Thermal Properties of a Simulated Lunar Material in Air and in Vacuum

Thermal properties of simulated lunar material in air and in vacuu

Gene set bagging for estimating replicability of gene set analyses

Background: Significance analysis plays a major role in identifying and ranking genes, transcription factor binding sites, DNA methylation regions, and other high-throughput features for association with disease. We propose a new approach, called gene set bagging, for measuring the stability of ranking procedures using predefined gene sets. Gene set bagging involves resampling the original high-throughput data, performing gene-set analysis on the resampled data, and confirming that biological categories replicate. This procedure can be thought of as bootstrapping gene-set analysis and can be used to determine which are the most reproducible gene sets. Results: Here we apply this approach to two common genomics applications: gene expression and DNA methylation. Even with state-of-the-art statistical ranking procedures, significant categories in a gene set enrichment analysis may be unstable when subjected to resampling. Conclusions: We demonstrate that gene lists are not necessarily stable, and therefore additional steps like gene set bagging can improve biological inference of gene set analysis.Comment: 3 Figure

Single-spin Azimuthal Asymmetries in the ``Reduced Twist-3 Approximation''

We consider the single-spin azimuthal asymmetries recently measured at the HERMES experiment for charged pions produced in semi-inclusive deep inelastic scattering of leptons off longitudinally polarized protons. Guided by the experimental results and assuming a vanishing twist-2 transverse quark spin distribution in the longitudinally polarized nucleon, denoted as ``reduced twist-3 approximation'', a self-consistent description of the observed single-spin asymmetries is obtained. In addition, predictions are given for the z dependence of the single target-spin asymmetry.Comment: 8 pages, 2 figures, typos corrected, very small changes to text, reference adde

The Theory of the Nucleon Spin

I discuss two topics of current interest in the study of the spin structure of the nucleon. First, I discuss whether there is a sum rule for the components of the nucleon's angular moments. Second, I discuss the measurement of the nucleon's transversity distribution in light of recent results reported by the HERMES collaboration at DESY.Comment: 15 pages, 8 figures, LaTeX using rspublic.cls and BoxedEPS macros; as submitted to Phil Trans A of the Royal Society for forthcoming volume: The Quark Structure of Matter; email correspondence to [email protected]

Low-temperature phases in Pb(Zr0.52Ti0.48)O3: A neutron powder diffraction study

A neutron powder diffraction study has been carried out on Pb(Zr0.52Ti0.48)O3 in order to resolve an ongoing controversy about the nature of the low-temperature structure of this strongly-piezoelectric and technologically-important material. The results of a detailed and systematic Rietveld analysis at 20 K are consistent with the coexistence of two monoclinic phases having space groups Cm and Ic respectively, in the approximate ratio 4:1, and thus support the findings of a recent electron diffraction study by Noheda et al. [Phys. Rev. B 66, 060103 (2002)]. The results are compared to those of two recent conflicting neutron powder diffraction studies of materials of the same nominal composition by Hatch et al. [Phys. Rev. B 65, 212101 (2002)] and Frantti et al. [Phys. Rev. B 66, 064108 (2002)].Comment: RevTex4, 16 pages, 6 color figure

Bounds on transverse momentum dependent distribution and fragmentation functions

We give bounds on the distribution and fragmentation functions that appear at leading order in deep inelastic 1-particle inclusive leptoproduction or in Drell-Yan processes. These bounds simply follow from positivity of the defining matrix elements and are an important guidance in estimating the magnitude of the azimuthal and spin asymmetries in these processes.Comment: 5 pages, Revtex, 3 Postscript figures, version with minor changes, to be published in Physical Review Letter

Two-hadron interference fragmentation functions. Part I: general framework

We investigate the properties of interference fragmentation functions measurable from the distribution of two hadrons produced in the same jet in the current fragmentation region of a hard process. We discuss the azimuthal angular dependences in the leading order cross section of two-hadron inclusive lepton-nucleon scattering as an example how these interference fragmentation functions can be addressed separately.Comment: RevTeX, 7 figures, first part of a work split in two, second part forthcoming in few day