207,077 research outputs found

    Fiber optic vibration transducer and analyzer Patent

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    Fiber optic transducers for monitoring and analysis of vibration in aerospace vehicles and onboard equipmen

    Systematic variation of the 12CO/13CO ratio as a function of star-formation rate surface density

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    We show that the12CO/13CO intensity ratio in nearby galaxies varies systematically as a function of the star formation rate surface density and gas surface density. The same effect is observed in different transitions, and in the 12CO/C18O ratio, while the 13CO/C18O ratio appears to remain constant as a function of the star formation rate surface density. We discuss the cause of these variations, considering both changes in the physical state of the gas, and chemical changes that lead to abundance variations. We used the observed correlations with C18O to suggest that abundance variations are unlikely to be causing the systematic trend observed with the star formation rate surface density, and thus that the mean gas temperature and/or velocity dispersion are systematically higher in higher star-formation rate surface density regions. We present the best fitting relations between the star formation rate surface density and the 12CO/13CO and 12CO/C18O ratios, and discuss how this effect can help us predict CO isotope emission from galaxies across the known universe.Comment: 7 pages, 4 figures, accepted to MNRA

    In Memoriam: James Arthur Scholtz, 1932-1978

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    Fatigue failure load indicator

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    An indicator for recording the load at which a fatigue specimen breaks during the last cycle of a fatigue test is described. A load cell is attached to the specimen which is alternately subjected to tension and compression loads. The output of the load cell which is proportional to the load on the specimen is applied to the input of a peak detector. Each time the specimen is subjected to a compression load, means are provided for applying a positive voltage to the rest of the peak detector to reset it. During the last cycle of the tension load the peak detector measures the maximum load on the specimen. Means are provided for disconnecting the load cell from the peak detector when there is a failure in the specimen

    Race and Policing: An Agenda for Action

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    This paper is organized into two parts -- Strategic Voice and Tactical Agency. Strategic Voice argues that problems of race in policing cannot be resolved by the police alone. Other people must help by understanding and ameliorating the social conditions that cause race to be associated with crime and hence become a dilemma for American policing. Rather than accepting these conditions as givens, police leaders with their powerful collective voice should actively call attention to what needs to be changed. Tactical Agency outlines what the police can do on their own initiative to deal with the operational dilemmas of race -- in the communities they serve and in their own organizations

    Conformal Inflation Coupled to Matter

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    We formulate new conformal models of inflation and dark energy which generalise the Higgs-Dilaton scenario. We embed these models in unimodular gravity whose effect is to break scale invariance in the late time Universe. In the early Universe, inflation occurs close to a maximum of both the scalar potential and the scalar coupling to the Ricci scalar in the Jordan frame. At late times, the dilaton, which decouples from the dynamics during inflation, receives a potential term from unimodular gravity and leads to the acceleration of the Universe. We address two central issues in this scenario. First we show that the Damour-Polyalov mechanism, when non-relativistic matter is present prior to the start of inflation, sets the initial conditions for inflation at the maximum of the scalar potential. We then show that conformal invariance implies that matter particles are not coupled to the dilaton in the late Universe at the classical level. When fermions acquire masses at low energy, scale invariance is broken and quantum corrections induce a coupling between the dilaton and matter which is still small enough to evade the gravitational constraints in the solar system.Comment: 24 page

    Two-dimensional double-quantum spectroscopy: peak shapes as a sensitive probe of carrier interactions in quantum wells

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    We identify carrier scattering at densities below which it has previously been observed in semiconductor quantum wells. These effects are evident in the peakshapes of 2D double-quantum spectra, which change as a function of excitation density. At high excitation densities (109\geq 10^{9} carriers/,cm2^{-2}) we observe untilted peaks similar to those reported in previous experiments. At low excitation densities (<10810^{8} carriers cm2^{-2}) we observe narrower, tilted peaks. Using a simple simulation, we show that tilted peak-shapes are expected in double-quantum spectra when inhomogeneous broadening is much larger than homogeneous broadening, and that fast pure-decoherence of the double-quantum coherence can obscure this peak tilt. These results show that carrier interactions are important at lower densities than previously expected, and that the `natural' double-quantum peakshapes are hidden by carrier interactions at the excitation densities typically used. Furthermore, these results demonstrate that analysis of 2D peak-shapes in double-quantum spectroscopy provides an incisive tool for identifying interactions at low excitation density
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