286 research outputs found
An Application and Defense of Ronald Dworkin\u27s Theory of Adjudication
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 “hard cases.” 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’s 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’s distinction between genuine and unconstrained interpretation. In this thesis, I apply Dworkin’s theory of legal interpretation to a “hard case,” 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.
Dissertação de mestrado em Biologia Celular e Molecular, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.A doença de Alzheimer (DA) é uma doença neurodegenerativa associada ao
envelhecimento e caracterizada por uma deterioração progressiva da memória e de
outras funções cognitivas. As características neuropatológicas desta doença incluem
perda sináptica e neuronal, acumulação extracelular de péptidos beta-amilóide (Aβ),
nas placas amilóides, e agregação de tau hiperfosforilada formando emaranhados
neurofibrilares intracelulares. Vários estudos sugerem que na DA a neurogénese no
hipocampo está alterada, contribuindo para os défices cognitivos ligados à
neurodegenerescência que ocorre nesta doença. A neurogénese adulta é um processo
através do qual as células estaminais neurais (CENs) têm capacidade de gerar novos
neurónios no cérebro mamífero pós-natal. A neurogénese ocorre em microambientes
especializados chamados nichos neurogénicos, onde a vasculatura desempenha um
papel importante no funcionamento das CENs. De acordo com descobertas recentes,
na DA existe uma associação entre disfunção cerebrovascular, défice cognitivo e
neurodegenerescência. Resultados anteriores do nosso grupo de investigação
demonstram uma diminuição na neurogénese no giro dentado (GD) do hipocampo de
ratinhos machos triplo transgénicos para a DA (3xTg-AD) com 3 meses de idade.
A nossa hipótese de trabalho considera que a disfunção vascular precoce na DA pode
contribuir para a deterioração observada na neurogénese. Para investigar esta hipótese
caracterizamos a vasculatura no GD de ratinhos 3xTg-AD com 3 meses de idade e
analisámos a relação entre os vasos sanguíneos e as CENs. Os nossos resultados
mostram um decréscimo no volume e na complexidade da vasculatura, dada pela
redução no número de ramificações e junções ao longo dos vasos sanguíneos. Além
disso, observámos a perda de funcionalidade e integridade dos vasos sanguíneos no
GD. Finalmente, um aumento na proximidade de CENS aos vasos sanguíneos foi
observado na camada molecular (CM) do GD. Todos os resultados obtidos suportam a
ocorrência de alterações precoces na vasculatura do GD de ratinhos 3xTg-AD e a
existência de uma estreita relação entre as CENs e os vasos sanguíneos na DA. Os
dados apoiam um possível papel dos vasos sanguíneos na redução da neurogénese
observada no modelo de ratinho da DA usado. Estes resultados podem assim trazer novas perspetivas no que diz respeito ao
envolvimento das alterações cerebrovasculares na redução da neurogénese que é
observada na DA.Alzheimer’s 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 (Aβ) 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
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
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 2
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
ppm in 30 minute bins for WASP-85-Ab---a factor of 4 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 ppm precision for a 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
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
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
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
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
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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