Fireball production in a quark-gluon plasma and the equilibrium of strange quarks

We study the quark-gluon plasma produced in nucleus-nucleus collisions where the laboratory kinetic energy goes from 4 to 25 GeV/ nucleon. The strange quark production is analyzed in detail and we look at the possibility for the plasma to lose energy by fireball production. Such fireballs are created inside the plasma via the dominent two-gluon fusion mechanism. Our results disagree with those of Biró and Zimányi concerning the equilibrium of the strange quark population. A prediction is made for the 15 GeV/nucleon BNL sulfur beam and for uranium-uranium collisions at 25 GeV/nucleon. In the most energetic case of uranium we obtain a saturation ratio of no more than 25%. On the other hand, a low amount of energy carried by the fireballs leads to an important increase of the ratio \({{N_s } \mathord{\left/ {\vphantom {{N_s } {N_{\bar q} }}} \right. \kern-0em} {N_{\bar q} }}\) . Using reasonable values for the parameters, we find that this ratio may reach a value of 3.5 in the most favorable case of uranium.     

Application of the extended geminal theory to the BH molecule

Extended geminal theory is applied to the ground state of BH at R=2.329 bohr. It is found that the inclusion of only one-electron transfer configurations leads to a lowering in the energy of 0.01 hartree, compared to the antisymmetrized geminal product wavefunction. This improvement is >90% of that achieved by a full configuration-interaction wavefunction. A contracted doublezeta basis set is also found to be quite good.

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Zusammenfassung Die erweiterte Geminaltheorie wird auf den Grundzustand des BH für R=2,329 Bohr angewendet. Es wird gefunden, da der Einschlu von nur Ein-Elektron-Transfer-Konfigurationen zu einer Energieerniedrigung von 0,01 Hartree, verglichen mit der antisymmetrisierten Geminal-Produkt-Wellenfunktion, führt. Diese Verbesserung beträgt mehr als 90% gegenüber dem Wert, der mit einer vollen CI-Funktion erreicht wird. Ein kontrahierter doppelt-zeta-Basis-Satz liefert ebenfalls gute Ergebnisse.

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Résumé La théorie des géminales généralisée est appliquée à l'état fondamental de BH pour R=2,329 bohr. On trouve que l'introduction des seules configurations à «un transfert d'électron» conduit à un abaissement de l'énergie de 0,01 hartree, par rapport à celle correspondant à un simple produit antisymmétrisé de géminales. Cette amélioration est supérieure à 90% de celle obtenue par I.C. complète. Une base double zèta «contractée» s'avère aussi fort bonne.

     

Determining the Wiedemann-Franz ratio from the thermal hall conductivity: application to Cu and YBa2Cu3O6.95

The Wiedemann-Franz (WF) ratio compares the thermal and electrical conductivities in a metal. We describe a new way to determine its value, based on the thermal Hall conductivity. The technique is applied to copper and to untwinned YBaCuO. In the latter, we uncover a T-linear dependence and suppression of the Hall-channel WF ratio. We discuss the implications of this suppression. The general suppression of the WF ratio in systems with predominant electron-electron scattering is discussed.     

Direct measurement of the angular dependence of the single-photon ionization of aligned N2 and CO2

By combining a state-of-the-art high-harmonic ultrafast soft X-ray source with field-free dynamic alignment, we map the angular dependence of molecular photoionization yields for the first time for a nondissociative molecule. The observed modulation in ion yield as a function of molecular alignment is attributed to the molecular frame transition dipole moment of single-photon ionization to the X, A and B states of N2(+) and CO2(+). Our data show that the transition dipoles for single-photon ionization of N2 and CO2 at 43 eV have larger perpendicular components than parallel ones. A direct comparison with published theoretical partial wave ionization cross-sections confirms these experimental observations, which are the first results to allow such comparison with theory for bound cation states. The results provide the first step toward a novel method for measuring molecular frame transition dipole matrix elements.     

Bovine red blood cell starvation age discrimination through a glutaraldehyde-amplified dielectrophoretic approach with buffer selection and membrane cross-linking

We report a novel buffer electric and dielectric relaxation time tuning technique, coupled with a glutaraldehyde (Glt.) cross-linking cell fixation reaction that allows for sensitive dielectrophoretic analysis and discrimination of bovine red blood cells of different starvation age. Guided by a single-shell oblate spheroid model, a zwitterion buffer composition is selected to ensure that two measurable crossover frequencies (cof's) near 500 kHz exist for dielectrophoresis (DEP) within a small range of each other. It is shown that the low cof is sensitive to changes in the cell membrane dielectric constant, in which cross-linking by Glt. reduces the dielectric constant of the cell membrane from 10.5 to 3.8, while the high cof is sensitive to cell cytoplasm conductivity changes. We speculate that this enhanced particle polarizability that results from the cross-linking reaction is because younger (reduced starvation time) cells possess more amino groups that the reaction can release to enhance the cell interior ionic strength. Such sensitive discrimination of cells with different age (surface protein density) by DEP is not possible without the zwitterion buffer and cleavage by Glt. treatment. It is then expected that rapid identification and sorting of healthy from diseased cells can be similarly sensitized.     

The accurate FROG characterization of attosecond pulses from streaking measurements

We describe a new attosecond FROG algorithm optimized for the characterization of sub-100 as pulses from streaked electron spectra. We make improvements upon the treatment of the attosecond streaking spectrogram, and show that these are necessary in order to accurately characterize shorter pulses with ever larger bandwidths. We investigate the effects of the approximations that must be made in order to apply the generalized projections scheme. PACS  31.15.xg; 32.90.+a; 33.60.+q