Smoothing parameter selection in nonparametric regression using an improved Akaike information criterion

Many different methods have been proposed to construct nonparametric estimates of a smooth regression function, including local polynomial, (convolution) kernel and smoothing spline estimators. Each of these estimators uses a smoothing parameter to control the amount of smoothing performed on a given data set. In this paper an improved version of a criterion based on the Akaike information criterion (AIC), termed AIC_C, is derived and examined as a way to choose the smoothing parameter. Unlike plug-in methods, AIC_C can be used to choose smoothing parameters for any linear smoother, including local quadratic and smoothing spline estimators. The use of AIC_C avoids the large variability and tendency to undersmooth (compared with the actual minimizer of average squared error) seen when other 'classical' approaches (such as generalized cross-validation (GCV) or the AIC) are used to choose the smoothing parameter. Monte Carlo simulations demonstrate that the AIC_C-based smoothing parameter is competitive with a plug-in method (assuming that one exists) when the plug-in method works well but also performs well when the plug-in approach fails or is unavailable.     

Statistical mechanical analysis of the dynamics of learning in perceptrons

We describe the application of tools from statistical mechanics to analyse the dynamics of various classes of supervised learning rules in perceptrons. The character of this paper is mostly that of a cross between a biased non-encyclopaedic review and lecture notes: we try to present a coherent and self-contained picture of the basics of this field, to explain the ideas and tricks, to show how the predictions of the theory compare with (simulation) experiments, and to bring together scattered results. Technical details are given explicitly in an appendix. In order to avoid distraction we concentrate the references in a final section. In addition this paper contains some new results: (i) explicit solutions of the macroscopic equations that describe the error evolution for on-line and batch learning rules; (ii) an analysis of the dynamics of arbitrary macroscopic observables (for complete and incomplete training sets), leading to a general Fokker–Planck equation; and (iii) the macroscopic laws describing batch learning with complete training sets. We close the paper with a preliminary expose´ of ongoing research on the dynamics of learning for the case where the training set is incomplete (i.e. where the number of examples scales linearly with the network size).     

Some useful Wishart expectations based on the multivariatet-model

In this note we derive some useful expectations of some functions of the Wishart matrix based on the multivariatet-model. The results are generalizations of similar expectations of the usual Wishart matrix. Some applications are outlined.     

Are We Playing the Same Game?: Publishing Task Environments and Research Productivity Among Management Specialists

Archival data on over 15,000 contributors to 33management journals are used to examine productivitydifferences among scholars in different areas ofmanagement. The results suggest that a fragmentedpublication network offers specialists from different areasdissimilar publication opportunities and experiences,and may contribute to varying levels of publicationproductivity among authors. The implications of our results for future research and facultyevaluation processes are explored.     

Agriculture,communities, and new social movements: East European ruralities in the process of restructuring

This paper examines the usefulness of the new social movements (NSMs) paradigm in the changing context of East European post-communist societies and their agricultural systems and rural communities. Starting with statements formulated in Western sociology in the context of Western democratic societies about NSMs as a protest against modernity, the paper analyses the role of such movements in the still modernizing Eastern European reality. The first part of the paper briefly examines some basic elements of the NSMs paradigm in European and American social science. The goal of this section is not only to identify the basic characteristics of NSMs, but also to identify the typical frames used by them. The second part of the paper focuses on the presence of NSMs in the communist era. Drawing on the idea of NSMs as indicators of a ‘post-materialist shift’ as well as of ‘anti-establishment’ and ‘pro-participatory democracy’, the paper examines the frames of democratic opposition in Eastern Europe before 1989. The final part of the paper considers several selected examples from Poland, Hungary, and the Czech Republic to explore the role of NSMs in the process of shaping new ruralities during the post-communist transformation.     

Mindfulness, vulnerability, and love: Spiritual lessons from frail elders, earnest young pilgrims, and middle aged rockers

Gerontologists have studied religion and spirituality for almost three decades. Much of this work focuses on determining how elders' religious and spiritual beliefs and practices affect various indicators of well-being. This paper critiques many of the assumptions underlying this research and suggests alternatives to individualistic formulations of well-being. Experiences in spiritual communities of various types may help aging persons to be mindfully present to others, to recognize that all are vulnerable to the afflictions of aging and the certainty of death, and to love and care for others while working to promote justice. In this paper, I describe how my marriage to a minister enabled me to develop relationships with frail elders and young adults seeking to live faithfully. These friends have influenced my work and have helped to shape my views on my own aging.     

On the trimmed mean and minimax-variance L-estimation in Kolmogorov neighbourhoods

We consider the properties of the trimmed mean, as regards minimax-variance L-estimation of a location parameter in a Kolmogorov neighbourhood K() of the normal distribution: We first review some results on the search for an L-minimax estimator in this neighbourhood, i.e. a linear combination of order statistics whose maximum variance in K_t() is a minimum in the class of L-estimators. The natural candidate – the L-estimate which is efficient for that member of K_t,() with minimum Fisher information – is known not to be a saddlepoint solution to the minimax problem. We show here that it is not a solution at all. We do this by showing that a smaller maximum variance is attained by an appropriately trimmed mean. We argue that this trimmed mean, as well as being computationally simple – much simpler than the efficient L-estimate referred to above, and simpler than the minimax M- and R-estimators – is at least “nearly” minimax.     

Cybersex: The Impact of a Contemporary Problem on the Practices of Marriage and Family Therapists

The number of people accessing the Internet for sexual purposes (cybersex) has increased dramatically over the last 10 years. However, little research has been conducted to determine how frequently clients present for treatment with cybersex‐related issues. One hundred sixty‐four clinical members of the American Association for Marriage and Family Therapy participated in the current study, which was conducted to identify the impacts of cybersex on MFTs’ practices. Most respondents report seeing clients with cybersex‐related issues, with client numbers increasing over the past 2 years. Although most respondents felt prepared to diagnose and treat adults with cybersex problems, half felt unprepared to diagnose and treat children. Lastly, most respondents reported that their required college courses were not helpful in preparing them to diagnose and treat cybersex‐related problems. The implications of study findings are discussed.