1,025 research outputs found

    Intracluster Comptonization of the CMB: Mean Spectral Distrortion and Cluster Number Counts

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    The mean sky-averaged Comptonization parameter, y, describing the scattering of the CMB by hot gas in clusters of galaxies is calculated in an array of flat and open cosmological and dark matter models. The models are globally normalized to fit cluster X-ray data, and intracluster gas is assumed to have evolved in a manner consistent with current observations. We predict values of y lower than the COBE/FIRAS upper limit. The corresponding values of the overall optical thickness to Compton scattering are < 10^{-4} for relevant parameter values. Of more practical importance are number counts of clusters across which a net flux (with respect to the CMB) higher than some limiting value can be detected. Such number counts are specifically predicted for the COBRAS/SAMBA and BOOMERANG missions.Comment: 23 pages, Latex, 11 PostScript figures, 5 PostScript tables, to appear in Ap

    Photon correlations for colloidal nanocrystals and their clusters

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    Images of semiconductor `dot in rods' and their small clusters are studied by measuring the second-order correlation function with a spatially resolving ICCD camera. This measurement allows one to distinguish between a single dot and a cluster and, to a certain extent, to estimate the number of dots in a cluster. A more advanced measurement is proposed, based on higher-order correlations, enabling more accurate determination of the number of dots in a small cluster. Nonclassical features of the light emitted by such a cluster are analyzed.Comment: 4 pages, 4 figure

    Impact of Coil Deformations on Field Quality in the Large Hadron Collider Main Dipole

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    In superconducting accelerator magnets the coils are usually pre-stressed in order to avoid conductor movements induced by electro-magnetic forces. In this paper we use a finite element mechanical model of the main LHC dipole to evaluate the coil deformations determined by the pre-stress and their impact on magnetic field quality. The model explains the origin of the offsets between the nominal multipole values and those measured at room temperature in prototype and pre-series dipole magnets. We also present an experiment carried out to analyse the impact on field quality and coil stresses of coil azimuthal spacers (pole shims). A 1 m long dipole collared coil has been re-assembled several times with pole shims of different thickness and the field components have been measured each time. Experimental data are compared to numerical computations based on the mechanical model.One finds that variations of shim thickness induce not only a change of the azimuthal coil length, but also a different pattern in coil deformations. A good agreement is found between measurements and simulations

    Role of contrast-enhanced ultrasound (CEUS) in paediatric practice: an EFSUMB position statement

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    The use of contrast-enhanced ultrasound (CEUS) in adults is well established in many different areas, with a number of current applications deemed off-label, but the use supported by clinical experience and evidence. Paediatric CEUS is also an off-label application until recently with approval specifically for assessment of focal liver lesions. Nevertheless there is mounting evidence of the usefulness of CEUS in children in many areas, primarily as an imaging technique that reduces exposure to radiation, iodinated contrast medium and the patient-friendly circumstances of ultrasonography. This position statement of the European Federation of Societies in Ultrasound and Medicine (EFSUMB) assesses the current status of CEUS applications in children and makes suggestions for further development of this technique

    Photocatalytic selective oxidation of 5-(hydroxymethyl)-2-furaldehyde to 2,5-furandicarbaldehyde in water by using anatase, rutile and brookite TiO2 nanoparticles

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    5-(Hydroxymethyl)-2-furaldehyde (HMF) was selectively oxidized to 2,5-furandicarbaldehyde (FDC) in aqueous medium by using home-prepared (HP) anatase, rutile, and brookite TiO2 nanoparticles. HP samples were prepared via a sol−gel method by using TiCl4 as the TiO2 precursor. Commercial TiO2 catalysts were also used for comparison. All samples were characterized by BET specific surface area, XRD, TGA, and SEM, and the reactivity results showed that HP catalysts are predominantly amorphous and give rise to selectivities toward FDC more than twice that of commercial and well-crystallized catalysts

    Local degradation of selectively oxidized AlGaAs/AlAs distributed Bragg reflectors in lateral-injection vertical-cavity surface-emitting lasers

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    We show the local degradation of a selectively oxidized top distributed Bragg reflector (DBR) in a lateral-junction vertical-cavity surface-emitting laser (LJ-VCSEL) working at room temperature in continuous-wave operation. The measurements were carried out by a scanning microluminescence system used in reflection mode. The injection of a few milliamps in continuous-wave operation at room temperature in the LJ-VCSEL induces damage both in the DBRs and in the active area. The submicron resolution maps of the reflected laser intensity, recorded from the top surface of the LJ-VCSEL, show a strong local change in the top DBR reflectivity before and after current injection. The Ό-photoluminescence map, recorded after the device failure, shows that the radiative recombination is strongly decreased in the damaged area of the device

    First Report of Soybean (Glycine max) Disease Caused by Pseudomonas aeruginosa in Cuba

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    Soybean (Glycine max L.) has become one of the most widely consumed foods, however diseases caused by microorganisms can affect yields and seed quality. In March 2015, during routine survey in a soybean growing area in Pinar del Rio province, Cuba; disease symptoms were observed in some leaves. These included water-soaked necrotic spots with surrounded chlorotic halos, especially on the margins of the leaves. To identify the possible pathogens involved, leaves were disinfected with tap water, 70% ethanol and were rinsed with sterile distilled water. Small segments from diseased tissue were macerated in sterile 0.85% NaCl solution, decimal dilutions were performed and 20 ”L aliquots were streaked onto KingŽs B medium (KB). After 24 hours of incubation at 28 oC, a fluorescent pseudomonad was isolated. Colonies were round, smooth and produced yellowish-green diffusible pigments on KB. Physiological and morphological characteristics were determined using standard microbiological techniques (Schaad et al., 200..
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