Estudio de fibras de Bromelia serra (chaguar morado) cultivadas en La Banda (Santiago del Estero)

Tres especies de bromeliáceas argentinas tiene aplicación en la industria textil: Bromelia Serra, Bromelia Hieronymiy Bromelia Sp. La primera es la de mayor importancia económica por constituír la gran mayoría de los matorrales explorados en el Norte Argentino; si bien la segunda provee fibras más resistentes suaves y flexibles. La tercera mucho más escasa es de menor valor industrial. La Bromelia Serra es conocida también con los nombres vernáculos de "chaguar morado", "karagwatá", "chaguar blanco común" ó "chaguar". El elevado costo de explotación por falta de un método apropiado y económico no ha hecho posible hasta ahora su aprovechamiento industrial como sustituto del yute, cáñamo, lino textil, etc. En Brasil, Colombia, Panamá, Jamaica, Islas Filipinas, etc., las fibras bromeliáceas se usan intensamente, confeccionándose tejidos delicados. En la actualidad se recurre al desfibrado mecánico exclusivamente, siendo un método costoso y de bajo rendimiento. No se ha intentado en nuestro país la obtención de la fibra, por enriado, método usado rudimentariamente por los habitantes de las zonas de producción y de excelentes resultados obtenidos en Alemania, Holanda, Bélgica, Italia, etc. En Egipto particularmente, se efectúa desde hace centenares de años, aprovechando las cálidas y quietas aguas del Nilo. Existen varios métodos de enriado, dependientes de varios factores: cantidad y naturaleza del material ceméntico que mantiene unidas las fibras, zona de agricultura, clima, suministro de agua, costo implicado y según sea efectuado en ríos, piletas u otros lugares. Los constituyentes principalesde la fibra en estudio son, como en todas las fibras, la celulosa, la xilosa, la hemicelulosa y la lignina. En sus cenizas se halla sílice, hierro, aluminio, calcio, magnesio, cloro, azufre, sodio, potasio, fósforo, cobre y manganeso. La mercerización confiere a la fibra brillo y afinidad por los colorantes. La fibra en estudio se tiñó con diversos colorantes, entre ellos el rojo de p-nitroanilina, escarlata directo 4B.S., azul de cobre 3R, amarillo C.H.T, etc. El chaguar morado, si bien posee menos resistencia a la tracción que otras fibras, puede aprovecharse ventajosamente, mezclada a otras fibras, en la confección de trencillas para alpargatas, bolsas, etc. Sería sumamente conveniente practicar el enriado en el lugar de producción para sacar resultados concluyentes, ya que el método, económico de por sí, puede verse dificultado por las propiedades del agua de zona en explotación. Consecuentemente debe asegurarse una legislación forestal que contemple la explotación equitativa, ya que aunque las fuentes naturales son muy abundantes, no son inagotables. El aprovechamiento de esta fuente de riqueza, beneficiaría a los pobladores de la zona, que mejorarían sus precarias condiciones de vida, contribuyéndose al engrandecimiento de nuestra floreciente industria nacional.Fil: Wicher, Carmela J.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Xylan decoration patterns and the plant secondary cell wall molecular architecture.

The molecular architecture of plant secondary cell walls is still not resolved. There are several proposed structures for cellulose fibrils, the main component of plant cell walls and the conformation of other molecules is even less well known. Glucuronic acid (GlcA) substitution of xylan (GUX) enzymes, in CAZy family glycosyl transferase (GT)8, decorate the xylan backbone with various specific patterns of GlcA. It was recently discovered that dicot xylan has a domain with the side chain decorations distributed on every second unit of the backbone (xylose). If the xylan backbone folds in a similar way to glucan chains in cellulose (2-fold helix), this kind of arrangement may allow the undecorated side of the xylan chain to hydrogen bond with the hydrophilic surface of cellulose microfibrils. MD simulations suggest that such interactions are energetically stable. We discuss the possible role of this xylan decoration pattern in building of the plant cell wall.We thank Nadine Anders for helpful comments on the manuscript. The work was supported by a Leverhulme Trust Programme Grant : The Centre for Natural Material Innovation and the Biotechnology and Biological Sciences Research Council grant numbers [BB/K005537/1] and [BB/G016240/1].This is the author accepted manuscript. The final version is available from Portland Press via http://dx.doi.org/10.1042/BST2015018

Prediction of sequential antigenic regions in proteins

AbstractPrediction of antigenic regions in a protein will be helpful for a rational approach to the synthesis of peptides which may elicit antibodies reactive with the intact protein. Earlier methods are based on the assumption that antigenic regions are primarily hydrophilic regions at the surface of the protein molecule. The method presented here is based on the amino acid composition of known antigenic regions in 20 proteins which is compared with that of 314 proteins [(1978) Atlas of Protein Sequence and Structure, vol. 5, suppl. 3, 363-373]. Antigenicity values were derived from the differences between the two data sets. The method was applied to bovine ribonuclease, the B-subunit of cholera toxin and herpes simplex virus type 1 glycoprotein D. There was a good correlation between the predicted regions and previously determined antigenic regions

Enteric infection with an obligate intracellular parasite, Encephalitozoon cuniculi, in an experimental model.

Rabbits were intrarectally infected with 3 doses (5 x 10(3), 5 x 10(5), and 5 x 10(7] of an obligate intracellular parasite, Encephalitozoon cuniculi, with or without prior colonic lavages. Although chronic administration of enemas seems to interfere to some degree with the intestinal translocation of the parasite, systemic infection was observed in both manipulated and nonmanipulated animals. The animals responded with antibodies of immunoglobulin A (IgA) and IgG isotypes, reflecting the route of infection. They also produced significant amounts of circulating immune complexes composed of IgA and IgG antibodies and E. cuniculi antigens. Lesions compatible with encephalitozoonosis were seen in the liver, kidney, lung, and brain. In all instances, nonmanipulated animals had more severe lesions than manipulated rabbits given the same dose of parasites. Levels of serum antibodies, circulating immune complexes, and histopathologic changes were associated with the infection dose. The presented data suggest that human microsporidiosis may also be transmitted via the rectal route. It is, therefore, of clinical relevance in view of several reports of microsporidian infections in patients with acquired immunodeficiency

Unlocking ultrastrong high-temperature ceramics: Beyond Equimolar Compositions in High Entropy Nitrides

Traditionally, increasing compositional complexity and chemical diversity of high entropy alloy ceramics whilst maintaining a stable single-phase solid solution has been a primary design strategy for the development of new ceramics. However, only a handful have shown properties that justify the increased alloying content. Here, we unveil a groundbreaking strategy based on deviation from conventional equimolar composition towards non-equimolar composition space, enabling tuning the metastability level of the supersaturated single-phase solid solution. By employing high-temperature micromechanical testing of refractory metal-based high entropy nitrides, we found that the activation of an additional strengthening mechanism upon metastable phase decomposition propels the yield strength of a non-equimolar nitride at 1000 C to a staggering 6.9 GPa, that is 30 % higher than the most robust equimolar nitride. We show that the inherent instability triggers the decomposition of the solid solution with non-equimolar composition at high temperatures, inducing strengthening due to the coherency stress of a spinodally modulated structure, combined with the lattice resistance of the product solid solution phase. In stark contrast, the strength of equimolar systems, boasting diverse chemical compositions, declines as a function of temperature due to the weakening of the lattice resistance and the absence of other strengthening mechanisms.Comment: 17 pages, 4 figures, 25 supplementary pages, 19 supplementary figures, 1 Supplementary Tabl

Applicability and accuracy of an intraoral scanner for scanning multiple implants in edentulous mandibles:A pilot study

Statement of problem. In the past 5 years, the use of intraoral digitizers has increased. However, data are lacking on the accuracy of scanning implant restorative platforms for prosthodontics with intraoral digitizers. Purpose. The purpose of this clinical pilot study was to assess the applicability and accuracy of intraoral scans by using abutments designed for scanning (scan abutments) in edentulous mandibles. Material and methods. Twenty-five participants with complete mandibular overdentures retained by 2 implants and frameworks were included in this study. Scan abutments were placed on the implants intraorally and scanned with the iTero intraoral scanner. Also, scan abutments were placed on the implant analogs of the definitive casts and scanned with an extraoral laboratory scanner (Lava Scan ST scanner). Two 3-dimensional computer-aided design models of the scan abutments with predetermined center lines were subsequently imported and registered, together with each of the scanned equivalents. The distance between the centers of the top of the scan abutments and the angulations between the scan abutments was assessed. These values were compared with the measurements made on the 3-dimensional scans ofthe definitive casts, which were the participants' original definitive casts used for fabrication of soldered bars. The threshold for distance error was established to be 100 mu m. Results. Four of the 25 intraoral scans were not suitable for research because the intraoral scanner was not able to stitch the separate scans together. Five of the 21 suitable scans demonstrated an interimplant distance error >100 Rm. Three of the 25 intraoral scans showed interimplant angulation errors >0.4 degrees. Only 1 scan showed both an acceptable interimplant distance ( Conclusions. Based on the intraoral scans obtained in this study, distance and angulation errors were too large to fabricate well-fitting frameworks on implants in edentulous mandibles. The main reason for the unreliable scans seemed to be the lack of anatomic landmarks for scanning