35,111 research outputs found

    Radiative properties of cirrus clouds inferred from broadband measurements during FIRE

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    It is well known that clouds are significant modulators of weather and climate because of their effects on the radiation field and thus on the energy balance of the earth atmosphere system. As a result, the accurate prediction of weather and climate depends to a significant degree on the accuracy with which cloud radiation interactions can be described. The broadband radiative and microphysical properties of five cirrus cloud systems are reported, as observed from the NCAR Sabreliner during the FIRE first Cirrus IFO, in order to better understand cirrus cloud-radiation interactions. A broadband infrared (BBIR) radiative transfer model is used to deduce BBIR absorption coefficients in order to assess the impact of the cirrus clouds on infrared radiation. The relationships of these absorption coefficients to temperature and microphysical characteristics are explored

    Temperature sensitivity of Eppley broadband radiometers

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    Broadband radiometers manufactured by Eppley Laboratories Inc. are commonly used to measure irradiance from both ground-based and aircraft platforms. Namely, the pyranometer (Model PSP) measures irradiance in the .3 to 3.0 micron spectral region while the pyrgeometer (Model PIR) senses energy in the 4 to 50 micron region. The two instruments have a similar thermopile construction but different filters to achieve the appropriate spectral selection. During the fall of 1986, the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) commenced with the first cirrus Intensive Field Observation (IFO) conducted in Central Wisconsin. Due to the nature of this field project, pyranometers and pyrgeometers manufactured by Eppley were flown on NCAR's high altitude research aircraft, the Sabreliner. Inherent in the construction of these radiometers is temperature compensation circuitry designed to make the instrument sensitivity nominally constant over a temperature range from -20 to +40 C. Because the Sabreliner flew at high altitudes where temperatures were as cold as -70 C, it was necessary to determine the radiometers relative sensitivity to temperatures below -20 C and apply appropriate corrections to the FIRE radiation data set. A procedure to perform this calibration is outlined. It is meant to serve as a supplement to calibration procedures

    A Morse index theorem for elliptic operators on bounded domains

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    Given a selfadjoint, elliptic operator LL, one would like to know how the spectrum changes as the spatial domain Ω⊂Rd\Omega \subset \mathbb{R}^d is deformed. For a family of domains {Ωt}t∈[a,b]\{\Omega_t\}_{t\in[a,b]} we prove that the Morse index of LL on Ωa\Omega_a differs from the Morse index of LL on Ωb\Omega_b by the Maslov index of a path of Lagrangian subspaces on the boundary of Ω\Omega. This is particularly useful when Ωa\Omega_a is a domain for which the Morse index is known, e.g. a region with very small volume. Then the Maslov index computes the difference of Morse indices for the "original" problem (on Ωb\Omega_b) and the "simplified" problem (on Ωa\Omega_a). This generalizes previous multi-dimensional Morse index theorems that were only available on star-shaped domains or for Dirichlet boundary conditions. We also discuss how one can compute the Maslov index using crossing forms, and present some applications to the spectral theory of Dirichlet and Neumann boundary value problems.Comment: 21 pages; weaker regularity assumptions than in the first versio

    Design Development of the Apollo Lunar Module

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    The lunar module autopilot is a first generation digital control system design. The two torque sources available for the control function of the descent stage configuration consist of 16 reaction jets and a slow, gimbaled, throttlable engine. Design history, the design requirements, criteria, constraints, and general design philosophy of the control system development are reviewed. Comparative flight test results derived from design testing are presented

    Small Energy Scale for Mixed-Valent Uranium Materials

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    We investigate a two-channel Anderson impurity model with a 5f15f^1 magnetic and a 5f25f^2 quadrupolar ground doublet, and a 5f25f^2 excited triplet. Using the numerical renormalization group method, we find a crossover to a non-Fermi liquid state below a temperature T∗T^* varying as the 5f25f^2 triplet-doublet splitting to the 7/2 power. To within numerical accuracy, the non-linear magnetic susceptibility and the 5f15f^1 contribution to the linear susceptibility are given by universal one-parameter scaling functions. These results may explain UBe13_{13} as mixed valent with a small crossover scale T∗T^*.Comment: 4 pages, 3 figures, REVTeX, to appear in Phys. Rev. Let

    A multi-centre cluster randomised controlled trial evaluating the effectiveness of e-cigarettes compared with usual care for smoking cessation when offered to smokers accessing homeless services: methodological challenges and experiences of collaboration.

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    Around 80% of people experiencing homelessness smoke. E-cigarettes (ECs) are an effective quitting aid, but they have not been widely tested in this population. Project SCeTcH aims to evaluate the offer of an EC or usual care (UC) to smokers accessing homeless centres. A multi-centre two-arm cluster randomised controlled trial (RCT), including 32 homeless centres across Great Britain (480 participants). Randomisation includes either an EC with weekly allocations of e-liquid for 4-weeks or UC comprising very brief advice and signposting to a stop smoking service. After year 1, 27 centres and 240 participants have been recruited and retention rates at 4- and 24- weeks are 67% and 70% respectively. Challenges include working with multiple centres with different structures, provision, and client needs; reconciling risk of bias with the practicalities of working in this sector; the ongoing impact of Covid; changing models of care and practice; and juggling the needs of different collaborators researchers and health and social care organisations This is the first cluster RCT to assign smokers experiencing homelessness to an EC and UC intervention to measure smoking abstinence and risky smoking practices. Running trials in this population requires the need to understand the realistic needs of these individuals and services, and to work pragmatically and flexibly within the remit of the trial protocol. Ultimately, if effective, the results will be used to inform the larger scale implementation of supporting homeless centres to aid smoking cessation

    Radiative properties of Cirrus clouds: FIRE IFO case October 28, 1986

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    A description of the radiative properties of two cirrus clouds sampled on 10/28/88 in the FIRE cirrus IFO is presented. The clouds are characterized in terms of the broadband infrared effective emittance, cloud fractional absorptance, shortwave heating rate, cloud albedo and vertical velocity. The broadband fluxes used in these calculations were obtained from measurements made by pyranometers and pyrgeometers. The shortwave irradiances were corrected to a horizontal plane and normalized to the same time by taking into account Sabreliner flight information (i.e., pitch, roll, heading and angle of attack), as well as sun-earth geometry considerations. Since only one aircraft was used, broadband fluxes at different levels in the cloud were not measured simultaneously. As a result, sampling errors may occur due to the nonsteady state of the cloud field or due to the possibility that the flight legs were not flown directly above or below each other. To minimize these errors and to simplify the analysis, the necessary variables were averaged and the averages used in the calculations. The downwelling shortwave and longwave irradiances were used as selection criteria to remove cloud free data encountered along the data sampling leg
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