3,557 research outputs found

    Precise Model for Small-Body Thermal Radiation Pressure Acting on Spacecraft

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    A precise representation of small-body surface thermal radiation pressure effects acting on orbiting spacecraft is discussed. The proposed framework takes advantage of a general Fourier series expansion to compute small-body surface thermal radiation pressure. Fourier series expansion has been used before for the precise representation of solar radiation pressure effects on spacecraft orbiting small bodies. This framework takes into account the geometric relationship of orbiting spacecraft with the small-body surface, surface thermal parameters of the small body, and the shape and surface properties of spacecraft allowing for the computation of thermal radiation pressure, which may also be used for the generation of precise orbit determination solutions. After presenting the general model, an example application of the model for the OSIRIS-REx spacecraft in orbit about Asteroid (101955) Bennu is provided. Simulation studies were used to evaluate the effect of mismodeling of thermal radiation pressure on the spacecraft and study the use of the proposed method for generating precise orbit determination solutions

    Extreme Weather and Climate Change: Understanding the Link, Managing the Risk

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    Examines recent extreme weather events, their consequences, and links to larger statistical trends toward higher frequency and severity. Calls for a probability-based risk management framework for adapting to and mitigating the effects of climate change

    Photochemical tyrosine oxidation with a hydrogen-bonded proton acceptor by bidirectional proton-coupled electron transfer

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    Amino acid radical generation and transport are fundamentally important to numerous essential biological processes to which small molecule models lend valuable mechanistic insights. Pyridyl-amino acid-methyl esters are appended to a rhenium(I) tricarbonyl 1,10-phenanthroline core to yield rhenium–amino acid complexes with tyrosine ([Re]–Y–OH) and phenylalanine ([Re]–F). The emission from the [Re] center is more significantly quenched for [Re]–Y–OH upon addition of base. Time-resolved studies establish that excited-state quenching occurs by a combination of static and dynamic mechanisms. The degree of quenching depends on the strength of the base, consistent with a proton-coupled electron transfer (PCET) quenching mechanism. Comparative studies of [Re]–Y–OH and [Re]–F enable a detailed mechanistic analysis of a bidirectional PCET process.National Institutes of Health (U.S.) (GM47274

    An Impermeant Ganetespib Analog Inhibits Extracellular Hsp90-Mediated Cancer Cell Migration that Involves Lysyl Oxidase 2-like Protein

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    Extracellular Hsp90 (eHsp90) activates a number of client proteins outside of cancer cells required for migration and invasion. Therefore, eHsp90 may serve as a novel target for anti-metastatic drugs as its inhibition using impermeant Hsp90 inhibitors would not affect the numerous vital intracellular Hsp90 functions in normal cells. While some eHsp90 clients are known, it is important to establish other proteins that act outside the cell to validate eHsp90 as a drug target to limit cancer spread. Using mass spectrometry we identified two precursor proteins Galectin 3 binding protein (G3BP) and Lysyl oxidase 2-like protein (LOXL2) that associate with eHsp90 in MDA-MB231 breast cancer cell conditioned media and confirmed that LOXL2 binds to eHsp90 in immunoprecipitates. We introduce a novel impermeant Hsp90 inhibitor STA-12-7191 derived from ganetespib and show that it is markedly less toxic to cells and can inhibit cancer cell migration in a dose dependent manner. We used STA-12-7191 to test if LOXL2 and G3BP are potential eHsp90 clients. We showed that while LOXL2 can increase wound healing and compensate for STA-12-7191-mediated inhibition of wound closure, addition of G3BP had no affect on this assay. These findings support of role for LOXL2 in eHsp90 stimulated cancer cell migration and provide preliminary evidence for the use of STA-12-7191 to inhibit eHsp90 to limit cancer invasion

    Dataset for large-scale, lateral-torsional buckling tests of continuous beams in a grillage system

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    A number of large-scale tests of a grillage system are summarized and reduced data are provided. The tests were completed in association with a Louisiana Transportation Research Center (LTRC) project for the Louisiana Department of Transportation and Development (LA DOTD) whose goal was to better quantify behavior and limit states of steel bridge floor systems to refine longitudinal member (stringer) load- rating calculations. A number of tests focused on the behavior of the stringers resting on transverse members (a floorbeam), a system akin to a grillage. The system was proportioned with the expectation that stringer lateral-torsional buckling, a key steel bridge beam design and load-rating limit state, would occur. The provided dataset includes specimen descriptions and output from 58 tests. Investigated parameters included: stringer unbraced lengths; bracing types (i.e., bolted steel diaphragms versus clamped timber struts); load locations; and support conditions. Sample tests are described and reduced results summarized and presented

    The Relationship between Lower-Body Strength and Power, and Load Carriage Tasks: A Critical Review

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    International Journal of Exercise Science 12(6): 1001-1022, 2019. The purpose of this review was to critically appraise articles that have investigated the association between lower-body strength and power during load carriage in tactical personnel. Literature databases were searched with specific search terms, yielding 921 articles. Additional studies found from article reference lists were also assessed for eligibility. Out of these articles, 16 met the inclusion/exclusion criteria and were critically appraised. Articles were assessed by the Downs and Black evaluation tool with inter-rater agreement determined by Cohen’s kappa and final results graded according to the Kennelly quality grading system. Of the 940 identified articles, 16 studies met the criteria for inclusion in this review. The average score of the eligible articles was 58%, considered to be of fair quality by the Kennelly grading system. The strength and volume of evidence reviewed suggests that: measures of lower-body strength and power can predict load carriage performance and appear to be important physical factors for load carriage ability, and that load carriage tasks negatively impact the performance of leg strength and power. Together these findings suggest that leg strength and power should be important considerations for tactical personnel training and assessment, as well as managing the impact of load carriage on tactical performance

    Development of Regional Supply Functions and a Least-Cost Model for Allocating Water Resources in Utah: A Parametric Linear Programming Approach

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    The development and allocation of the water resourcse within a state require water planners to prepare plans far in advance of the actual time new facilities are required. It is not easy to identify and evaluate all the possible alternatives for providing water which incorporate broad objectives such as economic efficiency, social welfare, regional development, recreation benefits, and conservation of environment. Water resources development entails the modification of a natural hydrologic system to better meet man\u27s needs. The interrelationships among elements of the hydrologic system to better meet man\u27s needs. The interrelationships among elements of the hydrologic system are relatively simple in comparison to the social, legal, economic, and institutional interdependencies involved. The relationships are so complex as to require that planning of water resource development be accomplished on a systems basis. It has become apparent that water resource planning must consider mass transfer of water encompassing areas which have potential for economic growth competing with other areas already highly developed economically. The wisest political decisions and the greatest benefit to the public will result if a method is used to explore the probable consequences of alternative water resources development and management policies and plans. The objective of this study is to extend the capability of systems analysis and operations research to the problem of interregional planning of water resources allocation for the State of Utah. The hydrologic characteristics and cost of water in each of the ten hydrologic study units of the state were determined. Hydrolgoci data from hydrologic inventories and estimates from the Utah Division of Water Resources were used to determine availability, reservoir storage-draft relationships, evaporation loss from reservoirs, agricultural use return flow, and municipal and industrial use return flow. Cost data were developed for storage facilities, diversion and canal works, artificial recharge facilties, treatment of waste water, and treatment of municipal supply. Supply functions for water in each of the ten hydrologic study units of the state were determined. Two sets of functions were developed--one for agricultural use and one for municipal and industrical use. Parametric linear programming was employed to develop a function map of the shadow price (marginal cost) of water for each of the two uses. The shadow price of imported water (value) to each of the study units was also determined to show the possible economic consequences of inter-basin transfers. In general, imported water was of little or no value if water presently being evaporated from Great Salt Lake is available for diversion upstream. A statewide model was developed to determine a least-cost allocation of water resources to meet projected requirements. This linear programming allocation model was developed subject to constraints such as hydrologic characteristics, limits on inter-basin transfers, limits on artificial groundwater recharge, and existing water requirements. Parametric programming was utilized to determine the impact of changing availability which reflects policies regarding inflow requirements of the Great Salt Lake and interstate agreemetns, increased agricultural use and municiapl and industrical use which reflects population increases projected for the future and changing groundwater availability which reflects legal constraints. The primary facotr affecting inter-basin transfer of Colorado River water is the degree to which evaporation from Great Salt Lake is reduced

    Adenosine Triphosphate and Carbon Efficient Route to Second Generation Biofuel Isopentanol.

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    Climate change necessitates the development of CO2 neutral or negative routes to chemicals currently produced from fossil carbon. In this paper we demonstrate a pathway from the renewable resource glucose to next generation biofuel isopentanol by pairing the isovaleryl-CoA biosynthesis pathway from Myxococcus xanthus and a butyryl-CoA reductase from Clostridium acetobutylicum. The best plasmid and Escherichia coli strain combination makes 80.50 ± 8.08 (SD) mg/L of isopentanol after 36 h under microaerobic conditions with an oleyl alcohol overlay. In addition, the system also shows a strong preference for isopentanol production over prenol in microaerobic conditions. Finally, the pathway requires zero adenosine triphosphate and can be paired theoretically with nonoxidative glycolysis, the combination being redox balanced from glucose thus avoiding unnecessary carbon loss as CO2. These pathway properties make the isovaleryl-CoA pathway an attractive isopentanol production route for further optimization
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