Effect of relative humidity on the mechanical properties of micro and nanocomposites of polyvinyl alcohol

The effect of relative humidity on the mechanical properties of poly(vinyl alcohol) (PVOH) micro and nanocomposites was evaluated. Two different commercial fillers (microcellulose and bentonite) were used as reinforcement. PVOH and PVOH composite films were prepared by casting technique. The incorporation of microcellulose increased the content of water absorption and the modulus, especially for the higher contents of filler. The effect of reinforcement on the mechanical properties was more pronounced at higher relative humidity. On the other hand, the incorporation of nanofiller produced a decrease in water absorption probably due to the decrease of mean free path of water molecules. The modulus of the nanocomposites improved from the matrix, but the mechanical properties are deteriorated by effect of the humidity.Fil: Ollier Primiano, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Pérez, Claudio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin

Smart release of antimicrobial ZnO nanoplates from a pH-responsive keratin hydrogel

A smart antibacterial biomaterial based on a keratin hydrogel with pH-dependent behavior and Zinc Oxide nanoplates as biocide agent has been developed. The pH of a chronic wound is basic due to bacterial metabolism. Originally shrank at acid pH, keratin hydrogels swell upon contact with a bacterial contaminated media leading to the release of the nanoparticles. The material has been thoroughly characterized by infrared spectroscopy, Raman, scanning electron microscope, swelling behavior, Differential scanning calorimetry, Small-angle X-ray scattering, rheology, antimicrobial activity and cytotoxicity. The results show that 5% of Zinc Oxide nanoparticles concentration is the optimum for wound dressing applications.Fil: Villanueva, María Emilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Cuestas, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Pérez, Claudio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Campodallorto, Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Copello, Guillermo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentin

Isolation and Pathogenic Characterization of Vibrio bivalvicida Associated With a Massive Larval Mortality Event in a Commercial Hatchery of Scallop Argopecten purpuratus in Chile

The VPAP30 strain was isolated as the highly predominant bacteria from an episode of massive larval mortality occurring in a commercial culture of the Chilean scallop Argopecten purpuratus. The main aims of this study were, to characterize and identify the pathogenic strain using biochemical and molecular methods, to demonstrate its pathogenic activity on scallop larvae, to characterize its pathogenic properties and to describe the chronology of the pathology. The pathogenic strain was identified as Vibrio bivalvicida based on its phenotypic properties, the multilocus sequence analysis (MLSA) of eight housekeeping genes (ftsZ, gapA, gyrB, mreB, pyrH, recA, rpoA, and topA) and different in silico genome-to-genome comparisons. When triplicate cultures of healthy 10 days old scallop larvae were challenged with 1 × 105 colony forming units (CFU) mL-1 of the VPAP30 strain, percentages of larval survival of 78.9 ± 3.3%, 34.3 ± 4.9%, and 0% were observed at 12, 2,4 and 36 h, respectively, whereas uninfected larval cultures showed survival rates of 97.4 ± 1.2% after of 48 h. Clinical symptoms exhibited by the scallop larvae infected with the VPAP30 strain include the accumulation of bacteria around the scallop larvae, velum disruption and necrosis of digestive gland. The 50% lethal dose (LD50) of VPAP30 strain at 24 and 48 h was 1.3 × 104 and 1.2 × 103 CFU mL-1, respectively. The invasive pathogenic activity of the VPAP30 strain was investigated with staining of the bacterial pathogen with 5-DTAF and analyzing bacterial invasion using epifluorescence, and a complete bacterial dissemination inside the larvae at 24 h post-infection was observed. When scallop larvae were inoculated with cell-free extracellular products (ECPs) of VPAP30, the larval survival rate was 59.5 ± 1.7%, significantly (P < 0.001) lower than the control group (97.4 ± 1.2%) whereas larvae treated with heat-treated ECPs exhibited a survival rate of 61.6 ± 1.8% after 48 h of exposure. V. bivalvicida VPAP30 exhibits high pathogenic activity on scallop larvae, mediated both by bacterial invasion and the production of toxigenic heat-stable compounds. This report constitutes the first isolation of V. bivalvicida out of Europe and extends the host range of this species, having demonstrated its pathogenic activity on the Chilean scallop larvae (A. purpuratus). These results supporting the pathogenic potential of V. bivalvicida to kill the larvae of a broad range of bivalve species reared in hatcheries located in the Atlantic and the Pacific coasts.This study was financially supported by the Science and Technology National Council (CONICYT) of Chile by the Postdoctoral Project Grant No. 3150395 and FONDECYT grant No. 1140734 and FONDEF ID16I10291S

Collagen Hydrogels Loaded with Silver Nanoparticles and Cannabis Sativa Oil

Wounds represent a major healthcare problem especially in hospital-associated infections where multi-drug resistant strains are often involved. Nowadays, biomaterials with therapeutic molecules play an active role in wound healing and infection prevention. In this work, the development of collagen hydrogels loaded with silver nanoparticles and Cannabis sativa oil extract is described. The presence of the silver nanoparticles gives interesting feature to the biomaterial such as improved mechanical properties or resistance to collagenase degradation but most important is the long-lasting antimicrobial effect. Cannabis sativa oil, which is known for its anti-inflammatory and analgesic effects, possesses antioxidant activity and successfully improved the biocompatibility and also enhances the antimicrobial activity of the nanocomposite. Altogether, these results suggest that this novel nanocomposite biomaterial is a promising alternative to common treatments of wound infections and wound healing.Fil: Antezana, Pablo Edmundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Municoy, Sofia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Pérez, Claudio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentin

Mechanical evaluation of polylactic acid (PLA) based composites reinforced with different calcium phosphates

In the present work, the mechanical performance of polylactic acid (PLA) based composites reinforced with hydroxyapatite (HA) or β-tricalcium phosphate (β-TCP) was investigated. The polymer was melt compounded with 1 and 2.5 wt% of particles by using an intensive mixer or a twin screw extruder. Morphological, thermal and rheological studies were performed to analyze the composites internal structure and filler-matrix interaction. The mechanical behavior was investigated through uniaxial tensile and quasi-static fracture tests. The different characterization techniques evidenced a better filler dispersion for composites obtained by extrusion independently of the filler used. A relatively weak filler-matrix interaction was revealed from morphological observations and rheological measurements. In addition, thermal analysis evidenced similar crystalline structure for all of the investigated materials. In general, uniaxial tensile parameters displayed almost constant values independently of the filler content or compounding method. Particularly, extruded composites with 2.5 wt% filler exhibited slightly increased ductility respect to neat PLA which was related to improved filler dispersion. The PLA matrix displayed load-displacement curves with ductile instability in quasi-static fracture tests. On the other hand, the composites with 2.5 wt% filler exhibited an increased stable crack growth followed by ductile instability. The fracture process was quantitatively described by means of critical stress intensity factor (K IQ) and strain energy release rate at propagation (G CP) parameters. The extruded composites with 2.5 wt% filler displayed improved propagation fracture toughness. Based on fractured surfaces analysis this enhanced behavior, not largely reported for untreated rigid fillers, was attributed to the effective activation of the toughening mechanisms of particle debonding and subsequent plastic void growth.Fil: Pérez, Claudio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Eisenberg, Patricia. Instituto Nacional de Tecnología Industrial; ArgentinaFil: Bernal, Celina Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Perez, Ezequiel Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentin

Mercados Informales y Control Vertical: Comercialización de Pesca Artesanal Perecible

This paper offers an in-depth case study analysis about institutional changes occurring since the late 1990s at the Chilean Austral Hake artisanal fishery. This high-value exporting fishery, specialized on selling fresh-chilled products, represents a pioneering example of self-government developments within artisanal fishermen's communities exploiting mobile marine resources in Chile. Despite entry restrictions and global catch quotas, this fishery faced a productivity crisis from the late 1980s up to the second half of the 1990s. As a response to this, fishermen initiated talks with the Government in order to introduce new management rules. After gradual evolution, today there prevails a well-developed system of de facto individual non-transferable quotas subject to a high degree of self-management by fishermen organizations. We discuss industrial organization issues which condition the exchange solutions found at this fishery. In particular, we discuss incentives derived from industrial concentration and buyer power, vertical integration and other strategies of vertical control between transacting parties at this industry; namely, between wholesale marketing brokers, exporters, processors, direct buyers of the catch and fishermen. Contractual issues of relevancy are: the use of informal markets; multi-dimensional contracting; temporal specificity due to product perishability; the use of different instruments for vertical control; and the influence of increasing degrees of industrial concentration as we advance through the wholesale commercialization channel, moving closer to the retailing stages at final export markets.Producción y comercialización de Alimentos; Cadenas de producción; Control y Coordinación Vertical; Pesca Artesanal en Chile; Merluza Austral.

Riboflavin-UVA gelatin crosslinking: Design of a biocompatible and thermo-responsive biomaterial with enhanced mechanical properties for tissue engineering

The main objective of this study is to develop an economic, environmentally friendly and malleable biomaterial for tissue engineering applications. Water and glycerol have been used as solvents for the gelatin hydrogel synthesis. This solvent mixture led to a biomaterial with improved thermal properties. Indeed, a 16 °C increase in thermal transition temperature was achieved. Furthermore, to enhance mechanical properties, riboflavin was used as a crosslinking agent. Chemical crosslinking step was initiated with UV radiation to obtain riboflavin radical polymerization of gelatin chains, hence, rheological properties of gelatin hydrogel were improved. Thus, Gelatin-UV-Riboflavin hydrogel showed good swelling and increased mechanical properties, obtaining a novel material for drug delivery and medical purposes.Fil: Galdopórpora, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Pérez, Claudio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Tuttolomondo, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentin

Chitin based hybrid composites reinforced with graphene derivatives: a nanoscale study

In this work, we present two novel nanostructured hybrid materials based on a chitin matrix loaded with increasing amounts of graphene oxide and reduced graphene oxide nanosheets (nGO and rGO, respectively). Both kinds of material (Chi:nGO and Chi:rGO) were studied using different spectroscopic and rheological techniques with the aim of understanding the interaction mechanism between chitin and nGO/rGO and explaining how the type of filler and its proportion affects its reinforcement. The production of these hybrids represents not only the obtention of low-cost materials with mechanical resistance but also a good opportunity for developing materials with several applications according to their composition. The nGO and rGO were characterised through FT-IR and ESR for the determination of the oxidation degree of each nanofiller. Then, the hybrids were spectroscopically analysed with FT-IR, ESR and SAXS which demonstrated that the components do not interact through covalent bonding and the nanosheets are well-dispersed among the chitin matrix. Finally, a rheological behavior assay was performed and its results were analysed in terms of G′ and η*. In short, all the results allowed us to conclude that nGO acts as a more efficient reinforcer than rGO due to the higher amount of hydrogen bonding established with chitin.Fil: González, Joaquín Antonio. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química Analítica Instrumental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco (i); ArgentinaFil: Villanueva, María Emilia. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química Analítica Instrumental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco (i); ArgentinaFil: Peralta Ramos, María Luz. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química Analítica Instrumental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco (i); ArgentinaFil: Pérez, Claudio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Piehl, Lidia Leonor. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Copello, Guillermo Javier. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química Analítica Instrumental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco (i); Argentin

Territorial planning and sustainability of an oasis. The case of the master plan of Topater in Calama

Uno de los temas menos explorados en nuestro país es cómo deben crecer nuestras ciudades insertas en zonas áridas, cuales son las pautas que debemos considerar para canalizar este fenómeno urbano, qué lecturas del paisaje nos dan las pistas para generar su intervención. En definitiva, ¿qué sucede cuando las ciudades se expanden repentinamente y crecen extendiendo sus límites urbanos sin control sobre un territorio desértico?Esta operación urbana y que recoge este trabajo, abre el debate sobre cuáles son los instrumentos más adecuados para ordenar un territorio desértico y cómo enfrentar los futuros crecimientos urbanos en zonas áridas.One of the least explored topics in our country is the matter of how cities located on arid areas should grow, what are the aspects to consider in order to guide this urban phenomenon and which elements of the landscape can give us indications for their intervention. In summary, what happens when cities grow and expand rapidly, extending their urban limits with no control over a desert territory?This article analyses this urban phenomenon and discusses the most appropriate instruments to organize the desert territory and ways for facing future urban growth in arid zones

Composición química del rastrojo de tres cultivares de maíz esterilizados y colonizados por micelio de Ganoderma lucidum

Nutritional quality in grain by-products such as corn stover can be improved with processes such as steam sterilization and fungus inoculation. The stover of two native corn cultivars and one commercial hybrid cultivar were steam sterilized or inoculated with mycelium of the white-rot fungus Ganoderma lucidum. The experimental design was completely random with a 3x4 factorial arrangement, one additional treatment and four replicates. The four treatments were untreated stover, sterilization and immediate drying, sterilization and drying after 15 d, and colonization with G. lucidum for 15 d; pure mycelia were also analyzed to establish values for the fungus. Five variables were measured: in vitro dry matter digestibility (IVDMD), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin and crude protein (CP). The three cultivars differed (P<0.0001) in terms of digestibility, with cultivar A having the highest values. Digestibility was lowest (P<0.05) in the G. lucidem-colonized stovers (P<0.05), intermediate in the untreated stovers and highest in the sterilized stovers. Contents of NDF, ADF, lignin, and CP differed (P<0.0001) between the cultivars and treatments (P<0.0001). Cultivar A had less NDF than the other cultivars. The untreated stovers had less NDF than the sterilized and G. lucidem-colonized stovers. For both ADF and lignin, the untreated stovers had the lowest values, the sterilized stovers had intermediate values and the colonized stovers had the highest. Crude protein (CP) differed between the cultivars (P<0.0001), and the colonized stovers had the highest values (P<0.05). Inoculation of corn stover with Ganoderma lucidum mycelia did not improve digestibility after fifteen days colonization, but slightly increased crude protein content./*/Se evaluó la calidad nutritiva del rastrojo de dos cultivares criollos de maíz y un híbrido, colonizados por micelio de Ganoderma lucidum. El diseño experimental fue completamente al azar con arreglo factorial 3x4 con un tratamiento adicional y cuatro repeticiones. Cada cultivar tuvo rastrojo colonizado por el hongo hasta los 15 días, rastrojo en su estado natural (sin tratar), a tiempo cero después de la esterilización, a 15 días después de la esterilización y el micelio puro (adicional). Se determinó digestibilidad in vitro (DIVMS), fibra detergente neutro (FDN) y ácido (FDA), lignina y proteína cruda (PC). Los cultivares difirieron (P<0.0001) en digestibilidad, el criollo A presentó valores mayores. Los rastrojos colonizados tuvieron menor (P<0.05) digestibilidad; los rastrojos sin tratar tuvieron valores medios y los esterilizados fueron los más digestibles. La concentración de FDN, FDA, lignina, y PC difirió (P<0.0001) en los cultivares y las condiciones del rastrojo (P<0.0001). El criollo A tuvo menos FDN que los otros cultivares. Los rastrojos en su forma natural tuvieron menos FDN que los esterilizados y los colonizados. En la FDA los rastrojos en su forma natural tuvieron concentración baja, los esterilizados una concentración media y los colonizados la concentración mayor, situación que fue similar para lignina. En PC los cultivares fueron diferentes (P<0.0001), siendo los rastrojos colonizados los que tuvieron valores mayores (P<0.05). En conclusión, la colonización del rastrojo por el micelio de Ganoderma lucidum no aumentó la digestibilidad a los 15 días de colonización, lo que mejoró ligeramente fue la concentración de proteína cruda