38,251 research outputs found

    Frustration of freezing in a two dimensional hard-core fluid due to particle shape anisotropy

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    The freezing mechanism suggested for a fluid composed of hard disks [Huerta et al., Phys. Rev. E, 2006, 74, 061106] is used here to probe the fluid-to-solid transition in a hard-dumbbell fluid composed of overlapping hard disks with a variable length between disk centers. Analyzing the trends in the shape of second maximum of the radial distribution function of the planar hard-dumbbell fluid it has been found that the type of transition could be sensitive to the length of hard-dumbbell molecules. From the NpT{NpT} Monte Carlo simulations data we show that if a hard-dumbbell length does not exceed 15% of the disk diameter, the fluid-to-solid transition scenario follows the case of a hard-disk fluid, i.e., the isotropic hard-dumbbell fluid experiences freezing. However, for a hard-dumbbell length larger than 15% of disk diameter, there is evidence that fluid-to-solid transition may change to continuous transition, i.e., such an isotropic hard-dumbbell fluid will avoid freezing.Comment: 9 pages, 7 figure

    The distance selling directive: consumer champion or complete irrelevance?

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    This paper investigates the origins, significant content, UK and EU implementation and outcomes of Directive 97/7/EC on distance selling, hereafter referred to as the Distance Selling Directive (DSD). The DSD has been implemented in national legislation by all EU Member States. In the UK this legislation was the Consumer Protection (Distance Selling) Regulations 2000 (SI 2000 No. 2334), hereafter referred to as the CPDSR

    Sonic-boom measurements in the focus region during the ascent of Apollo 17

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    Sonic-boom pressure signatures recorded during the ascent phase of Apollo 17 are presented. The measurements were obtained onboard six U.S. Navy ships positioned along the ground track of the spacecraft vehicle in the area of expected focus resulting from the flight path and acceleration of the vehicle. Tracings of the measured signatures are presented along with values of the maximum positive overpressure, positive impulse, signature duration, and bowshock rise time. Also included are brief descriptions of the ships and their location, the deployment of the sonic-boom instrumentation, flight profiles and operating conditions for the launch vehicle and spacecraft, surface-weather and sea-state information at the measuring sites, and high-altitude weather information for the general measurement areas. Comparisons of the measured and predicted sonic-boom overpressures for the Apollo 17 mission are presented. The measured data are also compared with data from the Apollo 15 and 16 missions and data from flight test programs of various aircraft

    Sonic-boom ground pressure measurements from the launch and reentry of Apollo 16

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    Sonic-boom pressure signatures recorded during the launch and reentry phases of the Apollo 16 mission are presented. Five measurements were obtained along the vehicle ground track: 69 km (37.3 n. mi.) 92 km (49.8 n. mi.), and 130 km (70.3 n. mi.) down range from the launch site during ascent, and at 185 km (100 n. mi.) and approximately 5.5 km (3 n. mi.) from the splash-down point during reentry. Tracings of the measured signatures are included along with values of the overpressure, impulse, time duration, and rise times. Also included are brief descriptions of the launch and recovery test areas in which the measurements were obtained, the sonic-boom instrumentation deployment, flight profiles, and operating conditions for the launch vehicle and spacecraft, surface weather information at the measuring sites, and high-altitude weather information for the general measurement areas. Comparisons of the sonic-boom overpressures from Apollo 15 and 16 along with those from current aircraft are also presented

    Do television and electronic games predict children's psychosocial adjustment? Longitudinal research using the UK Millennium Cohort Study

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    Background: Screen entertainment for young children has been associated with several aspects of psychosocial adjustment. Most research is from North America and focuses on television. Few longitudinal studies have compared the effects of TV and electronic games, or have investigated gender differences. Purpose: To explore how time watching TV and playing electronic games at age 5 years each predicts change in psychosocial adjustment in a representative sample of 7 year-olds from the UK. Methods: Typical daily hours viewing television and playing electronic games at age 5 years were reported by mothers of 11 014 children from the UK Millennium Cohort Study. Conduct problems, emotional symptoms, peer relationship problems, hyperactivity/inattention and prosocial behaviour were reported by mothers using the Strengths and Difficulties Questionnaire. Change in adjustment from age 5 years to 7 years was regressed on screen exposures; adjusting for family characteristics and functioning, and child characteristics. Results: Watching TV for 3 h or more at 5 years predicted a 0.13 point increase (95% CI 0.03 to 0.24) in conduct problems by 7 years, compared with watching for under an hour, but playing electronic games was not associated with conduct problems. No associations were found between either type of screen time and emotional symptoms, hyperactivity/inattention, peer relationship problems or prosocial behaviour. There was no evidence of gender differences in the effect of screen time. Conclusions: TV but not electronic games predicted a small increase in conduct problems. Screen time did not predict other aspects of psychosocial adjustment. Further work is required to establish causal mechanisms

    Variability in airplane noise measurements

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    Aircraft position and meteorological effects on accuracy of acoustic measurements for turbojet engine

    Smallpox: clinical and epidemiologic features.

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    Geometry-induced phase transition in fluids: capillary prewetting

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    We report a new first-order phase transition preceding capillary condensation and corresponding to the discontinuous formation of a curved liquid meniscus. Using a mean-field microscopic approach based on the density functional theory we compute the complete phase diagram of a prototypical two-dimensional system exhibiting capillary condensation, namely that of a fluid with long-ranged dispersion intermolecular forces which is spatially confined by a substrate forming a semi-infinite rectangular pore exerting long-ranged dispersion forces on the fluid. In the T-mu plane the phase line of the new transition is tangential to the capillary condensation line at the capillary wetting temperature, Tcw. The surface phase behavior of the system maps to planar wetting with the phase line of the new transition, termed capillary prewetting, mapping to the planar prewetting line. If capillary condensation is approached isothermally with T>Tcw, the meniscus forms at the capping wall and unbinds continuously, making capillary condensation a second-order phenomenon. We compute the corresponding critical exponent for the divergence of adsorption.Comment: 5 pages, 4 figures, 5 movie
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