Abstract
A front end system with spatiotemporal smoothing based on the use of multimode optical fibre has been developed on the Luch laser. The system consists of a broadband master oscillator, a ...smoothing fibre, preamplifiers, and subsystems for the formation of temporal and spatial radiation profile. The processes of generation of partially coherent radiation, its amplification and conversion into the second harmonic are experimentally investigated. At the amplifying channel output, the pulse energy of the first harmonic reaches up to 1200 J with a pulse duration of 4 ns; the technical coefficient of radiation conversion to the second harmonic is up to 44%, and the beam divergence is 0.2 – 0.25 mrad. When using smoothed radiation, the speckled structure in the far field is almost completely eliminated: the small-scale inhomogeneity of the target irradiation, integrated over the pulse time, is reduced by 1 – 2 orders of magnitude compared to unsmoothed radiation.
Abstract
A new version of the method for spatiotemporal smoothing of laser radiation using spectral dispersion is proposed, which does not require the use of high-frequency phase modulators, i.e. a ...method based on the use of a broadband master oscillator. An experimental study of this method has been conducted on the Luch laser facility.
After observing and investigating the double-exotic (a double-exotic atom is a bound system, in which both oppositely charged components are unstable particles like μ,π,K,…) π+π− atom with the ground ...state lifetime τ of about 3×10−15 s, the upgraded DIRAC experiment at the CERN PS accelerator observes for the first time long-lived states of the same atom with lifetimes of about 10−11 s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived π+π− atoms amounts to 436±61, corresponding to a signal-to-error ratio of better than 7 standard deviations. This observation opens a new possibility to measure energy differences between p and s atomic states and so to determine ππ scattering lengths.
The basic goal of this work is the development of investigation technique of space-time parameters of broadband oscillator of the powerful Luch Facility of the Russian Federal Nuclear Center designed ...to smooth radiation profile during passage of fiber optical line. The smoothing is achieved by means of modes mixing because of wave length dispersion in fiber optics, as a result the speckled radiation structure is removed. The optical scheme for recording radiation and the photochronograph with slot scan have been prepared to carry out measurements. The measurements of duration, impulse shape and space-time heterogeneity of laser radiation at output of formation system of reference radiation with fiber optical smoothing were carried out using that developed technique.
Selenium is an essential component of more than two dozen enzymes and other selenoproteins that play critical roles in reproduction, DNA synthesis, thyroid hormone metabolism, and protection from ...oxidative damage and infection. Selenium has a protective action against some forms of cancer and cardiovascular diseases, modulates levels of inflammatory mediators, promotes to maintain bone homeostasis and protects against bone loss. Selenium significance as a cardioprotective agent may be associated not only with its antioxidant properties, but also with its ability to prevent inflammation, autophagy, as well as the intrinsic and extrinsic apoptosis pathways. Signaling pathways, such as p-AMPK, PARP, Nrf2, STAT, are involved in the protective effects of selenium. Selenium protects against cardiovascular damage by increasing the survival rate of cardiomyocytes, including a mitochondria-dependent pathway and autophagy through peroxisome proliferator-activated receptors. Research demonstrating neuroprotective and cardioprotective effects of selenium preparations – selenoline, selenocysteine and selenomethionine – is growing at a rapid rate. It has been established that these compounds are able to normalize the levels of heat shock proteins (HSP70), which limit the cytotoxic effects of free radicals, produce energotropic action, prevent a decrease in the membrane mitochondria charge, and the opening of the mitochondrial pore. Also regulate the expression of transmembrane factors NF-kB, c-fos, which is associated with their main biological function of chaperone proteins, providing protection of neurons from damage. In this review, we want to emphasize pharmacological role of Selenium and its derivatives on human health is very complex and has yet to be fully understood.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The goal of the DIRAC experiment at CERN (PS212) is to measure the π+π− atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering ...lengths combination |a0−a2|. Based on part of the collected data we present a first result on the lifetime, τ=2.91−0.62+0.49×10−15 s, and discuss the major systematic errors. This lifetime corresponds to |a0−a2|=0.264−0.020+0.033mπ−1.
The DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a ...(16 660±270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C.L. upper limit on the dark matter–nucleon spin-independent cross section of 1.14×10−44 cm2 (3.78×10−44 cm2, 3.43×10−43 cm2) for a WIMP mass of 100 GeV/c2 (1 TeV/c2, 10 TeV/c2).
We present new constraints on sub-GeV dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This ...analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and 100 MeV/c^{2}.
Short-lived ( τ ∼ 3 × 10 − 15 s ) π + K − , K + π − and π + π − atoms as well as long-lived ( τ ≥ 1 × 10 − 11 s) π + π − atoms produced in proton-nucleus interactions at 24 GeV c-1 are observed and ...studied in the DIRAC experiment at the CERN Proton Synchroton. The purpose of this paper is to show that the yields of the short-lived π + K − , K + π − and π + π − atoms in proton-nucleus interactions at 450 GeV c-1 and θ lab = 4 ° are estimated to be, respectively 67 13, 31 6 and 15 2 times higher. This may allow a significant improvement of the precision of their lifetime measurement and π π and π K scattering length combinations a 0 − a 2 and a 1 / 2 − a 3 / 2 . The yields of the long-lived π + K − , K + π − and π + π − atoms at 450 GeV c-1 are estimated to be 265 53, 120 24 and 60 9 times higher per time unit than at 24 GeV c-1. This may allow the resonance method to be used for measuring the Lamb shift in the π π atom and a new π π scattering length combination 2 a 0 + a 2 to be obtained.
PDF
