Hard exclusive photoproduction of Φ\Phi and J/ΨJ/\Psi mesons

We present predictions for differential cross sections for the reaction $\gamma p \to \Phi p$ and give an outlook to which extent our calculations may be generalized to the photoproduction of $J/\Psi$ mesons. Our results are obtained within perturbative QCD treating the proton as a quark-diquark system.Comment: 4 pages, 1 figure, uses Elsevier style espcrc1.st

Non-equilibrium condensation and coarsening of field-driven dipolar colloids

In colloidal suspensions, self-organization processes can be easily fueled by external fields. One particularly interesting class of phenomena occurs in monolayers of dipolar particles that are driven by rotating external fields. Here we report results from a computer simulation study of such systems focusing on the clustering behavior also observed in recent experiments. The key result of this paper is a novel interpretation of this pattern formation phenomenon: We show the clustering to be a by-product of a vapor-liquid first order phase transition. In fact, the observed dynamic coarsening process corresponds to the spindodal demixing that occurs during such a transitionComment: 6 pages, 5 figure

Formation of PAHs and Carbonaceous Solids in Gas-Phase Condensation Experiments

Carbonaceous grains represent a major component of cosmic dust. In order to understand their formation pathways, they have been prepared in the laboratory by gas-phase condensation reactions such as laser pyrolysis and laser ablation. Our studies demonstrate that the temperature in the condensation zone determines the formation pathway of carbonaceous particles. At temperatures lower than 1700 K, the condensation by-products are mainly polycyclic aromatic hydrocarbons (PAHs), that are also the precursors or building blocks for the condensing soot grains. The low-temperature condensates contain PAH mixtures that are mainly composed of volatile 3-5 ring systems. At condensation temperatures higher than 3500 K, fullerene-like carbon grains and fullerene compounds are formed. Fullerene fragments or complete fullerenes equip the nucleating particles. Fullerenes can be identified as soluble components. Consequently, condensation products in cool and hot astrophysical environments such as cool and hot AGB stars or Wolf Rayet stars should be different and should have distinct spectral properties.Comment: 7 pages, 5 figure

A priori convergence estimates for a rough Poisson-Dirichlet problem with natural vertical boundary conditions

Stents are medical devices designed to modify blood flow in aneurysm sacs, in order to prevent their rupture. Some of them can be considered as a locally periodic rough boundary. In order to approximate blood flow in arteries and vessels of the cardio-vascular system containing stents, we use multi-scale techniques to construct boundary layers and wall laws. Simplifying the flow we turn to consider a 2-dimensional Poisson problem that conserves essential features related to the rough boundary. Then, we investigate convergence of boundary layer approximations and the corresponding wall laws in the case of Neumann type boundary conditions at the inlet and outlet parts of the domain. The difficulty comes from the fact that correctors, for the boundary layers near the rough surface, may introduce error terms on the other portions of the boundary. In order to correct these spurious oscillations, we introduce a vertical boundary layer. Trough a careful study of its behavior, we prove rigorously decay estimates. We then construct complete boundary layers that respect the macroscopic boundary conditions. We also derive error estimates in terms of the roughness size epsilon either for the full boundary layer approximation and for the corresponding averaged wall law.Comment: Dedicated to Professor Giovanni Paolo Galdi 60' Birthda

QCD Corrections to Vector-Boson Fusion Processes in Warped Higgsless Models

We discuss the signatures of a representative Higgsless model with ideal fermion delocalization in vector-boson fusion processes, focusing on the gold- and silver-plated decay modes of the gauge bosons at the CERN-Large Hadron Collider. For this purpose, we have developed a fully-flexible parton-level Monte-Carlo program, which allows for the calculation of cross sections and kinematic distributions within experimentally feasible selection cuts at NLO-QCD accuracy. We find that Kaluza-Klein resonances give rise to very distinctive distributions of the decay leptons. Similar to the Standard Model case, within the Higgsless scenario the perturbative treatment of the vector-boson scattering processes is under excellent control.Comment: 22 pages, 20 figure

Vector Boson Pair Production via Vector Boson Fusion at NLO QCD

NLO QCD corrections to Vector Boson Pair Production via Vector Boson Fusion have recently been calculated and implemented in a parton-level Monte-Carlo program with full experimental cuts. We briefly sketch the elements of the calculation and show numerical results for the Large Hadron Collider.Comment: 6 pages, 3 figures, presented by G.Bozzi at IFAE 2007 (Napoli, April 2007) and HEP 2007 (Manchester, July 2007

New insights into the dynamics of the glutathione-ascorbate redox system of plants

The Hallilwell-Asada-Foyer redox cascade (HAF) is viewed as a H2O2 detoxifying system with a great variety of responses against environmental changes. The functional consequences of these responses are interpreted intuitively because a systemic analysis of the inherent dynamic potential of the HAF is lacking. With the help of numerical modelling we show that in wheat roots parameter patterns are established which result in homeostatic states of HAF over a vast range of environmental changes. The reduced fractions glutathione (GSH) and ascorbate (ASC) remain on high levels even during dramatic changes in the enzyme activity ratios of glutathione reductase, dehydroascorbate reductase and ascorbat peroxidase. Necessarily their oxidised counterparts dithioglutathione (GSSG) and dehydroascorbate (DHA) stay in these buffered regions on very low concentration levels. Our modelling shows that redox ratios GSH/GSSG and ASC/DHA can be modified additionally via changes in NADPH/H2O2 ratios. Thus, the redox states of GSH and ASC can not simply be regarded as indicators for oxidative stress with respect to H2O2 levels. The involvement of the redox variables in other redox processes than the HAF reaction (redox proteome) and / or their utilisation in metabolism (protein modification, detoxification of xenobiotics) are viewed to cause system relaxations of the redox variables. The re-establishment of their homeostatic ratios follow time courses which are redox moiety specific and are balanced according to the existing parameter patterns. Despite of its detoxification function the HAF balances the glutathione / ascorbate redox state in cells according to the prevailing physiological conditions

On the relevance of polyynyl-substituted PAHs to astrophysics

We report on the absorption spectra of the polycyclic aromatic hydrocarbon (PAH) molecules anthracene, phenanthrene, and pyrene carrying either an ethynyl (-C2H) or a butadiynyl (-C4H) group. Measurements were carried out in the mid infrared at room temperature on grains embedded in CsI pellets and in the near ultraviolet at cryogenic temperature on molecules isolated in Ne matrices. The infrared measurements show that interstellar populations of polyynyl-substituted PAHs would give rise to collective features in the same way non-substituted PAHs give rise to the aromatic infrared bands. The main features characteristic of the substituted molecules correspond to the acetylenic CH stretching mode near 3.05 mum and to the almost isoenergetic acetylenic CCH in- and out-of-plane bending modes near 15.9 mum. Sub-populations defined by the length of the polyynyl side group cause collective features which correspond to the various acetylenic CC stretching modes. The ultraviolet spectra reveal that the addition of an ethynyl group to a non-substituted PAH molecule results in all its electronic transitions being redshifted. Due to fast internal energy conversion, the bands at shorter wavelengths are significantly broadened. Those at longer wavelengths are only barely affected in this respect. As a consequence, their relative peak absorption increases. The substitution with the longer butadiynyl chain causes the same effects with a larger magnitude, resulting in the spectra to show a prominent if not dominating pi-pi* transition at long wavelength. After discussing the relevance of polyynyl-substituted PAHs to astrophysics, we conclude that this class of highly conjugated, unsaturated molecules are valid candidates for the carriers of the diffuse interstellar bands.Comment: 29 pages, 9 figures, accepted for publication in ApJ 2 April 201

IL7RA haplotype-associated alterations in cellular immune function and gene expression patterns in multiple sclerosis

Interleukin-7 receptor alpha (IL7RA) is among the top listed candidate genes influencing the risk to develop multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system. Soluble IL-7RA (sIL-7RA) protein and mRNA levels vary among the four common IL7RA haplotypes. Here we show and confirm that protective haplotype carriers have three times lower sIL-7RA serum levels than the other three haplotypes. High sIL-7RA concentrations significantly decrease IL-7-mediated STAT5 phosphorylation in CD4(+) T cells. Transcriptome analysis of unstimulated and stimulated CD4(+) T cells of MS patients carrying the different IL7RA haplotypes revealed complex and overlapping patterns in genes participating in cytokine signaling networks, apoptosis, cell cycle progression and cell differentiation. Our findings indicate that genetic variants of IL7RA result in haplotype-associated differential responsiveness to immunological stimuli that influence MS susceptibility not exclusively by varying levels of sIL-7RA