Measured change in protein solvation with substrate binding and turnover

Osmotic stress is used to measure solvation changes that accompany the conformational changes of an active enzyme. For hexokinase both the equilibrium dissociation constant and the kinetic Michaelis-Menten constant for glucose vary linearly, and to the same extent, with the activity of water in the protein medium, as adjusted with large molecular weight (> 2000) osmolytes. The variation over the whole osmotic pressure range studied indicates that glucose binding is accompanied by the release of at least 65 +/- 10 water molecules, and this is reversed on enzyme turnover. The results indicate that near the physiological range of pressures the number may be higher. Most of this water, which behaves like an inhibitor, likely comes from the cleft which is induced to close around the substrate. Such large dehydration/rehydration reactions during turnover imply a significant contribution of solvation to the energetics of the conformational changes. Osmotic stress is a method of general applicability to probe water's contribution to functioning molecules.     

THE ESTIMATION OF RANDOM COEFFICIENT AUTOGRESSIVE MODELS. II

Abstract. In Nicholls and Quinn (1980) a procedure was proposed for the determination of strongly consistent estimates of random coefficient autoregressive models. These estimates are used here as starting values in a Newton-Raphson algorithm which is employed to obtain the maximum likelihood estimates of a class of random coefficient autoregressions. The maximum likelihood estimates are shown to be strongly consistent and to satisfy a central limit theorem. The problem of testing for the randomness of the coefficients is also briefly discussed. The results of a number of simulations are reported which illustrate the theoretical results obtained.     

Results of Delorme's procedure for rectal prolapse

PURPOSE: This study was designed to examine the results of Delorme's procedure. METHODS: Thirty-two patients (24 males and 8 females, mean age, 70 years) underwent Delorme's procedure between 1978 and 1990 following symptoms lasting between two weeks and ten years. Thirteen patients had had 21 previous operations for prolapse. RESULTS: The mean operation time was 65 minutes. No blood transfusions were needed, there was no operative mortality, and only two patients had complications (one chest infection and one anastomotic dehiscence). No patients were lost to follow-up. Over a mean follow-up of 24 months (4 months to 4 years), 9 patients died of unrelated conditions. There were four recurrences (12.5 percent), two in patients who had each had two previous procedures. Incontinence improved in 46 percent. No patient became constipated and 50 percent of those constipated preoperatively improved. CONCLUSION: Although abdominal rectopexy is safe and has a low recurrence rate (< 5 percent), it involves the hazards of a laparotomy. In addition, up to 40 percent of patients become constipated after rectopexy which may be debilitating. Delorme's procedure has a low morbidity, results in good bowel function, and has a low recurrence rate. It can be performed on unfit patients with possible advantages over rectopexy and perhaps should be used more readily.     

Computer-aided veterinary learning at the University of Cambridge

An approach of computer-assisted learning in veterinary education at the University of Cambridge, involving the development of four types of learning module, is outlined. A tutorial on regional perineural anaesthesia in the horse, based on the familiar tape-slide format but with significant improvements, is described. A question and answer self-assessment package and a computer-based 'digital lecture' are also discussed, together with a case simulation involving the investigation of a polydipsic dog. All the tutorials were developed using standard software packages and image digitising processes. The philosophy behind the development of these computer-assisted learning packages is discussed.     

Using PRA in support of maintenance optimisation

For a number of years the Plant Specific Probabilistic Risk Assessment of Koeberg Nuclear Power Station has been used to support maintenance optimisation. By ranking all components by their importance to nuclear safety we have ensured that the most stringent maintenance regimes are only applied to components where it is absolutely necessary. Further, the overall level of safety is set by our licensing authority. This implies that a certain level of reliability is required for each component involved in safety. By monitoring performance and using the Bayesian analysis technique, it can be deduced whether an acceptable reliability is being achieved and whether a reduction in the maintenance frequency may be justified.     

When a scale measures more than its name denotes: the case of the Test Anxiety Scale for Children

Administered a revision of the Test Anxiety Scale for Children (TASC) on which there were separate comparative Self-Evaluation and Anxiety scales to 133 females and 131 males in Form 1 (equivalent to Grade 6). Ss also responded to self-report measures (self-concept of attainment, causal attribution, independent reading, and friendship choices), and teachers rated Ss on their classroom behavior. Findings indicate that correlations between Ss' TASC scores and variables that had been found to be related to the original scale and assumed to be affected by anxiety were generally higher for the Self-Evaluation scale than the Anxiety scales. It is suggested that many results with the TASC may be better interpreted in terms of self-evaluation than anxiety effects. Results with measures of causal attributions suggest that self-evaluation measures are more effective predictors of achievement behavior than anxiety measures because anxiety is but one of a number of possible consequences of poor self-evaluation that could mediate relatively unproductive achievement behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gravel bed storage analysis for heat pump systems

The storage of solar heat in the earth beneath a building, using an air flow gravel bed heat exchanger to supply a heat pump, is analyzed. A simulation of annual performance is demonstrated, using a transient analysis to model heat flow ambients to and from the gravel bed, combined with iterative steady state approximations for the more slowly varying heat losses through the large thermal mass of soil. A cost analysis example is solved.Gravel bed heat exchangers are one means to provide large (seasonal) heat storage capacity for solar installations in new buildings at relatively low cost and without added space requirements.     

THE ESTIMATION OF RANDOM COEFFICIENT AUTOREGRESSIVE MODELS. I

Abstract. This paper is concerned with autoregressive models in which the coefficients are assumed to be not constant but subject to random perturbations so that we are considering a class of random coefficient autoregressive models. By means of a two stage regression procedure estimates of the unknown parameters of these models are obtained. The estimates are shown to be strongly consistent and to satisfy a central limit theorem. A number of Monte Carlo experiments was carried out to illustrate the estimation procedure and their results are reported.