5,098 research outputs found
Phase Transitions in Hexane Monolayers Physisorbed onto Graphite
We report the results of molecular dynamics (MD) simulations of a complete
monolayer of hexane physisorbed onto the basal plane of graphite. At low
temperatures the system forms a herringbone solid. With increasing temperature,
a solid to nematic liquid crystal transition takes place at K
followed by another transition at K into an isotropic fluid.
We characterize the different phases by calculating various order parameters,
coordinate distributions, energetics, spreading pressure and correlation
functions, most of which are in reasonable agreement with available
experimental evidence. In addition, we perform simulations where the
Lennard-Jones interaction strength, corrugation potential strength and dihedral
rigidity are varied in order to better characterize the nature of the two
transitions through. We find that both phase transitions are facilitated by a
``footprint reduction'' of the molecules via tilting, and to a lesser degree
via creation of gauche defects in the molecules.Comment: 18 pages, eps figures embedded, submitted to Phys. Rev.
Ground-state properties of trapped Bose-Fermi mixtures: role of exchange-correlation
We introduce Density Functional Theory for inhomogeneous Bose-Fermi mixtures,
derive the associated Kohn-Sham equations, and determine the
exchange-correlation energy in local density approximation. We solve
numerically the Kohn-Sham system and determine the boson and fermion density
distributions and the ground-state energy of a trapped, dilute mixture beyond
mean-field approximation. The importance of the corrections due to
exchange--correlation is discussed by comparison with current experiments; in
particular, we investigate the effect of of the repulsive potential energy
contribution due to exchange--correlation on the stability of the mixture
against collapse.Comment: 6 pages, 4 figures (final version as published in Physical Review
Electronic properties of molecular solids: the peculiar case of solid Picene
Recently, a new organic superconductor, K-intercalated Picene with high
transition temperatures (up to 18\,K) has been discovered. We have
investigated the electronic properties of the undoped relative, solid picene,
using a combination of experimental and theoretical methods. Our results
provide detailed insight into the occuopied and unoccupied electronic states
Threshold Corrections in Precision LHC Physics: QED otimes QCD
With an eye toward LHC processes in which theoretical precisions of 1 percent
are desired, we introduce the theory of the simultaneous YFS resummation of QED
and QCD to compute the size of the expected resummed soft radiative threshold
effects in precision studies of heavy particle production at the LHC. Our
results show that both QED and QCD soft threshold effects must be controlled to
be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200
Definition of Terms, Style, and Conventions Used in A.S.P.E.N. Guidelines and Standards
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141145/1/ncp0281.pd
A jet-cloud interaction in the 3C 196 environment
Powerful radio galaxies and radio-loud quasars at high redshifts are
frequently associated with extended emission-line regions (EELRs). Here we
investigate the [O II] EELR around the quasar 3C 196 at z=0.871 using integral
field spectroscopy. We also detect extended [Ne II] emission at a distance of
about 30 kpc from the core. The emission is aligned with the radio hot spots
and shows a redshifted and a blueshifted component with a velocity difference
of ~800 km s^-1. The alignment effect and large velocities support the
hypothesis that the EELR is caused by a jet-cloud interaction, which is
furthermore indicated by the presence of a pronounced bend in the radio
emission at the location of the radio hot spots. We also report observations of
two other systems which do not show as clear indications of interactions. We
find a weaker alignment of an [O II] EELR from the z=0.927 quasar 3C 336, while
no EELR is found around the core-dominated quasar OI 363 at z=0.63.Comment: 7 pages, accepted for publication in A&
One-loop corrections to the Drell-Yan process in SANC (I). The charged current case
Radiative corrections to the charged current Drell-Yan processes are
revisited. Complete one-loop electroweak corrections are calculated within the
automatic SANC system. Electroweak scheme dependence and the choice of the
factorization scale are discussed. Comparisons with earlier calculations are
presented.Comment: extended version submitted to EPJ
A Software Platform for Post-Processing Waveform-Based NDE
Ultrasonic, microwave, and terahertz nondestructive evaluation imaging systems generally require the acquisition of waveforms at each scan point to form an image. For such systems, signal and image processing methods are commonly needed to extract information from the waves and improve resolution of, and highlight, defects in the image. Since some similarity exists for all waveform-based NDE methods, it would seem a common software platform containing multiple signal and image processing techniques to process the waveforms and images makes sense where multiple techniques, scientists, engineers, and organizations are involved. This presentation describes NASA Glenn Research Center's approach in developing a common software platform for processing waveform-based NDE signals and images. This platform is currently in use at NASA Glenn and at Lockheed Martin Michoud Assembly Facility for processing of pulsed terahertz and ultrasonic data. Highlights of the software operation will be given. A case study will be shown for use with terahertz data. The authors also request scientists and engineers who are interested in sharing customized signal and image processing algorithms to contribute to this effort by letting the authors code up and include these algorithms in future releases
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