45,151 research outputs found

    Magnetic Component of Quark-Gluon Plasma

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    We describe recent developments of the "magnetic scenario" of sQGP. We show that at T=(0.8−1.3)TcT=(0.8-1.3)T_c there is a dense plasma of monopoles, capable of supporting metastable flux tubes. Their existence allows to quantitatively explained the non-trivial TT-dependence of the static QˉQ\bar Q Q potential energy calculated on the lattice. By molecular dynamics simulation we derived transport properties (shear viscosity and diffusion constant) and showed that the best liquid is given by most symmetric plasma, with 50%-50% of electric and magnetic charges. The results are close to those of the ``perfect liquid'' observed at RHIC.Comment: Contribution to the 20th International Conference on Nucleus Nucleus Collisions (Quark Matter 2008

    Two-dimensional gases of generalized statistics in a uniform magnetic field

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    We study the low temperature properties of two-dimensional ideal gases of generalized statistics in a uniform magnetic field. The generalized statistics considered here are the parafermion statistics and the exclusion statistics. Similarity in the behaviours of the parafermion gas of finite order pp and the gas with exclusion coefficient g=1/pg=1/p at very low temperatures is noted. These two systems become exactly equivalent at T=0T=0. Qumtum Hall effect with these particles as charge carriers is briefly discussed.Comment: Latex file, 14 pages, 5 figures available on reques

    Ageing and Temperature Influence on Polarization/Depolarization Current Behaviour of Paper Immersed in Natural Ester

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    Transformers play an important role in providing a reliable and efficient electricity supply and are one of the most critical equipments in electric power transmission and distribution systems. The most commonly used liquid in power transformers is mineral oil due to its low price and good properties. However the performance of mineral oil starts to be limited due to environmental consideration [1]. Natural ester insulating fluid offers fire safety, environment and insulation aging advantages over mineral oil and are found to be suitable for the use in transformer insulation system [1]. However, transformer owners require to assess the status of the cellulose insulation in transformer non-destructively. Polarization/depolarization Current (PDC) measurement [2] is one of the non-destructive techniques which have been used to achieve this aim. At the present, there are few publications about the PDC behaviour of natural ester-paper insulation, though the natural ester becomes more widely used in transformers. In this paper, the influence of ageing and temperature on the PDC behaviour of the paper immersed in natural ester and mineral oil were compared. Results show PDC technique can be used to assess the aging condition of the natural-ester paper insulation. The ageing and temperature have similar influence on the PDC behaviour of the paper immersed in natural ester and in mineral oil. The depolarization current of paper immersed in natural ester is lower than that immersed in mineral oil at the same test temperature. The depolarization current of the paper immersed in natural ester and mineral oil increase with the aging time increased. Therefore, the depolarization current can be used to indicate the aging status of natural ester-paper insulation

    Some Issues in a Gauge Model of Unparticles

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    We address in a recent gauge model of unparticles the issues that are important for consistency of a gauge theory, i.e., unitarity and Ward identity of physical amplitudes. We find that non-integrable singularities arise in physical quantities like cross section and decay rate from gauge interactions of unparticles. We also show that Ward identity is violated due to the lack of a dispersion relation for charged unparticles although the Ward-Takahashi identity for general Green functions is incorporated in the model. A previous observation that the unparticle's (with scaling dimension d) contribution to the gauge boson self-energy is a factor (2-d) of the particle's has been extended to the Green function of triple gauge bosons. This (2-d) rule may be generally true for any point Green functions of gauge bosons. This implies that the model would be trivial even as one that mimics certain dynamical effects on gauge bosons in which unparticles serve as an interpolating field.Comment: v1:16 pages, 3 figures. v2: some clarifications made and presentation improved, calculation and conclusion not modified; refs added and updated. Version to appear in EPJ

    Users’ Continued Usage of Online Healthcare Virtual Communities: An Empirical Investigation in the Context of HIV Support Communities

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    This study uses data from an online HIV/AIDS health support virtual community to examine whether users’ emotional states and the social support they receive influence their continued usage. We adopt grief theory to conceptualize the negative emotions that people living with HIV/AIDS could experience. Linguistic analysis is used to measure the emotional states of the users and the informational and emotional support that they receive. Results show that users showing a higher level of disbelief and yearning are more likely to leave the community while those with a high level of anger and depression are more likely to stay on. Users who receive more informational support are more likely to leave once they have obtained the information they sought, but those who receive more emotional support are more likely to stay on. The findings of this study can help us better understand users’ support seeking behavior in online support VCs
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