Precision Measurements of d(d,p)t and d(d,n)^3He Total Cross Sections at Big-Bang Nucleosynthesis Energies

Recent Wilkinson Microwave Anisotropy Probe (WMAP) measurements have determined the baryon density of the Universe $\Omega_b$ with a precision of about 4%. With $\Omega_b$ tightly constrained, comparisons of Big Bang Nucleosynthesis (BBN) abundance predictions to primordial abundance observations can be made and used to test BBN models and/or to further constrain abundances of isotopes with weak observational limits. To push the limits and improve constraints on BBN models, uncertainties in key nuclear reaction rates must be minimized. To this end, we made new precise measurements of the d(d,p)t and d(d,n)^3He total cross sections at lab energies from 110 keV to 650 keV. A complete fit was performed in energy and angle to both angular distribution and normalization data for both reactions simultaneously. By including parameters for experimental variables in the fit, error correlations between detectors, reactions, and reaction energies were accurately tabulated by computational methods. With uncertainties around 2% +/- 1% scale error, these new measurements significantly improve on the existing data set. At relevant temperatures, using the data of the present work, both reaction rates are found to be about 7% higher than those in the widely used Nuclear Astrophysics Compilation of Reaction Rates (NACRE). These data will thus lead not only to reduced uncertainties, but also to modifications in the BBN abundance predictions.Comment: 15 pages, 11 figures, minor editorial change

Caractérisation des techniques de séchage du cacao dans les principales zones de production en Côte d’Ivoire et détermination de leur influence sur la qualité des fèves commercialisées

Objectifs: Le séchage constitue une étape très importante dans la préparation du cacao marchand. Cette étude vise à caractériser les techniques utilisées par les producteurs en Côte d’Ivoire et déterminer leur influence sur la qualité des fèves. Méthodologie et résultats: Une enquête a été menée dans les principales zones de production (Est, Centre-Ouest et Sud-Ouest) en Côte d’Ivoire, afin de caractériser les techniques de séchage du cacao. Le questionnaire d’enquête a porté sur l’aire de séchage utilisée et la durée de l’opération. Par ailleurs, l’analyse au laboratoire des fèves prélevées après séchage a permis d’apprécier l’influence des techniques utilisées sur leur qualité. Les résultats obtenus ont révélé l’utilisation des claies préférentiellement par 90 % des producteurs pour le séchage dans l’Est du pays. Ceux du Centre-Ouest et du Sud-Ouest font simultanément usage des bâches noires et des aires cimentées. Respectivement 40 %, 38 % et 46 % des producteurs dans l’Est, le Centre-Ouest et Sud-Ouest ne déterminent pas la durée de séchage des fèves. Les durées déterminées sont relativement brèves et comprises entre 3 et 9 jours. Les analyses de qualité effectuées sur les échantillons collectés ont montré une corrélation linaire et négative (y = - 0,3706x + 9,9341 ; R = 0,8185) entre la durée de séchage et la teneur en eau des fèves. De même, le niveau d’impuretés à été plus élevé dans les échantillons prélevés au Centre-Ouest et au Sud-Ouest que dans ceux collectés à l’Est. La zone Est de la Côte d’Ivoire est caractérisée par l’usage des claies, un temps de séchage plus long et un cacao plus propre et plus sec. A l’opposé, le Centre-Ouest et le Sud-Ouest sont définis par l’utilisation des bâches noires et des aires cimentées, une durée de séchage relativement plus courte, surtout à Oumé, et un cacao moins propre et moins sec. Conclusion et application de résultats: Il ressort de cette étude que l’utilisation de la claie comme aire de séchage contribue à obtenir un cacao plus propre. Il est recommandé d’étendre son utilisation à l’ensemble des zones de production d’une part et d’autre part, prolonger la durée de séchage pour une bonne déshydratation des fèves, afin d’assurer une bonne qualité au cacao marchand. Mots clés: poste- récolte, aire de séchage, durée de séchage, cacao marchand, qualit

Supermatrix models and multi ZZ-brane partition functions in minimal superstring theories

We study (p,q)=(2,4k) minimal superstrings within the minimal superstring field theory constructed in hep-th/0611045. We explicitly give a solution to the W_{1+\infty} constraints by using charged D-instanton operators, and show that the (m,n)-instanton sector with m positive-charged and n negative-charged ZZ-branes is described by an (m+n)\times (m+n) supermatrix model. We argue that the supermatrix model can be regarded as an open string field theory on the multi ZZ-brane system.Comment: 15 pages, 1 figure, minor chang

Model for the on-site matrix elements of the tight-binding hamiltonian of a strained crystal: Application to silicon, germanium and their alloys

We discuss a model for the on-site matrix elements of the sp3d5s* tight-binding hamiltonian of a strained diamond or zinc-blende crystal or nanostructure. This model features on-site, off-diagonal couplings between the s, p and d orbitals, and is able to reproduce the effects of arbitrary strains on the band energies and effective masses in the full Brillouin zone. It introduces only a few additional parameters and is free from any ambiguities that might arise from the definition of the macroscopic strains as a function of the atomic positions. We apply this model to silicon, germanium and their alloys as an illustration. In particular, we make a detailed comparison of tight-binding and ab initio data on strained Si, Ge and SiGe.Comment: Submitted to Phys. Rev.

Resonances, instabilities, and structure selection of driven Josephson lattice in layered superconductors

We investigate dynamics of Josephson vortex lattice in layered high T$_{c}$ superconductors at high magnetic fields. It is shown that the average electric current depends on the lattice structure and is resonantly enhanced when the Josephson frequency matches the frequency of the plasma mode. We find the stability regions of moving lattice. It is shown that a specific lattice structure at given velocity is uniquely selected by the boundary conditions: at small velocities periodic triangular lattice is stable and looses its stability at some critical velocity. At even higher velocities a structure close to a rectangular lattice is restored.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let

Collective responses of Bi-2212 stacked junction to 100 GHz microwave radiation under magnetic field oriented along the c-axis

We studied a response of Bi-2212 mesa type structures to 100 GHz microwave radiation. We found that applying magnetic field of about 0.1 T across the layers enables to observe collective Shapiro step response corresponding to a synchronization of all 50 intrinsic Josephson junctions (IJJ) of the mesa. At high microwave power we observed up to 10th harmonics of the fundamental Shapiro step. Besides, we found microwave induced flux-flow step position of which is proportional to the square root of microwave power and that can exceed at high enough powers 1 THz operating frequency of IJJ oscillations.Comment: 11 pages including 5 figures, accepted for publication in JETP Letter

Functional interaction of Fas-associated phosphatase-1 (FAP-1) with p75NTR and their effect on NF-κB activation

AbstractThe common neurotrophin receptor p75NTR, a member of the tumor necrosis factor (TNF) receptor superfamily, plays an important role in several cellular signaling cascades, including that leading to apoptosis. FAP-1 (Fas-associated phosphatase-1), which binds to the cytoplasmic tail of Fas, was originally identified as a negative regulator of Fas-mediated apoptosis. Here we have shown by co-immunoprecipitation that FAP-1 also binds to the p75NTR cytoplasmic domain in vivo through the interaction between the third PDZ domain of FAP-1 and C-terminal Ser-Pro-Val residues of p75NTR. Furthermore, cells expressing a FAP-1/green fluorescent protein showed intracellular co-localization of FAP-1 and p75NTR at the plasma membrane. To elucidate the functional role of this physical interaction, we examined TRAF6 (TNF receptor-associated factor 6)-mediated NF-κB activation and tamoxifen-induced apoptosis in 293T cells expressing p75NTR. The results revealed that TRAF6-mediated NF-κB activation was suppressed by p75NTR and that the p75NTR-mediated NF-κB suppression was reduced by FAP-1 expression. Interestingly, a mutant of the p75NTR intracellular domain with a single substitution of a Met for Val in its C-terminus, which cannot interact with FAP-1, displayed enhanced pro-apoptotic activity in 293T transfected cells. Thus, similar to Fas, FAP-1 may be involved in suppressing p75NTR-mediated pro-apoptotic signaling through its interaction with three C-terminal amino acids (tSPV). Thus, FAP-1 may regulate p75NTR-mediated signal transduction by physiological interaction through its third PDZ domain