Trace metal leaching behavior studied through the use of parametric modeling of water borne soil particles fractionated with a split-flow thin cell

Leaching of particle-bound metals affects the ability of settling ponds and other engineered structures to remove metallic pollutants, and leaching behavior is related to particle size. In this investigation, water borne soil particles were leached and fractionated with a split-flow thin cell, and the metal loadings were quantified as a function of particle size. For comparison of the metal-loading curves, different empirical modeling procedures were investigated to convert the data to a precise functional form suitable for quantitative comparison of changes in differential loading as a function of particle size. Results of this investigation are presented for a soil sample before and after leaching caused by simulated acid rain conditions. Following simulated acid rain leaching, the shape of the differential distribution curves change, and these changes reflect the particle size mediated leaching behavior. For the soil used in this demonstration, simulated acid rain leaching shifted the differential loading toward larger particle sizes, and the magnitude of the shift varied significantly among the metals. Because settling rate decreases as the square of particle size, this could potentially affect management decisions for settling ponds receiving these particles. The high precision afforded by the analysis allows the development of insight into the leaching mechanisms through comparing "partial" acid rain leaching with "total recoverable" leaching by EPA Method 3050.     

Terahertz polariton propagation in patterned materials

Generation and control of pulsed terahertz-frequency radiation have received extensive attention, with applications in terahertz spectroscopy, imaging and ultrahigh-bandwidth electro-optic signal processing. Terahertz 'polaritonics', in which terahertz lattice waves called phonon-polaritons are generated, manipulated and visualized with femtosecond optical pulses, offers prospects for an integrated solid-state platform for terahertz signal generation and guidance. Here, we extend terahertz polaritonics methods to patterned structures. We demonstrate femtosecond laser fabrication of polaritonic waveguide structures in lithium tantalate and lithium niobate crystals, and illustrate polariton focusing into, and propagation within, the fabricated waveguide structures. We also demonstrate a 90 degrees turn within a structure consisting of two waveguides and a reflecting face, as well as a structure consisting of splitting and recombining elements that can be used as a terahertz Mach-Zehnder interferometer. The structures permit integrated terahertz signal generation, propagation through waveguide-based devices, and readout within a single solid-state platform.     

Quantitative study of concentration overload,peak asymmetry,and efficiency loss in micellar electrokinetic chromatography

An equation is derived for the velocity of a thin zone of specific analyte concentration in micellar electrokinetic chromatography. The velocity varies with analyte concentration, because micellar solubilization changes electrical conductivity, micellar electrophoretic mobility, and the partitioning of anabyte between mobile and micellar phases. Two studies based on a weakly and a strongly retained neutral analyte are made to test a limiting form of the equation in which the first two changes are ignored. In the first study, peak asymmetries are characterized and plate numbers are measured in two types of experiments: one of fixed surfactant concentration and variable analyte concentration and one of fixed analyte concentration and variable surfactant concentration. In the second study, the isotherm describing both experiment types is measured and interpreted by the Langmuir model to evaluate the velocity equation. The equation of continuity is solved numerically for the peak profiles governed by the velocity equation. In all but one case, a good agreement is found between theoretical and experimental peak asymmetries and plate numbers in both experiment types. An equation is derived for the relative change of analyte velocity caused by the Langmuir isotherm. The change depends on the relative migration time, micellar saturation, and retardation factor. The predicted velocity changes correlate well with peak asymmetries and efficiency losses.     

Analysis of consecutively sampled headspace and liquid fractions by gas chromatography/mass spectrometry

An existing gas chromatograph/mass spectrometer (GC/MS) can be used to analyze gas and liquid fractions from the same system within a few minutes. The technique was applied to (a) separate and identify the gaseous components of the products of cracking an alkane, (b) measure trace levels of acetone in ethyl acetate, (c) determine the relative partial pressures over a binary mixture, and (d) identify nine unknown compounds for the purpose of disposal.     

The effects of vitamin E and selenium intake on oxidative stress and plasma lipids in hamsters fed fish oil

The aim of the present work was to test the effects of large-dose supplementation of vitamin E (Vit E) and selenium (Se), either singly or in combination, on fish oil (FO)-induced tissue lipid peroxidation and hyperlipidemia. The supplementation of Se has been shown to lower blood cholesterol and increase tissue concentrations of the antioxidant glutathione (GSH); however, the effects of Se supplementation, either alone or in combination with supplemental Vit E, on FO-induced oxidative stress and hyperlipidemia have not been studied. Male Syrian hamsters received FO-based diets that contained 14.3 wt% fat and 0.46 wt% cholesterol supplemented with Vit E (129 IU d-α-tocopheryl acetate/kg diet) and/or Se (3.4 ppm as sodium selenate) or that contained basal requirements of both nutrients. The cardiac tissue of hamsters fed supplemental Se showed increased concentrations of lipid hydroperoxides (LPO) but decreased oxidized glutathione (GSSG) concentrations. The higher concentrations of LPO in the hearts of Se-supplemented hamsters were not lowered with concurrent Vit E supplementation. In the liver, Se supplementation was associated with higher Se-dependent glutathione peroxidase activity and an increase in the GSH/GSSG ratio, whereas a lower hepatic non-Se-dependent glutathione peroxidase activity was seen with Vit E supplementation. Supplemental intake of Se was associated with lower plasma concentrations of total cholesterol and low density lipoprotein cholesterol plus very low density lipoprotein cholesterol. In view of the pro-oxidative effects of Se supplementation on cardiac tissue, a cautionary approach needs to be taken regarding the plasma lipid-lowering properties of supplemental Se.     

Laser projection versus a CRT display in the visual perception of aircraft aspect

High-resolution visual displays have been designed for flight simulation so that observers may judge the aspect angle of aircraft at far distances. The present experiment compares two display devices as untrained observers judge the spatial orientation of two target aircraft: F-15 and F-16 jets. The display devices are a prototype direct-write microlaser projector and an SXGA-format CRT display. Observers' accuracy of aircraft identification is better with the laser projector, and recognition response times are faster. A simple rule was found to fit the observers' response times; it is expressed in terms of a statistic on the autocorrelation of black-and-white silhouette images of aircraft. Observers' estimates of aspect are biased by the laser projector, whereas observers' estimates of aspect are accurate on average with the SXGA display. This bias in estimation of aspect may be attributable to variations in line brightness introduced by the laser projector. Actual or potential applications of this research include the evaluation of high-resolution visual displays for the training of basic fighter maneuvers with military jet pilots.     

Efficacy of a tailored tobacco control program on long-term use in a population of U.S. Military troops.

The authors evaluated the effect of a brief tailored smoking control intervention delivered during basic military training on tobacco use in a population of military personnel (N = 33,215). Participants were randomized to either a tobacco use intervention (smoking cessation, smokeless tobacco use cessation, or prevention depending on tobacco use history) or a health education control condition. Results indicated that smokers who received intervention were 1.16 (95% confidence interval [CI] = 1.04, 1.30) times (7-day point prevalence) and 1.23 (95% CI = 1.07, 1.41) times (continuous abstinence) more likely to be abstinent than controls from smoking cigarettes at the 1-year follow-up (p p     

Age-related binding deficits and the content of false memories.

The authors examined effects of age-related binding deficits on feature information in false memories for imagined objects (e.g., lollipop) that were similar in shape to seen objects (e.g., magnifying glass). In Experiment 1, location memory for seen objects was lower in older than younger adults and lower still in old-old than young-old adults. Imagined objects, when falsely called seen, were less likely to be attributed to the location of similar seen objects (i.e., congruent attributions) by old-old than young-old adults. In Experiment 2, for younger adults, displaying seen objects for less time (1 s vs. 4 s) reduced both location memory for seen objects and congruent attributions for false memories. Thus, binding deficits may influence the specific content of false memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Starting low but ending high: A reversal of the anchoring effect in auctions.

Counter to the "start high, end high" effect of anchors in individual judgments and dyadic negotiations, 6 studies using a diverse set of methodologies document how and why, in the social setting of auctions, lower starting prices result in higher final prices. Three processes contribute to this effect. First, lower starting prices reduce barriers to entry, which increase traffic and generate higher final prices. Second, lower starting prices entice bidders to invest time and energy (creating sunk costs) and, consequently, escalate their commitments. Third, the traffic generated by lower starting prices can lead bidders to infer value in the item, thereby explaining previous findings that traffic begets more traffic. The authors show that barriers to entry that limit traffic (e.g., a misspelled brand name) lead to anchoring's normal assimilative effect rather than its reversal. By broadening the understanding of anchors to extended social interactions and open markets, the authors identify when and why starting prices anchor. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-maintenance interaction: Inefficient social coordination impairs self-regulation.

Tasks requiring interpersonal coordination permeate all spheres of life. Although social coordination is sometimes efficient and effortless (low maintenance), at other times it is inefficient and effortful (high maintenance). Across 5 studies, participants experienced either a high- or a low-maintenance interaction with a confederate before engaging in an individual-level task requiring self-regulation. Self-regulation was operationalized with measures of (a) preferences for a challenging task with high reward potential over an easy task with low reward potential (Study 1) and (b) task performance (anagram performance in Study 1, Graduate Record Exam performance in Studies 2 and 3, physical stamina in Study 4, and fine motor control in Study 5). Results uniformly supported the hypothesis that experiencing high-maintenance interaction impairs one's self-regulatory success on subsequent, unrelated tasks. These effects were not mediated through participants' conscious processes and emerged even with a nonconscious manipulation of high-maintenance interaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)