The effects of attention problems on depression: Developmental, academic, and cognitive pathways.

The present study investigated developmental pathways between inattention and depression, particularly the roles of school maladjustment and child cognitions. Additionally, a measure of conduct problems was included in all analyses to test competing theories about the emergence of depressive symptoms. Results supported the hypothesized path models from inattention to depression for younger and older children. Consistent with developmental theories, only an environmental variable, school maladjustment, was needed to explain the relationship between inattention and depression for the younger group (under 8 years old). For children in the middle group (8-9 years old), school maladjustment continued to uniquely account for part of the path to child depressive symptoms, but a cognitive variable, control-related beliefs, emerged as a significant mediator as well. For older children (10 years and older), control-related beliefs fully mediated the effects of school maladjustment on depressive symptoms. The hypothesized paths from conduct problems to depression, however, were not supported. Implications for designing interventions and prevention strategies for children with inattention and conduct problems are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging effects on microstructural and mechanical properties of select refractory metal alloys for space-reactor applications

Refractory alloys based on niobium, tantalum and molybdenum are potential candidate materials for structural applications in proposed space nuclear reactors. Long-term microstructural stability is a requirement of these materials for their use in this type of creep dominated application. Early work on refractory metal alloys has shown aging embrittlement occurring for some niobium and tantalum-base alloys at temperatures near 40% of their melting temperatures in either the base metal or in weldments. Other work has suggested microstructural instabilities during long-term creep testing, leading to decreased creep performance. This paper examines the effect of aging 1100 h at 1098, 1248 and 1398 K on the microstructural and mechanical properties of two niobium (Nb-1Zr and FS-85), tantalum (T-111 and ASTAR-811C) and molybdenum (Mo-41Re and Mo-47.5Re) base alloys. Changes in material properties are examined through mechanical tensile testing coupled with electrical resistivity changes and microstructural examination through optical and electron microscopy analysis.     

A prospective study of short- and long-term outcomes after traumatic brain injury in children: Behavior and achievement.

Longitudinal behavior and achievement outcomes of traumatic brain injury (TBI) were investigated in 53 children with severe TBI, 56 children with moderate TBI, and 80 children with orthopedic injuries not involving brain insult. Measures of preinjury child and family status and of postinjury achievement skills were administered shortly after injury. Assessments were repeated 3 times across a mean follow-up interval of 4 years. Results from mixed model analysis revealed persisting sequelae of TBI. Recovery of math skills was observed in the severe TBI group but only for children from less stressed families. Social disadvantage in children with TBI predicted more adverse behavioral sequelae and less favorable changes in some outcome measures. The findings suggest that pediatric TBI has long-term effects on behavior and achievement but that postinjury progress is influenced by the family environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Linking sportfishing trip attributes,participation decisions,and regional economic impacts in Lower and Central Cook Inlet,Alaska

Forecasts of the regional economic impacts of changes in the demand for recreation occasioned by regulatory changes, changes in the quality of the recreation experience, or changes in average trip costs require a model that links changes in these trip attributes to individual participation decisions and population participation rates. The probability that an individual will take a particular recreational trip is described using a nonlinear random effects probit model based on variable trip attributes and individual economic and demographic characteristics. These conditional individual probabilities are transformed into predictions of changes in total recreation demand using a simulation-based sample enumeration method. The regional impacts associated with ensuing changes in primary and secondary expenditure patterns are elucidated with a stand-alone recreation-sector module linked to a regionally adjusted zip code-level input-output model. Because the participation model allows for non-constant marginal utility, primary and secondary impacts exhibit nonlinear responses to variations in trip attributes. The modeling approach is demonstrated in an application to the saltwater sport fisheries for Pacific halibut and salmon in Lower and Central Cook Inlet, Alaska. Received: February 2001/Accepted: December 2001     

The domain specificity and generality of disjunctive reasoning: Searching for a generalizable critical thinking skill.

The domain specificity and generality of an important critical thinking skill was examined by administering 9 reasoning and decision-making tasks to 125 adults. Optimal performance on all of the tasks required that disjunctive processing strategies--strategies requiring the exhaustive consideration of all of the possible states of the world--be adopted. Performance across these disjunctive reasoning tasks displayed considerable domain specificity, but 5 of the tasks displayed moderate convergence. Cognitive ability was associated with performance on only 3 of 9 tasks. Six of the 9 tasks displayed associations with 1 of 2 cognitive styles that were examined in the multivariate task battery (need for cognition and reflectivity). Performance on the 5 tasks that displayed some domain generality was also more associated with thinking styles than with cognitive ability in several regression analyses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature and congener structure affect the enantioselectivity of toxaphene elimination by fish

Recent advances in enantioselective separation techniques have enabled scientists to investigate environmental fate processes of chiral pollutants. In this study, congener- and enantiomer-specific toxaphene residues were monitored in captive, naturally contaminated fish (Fundulus heteroclitus) to characterize the effect of temperature and compound structure on the enantioselectivity of the elimination process. A previous study performed under warm water conditions (Tmean = 25 degrees C) demonstrated relatively rapid (t(1/2) approximately = 7-14 d) and enantioselective elimination of the reductive dechlorination metabolites 2-exo,3-endo,6-exo,8,9,-10-hexachlorobornane (B6-923 or Hx-Sed) and 2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane (B7-1001 or Hp-Sed). As expected, repetition of this experiment at cooler water temperatures (Tmean = 15 degrees C) resulted in a decrease in overall (i.e., both enantiomers) first-order elimination rate constants. Enantiomer fractions or ratios (EFs/ERs) during elimination, however, varied by congener, ranging from racemic for very rapidly eliminated Cl5 homologues to increasingly nonracemic for selected Cl6-Cl8 homologues (including 86-923, several unknown Cl7 compounds, B8-1414, and B8-1945). As a result, we propose a classification to describe the environmental persistence of chiral toxaphene pollutants based on congener-specific elimination kinetics and susceptibility to biotransformation as measured by EFs/ERs.     

Autocorrelation and cepstral methods for measurement of tibial cortical thickness

Cortical thickness of the tibia is related to stress fracture risk and overall skeletal status. Two methods are proposed for estimating tibial cortical thickness based on power spectra of ultrasonic echoes containing reflections from front and back surfaces of the cortex. The locations of the peaks in the autocorrelation function and the cepstrum are related to cortical thickness. Data were acquired on plastic plates in order to validate the methodology. These data indicate high correlations between estimated and true thickness with correlation coefficients r=0.99, (95% confidence interval: 0.993-1.00) for the autocorrelation method and r=0.99 (95% CI: 0.996-1.00) for the cepstral method. Data on six tibia samples in vitro indicate correlation coefficients of r=0.92 (95% CI: 0.72-1.00) for the autocorrelation method and r=0.85 (95% CI: 0.62-0.94) for the cepstral method. Estimates of precisions of the two methods were 0.3/spl plusmn/0.1 mm (autocorrelation method) and 0.5/spl plusmn/0.2 mm (cepstral method). One measurement in a human volunteer in vivo demonstrated clinical feasibility of the measurement and good agreement with cortical thickness assessed using peripheral quantitative computed tomography (QCT). This technology offers the promise of an inexpensive, fast, portable, simple, nonionizing technique for assessing skeletal status.     

The dependence of ultrasonic backscatter on trabecular thickness in human calcaneus: theoretical and experimental results

Trabecular thickness within cancellous bone is an important determinant of osteoporotic fracture risk. Noninvasive assessment of trabecular thickness potentially could yield useful diagnostic information. Faran's theory of elastic scattering from a cylindrical object immersed in a fluid has been used to predict the dependence of ultrasonic backscatter on trabecular thickness. The theory predicts that, in the range of morphological and material properties expected for trabecular bone, the backscatter coefficient at 500 kHz should be approximately proportional to trabecular thickness to the power of 2.9. Experimental measurements of backscatter coefficient were performed on 43 human calcaneus samples in vitro. Mean trabecular thicknesses on the 43 samples were assessed using micro computed tomography (CT). A power law fit to the data showed that the backscatter coefficient empirically varied as trabecular thickness to the 2.8 power. The 95% confidence interval for this exponent was 1.7 to 3.9. The square of the correlation coefficient for the linear regression to the log transformed data was 0.40. This suggests that 40% of variations in backscatter may be attributed to variations in trabecular thickness. These results reinforce previous studies that offered validation for the Faran cylinder model for prediction of scattering properties of cancellous bone, and provide added evidence for the potential diagnostic utility of the backscatter measurement.     

Total protein determinations by particle beam/hollow cathode optical emission spectroscopy

A novel method for quantitative total protein determinations is presented. Total protein content is determined by particle beam/hollow cathode optical emission spectroscopy (PB/HC-OES) through monitoring of carbon atomic emission. The PB/HC-OES offers such advantages as ease of operation, exclusion of labor-intensive sample pretreatment processes, rapid analysis, high sensitivity, and low detection limit. The method could also be adapted to be integrated to current microfluidics devices. Parametric optimization for sample introduction, nebulization, desolvation, and hollow cathode source conditions is performed for the analysis of aqueous bovine serum albumin solutions. Response curves of C (I) 193.0-nm emission were obtained under the optimized conditions with both 10% HCl and 100 micromL KCl added to the sample matrix as potential carriers. The detection limit for triplicate injections of bovine serum albumin standards was found to be on the single-nanogram level with 200-microL injections. The addition of KCl significantly improved the sensitivity, supporting the proposed "carrier effect" of chloride salts in the particle transport process. Results obtained here suggest a range of applications for the use of the PB/HC-OES source for total protein determinations; emphasis here is future use in assessing protein quantification in microfluidic systems.     

Distribution and mass inventory of total dichlorodiphenyldichloroethylene in the water column of the southern California bight

A large-scale survey on the area and depth stratified distribution of dichlorodiphenyltrichloroethane (DDT; mainly p,p'- and o,p'-dichlorodiphenyldichloroethylene (DDE)) contamination in the water column of the Southern California Bight (SCB) was conducted in 2003-2004 using a solid-phase microextraction-based sampling technique. Dissolved-phase DDEs were clearly widespread, with the central SCB containing the highest levels, and the Palos Verdes Shelf sediments have remained the dominant source of DDT compounds to the SCB. The p,p'- and o,p'-DDE concentrations ranged from < 0.073 to 2.6 ng/L and from < 0.043 to 0.26 ng/L, respectively, clearly elevated with respect to measured values from across the globe. DDEs were hypothesized to have been transported from the historically contaminated zone on the Palos Verdes Shelf to other areas via a repeated process of sediment resuspension/deposition and short-range advection. Total mass inventories were estimated at 14 and 0.86 kg for p,p'- and o,p'-DDE, respectively, for the sampled area, resulting in p,p'- and o,p'-DDE mass inventories for the entire SCB of 230 and 14 kg, respectively. Furthermore, total fluxes of p,p'-DDE were estimated to be in the range of 0.8 to 2.3 metric tons per year. These results suggest that the SCB has been and continues to be a significant source of DDT contamination to the global oceans.