demonstrated the feasibility and reliability of integrating the OG injection with UV/vis detection for sequential online CE analysis, which could be of potential value for online monitoring various chemical reaction and bioprocesses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Neutron-induced cross sections of short-lived nuclei via the surrogate reaction method

    Directory of Open Access Journals (Sweden)

    Morel P.

    2011-10-01

    Full Text Available The measurement of neutron-induced cross sections of short-lived nuclei is extremely difficult due to the radioactivity of the samples. The surrogate reaction method is an indirect way of determining cross sections for nuclear reactions that proceed through a compound nucleus. This method presents the advantage that the target material can be stable or less radioactive than the material required for a neutron-induced measurement. We have successfully used the surrogate reaction method to extract neutron-induced fission cross sections of various short-lived actinides. In this work, we investigate whether this technique can be used to determine neutron-induced capture cross sections in the rare-earth region.

  1. Neutron-induced cross sections of short-lived nuclei via the surrogate reaction method

    Directory of Open Access Journals (Sweden)

    Tassan-Got L.

    2012-02-01

    Full Text Available The measurement of neutron-induced cross sections of short-lived nuclei is extremely difficult due to the radioactivity of the samples. The surrogate reaction method is an indirect way of determining cross sections for nuclear reactions that proceed through a compound nucleus. This method presents the advantage that the target material can be stable or less radioactive than the material required for a neutron-induced measurement. We have successfully used the surrogate reaction method to extract neutron-induced fission cross sections of various short-lived actinides. In this work, we investigate whether this technique can be used to determine neutron-induced capture cross sections in the rare-earth region.

  2. Cross-sections of 45Sc(n,2n)44m,gSc reaction from the reaction threshold to 20 MeV

    International Nuclear Information System (INIS)

    Luo, J.; Peking Univ., Beijing; Liu, R.; Jiang, L.; Liu, Z.; Sun, G.; Ge, S.

    2013-01-01

    Cross sections of 45 Sc(n,2n) 44m,g Sc reactions and their isomeric cross section ratios σ m /σ g have been measured at three neutron energies between 13.5 and 14.8 MeV using the activation technique. The pure cross section of the groundstate was then obtained by utilizing the absolute cross section of the metastable state and analysis methods of residual nuclear decay. The monoenergetic neutron beam was produced via the 3 H(d, n) 4 He reaction. The cross sections were also estimated with the TALYS-1.2 nuclear model code using different level density options, at neutron energies varying from the reaction threshold to 20 MeV. Results are also discussed and compared with some corresponding values found in the literature. (orig.)

  3. Differential cross section measurement for the 6Li(n,t)4He Reaction

    International Nuclear Information System (INIS)

    Zhang Guohui; Tang Guoyou; Chen Jinxiang; Shi Zhaomin

    2002-01-01

    The differential cross sections and integrated cross sections of the 6 Li(n,t) 4 He reaction were measured at 1.85 and 2.67 MeV by using a gridded ionization chamber. Neutrons were produced through the T(p, n) 3 He reaction. The absolute neutron flux was determined through the 238 U(n, f) reaction. Present results are compared with existing data

  4. Measurement of cross-sections of yttrium (n,xn) threshold reactions by means of gamma spectroscopy

    CERN Document Server

    Chudoba, Petr; Wagner, V; Vrzalova, J; Svoboda, O; Majerle, M; Stefanik, M; Suchopar, M; Kugler, A; Bielewicz, M; Strugalska-Gola, E; Szuta, M; Hervas, D; Herman, T; Geier, B

    2014-01-01

    Neutron activation and gamma spectrometry are usable also f or the determination of cross-sections of different neutron reactions. We have studied the cross-sections of yttrium (n, x n) threshold reactions using quasi-monoenergetic neutron source based on the reaction on 7 Li target at Nuclear Physics Institute of ASCR in Rez. Yttrium (n, x n) threshold reactions are suitable candidates for fast neutron field measurement by activation detectors. Fast neutron field monitoring is necessary already today at a wide range of accelerator facilities and will gain on importance in future fast reactors of generation IV, accelerator transmutation systems or fusion reactors. The knowledge of the cross-sections is crucial for such purpose. Unfortunately, the cross-section is sufficiently known only for 89 Y(n,2n) 88 Y reaction. For higher orders of reactions there are almost no experimental data. Special attention was paid to t he 89 Y(n,3n) 87 Y reaction. The cross-sections of both 89 Y(n,2n) 88 Y and 89 Y(n,3n) 87 Y re...

  5. Cross section asymmetry of deuteron photodesintegration reaction with polarized gamma quanta

    International Nuclear Information System (INIS)

    Gorbenko, V.G.; Zhebrovskij, Yu.V.; Kolesnikov, L.Ya.; Rubashkin, A.L.; Sorokin, P.V.

    1982-01-01

    The parameters of the reaction cross section asymmetry are determined to investigate the γ+d → n+p reaction. The measurements are exercised on a beam of linearly polarized photons of a linear 2 GeV electron accelerator by means of two magnetic spectrometers in the Esub(γ)=80-600 MeV energy range for 75-105 deg angles of proton escape in scm. The flowsheet of an experimental facility is presented. Technique of the experiment execution is presented. The obtained values of the cross section asymmetry parameter are presented in the table form for the 75, 90, 105, 120, 135, 150 deg angles. Calculation of the differential cross sections is carried out in pulse approximation. Energy Dependence and angutar distribUtions of the cross section asymmetry parameter of the investigated reaction are presented graphically. The obtained results are compared with the present experimental and theoretical data at 80 and 300 MeV photon energy. The comparison has revealed that none of the calculation methods is more preferable as well as no simple conclusion can be made on the existence of dibarin resonances

  6. Derivation of capture and reaction cross sections from experimental quasi-elastic and elastic backscattering probabilities

    International Nuclear Information System (INIS)

    Sargsyan, V.V.; Adamian, G.G.; Antonenko, N.V.; Gomes, P.R.S.

    2014-01-01

    We suggest simple and useful methods to extract reaction and capture (fusion) cross sections from the experimental elastic and quasi-elastic backscattering data.The direct measurement of the reaction or capture (fusion) cross section is a difficult task since it would require the measurement of individual cross sections of many reaction channels, and most of them could be reached only by specific experiments. This would require different experimental setups not always available at the same laboratory and, consequently, such direct measurements would demand a large amount of beam time and would take probably some years to be reached. Because of that, the measurements of elastic scattering angular distributions that cover full angular ranges and optical model analysis have been used for the determination of reaction cross sections. This traditional method consists in deriving the parameters of the complex optical potentials which fit the experimental elastic scattering angular distributions and then of deriving the reaction cross sections predicted by these potentials. Even so, both the experimental part and the analysis of this latter method are not so simple. In the present work we present a much simpler method to determine reaction and capture (fusion) cross sections. It consists of measuring only elastic or quasi-elastic scattering at one backward angle, and from that, the extraction of the reaction or capture cross sections can easily be performed. (author)

  7. Systematics of the (n, t) reaction cross sections at 14 MeV

    International Nuclear Information System (INIS)

    Yao Lishan

    1992-01-01

    The systematic behaviour of the (n, t) reaction cross sections have been studied for medium and heavy mass nuclei at 14 MeV. An analysis of the gross trend, the isotope and odd-even effects are given. Possible reaction mechanisms are also discussed. A set of the systematics parameters have been extracted on the basis of the analyzing and fitting of the available data. The (n, t) reaction cross sections of some nuclei have been predicted and a good agreement with the measured data has been obtained

  8. Sequential fission process observed in the reaction (16.7 MeV/u) {sup 238}U + {sup nat.}Au using mica as dielectric track detector

    Energy Technology Data Exchange (ETDEWEB)

    Shahzad, Muhammad Ikram; Qureshi, Imtinan Elahi; Manzoor, Shahid; Khan, Hameed Ahmed

    1999-01-04

    The evidence of sequential fission has been found in the heavy-ion reaction (16.7 MeV/u) {sup 238}U + {sup nat.}Au, using muscovite mica as Dielectric Track Detector (DTD) placed in a 2{pi}-geometry configuration. The reaction products originating from the interactions of {sup 238}U ions with the atoms of gold were registered in the detector in the form of tracks and identified for performing a detailed kinematical analysis. For this purpose the spherical polar coordinates of the correlated tracks of the multipronged events have been analyzed on an event-by-event basis. Automatic, semi-automatic and manual measuring methods have been employed to collect and manipulate the track data. The known characteristics of binary and ternary events observed in the reaction have been used for the calibration of the detectors. The computed masses, Q-values and relative velocities of the reaction products determined in this analysis are compared with theoretical predictions based on sequential fission process. Agreement within one standard deviation with respect to the experimental values has been found for the majority of analyzed events. Therefore, it is concluded that three particles in the exit channel of the reaction are produced in two successive steps. In the first step of the reaction, two intermediate nuclei are formed as a result of an inelastic collision between projectile and target atoms while in the second step the fission of one of the intermediate nuclei of the previous step takes place. Furthermore no proximity effects have been observed.

  9. Theoretical study of cross sections of proton-induced reactions on cobalt

    Directory of Open Access Journals (Sweden)

    Mustafa Yiğit

    2018-04-01

    Full Text Available Nuclear fusion may be among the strongest sustainable ways to replace fossil fuels because it does not contribute to acid rain or global warming. In this context, activated cobalt materials in corrosion products for fusion energy are significant in determination of dose levels during maintenance after a coolant leak in a nuclear fusion reactor. Therefore, cross-section studies on cobalt material are very important for fusion reactor design. In this article, the excitation functions of some nuclear reaction channels induced by proton particles on 59Co structural material were predicted using different models. The nuclear level densities were calculated using different choices of available level density models in ALICE/ASH code. Finally, the newly calculated cross sections for the investigated nuclear reactions are compared with the experimental values and TENDL data based on TALYS nuclear code. Keywords: Cobalt, Nuclear Structural Materials, Reaction Cross Section, TENDL Database

  10. Upgrading Lignocellulosic Products to Drop-In Biofuels via Dehydrogenative Cross-Coupling and Hydrodeoxygenation Sequence.

    Science.gov (United States)

    Sreekumar, Sanil; Balakrishnan, Madhesan; Goulas, Konstantinos; Gunbas, Gorkem; Gokhale, Amit A; Louie, Lin; Grippo, Adam; Scown, Corinne D; Bell, Alexis T; Toste, F Dean

    2015-08-24

    Life-cycle analysis (LCA) allows the scientific community to identify the sources of greenhouse gas (GHG) emissions of novel routes to produce renewable fuels. Herein, we integrate LCA into our investigations of a new route to produce drop-in diesel/jet fuel by combining furfural, obtained from the catalytic dehydration of lignocellulosic pentose sugars, with alcohols that can be derived from a variety of bio- or petroleum-based feedstocks. As a key innovation, we developed recyclable transition-metal-free hydrotalcite catalysts to promote the dehydrogenative cross-coupling reaction of furfural and alcohols to give high molecular weight adducts via a transfer hydrogenation-aldol condensation pathway. Subsequent hydrodeoxygenation of adducts over Pt/NbOPO4 yields alkanes. Implemented in a Brazilian sugarcane biorefinery such a process could result in a 53-79% reduction in life-cycle GHG emissions relative to conventional petroleum fuels and provide a sustainable source of low carbon diesel/jet fuel. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Limit Theory for Panel Data Models with Cross Sectional Dependence and Sequential Exogeneity.

    Science.gov (United States)

    Kuersteiner, Guido M; Prucha, Ingmar R

    2013-06-01

    The paper derives a general Central Limit Theorem (CLT) and asymptotic distributions for sample moments related to panel data models with large n . The results allow for the data to be cross sectionally dependent, while at the same time allowing the regressors to be only sequentially rather than strictly exogenous. The setup is sufficiently general to accommodate situations where cross sectional dependence stems from spatial interactions and/or from the presence of common factors. The latter leads to the need for random norming. The limit theorem for sample moments is derived by showing that the moment conditions can be recast such that a martingale difference array central limit theorem can be applied. We prove such a central limit theorem by first extending results for stable convergence in Hall and Hedye (1980) to non-nested martingale arrays relevant for our applications. We illustrate our result by establishing a generalized estimation theory for GMM estimators of a fixed effect panel model without imposing i.i.d. or strict exogeneity conditions. We also discuss a class of Maximum Likelihood (ML) estimators that can be analyzed using our CLT.

  12. A simple functional form for proton-208Pb total reaction cross sections

    International Nuclear Information System (INIS)

    Majumdar, S.; Deb, P.K.; Amos, K.

    2001-01-01

    A simple functional form has been found that gives a good representation of the total reaction cross sections for the scattering from 208 Pb of protons with energies in the range 30 to 300 MeV. The ratios of the total reaction cross sections calculated under this approximations compared well (to within a few percent) to those determined from the microscopic optical model potentials

  13. Neutron-induced cross sections of actinides via the surrogate-reaction method

    Directory of Open Access Journals (Sweden)

    Ducasse Q.

    2013-12-01

    Full Text Available The surrogate-reaction method is an indirect way of determining cross sections for reactions that proceed through a compound nucleus. This technique may enable neutron-induced cross sections to be extracted for short-lived nuclei that otherwise cannot be measured. However, the validity of the surrogate method has to be investigated. In particular, the absence of a compound nucleus formation and the Jπ dependence of the decay probabilities may question the method. In this work we study the reactions 238U(d,p239U, 238U(3He,t238Np, 238U(3He,4He237U as surrogates for neutron-induced reactions on 238U, 237Np and 236U, respectively, for which good quality data exist. The experimental set-up enabled the measurement of fission and gamma-decay probabilities. The first results are hereby presented.

  14. Relations between the simultaneous and sequential transfer of two nucleons

    International Nuclear Information System (INIS)

    Satchler, G.R.

    1982-01-01

    The author discusses the perturbative treatment of simultaneous and sequential two-nucleon transfer reactions with special regards to the DWBA. As examples the (t,p), (p,t), and (α,d) reactions are considered. (HSI)

  15. A Highly Efficient Method for Synthesis of Bisarylmethylidenes of Cyclic Ketones in [BMIm]Cl/NaOH System as New and Recyclable Catalyst

    Directory of Open Access Journals (Sweden)

    Shahrzad Javanshir

    2014-03-01

    Full Text Available An ionic liquid 1-Butyl-3-methylimidazoliumchloride[BMIm]Cl/sodium hydroxide system, was employed as a catalyst for the fast and one-pot crossed aldol-condensation of various aromatic aldehydes and cyclic ketones, to produce a variety of substituted α,α'-bis(benzylidene-cycloalkanones under neat conditions. This process is simple, efficient and environmentally benign and proceeds in high yield and short reaction times. The ionic liquid can be recycled for subsequent reactions without any appreciable loss of efficiency.

  16. THE LATEST ADVANCEMENTS IN THE ACYLATION REACTIONS VIA CROSS-DEHYDROGENATIVE COUPLING AND/OR METAL CATALYSTS

    Directory of Open Access Journals (Sweden)

    Soykan Ağar

    2017-12-01

    Full Text Available There are quite many examples in the scientific literature regarding the acylation reactions, especially the metal-catalyzed acylation reactions, metal-free acylation reactions, metal-catalyzed acylation via cross-dehydrogenative coupling (CDC reactions and metal-free acylation via cross-dehydrogenative coupling (CDC reactions. In this review paper, the most important examples of these domains were brought together and their mechanisms were exhibited in a clear, chronological format. Following these, the best example study towards green chemistry with a metal-free and high-yielding route was mentioned and discussed to demonstrate what has achieved in this field regarding the new acylation reaction mechanisms using the advantages of cross-dehydrogenative coupling (CDC reactions. The most prominent studies regarding these domains have been examined thoroughly and the latest progress in this field was explained in detail.

  17. Crossed-beam studies of the dynamics of radical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, K. [Argonne National Laboratory, IL (United States)

    1993-12-01

    The objective of this program is to characterize the detailed dynamics of elementary radical reactions and to provide a better understanding of radical reactivity in general. The radical beam is typically generated by a laser photolysis method. After colliding with the reacting molecule in a crossed-beam apparatus, the reaction product state distribution is interrogated by laser spectroscopic techniques. Several radicals of combustion significance, such as O, CH, OH, CN and NCO have been successfully generated and their collisional behavior at the state-to-state integral cross section level of detail has been studied in this manner. During the past year, the detection system has been converted from LIF to REMPI schemes, and the emphasis of this program shifted to investigate the product angular distributions. Both inelastic and reactive processes have been studied.

  18. Synthesis of substituted mono- and diindole C-nucleoside analogues from sugar terminal alkynes by sequential sonogashira/heteroannulation reaction.

    Science.gov (United States)

    Zhang, Fuyi; Mu, Delong; Wang, Liming; Du, Pengfei; Han, Fen; Zhao, Yufen

    2014-10-17

    The synthesis of substituted mono- and diindole C-nucleoside analogues has been achieved in good to excellent yields by sequential Sonogashira coupling/NaAuCl4-catalyzed heteroannulation reactions of substituted 2-iodoanilines with various sugar terminal alkynes in one pot. The method is general, mild, and efficient and suitable for a wide range of sugar substrates, and 42 examples are given. The amino group of the substituted 2-iodoanilines is unprotected. The sugar terminal alkynes include furanosides, pyranosides, and acyclic glycosides with free hydroxyl groups, sensitive functional subtituents, and various protecting groups having different steric hindrance.

  19. Comparison of sugar molecule decomposition through glucose and fructose: a high-level quantum chemical study.

    Energy Technology Data Exchange (ETDEWEB)

    Assary, R. S.; Curtiss, L. A. (Center for Nanoscale Materials); ( MSD); (Northwestern Univ.)

    2012-02-01

    Efficient chemical conversion of biomass is essential to produce sustainable energy and industrial chemicals. Industrial level conversion of glucose to useful chemicals, such as furfural, hydroxymethylfurfural, and levulinic acid, is a major step in the biomass conversion but is difficult because of the formation of undesired products and side reactions. To understand the molecular level reaction mechanisms involved in the decomposition of glucose and fructose, we have carried out high-level quantum chemical calculations [Gaussian-4 (G4) theory]. Selective 1,2-dehydration, keto-enol tautomerization, isomerization, retro-aldol condensation, and hydride shifts of glucose and fructose molecules were investigated. Detailed kinetic and thermodynamic analyses indicate that, for acyclic glucose and fructose molecules, the dehydration and isomerization require larger activation barriers compared to the retro-aldol reaction at 298 K in neutral medium. The retro-aldol reaction results in the formation of C2 and C4 species from glucose and C3 species from fructose. The formation of the most stable C3 species, dihydroxyacetone from fructose, is thermodynamically downhill. The 1,3-hydride shift leads to the cleavage of the C-C bond in the acyclic species; however, the enthalpy of activation is significantly higher (50-55 kcal/mol) than that of the retro-aldol reaction (38 kcal/mol) mainly because of the sterically hindered distorted four-membered transition state compared to the hexa-membered transition state in the retro-aldol reaction. Both tautomerization and dehydration are catalyzed by a water molecule in aqueous medium; however, water has little effect on the retro-aldol reaction. Isomerization of glucose to fructose and glyceraldehyde to dihydroxyacetone proceeds through hydride shifts that require an activation enthalpy of about 40 kcal/mol at 298 K in water medium. This investigation maps out accurate energetics of the decomposition of glucose and fructose molecules

  20. Use of nuclear reaction models in cross section calculations

    International Nuclear Information System (INIS)

    Grimes, S.M.

    1975-03-01

    The design of fusion reactors will require information about a large number of neutron cross sections in the MeV region. Because of the obvious experimental difficulties, it is probable that not all of the cross sections of interest will be measured. Current direct and pre-equilibrium models can be used to calculate non-statistical contributions to neutron cross sections from information available from charged particle reaction studies; these are added to the calculated statistical contribution. Estimates of the reliability of such calculations can be derived from comparisons with the available data. (3 tables, 12 figures) (U.S.)

  1. Studies of combustion reactions at the state-resolved differential cross section level

    Energy Technology Data Exchange (ETDEWEB)

    Houston, P.L.; Suits, A.G.; Bontuyan, L.S.; Whitaker, B.J. [Cornell Univ., Ithaca, NY (United States)

    1993-12-01

    State-resolved differential reaction cross sections provide perhaps the most detailed information about the mechanism of a chemical reaction, but heretofore they have been extremely difficult to measure. This program explores a new technique for obtaining differential cross sections with product state resolution. The three-dimensional velocity distribution of state-selected reaction products is determined by ionizing the appropriate product, waiting for a delay while it recoils along the trajectory imparted by the reaction, and finally projecting the spatial distribution of ions onto a two dimensional screen using a pulsed electric field. Knowledge of the arrival time allows the ion position to be converted to a velocity, and the density of velocity projections can be inverted mathematically to provide the three-dimensional velocity distribution for the selected product. The main apparatus has been constructed and tested using photodissociations. The authors report here the first test results using crossed beams to investigate collisions between Ar and NO. Future research will both develop further the new technique and employ it to investigate methyl radical, formyl radical, and hydrogen atom reactions which are important in combustion processes. The authors intend specifically to characterize the reactions of CH{sub 3} with H{sub 2} and H{sub 2}CO; of HCO with O{sub 2}; and of H with CH{sub 4}, CO{sub 2}, and O{sub 2}.

  2. Nuclear structure effects on calculated fast neutron reaction cross sections

    International Nuclear Information System (INIS)

    Avrigeanu, V.

    1992-01-01

    The importance of accurate low-lying level schemes for reaction cross section calculation and need for microscopically calculated levels are proved with reference to fast neutron induced reactions in the A = 50 atomic mass range. The uses of the discrete levels both for normalization of phenomenological level density approaches and within Hauser-Feshbach calculations are discussed in this respect. (Author)

  3. Geometrical aspects of reaction cross sections for 3He, 4He and 12C projectiles

    International Nuclear Information System (INIS)

    Ingemarsson, A.; Lantz, M.

    2003-04-01

    A black-disc model combined with accurate matter densities has been used for an investigation of reaction cross sections for 3 He, 4 He and 12 C projectiles. A simple relation is derived between the energy dependence of the reaction cross sections and the strength of the nucleon-nucleon interaction. A comparison is also made of the reaction cross sections for 3 He and 4 He for six different nuclei 12 C, 16 O, 40 Ca, 58,60 Ni and 208 Pb

  4. Approximation of the cross-sections for charged-particle emission reactions near the threshold

    International Nuclear Information System (INIS)

    Badikov, S.A.; Pashchenko, A.B.

    1990-01-01

    We perform an analytical approximation of the energy dependence of the cross-sections for the reactions (n,p) and (n,γ) from the BOSPOR library, correct them for the latest differential and integral experimental data using the common features, characteristic of the energy dependence of the threshold reaction cross-section and making some physical assumptions. 19 refs, 1 fig., 1 tab

  5. Intramolecular Diels–Alder reaction as a key step in tandem or sequential processes: a versatile tool for the synthesis of fused and bridged bicyclic or polycyclic compounds.

    Digital Repository Service at National Institute of Oceanography (India)

    Parvatkar, P.T.; Kadam, H.K.; Tilve, S.G.

    This review summarizes the recent examples of tandem or sequential reactions used for the last 10 years for the synthesis of fused and bridged bicyclic or polycyclic compounds with IMDA cycloaddition as the key means to access these compounds...

  6. Sequential reduction–oxidation for photocatalytic degradation of tetrabromobisphenol A: Kinetics and intermediates

    International Nuclear Information System (INIS)

    Guo, Yaoguang; Lou, Xiaoyi; Xiao, Dongxue; Xu, Lei; Wang, Zhaohui; Liu, Jianshe

    2012-01-01

    Highlights: ► Sequential photocatalytic reduction–oxidation degradation of TBBPA was firstly examined. ► Different atmospheres were found to have significant effect on debromination reaction. ► A possible sequential photocatalytic reduction–oxidation pathway was proposed. - Abstract: C-Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC–MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N 2 -saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a two-stage reductive debromination/subsequent oxidative decomposition process in the UV-TiO 2 system by changing the reaction atmospheres.

  7. Cross Section Measurements of the Reaction 23Na(p, γ)24Mg

    Science.gov (United States)

    Boeltzig, Axel; Deboer, Richard James; Macon, Kevin; Wiescher, Michael; Best, Andreas; Imbriani, Gianluca; Gyürky, György; Strieder, Frank

    2017-09-01

    The reaction 23Na(p, γ)24Mg can provide a link from the NeNa to the MgAl cycle in stellar burning and is therefore of interest in nuclear astrophysics. To determine the reaction rates at stellar temperatures, new cross section measurements at low proton energies have been performed recently, and further experiments are underway. The current cross section data implies that the reaction rate up to temperatures of 1 GK is determined by a few narrow resonances and direct capture. Complementary to these experimental efforts at low proton energies, cross section measurements at higher energies can help to constrain the direct capture and broad resonance contributions to the cross section and reduce the uncertainty of the extrapolation towards stellar energies. In this paper we report an experiment to measure the 23Na(p, γ)24Mg cross section with a solid target setup at the St. ANA 5U accelerator at the University of Notre Dame. The experiment and the current status of data analysis will be described. This work benefited from support by the National Science Foundation under Grant No. PHY-1430152 (JINA-CEE), the Nuclear Science Laboratory (NSL), the Istituto Nazionale di Fisica Nucleare (INFN), and the Gran Sasso Science Institute (GSSI).

  8. Investigation of the 10B(n,t) reaction cross-section in the subthreshold energy region

    International Nuclear Information System (INIS)

    Kornilov, N.V.; Balitskij, A.V.; Baryba, V.Ya.; Druzhnin, V.I.; Kagalenko, A.B.; Kharitonov, A.K.

    1991-01-01

    The 10 B(n,t) reaction cross-section has been measured at incident neutron energies of 0.025 eV, 420 KeV and 5 MeV. A detailed description of the experimental technique and the Monte Carlo simulation is given. It was confirmed that the cross-section of this reaction in the subthreshold region is non-zero. The recommended value of the 10 B(n,t) reaction cross-section at thermal is 8.5±2.0 mb. (author). 16 refs, 3 figs

  9. Cross-Aldol Reaction of Isatin with Acetone Catalyzed by Leucinol: A Mechanistic Investigation

    Czech Academy of Sciences Publication Activity Database

    Kabeshov, M. A.; Kysilka, O.; Rulíšek, Lubomír; Suleimanov, Y. V.; Bella, M.; Malkov, A. V.; Kočovský, Pavel

    2015-01-01

    Roč. 21, č. 34 (2015), s. 12026-12033 ISSN 0947-6539 R&D Projects: GA ČR(CZ) GA14-31419S Institutional support: RVO:61388963 Keywords : computational studies * enamines * isatins * oxazolidines * self-catalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.771, year: 2015

  10. Cross-sections of {sup 45}Sc(n,2n){sup 44m,g}Sc reaction from the reaction threshold to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Luo, J. [Hexi Univ., Zhangye (China). School of Physics and Electromechanical Engineering; Peking Univ., Beijing (China). State Key Laboratory of Nuclear Physics and Technology; Liu, R.; Jiang, L. [Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Nuclear Physics and Chemistry; Liu, Z.; Sun, G.; Ge, S. [Hexi Univ., Zhangye (China). School of Physics and Electromechanical Engineering

    2013-07-01

    Cross sections of {sup 45}Sc(n,2n){sup 44m,g}Sc reactions and their isomeric cross section ratios {sigma}{sub m}/{sigma}{sub g} have been measured at three neutron energies between 13.5 and 14.8 MeV using the activation technique. The pure cross section of the groundstate was then obtained by utilizing the absolute cross section of the metastable state and analysis methods of residual nuclear decay. The monoenergetic neutron beam was produced via the {sup 3}H(d, n){sup 4}He reaction. The cross sections were also estimated with the TALYS-1.2 nuclear model code using different level density options, at neutron energies varying from the reaction threshold to 20 MeV. Results are also discussed and compared with some corresponding values found in the literature. (orig.)

  11. Subcritical hydrothermal conversion of organic wastes and biomass. Reaction pathways

    Directory of Open Access Journals (Sweden)

    Alejandro Amadeus Castro Vega

    2007-01-01

    Full Text Available Hydrothermal conversion is a procedure which emulates organic matter’s natural conversion into bio-crude having physical and chemical properties analogous to petroleum. The artificial transformation of biomass requi- res previous knowledge of the main reaction routes and product availability. The main component of biomass (depolymerisation by hydrolysis is presented in hydrothermal cellulose conversion, producing oligosaccharides which exhibit dehydration and retro-aldol condensation reactions for transforming into furfurals and carboxylic acids. Other biomass components (such as lignin, proteins, and fat esters present both hydrolysis and pyrolysis reaction routes. As long as biomass mainly contains carbohydrates, subcritical hydrothermal conversion products and their wastes will be fundamentally analogous to those displaying cellulose. These substances have added- value by far surpassing raw material’s acquisition cost. When the main hydrothermal conversion products’ O/C, H/C molar ratios as reported in literature are plotted, an evolutionary tralectory for conversion products appears to be closely or even overlapped with fossil fuels’ geological evolution.

  12. Universal trend for heavy-ion total reaction cross sections at energies above the Coulomb barrier

    International Nuclear Information System (INIS)

    Tavares, O.A.P.; Medeiros, E.L.; Morcelle, V.

    2010-06-01

    Heavy-ion total reaction cross section measurements for more than one thousand one hundred reaction cases covering 61 target nuclei in the range 6 Li- 238 U, and 158 projectile nuclei from 2 H up to 84 Kr (mostly exotic ones) have been analysed in a systematic way by using an empirical, three-parameter formula which is applicable to cases for projectile kinetic energies above the Coulomb barrier. The analysis has shown that the average total nuclear binding energy per nucleon of the interacting nuclei and their radii are the chief quantities which describe the cross section patterns. A great number of cross section data (87%) has been quite satisfactorily reproduced by the proposed formula, therefore total reaction cross section predictions for new, not yet experimentally investigated reaction cases can be obtained within 25 percent (or much less) of uncertainty (author)

  13. Total reaction cross section for 12C+16O below the Coulomb barrier

    International Nuclear Information System (INIS)

    Cujec, B.; Barnes, C.A.

    1976-01-01

    The energy dependence of the total reaction cross section, sigma(E), for 12 C+ 16 0 has been measured over the range Esub(c.m.)=4-12 MeV, by detecting γ-rays from the various possible residual nuclei with two large NaI(Tl) detectors placed close to the target. This technique for measuring total reaction cross sections was explored in some detail and shown to yield reliable values for sigma(E). Although the principal emphasis of this work was placed on obtaining reliable cross sections, a preliminary study has been made of the suitability of various methods for extrapolating the cross section to still lower energies. The statistical model provides a good fit with a reasonable value for the strength function, 2 >/ =6.8x10 -2 , over the range Esub(c.m.)=6.5-12 MeV, but predicts cross sections which are much too large for Esub(c.m.)<6.5 MeV. Optical model fits at low energies are especially sensitive to the radius and diffuseness of the imaginary component of the potential and, since these are still poorly known at present, such extrapolations may be wrong by orders of magnitude. A simple barrier penetration model gives a moderately good fit to the data and seems to provide the safest extrapolation to lower energies at the present time. It is clear, however, that our knowledge of the heavy-ion reaction mechanism at low energies is incomplete, and that cross-section measurements at still lower energies are needed to establish the correct procedure for extrapolating heavy-ion reaction cross sections to low energies. (Auth.)

  14. Gamma-ray emission cross section from proton-incident spallation reaction

    International Nuclear Information System (INIS)

    Iga, Kiminori; Ishibashi, Kenji; Shigyo, Nobuhiro

    1996-01-01

    Gamma-ray emission double differential cross sections from proton-incident spallation reaction have been measured at incident energies of 0.8, 1.5 and 3.0 GeV with Al, Fe, In and Pb targets. The experimental results have been compared with calculate values of HETC-KFA2. The measured cross sections disagree with the calculated results in the gamma ray energies above 10 MeV. (author)

  15. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    An efficient synthesis of (-)-wodeshiol 1 is described. The key reactions include highly stereoselective aldol condensation of piperonal with the dianion of chiral oxazolidinone, subsequent intramolecular ring cyclization of the aldol product 8 and a diastereocontrolled oxygenation of dilactone 7 in good yield.

  16. Inhibition study of alanine aminotransferase enzyme using sequential online capillary electrophoresis analysis.

    Science.gov (United States)

    Liu, Lina; Chen, Yuanfang; Yang, Li

    2014-12-15

    We report the study of several inhibitors on alanine aminotransferase (ALT) enzyme using sequential online capillary electrophoresis (CE) assay. Using metal ions (Na(+) and Mg(2+)) as example inhibitors, we show that evolution of the ALT inhibition reaction can be achieved by automatically and simultaneously monitoring the substrate consumption and product formation as a function of reaction time. The inhibition mechanism and kinetic constants of ALT inhibition with succinic acid and two traditional Chinese medicines were derived from the sequential online CE assay. Our study could provide valuable information about the inhibition reactions of ALT enzyme. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Cross-diffusional effect in a telegraph reaction diffusion Lotka-Volterra two competitive system

    International Nuclear Information System (INIS)

    Abdusalam, H.A; Fahmy, E.S.

    2003-01-01

    It is known now that, telegraph equation is more suitable than ordinary diffusion equation in modelling reaction diffusion in several branches of sciences. Telegraph reaction diffusion Lotka-Volterra two competitive system is considered. We observed that this system can give rise to diffusive instability only in the presence of cross-diffusion. Local and global stability analysis in the cross-diffusional effect are studied by considering suitable Lyapunov functional

  18. Multiple and sequential data acquisition method: an improved method for fragmentation and detection of cross-linked peptides on a hybrid linear trap quadrupole Orbitrap Velos mass spectrometer.

    Science.gov (United States)

    Rudashevskaya, Elena L; Breitwieser, Florian P; Huber, Marie L; Colinge, Jacques; Müller, André C; Bennett, Keiryn L

    2013-02-05

    The identification and validation of cross-linked peptides by mass spectrometry remains a daunting challenge for protein-protein cross-linking approaches when investigating protein interactions. This includes the fragmentation of cross-linked peptides in the mass spectrometer per se and following database searching, the matching of the molecular masses of the fragment ions to the correct cross-linked peptides. The hybrid linear trap quadrupole (LTQ) Orbitrap Velos combines the speed of the tandem mass spectrometry (MS/MS) duty circle with high mass accuracy, and these features were utilized in the current study to substantially improve the confidence in the identification of cross-linked peptides. An MS/MS method termed multiple and sequential data acquisition method (MSDAM) was developed. Preliminary optimization of the MS/MS settings was performed with a synthetic peptide (TP1) cross-linked with bis[sulfosuccinimidyl] suberate (BS(3)). On the basis of these results, MSDAM was created and assessed on the BS(3)-cross-linked bovine serum albumin (BSA) homodimer. MSDAM applies a series of multiple sequential fragmentation events with a range of different normalized collision energies (NCE) to the same precursor ion. The combination of a series of NCE enabled a considerable improvement in the quality of the fragmentation spectra for cross-linked peptides, and ultimately aided in the identification of the sequences of the cross-linked peptides. Concurrently, MSDAM provides confirmatory evidence from the formation of reporter ions fragments, which reduces the false positive rate of incorrectly assigned cross-linked peptides.

  19. Evaluation of the D(γ,n) reaction cross section

    International Nuclear Information System (INIS)

    Murata, T.

    1994-01-01

    Evaluation was performed for the cross section of photo-disintegration of Deuteron in the photon energy range between the threshold energy of the reaction (2.224 MeV) and pion production threshold (140 MeV). Angular distributions of the emitted neutrons were also evaluated. (author)

  20. Sequential and double sequential fission observed in heavy ion interaction of (11.67 MeV/u)197Au projectile with 197Au target

    International Nuclear Information System (INIS)

    Nasir, Tabassum; Khan, Ehsan Ullah; Baluch, Javaid Jahan; Shafi-Ur-Rehman; Matiullah; Rafique, Muhammad

    2009-01-01

    The heavy ion interaction of 11.67 MeV/u 197 Au+ 197 Au has been investigated using mica as a passive detector. By employing Solid State Nuclear Track Detection Technique the data of elastic scattering as well as inelastic reaction channel was collected. The off-line data analysis of multi-pronged events was performed by measuring the three-dimensional geometrical coordinates of correlated tracks on event-by-event basis. Multi pronged events observed in this reaction were due to sequential and double sequential fission. Using a computer code PRONGY based on the procedure of internal calibration, it was possible to derive quantities like mass transfer, total kinetic energy loss and scattering angles. (author)

  1. Universal trend for heavy-ion total reaction cross sections at energies above the Coulomb barrier

    Energy Technology Data Exchange (ETDEWEB)

    Tavares, O.A.P.; Medeiros, E.L., E-mail: emil@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Morcelle, V. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica

    2010-06-15

    Heavy-ion total reaction cross section measurements for more than one thousand one hundred reaction cases covering 61 target nuclei in the range {sup 6}Li-{sup 238}U, and 158 projectile nuclei from {sup 2}H up to {sup 84}Kr (mostly exotic ones) have been analysed in a systematic way by using an empirical, three-parameter formula which is applicable to cases for projectile kinetic energies above the Coulomb barrier. The analysis has shown that the average total nuclear binding energy per nucleon of the interacting nuclei and their radii are the chief quantities which describe the cross section patterns. A great number of cross section data (87%) has been quite satisfactorily reproduced by the proposed formula, therefore total reaction cross section predictions for new, not yet experimentally investigated reaction cases can be obtained within 25 percent (or much less) of uncertainty (author)

  2. 6,7Li + 28Si total reaction cross sections at near barrier energies

    International Nuclear Information System (INIS)

    Pakou, A.; Musumarra, A.; Pierroutsakou, D.; Alamanos, N.; Assimakopoulos, P.A.; Divis, N.; Doukelis, G.; Gillibert, A.; Harissopulos, S.; Kalyva, G.; Kokkoris, M.; Lagoyannis, A.; Mertzimekis, T.J.; Nicolis, N.G.; Papachristodoulou, C.; Perdikakis, G.; Roubos, D.; Rusek, K.; Spyrou, S.; Zarkadas, Ch.

    2007-01-01

    Total reaction cross section measurements for the 6,7 Li + 28 Si systems have been performed at near-barrier energies. The results indicate that, with respect to the potential anomaly at barrier, 6 Li and 7 Li on light targets exhibit similar energy dependence on the imaginary potential. Comparisons are made with 6,7 Li cross sections on light and heavy targets, extracted via previous elastic scattering measurements and also with CDCC calculations. Energy dependent parametrisations are also obtained for total reaction cross sections of 6,7 Li on Si, as well as on any target, at near barrier energies

  3. Alpha-induced reaction cross section measurements on 151Eu for the astrophysical γ-process

    International Nuclear Information System (INIS)

    Gyuerky, Gy.; Elekes, Z.; Farkas, J.; Fueloep, Zs.; Halasz, Z.; Kiss, G.G.; Somorjai, E.; Szuecs, T.; Gueraya, R.T.; Oezkana, N.

    2010-01-01

    Compete text of publication follows. The astrophysical γ-process is the main production mechanism of the p-isotopes, the heavy, proton-rich nuclei not produced by neutron capture reactions in the astrophysical sand r-processes. The γ-process is a poorly known process of nucleosynthesis, the models are not able to reproduce well the p-isotope abundances observed in nature. Experimental data on nuclear reactions involved in γ-process reaction networks are clearly needed to provide input for a more reliable γ-process network calculation. As a continuation of our systematic study of reactions relevant for the γ-process, the cross sections of the 151 Eu(α, γ) 155 Tb and 151 Eu(α,n) 154 Tb reactions have been measured. These reactions have been chosen because α-induced cross section data in the region of heavy p-isotopes are almost completely missing although the calculations show a strong influence of these cross section on the resulting abundances. Since the reaction products of both reactions are radioactive, the cross sections have been measured using the activation technique. The targets have been prepared by evaporating Eu 2 O 3 enriched to 99.2% in 151 Eu onto thin Al foils. The target thicknesses have been measured by weighing and Rutherford Backscattering Spectroscopy. The targets have been irradiated by typically 1-2 μA intensity α-beams from the cyclotron of ATOMKI. The investigated energy range between 12 and 17 MeV was covered with 0.5 MeV steps. This energy range is somewhat higher than the astrophysically relevant one, but the cross section at astrophysical energies is so low that the measurements are not possible there. The γ- activity of the reaction products has been measured by a shielded HPGe detector. The absolute efficiency of the detector was measured with several calibration sources. Since 154 Tb has two long lived isomeric states, partial cross sections of the 151 Eu(α,n) 154 Tb reaction leading to the ground and isomeric states

  4. Determination of reaction cross sections with the aid of α decay in the 12C, 14C + 209Bl reactions

    International Nuclear Information System (INIS)

    Hick, H.

    1980-01-01

    For the reactions 14 C + 209 Bi and 12 C + 209 Bi excitation functions at energies in the range between 57 MeV and 76 MeV are measured. Radiative capture and particle evaporation cross sections were determined by means of α-spectroscopy, and fission cross sections were determined by the measurement of the γ-radiation after the β-decay of the fission products. For the radiative capture for the reaction 14 C + 209 Bi upper limits for the cross section from 21 nbarn to 178 nbarn in the energy interval 61-74 MeV were determined. The fission cross sections were 80 +- 30 mbarn at 490 +- 200 mbarn at 76 MeV. For the reaction 12 C + 209 Bi three new α-lines were found. They were due to the slope at their excitation functions assigned to the decay of isomeric states of following nuclei: 219 Ac Esub(α) = 9419 +- 4 keV Tsub(1/2) = 830 +- 100/μsec, 218 Ac Esub(α) = 9271 +- 4 keV Tsub(1/2) = 810 +- 70/μsec, 217 Ac Eα = 9730 +- 5 keV Tsub(1/2) = 970 +- 190/μsec. For the reactions respectively 12 C + 209 Bi calculations using the statistical model code Grogi of J. Gilat are performed. The calculated branchings of the evaporation channels were compared with the experiment. (orig./HSI) [de

  5. Cross-Sequential Results on Creativity Development in Childhood Within two Different School Systems: Divergent Performances in Luxembourg Versus German Kindergarten and Elementary School Students

    Directory of Open Access Journals (Sweden)

    Günter Krampen

    2012-08-01

    Full Text Available The aim of the study is conducting methodologically sound, cross-sequential analyses of the creativity development of children attending different school systems. Culture-free tests of creativity (ideational fluency and flexibility and intelligence were administered in 5 cohorts (two kindergarten and first three elementary school years, which were retested in three consecutive years. Samples include 244 Luxembourg and 312 German children enrolled in educational systems with obligatory kindergarten and 6-year comprehensive elementary school versus optional kindergarten, 4-year comprehensive elementary school and educational placement thereafter. Results demonstrate (1 linear increases in intelligence, (2 declines of divergent performances after school enrollment in both samples, (3 increases in divergent performances up to the 5th elementary school year in Luxembourg and up to the 3rd elementary school year in Germany (i.e., the next to last school year before educational placement followed by a second creativity slump. Cross-sequential results confirm discontinuities in the development of divergent productions in childhood.

  6. Differential cross section measurement for the {sup 6}Li(n,t){sup 4}He Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Guohui, Zhang; Guoyou, Tang; Jinxiang, Chen; Zhaomin, Shi [Beijing Univ., Beijing (China). Inst. of Heavy Ion Physics and MOE Key Laboratory of Heavy Ion Physics; Zemin, Chen [Tsinghua Univ., Beijing (China). Dept. of Physics; Gledenov, Yu M; Sedysheva, M; Khuukhenkhuu, G [Joint Institute for Nuclear Research, Frank Laboratory of Neutron Physics, Dubna (Russian Federation)

    2002-06-01

    The differential cross sections and integrated cross sections of the {sup 6}Li(n,t){sup 4}He reaction were measured at 1.85 and 2.67 MeV by using a gridded ionization chamber. Neutrons were produced through the T(p, n){sup 3}He reaction. The absolute neutron flux was determined through the {sup 238}U(n, f) reaction. Present results are compared with existing data.

  7. Suzuki-Miyaura cross-coupling reactions in aqueous media: Green and sustainable syntheses of biaryls

    KAUST Repository

    Polshettiwar, Vivek; Decottignies, Audrey; Len, Christophe; Fihri, Aziz

    2010-01-01

    Carbon-carbon cross-coupling reactions are among the most important processes in organic chemistry, and Suzuki-Miyaura reactions are among the most widely used protocols for the formation of carbon-carbon bonds. These reactions are generally

  8. Crossed molecular beam study of the reactions of methyl bromide with potassium and rubidium

    International Nuclear Information System (INIS)

    Pang, H.F.; Wu, K.T; Bernstein, R.B.

    1978-01-01

    Using the crossed molecular beam method, the yields of the alkali halide product MBr from the exoergic reactions CH 3 Br+M→MBr+CH 3 (MequivalentK, Rb) have been measured as a function of relative translational energy up to 0.9 and 1.3 eV for K and Rb, respectively. Supersonic seeded beams of CH 3 Br are crossed with thermal alkali beams and the in-plane angular distribution of MBr measured at different average relative translational energies E-bar/sub tr/. The reactions are found to have appreciable energy thresholds, 0.24 +- 0.06 and 0.20 +- 0.06 eV for the K and Rb-reactions, respectively. The product yields increase monotonically with E-bar/sub tr/ above threshold. The postthreshold energy dependence of the cross sections has been obtained by deconvoluting these data from the crossed beam velocity distributions. The MBr angular distributions are characteristic of a direct, rebound mechanism, with a large fraction of the available energy going into product translation. The average recoil energy E-bar'/sub tr/ of the product MBr increases linearly with E-bar/sub tr/ (dE-bar'/sub tr//dE-bar/sub tr/approx. =0.73). The present data for the M+CH 3 Br systems are compared with previous results for the analogous CH 3 I reactions and with predictions of several theoretical models. The significantly higher activation barriers for the CH 3 Br reactions account for their smaller thermal reaction rate constants relative to the analogous CH 3 I reactions

  9. High transfer cross sections from reactions with 254Es

    International Nuclear Information System (INIS)

    Schaedel, M.; Bruechle, W.; Bruegger, M.; Gaeggeler, H.; Moody, J.; Schardt, D.; Suemmerer, K.; Hulet, E.K.; Dougan, A.D.; Dougan, R.J.; Landrum, J.H.; Lougheed, R.W.; Wild, J.F.; O'Kelly, G.D.

    1985-08-01

    We report radiochemically determined cross sections for the heaviest known actinides produced in transfer reactions of 101 MeV 16 O, 98 MeV 18 O and 127 MeV 22 Ne with 254 Es as a target. A comparison with data for similar transfers from 248 Cm targets is made. Transfer cross sections are extrapolated for the production of unknown, neutron-rich isotopes of elements 101 through 105, and the unique potential of 254 Es as a target to make these exotic nuclei accessible is demonstrated. (orig.)

  10. Atlas of giant dipole resonances. Parameters and graphs of photonuclear reaction cross sections

    International Nuclear Information System (INIS)

    Varlamov, A.V.; Varlamov, V.V.; Rudenko, D.S.; Stepanov, M.E.

    1999-01-01

    Parameters of giant dipole resonances (GDR) observed in photonuclear reaction cross sections using various beams of incident photons are presented. Data, given for 200 stable isotopes from 2 H to 243 Am including their natural compositions, were collected from papers published over the years 1951-1996. GDR parameters, such as energy positions, amplitudes and widths, are included into the table and organized by element, isotope and reaction. Graphs of the majority of the photonuclear reaction cross sections, included in the international nuclear data library EXFOR by the end of 1998, are presented. The graphs are provided for 182 stable isotopes and natural compositions. (author)

  11. Cross sections and rate coefficients for charge exchange reactions of protons with hydrocarbon molecules

    International Nuclear Information System (INIS)

    Janev, R.K.; Kato, T.; Wang, J.G.

    2001-05-01

    The available experimental and theoretical cross section data on charge exchange processes in collisions of protons with hydrocarbon molecules have been collected and critically assessed. Using well established scaling relationships for the charge exchange cross sections at low and high collision energies, as well as the known rate coefficients for these reactions in the thermal energy region, a complete cross section database is constructed for proton-C x H y charge exchange reactions from thermal energies up to several hundreds keV for all C x H y molecules with x=1, 2, 3 and 1 ≤ y ≤ 2x + 2. Rate coefficients for these charge exchange reactions have also been calculated in the temperature range from 0.1 eV to 20 keV. (author)

  12. Neutron induced reaction cross-sections on 115In at around 14 MeV

    International Nuclear Information System (INIS)

    Csikai, J.; Lantos, Z.; Buczko, C.M.; Sudar, S.

    1990-01-01

    A systematic investigation was carried out on 115 In isotope to determine the contribution of different reactions to the total non-elastic cross-section in the 13.43 and 14.84 MeV range. All the major component cross-sections of σ NE were measured with exception of the σ g (n,n'). In the knowledge of σ NE , the energy dependence of σ g (n,n') could be deduced. The isomeric cross section ratios both for (n,2n) and (n,n') processes were also determined in the given energy range. The present experiment proves the dependence of σ m /(σ g +σ m ) ratio on the spin value (I m ) of the isomeric state in (n,2n) reaction. Excitation functions of (n,2n), (n,n') and (n,ch) reactions were compared with results calculated by STAPRE code. (author). 37 refs, 5 figs, 4 tabs

  13. Fusion cross sections for 6,7Li + 24Mg reactions at energies below and above the barrier

    International Nuclear Information System (INIS)

    Ray, M.; Mukherjee, A.; Pradhan, M. K.; Kshetri, Ritesh; Sarkar, M. Saha; Dasmahapatra, B.; Palit, R.; Majumdar, I.; Joshi, P. K.; Jain, H. C.

    2008-01-01

    Measurement of fusion cross sections for the 6,7 Li + 24 Mg reactions by the characteristic γ-ray method has been done at energies from below to well above the respective Coulomb barriers. The fusion cross sections obtained from these γ-ray cross sections for the two systems are found to agree well with the total reaction cross sections at low energies. The relatively large difference between total cross sections and measured fusion cross sections at higher energies is consistent with the fact that other channels, in particular breakup, open up with an increase of bombarding energy. The breakup channel, however, appears not to have any influence on fusion cross sections. The critical angular momenta (l cr ) deduced from the fusion cross sections are found to have an energy dependence similar to other Li-induced reactions

  14. Asymmetric Total Synthesis of Ieodomycin B

    Directory of Open Access Journals (Sweden)

    Shuangjie Lin

    2017-01-01

    Full Text Available Ieodomycin B, which shows in vitro antimicrobial activity, was isolated from a marine Bacillus species. A novel asymmetric total synthetic approach to ieodomycin B using commercially available geraniol was achieved. The approach involves the generation of 1,3-trans-dihydroxyl at C-3 and C-5 positions via a Crimmins-modified Evans aldol reaction and a chelation-controlled Mukaiyama aldol reaction of a p-methoxybenzyl-protected aldehyde, as well as the generation of a lactone ring in a deprotection–lactonization one-pot reaction.

  15. Method of identification of unbranched chain reaction with cross termination of chain

    International Nuclear Information System (INIS)

    Poluehktov, V.A.; Begishev, I.R.

    1977-01-01

    Gas-phase chlorination of unsymmetrical difluoroethane initiated by gamma quanta of Co 60 has been studied. At decreased temperatures the only hydrogen is replaced by a chlorine atom. Over a wide range of ratios of the initial reagents, the reaction occurs with a chain rupture. An analysis of the kinetics of such a reaction provides a method for identification of an unbranched chain reaction with a cross-rupture of the chain

  16. Time scale of random sequential adsorption.

    Science.gov (United States)

    Erban, Radek; Chapman, S Jonathan

    2007-04-01

    A simple multiscale approach to the diffusion-driven adsorption from a solution to a solid surface is presented. The model combines two important features of the adsorption process: (i) The kinetics of the chemical reaction between adsorbing molecules and the surface and (ii) geometrical constraints on the surface made by molecules which are already adsorbed. The process (i) is modeled in a diffusion-driven context, i.e., the conditional probability of adsorbing a molecule provided that the molecule hits the surface is related to the macroscopic surface reaction rate. The geometrical constraint (ii) is modeled using random sequential adsorption (RSA), which is the sequential addition of molecules at random positions on a surface; one attempt to attach a molecule is made per one RSA simulation time step. By coupling RSA with the diffusion of molecules in the solution above the surface the RSA simulation time step is related to the real physical time. The method is illustrated on a model of chemisorption of reactive polymers to a virus surface.

  17. Measurement of total reaction cross sections of exotic neutron rich nuclei

    International Nuclear Information System (INIS)

    Mittig, W.; Chouvel, J.M.; Wen Long, Z.

    1987-01-01

    Total reaction cross-sections of neutron rich nuclei from C to Mg in a thick Si-target have been measured using the detection of the associated γ-rays in a 4Π-geometry. This cross-section strongly increases with neutron excess, indicating an increase of as much as 15% of the reduced strong absorption radius with respect to stable nuclei

  18. Reaction mechanisms and kinetics of processing glucose, xylose and glucose-xylose mixtures under hot compressed water conditions for predicting bio-crude composition

    DEFF Research Database (Denmark)

    Grigoras, Ionela; Toor, Saqib Sohail; Rosendahl, Lasse Aistrup

    Mechanisms for bio-crude formation during the conversion of glucose, xylose and glucose-xylose mixtures as biomass model compounds under hot compressed water conditions are investigated. Studies in literature have shown that the diverse products formed at the early stages of glucose or xylose...... conversion are 5-HMF, erythrose, glyceraldehyde, dihydroxyacetone, pyruvaldehyde, and saccharinic acids resulted through reactions such as dehydration, retro-aldol condensation and isomerization. However, these compounds are mostly water soluble compounds and lack the final steps towards formation of water...... insoluble components at longer reaction times. The effects of pressure, pH, catalyst and reaction time on the main products are examined thoroughly. The possible routes for the formation of oil compounds are developed....

  19. Spectroscopy of $^{46}$Ar by the $(t,p)$ two-neutron transfer reaction

    CERN Document Server

    Nowak, K.; Hellgartner, S.; Mücher, D.; Bildstein, V.; Diriken, J.; Elseviers, J.; Gaffney, L.P.; Gernhäuser, R.; Iwanicki, J.; Johansen, J.G.; Huyse, M.; Konki, J.; Kröll, T.; Krücken, T.; Lutter, R.; Orlandi, R.; Pakarinen, J.; Raabe, R.; Reiter, P.; Roger, T.; Schrieder, G.; Seidlitz, M.; Sorlin, O.; Van Duppen, P.; Warr, N.; De Witte, H.; Zielinska, M.

    2016-04-27

    States in the $N=28$ nucleus $^{46}$Ar have been studied by a two-neutron transfer reaction at REX-ISOLDE (CERN). A beam of radioactive $^{44}$ at an energy of 2.16~AMeV and a tritium loaded titanium target were used to populate $^{46}$ by the t($^{44}$,p) two-neutron transfer reaction. Protons emitted from the target were identified in the T-REX silicon detector array. The excitation energies of states in $^{46}$ have been reconstructed from the measured angles and energies of recoil protons. Angular distributions for three final states were measured and based on the shape of the differential cross section an excited state at 3695~keV has been identified as $J^\\pi = 0^+$. The angular differential cross section for the population of different states are compared to calculations using a reaction model employing both sequential and direct transfer of two neutrons. Results are compared to shell model calculations using state-of-the-art effective interactions.

  20. Cross sections and rate coefficients for charge exchange reactions of protons with hydrocarbon molecules

    Energy Technology Data Exchange (ETDEWEB)

    Janev, R.K.; Kato, T. [National Inst. for Fusion Science, Toki, Gifu (Japan); Wang, J.G. [Department of Physics and Astronomy, University of Georgia, Athens (United States)

    2001-05-01

    The available experimental and theoretical cross section data on charge exchange processes in collisions of protons with hydrocarbon molecules have been collected and critically assessed. Using well established scaling relationships for the charge exchange cross sections at low and high collision energies, as well as the known rate coefficients for these reactions in the thermal energy region, a complete cross section database is constructed for proton-C{sub x}H{sub y} charge exchange reactions from thermal energies up to several hundreds keV for all C{sub x}H{sub y} molecules with x=1, 2, 3 and 1 {<=} y {<=} 2x + 2. Rate coefficients for these charge exchange reactions have also been calculated in the temperature range from 0.1 eV to 20 keV. (author)

  1. Schreibersite: an effective catalyst in the formose reaction network

    Science.gov (United States)

    Pallmann, S.; Šteflová (neé Svobodová, J.; Haas, M.; Lamour, S.; Henß, A.; Trapp, O.

    2018-05-01

    We report on the ability of the meteoritic material schreibersite to catalyze the generation of higher sugars from simple carbohydrates in the formose reaction network. Since the analysis of carbonaceous meteorites like the Murchison meteorite it has become generally accepted that a substantial amount of organic material has been delivered to the early earth and, therefore, ought to be considered in scenarios for the origin(s) of life. Also for the open question of accessible phosphorus sources, an extraterrestrial material called schreibersite has been identified that is capable of releasing soluble and reactive phosphorus oxyanions that would react with organics to form for instance nucleotides and membrane associated molecules. We have reinvestigated this material using capillary electrophoresis to monitor its corrosion process in water and probed its ability to phosphorylate a wide range of organics. Although showing a poor reactivity of schreibersite, we have found that the material catalyzes the aldol reaction of small carbohydrates forming larger sugar molecules. This reaction in the formose reaction network is a prebiotically likely route to biologically relevant sugars. The results of our study present one of the first instances of connecting extraterrestrial material to prebiotic chemistry on the early earth.

  2. Independent control of the shape and composition of ionic nanocrystals through sequential cation exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Luther, Joseph Matthew; Zheng, Haimei; Sadtler, Bryce; Alivisatos, A. Paul

    2009-07-06

    Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

  3. Bioinspired synthesis of pentalene-based chromophores from an oligoketone chain.

    Science.gov (United States)

    Saito, Yuki; Higuchi, Masayuki; Yoshioka, Shota; Senboku, Hisanori; Inokuma, Yasuhide

    2018-04-24

    We report a bioinspired synthesis of 2,5-dihydropentalene-based chromophores from an aliphatic oligoketone bearing 1,3- and 1,4-diketone subunits. Unlike the natural polyketone sequence, fused five-membered rings were formed via an intramolecular aldol condensation. A subsequent Knoevenagel condensation reaction with malononitrile furnished a multiply cross-conjugated π-system with low-lying LUMO levels. Furthermore, pentalenes obtained from a non-conjugated aliphatic chain exhibited visible absorption and solid-state fluorescence.

  4. Effect of γ-ray emission on transuranium element production cross sections in heavy ion reactions

    International Nuclear Information System (INIS)

    Il'inov, A.S.; Oganesyan, Yu.Ts.; Cherepanov, E.A.

    1980-01-01

    The effect of competition of the γ ray emission with neutron evaporation and of compound nuclei fission induced by heavy ion reactions on the production cross sections for transuranium elements is considered. It is shown that taking account of γ ray emission leads to the broadening of the excitation functions of the (HI, xny) reactions such as 18 O+ 238 U, 40 Ar+ 206 Pb, 40 Ar+ 207 Pb and 40 Ar+ 208 Pb reactions and to the displacement of their maximum toward the higher energies as well as to an increase of the absolute cross sections which is especially strong close to the fusion barrier. Cross sections for the radiative capture of heavy ions by a heavy target nucleus in 40 Ar+ 206 Pb, 40 Ar+ 208 Pb, 48 Ca+ 204 Pb and 48 Ca+ 208 Pb reactions are estimated

  5. Sequential and double sequential fission observed in heavy ion interaction of (11.67 MeV/u){sup 197}Au projectile with {sup 197}Au target

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, Tabassum [Gomal University, Dera Ismail Khan (Pakistan). Dept. of Physics; Khan, Ehsan Ullah [COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan). Dept. of Physics; Baluch, Javaid Jahan [COMSATS Institute of Information Technology (CIIT), Abbottabad, (Pakistan). Dept. of Environmental Sciences; Shafi-Ur-Rehman, [PAEC, Dera Ghazi Khan (Pakistan). ISL Project; Matiullah, [PINSTECH, Nilore, Islamabad (Pakistan). Physics Div.; Rafique, Muhammad [University of Azad Jammu and Kashmir, Muzaffarabad (Pakistan). Dept. of Physics

    2009-09-15

    The heavy ion interaction of 11.67 MeV/u {sup 197}Au+ {sup 197}Au has been investigated using mica as a passive detector. By employing Solid State Nuclear Track Detection Technique the data of elastic scattering as well as inelastic reaction channel was collected. The off-line data analysis of multi-pronged events was performed by measuring the three-dimensional geometrical coordinates of correlated tracks on event-by-event basis. Multi pronged events observed in this reaction were due to sequential and double sequential fission. Using a computer code PRONGY based on the procedure of internal calibration, it was possible to derive quantities like mass transfer, total kinetic energy loss and scattering angles. (author)

  6. Slips of action and sequential decisions: a cross-validation study of tasks assessing habitual and goal-directed action control

    Directory of Open Access Journals (Sweden)

    Zsuzsika Sjoerds

    2016-12-01

    Full Text Available Instrumental learning and decision-making rely on two parallel systems: a goal-directed and a habitual system. In the past decade, several paradigms have been developed to study these systems in animals and humans by means of e.g. overtraining, devaluation procedures and sequential decision-making. These different paradigms are thought to measure the same constructs, but cross-validation has rarely been investigated. In this study we compared two widely used paradigms that assess aspects of goal-directed and habitual behavior. We correlated parameters from a two-step sequential decision-making task that assesses model-based and model-free learning with a slips-of-action paradigm that assesses the ability to suppress cue-triggered, learnt responses when the outcome has been devalued and is therefore no longer desirable. Model-based control during the two-step task showed a very moderately positive correlation with goal-directed devaluation sensitivity, whereas model-free control did not. Interestingly, parameter estimates of model-based and goal-directed behavior in the two tasks were positively correlated with higher-order cognitive measures (e.g. visual short-term memory. These cognitive measures seemed to (at least partly mediate the association between model-based control during sequential decision-making and goal-directed behavior after instructed devaluation. This study provides moderate support for a common framework to describe the propensity towards goal-directed behavior as measured with two frequently used tasks. However, we have to caution that the amount of shared variance between the goal-directed and model-based system in both tasks was rather low, suggesting that each task does also pick up distinct aspects of goal-directed behavior. Further investigation of the commonalities and differences between the model-free and habit systems as measured with these, and other, tasks is needed. Also, a follow-up cross-validation on the neural

  7. Cross section measurements of proton capture reactions on Se isotopes relevant to the astrophysical p process

    Science.gov (United States)

    Foteinou, V.; Harissopulos, S.; Axiotis, M.; Lagoyannis, A.; Provatas, G.; Spyrou, A.; Perdikakis, G.; Zarkadas, Ch.; Demetriou, P.

    2018-03-01

    Cross sections of proton capture reactions on 74Se, 78Se, and 80Se have been measured at incident beam energies from 2 to 6 MeV, 1.7 to 3 MeV, and 1.5 to 3.5 MeV, respectively. In the case of Se,8078, cross sections were obtained from in-beam γ -angular distribution measurements, whereas for the 74Se isotope they were derived from off-beam activity measurements. The measured cross sections were compared with calculations performed with the nuclear reaction code talys (version 1.6). A good agreement between theory and experiment was found. Astrophysical S factors and reaction rates deduced from the experimental and calculated cross sections were also compared and the impact of different nuclear ingredients in the calculations on the reaction rates was investigated. It was found that, for certain combinations of nuclear input models, the reaction rates obtained at temperatures relevant to p -process nucleosynthesis differ by a factor 2 at the most, differences that are well within the acceptable deviations of calculated p -nuclei abundances and observations.

  8. Vibrational state-resolved differential cross sections for the D + H2 → DH + H reaction

    International Nuclear Information System (INIS)

    Continetti, R.E.

    1989-11-01

    In this thesis, crossed-molecular-beams studies of the reaction D + H 2 → DH + H at collision energies of 0.53 and 1.01 eV are reported. Chapter 1 provides a survey of important experimental and theoretical studies on the dynamics of the hydrogen exchange reaction. Chapter 2 discusses the development of the excimer-laser photolysis D atom beam source that was used in these studies and preliminary experiments on the D + H 2 reaction. In Chapter 3, the differential cross section measurements are presented and compared to recent theoretical predictions. The measured differential cross sections for rotationally excited DH products showed significant deviations from recent quantum scattering calculations, in the first detailed comparison of experimental and theoretical differential cross sections. These results indicate that further work on the H 3 potential energy surface, particularly the bending potential, is in order

  9. Measurement of reaction cross sections of fission products induced by DT neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Daisuke; Murata, Isao; Takahashi, Akito [Osaka Univ., Suita (Japan)

    1998-03-01

    With the view of future application of fusion reactor to incineration of fission products, we have measured the {sup 129}I(n,2n){sup 128}I reaction cross section by DT neutrons with the activation method. The measured cross section was compared with the evaluated nuclear data of JENDL-3.2. From the result, it was confirmed that the evaluation overestimated the cross section by about 20-40%. (author)

  10. Cross Sections for Neutron-induced Reactions on Actinide Targets Extracted from Surrogate Experiments: A Status Report

    International Nuclear Information System (INIS)

    Escher, J.E.; Burke, J.T.; Dietrich, F.S.; Lesher, S.R.; Scielzo, N.D.; Thompson, I.J.; Younes, W.

    2009-01-01

    The Surrogate nuclear reactions method, an indirect approach for determining cross sections for compound-nuclear reactions involving difficult-to-measure targets, is reviewed. Focusing on cross sections for neutron-induced reactions on actinides, we review the successes of past and present applications of the method and assess its uncertainties and limitations. The approximations used in the analyses of most experiments work reasonably well for (n,f) cross sections for neutron energies above 1-2 MeV, but lead to discrepancies for low-energy (n,f) reactions, as well as for (n,γ) applications. Correcting for some of the effects neglected in the approximate analyses leads to improved (n,f) results. We outline steps that will further improve the accuracy and reliability of the Surrogate method and extend its applicability to reactions that cannot be approached with the present implementation of the method.

  11. Cross Sections for Neutron-induced Reactions on Actinide Targets Extracted from Surrogate Experiments: A Status Report

    Energy Technology Data Exchange (ETDEWEB)

    Escher, J E; Burke, J T; Dietrich, F S; Lesher, S R; Scielzo, N D; Thompson, I J; Younes, W

    2009-10-01

    The Surrogate nuclear reactions method, an indirect approach for determining cross sections for compound-nuclear reactions involving difficult-to-measure targets, is reviewed. Focusing on cross sections for neutron-induced reactions on actinides, we review the successes of past and present applications of the method and assess its uncertainties and limitations. The approximations used in the analyses of most experiments work reasonably well for (n,f) cross sections for neutron energies above 1-2 MeV, but lead to discrepancies for low-energy (n,f) reactions, as well as for (n,{gamma}) applications. Correcting for some of the effects neglected in the approximate analyses leads to improved (n,f) results. We outline steps that will further improve the accuracy and reliability of the Surrogate method and extend its applicability to reactions that cannot be approached with the present implementation of the method.

  12. Activation cross section of 63Cu(n,α)60Co reaction

    International Nuclear Information System (INIS)

    Lu Hanlin; Zhao Wenrong; Yu Weixiang; Yuan Xialin

    1990-01-01

    The mechanical properties of copper during the irradiation with intensive neutron fluence rate are significant for the safe operation of D-T fusion power reactors. The cross sections measured by activation method show a large discrepancy from 36 to 54 mb in 14 MeV region. The cross sections of 69 Cu(n, α) 60 Co reaction were measured by activation method. Two irradiations were carried out at the Cockcroft-wallon and Van de Graaff accelerators of CIAE using T(d, n) 4 He reaction to produce neutrons. The activities of 24 Na and 60 Co γ-rays for monitor and sample foils were determined absolutely by a calibrated Ge(Li) detector system with an accuracy better than 1%. The present results are compared with the others

  13. Production cross sections of proton-induced reactions on yttrium

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Sung-Chul; Song, Tae-Yung; Lee, Young-Ouk [Nuclear Data Center, Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Kim, Guinyun, E-mail: gnkim@knu.ac.kr [Department of Physics, Kyungpook National University, Daegu 41566 (Korea, Republic of)

    2017-05-01

    The production cross sections of residual radionuclides such as {sup 86,88,89g}Zr, {sup 86g,87m,87g,88}Y, {sup 83g,85g}Sr, and {sup 83,84g}Rb in the {sup 89}Y(p,x) reaction were measured using a stacked-foil activation and offline γ-ray spectrometric technique with proton energies of 57 MeV and 69 MeV at the 100 MeV proton linac in the Korea Multi-purpose Accelerator Complex (KOMAC), Gyeongju, Korea. The induced activities of the activated samples were measured using a high purity germanium (HPGe) detector, and the proton flux was determined using the {sup nat}Cu(p,x){sup 62}Zn reaction. The measured data was compared with other experimental data and the data from the TENLD-2015 library based on the TALYS code. The present results are generally lower than those in literature, but are found to be in agreement with the shape of the excitation functions. The integral yields for the thick target using the measured cross sections are given.

  14. Aqueous microwaves assisted cross-coupling reactions applied to unprotected nucleosides.

    Directory of Open Access Journals (Sweden)

    CHRISTOPHE eLEN

    2015-02-01

    Full Text Available Nucleoside analogues have attracted much attention due to their potential biological activities. Amongst all synthetic nucleosides, C5-modified pyrimidines and C7- or C8-modified purines have mostly been prepared using palladium cross-coupling reactions and then studied as antitumoral and antiviral agents. Our objective is to focus this review on the Suzuki-Miyaura and on the Heck cross-couplings of nucleosides using microwave irradiations which are an alternative technology compatible with green chemistry and sustainable development.

  15. Evaluation of photonuclear reaction cross-sections using the reduction method for large systematic uncertainties

    International Nuclear Information System (INIS)

    Varlamov, V.V.; Efimkin, N.G.; Ishkhanov, B.S.; Sapunenko, V.V.

    1994-12-01

    The authors describe a method based on the reduction method for the evaluation of photonuclear reaction cross-sections obtained under conditions where there are large systematic uncertainties (different instrumental functions, calibration and normalization errors). The evaluation method involves using the actual instrumental function (photon spectrum) of each individual experiment to reduce the data to a representation generated by an instrumental function of better quality. The objective is to find the most reasonably achievable monoenergetic representation of the information on the reaction cross-section derived from the results of various experiments and to take into account the calibration and normalization errors in these experiments. The method was used to obtain the evaluated total photoneutron reaction cross-section (γ,xn) for a large number of nuclei. Data obtained for 16 O and 208 Pb are presented. (author). 36 refs, 6 figs, 4 tabs

  16. The Glauber model and heavy ion reaction and elastic scattering cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Mehndiratta, Ajay [Physics Department, Indian Institute of Technology, Guwahati (India); Shukla, Prashant, E-mail: pshukla@barc.gov.in [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400094 (India)

    2017-05-15

    We revisit the Glauber model to study the heavy ion reaction cross sections and elastic scattering angular distributions at low and intermediate energies. The Glauber model takes nucleon–nucleon cross sections and nuclear densities as inputs and has no free parameter and thus can predict the cross sections for unknown systems. The Glauber model works at low energies down to Coulomb barrier with very simple modifications. We present new parametrization of measured total cross sections as well as ratio of real to imaginary parts of the scattering amplitudes for pp and np collisions as a function of nucleon kinetic energy. The nuclear (charge) densities obtained by electron scattering form factors measured in large momentum transfer range are used in the calculations. The heavy ion reaction cross sections are calculated for light and heavy systems and are compared with available data measured over large energy range. The model gives excellent description of the data. The elastic scattering angular distributions are calculated for various systems at different energies. The model gives good description of the data at small momentum transfer but the calculations deviate from the data at large momentum transfer.

  17. Cross-sections of spallation residues produced in Proton –Induced reactions

    International Nuclear Information System (INIS)

    Al-Haydari, A.; Khan, A.A.; Abdul Ganai, A.; Hassan, G.S.

    2013-01-01

    The recent available GSI data for proton-induced spallation reactions by using inverse kinematics at different energies are analyzed for different reactions in terms of the percolation model together with the intranuclear cascade model (MCAS). The simulation results obtained for the cross sections of production of light ions and isotopes as a function of mass and charge number is calculated. Results of calculations are in good agreement with experiment

  18. Dihydroazulene photoswitch operating in sequential tunneling regime

    DEFF Research Database (Denmark)

    Broman, Søren Lindbæk; Lara-Avila, Samuel; Thisted, Christine Lindbjerg

    2012-01-01

    to electrodes so that the electron transport goes by sequential tunneling. To assure weak coupling, the DHA switching kernel is modified by incorporating p-MeSC6H4 end-groups. Molecules are prepared by Suzuki cross-couplings on suitable halogenated derivatives of DHA. The synthesis presents an expansion of our......, incorporating a p-MeSC6H4 anchoring group in one end, has been placed in a silver nanogap. Conductance measurements justify that transport through both DHA (high resistivity) and VHF (low resistivity) forms goes by sequential tunneling. The switching is fairly reversible and reenterable; after more than 20 ON...

  19. Triple-differential cross sections of the (π+/,pp) reaction on lithium isotopes

    International Nuclear Information System (INIS)

    Rieder, R.; Barnes, P.D.; Bassalleck, B.

    1985-01-01

    The (π + ,pp) reactions on 6 Li and 7 Li have been studied at T/sub π/ = 59.4 MeV with high resolution. The first triple-differential cross sections for these reactions are presented. The data are fitted to a T-matrix and compared to the π + d → pp reaction. A model in which the pion is absorbed on a 3 S 1 (pn) pair in the lithium nucleus describes many features of the data very well. An extrapolation of our data into unmeasured regions of phase space suggests that about 60% of the pion absorption cross section on 6 Li at 59.4 MeV goes into the (π + ,pp) channel. One surprising feature of the data is that the 6 Li(π + ,pp) 4 He (2 - ) transition at 22.1 MeV excitation is strongly populated, similar to what is observed in the 6 Li(d,α) 4 He reaction. This transition involves removing one nucleon from the 1p shell and one from the 1s shell. 25 refs., 15 figs., 3 tabs

  20. Cross-section of the reaction {sup 7}Li(p,n){sup 7}Be close to the threshold

    Energy Technology Data Exchange (ETDEWEB)

    Shorin, V S [Institute of Physics and Power Engineering, Obninsk (Russian Federation)

    1997-06-01

    The status of data on the cross-section of the reaction {sup 7}Li(p,n){sup 7}Be close to the threshold is reviewed. On the basis of recent data on the cross-section of the inverse reaction {sup 7}Be(n,p){sup 7}Li and certain theoretical models, an evaluation is performed of the total cross-section of the {sup 7}Li(p,n)-reaction in the proton energy region up to 2 MeV. (author). 16 refs, 1 fig., 1 tab.

  1. (n,2n) reaction cross-sections at 14 MeV

    Indian Academy of Sciences (India)

    The need for fast neutron-induced reaction cross-section data has been increasing in several applied fields; for example, biomedical applications such as production of radioisotopes and cancer therapy, accelerator-driven transmutation of long-lived radioactive nuclear wastes to short-lived or stable isotopes by secondary ...

  2. Pd-Catalyzed Cross-Coupling Reactions of Amides and Aryl Mesylates

    Science.gov (United States)

    Dooleweerdt, Karin; Fors, Brett P.; Buchwald, Stephen L.

    2010-01-01

    A catalyst, based on a biarylphosphine ligand, for the Pd-catalyzed cross-coupling reactions of amides and aryl mesylates is described. This system allows an array of aryl and heteroaryl mesylates to be transformed into the corresponding N-arylamides in moderate to excellent yields. PMID:20420379

  3. 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

  4. Estimation of (n,f) Cross-Sections by Measuring Reaction Probability Ratios

    Energy Technology Data Exchange (ETDEWEB)

    Plettner, C; Ai, H; Beausang, C W; Bernstein, L A; Ahle, L; Amro, H; Babilon, M; Burke, J T; Caggiano, J A; Casten, R F; Church, J A; Cooper, J R; Crider, B; Gurdal, G; Heinz, A; McCutchan, E A; Moody, K; Punyon, J A; Qian, J; Ressler, J J; Schiller, A; Williams, E; Younes, W

    2005-04-21

    Neutron-induced reaction cross-sections on unstable nuclei are inherently difficult to measure due to target activity and the low intensity of neutron beams. In an alternative approach, named the 'surrogate' technique, one measures the decay probability of the same compound nucleus produced using a stable beam on a stable target to estimate the neutron-induced reaction cross-section. As an extension of the surrogate method, in this paper they introduce a new technique of measuring the fission probabilities of two different compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. This method was benchmarked in this report by measuring the probability of deuteron-induced fission events in coincidence with protons, and forming the ratio P({sup 236}U(d,pf))/P({sup 238}U(d,pf)), which serves as a surrogate for the known cross-section ratio of {sup 236}U(n,f)/{sup 238}U(n,f). IN addition, the P({sup 238}U(d,d{prime}f))/P({sup 236}U(d,d{prime}f)) ratio as a surrogate for the {sup 237}U(n,f)/{sup 235}U(n,f) cross-section ratio was measured for the first time in an unprecedented range of excitation energies.

  5. The Suzuki-Miyaura Cross-Coupling Reaction of Halogenated Aminopyrazoles: Method Development, Scope, and Mechanism of Dehalogenation Side Reaction.

    Science.gov (United States)

    Jedinák, Lukáš; Zátopková, Renáta; Zemánková, Hana; Šustková, Alena; Cankař, Petr

    2017-01-06

    The efficient Suzuki-Miyaura cross-coupling reaction of halogenated aminopyrazoles and their amides or ureas with a range of aryl, heteroaryl, and styryl boronic acids or esters has been developed. The method allowed incorporation of problematic substrates: aminopyrazoles bearing protected or unprotected pyrazole NH, as well as the free amino or N-amide group. Direct comparison of the chloro, bromo, and iodopyrazoles in the Suzuki-Miyaura reaction revealed that Br and Cl derivatives were superior to iodopyrazoles, as a result of reduced propensity to dehalogenation. Moreover, the mechanism and factors affecting the undesired dehalogenation side reaction were revealed.

  6. First Year Report: Nuclear Reaction Measurements with Radioactive Beams and Targets- Progress in Measurements of the 89Zr (n,xnyp) Reaction Cross Sections

    International Nuclear Information System (INIS)

    Joseph Cerny; Dennis Moltz; Sylvia La; Ed Morse; Larry Ahle; Lee Bernstein; Ken Moody; Kevin Roberts; Margaret Moody; James Powell; Jim O'Neil; Anthony Belian

    2004-01-01

    OAK-B135 During the underground nuclear tests in Nevada, some of the most important information was obtained by radiochemical analysis of post-test excavations. By adding small samples of refractory and rare earth elements not commonly present in the surrounding soil to the device, a detailed look could be had of the actual event. In order to properly analyze these data, several hundred cross sections are needed at a neutron energy of 14 MeV (a d-t-burn product). Although it has always been assumed that these calculations are correct, insufficient experimental data exist to corroborate this assumption. The purpose of this experiment is to measure two reaction cross sections, namely the 89 Zr (n, 2n) 88 Zr and 89 Zr (n, np) 88 Y reactions. Although the former reaction has been measured in an unpublished report ( A. A. Delucchi and W. Goishi, LANL Report LA-7841-C (1977) pp. 33-36), we intend to reduce the experimental error in this cross section. The latter cross section has not been measured. This case is much simplified because these reaction products have half-lives ∼100 days compared with ∼3 days for the target nuclide. Therefore the assay can be accomplished long after the target nuclei have decayed away

  7. Cross section measurements of the (n,2n) reaction with 14 MeV neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Kaji, Harumi; Shiokawa, Takanobu [Tohoku Univ., Sendai (Japan). Faculty of Science; Suehiro, Teruo; Yagi, Masuo

    1975-07-01

    Cross sections are measured for the reactions /sup 64/Zn(n, 2n)/sup 63/Zn, /sup 75/As(n, 2n)/sup 74/As, /sup 79/Br(n, 2n)/sup 78/Br, /sup 90/Zr(n, 2n)/sup 89/Zr, /sup 141/Pr(n, 2n)/sup 140/Pr and /sup 144/Sm(n, 2n)/sup 143/Sm by activation method in the energy range 13.5-14.8 MeV. The cross sections are determined relatively to the cross section for the /sup 63/Cu(n, 2n)/sup 62/Cu and /sup 19/F(n, 2n)/sup 18/F reactions. Before the cross section measurement, incident-neutron energies are measured by recoil proton method. The results of the cross sections are compared with data existing in the literatures and are discussed with reference to the theory of Weisskopf and Ewing.

  8. Cross sections of (p, xn) reactions in the isotopes of lead and bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Bell, R E [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada); Skarsgard, H M [Atomic Energy Research Establishment, Reactor Research Div., Harwell (United Kingdom)

    1956-07-01

    Measurements have been made by the activation method of cross sections of (p, xn) reactions in Bi{sup 209}, Pb{sup 206}, Pb{sup 207}, and Pb{sup 208}. The present results cover x = 3 to 7 in Bi{sup 209}, 2 to 6 in Pb{sup 206}, 2 to 4 in Pb{sup 207}, and 3 and 4 in Pb{sup 208}, over a total proton energy range from 12 to 85 Mev. The absolute accuracy is about 15%. Each cross section plotted as a function of proton energy rises above its threshold to a peak whose height is of the order of one barn, and then falls again to a low and fairly constant value. The results from x = 3 to 7 are consistent with a compound nucleus plus prompt nucleon-nucleon cascade model using reasonable nuclear parameters, but the experimental (p, 2n) cross section appears to be almost double the value so predicted. Since (p, xn) reactions are dominant in the energy range 10 to 40 Mev., their sum approximates the total reaction cross section; the experimental sum fluctuates around the smooth curve computed for the compound nucleus model with r{sub 0} = 1.3 X 10{sup -13} cm. The fluctuations are similar to, but more marked than, those in the total neutron cross section of heavy elements in the same energy range. A more detailed theoretical discussion of these results is given by Jackson in the paper immediately following. (author)

  9. Total reaction cross section and foward glory for 12C + 16O

    International Nuclear Information System (INIS)

    Villari, A.C.C.; Lepine-Szily, A.; Lichtenthaler Filho, R.; Portezan Filho, O.; Obuti, M.M.

    1988-12-01

    A model-independent method is proposed for the determination of the total reaction cross section from elastic angular distributions. This method based on the generalized optical theorem, was applied to 16 complete elastic angular distributions of the system 12 C + 16 O at energies between E CM =8.55 MeV and E CM = 26.74 MeV. Some of the angular distributions were measured at the Sao Paulo Pelletron Laboratory. Angular distributions measured by the Erlangen and Saclay groups were also used. The reaction cross section is compared with fusion measurements and with σ R obtained by indirect methods. The existence and conditions for the observation of the nuclear forward glory scattering are investigated. (author) [pt

  10. Measurement of activation cross sections for quasi-monoenergetic neutron induced reactions of {sup 89}Y

    Energy Technology Data Exchange (ETDEWEB)

    Zaman, Muhammad; Kim, Guinyun; Kim, Kwangsoo; Nadeem, Muhammad [Kyungpook National University, Department of Physics and Center for High Energy Physics, Daegu (Korea, Republic of); Naik, Haladhara [Kyungpook National University, Department of Physics and Center for High Energy Physics, Daegu (Korea, Republic of); Bhabha Atomic Research Centre, Radiochemistry Division, Mumbai (India); Lee, Manwoo [Dongnam Inst. of Radiological and Medical Sciences, Research Center, Busan (Korea, Republic of)

    2017-09-15

    The neutron induced cross sections of the {sup 89}Y(n, 2n){sup 88}Y, {sup 89}Y(n, 3n){sup 87}Y and {sup 89}Y(n, 4n){sup 86}Y reactions were measured in the neutron energy range of 15.2 to 37.2 MeV by using an activation and off-line γ-ray spectrometric technique. The quasi-monoenergetic neutrons used for the above reactions are based on a {sup 9}Be(p, n) reaction. Simulations of the neutron spectra from the Be target were done using the MCNPX 2.6.0 program. Theoretical calculations were performed for the {sup 89}Y(n, 2n){sup 88}Y, {sup 89}Y(n, 3n){sup 87}Y and {sup 89}Y(n, 4n){sup 86}Y reaction cross sections using nuclear model code Talys 1.8. The measured and calculated cross sections were compared with the literature data given in EXFOR and the TENDL-2015 data libraries. The present data of the {sup 89}Y(n, xn) reaction were also compared with the similar data of the {sup 89}Y(γ, xn) reaction to examine the effect of the entrance channel parameters as well as the role of projectiles and ejectiles. (orig.)

  11. 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

  12. Binary and tertiary neutron induced reaction cross sections of chromium and iron

    International Nuclear Information System (INIS)

    Garg, S.B.

    1989-01-01

    Investigation has been carried out for the following binary and tertiary reaction cross-sections of Cr-52 and Fe-56: (n,p), (n,pn), (n,np), (n,α), (n, nα), (n, 2n) and (n, 3n), energy spectra of the emitted neutron, proton, α-particle and γ-rays, angle-energy correlated double differential cross-sections for the secondary emitted neutrons and total production cross-sections for neutron, hydrogen, helium and gamma-rays. 12 refs, 20 figs, 1 tab

  13. Study of activation cross-sections of deuteron induced reactions on rhodium up to 40 MeV

    International Nuclear Information System (INIS)

    Ditroi, F.; Tarkanyi, F.; Takacs, S.; Hermanne, A.; Yamazaki, H.; Baba, M.; Mohammadi, A.; Ignatyuk, A.V.

    2011-01-01

    Highlights: → Excitation function measurement of deuteron induced reactions on rhodium up to 40 MeV. → Model code calculations with EMPIRE, ALICE and TALYS. → Integral production yield calculation. → Thin layer activation (TLA) with the produced isotopes. - Abstract: In the frame of a systematic study of the activation cross-sections of deuteron induced nuclear reactions, excitation functions of the 103 Rh(d,x) 100,101,103 Pd, 100g,101m,101g,102m,102g Rh and 103g Ru reactions were determined up to 40 MeV. Cross-sections were measured with the activation method using a stacked foil irradiation technique. Excitation functions of the contributing reactions were calculated using the ALICE-IPPE, EMPIRE-II and TALYS codes. From the measured cross-section data integral production yields were calculated and compared with experimental integral yield data reported in the literature. From the measured cross-sections and previous data, activation curves were deduced to support thin layer activation (TLA) on rhodium and Rh containing alloys.

  14. Reaction cross section for Ne isotopes

    International Nuclear Information System (INIS)

    Panda, R.N.; Sahu, B.K.; Patra, S.K.

    2012-01-01

    In the present contribution, first the bulk properties are calculated, such as binding energy (BE), root mean square charge radius r ch , matter radius r m and quadrupole deformation parameter β 2 for 18-32 Ne isotopes in the Relativistic mean field (RMF) and effective field theory motivated RMF (E-RMF) formalisms . Then the total nuclear reaction cross section σR is analyzes for the scattering of 20 Ne and 28-32 Ne from a 12 C target at 240 MeV/nucleon by using the RMF model. Thus the objective of the present study is to calculate the bulk properties as well as a systematic analysis of σR over a range of neutron rich nuclei in the frame work of Glauber model

  15. Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation.

    Science.gov (United States)

    Abou Samra, Waleed Ali; El Emam, Dalia Sabry; Farag, Rania Kamel; Abouelkheir, Hossam Youssef

    2016-01-01

    Aim . To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods . 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results . All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.

  16. 26Al/sup g,m/ production cross sections from the 23Na(α,n)26Al reaction

    International Nuclear Information System (INIS)

    Norman, E.B.; Chupp, T.E.; Lesko, K.T.; Schwalbach, P.; Grant, P.J.

    1981-01-01

    Cross sections have been determined for the production of 26 Al/sup g,m/ from the 23 Na(α,n) reaction. Total 26 Al production cross sections were obtained from measurements of the thick-target neutron yield. 26 Al/sup m/ cross sections were measured using an activation technique. 26 Al/sup g/ cross sections were deduced by subtracting the 26 Al/sup m/ cross sections from the total (α,n) cross sections. The principle of detailed balance has been applied to the low energy data to obtain cross sections for the astrophysically interesting 26 Al/sup g/(n,α 0 ) 23 Na reaction. These results are compared with the results of Hauser-Feshbach calculations

  17. Cross-correlation patterns in social opinion formation with sequential data

    Science.gov (United States)

    Chakrabarti, Anindya S.

    2016-11-01

    Recent research on large-scale internet data suggests existence of patterns in the collective behavior of billions of people even though each of them may pursue own activities. In this paper, we interpret online rating activity as a process of forming social opinion about individual items, where people sequentially choose a rating based on the current information set comprising all previous ratings and own preferences. We construct an opinion index from the sequence of ratings and we show that (1) movie-specific opinion converges much slower than an independent and identically distributed (i.i.d.) sequence of ratings, (2) rating sequence for individual movies shows lesser variation compared to an i.i.d. sequence of ratings, (3) the probability density function of the asymptotic opinions has more spread than that defined over opinion arising from i.i.d. sequence of ratings, (4) opinion sequences across movies are correlated with significantly higher and lower correlation compared to opinion constructed from i.i.d. sequence of ratings, creating a bimodal cross-correlation structure. By decomposing the temporal correlation structures from panel data of movie ratings, we show that the social effects are very prominent whereas group effects cannot be differentiated from those of surrogate data and individual effects are quite small. The former explains a large part of extreme positive or negative correlations between sequences of opinions. In general, this method can be applied to any rating data to extract social or group-specific effects in correlation structures. We conclude that in this particular case, social effects are important in opinion formation process.

  18. Enzyme sequence similarity improves the reaction alignment method for cross-species pathway comparison

    Energy Technology Data Exchange (ETDEWEB)

    Ovacik, Meric A. [Chemical and Biochemical Engineering Department, Rutgers University, Piscataway, NJ 08854 (United States); Androulakis, Ioannis P., E-mail: yannis@rci.rutgers.edu [Chemical and Biochemical Engineering Department, Rutgers University, Piscataway, NJ 08854 (United States); Biomedical Engineering Department, Rutgers University, Piscataway, NJ 08854 (United States)

    2013-09-15

    Pathway-based information has become an important source of information for both establishing evolutionary relationships and understanding the mode of action of a chemical or pharmaceutical among species. Cross-species comparison of pathways can address two broad questions: comparison in order to inform evolutionary relationships and to extrapolate species differences used in a number of different applications including drug and toxicity testing. Cross-species comparison of metabolic pathways is complex as there are multiple features of a pathway that can be modeled and compared. Among the various methods that have been proposed, reaction alignment has emerged as the most successful at predicting phylogenetic relationships based on NCBI taxonomy. We propose an improvement of the reaction alignment method by accounting for sequence similarity in addition to reaction alignment method. Using nine species, including human and some model organisms and test species, we evaluate the standard and improved comparison methods by analyzing glycolysis and citrate cycle pathways conservation. In addition, we demonstrate how organism comparison can be conducted by accounting for the cumulative information retrieved from nine pathways in central metabolism as well as a more complete study involving 36 pathways common in all nine species. Our results indicate that reaction alignment with enzyme sequence similarity results in a more accurate representation of pathway specific cross-species similarities and differences based on NCBI taxonomy.

  19. Enzyme sequence similarity improves the reaction alignment method for cross-species pathway comparison

    International Nuclear Information System (INIS)

    Ovacik, Meric A.; Androulakis, Ioannis P.

    2013-01-01

    Pathway-based information has become an important source of information for both establishing evolutionary relationships and understanding the mode of action of a chemical or pharmaceutical among species. Cross-species comparison of pathways can address two broad questions: comparison in order to inform evolutionary relationships and to extrapolate species differences used in a number of different applications including drug and toxicity testing. Cross-species comparison of metabolic pathways is complex as there are multiple features of a pathway that can be modeled and compared. Among the various methods that have been proposed, reaction alignment has emerged as the most successful at predicting phylogenetic relationships based on NCBI taxonomy. We propose an improvement of the reaction alignment method by accounting for sequence similarity in addition to reaction alignment method. Using nine species, including human and some model organisms and test species, we evaluate the standard and improved comparison methods by analyzing glycolysis and citrate cycle pathways conservation. In addition, we demonstrate how organism comparison can be conducted by accounting for the cumulative information retrieved from nine pathways in central metabolism as well as a more complete study involving 36 pathways common in all nine species. Our results indicate that reaction alignment with enzyme sequence similarity results in a more accurate representation of pathway specific cross-species similarities and differences based on NCBI taxonomy

  20. Experience in using the covariances of some ENDF/B-V dosimetry cross sections: proposed improvements and addition of cross-reaction covariances

    International Nuclear Information System (INIS)

    Fu, C.Y.; Hetrick, D.M.

    1982-01-01

    Recent ratio data, with carefully evaluated covariances, were combined with eleven of the ENDF/B-V dosimetry cross sections using the generalized least-squares method. The purpose was to improve these evaluated cross sections and covariances, as well as to generate values for the cross-reaction covariances. The results represent improved cross sections as well as realistic and usable covariances. The latter are necessary for meaningful intergral-differential comparisons and for spectrum unfolding

  1. α -induced reactions on 115In: Cross section measurements and statistical model analysis

    Science.gov (United States)

    Kiss, G. G.; Szücs, T.; Mohr, P.; Török, Zs.; Huszánk, R.; Gyürky, Gy.; Fülöp, Zs.

    2018-05-01

    Background: α -nucleus optical potentials are basic ingredients of statistical model calculations used in nucleosynthesis simulations. While the nucleon+nucleus optical potential is fairly well known, for the α +nucleus optical potential several different parameter sets exist and large deviations, reaching sometimes even an order of magnitude, are found between the cross section predictions calculated using different parameter sets. Purpose: A measurement of the radiative α -capture and the α -induced reaction cross sections on the nucleus 115In at low energies allows a stringent test of statistical model predictions. Since experimental data are scarce in this mass region, this measurement can be an important input to test the global applicability of α +nucleus optical model potentials and further ingredients of the statistical model. Methods: The reaction cross sections were measured by means of the activation method. The produced activities were determined by off-line detection of the γ rays and characteristic x rays emitted during the electron capture decay of the produced Sb isotopes. The 115In(α ,γ )119Sb and 115In(α ,n )Sb118m reaction cross sections were measured between Ec .m .=8.83 and 15.58 MeV, and the 115In(α ,n )Sb118g reaction was studied between Ec .m .=11.10 and 15.58 MeV. The theoretical analysis was performed within the statistical model. Results: The simultaneous measurement of the (α ,γ ) and (α ,n ) cross sections allowed us to determine a best-fit combination of all parameters for the statistical model. The α +nucleus optical potential is identified as the most important input for the statistical model. The best fit is obtained for the new Atomki-V1 potential, and good reproduction of the experimental data is also achieved for the first version of the Demetriou potentials and the simple McFadden-Satchler potential. The nucleon optical potential, the γ -ray strength function, and the level density parametrization are also

  2. Monitoring sequential electron transfer with EPR

    International Nuclear Information System (INIS)

    Thurnauer, M.C.; Feezel, L.L.; Snyder, S.W.; Tang, J.; Norris, J.R.; Morris, A.L.; Rustandi, R.R.

    1989-01-01

    A completely general model which treats electron spin polarization (ESP) found in a system in which radical pairs with different magnetic interactions are formed sequentially has been described. This treatment has been applied specifically to the ESP found in the bacterial reaction center. Test cases show clearly how parameters such as structure, lifetime, and magnetic interactions within the successive radical pairs affect the ESP, and demonstrate that previous treatments of this problem have been incomplete. The photosynthetic bacterial reaction center protein is an ideal system for testing the general model of ESP. The radical pair which exhibits ESP, P 870 + Q - (P 870 + is the oxidized, primary electron donor, a bacteriochlorophyll special pair and Q - is the reduced, primary quinone acceptor) is formed via sequential electron transport through the intermediary radical pair P 870 + I - (I - is the reduced, intermediary electron acceptor, a bacteriopheophytin). In addition, it is possible to experimentally vary most of the important parameters, such as the lifetime of the intermediary radical pair and the magnetic interactions in each pair. It has been shown how selective isotopic substitution ( 1 H or 2 H) on P 870 , I and Q affects the ESP of the EPR spectrum of P 870 + Q - , observed at two different microwave frequencies, in Fe 2+ -depleted bacterial reaction centers of Rhodobacter sphaeroides R26. Thus, the relative magnitudes of the magnetic properties (nuclear hyperfine and g-factor differences) which influence ESP development were varied. The results support the general model of ESP in that they suggest that the P 870 + Q - radical pair interactions are the dominant source of ESP production in 2 H bacterial reaction centers

  3. Cross section measurement and integral test for several activation reactions using T + d and thick-Li + d sources

    International Nuclear Information System (INIS)

    Dumais, J.R.; Tanaka, S.; Odano, N.; Iwasaki, S.; Sugiyama, K.

    1988-01-01

    Recent activities on the area of the cross section measurement for several activation reactions at Department of Nucl. Eng., Tohoku Univ. are described. The first subject is the cross section measurement for (n,2n) reaction on aluminum using the RTNS-II neutron source. Cross sections with rather small error band were obtained for the incident neutron energies from 14 to 14.7 MeV. The second one is the status of the program for the integral experiments on several reactions using the thick Li + d source at Tohoku Fast Neutron Lab. The experimental results showed the usefullness of the source as a tool for the cross section assessment. (author)

  4. Analysis of reaction cross-section production in neutron induced fission reactions on uranium isotope using computer code COMPLET.

    Science.gov (United States)

    Asres, Yihunie Hibstie; Mathuthu, Manny; Birhane, Marelgn Derso

    2018-04-22

    This study provides current evidence about cross-section production processes in the theoretical and experimental results of neutron induced reaction of uranium isotope on projectile energy range of 1-100 MeV in order to improve the reliability of nuclear stimulation. In such fission reactions of 235 U within nuclear reactors, much amount of energy would be released as a product that able to satisfy the needs of energy to the world wide without polluting processes as compared to other sources. The main objective of this work is to transform a related knowledge in the neutron-induced fission reactions on 235 U through describing, analyzing and interpreting the theoretical results of the cross sections obtained from computer code COMPLET by comparing with the experimental data obtained from EXFOR. The cross section value of 235 U(n,2n) 234 U, 235 U(n,3n) 233 U, 235 U(n,γ) 236 U, 235 U(n,f) are obtained using computer code COMPLET and the corresponding experimental values were browsed by EXFOR, IAEA. The theoretical results are compared with the experimental data taken from EXFOR Data Bank. Computer code COMPLET has been used for the analysis with the same set of input parameters and the graphs were plotted by the help of spreadsheet & Origin-8 software. The quantification of uncertainties stemming from both experimental data and computer code calculation plays a significant role in the final evaluated results. The calculated results for total cross sections were compared with the experimental data taken from EXFOR in the literature, and good agreement was found between the experimental and theoretical data. This comparison of the calculated data was analyzed and interpreted with tabulation and graphical descriptions, and the results were briefly discussed within the text of this research work. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  5. Vibrational state-resolved differential cross sections for the D + H sub 2 yields DH + H reaction

    Energy Technology Data Exchange (ETDEWEB)

    Continetti, R.E.

    1989-11-01

    In this thesis, crossed-molecular-beams studies of the reaction D + H{sub 2} {yields} DH + H at collision energies of 0.53 and 1.01 eV are reported. Chapter 1 provides a survey of important experimental and theoretical studies on the dynamics of the hydrogen exchange reaction. Chapter 2 discusses the development of the excimer-laser photolysis D atom beam source that was used in these studies and preliminary experiments on the D + H{sub 2} reaction. In Chapter 3, the differential cross section measurements are presented and compared to recent theoretical predictions. The measured differential cross sections for rotationally excited DH products showed significant deviations from recent quantum scattering calculations, in the first detailed comparison of experimental and theoretical differential cross sections. These results indicate that further work on the H{sub 3} potential energy surface, particularly the bending potential, is in order.

  6. Evaluation of {sup 23}Na(n,2n){sup 22}Na reaction cross-sections

    Energy Technology Data Exchange (ETDEWEB)

    Manokhin, V N [Institute of Physics and Power Engineering, Obninsk (Russian Federation)

    1997-06-01

    Using available experimental data and (n,2n) excitation function systematics {sup 23}Na(n,2n){sup 22}Na reaction cross-sections were evaluated for energies ranging from the reaction threshold to 20 MeV. (author). 21 refs, 1 fig., 2 tabs.

  7. Event-shape analysis: Sequential versus simultaneous multifragment emission

    International Nuclear Information System (INIS)

    Cebra, D.A.; Howden, S.; Karn, J.; Nadasen, A.; Ogilvie, C.A.; Vander Molen, A.; Westfall, G.D.; Wilson, W.K.; Winfield, J.S.; Norbeck, E.

    1990-01-01

    The Michigan State University 4π array has been used to select central-impact-parameter events from the reaction 40 Ar+ 51 V at incident energies from 35 to 85 MeV/nucleon. The event shape in momentum space is an observable which is shown to be sensitive to the dynamics of the fragmentation process. A comparison of the experimental event-shape distribution to sequential- and simultaneous-decay predictions suggests that a transition in the breakup process may have occurred. At 35 MeV/nucleon, a sequential-decay simulation reproduces the data. For the higher energies, the experimental distributions fall between the two contrasting predictions

  8. Five-nucleon simultaneous and sequential transfer in the 12C(11B,6Li)17O and 12C(d,7Li)7Be reactions

    International Nuclear Information System (INIS)

    Jarczyk, L.; Kamys, B.; Kistryn, M.; Magiera, A.; Rudy, Z.; Strzal/kowski, A.; Barna, R.; DAmico, V.; De Pasquale, D.; Italiano, A.; Licandro, M.

    1996-01-01

    Measurements of the angular distributions of the 12 C( 11 B, 6 Li) 17 O reaction were performed at three energies of a 11 B beam: 28, 35, and 40 MeV. The results were analyzed in the frame of the exact finite range distorted wave Born approximation of the first and the second order assuming the simultaneous and sequential transfer of the neutron and the α particle. Such an analysis was also performed for previously measured angular distributions of the 12 C(d, 7 Li) 7 Be reaction at E lab = 78 MeV. In both reactions under investigation dominance was found of the simultaneous transfer of the α particle and the nucleon correlated to the 5 He ( 5 Li) cluster in the ground or the first excited state. copyright 1996 The American Physical Society

  9. Evaluation of cross sections for 14 important neutron-dosimetry reactions

    International Nuclear Information System (INIS)

    Wagner, M.; Vonach, H.; Pavlik, A.; Strohmaier, B.; Tagesen, S.; Martinez-Rico, J.

    1990-01-01

    The evaluation of the cross sections for the neutron dosimetry reactions 24 Mg(n,p) 24 Na, 27 Al(n,α) 24 Na, 58 Ni(n,2n) 57 Ni, 64 Zn(n,p) 64 Cu, 90 Zr(n,2n) 89 Zr and 93 Nb(n,n') 93m Nb carried out at the IRK about ten years ago were updated taking into account recent experimental results. Besides, new evaluations were performed for four additional dosimetry reactions, namely 52 Cr(n,2n) 51 Cr, 59 Co(n,2n) 58 Co, 93 Nb(n,2n) 92m Nb and 197 Au(n,2n) 196 Au. The deadlines for the retrieval of data for the different reactions lay between March 1989 and February 1990. The evaluations comprise the neutron energy range from threshold to 20 MeV, in a few cases this range is extended up to 21 MeV or 30 MeV. Cross sections and their uncertainties were evaluated in energy groups with widths of 0.1 MeV to 2.0 MeV, and relative correlation matrices of the evaluated cross sections at different energies were derived. The results of the evaluations are compared to the previous ones and to other recent evaluations reported in the literature. The main results of our previous evaluations for the reactiosn 19 F(n,2n) 18 F, 31 P(n,p) 31 Si, 63 Cu(n,2n) 62 Cu and 103 Rh(n,n') 103m Rh which remain unchanged are also given for completeness. The evaluations reported in this work will be included in the new version of the IRDF (International Reactor Dosimetry File) of the IAEA in ENDF/B-VI format. (orig.)

  10. Polarization control of direct (non-sequential) two-photon double ionization of He

    International Nuclear Information System (INIS)

    Pronin, E A; Manakov, N L; Marmo, S I; Starace, Anthony F

    2007-01-01

    An ab initio parametrization of the doubly-differential cross section (DDCS) for two-photon double ionization (TPDI) from an s 2 subshell of an atom in a 1 S 0 -state is presented. Analysis of the elliptic dichroism (ED) effect in the DDCS for TPDI of He and its comparison with the same effect in the concurrent process of sequential double ionization shows their qualitative and quantitative differences, thus providing a means to control and to distinguish sequential and non-sequential processes by measuring the relative ED parameter

  11. Evaluation of nuclear reaction cross section of some isotopes of ...

    African Journals Online (AJOL)

    Coupled-channels optical model code OPTMAN is used as an alternative to experimental approach to evaluate the total reaction cross section for four different isotopes of Plutonium as an example of heavy rotational nuclei of the transuranium elements over an energy range of 10 to 20 MeV. The selected isotopes are the ...

  12. Geometrical aspects of reaction cross sections for {sup 3}He, {sup 4}He and {sup 12}C projectiles

    Energy Technology Data Exchange (ETDEWEB)

    Ingemarsson, A. [Uppsala Univ. (Sweden). Dept. of Radiation Sciences; Lantz, M. [Uppsala Univ. (Sweden). The Svedberg Laboratory

    2003-04-01

    A black-disc model combined with accurate matter densities has been used for an investigation of reaction cross sections for {sup 3}He, {sup 4}He and {sup 12}C projectiles. A simple relation is derived between the energy dependence of the reaction cross sections and the strength of the nucleon-nucleon interaction. A comparison is also made of the reaction cross sections for {sup 3}He and {sup 4}He for six different nuclei {sup 12}C, {sup 16}O, {sup 40}Ca, {sup 58,60}Ni and {sup 208}Pb.

  13. Position paper of the EAACI: food allergy due to immunological cross-reactions with common inhalant allergens.

    Science.gov (United States)

    Werfel, T; Asero, R; Ballmer-Weber, B K; Beyer, K; Enrique, E; Knulst, A C; Mari, A; Muraro, A; Ollert, M; Poulsen, L K; Vieths, S; Worm, M; Hoffmann-Sommergruber, K

    2015-09-01

    In older children, adolescents, and adults, a substantial part of all IgE-mediated food allergies is caused by cross-reacting allergenic structures shared by inhalants and foods. IgE stimulated by a cross-reactive inhalant allergen can result in diverse patterns of allergic reactions to various foods. Local, mild, or severe systemic reactions may occur already after the first consumption of a food containing a cross-reactive allergen. In clinical practice, clinically relevant sensitizations are elucidated by skin prick testing or by the determination of specific IgE in vitro. Component-resolved diagnosis may help to reach a diagnosis and may predict the risk of a systemic reaction. Allergy needs to be confirmed in cases of unclear history by oral challenge tests. The therapeutic potential of allergen immunotherapy with inhalant allergens in pollen-related food allergy is not clear, and more placebo-controlled studies are needed. As we are facing an increasing incidence of pollen allergies, a shift in sensitization patterns and changes in nutritional habits, and the occurrence of new, so far unknown allergies due to cross-reactions are expected. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. Energy dependence of fusion evaporation-residue cross sections in the 28Si+12C reaction

    International Nuclear Information System (INIS)

    Vineyard, M.F.; Mateja, J.F.; Beck, C.; Atencio, S.E.; Dennis, L.C.; Frawley, A.D.; Henderson, D.J.; Janssens, R.V.F.; Kemper, K.W.; Kovar, D.G.; Maguire, C.F.; Padalino, S.J.; Prosser, F.W.; Stephans, G.S.F.; Tiede, M.A.; Wilkins, B.D.; Zingarelli, R.A.

    1993-01-01

    Fusion evaporation-residue cross sections for the 28 Si+ 12 C reaction have been measured in the energy range 18≤E c.m. ≤136 MeV using time-of-flight techniques. Velocity distributions of mass-identified reaction products were used to identify evaporation residues and to determine the complete-fusion cross sections at high energies. The data are in agreement with previously established systematics which indicate an entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models

  15. Angular distribution and cross section measurement for 64Zn(n,α)61Ni reaction

    International Nuclear Information System (INIS)

    Yuan Jing; Chen Zemin; Dledenov, Y.M.; Sedysheva, M.; Khuuknenkhuu, G.

    2001-01-01

    Using a gridded ionization chamber, the differential cross section for 64 Zn(n,α) 61 Ni reaction was measured at 5.0, 5.7 and 6.7 MeV. The neutrons were produced through D(d,n) 3 He reaction. Absolute neutron flux was determined through 238 U(n,f) reaction. The results show obviously backward peak in the center of mass reference system

  16. The heavy-ion total reaction cross-section and nuclear transparancy

    International Nuclear Information System (INIS)

    Rego, R.A.; Hussein, M.S.

    1982-10-01

    The total reaction cross section of heavy ions at intermediate energies is discussed. The special role played by the individual nucleon-nucleon collisions in determining the nuclear transparancy is analysed. Several competing effects arising from the nuclear and Coulomb interactions between the two ions are found to be important in determing σ sub(R) at lower energies. (Author) [pt

  17. The heavy-ion total reaction cross-section and nuclear transparency

    International Nuclear Information System (INIS)

    Rego, R.A.; Hussein, M.S.

    1982-01-01

    The total reaction cross section of heavy ions at intermediate energies is discussed. The special role played by the individual nucleon-nucleon collisions in determining the nuclear transparency is analysed. Several competing effects arising from the nuclear and Coulomb interactions between the two ions are found to be important in determining σ(sub R) at lower energies. (Author) [pt

  18. Aqueous-phase Suzuki-Miyaura cross-coupling reactions of free halopurine bases

    Czech Academy of Sciences Publication Activity Database

    Čapek, Petr; Vrábel, Milan; Hasník, Zbyněk; Pohl, Radek; Hocek, Michal

    -, č. 20 (2006), s. 3515-3526 ISSN 0039-7881 R&D Projects: GA ČR(CZ) GA203/05/0043 Institutional research plan: CEZ:AV0Z40550506 Keywords : purines * cross-coupling * reactions Subject RIV: CC - Organic Chemistry Impact factor: 2.333, year: 2006

  19. Study of the influence of decay data in activation reaction cross section

    International Nuclear Information System (INIS)

    Huang Xiaolong; Lu Hanlin

    2002-01-01

    The effect of the decay data on the measured activation cross section is investigated carefully and testified by several examples. These decay data include the half-life of the product, γ branching ratio of the product and decay scheme. Present work shows that these effects must be considered carefully when evaluating the activation reaction cross section. Sometimes they are main reason for causing the discrepancies among the experimental data

  20. Cross-section studies of relativistic deuteron reactions obtained by activation method

    CERN Document Server

    Wagner, V; Svoboda, O; Vrzalová, J; Majerle, M; Krása, A; Chudoba, P; Honusek, M; Kugler, A; Adam, J; Baldin, A; Furman, W; Kadykov, M; Khushvaktov, J; Sol-nyskhin, A; Tsoupko-Sitnikov, V; Závorka, L; Tyutyunnikov, S; Vladimirova, N

    2014-01-01

    The cross-sections of relativistic deuteron reactions on natural copper were studied in detail by means of activation method. The copper foils were irradiated during experiments with the big Quinta uranium target at Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The deuteron beams with energies ranging from 1 GeV up to 8 GeV were produced by JINR Nuclotron. Residual nuclides were identified by the gamma spectrometry. Lack of such experimental cross-section values prevents the usage of copper foils from beam integral monitoring.

  1. Quasi-free and sequential processes in the 9Be(3He,αα)4He reaction at 2,8 MeV

    International Nuclear Information System (INIS)

    Barbarino, S.; Lattuada, M.; Riggi, F.; Spitaleri, C.; Vinciguerra, D.

    1979-01-01

    The quasi-free contribution to the 9 Be( 3 He,αα) 4 He reaction at low incident energy is studied under various detection configurations. The measurements performed at quasi-free angles (symmetrical and non-symmetrical configurations) furter confirm that a large region in the energy spectra is dominated by the quasi-free 5 He( 3 He,α) 4 He process. From a comparison of these results with those taken at symmetrical angles where the minimum accepted momentum of the spectator is around 70 MeV/c, the conclusion is drawn that no significant distortion is introduced by the sequential peak tails in the deduced 5 He- 4 He momentum distribution

  2. Synthesis of a novel chemotype via sequential metal-catalyzed cycloisomerizations

    Directory of Open Access Journals (Sweden)

    Bo Leng

    2012-08-01

    Full Text Available Sequential cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes are reported. The reaction sequence involves initial Cu(I-mediated cycloisomerization/nucleophilic addition to an isochromene followed by diastereoselective Pt(II-catalyzed enyne cycloisomerization.

  3. A Comparative Study of Basic, Amphoteric, and Acidic Catalysts in the Oxidative Coupling of Methanol and Ethanol for Acrolein Production.

    Science.gov (United States)

    Lilić, Aleksandra; Wei, Tiantian; Bennici, Simona; Devaux, Jean-François; Dubois, Jean-Luc; Auroux, Aline

    2017-09-11

    The impact of acid/base properties (determined by adsorption microcalorimetry) of various catalysts on the cross-aldolization of acetaldehyde and formaldehyde leading to acrolein was methodically studied in oxidizing conditions starting from a mixture of methanol and ethanol. The aldol condensation and further dehydration to acrolein were carried out on catalysts presenting various acid/base properties (MgO, Mg-Al oxides, Mg/SiO 2 , NbP, and heteropolyanions on silica, HPA/SiO 2 ). Thermodynamic calculations revealed that cross-aldolization is always favored compared with self-aldolization of acetaldehyde, which leads to crotonaldehyde formation. The presence of strong basic sites is shown to be necessary, but a too high amount drastically increases CO x production. On strong acid sites, production of acrolein and carbon oxides (CO x ) does not increase with temperature. The optimal catalyst for this process should be amphoteric with a balanced acid/base cooperation of medium strength sites and a small amount (150 kJ mol -1 ). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Energy-differential cross section measurement for the 51V(n,α)48Sc reaction

    International Nuclear Information System (INIS)

    Kanno, I.; Meadows, J.W.; Smith, D.L.

    1984-07-01

    The activation method was used to measure cross sections for the 51 V(n,α) 48 Sc reaction in the threshold region, from 5.515 MeV up to 9.567 MeV. Twenty approximately-monoenergetic cross section values were obtained in this experiment. These data points span the energy region at roughly equal intervals. The experimental resolutions were in the range 0.153 to 0.233 MeV (FWHM). The present differential data cover approx. 50% of the total integral response of this reaction for the standard 235 U thermal-neutron-induced-fission neutron spectrum, and approx. 44% of the corresponding response for the standard 252 Cf spontaneous-fission neutron spectrum. Over the range 7.6 to 9.5 MeV the present experimental cross sections are noticeably larger (e.g., by approx. 50% at approx. 8.6 MeV) than the corresponding values from the ENDF/B-V evaluation. From approx. 6.7 to 7.5 MeV, the present values are somewhat below those of ENDF/B-V. At still lower energies the agreement is reasonably good considering the uncertainties introduced by energy scale definition very near the effective threshold where the cross section varies rapidly with neutron energy. Calculated integral cross sections based in part on the present work agree reasonably well within errors with reported integral results, provided that the reported data are renormalized to conform with recently-accepted values for appropriate standard reactions. 70 references

  5. Status report on cross-sections of monitor reactions for radioisotope production

    International Nuclear Information System (INIS)

    Schwerer, O.; Okamoto, K.

    1989-12-01

    The status of data on cross-sections of 19 monitor reactions, especially for cyclotron operation, is summarized. Most of the information was extracted from the data compiled in EXFOR (EXchange FORmat) which is a common format used by the co-operating nuclear data centres in the world. The EXFOR data were supplemented by a number of additional data sets found in the literature. For each reaction a brief status summary, graphical plots of the available experimental and evaluated data, and a table of all experimental data sorted by incident particle energy, are given

  6. Macroscopic Dynamic Modeling of Sequential Batch Cultures of Hybridoma Cells: An Experimental Validation

    Directory of Open Access Journals (Sweden)

    Laurent Dewasme

    2017-02-01

    Full Text Available Hybridoma cells are commonly grown for the production of monoclonal antibodies (MAb. For monitoring and control purposes of the bioreactors, dynamic models of the cultures are required. However these models are difficult to infer from the usually limited amount of available experimental data and do not focus on target protein production optimization. This paper explores an experimental case study where hybridoma cells are grown in a sequential batch reactor. The simplest macroscopic reaction scheme translating the data is first derived using a maximum likelihood principal component analysis. Subsequently, nonlinear least-squares estimation is used to determine the kinetic laws. The resulting dynamic model reproduces quite satisfactorily the experimental data, as evidenced in direct and cross-validation tests. Furthermore, model predictions can also be used to predict optimal medium renewal time and composition.

  7. Cross section measurement of alpha particle induced nuclear reactions on natural cadmium up to 52 MeV

    OpenAIRE

    Ditrói, F.; Takács, S.; Haba, H.; Komori, Y.; Aikawa, M.

    2016-01-01

    Cross sections of alpha particle induced nuclear reactions have been measured on thin natural cadmium targets foils in the energy range from 11 to 51.2 MeV. This work was a part of our systematic study on excitation functions of light ion induced nuclear reactions on different target materials. Regarding the cross sections, the alpha induced reactions are not deeply enough investigated. Some of the produced isotopes are of medical interest, others have application in research and industry. Th...

  8. Measurement of the effective thermal cross section of {sup 134}Cs by triple neutron capture reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Shoji; Harada, Hideo; Katoh, Toshio [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works; Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro; Kobayashi, Katsutoshi; Motoishi, Shoji; Tanase, Masakazu

    1998-03-01

    The effective thermal cross section ({sigma}{sub eff}) of the {sup 134}Cs(n,{gamma}){sup 135}Cs reaction was measured by the activation method and the {gamma}-ray spectroscopic method in order to obtain fundamental data for research on the transmutation of nuclear wastes. The effective thermal cross section of the reaction {sup 134}Cs(n,{gamma}){sup 135}Cs was found to be 140.6{+-}8.5 barns. (author)

  9. Advanced modeling of reaction cross sections for light nuclei

    International Nuclear Information System (INIS)

    Resler, D.A.

    1991-01-01

    The shell model/R-matrix technique of calculating nuclear reaction cross sections for light projectiles incident on light nuclei is discussed, particularly in the application of the technique to thermonuclear reactions. Details are presented on the computational methods for the shell model which display how easily the calculations can be performed. Results of the shell model/R-matrix technique are discussed as are some of the problems encountered in picking an appropriate nucleon-nucleon interaction for the large model spaces which must be used for current problems. The status of our work on developing an effective nucleon-nucleon interaction for use in large-basis shell model calculations is presented. This new interaction is based on a combination of global constraints and microscopic nuclear data. 23 refs., 6 figs., 2 tabs

  10. Crossed molecular beam study of the reaction O(3P) + allene

    Science.gov (United States)

    Schmoltner, A. M.; Huang, S. Y.; Brudzynski, R. J.; Chu, P. M.; Lee, Y. T.

    1993-08-01

    The reaction between ground state (3P) oxygen atoms and allene was studied under single collision conditions using the crossed molecular beams method. Product angular distributions and the translational energy distribution were determined for each channel. Two major reaction channels could be identified unambiguously: the formation of carbon monoxide and ethylene following oxygen atom attack on the central carbon atom, and the formation of allenyloxy (formyl-vinyl) radical and hydrogen atom following oxygen atom attack on the terminal carbon atom. In addition, at least one other reaction channel, which could be identified as the production of vinyl and formyl radicals, occurs. This channel involves the decomposition of acrolein which is formed by the addition of oxygen to the terminal carbon atom, followed by 1,2-hydrogen migration.

  11. Fusion cross-sections of 16O+16O reaction in pseudonucleon picture

    International Nuclear Information System (INIS)

    Mishra, R.C.; Waghmare, Y.R.

    1991-01-01

    Fusion cross-sections for 16 O+ 16 O reaction are calculated in classical equations of motion approach using the pseudonucleon picture. These calculated fusion cross-sections are very close to measured values than earlier calculated using the same NN interaction. The aim of the paper is to test the pseudonucleon picture. Use of this picture does not require one to consider the number of relative random orientations of the colliding clusters. (author). 22 refs., 2 tabs., 4 figs

  12. Competitive interactions affect working memory performance for both simultaneous and sequential stimulus presentation

    OpenAIRE

    Ahmad, J; Swan, G; Bowman, H; Wyble, B; De Ozorio Nobre, AC; Shapiro, KL; McNab, F

    2017-01-01

    Competition between simultaneously presented visual stimuli lengthens reaction time and reduces both the BOLD response and neural firing. In contrast, conditions of sequential presentation have been assumed to be free from competition. Here we manipulated the spatial proximity of stimuli (Near versus Far conditions) to examine the effects of simultaneous and sequential competition on different measures of working memory (WM) for colour. With simultaneous presentation, the measure of WM precis...

  13. Computational investigation of kinetics of cross-linking reactions in proteins: importance in structure prediction.

    Science.gov (United States)

    Bandyopadhyay, Pradipta; Kuntz, Irwin D

    2009-01-01

    The determination of protein structure using distance constraints is a new and promising field of study. One implementation involves attaching residues of a protein using a cross-linking agent, followed by protease digestion, analysis of the resulting peptides by mass spectroscopy, and finally sequence threading to detect the protein folds. In the present work, we carry out computational modeling of the kinetics of cross-linking reactions in proteins using the master equation approach. The rate constants of the cross-linking reactions are estimated using the pKas and the solvent-accessible surface areas of the residues involved. This model is tested with fibroblast growth factor (FGF) and cytochrome C. It is consistent with the initial experimental rate data for individual lysine residues for cytochrome C. Our model captures all observed cross-links for FGF and almost 90% of the observed cross-links for cytochrome C, although it also predicts cross-links that were not observed experimentally (false positives). However, the analysis of the false positive results is complicated by the fact that experimental detection of cross-links can be difficult and may depend on specific experimental conditions such as pH, ionic strength. Receiver operator characteristic plots showed that our model does a good job in predicting the observed cross-links. Molecular dynamics simulations showed that for cytochrome C, in general, the two lysines come closer for the observed cross-links as compared to the false positive ones. For FGF, no such clear pattern exists. The kinetic model and MD simulation can be used to study proposed cross-linking protocols.

  14. Experimental Cross Sections for Reactions of Heavy Ions and 208Pb, 209Bi, 238U, and 248Cm Targets

    International Nuclear Information System (INIS)

    Patin, Joshua B.

    2002-01-01

    The study of the reactions between heavy ions and 208 Pb, 209 Bi, 238 U, and 248 Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the 238 U( 18 O,xn) 256-x Fm, 238 U( 22 Ne,xn) 260-x No, and 248 Cm( 15 N,xn) 263-x Lr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The 208 Pb( 48 Ca,xn) 256-x No, 208 Pb( 50 Ti,xn) 258-x Rf, 208 Pb( 51 V,xn) 259-x Db, 209 Bi( 50 Ti,xn) 259-x Db, and 209 Bi( 51 V,xn) 260-x Sg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics

  15. Elastic scattering and total reaction cross section for the 6He + 27Al system

    International Nuclear Information System (INIS)

    Benjamim, E.A.; Lepine-Szily, A.; Mendes Junior, D.R.; Lichtenthaeler, R.; Guimaraes, V.; Gomes, P.R.S.; Chamon, L.C.; Hussein, M.S.; Moro, A.M.; Arazi, A.; Padron, I.; Alcantara Nunez, J.; Assuncao, M.; Barioni, A.; Camargo, O.; Denke, R.Z.; Faria, P.N. de; Pires, K.C.C.

    2007-01-01

    The elastic scattering of the radioactive halo nucleus 6 He on 27 Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The Sao Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of 6 He on 27 Al are similar to those for stable, weakly bound projectiles as 6,7 Li, 9 Be and larger than stable, tightly bound projectile as 16 O on 27 Al

  16. KAPSIES: A program for the calculation of multi-step direct reaction cross sections

    International Nuclear Information System (INIS)

    Koning, A.J.; Akkermans, J.M.

    1994-09-01

    We present a program for the calculation of continuum cross sections, sepctra, angular distributions and analyzing powers according to various quantum-mechanical theories for statistical multi-step direct nuclear reactions. (orig.)

  17. Theoretical and experimental cross sections for neutron reactions on 64Zinc

    International Nuclear Information System (INIS)

    Rutherford, D.A.

    1987-01-01

    Accurate measurements of the 64 Zn (n,2n) 64 Cu and 64 Zn (n,p) 63 Zn cross sections at 14.8 MeV have been made using a Texas Nuclear Neutron Generator and the activation technique. A NaI(T1) spectrometer (using two 6'' x 6'' NaI detectors/crystals) was used to measure the gamma radiation emitted in coincidence from the positron-emitting decay products. The measurements were made relative to 65 Cu (n,2n) /64/Cu and 63 Cu (n,2n) 62 Cu cross sections, which have similar half-lives, radiation emission, and were previously measured to high accuracy (2 percent). The value obtained for the (n,2n) measurement was 199 /+-/ 6 millibarns, and a value of 176 /+-/ 4.5 millibarns was obtained for the (n,p) measurement. In concert, a theoretical analysis of neutron induced reactions on /64/Zn was performed at Los Alamos National Laboratory using the Hauser-Feshbach statistical theory in the GNASH code over an energy range of 100 keV to 20 MeV. Calculations included width fluctuation corrections, direct reaction contributions, and preequilibrium corrections above 6 MeV. Neutron optical model potentials were determined for zinc. The theoretical values agree with the new 14.8 MeV measurements approximately within experimental error, with calculations of 201 millibarns for the (n,2n) cross section and 170 millibarns for the (n,p) cross section. Results from the analysis will be made available in National Evaluated Nuclear Data Format (ENDF/B) for fusion energy applications. 50 refs., 34 figs., 10 tabs

  18. Calculations of radiation defect formation cross sections in reactor materials in (n,p) and (n,α) reactions

    International Nuclear Information System (INIS)

    Kupchishin, A.A.; Kupchishin, A.I.; Omarbekova, Zh.

    2001-01-01

    In the work an experimental data analysis by integral σ(E 1 ) and differential [dσ(E 1 ,E 2 )]/dE 2 neutron interaction cross sections with reactor materials with the secondary protons and alpha particles generation as well as with the primarily knock-on atoms production in such reactions are carried out. It is shown, that in the (n,p) and (n',α) reactions the recoil nuclei receive essential energy portion and they are the patriarchs for atom-atom cascades in the substance. Nuclear reactions with formation of the secondary α-particles and and recoil nuclei are considered. It is shown, that these reactions are effectively proceeding within neutrons energy range 0.3-15 MeV. The nuclear reactions kinematics of above mentioned processes is studied. Energy conservation law for these reaction is applied. Deferential cross section conservation and transformation law for radiation defect formation in the (n,α) reaction are considered as well

  19. Light particle revelation on incomplete fusion reactions

    International Nuclear Information System (INIS)

    Gillibert, A.

    1984-01-01

    Incomplete fusion reactions have been studied through light particles emission in the reaction 116 Sn + 16 O at 125 MeV (ALICE facility in Orsay). We measured energy angular distributions and correlations between any two of these particles (α particles, protons, neutrons), while γ multiplicity measurements provide us fuller informations. From collected data, the following pictures can be drawn: - the only fast particles observed are α particles, while protons and neutrons seem to come only from statistical evaporation; - outgoing channels where two α particles are emitted cannot be solely explained by the sequential emission of 8 Be → 2α: about half of the cross section proceeds from statistical evaporation of one α particle. Accordingly, 2αxn channels do not necessarily agree with high value of angular momentum in the entrance channel. From the study of experimental results in the yrast plane, we can assign a large width to the angular momentum distribution [fr

  20. 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)

  1. On the geometric nature of high energy nucleus-nucleus reaction cross sections

    International Nuclear Information System (INIS)

    Townsend, L.W.; Wilson, J.W.; Bidasaria, H.B.

    1982-01-01

    Within the context of a high energy double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series, eikonal scattering theory is used to investigate the validity of geometric reaction cross sections in relativistic heavy ion collisions. The potential used includes a finite range interaction and nuclear single-particle densities extracted from nuclear charge distributions by unfolding the proton charge distribution. Pauli correlation effects are also included in an approximate way. The sensitivity of the predictions to be assumed interaction, Pauli correlation approximation, and nuclear density distributions is investigated. These results are in agreement with early predictions concerning the geometric nature of relativistic heavy ion collisions and in disagreement with a recent analysis, utilizing the zero range approximation, which suggested otherwise. Reasons for the lack of agreement between the analyses are also presented. Finally, approximate applicability for geometric reaction cross sections are determined

  2. The cross sections of fusion-evaporation reactions: the most promising route to superheavy elements beyond Z=118

    Directory of Open Access Journals (Sweden)

    Jadambaa Khuyagbaatar

    2017-01-01

    Full Text Available The synthesis of superheavy elements beyond oganesson (Og, which has atomic number Z = 118, is currently one of the main topics in nuclear physics. An absence of sufficient amounts of target material with atomic numbers heavier than californium (Z = 98 forces the use of projectiles heavier than 48Ca (Z = 20, which has been successfully used for the discoveries of elements with Z = 114 - 118 in complete fusion reactions. Experimental cross sections of 48Ca with actinide targets behave very differently to “cold” and “hot” fusion-evaporation reactions, where doubly-magic lead and deformed actinides are used as targets, respectively. The known cross sections of these reactions have been analysed compared to calculated fission barriers. It has been suggested that observed discrepancies between the cross sections of 48Ca-induced and other fusionevaporation reactions originate from the shell structure of the compound nucleus, which lies in the island of the stability. Besides scarcely known data on other reactions involving heavier projectiles, the most promising projectile for the synthesis of the elements beyond Og seems to be 50Ti. However, detailed studies of 50Ti, 54Cr, 58Fe and 64Ni-induced reactions are necessary to be performed in order to fully understand the complexities of superheavy element formation.

  3. The cross sections of fusion-evaporation reactions: the most promising route to superheavy elements beyond Z=118

    Science.gov (United States)

    Jadambaa, Khuyagbaatar

    2017-11-01

    The synthesis of superheavy elements beyond oganesson (Og), which has atomic number Z = 118, is currently one of the main topics in nuclear physics. An absence of sufficient amounts of target material with atomic numbers heavier than californium (Z = 98) forces the use of projectiles heavier than 48Ca (Z = 20), which has been successfully used for the discoveries of elements with Z = 114 - 118 in complete fusion reactions. Experimental cross sections of 48Ca with actinide targets behave very differently to "cold" and "hot" fusion-evaporation reactions, where doubly-magic lead and deformed actinides are used as targets, respectively. The known cross sections of these reactions have been analysed compared to calculated fission barriers. It has been suggested that observed discrepancies between the cross sections of 48Ca-induced and other fusionevaporation reactions originate from the shell structure of the compound nucleus, which lies in the island of the stability. Besides scarcely known data on other reactions involving heavier projectiles, the most promising projectile for the synthesis of the elements beyond Og seems to be 50Ti. However, detailed studies of 50Ti, 54Cr, 58Fe and 64Ni-induced reactions are necessary to be performed in order to fully understand the complexities of superheavy element formation.

  4. Sequential decay of Reggeons

    International Nuclear Information System (INIS)

    Yoshida, Toshihiro

    1981-01-01

    Probabilities of meson production in the sequential decay of Reggeons, which are formed from the projectile and the target in the hadron-hadron to Reggeon-Reggeon processes, are investigated. It is assumed that pair creation of heavy quarks and simultaneous creation of two antiquark-quark pairs are negligible. The leading-order terms with respect to ratio of creation probabilities of anti s s to anti u u (anti d d) are calculated. The production cross sections in the target fragmentation region are given in terms of probabilities in the initial decay of the Reggeons and an effect of manyparticle production. (author)

  5. Stereoselective Synthesis of Highly Functionalized α-Diazo-β-ketoalkanoates via Catalytic Onepot Mukaiyama-Aldol Reactions

    Science.gov (United States)

    Zhou, Lei; Doyle, Michael P.

    2010-01-01

    Methyl diazoacetoacetate undergoes zinc triflate catalyzed condensation with a broad selection of aldehydes to produce δ-siloxy-α-diazo-β-ketoalkanoates in good yield, and δ-hydroxy-α-diazo-β-ketoalkanoates are formed with high diastereoselectivity in reactions with α-diazo-β-ketopentanoate promoted by dibutylboron triflate. PMID:20102172

  6. Reaction mechanism of oxygen atoms with unsaturated hydrocarbons by the crossed molecular beams method

    Energy Technology Data Exchange (ETDEWEB)

    Buss, R.J.; Baseman, R.J.; Guozhong, H.; Lee, Y.T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  7. Reaction Mechanism of Oxygen Atoms with Unsaturated Hydrocarbons by the Crossed-Molecular-Beams Method

    Science.gov (United States)

    Buss, R. J.; Baseman, R. J.; Guozhong, H.; Lee, Y. T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  8. Decomposition of Copper (II) Sulfate Pentahydrate: A Sequential Gravimetric Analysis.

    Science.gov (United States)

    Harris, Arlo D.; Kalbus, Lee H.

    1979-01-01

    Describes an improved experiment of the thermal dehydration of copper (II) sulfate pentahydrate. The improvements described here are control of the temperature environment and a quantitative study of the decomposition reaction to a thermally stable oxide. Data will suffice to show sequential gravimetric analysis. (Author/SA)

  9. Determination of minor actinides fission cross sections by means of transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Jurado, B.; Aiche, M.; Barreau, G.; Boyer, S.; Czajkowski, S.; Dassie, D.; Grosjean, C.; Guiral, A.; Haas, B.; Osmanov, B.; Petit, M. [CENBG - UMR 5795 CNRS/IN2P3-Univ. Bordeaux 1- Le Haut Vigneau, 33175 Gradignan (France); Berthoumieux, E.; Gunsing, F.; Perrot, L.; Theisen, Ch. [CEN Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette cedex (France); Bauge, E. [CEA, SPhN, BP12 91680 Bruyeres-le-Chatel (France); Michel-Sendis, F. [IPN, 15 rue G. Clemenceau, 91406 Orsay cedex (France); Billebaud, A. [LPSC, 53 Avenue des Martyrs, 38026 Grenoble cedex (France); Wilson, J. N. [IPN, 15 rue G. Clemenceau, 91406 Orsay cedex (France); LPSC, 53 Avenue des Martyrs, 38026 Grenoble cedex (France); Ahmad, I.; Greene, J.P.; Janssens, R. V. F. [ANL, 9700 S. Cass Avenue, Argonne, IL 60439 (United States)

    2005-07-01

    We present an original method that allows to determine neutron-induced cross sections of very short-lived minor actinides. This indirect method, based on the use of transfer reactions, has already been applied with success for the determination of the neutron-induced fission and capture cross section of {sup 233}Pa, a key nucleus in the {sup 232}Th - {sup 233}U fuel cycle. A recent experiment using this technique has been performed to determine the neutron-induced fission cross sections of {sup 242,243,244}Cm and {sup 241}Am which are present in the nuclear waste of the current U-Pu fuel cycle. These cross sections are highly relevant for the design of reactors capable to incinerate minor actinides. The first results will be illustrated. (authors)

  10. Mean-Variance-Validation Technique for Sequential Kriging Metamodels

    International Nuclear Information System (INIS)

    Lee, Tae Hee; Kim, Ho Sung

    2010-01-01

    The rigorous validation of the accuracy of metamodels is an important topic in research on metamodel techniques. Although a leave-k-out cross-validation technique involves a considerably high computational cost, it cannot be used to measure the fidelity of metamodels. Recently, the mean 0 validation technique has been proposed to quantitatively determine the accuracy of metamodels. However, the use of mean 0 validation criterion may lead to premature termination of a sampling process even if the kriging model is inaccurate. In this study, we propose a new validation technique based on the mean and variance of the response evaluated when sequential sampling method, such as maximum entropy sampling, is used. The proposed validation technique is more efficient and accurate than the leave-k-out cross-validation technique, because instead of performing numerical integration, the kriging model is explicitly integrated to accurately evaluate the mean and variance of the response evaluated. The error in the proposed validation technique resembles a root mean squared error, thus it can be used to determine a stop criterion for sequential sampling of metamodels

  11. Library of neutron reaction cross-sections in the ABBN-93 constant system

    International Nuclear Information System (INIS)

    Zabrodskaya, S.V.; Korchagina, Zh.A.; Koshcheev, V.N.; Nikolaev, M.N.; Tsibulya, A.M.

    2001-01-01

    The library of neutron reaction group cross-sections in the ABBN-93 constant set is described. The format used for data representation, the content and purpose of the sub-libraries and their practical application in the SCALE criticality safety estimation system are discussed. (author)

  12. Cyclopentanone: A raw material for production of C15 and C17 fuel precursors

    International Nuclear Information System (INIS)

    Hronec, Milan; Fulajtárova, Katarína; Liptaj, Tibor; Štolcová, Magdaléna; Prónayová, Naďa; Soták, Tomáš

    2014-01-01

    The synthesis of diesel or jet fuels intermediates from furfural or 5-hydroxymethylfurfural (HMF) via aqueous aldol-condensation with cyclopentanone was studied. Cyclopentanone is the product of furfural rearrangement in an aqueous system. Since the aldol-condensation reaction is conducted in an aqueous solution all these biomass-derived reactants can be applied as water solutions formed in the processes of their preparation. The aldol condensation of furfural with cyclopentanone is at low concentration of base and molar ratio of reactants 2:1 highly selective and after 40–80 min of reaction at a temperature of 40–100 °C more than 95 mol% yield of 2,5-bis (2-furylmethylidene) cyclopentan-1-one (F 2 C) was obtained. When instead of furfural as a reactant HMF was used higher than 98 mol% yield of 2,5-bis (5-hydroxymethyl-2-furylmethylidene) cyclopentan-1-one was achieved. The final products of aldol condensation of furfural and HMF are exclusively corresponding dimers, what enables to obtain after subsequent hydrogenation/hydrodeoxygenation step dialkylcyclopentane type of diesel or jet fuels having C 15 or C 17 molecules. - Highlights: • The aldol condensation of biomass derived cyclopentanone with furfural and HMF. • More than 95 mol % yields of products are achieved. • The products are compounds having exclusively 15 or 17 carbon atoms in molecule. • Reactants can be used as diluted aqueous solutions. • The products are separated as solids insoluble in water

  13. Reaction and total cross sections for low energy π+ and π- on isospin zero nuclei

    International Nuclear Information System (INIS)

    Saunders, A.; Ho/ibraten, S.; Kraushaar, J.J.; Kriss, B.J.; Peterson, R.J.; Ristinen, R.A.; Brack, J.T.; Hofman, G.; Gibson, E.F.; Morris, C.L.

    1996-01-01

    Reaction and total cross sections for π + and π - on targets of 2 H, 6 Li, C, Al, Si, S, and Ca have been measured for beam energies from 42 to 65 MeV. The cross sections are proportional to the target mass at 50 MeV, consistent with transparency to these projectiles. The cross sections are compared to theoretical calculations. copyright 1996 The American Physical Society

  14. The subtyping of primary aldosteronism by adrenal vein sampling: sequential blood sampling causes factitious lateralization.

    Science.gov (United States)

    Rossitto, Giacomo; Battistel, Michele; Barbiero, Giulio; Bisogni, Valeria; Maiolino, Giuseppe; Diego, Miotto; Seccia, Teresa M; Rossi, Gian Paolo

    2018-02-01

    The pulsatile secretion of adrenocortical hormones and a stress reaction occurring when starting adrenal vein sampling (AVS) can affect the selectivity and also the assessment of lateralization when sequential blood sampling is used. We therefore tested the hypothesis that a simulated sequential blood sampling could decrease the diagnostic accuracy of lateralization index for identification of aldosterone-producing adenoma (APA), as compared with bilaterally simultaneous AVS. In 138 consecutive patients who underwent subtyping of primary aldosteronism, we compared the results obtained simultaneously bilaterally when starting AVS (t-15) and 15 min after (t0), with those gained with a simulated sequential right-to-left AVS technique (R ⇒ L) created by combining hormonal values obtained at t-15 and at t0. The concordance between simultaneously obtained values at t-15 and t0, and between simultaneously obtained values and values gained with a sequential R ⇒ L technique, was also assessed. We found a marked interindividual variability of lateralization index values in the patients with bilaterally selective AVS at both time point. However, overall the lateralization index simultaneously determined at t0 provided a more accurate identification of APA than the simulated sequential lateralization indexR ⇒ L (P = 0.001). Moreover, regardless of which side was sampled first, the sequential AVS technique induced a sequence-dependent overestimation of lateralization index. While in APA patients the concordance between simultaneous AVS at t0 and t-15 and between simultaneous t0 and sequential technique was moderate-to-good (K = 0.55 and 0.66, respectively), in non-APA patients, it was poor (K = 0.12 and 0.13, respectively). Sequential AVS generates factitious between-sides gradients, which lower its diagnostic accuracy, likely because of the stress reaction arising upon starting AVS.

  15. Sequential Functionalization of Alkynes and Alkenes Catalyzed by Gold(I) and Palladium(II) N-Heterocyclic Carbene Complexes

    KAUST Repository

    Gó mez-Herrera, Alberto; Nahra, Fady; Brill, Marcel; Nolan, Steven P.; Cazin, Catherine S. J.

    2016-01-01

    The iodination of terminal alkynes for the synthesis of 1-iodoalkynes using N-iodosuccinimide in the presence of a AuI-NHC (NHC=N-heterocyclic carbene) catalyst is reported. A series of aromatic alkynes was transformed successfully into the corresponding 1-iodoalkynes in good to excellent yields under mild reaction conditions. The further use of these compounds as organic building blocks and the advantageous choice of metal-NHC complexes as catalysts for alkyne functionalization were further demonstrated by performing selective AuI-catalyzed hydrofluorination to yield (Z)-2-fluoro-1-iodoalkenes, followed by a Suzuki–Miyaura cross-coupling with aryl boronic acids catalyzed by a PdII-NHC complex to access trisubstituted (Z)-fluoroalkenes. All methodologies can be performed sequentially with only minor variations in the optimized individual reaction conditions, maintaining high efficiency and selectivity in all cases, which therefore, provides straightforward access to valuable fluorinated alkenes from commercially available terminal alkynes.

  16. Sequential Functionalization of Alkynes and Alkenes Catalyzed by Gold(I) and Palladium(II) N-Heterocyclic Carbene Complexes

    KAUST Repository

    Gómez-Herrera, Alberto

    2016-08-22

    The iodination of terminal alkynes for the synthesis of 1-iodoalkynes using N-iodosuccinimide in the presence of a AuI-NHC (NHC=N-heterocyclic carbene) catalyst is reported. A series of aromatic alkynes was transformed successfully into the corresponding 1-iodoalkynes in good to excellent yields under mild reaction conditions. The further use of these compounds as organic building blocks and the advantageous choice of metal-NHC complexes as catalysts for alkyne functionalization were further demonstrated by performing selective AuI-catalyzed hydrofluorination to yield (Z)-2-fluoro-1-iodoalkenes, followed by a Suzuki–Miyaura cross-coupling with aryl boronic acids catalyzed by a PdII-NHC complex to access trisubstituted (Z)-fluoroalkenes. All methodologies can be performed sequentially with only minor variations in the optimized individual reaction conditions, maintaining high efficiency and selectivity in all cases, which therefore, provides straightforward access to valuable fluorinated alkenes from commercially available terminal alkynes.

  17. Energy loss, range and fluence distributions, total reaction and projectile fragment production cross sections for proton-nucleus and nucleus-nucleus interactions

    International Nuclear Information System (INIS)

    Sihver, L.; Kanai, T.

    1992-07-01

    We have developed a computer code for calculations of energy loss (dE/dx) and range distributions for heavy ions in any media. The results from our calculations are in very good agreement with previous calculations. We have developed semiempirical total reaction cross section formulae for proton-nucleus (with Z p ≤26) and nucleus-nucleus (with Z p and Z t ≤26) reactions. These formulae apply for incident energies above 15 MeV and 100 MeV/nucleon respectively. From the total reaction cross sections, we can calculate the mean free paths and the fluence distributions of protons and heavy ions in any media. We have compared all the calculated reaction cross sections and the mean free paths with experimental data, and the agreement is good. We have also constructed a procedure for calculating projectile fragment production cross sections, by scaling semiempirical proton-nucleus partial cross section systematics. The scaling is performed using a scaling parameter deduced from our reaction cross sections formulae, and additional enhancements factors. All products with atomic number ranging from that of the projectile (Z p ) down to Z=2 can be calculated. The agreement between the calculated cross sections and the experimental data is better than earlier published results. (author)

  18. Verification of dosimetry cross sections above 10 MeV based on measurement of activation reaction rates in fission neutron field

    International Nuclear Information System (INIS)

    Odano, Naoteru; Miura, Toshimasa; Yamaji, Akio.

    1996-01-01

    To validate the dosimetry cross sections in fast neutron energy range, activation reaction rates were measured for 5 types of dosimetry cross sections which have sensitivity in the energy rage above 10 MeV utilizing JRR-4 reactor of JAERI. The measured reaction rates were compared with the calculations reaction rates by a continuous energy monte carlo code MVP. The calculated reaction rates were based on two dosimetry files, JENDL Dosimetry File and IRDF-90.2. (author)

  19. The Manganese-Catalyzed Cross-Coupling Reaction and the Influence of Trace Metals

    DEFF Research Database (Denmark)

    Santilli, Carola; Beigbaghlou, Somayyeh Sarvi; Ahlburg, Andreas

    2017-01-01

    The substrate scope of the MnCl2-catalyzed cross-coupling between aryl halides and Grignard reagents has been extended to several methyl-substituted aryl iodides by performing the reaction at elevated temperature in a microwave oven. A radical clock experiment revealed the presence of an aryl...

  20. Cross-section studies of relativistic deuteron reactions on copper by activation method

    Czech Academy of Sciences Publication Activity Database

    Suchopár, Martin; Wagner, Vladimír; Svoboda, Ondřej; Vrzalová, Jitka; Chudoba, Petr; Kugler, Andrej; Adam, Jindřich; Závorka, L.; Baldine, A.; Furman, W.; Kadykov, M. G.; Khushvaktov, J.; Solnyshkin, A. A.; Tsoupko-Sitnikov, V. V.; Tyutyunnikov, S. I.

    2015-01-01

    Roč. 344, FEB (2015), s. 63-69 ISSN 0168-583X R&D Projects: GA MŠk LG14004 Institutional support: RVO:61389005 Keywords : relativistic deuteron reactions * cross-sections * copper Subject RIV: BG - Nuclear , Atomic and Molecular Physics, Colliders Impact factor: 1.389, year: 2015

  1. A sequential hypothesis test based on a generalized Azuma inequality

    NARCIS (Netherlands)

    Reijsbergen, D.P.; Scheinhardt, Willem R.W.; de Boer, Pieter-Tjerk

    We present a new power-one sequential hypothesis test based on a bound for the probability that a bounded zero-mean martingale ever crosses a curve of the form $a(n+k)^b$. The proof of the bound is of independent interest.

  2. Direct measurement of the 7Be(n, α4 He reaction cross sections for the cosmological Li problem

    Directory of Open Access Journals (Sweden)

    Kawabata Takahiro

    2017-01-01

    Full Text Available The cross sections of the 7Be(n, α4He reaction for p-wave neutrons were experimentally determined at Ec.m. = 0.20−0.81 MeV close to the Big Bang nucleosynthesis (BBN energy window for the first time on the basis of the detailed balance principle by measuring the time-reverse reaction. The obtained cross sections are much larger than the cross sections for s-wave neutrons inferred from the recent measurement at the n_TOF facility in CERN, but significantly smaller than the theoretical estimation widely used in the BBN calculations. The present results suggest the 7Be(n, α4 He reaction rate is not large enough to solve the cosmological lithium problem

  3. Comparison of sequential vs same-day simultaneous collagen cross-linking and topography-guided PRK for treatment of keratoconus.

    Science.gov (United States)

    Kanellopoulos, Anastasios John

    2009-09-01

    The safety and efficacy of corneal collagen cross-linking (CXL) and topography-guided photorefractive keratectomy (PRK) using a different sequence and timing were evaluated in consecutive keratoconus cases. This study included a total of 325 eyes with keratoconus. Eyes were divided into two groups. The first group (n=127 eyes) underwent CXL with subsequent topography-guided PRK performed 6 months later (sequential group) and the second group (n=198 eyes) underwent CXL and PRK in a combined procedure on the same day (simultaneous group). Statistical differences were examined for pre- to postoperative changes in uncorrected (UCVA, logMAR) and best-spectacle-corrected visual acuity (BSCVA, logMAR), manifest refraction spherical equivalent (MRSE), keratometry (K), topography, central corneal thickness, endothelial cell count, corneal haze, and ectatic progression. Mean follow-up was 36+/-18 months (range: 24 to 68 months). At last follow-up in the sequential group, the mean UCVA improved from 0.9+/-0.3 logMAR to 0.49+/-0.25 logMAR, and mean BSCVA from 0.41+/-0.25 logMAR to 0.16+/-0.22 logMAR. Mean reduction in spherical equivalent refraction was 2.50+/-1.20 diopters (D), mean haze score was 1.2+/-0.5, and mean reduction in K was 2.75+/-1.30 D. In the simultaneous group, mean UCVA improved from 0.96+/-0.2 logMAR to 0.3+/-0.2 logMAR, and mean BSCVA from 0.39+/-0.3 logMAR to 0.11+/-0.16 logMAR. Mean reduction in spherical equivalent refraction was 3.20+/-1.40 D, mean haze score was 0.5+/-0.3, and mean reduction in K was 3.50+/-1.3 D. Endothelial cell count preoperatively and at last follow-up was unchanged (PPRK and CXL appears to be superior to sequential CXL with later PRK in the visual rehabilitation of progressing keratoconus. Copyright 2009, SLACK Incorporated.

  4. Density distribution of {sup 14}Be from reaction cross-section measurements

    Energy Technology Data Exchange (ETDEWEB)

    Moriguchi, T. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Ozawa, A., E-mail: ozawa@tac.tsukuba.ac.jp [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Ishimoto, S. [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Abe, Y. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Fukuda, M. [Department of Physics, Osaka University, Osaka 560-0043 (Japan); Hachiuma, I. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Ishibashi, Y.; Ito, Y. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Kuboki, T. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Lantz, M. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Nagae, D. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Namihira, K. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Nishimura, D. [Department of Physics, Osaka University, Osaka 560-0043 (Japan); Ohtsubo, T. [Department of Physics, Niigata University, Niigata 950-2181 (Japan); Ooishi, H. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Suda, T. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Suzuki, H. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Suzuki, T. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Takechi, M.; Tanaka, K. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); and others

    2014-09-15

    We measured the reaction cross sections of the two-neutron halo nucleus {sup 14}Be with proton and carbon targets at about 41 and 76 MeV/nucleon. Based on a Glauber model calculation, we deduced the matter density distribution of {sup 14}Be in which previously measured interaction cross sections at relativistic energies were also included. An s-wave dominance in {sup 14}Be has been confirmed, although the halo tail of {sup 14}Be is not distributed as much as that of {sup 11}Li. Significant mixing of the p-wave in addition to the s- and d-wave is also suggested.

  5. Sequential immunization with V3 peptides from primary human immunodeficiency virus type 1 produces cross-neutralizing antibodies against primary isolates with a matching narrow-neutralization sequence motif.

    Science.gov (United States)

    Eda, Yasuyuki; Takizawa, Mari; Murakami, Toshio; Maeda, Hiroaki; Kimachi, Kazuhiko; Yonemura, Hiroshi; Koyanagi, Satoshi; Shiosaki, Kouichi; Higuchi, Hirofumi; Makizumi, Keiichi; Nakashima, Toshihiro; Osatomi, Kiyoshi; Tokiyoshi, Sachio; Matsushita, Shuzo; Yamamoto, Naoki; Honda, Mitsuo

    2006-06-01

    An antibody response capable of neutralizing not only homologous but also heterologous forms of the CXCR4-tropic human immunodeficiency virus type 1 (HIV-1) MNp and CCR5-tropic primary isolate HIV-1 JR-CSF was achieved through sequential immunization with a combination of synthetic peptides representing HIV-1 Env V3 sequences from field and laboratory HIV-1 clade B isolates. In contrast, repeated immunization with a single V3 peptide generated antibodies that neutralized only type-specific laboratory-adapted homologous viruses. To determine whether the cross-neutralization response could be attributed to a cross-reactive antibody in the immunized animals, we isolated a monoclonal antibody, C25, which neutralized the heterologous primary viruses of HIV-1 clade B. Furthermore, we generated a humanized monoclonal antibody, KD-247, by transferring the genes of the complementary determining region of C25 into genes of the human V region of the antibody. KD-247 bound with high affinity to the "PGR" motif within the HIV-1 Env V3 tip region, and, among the established reference antibodies, it most effectively neutralized primary HIV-1 field isolates possessing the matching neutralization sequence motif, suggesting its promise for clinical applications involving passive immunizations. These results demonstrate that sequential immunization with B-cell epitope peptides may contribute to a humoral immune-based HIV vaccine strategy. Indeed, they help lay the groundwork for the development of HIV-1 vaccine strategies that use sequential immunization with biologically relevant peptides to overcome difficulties associated with otherwise poorly immunogenic epitopes.

  6. Capture cross-section and rate of the 14 C (n, γ) 15 C reaction from ...

    Indian Academy of Sciences (India)

    We calculate the Coulomb dissociation of 15C on a Pb target at 68 MeV/u incident beam energy within the fully quantum mechanical distorted wave Born approximation formalism of breakup reactions. The capture cross-section and the subsequent rate of the 14C(, )15C reaction are calculated from the ...

  7. High resolution time-of-flight spectrometer for crossed molecular beam study of elementary chemical reactions

    International Nuclear Information System (INIS)

    Qiu Minghui; Che Li; Ren Zefeng; Dai Dongxu; Wang Xiuyan; Yang Xueming

    2005-01-01

    In this article, we describe an apparatus in our laboratory for investigating elementary chemical reactions using the high resolution time-of-flight Rydberg tagging method. In this apparatus, we have adopted a rotating source design so that collision energy can be changed for crossed beam studies of chemical reactions. Preliminary results on the HI photodissociation and the F atom reaction with H 2 are reported here. These results suggest that the experimental apparatus is potentially a powerful tool for investigating state-to-state dynamics of elementary chemical reactions

  8. Suzuki-Miyaura cross-coupling reactions in aqueous media: green and sustainable syntheses of biaryls.

    Science.gov (United States)

    Polshettiwar, Vivek; Decottignies, Audrey; Len, Christophe; Fihri, Aziz

    2010-05-25

    Carbon-carbon cross-coupling reactions are among the most important processes in organic chemistry, and Suzuki-Miyaura reactions are among the most widely used protocols for the formation of carbon-carbon bonds. These reactions are generally catalyzed by soluble palladium complexes with various ligands. However, the use of toxic organic solvents remains a scientific challenge and an aspect of economical and ecological relevance. This Review will summarize various recently developed significant methods by which the Suzuki-Miyaura coupling was conducted in aqueous media, and analyzes if they are "real green" protocols.

  9. Cross Sections Calculations of ( d, t) Nuclear Reactions up to 50 MeV

    Science.gov (United States)

    Tel, E.; Yiğit, M.; Tanır, G.

    2013-04-01

    In nuclear fusion reactions two light atomic nuclei fuse together to form a heavier nucleus. Fusion power is the power generated by nuclear fusion processes. In contrast with fission power, the fusion reaction processes does not produce radioactive nuclides. The fusion will not produce CO2 or SO2. So the fusion energy will not contribute to environmental problems such as particulate pollution and excessive CO2 in the atmosphere. Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production is still believed to be unlikely before 2050. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. In the fusion reactor, tritium self-sufficiency must be maintained for a commercial power plant. Therefore, for self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of ( d, t) nuclear reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. Since the experimental data of charged particle induced reactions are scarce, self-consistent calculation and analyses using nuclear theoretical models are very important. In this study, ( d, t) cross sections for target nuclei 19F, 50Cr, 54Fe, 58Ni, 75As, 89Y, 90Zr, 107Ag, 127I, 197Au and 238U have been investigated up to 50 MeV deuteron energy. The excitation functions for ( d, t) reactions have been calculated by pre-equilibrium reaction mechanism. Calculation results have been also compared with the available measurements in

  10. Methods of calculation of cross section of reaction 115In(gamma, n)114mIn

    International Nuclear Information System (INIS)

    Zhaba, V.I.; Parlag, A.M.

    2015-01-01

    The cross section of reaction 115 In(gamma, n) 114m In is expected by different methods. Results of the got cross section it is well comported inter se the Penfold-Leiss and Tikhonov's methods. The calculation of cross section is conducted the Penfold-Leiss method with smoothing out by the method of iterations. Number of iterations n = 1; 3; 5. In the programmatic package of TALYS-1.4 got cross section for five models of closeness of levels. Theoretical and experimental results well coincide in a maximum.

  11. Hexacationic Dendriphos ligands in the Pd-catalyzed Suzuki-Miyaura cross-coupling reaction: scope and mechanistic studies

    NARCIS (Netherlands)

    Snelders, D.J.M.; van Koten, G.; Klein Gebbink, R.J.M.

    2009-01-01

    The combination of Pd2dba3·CHCl3and hexacationic triarylphosphine-based Dendriphos ligands (1-3) leads to a highly active catalytic system in the Suzuki-Miyaura cross-coupling reaction. Under relatively mild reaction conditions, nonactivated aryl bromides and activated aryl chlorides can be coupled

  12. Bite angle effects of diphosphines in C-C and C-X bond forming cross coupling reactions

    NARCIS (Netherlands)

    Birkholz, M.N.; Freixa, Z.; van Leeuwen, P.W.N.M.

    2009-01-01

    Catalytic reactions of C-C and C-X bond formation are discussed in this critical review with particular emphasis on cross coupling reactions catalyzed by palladium and wide bite angle bidentate diphosphine ligands. Especially those studies have been collected that allow comparison of the ligand bite

  13. Neutral strange particle production and inelastic cross section in p-bar+Ta reaction at 4 GeV/c

    International Nuclear Information System (INIS)

    Miyano, K.; Noguchi, Y.; Yoshimura, Y.

    1988-01-01

    The inclusive production of K/sub s//sup 0/, /Lambda/ Lambda-bar, and K/sub s//sup 0//Lambda/in the p-barTa reaction at 4 GeV/c was measured and compared with that in the p-barp reaction. The total inelastic and topological cross sections were also measured. The number of /Lambda/s produced in the p-barTa reaction was 11.3 times larger than that expected from the geometrical cross section, which is defined as A/sup 2/3/ times the cross section for the p-barp reaction. The yield ratio Lambda-bar//Lambda/was found to be 2 x 10/sup -2/. These values cannot be accounted for by a straightforward extension of the p-barN reaction. Besides, a correlation of 2 vees like K/sub s//sup 0/-/Lambda/could not prove their simultaneous production. Nuclear temperatures of 135 and 97 MeV were obtained from the kinetic energy spectra of K/sub s//sup 0/ and /Lambda/ respectively. The kinematical characteristics of the K/sub s//sup 0/ and /Lambda/produced were analyzed in terms of the fireball model

  14. 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

  15. Neutrino-induced neutral-current reaction cross sections for r-process nuclei

    CERN Document Server

    Langanke, K

    2002-01-01

    Neutrino-induced reactions play an important role during and after the r-process, if the latter occurs in an environment with extreme neutrino fluxes such as the neutrino-driven wind model or neutron star mergers. Recently we have evaluated the charged-current neutrino-nucleus cross sections relevant for r-process simulations. We extend our approach here to the neutral-current cross sections. Our tabulation considers neutron-rich nuclei with neutron numbers N=41-135 and charge numbers Z=21-82 and lists total as well as partial neutron spallation cross sections. The calculations have been performed within the random phase approximation considering multipole transitions with J<=3 and both parities. 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.

  16. 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.

  17. Gold(I)-catalyzed diazo cross-coupling: a selective and ligand-controlled denitrogenation/cyclization cascade.

    Science.gov (United States)

    Xu, Guangyang; Zhu, Chenghao; Gu, Weijin; Li, Jian; Sun, Jiangtao

    2015-01-12

    An unprecedented gold-catalyzed ligand-controlled cross-coupling of diazo compounds by sequential selective denitrogenation and cyclization affords N-substituted pyrazoles in a position-switchable mode. This novel transformation features selective decomposition of one diazo moiety and simultaneous preservation of the other one from two substrates. Notably, the choice of the ancillary ligand to the gold complex plays a pivotal role on the chemo- and regioselectivity of the reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Parameterization of α-nucleus total reaction cross section at intermediate energies

    International Nuclear Information System (INIS)

    Alvi, M A; Abdulmomen, M A

    2008-01-01

    Applying a Coulomb correction factor to the Glauber model we have derived a closed expression for α-nucleus total reaction cross section, σ R . Under the approximation of rigid projectile model, the elastic S-matrix element S el (b) is evaluated from the phenomenological N-α amplitude and a Gaussian fit to the Helm's model form factor. Excellent agreements with the experimental data have been achieved by performing two-parameter fits to the α-nucleus σ R data in the energy range about 75 to 193 MeV. One of the parameters was found to be energy independent while the other, as expected, shows the energy dependence similar to that of N-α total cross section.

  19. Production cross-sections of radionuclides from α-induced reactions on natural copper up to 50 MeV

    International Nuclear Information System (INIS)

    Usman, Ahmed Rufai; Khandaker, Mayeen Uddin; Haba, Hiromitsu; Otuka, Naohiko; Murakami, Masashi; Komori, Yukiko

    2016-01-01

    The excitation functions were measured for the "n"a"tCu(α,x)"6"6","6"7Ga,"6"5Zn,"5"7","5"8","6"0Co reactions in the energy range of 16.5 −50 MeV. A conventional stacked-foil activation technique combined with HPGe γ-ray spectrometry was employed to determine cross-sections. The measured cross-sections were critically compared with relevant previous experimental data and also with the evaluated data in the TENDL-2014 library. Present results confirmed some of the previous experimental data, whereas only a partial agreement was found with the evaluated data. The measured data are useful for reducing the existing discrepancies in the literature, to improve the nuclear reaction model codes, and to enrich the experimental database towards various applications. - Highlights: • New measurements of gallium radionuclides for monitor reactions. • Production of cobalt radionuclides via alpha route on natural Copper. • Extensive critical review of earlier reported cross-sections.

  20. Breakup reactions at intermediate and high energy

    International Nuclear Information System (INIS)

    Shotter, A.C.; Bice, A.N.

    1981-01-01

    Having considered some general aspects of peripheral break-up reactions involving heavy ions for the incident energy range 10-2000 MeV/A, specific experiments carried out at Berkeley in 1980 in the energy range 10-20 MeV/A are discussed. These indicate that sequential break-up processes from non-sequential inelastic processes both play significant roles in the mechanism. (UK)

  1. 180Ta/sup g,m/ production cross sections form the 180Hf(p,n) reaction

    International Nuclear Information System (INIS)

    Norman, E.B.; Renner, T.R.; Grant, P.J.

    1981-01-01

    Cross sections have been determined for the production of the J/sup π/ = 1 + 180 Ta/sup g/ and the J/sup π/= 9 - 180 Ta/sup m/ from the 180 Hf(p,n) reaction. The 180 Ta/sup g/ cross sections were determined from measurements of γ-rays emitted following the electron-capture and β-decay of this 8.1-hour state. Total 180 Ta production cross sections were determined from measurements of the thick-target (p,n) yield. 180 Ta/sup m/ cross sections were calculated by subtracting the 180 Ta/sup g/ cross sections from the total (p,n) cross sections. These measurements are compared with the results of a statistical-model evaporation calculation

  2. Reaction and fusion cross sections for 32S on 27Al and 48Ti

    International Nuclear Information System (INIS)

    Porto, F.; Sambataro, S.; Kusterer, K.; Liu Ken Pao; Doukellis, G.; Harney, H.L.

    1981-01-01

    Elastic scattering and evaporation residues have been measured for the system 32 S + 27 Al at Esub(c)sub(.)sub(m)sub(.) = 66.4, 73.2 MeV and 32 S + 48 Ti at Esub(c)sub(.)sub(m)sub(.) = 96.0 MeV. Reaction cross sections have been obtained by use of the optical theorem and are found to be about 60% larger than the fusion cross sections. (orig.)

  3. Inclusive proton spectra and total reaction cross sections for proton-nucleus scattering at 800 MeV

    International Nuclear Information System (INIS)

    McGill, J.A.

    1981-08-01

    Current applications of multiple scattering theory to describe the elastic scattering of medium energy protons from nuclei have been shown to be quite successful in reproducing the experimental cross sections. These calculations use the impulse approximation, wherein the scattering from individual nucleons in the nucleus is described by the scattering amplitude for a free nucleon. Such an approximation restricts the inelastic channels to those initiated by nucleon-nucleon scattering. As a first step in determining the nature of p + nucleus scattering at 800 MeV, both total reaction cross sections and (p,p') inclusive cross sections were measured and compared to the free p + p cross sections for hydrogen, deuterium, calcium 40, carbon 12, and lead 208. It is concluded that as much as 85% of all reactions in a nucleus proceed from interactions with a single nucleon in the nucleus, and that the impulse approximation is a good starting point for a microscopic description of p + nucleus interactions at 800 MeV

  4. Temperature-controlled cross-linking of silver nanoparticles with Diels-Alder reaction and its application on antibacterial property

    International Nuclear Information System (INIS)

    Liu, Lian; Yang, Pengfei; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

    2017-01-01

    Highlights: • Silver nanoparticles were functionalized by furan groups. • The DA reaction of furan with bismaleimide was used to cross-link the particles. • The reverse cross-linking could be controlled by temperature. • The antibacterial activity of silvers could be adjusted by the cross-linking. - Abstract: Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV–vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

  5. Temperature-controlled cross-linking of silver nanoparticles with Diels-Alder reaction and its application on antibacterial property

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lian; Yang, Pengfei, E-mail: ypf@qlu.edu.cn; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

    2017-05-01

    Highlights: • Silver nanoparticles were functionalized by furan groups. • The DA reaction of furan with bismaleimide was used to cross-link the particles. • The reverse cross-linking could be controlled by temperature. • The antibacterial activity of silvers could be adjusted by the cross-linking. - Abstract: Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV–vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

  6. Suzuki-Miyaura cross-coupling reactions in aqueous media: Green and sustainable syntheses of biaryls

    KAUST Repository

    Polshettiwar, Vivek

    2010-02-28

    Carbon-carbon cross-coupling reactions are among the most important processes in organic chemistry, and Suzuki-Miyaura reactions are among the most widely used protocols for the formation of carbon-carbon bonds. These reactions are generally catalyzed by soluble palladium complexes with various ligands. However, the use of toxic organic solvents remains a scientific challenge and an aspect of economical and ecological relevance. This Review will summarize various recently developed significant methods by which the Suzuki-Miyaura coupling was conducted in aqueous media, and analyzes if they are "real green" protocols. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. GRAPhEME: a setup to measure (n, xn γ) reaction cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Henning, Greg; Bacquias, A.; Capdevielle, O.; Dessagne, P.; Kerveno, M.; Rudolf, G. [Universite de Strasbourg, IPHC, 23 rue du Loess 67037 Strasbourg (France); CNRS, UMR7178, 67037 Strasbourg (France); Borcea, C.; Negret, A.; Olacel, A. [Nat. Inst. Of Phys. And Nucl. Eng., Bucharest (Romania); Drohe, J.C.; Plompen, A.J.M.; Nyman, M. [EU/ JRC-IRMM, Geel (Belgium)

    2015-07-01

    Most of nuclear reactor developments are using evaluated data base for numerical simulations. However, the considered databases present still large uncertainties and disagreements. To improve their level of precision, new measurements are needed, in particular for (n, xn) reactions, which are of great importance as they modify the neutron spectrum, the neutron population, and produce radioactive species. The IPHC group started an experimental program to measure (n, xn gamma) reaction cross sections using prompt gamma spectroscopy and neutron energy determination by time of flight. Measurements of (n, xn gamma) cross section have been performed for {sup 235,238}U, {sup 232}Th, {sup nat,182,183,184,186}W, {sup nat}Zr. The experimental setup is installed at the neutron beam at GELINA (Geel, Belgium). The setup has recently been upgraded with the addition of a highly segmented 36 pixels planar HPGe detector. Significant efforts have been made to reduce radiation background and electromagnetic perturbations. The setup is equipped with a high rate digital acquisition system. The analysis of the segmented detector data requires a specific procedure to account for cross signals between pixels. An overall attention is paid to the precision of the measurement. The setup characteristic and the analysis procedure will be presented along with the acquisition and analysis challenges. Examples of results and their impact on models will be discussed. (authors)

  8. Determination of Cross-Sections of Fast-Muon-Induced Reactions to Cosmogenic Radionuclides

    CERN Multimedia

    Hagner, T; Heisinger, B; Niedermayer, M; Nolte, E; Oberauer, L; Schonert, S; Kubik, P W

    2002-01-01

    %NA54 %title\\\\ \\\\We propose to measure cross-sections for fast muon-induced production of radionuclides. Firstly to study the contribution of fast-muon-induced reactions to the in-situ production of cosmogenic radionuclides in the lithosphere. Concrete is used to simulate the rock and to generate a secondary particle shower. The reaction channels to be measured are: C to $^{10}$Be, O to $^{10}$Be and $^{14}$C, Si to $^{26}$Al, S to $^{26}$Al, Ca to $^{36}$Cl, Fe to $^{53}$Mn and $^{205}$Tl to $^{205}$Pb. The energy dependent cross-section can be described by one single parameter $\\sigma_0$ and the energy dependence $\\rm\\overline{E}^{0.7}$ on the mean energy $\\rm\\overline{E}$. The irradiations of the targets is done at CERN. The produced radionuclides are measured by accelerator mass spectrometry in Munich and Zurich.\\\\ \\\\Secondly, muon induced signals can be a major source of background in experiments with low event rates located deep underground. We intent to study the produced radioactivity by fast-muon-ind...

  9. Measurements and systematics studies of the (n,p), (n,α) and (n,2n) reactions cross-sections at 14.5 MeV neutrons

    International Nuclear Information System (INIS)

    Osman, Khalda

    2000-01-01

    Accurate knowledge of the cross-sections for fast neutron-induced reactions utilizing the D-T reaction is important not only because of the wide spread of data observed in the literature, but also because of the world wide demand and requests for such data, in view of the increasing interest in the fusion reactor technology, which is based on the same reactions. Cross-sections are needed also for various practical purposes, including neutron activation analysis and dosimetry. In this work the (n.p), (n,2n) and (n,α) reactions cross-sections were measured at 14.5 MeV for isotopes of the elements: Cr, Ti, Ni, Co, Zr, and Mo using the activation method. The measured cross-sections were compared with recently published data. Good agreement was observed for most of the measurements. The discrepancies observed were attributed to difficulties related to the long half-life of the product nuclei and small abundances of the target isotopes. Attempts were also made to study the dependence of the (n,p), (n,2n) and (n,α) reactions cross-sections on the on the asymmetry parameter (N-Z)/A. The results confirmed the trend theoretically suggested by Levkovskii and experimentally realized by Qaim and co-workers. The isotopic dependence of (n,p) reaction cross-sections and the variation of the ration σ n ,p/σ n ,α with Z-number of the target isotopes were also studied in this work and the results obtained were found to be in agreement with theoretical predictions. In this work studies carried out for the systematics of the (n,p), (n,2n) and (n,α) reactions cross-sections at 14 MeV neutrons and formula based on the statistical model presented, with the aim of improving the systematics of these cross-sections. Comparison of present proposed systematics were for the (n,p), (n,2n) and (n,α) reactions cross-sections with the cross-section values measured in this work was made. Good agreement was generally noted, but some discrepancies were also observed. These discrepancies were

  10. Investigation of excitation functions using new evaluated empirical and semi-empirical systematic for 14-15 MeV (n, t) reaction cross sections

    International Nuclear Information System (INIS)

    Tel, E.; Aydin, E. G.; Aydin, A.; Kaplan, A.

    2007-01-01

    The hybrid reactor is a combination of the fusion and fission processes. In the fusion-fission hybrid reactor, tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of (n,t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at energies up to 20 MeV. In this study, we have investigated the asymmetry term effect for the (n,t) reaction cross sections at 14-15 neutron incident energy. It has been discussed the odd even effect and the pairing effect considering binding energy systematic of the nuclear shell model for the new experimental data and new cross section formulas (n,t) reactions developed by Tel et al. We have determined a different parameter groups by the classification of nuclei into even-even, even-odd and odd-even for (n,t) reactions cross sections. The obtained empirical formulas by fitting two parameter for (n,t) reactions were given. All calculated results have been compared with the experimental data. By using the new cross sections formulas (n,t) reactions the obtained results have been discussed and compared with the available experimental data

  11. Cross section measurements of the 10B(d,n0)11C reaction below 160 keV

    International Nuclear Information System (INIS)

    Stave, S.; Ahmed, M. W.; Blackston, M. A.; Crowell, A. S.; Henshaw, S. S.; Howell, C. R.; Kingsberry, P.; Perdue, B. A.; Weller, H. R.; Antolak, A. J.; Doyle, B. L.; Rossi, P.; Prior, R. M.; Spraker, M. C.

    2008-01-01

    New data were taken at the Triangle Universities Nuclear Laboratory to investigate the plausibility of using low energy deuterons and the 10 B(d,n) 11 C reaction as a portable source of 6.3 MeV neutrons. Analysis of the data at and below incident deuteron energies of 160 keV indicates an n 0 neutron cross section that is lower than previous estimates by at least three orders of magnitude. In separate runs, deuterons with two different energies (160 and 140 keV) were stopped in a 10 B target. The resulting n 0 neutrons of approximately 6.3 MeV were detected at angles between 0 deg. and 150 deg. The angle integrated yields were used to determine the astrophysical S factor for this reaction assuming a constant value for the S factor below 160 keV. The cross sections reported between 130 and 160 keV were calculated using the extracted value of the S factor. The measured n 0 cross section is several orders of magnitude smaller than previous results, thus eliminating 10 B(d,n) 11 C as a portable source of intense neutrons with low energy deuteron beams on the order of tens of microamps. In order to gain insight into the reaction dynamics at these low energies the cross section results have been compared with results from calculations using the distorted wave Born approximation (DWBA) and a detailed Hauser-Feshbach calculation performed by the authors. The angular distribution is consistent with the Hauser-Feshbach calculation suggesting a statistical compound nucleus reaction rather than a direct reaction

  12. Experimental cross-sections for proton-induced nuclear reactions on Mo-nat

    Czech Academy of Sciences Publication Activity Database

    Červenák, Jaroslav; Lebeda, Ondřej

    2016-01-01

    Roč. 380, AUG (2016), s. 32-49 ISSN 0168-583X R&D Projects: GA MŠk(CZ) LM2011019 Institutional support: RVO:61389005 Keywords : cross-sections * excitation functions * proton-induced nuclear reactions * natural molybdenum * Mo-99 * Tc-99m * Tc96m+g * Tc-95m * thick target yields * U-120M cyclotron Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.109, year: 2016

  13. Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

    NARCIS (Netherlands)

    Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

  14. Oscillatory pulses and wave trains in a bistable reaction-diffusion system with cross diffusion.

    Science.gov (United States)

    Zemskov, Evgeny P; Tsyganov, Mikhail A; Horsthemke, Werner

    2017-01-01

    We study waves with exponentially decaying oscillatory tails in a reaction-diffusion system with linear cross diffusion. To be specific, we consider a piecewise linear approximation of the FitzHugh-Nagumo model, also known as the Bonhoeffer-van der Pol model. We focus on two types of traveling waves, namely solitary pulses that correspond to a homoclinic solution, and sequences of pulses or wave trains, i.e., a periodic solution. The effect of cross diffusion on wave profiles and speed of propagation is analyzed. We find the intriguing result that both pulses and wave trains occur in the bistable cross-diffusive FitzHugh-Nagumo system, whereas only fronts exist in the standard bistable system without cross diffusion.

  15. Relations between the simultaneous and sequential transfer of two nucleons

    International Nuclear Information System (INIS)

    Satchler, G.R.

    1982-01-01

    The transfer of two nucleons between projectile and target in a direct or peripheral reaction such as (p,t) or ( 16 O, 14 C) may occur in one-step or two-steps. These we refer to as simultaneous and sequential transfers, respectively. In the former, the interaction acts once and both nucleons are transferred. In the latter, the interaction acts once to transfer one nucleon, the system then propagates in one or more intermediate states and is followed by a second action of the interaction to transfer the second nucleon. This process may be symbolized for the examples as (p,d; d,t) and ( 16 O, 15 N; 15 N, 14 C), implying the intermediate formation of a deuteron or the nucleus 15 N. In terms of a perturbation theory expansion, such as the distorted-wave Born series, simultaneous transfer is possible in first order while sequential transfer requires second order. The nuclear forces are predominantly two-body in character; hence, in first-order only one of the two nucleons experiences an interaction. The possibility of finding that the other nucleon has also transferred arises only because its state within the projectile is not orthogonal to the state in the target into which it transfers. In the two-step process each nucleon is transferred under the direct influence of an interaction with the target. The one-step and two-step amplitudes are frequently comparable in magnitude for light-ion reactions while the two-step may dominate in reactions with heavy ions. Our purpose here is to gain some insight into the relationship between the two amplitudes by using a simple approximate form of the theory. For simplicity, we shall discuss a light-ion reaction and, to be specific, we choose the (t,p) reaction (or the inverse (p,t) reaction)

  16. Isomeric cross sections of neutron induced reactions on Ge and Ir isotopes

    International Nuclear Information System (INIS)

    Vlastou, R.; Papadopoulos, C.T.; Kokkoris, M.; Perdikakis, G.; Galanopoulos, S.; Patronis, N.; Serris, M.; Perdikakis, G.; Harissopulos, S.; Demetriou, P.

    2008-01-01

    The 72 Ge(n,α) 69m Zn, 74 Ge(n,α) 71m Zn, 76 Ge(n,2n) 75g+m Ge and 191 Ir(n,2n) 190 Ir g+m1 and 191 Ir(n,2n) 190 Ir m2 reaction cross sections were measured from 9.6 to 11.4 MeV relative to the 27 Al(n,α) 24 Na reference reaction via the activation method. The quasi-monoenergetic neutron beams were produced via the 2 H(d,n) 3 He reaction at the 5 MV VdG Tandem T11/25 accelerator of NCSR 'Demokritos'. Statistical model calculations using the codes STAPRE-F and EMPIRE (version 2.19) and taking into account pre-equilibrium emission were performed on the data measured in this work as well as on data reported in literature. (authors)

  17. Sequential Condensation and Hydrodeoxygenation Reaction of Furfural-Acetone Adduct over Mix Catalysts Ni/SiO2 and Cu/SiO2 in Water

    Directory of Open Access Journals (Sweden)

    Siti Mariyah Ulfa

    2018-05-01

    Full Text Available Sequential condensation and hydrodeoxygenation reaction were perform using autoclave batch reactor in the presence of water as a solvent. The condensation of furfural and acetone was performed using MgO catalyst followed by hydrodeoxygenation using mix catalyst Ni/SiO2 and Cu/SiO2. The catalyst was prepared by wet-impregnation method and analyzed by XRD, SEM-EDX as well as BET surface. Condensation of furfural and acetone in 1:2 mol ratio was carried out by reflux gave 4-(2-furyl-3-buten-2-one and 1,5-bis-(2-furanyl-1,4-pentadien-3-one. The condensation product was then subjected for hydrodeoxygenation using batch reactor, catalyzed by mixed Ni/SiO2 and Cu/SiO2 at 150 and 180 °C for 2 h. The product identified as alkane derivatives with the conversion at 38.83 and 50.35%, respectively. The selectivity of hydrocarbon is 61.39% at 150 °C and 16.55% at 180 °C. Increasing the reaction temperature to 200 °C did not give any products except the recovery of the precursor. It showed that higher temperature enhanced the catalyst activity but the selectivity is controlled by low reaction temperature.

  18. Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation

    Directory of Open Access Journals (Sweden)

    Waleed Ali Abou Samra

    2016-01-01

    Full Text Available Aim. To compare objective and subjective outcome after simultaneous wave front guided (WFG PRK and accelerated corneal cross-linking (CXL in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods. 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results. All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P<0.001. A significant improvement was observed in keratometric and Q values. The improvement in all parameters was stable till the end of follow-up. Likewise, no significant difference was determined in between the 2 groups in any of recorded parameters. Subjective data revealed similarly significant improvement in both groups. Conclusions. WFG PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.

  19. Competitive interactions affect working memory performance for both simultaneous and sequential stimulus presentation.

    Science.gov (United States)

    Ahmad, Jumana; Swan, Garrett; Bowman, Howard; Wyble, Brad; Nobre, Anna C; Shapiro, Kimron L; McNab, Fiona

    2017-07-06

    Competition between simultaneously presented visual stimuli lengthens reaction time and reduces both the BOLD response and neural firing. In contrast, conditions of sequential presentation have been assumed to be free from competition. Here we manipulated the spatial proximity of stimuli (Near versus Far conditions) to examine the effects of simultaneous and sequential competition on different measures of working memory (WM) for colour. With simultaneous presentation, the measure of WM precision was significantly lower for Near items, and participants reported the colour of the wrong item more often. These effects were preserved when the second stimulus immediately followed the first, disappeared when they were separated by 500 ms, and were partly recovered (evident for our measure of mis-binding but not WM precision) when the task was altered to encourage participants to maintain the sequentially presented items together in WM. Our results show, for the first time, that competition affects the measure of WM precision, and challenge the assumption that sequential presentation removes competition.

  20. Pd/NbOPO₄ multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.

    Science.gov (United States)

    Xia, Qi-Neng; Cuan, Qian; Liu, Xiao-Hui; Gong, Xue-Qing; Lu, Guan-Zhong; Wang, Yan-Qin

    2014-09-08

    Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256 h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1) The noble metal (in this case Pd) is the active center for hydrogenation; 2) NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3) a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Thermal neutron radiative capture cross-section of 186W(n, γ)187W reaction

    International Nuclear Information System (INIS)

    Tan, V H; Son, P N

    2016-01-01

    The thermal neutron radiative capture cross section for 186 W(n, γ) 187 W reaction was measured by the activation method using the filtered neutron beam at the Dalat research reactor. An optimal composition of Si and Bi, in single crystal form, has been used as neutron filters to create the high-purity filtered neutron beam with Cadmium ratio of R cd = 420 and peak energy E n = 0.025 eV. The induced activities in the irradiated samples were measured by a high resolution HPGe digital gamma-ray spectrometer. The present result of cross section has been determined relatively to the reference value of the standard reaction 197 Au(n, γ) 198 Au. The necessary correction factors for gamma-ray true coincidence summing, and thermal neutron self-shielding effects were taken into account in this experiment by Monte Carlo simulations. (paper)

  2. Long-range versus short-range correlations in the two-neutron transfer reaction 64Ni(18O,16O)66Ni

    Science.gov (United States)

    Paes, B.; Santagati, G.; Vsevolodovna, R. Magana; Cappuzzello, F.; Carbone, D.; Cardozo, E. N.; Cavallaro, M.; García-Tecocoatzi, H.; Gargano, A.; Ferreira, J. L.; Lenzi, S. M.; Linares, R.; Santopinto, E.; Vitturi, A.; Lubian, J.

    2017-10-01

    Recently, various two-neutron transfer studies using the (18O,16O) reaction were performed with a large success. This was achieved because of a combined use of the microscopic quantum description of the reaction mechanism and of the nuclear structure. In the present work we use this methodology to study the two-neutron transfer reaction of the 18O+64Ni system at 84 MeV incident energy, to the ground and first 2+ excited state of the residual 66Ni nucleus. All the experimental data were measured by the large acceptance MAGNEX spectrometer at the Instituto Nazionale di Fisica Nucleare -Laboratori Nazionali del Sud (Italy). We have performed exact finite range cross section calculations using the coupled channel Born approximation (CCBA) and coupled reaction channel (CRC) method for the sequential and direct two-neutron transfers, respectively. Moreover, this is the first time that the formalism of the microscopic interaction boson model (IBM-2) was applied to a two-neutron transfer reaction. From our results we conclude that for two-neutron transfer to the ground state of 66Ni, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of 66Ni, the sequential process dominates. A competition between long-range and short-range correlations is discussed, in particular, how the use of two different models (Shell model and IBM's) help to disentangle long- and short-range correlations.

  3. Calculation of the Reaction Cross Section for Several Actinides

    International Nuclear Information System (INIS)

    Hambsch, Franz-Josef; Oberstedt, Stephan; Vladuca, Gheorghita; Tudora, Anabella; Filipescu, Dan

    2005-01-01

    New, self-consistent, neutron-induced reaction cross-section calculations for 235,238U, 237Np, and 231,232,233Pa have been performed. The statistical model code STATIS was extended to take into account the multi-modality of the fission process. The three most dominant fission modes, the two asymmetric standard I (S1) and standard II (S2) modes, and the symmetric superlong (SL) mode have been taken into account. De-convoluted fission cross sections for these modes in 235,238U(n,f) and 237Np(n,f) based on experimental branching ratios, were calculated for the first time up to the second chance fission threshold. For 235U(n,f) and 233Pa(n,f), the calculations being made up to 50 MeV and 20 MeV incident neutron energy, respectively, higher fission chances have been considered. This implied the need for additional calculations for the neighbouring isotopes.As a side product also mass yield distributions could be calculated at energies hitherto not accessible by experiment. Experimental validation of the predictions is being envisaged

  4. Integral cross-section measurements for investigating the emission of complex particles in 14 MeV neutron-induced nuclear reactions

    International Nuclear Information System (INIS)

    Qaim, S.M.

    1981-01-01

    Some of the off-line techniques used for the determination of integral cross-section data are reviewed and, as a critical check, some typical data sets are compared. The systematic trends reported in the cross-section data for (n,d), (n,t), (n, 3 He) and (n,α) reactions are discussed. A brief discussion of the possible reaction mechanisms is given. Some of the applications of the data are outlined. (author)

  5. Extracting integrated and differential cross sections in low energy heavy-ion reactions from backscattering measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sargsyan, V. V. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Yerevan State University, 0025 Yerevan (Armenia); Adamian, G. G., E-mail: adamian@theor.jinr.ru [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Antonenko, N. V. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Mathematical Physics Department, Tomsk Polytechnic University, 634050 Tomsk (Russian Federation); Diaz-Torres, A. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas, I-38123 Villazzano, Trento (Italy); Gomes, P. R. S. [de Fisica, Universidade Federal Fluminense, Av. Litorânea, s/n, Niterói, R.J. 24210-340 (Brazil); Lenske, H. [Institut für Theoretische Physik der Justus–Liebig–Universität, D–35392 Giessen (Germany)

    2016-07-07

    We suggest new methods to extract elastic (quasi-elastic) scattering angular distribution and reaction (capture) cross sections from the experimental elastic (quasi-elastic) backscattering excitation function taken at a single angle.

  6. Quantum mechanical calculations of state-to-state cross sections and rate constants for the F + DCl → Cl + DF reaction.

    Science.gov (United States)

    Bulut, Niyazi; Kłos, Jacek; Roncero, Octavio

    2015-06-07

    We present accurate state-to-state quantum wave packet calculations of integral cross sections and rate constants for the title reaction. Calculations are carried out on the best available ground 1(2)A' global adiabatic potential energy surface of Deskevich et al. [J. Chem. Phys. 124, 224303 (2006)]. Converged state-to-state reaction cross sections have been calculated for collision energies up to 0.5 eV and different initial rotational and vibrational excitations, DCl(v = 0, j = 0 - 1; v = 1, j = 0). Also, initial-state resolved rate constants of the title reaction have been calculated in a temperature range of 100-400 K. It is found that the initial rotational excitation of the DCl molecule does not enhance reactivity, in contract to the reaction with the isotopologue HCl in which initial rotational excitation produces an important enhancement. These differences between the isotopologue reactions are analyzed in detail and attributed to the presence of resonances for HCl(v = 0, j), absent in the case of DCl(v = 0, j). For vibrational excited DCl(v = 1, j), however, the reaction cross section increases noticeably, what is also explained by another resonance.

  7. Influence of vibrations of gas molecules on neutron reaction cross sections

    Science.gov (United States)

    Bowman, C. D.; Schrack, R. A.

    1980-01-01

    The change in molecular vibrational energy upon absorption of a neutron by a nucleus bound in a free molecule can influence resonance shape and other aspects of neutron reaction cross sections. A formalism is developed for centrosymmetric molecules such as UF6 and applied to the shape of the 6.67 eV resonance in 238U. The ratio of the resonance shape for 238UF6 gas and for solid 238U3O8 has been measured and compared with the calculation. Reasonable agreement is obtained indicating the validity of the calculation and the necessity to include vibration effects to avoid large errors in measurements and calculations on gascontaining systems. NUCLEAR REACTIONS 238U(n,γ) measured at 6.67 eV resonance; Effect of molecular vibrations studied experimentally and theoretically.

  8. Serological cross-reaction between O-antigens of Shigella dysenteriae type 4 and an environmental Escherichia albertii isolate.

    Science.gov (United States)

    Rahman, Mohammed Ziaur; Akter, Selina; Azmuda, Nafisa; Sultana, Munawar; Weill, François-Xavier; Khan, Sirajul Islam; Grimont, Patrick A D; Birkeland, Nils-Kåre

    2013-11-01

    An environmental freshwater bacterial isolate, DM104, appearing as Shigella-like colonies on selective agar plates was found to show strong and specific serological cross-reactivity with Shigella dysenteriae type 4. Biochemical identification according to the analytical profile index, molecular serotyping by restriction of the amplified O-antigen gene cluster (rfb-RFLP), together with phylogenetic analysis of the 16S rRNA gene and multi-locus sequence analysis, identified the isolate as Escherichia albertii. rfb-RFLP of DM104, revealed a profile different from that of S. dysenteriae type 4. However, western blot analysis of extracted lipopolysaccharides demonstrated strong cross-reactivity with S. dysenteriae type 4 using specific monovalent antisera and a lipopolysaccharide gel banding profile similar to that of S. dysenteriae type 4. The observed O-antigen cross-reaction between an E. albertii isolate and S. dysenteriae extends our knowledge of the extent of O-antigen cross-reaction within the Escherichia/Shigella group of organisms, and offers the possibility of using DM104 and similar cross-reacting strains as shigellosis vaccine candidates.

  9. Determination of cross sections of nuclear reactions to use Al as monitoring foil in heavy ion irradiation with 20Ne projectile

    International Nuclear Information System (INIS)

    Chowdhury, D.P.; Datta, J.; Guin, R.; Verma, R.

    2009-01-01

    The beam current is generally accurately measured using monitoring foils during the irradiation of thick samples by high energy ion beams. The cross sections of many nuclear reactions induced by light particles are available in literature for use as monitoring foil. However, such cross sections of heavy ion induced reactions are not reported much for their use in applied works. We have determined cross sections of two nuclear reactions, 27 Al ( 20 Ne,2p2n) 43 Sc and 27 Al ( 20 Ne, 2pn) 44m Sc, to use Al as monitoring foil for the irradiation with 20 Ne heavy ion beam. (author)

  10. Sequential Power-Dependence Theory

    NARCIS (Netherlands)

    Buskens, Vincent; Rijt, Arnout van de

    2008-01-01

    Existing methods for predicting resource divisions in laboratory exchange networks do not take into account the sequential nature of the experimental setting. We extend network exchange theory by considering sequential exchange. We prove that Sequential Power-Dependence Theory—unlike

  11. Combined cross-linked enzyme aggregates of horseradish peroxidase and glucose oxidase for catalyzing cascade chemical reactions.

    Science.gov (United States)

    Nguyen, Le Truc; Yang, Kun-Lin

    2017-05-01

    Cascade reactions involved unstable intermediates are often encountered in biological systems. In this study, we developed combined cross-linked enzyme aggregates (combi-CLEA) to catalyze a cascade reaction which involves unstable hydrogen peroxide as an intermediate. The combi-CLEA contains two enzymes̶ glucose oxidase (GOx) and horseradish peroxidase (HRP) which are cross-linked together as solid aggregates. The first enzyme GOx catalyzes the oxidation of glucose and produces hydrogen peroxide, which is used by the second enzyme HRP to oxidize 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). The apparent reaction rate of the cascade reaction reaches 10.5±0.5μM/min when the enzyme ratio is 150:1 (GOx:HRP). Interestingly, even in the presence of catalase, an enzyme that quickly decomposes hydrogen peroxide, the reaction rate only decreases by 18.7% to 8.3±0.3μM/min. This result suggests that the intermediate hydrogen peroxide is not decomposed by catalase due to a short diffusion distance between GOx and HRP in the combi-CLEA. Scanning electron microscopy images suggest that combi-CLEA particles are hollow spheres and have an average diameter around 250nm. Because of their size, combi-CLEA particles can be entrapped inside a nylon membrane for detecting glucose by using the cascade reaction. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Study of (n,2n reaction on 191,193Ir isotopes and isomeric cross section ratios

    Directory of Open Access Journals (Sweden)

    Vlastou R.

    2017-01-01

    Full Text Available The cross section of 191Ir(n,2n190Irg+m1 and 191Ir(n,2n190Irm2 reactions has been measured at 17.1 and 20.9 MeV neutron energies at the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR “Demokritos”, using the activation method. The neutron beams were produced by means of the 3H(d,n4He reaction at a flux of the order of 2 × 105 n/cm2s. The neutron flux has been deduced implementing the 27Al(n,α reaction, while the flux variation of the neutron beam was monitored by using a BF3 detector. The 193Ir(n,2n192Ir reaction cross section has also been determined, taking into account the contribution from the contaminant 191Ir(n,γ192Ir reaction. The correction method is based on the existing data in ENDF for the contaminant reaction, convoluted with the neutron spectra which have been extensively studied by means of simulations using the NeusDesc and MCNP codes. Statistical model calculations using the code EMPIRE 3.2.2 and taking into account pre-equilibrium emission, have been performed on the data measured in this work as well as on data reported in literature.

  13. Cross sections of nuclear reactions induced by protons, deuterons, and alpha particles. Pt.6. Phosphorus

    International Nuclear Information System (INIS)

    Tobailem, Jacques.

    1981-11-01

    Cross sections are reviewed for nuclear reactions induced by protons, deuterons, and alpha particles on phosphorus targets. When necessary, published experimental data are corrected, and, when possible, excitation functions are proposed [fr

  14. Illustrating the Utility of X-Ray Crystallography for Structure Elucidation through a Tandem Aldol Condensation/Diels-Alder Reaction Sequence

    Science.gov (United States)

    Hoang, Giang T.; Kubo, Tomohiro; Young, Victor G., Jr.; Kautzky, Jacob A.; Wissinger, Jane E.

    2015-01-01

    Two introductory organic chemistry laboratory experiments are described based on the Diels-Alder reaction of 2,3,4,5-tetraphenylcyclopentadienone, which is synthesized prior to or in a one-pot reaction, with styrene. Students are presented with three possible products, the "endo" and "exo" diastereomers and the decarbonylated…

  15. Directed ortho metalation-based methodology. Halo-, nitroso-, and boro-induced ipso-desilylation. Link to an in situ Suzuki reaction.

    Science.gov (United States)

    Zhao, Zhongdong; Snieckus, Victor

    2005-06-23

    [reaction: see text] Treatment of DoM-derived silylated aromatics 2-4 under standard electrophilic halogenation conditions cleanly affords ipso-desilyation products 5-7, while nitration of methoxy-substituted analogues 8, 9 leads to non-ipso isomers 10, 12 and 11, 13, controlled by a silicon steric effect. Sequential ipso-borodesilylation of 2a, 3a, and 20 followed by treatment with aryl halides under Pd-catalyzed conditions constitutes an in situ Suzuki-Miyaura cross-coupling protocol to biaryls and heterobiaryls 23.

  16. Cross sections for nuclide production in proton- and deuteron-induced reactions on 93Nb measured using the inverse kinematics method

    Directory of Open Access Journals (Sweden)

    Nakano Keita

    2017-01-01

    Full Text Available Isotopic production cross sections were measured for proton- and deuteron-induced reactions on 93Nb by means of the inverse kinematics method at RIKEN Radioactive Isotope Beam Factory. The measured production cross sections of residual nuclei in the reaction 93Nb + p at 113 MeV/u were compared with previous data measured by the conventional activation method in the proton energy range between 46 and 249 MeV. The present inverse kinematics data of four reaction products (90Mo, 90Nb, 88Y, and 86Y were in good agreement with the data of activation measurement. Also, the model calculations with PHITS describing the intra-nuclear cascade and evaporation processes generally well reproduced the measured isotopic production cross sections.

  17. STEEP4 code for computation of specific thermonuclear reaction rates from pointwise cross sections

    International Nuclear Information System (INIS)

    Harris, D.R.; Dei, D.E.; Husseiny, A.A.; Sabri, Z.A.; Hale, G.M.

    1976-05-01

    A code module, STEEP4, is developed to calculate the fusion reaction rates in terms of the specific reactivity [sigma v] which is the product of cross section and relative velocity averaged over the actual ion distributions of the interacting particles in the plasma. The module is structured in a way suitable for incorporation in thermonuclear burn codes to provide rapid and yet relatively accurate on-line computation of [sigma v] as a function of plasma parameters. Ion distributions are modified to include slowing-down contributions which are characterized in terms of plasma parameters. Rapid and accurate algorithms are used for integrating [sigma v] from cross sections and spectra. The main program solves for [sigma v] by the method of steepest descent. However, options are provided to use Gauss-Hermite and dense trapezoidal quadrature integration techniques. Options are also provided for rapid calculation of screening effects on specific reaction rates. Although such effects are not significant in cases of plasmas of laboratory interest, the options are included to increase the range of applicability of the code. Gamow penetration form, log-log interpolation, and cubic interpolation routines are included to provide the interpolated values of cross sections

  18. Total reaction cross sections and neutron-removal cross sections of neutron-rich light nuclei measured by the COMBAS fragment-separator

    Science.gov (United States)

    Hue, B. M.; Isataev, T.; Erdemchimeg, B.; Artukh, A. G.; Aznabaev, D.; Davaa, S.; Klygin, S. A.; Kononenko, G. A.; Khuukhenkhuu, G.; Kuterbekov, K.; Lukyanov, S. M.; Mikhailova, T. I.; Maslov, V. A.; Mendibaev, K.; Sereda, Yu M.; Penionzhkevich, Yu E.; Vorontsov, A. N.

    2017-12-01

    Preliminary results of measurements of the total reaction cross sections σR and neutron removal cross section σ-xn for weakly bound 6He, 8Li, 9Be and 10Be nuclei at energy range (20-35) A MeV with 28Si target is presented. The secondary beams of light nuclei were produced by bombardment of the 22Ne (35 A MeV) primary beam on Be target and separated by COMBAS fragment-separator. In dispersive focal plane a horizontal slit defined the momentum acceptance as 1% and a wedge degrader of 200 μm Al was installed. The Bρ of the second section of the fragment-separator was adjusted for measurements in energy range (20-35) A MeV. Two-neutron removal cross sections for 6He and 10Be and one -neutron removal cross sections 8Li and 9Be were measured.

  19. Adaptive sequential controller

    Energy Technology Data Exchange (ETDEWEB)

    El-Sharkawi, Mohamed A. (Renton, WA); Xing, Jian (Seattle, WA); Butler, Nicholas G. (Newberg, OR); Rodriguez, Alonso (Pasadena, CA)

    1994-01-01

    An adaptive sequential controller (50/50') for controlling a circuit breaker (52) or other switching device to substantially eliminate transients on a distribution line caused by closing and opening the circuit breaker. The device adaptively compensates for changes in the response time of the circuit breaker due to aging and environmental effects. A potential transformer (70) provides a reference signal corresponding to the zero crossing of the voltage waveform, and a phase shift comparator circuit (96) compares the reference signal to the time at which any transient was produced when the circuit breaker closed, producing a signal indicative of the adaptive adjustment that should be made. Similarly, in controlling the opening of the circuit breaker, a current transformer (88) provides a reference signal that is compared against the time at which any transient is detected when the circuit breaker last opened. An adaptive adjustment circuit (102) produces a compensation time that is appropriately modified to account for changes in the circuit breaker response, including the effect of ambient conditions and aging. When next opened or closed, the circuit breaker is activated at an appropriately compensated time, so that it closes when the voltage crosses zero and opens when the current crosses zero, minimizing any transients on the distribution line. Phase angle can be used to control the opening of the circuit breaker relative to the reference signal provided by the potential transformer.

  20. Adaptive sequential controller

    Science.gov (United States)

    El-Sharkawi, Mohamed A.; Xing, Jian; Butler, Nicholas G.; Rodriguez, Alonso

    1994-01-01

    An adaptive sequential controller (50/50') for controlling a circuit breaker (52) or other switching device to substantially eliminate transients on a distribution line caused by closing and opening the circuit breaker. The device adaptively compensates for changes in the response time of the circuit breaker due to aging and environmental effects. A potential transformer (70) provides a reference signal corresponding to the zero crossing of the voltage waveform, and a phase shift comparator circuit (96) compares the reference signal to the time at which any transient was produced when the circuit breaker closed, producing a signal indicative of the adaptive adjustment that should be made. Similarly, in controlling the opening of the circuit breaker, a current transformer (88) provides a reference signal that is compared against the time at which any transient is detected when the circuit breaker last opened. An adaptive adjustment circuit (102) produces a compensation time that is appropriately modified to account for changes in the circuit breaker response, including the effect of ambient conditions and aging. When next opened or closed, the circuit breaker is activated at an appropriately compensated time, so that it closes when the voltage crosses zero and opens when the current crosses zero, minimizing any transients on the distribution line. Phase angle can be used to control the opening of the circuit breaker relative to the reference signal provided by the potential transformer.

  1. Measurement of the cross section of the 8Li(d,α)6He reaction of possible relevance to big bang nucleosynthesis

    International Nuclear Information System (INIS)

    Sahin, L.; Boyd, R.N.; Cole, A.L.; Famiano, M.; Gueray, R.T.; Murphy, A. St.J.; Oezkan, N.; Kolata, J.J.; Guimaraes, V.; Hencheck, M.

    2002-01-01

    We report measurements of the cross section of the 8 Li(d,α) 6 He reaction in the energy range E c.m. =2.3-3.5 MeV using a 8 Li-radioactive beam on a CD 2 foil. The astrophysical S factor and reaction rate were calculated from the measured cross section. The 6 He nuclei produced in the reaction were detected in solid-state detector telescopes. This reaction might have affected the primordial abundance of 6 Li in big bang nucleosynthesis, since 6 He beta decays to 6 Li. However, several big bang nucleosynthesis network calculations were found to be insensitive to this reaction, suggesting that the 8 Li(d,α) 6 He reaction does not affect 6 Li primordial production

  2. Catalytic Routes for the Conversion of Biomass Derivatives to Hydrocarbons and/or Platform Chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Silks, III, Louis A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-07

    Unprotected carbohydrates were reacted in amine-catalyzed cascade reactions with various methyl ketones to give a direct access to C-glycosides by an operationally simple protocol. As the reaction mechanism,an aldol condensation followed by an intramolecular conjugate addition is assumed.

  3. Study of the surrogate-reaction method applied to neutron-induced capture cross sections

    International Nuclear Information System (INIS)

    Boutoux, G.; Jurado, B.; Méot, V.; Roig, O.; Mathieu, L.; Aïche, M.; Barreau, G.; Capellan, N.; Companis, I.; Czajkowski, S.; Schmidt, K.-H.; Burke, J.T.; Bail, A.; Daugas, J.M.; Faul, T.; Morel, P.; Pillet, N.; Théroine, C.; Derkx, X.; Sérot, O.

    2012-01-01

    Gamma-decay probabilities of 173 Yb and 176 Lu have been measured using the surrogate reactions 174 Yb( 3 He,αγ) 173 Yb* and 174 Yb( 3 He,pγ) 176 Lu*, respectively. For the first time, the gamma-decay probabilities have been obtained with two independent experimental methods based on the use of C 6 D 6 scintillators and Germanium detectors. Our results for the radiative-capture cross sections are several times higher than the corresponding neutron-induced data. To explain these differences, we have used our gamma-decay probabilities to extract rather direct information on the spin distributions populated in the transfer reactions used. They are about two times wider and the mean values are 3 to 4 ℏ higher than the ones populated in the neutron-induced reactions. As a consequence, in the transfer reactions neutron emission to the ground and first excited states of the residual nucleus is strongly suppressed and gamma-decay is considerably enhanced.

  4. Parameterization of pion production and reaction cross sections at LAMPF energies

    International Nuclear Information System (INIS)

    Burman, R.L.; Smith, E.S.

    1989-05-01

    A parameterization of pion production and reaction cross sections is developed for eventual use in modeling neutrino production by protons in a beam stop. Emphasis is placed upon smooth parameterizations for proton energies up to 800 MeV, for all pion energies and angles, and for a wide range of materials. The resulting representations of the data are well-behaved and can be used for extrapolation to regions where there are no measurements. 22 refs., 16 figs., 2 tabs

  5. Determination of the fission-neutron averaged cross sections of some high-energy threshold reactions of interest for reactor dosimetry

    International Nuclear Information System (INIS)

    Arribere, M.A.; Kestelman, A.J.; Korochinsky, S.; Blostein, J.J.

    2003-01-01

    For three high threshold reactions, we have measured the cross sections averaged over a 235 U fission neutron spectrum. The measured reactions, and corresponding averaged cross sections found, are: 127 I(n,2n) 126 I, (1.36±0.12) mb; 90 Zr(n,2n) 89m Zr, (13.86±0.83) μb; and 58 Ni(n,d+np+pn) 57 Co, (274±15) μb; all referred to the well known standard of (111±3) mb for the 58 Ni(n,p) 58m+g Co averaged cross section. The measured cross sections are of interest in nuclear engineering for the characterization of the fast neutron component in the energy distribution of reactor neutrons. (author)

  6. On-line monitoring of Glucose and penicillin by sequential injection analysis

    DEFF Research Database (Denmark)

    Min, R.W.; Nielsen, Jens Bredal; Villadsen, John

    1996-01-01

    and a detector. The glucose analyzer is based on an enzymatic reaction using glucose oxidase, which converts glucose to glucono-lactone with formation of hydrogen peroxide and subsequent detection of H2O2 by a chemiluminescence reaction involving luminol. The penicillin analysis is based on formation......A sequential injection analysis (SIA) system has been developed for on-line monitoring of glucose and penicillin during cultivations of the filamentous fungus Penicillium chrysogenum. The SIA system consists of a peristaltic pump, an injection valve, two piston pumps, two multi-position valves...

  7. Activation cross-sections of deuteron induced nuclear reactions on manganese up to 40 MeV

    International Nuclear Information System (INIS)

    Ditroi, F.; Tarkanyi, F.; Takacs, S.; Hermanne, A.; Yamazaki, H.; Baba, M.; Mohammadi, A.; Ignatyuk, A.V.

    2011-01-01

    In the frame of a systematic study on activation cross-sections of deuteron induced reactions experimental excitation functions on 55 Mn were measured with the activation method using the stacked foil irradiation technique up to 40 MeV. By using high resolution γ-ray spectrometry, cross-section data for the production of 56,54,52 Mn and 51 Cr were determined. Comparison with the earlier published data and with the results predicted by the ALICE-IPPE and EMPIRE-II theoretical codes - improved for more reliable calculations for d-induced reactions - and with data in the TENDL 2010 libraries are also included. Thick target yields were calculated from a fit to our experimental excitation curves and implications for practical applications in industrial (Thin Layer Activation) accelerator technology are discussed.

  8. The importance of a hot-sequential mechanism in triplet-state formation by charge recombination in reaction centers of bacterial photosynthesis

    International Nuclear Information System (INIS)

    Saito, K.; Mukai, K.; Sumi, H.

    2006-01-01

    In photosynthesis, pigment-excitation energies in the antenna system produced by light harvesting are transferred among antenna pigments toward the core antenna, where they are captured by the reaction center and initially fixed in the form of a charge separation. Primary charge separation between an oxidized special pair (P + ) and a reduced bacteriopheohytin (H - ) is occasionally intervened by recombination, and a spin-triplet state ( 3 P*) is formed on P in the bacterial reaction center. The 3 P* state is harmful to bio-organisms, inducing the formation of the highly damaging singlet oxygen species. Therefore, understanding the 3 P*-formation mechanism is important. The 3 P* formation is mediated by a state |m> of intermediate charge separation between P and the accessory chlorophyll, which is located between P and H. It will be shown theoretically in the present work that at room temperature, not only the mechanism of superexchange by quantum-mechanical virtual mediation at |m>, but also a hot-sequential mechanism contributes to the mediation. In the latter, although |m> is produced as a real state, the final state 3 P* is quickly formed during thermalization of phonons in the protein matrix in |m>. In the former, the final state is formed more quickly before dephasing-thermalization of phonons in |m>. 3 P* is unistep formed from the charge-separated state in the both mechanisms

  9. Depth treatment of coal-chemical engineering wastewater by a cost-effective sequential heterogeneous Fenton and biodegradation process.

    Science.gov (United States)

    Fang, Yili; Yin, Weizhao; Jiang, Yanbin; Ge, Hengjun; Li, Ping; Wu, Jinhua

    2018-05-01

    In this study, a sequential Fe 0 /H 2 O 2 reaction and biological process was employed as a low-cost depth treatment method to remove recalcitrant compounds from coal-chemical engineering wastewater after regular biological treatment. First of all, a chemical oxygen demand (COD) and color removal efficiency of 66 and 63% was achieved at initial pH of 6.8, 25 mmol L -1 of H 2 O 2 , and 2 g L -1 of Fe 0 in the Fe 0 /H 2 O 2 reaction. According to the gas chromatography-mass spectrometer (GC-MS) and gas chromatography-flame ionization detector (GC-FID) analysis, the recalcitrant compounds were effectively decomposed into short-chain organic acids such as acetic, propionic, and butyric acids. Although these acids were resistant to the Fe 0 /H 2 O 2 reaction, they were effectively eliminated in the sequential air lift reactor (ALR) at a hydraulic retention time (HRT) of 2 h, resulting in a further decrease of COD and color from 120 to 51 mg L -1 and from 70 to 38 times, respectively. A low operational cost of 0.35 $ m -3 was achieved because pH adjustment and iron-containing sludge disposal could be avoided since a total COD and color removal efficiency of 85 and 79% could be achieved at an original pH of 6.8 by the above sequential process with a ferric ion concentration below 0.8 mg L -1 after the Fe 0 /H 2 O 2 reaction. It indicated that the above sequential process is a promising and cost-effective method for the depth treatment of coal-chemical engineering wastewaters to satisfy discharge requirements.

  10. Measurement of the ${240}$Pu(n,f) reaction cross-section

    CERN Multimedia

    Following proposal CERN-INTC-2010-042 / INTC-P-280 (“Measurement of the fission cross-section of $^{240}$Pu and $^{242}$Pu at CERN’s n_TOF Facility”), the parallel measurement of the $^{240}$Pu(n,f) and $^{242}$Pu(n,f) reaction cross-sections was carried out at n_TOF EAR-1. While the $^{242}$Pu measurement was successful, unexpected sample-induced damage to the detectors caused by the high α-activity of the 240Pu samples resulted in a deterioration of the detector performance over the data taking period of several months, which compromised the measurement. This obstacle can be eliminated by performing the measurement in EAR-2, where the higher neutron flux will allow collecting data in a much shorter time, thus preventing the degradation of the detectors. In addition to this obvious advantage, the measurement would also benefit from the stronger suppression of the sample-induced α-background, due to the shorter times-of-flight involved.

  11. A new closed form expression for the total reaction cross-section of heavy ions

    International Nuclear Information System (INIS)

    Rego, R.A.; Hussein, M.S.

    1989-02-01

    A new analytical expression for the HI total reaction cross-section which exhibits the macroscopic features of the transparency factor is derived. Comparison with optical model calculation are made for the 12 C+ 208 Pb and 16 O + 208 Pb at several energies. (author)

  12. The (p→,t) reaction on 58Ni and 56Fe at 24.6 MeV

    International Nuclear Information System (INIS)

    Polane, J.H.; Feix, W.F.; Hall, P.J. van; Klein, S.S.; Nijgh, G.J.; Poppema, O.J.; Wassenaar, S.D.

    1989-01-01

    The (p, t) reactions on 56 Fe and 58 Ni initiated by 24.6 MeV polarised protons has been investigated. The reaction process is described in terms of simultaneous and sequential neutron transfer. For all five final states studied the sequential process competes strongly with simultaneous transfer of a neutron pair. Theoretical values for the spectroscopic amplitudes were derived from shell-model wavefunctions; these seem to give a reliable description of the reaction process. (author)

  13. A Cross-Cultural Validation of the Sequential-Simultaneous Theory of Intelligence in Children.

    Science.gov (United States)

    Moon, Soo-Back; McLean, James E.; Kaufman, Alan S.

    2003-01-01

    The Kaufman Assessment Battery for Children - Korean (K-ABC-K) was developed to assess the intelligence and achievement of preschool and school-aged Korean children. This study examined the validity of the Sequential Processing, Simultaneous Processing and Achievement scales of the K-ABC-K. The factor analyses provided strong support for the…

  14. Model reduction of detailed-balanced reaction networks by clustering linkage classes

    NARCIS (Netherlands)

    Rao, Shodhan; Jayawardhana, Bayu; van der Schaft, Abraham; Findeisen, Rolf; Bullinger, Eric; Balsa-Canto, Eva; Bernaerts, Kristel

    2016-01-01

    We propose a model reduction method that involves sequential application of clustering of linkage classes and Kron reduction. This approach is specifically useful for chemical reaction networks with each linkage class having less number of reactions. In case of detailed balanced chemical reaction

  15. Instability induced by cross-diffusion in reaction-diffusion systems

    DEFF Research Database (Denmark)

    Tian, Canrong; Lin, Zhigui; Pedersen, Michael

    2010-01-01

    In this paper the instability of the uniform equilibrium of a general strongly coupled reaction–diffusion is discussed. In unbounded domain and bounded domain the sufficient conditions for the instability are obtained respectively. The conclusion is applied to the ecosystem, it is shown that cros...... can induce the instability of an equilibrium which is stable for the kinetic system and for the self-diffusion–reaction system.......In this paper the instability of the uniform equilibrium of a general strongly coupled reaction–diffusion is discussed. In unbounded domain and bounded domain the sufficient conditions for the instability are obtained respectively. The conclusion is applied to the ecosystem, it is shown that cross-diffusion...

  16. Fusion reaction cross-sections using the Wong model within Skyrme energy density based semiclassical extended Thomas Fermi approach

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Raj, E-mail: rajkumarfzr@gmail.com [Department of Physics, Panjab University, Chandigarh-160014 (India); School of Physics and Material Science, Thapar University, Patiala-147004 (India); Sharma, Manoj K. [School of Physics and Material Science, Thapar University, Patiala-147004 (India); Gupta, Raj K. [Department of Physics, Panjab University, Chandigarh-160014 (India)

    2011-11-15

    First, the nuclear proximity potential, obtained by using the semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), is shown to give more realistic barriers in frozen density approximation, as compared to the sudden approximation. Then, taking advantage of the fact that, in ETF method, different Skyrme forces give different barriers (height, position and curvature), we use the l-summed extended-Wong model of Gupta and collaborators (2009) under frozen densities approximation for calculating the cross-sections, where the Skyrme force is chosen with proper barrier characteristics, not-requiring additional 'barrier modification' effects (lowering or narrowing, etc.), for a best fit to data at sub-barrier energies. The method is applied to capture cross-section data from {sup 48}Ca + {sup 238}U, {sup 244}Pu, and {sup 248}Cm reactions and to fusion-evaporation cross-sections from {sup 58}Ni + {sup 58}Ni, {sup 64}Ni + {sup 64}Ni, and {sup 64}Ni + {sup 100}Mo reactions, with effects of deformations and orientations of nuclei included, wherever required. Interestingly, whereas the capture cross-sections in Ca-induced reactions could be fitted to any force, such as SIII, SV and GSkI, by allowing a small change of couple of units in deduced l{sub max}-values at below-barrier energies, the near-barrier data point of {sup 48}Ca + {sup 248}Cm reaction could not be fitted to l{sub max}-values deduced for below-barrier energies, calling for a check of data. On the other hand, the fusion-evaporation cross-sections in Ni-induced reactions at sub-barrier energies required different Skyrme forces, representing 'modifications of the barrier', for the best fit to data at all incident center-of-mass energies E{sub c.m.}'s, displaying a kind of fusion hindrance at sub-barrier energies. This barrier modification effect is taken into care here by using different Skyrme forces for reactions belonging to different regions of

  17. Measurements of the Fe-54 (n,p) Mn-54 Reaction Cross Section in the Neutron Energy Range 2.3-3.8 MeV

    International Nuclear Information System (INIS)

    Lauber, A.; Malmskog, S.

    1964-10-01

    We have measured the 54 Fe (n, p) 54 Mn reaction cross section using a surface barrier detector to record the number of protons released in the reaction. The neutron flux was determined by means of a hydrogenous radiator, detecting the scattered protons with the solid state detector, and calculating the number of impinging neutrons from the well known n-p scattering cross section. The 54 Fe (n, p) 54 Mn reaction cross section is found to increase from 25 mb at 2.3 MeV to 208 mb at 3.5 MeV

  18. Photo-neutron reaction cross-section for 93Nb in the end-point bremsstrahlung energies of 12–16 and 45–70 MeV

    International Nuclear Information System (INIS)

    Naik, H.; Kim, G.N.; Schwengner, R.; Kim, K.; Zaman, M.; Tatari, M.; Sahid, M.; Yang, S.C.; John, R.; Massarczyk, R.; Junghans, A.; Shin, S.G.; Key, Y.; Wagner, A.; Lee, M.W.; Goswami, A.; Cho, M.-H.

    2013-01-01

    The photo-neutron cross-sections of 93 Nb at the end-point bremsstrahlung energies of 12, 14 and 16 MeV as well as 45, 50, 55, 60 and 70 MeV have been determined by the activation and the off-line γ-ray spectrometric techniques using the 20 MeV electron linac (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany, and 100 MeV electron linac at Pohang Accelerator Laboratory (PAL), Pohang, Korea. The 93 Nb(γ, xn, x=1–4) reaction cross-sections as a function of photon energy were also calculated using computer code TALYS 1.4. The flux-weighted average values were obtained from the experimental and the theoretical (TALYS) values based on mono-energetic photons. The experimental values of present work are in good agreement with the flux-weighted theoretical values of TALYS 1.4 but are slightly higher than the flux-weighted experimental data of mono-energetic photons. It was also found that the theoretical and the experimental values of present work and literature data for the 93 Nb(γ, xn) reaction cross-sections increase from the threshold values to a certain energy, where other reaction channels opens. However, the increase of 93 Nb(γ, n) and 93 Nb(γ, 2n) reaction cross-sections are sharper compared to 93 Nb(γ, 3n) and 93 Nb(γ, 4n) reaction cross-sections. The sharp increase of 93 Nb(γ, n) and 93 Nb(γ, 2n) reaction cross-sections from the threshold value up to 17–22 MeV is due to the Giant Dipole Resonance (GDR) effect besides the role of excitation energy. After a certain values, the individual 93 Nb(γ, xn) reaction cross-sections decrease with increase of bremsstrahlung energy due to opening of other reaction channels

  19. Ground-state and isomeric-state cross sections for the {sup 138}Ce(n,2n){sup 137}Ce reaction from its threshold to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Junhua [Hexi Univ., Zhangye (China). Inst. of Theoretical Physics; Hexi Univ., Zhangye (China). School of Physics and Electromechanical Engineering; An, Li; Jiang, Li [Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Nuclear Physics and Chemistry

    2015-07-01

    The cross sections of the {sup 138}Ce(n,2n){sup 137}Ce reactions and their isomeric cross section ratios σ{sub m}/σ{sub g} were measured at three neutron energies between 13.5 and 14.8 MeV using the activation technique. CeO{sub 2} samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The monoenergetic neutron beams were formed via the {sup 3}H(d,n){sup 4}He reaction. The activities induced in the reaction products were measured using high-resolution γ-ray spectroscopy. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The cross sections were also estimated using the nuclear model code, TALYS-1.6 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature data.

  20. Understanding the two neutron transfer reaction mechanism in {sup 206}Pb({sup 18}O,{sup 16}O){sup 208}Pb

    Energy Technology Data Exchange (ETDEWEB)

    Parmar, A.; Sonika [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400 085 (India); Roy, B.J., E-mail: bjroy@barc.gov.in [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400 085 (India); Jha, V.; Pal, U.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400 085 (India); Sinha, T. [High Energy Nuclear and Particle Physics Division, Saha Institute of Nuclear Physics, Kolkata - 700 064 (India); Pandit, S.K.; Parkar, V.V.; Ramachandran, K.; Mahata, K.; Santra, S.; Mohanty, A.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400 085 (India)

    2015-08-15

    The absolute cross sections for elastic scattering and two-neutron transfer reaction for {sup 18}O + {sup 206}Pb system have been measured at an incident energy near the Coulomb barrier. Detailed coupled reaction channel calculations have been carried out for description of the measured angular distributions for the elastic scattering and transfer reactions simultaneously. The two-neutron transfer reaction {sup 206}Pb({sup 18}O, {sup 16}O){sup 208}Pb in the g.s. → g.s. transition is analyzed in (i) extreme cluster model assuming a di-neutron transfer, (ii) two-step successive transfer, and (iii) microscopic approach (independent coordinate scheme) of simultaneous transfer of two neutrons. The relative importance of one step simultaneous transfer versus two-step successive transfer has been studied. Present analysis suggests dominance of cluster transfer of a di-neutron. The contribution from the two-step sequential processes is less significant, however, the combined “two-step plus simultaneous (microscopic)” calculations give a reasonably good agreement with the measurement. The possibility of multi-step route via projectile and target excitations and contribution from such indirect transfer paths to the present two-neutron transfer cross section has been investigated.

  1. Complexation Key to a pH Locked Redox Reaction

    Science.gov (United States)

    Rizvi, Masood Ahmad; Dangat, Yuvraj; Shams, Tahir; Khan, Khaliquz Zaman

    2016-01-01

    An unfavorable pH can block a feasible electron transfer for a pH dependent redox reaction. In this experiment, a series of potentiometric titrations demonstrate the sequential loss in feasibility of iron(II) dichromate redox reaction over a pH range of 0-4. The pH at which this reaction failed to occur was termed as a pH locked reaction. The…

  2. Neutron halo in 14B studied via reaction cross sections

    International Nuclear Information System (INIS)

    Fukuda, M.; Tanaka, M.; Iwamoto, K.; Wakabayashi, S.; Yaguchi, M.; Ohno, J.; Morita, Y.; Kamisho, Y.; Mihara, M.; Matsuta, K.; Nishimura, D.; Suzuki, S.; Nagashima, M.; Ohtsubo, T.; Ogura, T.; Abe, K.; Kikukawa, N.; Sakai, T.; Sera, D.; Takechi, M.; Izumikawa, T.; Suzuki, T.; Yamaguchi, T.; Sato, K.; Furuki, H.; Miyazawa, S.; Ichihashi, N.; Kohno, J.; Yamaki, S.; Kitagawa, A.; Sato, S.; Fukuda, S.

    2014-01-01

    Reaction cross sections (σ R ) for the neutron-rich nucleus 14 B on Be, C, and Al targets have been measured at several energies in the intermediate energy range of 45-120 MeV/nucleon. The present experimental σ R show a significant enhancement relative to the systematics of stable nuclei. The nucleon density distribution was deduced through the fitting procedure with the modified Glauber calculation. The necessity of a long tail in the density distribution was found, which is consistent with the valence neutron in 2s 1/2 orbital with the small empirical one-neutron separation energy in 14 B. (authors)

  3. Measurement of angle-correlated differential (n,2n) reaction cross section with pencil-beam DV neutron source

    International Nuclear Information System (INIS)

    Takaki, S.; Kondo, K.; Shido, S.; Miyamaru, H.; Murata, I.; Ochiai, Kentaro; Nishitani, Takeo

    2006-01-01

    Angle-correlated differential cross-section for 9 Be(n,2n) reaction has been measured with the coincidence detection technique and a pencil-beam DT neutron source at FNS, JAEA. Energy spectra of two emitted neutrons were obtained for azimuthal and polar direction independently. It was made clear from the experiment that there are noise signals caused by inter-detector scattering. The ratio of the inter-detector scattering components in the detected signals was estimated by MCNP calculation to correct the measured result. By considering the inter-detector scattering components, the total 9 Be(n,2n) reaction cross-section agreed with the evaluated nuclear data within the experimental error. (author)

  4. Nuclear reactions cross section measurement using Z-pinch technology

    Energy Technology Data Exchange (ETDEWEB)

    Bulgakov, T; Bystritskij, V; Mesyats, G A [Russian Academy of Sciences, Tomsk (Russian Federation). Institute of Electrophysics; and others

    1997-12-31

    Direct experimental estimate of the upper limit of the d + d {yields} {sup 3}He + n cross-section at deuteron energies below the keV region was obtained for the first time. The experiment was performed at the Pulsed Ion Beam Accelerator of the High-Current Electronics Institute in Tomsk, using high intensity, radially converging deuteron beams, generated during implosion of liner plasma. A two-jet liner made of 17% D{sub 2} + 83% N{sub 2} gas was used, with the inner jet serving as the target. The dd-fusion neutrons were registered by time-of-flight scintillator spectrometers and BF{sub 3} detectors of thermal neutrons placed in a polyethylene moderator. The upper limit obtained for the d + d {yields} {sup 3}He + n cross-section for a deuteron energy of 440 eV is {sigma} < 2 x 10{sup -34} cm{sup 2} at the 90% confidence level. The result demonstrates that the liner implosion technique can be used in the investigation of nuclear reactions between light nuclei at infra low energies, previously not accessible in experiments with classical beam accelerators. (author). 7 refs.

  5. Kerma factors and reaction cross sections for n + 12C between 15 and 18 MeV

    International Nuclear Information System (INIS)

    Tornow, W.; Chen, Z.M.; Baird, K.; Walter, R.L.

    1988-01-01

    Differential elastic and inelastic (4.44 MeV) neutron scattering cross sections from 12 C are presented at 15.6, 16.8 and 17.3 MeV. The existing 18.2 MeV differential cross-section data were combined with newly measured analysing power data to parametrise neutron scattering at this energy. The 12 C recoil kerma factors were calculated and reaction cross sections were obtained from a phase-shift analysis and coupled channel analyses in the 15.6-18.2 MeV energy range. (author)

  6. Cross section measurement for (n,n{alpha}) reactions by 14 MeV neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Kasugai, Y.; Ikeda, Y.; Uno, Y. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Yamamoto, H.; Kawade, K.

    1997-03-01

    Nine (n,n{alpha}) cross sections for (n,n{alpha}) reactions induced by 13.5-14.9 MeV neutrons were measured for {sup 51}V, {sup 65}Cu, {sup 71}Ga, {sup 76}Ge, {sup 87}Rb, {sup 91}Zr, {sup 93}Nb, {sup 96}Zr and {sup 109}Ag isotopes by using Fusion Neutronics Source (FNS) at JAERI. The reactions for 91Zr and 96Zr were measured for the first time. The evaluated data of JENDL-3 and ENDF/B-VI were compared with the present data. Some of the evaluated values are much different from our data by a factor more than ten. (author)

  7. Neutron Thermal Cross Sections, Westcott Factors, Resonance Integrals, Maxwellian Averaged Cross Sections and Astrophysical Reaction Rates Calculated from the ENDF/B-VII.1, JEFF-3.1.2, JENDL-4.0, ROSFOND-2010, CENDL-3.1 and EAF-2010 Evaluated Data Libraries

    Science.gov (United States)

    Pritychenko, B.; Mughabghab, S. F.

    2012-12-01

    We present calculations of neutron thermal cross sections, Westcott factors, resonance integrals, Maxwellian-averaged cross sections and astrophysical reaction rates for 843 ENDF materials using data from the major evaluated nuclear libraries and European activation file. Extensive analysis of newly-evaluated neutron reaction cross sections, neutron covariances, and improvements in data processing techniques motivated us to calculate nuclear industry and neutron physics quantities, produce s-process Maxwellian-averaged cross sections and astrophysical reaction rates, systematically calculate uncertainties, and provide additional insights on currently available neutron-induced reaction data. Nuclear reaction calculations are discussed and new results are presented. Due to space limitations, the present paper contains only calculated Maxwellian-averaged cross sections and their uncertainties. The complete data sets for all results are published in the Brookhaven National Laboratory report.

  8. Exploring Tyrosine-Triazolinedione (TAD) Reactions for the Selective Conjugation and Cross-Linking of N-Carboxyanhydride (NCA) Derived Synthetic Copolypeptides.

    Science.gov (United States)

    Hanay, Saltuk B; Ritzen, Bas; Brougham, Dermot; Dias, Aylvin A; Heise, Andreas

    2017-07-01

    Highly efficient functionalization and cross-linking of polypeptides is achieved via tyrosine-triazolinedione (TAD) conjugation chemistry. The feasibility of the reaction is demonstrated by the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) with tyrosine containing block copolymer poly(ethylene glycol)-Tyr 4 as well as a statistical copolymer of tyrosine and lysine (poly(Lys 40 -st-Tyr 10 )) prepared form N-carboxyanhydride polymerization. Selective reaction of PTAD with the tyrosine units is obtained and verified by size exclusion chromatography and NMR spectroscopy. Moreover, two monofunctional and two difunctional TAD molecules are synthesized. It is found that their stability in the aqueous reaction media significantly varied. Under optimized reaction conditions selective functionalization and cross-linking, yielding polypeptide hydrogels, can be achieved. TAD-mediated conjugation can offer an interesting addition in the toolbox of selective (click-like) polypeptide conjugation methodologies as it does not require functional non-natural amino acids. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Calculation of homogenized Pickering NGS stainless steel adjuster rod neutron cross-sections using conservation of reaction rates

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, R C [Atlantic Nuclear Services Ltd. (Canada); Tran, F [Ontario Hydro, Pickering, ON (Canada). Pickering Generating Station

    1996-12-31

    A homogenization methodology for calculation of reactivity device incremental cross-sections has been developed using reaction rate conservation (RRC). A heterogeneous transport calculation of flux was utilised to produce the homogenized cross-sections for a finite difference two group diffusion code. The RRC cross-sections have been shown to improve significantly the prediction of reactivity worth for stainless steel adjuster rods installed in Pickering NGS reactors. (author). 10 refs., 3 tabs., 6 figs.

  10. 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.

  11. 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.

  12. CRSEC: a general purpose Hauser--Feshbach code for the calculation of nuclear cross-sections and thermonuclear reaction rates

    International Nuclear Information System (INIS)

    Woosley, S.; Fowler, W.A.

    1977-09-01

    CRSEC is a FORTRAN IV computer code designed for the efficient calculation of average nuclear cross sections in situations where a statistical theory of nuclear reactions is applicable and where compound nuclear formation is the dominant reaction mechanism. This code generates cross sections of roughly factor of 2 accuracy for incident particle energies in the range of 10 keV to 10 MeV for most target nuclei from magnesium to bismuth. Exceptions usually involve reactions that enter the compound nucleus at such a low energy that fewer than 10 levels are present in the ''energy window of interest.'' The incident particle must be a neutron, proton, or alpha particle, and only binary reactions resulting in the emission of a single n, p, α, or γ (cascade) are calculated. CRSEC is quite fast, a complete calculation of 12 different reactions over a grid of roughly 150 energy points and the generation of Maxwellian averaged rates taking about 30 seconds of CDC7600 time. Also the semi-empirical parameterization of nuclear properties contained in CRSEC is very general. Greater accuracy may be obtained, however, by furnishing specific low-lying excited states, level density parameterization, and nuclear strength functions. A more general version of CRSEC, called CRSECI, is available that conserves isospin properly in all reactions and allows the user to specify a given degree of isospin mixing in the highly excited states of the compound nucleus. Besides the cross section as a function of center-of-mass energy, CRSEC also generates the Maxwell--Boltzmann averaged thermonuclear reaction rate and temperature dependent nuclear partition function for a grid of temperatures from 10 8 to 10 10 0 K. Sections of this report describe in greater detail the physics employed in CRSEC and how to use the code. 2 tables

  13. Cross sections for Discrete γ ray production in interactions of 14.6 MeV neutrons with light and medium heavy nuclei

    International Nuclear Information System (INIS)

    Hlavac, S.; Benovic, M.; Betak, E.; Dostal, L.; Turzo, I.; Simakov, S.P.

    1999-01-01

    We measured cross section of prompt discrete γ ray transitions produced in 14.6 MeV neutron interactions with 23 Na, 27 Al, 28 Si, 31 P 39 K, 51 V, 55 Mn and nat Mo. Cross sections were measured relative to reference cross sections with low uncertainties using a dedicated experimental setup with a 244 cm 3 HPGe photon detector and associated α particle timing. In addition to photons from inelastic scattering we observed discrete transitions from (n,p), (n,n'p), (n,α), and (n,2n) reactions. Discrete γ transitions in 28 Si(n,n'p) 27 Al, the majority of transitions in Mn+n, and all transitions in Mo+n reactions were observed for the first time. Where available, our experimental data are compared with existing data. This comparison shows that existing data are in disagreement with present data in many cases, a finding which stresses the necessity of standardization of measurement procedure. For some reactions we compared our results with statistical model predictions, calculated with the advanced code GNASH as well as with a technically simpler code DEGAS, developed in our lab. In several instances, mostly in reactions where only a single nucleon is emitted, the statistical model calculations describe the observed cross sections well. In other cases, where several nucleons are emitted sequentially or in a cluster, the agreement is less satisfactory. (author)

  14. Measurements of the Fe-54 (n,p) Mn-54 Reaction Cross Section in the Neutron Energy Range 2.3-3.8 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Lauber, A; Malmskog, S

    1964-10-15

    We have measured the {sup 54}Fe (n, p) {sup 54}Mn reaction cross section using a surface barrier detector to record the number of protons released in the reaction. The neutron flux was determined by means of a hydrogenous radiator, detecting the scattered protons with the solid state detector, and calculating the number of impinging neutrons from the well known n-p scattering cross section. The {sup 54}Fe (n, p) {sup 54}Mn reaction cross section is found to increase from 25 mb at 2.3 MeV to 208 mb at 3.5 MeV.

  15. {sup 16}O({gamma},n) reaction cross section for 35 MeV

    Energy Technology Data Exchange (ETDEWEB)

    O`Keefe, G.J.; Bates, A.D.; Rassool, R.P.; McLean, D.J.; Thompson, M.N. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Terasawa, T.; Sugawara, M. [Tohoku Univ., Sendai (Japan). Lab. of Nuclear Science

    1994-12-31

    Double differential cross sections for the {sup 16}O({gamma},n) and {sup 16}O({gamma},nn)reactions have been measured with the photon tagging facility at Tohoku University. These measurements provide information on the important aspects of the reaction mechanism at a microscopic level. 6 refs., 4 figs.

  16. Chiral 1,3,2-oxazaborolidines in asymmetric synthesis: recent advances

    International Nuclear Information System (INIS)

    Glushkov, Vladimir A; Tolstikov, Alexander G

    2004-01-01

    The use of chiral 1,3,2-oxazaborolidines in asymmetric organic synthesis, particularly, in enantioselective reduction of ketones, imines and oxime ethers, asymmetric Diels-Alder reactions, aldol condensation and atroposelective reduction of lactones is reviewed. Reactions of immobilised 1,3,2-oxazaborolidines are also considered.

  17. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Rhodanine derivatives are highly valuable heterocycles in drug discovery. Here, we developed aldol reaction of N-substituted rhodanines and aromatic aldehydes on water. The reaction was performed at room temperature affording the products in good to high yield. This synthetic protocol uses simple experimental ...

  18. Analytical total reaction cross-section calculations via Fermi-type functions. I. Fermi-step nuclear densities

    International Nuclear Information System (INIS)

    Abul-Magd, A.Y.; Talib aly al Hinai, M.

    2000-01-01

    In the framework of Glauber's multiple scattering theory we propose a closed form expression for the total nucleus-nucleus reaction cross-section. We adopt the Gaussian and the two-parameter Fermi step radial shapes to describe the nuclear density distributions of the projectile and the target, respectively. The present formula is used to study different systems over a wide energy range including low energy reactions, where the role of the Coulomb repulsion is taken into account. The present predictions reasonably reproduce experiment

  19. Secondary standard neutron detector for measuring total reaction cross sections

    International Nuclear Information System (INIS)

    Sekharan, K.K.; Laumer, H.; Gabbard, F.

    1975-01-01

    A neutron detector has been constructed and calibrated for the accurate measurement of total neutron-production cross sections. The detector consists of a polyethylene sphere of 24'' diameter in which 8- 10 BF 3 counters have been installed radially. The relative efficiency of this detector has been determined for average neutron energies, from 30 keV to 1.5 MeV by counting neutrons from 7 Li(p,n) 7 Be. By adjusting the radial positions of the BF 3 counters in the polyethylene sphere the efficiency for neutron detection was made nearly constant for this energy range. Measurement of absolute efficiency for the same neutron energy range has been done by counting the neutrons from 51 V(p,n) 51 Cr and 57 Fe(p,n) 57 Co reactions and determining the absolute number of residual nuclei produced during the measurement of neutron yield. Details of absolute efficiency measurements and the use of the detector for measurement of total neutron yields from neutron producing reactions such as 23 Na(p,n) 23 Mg are given

  20. On the Determination of the 7Be(n, α)4He Reaction Cross Section at BBN Energies

    Science.gov (United States)

    Lamia, L.; Spitaleri, C.; Bertulani, C. A.; Hou, S. Q.; La Cognata, M.; Pizzone, R. G.; Romano, S.; Sergi, M. L.; Tumino, A.

    2017-12-01

    7Be destruction channels are currently a matter of study because of their influence on the 7Li cosmological abundances. Here, we determine the cross section of the (n, α) reaction by using Trojan Horse experimental data for the 7Li(p, α)4He reaction and correcting for Coulomb effects. The deduced 7Be(n, α)4He data overlap with the Big Bang nucleosynthesis energies and the deduced reaction rate allows us to evaluate the corresponding cosmological implications.

  1. Multimodal sensory integration during sequential eating--linking chewing activity, aroma release, and aroma perception over time.

    Science.gov (United States)

    Leclercq, Ségolène; Blancher, Guillaume

    2012-10-01

    The respective effects of chewing activity, aroma release from a gelled candy, and aroma perception were investigated. Specifically, the study aimed at 1) comparing an imposed chewing and swallowing pattern (IP) and free protocol (FP) on panelists for in vivo measurements, 2) investigating carryover effects in sequential eating, and 3) studying the link between instrumental data and their perception counterpart. Chewing activity, in-nose aroma concentration, and aroma perception over time were measured by electromyography, proton transfer reaction-mass spectrometry, and time intensity, respectively. Model gel candies were flavored at 2 intensity levels (low-L and high-H). The panelists evaluated 3 sequences (H then H, H then L, and L then H) in duplicates with both IP and FP. They scored aroma intensity over time while their in-nose aroma concentrations and their chewing activity were measured. Overall, only limited advantages were found in imposing a chewing and swallowing pattern for instrumental and sensory data. In addition, the study highlighted the role of brain integration on perceived intensity and dynamics of perception, in the framework of sequential eating without rinsing. Because of the presence of adaptation phenomena, contrast effect, and potential taste and texture cross-modal interaction with aroma perception, it was concluded that dynamic in-nose concentration data provide only one part of the perception picture and therefore cannot be used alone in prediction models.

  2. Measurement of (n,Xn) reaction cross sections at 96 MeV; Measure des sections efficaces (n,Xn) a 96 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Sagrado Garcia, Melle Inmaculada C. [Ecole Doctorale: SINEM, U.F.R. de Sciences, Universite de Caen/Basse-Normandie, Esplanade Paix14000 Caen (France)

    2006-10-15

    Nucleon induced reactions in the 20-200 MeV energy range are intensively studied since a long time. The evaporation and the pre-equilibrium processes correspond to an important contribution of the production cross section in these reactions. Several theoretical approaches have been proposed and their predictions must be tested. The experimental results shown in this work are the only complete set of data for the (n,Xn) reactions in this energy range. Neutron double differential cross section measurements using lead and iron targets for an incident neutron beam at 96 MeV were carried out at TSL Laboratory in Uppsala, Sweden. The measurements have been performed for the first time with an energy threshold of 2 MeV and for a wide angular range (15 angle - 98 angle). Neutrons have been detected using two independent setups, DECOI and DEMON and CLODIA and SCANDAL, in order to cover the whole energy range (2-100) MeV. The angular distributions, the differential cross sections and the total inelastic production cross sections have been calculated using the double differential cross sections. The comparison between the experimental data and the predictions given by two of the most popular simulation codes, GEANT3 and MCNPX, have been performed, as well as the comparison with the predictions of the microscopic simulation model DYWAN, selected for its treatment of nucleon-nucleon reactions. (author)

  3. Remarks concerning the accurate measurement of differential cross sections for threshold reactions used in fast-neutron dosimetry for fission reactors

    International Nuclear Information System (INIS)

    Smith, D.L.

    1976-12-01

    Some remarks are submitted concerning the measurement of differential cross sections for threshold reactions which are used in fast-neutron dosimetry for fission reactors. The objective is to familiarize the reader with some of the problems associated with these measurements and, in the process, to explain why the existence of large discrepancies in the data sets for many of these reactions is not surprising. Limits to the accuracy which can be expected for these cross sections in the near future--using current technology and available resources--are examined in a general way and recommendations for improving the accuracy of the differential data base for dosimetry reactions are presented

  4. A combined crossed molecular beams and theoretical study of the reaction CN + C2H4

    International Nuclear Information System (INIS)

    Balucani, Nadia; Leonori, Francesca; Petrucci, Raffaele; Wang, Xingan; Casavecchia, Piergiorgio; Skouteris, Dimitrios; Albernaz, Alessandra F.; Gargano, Ricardo

    2015-01-01

    Highlights: • The CN + C 2 H 4 reaction was investigated in crossed beam experiments. • Electronic structure calculations of the potential energy surface were performed. • RRKM estimates qualitatively reproduce the experimental C 2 H 3 NC yield. - Abstract: The CN + C 2 H 4 reaction has been investigated experimentally, in crossed molecular beam (CMB) experiments at the collision energy of 33.4 kJ/mol, and theoretically, by electronic structure calculations of the relevant potential energy surface and Rice–Ramsperger–Kassel–Marcus (RRKM) estimates of the product branching ratio. Differently from previous CMB experiments at lower collision energies, but similarly to a high energy study, we have some indication that a second reaction channel is open at this collision energy, the characteristics of which are consistent with the channel leading to CH 2 CHNC + H. The RRKM estimates using M06L electronic structure calculations qualitatively support the experimental observation of C 2 H 3 NC formation at this and at the higher collision energy of 42.7 kJ/mol of previous experiments

  5. The cross sections of reactions resulting in transmutation of long-lived radionuclides of exhausted nuclear fuel exposed to fast neutrons

    International Nuclear Information System (INIS)

    Konodeev, A.Yu.; Korovin, Yu.A.; Erview, K.

    1993-01-01

    Research is at present concerned with the possible transmutation of long-lived radionuclides of spent nuclear fuel in the flux of fast neutrons from neutron generators which are distinguished by their energy spectrum and density of the flux generated. For this purpose one must know the cross sections of the nuclear reactions resulting in the transmutation and formation of new long-lived radionuclides due to the irradiation. The transmutation rate of radioisotope irradiated with neutrons have a known energy spectrum is determined by calculating the transmutation cross section which is equal to the sum of the cross sections of neutron reactions causing conversion of a particular isotope into another after the decay of short-lived residual nuclei. The presently available neutron cross section data of long-lived radionuclides, i.e., the products of the fission of nuclear fuel, are insufficient for research on these effects as transmutations occur in a flux of high-energy neutrons. This paper presents the cross sections of reactions accounting for the transmutation of the most important long-lived radionuclides of exhausted nuclear fuel during its irradiation with neutron having energies of up to 100 MeV. The neutron cross sections were calculated for 79 Se, 90 Sr, 93 Zr, 99 Tc, 107 Pd, 126 Sn, 129 I, 135 Cs and 137 Cs with a half-life ≥30 years

  6. On-line Flagging of Anomalies and Adaptive Sequential Hypothesis Testing for Fine-feature Characterization of Geosynchronous Satellites

    Science.gov (United States)

    2015-10-18

    model-based evidence. This work resolves cross-tag using three methods (Z-test for dependent data, classical sequential analysis and Brownian motion...Slider Movement The two-facet model is used as the Inversion Model. It represents a three-axis stabilized satellite as two facets, namely a body...the sequential analysis. If is independent and has an approximately normal distribution then Brownian motion drift analysis is used. If is

  7. Evaluation of the 93Nb (n,n')93mNb reaction cross section from the threshold up to 20 MeV

    International Nuclear Information System (INIS)

    Badikov, S.A.; Zolotarev, K.I.; Pashchenko, A.B.

    1992-01-01

    The data base comprising the results of the 93 Nb(n,n') 93m Nb reactions cross section measurements up to 1991 has been compiled. The experimental data have been renormalized to new values of standard cross-sections from the ENDF/B-6 and the IRDF-90 libraries. The evaluation of excitation function for the 93 Nb(n,n') 93m Nb reaction was carried out on the basis of procedure taking the correlation of experimental data into account. The files of evaluated cross-sections and covariance were prepared in the ENDF/B-6 format. The cross-section evaluations from present work and the IRDF-90 library are compared. 37 refs.; 3 figs.; 6 tabs

  8. Approximate quantum differential cross section for the F + HD → HF + D and DF + H reactions

    International Nuclear Information System (INIS)

    Lee, K.T.; Bowman, J.M.

    1982-01-01

    In a previous paper we proposed a novel way to obtain approximate quantum mechanical differential cross sections. Here, we use this approximate method to study the reactions F + HD(nu = 0) → FH(nu' = 2) + D and F + DH(nu = 0) → DF(nu' = 3) + H. Backward and forward scattering are found for the first reaction and only backward scattering for the second one. These results agree qualitatively with experiment. 1 figure

  9. Isomeric cross-section ratios of some (n,2n) reactions at 14. 7 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Garg, K C; Khurana, C S [Punjabi Univ., Patiala (India). Nuclear Science Labs.

    1979-08-01

    Isomeric cross-section ratios of (n,2n) reactions at 14.7 MeV leading to the millisecond isomeric levels have been calculated theoretically using the statistical theory of nuclear reactions and the spin distribution form due to Bethe and Bloch. The theoretical ratios have been compared with the experimentally measured values in order to evaluate the spin cut-off parameter sigma. This parameter has been used to calculate the effective moment of inertia of the nucleus to draw useful conclusions from the results of present calculations.

  10. Comments on the sequential probability ratio testing methods

    Energy Technology Data Exchange (ETDEWEB)

    Racz, A. [Hungarian Academy of Sciences, Budapest (Hungary). Central Research Inst. for Physics

    1996-07-01

    In this paper the classical sequential probability ratio testing method (SPRT) is reconsidered. Every individual boundary crossing event of the SPRT is regarded as a new piece of evidence about the problem under hypothesis testing. The Bayes method is applied for belief updating, i.e. integrating these individual decisions. The procedure is recommended to use when the user (1) would like to be informed about the tested hypothesis continuously and (2) would like to achieve his final conclusion with high confidence level. (Author).

  11. Psychosocial reactions to upper extremity limb salvage: A cross-sectional study.

    Science.gov (United States)

    Sposato, Lindsay; Yancosek, Kathleen; Lospinoso, Josh; Cancio, Jill

    2017-08-09

    Descriptive cross-sectional survey study. Limb salvage spares an extremity at risk for amputation after a major traumatic injury. Psychosocial recovery for individuals with lower extremity limb salvage has been discussed in the literature. However, to date, psychosocial reactions for individuals with upper extremity (UE) limb salvage have not been examined. To determine which factors may influence psychosocial adaptation to UE limb salvage. Participants (n = 30; 28 males) were adults (mean, 30.13; range, 18-61) who sustained an UE limb salvage from a traumatic event. Adaptation was measured using a modified version of the Reactions to Impairment and Disability Inventory. A linear mixed-effects regression found that worse psychosocial adaptation was associated with having less than a college degree, being less than 6 months post-injury, being older than 23 years, and having more pain. Dominant hand injuries were found to influence poor adaptation on the denial Reactions to Impairment and Disability Inventory subscale only. The results of this study indicate that there is potential for nonadaptive reactions and psychological distress with certain variables in UE limb salvage. Therapists may use these results to anticipate which clients may be at risk for poor psychosocial outcomes. This study indicates the need for early consideration to factors that affect psychological prognosis for the UE limb salvage population. However, future research is indicated to better understand the unique psychosocial challenges and needs of these individuals. 4. Copyright © 2017 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

  12. Measurement and calculation of cross section for (p,x) reactions on natural Fe for 650 MeV protons

    International Nuclear Information System (INIS)

    Janczyszyn, J.; Pohorecki, W.; Domanska, G.; Loska, L.; Taczanowski, S.; Shvetsov, V.

    2006-01-01

    Cross sections for production of radionuclides in (p,x) reactions on natural iron were measured for protons of 650 ± 4 MeV with the use of HPGe gamma spectrometry and calculated with the MCNPX code. The determined cross section values were compared with the computed and other experimental ones

  13. Measurement of the thermal cross section of the reaction 64Zn(n,γ)65Zn in a mixed neutron flux

    International Nuclear Information System (INIS)

    Dorval, E. L; Arribere, M. A; Ribeiro Guevara, S

    2006-01-01

    Zinc is an element that is present in a great variety of biological and geological samples.For its determination by Instrumental Neutron Activation Analysis, the reaction 64 Z n(n,γ) 6 5Zn is used, due to the long half life of the reaction product, the target's bigger isotopic abundance, and an easily measurable 1115 keV main gamma line.In a recent evaluation of thermal cross sections and resonance integrals, a thermal cross section value that is 44.7% bigger than the previous evaluation has been published by the same reference.This difference is not within reported uncertainties.Besides, the relative uncertainty of the new evaluation is much bigger than the one corresponding to the previous evaluation.The adoption of the thermal cross section corresponding to different evaluations may imply, in the case of an irradiation in the peripheral I 6 position at the R A-6 reactor, discrepancies of about 43% in the calculated concentrations.These inconsistencies were evident during the irradiation of certified standard materials.This motivated the measurement of the thermal cross section for the reaction 64 Z n(n,γ) 6 5Zn in the I 6 position at the R A-6 reactor.For the analysis of results, a code was written in order to calculate correction factors from an accurate characterization of the neutron spectrum.The thermal cross section value of the reaction 64 Z n(n,γ) 6 5Zn measured is (0.76± 0.03) b [es

  14. Measurements of neutron cross section of the {sup 243}Am(n,{gamma}){sup 244}Am reaction

    Energy Technology Data Exchange (ETDEWEB)

    Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    The effective thermal neutron cross section of {sup 243}Am(n,{gamma}){sup 244}Am reaction was measured by the activation method. Highly-purified {sup 243}Am target was irradiated in an aluminum capsule by using a research reactor JRR-3M. The tentative effective thermal neutron cross sections are 3.92 b, and 84.44 b for the production of {sup 244g}Am and {sup 244m}Am, respectively. (author)

  15. Establishment of the BOSPOR-80 machine library of evaluated threshold reaction cross-sections and its testing by means of integral experiments

    International Nuclear Information System (INIS)

    Bychkov, V.M.; Zolotarev, K.I.; Pashchenko, A.B.; Plyaskin, V.I.

    1982-08-01

    A paper was published in 1979 containing a compilation of experimental data on the cross-sections of (n,p), (n,α) and (n,2n) threshold reactions and recommended excitation functions. A further paper considered the development of evaluation methods based on the use of theoretical model calculations, an increase in the number of recommended excitation functions, correction of the recommended cross-sections on the basis of integral experiments and allowance for recent experimental data. To satisfy the wide circle of users, BOSPOR-80 - a machine library of evaluated threshold reaction cross-sections - was set up

  16. Kinematic relations in heavy-ion reactions

    International Nuclear Information System (INIS)

    Gippner, P.; Kalpakchieva, R.

    1988-01-01

    The present work gives a short overview of the non-relativistic kinematics of nuclear reactions derived on the basis of the conservation laws of energy and linear momentum. Section 2 contains kinematic relations valid for two-body reactions, sections 3 makes use of these relations to describe sequential fission as a special case of reactions with three particles in the exit channel. It is the aim of this work to comprise the kinematic formulae essential for planning of experiments, data analysis and critical examination of the obtained results. (author)

  17. Evaluation of cross sections for 197Au(n,3n) and 197Au(n,4n) reactions from threshold to 50 MeV

    International Nuclear Information System (INIS)

    Yu Baosheng; Shen Qingbiao; Cai Dunjiu

    1994-01-01

    The measured data of cross sections for 197 Au(n,3n) and 197 Au(n,4n) reactions were collected and analysed. The theoretical calculations of above mentioned reactions were carried out to predict the data in higher energy region. The sets of cross sections for 197 Au(n,3n) and 197 Au(n,4n) reactions from threshold to 50 MeV were recommended on the basis of the experimental and calculated data. (2 figs)

  18. Preparation and characterization of Mg-Zr mixed oxide aerogels and their application as aldol condensation catalysts.

    Science.gov (United States)

    Sádaba, Irantzu; Ojeda, Manuel; Mariscal, Rafael; Richards, Ryan; López Granados, Manuel

    2012-10-08

    A series of Mg-Zr mixed oxides with different nominal Mg/(Mg+Zr) atomic ratios, namely 0, 0.1, 0.2, 0.4, 0.85, and 1, is prepared by alcogel methodology and fundamental insights into the phases obtained and resulting active sites are studied. Characterization is performed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N(2) adsorption-desorption isotherms, and thermal and chemical analysis. Cubic Mg(x)Zr(1-x)O(2-x) solid solution, which results from the dissolution of Mg(2+) cations within the cubic ZrO(2) structure, is the main phase detected for the solids with theoretical Mg/(Mg+Zr) atomic ratio ≤0.4. In contrast, the cubic periclase (c-MgO) phase derived from hydroxynitrates or hydroxy precursors predominates in the solid with Mg/(Mg+Zr)=0.85. c-MgO is also incipiently detected in samples with Mg/(Mg+Zr)=0.2 and 0.4, but in these solids the c-MgO phase mostly arises from the segregation of Mg atoms out of the alcogel-derived c-Mg(x)Zr(1-x)O(2-x) phase during the calcination process, and therefore the species c-MgO and c-Mg(x)Zr(1-x)O(2-x) are in close contact. Regarding the intrinsic activity in furfural-acetone aldol condensation in the aqueous phase, these Mg-O-Zr sites located at the interface between c-Mg(x)Zr(1-x)O(2-x) and segregated c-MgO display a much larger intrinsic activity than the other noninterface sites that are present in these catalysts: Mg-O-Mg sites on c-MgO and Mg-O-Zr sites on c-Mg(x)Zr(1-x)O(2-x). The very active Mg-O-Zr sites rapidly deactivate in the furfural-acetone condensation due to the leaching of active phases, deposition of heavy hydrocarbonaceous compounds, and hydration of the c-MgO phase. Nonetheless, these Mg-Zr materials with very high specific surface areas would be suitable solid catalysts for other relevant reactions catalyzed by strong basic sites in nonaqueous environments. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. From Cycling Between Coupled Reactions to the Cross-Bridge Cycle: Mechanical Power Output as an Integral Part of Energy Metabolism

    Directory of Open Access Journals (Sweden)

    Frank Diederichs

    2012-10-01

    Full Text Available ATP delivery and its usage are achieved by cycling of respective intermediates through interconnected coupled reactions. At steady state, cycling between coupled reactions always occurs at zero resistance of the whole cycle without dissipation of free energy. The cross-bridge cycle can also be described by a system of coupled reactions: one energising reaction, which energises myosin heads by coupled ATP splitting, and one de-energising reaction, which transduces free energy from myosin heads to coupled actin movement. The whole cycle of myosin heads via cross-bridge formation and dissociation proceeds at zero resistance. Dissipation of free energy from coupled reactions occurs whenever the input potential overcomes the counteracting output potential. In addition, dissipation is produced by uncoupling. This is brought about by a load dependent shortening of the cross-bridge stroke to zero, which allows isometric force generation without mechanical power output. The occurrence of maximal efficiency is caused by uncoupling. Under coupled conditions, Hill’s equation (velocity as a function of load is fulfilled. In addition, force and shortening velocity both depend on [Ca2+]. Muscular fatigue is triggered when ATP consumption overcomes ATP delivery. As a result, the substrate of the cycle, [MgATP2−], is reduced. This leads to a switch off of cycling and ATP consumption, so that a recovery of [ATP] is possible. In this way a potentially harmful, persistent low energy state of the cell can be avoided.

  20. Cross section measurement of alpha particle induced nuclear reactions on natural cadmium up to 52MeV.

    Science.gov (United States)

    Ditrói, F; Takács, S; Haba, H; Komori, Y; Aikawa, M

    2016-12-01

    Cross sections of alpha particle induced nuclear reactions have been measured on thin natural cadmium targets foils in the energy range from 11 to 51.2MeV. This work was a part of our systematic study on excitation functions of light ion induced nuclear reactions on different target materials. Regarding the cross sections, the alpha induced reactions are not deeply enough investigated. Some of the produced isotopes are of medical interest, others have application in research and industry. The radioisotope 117m Sn is a very important theranostic (therapeutic + diagnostic) radioisotope, so special care was taken to the results for that isotope. The well-established stacked foil technique followed by gamma-spectrometry with HPGe gamma spectrometers were used. The target and monitor foils in the stack were commercial high purity metal foils. From the irradiated targets 117m Sn, 113 Sn, 110 Sn, 117m,g In, 116m In, 115m In, 114m In, 113m In, 111 In, 110m,g In, 109m In, 108m,g In, 115g Cd and 111m Cd were identified and their excitation functions were derived. The results were compared with the data of the previous measurements from the literature and with the results of the theoretical nuclear reaction model code calculations TALYS 1.8 (TENDL-2015) and EMPIRE 3.2 (Malta). From the cross section curves thick target yields were calculated and compared with the available literature data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Kerma factors and reaction cross sections for n + /sup 12/C between 15 and 18 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tornow, W.; Chen, Z.M.; Baird, K.; Walter, R.L.

    1988-07-01

    Differential elastic and inelastic (4.44 MeV) neutron scattering cross sections from /sup 12/C are presented at 15.6, 16.8 and 17.3 MeV. The existing 18.2 MeV differential cross-section data were combined with newly measured analysing power data to parametrise neutron scattering at this energy. The /sup 12/C recoil kerma factors were calculated and reaction cross sections were obtained from a phase-shift analysis and coupled channel analyses in the 15.6-18.2 MeV energy range.

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

    Directory of Open Access Journals (Sweden)

    Kin Hong Liew

    2014-01-01

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

  3. Measurements of the thermal neutron cross-section and resonance integral for the 108Pd(n,γ)109Pd reaction

    Science.gov (United States)

    Hien, Nguyen Thi; Kim, Guinyun; Kim, Kwangsoo; Do, Nguyen Van; Khue, Pham Duc; Thanh, Kim Tien; Shin, Sung-Gyun; Cho, Moo-Hyun

    2018-06-01

    The thermal neutron capture cross-section (σ0) and resonance integral (I0) of the 108Pd(n,γ)109Pd reaction have been measured relative to that of the monitor reaction 197Au(n,γ)198Au. The measurements were carried out using the neutron activation with the cadmium ratio method. Both the samples and monitors were irradiated with and without cadmium cover of 0.5 mm thickness. The induced activities of the reaction products were measured with a well calibrated HPGe γ-ray detector. In order to improve the accuracy of the results, the necessary corrections for the counting losses were made. The thermal neutron capture cross-section and resonance integral of the 108Pd(n,γ)109Pd reaction were determined to be σ0,Pd = 8.68 ± 0.41 barn and I0,Pd = 245.6 ± 24.8 barn, respectively. The obtained results are compared with literature values and discussed.

  4. Mechanism of the Suzuki–Miyaura Cross-Coupling Reaction Mediated by [Pd(NHC)(allyl)Cl] Precatalysts

    KAUST Repository

    Meconi, Giulia Magi; Vummaleti, Sai V. C.; Luque-Urrutia, Jesú s Antonio; Belanzoni, Paola; Nolan, Steven P.; Jacobsen, Heiko; Cavallo, Luigi; Solà , Miquel; Poater, Albert

    2017-01-01

    (IPr); R = H (1), Me (2), gem-Me2 (3), Ph (4), X = Cl, Br). Next, we have investigated the Suzuki–Miyaura cross-coupling reaction for the active catalyst species IPr-Pd(0) using 4-chlorotoluene and phenylboronic acid as substrates and isopropyl alcohol as a

  5. Average cross-sections for /n, p/ reactions on calcium in a fission-type reactor spectrum

    International Nuclear Information System (INIS)

    Bruggeman, A.; Maenhaut, W.; Hoste, J.

    1974-01-01

    The average cross-section in a fission-type reactor spectrum sigmasub(F) was experimentally determined for the reactions 42 Ca/n,p/ 42 K, 43 Ca/n,p/ 43 K and 44 Ca/n,p/ 44 K. Calcium carbonate samples and fast neutron flux monitors were irradiated with and without cadmium shielding in the Thetis reactor (Institute for Nuclear Sciences, Rijksuniversiteit Gent). The potassium activities induced in the calcium carbonate samples were separated and purified by tetraphenylborate precipitation, after which they were measured with a Ge/Li/-detector of calibrated detection efficiency. On the basis of sigmasub(F)=0.64 mb for the reaction 27 Al/n,α/ 24 Na, the average cross-sections were as follows: 42 Ca/n,p/ 42 K: 2.82+-0.07 mb; 43 Ca/n,p/ 43 K: 1.89+-0.05 mb; 44 Ca/n,p/ 44 K: 0.065+-0.003 mb. (T.G.)

  6. EDITAR: a module for reaction rate editing and cross-section averaging within the AUS neutronics code system

    International Nuclear Information System (INIS)

    Robinson, G.S.

    1986-03-01

    The EDITAR module of the AUS neutronics code system edits one and two-dimensional flux data pools produced by other AUS modules to form reaction rates for materials and their constituent nuclides, and to average cross sections over space and energy. The module includes a Bsub(L) flux calculation for application to cell leakage. The STATUS data pool of the AUS system is used to enable the 'unsmearing' of fluxes and nuclide editing with minimal user input. The module distinguishes between neutron and photon groups, and printed reaction rates are formed accordingly. Bilinear weighting may be used to obtain material reactivity worths and to average cross sections. Bilinear weighting is at present restricted to diffusion theory leakage estimates made using mesh-average fluxes

  7. Measurement of formation cross-section of 99Mo from the 98Mo(n,γ) and 100Mo(n,2n) reactions.

    Science.gov (United States)

    Badwar, Sylvia; Ghosh, Reetuparna; Lawriniang, Bioletty M; Vansola, Vibha; Sheela, Y S; Naik, Haladhara; Naik, Yeshwant; Suryanarayana, Saraswatula V; Jyrwa, Betylda; Ganesan, Srinivasan

    2017-11-01

    The formation cross-section of medical isotope 99 Mo from the 98 Mo(n,γ) reaction at the neutron energy of 0.025eV and from the 100 Mo(n,2n) reaction at the neutron energies of 11.9 and 15.75MeV have been determined by using activation and off-line γ-ray spectrometric technique. The thermal neutron energy of 0.025eV was used from the reactor critical facility at BARC, Mumbai, whereas the average neutron energies of 11.9 and 15.75MeV were generated using 7 Li(p,n) reaction in the Pelletron facility at TIFR, Mumbai. The experimentally determined cross-sections were compared with the evaluated nuclear data libraries of ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and JEFF-3.2 and are found to be in close agreement. The 100 Mo(n,2n) 99 Mo reaction cross-sections were also calculated theoretically by using TALYS-1.8 and EMPIRE-3.2 computer codes and compared with the experimental data. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Heuristic and optimal policy computations in the human brain during sequential decision-making.

    Science.gov (United States)

    Korn, Christoph W; Bach, Dominik R

    2018-01-23

    Optimal decisions across extended time horizons require value calculations over multiple probabilistic future states. Humans may circumvent such complex computations by resorting to easy-to-compute heuristics that approximate optimal solutions. To probe the potential interplay between heuristic and optimal computations, we develop a novel sequential decision-making task, framed as virtual foraging in which participants have to avoid virtual starvation. Rewards depend only on final outcomes over five-trial blocks, necessitating planning over five sequential decisions and probabilistic outcomes. Here, we report model comparisons demonstrating that participants primarily rely on the best available heuristic but also use the normatively optimal policy. FMRI signals in medial prefrontal cortex (MPFC) relate to heuristic and optimal policies and associated choice uncertainties. Crucially, reaction times and dorsal MPFC activity scale with discrepancies between heuristic and optimal policies. Thus, sequential decision-making in humans may emerge from integration between heuristic and optimal policies, implemented by controllers in MPFC.

  9. Modelling sequentially scored item responses

    NARCIS (Netherlands)

    Akkermans, W.

    2000-01-01

    The sequential model can be used to describe the variable resulting from a sequential scoring process. In this paper two more item response models are investigated with respect to their suitability for sequential scoring: the partial credit model and the graded response model. The investigation is

  10. 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.

  11. Energy dependence of fusion evaporation-residue cross sections in the 28Si+28Si reaction

    International Nuclear Information System (INIS)

    Vineyard, M.F.; Bauer, J.S.; Gosdin, C.H.; Trotter, R.S.; Kovar, D.G.; Beck, C.; Henderson, D.J.; Janssens, R.V.F.; Wilkins, B.D.; Rosner, G.; Chowdhury, P.; Ikezoe, H.; Kuhn, W.; Kolata, J.J.; Hinnefeld, J.D.; Maguire, C.F.; Mateja, J.F.; Prosser, F.W.; Stephans, G.S.F.

    1990-01-01

    Velocity distributions of mass-identified evaporation residues produced in the 28 Si+ 28 Si reaction have been measured at bombarding energies of 174, 215, 240, 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and total cross sections were extracted at all six bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with lower energy data and the predictions of existing models

  12. Studies on the Model Synthesis of the Brassinolide and Dolicholide Side Chains

    Institute of Scientific and Technical Information of China (English)

    Li Zeng PENG; Feng Zhi ZHANG; Tian Sheng MEI; Yu Lin LI

    2003-01-01

    A stereoselective synthesis of brassinolide and dolicholide, which involves constructionof the side chain enantiomers by a highly stereoselective aldol reaction of aldehyde 5 with theanion of α-silyloxy ketone 6 is described.

  13. Low-lying electric-dipole strengths of Ca, Ni, and Sn isotopes imprinted on total reaction cross sections

    Science.gov (United States)

    Horiuchi, W.; Hatakeyama, S.; Ebata, S.; Suzuki, Y.

    2017-08-01

    Low-lying electric-dipole (E 1 ) strength of a neutron-rich nucleus contains information on neutron-skin thickness, deformation, and shell evolution. We discuss the possibility of making use of total reaction cross sections on 40Ca, 120Sn, and 208Pb targets to probe the E 1 strength of neutron-rich Ca, Ni, and Sn isotopes. They exhibit large enhancement of the E 1 strength at neutron number N >28 , 50, and 82, respectively, due to a change of the single-particle orbits near the Fermi surface participating in the transitions. The density distributions and the electric-multipole strength functions of those isotopes are calculated by the Hartree-Fock+BCS and the canonical-basis-time-dependent-Hartree-Fock-Bogoliubov methods, respectively, using three kinds of Skyrme-type effective interaction. The nuclear and Coulomb breakup processes are respectively described with the Glauber model and the equivalent photon method in which the effect of finite-charge distribution is taken into account. The three Skyrme interactions give different results for the total reaction cross sections because of different Coulomb breakup contributions. The contribution of the low-lying E 1 strength is amplified when the low-incident energy is chosen. With an appropriate choice of the incident energy and target nucleus, the total reaction cross section can be complementary to the Coulomb excitation for analyzing the low-lying E 1 strength of unstable nuclei.

  14. ZZ RRDF-98, Cross-sections and covariance matrices for 22 neutron induced dosimetry reactions

    International Nuclear Information System (INIS)

    Zolotarev, K.I.; Ignatyuk, A.V.; Mahokhin, V.N.; Pashchenko, A.B.

    2005-01-01

    1 - Description of program or function: Format: ENDF-6 format; Number of groups: Continuous energy; Dosimetry reactions: 6-C-12(n,2n), 8-O-16(n,2n), 9-F-19(n,2n), 12-Mg-24(n,p), 22-Ti-46(n,2n), 22-Ti-46(n,p), 22-Ti-47(n,x), 22-Ti-48(n,p), 22-Ti-48(n,x), 22-Ti-49(n,x), 23-V-51(n,alpha), 26-Fe-54(n,2n), 26-Fe-54(n,alpha), 26-Fe-56(n,p), 27-Co-59(n,alpha), 29-Cu-63(n,alpha), 33-As-75(n,2n), 41-Nb-93(n,2n), 41-Nb-93(n,n'), 45-Rh-103(n,n'), 49-In-115(n,n'), 59-Pr-141(n,2n); Origin: Russian Federation; Weighting spectrum: None. RRDF-98 contains original evaluations of cross section data performed at the Institute of Physics and Power Engineering, Obninsk, for 22 neutron induced dosimetry reactions. The dataset also contains the corresponding covariance matrices. 2 - Methods: The evaluation of excitation functions was performed on the basis of statistical analysis of corrected experimental data in the framework of generalized least squares method and taking into account the results of optical-statistical STAPRE and GNASH calculations. The experimental cross section data including the most recent results were critically reviewed and processed in this study. If necessary, the data were normalized in order to make adjustments in relevant cross sections and decay schemes. The covariance matrices were prepared and the evaluated cross section data are presented in ENDF-6 format (Files 3, 33). For estimation of correlations between experimental data the total uncertainties of measured cross sections have been separated into statistical and systematic parts and correlation coefficients between components of systematic parts were assigned according to information given in the original publications and EXFOR library. Then the correlation matrix of cross sections measured within one experiment was calculated and approximated by matrix with a constant (average) correlation coefficient. The overall correlation matrix was composed of such sub-matrices in the assumption that the cross

  15. Measurement of (n,xn) reaction cross-sections using prompt {gamma} spectroscopy at neutron beams with high instantaneous flux; Mesure de sections efficaces de reaction (n,xn) par spectroscopie {gamma} prompte aupres d'un faisceau a tres haut flux instantane

    Energy Technology Data Exchange (ETDEWEB)

    Lukic, S

    2004-10-15

    The work presented in this thesis is situated in the context of the GEDEON program of neutron cross-section measurements. This program is motivated by the perspectives recently opened by projects of nuclear waste treatment and energy production. There is an obvious lack of experimental data on (n,xn) reactions in the databases, especially in the case of very radioactive isotopes. An important technique to measure cross-sections of these reactions is the prompt {gamma}-ray spectroscopy at white pulsed neutron beams with very high instantaneous flux. In this work, inelastic scattering and (n,xn) reactions cross-section measurements were performed on a lead sample from threshold to 20 MeV by prompt {gamma}-ray spectroscopy at the white neutron beam generated by GELINA facility in Geel, Belgium. Digital methods were developed to treat HPGe CLOVER detector signals and separate {gamma}-rays induced by the fastest neutrons from those belonging to the flash. Partial cross-sections for the production of several transitions in natural lead were measured and analyzed using theoretical calculations in order to separate the contributions of different reactions leading to the same residual isotope. Total cross-sections of the reactions in question were estimated. The results were compared to the TALYSS code theoretical calculations, as well as to other experimental results. This experiment has served to validate the method and it opens the way to measure (n,xn) reactions cross-sections with high instantaneous neutron flux on actinides, particularly the U{sup 233}(n,2n) reaction which is important for the thorium cycle. (author)

  16. Crossed Molecular Beams and Quasiclassical Trajectory Surface Hopping Studies of the Multichannel Nonadiabatic O((3)P) + Ethylene Reaction at High Collision Energy.

    Science.gov (United States)

    Balucani, Nadia; Leonori, Francesca; Casavecchia, Piergiorgio; Fu, Bina; Bowman, Joel M

    2015-12-17

    The combustion relevant O((3)P) + C2H4 reaction stands out as a prototypical multichannel nonadiabatic reaction involving both triplet and singlet potential energy surfaces (PESs), which are strongly coupled. Crossed molecular beam (CMB) scattering experiments with universal soft electron ionization mass spectrometric detection have been used to characterize the dynamics of this reaction at the relatively high collision energy Ec of 13.7 kcal/mol, attained by crossing the reactant beams at an angle of 135°. This work is a full report of the data at the highest Ec investigated for this reaction. From laboratory product angular and velocity distribution measurements, angular and translational energy distributions in the center-of-mass system have been obtained for the five observed exothermic competing reaction channels leading to H + CH2CHO, H + CH3CO, CH3 + HCO, CH2 + H2CO, and H2 + CH2CO. The product branching ratios (BRs) have been derived. The elucidation of the reaction dynamics is assisted by synergic full-dimensional quasiclassical trajectory surface-hopping calculations of the reactive differential cross sections on coupled ab initio triplet/singlet PESs. This joint experimental/theoretical study extends and complements our previous combined CMB and theoretical work at the lower collision energy of 8.4 kcal/mol. The theoretically derived BRs and extent of intersystem crossing (ISC) are compared with experimental results. In particular, the predictions of the QCT results for the three main channels (those leading to vinoxy + H, methyl + HCO and methylene + H2CO formation) are compared directly with the experimental data in the laboratory frame. Good overall agreement is noted between theory and experiment, although some small, yet significant shortcomings of the theoretical differential cross section are noted. Both experiment and theory find almost an equal contribution from the triplet and singlet surfaces to the reaction, with a clear tendency of the

  17. Multi-agent sequential hypothesis testing

    KAUST Repository

    Kim, Kwang-Ki K.

    2014-12-15

    This paper considers multi-agent sequential hypothesis testing and presents a framework for strategic learning in sequential games with explicit consideration of both temporal and spatial coordination. The associated Bayes risk functions explicitly incorporate costs of taking private/public measurements, costs of time-difference and disagreement in actions of agents, and costs of false declaration/choices in the sequential hypothesis testing. The corresponding sequential decision processes have well-defined value functions with respect to (a) the belief states for the case of conditional independent private noisy measurements that are also assumed to be independent identically distributed over time, and (b) the information states for the case of correlated private noisy measurements. A sequential investment game of strategic coordination and delay is also discussed as an application of the proposed strategic learning rules.

  18. Activation cross-sections of deuteron induced nuclear reactions on neodymium up to 50 MeV

    International Nuclear Information System (INIS)

    Tárkányi, F.; Takács, S.; Ditrói, F.; Hermanne, A.; Yamazaki, H.; Baba, M.; Mohammadi, A.; Ignatyuk, A.V.

    2014-01-01

    Highlights: • Experimental excitation function of deuteron induced reactions on natural Nd. • Model code calculations with EMPIRE-D, ALICE-D and TALYS (TENDL-2012). • Physical yield calculation and comparison. • Discussion of medical and industrial applications. - Abstract: In the frame of a systematic study of activation cross sections of deuteron induced nuclear reactions on rare earths, the reactions on neodymium for production of therapeutic radionuclides were measured for the first time. The excitation functions of the nat Nd(d,x) 151,150,149,148m,148g,146,144,143 Pm, 149,147,139m Nd, 142 Pr and 139g Ce nuclear reactions were assessed by using the stacked foil activation technique and high resolution γ-spectrometry. The experimental excitation functions were compared to the theoretical predictions calculated with the modified model codes ALICE-IPPE-D and EMPIRE-II-D and with the data in the TENDL-2012 library based on latest version of the TALYS code. The application of the data in the field of medical isotope production and nuclear reaction theory is discussed

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

    Directory of Open Access Journals (Sweden)

    Skrollan Stockinger

    2013-09-01

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

  20. Fission cross section calculations for 209Bi target nucleus based on fission reaction models in high energy regions

    Directory of Open Access Journals (Sweden)

    Kaplan Abdullah

    2015-01-01

    Full Text Available Implementation of projects of new generation nuclear power plants requires the solving of material science and technological issues in developing of reactor materials. Melts of heavy metals (Pb, Bi and Pb-Bi due to their nuclear and thermophysical properties, are the candidate coolants for fast reactors and accelerator-driven systems (ADS. In this study, α, γ, p, n and 3He induced fission cross section calculations for 209Bi target nucleus at high-energy regions for (α,f, (γ,f, (p,f, (n,f and (3He,f reactions have been investigated using different fission reaction models. Mamdouh Table, Sierk, Rotating Liquid Drop and Fission Path models of theoretical fission barriers of TALYS 1.6 code have been used for the fission cross section calculations. The calculated results have been compared with the experimental data taken from the EXFOR database. TALYS 1.6 Sierk model calculations exhibit generally good agreement with the experimental measurements for all reactions used in this study.

  1. Requirements for design of accelerator, beam transport, and target in a study of thermonuclear reaction cross section

    Energy Technology Data Exchange (ETDEWEB)

    Itahashi, T; Takahisa, K; Fujiwara, M; Toki, H; Ejiri, H [Osaka Univ., Ibaraki (Japan). Research Center for Nuclear Physics; Ohsumi, H; Komori, M

    1997-03-01

    A compact accelerator with high current ion source, low energy beam transport elements and windowless gas target was designed to investigate the thermonuclear reaction cross section. The idea of this project focused on the cross section measurement of the fusion reaction data {sup 3}He+{sup 3}He-{sup 4}He+p+p at 25keV. The system will be installed in Otoh Cosmo Observatory (1270m.w.e.) to get rid of the huge cosmic and environmental background. It consists of NANOGUN ECR ion source, focusing elements made of permanent magnets window less {sup 3}He gas target and/or He{sup 3} plasma target and detector telescopes with low noise and low background. Requirements for these were discussed technically and various ideas were proposed. (author)

  2. Cross section of α-induced reactions on iridium isotopes obtained from thick target yield measurement for the astrophysical γ process

    Directory of Open Access Journals (Sweden)

    T. Szücs

    2018-01-01

    Full Text Available The stellar reaction rates of radiative α-capture reactions on heavy isotopes are of crucial importance for the γ process network calculations. These rates are usually derived from statistical model calculations, which need to be validated, but the experimental database is very scarce. This paper presents the results of α-induced reaction cross section measurements on iridium isotopes carried out at first close to the astrophysically relevant energy region. Thick target yields of 191Ir(α,γ195Au, 191Ir(α,n194Au, 193Ir(α,n196mAu, 193Ir(α,n196Au reactions have been measured with the activation technique between Eα=13.4 MeV and 17 MeV. For the first time the thick target yield was determined with X-ray counting. This led to a previously unprecedented sensitivity. From the measured thick target yields, reaction cross sections are derived and compared with statistical model calculations. The recently suggested energy-dependent modification of the α+nucleus optical potential gives a good description of the experimental data.

  3. Measurement method of activation cross-sections of reactions producing short-lived nuclei with 14 MeV neutrons

    CERN Document Server

    Kawade, K; Kasugai, Y; Shibata, M; Iida, T; Takahashi, A; Fukahori, T

    2003-01-01

    We describe a method for obtaining reliable activation cross-sections in the neutron energy range between 13.4 and 14.9 MeV for the reactions producing short-lived nuclei with half-lives between 0.5 and 30 min. We noted neutron irradiation fields and measured induced activities, including (1) the contribution of scattered low-energy neutrons, (2) the fluctuation of the neutron fluence rate during the irradiation, (3) the true coincidence sum effect, (4) the random coincidence sum effect, (5) the deviation in the measuring position due to finite sample thickness, (6) the self-absorption of the gamma-ray in the sample material and (7) the interference reactions producing the same radionuclides or the ones emitting the gamma-ray with the same energy of interest. The cross-sections can be obtained within a total error of 3.6%, when good counting statistics are achieved, including an error of 3.0% for the standard cross-section of sup 2 sup 7 Al (n, alpha) sup 2 sup 4 Na. We propose here simple methods for measuri...

  4. A phosphine mediated sequential annulation process of 2-tosylaminochalcones with MBH carbonates to construct functionalized aza-benzobicyclo[4.3.0] derivatives.

    Science.gov (United States)

    Zhang, Qinglong; Zhu, Yannan; Jin, Hongxing; Huang, You

    2017-04-04

    A novel phosphine mediated sequential annulation process to construct functionalized aza-benzobicyclo[4.3.0] derivatives has been developed involving a one-pot sequential catalytic and stoichiometric process, which generates a series of benzobicyclo[4.3.0] compounds containing one quaternary center with up to 94% yield and 20 : 1 dr value. In this reaction, MBH carbonates act as 1,2,3-C 3 synthons.

  5. Comparison of cross sections for C+O reactions in the second regime of complete fusion

    International Nuclear Information System (INIS)

    Beck, C.; Haas, F.; Freeman, R.M.; Heusch, B.; Coffin, J.P.; Guillaume, G.; Rami, F.; Wagner, P.

    1985-01-01

    Kinetic energy spectra, angular distributions, and elemental yield distributions have been measured for the 12 C + 16 O, 12 C + 18 O and 13 C + 17 O reaction products over an energy range from 2 to 7 times the Coulomb barrier energy. A careful kinematic analysis of the evaporation residues and comparisons with statistical model calculations show that fusion proceeds with full momentum transfer followed by a statistical decay of the compound nucleus. The competition between complete fusion process and peripheral reactions in the 12 C + 16 O system is less important than for the 12 C + 18 O and 13 C + 17 O reactions. The unexpectedly high 12 C + 16 O complete fusion cross sections are related to the possible occurence of a superdeformation of the 28 Si compound nucleus

  6. Modeled Neutron Induced Nuclear Reaction Cross Sections for Radiochemsitry in the region of Thulium, Lutetium, and Tantalum I. Results of Built in Spherical Symmetry in a Deformed Region

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-09-06

    We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron induced nuclear reaction cross sections for targets ranging from Terbium (Z = 65) to Rhenium (Z = 75). Of particular interest are the cross sections on Tm, Lu, and Ta including reactions on isomeric targets.

  7. Multiparticle production in heavy-ion reactions

    International Nuclear Information System (INIS)

    Pelte, D.

    1980-01-01

    This lecture is concerned with the question how many particles and what kind of them are produced in heavy-ion collisions at energies about 10 MeV/n. We tend to assume that heavy-ion reactions at this energy are binary reactions. The experimental set consisting of two large ionization chambers serving to detection, in coincidence, the reaction fragments is described. With this set-up a number of reactions induced on 27 Al, 28 Si and 40 Ca by the 32 S beam of 135 and 190 MeV energy has been studied. Two-fragments inclusive and exclusive reactions were investigated. The assumption of a sequential statistical decay gives the best agreement with the data for all analyzed cases. (H.M.)

  8. Simultaneous and sequential transfer of proton and alpha-particle in the elastic 11B+16O scattering

    International Nuclear Information System (INIS)

    Kamys, B.; Rudy, Z.; Kisiel, J.; Kwasniewicsz, E.; Wolter, H.H.

    1992-01-01

    We have developed a method to treat multi-nucleon transfer as the transfer of two - possible different - subclusters, as e.g. with ' 5 Li'=(α,p). As a consequence we take into account two reaction mechanisms, the one-step simultaneous and the two-step sequential transfer of the two clusters. We formulate the method of calculation of the simultaneous transfer form factor for two non-identifical particles and also of the two-cluster spectroscopic amplitudes from shell model wave functions. We apply the method to the elastic transfer reaction 11 B( 16 O, 11 B) 11 O together with the single α and p transfer reaction 11 B( 16 O, 15 N) 12 C for E lab between 30 and 60 MeV. We obtain a consistently good description of all the data by reasonable adjustment of the spectroscopic amplitudes. In particular we find that the simultaneous (αp) transfer is considerably more important than the sequential transfer indicating strong five-nucleon correlations in these light nuclei. (orig.)

  9. Elastic scattering and total reaction cross section for the 6He +58Ni system

    Science.gov (United States)

    Morcelle, V.; Lichtenthäler, R.; Lépine-Szily, A.; Guimarães, V.; Mendes, D. R., Jr.; Pires, K. C. C.; de Faria, P. N.; Barioni, A.; Gasques, L.; Morais, M. C.; Shorto, J. M. B.; Zamora, J. C.; Scarduelli, V.; Condori, R. Pampa; Leistenschneider, E.

    2014-11-01

    Elastic scattering measurements of 6He + 58Ni system have been performed at the laboratory energy of 21.7 MeV. The 6He secondary beam was produced by a transfer reaction 9Be (7Li , 6He ) and impinged on 58Ni and 197Au targets, using the Radioactive Ion Beam (RIB) facility, RIBRAS, installed in the Pelletron Laboratory of the Institute of Physics of the University of São Paulo, Brazil. The elastic angular distribution was obtained in the angular range from 15° to 80° in the center of mass frame. Optical model calculations have been performed using a hybrid potential to fit the experimental data. The total reaction cross section was derived.

  10. Temperature-dependent cross sections for meson-meson nonresonant reactions in hadronic matter

    International Nuclear Information System (INIS)

    Zhang Yiping; Xu Xiaoming; Ge Huijun

    2010-01-01

    We present a potential of which the short-distance part is given by one gluon exchange plus perturbative one- and two-loop corrections and of which the large-distance part exhibits a temperature-dependent constant value. The Schroedinger equation with this temperature-dependent potential yields a temperature dependence of the mesonic quark-antiquark relative-motion wave function and of meson masses. The temperature dependence of the potential, the wave function and the meson masses brings about temperature dependence of cross sections for the nonresonant reactions ππ→ρρ for I=2, KK→K*K* for I=1, KK*→K*K* for I=1, πK→ρK* for I=3/2, πK*→ρK* for I=3/2, ρK→ρK* for I=3/2 and πK*→ρK for I=3/2. As the temperature increases, the rise or fall of peak cross sections is determined by the increased radii of initial mesons, the loosened bound states of final mesons, and the total-mass difference of the initial and final mesons. The temperature-dependent cross sections and meson masses are parametrized.

  11. Validation and upgrading of the recommended cross-section data of charged particle reactions: Gamma emitter radioisotopes

    International Nuclear Information System (INIS)

    Takacs, S.; Tarkanyi, F.; Hermanne, A.

    2005-01-01

    An upgrade and validation test of the recommended cross-section database for production of gamma emitter radioisotopes by charged particle induced reactions, published by the IAEA in 2001, was performed. Experimental microscopic cross-section data published earlier or measured recently and not yet included in the evaluation work were collected and added to the primary database in order to improve the quality of the recommended data. The newly compiled experimental data in general supported the previous recommended data, but in a few cases they influenced the decision and resulted in different selected cross-section data sets. A Spline fitting method was used to calculate the recommended data from the selected data sets. Integral thick target yields were deduced from the newly calculated recommended cross-sections and were critically compared with the available experimental yield data

  12. The D(+) + H2 reaction: differential and integral cross sections at low energy and rate constants at low temperature.

    Science.gov (United States)

    González-Lezana, Tomás; Scribano, Yohann; Honvault, Pascal

    2014-08-21

    The D(+) + H2 reaction is investigated by means of a time independent quantum mechanical (TIQM) and statistical quantum mechanical (SQM) methods. Differential cross sections and product rotational distributions obtained with these two theoretical approaches for collision energies between 1 meV and 0.1 eV are compared to analyze the dynamics of the process. The agreement observed between the TIQM differential cross sections and the SQM predictions as the energy increases revealed the role played by the complex-forming mechanism. The importance of a good description of the asymptotic regions is also investigated by calculating rate constants for the title reaction at low temperature.

  13. Angular distribution and cross section measurements of 64Zn(n,α)61Ni reaction for neutron energy 5 MeV

    International Nuclear Information System (INIS)

    Chen Yingtang; Chen Zemin; Qi Huiquan; Li Mingtao

    1995-01-01

    A twin gridded ionization chamber with dual parameter data acquisition system is used to study neutron induced charged particle emission reaction. The angular distribution and cross section of α-particles from the 64 Zn(n,α) 61 Ni reaction are measured at neutron energy 5 MeV

  14. Programming Cell Adhesion for On-Chip Sequential Boolean Logic Functions.

    Science.gov (United States)

    Qu, Xiangmeng; Wang, Shaopeng; Ge, Zhilei; Wang, Jianbang; Yao, Guangbao; Li, Jiang; Zuo, Xiaolei; Shi, Jiye; Song, Shiping; Wang, Lihua; Li, Li; Pei, Hao; Fan, Chunhai

    2017-08-02

    Programmable remodelling of cell surfaces enables high-precision regulation of cell behavior. In this work, we developed in vitro constructed DNA-based chemical reaction networks (CRNs) to program on-chip cell adhesion. We found that the RGD-functionalized DNA CRNs are entirely noninvasive when interfaced with the fluidic mosaic membrane of living cells. DNA toehold with different lengths could tunably alter the release kinetics of cells, which shows rapid release in minutes with the use of a 6-base toehold. We further demonstrated the realization of Boolean logic functions by using DNA strand displacement reactions, which include multi-input and sequential cell logic gates (AND, OR, XOR, and AND-OR). This study provides a highly generic tool for self-organization of biological systems.

  15. Measurement of D(d,p)T Reaction Cross Sections in Sm Metal in Low Energy Region (10(≤) Ed(≤)20 keV)

    Institute of Scientific and Technical Information of China (English)

    WANG Tie-Shan; YANG Zhen; H. Yunemura; A. Nakagawa; LV Hui-Yi; CHEN Jian-Yong; LIU Sheng-Jin; J. Kasagi

    2007-01-01

    To study the screening effect of nuclear reactions in metallic environments, the thick target yields, the cross sections and the experimental S(E) factors of the D{d,p)T reaction have been measured on deuterons implanted in Sm metal at 133.2 K for beam energies ranging from 10 to 20keV. The thick target yields of protons emitted in the D(d,p)T reaction are measured and compared with those data extrapolated from cross sections and stopping power data at higher energies. The screening potential in Sm metal at 133.2K is deduced to be 520±56eV. As compared with the value achieved in the gas target, the calculated screening potential values are much larger. This screening potential cannot be simply interpreted only by the electron screening. Energy dependences of the cross section cr(E) and the experimental S(E) factor for D(d,p)T reaction in Sm metal at 133.2K are obtained, respectively.

  16. Measurement of fission cross-section for the {sup 232}Th(n,f){sup 141}Ba reaction induced by neutrons around 14 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Chang-Lin; Fang, Kai-Hong [Lanzhou University, School of Nuclear Science and Technology, Lanzhou, Gansu Province (China); Lanzhou University, Engineering Research Center for Neutron Application, Ministry of Education, Lanzhou, Gansu Province (China); Liu, Shuang-Tong; Lv, Tao; Wang, Qiang; Zhang, Zheng-Wei [Lanzhou University, School of Nuclear Science and Technology, Lanzhou, Gansu Province (China); Lai, Cai-Feng [Chinese Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, Sichuan Province (China)

    2016-11-15

    The fission cross-section of the {sup 232}Th(n,f){sup 141}Ba reaction induced by neutrons around 14 MeV was measured precisely with the neutron activation and off-line gamma-ray spectrometric technique. Neutron fluence was monitored on-line using the accompanying α-particles from the {sup 3}H({sup 2}H,n){sup 4}He reaction, whereas the neutron energies were measured by the method of cross-section ratios of {sup 90}Zr(n,2n){sup 89}Zr to {sup 93}Nb(n,2n){sup 92m}Nb reactions. The experimentally determined {sup 232}Th(n,f){sup 141}Ba reaction cross-sections were 12.2 ± 0.4 mb at E{sub n} = 14.1 ± 0.3 MeV, 13.0 ± 0.5 mb at E{sub n} = 14.5 ± 0.3 MeV and 13.3 ± 0.5 mb at E{sub n} = 14.7 ± 0.3 MeV, respectively. (orig.)

  17. Eyewitness confidence in simultaneous and sequential lineups: a criterion shift account for sequential mistaken identification overconfidence.

    Science.gov (United States)

    Dobolyi, David G; Dodson, Chad S

    2013-12-01

    Confidence judgments for eyewitness identifications play an integral role in determining guilt during legal proceedings. Past research has shown that confidence in positive identifications is strongly associated with accuracy. Using a standard lineup recognition paradigm, we investigated accuracy using signal detection and ROC analyses, along with the tendency to choose a face with both simultaneous and sequential lineups. We replicated past findings of reduced rates of choosing with sequential as compared to simultaneous lineups, but notably found an accuracy advantage in favor of simultaneous lineups. Moreover, our analysis of the confidence-accuracy relationship revealed two key findings. First, we observed a sequential mistaken identification overconfidence effect: despite an overall reduction in false alarms, confidence for false alarms that did occur was higher with sequential lineups than with simultaneous lineups, with no differences in confidence for correct identifications. This sequential mistaken identification overconfidence effect is an expected byproduct of the use of a more conservative identification criterion with sequential than with simultaneous lineups. Second, we found a steady drop in confidence for mistaken identifications (i.e., foil identifications and false alarms) from the first to the last face in sequential lineups, whereas confidence in and accuracy of correct identifications remained relatively stable. Overall, we observed that sequential lineups are both less accurate and produce higher confidence false identifications than do simultaneous lineups. Given the increasing prominence of sequential lineups in our legal system, our data argue for increased scrutiny and possibly a wholesale reevaluation of this lineup format. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  18. Sequential strand displacement beacon for detection of DNA coverage on functionalized gold nanoparticles.

    Science.gov (United States)

    Paliwoda, Rebecca E; Li, Feng; Reid, Michael S; Lin, Yanwen; Le, X Chris

    2014-06-17

    Functionalizing nanomaterials for diverse analytical, biomedical, and therapeutic applications requires determination of surface coverage (or density) of DNA on nanomaterials. We describe a sequential strand displacement beacon assay that is able to quantify specific DNA sequences conjugated or coconjugated onto gold nanoparticles (AuNPs). Unlike the conventional fluorescence assay that requires the target DNA to be fluorescently labeled, the sequential strand displacement beacon method is able to quantify multiple unlabeled DNA oligonucleotides using a single (universal) strand displacement beacon. This unique feature is achieved by introducing two short unlabeled DNA probes for each specific DNA sequence and by performing sequential DNA strand displacement reactions. Varying the relative amounts of the specific DNA sequences and spacing DNA sequences during their coconjugation onto AuNPs results in different densities of the specific DNA on AuNP, ranging from 90 to 230 DNA molecules per AuNP. Results obtained from our sequential strand displacement beacon assay are consistent with those obtained from the conventional fluorescence assays. However, labeling of DNA with some fluorescent dyes, e.g., tetramethylrhodamine, alters DNA density on AuNP. The strand displacement strategy overcomes this problem by obviating direct labeling of the target DNA. This method has broad potential to facilitate more efficient design and characterization of novel multifunctional materials for diverse applications.

  19. Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

    Directory of Open Access Journals (Sweden)

    Veli ÇAPALI

    2016-05-01

    Full Text Available BeO is one of the most common moderator material for neutron moderation; due to its high density, neutron capture cross section and physical-chemical properties that provides usage at elevated temperatures. As it’s known, for various applications in the field of reactor design and neutron capture, reaction cross–section data are required. The cross–sections of (n,α, (n,2n, (n,t, (n,EL and (n,TOT reactions for 9Be and 16O nuclei have been calculated by using TALYS 1.6 Two Component Exciton model and EMPIRE 3.2 Exciton model in this study. Hadronic interactions of low energetic neutrons and generated isotopes–particles have been investigated for a situation in which BeO was used as a neutron moderator by using GEANT4, which is a powerful simulation software. In addition, energy deposition along BeO material has been obtained. Results from performed calculations were compared with the experimental nuclear reaction data exist in EXFOR.

  20. Nuclear Reactions for Astrophysics and Other Applications

    Energy Technology Data Exchange (ETDEWEB)

    Escher, J E; Burke, J T; Dietrich, F S; Scielzo, N D; Ressler, J J

    2011-03-01

    Cross sections for compound-nuclear reactions are required for many applications. The surrogate nuclear reactions method provides an indirect approach for determining cross sections for reactions on unstable isotopes, which are difficult or impossible to measure otherwise. Current implementations of the method provide useful cross sections for (n,f) reactions, but need to be improved upon for applications to capture reactions.

  1. Calculation and evaluation of the activation cross sections for 187Re(n,2n)186m,gRe reactions

    International Nuclear Information System (INIS)

    Huang Xiaolong; Lu Hanlin; Zhou Chunmei

    1998-01-01

    The activation cross sections for 187 Re(n,2n) 186m,g Re reactions are calculated using UNF code. The calculations are in good agreement with the re-evaluated measured data. Finally the excitation function for 187 Re(n,2n) 186m,g Re reactions are evaluated and recommended based on present calculations and evaluated decay data

  2. Common Ground in Cross Cultural Communication: Sequential and Institutional Contexts in Front Desk Service Encounters.

    Science.gov (United States)

    Kidwell, Mardi

    2000-01-01

    Looks at interactions between English-as-a-Second-Language students and English-speaking staff at the front desk of a language institute. Analysis focuses on the sequential organization of front desk encounters, revealing ways the participant's shared orientations to the organization and goals of these encounters facilitate native…

  3. Cross sections for the (n,p), (n,α) and (n,2n) threshold reactions

    International Nuclear Information System (INIS)

    Bychkov, V.M.; Manokhin, V.N.; Pashchenko, A.B.; Plyaskin, V.I.

    1980-07-01

    The (n,p), (n,α), (n,2n) threshold reactions are reviewed for nuclei with Z>=20 in the neutron energy range from the threshold up to 20MeV. The review consists of four parts. In the first part the theoretical methods of cross-section calculations and the empirical or semi-empirical systematics are considered. In the second, third and fourth parts the experimental data compilations on the (n,p), (n,α) and (n,2n) excitation functions are given. The recommended values of cross-sections at 14.5MeV neutron energy are given in tables. For some isotopes the recommended curves of excitation functions also are given in graphs. (author)

  4. Differential cross section measurements for the 6Li(n,t)alpha reaction in the few MeV region

    Energy Technology Data Exchange (ETDEWEB)

    Devlin, Matthew J [Los Alamos National Laboratory; Taddeucci, Terence N [Los Alamos National Laboratory; Hale, Gerald M [Los Alamos National Laboratory; Haight, Robert C [Los Alamos National Laboratory; O' Donnell, Johhn M [Los Alamos National Laboratory

    2008-01-01

    New measured differential cross sections of tritons and alpha particles following the {sup 6}Li(n,t){alpha} reaction are reported for incident neutron energies between 0.2 and approximately 20 MeV. The neutrons were produced by spallation at the WNR facility at the Los Alamos Neutron Science CEnter (LANSCE), with the incident neutron energy determined by the time-of-flight method. Four E-{Delta}E telescopes were used at eight laboratory angles. These data have been incorporated into a prior R-matrix fit for the compound {sup 7}Li system, and result in an (n,t) reaction cross section that is 4% to 10% higher than previous evaluations in the 1-3 MeV incident neutron energy region.

  5. Sn-Beta catalysed conversion of hemicellulosic sugars

    DEFF Research Database (Denmark)

    Holm, Martin; Pagán-Torres, Yomaira J.; Shunmugavel, Saravanamurugan

    2012-01-01

    are observed for the pentoses. This finding is in accordance to a reaction pathway that involves the retro aldol condensation of the sugars to form a triose and glycolaldehyde for the pentoses, and two trioses for hexoses. When reacting glycolaldehyde (formally a C2-sugar) in the presence of Sn-Beta, aldol...... condensation occurs, leading to the formation of methyl lactate, methyl vinylglycolate and methyl 2-hydroxy-4-methoxybutanoate. In contrast, when converting the sugars in water at low temperatures (100 °C), Sn-Beta catalyses the isomerisation of sugars (ketose–aldose epimers), rather than the formation...

  6. Linear response theory applied to the computation of multi-differential cross sections in deep inelastic reactions

    International Nuclear Information System (INIS)

    Ngo, C.

    1978-01-01

    Correlations between observable quantities in deep inelastic reactions, which are observed through multidifferential cross sections measurements, provide a severe test for the models by making strong constraints. Nevertheless these multicorrelated measurements provide hints for the physical features which they have to take into account. (orig.) [de

  7. 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< En<300 MeV. An estimate of the population of isomers in the (n, n'), (n, 2n) and (n, 3n) channels was made.

  8. Comparison of simultaneous and sequential SPECT imaging for discrimination tasks in assessment of cardiac defects.

    Science.gov (United States)

    Trott, C M; Ouyang, J; El Fakhri, G

    2010-11-21

    Simultaneous rest perfusion/fatty-acid metabolism studies have the potential to replace sequential rest/stress perfusion studies for the assessment of cardiac function. Simultaneous acquisition has the benefits of increased signal and lack of need for patient stress, but is complicated by cross-talk between the two radionuclide signals. We consider a simultaneous rest (99m)Tc-sestamibi/(123)I-BMIPP imaging protocol in place of the commonly used sequential rest/stress (99m)Tc-sestamibi protocol. The theoretical precision with which the severity of a cardiac defect and the transmural extent of infarct can be measured is computed for simultaneous and sequential SPECT imaging, and their performance is compared for discriminating (1) degrees of defect severity and (2) sub-endocardial from transmural defects. We consider cardiac infarcts for which reduced perfusion and metabolism are observed. From an information perspective, simultaneous imaging is found to yield comparable or improved performance compared with sequential imaging for discriminating both severity of defect and transmural extent of infarct, for three defects of differing location and size.

  9. Comparison of simultaneous and sequential SPECT imaging for discrimination tasks in assessment of cardiac defects

    International Nuclear Information System (INIS)

    Trott, C M; Ouyang, J; El Fakhri, G

    2010-01-01

    Simultaneous rest perfusion/fatty-acid metabolism studies have the potential to replace sequential rest/stress perfusion studies for the assessment of cardiac function. Simultaneous acquisition has the benefits of increased signal and lack of need for patient stress, but is complicated by cross-talk between the two radionuclide signals. We consider a simultaneous rest 99m Tc-sestamibi/ 123 I-BMIPP imaging protocol in place of the commonly used sequential rest/stress 99m Tc-sestamibi protocol. The theoretical precision with which the severity of a cardiac defect and the transmural extent of infarct can be measured is computed for simultaneous and sequential SPECT imaging, and their performance is compared for discriminating (1) degrees of defect severity and (2) sub-endocardial from transmural defects. We consider cardiac infarcts for which reduced perfusion and metabolism are observed. From an information perspective, simultaneous imaging is found to yield comparable or improved performance compared with sequential imaging for discriminating both severity of defect and transmural extent of infarct, for three defects of differing location and size.

  10. Reaction cross section measurements for the production of /sup 6/He(805 ms) and /sup 6/Li(175 ms) with 14. 7 Mev neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Garg, K C; Khurana, C S [Punjabi Univ., Patiala (India). Dept. of Physics

    1979-01-01

    The automatic electronic programmer developed to handle the millisecond isomers has been utilized to measure the reaction cross-sections for the production of /sup 6/He from sup(7,6)Li((n,d)+(n,p))/sup 6/He and /sup 9/Be(n,..cap alpha..)/sup 6/He reactions and /sup 9/Li from /sup 9/Be(n,p)/sup 9/Li reaction. An on-line gated G.M. counter has been used to follow the decay curves of beta-activities of /sup 6/He(805 ms.) and /sup 9/Li(175 ms.) produced in the reactions. Values of measured cross sections are 10.4 +- 1.0 mb., 10.6 +- 1.1 mb. and 40.3 +- 4.0 mb respectively for the above the three reactions.

  11. Improvement of one-nucleon removal and total reaction cross sections in the Liège intranuclear-cascade model using Hartree-Fock-Bogoliubov calculations

    Science.gov (United States)

    Rodríguez-Sánchez, Jose Luis; David, Jean-Christophe; Mancusi, Davide; Boudard, Alain; Cugnon, Joseph; Leray, Sylvie

    2017-11-01

    The prediction of one-nucleon-removal cross sections by the Liège intranuclear-cascade model has been improved using a refined description of the matter and energy densities in the nuclear surface. Hartree-Fock-Bogoliubov calculations with the Skyrme interaction are used to obtain a more realistic description of the radial-density distributions of protons and neutrons, as well as the excitation-energy uncorrelation at the nuclear surface due to quantum effects and short-range correlations. The results are compared with experimental data covering a large range of nuclei, from carbon to uranium, and projectile kinetic energies. We find that the new approach is in good agreement with experimental data of one-nucleon-removal cross sections covering a broad range in nuclei and energies. The new ingredients also improve the description of total reaction cross sections induced by protons at low energies, the production cross sections of heaviest residues close to the projectile, and the triple-differential cross sections for one-proton removal. However, other observables such as quadruple-differential cross sections of coincident protons do not present any sizable sensitivity to the new approach. Finally, the model is also tested for light-ion-induced reactions. It is shown that the new parameters can give a reasonable description of the nucleus-nucleus total reaction cross sections at high energies.

  12. Isomeric cross section ratios in 55Mn(α, n)58m,gCo reaction

    International Nuclear Information System (INIS)

    Long Xianguan; He Fuqing; Peng Xiufen; Liu Mantian

    1989-01-01

    The isomeric cross section ratios in 55 Mn(α, n) 58m,g Co reaction are measured for incident alpha-particle energies ranging from 10.4 to 26.5 MeV by using activation method and stacked-foil technique. The measured values are compared with theoretical calculations performed by using Huizenga and Vandenbosch method and the values of spin cutoff factor are obtained for product nucleus 58 Co

  13. Accurate Quantum Wave Packet Study of the Deep Well D+ + HD Reaction: Product Ro-vibrational State-Resolved Integral and Differential Cross Sections.

    Science.gov (United States)

    He, Haixiang; Zhu, Weimin; Su, Wenli; Dong, Lihui; Li, Bin

    2018-03-08

    The H + + H 2 reaction and its isotopic variants as the simplest triatomic ion-molecule reactive system have been attracting much interests, however there are few studies on the titled reaction at state-to-state level until recent years. In this work, accurate state-to-state quantum dynamics studies of the titled reaction have been carried out by a reactant Jacobi coordinate-based time-dependent wave packet approach on diabatic potential energy surfaces constructed by Kamisaka et al. Product ro-vibrational state-resolved information has been calculated for collision energies up to 0.2 eV with maximal total angular momentum J = 40. The necessity of including all K-component for accounting the Coriolis coupling for the reaction has been illuminated. Competitions between the two product channels, (D + + HD' → D' + + HD and D + + HD' → H + + DD') were investigated. Total integral cross sections suggest that resonances enhance the reactivity of channel D + + HD'→ H + + DD', however, resonances depress the reactivity of the another channel D + + HD' → D' + + HD. The structures of the differential cross sections are complicated and depend strongly on collision energies of the two channels and also on the product rotational states. All of the product ro-vibrational state-resolved differential cross sections for this reaction do not exhibit rigorous backward-forward symmetry which may indicate that the lifetimes of the intermediate resonance complexes should not be that long. The dynamical observables of this deuterated isotopic reaction are quite different from the reaction of H + + H 2 → H 2 + H + reported previously.

  14. The Trojan Horse Method application on the 10B(p,α0)7Be reaction cross section measurements

    Science.gov (United States)

    Cvetinović, A.; Spitaleri, C.; Spartá, R.; Rapisarda, G. G.; Puglia, S. M.; La Cognata, M.; Cherubini, S.; Guardo, G. L.; Gulino, M.; Lamia, L.; Pizzone, R. G.; Romano, S.; Sergi, M. L.

    2018-01-01

    The 10B(p,α0)7Be reaction cross section has been measured in an wide energy range from 2.2 MeV down to 3 keV in a single experiment applying THM. Optimized experimental set-up ensured good energy resolution leading to a good separation of α0 and α1 contributions to the cross section coming from the 7Be ground and first excited state, respectively.

  15. Cross sections for the reactions 54Fe(n,α)51Cr, 54Fe(n,p)54Mn, and 56Fe(n,p)56Mn

    International Nuclear Information System (INIS)

    Paulsen, A.; Widera, R.; Arnotte, F.; Liskien, H.

    1979-01-01

    Ratios of cross sections for the reactions 54 Fe(n,α) 51 Cr, 54 Fe(n,p) 54 Mn, and 56 Fe(n,p) 56 Mn were measured by the activation technique. In the 6- to 10-MeV energy range, quasi-monoenergetic neutrons produced by the D(d,n) source reaction were used, while additional data were obtained between 12 and 17 MeV by use of the T(d,n) source reaction. The cross-section ratios have accuracies between 1.5 and 4.5%. 1 figure, 3 tables

  16. Sequential Au(I-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates

    Directory of Open Access Journals (Sweden)

    Jianbo Wang

    2011-05-01

    Full Text Available The gold(I-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates provides 1H-isochromene derivatives in good yields. The reaction follows a catalytic sequence of gold carbene formation/water O–H insertion/alcohol-alkyne cyclization. The gold(I complex is the only catalyst in each of these steps.

  17. Remarks on sequential designs in risk assessment

    International Nuclear Information System (INIS)

    Seidenfeld, T.

    1982-01-01

    The special merits of sequential designs are reviewed in light of particular challenges that attend risk assessment for human population. The kinds of ''statistical inference'' are distinguished and the problem of design which is pursued is the clash between Neyman-Pearson and Bayesian programs of sequential design. The value of sequential designs is discussed and the Neyman-Pearson vs. Bayesian sequential designs are probed in particular. Finally, warnings with sequential designs are considered, especially in relation to utilitarianism

  18. Calculations of (n,2n) reaction cross sections for Barium isotopes from 5 to 20 MeV

    Science.gov (United States)

    Sahan, Halide; Sahan, Muhittin; Tel, Eyyup

    2017-09-01

    In this study, the excitation functions of (n,2n) reactions for 30,32,34,35,37,38Ba isotopes are calculated using TALYS 1.6, EMPIRE-3.2.2, and ALICE-GDH codes based on statistical model up to 20 MeV. Moreover, the cross section for each isotope have also been estimated at 14.2 MeV using semi empirical formula developed by four different authors. The calculated and estimated cross-sections are compared with experimental cross-sections from EXFOR and compared with the evaluation data in ENDF/B-VII.1 library. Results are close agreement with the experimental data from literature.

  19. Kinetics and Mechanism of the Reaction of Coherently Synchronized Oxidation and Dehydrogenation of Cyclohexane by Hydrogen Peroxide

    Directory of Open Access Journals (Sweden)

    Aghamammadova S.

    2016-01-01

    Based on this experimental researches, the complex reaction, consisting of parallel-sequential oxidation and dehydrogenation reactions, which are coherently synchronized, proceeds during the process of cyclohexane oxidation with biomimetic catalyst. Depending on the reaction parameters it is possible to deliberately adjust the direction of oxidation reaction and reaction rate.

  20. Study of p-4He Total Reaction cross section using Glauber and Modified Glauber Models

    International Nuclear Information System (INIS)

    Tag El Din, I.M.A.; Taha, M.M.; Hassan, S.S.A.

    2012-01-01

    The total nuclear reaction cross-section for p - 4 He in the energy range from 25 to 1000 MeV is calculated within Glauber and modified Glauber models. The modified Glauber model is introduced via both Coulomb trajectory of the projectile and calculation of the effective radius of interaction. The effects of density dependent total cross-section and phase variation of nucleon-nucleon scattering amplitude are studied. It is pointed out that the phase variation of the nucleon-nucleon amplitude plays a significant role in describing σR at E p 2 at e = e0 = 0 and γ=2fm 2 at e = e0 = 0.17fm -3 .

  1. The K + - Nucleus Microscopic Optical Potential and Calculations of the Corresponding Differential Elastic and Total Reaction Cross Sections

    International Nuclear Information System (INIS)

    Zemlyanaya, E.V.; Lukyanov, K.V.; Lukyanov, V.K.; Hanna, K.M.

    2009-01-01

    The microscopic optical potential (OP) is calculated for the K+-meson scattering on the 12 C and 40 Ca nuclei at intermediate energies. This potential has no free parameters and based on the known kaon-nucleon amplitude and nuclear density distribution functions. Then, the Klein-Gordon equation is written in the form of the relativistic Schrodinger equation where terms quadratic in the potential was estimated can be neglected. The latter equations adapted to the considered task and solved numerically. The effect of revitalization is shown to play a significant role. A good agreement with the experimental data on differential elastic cross sections is obtained. However, to explain the data on total reaction cross sections the additional surface term of OP was introduced to account for influence of the peripheral nuclear reaction channels

  2. Experimental determination of proton induced reaction cross sections on {sup nat}Ni near threshold energy

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, Md. Shuza [Atomic Energy Research Establishment, Dhaka (Bangladesh). Tandem Accelerator Facilities; Forschungszentrum Juelich GmbH (Germany). Inst. fuer Neurowissenschaften und Medizin, INM-5: Nuklearchemie; Chakraborty, Animesh Kumer [Atomic Energy Research Establishment, Dhaka (Bangladesh). Tandem Accelerator Facilities; Chittagong University of Engineering and Technology (Bangladesh). Dept. of Physics; Spellerberg, Stefan; Spahn, Ingo; Qaim, Syed M. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Neurowissenschaften und Medizin, INM-5: Nuklearchemie; Shariff, Md. Asad; Das, Sopan [Atomic Energy Research Establishment, Dhaka (Bangladesh). Tandem Accelerator Facilities; Rashid, Md. Abdur [Chittagong University of Engineering and Technology (Bangladesh). Dept. of Physics

    2016-08-01

    A newly developed facility at the 3 MV Tandem Accelerator at Dhaka for measurement of proton induced reaction cross sections in the energy region below 5 MeV is outlined and tests for the beam characterization are described. The results were validated by comparison with the well-known excitation function of the {sup 64}Ni(p, n){sup 64}Cu reaction. Excitation functions of the reactions {sup nat}Ni(p, x){sup 60,61}Cu, {sup nat}Ni(p, x){sup 55,57,58m+g}Co and {sup nat}Ni(p, x){sup 57}Ni were also measured from threshold to 16 MeV using the stacked-foil technique, whereby irradiations were performed with 5 MeV protons available at the Tandem Accelerator and 16.7 MeV protons at the BC 1710 cyclotron at Juelich, Germany. The radioactivity was measured using HPGe γ-ray detectors. A few results are new, the others strengthen the database. In particular, the results of the reaction {sup nat}Ni(p, x){sup 61}Cu below 3 MeV could serve as beam monitor.

  3. Line-emission cross sections for the charge-exchange reaction between fully stripped carbon and atomic hydrogen in tokamak plasma

    International Nuclear Information System (INIS)

    Ida, K.; Kato, T.

    1992-01-01

    Line-emission cross sections of the charge-exchange reaction between fully stripped carbon and atomic hydrogen are measured in the energy range of 18 - 38 keV/amu in tokamak plasmas. The energy dependence of the emission cross sections for the transition of Δn = 8 - 7 and Δn = 7 - 6 and their ratios are compared with theoretical calculations. (author)

  4. Binary and tertiary reaction cross-sections of V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes

    International Nuclear Information System (INIS)

    Garg, S.B.

    1982-01-01

    Neutron induced binary and tertiary reaction cross-sections have been evaluated for V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes in the 'energy range 0.5 MeV to 20 MeV using the nuclear statistical empirical model. The reactions considered are (n,n'), (n,2n), (n,3n), (n,p), (n,d), (n,t), (n, 3 He), (n,α), (n,np), (n,nd), (n,nt), (n,n 3 He), (n,nα), (n,pn), (n,2p), (n,ν), (n,αp), (n,dn) and (n,pα). Most of the above mentioned elements are used as structural materials in nuclear reactors and the measured cross-section data for the above listed reactions are seldom available for the radiation damage and safety analysis. With a view to providing these data, this nuclear model based evaluation has been undertaken. The associated uncertainties in the cross-sections and their fission averages have also been evaluated. (author)

  5. Sequential lineup laps and eyewitness accuracy.

    Science.gov (United States)

    Steblay, Nancy K; Dietrich, Hannah L; Ryan, Shannon L; Raczynski, Jeanette L; James, Kali A

    2011-08-01

    Police practice of double-blind sequential lineups prompts a question about the efficacy of repeated viewings (laps) of the sequential lineup. Two laboratory experiments confirmed the presence of a sequential lap effect: an increase in witness lineup picks from first to second lap, when the culprit was a stranger. The second lap produced more errors than correct identifications. In Experiment 2, lineup diagnosticity was significantly higher for sequential lineup procedures that employed a single versus double laps. Witnesses who elected to view a second lap made significantly more errors than witnesses who chose to stop after one lap or those who were required to view two laps. Witnesses with prior exposure to the culprit did not exhibit a sequential lap effect.

  6. Sequential Proton Loss Electron Transfer in Deactivation of Iron(IV) Binding Protein by Tyrosine Based Food Components

    DEFF Research Database (Denmark)

    Tang, Ning; Skibsted, Leif Horsfelt

    2017-01-01

    The iron(IV) binding protein ferrylmyoglobin, MbFe(IV)=O, was found to be reduced by tyrosine based food components in aqueous solution through a sequential proton loss electron transfer reaction mechanism without binding to the protein as confirmed by isothermal titration calorimetry. Dopamine a...

  7. Study of sample preparation in the measurement of 36Ar(n, p)36Cl reaction cross section

    International Nuclear Information System (INIS)

    Jiang Songsheng; Hemick, T.K.

    1992-01-01

    The preparation of enriched 36 Ar gas samples and 36 Cl samples for the use in the AMS measurement of 36 Ar(n, p) 36 Cl reaction cross section was described. The 36 Ar samples prepared had the volumes of about 0.4 ml and the weights of about 0.5 mg. The uncertainty in atomic numbers of 36 Ar was (0.3∼0.4)%. The reaction product, 36 Cl, in the 36 Ar was collected and the AgCl samples were prepared

  8. Update of ENDF/B-V Mod 3 iron: neutron-producing reaction cross sections and energy-angle correlations

    International Nuclear Information System (INIS)

    Fu, C.Y.; Hetrick, D.M.

    1986-07-01

    An update of the ENDF/B-V Mod-3 evaluation for natural iron is described. The cross sections of (n,n') and (n,2n) reactions are revised. Energy-angle correlations in the secondary (n,n') neutrons are introduced in the ENDF/B-V formats. Anisotropic angular distributions are provided for the secondary neutrons in (n,2n), (n,np), and (n,nα) reactions. Revelant integral results, microscopic data, and nuclear model calculations that influence the revised results are summarized. 54 refs., 9 figs., 2 tabs

  9. Intersystem crossing and dynamics in O(3P) + C2H4 multichannel reaction: Experiment validates theory

    Science.gov (United States)

    Fu, Bina; Han, Yong-Chang; Bowman, Joel M.; Angelucci, Luca; Balucani, Nadia; Leonori, Francesca; Casavecchia, Piergiorgio

    2012-01-01

    The O(3P) + C2H4 reaction, of importance in combustion and atmospheric chemistry, stands out as a paradigm reaction involving triplet- and singlet-state potential energy surfaces (PESs) interconnected by intersystem crossing (ISC). This reaction poses challenges for theory and experiments owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of the collision complexes. Primary products from five competing channels (H + CH2CHO, H + CH3CO, H2 + CH2CO, CH3 + HCO, CH2 + CH2O) and branching ratios (BRs) are determined in crossed molecular beam experiments with soft electron-ionization mass-spectrometric detection at a collision energy of 8.4 kcal/mol. As some of the observed products can only be formed via ISC from triplet to singlet PESs, from the product BRs the extent of ISC is inferred. A new full-dimensional PES for the triplet state as well as spin-orbit coupling to the singlet PES are reported, and roughly half a million surface hopping trajectories are run on the coupled singlet-triplet PESs to compare with the experimental BRs and differential cross-sections. Both theory and experiment find almost equal contributions from the two PESs to the reaction, posing the question of how important is it to consider the ISC as one of the nonadiabatic effects for this and similar systems involved in combustion chemistry. Detailed comparisons at the level of angular and translational energy distributions between theory and experiment are presented for the two primary channel products, CH3 + HCO and H + CH2CHO. The agreement between experimental and theoretical functions is excellent, implying that theory has reached the capability of describing complex multichannel nonadiabatic reactions. PMID:22665777

  10. Random and cooperative sequential adsorption

    Science.gov (United States)

    Evans, J. W.

    1993-10-01

    Irreversible random sequential adsorption (RSA) on lattices, and continuum "car parking" analogues, have long received attention as models for reactions on polymer chains, chemisorption on single-crystal surfaces, adsorption in colloidal systems, and solid state transformations. Cooperative generalizations of these models (CSA) are sometimes more appropriate, and can exhibit richer kinetics and spatial structure, e.g., autocatalysis and clustering. The distribution of filled or transformed sites in RSA and CSA is not described by an equilibrium Gibbs measure. This is the case even for the saturation "jammed" state of models where the lattice or space cannot fill completely. However exact analysis is often possible in one dimension, and a variety of powerful analytic methods have been developed for higher dimensional models. Here we review the detailed understanding of asymptotic kinetics, spatial correlations, percolative structure, etc., which is emerging for these far-from-equilibrium processes.

  11. Robustness of the Sequential Lineup Advantage

    Science.gov (United States)

    Gronlund, Scott D.; Carlson, Curt A.; Dailey, Sarah B.; Goodsell, Charles A.

    2009-01-01

    A growing movement in the United States and around the world involves promoting the advantages of conducting an eyewitness lineup in a sequential manner. We conducted a large study (N = 2,529) that included 24 comparisons of sequential versus simultaneous lineups. A liberal statistical criterion revealed only 2 significant sequential lineup…

  12. Fusion, reaction and break-up cross sections of weakly bound projectiles on 64Zn

    International Nuclear Information System (INIS)

    Gomes, P.R.S.; Padron, I.; Rodriguez, M.D.; Marti, G.V.; Anjos, R.M.; Lubian, J.; Veiga, R.; Liguori Neto, R.; Crema, E.; Added, N.; Chamon, L.C.; Fernandez Niello, J.O.; Capurro, O.A.; Pacheco, A.J.; Testoni, J.E.; Abriola, D.; Arazi, A.; Ramirez, M.; Hussein, M.S.

    2004-01-01

    We present new measurements and a general discussion of the behavior of the fusion, break-up and reaction cross sections of different projectiles on the same target 64 Zn, at near and above barrier energies. The projectiles are the tightly bound 16 O, the stable weakly bound 6 Li, 7 Li and 9 Be and the radioactive very weakly bound 6 He nuclei. We also compare the results with the ones for heavier targets

  13. A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

    Directory of Open Access Journals (Sweden)

    Mariano Goldberg

    2016-08-01

    Full Text Available Starting from (S-β-phenylalanine, easily accessible by lipase-catalyzed kinetic resolution, a chiral triamine was assembled by a reductive amination and finally cyclized to form the title compound 10. In the crystals of the guanidinium benzoate salt the six membered rings of 10 adopt conformations close to an envelope with the phenyl substituents in pseudo-axial positions. The unprotonated guanidine 10 catalyzes Diels–Alder reactions of anthrones and maleimides (25–30% ee. It also promotes as a strong Brønsted base the retro-aldol reaction of some cycloadducts with kinetic resolution of the enantiomers. In three cases, the retro-aldol products (48–83% ee could be recrystallized to high enantiopurity (≥95% ee. The absolute configuration of several compounds is supported by anomalous X-ray diffraction and by chemical correlation.

  14. Synthesis of stimuli-responsive chitosan-based hydrogels by Diels-Alder cross-linking `click´ reaction as potential carriers for drug administration.

    Science.gov (United States)

    Guaresti, O; García-Astrain, C; Aguirresarobe, R H; Eceiza, A; Gabilondo, N

    2018-03-01

    Stimuli-responsive chitosan-based hydrogels for biomedical applications using the Diels-Alder reaction were prepared. Furan modified chitosan (Cs-Fu) was cross-linked with polyetheramine derived bismaleimide at different equivalent ratios in order to determine the effect in the swelling and release properties on the final CsFu:BMI hydrogels. The Diels Alder cross-linking reaction was monitored by UV-vis spectroscopy and rheological measurements. Both the sol-gel transition value and the final storage modulus for the different formulations were similar and close to 40 min and 400 Pa, respectively. On the contrary, the swelling degree was found to be strongly dependent on the amount of bismaleimide, mainly in acidic medium, where the increased cross-linking reduced the swelling value in 25%, but maintaining the sustained drug release in the simulated gastrointestinal environment. Our study suggested that these DA-cross-linked chitosan hydrogels could be potential carriers for targeted drug administration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Cross-linked polyelectrolyte multilayers for marine antifouling applications

    NARCIS (Netherlands)

    Zhu, X.; Janczewski, D.; Lee, S.S.C.; Teo, S.L-M.; Vancso, Gyula J.

    2013-01-01

    A polyionic multilayer film was fabricated by layer-by-layer (LbL) sequential deposition followed by cross-linking under mild conditions on a substrate surface to inhibit marine fouling. A novel polyanion, featuring methyl ester groups for an easy cross-linking was used as a generic solution for

  16. Indirect measurement of the 15N(p,α)12C reaction cross section through the THM

    International Nuclear Information System (INIS)

    Romano, S.; La Cognata, M.; Spitaleri, C.; Cherubini, S.; Gulino, M.; Lamia, L.; Musumarra, A.; Tribble, R.; Trache, C.L.; Fu, C.

    2005-01-01

    Among the reactions of the stellar CNO cycle, the 15 N(p,α) 12 C plays a crucial role. In particular its reaction rate is important for understanding the CNOI escape towards CNOII. Thus it is important to study its bare nucleus cross section at the energies typical of such astrophysical environments, i.e. few tens of keV. At these energies such a measurement is hard to perform in a direct way because of the electron screening effect as pointed out for several cases. A possibility is then given by indirect methods and in particular the Trojan Horse Method (THM) has been applied in this case. The preliminary validity test for the study of 15 N(p,α) 12 C via the 15 N(d,α 12 C)n three body reaction is reported in this work. A 15 N beam was provided by the cyclotron at Texas A and M University with energy 60 MeV/c and delivered onto a CD 2 target. A ΔE/E telescope (PSD + ionization chamber) and a pair of PSD's were mounted in a coplanar geometry. Coincidences between the detectors were considered and the 15 N-p quasi-free contribution to the overall three-body cross-section was selected. Data analysis and preliminary results will be discussed and compared with direct data. (author)

  17. Cross-sections of spallation residues produced in 1A GeV 208Pb on proton reactions

    International Nuclear Information System (INIS)

    Wlazlo, W.; Uniwersytet Jagiellonski, Cracow; Enqvist, T.; Armbruster, P.

    2000-02-01

    Spallation residues produced in 1 GeV per nucleon 208 Pb on proton reactions have been studied using the fragment separator facility at GSI. Isotopic production cross-sections of elements from 61 Pm to 82 Pb have been measured down to 0.1 mb with a high accuracy. The recoil kinetic energies of the produced fragments were also determined. The obtained cross-sections agree with most of the few existing gamma-spectroscopy data. Data are compared with different intranuclear-cascade and evaporation-fission models. Drastic deviations were found for a standard code used in technical applications. (orig.)

  18. Multi-agent sequential hypothesis testing

    KAUST Repository

    Kim, Kwang-Ki K.; Shamma, Jeff S.

    2014-01-01

    incorporate costs of taking private/public measurements, costs of time-difference and disagreement in actions of agents, and costs of false declaration/choices in the sequential hypothesis testing. The corresponding sequential decision processes have well

  19. Aqueous two-phase system patterning of detection antibody solutions for cross-reaction-free multiplex ELISA

    Science.gov (United States)

    Frampton, John P.; White, Joshua B.; Simon, Arlyne B.; Tsuei, Michael; Paczesny, Sophie; Takayama, Shuichi

    2014-05-01

    Accurate disease diagnosis, patient stratification and biomarker validation require the analysis of multiple biomarkers. This paper describes cross-reactivity-free multiplexing of enzyme-linked immunosorbent assays (ELISAs) using aqueous two-phase systems (ATPSs) to confine detection antibodies at specific locations in fully aqueous environments. Antibody cross-reactions are eliminated because the detection antibody solutions are co-localized only to corresponding surface-immobilized capture antibody spots. This multiplexing technique is validated using plasma samples from allogeneic bone marrow recipients. Patients with acute graft versus host disease (GVHD), a common and serious condition associated with allogeneic bone marrow transplantation, display higher mean concentrations for four multiplexed biomarkers (HGF, elafin, ST2 and TNFR1) relative to healthy donors and transplant patients without GVHD. The antibody co-localization capability of this technology is particularly useful when using inherently cross-reactive reagents such as polyclonal antibodies, although monoclonal antibody cross-reactivity can also be reduced. Because ATPS-ELISA adapts readily available antibody reagents, plate materials and detection instruments, it should be easily transferable into other research and clinical settings.

  20. Sequential stochastic optimization

    CERN Document Server

    Cairoli, Renzo

    1996-01-01

    Sequential Stochastic Optimization provides mathematicians and applied researchers with a well-developed framework in which stochastic optimization problems can be formulated and solved. Offering much material that is either new or has never before appeared in book form, it lucidly presents a unified theory of optimal stopping and optimal sequential control of stochastic processes. This book has been carefully organized so that little prior knowledge of the subject is assumed; its only prerequisites are a standard graduate course in probability theory and some familiarity with discrete-paramet