645 research outputs found

    Passenger Age and Gender Effects on Adult Driver Fatal Crash Rate

    Get PDF
    Driver behavior and crash rates vary with the presence of passengers but the details of this relationship are not well understood. The literature generally does not take into account the characteristics of passengers, yet effects on crashes may vary dramatically with passenger age and gender. This study estimated the amount of exposure (driving miles) done by various driver age/gender categories with various combinations of passengers. Statistical imputation techniques were used to derive travel estimates for various pairings using data from the 2001 National Household Travel Survey. Crash frequencies for every pairing were obtained from the Fatality Analysis Reporting System and were used to compute fatal crash rates (per 10 million trip miles). The findings reported here focus on adult (21 and older) drivers. The results show that drivers of a given type (age/gender group) show dramatically different crash rates as a function of passenger type. Some passenger types are associated with fatal crash rates higher than that with no passenger, while other passenger types are associated with lower crash rates. The details of this relationship depend to some degree on driver characteristics. Crash rates for different driver age/gender groups overlap substantially based on the passenger, so that the “best” and “worst” driver groups are passenger-specific. For adult male drivers, female passengers are generally associated with lower crash rates. For male drivers, there is a higher crash rate with a male passenger of a given age than with a female passenger of the same age, even for child passengers

    The metabolic syndrome adds utility to the prediction of mortality over its components: The Vietnam Experience Study

    Get PDF
    Background\ud The metabolic syndrome increases mortality risk. However, as “non-affected” individuals may still have up to two risk factors, the utility of using three or more components to identify the syndrome, and its predictive advantage over individual components have yet to be determined.\ud \ud Methods\ud Participants, male Vietnam-era veterans (n = 4265) from the USA, were followed-up from 1985/1986 for 14.7 years (61,498 person-years), and all-cause and cardiovascular disease deaths collated. Cox's proportional-hazards regression was used to assess the effect of the metabolic syndrome and its components on mortality adjusting for a wide range of potential confounders.\ud \ud Results\ud At baseline, 752 participants (17.9%) were identified as having metabolic syndrome. There were 231 (5.5%) deaths from all-causes, with 60 from cardiovascular disease. After adjustment for a range of covariates, the metabolic syndrome increased the risk of all-cause, HR 2.03, 95%CI 1.52, 2.71, and cardiovascular disease mortality, HR 1.92, 95%CI 1.10, 3.36. Risk increased dose-dependently with increasing numbers of components. The increased risk from possessing only one or two components was not statistically significant. The adjusted risk for four or more components was greater than for only three components for both all-cause, HR 2.30, 95%CI 1.45, 3.66 vs. HR 1.70, 95%CI 1.11, 2.61, and cardiovascular disease mortality, HR 3.34, 95%CI 1.19, 9.37 vs. HR 2.81, 95%CI 1.07, 7.35. The syndrome was more informative than the individual components for all-cause mortality, but could not be assessed for cardiovascular disease mortality due to multicollinearity. Hyperglycaemia was the individual strongest parameter associated with mortality.\ud \u

    Caffeine-induced synaptic potentiation in hippocampal CA2 neurons

    Get PDF
    Caffeine enhances cognition, but even high non-physiological doses have modest effects on synapses. A 1 adenosine receptors (A 1 Rs) are antagonized by caffeine and are most highly enriched in hippocampal CA2, which has not been studied in this context. We found that physiological doses of caffeine in vivo or A 1 R antagonists in vitro induced robust, long-lasting potentiation of synaptic transmission in rat CA2 without affecting other regions of the hippocampus

    Quantum chaos in a deformable billiard: Applications to quantum dots

    Full text link
    We perform a detailed numerical study of energy-level and wavefunction statistics of a deformable quantum billiard focusing on properties relevant to semiconductor quantum dots. We consider the family of Robnik billiards generated by simple conformal maps of the unit disk; the shape of this family of billiards may be varied continuously at fixed area by tuning the parameters of the map. The classical dynamics of these billiards is well-understood and this allows us to study the quantum properties of subfamilies which span the transition from integrability to chaos as well as families at approximately constant degree of chaoticity (Kolmogorov entropy). In the regime of hard chaos we find that the statistical properties of interest are well-described by random-matrix theory and completely insensitive to the particular shape of the dot. However in the nearly-integrable regime non-universal behavior is found. Specifically, the level-width distribution is well-described by the predicted χ2\chi^2 distribution both in the presence and absence of magnetic flux when the system is fully chaotic; however it departs substantially from this behavior in the mixed regime. The chaotic behavior corroborates the previously predicted behavior of the peak-height distribution for deformed quantum dots. We also investigate the energy-level correlation functions which are found to agree well with the behavior calculated for quasi-zero-dimensional disordered systems.Comment: 25 pages (revtex 3.0). 16 figures are available by mail or fax upon request at [email protected]

    “It’s my dream to work with Olympic athletes”: Neophyte sport psychologists’ expectations and initial experiences regarding service delivery

    Get PDF
    We examined trainee practitioners' initial experiences of applied sport psychology practice. Semi-structured interviews (4) were conducted over 6 months with 7 full-time MSc students before, during, and after the applied sport psychology module, when they were working with clients. Participants also kept reflective diaries over an 8-week period whilst working with clients. Findings included: (a) motivations and expectations of an ASP practice career, (b) perceptions of service delivery, (c) emotional demands, and (d) pivotal experiences. Findings extend previous literature on the initial stages of practitioner development, providing micro-level detail on aspects of the intense development process during this pivotal perio

    Myelination generates aberrant ultrastructure that is resolved by microglia

    Get PDF
    To enable rapid propagation of action potentials, axons are ensheathed by myelin, a multilayered insulating membrane formed by oligodendrocytes. Most of the myelin is generated early in development, resulting in the generation of long-lasting stable membrane structures. Here, we explored structural and dynamic changes in central nervous system myelin during development. To achieve this, we performed an ultrastructural analysis of mouse optic nerves by serial block face scanning electron microscopy (SBF-SEM) and confocal time-lapse imaging in the zebrafish spinal cord. We found that myelin undergoes extensive ultrastructural changes during early postnatal development. Myelin degeneration profiles were engulfed and phagocytosed by microglia using exposed phosphatidylserine as one “eat me” signal. In contrast, retractions of entire myelin sheaths occurred independently of microglia and involved uptake of myelin by the oligodendrocyte itself. Our findings show that the generation of myelin early in development is an inaccurate process associated with aberrant ultrastructural features that require substantial refinement.</p

    Electrophysiological Heterogeneity of Fast-Spiking Interneurons: Chandelier versus Basket Cells

    Get PDF
    In the prefrontal cortex, parvalbumin-positive inhibitory neurons play a prominent role in the neural circuitry that subserves working memory, and alterations in these neurons contribute to the pathophysiology of schizophrenia. Two morphologically distinct classes of parvalbumin neurons that target the perisomatic region of pyramidal neurons, chandelier cells (ChCs) and basket cells (BCs), are generally thought to have the same "fast-spiking" phenotype, which is characterized by a short action potential and high frequency firing without adaptation. However, findings from studies in different species suggest that certain electrophysiological membrane properties might differ between these two cell classes. In this study, we assessed the physiological heterogeneity of fast-spiking interneurons as a function of two factors: species (macaque monkey vs. rat) and morphology (chandelier vs. basket). We showed previously that electrophysiological membrane properties of BCs differ between these two species. Here, for the first time, we report differences in ChCs membrane properties between monkey and rat. We also found that a number of membrane properties differentiate ChCs from BCs. Some of these differences were species-independent (e.g., fast and medium afterhyperpolarization, firing frequency, and depolarizing sag), whereas the differences in the first spike latency between ChCs and BCs were species-specific. Our findings indicate that different combinations of electrophysiological membrane properties distinguish ChCs from BCs in rodents and primates. Such electrophysiological differences between ChCs and BCs likely contribute to their distinctive roles in cortical circuitry in each species. © 2013 Povysheva et al
    • 

    corecore