5,136 research outputs found
Solving the Solar Neutrino Problem 2 km Underground -- the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) is capable of measuring simultaneously
the flux of electron-type neutrinos and the total flux of all active flavours
of neutrinos originating from the Sun. A model-independent test of neutrino
flavour transformation was performed by comparing these two measurements.
Assuming an undistorted neutrino energy spectrum, this transformation has been
definitively demonstrated in the pure D2O phase of the SNO experiment. In the
second phase with dissolved NaCl in the D2O, the total active solar neutrino
flux was measured without any assumption on the energy dependence of flavour
transformation. In this talk, results from these measurements, their physics
implications and the current status of the SNO experiment are presented.Comment: Proceedings of the 8th ICATPP Conference on Astroparticle, Particle,
Space Physics, Detectors and Medical Physics Applications (Como, Italy, Oct
6-10, 2003) 10 pages, 3 figures, 2 table
Recent Results from the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) measures both the flux of the
electron-type neutrinos and the total flux of all active flavours of neutrinos
originating from the Sun. A model-independent test of neutrino flavour
transformation was performed by comparing these two measurements. In 2002, this
flavour transformation was definitively demonstrated. In this talk, results
from these measurements and the current status of the SNO detector are
presented.Comment: Proceedings of the International Europhysics Conference on High
Energy Physics (EPS2003) 3 pages, 2 figures, 2 table
Low-background temperature sensors fabricated on parylene substrates
Temperature sensors fabricated from ultra-low radioactivity materials have
been developed for low-background experiments searching for neutrinoless
double-beta decay and the interactions of WIMP dark matter. The sensors consist
of electrical traces photolithographically-patterned onto substrates of
vapor-deposited parylene. They are demonstrated to function as expected, to do
so reliably and robustly, and to be highly radio-pure. This work is a
proof-of-concept study of a technology that can be applied to broad class of
electronic circuits used in low-background experiments
Solar Neutrino Observations at the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov
detector. Its usage of \dto as target allows the simultaneous measurements of
the flux from B decay in the Sun and the total flux of all active
neutrino species through the charged-current and the neutral-current
interactions on the deuterons. Assuming the standard B shape, the
component of the B solar neutrino flux is measured to be for a kinetic energy threshold of 5 MeV. The non-\nue component
is found to be \phinumutau = 3.41^{+0.45}_{-0.45}{(stat.)}^{+0.48}_{-0.45}
{(syst.)} x 10^6 {\rm cm}^{-2} {\rm s}^{-1}. This difference
provides strong evidence for flavor transformation in the solar
neutrino sector. The total active neutrino flux is measured with the
neutral-current reaction at a neutrino energy threshold of 2.2 MeV. This flux
is determined to be , and is consistent with solar
model predictions. Assuming an undistorted B spectrum, the night minus day
rate is 14.06.3(stat.)(sys.)\% of the average rate in the
charged-current channel. If the total active neutrino flux is constrained to
have no asymmetry, the night-day asymmetry in the flux is found to be
7.04.9(stat.)(sys.)\%. A global analysis of all the
available solar neutrino data in terms of matter-enhanced oscillations of two
active flavors strongly favors the Large Mixing Angle (LMA) solution.Comment: invited talk at the SLAC Summer Institute Topical Conference
(SSI02-TTh01), 2002, 43 pages, 19 figures, 10 table
Potential one-forms for hyperk\"ahler structures with torsion
It is shown that an HKT-space with closed parallel potential 1-form has
-symmetry. Every locally conformally hyperk\"ahler manifold
generates this type of geometry. The HKT-spaces with closed parallel potential
1-form arising in this way are characterized by their symmetries and an
inhomogeneous cubic condition on their torsion.Comment: 16 pages, Latex, no figure
Distribution of the second virial coefficients of globular proteins
George and Wilson [Acta. Cryst. D 50, 361 (1994)] looked at the distribution
of values of the second virial coefficient of globular proteins, under the
conditions at which they crystallise. They found the values to lie within a
fairly narrow range. We have defined a simple model of a generic globular
protein. We then generate a set of proteins by picking values for the
parameters of the model from a probability distribution. At fixed solubility,
this set of proteins is found to have values of the second virial coefficient
that fall within a fairly narrow range. The shape of the probability
distribution of the second virial coefficient is Gaussian because the second
virial coefficient is a sum of contributions from different patches on the
protein surface.Comment: 5 pages, including 3 figure
Randomized crossover comparison of proportional assist ventilation and patient-triggered ventilation in extremely low birth weight infants with evolving chronic lung disease
Background: Refinement of ventilatory techniques remains a challenge given the persistence of chronic lung disease of preterm infants. Objective: To test the hypothesis that proportional assist ventilation ( PAV) will allow to lower the ventilator pressure at equivalent fractions of inspiratory oxygen (FiO(2)) and arterial hemoglobin oxygen saturation in ventilator-dependent extremely low birth weight infants in comparison with standard patient-triggered ventilation ( PTV). Methods: Design: Randomized crossover design. Setting: Two level-3 university perinatal centers. Patients: 22 infants ( mean (SD): birth weight, 705 g ( 215); gestational age, 25.6 weeks ( 2.0); age at study, 22.9 days ( 15.6)). Interventions: One 4- hour period of PAV was applied on each of 2 consecutive days and compared with epochs of standard PTV. Results: Mean airway pressure was 5.64 ( SD, 0.81) cm H2O during PAV and 6.59 ( SD, 1.26) cm H2O during PTV ( p < 0.0001), the mean peak inspiratory pressure was 10.3 ( SD, 2.48) cm H2O and 15.1 ( SD, 3.64) cm H2O ( p < 0.001), respectively. The FiO(2) ( 0.34 (0.13) vs. 0.34 ( 0.14)) and pulse oximetry readings were not significantly different. The incidence of arterial oxygen desaturations was not different ( 3.48 ( 3.2) vs. 3.34 ( 3.0) episodes/ h) but desaturations lasted longer during PAV ( 2.60 ( 2.8) vs. 1.85 ( 2.2) min of desaturation/ h, p = 0.049). PaCO2 measured transcutaneously in a subgroup of 12 infants was similar. One infant met prespecified PAV failure criteria. No adverse events occurred during the 164 cumulative hours of PAV application. Conclusions: PAV safely maintains gas exchange at lower mean airway pressures compared with PTV without adverse effects in this population. Backup conventional ventilation breaths must be provided to prevent apnea-related desaturations. Copyright (c) 2007 S. Karger AG, Base
Glasses in hard spheres with short-range attraction
We report a detailed experimental study of the structure and dynamics of
glassy states in hard spheres with short-range attraction. The system is a
suspension of nearly-hard-sphere colloidal particles and non-adsorbing linear
polymer which induces a depletion attraction between the particles. Observation
of crystallization reveals a re-entrant glass transition. Static light
scattering shows a continuous change in the static structure factors upon
increasing attraction. Dynamic light scattering results, which cover 11 orders
of magnitude in time, are consistent with the existence of two distinct kinds
of glasses, those dominated by inter-particle repulsion and caging, and those
dominated by attraction. Samples close to the `A3 point' predicted by mode
coupling theory for such systems show very slow, logarithmic dynamics.Comment: 22 pages, 18 figure
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