22,594 research outputs found

    Quantum control of the motional states of trapped ions through fast switching of trapping potentials

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    We propose a new scheme for supplying voltages to the electrodes of microfabricated ion traps, enabling access to a regime in which changes to the trapping potential are made on timescales much shorter than the period of the secular oscillation frequencies of the trapped ions. This opens up possibilities for speeding up the transport of ions in segmented ion traps and also provides access to control of multiple ions in a string faster than the Coulomb interaction between them. We perform a theoretical study of ion transport using these methods in a surface-electrode trap, characterizing the precision required for a number of important control parameters. We also consider the possibilities and limitations for generating motional state squeezing using these techniques, which could be used as a basis for investigations of Gaussian-state entanglement.Comment: Accepted by New Journal of Physic

    Causality detection and turbulence in fusion plasmas

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    This work explores the potential of an information-theoretical causality detection method for unraveling the relation between fluctuating variables in complex nonlinear systems. The method is tested on some simple though nonlinear models, and guidelines for the choice of analysis parameters are established. Then, measurements from magnetically confined fusion plasmas are analyzed. The selected data bear relevance to the all-important spontaneous confinement transitions often observed in fusion plasmas, fundamental for the design of an economically attractive fusion reactor. It is shown how the present method is capable of clarifying the interaction between fluctuating quantities such as the turbulence amplitude, turbulent flux, and Zonal Flow amplitude, and uncovers several interactions that were missed by traditional methods.Comment: 26 pages, 14 figure

    Survey for Emission-Line Galaxies: Universidad Complutense de Madrid List 3

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    A new low-dispersion objective-prism search for low-redshift (z<0.045) emission-line galaxies (ELG) has been carried out by the Universidad Complutense de Madrid with the Schmidt Telescope at the Calar-Alto Observatory. This is a continuation of the UCM Survey, which was performed by visual selection of candidates in photographic plates via the presence of the Halpha+[NII]6584 blend in emission. In this new list we have applied an automatic procedure, fully developed by us, for selecting and analyzing the ELG candidates on the digitized images obtained with the MAMA machine. The analyzed region of the sky covers 189 square degrees in nine fields near R.A.=14h & 17h, Dec=25 deg. The final sample contains 113 candidates. Special effort has been made to obtain a large amount of information directly from our uncalibrated plates by using several external calibrations. The parameters obtained for the ELG candidates allow for the study of the statistical properties for the sample.Comment: 13 pages, 18 PostScript figures, 6 JPEG figures, Table 2 corrected. Accepted for publication in Astrophysical Journal Supplements, also available at http://www.ucm.es/info/Astrof/opera/LIST3_ApJS99

    Abundances in Stars from the Red Giant Branch Tip to the Near the Main Sequence in M71: I. Sample Selection, Observing Strategy and Stellar Parameters

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    We present the sample for an abundance analysis of 25 members of M71 with luminosities ranging from the red giant branch tip to the upper main sequence. The spectra are of high dispersion and of high precision. We describe the observing strategy and determine the stellar parameters for the sample stars using both broad band colors and fits of Hα\alpha profiles. The derived stellar parameters agree with those from the Yale2^2 stellar evolutionary tracks to within 50 -- 100K for a fixed log g, which is within the level of the uncertainties.Comment: Minor changes to conform to version accepted for publication, with several new figures (Paper 1 of a pair

    Sibling competition and not maternal allocation drives differential offspring feeding in a sexually size-dimorphic bird

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    Sex allocation models still fail to predict the complex sex ratio patterns in broods of vertebrates. A major problem when studying mother–brood interactions is the difficulty in disentangling hypotheses involving maternal preferences from processes that do not imply maternal manipulation. We studied maternal resource allocation in mixed-sex, same-sex and single-chick broods in the great bustard, Otis tarda. Females normally rear a single chick, and previous work has shown that maternal investment influences male more than female breeding success. Therefore, mothers of two-chick broods were assumed to be in good condition and candidates to show a preference for sons. Results showed that male chicks of mixed-sex broods remained close to the mother for twice as long as their sisters, and received double the number of maternal feedings. However, sex differences in maternal feeding rate disappeared when considering only simultaneous begging approaches from both siblings. Proximity to the mother and its interaction with begging approach intensity were the factors determining the higher begging success of male chicks. In single-chick broods, females did not receive fewer maternal feedings than males. Overall, our results suggest that female chicks of mixed-sex broods become outcompeted by their larger brothers, which remain close to the mother much longer, preventing their sisters from taking a larger share of maternal feedings. We conclude that mothers do not show a preference for feeding male over female chicks, and that the sex differences in feeding rate are determined by the higher food requirements of male chicks due to their sexually selected, much faster growth rates. The higher mortality of females in mixed-sex broods contrasts with the pattern of male-biased mortality typical in this species, and supports our interpretation of an asymmetric competitive ability of male offspring as the mechanism responsible for the sex bias in maternal expenditure.This work was supported by the Dirección General de Investigación Científica y Técnica (projects PB91-0081 and PB94-0068, with contributions from other projects awarded to J.C.A. for marking and radiotracking birds 1987–2013); the Instituto Nacional para la Conservación de la Naturaleza; and the Junta de Castilla y León. During the study, E.M. benefitted from a predoctoral fellowship of the Dirección General de Investigación Científica y Técnica. Research by J.C.A. and J.A.A. was supported by project CGL2012-36345 during the writing of the pape

    Heat conduction in one dimensional systems: Fourier law, chaos, and heat control

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    In this paper we give a brief review of the relation between microscopic dynamical properties and the Fourier law of heat conduction as well as the connection between anomalous conduction and anomalous diffusion. We then discuss the possibility to control the heat flow.Comment: 15 pages, 11 figures. To be published in the Proceedings of the NATO Advanced Research Workshop on Nonlinear Dynamics and Fundamental Interactions, Tashkent, Uzbekistan, Octo. 11-16, 200
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