Eyeblink conditioning leads to fewer synapses in the rabbit cerebellar cortex.

Eyeblink conditioning involves the pairing of a conditioned stimulus (tone) to an aversive unconditioned stimulus (air puff). Although the circuitry that underlies this form of learning is well defined, synaptic changes in these structures have not been fully investigated. This experiment examined synaptic structural plasticity in the cerebellar cortex, a structure that has been found to modulate the acquisition and timing of the conditioned response. Long-term depression of Purkinje cells (PCs) in the cerebellar cortex has been proposed as a mechanism for releasing inhibition of the interpositus nuclei, a structure critical for the formation of the CR. Adult albino rabbits were randomly allocated to either a paired, unpaired, or exposure-only condition. The results showed a significant decrease in the number of excitatory synapses in the outer layer of the cerebellar cortex in the conditioned rabbits compared with controls. This finding suggests that a reduction in the number of excitatory synapses may contribute to the lasting depression of PC activity that is associated with eyeblink conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermodynamics of DNA interactions from single molecule stretching experiments

On the basis of our analysis of detailed measurements of the dependence of the overstretching transition of double-stranded DNA (dsDNA) on temperature, pH, and ionic strength, we have demonstrated that a model of force-induced melting accurately describes the thermodynamics of DNA overstretching. Measurements of this transition allow us to determine the stability of dsDNA and obtain information similar to that obtained in thermal melting studies. This single-molecule technique has the advantage that it can be used to measure DNA stability at any temperature. We discuss the use of this technique to study the nucleic acid chaperone activity of the HIV-1 nucleocapsid protein.     

Multilayer transducer transfer matrix formalism

A complete formulation of direct and inverse 4 /spl times/ 4 transfer matrices for parallel and series, electrically connected, mechanically stacked, 1-D thickness mode multilayer piezoelectric transducers is presented. Complex coefficients account for the mechanical, dielectric, and piezoelectric losses. The direct or inverse 4 /spl times/ 4 transfer matrix transfers quantities at the top surface into their values at the bottom surface or vice versa, respectively. The 4 /spl times/ 4 transfer matrices derive from the 3 /spl times/ 3 transfer matrices, which follow from the 3 /spl times/ 3 matrix for the general three-port. For both parallel and series connections, the 3 /spl times/ 3 and 4 /spl times/ 4 direct and inverse transfer matrices are interrelated through transformation symmetries; also, the inverse matrix can be obtained from the direct matrix by changing the sign of both the piezoelectric coefficient and the explicitly occurring complex variable, j. For the electrically parallel connected case, explicit voltage orientation reversals occur at successive piezoelectric layers. Cascading the 4 /spl times/ 4 matrices yields the sum of the currents through the piezoelectric layers for the electrically parallel-connected case and the sum of the voltage differences across the layers for the electrically series-connected case. The resultant matrices are calculated for the cascading of n identical piezoelectric layers connected in parallel and series.     

Understanding the social practices of systems developers

Abstract. The aim of this paper is to explore some of the ways in which we think about the development of information systems by drawing upon arguments articulated within the philosophy of science and the sociology of technology. It argues that many of these approaches operate on the basis of a reified and sociologically restricted view of technology. Drawing upon recent work in the sociology of technology the paper proposes a more thorough-going analysis of the social practice of information systems development and discusses examples from knowledge engineering and requirements analysis to illustrate its argument.     

Economic evaluation of chemotherapy with mitoxantrone plus prednisone for symptomatic hormone-resistant prostate cancer: based on a Canadian randomized trial with palliative end points

PURPOSE: To evaluate the economic consequences of the use of chemotherapy in patients with symptomatic hormone-resistant prostate cancer (HRPC) in the context of a previously published Canadian open-label, phase III, randomized trial with palliative end points. PATIENTS AND METHODS: The trial randomized 161 patients to initial treatment with mitoxantrone and prednisone (M + P) or to prednisone alone (P) and showed better palliation with M + P. There was no significant difference in survival. A detailed retrospective chart review was performed of resources used from randomization until death of 114 of 161 patients enrolled at the three largest centers: these included hospital admissions, outpatient visits, investigations, therapies (which included all chemotherapy and radiation), and palliative care. Cancer center and community hospital costs were calculated by using the hotel approximation method and case costing from the Ontario Case Cost Project, respectively. Cost-utility analysis was performed by transforming the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 global quality-of-life item measured every 3 weeks on trial to an estimate of utility, and extending the last known value through to death or last follow-up. RESULTS: The mean total cost until death or last follow-up by intention-to-treat was M + P CDN $27,300; P CDN $29,000. The 95% confidence intervals on the observed cost difference ranged from a saving of $9,200 for M + P (with palliative benefit) to an increased cost of $5,800 for M + P. The major proportion of cost (M + P 53% v P 66%; CDN $14,500 v $19,100) was for inpatient care. Initial M + P was consistently less expensive in whichever time period was used to compare costs. Cost-utility analysis showed M + P to be the preferred strategy with an upper 95% confidence interval for the incremental cost-utility ratio of CDN $19,700 per quality-adjusted life-year (QALY). CONCLUSION: A treatment that reduces symptoms and improves quality of life has the potential to reduce costs in other areas. Economic factors should not influence the clinical decision as to whether to use M + P in a symptomatic patient.     

Effects of proteins, blood cells and glucose on the viscosity of cerebrospinal fluid

It has long been assumed that cerebrospinal fluid (CSF) is a newtonian fluid with viscosity similar to water, yet high protein content, has been postulated to increase the viscosity of CSF in vivo. Such an increase in viscosity may have serious implications for the effectiveness of surgical shunts implanted to re-establish the CSF flow in cases of abnormal CSF circulation. In this study, glucose content, total protein content and blood cell count in the CSF of 23 patients undergoing brain surgery were measured. Viscosity measurements were performed on duplicate CSF samples over a range of shear strain rates of 25-1,460 s-1. The results indicated that high protein or high cell concentration in CSF does not significantly affect the viscosity of the cerebral fluid at those shear rates. CSF is clearly newtonian, and its viscosity at 37 degreesC is in the range of 0.7-1 mPa.s.     

IE A Task VIII - the UK experience

D. Bloomfield and R. Brewer from the Building Research Establishment, I. Cooper and S. Lera from Eclipse Research Consultants and B. Stringer from the Energy Technology Support Unit at the Harwell Laboratory describe the UK experience gained by participation in the International Energy Agency programme on passive solar gain and hybrid low-energy building. It concludes that much work is still to be done on modelling, that presentation of design guidelines needs to be appropriate to the audience, and building practice and occupant behaviour should not be underestimated when collaborating on international ventures.