Papers by Ricardo Osuna Olivares
NeuroReport, 1996
We found positive correlations between the number of myelinated callosal fibres &... more We found positive correlations between the number of myelinated callosal fibres > 1 micron in diameter and age in humans. The relatively abundant axons with diameters between 1 and 3 microns correlated with age only in females, while the scarce fibres > 3 microns in diameter correlated significantly with age only in males. When analysing different callosal segments, it was found that in the midbody (but not in the splenium) of females the number of fibres > 3 microns also increased with age. In males, the relationship between these large diameter fibres and age disappeared after dividing the callosum into distinct segments. There may, therefore, be sex differences in the course of callosal fibre growth and myelination during the normal lifespan.
Brain, Behavior and Evolution, 2001
A cross-species ultrastructural study of the corpus callosum was performed in six domestic specie... more A cross-species ultrastructural study of the corpus callosum was performed in six domestic species: the rat, the rabbit, the cat, the dog, the horse and the cow. The results indicate cross-species conservatism in callosal fiber composition with a good interspecies relation between fiber number and brain size. Across species, increases in both brain size and callosal area indicate more callosal fibers, although less than expected from the estimated increase in cortical cell number. Within each species, the correlation between fiber number and brain weight tends to disappear, although in most cases a larger callosum implies a larger number of callosal fibers. The median fiber diameter was conservative across species (0.11-0.2 microm), indicating the maintenance of conduction velocity of most callosal fibers regardless of interhemispheric distance. Nevertheless, the maximal fiber diameters tended to be higher in species with larger brains. Therefore, there is a population of coarse-diameter fibers that tend to increase their diameter and conduction velocity with increasing brain size. However, allometric calculations suggest that the associated increase in velocity in these large fibers may not be sufficient to maintain a constant interhemispheric transmission time in different species.
Brain, Behavior and Evolution, 2000
A cross-species morphometric study of the corpus callosum was performed in the rat, rabbit, cat, ... more A cross-species morphometric study of the corpus callosum was performed in the rat, rabbit, cat, dog, horse, cow and human. Across species, the results indicate a strong, although less than linear, dependency of callosal size on brain weight. This relation tends to lose significance within species. This is consistent with other morphometric studies indicating a tendency to decrease the correlations between morphometric variables in within-species analyses as compared to between-species analyses. There are species differences in the relative size of some callosal segments particularly in the posterior third, which is larger in frontally-looking species than in laterally-looking species. No sex differences in callosal size were detected in any of the species examined. These findings are discussed in the light of possible developmental and functional correlates of the variability observed.
International Journal of Morphology, 2014
International Journal of Morphology, 2013
ROJAS, M. Esqueleto axial y apendicular de vertebrados. Int. J. Morphol., 31(2):378-387, 2013.
International Journal of Morphology, 2014
2011 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC 2011), 2011
WRONs often involve channel drop/add procedures affecting the transmission quality due to the int... more WRONs often involve channel drop/add procedures affecting the transmission quality due to the introduction of power excursions by the optical amplifiers. In this work, the Hybrid Amplifier (HA) transient response under WDM channel drop/add scenarios is analyzed by means of numerical simulation. When 17 out of 20 channels are dropped/added, the HA transient response is larger and faster for forward DFRA hybrid configurations. Two different reactions were identified: initial disturbances and steady state regions, both intensified by a cascade of 12 HAs. The amplifier's relative location determines power excursions up to the third amplification stage, being larger for "DFRA + EDFA" configurations. For the "backward DFRA + EDFA" configuration, 6.41 dB to 8.45 dB overshoots between the second and the sixth amplification stages were observed and the steady state power excursion reached 7.83 dB. For the "forward DFRA + EDFA" configuration a 7.75 dB overshoot and a 7.98 dB steady state power excursion response in the fourth amplification stage were obtained.
2011 IEEE Third Latin-American Conference on Communications, 2011
A dynamic lightpath allocation algorithm that considers the impact of Raman amplification on the ... more A dynamic lightpath allocation algorithm that considers the impact of Raman amplification on the quality of the signal is proposed. To do so, an exhaustive theoretical model that includes fiber attenuation, Rayleigh scattering, stimulated Raman scattering (gain and depletion of channels and pumps) and spontaneous Stokes and anti-Stokes scattering caused by Distributed Fiber Raman Amplifiers (DFRAs) is used to quantify the Optical Signal to Noise Ratio (OSNR) of the lightpaths found by the lightpath allocation algorithm. The performance of the proposed algorithm was evaluated by means of computer simulation. Results show that, due to the rigorous modeling of the Raman amplification, the blocking probability of the proposed lightpath algorithm can be several orders of magnitude higher than that of classical Routing and Wavelength Assignment (RWA) algorithms or previous OSNR-aware algorithms applying a much simpler model for the signal power propagation of DFRAs. We expect these results help network operators to better design and operate their future Raman-amplified dynamic networks.
IEEE Communications Magazine, 2000
ABSTRACT We present a generic step-by-step methodology for evaluating the total cost of migrating... more ABSTRACT We present a generic step-by-step methodology for evaluating the total cost of migrating from a capacity-exhausted WDM network to different upgraded alternatives. The presented methodology is the first effort to provide a generic evaluation framework (allowing the evaluation of scenarios with different traffic growth rates, optical technologies, network architectures, and resource allocation algorithms) that considers both capital and operational expenditures of the upgraded alternatives to then identify the lowest-cost option. Previous works have just evaluated specific scenarios or only CapEx or OpEx (not both). As a way of illustration, the proposed methodology was applied to compare the migration cost of two upgrading scenarios. The methodology allowed identifying the lowest-cost alternative, categorizing the key cost factors of CapEx and OpEx, and evaluating its impact on the migration cost. Surprisingly, results for the study case presented show that migrating to an automatically provisioned network does not necessarily lead to cost savings.
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Papers by Ricardo Osuna Olivares