874 research outputs found
Bank Charge Cards: New Cash or New Credit
It is the premise of this Article that the bank charge card systems constitute a new, highly useful, and efficient payment and credit mechanism; that any decision-making body that promulgates a rule on the issue of the assertability of consumer defenses must carefully evaluate the true functions of bank charge cards, particularly their role as part of a sophisticated payment mechanism, and weigh the relative interests of the consuming public, merchants, and members of the banking industry to derive the best solution for society; that courts are ill-equipped to perform this function; and, that, given the national and international usage of bank charge cards, a uniform rule is imperative. The Article will first analyze each of these premises and then proceed to suggest a rule that seems effectively to balance the various interests involved
Getting the phase consistent: The importance of phase description in balanced steady-state free precession MRI of multicompartment systems
Purpose: Determine the correct mathematical phase description for balanced
steady-state free precession (bSSFP) signals in multicompartment systems.
Theory and Methods: Based on published bSSFP signal models, two distinct phase
descriptions can be formulated: one predicting the presence and the other
predicting the absence of destructive interference effects in multicompartment
systems. Numerical simulations of bSSFP signals of water and acetone were
performed to evaluate the predictions of these two distinct phase descriptions.
For experimental validation, bSSFP profiles were measured at 3T using
phase-cycled bSSFP acquisitions performed in a phantom containing mixtures of
water and acetone, which replicates a system with two signal components.
Localized single voxel MRS was performed at 7T to determine the relative
chemical-shift of the acetone-water mixtures. Results: Based on the choice of
phase description, the simulated bSSFP profiles of water-acetone mixtures
varied significantly, either displaying or lacking destructive interference
effects, as predicted theoretically. In phantom experiments, destructive
interference was consistently observed in the measured bSSFP profiles of
water-acetone mixtures, an observation which excludes the phase description
that predicts an absence of destructive interference. The connection between
the choice of phase description and predicted observation enables an
unambiguous experimental identification of the correct phase description for
multicompartment bSSFP profiles, which is consistent with Bloch equations.
Conclusion: The study emphasizes that consistent phase descriptions are crucial
for accurately describing multi-compartment bSSFP signals, as incorrect phase
descriptions result in erroneous predictions.Comment: Submitted to Magn. Reson. Me
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Evaluating relocation extent versus covariate resolution in habitat selection models across spatiotemporal scales
Many habitat selection studies have focused on the importance of spatiotemporal scales and sample size, yet often hidden within is a trade-off between using more animal locations versus more predictive covariates. Few have evaluated the outcome of choosing between these two different paths even though the trade-off can have significant impacts on the conclusions drawn from habitat modeling. We evaluated the covariate resolution versus relocation trade-off across multiple spatiotemporal scales by building habitat selection models using a data-mining approach with 22 years of VHF collar data from the Denali Caribou Herd. We asked whether caribou selected winter habitat based on forage resources after accounting for snow depth. Habitat selection models at three temporal scales (decadal, inter-annual and intra-annual) provide correlative evidence of active selection for winter forage. Based on model performance and predicted occupancy, we found that acquiring appropriate covariate layers is critical and likely even more important than using more animal locations. Based on analyses that utilized more covariates, caribou predominantly selected high graminoid cover, their second most important winter food, over areas with high lichen cover, their primary winter food, at all spatial scales implying a need to balance food quality and accessibility. However, habitat selection differed between temporal scales. Two years in a row, caribou switched to flatter areas with higher lichen cover and low shrub cover while intra-annual variation in habitat selection showed caribou congregated in areas of higher lichen cover and lower snow depths as winter progressed. We conclude that large patches of tussock tundra are high-use areas for wintering caribou in Denali at decadal scales while lichen-rich areas were used at inter-annual and intra-annual temporal scales. Lower snow levels in the future may allow heavier use of lichen woodlands but increased wildfire activity and shrub encroachment may counteract increased lichen availability in woodlands
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Patterns in the occupancy and abundance of the globally rare lichen Erioderma pedicellatum in Denali National Park and Preserve, Alaska
We investigated habitat attributes related to the occupancy of the globally rare and endangered
epiphytic lichen, Erioderma pedicellatum, in a newly discovered (2009) population center in Denali National
Park and Preserve (DNPP), Alaska. We measured forest, tree and epiphytic lichen community
characteristics on eighty-five systematically selected plots in four study areas. We aggregated these data
at three spatial scales (tree, plot and study area) at which to compare E. pedicellatum occupancy (probability
of occurrence) and abundance to environmental covariates. We observed 2,035 E. pedicellatum thalli on 278
individual Picea glauca stems. The species occurred in 61% of the plots measured. Occupancy of E.
pedicellatum at the individual tree-scale was influenced by stem diameter, study area, live crown length, plot
P. glauca basal area, plot canopy cover and distance to open water. Our models for E. pedicellatum
occupancy at the plot-scale identified study area, P. glauca density, deciduous basal area (Betula neoalaskana
and Populus trichocarpa), and tall shrub cover ($ 200 cm in height) as significant covariates. Our estimates
of the DNPP population size increase the world population by at least tenfold to approximately 100,000
thalli. We suggest important topics for further research on E. pedicellatum.Keywords: Cyanolichens, Boreal forest, Pannariaceae, Habitat model, Logistic regressio
Weather-driven change in primary productivity explains variation in the amplitude of two herbivore population cycles in a boreal system
Vertebrate populations throughout the circumpolar north often exhibit cyclic dynamics, and predation is generally considered to be a primary driver of these cycles in a variety of herbivore species. However, weather and climate play a role in entraining cycles over broad landscapes and may alter cyclic dynamics, although the mechanism by which these processes operate is uncertain. Experimental and observational work has suggested that weather influences primary productivity over multi-year time periods, suggesting a pathway through which weather and climate may influence cyclic herbivore dynamics. Using long-term monitoring data, we investigated the relationships among multi-year weather conditions, measures of primary productivity, and the abundance of two cyclic herbivore species: snowshoe hare and northern red-backed vole. We found that precipitation (rain and snow) and growing season temperatures were strongly associated with variation in primary productivity over multi-year time horizons. In turn, fourfold variation in the amplitude of both the hare and vole cycles observed in our study area corresponded to long-term changes in primary productivity. The congruence of our results for these two species suggests a general mechanism by which weather and climate might influence cyclic herbivore population dynamics. Our findings also suggested that the association between climate warming and the disappearance of cycles might be initiated by changes in primary productivity. This work provides an explanation for observed influences of weather and climate on primary productivity and population cycles and will help our collective understanding of how future climate warming may influence these ecological phenomena in the future.PostprintPeer reviewe
A second horizon scan of biogeography:golden ages, Midas touches, and the Red Queen
Are we entering a new ‘Golden Age’ of biogeography, with continued development of infrastructure
and ideas? We highlight recent developments, and the challenges and opportunities they bring, in
light of the snapshot provided by the 7th biennial meeting of the International Biogeography Society
(IBS 2015). We summarize themes in and across 15 symposia using narrative analysis and word
clouds, which we complement with recent publication trends and ‘research fronts’. We find that
biogeography is still strongly defined by core sub-disciplines that reflect its origins in botanical,
zoological (particularly bird and mammal), and geographic (e.g., island, montane) studies of the
1800s. That core is being enriched by large datasets (e.g. of environmental variables, ‘omics’,
species’ occurrences, traits) and new techniques (e.g., advances in genetics, remote sensing,
modeling) that promote studies with increasing detail and at increasing scales; disciplinary
breadth is being diversified (e.g., by developments in paleobiogeography and microbiology) and
integrated through the transfer of approaches and sharing of theory (e.g., spatial modeling and
phylogenetics in evolutionary–ecological contexts). Yet some subdisciplines remain on the fringe
(e.g., marine biogeography, deep-time paleobiogeography), new horizons and new theory may be
overshadowed by popular techniques (e.g., species distribution modelling), and hypotheses, data,
and analyses may each be wanting. Trends in publication suggest a shift away from traditional
biogeography journals to multidisciplinary or open access journals. Thus, there are currently many stewardship of, the planet (e.g., Intergovernmental Science-Policy Platform on Biodiversity and
Ecosystem Services). As in the past, biogeographers doubtless will continue to be engaged by
new data and methods in exploring the nexus between biology and geography for decades into
the future. But golden ages come and go, and they need not touch every domain in a discipline
nor affect subdisciplines at the same time; moreover, what appears to be a Golden Age may
sometimes have an undesirable ‘Midas touch’. Contexts within and outwith biogeography—e.g.,
methods, knowledge, climate, biodiversity, politics—are continually changing, and at times it can
be challenging to establish or maintain relevance. In so many races with the Red Queen, we
suggest that biogeography will enjoy greatest success if we also increasingly engage with the
epistemology of our disciplinePeer reviewe
Cytoplasmic keratins couple with and maintain nuclear envelope integrity in colonic epithelial cells
Keratin intermediate filaments convey mechanical stability and protection against stress to epithelial cells. Keratins are essential for colon health, as seen in keratin 8 knockout (K8−/−) mice exhibiting a colitis phenotype. We hypothesized that keratins support the nuclear envelope and lamina in colonocytes. K8−/− colonocytes in vivo exhibit significantly decreased levels of lamins A/C, B1, and B2 in a colon-specific and cell-intrinsic manner. CRISPR/Cas9- or siRNA-mediated K8 knockdown in Caco-2 cells similarly decreased lamin levels, which recovered after reexpression of K8 following siRNA treatment. Nuclear area was not decreased, and roundness was only marginally increased in cells without K8. Down-regulation of K8 in adult K8flox/flox;Villin-CreERt2 mice following tamoxifen administration significantly decreased lamin levels at day 4 when K8 levels had reduced to 40%. K8 loss also led to reduced levels of plectin, LINC complex, and lamin-associated proteins. While keratins were not seen in the nucleoplasm without or with leptomycin B treatment, keratins were found intimately located at the nuclear envelope and complexed with SUN2 and lamin A. Furthermore, K8 loss in Caco-2 cells compromised nuclear membrane integrity basally and after shear stress. In conclusion, colonocyte K8 helps maintain nuclear envelope and lamina composition and contributes to nuclear integrity.</p
Microstructural Evolution in Thin Films of Electronic Materials
Contains reports on five research projects and a list of publications and theses.Joint Services Electronics Program Contract DAAL03-89-C-0001Semiconductor Research CorporationNational Science FoundationU.S. Army Research OfficeHitachi LimitedIBM Corporatio
Development of a Highly Selective Plasmodium falciparum Proteasome Inhibitor with Anti-malaria Activity in Humanized Mice.
Plasmodium falciparum proteasome (Pf20S) inhibitors are active against Plasmodium at multiple stages-erythrocytic, gametocyte, liver, and gamete activation stages-indicating that selective Pf20S inhibitors possess the potential to be therapeutic, prophylactic, and transmission-blocking antimalarials. Starting from a reported compound, we developed a noncovalent, macrocyclic peptide inhibitor of the malarial proteasome with high species selectivity and improved pharmacokinetic properties. The compound demonstrates specific, time-dependent inhibition of the β5 subunit of the Pf20S, kills artemisinin-sensitive and artemisinin-resistant P. falciparum isolates in vitro and reduces parasitemia in humanized, P. falciparum-infected mice
Antimalarial proteasome inhibitor reveals collateral sensitivity from intersubunit interactions and fitness cost of resistance.
We describe noncovalent, reversible asparagine ethylenediamine (AsnEDA) inhibitors of the Plasmodium falciparum proteasome (Pf20S) β5 subunit that spare all active subunits of human constitutive and immuno-proteasomes. The compounds are active against erythrocytic, sexual, and liver-stage parasites, against parasites resistant to current antimalarials, and against P. falciparum strains from patients in Africa. The β5 inhibitors synergize with a β2 inhibitor in vitro and in mice and with artemisinin. P. falciparum selected for resistance to an AsnEDA β5 inhibitor surprisingly harbored a point mutation in the noncatalytic β6 subunit. The β6 mutant was resistant to the species-selective Pf20S β5 inhibitor but remained sensitive to the species-nonselective β5 inhibitors bortezomib and carfilzomib. Moreover, resistance to the Pf20S β5 inhibitor was accompanied by increased sensitivity to a Pf20S β2 inhibitor. Finally, the β5 inhibitor-resistant mutant had a fitness cost that was exacerbated by irradiation. Thus, used in combination, multistage-active inhibitors of the Pf20S β5 and β2 subunits afford synergistic antimalarial activity with a potential to delay the emergence of resistance to artemisinins and each other
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