414 research outputs found
Testing the interaction of dark energy to dark matter through the analysis of virial relaxation of clusters Abell Clusters A586 and A1689 using realistic density profiles
Interaction between dark energy and dark matter is probed through deviation
from the virial equilibrium for two relaxed clusters: A586 and A1689. The
evaluation of the virial equilibrium is performed using realistic density
profiles. The virial ratios found for the more realistic density profiles are
consistent with the absence of interaction.Comment: 16pp 1 fig; accepted by GeR
Hypoxia modulates platelet purinergic signalling pathways.
BACKGROUND: Hypoxia resulting from ascent to high-altitude or pathological states at sea level is known to increase platelet reactivity. Previous work from our group has suggested that this may be adenosine diphosphate (ADP)-specific. Given the clinical importance of drugs targeting ADP pathways, research into the impact of hypoxia on platelet ADP pathways is highly important.
METHODS: Optimul aggregometry was performed on plasma from 29 lowland residents ascending to 4,700 m, allowing systematic assessment of platelet reactivity in response to several platelet agonists. Aggregometry was also performed in response to ADP in the presence of inhibitors of the two main ADP receptors, P2Y1 and P2Y12 (MRS2500 and cangrelor, respectively). Phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a key determinant of platelet aggregation, was analysed using the VASPFix assay.
RESULTS: Hypobaric hypoxia significantly reduced the ability of a fixed concentration of cangrelor to inhibit ADP-induced aggregation and increased basal VASP phosphorylation. However, in the absence of P2Y receptor inhibitors, we did not find evidence of increased platelet sensitivity to any of the agonists tested and found reduced sensitivity to thrombin receptor-activating peptide-6 amide.
CONCLUSION: Our results provide evidence of increased P2Y1 receptor activity at high altitude and suggest down-regulation of the P2Y12 pathway through increased VASP phosphorylation. These changes in ADP pathway activity are of potential therapeutic significance to high-altitude sojourners and hypoxic sea level patients prescribed platelet inhibitors and warrant further investigation
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Advanced technology for nitrogen oxide (NO{sub x}) abatement in flue gas using microwave irradiation of coal char
This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project sought to demonstrate a new technology for the elimination of oxides of nitrogen (NO{sub x}) emission from fossil-fuel-fired industrial processes and power plants. The current technologies are not capable of meeting the government mandates for NO{sub x} emission scheduled for implementation in 1997. The approach is completely new in that microwave energy is the driver for the NO{sub x} removal process that operates at greater than 98% NO{sub x} removal efficiency. Flue gas containing NO{sub x} was passed through a bed of carbon-based reducing agent (coal char) that adsorbed the NO{sub x}. The NO{sub x}-laden char was irradiated with microwave energy that reduced the NO{sub x} to nitrogen and carbon dioxide. The process has been empirically demonstrated in the laboratory on a small scale
Squeezing of Atoms in a Pulsed Optical Lattice
We study the process of squeezing of an ensemble of cold atoms in a pulsed
optical lattice. The problem is treated both classically and
quantum-mechanically under various thermal conditions. We show that a dramatic
compression of the atomic density near the minima of the optical potential can
be achieved with a proper pulsing of the lattice. Several strategies leading to
the enhanced atomic squeezing are suggested, compared and optimized.Comment: Latex, 9 pages, 10 figures, submitted to PR
MRI of Breast Lesions
In Magnetic Resonance Mammography (MRM) high spatial as well as temporal resolution is of utmost importance for differentiating between malignant and benign lesions. Therefore, a so‐called dynamic technique (i.e., the repetitive imaging of the same slices before and in short time intervals after the injection of contrast medium) is essential to detect the differences in initial enhancements between malignant and benign lesions which are reflected by the tumorangiogenetic vascular network of malignant lesions. This unit presents a basic protocol and several alternate protocols for dynamic MRM.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145284/1/cpmia2101.pd
The status of GEO 600
The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode
Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider
This article is the Preprint version of the final published artcile which can be accessed at the link below.We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-→e+e- and (for the ϒ(4S) only) e+e-→μ+μ- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-→e+e- and e+e-→μ+μ-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the ϒ(3S) and ϒ(2S) resonances, an additional uncertainty arises due to ϒ→e+e-X background. For data collected off the ϒ resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the ϒ(4S), 0.58% (0.72%) for the ϒ(3S), and 0.68% (0.88%) for the ϒ(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat à l’Energie Atomique and Institut National de Physique Nucléaire et de Physiquedes Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e Innovación (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)
Chaos and the Quantum Phase Transition in the Dicke Model
We investigate the quantum chaotic properties of the Dicke Hamiltonian; a
quantum-optical model which describes a single-mode bosonic field interacting
with an ensemble of two-level atoms. This model exhibits a zero-temperature
quantum phase transition in the N \go \infty limit, which we describe exactly
in an effective Hamiltonian approach. We then numerically investigate the
system at finite and, by analysing the level statistics, we demonstrate
that the system undergoes a transition from quasi-integrability to quantum
chaotic, and that this transition is caused by the precursors of the quantum
phase-transition. Our considerations of the wavefunction indicate that this is
connected with a delocalisation of the system and the emergence of macroscopic
coherence. We also derive a semi-classical Dicke model, which exhibits
analogues of all the important features of the quantum model, such as the phase
transition and the concurrent onset of chaos.Comment: 51 pages, 15 figures, late
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