4,691 research outputs found
The equilibrium intrinsic crystal-liquid interface of colloids
We use confocal microscopy to study an equilibrated crystal-liquid interface
in a colloidal suspension. Capillary waves roughen the surface, but locally the
intrinsic interface is sharply defined. We use local measurements of the
structure and dynamics to characterize the intrinsic interface, and different
measurements find slightly different widths of this interface. In terms of the
particle diameter , this width is either (based on structural
information) or (based on dynamics), both not much larger than the
particle size. This work is the first direct experimental visualization of an
equilibrated crystal-liquid interface.Comment: 6 pages; revised version, submitted to PNA
Transverse excitations of ultracold matter waves upon propagation past abrupt waveguide changes
The propagation of ultracold atomic gases through abruptly changing waveguide
potentials is examined in the limit of non-interacting atoms. Time-independent
scattering calculations of microstructured waveguides with discontinuous
changes in the transverse harmonic binding potentials are used to mimic
waveguide perturbations and imperfections. Three basic configurations are
examined: step-like, barrier-like and well-like with waves incident in the
ground mode. At low energies, the spectra rapidly depart from single-moded,
with significant transmission and reflection of excited modes. The high-energy
limit sees 100 percent transmission, with the distribution of the transmitted
modes determined simply by the overlap of the mode wave functions and
interference.Comment: 20 pages, 7 figures, under review PR
Magnetic behavior of EuCu2As2: Delicate balance between antiferromagnetic and ferromagnetic order
The Eu-based compound, EuCu2As2, crystallizing in the ThCr2Si2-type
tetragonal structure, has been synthesized and its magnetic behavior has been
investigated by magnetization (M), heat-capacity (C) and electrical resistivity
(rho) measurements as a function of temperature (T) and magnetic field (H) as
well as by 151Eu Moessbauer measurements. The results reveal that Eu is
divalent ordering antiferromagnetically below 15 K in the absence of magnetic
field, apparently with the formation of magnetic Brillouin-zone boundary gaps.
A fascinating observation is made in a narrow temperature range before
antiferromagnetism sets in: That is, there is a remarkable upturn just below 20
K in the plot of magnetic susceptibility versus T even at low fields, as though
the compound actually tends to order ferromagnetically. There are corresponding
anomalies in the magnetocaloric effect data as well. In addition, a small
application of magnetic field (around 1 kOe at 1.8 K) in the antiferromagnetic
state causes spin-reorientation effect. These results suggest that there is a
close balance between antiferromagnetism and ferromagnetism in this compoundComment: Phys. Rev. B, in pres
New excitations in bcc He - an inelastic neutron scattering study
We report neutron scattering measurements on bcc solid % He. We studied
the phonon branches and the recently discovered ''optic-like'' branch along the
main crystalline directions. In addition, we discovered another, dispersionless
"optic-like'' branch at an energy around 1 meV (~11K). The properties of
the two "optic-like" branches seem different. Since one expects only 3 acoustic
phonon branches in a monoatomic cubic crystal, these new branches must
represent different type of excitations. One possible interpretation involves
localized excitations unique to a quantum solid.Comment: 4 pages, 3 figures, accepted by PRB, Rapid Communication
Effect of Insulin on Protein Synthesis in Skeletal Muscle of an Isolated Perfused Preparation of Rat Hemicorpus
- …