411 research outputs found
Reshocked Richtmyer-Meshkov instability: Numerical study and modeling of random multi-mode experiments
Does the Borexino experiment have enough resolution to detect the neutrino flavor day-night asymmetry?
The Earth's density distribution can be approximately considered piecewise
continuous at the scale of two-flavor oscillations of neutrinos with energies
about 1 MeV. This quite general assumption appears to be enough to analytically
calculate the day-night asymmetry factor. Using the explicit time averaging
procedure, we show that, within the leading-order approximation, this factor is
determined by the electron density immediately before the detector, i.e. in the
Earth's crust. Within the approximation chosen, the resulting asymmetry factor
does not depend either on the properties of the inner Earth's layers or on the
substance and the dimensions of the detector. For beryllium neutrinos, we
arrive at the asymmetry factor estimation of about , which
is at least one order of magnitude beyond the present experimental resolution,
including that of the Borexino experiment.Comment: 16 pages, 3 figures; Talk given at the 17th International Seminar on
High Energy Physics "QUARKS'2012" (Yaroslavl, Russia, June 4-10, 2012); to
appear in the Proceedings volum
Acoustic Probing of the Jamming Transition in an Unconsolidated Granular Medium
Experiments with acoustic waves guided along the mechanically free surface of
an unconsolidated granular packed structure provide information on the
elasticity of granular media at very low pressures that are naturally
controlled by the gravitational acceleration and the depth beneath the surface.
Comparison of the determined dispersion relations for guided surface acoustic
modes with a theoretical model reveals the dependencies of the elastic moduli
of the granular medium on pressure. The experiments confirm recent theoretical
predictions that relaxation of the disordered granular packing through
non-affine motion leads to a peculiar scaling of shear rigidity with pressure
near the jamming transition corresponding to zero pressure. Unexpectedly, and
in disagreement with the most of the available theories, the bulk modulus
depends on pressure in a very similar way to the shear modulus
Stress and Strain State Analysis of Defective Pipeline Portion
The paper presents computer simulation results of the pipeline having defects in a welded joint. Autodesk Inventor software is used for simulation of the stress and strain state of the pipeline. Places of the possible failure and stress concentrators are predicted on the defective portion of the pipeline
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Diabetes reversal by inhibition of the low-molecular-weight tyrosine phosphatase.
Obesity-associated insulin resistance plays a central role in type 2 diabetes. As such, tyrosine phosphatases that dephosphorylate the insulin receptor (IR) are potential therapeutic targets. The low-molecular-weight protein tyrosine phosphatase (LMPTP) is a proposed IR phosphatase, yet its role in insulin signaling in vivo has not been defined. Here we show that global and liver-specific LMPTP deletion protects mice from high-fat diet-induced diabetes without affecting body weight. To examine the role of the catalytic activity of LMPTP, we developed a small-molecule inhibitor with a novel uncompetitive mechanism, a unique binding site at the opening of the catalytic pocket, and an exquisite selectivity over other phosphatases. This inhibitor is orally bioavailable, and it increases liver IR phosphorylation in vivo and reverses high-fat diet-induced diabetes. Our findings suggest that LMPTP is a key promoter of insulin resistance and that LMPTP inhibitors would be beneficial for treating type 2 diabetes
Is weak temperature dependence of electron dephasing possible?
The first-principle theory of electron dephasing by disorder-induced two
state fluctuators is developed. There exist two mechanisms of dephasing. First,
dephasing occurs due to direct transitions between the defect levels caused by
inelastic electron-defect scattering. The second mechanism is due to violation
of the time reversal symmetry caused by time-dependent fluctuations of the
scattering potential. These fluctuations originate from an interaction between
the dynamic defects and conduction electrons forming a thermal bath. The first
contribution to the dephasing rate saturates as temperature decreases. The
second contribution does not saturate, although its temperature dependence is
rather weak, . The quantitative estimates based on the
experimental data show that these mechanisms considered can explain the weak
temperature dependence of the dephasing rate in some temperature interval.
However, below some temperature dependent on the model of dynamic defects the
dephasing rate tends rapidly to zero. The relation to earlier studies of the
dephasing caused by the dynamical defects is discussed.Comment: 14 pages, 6 figures, submitted to PR
Strong localization of electrons in quasi-one-dimensional conductors
We report on the experimental study of electron transport in sub-micron-wide
''wires'' fabricated from Si -doped GaAs. These quasi-one-dimensional
(Q1D) conductors demonstrate the crossover from weak to strong localization
with decreasing the temperature. On the insulating side of the crossover, the
resistance has been measured as a function of temperature, magnetic field, and
applied voltage for different values of the electron concentration, which was
varied by applying the gate voltage. The activation temperature dependence of
the resistance has been observed with the activation energy close to the mean
energy spacing of electron states within the localization domain. The study of
non-linearity of the current-voltage characteristics provides information on
the distance between the critical hops which govern the resistance of Q1D
conductors in the strong localization (SL) regime. We observe the exponentially
strong negative magnetoresistance; this orbital magnetoresistance is due to the
universal magnetic-field dependence of the localization length in Q1D
conductors. The method of measuring of the single-particle density of states
(DoS) in the SL regime has been suggested. Our data indicate that there is a
minimum of DoS at the Fermi level due to the long-range Coulomb interaction.Comment: 12 pages, 11 figures; the final version to appear in Phys. Rev.
The Effect of Synthesis Conditions of Layered Gadolinium-Terbium Hydroxides on the Properties of Hybrid Phosphor Powders
In this work, hybrid phosphors powders based on layered Gd-Tb nitrate hydroxide, synthesized by controlled double-jet precipitation, as a result of intercalation of terephthalate ions, were obtained. The influence of the pH value of the synthesis on the properties of hybrid phosphor was studied
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