2,264 research outputs found

    The magnetic form factor of the deuteron in chiral effective field theory

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    We calculate the magnetic form factor of the deuteron up to O(eP^4) in the chiral EFT expansion of the electromagnetic current operator. The two LECs which enter the two-body part of the isoscalar NN three-current operator are fit to experimental data, and the resulting values are of natural size. The O(eP^4) description of G_M agrees with data for momentum transfers Q^2 < 0.35 GeV^2.Comment: 4 pages, 2 figure

    Simulator for Microlens Planet Surveys

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    We summarize the status of a computer simulator for microlens planet surveys. The simulator generates synthetic light curves of microlensing events observed with specified networks of telescopes over specified periods of time. Particular attention is paid to models for sky brightness and seeing, calibrated by fitting to data from the OGLE survey and RoboNet observations in 2011. Time intervals during which events are observable are identified by accounting for positions of the Sun and the Moon, and other restrictions on telescope pointing. Simulated observations are then generated for an algorithm that adjusts target priorities in real time with the aim of maximizing planet detection zone area summed over all the available events. The exoplanet detection capability of observations was compared for several telescopes.Comment: Proc. IAU Symp. No. 293 "Formation, detection, and characterization of extrasolar habitable planets", ed. by N. Haghighipour. 4 pages, in pres

    Cellular Automaton Study of Time-Dynamics of Avalanche Breakdown in IMPATT Diodes

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    Employing a recently developed efficient cellular automaton technique for solving Boltzmann's transport equation for realistic devices, we present a detailed study of the carrier dynamics in GaAs avalanche p-i-n (IMPATT) diodes. We find that the impact ionization in reverse bias p-i-n diodes with ultrathin (less than 50 nm) intrinsic regions is triggered by Zener tunneling rather than by thermal generation. The impact generation of hot carriers occurs mainly in the low-field junction regions rather than in the high field intrinsic zone. The calculations predict significantly more minority carriers on the n-side than on the p-side

    Specialized odorant receptors in social insects that detect cuticular hydrocarbon cues and candidate pheromones.

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    Eusocial insects use cuticular hydrocarbons as components of pheromones that mediate social behaviours, such as caste and nestmate recognition, and regulation of reproduction. In ants such as Harpegnathos saltator, the queen produces a pheromone which suppresses the development of workers' ovaries and if she is removed, workers can transition to a reproductive state known as gamergate. Here we functionally characterize a subfamily of odorant receptors (Ors) with a nine-exon gene structure that have undergone a massive expansion in ants and other eusocial insects. We deorphanize 22 representative members and find they can detect cuticular hydrocarbons from different ant castes, with one (HsOr263) that responds strongly to gamergate extract and a candidate queen pheromone component. After systematic testing with a diverse panel of hydrocarbons, we find that most Harpegnathos saltator Ors are narrowly tuned, suggesting that several receptors must contribute to detection and discrimination of different cuticular hydrocarbons important in mediating eusocial behaviour.Cuticular hydrocarbons (CHC) mediate the interactions between individuals in eusocial insects, but the sensory receptors for CHCs are unclear. Here the authors show that in ants such as H. saltator, the 9-exon subfamily of odorant receptors (HsOrs) responds to CHCs, and ectopic expression of HsOrs in Drosophila neurons imparts responsiveness to CHCs

    Regression analysis of the results of examinations of students in probability theory

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    In this paper, is carried a study of the dependence of the results of tests with the help of linear and nonlinear regression analysis. As a result of an earlier statistical analysis with the same data, was found the relationship between them

    Low-energy neutron-deuteron reactions with N3LO chiral forces

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    We solve three-nucleon Faddeev equations with nucleon-nucleon and three-nucleon forces derived consistently in the framework of chiral perturbation theory at next-to-next-to-next-to-leading order in the chiral expansion. In this first investigation we include only matrix elements of the three-nucleon force for partial waves with the total two-nucleon (three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron elastic scattering and deuteron breakup reaction are studied. Emphasis is put on Ay puzzle in elastic scattering and cross sections in symmetric-space-star and neutron-neutron quasi-free-scattering breakup configurations, for which large discrepancies between data and theory have been reported.Comment: 22 pages, 7 figure

    Few-nucleon systems with state-of-the-art chiral nucleon-nucleon forces

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    We apply improved nucleon-nucleon potentials up to fifth order in chiral effective field theory, along with a new analysis of the theoretical truncation errors, to study nucleon-deuteron (Nd) scattering and selected low-energy observables in 3H, 4He, and 6Li. Calculations beyond second order differ from experiment well outside the range of quantified uncertainties, providing truly unambiguous evidence for missing three-nucleon forces within the employed framework. The sizes of the required three-nucleon force contributions agree well with expectations based on Weinberg's power counting. We identify the energy range in elastic Nd scattering best suited to study three-nucleon force effects and estimate the achievable accuracy of theoretical predictions for various observables.Comment: 5 pages, 5 figure
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