Analytical applications of ion/molecule reactions in a triple quadrupole mass spectrometer

International Nuclear Information System (INIS)

Kinter, M.T.

1986-01-01

The development of triple quadrupole mass spectrometers as a means of performing tandem mass spectrometry has provided a versatile instrument on which the ion/molecule reactions of a mass selected ion can be studied. This dissertation details the application of ion/molecule reactions in a triple quadrupole to two analytical problems. Part I. Ion/Molecule Reactions of Ammonia with Translationally Excited C 2 H 5 O + /Ions. The ability to impart low center-of-mass translational energies, which upon collision are converted into internal energy, allows the observation of reactions that require energy input. In addition, the systematic variation of the ion kinetic energy, often referred to as energy-resolved mass spectrometer, adds another dimension to the mass spectrum and can allow the observation of thresholds for reactions requiring energy input. This investigation develops methods for determining these thresholds. Part 2. The Use of Ion/Molecule Reactions in selected Reaction Monitoring GC/MSD/MS Analyses. An approach to improving the selectivity of an analysis is to improve the selectivity of the detection method. In GC/MS, one method has been to monitor a selected fragmentation reaction, either metastable or collisionally activated, in a selected reaction monitoring (SRM) analysis. This develops the use of ion/molecule reactions for selected reaction monitoring analyses

Thermonuclear 19F(p, {{\\boldsymbol{\\alpha }}}_{0})16O reaction rate

Science.gov (United States)

He, Jian-Jun; Lombardo, Ivano; Dell'Aquila, Daniele; Xu, Yi; Zhang, Li-Yong; Liu, Wei-Ping

2018-01-01

The thermonuclear 19F(p, {{{α }}}0)16O reaction rate in the temperature region 0.007-10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolations. Our new rate deviates by up to about 30% compared to the previous results, although all rates are consistent within the uncertainties. At very low temperature (e.g. 0.01 GK) our reaction rate is about 20% lower than the most recently published rate, because of a difference in the low energy extrapolated S-factor and a more accurate estimate of the reduced mass used in the calculation of the reaction rate. At temperatures above ˜1 GK, our rate is lower, for instance, by about 20% around 1.75 GK, because we have re-evaluated the previous data (Isoya et al., Nucl. Phys. 7, 116 (1958)) in a meticulous way. The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20% in the temperature region below 0.2 GK, and are mainly caused by the lack of low-energy experimental data and the large uncertainties in the existing data. Asymptotic giant branch (AGB) stars evolve at temperatures below 0.2 GK, where the 19F(p, {{α }})16O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, the fluorine over-abundances observed in AGB stars. Precise cross section (or S factor) data in the low energy region are therefore needed for astrophysical nucleosynthesis studies. Supported by National Natural Science Foundation of China (11490562, 11490560, 11675229) and National Key Research and Development Program of China (2016YFA0400503)

AVERAGE METALLICITY AND STAR FORMATION RATE OF Ly{alpha} EMITTERS PROBED BY A TRIPLE NARROWBAND SURVEY

Energy Technology Data Exchange (ETDEWEB)

Nakajima, Kimihiko; Shimasaku, Kazuhiro; Ono, Yoshiaki; Okamura, Sadanori [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Ouchi, Masami [Institute for the Physics and Mathematics of the Universe (IPMU), TODIAS, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Lee, Janice C.; Ly, Chun [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Foucaud, Sebastien [Department of Earth Sciences, National Taiwan Normal University, No. 88, Tingzhou Road, Sec. 4, Taipei 11677, Taiwan (China); Dale, Daniel A. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Salim, Samir [Department of Astronomy, Indiana University, Bloomington, IN (United States); Finn, Rose [Department of Physics, Siena College, Loudonville, NY (United States); Almaini, Omar, E-mail: nakajima@astron.s.u-tokyo.ac.jp [School of Physics and Astronomy, University of Nottingham, Nottingham (United Kingdom)

2012-01-20

We present the average metallicity and star formation rate (SFR) of Ly{alpha} emitters (LAEs) measured from our large-area survey with three narrowband (NB) filters covering the Ly{alpha}, [O II]{lambda}3727, and H{alpha}+[N II] lines of LAEs at z = 2.2. We select 919 z = 2.2 LAEs from Subaru/Suprime-Cam NB data in conjunction with Magellan/IMACS spectroscopy. Of these LAEs, 561 and 105 are observed with KPNO/NEWFIRM near-infrared NB filters whose central wavelengths are matched to redshifted [O II] and H{alpha} nebular lines, respectively. By stacking the near-infrared images of the LAEs, we successfully obtain average nebular-line fluxes of LAEs, the majority of which are too faint to be identified individually by NB imaging or deep spectroscopy. The stacked object has an H{alpha} luminosity of 1.7 Multiplication-Sign 10{sup 42} erg s{sup -1} corresponding to an SFR of 14 M{sub Sun} yr{sup -1}. We place, for the first time, a firm lower limit to the average metallicity of LAEs of Z {approx}> 0.09 Z{sub Sun} (2{sigma}) based on the [O II]/(H{alpha}+[N II]) index together with photoionization models and empirical relations. This lower limit of metallicity rules out the hypothesis that LAEs, so far observed at z {approx} 2, are extremely metal-poor (Z < 2 Multiplication-Sign 10{sup -2} Z{sub Sun }) galaxies at the 4{sigma} level. This limit is higher than a simple extrapolation of the observed mass-metallicity relation of z {approx} 2 UV-selected galaxies toward lower masses (5 Multiplication-Sign 10{sup 8} M{sub Sun }), but roughly consistent with a recently proposed fundamental mass-metallicity relation when the LAEs' relatively low SFR is taken into account. The H{alpha} and Ly{alpha} luminosities of our NB-selected LAEs indicate that the escape fraction of Ly{alpha} photons is {approx}12%-30%, much higher than the values derived for other galaxy populations at z {approx} 2.

Study of ({alpha}, {sup 3}He) and ({alpha}, t) reactions on {sup 28}Si at 45 MeV

Energy Technology Data Exchange (ETDEWEB)

Darshan, V.P.; Sathyavathiamma, M.P.; Ramaswamy, C.R.; Raja Rao, M.; Puttaswamy, N.G.; Banerjee, S.R.; Chintalapudi, S.N. [Dept. of Phys., Bangalore Univ. (India)

1995-03-01

The {sup 28}Si({alpha}, {sup 3}He){sup 29}Si, {sup 28}Si({alpha}, t){sup 29}P and Si({alpha}, {alpha})Si reactions were studied at E{sub {alpha}} = 45 MeV. Exact finite-range (EFR) DWBA analysis was carried out for the transitions to the ground state and to five excited states in {sup 29}Si and {sup 29}P. Spectroscopic strengths G were extracted for all the states and were compared with the predictions from shell-model and quasi-particle core-coupling calculations. Similar EFR-DWBA analyses were carried out from available (unpublished) data for the {sup 28}Si({alpha}, {sup 3}He){sup 29}Si reaction at E{sub {alpha}} = 64.9 and 120 MeV, and for the {sup 28}Si({alpha}, t){sup 29}P reaction at E{sub {alpha}} = 50 and 64.9 MeV. The comparison of experimental and theoretical values of G are provided. (author)

Structural analysis of bioengineered alpha-D-glucan produced by a triple mutant of the glucansucrase GTF180 enzyme from Lactobacillus reuteri strain 180 : Generation of (alpha 1 -> 4) linkages in a native (1 -> 3)(1 -> 6)-alpha-D-glucan

NARCIS (Netherlands)

van Leeuwen, Sander S.; Kralj, Slavko; Gerwig, Gerrit J.; Dijkhuizen, Lubbert; Kamerling, Johannis P.

Site-directed mutagenesis of the glucansucrase gtf180 gene from Lactobacillus reuteri strain 180 was used to transform the active site region. The alpha-D-glucan (mEPS-PNNS) produced by the triple mutant V1027P:S1137N: A1139S differed in structure from that of the wild-type alpha-D-glucan (EPS180).

Study of transfer reactions ({alpha},t), ({alpha},{sup 3}He) in the f-p shell: mechanism and spectroscopic use; Etude des reactions de transfert ({alpha},t), ({alpha},{sup 3}He) dans la couche f-p mecanisme et utilisation spectroscopique

Energy Technology Data Exchange (ETDEWEB)

Roussel, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-05-01

We describe an experimental study of ({alpha},t), ({alpha},{sup 3}He) reactions at 44 MeV using a solid-state identifier, on the target-nuclei {sup 54}Fe and {sup 58,60,62,64}Ni. A critical study of optical model and of disturbed wave analysis has been performed. We show the complementarity of different transfer-reactions, the ambiguity of spectroscopic factors, the importance of the problem of the reaction mechanism. (author) [French] On decrit une etude experimentale des reactions ({alpha},t), ({alpha},{sup 3}He) a 44 MeV utilisant un systeme identificateur de particules sur les noyaux-cibles {sup 54}Fe et {sup 58,60,62,64}Ni. Une etude critique de modele optique et d'analyse en ondes deformees (D.W.B.A.) a ete entreprise. On montre la complementarite des differentes reactions de transfert, l'ambiguite des facteurs spectroscopiques, l'importance du probleme du mecanisme. (auteur)

Inelastic Branch of the Stellar Reaction $^{14}$O$(\\alpha,p)^{17}$F

CERN Multimedia

Hass, M; Van duppen, P L E

2002-01-01

We propose to use the upgraded REX-ISOLDE beam energy to study the astrophysically important $^{14}$O($\\alpha$, p)$^{17}$F reaction in time reverse kinematics. In particular, we will use the highly efficient miniball + CD detection system to measure the previously undetermined inelastic proton branch of the 1$^-$ state at 6.15 MeV in $^{18}$Ne. This state dominates the reaction rate under X-ray burster conditions.

AN UPDATED {sup 6}Li(p, {alpha}){sup 3}He REACTION RATE AT ASTROPHYSICAL ENERGIES WITH THE TROJAN HORSE METHOD

Energy Technology Data Exchange (ETDEWEB)

Lamia, L.; Spitaleri, C.; Sergi, M. L. [Dipartimento di Fisica e Astronomia, Universita di Catania, I-95123 Catania (Italy); Pizzone, R. G.; Tumino, A.; La Cognata, M. [INFN-Laboratori Nazionali del Sud, I-95125 Catania (Italy); Tognelli, E.; Degl' Innocenti, S.; Prada Moroni, P. G. [Dipartimento di Fisica, Universita di Pisa, I-56127 Pisa (Italy); Pappalardo, L. [Dipartimento di Fisica e Scienze della Terra, Universita di Ferrara, I-44100 Ferrara (Italy)

2013-05-01

The lithium problem influencing primordial and stellar nucleosynthesis is one of the most interesting unsolved issues in astrophysics. {sup 6}Li is the most fragile of lithium's stable isotopes and is largely destroyed in most stars during the pre-main-sequence (PMS) phase. For these stars, the convective envelope easily reaches, at least at its bottom, the relatively low {sup 6}Li ignition temperature. Thus, gaining an understanding of {sup 6}Li depletion also gives hints about the extent of convective regions. For this reason, charged-particle-induced reactions in lithium have been the subject of several studies. Low-energy extrapolations of these studies provide information about both the zero-energy astrophysical S(E) factor and the electron screening potential, U{sub e} . Thanks to recent direct measurements, new estimates of the {sup 6}Li(p, {alpha}){sup 3}He bare-nucleus S(E) factor and the corresponding U{sub e} value have been obtained by applying the Trojan Horse method to the {sup 2}H({sup 6}Li, {alpha} {sup 3}He)n reaction in quasi-free kinematics. The calculated reaction rate covers the temperature window 0.01 to 2T{sub 9} and its impact on the surface lithium depletion in PMS models with different masses and metallicities has been evaluated in detail by adopting an updated version of the FRANEC evolutionary code.

Laboratory investigations of the alpha-pinene/ozone gas-phase reaction

International Nuclear Information System (INIS)

Benner, C.L.

1985-01-01

In order to provide more insight into terpene photooxidation or ozonolysis reaction mechanisms, a radiotracer technique was developed. This technique was applied to an investigation of the 14 C-alpha-pinene/ozone reaction. In the first phase of the research, the carbon distribution at the conclusion of the ozonolysis reaction was determined by separating carbon-14-labelled gaseous products from labelled aerosols, and counting each phase by liquid scintillation methods. The resulting carbon balance was 38% to 60% filtered aerosols, 6% to 20% gas phase compounds, and 11% to 29% products absorbed on the reaction chamber walls. Recoveries of the alpha-pinene carbon-14 ranging from 79% to 97% were achieved using this method. The alpha-pinene concentrations in these experiments were close to ambient (1 part per billion), yet the carbon balance was similar to that observed at much higher concentrations (>1 part per million). In the second phase of the alpha-pinene study, both gas and aerosol products of the ozonolysis reaction were collected on cartridges impregnated with 2,4-dinitrophenylhydrazine, then analyzed by HPLC. In the final experiments, alpha-pinene aerosol was reacted with a silylating agent to improve the detection of organic acids and alcohols. The gas chromatographic/mass spectrometric analysis of the silylated aerosol products showed evidence of dimer/polymer formation occurring in the ozonolysis reaction

Application of multi-step direct reaction theory to 14 MeV neutron reaction, 3 (n,. cap alpha. )

Energy Technology Data Exchange (ETDEWEB)

Kumabe, I.; Matoba, M.; Fukuda, K. [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering; Ikegami, H.; Muraoka, M [eds.

1980-01-01

Multi-step direct-reaction theory proposed by Tamura et al. has been applied to continuous spectra of the 14 MeV (n, ..cap alpha..) reaction with some modifications. Calculated results reproduce well the experimental energy and angular distributions of the 14 MeV (n, ..cap alpha..) reactions.

Study of the {sup 18}F(p,{alpha}){sup 15}O reaction by transfer reaction for application to {gamma}-ray emission from Novae; Etude de la reaction {sup 18}F(p,{alpha}){sup 15}O par reaction de transfert pour application a l'emission {gamma} des Novae

Energy Technology Data Exchange (ETDEWEB)

Sereville, N. de

2003-12-15

The gamma emission from novae at/or below 511 keV is due to the annihilation of the positrons produced in the beta + decay of F{sup 18}. The interpretation of this emission through observations made by the Integral satellite for instance, requires a good knowledge of F{sup 18} nucleosynthesis. The reaction rate of the F{sup 18}(p,{alpha})O{sup 15} is the least known because of 2 resonances corresponding to the levels 6.419 and 6.449 MeV of Ne{sup 19} whose proton widths are completely unknown. We have determined these proton widths via the study of one-nucleon transfer reaction D(F{sup 18},p{alpha})N{sup 15} populating equivalent levels in F{sup 19}. We have used a 14 MeV F{sup 18} radioactive beam on a CD{sub 2} target for inverse kinematics studies and the multi-track silicon detector LEDA. A DWBA (Distorted Wave Bound Approximation) has enabled us to determine the proton width of both resonances and has showed that they have an impact in the calculation of the reaction rate. A thorough study of the remaining uncertainties of the reaction rate has been undertaken, particularly for those concerning interferences between these resonances and a higher resonance of Ne{sup 19}. The reaction rate that we have obtained is very similar to the previous rate used but now it rests on a more solid basis.

Alpha-decay within Feshbach theory of nuclear reactions

International Nuclear Information System (INIS)

Sandulescu, A.; Silisteanu, I.; Wunsch, R.

1977-01-01

In the frame of Feshbach theory of nuclear reactions the alpha-decay widths are determined by the alpha-daughter nucleus optical potential and by the formation factors. It is shown that the calculated absolute values of the alpha widths for Po light isotopes are in good agreement with experimental data, if the real part of the optical potential with the parameters fitted by the low energy α-scattering is used

Direct-acting antiviral-based triple therapy on alpha-fetoprotein level in chronic hepatitis C patients.

Science.gov (United States)

Takayama, Koji; Furusyo, Norihiro; Ogawa, Eiichi; Ikezaki, Hiroaki; Shimizu, Motohiro; Murata, Masayuki; Hayashi, Jun

2015-04-21

To investigate the impact of telaprevir-based triple therapy on the serum alpha-fetoprotein (AFP) level of chronic hepatitis C patients. A total of 210 patients with chronic hepatitis C genotype 1 of high viral load (baseline serum hepatitis C virus RNA > 5.0 log10 IU/mL) were divided into two groups by type of treatment: triple therapy with telaprevir, pegylated-interferon-α (PEG-IFNα), and ribavirin (RBV) for 24 wk (n = 88), or dual therapy with PEG-IFNα and RBV for 48 wk (n = 122). The relationship between virological response and the change in the serum AFP level from baseline to 24 wk after the end of treatment was examined. No significant difference in mean baseline AFP level was found between the triple and dual therapy groups (8.8 ng/mL vs 7.8 ng/mL). Triple therapy produced significant declines in the AFP level in sustained virological response (SVR) and non-SVR patients (7.8 ng/mL at baseline to 3.5 ng/mL at 24 wk after the end of treatment, P < 0.001 and 14.3 ng/mL to 9.5 ng/mL, P = 0.004, respectively). In contrast, dual therapy resulted in a significant decline in AFP level only in SVR patients (4.7 ng/mL to 2.8 ng/mL, P < 0.001), but not in non-SVR patients (10.2 ng/mL to 10.1 ng/mL). Among patients with a high-baseline AFP level (≥ 10 ng/mL), the decline in the AFP level was significantly higher in the triple therapy than in the dual therapy group (15.9 ng/mL vs 1.6 ng/mL, P = 0.037). Regardless of virological response, telaprevir-based triple therapy reduced the serum AFP level.

Triple composite tumor of stomach: A rare combination of alpha fetoprotein positive hepatoid adenocarcinoma, tubular adenocarcinoma and large cell neuroendocrine carcinoma

Directory of Open Access Journals (Sweden)

Lipika Lipi

2014-01-01

Full Text Available A 50-year-old male patient presented with pain abdomen of 6 months duration. Computed tomography scan revealed a large mass in the stomach occluding the lumen. Histopathology revealed a triple composite tumor comprising of tubular adenocarcinoma arising on a background of high-grade dysplasia, hepatoid adenocarcinoma (positive for Hep Par-1 and alpha fetoprotein and large cell neuroendocrine carcinoma (positive for synaptophysin and chromogranin with nodal metastasis.Triple composite tumors are distinctly rare with few reports in literature.

Astrophysical rate of O-15(alpha,gamma)Ne-19 via the (p, t) reaction in inverse kinematics

NARCIS (Netherlands)

Davids, B; van den Berg, AM; Dendooven, P; Fleurot, F; Hunyadi, M; de Huu, MA; Siemssen, RH; Wilschut, HW; Wortche, HJ; Hernanz, M; Jose, J; Rehm, KE; Wuosmaa, AH; Segel, RE

A recoil coincidence technique has been applied to measure the alpha-decay branching ratios of near-threshold states in Ne-19. Populating these states using the (p,t) reaction in inverse kinematics, we detected the recoils and their decay products with 100% geometric efficiency using a magnetic

Thermonuclear F-19(p,alpha(0))O-16 reaction rate

Czech Academy of Sciences Publication Activity Database

He, J. J.; Lombardo, I.; Dell'Aquila, D.; Xu, Yi; Zang, L. Y.; Liu, W. P.

2018-01-01

Roč. 42, č. 1 (2018), č. článku 015001. ISSN 1674-1137 Institutional support: RVO:61389005 Keywords : asymptotic giant branch (AGB) star * nucleosynthesis * astrophysical S factor * cross section * reaction rate Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.084, year: 2016

Structure of ¹²C and the triple-α process

DEFF Research Database (Denmark)

Fynbo, H.O.U.; Diget, C.Aa.

2014-01-01

We review experiments at IGISOL and associated work at ISOLDE and KVI on the use of the β-decays of 12N and 12B for the study of the structure of 12C and the consequences for the rate of the triple-α reaction in stars.......We review experiments at IGISOL and associated work at ISOLDE and KVI on the use of the β-decays of 12N and 12B for the study of the structure of 12C and the consequences for the rate of the triple-α reaction in stars....

{alpha}-particle induced reactions on yttrium and terbium

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, S.; Kumar, B.B. [School of Studies in Physics, Vikram University, Ujjain-456010 (India); Rashid, M.H. [Variable Energy Cyclotron Center, 1/AF, Bidhan Nagar, Calcutta (India); Chintalapudi, S.N. [Inter-University Consortium for DAE Facilities, 3/LB, Bidhan Nagar, Calcutta (India)

1997-05-01

The stacked foil activation technique has been employed for the investigation of {alpha}-particle induced reactions on the target elements yttrium and terbium up to 50 MeV. Six excitation functions for the ({alpha},xn) type of reactions were studied using high-resolution HPGe {gamma}-ray spectroscopy. A comparison with Blann{close_quote}s geometric dependent hybrid model has been made using the initial exciton number n{sub 0}=4(4p0h) and n{sub 0}=5(5p0h). A broad general agreement is observed between the experimental results and theoretical predictions with an initial exciton number n{sub 0}=4(4p0h). {copyright} {ital 1997} {ital The American Physical Society}

Determination of alpha-naphthol by an oscillating chemical reaction using the analyte pulse perturbation technique

International Nuclear Information System (INIS)

Yang Wu; Sun Kanjun; Lv Weilian; Bo Lili; He Xiaoyan; Suo Nan; Gao Jinzhang

2005-01-01

An analytical method for the determination of alpha-naphthol (α-NP) is proposed by the sequential perturbation caused by different amounts of alpha-naphthol on the oscillating chemical system involving the Cu(II)-catalyzed oscillating reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium with the aid of continuous-flow stirred tank reactor (CSTR). The method relies on the linear relationship between the changes in the oscillation amplitude of the chemical system and the concentration of alpha-naphthol. The use of the analyte pulse perturbation technique permits sequential determinations in the same oscillating system owing to the expeditiousness with which the steady state is regained after each perturbation. The calibration curve obeys a linear equation very well when the concentration of alpha-naphthol is over the range 0.034-530 umol/L (r = 0.9991). Influences of temperature, injection points, flow rate and reaction variables on the oscillating system are investigated in detail and the possible mechanism of action of alpha-naphthol to the chemical oscillating system is also discussed. The method has been successfully used for the determination of α-naphthol in carbaryl hydrolysates

Measurement of reaction rates of interest in stellar structure and evolution

Energy Technology Data Exchange (ETDEWEB)

Terrasi, F; D` Onofrio, A [Dipt. di Scienze Ambientali, Seconda Univ. di Napoli, Caserta (Italy); [INFN, Napoli (Italy); Campajola, L; Imbriani, G [INFN, Napoli (Italy); [Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); Gialanella, L [INFN, Napoli (Italy); [Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); [Inst. fuer Experimentalphysik III, Ruhr-Univ. Bochum, Bochum (Germany); Greife, U; Rolfs, C; Strieder, F; Trautvetter, H P [Inst. fuer Experimentalphysik III, Ruhr-Univ. Bochum, Bochum (Germany); Roca, V; Romano, M [INFN, Napoli (Italy); [Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); Straniero, O [Osservatorio Astronomico di Collurania, Teramo (Italy)

1998-06-01

Accurate determinations of reaction rates at astrophysical energies are very important in stellar structure and evolution studies. The cases of two key reactions, namely {sup 7}Be(p,{gamma}){sup 8}B and {sup 12}C({alpha},{gamma}){sup 16}O are discussed, both from the point of view of their astrophysical interest and of the experimental difficulties in the measurement of their cross section. (orig.)

Pre-equilibrium decay process in alpha particle induced reactions on thulium and tantalum

Energy Technology Data Exchange (ETDEWEB)

Mohan, Rao, A.V.; Chintalapudi, S.N. (Inter Univ. Consortium for Dept. of atomic Energy Facilities, Calcutta (India))

1994-01-01

Alpha particle induced reactions on the target elements Thulium and Tantalum were investigated upto 60 MeV using stacked foil activation technique and Ge(Li) gamma ray spectroscopy method. Excitation functions for six reactions of [sup 169]Tm([alpha],xn); x=1-4 and [sup 181]Ta([alpha],xn); x=2,4 were studied. The experimental results were compared with the updated version of Hybrid model (ALICE/90) using initial exciton configuration n[sub 0]=4(4pOh). A general agreement was found for all the reactions with this option. (author).

Effects of a new 3-alpha reaction on the s-process in massive stars

International Nuclear Information System (INIS)

Kikuch, Yukihiro; Ono, Masaomi; Matsuo, Yasuhide; Hashimoto, Masa-aki; Fujimoto, Shin-ichiro

2012-01-01

Effect of a new 3-alpha reaction rate on the s-process during the evolution of a massive star of 25 solar mass is investigated for the first time, because the s-process in massive stars have been believed to be established with only minor change. We find that the s-process with use of the new rate during the core helium burning is very inefficient compared to the case with the previous 3-alpha rate. However, the difference of the overproduction is found to be largely compensated by the subsequent carbon burning. Since the s-process in massive stars has been attributed so far to the neutron irradiation during core helium burning, our finding reveals for the first time the importance of the carbon burning for the s-process during the evolution of massive stars.

Measurement of Plutonium-240 Angular Momentum Dependent Fission Probabilities Using the Alpha-Alpha' Reaction

Science.gov (United States)

Koglin, Johnathon

Accurate nuclear reaction data from a few keV to tens of MeV and across the table of nuclides is essential to a number of applications of nuclear physics, including national security, nuclear forensics, nuclear astrophysics, and nuclear energy. Precise determination of (n, f) and neutron capture cross sections for reactions in high- ux environments are particularly important for a proper understanding of nuclear reactor performance and stellar nucleosynthesis. In these extreme environments reactions on short-lived and otherwise difficult-to-produce isotopes play a significant role in system evolution and provide insights into the types of nuclear processes taking place; a detailed understanding of these processes is necessary to properly determine cross sections far from stability. Indirect methods are often attempted to measure cross sections on isotopes that are difficult to separate in a laboratory setting. Using the surrogate approach, the same compound nucleus from the reaction of interest is created through a "surrogate" reaction on a different isotope and the resulting decay is measured. This result is combined with appropriate reaction theory for compound nucleus population, from which the desired cross sections can be inferred. This method has shown promise, but the theoretical framework often lacks necessary experimental data to constrain models. In this work, dual arrays of silicon telescope particle identification detectors and photovoltaic (solar) cell fission fragment detectors have been used to measure the fission probability of the 240Pu(alpha, alpha'f) reaction - a surrogate for the 239Pu(n, f) - and fission of 35.9(2)MeV at eleven scattering angles from 40° to 140° in 10° intervals and at nuclear excitation energies up to 16MeV. Within experimental uncertainty, the maximum fission probability was observed at the neutron separation energy for each alpha scattering angle. Fission probabilities were separated into five 500 keV bins from 5:5MeV to

Recoil-alpha-fission and recoil-alpha-alpha-fission events observed in the reaction Ca-48 + Am-243

NARCIS (Netherlands)

Forsberg, U.; Rudolph, D.; Andersson, L. -L.; Nitto, A. Di; Düllmann, Ch E.; Gates, J. M.; Golubev, P.; Gregorich, K. E.; Gross, C. J.; Herzberg, R. -D.; Hessberger, F. P.; Khuyagbaatar, J.; Kratz, J. V.; Rykaczewski, K.; Sarmiento, L. G.; Schädel, M.; Yakushev, A.; Åberg, S.; Ackermann, D.; Block, M.; Brand, H.; Carlsson, B. G.; Cox, D.; Derkx, X.; Dobaczewski, J.; Eberhardt, K.; Even, J.; Fahlander, C.; Gerl, J.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nazarewicz, W.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Ragnarsson, I.; Runke, J.; Schaffner, H.; Schausten, B.; Shi, Y.; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Ward, D. E.; Wiehl, N.

2016-01-01

Products of the fusion-evaporation reaction Ca-48 + Am-243 were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum f\\"ur Schwerionenforschung. Amongst the detected thirty correlated alpha-decay chains associated with the production of element Z=115, two

Determination of $\\alpha_{s}$ using Jet Rates at LEP with the OPAL detector

CERN Document Server

Abbiendi, G.; Akesson, P.F.; Alexander, G.; Anagnostou, G.; Anderson, K.J.; Asai, S.; Axen, D.; Bailey, I.; Barberio, E.; Barillari, T.; Barlow, R.J.; Batley, R.J.; Bechtle, P.; Behnke, T.; Bell, Kenneth Watson; Bell, P.J.; Bella, G.; Bellerive, A.; Benelli, G.; Bethke, S.; Biebel, O.; Boeriu, O.; Bock, P.; Boutemeur, M.; Braibant, S.; Brown, Robert M.; Burckhart, H.J.; Campana, S.; Capiluppi, P.; Carnegie, R.K.; Carter, A.A.; Carter, J.R.; Chang, C.Y.; Charlton, D.G.; Ciocca, C.; Csilling, A.; Cuffiani, M.; Dado, S.; De Roeck, A.; De Wolf, E.A.; Desch, K.; Dienes, B.; Donkers, M.; Dubbert, J.; Duchovni, E.; Duckeck, G.; Duerdoth, I.P.; Etzion, E.; Fabbri, F.; Ferrari, P.; Fiedler, F.; Fleck, I.; Ford, M.; Frey, A.; Gagnon, P.; Gary, John William; Geich-Gimbel, C.; Giacomelli, G.; Giacomelli, P.; Giunta, Marina; Goldberg, J.; Gross, E.; Grunhaus, J.; Gruwe, M.; Gunther, P.O.; Gupta, A.; Hajdu, C.; Hamann, M.; Hanson, G.G.; Harel, A.; Hauschild, M.; Hawkes, C.M.; Hawkings, R.; Hemingway, R.J.; Herten, G.; Heuer, R.D.; Hill, J.C.; Horvath, D.; Igo-Kemenes, P.; Ishii, K.; Jeremie, H.; Jovanovic, P.; Junk, T.R.; Kanzaki, J.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Keeler, R.K.; Kellogg, R.G.; Kennedy, B.W.; Kluth, S.; Kobayashi, T.; Kobel, M.; Komamiya, S.; Kramer, T.; Krasznahorkay, A.; Krieger, P.; von Krogh, J.; Kuhl, T.; Kupper, M.; Lafferty, G.D.; Landsman, H.; Lanske, D.; Lellouch, D.; Lettso, J.; Levinson, L.; Lillich, J.; Lloyd, S.L.; Loebinger, F.K.; Lu, J.; Ludwig, A.; Ludwig, J.; Mader, W.; Marcellini, S.; Martin, A.J.; Mashimo, T.; Mattig, Peter; McKenna, J.; McPherson, R.A.; Meijers, F.; Menges, W.; Merritt, F.S.; Mes, H.; Meyer, Niels T.; Michelini, A.; Mihara, S.; Mikenberg, G.; Miller, D.J.; Mohr, W.; Mori, T.; Mutter, A.; Nagai, K.; Nakamura, I.; Nanjo, H.; Neal, H.A.; Nisius, R.; O'Neale, S.W.; Oh, A.; Oreglia, M.J.; Orito, S.; Pahl, C.; Pasztor, G.; Pater, J.R.; Pilcher, J.E.; Pinfold, J.; Plane, David E.; Pooth, O.; Przybycien, M.; Quadt, A.; Rabbertz, K.; Rembser, C.; Renkel, P.; Roney, J.M.; Rossi, A.M.; Rozen, Y.; Runge, K.; Sachs, K.; Saeki, T.; Sarkisyan, E.K.G.; Schaile, A.D.; Schaile, O.; Scharff-Hansen, P.; Schieck, J.; Schorner-Sadenius, T.; Schroder, Matthias; Schumacher, M.; Seuster, R.; Shears, T.G.; Shen, B.C.; Sherwood, P.; Skuja, A.; Smith, A.M.; Sobie, R.; Soldner-Rembold, S.; Spano, F.; Stahl, A.; Strom, David M.; Strohmer, R.; Tarem, S.; Tasevsky, M.; Teuscher, R.; Thomson, M.A.; Torrence, E.; Toya, D.; Tran, P.; Trigger, I.; Trocsanyi, Z.; Tsur, E.; Turner-Watson, M.F.; Ueda, I.; Ujvari, B.; Vollmer, C.F.; Vannerem, P.; Vertesi, R.; Verzocchi, M.; Voss, H.; Vossebeld, J.; Ward, C.P.; Ward, D.R.; Watkins, P.M.; Watson, A.T.; Watson, N.K.; Wells, P.S.; Wengler, T.; Wermes, N.; Wilson, G.W.; Wilson, J.A.; Wolf, G.; Wyatt, T.R.; Yamashita, S.; Zer-Zion, D.; Zivkovic, Lidija

2006-01-01

Hadronic events produced in e+e- collisions by the LEP collider and recorded by the OPAL detector were used to form distributions based on the number of reconstructed jets. The data were collected between 1995 and 2000 and correspond to energies of 91 GeV, 130-136 GeV and 161-209 GeV. The jet rates were determined using four different jet-finding algorithms (Cone, JADE, Durham and Cambridge). The differential two-jet rate and the average jet rate with the Durham and Cambridge algorithms were used to measure alpha(s) in the LEP energy range by fitting an expression in which order alpah_2s calculations were matched to a NLLA prediction and fitted to the data. Combining the measurements at different centre-of-mass energies, the value of alpha_s (Mz) was determined to be alpha(s)(Mz)=0.1177+-0.0006(stat.)+-0.0012$(expt.)+-0.0010(had.)+-0.0032

About the reactions sup 3 H(alpha,gamma) sup 7 Li and sup 3 He(alpha,gamma) sup 7 Be

CERN Document Server

Loeffler, W

1993-01-01

In this article the current experimental and theoretical status of the radiative alpha capture reactions sup 3 H(alpha,gamma) sup 7 Li and sup 3 He(alpha,gamma) sup 7 Be and their relations to primordial nucleosynthesis and the solar neutrino problem are reviewed. (author)

A triple telescope for the simultaneous identification of light and heavy reaction products

CERN Document Server

Moura, M M D; Alonso, E E; Souza, F A; Fujii, R J; Morais, O B D; Szanto, E M; Szanto de Toledo, A; Carlin, N

2001-01-01

Sixteen triple telescopes were developed to be used in the study of light heavy-ion nuclear reactions at the University of Sao Paulo Pelletron Laboratory, with the purpose of providing simultaneous identification of light and heavy reaction products. Each telescope consists of one ionization chamber, one Si detector and one CsI detector with photodiode readout. The telescopes are encapsulated in such a way that they can be utilized in different setup geometries depending on the kind of experiment being performed. Results for the ionization chambers energy loss resolution, Si and CsI detectors energy resolution and general performance are presented.

Alpha resonant scattering for astrophysical reaction studies

International Nuclear Information System (INIS)

Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

2014-01-01

Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of 7 Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the 7 Be(α,γ) reaction, and proposed a new cluster band in 11 C

Complete primary structure of rainbow trout type I collagen consisting of alpha1(I)alpha2(I)alpha3(I) heterotrimers.

Science.gov (United States)

Saito, M; Takenouchi, Y; Kunisaki, N; Kimura, S

2001-05-01

The subunit compositions of skin and muscle type I collagens from rainbow trout were found to be alpha1(I)alpha2(I)alpha3(I) and [alpha1(I)](2)alpha2(I), respectively. The occurrence of alpha3(I) has been observed only for bonyfish. The skin collagen exhibited more susceptibility to both heat denaturation and MMP-13 digestion than the muscle counterpart; the former had a lower denaturation temperature by about 0.5 degrees C than the latter. The lower stability of skin collagen, however, is not due to the low levels of imino acids because the contents of Pro and Hyp were almost constant in both collagens. On the other hand, some cDNAs coding for the N-terminal and/or a part of triple-helical domains of proalpha(I) chains were cloned from the cDNA library of rainbow trout fibroblasts. These cDNAs together with the previously cloned collagen cDNAs gave information about the complete primary structure of type I procollagen. The main triple-helical domain of each proalpha(I) chain had 338 uninterrupted Gly-X-Y triplets consisting of 1014 amino acids and was unique in its high content of Gly-Gly doublets. In particular, the bonyfish-specific alpha(I) chain, proalpha3(I) was characterized by the small number of Gly-Pro-Pro triplets, 19, and the large number of Gly-Gly doublets, 38, in the triple-helical domain, compared to 23 and 22, respectively, for proalpha1(I). The small number of Gly-Pro-Pro and the large number of Gly-Gly in proalpha3(I) was assumed to partially loosen the triple-helical structure of skin collagen, leading to the lower stability of skin collagen mentioned above. Finally, phylogenetic analyses revealed that proalpha3(I) had diverged from proalpha1(I). This study is the first report of the complete primary structure of fish type I procollagen.

Estimation of the {alpha} particles and neutron distribution generated during a fusion reaction; Evaluation de la distribution des particules {alpha} et des neutrons issus de la reaction de fusion

Energy Technology Data Exchange (ETDEWEB)

Dellacherie, S.

1997-12-01

The respective distributions (or density probabilities) of {alpha} particles and neutrons have been modeled using a Monte-Carlo method for the thermonuclear fusion reaction D + T {yields} {alpha} + n + 17.6 MeV. (N.T.).

Hydrozirconation of lithium alkynylselenolate anions. Generation and reactions of alpha-zirconated vinyl selenide intermediates

Science.gov (United States)

Dabdoub; Begnini; Guerrero; Baroni

2000-01-14

Lithium alkynylselenolate anions react completely with 1.0 equiv of Cp(2)Zr(H)Cl in THF at room temperature to give exclusively the alpha-zirconated vinylselenolate intermediates 23-27, which by treatment with an alkyl halide afforded the alpha-zirconated vinyl alkylselenide intermediates 29-33. Reaction of 29-33 with butyltellurenyl bromide results in the formation of ketene telluro(seleno) acetals 35-39 with total control of the regio- and stereochemistry. The synthetic utility of the ketene telluro(seleno) acetals obtained here was demonstrated by reaction of 36 with butyllithium. This promotes the exclusive and stereospecific removal of the tellurium moiety and enables formation of the corresponding selenium-containing allylic alcohol of type 44, alpha-(alkylseleno)-alpha,beta-unsaturated aldehyde 45, ester 46, or carboxylic acid 47, after reaction with different types of electrophiles.

Crosschecking of alpha particle monitor reactions up to 50 MeV

Energy Technology Data Exchange (ETDEWEB)

Takács, S., E-mail: stakacs@atomki.hu [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Ditrói, F.; Szűcs, Z. [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Haba, H.; Komori, Y. [Nishina Center for Accelerator-Based Science, RIKEN, Wako 351-0198 (Japan); Aikawa, M. [Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, Wako 351-0198 (Japan); Saito, M. [Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, Wako 351-0198 (Japan)

2017-04-15

Selected reactions with well-defined excitation functions can be used to monitor the parameters of charged particle beams. The frequently used reactions for monitoring alpha particle beams are the {sup 27}Al(α,x){sup 22,24}Na, {sup nat}Ti(α,x){sup 51}Cr, {sup nat}Cu(α,x){sup 66,67}Ga and {sup nat}Cu(α,x){sup 65}Zn reactions. The excitation functions for these reactions were studied using the activation method and stacked target irradiation technique to crosscheck and to compare the above six reactions. Thin metallic foils with natural isotopic composition and well defined thickness were stacked together in sandwich targets and were irradiated at the AVF cyclotron of RIKEN with an alpha particle beam of 51.2 MeV. The activity of the target foils were assessed by using high-resolution gamma spectrometers of high purity Ge detectors. The data sets of the six processes were crosschecked with each other to provide consistent, cross-linked numerical cross section data.

Alpha resonant scattering for astrophysical reaction studies

Energy Technology Data Exchange (ETDEWEB)

Yamaguchi, H.; Kahl, D.; Nakao, T. [Center for Nuclear Study (CNS), University of Tokyo, RIKEN campus, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wakabayashi, Y.; Kubano, S. [The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Hashimoto, T. [Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Hayakawa, S. [Istituto Nazionale Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS), Via S. Sofia 62, 95125 Catania (Italy); Kawabata, T. [Department of Physics, Kyoto University, Kita-Shirakawa, Kyoto 606-8502 (Japan); Iwasa, N. [Department of Physics, Tohoku University, Aoba, Sendai, Miyagi 980-8578 (Japan); Teranishi, T. [Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan); Kwon, Y. K. [Institute for Basic Science, 70, Yuseong-daero 1689-gil, Yuseong-gu, Daejeon 305-811 (Korea, Republic of); Binh, D. N. [30 MeV Cyclotron Center, Tran Hung Dao Hospital, Hoan Kiem District, Hanoi (Viet Nam); Khiem, L. H.; Duy, N. G. [Institute of Physics, Vietnam Academy of Science and Technology, 18 Hong Quoc Viet, Nghia do, Hanoi (Viet Nam)

2014-05-02

Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

Alpha cluster states in light nuclei populated through the (6Li,d) reaction

Energy Technology Data Exchange (ETDEWEB)

Borello-Lewin, Thereza; Rodrigues, M.R.D.; Horodynski-Matsushigue, L.B.; Duarte, J.L.M.; Rodrigues, C.L.; Souza, M.A. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica; Cunsolo, A.; Cappuzzello, F. [Universita di Catania (Italy). Istituto Nazionale di Fisica Nucleare. Lab. Nazionali del Sud; Ukita, Gilberto Mitsuo [Universidade de Santo Amaro (UNISA), Sao Paulo, SP (Brazil). Fac. de Psicologia

2011-07-01

Full text: The alpha cluster correlation is an important concept in the nuclear physics of light nuclei. The main purpose of the research program in progress is the investigation of the alpha clustering phenomenon in (x{alpha}) and(x{alpha}+{nu}) nuclei through the ({sup 6}Li,d) alpha transfer reaction. In fact, there is scarce experimental information on the subject, in particular associated with resonant states predicted near (x{alpha}) and (x{alpha}+{nu}) thresholds. Measurements of the {sup 12},{sup 13}C({sup 6}Li,d) {sup 16},{sup 17}O reactions, at an incident energy of 25.5 MeV, have been performed employing the Sao Paulo Pelletron-Enge Split-Pole facility and the nuclear emulsion detection technique. The work is under way and an experimental energy resolution of 30 keV was obtained. Near the (4{alpha}) breakup threshold in {sup 16}O, three narrow alpha resonances, not previously measured, were detected, revealing important {alpha} + {sup 12}C(G.S.) components. One of these resonances corresponds to the known 0{sup +} state at 15.1 MeV[5] of excitation that has probably, according to Funaki et al., the gas like configuration of the 4{alpha} condensate state, with a very dilute density and a large component of {alpha} + {sup 12}C(Hoyle) configuration. As was already mentioned, our experimental information points to the necessity of including the {alpha} + {sup 12}C(G.S.) component in the wave function. (author)

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

Experimental investigation of the reactions {sup 25}Mg({alpha},n){sup 28}Si, {sup 26}Mg({alpha},n){sup 29}Si, {sup 18}O({alpha},n){sup 21}Ne and their impact on stellar nucleosynthesis

Energy Technology Data Exchange (ETDEWEB)

Falahat, Sascha

2010-06-10

In the present dissertation, the nuclear reactions {sup 25}Mg({alpha},n){sup 28}Si, {sup 26}Mg({alpha},n){sup 29}Si, {sup 18}O({alpha},n){sup 21}Ne are investigated in the astrophysically interesting energy region from E{sub {alpha}}=1000 keV to E{sub {alpha}}=2450 keV. The experiments were performed at the Nuclear Structure Laboratory of the University of Notre Dame (USA) with the Van-de-Graaff accelerator KN. Solid state targets with evaporated magnesium or anodized oxygen were bombarded with {alpha}-particles and the released neutrons detected. For the detection of the released neutrons, computational simulations were used to construct a neutron detector based on {sup 3}He counters. Because of the strong occurrence of background reactions, different methods of data analysis were employed. Finally, the impact of the reactions {sup 25}Mg({alpha},n){sup 28}Si, {sup 26}Mg({alpha},n){sup 29}Si, {sup 18}O({alpha},n){sup 21}Ne on stellar nucleosynthesis is investigated by means of network calculations. (orig.)

Frequency tripling with multimode-lasers

International Nuclear Information System (INIS)

Langer, H.; Roehr, H.; Wrobel, W.G.

1978-10-01

The presence of different modes with random phases in a laser beam leads to fluctuations in nonlinear optical interactions. This paper describes the influence of the linewidth of a dye laser on the generation of intensive Lyman-alpha radiation by frequency tripling. Using this Lyman-alpha source for resonance scattering on strongly doppler-broadened lines in fusion plasmas the detection limit of neutral hydrogen is nearly two orders higher with the multimode than the singlemode dye laser. (orig.) [de

Resonance analysis of the {sup 12}C,{sup 13}C({alpha},n) reactions and evaluation of neutron yield data of the reaction

Energy Technology Data Exchange (ETDEWEB)

Murata, Toru [AITEL Corp., Tokyo (Japan)

1998-03-01

The {sup 12}C({alpha},n){sup 15}O reaction and the {sup 13}C({alpha},n){sup 16}O reaction were analyzed with a resonance formula in the incident {alpha}-particle energy range of 1.0 to 16.0 MeV. With the obtained resonance parameters, branching ratios of the emitted neutrons to the several levels of the residual nucleus and their angular distributions were calculated to obtain the energy spectrum of emitted neutrons. Thick target neutron yield of carbon were also calculated and compared with the experimental data. (author)

Reaction /sup 56/Fe (. gamma. ,. cap alpha. /sub 0/) and /sup 56/Fe (. gamma. , p/sub 0/)

Energy Technology Data Exchange (ETDEWEB)

Tamae, T; Sugawara, M [Tohoku Univ., Sendai (Japan). Lab. of Nuclear Science; Tsubota, H

1975-06-01

Precise analysis was made on the cross section of the /sup 56/Fe (..gamma.., ..cap alpha../sub 0/) reaction and the angular distribution at Esub(e) = 17 MeV, including the systematic error. The (..gamma.., ..cap alpha../sub 0/) reaction cross section was compared with a calculation using the compound nucleus model, utilizing the photon absorption cross section derived from the experimental values of /sup 56/Fe (..gamma.., n) and /sup 56/Fe (..gamma.., p) cross sections. From the (..gamma.., ..cap alpha../sub 0/) reaction cross section data of various nuclei, an empirical formula was obtained for determining the position of a peak in the (..gamma.., ..cap alpha../sub 0/) reaction cross section. The /sup 56/Fe (..gamma.., p/sub 0/) reaction cross section measured at an excitation energy in the range of 14.6--25.0 MeV was compared with the calculated one with the compound nucleus model, but the form and size differ totally.

The fluorine destruction in stars: First experimental study of the {sup 19}F(p,{alpha}){sup 16}O reaction at astrophysical energies

Energy Technology Data Exchange (ETDEWEB)

La Cognata, M.; Mukhamedzhanov, A.; Spitaleri, C.; Indelicato, I.; Aliotta, M.; Burjan, V.; Cherubini, S.; Coc, A.; Gulino, M.; Hons, Z.; Kiss, G. G.; Kroha, V.; Lamia, L.; Mrazek, J.; Palmerini, S.; Piskor, S.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S. [INFN-LNS, Catania (Italy); Cyclotron Institute, Texas A and M University, College Station, Texas (United States); University of Catania and INFN-LNS, Catania (Italy); and others

2012-11-12

The {sup 19}F(p,{alpha}){sup 16}O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogendeficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E{sub cm}{approx} 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the {sup 2}H({sup 19}F,{alpha}{sup 16}O)n reaction. The TH measurement of the {alpha}{sub 0} channel, which is the dominant one at such energies, shows the presence of resonant structures not observed before that cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential important consequences for stellar nucleosynthesis.

Kramers Turnover Theory for a Triple Well Potential

International Nuclear Information System (INIS)

Pollak, E.; Talkner, P.

2001-01-01

Kramers turnover theory is solved for a particle in a symmetric triple well potential for temperatures above the crossover temperature between tunneling and activated barrier crossing. Comparison with the turnover theory for a double well potential shows that the presence of the intermediate well always leads to a decrease of the reaction rate. At most though, the rate is a factor of two smaller than in the case of a double well potential. (author)

Alpha-capture reaction rates for 22 Ne (α , n) via sub-Coulomb alpha-transfer and its effect on final abundances of s-process isotopes

Science.gov (United States)

Jayatissa, Heshani; Rogachev, Grigory; Koshchiy, Yevgeny; Goldberg, Vladilen; Hooker, Joshua; Hunt, Curtis; Magana, Cordero; Roeder, Brian; Saastamoinen, Antti; Spiridon, Alexandria; Upadhyayula, Sriteja; Trippella, Oscar

2017-09-01

The 22 Ne (α , n) reaction is a very important neutron source reaction for the slow neutron capture process (s-process) in asymptotic giant branch stars. These direct measurements are very difficult to carry out at the energy regimes of interest for astrophysics (Gamow energies) due to the extremely small reaction cross section. The large uncertainties introduced when extrapolating direct measurements at high energies down to the Gamow energies can be overcome by measuring the Asymptotic Normalization Coefficients (ANC) of the relevant states using α-transfer reactions at sub-Coulomb energies to reduce the optical model dependence. The study of the 22Ne(6Li,d) and 22Ne(7Li,t) reaction was carried out at the Cyclotron Institute at Texas A&M University. The α-ANC measurements for the near α-threshold resonances of 26Mg provide constraints for the 22Ne(α,n) reaction rate. The effect of this reaction rate on the final abundances of the s-process isotopes will be discussed.

Thermonuclear reaction rates. III

International Nuclear Information System (INIS)

Harris, M.J.; Fowler, W.A.; Caughlan, G.R.; Zimmerman, B.A.

1983-01-01

Stellar thermonuclear reaction rates are revised and updated, adding a number of new important reaction rates. Several reactions with large negative Q-values are included, and examples of them are discussed. The importance of the decay rates for Mg-26(p,n) exp 26 Al and Al-26(n,p) exp 26 Mg for stellar studies is emphasized. 19 references

Resonant thermonuclear reaction rate

International Nuclear Information System (INIS)

Haubold, H.J.; Mathai, A.M.

1986-01-01

Basic physical principles for the resonant and nonresonant thermonuclear reaction rates are applied to find their standard representations for nuclear astrophysics. Closed-form representations for the resonant reaction rate are derived in terms of Meijer's G-function. Analytic representations of the resonant and nonresonant nuclear reaction rates are compared and the appearance of Meijer's G-function is discussed in physical terms

Gas-Phase Reaction Pathways and Rate Coefficients for the Dichlorosilane-Hydrogen and Trichlorosilane-Hydrogen Systems

Science.gov (United States)

Dateo, Christopher E.; Walch, Stephen P.

2002-01-01

As part of NASA Ames Research Center's Integrated Process Team on Device/Process Modeling and Nanotechnology our goal is to create/contribute to a gas-phase chemical database for use in modeling microelectronics devices. In particular, we use ab initio methods to determine chemical reaction pathways and to evaluate reaction rate coefficients. Our initial studies concern reactions involved in the dichlorosilane-hydrogen (SiCl2H2--H2) and trichlorosilane-hydrogen (SiCl2H-H2) systems. Reactant, saddle point (transition state), and product geometries and their vibrational harmonic frequencies are determined using the complete-active-space self-consistent-field (CASSCF) electronic structure method with the correlation consistent polarized valence double-zeta basis set (cc-pVDZ). Reaction pathways are constructed by following the imaginary frequency mode of the saddle point to both the reactant and product. Accurate energetics are determined using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations (CCSD(T)) extrapolated to the complete basis set limit. Using the data from the electronic structure calculations, reaction rate coefficients are obtained using conventional and variational transition state and RRKM theories.

[Voluntary alpha-power increasing training impact on the heart rate variability].

Science.gov (United States)

Bazanova, O M; Balioz, N V; Muravleva, K B; Skoraia, M V

2013-01-01

In order to study the effect of the alpha EEG power increasing training at heart rate variability (HRV) as the index of the autonomic regulation of cognitive functions there were follow tasks: (1) to figure out the impact of biofeedback in the voluntary increasing the power in the individual high-frequency alpha-band effect on heart rate variability and related characteristics of cognitive and emotional spheres, (2) to determine the nature of the relationship between alpha activity indices and heart rate variability, depending on the alpha-frequency EEG pattern at rest (3) to examine how the individual alpha frequency EEG pattern is reflected in changes HRV as a result of biofeedback training. Psychometric indicators of cognitive performance, the characteristics of the alpha-EEG activity and heart rate variability (HRV) as LF/HF and pNN50 were recorded in 27 healthy men aged 18-34 years, before, during, and after 10 sessions of training of voluntary increase in alpha power in the individual high-frequency alpha band with eyes closed. To determine the biofeedback effect on the alpha power increasing training, data subjects are compared in 2 groups: experimental (14) with the real and the control group (13 people)--with mock biofeedback. The follow up effect of trainings was studied through month over the 10 training sessions. Results showed that alpha biofeedback training enhanced the fluency and accuracy in cognitive performance, decreased anxiety and frontal EMG, increased resting frequency, width and power in individual upper alpha range only in participants with low baseline alpha frequency. While mock biofeedback increased resting alpha power only in participants with high baseline resting alpha frequency and did change neither cognitive performance, nor HRV indices. Biofeedback training eliminated the alpha power decrease in response to arithmetic task in both with high and low alpha frequency participants and this effect was followed up over the month. Mock

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

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)

{sup 17}O({alpha},{gamma}){sup 21}Ne and {sup 17}O({alpha},n){sup 20}Ne for the weak s process

Energy Technology Data Exchange (ETDEWEB)

Best, A.; Goerres, J.; Beard, M.; Couder, M.; Boer, R. de; Falahat, S.; Gueray, R. T.; Kontos, A.; Kratz, K.-L.; LeBlanc, P. J.; Li, Q.; O' Brien, S.; Oezkan, N.; Pignatari, M.; Sonnabend, K.; Talwar, R.; Tan, W.; Uberseder, E.; Wiescher, M. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States) and Department for Biogeochemistry, Max-Planck-Institute for Chemistry, 55020 Mainz (Germany); Department of Physics, Kacaeli University, Umuttepe 41380, Kocaeli (Turkey); Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Department for Biogeochemistry, Max-Planck-Institute for Chemistry, 55020 Mainz (Germany); Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Physics, Kacaeli University, Umuttepe 41380, Kocaeli (Turkey); Department of Physics, University of Basel, Basel 4056 (Switzerland); Institute for Applied Physics, Goethe-University Frankfurt, 60325 Frankfurt (Germany); Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)

2012-11-20

The ratio of the reaction rates of the competing channels {sup 17}O({alpha}{gamma}){sup 21}Ne and {sup 17}O({alpha},n){sup 20}Ne determines the efficiency of {sup 16}O as a neutron poison in the s process in low metallicity rotating stars. It has a large impact on the element production, either producing elements to the mass range of A=90 in case of a significant poisoning effect or extending the mass range up to the region of A=150 if the {gamma} channel is of negligible strength. We present an improved study of the reaction {sup 17}O({alpha},n){sup 20}Ne, including an independent measurement of the {sup 17}O({alpha},n{sub 1}){sup 20}Ne channel. A simultaneous R-Matrix fit to both the n{sub 0} and the n{sub 1} channels has been performed. New reaction rates, including recent data on the {sup 17}O({alpha},{gamma}){sup 21}Ne reaction, have been calculated and used as input for stellar network calculations and their impact on the s process in rotating massive stars is discussed.

Evaluation of a second trimester triple marker screening test for fetal status using alpha-fetoprotein (aFP), human chorionic gonadotropin (hCG) and unconjugated estriol (uE3)

International Nuclear Information System (INIS)

Mi, Seong Young; Kim, Jong Ho; Choi, Seung Hun

1997-01-01

Our purpose was to assess the utility of maternal serum triple-marker screening test using alpha-fetoprotein (aFP), human Chorionic Gonadotropin (hCG) and unconjugated Estriol (uE 3 ) for fetal chromosomal abnormalities. 1,767 venous blood samples (4ml) between 15 and 20 week's gestation for maternal serum screening from January to October 1996, were tested with Kodak Amerix-M triple marker radioimmunoassay kits. Risk analysis was achieved with interpretive software such as Alpha (LMS, Kodak Clinical Diagnostics). Marker levels are transformed into multiples of median (MOM), which represent an interpretation of (weight regressed) patient marker levels relative to regressed median levels for stated gestation. By multivariate anaysis, the three MOM values are combined to generate a liklihood ratio. Calculation of a patient, risk is the product of liklihood ratio and age-related risk. Risk assessment is weight for maternal age. The median values of aFP, hCG and uE 3 were well correlated with gestational age, respectively (r=0.94, p=0.003; r=-0.97, p=0.029; r=0.99, p 3 weren't (r=-0.17, p=0.22; r=0.36, p=0.09, respectively). The values of aFP, CG and uE 3 between pregnancy younger than 35 years-old (n=87) and older than that (n=1640) were 51.67±27.44, vs 54.65±126.36, 46.45±30.08 vs 51.33±38.50 and 8.01±11.01 vs 6.68±7.23, respectively but all of them failed to show significant differences. A second-trimester risk for trisomy 21 > or = 1:270 was considered screen positive. Patients were screen positive for trisomy 21 if aFP or 2.1 MOM and E 3 2.5 MOM. The initial screen-positive rate for both Down' syndrome and neural tube defect were 1.46% (26/1767); 0.73% (13/1767) with each other. Among screen positive 26 patients, three and nine were normal karyotype and normal phenotype, respectively and five patients had still births. Reamining 9 patients underwent terminations. In conclusion, compared with the other group's data even in Koreans (Whang et al, and Song et al

Charged-particle thermonuclear reaction rates: II. Tables and graphs of reaction rates and probability density functions

International Nuclear Information System (INIS)

Iliadis, C.; Longland, R.; Champagne, A.E.; Coc, A.; Fitzgerald, R.

2010-01-01

Numerical values of charged-particle thermonuclear reaction rates for nuclei in the A=14 to 40 region are tabulated. The results are obtained using a method, based on Monte Carlo techniques, that has been described in the preceding paper of this issue (Paper I). We present a low rate, median rate and high rate which correspond to the 0.16, 0.50 and 0.84 quantiles, respectively, of the cumulative reaction rate distribution. The meaning of these quantities is in general different from the commonly reported, but statistically meaningless expressions, 'lower limit', 'nominal value' and 'upper limit' of the total reaction rate. In addition, we approximate the Monte Carlo probability density function of the total reaction rate by a lognormal distribution and tabulate the lognormal parameters μ and σ at each temperature. We also provide a quantitative measure (Anderson-Darling test statistic) for the reliability of the lognormal approximation. The user can implement the approximate lognormal reaction rate probability density functions directly in a stellar model code for studies of stellar energy generation and nucleosynthesis. For each reaction, the Monte Carlo reaction rate probability density functions, together with their lognormal approximations, are displayed graphically for selected temperatures in order to provide a visual impression. Our new reaction rates are appropriate for bare nuclei in the laboratory. The nuclear physics input used to derive our reaction rates is presented in the subsequent paper of this issue (Paper III). In the fourth paper of this issue (Paper IV) we compare our new reaction rates to previous results.

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...

Binary Black Hole Mergers from Field Triples: Properties, Rates, and the Impact of Stellar Evolution

Energy Technology Data Exchange (ETDEWEB)

Antonini, Fabio [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astrophysics, Northwestern University, Evanston, IL 60208 (United States); Toonen, Silvia [Astronomical Institute Anton Pannekoek, University of Amsterdam, P.O. Box 94249, 1090 GE, Amsterdam (Netherlands); Hamers, Adrian S. [Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ 08540 (United States)

2017-06-01

We consider the formation of binary black hole (BH) mergers through the evolution of field massive triple stars. In this scenario, favorable conditions for the inspiral of a BH binary are initiated by its gravitational interaction with a distant companion, rather than by a common-envelope phase invoked in standard binary evolution models. We use a code that follows self-consistently the evolution of massive triple stars, combining the secular triple dynamics (Lidov–Kozai cycles) with stellar evolution. After a BH triple is formed, its dynamical evolution is computed using either the orbit-averaged equations of motion, or a high-precision direct integrator for triples with weaker hierarchies for which the secular perturbation theory breaks down. Most BH mergers in our models are produced in the latter non-secular dynamical regime. We derive the properties of the merging binaries and compute a BH merger rate in the range (0.3–1.3) Gpc{sup −3} yr{sup −1}, or up to ≈2.5 Gpc{sup −3} yr{sup −1} if the BH orbital planes have initially random orientation. Finally, we show that BH mergers from the triple channel have significantly higher eccentricities than those formed through the evolution of massive binaries or in dense star clusters. Measured eccentricities could therefore be used to uniquely identify binary mergers formed through the evolution of triple stars. While our results suggest up to ≈10 detections per year with Advanced-LIGO, the high eccentricities could render the merging binaries harder to detect with planned space based interferometers such as LISA.

What Is a Reaction Rate?

Science.gov (United States)

Schmitz, Guy

2005-01-01

The definition of reaction rate is derived and demonstrations are made for the care to be taken while using the term. Reaction rate can be in terms of a reaction property, the extent of reaction and thus it is possible to give a definition applicable in open and closed systems.

Nuclear transfer reaction measurements at the ESR-for the investigation of the astrophysical O-15(alpha,gamma)Ne-19 reaction

NARCIS (Netherlands)

Doherty, D. T.; Woods, P. J.; Litvinov, Yu A.; Najafi, M. Ali; Bagchi, S.; Bishop, S.; Bo, M.; Brandau, C.; Davinson, T.; Dillmann, I.; Estrade, A.; Egelhof, P.; Evdokimov, A.; Gumberidze, A.; Heil, M.; Lederer, C.; Litvinov, S. A.; Lotay, G.; Kalantar-Nayestanaki, N.; Kiselev, O.; Kozhuharov, C.; Kroell, T.; Mahjour-Shafei, M.; Mutterer, M.; Nolden, F.; Petridis, N.; Popp, U.; Reifarth, R.; Rigollet, C.; Roy, S.; Steck, M.; Stoehlker, Th; Streicher, B.; Trotsenko, S.; von Schmid, M.; Yan, X. L.; Zamora, J. C.

2015-01-01

Astrophysical x-ray bursts are thought to be a result of thermonuclear explosions on the atmosphere of an accreting neutron star. Between these bursts, energy is thought to be generated by the hot CNO cycles. The O-15(alpha,gamma)Ne-19 reaction is one reaction that allows breakout from these CNO

Nuclear transfer reaction measurements at the ESR-for the investigation of the astrophysical O-15(alpha,gamma)Ne-19 reaction

NARCIS (Netherlands)

Doherty, D. T.; Woods, P. J.; Litvinov, Yu A.; Najafi, M. Ali; Bagchi, S.; Bishop, S.; Bo, M.; Brandau, C.; Davinson, T.; Dillmann, I.; Estrade, A.; Egelhof, P.; Evdokimov, A.; Gumberidze, A.; Heil, M.; Lederer, C.; Litvinov, S. A.; Lotay, G.; Kalantar-Nayestanaki, N.; Kiselev, O.; Kozhuharov, C.; Kroell, T.; Mahjour-Shafei, M.; Mutterer, M.; Nolden, F.; Petridis, N.; Popp, U.; Reifarth, R.; Rigollet, C.; Roy, S.; Steck, M.; Stoehlker, Th; Streicher, B.; Trotsenko, S.; von Schmid, M.; Yan, X. L.; Zamora, J. C.

Astrophysical x-ray bursts are thought to be a result of thermonuclear explosions on the atmosphere of an accreting neutron star. Between these bursts, energy is thought to be generated by the hot CNO cycles. The O-15(alpha,gamma)Ne-19 reaction is one reaction that allows breakout from these CNO

Astrophysical reaction rate for α(αn,γ)9Be by photodisintegration

International Nuclear Information System (INIS)

Sumiyoshi, K.; Utsunomiya, H.; Goko, S.; Kajino, T.

2002-01-01

We study the astrophysical reaction rate for the formation of 9 Be through the three body reaction α(αn,γ). This reaction is one of the key reactions which could bridge the mass gap at A=8 nuclear systems to produce intermediate-to-heavy mass elements in alpha- and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable 8 Be, α+α[rlhar2] 8 Be(n,γ) 9 Be. Off-resonant and on-resonant contributions from the ground state in 8 Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of 9 Be with laser-electron photon beams, which covers all relevant resonances in 9 Be. Experimental data near the neutron threshold are added with γ-ray flux corrections and a new least-squares analysis is made to deduce resonance parameters in the Breit-Wigner formulation. Based on the photodisintegration cross section, we provide the reaction rate for α(αn,γ) 9 Be in the temperature range from T 9 =10 -3 to T 9 =10 1 (T 9 is the temperature in units of 10 9 K) both in the tabular form and in the analytical form for potential usage in nuclear reaction network calculations. The calculated reaction rate is compared with the reaction rates of the CF88 and the NACRE compilations. The CF88 rate, which is based on the photoneutron cross section for the 1/2 + state in 9 Be by Berman et al., is valid at T 9 >0.028 due to lack of the off-resonant contribution. The CF88 rate differs from the present rate by a factor of two in a temperature range T 9 ≥0.1. The NACRE rate, which adopted different sources of experimental information on resonance states in 9 Be, is 4-12 times

Nonlinear triple-point problems on time scales

Directory of Open Access Journals (Sweden)

Douglas R. Anderson

2004-04-01

Full Text Available We establish the existence of multiple positive solutions to the nonlinear second-order triple-point boundary-value problem on time scales, $$displaylines{ u^{Delta abla}(t+h(tf(t,u(t=0, cr u(a=alpha u(b+delta u^Delta(a,quad eta u(c+gamma u^Delta(c=0 }$$ for $tin[a,c]subsetmathbb{T}$, where $mathbb{T}$ is a time scale, $eta, gamma, deltage 0$ with $Beta+gamma>0$, $0<alpha

Secondary isotope effects on alpha-cleavage reactions

International Nuclear Information System (INIS)

Ingemann, S.; Hammerum, S.

1980-01-01

Kinetic deuterium isotope effects on mass spectral reactions have in several instances been utilized to provide structural information and to answer mechanistic questions. Typically, the influence of the deuterium label on the rate of one of a number of competing reactions has been studied. Secondary isotope effects have usually been assumed to be relatively insignificant in comparison with the observed kinetic effects, even though various workers have shown that secondary isotope effects may indeed exert a considerable influence on the rates of competing simple cleavages. Recent studies have provided quantitative data to show that the mere presence of deuterium atoms up to six bonds away may influence the rate of a simple cleavage reaction. In relation to an investigation of rearrangements accompanying simple cleavage reactions, a semi-quantitative measure was needed of the variation of the secondary isotope effect with the number of bonds between the deuterium label and the point of rupture. The influence has therefore been examined of the presence of remote deuterium atoms on a typical simple cleavage reaction, the α-cleavage of aliphatic amines. As a model compound, N-methyldipentylamine was chosen, systematically labelled with deuterium. (author)

Mechanisms of the p(He 6,He 5)d, p(He 6,{alpha})t and p(He 6,t){alpha} reactions

Energy Technology Data Exchange (ETDEWEB)

Heiberg-Andersen, Henning

2002-07-01

This work was devoted to nucleon induced transfer reactions having the potential to probe the sub-cluster structures of the benchmark halo nucleus He 6, without the question marks the necessarily omitted exchange effects tend to put behind the CRC results when both collision partners are composite systems. Still, the exchange complications entered the analysis in an ironic way: The high Q-value of the p(He 6,{alpha})t and p(He 6, t){alpha} reactions caused sensitivity to the t - {alpha} optical potential at small radii, where the one-nucleon exchange effects are strongest. Since the attempt to throw them out of the extracted tau - {alpha} potential failed, it was necessary to extend the model space to avoid a too difficult modelling of the local equivalent t - {alpha} potential. By this step, all the complications originating from antisymmetrization within a larger model space entered the analysis. However, the persistent failures of the two-channel calculations of this and previous works can hardly be due to incorrect treatment of exchange effects only, so the loss of simplicity is probably illusory. Even at small angles, where the surface processes dominate, none of the two-channel calculations with various choices of t - {alpha} optical potentials managed to reproduce the p(He 6, {alpha})t (p(He 6,t){alpha}) data. This motivated inclusion of sequential transfers through the d + He 5 channel, where the sequential triton transfer process, included just for consistency in the coupling scheme of the four-channel calculation, turned out to be more influent than expected. The satisfactory reproduction of both the p(He 6, He 5)d and the p(He 6,{alpha})t (p(He 6,t){alpha}) data by the four-channel approach and the required re-normalization the real part of the p - He 6 optical potential are strong indications of substantial contributions from sequential transfer of the halo neutrons at this energy. The conclusions that can be drawn from this work are limited by the

Applications of Reaction Rate

Science.gov (United States)

Cunningham, Kevin

2007-01-01

This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…

The 65 keV resonance in the {sup 17}O(p,alpha){sup 14}N thermonuclear reaction

Energy Technology Data Exchange (ETDEWEB)

Sergi, M.L. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Spitaleri, C. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Coc, A. [CSNSM, UMR 8609, CNRS/IN2P3and Universite Paris Sud 11, Batiment 104, 91405 Orsay Campus (France); Mukhamedzhanov, A. [Cyclotron Institute, Texas A and M University, College Station, TX 77843 (United States); Burjan, S.V. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); Gulino, M. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Hammache, F. [IPN, IN2P3-CNRS et Universite de Paris-Sud 11, 91406 Orsay Cedex (France); Hons, Z. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); Irgaziev, B. [GIK Institute of Engineering Sciences and Technology Topi District Swabi NWFP (Pakistan); Kiss, G.G. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Kroha, V. [Nuclear Physics Institute of ASCR Rez near Prague (Czech Republic); La Cognata, M. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Lamia, L.; Pizzone, R.G. [Laboratori Nazionali del Sud, Catania (Italy); Dipartimento di Metodologie Fisiche e Chimiche per l' Ingegneria, Universita di Catania, Catania (Italy); Sereville, N. de [IPN, IN2P3-CNRS et Universite de Paris-Sud 11, 91406 Orsay Cedex (France); Somorjai, E. [ATOMKI, Debrecen (Hungary)

2010-03-01

The indirect measurement of {sup 17}O(p,alpha){sup 14}N cross section was performed by means of the Trojan Horse Method. This approach allowed to investigate the ultra-low energy range (E{sub c.m.}=0-300 keV) relevant for several astrophysics environments, where two resonant levels of {sup 18}F at E{sub c.m.}{sup R}=65 keV and E{sub c.m.}{sup R}=183 keV play a significant role in the reaction rate determination.

Determination of alpha dose rate profile at the HLW nuclear glass/water interface

Energy Technology Data Exchange (ETDEWEB)

Mougnaud, S., E-mail: sarah.mougnaud@cea.fr [CEA Marcoule, DEN/DTCD/SECM, BP 17171, 30207 Bagnols-sur-Cèze cedex (France); Tribet, M.; Rolland, S. [CEA Marcoule, DEN/DTCD/SECM, BP 17171, 30207 Bagnols-sur-Cèze cedex (France); Renault, J.-P. [CEA Saclay, NIMBE UMR 3685 CEA/CNRS, 91191 Gif-sur-Yvette cedex (France); Jégou, C. [CEA Marcoule, DEN/DTCD/SECM, BP 17171, 30207 Bagnols-sur-Cèze cedex (France)

2015-07-15

Highlights: • The nuclear glass/water interface is studied. • The way the energy of alpha particles is deposited is modeled using MCNPX code. • A model giving dose rate profiles at the interface using intrinsic data is proposed. • Bulk dose rate is a majoring estimation in alteration layer and in surrounding water. • Dose rate is high in small cracks; in larger ones irradiated volume is negligible. - Abstract: Alpha irradiation and radiolysis can affect the alteration behavior of High Level Waste (HLW) nuclear glasses. In this study, the way the energy of alpha particles, emitted by a typical HLW glass, is deposited in water at the glass/water interface is investigated, with the aim of better characterizing the dose deposition at the glass/water interface during water-induced leaching mechanisms. A simplified chemical composition was considered for the nuclear glass under study, wherein the dose rate is about 140 Gy/h. The MCNPX calculation code was used to calculate alpha dose rate and alpha particle flux profiles at the glass/water interface in different systems: a single glass grain in water, a glass powder in water and a water-filled ideal crack in a glass package. Dose rate decreases within glass and in water as distance to the center of the grain increases. A general model has been proposed to fit a dose rate profile in water and in glass from values for dose rate in glass bulk, alpha range in water and linear energy transfer considerations. The glass powder simulation showed that there was systematic overlapping of radiation fields for neighboring glass grains, but the water dose rate always remained lower than the bulk value. Finally, for typical ideal cracks in a glass matrix, an overlapping of irradiation fields was observed while the crack aperture was lower than twice the alpha range in water. This led to significant values for the alpha dose rate within the crack volume, as long as the aperture remained lower than 60 μm.

An optimized clarithromycin-free 14-day triple therapy for Helicobacter pylori eradication achieves high cure rates in Uruguay.

Science.gov (United States)

Dacoll, Cristina; Sánchez-Delgado, Jordi; Balter, Henia; Pazos, Ximena; Di Pace, María; Sandoya, Gabriela; Cohen, Henry; Calvet, Xavier

Strong acid inhibition increases cure rates with triple therapy and 14-day are more effective than 7-day treatments. The combination of amoxicillin plus metronidazole at full doses has been shown to overcome metronidazole resistance and to achieve good eradication rates even in patients harboring resistant strains. No previous studies have been reported in Latin-America with this optimized triple-therapy scheme. The aim of the present study was to assess the eradication rate and tolerance of a new first-line treatment regimen associating strong acid inhibition, amoxicillin and metronidazole. Patients from the Clínica de Gastroenterología of the Hospital de Clínicas (Montevideo, Uruguay) were included. Hp status was mainly assessed by at least one of the following: histologyor urea breath test (UBT). A 14-day treatment was prescribed comprising esomeprazole 40mg twice a day plus amoxicillin 1g and metronidazole 500mg, both three times a day. H. pylori cure was assessed by UBT. Forty-one patients were enrolled. Mean age was 53.3±13 years and 17.1% of patients were male. Main indications for treatment were: functional dyspepsia (27.5%), gastritis (45%), gastric or duodenal erosions (20%), gastric ulcer (5%) and intestinal metaplasia (2.5%). H. pylori eradication was achieved in 33 of the 37 patients who returned for follow-up. Eradication rates were 80.5% (95% CI: 68.4-92.6) by intention-to-treat (ITT) analysis and 89.2% (95% CI; 79.2-99.2) per protocol (PP). No major side effects were reported; 26 patients (65.8%) complained of mild side effects (nausea, diarrhea and headache). Cure rates of this triple therapy including esomeprazole, amoxicillin and metronidazole were 81% per ITT and the treatment was well tolerated. These optimal results with a simple clarithromycin-free triple therapy are better than described for standard triple therapy but there is still room for improvement to reach the desired target of 90% per ITT. Copyright © 2017 Elsevier España, S

Reconstruction of spin-tensor of 4. 43 MeV state density matrix of the /sup 12/C nucleus in the /sup 12/C(. cap alpha. ,. cap alpha. sub(1). gamma. sub(4,43))/sup 12/C reaction at Esub(. cap alpha. )=25 MeV

Energy Technology Data Exchange (ETDEWEB)

Gurevich, G.S.; Lebedev, V.M.; Orlova, N.V.; Spasskij, A.V.; Teplov, I.B.; Shakhvorostova, G.V.; Belkina, M.R. (Moskovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Yadernoj Fiziki)

1984-01-01

The results of measuring double differential cross sections of the reaction of inelastic scattering 24.8 MeV ..cap alpha..-particles sup(12)C(..cap alpha.., ..cap alpha..sub(1)..gamma..sub(4.43))sup(12)C in different planes of ..gamma..-quantum escape relatively to the plane of the reaction phisub(..gamma..)=30, 60 and 90 deg are presented. Non-monochromaticity of the beam made up 1%. Functions of angular correlation of the reaction are measured for four angles THETAsub(..cap alpha..)=21, 39, 59 and 135 deg corresponding to maxima of differential cross section in angular distribution of inelastically scattered ..cap alpha..-particles and for THETAsub(..cap alpha..)=89 deg corresponding to the minimum of angular distribution. The results of measurements permit to reconstruct all the components of irreducible spin-tensors of the matrix of state density 4.43 MeV (2/sup +/) formed in this reaction. The values of populations of substates by the projection of the spin of this state are obtained. The analysis of the obtained results testify to the fact that mechanism of inelastic scattering is not reduced to impulse approximation and mechanisms associated with delay in interaction do not make noticeable contribution for the given angles of ..cap alpha..-particle escape.

Pre-equilibrium decay process in alpha particle induced reactions on thulium and tantalum

International Nuclear Information System (INIS)

Mohan, Rao, A.V.; Chintalapudi, S.N.

1994-01-01

Alpha particle induced reactions on the target elements Thulium and Tantalum were investigated upto 60 MeV using stacked foil activation technique and Ge(Li) gamma ray spectroscopy method. Excitation functions for six reactions of 169 Tm(α,xn); x=1-4 and 181 Ta(α,xn); x=2,4 were studied. The experimental results were compared with the updated version of Hybrid model (ALICE/90) using initial exciton configuration n 0 =4(4pOh). A general agreement was found for all the reactions with this option. (author)

Investigation of (n, p) and (n, alpha) reactions with thermal and resonance energy neutrons

CERN Document Server

Gledenov, Yu M

2002-01-01

Influence of results of (n, alpha) and (n, p) reactions cross section and asymmetry measurements on certain branches of fundamental and applied science is considered. For instance, some of the cross sections are critical for comprehension of many scenarios of nuclear synthesis in the Universe. They are also used for studying some aspects of nuclear structure and fundamental symmetries, such as mixing of isospin and non-retaining of spatial parity. And, finally, cross sections of the reactions are of applied interest, for reactor materials technologies specifically. Types of sources and methods of (n, p) and (n, alpha) reactions measurements in energy range of thermal and resonance neutrons are described in the review. Special attention is paid to measurements in radioactive relatively short-lived samples and very small stable samples. Several examples of the measurements are provided, which are of scientific interest, as they permit demonstrating the method used. Possible future measurements are discussed in ...

Levels in {sup 227}Ac populated in the {sup 230}Th(p,{alpha}) reaction

Energy Technology Data Exchange (ETDEWEB)

Burke, D.G. E-mail: dgb@physics.mcmaster.ca; Garrett, P.E.; Qu, Tao

2003-09-08

The {sup 230,232}Th(p,{alpha}){sup 227,229}Ac reactions were studied using 20 MeV protons and a magnetic spectrograph to analyze the reaction products. Relative populations of levels in {sup 229}Ac correlated well with previously published (t,{alpha}) results for the same final levels, showing that the similarity of the two reactions observed empirically in the deformed rare earth region extends to actinides. The most strongly populated level in {sup 227}Ac is at 639 keV, and is assigned as the 1/2{sup +}[4 0 0] bandhead. The 435 keV level, previously adopted as the 1/2{sup +}[6 6 0] bandhead, also has a significant intensity that is attributed to {delta}N=2 mixing between these two K=1/2 proton orbitals. The {delta}N=2 matrix element estimated from these data is {approx}80 keV, similar to values observed for the same two Nilsson states as neutron orbitals in the dysprosium isotopes.

Alpha cluster states in light nuclei populated through the (6Li,d) reaction

International Nuclear Information System (INIS)

Borello-Lewin, Thereza; Rodrigues, M.R.D.; Horodynski-Matsushigue, L.B.; Duarte, J.L.M.; Rodrigues, C.L.; Souza, M.A.; Cunsolo, A.; Cappuzzello, F.; Ukita, Gilberto Mitsuo

2011-01-01

Full text: The alpha cluster correlation is an important concept in the nuclear physics of light nuclei. The main purpose of the research program in progress is the investigation of the alpha clustering phenomenon in (xα) and(xα+ν) nuclei through the ( 6 Li,d) alpha transfer reaction. In fact, there is scarce experimental information on the subject, in particular associated with resonant states predicted near (xα) and (xα+ν) thresholds. Measurements of the 12 , 13 C( 6 Li,d) 16 , 17 O reactions, at an incident energy of 25.5 MeV, have been performed employing the Sao Paulo Pelletron-Enge Split-Pole facility and the nuclear emulsion detection technique. The work is under way and an experimental energy resolution of 30 keV was obtained. Near the (4α) breakup threshold in 16 O, three narrow alpha resonances, not previously measured, were detected, revealing important α + 12 C(G.S.) components. One of these resonances corresponds to the known 0 + state at 15.1 MeV[5] of excitation that has probably, according to Funaki et al., the gas like configuration of the 4α condensate state, with a very dilute density and a large component of α + 12 C(Hoyle) configuration. As was already mentioned, our experimental information points to the necessity of including the α + 12 C(G.S.) component in the wave function. (author)

Reaction rate of propene pyrolysis.

Science.gov (United States)

Han, Peipei; Su, Kehe; Liu, Yan; Wang, Yanli; Wang, Xin; Zeng, Qingfeng; Cheng, Laifei; Zhang, Litong

2011-10-01

The reaction rate of propene pyrolysis was investigated based on the elementary reactions proposed in Qu et al., J Comput Chem 2009, 31, 1421. The overall reaction rate was developed with the steady-state approximation and the rate constants of the elementary reactions were determined with the variational transition state theory. For the elementary reaction having transition state, the vibrational frequencies of the selected points along the minimum energy path were calculated with density functional theory at B3PW91/6-311G(d,p) level and the energies were improved with the accurate model chemistry method G3(MP2). For the elementary reaction without transition state, the frequencies were calculated with CASSCF/6-311G(d,p) and the energies were refined with the multireference configuration interaction method MRCISD/6-311G(d,p). The rate constants were evaluated within 200-2000 K and the fitted three-parameter expressions were obtained. The results are consistent with those in the literatures in most cases. For the overall rate, it was found that the logarithm of the rate and the reciprocal temperature have excellent linear relationship above 400 K, predicting that the rate follows a typical first-order law at high temperatures of 800-2000 K, which is also consistent with the experiments. The apparent activation energy in 800-2000 K is 317.3 kJ/mol from the potential energy surface of zero Kelvin. This value is comparable with the energy barriers, 365.4 and 403.7 kJ/mol, of the rate control steps. However, the apparent activation energy, 215.7 kJ/mol, developed with the Gibbs free energy surface at 1200 K is consistent with the most recent experimental result 201.9 ± 0.6 kJ/mol. Copyright © 2011 Wiley Periodicals, Inc.

Double differential cross-sections of (n,{alpha}) reactions in aluminium and nickel at 14.77 MeV neutrons

Energy Technology Data Exchange (ETDEWEB)

Lalremruata, B.; Dhole, S.D. [Department of Physics, University of Pune, Pune-411007 (India); Ganesan, S. [Reactor Physics Design Division, BARC, Mumbai-400085 (India); Bhoraskar, V.N. [Department of Physics, University of Pune, Pune-411007 (India)], E-mail: vnb@physics.unipune.ernet.in

2009-04-15

The double differential cross-sections (DDX) for the emission of alpha particles from {sup 27}Al(n,{alpha}){sup 24}Na and Ni(n,{alpha}) reactions induced by 14.77 MeV neutrons were estimated from the alpha particle spectra recorded at 30 deg., 50 deg., 90 deg., 110 deg. angles for aluminium, and at 20 deg., 45 deg., 90 deg., 110 deg. for natural nickel. The results indicate that the alpha particles below and around the most probable energies ({approx}6.3 MeV from aluminium and {approx}8 MeV from natural nickel) are emitted predominantly through the compound nucleus formation process, and the higher energy alpha particles are emitted through the pre-equilibrium or the direct reaction. In general, the measured double-differential cross-sections are in agreement with the theoretical cross-sections estimated using Talys-1.0 and Preco2007 computer programs. The present value of the level density parameter for {sup 24}Na is close to the literature value and, therefore, these results reveal consistency in the alpha particle spectra recorded with a single silicon surface barrier detector at different scattering angles.

Reaction rate of hydrolysis of iodine

International Nuclear Information System (INIS)

Miyake, Yoshikazu; Eguchi, Wataru; Adachi, Motonari

1979-01-01

Absorption rates of dilute iodine vapor contained in air by aqueous mixtures of sodium hydroxide and boric acid were measured using a laminar liquid jet column absorber at 298 K. Absorption rates in this system are controlled by a series of complex reactions taking place in the liquid phase. The reaction rate constant of iodine hydrolysis in the aqueous phase was determined from the absorption rates observed under the conditions that the base-catalytic hydrolysis reaction of iodine can be considered to be irreversible and that other reactions can be neglected. The absorption rates calculated theoretically with the rate constant value obtained above were in good accordance with the whole experimental data observed for a wide range of experimental conditions. (author)

Transition-state structure in the yeast alcohol dehydrogenase reaction: the magnitude of solvent and alpha-secondary hydrogen isotope effects

International Nuclear Information System (INIS)

Welsh, K.M.; Creighton, D.J.; Klinman, J.P.

1980-01-01

Solvent and alpha-secondary isotope effects have been measured in the yeast alcohol dehydrogenase reaction, under conditions of a rate-limiting transfer of hydrogen between coenzyme and substrate. Determination of catalytic constants in H20 and D20 as a function of pH(D) has allowed the separation of solvent effects on pKa from kcat. The small effect of D20 on pKa is tentatively assigned to ionization of an active-site ZnOH 2 . The near absence of an isotope effect on kcat in the direction of alcohol oxidation rules out a mechanism involving concerted catalysis by an active-site base of hydride transfer. The near identity of kinetic and equilibrium alpha-secondary isotope effects in the direction of alcohol oxidation implicates a transition-state structure which resembles aldehyde with regard to bond hybridization properties. The result contrasts sharply with previously reported structure - reactivity correlations, which implicate a transition-state structure resembling alcohol with regard to charge properties. The significance of these findings to the mechanism of NAD(P)H-dependent redox reactions is discussed

High-yield acetonitrile | water triple phase boundary electrolysis at platinised Teflon electrodes

Energy Technology Data Exchange (ETDEWEB)

Watkins, John D.; MacDonald, Stuart M.; Fordred, Paul S.; Bull, Steven D. [Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Gu, Yunfeng; Yunus, Kamran; Fisher, Adrian C. [Department of Chemical Engineering, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB2 3RA (United Kingdom); Bulman-Page, Philip C. [School of Chemistry, University of East Anglia, Norwich, Norfolk NR4 7TJ (United Kingdom); Marken, Frank [Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)], E-mail: f.marken@bath.ac.uk

2009-11-30

A dynamic acetonitrile | aqueous electrolyte phase boundary in contact with platinised Teflon working electrodes is investigated. High concentrations of salt in the aqueous phase (2 M NaCl and 0.1 M NaClO{sub 4}) ensure immiscibility and the polar nature of acetonitrile aids the formation of a well-behaved triple phase boundary reaction zone. The one-electron oxidation of tert-butylferrocene in the organic phase without intentionally added electrolyte is studied. The limiting current for the flowing triple phase boundary process is shown to be essentially volume flow rate independent. The process is accompanied by the transfer of perchlorate from the aqueous into the organic phase and the flux of anions is shown to be approximately constant along the dynamic acetonitrile | aqueous electrolyte | platinum line interface. A high rate of conversion (close to 100%) is achieved at slow volume flow rates and at longer platinum electrodes.

Surface reaction rate and probability of ozone and alpha-terpineol on glass, polyvinyl chloride, and latex paint surfaces.

Science.gov (United States)

Shu, Shi; Morrison, Glenn C

2011-05-15

Ozone can react homogeneously with unsaturated organic compounds in buildings to generate undesirable products. However, these reactions can also occur on indoor surfaces, especially for low-volatility organics. Conversion rates of ozone with α-terpineol, a representative low-volatility compound, were quantified on surfaces that mimic indoor substrates. Rates were measured for α-terpineol adsorbed to beads of glass, polyvinylchloride (PVC), and dry latex paint, in a plug flow reactor. A newly defined second-order surface reaction rate coefficient, k(2), was derived from the flow reactor model. The value of k(2) ranged from 0.68 × 10(-14) cm(4)s(-1)molecule(-1) for α-terpineol adsorbed to PVC to 3.17 × 10(-14) cm(4)s(-1)molecule(-1) for glass, but was insensitive to relative humidity. Further, k(2) is only weakly influenced by the adsorbed mass but instead appears to be more strongly related to the interfacial activity α-terpineol. The minimum reaction probability ranged from 3.79 × 10(-6) for glass at 20% RH to 6.75 × 10(-5) for PVC at 50% RH. The combination of high equilibrium surface coverage and high reactivity for α-terpineol suggests that surface conversion rates are fast enough to compete with or even overwhelm other removal mechanisms in buildings such as gas-phase conversion and air exchange.

The reaction 32S(d,alpha)30P

International Nuclear Information System (INIS)

Lawrie, J.J.

1979-03-01

Cross sections for the reaction 32 S(d,alpha) 30 P were measured at an average deuteron energy of about 6 MeV over deuteron energy ranges of about 200 - 400 KeV with steps of 15 KeV and at laboratory angles of 90 degrees, 112 degrees, 125 degrees, 133 degrees, 137 degrees, 141 degrees, 148 degrees, 155 degrees and 175,5 degrees. The range of excitation pertaining to the study, extended to the 23rd excited state at 4,73 MeV in 30 P. The observed cross section fluctuations in the excitation functions are indicative of the statistical nature of the reaction. A coherence width of 43 plus minus 4 keV was obtained for the compound nucleus 34 Cl at 17,2 MeV excitation from fluctuation analyses for states up to the 7th excited level at 2,84 MeV in 30 P. By contrast the coherence width for the isospin forbidden transition to the T = 1 excited state at 2,94 MeV in 30 P was found to be 34 plus minus 6 keV. This difference can be accounted for in terms of isospin mixing in the compound nucleus. Spins of excited states in 30 P were determined by comparing experimental cross sections with Hauser-Feshbach predictions. The most probable spin values obtained from this study are: 1 + for the 10th (3,73 MeV),2 + for the 11th (3,83 MeV),3 + for the 12th (3,93 MeV),0 + for the 16th (4,235 MeV) and 1 + for the 23rd excited state at 4,73 MeV in 30 P. From the assumption that the spin of the 17th excited state (4,30 MeV) is 2 - , spin possibilities of 2 + , 3 - and 4 + could be deduced for the 18th excited state (4,34 MeV). An inhibition factor of 0,41 plus minus 0,06 for the isospin forbidden reaction 32 S(d,alpha) 30 P has been obtained and corresponds to a value of = 18 keV for the compound nucleus 34 Cl at 17,2 MeV excitation

Contribution to the study of the reaction p + {sup 11}B = 3 {alpha} by the coincidence method; Contribution a l'etude de la reaction p + {sup 11}B = 3 {alpha} par la methode des coincidences

Energy Technology Data Exchange (ETDEWEB)

Laugier, J Ph [Commissariat a l' Energie Atomique, Bruyeres-le-Chatel (France). Centre d' Etudes

1969-07-01

We have studied the production mode of the 3 {alpha} system in the reaction p + {sup 11}B = {sup 12}C{sup *} = {alpha} + {sup 8}Be{sup *}; {sup 8}Be{sup *} = {alpha} + {alpha}. We have got some information for three different effects: the influence of the {sup 8}Be residual nucleus states = sequential decay; the influence of the {sup 12}C compound nucleus states = spin effect; an interference effect. We give a theoretical expression of the different spectra which take into account the observed phenomena. We have taken, as a parameter, the phase shift, between the waves associated with the detected particles, which produce the interference effect. The main characteristics of the experimental devices are : self supporting boron targets; cooled semiconductor detectors; multi-parametric system: for each nuclear event three parameters are recorded: the energies of the detected particles and the time of the detection; Recording system: the information are recorded on a magnetic tape and at the same time treated with an on line CAE 510 computer. The CAE 510 computer is used in delayed time to analyse the experimental data. (author) [French] Nous avons etudie le mecanisme de production du systeme 3 {alpha} dans la reaction: p + {sup 11}B = {sup 12}C{sup *} = {alpha} + {sup 8}Be{sup *}; {sup 8}Be{sup *} = {alpha} + {alpha}. Cette etude nous a permis de mettre en evidence trois effets de nature differente: l'effet des niveaux du noyau intermediaire {sup 8}Be reaction sequentielle; l'effet des niveaux du noyau compose {sup 12}C = effet de spin; -un effet d'interferences. Nous avons pu donner une expression theorique du spectre, rendant compte d'une facon satisfaisante des phenomenes observes. Pour cela nous avons considere le dephasage, entre les ondes associees aux particules detectees, qui produit les interferences, comme un parametre arbitraire. Du point de vue experimental les caracteristiques principales du materiel utilise sont les suivantes: utilisation de cibles de

Age/race differences in HER2 testing and in incidence rates for breast cancer triple subtypes: a population-based study and first report.

Science.gov (United States)

Lund, Mary Jo; Butler, Ebonee N; Hair, Brionna Y; Ward, Kevin C; Andrews, Judy H; Oprea-Ilies, Gabriella; Bayakly, A Rana; O'Regan, Ruth M; Vertino, Paula M; Eley, J William

2010-06-01

Although US year 2000 guidelines recommended characterizing breast cancers by human epidermal growth factor receptor 2 (HER2), national cancer registries do not collect HER2, rendering a population-based understanding of HER2 and clinical "triple subtypes" (estrogen receptor [ER] / progesterone receptor [PR] / HER2) largely unknown. We document the population-based prevalence of HER2 testing / status, triple subtypes and present the first report of subtype incidence rates. Medical records were searched for HER2 on 1842 metropolitan Atlanta females diagnosed with breast cancer during 2003-2004. HER2 testing/status and triple subtypes were analyzed by age, race/ethnicity, tumor factors, socioeconomic status, and treatment. Age-adjusted incidence rates were calculated. Over 90% of cases received HER2 testing: 12.6% were positive, 71.7% negative, and 15.7% unknown. HER2 testing compliance was significantly better for women who were younger, of Caucasian or African-American descent, or diagnosed with early stage disease. Incidence rates (per 100,000) were 21.1 for HER2+ tumors and 27.8 for triple-negative tumors, the latter differing by race (36.3 and 19.4 for black and white women, respectively). HER2 recommendations are not uniformly adhered to. Incidence rates for breast cancer triple subtypes differ by age/race. As biologic knowledge is translated into the clinical setting eg, HER2 as a biomarker, it will be incumbent upon national cancer registries to report this information. Incidence rates cautiously extrapolate to an annual burden of 3000 and 17,000 HER2+ tumors for black and white women, respectively, and triple-negative tumors among 5000 and 16,000 respectively. Testing, rate, and burden variations warrant population-based in-depth exploration and clinical translation. (c) 2010 American Cancer Society.

Temperature effects on lithium-nitrogen reaction rates

International Nuclear Information System (INIS)

Ijams, W.J.; Kazimi, M.S.

1985-08-01

A series of experiments have been run with the aim of measuring the reaction rate of lithium and nitrogen over a wide spectrum of lithium pool temperatures. In these experiments, pure nitrogen was blown at a controlled flow rate over a preheated lithium pool. The pool had a surface area of approximately 4 cm 2 and a total volume of approximately 6 cm 3 . The system pressure varied from 0 to 4 psig. The reaction rate was very small - approximately 0.002 to 0.003 g Li min cm 2 for lithium temperatures below 500 0 C. Above 500 0 C the reaction rate began to increase sharply, and reached a maximum of approximately 0.80 g Li min cm 2 above 700 0 C. It dropped off beyond 1000 0 C and seemed to approach zero at 1150 0 C. The maximum reaction rate observed in these forced convection experiments was higher by 60% than those previously observed in experiments where the nitrogen flowed to the reaction site by means of natural convection. During a reaction, a hard nitride layer built up on the surface of the lithium pool - its effect on the reaction rate was observed. The effect of the nitrogen flow rate on the reaction rate was also observed

Determination of alpha-dose rates and chronostratigraphical study of travertine samples

International Nuclear Information System (INIS)

Oufni, L.; University Moulay Ismail, Errachidia; Misdaq, M.A.; Boudad, L.; Kabiri, L.

2001-01-01

Uranium and thorium contents in different layers of stratigraphical sedimentary deposits have been evaluated by using LR-115 type II and CR-39 solid state nuclear track detectors (SSNTD). A method has been developed for determining the alpha-dose rates of the sedimentary travertine samples. Using the U/Th dating method, we succeeded in age dating carbonated level sampled in the sedimentary deposits. Correlation between the stratigraphy, alpha-dose rates and age has been investigated. (author)

Measurement of inertial confinement fusion reaction rate

International Nuclear Information System (INIS)

Peng Xiaoshi; Wang Feng; Tang Daorun; Liu Shenye; Huang Tianxuan; Liu Yonggang; Xu Tao; Chen Ming; Mei Yu

2011-01-01

Fusion reaction rate is an important parameter for measuring compression during the implosion in inertial confinement fusion experiment. We have developed a system for fusion reaction history measurement with high temporal resolution. The system is composed of plastic scintillator and nose cone, optical system and streak camera. We have applied this system on the SG-III prototype for fusion reaction rate measuring. For the first time, fusion reaction rate history have been measured for deuterium-tritium filled targets with neutrons yields about 10 10 . We have analyzed possible influence factor during fusion reaction rate measuring. It indicates that the instrument measures fusion reaction bang time at temporal resolutions as low as 30 ps.(authors)

1H NMR studies of substrate hydrogen exchange reactions catalyzed by L-methionine gamma-lyase

International Nuclear Information System (INIS)

Esaki, N.; Nakayama, T.; Sawada, S.; Tanaka, H.; Soda, K.

1985-01-01

Hydrogen exchange reactions of various L-amino acids catalyzed by L-methionine gamma-lyase (EC 4.4.1.11) have been studied. The enzyme catalyzes the rapid exchange of the alpha- and beta-hydrogens of L-methionine and S-methyl-L-cysteine with deuterium from the solvent. The rate of alpha-hydrogen exchange was about 40 times faster than that of the enzymatic elimination reaction of the sulfur-containing amino acids. The enzyme also catalyzes the exchange reaction of alpha- and beta-hydrogens of the straight-chain L-amino acids which are not susceptible to elimination. The exchange rates of the alpha-hydrogen and the total beta-hydrogens of L-alanine and L-alpha-aminobutyrate with deuterium followed first-order kinetics. For L-norvaline, L-norleucine, S-methyl-L-cysteine, and L-methionine, the rate of alpha-hydrogen exchange followed first-order kinetics, but the rate of total beta-hydrogen exchange decreased due to a primary isotope effect at the alpha-position. L-Phenylalanine and L-tryptophan slowly underwent alpha-hydrogen exchange. The pro-R hydrogen of glycine was deuterated stereospecifically

Experimental measurements of the 15O(alpha,gamma)19Ne reaction rate and the stability of thermonuclear burning on accreting neutron stars

International Nuclear Information System (INIS)

Fisker, J; Tan, W; Goerres, J; Wiescher, M; Cooper, R

2007-01-01

Neutron stars in close binary star systems often accrete matter from their companion stars. Thermonuclear ignition of the accreted material in the atmosphere of the neutron star leads to a thermonuclear explosion which is observed as an X-ray burst occurring periodically between hours and days depending on the accretion rate. The ignition conditions are characterized by a sensitive interplay between the accretion rate of the fuel supply and its depletion rate by nuclear burning in the hot CNO cycle and the rp-process. For accretion rates close to stable burning the burst ignition therefore depends critically on the hot CNO breakout reaction 15 O(α, γ) 19 Ne that regulates the flow between the hot CNO cycle and the rapid proton capture process. Until recently, the 15 O(α, γ) 19 Ne reaction rate was not known experimentally and the theoretical estimates carried significant uncertainties. In this paper we perform a parameter study of the uncertainty of this reaction rate and determine the astrophysical consequences of the first measurement of this reaction rate. Our results corroborate earlier predictions and show that theoretically burning remains unstable up to accretion rates near the Eddington limit, in contrast to astronomical observations

Fine Tuning of Basic Forces through the Existence of Carbon-Based Life

CERN Multimedia

CERN. Geneva

2001-01-01

The bulk of the carbon in our universe is produced in the triple-alpha process in helium-burning red giant stars. We calculated the change of the triple-alpha reaction rate in a microscopic twelve-nucleon model of the 12C nucleus and looked for the effects of minimal variations of the strengths of the underlying strong and Coulomb interactions. Stellar model calculations are performed using the alternative reaction rates. We show that outside a narrow window of 0.5% of the strength or range of the strong interaction the stellar production of carbon or oxygen is reduced by factors of 130 to 1000. Therefore, outside this window the existence of carbon-based life in our universe would be strongly disfavored. These anthropically allowed strengths of the strong and electromagnetic forces also constrain the sum of the light quark masses and the Higgs vacuum expectation value.

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

Research on the reactions {sup 9}Be ({sup 3}He, 3 {alpha}) and {sup 10}B (d, 3 {alpha}); Contribution a l'etude experimentale des reactions {sup 9}Be ({sup 3}He, 3 {alpha}) et {sup 10}B (d, 3 {alpha})

Energy Technology Data Exchange (ETDEWEB)

Thouvenin, P [Commissariat a l' Energie Atomique, Bruyeres-le-Chatel (France). Centre d' Etudes

1967-06-15

For studying these reactions, the detection of the final particles emitted in coincidence in the directions {theta}{sub 1} and {theta}{sub 2}, together with the bi-parametric analysis of the corresponding pulses are used. This method enables us to obtain the orthogonal Dalitz diagrams (E{sub 1}, E{sub 2}). An examination of the spectra obtained shows that the sequential mechanism appears to predominate. The contribution of the purely statistical process is less than 15 per cent of the total spectrum. In the case of {sup 10}B (d, 3 {alpha}), for E{sub d} = 1.5 MeV, 2,66 MeV and 3 MeV, the width of the peak of the first particles emitted, with respect to {sup 8}Be excitations close to 11 MeV, is found to be equal to 2.6 {+-} 0.6 MeV, much less than the width of the 2. excited state observed by {alpha} - {alpha} scattering. The coincidence spectra and the free spectra give an excitation energy of E{sub x} = 2.68 {+-} 0.07 MeV for the first excited state of {sup 8}Be. Some remarks are made concerning the anomalies observed for E{sub d} = 5 MeV and 9 MeV. The excited levels of {sup 8}Be at 13.91 MeV and 7.56 MeV which have been described in the past are not observed. (author) [French] La detection de deux des particules finales emises en cofncidence dans les directions {theta}{sub 1} et {theta}{sub 2}, et l'analyse biparametrique des impulsions correspondantes sont utilisees pour etudier ces reactions. Cette methode nous permet d'obtenir des diagrammes de Dalitz orthogonaux (E{sub 1}, E{sub 2}). L'examen des spectres obtenus montre que le mecanisme sequentiel semble predominant. La contribution du processus purement statistique est inferieure a 15 pour cent du spectre total. Dans le cas de {sup 10}B (d, 3 {alpha}), pour E{sub d} = 1,5 MeV, 2,66 MeV et 3 MeV, la largeur du pic des premieres particules emises relatives a des excitations de {sup 8}Be voisines de 11 MeV, est trouvee egale a 2,6 {+-} 0,6 MeV, tres inferieure a la largeur du 2. etat excite observee a l

Coincidence study of alpha particle fragmentation at E/sub alpha/ = 140 MeV

International Nuclear Information System (INIS)

Koontz, R.W.

1980-01-01

Results of an experimental study of the interaction of 140 MeV alpha particles with 90 Zr nuclei resulting in fragmentation of the alpha particle are reported. The experimental observations of the study are analyzed and are found to show that alpha particle breakup reactions leading to at least 4-body final states, composed of two charged alpha particle fragments, contribute significantly to the singles yield of charged fragments observed at a fixed forward angle. The conclusions are based on coincidence measurements where one charged fragment is detected at a small forward angle which remains fixed, while the second charged fragment is detected at a series of coplanar secondary angles. The largest coincidence charged particle yield for the multiparticle final state events results from 90 Zr(α,pp)X reactions, where both of the measured protons have energy distributions similar to the proton singles energy distributions. The second largest observed coincidence yield involving two charged fragments arises from 90 Zr(α,pd)X reactions, where the p and d fragments, as in the 90 Zr(α,pp)X reactions also have energy distribution similar to the singles energy distributions. Analysis of additional measurements, where alpha particle fragments at the fixed angle are detected in coincidence with evaporation and nonequilibrium particles at many coplanar angles, show that the alpha particle fragmentation reactions are also generally associated with large energy transfer to the target nucleus. A multiple scattering model of the fragmentation reaction is employed, in conjunction with the experimental observations, to estimate the cross sections for alpha particle fragmentation into multi-particle final states resulting in n, 2n, p, pp, d, dn, dp, t and 3 He fragments. The estimated total cross section for all fragmentation reactions is 755 mb or approximately 38% of the total reaction cross section for 140 MeV alpha particle interactions with 90 Zr

Evaluation of a second trimester triple marker screening test for fetal status using alpha-fetoprotein (aFP), human chorionic gonadotropin (hCG) and unconjugated estriol (uE{sub 3})

Energy Technology Data Exchange (ETDEWEB)

Mi, Seong Young; Kim, Jong Ho; Choi, Seung Hun [Chung Ang Gil Hospital, Inchon (Korea, Republic of)

1997-07-01

Our purpose was to assess the utility of maternal serum triple-marker screening test using alpha-fetoprotein (aFP), human Chorionic Gonadotropin (hCG) and unconjugated Estriol (uE{sub 3}) for fetal chromosomal abnormalities. 1,767 venous blood samples (4ml) between 15 and 20 week's gestation for maternal serum screening from January to October 1996, were tested with Kodak Amerix-M triple marker radioimmunoassay kits. Risk analysis was achieved with interpretive software such as Alpha (LMS, Kodak Clinical Diagnostics). Marker levels are transformed into multiples of median (MOM), which represent an interpretation of (weight regressed) patient marker levels relative to regressed median levels for stated gestation. By multivariate anaysis, the three MOM values are combined to generate a liklihood ratio. Calculation of a patient, risk is the product of liklihood ratio and age-related risk. Risk assessment is weight for maternal age. The median values of aFP, hCG and uE{sub 3} were well correlated with gestational age, respectively (r=0.94, p=0.003; r=-0.97, p=0.029; r=0.99, p<0.001, respectively). The median value of hCG were correlated withmateral age (r=0.13, p=0.04) but those of aFP and eU{sub 3} weren't (r=-0.17, p=0.22; r=0.36, p=0.09, respectively). The values of aFP, CG and uE{sub 3} between pregnancy younger than 35 years-old (n=87) and older than that (n=1640) were 51.67{+-}27.44, vs 54.65{+-}126.36, 46.45{+-}30.08 vs 51.33{+-}38.50 and 8.01{+-}11.01 vs 6.68{+-}7.23, respectively but all of them failed to show significant differences. A second-trimester risk for trisomy 21 > or = 1:270 was considered screen positive. Patients were screen positive for trisomy 21 if aFP < or 0.7 multiples of median (MOM), hCG> or 2.1 MOM and E{sub 3} < or 0.7 MOM. Patients were screen positive for neural tube defect if aFP >2.5 MOM. The initial screen-positive rate for both Down' syndrome and neural tube defect were 1.46% (26/1767); 0.73% (13/1767) with each other

Representing Rate Equations for Enzyme-Catalyzed Reactions

Science.gov (United States)

Ault, Addison

2011-01-01

Rate equations for enzyme-catalyzed reactions are derived and presented in a way that makes it easier for the nonspecialist to see how the rate of an enzyme-catalyzed reaction depends upon kinetic constants and concentrations. This is done with distribution equations that show how the rate of the reaction depends upon the relative quantities of…

Angular distribution measurements of {sup 6}Li(p,{alpha}){sup 3}He reaction at 140 keV proton energy using nuclear track detectors

Energy Technology Data Exchange (ETDEWEB)

Al-Jarallah, M.I. E-mail: mibrahim@kfupm.edu.sa; Naqvi, A.A.; Abu-Jarad, F.A.; Fazal-ur-Rehman; Durrani, S.M.A.; Kidwai, S

2001-06-01

Angular distributions of a {sup 6}Li(p,{alpha}) {sup 3}He reaction were measured at six angles for 140 keV proton energy using nuclear track detectors (NTDs). The measurements were carried out over 60 deg. -160 deg. lab. angles in 20 deg. increments using a scattering chamber of 80 deg. beam line of the 350 kV accelerator. A semiconductor silicon surface barrier (SSB) detector was placed at +160 deg. and was used as a monitor. The results have shown that the CR-39 detector has excellent capabilities to distinguish 1.4-2.7 MeV {alpha}+ {sup 3}He particles from the {sup 6}Li(p,{alpha}) {sup 3}He reaction and 8-9.4 MeV {alpha}-particles from the {sup 7}Li(p,{alpha}) {sup 4}He reaction through their track diameters. However, it was not possible to distinguish between the 2.3 MeV {sup 3}He ions and the 1.7 MeV {sup 4}He ions from the {sup 6}Li(p,{alpha}) {sup 3}He reaction from their track diameter measurements, but it was possible to differentiate between the two, from the darker contrast of the {sup 3}He particles caused by its deeper tracks as compared to those of {sup 4}He.

The effect of individual upper alpha band enhancing neurofeedbac kon reaction-time as an indicator of short-term memory in women employee’s

Directory of Open Access Journals (Sweden)

Mersedeh Jahanseir

2014-11-01

Full Text Available Background: In neurofeedback systems, people are able to reinforce or hinder their basic EEG rhythms according to operant conditioninin recent studies the effect of neurofeedback training on improvement of working memory has been shown on the healthy subjects. Disadvantage of neurofeedback is the high number of training sessions and high cost. In previous studies, alpha band power within (8-12 Hz has been considered for all subjects. Previous research reached the conclusion that by using individual upper alpha in neurofeedback, learning rate will increase, so the training sessions and the cost of training will be reduced. Material and Methods: In this study, all participants were female, 10 adults (10 women, mean age 33.8 years, SD=3.56 years. Randomly assigned to control and test group, five in test group and five in control group. Each subject performed the memory test four times, two times before the start of the first neurofeedback training and two times after the end of the last neurofeedback session. Eight training sessions were held, each session had three trials. Results: Discriminate response to the color of the drawing, as well as reaction time hadsignificant effects for test group (p0.05. Before and after eight training sessions by individual upper alpha power neurofeedback, reaction time of discriminate response to the color of the drawing for test group decreased and had significant effects (p0.05. Conclusion: Increasing relative individual upper alpha power, caused by neurofeedback training during eight sessions, indicated that this method increases the memory of women employees, and improves the ability of discriminative response to the color (red & green of the drawing as well as reducing reaction time.

Contribution to the study of (d,p) and (d,{alpha}> reactions on {sup 16}O and {sup 11}B from 200 keV to 1 MeV; Contribution a l'etude des reactions (d,p) et (d,{alpha}) sur {sup 16}O et {sup 11}B de 200 keV a 1 MeV

Energy Technology Data Exchange (ETDEWEB)

Longequeue, N [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1965-05-01

The reactions {sup 16}O(d,{alpha}{sub 0}), (d,p{sub 0}), (d,p{sub 1}) and {sup 11}B(d,{alpha}{sub 0}), (d,{alpha}{sub 2}), (d,p{sub 0}) have been studied from 200 keV to 1 MeV. The interpretation of (d,{alpha}) reactions by the compound nucleus theory has shown the presence of {sup 18}F levels (7,94 MeV, 1+; 8,09 MeV, 1+ ) and of {sup 13}C level (19 MeV, 3/2{+-} or 5/2-). The interpretation of {sup 16}O(d,p{sub 1}) and {sup 11}B(d,p{sub 0}) reactions at energies lower than 400 keV has been given by a theory of Coulomb stripping. (author) [French] L'etude experimentale des reactions {sup 16}O(d,{alpha}{sub 0}); (d,p{sub 0}), (d,p{sub 1}) et {sup 11}B(d,{alpha}{sub 0}), (d,{alpha}{sub 2}), (d,p{sub 0}) a ete faite de 200 keV a 1 Mev. L'interpretation des reactions (d,a) par la theorie du noyau compose a permis la mise en evidence de niveaux du {sup 18}F (7,94 MeV, 1+; 8,09MeV, 1+ ) et du {sup 13}C(19 MeV, 3/2{+-} ou 5/2-). L'interpretation des reactions {sup 16}O(d,p{sub 1}) et {sup 11}B(d,p{sub 0}), a basse energie (< 400 keV), par une theorie de stripping de Coulomb, a ete donnee.

Rates of Thermonuclear Reactions in Dense Plasmas

International Nuclear Information System (INIS)

Tsytovich, V.N.; Bornatici, M.

2000-01-01

The problem of plasma screening of thermonuclear reactions has attracted considerable scientific interest ever since Salpeter's seminal paper, but it is still faced with controversial statements and without any definite conclusion. It is of relevant importance to thermonuclear reactions in dense astrophysical plasmas, for which charge screening can substantially affect the reaction rates. Whereas Salpeter and a number of subsequent investigations have dealt with static screening, Carraro, Schafer, and Koonin have drawn attention to the fact that plasma screening of thermonuclear reactions is an essentially dynamic effect. In addressing the issue of collective plasma effects on the thermonuclear reaction rates, the first critical overview of most of the work carried out so far is presented and the validity of the test particle approach is assessed. In contrast to previous investigations, we base our description on the kinetic equation for nonequilibrium plasmas, which accounts for the effects on the rates of thermonuclear reactions of both plasma fluctuations and screening and allows one to analyze explicitly the effects of the fluctuations on the reaction rates. Such a kinetic formulation is more general than both Salpeter's approach and the recently developed statistical approaches and makes it possible to obtain a more comprehensive understanding of the problem. A noticeable result of the fluctuation approach is that the static screening, which affects both the interaction and the self-energy of the reacting nuclei, does not affect the reaction rates, in contrast with the results obtained so far. Instead, a reduction of the thermonuclear reaction rates is obtained as a result of the effect of plasma fluctuations related to the free self-energy of the reacting nuclei. A simple physical explanation of the slowing down of the reaction rates is given, and the relation to the dynamically screened test particle approach is discussed. Corrections to the reaction rates

Coincidence measurement between. cap alpha. -particles and projectile-like fragments in reaction of 82. 7 MeV /sup 16/O on /sup 27/Al

Energy Technology Data Exchange (ETDEWEB)

Wen-Qing, Shen; Wen-long, Zhan; Yong-tai, Zhu; Shu-zhi, Yin; Zhong-yan, Guo; Wei-min, Qiao; Guo-ying, Fan; Gen-ming, Jin; Song-ling, Li; Zhen, Zhang; others, and

1987-01-01

In the coincidence measurement between ..cap alpha..-particles and projectile-like fragments in the reaction of 82.7 MeV /sup 16/O on /sup 27/Al, the contour plot of the C-..cap alpha.. coincidence in the velocity plane and the coincident angular correlation are obtained. Different mechanisms of ..cap alpha..-particle emission are analysed. A possible reaction mechanism of incomplete DIC is discussed.

Geodynamical simulation of the RRF triple junction

Science.gov (United States)

Wang, Z.; Wei, D.; Liu, M.; Shi, Y.; Wang, S.

2017-12-01

Triple junction is the point at which three plate boundaries meet. Three plates at the triple junction form a complex geological tectonics, which is a natural laboratory to study the interactions of plates. This work studies a special triple junction, the oceanic transform fault intersects the collinear ridges with different-spreading rates, which is free of influence of ridge-transform faults and nearby hotspots. First, we build 3-D numerical model of this triple junction used to calculate the stead-state velocity and temperature fields resulting from advective and conductive heat transfer. We discuss in detail the influence of the velocity and temperature fields of the triple junction from viscosity, spreading rate of the ridge. The two sides of the oceanic transform fault are different sensitivities to the two factors. And, the influence of the velocity mainly occurs within 200km of the triple junction. Then, we modify the model by adding a ridge-transform fault to above model and directly use the velocity structure of the Macquarie triple junction. The simulation results show that the temperature at both sides of the oceanic transform fault decreases gradually from the triple junction, but the temperature difference between the two sides is a constant about 200°. And, there is little effect of upwelling velocity away from the triple junction 100km. The model results are compared with observational data. The heat flux and thermal topography along the oceanic transform fault of this model are consistent with the observed data of the Macquarie triple junction. The earthquakes are strike slip distributed along the oceanic transform fault. Their depths are also consistent with the zone of maximum shear stress. This work can help us to understand the interactions of plates of triple junctions and help us with the foundation for the future study of triple junctions.

Measurement of sup 15 O(. alpha. ,. gamma. ) sup 19 Ne resonance strengths

Energy Technology Data Exchange (ETDEWEB)

Magnus, P V; Smith, M S; Howard, A J; Parker, P D [Yale Univ., New Haven, CT (USA). Nuclear Structure Lab.; Champagne, A E [Princeton Univ., NJ (USA). Dept. of Physics

1990-01-08

States in {sup 19}Ne above the {sup 15}O+{alpha} threshold were populated by means of the {sup 19}F({sup 3}He,t){sup 19}Ne* reaction, and their alpha-particle decays to the {sup 15}O ground state were measured. The branching ratios {Gamma}{sub {alpha}}/{Gamma}{sub total} for the E{sub c.m.}=850-, 1020-, 1971-, 1183- and 1563-keV resonances in {sup 15}O+{alpha} were determined. This information together with alpha-particle and/or gamma-ray partial widths (determined from knowledge of these quantities for the mirror states in {sup 19}F) determines the strengths of these {sup 15}O({alpha},{gamma}){sup 19}Ne resonances and the {sup 15}O({alpha},{gamma}){sup 19}Ne reaction rate for temperatures between 7x10{sup 8} and 3x10{sup 9} K. (orig.).

Research on the reactions {sup 9}Be ({sup 3}He, 3 {alpha}) and {sup 10}B (d, 3 {alpha}); Contribution a l'etude experimentale des reactions {sup 9}Be ({sup 3}He, 3 {alpha}) et {sup 10}B (d, 3 {alpha})

Energy Technology Data Exchange (ETDEWEB)

Thouvenin, P. [Commissariat a l' Energie Atomique, Bruyeres-le-Chatel (France). Centre d' Etudes

1967-06-15

For studying these reactions, the detection of the final particles emitted in coincidence in the directions {theta}{sub 1} and {theta}{sub 2}, together with the bi-parametric analysis of the corresponding pulses are used. This method enables us to obtain the orthogonal Dalitz diagrams (E{sub 1}, E{sub 2}). An examination of the spectra obtained shows that the sequential mechanism appears to predominate. The contribution of the purely statistical process is less than 15 per cent of the total spectrum. In the case of {sup 10}B (d, 3 {alpha}), for E{sub d} = 1.5 MeV, 2,66 MeV and 3 MeV, the width of the peak of the first particles emitted, with respect to {sup 8}Be excitations close to 11 MeV, is found to be equal to 2.6 {+-} 0.6 MeV, much less than the width of the 2. excited state observed by {alpha} - {alpha} scattering. The coincidence spectra and the free spectra give an excitation energy of E{sub x} = 2.68 {+-} 0.07 MeV for the first excited state of {sup 8}Be. Some remarks are made concerning the anomalies observed for E{sub d} = 5 MeV and 9 MeV. The excited levels of {sup 8}Be at 13.91 MeV and 7.56 MeV which have been described in the past are not observed. (author) [French] La detection de deux des particules finales emises en cofncidence dans les directions {theta}{sub 1} et {theta}{sub 2}, et l'analyse biparametrique des impulsions correspondantes sont utilisees pour etudier ces reactions. Cette methode nous permet d'obtenir des diagrammes de Dalitz orthogonaux (E{sub 1}, E{sub 2}). L'examen des spectres obtenus montre que le mecanisme sequentiel semble predominant. La contribution du processus purement statistique est inferieure a 15 pour cent du spectre total. Dans le cas de {sup 10}B (d, 3 {alpha}), pour E{sub d} = 1,5 MeV, 2,66 MeV et 3 MeV, la largeur du pic des premieres particules emises relatives a des excitations de {sup 8}Be voisines de 11 MeV, est trouvee egale a 2,6 {+-} 0,6 MeV, tres inferieure a la largeur du 2. etat excite

Typewriting rate as a function of reaction time.

Science.gov (United States)

Hayes, V; Wilson, G D; Schafer, R L

1977-12-01

This study was designed to determine the relationship between reaction time and typewriting rate. Subjects were 24 typists ranging in age from 19 to 39 yr. Reaction times (.001 sec) to a light were recorded for each finger and to each alphabetic character and three punctuation marks. Analysis of variance yielded significant differences in reaction time among subjects and fingers. Correlation between typewriting rate and average reaction time to the alphabetic characters and three punctuation marks was --.75. Correlation between typewriting rate and the difference between the reaction time of the hands was --.42. Factors influencing typewriting rate may include reaction time of the fingers, difference between the reaction time of the hands, and reaction time to individual keys on the typewriter. Implications exist for instructional methodology and further research.

The reaction of atomic hydrogen with germane - Temperature dependence of the rate constant and implications for germane photochemistry in the atmospheres of Jupiter and Saturn

Science.gov (United States)

Nava, David F.; Payne, Walter A.; Marston, George; Stief, Louis J.

1993-01-01

Studies of the formation and loss processes for GeH4 are required in order to provide data to help determine the major chemical form in which germanium exists in the atmospheres of Jupiter and Saturn. The reaction of hydrogen atoms with germane is one of the most important of these reactions. The absolute rate constant for this reaction as a function of temperature and pressure is studied. Flash photolysis of dilute mixtures of GeH4 in argon, combined with time-resolved detection of H atoms via Lyman alpha resonance fluorescence, is employed to measure the reaction rate. The reaction is shown to be moderately rapid, independent of total pressure, but possessing a positive temperature dependence.

Neutrino-induced charged-current reaction rates for r-process nuclei

CERN Document Server

Langanke, K

2001-01-01

Neutrino-induced reactions play an important role during and after the r-process if it occurs in an environment with extreme neutrino fluxes, as in the neutrino-driven wind model or neutron star mergers. The neutrino reactions can excite the daughter nucleus above the neutron threshold, which is quite low for r-process nuclei. Thus the daughter nucleus will decay by emission of one or several neutrons. We have calculated the relevant total (nu sub e , e sup -) cross sections as well as the partial neutron spallation cross sections for r-process nuclei with neutron numbers N=41-135 and proton numbers Z=21-82. The supernova neutrino spectrum is described by a Fermi-Dirac distribution with various temperature parameters between T=2.8 MeV and T=10 MeV and with the degeneracy parameters alpha=0 and alpha=3. Our calculations of the nuclear response are based on the random phase approximation and consider allowed as well as forbidden transitions.

Quasiresonant formation of dtμ mesic molecules in triple collisions

International Nuclear Information System (INIS)

Men'shikov, L.I.; Ponomarev, L.I.

1985-01-01

A quasiresonant mechanism of mesic molecules formation, in triple collisions of the type tμ+D 2 +D 2 → [(dtμ)d2e] * +D ν is considered. It is shown that at small resonance defects and big D 2 +T 2 mixture densities φ the rate of this process λ qr ∼ φ 2 and it is comparable with the rate λ r ∼ φ of the mesic molecules resonant formation in the reactions of the type tμ+D 2 → [(dtμ)d2e] ν *. The observable manifestations of the process considered and its role in the muon catalyzed fusion in deuterium-tritium mixture are discussed

Investigation of the Pygmy Dipole Resonance in (alpha, alpha 'gamma) coincidence experiments

NARCIS (Netherlands)

Savran, D.; Babilon, M.; van den Berg, A. M.; Harakeh, M. N.; Hasper, J.; Wortche, H. J.; Zilges, A.

2007-01-01

We report on first results from experiments using the (alpha, alpha'gamma) reaction at E alpha = 136 MeV to investigate bound electric dipole (El) excitations building the so-called Pygmy Dipole Resonance (PDR) in the semi-magic nucleus Ce-140. The method of (alpha, alpha'gamma) allows the

Effect of excited states on thermonuclear reaction rates

International Nuclear Information System (INIS)

Sargood, D.G.

1983-01-01

Values of the ratio of the thermonuclear reaction rate of a reaction, with target nuclei in a thermal distribution of energy states, to the reaction rate with all target nuclei in their ground states are tabulated for neutron, proton and α-particle induced reactions on the naturally occurring nuclei from 20 Ne to 70 Zn, at temperatures of 1, 2, 3.5 and 5x10 9 K. The ratios are determined from reaction rates based on statistical model cross sections

Contribution to the study of {sup 12}C excited levels resulting from the reactions {sup 11}B (P/ {alpha}{sub 0}) and {sup 11}B (p, {alpha}{sub 1}); Contribution a l'etude des niveaux excites du {sup 12}C obtenus par les reactions {sup 11}B (p, {alpha}{sub 0}) et {sup 11}B (p, {alpha}{sub l})

Energy Technology Data Exchange (ETDEWEB)

Longequeue, J P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1963-11-15

This work is made up of two parts. In the first part the differential cross-sections have been determined of the reactions {sup 11}B (p,{alpha}) from 130 to 500 keV thus confirming, at the 163 keV resonance, the (2{sup +}) characteristics of the 16.11 MeV level of {sup 12}C. Furthermore, the experimental results in the neighbourhood of the 163 keV resonance can be explained by the interference of the {sup 12}C levels: 2{sup +} at 16.11 MeV and 1{sup -} at 17.23 MeV for the {alpha}{sub 0}, 2{sup +} at 16.11 MeV and 2{sup -} at 16.58 MeV for the {alpha}{sub 1}. In the second part the ({alpha}{sup -8Be}) disintegration process of {sup 12}C has been studied in the neighbourhood of the 16.11 MeV level. It is shown that, if the ({alpha}{sup -8Be}) mode of disintegration is preponderant outside the E{sub p} = 163 keV resonance, it is also preponderant at this same resonance; a direct disintegration of the {sup 12}C to 3 {alpha}, with an approximate magnitude of 40 per cent has however not been excluded. (author) [French] Ce travail comprend deux parties: Dans la premiere, on a determine la section efficace differentielle des reactions {sup 11}B (p,{alpha}) de 130 a 500 keV, confirmant, a la resonance de 163 keV, les caracteristiques (2{sup +}) du niveau de 16,11 MeV du {sup 12}C. En outre, les resultats experimentaux au voisinage de la resonance de 163 keV sont explicables par l'interference des niveaux du {sup 12}C: 2{sup +} a 16,11 MeV et 1{sup -} a 17,23 MeV pour les {alpha}{sub 0}, 2{sup +} a 16,11 MeV et 2{sup -} a 16,58 MeV pour les {alpha}{sub 1}. Dans la deuxieme partie, on a etudie le mode de desintegration ({alpha}{sup -8Be}) du {sup 12}C au voisinage du niveau de 16,11 MeV. On a montre que, si le mode de desintegration ({alpha}{sup -8Be}) est preponderant en dehors de la resonance E{sub p} = 163 keV, il est egalement preponderant a cette resonance; une desintegration directe en 3{alpha} du {sup 12}C, dont l'ordre de grandeur maximum serait de 40 pour cent, n

Non-equilibrium reaction rates in chemical kinetic equations

Science.gov (United States)

Gorbachev, Yuriy

2018-05-01

Within the recently proposed asymptotic method for solving the Boltzmann equation for chemically reacting gas mixture, the chemical kinetic equations has been derived. Corresponding one-temperature non-equilibrium reaction rates are expressed in terms of specific heat capacities of the species participate in the chemical reactions, bracket integrals connected with the internal energy transfer in inelastic non-reactive collisions and energy transfer coefficients. Reactions of dissociation/recombination of homonuclear and heteronuclear diatomic molecules are considered. It is shown that all reaction rates are the complex functions of the species densities, similarly to the unimolecular reaction rates. For determining the rate coefficients it is recommended to tabulate corresponding bracket integrals, additionally to the equilibrium rate constants. Correlation of the obtained results with the irreversible thermodynamics is established.

Equilibration kinetics in isolated and membrane-bound photosynthetic reaction centers upon illumination: a method to determine the photoexcitation rate.

Science.gov (United States)

Manzo, Anthony J; Goushcha, Alexander O; Barabash, Yuri M; Kharkyanen, Valery N; Scott, Gary W

2009-07-01

Kinetics of electron transfer, following variation of actinic light intensity, for photosynthetic reaction centers (RCs) of purple bacteria (isolated and membrane-bound) were analyzed by measuring absorbance changes in the primary photoelectron donor absorption band at 865 nm. The bleaching of the primary photoelectron donor absorption band in RCs, following a sudden increase of illumination from the dark to an actinic light intensity of I(exp), obeys a simple exponential law with the rate constant alphaI(exp) + k(rec), in which alpha is a parameter relating the light intensity, measured in mW/cm(2), to a corresponding theoretical rate in units of reciprocal seconds, and k(rec) is the effective rate constant of the charge recombination in the photosynthetic RCs. In this work, a method for determining the alpha parameter value is developed and experimentally verified for isolated and membrane-bound RCs, allowing for rigorous modeling of RC macromolecule dynamics under varied photoexcitation conditions. Such modeling is necessary for RCs due to alterations of the forward photoexcitation rates and relaxation rates caused by illumination history and intramolecular structural dynamics effects. It is demonstrated that the classical Bouguer-Lambert-Beer formalism can be applied for the samples with relatively low scattering, which is not necessarily the case with strongly scattering media or high light intensity excitation.

Effect of nuclear reaction rates on primordial abundances

International Nuclear Information System (INIS)

Mishra, Abhishek; Basu, D.N.

2011-01-01

The theoretical predictions of the primordial abundances of elements in the big-bang nucleosynthesis (BBN) are dominated by uncertainties in the input nuclear reaction rates. The effect of modifying these reaction rates on light element abundance yields in BBN by replacing the thirty-five reaction rates out of the existing eighty-eight has been investigated. Also the study have been taken of these yields as functions of evolution time or temperature. Here it has been found that using these new reaction rates results in only a little increase in helium mass fraction over that obtained previously in BBN calculations. This allows insights into the role of the nuclear reaction rates in the setting of the neutron-to-proton ratio during the BBN epoch. We observe that most of these nuclear reactions have minimal effect on the standard BBN abundance yields of 6 Li and 7 Li

Dose-response effects of estrogenic mycotoxins (zearalenone, alpha- and beta-zearalenol on motility, hyperactivation and the acrosome reaction of stallion sperm

Directory of Open Access Journals (Sweden)

Colenbrander Ben

2011-10-01

Full Text Available Abstract Background The aim of this study was to investigate the in vitro effects of the Fusarium fungus-derived mycotoxin, zearalenone and its derivatives alpha-zearalenol and beta-zearalenol on motility parameters and the acrosome reaction of stallion sperm. Since the toxic effects of zearalenone and its derivatives are thought to result from their structural similarity to 17beta-estradiol, 17beta-estradiol was used as a positive control for 'estrogen-like' effects. Methods Stallion spermatozoa were exposed in vitro to zearalenone, alpha-zearalenol, beta-zearalenol or 17beta-estradiol at concentrations ranging from 1 pM - 0.1 mM. After 2 hours exposure, motility parameters were evaluated by computer-assisted analysis, and acrosome integrity was examined by flow cytometry after staining with fluoroscein-conjugated peanut agglutinin. Results Mycotoxins affected sperm parameters only at the highest concentration tested (0.1 mM after 2 hours exposure. In this respect, all of the compounds reduced the average path velocity, but only alpha-zearalenol reduced percentages of motile and progressively motile sperm. Induction of motility patterns consistent with hyperactivation was stimulated according to the following rank of potency: alpha-zearalenol >17beta-estradiol > zearalenone = beta-zearalenol. The hyperactivity-associated changes observed included reductions in straight-line velocity and linearity of movement, and an increase in the amplitude of lateral head displacement, while curvilinear velocity was unchanged. In addition, whereas alpha- and beta- zearalenol increased the percentages of live acrosome-reacted sperm, zearalenone and 17beta-estradiol had no apparent effect on acrosome status. In short, alpha-zearalenol inhibited normal sperm motility, but stimulated hyperactive motility in the remaining motile cells and simultaneously induced the acrosome reaction. Beta-zearalenol induced the acrosome reaction without altering motility

Quasi-bound alpha resonant states populated by the {sup 12}C({sup 6}Li, d) reaction

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, M.R.D.; Borello-Lewin, T.; Miyake, H.; Horodynski-Matsushigue, L.B.; Duarte, J.L.M.; Rodrigues, C.L.; Souza, M.A. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica; Cunsolo, A.; Cappuzzello, F.; Foti, A.; Agodi, C.; Cavallaro, M. [Istituto Nazionale di Fisica Nucleare (LNS/INFN), Catania (Italy). Lab. Nazionali del Sud; Ukita, G.M. [Universidade de Santo Amaro (UNISA), Sao Paulo, SP (Brazil). Faculdade de Psicologia

2012-07-01

Full text: The alpha cluster phenomenon in the light nuclei structure has been the subject of a long time investigation since the proposal of the Ikeda diagrams [1]. The main purpose of the research program in progress is the investigation of this phenomenon in (x{alpha}) and (x{alpha}+n) nuclei through the ({sup 6}Li, d) alpha transfer reaction [2-4]. Alpha resonant states around the (4{alpha}) threshold in the nucleus {sup 16}O are the focus of the present contribution. In fact, the importance of these resonances at the elements production in stars is recognized, as primarily pointed out by Hoyle in {sup 12}C [6]. The existence of a rotational band with the {alpha} +{sup 12} C (Hoyle) cluster state structure was recently demonstrated by Ohkubo and Hirabayashi [6]. In order to explore this region of interest, measurements of the {sup 12}C({sup 6}Li, d){sup 16}O reaction up to 17 MeV of excitation at an incident energy of 25.5 MeV, have been performed employing the Sao Paulo Pelletron-Enge Split-Pole facility and the nuclear emulsion detection technique (plates Fuji G6B, 50 {mu}m thick). Spectra associated with six scattering angles, from 5 deg to 29 deg in the laboratory frame, each one 50 cm along the focal surface, were measured. Several narrow resonances with a quasi-bound behavior embedded in the continuum were detected and the resolution of 25 keV allowed for the separation of doublets not resolved before [7,8]. The absolute cross sections and the respective deuteron angular distributions were determined and the analysis is in progress. [1] K. Ikeda et al., Prog. Theor. Phys. Suppl. E 68, 464 (1968); H. Horiuchi, K. Ikeda, and Y. Suzuki, ibid. 44, 225 (1978). [2] M.R.D.Rodrigues et al., in12th International Conference on Nuclear Reaction Mechanism, Varenna, Italy, edited by F. Cerutti and A. Ferrari , CERN Proceedings, 2010-2, pp. 331- 335. [3] T. Borello-Lewin et al., Proceedings of SOTANCP2, Brussels, Belgium 2010, edited by P. Descouvemount et al., Int. J

Recovery and normalization of triple coincidences in PET.

Science.gov (United States)

Lage, Eduardo; Parot, Vicente; Moore, Stephen C; Sitek, Arkadiusz; Udías, Jose M; Dave, Shivang R; Park, Mi-Ae; Vaquero, Juan J; Herraiz, Joaquin L

2015-03-01

Triple coincidences in positron emission tomography (PET) are events in which three γ-rays are detected simultaneously. These events, though potentially useful for enhancing the sensitivity of PET scanners, are discarded or processed without special consideration in current systems, because there is not a clear criterion for assigning them to a unique line-of-response (LOR). Methods proposed for recovering such events usually rely on the use of highly specialized detection systems, hampering general adoption, and/or are based on Compton-scatter kinematics and, consequently, are limited in accuracy by the energy resolution of standard PET detectors. In this work, the authors propose a simple and general solution for recovering triple coincidences, which does not require specialized detectors or additional energy resolution requirements. To recover triple coincidences, the authors' method distributes such events among their possible LORs using the relative proportions of double coincidences in these LORs. The authors show analytically that this assignment scheme represents the maximum-likelihood solution for the triple-coincidence distribution problem. The PET component of a preclinical PET/CT scanner was adapted to enable the acquisition and processing of triple coincidences. Since the efficiencies for detecting double and triple events were found to be different throughout the scanner field-of-view, a normalization procedure specific for triple coincidences was also developed. The effect of including triple coincidences using their method was compared against the cases of equally weighting the triples among their possible LORs and discarding all the triple events. The authors used as figures of merit for this comparison sensitivity, noise-equivalent count (NEC) rates and image quality calculated as described in the NEMA NU-4 protocol for the assessment of preclinical PET scanners. The addition of triple-coincidence events with the authors' method increased peak

Recovery and normalization of triple coincidences in PET

Energy Technology Data Exchange (ETDEWEB)

Lage, Eduardo, E-mail: elage@mit.edu; Parot, Vicente; Dave, Shivang R.; Herraiz, Joaquin L. [Madrid-MIT M+Visión Consortium, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Moore, Stephen C.; Sitek, Arkadiusz; Park, Mi-Ae [Division of Nuclear Medicine, Department of Radiology, Harvard Medical School and Brigham and Women’s Hospital, Boston, Massachusetts 02115 (United States); Udías, Jose M. [Grupo de Física Nuclear, Departamento de Física Atómica Molecular y Nuclear, Universidad Complutense de Madrid, CEI Moncloa, Madrid 28040 (Spain); Vaquero, Juan J. [Departamento de Ingeniería Biomédica e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Leganés 28911 (Spain)

2015-03-15

Purpose: Triple coincidences in positron emission tomography (PET) are events in which three γ-rays are detected simultaneously. These events, though potentially useful for enhancing the sensitivity of PET scanners, are discarded or processed without special consideration in current systems, because there is not a clear criterion for assigning them to a unique line-of-response (LOR). Methods proposed for recovering such events usually rely on the use of highly specialized detection systems, hampering general adoption, and/or are based on Compton-scatter kinematics and, consequently, are limited in accuracy by the energy resolution of standard PET detectors. In this work, the authors propose a simple and general solution for recovering triple coincidences, which does not require specialized detectors or additional energy resolution requirements. Methods: To recover triple coincidences, the authors’ method distributes such events among their possible LORs using the relative proportions of double coincidences in these LORs. The authors show analytically that this assignment scheme represents the maximum-likelihood solution for the triple-coincidence distribution problem. The PET component of a preclinical PET/CT scanner was adapted to enable the acquisition and processing of triple coincidences. Since the efficiencies for detecting double and triple events were found to be different throughout the scanner field-of-view, a normalization procedure specific for triple coincidences was also developed. The effect of including triple coincidences using their method was compared against the cases of equally weighting the triples among their possible LORs and discarding all the triple events. The authors used as figures of merit for this comparison sensitivity, noise-equivalent count (NEC) rates and image quality calculated as described in the NEMA NU-4 protocol for the assessment of preclinical PET scanners. Results: The addition of triple-coincidence events with the

Separation of reaction mechanisms at low energy. Study of the reactions: {sup 27}Al(d,p) {sup 28}Al, {sup 24}Mg(d,p) {sup 25}Mg, and {sup 24}Mg(d, {alpha}) {sup 22}Na; Sur la separation des mecanismes de reaction a basse energie. Etude des reactions: {sup 27}Al(d,p) {sup 28}Al, {sup 24}Mg(d,p) {sup 25}Mg, et {sup 24}Mg(d, {alpha}) {sup 22}Na

Energy Technology Data Exchange (ETDEWEB)

Mermaz, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-06-01

The two sets of angular distributions of (d,p) reactions on Al and Mg, measured between 2 and 6 MeV, have given the possibility to test, in analysing the statistical fluctuations of cross-section, the validity of the separation of their mean values in two parts, one 'direct', another given by the statistical mechanism. With the same method of analysis we have studied excitation functions for several alpha groups of the reaction {sup 24}Mg(d, {alpha}) {sup 22}Na and given an evidence for an intermediate structure for the alpha channel leading to the 3. excited state of {sup 22}Na. The angular distribution of the wide resonance at 15.9 MeV in {sup 26}Al has been obtained. (author) [French] Les deux ensembles de distributions angulaires des reactions (d,p) sur Al et Mg, mesures entre 2 et 6 MeV, nous ont permis, en analysant les fluctuations statistiques de sections efficaces, de verifier la possibilite de la separation de leurs valeurs moyennes en deux composantes: l'une 'directe', l'autre due au mecanisme statistique. Avec la meme methode d'analyse nous avons etudie les fonctions d'excitation des premiers groupes alpha de la reaction {sup 24}Mg(d,{alpha}) {sup 22}Na et mis en evidence une structure intermediaire pour la voie de reaction aboutissant au 3eme niveau de {sup 22}Na. Nous avons obtenu la distribution angulaire de la resonance large situee a une energie d'excitation de 15,9 MeV dans {sup 26}Al. (auteur)

Separation of reaction mechanisms at low energy. Study of the reactions: {sup 27}Al(d,p) {sup 28}Al, {sup 24}Mg(d,p) {sup 25}Mg, and {sup 24}Mg(d, {alpha}) {sup 22}Na; Sur la separation des mecanismes de reaction a basse energie. Etude des reactions: {sup 27}Al(d,p) {sup 28}Al, {sup 24}Mg(d,p) {sup 25}Mg, et {sup 24}Mg(d, {alpha}) {sup 22}Na

Energy Technology Data Exchange (ETDEWEB)

Mermaz, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-06-01

The two sets of angular distributions of (d,p) reactions on Al and Mg, measured between 2 and 6 MeV, have given the possibility to test, in analysing the statistical fluctuations of cross-section, the validity of the separation of their mean values in two parts, one 'direct', another given by the statistical mechanism. With the same method of analysis we have studied excitation functions for several alpha groups of the reaction {sup 24}Mg(d, {alpha}) {sup 22}Na and given an evidence for an intermediate structure for the alpha channel leading to the 3. excited state of {sup 22}Na. The angular distribution of the wide resonance at 15.9 MeV in {sup 26}Al has been obtained. (author) [French] Les deux ensembles de distributions angulaires des reactions (d,p) sur Al et Mg, mesures entre 2 et 6 MeV, nous ont permis, en analysant les fluctuations statistiques de sections efficaces, de verifier la possibilite de la separation de leurs valeurs moyennes en deux composantes: l'une 'directe', l'autre due au mecanisme statistique. Avec la meme methode d'analyse nous avons etudie les fonctions d'excitation des premiers groupes alpha de la reaction {sup 24}Mg(d,{alpha}) {sup 22}Na et mis en evidence une structure intermediaire pour la voie de reaction aboutissant au 3eme niveau de {sup 22}Na. Nous avons obtenu la distribution angulaire de la resonance large situee a une energie d'excitation de 15,9 MeV dans {sup 26}Al. (auteur)

Thermonuclear reaction rates in a deuterium-tritium plasma

International Nuclear Information System (INIS)

Beckman, L.

1978-12-01

In a deuterium-tritium plasma six thermonuclear reactions take place between the deuterons, tritons and the 3 He-particles formed in about half of the d-d-reactions. The rate constants for these six reactions have been calculated from the latest evaluations of the reaction cross sections which were available. In some cases, notably the reactions t+t, t+ 3 He and 3 He+ 3 He, the number of published cross section measurements is small, and the uncertainty in the calculated rate constants consequently large. Analytical expressions for the rate constants as functions of the plasma temperature have been set up. (author)

Dissolution rate of alpha-doped UO2 in natural groundwater

International Nuclear Information System (INIS)

Ollila, Kaija; Myllykylä, Emmi; Tanhua-Tyrkkö, Merja; Lavonen, Tiina

2013-01-01

The objective of this work is to determine whether the presence of trace elements in natural groundwaters affects the dissolution rate of uranium dioxide in the presence of alpha radiation that causes radiolysis of water. The study is a part of the project Reducing Uncertainty in Performance Prediction (REDUPP) under the Seventh Framework Programme of the European Atomic Energy Community (EURATOM). The project aims to reduce uncertainties related to the extrapolation of the results of laboratory experiments to the conditions expected under geologic disposal. Thus far, synthetic groundwater has been normally used in the experiments. The synthetic groundwaters used do not contain all of the chemical elements that occur in natural groundwaters. Three natural groundwaters were chosen for the dissolution experiments with 0%, 5%, and 10% 233 U-doped UO 2 samples. These include a brackish groundwater, a saline groundwater and a low ionic strength groundwater. At the time of writing this paper, the dissolution experiments have been finished in the first groundwater, which was a moderately saline, brackish groundwater. The groundwater samples for the experiments were taken from a borehole in the Olkiluoto site in Finland. The measurements for dissolution rates were conducted under reducing conditions established using metallic iron in solution and an argon atmosphere in the glove box. The isotope dilution method was used to decrease uncertainties due to precipitation and sorption effects. The resulting dissolution rates in OL-KR6 natural groundwater were generally somewhat higher than the rates measured previously in synthetic groundwaters under similar redox conditions. No clear effect of alpha radiolysis could be seen for tests with lower SA/V, while those for higher SA/V indicated that the dissolution rate was higher for the 10% 233 U-doped UO 2 , suggesting the effect of alpha radiolysis under these conditions

Summary of alpha-neutron sources in GADRAS

International Nuclear Information System (INIS)

Mitchell, Dean James; Thoreson, Gregory G.; Harding, Lee T.

2012-01-01

A common source of neutrons for calibration and testing is alpha-neutron material, named for the alpha-neutron nuclear reaction that occurs within. This material contains a long-lived alpha-emitter and a lighter target element. When the alpha particle from the emitter is absorbed by the target, neutrons and gamma rays are released. Gamma Detector Response and Analysis Software (GADRAS) includes built-in alpha-neutron source definitions for AcC, AmB, AmBe, AmF, AmLi, CmC, and PuC. In addition, GADRAS users may create their own alpha-neutron sources by placing valid alpha-emitters and target elements in materials within their one-dimensional models (1DModel). GADRAS has the ability to use pre-built alpha-neutron sources for plotting or as trace-sources in 1D models. In addition, if any material (existing or user-defined) specified in a 1D model contains both an alpha emitter in conjunction with a target nuclide, or there is an interface between such materials, then the appropriate neutron-emission rate from the alpha-neutron reaction will be computed. The gamma-emissions from these sources are also computed, but are limited to a subset of nine target nuclides. If a user has experimental data to contribute to the alpha-neutron gamma emission database, it may be added directly or submitted to the GADRAS developers for inclusion. The gadras.exe.config file will be replaced when GADRAS updates are installed, so sending the information to the GADRAS developers is the preferred method for updating the database. This is also preferable because it enables other users to benefit from your efforts.

Improved predictions of nuclear reaction rates with the TALYS reaction code for astrophysical applications

International Nuclear Information System (INIS)

Goriely, S.; Hilaire, S.; Koning, A.J

2008-01-01

Context. Nuclear reaction rates of astrophysical applications are traditionally determined on the basis of Hauser-Feshbach reaction codes. These codes adopt a number of approximations that have never been tested, such as a simplified width fluctuation correction, the neglect of delayed or multiple-particle emission during the electromagnetic decay cascade, or the absence of the pre-equilibrium contribution at increasing incident energies. Aims. The reaction code TALYS has been recently updated to estimate the Maxwellian-averaged reaction rates that are of astrophysical relevance. These new developments enable the reaction rates to be calculated with increased accuracy and reliability and the approximations of previous codes to be investigated. Methods. The TALYS predictions for the thermonuclear rates of relevance to astrophysics are detailed and compared with those derived by widely-used codes for the same nuclear ingredients. Results. It is shown that TALYS predictions may differ significantly from those of previous codes, in particular for nuclei for which no or little nuclear data is available. The pre-equilibrium process is shown to influence the astrophysics rates of exotic neutron-rich nuclei significantly. For the first time, the Maxwellian- averaged (n, 2n) reaction rate is calculated for all nuclei and its competition with the radiative capture rate is discussed. Conclusions. The TALYS code provides a new tool to estimate all nuclear reaction rates of relevance to astrophysics with improved accuracy and reliability. (authors)

Estimation of the rate of volcanism on Venus from reaction rate measurements

Science.gov (United States)

Fegley, Bruce, Jr.; Prinn, Ronald G.

1989-01-01

Laboratory rate data for the reaction between SO2 and calcite to form anhydrite are presented. If this reaction rate represents the SO2 reaction rate on Venus, then all SO2 in the Venusian atmosphere will disappear in 1.9 Myr unless volcanism replenishes the lost SO2. The required volcanism rate, which depends on the sulfur content of the erupted material, is in the range 0.4-11 cu km of magma erupted per year. The Venus surface composition at the Venera 13, 14, and Vega 2 landing sites implies a volcanism rate of about 1 cu km/yr. This geochemically estimated rate can be used to determine if either (or neither) of two discordant geophysically estimated rates is correct. It also suggests that Venus may be less volcanically active than the earth.

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.

Charged-particle thermonuclear reaction rates: IV. Comparison to previous work

International Nuclear Information System (INIS)

Iliadis, C.; Longland, R.; Champagne, A.E.; Coc, A.

2010-01-01

We compare our Monte Carlo reaction rates (see Paper II of this issue) to previous results that were obtained by using the classical method of computing thermonuclear reaction rates. For each reaction, the comparison is presented using two types of graphs: the first shows the change in reaction rate uncertainties, while the second displays our new results normalized to the previously recommended reaction rate. We find that the rates have changed significantly for almost all reactions considered here. The changes are caused by (i) our new Monte Carlo method of computing reaction rates (see Paper I of this issue), and (ii) newly available nuclear physics information (see Paper III of this issue).

Roads leading to roam. Role of triple fragmentation and of conical intersections in photochemical reactions: experiments and theory on methyl formate.

Science.gov (United States)

Tsai, Po-Yu; Chao, Meng-Hsuan; Kasai, Toshio; Lin, King-Chuen; Lombardi, Andrea; Palazzetti, Federico; Aquilanti, Vincenzo

2014-02-21

The exploration of alternative roads that open to molecules with sufficient energy to yield different products permits prediction and eventually control of the outcomes of chemical reactions. Advanced imaging techniques for monitoring laser-induced photodissociation are here combined with dynamical simulations, involving ample sets of classical trajectories generated on a quantum chemical potential energy surface. Methyl formate, HCOOCH3, is photodissociated at energies near the triple fragmentation threshold into H, CO and OCH3. Images of velocity and rotational distributions of CO exhibit signatures of alternative routes, such as those recently designated as transition-state vs. roaming-mediated. Furthermore, a demonstration of the triple fragmentation route is given, and also confirmed by H-atom product imaging and FTIR time-resolved spectra of the intermediate HCO radical. In addition, the relevance of nonadiabatic transitions promoted by a conical intersection is clarified by simulations as the privileged "reactivity funnel" of organic photochemistry, whereby the outcomes of molecular photoexcitation are delivered to electronic ground states.

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

Science.gov (United States)

Liechty, Derek S.; Lewis, Mark J.

2010-01-01

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

Triple helix-forming oligonucleotide corresponding to the polypyrimidine sequence in the rat alpha 1(I) collagen promoter specifically inhibits factor binding and transcription.

Science.gov (United States)

Kovacs, A; Kandala, J C; Weber, K T; Guntaka, R V

1996-01-19

Type I and III fibrillar collagens are the major structural proteins of the extracellular matrix found in various organs including the myocardium. Abnormal and progressive accumulation of fibrillar type I collagen in the interstitial spaces compromises organ function and therefore, the study of transcriptional regulation of this gene and specific targeting of its expression is of major interest. Transient transfection of adult cardiac fibroblasts indicate that the polypurine-polypyrimidine sequence of alpha 1(I) collagen promoter between nucleotides - 200 and -140 represents an overall positive regulatory element. DNase I footprinting and electrophoretic mobility shift assays suggest that multiple factors bind to different elements of this promoter region. We further demonstrate that the unique polypyrimidine sequence between -172 and -138 of the promoter represents a suitable target for a single-stranded polypurine oligonucleotide (TFO) to form a triple helix DNA structure. Modified electrophoretic mobility shift assays show that this TFO specifically inhibits the protein-DNA interaction within the target region. In vitro transcription assays and transient transfection experiments demonstrate that the transcriptional activity of the promoter is inhibited by this oligonucleotide. We propose that TFOs represent a therapeutic potential to specifically influence the expression of alpha 1(I) collagen gene in various disease states where abnormal type I collagen accumulation is known to occur.

APUAMA: a software tool for reaction rate calculations.

Science.gov (United States)

Euclides, Henrique O; P Barreto, Patricia R

2017-06-01

APUAMA is a free software designed to determine the reaction rate and thermodynamic properties of chemical species of a reagent system. With data from electronic structure calculations, the APUAMA determine the rate constant with tunneling correction, such as Wigner, Eckart and small curvature, and also, include the rovibrational level of diatomic molecules. The results are presented in the form of Arrhenius-Kooij form, for the reaction rate, and the thermodynamic properties are written down in the polynomial form. The word APUAMA means "fast" in Tupi-Guarani Brazilian language, then the code calculates the reaction rate on a simple and intuitive graphic interface, the form fast and practical. As program output, there are several ASCII files with tabulated information for rate constant, rovibrational levels, energy barriers and enthalpy of reaction, Arrhenius-Kooij coefficient, and also, the option to the User save all graphics in BMP format.

The effect of sintering time on synthesis of in situ submicron {alpha}-Al{sub 2}O{sub 3} particles by the exothermic reactions of CuO particles in molten pure Al

Energy Technology Data Exchange (ETDEWEB)

Dikici, Burak, E-mail: burakdikici@yyu.edu.tr [Yuzuncu Yil University, Department of Mechanical Engineering, 65080 Van (Turkey); Gavgali, Mehmet [Ataturk University, Department of Mechanical Engineering, 25240 Erzurum (Turkey)

2013-02-25

Highlights: Black-Right-Pointing-Pointer Al-Cu/Al{sub 2}O{sub 3} composites were prepared successfully by means of hot pressing method. Black-Right-Pointing-Pointer Sintering time of the Al-CuO system effect the reaction rate and formation of Al{sub 2}O{sub 3}. Black-Right-Pointing-Pointer Increase in sintering time accelerates formation of submicron in situ {alpha}-Al{sub 2}O{sub 3} phase. Black-Right-Pointing-Pointer Hardness of the sintered composite for 30 min at 1000 Degree-Sign C increased from 60 to 174 HV. - Abstract: In this study, in situ {alpha}-Al{sub 2}O{sub 3} reinforcing particles have been successfully synthesised in an Al-Cu matrix alloy by means of the conventional Hot Pressing (HP) method. The effect of sintering time on the forming of the {alpha}-Al{sub 2}O{sub 3} phase at 1000 Degree-Sign C was investigated using Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and a Scanning Electron Microscope (SEM). The sintered composites contained thermodynamically stable {alpha}-Al{sub 2}O{sub 3} particles and {theta}-Al{sub 2}Cu eutectic phases, which were embedded in the Al-Cu matrix. The in situ {alpha}-Al{sub 2}O{sub 3} particles were generally spherical and their mean size was observed to be less than 0.5 {mu}m. The results showed that sintering time influences not only the reaction rate of copper and the formation of Al{sub 2}O{sub 3}. Also, an increase in the sintering time accelerates the formation of submicron in situ {alpha}-Al{sub 2}O{sub 3} particles and decreases the quantity of {theta}-Al{sub 2}Cu intermetallic phase in the liquid aluminium. Additionally, sintering of composite for 30 min at 1000 Degree-Sign C increased the hardness from 60 to 174 HV.

Improved predictions of nuclear reaction rates for astrophysics applications with the TALYS reaction code

International Nuclear Information System (INIS)

Goriely, S.; Hilaire, S.; Koning, A.J.

2008-01-01

Nuclear reaction rates for astrophysics applications are traditionally determined on the basis of Hauser-Feshbach reaction codes, like MOST. These codes use simplified schemes to calculate the capture reaction cross section on a given target nucleus, not only in its ground state but also on the different thermally populated states of the stellar plasma at a given temperature. Such schemes include a number of approximations that have never been tested, such as an approximate width fluctuation correction, the neglect of delayed particle emission during the electromagnetic decay cascade or the absence of the pre-equilibrium contribution at increasing incident energies. New developments have been brought to the reaction code TALYS to estimate the Maxwellian-averaged reaction rates of astrophysics relevance. These new developments give us the possibility to calculate with an improved accuracy the reaction cross sections and the corresponding astrophysics rates. The TALYS predictions for the thermonuclear rates of astrophysics relevance are presented and compared with those obtained with the MOST code on the basis of the same nuclear ingredients for nuclear structure properties, optical model potential, nuclear level densities and γ-ray strength. It is shown that, in particular, the pre-equilibrium process significantly influences the astrophysics rates of exotic neutron-rich nuclei. The reciprocity theorem traditionally used in astrophysics to determine photo-rates is also shown no to be valid for exotic nuclei. The predictions obtained with different nuclear inputs are also analyzed to provide an estimate of the theoretical uncertainties still affecting the reaction rate prediction far away from the experimentally known regions. (authors)

Charged particle induced thermonuclear reaction rates: a compilation for astrophysics

International Nuclear Information System (INIS)

Grama, C.

1999-01-01

We report on the results of the European network NACRE (Nuclear Astrophysics Compilation of REaction rates). The principal reason for setting up the NACRE network has been the necessity of building up a well-documented and detailed compilation of rates for charged-particle induced reactions on stable targets up to Si and on unstable nuclei of special significance in astrophysics. This work is meant to supersede the only existing compilation of reaction rates issued by Fowler and collaborators. The main goal of NACRE network was the transparency in the procedure of calculating the rates. More specifically this compilation aims at: 1. updating the experimental and theoretical data; 2. distinctly identifying the sources of the data used in rate calculation; 3. evaluating the uncertainties and errors; 4. providing numerically integrated reaction rates; 5. providing reverse reaction rates and analytical approximations of the adopted rates. The cross section data and/or resonance parameters for a total of 86 charged-particle induced reactions are given and the corresponding reaction rates are calculated and given in tabular form. Uncertainties are analyzed and realistic upper and lower bounds of the rates are determined. The compilation is concerned with the reaction rates that are large enough for the target lifetimes shorter than the age of the Universe, taken equal to 15 x 10 9 y. The reaction rates are provided for temperatures lower than T = 10 10 K. In parallel with the rate compilation a cross section data base has been created and located at the site http://pntpm.ulb.ac.be/nacre..htm. (authors)

Was Proxima captured by Alpha Centauri A and B?

Science.gov (United States)

Feng, F.; Jones, H. R. A.

2018-01-01

The nearest stellar system consists of the stars Proxima, Alpha Centauri A and B and at least one planet Proxima b. The habitability of Proxima b and any other planets are likely to be significantly influenced by the orbital evolution of the system. To study the dynamical evolution of the system, we simulate the motions of Proxima and Alpha Centauri A and B due to the perturbations from the Galactic tide and stellar encounters in a Monte Carlo fashion. From 100 clones, we find that 74 per cent orbits of Proxima Centauri are bound to Alpha Centauri A and B while 17 per cent and 9 per cent orbits become unbound in the simulations over the past and future 5 Gyr. If the system migrated outward in the Milky Way to its current location, more than 50 per cent of clones could become unstable in backward simulations. The ratio of unstable clones increases with the simulation time-scale and encounter rate. This provides some evidence for a capture scenario for the formation of the current triple system. Despite large uncertainties, the metallicity difference between Proxima and Alpha Centauri A and B is also suggestive of their different origin. None the less, further improvements in the available data and models will be necessary for a reliable assessment of the history of the Proxima-Alpha Centauri system and its impact on the habitability of Proxima b.

The path to improved reaction rates for astrophysics

International Nuclear Information System (INIS)

Rauscher, T.

2011-01-01

This review focuses on nuclear reactions in astrophysics and, more specifically, on reactions with light ions (nucleons and α particles) proceeding via the strong interaction. It is intended to present the basic definitions essential for studies in nuclear astrophysics, to point out the differences between nuclear reactions taking place in stars and in a terrestrial laboratory, and to illustrate some of the challenges to be faced in theoretical and experimental studies of those reactions. The discussion revolves around the relevant quantities for astrophysics, which are the astrophysical reaction rates. The sensitivity of the reaction rates to the uncertainties in the prediction of various nuclear properties is explored and some guidelines for experimentalists are also provided. (author)

Alpha particles spectrometer with photodiode PIN

International Nuclear Information System (INIS)

Chacon R, A.; Hernandez V, R.; Hernandez D, V. M.; Vega C, H. R.; Ramirez G, J.

2009-10-01

The radiation propagates in form of electromagnetic waves or corpuscular radiation; if the radiation energy causes ionization in environment that crosses it is considered ionizing radiation. To detect radiation several detectors types are used, if the radiation are alpha particles are used detectors proportional type or trace elements. In this work the design results, construction and tests of an alpha particles spectrometer are presented, which was designed starting from a photodiode PIN type. The system design was simulated with a code for electronic circuits. With results of simulation phase was constructed the electronic phase that is coupled to a multichannel analyzer. The resulting electronic is evaluated analyzing the electronic circuit performance before an alphas triple source and alpha radiation that produce two smoke detectors of domestic use. On the tests phase we find that the system allows obtain, in a multichannel, the pulses height spectrum, with which we calibrate the system. (Author)

Raman Spectral Determination of Chemical Reaction Rate Characteristics

Science.gov (United States)

Balakhnina, I. A.; Brandt, N. N.; Mankova, A. A.; Chikishev, A. Yu.; Shpachenko, I. G.

2017-09-01

The feasibility of using Raman spectroscopy to determine chemical reaction rates and activation energies has been demonstrated for the saponification of ethyl acetate. The temperature dependence of the reaction rate was found in the range from 15 to 45°C.

Chemical changes in groundwater and their reaction rates

International Nuclear Information System (INIS)

Talma, A.S.

1981-01-01

The evolution of the major ion concentrations of groundwater (Na, K, Ca, Mg, HCO 3 , SO 4 , Cl and NO 3 ) can be described as the consequence of a number of competing chemical reactions. With the aid of the naturally occuring radioactive and stable isotopes some of these reactions can be separated, identified and followed in space and time. In some field studies, especialy of artesian water, the rates of reactions can be estimated. A number of processes observed in South African sandstones aquifers are discussed and the variable reaction rates demonstrated. Reactions that can be identified include carbonate solution, chemical weathering, salt leaching, cation exchange and redox processes

A high-resolution study of the sup 20 Ne( sup 3 He,t) sup 20 Na reaction and the sup 19 Ne(p,. gamma. ) sup 20 Na reaction rate

Energy Technology Data Exchange (ETDEWEB)

Smith, M S; Magnus, P V; Hahn, K I; Howard, A J; Parker, P D [A.W. Wright Nuclear Structure Lab., Yale Univ., New Haven, CT (United States); Champagne, A E; Mao, Z Q [Dept. of Physics, Princeton Univ., NJ (United States)

1992-01-13

A high-precision measurement of the {sup 20}Ne({sup 3}He,t){sup 20}Na reaction has been made using implanted {sup 20}Ne transmission targets to obtain pertinent information on the low-energy resonances in the {sup 19}Ne(p,{gamma}){sup 20}Na reaction. Resonance energies (447{+-}5, 658{+-}5, 787{+-}5, and 857{+-}5 keV) and upper limits on total intrinsic widths (<10, <6, <10, and <16 keV) have been measured for four excited states above the 2.199 MeV proton threshold in {sup 20}Na. The stellar {sup 19}Ne(p,{gamma}){sup 20}Na reaction rate is calculated for temperatures between 1x10{sup 8} and 1x10{sup 9} K. When combined with a recent study of the {sup 15}O({alpha},{gamma}){sup 19}Ne reaction, a new estimate is made of the conditions required for breakout from the Hot CNO cylce to the rapid proton capture process. (orig.).

Reaction Order Ambiguity in Integrated Rate Plots

Science.gov (United States)

Lee, Joe

2008-01-01

Integrated rate plots are frequently used in reaction kinetics to determine orders of reactions. It is often emphasised, when using this methodology in practice, that it is necessary to monitor the reaction to a substantial fraction of completion for these plots to yield unambiguous orders. The present article gives a theoretical and statistical…

Effective dynamics along given reaction coordinates, and reaction rate theory.

Science.gov (United States)

Zhang, Wei; Hartmann, Carsten; Schütte, Christof

2016-12-22

In molecular dynamics and related fields one considers dynamical descriptions of complex systems in full (atomic) detail. In order to reduce the overwhelming complexity of realistic systems (high dimension, large timescale spread, limited computational resources) the projection of the full dynamics onto some reaction coordinates is examined in order to extract statistical information like free energies or reaction rates. In this context, the effective dynamics that is induced by the full dynamics on the reaction coordinate space has attracted considerable attention in the literature. In this article, we contribute to this discussion: we first show that if we start with an ergodic diffusion process whose invariant measure is unique then these properties are inherited by the effective dynamics. Then, we give equations for the effective dynamics, discuss whether the dominant timescales and reaction rates inferred from the effective dynamics are accurate approximations of such quantities for the full dynamics, and compare our findings to results from approaches like Mori-Zwanzig, averaging, or homogenization. Finally, by discussing the algorithmic realization of the effective dynamics, we demonstrate that recent algorithmic techniques like the "equation-free" approach and the "heterogeneous multiscale method" can be seen as special cases of our approach.

Back Reaction And Local Cosmological Expansion Rate

CERN Document Server

Geshnizjani, G; Geshnizjani, Ghazal; Brandenberger, Robert

2002-01-01

We calculate the back reaction of cosmological perturbations on a general relativistic variable which measures the local expansion rate of the Universe. Specifically, we consider a cosmological model in which matter is described by a single field. We analyze back reaction both in a matter dominated Universe and in a phase of scalar field-driven chaotic inflation. In both cases, we find that the leading infrared terms contributing to the back reaction vanish when the local expansion rate is measured at a fixed value of the matter field which is used as a clock, whereas they do not appear to vanish if the expansion rate is evaluated at a fixed value of the background time. We discuss possible implications for more realistic models with a more complicated matter sector.

Rates for some reactions involving 42Ca and 44Ca

International Nuclear Information System (INIS)

Cheng, C.W.; King, J.D.

1980-01-01

Ground-state reaction rates have been deduced from recent cross section measurements for the 42 CA(α, n) 45 Ti, 42 Ca(p, γ) 43 Sc, and 44 Ca(p, n) 44 Sc reactions. Comparison of these rates with those calculated from a statistical model of nuclear reactions. (Woosley et al) shows good agreement for the first two, but the 44 Ca(p, n) rate is more than a factor of 2 less than the theoretical prediction. Stellar reaction rates have been derived from the ground-state rates by multiplying the ground-state rates by the ratio of stellar to ground-state rates given by the statistical model. Both ground-state and stellar rates have been represented by analytic functions of the temperature. The role of these reactions in the approach to quasi-equilibrium during explosive silicon burning is discussed

Theoretical and experimental studies of the efficiency of a solid-state track detector utilizing (neutron, alpha) reactions

International Nuclear Information System (INIS)

Palfalvi, J.

1983-04-01

The neutron sensitivity of Kodak-Pathe LR 115 II type cellulose nitrate track detectors with different (n,α) radiators was investigated by calculations and measurements. The α counting efficiency using an optical microscope is 95% for α particles with maximum energy of 2 MeV. When using an image analyzer the etched through-tracks (holes) with diameters greater than 2 μm are counted. The efficiency then depends only on the original and removed layer thickness but not on the etching temperature within the range of 40 to 60 deg C and the 2.5 to 6 N normality of the NaOH etchant. Efficiency varies from about 3 to 20% for alphas from the 6 Li/n, +a/T reaction if the removed layer lies in the range of 7 to 10 μm, and varies from 2 to 10% for 10 B/n, α/ 7 Li reaction alphas when the layer re--moval is 8 to 10 μm. (author)

Contribution to the study of excited levels of {sup 7}Be obtained from the reaction {sup 6}Li (p, {alpha}); Contribution a l'etude des niveaux excites du {sup 7}Be obtenus par la reaction {sup 6}Li (p, {alpha})

Energy Technology Data Exchange (ETDEWEB)

Beaumevieille, H. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-05-01

The interpretation of the results of the reaction {sup 6}Li (p, {alpha}) in the energy range 100 keV to 3 MeV has been done with the next levels of {sup 7}Be : 3/2- (5,9 MeV), 3/2+ (6,2 MeV), 5/2- (7,18 MeV) and a level the characteristics of which may be 1/2+ or {sup 4}P (9,5 MeV). (author) [French] L'interpretation des resultats de la reaction {sup 6}Li (p, {alpha}) dans la gamme d'energie 100 keV a 3 MeV a ete faite avec les niveaux suivants du {sup 7}Be : 3/2- (5,9 MeV), 3/2 + (6,2 MeV), 5/2- (7,18 MeV) et un niveau dont les caracteristiques doivent etre 1/2+ ou {sup 4}P (9,5 MeV). (auteur)

Contribution to the study of excited levels of {sup 7}Be obtained from the reaction {sup 6}Li (p, {alpha}); Contribution a l'etude des niveaux excites du {sup 7}Be obtenus par la reaction {sup 6}Li (p, {alpha})

Energy Technology Data Exchange (ETDEWEB)

Beaumevieille, H [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-05-01

The interpretation of the results of the reaction {sup 6}Li (p, {alpha}) in the energy range 100 keV to 3 MeV has been done with the next levels of {sup 7}Be : 3/2- (5,9 MeV), 3/2+ (6,2 MeV), 5/2- (7,18 MeV) and a level the characteristics of which may be 1/2+ or {sup 4}P (9,5 MeV). (author) [French] L'interpretation des resultats de la reaction {sup 6}Li (p, {alpha}) dans la gamme d'energie 100 keV a 3 MeV a ete faite avec les niveaux suivants du {sup 7}Be : 3/2- (5,9 MeV), 3/2 + (6,2 MeV), 5/2- (7,18 MeV) et un niveau dont les caracteristiques doivent etre 1/2+ ou {sup 4}P (9,5 MeV). (auteur)

Temperature dependence of muonium reaction rates in the gas phase

International Nuclear Information System (INIS)

Fleming, D.G.; Garner, D.M.; Mikula, R.J.; British Columbia Univ., Vancouver

1981-01-01

A study of the temperature dependence of reaction rates has long been an important tool in establishing reaction pathways in chemical reactions. This is particularly true for the reactions of muonium (in comparison with those of hydrogen) since a measurement of the activation energy for chemical reaction is sensitive to both the height and the position of the potential barrier in the reaction plane. For collision controlled reactions, on the other hand, the reaction rate is expected to exhibit a weak T 1 sup(/) 2 dependence characteristic of the mean collision velocity. These concepts are discussed and their effects illustrated in a comparison of the chemical and spin exchange reaction rates of muonium and hydrogen in the temperature range approx.300-approx.500 K. (orig.)

Deformation behaviour of {gamma}+{alpha}{sub 2} Ti aluminide processed through reaction synthesis

Energy Technology Data Exchange (ETDEWEB)

Gupta, R.K., E-mail: rohitkumar_gupta@vssc.gov.in [Vikram Sarabhai Space Centre, ISRO, Trivandrum, Kerala 695 022 (India); Pant, Bhanu [Vikram Sarabhai Space Centre, ISRO, Trivandrum, Kerala 695 022 (India); Kumar, Vinod [SAIL-RDCIS, Ranchi (India); Agarwala, Vijaya [Indian Institute of Technology, Roorkee 247 667 (India); Sinha, P.P. [Vikram Sarabhai Space Centre, ISRO, Trivandrum, Kerala 695 022 (India)

2013-01-01

{gamma}+{alpha}{sub 2} titanium aluminide alloys made through reaction synthesis have been used for deformation study. Hot isothermal compression test is carried out to study the deformation characteristics of the alloys using Gleeble thermomechanical simulator. Three alloys based on Ti48Al2Cr2Nb0.1B (at%) are tested at different temperatures and at different strain rates. True stress-true strain plots are analyzed along with analysis of tested specimens. Tested specimens are observed under optical and electron microscopes. Presence of various deformation morphologies and phases were confirmed. Microhardness evaluation and transmission electron microscopic examination are used to confirm the presence of different phases. It is found that dynamic recrystallization is mainly playing role in deformation of these alloys. Presence of dynamically recrystallized (DRX) grains and lamellar microstructures is confirmed at the intergranular area and inside the grains, respectively. A nucleation model is suggested for DRX and lamellar grain nucleation during deformation. Attempt has been made to quantify the presence of various phases through optical microscopy. Hot workability map is also suggested on the basis of microstructural and visual observation of compression tested specimens.

Techniques for measuring the alpha-particle distribution in magnetically confined plasmas

International Nuclear Information System (INIS)

Post, D.E.; Mikkelsen, D.R.; Hulse, R.A.; Stewart, L.D.; Weisheit, J.C.

1979-10-01

Methods are proposed for measuring the alpha-particle distribution in magnetically confined fusion plasmas using neutral-atom doping beams, ultraviolet spectroscopy, and neutral particle detectors. In the first method single charge exchange reactions, A 0 + He ++ - > A + (He + )*, are used to populate the n=2 and n=3 levels of He + . The ultraviolet photons from the decaying excited states are Doppler shifted by 5 to 10 Angstroms from those produced by the thermalized alpha-particle ash. In the second method double charge exchange reactions, A 0 + He ++ - > A ++ + He 0 , enable fast neutralized alpha-particles to escape from the plasma and be detected by neutral particle analysers. Detector configurations are analyzed, count rates are estimated and their detectability is discussed. A preliminary analysis of the feasibility of the required neutral beams is presented, and exploratory experiments on existing devices are suggested

Reaction rate of 24Mg(p,γ)25Al

International Nuclear Information System (INIS)

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

1999-01-01

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

General properties of astrophysical reaction rates in explosive nucleosynthesis

International Nuclear Information System (INIS)

Rauscher, Thomas

2013-01-01

Fundamental differences in the prediction of reaction rates with intermediate and heavy target nuclei compared to the ones with light nuclei are discussed, with special emphasis on stellar modifications of the rates. Ground and excited state contributions to the stellar rates are quantified, deriving a linear weighting of excited state contributions despite of a Boltzmann population of the nuclear states. A Coulomb suppression effect of the excited state contributions is identified, acting against the usual Q-value rule in some reactions. The proper inclusion of experimental data in revised stellar rates is shown, containing revised uncertainties. An application to the s-process shows that the actual uncertainties in the neutron capture rates are larger than would be expected from the experimental errors alone. Sensitivities of reaction rates and cross sections are defined and their application in reaction studies is discussed. The conclusion provides a guide to experiment as well as theory on how to best improve the rates used in astrophysical simulations and how to assess their uncertainties.

Accurate and approximate thermal rate constants for polyatomic chemical reactions

International Nuclear Information System (INIS)

Nyman, Gunnar

2007-01-01

In favourable cases it is possible to calculate thermal rate constants for polyatomic reactions to high accuracy from first principles. Here, we discuss the use of flux correlation functions combined with the multi-configurational time-dependent Hartree (MCTDH) approach to efficiently calculate cumulative reaction probabilities and thermal rate constants for polyatomic chemical reactions. Three isotopic variants of the H 2 + CH 3 → CH 4 + H reaction are used to illustrate the theory. There is good agreement with experimental results although the experimental rates generally are larger than the calculated ones, which are believed to be at least as accurate as the experimental rates. Approximations allowing evaluation of the thermal rate constant above 400 K are treated. It is also noted that for the treated reactions, transition state theory (TST) gives accurate rate constants above 500 K. TST theory also gives accurate results for kinetic isotope effects in cases where the mass of the transfered atom is unchanged. Due to neglect of tunnelling, TST however fails below 400 K if the mass of the transferred atom changes between the isotopic reactions

Calculus of radiolytic products generation in water due to alpha radiation. Determination of the spent nuclear fuels matrix alteration rate Determination of velocity of spent fuel matrix

International Nuclear Information System (INIS)

Quinones, J.; Serrano, J.; Diaz Arocas, P.; Rodriguez Almazan, J. L.; Bruno, J.; Cera, E.; Merino, J.; Esteban, J. A.; Martinez-Esparza, A.

2000-01-01

The generation of radiolytic products as a result of alpha radiation in the surface of the spent fuel is a key process in order to understand how the it becomes degraded in repository conditions. The present work has established a radiolytic model based on a set of reactions involving fuel oxidation-dissolution and radiolytic products recombination. It also includes the decrease of the dose rates as the main alpha emitters decay away. Four cases, with varying parameters of the system, have been assessed. The results show a decrease in both the concentration of the radiolytic products in the gap water and the degradation of the fuel matrix. It has been estimated that in the period of the evaluation (10''6 years) up to 52% of the pellet is altered in the conservative cases, whereas only 11% is altered in the realistic cases. No significant differences were observed when the carbonates reactions were included in the system. (Author)

Rates of the main thermonuclear reactions

International Nuclear Information System (INIS)

Abramovich, S.N.; Guzhovskii, B.Ya.; Dunaeva, S.A.; Fomushkin, E.F.

1992-01-01

The data on the cross sections of main thermonuclear reactions have been estimated with an account of the latest experimental results in a form of S-factor spline presentation. Based on this estimation, the reates of these reactions in 0.0001-1 MeV temperature range in the supposition of Maxwell distribution of relative velocities have been computed. The Maxwell-Boltzmann averaged -factors were calculated according to the table values of the reaction rates. Then the -factors were approximated with the 3 order spline-function. The necessity of the account of electron shielding and intramolecular movement at low temperatures is discussed (orig.)

Comparison of split double and triple twists in pair figure skating.

Science.gov (United States)

King, Deborah L; Smith, Sarah L; Brown, Michele R; McCrory, Jean L; Munkasy, Barry A; Scheirman, Gary I

2008-05-01

In this study, we compared the kinematic variables of the split triple twist with those of the split double twist to help coaches and scientists understand these landmark pair skating skills. High-speed video was taken during the pair short and free programmes at the 2002 Salt Lake City Winter Olympics and the 2003 International Skating Union Grand Prix Finals. Three-dimensional analyses of 14 split double twists and 15 split triple twists from eleven pairs were completed. In spite of considerable variability in the performance variables among the pairs, the main difference between the split double twists and split triple twists was an increase in rotational rate. While eight of the eleven pairs relied primarily on an increased rotational rate to complete the split triple twist, three pairs employed a combined strategy of increased rotational rate and increased flight time due predominantly to delayed or lower catches. These results were similar to observations of jumps in singles skating for which the extra rotation is typically due to an increase in rotational velocity; increases in flight time come primarily from delayed landings as opposed to additional height during flight. Combining an increase in flight time and rotational rate may be a good strategy for completing the split triple twist in pair skating.

Mechanisms of alpha emitter production in 12C induced reactions at 1 GeV

International Nuclear Information System (INIS)

Dufour, J.P.; Delagrange, H.; Del Moral, R.

1982-01-01

We present cross sections, mean projected recoil ranges and angular distributions of radioactive alpha emitters produced in 12 C-induced reactions at 1 GeV on targets ranging from Gd to Pb. We use a new technique of on-line electrostatic collection. The wide spectrum of produced isotopes corresponds to nuclei close to the target up to nuclei with as much as 60 nucleons less than the target. The intranuclear cascade calculations can reproduce the main features of nuclei having lost up

Rate constant for reaction of atomic hydrogen with germane

Science.gov (United States)

Nava, David F.; Payne, Walter A.; Marston, George; Stief, Louis J.

1990-01-01

Due to the interest in the chemistry of germane in the atmospheres of Jupiter and Saturn, and because previously reported kinetic reaction rate studies at 298 K gave results differing by a factor of 200, laboratory measurements were performed to determine the reaction rate constant for H + GeH4. Results of the study at 298 K, obtained via the direct technique of flash photolysis-resonance fluorescence, yield the reaction rate constant, k = (4.08 + or - 0.22) x 10(exp -12) cu cm/s.

Thermochemistry of uranium(VI), arsenic, and alkali metal triple oxides

International Nuclear Information System (INIS)

Karyakin, N.V.; Chernorukov, G.N.

1994-01-01

The standard enthalpies of reactions of stoichiometric mixtures of potassium dyhydrogen orthoarsenate, uranium(VI) oxide, alkali metal nitrates, and of mixtures of triple oxides with the general formula M I AsUO 6 (M I =Li, Na, K, Rb, and Cs) and potassium nitrate with aqueous solution of hydrofluoric acid were determined an an adiabatic calorimeter at 298.15 K. The standard enthalpies of formation of uranium(VI), arsenic, and alkali metal triple oxides at 298.15 K were calculated form the data obtained. 8 refs., 1 tab

A review of reaction rates in high temperature air

Science.gov (United States)

Park, Chul

1989-01-01

The existing experimental data on the rate coefficients for the chemical reactions in nonequilibrium high temperature air are reviewed and collated, and a selected set of such values is recommended for use in hypersonic flow calculations. For the reactions of neutral species, the recommended values are chosen from the experimental data that existed mostly prior to 1970, and are slightly different from those used previously. For the reactions involving ions, the recommended rate coefficients are newly chosen from the experimental data obtained more recently. The reacting environment is assumed to lack thermal equilibrium, and the rate coefficients are expressed as a function of the controlling temperature, incorporating the recent multitemperature reaction concept.

High-precision (p,t) reactions to determine reaction rates of explosive stellar processes

NARCIS (Netherlands)

Matić, Andrija

2007-01-01

The aim of my study was to investigate the nuclear structure of 22Mg and 26Si. These two nuclei play a significant role in stellar reaction processes at high temperatures. On base of the obtained nuclear structure we calculated the stellar reaction rates for the following reactions: 18Ne(α,p)21Na,

Reaction-rate formula in out of equilibrium quantum field theory

OpenAIRE

Niegawa, A.; Okano, K.; Ozaki, H.

1999-01-01

A complete derivation, from first principles, of the reaction-rate formula for a generic reaction taking place in an out of equilibrium quantum-field system is given. It is shown that the formula involves no finite-volume correction. Each term of the reaction-rate formula represents a set of physical processes that contribute to the reaction under consideration.

Survival and local control rates of triple-negative breast cancer patients treated with boost-IOERT during breast-conserving surgery

Energy Technology Data Exchange (ETDEWEB)

Fastner, Gerd; Zehentmayr, Franz; Kopp, Peter; Fussl, Christoph; Sedlmayer, Felix [Landeskrankenhaus, Paracelsus Medical University, Department of Radiotherapy and Radio-Oncology, Salzburg (Austria); Hauser-Kronberger, Cornelia [Landeskrankenhaus, Paracelsus Medical University, Department of Pathology, Salzburg (Austria); Moder, Angelika [Landeskrankenhaus, Paracelsus Medical University, Institute of Inborn Errors in Metabolism, Salzburg (Austria); Reitsamer, Roland; Fischer, Thorsten [Landeskrankenhaus, Paracelsus Medical University, Department of Special Gynecology, Salzburg (Austria); Landeskrankenhaus, Paracelsus Medical University, Department of Gynecology, Salzburg (Austria); Deutschmann, Heinrich [Landeskrankenhaus, Paracelsus Medical University, Department of Radiotherapy and Radio-Oncology, Salzburg (Austria); Paracelsus Medical University, Institute for Research and Development of Advanced Radiation Technologies (radART), Salzburg (Austria)

2016-01-15

The purpose of this work was to retrospectively evaluate survival and local control rates of triple-negative breast cancer subtypes classified as five marker negative (5NP) and core basal (CB), respectively, after breast-conserving surgery and intraoperative boost radiotherapy with electrons (IOERT) followed by whole breast irradiation. A total of 71 patients with triple-negative breast cancer were enrolled, who were treated with lumpectomy, axillary lymph node dissection, and IOERT with 9.6 Gy (median D{sub max}) followed by normofractionated whole breast irradiation to median total doses of 54 Gy. Chemotherapy was applied in a neoadjuvant (12 %), adjuvant (75 %), or combinational setting (7 %). After a median follow-up of 97 months (range 4-170 months), 5 in-breast recurrences were detected (7.0 %). For all patients, 8-year actuarial rates for local control, metastases-free survival, disease-specific survival, and overall survival amounted to 89, 75, 80, and 69 %, respectively. All local recurrences occurred in grade 3 (G3) tumors irrespective of their specific immunohistochemical phenotype; thus, the local control rate for grades 1/2 (G1/2) was 100 % for both 5NP and CB, while for G3 it was 88 % for 5NP and 90 % for CB (p = 0.65 and 0.82, respectively, n.s.). For disease-specific survival, only the difference of the best-prognosis group 5-NP/G3 vs. the worst-prognosis cohort CB/G1/2 was statistically significant: 90 % vs. 54 % (p = 0.03). Boost-IOERT provides acceptable long-term in-breast control in triple negative breast cancer. The best subgroup in terms of disease-specific survival was represented by 5NP in combination with tumor grading G3. (orig.) [German] Ziel der Studie war es, im Rahmen einer retrospektiven Analyse Ueberlebens- und Lokalkontrollraten bei triple-negativen Mammakarzinomen zu untersuchen. Die Tumoren waren in 5NP(5-Marker-negative)- und CB(core basal)-Subtypen klassifiziert und die Patientinnen hatten nach brusterhaltender Operation und

Phenomenological analisis of the p-even- and p,odd-angular asimmetry of alpha particles in the 10B(n, α)7Li reaction with thermal polarized neutrons

International Nuclear Information System (INIS)

Rzhevskij, E.S.

1983-01-01

The formalism for multilevel phenomfor munological analysis of angular asymmetry of alpha-particles escape from compound-nuclei in reactions induced by thermal polarized neutrons is suggested. The formalism is based on R-matrix theory of nuclear reactions. The connection of problems of angular correlations description with those of light nuclei structure is shown. The problems related to the selection of compound-resonance parameters, determination of alpha-cluster states, estimation of the role of these or those compound-resonances in neutron and alpha-particle channels are discussed. An explanation is given to the observed in the experiment p-even left/right angular asymmetry of alpha-particles. The values of p-odd angular correlations, the measurements of which are continued, are estimated

Cross sections and thermonuclear reaction rates of proton-induced reactions on 37Cl

International Nuclear Information System (INIS)

Weber, R.O.; Tingwell, C.I.W.; Mitchell, L.W.; Sevior, M.E.; Sargood, D.G.

1984-01-01

The yields of γ-rays from the reactions of 37 Cl(p,γ) 38 Ar and 37 Cl(p,αγ) 34 S have been measured as a of bombarding energy over the ranges 0.65 - 2.15 MeV and 1.25 -2.15 MeV respectively, and the yield of neutrons from 37 Cl(p,n) 37 Ar from threshold to 2.50 MeV. The results are compared with global statistical-model calculations and thermonuclear reaction rates are calculated for the temperature range 5 x 10 8 - 10 10 K. The significance of these thermonuclear reaction rates for stellar nucleosynthesis calculations is discussed

Charged-particle induced thermonuclear reaction rates: a compilation for astrophysics

International Nuclear Information System (INIS)

Grama, Cornelia; Angulo, C.; Arnould, M.

2000-01-01

The rapidly growing wealth of nuclear data becomes less and less easily accessible to the astrophysics community. Mastering this volume of information and making it available in an accurate and usable form for incorporation into stellar evolution or nucleosynthesis models become urgent goals of prime necessity. we report on the results of the European network NACRE (Nuclear Astrophysics Compilation of REaction rates). The principal motivation for the setting-up of the NACRE network has been the necessity of building up a well-documented and detailed compilation of rates for charged-particle induced reactions on stable targets up to Si and on unstable nuclei of special significance in astrophysics. This work is meant to supersede the only existing compilation of reaction rates issued by Fowler and collaborators. The cross section data and/or resonance parameters for a total of 86 charged-particle induced reactions are given and the corresponding reaction rates are calculated and given in tabular form. When cross section data are not available in the whole needed range of energies, the theoretical predictions obtained in the framework of the Hauser-Feshbach model is used. Uncertainties are analyzed and realistic upper and lower bounds of the rates are determined. Reverse reaction rates and analytical approximations of the adopted rates are also provided. (authors)

Charged-particle induced thermonuclear reaction rates: a compilation for astrophysics

International Nuclear Information System (INIS)

Grama, Cornelia

1999-01-01

The rapidly growing wealth of nuclear data becomes less and less easily accessible to the astrophysics community. Mastering this volume of information and making it available in an accurate and usable form for incorporation into stellar evolution or nucleosynthesis models become urgent goals of prime necessity. We report on the results of the European network NACRE (Nuclear Astrophysics Compilation of REaction rates). The principal motivation for the setting-up of the NACRE network has been the necessity of building up a well-documented and detailed compilation of rates for charged -particle induced reactions on stable targets up to Si and on unstable nuclei of special significance in astrophysics. This work is meant to supersede the only existing compilation of reaction rates issued by Fowler and collaborators. The cross section data and/or resonance parameters for a total of 86 charged-particle induced reactions are given and the corresponding reaction rates are calculated and given in tabular form. When cross section data are not available in the whole needed range of energies the theoretical predictions obtained in the framework of the Hauser-Feshbach model are used. Uncertainties are analyzed and realistic upper and lower bounds of the rates are determined. Reverse reaction rates and analytical approximations of the adopted rates are also provided. (author)

Effects of alpha and gamma radiation on glass reaction in an unsaturated environment

International Nuclear Information System (INIS)

Wronkiewicz, D.J.; Young, J.E.; Bates, J.K.

1990-01-01

Radiation may effect the long-term performance of glass in an unsaturated repository site by interacting with air, water vapor, or liquid water. The present study examines (1) the effects of alpha or gamma irradiation in a water vapor environment, and (2) the influence of radiolytic products on glass reaction. Results indicate that nitric and organic acids form in an irradiated water vapor environment and are dissolved in thin films of condensed water. Glass samples exposed to these conditions react faster and have a different assemblage of secondary phases than glasses exposed to nonirradiated water vapor environments. 23 refs., 4 figs., 2 tabs

BAYESIAN ESTIMATION OF THERMONUCLEAR REACTION RATES

Energy Technology Data Exchange (ETDEWEB)

Iliadis, C.; Anderson, K. S. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States); Coc, A. [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), CNRS/IN2P3, Univ. Paris-Sud, Université Paris–Saclay, Bâtiment 104, F-91405 Orsay Campus (France); Timmes, F. X.; Starrfield, S., E-mail: iliadis@unc.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1504 (United States)

2016-11-01

The problem of estimating non-resonant astrophysical S -factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied to this problem in the past, almost all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extrasolar planets, gravitational waves, and Type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present astrophysical S -factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the reactions d(p, γ ){sup 3}He, {sup 3}He({sup 3}He,2p){sup 4}He, and {sup 3}He( α , γ ){sup 7}Be, important for deuterium burning, solar neutrinos, and Big Bang nucleosynthesis.

Capture reactions on C-14 in nonstandard big bang nucleosynthesis

Science.gov (United States)

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

1990-01-01

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

Back reaction and the local cosmological expansion rate

CERN Document Server

Geshnizjani, G

2002-01-01

We calculate the back reaction of cosmological perturbations on a general relativistic variable which measures the local expansion rate of the Universe. Specifically, we consider a cosmological model in which matter is described by a single field. We analyze back reaction both in a matter-dominated Universe and in a phase of scalar field-driven chaotic inflation. In both cases, we find that the leading infrared terms contributing to the back reaction vanish when the local expansion rate is measured at a fixed value of the matter field which is used as a clock, whereas they do not appear to vanish if the expansion rate is evaluated at a fixed value of the background time. We discuss possible implications for more realistic models with a more complicated matter sector.

Synthesis and antimicrobial evaluation of new 3-alkyl/aryl-2-[((alpha,alpha-diphenyl-alpha-hydroxy)acetyl)hydrazono]-5-methyl-4-thiazolidinones.

Science.gov (United States)

Güzeldemirci, Nuray Ulusoy; Ilhan, Eser; Küçükbasmaci, Omer; Satana, Dilek

2010-01-01

New 4-thiazolidinone derivatives of benzilic acid (alpha,alpha-diphenyl-alpha-hydroxyacetic acid) have been synthesized and evaluated for antibacterial and antifungal activities. The reaction of 1- (alpha,alpha-diphenyl-alpha-hydroxy)acetyl-4-alkyl/arylthiosemicarbazides with ethyl 2-bromopropionate gave 3-alkyl/aryl-2-[((alpha,alpha-diphenyl-alpha-hydroxy)acetyl)hydrazono]-5-methyl-4-thiazolidinone derivatives. Their antibacterial and antifungal activities were evaluated against S. aureus ATCC 29213, P. aeruginosa ATCC 27853, E. coli ATCC 25922, C. albicans ATCC 10231, C. parapsilosis ATCC 22019, C. krusei ATCC 6258, T. mentagrophytes var. erinacei NCPF 375, M. gypseum NCPF 580 and T. tonsurans NCPF 245. 3e, 3f, 3g and 3h showed the highest antibacterial activity. Particularly 3a and 3e showed the highest antifungal activities against C. parapsilosis ATCC 22019, T. tonsurans NCPF 245 and M. gypseum NCPF 580.

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.

Enhancement of D-T reaction rate due to D-T contact

International Nuclear Information System (INIS)

Hitoki, Shigehisa; Ogasawara, Masatada; Aono, Osamu.

1979-09-01

The reaction rate that is appropriate for magnetized nonuniform plasma is numerically calculated to investigate the enhancement of the D-T reaction rate. Spatial separation of the guiding center distributions of D and T enhances the reaction rate. Cases of several guiding center configurations are investigated. The largest enhancement is obtained, when both guiding center distributions are delta-functions which are separated by a length that corresponds to the Gamow peak energy. As compared with the case of no separation of D and T, the maximum enhancing factors obtained are 2.3 for total reaction rate and 1.6 for local reaction rate. Cases of the guiding center distributions with finite widths are also investigated. (author)

Cobalt-mediated [3 + 2]-annulation reaction of alkenes with alpha,beta-unsaturated ketones and imines.

Science.gov (United States)

Schomaker, Jennifer M; Toste, F Dean; Bergman, Robert G

2009-08-20

The utility of cobalt dinitrosyl complexes for the [3 + 2] annulation of alkenes with unsaturated enones and ketimines has been demonstrated. Reaction of a series of cobalt dinitrosyl/alkene adducts with conjugate acceptors in the presence of Sc(OTf)(3)/LHMDS formed two new C-C bonds at the carbons alpha to the nitrosyl groups of the substrate, leading to unusual tri- and tetracycles. Retrocycloaddition of these products in the presence of norbornadiene yielded functionalized tetrasubstituted bicyclic olefins.

On the ambiguity of the reaction rate constants in multivariate curve resolution for reversible first-order reaction systems.

Science.gov (United States)

Schröder, Henning; Sawall, Mathias; Kubis, Christoph; Selent, Detlef; Hess, Dieter; Franke, Robert; Börner, Armin; Neymeyr, Klaus

2016-07-13

If for a chemical reaction with a known reaction mechanism the concentration profiles are accessible only for certain species, e.g. only for the main product, then often the reaction rate constants cannot uniquely be determined from the concentration data. This is a well-known fact which includes the so-called slow-fast ambiguity. This work combines the question of unique or non-unique reaction rate constants with factor analytic methods of chemometrics. The idea is to reduce the rotational ambiguity of pure component factorizations by considering only those concentration factors which are possible solutions of the kinetic equations for a properly adapted set of reaction rate constants. The resulting set of reaction rate constants corresponds to those solutions of the rate equations which appear as feasible factors in a pure component factorization. The new analysis of the ambiguity of reaction rate constants extends recent research activities on the Area of Feasible Solutions (AFS). The consistency with a given chemical reaction scheme is shown to be a valuable tool in order to reduce the AFS. The new methods are applied to model and experimental data. Copyright © 2016 Elsevier B.V. All rights reserved.

Evidence for fluctuations in statistical model cross sections from the study of {sup 27}Al(d,{alpha}) {sup 25}Mg reaction; Mise en evidence des fluctuations de sections efficaces du modele statistique par l'etude de la reaction {sup 27}Al(d,{alpha}) {sup 25}Mg

Energy Technology Data Exchange (ETDEWEB)

Papineau born Heller, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-06-01

A complete set of experimental data has been obtained for the reaction {sup 27}Al(d, {alpha}){sup 25}Mg for excitation energies in the compound nucleus {sup 29}Si between 19.7 and 27.4 MeV, in order to compare with the theoretical predictions of the statistical model of nuclear reactions including fluctuations. Numerical calculations of the theoretical cross sections were made and contributions to methods of analysis of fluctuating excitation functions are given. The results confirm strong evidence for statistical fluctuations in nuclear cross sections. (author) [French] On a obtenu un ensemble complet de donnees experimentales de la reaction {sup 27}Al(d, {alpha}){sup 25}Mg pour des energies d'excitation du noyau compose {sup 29}Si comprises entre 19,7 et 27,4 MeV, permettant la comparaison avec les previsions theoriques du modele statistique des reactions nucleaires dans sa version complete comprenant les fluctuations. Des calculs numeriques de sections efficaces theoriques ont ete effectues et des contributions ont ete apportees aux methodes d'analyse de fonctions d'excitation presentant des fluctuations. Les resultats ont clairement confirme l'existence de fluctuations statistiques de sections efficaces. (auteur)

Total synthesis of (+/-)-taiwaniaquinol B via a domino intramolecular friedel-crafts acylation/carbonyl alpha-tert-alkylation reaction.

Science.gov (United States)

Fillion, Eric; Fishlock, Dan

2005-09-28

The first synthesis of taiwaniaquinol B, a 6-nor-5(6-->7)abeoabietane-type diterpenoid exhibiting the uncommon fused 6-5-6 tricyclic carbon skeleton, was accomplished in 15 steps. A Lewis acid-promoted tandem intramolecular Friedel-Crafts/carbonyl alpha-tert-alkylation reaction was exploited as the core strategy for the synthesis of the sterically congested 1-indanone-containing tricyclic structure. This multiple carbon-carbon bond forming reaction exploits the unique reactivity of Meldrum's acid. The facile precursor synthesis makes this a useful methodology for the expedient modification and assembly of sterically congested 1-indanone-containing ring systems.

Rate coefficients for hydrogen abstraction reaction of pinonaldehyde

Indian Academy of Sciences (India)

The H abstraction reaction from the –CHO group was found to be the most dominant reaction channelamong all the possible reaction pathways and its corresponding rate coefficient at 300 K is kEckart's unsymmetrical= 3.86 ×10-10 cm3 molecule-1 s-1. Whereas the channel with immediate lower activation energy is the ...

Charged-particle thermonuclear reaction rates: I. Monte Carlo method and statistical distributions

International Nuclear Information System (INIS)

Longland, R.; Iliadis, C.; Champagne, A.E.; Newton, J.R.; Ugalde, C.; Coc, A.; Fitzgerald, R.

2010-01-01

A method based on Monte Carlo techniques is presented for evaluating thermonuclear reaction rates. We begin by reviewing commonly applied procedures and point out that reaction rates that have been reported up to now in the literature have no rigorous statistical meaning. Subsequently, we associate each nuclear physics quantity entering in the calculation of reaction rates with a specific probability density function, including Gaussian, lognormal and chi-squared distributions. Based on these probability density functions the total reaction rate is randomly sampled many times until the required statistical precision is achieved. This procedure results in a median (Monte Carlo) rate which agrees under certain conditions with the commonly reported recommended 'classical' rate. In addition, we present at each temperature a low rate and a high rate, corresponding to the 0.16 and 0.84 quantiles of the cumulative reaction rate distribution. These quantities are in general different from the statistically meaningless 'minimum' (or 'lower limit') and 'maximum' (or 'upper limit') reaction rates which are commonly reported. Furthermore, we approximate the output reaction rate probability density function by a lognormal distribution and present, at each temperature, the lognormal parameters μ and σ. The values of these quantities will be crucial for future Monte Carlo nucleosynthesis studies. Our new reaction rates, appropriate for bare nuclei in the laboratory, are tabulated in the second paper of this issue (Paper II). The nuclear physics input used to derive our reaction rates is presented in the third paper of this issue (Paper III). In the fourth paper of this issue (Paper IV) we compare our new reaction rates to previous results.

Chemical reactivity of {alpha}-isosaccharinic acid in heterogeneous alkaline systems

Energy Technology Data Exchange (ETDEWEB)

Glaus, M. A.; Loon, L. R. Van

2009-05-15

Cellulose degradation under alkaline conditions is of relevance for the mobility of many radionuclides in the near-field of a cementitious repository for radioactive waste, because metal-binding degradation products may be formed. Among these, {alpha}- isosaccharinic acid ({alpha}-ISA) is the strongest complexant. The prediction of the equilibrium concentration of {alpha}-ISA in cement pore water is therefore an important step in the assessment of the influence of cellulose degradation products on the speciation of radionuclides in such environments. The present report focuses on possible chemical transformation reactions of {alpha}-ISA in heterogeneous alkaline model systems containing either Ca(OH){sub 2} or crushed hardened cement paste. The transformation reactions were monitored by measuring the concentration of {alpha}-ISA by high performance anion exchange chromatography and the formation of reaction products by high performance ion exclusion chromatography. The overall loss of organic species from solution was monitored by measuring the concentration of non-purgeable organic carbon. The reactions were examined in diluted and compacted suspensions, at either 25 {sup o}C or 90 {sup o}C, and under anaerobic atmospheres obtained by various methods. It was found that {alpha}-ISA was transformed under all conditions tested to some extent. Reaction products, such as glycolate, formate, lactate and acetate, all compounds with less complexing strength than {alpha}-ISA, were detected. The amount of reaction products identified by the chromatographic technique applied was {approx} 50 % of the amount of {alpha}-ISA reacted. Sorption of {alpha}-ISA to Ca(OH){sub 2} contributed only to a minor extent to the loss of {alpha}-ISA from the solution phase. As the most important conclusion of the present work it was demonstrated that the presence of oxidising agents had a distinctive influence on the turnover of {alpha}-ISA. Under aerobic conditions {alpha}-ISA was

Analysis of reaction schemes using maximum rates of constituent steps

Science.gov (United States)

Motagamwala, Ali Hussain; Dumesic, James A.

2016-01-01

We show that the steady-state kinetics of a chemical reaction can be analyzed analytically in terms of proposed reaction schemes composed of series of steps with stoichiometric numbers equal to unity by calculating the maximum rates of the constituent steps, rmax,i, assuming that all of the remaining steps are quasi-equilibrated. Analytical expressions can be derived in terms of rmax,i to calculate degrees of rate control for each step to determine the extent to which each step controls the rate of the overall stoichiometric reaction. The values of rmax,i can be used to predict the rate of the overall stoichiometric reaction, making it possible to estimate the observed reaction kinetics. This approach can be used for catalytic reactions to identify transition states and adsorbed species that are important in controlling catalyst performance, such that detailed calculations using electronic structure calculations (e.g., density functional theory) can be carried out for these species, whereas more approximate methods (e.g., scaling relations) are used for the remaining species. This approach to assess the feasibility of proposed reaction schemes is exact for reaction schemes where the stoichiometric coefficients of the constituent steps are equal to unity and the most abundant adsorbed species are in quasi-equilibrium with the gas phase and can be used in an approximate manner to probe the performance of more general reaction schemes, followed by more detailed analyses using full microkinetic models to determine the surface coverages by adsorbed species and the degrees of rate control of the elementary steps. PMID:27162366

Two-week, high-dose proton pump inhibitor, moxifloxacin triple Helicobacter pylori therapy after failure of standard triple or non-bismuth quadruple treatments.

Science.gov (United States)

Gisbert, Javier P; Romano, Marco; Molina-Infante, Javier; Lucendo, Alfredo J; Medina, Enrique; Modolell, Inés; Rodríguez-Tellez, Manuel; Gomez, Blas; Barrio, Jesús; Perona, Monica; Ortuño, Juan; Ariño, Inés; Domínguez-Muñoz, Juan Enrique; Perez-Aisa, Ángeles; Bermejo, Fernando; Domínguez, Jose Luis; Almela, Pedro; Gomez-Camarero, Judith; Millastre, Judith; Martin-Noguerol, Elisa; Gravina, Antonietta G; Martorano, Marco; Miranda, Agnese; Federico, Alessandro; Fernandez-Bermejo, Miguel; Angueira, Teresa; Ferrer-Barcelo, Luis; Fernández, Nuria; Marín, Alicia C; McNicholl, Adrián G

2015-02-01

Aim was to evaluate the efficacy and tolerability of a moxifloxacin-containing second-line triple regimen in patients whose previous Helicobacter pylori eradication treatment failed. Prospective multicentre study including patients in whom a triple therapy or a non-bismuth-quadruple-therapy failed. Moxifloxacin (400mg qd), amoxicillin (1g bid), and esomeprazole (40 mg bid) were prescribed for 14 days. Eradication was confirmed by (13)C-urea-breath-test. Compliance was determined through questioning and recovery of empty medication envelopes. 250 patients were consecutively included (mean age 48 ± 15 years, 11% with ulcer). Previous (failed) therapy included: standard triple (n = 179), sequential (n = 27), and concomitant (n = 44); 97% of patients took all medications, 4 were lost to follow-up. Intention-to-treat and per-protocol eradication rates were 82.4% (95% CI, 77-87%) and 85.7% (95% CI, 81-90%). Cure rates were similar independently of diagnosis (ulcer, 77%; dyspepsia, 82%) and previous treatment (standard triple, 83%; sequential, 89%; concomitant, 77%). At multivariate analysis, only age was associated with eradication (OR = 0.957; 95% CI, 0.933-0.981). Adverse events were reported in 25.2% of patients: diarrhoea (9.6%), abdominal pain (9.6%), and nausea (9.2%). 14-day moxifloxacin-containing triple therapy is an effective and safe second-line strategy in patients whose previous standard triple therapy or non-bismuth quadruple (sequential or concomitant) therapy has failed, providing a simple alternative to bismuth quadruple regimen. Copyright © 2014 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Modular rate laws for enzymatic reactions: thermodynamics, elasticities and implementation.

Science.gov (United States)

Liebermeister, Wolfram; Uhlendorf, Jannis; Klipp, Edda

2010-06-15

Standard rate laws are a key requisite for systematically turning metabolic networks into kinetic models. They should provide simple, general and biochemically plausible formulae for reaction velocities and reaction elasticities. At the same time, they need to respect thermodynamic relations between the kinetic constants and the metabolic fluxes and concentrations. We present a family of reversible rate laws for reactions with arbitrary stoichiometries and various types of regulation, including mass-action, Michaelis-Menten and uni-uni reversible Hill kinetics as special cases. With a thermodynamically safe parameterization of these rate laws, parameter sets obtained by model fitting, sampling or optimization are guaranteed to lead to consistent chemical equilibrium states. A reformulation using saturation values yields simple formulae for rates and elasticities, which can be easily adjusted to the given stationary flux distributions. Furthermore, this formulation highlights the role of chemical potential differences as thermodynamic driving forces. We compare the modular rate laws to the thermodynamic-kinetic modelling formalism and discuss a simplified rate law in which the reaction rate directly depends on the reaction affinity. For automatic handling of modular rate laws, we propose a standard syntax and semantic annotations for the Systems Biology Markup Language. An online tool for inserting the rate laws into SBML models is freely available at www.semanticsbml.org. Supplementary data are available at Bioinformatics online.

Producing a compound Nucleus via Inelastic Scattering: The 90Zr(alpha,alpha')90Zr* Case

Energy Technology Data Exchange (ETDEWEB)

Escher, J E; Dietrich, F S

2008-05-23

In a Surrogate reaction a compound nucleus is produced via a direct reaction (pickup, stripping, or inelastic scattering). For a proper application of the Surrogate approach it is necessary to predict the resulting angular momentum and parity distribution in the compound nucleus. A model for determining these distributions is developed for the case of inelastic alpha scattering off a spherical nucleus. The focus is on obtaining a first, simple description of the direct-reaction process that produces the compound nucleus and on providing the basis for a more complete treatment of the problem. The approximations employed in the present description are discussed and the extensions required for a more rigorous treatment of the problem are outlined. To illustrate the formalism, an application to {sup 90}Zr({alpha},{alpha}{prime}){sup 90}Zr* is presented.

Measurement of the $^{44}$Ti($\\alpha$,p)$^{47}$V reaction cross section, of relevance to $\\gamma$-ray observation of core collapse supernovae, using reclaimed $^{44}$Ti

CERN Multimedia

Despite decades of research, fundamental uncertainties remain in the underlying explosion mechanism of core collapse supernovae. One of the most direct methods that might help resolve this problem is a comparison of the predicted to the observed flux of $\\gamma$-rays due to decay of $^{44}$Ti produced in the explosion, as it is believed this could reveal the location of the mass cut, a key hydrodynamical property of the explosion. Such a study is at present limited by the uncertainty in the $^{44}$Ti($\\alpha$,p)$^{47}$V reaction rate. In this experiment we propose to measure the cross section for this reaction at astrophysically relevant energies. The single previous measurement of this reaction was limited to higher energies due to low beam intensities. Here, a more intense beam will be employed, generated from $^{44}$Ti reclaimed as part of the ERAWAST project at PSI.

Zirconium metal-water oxidation kinetics. III. Oxygen diffusion in oxide and alpha Zircaloy phases

International Nuclear Information System (INIS)

Pawel, R.E.

1976-10-01

The reaction of Zircaloy in steam at elevated temperature involves the growth of discrete layers of oxide and oxygen-rich alpha Zircaloy from the parent beta phase. The multiphase, moving boundary diffusion problem involved is encountered in a number of important reaction schemes in addition to that of Zircaloy-oxygen and can be completely (albeitly ideally) characterized through an appropriate model in terms of oxygen diffusion coefficients and equilibrium concentrations for the various phases. Conversely, kinetic data for phase growth and total oxygen consumption rates can be used to compute diffusion coefficients. Equations are developed that express the oxygen diffusion coefficients in the oxide and alpha phases in terms of the reaction rate constants and equilibrium solubility values. These equations were applied to recent experimental kinetic data on the steam oxidation of Zircaloy-4 to determine the effective oxygen diffusion coefficients in these phases over the temperature range 1000--1500 0 C

Astrophysical Nuclear Reaction Rates in the Dense Metallic Environments

Science.gov (United States)

Kilic, Ali Ihsan

2017-09-01

Nuclear reaction rates can be enhanced by many orders of magnitude in dense and relatively cold astrophysical plasmas such as in white dwarfs, brown dwarfs, and giant planets. Similar conditions are also present in supernova explosions where the ignition conditions are vital for cosmological models. White dwarfs are compact objects that have both extremely high interior densities and very strong local magnetic fields. For the first time, a new formula has been developed to explain cross section and reaction rate quantities for light elements that includes not only the nuclear component but also the material dependence, magnetic field, and crystal structure dependency in dense metallic environments. I will present the impact of the developed formula on the cross section and reaction rates for light elements. This could have possible technological applications in energy production using nuclear fusion reactions.

A study of jet rates and measurement of {alpha}{sub S} at the Z{sup 0} resonance

Energy Technology Data Exchange (ETDEWEB)

Lauber, J.A.

1993-02-01

This experiment was performed with the SLD detector at the Stanford Linear Accelerator Center. Only charged tracks measured in the central drift chamber were used for the measurement of the jet production rates. The value of the strong coupling {alpha}{sub s}(M{sub Z}{sup o}) is determined from the production rates of jets in hadronic Z{sup 0} decays in e{sup +} e{sup {minus}} annihilations. The relative jet rates are obtained using the JADE-type algorithms. The results are compared with the jet rates obtained from a new jet algorithm proposed by N. Brown et al. called the ``Durham`` algorithm. The data can be well described by O({alpha}{sub s}{sup 2}) QCD calculations and by QCD shower model calculations. A fit of the theoretical predictions to the data taken with the SLD yields a value, {alpha}{sub s}(M{sub Z}{sup o}) = 0.120 {plus_minus} 0.002(stat.) {plus_minus} 0.003(exp.){sub {minus}0.009}{sup +0.011}(theor.). The error is dominated by the theoretical uncertainties. The measurement is compared with results from other experiments and it is shown that the value obtained for {alpha}{sub s} agrees well with these results and furthermore supports the evidence for the running of the strong coupling, consistent with the non-Abelian nature of QCD. The Stanford Linear Collider (SLC) can deliver partially longitudinally polarized electrons to the interaction point. Jet production rates and values for {alpha}{sub s} are calculated both for right-handed and left-handed initial state electrons. All results are consistent with the unpolarized result, as predicted by the Standard Model.

Method for calculation of upper limit internal alpha dose rates to aquatic organisms with application of plutonium-239 in plankton

International Nuclear Information System (INIS)

Paschoa, A.S.; Baptista, G.B.

1977-01-01

A method for the calculation of upper limit internal alpha dose rates to aquatic organisms is presented. The mean alpha energies per disintegration of radionuclides of interest are listed to be used in standard methodologies to calculate dose to aquatic biota. As an application, the upper limits for the alpha dose rates from 239 Pu to the total body of plankton are estimated based on data available in open literature [pt

Diffusion-controlled reaction. V. Effect of concentration-dependent diffusion coefficient on reaction rate in graft polymerization

International Nuclear Information System (INIS)

Imre, K.; Odian, G.

1979-01-01

The effect of diffusion on radiation-initiated graft polymerization has been studied with emphasis on the single- and two-penetrant cases. When the physical properties of the penetrants are similar, the two-penetrant problems can be reduced to the single-penetrant problem by redefining the characteristic parameters of the system. The diffusion-free graft polymerization rate is assumed to be proportional to the upsilon power of the monomer concentration respectively, and, in which the proportionality constant a = k/sub p/R/sub i//sup w//k/sub t//sup z/, where k/sub p/ and k/sub t/ are the propagation and termination rate constants, respectively, and R/sub i/ is the initiation rate. The values of upsilon, w, and z depend on the particular reaction system. The results of earlier work were generalized by allowing a non-Fickian diffusion rate which predicts an essentially exponential dependence on the monomer concentration of the diffusion coefficient, D = D 0 [exp(deltaC/M)], where M is the saturation concentration. A reaction system is characterized by the three dimensionless parameters, upsilon, delta, and A = (L/2)[aM/sup (upsilon--1)//D 0 ]/sup 1/2/, where L is the polymer film thickness. Graft polymerization tends to become diffusion controlled as A increases. Larger values of delta and ν cause a reaction system to behave closer to the diffusion-free regime. Transition from diffusion-free to diffusion-controlled reaction involves changes in the dependence of the reaction rate on film thickness, initiation rate, and monomer concentration. Although the diffusion-free rate is w order in initiation rate, upsilon order in monomer, and independent of film thickness, the diffusion-controlled rate is w/2 order in initiator rate and inverse first-order in film thickness. Dependence of the diffusion-controlled rate on monomer is dependent in a complex manner on the diffusional characteristics of the reaction system. 11 figures, 4 tables

Rate coefficient for the reaction N + NO

Science.gov (United States)

Fox, J. L.

1994-01-01

Evidence has been advanced that the rate coefficient for the reaction N + NO right arrow N2 + O has a small positive temperature dependence at the high temperatures (900 to 1500 K) that prevail in the terrestrial middle and upper thermosphere by Siskind and Rusch (1992), and at the low temperatures (100 to 200 K) of the Martian lower thermosphere by Fox (1993). Assuming that the rate coefficient recommended by the Jet Propulsion Laboratory evaluation (DeMore et al., 1992) is accurate at 300 K, we derive here the low temperature value of the activation energy for this reaction and thus the rate coefficient that best fits the Viking 1 measured NO densities. We find that the fit is acceptable for a rate coefficient of about 1.3 x 10(exp -10)(T/300)(exp 0.5)exp(-400/T) and better for a value of about 2.5 x 10(exp -10)(T/300)(exp 0.5)exp(-600/T)cu cm/s.

Estimating the Backup Reaction Wheel Orientation Using Reaction Wheel Spin Rates Flight Telemetry from a Spacecraft

Science.gov (United States)

Rizvi, Farheen

2013-01-01

A report describes a model that estimates the orientation of the backup reaction wheel using the reaction wheel spin rates telemetry from a spacecraft. Attitude control via the reaction wheel assembly (RWA) onboard a spacecraft uses three reaction wheels (one wheel per axis) and a backup to accommodate any wheel degradation throughout the course of the mission. The spacecraft dynamics prediction depends upon the correct knowledge of the reaction wheel orientations. Thus, it is vital to determine the actual orientation of the reaction wheels such that the correct spacecraft dynamics can be predicted. The conservation of angular momentum is used to estimate the orientation of the backup reaction wheel from the prime and backup reaction wheel spin rates data. The method is applied in estimating the orientation of the backup wheel onboard the Cassini spacecraft. The flight telemetry from the March 2011 prime and backup RWA swap activity on Cassini is used to obtain the best estimate for the backup reaction wheel orientation.

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

REACLIB: A Reaction Rate Library for the Era of Collaborative Science

Science.gov (United States)

Meisel, Zachary

2008-10-01

Thermonuclear reaction rates and weak decay rates are of great importance to modern nuclear astrophysics. They are critical in the study of many topics such as Big Bang Nucleosynthesis, X-ray bursts, Supernovae, and S-process element formation, among others. The Joint Institute for Nuclear Astrophysics (JINA) has been created to increase connectivity amongst nuclear astrophysicists in our modern age of highly collaborative science. Within JINA there has been an effort to create a frequently updated and readily accessible database of thermonuclear reactions and weak decay rates. This database is the REACLIB library, which can be accessed at the web address: http://www.nscl.msu.edu/˜nero/db/. Here I will discuss the JINA REACLIB Project, including a new procedure to fit reaction rates as a function of temperature that takes full advantage of physicality. With these updated reaction rates, astrophysical modelers will no longer have to worry about the adverse effects of using obsolete reaction rate libraries lacking physical behavior.

Thermonuclear reaction rate of 17O(p,γ)18F

International Nuclear Information System (INIS)

Fox, C.; Iliadis, C.; Champagne, A.E.; Fitzgerald, R.P.; Longland, R.; Newton, J.; Pollanen, J.; Runkle, R.

2005-01-01

The 17 O(p,γ) 18 F and 17 O(p,α) 14 N reactions have a profound influence on hydrogen-burning nucleosynthesis in a number of stellar sites, including red giants, asymptotic giant branch (AGB) stars, massive stars, and classical novae. Previously evaluated thermonuclear rates for both reactions carry large uncertainties. We investigated the proton-capture reaction on 17 O in the bombarding energy range of E p lab = 180-540 keV. We observed a previously undiscovered resonance at E R lab = 193.2 ± 0.9 keV. The resonance strength amounts to (ωγ) pγ (1.2±0.2)x10 -6 eV. With this value, the uncertainties of the 17 O(p,γ) 18 F reaction rates are reduced by orders of magnitude in the peak temperature range of classical novae (T=0.1-0.4 GK). We also report on a reevaluation of the 17 O(p,γ) 18 F reaction rates at lower temperatures that are pertinent to red giants, AGB stars, or massive stars. The present work establishes the 17 O(p,γ) 18 F reaction rates over a temperature range of T= 0.01-1.5 GK with statistical uncertainties of 10-50%. The new recommended reaction rates deviate from the previously accepted values by an order of magnitude around T≅0.2 GK and by factors of 2-3 at T < 0.1 GK

Testing an ionization chamber with gaseous samples and measurements of the (n, alpha) reaction cross sections

CERN Document Server

Gledenov, Yu M; Salatskii, V I; Sedyshev, P V; Andrzejewski, J; Szalanski, P

1999-01-01

A new ionization chamber with gaseous samples (GIC) has been designed and tested on the thermal and resonance neutron beams of FLNP's neutron sources. The exposed gas volume serves as a target for neutrons. The obtained thermal cross sections for the sup 1 sup 7 O(n, alpha) sup 1 sup 4 C, sup 2 sup 1 Ne(n, alpha) sup 1 sup 8 O and sup 3 sup 6 Ar(n, alpha) sup 3 sup 3 S reactions are (233+-12) mb, (0.18+-0.09) mb and (5.43+-0.27) mb, respectively. These measurements have been performed on a pure beam of thermal neutrons from the high flux reactor IBR-2; and they demonstrated high efficiency and reliability of the method. Compared to samples on substrates, the application of gaseous samples makes the beam background essentially lower, and what is more important, the background component is totally absent due to the absence of Li and B microimpurities in gaseous samples while they do present in the samples on substrates. The method is also applicable to measurements with resonance neutrons. The recovery capabili...

Effective reaction rates in diffusion-limited phosphorylation-dephosphorylation cycles

Science.gov (United States)

Szymańska, Paulina; Kochańczyk, Marek; Miekisz, Jacek; Lipniacki, Tomasz

2015-02-01

We investigate the kinetics of the ubiquitous phosphorylation-dephosphorylation cycle on biological membranes by means of kinetic Monte Carlo simulations on the triangular lattice. We establish the dependence of effective macroscopic reaction rate coefficients as well as the steady-state phosphorylated substrate fraction on the diffusion coefficient and concentrations of opposing enzymes: kinases and phosphatases. In the limits of zero and infinite diffusion, the numerical results agree with analytical predictions; these two limits give the lower and the upper bound for the macroscopic rate coefficients, respectively. In the zero-diffusion limit, which is important in the analysis of dense systems, phosphorylation and dephosphorylation reactions can convert only these substrates which remain in contact with opposing enzymes. In the most studied regime of nonzero but small diffusion, a contribution linearly proportional to the diffusion coefficient appears in the reaction rate. In this regime, the presence of opposing enzymes creates inhomogeneities in the (de)phosphorylated substrate distributions: The spatial correlation function shows that enzymes are surrounded by clouds of converted substrates. This effect becomes important at low enzyme concentrations, substantially lowering effective reaction rates. Effective reaction rates decrease with decreasing diffusion and this dependence is more pronounced for the less-abundant enzyme. Consequently, the steady-state fraction of phosphorylated substrates can increase or decrease with diffusion, depending on relative concentrations of both enzymes. Additionally, steady states are controlled by molecular crowders which, mostly by lowering the effective diffusion of reactants, favor the more abundant enzyme.

Thresholds and Q values of nuclear reactions induced by neutrons, protons, deuterons, tritons, 3He ions, alpha particles, and photons

International Nuclear Information System (INIS)

Howerton, R.J.

1981-01-01

The 1977 Wapstra and Bos nuclear mass data tables were used to derive tables for thresholds and Q values of nuclear reactions induced by neutrons, protons, deuterons, tritons, 3 He ions, alpha particles, and photons. The tables are displayed on microfiche included with the report

Quasi-bound alpha resonant states populated by the 12C(6Li, d) reaction

International Nuclear Information System (INIS)

Rodrigues, M.R.D.; Borello-Lewin, T.; Miyake, H.; Horodynski-Matsushigue, L.B.; Duarte, J.L.M.; Rodrigues, C.L.; Souza, M.A.; Cunsolo, A.; Cappuzzello, F.; Foti, A.; Agodi, C.; Cavallaro, M.; Ukita, G.M.

2012-01-01

Full text: The alpha cluster phenomenon in the light nuclei structure has been the subject of a long time investigation since the proposal of the Ikeda diagrams [1]. The main purpose of the research program in progress is the investigation of this phenomenon in (xα) and (xα+n) nuclei through the ( 6 Li, d) alpha transfer reaction [2-4]. Alpha resonant states around the (4α) threshold in the nucleus 16 O are the focus of the present contribution. In fact, the importance of these resonances at the elements production in stars is recognized, as primarily pointed out by Hoyle in 12 C [6]. The existence of a rotational band with the α + 12 C (Hoyle) cluster state structure was recently demonstrated by Ohkubo and Hirabayashi [6]. In order to explore this region of interest, measurements of the 12 C( 6 Li, d) 16 O reaction up to 17 MeV of excitation at an incident energy of 25.5 MeV, have been performed employing the Sao Paulo Pelletron-Enge Split-Pole facility and the nuclear emulsion detection technique (plates Fuji G6B, 50 μm thick). Spectra associated with six scattering angles, from 5 deg to 29 deg in the laboratory frame, each one 50 cm along the focal surface, were measured. Several narrow resonances with a quasi-bound behavior embedded in the continuum were detected and the resolution of 25 keV allowed for the separation of doublets not resolved before [7,8]. The absolute cross sections and the respective deuteron angular distributions were determined and the analysis is in progress. [1] K. Ikeda et al., Prog. Theor. Phys. Suppl. E 68, 464 (1968); H. Horiuchi, K. Ikeda, and Y. Suzuki, ibid. 44, 225 (1978). [2] M.R.D.Rodrigues et al., in12th International Conference on Nuclear Reaction Mechanism, Varenna, Italy, edited by F. Cerutti and A. Ferrari , CERN Proceedings, 2010-2, pp. 331- 335. [3] T. Borello-Lewin et al., Proceedings of SOTANCP2, Brussels, Belgium 2010, edited by P. Descouvemount et al., Int. J. Mod. Mod. Phys E 20, 1018-1021 (2011). [4] T. Borello

Human LT-alpha-mediated resistance to autoimmune diabetes is induced in NOD, but not NOD-scid, mice and abrogated by IL-12.

Science.gov (United States)

Miyaguchi, S; Satoh, J; Takahashi, K; Sakata, Y; Nakazawa, T; Miyazaki, J; Toyota, T

2001-01-01

Systemic administration of human lymphotoxin-alpha (hLT-alpha) made NOD mice resistant not only to spontaneous autoimmune type 1 diabetes mellitus but also to cyclophosphamide (CY)-induced diabetes and diabetes transfer by diabetic NOD spleen cells (triple resistance). In this study we analyzed the mechanisms of hLT-alpha-induced resistance, focusing on (1) hLT-alpha-induced resistance in the pancreatic beta cell, (2) CY-resistant suppressor cells, (3) suppression of induction or function of effector cells for beta cell destruction, or (4) others. To examine the first possibility in vitro, a NOD-derived beta cell line (MIN6N) was pretreated with hLT-alpha and then mixed with diabetic NOD spleen cells and MIN6N cell viability was measured. Treatment with hLT-alpha did not protect MIN6N cells but rather enhanced cytotoxicity. Next NOD-scid mice were pretreated with hLT-alpha and then transferred with diabetic NOD spleen. All the recipients developed diabetes. These results excluded the first possibility. The second possibility was also excluded by a cotransfer experiment, in which diabetic NOD spleen cells were cotransferred to NOD-scid mice with nontreated or hLT-alpha-treated nondiabetic NOD spleens. There was no significant difference in diabetes incidence between the two groups. To observe the third possibility, spleen cells of hLT-alpha-treated triple-resistant NOD mice were transferred to NOD-scid mice. Diabetes developed in the recipients, although the onset of diabetes was slightly delayed. Finally, hLT-alpha-treated triple-resistant NOD mice developed diabetes 1 week after daily IL-12 treatment. In summary, hLT-alpha administration made NOD mice resistant to effector cells for beta cell destruction. This resistance was induced in NOD, but not in NOD-scid, mice, indicating that lymphocytes were obligatory for the resistance. However, it was not mediated by transferable suppressor cells. Because effector cells were present in hLT-alpha-treated NOD spleen and

Structure analysis of tax revenue and inflation rate in Banda Aceh using vector error correction model with multiple alpha

Science.gov (United States)

Sofyan, Hizir; Maulia, Eva; Miftahuddin

2017-11-01

A country has several important parameters to achieve economic prosperity, such as tax revenue and inflation rate. One of the largest revenues of the State Budget in Indonesia comes from the tax sector. Meanwhile, the rate of inflation occurring in a country can be used as an indicator, to measure the good and bad economic problems faced by the country. Given the importance of tax revenue and inflation rate control in achieving economic prosperity, it is necessary to analyze the structure of tax revenue relations and inflation rate. This study aims to produce the best VECM (Vector Error Correction Model) with optimal lag using various alpha and perform structural analysis using the Impulse Response Function (IRF) of the VECM models to examine the relationship of tax revenue, and inflation in Banda Aceh. The results showed that the best model for the data of tax revenue and inflation rate in Banda Aceh City using alpha 0.01 is VECM with optimal lag 2, while the best model for data of tax revenue and inflation rate in Banda Aceh City using alpha 0.05 and 0,1 VECM with optimal lag 3. However, the VECM model with alpha 0.01 yielded four significant models of income tax model, inflation rate of Banda Aceh, inflation rate of health and inflation rate of education in Banda Aceh. While the VECM model with alpha 0.05 and 0.1 yielded one significant model that is income tax model. Based on the VECM models, then there are two structural analysis IRF which is formed to look at the relationship of tax revenue, and inflation in Banda Aceh, the IRF with VECM (2) and IRF with VECM (3).

Energy Efficient Triple IG Automation EEE (Triple-E)

Energy Technology Data Exchange (ETDEWEB)

McGlinchy, Timothy B

2013-02-28

GED Integrated Solutions collaborated with US window and door manufactures to investigate, design and verify technical and cost feasibility for producing high performance, high volume, low material and labor cost window, utilizing a modified window design containing a triple insulating glass unit (IGU). This window design approach when combined with a high volume IGU manufacturing system, can produce R5 rated windows for an approximate additional consumer cost of only $4 per square foot when compared to conventional Low-E argon dual pane IG windows, resulting in a verify practical, reliable and affordable high performance window for public use.

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

International Nuclear Information System (INIS)

Uda, Tatsuhiko

1992-01-01

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

Glutathione transferase mimics : Micellar catalysis of an enzymic reaction

NARCIS (Netherlands)

Lindkvist, Björn; Weinander, Rolf; Engman, Lars; Koetse, Marc; Engberts, Jan B.F.N.; Morgenstern, Ralf

1997-01-01

Substances that mimic the enzyme action of glutathione transferases (which serve in detoxification) are described. These micellar catalysts enhance the reaction rate between thiols and activated halogenated nitroarenes as well as alpha,beta-unsaturated carbonyls. The nucleophilic aromatic

Relationship among reaction rate, release rate and efficiency of nanomachine-based targeted drug delivery.

Science.gov (United States)

Zhao, Qingying; Li, Min; Luo, Jun

2017-12-04

In nanomachine applications towards targeted drug delivery, drug molecules released by nanomachines propagate and chemically react with tumor cells in aqueous environment. If the nanomachines release drug molecules faster than the tumor cells react, it will result in loss and waste of drug molecules. It is a potential issue associated with the relationship among reaction rate, release rate and efficiency. This paper aims to investigate the relationship among reaction rate, release rate and efficiency based on two drug reception models. We expect to pave a way for designing a control method of drug release. We adopted two analytical methods that one is drug reception process based on collision with tumors and another is based on Michaelis Menten enzymatic kinetics. To evaluate the analytical formulations, we used the well-known simulation framework N3Sim to establish simulations. The analytical results of the relationship among reaction rate, release rate and efficiency is obtained, which match well with the numerical simulation results in a 3-D environment. Based upon two drug reception models, the results of this paper would be beneficial for designing a control method of nanomahine-based drug release.

Alpha clustering in nuclei

International Nuclear Information System (INIS)

Hodgson, P.E.

1990-01-01

The effects of nucleon clustering in nuclei are described, with reference to both nuclear structure and nuclear reactions, and the advantages of using the cluster formalism to describe a range of phenomena are discussed. It is shown that bound and scattering alpha-particle states can be described in a unified way using an energy-dependent alpha-nucleus potential. (author)

Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

Energy Technology Data Exchange (ETDEWEB)

Guevara, Z. E., E-mail: zjguevaram@unal.edu.co; Torres, D. A., E-mail: datorresg@unal.edu.co [Physics Department, Universidad Nacional de Colombia, Bogotá D.C. (Colombia)

2016-07-07

In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of {sup 106}Cd to study excited states of {sup 110}Sn and the beam nuclei itself will be presented.

Reactions and reaction rates in the regional aquifer beneath the Pajarito Plateau, north-central New Mexico, USA

Science.gov (United States)

Hereford, Anne G.; Keating, Elizabeth H.; Guthrie, George D.; Zhu, Chen

2007-05-01

Reactions and reaction rates within aquifers are fundamental components of critical hydrological processes. However, reactions simulated in laboratory experiments typically demonstrate rates that are much faster than those observed in the field. Therefore, it is necessary to conduct more reaction rate analyses in natural settings. This study of geochemical reactions in the regional aquifer in the Pajarito Plateau near Los Alamos, New Mexico combines modeling with petrographic assessment to further knowledge and understanding of complex natural hydrologic systems. Groundwater geochemistry shows marked evolution along assumed flow paths. The flow path chosen for this study was evaluated using inverse mass balance modeling to calculate the mass transfer. X-ray diffraction and field emission gun scanning electron microscopy were used to identify possible reactants and products. Considering the mineralogy of the aquifer and saturation indices for the regional water refined initial interpretations. Calculations yielded dissolution rates for plagioclase on the order of 10-15 mol s-1 m-2 and for K-feldspar on the order of 10-17 mol s-1 m-2, orders of magnitude slower than laboratory rates. While these rates agree with other aquifer studies, they must be considered in the light of the uncertainty associated with geometric surface area estimates, 14C ages, and aquifer properties.

DEPENDENCE OF X-RAY BURST MODELS ON NUCLEAR REACTION RATES

Energy Technology Data Exchange (ETDEWEB)

Cyburt, R. H.; Keek, L.; Schatz, H. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Amthor, A. M. [Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837 (United States); Heger, A.; Meisel, Z.; Smith, K. [Joint Institute for Nuclear Astrophysics (JINA), Michigan State University, East Lansing, MI 48824 (United States); Johnson, E. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

2016-10-20

X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p, γ ), ( α , γ ), and ( α , p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the Kepler stellar evolution code. All relevant reaction rates on neutron-deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 changes in reaction rate with the highest impact were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape observables from X-ray bursts, and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.

Design of a preamplifier for an alpha particles spectrometer

International Nuclear Information System (INIS)

Murillo O, R.; Hernandez D, V. M.; Chacon R, A.; Vega C, H. R.

2010-09-01

To detect radiation diverse detector types are used, when these are alpha particles proportional type detectors are used, semiconductor, of scintillation or traces. In this work the design results, the construction and the first tests of a spectrometer (preamplifier) are presented for alpha particles that was designed starting from a Pin type photodiode. The system was designed and simulated with a program for electronic circuits. With the results of the simulation phase was constructed the electronics that is coupled to a spectroscopic amplifier and a multichannel analyzer. The total of the system is evaluated analyzing its performance before a triple source of alphas and that they are produced by two smoke detectors of domestic use. Of the tests phase we find that the system allows to obtain in a multichannel, the pulses height spectrum, with which we calibrate the system. (Author)

Isolation and characterization of a uranium(VI)-nitride triple bond

Science.gov (United States)

King, David M.; Tuna, Floriana; McInnes, Eric J. L.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.

2013-06-01

The nature and extent of covalency in uranium bonding is still unclear compared with that of transition metals, and there is great interest in studying uranium-ligand multiple bonds. Although U=O and U=NR double bonds (where R is an alkyl group) are well-known analogues to transition-metal oxo and imido complexes, the uranium(VI)-nitride triple bond has long remained a synthetic target in actinide chemistry. Here, we report the preparation of a uranium(VI)-nitride triple bond. We highlight the importance of (1) ancillary ligand design, (2) employing mild redox reactions instead of harsh photochemical methods that decompose transiently formed uranium(VI) nitrides, (3) an electrostatically stabilizing sodium ion during nitride installation, (4) selecting the right sodium sequestering reagent, (5) inner versus outer sphere oxidation and (6) stability with respect to the uranium oxidation state. Computational analyses suggest covalent contributions to U≡N triple bonds that are surprisingly comparable to those of their group 6 transition-metal nitride counterparts.

Nuclear collective flow from gaussian fits to triple differential distributions

International Nuclear Information System (INIS)

Gosset, J.; Babinet, R.; Cavata, C.; Marco, M. de; Demoulins, M.; Fanet, H.; Fodor, Z.; L'Hote, D.; Lucas, B.

1990-01-01

A simple characterization of triple differential cross sections is needed for a systematic study of the nuclear matter collective flow in relativistic nucleus-nucleus collisions. Our analysis is based upon a fitting procedure, so that the triple differential distributions need not be measured in the whole momentum space. If the detector acceptance eliminates most spectator particles or if it is artificially restricted for doing so, this method leads to a flow characterization of the participant nuclear matter. The center-of-mass triple-differential momentum distributions are fitted to a simple analytical shape, namely an anisotropic Gaussian distribution. The adjusted parameters (flow angle and aspect ratios) are corrected for uncertainty in the event-by-event determination of the reaction plane azimuth (finite-number effects). Results are presented for neon-nucleus and argon-nucleus collisions at incident energy between 400 and 800 MeV per nucleon. Flow is already significant for light systems, and depends clearly upon the impact parameter

Bicyclic Guanidine Catalyzed Asymmetric Tandem Isomerization Intramolecular-Diels-Alder Reaction: The First Catalytic Enantioselective Total Synthesis of (+)-alpha-Yohimbine.

Science.gov (United States)

Feng, Wei; Jiang, Danfeng; Kee, Choon-Wee; Liu, Hongjun; Tan, Choon-Hong

2016-02-04

Hydroisoquinoline derivatives were prepared in moderate to good enantioselectivities via a bicyclic guanidine-catalyzed tandem isomerization intramolecular-Diels-Alder (IMDA) reaction of alkynes. With this synthetic method, the first enantioselective synthesis of (+)-alpha-yohimbine was completed in 9 steps from the IMDA products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A triple-crystal phoswich detector with digital pulse shape discrimination for alpha/beta/gamma spectroscopy

International Nuclear Information System (INIS)

White, Travis L.; Miller, William H.

1999-01-01

Researchers at the University of Missouri - Columbia have developed a three-crystal phoswich detector coupled to a digital pulse shape discrimination system for use in alpha/beta/gamma spectroscopy. Phoswich detectors use a sandwich of scintillators viewed by a single photomultiplier tube to simultaneously detect multiple types of radiation. Separation of radiation types is based upon pulse shape difference among the phosphors, which has historically been performed with analog circuitry. The system uses a GaGe CompuScope 1012, 12 bit, 10 MHz computer-based oscilloscope that digitally captures the pulses from a phoswich detector and subsequently performs pulse shape discrimination with cross-correlation analysis. The detector, based partially on previous phoswich designs by Usuda et al., uses a 10 mg/cm 2 thick layer of ZnS(Ag) for alpha detection, followed by a 0.254 cm CaF 2 (Eu) crystal for beta detection, all backed by a 2.54 cm NaI(Tl) crystal for gamma detection. Individual energy spectra and count rate information for all three radiation types are displayed and updated periodically. The system shows excellent charged particle discrimination with an accuracy of greater than 99%. Future development will include a large area beta probe with gamma-ray discrimination, systems for low-energy photon detection (e.g. Bremsstrahlung or keV-range photon emissions), and other health physics instrumentation

New High-Precision Measurement of the Reaction Rate of the O-18(p, alpha)N-15 Reaction via THM

Czech Academy of Sciences Publication Activity Database

La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A. M.; Irgaziev, B.; Tribble, R. E.; Banu, A.; Cherubini, S.; Coc, A.; Crucilla, V.; Goldberg, V. Z.; Gulino, M.; Kiss, G. G.; Lamia, L.; Chengbo, L.; Mrázek, Jaromír; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tabacaru, G.; Trache, L.; Trzaska, W.; Tumino, A.

2009-01-01

Roč. 26, č. 3 (2009), s. 237-242 ISSN 1323-3580 Institutional research plan: CEZ:AV0Z10480505 Keywords : nuclear reactions * nucleosynthesis * abundances Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.786, year: 2009

Contribution to the study of nuclear reaction analysis with low energy alpha particles (<=3,5 MeV). Comparative study of Ag non destructive nuclear reaction determination in numismatology

International Nuclear Information System (INIS)

Basutcu, Mehmet.

1980-12-01

The first part of this work concerns the development of the new analytical possibilities offered by gamma spectrometry with a beam of low energy alpha particles. With this method twenty five elements can be analyzed by non-destructive methods. Special attention is given to the determination of light elements such as lithium, boron, fluorine and sodium. The reactions brought about by the low energy alpha particles on light elements are (α,n), (α,p) or (α,α') type reactions. The various applications developed are presented after the description of the experimental conditions and the method used for calculating the contents. The problems related to the calibration, accuracy and exactness of the determinations are also discussed. The second part is about the contribution of nuclear analysis methods and of X-ray fluorescence in the field of numismatic research. Attention is focused solely on the determination of the major ingredients of coins, silver in particular. The results provided by proton activation, neutron activation in a flux of 'thermalized' neutrons of a 252 Cf isotopic source on the one hand, and by the fast neutrons of the cyclotron on the other, by gamma spectrometry under a beam of protons and alpha particles and by X-ray fluorescence are thus compared for the same analytical problem in order to grasp in a better manner the specificity of each method and to bring into evidence the complementarity they present [fr

Bovine serum albumin-catalyzed deprotonation of [1-(13)C]glycolaldehyde: protein reactivity toward deprotonation of the alpha-hydroxy alpha-carbonyl carbon.

Science.gov (United States)

Go, Maybelle K; Malabanan, M Merced; Amyes, Tina L; Richard, John P

2010-09-07

Bovine serum albumin (BSA) in D(2)O at 25 degrees C and pD 7.0 was found to catalyze the deuterium exchange reactions of [1-(13)C]glycolaldehyde ([1-(13)C]GA) to form [1-(13)C,2-(2)H]GA and [1-(13)C,2,2-di-(2)H]GA. The formation of [1-(13)C,2-(2)H]GA and [1-(13)C,2,2-di-(2)H]GA in a total yield of 51 +/- 3% was observed at early reaction times, and at later times, [1-(13)C,2-(2)H]GA was found to undergo BSA-catalyzed conversion to [1-(13)C,2,2-di-(2)H]GA. The overall second-order rate constant for these deuterium exchange reactions [(k(E))(P)] equals 0.25 M(-1) s(-1). By comparison, (k(E))(P) values of 0.04 M(-1) s(-1) [Go, M. K., Amyes, T. L., and Richard, J. P. (2009) Biochemistry 48, 5769-5778] and 0.06 M(-1) s(-1) [Go, M. K., Koudelka, A., Amyes, T. L., and Richard, J. P. (2010) Biochemistry 49, 5377-5389] have been determined for the wild-type- and K12G mutant TIM-catalyzed deuterium exchange reactions of [1-(13)C]GA, respectively, to form [1-(13)C,2,2-di-(2)H]GA. These data show that TIM and BSA exhibit a modest catalytic activity toward deprotonation of the alpha-hydroxy alpha-carbonyl carbon. We suggest that this activity is intrinsic to many globular proteins, and that it must be enhanced to demonstrate meaningful de novo design of protein catalysts of proton transfer at alpha-carbonyl carbon.

RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

KAUST Repository

Suleimanov, Yu.V.

2013-03-01

We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the Bennett-Chandler method as a product of a static (centroid density quantum transition state theory (QTST) rate) and a dynamic (ring polymer transmission coefficient) factor. The computational procedure is general and can be used to treat bimolecular polyatomic reactions of any complexity in their full dimensionality. The program has been tested for the H+H2, H+CH 4, OH+CH4 and H+C2H6 reactions. © 2012 Elsevier B.V. All rights reserved.

RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

KAUST Repository

Suleimanov, Yu.V.; Allen, J.W.; Green, W.H.

2013-01-01

We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the Bennett-Chandler method as a product of a static (centroid density quantum transition state theory (QTST) rate) and a dynamic (ring polymer transmission coefficient) factor. The computational procedure is general and can be used to treat bimolecular polyatomic reactions of any complexity in their full dimensionality. The program has been tested for the H+H2, H+CH 4, OH+CH4 and H+C2H6 reactions. © 2012 Elsevier B.V. All rights reserved.

Trojan Horse Method and RIBs: The {sup 18}F(p,{alpha}){sup 15}O reaction at astrophysical energies

Energy Technology Data Exchange (ETDEWEB)

Cherubini, S.; Gulino, M.; Rapisarda, G. G.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Kubono, S.; Yamaguchi, H.; Hayakawa, S.; Wakabayashi, Y.; Iwasa, N.; Kato, S.; Komatsubara, H.; Teranishi, T.; Coc, A.; De Sereville, N.; Hammache, F. [Dipartimento di Fisica ed Astronomia, Universita di Catania and INFN-LNS, Catania (Italy); INFN-LNS, Catania (Italy) and UniKORE, Enna (Italy)

2012-11-12

The abundance of {sup 18}F in Nova explosions is an important issue for the understanding of this astrophysical phenomenon. For this reason it is necessary to study the nuclear reactions that produce or destroy this isotope in novae. Among these latter processes, the {sup 18}F(p,{alpha}){sup 15}O is one of the main {sup 18}F destruction channels. We report here on the preliminary results of the first experiment that applies the Trojan Horse Method to a Radioactive Ion Beam induced reaction. The experiment was performed using the CRIB apparatus of the Center for Nuclear Study of The Tokyo University.

Efficient one-pot enzymatic synthesis of alpha-(1 -> 4)-glucosidic disaccharides through a coupled reaction catalysed by Lactobacillus acidophilus NCFM maltose phosphorylase

DEFF Research Database (Denmark)

Nakai, Hiroyuki; Dilokpimol, Adiphol; Abou Hachem, Maher

2010-01-01

Lactobacillus acidophilus NCFM maltose phosphorylase (LaMalP) of glycoside hydrolase family 65 catalysed enzymatic synthesis of alpha-(1 -> 4)-glucostdic disacchandes from maltose and five monosacchandes in a coupled phosphorolysis/reverse phosphorolysis one-pot reaction Thus phosphorolysis...

High sensitivity boron quantification in bulk silicon using the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be nuclear reaction

Energy Technology Data Exchange (ETDEWEB)

Moro, Marcos V.; Silva, Tiago F. da; Added, Nemitala; Rizutto, Marcia A.; Tabacniks, Manfredo H. [Instituto de Fisica da Universidade de Sao Paulo, C.P. 66318, 05315-970 Sao Paulo, SP (Brazil); Neira, John B.; Neto, Joao B. F. [Institute of Research Tecnology, Cidade Universitaria, SP, 05508-091 (Brazil)

2013-05-06

There is a great need to quantify sub-ppm levels of boron in bulk silicon. There are several methods to analyze B in Si: Nuclear Reaction Analysis using the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be reaction exhibits a quantification limit of some hundreds ppm of B in Si. Heavy Ion Elastic Recoil Detection Analysis offers a detection limit of 5 to 10 at. ppm. Secondary Ion Mass Spectrometry is the method of choice of the semiconductor industry for the analysis of B in Si. This work verifies the use of NRA to quantify B in Si, and the corresponding detection limits. Proton beam with 1.6 up to 2.6 MeV was used to obtain the cross-section of the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be nuclear reaction at 170 Degree-Sign scattering angle. The results show good agreementwith literature indicating that the quantification of boron in silicon can be achieved at 100 ppm level (high sensitivity) at LAMFI-IFUSP with about 16% uncertainty. Increasing the detection solid angle and the collected beam charge, can reduce the detection limit to less than 100 ppm meeting present technological needs.

Measurement of Gross Alpha and Beta Emission Rates from Ceramic Tiles

International Nuclear Information System (INIS)

Wudthicharoonpun, Piyasak; Chankow, Nares

2007-08-01

Full text: Ceramic tiles normally used to cover floors and walls contain naturally occurring radioactive elements i.e. potassium-40, uranium, thorium and their daughters from raw materials. Thus, radioactivity was dependent upon source of raw materials and the amount used. The objective of this research was to measure gross alpha and beta emission rates to be used as a database for safety assessment and for selection of rooms to measure radioactive radon-222 gas

BIG-10 fission product generation and reaction rates

International Nuclear Information System (INIS)

Rogers, J.W.

1976-01-01

Fission product generation rates for high quality fission foils and reaction rates of nonfission foils have been measured by gamma ray activation analyses. These foils were irradiated in the BIG-10 facility and the activities were measured by NaI counting techniques

Study of the antioxidant effect of {alpha}-tocopherol on low-density lipoprotein peroxidation induced at low and high {gamma}-radiation dose rates

Energy Technology Data Exchange (ETDEWEB)

Khalil, Abdelouahed [Research Centre on Aging and Department of Medicine, University of Sherbrooke, Sherbrooke, QC, J1H 4C4 (Canada)]. E-mail: abdelouahed.khalil@usherbrooke.ca; Milochevitch, Christelle [Research Centre on Aging and Department of Medicine, University of Sherbrooke, Sherbrooke, QC, J1H 4C4 (Canada)

2005-02-01

It is well known that vitamin E ({alpha}-tocopherol, {alpha}-toc) is a very efficient lipid soluble antioxidant and several studies showed its beneficial action in the prevention and reduction of atherosclerosis. However, some in vitro studies suggest a prooxidant role of vitamin E, which could occur under given circumstances. This study was thus designed to investigate the antioxidant vs. prooxidant effect of vitamin E with regards to LDL peroxidation induced under different oxidative stress conditions. LDL was enriched with {alpha}-tocopherol and different {alpha}-toc/LDL ratios were studied (8.0{+-}2.5, 14.3{+-}3.0, 33.3{+-}3.7, 42.7{+-}3.5 and 48.2{+-}4.5 molecules of {alpha}-toc/LDL particle). Enriched and control LDL were oxidized by action of {sup {center_dot}}OH and O{sub 2}{sup {center_dot}}{sup -} free radicals produced by {gamma}-radiolysis at different dose rates. Susceptibility of LDL to oxidation was examined by the measure of conjugated diene and TBARS formation as well as LDL endogenous {alpha}-toc disappearance. Increasing LDL {alpha}-toc concentration reduced the LDL susceptibility to oxidation and their oxidizability. {alpha}-toc disappearance rates were comprised between 43 and 8.3x10{sup -10} M s{sup -1} and decreased with the radiation dose rate. Our results support an antioxidant role for {alpha}-tocopherol at high and low oxidative stress conditions.

The Investors- Reaction to Investment Rating Change Announcements

OpenAIRE

Chih-Hsiang Chang; Liang-Chien Lee; Shu-Ling Wu

2012-01-01

This study investigates the investors- behavioral reaction to the investment rating change announcements from the views of behavioral finance. The empirical results indicate that self-interest does affect the intention of securities firms to release investment ratings for individual stocks. In addition, behavioral pitfalls are also found in the response of retail investors to investment rating change announcements.

Effects of ion and electron screening on thermonuclear reaction rates

International Nuclear Information System (INIS)

Brady, L.R. Jr.

1977-01-01

The effects of screening by ions and electrons on thermonuclear reaction rates in stellar plasmas are considered. The enhancement of the reaction rate ranges from negligible to extremely large (on the order of 10 26 or greater). In order to calculate these effects, the potential about a given reacting nucleus is determined. First, Boltzmann-Vlasov and Poisson-Boltzmann equations are solved to yield a Yukawa potential. A suitable approximation to this potential is integrated in the action integral to give the barrier penetration. The screened reaction rate is then found by the saddle-point method. In developing a general formalism to calculate the screened reaction rate and the screening factor, effects due to the finite size of the nucleus are considered and found to be negligible. An expression for the screening factor for resonant reaction rates is also derived. A different and relatively simple approach, based on work of Stewart and Pyatt (1966), is used to find the barrier penetration from the action integral in two approximations: a modified Coulomb potential and a constant-shift potential. Screening factors are calculated for carbon burning at T 6 = 100 and T 6 = 400 for a wide range of densities and also for several examples in late stellar evolution. These screening factors are, for the most part, greater than those given by most others by a few percent at low density to 4 or more orders of magnitude at T 6 = 100 and rho = 10 10 g/cm 3 . Near the edge of the crystalline lattice region, however, they are significantly lower than those of some others. The increase in reaction rates for carbon burning indicates that carbon ignition may occur at lower densities than previously thought and may affect the density at which a supernova shock may occur

X particle effect for 6Li reaction rates calculations

International Nuclear Information System (INIS)

Kocak, G.; Balantekin, A. B.

2009-01-01

The inferred primordial 6 L i-7 L i abundances are different from standard big bang nucleosynthesis results, 6 L i is 1000 times larger and 7 L i is 3 times smaller than the big bang prediction. In big bang nucleosynthesis, negatively charged massive X particles a possible solution to explain this primordial Li abundances problem [1]. In this study, we consider only X particle effect for nuclear reactions to obtain S-factor and reaction rates for Li. All S-factors calculated within the Optical Model framework for d(α,γ)6 L i system. We showed that the enhancement effect of massive negatively charged X particle for 6 L i system reaction rate.(author)

Effect of bismuth addition to the triple therapy of Helicobacter pylori eradication

Directory of Open Access Journals (Sweden)

Ezel Taşdemir

2012-03-01

Full Text Available Objective: Success rates of amoxicillin, clarithromycin, and proton-pump inhibitor therapy in the Helicobacter pylori (Hp eradication have been decreasing. The aim of this study was to investigate the impact of bismuth subcitrate addition to triple therapy.Materials and methods: 148 patients diagnosed Hp infection with both histology and Hp stool antigen (HpSA tests were examined retrospectively. The patients were divided into 3 groups according to the eradication therapy. The first group received triple therapy with claritromycine 2x 500 mg, amoxicilline 2x1 g and PPI 2x1 for 14 days (n=40. The second group had bismuth subcitrate 4x120 mg with triple therapy for 14 days (n=73. The third group received 14 days pretreatment with bismuth subcitrate 4x1 together with PPI 2x1 then had triple therapy for 14 days (n=35. (14C urea breath and HpSA tests were used to detect posttreatment H.pylori status.Results: There were no statistical difference between the groups in terms of gender and age (p > 0.05. In group one 12 patients, in group two 20 patients and in group three 10 patients were identified as Hp positive after treatment. Eradication rates were 70% for group one, 72.6% for group two and 71.4% for group three respectively. There was no statistical difference between the groups in terms of eradication rates of treatment (p > 0.05.Conclusions: The addition of bismuth to conventional triple therapy did not affect treatment success rates.

Monte Carlo simulation of the alpha-amylolysis of amylopectin potato starch. 2. alpha-amylolysis of amylopectin

NARCIS (Netherlands)

Marchal, L.M.; Ulijn, R.V.; Gooijer, de C.D.; Franke, G.T.; Tramper, J.

2003-01-01

A model is presented that describes all the saccharides that are produced during the hydrolysis of starch by an alpha-amylase. Potato amylopectin, the substrate of the hydrolysis reaction, was modeled in a computer matrix. The four different subsite maps presented in literature for alpha-amylase

Quantifying strain partitioning between magmatic and amagmatic portions of the Afar triple junction of Ethiopia and Djibouti through use of contemporary and late Quaternary extension rates

Science.gov (United States)

Polun, S. G.; Hickcox, K.; Tesfaye, S.; Gomez, F. G.

2016-12-01

The central Afar rift in Ethiopia and Djibouti is a zone of accommodation between the onshore propagations of the Gulf of Aden and Red Sea oceanic spreading centers forming part of the Afar triple junction that divides the Arabia, Nubia, and Somalia plates. While extension in the onshore magmatic propagators is accommodated through magmatism and associated faulting, extension in the central Afar is accommodated solely by large and small faults. The contributions of these major faults to the overall strain budget can be well characterized, but smaller faults are more difficult to quantify. Sparse GPS data covering the region constrain the total extension budget across the diffuse triple junction zone. Late Quaternary slip rates for major faults in Hanle, Dobe, Guma, and Immino grabens were estimated using the quantitative analysis of faulted landforms. This forms a nearly complete transect from the onshore propagation of the Red Sea rift in Tendaho graben and the onshore propagation of the Gulf of Aden rift at Manda Inakir. Field surveying was accomplished using a combination of electronic distance measurer profiling and low altitude aerial surveying. Age constraints are provided from the Holocene lacustrine history or through terrestrial cosmogenic nuclide (TCN) dating of the faulted geomorphic surface. Along this transect, late Quaternary slip rates of major faults appear to accommodate 25% of the total horizontal stretching rate between the southern margin of Tendaho graben and the Red Sea coast, as determined from published GPS velocities. This constrains the proportion of total extension between Nubia and Arabia that is accommodated through major faulting in the central Afar, compared to the magmatism and associated faulting of the magmatic propagators elsewhere in the triple junction. Along the transect, individual fault slip rates decrease from the southeast to the northwest, suggesting a `Crank-Arm' model may be more applicable to explain the regional

The time dependence of rate constants of esub(aq)sup(-) reactions

International Nuclear Information System (INIS)

Burcl, R.; Byakov, V.M.; Grafutin, V.I.

1982-01-01

Published data about the time dependence of rate constants k(esub(aq)sup(-)+Ac) of esub(aq)sup(-) reactions with the acceptor Ac are analyzed, using the results of rate constant k(Ps+Ac) measurements for positronium reactions. It is shown that neither esub(aq)sup(-) nor Ps reaction rate constants depend on time in the observable range. Experimentally found concentration dependence of k(esub(aq)sup(-)+Ac) is due to other factors, connected with the existence of electric charge of esub(aq)sup(-), e.g. ionic strength, tunnelling effect etc. (author)

Constrained least squares methods for estimating reaction rate constants from spectroscopic data

NARCIS (Netherlands)

Bijlsma, S.; Boelens, H.F.M.; Hoefsloot, H.C.J.; Smilde, A.K.

2002-01-01

Model errors, experimental errors and instrumental noise influence the accuracy of reaction rate constant estimates obtained from spectral data recorded in time during a chemical reaction. In order to improve the accuracy, which can be divided into the precision and bias of reaction rate constant

Estimating reaction rate constants: comparison between traditional curve fitting and curve resolution

NARCIS (Netherlands)

Bijlsma, S.; Boelens, H. F. M.; Hoefsloot, H. C. J.; Smilde, A. K.

2000-01-01

A traditional curve fitting (TCF) algorithm is compared with a classical curve resolution (CCR) approach for estimating reaction rate constants from spectral data obtained in time of a chemical reaction. In the TCF algorithm, reaction rate constants an estimated from the absorbance versus time data

Detecting Energy Spectrum Of The Products Of Reaction 6Li(n,alpha)3H By The Home-Made Gaseous Detectors In Vietnam

International Nuclear Information System (INIS)

Luong Huu Phuoc; Phung Van Duan; Le Van Mien; Nguyen Tat Thang; Tran Hoai Nam

2008-01-01

There are shown some of results of study in designing and making first gaseous detectors of big sizes in Vietnam. The detectors were used for test measurement of detecting energy spectrum of the products of reaction 6 Li(n,alpha) 3 H caused by thermal neutrons. On the spectrum there were observed two energy peaks of tritons and alpha particles separately. In the test measurement there were used two neutron isotopic sources with total output 2x1.1x10 7 n/s. The study was implemented at Hanoi University of Technology. (author)

Nuclear reaction rates and the nova outburst

International Nuclear Information System (INIS)

Starrfield, S.G.; Iliadis, C.

2000-01-01

In this paper we examined the consequences of improving the nuclear reaction library on our simulations of TNRs on 1.25M, WD and 1.35M, WDS. We have found that the changes in the rates have affected the nucleosynthesis predictions of our calculations but not, to any great extent, the gross features. In addition, we have used a lower mass accretion rate than in our previous studies in order to accrete (and eject) more material. This has, as expected, caused the peak values of some important parameters to increase over our previous studies at the same WD mass. However, because some important reaction rates have declined in the new compilation this has not increased the abundances for nuclei above aluminum and, in fact, they have declined while the abundances of both 26 Al and 27 Al have increased at both WD masses. In contrast, the abundance of 22 Na has declined at both WD masses over the values predicted in our earlier work. This has important implications with respect to predictions of the observability of novae with INTEGRAL

Mechanism of Prototropy. III. Kinetics of the Tautomerization of Benzylidene-Benzylamine. comparison of the influence of hydrogen and alkyl groups on the S{sub E}2' reaction rate; mecanismo de la Prototropia. III. Cinetica de la tautomerizacion de la benciliden-bencilamina. Comparacion de la influencia del hidrogeno y grupos alcohilos sobre la velocidad de la reaccion S{sub E}2'

Energy Technology Data Exchange (ETDEWEB)

Perez Ossorio, R; Gamboa, J M; Martinez Utrilla, R

1961-07-01

The rate of the proto tropic change of benzylidene-benzylamine has been determined by using azomethine {sup 1}4C-labelled in the methylenic group and measuring the distribution of activity between benzaldehyde and benzylamine obtained by hydrolysis at different reaction times. this rate has been compared with those of tautomerization of benzylidene-{alpha}-alkyl benzylamine and {alpha}-alkyl benzylidene-benzyl amines in the same experimental conditions in order to establish ethe influence of alkyl group on this reaction. (Author) 14 refs.

Mechanism of Prototropy. III. Kinetics of the Tautomerization of Benzylidene-Benzylamine. comparison of the influence of hydrogen and alkyl groups on the S{sub E}2' reaction rate; mecanismo de la Prototropia. III. Cinetica de la tautomerizacion de la benciliden-bencilamina. Comparacion de la influencia del hidrogeno y grupos alcohilos sobre la velocidad de la reaccion S{sub E}2'

Energy Technology Data Exchange (ETDEWEB)

Perez Ossorio, R.; Gamboa, J. M.; Martinez Utrilla, R.

1961-07-01

The rate of the proto tropic change of benzylidene-benzylamine has been determined by using azomethine {sup 1}4C-labelled in the methylenic group and measuring the distribution of activity between benzaldehyde and benzylamine obtained by hydrolysis at different reaction times. this rate has been compared with those of tautomerization of benzylidene-{alpha}-alkyl benzylamine and {alpha}-alkyl benzylidene-benzyl amines in the same experimental conditions in order to establish ethe influence of alkyl group on this reaction. (Author) 14 refs.

Multiscale Investigation on Biofilm Distribution and Its Impact on Macroscopic Biogeochemical Reaction Rates: BIOFILM DISTRIBUTION AND RATE SCALING

Energy Technology Data Exchange (ETDEWEB)

Yan, Zhifeng [Institute of Surface-Earth System Science, Tianjin University, Tianjin China; Pacific Northwest National Laboratory, Richland WA USA; Liu, Chongxuan [Pacific Northwest National Laboratory, Richland WA USA; School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen China; Liu, Yuanyuan [Pacific Northwest National Laboratory, Richland WA USA; School of Earth Science and Engineering, Nanjing University, Nanjing China; Bailey, Vanessa L. [Pacific Northwest National Laboratory, Richland WA USA

2017-11-01

Biofilms are critical locations for biogeochemical reactions in the subsurface environment. The occurrence and distribution of biofilms at microscale as well as their impacts on macroscopic biogeochemical reaction rates are still poorly understood. This paper investigated the formation and distributions of biofilms in heterogeneous sediments using multiscale models, and evaluated the effects of biofilm heterogeneity on local and macroscopic biogeochemical reaction rates. Sediment pore structures derived from X-ray computed tomography were used to simulate the microscale flow dynamics and biofilm distribution in the sediment column. The response of biofilm formation and distribution to the variations in hydraulic and chemical properties was first examined. One representative biofilm distribution was then utilized to evaluate its effects on macroscopic reaction rates using nitrate reduction as an example. The results revealed that microorganisms primarily grew on the surfaces of grains and aggregates near preferential flow paths where both electron donor and acceptor were readily accessible, leading to the heterogeneous distribution of biofilms in the sediments. The heterogeneous biofilm distribution decreased the macroscopic rate of biogeochemical reactions as compared with those in homogeneous cases. Operationally considering the heterogeneous biofilm distribution in macroscopic reactive transport models such as using dual porosity domain concept can significantly improve the prediction of biogeochemical reaction rates. Overall, this study provided important insights into the biofilm formation and distribution in soils and sediments as well as their impacts on the macroscopic manifestation of reaction rates.

Some calculated (p,α) cross-sections using the alpha particle knock-on and triton pick-up reaction mechanisms: An optimisation of the single-step Feshbach-Kerman-Koonin (FKK) theory

Energy Technology Data Exchange (ETDEWEB)

Olise, Felix S.; Ajala, Afis; Olamiyl, Hezekiah B. [Dept. of Physics and Engineering Physics, Obafemi Awolowo University, Ile-Ife (Nigeria)

2016-04-15

The Feshbach-Kerman-Koonin (FKK) multi-step direct (MSD) theory of pre-equilibrium reactions has been used to compute the single-step cross-sections for some (p,α) reactions using the knock-on and pick-up reaction mechanisms at two incident proton energies. For the knock-on mechanism, the reaction was assumed to have taken place by the direct ejection of a preformed alpha cluster in a shell-model state of the target. But the reaction was assumed to have taken place by the pick-up of a preformed triton cluster (also bound in a shell-model state of the target core) by the incident proton for the pick-up mechanism. The Yukawa forms of potential were used for the proton-alpha (for the knock-on process) and proton-triton (for the pick-up process) interaction and several parameter sets for the proton and alpha-particle optical potentials. The calculated cross-sections for both mechanisms gave satisfactory fits to the experimental data. Furthermore, it has been shown that some combinations of the calculated distorted wave Born approximation cross-sections for the two reaction mechanisms in the FKK MSD theory are able to give better fits to the experimental data, especially in terms of range of agreement. In addition, the theory has been observed to be valid over a wider range of energy.

Some Calculated (p,α Cross-Sections Using the Alpha Particle Knock-On and Triton Pick-Up Reaction Mechanisms: An Optimisation of the Single-Step Feshbach–Kerman–Koonin (FKK Theory

Directory of Open Access Journals (Sweden)

Felix S. Olise

2016-04-01

Full Text Available The Feshbach–Kerman–Koonin (FKK multi-step direct (MSD theory of pre-equilibrium reactions has been used to compute the single-step cross-sections for some (p,α reactions using the knock-on and pick-up reaction mechanisms at two incident proton energies. For the knock-on mechanism, the reaction was assumed to have taken place by the direct ejection of a preformed alpha cluster in a shell-model state of the target. But the reaction was assumed to have taken place by the pick-up of a preformed triton cluster (also bound in a shell-model state of the target core by the incident proton for the pick-up mechanism. The Yukawa forms of potential were used for the proton-alpha (for the knock-on process and proton-triton (for the pick-up process interaction and several parameter sets for the proton and alpha-particle optical potentials. The calculated cross-sections for both mechanisms gave satisfactory fits to the experimental data. Furthermore, it has been shown that some combinations of the calculated distorted wave Born approximation cross-sections for the two reaction mechanisms in the FKK MSD theory are able to give better fits to the experimental data, especially in terms of range of agreement. In addition, the theory has been observed to be valid over a wider range of energy.

Hybrid perovskite resulting from the solid-state reaction between the organic cations and perovskite layers of alpha1-(Br-(CH(2))(2)-NH(3))(2)PbI(4).

Science.gov (United States)

Sourisseau, Sebastien; Louvain, Nicolas; Bi, Wenhua; Mercier, Nicolas; Rondeau, David; Buzaré, Jean-Yves; Legein, Christophe

2007-07-23

The alpha1-(Br-(CH(2))(2)-NH(3))(2)PbI(4) hybrid perovskite undergoes a solid-state transformation, that is, the reaction between the organic cations and the perovskite layers to give the new hybrid perovskite (Br-(CH(2))(2)-NH(3))(2-x)(I-(CH(2))(2)-NH(3))(x)PbBr(x)I(4-x), based on mixed halide inorganic layers. This transformation has been followed by a conventional powder X-ray diffraction system equipped with a super speed detector, and both solid-state (13)C NMR and ESI/MS measurements have been adopted in the estimation of the rate of halide substitution. The first reaction step leads to the special composition of x approximately 1 (A phase), while the complete substitution is not achieved even at elevated temperature (x(max) approximately 1.85 (B phase)). This unprecedented solid-state reaction between organic and inorganic components of a hybrid perovskite can be considered as a completely new strategy to achieve interesting hybrid perovskites.

Calculus of radiolytic products generation in water due to alpha radiation. Determination of the spent nuclear fuels matrix alteration rate Determination of velocity of spent fuel matrix; Calculo de la generacion de productos radioliticos en agua por radiacion {alpha}. Determinacion de la velocidad de alteracion de la matriz del combustible nuclear gastado

Energy Technology Data Exchange (ETDEWEB)

Quinones, J.; Serrano, J.; Diaz Arocas, P.; Rodriguez Almazan, J. L. [Ciemat. Madrid (Spain); Bruno, J.; Cera, E.; Merino, J.; Esteban, J. A.; Martinez-Esparza, A. [Enresa. Madrid (Spain)

2000-07-01

The generation of radiolytic products as a result of alpha radiation in the surface of the spent fuel is a key process in order to understand how the it becomes degraded in repository conditions. The present work has established a radiolytic model based on a set of reactions involving fuel oxidation-dissolution and radiolytic products recombination. It also includes the decrease of the dose rates as the main alpha emitters decay away. Four cases, with varying parameters of the system, have been assessed. The results show a decrease in both the concentration of the radiolytic products in the gap water and the degradation of the fuel matrix. It has been estimated that in the period of the evaluation (10''6 years) up to 52% of the pellet is altered in the conservative cases, whereas only 11% is altered in the realistic cases. No significant differences were observed when the carbonates reactions were included in the system. (Author)

In-depth evaluation of the cycloaddition-retro-Diels-Alder reaction for in vivo targeting with [{sup 111}In]-DTPA-RGD conjugates

Energy Technology Data Exchange (ETDEWEB)

Laverman, Peter [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)], E-mail: p.laverman@nucmed.umcn.nl; Meeuwissen, Silvie A. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands); Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Berkel, Sander S. van [Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Oyen, Wim J.G. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands); Delft, Floris L. van; Rutjes, Floris P.J.T. [Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Boerman, Otto C. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)

2009-10-15

Introduction: The spontaneous copper-free tandem 1,3-dipolar cycloaddition-retro-Diels-Alder (tandem crDA) reaction between cyclic Arg-Gly-Asp-D-Phe-Orn(N{sub 3}) [c(RGDfX)] and oxanorbornadiene-DTPA (o-DTPA) or methyloxanorbornadiene-DTPA (mo-DTPA) into two DTPA-c(RGDfX) regioisomers is characterized. Since there is no information on the stability and reaction rate of the tandem crDA reaction in biological media, we set out to characterize these reaction parameters. Methods: The effects of concentration of the reactants, temperature, pH and reaction environment (serum, blood) on the kinetics of the reaction were determined using {sup 111}In-labeled oxanorbornadiene-DTPA analogs. The affinity of the radiolabeled conjugate was determined in a solid-phase {alpha}{sub v}{beta}{sub 3} integrin binding assay. Furthermore, the octanol-water partition coefficient was determined and, finally, the biodistribution of the labeled compounds in mice with subcutaneous {alpha}{sub v}{beta}{sub 3}-expressing tumors was determined. Results: Fifty percent conversion was reached after 26 h. Kinetic experiments furthermore established that the reaction rate of the tandem crDA reaction follows temperature- and concentration-dependent second-order kinetics, but is independent of the pH of the medium. Affinity of the two [{sup 111}In]DTPA-cRGDfX conjugates for {alpha}{sub v}{beta}{sub 3} integrin is 191 nM. Biodistribution studies showed specific ({alpha}{sub v}{beta}{sub 3}-mediated) uptake of [{sup 111}In]DTPA-c(RGDfX) in the tumor and in {alpha}{sub v}{beta}{sub 3}-expressing tissues. Conclusion: The tandem crDA reaction using methyl-substituted oxanorbornadiene is a versatile method for a single-step ligation that proceeds independently of pH and also proceeds in serum and blood. Currently, we are further looking into enhancement of reaction kinetics and exploitation of tandem crDA in vivo.

The reaction rates of electrons with native and irradiated ribonuclease

International Nuclear Information System (INIS)

Schuessler, H.; Ebert, M.; Davies, J.V.

1977-01-01

The rate of reaction of hydrated electrons with proteins depends, amongst other things, on the conformational structure of the protein, and irradiation itself causes conformational changes in proteins. A study has been made of variations in the reaction rates of hydrated electrons with RNase pre-irradiated by the Linac or by a 60 Co γ-source. The reaction rate constants varied with the pre-irradiation dose, the concentration of phosphate buffer, the enzyme concentration and also the presence of 10 -2 M ethanol. These variations serve to emphasize the importance of the tertiary structure of biological molecules in irradiation processes and have significant implications in the mathematical analysis of the inactivation of enzymes in steady-state irradiation processes. (U.K.)

On the mechanism of effective chemical reactions with turbulent mixing of reactants and finite rate of molecular reactions

Energy Technology Data Exchange (ETDEWEB)

Vorotilin, V. P., E-mail: VPVorotilin@yandex.ru [Russian Academy of Sciences, Institute of Applied Mechanics (Russian Federation)

2017-01-15

A generalization of the theory of chemical transformation processes under turbulent mixing of reactants and arbitrary values of the rate of molecular reactions is presented that was previously developed for the variant of an instantaneous reaction [13]. The use of the features of instantaneous reactions when considering the general case, namely, the introduction of the concept of effective reaction for the reactant volumes and writing a closing conservation equation for these volumes, became possible due to the partition of the whole amount of reactants into “active” and “passive” classes; the reactants of the first class are not mixed and react by the mechanism of instantaneous reactions, while the reactants of the second class approach each other only through molecular diffusion, and therefore their contribution to the reaction process can be neglected. The physical mechanism of reaction for the limit regime of an ideal mixing reactor (IMR) is revealed and described. Although formally the reaction rate in this regime depends on the concentration of passive fractions of the reactants, according to the theory presented, the true (hidden) mechanism of the reaction is associated only with the reaction of the active fractions of the reactants with vanishingly small concentration in the volume of the reactor. It is shown that the rate constant of fast chemical reactions can be evaluated when the mixing intensity of reactants is much less than that needed to reach the mixing conditions in an IMR.

Non extensive corrections to stellar nuclear reactions rate

Energy Technology Data Exchange (ETDEWEB)

Assuncao, M. [Universidade Federal de Sao Paulo (DCET/UNIFESP), Diadema, SP (Brazil). Dept. de Ciencias Exatas e da Terra; Silveira, F.E.M. [Universidade Federal do ABC, Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Lima, J.A.S. [Universidade de Sao Paulo (IAG/USP), SP (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas

2010-07-01

Full text: Stellar nucleosynthesis is widely accepted as the basic mechanism for creation of chemical elements in the Universe. In particular, nuclear reactions occurring in the Sun are recognized as responsible for its energy generation. The problem of to determine the energy generation mechanism in stars was firstly attacked by Gamow in the framework of his quantum mechanical theory of potential barrier penetration. According to that approach, the reactions rate is calculated by averaging the penetration factor over the velocity distribution of the plasma particles. A randomization of that distribution is expected as a consequence of the reactions. However, diffusion processes in the macroscopic environment should balance the resulting particles number depletion. Therefore, matter, energy, and momentum might steadily flow. In other words, a quasi-stationary equilibrium state must be attained. In this work, the potential barrier penetration approach to stellar nuclear reactions rate has been rediscussed with basis on Tsallis nonextensive statistics. The investigation has been restricted to non-resonant reactions, for which the S-factor can be regarded as a constant. It has been found that, within the extended formulation, the nonextensive q-parameter is constrained to a maximum value. Accordingly, the q-energy has been shown to exhibit a minimum. The q-Gamow peak has been derived and, in connection with the usual Gaussian approximation, the corresponding half q-width has been also estimated. Plots of the q-energy, q-Gamow peak and half q-width for some reactions with stellar physics interest have been produced. (author)

Matching of experimental and statistical-model thermonuclear reaction rates at high temperatures

International Nuclear Information System (INIS)

Newton, J. R.; Longland, R.; Iliadis, C.

2008-01-01

We address the problem of extrapolating experimental thermonuclear reaction rates toward high stellar temperatures (T>1 GK) by using statistical model (Hauser-Feshbach) results. Reliable reaction rates at such temperatures are required for studies of advanced stellar burning stages, supernovae, and x-ray bursts. Generally accepted methods are based on the concept of a Gamow peak. We follow recent ideas that emphasized the fundamental shortcomings of the Gamow peak concept for narrow resonances at high stellar temperatures. Our new method defines the effective thermonuclear energy range (ETER) by using the 8th, 50th, and 92nd percentiles of the cumulative distribution of fractional resonant reaction rate contributions. This definition is unambiguous and has a straightforward probability interpretation. The ETER is used to define a temperature at which Hauser-Feshbach rates can be matched to experimental rates. This matching temperature is usually much higher compared to previous estimates that employed the Gamow peak concept. We suggest that an increased matching temperature provides more reliable extrapolated reaction rates since Hauser-Feshbach results are more trustwhorthy the higher the temperature. Our ideas are applied to 21 (p,γ), (p,α), and (α,γ) reactions on A=20-40 target nuclei. For many of the cases studied here, our extrapolated reaction rates at high temperatures differ significantly from those obtained using the Gamow peak concept

Compilation and R-matrix analysis of Big Bang nuclear reaction rates

International Nuclear Information System (INIS)

Descouvemont, Pierre; Adahchour, Abderrahim; Angulo, Carmen; Coc, Alain; Vangioni-Flam, Elisabeth

2004-01-01

We use the R-matrix theory to fit low-energy data on nuclear reactions involved in Big Bang nucleosynthesis. Special attention is paid to the rate uncertainties which are evaluated on statistical grounds. We provide S factors and reaction rates in tabular and graphical formats

Students' Ideas about Reaction Rate and Its Relationship with Concentration or Pressure

Science.gov (United States)

Cakmakci, Gultekin; Leach, John; Donnelly, James

2006-01-01

This cross-sectional study identifies key conceptual difficulties experienced by upper secondary school and pre-service chemistry teachers (N = 191) in the area of reaction rates. Students' ideas about reaction rates were elicited through a series of written tasks and individual interviews. In this paper, students' ideas related to reaction rate…

Quantum theory of enhanced unimolecular reaction rates below the ergodicity threshold

International Nuclear Information System (INIS)

Leitner, David M.; Wolynes, Peter G.

2006-01-01

A variety of unimolecular reactions exhibit measured rates that exceed Rice-Ramsperger-Kassel-Marcus (RRKM) predictions. We show using the local random matrix theory (LRMT) of vibrational energy flow how the quantum localization of the vibrational states of a molecule, by violating the ergodicity assumption, can give rise to such an enhancement of the apparent reaction rate. We present an illustrative calculation using LRMT for a model 12-vibrational mode organic molecule to show that below the ergodicity threshold the reaction rate may exceed many times the RRKM prediction due to quantum localization of vibrational states

Neutron detector for fusion reaction-rate measurements

International Nuclear Information System (INIS)

Lerche, R.A.; Phillion, D.W.; Tietbohl, G.L.

1993-01-01

We have developed a fast, sensitive neutron detector for recording the fusion reaction-rate history of inertial-confinement fusion (ICF) experiments. The detector is based on the fast rise-time of a commercial plastic scintillator (BC-422) and has a response 7 neutrons

Direct Amination of alpha-Hydroxy Amides

NARCIS (Netherlands)

Chandgude, Ajay L.; Dömling, Alexander

A TiCl4-mediated reaction for the direct amination of alpha-hydroxy amides has been developed. This simple, general, additive/base/ligand-free reaction is mediated by economical TiCl4. The reaction runs under mild conditions. This highly efficient C-N bond formation protocol is valid for diverse

Reaction rates for neutrino processes

International Nuclear Information System (INIS)

Shalitin, D.

1978-01-01

Some integrals involved in neutrino processes are evaluated by transformation to a special system of reference - usually to the center of mass system (CM). Rather simple analytic expressions are obtained for reaction rates and, though less simple, for moments. An interesting result thus obtained is for an isotropic interaction (in CM) of a neutrino with a monoenergetic isotropic gas of extreme relativistic electrons: it is found that the probability of the scattered neutrino to have energy in a certain range is independent of this energy. (Auth.)

Liquid Film Diffusion on Reaction Rate in Submerged Biofilters

DEFF Research Database (Denmark)

Christiansen, Pia; Hollesen, Line; Harremoës, Poul

1995-01-01

Experiments were carried out in order to investigate the influence of liquid film diffusion on reaction rate in a submerged biofilter with denitrification and in order to compare with a theoretical study of the mass transfer coefficient. The experiments were carried out with varied flow, identified...... by the empty bed velocity of inflow and recirculation, respectively 1.3, 2.8, 5.6 and 10.9 m/h. The filter material consisted of 3 mm biostyren spheres. The results indicate that the influence of liquid film diffusion on reaction rate can be ignored....

alpha-Amanitin induced apoptosis in primary cultured dog hepatocytes.

Directory of Open Access Journals (Sweden)

Adam Szelag

2010-06-01

Full Text Available Amatoxin poisoning is caused by mushroom species belonging to the genera Amanita, Galerina and Lepiota with the majority of lethal mushroom exposures attributable to Amanita phalloides. High mortality rate in intoxications with these mushrooms is principally a result of the acute liver failure following significant hepatocyte damage due to hepatocellular uptake of amatoxins. A wide variety of amatoxins have been isolated; however, alpha-amanitin (alpha-AMA appears to be the primary toxin. Studies in vitro and in vivo suggest that alpha-AMA does not only cause hepatocyte necrosis, but also may lead to apoptotic cell death. The objective of this study was to evaluate the complex hepatocyte apoptosis in alpha-AMA cytotoxicity. All experiments were performed on primary cultured canine hepatocytes. The cells were incubated for 12 h with alpha-AMA at a final concentration of 1, 5, 10 and 20 microM. Viability test (MTT assay, apoptosis evaluation (TUNEL reaction, detection of DNA laddering and electron microscopy were performed at 6 and 12 h of exposure to alpha-AMA. There was a clear correlation between hepatocyte viability, concentration of alpha-AMA and time of exposure to this toxin. The decline in cultured dog hepatocyte viability during the exposure to alpha-AMA is most likely preceded by enhanced cellular apoptosis. Our results demonstrate that apoptosis might contribute to pathogenesis of the severe liver injury in the course of amanitin intoxication, particularly during the early phase of poisoning.

Effects of network dissolution changes on pore-to-core upscaled reaction rates for kaolinite and anorthite reactions under acidic conditions

KAUST Repository

Kim, Daesang

2013-11-01

We have extended reactive flow simulation in pore-network models to include geometric changes in the medium from dissolution effects. These effects include changes in pore volume and reactive surface area, as well as topological changes that open new connections. The computed changes were based upon a mineral map from an X-ray computed tomography image of a sandstone core. We studied the effect of these changes on upscaled (pore-scale to core-scale) reaction rates and compared against the predictions of a continuum model. Specifically, we modeled anorthite and kaolinite reactions under acidic flow conditions during which the anorthite reactions remain far from equilibrium (dissolution only), while the kaolinite reactions can be near-equilibrium. Under dissolution changes, core-scale reaction rates continuously and nonlinearly evolved in time. At higher injection rates, agreement with predictions of the continuum model degraded significantly. For the far-from-equilibrium reaction, our results indicate that the ability to correctly capture the heterogeneity in dissolution changes in the reactive mineral surface area is critical to accurately predict upscaled reaction rates. For the near-equilibrium reaction, the ability to correctly capture the heterogeneity in the saturation state remains critical. Inclusion of a Nernst-Planck term to ensure neutral ionic currents under differential diffusion resulted in at most a 9% correction in upscaled rates.

On the existence of and mechanism for microwave-specific reaction rate enhancement.

Science.gov (United States)

Dudley, Gregory B; Richert, Ranko; Stiegman, A E

2015-04-01

The use of microwave radiation to drive chemical reactions has become ubiquitous in almost all fields of chemistry. In all of these areas it is principally due to rapid and convenient heating resulting in significantly higher rates of reaction, with other advantages including enhanced product selectivity and control of materials properties. Although microwave heating continues to grow as an enabling technology, fundamental research into the nature of microwave heating has not grown at the same rate. In the case of chemical reactions run in homogeneous solution, particularly synthetic organic reactions, there is considerable controversy over the origins of rate enhancement, with a fundamental question being whether there exist microwave-specific effects, distinct from what can be attained under conventional convective heating, that can accelerate a reaction rate. In this Perspective, we discuss unique aspects of microwave heating of molecules in solution and discuss the origin and nature of microwave-specific effects arising from the process of "selective heating" of reactants in solution. Integral to this discussion is work from the field of dielectric relaxation spectroscopy, which provides a model for selective heating by Debye relaxation processes. The Perspective also includes a critical discussion of hypotheses of non-thermal effects (alternatively classified here as resonant processes) and an outline of specific reaction parameters for chemical systems in which microwave-specific Debye relaxation processes can result in observable reaction rate enhancement.

Nuclear-reaction rates in the thermonuclear runaway phase of accreting neutron stars

International Nuclear Information System (INIS)

Wiescher, M.; Barnard, V.; Goerres, J.; Fisker, J.L.; Martinez-Pinedo, G.; Langanke, K.; Rembges, F.; Thielemann, F.K.; Schatz, H.

2002-01-01

The rp-process has been suggested as the dominant nucleosynthesis process in explosive hydrogen burning at high temperature and density conditions. The process is characterized by a sequence of fast proton capture reactions and subsequent β-decays. The reaction path of the rp-process runs along the drip line up to Z∼50. Most of the charged-particle reaction rates for the reaction path are presently based on statistical Hauser-Feshbach calculations. While these rates are supposed to be reliable within a factor of two for conditions of high density in the compound nuclei, discrepancies may occur for nuclei near closed shells or near the proton drip line where the Q-values of proton capture processes are typically very small. It has been argued that the thermonuclear runaway is less sensitive to the reaction rates because of the rapid time-scale of the event. However, since these processes may operate at the same time-scale as fast mixing and convection processes, a change in reaction rates indeed may have a significant impact. In this paper we present two examples, the break-out from the hot CNO cycles, and the thermonuclear runaway in X-ray bursts itself, where changes in reaction rates have a direct impact on time-scale, energy generation and nucleosynthesis predictions for the explosive event. (orig.)

Charge exchange of excited mesic atoms of hydrogen isotopes in triple collisions with molecules

International Nuclear Information System (INIS)

Men'shikov, L.I.; Ponomarev, L.I.

1985-01-01

At high densities of deuterium-tritium mixture the probability for the occurrence of the isotope-exchange reaction (dμ)/sub n/+t → d+(tμ)/sub n/ from the excited states of n mesic atoms of deuterium is high in the triple collisions of mesic atoms with the molecules of hydrogen isotopes. This reaction should be taken into account in describing the kinetics of muon catalysis

Different slopes for different folks: alpha and delta EEG power predict subsequent video game learning rate and improvements in cognitive control tasks.

Science.gov (United States)

Mathewson, Kyle E; Basak, Chandramallika; Maclin, Edward L; Low, Kathy A; Boot, Walter R; Kramer, Arthur F; Fabiani, Monica; Gratton, Gabriele

2012-12-01

We hypothesized that control processes, as measured using electrophysiological (EEG) variables, influence the rate of learning of complex tasks. Specifically, we measured alpha power, event-related spectral perturbations (ERSPs), and event-related brain potentials during early training of the Space Fortress task, and correlated these measures with subsequent learning rate and performance in transfer tasks. Once initial score was partialled out, the best predictors were frontal alpha power and alpha and delta ERSPs, but not P300. By combining these predictors, we could explain about 50% of the learning rate variance and 10%-20% of the variance in transfer to other tasks using only pretraining EEG measures. Thus, control processes, as indexed by alpha and delta EEG oscillations, can predict learning and skill improvements. The results are of potential use to optimize training regimes. Copyright © 2012 Society for Psychophysiological Research.

Chromatographic determination of the rate and extent of absorption of air pollutants by sea water

International Nuclear Information System (INIS)

Nikolakaki, S.; Vassilakos, C.; Katsanos, N.A.

1994-01-01

A simple chromatographic method is developed to determine the rate constant for expulsion of an air pollutant from water or its diffusion parameter in the liquid, the rate constant for chemical reaction of the pollutant with water, its mass transfer coefficient in the liquid, and the partition coefficient between liquid water and air. From these physicochemical parameters, the absorption rate by sea water and, therefore, the depletion rate of a polluting substance from the air can be calculated, together with the equilibrium state of this absorption. The method has been applied to nitrogen dioxide being absorbed by triple-distilled water and by sea water, at various temperatures. From the temperature variation of the reaction rate constant and of the partition coefficient, the activation energy for the reaction and the differential heat of solution were determined. (orig.)

Method and apparatus for obtaining enhanced production rate of thermal chemical reactions

Science.gov (United States)

Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Wegeng, Robert S [Richland, WA; Gao, Yufei [Kennewick, WA

2003-04-01

The present invention is a method and apparatus (vessel) for providing a heat transfer rate from a reaction chamber through a wall to a heat transfer chamber substantially matching a local heat transfer rate of a catalytic thermal chemical reaction. The key to the invention is a thermal distance defined on a cross sectional plane through the vessel inclusive of a heat transfer chamber, reaction chamber and a wall between the chambers. The cross sectional plane is perpendicular to a bulk flow direction of the reactant stream, and the thermal distance is a distance between a coolest position and a hottest position on the cross sectional plane. The thermal distance is of a length wherein the heat transfer rate from the reaction chamber to the heat transfer chamber substantially matches the local heat transfer rate.

Pulse radiolytic study of alpha-tocopherol radical mechanisms in ethanolic solution

International Nuclear Information System (INIS)

Jore, D.; Patterson, L.K.; Ferradini, C.

1986-01-01

Pulse radiolytic studies of alpha-tocopherol (alpha TH) oxidation-reduction processes were carried out with low doses (5 Gy) of high-energy electrons in O 2 -, N 2 -, and air-saturated ethanolic solutions. Depending on the concentration of oxygen in solution, two different radicals, A . and B ., were observed. The first, A ., was obtained under N 2 and results from alpha TH reaction with solvated electron (k alpha TH + e-solv = 3.4 X 10(8) mol-1 liter s-1) and with H 3 C-CH-OH, (R.) (k alpha TH + R. = 5 X 10(5) mol-1 liter s-1). B., observed under O 2 , is produced by alpha TH reaction with RO 2 . peroxyl radicals (k alpha TH + RO 2 . = 9.5 X 10(4) mol-1 liter s-1)

A kinetic-theory approach for computing chemical-reaction rates in upper-atmosphere hypersonic flows.

Science.gov (United States)

Gallis, Michael A; Bond, Ryan B; Torczynski, John R

2009-09-28

Recently proposed molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction-rate information) are investigated for chemical reactions occurring in upper-atmosphere hypersonic flows. The new models are in good agreement with the measured Arrhenius rates for near-equilibrium conditions and with both measured rates and other theoretical models for far-from-equilibrium conditions. Additionally, the new models are applied to representative combustion and ionization reactions and are in good agreement with available measurements and theoretical models. Thus, molecular-level chemistry modeling provides an accurate method for predicting equilibrium and nonequilibrium chemical-reaction rates in gases.

Computational and experimental studies on stabilities, reactions and reaction rates of cations and ion-dipole complexes

NARCIS (Netherlands)

Ervasti, H.K.

2008-01-01

In this thesis, ion stability, ion-molecule reactions and reaction rates are studied using mass spectrometry and molecular modelling. In Chapter 2 the effect of functional group substitution on neutral and ionised ketene are studied. Electron-donating substituents show a stabilising positive

A mesoscopic reaction rate model for shock initiation of multi-component PBX explosives.

Science.gov (United States)

Liu, Y R; Duan, Z P; Zhang, Z Y; Ou, Z C; Huang, F L

2016-11-05

The primary goal of this research is to develop a three-term mesoscopic reaction rate model that consists of a hot-spot ignition, a low-pressure slow burning and a high-pressure fast reaction terms for shock initiation of multi-component Plastic Bonded Explosives (PBX). Thereinto, based on the DZK hot-spot model for a single-component PBX explosive, the hot-spot ignition term as well as its reaction rate is obtained through a "mixing rule" of the explosive components; new expressions for both the low-pressure slow burning term and the high-pressure fast reaction term are also obtained by establishing the relationships between the reaction rate of the multi-component PBX explosive and that of its explosive components, based on the low-pressure slow burning term and the high-pressure fast reaction term of a mesoscopic reaction rate model. Furthermore, for verification, the new reaction rate model is incorporated into the DYNA2D code to simulate numerically the shock initiation process of the PBXC03 and the PBXC10 multi-component PBX explosives, and the numerical results of the pressure histories at different Lagrange locations in explosive are found to be in good agreements with previous experimental data. Copyright © 2016 Elsevier B.V. All rights reserved.

Reaction-rate coefficients, high-energy ions slowing-down, and power balance in a tokamak fusion reactor plasma

International Nuclear Information System (INIS)

Tone, Tatsuzo

1978-07-01

Described are the reactivity coefficient of D-T fusion reaction, slowing-down processes of deuterons injected with high energy and 3.52 MeV alpha particles generated in D-T reaction, and the power balance in a Tokamak reactor plasma. Most of the results were obtained in the first preliminary design of JAERI Experimental Fusion Reactor (JXFR) driven with stationary neutral beam injection. A manual of numerical computation program ''BALTOK'' developed for the calculations is given in the appendix. (auth.)

Co-{alpha}Al{sub 2}O{sub 3}-Cu as shaped catalyst in NaBH{sub 4} hydrolysis

Energy Technology Data Exchange (ETDEWEB)

Chamoun, R. [Universite Lyon 1, CNRS, UMR 5615, Laboratoire des Multimateriaux et Interfaces, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne (France); Universite Libanaise, Faculte des Sciences II, Laboratoire de physique appliquee, 90656 Jdeidet El Metn (Lebanon); Demirci, U.B.; Miele, P. [Universite Lyon 1, CNRS, UMR 5615, Laboratoire des Multimateriaux et Interfaces, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne (France); Zaatar, Y.; Khoury, A. [Universite Libanaise, Faculte des Sciences II, Laboratoire de physique appliquee, 90656 Jdeidet El Metn (Lebanon)

2010-07-15

A study about catalytic films of Co-supported-over-{alpha}Al{sub 2}O{sub 3} fabricated by electrophoretic deposition (EPD) is reported, the as-prepared shaped catalysts being intended to catalyze NaBH{sub 4} hydrolysis. Co-{alpha}Al{sub 2}O{sub 3} supported over Cu substrate can be prepared by a 2-step route: (i) preparation of the supported catalyst Co-{alpha}Al{sub 2}O{sub 3} (in powder form) by wet impregnation of CoCl{sub 2} over {alpha}Al{sub 2}O{sub 3}, followed by a reduction, and (ii) fabrication of Co-{alpha}Al{sub 2}O{sub 3}-Cu (thin film over Cu) by EPD. Both types of catalysts, whatever their form, are highly efficient in hydrolyzing NaBH{sub 4}, conversions of 100% and HGRs of tens of mL(H{sub 2}) min{sup -1} being achieved at 60-80 C. The Co-{alpha}Al{sub 2}O{sub 3}-Cu catalysts are even more reactive than the Co-{alpha}Al{sub 2}O{sub 3} catalysts because the surface of the former materials becomes much more acid than that of the latter ones in the course of the EPD process. The respective rate laws and reaction kinetics have been determined. Independently on the catalyst form, apparent activation energies of about 52 kJ mol{sup -1} and positive reaction orders versus the initial NaBH{sub 4} concentration (i.e. 0.3-0.7) were calculated, suggesting that the EPD does not affect the reaction mechanisms. Besides, it is showed that the hydrolysis is really catalytic as well as typical of a heterogeneous process. For example, an apparent reaction order versus the Co content of 0.9 was calculated. All of these results among others are reported and discussed in the present article. (author)

Analysis of the Clinicopathologic Features and Prognosis in Triple-Negative Breast Cancer

Institute of Scientific and Technical Information of China (English)

Dehong Yang; Hong Liu; Jing Zhao

2008-01-01

OBJECTIVE To investigate the clinical and pathological features,as well as prognosis in triple-negative breast cancer patients.METHODS A total of 509 cases of operable breast cancer from January,2002 to June,2002 treated in the Cancer Hospital of Tianjin Medical University were analyzed.The Her-2,ER and PR status was determined using immunohistochemistry.Of the total cases,one group was identified as triple negative breast cancer,ie defined as ER,PR and Her-2 negative.The other group was nontriple-negative breast cancer.Clinicopathologic features of the groups were compared and 5-year disease-free survival (DFS)analyzed by the Kaplan-Meier method.RESULTS Of the total cases,21.4% (109/509) of cases were found to be triple- negative while 78.6% (400/509) were non-triplenegative.The triple negative group had higher incidence rates than the non-triple-negative group of the medullary type and Grade Ⅲ tumors (P ＜ 0.05).There was no other difference in the clinicopathologic features between the 2 groups.From follow-up to June,2007,21.1% (23/109) of the triple-negative group and 12.7%(51/400) of the non-triple negative group had a local recurrence or distant metastasis,resulting in a significant difference (P ＜ 0.05).In the triple-negative group and non-triple-negative group,5-year DFS were 78.9% and 87.3% respectively.There was a statistically significant difference between the 2 groups (P = 0.031).CONCLUSION Compared with non-triple-negative breast cancer,triple-negative breast cancer patients have an increased likehood of a local recurrence or distant metastasis and a poorer prognosis.

Calculated /alpha/-induced thick target neutron yields and spectra, with comparison to measured data

International Nuclear Information System (INIS)

Wilson, W.B.; Bozoian, M.; Perry, R.T.

1988-01-01

One component of the neutron source associated with the decay of actinide nuclides in many environments is due to the interaction of decay /alpha/ particles in (/alpha/,n) reactions on low Z nuclides. Measurements of (/alpha/,n) thick target neutron yields and associated neutron spectra have been made for only a few combinations of /alpha/ energy and target nuclide or mixtures of actinide and target nuclides. Calculations of thick target neutron yields and spectra with the SOURCES code require /alpha/-energy-dependent cross sections for (/alpha/,n) reactions, as well as branching fractions leading to the energetically possible levels of the product nuclides. A library of these data has been accumulated for target nuclides of Z /le/ 15 using that available from measurements and from recent GNASH code calculations. SOURCES, assuming neutrons to be emitted isotopically in the center-of-mass system, uses libraries of /alpha/ stopping cross sections, (/alpha/,n) reaction cross reactions, product nuclide level branching fractions, and actinide decay /alpha/ spectra to calculate thick target (/alpha/,n) yields and neutron spectra for homogeneous combinations of nuclides. The code also calculates the thick target yield and angle intergrated neutron spectrum produced by /alpha/-particle beams on targets of homogeneous mixtures of nuclides. Illustrative calculated results are given and comparisons are made with measured thick target yields and spectra. 50 refs., 1 fig., 2 tabs

Ion-neutral gas reactions in a collision/reaction cell in inductively coupled plasma mass spectrometry: Correlation of ion signal decrease to kinetic rate constants

Energy Technology Data Exchange (ETDEWEB)

Gray, Patrick J. [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States); Department of Chemistry, The Ohio State University, 120 18th Avenue, Columbus, OH 43210 (United States); Olesik, John W., E-mail: olesik.2@osu.edu [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States)

2015-03-01

Reaction gas flow rate dependent Ar{sub 2}{sup +} and Ar{sup +} signals are correlated to fundamental kinetic rate coefficients. A simple calculation, assuming that gas exits the reaction cell due only to effusion, is described to estimate the gas pressure in the reaction cell. The value of the product of the kinetic rate constant and the ion residence time in the reaction cell can be determined from experimental measurement of the decrease in an ion signal as a function of reaction gas flow rate. New kinetic rate constants are determined for the reaction of CH{sub 3}F with Ar{sup +} and Ar{sub 2}{sup +}. - Highlights: • How to determine pressure and the product of the kinetic rate constant times the ion residence time in reaction cell • Relate measured ICP-DRC-MS signals versus gas flow rate to kinetic rate constants measured previously using SIFT-MS • Describe how to determine previously unmeasured kinetic rate constants using ICP-DRC-MS.

Correlations between the alpha particles and ejectiles in the 208 MeV 14N on 93Nb reaction at three different ejectile angles

International Nuclear Information System (INIS)

Fukuda, T.; Ishihara, M.; Tanaka, M.; Ogata, H.; Miura, I.; Inoue, M.; Shimoda, T.; Katori, K.; Nakayama, S.

1983-01-01

The in plane correlations between alpha particles and various ejectiles were investigated in the reaction of 208 MeV 14 N on 93 Nb at theta/sub HI/ = +22 0 , +50 0 , and +80 0 . There were three sources of coincident alpha particles: (i) the sequential alpha decay of the excited ejectiles, (ii) the equilibrium alpha emission from the targetlike fragments, and (iii) the nonequilibrium process. Process (i) contributed mainly to the cross sections with the angular range of theta/sub α/ close to theta/sub HI/. Process (ii) contributed to the lowest part of the alpha energy spectra irrespectively of theta/sub HI/ and theta/sub α/. The remaining part was ascribed to process (iii). For this process the differential coincidence cross section of the lower energy part of the alpha particles was approximately factorized as d 4 sigma/dΩ/sub HI/dΩ/sub α/dE/sub HI/dE/sub α/ = K (d 2 sigma/dΩ/sub HI/dE/sub HI/)/sub singles/ (d 2 sigma/dΩ/sub α/dE/sub α/)/sub singles/ with Kapprox.0.4/b, whereas the higher energy part of the alpha particles emitted at the forward angles had a tendency to coincide weakly with the ejectiles emitted at the backward angles (theta/sub HI/ = +50 0 and +80 0 ) as compared to the lower energy part of the alpha particles

Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Niobium

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

1.1 This test method describes procedures for measuring reaction rates by the activation reaction 93Nb(n,n′)93mNb. 1.2 This activation reaction is useful for monitoring neutrons with energies above approximately 0.5 MeV and for irradiation times up to about 30 years. 1.3 With suitable techniques, fast-neutron reaction rates for neutrons with energy distribution similar to fission neutrons can be determined in fast-neutron fluences above about 1016cm−2. In the presence of high thermal-neutron fluence rates (>1012cm−2·s−1), the transmutation of 93mNb due to neutron capture should be investigated. In the presence of high-energy neutron spectra such as are associated with fusion and spallation sources, the transmutation of 93mNb by reactions such as (n,2n) may occur and should be investigated. 1.4 Procedures for other fast-neutron monitors are referenced in Practice E 261. 1.5 Fast-neutron fluence rates can be determined from the reaction rates provided that the appropriate cross section information ...

alpha,beta-unsaturated 2-acyl imidazoles as a practical class of dienophiles for the DNA-Based catalytic asymmetric diels-alder reaction in water

NARCIS (Netherlands)

Boersma, A.J.; Feringa, B.L.; Roelfes, G.

2007-01-01

alpha,beta-Unsaturated 2-acyl imidazoles are a novel and practical class of dienophiles for the DNA-based catalytic asymmetric Diels-Alder reaction in water. The Diels-Alder products are obtained with very high diastereoselectivities and enantioselectivities in the range of 83-98%. The catalytic

Perturbative triples correction for local pair natural orbital based explicitly correlated CCSD(F12*) using Laplace transformation techniques.

Science.gov (United States)

Schmitz, Gunnar; Hättig, Christof

2016-12-21

We present an implementation of pair natural orbital coupled cluster singles and doubles with perturbative triples, PNO-CCSD(T), which avoids the quasi-canonical triples approximation (T0) where couplings due to off-diagonal Fock matrix elements are neglected. A numerical Laplace transformation of the canonical expression for the perturbative (T) triples correction is used to avoid an I/O and storage bottleneck for the triples amplitudes. Results for a test set of reaction energies show that only very few Laplace grid points are needed to obtain converged energy differences and that PNO-CCSD(T) is a more robust approximation than PNO-CCSD(T0) with a reduced mean absolute deviation from canonical CCSD(T) results. We combine the PNO-based (T) triples correction with the explicitly correlated PNO-CCSD(F12*) method and investigate the use of specialized F12-PNOs in the conventional triples correction. We find that no significant additional errors are introduced and that PNO-CCSD(F12*)(T) can be applied in a black box manner.

GATA3 expression in triple-negative breast cancers.

Science.gov (United States)

Byrne, David J; Deb, Siddhartha; Takano, Elena A; Fox, Stephen B

2017-07-01

GATA-binding protein 3 (GATA3) is a well-studied transcription factor found to be essential in the development of luminal breast epithelium and has been identified in a variety of tumour types, including breast and urothelial carcinomas, making it a useful immunohistochemistry marker in the diagnosis of both primary and metastatic disease. We investigated GATA3 protein expression in a 106 primary triple-negative breast carcinomas (100 basal-like, six non-basal-like) using Cell Marque mouse monoclonal anti-GATA3 (L50-823). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to quantify mRNA expression in 22 triple-negative breast cancers (TNBCs) (20 primary and two cell lines), four luminal (three primary and one cell line) and five human epidermal growth factor receptor 2 (HER2) (four primary and one cell line) amplified tumours. In 98 TNBCs where IHC was assessable, 47 (48%) had a 1+ or greater staining with 20 (21%) having high GATA3 expression when using a weighted scoring. Our study has demonstrated that GATA3 expression is common in primary triple-negative breast carcinomas. It also suggests that although GATA3 is an oestrogen receptor (ER) regulated gene, it still proves useful in differentiating between primary and metastatic tumours in patients with a history of breast cancer regardless of its molecular subtype. © 2017 John Wiley & Sons Ltd.

Rate Constant Change of Photo Reaction of Bacteriorhodopsin Observed in Trimeric Molecular System.

Science.gov (United States)

Tsujiuchi, Yutaka; Masumoto, Hiroshi; Goto, Takashi

2016-04-01

To elucidate the time evolution of photo reaction of bacteriorhodopsin in glycerol mixed purple membrane at around 196 K under irradiation by red light, a kinetic model was constructed. The change of absorption with irradiation at times of 560 nm and 412 nm was analyzed for the purpose of determining reaction rates of photo reaction of bacteriorhodopsin and its product M intermediate. In this study it is shown that reaction rates of conversion from bacteriorhodopsin to the M intermediate can be explained by a set of linear differential equations. This model analysis concludes that bacteriorhodopsin in which constitutes a trimer unit with other two bacteriorhodopsin molecules changes into M intermediates in the 1.73 of reaction rate, in the initial step, and according to the number of M intermediate in a trimer unit, from three to one, the reaction rate of bacteriorhodopsin into M intermediates smaller as 1.73, 0.80, 0.19 which caused by influence of inter-molecular interaction between bacteriorhodopsin.

Pycnonuclear reaction rates for binary ionic mixtures

Science.gov (United States)

Ichimaru, S.; Ogata, S.; Van Horn, H. M.

1992-01-01

Through a combination of compositional scaling arguments and examinations of Monte Carlo simulation results for the interparticle separations in binary-ionic mixture (BIM) solids, we have derived parameterized expressions for the BIM pycnonuclear rates as generalizations of those in one-component solids obtained previously by Salpeter and Van Horn and by Ogata et al. We have thereby discovered a catalyzing effect of the heavier elements, which enhances the rates of reactions among the lighter elements when the charge ratio exceeds a critical value of approximately 2.3.

Selective oxidation of methyl {alpha}-D-glucopyranoside with oxygen over supported platinum: Kinetic modeling in the presence of deactivation by overoxidation of the catalyst

Energy Technology Data Exchange (ETDEWEB)

Vleeming, J.H.; Kuster, B.F.M.; Marin, G.B. [Eindhoven Univ. of Technology (Netherlands)

1997-09-01

The selective oxidation of alcohols and carbohydrates with molecular oxygen in aqueous media is an industrial and environmental attractive process. A kinetic model is presented, which describes the platinum-catalyzed selective oxidation of methyl {alpha}-D-glucopyranoside to sodium methyl {alpha}-D-glucuronate with molecular oxygen in the presence of deactivation by overoxidation. Overoxidation is completely reversible and most adequately described by a reversible transformation of oxygen adatoms into inactive subsurface oxygen. A clear distinction is made between the rapid establishment of the steady-state degree of coverage by the reaction intermediates at the platinum surface and the much slower reversible process of overoxidation. This clear distinction is reflected in the rate equation, which can be written as the product of an initial rate and a deactivation function. The deactivation function is given as a function of the degree of coverage by inactive subsurface oxygen. The rate-determining step in the selective oxidation consists of the reaction between dissociatively chemisorbed oxygen and physisorbed methyl {alpha}-D-glucopyranoside. The corresponding standard activation entropy and enthalpy amount to respectively {minus}111 {+-} 12 J/mol K and 51 {+-} 4 kJ/mol. The standard reaction entropy for the transformation of oxygen atoms into subsurface oxygen amounts to {minus}35 {+-} 16 J/mol K and the standard reaction enthalpy to {minus}36 {+-} 15 kJ/mol.

[Incidence rate of adverse reaction/event by Qingkailing injection: a Meta-analysis of single rate].

Science.gov (United States)

Ai, Chun-ling; Xie, Yan-ming; Li, Ming-quan; Wang, Lian-xin; Liao, Xing

2015-12-01

To systematically review the incidence rate of adverse drug reaction/event by Qingkailing injection. Such databases as the PubMed, EMbase, the Cochrane library, CNKI, VIP WanFang data and CBM were searched by computer from foundation to July 30, 2015. Two reviewers independently screened literature according to the inclusion and exclusion criteria, extracted data and cross check data. Then, Meta-analysis was performed by using the R 3.2.0 software, subgroup sensitivity analysis was performed based on age, mode of medicine, observation time and research quality. Sixty-three studies involving 9,793 patients with Qingkailing injection were included, 367 cases of adverse reactions/events were reported in total. The incidence rate of adverse reaction in skin and mucosa group was 2% [95% CI (0.02; 0.03)]; the digestive system adverse reaction was 6% [95% CI(0.05; 0.07); the injection site adverse reaction was 4% [95% CI (0.02; 0.07)]. In the digestive system as the main types of adverse reactions/events, incidence of children and adults were 4.6% [0.021 1; 0.097 7] and 6.9% [0.053 5; 0.089 8], respectively. Adverse reactions to skin and mucous membrane damage as the main performance/event type, the observation time > 7 days and ≤ 7 days incidence of 3% [0.012 9; 0.068 3] and 1.9% [0.007 8; 0.046 1], respectively. Subgroup analysis showed that different types of adverse reactions, combination in the incidence of adverse reactions/events were higher than that of single drug, the difference was statistically significant (P reactions occur, and clinical rational drug use, such as combination, age and other fators, and the influence factors vary in different populations. Therefore, clinical doctors for children and the elderly use special care was required for a clear and open spirit injection, the implementation of individualized medication.

Interlaboratory reaction rate program. 12th progress report, November 1976-October 1979

International Nuclear Information System (INIS)

Lippincott, E.P.; McElroy, W.N.; Preston, C.C.

1980-09-01

The Interlaboratory Reaction Rate UILRR) program is establishing the capability to accurately measure neutron-induced reactions and reaction rates for reactor fuels and materials development programs. The goal for the principal fission reactions, 235 U, 238 U and 239 Pu, is an accuracy to within +- 5% at the 95% confidence level. Accurate measurement of other fission and nonfission reactions is also required, but to a lesser accuracy, between +- 5% and 10% at the 95% confidence level. A secondary program objective is improvement in knowledge of the nuclear parameters involved in the standarization of fuels and materials dosimetry measurements of neutron flux, spectra, fluence and burnup

Simulation of biochemical reactions with time-dependent rates by the rejection-based algorithm

Energy Technology Data Exchange (ETDEWEB)

Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Department of Mathematics, University of Trento, Trento (Italy)

2015-08-07

We address the problem of simulating biochemical reaction networks with time-dependent rates and propose a new algorithm based on our rejection-based stochastic simulation algorithm (RSSA) [Thanh et al., J. Chem. Phys. 141(13), 134116 (2014)]. The computation for selecting next reaction firings by our time-dependent RSSA (tRSSA) is computationally efficient. Furthermore, the generated trajectory is exact by exploiting the rejection-based mechanism. We benchmark tRSSA on different biological systems with varying forms of reaction rates to demonstrate its applicability and efficiency. We reveal that for nontrivial cases, the selection of reaction firings in existing algorithms introduces approximations because the integration of reaction rates is very computationally demanding and simplifying assumptions are introduced. The selection of the next reaction firing by our approach is easier while preserving the exactness.

Altered cortisol metabolism in polycystic ovary syndrome: insulin enhances 5alpha-reduction but not the elevated adrenal steroid production rates.

Science.gov (United States)

Tsilchorozidou, Tasoula; Honour, John W; Conway, Gerard S

2003-12-01

homeostasis model insulin resistance index (HOMA-R): alpha-THF/THF and HOMA-R (r = 0.34; P = 0.03), androsterone/etiocholanolone and HOMA-R (r = 0.32; P = 0.04), and total 5alpha /total 5beta and HOMA-R (r = 0.37; P = 0.02). A positive correlation was also found between measures of 5alpha-R and BMI (r = 0.37; P = 0.02). No correlation was found between measures of 11beta-HSD1 activity and indices of insulin sensitivity or BMI. We have demonstrated that there is an increased production rate of cortisol and androgens as measured in vivo in lean PCOS women. Insulin seems to enhance 5alpha reduction of steroids in PCOS but was not associated with the elevated cortisol production rate. The changes in 5alpha-R, 11beta-HSD1, and 20alpha/beta-HSD enzyme activities observed in PCOS may contribute to the increased production rates of cortisol and androgens, supporting the concept of a widespread dysregulation of steroid metabolism. This dysregulation does not seem to be the primary cause of PCOS because no correlation was found between serum androgen levels or urinary excretion of androgens with measurements of either 5alpha-R or 11beta-HSD1 activities.

Analyzing Reaction Rates with the Distortion/Interaction-Activation Strain Model

NARCIS (Netherlands)

Bickelhaupt, F. Matthias; Houk, Kendall N.

2017-01-01

The activation strain or distortion/interaction model is a tool to analyze activation barriers that determine reaction rates. For bimolecular reactions, the activation energies are the sum of the energies to distort the reactants into geometries they have in transition states plus the interaction

Pop-It Beads to Introduce Catalysis of Reaction Rate and Substrate Depletion Effects

Science.gov (United States)

Gehret, Austin U.

2017-01-01

A kinesthetic classroom activity was designed to help students understand enzyme activity and catalysis of reaction rate. Students served the role of enzymes by manipulating Pop-It Beads as the catalytic event. This activity illuminates the relationship between reaction rate and reaction progress by allowing students to experience first-hand the…

Metabolic control analysis of biochemical pathways based on a thermokinetic description of reaction rates

DEFF Research Database (Denmark)

Nielsen, Jens Bredal

1997-01-01

Metabolic control analysis is a powerful technique for the evaluation of flux control within biochemical pathways. Its foundation is the elasticity coefficients and the flux control coefficients (FCCs). On the basis of a thermokinetic description of reaction rates it is here shown...... that the elasticity coefficients can be calculated directly from the pool levels of metabolites at steady state. The only requirement is that one thermodynamic parameter be known, namely the reaction affinity at the intercept of the tangent in the inflection point of the curve of reaction rate against reaction...... of the thermokinetic description of reaction rates to include the influence of effecters. Here the reaction rate is written as a linear function of the logarithm of the metabolite concentrations. With this type of rate function it is shown that the approach of Delgado and Liao [Biochem. J. (1992) 282, 919-927] can...

In situ formation of a 3D core-shell and triple-conducting oxygen reduction reaction electrode for proton-conducting SOFCs

Science.gov (United States)

Zhang, Zhenbao; Wang, Jian; Chen, Yubo; Tan, Shaozao; Shao, Zongping; Chen, Dengjie

2018-05-01

BaZrxCeyY1-x-yO3-δ are recognized proton-conducting electrolyte materials for proton-conducting solid oxide fuel cells (H+-SOFCs) below 650 °C. Here Co cations are incorporated into the BaZr0.4Ce0.4Y0.2O3-δ (BZCY) scaffold to generate a 3D core-shell and triple-conducting (H+/O2-/e-) electrode in situ via infiltrating and reactive sintering. The core is the bulk BZCY scaffold, while the shell is composed of the cubic Ba(Zr0.4Ce0.4Y0.2)1-xCoxO3-δ, cubic spinel Co3O4 and cubic fluorite (Ce, Zr, Y)O2. The obtained electrode exhibits an excellent compatibility with the BZCY electrolyte, and performs well in yielding a low and stable polarization resistance for oxygen reduction reaction for intermediate-temperature H+-SOFCs. In particular, it achieves polarization resistances as low as 0.094 and 0.198 Ω cm2 at 650 and 600 °C in wet air (3% H2O) when the sintering temperature for the electrode is 900 °C. In addition, a symmetrical cell also exhibits operation stability of 70 h at 650 °C. Furthermore, a fuel cell assembled with the 3D core-shell and triple-conducting electrode delivers a peak power density of ∼330 mW cm-2 at 650 °C. The substantially improved electrochemical performance and high stability are ascribed to the unique core-shell structure and the formation of Ba(Zr0.4Ce0.4Y0.2)1-xCoxO3-δ in the shell.

Contributions to the study of heavy and superheavy nuclei stability in alpha-decay

International Nuclear Information System (INIS)

Silisteanu, I.

1978-01-01

Alpha-decay is treated in this work on the complete analogy of transfer reactions by means of nuclear shell models with continuous spectrum nucleons. Certain phenomenologically obtained or microscope evaluated data on low energy interactions between alpha-particles and nuclei, when related to nuclear structure data within the unified theory of nuclear reactions, allow of an improved accuracy in determining the alpha-particle wave function as well as of an estimation of alpha-probabilities in good keeping with experimental ones. The problem of alpha lifetimes thus narrows to the resolution of some homogeneous and inhomogeneous differential equations systems including the optic potential and the alpha formfactors. (author)

Study of the (p,d3He) reaction as a quasi-free reaction process

International Nuclear Information System (INIS)

Cowley, A.A.; Roos, P.G.; Chant, N.S.; Woody, R. III; Holmgren, H.D.; Goldberg, D.A.

1976-11-01

The (p,d 3 He) reaction on 6 Li, 7 Li, 9 Be, and 12 C has been investigated in conjunction with studies of the (p,pα) reaction on the same targets. Coincident data for all four targets were obtained at a bombarding energy of 100 MeV for numerous angle pairs in order to test the reaction mechanism. Comparisons of the (p,d 3 He) data to both (p,pα) data and distorted wave impulse approximation calculations (DWIA) indicate a dominance of the direct quasi-free reaction process (p + alpha yields d + 3 He). The absolute alpha-particle spectroscopic factors extracted using DWIA analysis are in agreement with the values obtained in the (p,pα) reaction

Rate constants for some electrophilic reactions of benzyl, benzhydryl, and trityl cations in solution

International Nuclear Information System (INIS)

Ujdak, R.J.; Jones, R.L.; Dorfman, L.M.

1976-01-01

Absolute rate constants have been determined by the pulse radiolysis technique for several electrophilic reactions of the benzyl, the benzhydryl, and the trityl cation in 1,2-dichloroethane solution. The rate constants for the reactions of these carbonium ions with chloride ion, with bromide ion, and with iodide ion are all very nearly the same, namely 6 x 10 10 M -1 s -1 at 24 0 C. The values very likely represent the diffusion controlled limit for the ion combination reactions. The rate constants for the reactions with triethylamine, tri-n-propylamine, and tri-n-butylamine range from 2.0 x 10 9 to 7 x 10 6 M -1 s -1 at 24 0 C. With increasing phenyl substitution, the decreasing trend in the magnitude of the rate constant is consistent with the combined electronic and steric effects. With increasing size of the amine, the decrease in the value of the rate constant seems to indicate that the steric effect predominates. The values of the rate constants for reactions of benzyl and benzhydryl cation with methanol, ethanol, and 2-propanol indicate the following. The rate constant is higher for reaction with the alcohol dimer in solution than with alcohol monomer. The rate constants for reaction with alcohol monomer have values of 1 x 10 8 M -1 s -1 or lower

Triple-differential cross section of the 208Pb(6Li, αd)208 Pb Coulomb breakup and astrophysical S-factor of the d(α,γ)6 Li reaction at extremely low energies

International Nuclear Information System (INIS)

Igamov, S.B.; Yarmukhamedov, R.

1999-10-01

A method of calculation of the triple-differential cross section of the 208 Pb( 6 Li, αd) 208 Pb Coulomb breakup at astrophysically relevant energies E of the relative motion of the breakup fragments, taking into account the three-body (α - d - 208 Pb) Coulomb effects and the contributions from the E1- and E2- multipoles, including their interference, has been proposed. The new results for the astrophysical S-factor of the direct radiative capture d(α, γ) 6 Li reaction at E ≤ 250 keV have been obtained. It is shown that the experimental triple-differential cross section of the 208 Pb( 6 Li, αd) 208 Pb Coulomb breakup can also be used to give information about the value of the modulus squared of the nuclear vertex constant for the virtual 6 Li → α + d. (author)

Multiscale Investigation on Biofilm Distribution and Its Impact on Macroscopic Biogeochemical Reaction Rates

Science.gov (United States)

Yan, Zhifeng; Liu, Chongxuan; Liu, Yuanyuan; Bailey, Vanessa L.

2017-11-01

Biofilms are critical locations for biogeochemical reactions in the subsurface environment. The occurrence and distribution of biofilms at microscale as well as their impacts on macroscopic biogeochemical reaction rates are still poorly understood. This paper investigated the formation and distributions of biofilms in heterogeneous sediments using multiscale models and evaluated the effects of biofilm heterogeneity on local and macroscopic biogeochemical reaction rates. Sediment pore structures derived from X-ray computed tomography were used to simulate the microscale flow dynamics and biofilm distribution in the sediment column. The response of biofilm formation and distribution to the variations in hydraulic and chemical properties was first examined. One representative biofilm distribution was then utilized to evaluate its effects on macroscopic reaction rates using nitrate reduction as an example. The results revealed that microorganisms primarily grew on the surfaces of grains and aggregates near preferential flow paths where both electron donor and acceptor were readily accessible, leading to the heterogeneous distribution of biofilms in the sediments. The heterogeneous biofilm distribution decreased the macroscopic rate of biogeochemical reactions as compared with those in homogeneous cases. Operationally considering the heterogeneous biofilm distribution in macroscopic reactive transport models such as using dual porosity domain concept can significantly improve the prediction of biogeochemical reaction rates. Overall, this study provided important insights into the biofilm formation and distribution in soils and sediments as well as their impacts on the macroscopic manifestation of reaction rates.

Semiclassical Calculation of Reaction Rate Constants for Homolytical Dissociations

Science.gov (United States)

Cardelino, Beatriz H.

2002-01-01

There is growing interest in extending organometallic chemical vapor deposition (OMCVD) to III-V materials that exhibit large thermal decomposition at their optimum growth temperature, such as indium nitride. The group III nitrides are candidate materials for light-emitting diodes and semiconductor lasers operating into the blue and ultraviolet regions. To overcome decomposition of the deposited compound, the reaction must be conducted at high pressures, which causes problems of uniformity. Microgravity may provide the venue for maintaining conditions of laminar flow under high pressure. Since the selection of optimized parameters becomes crucial when performing experiments in microgravity, efforts are presently geared to the development of computational OMCVD models that will couple the reactor fluid dynamics with its chemical kinetics. In the present study, we developed a method to calculate reaction rate constants for the homolytic dissociation of III-V compounds for modeling OMCVD. The method is validated by comparing calculations with experimental reaction rate constants.

Coloring Rate of Phenolphthalein by Reaction with Alkaline Solution Observed by Liquid-Droplet Collision.

Science.gov (United States)

Takano, Yuuka; Kikkawa, Shigenori; Suzuki, Tomoko; Kohno, Jun-ya

2015-06-11

Many important chemical reactions are induced by mixing two solutions. This paper presents a new way to measure rates of rapid chemical reactions induced by mixing two reactant solutions using a liquid-droplet collision. The coloring reaction of phenolphthalein (H2PP) by a reaction with NaOH is investigated kinetically. Liquid droplets of H2PP/ethanol and NaOH/H2O solutions are made to collide, which induces a reaction that transforms H2PP into a deprotonated form (PP(2-)). The concentration of PP(2-) is evaluated from the RGB values of pixels in the colored droplet images, and is measured as a function of the elapsed time from the collision. The obtained rate constant is (2.2 ± 0.7) × 10(3) M(-1) s(-1), which is the rate constant for the rate-determining step of the coloring reaction of H2PP. This method was shown to be applicable to determine rate constants of rapid chemical reactions between two solutions.

Rate of reaction of dimethylmercury with oxygen atoms in the gas phase

DEFF Research Database (Denmark)

Egsgaard, Helge

1986-01-01

The rate constant for the reaction of atomic oxygen (O(3P)) with dimethylmercury has been measured at room temperature at a pressure of about 1 Torr using a fast flow system with electron paramagnetic resonance and mass spectrometric detection. Some reaction products were identified. The rate...

Neutron Scattering in Hydrogenous Moderators, Studied by Time Dependent Reaction Rate Method

Energy Technology Data Exchange (ETDEWEB)

Larsson, L G; Moeller, E; Purohit, S N

1966-03-15

The moderation and absorption of a neutron burst in water, poisoned with the non-1/v absorbers cadmium and gadolinium, has been followed on the time scale by multigroup calculations, using scattering kernels for the proton gas and the Nelkin model. The time dependent reaction rate curves for each absorber display clear differences for the two models, and the separation between the curves does not depend much on the absorber concentration. An experimental method for the measurement of infinite medium reaction rate curves in a limited geometry has been investigated. This method makes the measurement of the time dependent reaction rate generally useful for thermalization studies in a small geometry of a liquid hydrogenous moderator, provided that the experiment is coupled to programs for the calculation of scattering kernels and time dependent neutron spectra. Good agreement has been found between the reaction rate curve, measured with cadmium in water, and a calculated curve, where the Haywood kernel has been used.

Reaction of atomic bromine with acetylene and loss rate of atmospheric acetylene due to reaction with OH, Cl, O, and Br

Science.gov (United States)

Payne, W. A.; Nava, D. F.; Brunning, J.; Stief, L. J.

1986-01-01

The first-order, diffusion, and bimolecular rate constants for the reaction Br + C2H2 yields C2H3Br are evaluated. The rate constants are measured at 210, 248, 298, and 393 K and at pressures between 15-100 torr Ar using flash photolysis combined with time-resolved detection of atomic bromine via Br resonance radiation. It is observed that the reaction is not affected by pressure or temperature and the bimolecular constant = (4.0 + or - 0.8) x 10 to the -15th cu cm/sec with an error of two standard deviations. The C2H2 + Br reaction rates are compared with reactions of C2H2 with Cl, OH, NH2, and H. The loss rates for atmospheric C2H2 for reactions with OH, Cl, O, and Br are calculated as a function of altitude.

Alpha particles spectrometer with photodiode PIN; Espectrometro de particulas alfa con fotodiodo PIN

Energy Technology Data Exchange (ETDEWEB)

Chacon R, A.; Hernandez V, R.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidades Academicas de Estudios Nucleares e Ingenieria Electrica, Calle Cipres No. 10, Fracc. La Penuela, 09869 Zacatecas (Mexico); Ramirez G, J. [Instituto Nacional de Estadistica Geografia e Informatica, Direccion General de Innovacion y Tecnologia de Informacion, Av. Heroes de Nacozari Sur 2301, Fracc. Jardines del Parque, 20276 Aguascalientes (Mexico)], e-mail: achruiz@hotmail.com

2009-10-15

The radiation propagates in form of electromagnetic waves or corpuscular radiation; if the radiation energy causes ionization in environment that crosses it is considered ionizing radiation. To detect radiation several detectors types are used, if the radiation are alpha particles are used detectors proportional type or trace elements. In this work the design results, construction and tests of an alpha particles spectrometer are presented, which was designed starting from a photodiode PIN type. The system design was simulated with a code for electronic circuits. With results of simulation phase was constructed the electronic phase that is coupled to a multichannel analyzer. The resulting electronic is evaluated analyzing the electronic circuit performance before an alphas triple source and alpha radiation that produce two smoke detectors of domestic use. On the tests phase we find that the system allows obtain, in a multichannel, the pulses height spectrum, with which we calibrate the system. (Author)

Comparing transfusion reaction rates for various plasma types: a systematic review and meta-analysis/regression.

Science.gov (United States)

Saadah, Nicholas H; van Hout, Fabienne M A; Schipperus, Martin R; le Cessie, Saskia; Middelburg, Rutger A; Wiersum-Osselton, Johanna C; van der Bom, Johanna G

2017-09-01

We estimated rates for common plasma-associated transfusion reactions and compared reported rates for various plasma types. We performed a systematic review and meta-analysis of peer-reviewed articles that reported plasma transfusion reaction rates. Random-effects pooled rates were calculated and compared between plasma types. Meta-regression was used to compare various plasma types with regard to their reported plasma transfusion reaction rates. Forty-eight studies reported transfusion reaction rates for fresh-frozen plasma (FFP; mixed-sex and male-only), amotosalen INTERCEPT FFP, methylene blue-treated FFP, and solvent/detergent-treated pooled plasma. Random-effects pooled average rates for FFP were: allergic reactions, 92/10 5 units transfused (95% confidence interval [CI], 46-184/10 5 units transfused); febrile nonhemolytic transfusion reactions (FNHTRs), 12/10 5 units transfused (95% CI, 7-22/10 5 units transfused); transfusion-associated circulatory overload (TACO), 6/10 5 units transfused (95% CI, 1-30/10 5 units transfused); transfusion-related acute lung injury (TRALI), 1.8/10 5 units transfused (95% CI, 1.2-2.7/10 5 units transfused); and anaphylactic reactions, 0.8/10 5 units transfused (95% CI, 0-45.7/10 5 units transfused). Risk differences between plasma types were not significant for allergic reactions, TACO, or anaphylactic reactions. Methylene blue-treated FFP led to fewer FNHTRs than FFP (risk difference = -15.3 FNHTRs/10 5 units transfused; 95% CI, -24.7 to -7.1 reactions/10 5 units transfused); and male-only FFP led to fewer cases of TRALI than mixed-sex FFP (risk difference = -0.74 TRALI/10 5 units transfused; 95% CI, -2.42 to -0.42 injuries/10 5 units transfused). Meta-regression demonstrates that the rate of FNHTRs is lower for methylene blue-treated compared with FFP, and the rate of TRALI is lower for male-only than for mixed-sex FFP; whereas no significant differences are observed between plasma types for allergic reactions, TACO

The effect of composition of mixture on rate of radiation initiation of chain reactions

International Nuclear Information System (INIS)

Poluehktov, V.A.; Begishev, I.R.; Podkhalyuzin, A.T.; Babkina, Eh.I.; Morozov, V.A.; Shapovalov, V.V.

1977-01-01

The effect of the composition of starting components on the rate of a number of chain liquid-phase reactions initiated by γ-quanta of Co 60 has been investigated at constant temperature and dosage rate. In regard to 1,1-difluoroethane chlorination, cyclohexene phosphorylation and adamantane alkylation with hexafluoropropylene reactions, abnormal effect of the reagent compositions on reaction rates has been discovered. The possible radical - starting molecule complexing reaction and molecular complexing from the starting components have been considered

Triple p-positive parenting program for mothers of ADHD children.

Science.gov (United States)

Aghebati, Asma; Gharraee, Banafsheh; Hakim Shoshtari, Mitra; Gohari, Mahmood Reza

2014-01-01

Attention deficit hyperactivity disorder (ADHD) is a chronic, highly prevalent neurodevelopmental disorder which affects 9% of school-age children. Triple P-Positive Parenting Program is an evidence-based parenting program reported to be useful in the management of this disorder. The aim of this randomized controlled trial was to evaluate the effectiveness of Triple P in mothers of ADHD children. In this study, 30 mothers with ADHD children aged between 6 to 10 were randomly assigned to two groups (15 participants in each group). Parenting style, mother-child relationship, maternal depression, anxiety and stress, and children's behavioral problems were evaluated. The intervention group received 120 minute sessions for 5 weeks and 15-30 minute telephone contacts for 3 weeks while no intervention was done for the control group. Analysis of covariance revealed that mothers of the Triple P group showed significant (p parenting style, mother-child relationship, and considerable decrease in depression, anxiety and stress. Women trained in the Triple P group also reported significantly lower rates of child misbehavior than women of the control group. Triple P-Positive Parenting intervention is effective and acceptable for mothers of ADHD children. None. Clinical Trial Registration-URL: http://www.irct.ir. Unique identifier: IRCT201111288234N1.

Almost convergence of triple sequences

OpenAIRE

Ayhan Esi; M.Necdet Catalbas

2013-01-01

In this paper we introduce and study the concepts of almost convergence and almost Cauchy for triple sequences. Weshow that the set of almost convergent triple sequences of 0's and 1's is of the first category and also almost everytriple sequence of 0's and 1's is not almost convergent.Keywords: almost convergence, P-convergent, triple sequence.

The alpha channeling effect

Science.gov (United States)

Fisch, N. J.

2015-12-01

Alpha particles born through fusion reactions in a tokamak reactor tend to slow down on electrons, but that could take up to hundreds of milliseconds. Before that happens, the energy in these alpha particles can destabilize on collisionless timescales toroidal Alfven modes and other waves, in a way deleterious to energy confinement. However, it has been speculated that this energy might be instead be channeled into useful energy, so as to heat fuel ions or to drive current. Such a channeling needs to be catalyzed by waves Waves can produce diffusion in energy of the alpha particles in a way that is strictly coupled to diffusion in space. If these diffusion paths in energy-position space point from high energy in the center to low energy on the periphery, then alpha particles will be cooled while forced to the periphery. The energy from the alpha particles is absorbed by the wave. The amplified wave can then heat ions or drive current. This process or paradigm for extracting alpha particle energy collisionlessly has been called alpha channeling. While the effect is speculative, the upside potential for economical fusion is immense. The paradigm also operates more generally in other contexts of magnetically confined plasma.

Über die Reaktion von [alpha]- und [beta]-Tetralon mit Kaliumsuperoxid

OpenAIRE

Lissel, Manfred

1984-01-01

The reaction of [alpha]- and [beta]-tetralone with potassium superoxide is described. In addition to 2-hydroxy-1,4-naphthoquinone [alpha]-naphthol is formed from [alpha]-tetralone and [beta]-naphthol and 2-carboxy-benzenepropionic acid from [beta]-tetralone.

Improvement of the high-accuracy O-17(p, alpha)N-14 reaction-rate measurement via the Trojan Horse method for application to O-17 nucleosynthesis

Czech Academy of Sciences Publication Activity Database

Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Tang, X. D.; Bucher, B.; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Lamm, L.; Ma, C.; Notani, M.; O'Brien, S.; Roberson, D.; Tan, W.; Wiescher, M.; Irgaziev, B.; Mukhamedzhanov, A.; Mrázek, Jaromír; Kroha, Václav

2015-01-01

Roč. 91, č. 6 (2015), s. 065803 ISSN 0556-2813 R&D Projects: GA MŠk LC07050 Institutional support: RVO:61389005 Keywords : thermonuclear reaction rates * cross section * O-17 Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.146, year: 2015

FcepsilonRI-alpha siRNA inhibits the antigen-induced activation of mast cells.

Science.gov (United States)

Safaralizadeh, Reza; Soheili, Zahra-Soheila; Deezagi, Abdolkhaleg; Pourpak, Zahra; Samiei, Shahram; Moin, Mostafa

2009-12-01

FcepsilonRI, The high affinity receptor for IgE plays a critical role in triggering the allergic reactions. It is responsible for inducing mast cell degranulation and deliberation of allergy mediators when it is aggregated by allergen and IgE complexes. FcepsilonRI on the mast cells consists of three subunits; alpha chain directly binds IgE, beta chain and dimmer of gamma chains together mediate intracellular signaling. Cross-linking of IgE-bound FcepsilonRI on the surface of mast cells and basophils by the multivalent antigen induces release of chemical mediators. The present in vitro study was designed to investigate the effect of synthetic FcepsilonRI-alpha siRNA on the antigen-induced activation of MC/9 cells. MC/9 cells which are murine mast cells were transfected by FcepsilonRI-alpha siRNA and negative control siRNA. After 6 h, anti-DNP (Dinitrophenyl) IgE was used for the cells sensitization. Then the cells were challenged with Dinitrophenyl-Human Serum Albumin (DNP-HSA) for mast cell degranulation induction before collection of supernatants. The amount of mRNA and protein expression was measured by Real Time PCR and western blot analysis, respectively. Determination of the expression rate of FcepsilonRI-alpha on cell surface was achieved by flow cytometry. ELISA and spectrophotometry methods were used subsequently for measuring the effects of FcepsilonRI-alpha siRNA on antigen-induced histamine and beta-hexosaminidase release. FcepsilonRI-alpha siRNA treated cells showed significant decrease in FcepsilonRI-alpha mRNA and protein expression in comparison to control cells. FcepsilonRI-mediated mast cell release of beta-hexosaminidase and histamine were also inhibited. In this study it was shown that FcepsilonRI-alpha siRNA could suppress FcepsilonRI-alpha expression and inhibited degranulation and histamine release in antigen-stimulated MC/9 cells. In conclusion, knock-down of FcepsilonRI-alpha by siRNA could be a promising method for inhibition of the mast

Accurate label-free reaction kinetics determination using initial rate heat measurements

Science.gov (United States)

Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R.

2015-01-01

Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity. PMID:26574737

Ozonation of norfloxacin and levofloxacin in water: Specific reaction rate constants and defluorination reaction.

Science.gov (United States)

Ling, Wencui; Ben, Weiwei; Xu, Ke; Zhang, Yu; Yang, Min; Qiang, Zhimin

2018-03-01

The degradation kinetics and mechanism of two typical fluoroquinolones (FQs), norfloxacin (NF) and levofloxacin (LOF), by ozone in water were investigated. Semi-continuous mode and competition kinetics mode experiments were conducted to determine the reaction rate constants of target FQs with ozone and OH, separately. Results indicate that both NF and LOF were highly reactive toward ozone, and the reactivity was strongly impacted by the solution pH. The specific reaction rate constants of the diprotonated, monoprotonated and deprotonated species were determined to be 7.20 × 10 2 , 8.59 × 10 3 , 4.54 × 10 5  M -1  s -1 respectively for NF and 1.30 × 10 3 , 1.40 × 10 4 , 1.33 × 10 6  M -1  s -1 respectively for LOF. The reaction rate constants of target FQs toward OH were measured to be (4.81-7.41) × 10 9  M -1  s -1 in the pH range of 6.3-8.3. Furthermore, NF was selected as a model compound to clarify the degradation pathways, with a particular focus on the defluorination reaction. The significant release of F - ions and the formation of three F-free organic byproducts indicated that defluorination was a prevalent pathway in ozonation of FQs, while six F-containing organic byproducts indicated that ozone also attacked the piperazinyl and quinolone moieties. Escherichia coli growth inhibition tests revealed that ozonation could effectively eliminate the antibacterial activity of target FQ solutions, and the residual antibacterial activity had a negative linear correlation with the released F - concentration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Temperature-Dependent Rate Coefficients for the Reaction of CH2OO with Hydrogen Sulfide.

Science.gov (United States)

Smith, Mica C; Chao, Wen; Kumar, Manoj; Francisco, Joseph S; Takahashi, Kaito; Lin, Jim Jr-Min

2017-02-09

The reaction of the simplest Criegee intermediate CH 2 OO with hydrogen sulfide was measured with transient UV absorption spectroscopy in a temperature-controlled flow reactor, and bimolecular rate coefficients were obtained from 278 to 318 K and from 100 to 500 Torr. The average rate coefficient at 298 K and 100 Torr was (1.7 ± 0.2) × 10 -13 cm 3 s -1 . The reaction was found to be independent of pressure and exhibited a weak negative temperature dependence. Ab initio quantum chemistry calculations of the temperature-dependent reaction rate coefficient at the QCISD(T)/CBS level are in reasonable agreement with the experiment. The reaction of CH 2 OO with H 2 S is 2-3 orders of magnitude faster than the reaction with H 2 O monomer. Though rates of CH 2 OO scavenging by water vapor under atmospheric conditions are primarily controlled by the reaction with water dimer, the H 2 S loss pathway will be dominated by the reaction with monomer. The agreement between experiment and theory for the CH 2 OO + H 2 S reaction lends credence to theoretical descriptions of other Criegee intermediate reactions that cannot easily be probed experimentally.

Putting Reaction Rates and Collision Theory in the Hands of Your Students.

Science.gov (United States)

Evenson, Andy

2002-01-01

Describes a simulation that can be used to give concrete analogies of collision theory and the factors that affect reaction rates including temperature, concentration, catalyst, and molecular orientation. The simulation works best if done as an introduction to the concepts to help prevent misconceptions about reaction rates and collision theory.…

Accurate quantum calculations of the reaction rates for H/D+ CH4

NARCIS (Netherlands)

Harrevelt, R. van; Nyman, G.; Manthe, U.

2007-01-01

In previous work [T. Wu, H. J. Werner, and U. Manthe, Science 306, 2227 (2004)], accurate quantum reaction rate calculations of the rate constant for the H+CH4 -> CH3+H-2 reaction have been presented. Both the electronic structure calculations and the nuclear dynamics calculations are converged with

Calculations on precompound reactions with alpha particles, A(α,α')X, at incident energies around 500 MeV

International Nuclear Information System (INIS)

Rittershausen, W.

1987-01-01

The model of Chiang et al. (1980) for nucleon induced precompound reactions, a generalization of the Glauber theory to lower energetical processes, was extended to heavier projectiles the elementary differential cross section of which may furthermore (at fixed incident energy) depend on the momentum transfer. The so modified model was applied to reactions of the type A(α,α')X at an incident energy of about 100 MeV/nucleon, excitation energies of the nucleus in the range 6 to 60 MeV, and for scattering angles from 3 to 6 0 . Thereby the Glauber coefficients were determined by means of the optical potentials known for the treated experiments. Local nucleon momentum distributions in the target nucleus were taken from calculations of Durand et al. (1982). The momentum distributions of the alpha particles after the first α-N collision were both for normalously and for homogeneously distributed nucleon momenta calculated analytically. The distributions after the second collision were determined by folding. For the control of these results and for the eventual calculation of the distributions after more than two collisions a Monte Carlo routine was written. The additional deviation of the alpha particles in real-valued potentials of the target nucleus were regarded. The results in which no free parameter occurs agree quite well in the shape with measured data. In one case it is also valid for the absolute quantities. (orig.) [de

Measurement of triple gauge boson couplings from $W^+ W^-$ production at $\\sqrt{s}$ = 172 GeV

CERN Document Server

Ackerstaff, K; Allison, J; Altekamp, N; Anderson, K J; Anderson, S; Arcelli, S; Asai, S; Axen, D A; Azuelos, Georges; Ball, A H; Barberio, E; Barlow, R J; Bartoldus, R; Batley, J Richard; Baumann, S; Bechtluft, J; Beeston, C; Behnke, T; Bell, A N; Bell, K W; Bella, G; Bentvelsen, Stanislaus Cornelius Maria; Bethke, Siegfried; Biebel, O; Biguzzi, A; Bird, S D; Blobel, Volker; Bloodworth, Ian J; Bloomer, J E; Bobinski, M; Bock, P; Bonacorsi, D; Boutemeur, M; Bouwens, B T; Braibant, S; Brigliadori, L; Brown, R M; Burckhart, Helfried J; Burgard, C; Bürgin, R; Capiluppi, P; Carnegie, R K; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Chrisman, D; Clarke, P E L; Cohen, I; Conboy, J E; Cooke, O C; Cuffiani, M; Dado, S; Dallapiccola, C; Dallavalle, G M; Davis, R; De Jong, S; del Pozo, L A; Desch, Klaus; Dienes, B; Dixit, M S; do Couto e Silva, E; Doucet, M; Duchovni, E; Duckeck, G; Duerdoth, I P; Eatough, D; Edwards, J E G; Estabrooks, P G; Evans, H G; Evans, M; Fabbri, Franco Luigi; Fanti, M; Faust, A A; Fiedler, F; Fierro, M; Fischer, H M; Fleck, I; Folman, R; Fong, D G; Foucher, M; Fürtjes, A; Futyan, D I; Gagnon, P; Gary, J W; Gascon, J; Gascon-Shotkin, S M; Geddes, N I; Geich-Gimbel, C; Geralis, T; Giacomelli, G; Giacomelli, P; Giacomelli, R; Gibson, V; Gibson, W R; Gingrich, D M; Glenzinski, D A; Goldberg, J; Goodrick, M J; Gorn, W; Grandi, C; Gross, E; Grunhaus, Jacob; Gruwé, M; Hajdu, C; Hanson, G G; Hansroul, M; Hapke, M; Hargrove, C K; Hart, P A; Hartmann, C; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Herndon, M; Herten, G; Heuer, R D; Hildreth, M D; Hill, J C; Hillier, S J; Hobson, P R; Homer, R James; Honma, A K; Horváth, D; Hossain, K R; Howard, R; Hüntemeyer, P; Hutchcroft, D E; Igo-Kemenes, P; Imrie, D C; Ingram, M R; Ishii, K; Jawahery, A; Jeffreys, P W; Jeremie, H; Jimack, Martin Paul; Joly, A; Jones, C R; Jones, G; Jones, M; Jost, U; Jovanovic, P; Junk, T R; Karlen, D A; Kartvelishvili, V G; Kawagoe, K; Kawamoto, T; Kayal, P I; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Kirk, J; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Koetke, D S; Kokott, T P; Kolrep, M; Komamiya, S; Kress, T; Krieger, P; Von Krogh, J; Kyberd, P; Lafferty, G D; Lahmann, R; Lai, W P; Lanske, D; Lauber, J; Lautenschlager, S R; Layter, J G; Lazic, D; Lee, A M; Lefebvre, E; Lellouch, Daniel; Letts, J; Levinson, L; Lloyd, S L; Loebinger, F K; Long, G D; Losty, Michael J; Ludwig, J; Macchiolo, A; MacPherson, A L; Mannelli, M; Marcellini, S; Markus, C; Martin, A J; Martin, J P; Martínez, G; Mashimo, T; Mättig, P; McDonald, W J; McKenna, J A; McKigney, E A; McMahon, T J; McPherson, R A; Meijers, F; Menke, S; Merritt, F S; Mes, H; Meyer, J; Michelini, Aldo; Mikenberg, G; Miller, D J; Mincer, A; Mir, R; Mohr, W; Montanari, A; Mori, T; Morii, M; Müller, U; Mihara, S; Nagai, K; Nakamura, I; Neal, H A; Nellen, B; Nisius, R; O'Neale, S W; Oakham, F G; Odorici, F; Ögren, H O; Oh, A; Oldershaw, N J; Oreglia, M J; Orito, S; Pálinkás, J; Pásztor, G; Pater, J R; Patrick, G N; Patt, J; Pearce, M J; Pérez-Ochoa, R; Petzold, S; Pfeifenschneider, P; Pilcher, J E; Pinfold, James L; Plane, D E; Poffenberger, P R; Poli, B; Posthaus, A; Rees, D L; Rigby, D; Robertson, S; Robins, S A; Rodning, N L; Roney, J M; Rooke, A M; Ros, E; Rossi, A M; Routenburg, P; Rozen, Y; Runge, K; Runólfsson, O; Ruppel, U; Rust, D R; Rylko, R; Sachs, K; Saeki, T; Sarkisyan-Grinbaum, E; Sbarra, C; Schaile, A D; Schaile, O; Scharf, F; Scharff-Hansen, P; Schenk, P; Schieck, J; Schleper, P; Schmitt, B; Schmitt, S; Schöning, A; Schröder, M; Schultz-Coulon, H C; Schumacher, M; Schwick, C; Scott, W G; Shears, T G; Shen, B C; Shepherd-Themistocleous, C H; Sherwood, P; Siroli, G P; Sittler, A; Skillman, A; Skuja, A; Smith, A M; Snow, G A; Sobie, Randall J; Söldner-Rembold, S; Springer, R W; Sproston, M; Stephens, K; Steuerer, J; Stockhausen, B; Stoll, K; Strom, D; Szymanski, P; Tafirout, R; Talbot, S D; Tanaka, S; Taras, P; Tarem, S; Teuscher, R; Thiergen, M; Thomson, M A; Von Törne, E; Towers, S; Trigger, I; Trócsányi, Z L; Tsur, E; Turcot, A S; Turner-Watson, M F; Utzat, P; Van Kooten, R; Verzocchi, M; Vikas, P; Vokurka, E H; Voss, H; Wäckerle, F; Wagner, A; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wermes, N; White, J S; Wilkens, B; Wilson, G W; Wilson, J A; Wolf, G; Wyatt, T R; Yamashita, S; Yekutieli, G; Zacek, V; Zer-Zion, D

1998-01-01

We present measurements of triple gauge boson coupling parameters using data recorded by the OPAL detector at LEP2 at a centre-of-mass energy of 172 GeV. A total of 120 W-pair candidates has been selected in the q q(bar) q q(bar), q q(bar) l nu(bar)_l, and l nu(bar)_l l(bar)' nu_l' decay channels, for an integrated luminosity of 10.4 pb^-1. We use these data to determine several different anomalous coupling parameters using the measured cross-section and the distributions of kinematic variables. We measure alpha_B-phi = 0.35 + 1.29 - 1.07 +/- 0.38, alpha_W-phi = 0.00 + 0.30 - 0.28 +/- 0.11, alpha_W = 0.18 + 0.49 - 0.47 +/- 0.23, Delta(g_1^z) = -0.03 + 0.40 -0.37 +/- 0.14, Delta(kappa_gamma^(HISZ)) = 0.03 + 0.55 - 0.51 +/- 0.20, and Delta(kappa) = 0.03 + 0.49 - 0.46 +/- 0.21. Combining the alpha_W-phi result with our previous result obtained from the 161 GeV data sample we measure alpha_W-phi = -0.08 + 0.28 - 0.25 +/- 0.10. All of these measurements are consistent with the Standard Model.

Pressure effects on enzyme reactions in mainly organic media: alpha-chymotrypsin in reversed micelles of Aerosol OT in octane.

Science.gov (United States)

Mozhaev, V V; Bec, N; Balny, C

1994-08-01

Biocatalytic transformations in reversed micelles formed by anionic surfactant Aerosol OT in octane have been studied at high pressures by an example of alpha-chymotrypsin-catalyzed hydrolysis of N-carbobenzoxy-L-tyrosine p-nitrophenyl ester and N-succinyl-L-phenylalanine p-nitroanilide. For the first time it has been found that the enzyme retains high activity in these water-in-oil microemulsions up to a pressure of 2 kbar. The value of the activation volume (delta V*) for the enzyme reactions shows a dependence on the water content in the system. When the size of the micellar aqueous inner cavity (as evaluated at 1 atm) approaches the molecular size of alpha-chymotrypsin, delta V* becomes significantly different from the value in aqueous solution and in the micelles with a larger size. Possibilities of regulating the enzyme activity by pressure in systems with a low content of water are discussed.

Enantioselective cycloadditions with alpha,beta-disubstituted acrylimides.

Science.gov (United States)

Sibi, Mukund P; Ma, Zhihua; Itoh, Kennosuke; Prabagaran, Narayanasamy; Jasperse, Craig P

2005-06-09

[reaction: see text] The use of N-H imide templates provides a solution to the problem of rotamer control in Lewis acid catalyzed reactions of alpha,beta-disubstituted acryloyl imides. Reactions proceed through the s-cis rotamer and with improved reactivity because A(1,3) strain is avoided. Enantioselective nitrone, nitrile oxide, and Diels-Alder cycloadditions demonstrate the principle.

Analyses of Alpha-Alpha Elastic Scattering Data in the Energy Range 140 - 280 MeV

Energy Technology Data Exchange (ETDEWEB)

Shehadeh, Zuhair F. [Taif University, Taif (Saudi Arabia)

2017-01-15

The differential and the reaction cross-sections for 4He-4He elastic scattering data have been nicely obtained at four energies ranging from 140 MeV to 280 MeV (lab system), namely, 140, 160, 198 and 280 MeV, by using a new optical potential with a short-range repulsive core. The treatment has been handled relativistically as υ/c > 0.25 for the two lower energies and υ/c > 0.31 for the two higher ones. In addition to explaining the elastic angular distributions, the adopted potentials accounted for the structure that may exist at angles close to 90◦ , especially for the 198 and the 280-MeV incident energies. No renormalization has been used, and all our potential parameters are new. The necessity of including a short-range repulsive potential term in our real nuclear potential part has been demonstrated. Our results contribute to solving a long-standing problem concerning the nature of the alpha-alpha potential. This is very beneficial in explaining unknown alpha-nucleus and nucleus-nucleus relativistic reactions by using the cluster formalism.

[Clinical effect of triple therapy combined with Saccharomyces boulardii in the treatment of Helicobacter pylori infection in children].

Science.gov (United States)

Zhao, Hong-Mei; Ou-Yang, Hong-Juan; Duan, Bo-Ping; Xu, Bin; Chen, Zhi-Yong; Tang, Juan; You, Jie-Yu

2014-03-01

To evaluate the clinical effect of proton pump inhibitor-based triple therapy combined with Saccharomyces boulardii in the treatment of Helicobacter pylori (Hp) infection among children in terms of Hp eradication rate and incidence of adverse events. A prospective randomised controlled study was conducted on 240 children with a confirmed diagnosis of Hp infection. These patients were randomized into triple therapy (n=120) and probiotics groups (n=120). The triple therapy group received amoxicillin [40 mg/(kg·d), Tid], clarithromycin [15 mg/(kg·d), Bid] and omeprazole [0.7-0.8 mg/(kg·d), Qd], while the probiotics group received Saccharomyces boulardii (250 mg, Bid) in addition to triple therapy. The course of treatment was 14 days in both groups. The adverse events in subjects were recorded by their parents during treatment. Hp eradiation was evaluated by (13)C breath test at 4 weeks after treatment, and the eradication rate and incidence of adverse events were compared between the two groups. The Hp eradication rates were 75.8% (91/120) in the triple therapy group and 85% (102/120) in the probiotics group (P>0.05). Compared with the triple therapy group, the probiotics group had nonsignificantly lower incidence of nausea, vomiting, and abdominal pain (P>0.05) and significantly lower incidence of stomatitis, constipation and diarrhea (PSaccharomyces boulardii cannot significantly increase Hp eradication rate, but can significantly reduce the incidence of stomatitis, constipation, and diarrhea during treatment.

Effects of Surfactants on the Rate of Chemical Reactions

Directory of Open Access Journals (Sweden)

B. Samiey

2014-01-01

Full Text Available Surfactants are self-assembled compounds that depend on their structure and electric charge can interact as monomer or micelle with other compounds (substrates. These interactions which may catalyze or inhibit the reaction rates are studied with pseudophase, cooperativity, and stoichiometric (classical models. In this review, we discuss applying these models to study surfactant-substrate interactions and their effects on Diels-Alder, redox, photochemical, decomposition, enzymatic, isomerization, ligand exchange, radical, and nucleophilic reactions.

Determination of the f and alpha parameters in the neutron multiplier CS-ISCTN

International Nuclear Information System (INIS)

Hernandez, O.; Ixquiac, M.; Contreras, R.; Herrera, E.; Diaz, O.; Lopez, R.; Alvarez, P.; Manso, M.V.; Padron, G.; D Alessandro, K.

1997-01-01

The values of the f and alpha parameters are determined in the irradiation position of the neutron multiplier CS-ISCTN, with the aim to show the possibility to applied the parametric neutron activation analysis. The more used conventions to calculate the reaction rate; Hogdhal, Modified Stoughton-Halpering and Modified Wescott, the last is presents with some new variations. This comparison is combined with R-Cd multi monitors method, Cd-Cover Multi monitor Methods and a new method introduced in the present paper to reduce the errors in the alpha parameter determination named Minimal Difference Method. This last method show better results, according to the epithermal hardeners of the CS-ISCT

Reaction rate calculations via transmission coefficients

International Nuclear Information System (INIS)

Feit, M.D.; Alder, B.J.

1985-01-01

The transmission coefficient of a wavepacket traversing a potential barrier can be determined by steady state calculations carried out in imaginary time instead of by real time dynamical calculations. The general argument is verified for the Eckart barrier potential by a comparison of transmission coefficients calculated from real and imaginary time solutions of the Schroedinger equation. The correspondence demonstrated here allows a formulation for the reaction rate that avoids difficulties due to both rare events and explicitly time dependent calculations. 5 refs., 2 figs

"Depletion": A Game with Natural Rules for Teaching Reaction Rate Theory.

Science.gov (United States)

Olbris, Donald J.; Herzfeld, Judith

2002-01-01

Depletion is a game that reinforces central concepts of reaction rate theory through simulation. Presents the game with a set of follow-up questions suitable for either a quiz or discussion. Also describes student reaction to the game. (MM)

Constructs for the expression of repeating triple-helical protein domains

International Nuclear Information System (INIS)

Peng, Yong Y; Werkmeister, Jerome A; Vaughan, Paul R; Ramshaw, John A M

2009-01-01

The development of novel scaffolds will be an important aspect in future success of tissue engineering. Scaffolds will preferably contain information that directs the cellular content of constructs so that the new tissue that is formed is closely aligned in structure, composition and function to the target natural tissue. One way of approaching this will be the development of novel protein-based constructs that contain one or more repeats of functional elements derived from various proteins. In the present case, we describe a strategy to make synthetic, recombinant triple-helical constructs that contain repeat segments of biologically relevant domains. Copies of a DNA fragment prepared by PCR from human type III collagen have been inserted in a co-linear contiguous fashion into the yeast expression vector YEpFlag-1, using sequential addition between selected restriction sites. Constructs containing 1, 2 and 3 repeats were designed to maintain the (Gly-X-Y) repeat, which is essential for the formation of an extended triple helix. All constructs gave expressed protein, with the best being the 3-repeat construct which was readily secreted. This material had the expected composition and N-terminal sequence. Incubation of the product at low temperature led to triple-helix formation, shown by reaction with a conformation dependent monoclonal antibody.

Constructs for the expression of repeating triple-helical protein domains

Energy Technology Data Exchange (ETDEWEB)

Peng, Yong Y; Werkmeister, Jerome A; Vaughan, Paul R; Ramshaw, John A M, E-mail: jerome.werkmeister@csiro.a [CSIRO Molecular and Health Technologies, Bag 10, Clayton South, VIC 3169 (Australia)

2009-02-15

The development of novel scaffolds will be an important aspect in future success of tissue engineering. Scaffolds will preferably contain information that directs the cellular content of constructs so that the new tissue that is formed is closely aligned in structure, composition and function to the target natural tissue. One way of approaching this will be the development of novel protein-based constructs that contain one or more repeats of functional elements derived from various proteins. In the present case, we describe a strategy to make synthetic, recombinant triple-helical constructs that contain repeat segments of biologically relevant domains. Copies of a DNA fragment prepared by PCR from human type III collagen have been inserted in a co-linear contiguous fashion into the yeast expression vector YEpFlag-1, using sequential addition between selected restriction sites. Constructs containing 1, 2 and 3 repeats were designed to maintain the (Gly-X-Y) repeat, which is essential for the formation of an extended triple helix. All constructs gave expressed protein, with the best being the 3-repeat construct which was readily secreted. This material had the expected composition and N-terminal sequence. Incubation of the product at low temperature led to triple-helix formation, shown by reaction with a conformation dependent monoclonal antibody.

Alpha Resonant States in 13C

International Nuclear Information System (INIS)

Rodrigues, M. R. D.; Borello-Lewin, T.; Horodynski-Matsushigue, L. B.; Duarte, J. L. M.; Rodrigues, C. L.; Souza, M. A.; Miyake, H.; Cunsolo, A.; Cappuzzello, F.; Ukita, G. M.

2011-01-01

The 9 Be( 6 Li,d) 13 C reaction was used to investigate alpha resonant states in 13 C up to 15 MeV of excitation. The reaction was measured at a bombarding energy of 25.5 MeV employing the Sao Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion detection technique. An energy resolution of 50 keV was obtained. Several narrow alpha resonant states not previously measured were detected, in particular the one at the (3α+n) threshold populated by an L = 2 transfer, revealing a 9 Be+α component for the 1/2 - cluster state candidate at this threshold. Experimental angular distributions are presented in comparison with DWBA predictions.

Cross sections of the reaction Pa-231(d,3n)U-230 for the production of U-230/Th-226 for targeted alpha therapy

Czech Academy of Sciences Publication Activity Database

Morgenstern, A.; Lebeda, Ondřej; Štursa, Jan; Capote, R.; Sin, M.; Bruchertseifer, F.; Zielinska, B.; Apostolidis, C.

2009-01-01

Roč. 80, č. 5 (2009), 054612/1-054612/6 ISSN 0556-2813 Institutional research plan: CEZ:AV0Z10480505 Keywords : Pa-231 * U-230 * Th-226 * reaction cross section * targeted alpha therapy Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.477, year: 2009

Estimation of the prevalence and rate of acute transfusion reactions occurring in Windhoek, Namibia

Science.gov (United States)

Meza, Benjamin P.L.; Lohrke, Britta; Wilkinson, Robert; Pitman, John P.; Shiraishi, Ray W.; Bock, Naomi; Lowrance, David W.; Kuehnert, Matthew J.; Mataranyika, Mary; Basavaraju, Sridhar V.

2014-01-01

Background Acute transfusion reactions are probably common in sub-Saharan Africa, but transfusion reaction surveillance systems have not been widely established. In 2008, the Blood Transfusion Service of Namibia implemented a national acute transfusion reaction surveillance system, but substantial under-reporting was suspected. We estimated the actual prevalence and rate of acute transfusion reactions occurring in Windhoek, Namibia. Methods The percentage of transfusion events resulting in a reported acute transfusion reaction was calculated. Actual percentage and rates of acute transfusion reactions per 1,000 transfused units were estimated by reviewing patients’ records from six hospitals, which transfuse >99% of all blood in Windhoek. Patients’ records for 1,162 transfusion events occurring between 1st January – 31st December 2011 were randomly selected. Clinical and demographic information were abstracted and Centers for Disease Control and Prevention National Healthcare Safety Network criteria were applied to categorize acute transfusion reactions1. Results From January 1 – December 31, 2011, there were 3,697 transfusion events (involving 10,338 blood units) in the selected hospitals. Eight (0.2%) acute transfusion reactions were reported to the surveillance system. Of the 1,162 transfusion events selected, medical records for 785 transfusion events were analysed, and 28 acute transfusion reactions were detected, of which only one had also been reported to the surveillance system. An estimated 3.4% (95% confidence interval [CI]: 2.3–4.4) of transfusion events in Windhoek resulted in an acute transfusion reaction, with an estimated rate of 11.5 (95% CI: 7.6–14.5) acute transfusion reactions per 1,000 transfused units. Conclusion The estimated actual rate of acute transfusion reactions is higher than the rate reported to the national haemovigilance system. Improved surveillance and interventions to reduce transfusion-related morbidity and mortality

Simulation of triple coincidences in PET

International Nuclear Information System (INIS)

Cal-González, J; Herranz, E; Vicente, E; Udias, J M; Lage, E; Dave, S R; Parot, V; Herraiz, J L; Moore, S C; Park, M-A

2015-01-01

Although current PET scanners are designed and optimized to detect double coincidence events, there is a significant amount of triple coincidences in any PET acquisition. Triple coincidences may arise from causes such as: inter-detector scatter (IDS), random triple interactions (R T ), or the detection of prompt gamma rays in coincidence with annihilation photons when non-pure positron-emitting radionuclides are used (β + γ events). Depending on the data acquisition settings of the PET scanner, these triple events are discarded or processed as a set of double coincidences if the energy of the three detected events is within the scanner’s energy window. This latter option introduces noise in the data, as at most, only one of the possible lines-of-response defined by triple interactions corresponds to the line along which the decay occurred. Several novel works have pointed out the possibility of using triple events to increase the sensitivity of PET scanners or to expand PET imaging capabilities by allowing differentiation between radiotracers labeled with non-pure and pure positron-emitting radionuclides. In this work, we extended the Monte Carlo simulator PeneloPET to assess the proportion of triple coincidences in PET acquisitions and to evaluate their possible applications. We validated the results of the simulator against experimental data acquired with a modified version of a commercial preclinical PET/CT scanner, which was enabled to acquire and process triple-coincidence events. We used as figures of merit the energy spectra for double and triple coincidences and the triples-to-doubles ratio for different energy windows and radionuclides. After validation, the simulator was used to predict the relative quantity of triple-coincidence events in two clinical scanners assuming different acquisition settings. Good agreement between simulations and preclinical experiments was found, with differences below 10% for most of the observables considered. For

A simple thermometric technique for reaction-rate determination of inorganic species, based on the iodide-catalysed cerium(IV)-arsenic(III) reaction.

Science.gov (United States)

Grases, F; Forteza, R; March, J G; Cerda, V

1985-02-01

A very simple reaction-rate thermometric technique is used for determination of iodide (5-20 ng ml ), based on its catalytic action on the cerium(IV)-arsenic(III) reaction, and for determination of mercury(II) (1.5-10 ng ml ) and silver(I) (2-10 ng ml ), based on their inhibitory effect on this reaction. The reaction is followed by measuring the rate of temperature increase. The method suffers from very few interferences and is applied to determination of iodide in biological and inorganic samples, and Hg(II) and Ag(I) in pharmaceutical products.

Angular correlation measurements for 4-{alpha} decaying states in {sup 16}O

Energy Technology Data Exchange (ETDEWEB)

Wuosmaa, A.H.; Back, B.B.; Betts, R.R. [and others

1995-08-01

Previous measurements of the {sup 12}C({sup 12}C,{sup 8}Be){sup 16}O{sup *}(4 {alpha}) reaction identified discrete levels in {sup 16}O which decay by breakup into 4 {alpha} particles through a number of different decay sequences, including {sup 16}O{sup *} {yields} {sup 8}Be + {sup 8}Be and {alpha} + {sup 12}C (O{sub 2}{sup +}). These states are observed in a range of excitation energies where resonances are observed in inelastic {alpha} + {sup 12}C scattering leading to the {sup 8}Be + {sup 8}Be and {alpha} + {sup 12}C final states. These resonances were associated with 4 {alpha}-particle chain configurations in {sup 16}O. Should the states populated in the {sup 12}C + {sup 12}C reaction possess this same extended structure, it would serve as an important piece of evidence supporting the idea that even more deformed structures are formed in the {sup 24}Mg compound system. In order to more firmly make this association, it is important to determine the spins of the states populated in the {sup 12}C + {sup 12}C reaction.

Reaction rate constant for uranium in water and water vapor

Energy Technology Data Exchange (ETDEWEB)

TRIMBLE, D.J.

1998-11-09

The literature on uranium oxidation in water and oxygen free water vapor was reviewed. Arrhenius rate equations were developed from the review data. These data and equations will be used as a baseline from which to compare reaction rates measured for K Basin fuel.

MCNP analysis and optimization of a triple crystal phoswich detector

CERN Document Server

Childress, N L

2002-01-01

Researchers at the University of Missouri-Columbia have designed a triple crystal phoswich detector that allows for simultaneous detection of alpha, beta, and gamma radiation. A ZnS:Ag layer detects alpha particles, a CaF sub 2 :Eu scintillator preferentially interacts with beta particles, and a NaI:Tl cell is used for gamma detection. The detector output is digitally collected, processed, and analyzed by a personal computer using custom software. Monte Carlo N-Particle version 4C simulations of this detector found that the phoswich design has inherent minimum energy limits of 250 keV E sub m sub a sub x for beta particles and 50 keV for gamma-rays. For a 2.54 cm thick NaI:Tl crystal, intrinsic gamma efficiency for photons ranges from a maximum of 80% at 100 keV to 26% for 2 MeV photons. Mischaracterized gamma events in the CaF sub 2 :Eu crystal above 175 keV can be corrected by subtracting 26+-4% of the total number of counts in the NaI:Tl crystal from the CaF sub 2 :Eu response. Beta induced events in the N...

Helium generation reaction rates for 6Li and 10B in benchmark facilities

International Nuclear Information System (INIS)

Farrar, Harry IV; Oliver, B.M.; Lippincott, E.P.

1980-01-01

The helium generation rates for 10 B and 6 Li have been measured in two benchmark reactor facilities having neutron spectra similar to those found in a breeder reactor. The irradiations took place in the Coupled Fast Reactivity Measurements Facility (CFRMF) and in the 10% enriched 235 U critical assembly, BIG-10. The helium reaction rates were obtained by precise high-sensitivity gas mass spectrometric analyses of the helium content of numerous small samples. Comparison of these reaction rates with other reaction rates measured in the same facilities, and with rates calculated from published cross sections and from best estimates of the neutron spectral shapes, indicate significant discrepancies in the calculated values. Additional irradiations in other benchmark facilities have been undertaken to better determine the energy ranges where the discrepancies lie

Guided search for triple conjunctions.

Science.gov (United States)

Nordfang, Maria; Wolfe, Jeremy M

2014-08-01

A key tenet of feature integration theory and of related theories such as guided search (GS) is that the binding of basic features requires attention. This would seem to predict that conjunctions of features of objects that have not been attended should not influence search. However, Found (1998) reported that an irrelevant feature (size) improved the efficiency of search for a Color × Orientation conjunction if it was correlated with the other two features across the display, as compared to the case in which size was not correlated with color and orientation features. We examined this issue with somewhat different stimuli. We used triple conjunctions of color, orientation, and shape (e.g., search for a red, vertical, oval-shaped item). This allowed us to manipulate the number of features that each distractor shared with the target (sharing) and it allowed us to vary the total number of distractor types (and, thus, the number of groups of identical items: grouping). We found that these triple conjunction searches were generally very efficient--producing very shallow Reaction Time × Set Size slopes, consistent with strong guidance by basic features. Nevertheless, both of the variables, sharing and grouping, modulated performance. These influences were not predicted by previous accounts of GS; however, both can be accommodated in a GS framework. Alternatively, it is possible, though not necessary, to see these effects as evidence for "preattentive binding" of conjunctions.

Prospective audit of a one-centre combined nuchal translucency and triple test programme for the detection of trisomy 21.

Science.gov (United States)

Babbur, Vijayalakshmi; Lees, Christoph C; Goodburn, Sandra F; Morris, Nigel; Breeze, Andrew C G; Hackett, Gerald A

2005-06-01

To determine detection and false-positive rates for trisomy 21 using two-stage combined nuchal translucency (NT) and triple testing, whilst disclosing abnormal nuchal measurements at the scan. A prospective audit in a UK women's hospital, of 3188 women with singleton pregnancies, requesting screening for trisomy 21. Median age was 37 years (range 19-46). Women were offered NT screening at 11 to 14 weeks. Those with NT > or =3 mm were offered chorionic villus sampling. Those declining CVS, and those with NT risk of trisomy 21 > or = 1:250, based on age, NT, and triple test results were offered amniocentesis. Using a 3-mm NT 'cut-off' identified 16/25 cases of trisomy 21 (64%; 95% CI 38.8, 78.9). Of 2725 women who had a combined nuchal plus triple test assessment, 79 (2.6%) had a > or = 1:250 term risk of trisomy 21. Forty (1.3%) had amniocentesis identifying 6/9 remaining cases (67%:95% CI:27.9, 92.5). Overall, the detection rate was 88% (95% CI:68.8, 97.5) for a 4.8% FPR. For the screened population, to achieve an 88% detection rate using the triple test alone, the predicted FPR would be 20%. Conversely, for an FPR of 4.8% using the triple test alone, the detection rate would be only 60%. In a high-risk group, the combination of NT with triple test offers detection of trisomy 21 at least equivalent to either test, while allowing disclosure of an abnormal NT at the scan and reducing the FPR. Importantly, the FPR is less than 5%, considerably lower than expected for triple test alone for this population.

The Influence of Particle Charge on Heterogeneous Reaction Rate Coefficients

Science.gov (United States)

Aikin, A. C.; Pesnell, W. D.

2000-01-01

The effects of particle charge on heterogeneous reaction rates are presented. Many atmospheric particles, whether liquid or solid are charged. This surface charge causes a redistribution of charge within a liquid particle and as a consequence a perturbation in the gaseous uptake coefficient. The amount of perturbation is proportional to the external potential and the square of the ratio of debye length in the liquid to the particle radius. Previous modeling has shown how surface charge affects the uptake coefficient of charged aerosols. This effect is now included in the heterogeneous reaction rate of an aerosol ensemble. Extension of this analysis to ice particles will be discussed and examples presented.

Communication: Rate coefficients from quasiclassical trajectory calculations from the reverse reaction: The Mu + H2 reaction re-visited

Science.gov (United States)

Homayoon, Zahra; Jambrina, Pablo G.; Aoiz, F. Javier; Bowman, Joel M.

2012-07-01

In a previous paper [P. G. Jambrina et al., J. Chem. Phys. 135, 034310 (2011), 10.1063/1.3611400] various calculations of the rate coefficient for the Mu + H2 → MuH + H reaction were presented and compared to experiment. The widely used standard quasiclassical trajectory (QCT) method was shown to overestimate the rate coefficients by several orders of magnitude over the temperature range 200-1000 K. This was attributed to a major failure of that method to describe the correct threshold for the reaction owing to the large difference in zero-point energies (ZPE) of the reactant H2 and product MuH (˜0.32 eV). In this Communication we show that by performing standard QCT calculations for the reverse reaction and then applying detailed balance, the resulting rate coefficient is in very good agreement with the other computational results that respect the ZPE, (as well as with the experiment) but which are more demanding computationally.

Slowing-down calculation for charged particles, application to the calculation of the (alpha, neutron) reaction yield in UO2 - PuO2 fuel

International Nuclear Information System (INIS)

Dulieu, P.

1967-11-01

There are no complete theory nor experimental data sufficient to predict exactly, in a systemic way, the slowing down power of any medium for any ion with any energy. However, in each case, the energy range can be divided in three areas, the low energiy range where the de/dx is an ascending energy function, the intermediate energy region where de/dx has a maximum, the high energy region where de/dx is a descending energy function. In practice, the code Irma 3 allows to obtain with a good precision de/dx for the protons, neutrons, tritons, alphas in any medium. For particles heavier than alpha it is better to use specific methods. In the case of calculating the yield of the (alpha, neutron) reaction in a UO 2 -PuO 2 fuel cell, the divergences of experimental origin, between the existing data lead to adopt a range a factor 1.7 on the yields [fr

Measurement and analysis of reaction rate distributions of cores with spectrum shifter region

International Nuclear Information System (INIS)

Matsuura, Shigekazu; Shiroya, Seiji; Unesaki, Hironobu; Takeda, Toshikazu; Aizawa, Otohiko; Kanda, Keiji.

1995-01-01

A study for the neutronic characteristics of the spectrum-controlled neutron irradiation fields using various reflector materials was performed. Spectrum shifter regions were constructed in the upper reflector region of the solid moderated core (B-Core) of the Kyoto University Critical Assembly (KUCA). Beryllium, graphite and aluminum were selected as the loading materials for the spectrum shifter. Two tight-pitch lattice cores with different moderator-to-fuel volume ratio (V m /V f ) of 0.97 and 0.65 have been used. Axial reaction rate distributions of gold, nickel and indium wires were measured, and the spectrum index was defined as the Cd ratio of the gold wire and the ratio of gold reaction rate to nickel reaction rate. Using the conventional design calculation procedure, the experimental and calculated reaction rate and spectrum index show several disagreements. Detailed treatment of the neutron streaming effect, heterogeneous cell structure and depression factor are shown to be necessary for improving the agreement between experimental and calculated values. (author)

Thermonuclear Reaction Rate Libraries and Software Tools for Nuclear Astrophysics Research

International Nuclear Information System (INIS)

Smith, Michael S.; Cyburt, Richard; Schatz, Hendrik; Smith, Karl; Warren, Scott; Ferguson, Ryan; Wiescher, Michael; Lingerfelt, Eric; Buckner, Kim; Nesaraja, Caroline D.

2008-01-01

Thermonuclear reaction rates are a crucial input for simulating a wide variety of astrophysical environments. A new collaboration has been formed to ensure that astrophysical modelers have access to reaction rates based on the most recent experimental and theoretical nuclear physics information. To reach this goal, a new version of the REACLIB library has been created by the Joint Institute for Nuclear Astrophysics (JINA), now available online at http://www.nscl.msu.edu/~nero/db. A complementary effort is the development of software tools in the Computational Infrastructure for Nuclear Astrophysics, online at nucastrodata.org, to streamline, manage, and access the workflow of the reaction evaluations from their initiation to peer review to incorporation into the library. Details of these new projects will be described

THE {sup 12}C + {sup 12}C REACTION AND THE IMPACT ON NUCLEOSYNTHESIS IN MASSIVE STARS

Energy Technology Data Exchange (ETDEWEB)

Pignatari, M. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Hirschi, R.; Bennett, M. [Astrophysics Group, EPSAM Institute, Keele University, Keele, ST5 5BG (United Kingdom); Wiescher, M.; Beard, M. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Gallino, R. [Universita' di Torino, Torino, Via Pietro Giuria 1, I-10126 Torino (Italy); Fryer, C.; Rockefeller, G. [Computational Physics and Methods (CCS-2), LANL, Los Alamos, NM 87545 (United States); Herwig, F.; Timmes, F. X., E-mail: marco.pignatari@unibas.ch [The Joint Institute for Nuclear Astrophysics, Notre Dame, IN 46556 (United States)

2013-01-01

Despite much effort in the past decades, the C-burning reaction rate is uncertain by several orders of magnitude, and the relative strength between the different channels {sup 12}C({sup 12}C, {alpha}){sup 20}Ne, {sup 12}C({sup 12}C, p){sup 23}Na, and {sup 12}C({sup 12}C, n){sup 23}Mg is poorly determined. Additionally, in C-burning conditions a high {sup 12}C+{sup 12}C rate may lead to lower central C-burning temperatures and to {sup 13}C({alpha}, n){sup 16}O emerging as a more dominant neutron source than {sup 22}Ne({alpha}, n){sup 25}Mg, increasing significantly the s-process production. This is due to the chain {sup 12}C(p, {gamma}){sup 13}N followed by {sup 13}N({beta} +){sup 13}C, where the photodisintegration reverse channel {sup 13}N({gamma}, p){sup 12}C is strongly decreasing with increasing temperature. Presented here is the impact of the {sup 12}C+{sup 12}C reaction uncertainties on the s-process and on explosive p-process nucleosynthesis in massive stars, including also fast rotating massive stars at low metallicity. Using various {sup 12}C+{sup 12}C rates, in particular an upper and lower rate limit of {approx}50,000 higher and {approx}20 lower than the standard rate at 5 Multiplication-Sign 10{sup 8} K, five 25 M {sub Sun} stellar models are calculated. The enhanced s-process signature due to {sup 13}C({alpha}, n){sup 16}O activation is considered, taking into account the impact of the uncertainty of all three C-burning reaction branches. Consequently, we show that the p-process abundances have an average production factor increased up to about a factor of eight compared with the standard case, efficiently producing the elusive Mo and Ru proton-rich isotopes. We also show that an s-process being driven by {sup 13}C({alpha}, n){sup 16}O is a secondary process, even though the abundance of {sup 13}C does not depend on the initial metal content. Finally, implications for the Sr-peak elements inventory in the solar system and at low metallicity are

Mometasone-based triple combination therapy in melasma: Is it really safe?

Directory of Open Access Journals (Sweden)

Majid Imran

2010-01-01

Full Text Available Background: Kligman′s triple combination formula has been one of the most popular treatment options in melasma over the last three decades. The original Kligman′s formula has been modified in many ways over the years and the most recent modification that has been introduced is a triple combination of 2% hydroquinone, 0.025% tretinoin, and 1% mometasone. The use of this triple combination in patients with melasma has seen a sharp rise over the last few years and with this rampant use the side-effect profile of this triple combination has also come to the fore. Aim : The aim of the present study was to assess the overall safety of the mometasone-based triple combination treatment in the management of melasma. Materials and Methods: This retrospective study was performed on 60 patients of melasma who had used a mometasone-based triple combination treatment for at least 3 weeks anytime in the previous 1 year. The patients were given a preformed questionnaire wherein they assessed the overall effect of the triple combination treatment on their melasma during its use as well as after its withdrawal. The patients were specifically asked about the status of their disease as well as the sun sensitivity of their skin before and after the use of triple combination treatment. In addition, the patients were assessed by a single trained dermatologist for the presence of any adverse effects arising out of the triple combination treatment in the form of telangiectasia, hypertrichosis, acne, skin atrophy, etc. Results: Majority of patients (51.7% had used the combination treatment well beyond the recommended duration. About one-third (36.7% of the patients rated their melasma as worse at the time of filling the questionnaire as compared with their disease before the use of triple combination treatment. On clinical examination, the evidence of steroid side effects was seen in 26 patients (43.3%. Steroid-induced telangiectasia was the commonest finding, seen

The rate coefficients of unimolecular reactions in the systems with power-law distributions

Science.gov (United States)

Yin, Cangtao; Guo, Ran; Du, Jiulin

2014-08-01

The rate coefficient formulae of unimolecular reactions are generalized to the systems with the power-law distributions based on nonextensive statistics, and the power-law rate coefficients are derived in the high and low pressure limits, respectively. The numerical analyses are made of the rate coefficients as functions of the ν-parameter, the threshold energy, the temperature and the number of degrees of freedom. We show that the new rate coefficients depend strongly on the ν-parameter different from one (thus from a Boltzmann-Gibbs distribution). Two unimolecular reactions, CH3CO→CH3+CO and CH3NC→CH3CN, are taken as application examples to calculate their power-law rate coefficients, which obtained with the ν-parameters slightly different from one can be exactly in agreement with all the experimental studies on these two reactions in the given temperature ranges.

A study of jet rates and measurement of [alpha][sub S] at the Z[sup 0] resonance

Energy Technology Data Exchange (ETDEWEB)

Lauber, J.A.

1993-02-01

This experiment was performed with the SLD detector at the Stanford Linear Accelerator Center. Only charged tracks measured in the central drift chamber were used for the measurement of the jet production rates. The value of the strong coupling [alpha][sub s](M[sub Z][sup o]) is determined from the production rates of jets in hadronic Z[sup 0] decays in e[sup +] e[sup [minus

Wakeless triple soliton accelerator

International Nuclear Information System (INIS)

Mima, K.; Ohsuga, T.; Takabe, H.; Nishihara, K.; Tajima, T.; Zaidman, E.; Horton, W.

1986-09-01

We introduce and analyze the concept of a wakeless triple soliton accelerator in a plasma fiber. Under appropriate conditions the triple soliton with two electromagnetic and one electrostatic waves in the beat-wave resonance propagates with velocity c leaving no plasma wake behind, while the phase velocity of the electrostatic wave is made also c in the fiber

Spent fuel reaction - the behavior of the ε-phase over 3.1 years

International Nuclear Information System (INIS)

Finn, P.A.; Hoh, J.C.; Wolf, S.F.

1996-01-01

The release fractions of the five elements in the ε-phase ( 99 Tc, 97 Mo, Ru, Rh, and Pd) as well as that of 238 U are reported for the reaction of two oxide fuels (ATM-103 and ATM-106) in unsaturated tests under oxidizing conditions. The 99 Tc release fractions provide a lower limit for the magnitude of the spent fuel reaction. The 99 Tc release fractions indicate that a surface reaction might be the rate controlling mechanism for fuel reaction under unsaturated conditions and the oxidant is possibly H 2 O 2 , a product of alpha radiolysis of water

Reaction rate constant for radiative association of CF{sup +}

Energy Technology Data Exchange (ETDEWEB)

Öström, Jonatan, E-mail: jonatan.ostrom@gmail.com; Gustafsson, Magnus, E-mail: magnus.gustafsson@ltu.se [Applied Physics, Division of Materials Science, Department of Engineering Science and Mathematics, Luleå University of Technology, 97187 Luleå (Sweden); Bezrukov, Dmitry S. [Department of Chemistry, M. V. Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); Nyman, Gunnar [Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg (Sweden)

2016-01-28

Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C{sup +}) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 1{sup 1}Π → X{sup 1}Σ{sup +} and rovibrational transitions on the X{sup 1}Σ{sup +} and a{sup 3}Π potentials. Semiclassical and classical methods are used for the direct contribution and Breit–Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius–Kooij formula in five temperature intervals with a relative difference of <3%. The fit parameters will be added to the online database KIDA. For a temperature of 10–250 K, the rate constant is about 10{sup −21} cm{sup 3} s{sup −1}, rising toward 10{sup −16} cm{sup 3} s{sup −1} for a temperature of 30 000 K.

Evaluation of Chemical Kinetic for Mathematics Model Reduction of Cadmium Reaction Rate, Constant and Reaction Orde in to Electrochemical Process

International Nuclear Information System (INIS)

Prayitno

2007-01-01

The experiment was reduction of cadmium rate with electrochemical influenced by time process, concentration, current strength and type of electrode plate. The aim of the experiment was to know the influence, mathematic model reduction of cadmium the reaction rate, reaction rate constant and reaction orde influenced by time process, concentration, current strength and type of electrode plate. Result of research indicate the time processing if using plate of copper electrode is during 30 minutes and using plate of aluminium electrode is during 20 minutes. Condition of strong current that used in process of electrochemical is only 0.8 ampere and concentration effective is 5.23 mg/l. The most effective type Al of electrode plate for reduction from waste and the efficiency of reduction is 98 %. (author)

Bromide-free TEMPO-mediated oxidation of primary alcohol groups in starch and methyl alpha-D-glucopyranoside.

Science.gov (United States)

Bragd, P L; Besemer, A C; van Bekkum, H

2000-09-22

TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)-mediated oxidation of potato starch and methyl alpha-D-glucopyranoside (MGP) was performed in the absence of sodium bromide (NaBr) as co-catalyst, solely using sodium hypochlorite (NaOCl) as the primary oxidant. The low reaction rate associated with a bromide-free process was increased by performing the oxidation at increased temperatures. The reaction proceeded stoichiometrically and with high selectivity and with only minor depolymerisation, provided that temperature and pH were kept or = 25 degrees C) and under more alkaline conditions (pH > or = 9.0) degradation of the starch skeleton occurred. Simultaneously, side-reactions of the nitrosonium ion lowered the yield of the oxidation. Despite the absence of the NaBr catalyst, the reaction rate-controlling step was found to be the oxidation of the primary hydroxyl groups with the nitrosonium ion. The reaction was first-order in MGP and in TEMPO.

Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Titanium

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

1.1 This test method covers procedures for measuring reaction rates by the activation reactions 46Ti(n,p) 46Sc + 47Ti(n, np)46Sc. Note 1—Since the cross section for the (n,np) reaction is relatively small for energies less than 12 MeV and is not easily distinguished from that of the (n,p) reaction, this test method will refer to the (n,p) reaction only. 1.2 The reaction is useful for measuring neutrons with energies above approximately 4.4 MeV and for irradiation times up to about 250 days (for longer irradiations, see Practice E 261). 1.3 With suitable techniques, fission-neutron fluence rates above 109 cm–2·s–1 can be determined. However, in the presence of a high thermal-neutron fluence rate, 46Sc depletion should be investigated. 1.4 Detailed procedures for other fast-neutron detectors are referenced in Practice E 261. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all...

Thermodynamic and molecular origin of interfacial rate enhancements and endo-selectivities of a Diels-Alder reaction.

Science.gov (United States)

Beniwal, Vijay; Kumar, Anil

2017-02-08

Organic reactions in general display large rate accelerations when performed under interfacial conditions, such as on water or at ionic liquid interfaces. However, a clear picture of the physicochemical factors responsible for this large rate enhancements is not available. To gain an understanding of the thermodynamic and molecular origin of these large rate enhancements, we performed a Diels-Alder reaction between cyclopentadiene and methyl acrylate at ionic liquid/n-hexane interfaces. This study describes, for the first time, a methodology for the calculation of the activation parameters of an interfacial reaction. It has been seen that the energy of activation for an interfacial reaction is much smaller than that of the corresponding homogeneous reaction, resulting into the large rate acceleration for the interfacial reaction. Furthermore, the study describes the effects of the alkyl chain length of ionic liquid cations, the extent of heterogeneity, and the polarity of ionic liquids on the rate constants and stereoselectivity of the reaction.

Amending triple superphosphate with chicken litter biochar improves phosphorus availability

Directory of Open Access Journals (Sweden)

Audrey Asap

2018-04-01

Full Text Available The reaction of H2PO42- and HPO4- with Al and Fe in acid soils to form a precipitate reduces P availability. Chicken litter biochar has been used to improve soil P availability for maize production but with limited information on optimum rates of biochar and Triple Superphosphate (TSP to increase P availability. This study determined the optimum amount of chicken litter biochar and TSP that could increase P availability. Different rates of chicken litter biochar and TSP were evaluated in an incubation study for 30, 60, and 90 days. Selected soil chemical properties before and after incubation were determined using standard procedures. Soil pH, total P, available P, and water soluble P increased in treatments with 75% and 50% biochar. Total acidity, exchangeable Al3+, and Fe2+ were significantly reduced by the chicken litter biochar. The chicken litter biochar also increased soil CEC and exchangeable cations (K, Ca, Mg and Na. The use of 75% and 50% of 5 t ha-1 biochar with 25% TSP of the existing recommendation can be used to increase P availability whilst minimizing soil Al and Fe content. This rates can be used to optimize chicken litter biochar and TSP use in acid soils for crop production especially maize and short term vegetables.

Nuclear collective flow from gaussian fits to triple differential distributions

International Nuclear Information System (INIS)

Gosset, J.; Demoulins, M.; Babinet, R.; Cavata, C.; Fanet, H.; L'Hote, D.; Lucas, B.; Poitou, J.; Valette, O.; Alard, J.P.; Augerat, J.; Bastid, N.; Charmensat, P.; Dupieux, P.; Fraysse, L.; Marroncle, J.; Montarou, G.; Parizet, M.J.; Qassoud, D.; Rahmani, A.; Brochard, F.; Gorodetzky, P.; Racca, C.

1990-01-01

In order to study the nuclear collective flow, the triple differential momentum distributions of charged baryons are fitted to a simple anisotropic gaussian distribution, within an acceptance which removes most of the spectator contribution. The adjusted flow angle and aspect ratios are corrected for systematic errors in the determination of the reaction plane. This method has been tested with Monte Carlo simulations and applied to experimental results and intranuclear cascade simulations of argon-nucleus collisions at 400 MeV per nucleon. (orig.)

NIM Realization of the Gallium Triple Point

Science.gov (United States)

Xiaoke, Yan; Ping, Qiu; Yuning, Duan; Yongmei, Qu

2003-09-01

In the last three years (1999 to 2001), the gallium triple-point cell has been successfully developed, and much corresponding research has been carried out at the National Institute of Metrology (NIM), Beijing, China. This paper presents the cell design, apparatus and procedure for realizing the gallium triple point, and presents studies on the different freezing methods. The reproducibility is 0.03 mK, and the expanded uncertainty of realization of the gallium triple point is evaluated to be 0.17 mK (p=0.99, k=2.9). Also, the reproducibility of the gallium triple point was compared with that of the triple point of water.

Effect of the new C-12(alpha, gamma)O-16 rate on the chemical evolution of the solar neighborhood

International Nuclear Information System (INIS)

Matteucci, F.

1986-01-01

New models of chemical evolution of the solar neighborhood have been computed by taking into account the effect of the revised rate of the C-12(alpha, gamma)O-16 reaction on the chemical yields from massive stars, together with the yields from low- and intermediate-mass stars which also include those from Type I supernova explosions (C-deflagration in white dwarfs). In particular, the evolution of C-12, N-14, O-16, Ne-20, Mg-24, Si-28, and Fe-56 has been followed in detail, and their predicted solar absolute abundances as well as their relative ratios, both in the sun and in metal-poor stars, have been compared with the observed ones. It is concluded that a model with the new yields combined with a Salpeter initial mass function, an upper cutoff mass of 100 solar masses (the mass beyond which stars are not contributing to the galactic enrichment), and an upper limiting mass for intermediate-mass stars of the order of 5 solar masses, is in best agreement with the observations. 34 references

Triple-coincidence with automatic chance coincidence correction

International Nuclear Information System (INIS)

Chase, R.L.

1975-05-01

The chance coincidences in a triple-coincidence circuit are of two types--partially correlated and entirely uncorrelated. Their relative importance depends on source strength and source and detector geometry so that the total chance correction cannot, in general, be calculated. The system described makes use of several delays and straightforward integrated circuit logic to provide independent evaluation of the two components of the chance coincidence rate. (auth)

Determination of rate constants for the oxygen reduction reaction

Energy Technology Data Exchange (ETDEWEB)

Racz, A.; Walter, T.; Stimming, U. [Munich Technical Univ., Garching (Germany). Dept. of Physics

2008-07-01

The oxygen reduction reaction (ORR) in fuel cells is a complex and fundamental electrochemical reaction. However, greater insight is needed into this multi-electron reaction in order to develop efficient and innovative catalysts. The rotating ring disc electrode (RRDE) is a useful tool for studying reaction intermediates of the ORR and to better understand the reaction pathway. Carbon materials such as carbon nanofilaments-platelets (CNF-PL) have high electrical conductivity and may be considered for fuel cells. In particular Pt and RuSe{sub x}, deposited on CNF-PL materials could act as efficient catalysts in fuel cells. This study used the RRDE to evaluate the oxygen reduction kinetics of these catalysts in oxygen-saturated, diluted sulphuric acid at room temperature. Kinetic data and hydrogen peroxide formation were determined by depositing a thin-film of the catalyst on the Au disc. The values for the constants k1, k2 and k3 were obtained using diagnostic criteria and expressions to calculate the rate constants of the cathodic oxygen reduction reaction for RuSe on new carbon supports. A potential dependency of the constants k1 and k2 for RuSe{sub x}/CNF-PL was observed. The transition of the Tafel slopes for this catalyst was obtained. 4 refs., 1 fig.

A randomised controlled trial of two infusion rates to decrease reactions to antivenom.

Directory of Open Access Journals (Sweden)

Geoffrey K Isbister

Full Text Available BACKGROUND: Snake envenoming is a major clinical problem in Sri Lanka, with an estimated 40,000 bites annually. Antivenom is only available from India and there is a high rate of systemic hypersensitivity reactions. This study aimed to investigate whether the rate of infusion of antivenom reduced the frequency of severe systemic hypersensitivity reactions. METHODS AND FINDINGS: This was a randomized comparison trial of two infusion rates of antivenom for treatment of non-pregnant adult patients (>14 y with snake envenoming in Sri Lanka. Snake identification was by patient or hospital examination of dead snakes when available and confirmed by enzyme-immunoassay for Russell's viper envenoming. Patients were blindly allocated in a 11 randomisation schedule to receive antivenom either as a 20 minute infusion (rapid or a two hour infusion (slow. The primary outcome was the proportion with severe systemic hypersensitivity reactions (grade 3 by Brown grading system within 4 hours of commencement of antivenom. Secondary outcomes included the proportion with mild/moderate hypersensitivity reactions and repeat antivenom doses. Of 1004 patients with suspected snakebites, 247 patients received antivenom. 49 patients were excluded or not recruited leaving 104 patients allocated to the rapid antivenom infusion and 94 to the slow antivenom infusion. The median actual duration of antivenom infusion in the rapid group was 20 min (Interquartile range[IQR]:20-25 min versus 120 min (IQR:75-120 min in the slow group. There was no difference in severe systemic hypersensitivity reactions between those given rapid and slow infusions (32% vs. 35%; difference 3%; 95%CI:-10% to +17%;p = 0.65. The frequency of mild/moderate reactions was also similar. Similar numbers of patients in each arm received further doses of antivenom (30/104 vs. 23/94. CONCLUSIONS: A slower infusion rate would not reduce the rate of severe systemic hypersensitivity reactions from current high

A compilation of information on the {sup 31}P(p,{alpha}){sup 28}Si reaction and properties of excited levels in the compound nucleus {sup 32}S

Energy Technology Data Exchange (ETDEWEB)

Miller, R.E.; Smith, D.L. [Argonne National Lab., IL (United States). Technology Development Div.

1997-11-01

This report documents a survey of the literature, and provides a compilation of data contained therein, for the {sup 31}P(p,{alpha}){sup 28}Si reaction. Attention is paid here to resonance states in the compound-nuclear system {sup 32}S formed by {sup 31}P + p, with emphasis on the alpha-particle decay channels, {sup 28}Si + {alpha} which populate specific levels in {sup 28}Si. The energy region near the proton separation energy for {sup 32}S is especially important in this context for applications in nuclear astrophysics. Properties of the excited states in {sup 28}Si are also considered. Summaries of all the located references are provided and numerical data contained in them are compiled in EXFOR format where applicable.

Estimating Reaction Rate Coefficients Within a Travel-Time Modeling Framework

Energy Technology Data Exchange (ETDEWEB)

Gong, R [Georgia Institute of Technology; Lu, C [Georgia Institute of Technology; Luo, Jian [Georgia Institute of Technology; Wu, Wei-min [Stanford University; Cheng, H. [Stanford University; Criddle, Craig [Stanford University; Kitanidis, Peter K. [Stanford University; Gu, Baohua [ORNL; Watson, David B [ORNL; Jardine, Philip M [ORNL; Brooks, Scott C [ORNL

2011-03-01

A generalized, efficient, and practical approach based on the travel-time modeling framework is developed to estimate in situ reaction rate coefficients for groundwater remediation in heterogeneous aquifers. The required information for this approach can be obtained by conducting tracer tests with injection of a mixture of conservative and reactive tracers and measurements of both breakthrough curves (BTCs). The conservative BTC is used to infer the travel-time distribution from the injection point to the observation point. For advection-dominant reactive transport with well-mixed reactive species and a constant travel-time distribution, the reactive BTC is obtained by integrating the solutions to advective-reactive transport over the entire travel-time distribution, and then is used in optimization to determine the in situ reaction rate coefficients. By directly working on the conservative and reactive BTCs, this approach avoids costly aquifer characterization and improves the estimation for transport in heterogeneous aquifers which may not be sufficiently described by traditional mechanistic transport models with constant transport parameters. Simplified schemes are proposed for reactive transport with zero-, first-, nth-order, and Michaelis-Menten reactions. The proposed approach is validated by a reactive transport case in a two-dimensional synthetic heterogeneous aquifer and a field-scale bioremediation experiment conducted at Oak Ridge, Tennessee. The field application indicates that ethanol degradation for U(VI)-bioremediation is better approximated by zero-order reaction kinetics than first-order reaction kinetics.

A model for reaction rates in turbulent reacting flows

Science.gov (United States)

Chinitz, W.; Evans, J. S.

1984-01-01

To account for the turbulent temperature and species-concentration fluctuations, a model is presented on the effects of chemical reaction rates in computer analyses of turbulent reacting flows. The model results in two parameters which multiply the terms in the reaction-rate equations. For these two parameters, graphs are presented as functions of the mean values and intensity of the turbulent fluctuations of the temperature and species concentrations. These graphs will facilitate incorporation of the model into existing computer programs which describe turbulent reacting flows. When the model was used in a two-dimensional parabolic-flow computer code to predict the behavior of an experimental, supersonic hydrogen jet burning in air, some improvement in agreement with the experimental data was obtained in the far field in the region near the jet centerline. Recommendations are included for further improvement of the model and for additional comparisons with experimental data.

Phosphorylated alpha(1 leads to 4) glucans as substrate for potato starch-branching enzyme I

International Nuclear Information System (INIS)

Vikso-Nielsen, A.; Blennow, A.; Nielsen, T.H.; Moller, B.L.

1998-01-01

The possible involvement of potato (Solanum tuberosum L.) starch-branching enzyme I (PSBE-I) in the in vivo synthesis of phosphorylated amylopectin was investigated in in vitro experiments with isolated PSBE-I using 33P-labeled phosphorylated and 3H end-labeled nonphosphorylated alpha(1 leads to 4) glucans as the substrates. From these radiolabeled substrates PSBE-I was shown to catalyze the formation of dual-labeled (3H/33P) phosphorylated branched polysaccharides with an average degree of polymerization of 80 to 85. The relatively high molecular mass indicated that the product was the result of multiple chain-transfer reactions. The presence of alpha(1 leads to 6) branch points was documented by isoamylase treatment and anion-exchange chromatography. Although the initial steps of the in vivo mechanism responsible for phosphorylation of potato starch remains elusive, the present study demonstrates that the enzyme machinery available in potato has the ability to incorporate phosphorylated alpha(1 leads to 4) glucans into neutral polysaccharides in an interchain catalytic reaction. Potato mini tubers synthesized phosphorylated starch from exogenously supplied 33PO4(3-) and [U-14C]Glc at rates 4 times higher than those previously obtained using tubers from fully grown potato plants. This system was more reproducible compared with soil-grown tubers and was therefore used for preparation of 33P-labeled phosphorylated alpha(1 leads to 4) glucan chains

Benchmark calculations of thermal reaction rates. I - Quantal scattering theory

Science.gov (United States)

Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

1991-01-01

The thermal rate coefficient for the prototype reaction H + H2 yields H2 + H with zero total angular momentum is calculated by summing, averaging, and numerically integrating state-to-state reaction probabilities calculated by time-independent quantum-mechanical scattering theory. The results are very carefully converged with respect to all numerical parameters in order to provide high-precision benchmark results for confirming the accuracy of new methods and testing their efficiency.

Ratio and rate effects of 32P-triple superphosphate and phosphate rock mixtures on corn growth

International Nuclear Information System (INIS)

Franzini, Vinicius Ide; Mendes, Fernanda Latanze

2009-01-01

The availability of phosphorus (P) from 'Patos de Minas' phosphate rock (PR) can be improved if it is applied mixed with a water-soluble P source. The objective of this study was to evaluate 32 P as a tracer to quantify the effect of the ratio of mixtures of triple superphosphate (TSP) with PR and the rates of application on P availability from PR. Two experiments were conducted in a greenhouse utilizing corn (Zea mays L.) plants as test crop. In the first experiment, the P sources were applied at the rate of 90 mg P kg -1 soil either separately or as compacted mixtures in several TSP:PR ratios (100:0, 80:20, 60:40, 50:50, 40:60, 20:80 and 0:100 calculated on the basis of the total P content). In the second experiment, the TSP was applied alone or as 50:50 compacted mixtures with PR applied at four P rates (15, 30, 60 and 90 mg P kg -1 ) while the sole PR treatment was applied at the 90 mg kg -1 P rate . The mixture of PR with TSP improved the P recovery from PR in the corn plant and this effect increased proportionally to the TSP amounts in the mixture. When compared with the plant P recovery from TSP (10.52%), PR-P recovery (2.57%) was much lower even when mixed together in the ratio of 80% TSP: 20% PR. There was no difference in PR-P utilization by the corn plants with increasing P rates in the mixture (1:1 proportion). Therefore, PR-P availability is affected by the proportions of the mixtures with water soluble P, but not by P rates. (author)

Eight-dimensional quantum reaction rate calculations for the H+CH4 and H2+CH3 reactions on recent potential energy surfaces.

Science.gov (United States)

Zhou, Yong; Zhang, Dong H

2014-11-21

Eight-dimensional (8D) transition-state wave packet simulations have been performed on two latest potential energy surfaces (PES), the Zhou-Fu-Wang-Collins-Zhang (ZFWCZ) PES [Y. Zhou, B. Fu, C. Wang, M. A. Collins, and D. H. Zhang, J. Chem. Phys. 134, 064323 (2011)] and the Xu-Chen-Zhang (XCZ)-neural networks (NN) PES [X. Xu, J. Chen, and D. H. Zhang, Chin. J. Chem. Phys. 27, 373 (2014)]. Reaction rate constants for both the H+CH4 reaction and the H2+CH3 reaction are calculated. Simulations of the H+CH4 reaction based on the XCZ-NN PES show that the ZFWCZ PES predicts rate constants with reasonable high accuracy for low temperatures while leads to slightly lower results for high temperatures, in line with the distribution of interpolation error associated with the ZFWCZ PES. The 8D H+CH4 rate constants derived on the ZFWCZ PES compare well with full-dimensional 12D results based on the equivalent m-ZFWCZ PES, with a maximum relative difference of no more than 20%. Additionally, very good agreement is shown by comparing the 8D XCZ-NN rate constants with the 12D results obtained on the ZFWCZ-WM PES, after considering the difference in static barrier height between these two PESs. The reaction rate constants calculated for the H2+CH3 reaction are found to be in good consistency with experimental observations.

Electrospray ionization mass spectrometric investigations of [alpha]-dicarbonyl compounds--Probing intermediates formed in the course of the nonenzymatic browning reaction of l-ascorbic acid

Science.gov (United States)

Schulz, Anke; Trage, Claudia; Schwarz, Helmut; Kroh, Lothar W.

2007-05-01

A new method is presented which allows the simultaneous detection of various [alpha]-dicarbonyl compounds generated in the course of the nonenzymatic browning reaction initiated by thermal treatment of l-ascorbic acid, namely: glyoxal, methylglyoxal, diacetyl, 3-deoxy-l-pentosone, and l-threosoneE 3-Deoxy-l-threosone was successfully identified as a new C4-[alpha]-dicarbonyl structure for the first time in the degradation of Vitamin C by application of this non-chromatographic mass spectrometric approach. Moreover, a more detailed elucidation of the mechanistic scenario with respect to the oxidative and nonoxidative pathways is presented by using dehydro-l-ascorbic acid and 2,3-diketo-l-gulonic acid instead of l-ascorbic acid as a starting material. Furthermore, the postulated pathways are corroborated with the aid of 13C-isotopic labeling studies. The investigations were extended to baby food, and the successful detection of [alpha]-dicarbonyl compounds characteristic for Vitamin C degradation proved the matrix tolerance of the introduced method.

Reaction rate and composition dependence of the stability of thermonuclear burning on accreting neutron stars

International Nuclear Information System (INIS)

Keek, L.; Cyburt, R. H.; Heger, A.

2014-01-01

The stability of thermonuclear burning of hydrogen and helium accreted onto neutron stars is strongly dependent on the mass accretion rate. The burning behavior is observed to change from Type I X-ray bursts to stable burning, with oscillatory burning occurring at the transition. Simulations predict the transition at a 10 times higher mass accretion rate than observed. Using numerical models we investigate how the transition depends on the hydrogen, helium, and CNO mass fractions of the accreted material, as well as on the nuclear reaction rates of 3α and the hot-CNO breakout reactions 15 O(α, γ) 19 Ne and 18 Ne(α, p) 21 Na. For a lower hydrogen content the transition is at higher accretion rates. Furthermore, most experimentally allowed reaction rate variations change the transition accretion rate by at most 10%. A factor 10 decrease of the 15 O(α, γ) 19 Ne rate, however, produces an increase of the transition accretion rate of 35%. None of our models reproduce the transition at the observed rate, and depending on the true 15 O(α, γ) 19 Ne reaction rate, the actual discrepancy may be substantially larger. We find that the width of the interval of accretion rates with marginally stable burning depends strongly on both composition and reaction rates. Furthermore, close to the stability transition, our models predict that X-ray bursts have extended tails where freshly accreted fuel prolongs nuclear burning.

Primary Alcohols from Terminal Olefins: Formal Anti-Markovnikov Hydration via Triple Relay Catalysis

KAUST Repository

Dong, G.

2011-09-15

Alcohol synthesis is critical to the chemical and pharmaceutical industries. The addition of water across olefins to form primary alcohols (anti-Markovnikov olefin hydration) would be a broadly useful reaction but has largely proven elusive; an indirect hydroboration/oxidation sequence requiring stoichiometric borane and oxidant is currently the most practical methodology. Here, we report a more direct approach with the use of a triple relay catalysis system that couples palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction cycles. Aryl-substituted terminal olefins are converted to primary alcohols by net reaction with water in good yield and excellent regioselectivity.

Measurements of rates of some reactions related to radiolytic effect on aqueous iodide solution

International Nuclear Information System (INIS)

Shiraishi, H.; Okuda, H.; Ishigure, K.

1986-01-01

A number of reactions takes place concurrently when aqueous iodide solution is subjected to radiation field. In order to help analyze this complicated radiation effect measurements of rate constants were undertaken for several important reactions. One of these concerns reduction of hypoiodous acid by hydrogen peroxide. For this reaction catalytic effect was found to be significant, and old rate data was revised. Measurements on reactions involving radicals were carried out by use of pulse radiolysis technique, which also include reexamination of results by previous workers. The reactions studied are (1) oxidation of iodide ion by hydroxyl radical (2) recombination reactions of atomic iodine and diiodide ion and (3) reduction of atomic and molecular iodine either by superoxide ion or by hydroperoxyl radical

Harmonic analysis on triple spaces

DEFF Research Database (Denmark)

Danielsen, Thomas Hjortgaard

In this thesis we study examples of triple spaces, both their structure theory, their invariant differential operators as well as analysis on them. The first major results provide us with some examples of triple spaces which are strongly spherical, i.e. satisfy some conditions reminiscent...

Corrosion potential detection method, potential characteristic simulation method for reaction rate and plant monitoring system using the same