15 research outputs found
Elasticity of Semiflexible Biopolymer Networks
We develop a model for gels and entangled solutions of semiflexible
biopolymers such as F-actin. Such networks play a crucial structural role in
the cytoskeleton of cells. We show that the rheologic properties of these
networks can result from nonclassical rubber elasticity. This model can explain
a number of elastic properties of such networks {\em in vitro}, including the
concentration dependence of the storage modulus and yield strain.Comment: Uses RevTeX, full postscript with figures available at
http://www.umich.edu/~fcm/preprints/agel/agel.htm
Dynamical mean-field theory of spiking neuron ensembles: response to a single spike with independent noises
Dynamics of an ensemble of -unit FitzHugh-Nagumo (FN) neurons subject to
white noises has been studied by using a semi-analytical dynamical mean-field
(DMF) theory in which the original -dimensional {\it stochastic}
differential equations are replaced by 8-dimensional {\it deterministic}
differential equations expressed in terms of moments of local and global
variables. Our DMF theory, which assumes weak noises and the Gaussian
distribution of state variables, goes beyond weak couplings among constituent
neurons. By using the expression for the firing probability due to an applied
single spike, we have discussed effects of noises, synaptic couplings and the
size of the ensemble on the spike timing precision, which is shown to be
improved by increasing the size of the neuron ensemble, even when there are no
couplings among neurons. When the coupling is introduced, neurons in ensembles
respond to an input spike with a partial synchronization. DMF theory is
extended to a large cluster which can be divided into multiple sub-clusters
according to their functions. A model calculation has shown that when the noise
intensity is moderate, the spike propagation with a fairly precise timing is
possible among noisy sub-clusters with feed-forward couplings, as in the
synfire chain. Results calculated by our DMF theory are nicely compared to
those obtained by direct simulations. A comparison of DMF theory with the
conventional moment method is also discussed.Comment: 29 pages, 2 figures; augmented the text and added Appendice
Tea drinking and cognitive function in oldest-old Chinese
10.1007/s12603-012-0077-1The Journal of Nutrition, Health & Aging169754-75
Cognitive and mood effects in healthy children during 12 weeks' supplementation with multi-vitamin/minerals
Adequate levels of vitamins and minerals are essential for optimal neural functioning. A high proportion of individuals, including children, suffer from deficiencies in one or more vitamins or minerals. This study investigated whether daily supplementation with vitamins/minerals could modulate cognitive performance and mood in healthy children. In this randomised, double-blind, placebo-controlled, parallel groups investigation, eighty-one healthy children aged from 8 to 14 years underwent laboratory assessments of their cognitive performance and mood pre-dose and at 1 and 3 h post-dose on the first and last days of 12 weeks' supplementation with a commercially available vitamins/mineral product (Pharmaton Kiddi). Interim assessments were also completed at home after 4 and 8 weeks at 3 h post-dose. Each assessment comprised completion of a cognitive battery, delivered over the Internet, which included tasks assessing mood and the speed and accuracy of attention and aspects of memory (secondary, semantic and spatial working memory). The vitamin/mineral group performed more accurately on two attention tasks: 'Arrows' choice reaction time task at 4 and 8 weeks; 'Arrow Flankers' choice reaction time task at 4, 8 and 12 weeks. A single task outcome (Picture Recognition errors) evinced significant decrements at 12 weeks. Mood was not modulated in any interpretable manner. Whilst it is possible that the significant improvements following treatment were due to non-significant numerical differences in performance at baseline, these results would seem to suggest that vitamin/mineral supplementation has the potential to improve brain function in healthy children. This proposition requires further investigation
Sado-Masochism, Criminal Law and Adjudicative Method: R v Brown in the House of Lords
Despite media and public expectation of efficacy, no study to date has investigated the cognitive and mood effects of omega l supplementation in healthy children.
This randomised, double-blind, placebo-controlled, parallel groups pilot study assessed the cognitive and mood effects of either 400 mg or 1000 mg of docosahexaenoic acid a (DHA) in si healthy children aged 10-12 years. Cognitive performance and mood was assessed prior toe and 8 weeks following, commencement of treatment.
There was a significant treatment effect on one cognitive measure a speed of word recognition),, with the lower dose speeding, and the higher dose slowing, performance. Overall, the pattern of results strongly suggests that this effect was due to chance fluctuations in performance and that the treatments had no consistent or interpretable effect on performance.
The results here do not suggest that supplementation with these doses of DHA for 8 weeks has any beneficial effect on brain function in cognitively intact children
Vitamin products, in particular multi-vitamins, may potentially enhance cognitive function, but more studies are needed
Cognitive function and tea consumption in community dwelling older Chinese in Singapore
10.1007/s12603-010-0095-9Journal of Nutrition, Health and Aging6141-
Tea and cognitive health in late life: Current evidence and future directions
10.1007/s12603-011-0139-9Journal of Nutrition, Health and Aging16131-34JNHA