7,537 research outputs found
Studies of the nucler equation of state using numerical calculations of nuclear drop collisions
A numerical calculation for the full thermal dynamics of colliding nuclei was developed. Preliminary results are reported for the thermal fluid dynamics in such processes as Coulomb scattering, fusion, fusion-fission, bulk oscillations, compression with heating, and collisions of heated nuclei
Impact of Electron-Phonon Coupling on Near-Field Optical Spectra
The finite momentum transfer () longitudinal optical response
of graphene has a peak at an energy
. This corresponds directly to a quasiparticle peak in the
spectral density at momentum relative to the Fermi momentum . Inclusion
of coupling to a phonon mode at results, for , in
a constant electron-phonon renormalization of the bare bands by a mass
enhancement factor and this is followed by a phonon kink at
where additional broadening begins. Here we study the corresponding
changes in the optical quasiparticle peaks which we find to continue to
directly track the renormalized quasiparticle energies until is large
enough that the optical transitions begin to sample the phonon kink region of
the dispersion curves where linearity in momentum is lost in the renormalized
Dirac Fermion dispersion curves and the correspondence to a single
quasiparticle energy is lost. Nevertheless there remains in
features analogous to the phonon kinks of the
dispersion curves which are observable through variation of and .Comment: 6 pages, 5 figure
Analysis of body calcium (regional changes in body calcium by in vivo neutron activation analysis)
The effect of space flight on urine and fecal calcium loss was documented during the three long-term Skylab flights. Neutron activation analysis was used to determine regional calcium loss. Various designs for regional analysis were investigated
Fast high-efficiency integrated waveguide photodetectors using novel hybrid vertical/butt coupling geometry
We report a novel coupling geometry for integrated waveguide photodetectorsâa hybrid vertical coupling/butt coupling scheme that allows the integration of fast, efficient, photodetectors with conventional double heterostructure waveguides. It can be employed to yield a planar, or pseudo-planar, surface that supports further levels of integration. The approach is demonstrated with a 25-”m-long p-i-n detector integrated with an InP/InGaAsP/InP waveguide, which displays a high (~90%) efficiency and large (~15 GHz) bandwidth. This is the fastest high-efficiency integrated waveguide photodetector reported to date
The Peierls substitution in an engineered lattice potential
Artificial gauge fields open new possibilities to realize quantum many-body
systems with ultracold atoms, by engineering Hamiltonians usually associated
with electronic systems. In the presence of a periodic potential, artificial
gauge fields may bring ultracold atoms closer to the quantum Hall regime. Here,
we describe a one-dimensional lattice derived purely from effective
Zeeman-shifts resulting from a combination of Raman coupling and radiofrequency
magnetic fields. In this lattice, the tunneling matrix element is generally
complex. We control both the amplitude and the phase of this tunneling
parameter, experimentally realizing the Peierls substitution for ultracold
neutral atoms.Comment: 6 pages, 5 figure
Monolithic InP-Based Grating Spectrometer for Wavelength-Division Multiplexed Systems at 1.5 ÎŒm
A monolithic InP-based grating spectrometer for use in wavelength-division multiplexed systems at 1.5 ÎŒm is reported.
The spectrometer uses a single etched reflective focusing diffraction grating and resolves >50 channels at 1 nm spacing with a ~0.3nm channel width and at least 19dB channel isolation. Operation is essentially of the state of the input polarisation
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