Scaling in a continuous time model for biological aging

In this paper we consider a generalization to the asexual version of the Penna model for biological aging, where we take a continuous time limit. The genotype associated to each individual is an interval of real numbers over which Dirac $\delta$--functions are defined, representing genetically programmed diseases to be switched on at defined ages of the individual life. We discuss two different continuous limits for the evolution equation and two different mutation protocols, to be implemented during reproduction. Exact stationary solutions are obtained and scaling properties are discussed.Comment: 10 pages, 6 figure

Clustering Approach to Quantify Long-Term Spatio-Temporal Interactions in Epileptic Intracranial Electroencephalography

Abnormal dynamical coupling between brain structures is believed to be primarily responsible for the generation of epileptic seizures and their propagation. In this study, we attempt to identify the spatio-temporal interactions of an epileptic brain using a previously proposed nonlinear dependency measure. Using a clustering model, we determine the average spatial mappings in an epileptic brain at different stages of a complex partial seizure. Results involving 8 seizures from 2 epileptic patients suggest that there may be a fixed pattern associated with regional spatio-temporal dynamics during the interictal to pre-post-ictal transition

Religiosity and Ways of Coping With Sport Injuries Among Christian Athletes

Although research evidence supports religiosity’s predominantly positive mental and physical health benefits to patients coping with varied health problems, there are few studies exploring the influence of religiosity on coping with sport injuries among athletes identifying with specific religions. This study examined the relationships between religiosity and the use of religious and non-religious ways of coping with sport injuries by athletes affiliated with diverse Christian denominations. Within a concurrent mixed methods design, adult athletes (N = 88) responded to an online survey asking about several religiosity factors, their most serious or challenging sport injuries, and their ways of coping with those injuries. Quantitative results showed that religious commitment correlated with specific religious beliefs and behaviors, positive religious ways of coping predominated over negative, and religious commitment fully mediated the relationship between athletes’ Christian denominations and their use of positive, but not negative, religious ways of coping with sport injuries. Thematic template analysis of qualitative data similarly revealed that religious ways of coping with sport injuries were predominantly positive in valence and benefitted physical and mental rehabilitation and recovery processes. Christian athletes relied on both religious and non-religious coping sources during their sport injury recoveries, and their ways of coping centered on their personal and religious identities. These results support that holistic care models encompassing sport psychology, sports medicine, and sports ministry should adapt intervention and treatment plans to accommodate personal religiosity and build on positive and adaptive religious ways of coping with sport injuries when working with religiously committed Christian athletes

The role of Physicists in the «rebirth of a scientific movement» in Portugal during the inter war period

The advent of Republic in 1910 brought important higher education reforms in Portugal. In spite of strong political and financial difficulties in the next two decades, Portuguese universities supported graduation studies of young physics teachers abroad. However these relevant initiatives Portuguese republican government was not successful in creating a national institution able to promote and funding the organization of scientific research. Only in 1929 the government was able to set up this kind of institution, the “National Board of Education” [Junta de Educação Nacional], with the aim of funding research centres in the universities, as well as of providing grants for students to continue their studies at advanced level both at home and abroad. In the thirties an important group of young researchers went on to study in universities and laboratories of European advanced scientific countries, where some of them got their PhD degree. In Chemistry, Mathematics and Physics the school more demanded was Paris University. During this period Curie’s laboratory received an important group of Portuguese students. After four years stay abroad, having established important international scientific links, back at home, some of these young scientists played an important role in their universities promoting a rebirth of a scientific movement. This lasted till the end of the Second World War, when a good number of them were dismissed from their positions because of their active opposition to Salazar’s regime. Arriving home having experienced living in cities with intense political activity, some of these young scientists demonstrated a strong political commitment against the dictatorship regime and supported important activity in scientific associations and cultural organizations. The study of the scientific, cultural and political activity of this group is the purpose of this communication

Synthetic properties of bright metal-poor variables. II. BL Her stars

We investigate the properties of the so-called BL Her stars, i.e., Population II Cepheids with periods shorter than 8 days, using updated pulsation models and evolutionary tracks computed adopting a metal abundance in the range of Z=0.0001 to Z=0.004. We derive the predicted Period-Magnitude (PM) and Period-Wesenheit (PW) relations at the various photometric bands and we show that the slopes of these relations are in good agreement with the slopes determined by observed variables in Galactic globular clusters, independently of the adopted M_V(RR)-[Fe/H] relation to get the cluster RR Lyrae-based distance. Moreover, we show that also the distances provided by the predicted PM and PW relations for BL Her stars agree within the errors with the RR Lyrae based values. The use of the predicted relations with W Vir stars, which are Population II Cepheids with periods longer than 8 days, provides no clear evidence for or against a change in the PM and PW slopes around P~10 days.Comment: 12 pages, 6 figures, 6 tables, accepted for publication in A&A on date 16/05/200

Effect of s-triazine ring substitution on the synthesis of organic resorcinol-formaldehyde xerogels

Resorcinol (R) and formaldehyde (F) gel synthesis has been well-studied along with alternative reagents. We present the synthesis of formaldehyde-based xerogels using chemically similar s-triazine precursors, with comparison to traditional analogues. The substitution ranges from tri-hydroxyl to tri-amine, with an intermediate species, allowing changing chemistry to be investigated. Each molecule (X) offers different acid/base properties, known to influence gel formation, as well as differences in crosslinking potential. Varying X/F ratios were selected to recreate the stoichiometry used in RF systems, where one represented higher F to match the increased reaction sites of the additives. X/C ratios were selected to probe different catalyst (C) ratios, while working within the range likely to produce viable gels. Results obtained show little impact for ammeline as an additive due to its similarity to resorcinol (activation sites and pKa); while melamine and cyanuric acid show differing behavior depending on the level of addition. Low concentrations show melamine to have the most impact due to increased activation and competition for formaldehyde; while at high concentrations, cyanuric acid is shown to have the greatest impact as it creates a more acidic environment, which diminishes textural character, possibly attributable to larger clusters and/or weaker cross-linking of the system