Search results for "NIH"
showing 10 items of 1190 documents
Pressure Dependence of Positron Annihilation in Si
1994
The pressure dependence of the electron-positron and the electron-electron momentum densities in silicon are studied. The observations that the electron-positron momentum density increases more rapidly with pressure than the electron-electron momentum density alone is explained in terms of increased positron penetration into the ion cores. The computational technique used here is based on the independent-particle model (IPM) coupled with the use of the electron pseudo-wave functions.
The Observation of Formation and Annihilation of Solitons and Standing Strain Wave Superstructures in a Two-Dimensional Colloidal Crystal
2008
Confining a colloidal crystal within a long narrow channel produced by two parallel walls can be used to impose a meso-scale superstructure of a predominantly mechanical elastic character [Chui et al., EPL 2008, 83, 58004]. When the crystal is compressed in the direction perpendicular to the walls, we obtain a structural transition when the number of rows of particles parallel to the walls decreases by one. All the particles of this vanishing row are distributed throughout the crystal. If the confining walls are structured (say with a corrugation along the length of the walls), then these extra particles are distributed neither uniformly nor randomly; rather, defect structures are created a…
Positron Annihilation in Polycrystalline Metals Deformed by Uniaxial Tension
2005
Angular distributions of the positron annihilation quanta were measured for polycrystalline samples deformed by uniaxial tension up to difierent deformation degrees. The S parameter as a function of the W parameter was determined. The data obtained for samples elongated up to difierent elongation degrees indicate that in the proportionality and limited proportionality regions the changes in the physical properties of samples are governed mainly by generation of vacancies and formation and kinetics of transformations of vacancy clusters occurring flrst of all on the grains of monocrystallites. In the region of plastic deformations the dominant defects are dislocations and vacancies and their…
Pseudo-bosons and Riesz Bi-coherent States
2016
After a brief review on D-pseudo-bosons we introduce what we call Riesz bi-coherent states, which are pairs of states sharing with ordinary coherent states most of their features. In particular, they produce a resolution of the identity and they are eigenstates of two different annihilation operators which obey pseudo-bosonic commutation rules.
Cooling and slowing of trapped antiprotons below 100 meV
1989
Electron cooling of trapped antiprotons allows their storage at energies 10 million times lower than is available in any antiproton storage ring. More than 60 000 antiprotons with energies from 0 to 3000 eV are stored in an ion trap from a single pulse of 5.9-MeV antiprotons from LEAR. Trapped antiprotons maintain their initial energy distribution over a storage lifetime exceeding 50 h unless allowed to collide with a cold buffer gas of trapped electrons, where- upon they cool dramatically to 1 eV in tens of seconds. The cooled antiprotons can be stacked into a harmonic potential well suited for long-term storage and precision measurements.
Searches for neutral Higgs bosons in e+e− collisions at centre-of-mass energies from 192 to 202 GeV
2000
Searches for neutral Higgs bosons are performed with the 237 pb-1 of data collected in 1999 by the ALEPH detector at LEP, for centre-of-mass energies between 191.6 and 201.6 GeV. These searches apply to Higgs bosons within the context of the Standard Model and its minimal supersymmetric extension (MSSM) as well as to invisibly decaying Higgs bosons. No evidence of a signal is seen. A lower limit on the mass of the Standard Model Higgs boson of 107.7 GeV/c2 at 95% confidence level is set. In the MSSM, lower limits of 91.2 and 91.6 GeV/c2 are derived for the masses of the neutral Higgs bosons h and A, respectively. For a Higgs boson decaying invisibly and produced with the Standard Model cros…
Using electric fields to prevent mirror-trapped antiprotons in antihydrogen studies
2013
The signature of trapped antihydrogen ($\overline{\mathrm{H}}$) atoms is the annihilation signal detected when the magnetic trap that confines the atoms is suddenly switched off. This signal would be difficult to distinguish from the annihilation signal of any trapped $\overline{p}$ that is released when the magnetic trap is switched off. This work deduces the large cyclotron energy ($g$137 eV) required for magnetic trapping of $\overline{p}$, considers the possibility that such $\overline{p}$ are produced, and explores the effectiveness of an electric field applied to clear charged particles from the trapping volume before $\overline{\mathrm{H}}$ detection. No mechanisms are found that can…
Electron-cooled accumulation of 4 × 109positrons for production and storage of antihydrogen atoms
2016
Four billion positrons (e+) are accumulated in a Penning–Ioffe trap apparatus at 1.2 K and <6 × 10−17 Torr. This is the largest number of positrons ever held in a Penning trap. The e+ are cooled by collisions with trapped electrons (e−) in this first demonstration of using e− for efficient loading of e+ into a Penning trap. The combined low temperature and vacuum pressure provide an environment suitable for antihydrogen () production, and long antimatter storage times, sufficient for high-precision tests of antimatter gravity and of CPT.
"La pura superficie" e la traslazione
2018
The article is a reading of the collected poems by Guido Mazzoni "La pura superficie" (Donzelli 2017)
Rationale and evidence on the use of tocilizumab in COVID-19: a systematic review
2020
Abstract Background Tocilizumab is an IL-6 receptor-blocking agent proposed for the treatment of severe COVID-19. The aim of this systematic review was to describe the rationale for the use of tocilizumab for the treatment of COVID-19 and to summarize the available evidence regarding its efficacy and safety. Methods MEDLINE, PubMed, EMBASE, pre-print repositories (bioRxiv and medRxiv) and two trial Registries were searched for studies on the use of tocilizumab in COVID-19 or SARS-CoV-2 infection, viral pneumonia, and/or sepsis until 20th June 2020. Results We identified 3 indirect pre-clinical studies and 28 clinical studies including 5776 patients with COVID-19 (13 with a comparison group,…