The Quantum Mechanics of Hyperion

This paper is motivated by the suggestion [W. Zurek, Physica Scripta, T76, 186 (1998)] that the chaotic tumbling of the satellite Hyperion would become non-classical within 20 years, but for the effects of environmental decoherence. The dynamics of quantum and classical probability distributions are compared for a satellite rotating perpendicular to its orbital plane, driven by the gravitational gradient. The model is studied with and without environmental decoherence. Without decoherence, the maximum quantum-classical (QC) differences in its average angular momentum scale as hbar^{2/3} for chaotic states, and as hbar^2 for non-chaotic states, leading to negligible QC differences for a macroscopic object like Hyperion. The quantum probability distributions do not approach their classical limit smoothly, having an extremely fine oscillatory structure superimposed on the smooth classical background. For a macroscopic object, this oscillatory structure is too fine to be resolved by any realistic measurement. Either a small amount of smoothing (due to the finite resolution of the apparatus) or a very small amount of environmental decoherence is sufficient ensure the classical limit. Under decoherence, the QC differences in the probability distributions scale as (hbar^2/D)^{1/6}, where D is the momentum diffusion parameter. We conclude that decoherence is not essential to explain the classical behavior of macroscopic bodies.Comment: 17 pages, 24 figure

Collisional cross sections and momentum distributions in astrophysical plasmas: dynamics and statistical mechanics link

We show that, in stellar core plasmas, the one-body momentum distribution function is strongly dependent, at least in the high velocity regime, on the microscopic dynamics of ion elastic collisions and therefore on the effective collisional cross sections, if a random force field is present. We take into account two cross sections describing ion-dipole and ion-ion screened interactions. Furthermore we introduce a third unusual cross section, to link statistical distributions and a quantum effect originated by the energy-momentum uncertainty owing to many-body collisions, and propose a possible physical interpretation in terms of a tidal-like force. We show that each collisional cross section gives rise to a slight peculiar correction on the Maxwellian momentum distribution function in a well defined velocity interval. We also find a possible link between microscopical dynamics of ions and statistical mechanics interpreting our results in the framework of non-extensive statistical mechanics.Comment: 8 page

Random paths and current fluctuations in nonequilibrium statistical mechanics

An overview is given of recent advances in nonequilibrium statistical mechanics about the statistics of random paths and current fluctuations. Although statistics is carried out in space for equilibrium statistical mechanics, statistics is considered in time or spacetime for nonequilibrium systems. In this approach, relationships have been established between nonequilibrium properties such as the transport coefficients, the thermodynamic entropy production, or the affinities, and quantities characterizing the microscopic Hamiltonian dynamics and the chaos or fluctuations it may generate. This overview presents results for classical systems in the escape-rate formalism, stochastic processes, and open quantum systems

Kinetic Theory of a Dilute Gas System under Steady Heat Conduction

The velocity distribution function of the steady-state Boltzmann equation for hard-core molecules in the presence of a temperature gradient has been obtained explicitly to second order in density and the temperature gradient. Some thermodynamical quantities are calculated from the velocity distribution function for hard-core molecules and compared with those for Maxwell molecules and the steady-state Bhatnagar-Gross-Krook(BGK) equation. We have found qualitative differences between hard-core molecules and Maxwell molecules in the thermodynamical quantities, and also confirmed that the steady-state BGK equation belongs to the same universality class as Maxwell molecules.Comment: 36 pages, 4 figures, 5 table

Determination of Omega_b From Big Bang Nucleosynthesis in the Presence of Regions of Antimatter

Production of regions of antimatter in the early universe is predicted in many baryogenesis models. Small scale antimatter regions would annihilate during or soon after nucleosynthesis, affecting the abundances of the light elements. In this paper we study how the acceptable range in Omega_b changes in the presence of antimatter regions, as compared to the standard big bang nucleosynthesis. It turns out that it is possible to produce at the same time both a low 4He value (Y_p < 0.240) and a low D/H value (D/H < 4e-5), but overproduction of 7Li is unavoidable at large Omega_b.Comment: 9 pages, PRD version, ref. 6 correcte

Growth Rate Responses of Missouri and Lower Yellowstone River Fishes to a Latitudinal Gradient

Notropis atherinoides, freshwater drums Aplodinotus grunniens, river carpsuckers Carpiodes carpio and saugers Stizostedion canadense collected in 1996-1998 from nine river sections of the Missouri and lower Yellowstone rivers at two life-stages (young-of-the-year and age 1+ years) were significantly different among sections. However, they showed no river-wide latitudinal trend except for age 1+ years emerald shiners that did show a weak negative relation between growth and both latitude and length of growing season. The results suggest growth rates of fishes along the Missouri River system are complex and could be of significance in the management and conservation of fish communities in this altered system

Pyrite-walled tube structures in a Mesoproterozoic sediment-hosted metal sulfide deposit

Unusual decimeter-scale structures occur in the sediment-hosted Black Butte Copper Mine Project deposit within lower Mesoproterozoic strata of the Belt Supergroup, Montana. These low domal and stratiform lenses are made up of millimeter-scale, hollow or mineral-filled tubes bounded by pyrite walls. X-ray micro−computed tomography (micro-CT) shows that the tube structures are similar to the porous fabric of modern diffuse hydrothermal vents, and they do not resemble textures associated with the mineralization of known microbial communities. We determined the sulfur isotopic composition of sulfide minerals with in situ secondary ion mass spectrometry (SIMS) and of texture-specific sulfate phases with multicollector−inductively coupled plasma−mass spectrometry (MC-ICP-MS). The sedimentological setting, ore paragenesis, sulfur isotope systematics, and porosity structure of these porous precipitates constrain the site of their formation to above the sediment-water interface where metalliferous hydrothermal fluids vented into the overlying water column. These data constrain the geochemistry of the Mesoproterozoic sediment-water interface and the site of deposition for copper-cobalt-silver mineralization. Metals in the hydrothermal fluids titrated sulfide in seawater to create tortuous fluid-flow conduits. Pyrite that precipitated at the vent sites exhibits large sulfur isotope fractionation (>50‰), which indicates a close association between the vents and sulfate-reducing microbiota. In the subsurface, base metal sulfides precipitated from sulfide formed during the reduction of early diagenetic barite, also ultimately derived from seawater. This model suggests dynamic bottom-water redox conditions at the vent site driven by the interplay between sulfate-reducing organisms and metalliferous fluid effluence

Lower limit on the neutralino mass in the general MSSM

We discuss constraints on SUSY models with non-unified gaugino masses and R_P conservation. We derive a lower bound on the neutralino mass combining the direct limits from LEP, the indirect limits from gmuon, bsgamma, Bsmumu and the relic density constraint from WMAP. The lightest neutralino (mneutralino=6GeV) is found in models with a light pseudoscalar with MA<200GeV and a large value for $tan\beta$. Models with heavy pseudoscalars lead to mneutralino>18(29)GeV for $\tan\beta=50(10)$. We show that even a very conservative bound from the muon anomalous magnetic moment can increase the lower bound on the neutralino mass in models with mu<0 and/or large values of $\tan\beta$. We then examine the potential of the Tevatron and the direct detection experiments to probe the SUSY models with the lightest neutralinos allowed in the context of light pseudoscalars with high $\tan\beta$. We also examine the potential of an e+e- collider of 500GeV to produce SUSY particles in all models with neutralinos lighter than the W. In contrast to the mSUGRA models, observation of at least one sparticle is not always guaranteed.Comment: 37 pages, LateX, 16 figures, paper with higher resolution figures available at http://wwwlapp.in2p3.fr/~boudjema/papers/bound-lsp/bound-lsp.htm

On modified simple reacting spheres kinetic model for chemically reactive gases

Versão dos autores para esta publicação.We consider the modiffed simple reacting spheres (MSRS) kinetic model that, in addition to the conservation of energy and momentum, also preserves the angular momentum in the collisional processes. In contrast to the line-of-center models or chemical reactive models considered in [1], in the MSRS (SRS) kinetic models, the microscopic reversibility (detailed balance) can be easily shown to be satisfied, and thus all mathematical aspects of the model can be fully justi ed. In the MSRS model, the molecules behave as if they were single mass points with two internal states. Collisions may alter the internal states of the molecules, and this occurs when the kinetic energy associated with the reactive motion exceeds the activation energy. Reactive and non-reactive collision events are considered to be hard spheres-like. We consider a four component mixture A, B, A*, B*, in which the chemical reactions are of the type A + B = A* + B*, with A* and B* being distinct species from A and B. We provide fundamental physical and mathematical properties of the MSRS model, concerning the consistency of the model, the entropy inequality for the reactive system, the characterization of the equilibrium solutions, the macroscopic setting of the model and the spatially homogeneous evolution. Moreover, we show that the MSRS kinetic model reduces to the previously considered SRS model (e.g., [2], [3]) if the reduced masses of the reacting pairs are the same before and after collisions, and state in the Appendix the more important properties of the SRS system.Fundação para a Ciência e a Tecnologi

The effect of 6-mercaptopurine on natural killer-cell activities in Crohn's disease

Crohn's disease patients on long-term 6-mercaptopurine therapy (more than 4 months) were evaluated for activity of peripheral blood natural killer cells. Natural killer-cell cytolytic activity against K-562 tumor-cell targets was examined, as was natural killer-cell suppression of lymphoblastoid B-cell antibody production. In addition, these patients were studied for their ability to generate antitetanus-specific IgG antibody-producing lymphoblastoid B cells following in vivo booster immunization. Crohn's disease patients on 6-mercaptopurine therapy had significant reductions in peripheral blood natural killer-cell activity against K-562 targets compared to normals, disease controls, and Crohn's disease patients not on 6-mercaptopurine. Natural killer-cell suppression of lymphoblastoid B-cell antibody production was like-wise decreased in 6-mercaptopurine-treated patients compared to normal controls. In contrast, the in vivo generated lymphoblastoid B-cell antibody responses of Crohn's disease patients on 6-mercaptopurine therapy were not decreased compared to normal, while Crohn's disease patients not on 6-mercaptopurine therapy had significantly impaired IgG antitetanus antibody responses. These findings suggest that 6-mercaptopurine therapy in Crohn's disease affects several lymphoid subpopulations, resulting in a decreased natural killer-cell cytotoxic activity against K-562 target cells and a decreased natural killer-cell ability to suppress lymphoblastoid B-cell antibody production, as well as an improved humoral immune response following tetanus toxoid booster immunization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44846/1/10875_2004_Article_BF00915512.pd