123 research outputs found

    Hyperbranched polymer stars with Gaussian chain statistics revisited

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    Conformational properties of regular dendrimers and more general hyperbranched polymer stars with Gaussian statistics for the spacer chains between branching points are revisited numerically. We investigate the scaling for asymptotically long chains especially for fractal dimensions df=3d_f = 3 (marginally compact) and df=2.5d_f = 2.5 (diffusion limited aggregation). Power-law stars obtained by imposing the number of additional arms per generation are compared to truly self-similar stars. We discuss effects of weak excluded volume interactions and sketch the regime where the Gaussian approximation should hold in dense solutions and melts for sufficiently large spacer chains.Comment: 13 pages, 14 figure

    Legal Institutions for the Allocation of Water and Their Impact on Coal Conversion Operations in Kentucky

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    The conversion of coal into other types of fuel through gasification and liquefaction has been proposed as a means of coping with America\u27s increasing energy needs. Coal conversion plants require large quantities of water for cooling purposes and for use as a raw material. There are three types of water allocation presently used in the United States, riparianism, prior appropriation, and administrative permit systems. The common law riparian system is undesirable because under it water rights are insecure and subject to locational use restrictions. Prior appropriation is better, but the permanent water right created under this system results in excessive rigidity. A system of administrative regulation by means of a consumptive use permit system offers the best allocation framework for both coal conversion facilities and other water users as well. Kentucky presently has such a system of administrative allocation. However, this legislation could be improved by (1) clarifying the planning functions of the Department for Natural Resources and Environmental Protection and the Water Resources Authority; (2) expanding the scope of the consumptive use permit system by removing most of the exempted use categories; (3) adopting beneficial use as the basis upon which consumptive use permits will be granted; (4) imposing a durational limit on water use permits and delineating renewal procedures; (5) adopting a scheme for both voluntary and involuntary transfers of water rights; and (6) specifying more explicit provision for dealing with temporary water shortages. Finally, it should be noted that the federal government has an important role with respect to navigation, water resources development, and water pollution control. Federal powers in these areas may impose some constraints on state allocation policies, although major conflicts can be avoided if proper coordination among state and federal officials is maintained

    Causal inference in generalizable environments: systematic representative design

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    Causal inference and generalizability both matter. Historically, systematic designs emphasize causal inference, while representative designs focus on generalizability. Here, we suggest a transformative synthesis – Systematic Representative Design (SRD) – concurrently enhancing both causal inference and “built-in” generalizability by leveraging today’s intelligent agent, virtual environments, and other technologies. In SRD, a “default control group” (DCG) can be created in a virtual environment by representatively sampling from real-world situations. Experimental groups can be built with systematic manipulations onto the DCG base. Applying systematic design features (e.g., random assignment to DCG versus experimental groups) in SRD affords valid causal inferences. After explicating the proposed SRD synthesis, we delineate how the approach concurrently advances generalizability and robustness, cause-effect inference and precision science, a computationally-enabled cumulative psychological science supporting both “bigger theory” and concrete implementations grappling with tough questions (e.g., what is context?) and affording rapidly-scalable interventions for real-world problems

    Internal medicine residency training for unhealthy alcohol and other drug use: recommendations for curriculum design

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    <p>Abstract</p> <p>Background</p> <p>Unhealthy substance use is the spectrum from use that risks harm, to use associated with problems, to the diagnosable conditions of substance abuse and dependence, often referred to as substance abuse disorders. Despite the prevalence and impact of unhealthy substance use, medical education in this area remains lacking, not providing physicians with the necessary expertise to effectively address one of the most common and costly health conditions. Medical educators have begun to address the need for physician training in unhealthy substance use, and formal curricula have been developed and evaluated, though broad integration into busy residency curricula remains a challenge.</p> <p>Discussion</p> <p>We review the development of unhealthy substance use related competencies, and describe a curriculum in unhealthy substance use that integrates these competencies into internal medicine resident physician training. We outline strategies to facilitate adoption of such curricula by the residency programs. This paper provides an outline for the actual implementation of the curriculum within the structure of a training program, with examples using common teaching venues. We describe and link the content to the core competencies mandated by the Accreditation Council for Graduate Medical Education, the formal accrediting body for residency training programs in the United States. Specific topics are recommended, with suggestions on how to integrate such teaching into existing internal medicine residency training program curricula.</p> <p>Summary</p> <p>Given the burden of disease and effective interventions available that can be delivered by internal medicine physicians, teaching about unhealthy substance use must be incorporated into internal medicine residency training, and can be done within existing teaching venues.</p
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