A0620-00 revisited: a black-hole transient case-study

For the first time we have performed a detailed study of the X-ray, optical and infra-red light curves of the 1975/1976 outburst of the famous black-hole transient A0620-00 (Nova Mon 1975, V616 Mon). During the various stages of its outburst the X-rays lag the optical by ~5-20 days. Moreover, the activity associated with the secondary maximum started even earlier in the infra-red. This suggests that most of the outburst processes occur in the outer parts of the disk. We also find various drops in the X-ray intensity (lasting ~1 day or more). Near one of these a local maximum in the optical light curve occurs. This maximum appears ~30 days after the secondary maximum, i.e. close to the viscous time scale of an irradiated disk. We suggest this feature to be an `echo' of the secondary maximum. At the end of the outburst a similar local optical maximum occurs, which might be an `echo' of the tertiary maximum. We find that the drops in the optical and X-rays near the tertiary maximum are also present in other SXTs. They always occur ~150 days after the start of the outburst. We find for the first time that the X-ray spectrum of A0620-00 starts to harden ~100-150 days after the start of its outburst, similar to GS2000+25 and GS1124-68. This suggests we witness the transition from the so-called high to low state at that time. We show that the optical outburst light curve of A0620-00 closely resembles that of the cataclysmic variable AL Com. This strengthens the similarity in the properties of the SXTs and TOADs (or WZ Sge stars), and shows that the optical outburst light curves of both groups are governed by the disk properties and not by the compact object. Since irradiation provides a natural mechanism to prolong the outburst of SXTs, we suggest this could be of influence as well during TOAD outbursts.Comment: 38 pages, 10 figures, accepted for New Astronomy Review

Looking for leakage or monitoring for public assurance?

Monitoring is a regulatory requirement for all carbon dioxide capture and geological storage (CCS) projects to verify containment of injected carbon dioxide (CO2) within a licensed geological storage complex. Carbon markets require CO2 storage to be verified. The public wants assurances CCS projects will not cause any harm to themselves, the environment or other natural resources. In the unlikely event that CO2 leaks from a storage complex, and into groundwater, to the surface, atmosphere or ocean, then monitoring methods will be required to locate, assess and quantify the leak, and to inform the community about the risks and impacts on health, safety and the environment. This paper considers strategies to improve the efficiency of monitoring the large surface area overlying onshore storage complexes. We provide a synthesis of findings from monitoring for CO2 leakage at geological storage sites both natural and engineered, and from monitoring controlled releases of CO2 at four shallow release facilities – ZERT (USA), Ginninderra (Australia), Ressacada (Brazil) and CO2 field lab (Norway)

Eye spots do not increase altruism in children

The evolutionary legacy hypothesis proposes that an evolved reciprocity-based psychology affects human behavior in anonymous one-shot interactions when reciprocity is not explicitly possible. Empirical support rests on experiments showing that altruism among adults increases in the presence of stylized eye spots or faces. Such stimuli do not affect material payoffs, but they are assumed to activate a person’s reciprocity-based psychology. We identify two versions of the evolutionary legacy hypothesis. The weak hypothesis posits that reputational concerns can generate altruism in the absence of opportunities for a good reputation. The strong hypothesis posits that reputational concerns alone can explain anonymous one-shot altruism, and they can do so specifically in lieu of explanations based on group selection. A number of experimental studies support the weak hypothesis but are merely consistent with the strong hypothesis. To address both the weak and strong hypotheses, we conducted an eye spot experiment with children. Altruism can vary by age or sex in childhood, and under the strong hypothesis this kind of variation should reveal associated variation in sensitivity to eye spots. Although we found significant variation in altruism among children, we found no corresponding variation in sensitivity to eye spots. More generally, we found no eye spot effects of any kind. We discuss the possibility that eye spots might only affect altruism under specific conditions. We further argue that conditional effects do not refute the weak hypothesis in any way, but they do suggest potential limitations on the explanatory scope of the strong hypothesis

The evolution of reproductive isolation in a simultaneous hermaphrodite, the freshwater snail Physa

<p>Abstract</p> <p>Background</p> <p>The cosmopolitan freshwater snail <it>Physa acuta </it>has recently found widespread use as a model organism for the study of mating systems and reproductive allocation. Mitochondrial DNA phylogenies suggest that <it>Physa carolinae</it>, recently described from the American southeast, is a sister species of <it>P. acuta</it>. The divergence of the <it>acuta/carolinae </it>ancestor from the more widespread <it>P. pomilia </it>appears to be somewhat older, and the split between a hypothetical <it>acuta/carolinae/pomilia </it>ancestor and <it>P. gyrina </it>appears older still.</p> <p>Results</p> <p>Here we report the results of no-choice mating experiments yielding no evidence of hybridization between <it>gyrina </it>and any of four other populations (<it>pomilia, carolinae</it>, Philadelphia <it>acuta</it>, or Charleston <it>acuta</it>), nor between <it>pomilia </it>and <it>carolinae</it>. Crosses between <it>pomilia </it>and both <it>acuta </it>populations yielded sterile F1 progeny with reduced viability, while crosses between <it>carolinae </it>and both <it>acuta </it>populations yielded sterile F1 hybrids of normal viability. A set of mate-choice tests also revealed significant sexual isolation between <it>gyrina </it>and all four of our other <it>Physa </it>populations, between <it>pomilia </it>and <it>carolinae</it>, and between <it>pomilia </it>and Charleston <it>acuta</it>, but not between <it>pomilia </it>and the <it>acuta </it>population from Philadelphia, nor between <it>carolinae </it>and either <it>acuta </it>population. These observations are consistent with the origin of hybrid sterility prior to hybrid inviability, and a hypothesis that speciation between <it>pomilia </it>and <it>acuta </it>may have been reinforced by selection for prezygotic reproductive isolation in sympatry.</p> <p>Conclusions</p> <p>We propose a two-factor model for the evolution of postzygotic reproductive incompatibility in this set of five <it>Physa </it>populations consistent with the Dobzhansky-Muller model of speciation, and a second two-factor model for the evolution of sexual incompatibility. Under these models, species trees may be said to correspond with gene trees in American populations of the freshwater snail, <it>Physa</it>.</p

Os novos sentidos da interdisciplinaridade

O artigo-conferência sugere que a partir de meados do século XX foi sendo gestado no campo científico um novo paradigma associado umbilicalmente à interdisciplinaridade. Explora as consequências disso para as ciências sociais e para as atividades de ciência e tecnologia em nosso país, bem como as suas implicações políticas e para o senso-comum do nosso tempo.<br>This paper suggests that from the mid 20th century onwards a new paradigm umbilically associated with interdisciplinarity began to gestate within the scientific field. It explores the consequences of the birth of this paradigm for the social sciences and for scientific and technological activities in Brazil, as well as its political implications and its effect on our present-day common sense