196 research outputs found
Study of the 10 micron continuum of water vapor
Radiation attenuation by atmospheric water vapor is considered. A formula based on laboratory data is recommended for approximating continuous absorption in the spectra region in question. Data of full scale measurements and laboratory experiments are compared. It was concluded that only molecular absorption need be taken into account under clear atmospheric conditions during the warm part of the year, while in winter or in cloudy conditions, the effect of aerosol can be significant
IR Bismuth active centers in optical fibers: Combined excitation-emission spectroscopy
3D excitation-emission luminescence spectra of Bi-doped optical fibers of
various compositions were measured in a wide wavelength range 450-1700 nm. Such
luminescence spectra were obtained for Bi-doped pure silica and germania
fibers, and for Bi-doped Al- or P-codoped silica fibers (at room and liquid
nitrogen temperatures). The energy level schemes of IR bismuth active centers
in pure silica and germania core fibers were derived from spectra obtained. The
energy level schemes similarity of bismuth active centers in these two types of
fibers was revealed.Comment: 12pages, 7 figures, 5 table
USP7/HAUSP stimulates repair of oxidative DNA lesions
USP7 is involved in the cellular stress response by regulating Mdm2 and p53 protein levels following severe DNA damage. In addition to this, USP7 may also play a role in chromatin remodelling by direct deubiquitylation of histones, as well as indirectly by regulating the cellular levels of E3 ubiquitin ligases involved in histone ubiquitylation. Here, we provide new evidence that USP7 modulated chromatin remodelling is important for base excision repair of oxidative lesions. We show that transient USP7 siRNA knockdown did not change the levels or activity of base excision repair enzymes, but significantly reduced chromatin DNA accessibility and consequently the rate of repair of oxidative lesions
Spectroscopic investigations of dispersion-shifted fiber with thin active Bi-doped ring and high nonlinear refractive index
A germanium-doped silica-core fiber with an active region in the form of a thin ring of silica doped with bismuth ions was fabricated. Bismuth doping in the ring surrounding the core allows to stabilize bismuth in silica glass, and it does not impose any restrictions on the composition of the core. The bismuth concentration in the ring is less than 0.2 wt.%. The GeO2 concentration in the core is more than 15 mol.%. A high germanium concentration in the core allows to shift the zero dispersion wavelength to 1860 nm and to obtain a high nonlinear refractive index (n2 more than 3,2*10-20 m2/W). Spectroscopic investigations were carried out in the visible and near infrared (800-1700 nm) spectral range. Despite the small concentration of bismuth, we observed the absorption and luminescence characteristic bands, confirming the presence of bismuth active centers in silica glass. Upon pumping at 1350 nm the on/off gain spectrum was measured on a 20-m fiber. The gain was observed throughout investigated range of 1430-1530 nm. The maximal gain of ~9.5 dB was obtained near 1430 nm. The results of the spectroscopic investigations of the fiber with a thin active Bi-doped ring showed prospects of the creation and application of such fiber type for laser and nonlinear optics
Optoacoustic solitons in Bragg gratings
Optical gap solitons, which exist due to a balance of nonlinearity and
dispersion due to a Bragg grating, can couple to acoustic waves through
electrostriction. This gives rise to a new species of ``gap-acoustic'' solitons
(GASs), for which we find exact analytic solutions. The GAS consists of an
optical pulse similar to the optical gap soliton, dressed by an accompanying
phonon pulse. Close to the speed of sound, the phonon component is large. In
subsonic (supersonic) solitons, the phonon pulse is a positive (negative)
density variation. Coupling to the acoustic field damps the solitons'
oscillatory instability, and gives rise to a distinct instability for
supersonic solitons, which may make the GAS decelerate and change direction,
ultimately making the soliton subsonic.Comment: 5 pages, 3 figure
Luminescent properties of Bi-doped polycrystalline KAlCl4
We observed an intensive near-infrared luminescence in Bi-doped KAlCl4
polycrystalline material. Luminescence dependence on the excitation wavelength
and temperature of the sample was studied. Our experimental results allow
asserting that the luminescence peaked near 1 um belongs solely to Bi+ ion
which isomorphically substitutes potassium in the crystal. It was also
demonstrated that Bi+ luminescence features strongly depend on the local ion
surroundings
- …