When Worlds Collide: Young People,Drugs and ‘Responsible Adulthood’

Young people's behaviours which are problematic to parents and therapists are also found in the wider adult community. Here these behaviours are often accepted as normal and legitimate, and as such they may occur even in the lives of these same parents and therapists. This paper considers some of the issues this raises in working with young people and their families.     

A reconsideration of the economic consequences of marital dissolution

A close look at the income flows in the years following a divorce or separation reveals marked differences in the distribution of effects. The economic consequences of divorce are especially adverse for women. In most cases, children remain with the mother, who usually has considerably lower potential labor market earnings than her former husband, partly because her responsibilities for the children are likely to reduce her labor supply and may have limited her past human capital investments. Alimony and child support are the principal mechanisms for transfers from the ex-husband to the ex-wife, but payments are rarely frequent or sizeable enough to make up for an appreciable amount of the labor income lost through the departure of the ex-husband. Human capital investments on the part of the mother have a modest effect on her economic situation in the years following the divorce. Most men who divorce or separate are immediately better off because they retain most of their labor incomes, typically do not pay large amounts of alimony and child support to their ex-wives, and no longer have to provide for the level of needs associated with their former families. Much more important than growth in the ex-wife's own labor income is the role of a new husband's labor income upon her remarriage. More than half of the white women remarry within five years following a divorce or separation; the comparable fraction for black women is less than half. An interesting question is whether the currently unmarried would enjoy the same kind of economic benefits, were they to remarry, as women who have remarried. Estimates from a model of the new husband's labor income, adjusted for selection bias inherent in the process of remarriage, indicate that the currently unmarried would probably not gain equal benefits if they were to remarry. The expected labor income of potential husbands of black women averages only about $5000--a modest amount when compared with the alternatives available to these women.     

Panel data and models of change: A comparison of first difference and conventional two-wave models

The method of first differences as an approach to modeling change is described and it is compared to more conventional two-wave panel models. Substantial advantages are found to the first-difference approach, especially if there are unmeasured, unchanging predictor variables in the model. It is also argued that there are substantial problems in the interpretation of results from the conventional two-wave models. Some of the analytic results are illustrated with a number of applications to the area of stressful life events.     

Reliability of normalisation methods for EMG analysis of neck muscles

Acceptable reliability of normalisation contractions in electromyography (EMG) is paramount for testing conducted over a number of days or if normal laboratory strength testing equipment is unavailable. This study examined the reliability of maximal voluntary isometric contractions (MVIC) and sub-maximal (60%) isometric contractions for use in neck muscle EMG studies. Surface EMG was recorded bilaterally from eight sites around the neck at C4/5 level from five healthy male subjects. Subjects performed MVIC and sub-maximal normalisation contractions using an isokinetic dynamometer (ID) and a portable cable dynamometer with attached strain gauge (PCD) in addition to a MVIC against a manual resistance (MR). Subjects were tested in flexion, extension, left and right lateral bending and were retested by the same tester within a two-week period. Intra class correlation co-efficients (ICC) were calculated for each testing method and contraction direction and a mean ICC was calculated across all contraction directions. All normalisation methods produced excellent within-day reliability (mean ICC >0.80) but only the MVICs using the ID and PCD had acceptable reliability when assessed between-days. This study confirmed the validity of using MVICs elicited using the ID and PCD as reliable reference contractions for the normalisation of neck EMG.     

An acarine predator-prey population infesting roses

Summary WhenPhytoseiulus persimilis was reared withTetranychus urticae, infesting roses propagated in a greenhouse at controlled daily temperatures of 24°C (12 hrs) and 18°C (12 hrs), prey numbers fluctuated with peaks of increasing amplitude. Differential dispersal of prey and predator species was one factor contributing to the inability of the natural enemy to control the pest population.