18,722 research outputs found
Infrared spectroscopic study of phonons coupled to charge excitations in FeSi
From an investigation of the optical conductivity of FeSi single crystals
using FTIR spectroscopy in the frequency range from 30 to 20000 wavenumbers we
conclude that the transverse effective charge of the Fe and Si ions is
approximately 4e. Of the five optical phonons which are allowed by symmetry we
observe only four, three of which have a Fano line shape presumably resulting
from an interaction of these modes with the electronic continuum. We show that
the large oscillator strength of the phonons results from a relatively weak
coupling (lambda of the order of 0.1) of the lattice degrees of freedom to an
electronic resonance above the semiconductor gap, which is also responsible for
the large electronic polarizability of the medium.Comment: Revtex, 10 pages, 2 postscript pictures, to be published in Phys.
Rev. B Rapid Comm
Female Mate Choice is Influenced by Male Sport Participation
Sexual selection theory argues that females invest more heavily in reproduction than males and thus tend to be choosier in terms of mate choice. Sport may provide a context within which females can gain information about male quality to inform this choice. Males may be able to display attractive traits such as athleticism, strength, and physique to females while participating in sport. We predicted that females would favor males that participated in team sports over individual sports and non-athletes because team sport athletes may be more likely to display qualities such as the ability to work well with others and role acceptance. We used a questionnaire, a photograph, and manipulated descriptions to gauge the effects of sport involvement, attractiveness, and status on 282 females’ willingness to participate in various types of relationships. Team sport athletes were perceived as being more desirable as potential mates than individual sport athletes and non-athletes. It is suggested that team sport athletes may have traits associated with good parenting such as cooperation, likeability, and role acceptance, and/or these athletes may be better able to assert dominance in a team setting. Results are discussed in terms of further implications and future research
Beam Dynamics Studies for the CLIC Main Linac
The implications of long-range wakefields on the beam quality are
investigated through a detailed beam dynamics study. Injection offsets are
considered and the resulting emittance dilution recorded, including systematic
sources of error. These simulations have been conducted for damped and detuned
structures (DDS) and for waveguide damped structures-both for the CLIC
collider.Comment: 3 pages, 6 figures, IPAC1
High current lightning test of space shuttle external tank lightning protection system
During lift-off, the shuttle launch vehicle (external tank, solid rocket booster and orbiter) may be subjected to a lightning strike. Tests of a proposed lightning protection method for the external tank and development materials which were subjected to simulated lightning strikes are described. Results show that certain of the high resistant paint strips performed remarkably well in diverting the 50 kA lightning strikes
Optimal Control for Generating Quantum Gates in Open Dissipative Systems
Optimal control methods for implementing quantum modules with least amount of
relaxative loss are devised to give best approximations to unitary gates under
relaxation. The potential gain by optimal control using relaxation parameters
against time-optimal control is explored and exemplified in numerical and in
algebraic terms: it is the method of choice to govern quantum systems within
subspaces of weak relaxation whenever the drift Hamiltonian would otherwise
drive the system through fast decaying modes. In a standard model system
generalising decoherence-free subspaces to more realistic scenarios,
openGRAPE-derived controls realise a CNOT with fidelities beyond 95% instead of
at most 15% for a standard Trotter expansion. As additional benefit it requires
control fields orders of magnitude lower than the bang-bang decouplings in the
latter.Comment: largely expanded version, superseedes v1: 10 pages, 5 figure
First Evaluation of Dynamic Aperture at Injection for FCC-hh
In the Hadron machine option, proposed in the context of the Future Circular
Colliders (FCC) study, the dipole field quality is expected to play an
important role, as in the LHC. A preliminary evaluation of the field quality of
dipoles, based on the NbSn technology, has been provided by the magnet
group. The effect of these field imperfections on the dynamic aperture, using
the present lattice design, is presented and first tolerances on the b and
b multipole components are evaluated
Biotic indicators of carabid species richness on organically and conventionally managed arable fields
Carabids, a species rich arthropod family, potentially contribute much to biodiversity in agroecosystems, but assessing and monitoring carabid diversity is costly and time consuming. Therefore, this study aimed at finding more easily measurable parameters indicating high carabid diversity within organic and conventional management systems. Cover and number of weed species as well as activity density of single carabid species and of total carabids were investigated as potential indicators of carabid species richness. The study was carried out near Reckenfeld in Westphalia on sandy Plaggenesch soils. Three organically and four conventionally managed fields (cereals and corn) were investigated at the field margins and in the field centres from April to August 1999. Additionally, data of carabid catches and weed flora in winter cereals from an extended study in Düren (Northrhine-Westphalia) were reanalysed to validate the results. However, neither of the potential indicators showed consistently significant positive correlation with carabid diversity. This is partly attributed to the low variability of management conditions within the management systems in the studies presented
- …