Wave Equation for Sound in Fluids with Vorticity

We use Clebsch potentials and an action principle to derive a closed system of gauge invariant equations for sound superposed on a general background flow. Our system reduces to the Unruh (1981) and Pierce (1990) wave equations when the flow is irrotational, or slowly varying. We illustrate our formalism by applying it to waves propagating in a uniformly rotating fluid where the sound modes hybridize with inertial waves.Comment: RevTeX, 27page

An empirical approach to determining speed limit credibility

There is now a body of literature on speed limit credibility, particularly in connection with speed management under the overall umbrella of “Safe Systems”. However, there is rather little empirical work on the underlying factors that determine the credibility of speed limits and on how to enhance credibility for a given type of road. The study reported here aimed to investigate how factors such as road layout and the roadside environment together with drivers’ perception of risk affect speed limit credibility. It also aimed to provide a measurement of speed limit credibility and how to set more credible speed limits to improve drivers’ speed compliance. A picture questionnaire and a driving simulator in an automated condition in a simulator were adopted to obtain the measurements. The results suggest that certain road layout and environment features influence speed limit credibility. The research results show that five new indicators can be used as a reference for deciding on a credible speed limit in a given road environment: the most common choice of speed limit by drivers; the highest credible rating score value; indication of comfort with speed in automated driving; risk rating in the range from feeling safe to very safe; arousal indicated by skin conductance. Applying these indicators makes it possible to determine a limit that is credible for most motorists in a given road environment. Improving the credibility of a speed limit will lead to better speed management overall

Enhanced hippocampal long-term potentiation and spatial learning in aged 11ß-hydroxysteroid dehydrogenase type 1 knock-out mice

Glucocorticoids are pivotal in the maintenance of memory and cognitive functions as well as other essential physiological processes including energy metabolism, stress responses, and cell proliferation. Normal aging in both rodents and humans is often characterized by elevated glucocorticoid levels that correlate with hippocampus-dependent memory impairments. 11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) amplifies local intracellular ("intracrine") glucocorticoid action; in the brain it is highly expressed in the hippocampus. We investigated whether the impact of 11ß-HSD1 deficiency in knock-out mice (congenic on C57BL/6J strain) on cognitive function with aging reflects direct CNS or indirect effects of altered peripheral insulin-glucose metabolism. Spatial learning and memory was enhanced in 12 month "middle-aged" and 24 month "aged" 11ß-HSD1<sup>–/–</sup> mice compared with age-matched congenic controls. These effects were not caused by alterations in other cognitive (working memory in a spontaneous alternation task) or affective domains (anxiety-related behaviors), to changes in plasma corticosterone or glucose levels, or to altered age-related pathologies in 11ß-HSD1<sup>–/–</sup> mice. Young 11ß-HSD1<sup>–/–</sup> mice showed significantly increased newborn cell proliferation in the dentate gyrus, but this was not maintained into aging. Long-term potentiation was significantly enhanced in subfield CA1 of hippocampal slices from aged 11ß-HSD1<sup>–/–</sup> mice. These data suggest that 11ß-HSD1 deficiency enhances synaptic potentiation in the aged hippocampus and this may underlie the better maintenance of learning and memory with aging, which occurs in the absence of increased neurogenesis

On the effects of mass and momentum transfer from droplets impacting on steady two-dimensional rimming flow in a horizontal cylinder

Motivated by applications in aero-engines, steady two-dimensional thin-filmflow on the inside of a circular cylinder is studied when the filmsurface is subject to mass and momentum transfer from impacting droplets. Asymptotic analysis is used systematically to identify distinguished limits that incorporate these transfer effects at leading order and to provide a new mathematical model. Applying both analytical and numerical approaches to the model, a set of stable steady, two-dimensional solutions that fit within the rational framework is determined. A number of these solutions feature steep fronts and associated recirculating pools, which are undesirable in an aeroengine since oil may be stripped away from the steep fronts when there is a core flow external to the film, and recirculation may lead to oil degradation. The model, however, provides a means of investigating whether the formation of the steep fronts on the filmsurface and of internal recirculation pools can be delayed, or inhibited altogether, by designing jets to deliver prescribed distributions of oil droplets or by the judicious siting of oil sinks. Moreover, by studying pathlines, oil-residence times can be predicted and systems optimized

Integrable Electron Model with Correlated Hopping and Quantum Supersymmetry

We give the quantum analogue of a recently introduced electron model which generalizes the Hubbard model with additional correlated hopping terms and electron pair hopping. The model contains two independent parameters and is invariant with respect to the quantum superalgebra $U_q(gl(2|1))$. It is integrable in one dimension by means of the quantum inverse scattering method.Comment: 7 pages, AmsTex fil

Dispersive wave runup on non-uniform shores

Historically the finite volume methods have been developed for the numerical integration of conservation laws. In this study we present some recent results on the application of such schemes to dispersive PDEs. Namely, we solve numerically a representative of Boussinesq type equations in view of important applications to the coastal hydrodynamics. Numerical results of the runup of a moderate wave onto a non-uniform beach are presented along with great lines of the employed numerical method (see D. Dutykh et al. (2011) for more details).Comment: 8 pages, 6 figures, 18 references. This preprint is submitted to FVCA6 conference proceedings. Other author papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh

Prevalence and self-regulation of drivers’ secondary task engagement at intersections: An evaluation using naturalistic driving data

On the basis of naturalistic driving data, this study examined the prevalence of secondary task engagement at intersections and investigated how drivers self-regulate and manage such activities in accordance with changing roadways and demand situations. Video recordings were viewed to identify secondary tasks in which drivers engaged and situational factors, specifically those related to the complexity of driving situations. Results showed that one-third of the total intersection time was allocated to secondary task engagement and that greater engagement occurred at upstream and downstream areas of intersections than at areas falling within intersections. Drivers tended to more frequently engage in secondary tasks when their vehicles were stationary than when the vehicles were moving. Elderly drivers were less likely to engage in secondary tasks than younger drivers. Finally, drivers were less likely to engage in secondary tasks when they did not have priority than when they had priority and at intersections managed through traffic signs than in those controlled by traffic lights. In conclusion, drivers appear to engage selectively in secondary tasks at intersections in accordance with changes in the demands imposed by driving and roadway situations. In such circumstances, drivers likely respond to increased demand and reduce secondary task engagement to preserve processing resources. The findings offer the preliminary information necessary to develop driver training/education and awareness programmes on managing distractions and safe driving strategies

Can infrastructure improvements mitigate unsafe traffic safety culture: A driving simulator study exploring cross cultural differences

This paper presents the results of a cross-cultural study to investigate the influence of traffic safety culture and infrastructure improvements on driver behaviour. To achieve this, the driving style of UK drivers was compared with that of Nigerians with and without experience of driving in the UK. A driving simulator experiment compared the actual driving style of these three groups of drivers in different safety critical scenarios. The simulated road environment varied depending on how much infrastructure was provided (low or high infrastructure). In addition, the Driver Behaviour Questionnaire was used to collect self-reported data on violations, errors and lapses. It was hypothesised that Nigerian drivers with no experience of driving in a UK road system would report and engage in more unsafe driving behaviour compared to the other two groups, and that increasing infrastructure would have little positive benefit. Overall, the results supported these hypotheses, indicating that the behaviours of drivers are interpretable in relation to their traffic safety culture, compared to changes in their driving environment

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