230 research outputs found
Defenses in Dispute: The Bureaucratic and Domestic Politics of the First Anti-Ballistic Missile Debate
Since the dawn of the missile age in the mid-1940s, policymakers have grappled with the question of whether and how to defend against ballistic missiles. The saga of the rise of the United States’ first anti-ballistic missile system, known initially as Sentinel and later as Safeguard, and its subsequent demise after the signing of the Anti-Ballistic Missile Treaty in 1972, has been well cataloged by historians and strategic thinkers. Although many scholars present the story of this ABM system as the logical and inexorable consequence of the acceptance of deterrence theory and mutual vulnerability by the U.S and the Soviet Union, I argue it was instead the product of a remarkably dynamic and contingent process. The combination of intense interagency and intercabinet debates on ABM, synthesized with the peculiar domestic politics of the arms race, help explain this complex story. Examining disputes within the executive branch in the context of foreign policy and domestic politics can help shed light on this process and how this resolution came about, making extensive use of publicly available and declassified documents
Late Light Curves of Normal Type Ia Supernovae
We present late-epoch optical photometry (BVRI) of seven
normal/super-luminous Type Ia supernovae: SN 2000E, SN 2000ce, SN 2000cx, SN
2001C, SN 2001V, SN 2001bg, SN 2001dp. The photometry of these objects was
obtained using a template subtraction method to eliminate galaxy light
contamination during aperture photometry. We show the optical light curves of
these supernovae out to epochs of up to ~640 days after the explosion of the
supernova. We show a linear decline in these data during the epoch of 200-500
days after explosion with the decline rate in the B,V,& R bands equal to about
1.4 mag/100 days, but the decline rate of the I-band is much shallower at 0.94
mag/100 days.Comment: 33 pages, 11 figures, Accepted for publication in The Astronomical
Journa
Late Light Curves of Normally-Luminous Type Ia Supernovae
The use of Type Ia supernovae as cosmological tools has reinforced the need
to better understand these objects and their light curves. The light curves of
Type Ia supernovae are powered by the nuclear decay of . The late time light curves can provide insight into the behavior of
the decay products and their effect of the shape of the curves. We present the
optical light curves of six "normal" Type Ia supernovae, obtained at late times
with template image subtraction, and the fits of these light curves to
supernova energy deposition models.Comment: Proceedings of Astronomy with Radioactivities V Conferenc
Anatomic and molecular characterization of the 1 endocrine pancreas of a teleostean fish: Atlantic wolffish (Anarhichas lupus)
Background: The biologic attributes of the endocrine pancreas and the comparative endocrinology of islet
amyloid polypeptide (IAPP) of fish are not well described in the literature. This study describes the endocrine
pancreas of one teleostean fish. Ten captive Atlantic wolffish (Anarhichas lupus) from the Montreal Biodome were
submitted for necropsy and their pancreata were collected.
Results: Grossly, all the fish pancreata examined contained 1-3 nodules of variable diameter (1-8 mm). Microscopically, the
nodules were uniform, highly cellular, and composed of polygonal to elongated cells. Immunofluorescence for pancreatic
hormones was performed. The nodules were immunoreactive for insulin most prominent centrally, but with IAPP and
glucagon only in the periphery of the nodules. Exocrine pancreas was positive for chromogranin A. Not previously
recognized in fish, IAPP immunoreactivity occurred in α, glucagon-containing, cells and did not co-localize with insulin in
β cells. The islet tissues were devoid of amyloid deposits. IAPP DNA sequencing was performed to compare the sequence
among teleost fish and the potency to form amyloid fibrils. In silico analysis of the amino acid sequences 19-34 revealed
that it was not amyloidogenic.
Conclusions: Amyloidosis of pancreatic islets would not be expected as a spontaneous disease in the Atlantic wolffish. Our
study underlines that this teleost fish is a potential candidate for pancreatic xenograft research
Estimating Animal Abundance Using Noninvasive DNA Sampling: Promise and Pitfalls
Advances in molecular biology offer promise to the study of demographic characteristics of rare or hard-re-capture species, because individuals can now be identified through noninvasive sampling such as fecal collection or hair snags. However, individual genotyping using such methods currently leads to a novel problem that we call a shadow effect, because some animals not captured previously are believed to be recaptures due to their DNA profile being an indistinguishable shadow of previously captured animals. We evaluate the impact of the shadow effect on the two methods most commonly used in applied population ecology to estimate the size of closed populations: Lincoln-Petersen and multiple-recapture estimators in program CAPTURE. We find that the shadow effect can cause a negative bias in the estimates of both the number of different animals and the number of different genotypes. Furthermore, with Lincoln-Petersen estimators, the shadow effect can cause estimated confidence intervals to decrease even as bias increases. Because the bias arises from heterogeneity in apparent capture probabilities for animals with genetic shadows vs. those without, a model in program CAPTURE that is robust to capture heterogeneity (Mh-jackknife) does not underestimate the number of genotypes in the population and only slightly underestimates the rotal number of individuals As the shadow effect increases, CAPTURE is better able to correctly identify heterogeneity in capture probability and to pick Mh-jackknife, so that the higher levels of shadow effect have less bias than medium levels. The shadow effect will occur in all estimates of demographic rates (including survival) that use DNA sampling to determine individual identity, but it can be minimized by increasing the number of individual loci sampled
A circle map in a human heart
A circle is divided into two regions, a black one and a white one. Successive iterates of an invertible nonlinear circle map generate a symbolic string indicating whether each iterate is in the black or white region. A number of remarkable properties of the symbolic sequences are described. These properties were previously described for a linear circle map corresponding to a rigid rotation in the "gaps and steps" problem. These results have direct application to a cardiac arrhythmia, parasystole, that results from the competition between two pacemakers in the heart, one in the sinus mode and the other in the ventricles. The theoretical results are directly applicable to a clinical case of a young man who had frequent extra heartbeats
Designing all-graphene nanojunctions by covalent functionalization
We investigated theoretically the effect of covalent edge functionalization,
with organic functional groups, on the electronic properties of graphene
nanostructures and nano-junctions. Our analysis shows that functionalization
can be designed to tune electron affinities and ionization potentials of
graphene flakes, and to control the energy alignment of frontier orbitals in
nanometer-wide graphene junctions. The stability of the proposed mechanism is
discussed with respect to the functional groups, their number as well as the
width of graphene nanostructures. The results of our work indicate that
different level alignments can be obtained and engineered in order to realize
stable all-graphene nanodevices
Effective stress analysis and set-up for shaft capacity of piles in clay
ABSTRACT A case history of repeated dynamic and static loading tests in Alberta on two pipe piles during dissipation of driving-induced pore pressures is presented together with three reanalyzed published case histories involving similar records. The four case histories demonstrate that, for each case, the same effective-stress proportionality coefficients, beta-coefficients, fit the capacities at different degrees of dissipation of excess pore pressures. For two of the test sites, the beta-coefficients back-calculated from the tests differed considerable from the values determined from the soil plasticity relation, while for two, the agreement is good. For one case, the backcalculated shaft resistance agreed well with the values of vane shear strength, while a less good agreement was found for the other tests. Neither case showed good agreement was found for methods combining undrained shear strength and effective overburden stress. Capacity calculations for two cases employing methods based on CPT soundings gave excellent agreement with one test and a poor agreement with the other. The increase of capacity due to aging after dissipation of excess pore pressures did not agree with cited recommendation for calculations of aging effect
Study of the cap structure of (3, 3),(4, 4) and (5, 5)-SWCNTs: Application of the sphere-in-contact model
We have applied the sphere-in-contact model supported by hybrid Density Functional Theory (DFT) calculations to elucidate the cap geometry of the sub-nanometer in dimension (3,3), (4,4) and (5,5) single-wall carbon-nanotubes (SWCNTs). Our approach predicts certain cap-geometries that do not comprise of the commonly known for their stability combination of pentagonal and hexagonal carbon rings but also tetragonal, trigonal and all-pentagonal structures. Based on hybrid-DFT calculations carbon atoms in these new cap geometries have similar stability to carbon found in other fullerene-like capped zig-zag and arm-chair nanotubes (i.e., (5,5), (6,6), (9,0) and (10,0)) that are known to be stable and synthetically accessible. We find that the cap structure of the (3,3)-CNTs is a pointy carbon geometry comprised of six pentagonal rings with a single carbon atom at the tip apex. In this tip geometry the carbon atom at the tip apex does not have the usual sp2 or sp3 geometry but an unusual trigonal pyramidal configuration. DFT calculations of the molecular orbitals and density-of-states of the tip show that this tip structure apart from being stable can be used in scanning probe microscopies such as STM for very high resolution imaging
Influence de la concentration sérique de CA 15-3 sur les performances diagnostiques de la TEP FDG chez des patientes ayant un cancer du sein avec imagerie négative
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