101,626 research outputs found
Characterization of a Resistive Half Plane over a Resistive Sheet
The diffraction of a resistive half plane over a planar resistive sheet under plane wave illum1ination is determined via the dual integral equation method (a variation of the Wiener-Hopf method). The solution is obtained upon splitting the associated Wiener-Hopf functions via a numerically efficient routine. Based on the derived exact half plane dliffraction coefficient, a simplified equivalent model of the structure is developed when the separation of the half plane and resistive plane is on the order of a tenth of a wavelength or less. The model preserves the geometrical optics field of the original structure for all angles and is based on an approximate image theory of the resistive plane. Good agreement is obtained with the diffracted field exact solution
Perceptions of coach-athlete relationship are more important to coaches than athletes in predicting dyadic coping and stress appraisals: An actor-partner independence mediation model
Most attempts to manage stress involve at least one other person, yet coping studies in sport tend to report an athlete’s individual coping strategies. There is a limited understanding of coping involving other people, particularly within sport, despite athletes potentially spending a lot of time with other people, such as their coach. Guided by the systemic-transactional model of stress and coping among couples (Bodenmann, 1995), from relationship psychology, we assessed dyadic coping, perceptions of relationship quality, and primary stress appraisals of challenge and threat among 158 coach–athlete dyads (n D 277 participants). The athletes competed at amateur (n D 123), semiprofessional (n D 31), or professional levels (n D 4). Coaches and athletes from the same dyad completed a measure of dyadic coping, coach–athlete relationship, and stress appraisals. We tested an Actor–Partner Interdependence Mediation Model to account for the non-independence of dyadic data. These actor–partner analyses revealed differences between athletes and coaches. Although the actor effects were relatively large compared to partner effects, perceptions of relationship quality demonstrated little impact on athletes. The mediating role of relationship quality was broadly as important as dyadic coping for coaches. These findings provide an insight in to how coach–athlete dyads interact to manage stress and indicate that relationship quality is of particular importance for coaches, but less important for athletes. In order to improve perceptions of relationship quality among coaches and athletes, interventions could be developed to foster positive dyadic coping among both coaches and athletes, which may also impact upon stress appraisals of challenge and threat
Product state control of bi-alkali chemical reactions
We consider ultracold, chemically reactive scattering collisions of the
diatomic molecules KRb. When two such molecules collide in an ultracold gas, we
find that they are energetically forbidden from reacting to form the trimer
species KRb or RbK, hence can only react via the bond-swapping reaction
2KRb K + Rb. Moreover, the tiny energy released in this reaction
can in principle be set to zero by applying electric or microwave fields,
implying a means of controlling the available reaction channels in a chemical
reaction.Comment: 4 pages double column, 2 figures, 2 table
The origins of nuclear astrophysics at Caltech
Shortly before the start of World War II, several theoretical
physicists, including Hans Bethe and Carl von Weizsacker, advanced the
idea that the sun derives it energy from nuclear reactions within its
core. C. C. Lauritsen and William Fowler, nuclear physicists at
Caltech's Kellogg Laboratory, were among the first experimentalists to
appreciate the application of nuclear physics to stellar interiors.
Post-war strategies for studying nuclear processes in the stars
included an innovative series of unofficial, weekly seminars with Mt.
Wilson astronomers at director Ira Bowen's house, the testing of
Bethe's carbon cycle in Kellogg, and the collaboration with a diverse
group of scientists ranging from cosmologist Fred Hoyle to astronomers
Margaret and Geoffrey Burbidge. The events leading up to the
publication of the 1957 paper by Fowler, Hoyle, Burbidge, and Burbidge,
in The Reviews of Modern Physics, now regarded as a watershed in the
history of nuclear astrophysics, are discussed. For his work in low-energy
nuclear astrophysics, Fowler won the 1983 Nobel Prize in
physics
Ion-Cyclotron Double Resonance
A charged particle in a uniform moving magnetic field H describes a circular orbit in a plance perpendicular to H with an angular frequency or "cyclotron frequency" omagae. When an alternating electric field E(t) is applied normal to H at omegae, the ions absorb energy from the alternating electric field, and are accelerated to larger velocities and orbital radii. [1] The absorption of energy from E(t) at the cyclotron resonance frequency can be conveniently detected using a marginal oscillator detector. When the ions accelerated by E(t) collide with other particles, they lose some of their excess energy. A mixture of ions and neutral molecules in the presence of H and E(t) then reaches a steady-state condition in which the energy gained by the ions from E(t) between collisions is lost to the neutral molecules in collisions
Locating the pseudogap closing point in cuprate superconductors: absence of entrant or reentrant behavior
Current descriptions of the pseudogap in underdoped cuprates envision a
doping-dependent transition line which descends monotonically towards
zero just beyond optimal doping. There is much debate as to the location of the
terminal point where vanishes, whether or not there is a phase
transition at and exactly how behaves below within the
superconducting dome. One perspective sees cutting the dome and
continuing to descend monotonically to zero at holes/Cu
referred to here as `entrant behavior'. Another perspective derived from
photoemission studies is that intersects the dome near holes/Cu then turns back below , falling to zero again
around referred to here as `reentrant behavior'. By
examining thermodynamic data for BiSrCaCuO we show
that neither entrant nor reentrant behavior is experimentally supported.
Rather, sharply delimits the pseudogap regime and for
the pseudogap is always present, independent of temperature. Similar
results are found for YCaBaCuO. For both
materials is not a temperature but a crossover scale, , reflecting instead the underlying pseudogap energy which
vanishes as .Comment: 20 Pages, 9 Figures, in press Phys. Rev.
"The Measurement of Chronic and Transitory Poverty: with Application to the United States"
This paper proposes a method of measuring chronic and transitory poverty based on any additively-decomposable index of aggregate poverty. Chronic poverty and transitory poverty in the United States are measured using data from the Panel Study of Income Dynamics (1987 interviewing year). In an attempt to identify the most impoverished subpopulations, poverty indices are decomposed according to race, type of household and educational qualifications of the head of the household.
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