726 research outputs found

    Current problems in Stellar Pulsation Instabilities

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    Instabilities of pulsating variable stars, such as Cepheid variables, Cepheid masses, early-type variable stars, White Dwarfs, and Mira variables, are discussed

    Public Benefits of Undeveloped Lands on Urban Outskirts: Non-Market Valuation Studies and their Role in Land Use Plans

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    Over the past three decades, the economics profession has developed methods for estimating the public benefits of green spaces, providing an opportunity to incorporate such information into land-use planning. While federal regulations routinely require such estimates for major regulations, the extent to which they are used in local land use plans is not clear. This paper reviews the literature on public values for lands on urban outskirts, not just to survey their methods or empirical findings, but to evaluate the role they have played--or have the potential to play-- in actual land use plans. Based on interviews with authors and representatives of funding agencies and local land trusts, it appears that academic work has had a mixed reception in the policy world. Reasons for this include a lack of interest in making academic work accessible to policy makers, emphasizing revealed preference methods which are inconsistent with policy priorities related to nonuse values, and emphasis on benefit-cost analyses. Nevertheless, there are examples of success stories that illustrate how such information can play a vital role in the design of conservation policies. Working Paper 07-2

    Resolution of Biphasic Binding of the Opioid Antagonist Naltrexone in Brain Membranes

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    In synaptosomal membranes from rat brain cortex, in the presence of 150 m M NaC1, the opioid antagonist [ 3 H] naltrexone bound to two populations of receptor sites with affinities of 0.27 and 4.3 n M , respectively. Guanosine-5â€Č-(3-thiotriphosphate) had little modulating effect and did not alter the biphasic nature of ligand binding. On the other hand, receptor-selective opioids differentially inhibited the two binding components of [ 3 H] naltrexone. As shown by nonlinear least-squares analysis, the Μ opioids Tyr-D-Ala-Gly-(Me)Phe-Gly-ol or sufentanil abolished high-affinity [ 3 H] naltrexone binding, whereas the Δ-selective ligands [D- Pen 2 , D-Pen 5 ] enkephalin, ICI 174, 864, and oxymorphindole inhibited and eventually eliminated the low-affinity component in a concentration-dependent manner. These results indicate that, in contrast to the guanine nucleotide-sensitive biphasic binding of opioid-alkaloid agonists, the heterogeneity of naltrexone binding in brain membranes reflects ligand interaction with different opioid-receptor types.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66340/1/j.1471-4159.1991.tb08288.x.pd

    Diblock copolymers at a homopolymer-homopolymer-interface: a Monte Carlo simulation

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    The properties of diluted symmetric A-B diblock copolymers at the interface between A and B homopolymer phases are studied by means of Monte Carlo (MC) simulations of the bond fluctuation model. We calculate segment density profiles as well as orientational properties of segments, of A and B blocks, and of the whole chain. Our data support the picture of oriented ``dumbbells'', which consist of mildly perturbed A and B Gaussian coils. The results are compared to a self consistent field theory (SCFT) for single copolymer chains at a homopolymer interface. We also discuss the number of interaction contacts between monomers, which provide a measure for the ``active surface'' of copolymers or homopolymers close to the interface

    Why Are Regulations Changed? A Parcel Analysis of Upzoning in Los Angeles

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    Planners, officials, and neighborhood groups often debate zoning changes, yet there is little empirical evidence explaining why zoning and other land use regulations are changed. I use logistic regression models to examine density-enabling rezoning (“upzoning”) in Los Angeles. I find that upzoning occurs where there are development opportunities combined with limited political resistance. Upzoning is most likely on well-located parcels zoned for low-intensity, nonresidential uses. Meanwhile, homeowners—and particularly homeowners with access to valuable amenities—are associated with regulatory stasis. I conclude by recommending strategies for addressing homeowners’ concerns about higher density housing

    Pass a Law, Any Law, Fast! State Legislative Responses to the Kelo Backlash

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    The Supreme Court in Kelo v. City of New London left protection of property against takings for economic development to the states. Since Kelo, thirty-seven states have enacted legislation to update their eminent domain laws. This paper is the first to theoretically and empirically analyze the factors that influence whether, in what manner, and how quickly states change their laws through new legislation. Fourteen of the thirty-seven new laws offer only weak protections against development takings. The legislative response to Kelo was responsive to measures of the backlash but only in the binary decision whether to pass any new law. The decision to enact a meaningful restriction was more a function of relevant political economy measures. States with more economic freedom, greater value of new housing construction, and less racial and income inequality are more likely to have enacted stronger restrictions, and sooner. Of the thirteen states that have not updated, Arkansas, Oklahoma and Mississippi are highly likely to do so in the future. Hawaii, Massachusetts and New York are unlikely to update ever if at all

    Impact of clerkship in the attitudes toward psychiatry among Portuguese medical students

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    <p>Abstract</p> <p>Background</p> <p>Given the shortage of human resources and the launching of a new Mental Health Plan, recruitment of psychiatrists is currently a major concern in Portugal, as well as in several other countries. Medical students' attitude toward psychiatry has been pointed as a predictor of recruitment. This study aims to evaluate the medical students' perception of psychiatry before and after a clerkship, and the impact on their intention to pursue psychiatry as a future specialty option.</p> <p>Methods</p> <p>Two self-report questionnaires were administered to all 6<sup>th </sup>year students in a medical school in Lisbon, before and after a 4-weeks full-time psychiatric clerkship, in order to evaluate attitudes toward psychiatry and intention to follow psychiatry in the future. Statistical analysis included Wilcoxon and Chi-square tests.</p> <p>Results</p> <p>153 students (60.8% female) filled in both questionnaires (no dropouts). After the clerkship, there was a significant improvement regarding the overall merits of psychiatry, efficacy, role definition and functioning of psychiatrists, use of legal powers to hospitalize patients and specific medical school factors. There was also a significant increase of students decided or considering the possibility to take a residency in psychiatry.</p> <p>However, perceptions of low prestige and negative pressure from family and peers regarding a future choice of psychiatry remained unchanged in about one-third of the students.</p> <p>Conclusions</p> <p>The results indicate clearly that the clerkship had a favorable overall impact on the student attitude towards psychiatry, as well as in the number of students considering a future career in psychiatry. Attitudes toward psychiatry seems a promising outcome indicator of the clerkship's quality, but further research is needed in order to assess its reliability as a sound predictor of recruitment.</p

    What is 'Open'? An Economic Analysis of Open Institutions

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    By examining several different types of open institutions including open source software, open science, open square and (open) urban planning, this paper presents a general analysis of open institutional structure that is complementary to traditional proprietary mode. We argue that open institutions, in whatever forms, are essentially about decentralized production of a collective good (or “commons”) that relies on voluntary collaboration of highly variable human-related input. In addition to providing a general definition of open institutional structure, we submit there are two necessary conditions for open institutions. The first is the integration of consumers into production. The second condition is that the efficiency gain from “production” commons is the objective and the tragedy of anticommons becomes a serious problem. In this sense, open institutions represent a positive approach toward externality and uncertainty
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