Papers by ALEJANDRO RODRIGUEZ CASTRO
Acta Médica Costarricense, 2009
Justificación y Objetivo: Este estudio señala los valores medios normales de alfa-fetoproteína (A... more Justificación y Objetivo: Este estudio señala los valores medios normales de alfa-fetoproteína (AFP) en 124 mujeres embarazadas costarricenses que acudieron a la consulta pre-natal del Hospital Rafael Angel Calderón Guardia, entre las semanas 15 y 20 de gestación, en las cuales se llevaron a cabo 554 determinaciones de alfa-fetoproteína por duplicado. Métodos: Para llevar a cabo las pruebas se utilizó un ensayo inmunoradiométrico (IRMA), con el fin de obtener la curva de valores normales. Los valores de la concentración de AFP se expresaron como múltiplos del valor medio, considerándose límite normal superior 2.5 múltiplos de la mediana y límite inferior 0.25 múltiplos de la mediana. Resultados y Conclusión: En el presente estudio los límites de confiabilidad en que se encuentran los valores de la mediana fueron de 24-57 KU[I mientras que el múltiplo de 2.5 se situó entre 60-143 KU/I.
Estudios Gerenciales, 2012
Las oportunidades para mejorar la calidad de vida en la base de la pirámide pueden ser capitaliza... more Las oportunidades para mejorar la calidad de vida en la base de la pirámide pueden ser capitalizadas, además de la subvención del Estado, por las alianzas de tipo Público-Privado-Social (PPS). El objetivo de este trabajo es diseñar un nuevo modelo de empresa -la empresa social- que cubre lo que el Estado y el sector privado solos no logran alcanzar. La propuesta está basada en alianzas con diferentes stakeholders, y se plantea un modelo de empresa para promover el acceso a servicios de saneamiento sostenible de calidad, a partir de incluir el cambio como elemento sustancial
IEEE Transactions on Industry Applications, 2019
The use of energy harvesting for supplying wireless sensors becomes a new market opportunity. Dur... more The use of energy harvesting for supplying wireless sensors becomes a new market opportunity. During lasts years, new low power transmitters, and also power conversion ICs specifically designed for energy harvesting, have become commercially available. However, as any other power supply circuit, the specific load behavior affects to the power converter, doing that just joining the two parts takes to a non-functional device. In this paper we will measure experimentally the transmitter current of some technologies, for the several sensor states. Some practical issues that affects directly to the sensor design will be shown. With this information, some required modifications in the power stage will be proposed. A complete temperature sensor design and assembly is showed. The sensor has been tested in a tandem cold mill, and several experimental results are included.
Wireless sensors supplied by energy harvesting thermoelectric generators
2016 IEEE Industry Applications Society Annual Meeting, 2016
The use of energy harvesting for supplying wireless sensors becomes a new market opportunity. Dur... more The use of energy harvesting for supplying wireless sensors becomes a new market opportunity. During lasts years, new low power transmitters, and also power conversion ICs specifically designed for energy harvesting, have become commercially available. However, as any other power supply circuit, the specific load behavior affects to the power converter, doing that just joining the two parts takes to a non-functional device. In this paper we will measure experimentally the transmitter current of some technologies, for the several sensor states. With this information, some required modifications in the power stage will be proposed. A complete temperature sensor design and assembly is showed. The sensor has been tested in a tandem cold mill, and several experimental results are included.
Revista De Lenguas Modernas, 2010
International Journal for Numerical Methods in Fluids, 2015
A methodology for improved robustness in the simulation of high void fraction free surface polydi... more A methodology for improved robustness in the simulation of high void fraction free surface polydisperse bubbly flows in curvilinear overset grids is presented. The method is fully two-way coupled in the sense that the bubbly field affects the continuous fluid and vice versa. A hybrid projection approach is used in which staggered contravariant velocities at cell faces are computed for transport and pressure-velocity coupling while the momentum equation is solved on a collocated grid arrangement. Conservation of mass is formulated such that a strong coupling between void fraction, pressure, and velocity is achieved within a partitioned approach, solving each field separately. A pressure-velocity projection solver is iterated together with a predictor stage for the void fraction to achieve a robust coupling. The implementation is described for general curvilinear grids detailing particulars in the neighborhood to overset interfaces or a free surface. A balanced forced method to avoid the generation of spurious currents is extended for curvilinear grids. The overall methodology allows simulation of high void fraction flows and is stable even when strong packing forces accounting for bubble collisions are included. Convergence and stability in one-dimensional (1D) and two-dimensional (2D) configurations is evaluated. Finally, a full-scale simulation of the bubbly flow around a flat-bottom boat is performed demonstrating the applicability of the methodology to complex problems of engineering interest.
Full Scale Simulations of the Bubbly Flow Around the Research Vessel Athena With Incoming Waves and Discretized Propeller
ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D, 2011
Simulations of the two-phase bubbly flow around the research vessel Athena are presented. These a... more Simulations of the two-phase bubbly flow around the research vessel Athena are presented. These are performed using a polydisperse model where several bubbles sizes are modeled. Intergroup transfer mechanisms such as breakup, coalescence and dissolution of air into water are considered. These simulations are performed on the fully appended Athena R/V including the rotating propeller. In this way the interaction of the stream of bubbles pushed down by the ship and the propeller is explicitly taken into account. Incoming regular waves are included in the simulations to mimic the observations of available data that show a pulsating entrainment of bubbles due to the waves. The effect of the several intergroup transfer mechanisms on the bubbly field around the ship is analyzed and discussed in depth. Simulations are performed in full scale to predict realistic turbulent structures and allow for a valid comparison with experiments.Copyright © 2011 by ASME
Diálogos Revista Electrónica, 2014
El objetivo principal de esta investigación es analizar las memorias emblemáticas creadas por los... more El objetivo principal de esta investigación es analizar las memorias emblemáticas creadas por los tinoquistas, los grupos revolucionarios y los trabajadores urbanos de la sociedad costarricense durante la dictadura de Federico Tinoco Granados (1917-1919) y la transición democrática, conocida como el Proceso de la Restauración (1920-1926). Se analizarán las confrontaciones de estas memorias en los medios de comunicación, el espacio público de la ciudad capital: San José, las instituciones del Estado y el efecto a largo plazo de las llamadas políticas de conciliación, aplicadas por los presidentes Julio Acosta García y Ricardo Jiménez Oreamuno, para poner fin al conflicto político y social interno del país, y para erradicar cualquier expresión de estas memorias emblemáticas, después de 1927.
International Journal of Multiphase Flow, 2010
Measurements of gas volume fraction, bubble velocity, chord length and bubble size distributions ... more Measurements of gas volume fraction, bubble velocity, chord length and bubble size distributions were performed on the research vessel Athena II operating in Saint Andrew Bay in the gulf coast near Panama City, FL. Double tipped sapphire optical local phase-detection probes were used to acquire indicator functions downstream of the breaking bow wave, behind the masker and at the stern. These indicator functions were also taken at different depths, operating speeds and headings respect to the waves. The data processing includes the computation of velocity of individual bubbles and chord lengths, resulting in chord length distributions. These chord length distributions are used to obtain bubble size distributions using a novel procedure described in detail herein. Uncertainty analysis is performed for gas volume fraction, average bubble velocity and chord length. The results indicate that air entrainment increases with ship speed and sailing against the waves at all positions. The bow wave exhibits unsteady breaking that creates bubble clouds, which were characterized and identified by signal processing. At the stern a very strong dependence of bubble size with depth was found, with evidence that small bubbles (smaller than 500 lm) are transported through the bottom of the hull and reach the transom. The roller present at the transom, the associated strong unsteadiness and bubble entrainment are well captured, as indicated by the stern results, showing the frothy nature of the upper layer.
International Journal of Multiphase Flow, 2013
Prediction of the bubble size distribution in the wake of a ship is important to analyze its acou... more Prediction of the bubble size distribution in the wake of a ship is important to analyze its acoustic signature. To achieve CFD simulation of dynamic ships with moving control surfaces and rotating propellers in waves, a robust implementation is paramount. In this work a mass conserving multigroup discretization strategy of the Boltzmann transport equation for polydispersed bubbly flows is presented, as well as an analysis of available breakup and coalescence models. Modifications of the discrete equations for the fixed pivot method at the boundaries are introduced that guarantee exact bubble mass conservation. The role of the time stepping scheme in the conservation of mass and number of bubbles is discussed. Though the conservation properties of the discrete system of equations are satisfied provided they are solved exactly, in practice an iterative procedure must be used since the ODE's are non-linear. Three iterative schemes are proposed and they are analyzed in terms of robustness and efficiency. Breakup, coalescence and dissolution models are analyzed from the numerical point of view. Available models of breakup and coalescence are studied finding appropriate choices for ship applications. Other models are appropriate as well, but are more costly numerically. As appropriate for ship applications, an extension to the model of Prince and Blanch for salt water is proposed and analyzed. The final model is tested against experimental data and computations by other researchers, and convergence properties in bubble size discretization is studied. It is found that for salt water the final steady state is dependent on the initial condition since there is a range of sizes for which coalescence and breakup are both negligible.
ChemInform Abstract: Preparation of (R)-(-)-3-Phenyl-2,3,5,6,7,8-hexahydrooxazolo[3,2-a]pyridin-4-ylium Bromide (II): Synthesis of (S)-(+)-Coniine (VIb), (R)-(-)-Coniceine (VII) and (R)-(+)-Anabasine (VIa)
ChemInform, 2008
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
A través de este trabajo se procura dar una visión general de la deuda convertible, como instrume... more A través de este trabajo se procura dar una visión general de la deuda convertible, como instrumento financiero híbrido que es, desde sus orígenes en el siglo XIX hasta finales del siglo XX. Dado que el primer bono convertible fue emitido en Estados Unidos, se comienza realizando una breve descripción de lo que ha sido la evolución de los convertibles en este país, para a continuación estudiar lo que ha ocurrido en España. Tanto desde el punto de vista del emisor como del inversor la deuda convertible presenta, en determinadas circunstancias, una serie de ventajas que la pueden hacer sumamente atractiva. Dichas circunstancias concurrieron en España en el tramo final de los años 80. A finales del siglo XX economías como las de Estados Unidos, Gran Bretaña, Francia o Alemania experimentaron un importante resurgir en el uso de la deuda convertible como alternativa de financiación. Los bajos niveles de los tipos de interés, la evolución al alza en los mercados de los valores vinculados ...
Tetrahedron Letters, 2009
In this Letter we describe the synthesis of new chiral cyclic zwitterionic pyridin-2-one compound... more In this Letter we describe the synthesis of new chiral cyclic zwitterionic pyridin-2-one compounds 5a,b via an intramolecular ring-closure reaction of a stabilize amide sulfur ylide 4a,b derived from (R)-(À)-2phenylglycinol and (R)-(+)-phenylethylamine in a high yield. In addition, we proved the utility of 5a,b to produce piperidine-2,4-dione 6a,b and pyridine-2-one 7a,b depending on the reaction conditions.
Regioselective Endocyclic Oxidation of Enantiopure 3‐Alkylpiperidines: Synthesis of (3 S ,5 S )‐(‐)‐3‐Ethyl‐5‐Methylpiperidine
Synthetic Communications, 2006
Abstract: An efficient regioselective endocyclic oxidation of enantiopure 3-alkylpiper-idines 1(a... more Abstract: An efficient regioselective endocyclic oxidation of enantiopure 3-alkylpiper-idines 1(ac) with bromine in acetic acid to generate the corresponding 5-alkylpiper-idin-2-ones 3(ac) as main product is described. In addition, starting from 3a or 3b, the synthesis of ...
Oncogene, 2010
Tuberous sclerosis complex (TSC) is an autosomally inherited disorder that causes tumors to form ... more Tuberous sclerosis complex (TSC) is an autosomally inherited disorder that causes tumors to form in many organs. It is frequently caused by inactivating mutations in the TSC2 tumor-suppressor gene. TSC2 negatively regulates the activity of the GTPase Rheb and thereby inhibits mammalian target of rapamycin complex 1 (mTORC1) signaling. Activation of mTORC1 as a result of lack of TSC2 function is observed in TSC and sporadic lymphangioleiomyomatosis (LAM). TSC2 deficiency has recently been associated with elevated AMP-activated protein kinase (AMPK) activity, which in turn correlated with cytoplasmic localization of p27Kip1 (p27), a negative regulator of cyclin-dependent kinase 2 (Cdk2). How AMPK in the absence of TSC2 is stimulated is not fully understood. In this study, we demonstrate that Rheb activates AMPK and reduces p27 levels in Tsc2-null cells. Importantly, both effects occur largely independent of mTORC1. Furthermore, increased p27 levels following Rheb depletion correlated with reduced Cdk2 activity and cell proliferation in vitro, and with inhibition of tumor formation by Tsc2-null cells in vivo. Taken together, our data suggest that Rheb controls proliferation of TSC2deficient cells by a mechanism that involves regulation of AMPK and p27, and that Rheb is a potential target for TSC/LAM therapy.
Microbiology, 2009
Treatment ofNeurospora crassacells with phytosphingosine (PHS) induces programmed cell death (PCD... more Treatment ofNeurospora crassacells with phytosphingosine (PHS) induces programmed cell death (PCD) by an unknown mechanism. To determine the relationship between PHS treatment and PCD, we determined changes in global gene expression levels inN. crassaduring a time-course of PHS treatment. Most genes having differential expression levels compared to untreated samples showed an increase in relative expression level upon PHS exposure. However, genes encoding mitochondrial proteins were highly enriched among ∼100 genes that showed a relative decrease in expression levels after PHS treatment, suggesting that repression of these genes might be related to the death-inducing effects of PHS. Since mutants in respiratory chain complex I are more resistant to both PHS and hydrogen peroxide (H2O2) than the wild-type strain, possibly related to the production of reactive oxygen species, we also compared gene expression profiles of a complex I mutant (nuo14) and wild-type in response to H2O2. Gen...
Materials Research, 2012
In this research, an ion milling equipment was used to elaborate nanoparticles from Cu-Zn-Al allo... more In this research, an ion milling equipment was used to elaborate nanoparticles from Cu-Zn-Al alloys with shape memory effect. Two different compositions were used, target A: 75.22Cu-17.12Zn-7.66Al at % with an Ms of-9 °C and target B: 76.18Cu-15.84Zn-7.98Al with an Ms of 20 °C. Nanoparticles were characterized by High Resolution Transmission Electron Microscopy, Electron Diffraction and Energy Dispersive X-ray Spectroscopy. The obtained nanoparticles showed a small dispersion, with a size range of 3.2-3.5 nm. Their crystal structure is in good agreement with the bulk martensitic structure of the targets. In this sense, results on morphology, composition and crystal structure have indicated that it is possible to produce nanoparticles of CuZnAl shape memory alloys with martensitic structure in a single process using Ion Milling.
Journal of Marine Science and Technology, 2010
A method that can be used to perform selfpropulsion computations of surface ships is presented. T... more A method that can be used to perform selfpropulsion computations of surface ships is presented. The propeller is gridded as an overset object with a rotational velocity that is imposed by a speed controller, which finds the self-propulsion point when the ship reaches the target Froude number in a single transient computation. Dynamic overset grids are used to allow different dynamic groups to move independently, including the hull and appendages, the propeller, and the background (where the far-field boundary conditions are imposed). Predicted integral quantities include propeller rotational speed, propeller forces, and ship's attitude, along with the complete flow field. The fluid flow is solved by employing a single-phase level set approach to model the free surface, along with a blended k-x/k-e based DES model for turbulence. Three ship hulls are evaluated: the single-propeller KVLCC1 tanker appended with a rudder, the twin propeller fully appended surface combatant model DTMB 5613, and the KCS container ship without a rudder, and the results are compared with experimental data obtained at the model scale. In the case of KCS, a more complete comparison with propulsion data is performed. It is shown that direct computation of self-propelled ships is feasible, and though very resource intensive, it provides a tool for obtaining vast flow detail.
Journal of Applied Electrochemistry, 2010
A one-dimensional model is developed for simulating the electrodialytic and dialytic treatment of... more A one-dimensional model is developed for simulating the electrodialytic and dialytic treatment of a fly ash containing cadmium, copper and lead. Two experimental systems have been used, a column of ash and a stirred ash suspension. The movement of Cd, Cu and Pb has been modeled taking into account the diffusion transport resulting from the concentration gradients of their compounds through the membranes and boundary layers and the electromigration of their ionic, simple and complex species during the operation. The model also includes the electromigration of the non-contaminant most important principal ionic species in the system, H ? and OH-, proceeding of the electrolysis at the electrodes, Ca 2? , CO 3 = , SO 4 = , etc. proceeding from the ash and Na ? and NO 3-, or citrate and ammonium ions incorporated as electrolyte solutions and/or as agent solution during the ash treatment. The simulation also takes into account that OHgenerated on the cathode, during the electrodialytic remediation, is periodically neutralized by the addition of nitric acid in the cathode compartment. The anion and cation-exchange membranes are simply represented as ionic filters that preclude the transport of the cations and anions, respectively, with the exception of H ? which is retarded but pass through the anion-exchange membrane.
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Papers by ALEJANDRO RODRIGUEZ CASTRO