Dynamic screening and energy loss of antiprotons colliding with excited Al clusters

We use time-dependent density functional theory to calculate the energy loss of an antiproton colliding with a small Al cluster previously excited. The velocity of the antiproton is such that non-linear effects in the electronic response of the Al cluster are relevant. We obtain that an antiproton penetrating an excited cluster transfers less energy to the cluster than an antiproton penetrating a ground state cluster. We quantify this difference and analyze it in terms of the cluster excitation spectrum.Comment: 23 pages, 4 figures, to be published in Nuclear Instruments and Methods B as a proceeding of the IISC-19 Workshop on Inelastic Ion-Surface Collision

Los pinceles de la química

La química desarrolla un papel muy importante en diferentes campos de investigación. Normalmente cuando se habla de química la gente piensa en reacciones y síntesis de nuevos proyectos. Sin embargo, un campo poco conocido para la química es el mundo de la restauración de pinturas. Nombres tan conocidos como Lewis, Hückel, Diels-Alder se imparten en nuestras aulas, pero por qué se menosprecia los disolventes. Los solventes son muy importantes en las reacciones químicas aunque muchas veces los obviemos. En cambio, toman mucha relevancia al restaurar pinturas

Phase separation of a driven granular gas in annular geometry

This work investigates phase separation of a monodisperse gas of inelastically colliding hard disks confined in a two-dimensional annulus, the inner circle of which represents a "thermal wall". When described by granular hydrodynamic equations, the basic steady state of this system is an azimuthally symmetric state of increased particle density at the exterior circle of the annulus. When the inelastic energy loss is sufficiently large, hydrodynamics predicts spontaneous symmetry breaking of the annular state, analogous to the van der Waals-like phase separation phenomenon previously found in a driven granular gas in rectangular geometry. At a fixed aspect ratio of the annulus, the phase separation involves a "spinodal interval" of particle area fractions, where the gas has negative compressibility in the azimuthal direction. The heat conduction in the azimuthal direction tends to suppress the instability, as corroborated by a marginal stability analysis of the basic steady state with respect to small perturbations. To test and complement our theoretical predictions we performed event-driven molecular dynamics (MD) simulations of this system. We clearly identify the transition to phase separated states in the MD simulations, despite large fluctuations present, by measuring the probability distribution of the amplitude of the fundamental Fourier mode of the azimuthal spectrum of the particle density. We find that the instability region, predicted from hydrodynamics, is always located within the phase separation region observed in the MD simulations. This implies the presence of a binodal (coexistence) region, where the annular state is metastable. The phase separation persists when the driving and elastic walls are interchanged, and also when the elastic wall is replaced by weakly inelastic one.Comment: 9 pages, 10 figures, to be published in PR

Ticagrelor: the evidence for its clinical potential as an oral antiplatelet treatment for the reduction of major adverse cardiac events in patients with acute coronary syndromes

Bernardo Lombo1, José G Díez21Department of Medicine, Yale School of Medicine, New Haven, CT, USA; 2Section of Cardiology, Baylor College of Medicine and the Texas Heart Institute at St. Luke's Episcopal Hospital, Houston, TX, USAIntroduction: Ticagrelor, the first direct-acting, reversibly binding oral P2Y12 receptor antagonist, appears to have a favorable efficacy and safety profile.Aims: To update the evidence and provide an overview of the available data on ticagrelor.Evidence review: Peer reviewed articles published and listed under Medline Search, and published updated guidelines for pharmacotherapies in acute coronary syndromes were reviewed.Place in therapy: Clinical evidence is increasing to support the use of new thienopyridines and the direct-acting P2Y12 receptor in the setting of acute coronary syndromes.Conclusion: The options for drugs to inhibit the platelet P2Y12 receptor for adenosine diphosphate are rapidly expanding. Ticagrelor has shown benefits in clinical trials. Its rapid onset of platelet inhibition and short half-life make it an attractive alternative to thienopyridines, especially when rapid inhibition of platelet aggregation or its quick reversal are required.Keywords: platelet, acute coronary syndromes, antiplatelet, coronary artery disease, percutaneous coronary intervention, sten

Competition between electron and phonon excitations in the scattering of nitrogen atoms and molecules off tungsten and silver surfaces

We investigate the role played by electron-hole pair and phonon excitations in the interaction of reactive gas molecules and atoms with metal surfaces. We present a theoretical framework that allows us to evaluate within a full-dimensional dynamics the combined contribution of both excitation mechanisms while the gas particle-surface interaction is described by an ab-initio potential energy surface. The model is applied to study energy dissipation in the scattering of N$_2$ on W(110) and N on Ag(111). Our results show that phonon excitation is the dominant energy loss channel whereas electron-hole pair excitations represent a minor contribution. We substantiate that, even when the energy dissipated is quantitatively significant, important aspects of the scattering dynamics are well captured by the adiabatic approximation.Comment: 4pages and 3 figure

End-pulled polymer translocation through a many-body flexible pore

This paper studies the features of a homopolymer translocating through a flexible pore. The channel is modeled as a monolayer tube composed by monomers with two elastic parameters: spring-like two body interaction and bending three body recall interaction. In order to guarantee the stability of the system, the membrane is compounded by a lipid bilayer structure having hydrophobic body (internal), while the pore is hydrophilic in both edges. The polymer is end-pulled from the cis-side to the trans-side by a cantilever, to which is connected through a spring able to measure the force acting on the polymer during the translocation. All the structure reacts to the impacts of the monomers of the polymer with vibrations generated by the movement of its constituent bodies. In these conditions, the work done by the cantilever shows a nonmonotonic behavior with the elastic constant, revealing a resonant-like behavior in a parameter region. Moreover, the force spectroscopy registered as a function of time, is able to record the main kinetics of the polymer progression inside the pore

Transferring Axial Molecular Chirality Through a Sequence of On-Surface Reactions

Fine management of chiral processes on solid surfaces has progressed over the years, yet still faces the need for the controlled and selective production of advanced chiral materials. Here, we report on the use of enantiomerically enriched molecular building blocks to demonstrate the transmission of their intrinsic chirality along a sequence of on-surface reactions. Triggered by thermal annealing, the on-surface reac-tions induced in this experiment involve firstly the coupling of the chiral reactants into chiral polymers and subsequently their transformation into planar prochiral graphene nanoribbons. Our study reveals that the axial chirality of the reactant is not only transferred to the polymers, but also to the planar chirality of the graphene nanoribbon end products. Such chirality transfer consequently allows, starting from ad-equate enantioenriched reactants, for the controlled production of chiral and prochiral organic nanoarchi-tectures with pre-defined handedness

Temporal rating habits: A valuable tool for rating discrimination

This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in CAMRa '11 Proceedings of the 2nd Challenge on Context-Aware Movie Recommendation, http://dx.doi.org/10.1145/2096112.2096118.In this paper, we describe the experiments conducted by the Information Retrieval Group at the Universidad Autónoma de Madrid (Spain) to tackle the Identifying Ratings (track 2) task of the CAMRa 2011 Challenge. The experiments performed include time-frequency probabilistic strategies, heuristic collaborative filtering (CF) and a model-based CF approach. Results show that probabilistic classifiers based on temporal behavior of users have better performance than traditional recommendation-based strategies, thus reflecting that temporal information is a valuable source for the identification or discrimination of user ratings.This work is supported by the Spanish Government (TIN 2008-06566-C04-02) and by the Comunidad de Madrid and Universidad Aut´onoma de Madrid (CCG10-UAM/TIC-5877). The authors acknowledge support from CCC at UAM

Non-equilibrium Anisotropic Phases, Nucleation and Critical Behavior in a Driven Lennard-Jones Fluid

We describe short-time kinetic and steady-state properties of the non--equilibrium phases, namely, solid, liquid and gas anisotropic phases in a driven Lennard-Jones fluid. This is a computationally-convenient two-dimensional model which exhibits a net current and striped structures at low temperature, thus resembling many situations in nature. We here focus on both critical behavior and details of the nucleation process. In spite of the anisotropy of the late--time spinodal decomposition process, earlier nucleation seems to proceed by Smoluchowski coagulation and Ostwald ripening, which are known to account for nucleation in equilibrium, isotropic lattice systems and actual fluids. On the other hand, a detailed analysis of the system critical behavior rises some intriguing questions on the role of symmetries; this concerns the computer and field-theoretical modeling of non-equilibrium fluids.Comment: 7 pages, 9 ps figures, to appear in PR

Development of Suitable CuO-Based Materials Supported on Al2O3, MgAl2O4, and ZrO2 for Ca/Cu H2 Production Process

Functional materials for the sorption enhanced reforming process for H2 production coupled to a Cu/CuO chemical loop have been synthesized. The performance of CuO-based materials supported on Al2O3, MgAl2O4, and ZrO2 and synthesized by different routes has been analyzed. Highly stable materials supported on Al2O3 or MgAl2O4 synthesized by coprecipitation and mechanical mixing with sufficient Cu loads (around 65% wt) have been successfully developed. However, it has been found that coprecipitation under these conditions is not a suitable route for ZrO2. Spray-drying and deposition precipitation did not provide the best chemical features to the materials. As the Ca/Cu process is operated in fixed bed reactors, the best candidates were pelletized and their stability was again assessed. Pellets with high chemical and mechanical stability, high oxygen transport capacity, and good mechanical properties have been finally obtained by coprecipitation. The good homogeneity that provides this route would allow an easy scaling up