48,799 research outputs found
Study of the state-of-the-art of the hermetic seals for secondary alkaline spacecraft cells Quarterly report, Sep. 20 - Dec. 20, 1967
Manufacturing methods, cost estimates, advantages, and limitations of various types of hermetic seals for secondary alkaline spacecraft cell
Fully Constrained Majorana Neutrino Mass Matrices Using
In 2002, two neutrino mixing ansatze having trimaximally-mixed middle
() columns, namely tri-chi-maximal mixing () and
tri-phi-maximal mixing (), were proposed. In 2012, it was
shown that with as well as
with leads to the solution,
, consistent with the
latest measurements of the reactor mixing angle, . To obtain
and
, the type~I see-saw
framework with fully constrained Majorana neutrino mass matrices was utilised.
These mass matrices also resulted in the neutrino mass ratios,
.
In this paper we construct a flavour model based on the discrete group
and obtain the aforementioned results. A Majorana neutrino
mass matrix (a symmetric matrix with 6 complex degrees of freedom)
is conveniently mapped into a flavon field transforming as the complex 6
dimensional representation of . Specific vacuum alignments
of the flavons are used to arrive at the desired mass matrices.Comment: 20 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:1402.085
Deviations from Tribimaximal Neutrino Mixing using a Model with Symmetry
We present a model of neutrino mixing based on the flavour group
in order to account for the observation of a non-zero reactor mixing angle
(). The model provides a common flavour structure for the
charged-lepton and the neutrino sectors, giving their mass matrices a
`circulant-plus-diagonal' form. Mass matrices of this form readily lead to
mixing patterns with realistic deviations from tribimaximal mixing, including
non-zero . With the parameters constrained by existing
measurements, our model predicts an inverted neutrino mass hierarchy. We obtain
two distinct sets of solutions in which the atmospheric mixing angle lies in
the first and the second octants. The first (second) octant solution predicts
the lightest neutrino mass, ()
and the phase, (), offering the possibility of large observable violating
effects in future experiments.Comment: 9 pages, 3 figure
The Full Re-Ionization of Helium
Observations of resolved HeII Lyman alpha absorption in spectra of two QSO's
suggest that the epoch of helium ionization occurred at z~3. Proximity zones in
the spectra of the quasars (z=3.18, 3.285) at 304 A resemble Stromgren spheres,
suggesting that the intergalactic medium is only singly ionized in helium. We
present models of the proximity effect which include the full physics of the
ionization, heating and cooling and an accurately simulated inhomogeneous gas
distribution. In these models the underdense intergalactic medium is heated to
at least 10,000-20,000 K after cooling to as low as a few 1000 K due to
cosmological expansion, with higher temperatures achieved farther away from the
quasar due to absorption-hardened ionizing spectra. The quasars turn on for a
few times 10^7 years with a fairly steady flux output at 228 A comparable to
the 304 A flux output directly observed with HST. The recoveries in the spectra
occur naturally due to voids in the IGM and may provide a fairly
model-independent probe of the baryon density.Comment: 5 pages, 3 figures, to appear in the proceedings of "After the Dark
Ages: When Galaxies were Young (the Universe at 2<z<5)", 9th Annual October
Astrophysics Conference in Marylan
Viscous Hydrodynamics and Relativistic Heavy Ion Collisions
The matter created in relativistic heavy ion collisions is fairly well
described by ideal hydrodynamics, and somewhat better described by viscous
hydrodynamics. To this point, most viscous calculations have been
two-dimensional, based on an assumption of Bjorken boost invariance along the
beam axis. Here, first results are presented for a fully three-dimensional
viscous model. The model is described and tests of the numerical accuracy of
the code are presented. Two- and three-dimensional runs are compared, and
modest changes are observed for mid-rapidity observables at the highest RHIC
(Relativistic Heavy Ion Collider) energies.Comment: 23 pages, 7 figure
An Ultraviolet-Excess Optical Candidate for the Luminous Globular Cluster X-ray Source in NGC1851
The intense, bursting X-ray source in the globular cluster NGC 1851 was one
of the first cluster sources discovered, but has remained optically
unidentified for 25 years. We report here on results from Hubble Space
Telescope WFPC2 multicolor images in NGC 1851. Our high spatial resolution
images resolve ~200 objects in the 3'' radius Einstein X-ray error circle, 40
times as many as in previous ground-based work. A color-magnitude diagram of
the cluster clearly reveals a markedly UV-excess object with B~21, (U-B) ~ -0.9
only 2'' from the X-ray position. The UV-excess candidate is 0.12'' distant
from a second, unremarkable star that is 0.5 mag brighter in B; thus
ground-based studies of this field are probably impractical. Three other
UV-excess objects are also present among the ~16,000 objects in the surveyed
region of the cluster, leaving a ~5% probability that a UV-excess object has
fallen in the X-ray error circle by chance. No variability of the candidate is
seen in these data, although a more complete study is required. If this object
is in fact the counterpart of the X-ray source, previous inferences that some
globular cluster X-ray sources are optically subluminous with respect to
low-mass X-ray binaries in the field are now strengthened.Comment: 13 pages including 1 table and 3 figures in AASTeX 4.0; To appear in
The Astrophysical Journal Letters, volume 472 (1996 December 1). Preprint
with full-resolution figures available at
http://www.astro.washington.edu/deutsch/pubs/pubs.htm
Soil erosion by landing rockets Final report
Cratering effect of descending rocket exhaust expected from soft earth landin
Giant electrocaloric effect in thin film Pb Zr_0.95 Ti_0.05 O_3
An applied electric field can reversibly change the temperature of an
electrocaloric material under adiabatic conditions, and the effect is strongest
near phase transitions. This phenomenon has been largely ignored because only
small effects (0.003 K V^-1) have been seen in bulk samples such as
Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)0.98O3 and there is no consensus on macroscopic
models. Here we demonstrate a giant electrocaloric effect (0.48 K V^-1) in 300
nm sol-gel PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of
222oC. We also discuss a solid state device concept for electrical
refrigeration that has the capacity to outperform Peltier or magnetocaloric
coolers. Our results resolve the controversy surrounding macroscopic models of
the electrocaloric effect and may inspire ab initio calculations of
electrocaloric parameters and thus a targeted search for new materials.Comment: 5 pages, 4 figure
The efficacy of Ivermectin against strongyles in yearlings on Thoroughbred breeding farms in New Zealand
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