498 research outputs found

    A Winged Zorotypus in Miocene Amber from the Dominician Republic (Zoraptera: Zorotypidae), with Discussion on Relationships of and within the Order

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    A new fossil zorapteran is described and figured in Miocene Dominican amber. The specimen is the first winged Zorotypus fossil, and is described as Zorotypus goeleti n.sp. The species is distinguished from the only other fossil zorapteran, Z. palaeus also in Dominican amber, as well as an extant species to which it appears most similar, Z. snyderi. The new fossil is significant in the possession of segmented cerci, a plesiomorphic character unique for the order. The classification of the order is briefly summarized and genera proposed by Kukalová - Peck and Peck (1993) and Chao and Chen (2000) are new ly synonymized under Zorotypus. Phylogenetic affinities within Zoraptera and of the order among other lower Neoptera are briefly discussed. The order is considered to be most closely allied to the webspinners, order Embiidina

    Total Hadronic Cross Section and the Elastic Slope: An Almost Model-Independent Connection

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    An almost model-independent parametrization for the ratio of the total cross section to the elastic slope, as function of the center of mass energy, is introduced. The analytical result is based on the approximate relation of this quantity with the ratio RR of the elastic to total cross section and empirical fits to the RR data from proton-proton scattering above 10 GeV, under the conditions of asymptotic unitarity and the black-disk limit. This parametrization may be useful in studies of extensive air showers and the determination of the proton-proton total cross section from proton-air production cross section in cosmic-ray experiments.Comment: 15 pages, 4 figures, v4: few typos corrected, final version to be published in Nucl. Phys.

    Search for Solar Axions Using Fe-57

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    We have made a search for Fe-57 gamma rays of energy 14.4 keV induced by resonant absorption of monochromatic solar axions, as proposed by Moriyama. The proposed axions are suggested to be emitted from the Sun, in M1 transitions between the first, thermally excited state and the ground state of Fe-57. An upper limit on hadronic axion mass of 745 eV is obtained at the 95% confidence level, it being assumed that z=0.56 and S=0.5.Comment: 4 pages, latex, revtex source, 1 postscript figure included, Title revised, some references added and expanded discussion. Version accepted by Phys. Lett.

    Prepregnancy Body Mass Index, Smoking During Pregnancy, and Infant Birth Weight

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    Purpose: Smoking during pregnancy is strongly associated with increased risk of small for gestational age (SGA) and low birth weight, whereas elevated prepregnancy body mass index (BMI) is associated with a decreased risk of SGA and greater birth weight. We investigated the combined effect of prenatal smoking and prepregnancy BMI on risk of SGA and on birth weight. Methods: A total of 34,928 singleton, term pregnancies in residents of New York City between 1995 and 2003 were evaluated in multivariable regression models of birth weight and risk of SGA. Results: Increasing prepregnancy BMI reduced the risk of SGA and increased birth weight. The effect of prenatal smoking on birth weight and SGA diminished in women as their prepregnancy BMI increased, such that prenatal smoking did not significantly impact the risk of SGA among women who were overweight or obese before pregnancy. Prenatal smoking decreased mean birth weight by 187 g (95% confidence interval [CI] -337, -37) among underweight women, by 129 g(95% CI -170, -87) among normal weight women, by 46 g (95% CI -113, +20) among overweight women, and by 75 g (95% CI -162, +11) among obese women. Conclusions: This study suggests that the effect of smoking during pregnancy on SGA and birth weight is present in underweight and normal weight women but markedly reduced among obese and overweight women

    Josephson Current in the Presence of a Precessing Spin

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    The Josephson current in the presence of a precessing spin between various types of superconductors is studied. It is shown that the Josephson current flowing between two spin-singlet pairing superconductors is not modulated by the precession of the spin. When both superconductors have equal-spin-triplet pairing state, the flowing Josephson current is modulated with twice of the Larmor frequency by the precessing spin. It was also found that up to the second tunneling matrix elements, no Josephson current can occur with only a direct exchange interaction between the localized spin and the conduction electrons, if the two superconductors have different spin-parity pairing states.Comment: 5 pages, 1 figur

    Charged-current neutrino-208Pb reactions

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    We present theoretical results on the non flux-averaged 208Pb(νe,e)208Bi^{208}Pb(\nu_{e},e^-)^{208}Bi and 208Pb(νμ,μ)208Bi^{208}Pb(\nu_{\mu},\mu^-)^{208}Bi reaction cross sections, obtained within the charge-exchange Random-Phase-Approximation. A detailed knowledge of these cross sections is important in different contexts. In particular, it is necessary to assess the possibility of using lead as a detector in future experiments on supernova neutrinos, such as OMNIS and LAND, and eventually detect neutrino oscillation signals by exploiting the spectroscopic properties of 208Bi^{208}Bi. We discuss the present status on the theoretical predictions of the reaction cross sections.Comment: 5 pages, latex, 3 figures. added discussion on present status, Submitted to Phys.Rev.

    Universal energy distribution for interfaces in a random field environment

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    We study the energy distribution function ρ(E)\rho (E) for interfaces in a random field environment at zero temperature by summing the leading terms in the perturbation expansion of ρ(E)\rho (E) in powers of the disorder strength, and by taking into account the non perturbational effects of the disorder using the functional renormalization group. We have found that the average and the variance of the energy for one-dimensional interface of length LL behave as, RLlnL_{R}\propto L\ln L, ΔERL\Delta E_{R}\propto L, while the distribution function of the energy tends for large LL to the Gumbel distribution of the extreme value statistics.Comment: 4 pages, 2 figures, revtex4; the distribution function of the total and the disorder energy is include

    Response of Mica to Weakly Interacting Massive Particles

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    We calculate spin-dependent cross sections for the scattering from mica of hypothetical weakly interacting dark-matter particles such as neutralinos. The most abundant odd-A isotopes in mica, Al27 and K39, require different shell-model treatments. The calculated cross sections will allow the interpretation of ongoing experiments that look for tracks due to the interaction of dark-matter particles with nuclei in ancient mica.Comment: 11 pages, RevTex, 2 uuencoded figures, submittted to Phys. Rev.

    Quantum walk on distinguishable non-interacting many-particles and indistinguishable two-particle

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    We present an investigation of many-particle quantum walks in systems of non-interacting distinguishable particles. Along with a redistribution of the many-particle density profile we show that the collective evolution of the many-particle system resembles the single-particle quantum walk evolution when the number of steps is greater than the number of particles in the system. For non-uniform initial states we show that the quantum walks can be effectively used to separate the basis states of the particle in position space and grouping like state together. We also discuss a two-particle quantum walk on a two- dimensional lattice and demonstrate an evolution leading to the localization of both particles at the center of the lattice. Finally we discuss the outcome of a quantum walk of two indistinguishable particles interacting at some point during the evolution.Comment: 8 pages, 7 figures, To appear in special issue: "quantum walks" to be published in Quantum Information Processin

    Neutrino induced transitions between the ground states of the A=12 triad

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    Neutrino induced reactions on 12^{12}C, an ingredient of liquid scintillators, have been studied in several experiments. We show that for currently available neutrino energies, EνE_{\nu} \le 300 MeV, calculated exclusive cross sections 12^{12}Cgs(ν,l)_{gs}(\nu,l)12^{12}Ngs_{gs} for both muon and electron neutrinos are essentially model independent, provided the calculations simultaneously describe the rates of several other reactions involving the same states or their isobar analogs. The calculations agree well with the measured cross sections, which can be therefore used to check the normalization of the incident neutrino spectrum and the efficiency of the detector.Comment: 9 pages REVTEX, 2 postscript figures, text and figures available at http://www.krl.caltech.edu/preprints/MAP.htm
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