23,521 research outputs found
Airborne observations of methane in Comet Kohoutek
The experiment is described for airborne observations of Comet Kohoutek using an infrared tilting-filter photometer. Preliminary analysis of the data established an upper limit to the Comet's fluorescence radiation in methane lines at 3.3 microns
Comparative analysis of rigidity across protein families
We present a comparative study in which 'pebble game' rigidity analysis is applied to multiple protein crystal structures, for each of six different protein families. We find that the main-chain rigidity of a protein structure at a given hydrogen bond energy cutoff is quite sensitive to small structural variations, and conclude that the hydrogen bond constraints in rigidity analysis should be chosen so as to form and test specific hypotheses about the rigidity of a particular protein. Our comparative approach highlights two different characteristic patterns ('sudden' or 'gradual') for protein rigidity loss as constraints are removed, in line with recent results on the rigidity transitions of glassy networks
Hartree-Fock-Bogoliubov Calculations in Coordinate Space: Neutron-Rich Sulfur, Zirconium, Cerium, and Samarium Isotopes
Using the Hartree-Fock-Bogoliubov (HFB) mean field theory in coordinate
space, we investigate ground state properties of the sulfur isotopes from the
line of stability up to the two-neutron dripline (). In particular,
we calculate two-neutron separation energies, quadrupole moments, and rms-radii
for protons and neutrons. Evidence for shape coexistence is found in the very
neutron-rich sulfur isotopes. We compare our calculations with results from
relativistic mean field theory and with available experimental data. We also
study the properties of neutron-rich zirconium (), cerium
(), and samarium () isotopes which exhibit very large
prolate quadrupole deformations.Comment: 7 pages, 6 figures, 2 tables submitted to Phys. Rev.
Understanding the role of promoters in catalysis: operando XAFS/DRIFTS study of CeO<sub>x</sub>/Pt/Al<sub>2</sub>O<sub>3</sub> during CO oxidation
A combined operando XAFS/DRIFTS study on CeOx/Pt/Al2O3 catalysts has been performed during CO oxidation and provides insights into the changes in nanoparticle structure and adsorbed species during the reaction profile. The onset of CO2 formation is shown to be concurrent with a rapid re-oxidation of the Pt nanoparticles, evidenced by XAFS spectroscopy, and the loss of bridge bonded CO adsorbed on Pt, as shown by simultaneous DRIFTS acquisition. The continued appearance of linear bound CO on the catalyst surface is shown to remain long after catalytic light off. The interaction of Pt and CeOx is evidenced by the improved performance towards CO oxidation, compared to the non-CeOx modified Pt/Al2O3, and changes in the CO adsorption properties on Pt previously linked to Pt-CeO2 interfaces
Rigidity analysis of HIV-1 protease
We present a rigidity analysis on a large number of X-ray crystal structures
of the enzyme HIV-1 protease using the 'pebble game' algorithm of the software
FIRST. We find that although the rigidity profile remains similar across a
comprehensive set of high resolution structures, the profile changes
significantly in the presence of an inhibitor. Our study shows that the action
of the inhibitors is to restrict the flexibility of the beta-hairpin flaps
which allow access to the active site. The results are discussed in the context
of full molecular dynamics simulations as well as data from NMR experiments.Comment: 4 pages, 3 figures. Conference proceedings for CMMP conference 2010
which was held at the University of Warwic
Solar radiation observation stations with complete listing of data archived by the National Climatic Center, Asheville, North Carolina and initial listing of data not currently archived
A listing is provided of organizations taking solar radiation data, the 166 stations where observations are made, the type of equipment used, the form of the recorded data, and the period of operation of each station. Included is a listing of the data from 150 solar radiation stations collected over the past 25 years and stored by the National Climatic Center
Cosmic Strings from Supersymmetric Flat Directions
Flat directions are a generic feature of the scalar potential in
supersymmetric gauge field theories. They can arise, for example, from D-terms
associated with an extra abelian gauge symmetry. Even when supersymmetry is
broken softly, there often remain directions in the scalar field space along
which the potential is almost flat. Upon breaking a gauge symmetry along one of
these almost flat directions, cosmic strings may form. Relative to the standard
cosmic string picture based on the abelian Higgs model, these flat-direction
cosmic strings have the extreme Type-I properties of a thin gauge core
surrounded by a much wider scalar field profile. We perform a comprehensive
study of the microscopic, macroscopic, and observational characteristics of
this class of strings. We find many differences from the standard string
scenario, including stable higher winding mode strings, the dynamical formation
of higher mode strings from lower ones, and a resultant multi-tension scaling
string network in the early universe. These strings are only moderately
constrained by current observations, and their gravitational wave signatures
may be detectable at future gravity wave detectors. Furthermore, there is the
interesting but speculative prospect that the decays of cosmic string loops in
the early universe could be a source of ultra-high energy cosmic rays or
non-thermal dark matter. We also compare the observational signatures of
flat-direction cosmic strings with those of ordinary cosmic strings as well as
(p,q) cosmic strings motivated by superstring theory.Comment: 58 pages, 16 figures, v2. accepted to PRD, added comments about
baryogenesis and boosted decay products from cusp annihilatio
Organizational Change and Justice: The Impact of Transparent and Ethical Leaders
In the sport industry, one thing that is constant is change. Since numerous forces may drive and guide the change process, the goal of this study was to examine ethical leadership, transparency, and organizational justice during an organizational change of a consolidating National Collegiate Athletic Association (NCAA) Division I men’s and women’s athletic department. Framed from the organizational change, ethical leadership, and organizational justice literature, this qualitative case study included interviews from nine university stakeholders and analysis of public documents published over the last decade. Results revealed transparent ethical leaders in an instrumental climate espoused positive organizational justice perceptions. In addition, employees’ perceptions of transparent ethical leaders and positive organizational justice helped champion favorable responses to the organizational change. Implications of this research include encouraging intercollegiate athletic administrators to consider the security and well-being of stakeholders, which helps garner favorable responses during an organizational change
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