486 research outputs found
Ionospheric effects during first 2 hours after the Chelyabinsk meteorite impact
This paper presents the analysis of ionospheric effects in the region close
to the Chelyabinsk meteorite explosion at 03:20UT 2013 February 15 from the
Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of
Sciences (ISTP SB RAS) EKB radar data, and from the Institute of Geophysics of
Ural Branch of Russian Academy of Sciences (IG UB RAS) PARUS ionosonde data.
Both instruments are located within the IG UB RAS Arti Observatory
approximately 200 km northward from the estimated explosion site. According to
the data obtained, the ionospheric disturbance caused by the meteorite flyby,
explosion, and impact had high dynamics and amplitude. However, it obviously
did not lead to a variation in the ionosphere mean parameters in the region
above the disturbance center during the first 2 hours. Essential effects,
however, were observed at more than 100-200 km from the explosion site and
farther up to 1500 km.Comment: 30 pages, 15 figures, submitted to JAST
New experimental limits on neutron - mirror neutron oscillations in the presence of mirror magnetic field
Present probes do not exclude that the neutron () oscillation into mirror
neutron (), a sterile state exactly degenerate in mass with the neutron,
can be a very fast process, in fact faster than the neutron decay itself. This
process is sensitive to the magnetic field. Namely, if the mirror magnetic
field exists at the Earth, oscillation probability can be
suppressed or resonantly amplified by the applied magnetic field ,
depending on its strength and on the angle between and
. We present the results of ultra-cold neutron storage measurements
aiming to check the anomalies observed in previous experiments which could be a
signal for oscillation in the presence of mirror magnetic field ~G. Analyzing the experimental data on neutron loses, we obtain a new lower
limit on oscillation time s (95 % C.L.) for any
between 0.08 and 0.17 G, and s (95 % C.L.)
for any in the interval () G
Hyperspectral system for Imaging of skin chromophores and blood oxygenation
We developed a compact, fast, hand-held hyperspectral imaging system for 2D neural network-based visualization of skin chromophores and blood oxygenation. Here, we present results of the system tests on healthy volunteers
Ultra cold neutron trap as a tool to search for dark matter with long-range radius of forces
The problem of possible application of an ultracold neutron (UCN) trap as a
detector of dark matter particles with long-range radius of forces has been
considered. Transmission of small recoil energy in scattering is a
characteristic of long-range forces. The main advantage of the ultracold
neutron technique lies in possibility of detecting recoil energy as small as
eV. Here are presented constraints on the interaction potential
parameters: for dark matter particles and
neutrons, as well as on the density value of long-range dark matter on the
Earth. The possible mechanism of accumulation of long-range dark matter on the
Earth surface is considered and the factor of density increase on the Earth
surface is evaluated. The results of the first experiment on search of
astronomical day variation of ultracold neutron storage time are under
discussion.Comment: 17 pages, 19 figures. arXiv admin note: substantial text overlap with
arXiv:1109.339
Kinetics of grain refinemet in metallic materials during large strain deformation
The development of ultrafine grained microstructures in austenitic stainless steel and pure titanium subjected to large strain deformation was comparatively studied. The change in the volume fractions of newly developed ultrafine grains was used to quantify the progress in grain refinement during plastic deformatio
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