11,016 research outputs found

    Phase Transition in Dimer Liquids

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    We study the phase transition in a system composed of dimers interacting with each other via a nearest-neighbor (NN) exchange JJ and competing interactions taken from a truncated dipolar coupling. Each dimer occupies a link between two nearest sites of a simple cubic lattice. We suppose that dimers are self-avoiding and can have only three orientations which coincide with the xx, yy or zz direction. The interaction JJ is attractive if the two dimers are parallel with each other at the NN distance, zero otherwise. The truncated dipolar interaction is characterized by two parameters: its amplitude DD and the cutoff distance rcr_c. Using the steepest-descent method, we determine the ground-state (GS) configuration as functions of DD and rcr_c. We then use Monte Carlo simulations to investigate the nature of the low-temperature phase and to determine characteristics of the phase transition from the ordered phase to the disordered phase at high temperatures at a given dimer concentration. We show that as the temperature increases, dimers remain in the compact state and the transition from the low-TT compact phase to the disordered phase where dimers occupy the whole space is of second order when DD is small, but it becomes of first order for large enough DD, for both polarized and non polarized dimers. This transition has a resemblance with the unfolding polymer transition. The effect of rcr_c is discussed

    The dyadic green's function for an infinite moving medium

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    Derivation of dyadic Green function for electromagnetic field in moving medium using Minkowski theory and method of Fourier analysi

    Detecting gravitational waves from highly eccentric compact binaries

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    In dense stellar regions, highly eccentric binaries of black holes and neutron stars can form through various n-body interactions. Such a binary could emit a significant fraction of its binding energy in a sequence of largely isolated gravitational wave bursts prior to merger. Given expected black hole and neutron star masses, many such systems will emit these repeated bursts at frequencies within the sensitive band of contemporary ground-based gravitational wave detectors. Unfortunately, existing gravitational wave searches are ill-suited to detect these signals. In this work, we adapt a "power stacking" method to the detection of gravitational wave signals from highly eccentric binaries. We implement this method as an extension of the Q-transform, a projection onto a multiresolution basis of windowed complex exponentials that has previously been used to analyze data from the network of LIGO/Virgo detectors. Our method searches for excess power over an ensemble of time-frequency tiles. We characterize the performance of our method using Monte Carlo experiments with signals injected in simulated detector noise. Our results indicate that the power stacking method achieves substantially better sensitivity to eccentric binary signals than existing localized burst searches.Comment: 17 pages, 20 figure

    Complete gradient-LC-ESI system on a chip for protein analysis

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    This paper presents the first fully integrated gradient-elution liquid chromatography-electrospray ionization (LC-ESI) system on a chip. This chip integrates a pair of high-pressure gradient pumps, a sample injection pump, a passive mixer, a packed separation column, and an ESI nozzle. We also present the successful on-chip separation of protein digests by reverse phase (RP)-LC coupled with on-line mass spectrometer (MS) analysis
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