oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2012 ( 5 )

2011 ( 11 )

2010 ( 3 )

2009 ( 2 )

Custom range...

Search Results: 1 - 10 of 29 matches for " Carriazo "
All listed articles are free for downloading (OA Articles)
Page 1 /29
Display every page Item
Laboratory projects using inquiry-based learning: an application to a practical inorganic course
Carriazo, José G.;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000600029
Abstract: this paper reports how laboratory projects (lp) coupled to inquiry-based learning (ibl) were implemented in a practical inorganic chemistry course. several coordination compounds have been successfully synthesised by students according to the proposed topics by the lp-ibl junction, and the chemistry of a number of metals has been studied. qualitative data were collected from written reports, oral presentations, lab-notebook reviews and personal discussions with the students through an experimental course with undergraduate second-year students at the universidad nacional de colombia during the last 5 years. positive skills production was observed by combining lp and ibl. conceptual, practical, interpretational, constructional (questions, explanations, hypotheses), communicational, environmental and application abilities were revealed by the students throughout the experimental course.
Thermal and structural study of guava (Psidium guajava L) powders obtained by two dehydration methods
Osorio, Coralia;Carriazo, José G.;Barbosa, Helber;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000400016
Abstract: two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. the powders were characterised by sensory and thermal analyses (tga-dsc), infrared spectroscopy (ir), x-ray diffraction (xrd) and scanning electron microscopy (sem). thermal, morphological and structural characterisations showed a similar behaviour for the two solids. tga-dsc and ir showed the presence of pectin as the main constituent of solids. a semi-crystalline profile was evidenced by xrd, and lamellar/spherical morphologies were observed by sem. sensory analyses revealed an aroma highly related to guava. these value-added food products are an alternative to process guava and avoid loss during postharvest handling.
CARACTERIZACIóN ESTRUCTURAL Y TEXTURAL DE UNA BENTONITA COLOMBIANA
Carriazo,José; Molina,Rafael; Moreno,Sonia;
Revista Colombiana de Química , 2007,
Abstract: in the present work a colombian bentonite (from valle del cauca) was characterized by x-ray diffraction, spectroscopic techniques (ir, nmr and epr) and textural analysis. the results indicate that dioctahedral (aluminian) smectite is the principal component in the natural material. in addition, both 29si nmr and 27al nmr analysis reveal the isomorphous substitution of al3+ by si4+ in the tetrahedral sheet. the epr study shows iron (iii) in octahedral sheet positions of the clay mineral besides ?nanoclusters? probably in oxides or oxyhydroxides form. the textural analysis indicates that the bentonite is predominantly a mesoporous material.
EVALUACIóN DEL EFECTO DE LA IMPREGNACIóN DE PLATINO SOBRE LAS CARACTERíSTICAS SUPERFICIALES Y ESTRUCTURALES DE UNA ZEOLITA Y
Carriazo,José; Barrera,Mario; Almanza,Ovidio;
Revista Colombiana de Química , 2007,
Abstract: the present paper shows the evaluation of texture, surface and structure changes on a zeolite y employed in the synthesis of solids based on supported platinum. the structure features were analyzed by x-ray diffraction (xrd) whereas the texture and morphologic properties were studied from nitrogen adsorption isotherms (77k) and scanning electron microscopy (sem). in addition, fractal dimension and adsorption potential distribution were determinedall solids. the results show that the synthesis process induces the microporosity formation, maintaining the zeolite structure and without important topographic or energetic alterations on the surface.
CARACTERIZACIóN TéRMICA Y ESPECTROSCóPICA DE ARCILLAS PILARIZADAS CON SOLUCIONES POLIHIDROXOCATIóNICAS DE Al, Ce, Fe
Carriazo,José; Molina,Rafael; Moreno,Sonia;
Revista Colombiana de Química , 2008,
Abstract: this work shows the characterization by ir spectroscopy, thermogravimetric analysis (tga), differential thermal analysis (dta) and nuclear magnetic resonance spectroscopy (29sinmrand 27al nmr) of a set of pillared clays synthesized with al, al-fe, al-ce or al-ce-fe polyhydroxocationic solutions. tgadta analyses indicate a favorable thermal effect (higher thermal stability) when ce, fe or ce-fe are added. ir and 29si nmr results reveal a probable formation of a bond between the alumina pillar and the clay (sio4)-tetrahedral sheet, whereas the 27al nmr does not evidence any isomorphous substitution of iron or cerium in the alumina pillars. moreover, by ir spectroscopy was not observed any structural difference between solids pillared with al and those pillared with al-ce, showing that cerium is possibly incorporated in an independent way to the alumina pillar.
Lactate dehydrogenase activity of rat epididymis and spermatozoa: Effect of constant light
RH Ponce,CS Carriazo,NT Vermouth
European Journal of Histochemistry , 2009, DOI: 10.4081/1624
Abstract: During its passage through the epididymis, the gamete undergoes a process of “maturation” leading to the acquisition of its fertilizing ability. The epididymis displays regional variations in the morphology and metabolic properties of its epithelium which are relevant for the progressive development of mature sperm characteristics. The epididymis has spontaneous peristaltic contractions and receives sympathetic innervation that is modulated by melatonin, a hormone synthesized and released by the pineal gland. Constant lighting disrupts melatonin synthesis and secretion. We have studied the effect of constant light on lactate dehydrogenase (LDH; EC 1.1.1.27) and its isozyme C4 activities and protein content in whole epididymis, epididymal tissue and in spermatozoa from caput and cauda segments. Animals were exposed from birth to an illumination schedule of 14 h light: 10 h dark (group L:D). At 60 days of age one group of animals was submitted to constant light over 50 days (group L:L). In order to test the fertilizing ability, the rats of each group were mated with soliciting estrous females. The percentage of pregnancies in females mated with males maintained in L:L was remarkably lower than those in females mated with males maintained in the L:D photoperiod (44% and 88% respectively). Constant light increased protein concentration and LDH activity in caput as well as in cauda of total epididymis. On the contrary, in epididymal tissue, the protein content decreased in both epididymal sections compared with controls. When enzymatic activity was expressed in Units per spermatozoa, constant light induced a significant reduction of total LDH and LDHC4 in caput and cauda spermatozoa while LDH activity of epididymal tissue was not affected. In spite of the decrease in LDH per sperm cell when rats were exposed to constant light, in total epididymis (epididymis tissue plus sperm cells content) and in spermatozoa, values of enzyme activities expressed per weight unit were higher than those of controls. This is explained by the increase in the amount of stored spermatozoa, both in caput and cauda, produced by exposure of animals to constant light.
Estudio de materiales adsorbentes de bajo costo para remover Cr(VI) de efluentes acuosos
Vargas-Nieto,C; Carriazo,J. G; Castillo,E;
Ingeniería e Investigación , 2011,
Abstract: the present paper shows very high potential for two types of solid (a commercial alumina and material obtained by composting, i.e. matured compost) on cr(vi) adsorption/elimination in aqueous solution using a concentration range close to those previously detected in waste-water from colombian industries. both had important properties for eliminating cr(vi), the compost being more important as it represents low-cost material. optimal conditions for chromium adsorption on alumina and compost were established. initial cr(vi) alumina concentration was 10 mgl- 1, with 100 ml/g volume of solution per adsorbent mass, ph=2.0, 1 hour equilibrium time and 150 rpm stirring. for compost, initial cr(vi) concentration was = 3 mg l-1, 50 ml/g volume of solution per adsorbent mass, ph=2.5, 3 hour equilibrium time and 150 rpm stirring. the experiments showed that compost adsorption properties could be enhanced by adding small quantities of alumina. compost could thus be chosen as a promising material for use in bioremediation chromium-containing waste water in a management programme for using solid waste in for minimising environmental impact.
Actitudes hacia la química de estudiantes de diferentes carreras universitarias en Colombia
Molina, Manuel F;Carriazo, José G;Farías, Diana M;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000900032
Abstract: this work reports a study on the attitudes of colombian students towards chemistry in different undergraduate programs. the research was performed on 769 students belonging to several chemistry courses, by applying an adaptation of salta and tzougraki's test and using likert's scale. the results revealed that chemistry is being considered as difficult and little useful, but very interesting. thus, the difficulty to learn chemistry may be associated with its language and abstract conceptual nature. in addition, more attention should be given to the class contents and methodologies provided to the students, in order to engage them with those interest aspects and meaningful topics of each program
Impregnación de platino y dimensión fractal en dos tipos de sólidos microporosos
Carriazo,José G.; Barrera-Vargas,Mario; Molina,Manuel F.;
Revista Ingenierías Universidad de Medellín , 2010,
Abstract: this research shows the modification of a zeolite y and a pillared clay (saponite) by impregnation with different platinum quantities (synthesis of pt catalysts). the solids were characterized about the chemical composition and texture. the textural characterization reveals important changes in the solids, showing that in the zeolitic catalysts microporosity is formed, whereas in the pillared clay the microporous structures are partially blocked. fractal dimension (by avnir-jaroniec method) indicates that the topographic features of the pillared clay surface are significantly affected due to the modification with platinum, probably as a consequence of platinum clusters formation.
Impregnación de platino y dimensión fractal en dos tipos de sólidos microporosos Platinum impregnation and fractal dimension on two types of micro-porous solids
José G. Carriazo,Mario Barrera-Vargas,Manuel F. Molina
Revista Ingenierías Universidad de Medellín , 2010,
Abstract: El presente trabajo muestra la modificación de una zeolita-Y y una arcilla pilarizada (tipo saponita) mediante impregnación con diferentes cargas de Pt (catalizadores a base de Pt). Los sólidos se caracterizaron en cuanto a su composición química y su textura. La caracterización textural revela cambios importantes en los sólidos, mostrando que se genera microporosidad en la serie de catalizadores zeolíticos y se bloquean las estructuras microporosas en la serie de catalizadores obtenidos a partir de la arcilla pilarizada. La determinación de la dimensión fractal (mediante el método de Avnir-Jaroniec) indica que la modificación con Pt afecta significativamente las características topográficas de la superficie de la arcilla pilarizada como consecuencia de la posible formación de agregados de Pt. This research shows the modification of a zeolite Y and a pillared clay (saponite) by impregnation with different platinum quantities (synthesis of Pt catalysts). The solids were characterized about the chemical composition and texture. The textural characterization reveals important changes in the solids, showing that in the zeolitic catalysts microporosity is formed, whereas in the pillared clay the microporous structures are partially blocked. Fractal dimension (by Avnir-Jaroniec method) indicates that the topographic features of the pillared clay surface are significantly affected due to the modification with platinum, probably as a consequence of platinum clusters formation.
Page 1 /29
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.