12,023 research outputs found

    Ultrasensitive and Wide-Bandwidth Thermal Measurements of Graphene at Low Temperatures

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    Graphene is a material with remarkable electronic properties[1] and exceptional thermal transport properties near room temperature, which have been well examined and understood[2, 3]. However at very low temperatures the thermodynamic and thermal transport properties are much less well explored[4, 5] and somewhat surprisingly, is expected to exhibit extreme thermal isolation. Here we demonstrate an ultra-sensitive, wide-bandwidth measurement scheme to probe the thermal transport and thermodynamic properties of the electron gas of graphene. We employ Johnson noise thermometry at microwave frequency to sensitively measure the temperature of the electron gas with resolution of 4mK/√Hz and a bandwidth of 80 MHz. We have measured the electron-phonon coupling from 2-30 K at a charge density of 2 •10^(11)cm^(-2). Utilizing bolometric mixing, we have sensed temperature oscillations with period of 430 ps and have determined the heat capacity of the electron gas to be 2 • 10^(-21)J/(K •µm^2) at 5 K which is consistent with that of a two dimensional, Dirac electron gas. These measurements suggest that graphene-based devices together with wide bandwidth noise thermometry can generate substantial advances in the areas of ultra-sensitive bolometry[6], calorimetry[7], microwave and terahertz photo-detection[8], and bolometric mixing for applications in areas such as observational astronomy[9] and quantum information and measurement[10]

    Phycobiliproteins

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    Use of a multi-look unfocussed SAR processor on spacecraft

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    Two methods of processing signals from a multi-look unfocussed synthetic-aperture radar are considered. A saving in the processor complexity is achieved in comparison to a fully focussed SAR system at the expense of slightly greater clutter levels and poorer along-track resolution. In addition, lower power consumption enables the unfocussed processor to increase the number of looks to compensate in part for the reduced resolution

    Youth Pitching Kinematics: Associations with Body Overweight Parameters

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    The objective of this study was to investigate associations between injury-related kinematic parameters and overweight measures for youth baseball pitchers. The injury-related kinematic parameters considered were measurements 1) at foot contact: stride length, front foot position, shoulder external rotation, shoulder abduction, and elbow flexion; 2) between FC and ball release: peak knee extension; and 3) at BR: shoulder abduction. Data from three separate collection sites examined pitching mechanics of 18 10- to 11-year-old pitchers, 11 14- to 16-year-old pitchers, and 104 16- to 18-year-old pitchers Linear regression analyses were performed to determine significant correlations between kinematic parameters and body mass index (BMI) for each of the three age groups (10- to 11-year-olds, 14- to 16-year-olds, 16- to 18-year-olds). The significant findings were 1) for 10- to 11-year-old pitchers, stride length was negatively correlated with BMI and front foot position was positively correlated with BMI and 2) for 16- to 18-year-old pitchers, shoulder external rotation was negatively correlated with BMI and elbow flexion was positively correlated with BMI. A key clinical implication of this study is that select kinematic parameters have been identified that could guide coaches and trainers when working with overweight pitchers. In addition, select kinematic parameters of concern have been identified for different age ranges
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