5,909 research outputs found

    Shock Tube Determination of Autoionization Lifetime and Oscillator Strengths of the 352 3P 2Po-353P2 2S1/2 Doublet of Al I Scientific Report No. 2

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    Shock tube measurement of autoionization lifetime and oscillator strengths of states above first ionization potential for aluminu

    Complete phase diagram of the spin-1/2 J1J_{1}-J2J_{2}-J3J_{3} model (with J3=J2J_{3}=J_{2}) on the honeycomb lattice

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    We use the coupled cluster method to investigate the ground-state (GS) properties of the frustrated spin-1/2 J1J_{1}-J2J_{2}-J3J_{3} model on the honeycomb lattice, with nearest-neighbor exchange coupling J1J_1 plus next-nearest-neighbor (J2J_2) and next-next-nearest-neighbor (J3J_3) exchanges of equal strength. In particular we find a direct first-order phase transition between the N\'eel-ordered antiferromagnetic phase and the ferromagnetic phase at a value J2/J1=1.17±0.01J_{2}/J_{1} = -1.17 \pm 0.01 when J1>0J_{1}>0, compared to the corresponding classical value of -1. We find no evidence for any intermediate phase. From this and our previous CCM studies of the model we present its full zero-temperature GS phase diagram.Comment: 4 pages, 4 figure

    A fuel-efficient cruise performance model for general aviation piston engine airplanes

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    A fuel-efficient cruise performance model which facilitates maximizing the specific range of General Aviation airplanes powered by spark-ignition piston engines and propellers is presented. Airplanes of fixed design only are considered. The uses and limitations of typical Pilot Operating Handbook cruise performance data, for constructing cruise performance models suitable for maximizing specific range, are first examined. These data are found to be inadequate for constructing such models. A new model of General Aviation piston-prop airplane cruise performance is then developed. This model consists of two subsystem models: the airframe-propeller-atmosphere subsystem model; and the engine-atmosphere subsystem model. The new model facilitates maximizing specific range; and by virtue of its implicity and low volume data storge requirements, appears suitable for airborne microprocessor implementation

    Transforming growth factor beta (TGF beta) mediates schwann cell death in vitro and in vivo: Examination of c-jun activation, interactions with survival signals, and the relationship of TGF beta-mediated death to schwann cell differentiation

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    In some situations, cell death in the nervous system is controlled by an interplay between survival factors and negative survival signals that actively induce apoptosis. The present work indicates that the survival of Schwann cells is regulated by such a dual mechanism involving the negative survival signal transforming growth factor beta (TGF beta), a family of growth factors that is present in the Schwann cells themselves. We analyze the interactions between this putative autocrine death signal and previously defined paracrine and autocrine survival signals and show that expression of a dominant negative c-Jun inhibits TGF beta -induced apoptosis. This and other findings pinpoint activation of c-Jun as a key downstream event in TGF beta -induced Schwann cell death. The ability of TGF beta to kill Schwann cells, like normal Schwann cell death in vivo, is under a strong developmental regulation, and we show that the decreasing ability of TGF beta to kill older cells is attributable to a decreasing ability of TGF beta to phosphorylate c-Jun in more differentiated cells

    Bayesian analysis of Friedmannless cosmologies

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    Assuming only a homogeneous and isotropic universe and using both the 'Gold' Supernova Type Ia sample of Riess et al. and the results from the Supernova Legacy Survey, we calculate the Bayesian evidence of a range of different parameterizations of the deceleration parameter. We consider both spatially flat and curved models. Our results show that although there is strong evidence in the data for an accelerating universe, there is little evidence that the deceleration parameter varies with redshift.Comment: 7 pages, 3 figure

    New directions in EEG measurement: an investigation into the fidelity of electrical potential sensor signals

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    Low frequency noise performance is the key indicator in determining the signal to noise ratio of a capacitively coupled sensor when used to acquire electroencephalogram signals. For this reason, a prototype Electric Potential Sensor device based on an auto-zero operational amplifier has been developed and evaluated. The absence of 1/f noise in these devices makes them ideal for use with signal frequencies ~10 Hz or less. The active electrodes are designed to be physically and electrically robust and chemically and biochemically inert. They are electrically insulated (anodized) and have diameters of 12 mm or 18 mm. In both cases, the sensors are housed in inert stainless steel machined housings with the electronics fabricated in surface mount components on a printed circuit board compatible with epoxy potting compounds. Potted sensors are designed to be immersed in alcohol for sterilization purposes. A comparative study was conducted with a commercial wet gel electrode system. These studies comprised measurements of both free running electroencephalogram and Event Related Potentials. Quality of the recorded electroencephalogram was assessed using three methods of inspection of raw signal, comparing signal to noise ratios, and Event Related Potentials noise analysis. A strictly comparable signal to noise ratio was observed and the overall conclusion from these comparative studies is that the noise performance of the new sensor is appropriate

    Absorption line series and autoionization resonance structure analysis in the ultraviolet spectrum of Sr I

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    Photoelectric spectrometer to measure absorption line series and autoionization resonance in ultraviolet spectrum of strontium vapo
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