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Search Results: 1 - 10 of 465263 matches for " A. Gonzalez-Falcon "
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Effects of pyruvate administration on infarct volume and neurological deficits following permanent focal cerebral ischemia in rats
A. Gonzalez-Falcon,E. Candelario-Jalil,M. Garcia-Cabrera,O. S. Leon
Quantitative Biology , 2007,
Abstract: Recent experimental evidences indicate that pyruvate, the final metabolite of glycolysis, has a remarkable protective effect against different types of brain injury. The purpose of this study was to assess the neuroprotective effect and the neurological outcome after pyruvate administration in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in rats. Three doses of pyruvate (250, 500 and 1000 mg/kg, i.p.) or vehicle were administered intraperitoneally 30 min after pMCAO. In other set of experiments, pyruvate was given either before, immediately after ischemia or in a long-term administration paradigm. Functional outcome, mortality and infarct volume were determined 24 h after stroke. Even when the lowest doses of pyruvate reduced mortality and neurological deficits, no concomitant reduction in infarct volume was observed. The highest dose of pyruvate increased cortical infarction by 27% when administered 30 min after pMCAO. In addition, when pyruvate was given before pMCAO, a significant increase in neurological deficits was noticed. Surprisingly, on the contrary of what was found in the case of transient global ischemia, present findings do not support a great neuroprotective role for pyruvate in permanent focal cerebral ischemia, suggesting two distinct mechanisms involved in the effects of this glycolytic metabolite in the ischemic brain.
Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats
E Candelario-Jalil,A Gonzalez-Falcon,M Garcia-Cabrera,OS Leon,BL Fiebich
Quantitative Biology , 2007,
Abstract: Several studies suggest that cyclooxygenase (COX)-2 plays a pivotal role in the progression of ischaemic brain damage. In the present study, we investigated the effects of selective inhibition of COX-2 with nimesulide (12 mg/kg) and selective inhibition of COX-1 with valeryl salicylate (VAS, 12-120 mg/kg) on prostaglandin E2 (PGE2) levels, myeloperoxidase (MPO) activity, Evans blue (EB) extravasation and infarct volume in a standardized model of transient focal cerebral ischaemia in the rat. Post-ischaemic treatment with nimesulide markedly reduced the increase in PGE2 levels in the ischaemic cerebral cortex 24 h after stroke and diminished infarct size by 48% with respect to vehicle-treated animals after 3 days of reperfusion. Furthermore, nimesulide significantly attenuated the blood-brain barrier (BBB) damage and leukocyte infiltration (as measured by EB leakage and MPO activity, respectively) seen at 48 h after the initial ischaemic episode. These studies provide the first experimental evidence that COX-2 inhibition with nimesulide is able to limit BBB disruption and leukocyte infiltration following transient focal cerebral ischaemia. Neuroprotection afforded by nimesulide is observed even when the treatment is delayed until 6 h after the onset of ischaemia, confirming a wide therapeutic window of COX-2 inhibitors in experimental stroke. On the contrary, selective inhibition of COX-1 with VAS had no significant effect on the evaluated parameters. These data suggest that COX-2 activity, but not COX-1 activity, contributes to the progression of focal ischaemic brain injury, and that the beneficial effects observed with non-selective COX inhibitors are probably associated to COX-2 rather than to COX-1 inhibition.
Wide therapeutic time window for nimesulide neuroprotection in a model of transient focal cerebral ischemia in the rat
E. Candelario-Jalil,A. Gonzalez-Falcon,M. Garcia-Cabrera,O. S. Leon,B. L. Fiebich
Quantitative Biology , 2007,
Abstract: Results from several studies indicate that cyclooxygenase-2 (COX-2) is involved in ischemic brain injury. The purpose of this study was to evaluate the neuroprotective effects of the selective COX-2 inhibitor nimesulide on cerebral infarction and neurological deficits in a standardized model of transient focal cerebral ischemia in rats. Three doses of nimesulide (3, 6 and 12 mg/kg; i.p.) or vehicle were administered immediately after stroke and additional doses were given at 6, 12, 24, 36 and 48 h after ischemia. In other set of experiments, the effect of nimesulide was studied in a situation in which its first administration was delayed for 3-24 h after ischemia. Total, cortical and subcortical infarct volumes and functional outcome (assessed by neurological deficit score and rotarod performance) were determined 3 days after ischemia. The effect of nimesulide on prostaglandin E(2) (PGE(2)) levels in the injured brain was also investigated. Nimesulide dose-dependently reduced infarct volume and improved functional recovery when compared to vehicle. Of interest is the finding that neuroprotection conferred by nimesulide (reduction of infarct size and neurological deficits and improvement of rotarod performance) was also observed when treatment was delayed until 24 h after ischemia. Further, administration of nimesulide in a delayed treatment paradigm completely abolished PGE(2) accumulation in the postischemic brain, suggesting that COX-2 inhibition is a promising therapeutic strategy for cerebral ischemia to target the late-occurring inflammatory events which amplify initial damage.
Neuroprotective efficacy of nimesulide against hippocampal neuronal damage following transient forebrain ischemia
E. Candelario-Jalil,D. Alvarez,A. Gonzalez-Falcon,M. Garcia-Cabrera,G. Martinez-Sanchez,N. Merino,A. Giuliani,O. S. Leon
Quantitative Biology , 2007,
Abstract: Cyclooxygenase-2 is involved in the inflammatory component of the ischemic cascade, playing an important role in the delayed progression of the brain damage. The present study evaluated the pharmacological effects of the selective cyclooxygenase-2 inhibitor nimesulide on delayed neuronal death of hippocampal CA1 neurons following transient global cerebral ischemia in gerbils. Administration of therapeutically relevant doses of nimesulide (3, 6 and 12 mg/kg; i.p.) 30 min before ischemia and at 6, 12, 24, 48 and 72 h after ischemia significantly (P<0.01) reduced hippocampal neuronal damage. Treatment with a single dose of nimesulide given 30 min before ischemia also resulted in a significant increase in the number of healthy neurons in the hippocampal CA1 sector 7 days after ischemia. Of interest is the finding that nimesulide rescued CA1 pyramidal neurons from ischemic death even when treatment was delayed until 24 h after ischemia (34+/-9% protection). Neuroprotective effect of nimesulide is still evident 30 days after the ischemic episode, providing the first experimental evidence that cyclooxygenase-2 inhibitors confer a long-lasting neuroprotection. Oral administration of nimesulide was also able to significantly reduce brain damage, suggesting that protective effects are independent of the route of administration. The present study confirms the ability of cyclooxygenase-2 inhibitors to reduce brain damage induced by cerebral ischemia and indicates that nimesulide can provide protection when administered for up to 24 h post-ischemia.
Corrosion Behavior of Mg-Al/TiC Composites in NaCl Solution
L. A. Falcon,E. Bedolla B.,J. Lemus,C. Leon,I. Rosales,J. G. Gonzalez-Rodriguez
International Journal of Corrosion , 2011, DOI: 10.1155/2011/896845
Abstract: The corrosion behavior of TiC particles reinforced Mg-Al alloy in 3.5% NaCl solution has been evaluated using electrochemical techniques. Tested alloys included an Mg-9Al (Mg AZ91E) alloy with and without 56?wt. % TiC particles. Electrochemical techniques included potentiodynamic polarization curves, linear polarization resistance, electrochemical noise, and electrochemical impedance spectroscopy measurements. All techniques showed that the composite exhibited a lower corrosion rate than the base alloy. Evidence of galvanic effects that increased the composite corrosion rate was found between the matrix and the TiC particles. Additionally, the tendency to suffer from pitting corrosion was higher for the base alloy than that for the composite. Electrochemical impedance results showed the importance of adsorption/diffusion phenomena in both materials. 1. Introduction Nowadays, aluminum matrixes are widely used in metallic matrix composites (MMCs), because they have the highest priority in applications where a combination of corrosion resistance, low density, and high mechanical performance are required, such as in the automotive and aerospace industry. The reinforcement of an aluminum matrix, based on the use of TiC particles is interesting because of its good wettability [1, 2] which results in a clean and strong interface [2–4]. While aluminum alloys are the most commonly used matrix in metal-ceramic composites, it has been reported that the addition of TiC, as reinforcement, improves the mechanical properties at room and high temperatures. However, research in new systems is required due to rapid increase in technological development. Therefore, it could be appreciated as an increasing interest in the use of magnesium and its alloys as a metallic matrix for MMC composites. The main disadvantage of magnesium is the high chemical reactivity due to its negative electrochemical potential; this greatly restricts its industrial applications, and the same disadvantage has been found for Mg-Al-Zn alloys, being Mg AZ91, the most significant alloy. Researches on metallic-based matrix composites using magnesium are considerable fewer than those done for aluminum [5–10]. Many studies have been carried out to determine the Mg-Al-Zn corrosion behavior. Pardo et al. [11] concluded that corrosion damage was mainly caused by formation of a Mg(OH)2 corrosion layer. AZ80 and AZ91D alloys revealed the highest corrosion resistance. The relatively fine β-phase (Mg17Al12) network and the aluminum enrichment produced on the corroded surface were the key factors limiting
Theoretical deduction of the Hubble law beginning with a MoND theory in context of the $Λ$FRW-Cosmology
N. Falcon,A. Aguirre
Physics , 2014,
Abstract: We deducted the Hubble law and the age of the Universe, through the introduction of the Inverse Yukawa Field (IYF), as a non-local additive complement of the Newtonian gravitation (Modified Newtonian Dynamics). As result we connected the dynamics of astronomical objects at great scale with the Friedmann-Robertson-Walker ($\Lambda$FRW) model. From the corresponding formalism, the Hubble law can be expressed as v = (4 $\pi$ [G]/c)r, which was derivated by evaluating the IYF force at distances much greater than 50Mpc, giving a maximum value for the expansion rate of the universe of $H_0=86,31$, consistent with the observational data of 392 astronomical objects from NASA/IPAC Extragalactic Database (NED). This additional field (IYF) provides a simple interpretation of dark energy as the action a large scale of baryonic matter. Additionally, we calculated the age of the universe as 11Gyr, in agreement with recent measurements of the age of the white dwarfs in the solar neighborhood.
Resolving galaxies in time and space: I: Applying STARLIGHT to CALIFA data cubes
R. Cid Fernandes,E. Perez,R. Garcia Benito,R. M. Gonzalez Delgado,A. L. de Amorim,S. F. Sanchez,B. Husemann,J. Falcon Barroso,P. Sanchez-Blazquez,C. J. Walcher,D. Mast
Physics , 2013, DOI: 10.1051/0004-6361/201220616
Abstract: Fossil record methods based on spectral synthesis techniques have matured over the past decade, and their application to integrated galaxy spectra fostered substantial advances on the understanding of galaxies and their evolution. Yet, because of the lack of spatial resolution, these studies are limited to a global view, providing no information about the internal physics of galaxies. Motivated by the CALIFA survey, which is gathering Integral Field Spectroscopy over the full optical extent of 600 galaxies, we have developed an end-to-end pipeline which: (i) partitions the observed data cube into Voronoi zones in order to, when necessary and taking due account of correlated errors, increase the S/N, (ii) extracts spectra, including propagated errors and bad-pixel flags, (iii) feeds the spectra into the STARLIGHT spectral synthesis code, (iv) packs the results for all galaxy zones into a single file, (v) performs a series of post-processing operations, including zone-to-pixel image reconstruction and unpacking the spectral and stellar population properties into multi-dimensional time, metallicity, and spatial coordinates. This paper provides an illustrated description of this whole pipeline and its products. Using data for the nearby spiral NGC 2916 as a show case, we go through each of the steps involved, presenting ways of visualizing and analyzing this manifold. These include 2D maps of properties such as the v-field, stellar extinction, mean ages and metallicities, mass surface densities, star formation rates on different time scales and normalized in different ways, 1D averages in the temporal and spatial dimensions, projections of the stellar light and mass growth (x,y,t) cubes onto radius-age diagrams, etc. The results illustrate the richness of the combination of IFS data with spectral synthesis, providing a glimpse of what is to come from CALIFA and future surveys. (Abridged)
On the k–Lucas Numbers of Arithmetic Indexes  [PDF]
Sergio Falcon
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.310175
Abstract: In this paper, we study the k–Lucas numbers of arithmetic indexes of the form an+r , where n is a natural number and r is less than r. We prove a formula for the sum of these numbers and particularly the sums of the first k-Lucas numbers, and then for the even and the odd k-Lucas numbers. Later, we find the generating function of these numbers. Below we prove these same formulas for the alternated k-Lucas numbers. Then, we prove a relation between the k–Fibonacci numbers of indexes of the form 2rn and the k–Lucas numbers of indexes multiple of 4. Finally, we find a formula for the sum of the square of the k-Fibonacci even numbers by mean of the k–Lucas numbers.
Relationships between Some k -Fibonacci Sequences  [PDF]
Sergio Falcon
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.515216
Abstract: In this paper, we will see that some -Fibonacci sequences are related to the classical Fibonacci sequence of such way that we can express the terms of a k -Fibonacci sequence in function of some terms of the classical Fibonacci sequence. And the formulas will apply to any sequence of a certain set of k' -Fibonacci sequences. Thus we find k -Fibonacci sequences relating to other k -Fibonacci sequences when σ'k is linearly dependent of \"\".
Resolving galaxies in time and space: II: Uncertainties in the spectral synthesis of datacubes
R. Cid Fernandes,R. M. Gonzalez Delgado,R. Garcia Benito,E. Perez,A. L. de Amorim,S. F. Sanchez,B. Husemann,J. Falcon Barroso,R. Lopez-Fernandez,P. Sanchez-Blazquez,N. Vale Asari,A. Vazdekis,C. J. Walcher,D. Mast
Physics , 2013, DOI: 10.1051/0004-6361/201321692
Abstract: In a companion paper we have presented many products derived from the application of the spectral synthesis code STARLIGHT to datacubes from the CALIFA survey, including 2D maps of stellar population properties and 1D averages in the temporal and spatial dimensions. Here we evaluate the uncertainties in these products. Uncertainties due to noise and spectral shape calibration errors and to the synthesis method are investigated by means of a suite of simulations based on 1638 CALIFA spectra for NGC 2916, with perturbations amplitudes gauged in terms of the expected errors. A separate study was conducted to assess uncertainties related to the choice of evolutionary synthesis models. We compare results obtained with the Bruzual & Charlot models, a preliminary update of them, and a combination of spectra derived from the Granada and MILES models. About 100k CALIFA spectra are used in this comparison. Noise and shape-related errors at the level expected for CALIFA propagate to 0.10-0.15 dex uncertainties in stellar masses, mean ages and metallicities. Uncertainties in A_V increase from 0.06 mag in the case of random noise to 0.16 mag for shape errors. Higher order products such as SFHs are more uncertain, but still relatively stable. Due to the large number statistics of datacubes, spatial averaging reduces uncertainties while preserving information on the history and structure of stellar populations. Radial profiles of global properties, as well as SFHs averaged over different regions are much more stable than for individual spaxels. Uncertainties related to the choice of base models are larger than those associated with data and method. Differences in mean age, mass and metallicity are ~ 0.15 to 0.25 dex, and 0.1 mag in A_V. Spectral residuals are ~ 1% on average, but with systematic features of up to 4%. The origin of these features is discussed. (Abridged)
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