303 research outputs found
E0 emission in alpha + ^12C fusion at astrophysical energies
We show that E0 emission in alpha + ^12C fusion at astrophysically
interesting energies is negligible compared to E1 and E2 emission.Comment: submitted to Phys. Rev. C, Brief Report
Comment on "Electromagnetic dissociation of ^8B and the astrophysical S-factor for ^7Be(p,gamma)^8B"
Recently, Davids and Typel recommended a "low" value of S_{17}(0) based on
fits to published direct and Coulomb dissociation data, in which they excluded
the precise result of Junghans et al. We show that their statistical analysis
is incorrect, due to a substantial underestimate of the experimental
uncertainties, and leads to conclusions that are not supported by a proper
analysis.Comment: submitted to Phys. Rev.
Coastal Impacts of Climate Change in the Northwest: A Summary of the Findings of the upcoming National Climate Assessment
The many thousands of miles of Northwest marine coastline are extremely diverse and contain important human-built and natural assets upon which our communities and ecosystems depend. Due to the variety of coastal landform types (e.g., sandy beaches, rocky shorelines, bluffs of varying slopes and composition, river deltas, and estuaries), the region’s marine coastal areas stand to experience a wide range of climate impacts, in both type and severity. These impacts include increases in ocean temperature and acidity, erosion, and more severe and frequent inundation from the combined effects of rising sea levels and storms, among others.Increases in coastal inundation and erosion are key concerns. A recent assessment determined that the coastal areas of Washington and Oregon contain over 56,656 hectares(140,000 acres) of land within 1.0-meter (3.3-feet) elevation of high tide (Strauss et al. 2012).Rising sea levels coupled with the possibility of intensifying coastal storms will increase the likelihood of more severe coastal flooding and erosion in these areas.The Northwest is also facing the challenge of increasing ocean acidification, and is experiencing these changes earlier, and more acutely, than most other regions around the globe(NOAA OAR 2012).The Third National Climate Assessment is scheduled for release in the spring of 2014.The authors will provide an overview of the key Northwest coastal findings in this report as well as a summary of its primary companion report published by Island Press in December 2013,Climate Change in the Northwest: Implications for Our Landscapes, Waters, and Communities(Dalton et al 2013)
Rep-tiling for triangles
AbstractIn this paper we prove that one can only tile a triangle with tiles all congruent to each other and similar to the original triangle when k2, l2 + k2, or 3k2 tiles are used. The result is based on the geometry of packing and a result of I. Niven's on rational trigonometric values. In addition we describe how to tile most triangles
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Recent results on giant dipole resonance decays in highly excited nuclei
Some recent results on Giant Dipole Resonance (GDR) decays in highly excited, equilibrated nuclei, are discussed based primarily on work done at Seattle. Four sections address the following topics: oblate shapes of rotating, highly excited Zr--Mo nuclei; adiabatic versus motionally narrowed' GDR decay; large spin-driven deformations observed in hot medium-mass nuclei; and search for entrance channel effects in GDR decay following [sup 58]Ni [plus] [sup 92]Zr fusion. 22 refs
Prevalence of sessile serrated adenoma/polyp in hyperplastic appearing diminutive rectosigmoid polyps
Background
The American Society for Gastrointestinal Endoscopy recommends that distal colon hyperplastic lesions can be left in place without resection if adenomatous histology can be excluded with > 90% negative predictive value. However, some of the lesions could be sessile serrated adenoma/polyp (SSA/P), which is also precancerous.
Aim
Describe the prevalence of SSA/P in hyperplastic appearing diminutive rectosigmoid polyps.
Methods
We prospectively placed 513 consecutive diminutive rectosigmoid polyps that appeared hyperplastic to an expert endoscopist in individual bottles for pathologic examination. Each polyp was examined by 3 expert gastrointestinal pathologists.
Results
The prevalence of SSA/P in the study polyps ranged from 0.6% to 2.1%. The endoscopists lowest negative predictive value for the combination of adenomas plus SSA/P was 96.7%
Conclusions
The prevalence of SSA/P in diminutive rectosigmoid hyperplastic appearing polyps is very low. These results support the safety and feasibility of a “do not resect” policy for diminutive hyperplastic appearing rectosigmoid polyps
A Limited Symmetry Found by Comparing Calculated Magnetic Dipole Spin and Orbital Strengths in ^4\mbox{He}
Allowing for admixtures in ^4\mbox{He} we find that the
summed magnetic dipole isovector orbital and spin strengths are equal. This
indicates a symmetry which is associated with interchanging the labels of the
spin with those of the orbit. Where higher admixtures are included, the orbital
sum becomes larger than the spin sum, but the sums over the low energy region
are still nearly the same.Comment: 13 pages, revtex, 1 ps file appende
Scaling Properties of the Giant Dipole Resonance Width in Hot Rotating nuclei
We study the systematics of the giant dipole resonance width in hot
rotating nuclei as a function of temperature , spin and mass . We
compare available experimental results with theoretical calculations that
include thermal shape fluctuations in nuclei ranging from A=45 to A=208. Using
the appropriate scaled variables, we find a simple phenomenological function
which approximates the global behavior of the giant dipole
resonance width in the liquid drop model. We reanalyze recent experimental and
theoretical results for the resonance width in Sn isotopes and Pb.Comment: LaTeX, 4 pages with 4 figures (to appear in Phys. Rev. Lett.
Absolute Determination of the 22Na(p,g) Reaction Rate in Novae
Gamma-ray telescopes in orbit around the Earth are searching for evidence of
the elusive radionuclide 22Na produced in novae. Previously published
uncertainties in the dominant destructive reaction, 22Na(p,g)23Mg, indicated
new measurements in the proton energy range of 150 to 300 keV were needed to
constrain predictions. We have measured the resonance strengths, energies, and
branches directly and absolutely by using protons from the University of
Washington accelerator with a specially designed beamline, which included beam
rastering and cold vacuum protection of the 22Na implanted targets. The
targets, fabricated at TRIUMF-ISAC, displayed minimal degradation over a ~ 20 C
bombardment as a result of protective layers. We avoided the need to know the
stopping power, and hence the target composition, by extracting resonance
strengths from excitation functions integrated over proton energy. Our
measurements revealed that resonance strengths for E_p = 213, 288, 454, and 610
keV are stronger by factors of 2.4 to 3.2 than previously reported. Upper
limits have been placed on proposed resonances at 198-, 209-, and 232-keV. We
have re-evaluated the 22Na(p,g) reaction rate, and our measurements indicate
the resonance at 213 keV makes the most significant contribution to 22Na
destruction in novae. Hydrodynamic simulations including our rate indicate that
the expected abundance of 22Na ejecta from a classical nova is reduced by
factors between 1.5 and 2, depending on the mass of the white-dwarf star
hosting the nova explosion.Comment: 20 pages, 18 figures; shortened paper, accepted in Phys. Rev.
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