323,233 research outputs found
P. Ubaldi : Di una lettera di S. Giovanni Crisostomo, Bessarione.
No full textBardou L. P. Ubaldi : Di una lettera di S. Giovanni Crisostomo, Bessarione.. In: Échos d'Orient, tome 4, n°5, 1901. p. 314
Cosmic ray-dark matter scattering: a new signature of (asymmetric) dark matter in the gamma ray sky
No full textWe consider the process of scattering of Galactic cosmic-ray electrons and protons off of dark matter with the radiation of a final-state photon. This process provides a novel way to search for Galactic dark matter with gamma rays. We argue that for a generic weakly interacting massive particle, barring effects such as co-annihilation or a velocity-dependent cross section, the gamma-ray emission from cosmic-ray scattering off of dark matter is typically smaller than that from dark matter pair-annihilation. However, if dark matter particles cannot pair-annihilate, as is the case for example in asymmetric dark matter scenarios, cosmic-ray scattering with final state photon emission provides a unique window to detect a signal from dark matter with gamma rays. We estimate the expected flux level and its spectral features for a generic supersymmetric setup, and we also discuss dipolar and luminous dark matter. We show that in some cases the gamma-ray emission might be large enough to be detectable with the Fermi Large Area Telescope. © 2011 IOP Publishing Ltd and SISSA
Investigation on temperatures and gases emitted during thermal abuse tests of commercial Li-ion 18650 cells
No full textIncreased use of lithium-ion batteries (LIBs) has shown the safety limits of these devices, especially when subjected to electrical, mechanical, or thermal abuse. Thermal abuse is caused by exposure of the cell to temperatures above or below the operating temperatures indicated by the safety window (i.e., specific temperature and voltage range). This abuse leads to the degradation of the internal components of the cell with consequent release of gases and vapors by venting, and the generation of heat which, when not exchanged efficiently, triggers thermal runaway (TR) with consequent fire or explosion. To characterize the different phases, in this work thermal abuse tests are conducted on Lithium Cobalt Oxide (NCR) 18650 cells. Abuse tests were performed in a stainless-steel tubular reactor, in inert gas (N2), heated up to 240°C at constant heating rate (2, 5 and 10°C/min). The analysis of gas emitted was conducted through a Fourier transform infrared spectroscope (FT-IR Spectrum 3, Perkin Elmer). The comparison between the results obtained at the three heating rates shown difference in terms of temperature and time for each event and the quantities of gases emitted. In a Li-ion cell heated by the slower heating rate the venting and the onset occurred a lower temperature (133.4 and 177.4°C) compared to the higher heating rate (197.1 and 221.9°C). The durations of catastrophic events are also not comparable, with longer durations for higher heating rate (such as TR of 125s vs 102s for 2°C/min). The intermediate test, 5°C/min, shows results closest to fast heating. The gases produced are similar in terms of composition, essentially composed by hydrofluoric acid (HF), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4) and the electrolytic solvents dimethyl carbonate (DMC), ethylene carbonate (EC) and diethyl carbonate (DEC), trend over time, greater release during venting and TR, and estimated concentration, HF maximum value above 400ppm while for the other gas percentages below 4%
Ubaldi Jean-Luc (coord.) (2006). Débuter dans l’enseignement
Get PDFOuvrage pédagogique ? On le dirait d’abord, puisqu’il est présenté comme une adresse aux nouveaux enseignants. Le tutoiement est celui d’une complicité éclairée, à la fois bienveillante et rigoureuse, qui s’impose d’emblée dans la préface de F. Bégaudeau et dans l’avant-propos de J.-L. Ubaldi. Dans la première partie, « Au cœur des disciplines », douze auteur(e)s formateurs, formatrices ou associé(e)s à l’IUFM de l’académie de Lyon, répondent aux nouveaux collègues à partir d’une belle écoute..
Probing dark matter with active galactic nuclei jets
No full textWe study the possibility of detecting a signature of particle dark matter in the spectrum of gamma-ray photons from active galactic nuclei (AGNs) resulting from the scattering of high-energy particles in the AGN jet off of dark matter particles. We consider particle dark matter models in the context of both supersymmetry and universal extra dimensions, and we present the complete lowest-order calculation for processes where a photon is emitted in dark matter-electron and/or dark matter-proton scattering, where electrons and protons belong to the AGN jet. We find that the process is dominated by a resonance whose energy is dictated by the particle spectrum in the dark matter sector (neutralino and selectron for the case of supersymmetry, Kaluza-Klein photon and electron for universal extra dimensions). The resulting gamma-ray spectrum exhibits a very characteristic spectral feature, consisting of a sharp break to a hard power-law behavior. Although the normalization of the gamma-ray flux depends strongly on assumptions on both the AGN jet geometry, composition and particle spectrum as well as on the particle dark matter model and density distribution, we show that for realistic parameters choices, and for two prominent nearby AGNs (Centaurus A and M87), the detection of this effect is in principle possible. Finally, we compare our predictions and results with recent gamma-ray observations from the Fermi, H.E.S.S., and VERITAS telescopes. © 2010 The American Physical Society
Ribosomal DNA analysis of culturable deuteromycetes from the Iceman's hay: comparison of living and mummified fungi.
No full textTool-use extends Peripersonal Space and Body Schema
No full textUsing a tool to reach objects placed in the far space modifies our action space,
extending the limits of the Peripersonal Space (PPS), i.e. the space surrounding the
body where stimuli from different sensory modalities are integrated. In the present
study we investigated whether the extension of PPS accompanies to a change in the
perceived dimension of the body, compatibly with an incorporation of the tool into the
Body Schema (BS). We assessed PPS around the forearm by means of an audio-tactile
integration task and the representation of the forearm by means of a tactile distance
confrontation task before and after a training consisting of using a 1m long tool to reach
far objects. Tool-use extended PPS representation along the tool axis: the point in space
where audio-tactile stimuli interacted shifted to a farther location after tool-use. A
similar effect was present in the task assessing the BS: after tool-use, subjects perceived
their forearm narrower and longer, such as their arm took the shape of the tool.
Therefore, even a brief training with a tool induces an extension of the representations
of both the arm and the space surrounding it, suggesting a possible incorporation of the
tool into the BS
Fire Risk Evaluation of the Internal Components of the Li-ion Batteries
No full textThe advantages of Lithium-ion batteries (LIBs) are well known, anyway the LIBs are even considered hazardous products. In fact, outside the safety windows the Li-ion cells can undergo to an abuse that leads to the degradation of the internal components with the release of gases, vapour, and solid products. The reactivity of the LIBs and the relative products composition is strictly correlated to the chemical composition of the internal components. Because of a lack of regulation, safety data sheets (SDSs) of Li-ion cells are not mandatory but, generally they are available. However, there is a gap between the information reported in the SDS and the internal chemical composition, and usually the quantity of components is expressed as a range of weight percentages, and the chemical composition is not well specified. The most common lack of information concerns the electrolyte, which is usually defined as a mixture of organic carbonates without reporting the type of solvents (e.g., dimethyl carbonate, diethyl carbonate, and ethylene carbonate), the ratio between these components, and possible additives. The aim of this work was to characterize the internal components of various cylindrical 18650 cells available on the market, i.e., cell with Lithium Nickel Cobalt Aluminium Oxide (NCA) as cathode and graphite (C) or Lithium Titanate Oxide (LTO) as anode, and cells with Lithium Iron Phosphate (LFP) as cathode and C as anode. For this purpose, the cells were disassembled in a glovebox filled with argon (O2 and H2O ≤ 0.1 ppm) and then the different components were analysed by various techniques to define their chemical composition, i.e., metals of the electrodes by ICP-OES, the electrolyte by GC-FID and SPME-GC-MS, and the separator by ATR-FT-IR and DSC. The identification of those compounds is fundamental to understand the reactions occurring inside the cells and to evaluate the risks for human health and environment
Morphine dependence is associated with changes in neuropeptide S receptor expression and function in rat brain.
No full textNeuropeptide S (NPS) is a newly identified ligand for the previously discovered G-protein coupled receptor 154 now named NPSR. Recently, it has been found that NPSR gene expression is altered during ethanol withdrawal. In this study we tried to elucidate if NPSR gene expression is modified in response to morphine withdrawal and its protracted abstinence. To induce opioid dependence Wistar rats were treated for seven days with morphine. Twelve hours and 7 days after the last morphine administration brains were removed and the expression of NPSR mRNA was analyzed by in situ hybridization (ISH). Succesful induction of opioid dependence was confirmed by the naloxone-precipitated withdrawal test 2hours after the last morphine administration. Moreover, 7 days after the last morphine dose animals were checked for signs of anxiety and for intracerebroventricular (ICV) NPS (0.3 and 1.0 nmol) induced anxiolytic effects by elevated plus maze (EPM). Results showed that in morphine treated rats strong somatic signs of naloxone-precipated withdrawal occurred. ISH data revealed changes in NPSR gene expression in the ventral tegmental area as well as in the basolateral amygdaloid and bed nucleus of stria terminalis at 12hours and 7 days into abstinence, respectively. At seven days into abstinence post dependent animals showed higher levels of anxiety than controls which were significantly attenuated by NPS. These results demonstrated that morphine dependence induction led to i) changes in NPSR mRNA expression; ii) increased anxiety; iii) more potent anxiolytic-like effect of NPS
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