John S. Lawson

Neurobehavioral sequelae of child sexual abuse.

This study examined intellectual and memory functioning in a sample of sexually abused children compared to demographically and age-matched controls. The severity of abuse and other pertinent factors were also examined in relation to cognitive performance. Elevated levels of psychopathology were present in the abused children, as well as diminished performance on tasks influenced by attention/concentration. However, after controlling for differences in IQ and socioeconomic status (SES), significant differences in memory function were not found. Results are discussed in the context of stress effects on cognition and the potential resiliency of cognitive function in children undergoing treatment for sexual abuse. This is based, in part, on the doctoral dissertation of the first author. We are grateful to Utah Valley Regional Medical Center and Primary Childrens Medical Center and therapists and public schools in Salt Lake and Utah counties for their assistance in recruiting participants for this study. We are also grateful for the editorial assistance of Jo Ann Petrie. Partial funding for this project came from the Ira Fulton Foundation.

Organic monoliths for high‐performance reversed‐phase liquid chromatography

RPLC is the most common mode of LC. It is widely used for separations of both small and large molecules. Monolithic columns, which are currently under intensive study by many groups, have the potential of becoming attractive alternatives to particle-packed columns. They are generally easier and faster to fabricate, and they demonstrate a lower pressure drop, less nonspecific adsorption, and richer chemistry (in the case of organic polymer monoliths) for providing broad selectivity. Silica monoliths, as is also true for columns packed with silica particles, are best applied to small-molecule separations. Organic polymer monoliths, on the other hand, have shown advantages for large-molecule separations. Recently, improvements in organic monoliths have led to efficiencies for small molecules that are approaching and even surpassing 100,000 plates/m. While this performance is still far short of what is currently available using modern small particles and silica monoliths in RPLC, steady progress is being made. This review describes recent developments in the synthesis and performance of organic polymer RPLC monoliths, and identifies areas where additional work is needed to significantly improve their performance for both small- and large-molecule separations.

Reading Disability Subtypes and the Test of Memory and Learning

For Study 1, 24 readers with dysphonetic dyslexia and 21 with dyseidetic dyslexia, classified by Boder criteria, were compared to 90 control group participants (45 matched for age and 45 for reading level) on the Composite Memory Index (CMI) score from the Test of Memory and Learning (TOMAL). CMI scores were significantly lower for children with dyslexia (p <.0001). Plotting average subtest score profiles for all reader groups revealed auditory sequential memory impairments for both types of readers with dyslexia, and multiple strengths for good readers. Dysphonetic and dyseidetic dyslexia profiles were nearly identical. For Study 2, average linkage cluster analysis was performed using principal components derived from subtests of the TOMAL. Homogeneous clusters of normal readers and children with reading disabilities emerged. Results indicated that qualitatively distinct subtypes of readers with dyslexia exist.

Memory Performance of Children with Dyslexia A Comparative Analysis of Theoretical Perspectives

This study examined the memory performance of children with reading disabilities (RD) using methodology representative of three theoretical perspectives on RD subtypes: the phonological deficit, dual route, and phonological-core variable-difference models. Analyses compared the serial memory, verbal learning, and abstract visual-spatial memory performance of 45 children with RD to that of chronological-age (CA)- and reading-level (RL)-matched controls, using subtype identification methods from each of the theoretical models to classify children with RD. Phonological deficit and dual route comparisons indicated that children with RD, regardless of subtype, performed more poorly than CA- and better than RL-matched participants on all memory tasks. Phonological-core variable-difference methodology yielded three RD subtypes, two of which exhibited distinctive memory deficits relative to both CA and RL control groups. The phonological-core variable-difference model accounted for more variance in memory performance than either of the other two models.

Use and Partitioning of Montane Habitat by Small Mammals

Structure of the microhabitat used by four species of rodents in a montane environment was investigated using principal-component analysis of trap-site characteristics. Most species of rodents were associated with fallen logs and brush during June but microhabitat use shifted to areas of more herbaceous growth in July–August. This shift was concurrent with rapid herbaceous growth. Females of each species occupied more structured microhabitat than males of the same species. Differential segregation of habitat by sex may be a function of the variability of resource use by the species as a whole. Unused microhabitat does not differ from random with respect to vegetative structure, and reasons for nonuse probably differ among sites.

Correlation of chromatographic performance with morphological features of organic polymer monoliths.

Monoliths are considered to be a low pressure alternative to particle packed columns for liquid chromatography (LC). However, the chromatographic performance of organic monoliths, in particular, has still not reached the level of particle packed columns. Since chromatographic performance can be attributed to morphological features of the monoliths, in-situ characterization of the monolith structure in three dimensions would provide valuable information that could be used to help improve performance. In this work, serial sectioning and imaging were performed with a dual-beam scanning electron microscope for reconstruction and quantitative characterization of poly(ethylene glycol) diacrylate (PEGDA) monoliths inside a capillary column. Chord lengths, homogeneity factors, porosities and tortuosities were calculated from three-dimensional (3D) reconstructions of two PEGDA monoliths. Chromatographic efficiency was better for the monolith with smaller mean chord length (i.e., 5.23μm), porosity (i.e., 0.49) and tortuosity (i.e., 1.50) compared to values of 5.90μm, 0.59 and 2.34, respectively, for the other monolithic column. Computational prediction of tortuosity (2.32) was found to be in agreement with the experimentally measured value (2.34) for the same column. The monoliths were found to have significant radial heterogeneity since the homogeneity factor decreased from 5.39 to 4.89 (from center to edge) along the column radius.

High efficiency polyethylene glycol diacrylate monoliths for reversed-phase capillary liquid chromatography of small molecules

Highly cross-linked monolithic networks (i.e., polyethylene glycol diacrylate, PEGDA) synthesized from monomers containing varying ethylene oxide chain lengths were fabricated inside fused silica capillary columns for use in liquid chromatography (LC) of small molecules. Tergitol was used as a surfactant porogen in combination with other typical organic liquid porogens. Column performance was correlated with quantitative descriptors of the physical/chemical properties of the monomers and porogens using a statistical model. Solubility and viscosity values of the components were identified as important predictors of monolith morphology and efficiency. The chromatographic retention mechanism was determined to be principally reversed-phase (RP) with additional hydrogen bonding between the polar groups of the analytes and the ethylene oxide groups embedded in the monolith structure. The fabricated monolithic columns were evaluated under RPLC conditions using phenols, hydroxy benzoic acids, and alkyl parabens as test compounds. Isocratic elution of hydroxy benzoic acids at a linear velocity of 0.04 cm/s using a PEGDA-700 monolith gave chromatographic peaks with little tailing (i.e., tailing factor<1.28). The chromatographic efficiency measured for a non-retained compound (uracil) using this column was 186,000 plates/m when corrected for injector dead volume. High resolution gradient separations of selected pharmaceutical compounds and phenylurea herbicides were achieved in less than 18 min. Optimized monoliths synthesized from all four crosslinking monomers exhibited high permeability and demonstrated little swelling or shrinking in different polarity solvents. Column preparation was highly reproducible, with relative standard deviation (RSD) values less than 2.1%, based on retention times of the phenol standards (3 different columns).

Regression analysis of experiments with complex confounding patterns guided by the alias matrix

Resolution III experiments with complex confounding patterns, often called main effect plans. Their main effects are partially confounded with two-factor interactions rather than being either independent or completely aliased, as they are in regular designs that are constructed from a defining relation. It is possible to detect some two-factor interactions, from experiments with complex confounding patterns if only a few of the factors are active. The partial confounding of interactions with main effects in these experiments allows one to estimate interactions with regression analysis. Recent papers have shown how the interactions can be detected using repeated runs of stepwise regression, or computationally intensive Bayesian methods. This paper shows that, with a short list of candidate interactions, the important interactions can be detected efficiently by a single pass of all subsets regression. The short list of candidates interactions for the all subsets regression are selected with regard to their potential for contributing to the value of the large estimated effects calculated from the data. The potential is determined by summing coefficients in the alias matrix. This paper reviews the concept of the alias matrix, and defines the alias plot that can be obtained from the alias matrix. The alias plot provides simple graphic for viewing the potential contribution of interactions to large estimated effects. The interactions identified on the alias plot, along with main effects, are used as candidates in an all subsets regression analysis of data from partially confounded experiments. The resulting strategy allows exploration of a wide range of the potential model space, can reveal several plausible models for the data if they exist, and can be completed using standard statistical software. Examples are presented.

Highly crosslinked polymeric monoliths with various C6 functional groups for reversed-phase capillary liquid chromatography of small molecules.

Three crosslinking monomers, i.e., 1,6-hexanediol dimethacrylate (HDDMA), cyclohexanediol dimethacrylate (CHDDMA) and 1,4-phenylene diacrylate (PHDA), were used to synthesize highly cross-linked monolithic capillary columns for reversed-phase liquid chromatography (RPLC) of small molecules. Selection of porogen type and concentration was investigated in detail. Isocratic elution of alkylbenzenes at a flow rate of 300nL/min was performed using HDDMA and CHDDMA monolithic columns. Gradient elution of alkylbenzenes using all three monolithic columns showed good separations. Optimized monoliths synthesized from all three crosslinking monomers possessed high permeabilities. Poly(HDDMA) monoliths demonstrated column efficiencies up to 86,000 plates/m. Column preparation of poly(HDDMA) monolithic columns was highly reproducible; the relative standard deviation (RSD) values (n=3) for run-to-run and column-to-column were less than 0.26% and 0.70%, respectively, based on retention times of alkylbenzenes.

Agricultural Investment and Internal Cash Flow Variables

Recent asymmetric information studies have used internal cash flow variables in empirical investment models. A composite model consisting of internal cash flow variables, neoclassical variables, and accelerator variables is developed to explain agricultural investment. Using firm-level data, we show that the addition of internal cash flow variables can increase the explanatory power of agricultural investment models.