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Mostrando ítems 53-72 de 79
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Nanostructure size determination in N+- type porous silicon bY X-Rya diffractometry and Raman Spectroscopy
(2011-02-07)A series of porous silicon surfaces were obstained after different exposition times of electrochemiscal etching on crystaline n+- type silicon in presence of hydrofluoric acid. These kind of surfaces show photoluminescence ... -
Niveles de radioactividad en tres regiones de Costa Rica
(2011-02-15)The establishment of the first radioactivity levels of natural radiation was carried out during the period 1991 to 1994 in three different regions of Costa Rica. The radionuclides studied belong to different soil types ... -
Nuevas lactonas sesquiterpénicas de Perymenium grande
(2009-01-13)Three new sesquiterpenes lactonaes were isolated from the aerial parts of Perymenium grande Hemsl. (Asteraceae), collected around Rincón de la Vieja Volcano, Costa Rica. In addition to the three new lactones 1, 3 and 5; ... -
Nuevo método para la obtención de quitina
(2009-04-29)A simple method for the isolation of chitin is described. It is based on the solubility of the biopolymer in concentrated aqueous HCl at low temperature. The solubility diagram of the system chitin-HCl-H2O is discussed as ... -
Odontología en el Renacimiento Español: la práctica profesional
(2011-02-07)Until the publication of the book Coloquio... Sobre la materia de la dentadura, y maravillosa obra de la boca by Franco Martínez del Catrillo in 1557, the dental subjet was relegated to an inferior plane below Medicine and ... -
On the classification of constrained extrema
(2011-07-18)Using simple arguments, accessible to students of advanced calculus with an interest in Mathematics, we show the equivalence of several criteria, scattered in the literature, to classify the critical points of functions ... -
On the right commutativity of loop rings
(2011-02-11)Its proved that extra loops and central loops are conjugated closed, consequently they are G-loops. It is also proved that extra loops and central loops are M-loops. -
Polymers of unidimentional coordination [M(sac)2(H2O)(pyz)]n, (M= Ni2+, Cu2+ and Zn2+, sac =saccharinate, pyz= pyrazine), spectroscopy and magnetic properties
(2011-07-18)Coordination polymers have been prepared by the hydrothermal reaction of M2+saccharinates (M = Ni, Cu and Zn) and pyrazine, pyz, in a ratio 1:1. The complexes of formula [M(sac)2(H2O)2pyz]n, M = Ni2+ and Zn2+ and ... -
Procesos emisores de fotones en dispersión de electrones
(2011-02-11)The investigations involving the scattering cross sections arising in virtual and real photon emission processes of electron and positron scattering by an atomic nucleus, have the need for thorough and complete calculations ... -
Producción de jarabe de fructosa con enzimas inmobilizadas en un proceso continuo a partir de tiquisque (<i>Xanthosoma sagittifolium</i>)
(2013-06-28)High fructose corn syrups (HFCS) are mainly used by the food industry and are produced by enzymatic hydrolysis from cornstarch. The main objective of this project was to produce fructose syrups using tiquisque starch ... -
Punto fijo una teoría interdisciplinaria
(2011-02-15)We show a survey of the theory of the fixed point by commenting the most important theorems and their applications in the mathematical fields as well as in other disciplines: economy, theory of games and optimization. We ... -
Purificación y cuantificación de glicerina cruda y adaptación del método ASTM D6584 para la determinación de glicerina en biodiesel
(2014-07-07)In this paper an analytical method is validated for the purification and quantification of the content of glycerol in samples of crude oil from the production of biodiesel fuel. We compared the purity of the glycerol present ... -
Semi- orthogonalities of class of Gauss hypergeometric functions
(2011-02-11)We presented three semi-orthogonalities for a class of Gauss hypergeometric functions. We further employ the semi-orthogonalities to generate a theory concerning finite series expansion involving our hypergeometric functions. -
Sismicidad y fallamiento en la zona de Arenal-Miramar
(2011-02-01)A review of the local tectonic frame was made, focusing on the faulting of The Tilaran Ridge and Montes de Aguacate. On a map of faults we plot historic and recent seismicity which was taken from Rojas (1993) and data bases ... -
Síntesis y caraterización del ligando tris-(2-tiosalicilamidoetil)amina y sus complejos de hierro e indio
(2009-01-13)The coordination chemistry of the hexadentate ligand, tris(2-thiosalicylamidoethyl)amine, (LH3), was studied. The reaction of the ligand trianion with iron(III) and indium(III) yields monomeric hexacoordinate complexes, ... -
Síntesis y evaluación de complejos de cobre (I/II) con ligandos polipiridínicos como mediadores redox en celdas solares sensibilizadas con tintes
(2020)En las celdas solares sensibilizadas con tintes (DSSCs), el mediador redox en el electrolito permite la transferencia de cargas al regenerar las moléculas del tinte durante su operación. Se sintetizaron y caracterizaron ... -
Soluciones de Einstein no asintóticamente planas
(2011-02-11)In this paper, a theorem id demostrated regarding the imposibility of the existence od asymptotically plane solutions in spaces with static cylindrycal symmetry, in the framework of the General Theory of Relativity, if the ... -
Soluciones interiores exactas a las ecuaciones de Einstein para un líquido ideal con simetría axial
(2011-07-18)Exact interior solutions of Einstein equations were obtained, using the ideal fluid model with axial symmetry (Weyl-Lewis-Papapetrou or Weyl-Papapetrou). -
SOLUCIÓN DE UNA ECUACIÓN DIFERENCIAL PARCIAL DE DIFUSIÓN
(2012-11-26)Utilizing the Laplace transform, an algorithm is shown that solves the partial differential equation, product from the application of the Fick ́s second law of diffusion. ... -
SYNTHESIS, CHARACTERIZATION AND REDOX BEHAVIOUR OF MIXED LIGAND COPPER(II) SACCHARINATE COMPLEXES
(2012-11-26)Three mixed-ligand complexes of Cu(II) with saccharin (sac), pyrazole, (Hpz), imidazole, (Himid) were synthesized and characterized on the basis of elemental analysis, FT-IR spectroscopy, magnetic susceptibility, EPR ...