111,884 research outputs found
Low temperature linear dynamical susceptibility of dipolar spin glasses
No full textThe dissipative part of the linear magnetic dynamic susceptibility of dipolar spin glasses is considered. Due to the transition of the system (at enough high concentration of the magnetic dipoles) from a paramagnetic phase to a magnetic dipolar one, an anomalous temperature dependence of the dissipative part of the magnetic susceptibility is found. Some considerations related to the experimental results for LiHoxY 1−xF4 are made
Linear dynamical susceptibility of Ising spin glass in the transverse field at low temperature
No full text
Low temperature nonequilibrium dynamics in transverse Ising spin glass
No full textThe real part of the time-dependent ac susceptibility of the short-range Ising spin glass in a
transverse field has been investigated at very low temperatures. We have used the quantum linear response
theory and domain coarsening ideas of quantum droplet scaling theory. It is found that after a temperature
quench to a temperature T1 (lower than the spin glass transition temperature Tg) the ac susceptibility
decreases with time approximately in a logarithmic way as the system tends to the equilibrium. It is shown
that the transverse field of “tunneling” has unessential effect on the nonequilibrium dynamical properties
of the magnetic droplet system. The role of quantum fluctuations in the behavior of the ac susceptibility
is discussed
Low-temperature heat capacity of a dipole spin glass
No full textLow-temperature behavior of the heat capacity of a dipole spin glass is studied analytically. Different
contributions to the heat capacity are investigated, their comparison is performed, and their relationship with
experimental data is analyzed
THIALYSINE UTILIZATION FOR PROTEIN-SYNTHESIS BY AN EXPONENTIALLY GROWING ESCHERICHIA-COLI CULTURE
No full textAspartokinase III repression and lysine analogs utilization for protein synthesis.
No full textThe extents of thialysine and selenalysine incorporation into cell proteins were compared in E. coli KL16 and in a mutant able to grow equally well in the presence or in the absence of both lysine analogs. The mutant differs from the parental strain in the repression of aspartokinase III (AKIII), the first enzyme of the lysine biosynthetic pathway. No analog incorporation into proteins was observed in mutant cells grown in the presence of either analog, whereas a marked analog incorporation was observed in the parental strain, where up to 17\% and 12\% of protein lysine can be substituted by thialysine and selenalysine respectively. In the parental strain grown in media containing either analog at different concentration the extent of analog incorporation into proteins is related to the extent of AKIII repression
Beta-selenaproline as competitive inhibitor of proline activation.
No full textBeta-Selenaproline, a proline analog having the beta-methylene group substituted by a selenium atom, has been tested in ATP-PPi exchange reaction catalyzed by either Escherichia coli or rat liver aminoacyl-tRNA synthetases. It has been shown that with both enzymatic systems beta-selenaproline does not give rise to ATP-PPi exchange, but specifically inhibits proline activation. The inhibition is of fully competitive type and the Ki values, lower than the Km values for proline, show that beta-selenaproline binds to the synthetases with high affinity. The inability to form the complex with AMP, taking into account also the behavior of gamma-selenaproline and other proline analogs, has been ascribed to the presence of the selenium atom in the beta-position
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