4,607 research outputs found
Estimating stratospheric temperature trends using satellite microwave radiances
The objective was to evaluate and intercompare stratospheric temperatures using Microwave Sounding Unit (MSU) data as a basis data set. The MSU, aboard the NOAA polar orbiter satellite series, provides twice daily global coverage over a layer (50-150 mb) at approximately a (170km)(exp 2) resolution. Conventional data sets will be compared to the satellite data in the lower stratosphere in order to assess their quality for trend computations
Variability in spawning frequency and reproductive development of the narrow-barred Spanish mackerel (Scomberomorus commerson) along the west coast of Australia
The narrow-barred Spanish mackerel (Scomberomorus commerson)
is widespread throughout the Indo-West Pacific region. This study describes the reproductive biology of S. commerson along the west coast of Australia, where it is targeted for
food consumption and sports fishing. Development of testes occurred at a smaller body size than for ovaries, and more than 90% of males were sexually mature by the minimum legal length of 900 mm TL compared to 50% of females. Females dominated overall catches although sex ratios within daily catches vary considerably and females were rarely caught
when spaw n ing. Scomberomorus commerson are seasonally abundant in coastal waters and most of the commercial catch is taken prior to the reproductive season. Spawning occurs between about August and November in the Kimberley region
and between October and January in the Pilbara region. No spawning activity was recorded in the more southerly West Coast region, and only in the north Kimberley region were
large numbers of fish with spawning gonads collected. Catches dropped to a minimum when spawning began in the Pilbara region, when fish became less abundant in inshore waters and inclement weather conditions limited fishing on still productive offshore reefs. Final maturation and ovulation of oocytes took place within a 24-hour period, and females spawned in the afternoon-evening every three days. A third of these spawning females released batches of eggs on consecutive days. Relationships between length, weight, and batch fecundity are presented
Surface Edge Explorer (SEE): Planning Next Best Views Directly from 3D Observations
Surveying 3D scenes is a common task in robotics. Systems can do so
autonomously by iteratively obtaining measurements. This process of planning
observations to improve the model of a scene is called Next Best View (NBV)
planning.
NBV planning approaches often use either volumetric (e.g., voxel grids) or
surface (e.g., triangulated meshes) representations. Volumetric approaches
generalise well between scenes as they do not depend on surface geometry but do
not scale to high-resolution models of large scenes. Surface representations
can obtain high-resolution models at any scale but often require tuning of
unintuitive parameters or multiple survey stages.
This paper presents a scene-model-free NBV planning approach with a density
representation. The Surface Edge Explorer (SEE) uses the density of current
measurements to detect and explore observed surface boundaries. This approach
is shown experimentally to provide better surface coverage in lower computation
time than the evaluated state-of-the-art volumetric approaches while moving
equivalent distances
Multimotion Visual Odometry (MVO): Simultaneous Estimation of Camera and Third-Party Motions
Estimating motion from images is a well-studied problem in computer vision
and robotics. Previous work has developed techniques to estimate the motion of
a moving camera in a largely static environment (e.g., visual odometry) and to
segment or track motions in a dynamic scene using known camera motions (e.g.,
multiple object tracking).
It is more challenging to estimate the unknown motion of the camera and the
dynamic scene simultaneously. Most previous work requires a priori object
models (e.g., tracking-by-detection), motion constraints (e.g., planar motion),
or fails to estimate the full SE(3) motions of the scene (e.g., scene flow).
While these approaches work well in specific application domains, they are not
generalizable to unconstrained motions.
This paper extends the traditional visual odometry (VO) pipeline to estimate
the full SE(3) motion of both a stereo/RGB-D camera and the dynamic scene. This
multimotion visual odometry (MVO) pipeline requires no a priori knowledge of
the environment or the dynamic objects. Its performance is evaluated on a
real-world dynamic dataset with ground truth for all motions from a motion
capture system.Comment: This updated manuscript corrects the experimental results published
in the proceedings of the 2018 IEEE/RSJ International Conference on
Intelligent Robots and Systems (IROS).. 8 Pages. 7 Figures. Video available
at https://www.youtube.com/watch?v=84tXCJOlj0
Domain Growth in Ising Systems with Quenched Disorder
We present results from extensive Monte Carlo (MC) simulations of domain
growth in ferromagnets and binary mixtures with quenched disorder. These are
modeled by the "random-bond Ising model" and the "dilute Ising model" with
either nonconserved (Glauber) spin-flip kinetics or conserved (Kawasaki)
spin-exchange kinetics. In all cases, our MC results are consistent with
power-law growth with an exponent which depends on the
quench temperature and the disorder amplitude . Such exponents
arise naturally when the coarsening domains are trapped by energy barriers
which grow logarithmically with the domain size. Our MC results show excellent
agreement with the predicted dependence of .Comment: 11 pages, 15 figure
Transitions of tethered polymer chains: A simulation study with the bond fluctuation lattice model
A polymer chain tethered to a surface may be compact or extended, adsorbed or
desorbed, depending on interactions with the surface and the surrounding
solvent. This leads to a rich phase diagram with a variety of transitions. To
investigate these transitions we have performed Monte Carlo simulations of a
bond-fluctuation model with Wang-Landau and umbrella sampling algorithms in a
two-dimensional state space. The simulations' density of states results have
been evaluated for interaction parameters spanning the range from good to poor
solvent conditions and from repulsive to strongly attractive surfaces. In this
work, we describe the simulation method and present results for the overall
phase behavior and for some of the transitions. For adsorption in good solvent,
we compare with Metropolis Monte Carlo data for the same model and find good
agreement between the results. For the collapse transition, which occurs when
the solvent quality changes from good to poor, we consider two situations
corresponding to three-dimensional (hard surface) and two-dimensional (very
attractive surface) chain conformations, respectively. For the hard surface, we
compare tethered chains with free chains and find very similar behavior for
both types of chains. For the very attractive surface, we find the
two-dimensional chain collapse to be a two-step transition with the same
sequence of transitions that is observed for three-dimensional chains: a
coil-globule transition that changes the overall chain size is followed by a
local rearrangement of chain segments.Comment: 17 pages, 12 figures, to appear in J. Chem. Phy
Asymmetric cationic phosphines: synthesis, coordination chemistry, and reactivity
A single enantiomer of a cationic phosphine, [α-CgPAmHMe]BF4 has been synthesized and coordinated to Rh(I), Au(I), Ag(I), Cu(I), and Pt(0). Analysis of pertinent empirical data reveals the ligand to be highly electron-withdrawing due to the cationic amidinium group directly bound to the phosphorus. The N−P bond connecting the amidinium and the phosphacycle is susceptible to attack by nucleophiles (H2O, OH−) when coordinated leading to bond rupture and release of the neutral amidine group. These fortuitous observations suggest that [α-CgPAmHMe]BF4 may be a very useful synthon for the production of novel asymmetric phosphines
The Response of Ozone and Nitrogen Dioxide to the Eruption of Mount Pinatubo
Observations have shown that the global mass of nitrogen dioxide decreased in both hemispheres in the year following the eruption of Mt. Pinatubo, indicating an enhanced heterogeneous chemistry. In contrast, the observed ozone response was largely asymmetrical with respect to the equator, with a decrease in the northern hemisphere and little change in the southern hemisphere. Simulations including enhanced heterogeneous chemistry due to the presence of the volcanic aerosol reproduce a decrease of ozone in the northern hemisphere, but also produce a comparable ozone decrease in the southern hemisphere, contrary to observations. Our simulations show that the heating due to the volcanic aerosol enhanced both the tropical upwelling and the extratropical downwelling. The enhanced extratropical downwelling, combined with the time of the eruption relative to the phase of the Brewer-Dobson circulation, increased the ozone in the southern hemisphere and counteracted the ozone depletion due to heterogeneous chemistry on volcanic aerosol
The relative timing of mutations in a breast cancer genome.
Many tumors have highly rearranged genomes, but a major unknown is the relative importance and timing of genome rearrangements compared to sequence-level mutation. Chromosome instability might arise early, be a late event contributing little to cancer development, or happen as a single catastrophic event. Another unknown is which of the point mutations and rearrangements are selected. To address these questions we show, using the breast cancer cell line HCC1187 as a model, that we can reconstruct the likely history of a breast cancer genome. We assembled probably the most complete map to date of a cancer genome, by combining molecular cytogenetic analysis with sequence data. In particular, we assigned most sequence-level mutations to individual chromosomes by sequencing of flow sorted chromosomes. The parent of origin of each chromosome was assigned from SNP arrays. We were then able to classify most of the mutations as earlier or later according to whether they occurred before or after a landmark event in the evolution of the genome, endoreduplication (duplication of its entire genome). Genome rearrangements and sequence-level mutations were fairly evenly divided earlier and later, suggesting that genetic instability was relatively constant throughout the life of this tumor, and chromosome instability was not a late event. Mutations that caused chromosome instability would be in the earlier set. Strikingly, the great majority of inactivating mutations and in-frame gene fusions happened earlier. The non-random timing of some of the mutations may be evidence that they were selected
Effect of change in systolic blood pressure between clinic visits on estimated 10-year cardiovascular disease risk
Background
Systolic blood pressure (SBP) often varies between clinic visits within individuals, which can affect estimation of cardiovascular disease (CVD) risk.
Methods and Results
We analyzed data from participants with two clinic visits separated by a median of 17 days in the Third National Health and Nutrition Examination Survey (n = 808). Ten-year CVD risk was calculated with SBP obtained at each visit using the Pooled Cohort Equations. The mean age of participants was 46.1 years, and 47.3% were male. The median SBP difference between the two visits was −1 mm Hg (1st to 99th percentiles: −23 to 32 mm Hg). The median estimated 10-year CVD risk was 2.5% and 2.4% at the first and second visit, respectively (1st to 99th percentiles −5.2% to +7.1%). Meaningful risk reclassification (ie, across the guideline recommended 7.5% threshold for statin initiation) occurred in 12 (11.3%) of 106 participants whose estimated CVD risk was between 5% and 10%, but only in two (0.3%) of 702 participants who had a 10-year estimated CVD risk of 10%.
Conclusions
SBP variability can affect CVD risk estimation, and can influence statin eligibility for individuals with an estimated 10-year CVD risk between 5% and 10%
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