Icosahedral Ni nanowires formed from nanocontacts breaking: Identification and characterization by Molecular Dynamics

We present and discuss an algorithm to identify and characterize the long icosahedral structures (staggered pentagonal nanowires with 1-5-1-5 atomic structure) that appear in Molecular Dynamics simulations of metallic nanowires of different species subjected to stretching. The use of this algorithm allows the identification of pentagonal rings forming the icosahedral structure as well as the determination of its number np , and the maximum length of the pentagonal nanowire Lpm. The algorithm is tested with some ideal structures to show its ability to discriminate between pentagonal rings and other ring structures. We applied the algorithm to Ni nanowires with temperatures ranging between 4K and 865K, stretched along the [111], [100] and [110] directions. We studied statistically the formation of pentagonal nanowires obtaining the distributions of length Lpm and number of rings np as function of the temperature. The Lpm distribution presents a peaked shape, with peaks located at fixed distances whose separation corresponds to the distance between two consecutive pentagonal rings.

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Notación musical en v. h. CXV-h. CXXVIII

The breaking of axisymmetric slender liquid bridges

Liquids held by surface tension forces can bridge the gap between two solid bodies placed not too far apart from each other. The equilibrium conditions and stability criteria for static, cylindrical liquid bridges are well known. However, the behaviour of an unstable liquid bridge, regarding both its transition toward breaking and the resulting configuration, is a matter for discussion. The dynamical problem of axisymmetric rupture of a long liquid bridge anchored at two equal coaxial disks is treated in this paper through the adoption of one-dimensional theories which are widely used in capillary jet problems

Stability limits of minimum volume and breaking axisymmetric liquid bridges between unequal disks

This paper deals with the stability limits of minimum volume and the breaking of axisymmetric liquid columns held by capillary forces between two concentric,circular solid disk of different radii. The problem has been analyzed both theoreti-cally and experimentally. A theoretical analysis concerning the breaking of liquid bridges has been performed by using a one-dimensional slice model already used in liquid bridge problems. Experiments have been carried out by using milli-metric liquid bridges, and minimum volume stability limits as well as the volumes of the drops resulting after breaking have been measured for a large number of liquid bridge configurations. Experimental results being in agreement with theoretical prediction.

Why neutron guides may end up breaking down? Some results on the macroscopic behaviour of alkali-borosilicate glass support plates under neutron irradiation

In this paper we report on a first part of a study on the mechanisms leading to brittle fracture in neutron guides made of glass as structural element. Such devices are widely used to deliver thermal and cold neu tron beams to experimental lines in most large neutron research facilities. We present results on macroscopic properties of samples of guide glass substrates which are subjected to neutron irradiation at relatively large fluences. The results show a striking dependence of some of the macroscopic properties such as density, shape or surface curvature upon the specific chemical composition of a given glass. The relevance of the present findings for the installation of either replacement guides at the existing facilities or for the deployment of instruments for ongoing projects such as the European Spallation Source is briefly discussed.

Torsional rigidity of single actin filaments and actin–actin bond breaking force under torsion measured directly by in vitro micromanipulation

Knowledge of the elastic properties of actin filaments is crucial for considering its role in muscle contraction, cellular motile events, and formation of cell shape. The stiffness of actin filaments in the directions of stretching and bending has been determined. In this study, we have directly determined the torsional rigidity and breaking force of single actin filaments by measuring the rotational Brownian motion and tensile strength using optical tweezers and microneedles, respectively. Rotational angular fluctuations of filaments supplied the torsional rigidity as (8.0 ± 1.2) × 10−26 Nm2. This value is similar to that deduced from the longitudinal rigidity, assuming the actin filament to be a homogeneous rod. The breaking force of the actin–actin bond was measured while twisting a filament through various angles using microneedles. The breaking force decreased greatly under twist, e.g., from 600–320 pN when filaments were turned through 90°, independent of the rotational direction. Our results indicate that an actin filament exhibits comparable flexibility in the rotational and longitudinal directions, but breaks more easily under torsional load.

Mirror symmetry breaking at the molecular level.

Reasoning from two basic principles of molecular physics, P invariance of electromagnetic interaction and the second law of thermodynamics, one would conclude that mirror symmetry retained in the world of chiral molecules. This inference is fully consistent with what is observed in inorganic nature. However, in the bioorganic world, the reverse is true. Mirror symmetry there is definitely broken. Is it possible to account for this phenomenon without going beyond conventional concepts of the kinetics of enantioselective processes? This study is an attempt to survey all existing hypotheses containing this phenomenon.

El color como recurso expresivo: análisis de las series de televisión Mad Men y Breaking Bad

La presente investigación tiene como objetivo reconocer y aprender a utilizar el color en el medio audiovisual, es decir, conocer sus cualidades, técnicas y estrategias para, de esta forma, dar justa dimensión a su gran capacidad expresiva. El mirar y, posteriormente, observar permite saber el tipo de atmósferas que son necesarias para sugerir determinados estados. Estas atmósferas se generan gracias a los elementos que las componen, cada uno de ellos con sus formas, colores, ubicación en el espacio, más la interrelación global entre ellos. La composición visual se da a partir del conjunto de elementos distribuidos en el espacio. Que se ven “envueltos” con la luz planteada. Toda esta suma, es la que consigue expresar una emoción por parte del creador y, si se sabe “leer”, una correcta interpretación por parte del espectador. Esta “alfabetización visual” establece nexos entre el creador y el receptor, lo que lleva a unos y otros a un mayor conocimiento en la utilización de las reglas. Ello permite reforzar el texto narrativo, que “se articula en dos niveles: la historia —lo narrado, el qué— y el discurso —el modo de narrarlo, el cómo—, es decir, el plano del contenido y el plano de la expresión” (García, F., 2011, p.12). El creador de la obra audiovisual guía al espectador por los caminos de la historia que está desarrollando, mientras que el espectador, al saber “leer”, puede conocer el camino por donde tiene que transitar para disfrutarlo y entenderlo en su totalidad. Comprender la información que proporciona el color parecería innato al ser humano del siglo XXI, dominado por un entorno netamente visual. Pero no es así. Por lo tanto, si se aprende a conocer los parámetros sobre los que se desarrolla la información que se presenta visualmente, se conseguirá hacer más eficaz la comunicación, a la vez que se fomentará la creatividad, por un lado, y el disfrute visual, por otro...