Pregalactic LiBeB Production by Supernova Cosmic Rays

I calculate the evolution of Be and B abundances produced by cosmic rays generated by massive stars in the pregalactic phase of the universe. The inputs for calculation, i.e. the star formation rate and the nuclear abundances of cosmic rays, which I assume to be the same as those of the ISM, are taken from the results of a detailed cosmic chemical evolution model with its parameters best fitted from several items of observational information including an early reionization of the IGM by $z\sim 15$. I found that when the $^6$Li plateau abundance observed in metal-poor halo stars originated in the pregalactic cosmological cosmic ray nucleosynthesis, Be and B simultaneously produced with $^6$Li amount to the lowest levels ever detected in metal-poor halo stars. It is desirable to observe Be and B abundances in metal-poor halo stars with [Fe/H]$\leq -3$ in order to elucidate the possibility of early $^6$LiBeB production by pregalactic supernova cosmic ray nucleosynthesis.Comment: 13 pages, 8 figures, ApJ accepte

On the validity of ADM formulation in 2D quantum gravity

We investigate 2d gravity quantized in the ADM formulation, where only the loop length $l(z)$ is retained as a dynamical variable of the gravitation, in order to get an intuitive physical insight of the theory. The effective action of $l(z)$ is calculated by adding scalar fields of conformal coupling, and the problems of the critical dimension and the time development of $l$ are addressed.Comment: 12 page

Crystal and magnetic structure of La_{1-x}Sr_{1+x}MnO_{4} : role of the orbital degree of freedom

The crystal and magnetic structure of La_{1-x}Sr_{1+x}MnO_4 (0<x<0.7) has been studied by diffraction techniques and high resolution capacitance dilatometry. There is no evidence for a structural phase transition like those found in isostructural cuprates or nickelates, but there are significant structural changes induced by the variation of temperature and doping which we attribute to a rearrangement of the orbital occupation.Comment: 8 pages, 6 figures, submitted to PR

Interplay of charge and orbital ordering in manganese perovskites

A model of localized classical electrons coupled to lattice degrees of freedom and, via the Coulomb interaction, to each other, has been studied to gain insight into the charge and orbital ordering observed in lightly doped manganese perovskites. Expressions are obtained for the minimum energy and ionic displacements caused by given hole and electron orbital configurations. The expressions are analyzed for several hole configurations, including that experimentally observed by Yamada et al. in La_{7/8}Sr_{1/8}MnO_3. We find that, although the preferred charge and orbital ordering depend sensitively on parameters, there are ranges of the parameters in which the experimentally observed hole configuration has the lowest energy. For these parameter values we also find that the energy differences between different hole configurations are on the order of the observed charge ordering transition temperature. The effects of additional strains are also studied. Some results for La_{1/2}Ca_{1/2}MnO_3 are presented, although our model may not adequately describe this material because the high temperature phase is metallic.Comment: 12 pages in RevTex, 5 figures in PS files, to appear in Phys. Rev. B (New paragraphs and references added, typos corrected

pre-miRNA profiles obtained through application of locked nucleic acids and deep sequencing reveals complex 5′/3′ arm variation including concomitant cleavage and polyuridylation patterns

Recent research hints at an underappreciated complexity in pre-miRNA processing and regulation. Global profiling of pre-miRNA and its potential to increase understanding of the pre-miRNA landscape is impeded by overlap with highly expressed classes of other non coding (nc) RNA. Here, we present a data set excluding these RNA before sequencing through locked nucleic acids (LNA), greatly increasing pre-miRNA sequence counts with no discernable effect on pre-miRNA or mature miRNA sequencing. Analysis of profiles generated in total, nuclear and cytoplasmic cell fractions reveals that pre-miRNAs are subject to a wide range of regulatory processes involving loci-specific 3′- and 5′-end variation entailing complex cleavage patterns with co-occurring polyuridylation. Additionally, examination of nuclear-enriched flanking sequences of pre-miRNA, particularly those derived from polycistronic miRNA transcripts, provides insight into miRNA and miRNA-offset (moRNA) production, specifically identifying novel classes of RNA potentially functioning as moRNA precursors. Our findings point to particularly intricate regulation of the let-7 family in many ways reminiscent of DICER1-independent, pre-mir-451-like processing, introduce novel and unify known forms of pre-miRNA regulation and processing, and shed new light on overlooked products of miRNA processing pathways

A natural renormalizable model of metastable SUSY breaking

We propose a model of metastable dynamical supersymmetry breaking in which all scales are generated dynamically. Our construction is a simple variant of the Intriligator-Seiberg-Shih model, with quark masses induced by renormalizable couplings to an auxiliary supersymmetric QCD sector. Since all scales arise from dimensional transmutation, the model has no fundamental dimensionful parameters. It also does not rely on higher-dimensional operators.Comment: 9 pages; v2: typos correcte