Breakdown of foster care placement: carer perspectives and system factors

A crisis in foster care is suggested by many of the national and international published reports. One seemingly intractable problem is placement instability, particularly for adolescents with behavioural problems. A qualitative study of foster carers who had ended a placement because of the young person's disruptive behaviour (n = 19) was conducted to examine ways in which system shortcomings might be affecting placement outcomes. Data were collected on the process of placement deterioration, the incident(s) that precipitated the decision to end placement, formal carer support, and the carer's response to the breakdown. All placements fell into one of two categories: those that, with certain interventions, might have been sustained (n = 9); and those that, regardless of intervention, appear to have been unsustainable (n = 10). This study contributes to the alternative care literature by highlighting the potential of some faltering placements to be maintained and of some failed placements to be renegotiated.     

Measurement Problems of Inflation Disaggregation

Why do the three quarterly GNP inflation measures differ so much when they are constructed from the same underlying price data? Algebraically and in tables using data of the second quarter of 1984, it is shown that these differences occur because of quarterly shifts in the composition of the nation's product. Disaggregation of the inflation contributions of the GNP components also makes it clear why, for quarterly analyses, the GNP chain price index is superior to both the implicit GNP deflator and the fixed-weight GNP price index. In particular, the implicit GNP deflator can give severely distorted inflation signals.     

Stepfamily Assessment

The increase in the number of stepfamilies in our soci- ety is reflected in the high number of stepfamilies requesting help in mental health facilities and social agencies. The rationale for developing a model for assessing remarried fam- ilies comes from an awareness of the complexities of remarried fam- ilies and of b e difficulty therapists have in assessing and organizing all relevant information. We do not imply any particular method to assess the families; we are simply suggesting a format which needs to be in the mind of the therapist when interviewing the family or a family member. Our model emphasizes particular aspects of remarried family life that play a crucial role in the successful adjustment of the remarried family, such as the resolution of the previous relationship, the influ- ence of the outside parent, the co-parental relationship, the mobility of the children between households, and the integration of the new partner.     

Same‐Sex Parent Families and Children's Academic Achievement

Children in traditional families (i.e., married, 2 biological parents) tend to do better than their peers in nontraditional families. An exception to this pattern appears to be children from same‐sex parent families. Children with lesbian mothers or gay fathers do not exhibit the poorer outcomes typically associated with nontraditional families. Studies of same‐sex parent families, however, have relied on a static conceptualization of the family and discounted the importance of the timing and number of family transitions for understanding children's outcomes. To examine whether same‐sex parent families represent an exception among nontraditional families, the author used data from the Early Childhood Longitudinal Study—Kindergarten cohort (N = 19,043) to create a dynamic indicator of children's family structure and tested its association with math assessment scores. The results indicated that children in same‐sex parent families scored lower than their peers in married, 2‐biological parent households, but the difference was nonsignificant net of family transitions.     

一类三阶非自治微分方程的不稳定性

本文运用构造李雅普诺夫函数的方法,给出了一类三阶非自治微分方程零解不稳定的充分条件。     

轻型桥墩稳定性的非线性分析

轻型桥墩是桥梁工程中常用到的一种桥墩。本文利用柔性桥墩失稳临界荷载非线性分析原理，分析了墩顶位移在非线性阶段对桥墩稳定性的影响。     

低浓度三分子模型差速流动引起的化学不稳定性

建立了低浓度三分子反应模型反应-流动-扩散方程,从理论上分析了出现差速流动化学不稳定的条件,得到了临界流动速率φc和扰动波包的群速度vg,讨论了扰动增长率与流速φ的关系,初步讨论了出现不稳定时的系统空间结构.研究表明,化学反应在低浓度条件下也可能出现差速流动引起的化学不稳定.     

Testing for Structural Instability in Moment Restriction Models: An Info-Metric Approach

In this paper, we develop an info-metric framework for testing hypotheses about structural instability in nonlinear, dynamic models estimated from the information in population moment conditions. Our methods are designed to distinguish between three states of the world: (i) the model is structurally stable in the sense that the population moment condition holds at the same parameter value throughout the sample; (ii) the model parameters change at some point in the sample but otherwise the model is correctly specified; and (iii) the model exhibits more general forms of instability than a single shift in the parameters. An advantage of the info-metric approach is that the null hypotheses concerned are formulated in terms of distances between various choices of probability measures constrained to satisfy (i) and (ii), and the empirical measure of the sample. Under the alternative hypotheses considered, the model is assumed to exhibit structural instability at a single point in the sample, referred to as the break point; our analysis allows for the break point to be either fixed a priori or treated as occuring at some unknown point within a certain fraction of the sample. We propose various test statistics that can be thought of as sample analogs of the distances described above, and derive their limiting distributions under the appropriate null hypothesis. The limiting distributions of our statistics are nonstandard but coincide with various distributions that arise in the literature on structural instability testing within the Generalized Method of Moments framework. A small simulation study illustrates the finite sample performance of our test statistics.     

A Unified Approach to Structural Change Tests Based on ML Scores,F Statistics,and OLS Residuals

This paper presents an easy-to-compute semi-parametric (SP) method to estimate a simple disequilibrium model proposed by Fair and Jaffee (1972). The proposed approach is based on a non-parametric interpretation of the EM (Expectation and Maximization) principle (Dempster et al; 1977) and the least squares method. The simple disequilibrium model includes the demand equation, the supply equation, and the condition that only the minimum of quantity demanded and quantity supplied is observed. The method used here allows one to consistently estimate the disequilibrium model without fully specifying the distribution of error terms in both demand and supply equations. Our Monte Carlo study suggests that the proposedestimator is better than the normal maximum likelihood estimator under asymmetric error distributions. and comparable to the nlaximunl likelihood estimator under synirnetric error distributions in finite samples. Aggregate U.S. labor market data from Quandt and Rosen (1988) is used to illustrate the procedure.