206 research outputs found
Semiclassical time--dependent propagation in three dimensions: How accurate is it for a Coulomb potential?
A unified semiclassical time propagator is used to calculate the
semiclassical time-correlation function in three cartesian dimensions for a
particle moving in an attractive Coulomb potential. It is demonstrated that
under these conditions the singularity of the potential does not cause any
difficulties and the Coulomb interaction can be treated as any other
non-singular potential. Moreover, by virtue of our three-dimensional
calculation, we can explain the discrepancies between previous semiclassical
and quantum results obtained for the one-dimensional radial Coulomb problem.Comment: 8 pages, 4 figures (EPS
The development, evaluation and application of O3 flux and flux-response models for additional agricultural crops
Avaliação da atividade antimicrobiana de extrato aquoso e etanólico de Acanthospermum australe.
As plantas medicinais tĂŞm sido amplamente empregadas na terapia de diversas patologias, constituindo parte das ferramentas terapĂŞuticas utilizadas no controle das mais variadas molĂ©stias humanas. A atividade antibacteriana dos extratos aquoso e etanĂłlico de Acanthospermum australe (Loefl.) O. Kuntze foi avaliada frente Ă s bactĂ©rias Staphylococcus aureus (ATCC 6538P) e Escherichia coli (ATCC 25922), pelo mĂ©todo de difusĂŁo em Agar. Foi observada a inibição de crescimento destes microrganismos por ambos os extratos, nas concentrações testadas. Paralelamente, foi realizada a análise fitoquĂmica dos extratos aquoso e hidroetanĂłlico para a determinação de compostos fenĂłlicos (taninos, flavonoides, ácidos fenĂłlicos e antraquinonas), alcaloides e compostos terpĂŞnicos. Os extratos apresentaram perfis qualitativamente semelhantes, apresentando taninos, flavonoides, ácidos fenĂłlicos e compostos terpĂŞnicos
Inelastic semiclassical Coulomb scattering
We present a semiclassical S-matrix study of inelastic collinear
electron-hydrogen scattering. A simple way to extract all necessary information
from the deflection function alone without having to compute the stability
matrix is described. This includes the determination of the relevant Maslov
indices. Results of singlet and triplet cross sections for excitation and
ionization are reported. The different levels of approximation -- classical,
semiclassical, and uniform semiclassical -- are compared among each other and
to the full quantum result.Comment: 9 figure
InAs nanowire hot-electron Josephson transistor
At a superconductor (S)-normal metal (N) junction pairing correlations can
"leak-out" into the N region. This proximity effect [1, 2] modifies the system
transport properties and can lead to supercurrent flow in SNS junctions [3].
Recent experimental works showed the potential of semiconductor nanowires (NWs)
as building blocks for nanometre-scale devices [4-7], also in combination with
superconducting elements [8-12]. Here, we demonstrate an InAs NW Josephson
transistor where supercurrent is controlled by hot-quasiparticle injection from
normal-metal electrodes. Operational principle is based on the modification of
NW electron-energy distribution [13-20] that can yield reduced dissipation and
high-switching speed. We shall argue that exploitation of this principle with
heterostructured semiconductor NWs opens the way to a host of
out-of-equilibrium hybrid-nanodevice concepts [7, 21].Comment: 6 pages, 6 color figure
The presence of Helicobacter pylori in oral cavities of patients with leukoplakia and oral lichen planus
Cluster Lenses
Clusters of galaxies are the most recently assembled, massive, bound
structures in the Universe. As predicted by General Relativity, given their
masses, clusters strongly deform space-time in their vicinity. Clusters act as
some of the most powerful gravitational lenses in the Universe. Light rays
traversing through clusters from distant sources are hence deflected, and the
resulting images of these distant objects therefore appear distorted and
magnified. Lensing by clusters occurs in two regimes, each with unique
observational signatures. The strong lensing regime is characterized by effects
readily seen by eye, namely, the production of giant arcs, multiple-images, and
arclets. The weak lensing regime is characterized by small deformations in the
shapes of background galaxies only detectable statistically. Cluster lenses
have been exploited successfully to address several important current questions
in cosmology: (i) the study of the lens(es) - understanding cluster mass
distributions and issues pertaining to cluster formation and evolution, as well
as constraining the nature of dark matter; (ii) the study of the lensed objects
- probing the properties of the background lensed galaxy population - which is
statistically at higher redshifts and of lower intrinsic luminosity thus
enabling the probing of galaxy formation at the earliest times right up to the
Dark Ages; and (iii) the study of the geometry of the Universe - as the
strength of lensing depends on the ratios of angular diameter distances between
the lens, source and observer, lens deflections are sensitive to the value of
cosmological parameters and offer a powerful geometric tool to probe Dark
Energy. In this review, we present the basics of cluster lensing and provide a
current status report of the field.Comment: About 120 pages - Published in Open Access at:
http://www.springerlink.com/content/j183018170485723/ . arXiv admin note:
text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author
COL4A3 is degraded in allergic asthma and degradation predicts response to anti-IgE therapy.
BACKGROUND: Asthma is a heterogeneous syndrome substantiating the urgent requirement for endotype-specific biomarkers. Dysbalance of fibrosis and fibrolysis in asthmatic lung tissue leads to reduced levels of the inflammation-protective collagen 4 (COL4A3). OBJECTIVE: To delineate the degradation of COL4A3 in allergic airway inflammation and evaluate the resultant product as a biomarker for anti-IgE therapy response. METHODS: The serological COL4A3 degradation marker C4Ma3 (Nordic Bioscience, Denmark) and serum cytokines were measured in the ALLIANCE cohort (paediatric cases/controls: n=134/n=35; adult cases/controls: n=149/n=31). Exacerbation of allergic airway disease in mice was induced by sensitising to ovalbumin (OVA), challenge with OVA aerosol and instillation of poly(cytidylic-inosinic). Fulacimstat (chymase inhibitor; Bayer) was used to determine the role of mast cell chymase in COL4A3 degradation. Patients with cystic fibrosis (n=14) and cystic fibrosis with allergic bronchopulmonary aspergillosis (ABPA; n=9) as well as patients with severe allergic uncontrolled asthma (n=19) were tested for COL4A3 degradation. Omalizumab (anti-IgE) treatment was assessed using the Asthma Control Test. RESULTS: Serum levels of C4Ma3 were increased in asthma in adults and children alike and linked to a more severe, exacerbating allergic asthma phenotype. In an experimental asthma mouse model, C4Ma3 was dependent on mast cell chymase. Serum C4Ma3 was significantly elevated in cystic fibrosis plus ABPA and at baseline predicted the success of the anti-IgE therapy in allergic, uncontrolled asthmatics (diagnostic OR 31.5). CONCLUSION: C4Ma3 levels depend on lung mast cell chymase and are increased in a severe, exacerbating allergic asthma phenotype. C4Ma3 may serve as a novel biomarker to predict anti-IgE therapy response
Interaction between Ammonium Toxicity and Green Tide Development Over Seagrass Meadows:A Laboratory Study
Eutrophication affects seagrasses negatively by increasing light attenuation through stimulation of biomass of fast-growing, bloom-forming algae and because high concentrations of ammonium in the water can be toxic to higher plants. We hypothesized nevertheless, that moderate amounts of nitrophilic macroalgae that coexists with seagrasses under eutrophic conditions, can alleviate the harmful effects of eutrophication on seagrasses by reducing ammonium concentrations in the seawater to non-toxic levels because such algae have a very large capacity to take up inorganic nutrients. We studied therefore how combinations of different ammonium concentrations (0, 25 and 50 ÎĽM) and different standing stocks of macroalgae (i.e. 0, 1 and 6 layers of Ulva sp.) affected survival, growth and net production of the seagrass Zostera noltei. In the absence of Ulva sp., increasing ammonium concentrations had a negative influence on the performance of Z. noltei. The presence of Ulva sp. without ammonium supply had a similar, but slightly smaller, negative effect on seagrass fitness due to light attenuation. When ammonium enrichment was combined with presence of Ulva sp., Ulva sp. ameliorated some of negative effects caused by high ammonium availability although Ulva sp. lowered the availability of light. Benthic microalgae, which increased in biomass during the experiment, seemed to play a similar role as Ulva sp.--they contributed to remove ammonium from the water, and thus, aided to keep the ammonium concentrations experienced by Z. noltei at relatively non-toxic levels. Our findings show that moderate amounts of drift macroalgae, eventually combined with increasing stocks of benthic microalgae, may aid seagrasses to alleviate toxic effects of ammonium under eutrophic conditions, which highlights the importance of high functional diversity for ecosystem resistance to anthropogenic disturbance
All You Can Eat: High Performance Capacity and Plasticity in the Common Big-Eared Bat, Micronycteris microtis (Chiroptera: Phyllostomidae)
Ecological specialization and resource partitioning are expected to be particularly high in the species-rich communities of tropical vertebrates, yet many species have broader ecological niches than expected. In Neotropical ecosystems, Neotropical leaf-nosed bats (Phyllostomidae) are one of the most ecologically and functionally diverse vertebrate clades. Resource partitioning in phyllostomids might be achieved through differences in the ability to find and process food. We selected Micronycteris microtis, a very small (5–7 g) animalivorous phyllostomid, to explore whether broad resource use is associated with specific morphological, behavioral and performance traits within the phyllostomid radiation. We documented processing of natural prey and measured bite force in free-ranging M. microtis and other sympatric phyllostomids. We found that M. microtis had a remarkably broad diet for prey size and hardness. For the first time, we also report the consumption of vertebrates (lizards), which makes M. microtis the smallest carnivorous bat reported to date. Compared to other phyllostomids, M. microtis had the highest bite force for its size and cranial shape and high performance plasticity. Bite force and cranial shape appear to have evolved rapidly in the M. microtis lineage. High performance capacity and high efficiency in finding motionless prey might be key traits that allow M. microtis, and perhaps other species, to successfully co-exist with other gleaning bats
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