8,208 research outputs found
Triaxial Black-Hole Nuclei
We demonstrate that the nuclei of galaxies containing supermassive black
holes can be triaxial in shape. Schwarzschild's method was first used to
construct self-consistent orbital superpositions representing nuclei with axis
ratios of 1:0.79:0.5 and containing a central point mass representing a black
hole. Two different density laws were considered, with power-law slopes of -1
and -2. We constructed two solutions for each power law: one containing only
regular orbits and the other containing both regular and chaotic orbits.
Monte-Carlo realizations of the models were then advanced in time using an
N-body code to verify their stability. All four models were found to retain
their triaxial shapes for many crossing times. The possibility that galactic
nuclei may be triaxial complicates the interpretation of stellar-kinematical
data from the centers of galaxies and may alter the inferred interaction rates
between stars and supermassive black holes.Comment: 4 pages, 4 postscript figures, uses emulateapj.st
Arthropod Fauna Associated with Wild and Cultivated Cranberries in Wisconsin
The cranberry (Vaccinium macrocarpon Aiton) is an evergreen, trailing shrub native to North American peatlands. It is cultivated commercially in the US and Canada, with major production centers in Wisconsin, Massachusetts, New Jersey, Washington, Québec, and British Columbia. Despite the agricultural importance of cranberry in Wisconsin, relatively little is known of its arthropod associates, particularly the arachnid fauna. Here we report preliminary data on the insect and spider communities associated with wild and cultivated cranberries in Wisconsin. We then compare the insect and spider communities of wild cranberry systems to those of cultivated cranberries, indexed by region. Approximately 7,400 arthropods were curated and identified, spanning more than 100 families, across 11 orders. The vast majority of specimens and diversity derived from wild ecosystems. In both the wild and cultivated systems, the greatest numbers of families were found among the Diptera (midges, flies) and Hymenoptera (bees, ants, wasps), but numerically, the Hymenoptera and Araneae (spiders) were dominant. Within the spider fauna, 18 new county records, as well as a new Wisconsin state record (Linyphiidae: Ceratinopsis laticeps (Em.)), were documented. While more extensive sampling will be needed to better resolve arthropod biodiversity in North American cranberry systems, our findings represent baseline data on the breadth of arthropod diversity in the Upper Midwest, USA
AOIPS water resources data management system
A geocoded data management system applicable for hydrological applications was designed to demonstrate the utility of the Atmospheric and Oceanographic Information Processing System (AOIPS) for hydrological applications. Within that context, the geocoded hydrology data management system was designed to take advantage of the interactive capability of the AOIPS hardware. Portions of the Water Resource Data Management System which best demonstrate the interactive nature of the hydrology data management system were implemented on the AOIPS. A hydrological case study was prepared using all data supplied for the Bear River watershed located in northwest Utah, southeast Idaho, and western Wyoming
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Effect of a Fruit and Vegetable Prescription Program on Children's Fruit and Vegetable Consumption.
IntroductionMost children in families with low income do not meet dietary guidance on fruit and vegetable consumption. Fruit and vegetable prescription programs improve access to and affordability of health-supporting foods for adults, but their effect on dietary behavior among children is not known. The objective of this study was to describe the extent to which exposure to a fruit and vegetable prescription program was associated with changes in consumption among participants aged 2 to 18.MethodsWe used data from a modified National Cancer Institute screener to calculate fruit and vegetable intake among 883 children who were overweight or had obesity and participated in a 4- to 6-month fruit and vegetable prescription program at federally qualified health centers during 4 years (2012-2015). Secondary analyses in 2017 included paired t tests to compare change in fruit and vegetable consumption (cups/day) between first and last visits and multivariable linear regressions, including propensity dose-adjusted models, to model this change as a function of sociodemographic and program-specific covariates, such as number of clinical visits and value of prescription redemption.ResultsWe found a dose propensity-adjusted increase of 0.32 cups (95% confidence interval, 0.19-0.45 cups) for each additional visit while holding constant the predicted number of visits and site. An equal portion of the change-score increase was attributed to vegetable consumption and fruit consumption (β = 0.16 for each).ConclusionFruit and vegetable prescription programs in clinical settings may increase fruit and vegetable consumption among children in low-income households. Future research should use a comparison group and consider including qualitative analysis of site-specific barriers and facilitators to success
Free Radicals in Superfluid Liquid Helium Nanodroplets: A Pyrolysis Source for the Production of Propargyl Radical
An effusive pyrolysis source is described for generating a continuous beam of
radicals under conditions appropriate for the helium droplet pick-up method.
Rotationally resolved spectra are reported for the vibrational mode of
the propargyl radical in helium droplets at 3322.15 cm. Stark spectra
are also recorded that allow for the first experimental determination of the
permanent electric dipole moment of propargyl, namely -0.150 D and -0.148 D for
ground and excited state, respectively, in good agreement with previously
reported ab initio results of -0.14 D [1]. The infrared spectrum of the
mode of propargyl-bromide is also reported. The future application of these
methods for the production of novel radical clusters is discussed
Chaotic mixing in noisy Hamiltonian systems
This paper summarises an investigation of the effects of low amplitude noise
and periodic driving on phase space transport in 3-D Hamiltonian systems, a
problem directly applicable to systems like galaxies, where such perturbations
reflect internal irregularities and.or a surrounding environment. A new
diagnsotic tool is exploited to quantify how, over long times, different
segments of the same chaotic orbit can exhibit very different amounts of chaos.
First passage time experiments are used to study how small perturbations of an
individual orbit can dramatically accelerate phase space transport, allowing
`sticky' chaotic orbits trapped near regular islands to become unstuck on
suprisingly short time scales. Small perturbations are also studied in the
context of orbit ensembles with the aim of understanding how such
irregularities can increase the efficacy of chaotic mixing. For both noise and
periodic driving, the effect of the perturbation scales roughly in amplitude.
For white noise, the details are unimportant: additive and multiplicative noise
tend to have similar effects and the presence or absence of a friction related
to the noise by a Fluctuation- Dissipation Theorem is largely irrelevant.
Allowing for coloured noise can significantly decrease the efficacy of the
perturbation, but only when the autocorrelation time, which vanishes for white
noise, becomes so large that t here is little power at frequencies comparable
to the natural frequencies of the unperturbed orbit. This suggests strongly
that noise-induced extrinsic diffusion, like modulational diffusion associated
with periodic driving, is a resonance phenomenon. Potential implications for
galaxies are discussed.Comment: 15 pages including 18 figures, uses MNRAS LaTeX macro
On gravitational-wave spectroscopy of massive black holes with the space interferometer LISA
Newly formed black holes are expected to emit characteristic radiation in the
form of quasi-normal modes, called ringdown waves, with discrete frequencies.
LISA should be able to detect the ringdown waves emitted by oscillating
supermassive black holes throughout the observable Universe. We develop a
multi-mode formalism, applicable to any interferometric detectors, for
detecting ringdown signals, for estimating black hole parameters from those
signals, and for testing the no-hair theorem of general relativity. Focusing on
LISA, we use current models of its sensitivity to compute the expected
signal-to-noise ratio for ringdown events, the relative parameter estimation
accuracy, and the resolvability of different modes. We also discuss the extent
to which uncertainties on physical parameters, such as the black hole spin and
the energy emitted in each mode, will affect our ability to do black hole
spectroscopy.Comment: 44 pages, 21 figures, 10 tables. Minor changes to match version in
press in Phys. Rev.
A high-resolution infrared spectroscopic investigation of the halogen atom-HCN entrance channel complexes solvated in superfluid helium droplets
Rotationally resolved infrared spectra are reported for the X-HCN (X = Cl,
Br, I) binary complexes solvated in helium nanodroplets. These results are
directly compared with that obtained previously for the corresponding X-HF
complexes [J. M. Merritt, J. K\"upper, and R. E. Miller, PCCP, 7, 67 (2005)].
For bromine and iodine atoms complexed with HCN, two linear structures are
observed and assigned to the and ground
electronic states of the nitrogen and hydrogen bound geometries, respectively.
Experiments for HCN + chlorine atoms give rise to only a single band which is
attributed to the nitrogen bound isomer. That the hydrogen bound isomer is not
stabilized is rationalized in terms of a lowering of the isomerization barrier
by spin-orbit coupling. Theoretical calculations with and without spin-orbit
coupling have also been performed and are compared with our experimental
results. The possibility of stabilizing high-energy structures containing
multiple radicals is discussed, motivated by preliminary spectroscopic evidence
for the di-radical Br-HCCCN-Br complex. Spectra for the corresponding molecular
halogen HCN-X complexes are also presented.Comment: 20 pages, 15 figures, 6 tables, RevTe
3D geological models and their hydrogeological applications : supporting urban development : a case study in Glasgow-Clyde, UK
Urban planners and developers in some parts of the United Kingdom can now access geodata in an easy-to-retrieve and understandable format. 3D attributed geological framework models and associated GIS outputs, developed by the British Geological Survey (BGS), provide a predictive tool for planning site investigations for some of the UK's largest regeneration projects in the Thames and Clyde River catchments.
Using the 3D models, planners can get a 3D preview of properties of the subsurface using virtual cross-section and borehole tools in visualisation software, allowing critical decisions to be made before any expensive site investigation takes place, and potentially saving time and money. 3D models can integrate artificial and superficial deposits and bedrock geology, and can be used for recognition of major resources (such as water, thermal and sand and gravel), for example in buried valleys, groundwater modelling and assessing impacts of underground mining. A preliminary groundwater recharge and flow model for a pilot area in Glasgow has been developed using the 3D geological models as a framework.
This paper focuses on the River Clyde and the Glasgow conurbation, and the BGS's Clyde Urban Super-Project (CUSP) in particular, which supports major regeneration projects in and around the City of Glasgow in the West of Scotland
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