Simultaneous acoustic wave propagation and dynamic mechanical analysis of curing of thermoset resins

A study of simultaneous acoustic and rheometric (dynamic mechanical) measurements of the epoxy curing process is undertaken to assess the validity of using acoustic cure-monitoring sensors for process control. Our results demonstrate that the acoustic technique provides a sensitive means for monitoring the cure of neat epoxy over the entire cure cycle. The acoustic modulus calculated from the shear velocity qualitatively tracks the mechanically measured dynamic modulus and correctly ranks the stiffness of two epoxy compositions. When the frequency difference is accounted for, using time-temperature superposition of the dynamic mechanical measurements, quantitative agreement between the acoustic and mechanical moduli for fully cured epoxy resins is also quite good.     

A twin study of cognitive function in chronic fatigue syndrome: The effects of sudden illness onset.

Variable reports of neuropsychological deficits in individuals with chronic fatigue syndrome (CFS) may, in part, be attributable to methodological limitations. In this study, these limitations were addressed by controlling for genetic and environmental influences and by assessing the effects of comorbid depression and mode of illness onset. Specifically, the researchers conducted a co-twin control study of 22 pairs of monozygotic twins, in which 1 twin met strict criteria for CFS and the co-twin was healthy. Twins underwent a structured psychiatric interview and comprehensive neuropsychological assessment evaluating 6 cognitive domains. Results indicated that twin groups had similar intellectual and visual memory functioning, but fatigued twins exhibited decreases in motor functions (p = .05), speed of information processing (p = .02), verbal memory (p = .02), and executive functioning (p = .01). Major depression did not affect neuropsychological functioning among fatigued twins, although twins with sudden illness onset demonstrated slowed information processing compared with those with gradual onset (p = .01). Sudden onset CFS was associated with reduced speed of information processing. If confirmed, these findings suggest the need to distinguish illness onset in future CFS studies and may have implications for treatment, cognitive rehabilitation, and disability determination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An Approach to the Synthesis of the Manzamine Alkaloids Via the Vinylogous Amide PHotocycloAddition/Retro-Mannich Fragmentation/Mannich Closure Cascade (pharM)

The application of the vinylogous amide [2+2] photocycloaddition/retro-Mannich fragmentation/ M annich closure cascade ( pharM ) to the synthesis of the pentacyclic ring system of the anti-leukemic marine alkaloid manzamine A is presented. Two approaches to the synthesis of the requisite pentacycle are described: (a) the transannular photocycloaddition of an 18-membered vinylogous amide; and (b) photocycloaddition of an acyclic vinylogous amide, followed by macrolactamization of the derived pharM closure product to generate the pentacyclic ring system.     

A new parametrization of the rain drop size distribution

This paper revisits the problem of finding a parametric form for the rain drop size distribution (DSD) which (1) is an appropriate model for tropical rainfall, and (2) involves statistically independent parameters. Using TOGA/COARE data, the authors derive a parametrization which meets these criteria. This new parametrization is an improvement on the one that was derived by Z. S. Haddad et al. (1996) using TRMM ground truth data from Darwin, Australia. The new COARE data allows the authors to verify that the spatial variability of the two “shape” parameters is relatively small, thus confirming that this parametrization should be particularly useful for remote sensing applications. They also derive new DSD-based radar-reflectivity-rain-rate power laws, whose coefficients are directly related to the shape parameters of the DSD. Perhaps most important, since the coefficients are independent of the rain-rate itself, and vary little spatially, the relations are ideally suited for rain retrieval algorithms. It should also prove straightforward to extend this method to the problems of estimating cloud hydrometeors from remote-sensing measurements     

Multiprocessing linear algebra algorithms on the CRAY X-MP-2: Experiences with small granularity

This paper gives a brief overview of the CRAY X-MP-2 general-purpose multiprocessor system and discusses how it can be used effectively to solve problems that have small granularity. An implementation is described for linear algebra algorithms that solve systems of linear equations when the matrix is general and when the matrix is symmetric and positive definite.     

Memory functions in children with early hydrocephalus.

Children with arrested, shunted, and no hydrocephalus were compared on verbal and nonverbal memory tasks assessing multiple components of memory. A gradient of severity was hypothesized, with the shunted hydrocephalus group expected to exhibit the most significant memory impairments and the arrested group expected to perform more poorly than children with no hydrocephalus. Etiologies of prematurity, spina bifida, and aqueductal stenosis were represented by 157 participants. Results supported the hypothesis; the shunted hydrocephalus group performed poorer on all memory measures. Differences for the arrested group were less frequently statistically significant relative to children with no hydrocephalus. Irrespective of etiology, the shunted hydrocephalus group exhibited a pattern of performance suggestive of encoding and retrieval deficits on both verbal and nonverbal tasks, showing a pervasive disturbance of memory processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Full‐scale in situ bioremediation of hexachlorocyclohexane‐contaminated soil

Daramend bioremediation technology was used to treat 1100 tonnes of hexachlorocyclohexane (HCH)‐contaminated soil at a former lindane manufacturing plant. Half of the site (area A) was treated using a cycled anoxic/oxic treatment, and the other half (area B) was treated under oxic conditions. Each area was divided east to west into five zones. A control area (area C) consisted of strips of soil along the north and east edges of the site. Total HCH concentrations along a west to east gradient ranged from 22 430 to 1069 mg kg^?1 in area A and from 21 100 to 730 mg kg^?1 in area B. Concentrations in area C ranged from 52 to 1427 mg kg^?1. The soil was treated for 371 days, during which time seven anoxic/oxic cycles were completed in area A and regular tillage was performed on area B. Soil samples (one per zone) were collected after 154 and 371 days of treatment. After 371 days, total HCH concentrations were reduced in the most highly contaminated zones of areas A and B by 60% (from 22 430 to 8910 mg kg^?1) and 75% (from 21 100 to 5120 mg kg^?1), respectively. The average HCH reductions for all five zones of areas A and B were 40 and 47%, respectively, with the data indicating decreased concentrations of selected isomers in certain zones of both areas. Less substantial changes in HCH concentrations were observed in control area C. Elevated chloride ion concentrations were observed in zones that had demonstrated HCH removal. This full scale project demonstrated the potential for solid phase bioremediation treatment of soil containing high HCH concentrations. Copyright © 2005 Society of Chemical Industry     

Foreign practice building is no holiday.

In this article, the author presents the evolution of RHR International, a firm that has provided advice and counsel to executives and managers to increase both individual and organizational effectiveness. This company specializes in foreign practice building and international business. RHR International has been doing business internationally for almost half a century. This company does consulting work in the U.S., Canada, Belgium, England, Germany and Russia. Throughout the years, the consultants of this company have come to respect and value the real meaning of multinational, transnational and global business, operated by people of diverse cultural and ethnic backgrounds. Despite encountering some roadblocks, RHR is undergoing a new period of expansion. The author concludes that the mission for organizations interested in the world of global management is a difficult and strenuous one and the intent at RHR International is to serve as diligently as they can in this mission. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduced order LQG controllers for linear time varying plants

The problem of reduced order LQG optimization is addressed in a finite horizon, linear time-varying (LTV) system setting. First-order necessary conditions for local optimality in the parameter space is provided in terms of four coupled matrix differential equations. This result provides a transparent generalization of the optimal projection equations of Hyland and Bernstein for the optimal, steady-state compensation of linear time-invariant (LTI) plants.     

Assessing the effects of selection bias on validity data for the General Aptitude Test Battery.

Previous analyses have suggested that the database of 755 studies of the validity of the General Aptitude Test Battery (GATB) demonstrates a small but consistent positive correlation with criteria relevant to job performance. Critics have noted that some of the validity studies conducted were not included in the database and have speculated that these studies may have found negligible or even negative validities, so that the extant database is subject to selection bias. The authors use a mathematical model to estimate the magnitude of possible selection and its effects on the mean and variance of GATB validities. Although evidence of selection is found for some GATB scales and composites, the estimated effect of selection is probably too small to influence conclusions about the validity of the GATB. (PsycINFO Database Record (c) 2010 APA, all rights reserved)