Mild acute stress improves response speed without impairing accuracy or interference control in two selective attention tasks: Implications for theories of stress and cognition.

Acute stress is generally thought to impair performance on tasks thought to rely on selective attention. This effect has been well established for moderate to severe stressors, but no study has examined how a mild stressor-the most common type of stressor-influences selective attention. In addition, no study to date has examined how stress influences the component processes involved in overall selective attention task performance, such as controlled attention, automatic attentional activation, decision-making, and motor abilities. To address these issues, we randomly assigned 107 participants to a mild acute stress or control condition. As expected, the mild acute stress condition showed a small but significant increase in cortisol relative to the control condition. Following the stressor, we assessed attention with two separate flanker tasks. One of these tasks was optimized to investigate component attentional processes using computational cognitive modeling, whereas the other task employed mouse-tracking to illustrate how response conflict unfolded over time. The results for both tasks showed that mild acute stress decreased response time (i.e., increased response speed) without influencing accuracy or interference control. Further, computational modeling and mouse-tracking analyses indicated that these effects were due to faster motor action execution time for chosen actions. Intriguingly, however, cortisol responses were unrelated to any of the observed effects of mild stress. These results have implications for theories of stress and cognition, and highlight the importance of considering motor processes in understanding the effects of stress on cognitive task performance

Structural durability of stiffened composite shells

The durability of a stiffened composite cylindrical shell panel is investigated under several loading conditions. An integrated computer code is utilized for the simulation of load induced structural degradation. Damage initiation, growth, and accumulation up to the stage of propagation to fracture are included in the computational simulation. Results indicate significant differences in the degradation paths for different loading cases. The effects of combined loading on structural durability and ultimate structural strength of a stiffened shell are assessed

Opportunities and challenges for modelling epidemiological and evolutionary dynamics in a multihost, multiparasite system: Zoonotic hybrid schistosomiasis in West Africa

Multihost multiparasite systems are evolutionarily and ecologically dynamic, which presents substantial trans‐disciplinary challenges for elucidating their epidemiology and designing appropriate control. Evidence for hybridizations and introgressions between parasite species is gathering, in part in line with improvements in molecular diagnostics and genome sequencing. One major system where this is becoming apparent is within the Genus Schistosoma, where schistosomiasis represents a disease of considerable medical and veterinary importance, the greatest burden of which occurs in sub‐Saharan Africa. Interspecific hybridizations and introgressions bring an increased level of complexity over and above that already inherent within multihost, multiparasite systems, also representing an additional source of genetic variation that can drive evolution. This has the potential for profound implications for the control of parasitic diseases, including, but not exclusive to, widening host range, increased transmission potential and altered responses to drug therapy. Here, we present the challenging case example of haematobium group Schistosoma spp. hybrids in West Africa, a system involving multiple interacting parasites and multiple definitive hosts, in a region where zoonotic reservoirs of schistosomiasis were not previously considered to be of importance. We consider how existing mathematical model frameworks for schistosome transmission could be expanded and adapted to zoonotic hybrid systems, exploring how such model frameworks can utilize molecular and epidemiological data, as well as the complexities and challenges this presents. We also highlight the opportunities and value such mathematical models could bring to this and a range of similar multihost, multi and cross‐hybridizing parasites systems in our changing world

Optimized perturbation theory for charged scalar fields at finite temperature and in an external magnetic field

Symmetry restoration in a theory of a self-interacting charged scalar field at finite temperature and in the presence of an external magnetic field is examined. The effective potential is evaluated nonperturbatively in the context of the optimized perturbation theory method. It is explicitly shown that in all ranges of the magnetic field, from weak to large fields, the phase transition is second order and that the critical temperature increases with the magnetic field. In addition, we present an efficient way to deal with the sum over the Landau levels, which is of interest especially in the case of working with weak magnetic fields.Comment: 18 pages, 7 eps figures. References added and some small improvements to the tex

ABC Transporter Required for Intercellular Transfer of Developmental Signals in a Heterocystous Cyanobacterium

In the filamentous cyanobacterium Anabaena, patS and hetN encode peptide-derived signals with many of the properties of morphogens. These signals regulate the formation of a periodic pattern of heterocysts by lateral inhibition of differentiation. Here we show that intercellular transfer of the patS- and hetN-dependent developmental signals from heterocysts to vegetative cells requires HetC, a predicted ATP-binding cassette transporter (ABC transporter). Relative to the wild type, in a hetC mutant differentiation resulted in a reduced number of heterocysts that were incapable of nitrogen fixation, but deletion of patS or hetN restored heterocyst number and function in a hetC background. These epistasis results suggest that HetC is necessary for conferring self-immunity to the inhibitors on differentiating cells. Nine hours after induction of differentiation, HetC was required for neither induction of transcription of patS nor intercellular transfer of the patS-encoded signal to neighboring cells. Conversely, in strains lacking HetC, the patS- and hetN-encoded signals were not transferred from heterocyst cells to adjacent vegetative cells. The results support a model in which the patS-dependent signal is initially transferred between vegetative cells in a HetC-independent fashion, but some time before morphological differentiation of heterocysts is complete, transfer of both signals transitions to a HetC-dependent process

Synchrotron Radiation Induced X-Ray Microanalysis: A Realistic Alternative for Electron- and Ion-Beam Microscopy?

Synchrotron radiation induced X-ray micro fluorescence analysis (μ-SRXRF) is compared with more conventional microanalytical techniques such as secondary ion microscopy (SIMS) and electron probe X-ray microanalysis (EPXMA) for two typical microanalytical applications. μ-SRXRF and EPXMA are employed for the analysis of individual particles, showing the complementary character of both techniques. By means of element mapping of trace constituents in a heterogeneous feldspar material, the strong and weak points of μ-SRXRF in comparison to EPXMA and SIMS are illustrated. The most striking difference between μ-SRXRF and the other two microanalytical methods is the ability of SRXRF to probe deep into the investigated material, whereas SIMS and EPXMA only investigate the upper surface of the material. The possibilities of μ-SRXRF using radiation from bending magnets of third generation synchrotron rings are briefly discussed. μ-SRXRF is considered to be a valuable method for the analysis of major, minor and trace elements which can be used profitably m parallel with electron-and ion-beam methods

How Phase Transitions induce classical behaviour

We continue the analysis of the onset of classical behaviour in a scalar field after a continuous phase transition, in which the system-field, the long wavelength order parameter of the model, interacts with an environment, of its own short-wavelength modes and other fields, neutral and charged, with which it is expected to interact. We compute the decoherence time for the system-field modes from the master equation and directly from the decoherence functional (with identical results). In simple circumstances the order parameter field is classical by the time the transition is complete.Comment: 10 pages, 1 figure: To be published in the International Journal of Theoretical Physics (2005) as part of the Proceedings of the "Peyresq Physics 9" meeting (2004) on "Micro and Macro structures of spacetime",ed. E. Verdague

Spontaneous Parity Violation in QCD At Finite Temperature: On the Inapplicability of the Vafa-Witten Theorem

The generalization of the Vafa-Witten theorem ruling out parity violation to QCD at finite temperature is considered. It is shown that this generalization of the theorem rules out Lorentz-invariant parity violating operators from spontaneously acquiring vacuum expectation values. However, it does not rule out Lorentz-noninvariant parity-violating operators from acquiring expectation values. Other situations where the theorem is inapplicable are also discussed.Comment: Minor typos correcte