28,396 research outputs found

    Design, development and delivery of one /1/ breadboard and three /3/ production units of a 75 VA integrated static inverter Monthly report no. 15

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    Flip-flop arrays, power transistors, epitaxial stress, and other technological developments in integrated static inverter progra

    Multi-excitonic complexes in single InGaN quantum dots

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    Cathodoluminescence spectra employing a shadow mask technique of InGaN layers grown by metal organic chemical vapor deposition on Si(111) substrates are reported. Sharp lines originating from InGaN quantum dots are observed. Temperature dependent measurements reveal thermally induced carrier redistribution between the quantum dots. Spectral diffusion is observed and was used as a tool to correlate up to three lines that originate from the same quantum dot. Variation of excitation density leads to identification of exciton and biexciton. Binding and anti-binding complexes are discovered.Comment: 3 pages, 4 figure

    Limits on nu_e and anti-nu_e disappearance from Gallium and reactor experiments

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    The deficit observed in the Gallium radioactive source experiments is interpreted as a possible indication of the disappearance of electron neutrinos. In the effective framework of two-neutrino mixing we obtain sin22ϑ0.03\sin^{2}2\vartheta \gtrsim 0.03 and Δm20.1eV2\Delta{m}^{2} \gtrsim 0.1 \text{eV}^{2}. The compatibility of this result with the data of the Bugey and Chooz reactor short-baseline antineutrino disappearance experiments is studied. It is found that the Bugey data present a hint of neutrino oscillations with 0.02sin22ϑ0.080.02 \lesssim \sin^{2}2\vartheta \lesssim 0.08 and Δm21.8eV2\Delta{m}^{2} \approx 1.8 \text{eV}^{2}, which is compatible with the Gallium allowed region of the mixing parameters. This hint persists in the combined analyses of Bugey and Chooz data, of Gallium and Bugey data, and of Gallium, Bugey, and Chooz data.Comment: 21 pages. Final version to be published in Phys. Rev.

    Spectroscopic signature of Alfv\'en waves damping in a polar coronal hole up to 0.4 solar radii

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    Between February 24-25, 2009, the EIS spectrometer onboard the Hinode spacecraft performed special "sit & stare" observations above the South polar coronal hole continuously over more than 22 hours. Spectra were acquired with the 1" slit placed off-limb covering altitudes up to 0.48 R_\odot (3.34×1023.34\times 10^2 Mm) above the Sun surface, in order to study with EIS the non-thermal spectral line broadenings. Spectral lines such as Fe {\sc xii} λ\lambda186.88, Fe {\sc xii} λ\lambda193.51, Fe {\sc xii} λ\lambda195.12 and Fe {\sc xiii} λ\lambda202.04 are observed with good statistics up to high altitudes and they have been analyzed in this study. Results show that the FWHM of Fe {\sc xii} λ\lambda195.12 line increases up to 0.14\simeq 0.14 R_\odot, then decreases higher up. EIS stray light has been estimated and removed. Derived electron density and non-thermal velocity profiles have been used to estimate the total energy flux transported by Alfv\'en waves off-limb in polar coronal hole up to 0.4\simeq 0.4 R_\odot. The computed Alfv\'en wave energy flux density fwf_w progressively decays with altitude from fw1.2106f_w \simeq 1.2 \cdot 10^6 erg cm2^{-2} s1^{-1} at 0.03 R_\odot down to fw8.5103f_w \simeq 8.5 \cdot 10^3 erg cm2^{-2} s1^{-1} at 0.4 R_\odot, with an average energy decay rate Δfw/Δh4.5105\Delta f_w / \Delta h \simeq -4.5 \cdot 10^{-5} erg cm3^{-3} s1^{-1}. Hence, this result suggests energy deposition by Alfv\'en waves in a polar coronal hole, thus providing a significant source for coronal heating.Comment: Physical units of the Alfv\'en wave Energy Decay Rate Δfw/Δh\Delta f_w / \Delta h revised with respect to the published version. Scientific results and conclusions unchange

    STATISTICAL ISSUES IN STUDIES OF THERMOREGULATION IN FARM ANIMALS

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    Patterns of tympanic temperature response were identified in ad-lib-fed cattle exposed to constant or cyclic (±7 C) conditions at two levels of air temperature: 10 C and 28 C. Use of time series analysis following the DDS approach of Pandit and Wu indicate the thermoregulatory control dynamics for steers at 28±7 C were markedly different from those at the other conditions. Preliminary evaluations using the ideas of chaos and non-linear dynamics show promise of further characterization of stress responses in farm animals

    Isoscaling Studies of Fission - a Sensitive Probe into the Dynamics of Scission

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    The fragment yield ratios were investigated in the fission of 238,233U targets induced by 14 MeV neutrons. The isoscaling behavior was typically observed for the isotopic chains of fragments ranging from the proton-rich to the most neutron-rich ones. The observed high sensitivity of neutron-rich heavy fragments to the target neutron content suggests fission as a source of neutron-rich heavy nuclei for present and future rare ion beam facilities, allowing studies of nuclear properties towards the neutron drip-line and investigations of the conditions for nucleosynthesis of heavy nuclei. The breakdowns of the isoscaling behavior around N=62 and N=80 manifest the effect of two shell closures on the dynamics of scission. The shell closure around N=64 can be explained by the deformed shell. The investigation of isoscaling in the spontaneous fission of 248,244Cm further supports such conclusion. The Z-dependence of the isoscaling parameter exhibits a structure which can be possibly related to details of scission dynamics. The fission isoscaling studies can be a suitable tool for the investigation of possible new pathways to synthesize still heavier nuclei.Comment: 7 pages, 3 figures, RevTex, final version, to appear in Phys. Rev. C as a regular articl

    Livestock production system management responses to thermal challenges

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    The adaptive capabilities of animals and livestock production systems have been emphasized in this report. Biometeorology has a key role in rational management to meet the challenges of thermal environments. While the focus is primarily on cattle in warm or hot climates, the importance of dynamic animal responses to environmental challenges applies to all species and climates. Methods used to mitigate environmental challenges focus on heat loss/heat production balance. Under cold stress, reduction of heat loss is the key. Under heat stress, reduction of heat load or increasing heat loss are the primary management tools, although heat-tolerant animals are also available. In general, livestock with health problems and the most productive animals (e.g., highest growth rate or milk production) are at greatest risk of heat stress, thereby requiring the most attention. Risk management, by considering perceived thermal challenges, then assessing the potential consequences and acting accordingly, will reduce the impact of such challenges. Appropriate actions include: shade, sprinkling, air movement, or active cooling. Summarizing, the most important element of proactive environmental management to reduce risk is preparation: be informed, develop a strategic plan, observe and recognize animals in distress, and take appropriate tactical action

    Higgs Phenomenology in Warped Extra-Dimensions with a 4th Generation

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    We study a warped extra-dimension scenario where the Standard Model fields lie in the bulk, with the addition of a fourth family of fermions. We concentrate on the flavor structure of the Higgs couplings with fermions in the flavor anarchy ansatz. Even without a fourth family, these couplings will be generically misaligned with respect to the SM fermion mass matrices. The presence of the fourth family typically enhances the misalignment effects and we show that one should expect them to be highly non-symmetrical in the (34){(34)} inter-generational mixing. The radiative corrections from the new fermions and their flavor violating couplings to the Higgs affect negligibly known experimental precision measurements such as the oblique parameters and ZbbˉZ\to b {\bar b} or Zμ+μZ \to \mu^+ \mu^-. On the other hand, ΔF=1,2\Delta F=1,2 processes, mediated by tree-level Higgs exchange, as well as radiative corrections to bsγb \to s \gamma and μeγ\mu \to e\gamma put some generic pressure on the allowed size of the flavor violating couplings. But more importantly, these couplings will alter the Higgs decay patterns as well as those of the new fermions, and produce very interesting new signals associated to Higgs phenomenology in high energy colliders. These might become very important indirect signals for these type of models as they would be present even when the KK mass scale is high and no heavy KK particle is discovered.Comment: 39 pages, 6 figure

    Hints of theta_13>0 from global neutrino data analysis

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    Nailing down the unknown neutrino mixing angle theta_13 is one of the most important goals in current lepton physics. In this context, we perform a global analysis of neutrino oscillation data, focusing on theta_13, and including recent results [Neutrino 2008, Proceedings of the XXIII International Conference on Neutrino Physics and Astrophysics, Christchurch, New Zealand, 2008 (unpublished)]. We discuss two converging hints of theta_13>0, each at the level of ~1sigma: an older one coming from atmospheric neutrino data, and a newer one coming from the combination of solar and long-baseline reactor neutrino data. Their combination provides the global estimate sin^2(theta_13) = 0.016 +- 0.010 (1sigma), implying a preference for \theta_13>0 with non-negligible statistical significance (~90% C.L.). We discuss possible refinements of the experimental data analyses, which might sharpen such intriguing indication.Comment: Minor changes in the text. Matches published version in PR
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