45,509 research outputs found

    Deciphering Deconfinement in Correlations of Conserved Charges

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    Diagonal and off-diagonal flavor and conserved charge susceptibilities reveal the prevalent degrees of freedom of heated strongly interacting matter. Results obtained from lattice simulations are compared with various model estimates in an effort to weed down various possible pictures of a quark gluon plasma. We argue that the vanishing of the off-diagonal quark flavor susceptibilities and its derivatives with respect to chemical potential, at temperatures above 1.5Tc, can only be understood in a picture of a gas or liquid composed of quasi-particles which carry the same quantum numbers as quarks and antiquarks. A potential new observable, blind to neutral and non-strange particles, is introduced and related via isospin symmetry to the ratio of susceptibilities of baryonic strangeness to strangeness generated in the excited matter created at RHIC.Comment: 5 pages, 3 figures, LATEX, To appear in the proceedings of the International Conference on Strangeness in Quark Matter, Los Angeles, CA, Mar 26-31, 200

    Surface Impedance Determination via Numerical Resolution of the Inverse Helmholtz Problem

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    Assigning boundary conditions, such as acoustic impedance, to the frequency domain thermoviscous wave equations (TWE), derived from the linearized Navier-Stokes equations (LNSE) poses a Helmholtz problem, solution to which yields a discrete set of complex eigenfunctions and eigenvalue pairs. The proposed method -- the inverse Helmholtz solver (iHS) -- reverses such procedure by returning the value of acoustic impedance at one or more unknown impedance boundaries (IBs) of a given domain, via spatial integration of the TWE for a given real-valued frequency with assigned conditions on other boundaries. The iHS procedure is applied to a second-order spatial discretization of the TWEs on an unstructured staggered grid arrangement. Only the momentum equation is extended to the center of each IB face where pressure and velocity components are co-located and treated as unknowns. The iHS is finally closed via assignment of the surface gradient of pressure phase over the IBs, corresponding to assigning the shape of the acoustic waveform at the IB. The iHS procedure can be carried out independently for different frequencies, making it embarrassingly parallel, and able to return the complete broadband complex impedance distribution at the IBs in any desired frequency range to arbitrary numerical precision. The iHS approach is first validated against Rott's theory for viscous rectangular and circular ducts. The impedance of a toy porous cavity with a complex geometry is then reconstructed and validated with companion fully compressible unstructured Navier-Stokes simulations resolving the cavity geometry. Verification against one-dimensional impedance test tube calculations based on time-domain impedance boundary conditions (TDIBC) is also carried out. Finally, results from a preliminary analysis of a thermoacoustically unstable cavity are presented.Comment: As submitted to AIAA Aviation 201

    DESIGN AND ANTIINFLAMATORY ACTIVITY OF SOME NOVEL OXADIAZOLE DERIVATIVES – AN OVERVIEW

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    Oxadiazole derivates play vital role in biological field suchas anti-microbial, anti-viral, anti-tubercular, antiinflammatoryand anti-convulsant activity. Therapeuticsignificance of these clinically useful drugs in treatment ofinflammation encouraged the development of some morepotent and significant compounds. oxadiazole derivativesare remarkably effective compounds for inflammation andanalgesic activity. Extensive biochemical andpharmacological studies have confirmed that thesemolecules are effective in inflammation. Thiscomprehensive overview summarizes the chemistry ofdifferent derivatives of substitute

    Cohesion of BaReH9_9 and BaMnH9_9: Density Functional Calculations and Prediction of (MnH9)2−_9)^{2-} Salts

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    Density functional calculations are used to calculate the structural and electronic properties of BaReH9_9 and to analyze the bonding in this compound. The high coordination in BaReH9_9 is due to bonding between Re 5dd states and states of dd-like symmetry formed from combinations of H ss orbitals in the H9_9 cage. This explains the structure of the material, its short bond lengths and other physical properties, such as the high band gap. We compare with results for hypothetical BaMnH9_9, which we find to have similar bonding and cohesion to the Re compound. This suggests that it may be possible to synthesize (MnH9)2−_9)^{2-} salts. Depending on the particular cation, such salts may have exceptionally high hydrogen contents, in excess of 10 weight

    Fluctuations, strangeness and quasi-quarks in heavy-ion collisions from lattice QCD

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    We report measurements of diagonal susceptibilities for the baryon number, chi_B, electrical charge, chi_Q, third component of isospin, chi_I, strangeness, chi_S, and hypercharge, chi_Y, as well as the off-diagonal chi_BQ, chi_BY, chi_BS, etc. We show that the ratios of susceptibilities in the high temperature phase are robust variables, independent of lattice spacing, and therefore give predictions for experiments. We also investigate strangeness production and flavour symmetry breaking matrix elements at finite temperature. Finally, we present evidence that in the high temperature phase of QCD the different flavour quantum numbers are excited in linkages which are exactly the same as one expects from quarks. We present some investigations of these quark-like quasi particles
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