80 research outputs found
The 8Li Calibration Source for the Sudbury Neutrino Obervatory
A calibration source employing 8Li (t_1/2 = 0.838s) has been developed for
use with the Sudbury Neutrino Observatory (SNO). This source creates a spectrum
of beta particles with an energy range similar to that of the SNO 8B solar
neutrino signal. The source is used to test the SNO detector's energy response,
position reconstruction and data reduction algorithms. The 8Li isotope is
created using a deuterium-tritium neutron generator in conjunction with a 11B
target, and is carried to a decay chamber using a gas/aerosol transport system.
The decay chamber detects prompt alpha particles by gas scintillation in
coincidence with the beta particles which exit through a thin stainless steel
wall. A description is given of the production, transport, and tagging
techniques along with a discussion of the performance and application of the
source.Comment: 11 pages plus 9 figures, Sumbitted to Nuclear Instruments and Methods
Estimates for heritability and consumer-validation of a penetrometer method for phenotyping softness of cooked cassava roots
Although breeders have made significant progress in the genetic
improvement of cassava ( Manihot esculenta Crantz) for agronomic
traits, lack of information on heritability and limited testing of
high-throughput phenotyping methods are major limitations to improving
root quality traits, such as softness after cooking, which rank high
among Ugandan consumers. The objectives of this study were to determine
heritability for softness of cooked cassava roots, and quantify the
relationship between penetrometer and consumer testing methods for
phenotyping softness of cassava roots. Softness defined as the maximum
force (N) needed to penetrate cooked root samples using a penetrometer,
was evaluated at four cooking time intervals: 15, 30, 45, and 60 min on
268 cassava genotypes. Estimates of broad-sense heritability
(repeatability) ranged from 0.17 to 0.37, with the highest value
observed at 45 min of cooking time interval. In the second study
involving 135 cassava consumers from Kibaale district in Uganda,
penetrometer measurements of cooked roots from six cassava varieties
were found to be in strong agreement (r2 = 0.91; P-value = 0.003) with
ordinal scores of root softness from consumer testing. These results
suggest that: (a) softness of cooked cassava roots is a trait amenable
for evaluation and selection; and (b) a penetrometer can readily be
used for assessment of cooked root softness. These findings form the
basis for operationalising the routine assessment of root softness in
cassava breeding trials, an output that will enhance ongoing efforts to
breed for desired end-user root quality traits.Les s\ue9lectionneurs ont fait des progr\ue8s consid\ue9rables
dans l\u2019am\ue9lioration g\ue9n\ue9tique des caract\ue8res
agronomiques du manioc ( Manihot esculenta Crantz). Cependant un
manque de m\ue9thodes de ph\ue9notypage haut-d\ue9bit
adapt\ue9es aux caract\ue8res de qualit\ue9s tel que la
fermet\ue9 de la racine apr\ue8s cuisson, essentiel pour les
consommateurs Ougandais. Cette \ue9tude ambitionne a) de determiner
l\u2019h\ue9ritabilit\ue9 de la fermete de racine cuite b) de
quantifier la relation entre l \ue9valuation de la fermet\ue9 de
racine cuite au p\ue9n\ue9trom\ue8tre et un panel consommateurs.
Cette \ue9valuation a \ue9t\ue9 realisee a quatre intervals de
temps: 15, 30, 45 et 60 minutes sur 268 genotypes de manioc. Pour
d\ue9finir l\u2019h\ue9ritabilit\ue9 de la fermet\ue9 de la
racine, celle ci a \ue9t\ue9 d\ue9finie par la force maximum (N)
n\ue9cessaire pour p\ue9n\ue9trer des \ue9chantillons de
racines incluant diff\ue8rent temps de cuisson (15, 30, 45, and 60
min) a l\u2019aide d\u2019un p\ue9n\ue9trom\ue8tre.
L\u2019h\ue9ritabilit\ue9 au sens large (ou
r\ue9p\ue9tabilit\ue9) observ\ue9e varie de 0.17 a 0.37, la
valeur la plus \ue9lev\ue9 \ue9tant observ\ue9e pour un temps
de cuisson de 45 minutes. Dans une seconde \ue9tude impliquant 135
consommateurs du district de Kibaale (Ouest de l\u2019Ouganda), les
mesures au p\ue9n\ue9trom\ue8tre de racines cuites de six
vari\ue9t\ue9s ont confirm\ue9es la forte correlation (r2 = 0.91;
P-value = 0.003) avec les valeurs ordinales de fermet\ue9 de racine
du panel consommateur. Les r\ue9sultats de cette \ue9tude indiquent
que cette m\ue9thodologie de ph\ue9notypage est a) utile pour
l\u2019 \ue9valuation de la fermet\ue9 sur des racines cuites en
selection et b) d\ue9montre que l\u2019usage du
p\ue9n\ue9trom\ue8tre est efficace pour celle ci. Ces
r\ue9sultats offrent aux s\ue9lectionneurs une methode d\u2019
\ue9valuation de routine de la qualite de racine pour les essais
experimentaux. Ceux ci contribueront aux efforts actuels pour
l\u2019am\ue9lioration des caract\ue8res qualit\ue9s chers aux
consommateurs
Parity nonconservation in deuteron photoreactions
We calculate the asymmetries in parity nonconserving deuteron
photodisintegration due to circularly polarized photons gamma+d to n+p with the
photon laboratory energy ranging from the threshold up to 10 MeV and the
radiative capture of thermal polarized neutrons by protons n+p to gamma+d. We
use the leading order electromagnetic Hamiltonian neglecting the smaller
nuclear exchange currents. Comparative calculations are done by using the
Reid93 and Argonne v18 potentials for the strong interaction and the DDH and
FCDH "best" values for the weak couplings in a weak one-meson exchange
potential. A weak NDelta transition potential is used to incorporate also the
Delta(1232)-isobar excitation in the coupled-channels formalism.Comment: 14 pages, 13 figures (18 eps files), LaTeX2
InfluĂȘncia do cloreto de cĂĄlcio no crescimento de explantes de Gypsophila paniculata L. (Caryophyllaceae), cultivados in vitro
The Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a second generation water Cherenkov
detector designed to determine whether the currently observed solar neutrino
deficit is a result of neutrino oscillations. The detector is unique in its use
of D2O as a detection medium, permitting it to make a solar model-independent
test of the neutrino oscillation hypothesis by comparison of the charged- and
neutral-current interaction rates. In this paper the physical properties,
construction, and preliminary operation of the Sudbury Neutrino Observatory are
described. Data and predicted operating parameters are provided whenever
possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and
epsf style files. For additional information about SNO see
http://www.sno.phy.queensu.ca . This version has some new reference
Education and selfâregulation of learning for gifted pupils: systemic design and development
Measurement of the Îœe and total 8B solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set
This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of 3He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active 8B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54-0.31+0.33(stat.)-0.34+0.36(syst.)Ă106 cm-2 s-1, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Îm2=7.59-0.21+0.19Ă10 -5eV2 and Ξ=34.4-1.2+1.3degrees
Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype
The DUNE far detector vertical drift technology. Technical design report
DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals
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