Evoked responses and neuronal activity in the lateral geniculate

Résumé Il a paru intéressant de préciser les relations de temps et de phase entre la réponse évoquée massive et la réponse des neurones du corps genouillé latéral. Des microéléctrodes ont été implantées dans le corps genouillé latéral du chat et des réponses ont été évoquées par stimulation visuelle. On a pu démontrer que la probabilité aussi bien que la fréquence de la décharge neuronique varient en raison de la première dérivée de la réponse massive à ondes lentes.

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Aided by grants Nos. NB 07145 and FO5 TW 1017 from the National Institutes of Health.     

Newtonianism in early Enlightenment Germany, c. 1720 to 1750: metaphysics and the critique of dogmatic philosophy

The acceptance of Newton’s ideas and Newtonianism in the early German Enlightenment is usually described as hesitant and slow. Two reasons help to explain this phenomenon. One is that those who might have adopted Newtonian arguments were critics of Wolffianism. These critics, however, drew on indigenous currents of thought, pre-dating the reception of Newton in Germany and independent of Newtonian science. The other reason is that the controversies between Wolffians and their critics focused on metaphysics. Newton’s reputation, however, was that of a mathematician, and one point, on which Wolffians and their opponents agreed, was that mathematics was of no use in the solution of metaphysical questions. The appeal to Newton as an authority in metaphysics, it was argued, was the fault of Newton’s over-zealous disciples in Britain, who tried to transform him from a mathematician into the author of a general philosophical system. It is often argued that the Berlin Academy after 1743 included a Newtonian group, but even there the reception of Newtonianism was selective. Philosophers such as Leonhard Euler were also reluctant to be labelled ‘Newtonians’, because this implied a dogmatic belief in Newton’s ideas. Only after the mid-eighteenth century is ‘Newtonianism’ increasingly accepted in the sense of a philosophical system.     

An examination of factors contributing to delphi accuracy

Three experiments examined the accuracy in the Delphi method. The first experiment assessed the accuracy of group predictions over 1-, 2- and 3- month time spans. Results indicated that predictions derived from the group were more accurate than those of 95 per cent of the individual panelists, but did not exceed in accuracy the best panelists. Experiment 2 evaluated the gross contributions of polling and feedback to Delphi accuracy. The manipulations did not improve the group's ability to forecast the probabilities of the occurrence of events, but did decrease the error in predicting when the events would occur. Experiment 3 separated the effects of polling and feedback as determinants of accuracy. Neither manipulation improved the accuracy of the group's predictions of whether an event would occur. The effect of iterated polling was to reduce the group's error in predicting the time course for those scenarios that did occur.     

Systems and reengineering: Relating the reengineering paradigm to systems methodologies

Recently the topic of business process reengineering (BPR) has emerged to prominence in a number of guises, e.g. Hammer and Champy (1993). BPR is accepted here as containing a core paradigm with the potential to mobilize and channel change to secure radical improvements in organizational performance. This is contrasted with Continuous Improvement methods which deliver gradual improvements. In this paper BPR is conceputalised as an approach comprised of an emerging group of systems methodologies. These are related to other approaches and methodologies using the Total Systems Intervention framework of Flood and Jackson (1991). In keeping with the framework the main assumptions and metaphors that underlie the BPR literature are examined. BPR methodologies are characterised as rooted mainly in the hard systems approach with the machine metaphor dominating. The possibility is discussed of BPR methodologies based around other than hard system approaches.     

Atrial natriuretic peptide inhibits angiotensin-stimulated proximal tubular sodium and water reabsorption

The discovery that atrial extracts have potent diuretic and natriuretic properties revealed a possible endocrine function of the heart in the regulation of extracellular fluid volume. Since that first report intense research activity has been directed towards determining the mechanism of action of the active atrial natriuretic polypeptides (ANP) found in these extracts. Despite these efforts it remains controversial whether the renal actions of ANP are exerted solely on the process of glomerular filtration or involve additional direct actions on tubular transport. We have investigated the possibility that atrial natriuretic polypeptides may induce natriuresis by suppression of proximal tubular sodium and water reabsorption. Using shrinking split-drop micropuncture combined with simultaneous capillary perfusion in anaesthetized rats we report that 20 nanomolar alpha-rANP (the main component of ANP in rat plasma) added to the peritubular fluid had no direct effect on proximal fluid uptake whereas picomolar angiotensin II had a marked stimulatory action as reported. The stimulatory effect of angiotensin II on fluid reabsorption was inhibited by peritubular ANP at physiological concentrations and abolished by higher concentrations of ANP. Thus at physiological concentrations ANP acts within the kidney to decrease proximal reabsorption by inhibition of angiotensin-stimulated sodium and water transport.     

A fossil entomogenous fungus from Dominican amber

Summary A worker ant (Formicidae: Hymenoptera) embedded in amber (25 million years old) from the Dominican Republic was covered with an entomogenous fungus containing characters very similar to present day strains ofBeauveria bassiana. This represents the first report of a fossil insect-pathogenic fungus belonging to the class Deuteromycetes.