Square-free class sizes in products of groups

We obtain some structural properties of a factorised group $G = AB$, given that the conjugacy class sizes of certain elements in $A\cup B$ are not divisible by $p^2$, for some prime $p$. The case when $G = AB$ is a mutually permutable product is especially considered

Mass-radius relation for magnetized strange quark stars

We review the stability of magnetized strange quark matter (MSQM) within the phenomenological MIT bag model, taking into account the variation of the relevant input parameters, namely, the strange quark mass, baryon density, magnetic field and bag parameter. A comparison with magnetized asymmetric quark matter in $\beta$-equilibrium as well as with strange quark matter (SQM) is presented. We obtain that the energy per baryon for MSQM decreases as the magnetic field increases, and its minimum value at vanishing pressure is lower than the value found for SQM, which implies that MSQM is more stable than non-magnetized SQM. The mass-radius relation for magnetized strange quark stars is also obtained in this framework.Comment: 7 pages, 6 figures. To be published in the Proceedings of 4th International Workshop on Relativistic Astrophysical and Astronomy IWARA0

Thermal and thermo-oxidative stability of reprocessed poly(ethylene terephthalate)

An exhaustive assessment of the behaviour of virgin and mechanically reprocessed poly(ethylene terephthalate) (PET) facing thermal and thermo-oxidative decomposition processes is presented in this work, as an approach for the energetic valorisation of post-consumer PET goods. Multi-rate linear-non-isothermal thermogravimetric (TGA) experiments under inert (Ar) and reactive (O2) conditions were performed to virgin PET and its recyclates in order to simulate the thermal behaviour of the materials facing pyrolysis and combustion processes. The release of gases was monitored by evolved gas analysis of the fumes of the TGA experiment, by in-line Fourier-transform infrared (IR) analysis, with the aid of 2D-correlation IR characterisation. A kinetic analysis methodology, consisting in the combination of six different methods (namely Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Vyazovkin, Master-Curves and Perez-Maqueda criterion along with Coats-Redfern equation) was applied. Its validity for being used for both constant and variable kinetic parameters was discussed. The kinetic model that described both thermal and thermo-oxidative decompositions of PET and its recyclates was of the type An: nucleation and growth of gas bubbles in the melt. Novel parameters and functions were proposed to characterise the thermal stability along the reprocessing cycles, as well as the variation of the activation energy and the pre-exponential factor during thermal and thermo-oxidative decompositions. The reliability of a simplified kinetic triplet with constant activation parameters was suitable only under thermal decomposition. The usability of PET after reprocessing showed a threshold in the thermal performance from the second recyclate on. During thermal and thermo-oxidative processes, reprocessed PET behaved similarly to virgin PET, and thus current energetic valorisation technologies could be assimilable for all materials

Hygrothermal ageing of reprocessed polylactide

The influence of an accelerated hygrothermal ageing simulation test on a commercial PLA and its three subsequent mechanically-reprocessed materials was studied. The analysis was focused on the water diffusion kinetics and the physico-chemical changes induced by the hygrothermal degradation. Water diffusion proceeded faster than chain relaxation processes, as defined by a Case II absorption model. It was proved that the water diffusion rate decreased with subsequent reprocessing cycles and increased with higher hygrothermal ageing temperatures. Hydrolytic chain scission provoked significant molar mass decays and consequent general losses of thermal and mechanical performance. The rearrangement into crystalline fractions of shorter chains provoked by hygrothermal ageing was qualitatively and quantitatively followed by both Fourier-Transform Infrared Spectroscopy and Differential Scanning Calorimetry. The microstructural changes were monitored by the cold-crystallization temperature, the crystallinity degree XC and the absorbance intensity ratio I921/I955. A Weibull model showed that the crystallites were formed faster at higher reprocessing cycles and at lower hygrothermal ageing temperatures. All these effects were particularly significant for PLA reprocessed more than one time

Magnetized strangelets at finite temperature

The main properties of magnetized strangelets, namely, their energy per baryon, radius and electric charge, are studied. Temperature effects are also taken into account in order to study their stability compared to the 56Fe isotope and non-magnetized strangelets using the liquid drop model. Massive quarks are considered with the aim to have a more realistic description for strangelets in the astrophysical context and the environment of heavy ion colliders, playing also an important role in the thermodynamical quantities of the quark gas. It is concluded that the presence of a magnetic field tends to stabilize more the strangelets, even when temperature effects are taken into account. Magnetized strangelets in a paired superconductor phase (magnetized color flavor locked phase) are also discussed. It is shown that they are more stable than ordinary magnetized strangelets for typical gap values of the order of O(100) MeV.Comment: 10 pages, 10 figures, discussion extended, new references adde

Análisis del rendimiento en salto vertical, agilidad,

Objetivo Analizar la influencia de la categoría de edad en la capacidad de salto, sprint, agilidad y velocidad de golpeo en futbolistas jóvenes. Método Estudio transversal en el que participaron 36 jugadores de nivel subélite provenientes de las categorías inferiores (cadete y juvenil) de equipos de fútbol andaluces (edad: 15,87 ± 1,43 años; masa corporal: 65,38 ± 10,84 kg; altura: 1,71 ± 0,06 m). Se evaluó la composición corporal, el rendimiento en salto vertical (CMJ), la agilidad mediante el test de Balsom, velocidad de sprint en 5, 10, 20 y 30 m y la velocidad de golpeo con ambas piernas. Resultados Los análisis mostraron que los jugadores juveniles tienen mayor rendimiento en los test de CMJ, agilidad y velocidad de golpeo con ambas piernas que los cadetes. No se aprecian diferencias significativas (p ≥ 0,05) en la prueba de velocidad, aunque se evidencia una clara tendencia a favor de los juveniles. Conclusión Existe efecto de la edad durante la etapa de la adolescencia sobre la capacidad de salto, la agilidad, la velocidad de golpeo y, en menor medida, sobre la velocidad de jóvenes jugadores de fútbol, además de asociación entre las capacidades condicionales más influyentes en el rendimiento del futbolista

Los productos petrolíferos en Hispanoamérica: Noticias anteriores al siglo XIX

Las sustancias petrolíferas han sido conocidas desde tiempos muy antiguos. Las aplicaciones que de ellas se hicieron se orientaron en un principio hacia fines arquitectónicos, artesanales y medicinales. Fueron los denominados en Geoquímica como Indicios Superficiales o filtraciones los que llamaron la atención de nuestros antepasados, sobre todo por su aspecto físico, ya fuera el color, el olor o el tacto. Los Indicios Superficiales son las diferentes manifestaciones de propiedades químicas de gases, aguas, rocas y suelos que están relacionadas en su origen con depósitos petrolíferos cercanos, o que señalan condiciones favorables a la existencia de los mismos

Anàlisi del rendiment en el salt vertical, agilitat i velocitat

Objectiu Analitzar la influència de la categoria d’edat en la capacitat de salt, esprint, agilitat i velocitat de xut de futbolistes joves. Mètode Estudi transversal en què participaren 36 jugadors de nivell subelit provinents de les categories inferiors (cadet i juvenil) d’equips de futbol andalusos (edat: 15,87 ± 1,43 anys; massa corporal: 65,38 ± 10,84 kg; alçada: 1,71 ± 0,06 m). S’avaluà la composició corporal, el rendiment en el salt vertical (CMJ), l’agilitat mitjançant el test de Balsom, la velocitat d’esprints en 5, 10, 20 i 30 m i la velocitat del xut amb ambdues cames. Resultats Les anàlisis mostraren que els jugadors juvenils tenien un rendiment major en els tests del CMJ, agilitat i velocitat de xut amb ambdues cames que els cadets. No s’aprecien diferències significatives (p ≥ 0,05) en la prova de velocitat, tot i que s’evidencia una tendència clara a favor dels juvenils. Conclusió Existeix l’efecte de l’edat durant l’etapa de l’adolescència sobre la capacitat de salt, l’agilitat, la velocitat de xut i, en menor mesura, sobre la velocitat dels jugadors de futbol joves, a més d’associació entre les capacitats condicionals, més influents en el rendiment del futbolista

A kinetic study of the formation of smectic phases in novel liquid crystal ionogens

A multi-rate non-isothermal kinetic analysis of the isotropic-melt to liquid crystalline phase transition of novel liquid crystalline ionogenic copolymers, LCIs, the 10-(4-methoxyazobenzene-4′-oxy)decyl methacrylate]-co-2-(acrylamido-2-methyl-1-propanesulfonic acid)s, 10-MeOAzB/AMPS, copolymers, has been performed by means of calorimetric experiments. An analytical methodology which includes the study of the phase transition rate parameter, the determination of the activation energies by using Kissinger and Flynn-Wall-Ozawa models, and the study of the phase transition kinetics by the use of the Avrami theory, has been applied. The formation of the mesophases from the isotropic state occurred close to thermodynamic equilibrium. The results evidence the presence of several individual processes in the formation of liquid crystalline phases from the melt and a strong dependence of phase transition rates and activation energies with acid contents. A decrease in the phase transition rate, related to a decrease in the overall change of the transition entropy, has been observed. The final inhibition of the liquid crystal (LC) behaviour is ascribed to an exponential increase in the activation energy of the phase transition, promoted by strong acid aggregation. An optimum composition of the 10-MeOAzB/AMPS copolymers to achieve the dual characteristics of LCIs (ionogenic and liquid crystalline behaviour) requires acid concentrations capable of promoting structure-forming effects on the LC phases and the evolution of phase separated morphologies