293 research outputs found
Asymptotic normalization coefficients for mirror virtual nucleon decays in a microscopic cluster model
It has been suggested recently (Phys. Rev. Lett. 91, 232501 (2003)) that
charge symmetry of nucleon-nucleon interactions relates the Asymptotic
Normalization Coefficients (ANCs) of proton and neutron virtual decays of
mirror nuclei. This relation is given by a simple analytical formula which
involves proton and neutron separation energies, charges of residual nuclei and
the range of their strong interaction with the last nucleon. Relation between
mirror ANCs, if understood properly, can be used to predict astrophysically
relevant direct proton capture cross sections using neutron ANCs measured with
stable beams. In this work, we calculate one-nucleon ANCs for several light
mirror pairs, using microscopic two-, three- and four-cluster models, and
compare the ratio of mirror ANCs to the predictions of the simple analytic
formula. We also investigate mirror symmetry between other characteristics of
mirror one-nucleon overlap integrals, namely, spectroscopic factors and
single-particle ANCs.Comment: 12 pages, submitted to Phys. Rev.
Note on the stability criteria for a new type of helical flows
In this paper, we proceed exploring the case of non-stationary helical flows
of the Navier-Stokes equations for incompressible fluids with variable
(spatially dependent) coefficient of proportionality between velocity and the
curl field of flow. Meanwhile, the system of Navier-Stokes equations (including
continuity equation) has been successfully explored previously with respect to
the existence of analytical way for presentation of non-stationary helical
flows of the aforementioned type. The main motivation of the current research
is the exploring the stability of previously obtained helical flows. Conditions
for the stability criteria of the exact solution for the aforementioned type of
flows are obtained, for which non-stationary helical flow with invariant
Bernoulli-function is considered. As it has been formulated before, the spatial
part of the pressure field of the fluid flow should be determined via
Bernoulli-function, if components of the velocity of the flow are already
obtained.Comment: 10 pages, 1 figures; Keywords: Navier-Stokes equations,
non-stationary helical flow, Bernoulli-function; this note corresponds to the
article which was accepted for publication in "Journal of King Saud
University - Science" (03 July 2018), DOI 10.1016/j.jksus.2018.07.00
Microbial carbonate build-ups at methane seeps near the upper boundary of the gas-hydrate stability zone in the Black Sea: results of EU project CRIMEA
Extensive dredging carried out in May-June 2004 in the deeper parts of the Dnepr paleo-delta area (NW Black Sea) yielded for the first time chimney-shaped carbonate microbial build-ups, which occur at methane seeps close to upper boundary of the gas-hydrate stability zone (~ 700 m). Carbonate samples taken with a benthic trawl represent fragments of the uppermost, middle and lowest parts of the build-up, which are similar to those found previously at the shallower and deeper methane seeps in the Black Sea. At the same time, the holed, plate-like carbonates in the lowest parts of the build-up provide first indications that gas channels are formed during the earliest growth phase of these microbial structures. Stable carbon isotope analyses of the carbonates from the uppermost fragments gave the d13C values ranging from -33.7 to -36.6 pro mil, while the d13C values of the lowermost fragments are significantly lighter, varying between -42.0 and -44.6 pro mil. Both these types of carbonates indicate that a major portion of the carbonate carbon originates from bacterial oxidation of the seeping methane. Oxygen isotopic values also show differences between the more irregular and porous samples from the uppermost part of the build-up, which are composed of a mixture of aragonite and Mg-calcite (d18O = 0.7 to 0.94 pro mil, and the only Mg-calcite cemented thin slabs of lowermost carbonates (d18O = 1.35 to 1.57 pro mil. The difference in d13C/d18O ratio found in the upper and lower parts of the build-up may reflect the changing of the water temperature and salinity during the chimney growth
Asymptotic normalization coefficients for α + 3He → 7Be from the peripheral α-particle transfer reactions and their astrophysical application
The results of the analysis of the α-particle transfer 12C(d, 6Li)8Be and 12Be(3He, 7Be)8Be reactions at the low energies performed within the modified DWBA have been presented. New estimates are obtained for values of the asymptotic normalization coefficients (ANCs) for α+3He → 7Be (g.s.) and α+3He → 7Be (E∗ =0 .429MeV) as well as of the astrophysical S34(0) factors for the direct capture 3He(α,γ)7Be reaction
Diode-pumped LiY<inf>0.3</inf>Lu<inf>0.7</inf>F<inf>4</inf>:Pr and LiYF<inf>4</inf>:Pr red lasers
© 2016 Astro Ltd.The laser quality LiY0.3Lu0.7F4:Pr and LiYF4:Pr fluoride single crystals were grown in Kazan University by the Bridgeman technique. Spectral-kinetic properties of LiY0.3Lu0.7F4:Pr and LiYF4:Pr crystals have been investigated. For the first time, laser oscillations of LiY0.3Lu0.7F4:Pr crystal have been obtained on 3P0 → 3F2 transitions (λ = 640 nm) under multimode diode pumping at 442 nm, with a slope efficiency of 9 %. Also, continuous-wave lasing has been obtained for LiYF4:Pr crystal at 640 nm under the same pumping condition with a slope efficiency of 8.5%. The maximum output power of 340 mW has been achieved for both crystals
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