437 research outputs found
Generation of Relativistic Electron Bunches with Arbitrary Current Distribution via Transverse-to-Longitudinal Phase Space Exchange
We propose a general method for tailoring the current distribution of
relativistic electron bunches. The technique relies on a recently proposed
method to exchange the longitudinal phase space emittance with one of the
transverse emittances. The method consists of transversely shaping the bunch
and then converting its transverse profile into a current profile via a
transverse-to-longitudinal phase-space-exchange beamline. We show that it is
possible to tailor the current profile to follow, in principle, any desired
distributions. We demonstrate, via computer simulations, the application of the
method to generate trains of microbunches with tunable spacing and
linearly-ramped current profiles. We also briefly explore potential
applications of the technique.Comment: 13 pages, 17 figure
Computing Hilbert Class Polynomials
We present and analyze two algorithms for computing the Hilbert class
polynomial . The first is a p-adic lifting algorithm for inert primes p
in the order of discriminant D < 0. The second is an improved Chinese remainder
algorithm which uses the class group action on CM-curves over finite fields.
Our run time analysis gives tighter bounds for the complexity of all known
algorithms for computing , and we show that all methods have comparable
run times
Singular values of some modular functions
We study the properties of special values of the modular functions obtained
from Weierstrass P-function at imaginary quadratic points.Comment: 19 pages,corrected typo
The Knight Anole (Anolis equestris) in Florida
In this paper, we discuss the likely modes of introduction of the Knight Anole (Anolis equestris) into and around Florida, provide data on its current geographic distribution, and summarize life history data in both its native and introduced Florida range. Our field data consist of collections made from 1992 through 2008 and locality data taken from the literature and systematic collections throughout the United States. Anolis equestris was first introduced in Miami-Dade County in 1952. The subsequent spread of this species in Florida has been both natural and assisted by human translocations to 10 additional counties, including Brevard, Broward, Collier, Highlands, Lee, Martin, Monroe, Palm Beach, Polk, and St. Lucie. Because this species is nonindigenous and known to consume a wide variety of items, including small vertebrates, it should be removed when encountered in the wild. A comprehensive study detailing its effects on the environment is needed
First Principles Calculation of Anomalous Hall Conductivity in Ferromagnetic bcc Fe
We perform a first principles calculation of the anomalous Hall effect in
ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the
anomalous Hall conductivity and relates it to the k-space Berry phase of
occupied Bloch states. The theory is able to account for both dc and
magneto-optical Hall conductivities with no adjustable parameters.Comment: 4 pages, 6 figures, author list correcte
The Knight Anole (Anolis equestris) in Florida
In this paper, we discuss the likely modes of introduction of the Knight Anole (Anolis equestris) into and around Florida, provide data on its current geographic distribution, and summarize life history data in both its native and introduced Florida range. Our field data consist of collections made from 1992 through 2008 and locality data taken from the literature and systematic collections throughout the United States. Anolis equestris was first introduced in Miami-Dade County in 1952. The subsequent spread of this species in Florida has been both natural and assisted by human translocations to 10 additional counties, including Brevard, Broward, Collier, Highlands, Lee, Martin, Monroe, Palm Beach, Polk, and St. Lucie. Because this species is nonindigenous and known to consume a wide variety of items, including small vertebrates, it should be removed when encountered in the wild. A comprehensive study detailing its effects on the environment is needed
Assessment of metal concentrations in the SOD1\u3csup\u3eG93A\u3c/sup\u3e mouse model of amyotrophic lateral sclerosis and its potential role in muscular denervation, with particular focus on muscle tissue
Background: Amyotrophic lateral sclerosis (ALS) is among the most common of the motor neuron diseases, and arguably the most devastating. During the course of this fatal neurodegenerative disorder, motor neurons undergo progressive degeneration. The currently best-understood animal models of ALS are based on the over-expression of mutant isoforms of Cu/Zn superoxide dismutase 1 (SOD1); these indicate that there is a perturbation in metal homeostasis with disease progression. Copper metabolism in particular is affected in the central nervous system (CNS) and muscle tissue.
Methods: This present study assessed previously published and newly gathered concentrations of transition metals (Cu, Zn, Fe and Se) in CNS (brain and spinal cord) and non-CNS (liver, intestine, heart and muscle) tissues from transgenic mice over-expressing the G93A mutant SOD1 isoform (SOD1 G93A), transgenic mice over-expressing wildtype SOD1 (SOD1WT) and non-transgenic controls.
Results: Cu accumulates in non-CNS tissues at pre-symptomatic stages in SOD1G93A tissues. This accumulation represents a potentially pathological feature that cannot solely be explained by the over-expression of mSOD1. As a result of the lack of Cu uptake into the CNS there may be a deficiency of Cu for the over-expressed mutant SOD1 in these tissues. Elevated Cu concentrations in muscle tissue also preceded the onset of symptoms and were found to be pathological and not be the result of SOD1 over-expression.
Conclusions: It is hypothesized that the observed Cu accumulations may represent a pathologic feature of ALS, which may actively contribute to axonal retraction leading to muscular denervation, and possibly significantly contributing to disease pathology. Therefore, it is proposed that the toxic-gain-of-function and dying-back hypotheses to explain the molecular drivers of ALS may not be separate, individual processes; rather our data suggests that they are parallel processes
The distinct roles of two intertidal foraminiferal species in phytodetrital carbon and nitrogen fluxes – results from laboratory feeding experiments
Benthic foraminifera play a major role as primary consumers and detrivores
redistributing organic carbon and nitrogen in intertidal environments. Here
we compared the differences of phytodetrital carbon and nitrogen intake and
turnover of two dominant intertidal foraminifera, Ammonia tepida and
Haynesina germanica. Their lifestyles in relation to feeding
behavior (feeding preferences, intake and turnover of phytodetrital carbon
and nitrogen) and temperature adaptations were compared to obtain a closer
definition of their specific roles in intertidal organic matter processing.
For this comparison, we carried out a series of short-term laboratory
incubations with stable-isotope-labeled (13C and 15N) detritus as
the food source. We compared the response of the two species to diatom detritus
at three different temperatures (15, 20,
25 °C). Ammonia tepida showed a very high,
temperature-influenced intake and turnover rates with more excessive carbon
turnover, compared to nitrogen. The fairly low metabolic nitrogen turnover in
H. germanica was not affected by temperature and was higher than the
carbon turnover. This might be related with the chloroplast husbandry in
H. germanica and its lower demands for food-derived nitrogen
sources. Ammonia tepida prefers a soft chlorophyte food source over
diatom detritus, which is harder to break down. In conclusion,
A. tepida shows a generalist behavior that links with high fluxes
of organic matter (OM). Due to its high rates of OM processing and
abundances, we conclude that A. tepida is an important key player in
intertidal carbon and nitrogen turnover, specifically in the short-term
processing of OM and the mediation of dissolved nutrients to associated
microbes and primary producers. In contrast, H. germanica is a
highly specialized species with low rates of carbon and nitrogen budgeting.</p
Interacting Constituents in Cosmology
Universe evolution, as described by Friedmann's equations, is determined by
source terms fixed by the choice of pressure energy-density equations
of state . The usual approach in Cosmology considers equations of
state accounting only for kinematic terms, ignoring the contribution from the
interactions between the particles constituting the source fluid. In this work
the importance of these neglected terms is emphasized. A systematic method,
based on the Statistical Mechanics of real fluids, is proposed to include them.
A toy-model is presented which shows how such interaction terms can engender
significant cosmological effects.Comment: 24 pages, 6 figures. It includes results presented in "Cosmic
Acceleration from Elementary Interactions" [arXiv:gr-qc/0512135]. Citations
added in v.
Prey Records for the Eastern Indigo Snake (Drymarchon couperi)
Prey items for the federally protected Eastern Indigo Snake (Drymarchon couperi) were compiled from published and gray literature, field observations, necropsies, dissection of museum specimens, and personal communications from reliable sources. One hundred and eighty-six records were obtained for 48 different prey species. Anurans, Gopher Tortoises, snakes, and rodents comprised ca. 85% of the prey items. Most records (n = 143) that mentioned size were from adult indigos; 17 were from juveniles. Prey records were collected from 1940-2008 and were available for all months of the year. These data confirm that Eastern Indigo Snakes eat a wide assortment of prey of varying sizes. This strategy allows D. couperi to potentially forage successfully in many different types of habitats and under fluctuating environmental conditions, a valuable trait for a top-level predator that requires a large home range
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