279 research outputs found

    An Application and Defense of Ronald Dworkin\u27s Theory of Adjudication

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    Laws are intended to put individuals on notice as to how they should act in society and what behavior they may expect from others. But what happens when the text of a law is vague and open to multiple interpretations? How can individuals be expected to conform to laws when the laws are unclear as to what they demand? If the law is to retain legitimacy, there must be a principled way of determining what the law requires in these so-called ‚Äúhard cases.‚ÄĚ Ronald Dworkin argues that if interpretation is not constrained, adjudicators are creating the law rather than simply interpreting it. He believes that such a constraint lies in considerations of coherence that will limit the range of plausible interpretations available for any given law. According to Dworkin, a good interpretation is one that both explains the settled legal materials and coheres with the political morality embedded in those materials. He believes that those constraints will result in one correct interpretation that best fulfills these requirements. Dworkin‚Äôs critics, however, argue that because the settled law has been composed by various individuals with differing goals and ideological convictions, any notion of constraint is illusory. They contend that those interpreting the law may choose among competing interpretations while relying on personal, extra-legal considerations in doing so. According to J.M. Balkin, this undermines Dworkin‚Äôs distinction between genuine and unconstrained interpretation. In this thesis, I apply Dworkin‚Äôs theory of legal interpretation to a ‚Äúhard case,‚ÄĚ and use this application to defend Dworkin and demonstrate the soundness of his characterization of legitimately constrained interpretation

    The levels of (accumulated) pesticides detected within honeybee comb wax.

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    Disserta√ß√£o de mestrado em Biologia Celular e Molecular, apresentada ao Departamento de Ci√™ncias da Vida da Faculdade de Ci√™ncias e Tecnologia da Universidade de Coimbra.A doen√ßa de Alzheimer (DA) √© uma doen√ßa neurodegenerativa associada ao envelhecimento e caracterizada por uma deteriora√ß√£o progressiva da mem√≥ria e de outras fun√ß√Ķes cognitivas. As caracter√≠sticas neuropatol√≥gicas desta doen√ßa incluem perda sin√°ptica e neuronal, acumula√ß√£o extracelular de p√©ptidos beta-amil√≥ide (Aő≤), nas placas amil√≥ides, e agrega√ß√£o de tau hiperfosforilada formando emaranhados neurofibrilares intracelulares. V√°rios estudos sugerem que na DA a neurog√©nese no hipocampo est√° alterada, contribuindo para os d√©fices cognitivos ligados √† neurodegeneresc√™ncia que ocorre nesta doen√ßa. A neurog√©nese adulta √© um processo atrav√©s do qual as c√©lulas estaminais neurais (CENs) t√™m capacidade de gerar novos neur√≥nios no c√©rebro mam√≠fero p√≥s-natal. A neurog√©nese ocorre em microambientes especializados chamados nichos neurog√©nicos, onde a vasculatura desempenha um papel importante no funcionamento das CENs. De acordo com descobertas recentes, na DA existe uma associa√ß√£o entre disfun√ß√£o cerebrovascular, d√©fice cognitivo e neurodegeneresc√™ncia. Resultados anteriores do nosso grupo de investiga√ß√£o demonstram uma diminui√ß√£o na neurog√©nese no giro dentado (GD) do hipocampo de ratinhos machos triplo transg√©nicos para a DA (3xTg-AD) com 3 meses de idade. A nossa hip√≥tese de trabalho considera que a disfun√ß√£o vascular precoce na DA pode contribuir para a deteriora√ß√£o observada na neurog√©nese. Para investigar esta hip√≥tese caracterizamos a vasculatura no GD de ratinhos 3xTg-AD com 3 meses de idade e analis√°mos a rela√ß√£o entre os vasos sangu√≠neos e as CENs. Os nossos resultados mostram um decr√©scimo no volume e na complexidade da vasculatura, dada pela redu√ß√£o no n√ļmero de ramifica√ß√Ķes e jun√ß√Ķes ao longo dos vasos sangu√≠neos. Al√©m disso, observ√°mos a perda de funcionalidade e integridade dos vasos sangu√≠neos no GD. Finalmente, um aumento na proximidade de CENS aos vasos sangu√≠neos foi observado na camada molecular (CM) do GD. Todos os resultados obtidos suportam a ocorr√™ncia de altera√ß√Ķes precoces na vasculatura do GD de ratinhos 3xTg-AD e a exist√™ncia de uma estreita rela√ß√£o entre as CENs e os vasos sangu√≠neos na DA. Os dados apoiam um poss√≠vel papel dos vasos sangu√≠neos na redu√ß√£o da neurog√©nese observada no modelo de ratinho da DA usado. Estes resultados podem assim trazer novas perspetivas no que diz respeito ao envolvimento das altera√ß√Ķes cerebrovasculares na redu√ß√£o da neurog√©nese que √© observada na DA.Alzheimer‚Äôs disease (AD) is an age-related neurodegenerative disease characterized by a progressive deterioration of memory and other cognitive functions. The neuropathological hallmarks of this disorder include synaptic and neuronal loss, extracellular accumulation of amyloid-beta (Aő≤) peptide in amyloid plaques and aggregation of hyperphosphorylated tau forming intracellular neurofibrillary tangles. Several findings suggest that impaired hippocampal neurogenesis may contribute to AD-related cognitive deficits linked to neurodegeneration. Adult neurogenesis is a process through which neural stem cells (NSCs) have the capacity to generate new neurons in the post-natal mammalian brain. Adult neurogenesis occurs within specialized microenvironments called neurogenic niches where vasculature plays an important role in NSCs fate. According to recent findings, there is an association between cerebrovascular dysfunction, cognitive deficit and neurodegeneration in AD. Previous results from our lab support a decrease in the neurogenesis occurring in the hippocampal dentate gyrus (DG) of 3 month-old triple transgenic (3xTg-AD) male mice. Therefore, we hypothesize that early AD-related vascular dysfunction may account for the observed impairment in neurogenesis. To explore this, we further characterize the vasculature in the DG of 3 month-old 3xTg-AD mice and analyze the relationship between blood vessels and NSCs. Our results show a decrease in the volume and complexity of the vasculature, given by a reduction in the number of branches and junctions per length of blood vessels. In addition, loss of functionality and integrity of blood vessels was also observed in this region. Furthermore, an increase in the proximity of stem cells processes to blood vessels was found in the molecular layer (ML) of DG. Taken together, these results support the occurrence of early alterations in the vasculature of the DG of 3xTg-AD mice and a close relationship between NSCs and blood vessels, which may play a role in reduced neurogenesis observed in this AD mouse model. These findings may bring new perspectives in the involvement of cerebrovascular changes in the neurogenesis impairment that occurs in AD

    Towards Space-like Photometric Precision from the Ground with Beam-Shaping Diffusers

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    We demonstrate a path to hitherto unachievable differential photometric precisions from the ground, both in the optical and near-infrared (NIR), using custom-fabricated beam-shaping diffusers produced using specialized nanofabrication techniques. Such diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. This PSF reshaping significantly increases the achievable dynamic range of our observations, increasing our observing efficiency and thus better averages over scintillation. Diffusers work in both collimated and converging beams. We present diffuser-assisted optical observations demonstrating 62‚ąí16+2662^{+26}_{-16}ppm precision in 30 minute bins on a nearby bright star 16-Cygni A (V=5.95) using the ARC 3.5m telescope---within a factor of ‚ąľ\sim2 of Kepler's photometric precision on the same star. We also show a transit of WASP-85-Ab (V=11.2) and TRES-3b (V=12.4), where the residuals bin down to 180‚ąí41+66180^{+66}_{-41}ppm in 30 minute bins for WASP-85-Ab---a factor of ‚ąľ\sim4 of the precision achieved by the K2 mission on this target---and to 101ppm for TRES-3b. In the NIR, where diffusers may provide even more significant improvements over the current state of the art, our preliminary tests have demonstrated 137‚ąí36+64137^{+64}_{-36}ppm precision for a KS=10.8K_S =10.8 star on the 200" Hale Telescope. These photometric precisions match or surpass the expected photometric precisions of TESS for the same magnitude range. This technology is inexpensive, scalable, easily adaptable, and can have an important and immediate impact on the observations of transits and secondary eclipses of exoplanets.Comment: Accepted for publication in ApJ. 30 pages, 20 figure

    Restoration of a Severely Impacted Riparian Wetland System - The Pen Branch Project

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    The Savannah River Swamp is a 3020 ha forested wetland on the floodplain of the Savannah River and is located on the Department of Energy’s Savannah River Site (SRS) near Aiken, SC (Fig. 1). Historically the swamp consisted ofapproximately 50% baldcypress-water tupelo stands, 40% mixed bottomland hardwood stands, and 10% shrub, marsh, and open water. Tributeries of the river were typical of Southeastern bottomland hardwood forests. The hydrology was controlled by flow from four creeks that drain into the swamp and by flooding of the Savannah River. Upstream dams on the Savannah River have caused some alteration of the water levels and timing of flooding within the floodplain(Schneider et al., 1989)

    Gene knockouts reveal separate functions for two cytoplasmic dyneins in Tetrahymena thermophila

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    In many organisms, there are multiple isoforms of cytoplasmic dynein heavy chains, and division of labor among the isoforms would provide a mechanism to regulate dynein function. The targeted disruption of somatic genes in Tetrahymena thermophila presents the opportunity to determine the contributions of individual dynein isoforms in a single cell that expresses multiple dynein heavy chain genes. Substantial portions of two Tetrahymena cytoplasmic dynein heavy chain genes were cloned, and their motor domains were sequenced. Tetrahymena DYH1 encodes the ubiquitous cytoplasmic dynein Dyh1, and DYH2 encodes a second cytoplasmic dynein isoform, Dyh2. The disruption of DYH1, but not DYH2, resulted in cells with two detectable defects: 1) phagocytic activity was inhibited, and 2) the cells failed to distribute their chromosomes correctly during micronuclear mitosis. In contrast, the disruption of DYH2 resulted in a loss of regulation of cell size and cell shape and in the apparent inability of the cells to repair their cortical cytoskeletons. We conclude that the two dyneins perform separate tasks in Tetrahymena

    Differences in the gas and dust distribution in the transitional disk of a sun-like young star, PDS 70

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    We present ALMA 0.87 mm continuum, HCO+ J=4--3 emission line, and CO J=3--2 emission line data of the disk of material around the young, Sun-like star PDS 70. These data reveal the existence of a possible two component transitional disk system with a radial dust gap of 0."2 +/- 0."05, an azimuthal gap in the HCO+ J=4--3 moment zero map, as well as two bridge-like features in the gas data. Interestingly these features in the gas disk have no analogue in the dust disk making them of particular interest. We modeled the dust disk using the Monte Carlo radiative transfer code HOCHUNK3D (Whitney et al. 2013) using a two disk components. We find that there is a radial gap that extends from 15-60 au in all grain sizes which differs from previous work

    Wavelength-Dependent Extinction and Grain Sizes in Dippers

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    We have examined inter-night variability of K2-discovered Dippers that are not close to being viewed edge-on, as determined from previously-reported ALMA images, using the SpeX spectrograph and the NASA Infrared Telescope facility (IRTF). The three objects observed were EPIC 203850058, EPIC 205151387, and EPIC 204638512 (2MASS J16042165-2130284). Using the ratio of the fluxes between two successive nights, we find that for EPIC 204638512 and EPIC 205151387, we find that the properties of the dust differ from that seen in the diffuse interstellar medium and denser molecular clouds. However, the grain properties needed to explain the extinction does resemble those used to model the disks of many young stellar objects. The wavelength-dependent extinction models of both EPIC 204638512 and EPIC 205151387 includes grains at least 500 microns in size, but lacks grains smaller than 0.25 microns. The change in extinction during the dips, and the timescale for these variations to occur, imply obscuration by the surface layers of the inner disks. The recent discovery of a highly mis-inclined inner disk in EPIC 204638512 is suggests that the variations in this disk system may point to due to rapid changes in obscuration by the surface layers of its inner disk, and that other face-on Dippers might have similar geometries. The He I line at 1.083 microns in EPIC 205151387 and EPIC 20463851 were seen to change from night to night, suggesting that we are seeing He I gas mixed in with the surface dust.Comment: 13 pages, 6 figures, 2 table

    Variability of Disk Emission in Pre-Main Sequence and Related Stars IV. Investigating the Structural Changes in the Inner Disk Region of MWC 480

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    We present five epochs of near IR observations of the protoplanetary disk around MWC 480 (HD31648) obtained with the SpeX spectrograph on NASA's Infrared Telescope Facility (IRTF) between 2007 and 2013, inclusive. Using the measured line fluxes in the Pa beta and Br gamma lines, we found the mass accretion rates to be (1.43 - 2.61)x10^-8 Msun y^-1 and (1.81 - 2.41)x10^-8 Msun y^-1 respectively, but which varied by more than 50% from epoch to epoch. The spectral energy distribution (SED)reveals a variability of about 30% between 1.5 and 10 microns during this same period of time. We investigated the variability using of the continuum emission of the disk in using the Monte-Carlo Radiative Transfer Code (MCRT) HOCHUNK3D. We find that varying the height of the inner rim successfully produces a change in the NIR flux, but lowers the far IR emission to levels below all measured fluxes. Because the star exhibits bipolar flows, we utilized a structure that simulates an inner disk wind to model the variability in the near IR, without producing flux levels in the far IR that are inconsistent with existing data. For this object, variable near IR emission due to such an outflow is more consistent with the data than changing the scale height of the inner rim of the disk.Comment: 19 pages, 14 figure
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