271 research outputs found
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
Gaussian superconducting fluctuations, thermal transport, and the Nernst effect
We calculate the contribution of superconducting fluctuations to thermal
transport in the normal state, for low magnetic fields. We do so in the
Gaussian approximation to their critical dynamics which is also the
Aslamazov-Larkin approximation in the microscopics. Our results for the thermal
conductivity tensor and the transverse thermoelectric response are new. The
latter compare favorably with the data of Ong and collaborators on the Nernst
effect in the cuprates.Comment: 4 pages, 1 figure; improved introduction, minor changes; published
versio
Probing the field-induced variation of the chemical potential in Bi(2)Sr(2)CaCu(2)O(y) via the magneto-thermopower measurements
Approximating the shape of the measured in
magneto-thermopower (TEP) by asymmetric linear triangle of the
form with positive and defined below and above , we observe that . In order to account for this asymmetry, we
explicitly introduce the field-dependent chemical potential of holes
into the Ginzburg-Landau theory and calculate both an average and fluctuation contributions to the total
magneto-TEP . As a result, we find a rather simple relationship
between the field-induced variation of the chemical potential in this material
and the above-mentioned magneto-TEP data around , viz. .Comment: REVTEX (epsf), 4 pages, 2 PS figures; to be published in JET
Comparative evaluation of antimicrobial activity of oligochitosans against Klebsiella pneumoniae
© 2015 Pleiades Publishing, Ltd. The Antibacterial activity of chitosan of different molecular weights was studied against gramnegative Klebsiella pneumoniae at different pH values. It was found that the dependence of the inhibitory activity of chitosan on its molecular weight was undergoes inversion when increasing the pH of the medium above 7.0. In acidic media, chitosan of the higher molecular weight had the higher antibacterial activity, while in weàk alkaline media, oligomeric forms of chitosan displayed only the inhibition effect. Our results showed that the antibacterial activity of chitosan against Klebsiella pneumoniae was closely associated with its polycationic nature, and depended on the degree of protonation of the chitosan amino groups, which, in turn was the function of the degree of polymerization and the pH values of the medium. The results allow one to explain, in part, the contradictory literature data concerning the relationship between the antibacterial activity and molecular weight of chitosan
Neutron lifetime measurements using gravitationally trapped ultracold neutrons
Our experiment using gravitationally trapped ultracold neutrons (UCN) to
measure the neutron lifetime is reviewed. Ultracold neutrons were trapped in a
material bottle covered with perfluoropolyether. The neutron lifetime was
deduced from comparison of UCN losses in the traps with different
surface-to-volume ratios. The precise value of the neutron lifetime is of
fundamental importance to particle physics and cosmology. In this experiment,
the UCN storage time is brought closer to the neutron lifetime than in any
experiments before:the probability of UCN losses from the trap was only 1% of
that for neutron beta decay. The neutron lifetime
obtained,878.5+/-0.7stat+/-0.3sys s, is the most accurate experimental
measurement to date.Comment: 38 pages, 19 figures,changed conten
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