27,763 research outputs found
Spinor BECs in a double-well: population transfer and Josephson oscillations
The dynamics of an F=1 spinor condensate in a two-well potential is studied
within the framework of the Gross-Pitaevskii equation. We derive two-mode
equations relating the population imbalances, the phase differences among the
condensates at each side of the barrier and the time evolution of the different
Zeeman populations for the case of small population imbalances. The case of
zero total magnetization is scrutinized in this limit demonstrating the ability
of a two mode analysis to describe to a large extent the dynamics observed in
the Gross-Pitaevskii equations. It is also demonstrated that the time evolution
of the different total populations fully decouples from the Josephson tunneling
phenomena. All the relevant time scales are clearly identified with microscopic
properties of the atom-atom interactions
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No sex-biased dispersal in a primate with an uncommon social system-cooperative polyandry.
An influential hypothesis proposed by Greenwood (1980) suggests that different mating systems result in female and male-biased dispersal, respectively, in birds and mammals. However, other aspects of social structure and behavior can also shape sex-biased dispersal. Although sex-specific patterns of kin cooperation are expected to affect the benefits of philopatry and dispersal patterns, empirical evidence is scarce. Unlike many mammals, Saguinus geoffroyi (Geoffroy's tamarin) has a breeding system in which typically multiple males mate with a single breeding female. Males typically form cooperative reproductive partnerships between relatives, whereas females generally compete for reproductive opportunities. This system of cooperative polyandry is predicted to result in female-biased dispersal, providing an opportunity to test the current hypotheses of sex-biased dispersal. Here we test for evidence of sex-biased dispersal in S. geoffroyi using demographic and genetic data from three populations. We find no sex bias in natal dispersal, contrary to the prediction based on the mating patterns. This pattern was consistent after controlling for the effects of historical population structure. Limited breeding opportunities within social groups likely drive both males and females to disperse, suggesting that dispersal is intimately related to the social context. The integration of genetic and field data revealed that tamarins are another exception to the presumed pattern of male-biased dispersal in mammals. A shift in focus from mating systems to social behavior, which plays a role in most all processes expected to influence sex-bias in dispersal, will be a fruitful target for research both within species and across taxa
The IACOB project: A grid-based automatic tool for the quantitative spectroscopic analysis of O-stars
We present the IACOB grid-based automatic tool for the quantitative
spectroscopic analysis of O-stars. The tool consists of an extensive grid of
FASTWIND models, and a variety of programs implemented in IDL to handle the
observations, perform the automatic analysis, and visualize the results. The
tool provides a fast and objective way to determine the stellar parameters and
the associated uncertainties of large samples of O-type stars within a
reasonable computational time.Comment: 8 pages, 2 figures, 1 table. Proceedings of the "GREAT-ESF Stellar
Atmospheres in the Gaia Era Workshop
The evolution of Local Labour Market Areas in contrasting region
In many European local labour markets, a growing minority of workers are making longer commuting trips. One consequence for research into journey-to-work flows, which usually seeks to identify the boundaries of local labour market areas (LLMAs), is that these boundaries represent a ¡¥snap shot¡¦ of an increasingly volatile pattern. The challenge for regional science is how best to represent the way LLMAs evolve. «Is it sufficient to simply update maps, using a consistent method which is applied to successive ¡¥snap-shot¡¦ datasets? This approach will be illustrated in contrasting regions. «Is it possible to produce new approaches to analysis which can better draw attention to those areas where change has been rather more, or less, strong? The paper will end with some explorations in pursuit of this aim.
A generic radio channel emulator to evaluate higher layer protocols in a CDMA system
Currently, we are involved in the standardisation process to specify the next mobile system generation. A wideband code division multiple access (WCDMA) system is considered in most of the region versions. It would be very useful to count on a radio channel emulator which allows one to evaluate higher layers protocols within this context. This paper presents a radio channel emulator developed for a code division multiple access (CDMA) based system. Its versatility and low complexity have been exposed, and the validation process to check the model accuracy has also been shown for this system as an example.Peer ReviewedPostprint (published version
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