Additive synthesis by sol-gel method for its use as antimicrobial

The antimicrobial activity of silver nanoparticles makes this chemical element attractive for their incorporation in different materials. Additionally, heteropolyacids (HPAs) have advantages as catalysts which make them environmentally very interesting. The objective of this work is to incorporate in a silica matrix obtained by sol-gel an HPA together with Ag, for their use as fillers in paints or adhesives. Six samples were synthesized, using tetraethoxysilane, methyltrimethoxysilane, acetic acid, molybdophosphoric acid and silver acetate. The silicas were characterized by potentiometric titration, XRD, SEM, TEM, SBET and FT-IR. When HPA is used instead of acetic acid, a variation on the final acidity is produced. The specific surface area decreases when HPA is incorporated into the silica synthesized using tetraethoxysilane as precursor, noticing a slight increase when Ag is added because a different distribution of HPA in the matrix. By SEM, it was observed that the particle size is bigger when the silicas are synthesized with TEOS-HPA, but it still shows the characteristic morphology of bulk silica. Additionally, preliminary test to evaluate the antimicrobial properties of the solids were carried out with fungi as Chaetomium globosum and Alternaria alternate, isolated from contaminated paints, and the first results are encouraging to continue with the development of these materials.Fil: Arreche, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Hernández, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Blanco, Mirta Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Vazquez, Patricia Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; Argentin

Differential access to educational establishments of initial and primary level. Formosa, prov. Formosa

Se analiza la accesibilidad espacial de la población a los equipamientos de educaciónpública (nivel inicial y nivel primario) de la ciudad de Formosa. Para ello, se aplicantécnicas de análisis espacial basadas en medidas de accesibilidad, tales como,densidad, distribución de servicios y usuarios y áreas de influencia. Se obtuvieronlos siguientes resultados: a) las áreas de influencia y demanda potencial; b) lasdistancias recorridas; c) la relación demanda calculada y matrícula; y d) las áreas deacceso diferencial. Se proporciona un panorama de las diferencias significativas encuanto a los beneficios socio-educativos que genera la distribución de equipamientoscolectivos y públicos como los educativos.Spatial accessibility of the population to public education facilities (initial level and primary level) is analyzed from the city of Formosa. Spatial analysis techniques based accessibility measures, such as density, distribution services and users and areas of influence are applied. The following results were obtained: a) the areas of influence and potential demand; b) the distances covered; c) demand and enrollment ratio calculated; and d) the areas of differential access. Therefore significant differences is provided, in terms of the socio-educational, which generates the distribution of collective and public facilities such as the educational.Fil: Blanco, Hector Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Universidad Nacional del Nordeste. Facultad de Humanidades. Instituto de Geografia; ArgentinaFil: Ramirez, Mirta Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Universidad Nacional del Nordeste. Facultad de Humanidades. Instituto de Geografia; Argentin

Student Perception of the Integrated PBL MBCHB-III Program Curriculum in a Medical University

Introduction: Integrated PBL is now an accepted method of teaching the medical curriculum. The objective of this study was to determine MBChB-III students’ perceptions about some key aspects related to our integrated PBL curriculum.Methods: This was an anonymous, questionnaire based, descriptive study, involving the Walter Sisulu University MBChB year 3 students as participants. The short questionnaire focused on key student perception areas related to integrated PBL curriculumResults: More than half of the students felt that the curriculum enhanced analytical skills, and was reasoning and learning centered. 29.5% of the students felt that the desired goals and objectives were not clear enough. About 90% felt that they felt they could recognize discipline interrelations. While 61.7% of students felt that the curriculum facilitated active learning opportunities, more than 70% felt that it increased the workload and stress levels. About half of the students expressed overall satisfaction with the level of content integration.Conclusion: Students generally presented favorable perceptions of the integrated MBChB-III PBL curriculum.  There were concerns about the associated heavy workload and stress. Student counseling with respect to time and stress management coupled with improvements in curriculum design would be helpful in addressing the issue

Synthesis and characterization of hollow silica spheres

The synthesis and characterization of mono-dispersed silica hollow spheres using polystyrene (PS) spheres as template from the hydrolysis and condensation of tetraethylorthosilicate (TEOS) is presented. Successive washing steps with toluene and subsequent calcination at different temperatures were performed, in order to remove the PS template. Furthermore, the PS core removal was studied using different calcination temperatures, but without the prior washing with toluene. The morphology of the materials was studied by scanning electron microscopy and by transmission electron microscopy. A shell formed by silica nanoparticles with 50 nm diameter, being the layer of 100 nm thickness, was observed when using a low concentration of catalyst in the sol-gel reaction. The textural properties of the silica coating, obtained from N2 adsorption-desorption isotherms, depend on the catalyst amount added for the TEOS hydrolysis. From the Fourier transform infrared spectra and the results of the thermogravimetric analyses, it was found that the almost complete removal of the polystyrene core can be directly achieved by calcining at 500 °C, without the need of carrying out any washing and minimizing the formation of cracks in the silica hollow spheres.Fil: Gorsd, Marina Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Pizzio, Luis Rene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Blanco, Mirta Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Synthesis of Polystyrene Microspheres to be Used as Template in the Preparation of Hollow Spherical Materials: Study of the Operative Variables

Mono-disperse polystyrene (PS) spheres were synthesized. The styrene polymerization was carried out using 4,4´-azobis 4-cyanovaleric acid (ACVA) or potassium persulfate (KPS) as initiators in the presence of polyvinyl pyrrolidone (PVP) as surfactant or stabilizing agent. Size measurement and its distribution were followed by scanning electron microscopy. A very narrow size distribution was obtained by controlling the synthesis temperature. For both initiators, it was observed that smaller PS particles are obtained when PVP amount increases. Besides, the ssphere size decreased when KPS amount increased at a fixed PVP concentration. Similar results were obtained for the polystyrene spheres synthesized using ACVA as initiator. On the other hand, the influence of a co-monomer addition in the sphere size was also analyzed. The suitable selection of the initiator type and its concentration, as well as the surfactant agent amount, led to a controlled obtainment of the polystyrene microspheres, appropriate to be used as template in the synthesis of hollow spherical materials.Fil: Gorsd, Marina Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Blanco, Mirta Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Pizzio, Luis Rene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Synthesis of polystyrene microspheres to be used as template in the preparation of hollow spherical materials: study of the operative variables

Mono-disperse polystyrene (PS) spheres were synthesized. The styrene polymerization was carried out using 4,4´-azobis 4-cyanovaleric acid (ACVA) or potassium persulfate (KPS) as initiators in the presence of polyvinyl pyrrolidone (PVP) as surfactant or stabilizing agent. Size measurement and its distribution were followed by scanning electron microscopy. A very narrow size distribution was obtained by controlling the synthesis temperature. For both initiators, it was observed that smaller PS particles are obtained when PVP amount increases. Besides, the ssphere size decreased when KPS amount increased at a fixed PVP concentration. Similar results were obtained for the polystyrene spheres synthesized using ACVA as initiator. On the other hand, the influence of a co-monomer addition in the sphere size was also analyzed. The suitable selection of the initiator type and its concentration, as well as the surfactant agent amount, led to a controlled obtainment of the polystyrene microspheres, appropriate to be used as template in the synthesis of hollow spherical materials.Centro de Investigación y Desarrollo en Ciencias Aplicada

Trophic analysis and parasitological aspects of liolaemus parvus (Iguania: Liolaemidae) in the central andes of Argentina

The objective of this study was to describe temporal variations in the diet and parasitological aspects in Liolaemus parvus. In order to examine the diet, we determined the volume, numerousness, and frequency of occurrence for each prey item and calculated the relative importance index. We removed nematodes from the stomach and estimated parasitic indicators. Liolaemus parvus presents an active searching mode. It is a predominantly insectivorous species with low intake of plant material and a specialist in feeding on prey items of the family Formicidae, although it also feeds on other arthropods like coleopterans, hemipterans, and spiders. We found temporal variations in its diet. The first record of Parapharyngodon riojensis nematodes is reported herein. Males showed higher nematode prevalence than females. We have expanded the number of host species and the distribution range of Parapharyngodon riojensis. The information provided about trophic ecology and parasitism is the first contribution to this lizard species’ biology.Fil: Castillo, Gabriel Natalio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Acosta, Juan Carlos. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; ArgentinaFil: Blanco, Graciela Mirta. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; Argentin

Synthesis of polystyrene microspheres to be used as template in the preparation of hollow spherical materials: study of the operative variables

Mono-disperse polystyrene (PS) spheres were synthesized. The styrene polymerization was carried out using 4,4´-azobis 4-cyanovaleric acid (ACVA) or potassium persulfate (KPS) as initiators in the presence of polyvinyl pyrrolidone (PVP) as surfactant or stabilizing agent. Size measurement and its distribution were followed by scanning electron microscopy. A very narrow size distribution was obtained by controlling the synthesis temperature. For both initiators, it was observed that smaller PS particles are obtained when PVP amount increases. Besides, the ssphere size decreased when KPS amount increased at a fixed PVP concentration. Similar results were obtained for the polystyrene spheres synthesized using ACVA as initiator. On the other hand, the influence of a co-monomer addition in the sphere size was also analyzed. The suitable selection of the initiator type and its concentration, as well as the surfactant agent amount, led to a controlled obtainment of the polystyrene microspheres, appropriate to be used as template in the synthesis of hollow spherical materials.Centro de Investigación y Desarrollo en Ciencias Aplicada

Adjustment of the reproductive activity of vulnerable lizard phymaturus williamsi at high altitudes

In environments with cold climates, reproduction of lizards is restricted to short seasonal periods of activity, from mid-spring to early autumn. We studied the reproductive biology of Phymaturus williamsi (William’s Andean Lizard), a vulnerable and viviparous lizard from the palluma phylogenetic group of genus Phymaturus, endemic to rocky outcrops in cold environments in the Andes of San Juan, Argentina. We determined adult size, male and female reproductive cycles, litter size, mean annual reproductive output, and the relationship between gonadal cycles, fat bodies, and climatic variables. The shortest reproductive male and female were 87.2 mm and 86.4 mm SVL, respectively. The litter size per female was of one or two offspring every two years, and the mean annual reproductive output was 0.95 offspring/female/year. Births occurred from late summer to early autumn. Males exhibited an annual postnuptial cycle, with spermatogenesis beginning in mid-spring, spermiogenesis occurring in summer and autumn, and sperm stored during brumation through early spring when mating occurs. The male post-nuptial cycle is common in species of the patagonicus group, but not in the palluma group, as is P. williamsi. Nevertheless, the biennial female cycle is common in the palluma group, and results from the adjustment of the reproductive activity to the physiological and environmental constraints of the harsh and cold climatic conditions prevailing at high altitudes in the Andes. The knowledge of the reproductive traits of the vulnerable P. williamsi has direct relevance for the development of conservation strategies, as this information is fundamental for population viability analyses.Fil: Castro, Susana Alejandra. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Boretto, Jorgelina Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Blanco, Graciela Mirta. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; ArgentinaFil: Acosta, Juan Carlos. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; Argentin

Additive synthesis by sol-gel method for its use as antimicrobial

The antimicrobial activity of silver nanoparticles makes this chemical element attractive for their incorporation in different materials. Additionally, heteropolyacids (HPAs) have advantages as catalysts which make them environmentally very interesting. The objective of this work is to incorporate in a silica matrix obtained by sol-gel an HPA together with Ag, for their use as fillers in paints or adhesives. Six samples were synthesized, using tetraethoxysilane, methyltrimethoxysilane, acetic acid, molybdophosphoric acid and silver acetate. The silicas were characterized by potentiometric titration, XRD, SEM, TEM, SBET and FT-IR. When HPA is used instead of acetic acid, a variation on the final acidity is produced. The specific surface area decreases when HPA is incorporated into the silica synthesized using tetraethoxysilane as precursor, noticing a slight increase when Ag is added because a different distribution of HPA in the matrix. By SEM, it was observed that the particle size is bigger when the silicas are synthesized with TEOS-HPA, but it still shows the characteristic morphology of bulk silica. Additionally, preliminary test to evaluate the antimicrobial properties of the solids were carried out with fungi as Chaetomium globosum and Alternaria alternate, isolated from contaminated paints, and the first results are encouraging to continue with the development of these materials.Centro de Investigación y Desarrollo en Ciencias Aplicada