Negative resistance in cadmium sulfide.

A light-sensitive, negative-resistance phenomenon has been observed in a special two-terminal CdS device fabricated from selected single crystals. The device differs from those used in previous investigations in that one end of the device was masked to keep out visible light and that the phenomenon was observed at room temperature. A method is described which enables the phenomenon to be observed on a reproducible basis. It was found that the CdS single crystal must have a relatively high density of traps. Possible mechanisms which may contribute to the phenomenon are discussed --Abstract, page ii

Service Delivery in Rural Municipalities: Privatize, Cooperate, or Go It Alone?

Choices in production and contracting arrangements for a wide range of services were studied using data from approximately 1,000 small, mostly rural municipalities from Illinois, New Hampshire and Wisconsin. Results suggest the use of both for-profit contractors and cooperative agreements with other governments correlate negatively with population. Small municipalities are less likely to use competitive bidding processes, compare costs between production options, or report that privatization produces savings. Median income, rural geography, and ideology show statistically-significant associations with contracting choices. Respondents generally consider themselves ―satisfied‖ with services provided by contract, although satisfaction levels are lower than those associated with self-provision. Satisfaction associated with services provided by other governments is lower than satisfaction with services provided by private contractors, suggesting no tradeoff in service quality directly attributable to ―for-profit‖ contractors.privatization, municipal services, cooperation, Community/Rural/Urban Development, Public Economics,

Mach number effects on transonic aeroelastic forces and flutter characteristics

Transonic aeroelastic stability analysis and flutter calculations are presented for a generic transport-type wing based on the use of the CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) finite-difference code. The CAP-TSD code was recently developed for transonic unsteady aerodynamic and aeroelastic analysis of complete aircraft configurations. A binary aeroelastic system consisting of simple bending and torsion modes was used to study aeroelastic behavior at transonic speeds. Generalized aerodynamic forces are presented for a wide range of Mach number and reduced frequency. Aeroelastic characteristics are presented for variations in freestream Mach number, mass ratio, and bending-torsion frequency ratio. Flutter boundaries are presented which have two transonic dips in flutter speed. The first dip is the usual transonic dip involving a bending-dominated flutter mode. The second dip is characterized by a single degree-of-freedom torsion oscillation. These aeroelastic results are physically interpreted and shown to be related to the steady state shock location and changes in generalized aerodynamic forces due to freestream Mach number

Prevalence and Effects of Child Exposure to Domestic Violence

In recent years, researchers have focused attention on children who are exposed to domestic violence. Although presently there are no scientifically credible estimates of the national prevalence of children exposed to domestic violence, existing data suggest that large numbers of American children are affected. This article discusses the limitations of current databases and describes a promising model for the collection of reliable and valid prevalence data, the Spousal Assault Replication Program, which uses data collected through collaboration between police and university researchers. Research examining the effects of childhood exposure to domestic violence is also limited by a range of methodological problems. Despite this, however, sufficient evidence from the body of studies exists to conclude that such exposure has adverse effects. The specific effects may differ depending on a host of variables, such as the children’s ages, the nature and severity of the violence, the existence of other risk factors in the children’s lives (for example, poverty, parental substance abuse), and whether the children are also directly physically abused. In general, childhood exposure to domestic violence can be associated with increased display of aggressive behavior, increased emotional problems such as depression and/or anxiety, lower levels of social competence, and poorer academic functioning. A scientifically credible body of research on the prevalence and effects of childhood exposure to domestic violence is necessary to promote the development of effective interventions and to permit the proper channeling of public and private funds. This article identifies some of the steps that can be taken to build the research capacity necessary to obtain the needed data

Out of the Frying Pan, Into the Fire: Trauma in the Lives of Homeless Youth Prior to and During Homelessness

Anecdotal evidence from those who work with homeless youth indicates that trauma permeates these young people\u27s lives. This paper presents the findings from a study of 100 homeless youth regarding the presence of trauma in their lives, both before and during homelessness. Participants living in the Maritime Provinces volunteered to take part in a semi-structured interview lasting one to two hours. The interview questionnaire was conducted by a trained interviewer, and was composed of standardized and adapted survey instruments, as well as questions regarding demographics, experiences prior to becoming homeless, assistance received while dealing with stressors, and current needs. The results indicate that trauma is both a cause and a consequence of youth being homeless, as a large majority of participants experienced a number of types of highly stressful events both preceding and during homelessness, and that trauma in the lives of both male and female homeless youth should be understood as a pervasive reality with serious implications. Implications for service delivery are discussed

La dualidad y la agregación de categorías sociales

La "dualidad" es una concepción del enlace micro-macro que implica que elementos correspondientes a dos niveles diferentes de la estructura (tales como personas y grupos, o -como en los datos que analizamos- identidades y prácticas) se co-constituyen mutuamente. Presentamos un algoritmo para la agregación de categorías sociales que son "duales" entre sí. Nuestro algoritmo es aplicable al estudio de datos en tablas de contingencia. Aplicamos nuestro algoritmo en un estudio de la construcción conjunta de identidades sociales (incluyendo etiquetas raciales y étnicas) y prácticas educativas en un contexto universitario."Duality" is a conception of micro-macro linkage that implies that elements at each of two different levels of structure (such as persons and groups, or-as in the data we analyze-identities and practices) co-constitute one another. We present an algorithm for the aggregation of social categories that are "dual" to each other. Our algorithm is applicable to the study of data in contingency tables. We apply our algorithm in a study of the joint construction of social identities (including racial and ethnic labels) and educational practices in a university context

An error prediction framework for interferometric SAR data

Three of the major error sources in interferometric synthetic aperture radar measurements of terrain elevation and displacement are baseline errors, atmospheric path length errors, and phase unwrapping errors. In many processing schemes, these errors are calibrated out by using ground control points (GCPs) (or an external digital elevation model). In this paper, a simple framework for the prediction of error standard deviation is outlined and investigated. Inputs are GCP position, a priori GCP accuracy, baseline calibration method along with a closed-form model for the covariance of atmospheric path length disturbances, and a model for phase unwrapping errors. The procedure can be implemented as a stand-alone add-on to standard interferometric processors. It is validated by using a set of single-frame interferograms acquired over Rome, Italy, and a double difference data set over Flevoland, The Netherlands

Mainely Gay, Vol.5, No.1 (January/February 1978)

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