15,699 research outputs found

    Ecology and Equity in Rights to Land and Water: A Study in South-Eastern Palakkad in Kerala

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    This article explores the impact of the existing property rights regime over land and water on the sustainable and equitable management and use of these resources, in the context of changing irrigation practices in a paddy-growing area in the south-eastern part of the Palakkad district in Kerala, India. Since land rights determine rights to water in the area, the article discusses the changing rights regime over land, primarily after the implementation of land reforms in 1970. It shows how the implementation of land reforms and nationalization of private forests have paid little attention to the ecological context in which redistribution was taking place. As a result, while an agricultural-cum- forested landscape was divided into privately owned and government owned parcels, the ecological relationships between these different land use categories were ignored. In the same vein, land and water were treated as separate entities, with redistribution of land rights overlooking the distribution of water rights. The compartmentalized view of resources coupled with the consolidation of the private property regime has resulted in a situation where landowners exploit the resource without any consideration for its ecological characteristics and inter-resource linkages. The failure to view land and water in integration has precipitated inequitable access and unsustainable use of water. In addition, the availability of external water supplies and the introduction of energised pumping facilitate the enclosure of water within privately owned land parcels. The article concludes that a re-envisioning of rights to resources within the concerned ecological context is necessary if sustainable and equitable resource use and management are to be achieve

    Mitochondrial Molecular Adaptations and Life History Strategies Coevolve in Plants

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    Messenger RNA secondary structure prevents mutations at functionally important sites. Mutations at exposed sites would cause micro-adaptations, niche-specialization, and therefore, can be thought to promote K-strategists. Exposing, rather than protecting, conserved sites, is also potentially adaptive because they probably promote macro-adaptive changes. This presumably fits r-strategists: their population dynamics tolerate decreased survival. We found that helix-forming tendencies are greater at evolutionary conserved sites of plant mitochondrial mRNAs than at evolutionary variable sites in a majority (73%) of species–gene combinations. K-strategists preferentially protect conserved sites in short genes, r-strategists protect them most in larger genes. This adaptive scenario resembles our earlier findings in chloroplast genes. Protection levels at various codon positions also display disparity with respect to life history strategies of the plants. Conserved site protection increases overall mRNA folding stabilities for some genes, while decreases it for some others. This contrast exists between homologous genes of r- and K- strategists. Such compensating interactions between variability, mRNA size, codon position, and secondary structure factors within r- and K-strategists are most likely, molecular adaptations of plants belonging to the two extreme life history strategies. Our results suggest coevolution between molecular and ecological adaptive strategies

    Gene amplifications associated with the development of hormone- resistant prostate cancer

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    Purpose: Hormone resistance remains a significant clinical problem in prostate cancer with few therapeutic options. Research into mechanisms of hormone resistance is essential. Experimental Design: We analyzed 38 paired (prehormone/posthormone resistance) prostate cancer samples using the Vysis GenoSensor. Archival microdissected tumor DNA was extracted, amplified, labeled, and hybridized to Amplione I DNA microarrays containing 57 oncogenes. Results: Genetic instability increased during progression from hormone-sensitive to hormone-resistant cancer (P = 0.008). Amplification frequencies of 15 genes (TERC, MYBL3, HRAS, PI3KCA, JUNB, LAMC2, RAF1, MYC, GARP, SAS, FGFR1, PGY1, MYCL1, MYB, FGR) increased by greater than 10% during hormone escape. Receptor tyrosine kinases were amplified in 73% of cases; this was unrelated to development of hormone resistance. However, downstream receptor tyrosine kinase signaling pathways showed increased amplification rates in resistant tumors for the mitogen-activated protein kinase (FGR/Src-2, HRAS, and RAF1; P = 0.005) and phosphatidylinositol 3'-kinase pathways (FGR/ Src-2, PI3K, and Akt; P = 0.046). Transcription factors regulated by these pathways were also more frequently amplified after escape (MYC family: 21% before versus 63% after, P = 0.027; MYB family: 26 % before versus 53 % after, P = 0.18). Conclusions: Development of clinical hormone escape is linked to phosphatidylinositol 3'-kinase and mitogen-activated protein kinase pathways. These pathways may function independently of the androgen receptor or via androgen receptor activation by phosphorylation, providing novel therapeutic targets

    Swift Pointing and Gravitational-Wave Bursts from Gamma-Ray Burst Events

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    The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar-mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. This requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gamma-ray bursts depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based ``figure of merit'' that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts.Comment: iop style, 1 figure, 6 pages, presented at GWDAW 200

    The EM Algorithm

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    The Expectation-Maximization (EM) algorithm is a broadly applicable approach to the iterative computation of maximum likelihood (ML) estimates, useful in a variety of incomplete-data problems. Maximum likelihood estimation and likelihood-based inference are of central importance in statistical theory and data analysis. Maximum likelihood estimation is a general-purpose method with attractive properties. It is the most-often used estimation technique in the frequentist framework; it is also relevant in the Bayesian framework (Chapter III.11). Often Bayesian solutions are justified with the help of likelihoods and maximum likelihood estimates (MLE), and Bayesian solutions are similar to penalized likelihood estimates. Maximum likelihood estimation is an ubiquitous technique and is used extensively in every area where statistical techniques are used. --
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