Mechanism of strength reduction along the graphenization pathway.

Even though polycrystalline graphene has shown a surprisingly high tensile strength, the influence of inherent grain boundaries on such property remains unclear. We study the fracture properties of a series of polycrystalline graphene models of increasing thermodynamic stability, as obtained from a long molecular dynamics simulation at an elevated temperature. All of the models show the typical and well-documented brittle fracture behavior of polycrystalline graphene; however, a clear decrease in all fracture properties is observed with increasing annealing time. The remarkably high fracture properties obtained for the most disordered (less annealed) structures arise from the formation of many nonpropagating prefracture cracks, significantly retarding failure. The stability of these reversible cracks is due to the nonlocal character of load transfer after a bond rupture in very disordered systems. It results in an insufficient strain level on neighboring bonds to promote fracture propagation. Although polycrystallinity seems to be an unavoidable feature of chemically synthesized graphenes, these results suggest that targeting highly disordered states might be a convenient way to obtain improved mechanical properties.

Microscopic superfluidity in 4He clusters stirred by a rotating impurity molecule.

The effective moment of inertia of a CO impurity molecule in 4HeN and p-(H2)N solvent clusters initially increases with N but then commences a nonclassical decrease at N=4 (4He) or N=6 (p-H2). This suggests molecule-solvent decoupling and a transition to microscopic superfluidity. However, the quantum decoupling mechanism has not been elucidated. To understand the decoupling mechanism, a one-dimensional model is introduced in which the 4He atoms are confined to a ring. This model captures the physics and shows that decoupling happens primarily because of bosonic solvent-solvent repulsion. Quantum Monte Carlo and basis set calculations suggest that the system can be modeled as a stirred Tonks-Girardeau gas. This allows the N-particle time-dependent Schrödinger equation to be solved directly. Computations of the integrated particle current reveal a threshold for stirring and current generation, indicative of superfluidity.

Automatic Differentiation of the Energy within Self-consistent Tight-Binding Methods.

We present and implement the calculation of analytical n-order geometric derivatives of the energy obtained within the framework of the density functional based tight binding approach. The use of automatic differentiation techniques allows a unique implementation for the calculation of derivatives up to any order providing that the computational facilities are sufficient. As first applications, the derivatives are used to build an analytical potential energy surface around the optimized geometry of acetylene. We also discuss the relevant anharmonic contributions that have to be considered when building such an analytical potential energy surface for acetylene, ethylene, ethane, benzene, and naphtalene.

Eficacia de la microdosis de captopril en el tratamiento de la hipertensión arterial esencial / Effectiveness of captopril microdosing in the treatment of essential arterial hypertension

Introducción: prescribir una terapéutica adecuada siempre es complejo, más aun cuando los índices de control y la seguridad de los medicamentos no satisfacen los objetivos esperados, la microdosis pudiera convertirse en una alternativa eficaz. Objetivo: evaluar la eficacia de la microdosis de captopril en el tratamiento de la hipertensión arterial esencial. Métodos: se realizó un ensayo clínico fase III, unicéntrico, aleatorizado y controlado, en el Hospital Universitario Manuel Ascunce Domenech, de Camagüey, entre enero de 2007 y diciembre de 2009. Se creó un formulario con las variables: control clinico, grupos etarios, grado hipertensivo, grado de riesgo cardiovascular, dosis mínima necesaria para control. La información obtenida fue sometida a un procesamiento estadístico de análisis en el programa SPSS versión 15.0. Se utilizaron técnicas estadísticas para hallar diferencias entre variables. Resultados: la microdosis de captopril resultó ser más eficaz que las tabletas en el tratamiento a largo plazo de la hipertensión arterial, en particular en pacientes con 60 años y más de edad, en los hipertensos grados II y III y con más alto riesgo, aún con el uso de una dosis menor. Conclusiones: la microdosis de captopril fue eficaz en el tratamiento de la hipertensión arterial esencial, al permitir mejor control clínico con una menor dosis de medicamento(AU)

Introduction: prescribing the appropriate therapeutic treatment is always a complex task, particularly when drug control and safety indices do not accomplish the expected goals. In such a context, microdosing could be an effective alternative. Objective: evaluate the effectiveness of captopril microdosing in the treatment of essential arterial hypertension. Methods: aunicenter controlled randomized phase III clinical trial was conducted at Manuel Ascunce Domenech University Hospital in the province of Camagüey from January 2007 to December 2009. A form was prepared which included the following variables: clinical control, age group, hypertension grade, cardiovascular risk grade, minimum dose required for control. The information collected was subjected to statistical processing and analysis with the software SPSS versión 15.0. Statistical techniques were used to find differences between the variables. Results: captopril microdosing was more effective than tablets for the long-term treatment of arterial hypertension, particularly in patients aged 60 and over, grade II and III hypertensives, and higher risk patients, even with the use of a smaller dose. Conclusions: captopril microdosing was found to be effective for the treatment of essential arterial hypertension, allowing a better clinical control with a smaller dose of the medication(AU)

Eficacia de la microdosis de captopril en el tratamiento de la hipertensión arterial esencial / Effectiveness of captopril microdosing in the treatment of essential arterial hypertension

Introducción: prescribir una terapéutica adecuada siempre es complejo, más aun cuando los índices de control y la seguridad de los medicamentos no satisfacen los objetivos esperados, la microdosis pudiera convertirse en una alternativa eficaz. Objetivo: evaluar la eficacia de la microdosis de captopril en el tratamiento de la hipertensión arterial esencial. Métodos: se realizó un ensayo clínico fase III, unicéntrico, aleatorizado y controlado, en el Hospital Universitario Manuel Ascunce Domenech, de Camagüey, entre enero de 2007 y diciembre de 2009. Se creó un formulario con las variables: control clinico, grupos etarios, grado hipertensivo, grado de riesgo cardiovascular, dosis mínima necesaria para control. La información obtenida fue sometida a un procesamiento estadístico de análisis en el programa SPSS versión 15.0. Se utilizaron técnicas estadísticas para hallar diferencias entre variables. Resultados: la microdosis de captopril resultó ser más eficaz que las tabletas en el tratamiento a largo plazo de la hipertensión arterial, en particular en pacientes con 60 años y más de edad, en los hipertensos grados II y III y con más alto riesgo, aún con el uso de una dosis menor. Conclusiones: la microdosis de captopril fue eficaz en el tratamiento de la hipertensión arterial esencial, al permitir mejor control clínico con una menor dosis de medicamento

Introduction: prescribing the appropriate therapeutic treatment is always a complex task, particularly when drug control and safety indices do not accomplish the expected goals. In such a context, microdosing could be an effective alternative. Objective: evaluate the effectiveness of captopril microdosing in the treatment of essential arterial hypertension. Methods: aunicenter controlled randomized phase III clinical trial was conducted at Manuel Ascunce Domenech University Hospital in the province of Camagüey from January 2007 to December 2009. A form was prepared which included the following variables: clinical control, age group, hypertension grade, cardiovascular risk grade, minimum dose required for control. The information collected was subjected to statistical processing and analysis with the software SPSS versión 15.0. Statistical techniques were used to find differences between the variables. Results: captopril microdosing was more effective than tablets for the long-term treatment of arterial hypertension, particularly in patients aged 60 and over, grade II and III hypertensives, and higher risk patients, even with the use of a smaller dose. Conclusions: captopril microdosing was found to be effective for the treatment of essential arterial hypertension, allowing a better clinical control with a smaller dose of the medication

Chaos in the classical mechanics of bound and quasi-bound HX-4He complexes with X = F, Cl, Br, CN.

The classical dynamics of weakly bound floppy van der Waals complexes have been extensively studied in the past except for the weakest of all, i.e., those involving He atoms. These complexes are of considerable current interest in light of recent experimental work focussed on the study of molecules trapped in small droplets of the quantum solvent (4)He. Despite a number of quantum investigations, details on the dynamics of how quantum solvation occurs remain unclear. In this paper, the classical rotational dynamics of a series of van der Waals complexes, HX-(4)He with X = F, Cl, Br, CN, are studied. In all cases, the ground state dynamics are found to be almost entirely chaotic, in sharp contrast to other floppy complexes, such as HCl-Ar, for which chaos sets in only at relatively high energies. The consequences of this result for quantum solvation are discussed. We also investigate rotationally excited states with J = 1 which, except for HCN-(4)He, are actually resonances that decay by rotational pre-dissociation.