Multiple comparison procedures for trimmed means.

Stepwise multiple comparison procedures (MCPs) based on least squares and trimmed estimators were compared for their rates of Type I error and their ability to detect true pairwise group differences. The MCPs were compared in unbalanced one-way completely randomized designs when normality and homogeneity of variance assumptions were violated. Results indicated that MCPs based on trimmed means and Winsorized variances controlled rates of Type I error, whereas MCPs based on least squares estimators typically could not, particularly when the data were highly skewed. However, MCPs based on least squares estimators were substantially more powerful than their counterparts based on trimmed means and Winsorized variances when the data were only moderately skewed, a finding which qualifies recommendations on the use of trimmed estimators offered in the literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Problems in the application of structural equation modeling: Comment on Randhawa, Beamer, and Lundberg (1993).

Critique methodological aspects of B. S. Randhawa's et al (see record 1993-23567-001) structural equation modeling (SEM) of relations between self-efficacy, attitudes, and achievement in mathematics. Major findings of their study were that self-efficacy mediated the effects of attitudes on achievement and that self-efficacy and attitudes were more strongly related to achievement for boys than for girls. The authors' reanalysis of their data does not substantiate these conclusions. Rather, it identifies inappropriate applications of SEM and the consequent misinterpretations of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mass spectrometric differentiation of linear peptides composed of L-amino acids from isomers containing one D-amino acid residue

MS/MS of electrosprayed ions is shown to have the capacity to discriminate between peptides that differ by configuration about their alpha-carbons. It is not necessary for the peptides to possess tertiary structures that are affected by stereochemistry, since five epimers of the pentapeptide, H2N-Gly-Leu-Ser-Phe-Ala-OH (GLSFA) all display different collisionally activated dissociation (CAD) patterns of their protonated parent ions. The figure of merit, r, is a ratio of ratios of fragment ion abundances between stereoisomers, where r = 1 corresponds to no stereochemical effect. Values of r as high as 3.8 are seen for diastereomer pairs. Stereochemical effects are also seen for the diprotonated dodecapeptide H2N-Leu-Val-Phe-Phe-Ala-Glu-Asp-Val-Gly-Ser-Asn-Lys-OH (LVFFAEDVGSNK), a tryptic fragment from the amyloid beta-protein. Triply charged complexes of the protonated dodecapeptide with cobalt(II) ions undergo CAD at lower collision energies than do doubly protonated LVFFAEDVGSNK ions. Statistically significant (p < 0.01) differences between the all-L-dodecapeptide and the ones containing a d-serine or a D-aspartic acid are observed.     

Discovery of a significant optical chromatographic difference between spores of Bacillus anthracis and its close relative, Bacillus thuringiensis

A significant difference between two closely related Bacillus spores has been discovered using optical chromatography. This difference can be harnessed for the separation of microscopic particles using opposing laser and fluid flow forces. Particles of different size, composition, and shape experience different optical and fluid forces and come to rest at unique equilibrium positions where the two forces balance. Separations in excess of 600 mum have been observed between Bacillus anthracis Sterne strain and its genetic relative, Bacillus thuringiensis. These findings open new possibilities for detection and characterization of the biological warfare agent, B. anthracis, the causative agent of anthrax, the deadly mammalian disease. The large optical separation between these species is surprising given their close genetic relationship but may be explained by differences in their shape and exosporium morphology, which may result in differences in fluid drag force. The observation of large differences due to less common variables indicates the complex nature of the force balance in optical chromatography, which may in the future be used to separate and characterize microbiological samples. In general, the discovery of such large differences between such closely related biological species suggests new possibilities for the separation and characterization of microorganisms using the full range of emerging techniques that employ radiation pressure (optical filtering, laser tweezers, optical chromatography, etc.).     

Super‐Absorbent Polymer Valves and Colorimetric Chemistries for Time‐Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin‐Mounted Soft Microfluidics

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin‐mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well‐defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances.     

The fixed charge maximal covering location problem

The maximal covering location problem is based on locatingp facilities in such a manner that coverage is maximized within set distance or time standards. This problem has been extended in a number of different ways where the main theme still involves locating a fixed number of facilities. In many applications site costs are not equal; this should cast doubt on the use of a constraint that fixes the number of facilities at a given number as compared to an approach that minimizes site costs and maximizes coverage. This paper addresses the use of site costs in a maximal covering location problem and presents several approaches to solutions, along with computational results. Theoretical linkages to other location models are also presented.     

Examining natural rock varnish and weathering rinds with laser-induced breakdown spectroscopy for application to ChemCam on Mars

A laser-induced breakdown spectroscopy (LIBS) instrument is traveling to Mars as part of ChemCam on the Mars Science Laboratory rover. Martian rocks have weathered exteriors that obscure their bulk compositions. We examine weathered rocks with LIBS in a martian atmosphere to improve interpretations of ChemCam rock analyses on Mars. Profile data are analyzed using principal component analysis, and coatings and rinds are examined using scanning electron microscopy and electron probe microanalysis. Our results show that LIBS is sensitive to minor compositional changes with depth and correctly identifies rock type even if the series of laser pulses does not penetrate to unweathered material.     

To lump or to split? Comparing individuals with traumatic and nontraumatic limb loss in the first year after amputation.

Objective: To compare individuals with traumatic (TE) vs. nontraumatic (NTE) amputation etiology on pain, psychological, and social variables over the first 12 months postamputation, and to explore changes in mean levels of and correlations between these variables over time. Participants: There were 111 adults with newly acquired limb loss. Settings: A VA medical center and a Level I trauma hospital in a large metropolitan area. Main Outcome Measures: Characteristic Pain Severity, Pain Interference, Patient Health Questionnaire depression module, Posttraumatic Stress Disorder Checklist, Social Constraints Scale, Aversive Emotional Support Scale, Centers for Disease Control and Prevention single item Social Support measure, single item loneliness measure. Results: The NTE group was significantly older, had lower income, and had greater medical comorbidity, preamputation pain, and physical disability. The etiology groups did not differ significantly in mean levels of outcome variables except that the TE group reported greater aversive emotional support at 6 and 12 months. The TE group demonstrated a quadratic change in pain interference, with highest levels at 6 months and a linear increase in social constraints. Both etiology groups showed a linear increase in PTSD symptoms over time. Correlations between physical, psychological, and social distress were observed earlier in the year for the NTE group. Conclusion: Despite significant demographic and preamputation experience differences, few differences in outcomes emerged by etiology group in the first year after amputation. Findings suggest that the year after amputation may be a time of greater change for those with traumatic amputation compared to those with nontraumatic amputation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An Elastomeric Poly(Thiophene‐EDOT) Composite with a Dynamically Variable Permeability Towards Organic and Water Vapors

An interpenetrating polymer network (IPN) material with controllable nanoporosity is developed for applications such as chemical protection. The IPN material is based on a conducting polymer backbone consisting of thiophene and 3,4 ethylenedioxythiophene (EDOT) repeat units–poly(thiophene‐EDOT)–formed within a soft polyurethane support. The IPN demonstrates reversible, electrochemically switchable nanoporosity in the absence of standard liquid electrolyte, with the oxidized state being the open (high porosity) state and the reduced state being the closed (low porosity) state. The switching of the IPN between its oxidized (open) and reduced (closed) states is actuated using application of ±1.0 V. The variability in the IPN porosity, induced by the electrochemical switching, is revealed by large changes in water vapor diffusivity, as well as changes in the diffusivities of the chemical agent simulants chloroethyl ethyl sulfide (CEES) and methyl salicylate (MeS). The closed state of the IPN is able to decrease CEES diffusivity by ≈99% compared to expanded Teflon (ePTFE), while the open state allows high MVT rates comparable to ePTFE. The IPN's ability to allow high MVT under non‐threat conditions (open state) and high protection from agents under threat conditions (closed state) is a unique and desirable characteristic of this novel IPN material.