Soft commutation in capacitive idling converters

The capacitive idling converters derived from the Cuk, SEPIC, Zeta, and flyback topologies allow soft commutation of power switches without the need for additional circuitry, making it possible to increase the switching frequency while maintaining high efficiency     

Quantization effects in digitally behaving circuit implementationsof Kohonen networks

Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation.     

Genetic evolution of the topology and weight distribution of neuralnetworks

This paper proposes a system based on a parallel genetic algorithm with enhanced encoding and operational abilities. The system, used to evolve feedforward artificial neural networks, has been applied to two widely different problem areas: Boolean function learning and robot control. It is shown that the good results obtained in both cases are due to two factors: first, the enhanced exploration abilities provided by the search-space reducing evolution of both coding granularity and network topology, and, second, the enhanced exploitational abilities due to a recently proposed cooperative local optimizing genetic operator.     

Large-deviation inequalities for parameter estimators in stochastic systems

Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.     

Components of random generation by normal subjects and patients with dysexecutive syndrome

The study presents a hypothesis on how randomness could be simulated by human subjects. Three sources of deviation from randomness are predicted: (1) the preferred application of overlearned production schemata for producing sequences of digits, (2) a wrong concept of randomness, and (3) the impossibility to monitor for redundancies of higher- than those of first-order. Deviations of random generation of digits produced by healthy subjects, patients with chronic frontal lobe damage, and patients with Parkinson's disease from random sequences produced by a computer program can be explained by the differential influence of these factors. Whereas incorrect concepts of randomness and limits on monitoring capacity distinguished all sequences produced by humans from actual random sequences, persistence on a single production strategy distinguished brain-damaged patients from controls. Random generation of digits appears to be a theoretically transparent and clinically useful test of executive function.     

A coverage plan for health centres in Murewa district in Zimbabwe: an example of action research

Good access to health facilities providing good first-level health care remains problematic in many developing countries. It is a hindrance to effective and efficient functioning of the hospital, as outpatient departments become overcrowded with patients from areas without health centres. In many cases the quality of care delivered to these patients is poor because within the district health system the hospital is not the best place for the supply of comprehensive, integrated and continuous care. Eventually, high hospital involvement in first-level care can jeopardize the delivery of adequate referral care for those patients who desperately need the hospital's technology and expertise. This paper provides an account of the way this problem was investigated and managed by the district health management team in the Murewa district in north-east Zimbabwe. The design of a comprehensive 'master plan' or 'coverage plan' is presented as well as the problems and difficulties encountered. The Murewa experience highlights the relevance of a coverage plan for rational and coherent health infrastructure planning at district level. The approach followed by the Murewa team illustrates the use of action research as an integral part of the management of district health systems.     

Insertional re-activation of a chloramphenicol acetyltransferase misfolding mutant protein

The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding.