The adaptation ability of neuronal models subject to a current step stimulus

1988 ◽  
Vol 59 (4-5) ◽  
pp. 295-302 ◽  
Author(s):  
F. Awiszus
1962 ◽  
Vol 45 (6) ◽  
pp. 1163-1179 ◽  
Author(s):  
M. G. F. Fuortes ◽  
Francoise Mantegazzini

Eccentric cells of Limulus respond with repetitive firing to sustained depolarizing currents. Following stimulation with a step of current, latency is shorter than first interval and later intervals increase progressively. A shock of intensity twice threshold can evoke firing 25 msec. after an impulse. But in the same cell, a current step twice rheobase evokes a second impulse more than 50 msec. after the first, and current intensity must be raised to over five times rheobase to obtain a first interval of about 25 msec. Repetitive firing was evoked by means of trains of shocks. With stimuli of moderate intensity, firing was evoked by only some of the shocks and intervals between successive impulses increased with time. This is ascribed to accumulation of refractoriness with successive impulses. Higher frequencies of firing are obtained with shocks of intensity n x threshold than with constant currents of intensity n x rheobase. It is concluded that prolonged currents depress the processes leading to excitation and that (in the cells studied) repetitive firing is controlled both by the after-effects of firing (refractoriness) and by the depressant effects of sustained stimuli (accommodation). Development of subthreshold "graded activity" is an important process leading to excitation of eccentric cells, but is not the principal factor determining frequency of firing in response to constant currents.


1994 ◽  
Vol 346 (1316) ◽  
pp. 129-150 ◽  

In this paper we begin by simplifying our previous model of a thalamic neuron (Rose & Hindmarsh Proc. R. Soc. Lond . B 237, 289-312 (1989 b )) by removal of the A current. A Ca 2+ -activated K + current, with Ca 2+ entering through T channels, is then added to give a model for a class of mammalian neurons in which the membrane potential oscillates in the subthreshold region following a hyperpolarizing current step. The properties of the model are represented using an experimentally observable bifurcation diagram. In the subthreshold region only three variables are required to explain the essential dynamic properties of the cell. In this three-dimensional space the solutions tend to lie on a surface which resembles a paraboloid. We use a simplified model of this model to explain both the dynamics of the solutions on this surface and the form of the bifurcation diagram.


2003 ◽  
Vol 17 (04n06) ◽  
pp. 757-761
Author(s):  
R. LATEMPA ◽  
G. CARAPELLA ◽  
G. COSTABILE ◽  
G. P. PEPE ◽  
L. PARLATO ◽  
...  

We report measurements of the switching induced by a rapidly varying magnetic field in a single, small, fully hysteretic Josephson junction. We demonstrate that the variation of the magnetic field, generated by a current step in a control line deposited on the top of the junction, can control the transitions from Josephson branch to the resistive branch and vice versa. The transition from resistive branch to Josephson branch is not trivial for an hysteretic junction. With a suitable choice of the magnetic pulse shape, a "deterministic flip-flop regime" can be achieved in this system.


Author(s):  
Christian Oettel ◽  
Liisa Rihko-Struckmann ◽  
Kai Sundmacher

The potential to improve the CO tolerance of a high temperature proton exchange membrane fuel cell (HT-PEMFC) was investigated by introducing a platinum-ruthenium alloy as anode catalyst. The electrolyte was a H3PO4 doped poly-2,5-benzimidazole polymer (ABPBI). The experiments were carried out at the temperatures between 403 and 443 K with a CO concentration in the H2 feed gas between 0 and 6.5 vol%. The alloy anode catalyst lowers significantly the negative influence of CO in the feed, exceeding the known temperature dependent CO poisoning mitigation in HT-PEMFCs. It was found that the voltage loss of a HT-PEMFC with PtRu anode catalyst was lower than that of a similar cell equipped with Pt anode. The dynamic cell voltage response to a current step was analyzed under CO influence, as well. The PtRu bimetallic anode electrode was found to lower the observed voltage overshoot behavior after a current step, if compared to conventional Pt anode.


2021 ◽  
Author(s):  
Luis Mata ◽  
Blythe Vogel ◽  
Estibaliz Palma ◽  
Mallik Malapatil

We present evidence of the recent introduction and quick spread of the European firebug Pyrrhocoris apterus in Australia, as documented on the citizen science platform iNaturalist. The first public record of the species was reported in December 2018 in the City of Brimbank (Melbourne, Victoria). Since then, the species distribution has quickly expanded into 15 local government areas surrounding this first observation, including areas in both Metropolitan Melbourne and regional Victoria. The number of records of the European firebug in Victoria has also seen a substantial increase, with a current tally of almost 100 observations in iNaturalist as of July 31st, 2021. The case of the European firebug in Australia adds to the list of examples of citizen scientists playing a key role in not only early detection of newly introduced species but in documenting their expansion across their non-native range. Citizen science presents an exciting opportunity to complement biosecurity efforts carried out by government agencies, which often lack resources to sufficiently fund detection and monitoring programs given the overwhelming number of current and potential invasive species. Recognising and supporting the invaluable contribution of citizen scientists to science and society can help reduce this gap by: (1) increasing the number of introduced species that are quickly detected; (2) gathering evidence of the species’ early expansion stage; and (3) prompting adequate monitoring and rapid management plans for potentially harmful species.Given the range expansion patterns of the European firebug worldwide, their adaptation ability, and future climate scenarios, we suspect this species will continue expanding beyond Victoria, including other parts of Australia, New Zealand, and the South Pacific. We firmly believe that most of the knowledge about how this expansion process continues to happen will be provided by citizen scientists.


2003 ◽  
Vol 37 (1) ◽  
pp. 55-63 ◽  
Author(s):  
R Bötticher ◽  
W Graser ◽  
A Kloss
Keyword(s):  

Author(s):  
R.A. Ploc

The optic axis of an electron microscope objective lens is usually assumed to be straight and co-linear with the mechanical center. No reason exists to assume such perfection and, indeed, simple reasoning suggests that it is a complicated curve. A current centered objective lens with a non-linear optic axis when used in conjunction with other lenses, leads to serious image errors if the nature of the specimen is such as to produce intense inelastic scattering.


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