Derivation of globally averaged lunar heat flow from the local heat flow values and the Thorium distribution at the surface: expected improvement by the LUNAR-A Mission

The relationship between the Th abundance and the heat flow data of the Apollo sites and the LUANR-A sites, where the Th concentrations are in the wide range from 1 ppm to 6 ppm, will allow for a more precise estimation of the averaged heat flow value

Thermal in situ measurements in the Lunar Regolith using the LUNAR-A penetrators: an outline of data reduction methods

For determining the lunar heat flow two parameters need to be measured: The thermal gradient and the thermal conductivity of the regolith. Methods for inferring these quantities from in situ measurements using the LUNAR-A penetrators will be presented

Giant tunnel magnetoresistance and high annealing stability in CoFeB/MgO/CoFeB magnetic tunnel junctions with synthetic pinned layer

We investigated the relationship between tunnel magnetoresistance (TMR) ratio and the crystallization of CoFeB layers through annealing in magnetic tunnel junctions (MTJs) with MgO barriers that had CoFe/Ru/CoFeB synthetic ferrimagnet pinned layers with varying Ru spacer thickness (tRu). The TMR ratio increased with increasing annealing temperature (Ta) and tRu, reaching 361% at Ta = 425C, whereas the TMR ratio of the MTJs with pinned layers without Ru spacers decreased at Ta over 325C. Ruthenium spacers play an important role in forming an (001)-oriented bcc CoFeB pinned layer, resulting in a high TMR ratio through annealing at high temperatures.Comment: 10 pages, 5 figures, submitted to Applied Physics Letter

Non-Random Assembly of Bacterioplankton Communities in the Subtropical North Pacific Ocean

The exploration of bacterial diversity in the global ocean has revealed new taxa and previously unrecognized metabolic potential; however, our understanding of what regulates this diversity is limited. Using terminal restriction fragment length polymorphism (T-RFLP) data from bacterial small-subunit ribosomal RNA genes we show that, independent of depth and time, a large fraction of bacterioplankton co-occurrence patterns are non-random in the oligotrophic North Pacific subtropical gyre (NPSG). Pair-wise correlations of all identified operational taxonomic units (OTUs) revealed a high degree of significance, with 6.6% of the pair-wise co-occurrences being negatively correlated and 20.7% of them being positive. The most abundant OTUs, putatively identified as Prochlorococcus, SAR11, and SAR116 bacteria, were among the most correlated OTUs. As expected, bacterial community composition lacked statistically significant patterns of seasonality in the mostly stratified water column except in a few depth horizons of the sunlit surface waters, with higher frequency variations in community structure apparently related to populations associated with the deep chlorophyll maximum. Communities were structured vertically into epipelagic, mesopelagic, and bathypelagic populations. Permutation-based statistical analyses of T-RFLP data and their corresponding metadata revealed a broad range of putative environmental drivers controlling bacterioplankton community composition in the NPSG, including concentrations of inorganic nutrients and phytoplankton pigments. Together, our results suggest that deterministic forces such as environmental filtering and interactions among taxa determine bacterioplankton community patterns, and consequently affect ecosystem functions in the NPSG

Condensation of Hard Spheres Under Gravity: Exact Results in One Dimension

We present exact results for the density profile of the one dimensional array of N hard spheres of diameter D and mass m under gravity g. For a strictly one dimensional system, the liquid-solid transition occurs at zero temperature, because the close-pakced density, $\phi_c$, is one. However, if we relax this condition slightly such that $phi_c=1-\delta$, we find a series of critical temperatures T_c^i=mgD(N+1-i)/\mu_o with \mu_o=const, at which the i-th particle undergoes the liquid-solid transition. The functional form of the onset temperature, T_c^1=mgDN/\mu_o, is consistent with the previous result [Physica A 271, 192 (1999)] obtained by the Enskog equation. We also show that the increase in the center of mass is linear in T before the transition, but it becomes quadratic in T after the transition because of the formation of solid near the bottom

Runaway Merging of Black Holes: Analytical Constraint on the Timescale

Following the discovery of a black hole (BH) with a mass of 10^3-10^6 M(sun) in a starburst galaxy M82, we study formation of such a BH via successive merging of stellar-mass BHs within a star cluster. The merging has a runaway characteristic. This is because massive BHs sink into the cluster core and have a high number density, and because the merging probability is higher for more massive BHs. We use the Smoluchowski equation to study analytically the evolution of the BH mass distribution. Under favorable conditions, which are expected for some star clusters in starburst galaxies, the timescale of the runaway merging is at most of order 10^7 yr. This is short enough to account for the presence of a BH heavier than 10^3 M(sun) in an ongoing starburst region.Comment: 10 pages, no figures, to appear in The Astrophysical Journal (Letters

MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers

The authors studied an effect of ferromagnetic (Co20Fe60B20 or Fe) layer insertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetic tunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJs with CoFeB/MgO/Fe stack reached 67% at an-nealing temperature (Ta) of 200 degree C and then decreased rapidly at Ta over 250 degree C. The degradation of the TMR ratio may be related to crystallization of CoFe(B) into fcc(111) or bcc(011) texture result-ing from diffusion of B into Pd layers. MTJs which were in-situ annealed at 350oC just after depo-siting bottom CoFe/Pd multilayer showed TMR ratio of 78% by post annealing at Ta =200 degree C.Comment: 12 pages, 4 figure

Thermodynamic Theory of Weakly Excited Granular Materials

We present a thermodynamic theory of weakly excited two-dimensional granular systems from the view point of elementary excitations of spinless Fermion systems. We introduce a global temperature T that is associated with the acceleration amplitude \Gamma in a vibrating bed. We show that the configurational statistics of weakly excited granular materials in a vibrating bed obey the Fermi statistics.Comment: 12 pages, 1 figure, To Appear in Phys. Rev. Lett. April, 199

Thermal convection in fluidized granular systems

Thermal convection is observed in molecular dynamic simulation of a fluidized granular system of nearly elastic hard disks moving under gravity, inside a rectangular box. Boundaries introduce no shearing or time dependence, but the energy injection comes from a slip (shear-free) thermalizing base. The top wall is perfectly elastic and lateral boundaries are either elastic or periodic. The observed convection comes from the effect of gravity and the spontaneous granular temperature gradient that the system dynamically develops.Comment: 4 pages, 5 figure

Hadronic Light-by-Light Contribution to Muon g-2 in Chiral Perturbation Theory

We compute the hadronic light-by-light scattering contributions to the muon anomalous magnetic moment, \amulbl, in chiral perturbation theory that are enhanced by large logarithms and a factor of $N_C$. They depend on a low-energy constant entering pseudoscalar meson decay into a charged lepton pair. The uncertainty introduced by this constant is $\pm 60\times 10^{-11}$, which is comparable in magnitude to the present uncertainty entering the leading-order vacuum polarization contributions to the anomalous moment. It may be reduced to some extent through an improved measurement of the $\pi^0\to e^+ e^-$ branching ratio. However, the dependence of \amulbl on non-logarithmically enhanced effects cannot be constrained except through the measurement of the anomalous moment itself. The extraction of information on new physics would require a future experimental value for the anomalous moment differing significantly from the 2001 result reported by the E821 collaboration.Comment: 7 pages, 2 figure