Threshold region for Higgs boson production in gluon fusion.

We provide a quantitative determination of the effective partonic kinematics for Higgs boson production in gluon fusion in terms of the collider energy at the LHC. We use the result to assess, as a function of the Higgs boson mass, whether the large m(t) approximation is adequate and Sudakov resummation advantageous. We argue that our results hold to all perturbative orders. Based on our results, we conclude that the full inclusion of finite top mass corrections is likely to be important for accurate phenomenology for a light Higgs boson with m(H)~125 GeV at the LHC with √s=14 TeV.

cAMP Response Element-Binding Protein Controls the Appearance of Neuron-Like Traits in Chorion Mesenchymal Cells.

BACKGROUND: Mesenchymal stromal cells (MSC) from bone marrow have been reported to undergo the initial phases of neural differentiation in response to an increase of intracellular cAMP. We investigated the possibility that a similar effect applies to chorion-derived MSC. METHODS: The intracellular concentration of cAMP was increased either by forskolin, to promote its synthesis, or by inhibitors of its degradation. The consequent reduction in the expression of mesenchymal markers was associated with the appearance of neuron-like morphology in a subset of cells. The effect was measured and characterized using biomarkers and an inhibitor of cAMP response element-binding protein (CREB). RESULTS: The dramatic morphological change induced by all the treatments that promoted intracellular cAMP was transient and peaked on the third day. After that, cells returned to the typical fibroblast-like appearance within 24 hours. The distinctive morphology was associated to the expression of neuregulin 1, doublecortin, neuron-specific class III ß-tubulin, and required cAMP response element-binding protein activity. Basic-fibroblast growth factor (b-FGF) treatment increased both the timeframe and number of cells undergoing the morphological change induced by the effect of forskolin. As opposite, arginine-vasopressin (AVP) and sphingosine-1-phosphate (S1P) reduced it. CONCLUSIONS: We conclude that cAMP and the ensuing CREB activation trigger a preliminary step towards neuronal differentiation of chorion-derived MSC. However, likewise other MSC, the stimulus is not sufficient to promote stable differentiation.

Influence of the side functionalization of quinquethiophene-S,S-dioxides on the morphology of blends with poly(3-hexylthiophene): scanning force microscopy reveals.

Blends of an electron donor, i.e. a regioregular poly(3-hexylthiophene) (P3HT), with electron acceptors, a series of soluble quinquethiophene-S,S-dioxides (T5Os) bearing different alkyl side groups were self-assembled at surfaces. Scanning Force Microscopy (SFM) studies revealed that while the T5O symmetrically functionalized with two hexyl groups in the central thiophene (1) self-organizes into micrometer sized crystals embedded in a grainy matrix of P3HT, by substituting the central thiophene of 1 with one hexyl and one methyl unit (2) smaller and less anisotropic crystals of the acceptor having a sub-micrometer scale size were formed. The generation of these crystals is due to the joint effect of different non-covalent intermolecular interactions between the T5Os that self-segregate from the P3HT. By derivatizing the compound 1 with cyclo-hexyl moieties in the four external thiophenes molecule 3 was obtained. Such system was found to assemble into grainy disordered structures when co-deposited with P3HT, providing evidence for the absence of a phase segregation between the two components. Generally, the self-assembly at surfaces is governed by the interplay of intramolecular as well as intermolecular and interfacial interactions. In the present case, the cyclo-hexyl side groups in 3 both induce an intramolecular loss of planarity of the thiophene rings and hinders intermolecular interactions, reducing the tendency of the molecules to self-associate forming large crystals, whereas the symmetrical functionalization of the two central thiophenes with hexyl chains favours the crystallization of the T5O. The reported results demonstrate that subtle differences in the chemical functionalization can lead to different types of molecular architectures at surfaces. This is of importance since controlling the self-organization of pi-conjugated molecules at surfaces towards pre-programmed assemblies is a viable approach to enhance their electronic and luminescent properties, which should help to improve the performance of organic devices.

Solar cells based on a fullerene-azothiophene dyad.

A power conversion efficiency of 0.37%, under white light of 80 mW cm-2 intensity, was obtained when a fullerene-azothiophene dyad was used as the active layer of a photovoltaic cell.

Synthesis, photophysics, and photoresponse of fullerene-based azoaromatic dyads.

The synthesis and photophysical characterization of a series of fullerene-based, donor-acceptor dyads is presented, along with a description of their behavior as single molecular components in photovoltaic cells. The spectroscopic and photophysical properties of the dyads, investigated by steady-state fluorescence spectroscopy, pico- and nanosecond transient optical spectroscopy and time-resolved electron paramagnetic resonance (EPR) spectroscopy, revealed that the dyads undergo multiple-step energy transfer from the donor singlet excited state to the fullerene triplet excited state, which in turn decays to the donor triplet state. The inefficient formation of a charge-separated state, both in solution and in the solid state, translates into a poor photovoltaic performance of dyads 2 b-4 b if compared to that of dyad 1 b, in which photoinduced electron transfer is operative in the solid state. In addition, the results of the photophysical investigation suggested that the performance of the solar cells was also limited by the low-lying donor triplet excited state that acts as a photoexcitation energy sink.