396 research outputs found
EPR studies of manganese centers in SrTiO3: Non-Kramers Mn3+ ions and spin-spin coupled Mn4+ dimers
X- and Q-band electron paramagnetic resonance (EPR) study is reported on the
SrTiO3 single crystals doped with 0.5-at.% MnO. EPR spectra originating from
the S = 2 ground state of Mn3+ ions are shown to belong to the three distinct
types of Jahn-Teller centres. The ordering of the oxygen vacancies due to the
reduction treatment of the samples and consequent formation of oxygen vacancy
associated Mn3+ centres are explained in terms of the localized charge
compensation. The EPR spectra of SrTiO3: Mn crystals show the presence of next
nearest neighbor exchange coupled Mn4+ pairs in the directions.Comment: 17 pages, 8 figure
Spatial-temporal dynamics of the terahertz field generated by femtosecond filament
We present the study on spatial distribution of the maximum of terahertz field amplitude in time domain when generated by a femtosecond filament. It is shown that as a result of the propagation of the terahertz field forms a spherical wave front, on the edge of which the maximum of amplitude has a temporary delay in contrary to its central part
The versatile terahertz reflection and transmission spectrometer with the location of objects of researches in the horizontal plane
The experimental setup of versatile pulse terahertz reflection and transmission spectrometer and operation concept were described. Using this setup the temporary forms of THz signal reflected from and transmitted through the samples like amino acids, dental tissue and normal were obtained. The possibility of structural determination of powdered media was demonstrated using this method
Atmospheric Gravity Perturbations Measured by Ground-Based Interferometer with Suspended Mirrors
A possibility of geophysical measurements using the large scale laser
interferometrical gravitational wave antenna is discussed. An interferometer
with suspended mirrors can be used as a gradiometer measuring variations of an
angle between gravity force vectors acting on the spatially separated
suspensions. We analyze restrictions imposed by the atmospheric noises on
feasibility of such measurements. Two models of the atmosphere are invoked: a
quiet atmosphere with a hydrostatic coupling of pressure and density and a
dynamic model of moving region of the density anomaly (cyclone). Both models
lead to similar conclusions up to numerical factors. Besides the hydrostatic
approximation, we use a model of turbulent atmosphere with the pressure
fluctuation spectrum f^{-7/3} to explore the Newtonian noise in a higher
frequency domain (up to 10 Hz) predicting the gravitational noise background
for modern gravitational wave detectors. Our estimates show that this could
pose a serious problem for realization of such projects. Finally, angular
fluctuations of spatially separated pendula are investigated via computer
simulation for some realistic atmospheric data giving the level estimate
10^{-11} rad/sqrt(Hz) at frequency 10^{-4} Hz. This looks promising for the
possibility of the measurement of weak gravity effects such as Earth inner core
oscillations.Comment: 13 pages, 4 pigures, LaTeX. To be published in Classical and Quantum
Gravit
The Role of Wind Waves in Dynamics of the Air-Sea Interface
Wind waves are considered as an intermediate small-scale dynamic process at
the air-sea interface,which modulates radically middle-scale dynamic processes
of the boundary layers in water and air. It is shown that with the aim of a
quantitative description of the impact said, one can use the numerical wind
wave models which are added with the blocks of the dynamic atmosphere boundary
layer (DABL) and the dynamic water upper layer (DWUL). A mathematical
formalization for the problem of energy and momentum transfer from the wind to
the upper ocean is given on the basis of the well known mathematical
representations for mechanisms of a wind wave spectrum evolution. The problem
is solved quantitatively by means of introducing special system parameters: the
relative rate of the wave energy input, IRE, and the relative rate of the wave
energy dissipation, DRE. For two simple wave-origin situations, the certain
estimations for values of IRE and DRE are found, and the examples of
calculating an impact of a wind sea on the characteristics of both the boundary
layer of atmosphere and the water upper layer are given. The results obtained
permit to state that the models of wind waves of the new (fifth) generation,
which are added with the blocks of the DABL and the DWUL, could be an essential
chain of the general model describing the ocean-atmosphere circulation.Comment: 11 pages, 4 figures, 1 tabl
Near-infrared fluorescence imaging with indocyanine green in diabetic patient with critical limb ischemia: a case report
A case report of type 2 diabetic patient with critical limb ischemia (CLI) after successful endovascular revascularization is reported. The diagnosis of CLI was established according to clinical data and results of lower limb ischemia assessment by non-invasive methods. The unique feature of this case is presentation of results of the new method of lower limb ischemia assessment fluorescent angiography in near infrared range using indocyanine green (ICG). Following parameters of fluorescent angiography in near infrared range are analyzed in different regions of interest: Tstart(sec) the time of fluorescence occurrence (Istart, unit) in the analyzed area after intravenous administration of ICG; Tmax (sec) time to achieve maximum fluorescence (Imax, unit) after intravenous injection of ICG; Tmax Tstart (sec) the time difference between Imax and Istart. In this clinical case, the time of achievement Istart, Imax, Tmax Tstart in different regions of interest decreased after successful endovascular revascularization of lower limb arteries
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