Psychosocial adaptation in juvenile rheumatic disease: A controlled evaluation.

Examined the psychosocial functioning of 93 children (aged 1–18 yrs) with severe or mild rheumatic disease and 93 healthy children from demographically matched families. Ss in the severe patient group showed more parent-reported psychological and physical problems than mild patients and healthy controls. Compared with the mild group, the severe group also missed more school due to illness. Older severe patients were more likely to miss school due to illness and to participate in fewer social activities than controls; however, older Ss reported comparable mood and functioning in other areas. A model for examining risk and resistance factors predictive of psychological and social dysfunction among children with severe chronic disease is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of rational (total) nonlinear dynamic system modelling,identification, and control

This paper is a summary of the research development in the rational (total) nonlinear dynamic modelling over the last two decades. Total nonlinear dynamic systems are defined as those where the model parameters and input (controller outputs) are subject to nonlinear to the output. Previously, this class of models has been known as rational models, which is a model that can be considered to belong to the nonlinear autoregressive moving average with exogenous input (NARMAX) model subset and is an extension of the well-known polynomial NARMAX model. The justification for using the rational model is that it provides a very concise and parsimonious representation for highly complex nonlinear dynamic systems and has excellent interpolatory and extrapolatory properties. However, model identification and controller design are much more challenging compared to the polynomial models. This has been a new and fascinating research trend in the area of mathematical modelling, control, and applications, but still within a limited research community. This paper brings several representative algorithms together, developed by the authors and their colleagues, to form an easily referenced archive for promotion of the awareness, tutorial, applications, and even further research expansion.     

Energy transfer properties of non-linear systems in the frequency domain

In this paper, an analysis of the energy transfer properties of non-linear systems in the frequency domain is studied based on a new concept known as non-linear output frequency response functions (NOFRFs). The new concept allows the analysis to be implemented in a manner similar to the analysis of linear systems in the frequency domain, and provides great insight into the mechanisms which dominate the non-linear behaviour. The new analysis is also helpful for the design of non-linear systems in the frequency domain.     

An investigation into the characteristics of non-linear frequency response functions. Part 1: Understanding the higher dimensional frequency spaces

The characteristics of generalized frequency response functions (GFRFs) of non-linear systems in higher dimensional space are investigated using a combination of graphical and symbolic decomposition techniques. It is shown how a systematic analysis can be achieved for a wide class of non-linear systems in the frequency domain using the proposed methods. The paper is divided into two parts. In Part 1, the concepts of input and output frequency subdomains are introduced to give insight into the relationship between one dimensional and multi-dimensional frequency spaces. The visualization of both magnitude and phase responses of third order generalized frequency response functions is presented for the first time. In Part 2 symbolic expansion techniques are introduced and new methods are developed to analyse the properties of generalized frequency response functions of non-linear systems described by the NARMAX class of models. Case studies are included in Part 2 to illustrate the application of the new methods.     

Frequency domain analysis for non-linear Volterra systems with a general non-linear output function

For non-linear Volterra systems which include a non-linear state equation and a general non-linear output function, the system frequency response functions and some related frequency response characteristics are developed and discussed in this study. These new results establish the frequency response functions for this general form of non-linear systems by extending some existing theory, and provide an analytical insight into the relationship between model parameters and frequency response functions, and the relationship between model parameters and the magnitude bound of frequency response functions. Several examples are given to illustrate the new results.     

Direct parameter identification of distributed parameter systems

A new direct approach to identifying the parameters of distributed parameter systems from noise-corrupted data is introduced. The model of the system which takes the form of a set of linear or nonlinear partial differential equations is assumed known with the exception of a set of constant parameters. Using finite-difference approximations of the spatial derivatives the original equation is transformed into a set of ordinary differential equations. The identification approach involves smoothing the measured data and estimating the temporal derivatives using a fixed interval smoother. A least-squares method is then employed to estimate the unknown parameters. Three examples that illustrate the applicability of the proposed approach are presented and discussed.     

The wavelet-NARMAX representation: A hybrid model structure combining polynomial models with multiresolution wavelet decompositions

A new hybrid model structure combing polynomial models with multiresolution wavelet decompositions is introduced for nonlinear system identification. Polynomial models play an important role in approximation theory and have been extensively used in linear and nonlinear system identification. Wavelet decompositions, in which the basis functions have the property of localization in both time and frequency, outperform many other approximation schemes and offer a flexible solution for approximating arbitrary functions. Although wavelet representations can approximate even severe nonlinearities in a given signal very well, the advantage of these representations can be lost when wavelets are used to capture linear or low-order nonlinear behaviour in a signal. In order to sufficiently utilize the global property of polynomials and the local property of wavelet representations simultaneously, in this study polynomial models and wavelet decompositions are combined together in a parallel structure to represent nonlinear input–output systems. As a special form of the NARMAX model, this hybrid model structure will be referred to as the WAvelet-NARMAX model, or simply WANARMAX. Generally, such a WANARMAX representation for an input–output system might involve a large number of basis functions and therefore a great number of model terms. Experience reveals that only a small number of these model terms are significant to the system output. A new fast orthogonal least-squares algorithm, called the matching pursuit orthogonal least squares (MPOLS) algorithm, is also introduced in this study to determine which terms should be included in the final model.     

Cell specificity in hepatocarcinogenesis: preferential accumulation of O6-methylguanine in target cell DNA during continuous exposure to rats to 1,2-dimethylhydrazine

Concentrations of the major methylated DNA purines were determined in two liver cell cell populations of Fischer 344 rats during administration of 30 ppm 1,2-dimethylhydrazine (SDMH) in the drinking water for periods of up to 4 weeks. Quantitation of 7-methylguanine and O6-methylguanine (O6MG) was achieved by highly sensitive optical methods following separation of DNA bases by high-performance liquid chromatography. Overall alkylation as indicated by the concentration of 7-methylguanine was near maximum in both hepatocytes and liver nonparenchymal cells by the third day of SDMH administration. Similar amounts of 7-methylguanine were present in the two liver cell populations at seven of nine time points during 4 weeks of exposure. In contrast, dramatic differences in the cumulative concentrations of O6MG were seen in the two cell populations. Nonparenchymal cells accumulated O6MG during the first 8 days of exposure and had up to a 30-fold greater concentration of this product than did the corresponding hepatocytes. In the hepatocytes, a rapid decline in O6MG concentration was observed between 1 and 3 days of exposure to SDMH. Thereafter, only low levels of this promutagenic lesion were present in hepatocytes. Exposure of rats to the same regimen of SDMH for up to 10 months caused angiosarcomas in the livers of over 90% of the animals, while hepatocellular carcinomas occurred in only 40%. Thus, a strong correlation exists between the inability to repair O6MG and cell specificity for carcinogenesis.     

Comparison of training methods for improving the psychometric quality of experimental and administrative performance ratings.

Studied 52 nursing supervisors to examine the effects of a lecture on rating errors, discussion about errors, and participation in scale construction on both experimental and subsequent administrative ratings. On experimental ratings, scale construction reduced halo and variability errors, lecture reduced variability errors, and discussion increased variability errors. These results held true only for raters who began making ratings within 1 wk after training, before administration of questionnaires designed to measure rater motivation and knowledge. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conflict resolution in distressed and nondistressed married couples.

Compared the communication interactions of 12 maritally distressed and 12 nondistressed (as determined by the Locke-Wallace Marital Adjustment Test) couples while they engaged in conflict resolution tasks. Analyses of ratings from 2 behavioral observation systems (Interpersonal Behavior Rating System and the Coding Scheme for Interpersonal Conflict) indicated that distressed couples made significantly more negative and fewer positive cognitive and problem-solving acts. Sequential analyses showed that distressed couples evidenced more reciprocity of negative communications as compared with nondistressed couples. The influence of individual spouse, couple type, and other experimental factors on communication patterns were quantified using multivariate analyses. The relationships of these findings to the etiology and treatment of marital distress are discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)