12,498 research outputs found

    The Prairie

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    This research is the third of a series of investigations of the prairie. The first dealt with the environment of the prairie (Weaver and Himmel, 1931). The second was concerned with the ecology and relative importance of the dominant grasses (Weaver and Fitzpatrick, 1932). The present study treats of the structure of the vegetation in the several types of prairie, the secondary grasses, the ecology of the forbs, together with a general survey of contacts, invasion, and succession. These investigations have resulted from years of intimate association with the great grasslands of North America. They were made in an endeavor to clarify some of the many problems presented by this vast natural unit of vegetation, to better understand the importance and significance of grassland and hence its utilization and to furnish a permanent record of a rapidly vanishing vegetation. It deals with the vegetation as it exists today; nature\u27s yearly productivity unmodified by the hand of man except as he harvests the crop of hay in autumn

    Comparison of Lutylase and Bovilene For Estrus Synchronization of Heifers

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    A total of 533 yearling heifers were used to compare the effect of Lutylase vs Bovilene on estrus response within 5 days of injection. There was no difference between products in the percentage of heifers showing estrus within 5 days of injection. The average time from injection until detection of estrus was longer for Bovilene than Lutylase (64.5 hours vs 60.7 hours, P\u3c.05)

    Energy Spectrum Evolution of a Diffuse Field in Elastic Body Caused by Weak Nonlinearity

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    We study the evolution of diffuse elastodynamic spectral energy density under the influence of weak nonlinearity. It is shown that the rate of change of this quantity is given by a convolution of the linear energy at two frequencies. Quantitative estimates are given for sample aluminum and fused silica blocks of experimental interest.Comment: 9 pages, 3 figures; revised for better presentatio

    Mission description and in-flight operations of ERBE instruments on ERBS, NOAA 9, and NOAA 10 spacecraft

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    Instruments of the Earth Radiation Budget Experiment (ERBE) are operating on three different Earth-orbiting spacecraft. The Earth Radiation Budget Satellite (ERBS) is operated by NASA, and NOAA 9 and NOAA 10 weather satellites are operated by the National Oceanic and Atmospheric Administration (NOAA). This paper is the second in a series that describes the ERBE mission, and data processing and validation procedures. This paper describes the spacecraft and instrument operations for the second full year of in-orbit operations, which extend from February 1986 through January 1987. Validation and archival of radiation measurements made by ERBE instruments during this second year of operation were completed in July 1991. This period includes the only time, November 1986 through January 1987, during which all ERBE instruments aboard the ERBE, NOAA 9, and NOAA 10 spacecraft were simultaneously operational. This paper covers normal and special operations of the spacecraft and instruments, operational anomalies, and the responses of the instruments to in-orbit and seasonal variations in the solar environment

    Nonequilibrium quantum-impurities: from entropy production to information theory

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    Nonequilibrium steady-state currents, unlike their equilibrium counterparts, continuously dissipate energy into their physical surroundings leading to entropy production and time-reversal symmetry breaking. This letter discusses these issues in the context of quantum impurity models driven out of equilibrium by attaching the impurity to leads at different chemical potentials and temperatures. We start by pointing out that entropy production is often hidden in traditional treatments of quantum-impurity models. We then use simple thermodynamic arguments to define the rate of entropy production. Using the scattering framework recently developed by the authors we show that the rate of entropy production has a simple information theoretic interpretation in terms of the Shannon entropy and Kullback-Leibler divergence of nonequilibrium distribution function. This allows us to show that the entropy production is strictly positive for any nonequilibrium steady-state. We conclude by applying these ideas to the Resonance Level Model and the Kondo model.Comment: 5 pages, 1 figure new version with minor clarification

    Sliding mode control of a nonlinear wave energy converter model

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    The most accurate wave energy converter models for heaving point absorbers include nonlinearities, which increase as resonance is achieved to maximize the energy capture. Over the power production spectrum and within the physical limits of the devices, the efficiency of wave energy converters can be enhanced by employing a control scheme that accounts for these nonlinearities. This paper proposes a sliding mode control for a heaving point absorber that includes the nonlinear effects of the dynamic and static Froude‐Krylov forces. The sliding mode controller tracks a reference velocity that matches the phase of the excitation force to ensure higher energy absorption. This control algorithm is tested in regular linear waves and is compared to a complex‐conjugate control and a nonlinear variation of the complex‐conjugate control. The results show that the sliding mode control successfully tracks the reference and keeps the device displacement bounded while absorbing more energy than the other control strategies. Furthermore, due to the robustness of the control law, it can also accommodate disturbances and uncertainties in the dynamic model of the wave energy converter

    Fungal Colonists of Maize Grain Conditioned at Constant Temperatures and Humidities

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    Fungal colonization of shelled maize (Pioneer 3320) harvested from a field near Furman, South Carolina, in 1992 was determined after 348 and 751 days of continuous storage at each of seven temperatures (10, 15, 20, 25, 30, 35, or 40°C) and four constant relative humidities, giving equilibrium grain moisture contents ranging from 9.4% to 17.5% m.c. in 28 grain conditioning environments. Twenty fungal species infected surface sterilized seeds and were recorded from these conditioned grain treatments, including species commonly found in preharvest maize [e.g. Acremonium zeae, Aspergillus flavus, Fusarium moniliforme (syn. F. verticillioides), Penicillium pinophilum (syn. P. funiculosum), etc.]. Eupenicillium cinnamopurpureum and Monascus ruber were recorded only from conditioned grain treatments. Eurotium chevalieri colonized 50-96% of the kernels from grain conditioning treatments with the highest moisture content for each incubation temperature. Grain samples with \u3e33% E. chevalieri infection had a decreased occurrence of F. moniliforme and A. zeae, and no kernels from these samples germinated. No fungi colonized more than 50% of the kernels conditioned at 30-40°C and 9.4-14.2% m.c. The results of this study indicate that individual patterns of fungal colonization during grain conditioning were a function of the survival rates for preharvest fungal colonists and their potential replacement by E. chevalieri

    Pilot testing a couples-focused intervention for mild cognitive impairment

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    The purpose of this pilot was to evaluate the acceptability, feasibility, and potential benefits of the multicomponent, Daily Enhancement of Meaningful Activity (DEMA) intervention, which was tailored to help couples facing mild cognitive impairment (MCI) work together to meet goals, remain engaged in meaningful activities, and adapt to changes over time. Using a single-group design, 10 individuals with MCI and their family caregivers were recruited to participate in the DEMA intervention over 6 biweekly sessions. Data were collected pre-and at 1 week and 3 months postintervention completion rates indicated the program and study procedures were well accepted. Qualitative and quantitative finding indicated positive trends in meaningful activity performance and maintenance of health-related outcomes, as well as high program satisfaction. The DEMA intervention is potentially promising but needs further testing in a randomized clinical trial
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