Isostaticity and the solidification of semiflexible polymer melts

Using molecular dynamics simulations of a tangent-soft-sphere bead-spring polymer model, we examine the degree to which semiflexible polymer melts solidify at isostaticity. Flexible and stiff chains crystallize when they are isostatic as defined by appropriate degree-of-freedom-counting arguments. Semiflexible chains also solidify when isostatic if a generalized isostaticity criterion that accounts for the slow freezing out of configurational freedom as chain stiffness increases is employed. The dependence of the average coordination number at solidification $Z(T_s)$ on chains' characteristic ratio $C_\infty$ has the same functional form [$Z \simeq a - b\ln(C_\infty)$] as the dependence of the average coordination number at jamming $Z(\phi_J)$ on $C_\infty$ in athermal systems, suggesting that jamming-related phenomena play a significant role in thermal polymer solidification

La minería y la industria del estaño

[Resumen] En este artículo se hace un breve repaso de la historia del estaño y su utilización por el hombre, desde los comienzos de la civilización hasta el presente. En él se enumeran los usos más relevantes del mismo y se sitúan, con la precisión histórica que es posible en cada caso, los momentos más florecientes de su industria y los hechos que condicionan su presente y muy probablemente su futuro.[Abstract] This article presents a short revision of the history of tin and its use by men from the beginnings of civilization to this day. The rrost important uses of tin are ennumerated in the paper, and the most flowishing moments of its industry, as well as the facts that determine its present and likely its future are stated with as much historic preciseness as possible

Special cantilever geometry for the access of higher oscillation modes in atomic force microscopy

Employing higher oscillation modes of microcantilevers promises higher sensitivity when applied as sensors, for example, for mass detection or in atomic force microscopy. Introducing a special cantilever geometry, we show that the relation between the resonance frequencies of the first and second resonance modes can be modified to separate them further or to bring them closer together. In atomic force microscopy the latter is of special interest as the photodiode of the beam deflection detection limits the accessible frequency range. Using finite element simulations, we optimized the design of the modified cantilever geometry for a maximum reduction of the frequency of the second oscillation mode with respect to the first mode. Cantilevers were fabricated by silicon micromachining and subsequently utilized in an ultrahigh vacuum Kelvin probe force microscope imaging the surface potential of C60 on graphit

On the maximum angle condition for the conforming longest-edge n-section algorithm for large values of n

In this note we introduce the conforming longest-edge $n$-section algorithm and show that for $n \ge 4$ it produces a family of triangulations which does not satisfy the maximum angle condition

Super-attracting periodic orbits for a classical third order method

AbstractWe use a classical third order root-finding iterative method for approximating roots of nonlinear equations. We present a procedure for constructing polynomials so that super-attracting periodic orbits of any prescribed period occur when this method is applied. This note can be considered as the second part of our previous study [S. Amat, S. Busquier, S. Plaza, A construction of attracting periodic orbits for some classical third order iterative methods, J. Comput. Appl. Math. 189(1–2) (2006) 22–33]

Evolución de la planta de concentración de la mina de estaño "El cubito" Salamanca

[Resumen] Durante los últimos diez años la mina de estaño "El Cubito", en la provincia de Salamanca, ha mantenido una producción regular e importante dentro del contexto español, pese a constituir un criadero de los habitualmente clasificados como "marginales" por su escasa ley media. La utilización de los recursos técnicos disponibles, que ha conseguido el elevado grado de eficacia necesario para hacer rentable la explotación del yacimiento, ha estado basada en la experiencia como método y la simplificación de procesos como objetivos.[Abstract] For the last ten years the tin mine "El Cubito" , in the province of Salamanca, has kept a regular and important production, within the Spanish context, in spite of to belong to mineral deposits classified as "marginal" because of their short grade. The use of the available technical means, which has made possible the high degree of efficacy needed to make profitable the exploitation, has been based on the experience as method and on a simplification of processes as objetives

Algunos métodos para la prosprección de estaño

[Resumen] Se hace una síntesis de datos, fundamentalmente bibliográficos, en relación con la geoquímica del Sn en áreas graníticas mineralizadas y con fines primordialmente prácticos para su uso en prospección. El trabajo se divide en dos partes: por un lado se estudian las aureolas de dispersión primarias del Sn en los propios granitoides, y por otro las aureolas de dispersión secundaria en los productos de su denudación[Abstract] In this work a synthesis of bibliographic information concerning to the granitoides geochemistry relation with tin deposits is made for practical purposes in their use in prospection. On the other hand the tin primary dispersion aureoles in the granitic rocks are studied, on the another hand the tin secundary dispersion aureoles are considered in their denudation products