6,873 research outputs found
Model of the Longitudinal Spin Seebeck Coefficient of InSb in a Magnetic Field
We develop a simple theory for the longitudinal spin Seebeck effect in
n-doped InSb in an external magnetic field. We consider spin- electrons in
the conduction band of InSb with a temperature gradient parallel to the applied
magnetic field. In the absence of spin-orbit interactions, a Boltzmann equation
approach leads to a spin current parallel to the field and proportional to the
temperature gradient. The calculated longitudinal spin Seebeck coefficients
oscillates as a function of magnetic field B; the peak positions are
approximately periodic in 1/B. The oscillations arise when the Fermi energy
crosses the bottom of a Landau band.Comment: 7 pages, 6 figure
Graphene with adatoms: tuning the magnetic moment with an applied voltage
We show that, in graphene with a small concentration of adatoms, the total
magnetic moment can be switched on and off by varying the Fermi energy
, either by applying a gate voltage or by suitable chemical doping. Our
calculation is carried out using a simple tight-binding model described
previously, combined with a mean-field treatment of the electron-electron
interaction on the adatom. The values of at which the moment is turned on
or off are controlled by the strength of the hopping between the graphene sheet
and the adatom, the on-site energy of the adatom, and the strength of the
electron-electron correlation energy U. Our result is in qualitatively
consistent with recent experiments by Nair {\it et al.} [Nat.\ Commun.\ {\bf
4}, 2010 (2013)].Comment: 4 Pages, 1 Figur
Theory of plasmonic waves on a chain of metallic nanoparticles in a liquid crystalline host
A chain of metallic particles, of sufficiently small diameter and spacing,
allows linearly polarized plasmonic waves to propagate along the chain. In this
paper, we describes how these waves are altered when the liquid crystal host is
a nematic or a cholesteric liquid crystal (NLC or CLC) with or without an
applied magnetic field. We find that, in general, the liquid crystal host,
either NLC or CLC, alters the dispersion relations of the transverse () and
longitudinal () waves significantly from the dispersion relations for an
isotropic host. We show that by altering the director axis of the liquid
crystal relative to the long axis of the metallic chain, that the branch
can be split into two non-degenerate linearly polarized branches (NLC host) or
two non-degenerate elliptically polarized branches (CLC host). When an external
magnetic field is applied parallel to both the long axis of the metallic
particles and the director of the CLC host, we find that the dispersion
relations are odd in an exchange in sign for for the non-degenerate
elliptically polarized branches. That is, the application of an external
magnetic field leads to the realization of a one-way waveguide.Comment: 9 Pages, 3 Figures. arXiv admin note: text overlap with
arXiv:1210.150
Interactions measurement payload for Shuttle
The Interactions Measurement Payload for Shuttle (IMPS) consisted of engineering experiments to determine the effects of the space environment on projected Air Force space systems. Measurements by IMPS on a polar-orbit Shuttle flight will lead to detailed knowledge of the interaction of the low-altitude polar-auroral environment on materials, equipment and technologies to be used in future large, high-power space systems. The results from the IMPS measurements will provide direct input to MIL-STD design guidelines and test standards that properly account for space-environment effects
Thermodynamic properties in polynomial form for carbon, hydrogen, nitrogen, and oxygen systems from 300 to 15000 K
Thermodynamic properties in polynomial form for carbon, hydrogen, nitrogen, and oxygen systems form 300 to 15000
VENUS NEFANDA: DIDO AND PASIPHAE IN VERGIL'S AENEID
In Book 6 of the Aeneid the hero, before entering the Underworld!, undergoes several
preliminary, more or less "initiatory" experiences. One of these is his examination of the
scenes depicted on the doors of the temple of Apollo at Cumae (allegedly built by
Daedalus: Aen. 6.18-19). On these doors Daedalus had depicted events from his own
experiences on Crete, including (most importantly for this paper) the passion of Queen
Pasiphae for the bull of Minos, the monstrous hybrid offspring of that union (the
Minotaur), and the intricate Labyrinth (inextricabi/is error, 6.27) in which the Minotaur
was kept hidden
Doing evolution in economic geography
Evolutionary approaches in economic geography face questions about the relationships between their concepts, theories, methods, politics, and policy implications. Amidst the growing but unsettled consensus that evolutionary approaches should employ plural methodologies, the aims here are, first, to identify some of the difficult issues confronting those working with different frameworks. The concerns comprise specifying and connecting research objects, subjects, and levels; handling agency and context; engaging and integrating the quantitative and the qualitative; comparing cases; and, considering politics, policy, and praxis. Second, the purpose is to articulate a distinctive geographical political economy approach, methods, and illustrative examples in addressing these issues. Bringing different views of evolution in economic geography into dialogue and disagreement renders methodological pluralism a means toward improved understanding and explanation rather than an end in itself. Confronting such thorny matters needs to be embedded in our research practices and supported by greater openness; more and better substantiation of our conceptual, theoretical, and empirical claims; enhanced critical reflection; and deeper engagement with politics, policy, and praxis
Optimization of resource allocation can explain the temporal dynamics and honesty of sexual signals
In species in which males are free to dynamically alter their allocation to sexual signaling over the breeding season, the optimal investment in signaling should depend on both a male’s state and the level of competition he faces at any given time. We developed a dynamic optimization model within a game‐theoretical framework to explore the resulting signaling dynamics at both individual and population levels and tested two key model predictions with empirical data on three‐spined stickleback (Gasterosteus aculeatus) males subjected to dietary manipulation (carotenoid availability): (1) fish in better nutritional condition should be able to maintain their signal for longer over the breeding season, resulting in an increasingly positive correlation between nutritional status and signal (i.e., increasing signal honesty), and (2) female preference for more ornamented males should thus increase over the breeding season. Both predictions were supported by the experimental data. Our model shows how such patterns can emerge from the optimization of resource allocation to signaling in a competitive situation. The key determinants of the honesty and dynamics of sexual signaling are the condition dependency of male survival, the initial frequency distribution of nutritional condition in the male population, and the cost of signaling
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