Observed planetary debris in white dwarf atmospheres predominately originate from the destruction of small bodies on highly eccentric (>0.99) orbits. Despite their importance, these minor planets ...have coupled physical and orbital evolution, which has remained largely unexplored. Here, we present a novel approach for estimating the influence of fast chaotic rotation on the orbital evolution of high-eccentricity triaxial asteroids, and formally characterize the propagation of their angular rotation velocities and orbital elements as random time processes. By employing the impulse approximation, we demonstrate that the violent gravitational interactions during periastron passages transfer energy between the orbit and asteroid's rotation. If the distribution of spin impulses were symmetric around zero, then the net result would be a secular decrease of the semimajor axis and a further increase of the eccentricity. We find evidence, however, that the chaotic rotation may be self regulated in such a manner that these effects are reduced or nullified. We discover that asteroids on highly eccentric orbits can break themselves apart-in a type of YORP-less (Yarkovsky-O'Keefe-Radzievskii-Paddack) rotational fission-without actually entering the Roche radius, with potentially significant consequences for the distribution of debris and energy requirements for gravitational scattering in metal-polluted white dwarf planetary systems. This mechanism provides a steady stream of material impacting a white dwarf without rapidly depleting the number of small bodies in the stellar system.
Abstract A large number of candidate binary stars with apparent acceleration on the sky has emerged from analysis of astrometric data collected by the Hipparcos, Tycho-2, and Gaia space missions. ...Although the apparent acceleration can serve as a relatively reliable indicator of binarity, it provides scarce information about the orbital and physical parameters of the components. With an emphasis on the search for stellar-mass black holes and neutron stars hidden in binary systems, we start a broader effort to characterize the most promising candidates using follow-up ground-based observations. Accurate quantification of orbital and physical parameters of systems with dim or invisible companions requires combination of Hipparcos, Gaia, and precision spectroscopic measurements. In this paper, we review the necessary steps in this implementation and describe the improved Hipparcos–Gaia sample of long-term astrometric accelerations, which includes correction of sky-correlated systematic errors using the vector spherical decomposition method. As an example, we study one Hipparcos star with a large acceleration, HIP 44842, where the companion is revealed to be a normal main-sequence star.
This guideline is structured to provide a clinical framework stratified by cancer severity to facilitate care decisions and guide the specifics of implementing the selected management options. The ...summary presented represents Part I of the two-part series dedicated to Clinically Localized Prostate Cancer: AUA/ASTRO/SUO Guideline discussing risk stratification and care options by cancer severity.
The systematic review utilized in the creation of this guideline was completed by the Agency for Healthcare Research and Quality and through additional supplementation by ECRI Institute. This review included articles published between January 2007 and March 2014 with an update search conducted through August 2016. When sufficient evidence existed, the body of evidence for a particular treatment was assigned a strength rating of A (high), B (moderate), or C (low) for support of Strong, Moderate, or Conditional Recommendations. Additional information is provided as Clinical Principles and Expert Opinions (table 2 in supplementary unabridged guideline, http://jurology.com/).
The AUA (American Urological Association), ASTRO, and SUO (Society of Urologic Oncology) formulated an evidence-based guideline based on a risk stratified clinical framework for the management of localized prostate cancer.
This guideline attempts to improve a clinician’s ability to treat patients diagnosed with localized prostate cancer, but higher quality evidence in future trials will be essential to improve the level of care for these patients. In all cases, patient preferences should be considered when choosing a management strategy.
This guideline is structured to provide a clinical framework stratified by cancer severity to facilitate care decisions and guide the specifics of implementing the selected management options. The ...summary presented herein represents Part II of the two-part series dedicated to Clinically Localized Prostate Cancer: AUA/ASTRO/SUO Guideline discussing risk stratification and care options by cancer severity. Please refer to Part I for discussion of specific care options and outcome expectations and management.
The systematic review utilized in the creation of this guideline was completed by the Agency for Healthcare Research and Quality and through additional supplementation by ECRI Institute. This review included articles published between January 2007 and March 2014 with an update search conducted through August 2016. When sufficient evidence existed, the body of evidence for a particular treatment was assigned a strength rating of A (high), B (moderate), or C (low) for support of Strong, Moderate, or Conditional Recommendations. Additional information is provided as Clinical Principles and Expert Opinions (table 2 in supplementary unabridged guideline, http://jurology.com/).
The AUA (American Urological Association), ASTRO, and SUO (Society of Urologic Oncology) formulated an evidence-based guideline based on a risk stratified clinical framework for the management of localized prostate cancer.
This guideline attempts to improve a clinician’s ability to treat patients diagnosed with localized prostate cancer, but higher quality evidence in future trials will be essential to improve the level of care for these patients. In all cases, patient preferences should be considered when choosing a management strategy.
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The distribution of Th and U was studied in the near-ground atmosphere of the city of Yakutsk. The chemical compositions of particulate matter (PM) in the summer atmosphere and in the solid and ...soluble phases of the snowpack were studied in 2019–2020. In the summer atmosphere, Th and U are concentrated mostly in the dust fraction of PM, together with a group of siderophile elements. The wintertime PM is characterized by a more homogeneous size of its particles. PM minerals with which concentrations of actinides correlate are amphiboles and pyroxene for Th and carbonates for U. The Th and U concentrations were found out to systematically decrease in the sequence soil–summer PM (dust)–winter PM (snow), at the dominance of Th, but the aqueous phase of the snow contains U concentrations one order of magnitude higher than those of Th. The bulk (close to 90%) of actinides is deposited during the warm season. The total amount of actinides falling out in Yakutsk is 63 mg/(m
2
year), with two-thirds of this amount being Th. This value may locally increase to 200 mg/(m
2
year) and more in areas of contrasting anomalies, with the predominance of Th. The main sources of actinides entering the near-ground atmosphere of Yakutsk are dusting from the soil surface and emissions from vehicles, with lesser amounts coming from energy-producing and construction-industry facilities.
We perform numerical simulations of the TRAPPIST-1 system of seven exoplanets orbiting a nearby M dwarf, starting with a previously suggested stable configuration. The long-term stability of this ...configuration is confirmed, but the motion of planets is found to be chaotic. The eccentricity values are found to vary within finite ranges. The rates of tidal dissipation and tidal evolution of orbits are estimated, assuming an Earth-like rheology for the planets. We find that under this assumption, the planets b, d, and e were captured in the 3:2 or higher spin-orbit resonances during the initial spin-down, but slipped further down into the 1:1 resonance. Depending on its rheology, the innermost planet b may be captured in a stable pseudosynchronous rotation. Nonsynchronous rotation ensures higher levels of tidal dissipation and internal heating. The positive feedback between the viscosity and the dissipation rate-and the ensuing runaway heating-are terminated by a few self-regulation processes. When the temperature is high and the viscosity is low enough, the planet spontaneously leaves the 3:2 resonance. Further heating is stopped either by passing the peak dissipation or by the emergence of partial melt in the mantle. In the post-solidus state, the tidal dissipation is limited to the levels supported by the heat transfer efficiency. The tides on the host star are unlikely to have had a significant dynamical impact. The tides on the synchronized inner planets tend to reduce these planets' orbital eccentricity, possibly contributing thereby to the system's stability.
Based on the mathematical model of hydro swirl orthokinetic inertia hetero coagulation, the hydro swirl nozzle parameters air identified for a dust suppression facility for prevention of blasts and ...induced accidents in mines. Using the similarity theory and dimensionality analysis, the similarity criteria are obtained for the process of atomization in the conditions of rotational motion of liquid drops. It is shown that the main pulverization efficiency criteria for liquid drop in the hydro swirl nozzle are the Weber number, Laplace criterion and three indicators of inertia and viscosity of liquid, and kinematic similarity. The calculations and tests reveal the possibility of enhancing atomization efficiency by 15%, reducing the average diameter of liquid drops by 2.5 times, and reducing the liquid flow rate by 10%.
Abstract
Making use of strong correlations between closely separated multiple or double sources and photometric and astrometric metadata in Gaia Early Data Release 3 (EDR3), we generate a catalog of ...candidate double- and multiply imaged lensed quasars and active galactic nuclei (AGNs), comprising 3140 systems. It includes two partially overlapping parts: a sample of distant (redshifts mostly greater than 1) sources with perturbed data; and systems that have been resolved into separate components by Gaia at separations less than 2″. For the first part, which is roughly one-third of the published catalog, we synthesized 0.617 million redshifts using multiple machine-learning prediction and classification methods, using independent photometric and astrometric data from Gaia EDR3 and the Wide-field Infrared Survey Explorer, with accurate spectroscopic redshifts from the Sloan Digital Sky Survey (SDSS) as a training set. Using these synthetic redshifts, we estimate a 4.9% rate of interlopers with spectroscopic redshifts below 1 in this part of the catalog. Unresolved candidate double and dual AGNs and quasars are selected as sources with a marginally high BP/RP excess factor (
phot
_
bp
_
rp
_
excess
_
factor
), which is sensitive to source extent, limiting our search to high-redshift quasars. For the second part of the catalog, additional filters on measured parallax and near-neighbor statistics are applied to diminish the propagation of the remaining stellar contaminants. The estimated rate of the positives (double or multiple sources) is 98%, and the estimated rate of dual (physically related) quasars is greater than 54%. A few dozen serendipitously found objects of interest are discussed in more detail, including known and new lensed images, planetary nebulae, young IR stars of peculiar morphology, and quasars with catastrophic redshift errors in SDSS.
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