2,178 research outputs found

    Measurement of CH2O in low and atmospheric pressure flames by Laser Induced Fluorescence and Cavity RingDown absorption

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    We have investigated the spatial structure of formaldehyde usinglaser-induced fluorescence (LIF), LIF imaging, and cavity ringdownspectroscopy (CRDS) in two flames. The first is an atmospheric pressureBunsen flame, into which are inserted various metal to simulatedifferent types of heat removal inserts in appliance flames. Here LIFimaging is used. The second is a low pressure flat flame that can bemodeled with a one-dimensional code. All three techniques are used. Theresults in both cases show that CH2O appears prior to CH, inlower pressure regions of the flame

    The QCD Phase Diagram at Nonzero Temperature, Baryon and Isospin Chemical Potentials in Random Matrix Theory

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    We introduce a random matrix model with the symmetries of QCD at finite temperature and chemical potentials for baryon number and isospin. We analyze the phase diagram of this model in the chemical potential plane for different temperatures and quark masses. We find a rich phase structure with five different phases separated by both first and second order lines. The phases are characterized by the pion condensate and the chiral condensate for each of the flavors. In agreement with lattice simulations, we find that in the phase with zero pion condensate the critical temperature depends in the same way on the baryon number chemical potential and on the isospin chemical potential. At nonzero quark mass, we remarkably find that the critical end point at nonzero temperature and baryon chemical potential is split in two by an arbitrarily small isospin chemical potential. As a consequence, there are two crossovers that separate the hadronic phase from the quark-gluon plasma phase at high temperature. Detailed analytical results are obtained at zero temperature and in the chiral limit.Comment: 13 pages, 5 figures, REVTeX

    Modulation of Functional Activities of Chicken Heterophils by Recombinant Chicken IFN-γ

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    The objective of the present studies was to examine the in vitro effects of recombinant chicken interferon-γ (rChIFN-γ) on shape change, phagocytosis, and the oxidative/nonoxidative killing activities of day-old chicken heterophils. Heterophils (4 × 106/ml) were incubated with various concentrations of recombinant ChIFN-γ from both Escherichia coli and transfected Cos cells for 2 h at 39°C. The incubation of the neonatal heterophils with rChIFN-γ resulted in significantly greater numbers of cells with membrane shape change when compared with the mock-treated heterophils. Both Cos cell-derived and E. coli-derived ChIFN-γ significantly increased (p < 0.01) the phagocytosis of opsonized or nonopsonized Salmonella enteritidis by the neonatal heterophils in a concentration-dependent manner. Incubation with ChIFN-γ induced no direct stimulation of the respiratory burst by the chicken heterophils but did prime the heterophils for a significantly strengthened respiratory burst to subsequent stimulation with opsonized zymosan (OZ). Lastly, incubation of the heterophils with ChIFN-γ primed the cells for a significant increase in the release of β-D-glucuronidase following stimulation with OZ. These results show that neonatal avian heterophils can respond to cytokine modulation with enhanced functional competence, suggesting that ChIFN-γ can enhance the immune competence of the innate defenses of chickens during the first week of life

    Modification of the pattern informatics method for forecasting large earthquake events using complex eigenvectors

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    Recent studies have shown that real-valued principal component analysis can be applied to earthquake fault systems for forecasting and prediction. In addition, theoretical analysis indicates that earthquake stresses may obey a wave-like equation, having solutions with inverse frequencies for a given fault similar to those that characterize the time intervals between the largest events on the fault. It is therefore desirable to apply complex principal component analysis to develop earthquake forecast algorithms. In this paper we modify the Pattern Informatics method of earthquake forecasting to take advantage of the wave-like properties of seismic stresses and utilize the Hilbert transform to create complex eigenvectors out of measured time series. We show that Pattern Informatics analyses using complex eigenvectors create short-term forecast hot-spot maps that differ from hot-spot maps created using only real-valued data and suggest methods of analyzing the differences and calculating the information gain.Comment: 13 pages, 1 figure. Submitted to Tectonophysics on 30 August 200

    A calculation of the QCD phase diagram at finite temperature, and baryon and isospin chemical potentials

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    We study the phases of a two-flavor Nambu-Jona-Lasinio model at finite temperature TT, baryon and isospin chemical potentials: μB=(μu+μd)/2\mu_{B}=(\mu_{u}+\mu_{d})/2, μI=(μuμd)/2\mu_{I}=(\mu_{u}-\mu_{d})/2. This study completes a previous analysis where only small isospin chemical potentials μI\mu_{I} were consideredComment: 21 pages, 13 figures included, two more refernces adde

    Counting matrices over finite fields with support on skew Young diagrams and complements of Rothe diagrams

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    We consider the problem of finding the number of matrices over a finite field with a certain rank and with support that avoids a subset of the entries. These matrices are a q-analogue of permutations with restricted positions (i.e., rook placements). For general sets of entries these numbers of matrices are not polynomials in q (Stembridge 98); however, when the set of entries is a Young diagram, the numbers, up to a power of q-1, are polynomials with nonnegative coefficients (Haglund 98). In this paper, we give a number of conditions under which these numbers are polynomials in q, or even polynomials with nonnegative integer coefficients. We extend Haglund's result to complements of skew Young diagrams, and we apply this result to the case when the set of entries is the Rothe diagram of a permutation. In particular, we give a necessary and sufficient condition on the permutation for its Rothe diagram to be the complement of a skew Young diagram up to rearrangement of rows and columns. We end by giving conjectures connecting invertible matrices whose support avoids a Rothe diagram and Poincar\'e polynomials of the strong Bruhat order.Comment: 24 pages, 9 figures, 1 tabl

    Phase structures of strong coupling lattice QCD with finite baryon and isospin density

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    Quantum chromodynamics (QCD) at finite temperature (T), baryon chemical potential (\muB) and isospin chemical potential (\muI) is studied in the strong coupling limit on a lattice with staggered fermions. With the use of large dimensional expansion and the mean field approximation, we derive an effective action written in terms of the chiral condensate and pion condensate as a function of T, \muB and \muI. The phase structure in the space of T and \muB is elucidated, and simple analytical formulas for the critical line of the chiral phase transition and the tricritical point are derived. The effects of a finite quark mass (m) and finite \muI on the phase diagram are discussed. We also investigate the phase structure in the space of T, \muI and m, and clarify the correspondence between color SU(3) QCD with finite isospin density and color SU(2) QCD with finite baryon density. Comparisons of our results with those from recent Monte Carlo lattice simulations on finite density QCD are given.Comment: 18 pages, 6 figures, revtex4; some discussions are clarified, version to appear in Phys. Rev.

    Sign Rules for Anisotropic Quantum Spin Systems

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    We present new and exact ``sign rules'' for various spin-s anisotropic spin-lattice models. It is shown that, after a simple transformation which utilizes these sign rules, the ground-state wave function of the transformed Hamiltonian is positive-definite. Using these results exact statements for various expectation values of off-diagonal operators are presented, and transitions in the behavior of these expectation values are observed at particular values of the anisotropy. Furthermore, the effects of sign rules in variational calculations and quantum Monte Carlo calculations are considered. They are illustrated by a simple variational treatment of a one-dimensional anisotropic spin model.Comment: 4 pages, 1 ps-figur

    Solitary wave solution to the generalized nonlinear Schrodinger equation for dispersive permittivity and permeability

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    We present a solitary wave solution of the generalized nonlinear Schrodinger equation for dispersive permittivity and permeability using a scaling transformation and coupled amplitude-phase formulation. We have considered the third-order dispersion effect (TOD) into our model and show that soliton shift may be suppressed in a negative index material by a judicious choice of the TOD and self-steepening parameter.Comment: 6 page

    Coronal mass ejections as expanding force-free structures

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    We mode Solar coronal mass ejections (CMEs) as expanding force-fee magnetic structures and find the self-similar dynamics of configurations with spatially constant \alpha, where {\bf J} =\alpha {\bf B}, in spherical and cylindrical geometries, expanding spheromaks and expanding Lundquist fields correspondingly. The field structures remain force-free, under the conventional non-relativistic assumption that the dynamical effects of the inductive electric fields can be neglected. While keeping the internal magnetic field structure of the stationary solutions, expansion leads to complicated internal velocities and rotation, induced by inductive electric field. The structures depends only on overall radius R(t) and rate of expansion \dot{R}(t) measured at a given moment, and thus are applicable to arbitrary expansion laws. In case of cylindrical Lundquist fields, the flux conservation requires that both axial and radial expansion proceed with equal rates. In accordance with observations, the model predicts that the maximum magnetic field is reached before the spacecraft reaches the geometric center of a CME.Comment: 19 pages, 9 Figures, accepted by Solar Physic
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