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Facilitation of transmitter release at squid synapses
Facilitation is shown to decay as a compound exponential with two
time constants (T1, T2) at both giant and non-giant synapses in squid steilate ganglia
bathed in solutions having low extracellular calcium concentrations ([Ca++]o).
Maximum values of facilitation (F~) were significantly larger, and T1 was significantly
smaller in giant than non-giant synapses. Decreases in [Ca++]o or increases in
[Mn++]o had variable effects on T1 and F1, whereas decreases in temperature
increased T~ but had insignificant effects on/'1. The growth of facilitation during
short trains of equal interval stimuli was adequately predicted by the linear
summation model developed by Mallart and Martin (1967.J. Physiol. (Lond.). 193:
676-694) for frog neuromuscular junctions. This result suggests that the underlying
mechanisms of facilitation are similar in squid and other synapses which release
many transmitter quanta.This work was supported by National Science Foundation research grant GB-36949, National
Research Council (Canada) and Grass Fellowships to Dr. Charlton, and a National Institutes of
Health career award (NS-00070) to Dr. Bittner.Neuroscienc
The extensive nature of group quality
We consider groups of interacting nodes engaged in an activity as many-body,
complex systems and analyse their cooperative behaviour from a mean-field point
of view. We show that inter-nodal interactions rather than accumulated
individual node strengths dominate the quality of group activity, and give rise
to phenomena akin to phase transitions, where the extensive relationship
between group quality and quantity reduces. The theory is tested using
empirical data on quantity and quality of scientific research groups, for which
critical masses are determined.Comment: 6 pages, 6 figures containing 13 plots. Very minor changes to
coincide with published versio
Developing interlanguage: Driving forces in children learning Dutch and German
Spontaneous language learning both in children learning their mother tongue and in adults learning a second language shows that language development proceeds in a stage-wise manner. Given that a developmental stage is defined as a coherent linguistic system, utterances of language learners can be accounted for in terms of what (Selinker, Larry. 1972. Interlanguage. International Review of Applied Linguistics 10. 209-231) referred to with the term Interlanguage. This paper is a study on the early interlanguage systems of children learning Dutch and German as their mother tongue. The present child learner systems, so it is claimed, are coherent lexical systems based on types of verb-argument structure that are either agentive (as in Dutch: kannie bal pakke 'cannot ball get', or German: mag nich nase putzen 'like not nose clean') or non-agentive (as in Dutch: popje valt bijna 'doll falls nearly', or in German: ente fällt 'duck falls'). At this lexical stage, functional morphology (e. g. morphological finiteness, tense), function words (e. g. auxiliary verbs, determiners) and word order variation are absent. For these typically developing children, both in Dutch and in German, it is claimed that developmental progress is driven by the acquisition of the formal properties of topicalization. It is, furthermore, argued that this feature seems to serve as the driving force in the instantiation of the functional, i. e. informational linguistic properties of the target-language syste
Flow establishment in a generic scramjet combustor
The establishment of a quasi-steady flow in a generic scramjet combustor was studied for the case of a time varying inflow to the combustor. Such transient flow is characteristic of the reflected shock tunnel and expansion tube test facilities. Several numerical simulations of hypervelocity flow through a straight duct combustor with either a side wall step fuel injector or a centrally located strut injector are presented. Comparisons were made between impulsively started but otherwise constant flow conditions (typical of the expansion tube or tailored operations of the reflected shock tunnel) and the relaxing flow produced by the 'undertailored' operations of the reflected shock tunnel. Generally the inviscid flow features, such as the shock pattern and pressure distribution, were unaffected by the time varying inlet conditions and approached steady state in approx. the times indicated by experimental correlations. However, viscous features, such as heat transfer and skin friction, were altered by the relaxing inlet flow conditions
Bound States in Sharply Bent Waveguides: Analytical and Experimental Approach
Quantum wires and electromagnetic waveguides possess common features since
their physics is described by the same wave equation. We exploit this analogy
to investigate experimentally with microwave waveguides and theoretically with
the help of an effective potential approach the occurrence of bound states in
sharply bent quantum wires. In particular, we compute the bound states, study
the features of the transition from a bound to an unbound state caused by the
variation of the bending angle and determine the critical bending angles at
which such a transition takes place. The predictions are confirmed by
calculations based on a conventional numerical method as well as experimental
measurements of the spectra and electric field intensity distributions of
electromagnetic waveguides
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