4,198 research outputs found

    Probing Low Energy Neutrino Backgrounds with Neutrino Capture on Beta Decaying Nuclei

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    We study the interaction of low energy neutrinos on nuclei that spontaneously undergo beta decay showing that the product of the cross section times neutrino velocity takes values as high as 10^{-42} cm^2 c for some specific nuclei that decay via allowed transitions. The absence of energy threshold and the value of the cross section single out these processes as a promising though very demanding approach for future experiments aimed at a direct detection of low energy neutrino backgrounds such as the cosmological relic neutrinos.Comment: Includes a discussion of local relic neutrino density effect on neutrino capture rate. Accepted for publication in JCA

    From Large Scale Rearrangements to Mode Coupling Phenomenology

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    We consider the equilibrium dynamics of Ising spin models with multi-spin interactions on sparse random graphs (Bethe lattices). Such models undergo a mean field glass transition upon increasing the graph connectivity or lowering the temperature. Focusing on the low temperature limit, we identify the large scale rearrangements responsible for the dynamical slowing-down near the transition. We are able to characterize exactly the dynamics near criticality by analyzing the statistical properties of such rearrangements. Our approach can be generalized to a large variety of glassy models on sparse random graphs, ranging from satisfiability to kinetically constrained models.Comment: 4 pages, 4 figures, minor corrections, accepted versio

    The SAX mission for wide-band X-ray astronomy

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    The SAX (Satellite per Astronomia X) mission is a major joint program of the Italian Space Agency (ASI) and the Netherlands Agency for Space Programs (NIVR). In the framework of past and future X-raymissions the SAX satellite, launched in April 1996, stands out for its very wide spectral coverage from 0.1 to 200 keV, with well-balanced performances of the low-energy and high-energy instrumentation. The sensitivity of the scientific payload will allow the exploitation of the full band of SAX also for weak sources (1/20 of 3C273), opening new perspectives in the study of spectral shape and variability of several classes of objects. In this paper we describe the main aspects of the mission, the instruments, the scientific objectives and operations

    The Imager on INTEGRAL

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    The EIDOS gamma-ray Imager has been proposed in response to the INTEGRAL Announcement of Opportunity issued on the 1st July 1994. Through a combination of different detector technologies, it provides high-quality imaging of celestial gamma-ray sources in the energy range between 20 keV and 10 MeV combined with high continuum sensitivity, high sensitivity to both narrow and broadened gammaray lines and good spectral resolution. The instrument also offers sensitive polarimetry of gamma-ray sources. The scientific objectives of this instrument are vast and range from studies of themost compact Galactic objects through to the structure of the Galaxy and on to active galactic nuclei. Careful attention has been taken to ensure that the design of the EIDOS Imager is compatible with the mission requirement for a Galactic Plane Survey

    VGF changes during the estrous cycle: a novel endocrine role for TLQP peptides?

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    Although the VGF derived peptide TLQP-21 stimulates gonadotropin-releasing hormone (GnRH) and gonadotropin secretion, available data on VGF peptides and reproduction are limited. We used antibodies specific for the two ends of the VGF precursor, and for two VGF derived peptides namely TLQP and PGH, to be used in immunohistochemistry and enzyme-linked immunosorbent assay complemented with gel chromatography. In cycling female rats, VGF C-/N-terminus and PGH peptide antibodies selectively labelled neurones containing either GnRH, or kisspeptin (VGF N-terminus only), pituitary gonadotrophs and lactotrophs, or oocytes (PGH peptides only). Conversely, TLQP peptides were restricted to somatostatin neurones, gonadotrophs, and ovarian granulosa, interstitial and theca cells. TLQP levels were highest, especially in plasma and ovary, with several molecular forms shown in chromatography including one compatible with TLQP-21. Among the cycle phases, TLQP levels were higher during metestrus-diestrus in median eminence and pituitary, while increased in the ovary and decreased in plasma during proestrus. VGF N- and C-terminus peptides also showed modulations over the estrous cycle, in median eminence, pituitary and plasma, while PGH peptides did not. In ovariectomised rats, plasmatic TLQP peptide levels showed distinct reduction suggestive of a major origin from the ovary, while the estrogen-progesterone treatment modulated VGF C-terminus and TLQP peptides in the hypothalamus-pituitary complex. In in vitro hypothalamus, TLQP-21 stimulated release of growth hormone releasing hormone but not of somatostatin. In conclusion, various VGF peptides may regulate the hypothalamus-pituitary complex via specific neuroendocrine mechanisms while TLQP peptides may act at further, multiple levels via endocrine mechanisms involving the ovary

    Charge dynamics of a single donor coupled to a few electrons quantum dot in silicon

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    We study the charge transfer dynamics between a silicon quantum dot and an individual phosphorous donor using the conduction through the quantum dot as a probe for the donor ionization state. We use a silicon n-MOSFET (metal oxide field effect transistor) biased near threshold in the SET regime with two side gates to control both the device conductance and the donor charge. Temperature and magnetic field independent tunneling time is measured. We measure the statistics of the transfer of electrons observed when the ground state D0 of the donor is aligned with the SET states
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