651 research outputs found

    Two particle correlations inside one jet at "Modified Leading Logarithmic Approximation" of Quantum Chromodynamics; I: exact solution of the evolution equations at small x

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    We discuss correlations between two particles in jets at high energy colliders and exactly solve the MLLA evolution equations in the small x limit. We thus extend the Fong-Webber analysis to the region away from the hump of the single inclusive energy spectrum. We give our results for LEP, Tevatron and LHC energies, and compare with existing experimental data.Comment: LaTeX, 49 pages, 57 .eps figures + one log

    Phosphorylation of p54NRB during mitosis

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    Comunicaciones a congreso

    Structure factor of polymers interacting via a short range repulsive potential: application to hairy wormlike micelles

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    We use the Random Phase Approximation (RPA) to compute the structure factor, S(q), of a solution of chains interacting through a soft and short range repulsive potential V. Above a threshold polymer concentration, whose magnitude is essentially controlled by the range of the potential, S(q) exhibits a peak whose position depends on the concentration. We take advantage of the close analogy between polymers and wormlike micelles and apply our model, using a Gaussian function for V, to quantitatively analyze experimental small angle neutron scattering profiles of semi-dilute solutions of hairy wormlike micelles. These samples, which consist in surfactant self-assembled flexible cylinders decorated by amphiphilic copolymer, provide indeed an appropriate experimental model system to study the structure of sterically interacting polymer solutions

    Effects of Short Range Correlations on Ca Isotopes

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    The effect of Short Range Correlations (SRC) on Ca isotopes is studied using a simple phenomenological model. Theoretical expressions for the charge (proton) form factors, densities and moments of Ca nuclei are derived. The role of SRC in reproducing the empirical data for the charge density differences is examined. Their influence on the depletion of the nuclear Fermi surface is studied and the fractional occupation probabilities of the shell model orbits of Ca nuclei are calculated. The variation of SRC as function of the mass number is also discussed.Comment: 11 pages (RevTex), 6 Postscript figures available upon request at [email protected] Physical Review C in prin

    Searching singlet extensions of the supersymmetric standard model in Z6II Z_{6-II} orbifold compactification of heterotic string

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    We search for supersymmetric standard model realizations with extra singlets and extra U(1) U(1) using the heterotic string compactification on the Z6II Z_{6-II} orbifold with two Wilson lines. We analyze the vacuum restabilization mechanism for three representative Pati-Salam string models obtained in the literature and present detailed results for the effective superpotential compatible with the string selection rules. An automated selection of semi-realistic vacua along flat directions in the non-Abelian singlet modes field space is performed by requiring the presence of massless pairs of electroweak Higgs bosons having trilinear superpotential couplings with massless singlet modes and the decoupling of color triplet exotic modes needed to suppress BB and L L number violating processes.Comment: revtex4 format, 21 pages, 7 tables, shortened version added reference

    A geometric approach to time evolution operators of Lie quantum systems

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    Lie systems in Quantum Mechanics are studied from a geometric point of view. In particular, we develop methods to obtain time evolution operators of time-dependent Schrodinger equations of Lie type and we show how these methods explain certain ad hoc methods used in previous papers in order to obtain exact solutions. Finally, several instances of time-dependent quadratic Hamiltonian are solved.Comment: Accepted for publication in the International Journal of Theoretical Physic

    Inhibiting thyroid activation in aged human explants prevents mechanical induced detrimental signalling by mitigating metabolic processes

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    Objectives To investigate whether the deiodinase inhibitor iopanoic acid (IOP) has chondroprotective properties, a mechanical stress induced model of human aged explants was used to test both repeated dosing and slow release of IOP. Methods Human osteochondral explants subjected to injurious mechanical stress (65%MS) were treated with IOP or IOP encapsulated in poly lactic-co-glycolic acid-polyethylene glycol nanoparticles (NP-IOP). Changes to cartilage integrity and signalling were determined by Mankin scoring of histology, sulphated glycosaminoglycan (sGAG) release and expression levels of catabolic, anabolic and hypertrophic markers. Subsequently, on a subgroup of samples, RNA sequencing was performed on 65%MS (n = 14) and 65%MS+IOP (n = 7) treated cartilage to identify IOP's mode of action. Results Damage from injurious mechanical stress was confirmed by increased cartilage surface damage in the Mankin score, increased sGAG release, and consistent upregulation of catabolic markers and downregulation of anabolic markers. IOP and, though less effective, NP-IOP treatment, reduced MMP13 and increased COL2A1 expression. In line with this, IOP and NP-IOP reduced cartilage surface damage induced by 65%MS, while only IOP reduced sGAG release from explants subjected to 65%MS. Lastly, differential expression analysis identified 12 genes in IOP's mode of action to be mainly involved in reducing metabolic processes (INSIG1, DHCR7, FADS1 and ACAT2) and proliferation and differentiation (CTGF, BMP5 and FOXM1). Conclusion Treatment with the deiodinase inhibitor IOP reduced detrimental changes of injurious mechanical stress. In addition, we identified that its mode of action was likely on metabolic processes, cell proliferation and differentiation.Molecular Epidemiolog

    Response of Wheat Fungal Diseases to Elevated Atmospheric CO2 Level

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    Infection with fungal pathogens on wheat varieties with different levels of resistance was tested at ambient (NC, 390 ppm) and elevated (EC, 750 ppm) atmospheric CO2 levels in the phytotron. EC was found to affect many aspects of the plant-pathogen interaction. Infection with most fungal diseases was usually found to be promoted by elevated CO2 level in susceptible varieties. Powdery mildew, leaf rust and stem rust produced more severe symptoms on plants of susceptible varieties, while resistant varieties were not infected even at EC. The penetration of Fusarium head blight (FHB) into the spike was delayed by EC in Mv Mambo, while it was unaffected in Mv Regiment and stimulated in Mv Emma. EC increased the propagation of FHB in Mv Mambo and Mv Emma. Enhanced resistance to the spread of Fusarium within the plant was only found in Mv Regiment, which has good resistance to penetration but poor resistance to the spread of FHB at NC. FHB infection was more severe at EC in two varieties, while the plants of Mv Regiment, which has the best field resistance at NC, did not exhibit a higher infection level at EC. The above results suggest that breeding for new resistant varieties will remain a useful means of preventing more severe infection in a future with higher atmospheric CO2 levels
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