3,705 research outputs found
The Effect of Projection on Derived Mass-Size and Linewidth-Size Relationships
Power law mass-size and linewidth-size correlations, two of "Larson's laws,"
are often studied to assess the dynamical state of clumps within molecular
clouds. Using the result of a hydrodynamic simulation of a molecular cloud, we
investigate how geometric projection may affect the derived Larson
relationships. We find that large scale structures in the column density map
have similar masses and sizes to those in the 3D simulation (PPP). Smaller
scale clumps in the column density map are measured to be more massive than the
PPP clumps, due to the projection of all emitting gas along lines of sight.
Further, due to projection effects, structures in a synthetic spectral
observation (PPV) may not necessarily correlate with physical structures in the
simulation. In considering the turbulent velocities only, the linewidth-size
relationship in the PPV cube is appreciably different from that measured from
the simulation. Including thermal pressure in the simulated linewidths imposes
a minimum linewidth, which results in a better agreement in the slopes of the
linewidth-size relationships, though there are still discrepancies in the
offsets, as well as considerable scatter. Employing commonly used assumptions
in a virial analysis, we find similarities in the computed virial parameters of
the structures in the PPV and PPP cubes. However, due to the discrepancies in
the linewidth- and mass- size relationships in the PPP and PPV cubes, we
caution that applying a virial analysis to observed clouds may be misleading
due to geometric projection effects. We speculate that consideration of
physical processes beyond kinetic and gravitational pressure would be required
for accurately assessing whether complex clouds, such as those with highly
filamentary structure, are bound.Comment: 25 pages, including 7 Figures; Accepted for publication in Ap
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Map and Data for Quaternary Faults in West Texas and Adjacent Parts of Mexico
The "World Map of Major Active Faults" Project is compiling a series of digital maps for the United States and other countries that show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds; the companion database includes published information on these seismogenic features. This effort is sponsored by International Lithosphere Program (ILP) Project 11-2 and funded by the Earthquake Hazards Reduction Program (EHRP) through the U.S. Geological Survey. The maps and accompanying databases represent a key contribution to the new Global Seismic Hazards Assessment Program (ILP Project II-0) for the International Decade for Natural Disaster Reduction. This compilation, which describes surface faulting in West Texas and adjacent parts of Mexico, is the first of many similar State and regional compilations that are planned for the project. This compilation is presented as a traditional map product and printed catalog of data; however both should be available in digital form in the future. The database provides referenced data on a variety of geographic, geologic, and paleoseismologic parameters. The fault data were compiled by the senior authors (Edward W. Collins and Jay A. Raney, Texas Bureau of Economic Geology) as part of ongoing studies of active faulting in the West Texas area and adjacent parts of Mexico. The U.S. Geological Survey authors are responsible for organizing and integrating State and regional products under the national project, including the coordination and oversight of contributions from individuals and groups (Michael N. Machette, Project Chief), database design and management (Kathleen M. Haller), and digitization and manipulation of map data (Richard L. Dart).Bureau of Economic Geolog
Cyclical 'flipping' of morphology in block copolymer films
We studied the kinetics of nanopattern evolution in (polystyrene-b-polyethylene oxide) diblock copolymer thin films. Using scanning force microscopy, a highly unexpected cylindrical flipping of morphology from normal to parallel to the film plane was detected during solvent annealing of the film (with average thickness of 30 nm) at high vapor pressure. Using an in situ time-resolved light scattering device combined with an environmental cell enabled us to obtain kinetic information at different vapor pressures. The data indicated that there is a threshold value for the vapor pressure necessary for the structural transition. We propose a swelling and deswelling mechanism for the orientation flipping of the morphology. The cyclic transition occurs faster in thick films (177 nm) where the mass uptake and solvent volume fraction is smaller and therefore the driving force for phase separation is higher. We induced a stronger segregation by confining the chains in graphoepitaxially patterned substrates. As expected, the cyclic transition occurred at higher rate. Our work is another step forward to understanding the structure evolution and also controlling the alignment of block copolymer nanocylinders independently of thickness and external fields
Comparison of Electrical Moisture Meters for Baled Alfalfa Hay
A primary concern in producing quality alfalfa hay is moisture measurement. Some precision in moisture measurement is required since hay can be too wet, leading to dry matter and quality loss through mold; it can be too dry, leading to shatter loss during baling, handling and storage.
Moisture measurement in hay can take many forms. One form of subjective (personal judgment) evaluation is brittleness of leaves and stems in the windrow or bale. Typical objective methods consist of electric meters with calibration curves and oven drying
Exploring the Impacts of Predictor Variables on Success in a Mental Health Diversion Program
Since the first Mental Health Court (MHC) in 1997, there has been a steady increase of MHCs all over the country. With the introduction of these new specialty courts have also come to introduction of diversion programs. Diversion programs work to connect offenders who have mental illnesses to community-based mental health treatment services as an alternative to incarceration. Typically, with the completion of the program comes with the benefit of having their charges dropped. Diversion programs aim to reduce recidivism in offenders with mental illness and improve their access to treatment
Addendum to "Sufficient conditions for three-particle entanglement and their tests in recent experiments"
A recent paper [M. Seevinck and J. Uffink, Phys. Rev. A 65, 012107 (2002)]
presented a bound for the three-qubit Mermin inequality such that the violation
of this bound indicates genuine three-qubit entanglement. We show that this
bound can be improved for a specific choice of observables. In particular, if
spin observables corresponding to orthogonal directions are measured at the
qubits (e.g., X and Y spin coordinates) then the bound is the same as the bound
for states with a local hidden variable model. As a consequence, it can
straightforwardly be shown that in the experiment described by J.-W. Pan et al.
[Nature 403, 515 (2000)] genuine three-qubit entanglement was detected.Comment: Two pages, no figures, revtex4; minor changes before publicatio
Multiple indices of diffusion identifies white matter damage in mild cognitive impairment and Alzheimer's disease
The study of multiple indices of diffusion, including axial (DA), radial (DR) and mean diffusion (MD), as well as fractional anisotropy (FA), enables WM damage in Alzheimer's disease (AD) to be assessed in detail. Here, tract-based spatial statistics (TBSS) were performed on scans of 40 healthy elders, 19 non-amnestic MCI (MCIna) subjects, 14 amnestic MCI (MCIa) subjects and 9 AD patients. Significantly higher DA was found in MCIna subjects compared to healthy elders in the right posterior cingulum/precuneus. Significantly higher DA was also found in MCIa subjects compared to healthy elders in the left prefrontal cortex, particularly in the forceps minor and uncinate fasciculus. In the MCIa versus MCIna comparison, significantly higher DA was found in large areas of the left prefrontal cortex. For AD patients, the overlap of FA and DR changes and the overlap of FA and MD changes were seen in temporal, parietal and frontal lobes, as well as the corpus callosum and fornix. Analysis of differences between the AD versus MCIna, and AD versus MCIa contrasts, highlighted regions that are increasingly compromised in more severe disease stages. Microstructural damage independent of gross tissue loss was widespread in later disease stages. Our findings suggest a scheme where WM damage begins in the core memory network of the temporal lobe, cingulum and prefrontal regions, and spreads beyond these regions in later stages. DA and MD indices were most sensitive at detecting early changes in MCIa
Reproducibility and comparative validity of a food frequency questionnaire for Australian children and adolescents
Dietary intake during childhood and adolescence is of increasing interest due to its influence on adult health, particularly obesity, cardiovascular disease and diabetes. There is a need to develop and validate dietary assessment methods suitable for large epidemiologic studies of children and adolescents. Limited large scale dietary studies of youth have been undertaken in Australia, due partly to the lack of a suitable dietary intake tool. A self-administered, semi-quantitative food-frequency questionnaire (FFQ), the 'Australian Child and Adolescent Eating Survey' (ACAES), was developed for youth aged 9-16 years. This study evaluated reproducibility and comparative validity of the ACAES FFQ using assisted food records (FRs) as the reference method. The ACAES FFQ was completed twice (FFQ1 and FFQ2) at an interval of 5 months, along with four one-day assisted FRs. Validity was evaluated by comparing the average of the FRs with FFQ2 (n = 113) as well as with the average of FFQ1 and FFQ2 (n = 101). Reproducibility was evaluated by comparing FFQ1 and FFQ2 (n = 101). The two methods were compared using correlations, Kappa statistics and Bland-Altman plots. Correlation coefficients for comparative validity ranged from 0.03 for retinol to 0.56 for magnesium for transformed, energy-adjusted, deattenuated nutrient data, with correlation coefficients greater than 0.40 for total fat, saturated fat, monounsaturated fat, carbohydrate, sugars, riboflavin, vitamin C, folate, beta-carotene, magnesium, calcium and iron. Correlation coefficients for reproducibility ranged from 0.18 for vitamin A to 0.50 for calcium for transformed, energy-adjusted, deattenuated nutrient data. The ACAES FFQ ranked individuals reasonably accurately, with the comparative validity analysis showing that over 50% of participants were classified within one quintile for all nutrients, with only a small percentage grossly misclassified (0-7%). The ACAES FFQ is the first child and adolescent specific FFQ available for ranking the dietary intakes of Australian children and adolescents for a range of nutrients in epidemiologic research and public health interventions
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