6,154 research outputs found
Saturation Effects in Deep Inelastic Scattering at low and its Implications on Diffraction
We present a model based on the concept of saturation for small and
small . With only three parameters we achieve a good description of all Deep
Inelastic Scattering data below . This includes a consistent treatment
of charm and a successful extrapolation into the photoproduction regime. The
same model leads to a roughly constant ratio of diffractive and inclusive cross
section.Comment: 24 pages, 12 figures, Latex-fil
First Report of the Alfalfa Blotch Leafminer (Diptera: Agromyzidae), and Selected Parasites (Hymenoptera: Eulophidae) in Minnesota and Wisconsin, USA
Alfalfa blotch leafminer, Agromyza frontella, has been a serious pest of alfalfa, Medicago sativa, in the northeastern U.S. and in eastern Ontario, Canada. Until recently, the western edge of the A. frontella distribution in the U.S. was limited to eastern Ohio. We document for the first time, the occurrence of A. frontella in Minnesota and Wisconsin. Alfalfa stems damaged by A. frontella, based on adult feeding punctures, obvious blotched leafmining or the presence of larvae, were first found in 3 northern Minnesota counties during October, 1994. Infested counties included Lake of the Woods, Cook and Lake, all bordering western Ontario, Canada. In 1995, A. frontella was again found in Cook and Lake counties, where 99-100% of the stems, and 18-35% of the trifoliates/stem, contained larvae or exhibited obvious feeding damage. In 1996, following a more expanded survey, a total of 11 and 5 counties, in Minnesota and Wisconsin, respectively, showed some level of A. frontella feeding damage (stem samples ranged from \u3c5 to 100% infested). Based on additional counties surveyed 11 October, 1996, where A. frontella was not found, we now have a reasonable estimate of the southern edge of the distribution in Minnesota and Wisconsin. A total of 2 and 6 A. frontella adults were identified from sweep-net samples taken from fields with obvious feeding damage during 1995 (Lake Co.) and 1996 (Cook Co,), respectively. Three eulophid (Hymenoptera) parasites were reared from A. frontella-infested alfalfa stems collected during October, 1994 in Cook Co., Minn., including: Diglyphus begini, D. pulchripes, and Diglyphus sp., prob. isaea, all of which are new records. Our hypothesis is that A. frontella moved into Minnesota from Ontario Canada, via alfalfa hay purchased by northern Minnesota growers
High Energy Quark-Antiquark Elastic scattering with Mesonic Exchange
We studies the high energy elastic scattering of quark anti-quark with an
exchange of a mesonic state in the channel with .
Both the normalization factor and the Regge trajectory can be calculated in
PQCD in cases of fixed (non-running) and running coupling constant. The
dependence of the Regge trajectory on the coupling constant is highly
non-linear and the trajectory is of order of in the interesting physical
range.Comment: 29 page
Double logarithms, , and the NLO DGLAP evolution for the non-singlet component of the nucleon spin structure function,
Theoretical predictions show that at low values of Bjorken the spin
structure function, is influenced by large logarithmic corrections,
, which may be predominant in this region. These corrections are
also partially contained in the NLO part of the standard DGLAP evolution. Here
we calculate the non-singlet component of the nucleon structure function,
, and its first moment, using a unified evolution
equation. This equation incorporates the terms describing the NLO DGLAP
evolution and the terms contributing to the resummation. In order
to avoid double counting in the overlapping regions of the phase-space, a
unique way of including the NLO terms into the unified evolution equation is
proposed. The scheme-independent results obtained from this unified evolution
are compared to the NLO fit to experimental data, GRSV'2000. Analysis of the
first moments of shows that the unified evolution including the
resummation goes beyond the NLO DGLAP analysis. Corrections
generated by double logarithms at low influence the -dependence of the
first moments strongly.Comment: 13 pages, latex, 2 figures; Appendix adde
Heritability of testosterone levels in 12-year-old twins and its relation to pubertal development
The aim of this study was to estimate the heritability of variation in testosterone levels in 12-year-old children, and to explore the overlap in genetic and environmental influences on circulating testosterone levels and androgen dependent pubertal development. Midday salivary testosterone samples were collected on two consecutive days in a sample of 183 unselected twin pairs. Androgen induced pubertal development was assessed using self report Tanner scales of pubic hair development (boys and girls) and genital development (boys). A significant contribution of genetic effects to the variance in testosterone levels was found.
Heritability was approximately 50% in both boys and girls. The remaining proportion of the variance in testosterone levels could be explained by non-shared environmental influences. The relatively high correlation between testosterone levels of opposite sex dizygotic twins suggests that sex differences in genes influencing variation in testosterone levels have not yet developed in pre- and early puberty. Variance in pubertal development was explained by a large genetic component, moderate shared environmental influences, and a small non-shared environmental effect. Testosterone levels correlated moderately (r = .31) with pubertal development; the covariance between testosterone levels and pubertal development was entirely accounted for by genetic influences
A Hypothesis for the Composition of the Tardigrade Brain and its Implications for Panarthropod Brain Evolution
Incredibly disparate brain types are found in Metazoa, which raises the question of how this disparity evolved. Ecdysozoa includes representatives that exhibit ring-like brains-the Cycloneuralia-and representatives that exhibit ganglionic brains-the Panarthropoda (Euarthropoda, Onychophora, and Tardigrada). The evolutionary steps leading to these distinct brain types are unclear. Phylogenomic analyses suggest that the enigmatic Tardigrada is a closely related outgroup of a Euarthropoda + Onychophora clade; as such, the brains of tardigrades may provide insight into the evolution of ecdysozoan brains. Recently, evolutionarily salient questions have arisen regarding the composition of the tardigrade brain. To address these questions, we investigated brain anatomy in four tardigrade species-Hypsibius dujardini, Milnesium n. sp., Echiniscus n. sp., and Batillipes n. sp.-that together span Tardigrada. Our results suggest that general brain morphology is conserved across Tardigrada. Based on our results we present a hypothesis that proposes direct parallels between the tardigrade brain and the segmental trunk ganglia of the tardigrade ventral nervous system. In this hypothesis, brain neuropil nearly circumscribes the tardigrade foregut. We suggest that the tardigrade brain retains aspects of an ancestral cycloneuralian brain, while exhibiting ganglionic structure characteristic of euarthropods and onychophorans
Charmonium-hadron interactions from QCD
The heavy quark system is an excellent probe to learn about the QCD dynamics
at finite density. First, we discuss the properties of the and
meson at finite nucleon density. We discuss why their properties should change
at finite density and then introduce an exact QCD relation among these hadron
properties and the energy momentum tensor of the medium. Second, we discuss
attempts to calculate charmonium-hadron total cross section using effective
hadronic models and perturbative QCD. We emphasize a recent calculation, where
the cross section is derived using QCD factorization theorem. We conclude by
discussing some challenges for SIS 200.Comment: 8 pages, Presented at 6th International Conference on Strange Quarks
in Matter: 2001: A Flavorspace Odyssey (SQM2001), Frankfurt, Germany, 25-29
Sep 2001, submitted to J. Phys.
Combined electrical transport and capacitance spectroscopy of a field effect transistor
We have measured both the current-voltage (-)
and capacitance-voltage (-) characteristics of a
field effect transistor. From the measured capacitance
we calculate the electron surface density and show that its gate voltage
dependence follows the theoretical prediction resulting from the
two-dimensional free electron model. This model allows us to fit the measured
- characteristics over the \emph{entire range} of
. Combining this experimental result with the measured
current-voltage characteristics, we determine the field effect mobility as a
function of gate voltage. We show that for our device this improved combined
approach yields significantly smaller values (more than a factor of 4) of the
electron mobility than the conventional analysis of the current-voltage
characteristics only.Comment: to appear in Applied Physics Letter
The K-theoretic Farrell-Jones Conjecture for hyperbolic groups
We prove the K-theoretic Farrell-Jones Conjecture for hyperbolic groups with
(twisted) coefficients in any associative ring with unit.Comment: 33 pages; final version; to appear in Invent. Mat
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