Placement report: 1971.

Reports an abrupt downturn in the market for psychologists as shown in a series of spring placement services studies. The number of positions advertised in the base-line year of 1969 was over twice the number advertised in 1971. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patient variables in emotional response to hospitalization for physical illness.

Emotional response to hospitalization was related to a variety of patient variables for 517 relatively long-term male medical patients from 10 VA hospitals across the country. Feelings of comfort with the hospitalization experience were greater for: (1) older patients, (2) patients who prefer an authoritarian approach by the staff, and (3) patients with lower characteristic trait anxiety. These 3 variables were essentially independent predictors. Neither current nor expected future medical status was significantly related to comfort when age was held constant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Matched-pair cohort methods in traffic crash research

Standard analysis of matched-pair cohort data requires information only from pairs in which at least one had the study outcome. This can be useful in traffic fatality studies of characteristics that can vary among vehicle occupants, such as seat belt use, as crash databases often lack information about vehicles in which all survived. However, matching crash victims who were in the same vehicle does not necessarily eliminate confounding by vehicle or crash related factors, because the matched occupants must be in different seat positions. This paper reviews three methods for estimating relative risks in matched-pair crash data. The first, Mantel-Haenszel stratified methods, may produce biased estimates if seat position is associated with the outcome. The second, the double-pair comparison method, was designed to deal with confounding by seat position. If the effects of seat position vary according to some vehicle or crash characteristic which is associated with the study exposure, adjustment for this characteristic may be needed to produce unbiased estimates. Third, conditional Poisson regression and Cox proportional hazards regression can produce unbiased estimates, but may require model interaction terms between seat position and vehicle or crash characteristics. This paper reviews some of the strengths and limitations of each of these methods, and illustrates their use in simulated and real crash data.     

Faceted design of channels for low-dispersion electrokinetic flows in microfluidic systems

A novel methodology for designing microfluidic channels for low-dispersion, electrokinetic flows is presented. The technique relies on trigonometric relations that apply for ideal electrokinetic flows, allowing faceted channels to be designed using common drafting software and a hand calculator. Flows are rotated and stretched along the abrupt interface between adjacent regions having differing specific permeability--a quantity with dimensions of length that we introduce to derive the governing equations. Two-interface systems are used to eliminate hydrodynamic rotation of bands injected into channels. Regions bounded by interfaces form faceted flow "prisms" with uniform velocity fields that can be combined with other prisms to obtain a wide range of turning angles and expansion ratios. Lengths of faceted prisms can be varied arbitrarily, simplifying chip layout and allowing the ability to reduce unwanted effects such as transverse diffusion and Joule heating for a given faceted prism. Designs are demonstrated using two-dimensional numerical solutions of the Laplace equation.     

Dielectrophoresis in microchips containing arrays of insulating posts: theoretical and experimental results

Dielectrophoresis (DEP), a nonlinear electrokinetic transport mechanism, can be used to concentrate and sort cells, viruses, and particles. To date, microfabricated DEP-based devices have typically used embedded metal electrodes to apply spatially nonuniform, time-varying (AC) electric fields. We have developed an alternative method in which arrays of insulating posts in a channel of a microchip produce the spatially nonuniform fields needed for DEP. Electrodes may be located remotely, allowing operation of the device down to zero frequency (DC) without excessive problems of electrolysis. Applying a sufficiently large electric field across an insulating-post array produces two flow regimes through a competition between electrokinetic flow (combined electrophoresis and electroosmosis) and dielectrophoresis. "Streaming DEP" is observed when DEP dominates diffusion but is overcome by electrokinetic flow. Particles concentrated by DEP forces in areas of electric field extrema travel electrokinetically down the array in flowing streams. In an array of posts, dielectrophoretic forcing within repeated rows adds coherently to produce flowing streams of highly concentrated and rarefied particles. We demonstrate that this reinforcement is a strong function of alignment of the array with respect to the applied electric field and that the particle concentrations can be "enhanced" or "depleted" along columns of posts, enabling a novel class of continuous-flow, selective particle filter/concentrator devices. To our knowledge, this is the first observation of streaming dielectrophoresis. The second regime is "trapping DEP," in which DEP forces dominate over both diffusion and electrokinetic flow, reversibly immobilizing particles on the insulating posts, enabling inexpensive and embedded batch filter/concentrator devices. Devices can be biased electrically to manipulate particles selectively by varying the field strength to vary the relative magnitudes of electrokinetic flow and DEP. Post shapes are contoured easily to control electric field gradients and, hence, DEP behavior. Simple simulations based on similitude of fluid flow and electric field that solve the Laplace equation to obtain fluid velocity have also been developed to predict the dielectrophoretic behavior in an array of posts. These simulations are in excellent agreement with the experimental observations and provide insight into electrokinetic behavior to enable design of dielectrophoretic concentrators and sorters.     

Composite carbon paste biosensor for phenolic derivatives based on in situ electrogenerated polypyrrole binder

Amperometric biosensors based on new composite carbon paste (CPE) electrodes have been designed for the determination of phenolic compounds. The composite CPEs were prepared by in situ generation of polypyrrole (PPy) within a paste containing the enzyme polyphenol oxidase (PPO). The best paste composition (enzyme/pyrrole monomer/carbon particles/Nujol) was determined for a model enzyme, glucose oxidase, according to the enzymatic activity of the resulting electrodes and to the enzyme leakage from the paste during storage in phosphate buffer. The in situ electrogenerated PPy enables improvement in enzyme immobilization within the paste since practically no enzyme was lost in solution after 72 h of immersion. Moreover, the enzyme activity remains particularly stable under storage since the biocomposite structure maintains 80% of its activity after 1-month storage. Following the optimization of the paste composition, PPO-based carbon paste biosensors were prepared and presented excellent analytical properties toward catechol detection with a sensitivity of 4.7 A M(-1) cm(-2) and a response time lower than 20 s. The resulting biosensors were finally applied to the determination of epicatechin and ferulic acid as flavonol and polyphenol model, respectively.     

Assessment of Load Transfer and Load Distribution in Bridges Utilizing FRP Panels

A primary means of demonstrating the feasibility and effectiveness of fiber-reinforced polymer (FRP) composite bridge materials is via in situ bridge load testing. For this study, the prescribed or assumed design factors for each of the study bridges were compared to those exhibited by the performance of the bridge. Specifically, the wheel load distribution factors and impact factors as defined by AASHTO were considered in order to assess the load transfer and distribution in structures utilizing FRP panels. The in situ testing configurations for the study bridges are outlined, including the truck and instrumentation placement to obtain the desired information. Furthermore, comparisons were drawn between the design values for deflection and those experienced by the structures during testing. It was found that although the deflections exhibited by the bridges were well within the design limits, further research is needed to be able to prescribe bridge design factors for FRP panels.     

Dopamine D? receptor stimulation of the nucleus accumbens or the medial preoptic area promotes the onset of maternal behavior in pregnancy-terminated rats.

There is good evidence that interference with the mesolimbic dopamine (DA) system results in impaired maternal responding in postpartum female rats. However, whether activation of the mesolimbic DA system is capable of promoting maternal behavior has not been investigated. This study examined whether increasing DA activity in various brain regions of pregnancy-terminated, naive female rats would stimulate the onset of maternal behavior. Experiments 1 and 2 examined the effects of microinjection of various doses (0, 0.2, or 0.5 μg/0.5 μl/side) of a D? DA receptor agonist, SKF 38393, or a D? DA receptor agonist, quinpirole, into the nucleus accumbens (NA) on latency to show full maternal behavior, and Experiment 3 determined the effects of SKF 38393 injection into a control site. Finally, because the medial preoptic area (MPOA) is also important for maternal behavior, receives DA input, and expresses DA receptors, the authors examined whether microinjection of SKF 38393 into MPOA was capable of stimulating the onset of maternal behavior. Results indicated that microinjection of SKF 38393 into either the NA or the MPOA facilitates maternal responding in pregnancy-terminated rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Linkages between spouses' psychological distress and marital conflict in the home.

To elucidate the processes that underlie the established association between psychopathology and marital functioning, researchers have given attention to how symptomatic individuals manage their interpersonal contexts, particularly during the handling of disagreements. In the current study, the authors evaluate the role of marital conflict strategies in relation to wives' and husbands' psychological distress levels. A sample of 100 community-based couples completed assessments of psychological distress and diaries describing marital conflict that occurred at home during a 15-day reporting period. Findings from multilevel modeling of dyadic data revealed associations between both spouses' psychological distress and multiple behavioral and emotional conflict expressions in the home. Psychological symptoms uniquely predicted the occurrence of certain conflict expressions, even when accounting for global negative marital sentiments. The findings encourage subsequent consideration of marital conflict expressions and resolution strategies when studying processes involved in the marriage-psychological adjustment link. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Algorithms for testing that sets of DNA words concatenate without secondary structure

We present an efficient algorithm for determining whether all moleculesin a combinatorial set of DNA or RNA strandsare structure free, and thus availablefor bonding to their Watson-Crick complements.This work is motivated by the goalof testing whether strands used in DNAcomputations or as molecular bar-codesare structure free, where the strands areconcatenations of short words. We alsopresent an algorithm for determining whetherall words in S*, for some finite setS of equi-length words, are structure free. This revised version was published online in June 2006 with corrections to the Cover Date.