2,764 research outputs found
Concentrations of Polychlorinated Biphenyls (PCBs), Polychlorinated Dibenzo-p-dioxins and Furans (PCDD/Fs), and Polybrominated Diphenyl Ethers (PBDEs) as Functions of Sample Depth in Killer Whale (Orcinus orca) Blubber
Concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs) were examined as a function of depth in killer whale (Orcinus orca) blubber samples. Lipid-normalized concentrations of PCBs, PCDD/Fs, and PBDEs did not display significant variation with depth in three distinct blubber layers (outer, central, and inner). Significantly more variation in contaminant concentrations were observed with depth on a wet weight basis for the killer whale sample. The current study indicates that non-invasive microdart biopsy sampling methods commonly used for monitoring contaminants in marine mammals yield representative details on contaminant burdens for chlorinated and brominated aromatic compounds in marine mammal blubber, regardless of the quantity and type of blubber sampled, provided that lipid normalization is performed on resulting analytical determinations
Adaptive Mesh Refinement for Supersonic Molecular Cloud Turbulence
We performed a series of three-dimensional numerical simulations of
supersonic homogeneous Euler turbulence with adaptive mesh refinement (AMR) and
effective grid resolution up to 1024^3 zones. Our experiments describe
non-magnetized driven supersonic turbulent flows with an isothermal equation of
state. Mesh refinement on shocks and shear is implemented to cover dynamically
important structures with the highest resolution subgrids and calibrated to
match the turbulence statistics obtained from the equivalent uniform grid
simulations.
We found that at a level of resolution slightly below 512^3, when a
sufficient integral/dissipation scale separation is first achieved, the
fraction of the box volume covered by the AMR subgrids first becomes smaller
than unity. At the higher AMR levels subgrids start covering smaller and
smaller fractions of the whole volume, which scale with the Reynolds number as
Re^{-1/4}. We demonstrate the consistency of this scaling with a hypothesis
that the most dynamically important structures in intermittent supersonic
turbulence are strong shocks with a fractal dimension of two. We show that
turbulence statistics derived from AMR simulations and simulations performed on
uniform grids agree surprisingly well, even though only a fraction of the
volume is covered by AMR subgrids. Based on these results, we discuss the
signature of dissipative structures in the statistical properties of supersonic
turbulence and their role in overall flow dynamics.Comment: 5 pages, 5 figures, revised versio
Performance of a Brief Assessment Tool for Identifying Substance Use Disorders
Objective: Evaluation of the performance of a brief assessment tool for identifying substance use disorders. The Triage Assessment for Addictive Disorders (TAAD) is a triage instrument that provides professionals with a tool to evaluate indications of current substance use disorders in accordance with the DSM-IV diagnostic criteria. The TAAD is a 31-item structured interview that addresses both alcohol and other drug issues to discriminate among those with no clear indications of a diagnosis, those with definite, current indications of abuse or dependence, and those with inconclusive diagnostic indications.
Methods: Employing a sample of 1325 women between the ages of 18 and 60, reliability estimates and problem profiles produced by the TAAD were evaluated.
Results: The Cronbach alpha coefficients for internal consistency for both the alcohol and drug dependence scales were .92. The alpha coefficients for the alcohol and drug abuse scales were .83 and .84 respectively. The diagnostic profiles elicited from the TAAD indicate that alcohol and drug dependences are the more definitive and distinct syndromes compared with the abuse syndromes.
Conclusions: The diagnostic profiles from this sample are consistent with previous research. The Cronbach alpha coefficients suggest that the TAAD provides an internally consistent index for alcohol and drug dependence and abuse. Implications for use in clinical practice and the need for further research regarding the psychometric properties of the TAAD are discussed
Scaling Laws and Intermittency in Highly Compressible Turbulence
We use large-scale three-dimensional simulations of supersonic Euler
turbulence to study the physics of a highly compressible cascade. Our numerical
experiments describe non-magnetized driven turbulent flows with an isothermal
equation of state and an rms Mach number of 6. We find that the inertial range
velocity scaling deviates strongly from the incompressible Kolmogorov laws. We
propose an extension of Kolmogorov's K41 phenomenology that takes into account
compressibility by mixing the velocity and density statistics and preserves the
K41 scaling of the density-weighted velocity v=rho^{1/3}u. We show that
low-order statistics of 'v' are invariant with respect to changes in the Mach
number. For instance, at Mach 6 the slope of the power spectrum of 'v' is -1.69
and the third-order structure function of 'v' scales linearly with separation.
We directly measure the mass dimension of the "fractal" density distribution in
the inertial subrange, D_m=2.4, which is similar to the observed fractal
dimension of molecular clouds and agrees well with the cascade phenomenology.Comment: 7 pages, 3 figures; in press, AIP Conference Proceedings: "Turbulence
and Nonlinear Processes in Astrophysical Plasmas", Waikiki Beach, Hawaii,
March 21, 200
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