2,847 research outputs found
The Anomalous Infrared Emission of Abell 58
We present a new model to explain the excess in mid and near infrared
emission of the central, hydrogen poor dust knot in the planetary nebula (PN)
Abell 58. Current models disagree with ISO measurement because they apply an
average grain size and equilibrium conditions only. We investigate grain size
distributions and temperature fluctuations affecting infrared emission using a
new radiative transfer code and discuss in detail the conditions requiring an
extension of the classical description. The peculiar infrared emission of V605
Aql, the central dust knot in Abell 58, has been modeled with our code. V605
Aql is of special interest as it is one of only three stars ever observed to
move from the evolutionary track of a central PN star back to the post-AGB
state.Comment: 17 pages, 4 figures; accepted and to be published in Ap
Tract-based spatial statistics to assess the neuroprotective effect of early erythropoietin on white matter development in preterm infants
In a randomized double-blind placebo-controlled trial, O'Gorman et al. show that administration of erythropoietin within the first 42 hours after preterm birth improves white matter development in preterm infants. Improvements are seen in the corpus callosum, the anterior and posterior limbs of the internal capsule, and the corticospinal tract bilaterall
A β-hairpin epitope as novel structural requirement for protein arginine rhamnosylation
For canonical asparagine glycosylation, the primary amino acid sequence that directs glycosylation at specific asparagine residues is well-established. Here we reveal that a recently discovered bacterial enzyme EarP, that transfers rhamnose to a specific arginine residue in its acceptor protein EF-P, specifically recognizes a beta-hairpin loop. Notably, while the in vitro rhamnosyltransferase activity of EarP is abolished when presented with linear substrate peptide sequences derived from EF-P, the enzyme readily glycosylates the same sequence in a cyclized beta-hairpin mimic. Additional studies with other substrate-mimicking cyclic peptides revealed that EarP activity is sensitive to the method used to induce cyclization and in some cases is tolerant to amino acid sequence variation. Using detailed NMR approaches, we established that the active peptide substrates all share some degree of beta-hairpin formation, and therefore conclude that the beta-hairpin epitope is the major determinant of arginine-rhamnosylation by EarP. Our findings add a novel recognition motif to the existing knowledge on substrate specificity of protein glycosylation, and are expected to guide future identifications of rhamnosylation sites in other protein substrates
Surtos da mosca-dos-estábulos, Stomoxys calcitrans, em Mato Grosso do Sul: novo problema para as cadeias produtivas da carne e sucroalcooleira?
No presente documento é registrada a ocorrência de infestações preocupantes pela mosca-dos-estábulos, Stomoxys calcitrans L. (Diptera: Muscidae), em propriedades pecuárias próximas de usinas sucroalcooleiras na região Sul de Mato Grosso do Sul, no ano de 2009. A biologia do inseto; sua importância epidemiológica, econômica e veterinária e; possíveis alternativas de controle são apresentadas e discutidas. Entre as alternativas de controle sugere-se, em especial, o revolvimento completo duas vezes por semana do material de compostagem nas usinas e a drenagem do local onde é executada, assim como o enterrio parcial da palha pós-colheita da cana-de-açúcar com uso de cultivador. Nas propriedades pecuárias recomenda-se a limpeza de locais de criação da mosca, representado por acúmulo de dejetos de animais domésticos e ou de resíduos alimentares, especialmente em confinamentos e leiterias, dentre outras recomendações. Somente com ações integradas será possível resolver o problema e contribuir para o desenvolvimento sustentável de duas importantes cadeias produtivas do agronegócio brasileiro.bitstream/CNPGC-2010/12957/1/DOC175.pd
PathOrganic – Risks and Recommendations Regarding Human Pathogens in Organic Vegetable Production Chains
PathOrganic assesses risks associated with the consumption of fresh and minimally
processed vegetables due to the prevalence of bacterial human pathogens in plant
produce. The project evaluates whether organic production poses a risk on food safety,
taking into consideration sources of pathogen transmission (e.g. animal manure).
The project also explores whether organic versus conventional production practices
may reduce the risk of pathogen manifestation. In Europe, vegetable-linked outbreaks
are not well investigated. A conceptual model together with novel sampling strategies
and specifically adjusted methods provides the basis for large-scale surveys of organically
grown plant produce in five European countries. Critical control points are
determined and evaluated and factors contributing to a food safety problem are analyzed
in greenhouse and field experiments. The project aims at developing a quantitative
risk assessment model and at formulating recommendations for improving food
safety in organic vegetable production
No Far-Infrared-Spectroscopic Gap in Clean and Dirty High-T Superconductors
We report far infrared transmission measurements on single crystal samples
derived from BiSrCaCuO. The impurity scattering rate of
the samples was varied by electron-beam irradiation, 50MeV O ion
irradiation, heat treatment in vacuum, and Y doping. Although substantial
changes in the infrared spectra were produced, in no case was a feature
observed that could be associated with the superconducting energy gap. These
results all but rule out ``clean limit'' explanations for the absence of the
spectroscopic gap in this material, and provide evidence that the
superconductivity in BiSrCaCuO is gapless.Comment: 4 pages and 3 postscript figures attached. REVTEX v3.0. Accepted for
publication in Phys. Rev. Lett. IRDIRT
Energy gap in superconducting fullerides: optical and tunneling studies
Tunneling and optical transmission studies have been performed on
superconducting samples of Rb3C60. At temperatures much below the
superconducting transition temperature Tc the energy gap is 2 Delta=5.2 +-
0.2meV, corresponding to 2 Delta/kB Tc = 4.2. The low temperature density of
states, and the temperature dependence of the optical conductivity resembles
the BCS behavior, although there is an enhanced ``normal state" contribution.
The results indicate that this fulleride material is an s-wave superconductor,
but the superconductivity cannot be described in the weak coupling limit.Comment: RevTex file with four .EPS figures. Prints to four pages. Also
available at http://buckminster.physics.sunysb.edu/papers/pubrece.htm
A Non-Abelian Variation on the Savvidy Vacuum of the Yang-Mills Gauge Theory
As a prelude to a truly non-perturbative evaluation of the effective
potential in terms of lattice QCD, the one loop effective potential for a
non-Abelian gauge configuration is calculated using the background field
method. Through a non-trivial correlation between the space and color
orientations the new background field avoids the possible coordinate
singularity, , observed recently by Ken Johnson and his
collaborators in their Schr\"{o}dinger functional study of the SU(2) Yang-Mills
theory. In addition, since our ansatz generates a constant color magnetic field
through the commutator terms rather than derivative terms, many of the
technical drawbacks the Savvidy ansatz suffers on a lattice can be avoided. Our
one loop study yields qualitatively the same result as that of Savvidy's.Comment: 9 pages, preprint BU-HEP-93-2
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