Nanosized patterns as reference structures for macroscopic transport properties and vortex phases in YBCO films

This paper studies the striking correlation between nanosized structural patterns in YBCO films and macroscopic transport current. A nanosized network of parallel Josephson junctions laced by insulating dislocations is almost mimicking the grain boundary structural network. It contributes to the macroscopic properties and accounts for the strong intergranular pinning across the film in the intermediate temperature range. The correlation between the two networks enables to find out an outstanding scaling law in the (Jc,B) plane and to determine meaningful parameters concerning the matching between the vortex lattice and the intergranular defect lattice. Two asymptotic behaviors of the pinning force below the flux flow regime are checked: the corresponding vortex phases are clearly individuated.Comment: 4 pages, 4 figure

Number of Collisions in the Glauber Model and Beyond

The so called number of hadron-nucleus collisions n_coll(b) at impact parameter b, and its integral value N_coll, which are used to normalize the measured fractional cross section of a hard process, are calculated within the Glauber-Gribov theory including the effects of nucleon short-range correlations. The Gribov inelastic shadowing corrections are summed to all orders by employing the dipole representation. Numerical calculations are performed at the energies of the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC). We found that whereas the Gribov corrections generally increase the value of N_coll, the inclusion of nucleon correlations, acting in the opposite directions, decreases it by a comparable amount. The interplay of the two effects varies with the value of the impact parameter.Comment: Text expanded; typos corrected; results and conclusions unchanged. To appear in Phys. Rev.

Slow Proton Production in Semi-Inclusive Deep Inelastic Scattering off Deuteron and Complex Nuclei: Hadronization and Final State Interaction Effects

The effects of the final state interaction in slow proton production in semi inclusive deep inelastic scattering processes off nuclei, A(e,e'p)X, are investigated in details within the spectator and target fragmentation mechanisms; in the former mechanism, the hard interaction on a nucleon of a correlated pair leads, by recoil, to the emission of the partner nucleon, whereas in the latter mechanism proton is produced when the diquark, which is formed right after the visrtual photon-quark interaction, captures a quark from the vacuum. Unlike previous papers on the subject, particular attention is paid on the effects of the final state interaction of the hadronizing quark with the nuclear medium within an approach based upon an effective time-dependent cross section which combines the soft and hard parts of hadronization dynamics in terms of the string model and perturbative QCD, respectively. It is shown that the final state interaction of the hadronizing quark with the medium plays a relevant role both in deuteron and complex nuclei; nonetheless, kinematical regions where final state interaction effects are minimized can experimentally be selected, which would allow one to investigate the structure functions of nucleons embedded in the nuclear medium; likewise, regions where the interaction of the struck hadronizing quark with the nuclear medium is maximized can be found, which would make it possible to study non perturbative hadronization mechanisms.Comment: 35 pages, 12 figures, accepted for pubblication in Phys. Rev.

Universality of nucleon-nucleon short-range correlations: two-nucleon momentum distributions in few-body systems

Using realistic wave functions, the proton-neutron and proton-proton momentum distributions in $^3He$ and $^4He$ are calculated as a function of the relative, $k_{rel}$, and center of mass, $K_{CM}$, momenta, and the angle between them. For large values of ${k}_{rel}\gtrsim 2\,\,fm^{-1}$ and small values of ${K}_{CM} \lesssim 1.0\,\,fm^{-1}$, both distributions are angle independent and decrease with increasing $K_{CM}$, with the $pn$ distribution factorizing into the deuteron momentum distribution times a rapidly decreasing function of $K_{CM}$, in agreement with the two-nucleon (2N) short range correlation (SRC) picture. When $K_{CM}$ and $k_{rel}$ are both large, the distributions exhibit a strong angle dependence, which is evidence of three-nucleon (3N) SRC. The predicted center-of-mass and angular dependence of 2N and 3N SRC should be observable in two-nucleon knock-out processes $A(e,e'pN)X$.Comment: 5 pages, 5 figure

Comparison of regeneration capacity and Agrobacterium-mediated cell transformation efficiency of different cultivars and rootstocks of Vitis spp. via organogenesis.

The success of in vitro plant regeneration and the competence of genetic transformation greatly depends on the genotype of the species of interest. In previous work, we developed a method for the efficient Agrobacterium-mediated genetic transformation via organogenesis of V. vinifera cultivar Thompson Seedless, by using meristematic bulk (MB) as starting tissue. In this study, we applied this method for the regeneration and transformation of MBs obtained from the Italian cultivar Ciliegiolo and two of the commonly used Vitis rootstocks, 110 Richter and Kober 5BB, in comparison with Thompson Seedless. The A. tumefaciens strain EHA105, harbouring pK7WG2 binary vector, was used for the transformation trials, which allowed selection through the enhanced-green fluorescent protein (eGFP) and the neomycin phosphotransferase (nptII) gene. Putative transformed tissues and/or shoots were identified by either a screening based on the eGFP expression alone or its use in combination with kanamycin in the medium. MBs obtained from Thompson Seedless showed the highest regeneration and transformation cell competence, which subsequently allowed the recovery of stably transformed plants. Ciliegiolo, 110 Richter, and Kober 5BB, produced actively growing transgenic calli showing eGFP fluorescence, more consistently on selective media, but had no regenerative competence

Clustering of loose groups and galaxies from the Perseus--Pisces Survey

We investigate the clustering properties of loose groups in the Perseus--Pisces redshift Survey (PPS). Previous analyses based on CfA and SSRS surveys led to apparently contradictory results. We investigate the source of such discrepancies, finding satisfactory explanations for them. Furthermore, we find a definite signal of group clustering, whose amplitude $A_G$ exceeds the amplitude $A_g$ of galaxy clustering ($A_G=14.5^{+3.8}_{-3.0}$, $A_g=7.42^{+0.20}_{-0.19}$ for the most significant case; distances are measured in \hMpc). Groups are identified with the adaptive Friends--Of--Friends (FOF) algorithms HG (Huchra \& Geller 1982) and NW (Nolthenius \& White 1987), systematically varying all search parameters. Correlation strenght is especially sensitive to the sky--link $D_L$ (increasing for stricter normalization $D_0$), and to the (depth \mlim of the) galaxy data. It is only moderately dependent on the galaxy luminosity function $\phi(L)$, while it is almost insensitive to the redshift--link $V_L$ (both to the normalization $V_0$ and to the scaling recipes HG or NW).Comment: 28 pages (LaTeX aasms4 style) + 5 Postscript figures ; ApJ submitted on May 4th, 1996; group catalogs available upon request ([email protected]

Short Range Correlations in Medium- and High-Energy Scattering off Nuclei

The effects of short range correlations in lepton and hadron scattering off nuclei at medium and high energies are discussed.Comment: 8 pages, 7 figures, invited talk at the 6th International Conference on Hadronic Physics, ICTP, Trieste, 12-16 May, 2008. To appear in AIP Proceedings Serie

Resistive state of superconducting structures with fractal clusters of a normal phase

The effect of morphologic factors on magnetic flux dynamics and critical currents in percolative superconducting structures is considered. The superconductor contains the fractal clusters of a normal phase, which act as pinning centers. The properties of these clusters are analyzed in the general case of gamma-distribution of their areas. The statistical characteristics of the normal phase clusters are studied, the critical current distribution is derived, and the dependencies of the main statistical parameters on the fractal dimension are found. The effect of fractal clusters of a normal phase on the electric field induced by the motion of the magnetic flux after the vortices have been broken away from pinning centers is considered. The voltage-current characteristics of fractal superconducting structures in a resistive state for an arbitrary fractal dimension are obtained. It is found that the fractality of the boundaries of normal phase clusters intensifies magnetic flux trapping and thereby increases the current-carrying capability of the superconductor.Comment: 15 pages with 8 figures, revtex3, alternative e-mail of author is [email protected]

Enhanced soluble CD40 ligand contributes to endothelial cell dysfunction in vitro and monocyte activation in patients with diabetes mellitus: effect of improved metabolic control

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Dynamics of the magnetic flux trapped in fractal clusters of normal phase in a superconductor

The influence of geometry and morphology of superconducting structure on critical currents and magnetic flux trapping in percolative type-II superconductor is considered. The superconductor contains the clusters of a normal phase, which act as pinning centers. It is found that such clusters have significant fractal properties. The main features of these clusters are studied in detail: the cluster statistics is analyzed; the fractal dimension of their boundary is estimated; the distribution of critical currents is obtained, and its peculiarities are explored. It is examined thoroughly how the finite resolution capacity of the cluster geometrical size measurement affects the estimated value of fractal dimension. The effect of fractal properties of the normal phase clusters on the electric field arising from magnetic flux motion is investigated in the case of an exponential distribution of cluster areas. The voltage-current characteristics of superconductors in the resistive state for an arbitrary fractal dimension are obtained. It is revealed that the fractality of the boundaries of the normal phase clusters intensifies the magnetic flux trapping and thereby raises the critical current of a superconductor.Comment: revtex, 16 pages with 1 table and 5 figures; text and figures are improved; more detailed version with geometric probability analisys of the distribution of entry points into weak links over the perimeter of a normal phase clusters and one additional figure is published in Phys.Rev.B; alternative e-mail of author is [email protected]