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Sample records for fusion reaction rates

  1. Method of controlling fusion reaction rates

    DOEpatents

    Kulsrud, Russell M.; Furth, Harold P.; Valeo, Ernest J.; Goldhaber, Maurice

    1988-01-01

    A method of controlling the reaction rates of the fuel atoms in a fusion reactor comprises the step of polarizing the nuclei of the fuel atoms in a particular direction relative to the plasma confining magnetic field. Fusion reaction rates can be increased or decreased, and the direction of emission of the reaction products can be controlled, depending on the choice of polarization direction.

  2. Method of controlling fusion reaction rates

    DOEpatents

    Kulsrud, Russell M.; Furth, Harold P.; Valeo, Ernest J.; Goldhaber, Maurice

    1988-03-01

    A method of controlling the reaction rates of the fuel atoms in a fusion reactor comprises the step of polarizing the nuclei of the fuel atoms in a particular direction relative to the plasma confining magnetic field. Fusion reaction rates can be increased or decreased, and the direction of emission of the reaction products can be controlled, depending on the choice of polarization direction.

  3. Fusion Reaction Rate in an Inhomogeneous Plasma

    SciTech Connect

    S. Son; N.J. Fisch

    2004-09-03

    The local fusion rate, obtained from the assumption that the distribution is a local Maxwellian, is inaccurate if mean-free-paths of fusing particles are not sufficiently small compared with the inhomogeneity length of the plasma. We calculate the first order correction of P0 in terms of the small spatial gradient and obtain a non-local modification of P(sub)0 in a shock region when the gradient is not small. Use is made of the fact that the fusion reaction cross section has a relatively sharp peak as a function of energy.

  4. Neutron detectors for fusion reaction-rate measurements

    SciTech Connect

    Lerche, R.A.; Phillion, D.W.; Landen, O.L.; Murphy, T.J.; Jaanimagi, P.A.

    1994-02-10

    Fusion reactions in an inertial-confinement fusion (ICF) target filled with deuterium or a deuterium/tritium fuel release nearly monoenergetic neutrons. Because most the neutrons leave the compressed target without collision, they preserve reaction-rate information as they travel radially outward from their point of origin. Three fast, neutron detector techniques, each capable of measuring the fusion reaction-rate of ICF targets, have been demonstrated. The most advanced detector is based on the fast rise-time of a commercial plastic scintillator material (BC-422) which acts as a neutron-to-light converter. Signals, which are recorded with a fast optical streak camera, have a resolution of 25 ps. Good signals can be recorded for targets producing only 5 x 10{sup 7} DT neutrons. Two other detectors use knock-on collisions between neutrons and protons in a thin polyethylene (CH{sub 2}) converter. In one, the converter is placed in front of the photocathode of an x-ray streak camera. Recoil protons pass through the photocathode and knock out electrons which are accelerated and deflected to produce a signal. Resolutions < 25 ps are possible. In the other, the converter is placed in front of a microchannel plate (MCP) with a gated microstrip. Recoil protons eject electrons from the gold layer forming the microstrip. If a gate pulse is present, the signal is amplified. Present gate times are about 80 ps.

  5. Neutron detector for fusion reaction-rate measurements

    SciTech Connect

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

    1993-09-03

    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 < 25-ps FWHM. A thin piece of scintillator material acts as a neutron-to- light converter. A zoom lens images light from the scintillator surface to a high-speed (15 ps) optical streak camera for recording. The zoom lens allows the scintillator to be positioned between 1 and 50 cm from a target. The camera simulaneously records an optical fiducial pulse which allows the camera time base to be calibrated relative to the incident laser power. Bursts of x rays formed by focusing 20-ps, 2.5-TW laser pulses onto gold disk targets demonstrate the detector resolution to be < 25 ps. We have recorded burn histories for deuterium/tritium-filled targets producing as few as 3 {times} 10{sup 7} neutrons.

  6. Nuclear fusion reaction rates for strongly coupled ionic mixtures

    SciTech Connect

    Chugunov, A. I.; DeWitt, H. E.

    2009-07-15

    We analyze the effect of plasma screening on nuclear reaction rates in dense matter composed of atomic nuclei of one or two types. We perform semiclassical calculations of the Coulomb barrier penetrability taking into account a radial mean-field potential of plasma ions. The mean-field potential is extracted from the results of extensive Monte Carlo calculations of radial pair distribution functions of ions in binary ionic mixtures. We calculate the reaction rates in a wide range of plasma parameters and approximate these rates by an analytical expression that is expected to be applicable to multicomponent ion mixtures. Also, we analyze Gamow-peak energies of reacting ions in various nuclear burning regimes. For illustration, we study nuclear burning in {sup 12}C-{sup 16}O mixtures.

  7. Strong screening by lattice confinement and resultant fusion reaction rates in fcc metals

    NASA Astrophysics Data System (ADS)

    Prados-Estévez, F. M.; Subashiev, A. V.; Nee, H. H.

    2017-09-01

    The effects of electronic screening on the cross sections and reactivities for the nuclear reactions between light nuclei in Pd and Ni is studied. We consider the applicability of the theory of thermonuclear burning in stars to the D-D nuclear reaction in metals. The screening model based on the mean field potential of the electron cloud in the metal plasma is used. We discuss the specifics of the screening for the H (D) atoms embedded in vacancies and divacancies. High concentration of hydrogen isotopes segregated to monovacancies and divacancies in face-centered cubic (fcc) metals such as Ni and Pd with densities of ∼ 6 ×1023atom /cm3 , makes the hydrogen cluster a favorable active site for the fusion reaction. Still the observation of a nuclear reaction requires an accumulation of energy in D nuclei of at least several eV, which is far above what can be achieved in the thermal heating experiments.

  8. Fusion reactions at low energy

    SciTech Connect

    Beckerman, M.

    1985-01-01

    Fusion measurement methods at low energies are briefly described, and experimental and theoretical fusion cross sections for /sup 58/Ni + /sup 58/Ni, /sup 58/Ni + /sup 64/Ni and /sup 64/Ni + /sup 64/Ni reactions are discussed. It is shown that quantal tunneling calculations do not describe the near- and sub-barrier behavior of the fusion data. Instead, the WKB predictions fall progressively further blow the experimental results as the energy is lowered. At far subbarrier energies the measured cross sections exceed the WKB predictions by more than three orders of magnitude. The unexpectedly strong dependence of the fusion probability upon the nuclear valence structure is illustrated and discussed. The relationship of channel coupling and quantal tunneling is discussed. In conclusion, it was established that atomic nuclei fuse far more readily at low energies that would be expected from quantal tunneling considerations alone. It was found that the behavior of the cross sections for fusion depends strongly upon the valence structure of the collision partners. This structural dependence extends from light 1p-shell systems to systems involving nearly 200 nucleons. These new phenomena may be viewed as characterizing the tunneling of a quantal system with many degrees of freedom. The failure of standard tunneling models may be understood as resulting from the ability of the dinuclear system to tunnel into the classically forbidden region by means of couplings to intrinsic degrees of freedom. 38 refs. (WHK)

  9. Penetration Factor for Nuclear Fusion Reaction in Nonthermal Astrophysical Plasmas

    NASA Astrophysics Data System (ADS)

    Ki, Dai-Han; Jung, Young-Dae

    2011-02-01

    The nonthermal effects on the nuclear fusion reaction process are investigated in Lorentzian astrophysical plasmas. The closed expression of the classical turning point in Lorentzian plasmas is obtained by the Lambert W-function. Using the WKB analysis with the effective screening length, the closed expressions of the fusion penetration factor and the cross section for the nuclear fusion reaction in Lorentzian plasmas are obtained as functions of the spectral index, relative kinetic energy, and plasma parameters. It is shown that the nonthermal character of the Lorentzian plasma enhances the fusion penetration factor. In addition, the nonthermal effect on the penetration factor is found to be more significant in plasmas with higher densities. It would be expected that the fusion reaction rates of the p-p chain and the CNO cycle in nonthermal plasmas are always greater than those in thermal Maxwellian plasmas.

  10. Applications of Reaction Rate

    ERIC Educational Resources Information Center

    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…

  11. Measurements of fusion reactions from a Tokamak plasma

    NASA Astrophysics Data System (ADS)

    Chrien, R. E.

    1981-11-01

    Tokamak fusion reaction diagnostics were extended to include measurements of d-t, dp-3He, and d-d (proton branch) reactions. The confinement and slowing down of 1 MeV d-d tritons were studied y measuring d-t meutrons. The first charged fusion products to be detected in a Tokamak were the 3 MeV d-d and 14.7 MeV d- 3He protons. Beam-target d-3He reactions were measured during deuterium beam injection to study the transport and vessel retention of helium. Large d-3He reaction rates were produced by ion cyclotron heating of a 3He minority in a deuterium plasma. Measurements of the reaction rate, energy spectrum, and decay time indicate that the reactions are produced by 200 - 400 keV3He ions. Sawtooth and m = 2 oscillations in the proton emission were observed.

  12. 28C fusion reactions at high energies

    NASA Astrophysics Data System (ADS)

    Kim, B. T.; Cha, D.

    1987-04-01

    We present a model based on the direct reaction concept which is able to describe the fusion cross section consistently throughout the entire range of the measured energies from the sub-barrier region to the very high energies where the cross section decreases linearly as the inverse of the center of mass energy. The model is applied to the fusion reaction of 28Si with 12C where Harmon et al. measured the cross section at energies up to three times the Coulomb barrier.

  13. Cherenkov neutron detector for fusion reaction and runaway electron diagnostics.

    PubMed

    Cheon, MunSeong; Kim, Junghee

    2015-08-01

    A Cherenkov-type neutron detector was newly developed and neutron measurement experiments were performed at Korea Superconducting Tokamak Advanced Research. It was shown that the Cherenkov neutron detector can monitor the time-resolved neutron flux from deuterium-fueled fusion plasmas. Owing to the high temporal resolution of the detector, fast behaviors of runaway electrons, such as the neutron spikes, could be observed clearly. It is expected that the Cherenkov neutron detector could be utilized to provide useful information on runaway electrons as well as fusion reaction rate in fusion plasmas.

  14. Cherenkov neutron detector for fusion reaction and runaway electron diagnostics

    NASA Astrophysics Data System (ADS)

    Cheon, MunSeong; Kim, Junghee

    2015-08-01

    A Cherenkov-type neutron detector was newly developed and neutron measurement experiments were performed at Korea Superconducting Tokamak Advanced Research. It was shown that the Cherenkov neutron detector can monitor the time-resolved neutron flux from deuterium-fueled fusion plasmas. Owing to the high temporal resolution of the detector, fast behaviors of runaway electrons, such as the neutron spikes, could be observed clearly. It is expected that the Cherenkov neutron detector could be utilized to provide useful information on runaway electrons as well as fusion reaction rate in fusion plasmas.

  15. Cherenkov neutron detector for fusion reaction and runaway electron diagnostics

    SciTech Connect

    Cheon, MunSeong Kim, Junghee

    2015-08-15

    A Cherenkov-type neutron detector was newly developed and neutron measurement experiments were performed at Korea Superconducting Tokamak Advanced Research. It was shown that the Cherenkov neutron detector can monitor the time-resolved neutron flux from deuterium-fueled fusion plasmas. Owing to the high temporal resolution of the detector, fast behaviors of runaway electrons, such as the neutron spikes, could be observed clearly. It is expected that the Cherenkov neutron detector could be utilized to provide useful information on runaway electrons as well as fusion reaction rate in fusion plasmas.

  16. Results of an attempt to measure increased rates of the reaction D-2 + D-2 yields He-3 + n in a nonelectrochemical cold fusion experiment

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Decker, Arthur J.; Blue, James W.

    1989-01-01

    An experiment was performed to look for evidence of deuterium fusion in palladium. The experiment, which involved introducing deuterium into the palladium filter of a hydrogen purifier, was designed to detect neutrons produced in the reaction D-2 + D-2 yields He-3 + n as well as heat production. The neutron counts for deuterium did not differ significantly from background or from the counts for a hydrogen control. Heat production was detected when deuterium, but not hydrogen, was pumped from the purifier.

  17. Fusion rate following extreme lateral lumbar interbody fusion.

    PubMed

    Berjano, Pedro; Langella, Francesco; Damilano, Marco; Pejrona, Matteo; Buric, Josip; Ismael, Maryem; Villafañe, Jorge Hugo; Lamartina, Claudio

    2015-04-01

    Lumbar fusion has been found to be a clinically effective procedure in adult patients. The lateral transpsoas approach allows for direct visualization of the intervertebral space, significant support of the vertebral anterior column, while avoiding the complications associated with the posterior procedures. The aim of this study is to determine the fusion rate of inter body fusion using computed tomography in patients treated by extreme lateral intersomatic fusion (XLIF) technique. All patients intervened by XLIF procedure between 2009 and 2013 by a single operating team at a single institution were recruited for this study. A clinical evaluation and a CT scan of the involved spinal segments were then performed with at least 1-year follow-up following the standard clinical practice in the center. A total of 77 patients met inclusion criteria, of which 53 were available for review with a mean follow-up of 34.5 (12-62) months. A total of 68 (87.1 %) of the 78 operated levels were considered as completely fused, 8 (10.2 %) were considered as stable, probably fused, and 2 (2.6 %) of the operated levels were diagnosed as pseudarthrosis. When stratified by type of graft material complete fusion was obtained in 75 % of patients in which autograft was used to fill the cages, compared to 89 % of patients in which calcium triphosphate was used, and 83 % of patients in which Attrax™ was used. Reports of XLIF fusion rate in the literature vary from 85 to 93 % at 1-year follow-up. Fusion rate in our series corroborates data from previous publications. The results of this series confirm that anterior inter body fusion by means of XLIF approach is a technique that achieves high fusion rate and satisfactory clinical outcomes.

  18. From nucleons to nuclei to fusion reactions

    NASA Astrophysics Data System (ADS)

    Quaglioni, S.; Navrátil, P.; Roth, R.; Horiuchi, W.

    2012-12-01

    Nuclei are prototypes of many-body open quantum systems. Complex aggregates of protons and neutrons that interact through forces arising from quantum chromo-dynamics, nuclei exhibit both bound and unbound states, which can be strongly coupled. In this respect, one of the major challenges for computational nuclear physics, is to provide a unified description of structural and reaction properties of nuclei that is based on the fundamental underlying physics: the constituent nucleons and the realistic interactions among them. This requires a combination of innovative theoretical approaches and high-performance computing. In this contribution, we present one of such promising techniques, the ab initio no-core shell model/resonating-group method, and discuss applications to light nuclei scattering and fusion reactions that power stars and Earth-base fusion facilities.

  19. From Nucleons To Nuclei To Fusion Reactions

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R; Horiuchi, W

    2012-02-15

    Nuclei are prototypes of many-body open quantum systems. Complex aggregates of protons and neutrons that interact through forces arising from quantum chromo-dynamics, nuclei exhibit both bound and unbound states, which can be strongly coupled. In this respect, one of the major challenges for computational nuclear physics, is to provide a unified description of structural and reaction properties of nuclei that is based on the fundamental underlying physics: the constituent nucleons and the realistic interactions among them. This requires a combination of innovative theoretical approaches and high-performance computing. In this contribution, we present one of such promising techniques, the ab initio no-core shell model/resonating-group method, and discuss applications to light nuclei scattering and fusion reactions that power stars and Earth-base fusion facilities.

  20. Neutron suppression in polarized dd fusion reaction

    NASA Astrophysics Data System (ADS)

    Zhang, J. S.; Liu, K. F.; Shuy, G. W.

    1999-11-01

    We report a model-independent partial-wave analysis of polarized dd fusion reactions at low energies. The radial transition amplitudes, designated by the central, spin-orbit, and tensor forces, are determined by fitting angular distributions of the tensor and vector analyzing powers AXZ(θ), AZZ(θ), AXX-YY(θ), and AY(θ), and the unpolarized cross section σ0(θ). The polarized fusion cross section σ1,1(θ) is then predicted from these radial transition amplitudes. We stress that this is feasible only when these amplitudes are separated according to the tensor rank of the interaction. This study includes the D-state components of the deuteron, triton, and 3He, and the partial-wave expansion is done up to the d wave for both the entrance and exit channels. Experimental data at Elab=30, 50, 70, and 90 keV for the d(d,p)t reaction are very well fitted with this method. It is found that the ratio of polarized to unpolarized cross sections is about 86% at 30 keV and goes down to 22% at 90 keV. The implication of the suppression of a polarized dd fusion reaction is discussed in the context of the neutron-lean fusion reactor with polarized D-3He fuel. It turns out that the important range of energy for suppressing the d(d,p)t and d(d,n)3He reactions at the plasma temperature T=60 keV is Ed=80-600 keV. More experimental data are needed in this range to make a detailed study of the neutron suppression.

  1. Microdroplet fusion mass spectrometry for fast reaction kinetics

    PubMed Central

    Lee, Jae Kyoo; Kim, Samuel; Nam, Hong Gil; Zare, Richard N.

    2015-01-01

    We investigated the fusion of high-speed liquid droplets as a way to record the kinetics of liquid-phase chemical reactions on the order of microseconds. Two streams of micrometer-size droplets collide with one another. The droplets that fused (13 μm in diameter) at the intersection of the two streams entered the heated capillary inlet of a mass spectrometer. The mass spectrum was recorded as a function of the distance x between the mass spectrometer inlet and the droplet fusion center. Fused droplet trajectories were imaged with a high-speed camera, revealing that the droplet fusion occurred approximately within a 500-μm radius from the droplet fusion center and both the size and the speed of the fused droplets remained relatively constant as they traveled from the droplet fusion center to the mass spectrometer inlet. Evidence is presented that the reaction effectively stops upon entering the heated inlet of the mass spectrometer. Thus, the reaction time was proportional to x and could be measured and manipulated by controlling the distance x. Kinetic studies were carried out in fused water droplets for acid-induced unfolding of cytochrome c and hydrogen–deuterium exchange in bradykinin. The kinetics of the former revealed the slowing of the unfolding rates at the early stage of the reaction within 50 μs. The hydrogen–deuterium exchange revealed the existence of two distinct populations with fast and slow exchange rates. These studies demonstrated the power of this technique to detect reaction intermediates in fused liquid droplets with microsecond temporal resolution. PMID:25775573

  2. Microdroplet fusion mass spectrometry for fast reaction kinetics.

    PubMed

    Lee, Jae Kyoo; Kim, Samuel; Nam, Hong Gil; Zare, Richard N

    2015-03-31

    We investigated the fusion of high-speed liquid droplets as a way to record the kinetics of liquid-phase chemical reactions on the order of microseconds. Two streams of micrometer-size droplets collide with one another. The droplets that fused (13 μm in diameter) at the intersection of the two streams entered the heated capillary inlet of a mass spectrometer. The mass spectrum was recorded as a function of the distance x between the mass spectrometer inlet and the droplet fusion center. Fused droplet trajectories were imaged with a high-speed camera, revealing that the droplet fusion occurred approximately within a 500-μm radius from the droplet fusion center and both the size and the speed of the fused droplets remained relatively constant as they traveled from the droplet fusion center to the mass spectrometer inlet. Evidence is presented that the reaction effectively stops upon entering the heated inlet of the mass spectrometer. Thus, the reaction time was proportional to x and could be measured and manipulated by controlling the distance x. Kinetic studies were carried out in fused water droplets for acid-induced unfolding of cytochrome c and hydrogen-deuterium exchange in bradykinin. The kinetics of the former revealed the slowing of the unfolding rates at the early stage of the reaction within 50 μs. The hydrogen-deuterium exchange revealed the existence of two distinct populations with fast and slow exchange rates. These studies demonstrated the power of this technique to detect reaction intermediates in fused liquid droplets with microsecond temporal resolution.

  3. A light water excess heat reaction suggests that cold fusion may be alkali-hydrogen fusion

    SciTech Connect

    Bush, R.T. )

    1992-09-01

    This paper reports that Mills and Kneizys presented data in support of a light water excess heat reaction obtained with an electrolytic cell highly reminiscent of the Fleischmann-Pons cold fusion cell. The claim of Mills and Kneizys that their excess heat reaction can be explained on the basis of a novel chemistry, which supposedly also explains cold fusion, is rejected in favor of their reaction being, instead, a light water cold fusion reaction. It is the first known light water cold fusion reaction to exhibit excess heat, it may serve as a prototype to expand our understanding of cold fusion. From this new reactions are deduced, including those common to past cold fusion studies. This broader pattern of nuclear reactions is typically seen to involve a fusion of the nuclides of the alkali atoms with the simplest of the alkali-type nuclides, namely, protons, deuterons, and tritons. Thus, the term alkali-hydrogen fusion seems appropriate for this new type of reaction with three subclasses: alkali-hydrogen fusion, alkali-deuterium fusion, and alkali-tritium fusion. A new three-dimensional transmission resonance model (TRM) is sketched. Finally, preliminary experimental evidence in support of the hypothesis of a light water nuclear reaction and alkali-hydrogen fusion is reported. Evidence is presented that appears to strongly implicate the transmission resonance phenomenon of the new TRM.

  4. Barrier Distributions for Cold-Fusion Reactions

    SciTech Connect

    Ikezoe, Hiroshi; Mitsuoka, Shin-ichi; Nishio, Katsuhisa; Tsuruta, Kaoru; Watanabe, Yutaka; Jeong, Sunchan; Satou, Ken-ichiro

    2006-08-14

    Coulomb barrier distributions for the capture process in the cold fusion reactions for 48Ti, 54Cr, 56Fe, 64Ni, 70Zn projectiles incident on 208Pb target are obtained by the measurement of the quasi-elastic scattering cross sections at backward angles. The obtained barrier distributions are compared with the result of a coupled-channels calculation. It is found that the barrier distributions are well reproduced by the calculation taking account of the coupling of one phonon of the quadrupole vibration for these projectile nuclei and two phonons of the octupole vibration for 208Pb.

  5. Comparative Investigation of Fusion Reactions for Space Propulsion Applications

    NASA Astrophysics Data System (ADS)

    Petkow, Dejan; Herdrich, Georg; Laufer, Rene; Gabrielli, Roland; Zeile, Oliver

    A space propulsion system based on the acceleration of fusion ash is discussed by use of the energy balance equation and a hypothetic ash extraction and acceleration system. The fusion reactions D-T, D-3He, p-11B and 3He-3He are investigated under the condition of thermal generation of high energy ions and equal plasma system conditions in terms of Ti/Te relation and plasma beta. External plasma heating is defined by an equal efficiency concerning thermal energy conversion and energy transfer back into the plasma. There is no additional external heating applied to the fusion system. Power losses are based on neutrons, bremsstrahlung, synchrotron radiation and convection. We compare the plasma pressures, volumetric power densities, magnetic field strengths, heat waste, exhaust velocities and thrust density levels depending on the temperature and the hot ion mode. We show that, based on the fusion products, the exhaust velocity may reach several percent of speed of light in the case of 3He-3He. The temperature driven radiation losses of the 3He-3He reaction puts the purely aneutronic property into perspective. The mass flow rate densities of the considered fusion products are very low leading to very low thrust power densities. Considering the supposed system masses of a fusion based space vessel the thrust density levels are negligible and reach the order of 1 N/m3 near the optimum in the case of 3He-3He. We conclude that a propulsion system based on the acceleration of fusion products or ash is unfeasible for typical manned missions e.g. to Mars.

  6. What Is a Reaction Rate?

    ERIC Educational Resources Information Center

    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.

  7. Trojan Horse particle invariance in fusion reactions

    NASA Astrophysics Data System (ADS)

    Pizzone, R. G.; Spitaleril, C.; Bertulani, C.; Mukhamedzhanov, A.; Blokhintsev, L.; La Cognata, M.; Lamia, L.; Spartá, R.; Tumino, A.

    2015-01-01

    Trojan Horse method plays an important part for the measurement of several charged particle induced reactions cross sections of astrophysical interest. In order to better understand its cornerstones and the related applications to different astrophysical scenarios several tests were performed to verify all its properties and the possible future perspectives. The Trojan Horse nucleus invariance for the binary reactions d(d,p)t, 6,7Li(p,α)3,4He was therefore tested using the appropriate quasi free break- ups, respectively. In the first cases results from 6Li and 3He break up were used, while for the lithium fusion reactions break-ups of 2H and 3He were compared. The astrophysical S(E)-factors for the different processes were then extracted in the framework of the PlaneWave Approximation applied to the different break-up schemes. The obtained results are compared with direct data as well as with previous indirect investigations. The very good agreement between data coming from different break-up schemes confirms the applicability of the plane wave approximation and suggests the independence of binary indirect cross section on the chosen Trojan Horse nucleus also for the present cases. Moreover the astrophysical implications of the results will also be discussed in details.

  8. Measuring time of flight of fusion products in an inertial electrostatic confinement fusion device for spatial profiling of fusion reactions

    SciTech Connect

    Donovan, D. C.; Boris, D. R.; Kulcinski, G. L.; Santarius, J. F.; Piefer, G. R.

    2013-03-15

    A new diagnostic has been developed that uses the time of flight (TOF) of the products from a nuclear fusion reaction to determine the location where the fusion reaction occurred. The TOF diagnostic uses charged particle detectors on opposing sides of the inertial electrostatic confinement (IEC) device that are coupled to high resolution timing electronics to measure the spatial profile of fusion reactions occurring between the two charged particle detectors. This diagnostic was constructed and tested by the University of Wisconsin-Madison Inertial Electrostatic Confinement Fusion Group in the IEC device, HOMER, which accelerates deuterium ions to fusion relevant energies in a high voltage ({approx}100 kV), spherically symmetric, electrostatic potential well [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, T. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)]. The TOF diagnostic detects the products of D(d,p)T reactions and determines where along a chord through the device the fusion event occurred. The diagnostic is also capable of using charged particle spectroscopy to determine the Doppler shift imparted to the fusion products by the center of mass energy of the fusion reactants. The TOF diagnostic is thus able to collect spatial profiles of the fusion reaction density along a chord through the device, coupled with the center of mass energy of the reactions occurring at each location. This provides levels of diagnostic detail never before achieved on an IEC device.

  9. Measuring time of flight of fusion products in an inertial electrostatic confinement fusion device for spatial profiling of fusion reactions

    NASA Astrophysics Data System (ADS)

    Donovan, D. C.; Boris, D. R.; Kulcinski, G. L.; Santarius, J. F.; Piefer, G. R.

    2013-03-01

    A new diagnostic has been developed that uses the time of flight (TOF) of the products from a nuclear fusion reaction to determine the location where the fusion reaction occurred. The TOF diagnostic uses charged particle detectors on opposing sides of the inertial electrostatic confinement (IEC) device that are coupled to high resolution timing electronics to measure the spatial profile of fusion reactions occurring between the two charged particle detectors. This diagnostic was constructed and tested by the University of Wisconsin-Madison Inertial Electrostatic Confinement Fusion Group in the IEC device, HOMER, which accelerates deuterium ions to fusion relevant energies in a high voltage (˜100 kV), spherically symmetric, electrostatic potential well [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, T. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)]. The TOF diagnostic detects the products of D(d,p)T reactions and determines where along a chord through the device the fusion event occurred. The diagnostic is also capable of using charged particle spectroscopy to determine the Doppler shift imparted to the fusion products by the center of mass energy of the fusion reactants. The TOF diagnostic is thus able to collect spatial profiles of the fusion reaction density along a chord through the device, coupled with the center of mass energy of the reactions occurring at each location. This provides levels of diagnostic detail never before achieved on an IEC device.

  10. Measuring time of flight of fusion products in an inertial electrostatic confinement fusion device for spatial profiling of fusion reactions.

    PubMed

    Donovan, D C; Boris, D R; Kulcinski, G L; Santarius, J F; Piefer, G R

    2013-03-01

    A new diagnostic has been developed that uses the time of flight (TOF) of the products from a nuclear fusion reaction to determine the location where the fusion reaction occurred. The TOF diagnostic uses charged particle detectors on opposing sides of the inertial electrostatic confinement (IEC) device that are coupled to high resolution timing electronics to measure the spatial profile of fusion reactions occurring between the two charged particle detectors. This diagnostic was constructed and tested by the University of Wisconsin-Madison Inertial Electrostatic Confinement Fusion Group in the IEC device, HOMER, which accelerates deuterium ions to fusion relevant energies in a high voltage (∼100 kV), spherically symmetric, electrostatic potential well [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, T. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)]. The TOF diagnostic detects the products of D(d,p)T reactions and determines where along a chord through the device the fusion event occurred. The diagnostic is also capable of using charged particle spectroscopy to determine the Doppler shift imparted to the fusion products by the center of mass energy of the fusion reactants. The TOF diagnostic is thus able to collect spatial profiles of the fusion reaction density along a chord through the device, coupled with the center of mass energy of the reactions occurring at each location. This provides levels of diagnostic detail never before achieved on an IEC device.

  11. Synthesis of the heaviest nuclei in cold fusion reactions

    NASA Astrophysics Data System (ADS)

    Münzenberg, G.; Morita, K.

    2015-12-01

    Cold fusion of heavy ions paved the way to superheavy elements. It was proposed by Yu.Ts. Oganessian more than forty years ago in 1974 [1,2]. First experiments were carried out at JINR Dubna, starting with the reaction 40Ar + 208Pb → 248Fm* where several hundreds to thousand atoms were produced on one day. The large production rate indicating an enhancement of the fusion cross section, especially for the evaporation of two or three neutrons, proved the concept of cold-fusion with the use of the doubly magic nucleus 208Pb as a target. The Dubna experiments were extended to the transactinide region beyond rutherfordium. The breakthrough came with the separation in-flight. Two different approaches were used: kinematic separation with the velocity filter SHIP [3] at GSI Darmstadt, and with the gasfilled separator GARIS [4,5] at RIKEN. With SHIP the concept of cold fusion of massive nuclear systems was convincingly confirmed by the observation of the one-neutron evaporation channel in the production of 247Rf in an irradiation of 208Pb with 50Ti [6] in 1981 which opened the way to the transactinide region. At SHIP the elements bohrium (107) to copernicium (112) were discovered [7]. A new closed shell region around hassium was found. The RIKEN experiments started in 2002. They confirmed the GSI results and in addition improved the data on structure and production of elements hassium to copernicium significantly. The heaviest element ever created in a cold fusion reaction, Z = 113, was observed at GARIS [8,9].

  12. Fusion reactions of Ni,6458+124Sn

    NASA Astrophysics Data System (ADS)

    Jiang, C. L.; Stefanini, A. M.; Esbensen, H.; Rehm, K. E.; Almaraz-Calderon, S.; Avila, M. L.; Back, B. B.; Bourgin, D.; Corradi, L.; Courtin, S.; Fioretto, E.; Galtarossa, F.; Goasduff, A.; Haas, F.; Mazzocco, M. M.; Montanari, D.; Montagnoli, G.; Mijatovic, T.; Sagaidak, R.; Santiago-Gonzalez, D.; Scarlassara, F.; Strano, E. E.; Szilner, S.

    2015-04-01

    Measurements of fusion excitation functions of 58Ni+124Sn and 64Ni+124Sn are extended towards lower energy to cross sections of 1 μ b and are compared to detailed coupled-channels calculations. The calculations clearly show the importance of including transfer reactions in a coupled-channels treatment for such heavy systems. This result is different from the conclusion made in a previous article which claimed that the influence of transfer on fusion is not important for fusion reactions of Ni +Sn . In the energy region studied in this experiment no indication of fusion hindrance has been observed, which is consistent with a systematic study of this behavior.

  13. Additive effects on the energy barrier for synaptic vesicle fusion cause supralinear effects on the vesicle fusion rate.

    PubMed

    Schotten, Sebastiaan; Meijer, Marieke; Walter, Alexander Matthias; Huson, Vincent; Mamer, Lauren; Kalogreades, Lawrence; ter Veer, Mirelle; Ruiter, Marvin; Brose, Nils; Rosenmund, Christian; Sørensen, Jakob Balslev; Verhage, Matthijs; Cornelisse, Lennart Niels

    2015-04-14

    The energy required to fuse synaptic vesicles with the plasma membrane ('activation energy') is considered a major determinant in synaptic efficacy. From reaction rate theory, we predict that a class of modulations exists, which utilize linear modulation of the energy barrier for fusion to achieve supralinear effects on the fusion rate. To test this prediction experimentally, we developed a method to assess the number of releasable vesicles, rate constants for vesicle priming, unpriming, and fusion, and the activation energy for fusion by fitting a vesicle state model to synaptic responses induced by hypertonic solutions. We show that complexinI/II deficiency or phorbol ester stimulation indeed affects responses to hypertonic solution in a supralinear manner. An additive vs multiplicative relationship between activation energy and fusion rate provides a novel explanation for previously observed non-linear effects of genetic/pharmacological perturbations on synaptic transmission and a novel interpretation of the cooperative nature of Ca(2+)-dependent release.

  14. Subtalar Fusion Rate in Patients With Previous Ipsilateral Ankle Arthrodesis.

    PubMed

    Zanolli, Diego H; Nunley, James A; Easley, Mark E

    2015-09-01

    Isolated subtalar arthrodesis is generally successful, with reported fusion rates of 84% to 100%. However, alteration of subtalar joint mechanics and talar body vasculature after ankle fusion may negatively influence subsequent ipsilateral subtalar joint fusion. Because there is very limited information on the subtalar fusion rate in patients with previous ipsilateral ankle fusion, the purpose of this study was to describe fusion rates in subtalar joint arthrodesis with and without preexisting ankle fusion in a large consecutive series of primary subtalar arthrodesis cases. All primary subtalar fusions performed between January 2000 and December 2010 were reviewed. Thirteen of 151 consecutive cases were in patients with existing ipsilateral ankle fusions. All patients were evaluated for clinical and radiographic evidence of nonunion at follow-up, and fusion rates in the groups with and without previous ipsilateral ankle fusion were compared. Five nonunions occurred in the 13 cases with prior ipsilateral ankle arthrodesis, a 61.5% fusion rate. Twelve nonunions were identified in the 138 cases without prior ankle arthrodesis, a significantly higher fusion rate of 91.3% (P = .007). In our series, the subtalar fusion rate in patients with previous ipsilateral ankle arthrodesis was significantly lower than that for subtalar arthrodesis in the absence of ipsilateral ankle arthrodesis. Level III, retrospective comparative study. © The Author(s) 2015.

  15. Transfer-type products accompanying cold fusion reactions

    SciTech Connect

    Adamian, G.G.; Antonenko, N.V.

    2005-12-15

    Production of nuclei heavier than the target is treated for projectile-target combinations used in cold fusion reactions leading to superheavy nuclei. These products are related to transfer-type or to asymmetry-exit-channel quasifission reactions. The production of isotopes in the transfer-type reactions emitting of {alpha} particles with large energies is discussed.

  16. Competition between complete fusion and quasifission in reactions with heavy nuclei

    SciTech Connect

    Antonenko, N. V.; Scheid, W.; Adamian, G. G.; Volkov, V. V.

    1998-02-15

    A model based on the dinuclear system concept is suggested for the calculation of the competition between complete fusion and quasifission in reactions with heavy nuclei. The fusion rate through the inner fusion barrier in mass asymmetry is found by using the Kramers-type expression. The calculated cross sections for the heaviest nuclei are in a good agreement with the experimental data. The experimentally observed rapid fall-off of the cross section of the cold fusion with increasing charge number Z of the compound nucleus is explained.

  17. The effect of proton halo on fusion reactions

    NASA Astrophysics Data System (ADS)

    Lay, J. A.; Kumar, Raj; Vitturi, A.

    2015-04-01

    In a recent brief report [Kumar et al., Phys. Rev. C 89, 027601 (2014)] we proposed a method to include the effect of a large break up in fusion reactions with neutron and proton halo nuclei. A stronger enhancement on the total fusion cross section was found for the proton case. However, neither complete nor incomplete fusion was studied and only one target was considered. Here, we revisit the problem in order to address the importance of complete and incomplete fusion. The sensitivity of the cross section to the target is also explored.

  18. Evaluation of charged-particle reactions for fusion applications

    SciTech Connect

    White, R.M.; Resler, D.A.; Warshaw, S.I.

    1991-01-01

    New evaluations of the total reaction cross sections for {sup 2}H(d,n){sup 3}He, {sup 2}H(d,p){sup 3}H, {sup 3}H(t,2n){sup 4}He,{sup 3}H(d,n){sup 4}He, and {sup 3}He(d,p){sup 4}He have been completed. These evaluations are based on all known published data from 1946 to 1990 and include over 1150 measured data points from 67 references. The purpose of this work is to provide a consistent and well-documented set of cross sections for use in calculations relating to fusion energy research. A new thermonuclear data file, TDF, and a library of FORTRAN subprograms to read the file have been developed. Calculated from the new evaluations, the TDF file contains information on the Maxwellian-averaged reaction rates as a function of reaction and plasma temperature and the Maxwellian-averaged average energy of the interacting particles and reaction products. Routines are included that provide thermally-broadened spectral information for the secondary reaction products. 67 refs., 18 figs.

  19. Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma

    NASA Astrophysics Data System (ADS)

    Labaune, C.; Baccou, C.; Depierreux, S.; Goyon, C.; Loisel, G.; Yahia, V.; Rafelski, J.

    2013-10-01

    The advent of high-intensity-pulsed laser technology enables the generation of extreme states of matter under conditions that are far from thermal equilibrium. This in turn could enable different approaches to generating energy from nuclear fusion. Relaxing the equilibrium requirement could widen the range of isotopes used in fusion fuels permitting cleaner and less hazardous reactions that do not produce high-energy neutrons. Here we propose and implement a means to drive fusion reactions between protons and boron-11 nuclei by colliding a laser-accelerated proton beam with a laser-generated boron plasma. We report proton-boron reaction rates that are orders of magnitude higher than those reported previously. Beyond fusion, our approach demonstrates a new means for exploring low-energy nuclear reactions such as those that occur in astrophysical plasmas and related environments.

  20. Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma.

    PubMed

    Labaune, C; Baccou, C; Depierreux, S; Goyon, C; Loisel, G; Yahia, V; Rafelski, J

    2013-01-01

    The advent of high-intensity-pulsed laser technology enables the generation of extreme states of matter under conditions that are far from thermal equilibrium. This in turn could enable different approaches to generating energy from nuclear fusion. Relaxing the equilibrium requirement could widen the range of isotopes used in fusion fuels permitting cleaner and less hazardous reactions that do not produce high-energy neutrons. Here we propose and implement a means to drive fusion reactions between protons and boron-11 nuclei by colliding a laser-accelerated proton beam with a laser-generated boron plasma. We report proton-boron reaction rates that are orders of magnitude higher than those reported previously. Beyond fusion, our approach demonstrates a new means for exploring low-energy nuclear reactions such as those that occur in astrophysical plasmas and related environments.

  1. Charge-exchange and fusion reaction measurements during compression experiments with neutral beam heating in the Tokamak Fusion Test Reactor

    SciTech Connect

    Kaita, R.; Heidbrink, W.W.; Hammett, G.W.; Chan, A.A.; England, A.C.; Hendel, H.W.; Medley, S.S.; Nieschmidt, E.; Roquemore, A.L.; Scott, S.D.

    1986-04-01

    Adiabatic toroidal compression experiments were performed in conjunction with high power neutral beam injection in the Tokamak Fusion Test Reactor (TFTR). Acceleration of beam ions to energies nearly twice the injection energy was measured with a charge-exchange neutral particle analyzer. Measurements were also made of 2.5 MeV neutrons and 15 MeV protons produced in fusion reactions between the deuterium beam ions and the thermal deuterium and /sup 3/He ions, respectively. When the plasma was compressed, the d(d,n)/sup 3/He fusion reaction rate increased a factor of five, and the /sup 3/He(d,p)/sup 4/He rate by a factor of twenty. These data were simulated with a bounce-averaged Fokker-Planck program, which assumed conservation of angular momentum and magnetic moment during compression. The results indicate that the beam ion acceleration was consistent with adiabatic scaling.

  2. Observation of d-3He Fusion Reactions in a Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Chrien, R. E.; Colestock, P. L.; Eubank, H. P.; Hosea, J. C.; Hwang, D. Q.; Strachan, J. D.; Thompson, H. R., Jr.

    1981-02-01

    d-3He reactions have been observed in the Princeton Large Torus by detecting the unconfined 14.7-MeV proton. Reaction rates as high as 2×1013 sec-1 resulting in 60 W of fusion power were obtained by 500-kW heating of a 3He minority in the ion-cyclotron range of frequencies to energies above 80 keV. The fusion-power multiplication of about 10-4 is equal to the highest obtained in any controlled-fusion experiment.

  3. On fusion/fission chain reactions in the Fleischmann-Pons cold fusion experiment

    SciTech Connect

    Anghaie, S.; Froelich, P.; Monkhorst, H.J. )

    1990-05-01

    In this paper the possibility of fusion/fission chain reactions following d-d source reactions in electrochemical cold fusion experiments have been investigated. The recycling factors for the charged particles in fusion reactions with consumable nuclei deuteron, {sup 6}Li nd {sup 7}Li, are estimated. It is concluded that, based on the established nuclear fusion cross sections and electronic stopping power, the recycling factor is four to five orders of magnitude less than required for close to critical conditions. It is argued that the cross generation of charged particles by neutrons does not play a significant role in this process, even if increased densities at the surface of electrodes do occur.

  4. Adiabatic self-consistent collective path in nuclear fusion reactions

    NASA Astrophysics Data System (ADS)

    Wen, Kai; Nakatsukasa, Takashi

    2017-07-01

    Collective reaction paths for fusion reactions 16O+α →20Ne and 16O+16O→32S are microscopically determined on the basis of the adiabatic self-consistent collective coordinate (ASCC) method. The collective path is maximally decoupled from other intrinsic degrees of freedom. The reaction paths turn out to deviate from those obtained with standard mean-field calculations with constraints on quadrupole and octupole moments. The potentials and inertial masses defined in the ASCC method are calculated along the reaction paths, which leads to the collective Hamiltonian used for calculation of the subbarrier fusion cross sections. The inertial mass inside the Coulomb barrier may have a significant influence on the fusion cross section at the deep subbarrier energy.

  5. Recent developments in heavy-ion fusion reactions

    NASA Astrophysics Data System (ADS)

    Back, B. B.; Esbensen, H.; Jiang, C. L.; Rehm, K. E.

    2014-01-01

    In this review the main advances in heavy-ion fusion research that have taken place over the last decade are addressed. During this period, experimental studies have been extended to deep sub-barrier energies to reveal the unexpected phenomenon of fusion hindrance. The coupled-channels descriptions have been refined to include the effects of nucleon transfer and to account for the fusion hindrance in terms of the ion-ion potential in the strongly overlapping region. Substantial progress has been made in time-dependent Hartree-Fock theory to the point that this approach now can make parameter-free predictions of heavy-ion fusion excitation functions. As several heavy-ion fusion reactions are of crucial importance in late-stage giant-star evolution, these reactions continue to be studied with better experimental and theoretical tools in order to provide improved input to astrophysical models. The effects of loosely bound valence nucleons on the fusion cross sections are the focus of a number of experimental studies involving radioactive beams, which have only recently become available. And finally, as the active field of synthesizing superheavy elements relies on heavy-ion fusion to reach the nuclei of interest, it is important to understand the fusion dynamics that plays a crucial role in both the "cold-fusion" and "hot-fusion" approaches to the superheavy island of stability. Also this area has seen significant progress in several different approaches to the problem of predicting the cross sections for formation and survival of these rare nuclei.

  6. /sup 18/O + /sup 12/C fusion-evaporation reaction

    SciTech Connect

    Heusch, B; Beck, C; Coffin, J P; Freeman, R M; Gallmann, A; Haas, F; Rami, F; Wagner, P; Alburger, D E

    1980-01-01

    A study of the /sup 18/O + /sup 12/C fusion evaporation reaction has been undertaken for 2 reasons: to make a systematic study of the formation cross section for each individual evaporation residue over a broad excitation energy region in the compound nucleus /sup 30/Si:30 to 62 MeV; and to compare all results to fusion-evaporation calculations done in the framework of the Hauser-Feschbach statistical model.

  7. Nucleus-nucleus cold fusion reactions analyzed with the l-dependent ``fusion by diffusion'' model

    NASA Astrophysics Data System (ADS)

    Cap, T.; Siwek-Wilczyńska, K.; Wilczyński, J.

    2011-05-01

    We present a modified version of the Fusion by Diffusion (FBD) model aimed at describing the synthesis of superheavy nuclei in cold fusion reactions, in which a low excited compound nucleus emits only one neutron. The modified FBD model accounts for the angular momentum dependence of three basic factors determining the evaporation residue cross section: the capture cross section σcap(l), the fusion probability Pfus(l), and the survival probability Psurv(l). The fusion hindrance factor, the inverse of Pfus(l), is treated in terms of thermal fluctuations in the shape degrees of freedom and is expressed as a solution of the Smoluchowski diffusion equation. The l dependence of Pfus(l) results from the l-dependent potential energy surface of the colliding system. A new parametrization of the distance of starting point of the diffusion process is introduced. An analysis of a complete set of 27 excitation functions for production of superheavy nuclei in cold fusion reactions, studied in experiments at GSI Darmstadt, RIKEN Tokyo, and LBNL Berkeley, is presented. The FBD model satisfactorily reproduces shapes and absolute cross sections of all the cold fusion excitation functions. It is shown that the peak position of the excitation function for a given 1n reaction is determined by the Q value of the reaction and the height of the fission barrier of the final nucleus. This fact could possibly be used in future experiments (with well-defined beam energy) for experimental determination of the fission barrier heights.

  8. Formation of superheavy nuclei in cold fusion reactions

    SciTech Connect

    Feng Zhaoqing; Jin Genming; Li Junqing; Scheid, Werner

    2007-10-15

    Within the concept of the dinuclear system (DNS), a dynamical model is proposed for describing the formation of superheavy nuclei in complete fusion reactions by incorporating the coupling of the relative motion to the nucleon transfer process. The capture of two heavy colliding nuclei, the formation of the compound nucleus, and the de-excitation process are calculated by using an empirical coupled channel model, solving a master equation numerically and applying statistical theory, respectively. Evaporation residue excitation functions in cold fusion reactions are investigated systematically and compared with available experimental data. Maximal production cross sections of superheavy nuclei in cold fusion reactions with stable neutron-rich projectiles are obtained. Isotopic trends in the production of the superheavy elements Z=110, 112, 114, 116, 118, and 120 are analyzed systematically. Optimal combinations and the corresponding excitation energies are proposed.

  9. Observed Multi-Decade DD and DT Z-Pinch Fusion Rate Scaling in 5 Dense Plasma Focus Fusion Machines

    SciTech Connect

    Hagen, E. C.; Lowe, D. R.; O'Brien, R.; Meehan, B. T.

    2013-06-18

    Dense Plasma Focus (DPF) machines are in use worldwide or a wide variety of applications; one of these is to produce intense, short bursts of fusion via r-Z pinch heating and compression of a working gas. We have designed and constructed a series of these, ranging from portable to a maximum energy storage capacity of 2 MJ. Fusion rates from 5 DPF pulsed fusion generators have been measured in a single laboratory using calibrated activation detectors. Measured rates range from ~ 1015 to more than 1019 fusions per second have been measured. Fusion rates from the intense short (20 – 50 ns) periods of production were inferred from measurement of neutron production using both calibrated activation detectors and scintillator-PMT neutron time of flight (NTOF) detectors. The NTOF detectors are arranged to measure neutrons versus time over flight paths of 30 Meters. Fusion rate scaling versus energy and current will be discussed. Data showing observed fusion cutoff at D-D fusion yield levels of approximately 1*1012, and corresponding tube currents of ~ 3 MA will be shown. Energy asymmetry of product neutrons will also be discussed. Data from the NTOF lines of sight have been used to measure energy asymmetries of the fusion neutrons. From this, center of mass energies for the D(d,n)3He reaction are inferred. A novel re-entrant chamber that allows extremely high single pulse neutron doses (> 109 neutrons/cm2 in 50 ns) to be supplied to samples will be described. Machine characteristics and detector types will be discussed.

  10. Effects of entrance channel on fusion probability in hot fusion reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Su, Jun; Huang, Ching-Yuan; Zhang, Feng-Shou

    2016-12-01

    Within the framework of the dinuclear system (DNS) model, the fusion reactions leading to the compound nuclei 274Hs* and 286Cn* are investigated. The fusion probability as a function of DNS excitation energy is studied. The calculated results are in good agreement with the available experimental data. The obtained results show that the fusion probabilities are obviously enhanced for the reactions located at high place in potential energy surface, although these reactions may have small values of mass asymmetry. It is found that the enhancement is due to the large potential energy of the initial DNS. Supported by Natural Science Foundation of Guangdong Province China (2016A030310208). National Natural Science Foundation of China (11605296, 11405278, 11505150, 11635003), Fundamental Research Funds for the Central Universities (15 lgpy 30) and China Postdoctoral Science Foundation (2015M582730)

  11. Ab initio calculations of light-ion fusion reactions

    SciTech Connect

    Hupin, G.; Quaglioni, S.; Navratil, P.

    2012-10-20

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches. The ab initio No-Core Shell Model/Resonating-Group Method (NCSM/RGM) complements a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. This approach is capable of describing simultaneously both bound and scattering states in light nuclei. Recent applications to light nuclei scattering and fusion reactions relevant to energy production in stars and Earth based fusion facilities, such as the deuterium-{sup 3}He fusion, are presented. Progress toward the inclusion of the three nucleon force into the formalism is outlined.

  12. Dynamical Dipole mode in heavy-ion fusion reactions

    NASA Astrophysics Data System (ADS)

    Parascandolo, C.; Pierroutsakou, D.; Alba, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Agodi, C.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; La Commara, M.; Martin, B.; Mazzocchi, C.; Mazzocco, M.; Rizzo, C.; Romoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifirò, A.; Trimarchi, M.

    2017-06-01

    In this work we give evidence for the first time of the Dynamical Dipole mode in a heavy system in the A˜190 mass region, in both fusion-evaporation and fission events. The 40,48Ca + 152,144Sm reactions at E lab =11(10.1) MeV/nucleon were employed. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.

  13. Analysis of quasifission competition in fusion reactions forming heavy nuclei

    NASA Astrophysics Data System (ADS)

    Hammerton, Kalee; Kohley, Zachary; Morrissey, Dave; Wakhle, Aditya; Stiefel, Krystin; Hinde, David; Dasgupta, Mahananda; Williams, Elizabeth; Simenel, Cedric; Carter, Ian; Cook, Kaitlin; Jeung, Dongyun; Luong, Duc Huy; McNeil, Steven; Palshetkar, Chandani; Rafferty, Dominic

    2015-10-01

    Heavy-ion fusion reactions have provided a mechanism for the production of superheavy elements allowing for the extension of both the periodic table and chart of the nuclides. However, fusion of the projectile and target, forming a compound nucleus, is hindered by orders of magnitude by the quasifission process in heavy systems. In order to fully understand this mechanism, and make accurate predictions for superheavy element production cross sections, a clear description of the interplay between the fusion-fission and quasifission reaction channels is necessary. The mass-angle distributions of fragments formed in 8 different Cr + W reactions were measured at the Australia National University in order to explore the N/Z dependence of the quasifission process. Two sets of data were measured: one at a constant energy relative to the fusion barrier and one at a constant compound nucleus excitation energy. The results of this analysis will provide insight into the effect of using more neutron-rich beams in superheavy element production reactions.

  14. The fusion rate in the transmission resonance model

    SciTech Connect

    Jaendel, M. )

    1992-03-01

    Resonant transmission of deuterons through a chain of target deuterons in a metal matrix has been suggested as an explanation for the cold fusion phenomena. In this paper the fusion rate in such transmission resonance models is estimated, and the basic physical constraints are discussed. The dominating contribution to the fusion yield is found to come from metastable states. The fusion rate is well described by the Wentzel-Kramer-Brillouin approximation and appears to be much too small to explain the experimental anomalies.

  15. Nucleus-nucleus cold fusion reactions analyzed with the l-dependent 'fusion by diffusion' model

    SciTech Connect

    Cap, T.; Siwek-Wilczynska, K.; Wilczynski, J.

    2011-05-15

    We present a modified version of the Fusion by Diffusion (FBD) model aimed at describing the synthesis of superheavy nuclei in cold fusion reactions, in which a low excited compound nucleus emits only one neutron. The modified FBD model accounts for the angular momentum dependence of three basic factors determining the evaporation residue cross section: the capture cross section {sigma}{sub cap}(l), the fusion probability P{sub fus}(l), and the survival probability P{sub surv}(l). The fusion hindrance factor, the inverse of P{sub fus}(l), is treated in terms of thermal fluctuations in the shape degrees of freedom and is expressed as a solution of the Smoluchowski diffusion equation. The l dependence of P{sub fus}(l) results from the l-dependent potential energy surface of the colliding system. A new parametrization of the distance of starting point of the diffusion process is introduced. An analysis of a complete set of 27 excitation functions for production of superheavy nuclei in cold fusion reactions, studied in experiments at GSI Darmstadt, RIKEN Tokyo, and LBNL Berkeley, is presented. The FBD model satisfactorily reproduces shapes and absolute cross sections of all the cold fusion excitation functions. It is shown that the peak position of the excitation function for a given 1n reaction is determined by the Q value of the reaction and the height of the fission barrier of the final nucleus. This fact could possibly be used in future experiments (with well-defined beam energy) for experimental determination of the fission barrier heights.

  16. Additive effects on the energy barrier for synaptic vesicle fusion cause supralinear effects on the vesicle fusion rate

    PubMed Central

    Schotten, Sebastiaan; Meijer, Marieke; Walter, Alexander Matthias; Huson, Vincent; Mamer, Lauren; Kalogreades, Lawrence; ter Veer, Mirelle; Ruiter, Marvin; Brose, Nils; Rosenmund, Christian

    2015-01-01

    The energy required to fuse synaptic vesicles with the plasma membrane (‘activation energy’) is considered a major determinant in synaptic efficacy. From reaction rate theory, we predict that a class of modulations exists, which utilize linear modulation of the energy barrier for fusion to achieve supralinear effects on the fusion rate. To test this prediction experimentally, we developed a method to assess the number of releasable vesicles, rate constants for vesicle priming, unpriming, and fusion, and the activation energy for fusion by fitting a vesicle state model to synaptic responses induced by hypertonic solutions. We show that complexinI/II deficiency or phorbol ester stimulation indeed affects responses to hypertonic solution in a supralinear manner. An additive vs multiplicative relationship between activation energy and fusion rate provides a novel explanation for previously observed non-linear effects of genetic/pharmacological perturbations on synaptic transmission and a novel interpretation of the cooperative nature of Ca2+-dependent release. DOI: http://dx.doi.org/10.7554/eLife.05531.001 PMID:25871846

  17. Macroscopic theory of heavy-ion fusion reactions

    NASA Astrophysics Data System (ADS)

    Hong, S.-W.; Lee, Y. J.; Kim, B. T.; Cha, D.

    1989-05-01

    We have studied the heavy-ion fusion reactions by a macroscopic model which was proposed by Bertsch several years ago. It employed the Newtonian dynamics and was constructed in such a way that the essential features of time-dependent Hartree-Fock results could be reproduced. We have applied the model to fusion of light heavy-ion systems leading to the same compound nucleus 56Ni. It is shown that the model, being incorporated with the angular-momentum-dependent extra-push energy of Swiatecki, can account well for the fusion cross sections up to very high energies where cross section decreases as energy increases, and that the main reason for the decrease is the opening of the low angular momentum window.

  18. Production cross sections of superheavy elements Z =119 and 120 in hot fusion reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Xie, Wen-Jie; Zhang, Feng-Shou

    2014-02-01

    The production cross sections of superheavy nuclei in hot fusion reactions are investigated systematically. In hot fusion reactions, the capture cross section can be obtained by calculating the weighted average of the transmission probability for different orientations of deformed colliding nuclei. An analytical formula for calculating the value of the fusion probability is proposed, which is suitable for both hot and cold fusion reactions. The orientation effects are considered empirically in calculating the fusion probability. The method proposed in the present work reproduces the measured evaporation residue (ER) cross sections in hot fusion reactions acceptably well. The formula also gives reasonable results for fusion probability in cold fusion reactions. Using this method the evaporation residue cross sections for synthesizing Z =119 and 120 are predicted. It is found that for hot fusion reaction's larger maximal ER cross section of the 4n channel corresponds to lower optimal incident energy.

  19. Angular momentum effects in fusion-fission and fusion-evaporation reactions

    SciTech Connect

    Plasil, F.

    1980-01-01

    The study of heavy-ion fusion reactions is complicated by the possible contributions of several mechanisms. The various types of heavy-ion-induced fission are discussed. Then compound-nucleus fission is considered with reference to fission barriers deduced from heavy-ion-induced fission. Next, the problems associated with measured values of evaporation-residue cross sections and the angular momentum dependence of incomplete fusion are examined. Finally, the de-excitation of compound nuclei is again taken up, this time with reference to the greatly enhanced ..cap alpha.. emission predicted on the basis of the rotating liquid drop model. 24 figures. (RWR)

  20. Reproducible cold fusion reaction using a complex cathode

    SciTech Connect

    Arata, Y.; Zhang, Y.C. )

    1992-09-01

    This paper discusses a new complex cathode which was developed, consisting of a nickel (or palladium) rod with a palladium layer applied by plasma spraying. High reproducibility of a cold fusion reaction is confirmed by using this cathode. The palladium layer activates the surface functions of the deuterated cathode, and reliable evidence is obtained that a new type of heat generation occurred in the complex cathode.

  1. Fusion rates for hydrogen isotopic molecules of relevance for 'cold fusion'

    NASA Astrophysics Data System (ADS)

    Szalewicz, K.; Morgan, J. D., III; Monkhorst, H. J.

    1989-09-01

    In response to the recent announcements of evidence for room-temperature fusion in the electrolysis of D2O, an analysis is presented of how the fusion rate depends on the reduced mass of the fusing nuclei, the effective mass of a 'heavy' electron, and the degree of vibrational excitation. The results have been obtained both by accurately solving the Schroedinger equation for the hydrogen molecule and by using the WKB approximation. It is found that in light of the reported d-d fusion rate, the excess heat in the experiment by Fleischmann, Pons, and Hawkins is difficult to explain in terms of conventional nuclear processes.

  2. The Rate Laws for Reversible Reactions.

    ERIC Educational Resources Information Center

    King, Edward L.

    1986-01-01

    Provides background information for teachers on the rate laws for reversible reactions. Indicates that although prediction of the form of the rate law for a reverse reaction given the rate law for the forward reaction is not certain, the number of possibilities is limited because of relationships described. (JN)

  3. Secondary Nuclear Reactions in Magneto-Inertial Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Knapp, Patrick

    2014-10-01

    The goal of Magneto-Inertial Fusion (MIF) is to relax the extreme pressure requirements of inertial confinement fusion by magnetizing the fuel. Understanding the level of magnetization at stagnation is critical for charting the performance of any MIF concept. We show here that the secondary nuclear reactions in magnetized deuterium plasma can be used to infer the magnetic field-radius product (BR), the critical confinement parameter for MIF. The secondary neutron yields and spectra are examined and shown to be extremely sensitive to BR. In particular, embedded magnetic fields are shown to affect profoundly the isotropy of the secondary neutron spectra. Detailed modeling of these spectra along with the ratio of overall secondary to primary neutron yields is used to form the basis of a diagnostic technique used to infer BR at stagnation. Effects of gradients in density, temperature and magnetic field strength are examined, as well as other possible non-uniform fuel configurations. Computational results employing a fully kinetic treatment of charged reaction product transport and Monte Carlo treatment of secondary reactions are compared to results from recent experiments at Sandia National Laboratories' Z machine testing the MAGnetized Liner Inertial Fusion (MagLIF) concept. The technique reveals that the charged reaction products were highly magnetized in these experiments. Implications for eventual ignition-relevant experiments with deuterium-tritium fuel are discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  4. Formation of superheavy elements in cold fusion reactions

    NASA Astrophysics Data System (ADS)

    Smolańczuk, Robert

    2001-04-01

    We calculate the formation cross sections of transactinides (superheavy elements), as well as heavy actinides (No and Lr), which have been or might be obtained in fusion reactions with the evaporation of only one neutron. We use both more realistic fusion barrier and survival probability of the compound nucleus in comparison with the original phenomenological model [Phys. Rev. C 59, 2634 (1999)] that prompted the Berkeley experiment on the synthesis of a new superheavy element 118 [Phys. Rev. Lett. 83, 1104 (1999)]. Calculations are performed for asymmetric and symmetric target-projectile combinations and for reactions with stable and radioactive-ion beams. The formation cross sections measured at GSI-Darmstadt for transactinides and heavy actinides, as well as that for superheavy element 118 reported by the LBNL-Berkeley group, are reproduced within a factor of 2.4, on average. Based on the obtained relatively large cross sections, we predict that optimal reactions with stable beams for the synthesis of so far unobserved superheavy elements 119, 120, and 121 are 209Bi(86Kr, 1n)294119, 208Pb(88Sr, 1n)295120, and 209Bi(88Sr, 1n)296121, respectively. This is because of the magic of both the target and the projectile that leads to larger Q value and, consequently, lower effective fusion barrier with larger transmission probability. The same effect is responsible for relatively large cross sections predicted for the symmetric reactions 136Xe(124Sn, 1n)259Rf, 136Xe(136Xe, 1n)271Hs,138Ba(136Xe, 1n)273110, and 140Ce(136Xe, 1n)275112. Although shell effects in the magic nuclei 124Sn, 136Xe, 138Ba, and 140Ce are not as strong as in 208Pb and 209Bi, they act on both the target and the projectile and lead to the prediction of measurable cross sections.

  5. A New Look at Reaction Rates

    NASA Astrophysics Data System (ADS)

    Cvitas, Tomislav

    1999-11-01

    Both rates of radioactive decays and rates of chemical reactions can be thought of as numbers of transformations per time. The rate of reaction, as an intensive quantity characteristic of the process, is obtained by dividing the amount of chemical transformations per time by the volume of the reaction system. The practical definition of the reaction rate found in the literature can then be derived by defining the stoichiometric numbers as changes in the number of specific molecules taking part in the reaction per chemical transformation. The name concentration of chemical transformations is introduced for what was previously called reaction variable. It is suggested that the conceptual definition of the advancement of reaction and reaction rate be introduced in general chemistry courses.

  6. New information on survival probabilities in hot fusion reactions

    NASA Astrophysics Data System (ADS)

    Loveland, Walter

    2014-09-01

    Recently we studied the fission-neutron emission competition in highly excited (E* = 63 MeV) 274Hs (Z = 108) (where the fission barrier is due to shell effects) formed by a hot fusion reaction. At this excitation energy, these shell effects are expected to be ``washed out'' leaving a barrier height of <= 1 MeV. Matching cross bombardments (26Mg + 248Cm and 25Mg + 248Cm) were used to identify the properties of first chance fission of 274Hs. A Harding-Farley analysis of the fission neutrons emitted in the 25,26Mg + 248Cm reaction was performed to identify the pre- and post-scission components of the neutron multiplicities in each system. (Γn/ Γt) for the first chance fission of 274Hs is 0.89 +/- 0.13, i.e., ~ 90% of the highly excited nuclei survive. The high value of that survival probability is due to dissipative effects (Kramers) during de-excitation. A proper description of the survival probabilities of excited superheavy nuclei formed in hot fusion reactions requires consideration of both dynamic and static (shell-related) effects. A re-analysis of several hot fusion survival probabilities under these constraints is presented. Recently we studied the fission-neutron emission competition in highly excited (E* = 63 MeV) 274Hs (Z = 108) (where the fission barrier is due to shell effects) formed by a hot fusion reaction. At this excitation energy, these shell effects are expected to be ``washed out'' leaving a barrier height of <= 1 MeV. Matching cross bombardments (26Mg + 248Cm and 25Mg + 248Cm) were used to identify the properties of first chance fission of 274Hs. A Harding-Farley analysis of the fission neutrons emitted in the 25,26Mg + 248Cm reaction was performed to identify the pre- and post-scission components of the neutron multiplicities in each system. (Γn/ Γt) for the first chance fission of 274Hs is 0.89 +/- 0.13, i.e., ~ 90% of the highly excited nuclei survive. The high value of that survival probability is due to dissipative effects (Kramers

  7. Sparking fusion: A step toward laser-initiated nuclear fusion reactions

    SciTech Connect

    Peterson, I.

    1996-10-19

    The fusion furnace at the sun`s core burns hydrogen to make helium. Each time two hydrogen nuclei, or protons, merge to create a deuterium nucleus, the process releases energy. A chain of additional energy-producing nuclear reactions then converts deuterium into helium. Because protons, with their like electric charges, naturally repel each other, high temperatures and tremendous pressures are needed to force them together closely enough to initiate and sustain the reactions. These mergers cost energy initially, but the return on that investment proves prodigious. On Earth, such an energy payoff has been achieved only in the uncontrolled fury of a detonated hydrogen bomb. The vision of harnessing and controlling nuclear fusion as a terrestrial energy source has yet to be fulfilled. The proposed National Ignition Facility (NIF) represents an ambitious effort to use powerful lasers to deposit sufficient energy in a small capsule of nuclear fuel to trigger fusion. The main justification for the project is to ensure that a core group of physicists and engineers maintains its expertise in the physics of nuclear weapons. This article presents both the scientific and political sides of the NIF facility.

  8. Impact of Reaction Cross Section on the Unified Description of Fusion Excitation Function

    NASA Astrophysics Data System (ADS)

    Basrak, Z.; Eudes, P.; de la Mota, V.; Sébille, F.; Royer, G.

    A systematics of over 300 complete and incomplete fusion cross section data points covering energies beyond the barrier for fusion is presented. Owing to a usual reduction of the fusion cross sections by the total reaction cross sections and an original scaling of energy, a fusion excitation function common to all the data points is established. A universal description of the fusion exci- tation function relying on basic nuclear concepts is proposed and its dependence on the reaction cross section used for the cross section normalization is discussed. The pioneering empirical model proposed by Bass in 1974 to describe the complete fusion cross sections is rather successful for the incomplete fusion too and provides cross section predictions in satisfactory agreement with the observed universality of the fusion excitation function. The sophisticated microscopic transport DYWAN model not only reproduces the data but also predicts that fusion reaction mechanism disappears due to weakened nuclear stopping power around the Fermi energy.

  9. Clinical Outcome and Fusion Rate Following Simultaneous Subtalar Fusion and Total Ankle Arthroplasty.

    PubMed

    Usuelli, Federico G; Maccario, Camilla; Manzi, Luigi; Gross, Christopher Edward

    2016-07-01

    Patients with arthritis or severe dysfunction involving both the ankle and subtalar joints can benefit from tibiotalocalcaneal (TTC) arthrodesis or total ankle replacement and subtalar fusion. TTC fusion is considered by many as a salvage operation resulting in a stiff ankle and hindfoot, considerably limiting global foot function. With the evolution of prosthetic design and operative techniques, total ankle replacement (TAR) has become a reasonable alternative to arthrodesis. The aim of this study was to investigate the fusion rate of the subtalar joint in patients simultaneously treated with total ankle replacement (TAR) and subtalar joint fusion. This study included 25 patients who underwent primary TAR and simultaneous subtalar fusion between May 2011 and November 2014. Sixteen males (64%) and 9 females (36%) were enrolled with a mean age of 58 years (25-82). Patients were clinically assessed preoperatively and at 6 and 12 months postoperatively. Total follow-up time was 24.2 ± 11.6 months. Radiographic examination included a postoperative computed tomographic (CT) scan obtained 12 months after surgery. Three surgeons independently reviewed the CT scans and interobserver reliability was calculated. Functional scores were also assessed. At 12 months postoperatively, the subtalar fusion rate in patients treated with TAR and simultaneous subtalar fusion was 92%. There was a statistically significant increase in American Orthopaedic Foot & Ankle Society ankle/hindfoot score from 27.9 to 75.1. Ankle range of motion significantly increased from 12 to 32.8 degrees. Additionally, there was a statistically significant decrease in visual analog scale pain score from 8.6 to 2.1. TAR and simultaneous subtalar joint fusion were reliable procedures for the treatment of ankle and subtalar joint arthritis. Furthermore, CT scans showed an excellent reliability among orthopedic surgeons in determining the degree of successful fusion of subtalar arthrodesis. Level IV, case

  10. A Radiological Comparison of Anterior Fusion Rates in Anterior Lumbar Interbody Fusion

    PubMed Central

    McCarthy, M. J. H.; Ng, L.; Vermeersch, G.; Chan, D.

    2012-01-01

    Aim To compare anterior fusion in standalone anterior lumbar interbody fusion (ALIF) using cage and screw constructs and anterior cage–alone constructs with posterior pedicle screw supplementation but without posterior fusion. Methods Eighty-five patients underwent single- or two-level ALIF procedure for degenerative disk disease or lytic spondylolisthesis (SPL). Posterior instrumentation was performed without posterior fusion in all cases of lytic SPL and when the anterior cage used did not have anterior screw through cage fixation. Results Seventy (82%) patients had adequate radiological follow-up at a mean of 19 months. Forty patients had anterior surgery alone (24 single level and 16 two levels) and 30 had front-back surgery (15 single level and 15 two levels). Anterior locked pseudarthrosis was only seen in the anterior surgery–alone group when using the STALIF cage (Surgicraft, Worcestershire, UK) (37 patients). This occurred in five of the single-level surgeries (5/22) and nine of the two-level surgeries (9/15). Fusion was achieved in 100% of the front-back group and only 65% (26/40) of the anterior surgery–alone group. Conclusion Posterior pedicle screw supplementation without posterolateral fusion improves the fusion rate of ALIF when using anterior cage and screw constructs. We would recommend supplementary posterior fixation especially in cases where more than one level is being operated. PMID:24353968

  11. Matched Comparison of Fusion Rates between Hydroxyapatite Demineralized Bone Matrix and Autograft in Lumbar Interbody Fusion

    PubMed Central

    Kim, Dae Hwan; Lee, Nam; Shin, Dong Ah; Yi, Seong; Kim, Keung Nyun

    2016-01-01

    Objective To compare the fusion rate of a hydroxyapatite demineralized bone matrix (DBM) with post-laminectomy acquired autograft in lumbar interbody fusion surgery and to evaluate the correlation between fusion rate and clinical outcome. Methods From January 2013 to April 2014, 98 patients underwent lumbar interbody fusion surgery with hydroxyapatite DBM (HA-DBM group) in our institute. Of those patients, 65 received complete CT scans for 12 months postoperatively in order to evaluate fusion status. For comparison with autograft, we selected another 65 patients who underwent lumbar interbody fusion surgery with post-laminectomy acquired autograft (Autograft group) during the same period. Both fusion material groups were matched in terms of age, sex, body mass index (BMI), and bone mineral density (BMD). To evaluate the clinical outcomes, we analyzed the results of visual analogue scale (VAS), Oswestry Disability Index (ODI), and Short Form Health Survey (SF-36). Results We reviewed the CT scans of 149 fusion levels in 130 patients (HA-DBM group, 75 levels/65 patients; Autograft group, 74 levels/65 patients). Age, sex, BMI, and BMD were not significantly different between the groups (p=0.528, p=0.848, p=0.527, and p=0.610, respectively). The HA-DBM group showed 39 of 75 fused levels (52%), and the Autograft group showed 46 of 74 fused levels (62.2%). This difference was not statistically significant (p=0.21). In the HA-DBM group, older age and low BMD were significantly associated with non-fusion (61.24 vs. 66.68, p=0.027; -1.63 vs. -2.29, p=0.015, respectively). VAS and ODI showed significant improvement after surgery when fusion was successfully achieved in both groups (p=0.004, p=0.002, HA-DBM group; p=0.012, p=0.03, Autograft group). Conclusion The fusion rates of the hydroxyapatite DBM and Autograft groups were not significantly different. In addition, clinical outcomes were similar between the groups. However, older age and low BMD are risk factors that might

  12. Detailed studies of survival probabilities in hot fusion reactions

    NASA Astrophysics Data System (ADS)

    Yao, Liangyu; Yanez, Ricardo; Loveland, Walter

    2011-10-01

    In the synthesis of new heavy nuclei by hot fusion reactions, the cross section for producing a new heavy nucleus, σEVR, can be represented as σEVR(EC.M.)=&Jmaxcirc;J=0σCN(Ec.m.,J) .Wsur(Ec.m.,J) where σCN is the complete fusion cross section and Wsur is the survival probability of the completely fused system. The survival probability is essentially the probability of de-exciting by neutron emission instead of fission. In this work, we are attempting to measure the survival probability, Wsur, for the first chance fission of excited Hs nuclei. We form the Hs nuclei using the ^25,26Mg + ^248Cm reaction. We measure the neutrons associated with pre-fission emission and those emitted by the fission fragments after fission using six BC501 neutron detectors and six silicon fission fragment detectors. We measure the angular distribution of the emitted neutrons and are able to separate the pre- and post-fission neutrons.

  13. Measurement of the Survival Probabilities for Hot Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Yanez, R.; Loveland, W.; Yao, L.; Barrett, J. S.; Zhu, S.; Back, B. B.; Khoo, T. L.; Alcorta, M.; Albers, M.

    2014-04-01

    We have studied the fission-neutron emission competition in highly excited Hs274 (Z =108) (where the fission barrier is due to shell effects) formed by a hot fusion reaction. Matching cross bombardments (Mg26+Cm248 and Mg25+Cm248) were used to identify the properties of first chance fission of Hs274. A Harding-Farley analysis of the fission neutrons emitted in the Mg25,26+Cm248 was performed to identify the prescission and postscission components of the neutron multiplicities in each system. (Γn/Γt) for the first chance fission of Hs274 (E*=63 MeV) is 0.89±0.13; i.e., ˜90% of the highly excited nuclei survive. The high value of that survival probability is due to dissipative effects during deexcitation. A proper description of the survival probabilities of excited superheavy nuclei formed in hot fusion reactions requires consideration of both dynamic and static (shell-related) effects.

  14. Astrophysical S factors for fusion reactions involving C, O, Ne, and Mg isotopes

    SciTech Connect

    Beard, M.; Afanasjev, A.V.; Chamon, L.C.; Gasques, L.R.; Wiescher, M.; Yakovlev, D.G.

    2010-09-15

    Using the Sao Paulo potential and the barrier penetration formalism we have calculated the astrophysical factor S(E) for 946 fusion reactions involving stable and neutron-rich isotopes of C, O, Ne, and Mg for center-of-mass energies E varying from 2 to {approx}18-30 MeV (covering the range below and above the Coulomb barrier). We have parameterized the energy dependence, S(E), by an accurate universal 9-parameter analytic expression and present tables of fit parameters for all the reactions. We also discuss the reduced 3-parameter version of our fit which is highly accurate at energies below the Coulomb barrier, and outline the procedure for calculating the reaction rates. The results can be easily converted to thermonuclear or pycnonuclear reaction rates to simulate various nuclear burning phenomena, in particular, stellar burning at high temperatures and nucleosynthesis in high density environments.

  15. Formation of superheavy elements in cold fusion reactions

    SciTech Connect

    Smolanczuk, Robert

    2001-04-01

    We calculate the formation cross sections of transactinides (superheavy elements), as well as heavy actinides (No and Lr), which have been or might be obtained in fusion reactions with the evaporation of only one neutron. We use both more realistic fusion barrier and survival probability of the compound nucleus in comparison with the original phenomenological model [Phys. Rev. C 59, 2634 (1999)] that prompted the Berkeley experiment on the synthesis of a new superheavy element 118 [Phys. Rev. Lett. 83, 1104 (1999)]. Calculations are performed for asymmetric and symmetric target-projectile combinations and for reactions with stable and radioactive-ion beams. The formation cross sections measured at GSI-Darmstadt for transactinides and heavy actinides, as well as that for superheavy element 118 reported by the LBNL-Berkeley group, are reproduced within a factor of 2.4, on average. Based on the obtained relatively large cross sections, we predict that optimal reactions with stable beams for the synthesis of so far unobserved superheavy elements 119, 120, and 121 are {sup 209}Bi({sup 86}Kr, 1n){sup 294}119, {sup 208}Pb({sup 88}Sr, 1n){sup 295}120, and {sup 209}Bi({sup 88}Sr, 1n){sup 296}121, respectively. This is because of the magic of both the target and the projectile that leads to larger Q value and, consequently, lower effective fusion barrier with larger transmission probability. The same effect is responsible for relatively large cross sections predicted for the symmetric reactions {sup 136}Xe({sup 124}Sn, 1n){sup 259}Rf, {sup 136}Xe({sup 136}Xe, 1n){sup 271}Hs,{sup 138}Ba({sup 136}Xe, 1n){sup 273}110, and {sup 140}Ce({sup 136}Xe, 1n){sup 275}112. Although shell effects in the magic nuclei {sup 124}Sn, {sup 136}Xe, {sup 138}Ba, and {sup 140}Ce are not as strong as in {sup 208}Pb and {sup 209}Bi, they act on both the target and the projectile and lead to the prediction of measurable cross sections.

  16. Spin polarization effects in the /sup 3/H(d,n)/sup 4/He fusion reaction

    SciTech Connect

    Conzett, H.E.; Rioux, C.

    1985-06-01

    A recent investigation has shown that the /sup 3/H(d,n)/sup 4/He fusion reaction rate could be enhanced by a factor of 3/2 if the fusion plasma consisted of both polarized deuterons and tritons, forming exclusively the channel-spin S = 3/2, J = 3/2/sup +/ state. This result follows simply from the statistical weights of the quartet S = 3/2 and doublet S = 1/2 initial states, with the assumption of the single J = 3/2/sup +/ reaction amplitude. Since, with a small but nonzero J = 1/2/sup +/ amplitude, the maximum enhancement of the reaction occurs at the peak of the J = 3/2/sup +/ resonance, corresponding to a deuteron lab energy of 107 keV, it is of obvious interest to know what the enhancement would be at the lower energies that are typical of fusion plasmas. We are able to address this question by extending earlier calculations which gave the values of all of the spin-polarization observables at this J = 3/2/sup +/ resonance in both the /sup 3/H(d,n)/sup 4/He and the /sup 3/He(d,p)/sup 4/He reactions.

  17. Reaction Order Ambiguity in Integrated Rate Plots

    ERIC Educational Resources Information Center

    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…

  18. Reaction Order Ambiguity in Integrated Rate Plots

    ERIC Educational Resources Information Center

    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…

  19. Redox reaction rates using potentiostatic coulometry

    SciTech Connect

    Ramette, R.W.; Harris, R.Z.; Bengali, A.A.; Noll, R.J.

    1987-01-01

    A new method based on potentiostatic coulometry was used to study the kinetics of the aqueous redox reactions between the ions chlorate/iodide, bromate/iodide, and bromate/bromide. The halogen product was continuously and rapidly reduced back to halide at a large platinum gauze cathode, the current being a direct measure of reaction rate and the accumulated charge serving to measure the extent of reaction. The reactions were studied at several temperatures, and activation entropies and enthalpies were calculated.

  20. Reaction rates for reaction-diffusion kinetics on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Hellander, Stefan; Petzold, Linda

    2017-02-01

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  1. pH & Rate of Enzymatic Reactions.

    ERIC Educational Resources Information Center

    Clariana, Roy B.

    1991-01-01

    A quantitative and inexpensive way to measure the rate of enzymatic reaction is provided. The effects of different pH levels on the reaction rate of an enzyme from yeast are investigated and the results graphed. Background information, a list of needed materials, directions for preparing solutions, procedure, and results and discussion are…

  2. pH & Rate of Enzymatic Reactions.

    ERIC Educational Resources Information Center

    Clariana, Roy B.

    1991-01-01

    A quantitative and inexpensive way to measure the rate of enzymatic reaction is provided. The effects of different pH levels on the reaction rate of an enzyme from yeast are investigated and the results graphed. Background information, a list of needed materials, directions for preparing solutions, procedure, and results and discussion are…

  3. Fusion by diffusion. II. Synthesis of transfermium elements in cold fusion reactions

    SciTech Connect

    Swiatecki, W.J.; Siwek-Wilczynska, K.; Wilczynski, J.

    2005-01-01

    We describe a method of estimating cross sections for the synthesis of very heavy nuclei by the fusion of two lighter ones. The cross section is considered to be the product of three factors: the cross section for the projectile to overcome the Coulomb barrier, the probability that the resulting composite nucleus reaches the compound nucleus configuration by a shape fluctuation treated as a diffusion of probability in one dimension, and the probability that the excited compound nucleus survives fission. Semi-empirical formulas for the mean Coulomb barrier height and its distribution around the mean are constructed. After overcoming the Coulomb barrier the system is assumed to be injected into an 'asymmetric fission valley' by a rapid growth of the neck between the target and projectile at approximately frozen asymmetry and elongation. Diffusion in the elongation coordinate in this valley can occasionally bring the system over the saddle separating the injection point from the compound nucleus configuration. This is the stage that accounts for the hindrance to fusion observed for very heavy reacting systems. The competition between deexcitation of the compound nucleus by neutron emission and fission is treated by standard methods, but an interesting insight allows one to predict in an elementary way the location of the maximum in the resulting excitation function. Adjusting one parameter in the theory causes the calculated peak cross sections to agree within about a factor of 2 or so with 12 measured or estimated values for 'cold' one-neutron-out reactions where targets of {sup 208}Pb and {sup 209}Bi are bombarded with projectiles ranging from {sup 48}Ca to {sup 70}Zn. The centroids of the excitation functions agree with theory to within 1 or 2 MeV for the six cases where they have been determined, and their widths are reproduced. 'Hot' fusion reactions, where several neutrons are emitted, are not treated, except that a comparison is made between the hindrance

  4. Effective reaction rates for diffusion-limited reaction cycles

    NASA Astrophysics Data System (ADS)

    Nałecz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miekisz, Jacek; Lipniacki, Tomasz

    2015-12-01

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.

  5. Effective reaction rates for diffusion-limited reaction cycles.

    PubMed

    Nałęcz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miękisz, Jacek; Lipniacki, Tomasz

    2015-12-07

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.

  6. Enhancement of Fusion Rate by Superthermal Tritium Ions

    NASA Astrophysics Data System (ADS)

    Castaldo, Carmine; Cardinali, Alessandro; Marinucci, Massimo

    2011-10-01

    We propose a new concept of a nuclear fusion reactor. It is based on the enhancement of the DT fusion rate in tokamak plasmas by a superthermal population of Tritium ions heated by ICRH. It was already shown that break-even conditions might be reached [C. Castaldo and A. Cardinali, Phys. Plasmas 17, 072513 (2010)]. Here we show that Q ~20, suitable for nuclear fusion power station, can be achieved in a compact tokamak configuration (major radius R=160cm, minor radius a=55cm, elongation k=1.9, triangularity δ=0.4, q95=3.5), operating with IP=8MA plasma current, BT=11.3T toroidal field, line averaged plasma density n=5X1020m-3, and 40% D, 35% H, 25% T concentrations of the Hydrogen isotopes. The burning plasma is obtained by the injection of 15 MW ICRF power, coupled by six antennas, with radiating areas of 0.25m2, at the operating frequency f=125 MHz and toroidal wave number n//=4. The heating scenario has been analyzed by the code TORIC, and approximated analytical equilibria are considered. As a result the total fusion power expected for the proposed scenario is about 350MW, with Q ~20, assuming that at least 70% of the fusion power carried by the α particles is absorbed by the electrons in the plasma core so that the expected central plasma temperature is about 10keV.

  7. Graft position and fusion rate following arthroscopic Latarjet.

    PubMed

    Casabianca, Laurent; Gerometta, Antoine; Massein, Audrey; Khiami, Frederic; Rousseau, Romain; Hardy, Alexandre; Pascal-Moussellard, Hugues; Loriaut, Philippe

    2016-02-01

    The arthroscopic Latarjet procedure is recently becoming an increasingly popular technique. Nevertheless, position and fusion of the autograft had not been well studied yet. The purpose of this study was to assess the positioning of the coracoid graft and the fusion rate on CT scan in the arthroscopic Latarjet procedure. The study design was a prospective series of 19 consecutive patients who received arthroscopic Latarjet procedure. Radiological assessment on CT scan performed 3 months post-operatively included an analysis of the fusion and the position of the coracoid bone graft using a validated method. 02:30-04:20 was considered an ideal positioning in the sagittal view. In the axial view, the positioning was considered as flush, congruent, medial, too medial, or lateral. The median age of patients was 27.6 (±6.9). Mean operative time was of 161 min ±34.8. The fusion rate was of 78 %. Coracoid grafts were positioned 01:52 h (56° ± 14°) to 4:04 h (122° ± 12.5°). In the axial view, 32 % of the grafts positioning were considered as flush, 38 % as congruent, 30 % as medial, and 6 % too medial. No lateral position was noted. Two complications occurred, one graft fracture during screwing requiring opening conversion and an early case of osteolysis in a medial-positioned graft. The arthroscopic Latarjet procedure is a technically challenging technique that provides satisfactory fusion rate and graft positioning with a low complication rate. The clinical importance of this study lies in the observation that it is the first study to evaluate the position of the coracoid bone graft in arthroscopic Latarjet according to a detailed and validated method. IV.

  8. Astrophysical Reaction Rates Obtained By Indirect Techniques

    SciTech Connect

    Tribble, R. E.; Al-Abdullah, T.; Alharbi, A.; Banu, A.; Chen, X.; Clark, H. L.; Fu, C.; Gagliardi, C. A.; Hardy, J. C.; Iacob, V. E.; Lui, Y.-W.; McCleskey, M.; Mukhamedzhanov, A.; Nica, N.; Park, H. I.; Roeder, B.; Simmons, E.; Tabacaru, G.; Tokimoto, Y.; Trache, L.

    2010-08-12

    Indirect techniques have been used to obtain information about reaction rates for several proton capture reactions that occur on short-lived nuclei. The techniques used to carry out the measurements are reviewed and the results obtained are presented. Also future prospects for further measurements with a new facility, T-REX are discussed.

  9. The Kinetic Rate Law for Autocatalytic Reactions.

    ERIC Educational Resources Information Center

    Mata-Perez, Fernando; Perez-Benito, Joaquin F.

    1987-01-01

    Presented is a method of obtaining accurate rate constants for autocatalytic reactions. The autocatalytic oxidation of dimethylamine by permanganate ion in aqueous solution is used as an example. (RH)

  10. Calibrating reaction rates for the CREST model

    NASA Astrophysics Data System (ADS)

    Handley, Caroline A.; Christie, Michael A.

    2017-01-01

    The CREST reactive-burn model uses entropy-dependent reaction rates that, until now, have been manually tuned to fit shock-initiation and detonation data in hydrocode simulations. This paper describes the initial development of an automatic method for calibrating CREST reaction-rate coefficients, using particle swarm optimisation. The automatic method is applied to EDC32, to help develop the first CREST model for this conventional high explosive.

  11. ACTIVE: a program to calculate and plot reaction rates from ANISN calculated fluxes

    SciTech Connect

    Judd, J.L.

    1981-12-01

    The ACTIVE code calculates spatial heating rates, tritium production rates, neutron reaction rates, and energy spectra from particle fluxes calculated by ANISN. ACTIVE has a variety of input options including the capability to plot all calculated spatial distributions. The code was primarily designed for use with fusion first wall/blanket systems, but could be applied to any one-dimensional problem.

  12. Rate constant for the Cl + Chloroform reaction

    SciTech Connect

    Brahan, K.M.; Hewitt, A.D.; Boone, G.D.

    1995-12-01

    The rate constant for the reaction of Cl with chloroform has been measured relative to the reaction of Cl with methane, methyl chloride, and carbon monoxide using long path FTIR spectroscopy. Our measured rate constant at 298 K and 1 atm of (1.2{plus_minus}0.1)x10{sup -13} cm{sup 3}molecule{sup -1}sec{sup -1} is 50% higher than that recommended for stratospheric modeling; however, it is within experimental error of the values measured by Clyne and Walker and by Watson. The implications of this reaction on the budgets of chloroform and phosgene in the troposphere will be discussed.

  13. Selected component failure rate values from fusion safety assessment tasks

    SciTech Connect

    Cadwallader, L.C.

    1998-09-01

    This report is a compilation of component failure rate and repair rate values that can be used in magnetic fusion safety assessment tasks. Several safety systems are examined, such as gas cleanup systems and plasma shutdown systems. Vacuum system component reliability values, including large vacuum chambers, have been reviewed. Values for water cooling system components have also been reported here. The report concludes with the examination of some equipment important to personnel safety, atmospheres, combustible gases, and airborne releases of radioactivity. These data should be useful to system designers to calculate scoping values for the availability and repair intervals for their systems, and for probabilistic safety or risk analysts to assess fusion systems for safety of the public and the workers.

  14. Selected Component Failure Rate Values from Fusion Safety Assessment Tasks

    SciTech Connect

    Cadwallader, Lee Charles

    1998-09-01

    This report is a compilation of component failure rate and repair rate values that can be used in magnetic fusion safety assessment tasks. Several safety systems are examined, such as gas cleanup systems and plasma shutdown systems. Vacuum system component reliability values, including large vacuum chambers, have been reviewed. Values for water cooling system components have also been reported here. The report concludes with the examination of some equipment important to personnel safety, atmospheres, combustible gases, and airborne releases of radioactivity. These data should be useful to system designers to calculate scoping values for the availability and repair intervals for their systems, and for probabilistic safety or risk analysts to assess fusion systems for safety of the public and the workers.

  15. Impact of subsidence on clinical outcomes and radiographic fusion rates in anterior cervical discectomy and fusion: a systematic review.

    PubMed

    Karikari, Isaac O; Jain, Deeptee; Owens, Timothy Ryan; Gottfried, Oren; Hodges, Tiffany R; Nimjee, Shahid M; Bagley, Carlos A

    2014-02-01

    Systematic review. To provide a systematic review of published literature on the impact of subsidence on clinical outcomes and radiographic fusion rates after anterior cervical discectomy and fusion with plates or without plates. Subsidence of interbody implants is common after anterior cervical spine fusions. The impact of subsidence on fusion rates and clinical outcomes is unknown. Systematic literature review on published articles on anterior cervical discectomy and fusion, which objectively measured graft subsidence, radiographic fusion rates, and clinical outcomes between April 1966 and December 2010. A total of 35 articles that measured subsidence and provided fusion rates and/or clinical outcomes were selected for inclusion. The mean subsidence rate ranged from 19.3% to 42.5%. The rate of subsidence based on the type of implant ranged from 22.8% to 35.9%. The incidence of subsidence was not impacted by the type of implant (P=0.98). The overall fusion rate of the combined studies was 92.8% and was not impacted by subsidence irrespective of subsidence definition or the measurement technique used (P=0.19). Clinical outcomes were evaluated in 27 of 35 studies with all studies reporting an improvement in patient outcomes postoperatively. Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and/or clinical outcomes. A validated definition and standard measurement technique for subsidence is needed to determine the actual incidence of subsidence and its impact on radiographic and clinical outcomes.

  16. Study of Complete Fusion Reactions Leading to the Production of Heavy and Superheavy Nuclei

    SciTech Connect

    Roman N. Sagaidak

    1999-12-31

    Cross section values for heavy evaporation residues (ER) produced in complete fusion reactions induced by heavy ions on spherical and deformed target nuclei are analyzed in the framework of barrier penetration and statistical model approximations. For the reactions leading to Rn-Pa nuclei, a strong influence of the entrance channel on the measured cross section values is observed for nearly symmetric projectile-target combinations. In order to reproduce the observed excitation functions in such combinations we had to introduce the quantity of fusion probability. Considering the asymmetric reactions leading to the heaviest nuclei we also had to use the fusion probability to reproduce the cross section values obtained for cold fusion reactions induced by {sup 50}Ti and heavier projectiles on the Pb and Bi target nuclei, and also the values obtained for hot fusion reactions induced by {sup 34}S on actinide target nuclei. The scaling of fusion probabilities derived for both the reactions allowed us to predict the values of cross sections for superheavy elements (SHE) produced in the {sup 48}Ca induced reactions on actinide target nuclei and in the cold fusion reactions induced by the Zn and heavier projectiles.

  17. Study of complete fusion reactions leading to the production of heavy and superheavy nuclei

    SciTech Connect

    Sagaidak, Roman N.

    1999-11-16

    Cross section values for heavy evaporation residues (ER) produced in complete fusion reactions induced by heavy ions on spherical and deformed target nuclei are analyzed in the framework of barrier penetration and statistical model approximations. For the reactions leading to Rn-Pa nuclei, a strong influence of the entrance channel on the measured cross section values is observed for nearly symmetric projectile-target combinations. In order to reproduce the observed excitation functions in such combinations we had to introduce the quantity of fusion probability. Considering the asymmetric reactions leading to the heaviest nuclei we also had to use the fusion probability to reproduce the cross section values obtained for cold fusion reactions induced by {sup 50}Ti and heavier projectiles on the Pb and Bi target nuclei, and also the values obtained for hot fusion reactions induced by {sup 34}S on actinide target nuclei. The scaling of fusion probabilities derived for both the reactions allowed us to predict the values of cross sections for superheavy elements (SHE) produced in the {sup 48}Ca induced reactions on actinide target nuclei and in the cold fusion reactions induced by the Zn and heavier projectiles.

  18. Enhanced aqueous photochemical reaction rates after freezing.

    PubMed

    Grannas, Amanda M; Bausch, Alexandra R; Mahanna, Kendell M

    2007-11-01

    Sunlit snow/ice is known to play an important role in the processing of atmospheric species, including photochemical production of NO(x), HONO, molecular halogens, alkyl halides, and carbonyl compounds, among others. It has been shown that a liquid-like (quasi-liquid or disordered) layer exists on the surface of pure ice and that this quasi-liquid layer is also found on the surface of ambient snow crystals and ice at temperatures similar to polar conditions. However, it is unclear what role the liquid-like fractions present in and on frozen water play in potential photochemical reactions, particularly with regard to organic substrates. Here, we report a detailed study of enhanced rates of photochemical nucleophilic substitution of p-nitroanisole (PNA) with pyridine, a well-characterized and commonly used actinometer system. Reaction rates were enhanced by a factor of up to approximately 40 when frozen at temperatures between 236 and 272 K. Reaction rates were dependent on temperature and solute concentration, both variables that control the nature of the liquid-like fraction in frozen water. The results obtained indicate that a major portion of the organic solutes is excluded to the liquid-like layer, significantly impacting the rate of the photochemical nucleophilic substitution reaction studied here. Also, the direct comparison of liquid-phase kinetics to reactions occurring in frozen water systems is drawn into question, indicating that a simple extrapolation of liquid-phase mechanisms to snow/ice may not be valid for certain reactions.

  19. The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction

    PubMed Central

    Liu, Yanjie; Pei, Jimin; Grishin, Nick; Snell, William J.

    2015-01-01

    Cell-cell fusion between gametes is a defining step during development of eukaryotes, yet we know little about the cellular and molecular mechanisms of the gamete membrane fusion reaction. HAP2 is the sole gamete-specific protein in any system that is broadly conserved and shown by gene disruption to be essential for gamete fusion. The wide evolutionary distribution of HAP2 (also known as GCS1) indicates it was present in the last eukaryotic common ancestor and, therefore, dissecting its molecular properties should provide new insights into fundamental features of fertilization. HAP2 acts at a step after membrane adhesion, presumably directly in the merger of the lipid bilayers. Here, we use the unicellular alga Chlamydomonas to characterize contributions of key regions of HAP2 to protein location and function. We report that mutation of three strongly conserved residues in the ectodomain has no effect on targeting or fusion, although short deletions that include those residues block surface expression and fusion. Furthermore, HAP2 lacking a 237-residue segment of the cytoplasmic region is expressed at the cell surface, but fails to localize at the apical membrane patch specialized for fusion and fails to rescue fusion. Finally, we provide evidence that the ancient HAP2 contained a juxta-membrane, multi-cysteine motif in its cytoplasmic region, and that mutation of a cysteine dyad in this motif preserves protein localization, but substantially impairs HAP2 fusion activity. Thus, the ectodomain of HAP2 is essential for its surface expression, and the cytoplasmic region targets HAP2 to the site of fusion and regulates the fusion reaction. PMID:25655701

  20. The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction.

    PubMed

    Liu, Yanjie; Pei, Jimin; Grishin, Nick; Snell, William J

    2015-03-01

    Cell-cell fusion between gametes is a defining step during development of eukaryotes, yet we know little about the cellular and molecular mechanisms of the gamete membrane fusion reaction. HAP2 is the sole gamete-specific protein in any system that is broadly conserved and shown by gene disruption to be essential for gamete fusion. The wide evolutionary distribution of HAP2 (also known as GCS1) indicates it was present in the last eukaryotic common ancestor and, therefore, dissecting its molecular properties should provide new insights into fundamental features of fertilization. HAP2 acts at a step after membrane adhesion, presumably directly in the merger of the lipid bilayers. Here, we use the unicellular alga Chlamydomonas to characterize contributions of key regions of HAP2 to protein location and function. We report that mutation of three strongly conserved residues in the ectodomain has no effect on targeting or fusion, although short deletions that include those residues block surface expression and fusion. Furthermore, HAP2 lacking a 237-residue segment of the cytoplasmic region is expressed at the cell surface, but fails to localize at the apical membrane patch specialized for fusion and fails to rescue fusion. Finally, we provide evidence that the ancient HAP2 contained a juxta-membrane, multi-cysteine motif in its cytoplasmic region, and that mutation of a cysteine dyad in this motif preserves protein localization, but substantially impairs HAP2 fusion activity. Thus, the ectodomain of HAP2 is essential for its surface expression, and the cytoplasmic region targets HAP2 to the site of fusion and regulates the fusion reaction.

  1. Comparison of Fusion Rates between Glycerol-Preserved and Frozen Composite Allografts in Cervical Fusion.

    PubMed

    Rodway, Ian; Gander, Julie

    2014-01-01

    Background. This retrospective, two cohort series study was designed to compare a room temperature, glycerol-preserved composite pinned bone allograft (G-CPBA) with the same graft type provided in a frozen state (F-CPBA) for use as a cervical interbody spacer in anterior cervical discectomy and fusion (ACDF). Methods. A comprehensive chart review was performed for 67 sequential patients that received either a F-CPBA or a G-CPBA and had at least one-year follow-up. Twenty-eight patients had received G-CPBA grafts and 37 patients had received F-CPBA grafts. Two additional 2-level patients had received one of each type of grafts. Results. At 3 months, 45.3% (29 of 64) of glycerol-preserved and 41.4% (29 of 70) of frozen allografts, respectively, were considered to be fused radiographically. At 12 months, 100% of both treatment groups (41 glycerol-preserved and 45 frozen) were considered fused. Fusion rates for G-CPBA were statistically similar to F-CPBA at both 3 and 12 months (P = 0.6535 and >0.999, resp.). There were no allograft related complications in either treatment group. Conclusions. 100% fusion rates were attained by both treatment groups at 12 months and were similar at short-term follow-up for all comparable levels. Level of Evidence. Level of evidence is III.

  2. Comparison of Fusion Rates between Glycerol-Preserved and Frozen Composite Allografts in Cervical Fusion

    PubMed Central

    Rodway, Ian; Gander, Julie

    2014-01-01

    Background. This retrospective, two cohort series study was designed to compare a room temperature, glycerol-preserved composite pinned bone allograft (G-CPBA) with the same graft type provided in a frozen state (F-CPBA) for use as a cervical interbody spacer in anterior cervical discectomy and fusion (ACDF). Methods. A comprehensive chart review was performed for 67 sequential patients that received either a F-CPBA or a G-CPBA and had at least one-year follow-up. Twenty-eight patients had received G-CPBA grafts and 37 patients had received F-CPBA grafts. Two additional 2-level patients had received one of each type of grafts. Results. At 3 months, 45.3% (29 of 64) of glycerol-preserved and 41.4% (29 of 70) of frozen allografts, respectively, were considered to be fused radiographically. At 12 months, 100% of both treatment groups (41 glycerol-preserved and 45 frozen) were considered fused. Fusion rates for G-CPBA were statistically similar to F-CPBA at both 3 and 12 months (P = 0.6535 and >0.999, resp.). There were no allograft related complications in either treatment group. Conclusions. 100% fusion rates were attained by both treatment groups at 12 months and were similar at short-term follow-up for all comparable levels. Level of Evidence. Level of evidence is III. PMID:27382618

  3. Reaction rates for mesoscopic reaction-diffusion kinetics

    DOE PAGES

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-23

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In thismore » paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. Finally, we show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.« less

  4. Reaction rates for mesoscopic reaction-diffusion kinetics

    SciTech Connect

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-23

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. Finally, we show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  5. Applications of Skyrme energy-density functional to fusion reactions for synthesis of superheavy nuclei

    SciTech Connect

    Wang Ning; Scheid, Werner; Wu Xizhen; Liu Min; Li Zhuxia

    2006-10-15

    The Skyrme energy-density functional approach has been extended to study massive heavy-ion fusion reactions. Based on the potential barrier obtained and the parametrized barrier distribution the fusion (capture) excitation functions of a lot of heavy-ion fusion reactions are studied systematically. The average deviations of fusion cross sections at energies near and above the barriers from experimental data are less than 0.05 for 92% of 76 fusion reactions with Z{sub 1}Z{sub 2}<1200. For the massive fusion reactions, for example, the {sup 238}U-induced reactions and {sup 48}Ca+{sup 208}Pb, the capture excitation functions have been reproduced remarkably well. The influence of structure effects in the reaction partners on the capture cross sections is studied with our parametrized barrier distribution. By comparing the reactions induced by double-magic nucleus {sup 48}Ca and by {sup 32}S and {sup 35}Cl, the ''threshold-like'' behavior in the capture excitation function for {sup 48}Ca-induced reactions is explored and an optimal balance between the capture cross section and the excitation energy of the compound nucleus is studied. Finally, the fusion reactions with {sup 36}S, {sup 37}Cl, {sup 48}Ca, and {sup 50}Ti bombarding {sup 248}Cm, {sup 247,249}Bk, {sup 250,252,254}Cf, and {sup 252,254}Es, as well as the reactions leading to the same compound nucleus with Z=120 and N=182, are studied further. The calculation results for these reactions are useful for searching for the optimal fusion configuration and suitable incident energy in the synthesis of superheavy nuclei.

  6. Calculations of Proton Emission Cross Sections in Deuteron Induced Reactions of Some Fusion Structural Materials

    NASA Astrophysics Data System (ADS)

    Yiğit, M.; Tel, E.; Tanır, G.

    2013-06-01

    The growing demands for energy consumption have led to the increase of the research and development activities on new energy sources. Fusion energy has the highest potential to become a very safe, clean and abundant energy source for the future. To get energy from fusion are needed for development of fusion reactor technology. Particularly, the design and development of international facilities as International Thermonuclear Experimental Reactor and International Fusion Material Irradiation Facility requires for the cross-section data of deuteron induced reactions. Moreover, the selection of fusion structural materials are an indispensable component for this technology. Therefore, the cross-section data of deuteron induced reactions on fusion structural materials are of great importance for development of fusion reactor technology. In this study, reaction model calculations of the cross sections of deuteron induced reactions on structural fusion materials such as 27Al, 59Co, 55Mn, 50Cr, 54Cr, 64Ni, 109Ag, 184W and 186W have been carried out for incident energies up to 50 MeV. In these calculations, the pre-equilibrium and equilibrium effects for ( d, p) stripping reactions have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model and hybrid model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. In the calculations the program code ALICE/ASH was used. The calculated results are discussed and compared with the experimental data taken from the literature.

  7. Possibilities for synthesis of new isotopes of superheavy nuclei in cold fusion reactions

    NASA Astrophysics Data System (ADS)

    Bao, X. J.; Gao, Y.; Li, J. Q.; Zhang, H. F.

    2016-04-01

    In order to find a way to produce superheavy nuclei (SHN), which appear in the gap between the SHN synthesized by cold fusion and those by hot fusion, or those so far not yet been produced in the laboratory, we tried to make use of a set of projectile isotopic chains, to use a radioactive beam projectile, and to test symmetric fusion reactions for gaining more neutrons to synthesize neutron-richer SHN based on the dinuclear system (DNS) model via cold fusion reactions. It is found that the nuclei 265Mt,Ds,272268,273Rg, and 274,275,276Cn may be produced with the detectable evaporation residual cross sections. The intensities of radioactive beams are significantly less than those of the stable beams, therefore using a stable beam is predicted to be the most favorable method for producing SHN. From the symmetric reaction system 136Xe+136Xe , no fusion event was found.

  8. Fusion and quasifission studies in reactions forming Rn via evaporation residue measurements

    NASA Astrophysics Data System (ADS)

    Shamlath, A.; Prasad, E.; Madhavan, N.; Laveen, P. V.; Gehlot, J.; Nasirov, A. K.; Giardina, G.; Mandaglio, G.; Nath, S.; Banerjee, Tathagata; Vinodkumar, A. M.; Shareef, M.; Jhingan, A.; Varughese, T.; Kumar, Dvgrks; Devi, P. Sandya; Khushboo, Jisha, P.; Kumar, Neeraj; Hosamani, M. M.; Kailas, S.

    2017-03-01

    Background: Formation of the compound nucleus (CN) is highly suppressed by quasifission in heavy-ion collisions involving massive nuclei. Though considerable progress has been made in the understanding of fusion-fission and quasifission, the exact dependence of fusion probability on various entrance channel variables is not completely clear, which is very important for the synthesis of new heavy and superheavy elements. Purpose: To study the interplay between fusion and quasifission in reactions forming CN in the boundary region where the fusion probability starts to deviate from unity. Methods: Fusion evaporation residue cross sections were measured for the Si,3028+180Hf reactions using the Hybrid Recoil Mass Analyser at IUAC, New Delhi. Experimental data were compared with data from other reactions forming the same CN or isotopes of the CN. Theoretical calculations were performed using the dinuclear system and statistical models. Results: Reduced evaporation residue cross sections were observed for the reactions studied compared with the asymmetric reaction forming the same CN, indicating fusion suppression in more symmetric systems. The observations are consistent with fission fragment measurements performed in the same or similar systems. Larger ER cross sections are observed with increase in mass in the isotopic chain of the CN. Conclusions: Fusion probability varies significantly with the entrance channels in reactions forming the same CN. While complete fusion occurs for the 16O+194Pt reaction, the fusion probability drops to approximately 60 -70 % for the 30Si+180Hf and less than 20 % for the 50Ti+160Gd reactions, respectively, forming the same CN at similar excitation energies.

  9. Reaction rates for a generalized reaction-diffusion master equation

    DOE PAGES

    Hellander, Stefan; Petzold, Linda

    2016-01-19

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model, and show inmore » two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is on the order of the reaction radius of a reacting pair of molecules.« less

  10. Reaction rates for a generalized reaction-diffusion master equation.

    PubMed

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  11. Reaction rates for a generalized reaction-diffusion master equation

    SciTech Connect

    Hellander, Stefan; Petzold, Linda

    2016-01-19

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model, and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is on the order of the reaction radius of a reacting pair of molecules.

  12. Microscopic dynamics simulations of heavy-ion fusion reactions induced by neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Ou, Li; Zhang, Yingxun; Li, Zhuxia

    2014-06-01

    The heavy-ion fusion reactions induced by neutron-rich nuclei are investigated with the improved quantum molecular dynamics (ImQMD) model. With a subtle consideration of the neutron skin thickness of nuclei and the symmetry potential, the stability of nuclei and the fusion excitation functions of heavy-ion fusion reactions O16 + Ge76, O16 + Sm154, Ca40 + Zr96, and Sn132 + Ca40 are systematically studied. The fusion cross sections of these reactions at energies around the Coulomb barrier can be well reproduced by using the ImQMD model. The corresponding slope parameter of the symmetry energy adopted in the calculations is L ≈78 MeV and the surface energy coefficient is gsur=18±1.5 MeV fm2. In addition, it is found that the surface-symmetry term significantly influences the fusion cross sections of neutron-rich fusion systems. For sub-barrier fusion, the dynamical fluctuations in the densities of the reaction partners and the enhanced surface diffuseness at neck side result in the lowering of the fusion barrier.

  13. Transfer/Breakup Channel Couplings in Sub-barrier Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Beck, C.

    2013-03-01

    With the recent availability of state-of-the-art radioactive ion beams, there has been a renew interest in the investigation of nuclear reactions with heavy ions near the Coulomb barrier. The role of inelastic and transfer channel couplings in fusion reactions induced by stable heavy ions can be revisited. Detailed analysis of recent experimental fusion cross sections by using standard coupled-channel calculations is first discussed. Multi-neutron transfer effects are introduced in the fusion process below the Coulomb barrier by analyzing 32S+90,96Zr as benchmark reactions. The enhancement of fusion cross sections for 32S+96Zr is well reproduced at sub-barrier energies by NTFus code calculations including the coupling of the neutrontransfer channels following the Zagrebaev semi-classical model. Similar effects for 40Ca+90Zr and 40Ca+96Zr fusion excitation functions are found. The breakup coupling in both the elastic scattering and in the fusion process induced by weakly bound stable projectiles is also shown to be crucial. In the second part of this work, full coupled-channel calculations of the fusion excitation functions are performed by using the breakup coupling for the more neutron-rich reaction and for the more weakly bound projectiles. We clearly demonstrate that Continuum-Discretized Coupled-Channel calculations are capable to reproduce the fusion enhancement from the breakup coupling in 6Li+59Co.

  14. Fusion, reaction, and breakup cross sections of {sup 9}Be on a light mass target

    SciTech Connect

    Marti, G.V.; Capurro, O.A.; Pacheco, A.J.; Testoni, J.E.; Ramirez, M.; Arazi, A.; Gomes, P.R.S.; Padron, I.; Anjos, R.M.; Lubian, J.; Crema, E.

    2005-02-01

    The total fusion cross section for the {sup 9}Be+{sup 27}Al system has been measured at energies close and above the Coulomb barrier. Reaction cross sections for this system were derived from elastic scattering data, and the breakup-plus-transfer-channel cross sections were estimated from the difference between these data and measured cross-section fusion.

  15. Analysis of the radial potential structure and neutron production rate in the spherical inertial electrostatic confinement fusion devices

    NASA Astrophysics Data System (ADS)

    Ramzanpour, M. A.; Pahlavani, M. R.

    2017-01-01

    The radial dependent potential and neutron production rate in spherical inertial electrostatic confinement fusion (IECF) devices is investigated. The electrostatic potential is determined by solving the Poisson equation for various deuteron and electron distribution functions. The fusion reaction rates are determined using energy distribution function. Also, dependence of potential structure and neutron production rate on some important parameters as the ion and electron convergence, working pressure, kinetic energy of the secondary electrons emitted from the cathode and the fraction of secondary electrons drawn inside the cathode are studied. Total produced neutrons as a function of input power at different working conditions are also obtained.

  16. Cold fusion reaction of 58Fe + 208Pb analyzed by a generalized model of fusion by diffusion

    NASA Astrophysics Data System (ADS)

    Liu, Zu-Hua; Bao, Jing-Dong

    2012-05-01

    A generalized version of the fusion by diffusion model is proposed, in which evolution from dinuclear to mononuclear regimes is taken into account in terms of the coupled Langevin equations in the three-dimensional collective space of neck, radial, and asymmetric degrees of freedom. By simulating numerically these dynamic equations, the probability distribution of sinj, the separation between the surfaces of two approaching nuclei at the injection point in the asymmetric fission valley, is obtained. From the injection points, the system starts its climb uphill over the saddle point in the presence of thermal fluctuation; thus for very heavy systems the injection-point distance is a very critical constituent in the calculations of fusion probability. The present model is applied for the study of the mass asymmetric system 58Fe+208Pb. The excitation function for the 208Pb(58Fe,n)265Hs reaction is calculated and compared with the experimental data. By comparing the theoretical results with and without taking the asymmetric degree of freedom into account, we have arrived at the conclusion that nucleon flow between the asymmetric reaction partners in the early stage of the fusion process plays an important role in the formation of superheavy nuclei in the cold fusion reactions.

  17. Basic distinctions between cold- and hot-fusion reactions in the synthesis of superheavy elements

    NASA Astrophysics Data System (ADS)

    Nasirov, A. K.; Muminov, A. I.; Giardina, G.; Mandaglio, G.

    2014-07-01

    Superheavy elements (SHE) of charge number in the range of Z = 106-112 were synthesized in so-called cold-fusion reactions. The smallness of the excitation energy of compound nuclei is the main advantage of cold-fusion reactions. However, the synthesis of SHEs of charge number in the region of Z ≥ 112 is strongly complicated in cold-fusion reactions by a sharp decrease in the cross section of a compound nucleus formation in the entrance channel because of superiority of quasifission in the competition with complete fusion. Two favorable circumstances contributed to the success of the experiments aimed at the synthesis of the Z = 113-118 elements and performed at the Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research: large cross sections for the production of a compound nucleus, which are characteristic of hot-fusion reactions, and an increase in the fission barrier for nuclei toward the stability island. The factor that complicates the formation of a compound nucleus in cold-fusion reactions is discussed.

  18. Comparative analysis of the fusion reactions 48Ti+58Fe and 58Ni+54Fe

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

    2017-05-01

    The experimental fusion excitation functions of the reactions 48Ti+58Fe and 58Ni+54Fe , measured down to the low sub-barrier energies, are described within the quantum diffusion approach and the universal fusion function representation. For these systems, the s -wave capture probabilities are extracted from the experimental excitation functions and are also analyzed. An enhancement of the sub-barrier fusion cross section observed in the 48Ti+58Fe reaction in comparison to the relatively close system 58Ni+54Fe is explained.

  19. Thermonuclear Reaction Rate Parameterization for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Sharp, Jacob; Kozub, Raymond L.; Smith, Michael S.; Scott, Jason; Lingerfelt, Eric

    2004-10-01

    The knowledge of thermonuclear reaction rates is vital to simulate novae, supernovae, X-ray bursts, and other astrophysical events. To facilitate dissemination of this knowledge, a set of tools has been created for managing reaction rates, located at www.nucastrodata.org. One tool is a rate parameterizer, which provides a parameterization for nuclear reaction rate vs. temperature values in the most widely used functional form. Currently, the parameterizer uses the Levenberg-Marquardt method (LMM), which requires an initial estimate of the best-fit parameters. The initial estimate is currently provided randomly from a preselected pool. To improve the quality of fits, a new, active method of selecting parameters has been developed. The parameters of each set in the pool are altered for a few iterations to replicate the input data as closely as possible. Then, the set which most nearly matches the input data (based on chi squared) is used in the LMM as the initial estimate for the final fitting procedure. A description of the new, active algorithm and its performance will be presented. Supported by the U. S. Department of Energy.

  20. Possibilities of production of transfermium nuclei in complete fusion reactions with radioactive beams

    NASA Astrophysics Data System (ADS)

    Hong, Juhee; Adamian, G. G.; Antonenko, N. V.

    2017-07-01

    The possibilities of direct production of new isotopes of transfermium nuclei 261,263,264No, 264Lr263, 263,264,266,268Rf, 265Db264, and 267,268,270,272Sg are studied in various asymmetric hot fusion-evaporation reactions with radioactive beams. The optimal reaction partners and conditions for the synthesis of new isotopes are suggested. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of heaviest nuclei obtained in the x n evaporation channels of the cold and hot complete fusion reactions with the stable beams.

  1. Two-temperature reaction and relaxation rates

    NASA Astrophysics Data System (ADS)

    Kolesnichenko, E.; Gorbachev, Yu.

    2017-05-01

    Within the method of solving the kinetic equations for gas mixtures with internal degrees of freedom developed by the authors and based on the approximate summational invariants (ASI) concept, gas-dynamic equations for a multi-temperature model for the spatially inhomogeneous case are derived. For the two-temperature case, the expressions for the non-equilibrium reaction and relaxation rates are obtained. Special attention is drawn to corresponding thermodynamic equations. Different possibilities of introducing the gas-dynamic variables related to the internal degrees of freedom are considered. One is based on the choice of quantum numbers as the ASI, while the other is based on the choice of internal (vibrational) energy as the ASI. Limits to a one-temperature situation are considered in all the cases. For the cutoff harmonic oscillator model, explicit expressions for the reaction and relaxation rates are derived.

  2. Thermodynamic limitations on microbially catalyzed reaction rates

    NASA Astrophysics Data System (ADS)

    LaRowe, Douglas E.; Dale, Andrew W.; Amend, Jan P.; Van Cappellen, Philippe

    2012-08-01

    Quantification of global biogeochemical cycles requires knowledge of the rates at which microorganisms catalyze chemical reactions. In order for models that describe these processes to capture global patterns of change, the underlying formulations in them must account for biogeochemical transformations over seasonal and millennial time scales in environments characterized by different energy levels. Building on existing models, a new thermodynamic limiting function is introduced. With only one adjustable parameter, this function that can be used to model microbial metabolism throughout the range of conditions in which organisms are known to be active. The formulation is based on a comparison of the amount of energy available from any redox reaction to the energy required to maintain a membrane potential, a proxy for the minimum amount of energy required by an active microorganism. This function does not require species- or metabolism-specific parameters, and can be used to model metabolisms that capture any amount of energy. The utility of this new thermodynamic rate limiting term is illustrated by applying it to three low-energy processes: fermentation, methanogenesis and sulfate reduction. The model predicts that the rate of fermentation will be reduced by half once the Gibbs energy of the catalyzed reaction reaches -12 kJ (mol e-)-1, and then slowing exponentially until the energy yield approaches zero. Similarly, the new model predicts that the low energy yield of methanogenesis, -4 to -0.5 kJ (mol e-)-1, for a partial pressure of H2 between 11 and 0.6 Pa decreases the reaction rate by 95-99%. Finally, the new function's utility is illustrated through its ability to accurately model sulfate concentration data in an anoxic marine sediment.

  3. Quantum theory of chemical reaction rates

    SciTech Connect

    Miller, W.H. |

    1994-10-01

    If one wishes to describe a chemical reaction at the most detailed level possible, i.e., its state-to-state differential scattering cross section, then it is necessary to solve the Schroedinger equation to obtain the S-matrix as a function of total energy E and total angular momentum J, in terms of which the cross sections can be calculated as given by equation (1) in the paper. All other physically observable attributes of the reaction can be derived from the cross sections. Often, in fact, one is primarily interested in the least detailed quantity which characterizes the reaction, namely its thermal rate constant, which is obtained by integrating Eq. (1) over all scattering angles, summing over all product quantum states, and Boltzmann-averaging over all initial quantum states of reactants. With the proper weighting factors, all of these averages are conveniently contained in the cumulative reaction probability (CRP), which is defined by equation (2) and in terms of which the thermal rate constant is given by equation (3). Thus, having carried out a full state-to-state scattering calculation to obtain the S-matrix, one can obtain the CRP from Eq. (2), and then rate constant from Eq. (3), but this seems like ``overkill``; i.e., if one only wants the rate constant, it would clearly be desirable to have a theory that allows one to calculate it, or the CRP, more directly than via Eq. (2), yet also correctly, i.e., without inherent approximations. Such a theory is the subject of this paper.

  4. Spectral photoplethysmographic imaging sensor fusion for enhanced heart rate detection

    NASA Astrophysics Data System (ADS)

    Amelard, Robert; Clausi, David A.; Wong, Alexander

    2016-03-01

    Continuous heart rate monitoring can provide important context for quantitative clinical assessment in scenarios such as long-term health monitoring and disability prevention. Photoplethysmographic imaging (PPGI) systems are particularly useful for such monitoring scenarios as contact-based devices pose problems related to comfort and mobility. Each pixel can be regarded as a virtual PPG sensor, thus enabling simultaneous measurements of multiple skin sites. Existing PPGI systems analyze temporal PPGI sensor uctuations related to hemodynamic pulsations across a region of interest to extract the blood pulse signal. However, due to spatially varying optical properties of the skin, the blood pulse signal may not be consistent across all PPGI sensors, leading to inaccurate heart rate monitoring. To increase the hemodynamic signal-to-noise ratio (SNR), we propose a novel spectral PPGI sensor fusion method for enhanced estimation of the true blood pulse signal. Motivated by the observation that PPGI sensors with high hemodynamic SNR exhibit a spectral energy peak at the heart rate frequency, an entropy-based fusion model was formulated to combine PPGI sensors based on the sensors' spectral energy distribution. The optical PPGI device comprised a near infrared (NIR) sensitive camera and an 850 nm LED. Spatially uniform irradiance was achieved by placing optical elements along the LED beam, providing consistent illumination across the skin area. Dual-mode temporally coded illumination was used to negate the temporal effect of ambient illumination. Experimental results show that the spectrally weighted PPGI method can accurately and consistently extract heart rate information where traditional region-based averaging fails.

  5. Fusion Reactions and Matter-Antimatter Annihilation for Space Propulsion

    DTIC Science & Technology

    2005-07-13

    Wittenberg, J.F. Santarius and G . Kulcinski , Lunar Source of He-3 for commercial fusion power, Fusion Technology 10, 167 (1986). [5] E. Stuhlinger...Nature, 258, 512 (1975). [13] J. Nuckolls, A. Thiessen, L . Wood and G . Zimmermann, Laser compression of matter to super high densities, Nature, 239...of rocket system to carry out each of these missions can be calculated from the rocket equation R = mv + m p m v = e∆V / vex = e ∆V / g Isp ^ , [1

  6. Pycnonuclear reaction rates for binary ionic mixtures

    NASA Technical Reports Server (NTRS)

    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.

  7. Pycnonuclear reaction rates for binary ionic mixtures

    NASA Technical Reports Server (NTRS)

    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.

  8. Reaction Rate Parameterization for Nuclear Astrophysics Research

    NASA Astrophysics Data System (ADS)

    Scott, J. P.; Lingerfelt, E. J.; Smith, M. S.; Hix, W. R.; Bardayan, D. W.; Sharp, J. E.; Kozub, R. L.; Meyer, R. A.

    2004-11-01

    Libraries of thermonuclear reaction rates are used in element synthesis models of a wide variety of astrophysical phenomena, such as exploding stars and the inner workings of our sun. These computationally demanding models are more efficient when libraries, which may contain over 60000 rates and vary by 20 orders of magnitude, have a uniform parameterization for all rates. We have developed an on-line tool, hosted at www.nucastrodata.org, to obtain REACLIB parameters (F.-K. Thielemann et al., Adv. Nucl. Astrophysics 525, 1 (1987)) that represent reaction rates as a function of temperature. This helps to rapidly incorporate the latest nuclear physics results in astrophysics models. The tool uses numerous techniques and algorithms in a modular fashion to improve the quality of the fits to the rates. Features, modules, and additional applications of this tool will be discussed. * Managed by UT-Battelle, LLC, for the U.S. D.O.E. under contract DE-AC05-00OR22725 + Supported by U.S. D.O.E. under Grant No. DE-FG02-96ER40955

  9. Impact of iliac crest bone graft harvesting on fusion rates and postoperative pain during instrumented posterolateral lumbar fusion

    PubMed Central

    Triantafyllopoulos, Dimitrios; Kosmopoulos, Victor; Stafylas, Kosmas

    2007-01-01

    This study aims to evaluate the influence of bone harvesting on postoperative pain and fusion rates. Group 1 patients received iliac crest bone graft (ICBG) either alone or augmented with local bone. Group 2 received only local bone. No statistical significance was found in radiological union or in the Oswestry Disability Index scores. Visual Analogue Scale scores showed less pain in group 2. Logistic regression showed no correlation between residual pain and occurrence of fusion. Harvesting ICBG did not appear to increase fusion rates and no relation was found between radiological non-union and pain. PMID:17724591

  10. Parametric Studies of Dense Plasma Focus for Fusion Space Propulsion with D - He3

    DTIC Science & Technology

    1991-03-01

    fusion fuels. The fusion fuels should have a high power density. Of all the fusion reactions being considered today, the D - 3He reaction has the highest... reaction rate parameters for some typical fusion fuels 6’. D -T has the highest reaction rate parameter at low temperatures and the D - 3He reaction rate...advanced fusion fuels, D - 3He fuel cycle, aneutronic fusion 20 08 19

  11. Role of Barrier Modification and Nuclear Structure Effects in Sub-Barrier Fusion Dynamics of Various Heavy Ion Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh; Vinod, K.; Kumar, Hitender

    2017-10-01

    The role of barrier modifications and the relevant nuclear structure effects in the fusion of the {}_8{}^{16}O+{}_{62}{}^{144,148,150,152,154}Sm and {}_3{}^{6,7}Li+{}_{62}{}^{152}Sm systems is analyzed within the context of the energy-dependent Woods-Saxon potential model (EDWSP model) and the coupled channel model. For the {}_8{}^{16}O+{}_{62}{}^{144,148,150,152,154}Sm reactions, where the colliding pairs are stable against breakup, the collective excitations and/or static deformations are sufficient to account for the observed fusion enhancement. In contrast, the model calculations overpredict the complete fusion data at above - barrier energies for the {}_3{}^{6,7}Li+{}_{62}{}^{152}Sm systems, where the importance of projectile breakup effects has been pointed out. Due to the low threshold of the alpha-breakup channel, the weakly bound projectiles ({}_3{}^{6,7}Li) break up into charged fragments before reaching the fusion barrier and consequently the complete fusion cross section is suppressed by 28% (25%) in the {}_3{}^6Li+{}_{62}{}^{152}Sm({}_3{}^7Li+{}_{62}{}^{152}Sm) reaction with respect to predictions of coupled channel calculations. However, the EDWSP model based calculations can minimize the suppression factor by as much as of 13% (8%) in the {}_3{}^6Li+{}_{62}{}^{152}Sm({}_3{}^7Li+{}_{62}{}^{152}Sm) reaction with reference to the predictions made by the coupled channel calculations. Therefore, the complete fusion data of the {}_3{}^6Li+{}_{62}{}^{152}Sm({}_3{}^7Li+{}_{62}{}^{152}Sm) reaction at above - barrier energies is reduced by 15% (17%) with respect to the expectations of the EDWSP model. The extracted suppression factors for the studied reactions are due to the modifications of the barrier profile as a consequence of the energy - dependence in nucleus-nucleus potential, and thus greater barrier modifications occur for more weakly bound system, which in turn, confirms the breakup of projectile in the incoming channel.

  12. Development of an inertial confinement fusion platform to study charged-particle-producing nuclear reactions relevant to nuclear astrophysics

    NASA Astrophysics Data System (ADS)

    Gatu Johnson, M.; Zylstra, A. B.; Bacher, A.; Brune, C. R.; Casey, D. T.; Forrest, C.; Herrmann, H. W.; Hohenberger, M.; Sayre, D. B.; Bionta, R. M.; Bourgade, J.-L.; Caggiano, J. A.; Cerjan, C.; Craxton, R. S.; Dearborn, D.; Farrell, M.; Frenje, J. A.; Garcia, E. M.; Glebov, V. Yu.; Hale, G.; Hartouni, E. P.; Hatarik, R.; Hohensee, M.; Holunga, D. M.; Hoppe, M.; Janezic, R.; Khan, S. F.; Kilkenny, J. D.; Kim, Y. H.; Knauer, J. P.; Kohut, T. R.; Lahmann, B.; Landoas, O.; Li, C. K.; Marshall, F. J.; Masse, L.; McEvoy, A.; McKenty, P.; McNabb, D. P.; Nikroo, A.; Parham, T. G.; Paris, M.; Petrasso, R. D.; Pino, J.; Radha, P. B.; Remington, B.; Rinderknecht, H. G.; Robey, H.; Rosenberg, M. J.; Rosse, B.; Rubery, M.; Sangster, T. C.; Sanchez, J.; Schmitt, M.; Schoff, M.; Séguin, F. H.; Seka, W.; Sio, H.; Stoeckl, C.; Tipton, R. E.

    2017-04-01

    This paper describes the development of a platform to study astrophysically relevant nuclear reactions using inertial-confinement fusion implosions on the OMEGA and National Ignition Facility laser facilities, with a particular focus on optimizing the implosions to study charged-particle-producing reactions. Primary requirements on the platform are high yield, for high statistics in the fusion product measurements, combined with low areal density, to allow the charged fusion products to escape. This is optimally achieved with direct-drive exploding pusher implosions using thin-glass-shell capsules. Mitigation strategies to eliminate a possible target sheath potential which would accelerate the emitted ions are discussed. The potential impact of kinetic effects on the implosions is also considered. The platform is initially employed to study the complementary T(t,2n)α, T(3He,np)α and 3He(3He,2p)α reactions. Proof-of-principle results from the first experiments demonstrating the ability to accurately measure the energy and yields of charged particles are presented. Lessons learned from these experiments will be used in studies of other reactions. The goals are to explore thermonuclear reaction rates and fundamental nuclear physics in stellar-like plasma environments, and to push this new frontier of nuclear astrophysics into unique regimes not reachable through existing platforms, with thermal ion velocity distributions, plasma screening, and low reactant energies.

  13. Development of an inertial confinement fusion platform to study charged-particle-producing nuclear reactions relevant to nuclear astrophysics

    DOE PAGES

    Gatu Johnson, M.; Zylstra, A. B.; Bacher, A.; ...

    2017-03-28

    Here, this paper describes the development of a platform to study astrophysically relevant nuclear reactions using inertial-confinement fusion implosions on the OMEGA and National Ignition Facility laser facilities, with a particular focus on optimizing the implosions to study charged-particle- producing reactions. Primary requirements on the platform are high yield, for high statistics in the fusion product measurements, combined with low areal density, to allow the charged fusion products to escape. This is optimally achieved with direct-drive exploding pusher implosions using thin-glass-shell capsules. Mitigation strategies to eliminate a possible target sheath potential which would accelerate the emitted ions are discussed. Themore » potential impact of kinetic effects on the implosions is also considered. The platform is initially employed to study the complementary T(t,2n)α, T(3He,np)α and 3He(3He,2p)α reactions. Proof-of-principle results from the first experiments demonstrating the ability to accurately measure the energy and yields of charged particles are presented. Lessons learned from these experiments will be used in studies of other reactions. Ultimately, the goals are to explore thermonuclear reaction rates and fundamental nuclear physics in stellarlike plasma environments, and to push this new frontier of nuclear astrophysics into unique regimes not reachable through existing platforms, with thermal ion velocity distributions, plasma screening, and low reactant energies.« less

  14. An approximate classical unimolecular reaction rate theory

    NASA Astrophysics Data System (ADS)

    Zhao, Meishan; Rice, Stuart A.

    1992-05-01

    We describe a classical theory of unimolecular reaction rate which is derived from the analysis of Davis and Gray by use of simplifying approximations. These approximations concern the calculation of the locations of, and the fluxes of phase points across, the bottlenecks to fragmentation and to intramolecular energy transfer. The bottleneck to fragment separation is represented as a vibration-rotation state dependent separatrix, which approximation is similar to but extends and improves the approximations for the separatrix introduced by Gray, Rice, and Davis and by Zhao and Rice. The novel feature in our analysis is the representation of the bottlenecks to intramolecular energy transfer as dividing surfaces in phase space; the locations of these dividing surfaces are determined by the same conditions as locate the remnants of robust tori with frequency ratios related to the golden mean (in a two degree of freedom system these are the cantori). The flux of phase points across each dividing surface is calculated with an analytic representation instead of a stroboscopic mapping. The rate of unimolecular reaction is identified with the net rate at which phase points escape from the region of quasiperiodic bounded motion to the region of free fragment motion by consecutively crossing the dividing surfaces for intramolecular energy exchange and the separatrix. This new theory generates predictions of the rates of predissociation of the van der Waals molecules HeI2, NeI2 and ArI2 which are in very good agreement with available experimental data.

  15. The effects of vacuum polarization on thermonuclear reaction rates

    NASA Technical Reports Server (NTRS)

    Gould, Robert J.

    1990-01-01

    Added to the pure Coulomb potential, the contribution from vacuum polarization increases the barrier, reducing the wave function (u) for reacting nuclei within the range of nuclear forces. The cross section and reaction rate are then reduced accordingly by a factor proportional to u squared. The effect is treated by evaluating the vacuum polarization potential as a small correction to the Coulomb term, then computing u in a WKB formulation. The calculation is done analytically employing the small r power-series expansion for the Uehling potential to express the final result in terms of convenient parameters. At a temperature of 1.4 x 10 to the 7th K the (negative) correction is 1.3 percent for the fundamental fusion process p + p yields d + e(+) + nu.

  16. Bayesian Estimation of Thermonuclear Reaction Rates

    NASA Astrophysics Data System (ADS)

    Iliadis, C.; Anderson, K. S.; Coc, A.; Timmes, F. X.; Starrfield, S.

    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)3He, 3He(3He,2p)4He, and 3He(α,γ)7Be, important for deuterium burning, solar neutrinos, and Big Bang nucleosynthesis.

  17. Docking, Not Fusion, as the Rate-Limiting Step in a SNARE-Driven Vesicle Fusion Assay

    PubMed Central

    Smith, Elizabeth A.; Weisshaar, James C.

    2011-01-01

    In vitro vesicle fusion assays that monitor lipid mixing between t-SNARE and v-SNARE vesicles in bulk solution exhibit remarkably slow fusion on the nonphysiological timescale of tens of minutes to several hours. Here, single-vesicle, fluorescence resonance energy transfer-based assays cleanly separate docking and fusion steps for individual vesicle pairs containing full-length SNAREs. Docking is extremely inefficient and is the rate-limiting step. Of importance, the docking and fusion kinetics are comparable in the two assays (one with v-SNARE vesicles tethered to a surface and the other with v-SNARE vesicles free in solution). Addition of the VC peptide synaptobrevin-2 (syb(57–92)) increases the docking efficiency by a factor of ∼30, but docking remains rate-limiting. In the presence of VC peptide, the fusion step occurs on a timescale of ∼10 s. In previous experiments involving bulk fusion assays in which the addition of synaptotagmin/Ca2+, Munc-18, or complexin accelerated the observed lipid-mixing rate, the enhancement may have arisen from the docking step rather than the fusion step. PMID:21539781

  18. Recent developments in heavy-ion fusion reactions around the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Hagino, K.; Rowley, N.; Yao, J. M.

    2016-06-01

    The nuclear fusion is a reaction to form a compound nucleus. It plays an important role in several circumstances in nuclear physics as well as in nuclear astrophysics, such as synthesis of superheavy elements and nucleosynthesis in stars. Here we discuss two recent theoretical developments in heavy-ion fusion reactions at energies around the Coulomb barrier. The first topic is a generalization of the Wong formula for fusion cross sections in a single-channel problem. By introducing an energy dependence to the barrier parameters, we show that the generalized formula leads to results practically indistinguishable from a full quantal calculation, even for light symmetric systems such as 12C+12C, for which fusion cross sections show an oscillatory behavior. We then discuss a semi-microscopic modeling of heavy-ion fusion reactions, which combine the coupled-channels approach to the state-of-the-art nuclear structure calculations for low-lying collective motions. We apply this method to subbarrier fusion reactions of 58Ni+58Ni and 40Ca+58Ni systems, and discuss the role of anharmonicity of the low-lying vibrational motions.

  19. Fusion-Evaporation Cross Sections in Reactions Leading to Production of Super-Heavy Nuclei

    SciTech Connect

    Siwek-Wilczynska, K.; Skwira-Chalot, I.; Wilczynski, J.

    2006-08-14

    Fusion-evaporation cross sections were calculated for the 48Ca+204-208Pb and 50Ti+206,208Pb reactions and compared with the existing experimental data of the Dubna and GSI groups. The survival probabilities of the compound Z 102 and Z = 104 nuclei formed in these reactions were calculated using a Monte Carlo program based on the conventional Bohr-Wheeler theory of fission and statistical model of particle evaporation with Reisdorf-Ignatyuk prescription for the level densities and Strutinsky shell corrections of Moeller et al. 'Empirical' magnitudes of the dynamical hindrance of fusion have been deduced for these reactions.

  20. Chlorination of Amino Acids: Reaction Pathways and Reaction Rates.

    PubMed

    How, Zuo Tong; Linge, Kathryn L; Busetti, Francesco; Joll, Cynthia A

    2017-05-02

    Chlorination of amino acids can result in the formation of organic monochloramines or organic dichloramines, depending on the chlorine to amino acid ratio (Cl:AA). After formation, organic chloramines degrade into aldehydes, nitriles and N-chloraldimines. In this paper, the formation of organic chloramines from chlorination of lysine, tyrosine and valine were investigated. Chlorination of tyrosine and lysine demonstrated that the presence of a reactive secondary group can increase the Cl:AA ratio required for the formation of N,N-dichloramines, and potentially alter the reaction pathways between chlorine and amino acids, resulting in the formation of unexpected byproducts. In a detailed investigation, we report rate constants for all reactions in the chlorination of valine, for the first time, using experimental results and modeling. At Cl:AA = 2.8, the chlorine was found to first react quickly with valine (5.4 × 10(4) M(-1) s(-1)) to form N-monochlorovaline, with a slower subsequent reaction with N-monochlorovaline to form N,N-dichlorovaline (4.9 × 10(2) M(-1) s(-1)), although some N-monochlorovaline degraded into isobutyraldehyde (1.0 × 10(-4) s(-1)). The N,N-dichlorovaline then competitively degraded into isobutyronitrile (1.3 × 10(-4) s(-1)) and N-chloroisobutyraldimine (1.2 × 10(-4) s(-1)). In conventional drinking water disinfection, N-chloroisobutyraldimine can potentially be formed in concentrations higher than its odor threshold concentration, resulting in aesthetic challenges and an unknown health risk.

  1. Discriminating Acquisition of 15-MeV Protons from D-3He Fusion Reaction in LHD

    NASA Astrophysics Data System (ADS)

    Watanabe, Tsuguhiro; Miyazawa, Junichi; Yamada, Hiroshi; Murakami, Sadayoshi; Masuzaki, Suguru; Osakabe, Masaki; Isobe, Mitsutaka; Tokitani, Masayuki; Motojima, Osamu

    Discriminating acquisition of 15-MeV protons is possible in LHD D-3He experiments (D+ beam to 3He plasma), due to the nonaxisymmetric structure of the magnetic field and the ultra-high energy of the fusion products. The collisionless orbits of D-3He fusion products are studied numerically in the standard magnetic field configuration of LHD. Three sets of fusion product acquisition systems are installed in LHD and numerical computations show the possibility of discriminating between fusion products and plasma particles. The acquisition rate of 15-MeV protons is expected to be in the range of 12 ˜ 28 %.

  2. Revised analysis of Ca40+Zr96 fusion reactions

    DOE PAGES

    Esbensen, H.; Montagnoli, G.; Stefanini, A. M.

    2016-03-10

    Fusion data for 40Ca + 96Zr are analyzed by coupled-channels calculations that are based on a standard Woods-Saxon potential and include couplings to multiphonon excitations and transfer channels. The couplings to multiphonon excitations are the same as those used in a previous work. The transfer couplings are calibrated to reproduce the measured neutron transfer data. This type of calculation gives a poor fit to the fusion data. However, by multiplying the transfer couplings with a √2 one obtains an excellent fit. Finally, the scaling of the transfer strengths is supposed to simulate the combined effect of neutron and proton transfer,more » and the calculated one- and two-nucleon transfer cross sections are indeed in reasonable agreement with the measured cross sections.« less

  3. Quasifission and fusion-fission in reactions with massive nuclei: Comparison of reactions leading to the Z=120 element

    SciTech Connect

    Nasirov, A. K.; Giardina, G.; Mandaglio, G.; Manganaro, M.; Hanappe, F.; Heinz, S.; Hofmann, S.; Muminov, A. I.; Scheid, W.

    2009-02-15

    The yields of evaporation residues, fusion-fission, and quasifission fragments in the {sup 48}Ca+{sup 144,154}Sm and {sup 16}O+{sup 186}W reactions are analyzed in the framework of the combined theoretical method based on the dinuclear system concept and advanced statistical model. The measured yields of evaporation residues for the {sup 48}Ca+{sup 154}Sm reaction can be well reproduced. The measured yields of fission fragments are decomposed into contributions coming from fusion-fission, quasifission, and fast-fission. The decrease in the measured yield of quasifission fragments in {sup 48}Ca+{sup 154}Sm at the large collision energies and the lack of quasifission fragments in the {sup 48}Ca+{sup 144}Sm reaction are explained by the overlap in mass angle distributions of the quasifission and fusion-fission fragments. The investigation of the optimal conditions for the synthesis of the new element Z=120 (A=302) show that the {sup 54}Cr+{sup 248}Cm reaction is preferable in comparison with the {sup 58}Fe+{sup 244}Pu and {sup 64}Ni+{sup 238}U reactions because the excitation function of the evaporation residues of the former reaction is some orders of magnitude larger than that for the last two reactions.

  4. Role of the neck degree of freedom in cold fusion reactions

    NASA Astrophysics Data System (ADS)

    Adamian, G. G.; Antonenko, N. V.; Lenske, H.

    2015-05-01

    Mass parameters for collective variables of dinuclear systems formed in cold fusion reactions are microscopically calculated with the linear response theory making use of the width of single-particle states and the fluctuation-dissipation theorem. The single-particle spectrum and potential energy surface of the adiabatic two-center shell model are used. The microscopical mass parameter in the neck is found to be much larger than one obtained with the hydrodynamical model. Therefore, the dinuclear system lives a rather long time, comparable to the characteristic time of fusion and, correspondingly, the fusion can be considered at fixed neck parameter. With an adiabatic melting of the dinuclear system along the internuclear distance into a compound system one cannot explain the experimental trends in cold fusion reactions.

  5. Simulation of a fusion gamma reaction history diagnostic for the Shenguang-III facility

    NASA Astrophysics Data System (ADS)

    Song, Zifeng; Chen, Jiabin; Xu, Tao; Liu, Zhongjie; Zhan, Xiayu; Tang, Qi

    2017-05-01

    The fusion gamma has an advantage to measure fusion reaction history in the deuterium-tritium (DT) fuel implosion experiments. A gas Cherenkov detector is available to measure DT fusion gamma in a high background environment. Simulation is carried out by Geant4 to evaluate the conversion efficiency and the time response of this Cherenkov detector. The background gamma rays are roughly estimated based on ENDF/B-VII.0 data, and the signal-to-noise (SNR) is evaluated based on the simulated energy response curve. The simulation result and the SNR analysis are helpful to construct the Cherenkov detector at Shenguang-III facility.

  6. Synthesis of transactinide nuclei in cold fusion reactions using radioactive beams

    SciTech Connect

    Smolanczuk, Robert

    2010-06-15

    Chances of synthesis of transactinide nuclei in cold fusion reactions (one-neutron-out reactions) using radioactive beams are evaluated. Because in most of the cases intensities of radioactive beams are significantly less than those of the stable beams, reactions with the greatest radioactive-beam intensities for the particular elements are considered. The results are compared with the recent ones obtained by Loveland [Phys. Rev. C 76, 014612 (2007)], who investigated the same nuclei.

  7. Probing systematic model dependence of complete fusion for reactions with the weakly bound projectiles Li,76

    NASA Astrophysics Data System (ADS)

    Kundu, A.; Santra, S.; Pal, A.; Chattopadhyay, D.; Nayak, B. K.; Saxena, A.; Kailas, S.

    2016-07-01

    Background: Complete fusion cross section measurements involving weakly bound projectiles show suppression at above-barrier energies compared to coupled-channels (CC) calculations, but no definite conclusion could be drawn for sub-barrier energies. Different CC models often lead to contrasting results. Purpose: We aim to investigate the differences in the fusion cross sections predicted by commonly used CC calculations, using codes such as fresco and ccfull, when compared to experimental data. Methods: The fusion cross sections are normalized to a dimensionless form by isolating the effect of only dynamic channel couplings calculated by both fresco and ccfull, by the method of fusion functions, and compared to a universal fusion function. This acts as a probe for obtaining the model dependence of fusion. Results: A difference is observed between the predictions of fresco and ccfull for all the reactions involving Li,76 as projectiles, and it is noticeably more for systems involving 7Li. Conclusions: With the theoretical foundations of the two CC models being different, their calculation of fusion is different even for the same system. The conclusion about the enhancement or suppression of fusion cross sections is model dependent.

  8. Fusion and quasi-fission dynamics in nearly-symmetric reactions

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Zhao, Kai; Li, ZhuXia

    2015-11-01

    Some nearly-symmetric fusion reactions are systematically investigated with the improved quantum molecular dynamics (ImQMD) model. By introducing two-body inelastic scattering in the Fermi constraint procedure, the stability of an individual nucleus and the description of fusion cross sections at energies near the Coulomb barrier can be further improved. Simultaneously, the quasifission process in 154Sm+160Gd is also investigated with the microscopic dynamics model for the first time. We find that at energies above the Bass barrier, the fusion probability is smaller than 10-5 for this reaction, and the nuclear contact time is generally smaller than 1500 fm/ c. From the central collisions of Sm+Gd, the neutron-rich fragments such as 164,165Gd, 192W can be produced in the ImQMD simulations, which implies that the quasi-fission reaction could be an alternative way to synthesize new neutron-rich heavy nuclei.

  9. Cross sections calculated for cold fusion reactions for producing superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Smolańczuk, Robert

    2008-08-01

    We propose a handy formula for calculating the formation cross sections for optimal bombarding energies for transactinides (superheavy elements). By means of the proposed formula the cross sections for asymmetric and symmetric cold fusion reactions (one-neutron-out reactions) are calculated. The fusion barrier and its position are calculated by using the folding heavy-ion potential that for spherical reaction partners has the form of a seventh-order polynomial of the radial coordinate with built-in dependence on the thickness of the nuclear surface, as well as on the separation energy of the least bound nucleon. Possibilities of further experimental exploitation of cold fusion in producing the superheavy nuclei are briefly discussed.

  10. Cross sections calculated for cold fusion reactions for producing superheavy nuclei

    SciTech Connect

    Smolanczuk, Robert

    2008-08-15

    We propose a handy formula for calculating the formation cross sections for optimal bombarding energies for transactinides (superheavy elements). By means of the proposed formula the cross sections for asymmetric and symmetric cold fusion reactions (one-neutron-out reactions) are calculated. The fusion barrier and its position are calculated by using the folding heavy-ion potential that for spherical reaction partners has the form of a seventh-order polynomial of the radial coordinate with built-in dependence on the thickness of the nuclear surface, as well as on the separation energy of the least bound nucleon. Possibilities of further experimental exploitation of cold fusion in producing the superheavy nuclei are briefly discussed.

  11. Possibilities for synthesis of new isotopes of superheavy elements in fusion reactions

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Greiner, Walter

    2012-01-01

    Background. In the “cold” fusion reactions based on the use of lead and bismuth targets, the proton-rich isotopes of superheavy (SH) elements up to Z=113 have been produced. More neutron-rich isotopes of SH elements (up to Z=118) have been synthesized in “hotter” fusion reactions of 48Ca with actinide targets. α-decay half-lives of different isotopes of the same SH elements (for example, 112) were found to vary by several orders of magnitude. This indicates strong shell effects in this area of the nuclear map. The understanding of these effects and other properties of SH nuclei is strongly impeded by the absence of experimental data on decay properties of the not-yet-synthesized isotopes of SH elements located between those produced in the “cold” fusion reactions and those produced in the “hot” fusion reactions and also by the yet missing neutron-enriched isotopes of these elements.Purpose. In this paper we search for the optimal fusion reactions which may be used to fill this gap of the nuclear map and significantly extend the area of known SH nuclei.Method. For the calculation of the cross sections we use the same approach which was employed earlier for successful predictions of all 48Ca induced fusion reactions.Results. Several fusion reactions of the stable projectiles 40Ar, 44Ca, and 48Ca with different isotopes of actinides (lighter and heavier than those that have been already utilized in the Dubna experiments) could be used for synthesis of new SH nuclei. Predicted cross sections for the production of new isotopes of SH nuclei were found to be quite large, and the corresponding experiments can be easily performed at existing facilities. For the first time a “narrow pathway” to the middle of the island of stability was found owing to possible β+ decay of SH nuclei 291115 and 291114 which could be formed in ordinary fusion reactions.

  12. Analysis of the role of neutron transfer in asymmetric fusion reactions at subbarrier energies

    SciTech Connect

    Ogloblin, A. A.; Zhang, H. Q.; Lin, C. J.; Jia, H. M.; Khlebnikov, S. V.; Kuzmin, E. A.; Danilov, A. N.; Demyanova, A. S.; Trzaska, W. H.; Xu, X. X.; Yang, F.; Sargsyan, V. V. Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2015-12-15

    The excitation functions were measured for the {sup 28}Si + {sup 208}Pb complete-fusion (capture) reaction at deep subbarrier energies. The results were compared with the cross sections predicted within the quantum diffusion approach. The role of neutron transfer in the case of positive Q values in the {sup 28}Si + {sup 124}Sn, {sup 208}Pb; {sup 30}Si + {sup 124}Sn, {sup 208}Pb; {sup 20}Ne + {sup 208}Pb; {sup 40}Ca + {sup 96}Zr; and {sup 134}Te + {sup 40}Ca complete-fusion (capture) reactions is discussed.

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

    NASA Astrophysics Data System (ADS)

    Lee, Myoung-Jae; Jung, Young-Dae

    2017-04-01

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

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

    PubMed

    Lee, Myoung-Jae; Jung, Young-Dae

    2017-04-01

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

  15. Lateral lumbar interbody fusion: a systematic review of complication rates.

    PubMed

    Hijji, Fady Y; Narain, Ankur S; Bohl, Daniel D; Ahn, Junyoung; Long, William W; DiBattista, Jacob V; Kudaravalli, Krishna T; Singh, Kern

    2017-10-01

    Lateral lumbar interbody fusion (LLIF) is a frequently used technique for the treatment of lumbar pathology. Despite its overall success, LLIF has been associated with a unique set of complications. However, there has been inconsistent evidence regarding the complication rate of this approach. To perform a systematic review analyzing the rates of medical and surgical complications associated with LLIF. Systematic review. 6,819 patients who underwent LLIF reported in clinical studies through June 2016. Frequency of complications within cardiac, vascular, pulmonary, urologic, gastrointestinal, transient neurologic, persistent neurologic, and spine (MSK) categories. This systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant studies that identified rates of any complication following LLIF procedures were obtained from PubMed, MEDLINE, and EMBASE databases. Articles were excluded if they did not report complications, presented mixed complication data from other procedures, or were characterized as single case reports, reviews, or case series containing less than 10 patients. The primary outcome was frequency of complications within cardiac, vascular, pulmonary, urologic, gastrointestinal, transient neurologic, persistent neurologic, and MSK categories. All rates of complications were based on the sample sizes of studies that mentioned the respective complications. The authors report no conflicts of interest directly or indirectly related to this work, and have not received any funds in support of this work. A total of 2,232 articles were identified. Following screening of title, abstract, and full-text availability, 63 articles were included in the review. A total of 6,819 patients had 11,325 levels fused. The rate of complications for the categories included were as follows: wound (1.38%; 95% confidence interval [CI]=1.00%-1.85%), cardiac (1.86%; CI=1.33%-2.52%), vascular (0.81%; CI=0

  16. Calculation of evaporation residue cross sections for the synthesis of superheavy nuclei in hot fusion reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Jinjuan; Wang, Chengbin; Ren, Zhongzhou

    2013-07-01

    A systematic calculation of the production cross sections of superheavy elements (SHEs) in hot fusion reactions is performed. First, we analyze the reactions of 48Ca + 238U, 244Pu, and 248Cm, from which the parameter values in the model for each process are determined by comparing the calculated capture, fusion, and evaporation residue (ER) cross sections, respectively, with the measured data. Then, we calculate the ER cross sections of other hot fusion reactions with the derived parameter values. The calculated results are in good agreement with the available data. Furthermore, the possible isotope production cross sections of elements 118 and 117 in the reactions of 48Ca + ACf and ABk are computed. We find that with the increase of the neutron number of the target, the production cross sections of the SHEs increase, primarily caused by the smaller neutron separation energies of the corresponding neutron-rich compound nucleus (CN). Finally, the production cross sections of elements 120 and 119 are evaluated in fusion-evaporation reactions with 50Ti as a projectile.

  17. Fusion reactions and experimental approaches to the synthesis of superheavy nuclei

    SciTech Connect

    Yeremin, A. V.; Utyonkov, V. K.; Oganessian, Yu. Ts.

    1998-02-15

    The question whether the asymmetric actinide based heavy ion reactions could be used for the synthesis of heavy (Z{>=}106) nuclides is essential from the point of view of the study of limitation on fusion, it is also important in such reactions new nuclides close to the magic number N=162 can be produced. Thus as the problem of a hindrance to fusion still remains unsolved the high excitation energy of the compound nucleus looks to be an obvious obstacle to using these reactions. Using the gas-filled recoil separator and electrostatic recoil separator VAS-SILISSA installed at the beam lines of the U-400 heavy ion cyclotron of the FLNR JINR we investigated the fusion reactions leading to 102, 103, 104, 105 and heaviest isotopes of the 106, 108 and 110 elements. The analysis of the measured cross-sections did not reveal any evidence of a hindrance to fusion at the ion bombarding energy close to the Coulomb barrier. {sup 48}Ca+{sup 232}Th{yields}{sup 280}110*, {sup 48}Ca+{sup 238}U{yields}{sup 286}112*, {sup 48}Ca+{sup 244}Pu{yields}{sup 292}114* appear to be the best reactions from the point of view of their cross-sections.

  18. A simple reaction-rate model for turbulent diffusion flames

    NASA Technical Reports Server (NTRS)

    Bangert, L. H.

    1975-01-01

    A simple reaction rate model is proposed for turbulent diffusion flames in which the reaction rate is proportional to the turbulence mixing rate. The reaction rate is also dependent on the mean mass fraction and the mean square fluctuation of mass fraction of each reactant. Calculations are compared with experimental data and are generally successful in predicting the measured quantities.

  19. Hydrogen generation arising from the {sup 59}Ni(n,p) reaction and its impact on fission-fusion correlations

    SciTech Connect

    Greenwood, L.R.; Garner, A.F.

    1996-04-01

    Whilte the influence of transmutant helium on radiation-induced microstructural evolution has often been studied, there is a tendency to overlook the influence of concurrently-generated hydrogen. There have been some recent speculation and studies, however, that suggest that the influence of hydrogen may be enhanced in the presence of large amounts of helium, especially at lower irradiation temperatures typical of projected ITER operation. The impact of the (n,p) reaction on both hydrogen generation rates and displacement rates are evaluated in this paper for a variety of neutron spectra employed in fission-fusion correlation.

  20. The new possibility of the fusion p + 11B chain reaction being induced by intense laser pulses

    NASA Astrophysics Data System (ADS)

    Belyaev, V. S.; Krainov, V. P.; Matafonov, A. P.; Zagreev, B. V.

    2015-09-01

    We discuss the experimental and theoretical principal schemes of a thermonuclear reactor, based on the fusion reaction p + 11B: beam collisions, fusion in degenerate plasmas, ignition at the plasma, particle acceleration by nonlinear ponderomotive forces and irradiation of the solid 11B target by a proton beam at the Coulomb explosion of hydrogen microdroplets. The fusion reaction p + 11B can be initiated by ultrashort high intensity laser pulses under conditions far from thermodynamic equilibrium. This may result in fusion products containing a small amount of neutrons and other nuclear radiation effects. It was found that the fusion reaction p + 11B produces further nuclear reactions and generates high-energy protons. The latter can support the chain reaction process. Our approach allows us to also investigate nuclear reactions in the early Universe and in stars.

  1. Inertial confinement fusion reaction chamber and power conversion system study

    SciTech Connect

    Maya, I.; Schultz, K.R.; Battaglia, J.M.; Buksa, J.J.; Creedson, R.L.; Erlandson, O.D.; Levine, H.E.; Roelant, D.F.; Sanchez, H.W.; Schrader, S.A.

    1984-09-01

    GA Technologies has developed a conceptual ICF reactor system based on the Cascade rotating-bed reaction chamber concept. Unique features of the system design include the use of low activation SiC in a reaction chamber constructed of box-shaped tiles held together in compression by prestressing tendons to the vacuum chamber. Circulating Li/sub 2/O granules serve as the tritium breeding and energy transport material, cascading down the sides of the reaction chamber to the power conversion system. The total tritium inventory of the system is 6 kg; tritium recovery is accomplished directly from the granules via the vacuum system. A system for centrifugal throw transport of the hot Li/sub 2/O granules from the reaction chamber to the power conversion system has been developed. A number of issues were evaluated during the course of this study. These include the response of first-layer granules to the intense microexplosion surface heat flux, cost effective fabrication of Li/sub 2/O granules, tritium inventory and recovery issues, the thermodynamics of solids-flow options, vacuum versus helium-medium heat transfer, and the tradeoffs of capital cost versus efficiency for alternate heat exchange and power conversion system option. The resultant design options appear to be economically competitive, safe, and environmentally attractive.

  2. Nuclear reaction products that would appear if substantial cold fusion occurred

    SciTech Connect

    Mueller, D.; Grisham, L.R. . Plasma Physics Lab.)

    1989-11-01

    This paper reports on recent claims of net energy production by cold fusion that have prompted an examination of all the positive Q value, two-body nuclear reactions that might result from the fusion of any of the isotopes in the apparatus used by Fleischmann and Pons. Any energy production that may result from cold fusion would be accompanied by copious production of nuclear reaction products (on the order of 10{sup 13}/s). Furthermore, the elementary properties of the alpha particle at the deuteron + deuteron threshold are discussed. An important property of the alpha at this high excitation is its nearly prompt (10{sup {minus}20} s) decay by particle emission to {sup 3}He + n or triton + proton.

  3. Dynamical Dipole mode in heavy-ion fusion reactions in the 192Pb mass region

    NASA Astrophysics Data System (ADS)

    Parascandolo, C.; Pierroutsakou, D.; Alba, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Agodi, C.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; La Commara, M.; Martin, B.; Mazzocchi, C.; Mazzocco, M.; Rizzo, C.; Romoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifiró, A.; Trimarchi, M.

    2015-04-01

    The dynamical dipole mode was investigated in the mass region of the 192Pb compound nucleus, by using the 40Ca + 152Sm and 48Ca + 144Sm reactions at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for the first time. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.

  4. Influence of projectile neutron number on cross section in cold fusion reactions

    SciTech Connect

    Dragojevic, Irena; Dragojevic, I.; Gregorich, K.E.; Dullmann, Ch.E.; Folden III, C.M.; Garcia, M.A.; Gates, J.M.; Nelson, S.L.; Sudowe, R.; Nitsche, H.

    2007-09-01

    Elements 107-112 [1,2] have been discovered in reactions between {sup 208}Pb or {sup 209}Bi targets and projectiles ranging from {sup 54}Cr through {sup 70}Zn. In such reactions, the compound nucleus can be formed at excitation energies as low as {approx}12 MeV, thus this type of reaction has been referred to as 'cold fusion'. The study of cold fusion reactions is an indispensable approach to gaining a better understanding of heavy element formation and decay. A theoretical model that successfully predicts not only the magnitudes of cold fusion cross sections, but also the shapes of excitation functions and the cross section ratios between various reaction pairs was recently developed by Swiatecki, Siwek-Wilczynska, and Wilczynski [3,4]. This theoretical model, also referred to as Fusion by Diffusion, has been the guide in all of our cold fusion studies. One particularly interesting aspect of this model is the large predicted difference in cross sections between projectiles differing by two neutrons. The projectile pair where this difference is predicted to be largest is {sup 48}Ti and {sup 50}Ti. To test and extend this model, {sup 208}Pb({sup 48}Ti,n){sup 255}Rf and {sup 208}Pb({sup 50}Ti,n){sup 257}Rf excitation functions were recently measured at the Lawrence Berkeley National Laboratory's (LBNL) 88-Inch Cyclotron utilizing the Berkeley Gas-filled Separator (BGS). The {sup 50}Ti reaction was carried out with thin lead targets ({approx}100 {micro}g/cm{sup 2}), and the {sup 48}Ti reaction with both thin and thick targets ({approx}470 {micro}g/cm{sup 2}). In addition to this reaction pair, reactions with projectile pairs {sup 52}Cr and {sup 54}Cr [5], {sup 56}Fe and {sup 58}Fe [6], and {sup 62}Ni [7] and {sup 64}Ni [8] will be discussed and compared to the Fusion by Diffusion predictions. The model predictions show a very good agreement with the data.

  5. Representing Rate Equations for Enzyme-Catalyzed Reactions

    ERIC Educational Resources Information Center

    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…

  6. Representing Rate Equations for Enzyme-Catalyzed Reactions

    ERIC Educational Resources Information Center

    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…

  7. Empirical rate formula for ion-dipolar molecule reactions

    NASA Astrophysics Data System (ADS)

    Sato, Shin

    2017-04-01

    New empirical rate formula for the low temperature reactions is proposed. The formula proposed previously has been simplified by using incomplete gamma function. A few examples of temperature dependence of rate constants for the reactions of ions with dipolar molecules and that for the reaction F +H2 →HF +H are demonstrated by using new rate formula.

  8. Charged particle decay of hot and rotating 88Mo nuclei in fusion-evaporation reactions

    NASA Astrophysics Data System (ADS)

    Valdré, S.; Piantelli, S.; Casini, G.; Barlini, S.; Carboni, S.; Ciemała, M.; Kmiecik, M.; Maj, A.; Mazurek, K.; Cinausero, M.; Gramegna, F.; Kravchuk, V. L.; Morelli, L.; Marchi, T.; Baiocco, G.; Bardelli, L.; Bednarczyk, P.; Benzoni, G.; Bini, M.; Blasi, N.; Bracco, A.; Brambilla, S.; Bruno, M.; Camera, F.; Chbihi, A.; Corsi, A.; Crespi, F. C. L.; D'Agostino, M.; Degerlier, M.; Fabris, D.; Fornal, B.; Giaz, A.; Krzysiek, M.; Leoni, S.; Matejska-Minda, M.; Mazumdar, I.; MÈ©czyński, W.; Million, B.; Montanari, D.; Myalski, S.; Nicolini, R.; Olmi, A.; Pasquali, G.; Prete, G.; Roberts, O. J.; Styczeń, J.; Szpak, B.; Wasilewska, B.; Wieland, O.; Wieleczko, J. P.; ZiÈ©bliński, M.

    2016-03-01

    A study of fusion-evaporation and (partly) fusion-fission channels for the 88Mo compound nucleus, produced at different excitation energies in the reaction 48Ti+40Ca at 300, 450, and 600 MeV beam energies, is presented. Fusion-evaporation and fusion-fission cross sections have been extracted and compared with the existing systematics. Experimental data concerning light charged particles have been compared with the prediction of the statistical model in its implementation in the gemini++ code, well suited even for high spin systems, in order to tune the main model parameters in a mass region not abundantly covered by exclusive experimental data. Multiplicities for light charged particles emitted in fusion evaporation events are also presented. Some discrepancies with respect to the prediction of the statistical model have been found for forward emitted α particles; they may be due both to pre-equilibrium emission and to reaction channels (such as deep inelastic collisions or quasifission/quasifusion) different from the compound nucleus formation.

  9. Recent experimental results in sub- and near-barrier heavy-ion fusion reactions

    NASA Astrophysics Data System (ADS)

    Montagnoli, Giovanna; Stefanini, Alberto M.

    2017-08-01

    Recent advances obtained in the field of near and sub-barrier heavy-ion fusion reactions are reviewed. Emphasis is given to the results obtained in the last decade, and focus is mainly on the experimental work performed concerning the influence of transfer channels on fusion cross sections and the hindrance phenomenon far below the barrier. Indeed, early data of sub-barrier fusion taught us that cross sections may strongly depend on the low-energy collective modes of the colliding nuclei, and, possibly, on couplings to transfer channels. The coupled-channels (CC) model has been quite successful in the interpretation of the experimental evidences. Fusion barrier distributions often yield the fingerprint of the relevant coupled channels. Recent results obtained by using radioactive beams are reported. At deep sub-barrier energies, the slope of the excitation function in a semi-logarithmic plot keeps increasing in many cases and standard CC calculations overpredict the cross sections. This was named a hindrance phenomenon, and its physical origin is still a matter of debate. Recent theoretical developments suggest that this effect, at least partially, may be a consequence of the Pauli exclusion principle. The hindrance may have far-reaching consequences in astrophysics where fusion of light systems determines stellar evolution during the carbon and oxygen burning stages, and yields important information for exotic reactions that take place in the inner crust of accreting neutron stars.

  10. Fusion of artificial membranes with mammalian spermatozoa. Specific involvement of the equatorial segment after acrosome reaction.

    PubMed

    Arts, E G; Kuiken, J; Jager, S; Hoekstra, D

    1993-11-01

    The fusogenic properties of bovine and human spermatozoa membranes were investigated, using phospholipid bilayers (liposomes) as target membranes. Fusion was monitored by following lipid mixing, as revealed by an assay based on resonance-energy transfer. In addition, fusion was visualized by fluorescence microscopy, using fluorescent lipid vesicles. Cryopreserved bovine sperm fused with liposomes before induction of the acrosome reaction, fluorescence being located in essentially all spermatozoa membrane domains. Fresh bovine and human spermatozoa fused with liposomes only after the induction of the acrosome reaction, as triggered by calcium ionophore A23187 or zonae pellucidae (proteins), while the fluorescence distribution was mainly restricted to the equatorial segment (ES). However, with spermatozoa that had undergone a freeze/thawing cycle, domains other than ES also became labeled. Hence, the redistribution of the lipid probes over the entire membrane occurring during lipid mixing with cryopreserved bovine sperm is probably related to membrane perturbations caused by long-term cryopreservation. Fusion with liposomes was governed by spermatozoa factors and required the presence of acidic phospholipids like cardiolipin and phosphatidylserine in the liposomal bilayer. Incorporation of the zwitterionic lipid phosphatidylcholine in the vesicles inhibited the fusion reaction. Fusion was pH dependent. The results indicate that the ES is the primary domain of spermatozoa membranes that harbours the fusogenic capacity of sperm. Liposomes appear a valuable tool in further characterizing the properties of this domain, which has been claimed [Yanagimachi, R. (1988) in The physiology of reproduction (Knobil, E. & Neill, J., eds) pp. 135-185, Raven Press, New York] to represent the putative, initial fusion site for the oocyte.

  11. Variables Affecting Fusion Rates in the Rat Posterolateral Spinal Fusion Model with Autogenic/Allogenic Bone Grafts: A Meta-analysis.

    PubMed

    Ishida, Wataru; Elder, Benjamin D; Holmes, Christina; Lo, Sheng-Fu L; Witham, Timothy F

    2016-11-01

    The rat posterolateral spinal fusion model with autogenic/allogenic bone graft (rat PFABG) has been increasingly utilized as an experimental model to assess the efficacy of novel fusion treatments. The objective of this study was to investigate the reliability of the rat PFABG model and examine the effects of different variables on spinal fusion. A web-based literature search from January, 1970 to September, 2015, yielded 26 studies, which included 40 rat PFABG control groups and 449 rats. Data regarding age, weight, sex, and strain of rats, graft volume, graft type, decorticated levels, surgical approach, institution, the number of control rats, fusion rate, methods of fusion assessment, and timing of fusion assessment were collected and analyzed. The primary outcome variable of interest was fusion rate, as evaluated by manual palpation. Fusion rates varied widely, from 0 to 96%. The calculated overall fusion rate was 46.1% with an I (2) value of 62.4, which indicated moderate heterogeneity. Weight >300 g, age >14 weeks, male rat, Sprague-Dawley strain, and autogenic coccyx grafts increased fusion rates with statistical significance. Additionally, an assessment time-point ≥8 weeks had a trend towards statistical significance (p = 0.070). Multi-regression analysis demonstrated that timing of assessment and age as continuous variables, as well as sex as a categorical variable, can predict the fusion rate with R (2) = 0.82. In an inter-institution reliability analysis, the pooled overall fusion rate was 50.0% [44.8, 55.3%], with statistically significant differences among fusion outcomes at different institutions (p < 0.001 and I (2) of 72.2). Due to the heterogeneity of fusion outcomes, the reliability of the rat PFABG model was relatively limited. However, selection of adequate variables can optimize its use as a control group in studies evaluating the efficacy of novel fusion therapies.

  12. Understanding Fuel Magnetization and Mix Using Secondary Nuclear Reactions in Magneto-Inertial Fusion

    NASA Astrophysics Data System (ADS)

    Schmit, P. F.; Knapp, P. F.; Hansen, S. B.; Gomez, M. R.; Hahn, K. D.; Sinars, D. B.; Peterson, K. J.; Slutz, S. A.; Sefkow, A. B.; Awe, T. J.; Harding, E.; Jennings, C. A.; Chandler, G. A.; Cooper, G. W.; Cuneo, M. E.; Geissel, M.; Harvey-Thompson, A. J.; Herrmann, M. C.; Hess, M. H.; Johns, O.; Lamppa, D. C.; Martin, M. R.; McBride, R. D.; Porter, J. L.; Robertson, G. K.; Rochau, G. A.; Rovang, D. C.; Ruiz, C. L.; Savage, M. E.; Smith, I. C.; Stygar, W. A.; Vesey, R. A.

    2014-10-01

    Magnetizing the fuel in inertial confinement fusion relaxes ignition requirements by reducing thermal conductivity and changing the physics of burn product confinement. Diagnosing the level of fuel magnetization during burn is critical to understanding target performance in magneto-inertial fusion (MIF) implosions. In pure deuterium fusion plasma, 1.01 MeV tritons are emitted during deuterium-deuterium fusion and can undergo secondary deuterium-tritium reactions before exiting the fuel. Increasing the fuel magnetization elongates the path lengths through the fuel of some of the tritons, enhancing their probability of reaction. Based on this feature, a method to diagnose fuel magnetization using the ratio of overall deuterium-tritium to deuterium-deuterium neutron yields is developed. Analysis of anisotropies in the secondary neutron energy spectra further constrain the measurement. Secondary reactions also are shown to provide an upper bound for the volumetric fuel-pusher mix in MIF. The analysis is applied to recent MIF experiments [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014), 10.1103/PhysRevLett.113.155003] on the Z Pulsed Power Facility, indicating that significant magnetic confinement of charged burn products was achieved and suggesting a relatively low-mix environment. Both of these are essential features of future ignition-scale MIF designs.

  13. SU-D-304-07: Application of Proton Boron Fusion Reaction to Radiation Therapy

    SciTech Connect

    Jung, J; Yoon, D; Shin, H; Kim, M; Suh, T

    2015-06-15

    Purpose: we present the introduction of a therapy method using the proton boron fusion reaction. The purpose of this study is to verify the theoretical validity of proton boron fusion therapy using Monte Carlo simulations. Methods: After boron is accumulated in the tumor region, the emitted from outside the body proton can react with the boron in the tumor region. An increase of the proton’s maximum dose level is caused by the boron and only the tumor cell is damaged more critically. In addition, a prompt gamma ray is emitted from the proton boron reaction point. Here we show that the effectiveness of the proton boron fusion therapy (PBFT) was verified using Monte Carlo simulations. Results: We found that a dramatic increase by more than half of the proton’s maximum dose level was induced by the boron in the tumor region. This increase occurred only when the proton’s maximum dose point was located within the boron uptake region (BUR). In addition, the 719 keV prompt gamma ray peak produced by the proton boron fusion reaction was positively detected. Conclusion: This therapy method features the advantages such as the application of Bragg-peak to the therapy, the accurate targeting of tumor, improved therapy effects, and the monitoring of the therapy region during treatment.

  14. Understanding fuel magnetization and mix using secondary nuclear reactions in magneto-inertial fusion.

    PubMed

    Schmit, P F; Knapp, P F; Hansen, S B; Gomez, M R; Hahn, K D; Sinars, D B; Peterson, K J; Slutz, S A; Sefkow, A B; Awe, T J; Harding, E; Jennings, C A; Chandler, G A; Cooper, G W; Cuneo, M E; Geissel, M; Harvey-Thompson, A J; Herrmann, M C; Hess, M H; Johns, O; Lamppa, D C; Martin, M R; McBride, R D; Porter, J L; Robertson, G K; Rochau, G A; Rovang, D C; Ruiz, C L; Savage, M E; Smith, I C; Stygar, W A; Vesey, R A

    2014-10-10

    Magnetizing the fuel in inertial confinement fusion relaxes ignition requirements by reducing thermal conductivity and changing the physics of burn product confinement. Diagnosing the level of fuel magnetization during burn is critical to understanding target performance in magneto-inertial fusion (MIF) implosions. In pure deuterium fusion plasma, 1.01 MeV tritons are emitted during deuterium-deuterium fusion and can undergo secondary deuterium-tritium reactions before exiting the fuel. Increasing the fuel magnetization elongates the path lengths through the fuel of some of the tritons, enhancing their probability of reaction. Based on this feature, a method to diagnose fuel magnetization using the ratio of overall deuterium-tritium to deuterium-deuterium neutron yields is developed. Analysis of anisotropies in the secondary neutron energy spectra further constrain the measurement. Secondary reactions also are shown to provide an upper bound for the volumetric fuel-pusher mix in MIF. The analysis is applied to recent MIF experiments [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z Pulsed Power Facility, indicating that significant magnetic confinement of charged burn products was achieved and suggesting a relatively low-mix environment. Both of these are essential features of future ignition-scale MIF designs.

  15. Synthesis of transactinide nuclei in cold fusion reactions using radioactive beams

    NASA Astrophysics Data System (ADS)

    Smolańczuk, Robert

    2010-06-01

    Chances of synthesis of transactinide nuclei in cold fusion reactions (one-neutron-out reactions) using radioactive beams are evaluated. Because in most of the cases intensities of radioactive beams are significantly less than those of the stable beams, reactions with the greatest radioactive-beam intensities for the particular elements are considered. The results are compared with the recent ones obtained by Loveland [Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.76.014612 76, 014612 (2007)], who investigated the same nuclei.

  16. Study of the mechanism of muon-catalyzed t + t fusion reaction

    SciTech Connect

    Bogdanova, L. N.; Demin, D. L.; Filchenkov, V. V.

    2015-01-15

    The mechanism for the muon catalyzed fusion reaction t + t → {sup 4}He + 2n + 11.33 MeV is investigated. The model of the cascade reaction with {sup 5}He as an intermediate state is considered, both the ground and the first exited states being taken into account. The neutron energy spectrum measured in the recent experiment is compared with the Monte-Carlo-simulated one. Varying reaction parameters, we obtain optimum values for the relative weights of the {sup 5}He ground and excited states and for the excitation energy and width of the excited state.

  17. Near threshold two meson production in hardonic fusion reactions

    NASA Astrophysics Data System (ADS)

    Jahn, Rainer

    1991-04-01

    An approved and funded exclusive COSY experiment is presented, which focuses on near threshold two meson production via the reactions p+d→3 He+π+π- and p+d→3 He+K+K-. It takes advantage of the high quality of the cooled external COSY beam and the existing spectrometer BIG KARL. The setup consists of a vertex wall and a scintillator cylinder and endcap covering a 4π solid angle. The large efficiency and high resolution of this detection method will yield precision data on the low energy (T<50 MeV) meson-meson interaction and probe into questions like the ABC-effect and KḲ molecule. The detector further allows a measurement of possible radiative φ (1020) decay, which will directly probe the strange quark content of the f0(975). Existing inclusive data as well as first results of a very recent `semi-exclusive' experiment performed at SATURNE will be also be presented.

  18. Systematics of calculated cold-fusion barriers for reactions leading to compound systems from Z=104 to Z=126

    SciTech Connect

    Moeller, P.; Armbruster, P.; Hofmann, S.; Muenzenberg, G.

    1998-12-21

    We have previously shown that just as the decay properties of nuclei in the heavy region depend strongly on shell structure, shell structure also dramatically affects the fusion entrance channel. The six most recently discovered new elements were all formed in cold-fusion reactions. We discuss here the effect of the doubly-magic structure of the target in cold-fusion reactions on the fusion barrier and present a systematic study of cold-fusion heavy-ion reaction barriers for elements from Rf to Z=126. We find that the systematics of the optimum reaction energy may change near Z=112, because here the highest point on the interaction barrier shifts in location from near the touching distance at r/R{sub 0}{approx_equal}1.5 to r/R{sub 0}{approx_equal}1.0, which is a shape configuration just slightly more deformed than the ground state.

  19. Systematics of calculated cold-fusion barriers for reactions leading to compound systems from Z=104 to Z=126

    SciTech Connect

    Moller, P.; Hofmann, S.; Munzenberg, G.

    1998-12-01

    We have previously shown that just as the decay properties of nuclei in the heavy region depend strongly on shell structure, shell structure also dramatically affects the fusion entrance channel. The six most recently discovered new elements were all formed in cold-fusion reactions. We discuss here the effect of the doubly-magic structure of the target in cold-fusion reactions on the fusion barrier and present a systematic study of cold-fusion heavy-ion reaction barriers for elements from Rf to Z=126. We find that the systematics of the optimum reaction energy may change near Z=112, because here the highest point on the interaction barrier shifts in location from near the touching distance at r/R{sub 0}{approx}1.5 to r/R{sub 0}{approx}1.0, which is a shape configuration just slightly more deformed than the ground state. {copyright} {ital 1998 American Institute of Physics.}

  20. Universal damping mechanism of quantum vibrations in deep sub-barrier fusion reactions

    NASA Astrophysics Data System (ADS)

    Ichikawa, Takatoshi; Matsuyanagi, Kenichi

    2015-08-01

    We demonstrate the damping of quantum octupole vibrations near the touching point when two colliding nuclei approach each other in the mass-asymmetric 16 O + 208 Pb system, for which the strong fusion hindrance was clearly observed. We, for the first time, apply the random-phase approximation method to the heavy-mass asymmetric dinuclear system to calculate the transition strength B (E 3 ) as a function of the center-of-mass distance. The obtained B (E 3 ) strengths are substantially damped near the touching point, because the single-particle wave functions of the two nuclei strongly mix with each other and a neck is formed. The energy-weighted sums of B (E 3 ) are also strongly correlated with the damping factor, which is phenomenologically introduced in the standard coupled-channel calculations to reproduce the fusion hindrance. This strongly indicates that the damping of the quantum vibrations universally occurs in the deep sub-barrier fusion reactions.

  1. Deep Sub-Barrier Fusion Enhancement in the {sup 6}He+{sup 206}Pb Reaction

    SciTech Connect

    Penionzhkevich, Yu.E.; Zagrebaev, V.I.; Lukyanov, S.M.; Kalpakchieva, R.

    2006-04-28

    The fusion of {sup 6}He with {sup 206}Pb has been studied at energies close to and below the Coulomb barrier. The experiment was carried out at the Dubna Radioactive Ion Beams complex of FLNR, JINR. The {sup 6}He beam intensity was about 5x10{sup 6} pps, the maximum energy being 60.3{+-}0.4 MeV. The yield of the {sup 210}Po isotope, produced in the 2n-evaporation channel, demonstrates an extremely large enhancement of the sub-barrier fusion cross section as compared with the {sup 4}He+{sup 208}Pb reaction. This enhancement is most likely due to the mechanism of 'sequential fusion' with an intermediate neutron transfer from {sup 6}He to the Pb nucleus with positive Q values.

  2. In-cell reaction rate distributions and cell-average reaction rates in fast critical assemblies

    SciTech Connect

    Brumbach, S.B.; Gasidlo, J.M.

    1985-08-01

    Measurements are described for determining average values of fission rates in /sup 235/U, /sup 238/U and /sup 239/Pu and capture rates in /sup 238/U for heterogeneous cells used to construct fast critical assemblies. The measurements are based on irradiations of foils of /sup 238/U, /sup 235/U and /sup 239/Pu with counting of fission and capture products using gamma-ray spectroscopy. Both plate and pin cells are considered. Procedures are described for inferring cell-average reaction rate values from a single foil location based on a cell using a quantity called a cell factor. Cell factors are determined from special measurements in which several foils are irradiated within a cell. Comparisons are presented between cell factors determined by measurements and by Monte Carlo calculations which lend credibility to the measurement procedures.

  3. Studies of Neutron-Deficient Nuclei Near the Z = 82 Shell Closure via Cold Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Carpenter, M. P.; Kondev, F. G.; Janssens, R. V. F.; Seweryniak, D.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Zhu, S.; Camera, F.; Bracco, A.; Million, B.; Leoni, S.; Jenkins, D. G.; Wadsworth, R.

    2009-03-01

    Over the last decade, we have performed in-beam experiments using Gammasphere+FMA to measure excited states in proton-rich Au, Hg, Tl and Pb isotopes. In these studies, the use of the FMA is essential in order to differentiate evaporation residues from the large fission background which dominates the reaction cross-section. In addition, we have found that using near-symmetric reactions at bombarding energies near the Coloumb barrier is beneficial in performing these studies. By keeping the bombarding energy low, fission is minimized and the reaction products are concentrated in only a few channels. New results have recently been obtained using the 90Zr+92Mo reaction to study shape co-existence in 181Tl via the lp evaporation channel. In addition, we have measured the total γ-ray energy and multiplicity associated with the surviving compund system, 179Au, following the fusion reaction, 90Zr+89Y.

  4. Suppression of the chain nuclear fusion reaction based on the p+{sup 11}B reaction because of the deceleration of alpha particles

    SciTech Connect

    Shmatov, M. L.

    2016-09-15

    It is shown that a rapid deceleration of alpha particles in matter of electron temperature up to 100 keV leads a strong suppression of the chain nuclear fusion reaction on the basis of the p+{sup 11}B reaction with the reproduction of fast protons in the α+{sup 11}B and n+{sup 10}B reactions. The statement that the chain nuclear fusion reaction based on the p+{sup 11}B reaction with an acceleration of {sup 11}B nuclei because of elastic alpha-particle scattering manifests itself in experiments at the PALS (Prague Asterix Laser System) facility is analyzed.

  5. Multi-Sampling Ionization Chamber (MUSIC) for measurements of fusion reactions with radioactive beams

    NASA Astrophysics Data System (ADS)

    Carnelli, P. F. F.; Almaraz-Calderon, S.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Digiovine, B.; Esbensen, H.; Fernández Niello, J.; Henderson, D.; Jiang, C. L.; Lai, J.; Marley, S. T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.; Ugalde, C.

    2015-11-01

    A detection technique for high-efficiency measurements of fusion reactions with low-intensity radioactive beams was developed. The technique is based on a Multi-Sampling Ionization Chamber (MUSIC) operating as an active target and detection system, where the ionization gas acts as both target and counting gas. In this way, we can sample an excitation function in an energy range determined by the gas pressure, without changing the beam energy. The detector provides internal normalization to the incident beam and drastically reduces the measuring time. In a first experiment we tested the performance of the technique by measuring the 10,13,15C+12C fusion reactions at energies around the Coulomb barrier.

  6. Computer Tomography assessment of the fusion rate after posterior arthroscopic subtalar arthrodesis.

    PubMed

    Thaunat, Mathieu; Bajard, Xavier; Boisrenoult, Philippe; Beaufils, Philippe; Oger, Philippe

    2012-05-01

    The purpose of this study was to assess the fusion rate on CT examinations and to correlate clinically the functional result with the degree of bone fusion in the subtalar joint after posterior arthroscopic subtalar arthrodesis (PASTA). Fourteen cases, from 36 to 84 years old, were retrospectively followed-up for a minimum of one year (range 12-92 months). A CT scan had been systematically performed at the six-month follow-up visit. The CT scans were examined in sagittal 2-mm-thick reformatted slices, measuring the length of the joint surface and the length of the fused portion of the joint space on each image. At six months, the average fusion ratio was 39±19% (range 0-69%). Fusion defined by a fusion ratio superior or equal to 33% on the CT scan was observed in 11 cases. One patient had a delayed union and required a revision of fixation. One patient had a bilateral nonunion. Mean average AOFAS score improved from 51±10 to 77±9 at last follow-up. Compared to open procedures, the posterior arthroscopic fusion seems to offer a promising alternative. However, our results suggest that the fusion rate following PASTA is not as favourable as reported in previous studies. Factors such as adequate compression and stable fixation provided by the screws together with the surgeons' experience with this demanding technique are of the utmost importance. A 33% CT fusion ratio threshold could accurately discriminate between clinical stability and instability.

  7. NACRE: A European Compilation of Reaction Rates for Astrophysics

    SciTech Connect

    Carmen Angulo

    1999-12-31

    We report on the program and results of the NACRE network (Nuclear Astrophysics Compilation of Reaction rates). We have compiled low-energy cross section data for 86 charged-particle induced reactions involving light (1 {<=} Z {<=} 14) nuclei. The corresponding Maxwellian-averaged thermonuclear reactions rates are calculated in the temperature range from 10{sup 6} K to 10{sup 10} K. The web site, http://pntpm.ulb.ac.be/nacre.htm, including the cross section data base and the reaction rates, allows users to browse electronically all the information on the reactions studied in this compilation.

  8. NACRE: A European Compilation of Reaction rates for Astrophysics

    SciTech Connect

    Angulo, Carmen

    1999-11-16

    We report on the program and results of the NACRE network (Nuclear Astrophysics Compilation of REaction rates). We have compiled low-energy cross section data for 86 charged-particle induced reactions involving light (1{<=}Z{<=}14) nuclei. The corresponding Maxwellian-averaged thermonuclear reactions rates are calculated in the temperature range from 10{sup 6} K to 10{sup 10} K. The web site http://pntpm.ulb.ac.be/nacre.htm, including the cross section data base and the reaction rates, allows users to browse electronically all the information on the reactions studied in this compilation.

  9. Effect of charge polarization on the Coulomb barrier for cold-fusion reactions

    SciTech Connect

    Ichikawa, Takatoshi; Iwamoto, Akira

    2005-06-01

    We estimate the decrease of the Coulomb-barrier height between colliding partners due to charge polarizations in the entrance channel for cold-fusion reactions. The resulting charge displacements between protons and neutrons are the sum of the surface- and volume-charge components. We show the difference between the charge polarization of light and heavy nuclei and the decrease of the Coulomb barrier height for synthesizing superheavy elements.

  10. A reassessment of surface friction model for maximum cold fusion reactions in superheavy mass region

    SciTech Connect

    Fukushima, A.; Wada, T.; Ohta, M.; Nasirov, A.; Aritomo, Y.

    2007-02-26

    We have made a study on the capture process of 40,48Ca+ 208Pb systems with a dynamical approach based on the surface friction model. The deformation of the nuclei due to the mutual excitation is taken into account. We have calculated the capture cross sections for several values of the friction coefficients. It was shown that, in the cold fusion reactions, the friction parameters of the surface friction model needs to be reexamined.

  11. Heavy-ion inertial fusion: influence of target gain on accelerator parameters for vacuum-propagation regimes in reaction chambers

    SciTech Connect

    Mark, J.W.K.; Bangerter, R.O.; Barletta, W.A.; Fawley, W.M.; Judd, D.L.

    1982-03-04

    Target physics imposes requirements on the design of inertial fusion drivers. The influence of beam propagation in near vacuum fusion reaction chambers is evaluated for the relation between target gain and the phase-space requirements of heavy-ion accelerators. Initial results suggest that neutralization of the ion beam has a much greater positive effect than the deleterious one of beam stripping provided that the fusion chamber pressure is < 10/sup -3/ torr (of Li vapor or equivalent).

  12. Ankle arthrodesis fusion rates for mesenchymal stem cell bone allograft versus proximal tibia autograft.

    PubMed

    Anderson, John J; Boone, Joshua J; Hansen, Myron; Brady, Chad; Gough, Adam; Swayzee, Zflan

    2014-01-01

    Ankle arthrodesis is commonly used in the treatment of ankle arthritis. The present study compared mesenchymal stem cell (MSC) bone allografts and proximal tibia autografts as adjuncts in performing ankle arthrodesis. A total of 109 consecutive ankle fusions performed from 2002 to 2008 were evaluated retrospectively. Of the 109 fusions, 24 were excluded from the present study, leaving 85 patients who had undergone ankle arthrodesis. Of the 85 patients, 41 had received a proximal tibia autograft and 44, an MSC bone allograft. These 2 groups were reviewed and compared retrospectively at least 2 years postoperatively for the overall fusion rate, interval to radiographic fusion, and interval to clinical fusion. A modified and adjusted American College of Foot and Ankle Surgeons ankle scale was used to measure patient satisfaction. The overall fusion rate was 84.1% in the MSC bone allograft group and 95.1% in the proximal tibia autograft group (p = .158). The corresponding mean intervals to radiographic fusion were 13.0 ± 2.5 weeks and 11.3 ± 2.8 weeks (p ≤ .001). The interval to clinical fusion was 13.1 ± 2.1 weeks and 11.0 ± 1.5 weeks (p ≤ .001) in the MSC bone allograft and proximal tibia autograft group, respectively. No statistically significant difference was found in the fusion rates between the MSC bone allograft and proximal tibia autograft groups. Also, no statistically significant difference was found between the preoperative and postoperative scores using a modified and adjusted American College of Foot and Ankle Surgeons ankle scale between the 2 groups (p = .41 and p = .44, respectively). A statistically significant delay to radiographic and clinical fusion was present in the MSC bone allograft group compared with the proximal tibia autograft group; however, no difference was found in patient satisfaction.

  13. Parameterization of fusion barriers for light-projectiles-induced reactions using the proximity approach

    NASA Astrophysics Data System (ADS)

    Gharaei, R.; Sheibani, J.

    2016-05-01

    In this article we propose a pocket formula for fusion barriers calculated by three versions of the proximity formalism, namely AW 95, Bass 80 and Prox. 2010 potentials, for fusion reactions involving the collisions of the proton and helium projectiles with different targets in mass ranges 51≤ AT ≤ 130 and 40≤ AT ≤ 233 , respectively. For the first type of the colliding systems, it is shown that the proposed pocket formulas are able to predict the actual values of RB and VB within accuracies of ±0.4% and ±0.45% , respectively. Moreover, for the second type of the selected reactions, these accuracies are obtained ±0.24% and ±0.36% , respectively. In this study, the ability of the present pocket formulas is also demonstrated to predict the exact values of the fusion cross sections for our selected mass ranges. A comparison with the results of the previous pocket formulas reveals that our parameterized forms are more successful to reproduce the empirical data of the barrier height and position in the proton- and helium-induced reactions.

  14. Fusion

    NASA Astrophysics Data System (ADS)

    Herman, Robin

    1990-10-01

    The book abounds with fascinating anecdotes about fusion's rocky path: the spurious claim by Argentine dictator Juan Peron in 1951 that his country had built a working fusion reactor, the rush by the United States to drop secrecy and publicize its fusion work as a propaganda offensive after the Russian success with Sputnik; the fortune Penthouse magazine publisher Bob Guccione sank into an unconventional fusion device, the skepticism that met an assertion by two University of Utah chemists in 1989 that they had created "cold fusion" in a bottle. Aimed at a general audience, the book describes the scientific basis of controlled fusion--the fusing of atomic nuclei, under conditions hotter than the sun, to release energy. Using personal recollections of scientists involved, it traces the history of this little-known international race that began during the Cold War in secret laboratories in the United States, Great Britain and the Soviet Union, and evolved into an astonishingly open collaboration between East and West.

  15. Dynamical Dipole Mode in Fusion Heavy-Ion Reactions in the Mass Region of a = 192

    NASA Astrophysics Data System (ADS)

    Parascandolo, C.; Pierroutsakou, D.; Agodi, C.; Alba, R.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; de Filippo, E.; Del Zoppo, A.; di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; La Commara, M.; Maiolino, C.; Martin, B.; Mazzocco, M.; Mazzocchi, C.; Rizzo, C.; Romoli, M.; Santonocito, D.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifirò, A.; Trimarchi, M.

    2013-06-01

    The dynamical dipole mode was investigated in the mass region of the 192Pb compound nucleus, by using the 40Ca + 152Sm and 48Ca +144Sm reactions at Elab = 11 and 10.1 MeV/nucleon, respectively. The -ray energy spectra at various polar angles were obtained for fusion-evaporation and fission events by detecting the high energy -rays with the MEDEA experimental apparatus in coincidence with evaporation residues and fission fragments. Our results show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously. However, its yield is lower than that expected within BNV calculations.

  16. Analysis of the energy transport and deposition within the reaction chamber of the prometheus inertial fusion energy reactor

    SciTech Connect

    Eggleston, J.E.; Abdou, M.A.; Tillack, M.S.

    1994-12-31

    One of the parameters affecting the feasibility of Inertial Fusion Energy (IFE) devices is the number of shots per unit time, i.e. the repetition rate. The repetition rate limits the achievable power that can be obtained from the reactor. To obtain an estimate of the allowable time between shots, a code named RECON was developed to model the response of the reaction chamber to the pellet explosion. This paper discusses how the code treats the thermodynamic response of the cavity gas and models the condensation/evaporation of this vapor to and from the first wall. A large amount of energy from the pellet microexplosion is carried by the pellet debris and the x-rays generated in the fusion reaction. Models of x-ray attenuation and ion slowing down are used to estimate the fraction of the pellet energy that is absorbed in the vapor. A large amount of energy is absorbed into the cavity gas, which causes it to become partially ionized. The ionization complicates the calculation of the temperature, pressure, and the radiative heat transfer from the gas to the first wall. To treat this problem, methods developed by Zel`dovich and Raizer are used in modeling the internal energy and the radiative heat flux. RECON was developed to run with a relatively short computational time, yet accurate enough for conceptual reactor design calculations.

  17. The fusion rate of calcium sulfate with local autograft bone compared with autologous iliac bone graft for instrumented short-segment spinal fusion.

    PubMed

    Chen, Wen-Jer; Tsai, Tsung-Ting; Chen, Lih-Huei; Niu, Chi-Chien; Lai, Po-Liang; Fu, Tsai-Sheng; McCarthy, Kevin

    2005-10-15

    A prospective study. To compare the efficacy of calcium sulfate pellets plus laminectomy bone chips with a fresh autologous iliac bone graft for short-segment lumbar fusion. Bone graft substitute material can be used to expand an existing quantity of available laminectomy bone chips. Seventy-four patients underwent surgery for instrumented one- or two-segment fusion with decompression. Autologous iliac crest bone graft was placed in one posterolateral gutter, while on the other side, an equal quantity of autogenous laminectomy bone supplemented with calcium sulfate was placed. Radiographic assessment included radiographs alone; this was performed every 3 months (3 months to 12 months), then annually. The status of fusion and the relative size of the fusion bone mass on either side of the vertebra were compared. Using iliac crest bone graft (control side) versus autograft laminectomy bone with calcium sulfate (test side), there was no significant difference between the fusion rate and sizes of the fusion bone mass (P > 0.05). Follow-up periods ranged from 30 months to 34 months, averaging 32.5 months. For the 39 patients who received single-segment fusion, 34 patients (87.2%) exhibited bone fusion on the test side, and 35 patients (89.7%) had evidence of fusion on the control side. For the 35 patients who received two-segment fusion, 29 patients (82.9%) exhibited bone fusion on the test side and 30 patients (85.7%) demonstrated complete fusion on the control side. The fusion rate and fusion size between the two groups are similar. Calcium sulfate pellets may play a role as a bone graft extender in short-segment spinal fusion.

  18. Absorption-Fluctuation Theorem for Nuclear Reactions: Brink-Axel, Incomplete Fusion and All That

    SciTech Connect

    Hussein, M. S.

    2008-04-17

    We discuss the connection between absorption, averages and fluctuations in nuclear reactions. The fluctuations in the entrance channel result in the compound-nucleus Hauser-Feshbach cross section, and the fluctuations in the intermediate channels result in modifications of multistep reaction cross sections, while the fluctuations in the final channel result in hybrid cross sections that can be used to describe incomplete fusion reactions. We discuss the latter in detail and comment on the validity of the assumptions used in the development of the Surrogate method. We also discuss the theory of multistep reactions with regards to intermediate state fluctuations and the energy dependence and non-locality of the intermediate-channel optical potentials.

  19. Multidimensional reaction rate theory with anisotropic diffusion.

    PubMed

    Berezhkovskii, Alexander M; Szabo, Attila; Greives, Nicholas; Zhou, Huan-Xiang

    2014-11-28

    An analytical expression is derived for the rate constant that describes diffusive transitions between two deep wells of a multidimensional potential. The expression, in contrast to the Kramers-Langer formula for the rate constant, is valid even when the diffusion is highly anisotropic. Our approach is based on a variational principle for the reactive flux and uses a trial function for the splitting probability or commitor. The theoretical result is validated by Brownian dynamics simulations.

  20. Fusion and quasifission studies for the 40Ca+186W,192Os reactions

    NASA Astrophysics Data System (ADS)

    Prasad, E.; Hinde, D. J.; Williams, E.; Dasgupta, M.; Carter, I. P.; Cook, K. J.; Jeung, D. Y.; Luong, D. H.; Palshetkar, C. S.; Rafferty, D. C.; Ramachandran, K.; Simenel, C.; Wakhle, A.

    2017-09-01

    Background: All elements above atomic number 113 have been synthesized using hot fusion reactions with calcium beams on statically deformed actinide target nuclei. Quasifission and fusion-fission are the two major mechanisms responsible for the very low production cross sections of superheavy elements. Purpose: To achieve a quantitative measurement of capture and quasifission characteristics as a function of beam energy in reactions forming heavy compound systems using calcium beams as projectiles. Methods: Fission fragment mass-angle distributions were measured for the two reactions 40Ca+186W and 40C+192Os, populating 226Pu and 232Cm compound nuclei, respectively, using the Heavy Ion Accelerator Facility and CUBE spectrometer at the Australian National University. Mass ratio distributions, angular distributions, and total fission cross sections were obtained from the experimental data. Simulations to match the features of the experimental mass-angle distributions were performed using a classical phenomenological approach. Results: Both 40Ca+186W and 40C+192Os reactions show strong mass-angle correlations at all energies measured. A maximum fusion probability of 60 -70 % is estimated for the two reactions in the energy range of the present study. Coupled-channels calculations assuming standard Woods-Saxon potential parameters overpredict the capture cross sections. Large nuclear potential diffuseness parameters ˜1.5 fm are required to fit the total capture cross sections. The presence of a weak mass-asymmetric quasifission component attributed to the higher angular momentum events can be reproduced with a shorter average sticking time but longer mass-equilibration time constant. Conclusions: The deduced above-barrier capture cross sections suggest that the dissipative processes are already occurring outside the capture barrier. The mass-angle correlations indicate that a compact shape is not achieved for deformation aligned collisions with lower capture barriers

  1. DSMC predictions of non-equilibrium reaction rates.

    SciTech Connect

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

    2010-04-01

    A set of Direct Simulation Monte Carlo (DSMC) chemical-reaction models recently proposed by Bird and based solely on the collision energy and the vibrational energy levels of the species involved is applied to calculate nonequilibrium chemical-reaction rates for atmospheric reactions in hypersonic flows. The DSMC non-equilibrium model predictions are in good agreement with theoretical models and experimental measurements. The observed agreement provides strong evidence that modeling chemical reactions using only the collision energy and the vibrational energy levels provides an accurate method for predicting non-equilibrium chemical-reaction rates.

  2. Measurement of the ^12C+^12C Fusion Reaction with MUSIC

    NASA Astrophysics Data System (ADS)

    Carnelli, P. F. F.; Almaraz-Calderon, S.; Henderson, D.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Esbensen, H.; Fernandez-Niello, J. O.; Jiang, C. L.; Lighthall, J. C.; Marley, S. T.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.

    2012-10-01

    The fusion of the ^12C+^12C system is of great interest in nuclear structure and nuclear astrophysics. Above the Coulomb barrier, the excitation function of this system exhibits oscillations, which are not well understood. There is also a significant discrepancy between the experimental fusion cross-section and recent coupled-channel calculations that is not present in other carbon systems. To address these issues, we have re-measured the fusion excitation function for ^12,13C+^12C in the energy range of 10 MeV < Ecm < 20 MeV using a Multi-Sampling Ionization Chamber (MUSIC) detector. The gas of the ionization chamber (CH4) served as both the target material and the counter gas. One of the main advantages of this method is that the excitation function is measured over a large range of energies using only one beam energy. This method has been proven to be successful and it will be used to measure fusion reactions in other light systems. The experimental results will be presented and compared to previous experimental data and theoretical models.

  3. Multi-intelligence critical rating assessment of fusion techniques (MiCRAFT)

    NASA Astrophysics Data System (ADS)

    Blasch, Erik

    2015-06-01

    Assessment of multi-intelligence fusion techniques includes credibility of algorithm performance, quality of results against mission needs, and usability in a work-domain context. Situation awareness (SAW) brings together low-level information fusion (tracking and identification), high-level information fusion (threat and scenario-based assessment), and information fusion level 5 user refinement (physical, cognitive, and information tasks). To measure SAW, we discuss the SAGAT (Situational Awareness Global Assessment Technique) technique for a multi-intelligence fusion (MIF) system assessment that focuses on the advantages of MIF against single intelligence sources. Building on the NASA TLX (Task Load Index), SAGAT probes, SART (Situational Awareness Rating Technique) questionnaires, and CDM (Critical Decision Method) decision points; we highlight these tools for use in a Multi-Intelligence Critical Rating Assessment of Fusion Techniques (MiCRAFT). The focus is to measure user refinement of a situation over the information fusion quality of service (QoS) metrics: timeliness, accuracy, confidence, workload (cost), and attention (throughput). A key component of any user analysis includes correlation, association, and summarization of data; so we also seek measures of product quality and QuEST of information. Building a notion of product quality from multi-intelligence tools is typically subjective which needs to be aligned with objective machine metrics.

  4. Refined Calculations of Secondary Nuclear Reactions in Magneto-Inertial Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Schmit, Paul; Knapp, Patrick; Hansen, Stephanie; Gomez, Matthew; Hahn, Kelly; Sinars, Daniel; Peterson, Kyle; Slutz, Stephen; Sefkow, Adam; Awe, Thomas; Harding, Eric; Jennings, Christopher

    2014-10-01

    Diagnosing the degree of magnetic flux compression at stagnation in magneto-inertial fusion (MIF) is critical for charting the performance of any MIF concept. In pure deuterium plasma, the transport of high-energy tritons produced by the aneutronic DD fusion reaction depends strongly on the magnetic field. The tritons probe and occasionally react with the fuel, emitting secondary DT neutrons. We show that the DT/DD neutron yield ratio and the secondary DT neutron spectra can be used to infer the magnetic field-radius product (BR), the critical confinement parameter for MIF. The amount of fuel-pusher mix also can be constrained by secondary reactions. We discuss the sensitivity to plasma inhomogeneities of the calculations and outline methods to relate secondary yields to alpha particle energy deposition in ignition-relevant experiments employing DT fuel. We compare our calculations to recent tests of the Magnetized Liner Inertial Fusion (MagLIF) concept on the Z Pulsed Power Facility. Supported in part by the SNL Truman Fellowship, which is part of the LDRD Program, and sponsored by Sandia Corporation (a wholly owned subsidiary of Lockheed Martin Corporation) as Operator of SNL under its U.S. DoE Contract No. DE-AC04-94AL85000.

  5. Cross Section Measurements of 12C+16O Fusion Reaction at Stellar Energies

    NASA Astrophysics Data System (ADS)

    Tan, Wanpeng; Fang, X.; Beard, M.; Gilardy, G.; Jung, H.; Liu, Q.; Lyons, S.; Robertson, D.; Setoodehnia, K.; Seymour, C.; Stech, E.; Vande Kolk, B.; Wiescher, M.; de Souza, R.; Hudan, S.; Singh, V.; Tang, X.; Uberseder, E.

    2016-09-01

    12C+16O is one of the three fusion reactions (12C+12C, 12C+16O, and 16O+16O) that play an important role at the late stage of stellar evolution in massive stars. The previous meassurements of its cross section at low energies rely on the singles measurements of either gamma rays or charged particles. New measurement was conducted for the 12C+16O reaction at Ecm = 3.64 - 4.93 MeV with the detection of both gammas and charged particles using the high intensity St ANA accelerator at the University of Notre Dame. The protons and alphas from the fusion evaporation were measured by a large area silicon strip detector array (SAND) while the gamma rays were detected by one large volume HPGe detector right after the target. Statistical model calculation were employed to interpret the experimental results. This provided a more reliable extrapolation for the 12C+16O fusion cross section, reducing substantially the uncertainty for stellar model simulations. This work was supported by the National Science Foundation through Grant Numbers PHY-1068192 and PHY-1419765 and the Joint Institute for Nuclear Astrophysics under Grant No. PHY-0822648.

  6. Inertial confinement fusion reaction chamber and power conversion system study. Final report

    SciTech Connect

    Maya, I.; Schultz, K.R.; Bourque, R.F.; Cheng, E.T.; Creedon, R.L.; Norman, J.H.; Price, R.J.; Porter, J.; Schuster, H.L.; Simnad, M.J.

    1985-10-01

    This report summarizes the results of the second year of a two-year study on the design and evaluation of the Cascade concept as a commercial inertial confinement fusion (ICF) reactor. We developed a reactor design based on the Cascade reaction chamber concept that would be competitive in terms of both capital and operating costs, safe and environmentally acceptable in terms of hazard to the public, occupational exposure and radioactive waste production, and highly efficient. The Cascade reaction chamber is a double-cone-shaped rotating drum. The granulated solid blanket materials inside the rotating chamber are held against the walls by centrifugal force. The fusion energy is captured in a blanket of solid carbon, BeO, and LiAlO/sub 2/ granules. These granules are circulated to the primary side of a ceramic heat exchanger. Primary-side granule temperatures range from 1285 K at the LiAlO/sub 2/ granule heat exchanger outlet to 1600 K at the carbon granule heat exchanger inlet. The secondary side consists of a closed-cycle gas turbine power conversion system with helium working fluid, operating at 1300 K peak outlet temperature and achieving a thermal power conversion efficiency of 55%. The net plant efficiency is 49%. The reference design is a plant producing 1500 MW of D-T fusion power and delivering 815 MW of electrical power for sale to the utility grid. 88 refs., 44 figs., 47 tabs.

  7. High lumbar noninstrumented fusion rates using lamina autograft and Nanoss/bone marrow aspirate

    PubMed Central

    Epstein, Nancy E.

    2017-01-01

    Background: Patients with marked osteoporosis and/or obesity/morbid obesity and severe multilevel lumbar stenosis and other pathology often undergo multilevel laminectomies with non instrumented posterolateral fusions (PLF). The other pathology may include combinations of degenerative spondylolisthesis/lysis, foraminal/far lateral discs, and/or synovial cysts requiring more extensive facet resections. Presently, spine surgeons often use bone graft expanders to supplement the lamina autograft harvested in the course of laminectomy/decompressions for the PLF mass. Methods: In 59 patients, we prospectively analyzed the fusion rates following multilevel laminectomies/noninstrumented fusions using lamina autograft and the bone graft expander Nanoss (RTI Surgical Alachua, FL, and USA) with autogenous bone marrow aspirate (BMA). Patients averaged 66.1 years of age; many exhibited marked osteoporosis (48 patients) and obesity (13 of 27 morbidly obese). Magnetic resonance (MR) and computed tomography (CT) studies documented stenosis/ossified yellow ligament (OYL) and degenerative spondylolisthesis (51 patients)/lysis (2 patients), synovial cysts (32 patients), and disc herniations (10 of 21 far lateral). Patients were followed remove up for an average of 3.12 years. Results: Average 4.0 level laminectomies/1.2 level noninstrumented fusions utilized lamina autograft and Nanoss/BMA. Both X-ray/CT studies performed an average of 4.9 months postoperatively documented a 97% fusion rate (57 of 59 patients). Two patients with severe osteoporosis, morbid obesity, and smoking histories exhibited pseudarthroses; neither was sufficiently symptomatic to require secondary surgery. Conclusions: Fifty-nine patients with multilevel lumbar stenosis/OYL and other pathology underwent multilevel lumbar laminectomies/noninstrumented fusions using lamina autograft and Nanoss/BMA. Both dynamic X-ray/CT studies confirmed a 97% fusion rate an average of 4.9 months postoperatively. Nanoss

  8. Evidence of complete fusion in the subbarrier {sup 16}O+{sup 238}U reaction

    SciTech Connect

    Nishio, K. Ikezoe, H.; Asai, M.; Tsukada, K.; Mitsuoka, S.; Tsuruta, K.; Satou, K.; Lin, C. J.; Ohsawa, T.

    2006-08-15

    Evaporation residue cross sections in the {sup 16}O+{sup 238}U reaction were measured for the energy range from above-to extreme subbarrier. We used a He-gas-jet system to transport the fusion products, and the {alpha} decay of the evaporation residues was measured by using a rotating wheel system. The measured cross sections for {sup 248,249,250}Fm are reproduced by a statistical model calculation, for which partial cross sections are calculated by a coupled-channel model taking into account the prolate deformation of {sup 238}U. We conclude that complete fusion is the main process in the subbarrier energy region, and quasifission is not an important channel.

  9. Cell-free mitochondrial fusion assay detected by specific protease reaction revealed Ca2+ as regulator of mitofusin-dependent mitochondrial fusion.

    PubMed

    Ishihara, Naotada; Maeda, Maki; Ban, Tadato; Mihara, Katsuyoshi

    2017-04-27

    Mitochondrial dynamic by frequent fusion and fission have important roles in various cellular signaling processes and pathophysiology in vivo. However, the molecular mechanisms that regulate mitochondrial fusion, especially in mammalian cells, are not well understood. Accordingly, we developed a novel biochemical cell-free mitochondrial fusion assay system using isolated human mitochondria. We used a protease and its specific substrate that are essential for yeast autophagy; Atg4 protease is required for maturation and the de-conjugation of the ubiquitin-like modifier Atg8. Atg4-FLAG and Atg8-GFP were separately expressed in the mitochondrial matrix of HeLa cells. Isolated mitochondria were then mixed and packed in the presence of energy regeneration mix. Immunoblotting with an anti-GFP antibody revealed Atg8 processing, suggesting that the double membranes of isolated mitochondria were indeed fused. The mitochondrial fusion reaction required GTP hydrolysis, mitochondrial membrane potential, and intact outer membrane proteins containing two mitofusin isoforms. Using this assay, we searched for stimulators of mitochondrial fusion and found that rabbit reticulocyte lysate and Ca2+ chelator EGTA stimulate mitochondrial fusion. This novel cell-free assay system using isolated human mitochondria is simple, sensitive, and reproducible; thus, it is useful for screening proteins and molecules that modulate mitochondrial fusion. © The Authors 2017. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

  10. Imaginary-time formalism for triple-α reaction rates

    NASA Astrophysics Data System (ADS)

    Akahori, T.; Funaki, Y.; Yabana, K.

    2015-08-01

    Using imaginary-time formalism, it is shown that the triple-α reaction rate can be reliably calculated without the need to solve scattering problems involving three charged particles. The calculated reaction rate is found to agree well with the empirical NACRE rate, which is widely adopted in stellar evolution calculations. The reason for this is explained using R -matrix theory. Extremely slow convergence is found to occur when a coupled-channel expansion is introduced, which helps to explain the very different reaction rates obtained using a coupled-channel approach.

  11. Non-resonant Triple- α Reaction Rate at Low Temperature

    NASA Astrophysics Data System (ADS)

    Tamii, A.; Aoi, N.; Fujita, H.; Fujita, Y.; Hatanaka, K.; Hashimoto, T.; Kawabata, T.; Miki, K.; Itoh, M.; Itoh, T.; Kamimura, M.; Ogata, K.; Ong, H. J.; Sakaguchi, H.; Shima, T.; Suzuki, T.; Yamamoto, T.

    2013-08-01

    The triple α reaction rate in stars is quite important in many astrophysical scenarios including the stellar evolution and carbon synthesis in stars. Recently the non-resonant triple α reaction rate has been reevaluated using a calculation with the continuum-discretized coupled-channels (CDCC) method, which dramatically increased the rate at low temperature compared to the widely-used NACRE compilation. Since the enhancement influences strongly on astrophysical model simulations, we have planned an experiment for drawing conclusion on the non-resonant triple α reaction rate at low temperature by measuring the three- α continuum state in 12C. We report the present situation of the experiment.

  12. Experimental Study of p-11B Reaction Related to the Clean Fusion Fuel

    NASA Astrophysics Data System (ADS)

    Lin, Erh-kang; Wang, Chang-wan; Yuan, Jian; Liu, Xiao-dong; Li, Cheng-bo; Sun, Zu-xun; Zhang, Pei-hua; Chen, Jin-xiang; Yang, Qi-xiang; Wang, Jian-yong; Ling-hua, Gong

    1998-11-01

    Whole continuous α spectra of the p-11B three-body sequential decay reaction have been measured by using a charge particle time-of-flight (TOF) spectrometer with the high-resolution passivated implanted planar silicon detector. A characteristic shape of the saddle-type distribution was obtained. The Monte Carlo calculations show that observed α spectra can be interpreted by anisotropy sequential decay process of the intermediate nucleus 8Be (1) for the p-11B reaction. In the measurement, angular distributions were obtained for proton energies at 667 and 1370 keV, respectively. Total cross-sections for the 11B(p,α)8Be(2α) reaction related to the clean fusion fuel were also reported at two bombarding energies.

  13. Study of near-stability nuclei populated as fission fragments in heavy-ion fusion reactions

    SciTech Connect

    Fotiadis, Nikolaos; Nelson, Ronald O; Devlin, Matthew; Cizewski, Jolie A; Krucken, Reiner; Clark, R M; Fallon, Paul; Lee, I Yang; Macchiavelli, Agusto O; Becker, John A; Younes, Walid

    2010-01-01

    Examples are presented to illustrate the power of prompt {gamma}-ray spectroscopy of fission fragments from compound nuclei with A {approx} 200 formed in fusion-evaporation reactions in experiments using the Gammasphere Ge-detector array. Complementary methods, such as Coulomb excitation and deep-inelastic processes, are also discussed. In other cases (n, xn{gamma}) reactions on stable isotopes have been used to establish neutron excitation functions for {gamma}-rays using a pulsed 'white'-neutron source, coupled to a high-energy-resolution germanium-detector array. The excitation functions can unambiguously assign {gamma}-rays to a specific reaction product. Results from all these methods bridge the gaps in the systematics of high-spin states between the neutron-deficient and neutron-rich nuclei. Results near shell closures should motivate new shell model calculations.

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

    NASA Technical Reports Server (NTRS)

    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.

  15. Application of proton boron fusion reaction to radiation therapy: A Monte Carlo simulation study

    SciTech Connect

    Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae Suk

    2014-12-01

    Three alpha particles are emitted from the point of reaction between a proton and boron. The alpha particles are effective in inducing the death of a tumor cell. After boron is accumulated in the tumor region, the emitted from outside the body proton can react with the boron in the tumor region. An increase of the proton's maximum dose level is caused by the boron and only the tumor cell is damaged more critically. In addition, a prompt gamma ray is emitted from the proton boron reaction point. Here, we show that the effectiveness of the proton boron fusion therapy was verified using Monte Carlo simulations. We found that a dramatic increase by more than half of the proton's maximum dose level was induced by the boron in the tumor region. This increase occurred only when the proton's maximum dose point was located within the boron uptake region. In addition, the 719 keV prompt gamma ray peak produced by the proton boron fusion reaction was positively detected. This therapy method features the advantages such as the application of Bragg-peak to the therapy, the accurate targeting of tumor, improved therapy effects, and the monitoring of the therapy region during treatment.

  16. Application of proton boron fusion reaction to radiation therapy: A Monte Carlo simulation study

    NASA Astrophysics Data System (ADS)

    Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae Suk

    2014-12-01

    Three alpha particles are emitted from the point of reaction between a proton and boron. The alpha particles are effective in inducing the death of a tumor cell. After boron is accumulated in the tumor region, the emitted from outside the body proton can react with the boron in the tumor region. An increase of the proton's maximum dose level is caused by the boron and only the tumor cell is damaged more critically. In addition, a prompt gamma ray is emitted from the proton boron reaction point. Here, we show that the effectiveness of the proton boron fusion therapy was verified using Monte Carlo simulations. We found that a dramatic increase by more than half of the proton's maximum dose level was induced by the boron in the tumor region. This increase occurred only when the proton's maximum dose point was located within the boron uptake region. In addition, the 719 keV prompt gamma ray peak produced by the proton boron fusion reaction was positively detected. This therapy method features the advantages such as the application of Bragg-peak to the therapy, the accurate targeting of tumor, improved therapy effects, and the monitoring of the therapy region during treatment.

  17. A Comparative Radiographic Analysis of Fusion Rate between L4-5 and L5-S1 in a Single Level Posterior Lumbar Interbody Fusion.

    PubMed

    Han, Sang-Hyun; Hyun, Seung-Jae; Jahng, Tae-Ahn; Kim, Ki-Jeong

    2015-06-01

    This study aimed to investigate radiographic fusion rates at L4-5 and L5-S1 after single level posterior lumbar interbody fusion (PLIF) and evaluate the relationship between fusion rates and preoperative disc slope angle (DSA), lumbar lordosis (LL), segmental angle (SA), and pelvic parameters. We conducted a retrospective review of patients who underwent single level PLIF at L4-5 or L5-S1 during May 2003-December 2012 at our institution. 73 patients were finally enrolled. Fusion was assessed by use of the Brantigan-Steffee classification, less than 2mm translation and less than 5° motion on the flexion-extension lateral radiographs. We analyzed the radiographic fusion rates, risk factors, and relationship of fusion rates with DSA, LL, SA, and pelvic parameters. There were 59 patients (80.8%) in the L4-5 group and 14 (19.2%) in L5-S1 (average follow-up, 34 months). The radiographic fusion rates were 89.8% in the L4-5 group (53/59) and 42.9% in L5-S1 (6/14) (p<0.001).The preoperative DSA was significantly lesser in the L4-5 group than in the L5-S1 group (13.1±8.1° vs. 27.2±6.7°, p<0.001). The LL, SA, and pelvic parameters were not related with radiographic fusion rates in both groups. Risk factors for non-union were not identified between the two groups except for the surgery level (p<0.001). The radiographic fusion rate at L5-S1 was less than half that at L4-5 after single level PLIF. This may be due to the anatomical and biomechanical differences between the two levels. More vigorous effort to achieve successful fusion at L5-S1 should be considered.

  18. Fission barriers for Po nuclei produced in complete fusion reactions with heavy ions

    SciTech Connect

    Sagaidak, R. N.; Andreyev, A. N.

    2009-05-15

    Evaporation residues and fission excitation functions obtained in complete fusion reactions leading to Po compound nuclei have been analyzed in the framework of the standard statistical model. Macroscopic fission barriers deduced from the cross-section data analysis are compared with the predictions of various theoretical models and available data. A drop in the Po barriers with the decrease in a neutron number was found, which is stronger than predicted by any theory. The presence of entrance channel effects and collective excitations in the compound nucleus decay is considered as a possible reason for the barrier reduction.

  19. Correlated uncertainties in Monte Carlo reaction rate calculations

    NASA Astrophysics Data System (ADS)

    Longland, Richard

    2017-07-01

    Context. Monte Carlo methods have enabled nuclear reaction rates from uncertain inputs to be presented in a statistically meaningful manner. However, these uncertainties are currently computed assuming no correlations between the physical quantities that enter those calculations. This is not always an appropriate assumption. Astrophysically important reactions are often dominated by resonances, whose properties are normalized to a well-known reference resonance. This insight provides a basis from which to develop a flexible framework for including correlations in Monte Carlo reaction rate calculations. Aims: The aim of this work is to develop and test a method for including correlations in Monte Carlo reaction rate calculations when the input has been normalized to a common reference. Methods: A mathematical framework is developed for including correlations between input parameters in Monte Carlo reaction rate calculations. The magnitude of those correlations is calculated from the uncertainties typically reported in experimental papers, where full correlation information is not available. The method is applied to four illustrative examples: a fictional 3-resonance reaction, 27Al(p, γ)28Si, 23Na(p, α)20Ne, and 23Na(α, p)26Mg. Results: Reaction rates at low temperatures that are dominated by a few isolated resonances are found to minimally impacted by correlation effects. However, reaction rates determined from many overlapping resonances can be significantly affected. Uncertainties in the 23Na(α, p)26Mg reaction, for example, increase by up to a factor of 5. This highlights the need to take correlation effects into account in reaction rate calculations, and provides insight into which cases are expected to be most affected by them. The impact of correlation effects on nucleosynthesis is also investigated.

  20. Rate constant for reaction of atomic hydrogen with germane

    NASA Technical Reports Server (NTRS)

    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.

  1. On the Initial Rate of Fluid-Solid Reactions

    NASA Astrophysics Data System (ADS)

    Sohn, Hong Yong; Fan, De-Qiu

    2017-02-01

    It is argued in this paper that the initial rate should not be used for the measurement or analysis the kinetics of a fluid-solid reaction, especially for a reaction in which the effect of pore diffusion starts appearing even moderately as the reaction proceeds. Even in the absence of external mass transfer effects, it is shown in this work by rigorous mathematical analysis that the range of conditions where the initial rate represents the intrinsic kinetics is very narrow. For an initially non-porous solid in the absence of external mass transfer effects, the very initial rate should mathematically be the intrinsic rate even when pore diffusion becomes important as the reaction proceeds. However, even in this case, the range of conditions for this statement is very limited. For the reaction of an initially porous solid, the rate at time zero is already affected by pore diffusion unless its effect is negligible over the entire range of conversion. Furthermore, the initial reaction rates of porous solids reacting under large values of k/D e ratio (chemical reactivity is much greater than the capacity for pore diffusion) have an apparent rate constant of √ {k \\cdot D_{e} } and thus pore diffusion alone does not control the initial rate no matter how large the effect of pore diffusion is overall.

  2. Reaction sintering of zinc ferrite during constant rates of heating

    SciTech Connect

    Rahaman, M.N. . Ceramic Engineering Dept.); De Jonghe, L.C. . Lawrence Berkeley Lab.)

    1993-07-01

    The reaction sintering of equimolar quantities of zinc oxide and ferric oxide was investigated under conditions of constant rates of heating and the data were compared with those for a calcined, single-phase zinc ferrite powder. For the heating rate of 1C/min, the densifications of the reaction-sintered sample and the calcined sample were approximately the same. However, as the heating rate increased, the density at any temperature increased slightly for the reaction-sintered sample but decreased slightly for the calcined powder. The factors responsible for this slight difference in sintering between the reaction-sintered sample and the calcined sample are discussed. For the constant heating rates used, the reaction was completed prior to any significant densification. Relative densities of >95% were obtained for both the reaction-sintered sample and the calcined sample under identical sintering conditions (1-10C/min to 1350C). Reaction sintering in a steep temperature gradient produced a nearly fully dense body prior to complete reaction; a composite microstructure consisting of fine zinc oxide grains in matrix of zinc ferrite was obtained.

  3. Product PCNPsurv or the "reduced" evaporation residue cross section σER/σfusion for "hot" fusion reactions studied with the dynamical cluster-decay model

    NASA Astrophysics Data System (ADS)

    Chopra, Sahila; Kaur, Arshdeep; Hemdeep, Gupta, Raj K.

    2016-04-01

    The product PCNPsurv of compound nucleus (CN) fusion probability PCN and survival probability Psurv is calculated to determine the reduced evaporation residue cross section σER/σfusion , denoted σERreduced, with (total) fusion cross section σfusion given as a sum of CN-formation cross section σCN and non-CN cross section σnCN for each reaction, where σCN is the sum of evaporation residue cross section σER and fusion-fission cross section σff and σnCN, if not measured, is estimated empirically as the difference between measured and calculated σfusion. Our calculations of PCN and Psurv, based on the dynamical cluster-decay model, were successfully made for some 17 "hot" fusion reactions, forming different CN of mass numbers ACN˜100 -300 , with deformations of nuclei up to hexadecapole deformations and "compact" orientations for both coplanar (Φc=0∘ ) and noncoplanar (Φc≠0∘ ) configurations, using various different nuclear interaction potentials. Interesting variations of σERreduced with CN excitation energy E*, fissility parameter χ , CN mass ACN, and Coulomb parameter Z1Z2 show that, independent of entrance channel, different isotopes of CN, and nuclear interaction potentials used, the dominant quantity in the product is Psurv, which classifies all the studied CN into three groups of weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, with relative magnitudes of σERreduced˜1 , ˜10-6 , and ˜10-11 , which, like for PCN, get further grouped in two dependencies of (i) weakly fissioning and strongly fissioning superheavy nuclei decreasing with increasing E* and (ii) radioactive nuclei increasing with increasing E*.

  4. Effect of fusion reaction products heating on the volume ignition of DT and D3He fuel pellets

    NASA Astrophysics Data System (ADS)

    Khoda-Bakhsh, R.

    1996-05-01

    Laser fusion simulations are carried out for the DT and D-3He pellets by using a hydrodynamic code including heating from all charged reaction products and neutron. It is shown that, the inclusion of the side reactions and heating from all reactions products in the fuel pellets has an appreciable affect on the plasma temperature, the ICF drive energy requirement, fusion gain and the ignition conditions. The total input energy is decreased, the burn efficiency and total gain are increased compared to the results of simple volume ignition calculations.

  5. An Improved Reaction Rate Equation for Simulating the Ignition and Growth of Reaction in High Explosives

    SciTech Connect

    Murphy, M J

    2010-03-08

    We describe an improved reaction rate equation for simulating ignition and growth of reaction in high explosives. It has been implemented into CALE and ALE3D as an alternate to the baseline the Lee-Tarver reactive flow model. The reactive flow model treats the explosive in two phases (unreacted/reactants and reacted/products) with a reaction rate equation to determine the fraction reacted, F. The improved rate equation has fewer parameters, is continuous with continuous derivative, results in a unique set of reaction rate parameters for each explosive while providing the same functionality as the baseline rate equation. The improved rate equation uses a cosine function in the ignition term and a sine function in the growth and completion terms. The improved rate equation is simpler with fewer parameters.

  6. Experimental study of proton rate density in a spherical inertial electrostatic confinement fusion device

    NASA Astrophysics Data System (ADS)

    Gu, Yibin

    The concept of spherical inertial-electrostatic confinement (SIEC) is to focus and accelerate ions and electrons radially inward into the center of a negatively biased, highly transparent spherical grid to create a space-charge double-potential well (a negative-potential well nested inside a positive-potential well) which confines the high-energy ions in the dense central core region such that appreciable nuclear fusion reactions are obtained. This experimental work has focused on creating the double-potential well at high perveance (I/V3/2) where there is a significant charge build-up in the center, and on proving the existence of the well from its characteristic radial proton rate density profile. Based on the spatial measurement of the D-D fusion protons by using a capillary proton collimator and the unfolding of this data, this work has been directed to evaluate the radial proton rate density profiles to explore the evolution of potential-well structure in the current and voltage (perveance) range where the double well is expected. Under the optimized operating conditions admitted by using the Star mode to improve focusing to 1.6× ballistic limit and double-grid setup to reduce the ion radial energy spread to <10%, the experiment has successfully created and, through identification of a distinct two-peak proton rate density profile, demonstrated the existence of the double- potential well. Experimental measurements of the two-peak proton rate density profiles have uniquely shown the emergence of the double potential well for perveances >0.34 mA/kV3/2. As the perveance increases, the feature of the double well becomes prominent. At 1.38 mA/kV3/2 (80 mA and 15 kV), the maximum negative potential well depth obtained from the measured proton rate density was calculated, using a beam-background fusion and charge-exchange model, to be ~22-27% of the applied voltage. Also, during the progress of this dissertation, two valuable SIEC derivatives-an SIEC wavelength

  7. Dynamical Dipole Mode in Heavy-Ion Fusion-Evaporation and Fission Reactions in the {sup 192}Pb Mass Region

    SciTech Connect

    Silvestri, R.; Inglima, G.; La Commara, M.; Martin, B.; Sandoli, M.; Pierroutsakou, D.; Parascandolo, C.; Boiano, A.; Romoli, M.; Agodi, C.; Alba, R.; Colonna, M.; Coniglione, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Baran, V.; De Filippo, E.; Di Toro, M.; Rizzo, C.

    2011-10-28

    The prompt {gamma}-ray emission related with the dynamical dipole mode decay was investigated in the {sup 192}Pb mass region by means of the {sup 40}Ca+{sup 152}Sm and {sup 48}Ca+{sup 144}Sm fusion-evaporation and fission reactions at E{sub lab} = 11 and 10.1 MeV/nucleon, respectively. The two reactions populate, through entrance channel having different charge asymmetries, the {sup 192}Pb compound nucleus at an excitation energy of 236 MeV with identical spin distribution. Preliminary results of this experiment show that the dynamical dipole mode survives in collisions involving heavier mass reaction partners than those studied previously. As a fast cooling mechanism on the fusion path, the prompt dipole {gamma} radiation could be of interest for the synthesis of super-heavy elements through ''hot'' fusion reactions.

  8. Role of angular momentum in the production of complex fragments in fusion and quasifission reactions

    SciTech Connect

    Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2011-05-15

    The influence of angular momentum on the competition between complete fusion followed by the decay of compound nucleus and quasifission channels is treated within the dinuclear system model. The charge distributions of the products in the reactions {sup 28}Si+{sup 96}Zr, {sup 4}He+{sup 130}Te, and {sup 40}Ca+{sup 82}Kr are predicted at bombarding energies above the Coulomb barrier. The results of calculations for the reactions {sup 93}Nb+{sup 9}Be,{sup 12}C,{sup 27}Al; {sup 84}Kr+{sup 27}Al; {sup 86}Kr+{sup 63}Cu; {sup 139}La+{sup 12}C,{sup 27}Al; and {sup 45}Sc+{sup 65}Cu are compared with the available experimental data.

  9. Advanced scheme for high-yield laser driven proton-boron fusion reaction

    NASA Astrophysics Data System (ADS)

    Margarone, D.; Picciotto, A.; Velyhan, A.; Krasa, J.; Kucharik, M.; Morrissey, M.; Mangione, A.; Szydlowsky, A.; Malinowska, A.; Bertuccio, G.; Shi, Y.; Crivellari, M.; Ullschmied, J.; Bellutti, P.; Korn, G.

    2015-02-01

    A low contrast nanosecond laser pulse with relatively low intensity (3 × 1016 W cm-2) was used to enhance the yield of induced nuclear reactions in advanced solid targets. In particular the "ultraclean" proton-boron fusion reaction, producing energetic alpha-particles without neutron generation, was chosen. A spatially well-defined layer of boron dopants in a hydrogen-enriched silicon substrate was used as target. The combination of the specific target geometry and the laser pulse temporal shape allowed enhancing the yield of alpha-particles up to 109 per steradian, i.e 100 times higher than previous experimental achievements. Moreover the alpha particle stream presented a clearly peaked angular and energy distribution, which make this secondary source attractive for potential applications. This result can be ascribed to the interaction of the long laser pre-pulse with the target and to the optimal target geometry and composition.

  10. Studies of Neutron-Deficient Nuclei Near the Z = 82 Shell Closure via Cold Fusion Reactions

    SciTech Connect

    Carpenter, M. P.; Kondev, F. G.; Janssens, R. V. F.; Seweryniak, D.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Zhu, S.; Camera, F.; Bracco, A.; Million, B.; Leoni, S.; Jenkins, D. G.; Wadsworth, R.

    2009-03-04

    Over the last decade, we have performed in-beam experiments using Gammasphere+FMA to measure excited states in proton-rich Au, Hg, Tl and Pb isotopes. In these studies, the use of the FMA is essential in order to differentiate evaporation residues from the large fission background which dominates the reaction cross-section. In addition, we have found that using near-symmetric reactions at bombarding energies near the Coloumb barrier is beneficial in performing these studies. By keeping the bombarding energy low, fission is minimized and the reaction products are concentrated in only a few channels. New results have recently been obtained using the {sup 90}Zr+{sup 92}Mo reaction to study shape co-existence in {sup 181}Tl via the lp evaporation channel. In addition, we have measured the total {gamma}-ray energy and multiplicity associated with the surviving compound system, {sup 179}Au, following the fusion reaction, {sup 90}Zr+{sup 89}Y.

  11. Entrance Channel Dynamics of Hot and Cold Fusion Reactions Leading to Superheavy Elements

    NASA Astrophysics Data System (ADS)

    Umar, Sait; Oberacker, Volker

    2010-11-01

    One of the most fascinating research areas involving low-energy nuclear reactions is the search for superheavy elements. Experimentally, two approaches have been used for the synthesis of these elements, one utilizing closed shell nuclei with lead-based targets (cold-fusion), the other utilizing deformed actinide targets with ^48Ca projectiles (hot-fusion). In this talk we investigate the entrance channel dynamics for the reactions ^70Zn+^208Pb and ^48Ca+^238U using the fully microscopic time-dependent Hartree-Fock (TDHF) theory coupled with a density constraint [1-3]. We calculate excitation energies and capture cross-sections relevant for the study of superheavy formations. We discuss the deformation dependence of the ion-ion potential for the ^48Ca+^238U system and perform an alignment angle averaging for the calculation of the capture cross-section. The results show that this approach can generate results in good agreement with experiment and other theories.[4pt] [1] Umar, Oberacker, PRC 74, 061601(R) (2006).[0pt] [2] Umar, Oberacker, EPJA 39, 243 (2009).[0pt] [3] Umar, Maruhn, Itagaki, and Oberacker, PRL 104, 212503.

  12. Detailed determination of the nuclear fusion radius by a simultaneous optical model calculation of elastic scattering and fusion cross sections in reactions involving weakly bound projectiles

    SciTech Connect

    Camacho, A. Gomez; Aguilera, E. F.; Gomes, P. R. S.; Lubian, J.

    2007-10-15

    Within the optical model for direct reactions, simultaneous calculations of elastic scattering, complete fusion, and total reaction cross sections for energies around the Coulomb barrier are presented for reactions involving the weakly bound projectile {sup 9}Be on {sup 64}Zn. Volume (W{sub F}) and surface (W{sub DR}) Woods-Saxon optical potentials are used such that the former is responsible only for complete fusion reactions while the latter for all direct reactions plus incomplete fusion. Simultaneous fits can be obtained with several sets of potential parameters, but if we impose the condition that the strength of W{sub F} is smaller than the strength of W{sub DR} at the tail region of the potential (this condition is discussed in detail), then values are required for r{sub F} and r{sub DR} of around 1.6 and 1.7-1.9 fm, respectively. These values are much larger than those frequently used in barrier penetration model calculations. Through the energy dependence of the real and imaginary parts of the polarization potentials, we show that the usual threshold anomaly does not show up for this system, but instead there is evidence of the presence of a breakup threshold anomaly.

  13. Occupational Injury Rate Estimates in Magnetic Fusion Experiments

    SciTech Connect

    cadwallader, lee

    2006-11-01

    In nuclear facilities, there are two primary aspects of occupational safety. The first aspect is radiological safety, which has rightly been treated in detail in nuclear facilities. Radiological exposure data have been collected from the existing tokamaks to serve as forecasts for ITER radiation safety. The second aspect of occupational safety, “traditional” industrial safety, must also be considered for a complete occupational safety program. Industrial safety data on occupational injury rates from the JET and TFTR tokamaks, three accelerators, and U.S. nuclear fission plants have been collected to set industrial safety goals for the ITER operations staff. The results of this occupational safety data collection and analysis activity are presented here. The data show that an annual lost workday case rate of 0.3 incidents per 100 workers is a conceivable goal for ITER operations.

  14. Non-resonant triple alpha reaction rate at low temperature

    SciTech Connect

    Itoh, T.; Tamii, A.; Aoi, N.; Fujita, H.; Hashimoto, T.; Miki, K.; Ogata, K.; Carter, J.; Donaldson, L.; Sideras-Haddad, E.; Furuno, T.; Kawabata, T.; Kamimura, M.; Nemulodi, F.; Neveling, R.; Smit, F. D.; Swarts, C.

    2014-05-02

    Our experimental goal is to study the non-resonant triple alpha reaction rate at low temperture (T < 10{sup 8} K). The {sup 13}C(p,d) reaction at 66 MeV has been used to probe the alpha-unbound continuum state in {sup 12}C just below the 2{sup nd} 0{sup +} state at 7.65 MeV. The transition strength to the continuum state is predicted to be sensitive to the non-resonant triple alpha reaction rate. The experiment has been performed at iThemba LABS. We report the present status of the experiment.

  15. Complete and incomplete fusion dynamics of 6,7Li + 159Tb reactions near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh; Grover, Neha; Sharma, Manoj K.

    2017-01-01

    The complete fusion (CF) and incomplete fusion (ICF) cross-sections are estimated for 6, 7Li + 159Tb reactions using the energy-dependent Woods-Saxon potential model (EDWSP model) and dynamical cluster-decay model (DCM). The CF data of the 6Li + 159Tb(7Li + 159Tb) reaction at above barrier energies is suppressed with reference to expectations of the EDWSP model by 25% (20%) which is smaller than the reported data by ˜ 9% (6%). This suppression is correlated with the projectile breakup effect. The projectiles 6,7Li are loosely bound systems, which may break up into charged fragments prior to reaching the fusion barrier and subsequently one of the fragment is captured by the target leading to the suppression of fusion data at above barrier energies. The sum of CF and ICF, which is termed as total fusion cross-section (TF), removes the discrepancies between theoretical predictions and the above barrier complete fusion data and hence is adequately explained via the EDWSP model over a wide range of energy spread across the Coulomb barrier. In addition to fusion, the decay mechanism of 6Li + 159Tb reaction is studied within the framework of the dynamical cluster-decay model (DCM). The breakup of the projectile (6Li) in the entrance channel indicates the presence of ICF, which is investigated further using the collective clusterization approach of DCM. The present theoretical analysis suggests that a larger barrier modification is needed to address the fusion data of chosen reactions in the below barrier energy region.

  16. Analysis of the Fusion and Graft Resorption Rates, as Measured by Computed Tomography, 1 Year After Posterior Cervical Fusion Using a Cervical Pedicle Screw.

    PubMed

    Lee, Jae Koo; Jung, Sang Ku; Lee, Young-Seok; Jeon, Sang Ryong; Roh, Sung Woo; Rhim, Seung Chul; Park, Jin Hoon

    2017-03-01

    We previously showed that cervical pedicle screw (CPS) placement is safe even with the freehand technique. The posterolateral fusion rate 1 year after CPS placement, as measured by computed tomography (CT), is reported here. The graft resorption rates when different graft materials were used were also analyzed. Between 2012 and 2015, 93 patients underwent posterior cervical fusion surgery with the CPS from C2 to C7. Of these patients, 56 consented to CT scans immediately and 1 year after surgery. These patients formed the present study group. The patients were categorized according to whether the graft material was local bone, allograft, or a mixture. Graft volume was measured at both CT scans. Graft resorption rate was determined by comparing the 2 scans. Radiologic fusion was assessed on the 1 year postoperative CT scan and radiography. The reason for surgery was trauma (n = 19), degenerative disease (n = 35), tumor (n = 1), and spondylitis (n = 1). Surgery was performed with CPS fixation and decompression. Even although iliac bone grafting was not performed, the overall fusion rate was 98.2% (55/56). The single fusion failure case received a mixture of local bone and allograft. Although the allograft group showed the greatest graft resorption rate (91.5%), all patients in this group had a bony bridge that crossed the facet joint on the 1 year CT scan. CPS placement yielded a posterolateral cervical fusion rate of 98.2%. Despite the high resorption rate of allograft only, this material yielded fusion rates that were similar to those of the other materials. Thus, the strong fixation power of CPS might compensate for the delayed fusion and high resorption rates of allograft bone chips. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Analysis of complete, incomplete and total fusion data of 9Be +169Tm, 187Re, 209Bi reactions

    NASA Astrophysics Data System (ADS)

    Kharab, Rajesh; Chahal, Rajiv; Kumar, Rajiv

    2016-11-01

    We have analyzed the incomplete fusion (ICF), complete fusion (CF) and total fusion (TF) excitation functions for reactions induced by 9Be on 169Tm, 187Re and 209Bi targets at near barrier energies using Wong’s formula in conjunction with the energy dependent Woods-Saxon potential. A phenomenological selection function is proposed to separate out the contribution of ICF and CF cross-sections in TF cross-section. The variation of relative contribution of ICF and CF in TF with respect to incident beam energy is very well reproduced through this approach.

  18. Analysis of reaction schemes using maximum rates of constituent steps

    NASA Astrophysics Data System (ADS)

    Hussain Motagamwala, Ali; Dumesic, James A.

    2016-05-01

    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.

  19. Analysis of reaction schemes using maximum rates of constituent steps.

    PubMed

    Motagamwala, Ali Hussain; Dumesic, James A

    2016-05-24

    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.

  20. Analysis of reaction schemes using maximum rates of constituent steps

    PubMed Central

    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

  1. Analysis of reaction schemes using maximum rates of constituent steps

    DOE PAGES

    Motagamwala, Ali Hussain; Dumesic, James A.

    2016-05-09

    In this paper, 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 themore » 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. Finally, 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.« less

  2. Increased D-D Fusion Reaction Boosted by Electron Screening at the Inner Shell of Metal Atoms

    NASA Astrophysics Data System (ADS)

    Luo, Nie; Miley, George

    2004-10-01

    Recent experiments indicate an abnormally high electron screening effect on the D-D fusion cross-section during low energy (< 10 keV) bombardment of select deuterated metals [1]. The authors attribute this effect to a contribution from core electrons ignored in normal screening calculations [2]. This research studies the contribution of the atomic potential distribution on the classical dynamics of keV deuterons in a host metal, taken here as Pd. A standard atomic code is used to obtain the atomic electron charge density and the potential profile in the metal atom. Using these results, the deuterons are found to spend most of their penetration time near the Pd M shell. This effect drastically increases the probability of a rendezvous between two deuterons in a rather confined area roughly 0.1 angstrom from the Pd nucleus. This mechanism, combined with the increased tunneling rate due to screening from the high electron density at M-shell, enhances the low energy D-D fusion cross-section for metal hydrides. Results from these calculations and comparisons with experimental data will be presented. [1] F. Strieder, C. Rolfs, C. Spitaleri, and P.Corvisiero, Naturwissenschaften, 88 (2001) 461. [2] G. H. Miley, H. Hora, N. Luo, ¡°Screening in Low Energy Nuclear Reactions of Importance to Nuclear Astrophysics¡±, APS April Mtg. (2004), Denver, CO.

  3. Comparison of a novel oxysterol molecule and rhBMP2 fusion rates in a rabbit posterolateral lumbar spine model.

    PubMed

    Scott, Trevor P; Phan, Kevin H; Tian, Haijun; Suzuki, Akinobu; Montgomery, Scott R; Johnson, Jared S; Atti, Elisa; Tetratis, Sotirios; Pereira, Renata C; Wang, Jeffrey C; Daubs, Michael D; Stappenbeck, Frank; Parhami, Farhad

    2015-04-01

    The nonunion rate after lumbar spinal fusion is as high as 25%. Recombinant human bone morphogenetic protein 2 (rhBMP2) has been used as a biological adjunct to promote bony fusion. However, recently there have been concerns about BMP2. Oxysterol 133 (Oxy133) has been shown to promote excellent fusion rates in rodent lumbar spine models and offers a potential alternative to rhBMP2. The purpose of this study was to compare the fusion rate of rhBMP2 and Oxy133 in a randomized controlled trial using a posterolateral lumbar rabbit spinal fusion model. This was a randomized control animal study. Twenty-four male adult white New Zealand rabbits (3-3.5 kg) underwent bilateral posterolateral lumbar spinal fusion at L4-L5. Rabbits were divided into four groups: control (A), 30-μg rhBMP2 (B), 20-mg Oxy133 (C), and 60-mg Oxy133 (D). At 4 weeks, fusion was evaluated by fluoroscopy, and at 8 weeks, the rabbits were sacrificed and fusion was evaluated radiographically, by manual palpation, and with microcomputed tomography. Fusion rates by radiographic analysis at 8 weeks were Group A, 40.0%; Group B, 91.7%; Group C, 91.7%; and Group D, 100%. Evaluation of fusion masses by manual palpation of excised spines after sacrifice showed the following fusion rates: Group A, 0%; Group B, 83.3%; Group C, 83.3%; and Group D, 90%. Microcomputed tomography scanning confirmed these findings. These findings in a rabbit model demonstrate that both 20- and 60-mg Oxy133 doses promote fusion that is equivalent to fusion induced by 30-μg rhBMP2 and significantly greater than the control group. The present findings confirm that Oxy133 is a promising candidate for therapeutic development as an alternative to rhBMP2 to promote spinal fusion. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Charge-exchange reaction by Reggeon exchange and W{sup +}W{sup −}-fusion

    SciTech Connect

    Schicker, R.

    2015-04-10

    Charge-exchange reactions at high energies are examined. The existing cross section data on the Reggeon induced reaction pp → n + Δ{sup ++} taken at the ZGS and ISR accelerators are extrapolated to the energies of the RHIC and LHC colliders. The interest in the charge-exchange reaction induced by W{sup ±}-fusion is presented, and the corresponding QCD-background is examined.

  5. Capture and Fusion-Fission Processes in Heavy Ion Induced Reactions

    NASA Astrophysics Data System (ADS)

    Itkis, M. G.; Beghini, S.; Behera, B. R.; Bogatchev, A. A.; Bouchat, V.; Corradi, L.; Dorvaux, O.; Fioretto, E.; Gadea, A.; Hanappe, F.; Itkis, I. M.; Jandel, M.; Kliman, J.; Knyazheva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Krupa, L.; Latina, A.; Lyapin, V. G.; Materna, T.; Montagnoli, G.; Oganessian, Yu. Ts.; Pokrovsky, I. V.; Prokhorova, E. V.; Rowley, N.; Rubchenya, V. A.; Rusanov, A. Ya.; Sagaidak, R. N.; Scarlassara, F.; Schmitt, C.; Stefanini, A. M.; Stuttge, L.; Szilner, S.; Trotta, M.; Trzaska, W. H.; Voskresenski, V. M.

    2005-11-01

    Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions 12C+204Pb, 48Ca+144,154Sm, 168Er, 208Pb, 238U, 244Pu, 248Cm; 58Fe+208Pb, 244Pu, 248Cm, and 64Ni+186W, 242Pu are presented. The choice of the above-mentioned reactions was inspired by the experiments on the production of the isotopes 283112, 289114 and 283116 at Dubna using the same reactions. The 58Fe and 64Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET and the neutron multi-detector DEMON. The role of shell effects and the influence of the entrance channel asymmetry and the deformations of colliding nucleus on the mechanism of the fusion-fission and the competitive process of quasi-fission are discussed.

  6. A D-D/D-T fusion reaction based neutron generator system for liver tumor BNCT

    SciTech Connect

    Koivunoro, H.; Lou, T.P.; Leung, K. N.; Reijonen, J.

    2003-04-02

    Boron-neutron capture therapy (BNCT) is an experimental radiation treatment modality used for highly malignant tumor treatments. Prior to irradiation with low energetic neutrons, a 10B compound is located selectively in the tumor cells. The effect of the treatment is based on the high LET radiation released in the {sup 10}B(n,{alpha}){sup 7}Li reaction with thermal neutrons. BNCT has been used experimentally for brain tumor and melanoma treatments. Lately applications of other severe tumor type treatments have been introduced. Results have shown that liver tumors can also be treated by BNCT. At Lawrence Berkeley National Laboratory, various compact neutron generators based on D-D or D-T fusion reactions are being developed. The earlier theoretical studies of the D-D or D-T fusion reaction based neutron generators have shown that the optimal moderator and reflector configuration for brain tumor BNCT can be created. In this work, the applicability of 2.5 MeV neutrons for liver tumor BNCT application was studied. The optimal neutron energy for external liver treatments is not known. Neutron beams of different energies (1eV < E < 100 keV) were simulated and the dose distribution in the liver was calculated with the MCNP simulation code. In order to obtain the optimal neutron energy spectrum with the D-D neutrons, various moderator designs were performed using MCNP simulations. In this article the neutron spectrum and the optimized beam shaping assembly for liver tumor treatments is presented.

  7. New Astrophysical Reaction Rate for the 12C(α, γ)16O Reaction

    NASA Astrophysics Data System (ADS)

    An, Zhen-Dong; Ma, Yu-Gang; Fan, Gong-Tao; Li, Yong-Jiang; Chen, Zhen-Peng; Sun, Ye-Ying

    2016-01-01

    A new astrophysical reaction rate for 12C(α, γ)16O has been evaluated on the basis of a global R-matrix fitting to the available experimental data. The reaction rates of 12C(α, γ)16O for stellar temperatures between 0.04 ≤ T9 ≤ 10 are provided in a tabular form and by an analytical fitting expression. At T9 = 0.2, the reaction rate is (7.83 ± 0.35) × 1015 cm3 mol-1 s-1, where stellar helium burning occurs.

  8. Reaction rate of beryllium with fluorine ion for Flibe redox control

    NASA Astrophysics Data System (ADS)

    Fukada, S.; Simpson, M. F.; Anderl, R. A.; Sharpe, J. P.; Katayama, K.; Smolik, G. R.; Oya, Y.; Terai, T.; Okuno, K.; Hara, M.; Petti, D. A.; Tanaka, S.; Sze, D.-K.; Sagara, A.

    2007-08-01

    An experimental effort to apply Flibe (a mixed molten salt of 2LiF + BeF 2) to a self-cooled liquid blanket of a fusion reactor was carried out under a Japan-US collaboration called JUPITER-II. Maintaining Flibe under a reducing atmosphere is a key issue to transform TF to T 2 with a faster reaction rate compared with the residence time in blanket. One of the tasks was to clarify whether or not the redox control of Flibe can be achieved with Be. The dissolution rate of a Be rod and the reaction rate of Be + 2HF = BeF 2 + H 2 in Flibe were experimentally determined. Sufficiently fast rates of the Be dissolution and the reduction reaction of HF to H 2 were clarified by our redox control experiment. Close agreement was obtained between experiments and our simplified complete-mixing model. In particular, the reaction between Be and a F - ion immediately after their contact was found to be limited by diffusion of the F - ion.

  9. On reaction rate constants IO+NO, IO+CO

    NASA Astrophysics Data System (ADS)

    Larin, Igor; Spasskiy, Alexandr; Trofimova, Elen

    2013-04-01

    A method, allowing to define, whether an investigated chemical reaction in a gas phase or on a surface of a reactor for those cases when dependence of the reaction rate on concentration of reagents for heterogeneous and for homogeneous reaction are identical, has been suggested. The method has been used for investigation of reactions of IO with nitric oxide and carbon monoxide. Experiments have been run in the flow reactor with using a method of resonance fluorescence to record atoms of iodine. It has been proved that the reaction of radical IO with nitric oxide proceeds in the gas phase, whereas the reaction of radical IO with carbon monoxide proceeds on the surface of the reactor. It has been obtained that reaction rate constant of IO with nitrogen monoxide in the temperature range 298-353 K is kNO(T)=(1,01±0,2)•10^-11•exp((210±80)/T) cm3*molecule*s-1 and the same for reaction of IO with carbon monoxide is kCO(T)=(1,14±0,64)•10^-14•exp((612±41)/T) cm3*molecule*s-1.

  10. An accurate analytic representation of the temperature dependence of nonresonant nuclear reaction rate coefficients

    NASA Astrophysics Data System (ADS)

    Shizgal, Bernie D.

    2016-12-01

    There has been intense interest for several decades by different research groups to accurately model the temperature dependence of a large number of nuclear reaction rate coefficients for both light and heavy nuclides. The rate coefficient, k(T) , is given by the Maxwellian average of the reactive cross section expressed in terms of the astrophysical factor, S(E) , which for nonresonant reactions is generally written as a power series in the relative energy E. A computationally efficient algorithm for the temperature dependence of nuclear reaction rate coefficients is required for fusion reactor research and for models of nucleosynthesis and stellar evolution. In this paper, an accurate analytical expression for the temperature dependence of nuclear reaction rate coefficients is provided in terms of τ = 3(b / 2) 2/3 or equivalently, T - 1/3 , where b = B /√{kB T }, B is the Gamow factor and kB is the Boltzmann constant. The methodology is appropriate for all nonresonant nuclear reactions for which S(E) can be represented as a power series in E. The explicit expression for the rate coefficient versus temperature is derived with the asymptotic expansions of the moments of w(E) = exp(- E /kB T - B /√{ E }) in terms of τ. The zeroth order moment is the familiar Gaussian approximation to the rate coefficient. Results are reported for the representative reactions D(d, p)T, D(d, n)3He and 7Li(p, α) α and compared with several different fitting procedures reported in the literature.

  11. A modified technique for occipitocervical fusion using compressed iliac crest allograft results in a high rate of fusion in the pediatric population.

    PubMed

    Iyer, Rajiv R; Tuite, Gerald F; Meoded, Avner; Carey, Carolyn C; Rodriguez, Luis F

    2017-08-05

    In children, high rates of occipitocervical (OC) fusion have been demonstrated using rigid instrumentation in combination with harvested autograft, with or without bone morphogenetic protein (BMP). Historically, the use of allograft materials demonstrated inferior OC fusion outcomes compared to autograft. However, autograft harvest harbors an increased risk of patient morbidity, and BMP use is costly and controversial in children. Thus, there remains a need for safer, less costly, yet efficacious techniques for OC fusion in the pediatric population. We retrospectively reviewed the charts of patients under 21 years of age who underwent OC fusion with structural allograft placement at our institution from 2010 to 2015. Data collected included age, gender, follow up duration, fusion outcomes and post-operative complications. 19 patients (8 female and 11 male) underwent OC fusion with our surgical technique. Mean age was 8.5 ± 4.3 years. Radiographic follow up data was available for 18/19 patients. One patient was lost to clinical follow up, but had radiographic confirmation of fusion. Thus, 18/18 (100%) of patients with radiographic follow up achieved successful arthrodesis as determined by computed tomography. Median duration to documented fusion was 4.5 months. Clinical follow up was available for 17/19 patients and was on average 18.8 ± 13.5 months. One patient required reoperation for graft fracture 8 months following radiographic confirmation of successful fusion. There were no vertebral artery injuries or other post-operative complications. We demonstrate a modified technique for OC fusion in children with unique structural allograft shaping and affixation, leading to excellent fusion outcomes at follow up. This technique obviates the need for autograft harvest and BMP, and may decrease post-operative morbidity. Copyright © 2017. Published by Elsevier Inc.

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Generalized rate equation for single-substrate enzyme catalyzed reactions.

    PubMed

    Kargi, Fikret

    2009-04-24

    The most widely used rate expression for single-substrate enzyme catalyzed reactions, namely the Michaelis-Menten kinetics is based upon the assumption that enzyme concentration is in excess of the substrate in the medium and the rate is mainly limited by the substrate concentration according to saturation kinetics. However, this is only a special case and the actual rate expression varies depending on the initial enzyme/substrate ratio (E(0)/S(0)). When the substrate concentration exceeds the enzyme concentration the limitation is due to low enzyme concentration and the rate increases with the enzyme concentration according to saturation kinetics. The maximum rate is obtained when the initial concentrations of the enzyme and the substrate are equal. A generalized rate equation was developed in this study and special cases were discussed for enzyme catalyzed reactions.

  14. Recording system and data fusion algorithm for enhancing the estimation of the respiratory rate from photoplethysmogram.

    PubMed

    Cernat, Roxana A; Ciorecan, Silvia I; Ungureanu, Constantin; Arends, Johan; Strungaru, Rodica; Ungureanu, G Mihaela

    2015-01-01

    The respiratory rate is a vital parameter that can provide valuable information about the health condition of a patient. The extraction of respiratory information from photoplethysmographic signal (PPG) was actually encouraged by the reported results, our main goal being to obtain accurate respiratory rate estimation from the PPG signal. We developed a fusion algorithm that identifies the best derived respiratory signals, from which is possible to extract the respiratory rate; based on these, a global respiratory rate is computed using the proposed fusion algorithm. The algorithm is qualitatively tested on real PPG signals recorded by an acquisition system we implemented, using a reflection pulse oximeter sensor. Its performance is also statistically evaluated using benchmark dataset publically available from CapnoBase.Org.

  15. Bone Union Rate Following Instrumented Posterolateral Lumbar Fusion: Comparison between Demineralized Bone Matrix versus Hydroxyapatite

    PubMed Central

    Nam, Woo Dong

    2016-01-01

    Study Design Retrospective study. Purpose To compare the union rate of posterolateral lumbar fusion (PLF) using demineralized bone matrix (DBM) versus hydroxyapatite (HA) as bone graft extender. Overview of Literature To our knowledge, there has been no clinical trial to compare the outcomes of DBM versus HA as a graft material for PLF. Methods We analyzed prospectively collected data from consecutive 79 patients who underwent instrumented PLF. Patients who received DBM were assigned to group B (n=38), and patients who received HA were assigned into group C (n=41). The primary study outcome was fusion rate assessed with radiographs. The secondary outcomes included pain intensity using a visual analogue scale, functional outcome using Oswestry disability index score, laboratory tests of inflammatory profiles and infection rate. Results One year postoperatively, bone fusion was achieved in 73% in group B and 58% in group C without significant difference between the groups (p=0.15). There were no differences between the groups with respect to secondary outcomes. Conclusions DBM would provide noninferior outcomes compared to the HA as a fusion material for PLF, and could be a notable alternative. PMID:27994793

  16. SIFT and FALP determinations of ionic reactions rate coefficients

    NASA Astrophysics Data System (ADS)

    Smith, D.; Adams, N. G.

    1990-06-01

    A brief review is presented of some recent results of studies of ionic reactions at thermal energies using the selected ion flow tube (SIFT) and the flowing afterglow/Langmuir probe (FALP) techniques in our laboratory. From the SIFT results, we summarise the recent data on positive ion-molecule reactions, much of which relate to the synthesis of interstellar molecules. Thus, for example, data are discussed relating to the reactions of some hydrocarbon ions in the series CnHm+, and phosphorus-bearing ions in the series PHn+, which can lead to interstellar hydrocarbon and phosphorus-bearing molecules. From the FALP results, we summarise the data obtained on the rate coefficients for dissociative recombination, highlighting the recent work on the determination of the products of some dissociative recombination reactions, and discuss recent results on studies of dissociative electron attachment reactions. Reference is also made to our earlier studies of ion-ion mutual neutralization.

  17. Do Trunk Muscles Affect the Lumbar Interbody Fusion Rate?: Correlation of Trunk Muscle Cross Sectional Area and Fusion Rates after Posterior Lumbar Interbody Fusion Using Stand-Alone Cage

    PubMed Central

    Choi, Man Kyu; Park, Bong Jin; Park, Chang Kyu; Kim, Sung Min

    2016-01-01

    Objective Although trunk muscles in the lumbar spine preserve spinal stability and motility, little is known about the relationship between trunk muscles and spinal fusion rate. The aim of the present study is to evaluate the correlation between trunk muscles cross sectional area (MCSA) and fusion rate after posterior lumbar interbody fusion (PLIF) using stand-alone cages. Methods A total of 89 adult patients with degenerative lumbar disease who were performed PLIF using stand-alone cages at L4–5 were included in this study. The cross-sectional area of the psoas major (PS), erector spinae (ES), and multifidus (MF) muscles were quantitatively evaluated by preoperative lumbar magnetic resonance imaging at the L3–4, L4–5, and L5–S1 segments, and bone union was evaluated by dynamic lumbar X-rays. Results Of the 89 patients, 68 had bone union and 21 did not. The MCSAs at all segments in both groups were significantly different (p<0.05) for the PS muscle, those at L3–4 and L4–5 segments between groups were significantly different (p=0.048, 0.021) for the ES and MF muscles. In the multivariate analysis, differences in the PS MCSA at the L4–5 and L5–S1 segments remained significant (p=0.048, 0.043 and odds ratio=1.098, 1.169). In comparison analysis between male and female patients, most MCSAs of male patients were larger than female's. Fusion rates of male patients (80.7%) were higher than female's (68.8%), too. Conclusion For PLIF surgery, PS muscle function appears to be an important factor for bone union and preventing back muscle injury is essential for better fusion rate. PMID:27226860

  18. Excitation functions for complete-fusion and transfer reactions in {sup 4}He interaction with {sup 197}Au nuclei

    SciTech Connect

    Kulko, A. A.; Demekhina, N. A.; Kalpakchieva, R.; Muzychka, Yu. A.; Penionzhkevich, Yu. E.; Rassadov, D. N.; Skobelev, N. K.; Testov, D. A.

    2007-04-15

    Excitation functions are measured for the fusion reactions {sup 197}Au({sup 4}He, xn){sup 201-xn}Tl that are induced by alpha-particle interaction with gold nuclei in the energy range 14-36 MeV and in which x neutrons (0 {<=} x {<=} 3) are evaporated. The stack-activation technique was used to record and separate reaction products. Experimental data on the fusion reactions followed by evaporation of one to three neutrons agree with results of previous studies. For the radiative-capture reaction {sup 197}Au({sup 4}He,{gamma}){sup 201}Tl, the upper limit on the cross section proved to be much lower. The excitation functions for the reactions subjected to measurements are compared with the results of calculations based on the statistical model and with the results of an experiment performed previously in a {sup 6}He beam.

  19. Excitation functions for complete-fusion and transfer reactions in 4He interaction with 197Au nuclei

    NASA Astrophysics Data System (ADS)

    Kulko, A. A.; Demekhina, N. A.; Kalpakchieva, R.; Muzychka, Yu. A.; Penionzhkevich, Yu. E.; Rassadov, D. N.; Skobelev, N. K.; Testov, D. A.

    2007-04-01

    Excitation functions are measured for the fusion reactions 197Au(4He, xn)201-xn Tl that are induced by alpha-particle interaction with gold nuclei in the energy range 14 36 MeV and in which x neutrons (0 ≤ x ≤ 3) are evaporated. The stack-activation technique was used to record and separate reaction products. Experimental data on the fusion reactions followed by evaporation of one to three neutrons agree with results of previous studies. For the radiative-capture reaction 197Au(4He,γ)201Tl, the upper limit on the cross section proved to be much lower. The excitation functions for the reactions subjected to measurements are compared with the results of calculations based on the statistical model and with the results of an experiment performed previously in a 6He beam.

  20. Benchmark calculations of thermal reaction rates. I - Quantal scattering theory

    NASA Technical Reports Server (NTRS)

    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.

  1. 7Li-induced reaction on natMo: A study of complete versus incomplete fusion

    NASA Astrophysics Data System (ADS)

    Kumar, Deepak; Maiti, Moumita; Lahiri, Susanta

    2017-07-01

    Background: Several investigations on the complete-incomplete fusion (CF-ICF) dynamics of α -cluster well-bound nuclei have been contemplated above the Coulomb barrier (˜4 -7 MeV/nucleon) in recent years. It is therefore expected to observe significant ICF over CF in the reactions induced by a weakly bound α -cluster nucleus at slightly above the barrier. Purpose: Study of the CF-ICF dynamics by measuring the populated residues in the weakly bound 7Li+natMo system at energies slightly above the Coulomb barrier to well above it. Method: In order to investigate CF-ICF in the loosely bound system, 7Li beam was bombarded on the natMo foils, separated by the aluminium (Al) catcher foils alternatively, within ˜3 -6.5 MeV/nucleon. Evaporation residues produced in each foil were identified by the off-line γ -ray spectrometry. Measured cross section data of the residues were compared with the theoretical model calculations based on the equilibrium (EQ) and pre-equilibrium (PEQ) reaction mechanisms. Results: The experimental cross section of Rh 101 m,100 ,99 m,97 ,Ru,9597,Tc 99 m,96 ,95 ,94 ,93 m+g , and 93mMo residues measured at various projectile energies were satisfactorily reproduced by the simplified coupled channel approach in comparison to single barrier penetration model calculation. Significant cross section enhancement in the α -emitting channels was observed compared to EQ and PEQ model calculations throughout observed energy region. The ICF process over CF was analyzed by comparing with EMPIRE. The increment of the incomplete fusion fraction was observed with increasing projectile energies. Conclusions: Theoretical model calculations reveal that the compound reaction mechanism is the major contributor to the production of residues in 7Li+natMo reaction. Theoretical evaluations substantiate the contribution of ICF over the CF in α -emitting channels. EMPIRE estimations shed light

  2. Reaction rates between water and the Karl Fischer reagent.

    PubMed

    Cedergren, A

    1974-04-01

    Reaction rates between water and the Karl Fischer reagent have been determined by potentiometric measurement for various compositions of the Karl Fischer reagent. The study has been made with an iodine complex concentration of 0.3-1.2 mM and sulphur dioxide complex at 0.01-0.5M. The concentration of excess of pyridine had no measurable effect on the rate of the main reaction. The reaction was found to be first-order with respect to iodine complex, to sulphur dioxide complex, and to water. The rate constant was (1.2+/-0.2) x 10(3) 1(2). mole(-2). sec(-1). In an ordinary titration it is therefore essential to keep the sulphur dioxide concentration high for the reaction to go to completion within a reasonable time. The extent of side-reactions was found to be independent of the iodine concentration at low concentrations. The side-reactions increased somewhat with increasing sulphur dioxide pyridine concentrations and decreased to about 60% when the temperature was lowered from 24 degrees to 7 degrees.

  3. Posterior Lumbar Interbody Fusion with Interspinous Fastener Provides Comparable Clinical Outcome and Fusion Rate to Pedicle Screws.

    PubMed

    Huang, Wei-Min; Yu, Xing-Ming; Xu, Xiao-Duo; Song, Ruo-Xian; Yu, Li-Li; Yu, Xiu-Chun

    2017-05-01

    To investigate the clinical feasibility and validity of interspinous fastener (ISF) for lumbar degenerative diseases. From October 2013 to March 2014, a total of 46 patients suffering from lumbar degenerative diseases underwent posterior lumbar interbody fusion (PLIF) randomly augmented by ISF or pedicle screws. The clinical outcome was primarily measured by Oswestry Disability Index (ODI) score. The minimal clinical important difference (MCID) was defined as an eight-point decrease in ODI. The second clinical outcome measurement was Japanese Orthopedic Association (JOA) score. Interbody fusion rates were evaluated by lumbar plain radiograph and computed tomography (CT) scan. Complications were also compared between groups. Statistical analyses were performed by SPSS version 13.0. Sample size calculation was performed before the study. The type I error α was set at 0.05 and the type II error β at 0.1. Based on these assumptions and adding 10% for possible drop-outs, sample size calculations indicated that a total of 46 patients were required for the study. Parametric data was compared by independent t-test and categorical variables were compared using χ(2) -tests or Fisher exact tests depending on the sample size. A P-value of less than 0.05 was considered significantly statistically different. Fleiss kappa coefficients were calculated for intra-observer and inter-observer reliability. A total of 43 patients completed the follow-up, with 22 cases in the ISF group and 21 patients in the pedicle screws group, respectively. Less intraoperative blood loss and shorter operation time were observed in the ISF group. The mean ODI significantly declined in both groups, with the ISF group's decreasing from preoperative 43.3 ± 8.2 to 21.4 ± 3.5 at 24-month follow-up and the pedicle screws group's decreasing from preoperative 42.9 ± 7.9 to 22.5 ±3.8 at 24-month follow-up, respectively. The ODI changes between groups had no statistical difference (P > 0.05). Of the 43

  4. Clustering effects in fusion evaporation reactions with light even-even N=Z nuclei

    NASA Astrophysics Data System (ADS)

    Morelli, L.; D'Agostino, M.; Bruno, M.; Frosin, C.; Gulminelli, F.; Gramegna, F.; Cinausero, M.; Marchi, T.; Fabris, D.; Degerlier, M.; Casini, G.; Barlini, S.; Bini, M.; Pasquali, G.; Olmi, A.; Piantelli, S.; Valdré, S.; Pastore, G.; Gelli, N.; Vardaci, E.

    2017-06-01

    In the recent years, cluster structures have been evidenced in many ground and excited states of light nuclei [1, 2]. In the currently experimental campaign, the NUCL-EX collaboration has measured the12C+12C and14N+10B reactions at 95 MeV and 80 MeV respectively. The experimental data corresponding to complete fusion of target and projectile into an excited24Mg nucleus was compared to the results of a pure statistical model [3, 4]. In addition, data from12C+12C have been analyzed to investigate the decay of the Hoyle state of12C* [12] obtained as an intermediate step in the 6α decay channel of the24Mg* formed in central events.

  5. Reaction-Based SiC Materials for Joining Silicon Carbide Composites for Fusion Energy

    SciTech Connect

    Lewinsohn, Charles A.; Jones, Russell H.; Singh, M.; Serizawa, H.; Katoh, Y.; Kohyama, A.

    2000-09-01

    The fabrication of large or complex silicon carbide-fiber-reinforced silicon carbide (SiC/SiC) components for fusion energy systems requires a method to assemble smaller components that are limited in size by manufacturing constraints. Previous analysis indicates that silicon carbide should be considered as candidate joint materials. Two methods to obtain SiC joints rely on a reaction between silicon and carbon to produce silicon carbide. This report summarizes preliminary mechanical properties of joints formed by these two methods. The methods appear to provide similar mechanical properties. Both the test methods and materials are preliminary in design and require further optimization. In an effort to determine how the mechanical test data is influenced by the test methodology and specimen size, plans for detailed finite element modeling (FEM) are presented.

  6. Reaction rates of atmospheric gases with lithium(silicon) alloy

    SciTech Connect

    Searcy, J Q; Reinhardt, F W

    1980-12-01

    Reaction rates of small pellets of Li(Si) alloy with atmospheric gases were studied as a prerequisite to specifying how this alloy should be handled during the production of thermal batteries. The results indicate that Li(Si) reacts with oxygen and nitrogen at ambient conditions too slowly to be of concern, but it reacts very rapidly with water vapor. Rate expressions and constants are developed that allow calculating the weight gain of Li(Si) after its reaction with water vapor, and calculated values are given for three water-vapor concentrations that typify those used in dry rooms where thermal batteries are produced.

  7. Particle emission in the light heavy-ion fusion reactions: 14N, 16,18O+ 12C

    NASA Astrophysics Data System (ADS)

    Carlin Filho, N.; Coimbra, M. M.; Acquadro, J. C.; Liguori Neto, R.; Szanto, E. M.; Farrelly-Pessoa, E.; Szanto de Toledo, A.

    1985-01-01

    From the energy spectra of light particles produced in light-heavy-ion-induced reactions, level densities of the final nuclei as well as the critical angular momenta for fusion may be obtained. The 14N, 16,18O+ 12C reactions were investigated in the energy range 30 MeVfusion critical angular momentum (Jcr), offering an alternative method for the total fusion cross-section determination.

  8. Indirect Study of the 16O+16O Fusion Reaction Toward Stellar Energies by the Trojan Horse Method

    NASA Astrophysics Data System (ADS)

    Hayakawa, S.; Spitaleri, C.; Burtebayev, N.; Aimaganbetov, A.; Figuera, P.; Fisichella, M.; Guardo, G. L.; Igamov, S.; Indelicato, I.; Kiss, G.; Kliczewski, S.; La Cognata, M.; Lamia, L.; Lattuada, M.; Piasecki, E.; Rapisarda, G. G.; Romano, S.; Sakuta, S. B.; Siudak, R.; Trzcińska, A.; Tumino, A.; Urkinbayev, A.

    2016-05-01

    The 16O+16O fusion reaction is important in terms of the explosive oxygen burning process during late evolution stage of massive stars as well as understanding of the mechanism of low-energy heavy-ion fusion reactions. We aim to determine the excitation function for the most major exit channels, α+28Si and p+31P, toward stellar energies indirectly by the Trojan Horse Method via the 16O(20Ne, α28Si)α and 16O(20Ne, p31P)α three-body reactions. We report preliminary results involving reaction identification, and determination of the momentum distribution of α-16O intercluster motion in the projectile 20Ne nucleus.

  9. Semiclassical Calculation of Reaction Rate Constants for Homolytical Dissociations

    NASA Technical Reports Server (NTRS)

    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.

  10. Reaction rate uncertainties and the {nu}p-process

    SciTech Connect

    Froehlich, C.; Rauscher, T.

    2012-11-12

    Current hydrodynamical simulations of core collapse supernovae find proton-rich early ejecta. At the same time, the models fail to eject neutron-rich matter, thus leaving the origin of the main r-process elements unsolved. However, the proton-rich neutrino-driven winds from supernovae have been identified as a possible production site for light n-capture elements beyond iron (such as Ge, Sr, Y, Zr) through the {nu}p-process. The detailed nucleosynthesis patterns of the {nu}p-process depend on the hydrodynamic conditions and the nuclear reaction rates of key reactions. We investigate the impact of reaction rate uncertainties on the {nu}p-process nucleosynthesis.

  11. Semiclassical Calculation of Reaction Rate Constants for Homolytical Dissociations

    NASA Technical Reports Server (NTRS)

    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.

  12. Prediction of Rate Constants for Catalytic Reactions with Chemical Accuracy.

    PubMed

    Catlow, C Richard A

    2016-08-01

    Ex machina: A computational method for predicting rate constants for reactions within microporous zeolite catalysts with chemical accuracy has recently been reported. A key feature of this method is a stepwise QM/MM approach that allows accuracy to be achieved while using realistic models with accessible computer resources.

  13. Reaction rates of graphite with ozone measured by etch decoration

    NASA Technical Reports Server (NTRS)

    Hennig, G. R.; Montet, G. L.

    1968-01-01

    Etch-decoration technique of detecting vacancies in graphite has been used to determine the reaction rates of graphite with ozone in the directions parallel and perpendicular to the layer planes. It consists essentially of peeling single atom layers off graphite crystals without affecting the remainder of the crystal.

  14. Quantum and semiclassical theories of chemical reaction rates

    SciTech Connect

    Miller, W.H. |

    1995-09-01

    A rigorous quantum mechanical theory (and a semiclassical approximation thereto) is described for calculating chemical reaction rates ``directly``, i.e., without having to solve the complete state-to-state reactive scattering problem. The approach has many vestiges of transition state theory, for which it may be thought of as the rigorous generalization.

  15. Renormalized reaction and relaxation rates for harmonic oscillator model

    NASA Astrophysics Data System (ADS)

    Gorbachev, Yuriy E.

    2017-07-01

    The thermal dissociation process is considered within the method of solving the kinetic equations for spatially inhomogeneous reactive gas mixtures developed in the previous papers. For harmonic oscillator model explicit expressions for reaction and relaxation rates in the renormalized form are derived.

  16. Rates of membrane-associated reactions: reduction of dimensionality revisited

    PubMed Central

    1986-01-01

    The hypothesis that reactions associated with intracellular membranes enjoy a kinetic advantage from a reduced dimensionality for diffusion is inconsistent with available data on lateral diffusion rates, membrane-substrate affinities, and endogenous concentrations of enzymes and their aqueous substrates. PMID:3001105

  17. Fusion hindrance and quasi-fission in heavy-ion induced reactions: disentangling the effect of different parameters

    SciTech Connect

    Fioretto, E.; Stefanini, A. M.; Behera, B. R.; Corradi, L.; Gadea, A.; Latina, A.; Trotta, M.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Chizhov, A. Yu.; Itkis, I. M.; Itkis, M. G.; Kniajeva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Pokrovsky, I. V.; Sagaidak, R. N.; Voskressensky, V. M.; Courtin, S.

    2006-04-26

    Experimental results on the fusion inhibition effect near the Coulomb barrier due to the onset of the quasi-fission mechanism are presented. The investigation was focused on reactions induced by 48Ca projectiles on different heavy targets and comparing them to reactions induced by light ions such as 12C and 16O leading to the same compound nuclei. Cross sections and angular distributions of evaporation residues and fission fragments have been measured.

  18. Noise slows the rate of Michaelis-Menten reactions.

    PubMed

    Van Dyken, J David

    2017-10-07

    Microscopic randomness and the small volumes of living cells combine to generate random fluctuations in molecule concentrations called "noise". Here I investigate the effect of noise on biochemical reactions obeying Michaelis-Menten kinetics, concluding that substrate noise causes these reactions to slow. I derive a general expression for the time evolution of the joint probability density of chemical species in arbitrarily connected networks of non-linear chemical reactions in small volumes. This equation is a generalization of the chemical master equation (CME), a common tool for investigating stochastic chemical kinetics, extended to reaction networks occurring in small volumes, such as living cells. I apply this equation to a generalized Michaelis-Menten reaction in an open system, deriving the following general result: 〈p〉≤p¯ and 〈s〉≥s¯, where s¯ and p¯ denote the deterministic steady-state concentration of reactant and product species, respectively, and 〈s〉 and 〈p〉 denote the steady-state ensemble average over independent realizations of a stochastic reaction. Under biologically realistic conditions, namely when substrate is degraded or diluted by cell division, 〈p〉≤p¯. Consequently, noise slows the rate of in vivo Michaelis-Menten reactions. These predictions are validated by extensive stochastic simulations using Gillespie's exact stochastic simulation algorithm. I specify the conditions under which these effects occur and when they vanish, therefore reconciling discrepancies among previous theoretical investigations of stochastic biochemical reactions. Stochastic slowdown of reaction flux caused by molecular noise in living cells may have functional consequences, which the present theory may be used to quantify. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Importance of lifetime effects in breakup and suppression of complete fusion in reactions of weakly bound nuclei

    NASA Astrophysics Data System (ADS)

    Cook, K. J.; Simpson, E. C.; Luong, D. H.; Kalkal, Sunil; Dasgupta, M.; Hinde, D. J.

    2016-06-01

    Background: Complete fusion cross sections in collisions of light weakly bound nuclei and high-Z targets show suppression of complete fusion at above-barrier energies. This has been interpreted as resulting from the breakup of the weakly bound nucleus prior to reaching the fusion barrier, reducing the probability of complete charge capture. Below-barrier studies of reactions of 9Be have found that the breakup of 8Be formed by neutron stripping dominates over direct breakup and that transfer-triggered breakup may account for the observed suppression of complete fusion. Purpose: This paper investigates how the above conclusions are affected by lifetimes of the resonant states that are populated prior to breakup. If the mean life of a populated resonance (above the breakup threshold) is much longer than the fusion time scale, then its breakup (decay) cannot suppress complete fusion. For short-lived resonances, the situation is more complex. This work explicitly includes the mean life of the short-lived 2+ resonance in 8Be in classical dynamical model calculations to determine its effect on energy and angular correlations of the breakup fragments and on model predictions of suppression of cross sections for complete fusion at above-barrier energies. Method: Previously performed coincidence measurements of breakup fragments produced in reactions of 9Be with 144Sm, 168Er, 186W, 196Pt, 208Pb, and 209Bi at energies below the barrier have been reanalyzed using an improved efficiency determination of the BALiN detector array. Predictions of breakup observables and of complete and incomplete fusion at energies above the fusion barrier are then made using the classical dynamical simulation code platypus, modified to include the effect of lifetimes of resonant states. Results: The agreement of the breakup observables is much improved when lifetime effects are included explicitly. Sensitivity to subzeptosecond lifetime is observed. The predicted suppression of complete fusion

  20. Dynamical Dipole and Equation of State in N/Z Asymmetric Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Giaz, Agnese; Corsi, Anna; Camera, Franco; Wieland, Oliver; Kravchuk, Vladimir L.; Barlini, Sandro; Alba, Rosa; Bednarczyk, P.; Bracco, Angela; Baiocco, Giorgio; Bardelli, Luigi; Benzoni, Giovanna; Bini, M.; Blasi, Nives; Brambilla, Sergio; Bruno, Mauro; Casini, Giovanni; Ciemala, Michal; Cinausero, Marco; Chiari, M.; Colonna, Maria; Crespi, Fabio Celso Luigi; D'Agostino, Michela; Degerlier, Meltem; Di Toro, Massimo; Gramegna, Fabiana; Kmiecik, Maria; Leoni, Silvia; Maiolino, C.; Maj, Adam; Marchi, Tommaso; Mazurek, K.; Meczynski, W.; Million, Benedicte; Montanari, Daniele; Morelli, Luca; Nannini, Adriana; Nicolini, Roberto; Pasquali, G.; Piantelli, S.; Ordine, A.; Poggi, Giacomo; Rizzi, V.; Rizzo, Carmelo; Santonocito, Domenico; Vandone, Valeria; Vannini, G.

    2014-03-01

    In heavy ion reactions, in the case of N/Z asymmetry between projectile and target, the process leading to complete fusion is expected to produce pre-equilibrium dipole γ-ray emission. It is generated during the charge equilibration process and it is known as Dynamical Dipole. A new measurement of the dynamical dipole emission was performed by studying 16O + 116Sn at 12 MeV/u. These data, together with those measured at 8.1 MeV/u and 15.6 MeV/u for the same reaction, provide the dependence on the Dynamical Dipole total emission yield with beam energy and they can be compared with theoretical expectations. The experimental results show a weak increase of the Dynamical Dipole total yield with beam energies and are in agreement with the prediction of a theoretical model based on the Boltzmann-Nordheim-Vlasov (BNV) approach. The measured trend with beam energy does not confirm the rise and fall behavior previously reported for the same fused compound but with a much higher dipole moment.

  1. Characterization of Discontinuous Coarsening Reaction Products in INCONEL® Alloy 740H® Fusion Welds

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H.; Dupont, John N.; Watanabe, Masashi; de Barbadillo, John J.

    2017-04-01

    Characterization of γ' coarsened zones (CZs) in alloy 740H fusion welds via a variety of electron microscopy techniques was conducted. The effects of solute partitioning during nonequilibrium solidification on the amount of strengthening precipitates along the grain boundaries were evaluated via electron-probe microanalysis and scanning electron microscopy. Electron backscatter diffraction was used to present evidence for the preferential growth of CZs toward regions of lower γ' content, even if growth in that direction increases grain boundary area. Scanning electron microscopy and image analysis were used to quantify the propensity for CZs to develop along certain segments of the grain boundaries, as governed by the local variations in γ' content. Scanning transmission electron microscopy with X-ray energy-dispersive spectrometry (XEDS) was used to assess the compositions of the matrix and precipitate phases within the CZs and to quantify the segregation of alloying components to the reaction front. Thermodynamic and kinetic modeling were used to compare calculated and experimental compositions. The work presented here provides new insight into the progression of the discontinuous coarsening (DC) reaction in a complex engineering alloy.

  2. Characterization of Discontinuous Coarsening Reaction Products in INCONEL® Alloy 740H® Fusion Welds

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H.; Dupont, John N.; Watanabe, Masashi; de Barbadillo, John J.

    2017-02-01

    Characterization of γ' coarsened zones (CZs) in alloy 740H fusion welds via a variety of electron microscopy techniques was conducted. The effects of solute partitioning during nonequilibrium solidification on the amount of strengthening precipitates along the grain boundaries were evaluated via electron-probe microanalysis and scanning electron microscopy. Electron backscatter diffraction was used to present evidence for the preferential growth of CZs toward regions of lower γ' content, even if growth in that direction increases grain boundary area. Scanning electron microscopy and image analysis were used to quantify the propensity for CZs to develop along certain segments of the grain boundaries, as governed by the local variations in γ' content. Scanning transmission electron microscopy with X-ray energy-dispersive spectrometry (XEDS) was used to assess the compositions of the matrix and precipitate phases within the CZs and to quantify the segregation of alloying components to the reaction front. Thermodynamic and kinetic modeling were used to compare calculated and experimental compositions. The work presented here provides new insight into the progression of the discontinuous coarsening (DC) reaction in a complex engineering alloy.

  3. Control of serpentinisation rate by reaction-induced cracking

    NASA Astrophysics Data System (ADS)

    Malvoisin, Benjamin; Brantut, Nicolas; Kaczmarek, Mary-Alix

    2017-10-01

    Serpentinisation of mantle rocks requires the generation and maintenance of transport pathways for water. The solid volume increase during serpentinisation can lead to stress build-up and trigger cracking, which ease fluid penetration into the rock. The quantitative effect of this reaction-induced cracking mechanism on reactive surface generation is poorly constrained, thus hampering our ability to predict serpentinisation rate in geological environments. Here we use a combined approach with numerical modelling and observations in natural samples to provide estimates of serpentinisation rate at mid-ocean ridges. We develop a micromechanical model to quantify the propagation of serpentinisation-induced cracks in olivine. The maximum crystallisation pressure deduced from thermodynamic calculations reaches several hundreds of megapascals but does not necessary lead to crack propagation if the olivine grain is subjected to high compressive stresses. The micromechanical model is then coupled to a simple geometrical model to predict reactive surface area formation during grain splitting, and thus bulk reaction rate. Our model reproduces quantitatively experimental kinetic data and the typical mesh texture formed during serpentinisation. We also compare the model results with olivine grain size distribution data obtained on natural serpentinised peridotites from the Marum ophiolite and the Papuan ultramafic belt (Papua New Guinea). The natural serpentinised peridotites show an increase of the number of olivine grains for a decrease of the mean grain size by one order of magnitude as reaction progresses from 5 to 40%. These results are in agreement with our model predictions, suggesting that reaction-induced cracking controls the serpentinisation rate. We use our model to estimate that, at mid-ocean ridges, serpentinisation occurs up to 12 km depth and reaction-induced cracking reduces the characteristic time of serpentinisation by one order of magnitude, down to values

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

    SciTech Connect

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

    2010-06-01

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

  5. Quasifission and fission rates and their lifetimes in asymmetric reactions forming 216Ra within a dinuclear system approach

    NASA Astrophysics Data System (ADS)

    Khanlari, M. Varasteh; Soheyli, S.

    2017-02-01

    Background: The study of evolution of asymmetric dinuclear systems (DNSs) formed in heavy ion collisions is a topic of intense research. The DNS evolution leads to a variety of reaction channels such as deep inelastic, complete fusion, quasifission, fast fission, fusion-fission, and evaporation of particles. The time evolution of the DNS in the quasifission process and the role of relevant parameters are still not fully understood. Purpose: The influence of the entrance channel mass asymmetry on the time evolution of an excited and rotating DNS, populated via four reactions with different entrance channel mass asymmetry parameters which all lead to the compound nucleus 216Ra, is explored. Method: The driving potential, emission barriers for the binary decay (namely the quasifission and intrinsic fusion barriers), rate of the quasifission channel, and the lifetime of an excited DNS, as well as the fission rate and fission lifetime of the compound nucleus 216Ra formed in the 12C+204Pb,19F+197Au,30Si+186W , and 48Ca+168Er reactions, are calculated by the dinuclear system approach. Results: Our results show that the intrinsic fusion barrier values are equal to zero for the 12C+204Pb and 19F+197Au reactions. Therefore, the quasifission signature is extremely hindered for these reactions, while the 30Si+186W and 48Ca+168Er calculated results contain quasifission contributions. Provided the quasifission rate is nonzero, the quasifission rate increases with increasing orbital angular momentum ℓ of the composite system for a given excitation energy ECN * of the compound nucleus. On the other hand, the quasifission lifetime decreases moderately with increasing ℓ . Furthermore, both quasifission and fission rates increase with increasing excitation energy ECN *, while the quasifission and fission lifetimes decrease with increasing ECN * for a given ℓ . Conclusions: Although these reactions with different entrance channels populate the same compound nucleus 216Ra at

  6. Abundances in Astrophysical Environments: Reaction Network Simulations with Reaction Rates from Many-nucleon Modeling

    NASA Astrophysics Data System (ADS)

    Amason, Charlee; Dreyfuss, Alison; Launey, Kristina; Draayer, Jerry

    2017-01-01

    We use the ab initio (first-principle) symmetry-adapted no-core shell model (SA-NCSM) to calculate reaction rates of significance to type I X-ray burst nucleosynthesis. We consider the 18O(p,γ)19F reaction, which may influence the production of fluorine, as well as the 16O(α,γ)20Ne reaction, which is key to understanding the production of heavier elements in the universe. Results are compared to those obtained in the no-core sympletic shell model (NCSpM) with a schematic interaction. We discuss how these reaction rates affect the relevant elemental abundances. We thank the NSF for supporting this work through the REU Site in Physics & Astronomy (NSF grant #1560212) at Louisiana State University. This work was also supported by the U.S. NSF (OCI-0904874, ACI -1516338) and the U.S. DOE (DE-SC0005248).

  7. Fusion-fission and quasifission in the reactions with heavy ions leading to the formation of Hs

    SciTech Connect

    Itkis, I. M.; Itkis, M. G.; Knyazheva, G. N.; Kozulin, E. M.

    2012-10-20

    Mass and energy distributions of binary reaction products obtained in the reactions {sup 22}Ne+{sup 249}Cf,{sup 26}Mg+{sup 248}Cm,{sup 36}S+{sup 238}U and {sup 58}Fe+{sup 208}Pb leading to Hs isotopes have been measured. At energies below the Coulomb barrier the bimodal fission of Hs*, formed in the reaction {sup 26}Mg+{sup 248}Cm, is observed. In the reaction {sup 36}S+{sup 238}U the considerable part of the symmetric fragments arises from the quasifission process. At energies above the Coulomb barrier the symmetric fragments originate mainly from fusion-fission process for both reactions with Mg and S ions. In the case of the {sup 58}Fe+{sup 208}Pb reaction the quasifission process dominates at all measured energies. The pre- and post-scission neutron multiplicities as a function of the fragment mass have been obtained for the reactions studied.

  8. Temperature Dependence of the Rate Constants of Charge Recombination Reactions in Bacterial Reaction Centers

    NASA Astrophysics Data System (ADS)

    Thuy, T. T.; Yen, V. T. H.; Thao, T. T.; Viet, Nguyen Ai

    The bacterial reaction center couples light-induced electron transfer via a tightly bound ubiquinone (QA) to a mobile ubiquinone (QB). Based on the electron transfer theory by Marcus, we have investigated the rate of charge recombination reactions from Rhodopseudomonas viridis and Rhodobacter sphaeroides, by mean of finding an approximation formula. The results obtained are verified for not only at high and low temperature as the previous works but also at the medium temperature range.

  9. Synthesis of superheavy element 120 via {sup 50}Ti+{sup A}Cf hot fusion reactions

    SciTech Connect

    Liu, Z. H.; Bao Jingdong

    2009-11-15

    Synthesis of superheavy element 120 in terms of the {sup 50}Ti+{sup 249-252}Cf fusion-evaporation reactions is evaluated and discussed. It is found that the reactions of {sup 250,251}Cf({sup 50}Ti,3n){sup 297,298}120 and {sup 251,252}Cf({sup 50}Ti,4n){sup 297,298}120 are relatively favorable with the maximum evaporation-residue cross sections of 0.12, 0.09, 0.11, and 0.25 pb, respectively. However, {sup 252}Cf may be difficult to be target because its spontaneous fission will bring about serious background in the experiment. Fusion probabilities for different target-projectile combinations leading to the formation of surperheavy nucleus {sup 302}120 are estimated with the ''fusion-by-diffusion'' model and presented as a function of the Coulomb parameter Z{sub 1}Z{sub 2}/(A{sub 1}{sup 1/3}+A{sub 2}{sup 1/3}). Among the reactions {sup 50}Ti+{sup 252}Cf, {sup 54}Cr+{sup 248}Cm, {sup 58}Fe+{sup 244}Pu, and {sup 64}Ni+{sup 238}U, the reaction {sup 50}Ti+{sup 252}Cf has the largest fusion probability. Synthesis of superheavy element 120 is of essential importance for determining whether the magic proton shell should be at Z=114 or at higher proton numbers Z=120-126. Therefore, the experiment to produce isotopes with Z=120 in the fusion reactions {sup 50}Ti+{sup 250,251}Cf is of great interest.

  10. Calculations of Excitation Functions of Some Structural Fusion Materials for ( n, t) Reactions up to 50 MeV Energy

    NASA Astrophysics Data System (ADS)

    Tel, E.; Durgu, C.; Aktı, N. N.; Okuducu, Ş.

    2010-06-01

    Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, the working out the systematics of ( n, t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. In this study, ( n, t) reactions for some structural fusion materials such as 27Al, 51V, 52Cr, 55Mn, and 56Fe have been investigated. The new calculations on the excitation functions of 27Al( n, t)25Mg, 51V( n, t)49Ti, 52Cr( n, t)50V, 55Mn( n, t)53Cr and 56Fe( n, t)54Mn reactions have been carried out up to 50 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model, hybrid model and the cascade exciton model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. Also in the present work, we have calculated ( n, t) reaction cross-sections by using new evaluated semi-empirical formulas developed by Tel et al. at 14-15 MeV energy. The calculated results are discussed and compared with the experimental data taken from the literature.

  11. Code System to Calculate Integral Parameters with Reaction Rates from WIMS Output.

    SciTech Connect

    LESZCZYNSKI, FRANCISCO

    1994-10-25

    Version 00 REACTION calculates different integral parameters related to neutron reactions on reactor lattices, from reaction rates calculated with WIMSD4 code, and comparisons with experimental values.

  12. Reaction rate constant for radiative association of CF+

    NASA Astrophysics Data System (ADS)

    Ã-ström, Jonatan; Bezrukov, Dmitry S.; Nyman, Gunnar; Gustafsson, Magnus

    2016-01-01

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C+) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 11Π → X1Σ+ and rovibrational transitions on the X1Σ+ and a3Π 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 10-21 cm3 s-1, rising toward 10-16 cm3 s-1 for a temperature of 30 000 K.

  13. The temperature-dependence of elementary reaction rates: beyond Arrhenius.

    PubMed

    Smith, Ian W M

    2008-04-01

    The rates of chemical reactions and the dependence of their rate constants on temperature are of central importance in chemistry. Advances in the temperature-range and accuracy of kinetic measurements, principally inspired by the need to provide data for models of combustion, atmospheric, and astrophysical chemistry, show up the inadequacy of the venerable Arrhenius equation--at least, over wide ranges of temperature. This critical review will address the question of how to reach an understanding of the factors that control the rates of 'non-Arrhenius' reactions. It makes use of a number of recent kinetic measurements and shows how developments in advanced forms of transition state theory provide satisfactory explanations of complex kinetic behaviour (72 references).

  14. Rate of reaction of OH with HNO3

    NASA Technical Reports Server (NTRS)

    Wine, P. H.; Ravishankara, A. R.; Kreutter, N. M.; Shah, R. C.; Nicovich, J. M.; Thompson, R. L.; Wuebbles, D. J.

    1981-01-01

    Measurements of the kinetics of the reaction of OH with HNO3, and mechanisms of HNO3 removal from the stratosphere, are reported. Bimolecular rate constants were determined at temperatures between 224 and 366 K by monitoring the concentrations of OH radicals produced by HNO3 photolysis and HNO3 according to their resonance fluorescence and 184.9-nm absorption, respectively. The rate constant measured at 298 K is found to be somewhat faster than previously accepted values, with a negative temperature dependence. Calculations of a one-dimensional transport-kinetic atmospheric model on the basis of the new rate constant indicate reductions in O3 depletion due to chlorofluoromethane release and NOx injection, of magnitudes dependent on the nature of the reaction products.

  15. Influence of laser induced hot electrons on the threshold for shock ignition of fusion reactions

    SciTech Connect

    Colaïtis, A.; Ribeyre, X.; Le Bel, E.; Duchateau, G.; Nicolaï, Ph.; Tikhonchuk, V.

    2016-07-15

    The effects of Hot Electrons (HEs) generated by the nonlinear Laser-Plasma Interaction (LPI) on the dynamics of Shock Ignition Inertial Confinement Fusion targets are investigated. The coupling between the laser beam, plasma dynamics and hot electron generation and propagation is described with a radiative hydrodynamics code using an inline model based on Paraxial Complex Geometrical Optics [Colaïtis et al., Phys. Rev. E 92, 041101 (2015)]. Two targets are considered: the pure-DT HiPER target and a CH-DT design with baseline spike powers of the order of 200–300 TW. In both cases, accounting for the LPI-generated HEs leads to non-igniting targets when using the baseline spike powers. While HEs are found to increase the ignitor shock pressure, they also preheat the bulk of the imploding shell, notably causing its expansion and contamination of the hotspot with the dense shell material before the time of shock convergence. The associated increase in hotspot mass (i) increases the ignitor shock pressure required to ignite the fusion reactions and (ii) significantly increases the power losses through Bremsstrahlung X-ray radiation, thus rapidly cooling the hotspot. These effects are less prominent for the CH-DT target where the plastic ablator shields the lower energy LPI-HE spectrum. Simulations using higher laser spike powers of 500 TW suggest that the CH-DT capsule marginally ignites, with an ignition window width significantly smaller than without LPI-HEs, and with three quarters of the baseline target yield. The latter effect arises from the relation between the shock launching time and the shell areal density, which becomes relevant in presence of a LPI-HE preheating.

  16. Influence of laser induced hot electrons on the threshold for shock ignition of fusion reactions

    NASA Astrophysics Data System (ADS)

    Colaïtis, A.; Ribeyre, X.; Le Bel, E.; Duchateau, G.; Nicolaï, Ph.; Tikhonchuk, V.

    2016-07-01

    The effects of Hot Electrons (HEs) generated by the nonlinear Laser-Plasma Interaction (LPI) on the dynamics of Shock Ignition Inertial Confinement Fusion targets are investigated. The coupling between the laser beam, plasma dynamics and hot electron generation and propagation is described with a radiative hydrodynamics code using an inline model based on Paraxial Complex Geometrical Optics [Colaïtis et al., Phys. Rev. E 92, 041101 (2015)]. Two targets are considered: the pure-DT HiPER target and a CH-DT design with baseline spike powers of the order of 200-300 TW. In both cases, accounting for the LPI-generated HEs leads to non-igniting targets when using the baseline spike powers. While HEs are found to increase the ignitor shock pressure, they also preheat the bulk of the imploding shell, notably causing its expansion and contamination of the hotspot with the dense shell material before the time of shock convergence. The associated increase in hotspot mass (i) increases the ignitor shock pressure required to ignite the fusion reactions and (ii) significantly increases the power losses through Bremsstrahlung X-ray radiation, thus rapidly cooling the hotspot. These effects are less prominent for the CH-DT target where the plastic ablator shields the lower energy LPI-HE spectrum. Simulations using higher laser spike powers of 500 TW suggest that the CH-DT capsule marginally ignites, with an ignition window width significantly smaller than without LPI-HEs, and with three quarters of the baseline target yield. The latter effect arises from the relation between the shock launching time and the shell areal density, which becomes relevant in presence of a LPI-HE preheating.

  17. Compactness of the {sup 48}Ca induced hot fusion reactions and the magnitudes of quadrupole and hexadecapole deformations

    SciTech Connect

    Gupta, Raj K.; Manhas, Monika; Greiner, Walter

    2006-05-15

    Based on fragmentation theory extended to include the orientation degrees of freedom and higher multipole deformations up to hexadecapole deformations, the compactness of {sup 48}Ca induced reactions on various actinides is studied for Ds (Z=110) to 118 nuclei. It is shown that the reactions leading to Z{>=}114 nuclei are 'compact' hot fusion reactions at {theta}=90 deg. orientation angles (equatorial compact or ec; collisions that are in the direction of the minor axis of the deformed reaction partner), but the ones for Z<114 nuclei are compact at {theta}<90 deg. (not-equatorial compact or nec). The phenomenon of 'barrier distribution in orientation degrees of freedom' is observed for the first time to be related to the magnitudes of both the quadrupole and hexadecapole deformations of the deformed reaction partner. The ec configurations are obtained for the cases of quadrupole deformation alone and with small (including negative values) hexadecapole deformations. The presence of large (positive) hexadecapole deformations result in the nec configurations. These results are found to be quite general, applicable also to other lighter targets such as W and Ra with the {sup 48}Ca beam and to Pb based reactions. Furthermore, for compact hot fusion reactions, in addition to the {sup 48}Ca reaction valley, a number of other new reaction valleys (target-projectile combinations) are obtained, the most important one (next to {sup 48}Ca) being the {sup 54}Ti nucleus used previously in Pb based cold fusion reaction studies but now proposed with deformed actinide nuclei such as {sup 226}Ra, {sup 232}Th, {sup 238}U, and {sup 242}Pu.

  18. Scaling of geochemical reaction rates via advective solute transport

    NASA Astrophysics Data System (ADS)

    Hunt, A. G.; Ghanbarian, B.; Skinner, T. E.; Ewing, R. P.

    2015-07-01

    Transport in porous media is quite complex, and still yields occasional surprises. In geological porous media, the rate at which chemical reactions (e.g., weathering and dissolution) occur is found to diminish by orders of magnitude with increasing time or distance. The temporal rates of laboratory experiments and field observations differ, and extrapolating from laboratory experiments (in months) to field rates (in millions of years) can lead to order-of-magnitude errors. The reactions are transport-limited, but characterizing them using standard solute transport expressions can yield results in agreement with experiment only if spurious assumptions and parameters are introduced. We previously developed a theory of non-reactive solute transport based on applying critical path analysis to the cluster statistics of percolation. The fractal structure of the clusters can be used to generate solute distributions in both time and space. Solute velocities calculated from the temporal evolution of that distribution have the same time dependence as reaction-rate scaling in a wide range of field studies and laboratory experiments, covering some 10 decades in time. The present theory thus both explains a wide range of experiments, and also predicts changes in the scaling behavior in individual systems with increasing time and/or length scales. No other theory captures these variations in scaling by invoking a single physical mechanism. Because the successfully predicted chemical reactions include known results for silicate weathering rates, our theory provides a framework for understanding changes in the global carbon cycle, including its effects on extinctions, climate change, soil production, and denudation rates. It further provides a basis for understanding the fundamental time scales of hydrology and shallow geochemistry, as well as the basis of industrial agriculture.

  19. STELLAR EVOLUTION CONSTRAINTS ON THE TRIPLE-{alpha} REACTION RATE

    SciTech Connect

    Suda, Takuma; Fujimoto, Masayuki Y.; Hirschi, Raphael

    2011-11-01

    We investigate the quantitative constraint on the triple-{alpha} reaction rate based on stellar evolution theory, motivated by the recent significant revision of the rate proposed by nuclear physics calculations. Targeted stellar models were computed in order to investigate the impact of that rate in the mass range of 0.8 {<=} M/M{sub sun} {<=} 25 and in the metallicity range between Z = 0 and Z = 0.02. The revised rate has a significant impact on the evolution of low- and intermediate-mass stars, while its influence on the evolution of massive stars (M {approx}> 10 M{sub sun}) is minimal. We find that employing the revised rate suppresses helium shell flashes on asymptotic giant branch phase for stars in the initial mass range 0.8 {<=} M/M{sub sun} {<=} 6, which is contradictory to what is observed. The absence of helium shell flashes is due to the weak temperature dependence of the revised triple-{alpha} reaction cross section at the temperature involved. In our models, it is suggested that the temperature dependence of the cross section should have at least {nu} > 10 at T = (1-1.2) Multiplication-Sign 10{sup 8} K where the cross section is proportional to T {sup {nu}}. We also derive the helium ignition curve to estimate the maximum cross section to retain the low-mass first red giants. The semi-analytically derived ignition curves suggest that the reaction rate should be less than {approx}10{sup -29} cm{sup 6} s{sup -1} mole{sup -2} at Almost-Equal-To 10{sup 7.8} K, which corresponds to about three orders of magnitude larger than that of the NACRE compilation. In an effort to compromise with the revised rates, we calculate and analyze models with enhanced CNO cycle reaction rates to increase the maximum luminosity of the first giant branch. However, it is impossible to reach the typical red giant branch tip luminosity even if all the reaction rates related to CNO cycles are enhanced by more than 10 orders of magnitude.

  20. High rate of fusion in sheep cervical spines following anterior interbody surgery with absorbable and nonabsorbable implant devices.

    PubMed

    Slivka, Michael A; Spenciner, David B; Seim, Howard B; Welch, William C; Serhan, Hassan A; Turner, A Simon

    2006-11-15

    Fourteen sheep were fused using anterior interbody implants at C2-C3 and C4-C5 and followed for 6 months. To evaluate the effect of absorbable and nonabsorbable implants on fusion rate, cage migration, and implant integrity. Despite the high clinical success rate with metallic plates and interbody grafting, complications such as dysphagia, imaging artifacts, and revision difficulties exist. Less permanent and lower profile implants could minimize these problems. Four treatments were studied: 1) carbon fiber-reinforced polymer (CFRP) cage alone, 2) CFRP cage with an absorbable tension band, 3) absorbable cage with an absorbable tension band, and 4) absorbable cage with a titanium plate. Fusion was assessed using radiographs, biomechanical testing, and micro-CT analysis. Treatments with the CFRP cage alone had the lowest fusion rate at 3 months (2/6) and 6 months (4/6). The CFRP cage with the absorbable strap treatments had 5/6 fusions at 6 months. The absorbable cage with absorbable strap also had 5/6 fusions, but two of the cages fractured. The absorbable cage with titanium plate had 5/6 fusions, but the one partial fusion was attributed to poor screw and plate placement. Using both absorbable and nonabsorbable implants, high fusion rates were achieved in the challenging sheep cervical spine model. However, the absorbable cages were not able to withstand the mechanical forces during the 6-month survival period.

  1. Measurement of the dmud quartet-to-doublet molecular formation rate ratio (lambdaq : lambdad) and the mu d hyperfine rate (lambdaqd) using the fusion neutrons from mu- stops in D2 gas

    NASA Astrophysics Data System (ADS)

    Raha, Nandita

    The MuSun experiment will determine the microd capture rate (micro - + d → n + n + nue) from the doublet hyperfine state Lambdad, of the muonic deuterium atom in the 1S ground state to a precision of 1.5%. Modern effective field theories (EFT) predict that an accurate measurement of Lambdad would determine the two-nucleon weak axial current. This will help in understanding all weak nuclear interactions such as the stellar thermonuclear proton-proton fusion reactions, the neutrino reaction nu + d (which explores the solar neutrino oscillation problem). It will also help us understand weak nuclear interactions involving more than two nucleons---double beta decay---as they do involve a two-nucleon weak axial current term. The experiment took place in the piE3 beam-line of Paul Scherrer Institute (PSI) using a muon beam generated from 2.2 mA proton beam---which is the highest intensity beam in the world. The muons first passed through entrance scintillator and multiwire proportional chamber for determining thier entrance timing and position respectively. Then they were stopped in a cryogenic time projection chamber (cryo-TPC) filled with D2 gas. This was surrounded by plastic scintillators and multiwire proportional chambers for detecting the decay electrons and an array of eight liquid scintillators for detecting neutrons. Muons in deuterium get captured to form microd atoms in the quartet and doublet spin states. These atoms undergo nuclear capture from these hyperfine states respectively. There is a hyperfine transition rate from quartet-to-doublet state---lambdaqd along with dmicrod molecular formation which further undergoes a fusion reaction with the muon acting as a catalyst (MCF). The goal of this dissertation is to measure the dmicro d quartet-to-doublet rate ratio (lambdaq : lambdad) and microd hyperfine rate (lambda qd) using the fusion neutrons from micro. stops in D2 gas. The dmicrod molecules undergo MCF reactions from the doublet and the quartet state

  2. Comparison of DSMC reaction models with QCT reaction rates for nitrogen

    NASA Astrophysics Data System (ADS)

    Wysong, Ingrid J.; Gimelshein, Sergey F.

    2016-11-01

    Four empirical models of chemical reactions extensively used in the direct simulation Monte Carlo method in the past are analyzed via comparison of temperature and vibrational level dependent equilibrium and non-equilibrium reaction rates with available classical trajectory and direct molecular simulations for nitrogen dissociation. The considered models are total collision energy, quantum kinetic, vibration-dissociation favoring, and weak vibrational bias. The weak vibrational bias model was found to provide good agreement with benchmark vibrationally-specific dissociation rates, while significant differences were observed for the others.

  3. Rate of reaction of OH with CS/sub 2/

    SciTech Connect

    Wine, P.H.; Shah, R.C.; Ravishankara, A.R.

    1980-10-02

    The flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction OH + CS/sub 2/ ..-->.. products (k/sub 1/) over the temperature range 251-363 K. Complicating secondary reactions involving CS/sub 2/ photofragments were eliminated only when the photoflash was filtered by 10 torr cm of CS/sub 2/ and SF/sub 6/ was used as the buffer gas. The rate constant was found to be much slower than previous measurements indicated. Based on our experiments, upper limits for k/sub 1/ (in units of 10/sup -15/ cm/sup 3/ molecule/sup -1/s/sup -1/) are 9.9 at 251 K, 1.5 at 297 K, and 1.6 at 363 K. Our results suggest that the title reaction is unimportant as a source for COS in the atmosphere.

  4. Rate constants for reactions of perhaloalkylperoxyl radicals with alkenes

    SciTech Connect

    Alfassi, Z.B.; Huie, R.E.; Neta, P. )

    1993-07-01

    Trichloro- and tribromomethylperoxyl radicals were produced by radiolytic reduction of CCl[sub 4] and CBr[sub 4] in various aerated solvents. Rate constants for the reactions of these radicals with unsaturated organic compounds were determined in methanol solutions by competition kinetics, using mainly chloropromazine as a reference. The rate constants were in the range k = 10[sup 4]-10[sup 7] L mol[sup [minus]1] s[sup [minus]1], and a good correlation was obtained between log k and the Taft substituent constants [sigma]*. Steric effects were also noticeable in some cases. The reactivities of the radicals were in the order CBr[sub 3]O[sub 2][center dot] < CCl[sub 3]O[sub 2][center dot] < C[sub 4]F[sub 9]O[sub 2][center dot], which is in contrast with the order observed in electron-transfer reactions. The rate constants for reaction of CCl[sub 3]O[sub 2][center dot] with 2,3-dimethyl-2-butene (DMB) and cyclohexene (CH) were studied in 12 solvents. In all cases DMB is considerably more reactive than CH, indicating that at least in the case of DMB the reaction is predominantly via addition. The rate constant for addition of CCl[sub 3]O[sub 2][center dot] to DMB varies by a factor of 7 in the different solvents. No correlation was found between these rate constants and thermodynamic or polarity parameters of the solvents, although viscosity appears to have an effect. 19 refs., 2 figs., 2 tabs.

  5. Reaction rates from pressure-gauge measurements in reacting explosives

    SciTech Connect

    Ginsberg, M.J.; Anderson, A.B.; Wackerle, J.

    1981-01-01

    The proper hydrodynamic data and an equation of state are sufficient to describe quantitatively the reaction rates of explosives during the shock-to-detonation transition. Manganin pressure gauges embedded in the reacting explosive have provided these data for the explosives PETN, PBX 9404, TATB, and TNT. Once a pressure-field history has been assembled from individual pressure histories at different depths in the explosive, the conservation equations can be applied in a Lagrangian analysis of the data. The combination of a reactant-product equation of state with this analysis then allows the calculation of the extent of reaction and reaction rate. Successful correlation of the calculated reaction rate values with other thermodynamic variables, such as pressure or temperature, allows formulation of a rate law and the prediction of initiation behavior under circumstances quite different from the experiments that led to the rate law. The best dynamic piezoresistive pressure gauge for most applications would have a substantial output voltage and present negligible disturbance to the flow. In explosives, however, requirements for survival in the extreme temperature and pressure environment encountered by the gauge dictate compromise. Low electrical resistance (approx. 20 m..cap omega..) helps to minimize shunt conductivity failures, but this drastically reduces output and demands that much attention be given to reducingnoise. Although relatively thick insulation perturbs the flow to some extent, survivability requirements dictate its use. Pressure measurements in reactive flow can now be made routinely with gauges that successfully produce data leading to a description of the flow and a powerful predictive capability.

  6. Possibilities of production of neutron-deficient isotopes of U, Np, Pu, Am, Cm, and Cf in complete fusion reactions

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Zubov, A. S.; Scheid, W.

    2008-10-15

    Within the dinuclear system model we analyze the production of yet unknown neutron-deficient isotopes of U, Np, Pu, Am, Cm, and Cf in various complete fusion reactions. Different deexcitation channels of the excited compound nucleus are treated. The results are obtained without special adjustment to the selected evaporation channel. The fusion probability is an important ingredient of the excitation function. The results are in good agreement with the available experimental data. The alpha decay half-life times in the neutron-deficient actinides are discussed.

  7. A classical approach in simple nuclear fusion reaction {sub 1}H{sup 2}+{sub 1}H{sup 3} using two-dimension granular molecular dynamics model

    SciTech Connect

    Viridi, S.; Kurniadi, R.; Waris, A.; Perkasa, Y. S.

    2012-06-06

    Molecular dynamics in 2-D accompanied by granular model provides an opportunity to investigate binding between nuclei particles and its properties that arises during collision in a fusion reaction. A fully classical approach is used to observe the influence of initial angle of nucleus orientation to the product yielded by the reaction. As an example, a simplest fusion reaction between {sub 1}H{sup 2} and {sub 1}H{sup 3} is observed. Several products of the fusion reaction have been obtained, even the unreported ones, including temporary {sub 2}He{sup 4} nucleus.

  8. Sensor fusion methods for reducing false alarms in heart rate monitoring.

    PubMed

    Borges, Gabriel; Brusamarello, Valner

    2016-12-01

    Automatic patient monitoring is an essential resource in hospitals for good health care management. While alarms caused by abnormal physiological conditions are important for the delivery of fast treatment, they can be also a source of unnecessary noise because of false alarms caused by electromagnetic interference or motion artifacts. One significant source of false alarms is related to heart rate, which is triggered when the heart rhythm of the patient is too fast or too slow. In this work, the fusion of different physiological sensors is explored in order to create a robust heart rate estimation. A set of algorithms using heart rate variability index, Bayesian inference, neural networks, fuzzy logic and majority voting is proposed to fuse the information from the electrocardiogram, arterial blood pressure and photoplethysmogram. Three kinds of information are extracted from each source, namely, heart rate variability, the heart rate difference between sensors and the spectral analysis of low and high noise of each sensor. This information is used as input to the algorithms. Twenty recordings selected from the MIMIC database were used to validate the system. The results showed that neural networks fusion had the best false alarm reduction of 92.5 %, while the Bayesian technique had a reduction of 84.3 %, fuzzy logic 80.6 %, majority voter 72.5 % and the heart rate variability index 67.5 %. Therefore, the proposed algorithms showed good performance and could be useful in bedside monitors.

  9. Attempt to produce the isotopes of element 108 in the fusion reaction {sup 136}Xe+{sup 136}Xe

    SciTech Connect

    Oganessian, Yu. Ts.; Dmitriev, S. N.; Yeremin, A. V.; Aksenov, N. V.; Bozhikov, G. A.; Chepigin, V. I.; Chelnokov, M. L.; Lebedev, V. Ya.; Malyshev, O. N.; Petrushkin, O. V.; Shishkin, S. V.; Svirikhin, A. I.; Tereshatov, E. E.; Vostokin, G. K.

    2009-02-15

    A setup of the experiment on the production of the isotopes with Z=108 in the fusion reaction {sup 136}Xe+{sup 136}Xe and the obtained results are presented. At the excitation energy 0{<=}E{sub x}{<=}30 MeV of the {sup 272}Hs* compound nucleus the upper limit of the cross section for evaporation residues {sigma}{sub (1-3)n}{<=}4 pb has been measured. The experimental results together with the data from asymmetric reactions point to a strong limitation of the Hs compound nucleus formation with increasing Coulomb forces in the entrance channel of the reaction.

  10. Petawatt laser pulses for proton-boron high gain fusion with avalanche reactions excluding problems of nuclear radiation

    NASA Astrophysics Data System (ADS)

    Hora, Heinrich; Lalousis, Paraskevas; Giuffrida, Lorenzo; Margarone, Daniele; Korn, Georg; Eliezer, Shalom; Miley, George H.; Moustaizis, Stavros; Mourou, Gérard

    2015-05-01

    An alternative way may be possible for igniting solid density hydrogen-11B (HB11) fuel. The use of >petawatt-ps laser pulses from the non-thermal ignition based on ultrahigh acceleration of plasma blocks by the nonlinear (ponderomotive) force, has to be combined with the measured ultrahigh magnetic fields in the 10 kilotesla range for cylindrical trapping. The evaluation of measured alpha particles from HB11 reactions arrives at the conclusion that apart from the usual binary nuclear reactions, secondary reactions by an avalanche multiplication may cause the high gains, even much higher than from deuterium tritium fusion. This may be leading to a concept of clean economic power generation.

  11. Measurement of tritium production rate distribution for a fusion-fission hybrid conceptual reactor

    NASA Astrophysics Data System (ADS)

    Wang, Xin-Hua; Guo, Hai-Ping; Mou, Yun-Feng; Zheng, Pu; Liu, Rong; Yang, Xiao-Fei; Yang, Jian

    2013-05-01

    A fusion-fission hybrid conceptual reactor is established. It consists of a DT neutron source and a spherical shell of depleted uranium and hydrogen lithium. The tritium production rate (TPR) distribution in the conceptual reactor was measured by DT neutrons using two sets of lithium glass detectors with different thicknesses in the hole in the vertical direction with respect to the D+ beam of the Cockcroft-Walton neutron generator in direct current mode. The measured TPR distribution is compared with the calculated results obtained by the three-dimensional Monte Carlo code MCNP5 and the ENDF/B-VI data file. The discrepancy between the measured and calculated values can be attributed to the neutron data library of the hydrogen lithium lack S(α, β) thermal scattering model, so we show that a special database of low-energy and thermal neutrons should be established in the physics design of fusion-fission hybrid reactors.

  12. Enhancement of thermonuclear reaction rates in extremely dense stellar plasmas

    NASA Astrophysics Data System (ADS)

    Itoh, Naoki; Kuwashima, Fumiyoshi; Munakata, Hiroharu

    1990-10-01

    The enhancement factor of the thermonuclear reaction rates is calculated for the extremely dense stellar plasmas in the liquid phase where the condition 3Gamma/tau less than or equal to 1.6 is not necessarily imposed. Here the parameter 3Gamma/tau corresponds to the ratio of the classical turning point radius at the Gamow peak and the mean interionic distance in the case of the pure Coulomb potential. Direct double integration is carried out to obtain the thermonuclear reaction rates. The result is presented in the form of an analytic fitting formula to facilitate applications. The present fitting formula is valid for 3Gamma/tau = 0-5.4. The present calculation is intended to serve as the best available one for the case that ions are in the semiquantum regime.

  13. A model for reaction rates in turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    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.

  14. Rate constant and reaction channels for the reaction of atomic nitrogen with the ethyl radical

    SciTech Connect

    Stief, L.J.; Nesbitt, F.L.; Payne, W.A. ); Kuo, S.C.; Tao, W.; Klemm, R.B. )

    1995-04-01

    The absolute rate constant and primary reaction products have been determined at [ital T]=298 K for the atom--radical reaction N([sup 4][ital S])+C[sub 2]H[sub 5] in a discharge flow system with collision-free sampling to a mass spectrometer. The rate constant measurements employed low energy electron impact ionization while the product study used dispersed synchrotron radiation as the photoionization source. The rate constant was determined under pseudo-first-order conditions by monitoring the decay of C[sub 2]H[sub 5] or C[sub 2]D[sub 5] as a function of time in the presence of excess N atoms. The result is [ital k]=(1.1[plus minus]0.3)[times]10[sup [minus]10] cm[sup 3] molecule[sup [minus]1] s[sup [minus]1]. For the reaction product experiments using photoionization mass spectrometry, products observed at 114 nm (10.9 eV) were CD[sub 3], D[sub 2]CN and C[sub 2]D[sub 4] for the N+C[sub 2]D[sub 5] reaction. The product identification is based on the unambiguous combination of product [ital m]/[ital z] values, the shift of the [ital m]/[ital z] peaks observed for the N+C[sub 2]D[sub 5] reaction products with respect to the N+C[sub 2]H[sub 5] reaction products and the photoionization threshold measured for the major products. The observed products are consistent with the occurrence of the reaction channels D[sub 2]CN+CD[sub 3](2a) and C[sub 2]D[sub 4]+ND(2c). Formation of C[sub 2]D[sub 4] product via channel (2c) accounts for approximately 65% of the C[sub 2]D[sub 5] reacted. Most, if not all, of the remaining 35% is probably accounted for by channel (2a). These rate constant and product results are compared with those for the N+CH[sub 3] reaction as well as other atom+C[sub 2]H[sub 5] reactions. The role of the N+C[sub 2]H[sub 5] reaction in the formation of HCN in the atmospheres of Titan and Neptune is briefly considered. (Abstract Truncated)

  15. Reaction Rate Measurements at the National Criticality Experiments Research Center

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.; Bounds, J. A.; Brooks, G. H., Jr.; Favorite, J. A.; Goda, J. M.; Hayes, D. K.; Jackman, K. R.; Little, R. C.; Macinnes, M. R.; Myers, W. L.; Oldham, W. J.; Rundberg, R. S.; Sanchez, R. G.; Schake, A. R.; White, M. C.; Wilkerson, C. W., Jr.

    2014-09-01

    With the resumption of regular operations of the Los Alamos Critical Assemblies at the National Criticality Experiments Research Center (NCERC), located at the Nevada National Security Site, we have embarked upon a series of campaigns to restore the capability to perform integral reaction rate and fission product yield measurements using historical radiochemical methods. This talk will present an overview of the current and future experimental plans, including results from our experimental campaigns on the Comet/Zeus and Flattop assemblies.

  16. Triple-{alpha} reaction rate constrained by stellar evolution models

    SciTech Connect

    Suda, Takuma; Hirschi, Raphael; Fujimoto, Masayuki Y.

    2012-11-12

    We investigate the quantitative constraint on the triple-{alpha} reaction rate based on stellar evolution theory, motivated by the recent significant revision of the rate proposed by nuclear physics calculations. Targeted stellar models were computed in order to investigate the impact of that rate in the mass range of 0.8{<=}M/M{sub Circled-Dot-Operator }{<=}25 and in the metallicity range between Z= 0 and Z= 0.02. The revised rate has a significant impact on the evolution of low-and intermediate-mass stars, while its influence on the evolution of massive stars (M > 10M{sub Circled-Dot-Operator }) is minimal. We find that employing the revised rate suppresses helium shell flashes on AGB phase for stars in the initial mass range 0.8{<=}M/M{sub Circled-Dot-Operator }{<=}6, which is contradictory to what is observed. The absence of helium shell flashes is due to the weak temperature dependence of the revised triple-{alpha} reaction cross section at the temperature involved. In our models, it is suggested that the temperature dependence of the cross section should have at least {nu} > 10 at T = 1-1.2 Multiplication-Sign 10{sup 8}K where the cross section is proportional to T{sup {nu}}. We also derive the helium ignition curve to estimate the maximum cross section to retain the low-mass first red giants. The semi-analytically derived ignition curves suggest that the reaction rate should be less than {approx} 10{sup -29} cm{sup 6} s{sup -1} mole{sup -2} at Almost-Equal-To 10{sup 7.8} K, which corresponds to about three orders of magnitude larger than that of the NACRE compilation.

  17. Application of semiclassical methods to reaction rate theory

    SciTech Connect

    Hernandez, Rigoberto

    1993-11-01

    This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e. most reactions. Second, we have developed a method to describe the fluctuations of decay rates of individual energy states from the average RRKM rate in systems where the direct calculation of individual rates would be impossible. Combined with the semiclassical theory this latter effort has provided a direct comparison to the experimental results of Moore and coworkers. In SCTST, the Hamiltonian is expanded about the barrier and the ``good`` action-angle variables are obtained perturbatively; a WKB analysis of the effectively one-dimensional reactive direction then provides the transmission probabilities. The advantages of this local approximate treatment are that it includes tunneling effects and anharmonicity, and it systematically provides a multi-dimensional dividing surface in phase space. The SCTST thermal rate expression has been reformulated providing increased numerical efficiency (as compared to a naive Boltzmann average), an appealing link to conventional transition state theory (involving a ``prereactive`` partition function depending on the action of the reactive mode), and the ability to go beyond the perturbative approximation.

  18. Constraining the equation of state of nuclear matter from fusion hindrance in reactions leading to the production of superheavy elements

    NASA Astrophysics Data System (ADS)

    Veselsky, M.; Klimo, J.; Ma, Yu-Gang; Souliotis, G. A.

    2016-12-01

    The mechanism of fusion hindrance, an effect preventing the synthesis of superheavy elements in the reactions of cold and hot fusion, is investigated using the Boltzmann-Uehling-Uhlenbeck equation, where Coulomb interaction is introduced. A strong sensitivity is observed both to the modulus of incompressibility of symmetric nuclear matter, controlling the competition of surface tension and Coulomb repulsion, and to the stiffness of the density-dependence of symmetry energy, influencing the formation of the neck prior to scission. The experimental fusion probabilities were for the first time used to derive constraints on the nuclear equation of state. A strict constraint on the modulus of incompressibility of nuclear matter K0=240 -260 MeV is obtained while the stiff density-dependences of the symmetry energy (γ >1 ) are rejected.

  19. Mitofusin 1 and 2 play distinct roles in mitochondrial fusion reactions via GTPase activity.

    PubMed

    Ishihara, Naotada; Eura, Yuka; Mihara, Katsuyoshi

    2004-12-15

    The mammalian homologues of yeast and Drosophila Fzo, mitofusin (Mfn) 1 and 2, are both essential for mitochondrial fusion and maintenance of mitochondrial morphology. Though the GTPase domain is required for Mfn protein function, the molecular mechanisms of the GTPase-dependent reaction as well as the functional division of the two Mfn proteins are unknown. To examine the function of Mfn proteins, tethering of mitochondrial membranes was measured in vitro by fluorescence microscopy using green fluorescence protein- or red fluorescent protein-tagged and Mfn1-expressing mitochondria, or by immunoprecipitation using mitochondria harboring HA- or FLAG-tagged Mfn proteins. These experiments revealed that Mfn1-harboring mitochondria were efficiently tethered in a GTP-dependent manner, whereas Mfn2-harboring mitochondria were tethered with only low efficiency. Sucrose density gradient centrifugation followed by co-immunoprecipitation revealed that Mfn1 produced oligomerized approximately 250 kDa and approximately 450 kDa complexes in a GTP-dependent manner. The approximately 450 kDa complex contained oligomerized Mfn1 from distinct apposing membranes (docking complex), whereas the approximately 250 kDa complex was composed of Mfn1 present on the same membrane or in the membrane-solubilized state (cis complex). These results were also confirmed using blue-native PAGE. Mfn1 exhibited higher activity for this reaction than Mfn2. Purified recombinant Mfn1 exhibited approximately eightfold higher GTPase activity than Mfn2. These findings indicate that the two Mfn proteins have distinct activities, and suggest that Mfn1 is mainly responsible for GTP-dependent membrane tethering.

  20. On the implementation of a chain nuclear reaction of thermonuclear fusion on the basis of the p+11B process

    NASA Astrophysics Data System (ADS)

    Belyaev, V. S.; Krainov, V. P.; Zagreev, B. V.; Matafonov, A. P.

    2015-07-01

    Various theoretical and experimental schemes for implementing a thermonuclear reactor on the basis of the p+11B reaction are considered. They include beam collisions, fusion in degenerate plasmas, ignition upon plasma acceleration by ponderomotive forces, and the irradiation of a solid-state target from 11B with a proton beam under conditions of a Coulomb explosion of hydrogen microdrops. The possibility of employing ultra-short high-intensity laser pulses to initiate the p+11B reaction under conditions far from thermodynamic equilibrium is discussed. This and some other weakly radioactive thermonuclear reactions are promising owing to their ecological cleanness—there are virtually no neutrons among fusion products. Nuclear reactions that follow the p+11B reaction may generate high-energy protons, sustaining a chain reaction, and this is an advantage of the p+11B option. The approach used also makes it possible to study nuclear reactions under conditions close to those in the early Universe or in the interior of stars.

  1. Tumor Growth Prediction with Reaction-Diffusion and Hyperelastic Biomechanical Model by Physiological Data Fusion

    PubMed Central

    Wong, Ken C. L.; Summers, Ronald M.; Kebebew, Electron; Yao, Jianhua

    2015-01-01

    The goal of tumor growth prediction is to model the tumor growth process, which can be achieved by physiological modeling and model personalization from clinical measurements. Although image-driven frameworks have been proposed with promising results, several issues such as infinitesimal strain assumptions, complicated personalization procedures, and the lack of functional information, may limit their prediction accuracy. In view of these issues, we propose a framework for pancreatic neuroendocrine tumor growth prediction, which comprises a FEM-based tumor growth model with coupled reaction-diffusion equation and nonlinear biomechanics. Physiological data fusion of structural and functional images is used to improve the subject-specificity of model personalization, and a derivative-free global optimization algorithm is adopted to facilitate the complicated model and accommodate flexible choices of objective functions. With this flexibility, we propose an objective function accounting for both the tumor volume difference and the root-mean-squared error of intracellular volume fractions. Experiments were performed on synthetic and clinical data to verify the parameter estimation capability and the prediction performance. Comparisons of using different biomechanical models and objective functions were also performed. From the experimental results of eight patient data sets, the average recall, precision, Dice coefficient, and relative volume difference between predicted and measured tumor volumes were 84.5±6.9%, 85.8±8.2%, 84.6±1.7%, and 14.2±8.4%, respectively. PMID:25962846

  2. Production of proton-rich nuclei around Z = 84-90 in fusion-evaporation reactions

    NASA Astrophysics Data System (ADS)

    Chen, Peng-Hui; Feng, Zhao-Qing; Niu, Fei; Guo, Ya-Fei; Zhang, Hong-Fei; Li, Jun-Qing; Jin, Gen-Ming

    2017-05-01

    Within the framework of the dinuclear system model, production cross sections of proton-rich nuclei with charged numbers of Z = 84-90 are investigated systematically. Possible combinations with the 28Si, 32S, 40Ar bombarding the target nuclides 165Ho, 169Tm, 170-174Yb, 175,176Lu, 174, 176-180Hf and 181Ta are analyzed thoroughly. The optimal excitation energies and evaporation channels are proposed to produce the proton-rich nuclei. The systems are feasible to be constructed in experiments. It is found that the neutron shell closure of N = 126 is of importance during the evaporation of neutrons. The experimental excitation functions in the 40Ar induced reactions can be nicely reproduced. The charged particle evaporation is comparable with neutrons in cooling the excited proton-rich nuclei, in particular for the channels with α and proton evaporation. The production cross section increases with the mass asymmetry of colliding systems because of the decrease of the inner fusion barrier. The channels with pure neutron evaporation depend on the isotopic targets. But it is different for the channels with charged particles and more sensitive to the odd-even effect.

  3. Effects of nuclear orientation on fusion and fission process for reactions using actinide target nuclei

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nishinaka, I.; Makii, H.; Nagame, Y.; Watanabe, Y.; Ohtsuki, T.; Hirose, K.; Hofmann, S.

    2010-04-30

    Fission fragment mass distributions in the reaction of {sup 30}Si+{sup 238}U were measured at the energies around the Coulomb barrier. At the above-barrier energies, the mass distribution showed Gaussian shape. At the sub-barrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at A{sub L}/A{sub H}approx =90/178. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections produced by {sup 30}Si+{sup 238}U. The cross-section for {sup 263}Sg at the above-barrier energy agree with the statistical model calculation which assumes that the measured fission cross-sections are equal to the fusion cross-sections, whereas the one for {sup 264}Sg measured at the sub-barrier energy is smaller than the calculation, indicating the presence for quasifission. We also report the results on the fragment mass distributions for {sup 36,34}S+{sup 238}U and {sup 40}Ar+{sup 238}U.

  4. Compound nucleus formation probability PCN determined within the dynamical cluster-decay model for various "hot" fusion reactions

    NASA Astrophysics Data System (ADS)

    Kaur, Arshdeep; Chopra, Sahila; Gupta, Raj K.

    2014-08-01

    The compound nucleus (CN) fusion/formation probability PCN is defined and its detailed variations with the CN excitation energy E*, center-of-mass energy Ec .m., fissility parameter χ, CN mass number ACN, and Coulomb interaction parameter Z1Z2 are studied for the first time within the dynamical cluster-decay model (DCM). The model is a nonstatistical description of the decay of a CN to all possible processes. The (total) fusion cross section σfusion is the sum of the CN and noncompound nucleus (nCN) decay cross sections, each calculated as the dynamical fragmentation process. The CN cross section σCN is constituted of evaporation residues and fusion-fission, including intermediate-mass fragments, each calculated for all contributing decay fragments (A1, A2) in terms of their formation and barrier penetration probabilities P0 and P. The nCN cross section σnCN is determined as the quasi-fission (qf) process, where P0=1 and P is calculated for the entrance-channel nuclei. The DCM, with effects of deformations and orientations of nuclei included in it, is used to study the PCN for about a dozen "hot" fusion reactions forming a CN of mass number A ˜100 to superheavy nuclei and for various different nuclear interaction potentials. Interesting results are that PCN=1 for complete fusion, but PCN<1 or PCN≪1 due to the nCN contribution, depending strongly on different parameters of the entrance-channel reaction but found to be independent of the nuclear interaction potentials used.

  5. Possibilities of synthesis of unknown isotopes of superheavy nuclei with charge numbers Z > 108 in asymmetric actinide-based complete fusion reactions

    NASA Astrophysics Data System (ADS)

    Hong, Juhee; Adamian, G. G.; Antonenko, N. V.

    2016-10-01

    The possibilities of production of new isotopes of superheavy nuclei with charge numbers Z = 109-114 in various asymmetric hot fusion reactions are studied for the first time. The excitation functions of the formation of these isotopes in the xn evaporation channels are predicted and the optimal conditions for the synthesis are proposed. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of the heaviest nuclei obtained in cold and hot complete fusion reactions.

  6. Fusion and subsidence rate of stand alone anterior lumbar interbody fusion using PEEK cage with recombinant human bone morphogenetic protein-2.

    PubMed

    Behrbalk, Eyal; Uri, Ofir; Parks, Ruth M; Musson, Rachel; Soh, Reuben Chee Cheong; Boszczyk, Bronek Maximilian

    2013-12-01

    Anterior lumbar interbody fusion (ALIF) is an established treatment for structural instability associated with symptomatic disk degeneration (SDD). Stand-alone ALIF offers many advantages, however, it may increase the risk of non-union. Recombinant human bone morphogenetic protein-2 (BMP-2) may enhance fusion rate but is associated with postoperative complication. The optimal dose of BMP-2 remains unclear. This study assessed the fusion and subsidence rates of stand-alone ALIF using the SynFix-LR interbody cage with 6 ml/level of BMP-2. Thirty-two ALIF procedures were performed by a single surgeon in 25 patients. Twenty-five procedures were performed for SDD without spondylolisthesis (SDD group) and seven procedures were performed for SDD with grade-I olisthesis (SDD-olisthesis group). Patients were followed-up for a mean of 17 ± 6 months. Solid fusion was achieved in 29 cases (90.6 %) within 6 months postoperatively. Five cases of implant subsidence were observed (16 %). Four of these occurred in the SDD-olisthesis group and one occurred in the SDD group (57 % vs. 4 % respectively; p = 0.004). Three cases of subsidence failed to fuse and required revision. The body mass index of patients with olisthesis who developed subsidence was higher than those who did not develop subsidence (29 ± 2.6 vs. 22 ± 6.5 respectively; p = 0.04). No BMP-2 related complications occurred. The overall fusion rate of stand-alone ALIF using the SynFix-LR system with BMP-2 was 90.6 %, comparable with other published series. No BMP-2 related complication occurred at a dose of 6 mg/level. Degenerative spondylolisthesis and obesity seemed to increase the rate of implant subsidence, and thus we believe that adding posterior fusion for these cases should be considered.

  7. Pulsed fusion space propulsion: Computational Magneto-Hydro Dynamics of a multi-coil parabolic reaction chamber

    NASA Astrophysics Data System (ADS)

    Romanelli, Gherardo; Mignone, Andrea; Cervone, Angelo

    2017-10-01

    Pulsed fusion propulsion might finally revolutionise manned space exploration by providing an affordable and relatively fast access to interplanetary destinations. However, such systems are still in an early development phase and one of the key areas requiring further investigations is the operation of the magnetic nozzle, the device meant to exploit the fusion energy and generate thrust. One of the last pulsed fusion magnetic nozzle design is the so called multi-coil parabolic reaction chamber: the reaction is thereby ignited at the focus of an open parabolic chamber, enclosed by a series of coaxial superconducting coils that apply a magnetic field. The field, beside confining the reaction and preventing any contact between hot fusion plasma and chamber structure, is also meant to reflect the explosion and push plasma out of the rocket. Reflection is attained thanks to electric currents induced in conductive skin layers that cover each of the coils, the change of plasma axial momentum generates thrust in reaction. This working principle has yet to be extensively verified and computational Magneto-Hydro Dynamics (MHD) is a viable option to achieve that. This work is one of the first detailed ideal-MHD analysis of a multi-coil parabolic reaction chamber of this kind and has been completed employing PLUTO, a freely distributed computational code developed at the Physics Department of the University of Turin. The results are thus a preliminary verification of the chamber's performance. Nonetheless, plasma leakage through the chamber structure has been highlighted. Therefore, further investigations are required to validate the chamber design. Implementing a more accurate physical model (e.g. Hall-MHD or relativistic-MHD) is thus mandatory, and PLUTO shows the capabilities to achieve that.

  8. Complication rate during multilevel lumbar fusion in patients above 60 years

    PubMed Central

    Mahesh, Bijjawara; Upendra, Bidre; Vijay, S; Kumar, GC Arun; Reddy, Srinivas

    2017-01-01

    Background: Spine surgery in elderly with comorbidities is reported to have higher complication rates and increased cost. However, the surgical outcome is good irrespective of the complications. Hence, it is essential to identify the factors affecting the complication rates in such patients and the measures to reduce them. This retrospective observational study determines the perioperative complications, their incidence and the measures to reduce complications in the elderly with comorbidities, operated by instrumented multilevel lumbar fusion. Materials and Methods: Patients aged 60 years and above with one or more comorbidities operated by multilevel instrumented lumbar fusion in our center between January 2012 and December 2013 were included in the study. Perioperative complications and their incidence were calculated. Age, number of levels fused, operative time, blood loss, and complication rates were correlated with the duration of stay and the incidence of perioperative complications using SPSS software. Measures to reduce complications are determined by these results and by review of literature. Results: Fifty two patients were included in the study (28 females and 24 males) with an average age of 69 years (range 60-84 years). Hypertension was the most common comorbidity followed by diabetes. Spondylolisthesis was the most common indication. Eleven complications were noted with an incidence of 21%. Three were systemic complications which required transfer to Intensive Care Unit. Local complications were incidental durotomy (three), transient root deficits (two), wound infections (one), and persistent radicular pain (two). Operative time and blood loss were significantly higher in patients with complications. Conclusion: Complication rates strongly correlate with the blood loss and operative time. Reducing the operative time and blood loss by intraoperative tranexamic acid, laminectomy using osteotome, simultaneous bilateral exposure and instrumentation and

  9. Temperature Dependent Rate Coefficients for the OH + Pinonaldehyde Reaction

    NASA Astrophysics Data System (ADS)

    Davis, M. E.; Talukdar, R.; Notte, G.; Ellison, G. B.; Ravishankara, A. R.; Burkholder, J. B.

    2005-12-01

    The biogenic emission of monoterpenes is an important source of volatile organic compounds (VOCs) to the atmosphere, approximately 10% of the biogenic hydrocarbons emitted yearly. The oxidation of alpha-pinene, the most abundant monoterpene in the atmosphere, by OH leads to the formation of pinonaldehyde (3-acetyl-2,2-dimethyl-cyclobutyl-ethanal) as a major oxidation product formed in yields > 50%. The atmospheric oxidation of pinonaldehyde will impact radical cycling, ozone formation and air quality on a regional scale. Previous laboratory studies of the OH + pinonaldehyde rate coefficient have used relative rate methods and were limited to room temperature. The reported rate coefficients are in poor agreement with values ranging from 4.0 to 9.1 × 10-11 cm#3 molecule-1 s-1. In this study we have measured absolute rate coefficients to resolve these discrepancies and have extended the measurements to include the temperature dependence. The rate coefficient for the gas phase reaction of OH with pinonaldehyde was measured over the temperature range 297 to 374 K and between 55 and 96 Torr under pseudo first order conditions in OH. Laser-induced fluorescence (LIF) was used to monitor the OH radical which was produced by pulsed laser photolysis. The pinonaldehyde concentration was determined in situ using Fourier transform infrared (FTIR) and UV (185 nm) absorption spectroscopy. The rate coefficient for the OH + pinonaldehyde reaction will be presented. Our results will be compared with previous rate coefficient measurements and the discrepancies and the atmospheric implications of these measurements will be discussed.

  10. Pseudoarthrosis rates in anterior cervical discectomy and fusion: a meta-analysis.

    PubMed

    Shriver, Michael F; Lewis, Daniel J; Kshettry, Varun R; Rosenbaum, Benjamin P; Benzel, Edward C; Mroz, Thomas E

    2015-09-01

    Anterior cervical discectomy and fusion (ACDF) is a commonly performed procedure for patients presenting with cervical radiculopathy, myelopathy, or deformity. A systematic literature review and meta-analysis of pseudoarthrosis rates associated with ACDF with plate fixation have not been previously performed. The purpose of this study was to identify all prospective studies reporting pseudoarthrosis rates for ACDF with plate fixation. This study is based on a systematic review and meta-analysis. Studies reporting pseudoarthrosis rates in patients who received one-, two-, or three-level ACDF surgeries were included. Outcomes of interest included reported pseudoarthrosis events after ACDF with plate fixation. We conducted a MEDLINE, SCOPUS, Web of Science, and EMBASE search for studies reporting complications for ACDF with plate fixation. We recorded pseudoarthrosis events from all included studies. A meta-analysis was performed to calculate effect summary mean values, 95% confidence intervals (CIs), Q statistics, and I(2) values. Forest plots were constructed for each analysis group. Of the 7,130 retrieved articles, 17 met the inclusion criteria. The overall pseudoarthrosis rate was 2.6% (95% CI: 1.3-3.9). Use of autograft fusion (0.9%, 95% CI: -0.4 to 2.1) resulted in a reduced pseudoarthrosis rate compared with allograft fusion procedures (4.8%, 95% CI: 1.7-7.9). Studies were separated based on the length of follow-up: 12 to 24 and greater than 24 months. These groups reported rates of 3.1% (95% CI: 1.2-5.0) and 2.3% (95% CI: 0.1-4.4), respectively. Studies performing single-level ACDF yielded a rate of 3.7% (95% CI: 1.6-5.7). Additionally, there was a large difference in the rate of pseudoarthrosis in randomized controlled trials (4.8%, 95% CI: 2.6-7.0) versus prospective cohort studies (0.2%, 95% CI: -0.1 to 0.5), indicating that the extent of follow-up criteria affects the rate of pseudoarthrosis. This review represents a comprehensive estimation of the actual

  11. Electron transfer properties and catalytic competence of cytochrome b5 in the fusion protein Hmwb5-EGFP in reactions catalyzed by cytochrome P450 3A4.

    PubMed

    Yantsevich, A V; Gilep, A A; Usanov, S A

    2009-08-01

    In the present paper we describe studies on molecular mechanisms of protein-protein interactions between cytochrome P450 3A4 (CYP3A4) and cytochrome b(5), the latter being incorporated into the artificial recombinant protein Hmwb(5)-EGFP containing full-length cytochrome b(5) (functional module) and a mutant form of the green fluorescent protein EGFP (signal module) fused into a single polypeptide chain. It is shown that cytochrome b(5) within the fusion protein Hmwb(5)-EGFP can be reduced by NADPH-cytochrome P450 reductase in the presence of NADPH, the rate of reduction being dependent on solution ionic strength, indicating that the signal module does not prevent the interaction of the flavo- and hemeproteins. Interaction of cytochrome P450 3A4 and Hmwb(5)-EGFP was estimated based on spin equilibrium shift of cytochrome P450 3A4 to high-spin state in the presence of Hmwb(5)-EGFP, as well as based on steady-state fluorescence anisotropy of the EGFP component of the fusion protein in the presence of CYP3A4. The engineering of chimeric protein Hmwb(5)-EGFP gives an independent method to determine dissociation constant for the complex of cytochrome P450 and cytochrome b(5) that is less sensitive to environmental factors compared to spectrophotometric titration used before. Reconstitution of catalytic activity of cytochrome P450 3A4 in the reaction of testosterone 6beta-hydroxylation in the presence of Hmwb(5)-EGFP indicates that cytochrome b(5) in the fusion protein is able to stimulate the hydroxylation reaction. Using other fusion proteins containing either cytochrome b(5) or its hydrophilic domain to reconstitute catalytic activity of cytochrome P450 3A4 showed that the hydrophobic domain of cytochrome b(5) participates not only in hemeprotein interaction, but also in electron transfer from cytochrome b(5) to cytochrome P450.

  12. Estimates of fission barrier heights for neutron-deficient Po to Ra nuclei produced in fusion reactions

    NASA Astrophysics Data System (ADS)

    Sagaidak, Roman

    2017-09-01

    The cross section data for fission and evaporation residue production in fusion reactions leading to nuclei from Po to Ra have been considered in a systematic way in the framework of the conventional barrier-passing (fusion) model coupled with the statistical model. The cross section data obtained in very asymmetric projectile-target combinations can be described within these models rather well with the adjusted model parameters. In particular, one can scale and fix the macroscopic (liquid-drop) fission barrier heights (FBHs) for nuclei involved in the de-excitation of compound nuclei produced in the reactions. The macroscopic FBHs for nuclei from Po to Ra have been derived in the framework of such analysis and compared with the predictions of various theoretical models.

  13. Fusion rates after thoracoscopic release and bone graft substitutes in idiopathic scoliosis.

    PubMed

    Weinzapfel, Brett; Son-Hing, Jochen P; Armstrong, Douglas G; Blakemore, Laurel C; Poe-Kochert, Connie; Thompson, George H

    2008-05-01

    A retrospective assessment of fusion rates using either morselized allograft bone or demineralized bone matrix (DBM) following video-assisted thoracoscopic surgery (VATS) in idiopathic scoliosis. To compare fusion rates between allograft bone and demineralized bone matrix (Grafton DBM Flex) following VATS using on standard standing lateral spine radiographs. Both VATS and bone graft substitutes are accepted surgical techniques. However, their concomitant use in spinal deformity surgery has not been previously reported. Bone graft substitute has the advantage of decreasing operative time, blood loss, and donor site morbidity associated with autografts. Anterior thoracic discectomies were performed using VATS. Forty patients with 1 year or more follow-up were evaluated-12 with morselized allograft bone (Allograft group) and 28 with folded Grafton DBM Flex (DBM group). Factors analyzed included age, number of anterior levels fused, operative time, anterior perioperative blood loss, curve correction, and fusion rates. Clinical and radiographic evaluations were performed before surgery and at month, 1 year, and at most recent follow-up. Interbody fusion was assessed on standing lateral radiographs using the Newton et al 4-level grading scale. There were no significant differences in age at surgery, number of anterior vertebral levels fused, anterior operative time per level, anterior intraoperative blood loss, chest tube drainage and duration, or total perioperative anterior blood loss between the 2 groups. Percent curve correction from before surgery to the most recent follow-up were very similar in both Allograft (68%) and DBM groups (67%). At most recent assessment, 60 of 73 disc spaces (82%) in the Allograft group and 100 of 109 disc spaces (92%) in the DBM group were rated as radiographically fused (Newton et al Grade I and II). There was no significant difference between the 2 groups (P = 0.088). No patients were observed to have crankshaft, pseudoarthrosis or

  14. Nuclear Fusion Rate Study of a Muonic Molecule via Nuclear Threshold Resonances

    NASA Astrophysics Data System (ADS)

    Faghihi, F.; Eskandari, M. R.

    This work follows our previous calculations of the ground state binding energy, size, and the effective nuclear charge of the muonic T3 molecule, using the Born-Oppenheimer adiabatic approximation. In our past articles, we showed that the system possesses two minimum positions, the first one at the muonic distance and the second at the atomic distance. Also, the symmetric planner vibrational model assumed between the two minima and the approximated potential were calculated. Following from the previous studies, we now calculate the fusion rate of the T3 muonic molecule according to the overlap integral of the resonance nuclear compound nucleus and the molecular wave functions.

  15. Excitation functions for {sup 208-211}Fr produced in the {sup 18}O+{sup 197}Au fusion reaction

    SciTech Connect

    Corradi, L.; Behera, B.R.; Fioretto, E.; Gadea, A.; Latina, A.; Stefanini, A.M.; Szilner, S.; Trotta, M.; Wu, Y.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Sagaidak, R.N.; Atutov, S.N.; Mai, B.; Stancari, G.; Tomassetti, L.; Mariotti, E.; Khanbekyan, A.; Veronesi, S.

    2005-01-01

    Excitation functions for {sup 208-211}Fr isotopes produced in the {sup 18}O+{sup 197}Au fusion-evaporation reaction have been measured at E{sub lab}=75-130 MeV via characteristic {alpha} decays by means of an electrostatic deflector and a semiconductor detector. Data have been compared with calculations giving barrier-passing (capture) cross sections and probabilities of the compound nucleus decay into different channels according to the standard statistical model.

  16. Complications and Rates of Subsequent Lumbar Surgery Following Lumbar Total Disc Arthroplasty and Lumbar Fusion.

    PubMed

    Eliasberg, Claire D; Kelly, Michael P; Ajiboye, Remi M; SooHoo, Nelson F

    2016-01-01

    Retrospective analysis. To examine complications and rates of subsequent surgery following lumbar spinal fusion (LF) and lumbar total disc arthroplasty (TDA) at up to 5-year follow-up. LF is commonly used in the management of degenerative disc disease causing pain refractory to nonoperative management. Lumbar TDA was developed as an alternative to fusion with the theoretical advantage of reducing rates of adjacent segment pathology and reoperation. Most prior reports comparing these 2 interventions have come from industry-sponsored investigational device exemption trials and no large-scale administrative database comparisons exist. The California Office of Statewide Health Planning and Development discharge database was queried for patients aged 18 to 65 years undergoing lumbar TDA and LF for degenerative disc disease from 2004 to 2010. Patient characteristics were collected, and rates of complications and readmission were identified. Rates of repeat lumbar surgery were calculated at 90-day and 1-, 3-, and 5-year follow-up intervals. A total of 52,877 patients met the inclusion criteria (LF = 50,462, TDA = 2415). Wound infections were more common following LF than TDA (1.03% vs. 0.25%, P < 0.001). Rates of subsequent lumbar surgery at 90-day and 1-year follow-up were lower with lumbar TDA than LF (90-day-TDA: 2.94% vs. LF: 4.01%, P = 0.007; 1-yr-TDA: 3.46% vs. LF: 4.78%, P = 0.009). However, there were no differences in rates of subsequent lumbar surgery between the 2 groups at 3-year and 5-year follow-up. Lumbar TDA was associated with fewer early reoperations, though beyond 1 year, rates of reoperation were similar. Lumbar TDA may be associated with fewer acute infections, though this may be approach related and unrelated to the device itself. 3.

  17. Complications and Rates of Subsequent Lumbar Surgery Following Lumbar Total Disc Arthroplasty and Lumbar Fusion

    PubMed Central

    Eliasberg, Claire D.; Kelly, Michael P.; Ajiboye, Remi M.; SooHoo, Nelson F.

    2015-01-01

    Study Design Retrospective analysis. Objectives To examine complications and rates of subsequent surgery following lumbar spinal fusion (LF) and lumbar total disc arthroplasty (TDA) at up to 5 years follow-up. Summary of Background Data LF is commonly used in the management of degenerative disc disease causing pain refractory to nonoperative management. Lumbar TDA was developed as an alternative to fusion with the theoretical advantage of reducing rates of adjacent segment pathology and reoperation. Most prior reports comparing these two interventions have come from industry-sponsored investigational device exemption trials and no large-scale administrative database comparisons exist. Methods The California Office of Statewide Health Planning and Development discharge database was queried for patients aged 18 to 65 years undergoing lumbar TDA and LF for degenerative disc disease from 2004 to 2010. Patient characteristics were collected, and rates of complications and readmission were identified. Rates of repeat lumbar surgery were calculated at 90-day and 1-, 3-, and 5-year follow-up intervals. Results A total of 52,877 patients met the inclusion criteria (LF = 50462, TDA = 2415). Wound infections were more common following LF than TDA (1.03% vs. 0.25%, p<0.001). Rates of subsequent lumbar surgery at 90-day and 1-year follow-up were lower with lumbar TDA than LF (90-day – TDA: 2.94% vs. LF: 4.01%, p=0.007; 1-year – TDA: 3.46% vs. LF: 4.78%, p=0.009). However, there were no differences in rates of subsequent lumbar surgery between the two groups at 3-year and 5-year follow-up. Conclusions Lumbar TDA was associated with fewer early reoperations, though beyond one year, rates of reoperation were similar. Lumbar TDA may be associated with fewer acute infections, though this may be approach-related and unrelated to the device itself. PMID:26751061

  18. Primordial lithium: New reaction rates, new abundances, new constraints

    SciTech Connect

    Kawano, L.; Schramm, D.; Steigman, G.

    1986-12-01

    Newly measured nuclear reaction rates for /sup 3/H(..cap alpha..,..gamma..)/sup 7/Li (higher than previous values) and /sup 7/Li(p,..cap alpha..)/sup 4/He (lower than previous values) are shown to increase the /sup 7/Li yield from big bang nucleosynthesis for lower baryon to photon ratio (eta less than or equal to 4 x 10/sup -10/); the yield for higher eta is not affected. New, independent determinations of Li abundances in extreme Pop II stars are in excellent agreement with the earlier work of the Spites and give continued confidence in the use of /sup 7/Li in big bang baryon density determinations. The new /sup 7/Li constraints imply a lower limit on eta of 2 x 10/sup -10/ and an upper limit of 5 x 10/sup -10/. This lower limit to eta is concordant with that obtained from considerations of D + /sup 3/He. The upper limit is consistent with, but even more restrictive than, the D bound. With the new rates, any observed primordial Li/H ratio below 10/sup -10/ would be inexplicable by the standard big bang nucleosynthesis. A review is made of the strengths and possible weaknesses of utilizing conclusions drawn from big bang lithium considerations. An appendix discusses the null effect of a factor of 32 increase in the experimental rate for the D(d,..gamma..)/sup 4/He reaction. 28 refs., 1 fig.

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

    SciTech Connect

    Öström, Jonatan Gustafsson, Magnus; Bezrukov, Dmitry S.; Nyman, Gunnar

    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.

  20. Thermal energy reaction rates of titanium monomer cation

    SciTech Connect

    MacTaylor, R.S.; Vann, W.D.; Castleman, A.W. Jr.

    1996-03-28

    New determinations of quantitative forward rate constants for reactions of titanium monomer cation with C{sub 2}H{sub 6}, C{sub 3}H{sub 8}, H{sub 2}O, NH{sub 3}, and O{sub 2} are accomplished using a high-pressure (multicollision) flow tube reactor. These experiments were prompted by our observation of conflicting reports in the literature. The reaction rates we consider have been determined previously by both single-collision and multicollision methods, with some systems having generated notably contrasting results. An effort is made to reconcile the difference in values by explicitly addressing possible potential sources of error which have been suggested in earlier publications as the most likely reasons for the discrepancies. A `titration` technique is employed which allows controlled collisional quenching of excited state titanium cations with nitrogen gas such that excited state ion effects can be selectively observed and subsequently eliminated. No evidence is found to cast doubt upon the validity of multicollision methods for the determination of thermal energy rate constants. 20 refs., 4 figs., 1 tab.

  1. Reaction rate constant for radiative association of CF(.).

    PubMed

    Öström, Jonatan; Bezrukov, Dmitry S; Nyman, Gunnar; Gustafsson, Magnus

    2016-01-28

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C(+)) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 1(1)Π → X(1)Σ(+) and rovibrational transitions on the X(1)Σ(+) and a(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(-21) cm(3) s(-1), rising toward 10(-16) cm(3) s(-1) for a temperature of 30,000 K.

  2. Experiments on screening effect in deuteron fusion reactions at extremely low energies

    NASA Astrophysics Data System (ADS)

    Targosz-Ślȩczka, N.; Czerski, K.; Huke, A.; Ruprecht, G.; Weissbach, D.; Martin, L.; Kiliç, A. i.; Kaczmarski, M.; Winter, H.

    2013-10-01

    The enhanced electron screening effect in nuclear reactions taking place in dense astrophysical plasmas is extremely important for determination of stellar reaction rates in terrestrial laboratories as well as in prediction of cross sections enhancement in interiors of stars such as White and Brown Dwarfs or Giant Planets. This effect resulting in reduction of the nuclear Coulomb potential by the atomic electrons has been confirmed in many laboratory experiments. Unfortunately, experimental screening energies are much higher than the theoretical predictions and the reason for that remains unknown. Here, we present absorbing results of the experiment studying d + d nuclear reactions in different deuterized metallic targets under ultra high vacuum conditions. The total cross sections and angular distributions of the 2H( d, p)3H and 2H( d, n)3He reactions have been measured using a deuteron beam of energies between 8 and 30 keV provided by the electron cyclotron ion source. The atomic cleanness of the target surface has been secured by combining Ar sputtering of the target and Auger electrons spectroscopy. Due to application of an on-line analysis method, the homogeneity of the implanted deuteron densities could be continuously monitored. We will discuss probable causes of the large discrepancy between theoretical and experimental data.

  3. RPMDRATE: Bimolecular chemical reaction rates from ring polymer molecular dynamics

    NASA Astrophysics Data System (ADS)

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

    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+CH4, OH+CH4 and H+C2H6 reactions. Catalogue identifier: AENW_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AENW_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: MIT license No. of lines in distributed program, including test data, etc.: 94512 No. of bytes in distributed program, including test data, etc.: 1395674 Distribution format: tar.gz Programming language: Fortran 90/95, Python (version 2.6.x or later, including any version of Python 3, is recommended). Computer: Not computer specific. Operating system: Any for which Python, Fortran 90/95 compiler and the required external routines are available. Has the code been vectorized or parallelized?: The program can efficiently utilize 4096+ processors, depending on problem and available computer. At low temperatures, 110 processors are reasonable for a typical umbrella integration run with an analytic potential energy function and gradients on the latest x86-64 machines.

  4. ZGB surface reaction model with high diffusion rates

    NASA Astrophysics Data System (ADS)

    Evans, J. W.

    1993-02-01

    The diffusionless ZGB (monomer-dimer) surface reaction model exhibits a discontinuous transition to a monomer-poisoned state when the fraction of monomer adsorption attempts exceeds 0.525. It has been claimed that this transition shifts to 2/3 with introduction of rapid diffusion of the monomer species, or of both species. We show this is not the case, 2/3 representing the spinodal rather than the transition point. For equal diffusion rates of both species, we find that the transition only shifts to 0.5951±0.0002.

  5. ZGB surface reaction model with high diffusion rates

    SciTech Connect

    Evans, J.W. )

    1993-02-01

    The diffusionless ZGB (monomer--dimer) surface reaction model exhibits a discontinuous transition to a monomer-poisoned state when the fraction of monomer adsorption attempts exceeds 0.525. It has been claimed that this transition shifts to 2/3 with introduction of rapid diffusion of the monomer species, or of both species. We show this is not the case, 2/3 representing the spinodal rather than the transition point. For equal diffusion rates of both species, we find that the transition only shifts to 0.5951[plus minus]0.0002.

  6. Novel technique for Constraining r -Process (n , γ ) Reaction Rates

    NASA Astrophysics Data System (ADS)

    Spyrou, A.; Liddick, S. N.; Larsen, A. C.; Guttormsen, M.; Cooper, K.; Dombos, A. C.; Morrissey, D. J.; Naqvi, F.; Perdikakis, G.; Quinn, S. J.; Renstrøm, T.; Rodriguez, J. A.; Simon, A.; Sumithrarachchi, C. S.; Zegers, R. G. T.

    2014-12-01

    A novel technique has been developed, which will open exciting new opportunities for studying the very neutron-rich nuclei involved in the r process. As a proof of principle, the γ spectra from the β decay of 76Ga have been measured with the SuN detector at the National Superconducting Cyclotron Laboratory. The nuclear level density and γ -ray strength function are extracted and used as input to Hauser-Feshbach calculations. The present technique is shown to strongly constrain the 75Ge (n ,γ )76Ge cross section and reaction rate.

  7. Metal-silicon reaction rates - The effects of capping

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1989-01-01

    Evidence is presented showing that the presence of the commonly used anti-reflection coating material Ta2O5 on the free surface of contact metallization can either suppress or enhance, depending on the system, the interaction that takes place at elevated temperatures between the metallization and the underlying Si. The cap layer is shown to suppress both the generation and annihilation of vacancies at the free surface of the metal which are necessary to support metal-Si interactons. Evidence is also presented indicating that the mechanical condition of the free metal surface has a significant effect on the metal-silicon reaction rate.

  8. Effect of gas flow rate on titanium sponge reaction

    NASA Astrophysics Data System (ADS)

    Wang, Zhiliang; Feng, Gaoping; Wang, Mingdong; Hong, Yanji

    2017-08-01

    This paper expounds the important application of titanium sponge adsorption in inert gas purification, the reaction mechanism of titanium with nitrogen and oxygen was introduced. Explored the relationship between the absorption capacity of sponge titanium on the active gas in air samples and the gas flow rate. The model of sponge titanium for flowing air absorption was established by data analysis. The designed experiment verified the relationship between the titanium processing capacity and the gas collecting device. Finally, the influence of the mass of the sponge titanium on the degassing capacity was studied through experiments.

  9. Complication rates following elective lumbar fusion in patients with diabetes: insulin dependence makes the difference.

    PubMed

    Golinvaux, Nicholas S; Varthi, Arya G; Bohl, Daniel D; Basques, Bryce A; Grauer, Jonathan N

    2014-10-01

    Retrospective cohort. To determine the effect of non-insulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) on postoperative complications after elective lumbar fusion surgery. Diabetes mellitus (DM) is a common chronic disease. The effects of NIDDM and IDDM on rates of postoperative complications, extended length of stay, and readmission after lumbar fusion surgery are not well established. A retrospective cohort study was conducted using the American College of Surgeons National Surgical Quality Improvement Program database. Patients undergoing lumbar fusion between 2005 and 2012 were identified and characterized as having NIDDM, IDDM, or neither. Bivariate and multivariate analyses were used to test patients with NIDDM and IDDM for increased risk of adverse postoperative outcomes over the initial 30 postoperative days. A total of 15,480 patients who underwent lumbar fusion were identified (13,043 were patients without DM, 1,650 patients had NIDDM, and 787 patients had IDDM).NIDDM was independently associated with an increased risk of wound dehiscence (relative risk = 2.3; P = 0.033) and extended length of stay (1.2; P < 0.003).IDDM was independently associated with an increased risk of death (2.7; P = 0.020), sepsis (2.2; P = 0.002), septic shock (3.3; P = 0.032), unplanned intubation (2.8; P = 0.003), ventilator-assisted respiration for more than 48 hours postoperatively (2.8; P = 0.005), wound-related infection (1.9; P = 0.001), urinary tract infection (1.6; P = 0.011), pneumonia (3.1; P < 0.001), extended length of stay (1.5; P < 0.001), and readmission within 30 days (1.5; P = 0.036). Compared with patients without DM, IDDM was associated with an increased risk of a considerably higher number of postoperative complications than NIDDM. These complications were also of greater severity. This important designation may improve preoperative risk stratification and counseling of patients with diabetes prior to lumbar fusion

  10. Return to Work Rates After Single-level Cervical Fusion for Degenerative Disc Disease Compared With Fusion for Radiculopathy in a Workers' Compensation Setting.

    PubMed

    Faour, Mhamad; Anderson, Joshua T; Haas, Arnold R; Percy, Rick; Woods, Stephen T; Ahn, Uri M; Ahn, Nicholas U

    2016-07-15

    A retrospective comparative cohort study. To compare return to work (RTW) rates for patients who underwent single-level cervical fusion for radiculopathy compared with fusion for degenerative disc disease (DDD) as an indication for surgery. Studies have shown that workers' compensation subjects have less favorable surgical and functional outcomes compared with the general population. Cervical decompression and fusion have provided great results with relieving radicular symptoms. Fusion for DDD, however, remains controversial. We retrospectively collected data of 21 169 subjects with cervical comorbidities who filed their claims for work-related injuries with Ohio Bureau of Workers' Compensation (BWC) between 1993 and 2011. The primary outcome was whether subjects met RTW criteria within 3-year follow-up after fusion. The secondary outcome measures and data on presurgical characteristics and secondary outcomes of each cohort were also collected. Successful RTW status was affected by a number of presurgical risk factors: DDD as an indication for surgery, age of more than 50 years, out of work for more than 6 months, psychological evaluation, opioid use, legal litigation, and permanent disability. The DDD group had lower rate of successful RTW status (50.9%) and was less likely to have a sustained RTW status (odds ratio = 0.61, 95% confidence interval: 0.48-0.79, P = 0.0001) compared with the radiculopathy group (successful RTW rate 62.9%). RTW rate within 1 year after surgery was lower in the DDD group (39.9%) compared with the radiculopathy group (53.1%; P = 0.0001). DDD patients were absent 112 days more on average after surgery compared with radiculopathy patients (P = 0.0003). Cervical fusion for DDD is associated with lower rate of successful RTW status when compared with fusion for radiculopathy in a worker's compensation setting. The decision to include surgical intervention in the management plan of cervical DDD should be approached with

  11. Comparison of DSMC Reaction Models with QCT Reaction Rates for Nitrogen

    DTIC Science & Technology

    2016-07-17

    Distribution A: Approved for Public Release, Distribution Unlimited PA #16299 Non-Equilibrium Reaction Rates N2-N2, Tv≠ Tt =Tr • TCE, QK, and VFD are over an...Release, Distribution Unlimited PA #16299 Non-Equilibrium Rates for Bias Model N2-N2, Tv≠ Tt =Tr • Bias model provides much better fit than Park 2-T model...Higher vibrational favoring for lower Tt : λ>2 works better than λ=4 for Tt >20,000 K Distribution A: Approved for Public Release, Distribution

  12. Primordial lithium - New reaction rates, new abundances, new constraints

    NASA Technical Reports Server (NTRS)

    Kawano, Lawrence; Schramm, David; Steigman, Gary

    1988-01-01

    Newly measured nuclear reaction rates for H-3(alpha, gamma)Li-7 (higher than previous values) and Li-7(p, alpha)He-4 (lower than previous values) are shown to increase the Li-7 yield from big band nucleosynthesis for lower baryon-to-photon ratio (less than about 4 x 10 to the 10th). Recent revisions in the He-3(alpha, gamma)Be-7 and the D(p, gamma)He-3 rates enhance the high (greater than 4 x 10 to the 10th) Li-7(Be) production. New, independent determinations of Li abundances in extreme population II stars are in excellent agreement with the work of Spites and give continued confidence in the use of Li-7 in big bang baryon density determinations.

  13. Moderator design studies for a new neutron reference source based on the D-T fusion reaction

    NASA Astrophysics Data System (ADS)

    Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.; McDonald, Joseph C.

    2016-06-01

    The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramatically in recent years. Neutron generators based on deuteriumtritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2-5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.

  14. Moderator design studies for a new neutron reference source based on the D–T fusion reaction

    SciTech Connect

    Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.; McDonald, Joseph C.

    2016-06-01

    The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramatically in recent years. Neutron generators based on deuterium-tritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14.6 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2 to 5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.

  15. Investigation of the reaction rates between uranium and liquid aluminum

    SciTech Connect

    Strum, M.J.; Sedillo, E.; Smugeresky, J.

    1995-05-05

    A limited study consisting of scoping experiments was carried out to determine if a uranium-niobium alloy was weakly or strongly resistant to penetration by liquid aluminum alloy 6061. Our investigation was limited to temperatures between 700{degrees}and 900{degrees}C and carried out using small cylindrical coupons of U-6wt.%Nb and unalloyed U in unsaturated molten aluminum and aluminum alloy 6061 baths. The results indicate that indeed, significant dissolution of uranium into molten aluminum occurs and in relatively short times. The diameters of U-6wt.%Nb test cylinders immersed in unsaturated Al-6061 decreased linearly with time at 700{degrees}C, 800{degrees}C, and 900{degrees}C at rates of 1.14 mm/h, 3.0 mm/h, and 3.5 mm/h, respectively. However, we have found that the reaction rates were significantly reduced by the alloying elements niobium and magnesium. These results suggest that a more detailed investigation could lead to a predictive capability for control of these reaction rates. In unalloyed U, the rate of U dissolution increased by up to a factor of ten relative to that in U- 6wt.%Nb. In both materials, the dissolution of the U core was found to occur by advance of a continuous intermetallic layer, which redissolves into the unsaturated liquid Al bath. The Nb additions resulted in the formation of a thick transition layer composed of intermetallic and U-saturated liquid. In unalloyed U, however, the transition layer was largely reduced in thickness, allowing unsaturated liquid adjacent to the continuous intermetallic layer. Another important variable identified was the influence of surface condition on interface reactivity. At 900{degrees}C, liquid attack was completely absent over large regions of U-6wt.% Nb samples immersed in Al-6061. Surface analysis by EDX identified the presence of up to 24 at.% Mg in unattacked areas.

  16. Kinetics of Imidazole Catalyzed Ester Hydrolysis: Use of Buffer Dilutions to Determine Spontaneous Rate, Catalyzed Rate, and Reaction Order.

    ERIC Educational Resources Information Center

    Lombardo, Anthony

    1982-01-01

    Described is an advanced undergraduate kinetics experiment using buffer dilutions to determine spontaneous rate, catalyzed rate, and reaction order. The reaction utilized is hydrolysis of p-nitro-phenyl acetate in presence of imidazole, which has been shown to enhance rate of the reaction. (Author/JN)

  17. Kinetics of Imidazole Catalyzed Ester Hydrolysis: Use of Buffer Dilutions to Determine Spontaneous Rate, Catalyzed Rate, and Reaction Order.

    ERIC Educational Resources Information Center

    Lombardo, Anthony

    1982-01-01

    Described is an advanced undergraduate kinetics experiment using buffer dilutions to determine spontaneous rate, catalyzed rate, and reaction order. The reaction utilized is hydrolysis of p-nitro-phenyl acetate in presence of imidazole, which has been shown to enhance rate of the reaction. (Author/JN)

  18. Cold nuclear fusion and muon-catalyzed fusion. (Latest citations from the INSPEC database). Published Search

    SciTech Connect

    1993-12-01

    The bibliography contains citations concerning a nuclear fusion process which occurs at lower temperatures and pressures than conventional fusion reactions. The references describe theoretical and experimental results for a proposed muon-catalyzed fusion reactor, and for studies on muon sticking and reactivation. The temperature dependence of fusion rates, and resolution of some engineering challenges are also discussed. (Contains 250 citations and includes a subject term index and title list.)

  19. Excitation Functions for Complete Fusion and Transfer Reactions in the Interaction of 4He Nuclei with 197Au

    NASA Astrophysics Data System (ADS)

    Kulko, A. A.; Demekhina, N. A.; Kalpakchieva, R.; Muzychka, Yu. A.; Penionzhkevich, Yu. E.; Rassadov, D. N.; Skobelev, N. K.; Testov, D. A.

    2007-05-01

    Excitation functions have been measured for the fusion reaction 197Au(αxn)201-xnTl with the evaporation of x neutrons (0⩽x⩽3) in the energy range 14-36 MeV. The induced-activation method was used for registration and identification of the reaction products. The experimental cross sections for the (1-3)-neutron evaporation residues are in good agreement with the results known from literature. For the radiation capture reaction 197Au(α,γ)201Tl, the upper limit was obtained essentially lower. The excitation functions for the measured reactions are compared with calculations in the frame of the statistical model, as well as with formerly measured similar data with a 6He beam.

  20. Excitation Functions for Complete Fusion and Transfer Reactions in the Interaction of 4He Nuclei with 197Au

    SciTech Connect

    Kulko, A. A.; Demekhina, N. A.; Kalpakchieva, R.; Muzychka, Yu. A.; Penionzhkevich, Yu. E.; Rassadov, D. N.; Skobelev, N. K.; Testov, D. A.

    2007-05-22

    Excitation functions have been measured for the fusion reaction 197Au({alpha}xn)201-xnTl with the evaporation of x neutrons (0{<=}x{<=}3) in the energy range 14-36 MeV. The induced-activation method was used for registration and identification of the reaction products. The experimental cross sections for the (1-3)-neutron evaporation residues are in good agreement with the results known from literature. For the radiation capture reaction 197Au({alpha},{gamma})201Tl, the upper limit was obtained essentially lower. The excitation functions for the measured reactions are compared with calculations in the frame of the statistical model, as well as with formerly measured similar data with a 6He beam.

  1. Cluster correlation effects in 12C+12C and 14N+10B fusion-evaporation reactions

    NASA Astrophysics Data System (ADS)

    Morelli, L.; Baiocco, G.; D'Agostino, M.; Gulminelli, F.; Bruno, M.; Cinausero, M.; Degerlier, M.; Fabris, D.; Gramegna, F.; Marchi, T.; Barlini, S.; Bini, M.; Casini, G.; Gelli, N.; Olmi, A.; Pasquali, G.; Piantelli, S.; Valdré, S.

    2015-04-01

    The decay of highly excited states of 24Mg is studied in fusion evaporation events completely detected in charge in the reactions 12C+12C and 14N+10B at 95 and 80 MeV incident energy respectively. The comparison of light charged particles measured spectra with statistical model predictions suggests that the dominant reaction mechanism is compound nucleus (CN) formation and decay. However, in both reactions, a discrepancy with statistical expectations is found for α particles detected in coincidence with Carbon, Oxigen and Neon residues. The comparison between the two reactions shows that this discrepancy is only partly explained by an entrance channel effect. Evidence for cluster correlations in excited 24Mg CN is suggested by the comparison between the measured and calculated branching ratios for the channels involving α particles.

  2. Effect of Viscosity on Growth Rates of Interchange Modes in Magnetic Inertial Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Morse, R. L.; Nachtrieb, R.

    1999-11-01

    Thermal insulating B fields in imploding MIF/MTF confinement systems, as in predecessor static wall confinement systems, must close in the confined plasma and, therefore, have unfavorable curvature for MHD interchange mode stability. Analytic inviscid estimates with typical compressed z-pinch fields Bth=1MG, plasma density n=3.e20 and radius a=1cm give max. m=0 mode growth rates, Gm, of order 1.e8s-1 with wavelengths Lz of .1a to .5a. Thermal conduction to the confining wall increases B there and Gm significantly, as Vekstein discusses in concluding in effect that such confinement would not be useful for fusion. These growth rates and mode forms are confirmed by two supporting compressible models(Freidberg/McCrory). Happily when viscosity(Braginskii) is included; G is reduced, esp. at longer wavelengths, Lz, with scaling Lz**-1, and viscosities of 1e2 to 1e4 poise for the example plasmas give Gm's of order 1.e7s-1 and less with realistic time dependent profiles. We conclude that these Gm's are consistent with significant fusion yields. This work was presented at the UCLA/DoE ICC conference, 3/3-6/97.

  3. X-ray ablation rates in inertial confinement fusion capsule materials

    SciTech Connect

    Olson, R. E.; Rochau, G. A.; Leeper, R. J.; Landen, O. L.

    2011-03-15

    X-ray ablation rates have been measured in beryllium, copper-doped beryllium, germanium-doped plastic (Ge-doped CH), and diamondlike high density carbon (HDC) for radiation temperatures T in the range of 160-260 eV. In beryllium, the measured ablation rates range from 3 to 12 mg/cm{sup 2}/ns; in Ge-doped CH, the ablation rates range from 2 to 6 mg/cm{sup 2}/ns; and for HDC, the rates range from 2 to 9 mg/cm{sup 2}/ns. The ablation rates follow an approximate T{sup 3} dependence and, for T below 230 eV, the beryllium ablation rates are significantly higher than HDC and Ge-doped CH. The corresponding implied ablation pressures are in the range of 20-160 Mbar, scaling as T{sup 3.5}. The results are found to be well predicted by computational simulations using the physics packages and computational techniques employed in the design of indirect-drive inertial confinement fusion capsules. An iterative rocket model has been developed and used to compare the ablation rate data set to spherical indirect-drive capsule implosion experiments and to confirm the validity of some aspects of proposed full-scale National Ignition Facility ignition capsule designs.

  4. Exploring contributions from incomplete fusion in Li,76+209Bi and Li,76+198Pt reactions

    NASA Astrophysics Data System (ADS)

    Parkar, V. V.; Jha, V.; Kailas, S.

    2016-08-01

    We use the breakup absorption model to simultaneously describe the measured cross sections of complete fusion (CF), incomplete fusion (ICF), and total fusion (TF) in nuclear reactions induced by weakly bound nuclei Li,76 on 209Bi and 198Pt targets. The absorption cross sections are calculated using the continuum discretized coupled channels (CDCC) method with different choices of short-range imaginary potentials to get the ICF, CF, and TF cross sections. It is observed that the cross sections for deuteron ICF / deuteron capture and α ICF / α capture are of similar magnitude, in the case of the 6Li projectile, while the cross sections for the triton ICF / triton capture is more dominant than that of α ICF / α capture in the case of the 7Li projectile. Both these observations are also corroborated by the experimental data. The ratio of ICF to TF cross sections, which defines the value of fusion suppression factor, is found to be in agreement with the data available from the literature. The cross-section ratios of CF/TF and ICF/TF show opposite behavior at below-barrier energies the former decreases while the latter increases as the energy is lowered, which shows the dominance of ICF at below-barrier energies. We have also studied the correlation of the ICF cross sections with the noncapture breakup (NCBU) cross sections as a function of energy, which shows that the NCBU is more significant than ICF at below-barrier energies.

  5. Rate Constant for the OH + CO Reaction at Low Temperatures.

    PubMed

    Liu, Yingdi; Sander, Stanley P

    2015-10-01

    Rate constants for the reaction of OH + CO → products (1) have been measured using laser photolysis/laser-induced fluorescence (LP/LIF) over the temperature range 193–296 K and at pressures of 50–700 Torr of Ar and N2. The reaction was studied under pseudo-first-order conditions, monitoring the decay of OH in the presence of a large excess of CO. The rate constants can be expressed as a combination of bimolecular and termolecular components. The bimolecular component was found to be temperature-independent with an expression given by kbi(T) = (1.54 ± 0.14) × 10(–13)[e(–(13±17)/T)] cm(3) molecule(–1) s(–1), with an error of one standard deviation. The termolecular component was fitted to the expression, kter = k0(T)[M]/[1 + (k0(T)[M]/k∞(T)] × 0.6({1+[log10(k0(T)[M]/k∞(T))]2}−1) where k0(T) = k0(300)(T/300)(−n) and k∞(T) = k∞(300)(T/300)(−m). The parameters for k0(T) were determined to be k0(300) = (6.0±0.5) × 10(−33) cm(6) molecule(–2) s(–1) in N2 and k0(300) = (3.4 ± 0.3) × 10(–33) cm(6) molecule(–2) s(–1) in Ar, with n = 1.9±0.5 and 2.0±0.4 in N2 and Ar, respectively. These parameters were determined using k0(T) and m from the NASA kinetics data evaluation (JPL Publication No. 10-6) since the experimental pressure range was far from the high-pressure limit. Addition of low concentrations of O2 had no discernible effect on the mechanism of the OH + CO reaction but resulted in secondary reactions which regenerated OH.

  6. The fusion-fission process in the reaction {sup 34}S+{sup 186}W near the interaction barrier

    SciTech Connect

    Harca, I. M.; Dmitriev, S.; Itkis, J.; Kozulin, E. M.; Knyazheva, G.; Loktev, T.; Novikov, K.; Azaiez, F.; Gottardo, A.; Matea, I.; Verney, D.; Hanappe, F.; Piot, J.; Schmitt, C.; Vardaci, E.

    2015-02-24

    The reaction {sup 34}S+{sup 186}W at E{sub lab}=160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF–γ coincidence method is of better use then the γ – γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

  7. Application of Semiclassical Methods to Reaction Rate Theory

    NASA Astrophysics Data System (ADS)

    Hernandez, Rigoberto

    This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller* to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e., most reactions. Second, we have developed a method to describe the fluctuations of decay rates of individual energy states from the average RRKM rate in systems where the direct calculation of individual rates would be impossible. Combined with the semiclassical theory this latter effort has provided a direct comparison to the experimental results of Moore and coworkers. ^dagger. In SCTST, the Hamiltonian is expanded about the barrier and the "good" action-angle variables are obtained perturbatively; a WKB analysis of the effectively one-dimensional reactive direction then provides the transmission probabilities. ^ddagger The advantages of this local approximate treatment are that it includes tunneling effects and anharmonicity, and it systematically provides a multi-dimensional dividing surface in phase space. The SCTST thermal rate expression has been reformulated providing increased numerical efficiency (as compared to a naive Boltzmann average), an appealing link to conventional transition state theory (involving a "pre-reactive" partition function depending on the action of the reactive mode), and the ability to go beyond the perturbative approximation. ^S. In addition, the distribution of unimolecular decay rates at threshold energies to dissociation has been modeled by describing the quasi-bound states as strongly -mixed. The possible existence of globally conserved symmetries --which would break this ansatz--is included by treating each symmetry block of the Hamiltonian separably and assuming the ansatz for each symmetry manifold. Use of SCTST to

  8. Regulation of mitochondrial morphology by membrane potential, and DRP1-dependent division and FZO1-dependent fusion reaction in mammalian cells.

    PubMed

    Ishihara, Naotada; Jofuku, Akihiro; Eura, Yuka; Mihara, Katsuyoshi

    2003-02-21

    Mitochondria are dynamic organelles that undergo frequent fission and fusion or branching. To analyze the mitochondrial fusion reaction, mitochondria were separately labeled with green or red fluorescent protein (GFP and RFP, respectively) in HeLa cells, and the cells were fused using hemagglutinating virus of Japan (HVJ). The resulting mixing of the fluorescent reporters was then followed using fluorescence microscopy. This system revealed that mitochondria fuse frequently in mammalian cells, and the fusion depends on the membrane potential across the inner membrane. The protonophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP), led to fragmentation of the mitochondria and inhibited the fusion reaction. Removal of CCCP recovered the fusion activity to reform filamentous mitochondrial networks. Analysis of the effects of GTP-binding proteins, DRP1 and two FZO1 isoforms, and the GTPase-domain mutants on the CCCP-induced mitochondrial morphologic changes revealed that DRP1 and FZO1 are involved in membrane budding and fusion, respectively. Furthermore, a HVJ-dependent cell fusion assay combined with RNA interference (RNAi) demonstrated that both FZO1 isoforms are essential and must be acting in cis for the mitochondrial fusion reaction to occur.

  9. Manual choice reaction times in the rate-domain.

    PubMed

    Harris, Christopher M; Waddington, Jonathan; Biscione, Valerio; Manzi, Sean

    2014-01-01

    Over the last 150 years, human manual reaction times (RTs) have been recorded countless times. Yet, our understanding of them remains remarkably poor. RTs are highly variable with positively skewed frequency distributions, often modeled as an inverse Gaussian distribution reflecting a stochastic rise to threshold (diffusion process). However, latency distributions of saccades are very close to the reciprocal Normal, suggesting that "rate" (reciprocal RT) may be the more fundamental variable. We explored whether this phenomenon extends to choice manual RTs. We recorded two-alternative choice RTs from 24 subjects, each with 4 blocks of 200 trials with two task difficulties (easy vs. difficult discrimination) and two instruction sets (urgent vs. accurate). We found that rate distributions were, indeed, very close to Normal, shifting to lower rates with increasing difficulty and accuracy, and for some blocks they appeared to become left-truncated, but still close to Normal. Using autoregressive techniques, we found temporal sequential dependencies for lags of at least 3. We identified a transient and steady-state component in each block. Because rates were Normal, we were able to estimate autoregressive weights using the Box-Jenkins technique, and convert to a moving average model using z-transforms to show explicit dependence on stimulus input. We also found a spatial sequential dependence for the previous 3 lags depending on whether the laterality of previous trials was repeated or alternated. This was partially dissociated from temporal dependency as it only occurred in the easy tasks. We conclude that 2-alternative choice manual RT distributions are close to reciprocal Normal and not the inverse Gaussian. This is not consistent with stochastic rise to threshold models, and we propose a simple optimality model in which reward is maximized to yield to an optimal rate, and hence an optimal time to respond. We discuss how it might be implemented.

  10. Multisensor data fusion for enhanced respiratory rate estimation in thermal videos.

    PubMed

    Pereira, Carina B; Xinchi Yu; Blazek, Vladimir; Venema, Boudewijn; Leonhardt, Steffen

    2016-08-01

    Scientific studies have demonstrated that an atypical respiratory rate (RR) is frequently one of the earliest and major indicators of physiological distress. However, it is also described in the literature as "the neglected vital parameter", mainly due to shortcomings of clinical available monitoring techniques, which require attachment of sensors to the patient's body. The current paper introduces a novel approach that uses multisensor data fusion for an enhanced RR estimation in thermal videos. It considers not only the temperature variation around nostrils and mouth, but the upward and downward movement of both shoulders. In order to analyze the performance of our approach, two experiments were carried out on five healthy candidates. While during phase A, the subjects breathed normally, during phase B they simulated different breathing patterns. Thoracic effort was the gold standard elected to validate our algorithm. Our results show an excellent agreement between infrared thermography (IRT) and ground truth. While in phase A a mean correlation of 0.983 and a root-mean-square error of 0.240 bpm (breaths per minute) was obtained, in phase B they hovered around 0.995 and 0.890 bpm, respectively. In sum, IRT may be a promising clinical alternative to conventional sensors. Additionally, multisensor data fusion contributes to an enhancement of RR estimation and robustness.

  11. Angular momentum effects and barrier modification in sub-barrier fusion reactions using the proximity potential in the Wong formula

    SciTech Connect

    Kumar, Raj; Bansal, Manie; Arun, Sham K.; Gupta, Raj K.

    2009-09-15

    Using the capture cross-section data from {sup 48}Ca+{sup 238}U, {sup 48}Ca+{sup 244}Pu, and {sup 48}Ca+{sup 248}Cm reactions in the superheavy mass region, and fusion-evaporation cross sections from {sup 58}Ni+{sup 58}Ni, {sup 64}Ni+{sup 64}Ni, and {sup 64}Ni+{sup 100}Mo reactions known for fusion hindrance phenomenon in coupled-channels calculations, the Wong formula is assessed for its angular momentum and barrier-modification effects at sub-barrier energies. The simple, l=0 barrier-based Wong formula is shown to ignore the modifications of the barrier due to its inbuilt l dependence via l summation, which is found to be adequate enough to explain the capture cross sections for all the three above-mentioned {sup 48}Ca-based reactions forming superheavy systems. For the capture (equivalently, quasifission) reactions, the complete l-summed Wong formula is shown to be the same as the dynamical cluster-decay model expression, of one of us (R.K.G.) and collaborators, with the condition of fragment preformation probability P{sub 0}{sup l}=1 for all the angular momentum l values. In the case of fusion-evaporation cross sections, however, a further modification of barriers is required for below-barrier energies, affected in terms of either the barrier 'lowering' or barrier 'narrowing' via the curvature constant. Calculations are made for use of nuclear proximity potential, with effects of multipole deformations included up to hexadecapole, and orientation degrees of freedom integrated for both the coplanar and noncoplanar configurations.

  12. Transcriptional dynamics with time-dependent reaction rates

    NASA Astrophysics Data System (ADS)

    Nandi, Shubhendu; Ghosh, Anandamohan

    2015-02-01

    Transcription is the first step in the process of gene regulation that controls cell response to varying environmental conditions. Transcription is a stochastic process, involving synthesis and degradation of mRNAs, that can be modeled as a birth-death process. We consider a generic stochastic model, where the fluctuating environment is encoded in the time-dependent reaction rates. We obtain an exact analytical expression for the mRNA probability distribution and are able to analyze the response for arbitrary time-dependent protocols. Our analytical results and stochastic simulations confirm that the transcriptional machinery primarily act as a low-pass filter. We also show that depending on the system parameters, the mRNA levels in a cell population can show synchronous/asynchronous fluctuations and can deviate from Poisson statistics.

  13. Measurements of fusion reactions of low-intensity radioactive carbon beams on 12C and their implications for the understanding of X-ray bursts.

    PubMed

    Carnelli, P F F; Almaraz-Calderon, S; Rehm, K E; Albers, M; Alcorta, M; Bertone, P F; Digiovine, B; Esbensen, H; Niello, J O Fernández; Henderson, D; Jiang, C L; Lai, J; Marley, S T; Nusair, O; Palchan-Hazan, T; Pardo, R C; Paul, M; Ugalde, C

    2014-05-16

    The interaction between neutron-rich nuclei plays an important role for understanding the reaction mechanism of the fusion process as well as for the energy production through pycnonuclear reactions in the crust of neutron stars. We have performed the first measurements of the total fusion cross sections in the systems (10,14,15)C+(12)C using a new active target-detector system. In the energy region accessible with existing radioactive beams, a good agreement between the experimental and theoretical cross sections is observed. This gives confidence in our ability to calculate fusion cross sections for systems which are outside the range of today's radioactive beam facilities.

  14. Measurements of Fusion Reactions of Low-Intensity Radioactive Carbon Beams on C12 and their Implications for the Understanding of X-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Carnelli, P. F. F.; Almaraz-Calderon, S.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Digiovine, B.; Esbensen, H.; Niello, J. O. Fernández; Henderson, D.; Jiang, C. L.; Lai, J.; Marley, S. T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.; Ugalde, C.

    2014-05-01

    The interaction between neutron-rich nuclei plays an important role for understanding the reaction mechanism of the fusion process as well as for the energy production through pycnonuclear reactions in the crust of neutron stars. We have performed the first measurements of the total fusion cross sections in the systems C10,14,15+C12 using a new active target-detector system. In the energy region accessible with existing radioactive beams, a good agreement between the experimental and theoretical cross sections is observed. This gives confidence in our ability to calculate fusion cross sections for systems which are outside the range of today's radioactive beam facilities.

  15. How the projectile neutron number influences the evaporation cross section in complete fusion reactions with heavy ions

    SciTech Connect

    Wang Chengbin; Zhang Jinjuan; Ren, Z. Z.; Shen, C. W.

    2010-11-15

    The influence of the projectile neutron number on the evaporation residue cross sections for the reactions {sup 208}Pb({sup 52,54}Cr,n,2n){sup 258-261}Sg and {sup 208}Pb({sup 48,50}Ti,n,2n){sup 254-257}Rf has been studied within the framework of a fusion-fission statistical model. The results obtained with the kewpie2 code are compared with recent experimental data. The excitation functions represent the experimental results well both in the maximum value and the lactation of the peak. The calculations show that the projectile neutron number greatly influences both the capture cross section and the fusion probability.

  16. Analysis of reaction rates of single molecules on metal surfaces

    NASA Astrophysics Data System (ADS)

    Ueba, H.

    2017-10-01

    The experimental results of the action spectra i.e., reaction rate R(V) as a function of a bias voltage V are analyzed for rotation of a single CCH (D) molecule on a Cu (100) surface [5] and hopping of a single H(D)2O molecule on Pd(111) surface [6]. In the former system it is identified that rotation occurs if enough energy stored in the C-H (D) in-plane bending (IPB) mode excited by tunneling electron is transferred to the C-H (D) out of plane bending (OPB) mode (reaction coordinate mode) via the anharmonic mode coupling in a single electron process. The calculated R(V) shows an excellent agreement with the experimental results except at the low bias voltages below V ≃ 60 mV where no experimental data is available for the nonlinear current I dependence of R(I). A reproduction of the experimental R(V) at the higher voltage region allows us to determine the vibrational density of states of the C-H IPB mode and its coupling rate to the C-H (D) OPB mode as well as the inelastic tunneling current to excite IPB mode. A change of a conductance upon excitation of the C-H IPB mode enables us to evaluate the electron-vibration coupling strength inducing the rotation motion of CCH molecule. In the latter system investigated at a high temperature of about 40 K, the constant R(V) due to thermal hopping followed by the rapid increase is satisfactory explained by anharmonic inter-mode coupling between the scissor mode excited by tunneling electrons and the frustrated translation mode for H(D)2O molecule on Pd(111).

  17. Atomic data for fusion

    SciTech Connect

    Hunter, H.T.; Kirkpatrick, M.I.; Alvarez, I.; Cisneros, C.; Phaneuf, R.A.; Barnett, C.F.

    1990-07-01

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research.

  18. Manual choice reaction times in the rate-domain

    PubMed Central

    Harris, Christopher M.; Waddington, Jonathan; Biscione, Valerio; Manzi, Sean

    2014-01-01

    Over the last 150 years, human manual reaction times (RTs) have been recorded countless times. Yet, our understanding of them remains remarkably poor. RTs are highly variable with positively skewed frequency distributions, often modeled as an inverse Gaussian distribution reflecting a stochastic rise to threshold (diffusion process). However, latency distributions of saccades are very close to the reciprocal Normal, suggesting that “rate” (reciprocal RT) may be the more fundamental variable. We explored whether this phenomenon extends to choice manual RTs. We recorded two-alternative choice RTs from 24 subjects, each with 4 blocks of 200 trials with two task difficulties (easy vs. difficult discrimination) and two instruction sets (urgent vs. accurate). We found that rate distributions were, indeed, very close to Normal, shifting to lower rates with increasing difficulty and accuracy, and for some blocks they appeared to become left-truncated, but still close to Normal. Using autoregressive techniques, we found temporal sequential dependencies for lags of at least 3. We identified a transient and steady-state component in each block. Because rates were Normal, we were able to estimate autoregressive weights using the Box-Jenkins technique, and convert to a moving average model using z-transforms to show explicit dependence on stimulus input. We also found a spatial sequential dependence for the previous 3 lags depending on whether the laterality of previous trials was repeated or alternated. This was partially dissociated from temporal dependency as it only occurred in the easy tasks. We conclude that 2-alternative choice manual RT distributions are close to reciprocal Normal and not the inverse Gaussian. This is not consistent with stochastic rise to threshold models, and we propose a simple optimality model in which reward is maximized to yield to an optimal rate, and hence an optimal time to respond. We discuss how it might be implemented. PMID:24959134

  19. The TDF System for Thermonuclear Plasma Reaction Rates, Mean Energies and Two-Body Final State Particle Spectra

    SciTech Connect

    Warshaw, S I

    2001-07-11

    The rate of thermonuclear reactions in hot plasmas as a function of local plasma temperature determines the way in which thermonuclear ignition and burning proceeds in the plasma. The conventional model approach to calculating these rates is to assume that the reacting nuclei in the plasma are in Maxwellian equilibrium at some well-defined plasma temperature, over which the statistical average of the reaction rate quantity {sigma}v is calculated, where {sigma} is the cross-section for the reaction to proceed at the relative velocity v between the reacting particles. This approach is well-understood and is the basis for much nuclear fusion and astrophysical nuclear reaction rate data. The Thermonuclear Data File (TDF) system developed at the Lawrence Livermore National Laboratory (Warshaw 1991), which is the topic of this report, contains data on the Maxwellian-averaged thermonuclear reaction rates for various light nuclear reactions and the correspondingly Maxwellian-averaged energy spectra of the particles in the final state of those reactions as well. This spectral information closely models the output particle and energy distributions in a burning plasma, and therefore leads to more accurate computational treatments of thermonuclear burn, output particle energy deposition and diagnostics, in various contexts. In this report we review and derive the theoretical basis for calculating Maxwellian-averaged thermonuclear reaction rates, mean particle energies, and output particle spectral energy distributions for these reactions in the TDF system. The treatment of the kinematics is non-relativistic. The current version of the TDF system provides exit particle energy spectrum distributions for two-body final state reactions only. In a future report we will discuss and describe how output particle energy spectra for three- and four-body final states can be developed for the TDF system. We also include in this report a description of the algorithmic implementation of the

  20. Photo-fusion reactions in a new compact device for ELI

    SciTech Connect

    Moustaizis, S. D.; Auvray, P.; Hora, H.; Lalousis, P.; Larour, J.; Mourou, G.

    2012-07-09

    In the last few years significant progress on technological, experimental and numerical studies on fusion process in high density and high temperature plasmas produced by a high intensity laser pulse interaction with clusters in a high external applied magnetic field, enable us to propose a compact photo-fusion magnetic device for high neutron production. For the purpose of the project a pulsed magnetic field driver with values up to 110 Tesla has been developed which allows increasing the trapping time of the high density plasma in the device and improving the neutron yield. Numerical simulations show that the proposed device is capable of producing up to 10{sup 9}-10{sup 10} neutrons per laser shot with an external magnetic field of 150 Tesla. The proposed device can be used for experiments and numerical code validation concerning different conventional and (or) exotic fusion fuels.

  1. Faster rates with less catalyst in template-directed reactions

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Baird, E. E.

    1995-01-01

    We have recently shown that the polycytidylic acid-directed polymerization of guanosine 5'-monophosphate 2-methylimidazolide (2-MeImpG) is amenable to kinetic study and that rate determinations as a function of 2-MeImpG concentration can reveal much mechanistic detail (Kanavarioti et al. 1993). Here we report kinetic data which show that, once the reaction has been initiated by the formation of dimers, the elongation of dimers to form longer oligomers is accelerated by decreasing polycytidylate (poly(C)) concentration from 0.05 to 0.002 M. This result is consistent with the previously proposed mechanism. The increase in the observed pseudo-first order rate constant for formation of the trimer, k3', and the corresponding constant for formation of oligomers longer than the trimer, ki' (ki' is independent of oligomer length for i > or = 4), with decreasing template concentration for a given monomer concentration is attributed to an increase in template occupancy as template concentration is reduced.

  2. Fusion reactions in collisions induced by Li isotopes on Sn targets

    SciTech Connect

    Fisichella, M.; Shotter, A. C.; Di Pietro, A.; Figuera, P.; Lattuada, M.; Marchetta, C.; Musumarra, A.; Pellegriti, M. G.; Ruiz, C.; Scuderi, V.; Strano, E.; Torresi, D.; Zadro, M.

    2012-10-20

    Fusion cross sections for the {sup 6}Li+{sup 120}Sn and {sup 7}Li+{sup 119}Sn systems have been measured. We aim to search for possible effects due to the different neutron transfer Q-values, by comparing the fusion cross sections for the two systems below the barrier. This experiment is the first step of a wider systematic aiming to study the above problems in collisions induced by stable and unstable Li isotopes on tin all forming the same compound nucleus.

  3. An Experiment To Demonstrate How a Catalyst Affects the Rate of a Reaction.

    ERIC Educational Resources Information Center

    Copper, Christine L.; Koubeck, Edward

    1999-01-01

    Describes a chemistry experiment that allows students to calculate rates of reaction, orders of reaction, and activation energies. The activity demonstrates that to increase a reaction's rate, a catalyst need only provide any additional pathway for the reaction, not necessarily a pathway having lower activation energy. (WRM)

  4. An Experiment To Demonstrate How a Catalyst Affects the Rate of a Reaction.

    ERIC Educational Resources Information Center

    Copper, Christine L.; Koubeck, Edward

    1999-01-01

    Describes a chemistry experiment that allows students to calculate rates of reaction, orders of reaction, and activation energies. The activity demonstrates that to increase a reaction's rate, a catalyst need only provide any additional pathway for the reaction, not necessarily a pathway having lower activation energy. (WRM)

  5. Pressure Dependence of Gas-Phase Reaction Rates

    ERIC Educational Resources Information Center

    De Persis, Stephanie; Dollet, Alain; Teyssandier, Francis

    2004-01-01

    It is presented that only simple concepts, mainly taken from activated-complex or transition-state theory, are required to explain and analytically describe the influence of pressure on gas-phase reaction kinetics. The simplest kind of elementary gas-phase reaction is a unimolecular decomposition reaction.

  6. Pressure Dependence of Gas-Phase Reaction Rates

    ERIC Educational Resources Information Center

    De Persis, Stephanie; Dollet, Alain; Teyssandier, Francis

    2004-01-01

    It is presented that only simple concepts, mainly taken from activated-complex or transition-state theory, are required to explain and analytically describe the influence of pressure on gas-phase reaction kinetics. The simplest kind of elementary gas-phase reaction is a unimolecular decomposition reaction.

  7. Description of nucleon-transfer and fusion reactions within time-dependent approaches and coupled-channel method

    SciTech Connect

    Samarin, V. V.

    2015-01-15

    The time-dependent Schrödinger equation and the method of perturbed stationary states that is based on the expansion of the total wave function for the system of two nuclear cores and a nucleon in a set of nucleon two-center functions are used to describe nucleon transfers and fusion in low-energy nuclear reactions. A set of multichannel equations that couple the relative motion of nuclei to the motion of the nucleon is obtained. The kinetic-energy coupling matrix is similar to the coupling matrix for collective excitations of nuclei.

  8. Reaction rate theory of radiation exposure:Effects of dose rate on mutation frequency

    NASA Astrophysics Data System (ADS)

    Bando, Masako; Nakamura, Issei; Manabe, Yuichiro

    2014-03-01

    We revisit the linear no threshold (LNT) hypothesis deduced from the prominent works done by H. J. Muller for the DNA mutation induced by the artificial radiation and by W. L. Russell and E. M. Kelly for that of mega-mouse experiments, developing a new kinetic reaction theory. While the existing theoretical models primarily rely on the dependence of the total dose D on the mutation frequency, the key ingredient in our theory is the dose rate d(t) that accounts for decrease in the mutation rate during the time course of the cellular reactions. The general form for the mutation frequency with the constant dose rate d is simply expressed as, dFm(t)/dt = A - BFm(t) , with A =a0 +a1(d +deff) and B =b0 +b1(d +deff) . We discuss the solution for a most likely case with B > 0 ; Fm(t) = [A/B -Fm(0) ] (1 -e-Bt) +Fm(0) with the control value Fm(0) . We show that all the data of mega-mouse experiments by Russel with different dose rates fall on the universal scaling function Φ(τ) ≡ [Fm(τ) -Fm(0) ]/[ A / B -Fm(0) ] = 1 - exp(- τ) with scaled time τ = Bt . The concept of such a scaling rule provides us with a strong tool to study different species in a unified manner.

  9. A simulation study for radiation treatment planning based on the atomic physics of the proton-boron fusion reaction

    NASA Astrophysics Data System (ADS)

    Kim, Sunmi; Yoon, Do-Kun; Shin, Han-Back; Jung, Joo-Young; Kim, Moo-Sub; Kim, Kyeong-Hyeon; Jang, Hong-Seok; Suh, Tae Suk

    2017-03-01

    The purpose of this research is to demonstrate, based on a Monte Carlo simulation code, the procedure of radiation treatment planning for proton-boron fusion therapy (PBFT). A discrete proton beam (60 - 120 MeV) relevant to the Bragg peak was simulated using a Monte Carlo n-particle extended (MCNPX, Ver. 2.6.0, National Laboratory, Los Alamos NM, USA) simulation code. After computed tomography (CT) scanning of a virtual water phantom including air cavities, the acquired CT images were converted using the simulation source code. We set the boron uptake regions (BURs) in the simulated water phantom to achieve the proton-boron fusion reaction. Proton sources irradiated the BUR, in the phantom. The acquired dose maps were overlapped with the original CT image of the phantom to analyze the dose volume histogram (DVH). We successfully confirmed amplifications of the proton doses (average: 130%) at the target regions. From the DVH result for each simulation, we acquired a relatively accurate dose map for the treatment. A simulation was conducted to characterize the dose distribution and verify the feasibility of proton-boron fusion therapy (PBFT). We observed a variation in proton range and developed a tumor-targeting technique for treatment that was more accurate and powerful than both conventional proton therapy and boron-neutron capture therapy.

  10. From cutting-edge pointwise cross-section to groupwise reaction rate: A primer

    NASA Astrophysics Data System (ADS)

    Sublet, Jean-Christophe; Fleming, Michael; Gilbert, Mark R.

    2017-09-01

    The nuclear research and development community has a history of using both integral and differential experiments to support accurate lattice-reactor, nuclear reactor criticality and shielding simulations, as well as verification and validation efforts of cross sections and emitted particle spectra. An important aspect to this type of analysis is the proper consideration of the contribution of the neutron spectrum in its entirety, with correct propagation of uncertainties and standard deviations derived from Monte Carlo simulations, to the local and total uncertainty in the simulated reactions rates (RRs), which usually only apply to one application at a time. This paper identifies deficiencies in the traditional treatment, and discusses correct handling of the RR uncertainty quantification and propagation, including details of the cross section components in the RR uncertainty estimates, which are verified for relevant applications. The methodology that rigorously captures the spectral shift and cross section contributions to the uncertainty in the RR are discussed with quantified examples that demonstrate the importance of the proper treatment of the spectrum profile and cross section contributions to the uncertainty in the RR and subsequent response functions. The recently developed inventory code FISPACT-II, when connected to the processed nuclear data libraries TENDL-2015, ENDF/B-VII.1, JENDL-4.0u or JEFF-3.2, forms an enhanced multi-physics platform providing a wide variety of advanced simulation methods for modelling activation, transmutation, burnup protocols and simulating radiation damage sources terms. The system has extended cutting-edge nuclear data forms, uncertainty quantification and propagation methods, which have been the subject of recent integral and differential, fission, fusion and accelerators validation efforts. The simulation system is used to accurately and predictively probe, understand and underpin a modern and sustainable understanding

  11. Enhanced reaction rates in NDP analysis with neutron scattering

    SciTech Connect

    Downing, R. Gregory

    2014-04-15

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  12. Enhanced reaction rates in NDP analysis with neutron scattering

    NASA Astrophysics Data System (ADS)

    Downing, R. Gregory

    2014-04-01

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  13. Enhanced reaction rates in NDP analysis with neutron scattering.

    PubMed

    Downing, R Gregory

    2014-04-01

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  14. Reaction and fusion cross sections for the near-symmetric system 129Xe+natSn from 8 A to 35 A MeV

    NASA Astrophysics Data System (ADS)

    Manduci, L.; Lopez, O.; Chbihi, A.; Rivet, M. F.; Bougault, R.; Frankland, J. D.; Borderie, B.; Galichet, E.; La Commara, M.; Le Neindre, N.; Lombardo, I.; Pârlog, M.; Rosato, E.; Roy, R.; Verde, G.; Vient, E.; Indra Collaboration

    2016-10-01

    Background: We study heavy-ion reactions from barrier up to Fermi energy. The data were acquired with the INDRA detector at the GANIL (Caen, France) facility. Purpose: We aim to determine the reaction and fusion cross sections for the reactions induced by 129Xe projectiles on natSn targets for incident energies ranging from 8 A to 35 A MeV. In particular, the evaluation of the fusion and incomplete fusion cross sections is the main purpose, altogether with the comparison with the systematics of Eudes et al. [Europhys. Lett. 104, 22001 (2013), 10.1209/0295-5075/104/22001]. Method: The reaction cross sections are evaluated at each beam energy with data acquired thanks to the INDRA 4 π array. The events are sorted with the help of the observable Eiso,max. We focus therefore our study on a selected sample of events, in such a way that the fusion and incomplete fusion cross sections can be estimated. Results: We present the excitation function of reaction and fusion cross sections for the heavy and nearly symmetric system 129Xe+natSn from 8 A to 35 A MeV. For the fusion excitation function the comparison with the systematics of Eudes et al. seems to be in a fair agreement starting from the beam energy 20 A MeV. For the lower beam energies (8 A and 12 A MeV) discrepancies are observed. Conclusions: The evaluated fusionlike cross sections show a good agrement with a recent systematics for beam energies greater than 20 A MeV. For low beam energies the cross-sectional values are lower than the expected ones. A probable reason for these low values is in the fusion hindrance at energies above or close to the barrier.

  15. Reaction mechanism and rate constants of the CH+CH4 reaction: a theoretical study

    NASA Astrophysics Data System (ADS)

    Ribeiro, Joao Marcelo; Mebel, Alexander M.

    2015-07-01

    Ab initio and density functional calculations have been performed to elucidate the mechanism of CH radical insertion into methane. The results show that the reaction can be viewed to occur via two stages. On the first stage, the CH radical approaches methane without large structural changes to acquire proper positioning for the subsequent stage, where H-migration occurs from CH4 to CH, along with a C-C bond formation. Where the first stage ends and the second begins, a tight transition state was located using the B3LYP/6-311G(d,p) and MP4(SDQ)/6-311++G(d,p) methods. Using a rigid rotor - harmonic oscillator approach within transition state theory, we show that at the MP5/6-311++G(d,p)//MP4(SDQ)/6-311++G(d,p) level the calculated rate constants are in a reasonably good agreement with experiment in a broad temperature range of 145-581 K. Even at low temperatures, the insertion reaction bottleneck is found about the location of the tight transition state, rather than at long separations between the CH and CH4 reactants. In addition, high level CCSD(T)-F12/CBS calculations of the remainder of the C2H5 potential energy surface predict the CH+CH4 reaction to proceed via the initial insertion step to the ethyl radical which then can emit a hydrogen atom to form highly exothermic C2H4+H products.

  16. Comparison of Ankle Fusion Rates With and Without Anterior Plate Augmentation.

    PubMed

    Mitchell, Phillip M; Douleh, Diana G; Thomson, A Brian

    2017-04-01

    The optimal fixation construct for tibiotalar arthrodesis continues to be debated. While biomechanical data and clinical series support anterior plate augmentation, comparative studies assessing its use are sparse. The purpose of this study was to compare the rates of successful tibiotalar arthrodesis with and without anterior plate augmentation of a compression screw construct. We studied 64 patients (65 ankles) undergoing tibiotalar arthrodesis done by a single surgeon over a 10-year period (2006-2016) with anterior plate augmentation beginning in 2010. Twenty-six ankles had a construct using compression screws only and 39 ankles had anterior plate augmentation of a compression screw construct. We reviewed clinical notes, operative reports, and postoperative radiographs to evaluate for union, incidence of revision, and postoperative complications. The nonunion rate in the compression screw (CS) cohort was 15.4% and 7.7% in the anterior plate augmentation (AP) cohort ( P = .33). The revision rate was 7.7% in the CS group and 2.6% in the AP cohort ( P = .34). The use of autograft harvested through a separate incision was 19.2% and 17.9% in the CS and AP cohorts, respectively. There were 2 deep postoperative infections in the AP group and none in the patients with CS only ( P = .24). There were no superficial wound complications in either group. Anterior plate augmentation was a viable fixation strategy in tibiotalar arthrodesis. In a trend toward an improved rate of fusion and decreased revision rate in the anterior plate augmentation cohort. Level III, retrospective comparative series.

  17. Comparison of allograft and polyetheretherketone (PEEK) cage subsidence rates in anterior cervical discectomy and fusion (ACDF).

    PubMed

    Yson, Sharon C; Sembrano, Jonathan N; Santos, Edward Rainier G

    2017-04-01

    Structural allografts and PEEK cages are commonly used interbody fusion devices in ACDF. The subsidence rates of these two spacers have not yet been directly compared. The primary aim of this study was to compare the subsidence rate of allograft and PEEK cage in ACDF. The secondary aim was to determine if the presence of subsidence affects the clinical outcome. We reviewed 67 cases (117 levels) of ACDF with either structural allograft or PEEK cages. There were 85 levels (48 cases) with PEEK and 32 levels (19 cases) with allograft spacers. Anterior and posterior disc heights at each operative level were measured at immediate and 6months post-op. Subsidence was defined as a decrease in anterior or posterior disc heights >2mm. NDI of the subsidence (SG) and non-subsidence group (NSG) were recorded. Chi-square test was used to analyze subsidence rates. T-test was used to analyze clinical outcomes (α=0.05). There was no statistically significant difference between subsidence rates of the PEEK (29%; 25/85) and allograft group (28%; 9/32) (p=0.69). Overall mean subsidence was 2.3±1.7mm anteriorly and 2.6±1.2mm posteriorly. Mean NDI improvement was 11.7 (from 47.1 to 35.4; average follow-up: 12mos) for the SG and 14.0 (from 45.8 to 31.8; average follow-up: 13mos) for the NSG (p=0.74). Subsidence rate does not seem to be affected by the use of either PEEK or allograft as spacers in ACDF. Furthermore, subsidence alone does not seem to be predictive of clinical outcomes of ACDF.

  18. Multinucleon transfer in O,1816,19F+208Pb reactions at energies near the fusion barrier

    NASA Astrophysics Data System (ADS)

    Rafferty, D. C.; Dasgupta, M.; Hinde, D. J.; Simenel, C.; Simpson, E. C.; Williams, E.; Carter, I. P.; Cook, K. J.; Luong, D. H.; McNeil, S. D.; Ramachandran, K.; Vo-Phuoc, K.; Wakhle, A.

    2016-08-01

    Background: Nuclear reactions are complex, involving collisions between composite systems where many-body dynamics determines outcomes. Successful models have been developed to explain particular reaction outcomes in distinct energy and mass regimes, but a unifying picture remains elusive. The irreversible transfer of kinetic energy from the relative motion of the collision partners to their internal states, as is known to occur in deep inelastic collisions, has yet to be successfully incorporated explicitly into fully quantal reaction models. The influence of these processes on fusion is not yet quantitatively understood. Purpose: To investigate the population of high excitation energies in transfer reactions at sub-barrier energies, which are precursors to deep inelastic processes, and their dependence on the internuclear separation. Methods: Transfer probabilities and excitation energy spectra have been measured in collisions of O,1816,19F+208Pb , at various energies below and around the fusion barrier, by detecting the backscattered projectile-like fragments in a Δ E -E telescope. Results: The relative yields of different transfer outcomes are strongly driven by Q values, but change with the internuclear separation. In 16O+208Pb , single nucleon transfer dominates, with a strong contribution from -2 p transfer close to the Coulomb barrier, though this channel becomes less significant in relation to the -2 p 2 n transfer channel at larger separations. For 18O+208Pb , the -2 p 2 n channel is the dominant charge transfer mode at all separations. In the reactions with 19F,-3 p 2 n transfer is significant close to the barrier, but falls off rapidly with energy. Multinucleon transfer processes are shown to lead to high excitation energies (up to ˜15 MeV), which is distinct from single nucleon transfer modes which predominantly populate states at low excitation energy. Conclusions: Kinetic energy is transferred into internal excitations following transfer, with this

  19. In-beam measurements of 13C+12C fusion reaction cross section at energies around and below Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Stefanescu, I.; Chilug, A.; Tudor, D.; Trache, L.; Straticiuc, M.; Burducea, I.; Focsa, I. M.; Ghita, D. G.; Zhang, N.; Tang, X.; Chen, H.

    2017-06-01

    The reaction cross section of the 12C+12C system is difficult to measure because of the presence of the resonances in the Gamow energy window. It has been proved that the 13C+12C reaction is a good alternative to study the behavior of the reaction cross section at energies relevant for astrophysics. We have measured it with activation and online techniques. During online measurements we were interested to determine the relative contributions of the open channels of the 13C+12C reaction. These determinations are necessary to evaluate the total fusion reaction cross section. Therefore, we have measured the γ-ray yields of proton, neutron and alpha particle evaporation channels from the resulting 25Mg compound nucleus using prompt γ-rays measurements. This complements the activation method. The irradiations took place at the 3 MV Tandetron Accelerator at IFIN-HH [1], Bucharest and the prompt gamma-rays were measured using a hyper-pure germanium detector with 100% relative efficiency, shielded with lead bricks. The energy range for the irradiation was from 4.6 up to 11 MeV (in laboratory frame), in steps of 0.2 MeV and the online measurements were performed from 6.4 up to 11 MeV.

  20. Fudge: a high-bandwidth fusion diagnostic of the NIF

    SciTech Connect

    Moran, M. J., LLNL

    1998-06-02

    Diagnostics for the National Ignition Facility (NIF)/Inertial Confinement Fusion (ICF) program must include good characterization of the fusion source. Ideally, diagnostics would measure the spatially-resolved history of the fusion reaction rate and temperature. Existing diagnostics can satisfy this goal only partially. One class of new techniques that could play a major role in high-yield diagnostics is measurements based on fusion {gamma} rays. The Fusion Diagnostic Gamma Experiment (FUDGE) can be used to perform energy-resolved measurements of (D,T) fusion reaction rates This diagnostic is based on the 16 7-MeV {gamma} rays that are produced by (D,T) fusion. The {gamma} rays are free of spectral dispersion and can be detected with a high bandwidth Cherenkov detector. A simple magnetic monochromator selects signals from the 16 7-MeV {gamma} rays and reduces background signals from non-fusion {gamma} rays.

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

    NASA Astrophysics Data System (ADS)

    Vorotilin, V. P.

    2017-01-01

    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.

  2. Investigation of cold fusion phenomena in deuterated metals. Final report, Volume 1. Overview, executive summary, chemistry, physics, gas reactions, metallurgy. Technical information series

    SciTech Connect

    Anderson, L.; Barrowes, S.C.; Bergeson, H.E.; Bourgeois, F.; Cedzynska, K.

    1991-06-01

    The March 1989 announcement by Pons and Fleischmann stimulated worldwide interest in the cold fusion phenomenon. In Utah the legislature appropriated $5 million to support cold fusion research and development. As cold fusion inquiries continue worldwide, this interim report has been written to document the scientific and legal work that has been funded by the Utah legislature. Partial contents include these titles of papers: Cold Fusion Studies in a High-Pressure Sealed Cell; Tritium and Neutron Generation in Palladium Cathodes with High Deuterium Loading; Deuterium-Gas Phase Reactions on Palladium; Excess Heat Estimation with the Kalman Filter; Ultrasonic Energy Effects on Palladium Electrodes in Cold Fusion Cells; Nuclear Measurements on Deuterium-Loaded Palladium and Titanium.

  3. Competition between fusion-fission and quasifission processes in the {sup 32}S+{sup 184}W reaction

    SciTech Connect

    Zhang, H. Q.; Zhang, C. L.; Lin, C. J.; Liu, Z. H.; Yang, F.; Nasirov, A. K.; Mandaglio, G.; Manganaro, M.; Giardina, G.

    2010-03-15

    The angular distributions of fission fragments for the {sup 32}S+{sup 184}W reaction at center-of-mass energies of 118.8, 123.1, 127.3, 131.5, 135.8, 141.1, and 144.4 MeV are measured. The experimental fission excitation function is obtained. The anisotropy (A{sub exp}) is found by extrapolating each fission fragment angular distribution. The measured fission cross sections of the {sup 32}S+{sup 182,184}W reaction are decomposed into fusion-fission, quasifission, and fast-fission contributions by the dinuclear system model (DNS). The angular momentum distributions of the dinuclear system and compound nucleus calculated by the DNS model are used to reproduce the experimental capture and fusion excitation functions for both reactions and quantities K{sub 0}{sup 2}, , and A{sub exp}, which characterize angular distributions of the fission products at the considered range of beam energy. The total evaporation residue excitation function for the {sup 32}S+{sup 184}W reaction calculated in the framework of the advanced statistical model is close to the available experimental data only up to about E{sub c.m.}approx =160 MeV. The underestimation of the experimental data at high excitation energies E{sub c.m.}>160 MeV is explained by the fact that the statistical model cannot reproduce the cross section of evaporation residues formed by the nonequilibrium mechanism, that is, without formation of the compound nucleus in the statistical equilibrium state.

  4. First measurements of deuterium-tritium and deuterium-deuterium fusion reaction yields in ignition-scalable direct-drive implosions

    DOE PAGES

    Forrest, C. J.; Radha, P. B.; Knauer, J. P.; ...

    2017-03-03

    In this study, the deuterium-tritium (D-T) and deuterium-deuterium neutron yield ratio in cryogenic inertial confinement fusion (ICF) experiments is used to examine multifluid effects, traditionally not included in ICF modeling. This ratio has been measured for ignition-scalable direct-drive cryogenic DT implosions at the Omega Laser Facility using a high-dynamic-range neutron time-of-flight spectrometer. The experimentally inferred yield ratio is consistent with both the calculated values of the nuclear reaction rates and the measured preshot target-fuel composition. These observations indicate that the physical mechanisms that have been proposed to alter the fuel composition, such as species separation of the hydrogen isotopes, aremore » not significant during the period of peak neutron production in ignition-scalable cryogenic direct-drive DT implosions.« less

  5. Some thoughts on a simple mechanism for the [sup 2]H + [sup 2]H [yields] [sup 4]He cold fusion reaction

    SciTech Connect

    Park, A.E.

    1993-11-01

    A speculative mechanism for the creation of [sup 4]He using cold fusion is proposed. The nuclear transformation can be made by the fusion of two excited rotating ground states of deuterium into a highly excited rotating ground state of [sup 4]He. Under compression and relatively stable conditions, the formation of such a bound, stretched-out pnnp state of [sup 4]He would be favored (with respect to Coulomb repulsion) over other nuclear ground states without as much angular momentum. The reaction likely occurs at the surface of palladium. A more descriptive name for this reaction is compressed-rotational-shielded (CRS) fusion. Potential experimental conditions for enhancing the initiation of CRS fusion are discussed. 8 refs., 2 figs.

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

    PubMed

    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.

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

    SciTech Connect

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

    2009-08-01

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

  8. Theory of the compactness of the hot fusion reaction {sup 48}Ca+{sup 244}Pu{yields}{sup 292}114*

    SciTech Connect

    Gupta, Raj K.; Manhas, Monika; Muenzenberg, G.; Greiner, Walter

    2005-07-01

    Within the fragmentation theory, extended to include the orientations degrees of freedom and hexadecupole deformations, for optimized orientations, the {sup 48}Ca+{sup 244}Pu{yields}{sup 292}114* reaction is shown to be a 'compact' hot fusion reaction. The barrier is highest (hot fusion) and interaction radius smallest (compact), which occur for the collisions in the direction of the minor axis of the deformed reaction partner (i.e. for 90 deg. orientation of {sup 244}Pu). In addition to the {sup 48}Ca+{sup 244}Pu reaction valley, a number of other new reaction valleys (target-projectile combinations) are shown to arise for the 'optimally oriented hot' fusion process, the {sup 48}Ca+{sup 244}Pu being the best (lowest barrier) and {sup 54}Ti+{sup 238}U as the next possible best reaction for forming the cold compound nucleus {sup 292}114*. A similar reaction valley for {sup 48}Ca+{sup 244}Pu is found absent in the 'optimally oriented cold' fusion process.

  9. Cross sections and reaction rates of relevance to aeronomy

    SciTech Connect

    Fox, J.L. )

    1991-01-01

    Experimental and theoretical data relevant to models and measurements of the chemical and thermal structures and luminosity of the thermospheres of the earth and planets published during the last four years are surveyed. Among chemical processes, attention is given to ion-molecule reactions, dissociative recombination of molecular ions, and reactions between neutral species. Both reactions between ground state species and species in excited states are considered, including energy transfer and quenching. Measured and calculated cross sections for interactions of solar radiation with atmospheric species, such as photoabsorption, photoionization, and photodissociation and related processes are surveyed.

  10. Probing dynamics of fusion reactions through cross-section and spin distribution measurement

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Behera, B. R.; Singh, Gulzar; Singh, Varinderjit; Madhavan, N.; Muralithar, S.; Nath, S.; Gehlot, J.; Mohanto, G.; Mukul, Ish; Siwal, D.; Thakur, M.; Kapoor, K.; Sharma, P.; Banerjee, T.; Jhingan, A.; Varughese, T.; Bala, Indu; Nayak, B. K.; Saxena, A.; Chatterjee, M. B.; Stevenson, P. D.

    2016-05-01

    Present work aims to explicate the effect of entrance channel mass asymmetry on fusion dynamics for the Compound Nucleus 80Sr populated through two different channels, 16O+64Zn and 32S+48Ti, using cross-section and spin distribution measurements as probes. The evaporation spectra studies for these systems, reported earlier indicate the presence of dynamical effects for mass symmetric 32S+48Ti system.The CCDEF and TDHF calculations have been performed for both the systems and an attempt has been made to explain the reported deviations in the α-particle spectrum for the mass symmetric system.

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

    ERIC Educational Resources Information Center

    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…

  12. A Priori Estimation of Rate Constants for Unimolecular Decomposition Reactions

    DTIC Science & Technology

    1979-02-01

    priori theoretical predictions for the decomposition rate of the formyl and the methoxy radicals have been made by application of the Rice-Ramsperger...Kassel-Marcus Theory. An ArrheniLus rate coefficient expression is derived for the formyl radical decomposition, and a modified Arrhenius type rate...9 IV. A PREDICTED RATE CONSTANT FOR FORMYL RADICAL DECOMPOSITION. .. .... .................... ........19 V. SUMMtARY

  13. Radioscapholunate Fusions

    PubMed Central

    McGuire, Duncan Thomas; Bain, Gregory Ian

    2012-01-01

    Radiocarpal fusions are performed for a variety of indications, most commonly for debilitating painful arthritis. The goal of a wrist fusion is to fuse the painful, diseased joints and to preserve motion through the healthy joints. Depending on the extent of the disease process, radiocarpal fusions may take the form of radiolunate, radioscapholunate, or total wrist fusions. Surgical techniques and instrumentation have advanced over the last few decades, and consequently the functional outcomes have improved and complications decreased. Techniques for partial carpal fusions have improved and now include distal scaphoid and triquetrum excision, which improves range of motion and fusion rates. In this article we discuss the various surgical techniques and fixation methods available and review the corresponding evidence in the literature. The authors' preferred surgical technique of radioscapholunate fusion with distal scaphoid and triquetrum excision is outlined. New implants and new concepts are also discussed. PMID:24179717

  14. Doc2b promotes GLUT4 exocytosis by activating the SNARE-mediated fusion reaction in a calcium- and membrane bending–dependent manner

    PubMed Central

    Yu, Haijia; Rathore, Shailendra S.; Davis, Eric M.; Ouyang, Yan; Shen, Jingshi

    2013-01-01

    The glucose transporter GLUT4 plays a central role in maintaining body glucose homeostasis. On insulin stimulation, GLUT4-containing vesicles fuse with the plasma membrane, relocating GLUT4 from intracellular reservoirs to the cell surface to uptake excess blood glucose. The GLUT4 vesicle fusion reaction requires soluble N-ethylmaleimide–sensitive factor attachment protein receptors (SNAREs) as the core fusion engine and a group of regulatory proteins. In particular, the soluble C2-domain factor Doc2b plays a key role in GLUT4 vesicle fusion, but its molecular mechanism has been unclear. Here we reconstituted the SNARE-dependent GLUT4 vesicle fusion in a defined proteoliposome fusion system. We observed that Doc2b binds to GLUT4 exocytic SNAREs and potently accelerates the fusion kinetics in the presence of Ca2+. The stimulatory activity of Doc2b requires intact Ca2+-binding sites on both the C2A and C2B domains. Using electron microscopy, we observed that Doc2b strongly bends the membrane bilayer, and this membrane-bending activity is essential to the stimulatory function of Doc2b in fusion. These results demonstrate that Doc2b promotes GLUT4 exocytosis by accelerating the SNARE-dependent fusion reaction by a Ca2+- and membrane bending–dependent mechanism. Of importance, certain features of Doc2b function appear to be distinct from how synaptotagmin-1 promotes synaptic neurotransmitter release, suggesting that exocytic Ca2+ sensors may possess divergent mechanisms in regulating vesicle fusion. PMID:23427263

  15. Doc2b promotes GLUT4 exocytosis by activating the SNARE-mediated fusion reaction in a calcium- and membrane bending-dependent manner.

    PubMed

    Yu, Haijia; Rathore, Shailendra S; Davis, Eric M; Ouyang, Yan; Shen, Jingshi

    2013-04-01

    The glucose transporter GLUT4 plays a central role in maintaining body glucose homeostasis. On insulin stimulation, GLUT4-containing vesicles fuse with the plasma membrane, relocating GLUT4 from intracellular reservoirs to the cell surface to uptake excess blood glucose. The GLUT4 vesicle fusion reaction requires soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) as the core fusion engine and a group of regulatory proteins. In particular, the soluble C2-domain factor Doc2b plays a key role in GLUT4 vesicle fusion, but its molecular mechanism has been unclear. Here we reconstituted the SNARE-dependent GLUT4 vesicle fusion in a defined proteoliposome fusion system. We observed that Doc2b binds to GLUT4 exocytic SNAREs and potently accelerates the fusion kinetics in the presence of Ca(2+). The stimulatory activity of Doc2b requires intact Ca(2+)-binding sites on both the C2A and C2B domains. Using electron microscopy, we observed that Doc2b strongly bends the membrane bilayer, and this membrane-bending activity is essential to the stimulatory function of Doc2b in fusion. These results demonstrate that Doc2b promotes GLUT4 exocytosis by accelerating the SNARE-dependent fusion reaction by a Ca(2+)- and membrane bending-dependent mechanism. Of importance, certain features of Doc2b function appear to be distinct from how synaptotagmin-1 promotes synaptic neurotransmitter release, suggesting that exocytic Ca(2+) sensors may possess divergent mechanisms in regulating vesicle fusion.

  16. Fusion Method for Solubility and Dissolution Rate Enhancement of Ibuprofen Using Block Copolymer Poloxamer 407.

    PubMed

    Dugar, Rohit P; Gajera, Bhavin Y; Dave, Rutesh H

    2016-12-01

    Aim of current research was to prepare ibuprofen-poloxamer 407 binary mixtures using fusion method and characterize them for their physicochemical and performance properties. Binary mixtures of ibuprofen and poloxamer were prepared in three different ratios (1:0.25, 1:0.5, and 1:0.75, respectively) using a water-jacketed high shear mixer. In vitro dissolution and saturation solubility studies were carried out for the drug, physical mixtures, and formulations for all ratios in de-ionized water, 0.1 N HCl (pH = 1.2), and phosphate buffer (pH = 7.2). Thermal and physical characterization of samples was done using modulated differential scanning calorimetry (mDSC), X-ray powder diffraction (XRD), and infrared spectroscopy (FTIR). Flow properties were evaluated using a powder rheometer. Maximum solubility enhancement was seen in acidic media for fused formulations where the ratio 1:0.75 had 18-fold increase. In vitro dissolution studies showed dissolution rate enhancement for physical mixtures and the formulations in all three media. The most pronounced effect was seen for formulation (1:0.75) in acidic media where the cumulative drug release was 58.27% while for drug, it was 3.67%. Model independent statistical methods and ANOVA based methods were used to check the significance of difference in the dissolution profiles. Thermograms from mDSC showed a characteristic peak for all formulations with Tpeak of around 45°C which suggested formation of a eutectic mixture. XRD data displayed that crystalline nature of ibuprofen was intact in the formulations. This work shows the effect of eutectic formation and micellar solubilization between ibuprofen and poloxamer at the given ratios on its solubility and dissolution rate enhancement.

  17. Rates of primary electron transfer reactions in the photosystem I reaction center reconstituted with different quinones as the secondary acceptor

    SciTech Connect

    Kumazaki, Shigeichi; Kandori, Hideki; Yoshihara, Keitaro ); Iwaki, Masayo; Itoh, Shigeru ); Ikegamu, Isamu )

    1994-10-27

    Rates of sequential electron transfer reactions from the primary electron donor chlorophyll dimer (P700) to the electron acceptor chlorophyll a-686 (A[sub 0]) and to the secondary acceptor quinone (Q[sub [phi

  18. Reaction rate oscillations during catalytic CO oxidation: A brief overview

    NASA Astrophysics Data System (ADS)

    Tsotsis, T. T.; Sane, R. C.

    1987-04-01

    It is not the intent here to present a comprehensive review of the dynamic behavior of the catalytic oxidation of CO. This reaction is one of the most widely studied in the field of catalysis. A review paper by Engel and Ertl has examined the basic kinetic and mechanistic aspects, and a comprehensive paper by Razon and Schmitz was recently devoted to its dynamic behavior. Those interested in further study of the subject should consult these reviews and a number of general review papers on catalytic reaction dynamics. The goal is to present a brief overview of certain interesting aspects of the dynamic behavior of this reaction and to discuss a few questions and issues, which are still the subject of study and debate.

  19. Reaction rate oscillations during catalytic CO oxidation: A brief overview

    NASA Technical Reports Server (NTRS)

    Tsotsis, T. T.; Sane, R. C.

    1987-01-01

    It is not the intent here to present a comprehensive review of the dynamic behavior of the catalytic oxidation of CO. This reaction is one of the most widely studied in the field of catalysis. A review paper by Engel and Ertl has examined the basic kinetic and mechanistic aspects, and a comprehensive paper by Razon and Schmitz was recently devoted to its dynamic behavior. Those interested in further study of the subject should consult these reviews and a number of general review papers on catalytic reaction dynamics. The goal is to present a brief overview of certain interesting aspects of the dynamic behavior of this reaction and to discuss a few questions and issues, which are still the subject of study and debate.

  20. Dynamical Dipole mode in the 40,48 Ca +152,144Sm fusion reactions at 11 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Parascandolo, C.; Pierroutsakou, D.; Alba, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Agodi, C.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; La Commara, M.; Martin, B.; Mazzocchi, C.; Mazzocco, M.; Rizzo, C.; Romoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifirò, A.; Trimarchi, M.

    2016-05-01

    The excitation of the dynamical dipole mode along the fusion path was investigated in the formation of a heavy compound nucleus in the A=190 mass region. To form the compound nucleus, the 40Ca + 152Sm and 48Ca + 144Sm reactions were employed at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for the first time. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.

  1. Study of the 20,22Ne+20,22Ne and 10,12,13,14,15C+12C Fusion Reactions with MUSIC

    NASA Astrophysics Data System (ADS)

    Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.; Carnelli, P. F. F.; DiGiovine, B.; Esbensen, H.; Hoffman, C. R.; Jiang, C. L.; Kay, B. P.; Lai, J.; Nusair, O.; Pardo, R. C.; Santiago-Gonzalez, D.; Talwar, R.; Ugalde, C.

    2016-05-01

    A highly efficient MUlti-Sampling Ionization Chamber (MUSIC) detector has been developed for measurements of fusion reactions. A study of fusion cross sections in the 10,12,13,14,15C+12C and 20,22Ne+20,22Ne systems has been performed at ATLAS. Experimental results and comparison with theoretical predictions are presented. Furthermore, results of direct measurements of the 17O(α, n)20Ne, 23Ne(α, p)26Mg and 23Ne(α, n)26Al reactions will be discussed.

  2. Isospin Dependence of Incomplete Fusion Reactions at 25 MeV/Nucleon

    SciTech Connect

    Amorini, F.; Agodi, C.; Alba, R.; Anzalone, A.; Coniglione, R.; Di Pietro, A.; Figuera, P.; Maiolino, C.; Santonocito, D.; Sapienza, P.; Cardella, G.; Papa, M.; De Filippo, E.; Pagano, A.; Pirrone, S.; Verde, G.; Giuliani, G.; Berceanu, I.; Pop, A.; Cavallaro, S.

    2009-03-20

    {sup 40}Ca+{sup 40,48}Ca,{sup 46}Ti reactions at 25 MeV/nucleon have been studied using the 4{pi} CHIMERA detector. An isospin effect on the competition between fusionlike and binarylike reaction mechanisms has been observed. The probability of producing a heavy residue is lower in the case of N{approx_equal}Z colliding systems as compared to the case of reactions induced on the neutron rich {sup 48}Ca target. Predictions based on constrained molecular dynamics II calculations show that the competition between fusionlike and binary reactions in the selected centrality bins can constrain the parametrization of the symmetry energy and its density dependence in the nuclear equation of state.

  3. PRODUCTION OF {sup 9}Be THROUGH THE {alpha}-FUSION REACTION OF METAL-POOR COSMIC RAYS AND STELLAR FLARES

    SciTech Connect

    Kusakabe, Motohiko; Kawasaki, Masahiro E-mail: kawasaki@icrr.u-tokyo.ac.jp

    2013-04-10

    Spectroscopic observations of metal-poor stars have indicated possible {sup 6}Li abundances that are much larger than the primordial abundance predicted in the standard big bang nucleosynthesis model. Possible mechanisms of {sup 6}Li production in metal-poor stars include pregalactic and cosmological cosmic-ray (CR) nucleosynthesis and nucleosynthesis by flare-accelerated nuclides. We study {sup 9}Be production via two-step {alpha}-fusion reactions of CR or flare-accelerated {sup 3,4}He through {sup 6}He and {sup 6,7}Li, in pregalactic structure, intergalactic medium, and stellar surfaces. We solve transfer equations of CR or flare particles and calculate nuclear yields of {sup 6}He, {sup 6,7}Li, and {sup 9}Be taking account of probabilities of processing {sup 6}He and {sup 6,7}Li into {sup 9}Be via fusions with {alpha} particles. Yield ratios, i.e., {sup 9}Be/{sup 6}Li, are then calculated for the CR and flare nucleosynthesis models. We suggest that the future observations of {sup 9}Be in metal-poor stars may find enhanced abundances originating from metal-poor CR or flare activities.

  4. Interactive Program System for Integration of Reaction Rate Equations.

    ERIC Educational Resources Information Center

    Chesick, John P.

    1988-01-01

    Describes a Pascal-language based kinetics rate package for the microcomputer. Considers possible ecological uses for the program and illustrates results for several rate laws. Discusses hardware and software needs for adequate operation. (ML)

  5. Quick and Easy Rate Equations for Multistep Reactions

    ERIC Educational Resources Information Center

    Savage, Phillip E.

    2008-01-01

    Students rarely see closed-form analytical rate equations derived from underlying chemical mechanisms that contain more than a few steps unless restrictive simplifying assumptions (e.g., existence of a rate-determining step) are made. Yet, work published decades ago allows closed-form analytical rate equations to be written quickly and easily for…

  6. Quick and Easy Rate Equations for Multistep Reactions

    ERIC Educational Resources Information Center

    Savage, Phillip E.

    2008-01-01

    Students rarely see closed-form analytical rate equations derived from underlying chemical mechanisms that contain more than a few steps unless restrictive simplifying assumptions (e.g., existence of a rate-determining step) are made. Yet, work published decades ago allows closed-form analytical rate equations to be written quickly and easily for…

  7. Cross section systematics for the lightest Bi and Po nuclei produced in complete fusion reactions with heavy ions

    SciTech Connect

    Andreyev, A.N.; Ackermann, D.; Muenzenberg, G.; Antalic, S.; Saro, S.; Streicher, B.; Darby, I.G.; Page, R.D.; Wiseman, D.R.; Franchoo, S.; Hessberger, F.P.; Kuusiniemi, P.; Lommel, B.; Kindler, B.; Mann, R.; Sulignano, B.; Hofmann, S.; Huyse, M.; Vel, K. van de; Duppen, P. van

    2005-07-01

    The production of the very neutron-deficient nuclides {sup 184-192}Bi and {sup 186-192}Po in the vicinity of the neutron midshell at N = 104 has been studied by using heavy-ion-induced complete fusion reactions in a series of experiments at the velocity filter SHIP. The cross sections for the xn and pxn evaporation channels of the {sup 46}Ti+{sup 144}Sm{yields}{sup 190}Po*,{sup 98}Mo+{sup 92}Mo{yields}{sup 190}Po*,{sup 50,52}Cr+{sup 142}Nd{yields}{sup 192,194}Po*, and {sup 94,95}Mo+{sup 93}Nb{yields}{sup 187,188}Bi* reactions were measured. The results obtained, together with the previously known cross section data for the heavier Bi and Po nuclides, are compared with the results of statistical model calculations carried out with the HIVAP code. It is shown that a satisfactory description of the experimental data requires a significant (up to 35%) reduction of the theoretical fission barriers. The optimal reactions for production of the lightest Bi and Po isotopes are discussed.

  8. Search for entrance channel effects in sub-barrier fusion reactions

    SciTech Connect

    Charlop, A.; Bierman, J.; Drebi, Z.; Garcia, A.; Gil, S.; Prindle, D.; Sonzogni, A.; Vandenbosch, R.; Ye, D. )

    1995-02-01

    In order to explore the possibility that previously observed anomalous mean angular momenta are related to the mass asymmetry of the entrance channel, we have studied three systems, [sup 28]Si + [sup 142]Ce, [sup 32]S + [sup 138]Ba, and [sup 48]Ti + [sup 122]Sn, all of which lead to the same compound nucleus, [sup 170]Hf. Gamma ray multiplicities for fusion have been determined using an electrostatic deflector and time of flight to identify the evaporation residues. Results have been obtained for bombarding energies from approximately 20% above the Coulomb barrier down to nearly 10% below the barrier. The mean angular momenta deduced from the gamma ray multiplicities are generally well reproduced by coupled channels calculations employing known deformation parameters and an estimate of the transfer strength and do not show any evidence of an unexpected effect related to the mass asymmetry of the entrance channel.

  9. Development of the new approach to the diffusion-limited reaction rate theory

    SciTech Connect

    Veshchunov, M. S.

    2012-04-15

    The new approach to the diffusion-limited reaction rate theory, recently proposed by the author, is further developed on the base of a similar approach to Brownian coagulation. The traditional diffusion approach to calculation of the reaction rate is critically analyzed. In particular, it is shown that the traditional approach is applicable only in the special case of reactions with a large reaction radius and the mean inter-particle distances, and become inappropriate in calculating the reaction rate in the case of a relatively small reaction radius. In the latter case, most important for chemical reactions, particle collisions occur not in the diffusion regime but mainly in the kinetic regime characterized by homogeneous (random) spatial distribution of particles on the length scale of the mean inter-particle distance. The calculated reaction rate for a small reaction radius in three dimensions formally (and fortuitously) coincides with the expression derived in the traditional approach for reactions with a large reaction radius, but notably deviates at large times from the traditional result in the planar two-dimensional geometry. In application to reactions on discrete lattice sites, new relations for the reaction rate constants are derived for both three-dimensional and two-dimensional lattices.

  10. What is the Rate-Limiting Step of a Multistep Reaction?

    ERIC Educational Resources Information Center

    Murdoch, Joseph R.

    1981-01-01

    Presents information concerning a fundamental concept for understanding reaction rate, the idea of a rate-limiting step for a chemical reaction. Discusses problems in using flow analogies and introduces an alternative approach to finding the rate-limiting step based on locating the transition state of highest energy. (CS)

  11. Sensitivity of fusion and quasi-elastic barrier distributions of {sub 16}O+{sub 144}Sm reaction on the coupling radius parameter

    SciTech Connect

    Zamrun, Muhammad; Usman, Ida; Variani, Viska Inda; Kassim, Hasan Abu

    2014-03-05

    We study the heavy-ion collision at sub-barrier energies of {sub 16}O+{sub 144}Sm system using full order coupled-channels formalism. We especially investigate the sensitivity of fusion and quasi-elastic barrier distributions for this system on the coupling radius parameter. We found that the coupled-channels calculations of the fusion and the quasi-elastic barrier distributions are sensitive to the coupling radius for this reaction in contrast to the fusion and quasi-elastic cross section. Our study indicates that the larger coupling radius, i.e., r{sub coup}=1.20, is required by the experimental quasi-elastic barrier distribution. However, the experimental fusion barrier distribution compulsory the small value, i.e., r{sub coup}=1.06.

  12. Excitation functions for the production of superheavy nuclei in cold fusion reactions

    SciTech Connect

    Smolanczuk, Robert

    2000-01-01

    Excitation energy dependence of the cross sections of the reactions {sup 208}Pb{sub 126}({sup 50}Ti{sub 28},1n){sup 257}Rf{sub 153} and {sup 208}Pb{sub 126}({sup 58}Fe{sub 32},1n){sup 265}Hs{sub 157} is calculated and compared with the experimental data measured at GSI-Darmstadt. Such a dependence is also calculated for the reaction {sup 208}Pb{sub 126}({sup 86}Kr{sub 50},1n){sup 293}118{sub 175} reported recently by the Berkeley group, and for reactions which may lead to the synthesis of element 119 and production of its odd-Z descendants. Recommendations for future experiments based on the present study are presented. (c) 1999 The American Physical Society.

  13. Dynamic ventricular overdrive stimulation in atrial fibrillation: effects on ventricular rate irregularity, ventricular pacing, and fusion beats.

    PubMed

    Nölker, Georg; Gutleben, Klaus-Jürgen; Asbach, Stefan; Ritscher, Guido; Marschang, Harald; Sinha, Anil M; Boileau, Peter; Benser, Michael E; Hallier, Benoit; Hümmer, Alexander; Brachmann, Johannes

    2011-12-01

    In pacemaker patients with preserved atrio-ventricular (AV) conduction, atrial fibrillation (AF) can lead to symptomatic ventricular rate irregularity and loss of ventricular stimulation. We tested if dynamic ventricular overdrive (DVO) as a potentially pacemaker-integrated algorithm could improve both aspects. Different settings of DVO and ventricular-ventricular-inhibited-pacing (VVI) with different base rates were tested in two consecutive phases during electrophysiological studies for standard indications. Mean heart rate (HR), HR irregularity and percentage of ventricular pacing were evaluated. A fusion index (FI) indicative of the proportion of fusion beats was calculated for each stimulation protocol. Dynamic ventricular overdrive from the right ventricular apex was acutely applied in 38 patients (11 females, mean age 62.1 ± 11.5 years) with sustained AF and preserved AV conduction. Dynamic ventricular overdrive at LOW/MEDIUM setting increased the amount of ventricular pacing compared with VVI pacing at 60, 70, and 80 beats per minute (bpm; to 81/85% from 11, 25, and 47%, respectively; P < 0.05). It also resulted in a maximum decrease in interval differences (to 48 ± 18 ms from 149 ± 28, 117 ± 38, and 95 ± 46 ms, respectively; P < 0.05) and fusion (to 0.13 from 0.41, 0.42, and 0.36, respectively; P < 0.05) compared with VVI pacing at 60, 70, and 80 bpm. However, the application of DVO resulted in a significant increase in HR compared with intrinsic rhythm and VVI pacing at 80 bpm (to 97 bpm from 89 and 94 bpm, respectively; P < 0.05). Dynamic ventricular overdrive decreases HR irregularity and increases ventricular pacing rate compared with VVI pacing at fixed elevated base rates and spontaneous rhythm. Fusion index might help to refine information on pacing percentages provided by device counters.

  14. The temperature dependence of the rate constant for the reaction of hydroxyl radicals with nitric acid

    NASA Technical Reports Server (NTRS)

    Kurylo, M. J.; Cornett, K. D.; Murphy, J. L.

    1982-01-01

    The rate constant for the reaction of hydroxyl radicals with nitric acid in the 225-443 K temperature range has been measured by means of the flash photolysis resonance fluorescence technique. Above 300 K, the rate constant levels off in a way that can only be explained by the occurrence of two reaction channels, of which one, operative at low temperatures, proceeds through the formation of an adduct intermediate. The implications of these rate constant values for stratospheric reaction constants is discussed.

  15. The temperature dependence of the rate constant for the reaction of hydroxyl radicals with nitric acid

    NASA Technical Reports Server (NTRS)

    Kurylo, M. J.; Cornett, K. D.; Murphy, J. L.

    1982-01-01

    The rate constant for the reaction of hydroxyl radicals with nitric acid in the 225-443 K temperature range has been measured by means of the flash photolysis resonance fluorescence technique. Above 300 K, the rate constant levels off in a way that can only be explained by the occurrence of two reaction channels, of which one, operative at low temperatures, proceeds through the formation of an adduct intermediate. The implications of these rate constant values for stratospheric reaction constants is discussed.

  16. Diffusion-controlled reaction rate to an active site

    NASA Astrophysics Data System (ADS)

    Traytak, S. D.

    1995-02-01

    The diffusion-controlled reactions of chemically anisotropic reactants are treated for the simplest model of Solc and Stockmayer (Intern. J. Chem. Kinet. 5 (1973) 733) in the absence of rotational diffusion. Using the dual series relations approach we can find the effective steric factor with any necessary accuracy. A few simple analytical approximations for the effective steric factor are proposed. The derived results we compare with the relevant analytical approximations and numerical calculations available in the literature.

  17. Fluctuation enhanced electrochemical reaction rates at the nanoscale

    PubMed Central

    García-Morales, Vladimir; Krischer, Katharina

    2010-01-01

    The electrode potential constitutes a dynamical variable whenever an electrode is resistively coupled to the electric circuit. We show that at the nanoscale, the discreteness and stochasticity of an electron transfer event causes fluctuations of the electrode potential that render all elementary electrochemical reactions to be faster on a nanoelectrode than predicted by the macroscopic (Butler–Volmer) electrochemical kinetics. This phenomenon is substantiated by means of a generalized (electro)chemical master equation. PMID:20176966

  18. The Trojan Horse Method as a tool for investigating astrophysically relevant fusion reactions

    NASA Astrophysics Data System (ADS)

    Lamia, L.; Spitaleri, C.; Tognelli, E.; Degl'Innocenti, S.; Pizzone, R. G.; Prada Moroni, P. G.

    2016-05-01

    The Trojan Horse Method (THM) has been largely adopted for investigating astrophysically relevant charged-particle induced reactions at Gamow energies. Indeed, THM allows one to by pass extrapolation procedures, thus overcoming this source of uncertainty. Here, the recent THM results and their impact in astrophysics are going to be discussed.

  19. Effect of delivery condition on desorption rate of ZrCo metal hydride bed for fusion fuel cycle

    SciTech Connect

    Kang, H.G.; Yun, S.H.; Chung, D.; Oh, Y.H.; Chang, M.H.; Cho, S.; Chung, H.; Song, K.M.

    2015-03-15

    For the safety of fusion fuel cycle, hydrogen isotope gases including tritium are stored as metal hydride form. To satisfy fueling requirement of fusion machine, rapid delivery from metal hydride bed is one of major factors for the development of tritium storage and delivery system. Desorption from metal hydride depends on the operation scenario by pressure and temperature control of the bed. The effect of operation scenario and pump performance on desorption rate of metal hydride bed was experimentally investigated using ZrCo bed. The results showed that the condition of pre-heating scenario before actual delivery of gas affected the delivery performance. Different pumps were connected to desorption line from bed and the effect of pump capacity on desorption rate were also found to be significant. (authors)

  20. Probing the Structure of {sup 74}Ge Nucleus with Coupled-channels Analysis of {sup 74}Ge+{sup 74}Ge Fusion Reaction

    SciTech Connect

    Zamrun F, Muhammad; Kasim, Hasan Abu

    2010-12-23

    We study the fusion reaction of the {sup 74}Ge+{sup 74}Ge system in term of the full order coupled-channels formalism. We especially calculated the fusion cross section as well as the fusion barrier distribution of this reaction using transition matrix suggested by recent Coulomb excitation experiment. We compare the results with the one obtained by coupling matrix based on pure vibrational and rotational models. The present coupled-channels calculations for the barrier distributions obtained using experiment coupling matrix is in good agreement with the one obtained with vibrational model, in contrast to the rotational model. This is indicates that {sup 74}Ge nucleus favor a spherical shape than a deformed shape in its ground state. Our results will resolve the debates concerning the structure of this nucleus.

  1. Dynamical dipole mode in fusion reactions at 16 MeV/nucleon and beam energy dependence

    NASA Astrophysics Data System (ADS)

    Pierroutsakou, D.; Martin, B.; Agodi, C.; Alba, R.; Baran, V.; Boiano, A.; Cardella, G.; Colonna, M.; Coniglione, R.; Filippo, E. De; Zoppo, A. Del; Toro, M. Di; Inglima, G.; Glodariu, T.; Commara, M. La; Maiolino, C.; Mazzocco, M.; Pagano, A.; Parascandolo, C.; Piattelli, P.; Pirrone, S.; Rizzo, C.; Romoli, M.; Sandoli, M.; Santonocito, D.; Sapienza, P.; Signorini, C.

    2009-08-01

    High-energy γ rays and light charged particles from the Ar36+Zr96 and Ar40+Zr92 reactions at Elab=16 and 15.1 MeV/nucleon, respectively, were measured in coincidence with evaporation residues by means of the MEDEA multidetector array coupled to four parallel plate avalanche counters. The aim of this experiment was to investigate the prompt γ radiation, emitted in the decay of the dynamical dipole mode, in the ~16 MeV/nucleon energy range and to map its beam energy dependence, comparing the present results with our previous ones obtained at lower energies. The studied reactions populate, through entrance channels having different charge asymmetries, a compound nucleus in the region of Ce under the same conditions of excitation energy and spin. Light charged particle energy spectra were used to pin down the average excitation energy and the average mass of the system. By studying the γ-ray spectra of the charge symmetric reaction Ar40+Zr92, the statistical giant dipole resonance (GDR) parameters and angular distribution were extracted, and a comparison of the linearized 90°γ-ray spectra of the two reactions revealed a 12% extra yield in the GDR energy region for the more charge asymmetric system. The center-of-mass angular distribution data of this extra γ yield, compatible with a dipole oscillating along the symmetry axis of the dinuclear system, support its dynamical nature. The experimental findings are compared with theoretical predictions performed within a Boltzmann-Nordheim-Vlasov transport model and based on a collective bremsstrahlung analysis of the entrance channel reaction dynamics. An interesting sensitivity to the symmetry term of the equation of state and to in-medium effects on nucleon-nucleon (nn) cross sections is finally discussed.

  2. Ab initio many-body calculations of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions.

    PubMed

    Navrátil, Petr; Quaglioni, Sofia

    2012-01-27

    We apply the ab initio no-core shell model combined with the resonating-group method approach to calculate the cross sections of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions. These are important reactions for the big bang nucleosynthesis and the future of energy generation on Earth. Starting from a selected similarity-transformed chiral nucleon-nucleon interaction that accurately describes two-nucleon data, we performed many-body calculations that predict the S factor of both reactions. Virtual three-body breakup effects are obtained by including excited pseudostates of the deuteron in the calculation. Our results are in satisfactory agreement with experimental data and pave the way for microscopic investigations of polarization and electron-screening effects, of the (3)H(d,γn)(4)He bremsstrahlung and other reactions relevant to fusion research.

  3. A comparison of simple reaction time, visual discrimination and critical flicker fusion frequency in professional divers at elevated pressure.

    PubMed

    Tikkinen, Janne; Wuorimaa, Tomi; Siimes, Martti A

    2016-06-01

    Inert gas narcosis (IGN) impairs cognitive performance and some divers are more susceptible to IGN than others. We compared the sensitivity of two reaction time tests to detect changes in performance at pressure and compared these results with critical flicker fusion frequency (CFF) changes at the same ambient pressures. The study assessed simple reaction time (RT), mean time correct of the discrimination reaction time (MTC) and CFF in 30 professional divers breathing air at 101 kPa and 608 kPa in a hyperbaric chamber. RT and MTC increased at 608 kPa by 5.1 ± 9.4% (P = 0.04) and 7.3 ± 12.3% (P = 0.01) respectively. RT decreased to pre-compression level after decompression and MTC decreased to a level lower than pre-compression (P < 0.001) values. CFF increased by 2.5 ± 2.8% (P < 0.001) at 608 kPa. CFF decreased to pre-compression level after decompression. An increase in CFF was inversely correlated with a decrease in RT (r = 0.38, P = 0.04) and in MTC (r = 0.43, P = 0.02) at 608 kPa. Response speeds of the same subjects were impaired in both reaction time tasks at 608 kPa, whereas CFF increased at depth. An association between changes in response times and changes in CFF suggests that divers susceptible to IGN may also be susceptible to the effects of elevated oxygen partial pressure. If this holds true, the future selection of professional divers could be improved by the use of simple cognitive tests.

  4. Rate of adverse reactions to more than 1 series of viscosupplementation.

    PubMed

    Webber, Tracy A; Webber, Anthony E; Matzkin, Elizabeth

    2012-04-01

    Viscosupplementation, hyaluronic acid treatment, is an ancillary method for treating patients with symptomatic stage I or II osteoarthritis. Previous studies reported that local reactions occurred more frequently in patients receiving >1 course of treatment compared with patients receiving their first course of treatment. One (2%) of 42 first series patients and 4 (21%) of 19 of repeated series patients had adverse reactions severe enough to seek unscheduled care.This study was performed to determine whether patients receiving >1 series of viscosupplementation had an increased adverse reaction rate. A retrospective chart review was performed on all patients who received >1 series of viscosupplementation during the study. A local adverse reaction was defined as acute swelling and pain in the knee, with no injury or trauma within 72 hours after hyaluronic acid injection.Twenty-eight knees received >1 series of viscosupplementation. The adverse reaction rate to second series injections was 1.28% (3.57% of knees). The adverse reaction rate to ≥3 series was 0.9% (6.67% of knees). This adverse reaction rate was significantly less than the 21% reported in previous studies for multiple series injections (z=-1.90; P<.05) and is not significantly different than the 2% rate of adverse reactions reported for first series injections. No significant difference existed in the adverse reaction rates between 2 series and ≥3 series of viscosupplementation.The current study suggests that the rate of adverse reaction was low at 1.28% of second series viscosupplementation.

  5. Gamma-ray fast-timing coincidence measurements from the 18O+18O fusion-evaporation reaction using a mixed LaBr3-HPGe array.

    PubMed

    Alharbi, T; Mason, P J R; Regan, P H; Podolyák, Zs; Mărginean, N; Nakhostin, M; Bowry, M; Bucurescu, D; Căta-Danil, G; Căta-Danil, I; Deleanu, D; Filipescu, D; Glodariu, T; Ghiţă, D; Mărginean, R; Mihai, C; Negret, A; Pascu, S; Sava, T; Stroe, L; Suliman, G; Zamfir, N V; Bruce, A M; Rodriguez Triguero, C; Bender, P C; Garg, U; Erduran, M N; Kusoglu, A; Bostan, M; Detistov, P; Alkhomashi, N; Sinha, A K; Chakrabarti, R; Ghugre, S S

    2012-07-01

    We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic transition rates in the pico-to-nanosecond time regime in 33,34P and 33S following fusion-evaporation reactions between an 18O beam and an isotopically enriched 18O implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, Iπ=4- "intruder" state previously reported in the N=19 isotone 34P. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f7/2→d5/2 single particle transition. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Error Rate Comparison during Polymerase Chain Reaction by DNA Polymerase

    DOE PAGES

    McInerney, Peter; Adams, Paul; Hadi, Masood Z.

    2014-01-01

    As larger-scale cloning projects become more prevalent, there is an increasing need for comparisons among high fidelity DNA polymerases used for PCR amplification. All polymerases marketed for PCR applications are tested for fidelity properties (i.e., error rate determination) by vendors, and numerous literature reports have addressed PCR enzyme fidelity. Nonetheless, it is often difficult to make direct comparisons among different enzymes due to numerous methodological and analytical differences from study to study. We have measured the error rates for 6 DNA polymerases commonly used in PCR applications, including 3 polymerases typically used for cloning applications requiring high fidelity. Errormore » rate measurement values reported here were obtained by direct sequencing of cloned PCR products. The strategy employed here allows interrogation of error rate across a very large DNA sequence space, since 94 unique DNA targets were used as templates for PCR cloning. The six enzymes included in the study, Taq polymerase, AccuPrime-Taq High Fidelity, KOD Hot Start, cloned Pfu polymerase, Phusion Hot Start, and Pwo polymerase, we find the lowest error rates with Pfu , Phusion, and Pwo polymerases. Error rates are comparable for these 3 enzymes and are >10x lower than the error rate observed with Taq polymerase. Mutation spectra are reported, with the 3 high fidelity enzymes displaying broadly similar types of mutations. For these enzymes, transition mutations predominate, with little bias observed for type of transition.« less

  7. Upper atmosphere research: Reaction rate and optical measurements

    NASA Technical Reports Server (NTRS)

    Stief, L. J.; Allen, J. E., Jr.; Nava, D. F.; Payne, W. A., Jr.

    1990-01-01

    The objective is to provide photochemical, kinetic, and spectroscopic information necessary for photochemical models of the Earth's upper atmosphere and to examine reactions or reactants not presently in the models to either confirm the correctness of their exclusion or provide evidence to justify future inclusion in the models. New initiatives are being taken in technique development (many of them laser based) and in the application of established techniques to address gaps in the photochemical/kinetic data base, as well as to provide increasingly reliable information.

  8. Isotopic resolution of fission fragments from 238U+12C transfer and fusion reactions

    NASA Astrophysics Data System (ADS)

    Caamaño, M.; Rejmund, F.; Derkx, X.; Schmidt, K.-H.; Andouin, L.; Bacri, C.-O.; Barreau, G.; Benlliure, J.; Casarejos, E.; Fernández-Domínguez, B.; Gaudefroy, L.; Golabek, C.; Jurado, B.; Lemasson, A.; Navin, A.; Rejmund, M.; Roger, T.; Shrivastava, A.; Schmitt, C.; Taieb, J.

    2009-10-01

    Recent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238U beam and a 12C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments.

  9. An overview on incomplete fusion reaction dynamics at energy range ∼ 3-8 MeV/A

    SciTech Connect

    Ali, Rahbar; Singh, D.; Ansari, M. Afzal; Kumar, Rakesh; Muralithar, S.; Golda, K. S.; Singh, R. P.; Bhowmik, R. K.; Rashid, M. H.; Guin, R.; Das, S. K.

    2014-08-14

    The information of ICF reaction has been obtained from the measurement of excitation function (EF) of ERs populated in the interaction of {sup 20}Ne and {sup 16}O on {sup 55}Mn, {sup 159}Tb and {sup 156}Gd targets. Sizable enhancement in the measured cross-sections has been observed in α-emitting channels over theoretical predictions, which has been attributed to ICF of the projectile. In order to confirm the findings of the measurements and analysis of EFs, the forward recoil range distributions of ERs populated in {sup 20}Ne+{sup 159}Tb (E ∼165MeV) and {sup 16}O+{sup 156}Gd (E ∼ 72, 82 and 93MeV) systems, have been measured. It has been observed that peaks appearing at different cumulative thicknesses in the stopping medium are related with different degree of linear momentum transfer from projectile to target nucleus by adopting the break-up fusion model consideration. In order to deduce the angular momentum involved in various CF and / or ICF reaction products, spin distribution and side-feeding intensity profiles of radio-nuclides populated via CF and ICF channels in {sup 16}O+{sup 160}Gd system at energy, E ∼ 5.6 MeV/A, have been studied. Spin distribution of ICF products are found to be distinctly different than that observed from CF products.

  10. High-precision (p,t) reaction measurement to determine Ne18(α,p)Na21 reaction rates

    NASA Astrophysics Data System (ADS)

    Matic, A.; van den Berg, A. M.; Harakeh, M. N.; Wörtche, H. J.; Berg, G. P. A.; Couder, M.; Fisker, J. L.; Görres, J.; Leblanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.; Fujita, H.; Wakasa, T.; Hess, P. O.; Brown, B. A.; Schatz, H.

    2009-11-01

    x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the αp process that describes a sequence of (α,p) reactions triggered by the Ne18(α,p)Na21 breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus Mg22 by measuring the Mg24(p,t)Mg22 reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of α-unbound states was identified and precise excitation energies were determined. Based on shell model and α-cluster model calculations we predict the level parameters for determining the stellar reaction rate of Ne18(α,p)Na21 for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.

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

    SciTech Connect

    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, /sup 235/U, /sup 238/U and /sup 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.

  12. Comparison of complication rates of minimally invasive transforaminal lumbar interbody fusion and lateral lumbar interbody fusion: a systematic review of the literature.

    PubMed

    Joseph, Jacob R; Smith, Brandon W; La Marca, Frank; Park, Paul

    2015-10-01

    OBJECT Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) and lateral lumbar interbody fusion (LLIF) are 2 currently popular techniques for lumbar arthrodesis. The authors compare the total risk of each procedure, along with other important complication outcomes. METHODS This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant studies (up to May 2015) that reported complications of either MI-TLIF or LLIF were identified from a search in the PubMed database. The primary outcome was overall risk of complication per patient. Secondary outcomes included risks of sensory deficits, temporary neurological deficit, permanent neurological deficit, intraoperative complications, medical complications, wound complications, hardware failure, subsidence, and reoperation. RESULTS Fifty-four studies were included for analysis of MI-TLIF, and 42 studies were included for analysis of LLIF. Overall, there were 9714 patients (5454 in the MI-TLIF group and 4260 in the LLIF group) with 13,230 levels fused (6040 in the MI-TLIF group and 7190 in the LLIF group). A total of 1045 complications in the MI-TLIF group and 1339 complications in the LLIF group were reported. The total complication rate per patient was 19.2% in the MI-TLIF group and 31.4% in the LLIF group (p < 0.0001). The rate of sensory deficits and temporary neurological deficits, and permanent neurological deficits was 20.16%, 2.22%, and 1.01% for MI-TLIF versus 27.08%, 9.40%, and 2.46% for LLIF, respectively (p < 0.0001, p < 0.0001, p = 0.002, respectively). Rates of intraoperative and wound complications were 3.57% and 1.63% for MI-TLIF compared with 1.93% and 0.80% for LLIF, respectively (p = 0.0003 and p = 0.034, respectively). No significant differences were noted for medical complications or reoperation. CONCLUSIONS While there was a higher overall complication rate with LLIF, MI-TLIF and LLIF both have

  13. Rate Constants for the Reactions of Hydroxyl Radical with Several Alkanes, Cycloalkanes, and Dimethyl Ether

    NASA Technical Reports Server (NTRS)

    DeMore, W.; Bayes, K.

    1998-01-01

    Relative rate experiements were used to measure rate constants and temperature denpendencies of the reactions of OH with propane, n-butane, n-pentane, n-hexane, cyclopropane, cyclobutane, cyclopentane, and dimethyl ether.

  14. Rate Constants for the Reactions of Hydroxyl Radical with Several Alkanes, Cycloalkanes, and Dimethyl Ether

    NASA Technical Reports Server (NTRS)

    DeMore, W.; Bayes, K.

    1998-01-01

    Relative rate experiements were used to measure rate constants and temperature denpendencies of the reactions of OH with propane, n-butane, n-pentane, n-hexane, cyclopropane, cyclobutane, cyclopentane, and dimethyl ether.

  15. Effect of temperature oscillation on chemical reaction rates in the atmosphere

    NASA Technical Reports Server (NTRS)

    Eberstein, I. J.

    1974-01-01

    The effect of temperature fluctuations on atmospheric ozone chemistry is examined by considering the Chapman photochemical theory of ozone transport to calculate globally averaged ozone production rates from mean reaction rates, activation energies, and recombination processes.

  16. Multi-rate cubature Kalman filter based data fusion method with residual compensation to adapt to sampling rate discrepancy in attitude measurement system.

    PubMed

    Guo, Xiaoting; Sun, Changku; Wang, Peng

    2017-08-01

    This paper investigates the multi-rate inertial and vision data fusion problem in nonlinear attitude measurement systems, where the sampling rate of the inertial sensor is much faster than that of the vision sensor. To fully exploit the high frequency inertial data and obtain favorable fusion results, a multi-rate CKF (Cubature Kalman Filter) algorithm with estimated residual compensation is proposed in order to adapt to the problem of sampling rate discrepancy. During inter-sampling of slow observation data, observation noise can be regarded as infinite. The Kalman gain is unknown and approaches zero. The residual is also unknown. Therefore, the filter estimated state cannot be compensated. To obtain compensation at these moments, state error and residual formulas are modified when compared with the observation data available moments. Self-propagation equation of the state error is established to propagate the quantity from the moments with observation to the moments without observation. Besides, a multiplicative adjustment factor is introduced as Kalman gain, which acts on the residual. Then the filter estimated state can be compensated even when there are no visual observation data. The proposed method is tested and verified in a practical setup. Compared with multi-rate CKF without residual compensation and single-rate CKF, a significant improvement is obtained on attitude measurement by using the proposed multi-rate CKF with inter-sampling residual compensation. The experiment results with superior precision and reliability show the effectiveness of the proposed method.

  17. Multi-rate cubature Kalman filter based data fusion method with residual compensation to adapt to sampling rate discrepancy in attitude measurement system

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoting; Sun, Changku; Wang, Peng

    2017-08-01

    This paper investigates the multi-rate inertial and vision data fusion problem in nonlinear attitude measurement systems, where the sampling rate of the inertial sensor is much faster than that of the vision sensor. To fully exploit the high frequency inertial data and obtain favorable fusion results, a multi-rate CKF (Cubature Kalman Filter) algorithm with estimated residual compensation is proposed in order to adapt to the problem of sampling rate discrepancy. During inter-sampling of slow observation data, observation noise can be regarded as infinite. The Kalman gain is unknown and approaches zero. The residual is also unknown. Therefore, the filter estimated state cannot be compensated. To obtain compensation at these moments, state error and residual formulas are modified when compared with the observation data available moments. Self-propagation equation of the state error is established to propagate the quantity from the moments with observation to the moments without observation. Besides, a multiplicative adjustment factor is introduced as Kalman gain, which acts on the residual. Then the filter estimated state can be compensated even when there are no visual observation data. The proposed method is tested and verified in a practical setup. Compared with multi-rate CKF without residual compensation and single-rate CKF, a significant improvement is obtained on attitude measurement by using the proposed multi-rate CKF with inter-sampling residual compensation. The experiment results with superior precision and reliability show the effectiveness of the proposed method.

  18. Determination of photochemical reaction rates using thermal lens spectrometry

    NASA Astrophysics Data System (ADS)

    Astrath, N. G. C.; Astrath, F. B. G.; Shen, J.; Zhou, J.; Michaelian, K. H.; Fairbridge, C.; Malacarne, L. C.; Pedreira, P. R. B.; Baesso, M. L.

    2010-03-01

    Considering the time dependence of the absorption coefficient due to the photo-induced chemical reaction (PCR) and species diffusion, we calculate the temperature rise in the thermal lens (TL) effect and the TL signal at the detector plane. This theoretical approach removes the restriction that the PCR time constant is much greater than the characteristic TL time constant, which was assumed in a previously published model. Aqueous Cr(VI)-diphenylcarbazide solution is investigated, and quantitative experimental results for the thermal, optical and PCR properties of the sample are obtained. The relative difference between the parameters extracted from the same experimental data of the Cr(VI) solution using the previous and present models is found to be less than 5%, showing the present model can be used to study the PCR. Moreover the present model is more general than the previous one.

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

    PubMed

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

    2012-07-14

    In a previous paper [P. G. Jambrina et al., J. Chem. Phys. 135, 034310 (2011)] various calculations of the rate coefficient for the Mu + H(2) → 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 H(2) 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.

  20. Entrance channel dynamics of hot and cold fusion reactions leading to superheavy elements

    NASA Astrophysics Data System (ADS)

    Umar, A. S.; Oberacker, V. E.; Maruhn, J. A.; Reinhard, P.-G.

    2010-06-01

    We investigate the entrance channel dynamics for the reactions Zn70+Pb208 and Ca48+U238 by using the fully microscopic time-dependent Hartree-Fock theory coupled with a density constraint. We calculate excitation energies and capture cross sections relevant for the study of superheavy formations. We discuss the deformation dependence of the ion-ion potential for the Ca48+U238 system and perform an alignment angle averaging for the calculation of the capture cross section. The results show that this approach can generate results in good agreement with experiments and other theories.

  1. Entrance channel dynamics of hot and cold fusion reactions leading to superheavy elements

    SciTech Connect

    Umar, A. S.; Oberacker, V. E.; Maruhn, J. A.; Reinhard, P.-G.

    2010-06-15

    We investigate the entrance channel dynamics for the reactions {sup 70}Zn+{sup 208}Pb and {sup 48}Ca+{sup 238}U by using the fully microscopic time-dependent Hartree-Fock theory coupled with a density constraint. We calculate excitation energies and capture cross sections relevant for the study of superheavy formations. We discuss the deformation dependence of the ion-ion potential for the {sup 48}Ca+{sup 238}U system and perform an alignment angle averaging for the calculation of the capture cross section. The results show that this approach can generate results in good agreement with experiments and other theories.

  2. Study of nuclear fusion-fission dynamics in 16O+194Pt reaction

    NASA Astrophysics Data System (ADS)

    Kapoor, K.; Verma, S.; Sharma, P.; Mahajan, R.; Kaur, N.; Kaur, G.; Behera, B. R.; Singh, K. P.; Singh, H.; Dubey, R.; Saneesh, N.; Jhingan, A.; Sugathan, P.; Mohanto, G.; Nayak, B. K.; Saxena, A.; Sharma, H. P.; Chamoli, S. K.; Mukul, I.; Kumar, A.

    2017-06-01

    Pre- and post-scission α-particle multiplicities have been measured for the reaction 16O + 194Pt at 98.4 MeV forming compound nucleus 210Rn. The α-particle's yield has been measured in coincidence with the fission fragments at various angles. The moving source analysis was performed to extract the alpha particle multiplicity which yielded the contribution of pre- and post- scission components. The pre-scission α-particle multiplicity has been compared with JOANNE2 statistical model code predictions to extract fission time scale and which is observed to be around 55zs (1zs=10-21s).

  3. Critical evaluation and rate constants of chemoselective ligation reactions for stoichiometric conjugations in water.

    PubMed

    Saito, Fumito; Noda, Hidetoshi; Bode, Jeffrey W

    2015-04-17

    Chemoselective ligation reactions have contributed immensely to the development of organic synthesis and chemical biology. However, the ligation of stoichiometric amounts of large molecules for applications such as protein-protein conjugates is still challenging. Conjugation reactions need to be fast enough to proceed under dilute conditions and chemoselective in the presence of unprotected functional groups; the starting materials and products must be stable under the reaction conditions. To compare known ligation reactions for their suitability under these conditions, we determined the second-order rate constants of ligation reactions using peptide substrates with unprotected functional groups. The reaction conditions, the chemoselectivity of the reactions, and the stability of the starting materials and products were carefully evaluated. In some cases, the stability could be improved by modifying the substrate structure. These data obtained under the ligation conditions provide a useful guide to choose an appropriate ligation reaction for synthesis of large molecules by covalent ligation reactions of unprotected substrates in water.

  4. Reaction rates between water and some modified rapidly-reacting Karl Fischer reagents.

    PubMed

    Cedergren, A

    1978-04-01

    Rate constants were determined for the reaction between water and various modified Karl Fischer reagents containing formamide, dimethylformamide or N-methylformamide. It was shown that the reaction rate can be increased by a factor of 100 by using a reagent containing 40% v/v formamide in pyridine compared to that obtained by use of the conventional methanolic reagent.

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

    ERIC Educational Resources Information Center

    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.…

  6. Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide

    NASA Technical Reports Server (NTRS)

    Klemm, R. B.; Stief, L. J.

    1974-01-01

    The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO, have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for reaction rate was measured over a temperature range of 263-502 K and the data were fitted to an Arrhenius expression with good linearity. A comparison of the present results with those from previous studies of this reaction is also presented.

  7. The Gaseous Explosive Reaction : the Effect of Pressure on the Rate of Propagation of the Reaction Zone and upon the Rate of Molecular Transformation

    NASA Technical Reports Server (NTRS)

    Stevens, F W

    1932-01-01

    This study of gaseous explosive reaction has brought out a number of important fundamental characteristics of the explosive reaction indicating that the basal processes of the transformation are much simpler and corresponds more closely to the general laws and principles of ordinary transformations than is usually supposed. The report calls attention to the point that the rate of molecular transformation within the zone was found in all cases to be proportional to pressure, that the transformation within the zone is the result of binary impacts. This result is of unusual interest in the case of the reaction of heavy hydrocarbon fuels and the reaction mechanism proposed by the recent kinetic theory of chain reactions.

  8. Fusion rate and clinical outcome in anterior lumbar interbody fusion with beta-tricalcium phosphate and bone marrow aspirate as a bone graft substitute. A prospective clinical study in fifty patients.

    PubMed

    Lechner, Ricarda; Putzer, David; Liebensteiner, Michael; Bach, Christian; Thaler, Martin

    2017-02-01

    Bone graft substitutes have been successfully used in posterolateral lumbar fusion, anterior cervical fusion and animal studies. This study has been conducted to assess the safety and efficacy of β-tricalcium phosphate (β-TCP) in instrumented anterior lumbar interbody fusion (ALIF) procedure. In a prospective clinical study, ALIF cages were prefilled with β-TCP and additionally fixated with posterior pedicle screw. Computed tomography (CT) and X-rays were performed one year after surgery. Fusion was assessed and functional status was evaluated before and one year after surgery. X-ray evaluation showed a definite fusion in 85.48 % of treated levels. CT assessment showed anterior and posterior intersegemental bone bridging in 77.78 % of treated levels. The X-ray fusion rate presented is comparable with those published for ALIF procedures with bone graft. Fusion rates β-TCP are similar to autologous bone. ALIF with β-TCP and additional posterior fixation is a safe and effective procedure.

  9. Thermal properties of light nuclei from 12C + 12C fusion-evaporation reactions

    NASA Astrophysics Data System (ADS)

    Morelli, L.; Baiocco, G.; D'Agostino, M.; Gulminelli, F.; Bruno, M.; Abbondanno, U.; Appannababu, S.; Barlini, S.; Bini, M.; Casini, G.; Cinausero, M.; Degerlier, M.; Fabris, D.; Gelli, N.; Gramegna, F.; Kravchuk, V. L.; Marchi, T.; Olmi, A.; Pasquali, G.; Piantelli, S.; Valdré, S.; Raduta, Ad R.

    2014-07-01

    The 12C + 12C reaction at 95 MeV has been studied through the complete charge identification of its products by means of the GARFIELD+RCo experimental set-up at INFN Laboratori Nazionali di Legnaro (LNL). In this paper, the first of a series of two, a comparison to a dedicated Hauser-Feshbach calculation allows selecting a set of dissipative events which corresponds, to a large extent, to the statistical evaporation of highly excited 24Mg. Information on the isotopic distribution of the evaporation residues in coincidence with their complete evaporation chain is also extracted. The set of data puts strong constraints on the behaviour of the level density (LD) of light nuclei above the threshold for particle emission. In particular, a fast increase of the LD parameter with excitation energy is supported by the data. Residual deviations from a statistical behaviour are seen in two specific channels, and tentatively associated with a contamination from direct reactions and/or α-clustering effects. These channels are studied in further details in the second paper of the series.

  10. Controlling the emotional heart: heart rate biofeedback improves cardiac control during emotional reactions.

    PubMed

    Peira, Nathalie; Fredrikson, Mats; Pourtois, Gilles

    2014-03-01

    When regulating negative emotional reactions, one goal is to reduce physiological reactions. However, not all regulation strategies succeed in doing that. We tested whether heart rate biofeedback helped participants reduce physiological reactions in response to negative and neutral pictures. When viewing neutral pictures, participants could regulate their heart rate whether the heart rate feedback was real or not. In contrast, when viewing negative pictures, participants could regulate heart rate only when feedback was real. Ratings of task success paralleled heart rate. Participants' general level of anxiety, emotion awareness, or cognitive emotion regulation strategies did not influence the results. Our findings show that accurate online heart rate biofeedback provides an efficient way to down-regulate autonomic physiological reactions when encountering negative stimuli.

  11. Pop-it beads to introduce catalysis of reaction rate and substrate depletion effects.

    PubMed

    Gehret, Austin U

    2017-03-04

    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 effect of substrate depletion on catalyzed reaction rate. Preliminary findings based on survey results and exam performance suggest the activity could prove beneficial to students in the targeted learning outcomes. Unique to previous kinesthetic approaches that model Michaelis-Menten kinetics, this activity models the effects of substrate depletion on catalyzed reaction rate. Therefore, it could prove beneficial for conveying the reasoning behind the initial rate simplification used in Michaelis-Menten kinetics. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(2):179-183, 2017. © 2016 The International Union of Biochemistry and Molecular Biology.

  12. Reaction Rates in Deformation and Hydrostatic Experiments in the Anhydrous System Anorthite - Forsterite

    NASA Astrophysics Data System (ADS)

    Stunitz, H.; de Ronde, A.; Tullis, J.

    2004-12-01

    The reaction anorthite + forsterite --> cpx + opx + spinel ± gnt proceeds at high temperatures and elevated pressures in the lower crust and upper mantle. This solid-solid reaction was studied experimentally at 900° C in the pressure range of 1000 to 1600 MPa in both shearing deformation and hydrostatic experiments. Powder mixtures (1:1 by vol) of anorthite (An92) and forsterite (Fo93) are hot pressed at 970° C, 750 MPa for 48 hrs in a Griggs apparatus and deformed (˙ γ = 5 × 105 sec-1) after adjustment of P and T to run conditions. H2O content of the samples has been measured by FTIR and is < 30 ppm. At small pressure overstepping (ca. 200 to 300 MPa) undeformed samples show only 10 % reaction progress after 168 hrs, whereas reaction progress in deformed samples after 72 hrs is 60 %. At greater pressure overstepping (700 to 800 MPa) the difference between deformed and undeformed samples is less pronounced (95 % after 60 hrs deformed, 75 % after 168 hrs undeformed) but still present. At greater pressure overstepping, undeformed samples show an exponential reaction rate, whereas that of deformed samples is always linear. Samples initially deformed and then kept hydrostatically show a fast initial reaction rate (85 % of total reaction progress after 0.25 of total run time), followed by a slower reaction progress (15 % reaction after 0.75 of total time) under hydrostatic conditions. The difference in reaction progress is mainly attributed to different nucleation rates. In all experiments, enstatite rims form around olivine grains separating those from other reaction products. Such coronas are indicative of diffusion-controlled reactions. Plots of rim thickness vs time indicate a relative increase of the bulk diffusion coefficient by a factor 5 in the deformed samples compared to undeformed. However, as the grain size of reaction products of deformed samples is 10 times smaller than in undeformed ones, the nucleation rate in deformed samples is ˜ 5000 times

  13. Stability of superheavy nuclei produced in actinide-based complete fusion reactions: Evidence for the next magic proton number at Z{>=}120

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.

    2009-05-15

    Using the experimental evaporation residue cross sections in the {sup 48}Ca-induced complete fusion reactions and the complete fusion cross sections calculated within the dinuclear system model, the survival probabilities of superheavy nuclei with charge numbers Z=112-116 and 118 in the xn-evaporation channels are extracted. The effects of angular momentum and deformations of colliding nuclei are taken into account. The obtained dependence of the survival probability on Z indicates the next doubly magic nucleus beyond {sup 208}Pb at Z{>=}120.

  14. Reoperation Rates After Anterior Cervical Discectomy and Fusion for Cervical Spondylotic Radiculopathy and Myelopathy: A National Population-based Study.

    PubMed

    Park, Moon Soo; Ju, Young-Su; Moon, Seong-Hwan; Kim, Tae-Hwan; Oh, Jae Keun; Makhni, Melvin C; Riew, K Daniel

    2016-10-15

    National population-based cohort study. To compare the reoperation rates between cervical spondylotic radiculopathy and myelopathy in a national population of patients. There is an inherently low incidence of reoperation after surgery for cervical degenerative disease. Therefore, it is difficult to sufficiently power studies to detect differences between reoperation rates of different cervical diagnoses. National population-based databases provide large, longitudinally followed cohorts that may help overcome this challenge. We used the Korean Health Insurance Review and Assessment Service national database to select our study population. We included patients with the diagnosis of cervical spondylotic radiculopathy or myelopathy who underwent anterior cervical discectomy and fusion from January 2009 to June 2014. We separated patients into two groups based on diagnosis codes: cervical spondylotic radiculopathy or cervical spondylotic myelopathy. Age, sex, presence of diabetes, osteoporosis, associated comorbidities, number of operated cervical disc levels, and hospital types were considered potential confounding factors. The overall reoperation rate was 2.45%. The reoperation rate was significantly higher in patients with cervical spondylotic myelopathy than in patients with cervical radiculopathy (myelopathy: P = 0.0293, hazard ratio = 1.433, 95% confidence interval 1.037-1.981). Male sex, presence of diabetes or associated comorbidities, and hospital type were noted to be risk factors for reoperation. The reoperation rate after anterior cervical discectomy and fusion was higher for cervical spondylotic myelopathy than for cervical spondylotic radiculopathy in a national population of patients. 3.

  15. An Experiment to Demonstrate How a Catalyst Affects the Rate of a Reaction

    NASA Astrophysics Data System (ADS)

    Copper, Christine L.; Koubek, Edward

    1999-12-01

    By performing this experiment, students in general and introductory physical chemistry can learn more about the effect of a catalyst on a chemical reaction. This experiment, which is a modified version of the traditional iodine clock reaction, allows students to calculate rates of reaction, orders of reactants, and activation energies. It also lets students discover that to increase a reaction's rate, a catalyst need only provide any additional pathway for the reaction, not necessarily a pathway having a lower activation energy. This experiment is designed so that students will notice that the amount of catalyst used is important. Furthermore, the slight amount (~10-5 M MoO42-) of catalyst needed to increase the overall reaction rate and the abrupt color change that occurs seem to pique the interest of our students.

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

    SciTech Connect

    Thanh, Vo Hong; Priami, Corrado

    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.

  17. Reaction of singlet oxygen with tryptophan in proteins: a pronounced effect of the local environment on the reaction rate.

    PubMed

    Jensen, Rasmus Lybech; Arnbjerg, Jacob; Ogilby, Peter R

    2012-06-13

    Singlet molecular oxygen, O(2)(a(1)Δ(g)), can influence many processes pertinent to the function of biological systems, including events that result in cell death. Many of these processes involve a reaction between singlet oxygen and a given amino acid in a protein. As a result, the behavior of that protein can change, either because of a structural alteration and/or a direct modification of an active site. Surprisingly, however, little is known about rate constants for reactions between singlet oxygen and amino acids when the latter are in a protein. In this report, we demonstrate using five separate proteins, each containing only a single tryptophan residue, that the rate constant for singlet oxygen reaction with tryptophan depends significantly on the position of this amino acid in the protein. Most importantly, the reaction rate constant depends not only on the accessibility of the tryptophan residue to oxygen, but also on factors that characterize the local molecular environment of the tryptophan in the protein. The fact that the local protein environment can either appreciably inhibit or accelerate the reaction of singlet oxygen with a given amino acid can have significant ramifications for singlet-oxygen-mediated events that perturb cell function.

  18. The influence of transfer reactions on the sub-barrier fusion enhancement in the systems {sup 58.64}Ni +, {sup 92,100}Mo

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    High resolution experiments performed during the past few years demonstrated that the various reaction modes occurring in heavy ion collisions can strongly influence each other. This interrelation of the different reaction modes brings a nuclear structure dependence to the fusion and deep-inelastic channels that were previously described in the framework of pure statistical models. In order to fully understand the interrelation between these reaction channels, a complete set of measurements including elastic and inelastic scattering, few-nucleon transfer and fusion is required. In continuation of our earlier measurements of the fusion cross sections in the system {sup 58,64}Ni + {sup 92,100}Mo we finished the studies of the quasielastic process in these systems. The experiments were done in inverse reaction kinematics using the split-pole spectrograph with its hybrid focal-plane detector for particle identification. The experiments with {sup 100}Mo beams were performed previously. First test runs with {sup 92}Mo showed the possible interference with {sup 98}Mo ions which could be eliminated by using the 13{sup +} charge state from the ECR source. The data from these experiments were completely analyzed. The smallest transfer cross sections are observed for the systems {sup 64}Ni + {sup 100}Mo and {sup 58}Ni + {sup 92}Mo, i.e., the most neutron-rich and neutron-deficient systems, respectively. For the other systems, {sup 64}Ni + {sup 92}Mo and {sup 58}Ni + {sup 100}Mo, the transfer cross sections at energies close to the barrier are about of equal magnitude. This observation does not correlate with the deviation of the experimental fusion cross sections from the coupled-channels predictions. While for {sup 58}Ni + {sup 100}Mo discrepancies between the experimental and theoretical fusion cross sections are observed, the system {sup 64}Ni + {sup 92}Mo which shows about the same transfer yields, is quite well described by the coupled-channels calculations.

  19. Technical description of oblique lateral interbody fusion at L1-L5 (OLIF25) and at L5-S1 (OLIF51) and evaluation of complication and fusion rates.

    PubMed

    Woods, Kamal R M; Billys, James B; Hynes, Richard A

    2017-04-01

    The oblique lateral interbody fusion (OLIF) procedure is aimed at mitigating some of the challenges seen with traditional anterior lumbar interbody fusion (ALIF) and transpsoas lateral lumbar interbody fusion (LLIF), and allows for interbody fusion at L1-S1. The study aimed to describe the OLIF technique and assess the complication and fusion rates. This is a retrospective cohort study. The sample is composed of 137 patients who underwent OLIF procedure. The outcome measures were adverse events within 6 months of surgery: infection, symptomatic pseudarthrosis, hardware failure, vascular injury, perioperative blood transfusion, ureteral injury, bowel injury, renal injury, prolonged postoperative ileus (more than 3 days), incisional hernia, pseudohernia, reoperation, neurologic deficits (weakness, numbness, paresthesia), hip flexion pain, retrograde ejaculation, sympathectomy affecting lower extremities, deep vein thrombosis, pulmonary embolism, myocardial infarction, pneumonia, and cerebrovascular accident. The outcome measures also include fusion and subsidence rates based on computed tomography (CT) done at 6 months postoperatively. Retrospective chart review of 150 consecutive patients was performed to examine the complications associated with OLIF at L1-L5 (OLIF25), OLIF at L5-S1 (OLIF51), and OLIF at L1-L5 combined with OLIF at L5-S1 (OLIF25+OLIF51). Only patients who had at least 6 months of postoperative follow-up, including CT scan at 6 months after surgery, were included. Independent radiology review of CT data was performed to assess fusion and subsidence rates at 6 months. A total of 137 patients underwent fusion at 340 levels. An overall complication rate of 11.7% was seen. The most common complications were subsidence (4.4%), postoperative ileus (2.9%), and vascular injury (2.9%). Ileus and vascular injuries were only seen in cases including OLIF51. No patient suffered neurologic injury. No cases of ureteral injury, sympathectomy affecting the lower

  20. Association of EWS-FLI1 Type 1 Fusion with Lower Proliferative Rate in Ewing’s Sarcoma

    PubMed Central

    de Alava, Enrique; Panizo, Angel; Antonescu, Cristina R.; Huvos, Andrew G.; Pardo-Mindán, F. Javier; Barr, Frederic G.; Ladanyi, Marc

    2000-01-01

    The Ewing’s sarcoma (ES) family of tumors, including peripheral neuroectodermal tumor (PNET), is defined genetically by specific chromosomal translocations resulting in fusion of the EWS gene with a member of the ETS family of transcription factors, either FLI1 (90–95%) or ERG (5–10%). A second level of molecular genetic heterogeneity stems from the variation in the location of the translocation breakpoints, resulting in the inclusion of different combinations of exons from EWS and FLI1 (or ERG) in the fusion products. The most common type of EWS-FLI1 fusion transcript, type 1, is associated with a favorable prognosis and appears to encode a functionally weaker transactivator, compared to other fusion types. We sought to determine whether the observed covariation of structure, function, and clinical course correlates with tumor cell kinetic parameters such as proliferative rate and apoptosis, and with expression of the receptor for insulin-like growth factor I (IGF-1R). In a group of 86 ES/PNET with defined EWS-ETS fusions (45 EWS-FLI1 type 1, 27 EWS-FLI1 non-type 1, 14 EWS-ERG), we assessed proliferation rate by immunostaining for Ki-67 using MIB1 antibody (n = 85), apoptosis by TUNEL assay (n = 66), and IGF-1R expression by immunostaining with antibody 1H7 (n = 78). Ki-67 proliferative index was lower in tumors with EWS-FLI1 type 1 than those with non-type 1 EWS-FLI1, whether analyzed as a continuous (P = 0.049) or categorical (P = 0.047) variable. Logistic regression analysis suggests that this association was secondary to the association of type 1 EWS-FLI1 and lower IGF-1R expression (P = 0.04). Comparing EWS-FLI1 to EWS-ERG cases, Ki-67 proliferative index was higher in the latter (P = 0.01, Mann-Whitney test; P = 0.02, Fisher’s exact test), but there was no significant difference in IGF-1R. TUNEL results showed no significant differences between groups. Our results suggest that clinical and functional differences between alternative forms of EWS-FLI1

  1. The effect of temperature fluctuations of reaction rate constants in turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Chinitz, W.; Antaki, P. J.; Kassar, G. M.

    1981-01-01

    Current models of turbulent reacting flows frequently use Arrhenius reaction rate constants obtained from static or laminar flow theory and/or experiments, or from best fits of static, laminar, and turbulent data. By treating the reaction rate constant as a continuous random variable which is temperature-dependent, the present study assesses the effect of turbulent temperature fluctuations on the reaction rate constant. This model requires that a probability density function (PDF) describing the nature of the fluctuations be specified. Three PDFs are examined: the clipped Gaussian, the beta PDF, and the ramp model. All the models indicate that the reaction rate constant is greater in a turbulent flow field than in an equivalent laminar flow. In addition, an amplification ratio, which is the ratio of the turbulent rate constant to the laminar rate constant, is defined and its behavior as a function of the mean temperature fluctuations is described

  2. The effect of temperature fluctuations of reaction rate constants in turbulent reacting flows

    NASA Technical Reports Server (NTRS)

    Chinitz, W.; Antaki, P. J.; Kassar, G. M.

    1981-01-01

    Current models of turbulent reacting flows frequently use Arrhenius reaction rate constants obtained from static or laminar flow theory and/or experiments, or from best fits of static, laminar, and turbulent data. By treating the reaction rate constant as a continuous random variable which is temperature-dependent, the present study assesses the effect of turbulent temperature fluctuations on the reaction rate constant. This model requires that a probability density function (PDF) describing the nature of the fluctuations be specified. Three PDFs are examined: the clipped Gaussian, the beta PDF, and the ramp model. All the models indicate that the reaction rate constant is greater in a turbulent flow field than in an equivalent laminar flow. In addition, an amplification ratio, which is the ratio of the turbulent rate constant to the laminar rate constant, is defined and its behavior as a function of the mean temperature fluctuations is described

  3. Determination of the Temperature Dependence of the Rate Constants for HO2/Acetonylperoxy Reaction and Acetonylperoxy Self-Reaction

    NASA Astrophysics Data System (ADS)

    Darby, E. C.; Grieman, F. J.; Hui, A. O.; Okumura, M.; Sander, S. P.

    2014-12-01

    Reactions of hydroperoxy radical, HO2, with carbonyl containing RO2 can play an important role in the oxidation chemistry of the troposphere. Discovered radical product channels in addition to radical termination channels have resulted in increased study of these important reactions. In our continued study of HO2 reactions with acetonylperoxy and acetylperoxy radicals, we report here our first results on the kinetics of the acetonylperoxy system. Previous studies have resulted in conflicting results and no temperature dependence of the rate constants. Using the Infrared Kinetic Spectroscopy (IRKS) method in which a temperature-controlled slow-flow tube apparatus and laser flash photolysis of Cl2 are used to produce HO2 and CH3C(O)CH2O2 from methanol and acetone, respectively, we studied the chemical kinetics involved over the temperature range of 295 to 240 K. Rates of chemical reaction were determined by monitoring the HO2 concentration as a function of time by sensitive near-IR diode laser wavelength modulation spectroscopy while simultaneously measuring the disappearance of [CH3C(O)CH2O2] in the ultraviolet at 300 nm. The simultaneous fits resulted in the determination of the temperature dependence of the rate constants for the HO2/acetonylperoxy reaction and the acetonylperoxy self-reaction. At the lower temperatures, the reactions of HO2 and CH3C(O)CH2O2 with the adducts HO2•CH3OH and HO2•CH3C(O)CH3 formed in significant concentrations needed to be included in the fitting models.

  4. Reaction kinetics and critical phenomena: rates of some first order gas evolution reactions in binary solvents with a consolute point.

    PubMed

    Kim, Yeong Woo; Baird, James K

    2005-06-02

    We have measured the rate of carbon dioxide evolution in the aniline catalyzed decomposition of acetone dicarboxylic acid in a mixture of isobutyric acid + water near its consolute point. Within a temperature interval of 1 degrees C, which included the critical solution temperature, the first-order rate constant oscillated in magnitude by about 10% as it passed through three complete cycles of slowing down followed by speeding up. Whereas we can find no ready explanation for the speeding up, we suggest that, because the mixture contained no inert components, the slowing down should belong to the Griffiths-Wheeler class of strong critical effects [Phys. Rev. A 1970, 2, 1047]. As a check on this conclusion, we have measured the rate of the SN1 decomposition of benzene diazonium tetrafluoroborate in 2-butoxyethanol + water near the lower critical solution temperature and also the rate of the acid-catalyzed decomposition of ethyl diazoacetate in isobutyric acid + water near the upper critical solution temperature. Both of these reactions evolve nitrogen. In the first reaction, 2-butoxyethanol is inert, whereas in the second, isobutyric acid is inert. In both cases, because there was one inert component, we regarded the response of the rate constant to temperature in the critical region to be representative of the Griffiths-Wheeler class of weak critical effects. Within our accuracy of measurement of about 2% in the rate constant and about 1 mK in the temperature, we could detect no effect of the critical point on the rates of either of these reactions, suggesting that a weak effect may be too small to be seen with our experimental apparatus. The successful observation of a critical effect in the rate of decomposition of acetone dicarboxylic acid proves, however, that kinetic critical phenomena are observable in heterogeneous reactions.

  5. Chiral Polymerization in Open Systems From Chiral-Selective Reaction Rates

    NASA Astrophysics Data System (ADS)

    Gleiser, Marcelo; Nelson, Bradley J.; Walker, Sara Imari

    2012-08-01

    We investigate the possibility that prebiotic homochirality can be achieved exclusively through chiral-selective reaction rate parameters without any other explicit mechanism for chiral bias. Specifically, we examine an open network of polymerization reactions, where the reaction rates can have chiral-selective values. The reactions are neither autocatalytic nor do they contain explicit enantiomeric cross-inhibition terms. We are thus investigating how rare a set of chiral-selective reaction rates needs to be in order to generate a reasonable amount of chiral bias. We quantify our results adopting a statistical approach: varying both the mean value and the rms dispersion of the relevant reaction rates, we show that moderate to high levels of chiral excess can be achieved with fairly small chiral bias, below 10%. Considering the various unknowns related to prebiotic chemical networks in early Earth and the dependence of reaction rates to environmental properties such as temperature and pressure variations, we argue that homochirality could have been achieved from moderate amounts of chiral selectivity in the reaction rates.

  6. Chiral polymerization in open systems from chiral-selective reaction rates.

    PubMed

    Gleiser, Marcelo; Nelson, Bradley J; Walker, Sara Imari

    2012-08-01

    We investigate the possibility that prebiotic homochirality can be achieved exclusively through chiral-selective reaction rate parameters without any other explicit mechanism for chiral bias. Specifically, we examine an open network of polymerization reactions, where the reaction rates can have chiral-selective values. The reactions are neither autocatalytic nor do they contain explicit enantiomeric cross-inhibition terms. We are thus investigating how rare a set of chiral-selective reaction rates needs to be in order to generate a reasonable amount of chiral bias. We quantify our results adopting a statistical approach: varying both the mean value and the rms dispersion of the relevant reaction rates, we show that moderate to high levels of chiral excess can be achieved with fairly small chiral bias, below 10%. Considering the various unknowns related to prebiotic chemical networks in early Earth and the dependence of reaction rates to environmental properties such as temperature and pressure variations, we argue that homochirality could have been achieved from moderate amounts of chiral selectivity in the reaction rates.

  7. A simple expression for the apparent reaction rate of large wood char gasification with steam.

    PubMed

    Umeki, Kentaro; Roh, Seon-Ah; Min, Tai-Jin; Namioka, Tomoaki; Yoshikawa, Kunio

    2010-06-01

    A simple expression for the apparent reaction rate of large wood char gasification with steam is proposed. Large char samples were gasified under steam atmosphere using a thermo-balance reactor. The apparent reaction rate was expressed as the product of the intrinsic rate and the effective factor. The effective factor was modified to include the effect of change in char diameter and intrinsic reaction rate during the reaction. Assuming uniform conversion ratio throughout a particle, the simplified reaction scheme was divided into three stages. In the initial stage, the local conversion ratio increases without particle shrinkage. In the middle stage, the particle shrinks following the shrinking core model without change in the local conversion ratio. In the final stage, the local conversion ratio increases without particle shrinkage. The validity of the modified effective value was confirmed by comparison with experimental results.

  8. Rate variations of a hetero-Diels--Alder reaction in supercritical fluid CO{sub 2}

    SciTech Connect

    Thompson, R.L.; Glaeser, R.; Bush, D.; Liotta, C.L.; Eckert, C.A.

    1999-11-01

    The hetero-Diels-Alder reaction between anthracene and excess 4-phenyl-1,2,4-triazoline-3,5-dione has been investigated in supercritical CO{sub 2} at 40 C and pressures between 75 and 216 bar. Biomolecular reaction rate constants have been measured via fluorescence spectroscopy by following the decrease in anthracene concentration with reaction time. The reaction rate is elevated in the vicinity of the critical pressure. This difference is consistent with local composition enhancement and can be modeled with the Peng-Robinson equation of state.

  9. Mathematical model of reaction rate oscillations on a chain of nm-sized catalyst particles

    NASA Astrophysics Data System (ADS)

    Peskov, N. V.; Slinko, M. M.; Jaeger, N. I.

    2003-05-01

    The model of reaction rate oscillations over the surface of nanoparticles embedded into zeolite matrix is numerically investigated. The reaction rate oscillations on each particle are described by a lumped model. The reactions on separate particles interact via the gas diffusion through the pores, which is modeled in the frame of the Maxwell-Stefan approach. The reaction reveals a complex dynamical behavior if a nonhomogeneous distribution of reagent concentrations exists along the chain of particles with a sufficiently large gradient near the ends of the chain.

  10. Stochastic behavior and stirring rate effects in the chlorite-iodide reaction

    NASA Astrophysics Data System (ADS)

    Nagypál, István; Epstein, Irving R.

    1988-12-01

    The autocatalytic reaction between chlorite and iodide ions in a closed system is a clock reaction, showing a sudden appearance of brown I2 followed by a rapid disappearance of the color. Under certain conditions, the reaction time displays a striking irreproducibility. This stochastic behavior is studied potentiometrically and spectrophotometrically as a function of initial [I- ], stirring rate and solution volume. The results imply that the irreproducibility is an inherent feature of the reaction generated by fluctuations in the solution after it is ``well mixed.'' The key contributors to the stochasticity are local concentration inhomogeneities resulting from imperfect stirring and the ``supercatalytic'' reaction kinetics. A qualitative explanation is given that incorporates these aspects.

  11. Cold nuclear fusion and muon-catalyzed fusion. (Latest citations from the INSPEC: Information services for the Physics and Engineering Communities data base). Published Search

    SciTech Connect

    Not Available

    1992-10-01

    The bibliography contains citations concerning a nuclear fusion process which occurs at lower temperatures and pressures than conventional fusion reactions. The references describe theoretical and experimental results for a proposed muon-catalyzed fusion reactor, and for studies on muon sticking and reactivation. The temperature dependence of fusion rates, and resolution of some engineering challenges are also discussed. (Contains 250 citations and includes a subject term index and title list.)

  12. On the implementation of a chain nuclear reaction of thermonuclear fusion on the basis of the p+{sup 11}B process

    SciTech Connect

    Belyaev, V. S.; Krainov, V. P.; Zagreev, B. V.; Matafonov, A. P.

    2015-07-15

    Various theoretical and experimental schemes for implementing a thermonuclear reactor on the basis of the p+{sup 11}B reaction are considered. They include beam collisions, fusion in degenerate plasmas, ignition upon plasma acceleration by ponderomotive forces, and the irradiation of a solid-state target from {sup 11}B with a proton beam under conditions of a Coulomb explosion of hydrogen microdrops. The possibility of employing ultra-short high-intensity laser pulses to initiate the p+{sup 11}B reaction under conditions far from thermodynamic equilibrium is discussed. This and some other weakly radioactive thermonuclear reactions are promising owing to their ecological cleanness—there are virtually no neutrons among fusion products. Nuclear reactions that follow the p+{sup 11}B reaction may generate high-energy protons, sustaining a chain reaction, and this is an advantage of the p+{sup 11}B option. The approach used also makes it possible to study nuclear reactions under conditions close to those in the early Universe or in the interior of stars.

  13. Simulation and Experimental Study on the Efficiency of Traveling Wave Direct Energy Conversion for Application to Aneutronic Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Tarditi, Alfonso; Chap, Andrew; Miley, George; Scott, John

    2013-10-01

    A study based on both Particle-in-cell (PIC) simulation and experiments is being developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC,) with the perspective of application to aneutronic fusion reaction products and space propulsion. The PIC model is investigating in detail the key TWDEC physics process by simulating the time-dependent transfer of energy from the ion beam to an electric load connected to ring-type electrodes in cylindrical symmetry. An experimental effort is in progress on a TWDEC test article at NASA, Johnson Space Center with the purpose of studying the conditions for improving the efficiency of the direct energy conversion process. Using a scaled-down ion energy source, the experiment is primarily focused on the effect of the (bunched) beam density on the efficiency and on the optimization of the electrode design. The simulation model is guiding the development of the experimental configuration and will provide details of the beam dynamics for direct comparison with experimental diagnostics. Work supported by NASA, Johnson Space Center.

  14. Effects of nuclear orientation on fusion and fission process for reactions using {sup 238}U target nucleus

    SciTech Connect

    Nishio, K.; Ikezoe, H.; Mitsuoka, S.; Nishinaka, I.; Makii, H.; Nagame, Y.; Watanabe, Y.; Ohtsuki, T.; Hirose, K.; Hofmann, S.

    2010-06-01

    Fission fragment mass distributions in the reaction of {sup 30}Si+{sup 238}U were measured at the energies around the Coulomb barrier. At the above-barrier energies, the mass distribution showed Gaussian shape. At the sub-barrier energies, asymmetric fission mode peaked at A{sub L}/A{sub H}approx =90/178 was observed. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections produced by {sup 30}Si+{sup 238}U. The cross-section for {sup 263}Sg at the above-barrier energy agree with the statistical model calculation which assumes that the measured fission cross-sections are equal to the fusion cross-sections, whereas the one for {sup 264}Sg measured at the sub-barrier energy is smaller than the calculation, indicating the presence for quasifission. The fragment mass distributions are compared to those for {sup 36}S+{sup 238}U and {sup 40}Ar+{sup 238}U.

  15. Nuclear reaction rate uncertainties and the 22Ne( p,gamma)23Na reaction: Classical novae and globular clusters

    NASA Astrophysics Data System (ADS)

    Kelly, Keegan John

    The overall theme of this thesis is the advancement of nuclear astrophysics via the analysis of stellar processes in the presence of varying levels of precision in the available nuclear data. With regard to classical novae, the level of mixing that occurs between the outer layers of the white dwarf core and the solar accreted material in oxygen-neon novae is presently undetermined by stellar models, but the nuclear data relevant to these explosive phenomena are fairly precise. This precision allowed for the identification of a series of elemental ratios indicative of the level of mixing occurring in novae. Direct comparisons of the modelled elemental ratios to observations showed that there is likely to be much less of this mixing than was previously assumed. Thus, our understanding of classical novae was altered via the investigation of the nuclear reactions relevant to this phenomenon. However, this level of experimental precision is rare and large nuclear reaction uncertainties can hinder our understanding of certain astrophysical phenomena. For example, it is commonly believed that uncertainties in the 22Ne(p,g)23Na reaction rate at temperatures relevant to thermally-pulsing asymptotic giant branch stars are largely responsible for our inability to explain the observed sodium-oxygen anti-correlation in globular clusters. With this motivation, resonances in the 22Ne(p,g) 23Na reaction at E_{c.m.} = 458, 417, 178, and 151 keV were measured. The direct-capture contribution was also measured at E_{lab} = 425 keV. It was determined that the 22Ne(p,g)23Na reaction rate in the astrophysically relevant temperature range is dominated by the resonances at 178 and 151 keV and that the total reaction rate is greater than the previously assumed rate by a factor of approximately ˜40 at 0.15 GK. This increased reaction rate impacts the expected nucleosynthesis that occurs in these stars and will shed light onto the origin of this anti-correlation as it is incorporated into

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

    PubMed Central

    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

  17. Temperature trends for reaction rates, hydrogen generation, and partitioning of iron during experimental serpentinization of olivine

    NASA Astrophysics Data System (ADS)

    McCollom, Thomas M.; Klein, Frieder; Robbins, Mark; Moskowitz, Bruce; Berquó, Thelma S.; Jöns, Niels; Bach, Wolfgang; Templeton, Alexis

    2016-05-01

    A series of laboratory experiments were conducted to examine how partitioning of Fe among solid reaction products and rates of H2 generation vary as a function of temperature during serpentinization of olivine. Individual experiments were conducted at temperatures ranging from 200 to 320 °C, with reaction times spanning a few days to over a year. The extent of reaction ranged from <1% to ∼23%. Inferred rates for serpentinization of olivine during the experiments were 50-80 times slower than older studies had reported but are consistent with more recent results, indicating that serpentinization may proceed more slowly than previously thought. Reaction products were dominated by chrysotile, brucite, and magnetite, with minor amounts of magnesite, dolomite, and iowaite. The chrysotile contained only small amounts of Fe (XFe = 0.03-0.05, with ∼25% present as ferric Fe in octahedral sites), and displayed little variation in composition with reaction temperature. Conversely, the Fe contents of brucite (XFe = 0.01-0.09) increased steadily with decreasing reaction temperature. Analysis of the reaction products indicated that the stoichiometry of the serpentinization reactions varied with temperature, but remained constant with increasing reaction progress at a given temperature. The observed distribution of Fe among the reaction products does not appear to be entirely consistent with existing equilibrium models of Fe partitioning during serpentinization, suggesting improved models that include kinetic factors or multiple reaction steps need to be developed. Rates of H2 generation increased steeply from 200 to 300 °C, but dropped off at higher temperatures. This trend in H2 generation rates is attributable to a combination of the overall rate of serpentinization reactions and increased partitioning of Fe into brucite rather than magnetite at lower temperatures. The results suggest that millimolal concentration of H2 could be attained in moderately hot hydrothermal

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

    PubMed

    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

    2014-07-01

    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. 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 1(st) January - 31(st) 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 reactions. 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. 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 are required in Namibia.

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

    PubMed

    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 CH2OO 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 CH2OO with H2S is 2-3 orders of magnitude faster than the reaction with H2O monomer. Though rates of CH2OO scavenging by water vapor under atmospheric conditions are primarily controlled by the reaction with water dimer, the H2S loss pathway will be dominated by the reaction with monomer. The agreement between experiment and theory for the CH2OO + H2S reaction lends credence to theoretical descriptions of other Criegee intermediate reactions that cannot easily be probed experimentally.

  20. Viscosity Dependence of Some Protein and Enzyme Reaction Rates: Seventy-Five Years after Kramers.

    PubMed

    Sashi, Pulikallu; Bhuyan, Abani K

    2015-07-28

    Kramers rate theory is a milestone in chemical reaction research, but concerns regarding the basic understanding of condensed phase reaction rates of large molecules in viscous milieu persist. Experimental studies of Kramers theory rely on scaling reaction rates with inverse solvent viscosity, which is often equated with the bulk friction coefficient based on simple hydrodynamic relations. Apart from the difficulty of abstraction of the prefactor details from experimental data, it is not clear why the linearity of rate versus inverse viscosity, k ∝ η(-1), deviates widely for many reactions studied. In most cases, the deviation simulates a power law k ∝ η(-n), where the exponent n assumes fractional values. In rate-viscosity studies presented here, results for two reactions, unfolding of cytochrome c and cysteine protease activity of human ribosomal protein S4, show an exceedingly overdamped rate over a wide viscosity range, registering n values up to 2.4. Although the origin of this extraordinary reaction friction is not known at present, the results indicate that the viscosity exponent need not be bound by the 0-1 limit as generally suggested. For the third reaction studied here, thermal dissociation of CO from nativelike cytochrome c, the rate-viscosity behavior can be explained using Grote-Hynes theory of time-dependent friction in conjunction with correlated motions intrinsic to the protein. Analysis of the glycerol viscosity-dependent rate for the CO dissociation reaction in the presence of urea as the second variable shows that the protein stabilizing effect of subdenaturing amounts of urea is not affected by the bulk viscosity. It appears that a myriad of factors as diverse as parameter uncertainty due to the difficulty of knowing the exact reaction friction and both mode and consequences of protein-solvent interaction work in a complex manner to convey as though Kramers rate equation is not absolute.