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
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
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 of the elastic to total cross section and empirical
fits to the 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
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
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
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
We present theoretical results on the non flux-averaged
and
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 . 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
We study the energy distribution function for interfaces in a
random field environment at zero temperature by summing the leading terms in
the perturbation expansion of 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 behave as,
, , while the distribution
function of the energy tends for large 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
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
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
Neutrino induced reactions on C, an ingredient of liquid
scintillators, have been studied in several experiments. We show that for
currently available neutrino energies, 300 MeV, calculated
exclusive cross sections CN 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
- …