Local and global dynamical control parameters are not so easily separated

2000 ◽  
Vol 23 (3) ◽  
pp. 407-408
Author(s):  
David T. J. Liley

Hierarchical systems such as cortical tissue will indeed exhibit dynamics that are scale-dependent, but Nunez's conjecture that theoretically independent transfer functions for each level can be specified and then combined ignores the fact that, in cortex, the same excitatory neuronal populations will contribute to both local and global dynamics.

2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
Serena Brianzoni ◽  
Cristiana Mammana ◽  
Elisabetta Michetti

We study the dynamics shown by the discrete time neoclassical one-sector growth model with differential savings while assuming a nonconcave production function. We prove that complex features exhibited are related both to the structure of the coexixting attractors and to their basins. We also show that complexity emerges if the elasticity of substitution between production factors is low enough and shareholders save more than workers, confirming the results obtained while considering concave production functions.


Author(s):  
Vincenzo Crunelli ◽  
Adam C. Errington ◽  
Stuart W. Hughes ◽  
Tibor I. Tóth

During non-rapid eye movement sleep and certain types of anaesthesia, neurons in the neocortex and thalamus exhibit a distinctive slow (<1 Hz) oscillation that consists of alternating UP and DOWN membrane potential states and which correlates with a pronounced slow (<1 Hz) rhythm in the electroencephalogram. While several studies have claimed that the slow oscillation is generated exclusively in neocortical networks and then transmitted to other brain areas, substantial evidence exists to suggest that the full expression of the slow oscillation in an intact thalamocortical (TC) network requires the balanced interaction of oscillator systems in both the neocortex and thalamus. Within such a scenario, we have previously argued that the powerful low-threshold Ca 2+ potential (LTCP)-mediated burst of action potentials that initiates the UP states in individual TC neurons may be a vital signal for instigating UP states in related cortical areas. To investigate these issues we constructed a computational model of the TC network which encompasses the important known aspects of the slow oscillation that have been garnered from earlier in vivo and in vitro experiments. Using this model we confirm that the overall expression of the slow oscillation is intricately reliant on intact connections between the thalamus and the cortex. In particular, we demonstrate that UP state-related LTCP-mediated bursts in TC neurons are proficient in triggering synchronous UP states in cortical networks, thereby bringing about a synchronous slow oscillation in the whole network. The importance of LTCP-mediated action potential bursts in the slow oscillation is also underlined by the observation that their associated dendritic Ca 2+ signals are the only ones that inform corticothalamic synapses of the TC neuron output, since they, but not those elicited by tonic action potential firing, reach the distal dendritic sites where these synapses are located.


2021 ◽  
pp. 1-25
Author(s):  
SRIJANA GHIMIRE ◽  
XIANG-SHENG WANG

In this paper, we investigate two predator–prey models which take into consideration hunting cooperation (i.e., mutualism) between two different predators and within one predator species, respectively. Local and global dynamics are obtained for the model systems. By a detailed bifurcation analysis, we investigate the dependence of predation dynamics on mutualism (cooperative predation). From our study, we prove that mutualism may enhance the survival of mutualist predators in a severe condition and break the competitive exclusion principle. We further provide quantitative information about how the cooperative predation (mutualism) may (i) establish multiple stability switches on the positive equilibrium; (ii) generate backward bifurcation on equilibria; (iii) induce supercritical or subcritical Hopf bifurcations; and (iv) establish bi-stability phenomenon between the predator-free equilibrium and a positive equilibrium (or a limit cycle).


Biosystems ◽  
2018 ◽  
Vol 173 ◽  
pp. 36-51 ◽  
Author(s):  
Lev V. Beloussov ◽  
Tatiana G. Troshina ◽  
Nadezhda S. Glagoleva ◽  
Stanislav V. Kremnyov

Biochemistry ◽  
2011 ◽  
Vol 50 (12) ◽  
pp. 2371-2380 ◽  
Author(s):  
Sang Ho Park ◽  
Fabio Casagrande ◽  
Bibhuti B. Das ◽  
Lauren Albrecht ◽  
Mignon Chu ◽  
...  

Author(s):  
Eshete Tibebe

Emperor Haile Selassie I is a household name in Africa and across the globe. His name evokes a variety of feelings in people. To the radical elite of the 1970s he was seen as despot; for the older generation of the same period, he was a redeemer who restored the nation’s independence. For people of African descent Haile Selassie echoes an iconic significance of pride and black identity. The Emperor was a complex personality, preventing anyone from viewing him from a singular optic. No single conceptual category can encapsulate Haile Selassie; not facile Western constructs such as absolutist, reformer, or modernizer or autocrat. All constructs touch aspects of his many-ness, and none wholly reflect the complexity and multiplicity of his character and actions. His life and political career were shaped by various domestic and external circumstances. Changing local and global dynamics molded his thoughts, actions, persona, and policies. The Emperor presided for the most part of his reign over a nation whose state structure was, by and large, weak: hence the sense of incumbency he felt to guide the process of the nation’s progress under the care of a father figure. Managing the unity of a multiethnic and multireligious nation with a complex history was a political experiment entailing huge responsibilities and challenges. His story is not easy to tell since it is shrouded in paradoxes and ironies. In understanding the Emperor and his leadership style, it is vital to put him in the context of the many-layered history of the nation and the changing political dynamics of Africa. Haile Selassie led a nation rapidly encountering social and political changes in the 20th century while at the same time championing pan-Africanism. Thus, there is a great need to present a full picture and a nuanced contribution to understanding this influential Emperor.


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