98 research outputs found
Sum rules in the geminal expansion of many-electron wavefunctions.
An interpretation of certain sum rules in the method of Bopp is given in terms of the irreducible representations of the rotation group. It is accompanied by a simple numerical table, from which the sum rules may be obtained by inspection
Measurement of water uptake in thin-film Nafion and anion alkaline exchange membranes using the quartz crystal microbalance
Water uptake, sorption mechanics and swelling characteristics of thin-film Nafion and a commercially available Tokuyama alkaline anion exchange membrane ionomer from the vapour phase is explored using a quartz crystal microbalance (QCM). The water uptake measures the number of water molecules adsorbed by the ionomer per functional group and is determined in-situ using the QCM frequency responses allowing for comparison with nanogram precision. Crystal admittance spectroscopy, along with equivalent circuit fitting, is applied to both thin films for the first time and is used to investigate the ionomer's viscoelastic changes during hydration; to elucidate the mechanisms at play during low, medium and high relative humidities
Alkaline anion exchange membrane degradation as a function of humidity measured using the quartz crystal microbalance
The solid polymer electrolyte (SPE) alkaline anion exchange membrane (AAEM) fuel cell exhibits facile oxygen reduction reaction (ORR) kinetics and has the ability to utilise non-precious metal electrocatalysts. However, the AAEM is reported to suffer from increased instability within the alkaline media (degradation) via a number of routes, including nucleophilic elimination when operated at temperatures above 60 °C, somewhat eliminating the kinetic advantage of operating at higher temperatures. Nonetheless, modelling studies have indicated that the membrane hydration could show improved resistance to alkaline instability and subsequent degradation when operated at elevated temperatures. This investigation uses the quartz crystal microbalance (QCM) to examine the thermal stability of a commercial AAEM as a function of humidity. The results show that hydration improves ionomer resistance to degradation, as the ions within the system (namely the OH- nucleophile and cationic headgroups) become less reactive. In-line mass spectrometry data confirms that the ionomer degrades during the elevated temperature excursions used in this study
Fact or Factitious? A Psychobiological Study of Authentic and Simulated Dissociative Identity States
BACKGROUND: Dissociative identity disorder (DID) is a disputed psychiatric disorder. Research findings and clinical observations suggest that DID involves an authentic mental disorder related to factors such as traumatization and disrupted attachment. A competing view indicates that DID is due to fantasy proneness, suggestibility, suggestion, and role-playing. Here we examine whether dissociative identity state-dependent psychobiological features in DID can be induced in high or low fantasy prone individuals by instructed and motivated role-playing, and suggestion. METHODOLOGY/PRINCIPAL FINDINGS: DID patients, high fantasy prone and low fantasy prone controls were studied in two different types of identity states (neutral and trauma-related) in an autobiographical memory script-driven (neutral or trauma-related) imagery paradigm. The controls were instructed to enact the two DID identity states. Twenty-nine subjects participated in the study: 11 patients with DID, 10 high fantasy prone DID simulating controls, and 8 low fantasy prone DID simulating controls. Autonomic and subjective reactions were obtained. Differences in psychophysiological and neural activation patterns were found between the DID patients and both high and low fantasy prone controls. That is, the identity states in DID were not convincingly enacted by DID simulating controls. Thus, important differences regarding regional cerebral bloodflow and psychophysiological responses for different types of identity states in patients with DID were upheld after controlling for DID simulation. CONCLUSIONS/SIGNIFICANCE: The findings are at odds with the idea that differences among different types of dissociative identity states in DID can be explained by high fantasy proneness, motivated role-enactment, and suggestion. They indicate that DID does not have a sociocultural (e.g., iatrogenic) origin
Effect of humidity on the interaction of CO2 with alkaline anion exchange membranes probed using the quartz crystal microbalance
The alkaline anion exchange membrane fuel cell (AAEM-FC) is able to deliver a comparable performance to the traditional proton exchange membrane fuel cell (PEM-FC) without the use of precious metal electrocatalysts, making it a more cost-competitive alternative for low-temperature fuel cell applications. However, issues relating to degradation and specifically interaction with CO 2 still hinder the technology's commercialisation prospects. With hydration playing a key role in solid polymer electrolyte fuel cell operation, this study examines how membrane hydration affects the AAEM interaction with CO 2 . The change of membrane conductivity upon exposure to atmospheric CO 2 has been compared with the change in viscoelastic properties of a cast thin-film ionomer, both as a function of humidity. The effect of CO 2 on the membrane as a function of hydration suggests a link to its solvation and swelling regimes and thus the access of CO 2 to the ionic channels within the membrane. The thin-film QCM composite resonator study has suggested that during the solvation (pore opening) regime, there is a linear increase in CO 2 uptake as water can further permeate the pore system and the cationic headgroups become increasingly accessible. During the transition to the pore swelling regime, there is a step increase in CO 2 uptake as the network is thought to be fully open; as such, subsequent increases in RH do not lead to any significant increase in CO 2 uptake
Deafening silence? Marxism, international historical sociology and the spectre of Eurocentrism
Approaching the centenary of its establishment as a formal discipline, International Relations today challenges the ahistorical and aspatial frameworks advanced by the theories of earlier luminaries. Yet, despite a burgeoning body of literature built on the transdisciplinary efforts bridging International Relations and its long-separated nomothetic relatives, the new and emerging conceptual frameworks have not been able to effectively overcome the challenge posed by the ‘non-West’. The recent wave of international historical sociology has highlighted possible trajectories to problematise the myopic and unipolar conceptions of the international system; however, the question of Eurocentrism still lingers in the developing research programmes. This article interjects into the ongoing historical materialist debate in international historical sociology by: (1) conceptually and empirically challenging the rigid boundaries of the extant approaches; and (2) critically assessing the postulations of recent theorising on ‘the international’, capitalist states-system/geopolitics and uneven and combined development. While the significance of the present contributions in international historical sociology should not be understated, it is argued that the ‘Eurocentric cage’ still occupies a dominant ontological position which essentially silences ‘connected histories’ and conceals the role of inter-societal relations in the making of the modern states-system and capitalist geopolitics
Population growth of Mexican free-tailed bats (Tadarida brasiliensis mexicana) predates human agricultural activity
Background
Human activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although many species have suffered population declines, increased population fragmentation, or even extinction in connection with these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed to the widespread expansion of agriculture in North America following European settlement. Colonies of T. b. mexicana are extremely large (~106 individuals) and, in the modern era, major agricultural insect pests form an important component of their food resource. It is thus hypothesized that the growth of these insectivorous bat populations was coupled to the expansion of agricultural land use in North America over the last few centuries. Results
We sequenced one haploid and one autosomal locus to determine the rate and time of onset of population growth in T. b. mexicana. Using an approximate Maximum Likelihood method, we have determined that T. b. mexicana populations began to grow ~220 kya from a relatively small ancestral effective population size before reaching the large effective population size observed today. Conclusions
Our analyses reject the hypothesis that T. b. mexicana populations grew in connection with the expansion of human agriculture in North America, and instead suggest that this growth commenced long before the arrival of humans. As T. brasiliensis is a subtropical species, we hypothesize that the observed signals of population growth may instead reflect range expansions of ancestral bat populations from southern glacial refugia during the tail end of the Pleistocene
The importance of the altricial – precocial spectrum for social complexity in mammals and birds:A review
Various types of long-term stable relationships that individuals uphold, including cooperation and competition between group members, define social complexity in vertebrates. Numerous life history, physiological and cognitive traits have been shown to affect, or to be affected by, such social relationships. As such, differences in developmental modes, i.e. the ‘altricial-precocial’ spectrum, may play an important role in understanding the interspecific variation in occurrence of social interactions, but to what extent this is the case is unclear because the role of the developmental mode has not been studied directly in across-species studies of sociality. In other words, although there are studies on the effects of developmental mode on brain size, on the effects of brain size on cognition, and on the effects of cognition on social complexity, there are no studies directly investigating the link between developmental mode and social complexity. This is surprising because developmental differences play a significant role in the evolution of, for example, brain size, which is in turn considered an essential building block with respect to social complexity. Here, we compiled an overview of studies on various aspects of the complexity of social systems in altricial and precocial mammals and birds. Although systematic studies are scarce and do not allow for a quantitative comparison, we show that several forms of social relationships and cognitive abilities occur in species along the entire developmental spectrum. Based on the existing evidence it seems that differences in developmental modes play a minor role in whether or not individuals or species are able to meet the cognitive capabilities and requirements for maintaining complex social relationships. Given the scarcity of comparative studies and potential subtle differences, however, we suggest that future studies should consider developmental differences to determine whether our finding is general or whether some of the vast variation in social complexity across species can be explained by developmental mode. This would allow a more detailed assessment of the relative importance of developmental mode in the evolution of vertebrate social systems
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