Noise, transient dynamics, and the generation of realistic interspike interval variation in square-wave burster neurons

First return maps of interspike intervals for biological neurons that generate repetitive bursts of impulses can display stereotyped structures (neuronal signatures). Such structures have been linked to the possibility of multicoding and multifunctionality in neural networks that produce and control rhythmical motor patterns. In some cases, isolating the neurons from their synaptic network revealsirregular, complex signatures that have been regarded as evidence of intrinsic, chaotic behavior. We show that incorporation of dynamical noise into minimal neuron models of square-wave bursting (either conductance-based or abstract) produces signatures akin to those observed in biological examples, without the need for fine-tuning of parameters or ad hoc constructions for inducing chaotic activity. The form of the stochastic term is not strongly constrained, and can approximate several possible sources of noise, e.g. random channel gating or synaptic bombardment. The cornerstone of this signature generation mechanism is the rich, transient, but deterministic dynamics inherent in the square-wave (saddle-node/homoclinic) mode of neuronal bursting. We show that noise causes the dynamics to populate a complex transient scaffolding or skeleton in state space, even for models that (without added noise) generate only periodic activity (whether in bursting or tonic spiking mode).Comment: REVTeX4-1, 18 pages, 9 figure

Effect of body movements in the venous blood flow and lymphatic circulation

The studies of ballistocardiography about the effect of cardiovascular activity in body motion raised the author interest in the research of the influence of body movements in the circulatory flow in venous and lymphatic vessels. These effects follow Sir Isaac Newton laws. With the body movement, the one-way valve structure of these vessels will cause a mobilization of venous blood and lymph to the proximal side. A model was built to demonstrate the effect of oscillatory movement in a liquid flow in a system of one-way valve. There was a rise of the liquid with difference in level that ranged from 9 cm up to 34 cm, depending on the amplitude and frequency. The model tried to mimic a segment of vein with its valve, and evaluate the effectiveness of oscillatory movements in the progression of the liquid, In a preliminary study, to assess the effect of oscillatory movements on leg swelling, this movements was applied in a clinical cases. There was regression of the oedema and circumference on the leg, by oscillatory movements, that was correlated with increase in lymphatic and venous drainage. Venous stasis is a predisposing factor of venous thromboembolism. How we extrapolate from the experimental model, the oscillatory movements of the legs improving venous circulation may contribute to the prophylaxis of venous thromboembolism. In conclusion, it is of interest to study its application in some situations of venous thromboembolism risk

Las PYMES familiares: un modelo económico viable

Teniendo en cuenta que las Pymes constituyen gran parte de la economía colombiana y que estas tienen que enfrentar constantes cambios, este trabajo busca identificar todos aquellos desafíos a los que se ven enfrentadas las empresas familiares, lo mismo que los factores que hacen que muchas de estas empresas fracasen poco tiempo después de haber sido dado que la mayoría de estas han sido creadas por fundadores empíricos y por ende ellos no se sujetan fácilmente a los cambios que exige el mundo globalizad

Genetic diversity of sorghum (Sorghum bicolor L. Moench) germplasm and hybrid potential under contrasting environments in Mozambique.

Doctor of Philosophy in Plant Breeding. University of KwaZulu-Natal, Pietermaritzburg, 2017.Abstract available in PDF file

World Equity Markets: A New Approach for Segmentation (in English)

This paper is an assessment of international equity-market integration and uses an innovative approach to segment equity markets into related geographic areas. The authors´ focus is on the relationships among the returns of the dominant national equity indexes by continent. To understand how these indexes have evolved, the authors will concentrate on a reduced number of dimensions extracted from principal components analysis. They will demonstrate that each one of these components is particularly associated with certain groups of nations and less associated with others.interaction, principal components analysis, returns

Níveis nutricionais de fósforo disponível em diferentes granulometrias de fosfato para codornas japonesas em postura

Com este estudo objetivou-se determinar os níveis de fósforo disponível (Pdisp) para codornas japonesas (Coturnix coturnix japonica) em período de postura. Foram utilizadas 648 codornas japonesas produtoras de ovos para consumo, alojadas em gaiolas do tipo bateria, com dimensões de 0,9 x 0,33 x 0,15 m, e distribuídas em delineamento inteiramente ao acaso, com cinco tratamentos, oito repetições sendo nove aves/unidade experimental. Foi elaborada dieta a base de milho e farelo de soja, formulada para atender as recomendações nutricionais, exceto para fósforo disponível. Esta continha 2.900 kcal EM/ kg de ração, 20% de proteína bruta, 3,05% de cálcio, 0,10% de fósforo disponível, 1,05% de lisina digestível, 0,720% de metionina+cistina e 0,730% de treonina digestível. A esta dieta basal, foi adicionado fosfato com diferentes granulometrias (fina ou grossa) e o calcário, em substituição ao material inerte, de forma a obter cinco níveis de fósforo disponível (0,10; 0,20; 0,30; 0,40 e 0,50%) para cada granulometria utilizada. Em conclusão, a recomendação de fósforo disponível, varia em função da granulometria do fosfato utilizado. Desta forma, para granulometria fina foi encontrado o nível 0,44% de fósforo disponível, e para fosfato de granulometria grossa, o nível de 0,385% de fósforo disponível para codornas no segundo ciclo de postura.The aim of this study was to determine the levels of available phosphorus forJapanese quail (Coturnix coturnix japonica) in the laying period. 648 Japanese quails were used producing eggs for consumption, in cages like battery, with dimensions of 0.9 x 0.33 x 0.15 m, and distributed in a completely randomized design with five treatments, eight replicates and nine hens/experimental unit. Was prepared diet based on corn and soybean meal, formulated to meet nutritional recommendations, except for available phosphorus. It contained 2900 kcal/kg, 20% crude protein, 3.05% calcium, 0.10% phosphorus, 1.05% of lysine, 0.720% methionine+cystine and threonine 0.730% digestible. To this basal diet, phosphate was added with different particle sizes (fine or coarse) and limestone, replacing the inert material in order to obtain five levels of available phosphorus (0.10, 0.20, 0.30, 0.40 and 0.50%) for each particle size used. In conclusion, the recommendation phosphorus, varies depending on the granulometry of phosphate used. Thus, for finely was found at 0.44% available phosphorus, and coarse, the level of 0.385% phosphorus for quails position in the second cycle