Use of antimicrobial agents in patients with cardiovascular disease

Antimicrobial agents are widely utilized in the prevention and treatment of infection in patients with cardiovascular diseases. Knowledge of spectrum of activity, pharmacology, adverse effect and toxicity profile, and emergence of resistant pathogens is critical to the appropriate use of these agents. The following review will emphasize the safe, effective use of antimicrobial drugs in the cardiovascular patient.     

A pseudo-neural system for hypothesis selection

The article describes a system for hypothesis elicitation and ranking formed by a net of computational elements obtained by modifying the classical neural model of Caianiello. This neural structure was chosen on the basis both of knowledge representation and of parallel processing considerations. the two fundamental components of the system are an elaboration layer and, in case the available evidences are insufficient to trigger explanatory hypotheses, a query layer that enables the system to gather additional information. Algorithms that help setting the crucial variable parameters of the net are described in the Appendix. © 1992 John Wiley & Sons, Inc.     

Beta-1-integrin expression in adult acute lymphoblastic leukemia: possible relationship with the stem cell antigen CD34

In the hemopoietic system, interactions between stem cells and components of the bone marrow microenvironment play a pivotal role in blood cell proliferation and differentiation. Among the adhesion molecules, the integrins of the beta 1-subfamily are known to direct cell-cell and cell-matrix interactions and evidence has been provided that CD34-positive stem cells bind either to the bone marrow stroma or to the extracellular matrix proteins through the beta 1-integrins. It seems that changes in their expression pattern or signalling function are likely to reflect disturbances at the hemopoietic bone marrow microenvironmental level. Any alteration of their biological functions makes them attractive candidates for playing decisive roles in the leukemic processes. In this view, beta 1-integrins have been recognized to mediate those cellular interactions and migrations that are important in the biology of leukemia. In this paper we review some aspects of the role played by beta 1-integrins, especially VLA-4 and VLA-5, in adult acute lymphoblastic leukemia in relation with the expression rate of the stem cell antigen CD34.     

Tetra-anionic porphyrin loading onto ZnO nanoneedles: A hybrid covalent/non covalent approach

A stepwise surface functionalization procedure, based on hybrid covalent and non-covalent approach is herein proposed to anchor tetra-anionic meso-tetrakis(4-sulfonatophenyl)porphyrin on ZnO nanorods. Carboxyalkylphosphonic acids have been proven effective to form stable self-assembled monolayers through the surface grafting of –PO₃H₂ headgroups. The exposed carboxylic functionalities are suitable for the successful grafting of cationic poly-l-lysine that drives, in water, the non-covalent anchoring of the anionic porphyrin. A stepwise surface characterization, provided by X-ray photoelectron spectroscopy, elucidates the multilayers deposition and surface composition after each process step, thus, giving interesting insights on the chemical speciation of the exposed functionalities. UV–vis spectroscopy confirms the role of ZnO morphology to increase the porphyrin loading onto the investigated surfaces. The proposed approach is effective to achieve deposition of anionic porphyrins on ZnO nanostructures and combines the robustness of covalent functionalization with the versatility and full reversibility of the non-covalent strategies.     

Charge Photogeneration in Few‐Layer MoS2

The 2D semiconductor MoS₂ in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS₂. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS₂ photovoltaic and photodetector devices are made.     

The Role of Higher Lying Electronic States in Charge Photogeneration in Organic Solar Cells

The role of excess photon energy on charge generation efficiency in bulk heterojunction solar cells is still an open issue for the organic photovoltaic community. Here, the spectral dependence of the internal quantum efficiency (IQE) for a poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b]­dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)]:6,6‐phenyl‐C₆₁‐butyric acid methyl ester (PCPDTBT:PC60BM)‐based solar cell is derived combining accurate optoelectronic characterization and comprehensive optical modeling. This joint approach is shown to be essential to get reliable values of the IQE. Photons with energy higher than the bandgap of the donor material can effectively contribute to enhance the IQE of the solar cell. This holds true independently of the device architecture, reflecting an intrinsic property of the active material. Moreover, the nanomorphology of the bulk heterojunction plays a crucial role in determining the IQE spectral dependence: the coarser and more crystalline, the lesser the gain in IQE upon high energy excitation.     

Approximation des equations d'evolution du premier ordre ent par des schemas a un degre de liberte

Resume L'objet du présent travail est de montrer comment l'emploi d'approximatious contenant des éléments arbitraires permet d'élargir les critéres de stabilité habituellement utilisés avec les schémas approchés explicites associés aux équations aux dérivées paraboliques. La méthode utilisée qui est décrite pour des équations d'évolution du premier ordre peut naturellement étre utilisée aussi pour des équations d'ordre plus élevé ainsi que pour des schémas approchés à plusieurs niveaux de temps.

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Summary The purpose of the present paper is to show that the use of approximations of the Sobolev spaces with arbitrary parameters permits to enlarge the usual stability criteria for approximate explicit schemes associated with time dependent parabolic partial differential equations. This method which is applied here and numerically tested for first order time dependent equations can be used also for higher order time dependent equations and for multilevel explicit schemes.

     

On the Mechanisms Governing Aluminum-Mediated Solid-Phase Epitaxy of Silicon

Mechanisms governing the aluminum-mediated solid-phase epitaxy of Si on patterned crystalline Si substrates have been identified by studying the deposited material as a function of growth conditions when varying parameters such as temperature, growth time, and layer-stack properties. Early growth stages can be discerned as first formation of “free” Si at the Al/α-Si interface, then diffusion of Si along the Al grain boundaries, nucleation at the Si substrate surface, nuclei rearrangement, and finally crystal growth. The acquired understanding is applied to control the selectivity and completeness of single-crystal growth in various sizes of contact windows to the Si substrate.     

A dynamic variational multiscale method for viscoelasticity using linear tetrahedral elements

In this article, we develop a dynamic version of the variational multiscale (D‐VMS) stabilization for nearly/fully incompressible solid dynamics simulations of viscoelastic materials. The constitutive models considered here are based on Prony series expansions, which are rather common in the practice of finite element simulations, especially in industrial/commercial applications. Our method is based on a mixed formulation, in which the momentum equation is complemented by a pressure equation in rate form. The unknown pressure, displacement, and velocity are approximated with piecewise linear, continuous finite element functions. To prevent spurious oscillations, the pressure equation is augmented with a stabilization operator specifically designed for viscoelastic problems, in that it depends on the viscoelastic dissipation. We demonstrate the robustness, stability, and accuracy properties of the proposed method with extensive numerical tests in the case of linear and finite deformations.