The chromatographic behaviour of liquid crystalline compounds benzylidene-p-aminobenzoic acid and 4-(p-methyl benzylidene)-p-aminobenzoic acid as stationary phases for the separation of dimethylphenol isomers was investigated. These isomers were analysed on benzylidene-p-aminobenzoic acid within a nematic range of 169-194 ◦C with a temperature interval of 5 ◦C. Better peak resolution was at a column temperature of 190 ◦C. The analysis was repeated on a 4-(p-methyl benzylidene)-p-aminobenzoic acid column at a nematic temperature of 256 ◦C, which represented the end of the nematic range, and gave the optimum peak resolution. It was found that isomer better separation was obtained at 20% loading for both liquid crystal materials. Other columns of different liquid crystalline percentages (15% and 25%) were used. A chromatogram with unoverlapped peaks was only obtained in both cases at 20% column loading. The order of elution isomers under the applied chromatographic conditions is discussed. The separation of these isomers is also discussed on the basis of stereo chemical confirmations.
El presente trabajo es un estudio sintáctico y práctico en que se trata de explicar el funcionamiento de "ya" en la oración, el objetivo principal de este estudio es el análisis del complejo significado de "ya" teniendo en cuenta el modo de la acción del verbo sobre el que incide semánticamente el adverbio.
En este estudio empírico aclaramos los distintos valores de "ya" e intentamos demostrar que es un adverbio que significa una determinada modalidad del enunciado.
Pero antes de explicar detalladamente nuestro estudio presentaremos un resumen del adverbio en general , porque "ya" es uno de los adverbios de tiempo , este p
... Show MoreCuáles son los escritores que aun triunfan en España? ¿A cuáles tendencias o escuelas representan? ¿Todavía mantiene prestigio fecundo en el estudio literario? A todas tales preguntas queríamos ofrecer nuestro planteamiento investigativo en la página de las más importantes de la literatura española contemporánea, pero según nuestro punto de ver a las cosas.
La panorámica de la literatura española a partir del año 1860 no ofrece un tema o un estilo mutuamente románticos, aun cuando en este romanticismo decaído ya se advierten muy acusados los tones que se decoloran y los dibujos que se desvanecen. De esta realidad surge la necesidad del toque tan importante como el de Ramón del Valle Inclán cuya obra se encuentra nue
Desde la Salamanca de doradas piedras que tantas veces cantara, don Miguel de Unamuno dio a la literatura y al pensamiento españoles unas obras que, a pesar de muchos pesares, perdura viva, como viva fue su agónica existencia.
El bilbaíno Miguel de Unamuno (1864-1936) es autor de al menos, doce obras teatrales. Su costumbre de mezclar géneros literarios, sin distinguir claramente el drama de la novela dialogada, le llevó a preferir el teatro leído. De ahí que sus estrenos fuesen, frecuentemente, muy posteriores a las ediciones impresas.
Abstract:
The Bilbao Miguel de Unamuno (1864-1936) is the author of at least twelve plays. His habit of mixing genres,
... Show MoreAll alive languages had passed linguistic changes that made the mother language not recognized by its present speakers. Some of these changes are: syntactical, semantical, orthographical, phonetical and lexical.During the period of changes which extends over centuries, there had been a lof of written texts, such as literately texts, biographies, personal memories and manuscripts which are conserved until now as a literatel, historic and linguistic testimonies.Spanish is one of these languages that had been changed, so, the poem of the Cid (1145) was written in a Spanish which differs from the Spanish in which Cervantes wrote the Don Quixote in (1605/1615) and the Spanish of both of them differs from the Spanish of Francisco Ayala and Azorin
... Show MoreEn el contexto de la disponibilidad léxica, Esta investigación surge de la necesidad de enseñar, a los estudiantes extranjeros de comunicación que cursan sus estudios en nuestra universidad, el español especializado que realmente necesitan. La metodología disponibilidad léxica ofrece una oportunidad en cuanto a la elaboración de los manuales.
Abstract
This article presents the lexical availability as a practical tool, this research can be exploited didactically in the teaching of vocabulary as a foreign languages LE.
Experimental measurements were done for characterizing current-voltage and power-voltage of two types of photovoltaic (PV) solar modules; monocrystalline silicon (mc-Si) and copper indium gallium di-selenide (CIGS). The conversion efficiency depends on many factors, such as irradiation and temperature. The assembling measures as a rule cause contrast in electrical boundaries, even in cells of a similar kind. Additionally, if the misfortunes because of cell associations in a module are considered, it is hard to track down two indistinguishable photovoltaic modules. This way, just the I-V, and P-V bends' trial estimation permit knowing the electrical boundaries of a photovoltaic gadget with accuracy. This measure
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Denture cleansing is an essential step that can stop cross‑contamination and adds to the health of the patient, denture durability, and the general quality of life. A disinfection technique must be practical and devoid of damaging effects on the material's properties used to construct the denture base. The main aim of this study is to evaluate the effect of three concentrations of electrolyzed water denture cleanser on heat cure acrylic and polyamide after immersion in electrolyzed water. The evaluation is based on their efficacy on surface hardness, wettability, and color stability compared with one submerged in distilled water as a control group. The method consists of eighty samples of heat-cured acrylic and polyamide material.
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Pyrolysis of high density polyethylene (HDPE) was carried out in a 750 cm3 stainless steel autoclave reactor, with temperature ranging from 470 to 495° C and reaction times up to 90 minute. The influence of the operating conditions on the component yields was studied. It was found that the optimum cracking condition for HDPE that maximized the oil yield to 70 wt. % was 480°C and 20 minutes. The results show that for higher cracking temperature, and longer reaction times there was higher production of gas and coke. Furthermore, higher temperature increases the aromatics and produce lighter oil with lower viscosity.
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