A public key cryptosystem based on block upper triangular matrices

We propose a public key cryptosystem based on block upper triangular matrices. This system is a variant of the Discrete Logarithm Problem with elements in a finite group, capable of increasing the difficulty of the problem while maintaining the key size. We also propose a key exchange protocol that guarantees that both parties share a secret element of this group and a digital signature scheme that provides data authenticity and integrity.

Quantitative stability of linear infinite inequality systems under block perturbations with applications to convex systems

The original motivation for this paper was to provide an efficient quantitative analysis of convex infinite (or semi-infinite) inequality systems whose decision variables run over general infinite-dimensional (resp. finite-dimensional) Banach spaces and that are indexed by an arbitrary fixed set J. Parameter perturbations on the right-hand side of the inequalities are required to be merely bounded, and thus the natural parameter space is l ∞(J). Our basic strategy consists of linearizing the parameterized convex system via splitting convex inequalities into linear ones by using the Fenchel–Legendre conjugate. This approach yields that arbitrary bounded right-hand side perturbations of the convex system turn on constant-by-blocks perturbations in the linearized system. Based on advanced variational analysis, we derive a precise formula for computing the exact Lipschitzian bound of the feasible solution map of block-perturbed linear systems, which involves only the system’s data, and then show that this exact bound agrees with the coderivative norm of the aforementioned mapping. In this way we extend to the convex setting the results of Cánovas et al. (SIAM J. Optim. 20, 1504–1526, 2009) developed for arbitrary perturbations with no block structure in the linear framework under the boundedness assumption on the system’s coefficients. The latter boundedness assumption is removed in this paper when the decision space is reflexive. The last section provides the aimed application to the convex case.

Factores que influyen en la decisión de utilizar anestesia epidural en las mujeres

Justificación: La inmigración en España es un fenómeno de gran importancia que repercute en el área de la salud. Objetivo: Investigar la relación entre la elección de la anestesia epidural y la nacionalidad de la mujer, y a su vez, observar si influyen además otros factores en esta decisión. Diseño y Metodología: Estudio cuantitativo, transversal y descriptivo con una muestra de 634 mujeres que han dado a luz en el Hospital del Noroeste de la Región de Murcia. Las variables seleccionadas fueron: antecedentes obstétricos, edad, tipo de anestesia, nacionalidad de la mujer y motivo por el rechazo de la anestesia epidural. Resultados: El 8,51% de las mujeres que dieron a luz en el hospital del Noroeste de la Región de Murcia durante el año 2010 fueron inmigrantes. En cuanto a la nacionalidad, el 20,37% de las mujeres inmigrantes no han utilizado ningún tipo de anestesia. Se ha encontrado una significante diferencia con las mujeres no inmigrantes españolas en las que sólo el 4,31% la rechazó (P<0,001). En relación a los abortos, las mujeres que no prefieren ningún tipo de anestesia son aquellas que sí han tenido abortos (P<0.05). Las edades más jóvenes de las mujeres, de 16 a 25 años, se relaciona con el no uso de la anestesia epidural (P<0,05). Conclusión: Las mujeres inmigrantes hacen menos uso de la anestesia epidural. Es un reto para la enfermera aprender las diferentes culturas ya que realiza su trabajo en una sociedad cada vez más multicultural.

Comparison of Lattice-Fluid Binary Parameters For Mixtures and Block Copolymers

The aim of this report is to discuss the method of determination of lattice-fluid binary interaction parameters by comparing well characterized immiscible blends and block copolymers of poly(methyl methacrylate) (PMMA) and poly(ϵ−caprolactone) (PCL). Experimental pressure-volume-temperature (PVT) data in the liquid state were correlated with the Sanchez—Lacombe (SL) equation of state with the scaling parameters for mixtures and copolymers obtained through combination rules of the characteristic parameters for the pure homopolymers. The lattice-fluid binary parameters for energy and volume were higher than those of block copolymers implying that the copolymers were more compatible due to the chemical links between the blocks. Therefore, a common parameter cannot account for both homopolymer blend and block copolymer phase behaviors based on current theory. As we were able to adjust all data of the mixtures with a single set of lattice-binary parameters and all data of the block copolymers with another single set we can conclude that both parameters did not depend on the composition for this system. This characteristic, plus the fact that the additivity law of specific volumes can be suitably applied for this system, allowed us to model the behavior of the immiscible blend with the SL equation of state. In addition, a discussion on the relationship between lattice-fluid binary parameters and the Flory–Huggins interaction parameter obtained from Leibler's theory is presented.