45,836 research outputs found
CsCl-type compounds in binary alloys of rare-earth metals with gold and silver
In binary alloys of silver with Sm, Tb, Ho, and Tm, and of gold with Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm, intermediate phases containing stoichiometric proportions of the two metals were found to crystallize into the CsCl (B2)-type structure. The lattice parameters of these phases are reported and a correlation has been found between these lattice parameters and the trivalent ionic radii of the rare-earth metals
Mixed-Spin Pairing Condensates in Heavy Nuclei
We show that the Bogoliubov-de Gennes equations for nuclear ground-state wave
functions support solutions in which the condensate has a mixture of
spin-singlet and spin-triplet pairing. We find that such mixed-spin condensates
do not occur when there are equal numbers of neutrons and protons, but only
when there is an isospin imbalance. Using a phenomenological Hamiltonian, we
predict that such nuclei may occur in the physical region within the proton
dripline. We also solve the Bogoliubov-de Gennes equations with variable
constraints on the spin-singlet and spin-triplet pairing amplitudes. For nuclei
that exhibit this new pairing behavior, the resulting energy surface can be
rather soft, suggesting that there may be low-lying excitations associated with
the spin mixing.Comment: 4+ pages, 3 figures, 1 table; 1 reference added; v2 corresponds to
the published versio
CDC42 and Rac1 control different actin-dependent processes in the Drosophila wing disc epithelium.
Cdc42 and Rac1 are members of the rho family of small guanosinetriphosphatases and are required for a diverse set of cytoskeleton-membrane interactions in different cell types. Here we show that these two proteins contribute differently to the organization of epithelial cells in the Drosophila wing imaginal disc. Drac1 is required to assemble actin at adherens junctions. Failure of adherens junction actin assembly in Drac1 dominant-negative mutants is associated with increased cell death. Dcdc42, on the other hand, is required for processes that involve polarized cell shape changes during both pupal and larval development. In the third larval instar, Dcdc42 is required for apico-basal epithelial elongation. Whereas normal wing disc epithelial cells increase in height more than twofold during the third instar, cells that express a dominant-negative version of Dcdc42 remain short and are abnormally shaped. Dcdc42 localizes to both apical and basal regions of the cell during these events, and mediates elongation, at least in part, by effecting a reorganization of the basal actin cytoskeleton. These observations suggest that a common cdc42-based mechanism may govern polarized cell shape changes in a wide variety of cell types
Phase structures of strong coupling lattice QCD with overlap fermions at finite temperature and chemical potential
We perform the first study of lattice QCD with overlap fermions at finite
temperature and chemical potential . We start from the Taylor expanded
overlap fermion action, and derive in the strong coupling limit the effective
free energy by mean field approximation. On the () plane and in the
chiral limit, there is a tricritical point, separating the second order chiral
phase transition line at small and large , and first order chiral
phase transition line at large and small
Beating of the oscillations in the transport coefficients of a one-dimensionally periodically modulated two-dimensional electron gas in the presence of spin-orbit interaction
Transport properties of a two-dimensional electron gas (2DEG) are studied in
the presence of a perpendicular magnetic field , of a {\it weak}
one-dimensional (1D) periodic potential modulation, and of the spin-orbit
interaction (SOI) described only by the Rashba term. In the absence of the
modulation the SOI mixes the spin-up and spin-down states of neighboring Landau
levels into two new, unequally spaced energy branches. The levels of these
branches broaden into bands in the presence of the modulation and their
bandwidths oscillate with the field . Evaluated at the Fermi energy, the
-th level bandwidth of each series has a minimum or vanishes at different
values of the field . In contrast with the 1D-modulated 2DEG without SOI,
for which only one flat-band condition applies, here there are two flat-band
conditions that can change considerably as a function of the SOI strength
and accordingly influence the transport coefficients of the 2DEG. The
phase and amplitude of the Weiss and Shubnikov-de Haas (SdH) oscillations
depend on the strength . For small values of both oscillations
show beating patterns. Those of the former are due to the independently
oscillating bandwidths whereas those of the latter are due to modifications of
the density of states, exhibit an even-odd filling factor transition, and are
nearly independent of the modulation strength. For strong values of
the SdH oscillations are split in two
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