151 research outputs found
DASH: Dynamic Attention-Based Substructure Hierarchy for Partial Charge Assignment
We present a robust and computationally efficient approach for assigning
partial charges of atoms in molecules. The method is based on a hierarchical
tree constructed from attention values extracted from a graph neural network
(GNN), which was trained to predict atomic partial charges from accurate
quantum-mechanical (QM) calculations. The resulting dynamic attention-based
substructure hierarchy (DASH) approach provides fast assignment of partial
charges with the same accuracy as the GNN itself, is software-independent, and
can easily be integrated in existing parametrization pipelines as shown for the
Open force field (OpenFF). The implementation of the DASH workflow, the final
DASH tree, and the training set are available as open source / open data from
public repositories
Col-OSSOS: The Colours of the Outer Solar System Origins Survey
The Colours of the Outer Solar System Origins Survey (Col-OSSOS) is acquiring
near-simultaneous , , and photometry of unprecedented precision with
the Gemini North Telescope, targeting nearly a hundred trans-Neptunian objects
(TNOs) brighter than mag discovered in the Outer Solar System
Origins Survey. Combining the optical and near-infrared photometry with the
well-characterized detection efficiency of the Col-OSSOS target sample will
provide the first flux-limited compositional dynamical map of the outer Solar
System. In this paper, we describe our observing strategy and detail the data
reduction processes we employ, including techniques to mitigate the impact of
rotational variability. We present optical and near-infrared colors for 35
TNOs. We find two taxonomic groups for the dynamically excited TNOs, the
neutral and red classes, which divide at . Based on simple
albedo and orbital distribution assumptions, we find that the neutral class
outnumbers the red class, with a ratio of 4:1 and potentially as high as 11:1.
Including in our analysis constraints from the cold classical objects, which
are known to exhibit unique albedos and colors, we find that within our
measurement uncertainty, our observations are consistent with the primordial
Solar System protoplanetesimal disk being neutral-class-dominated, with two
major compositional divisions in color space.Comment: Accepted to ApJS; on-line supplemental files will be available with
the AJS published version of the pape
Col-OSSOS: Z-Band Photometry Reveals Three Distinct TNO Surface Types
Several different classes of trans-Neptunian objects (TNOs) have been
identified based on their optical and near-infrared colors. As part of the
Colours of the Outer Solar System Origins Survey, we have obtained , ,
and band photometry of 26 TNOs using Subaru and Gemini Observatories.
Previous color surveys have not utilized band reflectance, and the
inclusion of this band reveals significant surface reflectance variations
between sub-populations. The colors of TNOs in and show obvious
structure, and appear consistent with the previously measured bi-modality in
. The distribution of colors of the two dynamically excited surface types
can be modeled using the two-component mixing models from Fraser \& Brown
(2012). With the combination of and , the dynamically excited
classes can be separated cleanly into red and neutral surface classes. In and , the two dynamically excited surface groups are also clearly
distinct from the cold classical TNO surfaces, which are red, with
0.85 and 0.6, while all dynamically excited objects
with similar colors exhibit redder colors. The band photometry
makes it possible for the first time to differentiate the red excited TNO
surfaces from the red cold classical TNO surfaces. The discovery of different
colors for these cold classical TNOs makes it possible to search for cold
classical surfaces in other regions of the Kuiper belt and to completely
separate cold classical TNOs from the dynamically excited population, which
overlaps in orbital parameter space.Comment: 11 pages, 2 figures, Accepted to A
Trapped surfaces and symmetries
We prove that strictly stationary spacetimes cannot contain closed trapped
nor marginally trapped surfaces. The result is purely geometric and holds in
arbitrary dimension. Other results concerning the interplay between
(generalized) symmetries and trapped submanifolds are also presented.Comment: 9 pages, no figures. Final corrected version to appear in Class.
Quantum Gra
Improving Oral Hygiene Skills by Computer-Based Training: A Randomized Controlled Comparison of the Modified Bass and the Fones Techniques
Background: Gingivitis and other plaque-associated diseases have a high prevalence in western communities even though the majority of adults report daily oral hygiene. This indicates a lack of oral hygiene skills. Currently, there is no clear evidence as to which brushing technique would bring about the best oral hygiene skills. While the modified Bass technique is often recommended by dentists and in textbooks, the Fones technique is often recommended in patient brochures. Still, standardized comparisons of the effectiveness of teaching these techniques are lacking.
Methodology/Principal Findings: In a final sample of n=56 students, this multidisciplinary, randomized, examiner-blinded, controlled study compared the effects of parallel and standardized interactive computer presentations teaching either the Fones or the modified Bass technique. A control group was taught the basics of tooth brushing alone. Oral hygiene skills (remaining plaque after thorough oral hygiene) and gingivitis were assessed at baseline and 6, 12, and 28 weeks after the intervention. We found a significant group×time interaction for gingivitis (F(4/102)=3.267; p=0.016; e=0.957; ?2=0.114) and a significant main effect of group for oral hygiene skills (F(2/51)=7.088; p=0.002; ?2=0.218). Fones was superior to Bass; Bass did not differ from the control group. Group differences were most prominent after 6 and 12 weeks.
Conclusions/Significance: The present trial indicates an advantage of teaching the Fones as compared to the modified Bass technique with respect to oral hygiene skills and gingivitis. Future studies are needed to analyze whether the disadvantage of teaching the Bass technique observed here is restricted to the teaching method employed.
Trial Registration: German Clinical Trials Register http://www.drks.de/DRKS0000348
Worldwide impacts of climate change on energy for heating and cooling
The energy sector is not only a major contributor to greenhouse gases, it is also vulnerable to climate change and will have to adapt to future climate conditions. The objective of this study is to analyze the impacts of changes in future temperatures on the heating and cooling services of buildings and the resulting energy and macro-economic effects at global and regional levels. For this purpose, the techno-economic TIAM-WORLD (TIMES Integrated Assessment Model) and the general equilibrium GEMINI-E3 (General Equilibrium Model of International-National Interactions between Economy, Energy and Environment) models are coupled with a climate model, PLASIM-ENTS (Planet-Simulator - Efficient Numerical Terrestrial Scheme). The key results are as follows. At the global level, the climate feedback induced by adaptation of the energy system to heating and cooling is found to be insignificant, partly because heating and cooling-induced changes compensate and partly because they represent a limited share of total final energy consumption. However, significant changes are observed at regional levels, more particularly in terms of addi- tional power capacity required to satisfy additional cooling services, resulting in increases in electricity prices. In terms of macro-economic impacts, welfare gains and losses are associated more with changes in energy exports and imports than with changes in energy consumption for heating and cooling. The rebound effect appears to be non-negligible. To conclude, the coupling of models of different nature was successful and showed that the energy and economic impacts of climate change on heating and cooling remain small at the global level, but changes in energy needs will be visible at more local scale
OSSOS. IV. DISCOVERY OF A DWARF PLANET CANDIDATE IN THE 9 : 2 RESONANCE WITH NEPTUNE
We report the discovery and orbit of a new dwarf planet candidate, 2015 RR245, by the Outer Solar System Origins Survey (OSSOS). The orbit of 2015 RR245 is eccentric (e = 0.586), with a semimajor axis near 82 au, yielding a perihelion distance of 34 au. 2015 RR245 has g - r = 0.59 +/- 0.11 and absolute magnitude H-r = 3.6 +/- 0.1; for an assumed albedo of p(V) = 12%, the object has a diameter of similar to 670. km. Based on astrometric measurements from OSSOS and Pan-STARRS1, we find that 2015 RR245 is securely trapped on ten-megayear timescales in the 9: 2 mean-motion resonance with Neptune. It is the first trans-Neptunian object (TNO) identified in this resonance. On hundred-megayear. timescales, particles in 2015 RR245-like orbits depart and sometimes return to the resonance, indicating that 2015 RR245 likely forms part of the long-lived metastable population of distant TNOs that drift between resonance sticking and actively scattering via gravitational encounters with Neptune. The discovery of a 9: 2 TNO stresses the role of resonances in the long-term evolution of objects in the scattering disk. and reinforces the view that distant resonances are heavily populated in the current solar system. This object further motivates detailed modeling of the transient sticking population.Peer reviewe
Supersymmetric Dark Matter
There is almost universal agreement among astronomers that most of the mass
in the Universe and most of the mass in the Galactic halo is dark. Many lines
of reasoning suggest that the dark matter consists of some new, as yet
undiscovered, weakly-interacting massive particle (WIMP). There is now a vast
experimental effort being surmounted to detect WIMPS in the halo. The most
promising techniques involve direct detection in low-background laboratory
detectors and indirect detection through observation of energetic neutrinos
from annihilation of WIMPs that have accumulated in the Sun and/or the Earth.
Of the many WIMP candidates, perhaps the best motivated and certainly the most
theoretically developed is the neutralino, the lightest superpartner in many
supersymmetric theories. We review the minimal supersymmetric extension of the
Standard Model and discuss prospects for detection of neutralino dark matter.
We review in detail how to calculate the cosmological abundance of the
neutralino and the event rates for both direct- and indirect-detection schemes,
and we discuss astrophysical and laboratory constraints on supersymmetric
models. We isolate and clarify the uncertainties from particle physics, nuclear
physics, and astrophysics that enter at each step in the calculation. We
briefly review other related dark-matter candidates and detection techniques.Comment: The complete postscript file is available at
ftp://ftp.npac.syr.edu/pub/users/jungman/susyreview/susyreview.ps.Z The TeX
source and figures (plain TeX; macros included) are at
ftp://ftp.npac.syr.edu/pub/users/jungman/susyreview/susyreview.tar.Z Full
paper NOT submitted to lanl archive: table of contents only. To appear in
Physics Report
OSSOS. VII. 800+Trans-Neptunian Objects-The Complete Data Release
The Outer Solar System Origins Survey (OSSOS), a wide-field imaging program in 2013-2017 with the Canada-France-Hawaii Telescope, surveyed 155 deg(2) of sky to depths of m(r) = 24.1-25.2. We present 838 outer solar system discoveries that are entirely free of ephemeris bias. This increases the inventory of trans-Neptunian objects (TNOs) with accurately known orbits by nearly 50%. Each minor planet has 20-60 Gaia/Pan-STARRS-calibrated astrometric measurements made over 2-5 oppositions, which allows accurate classification of their orbits within the trans-Neptunian dynamical populations. The populations orbiting in mean-motion resonance with Neptune are key to understanding Neptune's early migration. Our 313 resonant TNOs, including 132 plutinos, triple the available characterized sample and include new occupancy of distant resonances out to semimajor axis a similar to 130 au. OSSOS doubles the known population of the nonresonant Kuiper Belt, providing 436 TNOs in this region, all with exceptionally high-quality orbits of a uncertainty sigma(a)Peer reviewe
The Outer Solar System Origins Survey : I. Design and First-Quarter Discoveries
We report the discovery, tracking, and detection circumstances for 85 trans-Neptunian objects (TNOs) from the first 42 deg(2) of the Outer Solar System Origins Survey. This ongoing r-band solar system survey uses the 0.9 deg(2) field of view MegaPrime camera on the 3.6m Canada-France-Hawaii Telescope. Our orbital elements for these TNOs are precise to a fractional semimajor axis uncertaintyPeer reviewe
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