811 research outputs found
L'acceptation de la nothion philosophique de Dieu comme probleme doctrinal de la theologie chretienne des premiers siecles
SNO and Supernovae
The Sudbury Neutrino Observatory (SNO) has unique capabilities as a supernova
detector. In the event of a galactic supernova there are opportunities, with
the data that SNO would collect, to constrain certain intrinsic neutrino
properties significantly, to test details of the various models of supernova
dynamics, and to provide prompt notification to the astronomical community
through the Supernova Early Warning System (SNEWS). This paper consists of a
discussion of these opportunities illustrated by some preliminary Monte Carlo
results.Comment: 7 pages, latex, 3 eps figures, Invited paper at Neutrino Oscillations
Workshop (NOW 2000), Otranto, Italy, September 9-16, 2000, to be published in
the Proceeding
FLUID-BED CONVERSION OF URANIUM TETRAFLUORIDE TO URANIUM HEXAFLUORIDE
Experiments conducted in a 2 1/2-inch diameter reactor have demonstrated that the continuous fluorination of uranium tetrafluoride to hexafluoride with elemental fluorine in a fluidized bed is possible. Practicable fluorine efficiencies and conversion rates were attained with good temperature control in experiments with refined uranium tetrafluoride. Runs made with crude uranium tetrafluoride, derived from the reduction and hydrofluorination of ore concentrates produced by the acid-leach process, indicated that these also can be processed at satisfactory ratss and efficiencies. Uranium tetrafluoride derived from carbonate-leached ore concentrate gave a lower production rate and was more difficult to process because of sintering tendencies. (auth
Nitrate fertilisation does not enhance CO₂ responses in two tropical seagrass species
Seagrasses are often considered "winners" of ocean acidification (OA); however, seagrass productivity responses to OA could be limited by nitrogen availability, since nitrogen-derived metabolites are required for carbon assimilation. We tested nitrogen uptake and assimilation, photosynthesis, growth, and carbon allocation responses of the tropical seagrasses Halodule uninervis and Thalassia hemprichii to OA scenarios (428, 734 and 1213 μatm pCO₂) under two nutrients levels (0.3 and 1.9 μM NO₃⁻). Net primary production (measured as oxygen production) and growth in H. uninervis increased with pCO₂ enrichment, but were not affected by nitrate enrichment. However, nitrate enrichment reduced whole plant respiration in H. uninervis. Net primary production and growth did not show significant changes with pCO₂ or nitrate by the end of the experiment (24 d) in T. hemprichii. However, nitrate incorporation in T. hemprichii was higher with nitrate enrichment. There was no evidence that nitrogen demand increased with pCO₂ enrichment in either species. Contrary to our initial hypothesis, nutrient increases to levels approximating present day flood plumes only had small effects on metabolism. This study highlights that the paradigm of increased productivity of seagrasses under ocean acidification may not be valid for all species under all environmental conditions
Detection of Supernova Neutrinos by Neutrino-Proton Elastic Scattering
We propose that neutrino-proton elastic scattering, ,
can be used for the detection of supernova neutrinos in scintillator detectors.
Though the proton recoil kinetic energy spectrum is soft, with , and the scintillation light output from slow, heavily ionizing
protons is quenched, the yield above a realistic threshold is nearly as large
as that from . In addition, the measured proton
spectrum is related to the incident neutrino spectrum, which solves a
long-standing problem of how to separately measure the total energy and
temperature of , , , and .
The ability to detect this signal would give detectors like KamLAND and
Borexino a crucial and unique role in the quest to detect supernova neutrinos.Comment: 10 pages, 9 figures, revtex
Ground-state properties of tubelike flexible polymers
In this work we investigate structural properties of native states of a
simple model for short flexible homopolymers, where the steric influence of
monomeric side chains is effectively introduced by a thickness constraint. This
geometric constraint is implemented through the concept of the global radius of
curvature and affects the conformational topology of ground-state structures. A
systematic analysis allows for a thickness-dependent classification of the
dominant ground-state topologies. It turns out that helical structures,
strands, rings, and coils are natural, intrinsic geometries of such tubelike
objects
Structure of the ovaries of the Nimba otter shrew, Micropotamogale lamottei, and the Madagascar hedgehog tenrec, Echinops telfairi
The otter shrews are members of the subfamily Potamogalinae within the family Tenrecidae. No description of the ovaries of any member of this subfamily has been published previously. The lesser hedgehog tenrec, Echinops telfairi, is a member of the subfamily Tenrecinae of the same family and, although its ovaries have not been described, other members of this subfamily have been shown to have ovaries with non-antral follicles. Examination of these two species illustrated that non-antral follicles were characteristic of the ovaries of both species, as was clefting and lobulation of the ovaries. Juvenile otter shrews range from those with only small follicles in the cortex to those with 300- to 400-mu m follicles similar to those seen in non-pregnant and pregnant adults. As in other species, most of the growth of the oocyte occurred when follicles had one to two layers of granulosa cells. When larger follicles became atretic in the Nimba otter shrew, hypertrophy of the theca interna produced nodules of glandular interstitial tissue. In the tenrec, the hypertrophying theca interna cells in most large follicles appeared to undergo degeneration. Both species had some follicular fluid in the intercellular spaces between the more peripheral granulosa cells. It is suggested that this fluid could aid in separation of the cumulus from the remaining granulosa at ovulation. The protruding follicles in lobules and absence of a tunica albuginea might also facilitate ovulation of non-antral follicles. Ovaries with a thin-absent tunica albuginea and follicles with small-absent antra are widespread within both the Eulipotyphla and in the Afrosoricida, suggesting that such features may represent a primitive condition in ovarian development. Lobulated and deeply crypted ovaries are found in both groups but are not as common in the Eulipotyphla making inclusion of this feature as primitive more speculative. Copyright (C) 2005 S. Karger AG, Basel
Measuring the elements of the optical density matrix
Most methods for experimentally reconstructing the quantum state of light
involve determining a quasiprobability distribution such as the Wigner
function. In this paper we present a scheme for measuring individual density
matrix elements in the photon number state representation. Remarkably, the
scheme is simple, involving two beam splitters and a reference field in a
coherent state.Comment: 6 pages and 1 figur
Potential for Supernova Neutrino Detection in MiniBooNE
The MiniBooNE detector at Fermilab is designed to search for oscillation appearance at and to make a
decisive test of the LSND signal. The main detector (inside a veto shield) is a
spherical volume containing 0.680 ktons of mineral oil. This inner volume,
viewed by 1280 phototubes, is primarily a \v{C}erenkov medium, as the
scintillation yield is low. The entire detector is under a 3 m earth
overburden. Though the detector is not optimized for low-energy (tens of MeV)
events, and the cosmic-ray muon rate is high (10 kHz), we show that MiniBooNE
can function as a useful supernova neutrino detector. Simple trigger-level cuts
can greatly reduce the backgrounds due to cosmic-ray muons. For a canonical
Galactic supernova at 10 kpc, about 190 supernova
events would be detected. By adding MiniBooNE to the international network of
supernova detectors, the possibility of a supernova being missed would be
reduced. Additionally, the paths of the supernova neutrinos through Earth will
be different for MiniBooNE and other detectors, thus allowing tests of
matter-affected mixing effects on the neutrino signal.Comment: Added references, version to appear in PR
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