11,163 research outputs found
Stellar wind-magnetosphere interaction at exoplanets: computations of auroral radio powers
We present calculations of the auroral radio powers expected from exoplanets
with magnetospheres driven by an Earth-like magnetospheric interaction with the
solar wind. Specifically, we compute the twin cell-vortical ionospheric flows,
currents, and resulting radio powers resulting from a Dungey cycle process
driven by dayside and nightside magnetic reconnection, as a function of
planetary orbital distance and magnetic field strength. We include saturation
of the magnetospheric convection, as observed at the terrestrial magnetosphere,
and we present power law approximations for the convection potentials, radio
powers and spectral flux densities. We specifically consider a solar-age system
and a young (1 Gyr) system. We show that the radio power increases with
magnetic field strength for magnetospheres with saturated convection potential,
and broadly decreases with increasing orbital distance. We show that the
magnetospheric convection at hot Jupiters will be saturated, and thus unable to
dissipate the full available incident Poynting flux, such that the magnetic
Radiometric Bode's Law (RBL) presents a substantial overestimation of the radio
powers for hot Jupiters. Our radio powers for hot Jupiters are 5-1300 TW
for hot Jupiters with field strengths of 0.1-10 orbiting a Sun-like star,
while we find that competing effects yield essentially identical powers for hot
Jupiters orbiting a young Sun-like star. However, in particular for planets
with weaker magnetic fields our powers are higher at larger orbital distances
than given by the RBL, and there are many configurations of planet that are
expected to be detectable using SKA.Comment: Accepted for publication in Mon. Not. R. Astron. So
Towards a geometrical interpretation of quantum information compression
Let S be the von Neumann entropy of a finite ensemble E of pure quantum
states. We show that S may be naturally viewed as a function of a set of
geometrical volumes in Hilbert space defined by the states and that S is
monotonically increasing in each of these variables. Since S is the Schumacher
compression limit of E, this monotonicity property suggests a geometrical
interpretation of the quantum redundancy involved in the compression process.
It provides clarification of previous work in which it was shown that S may be
increased while increasing the overlap of each pair of states in the ensemble.
As a byproduct, our mathematical techniques also provide a new interpretation
of the subentropy of E.Comment: 11 pages, latex2
Estimates of body sizes at maturation and at sex change, and the spawning seasonality and sex ratio of the endemic Hawaiian grouper (Hyporthodus quernus, F. Epinephelidae)
A case study of the reproductive biology of the endemic Hawaiian grouper or hapuâupuâu (Hyporthodus quernus) is presented as a model for comprehensive future studies of
economically important epinephelid groupers. Specimens were collected throughout multiple years (1978â81, 1992â93, and 2005â08) from most reefs and banks of the Northwestern
Hawaiian Islands. The absence of small males, presence of atretic oocytes and brown bodies in testes of mature males, and both developed ovarian and testicular tissues in the gonads of five transitional fish provided evidence of protogynous hermaphroditism. No small mature males were collected, indicating that Hawaiian grouper are monandrous
(all males are sex-changed females). Complementary microscopic criteria also were used to assign reproductive
stage and estimate median body sizes (L50) at female sexual maturity and at adult sex change from female to male. The L50 at maturation and at sex change was 580 ±8 (95% confidence interval [CI]) mm total length (TL) and 895 ±20 mm TL, respectively. The adult sex ratio was strongly female
biased (6:1). Spawning seasonality was described by using gonadosomatic indices. Females began ripening in the fall and remained ripe through April. A FebruaryâJune main spawning period that followed peak ripening was deduced from the proportion of females whose ovaries contained hydrated oocytes, postovulatory follicles, or both. Testes
weights were not affected by season; average testes weight was only about 0.2% of body weightâan order of magnitude smaller than that for ovaries that peaked at 1â3% of body
weight. The speciesâ reproductive life history is discussed in relation to its management
Dynamic filtering of static dipoles in magnetoencephalography
We consider the problem of estimating neural activity from measurements
of the magnetic fields recorded by magnetoencephalography. We exploit
the temporal structure of the problem and model the neural current as a
collection of evolving current dipoles, which appear and disappear, but whose
locations are constant throughout their lifetime. This fully reflects the physiological
interpretation of the model.
In order to conduct inference under this proposed model, it was necessary
to develop an algorithm based around state-of-the-art sequential Monte
Carlo methods employing carefully designed importance distributions. Previous
work employed a bootstrap filter and an artificial dynamic structure
where dipoles performed a random walk in space, yielding nonphysical artefacts
in the reconstructions; such artefacts are not observed when using the
proposed model. The algorithm is validated with simulated data, in which
it provided an average localisation error which is approximately half that of
the bootstrap filter. An application to complex real data derived from a somatosensory
experiment is presented. Assessment of model fit via marginal
likelihood showed a clear preference for the proposed model and the associated
reconstructions show better localisation
Weak Hopf algebras corresponding to Cartan matrices
We replace the group of group-like elements of the quantized enveloping
algebra of a finite dimensional semisimple Lie algebra
by some regular monoid and get the weak Hopf algebra
. It is a new subclass of weak Hopf algebras
but not Hopf algebras. Then we devote to constructing a basis of
and determine the group of weak Hopf algebra
automorphisms of when is not a root of
unity.Comment: 21 page
Tuning electronic structures via epitaxial strain in Sr2IrO4 thin films
We have synthesized epitaxial Sr2IrO4 thin-films on various substrates and
studied their electronic structures as a function of lattice-strains. Under
tensile (compressive) strains, increased (decreased) Ir-O-Ir bond-angles are
expected to result in increased (decreased) electronic bandwidths. However, we
have observed that the two optical absorption peaks near 0.5 eV and 1.0 eV are
shifted to higher (lower) energies under tensile (compressive) strains,
indicating that the electronic-correlation energy is also affected by in-plane
lattice-strains. The effective tuning of electronic structures under
lattice-modification provides an important insight into the physics driven by
the coexisting strong spin-orbit coupling and electronic correlation.Comment: 9 pages, 5 figures, 1 tabl
Heavy ion induced Single Event Phenomena (SEP) data for semiconductor devices from engineering testing
The accumulation of JPL data on Single Event Phenomena (SEP), from 1979 to August 1986, is presented in full report format. It is expected that every two years a supplement report will be issued for the follow-on period. This data for 135 devices expands on the abbreviated test data presented as part of Refs. (1) and (3) by including figures of Single Event Upset (SEU) cross sections as a function of beam Linear Energy Transfer (LET) when available. It also includes some of the data complied in the JPL computer in RADATA and the SPACERAD data bank. This volume encompasses bipolar and MOS (CMOS and MHNOS) device data as two broad categories for both upsets (bit-flips) and latchup. It also includes comments on less well known phenomena, such as transient upsets and permanent damage modes
Comparison of Cellulosic Ethanol Yields from Midwestern Maize and Reconstructed Tallgrass Prairie Systems Managed for Bioenergy
Maize- and prairie-based systems were investigated as cellulosic feedstocks by conducting a 9 ha side-by-side comparison on fertile soils in the Midwestern United States. Maize was grown continuously with adequate fertilization over years both with and without a winter rye cover crop, and the 31-species reconstructed prairie was grown with and without spring nitrogen fertilization. Both maize stover and prairie biomass were harvested in the fall. We compared amounts of cellulosic biomass produced and harvested, carbohydrate contents as measured by both dietary and detergent methods, and estimated cellulosic ethanol yields per hectare. From 2009â2013, the cropping system with the largest non-grain biomass yield was fertilized prairie, averaging 10.4 Mg haâ1 yearâ1 aboveground biomass with average harvest removals of 7.8 Mg haâ1 yearâ1. The unfertilized prairie produced 7.4 Mg haâ1 yearâ1 aboveground biomass, with average harvests of 5.3 Mg haâ1 yearâ1. Lowest cellulosic (non-grain) biomass harvests were obtained from continuous maize systems, averaging 3.5 Mg haâ1 yearâ1 when grown with, and 3.7 Mg haâ1 yearâ1 when grown without a winter rye cover crop, respectively. Unfertilized prairie biomass and maize stover had equivalent dietary-determined potential biomass ethanol yields at 330 g ethanol kgâ1 dry biomass, but fertilized prairie was lower at 315. The detergent method did not accurately capture these differences. Over the five-year period of the experiment, unfertilized and fertilized prairie systems averaged 810 and 1,790 L potential cellulosic ethanol haâ1 yearâ1 more than the maize systems, respectively. Differences in harvested biomass accounted for \u3e90 % of ethanol yield variation
A SVD-based transient error method for analyzing noisy multicomponent exponential signals
The problem of estimating the parameters of noisy multicomponent signals using
parametric modeling technique is considered in this paper. The multicomponent signal of
interest is formed by a superposition of basic functions having the same location in time
but different widths and amplitudes. Based on the modified Gardner transformation, some
samples of deconvolved data are derived from the multicomponent signals. The
deconvolved data are then modeled using a special nonstationary autoregressive moving
average (ARMA) process in which the parameters of the ARMA model are obtained by
linear least-squares procedure. The least-squares procedure is based on the singular
value decomposition (SVD) to overcome the limitations of the transient error method
(TEM) of analysis that uses cholesky decomposition to determine its AR coefficients. The
moving average (MA) coefficients corresponds to the initial residual error sequences so
as to account for the nonstationary noise in the deconvolved data. This new method of
analysis, termed the SVD-based transient error method, produces high resolution
estimates of the exponents of multicomponent signals at both low and high signal to noise
(SNR) ratios
Reversing microcrystalline tests: an analytical approach to recycling of microcrystals from drugs of abuse
A combined analysis of microcrystalline tests followed by LC-MS or GC-MS analysis is described. Microcrystalline tests are shown to be non-destructive as addition products formed were easily dissociated after the application of an appropriate solvent. Subsequent analysis of the sample was done to quantify the recovery of the drug. Examples were performed using the date rape drug Îł-hydroxybutyrate (GHB) and the synthetic opioid methadone
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