139,887 research outputs found
Dispersal and extinction in fragmented landscapes
Evolutionary and population dynamics models suggest that the migration rate will affect the probability of survival in fragmented landscapes. Using data for butterfly species in the fragmented British landscape and in immediately adjoining areas of the European continent, this paper shows that species of intermediate mobility have declined most, followed by those of low mobility whereas high-mobility species are generally surviving well. Compared to the more sedentary species, species of intermediate mobility require relatively large areas where they breed at slightly lower local densities. Intermediate mobility species have probably fared badly through a combination of metapopulation (extinction and colonization) dynamics and the mortality of migrating individuals which fail to find new habitats in fragmented landscapes. Habitat fragmentation is likely to result in the non-random extinction of populations and species characterized by different levels of dispersal, although the details are likely to depend on the taxa, habitats and regions considered
Exclusive pi^+ production at HERMES
Hard exclusive production in deep inelastic lepton scattering provides access
to the unknown Generalized Parton Distributions (GPDs) of the nucleon. At
HERMES, different observables for hard exclusive pi^+ production have been
measured with a 27.6 GeV positron beam on an internal hydrogen gas target.
First preliminary results for the unpolarized ep->enpi^+ total cross section
for 1.5<Q^2<10.5 GeV^2 and for 0.02<x<0.8 are presented and compared to GPD
calculations. The final result for the single-spin asymmetry using a
longitudinal polarized target is also reported.Comment: 5 pages, 3 figures, contribution to the XII International Workshop on
Deep Inelastic Scattering, April 14-18, 2004, Strbske Pleso, Slovaki
Energy spectra of two interacting fermions with spin-orbit coupling in a harmonic trap
We explore the two-body spectra of spin- fermions in isotropic harmonic
traps with external spin-orbit potentials and short range two-body
interactions. Using a truncated basis of total angular momentum eigenstates,
non-perturbative results are presented for experimentally realistic forms of
the spin-orbit coupling: a pure Rashba coupling, Rashba and Dresselhaus
couplings in equal parts, and a Weyl-type coupling. The technique is easily
adapted to bosonic systems and other forms of spin-orbit coupling.Comment: 12 pages, 9 figure
Does nitrate deposition following astrophysical ionizing radiation events pose an additional threat to amphibians?
It is known that amphibians are especially susceptible to the combination of
heightened UVB radiation and increased nitrate concentrations. Various
astrophysical events have been suggested as sources of ionizing radiation that
could pose a threat to life on Earth, through destruction of the ozone layer
and subsequent increase in UVB, followed by deposition of nitrate. In this
study, we investigate whether the nitrate deposition following an ionizing
event is sufficiently large to cause an additional stress beyond that of the
heightened UVB previously considered. We have converted predicted nitrate
depositions to concentration values, utilizing data from the New York State
Department of Environmental Conservation Acid Rain Monitoring Network web site.
Our results show that the increase in nitrate concentration in bodies of water
following the most intense ionization event likely in the last billion years
would not be sufficient to cause a serious additional stress on amphibian
populations and may actually provide some benefit by acting as fertilizer.Comment: This version is a longer, more detailed draft of an article submitted
to the journal Astrobiolog
Bedside differentiation of vestibular neuritis from central "vestibular pseudoneuritis".
Acute unilateral peripheral and central vestibular lesions
can cause similar signs and symptoms, but they require
different diagnostics and management. We therefore
correlated clinical signs to differentiate vestibular neuritis
(40 patients) from central ‘‘vestibular pseudoneuritis’’ (43
patients) in the acute situation with the final diagnosis
assessed by neuroimaging. Skew deviation was the only
specific but non-sensitive (40%) sign for pseudoneuritis.
None of the other isolated signs (head thrust test,
saccadic pursuit, gaze evoked nystagmus, subjective
visual vertical) were reliable; however, multivariate
logistic regression increased their sensitivity and specificity
to 92%
Possible Suppression of Resonant Signals for Split-UED by Mixing at the LHC?
The mixing of the imaginary parts of the transition amplitudes of nearby
resonances via the breakdown of the Breit-Wigner approximation has been shown
to lead to potentially large modifications in the signal rates for new physics
at colliders. In the case of suppression, this effect may be significant enough
to lead to some new physics signatures being initially missed in searches at,
e.g., the LHC. Here we explore the influence of this `width mixing' on the
production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge
bosons present in Split-UED. We demonstrate that in this particular case large
cross section modifications in the resonance region are necessarily absent and
explain why this is so based on the group theoretical structure of the SM.Comment: 10 pages, 2 figures; discussion and references adde
So what do we do with the rest of the day? Going beyond the pre-shot routine in professional golf
Optimally focused attention has been shown to be a key psychological characteristic for peak performance in golf; a feature commonly achieved with a pre-shot routine. However, research to date has yet to address how a golfer’s attention should best shift across the broader period of a whole game, or even including pre-event preparations, to support the pre-shot process and, ultimately, performance. Reflecting this knowledge gap, the present review aims to clarify current conceptual understanding and best practice against this wider perspective on attentional control, as well as highlight areas which must be considered for advances to be made. Specifically, research is required on the cognitive, behavioral, and temporal elements of routines used between shots and holes. Furthermore, to manage the attentional demands of the entire golf performance experience, such investigation also needs to explore the critical role of the support team and pre-tournament planning
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