The value of rescheduling functionality within standard MRP packages

One of the basic functions of an MRP system is to issue rescheduling messages that urge the planner tospeed up or slow down open orders. It seems in practice that these messages are not used at all by planners. This is mostly due to the inaccuracy of MRP, that more or less ignores safety time, safety stocks and lotsize flexibility in the calculation of reschedule-in messages. Reschedule-out messages are usually ignored because planners do not see the value of the message. Other reasons for not adhering to rescheduling messages are a lack of maintenance of MRP parameters or simply the wrong use of the MRP function. In the future, MRP rescheduling functionality will be used even less than today, due to the changing role of MRP within the planning framework. With the uprise of finite capacity scheduling packages, MRP is being pushed one level upward in the planning hierarchy. This means that rescheduling functionalities for the short term will become completely obsolete in MRP systems.     

Variance bounds for estimators in autoregressive models with constraints

We consider nonlinear and heteroscedastic autoregressive models whose residuals are martingale increments with conditional distributions that fulfil certain constraints. We treat two classes of constraints: residuals depending on the past through some function of the past observations only, and residuals that are invariant under some finite group of transformations. We determine the efficient influence function for estimators of the autoregressive parameter in such models, calculate variance bounds, discuss information gains, and suggest how to construct efficient estimators. Without constraints, efficient estimators can be given by weighted least squares estimators. With the constraints considered here, efficient estimators are obtained differently, as one-step improvements of some initial estimator, similarly as in autoregressive models with independent increments.     

Model diagnostics for marginal regression analysis of correlated binary data

We propose several diagnostic methods for checking the adequacy of marginal regression models for analyzing correlated binary data. We use a parametric marginal model based on latent variables and derive the projection (hat) matrix, Cook's distance, various residuals and Mahalanobis distance between the observed binary responses and the estimated probabilities for a cluster. Emphasized are several graphical methods including the simulated Q-Q plot, the half-normal probability plot with a simulated envelope, and the partial residual plot. The methods are illustrated with a real life example.     

Posture Development in Infants at Heightened versus Low Risk for Autism Spectrum Disorders

Evidence suggests that children and adults diagnosed with autism spectrum disorders (ASD) exhibit difficulties with postural control. Retrospective video studies of infants later diagnosed with ASD indicate that infants who eventually receive an ASD diagnosis exhibit delays in postural development. This study investigates early posture development prospectively and longitudinally in 22 infants at heightened biological risk for ASD (HR) and 18 infants with no such risk (Low Risk; LR). Four HR infants received an autism diagnosis (AD infants) at 36 months. Infants were videotaped at home at 6, 9, 12, and 14 months during everyday activities and play. All infant postures were coded and classified as to whether or not they were infant‐initiated. Relative to LR infants, HR infants were slower to develop skill in sitting and standing postures. AD infants exhibited substantial delays in the emergence of more advanced postures and initiated fewer posture changes. Because posture advances create opportunities for infants to interact with objects and people in new and progressively more sophisticated ways, postural delays may have cascading effects on opportunities for infant exploration and learning. These effects may be greater for infants with ASD, for whom posture delays are more significant.     

The 'improved' brown and forsythe test for mean equality: some things can't be fixed

Mehrotra (1997) presented an ‘;improved’ Brown and Forsythe (1974) statistic which is designed to provide a valid test of mean equality in independent groups designs when variances are heterogeneous. In particular, the usual Brown and Fosythe procedure was modified by using a Satterthwaite approximation for numerator degrees of freedom instead of the usual value of number of groups minus one. Mehrotra then, through Monte Carlo methods, demonstrated that the ‘improved’ method resulted in a robust test of significance in cases where the usual Brown and Forsythe method did not. Accordingly, this ‘improved’ procedure was recommended. We show that under conditions likely to be encountered in applied settings, that is, conditions involving heterogeneous variances as well as nonnormal data, the ‘improved’ Brown and Forsythe procedure results in depressed or inflated rates of Type I error in unbalanced designs. Previous findings indicate, however, that one can obtain a robust test by adopting a heteroscedastic statistic with the robust estimators, rather than the usual least squares estimators, and further improvement can be expected when critical significance values are obtained through bootstrapping methods.     

Transnational youth transitions: becoming adults between Vancouver and Hong Kong

In the context of the academic interest shown in the enduring transnationalism of contemporary migrants and in the modes of transitions to adulthood in different global settings, in this article we examine the transnational lives of adolescents moving between Vancouver (Canada) and Hong Kong. While there is a lot of literature on the parents' political and economic calculations, there is very little on how adolescents in these situations articulate their geographical sensibilities. We draw on three periods of fieldwork undertaken in 2002, 2008 and 2010 during which we employed a transnational methodology to interview young people in Vancouver and Hong Kong. We argue that becoming an adult involves a process in which, in their discussions about the geographical and emotional distance between themselves and their families, young people articulate their own complex emotions towards specific places in their transnational social field. Their families sporadically interrupt the adolescents' otherwise independent lives with fragmented modes of supervision. By examining the complex intentions and emotions behind circular migration from the perspective of transnational youth in a community of split families, we advance the discussion on transnational geographies, particularly of the family in the context of a flexible global economy.     

A Collaborative Student Affairs and Faculty Health Assessment and Intervention Initiative

Abstract

The authors describe a collaborative partnership forged between faculty and student affairs staff to improve student health at a large urban university. They examine skills and reward structures of each constituency and the stages of the collaboration in the context of 2 theoretical models. A comprehensive data collection and dissemination process in the campus community provided goals for the initial stage of the partnership, leading to implementation of campus initiatives that use the reciprocal skills of each stakeholder. Outcomes of the collaboration included (1) a working relationship between faculty and student affairs staff, (2) increased dialogue with high-level administrators, (3) more coordinated campus efforts to decrease high-risk drinking, (4) use of outcome measures for implementing and evaluating health programs, and (5) an opportunity for interdisciplinary research. The authors offer suggestions for implementing the process on other campuses.     

Negotiating narratives surrounding children's mental health diagnoses: Children and their contribution to the discourse

Despite increasing numbers of children diagnosed with mental health disorders, there is limited research on how children come to understand these diagnoses in childhood. This study examines the retrospective accounts of emerging adults who were diagnosed with mental health disorders in childhood to better understand how they made sense of their diagnoses over time. In-depth, semi-structured interviews were conducted with 42 emerging adults (ages 18 to 22) who were diagnosed with attention deficit hyperactivity disorder (ADHD), depression, generalized anxiety disorder (GAD), and/or bipolar disorder in childhood. Interviews elicited participants' experiences learning about their diagnoses and suggestions for how diagnoses should best be explained to children. Findings demonstrate that participants actively sought and obtained information about their diagnoses over time. They negotiated narratives from several sources, including parents, teachers, mental health professionals, peers, siblings, the media, reading materials, and the Internet. Many of those who embraced medical accounts of their diagnoses did so as they obtained in-depth medical information over time. Meanwhile, those whose parents were open and communicative without using medical narratives suggest it is possible to share information with children without utilizing the terminology of “disorder.” Participants emphasize the importance of being open with children and providing them assurances, explaining that their problems are legitimate, common, and “not their fault.” Implications for social work practice are discussed.