Rescaled density expansions and demixing in hard-sphere binary mixtures

The demixing transition of a binary fluid mixture of additive hard spheres is analyzed for different size asymmetries by starting from the exact low-density expansion of the pressure. Already within the second virial approximation the fluid separates into two phases of different composition with a lower consolute critical point. By successively incorporating the third, fourth, and fifth virial coefficients, the critical consolute point moves to higher values of the pressure and to lower values of the partial number fraction of the large spheres. When the exact low-density expansion of the pressure is rescaled to higher densities as in the Percus-Yevick theory, by adding more exact virial coefficients a different qualitative movement of the critical consolute point in the phase diagram is found. It is argued that the Percus-Yevick factor appearing in many empirical equations of state for the mixture has a deep influence on the location of the critical consolute point, so that the resulting phase diagram for a prescribed equation has to be taken with caution.Comment: 5 pages, 1 figure; to be published in The Journal of Chemical Physic

Stability of a hard-sphere binary quasicrystal

The stability of a quasicrystalline structure, recently obtained in a molecular-dynamics simulation of rapid cooling of a binary melt, is analyzed for binary hard-sphere mixtures within a density-functional approach. It is found that this quasicrystal is metastable relative to crystalline and fluid phases for diameter ratios above 0.83. Such trend is partially reversed for lower diameter ratios, since the quasicrystal becomes stable with respect to the crystal but does not reach a coexistence with the fluid.Comment: 14 pages, 6 eps figures included. Revised version to appear in Phil. Mag.

El nombre de corredors a peu s’ha incrementat a Espanya durant la primera dècada del segle XXI

És habitual trobar en els mitjans de comunicació de l’Estat espanyol, notícies o articles que subratllen l’auge de les curses populars a Espanya. L’objectiu d’aquesta carta científica ha estat comprovar amb rigor sociològic si s’ha incrementat en els últims anys el nombre de practicants de cursa a peu. Amb aquesta finalitat, han estat analitzades les tres últimes enquestes sobre hàbits esportius dels espanyols, les quals van ser dutes a terme pel Centre d’Investigacions Sociològiques, sota el patrocini del Consell Superior d’Esports, durant els anys 2000, 2005 i 2010. Les dades indiquen que sí que s’ha produït un increment en la pràctica de la cursa a peu entre l’acabament del segle xx i la primera dècada del segle xxi, passant d’un 3,8 % de corredors l’any 2000 a un 5,1 % l’any 2010. Cal destacar que l’any 2010 residien a Espanya al voltant de dos milions de persones majors de 14 anys que eren practicants de la cursa a peu

Análisis sociodemográfico comparativo entre corredores populares y el resto de la población en España

The purpose of this study was to analyze the socio-demographic characteristics of popular races’ runners (PRRs) and establish differences with the rest of the Spanish population. It was analyzed the survey conducted in 2010 about sport habits in Spain. A final sample consisting of 8,389 interviews with participants with ages ranging between 15 and 97 years was drawn. The descriptive results revealed that 3.5% of the interviewees were PRRs. Afterwards, a model of logistical regression was executed in order to identify the cohorts that were more likely to belong to the non-PRRs group once the possible interaction effects or confusion among variables had been controlled. Here, the results showed that women were more likely to belong to the non-PRRs group (OR = 6.55). Regarding age, the possibility of belonging to the non-PRRs group progressively increased as the age factor also increased. It was also ascertained that the possibility of pertaining to the non-PRRs group increased insofar as the educational level decreased. Finally, neither socio-economic status nor participants’ town population size was associated with being a PRRs group memberEl objetivo de este estudio fue analizar las características sociodemográficas de los corredores populares y establecer diferencias con el resto de la población española. Se analizó la encuesta del año 2010 sobre hábitos deportivos en España. La muestra final estuvo formada por un total de 8.389 participantes, con edades de entre 15 y 97 años. Los resultados descriptivos revelaron que el 3,5% de la población residente en España pueden ser considerados corredores populares. Asimismo, para identificar qué variables sociodemográficas estuvieron más asociadas a la posibilidad de no ser corredor popular, se procedió con regresión logística, donde las variables fueron ajustadas al resto de variables en aras de controlar sus posibles efectos de interacción o confusión. Los resultados mostraron que las mujeres tienen más posibilidad de pertenecer al grupo de no corredores populares (OR = 6,55). Además, se observó que la posibilidad de pertenecer al grupo de no corredores es mayor a medida que aumenta la edad y también a medida que desciende el nivel académico. Finalmente, se encontró que ni el estatus socioeconómico ni el tamaño poblacional estuvieron asociados al hecho de ser corredor popula

Participating in sports and practicing a religion are related to levels of happiness

The objective of this study was to ascertain whether happiness varies depending on sports participation and religious practice. The sample comprised 2,378 participants aged between 18 and 92 years. All analysis were carried out by testing the interaction effects of the variables of sex and age on sports participation, religious practice, and happiness. We found a high average level of happiness (M = 7.299, range 0-10). However, people who do not participate in sports or practice a religion indicated a level of happiness (M = 6.979) that was statistically lower than that of the other groups: people who practice a religion but do not participate in sports (M = 7.135); people who participate in sports but do not practice a religion (M = 7.478); and people who both participate in sports and practice a religion (M = 7.717). We conclude that happiness is associated with sports participation and religious practice, although with small or very small effect sizes (all p< 0.050; η between 0.008 and 0.020). 2

Stability of the hard-sphere icosahedral quasilattice

The stability of the hard-sphere icosahedral quasilattice is analyzed using the differential formulation of the generalized effective liquid approximation. We find that the icosahedral quasilattice is metastable with respect to the hard-sphere crystal structures. Our results agree with recent findings by McCarley and Ashcroft [Phys. Rev. B {\bf 49}, 15600 (1994)] carried out using the modified weighted density approximation.Comment: 15 pages, 2 figures available from authors upon request, (revtex), submitted to Phys. Rev.

Esterification of levulinic acid with butanol over ion exchange resins

Alkyl levulinates are biobased chemicals with a great number of applications and great biofuel potential for blending to conventional diesel or gasoline. The present work focuses on the liquid-phase synthesis of butyl levulinate (BL) by esterification of levulinic acid (LA) with 1-butanol (BuOH) using a set of acidic ion-exchange resins. Experiments were performed at 80 °C and 2.5 MPa in a batch reactor by using an initial molar ratio AL/BuOH of 1/3 and a catalyst loading of 0.8%. It has been found that BL could be successfully obtained over ion-exchange resins with a selectivity higher than 99.5%. LA conversions ranged from 64% (Amberlyst 46, macroreticular, surface sulfonated) to 94% (Dowex 50Wx2, gel-type resin, conventionally sulfonated) at 8 h reaction time. By comparing their catalytic behavior, it was seen that resins morphology plays a very important role in the synthesis of BL making easier the access of reactants to acid sites. Accessibility of LA and BuOH to acid centers was high over highly swollen and low polymer density resins. Thus, gel-type resins with low divinylbenzene (DVB) content have been found as the most suitable to produce BL, e.g. Dowex 50Wx2, Dowex 50Wx4 and Purolite® CT224. Among them, Dowex 50Wx2 (2% DVB) is the most efficient catalyst tested

Osteoartropatía hipertrofiante néumica canina : un caso clínico

Se describe un caso de osteoartropatía hipertrofiante néumica (OAHN) en un perro mastín español de 8 años de edad.A case of hypertrophic pulmonary osteoarthropathy in a spanish mastin, eight years old, is presented