Application of Petrov-Galerkin methods to transient boundary value problems in chemical engineering: adsorption with steep gradients in bidisperse solids

Petrov-Galerkin methods are known to be versatile techniques for the solution of a wide variety of convection-dispersion transport problems, including those involving steep gradients. but have hitherto received little attention by chemical engineers. We illustrate the technique by means of the well-known problem of simultaneous diffusion and adsorption in a spherical sorbent pellet comprised of spherical, non-overlapping microparticles of uniform size and investigate the uptake dynamics. Solutions to adsorption problems exhibit steep gradients when macropore diffusion controls or micropore diffusion controls, and the application of classical numerical methods to such problems can present difficulties. In this paper, a semi-discrete Petrov-Galerkin finite element method for numerically solving adsorption problems with steep gradients in bidisperse solids is presented. The numerical solution was found to match the analytical solution when the adsorption isotherm is linear and the diffusivities are constant. Computed results for the Langmuir isotherm and non-constant diffusivity in microparticle are numerically evaluated for comparison with results of a fitted-mesh collocation method, which was proposed by Liu and Bhatia (Comput. Chem. Engng. 23 (1999) 933-943). The new method is simple, highly efficient, and well-suited to a variety of adsorption and desorption problems involving steep gradients. (C) 2001 Elsevier Science Ltd. All rights reserved.

Solution techniques for transport problems involving steep concentration gradients: application to noncatalytic fluid solid reactions

Some efficient solution techniques for solving models of noncatalytic gas-solid and fluid-solid reactions are presented. These models include those with non-constant diffusivities for which the formulation reduces to that of a convection-diffusion problem. A singular perturbation problem results for such models in the presence of a large Thiele modulus, for which the classical numerical methods can present difficulties. For the convection-diffusion like case, the time-dependent partial differential equations are transformed by a semi-discrete Petrov-Galerkin finite element method into a system of ordinary differential equations of the initial-value type that can be readily solved. In the presence of a constant diffusivity, in slab geometry the convection-like terms are absent, and the combination of a fitted mesh finite difference method with a predictor-corrector method is used to solve the problem. Both the methods are found to converge, and general reaction rate forms can be treated. These methods are simple and highly efficient for arbitrary particle geometry and parameters, including a large Thiele modulus. (C) 2001 Elsevier Science Ltd. All rights reserved.

The supportive care needs of men with prostate cancer (2000)

The diagnosis and subsequent treatment of prostate cancer is followed by a range of significant disease specific and iatrogenic sequelae. However, the supportive care needs of men with prostate cancer are not well described in the literature. The present study assesses the supportive care needs of men with prostate cancer who are members of prostate cancer self-help groups in Queensland, Australia. In all, 206 men aged between 48 and 85 years (mean = 68) completed the Supportive Care Needs Survey (SCNS) (62% response). The SCNS is a validated measure assessing perceived need in the domains of psychological needs, health system and information needs, physical and daily living needs, patient care and support, and sexuality. Items assessing need for access to services and resources were also included. One third of the sample reported a moderate to high need for help for multiple items in the sexuality, psychological and health system and information domains. Younger men reported greater need in the sexuality domain; living in major urban centres was predictive of greater psychological need; being closer to the time of diagnosis was related to greater need for help in the physical and daily living domain; having prostate cancer that is not in remission, having received radiation therapy, and lower levels of education were predictive of greater need for help in patient care and support. Of the total sample, 55% of men had used alternative cancer treatments in the past 12 months, with younger and more educated men more likely to use alternative therapies. Interventions in sexuality, psychological concerns and informational support are priorities for men with prostate cancer. Copyright (C) 2001 John Wiley & Sons, Ltd.

Helping the female partners of men abusing alcohol: a comparison of three treatments

Aim. To evaluate the effectiveness of three approaches to assisting the female partners of male problem drinkers with the stress imposed by the male's drinking. Design. Participants were assigned randomly via random number tables to one of three treatment conditions: supportive counselling, stress management or alcohol-focused couples therapy. Setting. The intervention took place at the Behaviour Research and Therapy Centre (BRTC), The University of Queensland. This research and training centre offers outpatient psychology services to the community. Participants. Sixty-one married women whose husbands drank heavily. Participants reported protracted alcohol problems, severe impact of alcohol on social functioning and severe marital distress. Measurement. The women's stress, alcohol consumption by the male, and relationship functioning were assessed at pre- and post-treatment and at 6-month follow-up. Interventions. All three treatments involved 15 1-hour sessions with the woman. In the alcohol-focused couple therapy, attempts were made to engage the man in these sessions. Results. Contrary to our predictions, there were few differences between the treatments. All three treatments were associated with reductions in the women's reported stress, with trends for somewhat greater reduction in the women's stress in the stress management and alcohol-focused couples therapy conditions than for supportive counselling. None of the treatments produced clinically significant reductions in men's drinking or relationship distress. Conclusion. The treatments ease stresses and burden but do not improve drinking or relationships. Limited power in the design restricted the capacity to detect differential treatment effects.

Specific orofacial problems experienced by musicians

Background: Patients who play musical instruments (especially wind and stringed instruments) and vocalists are prone to particular types of orofacial problems. Some problems are caused by playing and some are the result of dental treatment. This paper proposes to give an insight into these problems and practical guidance to general practice dentists. Method: Information in this paper is gathered from studies published in dental, music and occupational health journals, and from discussions with career musicians and music teachers. Results: Orthodontic problems, soft tissue trauma, focal dystonia, denture retention, herpes labialis, dry mouth and temporomandibular joint (TMJ) disorders were identified as orofacial problems of career musicians. Options available for prevention and palliative treatment as well as instrument selection are suggested to overcome these problems. Conclusions: Career musicians express reluctance to attend dentists who are not sensitive to their specific needs. General practitioner dentists who understand how the instruments impact on the orofacial structures and are aware of potential problems faced by musicians are able to offer preventive advice and supportive treatment to these patients, especially those in the early stages of their career.

Resolving the puzzle of productive and destructive conflict in culturally heterogeneous workgroups: A communication accommodation theory approach

This study presents an investigation of the communicative behaviors and strategies employed in the stimulation and management of productive and destructive conflict in culturally heterogeneous workgroups. Using communication accommodation theory (CAT), we argue that the type and course of conflict in culturally heterogeneous workgroups is impacted by the communicative behaviors and strategies employed by group members during interactions. Analysis of data from participant observations, non-participant observations, semi-structured interviews, and self-report questionnaires support CA T-based predictions and provide fresh insights into the triggers and management strategies associated with conflict in culturally heterogeneous workgroups. In particular, results indicated that the more groups used discourse management Strategies, the more they experienced productive conflict. In addition, the use of explanation and checking of own and others' understanding was a major feature of productive conflict, while speech interruptions emerged as a strategy leading to potential destructive conflict. Groups where leaders emerged and assisted in reversing communication breakdowns were better able to manage their discourse, and achieved consensus On task processes. Contributions to the understanding of the triggers and the management of productive conflict in culturally heterogeneous workgroups are discussed.

Short communication: Extended shifts in ambulance work: influences on health

Shiftwork is a major source of stress for many worker's. This study highlights the role that organizational and psychosocial variables play in alleviating the negative health effects of 10 and 14-h shifts. It examines the direct and mediated effects of coping strategies, social support and control of shifts on work/non-work conflict and subjective health. Participants are 60 ambulance workers, aged 22 to SS years. A structural equation model with good fit demonstrates complex effects of social support from various sources (supervisors, co-workers and family), coping and control on work/non-work conflict and subjective health., Conceptually, the research contributes to the development of a theoretical framework that can assist in explaining how key psychosocial and organizational variables influence the psychological and physical symptoms experienced by shiftworkers. Copyright (C) 2002 John Wiley Sons, Ltd.

Air target detection via bistatic radar based on LEOS communication signals

The paper discusses the bistatic radar parameters for the case when the transmitter is a satellite emitting communication signals. The model utilises signals from an Iridium-like low earth orbiting satellite system. The maximum detection range, when thermal noise-limited, is discussed at the theoretical level and these results are compared with experimentation. Satellite-radar signal levels and the power of ground reflections are evaluated.