Weak-beam stereomicrography of defects in GaAs/In x Ga1−x As interfaces

Weak-beam stereomicrography was used to image dislocation arrays at the two interfaces in GaAs/In _x Ga_1−x As/GaAs sandwich structures. For samples with mismatch equal to 1.8%, separate dislocation arrays were found at each interface. The measured dislocation density at the upper interface was only 10% of the density found at the lower interface. This is attributed to reduced mismatch at the upper interface due to strain in the In_0.25Ga_0.75As layer. Also, the dislocation spacing asymmetry along the [01l] and [01l] directions is exhibited at each interface. In the upper interface, it is attributed to growth on asymmetrically strained In_0.25Ga_0.75As. Stereo-imaging of samples with higher mismatch (f = 2.9%) showed 3-dimensional details of dislocation half-loop nucleation that leads to a semiorthogonal array with increasing In_0.4Ga_0.6As layer thickness.     

Effect of quality of day care environment on children's language development.

Tested the hypothesis that the amount of verbal interaction with caregivers would be a salient index of daycare center quality, in that it would be a particularly important determinant of children's language skill. 166 36–68 mo old children and their parents from 9 daycare centers participated in this study. Quality of the daycare environment, as assessed by observation and items from the Day Care Environment Inventory, was predictive of all 4 measures of intellectual and language development, which included the PPVT and Preschool Language Assessment Instrument, after controlling for family background and current center care experience. The importance of verbal interaction with caregivers was also demonstrated. Ss from centers with high levels of caregiver speech performed better on tests of language development than Ss from centers with a high level of peer speech. The predictive power of other environmental variables was also investigated. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading aloud begins when the computation of phonology is complete.

Naming latency experiments in which monosyllabic items are read aloud are based on the assumption that the vocal response is not initiated until the phonology of the entire syllable has been computed. Recently, this assumption has been challenged by A. H. Kawamoto, C. T. Kello, R. Jones, and K. Bame (1998), who argued instead that the reading-aloud response begins as soon as the initial phoneme is computed. This view would be refuted by evidence of anticipatory coarticulation effects on the initial phoneme due to the nature of the following vowel in the speeded reading-aloud task. The authors provide such evidence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of investments in autonomous maintenance activities

In this paper, we model the situation where operator maintenance activities improve the failure process of equipment. We analyze the business decision to reduce both the mean and variance of the production cycle time and the overall inventory level through an investment in planned autonomous maintenance. We answer: (i) when do optimal autonomous maintenance decisions most improve inventory levels?; and (ii) how do capacity restrictions, equipment characteristics the maintenance response function, and product characteristics impact the autonomous maintenance investment decision? Extensive numerical analyses are performed to develop an approximation to the optimal response for both inventory and autonomous maintenance investments over a wide range of problem parameters. Our solutions provide guidelines on how much time should be invested in autonomous maintenance activities and describe when companies can most benefit from autonomous maintenance programs that increase equipment reliability. We determine the investment in autonomous maintenance activities as a function of available capacity, equipment reliability and demand characteristics.     

Hypochlorite oxidation of select androgenic steroids

Steroid hormones are vital for regulation of various biological functions including sexual development. Elevated concentrations of natural and synthetic androgenic steroids have been shown to adversely affect normal development in indigenous aqueous species. Androgens and their synthetic analogs released from agricultural activities and wastewater discharge may be introduced into drinking water sources. The fate of androgenic steroids during drinking water treatment, specifically the use of chlorine for biological control, has not been extensively studied. As such, this study focuses on the hypochlorite oxidation of a select number of androgenic compounds that vary in their structural composition. Where a favorable reaction is observed, we also attempt to describe the product distribution. The results show compounds that possess a ketonic functional group conjugated with a double bond inhibit oxidation by hypochlorite in the absence of biological or indirect oxidative pathways. Oxidative reactivity in the presence of hypochlorite was favorably correlated with the presence of isolated unsaturated carbon bonds and resulted in various transformation products.     

Count Algarotti on the Camera Obscura

Abstract

Count Franzesco Algarotti was born in Venice toward the close of 1712, of ail opulent and ancient patrician family¹. In a Nazarene college ill Rome he studied the ‘learned languages’, and when he had mastered these he proceeded to the study of things, soon filling his mind with rich treasures of scientific knowledge.